Colour Forming Compositions

Field of the Invention

The present invention relates to compositions, in particular compositions for forming an image on or within a substrate.

Background to the Invention

In-line digital printing is a process known for the formation of greyscale, single- coloured (monochromic), or multi-coloured images on or within substrates. Radiation from a laser source(s) effects laser-reactive components in compositions applied on or incorporated within substrates such that they change colour upon application of the radiation. However, problems arise in that when using these laser-reactive components, access to a full colour gamut and the full range of primary colours required to form multi-coloured images is difficult to achieve.

There is therefore a desire to provide a laser-reactive composition for the formation of an image on or within a substrate that can provide a broad colour gamut for in-line digital printing via laser excitation, enabling real-time marketing and personalisation response capabilities for users. In order to achieve this, it is important to have compositions that have components able to form stable predictable colours upon application of radiation or other stimuli.

Summary of the Invention

According to a first aspect of the present invention, there is provided a composition comprising two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature; (ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour.

According to a second aspect of the present invention, there is provided a substrate comprising a composition applied to or incorporated within, the composition comprising two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour.

According to a third aspect of the present invention, there is provided a method of forming a substrate comprising applying to or incorporating within the substrate a composition comprising two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour.

According to a fourth aspect of the present invention there is provided a method of forming colour on or within a substrate comprising a composition applied to or incorporated within, the composition comprising two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour; and wherein the method comprises applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, second temperature and third temperature as required to develop the coloured states of the components of groups (i) to (iii) present in the composition.

According to a fifth aspect of the present invention there is provided a method of forming an image on or within a substrate comprising a composition applied to or incorporated within, the composition comprising two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and wherein the method comprises applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, first temperature, second temperature and third temperature as required to develop the non-coloured and/or coloured states of the components of groups (i) to (iii) present in the composition, and thereby create an image on or within the substrate.

According to an sixth aspect of the present invention, there is provided a use of a composition in the formation of colour on or within a substrate, the composition comprising two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature; (ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour.

According to an seventh aspect of the present invention, there is provided a use of a composition in the formation of an image on or within a substrate, the composition comprising two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour.

According to an eighth aspect of the present invention, there is provided a substrate having applied thereon a plurality of discrete layers, wherein the plurality of discrete layers comprise two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow the transition to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and the two or more components selected from groups (i) to (iii) are present in different layers of the plurality of discrete layers applied on the substrate. According to a ninth aspect of the present invention there is provided a method of forming a substrate, the substrate having applied thereon a plurality of discrete layers, wherein the plurality of discrete layers comprise two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow the transition to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and the two or more components selected from groups (i) to (iii) are present in different layers of the plurality of discrete layers applied on the substrate, the method comprising applying to a substrate the plurality of discrete layers.

According to a tenth aspect of the present invention, there is provided a method of forming colour on a substrate, the substrate having applied thereon a plurality of discrete layers, wherein the plurality of discrete layers comprise two or more components selected from the following groups (i) to (iii): (i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow the transition to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and the two or more components selected from groups (i) to (iii) are present in different layers of the plurality of discrete layers applied on the substrate, and wherein the method comprises applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, second temperature and third temperature as required to develop the coloured states of the components of groups (i) to (iii) present in the plurality of discrete layers.

According to an eleventh aspect of the present invention there is provided a method of forming an image on a substrate, the substrate having applied thereon a plurality of discrete layers, wherein the plurality of discrete layers comprise two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow the transition to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and the two or more components selected from groups (i) to (iii) are present in different layers of the plurality of discrete layers applied on the substrate, and wherein the method comprises applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, first temperature, second temperature and third temperature as required to develop the non-coloured and/or coloured states of the components of groups (i) to (iii) present in the plurality of discrete layers, and thereby create an image on the substrate.

According to a twelfth aspect of the present invention, there is provided a composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature; (ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and optionally, wherein the composition does not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or oxyanion of a multivalent metal.

According to a thirteenth aspect of the present invention, there is provided a substrate having a composition applied to or incorporated within, the composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and optionally, wherein the composition does not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or oxyanion of a multivalent metal.

According to a fourteenth aspect of the present invention, there is provided a method of forming a substrate comprising applying to or incorporating within a substrate a composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur; (iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and optionally, wherein the composition does not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or oxyanion of a multivalent metal.

According to a fifteenth aspect of the present invention, there is provided a method of forming colour on or within a substrate comprising a composition applied to or incorporated within, the composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, wherein the method comprises applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, second temperature, third temperature and fourth temperature as required to develop the coloured states of the components of groups (i) to (iv) present in the composition, and optionally, wherein the composition does not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or oxyanion of a multivalent metal.

According to a sixteenth aspect of the present invention, there is provided a method of forming an image on or within a substrate comprising a composition applied to or incorporated within, the composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur; (iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, wherein the method comprising applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, first temperature, second temperature, third temperature and fourth temperature as required to develop the non-coloured and/or coloured states of the components of groups (i) to (iv) present in the composition, and thereby create an image on or within the substrate, and optionally, wherein the composition does not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or oxyanion of a multivalent metal.

According to a seventeenth aspect of the present invention, there is provided a use of the composition in the formation of colour on or within a substrate, the composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and optionally, wherein the composition does not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or an oxyanion of a multivalent metal.

According to an eighteenth aspect of the present invention, there is provided a use of the composition in the formation of an image on or within a substrate, the composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur; (iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and optionally, wherein the composition does not comprise a combination of only components of groups (iii) and (iv) where the components of group (iv) is an oxyanion of a multivalent metal or a leuco dye.

According to a nineteenth aspect of the present invention, there is provided a substrate having applied thereon a plurality of discrete layers, the plurality of discrete layers comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, wherein the two or more components selected from groups (i) to (iv) are present in different layers of the plurality of discrete layers applied on the substrate, and optionally, wherein the plurality of discrete layers does not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or an oxyanion of a multivalent metal.

According to a twentieth aspect of the present invention, there is provided a method of forming a substrate, the substrate having applied thereon a plurality of discrete layers, the plurality of discrete layers comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, wherein the two or more components selected from groups (i) to (iv) are present in different layers of the plurality of discrete layers applied on the substrate, the method comprising applying to a substrate the plurality of discrete layers, and optionally, wherein the plurality of discrete layers do not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or oxyanion of a multivalent metal.

According to a twenty-first aspect of the present invention, there is provided a method of forming colour on the substrate, the substrate having applied thereon a plurality of discrete layers, the plurality of discrete layers comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, wherein the two or more components selected from groups (i) to (iv) are present in different layers of the plurality of discrete layers applied on the substrate, and wherein the method comprises applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, second temperature, third temperature and fourth temperature as required to develop the coloured states of the components of groups (i) to (iv) present in the plurality of discrete layers, and optionally wherein the plurality of discrete layers do not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is a leuco dye or an oxyanion of a multivalent metal.

According to a twenty-second aspect of the present invention, there is provided a method of forming an image on the substrate, the substrate having applied thereon a plurality of discrete layers, the plurality of discrete layers comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur; (iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and wherein the two or more components selected from groups (i) to (iv) are present in different layers of the plurality of discrete layers applied on the substrate, and wherein the method comprises applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, first temperature, second temperature, third temperature and fourth temperature as required to develop the non-coloured and/or coloured states of the components of groups (i) to (iv) present in the plurality of discrete layers, and thereby create an image on the substrate, and optionally, wherein the plurality of discrete layers do not comprise a combination of only components of groups (iii) and (iv) where the component of group (iv) is an oxyanion of a multivalent metal or a leuco dye.

Detailed Description of the Invention

The intention of the present invention is to provide a laser-reactive composition that is capable of providing an image on or within a substrate using a laser source(s) to manipulate colour changes in the components of the laser-reactive composition at localised positions so as to create images having any desired colour.

The present invention is of particular use in in-line printing, and allows compositions to be prepared with components that can respond to radiation or other stimuli to generate predictable colours for image formation. A broad colour gamut can therefore be achieved using these laser-reactive components. It will be appreciated that a composition according to the first aspect of the present invention disclosed herein enables the production of a broad range of colours in the formation of an image. The different first, second and third applied stimuli and first, second and third temperatures can be applied in different combinations as required at particular localised positions, enabling the formation of a broad range of colours. The invention thus enables the formation of desired single- and multi-coloured images with a broad colour gamut.

"Non-coloured state" and like terms as used herein, refers to the natural state of a component before the first applied stimulus, second applied stimulus or third applied stimulus is applied to it. The non-coloured state of a component may be white, off-white or colourless i.e. clear, or have reduced, or low visible, colour, i.e. is paler in colour (a lighter shade or less intense colour) than a coloured state of the same colour. Alternatively, the natural state (non-coloured state) of a component may possess an initial colour which will change following application of the first applied stimulus, second applied stimulus or third applied stimulus to a more intense colour (coloured state) or a different colour (coloured state). It will therefore be appreciated by a skilled person that, in the natural state, the component may often appear to display a colour, but that when compared with a coloured state of the same component, it will be paler in colour, i.e. less intensely coloured, or a different colour. It will be appreciated that, when the non-coloured state of the component is colourless, any underlying colour of the substrate on which the component is applied to or incorporated within will be visible.

"Coloured state" and like terms as used herein, refers to the state of a component in which the component displays a colour, i.e. is substantially or highly coloured, in the visible spectrum and to a human eye. The "coloured state" will be more intensely coloured that the "non-coloured state" of the same component. This may be a more intense colouration of the same colour, but also may be a more intense colouration of a different colour to that of the non- coloured state as discussed above. In relation to the term "coloured state", the singular encompasses the plural and vice versa. For example, although reference is made herein to "a" coloured state, the term encompasses one or more coloured states. For example, a component of group (ii) or (iii) typically has two coloured states, such as a first and a second coloured state, each of the first and second coloured states being different in colour. By the term "colour" and like terms as used herein, is meant the colours and hues of the visible light colour spectrum, i.e. red, orange, yellow, green, blue and violet, in addition to magenta, pink, purple, cyan, turquoise, brown, and black, and combinations thereof. Both primary and secondary colours are encompassed, i.e. it will be appreciated by a skilled person that a coloured state formed by a component may have a primary or secondary colour. In the context of the present invention, the term may also be used to describe differing shades of each of the colours of the visible light colour spectrum, in addition to magenta, pink, turquoise, brown, purple, cyan and black.

By "two or more" in relation to the components of groups (i) to (iii), is meant that there always have to be at least two components present in the composition, the first of the two components being selected from one of the component groups (i) to (iii), and the second of the two components being selected from a different one of the component groups (i) to (iii). However, in the context of the present invention, if the composition comprises three or more components, as long as at least two of the components are selected from different component groups (i) to (iii), the third component may be a component of any of the component groups (i) to (iii), such that there may be two components in the same component groups (i) to (iii) (however these components themselves will not be the same). It will be appreciated by a skilled person that no matter how many components from groups (i) to (iii) are present in the composition, if formed, each of the coloured states of the components will have a different colour, even if two components from the same group are present in the composition. It will also be appreciated by a skilled person that if two components in the composition are from the same component group (i), (ii) or (iii), the appropriate temperature and applied stimuli associated with each of those components will vary dependent upon the individual components. "Stable coloured state" and like terms as used herein, refers to the coloured state of a component that is stable under ambient conditions, i.e. maintains essentially its colour under ambient conditions. "Ambient conditions" and like terms as used herein, refers to the normal range of conditions of the surrounding environment to which the components are exposed, i.e. the range of temperatures, pressures and atmospheric conditions to which the components are exposed during use, storage and otherwise. This includes solar radiation including electromagnetic radiation of X-rays, ultraviolet (UV) and infrared (IR) radiation. Typically, ambient conditions include a temperature of from 10 to 35 °C, a pressure of from 20 to 100 kPa, and the environment is typically an oxygen-containing atmosphere. It will be appreciated by a skilled person that the required stability of the coloured state of a component will be dependent upon the application for which a substrate having the composition and therefore the component applied to or incorporated within is intended to be used. For example, if the composition comprising the component is to be utilised in a laser reactive patch for a disposable item such as a hot or cold beverage container, the required stability of the component of the composition will only need to be for a relatively short period of time, for example, a number of hours such as 6 to 12 hours, or a number of days such as 3 or 4 days. Whereas, if the composition comprising the component is to be utilised in a laser-reactive composition applied on or incorporated within a cosmetic container or outdoor signage, the required stability of the component will be greater, for example, a number of months, or even a number of years for outdoor signage uses. In general however, stable under ambient conditions is meant that when exposed to ambient conditions for at least a number of hours or a number of days, such as for at least two weeks, the coloured state maintains essentially its colour. Preferably, the component will permanently remain in the particular coloured state. Accordingly, it is preferred that a component remains in the coloured state for at least 3 days, preferably for at least 4 days, more preferably for at least 1 or even at least 2 weeks, and most preferably, for at least 2 months.

"Monochromic" or "single-coloured image" and like terms used herein, refer to an image that is human or machine readable and has a single colour that is visible to the human eye. In the context of the present invention, the non- coloured state can form part of the monochromic image. In particular, when the non-coloured state of a component is non-colour, i.e. white, off-white, or colourless, the non-coloured state can form part of the monochromic image.

"Multi-coloured image" and like terms as used herein, refers to an image that is human or machine readable having multiple colours, i.e. displaying 2 or more colours that are visible to the human eye. In the context of the present invention, the non-coloured state can form part of the multi-coloured image. In particular, when the non-coloured state of a component is non-colour, i.e. white, off-white or colourless, the non-coloured state can form part of the multi-coloured image.

The term "image" incorporates both single- and multi-coloured images. The term incorporates, but is not limited to: graphics, pictures, logos, symbols, figures and text. It will be appreciated that it is the manipulation of the components of the composition that facilitates the formation of an image.

"Reversibly transitioning" and "reversible transition" and like terms as used herein in relation to components of group (i), refer to the component having the ability to transition from the non-coloured state to a coloured state upon application of the first applied stimulus, and transition back to the non-coloured state from the coloured state upon application of the first temperature. It will be understood by a skilled person that this is an intentional transition facilitated by the application of the first applied stimulus (non-coloured to coloured state) or first temperature (coloured to non-coloured state) to the component. It will further be appreciated by a skilled person that once the coloured state of the component has been achieved, it will be stable under ambient conditions.

"Transitioning" and "transition" and like terms as used herein in relation to the components of groups (ii) and (iii), refer to the components changing from a non- coloured state to a coloured state upon respective application of the second or third applied stimuli. It will be appreciated by a skilled person that this is an intentional transition facilitated by the application of the second or third applied stimuli as required to the component of group (ii) or (iii) respectively. The term also encompasses a component of group (ii) changing from a first coloured state to a second coloured state upon application of the second temperature, or a component of group (iii) changing from a first coloured state to a second coloured state upon application of an additional temperature as discussed below. Once the coloured state of the components of groups (ii) and (iii) has been formed, it will be stable under ambient conditions.

"Subsequent" or "subsequent transitioning", and like terms as used herein in relation to the component of group (ii), refer to any transition following (taking place after) the deactivation of the component of group (ii). This is an intentional transition, i.e. intentional exposure to radiation or temperature, including UV radiation provided by a germicidal lamp or broadband UV radiation provided by a medium-pressure mercury lamp.

"Printing", "in-line digital printing" or "laser printing" and like terms as used herein, refer to the process of using radiation to achieve colour and form an image on a substrate.

"Radiation" and like terms as used herein, refers to energy in the form of waves or particles, and in particular, refers to electromagnetic radiation such as ultraviolet (UV), visible, near-infrared (NIR), and infrared (IR) particle radiation, e.g. alpha (a) radiation, beta (b) radiation, neutron radiation and plasma. It will be appreciated that, in the context of the present invention, a distinction is made between radiation of greater than 400 nm, e.g. near-infrared radiation, which causes vibrational, conductive and radiative excitation to the components upon application and therefore provides a‘temperature’, and radiation of 400 nm or less (e.g. ultraviolet radiation), or microwave radiation, which does not. In the context of the present invention, the "temperature" applied to the compositions and compounds is intended to include the temperature provided to the compositions and compounds through the application of thermal energy in different conductive, radiative and vibrational forms. As discussed, this may be through application of radiation of greater than 400 nm.

By the term "laser source(s)" and like terms as used herein includes any suitable commercial laser source(s). "Deactivatable", "deactivated" or "deactivating" and like terms as used herein in relation to the components of group (ii), refer to the inability of the component of group (ii) to undergo any subsequent transition upon exposure to intentionally applied radiation or temperature. This intentionally applied radiation or temperature may be provided by a germicidal lamp, medium-pressure mercury lamp or ultravitalux bulb. It will be appreciated that during deactivation of the component of group (ii), the component of group (ii) may transition to another coloured state at the same time. This coloured state will be stable under ambient conditions. For example, the component of group (ii) may transition from a first coloured state to a second coloured state upon application of the second temperature. The component of group (ii) will be considered "deactivated" if it remain essentially unchanged for at least 1 minute, such as for at least 1 hour. Preferably, the component of group (ii) remains in essentially unchanged for at least 1 day, such as for even 1 week. Most preferably, the component of group (ii) remains permanently essentially unchanged.

Without being bound by theory, the present inventors consider that it is the monomer form of the component of group (ii) that is being deactivated, i.e. in the non-coloured state, the component of group (ii) is present in monomer form and these monomers are‘deactivated’ upon application of the second temperature, and in a coloured state, it is the residual monomers that have not been polymerised and are still in their non-coloured state (and therefore still have colour-forming ability) that are‘deactivated’.

"Activated" and like terms as used herein in relation to the components of group (iii), refer to the non-coloured state of the component when it is capable of undergoing a transition to the coloured state. It will be appreciated by a skilled person that the non-coloured state can exist in (a) an unactivated form, i.e. incapable of undergoing a transition from the non-coloured state to a coloured state when the third applied stimulus is applied to the composition and thus, the activatable component; or (b) an activated form, i.e. capable of undergoing a transition from the non-coloured state to a coloured state when the third applied stimulus is applied to the composition and thus, the activatable component. "Activation" and like terms as used herein in relation to the activatable component, refer to the process by which the non-coloured state of the component is activated, i.e. changes from an unactivated to activated form. This is facilitated by the application of an activation temperature.

All references to particular chemical compounds herein are to be interpreted as covering the compounds per se, and also, where appropriate, derivatives, hydrates, solvates, complexes, isomers, tautomers thereof.

The transition of the component of group (i) from the non-coloured state to a coloured state is reversible when the first applied stimulus is applied to the component to facilitate a transition from the non-coloured to a coloured state of the component. Once the coloured state of the component has been formed, a transition from the coloured state back to the non-coloured state can be intentionally facilitated through the application of a first temperature to the coloured state of the component.

It will be appreciated that the structure of the component facilitates the formation of colour (formation of a coloured state) through tautomerisation from the enol to the keto form. The component of group (i) may be selected from any suitable component that is capable of reversibly transitioning between a non-coloured state and a coloured state. Suitable examples of components include, but are not limited to components having the formula (I):

wherein each of A, B, C and D are independently selected from: C1-18 alkyl; -CCI ₃ ; -CF ₃ ; C ₆ -12 aryl optionally substituted with Ci-i ₈ alkoxy, -CN, - CF ₃ , halogen, -N0 ₂ , or Ci-i ₈ alkyl; a heterocyclic ring; and a heteroaryl.

Preferably, A is selected from C ₆ -12 aryl optionally substituted with Ci-i ₈ alkoxy, - CN, -CF ₃ , halogen, -N0 ₂ , or Ci-i ₈ alkyl, more preferably from C ₆ -s aryl, and most preferably phenyl.

Preferably, B is selected from Ci-i ₈ alkyl and C ₆ -12 aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, -N0 ₂ , or Ci-i ₈ alkyl, more preferably from Ci _-4 alkyl and C ₆ -s aryl, and most preferably from methyl and phenyl.

Preferably, C is selected from C ₆ -12 aryl optionally substituted with Ci-i ₈ alkoxy, - CN, -CF ₃ , halogen, -N0 ₂ , or Ci-i ₈ alkyl; -CCI ₃ ; and Ci-i ₈ alkyl; more preferably from C _6-8 aryl optionally substituted with Ci _-4 alkoxy, -CN, -CF ₃ or -N0 ₂ ; -CCI ₃ ; and Ci _-4 alkyl, and most preferably, from phenyl, 4-methoxy phenyl, 4- cyanophenyl, 4-(trifluoromethyl)phenyl, 4-nitrophenyl; -CCI ₃ ; and C(CH ₃ ) ₃ .

Preferably, D is selected from C ₆ -12 aryl optionally substituted with Ci-i ₈ alkoxy, - CN, -CF ₃ , halogen, -N0 ₂ , or Ci-i ₈ alkyl, more preferably from C ₆ -s aryl, and most preferably phenyl.

The component of group (i) may be a component having the formula (II):

wherein B is selected from Ci-i ₈ alkyl and C ₆ -12 aryl optionally substituted with Ci_ 18 alkoxy, -CN, -CF ₃ , halogen, -N0 ₂ , or Ci-i ₈ alkyl, preferably from Ci _-4 alkyl and C _6-8 aryl, and more preferably from methyl and phenyl, and C is selected from C _6- 12 aryl optionally substituted with C _{M S} alkoxy, -CN, -CF ₃ , halogen, -N0 ₂ , or C _{M S} alkyl; -CCI ₃ ; and C _{M S} alkyl; preferably from C ₆ -s aryl optionally substituted with Ci _-4 alkoxy, -CN, -CF ₃ or -N0 ₂ ; -CCI ₃ ; and Ci _-4 alkyl, and more preferably, from phenyl, 4-methoxy phenyl, 4-cyanophenyl, 4- (trifluoromethyl)phenyl, 4-nitrophenyl; -CCI ₃ ; and C(CH ₃ ) ₃ .

Preferably, the component of group (i) is selected from (£)-2-((5-hydroxy-1 ,3- diphenyl-1 /-/-pyrazol-4-yl)(phenyl)methylene)-A/-phenylhydrazine-1 -carboxamide (B and C are phenyl), (£)-2-((5-hydroxy-3-methyl-1 -phenyl-1 /-/-pyrazol-4- yl)(phenyl)methylene)-A/-phenylhydrazine-1 -carboxamide (B is methyl and C is phenyl), (£)-2-((5-hydroxy-1 ,3-diphenyl-1 /-/-pyrazol-4-yl)(4- nitrophenyl)methylene)-A/-phenylhydrazine-1 -carboxamide (B is phenyl and C is 4-nitrophenyl), (£)-2-((5-hydroxy-1 ,3-diphenyl-1 /-/-pyrazol-4-yl)(4-

(trifluoromethyl)phenyl)methylene)-A/-phenylhydrazine-1 -carboxamide (B is phenyl and C is 4-(trifluoromethyl)phenyl), (£)-2-((5-hydroxy-1 ,3-diphenyl-1 /-/- pyrazol-4-yl)(4-methoxyphenyl)methylene)-A/-phenylhydrazine- 1 -carboxamide (B is phenyl and C is 4-methoxyphenyl), (£)-2-((5-hydroxy-3-methyl-1 -phenyl-1 H- pyrazol-4-yl)(4-(trifluoromethyl)phenyl)methylene)-A/-phenyl hydrazine-1 - carboxamide (B is methyl and C is 4-(trifluoromethyl)phenyl), and (E)-2-((4- cyanophenyl)(3-hydroxy-2,5-diphenyl-2,3-dihydro-1 H-pyrazol-4-yl)methylene)-N- phenylhydrazine-1 -carboxamide (B is phenyl, and C is 4-cyanophenyl). More preferably, the component of group (i) is selected from (£)-2-((5-hydroxy-1 ,3- diphenyl-1 /-/-pyrazol-4-yl)(phenyl)methylene)-A/-phenylhydrazine-1 -carboxamide (B and C are phenyl), and (£)-2-((5-hydroxy-1 ,3-diphenyl-1 /-/-pyrazol-4-yl)(4- (trifluoromethyl)phenyl)methylene)-A/-phenylhydrazine-1 -carboxamide (B is phenyl and C is 4-(trifluoromethyl)phenyl).

All references to the components of formulas (I) and (II) are to be interpreted as covering the components of the formulas (I) and (II) per se, and also, all tautomers or isomers thereof.

It will be understood by a skilled person that the coloured state of the component of group (i) is stable under ambient conditions. The component of group (i) may be present in the composition in any suitable amount. It will be appreciated that the amount of the component of group (i) present in the composition will depend upon the other components present in the composition, the application method utilised for applying or incorporating the composition to or into the substrate, the substrate type and the desired end use of the substrate.

Preferably, the composition comprises from 0 to 50 %, such as from 0.1 to 40 %, or even from 3 to 30 % of a component of group (i) based on the total solid weight of the composition. Most preferably, the composition comprises from 5 to 25 % of a component of group (i) based on the total solid weight of the composition.

The first applied stimulus may be radiation. It will be appreciated that the radiation selected will be the radiation required to facilitate a transition of the component of group (i) from the non-coloured to a coloured state. The radiation selected will therefore be dependent upon the component of group (i) present in the composition according to the first aspect of the present invention. The radiation is selected from gamma radiation with a wavelength of less than 0.01 nm, X-ray radiation with a wavelength of from 0.01 to 10 nm, ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, and microwave radiation with a wavelength of from 1 mm to 1 m. Preferably, the first applied stimulus is selected from ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm. More preferably, the first applied stimulus is selected from ultraviolet (UV) radiation with a wavelength of from 100 to 400 nm.

The first applied stimulus may be applied to the component of group (i) of the composition according to the first aspect of the present invention by any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the component by a laser source(s). It will be understood by a skilled person that the first applied stimulus may be applied to the composition at localised positions to selectively develop the coloured state of the component at these localised positions. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the first applied stimulus may be applied to the composition on or within the substrate by flood illumination, meaning that the composition as a whole is flooded with radiation. This can be done using any suitable lamp or bulb, such as a UV lamp, or medium pressure mercury or amalgam lamp or microwave powered UV lamp, a Xe, Hg or XeHg arc (broadband UV sources); a germicidal lamp, a diode bar; or LED(s). When a broadband UV source is utilised, it will be appreciated that a range of wavelengths over the 10 to 400 nm range will be emitted. It will also be understood by a skilled person that the radiation is applied to the composition for an appropriate amount of time required to facilitate the transition of the component from the non-coloured state to the coloured state. Typically the time required to deliver sufficient radiation will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, or by flood illumination. For example, in one embodiment, the first applied stimulus may be applied to the component for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds), or for less than 60 seconds, such as for less than 20 seconds, or even for less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the radiation dosage applied for the first applied stimulus can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage) and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ²

The coloured state of the component of group (i) may have any colour. It will be appreciated by a skilled person that the means used to apply the first applied stimulus will affect the colour of the coloured state formed. For example, where a laser source(s) is used to apply the first applied stimulus by radiation, the fluence (amount of energy delivered per unit area) may affect the colour, intensity or lightness of the coloured state formed. In the context of the present invention, the fluence is dependent upon the power of the means used to apply the radiation of the first applied stimulus (wattage), and the time for which the radiation of the first applied stimulus is applied to a particular localised position on the substrate, which can be controlled by the scanning speed of the laser or the speed of the moving stage. These two variables can be altered to change the fluence. Where the fluence is low (e.g. lower power and/or shorter irradiation times), the coloured state of the component of group (i) will be of a less intense colour, and where the fluence is high (e.g. higher power and/or longer irradiation times), the coloured state of the component of group (i) will be of a more intense colour. Changing the fluence may also result in a coloured state of the component of group (i) changing colour. For example, low fluence may form a coloured state of the component of group (i) having a yellow colour, and higher fluence may form the same coloured state of the component of group (i) having an orange or red colour. In the context of the present invention, fluence values may range from 0.01 to 20 J/cm ² , such as from 0.1 to 10 J/cm ² and even from 0.5 to 5 J/cm ² .

Preferably, the coloured state of the component of group (i) has a coloured state having a colour selected from yellow, orange and red.

The first temperature may be any suitable temperature. It will be appreciated by a skilled person that the first temperature will be the temperature required to facilitate a transition of the component of group (i) from the coloured state to the non-coloured state. The temperature selected will therefore be dependent upon the component of group (i) present in the composition according to the first aspect of the present invention. The first temperature may be a temperature of from 60 to 180 °C. Preferably, the first temperature is from 70 to 140 °C.

The first temperature may be applied to the component of group (i) of the composition according to the first aspect of the present invention by any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the component by a laser source(s). It will be understood by a skilled person that the first temperature may be applied to the composition at localised positions to selectively develop the non-coloured state of the component at these localised positions in the composition. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the first temperature may be applied to the component by flood illumination, meaning that the composition as a whole is flooded with radiation. This may be done using a lamp or bulb, such as an IR lamp; diode bar; or LED(s). It will further be appreciated that the first temperature may be applied to the component using a conductive temperature source. Conductive temperature sources include sources of steam and hot air, lamps, heat tunnels, LED(s), thermal print heads, thermal conductors, hot liquids, hotplates and heated substrates. It will be understood by a skilled person that the first temperature is applied to the composition for an appropriate amount of time required to facilitate the transition of the component from the coloured state to the non-coloured state. Typically the time required to deliver sufficient temperature will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, by flood illumination or using a conductive temperature source. For example, in one embodiment, the first temperature may be applied to the component of group (i) for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds), or for less than 60 seconds, such as for less than 20 seconds, or even less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the first temperature can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage), and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ²

In addition, it will be appreciated that where the first temperature is applied using radiation, i.e. at localised positions using a laser source(s) or by flood illumination, the composition and thus the component of group (i) may be exposed to a temperature in excess of the stated temperature ranges for a very short period of time, i.e. microseconds. It will be understood that this will not have any significant effect on the result to be achieved.

It will be appreciated by a skilled person that the first temperature may be applied to the component of group (i) using a combination of the suitable means listed above, i.e. using combinations of laser excitation at localised positions, flood illumination, and a conductive temperature source. For example, in one embodiment, the first temperature may be applied to the component using laser excitation at localised positions, in addition to using a conductive thermal energy source.

The first temperature may be applied to the component of group (i) using radiation selected from visible radiation with a wavelength of from 400 to 700 nm, and infrared (IR) radiation with a wavelength of from 700 nm to 1 mm, including near-infrared (NIR) radiation with a wavelength of from 700 to 1600 nm. Preferably, the first temperature is applied using infrared radiation with a wavelength of 10600 nm (using a C0 ₂ laser), or near-infrared (NIR) radiation with a wavelength of from 700 to 1600 nm.

The transition from the coloured state to the non-coloured state of the component of group (i) affected by the application of the first temperature is known in the art as "thermal bleaching".

The component of group (ii) may be selected from any suitable component. The component of group (ii) may be a diacetylene compound, i.e. a compound comprising a diacetylene moiety ( ' c=c-

The component of group (ii) may be a diacetylene compound comprising a protecting group.

The component of group (ii) may be a diacetylene compound having the following formula (III): wherein x is from 2 to 12, preferably 2 to 10, and more preferably 2 to 8; o

\ N-]

L is selected from an amide having the formula: H , and an ester having the formula: , ¾A· ₀ ^_ _t preferably L is an amide having the formula y H j , y is from 0 to 10, preferably 0 to 8, and more preferably 0 to 6;

E may be absent or present, and when present, E is selected from NH, O, and CH ₂ ; preferably E is NH;

P is a protecting group; and

T is selected from hydrogen, a -(CH ₂ ) _X (CH ₃ ) linear alkyl chain wherein x is defined as above for formula (III), and -(CH ₂ ) _x -L-(CH ₂ ) _y -E-P, wherein x, y, L , E and P are defined as above for formula (III).

It will be appreciated by a skilled person that the diacetylene compound can be either symmetrical or unsymmetrical, i.e. T is -(CH ₂ ) _x -L-(CH ₂ ) _y -E-P and the values of x, y, L, E and P are the same as those on the other side of the diacetylene moiety (symmetrical), or T is hydrogen, a -(CH ₂ ) _X (CH ₃ ) linear alkyl chain, or -(CH ₂ ) _x -L-(CH ₂ ) _y -E-P and the values of x, y, L, E and P are different to those on the other side of the diacetylene moiety.

Preferably, the diacetylene compound is symmetrical.

By the term "protecting group" is meant, any cleavable organic chemical moiety that can be cleaved/removed from the diacetylene compound when exposed to certain conditions, including but not limited to: acid, base, heat, hydrogenation, and reduction. Without being bound by theory, it is understood by the present inventors that, in the context of the present invention, the protecting group is cleaved from the deactivatable compound upon exposure to the deactivation temperature. To achieve deactivation, it is not necessary that all of the protecting groups are cleaved (of the monomers and polymer of the diacetylene compound as defined below). The protecting group according to the present invention is therefore cleavable upon exposure to the deactivation temperature, i.e. upon exposure to temperature applied by radiation of a wavelength of greater than 400 nm.

Examples of suitable protecting include, but are not limited to: alkyl and aryl oxycarbonyl groups selected from tert- butyloxycarbonyl (BOC), 2,4- dimethylpent-3-yloxycarbonyl (DOC), dioctyl(((docosa-10,12- diynedioyl)bis(azanediyl))bis(ethane-2, 1 -diyl))dicarbamate (SOC), 9- fluorenylmethyl oxycarbonyl and benzyl oxycarbonyl; benzoyl; carboxy benzyl; and allyloxycarbonyl; cycloalkyls such as cyclododecane and cyclooctane; amide groups such as acetamide and trifluoroacetamide; phthalimide; triphenylmethyl; benzylidene; and p-toluenesulfonyl.

Preferably, P is an alkyl or aryl oxycarbonyl group or a cycloalkyl, more preferably P is selected from tert- butyloxycarbonyl (BOC), benzoyl, carboxybenzyl, cyclododecane, cyclooctane, 9-fluorenylmethyl oxycarbonyl , 2,4-dimethylpent-3-yloxycarbonyl (DOC), and dioctyl(((docosa-10,12- diynedioyl)bis(azanediyl))bis(ethane-2, 1 -diyl))dicarbamate (SOC). More preferably, P is an alkyl or aryl oxycarbonyl group, and most preferably P is selected from tert- butyloxycarbonyl (BOC), 9-fluorenylmethyl oxycarbonyl , benzoyl, carboxybenzyl, 2,4-dimethylpent-3-yloxycarbonyl (DOC), and dioctyl(((docosa-10, 12-diynedioyl)bis(azanediyl))bis(ethane-2, 1 - diyl))dicarbamate (SOC).

The component of group (ii) may be a diacetylene compound having the following formula (IV):

wherein x is from 2 to 8, y is from 0 to 6, and P is selected from tert- butyloxycarbonyl (BOC), benzoyl, carboxybenzyl, cyclodecane, 9- fluorenylmethyl oxycarbonyl , cyclooctane, 2,4-dimethylpent-3-yloxycarbonyl (DOC) and dioctyl(((docosa-10, 12-diynedioyl)bis(azanediyl))bis(ethane-2, 1 - diyl))dicarbamate (SOC). Preferably, the component of group (ii) is selected from di-tert-butyl 2,2'- (tetradeca-6,8-diynedioyl)bis(hydrazine-1 -carboxylate), di-tert-butyl(((docosa- 10, 12-diynedioyl)bis(azanediyl))bis(ethane-2, 1 -diyl))dicarbamate, di-tert-butyl 2,2'-(docosa-10, 12-diynedioyl)bis(hydrazine-1 -carboxylate), dibenzyl 2,2'-

(docosa-10,12-diynedioyl)bis(hydrazine-1 -carboxylate), N'1 ,N'22- dibenzoyldocosa-10, 12-diynedihydrazide, tert-butyl 2-(pentacosa-10, 12- diynoyl)hydrazine-1 -carboxylate, N 1 , N22-dicyclodecyldocosa-10, 12- diynediamide, and di-tert-butyl(((docosa-10,12- diynedioyl)bis(azanediyl))bis(hexane-6, 1 -diyl))dicarbamate.

