Diacetylene Compound

Field of the Invention

The present invention relates to a method of forming a stable non-coloured or coloured state of a diacetylene compound, and a substrate comprising a diacetylene compound having a stable non-coloured or coloured state applied to or incorporated within the substrate. The present invention further relates to a method of forming an image on or within a substrate comprising said diacetylene compound applied to or incorporated within.

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 radiation-reactive components in compositions applied on or incorporated within substrates, such that they change colour upon exposure to the radiation. Diacetylene compounds are known components of a number of radiation-reactive compositions. Upon exposure to a stimulus, diacetylene compounds polymerise and display colour. Diacetylene compounds may have non-coloured, first coloured and second coloured states. Typically, diacetylene compounds are first irradiated with radiation to effect a transition from the non-coloured state to the first coloured state. The diacetylene compound may then be thermally treated to achieve a second coloured state. However, over time and under ambient conditions, this second coloured state often fades or reverts back to the first coloured state. In some instances, a mixture of the colours of the first and second coloured states are displayed. Furthermore, over time and under ambient conditions, the non coloured states of the diacetylene compounds often unintentionally acquire the colours of the coloured states. This instability, and the inaccessibility of a stable second coloured state, means that certain diacetylene compounds cannot be utilised as radiation-reactive components capable of achieving two stable coloured states using a single compound. The utility of these diacetylene compounds is thus limited to a far narrower range of applications.

WO 2012/114121 discloses the transition from a non-coloured state to a first coloured state of certain‘reversibly activated’ diacetylene compounds of formula Y-CECEC-(CH ₂ ) _n -T-Q-Z, the alkyl chain n between the diacetylene group and the terminal group (T-Q-Z) of these diacetylene compounds having an odd number of carbon atoms, preferably three carbon atoms (n=3).

WO2013/014436 discloses a transition from a non-coloured state to a first coloured state of diacetylene compounds, the disclosure focusing on the use of visible radiation to effect further colour changes.

Summary of the Invention

According to a first aspect of the present invention, there is provided a method of forming a stable non-coloured or coloured state of a diacetylene compound having non-coloured, first coloured and second coloured states, the diacetylene compound being capable of transitioning from the non-coloured state to the first or second coloured state and from the first to the second coloured state, the method comprising simultaneously exposing to both thermal energy and radiation the non-coloured state or, if formed, the first coloured state of the diacetylene compound, wherein the radiation has a wavelength of 400 nm or less, and the thermal energy is selected to:

(i) form a stable non-coloured state; or

(ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or

(iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state; wherein in (ii) and (iii), the resulting second coloured state is stable. It has been surprisingly and advantageously found that simultaneous exposure of the non-coloured state of the diacetylene compound to selected thermal energy and radiation enables the formation of a stable non-coloured state or a stable second coloured state. It has also been surprisingly and advantageously found that simultaneous exposure of the first coloured state, if formed, of the diacetylene compound to selected thermal energy and radiation enables the formation of a stable second coloured state. This is in contrast to WO 2012/114121 and WO 2013/014436 which disclose only the transition from a non-coloured to a first coloured state of a diacetylene compound, with WO 2012/144121 only disclosing very specific ‘reversibly activated’ diacetylene compounds of formula Y-CECEC-(CH ₂ ) _n -T-Q-Z, n being an odd number.

It has been surprisingly and advantageously found that the simultaneous exposure of the non-coloured state of the diacetylene compound to selected thermal energy and radiation results in the formation of a stable non-coloured state.

It has further been advantageously found that simultaneous exposure of the non coloured state or, if formed, the first coloured state of the diacetylene compound to selected thermal energy and radiation can effect a transition to a second coloured state of the diacetylene compound, the resulting second coloured state being stable. This formation of a stable second coloured state enables both the first and second coloured states of the diacetylene compound to be accessed. The simultaneous exposure of the non-coloured state or, if formed, the first coloured state of the diacetylene compound to both thermal energy and radiation thus provides a stable second coloured state, in addition to facilitating a transition thereto.

