Field of the Invention

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

Background of 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 compound 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 compounds, 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 laser-reactive compositions for use in 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 necessary 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: a compound of formula (I)

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour.

According to a second aspect of the present invention, there is provided a substrate having a composition applied to or incorporated within, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour.

According to a third aspect of the present invention, there is provided a method of forming a substrate comprising applying a composition to or incorporating a composition within the substrate, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in 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: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour; the method comprising applying the applied transition stimulus or first applied temperature, and the additional applied stimulus or additional temperature, to the substrate as required to develop the coloured states of the compound of formula (I) and the at least one additional compound of 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: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour; the method comprising applying the applied transition stimulus or first applied temperature, and the additional applied stimulus or additional temperature, and if required, the second applied temperature, to the substrate as required to develop the non-coloured and/or coloured states of the compound of formula (I) and the at least one additional compound of the composition, and thereby create an image on or within the substrate.

According to a 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: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour.

According to a 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: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour. According to an eighth aspect of the present invention, there is provided a substrate having applied thereon a plurality of discrete layers, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one of the discrete layers comprises an at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour, and the discrete layer comprising the compound of formula (I) is a different layer to the discrete layer comprising the at least one additional compound.

According to a ninth aspect of the present invention, there is provided a method of forming a substrate having applied thereon a plurality of discrete layers, the method comprising applying to a substrate the plurality of discrete layers, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one of the discrete layers comprises an at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour, and the discrete layer comprising the compound of formula (I) is a different layer to the discrete layer comprising the at least one additional compound. According to a tenth aspect of the present invention there is provided a method of forming colour on a substrate having a plurality of discrete layers applied thereon, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one of the discrete layers comprises an at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour, and the discrete layer comprising the compound of formula (I) is a different layer to the discrete layer comprising the at least one additional compound; and wherein the method comprises applying the applied transition stimulus or first applied temperature, and the additional applied stimulus or additional temperature, to the substrate as required to develop the coloured states of the compound of formula (I) and the at least one additional compound.

According to an eleventh aspect of the present invention there is provided a method of forming an image on a substrate having a plurality of discrete layers applied thereon, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one of the discrete layers comprises an at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour, and the discrete layer comprising the compound of formula (I) is a different layer to the discrete layer comprising the at least one additional compound; and wherein the method comprises applying the applied transition stimulus or first applied temperature, and the additional applied stimulus or additional temperature, and if required, the second applied temperature, to the substrate as required to develop the non-coloured and/or coloured states of the compound of formula (I) and the at least one additional compound, and thereby create an image on or within the substrate.

According to a twelfth aspect of the present invention, there is provided a method of forming colour on a substrate comprising a composition applied to or incorporated within, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus; the method comprising applying the first applied temperature or applied transition stimulus to the substrate as required to develop the coloured state of the compound of formula (I) of the composition. According to a thirteenth aspect of the present invention, there is provided a method of forming an image on a substrate comprising a composition applied to or incorporated within, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus; the method comprising applying the first applied temperature or applied transition stimulus to the substrate as required to develop the coloured state of the compound of formula (I) of the composition. According to a fourteenth aspect of the present invention, there is provided a use of a composition in the formation of colour on a substrate, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus.

According to a fifteenth aspect of the present invention, there is provided a use of a composition in the formation of an image on a substrate, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus.

According to an sixteenth aspect of the present invention, there is provided a method of forming colour on a substrate having a plurality of discrete layers applied thereto, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus; and wherein at least one of the discrete layers comprising at least one additional compound capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; the method comprising applying the first applied temperature or applied transition stimulus, and additional applied stimulus or additional temperature to the substrate as required to develop the coloured state of the compound of formula (I) and the at least one additional compound.

According to an seventeeth aspect of the present invention, there is provided a method of forming an image on a substrate having a plurality of discrete layers applied thereto, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus; and wherein at least one of the discrete layers comprising at least one additional compound capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; the method comprising applying the first applied temperature or applied transition stimulus, and additional applied stimulus or additional temperature to the substrate as required to develop the coloured state of the compound of formula (I) and the at least one additional compound, and thereby form an image on the substrate.

Detailed Description of the Invention

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

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 predicated colours for image formation. The compound of formula (I) of the present invention may therefore have use independently or in combination with other colour-forming compounds, depending on desired use. A broad colour gamut can therefore be accessed using these laser-reactive components.

It has been surprisingly and advantageously found that the compound of formula (I) can advantageously form colour upon exposure to an applied transition stimulus or first applied temperature. The colour formation upon exposure to an applied transition stimulus is reversible, whereas the colour formation upon exposure to an applied temperature is irreversible.

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

"Coloured state" and like terms as used herein, refers to the state of a compound of formula (I) in which the compound 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 highly coloured than the "non-coloured state" of the same compound. This may be a more intense colouration of the same colour, but may also 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. It will be appreciated that some compounds may have more than one coloured state, such as a first and a second coloured state, each of the first and second coloured states having a different 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 mixtures thereof. Both primary and secondary colours are encompassed, i.e. the coloured state of the compound 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, cyan, turquoise, brown, pink, purple, and black.

"Stable coloured state" and like terms as used herein, refers to the coloured state of a compound of formula (I) 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 compounds are exposed, i.e. the range of temperatures, pressures and atmospheric conditions to which the compounds 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 compound will be dependent upon the application for which a substrate having the compound or the composition and therefore the compound applied to or incorporated within is intended to be used. For example, if the compound 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 coloured state of the compound 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 compound is to be utilised as a laser-reactive compound or in a laser-reactive composition applied on or incorporated within a cosmetic container or outdoor signage, the required stability of the coloured state of the compound 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 compound of formula (I) will permanently remain in the particular coloured state. Accordingly, it is preferred that the compound remains in a coloured state for at least 3 days, preferably for at least 4 days, more preferably for at least 1 or even 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 a monochromic image. In particular, when the non-coloured state of a compound 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 a multi-coloured image. In particular, when the non-coloured state of a compound 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, but is not limited to: text, logos, graphics, symbols and pictures. The term also incorporates both single- and multi- coloured images. It will be appreciated that in the context of the present invention, for both single- and multi-coloured images, it is the manipulation of the compounds that facilitates the formation of an image.

"Transitioning" and "transition" and like terms as used herein, refer to a compound of formula (I) changing from a non-coloured state to a coloured state upon application of the applied transition stimulus or first applied temperature,. It will be appreciated by a skilled person that this is an intentional transition facilitated by the application of the applied transition stimulus or first applied temperature. The term "subsequent transition" refers to a compound changing from a coloured state to a non-coloured state upon application of the second applied temperature. It will be appreciated by a skilled person that this is an intentional transition facilitated by the application of the second applied temperature.

For a compound of formula (I), the transition may be "irreversible" or "reversible". By "irreversible" is meant that once the coloured state of the compound of formula (I) has been formed, the coloured state maintains essentially its colour when the compound of formula (I) is exposed to the intentionally applied second applied temperature. In addition, once the coloured state of the compound has been achieved, the coloured state of the compound of formula (I) will be stable under ambient conditions. By "reversible" is meant that once the coloured state of the compound of formula (I) has been formed, the coloured state reverts back to the non-coloured state when the compound of formula (I) is exposed to intentionally applied second applied temperature. This is an intentional transition facilitated solely by the application of a second applied temperature to the compound of formula (I). It will be appreciated by a skilled person that the transition from coloured state to non-coloured state is only being facilitated by the application of the second applied temperature and otherwise, once the coloured state of the compound has been achieved, the coloured state of the compound will be stable under ambient conditions.

"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 or non-commercial laser source(s).

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 compound of formula (I) from the non-coloured state to a coloured state is reversible when the applied transition stimulus is applied to the compound to facilitate a transition from the non-coloured to a coloured state of the compound. Once the coloured state of the compound has been formed, a transition from the coloured state back to the non-coloured state can be intentionally facilitated through the application of the second applied temperature to the coloured state of the compound of formula (I).

The transition of the compound of formula (I) from the non-coloured state to a coloured state is irreversible when the first applied temperature is applied to the compound to facilitate a transition from the non-coloured to a coloured state of the compound. Once the coloured state of the compound has been formed, a transition from the coloured state back to the non-coloured state cannot occur through the intentional application of the second applied temperature to the coloured state of the compound of formula (I). The compound of formula (I) may optionally be accompanied by an acid- or base generating agent in the composition according to the first aspect of the present invention as defined below to facilitate the irreversible transition from the non-coloured state to a coloured state. Additionally, the transition of the compound of formula (I) from the non-coloured state to a coloured state is irreversible when the first applied stimulus is applied to the compound and the compound is accompanied by an acid- or base-generating agent in the composition according to the first aspect of the present invention. Preferably, to facilitate an irreversible transition, the first applied temperature is applied to the compound of formula (I).

It will be appreciated by a skilled person that the structure of the compound of formula (I) facilitates the formation of colour (formation of a coloured state) through tautomerisation from the enol to the keto form.

It will be appreciated that for a compound of formula (I), for the compound to demonstrate reversibility as discussed herein, the transition from the non- coloured state to a coloured state of the compound of formula (I) is preferentially driven by the applied transition stimulus, as opposed to by the first applied temperature. By "preferentially driven by the applied transition 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 applied transition stimulus is applied as opposed to the first applied temperature. It will be appreciated by a skilled person that a compound of formula (I) being preferentially driven by the first applied temperature, will not demonstrate reversibility upon application of the second applied temperature, as the coloured state is preferentially formed through the application of the first applied temperature. Thus, upon application of the second applied temperature, DE in comparison with the non-coloured state will either remain approximately the same (i.e. no change in the coloured state) or will increase (i.e. an increase in the intensity of the coloured state). Preferably, in the compound of formula (I), A 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, more preferably from C ₆ -s aryl, and most preferably phenyl.

Preferably, in the compound of formula (I), B is selected from C _1-18 alkyl and 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 Ci _-4 alkyl and C ₆ -s aryl, and most preferably from methyl and phenyl.