Diacetylene compounds are well known to a skilled person as compounds capable of forming colour. Typical diacetylene compounds are disclosed for this purpose in WO 2012/114121 , the content of which is incorporated herein by reference. Suitable examples of diacetylene compounds and the synthesis of such are taught in W02009/093028, WO2010/001171 , WO2010/029329, and WO2013/068729, the content of each of which is incorporated herein by reference. Known methods of synthesis of diacetylene compounds include the formation of a reactive acid chloride and subsequent addition of an amine or alcohol, or the formation of a mixed anhydride and subsequent reactions with an amine or alcohol. For the diacetylene compounds disclosed herein for the component of group (ii), such syntheses include the installation of a protecting group P. Typically, the diacetylene compounds of the component of group (ii) have first and second coloured states. It will be appreciated by a skilled person that when the diacetylene compounds of component (ii) are in the non-coloured state, they are considered to be monomers. The first coloured state of the diacetylene compounds are formed on account of polymerisation of these monomers upon exposure to the second applied stimulus. Polymerisation of at least a portion of the monomers enables the formation of the first coloured states of the diacetylene compounds. In addition, without being bound by theory, the inventors consider that the different first and second coloured states are achieved through changes in conjugation of the diacetylene polymer, i.e. a structural change. As discussed above, the second coloured state of the diacetylene compounds disclosed herein for the component of group (ii) may be reached by applying the second temperature to the first coloured state of the diacetylene compound. It will be understood by a skilled person that a coloured state of the component of group (ii) is stable under ambient conditions.

The component of group (ii) may be present in the composition in any suitable amount. It will be appreciated that the amount of the component of group (ii) present in the composition will depend upon the other components present in the composition, the application method utilised for applying or incorporating the composition to or into the substrate, the substrate type and the desired end use of the substrate.

Preferably, the composition comprises from 0 to 50 %, such as from 0.1 to 40 %, or even from 3 to 30 % of the component of group (ii) based on the total solid weight of the composition. Most preferably, the composition comprises from 5 to 25 % of the component of group (ii) based on the total solid weight of the composition.

The second applied stimulus may be radiation. It will be appreciated that the radiation selected will be the radiation required to facilitate a transition of the component of group (ii) from the non-coloured to a coloured state. The radiation is selected from gamma radiation with a wavelength of less than 0.01 nm, X-ray radiation with a wavelength of from 0.01 to 10 nm, ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, and microwave radiation with a wavelength of from 1 mm to 1 m. Preferably, the second applied stimulus is ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm. More preferably, the second applied stimulus is ultraviolet (UV) radiation with a wavelength of from 100 to 400 nm.

The second applied stimulus may be applied to the component of group (ii) of the composition according to the first aspect of the present invention using any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the component by a laser source(s). It will be understood by a skilled person that the second applied stimulus may be applied to the composition at localised positions to selectively develop the coloured state of the component at these localised positions. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the second applied stimulus may be applied to the composition on or within a substrate by flood illumination, meaning that the composition as a whole is flooded with radiation This can be done using any suitable lamp or bulb, such as a UV lamp, or medium pressure mercury or amalgam lamp or microwave powered UV lamp, a Xe, Hg or XeHg arc (broadband UV sources); a germicidal lamp, a diode bar; or LED(s). Where a broadband UV source is utilised, it will be appreciated that a range of wavelengths over the 10 to 400 nm range will be emitted. It will be understood by a skilled person that the radiation is applied to the composition for an appropriate amount of time required to facilitate the transition of the component from the non-coloured state to the coloured state. Typically the time required to deliver sufficient radiation will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, or by flood illumination. For example, in one embodiment, the second applied stimulus may be applied to the component of group (ii) for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds), or for less than 60 seconds, such as for less than 20 seconds, or even for less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the radiation dosage applied for the second applied stimulus can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage) and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ²

The second temperature may be any suitable temperature. It will be appreciated that the second temperature will be the temperature required to deactivate the non-coloured or coloured state of the component of group (ii). As discussed above, for the deactivation of a coloured state, this may be accompanied by a transition to another coloured state, i.e. the first coloured state to a second deactivated coloured state. The second temperature may be a temperature of from 50 to 160°C. Preferably, the second temperature is from 55 to 140 °C. The second temperature may be applied to the component of group (ii) either prior to the transition to the coloured state effected by the application of the second applied stimulus, i.e. when the component is in the non-coloured state, or after the transition to the coloured state effected by the application of the second applied stimulus, i.e. when the component (ii) is in the coloured state.

After the application of the second temperature, the component of group (ii) is ‘deactivated’ and will not undergo any subsequent transitions.

As discussed above, when the second temperature is applied to a first coloured state of a component of group (ii), the component may transition from the first coloured state to the second coloured state.

The second temperature may be applied to the component of group (ii) of the composition according to the first aspect of the present invention by any suitable means. Suitable means include laser excitation through application of radiation to the component by a laser source(s). It will be understood by a skilled person that when the second temperature may be applied to the composition at localised positions to selectively deactivate the non-coloured or the coloured state of the component at these localised positions in the composition. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the second temperature may be applied to the component by flood illumination, meaning that the composition as a whole is flooded with radiation. This may be done using a lamp or bulb, such as an IR lamp; diode bar; or LED(s). It will further be appreciated that the second temperature may be applied to the component using a conductive temperature source. Conductive temperature sources include sources of steam and hot air, lamps, heat tunnels, LED(s), thermal print heads, hotplates, thermal conductors, hot liquids and heated substrates. It will be understood by a skilled person that the second temperature is applied to the composition for an appropriate amount of time required to cause the deactivation of the non-coloured or coloured state of the component. Typically the time required to deliver sufficient temperature will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, by flood illumination, or using a conductive temperature source. For example, in one embodiment, the second temperature may be applied to the component of group (ii) for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds), or for less than 60 seconds, such as for less than 20 seconds, or even for less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the radiation dosage applied to achieve the second temperature can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage) and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ²

It will be appreciated by a skilled person that the second temperature may be applied to the component of group (ii) using a combination of the suitable means listed above, i.e. using combinations of laser excitation at localised positions, flood illumination, and a conductive temperature source. For example, in one embodiment, the second temperature may be applied to the component using laser excitation at localised positions, in addition to using a conductive thermal energy source.

In addition, it will be appreciated that where the second temperature is applied using radiation, i.e. at localised positions using a laser source(s) or by flood illumination, the composition and thus the component of group (ii) may be exposed to a temperature in excess of the stated temperature ranges for a very short period of time, i.e. microseconds. It will be understood that this will not have any significant effect on the result to be achieved.

The second temperature may be applied to the component of group (ii) using electromagnetic radiation selected from visible radiation with a wavelength of from 400 to 700 nm, infrared (IR) with a wavelength of from 700 nm to 1 mm, including near-infrared (NIR) with a wavelength of from 700 to 1600 nm. Preferably, the second temperature is applied using visible radiation with a wavelength of from 400 to 700 nm, infrared (IR) radiation with a wavelength of 10600 nm (from a C0 ₂ laser), and near-infrared (NIR) radiation with a wavelength of from 700 to 1600 nm. A coloured state of the component of group (ii) may have any colour. It will be appreciated by a skilled person that the means used to apply the second applied stimulus or second temperature will affect the colour of the coloured state formed. For example, where a laser source(s) is used to apply the second applied stimulus or second temperature, the fluence (amount of energy delivered per unit area) may affect the colour, intensity or lightness of the coloured state formed. In the context of the present invention, the fluence is dependent upon the power of the means used to apply the second applied stimulus or second temperature (wattage), and the time for which the second applied stimulus or second temperature is applied to a particular localised position on the substrate, which can be controlled by the scanning speed of the laser, or the speed of the moving stage. These two variables can be altered to change the fluence. Where the fluence is low (e.g. lower power and/or shorter irradiation times), a coloured state of the component of group (ii) will be of a less intense colour, and where the fluence is high (e.g. higher power and/or longer irradiation times), a coloured state of the component of group (ii) will be of a more intense colour. In the context of the present invention, fluence values may range from 0.01 to 20 J/cm ² , such as from 0.1 to 10 J/cm ² and even from 0.5 to 5 J/cm ²

Preferably, the coloured state of the component of group (ii) has a colour selected from red, yellow or blue.

The component of group (iii) may be selected from any suitable component. The component of group (iii) may be a diacetylene compound, i.e. a compound comprising a diacetylene moiety ( ' c=c-

The component of group (iii) may be a diacetylene compound having the following formula (V):

T- (CH ₂ ) _X - L - Q (V) wherein x is from 2 to 12, preferably 2 to 10, and more preferably 2 to 8; O

\ N-]

L is selected from an amide having the formula: H , and an ester having the formula: , ¾A· ₀ ^_ _t preferably L is an amide having the formula y H j ,

Q is selected from cyclopropyl and a -(CH ₂ ) _y -CH ₃ linear alkyl chain, y being selected from 1 to 20, preferably 5 to 19, and more preferably 5 to 17; and T is selected from hydrogen, a -(CH ₂ ) _X (CH ₃ ) linear alkyl chain wherein x is defined as above for formula (V), and -(CH ₂ ) _X -L-Q, wherein x, L and Q are as defined above for formula (V).

It will be appreciated by a skilled person that the diacetylene compound can be either symmetrical or unsymmetrical, i.e. T is -(CH ₂ ) _X -L-Q and the values of x, L and Q are the same as those on the other side of the diacetylene moiety (symmetrical), or T is hydrogen, a -(CH ₂ ) _X (CH ₃ ) linear alkyl chain, or -(CH ₂ ) _X -L-Q and the values of x, L and Q are not the same on both sides of the diacetylene moiety (unsymmetrical). Preferably, T is -(CH ₂ ) _X -L-Q and the values of x, L and Q are the same on both side of the diacetylene moiety, such that the diacetylene compound is symmetrical.

The component of group (iii) may be a diacetylene compound of formula (VI):

wherein x is from 4 to 8, and Q is selected from cyclopropyl and a -(CH ₂ ) _y (CH ₃ ) linear alkyl chain wherein y is 5 to 17. Examples of suitable diacetylene compounds include, but are not limited to the following: N1 ,N22-dioctadecyldocosa-10,12-diynediamide, N1 ,N22- dihexadecyldocosa-10-12-diynediamide, N 1 , N22-ditetradecyldocoda-10,12- diynediamide, N1 ,N22-didodecyldocosa-10,12-diynediamide, N1 ,N22- didecyldocosa-10, 12-diynediamide, N 1 , N22-dioctyldocosa-10, 12-diynediamide, N 1 , N22-dihexyldocosa-10, 12-diynediamide, N 1 , N22-dicyclopropyldocosa-

10.12-diynediamide.

Preferably, the diacetylene compound is a diacetylene compound selected from N 1 , N22-dioctadecyldocosa-10, 12-diynediamide, N 1 , N22-dihexadecyldocosa-

10.12-diynediamide, N 1 , N22-ditetradecyldocosa-10, 12-diynediamide, N 1 , N22- didodecyldocosa-10, 12-diynediamide, and N 1 , N22-dicyclopropyldocosa-10, 12- diynediamide.

Diacetylene compounds as components of group (iii) are well known to a skilled person as compounds capable of forming colour. Typical diacetylene compounds are disclosed for this purpose in WO 2012/114121 , the content of which is incorporated herein by reference. Suitable examples are taught in W02009/093028, WO2010/001171 , WO2010/029329, and WO2013/068729, the content of each of which is incorporated herein by reference. Known methods of synthesis of diacetylene compounds include the formation of a reactive acid chloride and subsequent addition of an amine or alcohol, or the formation of a mixed anhydride and subsequent reactions with an amine or alcohol. It will be appreciated by a skilled person that when the diacetylene compounds of components of group (iii) are in the non-coloured state, they are considered to be monomers. Typically, the diacetylene compounds of component (iii) have two coloured states, such as a first and second coloured state. These first coloured states of the diacetylene compounds are formed on account of polymerisation of these monomers upon exposure to the third applied stimulus. Polymerisation of at least a portion of the monomers enables the formation of the coloured state of the diacetylene compounds. In addition, without being bound by theory, the inventors consider that the different first and second coloured states are achieved through changes in conjugation of the diacetylene polymer, i.e. a structural change. For the diacetylene compounds of components of group (iii), it will be understood that the diacetylene compounds will typically have a first and a second coloured state, and the second coloured state can be subsequently accessed from the first coloured state by the application of an additional temperature. The additional temperature may be 50 to 200 °C, such as from 50 to 180 °C, and be applied by the same means as defined below for the third temperature.

It will be understood by a skilled person that a coloured state of the component of group (iii) is stable under ambient conditions.

The component of group (iii) may be present in the composition in any suitable amount. It will be appreciated that the amount of the component of group (iii) present in the composition will depend upon the other components present in the composition, the application method utilised for applying or incorporating the composition to or into the substrate, the substrate type and the desired end use of the substrate.

Preferably, the composition comprises from 0 to 50 %, such as from 0.1 to 40 %, or even from 3 to 30 % of the component of group (iii) based on the total solid weight of the composition. Preferably, the composition comprises from 5 to 25 % of the component of group (iii) based on the total solid weight of the composition.

The third applied stimulus facilitates the transition of the component of group (iii) from the non-coloured to a coloured state. In the context of the present invention, application of the third applied stimulus facilitates a transition of the component of group (iii) from the non-coloured to a first coloured state. The second coloured state may be subsequently accessed by application of an additional temperature to the first coloured state.

The third applied stimulus applied to the component of group (iii) is radiation. It will be appreciated that the radiation will be the radiation required to facilitate a transition of the component of group (iii) from the non-coloured to a coloured state. The radiation is selected from gamma radiation with a wavelength of less than 0.01 nm, X-ray radiation with a wavelength of from 0.01 to 10 nm, ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, and microwave radiation with a wavelength of from 1 mm to 1 m. Preferably, the third applied stimulus is selected from ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm. More preferably, the third applied stimulus is selected from ultraviolet (UV) radiation with a wavelength of from 100 to 400 nm.

The third applied stimulus may be applied to the component of group (iii) of the composition according to the first aspect of the present invention using any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the component by a laser source(s). It will be understood by a skilled person that the third applied stimulus may be applied to the composition at localised positions to selectively develop the coloured state of the component at these localised positions. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the third applied stimulus may be applied to the composition on or within a substrate by flood illumination, meaning that the composition as a whole is flooded with radiation. This can be done using any suitable lamp or bulb, such as a UV lamp, or medium pressure mercury or amalgam lamp or microwave powered UV lamp, a Xe, Hg or XeHg arc (broadband UV sources); a germicidal lamp, a diode bar; or LED(s). When a broadband UV source is utilised, it will be applreciated that a range of wavelengths over the 10 to 400 nm range will be emitted. It will be understood by a skilled person that the radiation is applied to the composition for an appropriate amount of time required to facilitate the transition of the component from the non-coloured state to the coloured state. Typically the time required to deliver sufficient radiation will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, or by flood illumination. For example, in one embodiment, the third applied stimulus may be applied to the component of group (iii) for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds), or for less than 60 seconds, such as for less than 20 seconds, or even for less than 10 seconds.

It will be appreciated that when using a laser source(s), the radiation dosage applied for the third applied stimulus can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage) and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ² A coloured state of the component of group (iii) may have any colour. It will be appreciated by a skilled person that the means used to apply the third applied stimulus will affect the colour of the coloured state formed. For example, where a laser source(s) is used to apply the third applied stimulus, the fluence (amount of energy delivered per unit area) may affect the colour, lightness or intensity of the coloured state formed. In the context of the present invention, the fluence is dependent upon the power of the means used to apply the third applied stimulus (wattage), and the time for which the third applied stimulus is applied to a particular localised position on the substrate, which can be controlled by the scanning speed of the laser or the speed of the moving stage. These three variables can be altered to change the fluence. Where the fluence is low (e.g. lower power and/or shorter irradiation times), the coloured state of the component of group (iii) will be of a less intense colour, and where the fluence is high (e.g. higher power and/or longer irradiation times), the coloured state of the component of group (iii) will be of a more intense colour. In the context of the present invention, fluence values may range from 0.01 to 20 J/cm ² , such as from 0.1 to 10 J/cm ² and even from 0.5 to 5 J/cm ² .

Preferably, the coloured state of the component of group (iii) formed following the transition from the non-coloured state is blue.

In the context of the present invention, the non-coloured state of the component of group (iii) must be ‘activated’ prior to the application of the third applied stimulus such that a transition from the non-coloured state to a coloured state can occur. As detailed above, ‘activation’ is the process of making the non- coloured state of the component capable of undergoing a transition from the non-coloured state to a coloured state, i.e. changing it from an unactivated form (incapable of undergoing a transition) to an activated form (capable of undergoing such a transition). This is facilitated by the application of the third temperature. The third temperature may be any suitable temperature. The third temperature may be a temperature of from 40 to 140°C. Preferably, the third temperature is from 60 to 140 °C, and more preferably, from 70 to 140 °C. The third temperature may be applied to the component of group (iii) of the composition according to the first aspect of the present invention by any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the component by a laser source(s). It will be understood by a skilled person that the third temperature may be applied to the composition at localised positions to selectively activate the non-coloured state of the component at these localised positions. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the third temperature may be applied to the component by flood illumination, meaning that the composition as a whole is flooded with radiation. This may be done using a lamp or bulb, such as an IR lamp; diode bar; or LED(s). It will further be appreciated that the third temperature may be applied to the component using a conductive temperature source. Conductive temperature sources include sources of steam and hot air, lamps, hotplates, heat tunnels, LED(s), thermal print heads, thermal conductors, hot liquids and heated substrates. It will be understood by a skilled person that the third temperature is applied to the composition for an appropriate amount of time required to activate the non-coloured state of the component. Typically the time required to deliver sufficient temperature will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, by flood illumination, or using a conductive temperature source. For example, in one embodiment, the third temperature may be applied to the component of group (iii) for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds) or for less than 60 seconds, such as for less than 20 seconds, or even for less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the radiation dosage applied to achieve the third temperature can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage) and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ²

It will be appreciated by a skilled person that the third temperature may be applied to the component of group (iii) using a combination of the suitable means listed above, i.e. using combinations of laser excitation at localised positions, flood illumination, and a conductive temperature source. For example, in one embodiment, the third temperature may be applied to the component using laser excitation at localised positions, in addition to using a conductive thermal energy source.

In addition, it will be appreciated that where the third temperature is applied using radiation, i.e. at localised positions using a laser source(s) or by flood illumination, the composition and thus the component of group (iii) may be exposed to a temperature in excess of the stated temperature ranges for a very short period of time, i.e. microseconds. It will be understood that this will not have any significant effect on the result to be achieved.

The third temperature may be applied to the component of group (iii) using electromagnetic radiation selected from visible radiation with a wavelength of from 400 to 700 nm, infrared (IR) with a wavelength of from 700 nm to 1 mm, including near-infrared (NIR) with a wavelength of from 700 to 1600 nm. Preferably, the third temperature is applied using visible radiation with a wavelength of from 400 to 700 nm, infrared (IR) radiation with a wavelength of 10600 nm (from a C0 ₂ laser), and near-infrared (NIR) radiation with a wavelength of from 700 to 1600 nm.

It will be appreciated that from the radiation and wavelength ranges detailed herein for the components of groups (i), (ii) and (iii), a skilled person would select a specific first, second or third applied stimulus as required to achieve the desired transitions of the components from a non-coloured to a coloured state. It will be appreciated that the specifically selected first, second and third applied stimuli will differ depending upon the components in the composition.

It will further be appreciated that from the temperature and wavelength ranges detailed herein for the components of groups (i), (ii) and (iii), a skilled person would select a specific first, second or third temperature as required to achieve either the desired transition of the component of group (i) from the coloured state back to the non-coloured state, the desired deactivation of the non-coloured or a coloured state of the component of group (ii), or the desired activation of the non-coloured state of the component of group (iii). It will be appreciated that the specifically selected first, second and third temperatures will differ depending upon the components in the composition.

Preferably, the third temperature is greater than the first and second temperatures. Preferably, the second temperature is lower than the first temperature, which in turn is lower than the third temperature, i.e. second temperature < first temperature < third temperature.

The composition according to the first aspect of the present invention may comprise 2 or more components selected from the component groups (i) to (iii). For example, the composition may comprise a component of group (i) and a component of group (ii), or a component of group (ii) and a component of group (iii), or a component of group (i) and a component of group (iii). In addition, as discussed above, the composition may comprise, for example, a component of group (iii) and two components selected from the group (ii).

It will be appreciated that the selection of the two or more components from groups (i) to (iii) will be based on the colour(s) of their coloured states that can be achieved. Furthermore, the two or more components from groups (i) to (iii) will be selected such that their colour formation is triggered by different conditions. ‘Different conditions’ encompasses the differing orders of application of the first, second and third applied stimuli and the first, second and third temperatures as required, for the formation of colour for the two or more component of groups (i) to (iii).

The composition may comprise a component from each of groups (i), (ii) and (iii).

Preferably, the composition comprises a component from each of the groups (ii) and (iii), or a component from each of the groups (i) and (ii), or a component from each of the groups (i) and (iii).

The composition according to the first aspect of the present invention may further comprise a binder. Suitable binders will be well known to a person skilled in the art. Examples of suitable binders include, but are not limited to the following: polymeric binders such as acrylic polymers, styrene polymers and hydrogenated products thereof; vinyl polymers; polyolefins and hydrogenated or epoxidised products thereof; aldehyde-containing polymers; epoxide-containing polymers; polyamides; polyesters; polyurethanes; sulphone-containing polymers; natural products and derivatives thereof; and combinations thereof. The binder may be present in the composition in any suitable amount. Preferably, the composition comprises from 1 to 50 %, such as from 5 to 40 % and most preferably, from 10 to 35 % of binder based on the total solid weight of the composition.

The composition according to the first aspect of the present invention may further comprise a near-infrared (NIR) absorber. It will be appreciated that an NIR absorber may be utilised when NIR radiation is to be utilised, the NIR absorber being capable of enhancing absorption of the NIR radiation. Examples of suitable NIR absorbers include, but are not limited to the following: inorganic copper salts such as copper (II) hydroxyl phosphate; organic NIR dyes and pigments such as N,N,N’,N’-tetrakis(4-dibutylaminophenyl)-p-benzoquinone bis(iminium hexafluoro-antimonate); non-stoichiometric inorganic compounds such as reduced indium tin oxide, reduced zinc oxide, reduced tungsten oxide (tungsten bronze), reduced doped tungsten oxide, reduced antimony tin oxide, or doped metal oxides such as aluminium-doped zinc oxide (AZO) and fluorine- doped tin oxide (FTO); conductive polymers such as poly polystyrene sulfonate (PEDOT); and combinations thereof. Preferably, the NIR absorber is a non- stoichiometric inorganic compound. Preferably, the composition comprises from 0.05 to 25 %, such as from 0.05 to 20 % of an NIR absorber based on the total solid weight of the composition.

The composition according to the first aspect of the present invention may further comprise a curable compound. Suitable curable compounds will be well known to a person skilled in the art. Examples of suitable curable compounds include, but are not limited to: any commercially available monomers, oligomers, monomer and oligomer mixtures, or photoinitiators. The curable compound may be present in the composition in any suitable amount. The composition according to the first aspect of the present invention may further comprise an additive or combination of additives. Suitable additives will be well known to a person skilled in the art. Examples of suitable additives include, but are not limited to the following: polymers; light or energy absorbing agents; UV absorbers; surfactants; wetting agents; drying promoters; colourants such as pigments; tinting agents; fluorescent agents; plasticisers; optical brighteners; oxidising or reducing agents; stabilisers; light stabilising agents such as hindered amines; rheology modifiers such as thickening or thinning agents; humectants; solvents; adhesion promotors; acid or base scavenging agents; retarders; defoamers; antifoaming agents; and combinations thereof. Preferably, the composition comprises 0.1 to 9 %, such as from 0.1 to 8%, or even from 0.1 to 7 % of additives based on the total solid weight of the composition.

The composition according to the first aspect of the present invention may further comprise a solvent. The composition may comprise a single solvent or a mixture of solvents. The solvent may comprise water, an organic solvent, a mixture of water and an organic solvent, or a mixture of organic solvents. Suitable organic solvent include, but are not limited to the following: alcohols such as ethanol, n-propanol, isopropanol and n-butanol; esters such as ethyl acetate, butyl acetate, and n-hexyl acetate; aromatic hydrocarbons such as benzene, toluene, xylene, and solvent naphtha 100, 150, 200; ketones such as acetone, cyclohexanone, methylisobutyl ketone, and methyl ethyl ketone; glycols such as butyl glycol; glycol ethers such as methoxy propanol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether; and combinations thereof. Preferably, the solvent is present in the composition in amounts of from 15 to 70 %, such as from 15 to 60 %, or even from 20 to 55 % based on the total solid weight of the composition.

The composition according to the first aspect of the present invention may have a viscosity of from 14 to 120 Zahn seconds (efflux time), suitably measured using a Zahn cup #2 viscosity measurement device at a temperature of 16 to 30 °C. It will be appreciated that the viscosity of the composition is dependent upon a number of factors, including the number, type and amount of the components present in the composition, in addition to the printing application and desired coat weight of the composition when applied on a substrate.

The composition according to the first aspect of the present invention preferably comprises, in addition to two or more components selected from the groups (i) to (iii), a binder, an additive or combination of additives, and a solvent or combination of solvents. If near infrared radiation is to be used as at least one of the first, second or third temperatures, an NIR absorber is preferably present.

It will be appreciated by a skilled person that the composition according to the first aspect of the invention may be formed through the combination of formulations containing different components of the composition, for example, a component of group (ii) may be in a separate formulation to component of group

(iii), the formulations being combined to form the composition according to the first aspect of the present invention.

The composition according to the present invention may further comprise at least one component selected from the following group (iv):

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature, wherein, if formed, the coloured states of the two or more components from groups (i) to (iii) and the at least one component of group (iv) are different in colour.

The component of group (iv) may be any suitable component. It will be appreciated that the selection of the two or more components from groups (i) to (iii) and the component of group (iv) will be selected based on the colour(s) of their coloured states that can be achieved. Furthermore, the two or more components from groups (i) to (iii) and the component of group (iv) will be selected such that their colour formation is triggered by different conditions. ‘Different conditions’ encompasses the differing orders of application of the first, second, third and fourth applied stimuli, and first, second, third and fourth temperatures, as required, for the formation of colour of the two or more components of groups (i) to (iii) and the component of group (iv).

It will be appreciated that when the composition according to the first aspect of the present invention disclosed herein further comprises a component of group (iv), this enables the production of a broad range of colours in the formation of an image. The different first, second, third and fourth applied stimuli and first, second, third and fourth temperatures can be applied in different combinations as required by either flood illumination or at particular localised positions, enabling the formation of stable coloured states of predictable colours. It will be appreciated that the stimuli and temperatures used are dependent upon the components present in the composition. The invention thus enables the formation of desired single- and multi-coloured images with a broad colour gamut.

The terms "non-coloured state", "coloured state", "stable coloured state" as defined above in relation to the components of groups (i) to (iii) are applicable to the component of group (iv). The term "transition" as defined above in relation to the components of groups (ii) to (iii) is also applicable to the component of group (iv), the second applied stimulus or third applied stimulus being replaced by the fourth applied stimulus or fourth temperature.

The component of group (iv) may be selected from any suitable component. Suitable examples of the component of group (iv) include, but are not limited to the following (a) to (e):

(a) a pyrazole (thio)semicarbazone compound;

(b) a keto acid compound;

(c) a leuco dye;

(d) a compound formed from a salicylic aldehyde or salicylic ketone compound; and

(e) an oxyanion of a multivalent metal. (a) to (e) are as defined below:

(a) a pyrazole (thio)semicarbazone compound.

By the term "pyrazole (thio)semicarbazone compound" is meant a compound having a pyrazole group and a (thio) semicarbazone group. The brackets around thio indicate that the moeity may be present or absent. The term pyrazole group encompasses derivatives of a pyrazole group. Preferably, the pyrazole group is a pyrazolone, including the enol (C-OH) tautomer form. Preferably, the (thio) semicarbazone group is a semicarbazone.

Preferably, the pyrazole (thio)semicarbazone compound is a pyrazolone semicarbazone compound.

Preferably, the pyrazole (thio)semicarbazone compound is a compound having the formula (VII):

wherein each of A, B, C and D are independently selected from: Ci-is alkyl; -CCI ₃ ; -CF ₃ ; C ₆ -12 aryl optionally substituted with C _{M S} alkoxy, -CN, - CF ₃ , halogen, -N0 ₂ , or C _{M S} alkyl; a heterocyclic ring and a heteroaryl.

Preferably, A is selected from C _6- 12 aryl optionally substituted with C _{M S} alkoxy, - CN, -CF ₃ , halogen, -N0 ₂ , or C _{M S} alkyl, more preferably from C ₆ -s aryl, and most preferably phenyl. Preferably, B is selected from C _{M S} alkyl and C _6- 12 aryl optionally substituted with Ci-is alkoxy, -CN, -CF ₃ , halogen, -N0 ₂ , or C _{M S} alkyl, more preferably from Ci _-4 alkyl and C ₆ -s aryl, and most preferably from methyl and phenyl. Preferably, C is selected from C _6- 12 aryl optionally substituted with C _{M S} alkoxy, - CN, -CF ₃ , halogen, -N0 ₂ , or C _{M S} alkyl; -CCI ₃ ; and C _{M S} alkyl; more preferably from C _6-8 aryl optionally substituted with Ci _-4 alkoxy, -CN, -CF ₃ or -N0 ₂ ; -CCI ₃ ; and Ci _-4 alkyl, and most preferably, from phenyl, 4-methoxy phenyl, 4- cyanophenyl, 4-(trifluoromethyl)phenyl, 4-nitrophenyl; -CCI ₃ ; and C(CH ₃ ) ₃ .

Preferably, D is selected from C _6- 12 aryl optionally substituted with C _{M S} alkoxy, - CN, -CF ₃ , halogen, -N0 ₂ , or C _{M S} alkyl, more preferably from C ₆ -s aryl, and most preferably phenyl.

The pyrazole (thio)semicarbazone compound may be a component having the formula (VIII):

wherein B is selected from C _{M S} alkyl and C _6- 12 aryl optionally substituted with Ci_ 18 alkoxy, -CN, -CF ₃ , halogen, -N0 ₂ , or Ci-i ₈ alkyl, preferably from Ci _-4 alkyl and C _6-8 aryl, and more preferably from methyl and phenyl, and C is selected from C _6- 12 aryl optionally substituted with C _{1 -18} alkoxy, -CN, -CF ₃ , halogen, -N0 ₂ , or C _{1 -18} alkyl; -CCI ₃ ; and C _1-18 alkyl; preferably from C ₆ -s aryl optionally substituted with Ci _-4 alkoxy, -CN, -CF ₃ or -N0 ₂ ; -CCI ₃ ; and Ci _-4 alkyl, and more preferably, from phenyl, 4-methoxy phenyl, 4-cyanophenyl, 4- (trifluoromethyl)phenyl, 4-nitrophenyl; -CCI ₃ ; and C(CH ₃ ) ₃ . Preferably, the pyrazole (thio)semicarbazone compound is selected from (£)- 2- ((5-hydroxy-1 ,3-diphenyl-1 /-/-pyrazol-4-yl)(phenyl)methylene)-A/- phenylhydrazine-1 -carboxamide (B and C are phenyl), (£)-2-((5-hydroxy-3- methyl-1 -phenyl-1 /-/-pyrazol-4-yl)(phenyl)methylene)-A/-phenylhydrazine-1 - carboxamide (B is methyl and C is phenyl), (£)-2-((5-hydroxy-1 ,3-diphenyl-1 /-/- pyrazol-4-yl)(4-nitrophenyl)methylene)-A/-phenylhydrazine-1 -carboxamide (B is phenyl and C is 4-nitrophenyl), (£)-2-((5-hydroxy-1 ,3-diphenyl-1 /-/-pyrazol-4- yl)(4-(trifluoromethyl)phenyl)methylene)-A/-phenylhydrazine- 1 -carboxamide (B is phenyl and C is 4-(trifluoromethyl)phenyl), (£)-2-((5-hydroxy-1 ,3-diphenyl-1 /-/- pyrazol-4-yl)(4-methoxyphenyl)methylene)-A/-phenylhydrazine- 1 -carboxamide (B is phenyl and C is 4-methoxyphenyl), (£)-2-((5-hydroxy-3-methyl-1 -phenyl-1 H- pyrazol-4-yl)(4-(trifluoromethyl)phenyl)methylene)-A/-phenyl hydrazine-1 - carboxamide (B is methyl and C is 4-(trifluoromethyl)phenyl), and (E)-2-((4- cyanophenyl)(3-hydroxy-2,5-diphenyl-2,3-dihydro-1 H-pyrazol-4-yl)methylene)-N- phenylhydrazine-1 -carboxamide (B is phenyl, and C is 4-cyanophenyl). More preferably, the pyrazole (thio)semicarbazone compound is (E)-2-((4- cyanophenyl)(3-hydroxy-2,5-diphenyl-2,3-dihydro-1 H-pyrazol-4-yl)methylene)-N- phenylhydrazine-1 -carboxamide (B is phenyl, and C is 4-cyanophenyl).

All references to the components of formulas (VII) and (VIII) are to be interpreted as covering the components of the formulas (VII) and (VIII) per se, and also, all tautomers or isomers thereof.

It will be appreciated that components of group (i) and components of group (iv) when compounds of formula (VII) or (VIII) may be the same component. Accordingly, the composition according to the first aspect of the present invention does not comprise a combination of a component of groups (i) and (iv) when the component of group (iv) is a compound of formula (VII) or (VIII).

It will be appreciated that the distinction between the component of group (i) and the component of group (iv) when a compound of formula (VII) or (VIII) is that the transition of the component of group (i) from the non-coloured state to a coloured state is effected by the application of the first applied stimulus and is reversible, i.e. a transition from the same coloured state back to the non- coloured state can be effected by the application of the first temperature. In contrast, the transition of the component of group (iv) is‘irreversible’, i.e. once the coloured state has been formed, upon exposure to the first temperature, there will be no transition from the coloured state back to the non-coloured state and the coloured state maintains essentially its colour. The ‘irreversible’ transition of the component of group (iv) when a compound of formula (VII) or (VIII) from the non-coloured state to a coloured state is effected by the application of the fourth temperature as defined below. An acid- or base - generating agent as defined below may optionally accompany the component of group (iv) when a compound of formula (VII) or (VIII) to facilitate this‘irreversible’ transition. Alternatively, the‘irreversible’ transition of the component of group (iv) when a compound of formula (VII) or (VIII) from the non-coloured state to a coloured state is effected by the application of the fourth applied stimulus as defined below, but in this instance an acid- or base -generating agent as defined below accompanies the component of group (iv) when a compound of formula (VII) or (VIII) to facilitate this‘irreversible’ transition.

In order for the component of group (i) to demonstrate the reversibility discussed above in comparison to the irreversible transition of the component of group (iv), the transition from the non-coloured state to a coloured state of the component of group (i) is preferentially driven by the first applied stimulus, as opposed to the fourth temperature. By "preferentially driven by the first applied stimulus" is meant that the DE value (based on L*a*b* measurements) calculated for the transition between the background colour of the substrate to which the component is applied or incorporated within and the coloured state is higher when the first applied stimulus is applied as opposed to the fourth temperature. It is therefore noted that components of group (i) that are preferentially driven by the first applied stimulus may also act as components of group (iv) upon exposure to the fourth temperature, but components of group (iv) that are preferentially driven by the fourth temperature, i.e. irreversibly transition upon exposure to the fourth temperature, and will not act as components of group (i).