It will be appreciated by a skilled person that the selected thermal energy and radiation required to facilitate each of (i) to (iii) will be different. In the present invention, it is the thermal energy that is altered to achieve the different results (i) to (iii). It will be appreciated by a skilled person that in all aspects of the present invention, the transition from the first coloured state to the second coloured state of the diacetylene compound may only occur if the first coloured state of the diacetylene compound has been formed prior to (iii) taking place. This first coloured state may be formed either by effecting a transition from the non coloured state to the first coloured state through the simultaneous exposure of the diacetylene compound to both selected thermal energy and radiation, or otherwise, such as through exposure of the non-coloured state of the diacetylene compound to a stimulus such as radiation to effect a transition from the non-coloured state to the first coloured state.

"Non-coloured state" and like terms used herein, refers to the state of the diacetylene compound in which the compound is white, off-white or colourless, i.e. clear, or has reduced or low level visible colour, i.e. is paler in colour (a lighter shade) than a coloured state of the same colour. The non-coloured state of the diacetylene compound displays the natural colour of the diacetylene compound before any thermal energy or radiation is applied thereto. It will be appreciated by a skilled person that when the non-coloured state of the diacetylene compound is colourless, any colour of the substrate on which the diacetylene compound is applied to or incorporated within will be visible.

"Coloured state", "first coloured state", or "second coloured state" and like terms as used herein, refer to the state of the diacetylene compound in which the compound displays a colour, i.e. is substantially or highly coloured, in the visible spectrum and to the human eye. In relation to the term "coloured state", the singular encompasses the plural and vice versa. For example, if reference is made to‘a’ coloured state, the term may be understood to refer to one of the first or second coloured states, or both of the first and second coloured states. By the term "colour" and like terms used herein, is meant the colours of the visible light colour spectrum, i.e. red, orange, yellow, green, blue and violet, in addition to black, purple, pink, cyan and magenta, and mixtures thereof. Both primary and secondary colours are encompassed, i.e. it will be appreciated by a skilled person that a coloured state formed by a diacetylene compound may have a primary or secondary colour. The term "colour" as used herein also refers to the different shades of each of these colours.

"Stable" and like terms as used herein, refers to the non-coloured or a coloured state of the diacetylene compound that is stable under ambient conditions i.e. maintains its non-colour or colour under ambient conditions by remaining in the non-coloured or coloured state and not fading or reverting, or developing into a colour or a mixture of colours of the different coloured states to any significant degree. "Ambient conditions" and like terms as used herein, refers to the normal range of conditions of the surrounding environment to which the components are exposed, i.e. the range of temperatures, pressures and atmospheric conditions to which the components are exposed during use, storage or 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 non-coloured or coloured state of the diacetylene compound will be dependent upon the application for which a substrate comprising the diacetylene compound having stable non coloured or coloured states is intended to be used. For example, if the diacetylene 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 non coloured or the coloured state of the diacetylene compound will only need to be for a relatively short period of time, for example, a number of days such as 3 or 4 days. Whereas, if the diacetylene compound is to be utilised in a laser-reactive composition applied on or incorporated within a cosmetic container or outdoor signage, the required stability of the non-coloured or the coloured state of the diacetylene compound will be greater, for example, a number of months. In general however, stable under ambient conditions is meant that when exposed to ambient conditions for at least a number of days, such as for at least two weeks, the diacetylene compound will remain in the particular non-coloured or coloured state and will not fade or revert, or develop into a colour or a mixture of colours of the different colour states to any significant degree. Accordingly, it is preferred that the diacetylene compound remains in the non-coloured or coloured state for at least 3 days, preferably for at least 4 days, more preferably for at least 1 or even at least 2 weeks, and most preferably, for at least 2 months.

"Monochromic" or "single-coloured image" and like terms used herein, refer to an image or text 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, when the non-coloured state of the diacetylene 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 or text that is human or machine readable having multiple colours, i.e. two or more that are visible to the human eye. In the context of the present invention, when the non-coloured state of the diacetylene 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 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 diacetylene compound or composition comprising the diacetylene compound that facilitates the formation of an image.

"Transitioning" or "transition" and like terms as used herein, refer to the diacetylene compound changing from a non-coloured state to the first or second coloured states, or from the first coloured state to the second coloured state upon exposure to selected thermal energy and radiation. It will be understood by a skilled person that this is an intentional transition.

"Resulting coloured state" and like terms as used herein, is meant the coloured state following a transition. "Printing", 'in-line 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 or within 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.