Preferably, in the compound of formula (I), 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 Ci-is alkyl; more 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 most preferably, from phenyl, 4- methoxy phenyl, 4-cyanophenyl, 4-(trifluoromethyl)phenyl, 4-nitrophenyl; -CCI ₃ ; and C(CH ₃ ) ₃ .

Preferably, in the compound of formula (I), 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.

Preferably, the compound of formula (I) has the formula (II):

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 compound of formula (I) or (II) 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 H- 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). Preferably, when the transition of the compound of formula (I) or (II) from the non-coloured state to a coloured state is reversible, the compound of formula (I) or (II) 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),

Preferably, when the transition of the compound of formula (I) or (II) from the non-coloured state to the coloured state is irreversible, the compound of formula (I) or (II) 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 compounds of formulas (I) and (II) are to be interpreted as covering the compounds 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 compounds of formulas (I) and (II) is stable under ambient conditions.

The applied transition stimulus may be radiation. It will be appreciated that the radiation selected will be the radiation required to facilitate a transition of the compound of formula (I) from the non-coloured to a coloured state. The radiation selected will therefore be dependent upon the compound of formula (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 applied transition stimulus is selected from ultraviolet (UV) with a wavelength of from 10 to 400 nm, more preferably with a wavelength of from 100 to 400 nm.

It will be appreciated that from the radiation and wavelength ranges detailed herein, a skilled person would select a specific applied transition stimulus as required to achieve the desired transition of the compound from the non- coloured to a coloured state. It will be appreciated that the specifically selected applied transition stimulus will differ depending upon the components of the composition according to the first aspect of the present invention.

The applied transition stimulus may be applied to the compound of formula (I) by any suitable means. Suitable means include laser excitation through application of radiation to the compound or composition and thus the compound by a laser source(s). It will be understood by a skilled person that the applied transition stimulus may be applied to the compound or composition at localised positions to selectively develop the coloured state of the compounds at these localised positions. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the applied transition stimulus may be applied to the compound or 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). 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 also be understood by a skilled person that the radiation is applied to the compound or composition for an appropriate amount of time required to facilitate the transition of the compound from the non-coloured state to a 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 applied transition stimulus may be applied to the compound of formula (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 for less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the radiation dosage applied for the applied transition 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), e.g. J/cm ²

The first applied temperature may be any suitable temperature. It will be appreciated by a skilled person that the first applied temperature will be the temperature required to facilitate a transition of the compound of formula (I) from the non-coloured to a coloured state. The temperature selected will therefore be dependent upon the compound of formula (I) present in the composition according to the first aspect of the present invention. The first applied temperature may be a temperature of from 80 to 300 °C, such as from 80 to 250 °C, or even from 80 to 180 °C.

The first applied temperature may be applied to the compound of formula (I) by any suitable means. Suitable means include laser excitation through application of radiation to the compound or composition and thus the compound by a laser source(s). It will be understood by a skilled person that the first applied temperature may be applied to the compound or composition at localised positions to selectively develop the coloured state of the compound 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 temperature may be applied to the compound or composition 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 a IR lamp; diode bar; or LED(s). It will further be appreciated that the first applied temperature may be applied to the compound of formula (I) using a conductive temperature source. Conductive temperature sources include sources of steam and hot air, lamps, heat tunnels, hotplates, LED(s), thermal print heads, thermal conductors, hot liquids and heated substrates. It will be understood by a skilled person that the first applied temperature is applied to the compound or composition for an appropriate amount of time required to facilitate the transition of the compound of formula (I) from the non-coloured state to a 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 applied temperature may be applied to the compound of formula (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 for less than 10 seconds.

It will be appreciated that when applied using a laser source(s), the first applied 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), e.g. J/cm ²

It will be appreciated by a skilled person that the first applied temperature may be applied to the compound of formula (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 applied temperature may be applied to the compound using laser excitation at localised positions, in addition to using a conductive temperature source.

In addition, it will be appreciated that where the first applied temperature is applied using radiation, i.e. at localised positions using a laser source(s) or by flood illumination, the compound or composition and thus the compound of formula (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.

The first applied temperature may be applied to the compound of formula (I) 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 first applied temperature is applied using 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), 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 first applied temperature, a skilled person would select a specific first applied temperature as required to achieve the desired transition of the compound of formula (I) from the non-coloured state to a coloured state. Furthermore, it will be appreciated that the specifically selected first applied temperature will differ depending upon the components of the composition.

The coloured state of the compound of formula (I) may have any colour. It will be appreciated by a skilled person that the means used to apply the applied transition stimulus or first applied temperature will affect the colour of the coloured state formed. For example, where a laser source(s) is used to apply the applied transition stimulus or first applied temperature 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 applied transition stimulus or first applied temperature (wattage), and the time for which the radiation of the applied transition stimulus or first applied 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 compound of formula (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 compound of formula (I) will be of a more intense colour. Changing the fluence may also result in a coloured state of the compound of formula (I) changing colour. For example, low fluence may form a coloured state of the compound of formula (I) having a yellow colour, and higher fluence may form the same coloured state of the compound of formula (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 .

When the transition of compound (I) from the non-coloured state to a coloured state is reversible, the transition is effected by the application of the applied transition stimulus and the reverse transition from that same coloured state back to the non-coloured state can be intentionally facilitated through the intentional application of a second applied temperature to the coloured state of the compound of formula (I). This transition from the coloured state back to the non- coloured state of the compound of formula (I) is known in the art as "thermal bleaching".

The second applied temperature may be any suitable temperature. It will be appreciated by a skilled person that the second applied temperature will be the temperature required to facilitate a transition of the compound of formula (I) from the coloured state to the non-coloured state. The temperature selected will therefore be dependent upon the compound of formula (I) present in the composition according to the first aspect of the present invention. The second applied temperature may be a temperature of from 60 to 200 °C, such as from 70 to 160 °C.

The second applied temperature may be applied to the compound of formula (I) by any suitable means. Suitable means include laser excitation through application of radiation to the composition and thus the compound of formula (I) by a laser source(s). It will be understood by a skilled person that the second applied temperature may be applied to the composition comprising the compound of formula (I) at localised positions to selectively develop the non- coloured state of the compound 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 temperature may be applied to the composition 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 a IR lamp; diode bar; or LED(s). It will further be appreciated that the second applied temperature may be applied to the compound 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 applied temperature is applied to the composition for an appropriate amount of time required to facilitate the transition of the compound 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 second applied temperature may be applied to the compound of formula (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 second applied temperature can be controlled by alteration of the time for which the radiation dosage 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), e.g. J/cm ²

In addition, it will be appreciated that where the second applied temperature is applied using radiation, i.e. at localised positions using a laser source(s) or by flood illumination, the composition and thus the compound of formula (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 second applied temperature may be applied to the compound of formula (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 second applied temperature may be applied to the compounds using laser excitation at localised positions, in addition to using a conductive temperature source.

The second applied temperature may be applied to the compound of formula (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 second temperature is applied using infrared radiation with a wavelength of from 700 nm to 1 mm, 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.

It will be appreciated that from the temperature and wavelength ranges detailed herein for the second applied temperature, a skilled person would select a specific second applied temperature as required to achieve the desired transition of the compound of formula (I) from the coloured state to the non-coloured state. Furthermore, it will be appreciated that the specifically selected second applied temperature will differ depending upon the components of the composition according to the first aspect of the present invention.

The compound of formula (I) may be present in the composition according to the first aspect of the present invention in any suitable amount. Preferably, the composition comprises from 0.1 to 50 %, such as from 0.1 to 40 %, or even from 3 to 30 % of a compound of formula (I) based on the total solid weight of the composition. Most preferably, the composition comprises from 5 to 25 % of a compound of formula (I) based on the total solid weight of the composition.

When the transition of the compound of formula (I) is facilitated by the application of the first applied temperature, and the transition from the non- coloured state to a coloured state of the compound of formula (I) is irreversible, the composition may further comprise an acid- or base-generating agent to help facilitate the transition. In addition, to achieve an irreversible transition of the compound of formula (I) from the non-coloured to a coloured state upon application of the applied transition stimulus, the composition further comprises an acid- or base-generating agent.

It will be appreciated by a skilled person that the acid- or base-generating agent and the compound of formula (I) interact to achieve colour formation. The acid- or base-generating agent is present to facilitate a pH change through generation of acid or base respectively upon application of the first applied temperature. This acid or base generation facilitates the transition of the compound of formula (I) from the non-coloured state to a coloured state in combination with the application of the first applied temperature. 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 the vacant orbital of some other species. By "acid" is meant a molecular entity or chemical species capable of donating a proton, or capable of forming a covalent bond with an electron pair.

Suitable acid-generating agents for use in the composition according to the first aspect of the present invention 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 each of which is incorporated herein by reference.

Preferably, the acid-generating agent is a thermal acid-generating agent.

Suitable base-generating agents for use in the composition according to the first aspect of the present invention 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.

Preferably, the base-generating agent is a thermal base-generating agent It will further be appreciated by a skilled person that the selection of the acid- or base-generating agent is dependent upon the particular compound of formula (I) utilised in the composition, and the selection of the first applied temperature or applied transition stimulus. For example, if the first applied temperature is utilised, a thermal acid- or base-generating agent will be utilised, and if the applied transition stimulus is utilised, a photoacid- or photobasic-generating agent will be utilised. The requirement of either an acid-generating agent or a base-generating agent can be determined by the skilled person.

If present, the acid or base-generating agent relating to the compound of formula (I) may be present in the composition according to the first aspect of the present invention 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 present, the ratio of acid- or base-generating agent relating to the compound of formula (I) to the compound of formula (I) based on the total solid weight of the composition is from 4: 1 to 1 :4, preferably from 3:1 to 1 :3, and more preferably from 2:1 to 1 :2.

The at least one additional compound may be selected from a leuco dye, a diacetylene compound comprising a diacetylene moiety ( _anc | an oxyanion of a multivalent metal.