Preferably, for the pyrazole (thio)semicarbazone compounds of component group (iv), the transition from the non-coloured to a coloured state is effected by the fourth temperature.

(b) a keto acid compound.

By the term "keto acid compound" is meant a compound having a carboxylic acid group and a ketone group. Preferably, the keto acid compound is of formula (IX):

wherein Xi _a , X _2a , and X _3a are independently selected from C, N, B and S; the two R groups may be the same or different, and are independently selected from: hydrogen; Ci-i ₈ alkyl; C ₆ -i ₂ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -

CF ₃ , -N0 ₂ , halogen, or CMS alkyl; halogen; -N0 _2; -CF ₃ ; -OR ³ ; -NR CN; -SR

COR ³ ; -C0 ₂ R ³ ; and -CONR ³ ₂ ; wherein R ³ is selected from an alkali metal; hydrogen; Ci-i ₈ alkyl; and C ₆ -i ₂ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, - CF ₃ , -N0 ₂ , halogen, or CMS alkyl; or both R groups, together with the nitrogen atom to which they are attached, join together to form a cyclic amino group, wherein the cyclic amino group is optionally substituted with CMS alkoxy, -CN, - CF ₃ , -N0 ₂ , halogen, or CMS alkyl .

A may be the same as or different to B’ (defined below), and is independently selected from: hydrogen; Ci-i ₈ alkyl; C _6-i2 aryl optionally substituted with CM S alkoxy, -CN, -CF ₃ , -N0 ₂ , halogen, or CMS alkyl; a heterocyclic ring; a heteroaryl; halogen; -N0 ₂ ; -CF ₃ ; -OR ³ ; -NR ³ ₂ ; -CN; -SR ³ ; -COR ³ ; -C0 ₂ R ³ ; -CONR ³ ₂ ; wherein R ³ is selected from an alkali metal; hydrogen; Ci-i ₈ alkyl; and C _6-i2 aryl optionally substituted with CMS alkoxy, -CN, -CF ₃ , -N0 ₂ , halogen, or CMS alkyl; and R ¹ is selected from wherein Xi _b , X _2b , X3 _b and X _4b are independently selected from C, N, B and S; and B’ is the same or different to A and is independently selected from hydrogen; C1-18 alkyl; C ₆ -12 aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , -N0 ₂ , halogen, or Ci-i ₈ alkyl; a heterocyclic ring; a heteroaryl; halogen; -N0 _2; -CF _3; - OR ³ ; -NR ³ ₂ ; -CN; -SR ³ ; -COR ³ ; -C0 ₂ R ³ ; -CONR ³ ₂ ; wherein R ³ is selected from an alkali metal; hydrogen; Ci-i ₈ alkyl; and C ₆ -i ₂ aryl optionally substituted with Ci_ 18 alkoxy, -CN, -CF ₃ , -N0 ₂ , halogen, Ci-i ₈ alkyl, hydroxyl (-OH), or -NR ₂ wherein R is as defined above.

It will be appreciated that A and B’ may constitute a substituent at a single position on the benzene ring to which each of A and B’ relates or A and B’ may constitute multiple independently selected substituents at any of the available positions on the benzene ring to which each of A and B’ relates. For example, the benzene ring to which B’ relates may be substituted with a single substituent or up to 4 independently selected substituents.

Preferably, the keto acid compound is selected from formula (X):

wherein Xi _a , X _2a , X3 _a , Xi _b , X2 _b , X3 _b and X _4b , R, A and B’ are as described above for formula (IX).

Preferably, the keto acid compound is selected from formula (XI):

wherein R and B’ are as described above for formula (IX). Preferably, the two R groups are the same and are selected from Ci-i ₈ alkyl; and C _6-i2 aryl optionally substituted with C _{M S} alkoxy, -CN, -CF ₃ , -N0 ₂ , halogen, or C _{M S} alkyl. More preferably, the two R groups are the same and C _{M S} alkyl, more preferably Ci _-6 alkyl. Preferably, B’ is independently selected from hydrogen; -N0 ₂ and halogen, more preferably, hydrogen and chlorine, and most preferably hydrogen.

Preferably, the keto acid compound is selected from2-(4-(dimethylamino)-2- hydroxybenzoyl)benzoic acid, 2-(4-(dibutylamino)-2-hydroxybenzoyl)benzoic acid, 2-(4-(diethylamino)-2-hydroxybenzoyl)benzoic acid, and 2, 3,4,5- tetrachloro-6-(4-(diethylamino)-2-hydroxybenzoyl)benzoic acid. More preferably, 2-(4-(dimethylamino)-2-hydroxybenzoyl)benzoic acid, 2-(4-(dibutylamino)-2- hydroxybenzoyl)benzoic acid, and 2-(4-(diethylamino)-2-hydroxybenzoyl)benzoic acid,

The keto acid compounds of formulas (IX) to (XI) are commercially available, for example, they can be sourced from Chameleon Speciality Chemicals Limited. It is noted that in one embodiment, the keto acid compound may be in the form of a‘dimer’, whereby B’ denotes a -C0 ₂ R ³ group (where R ³ is hydrogen such that the benzene ring carries two carboxyl groups) and also, an independently selected -COR ³ group, where R ³ is a C _6-i2 aryl substituted with hydroxyl (-OH) and NR ₂ , wherein R is as defined above for formula (IX). Preferably, the -C0 ₂ R ³ group (where R ³ is hydrogen such that the benzene ring carries two carboxyl groups) is at X _2b and the -COR ³ group is at X _3b .

(c) a leuco dye.

Leuco dyes are well known to a skilled person as compounds capable of forming colour. They can be photochromic (change colour on exposure to light such as UV light), chemochromic, thermochromic or halochromic (change colour on exposure to change in environmental pH). Examples of suitable leuco dyes are contained in WO2015/015200 and WO2013/068729, the content of which is incorporated by reference. Suitable leuco dyes include, but are not limited to any commercially available or chemically synthesisable leuco dye, including but not limited to: commercially available photochromic, thermochromic, chemochromic, and halochromic leuco dyes. Examples of suitable leuco dyes include, but are not limited to: spiroxazines, naphthopyrans, phthalides, fluorans, triarylmethanes, benzoxazines, quinazolines, spiropyrans, quinones, tetrazolium salts, thiazines, phenazines and oxazines.

Suitable suppliers of leuco dyes include, but are not limited to: Yamada Chemical Company Limited, Chameleon Speciality Chemicals Limited, and Connect Chemicals.

The leuco dye may be selected from: 2-Anilino-3-diethylamino-6-methylfluoran (Chameleon Black 1 ), 2-Anilino-6-dibutylamino-3-methylfluoran (Chameleon Black 2), 6-(Dimethylamino)-3,3-bis [4-(dimethylamino) phenyl] phthalide (Chameleon Blue 3), 4,4'-[(9-butyl-9H-carbazol-3-yl)methylene]bis[N-methyl-N- phenylaniline] (Chameleon Blue 4), 3,3'-Bis(1 -n-octyl-2-methylindol-3- yl)phthalide (Chameleon Red 5), 6'-(Diethylamino)-3-oxo-spiro [isobenzofuran- 1 (3H),9'-[9H] xanthene]-2'-carboxylic acid ethyl ester (Chameleon Orange 6), 7- [4-(diethylamino)-2-ethoxyphenyl]-7-(2-methyl-1 -octyl-1 H-indol-3-yl) Furo[3,4- b]pyridin-5(7H)-one (Chameleon Blue 8),

2'-(Dibenzylamino)-6'- (diethylamino)fluoran (Chameleon Blue 9), N,N-dimethyl-4-[2-[2-(octyloxy)phenyl]-6-phenyl-4-pyridinyl] - Benzenamine (Chameleon Yellow 10), and 6'-(diethylamino)-2'-[(dimethylphenyl) amino]-3'- methylspiro [isobenzofuran-1 (3H),9'-[9H]xanthene]-3-one (chameleon Black 15). Preferably, the leuco dye is 6-(dimethylamino)-3,3-bis [4-(dimethylamino) phenyl] phthalide (Chameleon Blue 3), 7-[4-(diethylamino)-2-ethoxyphenyl]-7-(2-methyl- 1 -octyl-1 H-indol-3-yl) furo[3,4-b]pyridin-5(7H)-one (Chameleon Blue 8), 3,3'- bis(1 -n-octyl-2-methylindol-3-yl)phthalide (Chameleon Red 5), 2-anilino-3- diethylamino-6-methylfluoran (Chameleon Black 1 , ODB-1 ), 2-anilino-6- dibutylamino-3-methylfluoran, (Chameleon Black 2, ODB-2), N,N-dimethyl-4-[2- [2-(octyloxy)phenyl]-6-phenyl-4-pyridinyl]- benzenamine (Chameleon Yellow 10), 6'-(diethylamino)-2'-[(dimethylphenyl) amino]-3'-methylspiro [isobenzofuran- 1 (3H),9'-[9H]xanthene]-3-one (Chameleon Black 15); all commercially available from Chameleon Speciality Chemicals Limited.

(d) a compound formed from a salicylic aldehyde or salicylic ketone compound.

By the term "a compound formed from a salicylic aldehyde or salicylic ketone compound" is meant a compound formed from a parent salicylic aldehyde or salicylic ketone compound (aldehyde or ketone derivatives of salicylic acid).

Preferably, the compound formed from a salicylic aldehyde or salicylic ketone compound is a compound formed from the condensation reaction of a linked primary diamine and independently selected from two salicylic aldehyde or salicylic ketone compounds.

By the term "linked primary diamine" is meant a compound comprising two primary amine groups joined by a carbon chain of 0 to 20 carbon atoms, preferably 0 to 10 carbon atoms, more preferably 0 to 8 carbon atoms, and most preferably 0 to 6 carbon atoms.

Preferably, the compound formed from a salicylic aldehyde or salicylic ketone compound is a compound formed from the condensation reaction of hydrazine and independently selected from two salicylic aldehyde or salicylic ketone compounds.

The compound formed from a salicylic aldehyde or salicylic ketone compound may have the following formula (XII): wherein R ¹ and R ² may be the same or different and are independently selected from hydrogen; halogen; hydroxyl; C _{M S} alkoxy; C _{M S} alkyl; C _{M S} cycloalkyl; a primary, secondary or tertiary amino group; -CN; -N0 ₂ ; -CF ₃ ; -COOH; -COR ³ ; - CONR ³ ₂ ; a heterocyclic ring; a heteroaryl and Ce-^aryl optionally substituted with Ci-is alkoxy, -CN, -CF ₃ , -N0 ₂ , halogen, or C _{M S} alkyl;

R ³ and R ⁴ may be the same or different and are independently selected from hydrogen, Ci-i ₈ alkyl, Ce-^aryl, and Ci-i ₈ alkyl-C ₆ -i2aryl; and

Xia, X2a, X3a, X _4a , Xi _b , X2 _b , Xs _b and X _4b are independently selected from C, N or S.

It will be appreciated that R ¹ and R ² may constitute a substituent at a single position on the benzene ring to which each of R ¹ and R ² relates or R ¹ and R ² may constitute multiple independently selected substituents at any of the available positions on the benzene ring to which each of R ¹ and R ² relates. . For example, R ¹ or R ² may constitute a single substituent on the benzene ring to which it relates, or R ¹ or R ² may constitute two substituents on the benzene ring to which it relates, the two substituents being different and situated at different positions on the benzene ring. For example, R ¹ or R ² may constitute a single substituent on the benzene ring to which it relates, or R ¹ or R ² may constitute two substituents on the benzene ring to which it relates, the two substituents being different and situated at different available positions on the benzene ring. Preferably, R ¹ and R ² are the same and are selected from hydrogen; halogen; hydroxyl; C _{M S} alkoxy including methoxy; C _{M S} alkyl including methyl, tertiary butyl and isopropyl; a secondary amino group (including -NR ₂ wherein R is Ci _-6 alkyl such as diethylamino and dimethylamino); -CN, -N0 ₂ , -CF ₃ , -COOH; C _6- i ₂ aryl optionally substituted with C _{M S} alkoxy, -CN, -CF ₃ , -N0 ₂ , halogen, or C _{M S} alkyl, including phenyl; and a heterocyclic ring such as pyridyl. More preferably, R ¹ and R ² are the same and are selected from hydrogen; halogen; hydroxyl; Ci_ i ₈ alkoxy including methoxy; a secondary amino group (including -NR ₂ wherein R is Ci-e alkyl such as diethylamino and dimethylamino); and N0 ₂ . Preferably, R ³ and R ⁴ are the same and are selected from hydrogen and Ci_ i ₂ alkyl. More preferably, R ³ and R ⁴ are the same and are selected from hydrogen and Ci _-6 alkyl. Most preferably, R ³ and R ⁴ are the same and are hydrogen.

Preferably, Xi _a , X _2a , ^x _3a , X _4a , Xi _b , X _2b , ^x _3b and X _4b are independently selected from C or N. More preferably, Xi _a , X _2a , X _3a , X _4a , Xi _b , X _2b , ^x _3b and X _4b are C.

Or, the compound formed from a salicylic aldehyde or salicylic ketone compound has the following formula (XIII):

wherein R ¹ , R ² , R ³ and R ⁴ and Xi _a , X _2a , X _3a , X _4a , Xi _b , X _2b , X _3b and X _4b are as defined above for formula (XI I). Preferably, the compound formed from a salicylic aldehyde or salicylic ketone compound is 2,2'-((1 E, 1 'E)-hydrazine-1 ,2-diylidenebis(methaneylylidene))diphenol, 6,6'- ((1 E, 1 'E)-hydrazine-1 ,2-diylidenebis(methaneylylidene))bis(3-nitrophenol), 3,3’- ((1 E, 1’E)-hydrazine-1 ,2-diylidenebis(methaneylylidene))bis(benzene-1 ,2-diol), 6,6’-((1 E, 1’E)-hydrazine-1 ,2-diylidenebis(methaneylylidene))bis(4-bromo-2- methoxyphenol), 6,6’-((1 E, 1’E)-hydrazine-1 ,2- diylidenebis(methaneylylidene))bis(3-(diethylamino)phenol), 2,2’-((1 E,1’E)- hydrazine-1 ,2-diylidenebis(ethan-1 -yl-1 -ylidene))diphenol and 1 , 1’-((1 E, 1 Έ)- hydrazine-1 ,2-diylidenebis(methaneylylidene))bis(naphthalene-2-ol). Most preferably, the compound of formula (I) or (II) is 6,6’-((1 E, 1’E)-hydrazine-1 ,2- diylidenebis(methaneylylidene))bis(3-nitrophenol).

(e) an oxyanion of a multivalent metal.

The use of oxyanions of multivalent metals in laser-markable compositions are disclosed in US7485403, the content of which is incorporated herein by reference. A particularly preferred oxyanion is ammonium octamolybdate (NH ₄ ) ₄ MO ₈ 0 ₂₆ or“AOM”, which is a commercially available molybdenum composition with the CAS number 1241 1 -64-2. The AOM pigment will typically be formulated together with a binder, e.g. a polymeric binder, in the compositions of the invention. Suitable oxyanions include molybdate, tungstate or analogous transition metal compounds, including di- and hept-molybdates. Preferably, the oxyanion of a multivalent metal is ammonium octamolybdate.

It will be appreciated by a skilled person that the selection of the fourth applied stimulus or fourth temperature is dependent upon the nature of component of group (iv).

When the component of group (iv) is a compound of formula (VII) or (VIII), (IX), (X) or (XI), a leuco dye or a compound of formula (XII or XIII), the fourth applied stimulus may be utilised to facilitate a transition from the non-coloured state to a coloured state of the component of group (iv). Further, when the one or more additional component is a compound of formula (VII) or (VIII), a compound of formula (IX), (X) or (XI), a lecuo dye, an oxyanion of a multivalent metal or a compound of formula (XII) or (XIII), the fourth temperature may be utilised to facilitate a transition from the non-coloured state to a coloured state of the component of group (iv).

When the component of group (iv) is a compound of formula (VII) or (VIII), and the transition from the non-coloured state to a coloured state of the component of group (iv) is effected by the fourth applied stimulus, the component of group (iv) must be accompanied by an acid- or base-generating agent. When the component of group (iv) is a compound of formula (VII) or (VIII), and the transition from the non-coloured state to a coloured state of the component of group (iv) is effected by the fourth temperature, the component of group (iv) may be accompanied in the composition by an acid or base-generating agent. It will be appreciated by a skilled person that the acid or base-generating agent and the component of group (iv) of formula (VII) or (VIII) interact to achieve colour formation. The acid- or base-generating agent is present to facilitate a pH change through generation of acid or base (for the acid-generating or base- generating agents respectively) upon application of the fourth temperature to the composition and thus the compound of formula (VII) or (VIII) and acid or base- generating agent. This acid or base generation facilitates the transition of the component of group (iv) of formula (VII) or (VIII) to transition from a non-coloured state to a coloured state. By‘acid’ is meant any molecular entity or chemical species capable of donating a hydrogen (proton) or capable of forming a covalent bond with an electron pair. By‘base’ is meant a chemical species or molecular entity having an available pair of electrons capable of forming a covalent bond with a proton, or with a vacant orbital of some other species.

Suitable acid-generating agents include any suitable commercially available or chemically synthesisable acid-generating agents. Suitable acid-generating agents include, but are not limited to the following: thermal acid-generating agents (TAGs) based on amine salts of borobenzilate and tri-n-butylammonium borodisalicylate; photoacid-generating agents such as but not limited to triphenylsulfonium triflate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium perluorobutane sulfonate, triphenylsulfonium trifluoromethylsulfonate, N-phenylbis(trifluoromethanesulfonimide), Bisphenol derivatives including but not limited to bisphenol A, bisphenol F, bisphenol S, bisphenol E, bisphenol B, bisphenol AF, bisphenol AP, and bisphenol BP. Suitable photoacid-generating agents include those described in US 8932797, the content of which is incorporated herein by reference.

Suitable base-generating agents include any suitable commercially available or chemically synthesisable base-generating agents. Suitable base-generating agents include, but are not limited to the following: thermal base-generating agents such as n-phenyliminodiacetic acid, 1 ,2-bis(2-aminophenoxy)-ethane- N,N,N’,N’-tetraacetic acid, and N-methylpyridinium oxalate; and photobasic- generating agents such as 9-anthrylmethyl 4’-nitrophenylcarbonate, 9- anthrylmethyl 1 -piperidinecarboxylate, and 2-anthraquinonylmethyl 4’nitrophenylcarbonate. Suitable thermal base-generating agents include those described in WO2015199219 and photobase-generating agents include those described in EP2368875, the content of each of which is incorporated herein by reference.

It will be understood by a skilled person that the selection of the acid- or base- generating agent is dependent upon the particular compound of formula (VII) or (VIII) utilised in the composition. The requirement of either an acid- or a base- generating agent can be determined by a skilled person.

It will further be appreciated by a skilled person that the selection of the fourth applied stimulus or fourth temperature is dependent upon the nature of the acid- or base-generating agent accompanying the compound of formula (VII) or (VIII). It will be appreciated by a skilled person that the fourth applied stimulus is utilised to facilitate a transition when a photoacid- or photobase-generating agent is present in relation to the compound of formula (VII) or (VIII), and the fourth temperature is utilised to facilitate a transition when a thermal acid- or base- generating agent is present in relation to the compound of formula (VII) or (VIII).

When the component of group (iv) is a compound of formula (IX), (X) or (XI) or a leuco dye, the component of group (iv) is accompanied in the composition by an acid-generating agent, the acid-generating agent being as described above. The fourth applied stimulus or fourth temperature is applied to the composition as described above to facilitate a transition from the non-coloured to the coloured state of the component of group (iv). It will be appreciated by a skilled person that the acid-generating agent and the component of group (iv) of formula (IX), (X) or (XI) or a leuco dye interact to achieve colour formation. The acid-generating agent is present to facilitate a pH change through generation of acid upon application of the fourth applied stimulus or fourth temperature to the composition and thus the component of group (iv) and acid -generating agent. This acid generation facilitates the transition of the compound of formula (IX), (X) or (XI) or the leuco dye from a non-coloured state to a coloured state.

It will be understood by a skilled person that the selection of the acid-generating agent is dependent upon the particular compound of formula (IX), (X) or (XII), or leuco dye utilised in the composition. It will further be appreciated by the skilled person that the selection of the fourth applied stimulus or fourth temperature is dependent upon the nature of the acid-generating agent accompanying the compound of formula (IX), (X) or (XI), or the leuco dye. It will be appreciated by a skilled person that the fourth applied stimulus is utilised to facilitate a transition when a photoacid-generating agent is present in relation to the compound of formula (IX), (X) or (XI), or lecuo dye, and the fourth temperature is utilised to facilitate a transition when a thermal acid-generating agent is present in relation to the compound of formula (IX), (XI) or (XI), or a leuco dye.

When the component of group (iv) is a compound of formula (XII) or (XIII), the component of group (iv) is preferably accompanied in the composition by an acid- or base-generating agent, the acid- or base-generating agent being as described above. The fourth applied stimulus or fourth temperature is applied to the composition as described above to facilitate a transition from the non- coloured to the coloured state of the compound of group (iv) of formula (XII) or (XIII). It will be appreciated by a skilled person that the acid or base-generating agent and the component of group (iv) of formula (XII) or (XIII) interact to achieve colour formation. The acid- or base-generating agent is present to facilitate a pH change through generation of acid or base upon application of the fourth applied stimulus or fourth temperature to the composition and thus the one or more additional component and acid- or base-generating agent. This acid or base generation facilitates the transition of the component of group (iv) of formula (XII) or (XIII) to transition from a non-coloured state to a coloured state.

It will be understood by a skilled person that the selection of the acid- or base- generating agent is dependent upon the particular compound of formula (XII) or (XIII) utilised in the composition. The requirement of either an acid- or a base- generating agent can be determined by a skilled person.

It will further be appreciated by a skilled person that the selection of the fourth applied stimulus or fourth temperature is dependent upon the nature of the acid- or base-generating agent accompanying the compound of formula (XII) or (XIII). It will be appreciated by a skilled person that the fourth applied stimulus is utilised to facilitate a transition when a photoacid- or photobase-generating agent is present in relation to the compound of formula (XII) or (XIII), and the fourth temperature is utilised to facilitate a transition when a thermal acid- or base- generating agent is present in relation to the compound of formula (XII) or (XIII).

The fourth applied stimulus is radiation. It will be appreciated that the radiation will be the radiation required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. The radiation selected will therefore be dependent upon the component of group (iv) present in the composition. The radiation is selected from gamma radiation with a wavelength of less than 0.01 nm, X-ray radiation with a wavelength of from 0.01 to 10 nm, ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, and microwave radiation with a wavelength of from 1 mm to 1 m. Preferably, the fourth applied stimulus is ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm. More preferably, the fourth applied stimulus is ultraviolet (UV) radiation with a wavelength of from 100 to 400 nm.

It will be appreciated that from the radiation and wavelength ranges detailed herein for the component of group (iv), a skilled person would select a specific fourth applied stimulus as required to achieve the desired transition of the component from a non-coloured state to a coloured state. It will be appreciated that the specifically selected fourth applied stimuli will differ depending upon the components in the composition.

The fourth applied stimulus may be applied to the component of group (iv) of the composition by any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the component by a laser source(s). It will be understood by a skilled person that the fourth applied stimulus may be applied to the composition at localised positions to selectively develop the coloured state of the component at these localised positions. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the fourth applied stimulus may be applied to the composition on or within the substrate by flood illumination, meaning that the composition as a whole is flooded with radiation. This can be done using any suitable lamp or bulb, such as a UV lamp, or medium pressure mercury or amalgam lamp or microwave powered UV lamp, a Xe, Hg or XeHg arc (broadband UV sources); a germicidal lamp, a diode bar; or LED(s). When a broadband UV source is utilised, it will be appreciated by a skilled person that a range of wavelengths will be emitted over the 10 to 400 nm range. It will also be understood by a skilled person that the radiation is applied to the composition for an appropriate amount of time required to facilitate the transition of the component from the non-coloured state to the coloured state. Typically the time required to deliver sufficient radiation will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, or by flood illumination. For example, in one embodiment, the fourth applied stimulus may be applied to the one or more additional component for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds), or for less than 60 seconds, such as for less than 20 seconds, or even for less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the radiation dosage of the fourth applied stimulus can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage) and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ² The fourth temperature may be any suitable temperature. It will be appreciated by a skilled person that the fourth temperature will be a temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. The fourth temperature will therefore be selected dependent upon the component of group (iv) present in the composition. The fourth temperature may be a temperature of from 50 to 300 °C, such as from 50 to 280 °C, or even 80 to 200 °C.

The fourth temperature may be applied to the component of group (iv) of the composition by any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the component by a laser source(s). It will be understood by a skilled person that the fourth temperature may be applied to the composition on or within the substrate at localised positions to selectively develop the coloured state of the component at these localised positions. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the fourth temperature may be applied to the component by flood illumination, meaning that the composition as a whole is flooded with radiation. This may be done using a lamp or bulb, such as an IR lamp; diode bar; or LED(s). It will further be appreciated that the fourth temperature may be applied to the fourth component using a conductive temperature source. Conductive temperature sources include sources of steam and hot air, lamps, heat tunnels, LED(s), thermal print heads, thermal conductors, hotplates, hot liquids and heated substrates. It will be understood by a skilled person that the fourth temperature is applied to the composition for an appropriate amount of time required to facilitate the transition of the component from the non-coloured state to the coloured state. Typically the time required to deliver sufficient temperature will depend upon the power of the means used to apply radiation and the method of application i.e. at localised positions, by flood illumination, or using a conductive temperature source. For example, in one embodiment, the fourth temperature may be applied to the component of group (iv) for less than 120 seconds (such as between 30 to 110 seconds, or even between 75 to 105 seconds), or for less than 60 seconds, such as for less than 20 seconds, or even for less than 10 seconds. It will be appreciated that when applied using a laser source(s), the fourth temperature can be controlled by alteration of the time for which the radiation is applied, the power of the means used to apply the radiation (wattage) and thus, the fluence (amount of energy delivered per unit area) delivered by a laser source(s), i.e. J/cm ²

It will be appreciated by a skilled person that the fourth temperature may be applied to the component of group (iv) using a combination of the suitable means listed above, i.e. using combinations of laser excitation at localised positions, flood illumination, and a conductive temperature source. For example, in one embodiment, the fourth temperature may be applied to the component using laser excitation at localised positions, in addition to using a conductive thermal energy source.

In addition, it will be appreciated that where the fourth temperature is applied using radiation, i.e. at localised positions using a laser source(s) or by flood illumination, the composition and thus the component of group (iv) may be exposed to a temperature in excess of the stated temperature ranges for a very short period of time, i.e. microseconds. It will be understood that this will not have any significant effect on the result to be achieved.

The fourth temperature may be applied to the component of group (iv) using radiation selected from visible radiation with a wavelength of from 400 to 700 nm, infrared (IR) radiation with a wavelength of from 700 nm to 1 mm, including near-infrared (NIR) radiation with a wavelength of from 700 to 1600 nm. Preferably, the fourth temperature is selected from visible radiation with a wavelength of from 400 to 700 nm, infrared (IR) radiation with a wavelength of 10600 nm (using a C0 ₂ laser), infrared radiation with a wavelength of from 700 nm to 1 mm, and near-infrared (NIR) radiation with a wavelength of 700 to 1600 nm.

It will be appreciated that from the temperature and wavelength ranges detailed herein for the component of group (iv), a skilled person would select a specific fourth temperature as required to achieve the desired transition of the component from the non-coloured state to a coloured state. It will be appreciated that the specifically selected fourth temperature will differ depending upon the components in the composition.

The coloured state of the component of group (iv) may have any colour. It will be appreciated by a skilled person that the means used to apply the fourth applied stimulus or fourth temperature will affect the colour of the coloured state formed. For example, where a laser source(s) is used to apply the fourth applied stimulus or fourth temperature, the fluence (amount of energy delivered per unit area) may affect the colour, intensity or lightness of the coloured state of the component of group (iv) formed. In the context of the present invention, the fluence is dependent upon the power of the means used to apply the fourth applied stimulus or fourth temperature (wattage), and the time for which the fourth applied stimulus or fourth temperature is applied to a particular localised position on the substrate, which can be controlled by the scanning speed of the laser or the speed of the moving stage. These two variables can be altered to change the fluence. Where the fluence is low (e.g. lower power and/or shorter irradiation times), the coloured state of the component of group (iv) will be of a less intense colour, and where the fluence is high (e.g. higher power and/or longer irradiation times), the coloured state of the component of group (iv) will be of a more intense colour. Changing the fluence may also result in the coloured state of the component of group (iv) changing colour. For example, low fluence may form a coloured state of the component of group (iv) having a yellow colour, and higher fluence may form the same coloured state but having an orange or red colour. This is particularly applicable for (a), (b) and (d). In the context of the present invention, fluence values may range from 0.01 to 20 J/cm ² , such as from 0.1 to 10 J/cm ² and even from 0.5 to 5 J/cm ² .

It will be understood by a skilled person that if an acid- or base-generating agent accompanies the component of group (iv) in the composition according to the first aspect of the present invention, the acid- or base-generating agent is exclusive to the additional component and will not affect the two or more components of groups (i) to (iii). It will be appreciated by a skilled person that if two components of group (iv) are selected, the components of group (iv) cannot be selected to both by accompanied by an acid- or base-generating agent, i.e. the composition may only comprise one acid- or base-generating agent. If two components of group (iv) are present in the composition, the two components of group (iv) will be selected such that only one requires an acid- or base-generating agent, or in certain instances, the acid- or base-generating agent associated with one of the two components will also interact with the other of the two components as discussed above.

It will be appreciated that more than one component from group (iv) may be present in the composition according to the first aspect of the present invention.

Preferably, the component of group (iv) is selected from a pyrazole

(thio)semicarbazone compound, a keto acid compound, a leuco dye or a compound formed from a salicylic aldehyde or salicylic ketone compound.

Preferably, the component of group (iv) is selected from a pyrazole

(thio)semicarbazone compound, a keto acid compound, an oxyanion of a multivalent metal or a compound formed from a salicylic aldehyde or salicylic ketone compound.

Preferably, the composition comprises a component of group (ii), a component of group (iii) and an oxyanion of a multivalent metal (a component of group (iv)).

Preferably, the composition comprises a component of group (i), a component of group (ii) and an oxyanion of a multivalent metal (a component of group (iv)).

It will be understood by a skilled person that the coloured state of the component of group (iv) is stable under ambient conditions.

It will be appreciated that a composition comprising the two or more components of groups (i) to (iii) and at least one component of group (iv) enables the production of a broad range of colours in the formation of an image. The different first, second, third and fourth stimuli and temperatures can be applied in different combinations as required across the whole composition or at particular localised positions, enabling the formation many different colours. It will be appreciated that the stimuli and temperatures used are dependent upon the components present in the composition. The invention thus enables the formation of desired single- and multi-coloured images with a broad colour gamut.

Preferably, the colour of the coloured state of the component of group (iv) is selected from red, orange, black, blue and yellow.

If present, the component of group (iv) may be present in the composition in any suitable amount. It will be appreciated that the amount of the component of group (iv) individually present in the composition will depend upon the other components present in the composition, the application method utilised for applying or incorporating the composition to or into the substrate, the substrate type and the desired end use of the substrate. Preferably, the composition comprises from 0.1 to 50%, such as from 0.1 to 40 %, or even from 3 to 30 % of the component of group (iv) based on the total solid weight of the composition. Most preferably, the composition comprises from 5 to 25 % of the component of group (iv) based on the total solid weight of the composition.

If required, the acid or base-generating agent relating to the component of group (iv) may be present in the composition in any suitable amount. Preferably, the composition comprises from 1 to 50 %, such as from 5 to 40 % of the acid or base-generating agent based on the total solid weight of the composition. Most preferably, the composition comprises from 5 to 30 % of the acid or base- generating agent based on the total solid weight of the composition.

If required, the ratio of the acid- or base-generating agent to the component of group (iv) based on the total solid weight of the composition may be from 4: 1 to 1 :4, preferably from 3: 1 to 1 :3, and more preferably from 2:1 to 1 :2.

It will be appreciated that if the composition according to the first aspect of the present invention comprises a component of group (iv), the composition may be formed through the combination of formulations containing different components of the composition, for example a component of group (ii) may be in a separate formulation to the component of group (iv), the two formulations being combined to form the composition according to the first aspect of the present invention. It will further be appreciated formulation of the component of group (iv) may itself be formulated in two formulations if, for example, the component of group (iv) requires an accompanying acid- or base-generating agent, this may be in a separate formulation to the component of group (iv).

The compositions according to the first aspect of the present invention may be applied to or incorporated within any suitable substrate. It will be appreciated by a skilled person that the components of a composition will likely vary depending on the substrate to which the composition is to be applied or incorporated within.

Thus, according to a second aspect of the present invention, there is provided a substrate comprising the composition according to the first aspect of the present invention applied to or incorporated within.

Examples of suitable substrates to which the composition may be applied, include, but are not limited to: polymers and recycled polymer materials such as polyethylene terephthalate (PET), polyethylene (PE), low density polyethylene (LDPE), high density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), orientated polypropylene (OPP), biaxially orientated polypropylene (BOPP), cast polypropylene (CPP), polyamide (PA) such as nylon, polyvinyl chloride (PVC), or combinations thereof; cellulose; glass; plastic; metal and metal foils; textiles; paper; corrugated paperboard, cardboard, and equivalent recycled analogues, or combinations thereof; ceramics; foodstuffs and pharmaceutical preparations; or combinations thereof, e.g. polymer lined paper. The polymer and recycled polymer materials may be in the form of polymer film substrates.

Examples of suitable substrates within which the composition may be incorporated include, but are not limited to: polymers and recycled polymer materials such as polyethylene terephthalate (PET), polyethylene (PE), low density polyethylene (LDPE), high density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), orientated polypropylene (OPP), biaxially orientated polypropylene (BOPP), cast polypropylene (CPP), polyamide (PA) such as nylon, polyvinyl chloride (PVC), or combinations thereof; and any thermoplastic material such as plastic; or combinations thereof. The polymer and recycled polymer materials may be in the form of polymer film substrates.

Preferably, the substrate to which the composition is applied is a polymer film substrate. Preferably, the substrate is colourless (i.e. transparent or translucent), off-white or white. Preferably, the substrate is colourless, and is a polymer film substrate.

It will be appreciated by a skilled person that the substrate to which the composition has been applied to or incorporated within may itself be applied to a further substrate. Examples of further substrates include, but are not limited to the following: polymers and recycled polymer materials such as polyethylene terephthalate (PET), polyethylene (PE), low density polyethylene (LDPE), high density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), orientated polypropylene (OPP), biaxially orientated polypropylene (BOPP), cast polypropylene (CPP), polyamide (PA) such as nylon, polyvinyl chloride (PVC), or combinations thereof; cellulose; glass; plastic; metal and metal foils; textiles; paper; corrugated paperboard, cardboard, and equivalent recycled analogues, or combinations thereof; ceramics; foodstuffs and pharmaceutical preparations; or combinations thereof e.g. polymer lined paper. The polymers and recycled polymer materials may be in the form of polymer film substrates.

The composition according to the first aspect of the present invention, or substrate according to the second aspect of the present invention to which the composition has been applied to or incorporated within, may be suitable for end use as labels (adhesive or wraparound) and/or in, for example, fast-moving consumer goods; packaging such as disposable packaging including food and hot or cold beverage containers; hygiene and personal care product packaging such as shampoo bottles; cosmetic product packaging; medical and diagnostic devices and associated packaging; and outdoor products such as signage.