By the term "laser source(s)" and like terms as used herein includes any suitable commercial laser source(s). Suitable examples include, but are not limited to a 940 nm 10 watt IR fibre laser (Lumentum) for providing infrared radiation.

In the context of the present invention, the "thermal energy" to which the diacetylene compound is exposed provides temperature to the diacetylene compound.

It will be appreciated by a skilled person that the diacetylene compound according to the present invention comprises a diacetylene moiety

The diacetylene compound may have the following formula (I): wherein x is from 1 to 20, such as 2 to 12, preferably 2 to 10, and more preferably 2 to 8;

O

L is selected from an amide having the formula: H ^V , and an ester having

O the formula: L preferably L is an amide having the formula Q is selected from a cyclopropyl group and a -(CH ₂ ) _y -CH ₃ linear alkyl chain, y being selected from 1 to 20, preferably Q is a -(CH ₂ ) _y -CH ₃ linear alkyl chain and y is selected from 5 to 19, and more preferably 5 to 17; and

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

It will be appreciated by a skilled person that the diacetylene compound can be either symmetrical i.e. T is -(CH ₂ ) _X -L-Q and the values of x, L and Q are the same on both sides of the diacetylene moiety, or unsymmetrical i.e. T is other than— (CH ₂ ) _X -L-Q, or T is -(CH ₂ ) _X -L-Q and the values of x, L and Q are different on either side of the diacetylene moiety of the diacetylene compound. Preferably, T is-(CH ₂ ) _x -L-Q and the values of x, L and Q are the same on both sides of the diacetylene moiety such that the diacetylene compound is symmetrical.

The value of x as defined for formula (I) may be either odd or even. Preferably, the value of x is even. For example, for the range 1 to 20, x may be selected from 2, 4, 8, 10, 12, 14, 16, 18 and 20, and for the range 2 to 8, x may be selected from 2, 4, 6 and 8.

The value of y for Q and/or T as defined for formula (I) may be either odd or even. Preferably, the value of y for Q and/or T as defined for formula (I) is even. For example, for the range 1 to 20, y may be selected from 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20, and for the range 5 to 17, y may be selected from 8, 10, 12, 14 and 16.

The value of x and the value of y for Q and/or T as defined for formula (I) may both be odd or both be even. Preferably, the value of x and the value of y for Q and/or T as defined for formula (I) are both even.

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, N1 ,N22-ditetradecyldocosa-10,12- diynediamide, N1 ,N22-didodecyldocosa-10,12-diynediamide, N1 ,N22- didecyldocosa-10,12-diynediamide, N1 ,N22-dioctyldocosa-10,12-diynediamide, N1 , N22-dihexyldocosa-10,12-diynediamide, and N1 ,N22-dicyclopropyldocosa-

10.12-diynediamide.

Preferably, the diacetylene compound is a diacetylene compound selected from N1 ,N22-dioctadecyldocosa-10,12-diynediamide, N1 ,N22-dihexadecyldocosa-

10.12-diynediamide, N1 ,N22-ditetradecyldocosa-10,12-diynediamide, and

N1 ,N22-didodecyldocosa-10,12-diynediamide.

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. It will be appreciated by a skilled person that when the diacetylene compounds of the present invention are in the non-coloured state, they are considered to be monomers. The first and second coloured states of the diacetylene compounds of the present invention are formed on account of polymerisation of these monomers upon exposure to radiation and thermal energy. Polymerisation of at least a portion of the monomers enables the formation of the coloured states of the diacetylene compounds. In addition, without being bound by theory, the inventors consider that the different first and second coloured states are achieved through changes in conjugation of the diacetylene polymer, i.e. a structural change.

The radiation to which the diacetylene compound is exposed has a wavelength of 400 nm or less. Suitable radiation includes ultraviolet (UV) radiation having a wavelength of from 10 to 400 nm; X-ray radiation having a wavelength of from 0.01 to 10 nm and gamma radiation having a wavelength of less than 0.01 nm. Preferably, the radiation to which the diacetylene compound is exposed is ultraviolet (UV) radiation, the ultraviolet (UV) radiation having a wavelength of from 100 to 400 nm, and more preferably from 200 to 400 nm.