It will be appreciated that the at least one additional compound and the compound of formula (I) will be selected based on the colour(s) of their coloured states that can be achieved. Furthermore, the at least one additional compound and the compound of formula (I) will be selected such that their colour formation is triggered by different conditions. This is also applicable to the selection of the second applied temperature in relation to the at least one additional compound. By triggered by different conditions it is meant that even if the first applied temperature and the additional temperature are applied, the temperatures of the first applied temperature and the additional temperature required to facilitate the transition will be different. In addition, if the second applied temperature and the additional temperature are applied, the temperatures of each required to facilitate the transition will be different. The same is application for the applied transition stimulus and the additional applied stimulus. ‘Different conditions’ encompasses the differing orders of application of the first applied stimulus or first applied temperature, second applied temperature, applied transition stimulus, activation temperature, additional temperature or additional applied stimulus, as required, for the formation of colour for each of the at least one additional compound and the compound of formula (I).

The terms "non-coloured state", "coloured state", "stable coloured state" as detailed above in relation to the compound of formula (I) are applicable to the at least one additional compound. The term "transition" as described above in relation to the compound of formula (I) is also applicable to the at least one additional compound, the applied transition stimulus or first applied temperature being replaced by the additional applied stimulus or additional temperature. It is noted that when referring to the at least one additional compound, the transition is deemed to be "irreversible" as defined above.

The at least one additional compound may be a leuco dye only when the compound of formula (I) is not accompanied in the composition by an acid- or base-generating agent.

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, thermochrmoic, or halochromic (change colour on exposure to change in environmental pH). Halochromic leuco dyes can be used in combination with an acid-generating agent such as a Lewis acid compound, or acid-generating agent such as a thermal acid generating (TAG) agent or a photoacid-generating agent. Examples of suitable leuco dyes are contained in WO2015/015200 and WO2013/068729, the content of each of which is incorporated herein by reference. Examples of suitable acid-generating agents are as discussed above in relation to the acid-generating agents relating to the compound of formula (I) or (II). Preferably, the halochromic lecuo dyes are used in combination with an acid- or base-generating agent. The at least one additional compound may be a leuco dye, including any commercially available or chemically synthesisable leuco dye, including but not limited: commercially available photochromic, thermochromic, chemochromic, and halochromic lecuo 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 a halochromic leuco dye. Preferably, the leuco dye is a halochromic leuco dye in combination with an acid- or base-generating agent.

The at least one additional compound may be 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 _s 0 ₂ e or“AOM”, which is a commercially available molybdenum composition with the CAS number 12411-64-2. 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 (AOM).

The at least one additional compound may be a diacetylene compound. 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. 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. Diacetylene compounds typically have two coloured states, such as a first and a second coloured state, each of the first and second coloured states having a different colour. It will be appreciated that the access the first coloured state of the diacetylene compound, an additional applied stimulus will be required, and to access the second coloured state of the diacetylene compound, additional temperature will be required. It will further be appreciated by a skilled person that when diacetylene compounds are in the non-coloured state, they are considered to be monomers. The first and second coloured states of the diacetylene compounds are formed on account of polymerisation of at least a portion of these monomers upon exposure to the additional applied stimulus. Polymerisation of at least a portion of the monomers enables the formation of the coloured states. In addition, without being bound by theory, it is considered that the different first and second coloured states are achieved through changes in conjugation of the diacetylene polymer, i.e. a structural change.

The at least one additional compound may be any suitable diacetylene compound. The at least one additional compound may be a diacetylene compound having the following formula (III):

T- (CH ₂ ) _X - L - Q wherein x is from 2 to 12, preferably 2 to 10, and more preferably 2 to 8; o L is selected from an amide having the formula: v H \ and an ester having

° 9

, A ₀ , _{x N} _ _f the formula: ^u ¾, preferably L is an amide having the formula H ,

Q is selected from a 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 7 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 (I), and -(CH ₂ ) _X -L-Q, wherein x, L and Q are as defined above for formula (I).

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 at least one additional compound may be a diacetylene compound of formula (IV):

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 7 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.

It will be appreciated by a skilled person that the non-coloured state of certain diacetylene compounds may preferably need to be‘activated; (i.e. made capable of undergoing a transition to a coloured state) prior to exposure to the additional applied stimulus to enable a transition from the non-coloured state to a coloured state to be possible. If required, activation can be facilitated by exposure of the non-coloured state of the diacetylene compound to an activation temperature. It will be appreciated by a skilled person that this activation may take place prior to the exposure to the additional applied stimulus to effect the transition from the non-coloured state to a coloured state, or alternatively, the non-coloured state of the diacetylene compound may be activated during this exposure. If the activation takes place prior to the exposure to the additional applied stimulus, the activation temperature is a temperature between ambient temperatures (10 to 35 °C) and the decomposition temperature of the diacetylene compound. The activation temperature may be from 40 to 150 °C. The diacetylene compound may be exposed to the activation temperature using any suitable means, including radiation source(s) such as laser source(s). The radiation may be selected from visible light with a wavelength of from 400 to 700nm, infrared radiation with a wavelength of from 700nm to 1 mm, in particular 100nm, and near-infrared radiation with a wavelength of from 700 to 1600nm.

Preferably, the composition comprises a compound of formula (I) and a diacetylene compound.

It will be appreciated that a composition comprising a compound of formula (I) and at least one additional compound enables the production of a broad range of colours in the formation of an image. The different stimuli and temperatures (applied transition stimulus, additional applied stimulus, first applied temperature, second applied temperature and additional temperature) can be applied in different combinations at particular localised positions, enabling the formation of single- and multi-coloured images with a broad colour gamut.

It will be appreciated by a skilled person that the selection of the additional applied stimulus or additional temperature is dependent upon the nature of the at least one additional compound.

For example, if the at least one additional compound is a diacetylene compound, the application of the additional applied stimulus effects the transition of the at least one compound from the non-coloured state to a coloured state, and the additional applied stimulus will be selected to achieve this transition. In addition, if the at least one additional compound is an oxyanion of a multivalent metal such as AOM, the application of the additional temperature effects the transition of the at least one compound from the non-coloured state to a coloured state, and the additional temperature will be selected to achieve this transition. It will be appreciated that, in the context of the present invention, the diacetylene compounds typically have two coloured state, such as a first and a second coloured state, each of the first and second coloured states having a different colour. For such diacetylene compounds, the application of the additional applied stimulus effects the transition of the at least one additional compound from the non-coloured to the first coloured state, and the application of the additional temperature effects the transition from the first coloured to the second coloured state. In addition, if the at least one additional compound is a leuco dye, the application of additional applied stimulus or additional temperature effects the transition of the at least one compound from the non-coloured state to a coloured state. It will be appreciated by a skilled person that the selection of the additional applied stimulus or additional temperature will be dependent upon the type of leuco dye selected for use, and if present, the nature of the acid- generating agent utilised such as a thermal acid generating agent or a photoacid-generating agent. For example, if the at least one additional compound is a halochromic leuco dye accompanied by a photoacid-generating agent, the additional applied stimulus is utilised to facilitate a transition from the non-coloured to a coloured state of the leuco dye, and if the at least one additional compound is a halochromic leuco dye accompanied by a thermal acid- generating agent, the additional temperature is utilised to facilitate a transition from the non-coloured to a coloured state of the leuco dye. It will be appreciated by a skilled person that given the interaction between the acid-generating agent and the leuco dye to form colour, the additional applied stimulus or additional temperature will be selected to achieve the acid generation of the acid- generating agent. These selections are well within the capabilities of a skilled person.

It will further be appreciated that the composition may not comprise more than one acid- or base-generating agent. If the compound of formula (I) is accompanied by an acid- or base-generating agent, either the at least one additional compound will be selected so as to not require an acid- or base- generating agent, or in certain instances, the acid- or base-generating agent associated with the compound of formula (I) will also interact with the at least one additional compound as discussed above.

The additional applied stimulus may be radiation. It will be appreciated that the additional applied stimulus will be the radiation required to facilitate a transition of the at least one additional compound from the non-coloured to a coloured state. The radiation for the additional applied stimulus will therefore be selected dependent upon the at least one additional compound present in the composition. Radiation will be utilised as the additional applied stimulus when the at least one additional compound is a diacetylene compound, for the transition of the diacetylene compound 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 additional applied stimulus is ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, more preferably with a wavelength of from 100 to 400 nm.

It will be appreciated that from the radiation and wavelength ranges detailed herein for the additional applied stimulus, a skilled person would select radiation of a specific wavelength as required to achieve the desired transition of the at least one additional compound from the non-coloured state to a coloured state. It will be appreciated that the specifically selected additional applied stimulus will differ depending upon the components of the composition.

The additional applied stimulus may be applied to the at least one additional component of the composition by any suitable means. Suitable means and relevant considerations for the application of the additional applied stimulus are as described above in relation to the applied transition stimulus.

The additional temperature may be any suitable temperature. It will be appreciated by a skilled person that the additional temperature will be a temperature required to facilitate a transition of the at least one additional compound form the non-coloured to a coloured state. The additional temperature selected with therefore be dependent upon the at least one additional compound present in the composition. Temperature will be utilised as the additional applied stimulus when the at least one additional compound is an oxyanion of a multivalent metal. In addition, temperature may be utilised for the transition of the diacetylene compound from the first coloured state to the second coloured state. The additional temperature may be a temperature of from 50 to 300 °C, such as from 50 to 280 °C, or even from 80 to 200 °C.

The additional temperature may be applied to the at least one additional component of the composition by any suitable means. Suitable means and relevant considerations for the application of the additional temperature are as described above in relation to the first and second applied temperatures. It will be appreciated that from the temperature and wavelength ranges detailed herein for the additional temperature, a skilled person would select a specific additional temperature as required to achieve the desired transition of the at least one additional compound from the non-coloured state to a coloured state. It will be appreciated that the specifically selected additional temperature will differ depending upon the components of the composition. It will further be appreciated that for diacetylene compounds, the additional temperature may be the temperature required to achieve a transition of the at least one additional compound from the first coloured state to a second coloured state.