Preferably, the substrate comprises an additional adhesive layer. It will be appreciated that this additional adhesive layer is operable to apply the substrate to a further substrate and any other material and is therefore on an exterior surface of the substrate. The adhesive layer may cover all, substantially all, or part of the surface area of an exterior surface of the substrate. When the composition is applied to the substrate, the additional adhesive layer is preferably on an exterior surface of the substrate other than that to which the composition is applied.

Preferably, the composition according to the first aspect of the present invention is applied on a substrate.

When the composition according to the first aspect of the present invention is applied on a substrate, the substrate may further comprise an additional component of group (i) to (iv) either incorporated within or applied to the substrate. Preferably, the additional component of group (i) to (iv) is applied to the substrate. If the additional component of group (i) to (iv) is applied to the substrate, this may be in a layer on the substrate formed from a composition comprising the additional component of group (i) to (iv), the composition being as defined above for the composition according to the first aspect of the present invention, the two or more components of groups (i) to (iii) being replaced by the additional component of group (i) to (iv). This layer comprising the additional component of group (i) to (iv) may be applied to the substrate underneath the composition according to the first aspect of the present invention applied to the substrate, or applied over the composition according to the first aspect of the present invention applied on the substrate. Preferably, the additional component of group (i) to (iv) is a component of group (iv), and applied to the substrate as a composition comprising a component of group (iv).

Thus, according to a third aspect of the present invention, there is provided a method of forming a substrate comprising applying to or incorporating within the substrate the composition according to the first aspect of the present invention.

The composition may be applied to the substrate by any suitable method. Methods of applying the composition to a substrate will be well known to a person skilled in the art. Suitable application methods include, but are not limited to the following: flexographic printing, gravure printing, screen printing, offset printing and meyer bar coating. The composition may be applied to all, substantially all or part of the surface area of an exterior surface of the substrate.

The composition may be applied on the substrate to any suitable coat weight dependent upon both the substrate to which the composition is applied and the application method. Preferably, the composition is applied to a coat weight of from 0.1 to 50 gsm (grams per square metre), more preferably from 0.1 to 25 gsm and most preferably, 0.1 to 15 gsm. This coat weight is per individual layer of the composition that is applied to the substrate.

The coat weight may be measured by any suitable method. Suitable measuring methods will be well known to those skilled in the art. Preferably, the coat weight is measured by weighing the same area of substrate with and without the composition applied thereto, and comparing the two weights.

The composition may be applied to the substrate as a single layer or as part of a multi-layer system. The composition may be applied to the substrate as an undercoat or an overcoat, on top of a primer or as a primer layer. The composition may be applied to the substrate once or multiple times. The composition may be applied to at least part or all of an exterior surface of the substrate. As discussed above in relation to the second aspect of the present invention, a layer comprising an additional component of group (i) to (iv) may be applied underneath the composition applied to the substrate, or applied over the composition applied on the substrate.

The composition according to the present invention may be incorporated within the substrate by any suitable method. Methods of incorporating the composition within a substrate will be well known to a person skilled in the art. Suitable incorporation methods include, but are not limited to: extrusion methods including melt extrusion; injection molding; blow molding; compression molding; film insert molding; gas assisted molding; rotational molding; structural foam molding; thermoforming; and combinations thereof. It will be appreciated by a skilled person that the composition may be incorporated within the substrate on its own or as part of a solid and/or liquid masterbatch.

The composition may be incorporated within a substrate to any suitable weight percentage of the total solid weight of the substrate. Preferably, the substrate comprises 0.001 to 50 % of the composition incorporated within, based on the total solid weight of the substrate. More preferably, the substrate comprises 0.002 to 30 % of the composition incorporated within, based on the total solid weight of the substrate. Most preferably, the substrate comprises 0.003 to 20 % of the composition incorporated within, based on the total solid weight of the substrate.

Preferably, the composition according to the first aspect of the present invention is applied to the substrate.

The application to, or incorporation of the composition within the substrate enables an image to be formed on or within the substrate. It will be appreciated that the composition enables a single- or multi-coloured image to be formed on or within the substrate.

Thus, according to a fourth aspect of the present invention there is provided a method of forming colour on or within a substrate comprising the composition according to the first aspect of the present invention applied to or incorporated within, the method comprising applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, second temperature and third temperature as required to develop the coloured states of the components of groups (i) to (iii) present in the composition.

According to a fifth aspect of the present invention there is provided a method of forming an image on or within a substrate comprising the composition according to the first aspect of the present invention applied to or incorporated within, the method comprising applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, first temperature, second temperature and third temperature as required to develop the non-coloured and/or coloured states of the components of groups (i) to (iii) present in the composition, and thereby create an image on or within the substrate.

It will be understood by a skilled person that the first, second and third applied stimuli and first, second and third temperatures may each be applied to the composition such that the non-coloured states and/or coloured states of the components of groups (i) to (iii) are present at different localised positions of the composition to create an image. The non-coloured states and coloured states of the components of groups (i) to (iii) present in the composition can be selectively developed at localised positions. Suitable means for applying the first, second and third applied stimuli and first, second and third temperatures are as discussed above.

It will further be understood by a skilled person that the application of the first, second, and third applied stimuli and first, second and third temperatures to the composition, will be conducted in the appropriate order required to form the desired image. This can facilitate the formation of a multi-coloured image.

It will be understood by a skilled person that more than one of the first applied stimulus, second applied stimulus, third applied stimulus, first temperature, second temperature an third temperature may be applied at the same localised position. For example, in order to form a colour resulting from the mixing of two colours (i.e. the mixing of the colours of a coloured state of a component of group (ii) and a coloured state of a component of group (iii) of a different colour) the second applied stimulus, the third temperature and the third applied stimulus may be applied to that particular localised position of the composition.

It will be appreciated by a skilled person that the relationship between the first, second and third temperatures will vary dependent upon the colours required in the image that is to be formed. It will be appreciated by a skilled person that the relationship between the wavelengths of the first, second and third applied applied stimuli will vary dependent upon the colours required in the image that is to be formed so as to facilitate formation of the desired image. Optionally, a separate conductive source of temperature may also be provided to the composition before, during or after the formation of the image. Conductive sources of temperature include, but are not limited to the following: sources of steam and hot air, lamps, heat tunnels, LED(s), thermal print heads, hotplates, thermal conductors, hot liquids, and heated substrates.

It will further be appreciated that where the composition according to the first aspect of the present invention applied to or incorporated within the substrate further comprises a component of group (iv), the method of forming an image on the substrate comprising the composition may include the application of a fourth applied stimulus or fourth temperature to effect the transition of the component of group (iv) from its non-coloured state to a coloured state. In addition, if the composition comprises at least one component of group (iv), it will be appreciated that the application of the first, second, third and fourth applied stimuli and the first, second, third and fourth temperatures will be conducted in the appropriate order as required to selectively develop the non-coloured and/or coloured states of the components of groups (i) to (iv) present in the composition at localised positions of the composition. When the composition comprises a component of group (iv), suitable means for applying the fourth applied stimulus or fourth temperature are as discussed above.

It will be understood by a skilled person that more than one of the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, first, temperature, second temperature, third temperature and fourth temperature may be applied at the same localised position. For example, in order to form a colour resulting from the mixing of two colours (i.e. the mixing of the colours of a coloured state of a component of group (iii) and a coloured state of a component of group (iv) of a different colour) the third temperature, third applied stimulus and fourth temperature may be applied to that particular localised position of the composition.

It will be appreciated by a skilled person that the relationship between the first, second, third and fourth temperatures will vary dependent upon the colours required in the image that is to be formed. It will be appreciated by a skilled person that the relationship between the wavelengths of the first, second, third and fourth applied stimuli will vary dependent upon the colours required in the image that is to be formed so as to facilitate formation of the desired image.

According to a sixth aspect of the present invention, there is provided a use of the composition according to the first aspect of the present invention in the formation of colour on or within a substrate.

According to an seventh aspect of the present invention, there is provided a use of the composition according to the first aspect of the present invention in the formation of an image on or within a substrate.

According to an eighth aspect of the present invention, there is provided a substrate having applied thereon a plurality of discrete layers, wherein the plurality of discrete layers comprise two or more components selected from the following groups (i) to (iii):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow the transition to occur, where said activation occurs by application of a third temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and the two or more components selected from groups (i) to (iii) are present in different layers of the plurality of discrete layers applied on the substrate.

In the eighth aspect of the present invention, components of groups (i) to (iii) are as defined above throughout the first to seventh aspects of the present invention. In addition, the first applied stimulus, second applied stimulus, third applied stimulus, first temperature, second temperature and third temperature are as defined throughout the first to seventh aspects of the present invention, and the term "two or more" is as defined throughout the first to seventh aspects of the present invention. It will be further appreciated that the substrate according to the eighth aspect of the present invention is based upon the substrate according to the second aspect of the present invention, the substrate according to the second aspect of the present invention having a composition layer applied to or incorporated within, and the substrate according to the eighth aspect of the present invention having a plurality of discrete layers applied thereon.

It will also be appreciated that by the two or more components of groups (i) to (iii) being in different layers is meant that at least two of the two or more components are present in different discrete layers of the plurality of discrete layers of the substrate according to the eighth aspect of the present invention. If more than two components are present, e.g. three components are present, the plurality of discrete layers may comprise:

(a) a component of group (i) to (iii) in a first discrete layer, a component of group (i) to (iii) in a second different discrete layer, and a component of group (i) to (iii) in a third different discrete layer (different to the first and second discrete layers); or

(b) a component of group (i) to (iii) in a first layer, and a component of group (i) to (iii) in a second different discrete layer, and a component of group (i) to (iii) additionally present in either of the first or second discrete layers. Preferably, (a) a component of group (i) to (iii) in a first discrete layer, a component of group (i) to (iii) in a second different discrete layer, and a component of group (i) to (iii) in a third different discrete layer (different to the first and second discrete layers).

The layers can be in any order on the substrate.

The plurality of discrete layers may comprise one or more additional layers. Suitable additional layers may be selected from, but not limited to: thermal insulating layers; polymer layers; radiation blocking layers such as layers comprising UV absorbing components or layers comprising UV absorbing components; primers; adhesion promoting layers; overprint varnish layers; quenching layers; layers comprising hindered amine light stabilisers; barrier layers; diffusion barrier layers; and combinations thereof.

Preferably, the plurality of discrete layers comprises a discrete layer comprising a component of group (ii) and a different discrete layer comprising a component of group (iii), or a discrete layer comprising a component of group (ii) and a different discrete layer comprising a component of group (i), or a discrete layer comprising a component of group (i) and a different discrete layer comprising a component of group (ii).

The plurality of discrete layers may further comprise a component selected from group (iv), i.e. a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature. The components of group (iv), fourth applied stimulus and fourth temperature are as defined above for the first to seventh aspects of the present invention. The component of group (iv) may be present in one of the discrete layers comprising a component of group (i) to (iii) of the substrate according to the eighth aspect of the present invention, or the component of group (iv) may be in a different separate discrete layer of the plurality of discrete layers. Preferably, the component of group (iv) is present in a separate discrete layer of the plurality of discrete layers, i.e. the layer comprising a component of group (iv) is different to the layers of the plurality of discrete layers that comprise the two or more components of groups (i) to (iii). For example, the substrate according to the eighth aspect of the present invention may comprise a first discrete layer comprising a component of group (i) to (iii), a second different discrete layer comprising a component of group (i) to (iii), and a third different discrete layer comprising a component of group (iv). If more than one component of group (iv) is required, this may be present in any of the defined discrete layers.

Preferably, the component of group (iv) is selected from a pyrazole

(thio)semicarbazone compound, a keto acid compound, a leuco dye or a compound formed from a salicylic aldehyde or salicylic ketone compound.

Preferably, the component of group (iv) is selected from a pyrazole

(thio)semicarbazone compound, a keto acid compound, an oxyanion of a multivalent metal or a compound formed from a salicylic aldehyde or salicylic ketone compound.

Preferably, the plurality of discrete layers comprise a component of group (ii), a component of group (iii) and an oxyanion of a multivalent metal (a component of group (iv)). Preferably, each of the three components are in different discrete layers of the plurality of discrete layers.

Preferably, the composition comprises a component of group (i), a component of group (ii) and an oxyanion of a multivalent metal (a component of group (iv)). Preferably, each of the three components are in different discrete layers of the plurality of discrete layers.

It will be understood by a skilled person that the coloured state of the component of group (iv) is stable under ambient conditions.

It will further be appreciated that each discrete layer comprising one of the two or more components of groups (i) to (iii) and/or component of group (iv) is preferably formed of a composition applied to the substrate. When the discrete layers are formed from such compositions, each of the two or more components of groups (i) to (iii), and/or component of group (iv) may be present in those individual compositions in any suitable amount, preferably from 5 to 60% of the total solid weight of the composition, or even from 5 to 50%, or 5 to 35% of the total solid weight of the composition, or even from 5 to 15% of the total solid weight of the composition. Such compositions are formulated with other components such as NIR absorbers, binders, solvents and additives as defined above for the composition according any aspects of the present invention disclosed herein. It will be further be appreciated that any acid- or base- generating agent associated with a component of group (iv) will be as defined above in relation to the previous aspects of the present invention, and will be present in the same layer of the plurality of discrete layers as the component of group (iv) to which it relates, i.e. will be present in the same composition forming the discrete layer comprising the component of group (iv) in amounts as defined above in relation to the previous aspects of the present invention.

It will further be appreciated that, as defined above for the composition according to the first aspect of the present invention, the plurality of discrete layers of the substrate according to the eighth aspect of the present invention will not comprise a component of group (i) and a component of group (iv) where the component of group (iv) is a compound of formula (VII) or (VIII).

It will be appreciated by a skilled person that if the plurality of discrete layers comprises one or more additional layers and these one or more additional layers are positioned between the discrete layers comprising each of the two or more components of groups (i) to (iii) and/or component of group (iv), the one or more additional layers mean that the first applied stimulus, second applied stimulus, third applied stimulus, first temperature, second temperature, third temperature and if required, fourth applied stimulus or fourth temperature can be applied to the substrate from both sides in order to form multi-coloured images, the two sides being defined by the one or more additional layers separating the layers comprising the each of the two or more components of groups (i) to (iiiof component of group (iv). The plurality of discrete layers may have any suitable overall coat weight. Preferably, the plurality of discrete layers individually have a coat weight as set out above in relation to the composition according to the first aspect of the present invention. Further, preferably the plurality of discrete layers have an overall coat weight (encompassing all layers) of less than 100 gsm (grams per square metre), more preferably less than 50 gsm, and most preferably less than 30 gsmlt will be appreciated by a skilled person that the overall coat weight of the plurality of discrete layers will be dependent upon the layer formation.

The substrate according to the eighth aspect of the present invention may be suitable for end use as labels (adhesive or wraparound) and/or, in fast-moving consumer goods; packaging such as disposable packaging including food and hot or cold beverage containers; hygiene and personal care product packaging such as shampoo bottles; cosmetic product packaging; medical and diagnostic devices and associated packaging; and outdoor products such as signage.

In the context of the eighth aspect of the present invention, the plurality of discrete layers may be applied to any suitable substrate. It will be appreciated by a skilled person that the layer structure of the plurality of discrete layers may vary depending on the substrate to which it is to be applied. The substrates to which the plurality of discrete layers may be applied are as described above in relation to the substrate according to the second aspect of the present invention.

Examples of suitable substrates to which the plurality of discrete layers may be applied to, include, but are not limited to: polymers and recycled polymer materials such as polyethylene terephthalate (PET), polyethylene (PE), low density polyethylene (LDPE), high density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), orientated polypropylene (OPP), biaxially orientated polypropylene (BOPP), cast polypropylene (CPP), polyamide (PA) such as nylon, polyvinyl chloride (PVC), or combinations thereof; cellulose; glass; plastic; metal and metal foils; textiles; paper; corrugated paperboard, cardboard, and equivalent recycled analogues, or combinations thereof; ceramics; foodstuffs and pharmaceutical preparations; or combinations thereof, e.g. polymer lined paper. The polymers and recycled polymer materials may be in the form of polymer film substrates.

Preferably, the substrate to which the plurality of discrete layers are applied is a polymer film substrate. Preferably, the substrate is colourless (i.e. transparent or translucent), off-white or white. Preferably, the substrate is colourless, and is a polymer film substrate.

It will be appreciated by a skilled person that the substrate to which the plurality of discrete layers have been applied to may itself be applied to a further substrate. Examples of further substrates include, but are not limited to the following: polymers and recycled polymer materials such as polyethylene terephthalate (PET), polyethylene (PE), low density polyethylene (LDPE), high density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), orientated polypropylene (OPP), biaxially orientated polypropylene (BOPP), cast polypropylene (CPP), polyamide (PA) such as nylon, polyvinyl chloride (PVC), or combinations thereof; cellulose; glass; plastic; metal and metal foils; textiles; paper; corrugated paperboard, cardboard, and equivalent recycled analogues, or combinations thereof; ceramics; foodstuffs and pharmaceutical preparations; or combinations thereof, e.g. polymer lined paper. The polymers and recycled polymer materials may be in the form of polymer film substrates.

Preferably, the substrate to which the plurality of discrete layers are applied comprises an additional adhesive layer. It will be appreciated that this additional adhesive layer is operable to apply the substrate to a further substrate and is therefore on an exterior surface of the substrate. The adhesive layer may cover all, substantially all, or part of the surface area of an exterior surface of the substrate.

Thus, according to a ninth aspect of the present invention there is provided a method of forming a substrate according to the eighth aspect of the present invention, the method comprising applying to a substrate the plurality of discrete layers. It will be appreciated that the method of forming the substrate according to the thirteenth aspect of the present invention is as defined above for the third aspect of the present invention.

The plurality of discrete layers may be applied to the substrate by any suitable method. Methods of applying the plurality of discrete layers to a substrate will be well known to a person skilled in the art. Suitable application methods include, but are not limited to the following: flexographic printing, gravure printing, screen printing, offset printing and meyer bar coating. The plurality of discrete layers may be applied to all, substantially all or part of the surface area of the substrate. The plurality of discrete layers are applied to the substrate layer by layer in the required order. The application of the plurality of discrete layers to the substrate enables an image to be formed on the substrate.

Thus, according to a tenth aspect of the present invention, there is provided a method of forming colour on a substrate according to the eighth aspect of the present invention, the method comprising applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, second temperature and third temperature as required to develop the coloured states of the components of groups (i) to (iii) present in the plurality of discrete layers.

According to an eleventh aspect of the present invention there is provided a method of forming an image on a substrate according to the eighth aspect of the present invention, the method comprising applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, first temperature, second temperature and third temperature as required to develop the non-coloured and/or coloured states of the components of groups (i) to (iii) present in the plurality of discrete layers, and thereby create an image on the substrate.

It will be appreciated that the methods of forming colour and an image according to the tenth and eleventh aspects of the present invention require similar considerations to those defined above for the fourth and fifth aspects of the present invention. It will be understood by a skilled person that the first, second and third applied stimuli and first, second and third temperatures may each be applied to the substrate such that the non-coloured states and/or coloured states of the components of groups (i) to (iii) are present at different localised positions. The non-coloured states and coloured states of the components of groups (i) to (iii) present in the plurality of discrete layers can be selectively developed at localised positions. Suitable means for applying the first, second and third applied stimuli and first, second and third temperatures are as discussed above.

It will further be understood by a skilled person that the application of the first, second, and third applied stimuli and first, second and third temperatures to the substrate will be conducted in the appropriate order required to form the desired image. This can facilitate the formation of a multi-coloured image.

It will be understood by a skilled person that more than one of the first applied stimulus, second applied stimulus, third applied stimulus and first, temperature, second temperature and third temperature may be applied at the same localised position. For example, in order to form a colour resulting from the mixing of two colours (i.e. the mixing of the colours of a coloured state of a component of group (ii) and a coloured state of a component of group (iii) of a different colour) the second applied stimulus, the third temperature and the third applied stimulus may be applied to that particular localised position of the composition.

It will be appreciated that the ordering of the plurality of discrete layers on the substrate according to the eighth aspect of the invention can have an effect on colour formed. When the means used to apply the first applied stimulus, second applied stimulus, third applied stimulus and second temperature is a laser source(s), the fluence received by each layer varies dependent upon the position of the two or more components of groups (i) to (iii) in the layer structure of the plurality of discrete layers relative to the means.

It will be appreciated by a skilled person that the relationship between the first, second and third temperatures will vary dependent upon the colours required in the image that is to be formed. It will be appreciated by a skilled person that the relationship between the wavelengths of the first, second and third applied stimuli will vary dependent upon the colours required in the image that is to be formed so as to facilitate formation of the desired image.

Optionally, a separate conductive source of temperature may also be provided to the composition before, during or after the formation of the image. Conductive sources of temperature include, but are not limited to the following: sources of steam and hot air, lamps, heat tunnels, LED(s), thermal print heads, hotplates, thermal conductors, hot liquids, and heated substrates.

It will further be appreciated that where the plurality of discrete layers of the substrate of the eighth aspect of the present invention may further comprise a discrete layer comprising a component of group (iv), the method of forming an image on the substrate may include the application of a fourth applied stimulus or fourth temperature to effect the transition of the component of group (iv) from its non-coloured state to a coloured state. In addition, if the plurality of discrete layers comprise at least one component of group (iv), it will be appreciated that the application of the first, second, third and fourth applied stimuli and the first, second, third and fourth temperatures will be conducted in the appropriate order as required to selectively develop the non-coloured and/or coloured states of the components of groups (i) to (iv) present in the plurality of discrete layers at localised positions. When the plurality of discrete layers comprises a component of group (iv), suitable means for applying the fourth applied stimulus or fourth temperature are as discussed above.

It will be understood by a skilled person that more than one of the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, first temperature, second temperature, third temperature and fourth temperature may be applied at the same localised position. For example, in order to form a colour resulting from the mixing of two colours (i.e. the mixing of the colours of a coloured state of a component of group (iii) and a coloured state of a component of group (iv) of a different colour) the third temperature, third applied stimulus and fourth temperature may be applied to that particular localised position of the composition. It will be appreciated by a skilled person that the relationship between the first, second, third and fourth temperatures will vary dependent upon the colours required in the image that is to be formed. It will be appreciated by a skilled person that the relationship between the wavelengths of the first, second, third and fourth applied stimuli will vary dependent upon the colours required in the image that is to be formed so as to facilitate formation of the desired image.

According to a twelfth aspect of the present invention, there is provided a composition comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, and optionally wherein the composition does not comprise a combination of only components of groups (iii) and (iv) wherein the component of group (iv) is a leuco dye or oxyanion of a multivalent metal.

By "two or more" in relation to the components of groups (i) to (iv), is meant that there always has to be at least two components present in the composition, the first of the two components being selected from one of the component groups (i) to (iv), and the second of the two components being selected from a different one of the first, second, third and fourth component groups (i) to (iv). However, in the context of the present invention, if the composition comprises more than two components, as long as at least two of the components are selected from different component groups (i) to (iv), the remaining components may be a component of any of the component groups (i) to (iv), such that there may be two components in the same component groups (i) to (iv), e.g. two components from component group (iv). It will be appreciated by a skilled person that no matter how many components from groups (i) to (iv) are present in the composition, if formed, each of the coloured states of the components will have a different colour, even if two components from the same group are present in the composition. It will also be appreciated by a skilled person that if two components in the composition are from the same component group (i), (ii), (iii) or (iv), the appropriate temperatures and applied stimuli associated with each of those components will vary dependent upon the individual component.

The components of groups (i) to (iv) of the composition of the twelfth aspect of the present invention are as defined above in relation to the first or any previous aspects of the present invention. In addition, each of the first, second, third and fourth applied stimuli and temperatures are as defined above in relation to the first or any previous aspects of the present invention. It will be appreciated that the composition of the twelfth aspect of the present invention is based upon the composition according to the first aspect of the present invention with the additional selection option of a component from group (iv) for the two or more components.

Preferably, the composition comprises a component of group (ii) and a leuco dye (component of group (iv)). Preferably, the composition comprising a component of group (ii), a leuco dye (component of group (iv)), and an oxyanion of a multivalent metal (component of group (iv)).

Preferably, the composition comprises a component of group (ii), a component of group (ii) and an oxyanion of a multivalent metal (component of group (iv)).

Preferably, the composition comprises a component of group (i) and a component of group (iii).

Preferably, the composition comprises a component of group (iii) and a pyrazole (thio)semicarbazone (component of group (iv)). Preferably, the composition comprises a component of group (i), a component of group (ii) and an oxyanion of a multivalent metal (component of group (iv)).

Preferably, the composition comprises a component of group (ii), a pyrazole (thio)semicarbazone (component of group (iv)) and an oxyanion of a multivalent metal (component of group (iv)). Preferably, the composition comprises a component of group (iii), a keto acid compound (component of group (iv)) and an oxyanion of a multivalent metal (component of group (iv)).

Preferably, the composition comprises a component of group (iii) and a keto acid compound (component of group (iv)). Preferably, the composition comprises a component of group (ii) and a keto acid compound (component of group (iv)).

Preferably, the composition comprises a component of group (ii) and a compound formed from a salicylic aldehyde or salicylic ketone compound (a component of group (iv)). Preferably, the composition comprises a component of group (iii) and a compound formed from a salicylic aldehyde or salicylic ketone compound (a component of group (iv)).

According to a thirteenth aspect of the present invention, there is provided a substrate having the composition according to the twelfth aspect of the present applied to or incorporated within.

It will be appreciated that the substrate according to the thirteenth aspect of the present invention is as defined above for the substrate according to the second aspect of the present invention, the composition of the first aspect being replaced by the composition of the twelfth aspect of the present invention.

According to a fourteenth aspect of the present invention, there is provided a method of forming a substrate comprising applying to or incorporating within a substrate the composition according to the twelfth aspect of the present invention.

It will be appreciated that the method according to the fourteenth aspect of the present invention is as defined for the method according to the third aspect of the present invention, the composition of the first aspect being replaced by the composition of the twelfth aspect of the present invention.

According to a fifteenth aspect of the present invention, there is provided a method of forming colour on or within a substrate comprising the composition according to the twelfth aspect of the present invention applied to or incorporated within, the method comprising applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, second temperature, third temperature and fourth temperature as required to develop the coloured states of the components of groups (i) to (iv) present in the composition.

According to a sixteenth aspect of the present invention, there is provided a method of forming an image on or within a substrate comprising the composition according to the twelfth aspect of the present invention applied to or incorporated within, the method comprising applying to the composition on or within the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, first temperature, second temperature, third temperature and fourth temperature as required to develop the non- coloured and/or coloured states of the components of groups (i) to (iv) present in the composition, and thereby create an image on or within the substrate.

It will be appreciated that the methods of the fifteenth and sixteenth aspects of the present invention are as defined for the fourth and fifth aspects of the present invention, the composition of the first aspect being replaced by the composition of the twelfth aspect of the present invention.

According to a seventeenth aspect of the present invention, there is provided a use of the composition according to the twelfth aspect of the present invention in the formation of colour on or within a substrate.

According to an eighteenth aspect of the present invention, there is provided a use of the composition according to the thirteenth aspect of the present invention in the formation of an image on or within a substrate.

According to a nineteenth aspect of the present invention, there is provided a substrate having applied thereon a plurality of discrete layers, the plurality of discrete layers comprising two or more components selected from the following groups (i) to (iv):

(i) a component capable of reversibly transitioning between a non-coloured state and a coloured state, the transition from the non-coloured state to the coloured state being effected by the application of a first applied stimulus and the transition from the coloured state to the non-coloured state being effected by the application of a first temperature;

(ii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a second applied stimulus, wherein the component can be deactivated, either before or after transitioning, by application of a second temperature, such that subsequent transitioning cannot occur;

(iii) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a third applied stimulus, wherein said component requires activation to allow transitioning to occur, where said activation occurs by application of a third temperature;

(iv) a component capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a fourth applied stimulus or fourth temperature; wherein, if formed, each of the coloured states of the two or more components has a different colour, wherein the two or more components selected from groups (i) to (iv) are present in different layers of the plurality of discrete layers applied on the substrate, and optionally, wherein the plurality of discrete layers do not comprise a combination of only components of groups (iii) and (iv) wherein the component of group (iv) is an oxyanion of a multivalent metal or a leuco dye.

It will be appreciated that the substrate of the nineteenth aspect of the present invention is based upon the substrate according to the eighth aspect of the present invention with the additional selection option of a component from group (iv) for the two or more components. It will be further appreciated that the substrate of the nineteenth aspect of the present invention is also based upon the substrate according to the thirteenth aspect of the present invention. It will be appreciated that the components of groups (i) to (iv) of the nineteenth aspect of the present invention are as defined above in relation to any of the previous aspects of the present invention. In addition, each of the first, second, third and fourth applied stimuli and temperatures are as defined above in relation to any of the previous aspects of the present invention.

It will be further appreciated that by the two or more components from groups (i) to (iv) being in different layers is meant that at least two of the two or more components are present in different discrete layers of the plurality of discrete layers of the substrate according to the nineteenth aspect of the present invention. If more than two components are present, e.g. three components are present, the plurality of discrete layers may comprise:

(a) a component of group (i) to (iv) in a first discrete layer, a component of group (i) to (iv) in a second different discrete layer, and a component of group (i) to (iv) in a third different discrete layer (different to the first and second discrete layers); or

(b) a component of group (i) to (iv) in a first layer, and a component of group (i) to (iv) in a second different discrete layer, and a component of group (i) to (iv) additionally present in either of the first or second discrete layers.

Preferably, (a) a component of group (i) to (vi) in a first discrete layer, a component of group (i) to (iv) in a second different discrete layer, and a component of group (i) to (iv) in a third different discrete layer (different to the first and second discrete layers).

The layers can be in any order on the substrate.

It is noted that two components may be present from the same group (i) to (iv), either in the same or different layers of the plurality of discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (ii) and a leuco dye (component of group (iv)), the two components being in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (ii), a leuco dye (component of group (iv)), and an oxyanion of a multivalent metal (component of group (iv)). Preferably, the three components are each present in different discrete layers. Preferably, the plurality of discrete layers comprises a component of group (ii), a component of group (ii) and an oxyanion of a multivalent metal (component of group (iv)). Preferably, the three components are each present in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (i) and a component of group (iii), the two components being in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (iii) and a pyrazole (thio)semicarbazone (component of group (iv)), the two components being in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (i), a component of group (ii) and an oxyanion of a multivalent metal (component of group (iv)). Preferably, the three components are each present in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (ii), a pyrazole (thio)semicarbazone (component of group (iv)) and an oxyanion of a multivalent metal (component of group (iv)). Preferably, the three components are each present in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (iii), a keto acid compound (component of group (iv)) and an oxyanion of a multivalent metal (component of group (iv)). Preferably, the three components are each present in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (iii) and a keto acid compound (component of group (iv)), the two components being in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (ii) and a keto acid compound (component of group (iv)), the two components being in different discrete layers. Preferably, the plurality of discrete layers comprises a component of group (ii) and a compound formed from a salicylic aldehyde or salicylic ketone compound (a component of group (iv)), the two components being in different discrete layers.

Preferably, the plurality of discrete layers comprises a component of group (iii) and a compound formed from a salicylic aldehyde or salicylic ketone compound (a component of group (iv)), the two components being in different discrete layers.

The plurality of discrete layers of the substrate according to the nineteenth aspect of the present invention preferably comprises three components, i.e. three components selected from groups (i) to (iv), each being in a different discrete layer of the plurality of discrete layers on the substrate.

According to a twentieth aspect of the present invention, there is provided a method of forming a substrate according to the nineteenth aspect of the present invention, the method comprising applying to a substrate the plurality of discrete layers.

It will be appreciated that the method according to the twentieth aspect of the present invention is as defined for the method according to the ninth aspect of the present invention, the plurality of discrete layers having the additional selection option of a component of group (iv) for the two or more components.

According to a twenty-first aspect of the present invention, there is provided a method of forming colour on the substrate according to the nineteenth aspect of the present invention, the method applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, second temperature, third temperature and fourth temperature as required to develop the coloured states of the components of groups (i) to (iv) present in the plurality of discrete layers.

According to a twenty-second aspect of the present invention, there is provided a method of forming an image on the substrate according to the nineteenth aspect of the present invention, the method comprising applying to the substrate, the first applied stimulus, second applied stimulus, third applied stimulus, fourth applied stimulus, first temperature, second temperature, third temperature and fourth temperature as required to develop the non-coloured and/or coloured states of the components of groups (i) to (iv) present in the plurality of discrete layers, and thereby create an image on the substrate.

It will be appreciated that the methods according to the twenty-first and twenty- second aspects of the present invention is as defined for the methods according to the tenth and eleventh aspects of the present invention, the plurality of discrete layers having the additional selection option of a component of group (iv) for the two or more components.

It will be appreciated by a skilled person that the radiation applied to the compositions or substrates disclosed herein, whether by a laser source(s) or flood illumination, is applied using an apparatus suitable for such purpose, i.e. suitable for calculating the radiation required relating to the different stimuli and temperatures required to produce a desired image and applying it to a composition or substrate. It will be appreciated that the apparatus will be programmed to effect the application of the different stimuli and temperatures to the compositions or substrates in the required order and facilitate the formation of an image.

Chemical Definitions

The term "C _{M S} alkyl" demotes a straight or branched saturated alkyl group having from 1 to 18 carbon atoms; optionally "C _{M S} alkyl" groups can contain some degree of unsaturation (partial unsaturation) i.e. may contain one or more alkene/alkenyl moiety(s). For parts of the range C _{M S} alkyl, all sub-groups thereof are contemplated, such as C _{M O} alkyl, C _{5-i 5} alkyl, C _5-i0 alkyl, and Ci _-6 alkyl. Examples of said Ci _-4 alkyl groups include methyl, ethyl, n-propyl, iso- propyl, n-butyl, iso-butyl, sec-butyl, and tert-butyl. The alkyl groups may be optionally substituted with one or more functional groups, including C _{M S} alkyl groups, "C _6- 12 aryl", and "C _{M S} alkoxy", halogen, and "C ₃ -i ₈ cycloalkyl". The term "C ₆ -12 aryl" denotes a monocyclic or polycyclic conjugated unsaturated ring system having from 6 to 12 carbon atoms. For parts of the range C _6- 12 aryl, all sub-groups thereof are contemplated, such as C _6-i o aryl, C _10-12 aryl, and C ₆ -s aryl. An aryl group includes condensed ring groups such as monocyclic ring groups, or bicyclic ring groups. Examples of C _6- 12 aryl groups include phenyl, biphenyl, indenyl, naphthyl or azulenyl. Condensed rings such as indan and tetrahydro naphthalene are also included in the C _6- 12 aryl group. The aryl groups may be optionally substituted with other functional groups. The aryl groups may be optionally substituted with one or more functional groups, including Ci-i ₈ alkyl groups, halogen, and "Ci-i ₈ alkoxy". The aryl groups may be substituted with these substituents at a single position on their unsaturated ring system, or may be substituted with these substituents at multiple positions on their unsaturated ring system.

The term "Ci-i ₈ alkoxy" denotes a straight of branched Ci-i ₈ alkyl group which is attached to the remainder of the molecule through an oxygen atom. For parts of the range Ci-i ₈ alkoxy, all sub-groups thereof are contemplated such as C1-10 alkoxy, C _{5-i 5} alkoxy, C _5-i0 alkoxy, and Ci _-6 alkoxy. Examples of said Ci _-4 alkoxy groups include methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, iso-butoxy, sec-butoxy, and tert-butoxy. The alkoxy groups may be optionally substituted with other functional groups. The alkoxy groups may be optionally substituted with one or more functional groups, including Ci-i ₈ alkyl groups, "C ₆ -12 aryl", and "Ci-i ₈ alkoxy", halogen, and "C _3-i8 cycloalkyl".