The diacetylene compound may be exposed to the radiation using any suitable means. Suitable means include laser excitation through exposure of the diacetylene compound to radiation applied by a laser source(s). It will be understood to a skilled person that the radiation may be applied to the diacetylene compound at localised positions to selectively (i) form a stable non coloured state; or (ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or (iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the diacetylene compound may be exposed to the radiation by flood illumination, meaning that the diacetylene compound as a whole is flooded with radiation. This can be done using a lamp, such as a UV lamp; a diode bar; or LED(s). It will further be appreciated by a skilled person that the diacetylene compound is exposed to the radiation for an appropriate amount of time required to (i) form a stable non-coloured state; or (ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or (iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state. Typically the time required to deliver sufficient radiation will depend upon the power of the means utilised to apply the radiation and the method of exposure, i.e. at localised positions or flood illumination. For example, in one embodiment, the diacetylene compound may be exposed to radiation via flood illumination using a UV lamp for less than 120 seconds, such as between 30 to 110 seconds, such as between 75 and 105 seconds.

The thermal energy to which the diacetylene compound is exposed to selectively (i) form a stable non-coloured state; or (ii) effect a transition from the non coloured state of the diacetylene compound to the second coloured state; or (iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state, is dependent upon the melting point and to an extent, the decomposition temperature (the temperature at which the diacetylene compound chemically decomposes) of the diacetylene compound. It will be appreciated by a skilled person that such features (melting point and decomposition temperature) are directly related to the structure of the diacetylene compound. Typically, the thermal energy is such that the diacetylene compound is exposed to a temperature of from 40 to 250 °C, such as from 50 to 200 °C, and is varied to achieve (i) to (iii) as set out below. Where the diacetylene compound is exposed to thermal energy from a radiative source, i.e. at localised positions using a laser source(s) or by flood illumination, it will be appreciated by a skilled person that the diacetylene compound 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.

Typically, the melting point of the diacetylene compound is between 60 to 200 °C, such as between 80 to 180 °C.

The melting point may be measured using any suitable method. Suitable measuring methods will be well known to those skilled in the art. Preferably, the melting point is measured using melting point tubes (capillary method), or using differential scanning calorimetry (DSC).

Typically, the decomposition temperature of the diacetylene compound is >200 °C.

The decomposition temperature may be measured using any suitable method. Suitable measuring methods will be well known to those skilled in the art. Preferably, the decomposition temperature is measured using differential scanning calorimetry (DSC).

The thermal energy to which the diacetylene compound is exposed is intended to refer to thermal energy that it not provided by the means used to expose the diacetylene compound to the radiation. The diacetylene compound may be exposed to the thermal energy using any suitable means. Suitable means include laser excitation through exposure of the diacetylene compound to thermal energy applied by a laser source(s), i.e. radiative source. It will be understood to a skilled person that localised positions of the diacetylene compound may be exposed to the thermal energy so as to selectively (i) form a stable non-coloured state; (ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or (iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state. These localised positions may overlap with each other. Alternatively, it will be appreciated by a skilled person that the diacetylene compound may be exposed to thermal energy by flood illumination, meaning that the whole of the diacetylene compound is flooded with thermal energy. This can be done using a lamp; diode bar; or LED(s). It will further be appreciated that the diacetylene compound may alternatively be exposed to thermal energy using a conductive thermal energy source. Conductive thermal energy sources include sources of steam and hot air, lamps, heat tunnels, LED(s), thermal print heads, thermal conductors, hot liquids and heated substrates. It will be understood by a skilled person that the diacetylene compound is exposed to the thermal energy for an appropriate amount of time required to (i) form a stable non-coloured state; or (ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or (iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state. Typically the time required to deliver sufficient thermal energy will depend upon the power of the means used to apply the thermal energy and the method of exposure i.e. at localised positions, by flood illumination or using a conductive thermal energy source. For example, in one embodiment, the diacetylene compound may be exposed to thermal energy for less than 120 seconds, such as between 30 to 110 seconds, such as between 75 and 105 seconds.