It will be appreciated by a skilled person that the means used to apply the additional applied stimulus or additional temperature will affect the colour of the coloured state of the at least one additional compound that is formed. For example, where a laser source(s) is used to apply the additional applied stimulus or additional temperature through 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 a measure of the power of means used to apply the radiation of the additional applied stimulus or additional temperature (wattage), and the time for which the radiation of the additional applied stimulus or additional temperature is applied to a particular position on the substrate, which may be controlled by the scanning speed of the laser or the speed of a moving stage. The 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 at least one additional compound 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 at least one additional compound 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 , or even from 0.5 to 5 J/cm ² .

Further, it will be appreciated by a skilled person that the required fluence from the additional applied stimulus or additional temperature necessary to facilitate a transition from the non-coloured state to a coloured state of the at least one additional compound may be different to the required fluence from the applied transition stimulus or additional temperature necessary to facilitate a transition from the non-coloured state to a coloured state of the compound of formula (I). Preferably, the required fluence from the additional applied stimulus or additional temperature necessary to facilitate a transition from the non-coloured state to a coloured state of the at least one additional compound will be different to the required fluence from the applied transition stimulus or additional temperature necessary to facilitate a transition from the non-coloured state to a coloured state of the compound of formula (I).

The coloured state of the at least one additional compound may have any colour. Preferably, the coloured state of the at least one additional compound is selected from blue, red and black. Preferably, the coloured state of the at least one additional compound is stable.

It will be appreciated by a skilled person that the composition according to the first aspect of the present invention may comprise more than one at least one additional compound.

The at least one additional compound may be present in the composition according to the first aspect of the present invention in any suitable amount. Preferably, the composition comprises from 0.1 to 50%, such as from 0.1 to 40%, or even from 3 to 30% of the at least one additional compound based on the total solid weight of the composition. More preferably, the composition comprises from 5 to 25%, or even from 15 to 25% of the at least one additional compound based on the total solid weight of the composition.

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 radiation (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 the 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; 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 compounds present in the composition and application or incorporation method, in addition to the printing application and, if applied to a substrate, the desired coat weight of the composition on the substrate.

The composition according to the first aspect of the present invention preferably comprises, in addition to the compound of formula (I) and the at least one additional compound, an optional acid-or base-generating agent, a binder, an additive or combination of additives, and a solvent or combination of solvents. If NIR is to be used as the applied transition stimulus, first applied temperature or second applied temperature, an NIR absorber is preferably present in the composition.

It will be appreciated that the composition according to the first aspect of the present invention may be formulated through the combination of formulations containing the different components of the composition. For example, the compound of formula (I), optional acid- or base-generating agent, and the at least one additional compound may be each in separate formulations, which are combined together to form the composition according to the first aspect of the present invention.

The composition 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 the composition according to the first aspect of the present invention 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.

The composition according to the first aspect of the present invention, or the substrate according to the second aspect of the present invention may be suitable for end use as labels (adhesive and 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.

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.

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.

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 or 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 at least one additional compound either incorporated within or applied to the substrate. Preferably, this further at least one additional compound is applied to the substrate. If the at least one additional compound is applied to the substrate, this may be in a layer on the substrate formed from a composition comprising the at least one additional compound, the composition being as defined above for the composition according to the first aspect of the present invention, the compound of formula (I) replaced by the at least one additional compound. This layer comprising the at least one additional compound may be applied to the substrate underneath the composition applied to the substrate, or applied over the composition applied on the substrate. If an at least one additional compound is present in the composition according to the first aspect of the present invention, the at least one additional compound in the separate composition will be different. By different is meant that the at least one additional compound in the composition according to the present invention and the further at least one additional compound are selected either from different groups of (a) a diacetylene compound, (b) oxyanion of a multivalent metal or (c) leuco dye as defined above, or are selected from the same group (a), (b) or (c), but are selected so as to be different compounds in that group, e.g. two different leuco dyes. Preferably, the at least one additional compound in the composition according to the present invention and the further at least one additional compound are selected from different groups of (a) a diacetylene compound, (b) oxyanion of a multivalent metal or (c) leuco dye as defined above. Preferably, the further at least one additional compound (other than that in the composition according to the first aspect of the present invention) is a leuco dye or oxyanion of a multivalent metal and applied to the substrate as a composition.

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 a substrate to any suitable coat weight dependent upon both the substrate to which the composition is applied and the application method. It will be appreciated by a skilled person that the coat weight of the composition on the substrate will affect the intensity of the colour of the coloured state of the compound of formula (I) and at least one additional compound. Preferably, the composition is applied to a coat weight of from 0.1 to 50 gsm (grams per square metre), more preferably from 01 to 25 gsm and most preferably, from 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 at least one additional compound 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.

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 the applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, to the substrate as required to develop the coloured states of the compound of formula (I) and the at least one additional compound of 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 the applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, and if required, the second applied temperature, to the substrate as required to develop the non-coloured and/or coloured states of the compound of formula (I) and the at least one additional compound of the composition, and thereby create an image on or within the substrate.

It will be understood by a skilled person that the applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature may be applied to the composition such that the non-coloured state and/or coloured state of the compound of formula (I) and the at least one additional compound are present at different localised positions of the compound of formula (I) or composition to create an image. The coloured state of the compound of formula (I) and the at least one additional compound may be selectively developed at localised positions on the substrate.

It will further be appreciated that where the transition from the non-coloured state to the coloured state is reversible, i.e. the transition of the compound of formula (I) from the non-coloured state to a coloured state is effected by the application of the applied transition stimulus, the second applied temperature may also be applied, as required, to the composition on or within the substrate following application of the applied transition stimulus to develop the non-coloured state of the compound of formula (I) at of the composition. This application of the second applied temperature will typically be done at localised position of the composition.

Suitable means for applying the applied transition stimulus, first applied temperature, second applied temperature, additional applied stimulus and additional temperature as required are as discussed above. It will be further understood by a skilled person that the application of the applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, and if required, the second applied temperature, will be conducted in the appropriate order required to selectively develop the non- coloured and/or coloured states of the compound of formula (I) and at least one additional compound at localised positions of the composition and form the desired image. This can facilitate the formation of a multi-coloured image. It will be appreciated by a skilled person that the relationship between the first applied temperature, second applied temperature and additional temperature, will vary dependent upon the colours required in the image that is to be formed. It will further be appreciated by a skilled person that the relationship between the wavelengths of the applied transition stimulus and additional applied stimulus will vary dependent upon the colours required in the image that is to be formed.

It will be understood by a skilled person that more than one of the applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, may be applied at the same localised position. For example, in order to form a colour resulting from the mixing of two colours (e.g. the mixing of the colours of a coloured state of the compound of formula (I) and a coloured state of the at least one additional compound of a different colour), the applied transition stimulus or first applied temperature and the additional applied stimulus or additional temperature, may be applied at that particular localised position of the composition.

It will be further appreciated by a skilled person that the specific applied transition stimulus or first applied temperature, (and if required, the specific second applied temperature) and the specific additional applied stimulus or additional temperature, will be selected dependent upon the colours required in the image to be formed, so as to facilitate the 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 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. 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 a 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 at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an applied transition stimulus or first applied temperature; and at least one of the discrete layers comprises an at least one additional compound capable of transitioning from a non-coloured to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; wherein, if formed, the coloured state of the compound of formula (I) and the at least one additional compound are different in colour, and the discrete layer comprising the compound of formula (I) is a different layer to the discrete layer comprising the at least one additional compound. In the eighth aspect of the present invention, the compound of formula (I) and at least one additional compound are as defined above throughout the first to seventh aspects of the present invention. In addition, the applied transition stimulus, first applied temperature, second applied temperature, additional applied stimulus and additional temperature are as defined above throughout the first to seventh aspects of the present invention. It will further be 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 be appreciated by a skilled person that the plurality of discrete layers may comprise more than one at least one additional compound.

The plurality of discrete layers may further comprise a second of an at least one additional compound. This second of an at least one additional compound may be present in the discrete layer comprising the compound of formula (I), the different discrete layer comprising the at least one additional compound, or a separate different discrete layer of the plurality of discrete layers. Preferably, the second of the at least one additional compound is present in a separate discrete layer of the plurality of discrete layers. Accordingly, the substrate may comprise a first discrete layer comprising the compound of formula (I), a second different discrete layer comprising an at least one additional compound, and a third different discrete layer comprising the second of an at least one additional compound. It will be understood that the at least one additional compound and the second of an least one additional compound will be selected dependent upon the colours required, and will be different. By different is meant that the two at least one additional compounds are selected either from different groups of (a) a diacetylene compound, (b) oxyanion of a multivalent metal or (c) leuco dye as defined above, or are selected from the same group (a), (b) or (c), but are selected so as to be different compounds in that group, e.g. two different lecuo dyes. Preferably, the two at least one additional compounds are selected from different groups of (a) a diacetylene compound, (b) an oxyanion of a multivalent metal or (c) leuco dye as defined above. Preferably, the plurality of discrete layers comprises a compound of formula (I) and a diacetylene compound.

It will be further appreciated that the discrete layer comprising the compound of formula (I) may be formed of a composition applied to the substrate. In this regard, the composition is as defined above for the first aspect of the present invention. The at least one additional compound present in a different discrete layer of the plurality of discrete layers applied to the substrate according to the eighth aspect of the present invention may be present as a composition that forms the different layer of the plurality of discrete layers. When the at least one additional compound is present in a composition in a separate layer of the plurality of discrete layers, the at least one additional compound may be present in any suitable amount, preferably from 5 to 60% of the total solid weight of the composition, more preferably 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 in relation to the composition of the first aspect of the present invention, the compound of formula (I) being replaced by the at least one additional compound.

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; quenching layers; layers comprising hindered amine light stabilisers; overprint varnish layers; barrier layers; diffusion barrier layers; and combinations thereof.