The term "C _3-i8 cycloalkyl" denotes a non-aromatic, saturated or partially saturated (i.e. may contain one or more alkene or alkenyl moiety(s)) monocyclic ring system having from 3 to 18 carbon atoms. For parts of the range C _{3-i 8} cycloalkyl, all sub-groups thereof are contemplated, such as C _3-8 cycloalkyl, C _{5-i 5} cycloalkyl, and C _5-i0 cycloalkyl. Examples of suitable C _3-i0 cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. The cycloalkyl groups may be optionally substituted with other functional groups. The cycloalkyl groups may be optionally substituted with one or more functional groups, including C _{1 -20} alkyl groups, "C _5-2 o aryl", "Ci _-20 alkoxy", "hydroxylCi _-20 alkoxy" and "C _3-i8 cycloalkyl". The terms“unsaturated” and“partially saturated” refer to rings wherein the ring structure(s) contains atoms sharing more than one valence bond i.e. the ring contains at least one multiple bond e.g. a C=C, CºC or N=C bond. The term “fully saturated” refers to rings where there are no multiple bonds between ring atoms.

“Optional” or “optionally” means that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances in which it does not.

"Halogen" refers to fluorine, chlorine, bromine or iodine.

The term "heterocycle" and "heterocyclic ring" denotes a non-aromatic, saturated or partially saturated monocyclic or polycylic ring system having from 4 to 18 ring atoms in which one or more of the ring atoms is not carbon, e.g. nitrogen, sulphur or oxygen. The said ring system may be attached to the rest of the molecule through either a heteroatom or a carbon atom of the ring system. Examples of heterocyclic groups include but are not limited to: piperidinyl, morpholinyl, homomorpholinyl, azepanyl, piperazinyl, oxo-piperazinyl, diazepinyl, tetrahydropyridinyl, tetrahydropyranyl, pyrrolidinyl, tetrahydrofuranyl and dihydropyrrolyl.

The terms “heteroaryl” and “heteroaromatic ring” denote a monocyclic or polycyclic hetero-aromatic group comprising 5 to 18 atoms in which one or more of the atoms are other than carbon, such as nitrogen, phosphorus, sulphur or oxygen. The said hetero-aromatic ring may be attached to the rest of the molecule through either a heteroatom or a carbon atom of the ring system. Examples of heteroaryl groups include but are not limited to furyl, pyrrolyl, thienyl, oxazolyl, isoxazolyl, oxadiazolyl, imidazolyl, oxatriazoly, thiazolyl, isothiazolyl, tetrazolyl, pyrazolyl, pyridinyl, pyrimidinyl, pyridazinyl, pyrazinyl, triazinyl and thiadiazolyl. In some embodiments, the heteroaryl group contains at least one ring nitrogen atom. The nitrogen atoms in the heteroaryl groups can be basic, as in the case of an imidazole or pyridine, or essentially non-basic as in the case of an indole or pyrrole nitrogen. In general the number of basic nitrogen atoms present in the heteroaryl group, including any amino group substituents of the ring, will be less than five.

The term“cyclic amino group” refers to a non-aromatic, fully saturated or partially unsaturated monocyclic ring system having from 4 to 18 ring atoms in which one of the ring atoms is nitrogen and the group is attached to the rest of the molecule via this nitrogen atom. In such cyclic amino groups, one or more of the remaining ring atoms may be other than carbon, such as nitrogen, sulphur or oxygen. Examples of such cyclic amino groups include piperidine (1-piperidinyl), pyrrolidine (1- pyrrolidinyl), pyrrolidone, morpholine or piperazine.

By "secondary amino group" is meant an amine group formed by replacement of two of the hydrogen atoms in ammonia by groups or atoms other than the hydrogen atoms, the group being attached to the rest of the molecule by the bond other than the two joining the two groups or atoms replacing the hydrogen atoms to the nitrogen atom.

All of the features contained herein may be combined with any of the above aspects and in any combination.

For a better understanding of the present invention, and to show embodiments of the same may be carried into effect, reference will now be made, by way of example, to the following experimental data.

Examples

General Procedure for the Synthesis of Components of Group (i) or Group (iv) of Compounds of Formula (VII) or (VIII)

Provided below is a general synthetic procedure for the production of components of group (i) or group (iv) of compounds of formula (VII) or (VIII):

Step 1 : Synthesis of a pyrazaole ring

A hydrazine and an ethyl-3-oxo-3-propanoate are refluxed together releasing ethanol and water, and forming a pyrazalone ring product having substituents A and B on the ring. The product is purified by precipitation or recrystallization from an appropriate solvent.

Step 2: Addition of a reactive ketone substituent

The pyrazalone ring product from step 1 is reacted with an acyl chloride in the presence of calcium hydroxide under reflux. The reactive ketone product is purified by either precipitation or recrystallization from an appropriate solvent.

Step 3: Formation of the semicarbazide

The condensation of the reactive ketone product from step with a hydrazine carboxamide in the presence of an acetic acid catalyst produces the final reaction product. The product is then purified by precipitation or recrystallization from an appropriate solvent.

Reversible and Irreversible Transition Data for Components of Group (i) and Components of Group (iv) of Compounds of Formula (VII) or (VIII) Compositions comprising a Component of Group (i) or Component of Group (iv) of Compounds of Formula (VII) or (VIII)

A composition 1 was formulated according to Table 1.

Table 1

A composition 2 was formulated according to Table 2.

Table 2

These two compositions represent a composition comprising a component of group (i) or component of group (iv) of a compound of formula (VII) or (VIII).

Compositions comprising a Component of Group (iv) of Formula (VII) or (VIII) and an acid-generating agent

A composition 3 comprising a component of group (iv) and an acid-generating agent is formulated according to a 50:50 mixture of the formulation of Table 1 with Table 3.

Table 3

A composition 4 comprising a component of group (iv) and an acid-generating agent is formulated according to a 50:50 mixture of the formulation of Table 2 with Table 3.

These two compositions represent a composition comprising a component of group (iv) and an acid-generating agent. Compositions comprising a Component of Group (iv) and a base-generating agent

A composition 5 comprising a component of group (iv) and a base-generating agent is formulated according to a 50:50 mixture of the formulation of Table 1 with Table 4.

Table 4

A composition 6 comprising a component of group (iv) and a base-generating agent is formulated according to a 50:50 mixture of the formulation of Table 2 with Table 4.

These two compositions represent a composition comprising a component of group (iv) and a base-generating agent.

Data Measurements

Compositions 1 to 6 are each applied to a 50 pm polyethylene substrate and a paper substrate using a 30pm K-bar applicator. For compositions 1 and 2, the compositions are also each applied to an additional 50 pm polyethylene substrate and a paper substrate. Component of group (iv): One set of the substrates coated with compositions 1 and 2, and the substrates coated with compositions 3 to 6 are exposed to IR radiation using a C0 ₂ laser such that the pale yellow coloured state of the component of group (iv) is formed (representative of the fourth temperature).

Component of group (i): The other set of the substrates coated with compositions 1 and 2 are exposed to broadband UV for 15 minutes using a mercury lamp such that the pale yellow coloured state is formed (representative of the first applied stimulus).

L*a*b* values of each of the coloured states of the compound of formula (I) in the compositions 1 to 6 (including both sets of compositions 1 and 2 were measured (CIE L*a*b* colour system, L* denotes lightness, a* denotes the red/green values, and b* denotes the yellow/blue values). DE is then calculated from the L*a*b* measurements and L*a*b* measurements for a standard white tile (before the application of a fourth temperature or first applied stimulus). DE Is a standard mathematical calculation which allows for the quantification of the visual perception of the difference between two colours (i.e. between the coloured state formed and the white tile). The calculation is given below:

Next, each substrate coated with the compositions (x2 sets of substrates coated with compositions 1 and 2, and the substrates coated with compositions 3 to 6) is heated to 140 °C using a hotplate and held for 5 minutes at this temperature (representative of the first temperature).

L*a*b measurements were then taken for each sample at the same imaged location as used previously, and the DE value in comparison to a standard white tile was again calculated for each composition.

By measuring the L*a*b* values and calculating DE values before and after the application of the fourth temperature and first applied stimulus, and again following the application of the first temperature, it could be determined where the coloured state remains the same (no different in DE after the application of the first temperature), or becomes less coloured, i.e. reverts back to the non- coloured state (a negative change in DE value after the application of the first temperature)

Resulting DE difference values in the range of -3 to 3 indicate that there is little change in the colour displayed upon application of the first temperature, whilst more negative DE values indicate thermal bleaching (i.e. a transition from the pale yellow coloured state back to the non-coloured state has occurred upon application of the first temperature). It is noted that for a DE of between -3 and 3, a difference in colour cannot be distinguished by the human eye. The results are tabulated below in Table 5. From these results, it is clear that if the fourth temperature is used to facilitate a transition from the non-coloured state to a coloured state, whether the compound of group (iv) is present in the composition alone or in combination with an acid- or base-generating agent, the transition is irreversible (i.e. DE difference values are between -3 and 3). In addition, if the first applied stimulus is used to facilitate a transition of the component of group (i) from the non-coloured to a coloured state (with no accompanying acid- or base-generating agent), the transition is reversible (i.e. DE difference values are large and negative) and the application of the first temperature facilitates a transition from the coloured state back to the non- coloured state.

Table 5

Specific Synthesis of a Component of Group (i) or Group (iv) of Compounds of

Formula (VII) or (VIII): (E)-2-((5-hvdroxy-1.3-diphenyl-1 H-oyrazol-4-yl)(4-

(trifluoromethyl)phenyl)methylene)-N-phenylhvdrazine-1 -carboxamide

For (E)-2-((5-hydroxy-1 ,3-diphenyl-1 H-pyrazol-4-yl)(4- (trifluoromethyl)phenyl)methylene)-N-phenylhydrazine-1 -carboxamide: A = phenyl, B = phenyl, C = phenyl substituted with CF ₃ , and D = phenyl.

Step One: Synthesis of 1 ,3-diphenyl-5-pyrazalone (DPP)

1. A 3 neck round bottom flask (rbf) fitted with a thermometer and stirrer bar is charged with Toluene (50 ml_, colourless liquid). 2. Ethyl 3-oxo-3-phenylpropanoate (100 g, 0.52 mmol, colourless liquid) is added to the round bottom flask.

3. Phenylhydrazine (56 g, 0.51 mmol, yellow liquid) is added to the round bottom flask and the mixture is stirred resulting in a pale-yellow solution. 50 ml of additional toluene is used to rinse any excess phenylhydrazine into the reaction.

4. A dean stark trap is fitted to the flask with a reflux condenser attached.

5. A heating block is used to heat the reaction solution to 110 °C.

6. The dean stark apparatus is used to remove water/ethanol and assess when the reaction has gone to completion (TLC may also be used to assess progress of reaction eluting with DCM/Heptane 4:1 ).

7. The reaction mixture is allowed to cool with stirring to avoid the formation of large clumps of product.

8. Once the reaction mixture is cool enough to handle, it is poured into a large beaker and any large product clumps are broken up with a spatula. 9. Heptane (-100 ml_) is added to the beaker and a large spatula is used to break up all the clumps rending the material into a relatively free flowing crystalline powder.

10. An additional 1.4 L of heptane is added and the product slurried overnight. 11. The pale-yellow solids are vacuum filtered and dried under vacuum (108.4 g,

88 %).

Step Two: Synthesis of (5-hvdroxy-1 ,3-diphenyl-1 H-pyrazol-4-yl)(4-

(trifluoromethvDphenvDmethanone Bn-DPP)

1. DPP (25.75 g, 109.0 mmol) is weighed and placed in a 3-neck round bottom flask (rbf) fitted with a stirrer, thermometer and dropping funnel.

2. 1 ,4-dioxane (300 ml_) is added and the mixture stirred until the DPP is dissolved, giving a pale-yellow solution.

3. Calcium hydroxide (24.22 g, 326.9 mmol) is added and the suspension stirred. 4. 4-(trifluoromethyl)benzoyl chloride (25.00 g, 119.9 mmol) is weighed into a beaker and dissolved in 1 ,4-dioxane (100 ml_).

5. The 4-(trifluoromethyl)benzoyl chloride solution is transferred to the dropping funnel.

6. The reaction suspension is cooled using a cold water-bath. 7. The 4-(trifluoromethyl)benzoyl chloride solution is added dropwise over 40 minutes ensuring that the reaction mixture does not exceed 50 °C.

8. The dropping funnel is replaced by a reflux condenser and the reaction mixture is heated to reflux and followed by TLC (DCM 20% EtOAc).

9. The reaction is stirred for 2 hours. 10. The reaction solution is allowed to cool back to 50 °C.

11. The reaction solution is poured into aqueous HCI (2 M,1.1 L, 2.18 mol) with strong stirring causing a pale-yellow precipitate to form which rapidly clumps and turns brown. 12. The suspension is stirred vigorously for approximately 2 hours.

13. The precipitate is vacuum filtered on paper and partially dried by suction giving a sandy brown solid.

14. The brown solids are transferred to a large beaker and slurried in hot I PA for around 3 hours, the solvent is allowed to cool while still slurrying. 15. The yellow solids are then vacuum filtered on paper and dried by suction for around 1 hour.

16. The yellow solids are transferred to a drying dish and dried in a vacuum oven (30 °C) over night (36.60 g, 82.24 %).

Step Three: Synthesis of (E)-2-((5-hvdroxy-1 ,3-diphenyl-1 H-oyrazol-4-yl)(4- (trifluoromethyl)phenyl)methylene)-N-phenylhvdrazine-1 -carboxamide

1. CF ₃ -Bn-DPP (20.08 g, 49.17 mmol) is weighed and placed into a 3-neck round bottom flask (rbf) fitted with a stirrer bar, thermometer and condenser.

2. 4-phenylsemicarbazide (8.18 g, 54.09 mmol) is weighed and placed into the round bottom flask. 3. Ethanol (200 ml_) is added to the reaction vessel and the mixture stirred.

4. Glacial acetic acid (0.1 M in ethanol, 5 ml_, 0.49 mmol) is added to the reaction mixture.

5. The reaction mixture is heated to reflux (80 °C) and followed by TLC (DCM 40% ethylacetate). 6. The reaction kis refluxed for 6 hours and then left to cool and stand over the weekend.

7. Over the weekend a large quantity of white precipitate formed, this is vacuum filtered on paper, washed with I PA and dried by suction for an hour.

8. The solids are placed in a beaker and dried under vacuum overnight (30 °C) giving an off-white fluffy powder (22.35 g, 83.9 %).

Specific Synthesis of a Component of Group (i) or Group (iv) of Compounds of Formula (VII) or (VIII): (E)-2-((5-hydroxy-1 ,3-diphenyl-1 H-pyrazole-4- yl)(phenyl)methylene)-N-phenylhydrazine-1 -carboxamide

For E)-2-((5-hydroxy-1 ,3-diphenyl-1 H-pyrazole-4-yl)(phenyl)methylene)-N- phenylhydrazine-1 -carboxamide: A = phenyl, B = phenyl, C = phenyl, and D = phenyl.

Step One: Synthesis of 1 ,3-diphenyl-5-pyrazalone (DPP)

1. A 3 neck round bottom flask (rbf) fitted with a thermometer and stirrer bar is charged with Toluene (50 ml_, colourless liquid).

2. Ethyl 3-oxo-3-phenylpropanoate (100 g, 0.52 mmol, colourless liquid) is added to the round bottom flask.

3. Phenylhydrazine (56 g, 0.51 mmol, yellow liquid) is added to the round bottom flask and the mixture is stirred resulting in a pale-yellow solution. 50 ml of additional toluene is used to rinse any excess phenylhydrazine into the reaction.

4. A dean stark trap is fitted to the flask with a reflux condenser attached.

5. A heating block is used to heat the reaction solution to 110 °C.

6. The dean stark apparatus is used to remove water/ethanol and assess when the reaction has gone to completion (TLC may also be used to assess progress of reaction eluting with DCM/Heptane 4:1 ). 7. The reaction mixture is allowed to cool with stirring to avoid the formation of large clumps of product.

8. Once the reaction mixture is cool enough to handle, it is poured into a large beaker and any large product clumps are broken up with a spatula.

9. Heptane (-100 ml_) is added to the beaker and a large spatula is used to break up all the clumps rending the material into a relatively free flowing crystalline powder.

10. An additional 1.4 L of heptane is added and the product slurried overnight.

11. The pale-yellow solids are vacuum filtered and dried under vacuum (108.4 g, 88 %).

Step Two: Synthesis of (5-hydroxy-1 ,3-diphenyl-1 H-pyrazol-4- yl)(phenyl)methanone (BnDPP)

1. DPP (18.39 g, 77.83 mmol) is weighed and placed in a 3-neck round bottom flask (rbf) fitted with a stirrer, thermometer and dropping funnel.

2. 1 ,4-dioxane (270 ml_) is added and the mixture stirred until the DPP is dissolved, giving a pale yellow solution.

3. Calcium Hydroxide (17.30 g, 233.5 mmol) is added and the suspension stirred.

4. Benzoyl chloride (9.94 ml_, 85.62 mmol) is added to the reaction mixture by syringe.

5. The reaction is heated to relux and monitored by TLC, after around 1.5 hours the reaction is complete.

6. The reaction solution is allowed to cool back to 70 °C.

7. The reaction solution is poured into aqueous HCI (2M, 500 ml_) with strong stirring causing a sandy coloured precipitate to form. 8. The precipitate is slurried in the HCI solution for around 40 minutes during which time the precipitate clumps together into brown lumps.

9. The precipitate is vacuum filtered on paper and partially dried by suction for around 10 minutes. 10. The solids are then slurried in hot I PA (300 ml_).

11. After 1 hour the slurry is allowed to cool and stirred for another 2 hours.

12. The now yellow solids are vacuum filtered on paper and transferred to a drying dish and then under vacuum giving a yellow solid (20.30 g, 76.2 %).

Step Three: Synthesis of E)-2-((5-hvdroxy-1 ,3-diphenyl-1 H-pyrazole-4- yl)(phenyl)methylene)-N-phenylhydrazine-1 -carboxamide

1. Bn-DPP (20.44 g, 60.05 mmol) and 4-phenylsemicarbazide (10.03 g, 66.35 mmol) are weighed and placed into a 3-neck round bottom flask fitted with a stirrer bar, thermometer and condenser.

2. Ethanol (230 ml_) is added to the reaction vessel and the mixture stirred giving a yellow suspension.

3. Glacial acetic acid solution (0.1 M in Ethanol, 6 ml_, 0.6 mmol) is added to the reaction mixture.

4. The reaction mixture is heated to reflux (79 °C) and stirred for around 6.5 hours. 5. The reaction is left to cool and stand overnight.

6. The reaction mixture is evaporated to dryness under vacuum yielding an amorphous yellow solid.

7. The product is then recrystallised from the minimum quantity of equal parts hot ethanol and isopropyl alcohol (IPA). 8. This results in a fine white precipitate forming which is broken up, vacuum filtered on paper and washed with a little I PA.

9. The product is dried under vacuum overnight giving a white powder (20.0 g, 70.3 %). General Procedure for the Synthesis of Components of Group (iv) of Formula

(XII) or (XIII):

1. The selected 2-hydroxyarylcarbonyl (aldehyde or ketone) (2.1 molar equivalent) is dissolved/suspended in ethanol (0.3 to 1.2 molar equivalent) in a 3-neck round bottom flask fitted with a dropping funnel, stirrer bar and thermometer.

2. A solution of hydrazine hydrate (35% or 79% w/v, 1.0 molar equivalent) in ethanol is prepared and placed in the dropping funnel.

3. The hydrazine hydrate solution is added with stirring over the course of 5 to 20 minutes to the solution of the 2-hydroxyarylcarbonyl. This addition may result in a small exotherm.

4. The dropping funnel is replaced with a condenser and the reaction mixture brought to reflux (80 °C).

5. The reaction mixture is refluxed with stirring for 5 hours and then left to cool overnight. 6. Once cooled, any precipitate which is formed is vacuum filtered on paper and washed with additional ethanol and optionally, additional water, to ensure the complete removal of any remaining hydrazine hydrate.

7. The collected solids may be vacuum filtered on paper and dried in a vacuum oven overnight; or the collected solids may be dissolved with heating in solvent and then precipitated by addition of further solvent, and the resulting solids vacuum filtered on paper and dried in a vacuum oven overnight; or the collected solids may be recrystallised from hot ethanol, and vacuum filtered on sintered glass and left to air dry.

It will be appreciated that the selection of the methodology in step 7 will be dependent upon the properties of the specific solids formed.

Synthesis of a Component of Group (iv) of Formula (XII): 2,2'-((1 E,TE)- hvdrazine-1 ,2-diylidenebis(methaneylylidene))diphenol

For 2,2'-((1 E,1 'E)-hydrazine-1 ,2-diylidenebis(methaneylylidene))diphenol: Xi _a , X _2a , X3 _a , X _4a , Xi _b , X2 _b , X3 _b and X _4b are C, R ¹ and R ² are hydrogen, and R ³ and R ⁴ are hydrogen.

1. A solution of salicylaldehyde (45 g, 0.37 mol) in ethanol (100 ml) was prepared in a 3-neck round bottom flask (rbf) fitted with a dropping funnel, stirrer bar and thermometer.

2. A solution of hydrazine hydrate (35 % w/v, 15.8 ml, 0.17 mol) in ethanol (50 ml) is prepared and placed in the dropping funnel.

3. The hydrazine hydrate solution is added with stirring over the course of 20 minutes to the salicylaldehyde solution resulting in a small exotherm (initial temperature 20 °C, final temperature 50 °C).

4. During the addition, the suspension thickens to the point where stirring is ineffective, therefore three additional portions of ethanol (50 ml each) are added to the flask during the addition to maintain stirring of the suspension.

5. The dropping funnel is replaced with a condenser and the reaction brought to reflux (80 °C).

6. The reaction is refluxed with stirring for 5 hours and then left to cool overnight 7. The cooled crystalline yellow precipitate that formed is vacuum filtered on paper and washed with additional ethanol.

8. The collected solids are recrystallised from hot ethanol yielding a pale yellow crystalline solid.

9. The resulting solids are vacuum filtered on sintered glass and left to air dry to yield a pale-yellow crystalline product (40.4 g, 96 %).

Synthesis of Components of Group (iv) of Formula (IX)

The compounds of formula (V) can be purchased from Chameleon Speciality Chemicals Ltd, or formulated according ot the following syntheses.

Generic Synthesis of a Component of Group (iv) of Formula (IX)

The amino-phenol (1 equivalent) and anhydride (1 equivalent) are weighed into a round bottom flask fitted with a stirrer bar, thermometer and reflux condenser. The solids are suspended in toluene (0.3 to 2.0 molar solution) and refluxed for 18 hours. The reaction mixture is allowed to cool to room temperature and the solvent removed on a roto-evaporator. The product is isolated by flash column chromatography eluting with a polarity gradient from Heptane/DCM 1 :1 to DCM 20 % Ethyl Acetate. The column fractions are concentrated on a roto-evaporator to ~0.5 L and precipitated by adding the solution to a beaker of stirred Heptane (1 to 2 L). The precipitate is vacuum filtered onto paper, dried by suction for around 10 minutes then transferred to a drying dish and dried in a vacuum oven (20 °C) overnight yielding the product as a pale coloured powder.

Specific Synthesis of a Component of Group (iv) of Formula (IX): (2-(4- (dimethylamino)-2-hvdroxybenzoyl)benzoic acid)

3-(Dimethylamino)phenol (26.0 g, 190 mmol) and Phthalic anhydride (28.07 g, 189.5 mmol) were weighed into a round bottom flask fitted with a stirrer bar, thermometer and reflux condenser. The solids were suspended in toluene (100 ml_) and reflux for 18 hours. The reaction mixture was allowed to cool to room temperature and the solvent removed on a roto-evaporator. The residue was extracted into Ethyl Acetate (500 ml_) with sonication and heating. The mixture was filtered through sintered glass. The filtrate was precipitated by addition of heptane (500 ml_) and the dark solids vacuum filtered onto paper. The solids were dissolved in dichloromethane (300 ml_) and passed through a silica pad eluting with dichloromethane until the filtrate ran clear. The dichloromethane solution was concentrated on a roto-evaporator to ~0.5 L and was precipitated by adding the dichloromethane solution to a beaker of stirred Heptane (1 L). The precipitate was vacuum filtered onto paper, dried by suction for - 10 mins then transferred to a drying dish and dried in a vacuum oven (20 °C) overnight yielding the product as a beige coloured powder (22.23 g, 77.92 mmol, 41.1 %).

Specific Synthesis of a Component of Group (iv) of Formula (IX): (2-(4- (diethylamino)-2-hvdroxybenzoyl)-5-nitrobenzoic acid

3-(Diethylamino)phenol (21.47 g, 129.9 mmol) and 4-nitro-phthalic anhydride (25.07 g, 129.8 mmol) were weighed into a round bottom flask fitted with a stirrer bar, thermometer and reflux condenser. The solids were suspended in toluene (100 ml_) and reflux for 18 hours. The reaction mixture was allowed to cool to room temperature and the solvent removed on a roto-evaporator. The product was isolated by flash column chromatography eluting with a polarity gradient from Heptane/DCM 1 :1 to DCM 10 % Ethyl Acetate. The column fractions were concentrated on a roto-evaporator to -0.5 L and was precipitated by adding the solution to a beaker of stirred heptane (1 L). The precipitate was vacuum filtered onto paper, dried by suction for around 10 minutes then transferred to a drying dish and dried in a vacuum oven (20 °C) overnight yielding the product as a pale-yellow coloured powder (7.60 g, 21.2 mmol, 16.3 %).

Specific Synthesis of a Component of Group (iv) of Formula (IX): (2, 3, 4, 5- tetrachloro-6-(4-(diethylamino)-2-hvdroxybenzoyl)benzoic acid

3-(Diethylamino)phenol (22.00 g, 131.1 mmol) and tetrachloro-phthalic anhydride (38.06 g, 131.1 mmol) were weighed into a round bottom flask fitted with a stirrer bar, thermometer and reflux condenser. The solids were suspended in toluene (100 ml_) and reflux for 18 hours. The reaction mixture was allowed to cool to room temperature and the solvent removed on a roto-evaporator. The product was isolated by flash column chromatography eluting with a polarity gradient from Heptane/DCM 1 :1 to DCM 10 % Ethyl Acetate. The column fractions were concentrated on a roto-evaporator to ~0.5 L and was precipitated by adding the solution to a beaker of stirred heptane (1 L). The precipitate was vacuum filtered onto paper, dried by suction for around 10 minutes then transferred to a drying dish and dried in a vacuum oven (20 °C) overnight yielding the product as a yellow coloured powder (15.63 g, 34.65 mmol, 26.02 %). Synthesis of a Component of Group (iv) of Formula (IX): (2,5-bis(4- (diethylamino)-2-hvdroxybenzoyl)terephthalic acid

3-(Diethylamino)phenol (39.3 g, 230 mmol) and Pyromellitic anhydride (25.0 g, 114.6 mmol) were weighed into a round bottom flask fitted with a stirrer bar, thermometer and reflux condenser. The solids were suspended in toluene (400 ml_) and reflux for 18 hours. The reaction mixture was allowed to cool to room temperature and the solvent removed on a roto-evaporator. The product was isolated by flash column chromatography eluting with a polarity gradient from Heptane/DCM 1 :1 to DCM 20 % Ethyl Acetate. The column fractions were concentrated on a roto-evaporator to ~0.5 L and was precipitated by adding the solution to a beaker of stirred Heptane (2 L). The precipitate was vacuum filtered onto paper, dried by suction for around 10 minutes then transferred to a drying dish and dried in a vacuum oven (20 °C) overnight yielding the product as a yellow coloured powder (5.84 g, 10.6 mmol, 9.29 %).

Specific Examples of the Synthesis of Components of Group (ii) According to the Present Invention

Synthesis of di-tert-butyl(((docosa-10,12-divnedioyl)bis(azanediyl))bis(e thane- 2,1 -diyl))dicarbamate

1 . Weigh docosa-10,12-diynedioic acid (DCDA) (27.6 mmol, 1 equiv.) into a beaker.

2. Dissolve DCDA in THF (200 ml_) and stir for 10 minutes.

3. Meanwhile weigh 3-(((ethylimino)methylene)amino)-N,N-dimethylpropan-1- amine hydrochloride (EDAC) (57.9 mmol 2.1 equiv.) into a round bottom flask fitted with a stirrer bar.

4. Weigh N,N-dimethylpyridin-4-amine (DMAP) (0 2.76 mmol, 0.1 equiv) into the round bottom flask. 5. Weigh tert-butyl (2-aminoethyl)carbamate (57.9 mmol, 2.1 equiv.) into the round bottom flask.

6. Add THF (50 ml_) to the round bottom flask and stir the solids creating a white suspension.

7. Weigh and flute a filter paper.

8. Filter the DCDA solution into the round bottom flask using the pre-weighed filter paper.

9. Dry and weigh the used filter paper to calculate exact quantity of DCDA used.

10. Add the filtrate to the above reaction mixture at room temperature and stir overnight.

1 1 . Vacuum filter solids on paper to obtain an off-white solid (crop 1 ).

12. Transfer the solids (crop 1 ) to a beaker and slurry for 2 hours in water (200 ml_).

13. Concentrate the filtrate using a rotary evaporator resulting in a white solid

(crop 2).

14. Slurry this solid (crop 2) with 250 ml_ of de-ionised water for 1 hour.

15. Vacuum filter crop 1 on paper.

16. Stir the solids obtained (crop 1 ) with 200 mL of acetone for 1 hour.

17. Vacuum filter crop 2 on paper.

18. Stir the solids obtained (crop 2 with 200 mL of acetone for 1 hour.

19. Vacuum filter crop 1 on paper to obtain off-white solid and leave to air dry overnight.

20. Vacuum filter crop 2 on paper to obtain off-white solid and leave to air dry overnight.

21 . Dry both crop 1 & 2 further at 20 °C in a vacuum oven for 1 hour, and combine crops 1 & 2 to obtain resulting solids (10.7 g, 60%).

Synthesis of di-tert-butyl 2,2'-(tetradeca-6,8-divnedioyl)bis(hvdrazine-1 - carboxylate

d i -ierf-buty t 2: , '-(tet radeca-6 , 3~diy nedioy f ) bi s { hyd raztne- 1 ~ca rfaoxy late)

1. Tetradeca-6,8-diynedioic acid (40 mmol, 1.0 equiv.) was stirred in tetrahydrofuran (THF) (100 equiv.) in a 500 ml_ round bottom flask.

2. Triethyl amine (87.9 mmol, 2.2 equiv.) and ethyl chloroformate (87.9 mmol, 2.2 equiv) were added to the above stirring mixture.

3. The reaction mixture was stirred for 1 hour.

4. The resultant precipitate was removed by vacuum filtration on paper.

5. The filtrate was added to a solution of tert-butyl carbazate (87.9 mmol, 2.2 equiv.) and N-methylmorpholine (132 mmol, 3.3 equiv.) in THF (20 ml_) in a 500 ml_ round bottom flask at room temperature.

6. The reaction was wrapped in tin foil and stirred.

7. The reaction mixture was concentrated using rotary evaporator to afford a light brown syrup.

8. The residue was dissolved in Acetone (20 ml_) and poured into a beaker containing Dl water (40 ml_) causing a precipitate to form.

9. The suspension was stirred for 1 hour at room temperature.

10. The solids were vacuum filtrated on paper to afford a white solid.

1 1. The solids were stirred with 100 ml_ de-ionised water for 1 hour.

12. The solids were vacuum filtered on paper and allowed to air dry overnight.

13. This white solid material was dried again at 20 °C in a vacuum oven for 1 hour (8.84 g, 71 %).

Colour Formation According to the Present Invention

For each of the examples, unless otherwise stated, the natural state (non- coloured state) of the components of groups (i) to (iv) is either off-white or white. For each of the examples, unless otherwise indicated, the 10.6 pm C0 ₂ laser is set at a speed of 2600 - 5350 mm/s and at 38% power. The speed or power of the laser can be altered to vary the fluence applied by the laser source. Marking speeds within the 2600-5350 mm/s range are 2600, 2975, 3325, 3600, 3850, 4100, 4300, 4750, 5050 and 5350 mm/s.

Example 1 A composition comprising a component of group (iii) was formulated according to Table 8, using the millbase formulations of Tables 6 and 7. All amounts are provided in weight percentage (wt%).

Table 6 - Millbase Formulation of Component of Group (iii)

Table 7 - Millbase Formulation of NIR absorber

Table 8

A composition comprising a component of group (ii) was formulated according to Table 11 , using the millbase formulations of Tables 9 and 10. All amounts are provided in weight percentage (wt%). Table 9 - Millbase Formulation of Component of Group (ii)

Table 10 - Millbase Formulation of NIR absorber

Table 11

A layer of the composition comprising the component of group (ii) was applied to a PET substrate using a 16 pm K-bar applicator and dried with a warm air stream. A layer of the composition comprising the component of group (iii) was applied on top of the layer of the composition comprising the component of group (ii) in an identical manner.

(Note: The composition comprising the component of group (ii) and the composition comprising the component of group (iii) can also be combined and applied to the substrate as a single layer, i.e. a composition according to the first aspect present invention).

Following application to the substrate, the component of group (ii) and the component of group (iii) are in their non-coloured states.

To provide a red colour, a second applied stimulus was applied by flood illumination using a 254 nm low pressure mercury lamp to form a red first coloured state of the component of group (ii) across the substrate. It is noted that the transition of the component of group (iii) from the non-coloured to a coloured state is not effected by the application of the 254 nm radiation as the non-coloured state of the component of group (iii) has not been exposed to a third temperature to‘active’ the non-coloured state of the component and thus the non-coloured state of the component of group (iii) is in the‘unactivated’ form.

To provide a yellow colour, a second temperature of around 60 to 65 °C was applied to localised positons using a 1070 nm NIR fibre laser such that the component of group (ii) transitions from the red first coloured state to a second yellow coloured state at these localised positions. The component of group (ii) is deactivated at these localised positions and will not undergo any subsequent transitions (tested using a germicidal lamp). The intensity of the colour of the coloured state can be altered by variation of the fluence of the means used to apply the radiation.

This second temperature is not high enough to‘activate’ the non-coloured state of the component of group (iii). However, to provide a black or green colour, a third temperature of around 80 to 85 °C was applied using a 1070 nm NIR fibre laser at some of the localised positions having the deactivated yellow coloured state such that the non-coloured state of the component of group (iii) is activated at those particular localised positions. A third applied stimulus was then applied to the substrate by flood illumination using a 254 nm UV lamp and at only the localised positions at which the non-coloured state of the component of group (iii) had been activated, there was a transition from the activated non-coloured state to a blue coloured state of the component of group (iii). The intensity of the colour of the coloured state formed can be made to vary by variation of the fluence of the means used to apply the radiation. At the localised positions at which the yellow second coloured state of the component of group (ii) and the blue coloured state of the component of group (iii) have been formed, the final colour displayed at these localised positions is dependent upon the intensity of the each of the colours of the coloured states formed, i.e. the final colour at each of the localised positions results from the combination of the coloured of the coloured states of the two components. Accordingly, green and black colours can be formed. A black colour is formed when the blue coloured state has higher colour intensity, and a green colour is formed when the yellow coloured state has higher colour intensity.

To provide a blue colour, prior to the application of the second applied stimulus, a second temperature of around 60 to 65 °C was applied to localised positions of the substrate to deactivate the component of group (ii) at those localised positions. The non-coloured state of the component of group (ii) at these localised positions is deactivated and cannot undergo any subsequent transitions. A third temperature of around 80 to 85 °C was then applied to those ‘deactivated’ localised positions on the substrate using a 1070 NIR fibre laser to ‘activate’ the non-coloured state of the component of group (iii) at those localised positions. Upon application of the third applied stimulus (and second applied stimulus for the formation of the red colour) using a 254nm UV lamp, only the component of group (iii) solely at those localised positions transitioned from the non-coloured to the blue coloured state.

A multi-coloured image displaying red, yellow, blue, green and black colours can be formed.

Example 2

A composition comprising a component of group (iii) was formulated according to Table 14, using the millbase formulations of Tables 12 and 13. All amounts are provided in weight percentage (wt%).

Table 12 - Millbase Formulation of Component of Group (iii)

Table 13 - Millbase Formulation of NIR absorber

Table 14

A composition comprising a component of group (ii) was formulated according to Table 17, using the millbase formulations of Tables 15 and 16. All amounts are provided in weight percentage (wt%). Table 15 - Millbase Formulation of Component of Group (ii)

Table 16 - Millbase Formulation of NIR absorber

Table 17

A layer of the composition comprising the component of group (ii) was applied to a PET substrate using a 16 pm K-bar applicator and dried with a warm air stream. A layer of the composition comprising the component of group (iii) was then applied on top of the layer of the composition comprising the component of group (ii) in an identical manner.

(Note: The composition comprising the component of group (ii) and the composition comprising the component of group (iii) can also be combined and applied to the substrate as a single layer, i.e. a composition according to the first aspect present invention).

Following application to the substrate, the component of group (ii) and the component of group (iii) are in their non-coloured states.

To provide a red colour, a second applied stimulus was applied by flood illumination using a 254 nm low pressure mercury lamp to form a red first coloured state of the component of group (ii) across the substrate. It is noted that the transition of the component of group (iii) from the non-coloured to a coloured state is not effected by the application of the 254 nm radiation as the non-coloured state of the component of group (iii) has not been exposed to a third temperature to‘active’ the non-coloured state of the component and thus the non-coloured state of the component of group (iii) is in the‘unactivated’ form.

To provide a yellow colour, a second temperature of around 60 to 65 °C was applied to localised positons using a 1070 nm NIR fibre laser such that the component of group (ii) transitions from the red first coloured state to a second yellow coloured state at these localised positions. The component of group (ii) is deactivated at these localised positions and will not undergo any subsequent transitions (tested using a germicidal lamp). The intensity of the yellow coloured state can be altered by variation of the fluence of the means used to apply the radiation.

This second temperature is not high enough to‘activate’ the non-coloured state of the component of group (iii). However, to provide a green colour, a third temperature of around 80 to 85 °C was applied using a 1070 nm NIR fibre laser at some of the localised positions having the deactivated yellow coloured state such that the non-coloured state of the component of group (iii) is activated at those particular localised positions. A third applied stimulus was then applied to the substrate by flood illumination using a 254 nm UV lamp and at only the localised positions at which the non-coloured state of the component of group (iii) had been activated, there was a transition from the activated non-coloured state to a blue coloured state of the component of group (iii). The intensity of the colours of the coloured states formed can be made to vary by variation of the fluence of the means used to apply the radiation. At the localised positions at which the yellow second coloured state of the component of group (ii) and the blue coloured state of the component of group (iii) have been formed, the final colour displayed at these localised positions is dependent upon the intensity of the each of the colours of the coloured states formed, i.e. the final colour at each of the localised positions results from the combination of the coloured of the coloured states of the two components. Accordingly, a green colour can be formed.

To provide a blue colour, prior to the application of the second applied stimulus, a second temperature of around 60 to 65 °C was applied to localised positions of the substrate to deactivate the component of group (ii) at those localised positions. The non-coloured state of the component of group (ii) at these localised positions is deactivated and cannot undergo any subsequent transitions. A third temperature of around 80 to 85 °C was then applied to those ‘deactivated’ localised positions on the substrate using a 1070 NIR fibre laser to ‘activate’ the non-coloured state of the component of group (iii) at those localised positions. Upon application of the third applied stimulus (and second applied stimulus for the formation of the red colour) using a 254nm UV lamp, only the component of group (iii) solely at those localised positions transitioned from the non-coloured to the blue coloured state. A multi-coloured image displaying red, yellow, blue and green colours can be formed.

Example 3

A composition comprising a component of group (iv) of formula (IX) was formulated according to Table 18. All amounts are provided in weight percentage (wt%).

Table 18

A composition comprising a component of group (iii) was formulated according to Table 21 , using the millbase formulations of Tables 19 and 20.

Table 19 - Millbase formulation of diacetylene compound

Table 20 - Millbase formulation of NIR absorber

Table 21

A layer of the composition comprising the component of group (iv) was applied to a PET substrate to a suitable thickness using a K-bar applicator. A layer of the composition comprising the component of group (iii) was then applied on top of the layer of the composition comprising the component of group (iv).

(Note: The composition comprising the component of group (iv) and the composition comprising the component of group (iii) can also be combined and applied to the substrate as a single layer, i.e. a composition according to the present invention). A fourth temperature of around 140 °C was applied to the substrate at localised positions using a 1070 nm NIR fibre laser to facilitate a transition from the non- coloured to a coloured state of component of group (iv) (keto acid compound of formula (IX). The colour of the coloured state can be changed between yellow or orange by variation of fluence. The third temperature (around 95 °C) required to activate the non-coloured state of the component of group (iii) is lower than that of the required to facilitate the transition of the component of group (iv) from the non-coloured to a coloured state. Therefore, upon application of the fourth temperature, the non-coloured state of the component of group (iii) is also‘activated’ at these localised positions by the NI R radiation. There is no colour formation at these positions for the diacetylene compound as the coloured state of the diacetylene compound has not yet been formed.

Following application of the NI R radiation, a third applied stimulus is applied to the substrate by flood illumination using a 254 nm UV lamp to effect a transition from the activated non-coloured state of the component of group (iii) to a blue coloured state solely at the localised positions at which the non-coloured state of the component of group (iii) had been activated. As the coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the compound of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the blue colour of the formed coloured state of the component of group (iii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, orange and green colours may be formed.

To provide a blue colour, prior to the application of the fourth temperature, third temperature of around 95 °C can be applied at different localised positions using a 1070 NI R fibre laser to‘activate’ the non-coloured state of the component of group (iii) at those localised positions. The coloured state of the component of group (iv) is not formed as the third temperature is lower than the fourth temperature such that the transition is not facilitated. Following further application of the third applied stimulus using a 254nm UV lamp, the component of group (iii) transitioned from the non-coloured to the blue coloured state at the localised positions. A multi-coloured image may be formed displaying yellow, orange, blue and green colours.

Example 4

A composition comprising a component of group (i) and a component of group (iii) is formulated by combining 1 part of the formulation of Table 22 with 1 part of the formulation of Table 25, formed from the millbases formulations of Tables 23 and 24.

Table 22

Table 23 - Diacetylene compound millbase

Table 24 - NIR absorber millbase

Table 25

A layer of the composition is applied to a paper substrate using a k2k-bar applicator. Following application to the substrate, the component of group (i) and the component of group (iii) are in the non-coloured state.

NIR radiation is applied to the composition using a 1064 nm Nd:YAG laser (2000 mm/s, 100% power) at localised positions (to provide an third temperature), the non-coloured state of the component of group (iii) is‘activated’ at these localised positions.

Next, a medium pressure mercury lamp is used to first apply UV radiation (first applied stimulus) to the composition via flood illumination. The component of group (i) transitions from the non-coloured to a pale yellow coloured state across the substrate. In addition, the UV radiation acts as the third applied stimulus and causes the component of group (iii) to transition from the non-coloured state to a first blue coloured state at the localised positions at which the non-coloured state of the component of group (iii) has been‘activated’. At the localised positions at which the first blue coloured state of the component of group (iii) has been formed, the pale yellow coloured state of the component of group (i) has also been formed, and therefore the final colour displayed at these localised positions is the combination of the first blue coloured state of the component of group (iii) and the pale yellow coloured state of the component of group (i). A blue colour is displayed at these localised positions.

Half of the substrate is then exposed to NIR radiation using a 1064 nm Nd:YAG laser (2000 mm/s, 100% power) (additional temperature), and the localised positions at which the first blue coloured state of the component of group (iii) have been formed undergo a transition to a red second coloured state. In addition, the NIR radiation acts as a first temperature and the component of group (i) across the exposed half of the substrate transitions from the pale yellow coloured state to the non-coloured state, such that the localised positions of the substrate exposed to NIR radiation are in the non-coloured state.

A multi-coloured image displaying red, yellow and blue colours can therefore be formed. In addition, the non-coloured state of the component of group (i) can form part of the multi-coloured image. Example 5

A composition comprising a component of group (iii) is formulated according to Table 25 using the millbases of Tables 23 and 24, the component of group (iii) being replaced by N1 ,N22-dicyclopropyldocosa-10,12-diyndiamide. A composition comprising a component of group (i) is formulated according to Table 2 above.

A layer of the composition comprising the component of group (iii) is applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (i) is then applied to the paper substrate using a k2 k-bar applicator over the layer of the composition comprising a component of group (iii).

Following application on the substrate, the component of group (i) and the component of group (iii) are in the non-coloured state.

If a germicidal UV lamp is used to apply UV radiation (first applied stimulus) to the substrate via flood illumination, the component of group (i) transitions from the non-coloured to a pale yellow coloured state, such that a pale yellow colour is displayed on the substrate. The component of group (iii)’s non-coloured state is not activated by the application of UV radiation.

If IR radiation using a 1064 nm Nd:YAG laser (2000 mm/s, 100% power) is subsequently applied to localised positions of the substrate (third temperature), the non-coloured state of the component of group (iii) is ‘activated’ at these localised positions. The subsequent addition of UV radiation (third applied stimulus) by flood illumination causes the component of group (iii) to transition from the non-coloured state to a first blue coloured state at these localised positions. It is noted that at these localised positions, the component of group (i) also transitions from the pale yellow coloured state to the non-coloured state. However, as the final colour displayed at these localised positions is dependent upon the combination of the blue first coloured state of the component of group (iii) and the non-coloured state of the component of group (i), a blue colour is displayed at the localised positions. Further application of NIR radiation (additional temperature) using the 1064 nm Nd:YAG laser (2000 m/s, 100% power) at a proportion of the localised positions, facilitates the transition of the component of group (iii) from the first blue coloured state to the second red coloured state at this proportion of localised positions.

A multi-coloured image may therefore be formed displaying yellow, blue and red colours.

Example 6

A composition comprising a component of group (ii) and a component of group (i) was formulated by combining 1 part of the formulation of Table 28, forming using the millbase formulations of Tables 26 and 27, and 1 part of the formulation of Table 2 above.

Table 26 - Millbase Formulation of Component of Group (ii)

Table 27 - Millbase Formulation of NIR absorber

Table 28

A layer of the composition was applied onto a paper substrate (craft paper) using a k2 k-bar applicator.

Following application of the composition to the paper substrate, the component of group (ii) and component of group (i) are in their non-coloured states.

Upon application of IR radiation to localised positions of the substrate using a 10.6 pm C0 ₂ laser (3000-5350 mm/s, 38-80% power) (second temperature), the component of group (ii) is‘deactivated’ and these localised positions such that it remains in the non-coloured state and will not undergo any subsequent transitions. Following application of UV radiation by flood illumination (second applied stimulus) using a germicidal lamp, the component of group (ii) transitions from the non-coloured state to a first blue coloured state across the substrate, apart from at those localised positions at which the component of group (ii) has been‘deactivated’. In addition, the UV radiation acts as an first applied stimulus such that the non-coloured state of the component of group (i) transitions to a pale yellow coloured state across the substrate. As the colour displayed by the substrate, except at those positions at which the component of group (ii) has been deactivated, is a combination of the blue first coloured state of the component of group (ii) and the pale yellow coloured state of the component of group (i), a blue colour is displayed. However, at the localised positons at which the component of group (ii) has been deactivated, the pale yellow colour of the coloured state of the component of group (i) can be seen.

Alternatively, following application of the composition to the substrate, UV radiation by flood illumination using a germicidal lamp (second applied stimulus) can be applied to the substrate such that the component of group (ii) transitions from the non-coloured state to the first blue coloured state across the substrate. The component of group (i) also transitions from the non-coloured state to a pale yellow coloured state upon application of the UV radiation (first applied stimulus) across the substrate. However, as the colour displayed by the substrate is a combination of the blue first coloured state of the component of group (ii) and the pale yellow coloured state of the component of group (i), a blue colour is displayed.

Following application of the UV radiation, IR radiation is applied at localised positions using a 10.6 pm C0 ₂ laser (3000-5350 mm/s, 38-80% power) (second temperature) and the first blue coloured state of the component of group (ii) transitions to a second red coloured state at these localised positions. The component of group (ii) is deactivated at these localised positions and will not undergo any subsequent transitions. The IR radiation also acts as the first temperature and the coloured state of the component of group (i) returns back to its non-coloured state.

A multi-coloured image displaying blue, yellow and red colours can therefore be formed.

Example 7

A composition comprising a component of group (ii), a component of group (iii) and a component of group (i) was formulated by combing (a) 1 part of the formulation according to Table 28, formed from the millbase formulations of Tables 26 and 27, but replacing the component of group (ii) with di-tert-butyl-2,2’- (tetradeca-6,8-diynedioyl)bis(hydrazine-1 ,20-carboxylate), (b) 1 part of the formulation according to Table 25, formed from the millbase formulations of Tables 23 and 24, but replacing the component of group (iii) with N1 ,N22- didecyldocosa-10,12-diynediamide, and (c) 1 part of the formulation of Table 2.

A layer of the composition was applied to a paper substrate using a k2 k-bar applicator.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (38% power) (third temperature) at localised positions of the composition, the non-coloured state of the component of group (iii) is‘activated’ at these localised positions. It is noted that the second temperature is less than the third temperature, and therefore upon application of the IR radiation, the second temperature is also reached and the component of group (ii) is‘deactivated’ at these localised positions. The non-coloured state of the component of group (ii) at these localised positions is thus not capable of undergoing any subsequent transitions.

Further application of UV radiation using a germicidal lamp (third applied stimulus) causes the activated non-coloured state of the component of group (iii) to transition to a blue coloured state at these localised positions only. The intensity of the colour formed can be altered by variation of fluence. It is noted that upon application of the UV radiation, the component of group (ii) also transitions from the non-coloured state to a first red coloured state across the whole substrate apart from the localised positions at which the coloured state of the component of group (iii) has been formed and the component of group (ii) has been deactivated. In addition, upon application of the UV radiation, the component of group (i) also transitions from the non-coloured to a pale yellow coloured state across the substrate. The final colour displayed at the localised positions is a combination of the blue coloured state of the component of group (iii) and the pale yellow coloured state of the component of group (i). The final colour displayed across the rest of the substrate is a combination of the red coloured state of the component of group (ii) and the pale yellow coloured state of the component of group (ii). Accordingly, different red and orange colours can be formed.

Alternatively, following application of the composition to the substrate, UV radiation by flood illumination using a germicidal lamp is applied to the substrate (second applied stimulus). The component of group (ii) transitions from the non- coloured state to a red first coloured state across the whole substrate. In addition, the UV radiation acts as the first applied stimulus and the component of group (i) also transitions from the non-coloured to a pale yellow coloured state across the whole substrate. As the final colour displayed across the substrate is a combination of the red coloured state of the component of group (ii) and the pale yellow coloured state of the component of group (ii), different red and orange colours can be formed.

Upon further application of IR radiation using a 10.6 pm C0 ₂ laser (38% power) at the localised positions of the substrate (second temperature), the first coloured state of the component of group (ii) transitions to a second yellow coloured state, and the component of group (ii) is deactivated at these localised positions. The intensity of the colour of the coloured state formed can be varied by alteration of the fluence applied by the laser. A yellow colour is displayed at the localised positions.

A multi-coloured image displaying red, orange, yellow and blue colours may therefore be formed.

Example 8

A composition comprising a component of group (i) is formulated according to Table 2 above.

A composition comprising a component of group (iii) was formulated according to Table 25 above, using the millbase formulations of Tables 23 and 24.

A composition comprising a compound of group (iv) was formulated according to Table 29. All amounts are provided in weight percetnages (wt%). Table 29

A layer of the composition comprising the component of group (iv) is applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (iii) is applied over the layer of the composition comprising a component of group (iv) using a k2 k-bar applicator. A layer of the composition comprising a component of group (i) is then applied over the layer of the composition comprising a component of group (iii) using a k2 k-bar applicator. Following application to the substrate, the component of group (i), the component of group (iii) and the component of group (iv) are in the non-coloured state.

If a germicidal UV lamp is used to apply UV radiation (first applied stimulus) to the substrate via flood illumination, the component of group (i) transitions from the non-coloured to a pale yellow coloured state, such that a pale yellow colour is displayed on the substrate.

A fourth temperature is applied using a 10.6 pm C0 ₂ laser (38% power) to provide IR radiation to localised positions of the substrate either prior to or subsequent to the application of the UV radiation. At these localised positions, the component of group (iv) transitions from its non-coloured to a black coloured state. The intensity of the colour formed can be varied by variation of the fluence provided by the C0 ₂ laser, such that grey and black coloured states can be formed.

It is noted that the fourth temperature required to facilitate the transition of the component of group (iv) from the non-coloured to a coloured state is higher than the third temperature (i.e. activation temperature) of the component of group (iii). Accordingly, upon application of the fourth temperature required to facilitate the transition of the component of group (iv) from the non-coloured to a coloured state, the non-coloured state of the component of group (iii) is also‘activated’ at these localised positions. Furthermore, at these localised positions, the component of group (i) transitions from the coloured state back to the non- coloured state, the IR radiation applying the first temperature.

Upon further application of UV radiation (third applied stimulus) via flood illumination using a germicidal lamp, the component of group (iii) transitions from the activated non-coloured state to a blue coloured state at these localised positions. As the coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the initial colour formed by the blue coloured state of the component of group (iii), and the black coloured state of the component of group (iv), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of the two components. Accordingly, different colours of blue and black can be formed.

A multi-coloured image may therefore be formed displaying yellow, blue and black colours.

Example 9

A composition comprising a component of group (iv) was formulated according to Table 29 above. A composition comprising a component of group (iii) was formulated according to Table 25, formed from the millbase formulations of Tables 23 and 24, but replacing the component of group (iii) with N1 ,N22-didecyldocosa-10,12- diynediamide

A composition comprising a component of group (ii) was formulated according to Table 28, formed from the millbase formulations of Tables 26 and 27, but replacing the component of group (ii) with di-tert-butyl-2,2’-(tetradeca-6,8- diynedioyl)bis(hydrazine-1 ,20-carboxylate).

A layer of the composition comprising the component of group (iv) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising the component of group (iii) was applied using a k2 k-bar applicator over the layer of the composition comprising the component of group (iv). A layer of the composition comprising the component of group (ii) was applied using a k2 k-bar applicator over the layer of the composition comprising the component of group (iii).

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20% power) (third temperature) at localised positions of the composition, the non-coloured state of the component of group (iii) is‘activated’ at these localised positions. It is noted that the second temperature is lower than the third temperature, such that application of the IR radiation also causes the second temperature to be reached such that the component of group (ii) is‘deactivated’ at these localised positions. The component of group (ii) at these localised positions is thus not capable of undergoing any subsequent transitions. It is further noted that the fourth temperature required to facilitate a transition of the component of group (iv) from a non-coloured to a coloured state is higher than the third temperature. Therefore, using a C0 ₂ laser at 20% power, the fourth temperature is not reached and the component of group (iv) does not transition from the non- coloured state to a coloured state.

However, if the colour of the coloured state of the component of group (iv) is desired, the temperature can be increased to the fourth temperature by increasing the power of the C0 ₂ laser to 38% power. The component of group (iv) will then transition from the non-coloured state to a black coloured state at these localised positions. The intensity of the colour of the coloured state formed can be varied by altering the fluence of the C0 ₂ laser being used.

Upon further application of UV radiation using a germicidal lamp (third applied stimulus, the component of group (iii) transitions from the activated non-coloured state to a blue coloured state at only the localised positions at which the non- coloured state of the component of group (iii) has been activated. If the coloured state of the component of group (iv) has not been formed at the localised positions, the localised positions display a blue colour. However, if the coloured state of the component of group (iv) has also been formed at these localised positions, the final colour displayed at these localised positions is dependent upon the colour formed by the blue coloured state of the component of group (iii), and the black coloured state of the component of group (iv), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of the two components. Accordingly, different blue and black colours can be formed at these localised positions. The application of the UV radiation also acts as the second applied stimulus and facilitates a transition of the component of group (ii) from the non-coloured state to a first red coloured state across the substrate except at the localised positions of the substrate at which the non-coloured state of the component of group (ii) has been deactivated.

Alternatively, following application of the layers to the substrate, UV radiation is applied to the substrate (second applied stimulus) by flood illumination using a germicidal lamp. The non-coloured state of the diacetylene compound transitions to a first red coloured state across the substrate. Upon application of IR radiation using a 10.6 pm C0 ₂ laser (10% power) at localised positions (second temperature), the red first coloured state of the component of group (ii) transitions to a second yellow coloured state. The intensity of the colour of the yellow coloured state formed can be varied by altering the fluence applied by the laser. As the second temperature is lower than the third temperature of the component of group (iii) and the fourth temperature required for the transition of the component of group (iv), only the yellow second coloured state is formed at these localised positons and a yellow colour displayed.

A multi-coloured image displaying yellow, red, blue and black can therefore be formed.

Example 10

A composition comprising a component of group (ii) and a component of group (i) was formulated using 1 part of the formulation according to Table 28, using the millbase formulations of Tables 26 and 27, and 1 part of the formulation according to Table 2.

A layer of the composition was applied to a paper substrate using a k2 k-bar applicator.

Following application of the composition to the paper substrate, the component of group (i) and the component of group (ii) are in their non-coloured states.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20% power) to localised positions of the substrate (second temperature), the component of group (ii) will be‘deactivated’ at those localised positions, such that it is not capable of undergoing any subsequent transitions and remains in the non- coloured state at these localised positions.

UV radiation is then applied to the substrate by flood illumination using a germicidal UV lamp (second applied stimulus). The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first blue coloured state across the substrate except from those localised positions where the component of group (ii) has been‘deactivated’. In addition, upon application of the UV radiation, the component of group (i) transitions from the non-coloured to a yellow coloured state across the substrate. At the localised positions at which the non-coloured state of the component of group (ii) has been deactivated, solely the yellow colour of the coloured state of the component of group (i) is displayed. For the rest of the substrate, the colour displayed is a combination of the yellow colour of the coloured state of the component of group (i) and the blue colour of the first coloured state of the component of group (ii). Accordingly, other than at the localised positions discussed above, the substrate displays a turquoise colour. An increased length of application of the UV radiation provides a more intense turquoise colour.

A multi-coloured image displaying yellow and turquoise colours can therefore be formed.

Example 11

A composition comprising a component of group (i) was formulated according to Table 1.

A composition comprising a component of group (iii) was formulated according to Table 25, formed from the millbase formulations of Tables 23 and 24, but replacing the component of group (iii) with N1 ,N22-didecyldocosa-10,12- diynediamide

A layer of the composition comprising a component of group (i) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (iii) is applied over the layer of the composition comprising AOM using a k2 k-bar applicator.

Following application to the substrate, the component of group (i) and the component of group (iii) are in the non-coloured state.

A germicidal UV lamp is used to apply UV radiation (first applied stimulus) to the substrate via flood illumination, and the component of group (i) transitions from the non-coloured to a pale yellow coloured state, such that a pale yellow colour is displayed on the substrate.

Following application of the first applied stimulus such that a pale yellow colour is displayed on the substrate, the non-coloured state of the component of group (iii) can be‘activated’ at localised positions through the application of the third temperature using a 10.6 pm C0 ₂ laser (20% power) to apply IR radiation at these localised positions. This IR radiation also effects a transition of the component of group (i) from the pale yellow coloured state back to the non- coloured state, the IR radiation providing the first temperature. The subsequent application of UV germicidal radiation by flood illumination (third applies stimulus) will then facilitate the transition of the component of group (iii) from the non-coloured state to a first blue coloured state at solely those localised positions such that a blue colour is displayed at those localised positions.

Further application of IR radiation using a 10.6 pm C0 ₂ laser (20% power) for an additional temperature at a selection of the localised positions then facilitates a transition of the component of group (ii) from the blue first coloured state to a second red coloured state at those localised positions.

A multi-coloured image displaying yellow, blue and red colours can therefore be formed.

Example 12

A composition comprising a component of group (iv) was formulated according to Table 29.

A composition comprising a component of group (ii) and a component of group (i) formulated according to 1 part of the formulation of Table 28, using the millbase formulations of Tables 26 and 27, and 1 part of the formulation of Table 2.

A layer of the composition comprising the component of group (iv) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising the component of group (ii) and the component of group (i) was applied using a k2 k-bar applicator over the layer of the composition comprising the component of group (iv).

Following application of the layers to the paper substrate, the all of the components are in their non-coloured states. Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20% power) to localised positions of the substrate (second temperature), the component of group (ii) is‘deactivated’ in its non-coloured state at the localised positions, such that it is not capable of undergoing any subsequent transitions. It is noted that the temperature required for the fourth temperature to facilitate a transition of the component of group (iv) is higher than the second temperature. The temperature applied by the 20% power C0 ₂ laser is thus not great enough to facilitate such transitions, and the component of group (iv) remains in its non- coloured state at these localised positions. However, if the power of the laser is increased to 38% power, the fourth temperature is reached and the component of group (iv) transitions from the non-coloured to a black coloured state. The intensity of the black coloured state can be made to vary by variation of fluence.

UV radiation is then applied to the substrate by flood illumination using a germicidal UV lamp (second applied stimulus). The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first blue coloured state across the substrate except from those localised positions where the non-coloured state of the component of group (ii) has been‘deactivated’, and the coloured state of the component of group (iv) optionally formed. An increased length of application of the UV radiation provides a more intense colour. The UV radiation also acts as the fourth applied stimulus and the component of group (iv) transitions from the non-coloured to a pale yellow coloured state across the substrate. The pale yellow colour can be seen at the localised positions at which the component of group (ii) has been deactivated.

Alternatively, following application of the layers to the paper substrate, UV radiation by flood illumination using a germicidal UV lamp (second transition stimulus) is applied to the substrate. Across the substrate, the non-coloured state of the component of group (ii) transitions from the non-coloured to a first blue coloured state. An increased length of application of the UV radiation provides a more intense colour. The UV radiation also acts as the fourth applied stimulus and the component of group (iv) transitions from the non-coloured to a pale yellow coloured state across the substrate. As the colour displayed across the substrate is a combination of the pale yellow coloured state of the component of group (iv) and the blue colour of the coloured state of the component of group (ii), the colour displayed across the substrate is blue.

IR radiation is then applied using a 10.6 pm C0 ₂ laser (20% power) to localised positions of the substrate (second temperature), and the component of group (ii) transitions from its blue first coloured state to its red second coloured state at these localised positions. The intensity of the colour of the second coloured state can be made to vary by altering the fluence applied by the C0 ₂ laser. As discussed above, the temperature applied by the 20% power C0 ₂ laser is not great enough to facilitate the transition of the component of group (iv) from the non-coloured to a coloured state, and the component of group (iv) remains in its non-coloured state at these localised positions. However, if the power of the laser is increased to 38% power, the fourth temperature for the component of group (iv) is reached and the component of group (iv) also transitions from the non-coloured to a black coloured state. The intensity of the black coloured state can be made to vary by variation of fluence. As the second coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the component of group (iv) is formed, the final colour displayed at these localised positions is dependent upon the black colour of the coloured state of the component of group (iv), and the red second coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, black and brown colours may be formed.

A multi-coloured image displaying black, orange, red, brown and blue colours can be formed. In addition, the non-coloured state of the deactivatable component can form part of the multi-coloured image.

Example 13

A composition comprising a component of group (iv) and an acid-generating agent is formulated according to a 50:50 mixture of the formulations of Tables 30 and 31. All amounts are provided in weight percentage (wt%).

Table 30 - Formulation comprising component of group (iv)

Table 31 - Formulation comprising acid-generating agent

A composition comprising a component of group (iii) is formulated according to Table 25, using the millbase formulations of Tables 23 and 24, but replacing the component of group (iii) with N1 ,N22-dioctadecyldocosa-10,12-diynediamide.

A layer of the composition comprising a component of group (iv) and an acid- generating agent is applied to a PET substrate using a 16 pm K-bar applicator. A layer of the composition comprising a component of group (iii) is applied to the PET substrate over the layer of the composition comprising a component of group (iv) and an acid-generating agent using a 16 pm K-bar applicator, to form a plurality of discrete layers on the substrate. Following application of the layers to the substrate, the component of group (iv) and the component of group (iii) are in the non-coloured state. The natural state (non-coloured state) of the component of group (iv) is yellow, and therefore the PET substrate displays this colour.

If localised positions of the PET substrate are subjected to IR radiation (fourth temperature) using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 38% power), the component of group (iv) transitions from its yellow non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of the fluence applied using the laser. It is noted that the third temperature of the component of group (iii) is lower than the temperature of the fourth temperature required to facilitate a transition of the component of group (iv) from the non- coloured to a coloured state. Accordingly, upon application of the IR radiation detailed above, the non-coloured state of the diacetylene compound is also ‘activated’ by the IR radiation (providing the third temperature) at the localised positions to which it is applied. There is no colour formation at these positions for the diacetylene compound as the coloured state of the diacetylene compound has not yet been formed.

Following the application of the IR radiation detailed above to the localised positions of the PET substrate, the PET substrate is exposed to UV radiation by flood illumination using a germicidal lamp (third applied stimulus) for 10 seconds. At each of the localised positions discussed above, the‘activated’ non-coloured state of the component of group (iii) transitions from the ‘active’ non-coloured state to a blue coloured state. As the coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the blue colour of the coloured state of the component of group (iii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, orange, blue and green colours may be formed. It is noted that as the third temperature for the component of group (iii) is lower than the temperature of the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to the coloured state, the non-coloured state of the component of group (iii) can be activated upon application of the third temperature at localised positions, but the component of group (iv) will remain in the non-coloured state, as the temperature is not high enough to effect a transition from its non-coloured state to a coloured state. Upon application of UV radiation using a germicidal lamp by flood illumination, the ‘activated’ non-coloured state of the component of group (iii) at those localised positons only will transition to a blue coloured state, such that a blue colour can be formed.

A multi-coloured image may therefore be formed displaying yellow, orange, blue and green colours.

Example 14

A composition comprising a component of group (iv) and an acid-generating agent is formulated according to agent is formulated according to a 50:50 mixture of the formulations of Tables 30 and 31.

A composition comprising a component of group (iii) is formulated according to Table 25, using the millbase formulations of Tables 23 and 24, but replacing the component of group (iii) with N1 ,N22-dioctadecyldocosa-10,12-diynediamide.

A layer of the composition comprising the component of group (iii) is applied to a PET substrate using an 8 pm K-bar applicator. A layer of the composition comprising a component of group (iv) and an acid-generating agent is then applied over the layer of the composition comprising a component of group (iii) using an 8 pm K-bar applicator, to form a plurality of discrete layers on the substrate.

Following the application of the layers to the PET substrate, the component of group (iv) and the component of group (iii) are in the non-coloured state. The natural state (non-coloured state) of the component of group (iv) is yellow, and therefore the PET substrate displays this colour.

If localised positions of the PET substrate are subjected to IR radiation (fourth temperature) using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 5-38% power), the component of group (iv) transitions from its pale yellow non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary between orange or yellow by variation of power of fluence applied by the laser. It is noted that the third temperature of the component of group (iii) is lower than the temperature of the fourth temperature required to facilitate a transition of the component of group (iv) from the non- coloured to a coloured state. Accordingly, upon application of the IR radiation detailed above, the non-coloured state of the component of group (iii) is also ‘activated’ by the IR radiation (providing a third temperature) at these localised positions to which it is applied. There is no colour formation at these positions for the component of group (iii) as the coloured state of the component has not yet been formed.

Following the application of the IR radiation detailed above to the localised positions of the PET substrate, the PET substrate is exposed to UV radiation by flood illumination using a 30W germicidal 254 nm lamp (third applied stimulus) for 20 seconds. At each of the localised positions at which the non-coloured state of the component of group (iii) has been‘activated’, the non-coloured state of the component of group (iii) transitions to a blue coloured state. As the coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the blue colour of the formed coloured state of the component of group (iii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, orange, blue and green colours may be formed. It is noted that as the third temperature of the component of group (iii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to the coloured state, the non-coloured state of the component of group (iii) can be activated upon application of the third temperature at localised positions, but the component of group (iv) will remain in the non-coloured state, as the temperature is not high enough to effect a transition from its non-coloured state to a coloured state. Upon application of UV radiation using a germicidal lamp by flood illumination, the ‘activated’ non- coloured state of the component of group (iv) at those localised positons only will transition to a blue coloured state, such that a blue colour can be formed.

A multi-coloured image may therefore be formed displaying yellow, orange, blue and green colours.

Example 15

A composition comprising a component of group (iv) and an acid-generating agent is formulated according to a 50:50 mixture of the formulations of Tables 30 and 31.

A composition comprising a component of group (iii) is formulated according to Table 25, from the millbase formulations of Tables 23 and 24, but replacing the component of group (iii) with N1 , N22-didecyldocosa-10,12-diynediamide.

To a first PET substrate, a layer of the composition comprising a component of group (iii) is applied using a 16 pm K-bar applicator, followed by a layer of the composition comprising a component of group (iv) and an acid-generating agent applied over the layer of the composition comprising a component of group (iii) using a 16 pm K-bar applicator, to form a plurality of discrete layers.

To a second PET substrate, a layer of the composition comprising a component of group (iv) and an acid-generating agent is applied using a 16 pm K-bar applicator, followed by a layer of the composition comprising a component of group (iii) using a 16 pm K-bar applicator, to form a plurality of discrete layers. Prior to the application of any stimulus, the component of group (iv) and the component of group (iii) are in the non-coloured state. The natural state (non- coloured state) of the component of group (iv) is yellow, and therefore the PET substrate displays this colour.

If localised positions of the PET substrates are subjected to IR radiation (fourth temperature) using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 5%, 10% and 38% power), the component of group (iv) transitions from its yellow non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by altering the fluence applied by the laser. It is noted that the third temperature (activation temperature) of the component of group (iii) is lower than the temperature of the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. Accordingly, upon application of the IR radiation detailed above, the non-coloured state of the component of group (iii) is also‘activated’ by the IR radiation at these localised positions to which it is applied. There is no colour formation at these positions for the component of group (iii) as the coloured state of the component of group (iii) has not yet been formed.

Following the application of the IR radiation detailed above to the localised positions of the PET substrates, the PET substrates are exposed to 30W germicidal (254 nm) UV radiation by flood illumination (third applied stimulus) for 20 seconds. At each of the localised positions discussed above, the‘activated’ non-coloured state of the component of group (iii) transitions from the‘active’ non-coloured state to a blue coloured state. As the coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the blue coloured state of the component of group (iii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, orange, blue and green colours may be formed. A multi-coloured image may therefore be formed displaying yellow, orange, blue and green colours.

It is noted that as the third temperature of the component of group (iii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to the coloured state, the non-coloured state of the component of group (iii) can be activated upon application of the third temperature at localised positions, but the component of group (iv) will remain in the non-coloured state, as the temperature is not high enough to effect a transition from its non-coloured state to a coloured state. Upon application of UV radiation using a germicidal lamp by flood illumination, the ‘activated’ non- coloured state of the component of group (iv) at those localised positons only will transition to a blue coloured state, such that a blue colour can be formed.