The discrete layer that comprises the compound of formula (I) may further comprise an acid- or base-generating agent associated with the compound of formula (I) as defined above in relation to the composition according to the first aspect of the present invention. 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 layer comprising the compound of formula (I) and the discrete layer comprising the at least one additional compound, the one or more additional layers mean that the applied transition stimulus or first applied temperature and additional applied stimulus or additional 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.

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 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 gsm. It will be appreciated by a skilled person that the overall coat weight of the plurality of discrete layers will be dependent upon discrete layer formation and individual layer coat weights and the substrate.

The substrate according to the eighth aspect of the present invention may be suitable for end use as labels (adhesive and 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.

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.

It will be appreciated by a skilled person that the substrate to which the plurality of discrete layers are 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 the 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 eighth 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 the applied transition stimulus or first applied temperature, and the additional applied stimulus or additional temperature, to the substrate as required to develop the coloured states of the compound of formula (I) and the at least one additional compound.

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 the applied transition stimulus or first applied temperature, and the additional applied stimulus or additional temperature, and if required, second applied temperature, to the substrate as required to develop the non-coloured and/or coloured states of the compound of formula (I) and the at least one additional compound, 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 required 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 applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, and if required, the second applied temperature, may be applied to the substrate such that the non-coloured state and/or coloured state of the compound of formula (I) and the at least one additional compound are present at different localised positions. The coloured states of the compound formula (I) and the at least one additional compound may be selectively developed at localised positions. Suitable means for applying the applied transitions stimulus, first applied temperature, additional applied stimulus and additional temperature are as defined above.

It will further be appreciated that where the transition from the non-coloured state to the coloured state is reversible, i.e. the transition of the compound of formula (I) from the non-coloured state to a coloured state is effected by the application of the applied transition stimulus, and the transition from that same coloured state back to the non-coloured state is effected by the application of a second applied temperature, the second applied temperature may also be applied to the substrate as required to develop the non-coloured state of the compound of formula (I). The second applied temperature is preferably applied at localised positions so as to cause thermal bleaching at these localised positions. Suitable means for applying the second applied temperature are as defined above.

It will be understood by a skilled person that more than one of the applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, may be applied at the same localised position. For example, in order to form a colour resulting from the mixing of two colours (e.g. the mixing of the colours of a coloured state of the compound of formula (I) and a coloured ate of the at least one additional compound of a different colour), the applied transition stimulus or first applied temperature and the additional applied stimulus or additional temperature, may be applied at that particular localised position. The application of the applied transition stimulus or first applied temperature and the additional applied stimulus or additional temperature, and if required, the second applied temperature, will be conducted in the appropriate order as required to develop the coloured state of the compound of formula (I) or (II) and the at least one additional compound. It will further be appreciated that when the at least one additional compound is a diacetylene compound, the additional applied stimulus and the additional temperature may be applied at the same localised position to facilitate a transition from the non-coloured state to the first coloured state (additional applied stimulus), as well as a transition from the first coloured state to the second coloured state (additional temperature). Multi-coloured images can be formed.

It will be appreciated that if the compound of formula (I) and the at least one additional compound are in different layers of the plurality of discrete layers, the ordering of the plurality of discrete layers can have an effect on the colour formed. When the means used to apply the applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, is a laser source(s), the fluence received by each layer varies dependent upon the position of the compound of formula (I) and the at least one additional compound in the layer structure of the plurality of discrete layers relative to the means.

It will further be appreciated by a skilled person that the relationship between the wavelengths of the applied transition stimulus and additional applied stimulus if required will vary dependent upon the colours required in the image to be formed. It will further be appreciated that the relationship between the first applied temperature, second applied temperature and additional temperature if required will vary dependent upon the colours required in the image to be formed. The specific applied transition stimulus or first applied temperature, and additional applied stimulus or additional temperature, will be selected dependent upon the required image to be formed.

Optionally, a separate conductive source of temperature may also be provided to the substrate of the product before, during or after the formation of the image using a conductive source. Conductive sources 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.

According to a twelfth aspect of the present invention, there is provided a method of forming colour on a substrate comprising a composition applied to or incorporated within, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or an applied transition stimulus; the method comprising applying the first applied temperature or applied transition stimulus to the substrate as required to develop the coloured state of the compound of formula (I) of the composition.

According to a thirteenth aspect of the present invention, there is provided a method of forming an image on a substrate comprising a composition applied to or incorporated within, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or C1 -18 alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or an applied transition stimulus; the method comprising applying the first applied temperature or applied transition stimulus to the substrate as required to develop the coloured state of the compound of formula (I) of the composition.

Preferably, the transition from the non-coloured state to a coloured state of the compound of formula (I) is effected by the application of the first applied temperature.

When the applied transition stimulus is utilised to effect the transition from the non-coloured state to a coloured state of a compound of formula (I), the compound of formula (I) is accompanied in the composition by an acid- or base- generating agent as defined above for all previous aspects of the present invention.

Preferably, when the transition of the compound of formula (I) 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).

It will be appreciated by a skilled person that for the twelfth and thirteenth aspects of the present invention, the compound of formula (I) is as defined above in relation to the previous aspects of the present invention. In addition, the first applied temperature and applied transition stimulus are as defined above in relation to the previous aspects of the present invention. Furthermore, the substrate is as defined above in relation to the previous aspects of the present invention. The method of forming an image according to the twelfth and thirteenth aspects of the present invention requires all of the considerations as detailed for the methods of the fourth and fifth aspects of the present invention.

It will be appreciated that the first applied temperature or applied transition stimulus may be selectively applied at localised positions on the substrate such that colour is formed at localised positions. The non-coloured and coloured state of the compound of formula (I) may thus be formed at different localised positions.

It will be appreciated that the transition from the non-coloured state to a coloured state of the compound of formula (I) is irreversible. The first applied temperature is utilised to facilitate a transition of the compound of formula (I) from the non- coloured to a coloured state, and once the coloured state has been formed, a transition from the coloured state back to the non-coloured state cannot occur through the intentional application of the second applied temperature. The second applied temperature is as defined above for previous aspects of the present invention. In addition, the applied transition stimulus is utilised facilitate a transition of the compound of formula (I) from the non-coloured to a coloured state, the compound of formula (I) being accompanied by an acid- or base- generating agent. Once the coloured state has been formed, a transition from the coloured state back to the non-coloured state cannot occur through the intentional application of the second applied temperature.

The composition applied on or incorporated within the substrate utilised in the method of the twelfth and thirteenth aspects of the present invention may further comprise an acid- or base-generating agent to aid the transition of the compound of formula (I) from the non-coloured to the coloured state when the first applied temperature is utilised. The acid- or base-generating is as defined above in relation to the previous aspects of the present invention.

The composition applied on or incorporated within the substrate utilised in the method of the fourteenth and fifteenth aspects of the present invention may further comprise at least one additional compound, the at least one additional compound being as defined above in relation to the previous aspects of the present invention.

Preferably, the at least one additional compound is a diacetylene compound. The remaining components of the composition applied on or incorporated within the substrate utilised in the method of the twelfth and thirteenth aspects of the present invention are as discussed above in relation to the first and previous aspects of the present invention.

According to a fourteenth aspect of the present invention, there is provided a use of a composition in the formation of colour on a substrate, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus. According to a fifteenth aspect of the present invention, there is provided a use of a composition in the formation of an image on a substrate, the composition comprising: a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus.

It will be appreciated that for the fourteenth and fifteenth aspects of the present invention, the compound of formula (I) and first applied temperature are as defined above for previous aspects of the present invention.

According to an sixteenth aspect of the present invention, there is provided a method of forming colour on a substrate having a plurality of discrete layers applied thereto, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ 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; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus; and wherein at least one of the discrete layers comprising at least one additional compound capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; the method comprising applying the first applied temperature or applied transition stimulus, and additional applied stimulus or additional temperature to the substrate as required to develop the coloured state of the compound of formula (I) and the at least one additional compound.

According to a seventeenth aspect of the present invention, there is provided a method of forming an image on a substrate having a plurality of discrete layers applied thereto, wherein at least one of the discrete layers comprises a compound of formula (I):

wherein each of A, B, C and D are independently selected from: C _{M S} alkyl; - CCI ₃ ; -CF ₃ ; Ce-^ aryl optionally substituted with Ci-i ₈ alkoxy, -CN, -CF ₃ , halogen, - N0 ₂ , or Ci-is alkyl; a heterocyclic ring; and a heteroaryl; and wherein the compound is capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of a first applied temperature or applied transition stimulus; and wherein at least one of the discrete layers comprising at least one additional compound capable of transitioning from a non-coloured state to a coloured state, the transition being effected by the application of an additional applied stimulus or additional temperature; the method comprising applying the first applied temperature or applied transition stimulus, and additional applied stimulus or additional temperature to the substrate as required to develop the coloured state of the compound of formula (I) and the at least one additional compound, and thereby form an image on the substrate.

It will be appreciated by a skilled person that for the sixteenth and seventeenth aspects of the present invention, the compound of formula (I) and at least one additional compound are as defined above in relation to the previous aspects of the present invention. In addition, the first applied temperature, applied transition stimulus, additional applied stimulus and additional temperature are as defined above in relation to the previous aspects of the present invention. Furthermore, the substrate is as defined above in relation to the previous aspects of the present invention. The method of forming an image according to the sixteenth and seventeenth aspects of the present invention requires all of the considerations as detailed for the methods of the fourth and fifth aspects of the present invention.

It will be appreciated that the first applied temperature or applied transition stimulus may be selectively applied at localised positions on the substrate such that colour is formed at localised positions. The non-coloured and coloured state of the compound of formula (I) may thus be formed at different localised positions.