Differences in final colours formed on the first and second PET substrates can be seen. This is a result of the different ordering of the layers on the PET substrates. Absorption of the applied radiation (and thus depth of colour formation) by the component of group (iv) or component of group (iii) differs dependent upon their distance from the laser, i.e. the layer in which they are situated.

Example 16 A composition comprising a component of group (ii) was formulated according to Table 34, using the millbase formulations of Tables 32 and 33. All amounts are provided in weight percentage (wt%).

Table 32 - Millbase Formulation of Component of Group (ii)

Table 33 - Millbase Formulation of NIR absorber

Table 34

A composition comprising a component of group (iv) and an acid-generating agent is formulation according to a 50:50 mixture of the formulations of Tables 30 and 31.

To a first PET substrate, a layer of the composition comprising the component of group (ii) is applied using a 16 pm k-bar applicator. A layer of the composition comprising the component of group (iv) and acid-generating agent was then applied using a 16 pm k-bar applicator over the layer of the composition comprising the component of group (ii).

To a second PET substrate, a layer of the composition comprising the component of group (iv) and acid-generating agent is applied using a 16 pm k- bar applicator. A layer of the composition comprising the component of group (ii) was then applied using a 16 pm k-bar applicator over the layer of the composition comprising the component of group (iv) and acid-generating agent.

Following application of the layers to the first and second PET substrates, the component of group (ii) and component of group (iv) are in their non-coloured states. The natural state (non-coloured state) of the component of group (iv) is yellow, and therefore the PET substrates display this colour.

Upon application of UV radiation by flood illumination using a 30W germicidal UV lamp for 20 seconds (second applied stimulus), the non-coloured state of the component of group (ii) transitions from the non-coloured to a first coloured state. It is noted that the component of group (iv) does not transition as it is accompanied by a thermal acid-generating agent, and thus required additional temperature to facilitate a transition from the non-coloured state to a coloured state of the component of group (iv). The first coloured state of the component of group (ii) is blue in colour. For the first PET substrate having the component of group (ii) applied first to the substrate, the colour displayed on the PET substrate appears to remain predominantly yellow, i.e. predominantly display the non-coloured state of the component of group (ii). However, for the second PET substrate having the component of group (ii) applied over the layer comprising the component of group (iv), the colour displayed on the PET substrate is green, i.e. a mixture of the yellow displayed by the non-coloured state of the component of group (iv) and the blue first coloured state of the component of group (ii). This difference is as a result of the different ordering of the layers on the PET substrate. Absorption of the applied radiation (and thus depth of colour formation) by the component of group (ii) differs dependent upon its distance from the laser, i.e. the layer in which it is situated. Following the application of the second applied stimulus to the two PET substrates, IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 38% power) is applied to localised positions of the substrates (fourth temperature). At these localised positions, the component of group (iv) transitions from its yellow non-coloured state to a coloured state. The colour of the coloured state, and the intensity thereof, can be made to vary between yellow or orange by variation of the fluence applied by the laser. It is noted that the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. Therefore, upon application of the IR radiation, the second temperature is also reached and at these localised positions, the component of group (ii) also transitions from the first blue coloured state to a red second coloured state. The component of group (ii) is deactivated at these localised positions and will not undergo subsequent transitions (tested using a germicidal lamp or ultravitalux bulb). The intensity of the coloured state can be made to vary by variation of the fluence applied by the C0 ₂ laser. As the second coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the colour of the red second coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, yellow and orange colours may be formed.

Alternatively, following application of the layers to the first and second PET substrates, IR radiation (fourth temperature) using a 10.6 pm C0 ₂ laser (2600- 5350 mm/s, 38% power) is applied at localised positions of the substrate. At these localised positions, the component of group (iv) transitions from its yellow non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of the fluence applied by the C0 ₂ laser. It is noted that, as discussed above, the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. It will therefore be appreciated that upon application of the IR radiation, the second temperature will also be reached and the component of group (ii) will be‘deactivated’ at the localised positions, such that it is not capable of undergoing any subsequent transitions.

The application of the fourth temperature can then be followed by the application of UV radiation by flood illumination using a 30W germicidal (254nm) lamp such that the non-coloured state of the component of group (ii) transitions from the non-coloured to a first coloured state. This occurs across all of the substrate apart from the localised positions at which the coloured state of the component of group (iv) has been formed and the component of group (ii)‘deactivated’. The first coloured state of the component of group (ii) is blue in colour. The same difference in colour displayed by the first and second PET substrates (i.e. a green or a yellow colour displayed) is seen as described above as a result of the different ordering of the layers applied on the PET substrates. Absorption of the applied radiation (and thus depth of colour formation) by the component of group (ii) differs dependent upon its distance from the laser, i.e. the layer in which it is situated.

A multi-coloured image displaying yellow, orange, and green colours can therefore be formed.

Example 17

A composition comprising a component of group (ii) was formulated according to Table 34, using the millbase formulations of Tables 32 and 33 above.

A composition comprising a component of group (iv) and an acid-generating agent is formulated according to a 50:50 mixture of the formulations of Tables 30 and 31 above.

To a paper substrate, a layer of the composition comprising the component of group (iv) and acid-generating agent is applied using a 16 pm k-bar applicator. A layer of the composition comprising the component of group (ii) was then applied using a 16 pm k-bar applicator over the layer of the composition comprising the component of group (iv) and the acid-generating agent.

Following application of the layers to the paper substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states. The non-coloured state (natural state) of the component of group (iv) is yellow, and therefore the PET substrate displays this colour.

Upon application of UV radiation by flood illumination using a 30W germicidal UV lamp for 20 seconds (second applied stimulus), the non-coloured state of the component of group (ii) transitions from the non-coloured to a first coloured state. It is noted that the component of group (iv) does not transition as it is accompanied by a thermal acid-generating agent, and thus requires a fourth temperature to facilitate a transition from its non-coloured state to a coloured state. The first coloured state of the component of group (ii) is blue in colour, and as the layer comprising the component of group (ii) is closest to the laser source, a more intense blue colour is developed as opposed to if the layer comprising the component of group (ii) had been the first applied onto the substrate. The PET substrate therefore displays a green colour following application of the UV radiation, i.e. a mixture of the yellow displayed by the non- coloured state of the component of group (iv) and the blue first coloured state of the component of group (ii).

Following the application of the second applied stimulus to the substrate, IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 5%, 10% and 38% power) is applied to localised positions of the substrates (fourth temperature). At these localised positions, the component of group (iv) transitions from its yellow non-coloured state to a coloured state. The colour of the coloured state, and the intensity thereof, can be made to vary between yellow or orange by variation of the fluence applied by the laser. It is noted that the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. Therefore, upon application of the I R radiation, the second temperature is also reached and at these localised positions, the component of group (ii) also transitions from the first blue coloured state to a red second coloured state. The component of group (ii) is deactivated and will not undergo any subsequent transition (tested using a germicidal lamp or ultravitalux bulb). The intensity of the coloured state can be made to vary by variation of the fluence applied by the C0 ₂ laser. As the second coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the colour of the red second coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, yellow and orange colours may be formed.

Alternatively, following application of the layers to the first and second PET substrates, IR radiation (fourth temperature) using a 10.6 pm C0 ₂ laser (2600- 5350 mm/s, 38% power) is applied at localised positions of the substrate. At these localised positions, the component of group (iv) transitions from its yellow non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of the fluence applied by the C0 ₂ laser. It is noted that, as discussed above, the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. It will therefore be appreciated that upon application of the IR radiation, the second temperature will also be reached and the component of group (ii) will be‘deactivated’ at the localised positions, such that it is not capable of undergoing any subsequent transitions.

The application of the fourth temperature can then be followed by the application of UV radiation by flood illumination using a 30W germicidal (254nm) lamp (second applied stimulus) such that the non-coloured state of the component of group (ii) transitions from the non-coloured to a first coloured state. This occurs across all of the substrate apart from the localised positions at which the coloured state of the component of group (iv) has been formed and the component of group (ii)‘deactivated’. The first coloured state of the component of group (ii) is blue in colour. The same difference in colour displayed by the first and second PET substrates (i.e. a green or a yellow colour displayed) is seen as described above as a result of the different ordering of the layers applied on the PET substrates. Absorption of the applied radiation (and thus depth of colour formation) by the component of group (ii) differs dependent upon its distance from the laser, i.e. the layer in which it is situated.

A multi-coloured image displaying yellow, orange, and green colours can therefore be formed. Example 18

A composition comprising a component of group (ii) was formulated according to Table 34, using the millbase formulations of Tables 32 and 33 above.

A composition comprising a component of group (iv) and a base-generating agent is formulated according to a 50:50 mixture of the formulations of Tables 35 and 36.

Table 35 - Formulation comprising compound of formula (XII)

Table 36 - Formulation comprising base-generating agent

To a PET substrate, a layer of the composition comprising the component of group (iv) and base-generating agent is applied using a 16 pm k-bar applicator. A layer of the composition comprising the component of group (ii) was then applied using a 16 pm k-bar applicator over the layer of the composition comprising the component of group (iv) and the base-generating agent.

Following application of the layers to the PET substrate, the component of group (ii) and component of group (iv) are in their non-coloured states.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 1 %, 38% and 80% power) to localised positions of the substrate (fourth temperature). At these localised positions, the component of group (iv) transitions from its non-coloured state to a pale yellow coloured state at these localised positions. The intensity of the colour of the coloured state can be made to vary by altering the fluence applied by the laser, e.g. by varying the power of the C0 ₂ laser. It is noted that the second temperature is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. Therefore, it will be appreciated that upon application of the IR radiation, the second temperature is reached and the component of group (ii) will also be‘deactivated’ at the localised positions, such that it is not capable of undergoing any subsequent transitions.

It is noted that if the C0 ₂ laser is applied at lower power, only the second temperature will be reached and therefore the component of group (ii) is deactivated at the localised positions, but the component of group (iv) does not transition from the non-coloured to a pale yellow coloured state, such that the colour displayed by the substrate at the localised positions is dependent solely on the non-coloured state of the component of group (ii).

UV radiation is then applied to the substrate by flood illumination using a 30W germicidal UV lamp for 1 minute. The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first blue coloured state across the substrate except from those localised positions where the coloured state of the component of group (iv) has been formed and component of group (ii) has been‘deactivated’.

Alternatively, after application of the layers to the PET substrate, UV radiation is applied by flood illumination using a 30W germicidal lamp (second applied stimulus). The non-coloured state of the component of group (ii) transitions from the non-coloured to the first blue coloured state across the whole substrate. Following application of IR radiation using a 10.6 C0 ₂ pm laser (2600-5350 mm/s, 38% power) (second temperature) to localised positions of the substrate, the component of group (ii) at these positions transitions from the first blue coloured state to the second red coloured state. The intensity of the red second coloured state can be varied by alteration of the fluence applied by the C0 ₂ laser. Upon application of the IR radiation, the fourth temperature has also been reached and the component of group (iv) transitions from the non-coloured to a coloured state. As the second coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the colour of the second red coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, orange and red colours may be formed. A multi-coloured image can therefore be formed displaying yellow, blue, orange and red colours. In addition, the non-coloured state of the component of group (ii) can form part of the multi-coloured image.

Example 19

A composition comprising a component of group (ii) and a component of group (iv) and an acid-generating agent is formulated by combing 1 part of the formulation of Table 34, using the millbase formulations of Tables 32 and 33 above, and 1 part of a 50:50 mixture of the formulations of Tables 30 and 31 above.

A layer of the composition was applied onto a paper substrate (paperboard) using a 20 pm k-bar applicator.

Following application of the layer to the paper substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states. The natural state (non-coloured state) of the component of group (iv) is a pale yellow, and therefore the PET substrate displays this colour.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 38%, power) or NIR radiation using a Nd:YAG laser 1064 nm NIR laser (50% speed, 20-80% power) to localised positions of the substrate (fourth temperature), the component of group (iv) transitions from its non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, of the component of group (iv) can be made to vary between yellow or orange by variation of fluence, e.g. by varying the power of the C0 ₂ or NIR laser. It is noted that the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. It will therefore be appreciated that upon application of the NIR or IR radiation, the second temperature will also be reached and the component of group (ii) will be ‘deactivated’ at the localised positions, such that it is not capable of undergoing any subsequent transitions. UV radiation is then applied to the substrate by flood illumination using a 30W germicidal UV lamp for 20 seconds (second applied stimulus). The non- coloured state of the component of group (ii) therefore transitions from the non- coloured to a first blue coloured state across the substrate except from those localised positions where the coloured state of the component of group (iv) has been formed and the component of group (ii) has been‘deactivated’. The first coloured state of the component of group (ii) is blue in colour, and in combination with the pale yellow colour displayed by the non-coloured state of the component of group (iv), the substrate displays a green colour where the first coloured state of the component of group (ii) has been formed.

Alternatively, following application of the layers to the paper substrate, UV radiation by flood illumination using a 30W germicidal UV lamp for 30 seconds (second applied stimulus) is applied to the substrate. Across the substrate, the non-coloured state of the component of group (ii) transitions from the non- coloured to a first blue coloured state. It is noted that the component of group (iv) does not transition as it is accompanied by a thermal acid-generating agent, and thus requires a fourth temperature to facilitate a transition from its non- coloured state to a coloured state. However, following the application of the applied transition stimulus to the substrate, IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 38% power) or NIR radiation using a Nd:YAG 1064 nm NIR laser (50% speed, 20-80% power) is applied to localised positions of the substrate (fourth temperature). At these localised positions, the component of group (iv) transitions from its non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of fluence, e.g. by varying the power of the C0 ₂ or NIR laser. It is noted that, as discussed above, the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. It will therefore be appreciated that upon application of the NIR or IR radiation, the second temperature will also be reached and the component of group (ii) transitions from the first blue coloured state to a red second coloured state. The component of group (ii) is deactivated and will not undergo subsequent transitions. The intensity of the coloured state can be made to vary by variation of the fluence. As the second coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the component of group (iv), and the colour of the second red coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, orange and red colours may be formed.

A multi-coloured image displaying blue, yellow, orange, green and red colours may therefore be formed.

Example 20

A composition comprising a component of group (ii) and a component of group (iv) and an acid-generating agent is formulated by combing 1 part of the formulation of Table 34, using the millbase formulations of Tables 32 and 33 above, but replacing the component of group (ii) with di-tert-butyl 2,2’-(tetradeca- 6,8-diynedioyl)bis(hydrazine-1 ,20 carboxylate)), and 1 part of a 50:50 mixture of the formulations of Tables 30 and 31 above.

A layer of the composition was applied onto a paper substrate (folding carton) using a 20 pm k-bar applicator.

Following application of the layer to the paper substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states. The natural state (non-coloured state) of the component of group (iv) is a pale yellow, and therefore the PET substrate displays this colour.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 38%, power) to localised positions of the substrate (fourth temperature), the component of group (iv) transitions from its non-coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of the fluence applied by the laser, e.g. by varying the power of the C0 ₂ or NIR laser. It is noted that the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. It will therefore be appreciated that upon application of the IR radiation, the second temperature will also be reached and the component of group (ii) will be‘deactivated’ at the localised positions, such that it is not capable of undergoing any subsequent transitions.

UV radiation is then applied to the substrate by flood illumination using a germicidal UV lamp (second applied stimulus). The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first red coloured state across the substrate except from those localised positions where the coloured state of the component of group (iv) has been formed and the component of group (ii) has been‘deactivated’.

Alternatively, following application of the layers to the paper substrate, UV radiation by flood illumination using a germicidal UV lamp (second applied stimulus) is applied to the substrate. Across the substrate, the non-coloured state of the component of group (ii) transitions from the non-coloured to a first red coloured state. It is noted that the component of group (ivO does not transition as it is accompanied by a thermal acid-generating agent, and thus requires a fourth temperature to facilitate a transition from its non-coloured state to a coloured state. However, following the application of the second applied stimulus to the substrate, IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 38% power) is applied to localised positions of the substrate (fourth temperature,). At these localised positions, the component of group (iv) transitions from its non-coloured state to a coloured state. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of fluence, e.g. by varying the power of the C0 ₂ laser. It is noted that, as discussed above, the second ttemperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. It will therefore be appreciated that upon application of the IR radiation, the second temperature will also be reached and the component of group (ii) transitions from the first red coloured state to a second yellow coloured state. The intensity of the coloured state can be made to vary by variation of the fluence. As the second coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the initial colour formed by the coloured state of the component of group (iv), and the colour of the second coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, yellow and orange colours may be formed.

A multi-coloured image displaying different red, yellow and orange colours can therefore be formed.

Example 21

A composition comprising a component of group (iv) and an acid-generating agent, and a component of group (iii) is formulated by combining 1 part of a 50:50 mixtures of the formulations of Tables 37 and 38 and 1 part of the formulation according to Table 41 , using the millbases of Tables 39 and 40.

Table 37 - Formulation comprising a component of group (iv)

Table 38 - Formulation comprising acid-generating agent

Table 39 - Millbase of a Component of Group (iii)

Table 40 - NIR absorber millbase

Table 41

A layer of the composition is applied to a PET substrate using a 20 pm K-bar applicator.

Following application of the layer to the substrate, the component of group (iv) and the component of group (iii) are in the non-coloured state. The natural state (non-coloured state) of the component of group (iv) is pale yellow, and therefore the PET substrate displays this colour. Upon application of UV radiation to the PET substrate by flood illumination using a germicidal lamp, there is no change in the colour displayed on the substrate. This is on account of the selection of the acid-generating agent. In this example, the acid-generating agent utilised in relation to the component of group (iv) is a thermal acid-generating agent. UV radiation has no effect on the non-coloured state of the component of group (iv) in the composition, i.e. does not facilitate a transition from the non-coloured to a coloured state of the component of group (iv).

If localised positions of the PET substrate are subjected to IR radiation (fourth temperature) using a 10.6 pm C0 ₂ laser (2600-5350 mm/s, 38% power) or NIR radiation (fourth temperature) using a Nd:YAG 1064 nm NIR laser (50% speed, 20-80% power), the component of group (iv) transitions from its pale yellow non- coloured state to a coloured state at these localised positions. The colour of the coloured state, and intensity thereof, can be made to vary from yellow or orange by altering the fluence applied by the laser. It is noted that the third temperature of the component of group (iii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. Accordingly, upon application of the IR or NIR radiation detailed above, the third temperature is reached and the non-coloured state of the component of group (iii) is also‘activated’ by the NIR radiation at the localised positions to which it is applied. There is no colour formation at these positions for the component of group (iii) as the coloured state of the component of group (iii) has not yet been formed.

Following the application of the NIR or IR radiation detailed above to the localised positions of the PET substrate, the PET substrate is exposed to UV radiation by flood illumination using a germicidal UV lamp (third applied stimulus). At each of the localised positions discussed above, the‘activated’ non-coloured state of the component of group (iii) transitions from the‘active’ non-coloured state to a coloured state. The coloured state of the component of group (iii) is formed. The final colour displayed at these localised positions is dependent upon the initial colour formed by the coloured state of the component of group (iv), and the blue colour of the formed coloured state of the component of group (iii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, blue and green colours may be formed.

It is noted that as the third temperature (activation temperature) of the component of group (iii) is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to the coloured state, the non-coloured state of the component of group (iii) can be activated upon application of the third temperature at localised positions, but the component of group (iv) will remain in the non-coloured state, as the temperature is not high enough to effect a transition from its non-coloured state to a coloured state. Upon application of UV radiation using a germicidal lamp by flood illumination, the‘activated’ non-coloured state of the component of group (iii) at those localised positons only will transition to a blue coloured state, such that a blue colour is formed. A multi-coloured image may therefore be formed displaying blue, green and yellow colours.

Example 22

A composition comprising component of group (i) and a component of group (iv) is formulated by combining 1 part of the formulation of Table 2, and 1 part of the formulation of Table 42.

Table 42 - Formulation of a Component of Group (iv)

Table 43

A layer of the composition is applied to a PET substrate using a k2 k-bar applicator. Following application to the PET substrate, the component of group (i) and the component of group (iv) are in the non-coloured state.

If a germicidal UV lamp is used to apply UV radiation (first applied stimulus) to the composition via flood illumination, the component of group (i) transitions from the non-coloured to a yellow coloured state, such that the composition displays a yellow colour on the substrate. The transition of the component of group (iv) from the non-coloured state to a coloured state does not occur as the acid- generating agent is a thermal acid-generating agent and requires the additional temperature to transition.

If IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 m/s, 5% and 38% power) is subsequently applied to localised positions of the composition (fourth temperature), the component of group (iv) transitions from the non-coloured state to a blue coloured state at these localised positions. A blue colour is formed at these localised positions. The intensity of the blue coloured state can be changed by variation in fluence applied by the C0 ₂ laser, e.g. through varying the power of the laser. It is noted that at these localised positions, the component of group (i) also transitions from the pale yellow coloured state to the non-coloured state. However, as the final colour displayed at these localised positions is dependent upon the combination of the coloured state of the component of group (iv) and the non-coloured state of the component of group (i), the blue colour of the coloured state of the component of group (iv) is displayed at the localised positions.

A multi-coloured image may therefore be formed displaying yellow and blue colours.

Example 23

A composition comprising a component of group (iv) is formulated according to Table 29 above.

A composition comprising a component of group (i) was formulated according to Table 2 above.

A layer of the composition comprising a component of group (iv) is applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (i) is then applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (iv).

Following application to the substrate, the component of group (i) and the component of group (iv) are in the non-coloured state.

If a germicidal UV lamp is used to apply UV radiation (first applied stimulus) to the substrate via flood illumination, the component of group (i) transitions from the non-coloured to a pale yellow coloured state, such that a pale yellow colour is displayed on the substrate.

If IR radiation using a 10.6 pm C0 ₂ laser (2600-5350 m/s, 38% power) is applied to localised positions of the substrate (fourth temperature) either prior to or subsequent to the application of the UV radiation, the component of group (iv) transitions from the non-coloured state to a black coloured state at these localised positions. The intensity of the black coloured state can be changed by varying the fluence applied by the C0 ₂ laser. It is noted that at these localised positions, the component of group (i) also transitions from the pale yellow coloured state to the non-coloured state. However, as the final colour displayed at these localised positions is dependent upon the combination of the black coloured state of the component of group (iv) and the non-coloured state of the component of group (i), a black colour is displayed at the localised positions.

A multi-coloured image may therefore be formed displaying yellow and black colours.

Example 24

A composition comprising a component of group (iv) (oxyanion of a multivalent metal) is formulated according to Table 29 above.

A composition comprising a component of group (iv) (leuco dye) is formulated according to Table 42 above, the leuco dye replaced with 3,3'-bis(1 -n-octyl-2- methylindol-3-yl)phthalide (Chameleon Red 5).

A composition comprising a component of group (i) was formulated according to Table 2 above.

A layer of the composition comprising an oxyanion of a multivalent metal is applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a leuco dye is then applied using a k2 k-bar applicator over the layer of the composition comprising an oxyanion of a multivalent metal. A layer of the composition comprising a component of group (i) is then applied using a k2 k-bar applicator over the layer of the composition comprising a leuco dye.

Following application to the substrate, the component of group (i), the leuco dye, and the AOM are in the non-coloured state.

If a germicidal UV lamp is used to apply UV radiation (first applied stimulus) to the substrate via flood illumination, the component of group (i) transitions from the non-coloured to a pale yellow coloured state, such that the composition displays a pale yellow colour on the substrate.

For the application of a fourth temperature, a 10.6 pm C0 ₂ laser (3000-5350 m/s, 38-80% power) was used to provide IR radiation to localised positions either prior to or subsequent to the application of the UV radiation. It will be noted that the fourth temperature required to facilitate the transition of the oxyanion of a multivalent metal from the non-coloured to a coloured state is higher than the fourth temperature required for the leuco dye to transition from the non-coloured to a coloured state. This temperature can be varied through variation of the fluence provided by the C0 ₂ laser. When a lower fluence is applied, e.g. a lower power is utilised for the C0 ₂ laser, the leuco dye transitions from the non-coloured state to a magenta coloured state at these localised positions. The intensity of the magenta colour can be further varied by alteration of the fluence applied by the C0 ₂ laser. Alternatively, if higher fluence is applied, e.g. a higher power is utilised for the C0 ₂ laser, the leuco dye transitions from the non-coloured state to a magenta coloured state and the oxyanion of a multivalent metal also transitions from the non-coloured state to a black coloured state at these localised positions. The intensity of the black colour can be further varied by alteration of the fluence applied by the C0 ₂ laser. Where both the coloured state of the leuco dye and the oxyanion of a multivalent metal are formed at the same localised position, the colour displayed at these localised positions is a combination of the magenta colour of the coloured state of the leuco dye and the black colour of the coloured state of the oxyanion of a multivalent metal.

A multi-coloured image may therefore be formed displaying yellow, magenta and black colours.

Example 25

A composition comprising a component of group (iv) (oxyanion of a multivalent metal) was formulated according to Table 29 above. A composition comprising a component of group (iv) (leuco dye) was formulated according to Table 42 above.

A composition comprising a component of group (ii) was formulated according to Table 34, using the millbase formulations of Tables 32 and 33, but replacing the component of group (ii) with di-tert-butyl-2,2’-(tetradeca-6,8- diynedioyl)bis(hydrazine-l -carboxylate).

A layer of the composition comprising the oxyanion of a multivalent metal was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising the leuco dye was then applied using a k2 k-bar applicator over the layer of the composition comprising the oxyanion of a multivalent metal. A layer of the composition comprising the component of group (ii) was then applied using a k2 k-bar applicator over the layer of the composition comprising the leuco dye.

Following application of the layers to the paper substrate, the component of group (ii), the leuco dye and the oxyanion of a multivalent metal are in their non- coloured states.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (38% power) to localised positions of the substrate (fourth temperature), the oxyanion of a multivalent metal transitions from its non-coloured state to a coloured state at these localised positions. The colour of the coloured state of the oxyanion of a multivalent metal is black, the intensity of which can be altered by variation of fluence. In addition, the leuco dye also transitions from its non-coloured to a blue coloured state at these localised positions, the fourth temperature for this component being very similar to the fourth temperature required to effect the transition of the oxyanion of a multivalent metal. The intensity of the blue colour formed can be altered by varying the fluence applied by the laser. It is further noted that the second temperature of the component of group (ii) is lower than the fourth temperature required to facilitate a transition of the oxyanion of a multivalent metal from the non-coloured to a coloured state. It will therefore be appreciated that upon application of the IR radiation, the second temperature will also be reached and the component of group (ii) will be‘deactivated’ at the localised positions, such that it is not capable of undergoing any subsequent transitions. The final colour displayed at the localised positions is a combination of the blue colour of the coloured state of the leuco dye and the black colour of the coloured state of the oxyanion of a multivalent metal. Accordingly, different black and blue colours can be formed.

UV radiation is then applied to the substrate by flood illumination using a germicidal UV lamp (second applied stimulus). The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first red coloured state across the substrate except from those localised positions where the coloured state of the oxyanion of a multivalent metal has been formed and the component of group (ii) has been‘deactivated’.

Alternatively, following application of the layers to the paper substrate, UV radiation by flood illumination using a germicidal UV lamp (second applied stimulus) is applied to the substrate. Across the substrate, the non-coloured state of the component of group (ii) transitions from the non-coloured to a first red coloured state. It is noted that the oxyanion of anion of a multivalent metal and the leuco dye do not transition as they require an additional temperature to facilitate a transition from the non-coloured state to a coloured state.

Following the application of the UV radiation to the substrate, IR radiation using a 10.6 pm C0 ₂ laser (10-20% power) is applied to localised positions of the substrate (second temperature). At these localised positions, the component of group (ii) transitions from the first red coloured state to a yellow second coloured state. The deactivatable component is deactivated and will not undergo subsequent transition. The intensity of the coloured state can be made to vary by variation of the fluence. However, the 10-20% power of the C0 ₂ laser means that the temperature applied to the localised positions is not high enough to facilitate a transition of the oxyanion of a multivalent metal or the leuco dye as the fourth temperature for transition of the oxyanion of a multivalent metal and leuco dye are higher than the second temperature for the component of group (ii). The coloured state of the oxyanion of a multivalent metal or leuco dye is therefore not formed at these positions. However, if the power of the 10.6 pm C0 ₂ laser is increased to 38%, the component of group (ii) transitions from the red first coloured state to the yellow second coloured state, and the oxyanion of a multivalent metal and leuco dye also transitions from a non-coloured to a black coloured state and a blue coloured state respectively. The intensity of the black colour of the coloured state of the oxyanion of a multivalent metal and the blue colour of the leuco dye can be varied by alteration of the fluence of the C0 ₂ laser. As the second yellow coloured state of the component of group (ii) is formed at the same localised position at which the black coloured state of the oxyanion of a multivalent metal and the blue coloured state of the leuco dye are formed, the final colour displayed at these localised positions is dependent upon the black colour of the coloured state of the oxyanion of the multivalent metal, the blue colour of the coloured state of the leuco dye and the yellow colour of the second coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, black-yellow, black-blue and black colours may be formed.

A multi-coloured image displaying yellow, black, red, blue, black-yellow and black-blue colours can therefore be formed.

Example 26

A composition comprising a component of group (iv) was formulated according to Table 29.

A composition comprising a component of group (ii) was formulated according to Table 34, using the millbase formulations of Tables 32 and 33, but replacing the diacetylene compound with di-tert-butyl-2,2’-(tetradeca-6,8- diynedioyl)bis(hydrazine-1 ,20-carboxylate).

A layer of the composition comprising the component of group (iv) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising the component of group (ii) was then applied using a k2 k-bar applicator over the layer of the composition comprising the component of group (iv). Following application of the layers to the paper substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (10% power) to localised positions of the substrate (second temperature), the component of group (ii) is‘deactivated’ in its non-coloured state at the localised positions, such that it is not capable of undergoing any subsequent transitions. It is noted that the temperature required for the fourth temperature to facilitate a transition of the oxyanion of a multivalent metal is higher than the second temperature. The temperature applied by the 10% power C0 ₂ laser is thus not great enough to facilitate such a transition, and the component of group (iv) remains in its non- coloured state and these localised positions.

UV radiation is then applied to the substrate by flood illumination using a germicidal UV lamp (second applied stimulus). The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first red coloured state across the substrate except from those localised positions where the component of group (ii) has been‘deactivated’.

Alternatively, following application of the layers to the paper substrate, IR radiation using a 10.6 pm C0 ₂ laser (38% power) is applied to localised positions of the substrate (second temperature/fourth temperature). At these localised positions, not only is the component of group (ii)‘deactivated’ such that it is not capable of undergoing any subsequent transitions, but the transition of the component of group (iv) is facilitated as the 38% power provides the higher temperature required for the fourth temperature. The coloured state of the component of group (iv) formed is black, and the intensity of the colour can be altered by variation of the fluence of the C0 ₂ laser. UV radiation is then applied to the substrate by flood illumination using a germicidal UV lamp (second applied stimulus). The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first red coloured state across the substrate except from those localised positions where the coloured state of the component of group (iv) has been formed and the component of group (ii) has been‘deactivated’. Alternatively, following application of the layers to the paper substrate, UV radiation by flood illumination using a germicidal UV lamp (second applied stimulus) is applied to the substrate. Across the substrate, the non-coloured state of the component of group (ii) transitions from the non-coloured to a first red coloured state. Following the application of the second applied stimulus to the substrate, IR radiation using a 10.6 pm C0 ₂ laser (10% power) is applied to localised positions of the substrate (second temperature). At these localised positions, the component of group (ii) transitions from the first red coloured state to a yellow second coloured state. The component of group (ii) is deactivated and will not undergo any subsequent transition. The intensity of the coloured state can be made to vary by variation of the fluence. However, as discussed above, the 10% power of the C0 ₂ laser means that the temperature applied to the localised positions is not high enough to facilitate a transition of the component of group (iv) as the fourth temperature required to effect the transition of the component of group (iv) is higher than the second temperature for the component of group (ii). The coloured state of the component of group (iv) is therefore not formed at these positions. However, if the power of the 10.6 pm C0 ₂ laser is increased to 20%, the component of group (ii) transitions from the red first coloured state to the yellow second coloured state, and the component of group (iv) also transitions from a non-coloured to a black coloured state. The intensity of the colour of the coloured state can be varied by alteration of the fluence of the C0 ₂ laser. If the transition from the non-coloured state to the coloured state of the component of group (iv) is facilitated, as the second coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the component of group (iv) is formed, the final colour displayed at these localised positions is dependent upon the initial colour formed by the coloured state of the component of group (iv), and the colour of the second coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, yellow, brown and black colours can be formed. A multi-coloured image can therefore be formed having black, brown, red and yellow colours. In addition, the non-coloured state of the component of group (ii) can form part of the multi-coloured image.

Example 27

A composition comprising a component of group (iv) (oxyanion of a multivalent metal) was formulated according to Table 29.

A composition comprising a component of group (iv) (compound of formula (XII)) and acid-generating agent was formulated according to a 50:50 mixture of the formulations of Tables 30 and 31.

A composition comprising a component of group (ii) was formulated according to Table 34, using the millbase formulations of Tables 32 and 33.

A layer of the composition comprising the oxyanion of a multivalent metal was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising the compound of formula (XII) and acid-generating agent was applied using a k2 k-bar applicator over the layer of the composition comprising the oxyanion of a multivalent metal. A layer of the composition comprising the component of group (ii) was then applied using a k2 k-bar applicator over the layer of the composition comprising the compound of formula (XII) and acid-generating agent.

Following application of the layers to the paper substrate, the component of group (ii), the oxyanion of a multivalent metal and the compound of formula (XII) are in their non-coloured states. The natural state (non-coloured state) of the compound of formula (XII) is pale yellow and therefore, the substrate displays this colour.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20% power) to localised positions of the substrate (fourth temperature), the non-coloured state of the compound of formula (XII) transitions from the pale yellow non-coloured to a coloured state. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of the fluence applied by the laser. It is noted that the second temperature is lower than the fourth temperature required to facilitate a transition of the compound of formula (XII) from the non-coloured to a coloured state. Therefore, it will be appreciated that upon application of the IR radiation for the fourth temperature, the second temperature is also reached and the component of group (ii) will be‘deactivated’ at those localised positions, such that it is not capable of undergoing any subsequent transitions and remains in the non-coloured state at these localised positions. It is noted that the application of IR radiation using a C0 ₂ laser at 10% power does not apply a temperature high enough to facilitate a transition of the oxyanion of a multivalent metal from the non-coloured state to a coloured state. This is on account of the fact that the fourth temperature of the oxyanion of a multivalent metal is higher than the fourth temperature required for the compound of formula (XII) to transition, and the second temperature of the component of group (ii). However, if the power of the laser is increased to 38% power, the fourth temperature for the oxyanion of a multivalent metal is reached and the oxyanion of a multivalent metal transitions from the non-coloured to a black coloured state. The intensity of the black coloured state can be made to vary by variation of fluence. As the coloured state of the compound of formula (XII) is formed at the same localised position at which the coloured state of the oxyanion of a multivalent metal is formed, the final colour displayed at these localised positions is dependent upon the black colour of the coloured state of the oxyanion of the multivalent metal, and the colour of the coloured state of the compound of formula (xll), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, black, brown and yellow colours can be formed.

UV radiation is then applied to the substrate by flood illumination using a germicidal UV lamp (second applied stimulus). The non-coloured state of the component of group (ii) therefore transitions from the non-coloured to a first blue coloured state across the substrate except from those localised positions where the component of group (ii) has been‘deactivated’. It will be appreciated that the colour displayed is a combination of the pale yellow colour displayed by the non-coloured state of the compound of formula (XII) and the blue colour of the first coloured state of the component of group (ii). Accordingly, other than at the localised positions discussed above, the substrate displays a turquoise colour. An increased length of application of the UV radiation provides a more intense turquoise colour.