It will be appreciated that the transition from the non-coloured state to a coloured state of the compound of formula (I) is irreversible. The first applied temperature is utilised to facilitate a transition of the compound of formula (I) from the non- coloured to a coloured state, and once the coloured state has been formed, a transition from the coloured state back to the non-coloured state cannot occur through the intentional application of the second applied temperature. The second applied temperature is as defined above for previous aspects of the present invention. In addition, the applied transition stimulus may be utilised to facilitate an irreversible transition of the compound of formula (I) from the non- coloured to a coloured state, the compound of formula (I) being accompanied by an acid- or base-generating agent in this instance (the acid- or base-generating agent being as defined above in relation to the previous aspects of the present invention). Once the coloured state has been formed, a transition from the coloured state back to the non-coloured state cannot occur through the intentional application of the second applied temperature.

When the first applied temperature is utilised to facilitate the irreversible transition from the non-coloured to a coloured state, the at least one discrete layer comprising the compound of formula (I) may further comprise an acid- or base-generating agent to aid the transition of the compound of formula (I) from the non-coloured to the coloured state. The acid- or base-generating is as defined above in relation to the previous aspects of the present invention.

Preferably, the at least one additional compound is a diacetylene compound. It will be appreciated by a skilled person that the radiation applied to the compositions or substrates disclosed herein as any of the applied transition stimulus, applied additional stimulus or additional temperature, 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 on or within a substrate or substrate having a plurality of discrete layers. It will be appreciated that the apparatus will be programmed to effect the application of the different stimuli and temperature 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 C _{M S} alkyl groups, halogen, and "C _{M S} 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 "C _{M S} alkoxy" denotes a straight of branched C _{M S} alkyl group which is attached to the remainder of the molecule through an oxygen atom. For parts of the range C _{M S} alkoxy, all sub-groups thereof are contemplated such as C _{M O} 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 C _{M S} alkyl groups, "C _6-12 aryl", and "C _1-18 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 Ci _-20 alkyl groups, "C _5-2 o aryl", "Ci _-20 alkoxy", "hydroxylCi _-2 o alkoxy" and "C _{3-i 8} 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.

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 Compounds According to Formula (I) Provided below is a general synthetic procedure for the production of compounds according to formula (I):

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 2 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.

Specific Examples

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. 1 1. 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)(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).

1 1. 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-pyrazol-4- yl)(phenyl)methylene)-N-phenylhydrazine-1 -carboxamide

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

Step Two: Synthesis of (5-hvdroxy-1 ,3-diphenyl-1 H-pyrazol-4-yl)(4- (trifluoromethyl)phenyl)methanone 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, 1 19.9 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.

1 1. 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-pyrazol-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.

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 %).

Step One: Synthesis of 5-methyl-2-phenyl-1 ,2-dihvdro-3H-pyrazol-3-one (MPP)

1. A 3-neck round bottom flask (rbf) fitted with a stirrer bar and thermometer is charged with ethylacetoacetate (30 mL, 237 mmol).

2. Phenylhydrazine (23.1 mL, 235 mmol) is added to the round bottom flask. 3. Toluene (50 ml_) is used to rinse the excess phenylhydrazine into the reaction.

4. Immediately upon addition of the reagents the reaction begins with a

moderate exotherm taking the reaction mixture to a max of 45 °C. 5. A dean stark trap is fitted to the flask with a reflux condenser attached.

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

7. 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 Heptane/EtOAc 4:1 ). 8. After 2 hours, low boiling condensates have stopped being formed and

removed and TLC indicates that the reaction has gone to completion.

9. The reaction mixture is allowed to cool while continuing to stir, meanwhile 250 mL of Heptane is heated to close to boiling on a hot plate with strong stirring. 10. When the temperatures of the reaction mixture and heptane are close to 80

°C, the reaction mixture is poured onto the hot heptane with strong stirring, a yellow suspension immediately forms.

1 1. The hotplate is turned off and the heptane slurry is left to slowly cool on the hotplate with strong stirring. 12. The solids are slurried overnight in the heptane.

13. The solids are vacuum filtered on paper and washed with plenty of heptane until the filtrate runs clear.

14. The solids are transferred to a drying dish and dried in the vacuum oven (20 °C) overnight yielding the product as a slightly off-white/creamy powder (34.495 g, 83.5 %). Step Two: Synthesis of (5-hvdroxy-3-methyl-1 -phenyl-1 H-pyrazol-4- yl)(phenyl)methanone (BnMPP)

I . MPP (17.10 g, 98.16 mmol) is weighed and placed in a 3-neck round bottom flask (rbf) fitted with a stirrer, thermometer and condenser. 2. 1 ,4-dioxane (200 ml_) is added and the mixture stirred with heating (50 °C) until the MPP is dissolved.

3. Calcium hydroxide (21.82 g, 294.5 mmol) is added and the suspension

stirred.

4. Benzoyl chloride (12.5 ml_, 108.0 mmol) is added slowly over 5

minutes using a funnel.

5. The reaction mixture is heated to reflux for 30 minutes, follow the reaction by TLC (eluting with DCM).

6. The reaction solution is allowed to cool back to 50 °C.

7. The reaction solution is poured into aqueous HCI (2 M, 0.98 L) with strong stirring causing a yellow/brown precipitate to form.

8. The solids are stirred in the acid solution for around 30 minutes.

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

10. The product is slurried in IPA/Water (1 : 1 , 1 L) and heated until all the solids have dissolved.

I I . The IPA/water solution is allowed to cool back to RT with stirring and is slurried overnight.

12. The precipitate is vacuum filtered on paper and partially dried by suction yielding a yellow/brown solid. 13. The solids are transferred to a crystalising dish and dried in the vacuum oven (20 °C, overnight) leaving a yellow brown solid (21.2 g, 77.6 %).

Step Three: Synthesis of (E)-2-((5-hvdroxy-3-methyl-1 -phenyl-1 H-pyrazol-4- yl)(phenyl)methylene)-N-phenylhydrazine-1 -carboxamide For (E)-2-((5-hydroxy-3-methyl-1 -phenyl-1 H-pyrazol-4-yl)(phenyl)methylene)-N- phenylhydrazine-1 -carboxamide: A = phenyl, B = methyl, C = phenyl, and D = phenyl.

1. Bn-MPP (21.19 g, 76.14 mmol) is weighed and placed into a 3-neck round bottom flask (rbf) fitted with a stirrer bar, thermometer and condenser. 2. 4-phenylsemicarbazide (12.66 g, 83.75 mmol) is weighed and placed into the round bottom flask.

3. Ethanol (250 ml_) is added to the reaction vessel and the mixture stirred, resulting in a dark brown solution.

4. Glacial Acetic Acid (0.1 M in ethanol, 8 ml_, 0.76 mmol) is added to the

reaction mixture.

5. The reaction mixture is heated to reflux (79 °C) and followed by TLC

(Hept:EtOAc 1 :4).

6. After around 5 hours TLC indicated the reaction was complete with the

consumption of the Bn-MPP. 7. The reaction mixture is left to cool overnight.

8. The reaction mixture is evaporated to dryness on the under vacuum yielding an amorphous yellow solid.

9. The solid is then dissolved in around 150-200 mL of Acetone with the aid of sonication. 10. The Acetone solution/suspension is left to stand overnight in a sealed container.

1 1. The solids are vacuum filtered on paper.

12. The product is allowed to air dry giving a white powder (25.34 g, 80.9 %). Colour Formation Using the Compounds of Formula (I)

For each of the examples, unless otherwise stated, the natural state (non- coloured state) of the compound of formula (I) and at least one additional compound is either off-white or white.

For each of the examples, unless otherwise stated, the 10.6 pm C0 ₂ laser is set at a speed of 2600-5350 /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 compound of formula (I) was formulated according to Table 1. All amounts are provided in weight percentage (wt%).

(E)-2-((5-hydroxy-1 ,3-diphenyl-1 H-pyrazol-4-yl)(4- (trifluoromethyl)phenyl)methylene)-N-phenylhydrazine-1 -carboxamide was synthesised using the above synthesis.

Table 1

A layer of the composition was applied to a PET substrate (using a 30pm K-bar applicator (higher intensity images can be achieved by using a higher loading of the compound of formula (I) or a higher coat weight). Once applied to the substrate, the compound of formula (I) is in the non-coloured state. An applied transition stimulus was applied to the composition by flood illumination (a 254 nm UV lamp) to form a yellow coloured state of the compound of formula (I) across the whole composition.

A second applied temperature of 80 °C was subsequently applied to localised positions of the composition using a hotplate to effect a transition from the yellow coloured state of the compound of formula (I) back to the non-coloured state.

Example 2

A composition comprising a compound of formula (I) was formulated according to Table 2. All amounts are provided in weight percentage (wt%).

(E)-2-((5-hydroxyl-1 ,3-diphenyl-1 H-pyrazol-4-yl)(phenyl)methylene)-N- phenylhydrazine-1 -carboxamide was synthesised using the above synthesis.

Table 2

A layer of the composition was applied to a PET substrate using a 30pm K-bar applicator (higher intensity images can be achieved by using a higher loading of the compound of formula (I) or higher coat weight). Once applied to the substrate, the compound of formula (I) is in the non-coloured state. A portion of the composition on the substrate was covered. An applied transition stimulus was applied to the composition on the uncovered portion by flood illumination (a high pressure mercury bulb fitted with a 365 nm bandpass filter) to form a yellow coloured state of the compound of formula (I) on the uncovered portion of the substrate. The compound of formula (I) in the composition under the covered portion on the substrate remains in the non-coloured state.

A second applied temperature of 80 °C was subsequently applied to the composition on the uncovered portion (yellow coloured portion) of the substrate using a hotplate to effect a transition from the yellow coloured state of the compound of formula (I) back to the non-coloured state.

Example 3

A composition comprising a compound of formula (I) and an acid-generating agent was formulated by combining the formulations according to Tables 3 and 4 in a 50:50 ratio. All amounts are provided in weight percentage (wt%).

(E)-2-((4-cyanophenyl)(3-hydroxy-2,5-diphenyl-2,3-dihydro -1 H-pyrazol-4- yl)methylene)-N-phenylhydrazine-1 -carboxamide was synthesised using the above synthesis. Table 3

Table 4

A layer of the composition was applied to a PET substrate using a 30pm K-bar applicator (higher intensity images can be achieved by using a higher loading of the compound of formula (I) or higher coat weight). Once applied to the substrate, the compound of formula (I) is in the non-coloured state.