Alternatively, following application of the layers to the paper substrate, UV radiation by flood illumination using a germicidal UV lamp (second applied stimulus) is applied to the substrate. Across the substrate, the non-coloured state of the component of group (ii) transitions from the non-coloured to a first blue coloured state. It will be appreciated that the colour displayed is a combination of the pale yellow colour displayed by the non-coloured state of the compound of formula (XII) and the blue colour of the first coloured state of the component of group (ii). Accordingly, other than at the localised positions discussed above, the substrate displays a turquoise colour. An increased length of application of the UV radiation provides a more intense turquoise colour.

IR radiation is then applied using a 10.6 pm C0 ₂ laser (20% power) to localised positions of the substrate (fourth temperature), as discussed above the non- coloured state of the compound of formula (XII) transitions from the pale yellow non-coloured to a coloured state. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by variation of fluence. As discussed above, the second temperature is lower than the fourth temperature required to facilitate a transition of the compound of formula (XII) from the non-coloured to a coloured state. Therefore, upon application of the IR radiation, the second temperature is reached and the first blue coloured state of the component of group (ii) transitions to a second red coloured state. The component of group (ii) is deactivated. As the second red coloured state of the component of group (ii) is formed at the same localised position at which the coloured state of the compound of formula (XII) is formed, the final colour displayed at these localised positions is dependent upon the colour of the coloured state of the compound of formula (XII), and the second red coloured state of the component of group (ii), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, orange and brown colours can be formed. It is noted that the application of IR radiation using a C0 ₂ laser at 20% power does not apply a temperature high enough to facilitate a transition of the oxyanion of a multivalent metal from the non-coloured state to a coloured state. This is on account of the fact that the fourth temperature of the oxyanion of a multivalent metal is higher than the additional temperature required for the compound of formula (XII) to transition, and the second temperature of the component of group (ii). However, if the power of the laser is increased to 38% power, the fourth temperature for the oxyanion of a multivalent metal is also reached and the oxyanion of a multivalent metal transitions from the non- coloured to a black coloured state. The intensity of the black coloured state can be made to vary by variation of the fluence applied by the laser. As the black coloured state of the oxyanion of a multivalent metal is formed at the same localised position at which the coloured state of the component of group (ii) and the compound of formula (XII) is formed, the final colour displayed at these localised positions is dependent upon the black colour of the coloured state of the oxyanion of the multivalent metal, and the red second coloured state of the component of group (ii) and the compound of formula (XII), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, black and orange colours can be formed.

A multi-coloured image displaying yellow, orange, red, black, brown and turquoise can therefore be formed.

Example 28

A composition comprising a component of group (iv) (keto acid compound of formula (IX)) was formulated according to Table 44. All amounts are provided in weight percentage (wt%).

Table 44 - Formulation comprising a Component of Group (iv)

A composition comprising an component of group (iv) (oxyanion of a multivalent metal) was formulated according to Table 29 above.

A composition comprising a component of group (iii) was formulated according to Table 41 , using the millbase formulations of Tables 39 and 40.

A layer of the composition comprising an oxyanion of a multivalent metal was applied to a paper substrate using a K2 K-bar applicator. A layer of the composition comprising a keto acid compound of formula (IX) was then applied using a k2 k-bar applicator over the layer of the composition comprising an oxyanion of a multivalent metal. A layer of the composition comprising a component of group (iii) was then using a k2 k-bar applicator over the layer of the composition comprising a keto acid compound of formula (IX).

The oxyanion of a multivalent metal, keto acid compound of formula (IX) and component of group (iii) are in their non-coloured states. Following application of the layers to the substrate, a fourth temperature is applied to localised positions by IR radiation using a 10.6 pm C0 ₂ laser (20% power). The keto acid compound of formula (IX) transitions from the non- coloured state to a yellow coloured state at the localised positions. The intensity of the yellow colour can be varied by alteration of the fluence provided by the C0 ₂ laser. It is noted that the fourth temperature required to facilitate a transition of the keto acid compound of formula (IX) from the non-coloured state to a coloured state is slightly lower than the fourth temperature required to facilitate a transition of the oxyanion of a multivalent metal from a non-coloured to a coloured state. To provide such a fourth temperature to facilitate the transition of the oxyanion of a multivalent metal from a non-coloured to a coloured state, the power of the C0 ₂ laser is increased to 38%. This facilitates the formation of the black coloured state of the oxyanion of a multivalent metal. The intensity of the black colour formed can be made to vary by variation of the fluence provided by the C0 ₂ laser. If the 38% power is utilised, as the coloured state of the oxyanion of a multivalent metal is formed at the same localised position at which the coloured state of the keto acid compound of formula (IX) has been formed, the final colour displayed at these localised positions is dependent upon the black colour of the coloured state of the oxyanion of a multivalent metal, and the yellow colour of the coloured state of the keto acid compound of formula (IX), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of the two components. Accordingly, different yellow and black coloured states can be formed. It is noted that the third temperature of the component of group (iii) is lower than both the fourth temperatures for the keto acid compound of formula (IX) and the oxyanion of a multivalent metal. Accordingly, upon application of the IR radiation at the localised positions of the substrate, the non-coloured state of the component of group (iii) is activated at these localised positions.

Upon application of UV radiation to the substrate by flood illumination using a germicidal lamp (third applied stimulus), the component of group (iii) transitions from the non-coloured state to a first blue coloured state at the localised positions at which the non-coloured state has been ‘activated’. If the UV radiation has been applied following only the application of IR radiation using the C0 ₂ laser at 20% power, the colour displayed at the localised positions will be a combination of the blue of the first coloured state of the component of group (iii) and the yellow coloured state of the keto acid compound of formula (IX). Accordingly, different blue and green colours can be formed. If further IR radiation (additional temperature) is applied using the C0 ₂ laser at 20% power at the localised positions at which the first coloured state of the component of group (iii) have been formed, the component of group (iii) transitions from the blue first coloured state to a red second coloured state. The intensity of the colour can be varied by variation of the fluence applied by the C0 ₂ laser. The colour displayed at the localised positions will be a combination of the red of the second coloured state of the component of group (iii) and the yellow coloured state of the keto acid compound of formula (IX). Accordingly, different orange and red colours can be formed. It is noted that the applied temperature is lower than the fourth temperature required to facilitate a transition of the oxyanion of a multivalent metal from the non-coloured to the coloured state. Accordingly, if instead the further IR radiation is applied using the C0 ₂ laser at 38% power, the fourth temperature is reached and the oxyanion of a multivalent metal transitions from the non-coloured to a black coloured state. The intensity of the colour can be varied by variation of the fluence applied by the C0 ₂ laser. The colour displayed at the localised positions will be a combination of the red of the second coloured state of the component of group (iii), the yellow coloured state of the keto acid compound of formula (IX), and the black coloured state of the oxyanion of a multivalent metal. Accordingly, different red, brown and black colours can be formed.

Alternatively, if the UV radiation (second applied stimulus) has been applied following the application of IR radiation using a C0 ₂ laser at 38% power, the colour displayed at the localised positions will be a combination of the blue of the first coloured state of the component of group (iii), the yellow coloured state of the keto acid compound of formula (IX), and the black coloured state of the oxyanion of a multivalent metal. Accordingly, different green and black colours can be formed.

A multi-coloured image displaying yellow, black, green, blue, red, orange and brown colours can therefore be formed. Example 29

A composition comprising a component of group (iv) was formulated according to Table 44 above.

A composition comprising a component of group (iii) was formulated according to Table 41 , using the millbase formulations of Tables 39 and 40.

A layer of the composition comprising a component of group (iv) was applied to a paper substrate using a K2 k-bar applicator. A layer of the composition comprising a component of group (iii) was then applied on top of the layer of the composition comprising a component of group (iv) using a K2 k-bar applicator. The component of group (iv) and component of group (iii) are in their non- coloured states.

Upon application of a third temperature using a C0 ₂ laser (20% power) to provide IR radiation at localised positions, the non-coloured state of the component of group (iii) is activated. It is noted that the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state is higher than that of the third temperature applied using the C0 ₂ laser at 20% power, and thus there is no transition from the non-coloured state to the coloured state of the component of group (iv). Upon application of UV radiation by flood illumination using a germicidal lamp as the third applied stimulus, the non-coloured state of the component of group (iii) transitions to a blue coloured state solely at the localised positions at which the non-coloured state of the component of group (iii) has been‘activated’.

If following application of the third temperature, UV radiation is applied by flood illumination to the substrate using a germicidal lamp, the non-coloured state of the component of group (iii) transitions to a first blue coloured state solely at the localised positions at which the non-coloured state of the component of group (iii) has been‘activated’. A blue colour can therefore be formed. Subsequent application of IR radiation using a 10.6 pm C0 ₂ laser (20% power) to the localised positions at which the first blue coloured state has been formed then acts as the additional temperature and the component of group (iii) transitions at these localised positions from the first blue coloured state to a second red coloured state. The intensity of the colour formed can be varied by altering the fluence applied by the C0 ₂ laser.

Alternatively, following application of the layers to the substrate, the third temperature is applied using a C0 ₂ laser (38% power), i.e. at increased fluence, to provide IR radiation at localised positions. It will be appreciated that a higher temperature is applied such that as well as activating the non-coloured state of the component of group (iii) at these localised positions, the transition of the component of group (iv) from the non-coloured state to a coloured state is facilitated, i.e. the fourth temperature is reached. The colour of the coloured state of the component of group (iv), and the intensity thereof, can be changed between yellow or orange by variation of the fluence applied by the C0 ₂ laser.

If following application of the fourth temperature that formed the coloured state of the component of group (iv) at those localised positions, UV radiation is applied by flood illumination using a germicidal lamp as the third applied stimulus, the ‘activated’ non-coloured state of the component of group (iii) transitions to a blue coloured state solely at these localised positions that have been‘activated’. As the coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the blue coloured state of the component of group (iii), and the colour of the coloured state of the component of group (iv), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of the two components. Accordingly, blue, green and orange coloured states can be formed.

A multi-coloured image may therefore be formed displaying yellow, orange, red, green and blue colours.

Example 30 A composition comprising a component of group (iv) (oxyanion of a multivalent metal) was formulated according to Table 29 above.

A composition comprising a component of group (iv) (a compound of formula (XII)) was formulated according to a 50:50 mixture of the formulations of Tables 35 and 36.

A composition comprising a component of group (ii) was formulated according to Table 34 above, using the millbase formulations of Tables 32 and 33.

A layer of the composition comprising an oxyanion of a multivalent metal was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a compound of formula (XII) was then applied using a k2 k-bar applicator over the layer of the composition comprising an oxyanion of a multivalent metal. A layer of the composition comprising a component of group (ii) was then applied using a k2 k-bar applicator over the layer of the composition comprising a compound of formula (XII).

Following application of the layers to the substrate, UV radiation (second applied stimulus) was applied by flood illumination using a germicidal lamp. The component of group (ii) transitions from the non-coloured state to a first coloured state across the substrate, such that a blue colour is displayed across the substrate. Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20% power) at localised positions (second temperature), this first blue coloured state transitions to a second red coloured state, the component of group (ii) being deactivated and unable to undergo any subsequent transitions. The intensity of the red second coloured state formed can be varied by altering the fluence applied by the laser. In addition, upon application of the IR radiation, the fourth temperature for the compound of formula (XII) is also reached (the fourth temperature is slightly lower than the second temperature in this case) and the compound of formula (XII) transitions from the non-coloured state to a yellow coloured state at the localised positions. It will be appreciated that the intensity of this coloured state can be varied by altering the fluence applied by the laser. As the coloured state of the compound of formula (XII) is formed at the same localised position at which the second red coloured state of the component of group (ii) has been formed, the final colour displayed at these localised positions is dependent upon the red second coloured state of the component of group (ii), and the yellow coloured state of the compound of formula (XII), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of the two components. Accordingly, different orange colours can be formed.

It is noted that the application of the IR radiation using a 10.6 pm C0 ₂ laser at 20% does not provide a fourth temperature high enough to facilitate a transition of the oxyanion of a multivalent metal from its non-coloured state to a coloured state. This is on account of the fact that the fourth temperature required for the transition of the oxyanion of a multivalent metal to be effected is higher than the fourth temperature required for the transition of the compound of formula (XII) to be effected, and the second temperature of the deactivatable component. Accordingly, when IR radiation is applied using a 10.6 pm C0 ₂ laser at 38% power, i.e. increased power, the fourth temperature for the oxyanion of a multivalent metal is reached and the oxyanion of a multivalent metal transitions from the non-coloured to a black coloured state. The intensity of this black coloured state can be varied by alteration of the applied fluence. If the coloured state of the oxyanion of a multivalent metal is formed, as the coloured state will be formed at the same localised position at which the second red coloured state of the component of group (ii) and the yellow or orange coloured state of the compound of formula (XII) has been formed, the final colour displayed at these localised positions is dependent upon the colour of the red second coloured state of the component of group (ii), the yellow or orange colour of the coloured state of the compound of formula (XII) and the black coloured state of the oxyanion of a multivalent metal i.e. the final colour at these localised positions results from the combination of colours of the coloured states of the three components. Accordingly, different orange, brown and black colours can be formed.

Alternatively, following application of the layers to the substrate, IR radiation is applied to the substrate using a 10.6 pm C0 ₂ laser (38% power) (fourth temperature). As discussed above, given the power of the C0 ₂ laser, a transition from the non-coloured to a black coloured state of the oxyanion of a multivalent metal is effected. The intensity of the coloured state formed can be varied by altering the applied fluence. As the fourth temperature required to facilitate the transition of the oxyanion of a multivalent metal is greater than the fourth temperature required for the transition of the compound of formula (XII) from the non-coloured to a coloured state, the transition of the compound of formula (XII) to a yellow coloured state is also effected upon application of the IR radiation. If the C0 ₂ laser is utilised at a lower power, as discussed above, only the compound of formula (XII) will transition to a coloured state and a yellow colour is displayed at those localised positions on the substrate.

A multi-coloured image displaying black, yellow, blue, orange, brown and black colours can therefore be formed.

Example 31

A composition comprising a component of group (iv) and an acid-generating agent is formulated according to Table 44 above.

A composition comprising a component of group (ii) is formulated according to Table 34 above, using the millbase formulations of Tables 32 and 33.

A layer of the composition comprising a component of group (iv) and an acid- generating agent is applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (ii) is applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (iv) and an acid-generating agent.

Upon application to the substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states. The non-coloured state of the component of group (iv) is pale yellow, and therefore the paper substrate displays this colour.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20%) (second temperature) at localised positions of the substrate, the component of group (ii) is‘deactivated’ and will remain in the non-coloured state, i.e. not be capable of undergoing any subsequent transitions. It is noted that the second temperature is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a yellow coloured state. Therefore, upon application of the IR radiation with the laser only a 20% power, the transition of the component of group (iv) does not occur. However, if the power of the C0 ₂ laser is increased to 38%, the component of group (iv) transitions from the non-coloured state to a yellow coloured state. The intensity of the colour of the formed coloured state can be varied by variation of the fluence, e.g. by varying the power of the C0 ₂ laser.

Following application of UV radiation by flood illumination using a germicidal lamp (second applied stimulus), the component of group (ii) transitions from the non-coloured state to a blue first coloured state across the substrate, apart from at those localised positions at which the component of group (ii) has been deactivated. If the transition of the component of group (iv) was not facilitated by the previous IR radiation, the localised positions display the non-coloured state of the component of group (ii). If the transition of the component of group (iv) was facilitated by the IR radiation, the localised positions display the yellow coloured state of the component of group (iv).

Alternatively, following application of the layers to the substrate, if UV radiation is applied by flood illumination using a germicidal lamp to the substrate (second applied stimulus), the component of group (ii) transitions from the non-coloured state to a blue first coloured state across the substrate. Following subsequent application of IR radiation at localised positions of the substrate using a 10.6 pm C0 ₂ laser (20% power) (second temperature), the first blue coloured state transitions to a red second coloured state at those localised positions. The component of group (ii) is deactivated and will not undergo any further transitions. The intensity of the colour of the red second coloured state can be made to vary by altering the fluence applied by the laser. As discussed above, the component of group (iv) does not also transition to a coloured state as the fourth temperature required is greater than the second temperature. However, if the power of the C0 ₂ laser is increased to 38%, the component of group (iv) also transitions at the localised positions from the non-coloured to a yellow coloured state. The intensity of the colour of the coloured state can be made to vary by altering the fluence applied by the laser. As both the yellow coloured state of the component of group (iv) and the red second coloured state of the component of group (ii) are formed at the same localised positions on the substrate, the colour displayed is a combination of these colours. Accordingly, different orange colours can be formed.

A multi-coloured image displaying blue, yellow and orange colours can therefore be formed. In addition, the non-coloured state of the component of group (ii) can form part of the multi-coloured image.

Example 32

A composition comprising a component of group (iv) and an acid-generating was formulated according to Table 45.

Table 45 - Formulation of a Component of Group (iv)

A composition comprising a component of group (ii) was formulated according to Table 34 above, using the millbase formulations of Tables 32 and 33.

A layer of the composition comprising a component of group (iv) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (ii) was applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (iv).

Following application of the layers to the substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20%) (second temperature) at localised positions of the substrate, the component of group (ii) is‘deactivated’ and will remain in the non-coloured state, i.e. not be capable of undergoing any subsequent transitions. It is noted that the second temperature is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a yellow coloured state. Therefore, upon application of the IR radiation with the laser only a 20% power, the transition of the component of group (iv) does not occur. However, if the power of the C0 ₂ laser is increased to 38%, the component of group (iv) transitions from the nonOcoloured state to a yellow coloured state. The intensity of the colour of the formed coloured state can be varied by variation of the fluence, e.g. by varying the power of the C0 ₂ laser.

Upon application of UV radiation by flood illumination using a germicidal lamp (second applied stimulus), the non-coloured state of the component of group (ii) transitions to a first blue coloured state across the substrate apart from those localised positions at which the component of group (ii) has been‘deactivated’. If the transition of the component of group (iv) was not facilitated by the previous IR radiation, the localised positions display the non-coloured state of the component of group (ii). If the transition of the component of group (iv) was facilitated by the IR radiation, the localised positions display the yellow coloured state of the component of group (iv)).

Alternatively, following application of the layers to the substrate, if UV radiation is applied by flood illumination using a germicidal lamp to the substrate (second applied stimulus), the component of group (ii) transitions from the non-coloured state to a blue first coloured state across the substrate. Following subsequent application of IR radiation at localised positions of the substrate using a 10.6 pm C0 ₂ laser (20% power) (second temperature), the first blue coloured state transitions to a red second coloured state at those localised positions. The component of group (ii) is deactivated and will not undergo any further transitions. The intensity of the colour of the red second coloured state can be made to vary by altering the fluence applied by the laser. As discussed above, the component of group (iv) does not also transition to a coloured state as the fourth temperature required is greater than the second temperature. However, if the power of the C0 ₂ laser is increased to 38%, the component of group (iv) also transitions at the localised positions from the non-coloured to a yellow coloured state. The intensity of the colour of the coloured state can be made to vary by altering the fluence applied by the laser. As both the yellow coloured state of the component of group (iv) and the red second coloured state of the component of group (ii) are formed at the same localised positions on the substrate, the colour displayed is a combination of these colours. Accordingly, different orange colours can be formed.

A multi-coloured image displaying blue, yellow and orange colours can therefore be formed. In addition, the non-coloured state of the component of group (ii) can form part of the multi-coloured image.

Example 33

A composition comprising a component of group (iv) was formulated according to Table 45, but the keto acid compound of formula (IX) was replaced with (2-(4- (diethylamino)-2-hydroxybenzoyl)-5-nitrobenzoic acid. A composition comprising a component of group (ii) was formulated according to Table 34 above, using the millbase formulations of Tables 32 and 33.

A layer of the composition comprising a component of group (iv) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (ii) was then applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (iv).

Following application of the layers to the substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states. The non- coloured state of the component of group (iv) is pale yellow, and therefore the paper substrate displays this colour.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser (20%) (second temperature) at localised positions of the substrate, the component of group (ii) is‘deactivated’ and will remain in the non-coloured state, i.e. not be capable of undergoing any subsequent transitions. It is noted that the second temperature is lower than the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state. Therefore, upon application of the IR radiation with the laser only a 20% power, the transition of the component of group (iv) does not occur. However, if the power of the C0 ₂ laser is increased to 38%, the component of group (iv) transitions from the non-coloured state to a yellow coloured state. The colour of the coloured state, and intensity thereof can be made to vary between yellow and orange by altering the fluence applied by the laser.

Upon application of UV radiation by flood illumination using a germicidal lamp (second applied stimulus), the non-coloured state of the component of group (ii) transitions to a first blue coloured state across the substrate apart from those localised positions at which the component of group (ii) has been‘deactivated’. If the transition of the component of group (iv) was not facilitated by the previous IR radiation, the localised positions display the non-coloured state of the component of group (ii). If the transition of the component of group (iv) was facilitated by the IR radiation, the localised positions display the coloured state of the component of group (iv).

Alternatively, following application of the layers to the substrate, if UV radiation is applied by flood illumination using a germicidal lamp to the substrate (second applied stimulus), the component of group (ii) transitions from the non-coloured state to a blue first coloured state across the substrate. Following subsequent application of IR radiation at localised positions of the substrate using a 10.6 pm C0 ₂ laser (20% power) (second temperature), the first blue coloured state transitions to a red second coloured state at those localised positions. The component of group (ii) is deactivated and will not undergo any further transitions. The intensity of the colour of the red second coloured state can be made to vary by altering the fluence applied by the laser. As discussed above, the component of group (iv) does not also transition to a coloured state as the fourth temperature required is greater than the second temperature. However, if the power of the C0 ₂ laser is increased to 38%, the component of group (iv) also transitions at the localised positions from the non-coloured to a yellow coloured state. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by altering the fluence applied by the laser. As both the coloured state of the component of group (iv) and the red second coloured state of the component of group (ii) are formed at the same localised positions on the substrate, the colour displayed is a combination of these colours. Accordingly, different red, brown and orange colours can be formed.

A multi-coloured image displaying blue, yellow, red, brown and orange colours can therefore be formed. In addition, the non-coloured state of the component of group (ii) can form part of the multi-coloured image.

Example 34

A composition comprising a component of group (iv) and an acid-generating agent was formulated according to Table 44 above.

A composition comprising a component of group (iii) was formulated according to Table 41 , using the millbase formulations of Tables 39 and 40. A layer of the composition comprising a component of group (iv) and acid- generating agent was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (iii) was applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (liv) and acid-generating agent.

Following application of the layers to the substrate, IR radiation is applied using a 10.6 pm C0 ₂ laser (20% power) (third temperature) to localised positions of the substrate so as to ‘activate’ the non-coloured state of the component of group (iii). It is noted that this third temperature is lower than the fourth temperature required to facilitate a transition of the non-coloured state of the component of group (iv) from the non-coloured to a coloured state. Accordingly, when a coloured state of the component of group (iv) is also required at the localised positions, the power of the laser is increased to 38% power, such that a higher temperature is provided and the component of group (iv) transitions from the non-coloured state to a yellow coloured state. The intensity of the yellow coloured state formed can be varied by alteration of the fluence applied by the C0 ₂ laser. At these localised positions, the non-coloured state of the component of group (iii) is‘activated’.

Upon further application of UV radiation using a germicidal lamp, the‘activated’ non-coloured state of the component of group (iii) at the localised positions transition to a blue first coloured state. If the coloured state of the component of group (iv) has been formed, the final colour displayed at the localised positions will be a combination of the blue first coloured state of the component of group (iii) and the yellow coloured state of the component of group (iv). Accordingly, blue and green colours can be formed.

Upon application of the fourth temperature by flood illumination using a heat gun, the first blue coloured states formed will transition from the first blue coloured state to the second red coloured state. Again, if the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positons will be a combination of the colour of the red second coloured state of the component of group (iii) and the yellow coloured state of the component of group (iv). Accordingly, red and orange colours can be formed.

A multi-coloured image displaying red, yellow, blue, orange and green colours may therefore be formed.

Example 35

A composition comprising a component of group (iv) and an acid-generating agent was formulated according to Table 44, but with the compound of formula (IX) being replaced with (2,5-bis(4-(diethylamino)-2-hydroxybenzoyl)terephthalic acid.

A composition comprising a component of group (iii) is formulated according to Table 25, using the millbase formulations of Tables 23 and 24.

A layer of the composition comprising a component of group (iv) and an acid generating agent is applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (iii) was applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (iv) and an acid-generating agent.

Following application of the layers to the substrate, the component of group (iii) and the component of group (iv) are in their non-coloured states. The non- coloured state of the component of group (iv) is yellow in colour and therefore the substrate displays this colour. It is noted that the component of group (iii) utilised in this example has a non-coloured state that requires‘activation’, i.e. application of a third temperature to make it capable of transitioning from the non-coloured to a coloured state.

Following application of the layers to the substrate, IR radiation is applied at localised positions using a 10.6 pm C0 ₂ laser (fourth temperature) to localised positions of the substrate to facilitate a transition of the non-coloured state of the component of group (iv) to a coloured state. The colour of the coloured state, and intensity thereof, can be changed between yellow, orange and red by variation of the fluence applied by the C0 ₂ laser. It is noted that the third temperature of the component of group (iii) is lower than the fourth temperature. Accordingly, the IR radiation also provides a third temperature at these localised positions such that the non-coloured state of the component of group (ii) is activated and capable of undergoing a transition.

Upon further application of UV radiation using a germicidal lamp (third applied stimulus), the non-coloured state of the component of group (iii) transitions to a blue first coloured state at the localised positions at which the non-coloured state of the component of group (iii) has been activated. As the coloured state of the first blue coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the blue colour of the first coloured state of the component of group (iii), and the colour of the coloured state of the component of group (iv), i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, blue, green and purple colours can be formed.

Upon further application of an additional temperature to the substrate by flood illumination using a heat gun, the first blue coloured state of the component of group (iii) transitions to a second red coloured state. As before, in light of the combination of the red second coloured state of the component of group (iii) and the colour of the coloured state of the component of group (iv), red, orange and purple colours can be formed.

A multi-coloured image displaying yellow, orange, red, blue, green and purple colours may therefore be formed.

Example 36

A composition comprising a component of group (iv) and an acid-generating agent was formulated according to Table 44, but with the compound of formula (IX) being replaced with (2,5-bis(4-(diethylamino)-2-hydroxybenzoyl)terephthalic acid. A composition comprising a component of group (ii) is formulated according to Table 34, using the millbase formulations of Tables 32 and 33, but replacing the component of group (ii) with di-tert-butyl(((docosa-10,12- diynedioyl)bis(azanediyl)bis(ethane-2, 1 -diyl))dicarbamate.

A layer of the composition comprising a component of group (iv) and an acid generating agent is applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (ii) was applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (iv) and an acid-generating agent.

Following application of the layers to the substrate, the component of group (ii) and the component of group (iv) are in their non-coloured states. The non- coloured state of the component of group (iv) is yellow and therefore the substrate displays this colour.

Upon application of UV radiation using a germicidal lamp (second applied stimulus), the non-coloured state of the component of group (ii) transitions to a red first coloured state across the whole substrate. Following further application of IR radiation using a 10.6 pm C0 ₂ laser (38% power) (second temperature) to localised positions of the substrate, the first red coloured state of the component of group (ii) transitions to a blue second coloured state. The intensity of the colour of the second coloured state formed can be varied by altering the fluence of the C0 ₂ laser. It is noted that the component of group (ii) is deactivated, and cannot undergo any subsequent transitions. It is further noted that the fourth temperature required to facilitate a transition of the component of group (iv) from the non-coloured to a coloured state is greater than the second temperature. In this instance, the 38% power C0 ₂ laser provides a high enough temperature to reach the fourth temperature and effect the transition of the component of group (iv) from the non-coloured state to a coloured state. The colour of the coloured state, and intensity thereof, of the component of group (iv) can be varied between yellow or orange by variation of fluence applied by the laser. As the coloured state of the component of group (iv) is formed at the same localised position at which the second coloured state of the component of group (ii) has been formed, the final colour displayed at these localised positions is dependent upon the blue colour of the second coloured state of the component of group (ii), and the colour of the coloured state of the component of group (iv) has been formed, i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, different orange, yellow and blue colours can be formed.

Upon further application of the second temperature by flood illumination using a heat gun, the component of group (ii) transitions across the substrate from the first red coloured state to a blue second coloured state apart from at those localised positions at which the component of group (ii) has already been deactivated. The component of group (ii) remains unchanged at these localised positions, demonstrating that, when deactivated, the component of group (ii) will not undergo any further transitions.

A multi-coloured image displaying yellow, orange, red and blue colours can be formed.

Example 37

A layer of the composition comprising a component of group (iii) was formulated according to Table 25 above, using the millbase formulations of Tables 23 and 24. A layer of the composition comprising a component of group (iv) was formulated according to 2:1 blend of the formulations of Table 46 with the formulation of Table 47. All amounts are provided in weight percentages (wt%).

Table 46

Table 47

A layer of the composition comprising a component of group (iii) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (iv) and acid-generating agent was then applied using a k2 k-bar applicator over the layer of the composition comprising the component of group (iii).

Following application of the layers to the substrate, the component of group (iii) and the component of group (iv) are in their non-coloured states.

Following application of the layers to the substrate, IR radiation was applied at localised positions of the substrate using a 10.6 pm C0 ₂ laser (fourth temperature). At these localised positions, the component of group (iv) transitions to a yellow coloured state. It is noted that the third temperature of the component of group (iii) is lower than the fourth temperature. Therefore, the non-coloured state of the component of group (iii) is also‘activated’ at these localised positions.

Upon application of UV radiation by flood illumination using a germicidal lamp (third applied stimulus), the’activated’ non-coloured state of the component of group (iii) at the localised positions transition to a blue first coloured state. As the coloured state of the component of group (iii) is formed at the same localised position at which the coloured state of the component of group (iv) has been formed, the final colour displayed at these localised positions is dependent upon the blue colour of the coloured state of the component of group (iii), and the colour of the yellow coloured state of the component of group (iv) that has been formed, i.e. the final colour at these localised positions results from the combination of colours of the coloured states of these two components. Accordingly, a green colour can be formed.

Upon further application of a first temperature to the whole substrate by flood illumination using a heat gun, there is no transition of the component of group (iv) from the yellow coloured state back to the non-coloured state. The component of group (iv) remains in the yellow coloured state. However, this first temperature acts as an additional temperature and facilitates the transition of the component of group (iii) from the blue first coloured state to a second red coloured state at the localised positions at which the first blue coloured state had been formed. The final colour displayed at the localised positions is now the combination of the red second coloured state of the component of group (iii) and the yellow coloured state of the component of group (iv). Orange and red colours can be formed.

A multi-coloured image displaying yellow, orange, yellow, green and red colours can therefore be formed.

Example 38

A layer of a composition comprising a component of group (iv) and a base- generating agent was formulated according to Table according to 2:1 blend of the formulation of Table 46 with the formulation of Table 4. A layer of a composition comprising a component of group (ii) was formulated according to Table 34, using the millbase formulations of Tables 32 and 33, but replacing the component of group (ii) with di-tert-butyl(((docosa-10,12- diynedioyl)bis(azanediyl)bis(ethane-2, 1 -diyl))dicarbamate.

A layer of the composition comprising a component of group (iv) and a base- generating agent was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (ii) was then applied using a k2 k-bar applicator over the layer of the composition comprising a component of group (iv) and a base-generating agent.

Following application of the layers to the substrate, UV radiation by flood illumination using a germicidal lamp was applied to the substrate (second applied stimulus). The non-coloured state of the component of group (ii) transitions to a first red coloured state across the substrate. It is noted that the transition of the component of group (iv) from the non-coloured to a coloured state does not occur as a thermal acid-generating agent is utilised such that the fourth temperature is required to facilitate the formation of colour with the component of group (iv). Following application of IR radiation using a 10.6 pm C0 ₂ laser (38% power) to localised positions on the substrate (fourth temperature), a transition from the non-coloured state to the coloured state of the component of group (iv) is effected. The colour of the coloured state formed can be changed between yellow or orange, and the intensity thereof, by variation of the fluence of the C0 ₂ laser. It is noted that the second temperature of the component of group (ii) is lower than the fourth temperature and therefore, upon application of the IR radiation, the second temperature is reached and the component of group (ii) transitions from the red first coloured state to a blue second coloured state at those positions. As the second blue coloured state of the component of group (ii) is formed at the same localised positions as the coloured state of the component of group (iv), the colour displayed at these localised positions is a combination of the colour of the coloured state of the component of group (iv) and the second blue coloured state of the component of group (ii). Accordingly, blue, yellow, green and orange colours can be formed. Upon further application of either UV radiation by flood illumination using a germicidal lamp or application of temperature by flood illumination using a heat gun, the substrate displays no change. The second coloured state of the component of group (ii) has been deactivated and thus does not undergo any subsequent transitions.

A multi-coloured image displaying blue, red, yellow, green and orange colours can therefore be formed.

Example 39

A composition comprising a component of group (iv) and a thermal base generating agent was formulated according to a 2:1 blend of. the formulation of Table 46 with the formulation of Table 4.

A composition comprising a component of group (iii) was formulated according to Table 25 above, using the millbase formulations of Tables 23 and 24.

A layer of the composition comprising a component of group (iv) and base- generating agent was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a component of group (iii) was then applied using a k2 k-bar applicator over the layer of the composition comprising the component of group (iv) and base-generating agent.

Following application of the layers to the substrate, the component of group (iii) and the component of group (iv) are in their non-coloured states.

Upon application of the layers to the substrate, no change occurs upon application of UV radiation as the non-coloured state of the component of group (iii) requires activation through application of a third temperature, and the component of group (iv) is accompanied by a thermal base-generating agent and therefore requires a fourth temperature in order to facilitate a transition from the non-coloured state to a coloured state of the component of group (iv).

Upon application of IR radiation using a 10.6 pm C0 ₂ laser at localised positions of the substrate (fourth temperature), the component of group (iv) transitions from the non-coloured state to a coloured state. The colour of the coloured state, and intensity thereof, can be made to vary between yellow or orange by changing the fluence applied by the C0 ₂ laser. It is noted that the third temperature of the component of group (iii) is lower than the fourth temperature required to facilitate the transition of the component of group (iv) from the non- coloured to a coloured state. Therefore, upon application of the IR radiation, the non-coloured state of the component of group (iii) is activated at the localised positions at which the IR radiation is applied. Following further application of UV radiation by flood illumination to the substrate using a germicidal lamp (third applied stimulus), the non-coloured state of the component of group (iii) transitions to a blue coloured state solely at the localised positions at which the non-coloured state has been activated. As the blue first coloured state of the component of group (iii) has been formed at the same localised positions as the coloured state of the component of group (iv), the final colour displayed at these localised positions is a combination of the colour of the coloured state of the component of group (iv) and the blue first coloured state of the component of group (iii). Accordingly, green, blue and orange colours can be formed.

Upon further application of a first temperature to the whole substrate by flood illumination using a heat gun, there is no transition of the component of group (iv) from the coloured state back to the non-coloured state. The component of group (iv) remains in its coloured state. However, this first temperature acts as an additional temperature and facilitates the transition of the component of group (iii) from the blue first coloured state to a second red coloured state at the localised positions at which the first blue coloured state had been formed. The final colour displayed at the localised positions is now the combination of the red second coloured state and the coloured state of the component of group (iv). Red, purple and orange colours can be formed.

A multi-coloured image displaying yellow, orange, red, blue, purple and green colours can therefore be formed.