A first applied temperature of around 140 °C was applied to the composition using a C0 ₂ laser emitting at 10600 nm to form a yellow coloured state of the compound of formula (I) at localised positions of the composition. Upon subsequent application of a second applied temperature of around 140 °C using a hotplate, the yellow coloured state of the compound of formula (I) remained.

Example 4

A composition comprising a compound of formula (I) and an acid-generating agent was formulated by combining the formulations according to Tables 5 and 6 in a 50:50 ratio. All amounts are provided in weight percentage (wt%). ((E)-2-((5-hydroxy-1 ,3-diphenyl-1 H-pyrazol-4-yl)(phenyl)methylene)-N- phenylhydrazine-1 -carboxamide was synthesised using the above synthesis. Table 5

Table 6

A layer of the composition was applied to a PET substrate using a 30 pm K-bar applicator (higher intensity images can be achieved by using a higher loading of the compound of formula (I) or higher coat weight). Once applied to the substrate, the compound of formula (I) is in the non-coloured state. A first applied temperature of around 140 °C was applied to the composition using a C0 ₂ laser emitting at 10600 nm to form a yellow coloured state of the compound of formula (I) at localised positions of the composition. Upon subsequent application of a second applied temperature of around 140 °C using a hotplate, the yellow coloured state of the compound of formula (I) remained.

Colour Formation Using the Compounds of Formula (I) and At Least One Additional Compound

Example 5

A composition comprising a compound of formula (I) and a diacetylene compound (an‘at least one additional compound’) is formulated by combining 1 part of the formulation of Table 1 with 1 part of the formulation of Table 8, the formulation of Table 8 being formed from the millbases of Tables 6 and 7. All amount are provided in weight percentage (wt%).

Table 6 - Diacetylene compound millbase

Table 7 - NIR absorber millbase

Table 8

A layer of the composition is applied to a paper substrate using a 20 pm k2 k-bar applicator.

Following application to the substrate, the compound of formula (I) and the diacetylene compound are in the non-coloured state. It is noted that the diacetylene compound utilised in this example has a non-coloured state that requires ‘activation’, i.e. application of an activation temperature, to make it capable of transition from the non-coloured state to a 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 activation temperature), the non-coloured state of the diacetylene compound is ‘activated’ at these localised positions. Next, a medium pressure mercury lamp is used to first apply UV radiation (applied transition stimulus) to the composition via flood illumination. The compound of formula (I) transitions from the non-coloured to a pale yellow coloured state across the substrate. In addition, the UV radiation acts as the additional applied stimulus and causes the diacetylene compound 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 diacetylene compound has been ‘activated’. At the localised positions at which the first blue coloured state of the diacetylene compound has been formed, the pale yellow coloured state of the compound of formula (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 diacetylene compound and the pale yellow coloured state of the compound of formula (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 diacetylene compound have been formed undergo a transition to a red second coloured state. In addition, the NIR radiation acts as a second applied temperature and the compound of formula (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 compound of formula (I) can form part of the multi-coloured image. [Example 6

A composition comprising a compound of formula (I) and a leuco dye (an‘at least one additional compound’) is formulated by combining 1 part of the formulation of Table 1 with 1 part of the formulation of Table 9. All amounts are provided in weight percentage (wt%). Table 9 - Formulation comprising leuco dye

Table 10

A layer of the composition is applied to a PET substrate using a 20 pm k2 k-bar applicator. Following application to the PET substrate, the compound of formula (I) and the leuco dye are in the non-coloured state.

If a germicidal UV lamp is used to apply UV radiation (applied transition stimulus) to the composition via flood illumination, the compound of formula (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 leuco dye 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 (additional temperature), the leuco dye 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 compound of formula (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 leuco dye and the non- coloured state of the compound of formula (I), the blue colour of the coloured state of the leuco dye is displayed at the localised positions.

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

Example 7

A composition comprising a diacetylene compound (an‘at least one additional compound’) is formulated according to Table 8, using the millbase formulations of Tables 6 and 7, but replacing the diacetylene compound with N1-N22- dicyclopropyldocosa-10, 12-diynediamide.

A composition comprising a compound of formula (I) is formulated according to Table 1. A layer of the composition comprising the diacetylene compound is applied to a paper substrate using a 16 pm k2 k-bar applicator. A layer of the composition comprising a compound of formula (I) is then applied using a 16 pm k2 k-bar applicator over the layer of the composition comprising a diacetylene compound.

Following application of the layers to the substrate, the compound of formula (I) and the diacetylene compound are in the non-coloured state. It is noted that the diacetylene compound utilised in this example has a non-coloured state that requires ‘activation’, i.e. application of an activation temperature, to make it capable of transition from the non-coloured state to a coloured state.

If a germicidal UV lamp is used to apply UV radiation (applied transition stimulus) to the substrate via flood illumination, the compound of formula (I) transitions from the non-coloured to a yellow coloured state, such that a pale yellow colour is displayed on the substrate. The diacetylene compound’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 (activation temperature), the non-coloured state of the diacetylene compound is‘activated’ at these localised positions. The subsequent addition of UV radiation (additional applied stimulus) by flood illumination causes the diacetylene compound to transition from the non-coloured state to a first blue coloured state at these localised positions at which the non-coloured state of the diacetylene compound has been‘activated’. It is noted that at these localised positions, the compound of formula (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 first blue coloured state of the diacetlyene compound and the non-coloured state of the compound of formula (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 diacetylene compound from the first blue coloured state to the second red coloured state at these particular localised positions. A multi-coloured image may therefore be formed displaying yellow, blue and red colours.

Example 8

A composition comprising an oxyanion of a multivalent metal (an at least one additional compound) is formulated according to Table 11. All amounts are provided in weight percentages (wt%).

Table 11

A composition comprising a compound of formula (I) was formulated according to Table 1.

A layer of the composition comprising an oxyanion of a multivalent metal is applied to a paper substrate using a 16 pm k2 k-bar applicator. A layer of the composition comprising a compound of formula (I) is then applied using a 16 pm k2 k-bar applicator over the layer of the composition comprising an oxyanion of a multivalent metal.

Following application to the substrate, the compound of formula (I) and the oxyanion of a multivalent metal are in the non-coloured state. If a germicidal UV lamp is used to apply UV radiation (applied transition stimulus) to the substrate via flood illumination, the compound of formula (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 (additional temperature) either prior to or subsequent to the application of the UV radiation, the oxyanion of a multivalent metal 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 compound of formula (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 oxyanion of a multivalent metal and the non-coloured state of the compound of formula (I), a black colour is displayed at the localised positions.

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

Example 9 A composition comprising an oxyanion of a multivalent metal (an‘at least one additional compound’) is formulated according to Table 11 above.

A composition comprising a leuco dye (an‘at least one additional compound’) is formulated according to Table 9, the leuco dye being replaced by 3,3'-bis(1-n- octyl-2-methylindol-3-yl)phthalide (Chameleon Red 5). A composition comprising a compound of formula (I) was formulated according to Table 1 above.

A layer of the composition comprising an oxyanion of a multivalent metal is applied to a paper substrate using a 16 pm k2 k-bar applicator. A layer of the composition comprising a leuco dye is then applied using a 16 pm k2 k-bar applicator over the layer of the composition comprising an oxyanion of a multivalent metal. A layer of the composition comprising a compound of formula (I) is then applied using a 16 pm k2 k-bar applicator over the layer of the composition comprising a leuco dye.

Following application to the substrate, the compound of formula (I), the leuco dye, and the AOM are in the non-coloured state.

If a germicidal UV lamp is used to apply UV radiation (applied transition stimulus) to the substrate via flood illumination, the compound of formula (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 an additional 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 additional 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 additional 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 10

A composition comprising an oxyanion of a multivalent metal (an‘at least one additional compound’) is formulated according to Table 11 above.

A composition comprising a diacetylene compound (an‘at least one additional compound’) is formulated according to Table 8, using the millbase formulations of Tables 6 and 7.

A composition comprising a compound of formula (I) was formulated according to Table 1.

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 diacetylene compound is applied over the layer of the composition comprising AOM using a k2 k-bar applicator. A layer of the composition comprising a compound of formula (I) is then applied over the layer of the composition comprising a diacetylene compound using a k2 k-bar applicator.

Following application to the substrate, the compound of formula (I), the diacetylene compound and the AOM are in the non-coloured state. It is noted that the diacetylene compound utilised in this example has a non-coloured state that requires‘activation’, i.e. application of an activation temperature, to make it capable of transition from the non-coloured state to a coloured state.

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

An additional temperature is applied using a 10.6 pm C0 ₂ laser (38% power) to provide NIR radiation to localised positions of the substrate either prior to or subsequent to the application of the UV radiation. At these localised positions, the AOM transitions from its non-coloured to a black coloured state. The intensity of the black colour formed can be varied by variation of the fluence provided by the C0 ₂ laser. It is noted that at these localised positions, the additional temperature acts as a second applied temperature, and the coloured state of the compound of formula (I) transitions back from the pale yellow coloured state to the non-coloured state. However, as the coloured state of the oxyanion of a multivalent metal is formed at these localised positions, the substrate displays the black colour of the coloured state of the oxyanion of a multivalent metal.

It is noted that the additional 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 activation temperature of the diacetylene compound. Accordingly, upon application of the additional temperature required to facilitate the transition of the oxyanion of a multivalent metal from the non-coloured to a coloured state, the non coloured state of the diacetylene compound is also‘activated’ at these localised positions. Upon further application of UV radiation (additional applied stimulus) via flood illumination using a germicidal lamp, the diacetylene compound transitions from the activated non-coloured state to a blue coloured state at these localised positions at which the non-coloured state of the diacetylene compound has been ‘activated’. As the coloured state of the diacetylene compound is formed at the same localised position at which the coloured state of the oxyanion of a multivalent metal has been formed, the final colour displayed at these localised positions is dependent upon the blue coloured state of the diacetylene compound, and the black coloured state of the AOM, 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.

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

Example 11 A composition comprising a compound of formula (I) was formulated according to Table 2.

A composition comprising a diacetylene compound (an‘at least one additional compound’) was formulated according to Table 8, using the millbase formulations of Tables 6 and 7, but the diacetylene compound was replaced with N 1 , N22-didecyldocosa-10, 12-diynediamide.

A layer of the composition comprising a compound of formula (I) was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a diacetylene compound is applied over the layer of the composition comprising AOM using a k2 k-bar applicator.

Following application of the layers to the substrate, the compound of formula (I) and the diacetylene compound are in the non-coloured state. It is noted that the diacetylene compound utilised in this example has a non-coloured state that requires ‘activation’, i.e. application of an activation temperature, to make it capable of transition from the non-coloured state to a coloured state.

If a germicidal UV lamp is used to apply UV radiation (applied transition stimulus) to the substrate via flood illumination, the compound of formula (I) transitions from the non-coloured to a pale yellow coloured state, such that a pale yellow colour is displayed on the substrate. Alternatively, following application of the layers to the substrate, the non- coloured state of the diacetylene compound can be ‘activated’ at localised positions through the application of the activation temperature using a 10.6 pm C0 ₂ laser (20% power) to apply IR radiation at these localised positions. The subsequent application of UV germicidal radiation by flood illumination (additional applied stimulus) will then facilitate the transition of the diacetylene compound from the non-coloured state to a first blue coloured state at solely 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 diacetylene compound 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 layer of the composition comprising a diacetylene compound (an‘at least one additional compound’ was formulated according to Table 8, using the millbase formulations of Tables 6 and 7.

A layer of the composition comprising a compound of formula (I) and an acid- generating agent was formulated according to a 2:1 blend of the formulations of Table 12 with the formulation of Table 13. All amounts are provided in weight percentages (wt%).

Table 12

Table 13

A layer of the composition comprising a diacetylene compound was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a compound of formula (I) and acid-generating agent was then applied using a k2 k-bar applicator over the layer of the composition comprising the diacetylene compound.

Following application of the layers to the substrate, the compound of formula (I) and the diacetylene compound are in their non-coloured states. It is noted that the diacetylene compound utilised in this example has a non-coloured state that requires ‘activation’, i.e. application of an activation temperature, to make it capable of transition from the non-coloured state to a coloured state.

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 (first applied temperature). At these localised positions, the compound of formula (I) transitions to a yellow coloured state. It is noted that the activation temperature of the diacetylene compound is lower than the first applied temperature. Therefore, the non-coloured state of the diacetylene compound is also‘activated’ at these localised positions.

Upon application of UV radiation by flood illumination using a germicidal lamp (additional applied stimulus), the’activated’ non-coloured state of the diacetylene compound at the localised positions transition to a blue first coloured state. As the coloured state of the diacetylene compound is formed at the same localised position at which the coloured state of the compound of formula (I) has been formed, the final colour displayed at these localised positions is dependent upon the blue colour of the coloured state of the diacetylene compound, and the colour of the yellow coloured state of the compound of formula (I) 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 second applied temperature to the whole substrate by flood illumination using a heat gun, there is no transition of the compound of formula (I) from the yellow coloured state back to the non-coloured state. The compound of formula (I) remains in the yellow coloured state. However, this second applied temperature acts as an additional temperature and facilitates the transition of the diacetylene compound 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 yellow coloured state of the compound of formula (I). Orange and red colours can be formed. A multi-coloured image displaying yellow, orange, yellow, green and red colours can therefore be formed.

Example 13

A layer of the composition comprising a compound of formula (I) and a base- generating agent was formulated according to a 2:1 blend of the formulation of Table 12 above with the formulation of Table 14. All amounts are provided in weight percentages (wt%).

Table 14

A composition comprising a diacetylene compound (an‘at least one additional compound’) was formulated according to Table 8, using the millbase formulations of Tables 6 and 7. A layer of the composition comprising a compound of formula (I) and base- generating agent was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a diacetylene compound was then applied using a k2 k-bar applicator over the layer of the composition comprising the compound of formula (I) and base-generating agent. Following application of the layers to the substrate, the compound of formula (I) and the diacetylene compound are in their non-coloured states. It is noted that the diacetylene compound utilised in this example has a non-coloured state that requires ‘activation’, i.e. application of an activation temperature, to make it capable of transition from the non-coloured state to a coloured state. Upon application of the layers to the substrate, no change occurs upon application of UV radiation as the non-coloured state of the diacetylene compound requires activation through application of an activation temperature, and the compound of formula (I) is accompanied by a thermal base-generating agent and therefore requires an additional temperature in order to facilitate a transition from the non-coloured state to a coloured state of the compound of formula (I).

Upon application of IR radiation using a 10.6 pm C0 ₂ laser at localised positions of the substrate (first applied temperature), the compound of formula (I) 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 activation temperature of the diacetylene compound is lower than the first applied temperature required to facilitate the transition of the compound of formula (I) from the non-coloured to a coloured state. Therefore, upon application of the IR radiation, the non-coloured state of the diacetylene compound 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 (additional applied stimulus), the non-coloured state of the diacetylene compound 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 diacetylene compound has been formed at the same localised positions as the coloured state of the compound of formula (I), the final colour displayed at these localised positions is a combination of the colour of the coloured state of the compound of formula (I) and the blue first coloured state of the diacetylene compound. Accordingly, green, blue and orange colours can be formed.

Upon further application of a second applied temperature to the whole substrate by flood illumination using a heat gun, there is no transition of the compound of formula (I) form the coloured state back to the non-coloured state. The compound of formula (I) remains in its coloured state. However, this second applied temperature acts as an additional temperature and facilitates the transition of the diacetylene compound 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 compound of formula (I). 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.

Example 14

A layer of the composition comprising a compound of formula (I) and a base- generating agent was formulated according to a 2:1 blend of the formulation of T able 12 with the formulation of T able 14 above. A composition comprising a diacetylene compound (an‘at least one additional compound’) was formulated according to Table 8, using the millbase formulations of Tables 6 and 7.

A layer of the composition comprising a compound of formula (I) and base- generating agent was applied to a paper substrate using a k2 k-bar applicator. A layer of the composition comprising a diacetylene compound was then applied using a k2 k-bar applicator over the layer of the composition comprising the compound of formula (I) and base-generating agent.

Following application of the layers to the substrate, the compound of formula (I) and the diacetylene compound are in their non-coloured states. It is noted that the diacetylene compound utilised in this example has a non-coloured state that requires ‘activation’, i.e. application of an activation temperature, to make it capable of transition from the non-coloured state to a coloured state.

Upon application of IR radiation using a 10.6 pm C0 ₂ laser at localised positions of the substrate (first applied temperature), the compound of formula (I) 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 activation temperature of the diacetylene compound is lower than the first applied temperature required to facilitate the transition of the compound of formula (I) from the non-coloured to a coloured state. Therefore, upon application of the IR radiation, the non-coloured state of the diacetylene compound 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 (additional applied stimulus), the non-coloured state of the diacetylene compound 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 diacetylene compound has been formed at the same localised positions as the coloured state of the compound of formula (I), the final colour displayed at these localised positions is a combination of the colour of the coloured state of the compound of formula (I) and the blue first coloured state of the diacetylene compound. Accordingly, green, blue and orange colours can be formed.

Upon further application of a second applied temperature to the whole substrate by flood illumination using a heat gun, there is no transition of the compound of formula (I) form the coloured state back to the non-coloured state. The compound of formula (I) remains in its coloured state. However, this second applied temperature acts as an additional temperature and facilitates the transition of the diacetylene compound 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 compound of formula (I). 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.

Reversible and Irreversible Transition Data for Compounds of Formula (I)

Compositions comprising a compound of formula (I)

A composition 1 comprising a compound of formula (I) was formulated according to Table 2. A composition 2 comprising a compound of formula (I) as formulated according to Table 1.

Compositions comprising a compound of formula (I) and an acid-generating agent

A composition 3 comprising a compound of formula (I) and an acid-generating agent is formulated according to a 50:50 mixture of the formulations of Tables 5 and 10. A composition 4 comprising a compound of formula (I) and an acid-generating agent is formulated according to a 50:50 mixture of the formulations of Tables 5 and 10, but with the compound of formula (I) replaced with (E)-2-((5-hydroxy-1 ,3- diphenyl-1 H-pyrazol-4-yl)(4-(trifluoromethyl)phenyl)methylene)-N- phenylhydrazine-1 -carboxamide.

These two compositions represent a composition comprising a compound of formula (I) and an acid-generating agent.

Compositions comprising a compound of formula (I) and a base-generating agent) A composition 5 comprising a compound of formula (I) and a base-generating agent was formulated according to a 50:50 mixture of the formulation of Table 2 and the formulation of Table 14.

A composition 6 comprising a compound of formula (I) and a base-generating agent was formulated according to a 50:50 mixture of the formulation of Table 1 and the formulation of Table 14.

These two compositions represent a composition comprising a compound of formula (I) 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.

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 compound of formula (I) is formed (representative of the first applied temperature). 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 of the compound of formula (I) is formed (representative of the applied transition 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 first applied temperature or applied transition 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 second applied 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 first applied temperature and applied transition stimulus, and again following the application of the second applied temperature, it could be determined where the coloured state remains the same (no different in DE after the application of the second applied 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 second applied 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 second applied 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 second applied 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 15. From these results, it is clear that if the first applied temperature is used to facilitate a transition of the compound of formula (I) from the non-coloured state to a coloured state, whether the compound of formula (I) 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 applied transition stimulus is used to facilitate a transition of the compound of formula (I) from the non-coloured to a coloured state, the transition is reversible (i.e. DE difference values are large and negative) and the application of the second applied stimulus facilitates a transition from the coloured state back to the non-coloured state.

Table 15