It will be appreciated by a skilled person that the diacetylene compound may be exposed to the thermal energy using a combination of the suitable means listed above i.e. using different combinations of laser excitation at localised positions, flood illumination, and a conductive thermal energy source. For example, in one embodiment, the diacetylene compound may be exposed to the thermal energy using laser excitation at localised positions, in addition to a conductive thermal energy source.

The thermal energy may be provided to the diacetylene compound using visible light with a wavelength of from 400 to 700 nm, infrared (IR) with a wavelength of from 700 nm to 1 mm, in particular 10600 nm using a C0 ₂ laser, and near- infrared (NIR) with a wavelength of from 700 to 1600 nm. Preferably, the thermal energy is provided using infrared (IR) with a wavelength of 10600nm, near-infrared (NIR) with a wavelength of from 700 to 1600 nm, or visible radiation with a wavelength of from 400 to 700 nm.

It will be appreciated by a skilled person that the means used to simultaneously expose the diacetylene compound to thermal energy and radiation may, in some instances, be provided by the same source. For example, in one embodiment, a diode array can be utilised to simultaneously expose the diacetylene compound to both thermal energy using near-infrared lasers and radiation using UV lasers, the lasers forming the diode array.

It will be appreciated by a skilled person that the simultaneous exposure to both thermal energy and radiation of the diacetylene compound will differ depending on whether it is desired to (i) form a stable non-coloured state; or (ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or (iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state. As discussed above, in the present invention, it is the thermal energy that is altered to achieve the different results (i) to (iii) as will be described below.

Preferably, to (i) form a stable non-coloured state of the diacetylene compound, the thermal energy is such that the diacetylene compound is exposed to a temperature greater than the melting point of the diacetylene compound. Preferably, this temperature T ₍ , ₎ is from 50 to 200 °C, such as from 80 to 200 °C, or even from 100 to 200 °C. Preferably, to (ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state, the thermal energy is such that the diacetylene compound is exposed to a temperature close to (within 5°C or less), but lower than the melting point of the diacetylene compound. The transition from the non-coloured state of the diacetylene compound to the second coloured state will not occur if the thermal energy is such that the diacetylene compound is exposed to a temperature equal to or greater than the melting point of the diacetylene compound. Preferably, this temperature T ₍ ,, ₎ is from 50 to 200 °C, such as from 80 to 170 °C, or even from 100 to 170 °C. Preferably, to (iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state, the thermal energy is such that the diacetylene compound is exposed to a temperature that is close to (within 5°C or less), but lower than the melting point of the diacetylene compound, equal to the melting point of the diacetylene compound, or greater than the melting point, but below the decomposition temperature of the diacetylene compound. Preferably, the thermal energy is such that the diacetylene compound is exposed to a temperature equal to the melting point of the diacetylene compound or greater than the melting point, but below the decomposition temperature of the diacetylene compound. More preferably, the thermal energy is such that the diacetylene compound is exposed to a temperature greater than the melting point, but below the decomposition temperature of the diacetylene compound. Preferably, this temperature T ₎ is from 50 to 200 °C, such as from 80 to 200 °C, or even from 100 to 200 °C.

Preferably, T _(i) > ¾ > T _(M) . The first and second coloured states of the diacetylene compound are different in colour. The first and second coloured states of the diacetylene compound may have any colour. It will be appreciated by a skilled person that the colour of the first and second coloured states is dependent upon the particular diacetylene compound utilised. The first coloured state of the diacetylene compound may be blue. The second coloured state of the diacetylene compound may be red. It will be appreciated by a skilled person that the non-coloured state of certain diacetylene compounds may need to be activated prior to exposure of the non coloured state to thermal energy and radiation in order to enable the diacetylene compound to transition from the non-coloured state to a coloured state. The terms "activated" and like terms as used herein, refer to the non-coloured state of these certain diacetylene compounds when the non-coloured state is capable of undergoing a transition to a coloured state. It will therefore be appreciated by a skilled person that for these certain diacetylene compounds, the non-coloured state can either exist in (a) an‘unactivated’ form, i.e. incapable of undergoing a transition from the non-coloured state to a coloured state when the non-coloured state of the diacetylene compound is simultaneously exposed to radiation and thermal energy, or (b) an "activated" form i.e. capable of undergoing a transition from the non-coloured state to a coloured state when the non-coloured state of the diacetylene compound is simultaneously exposed to radiation and thermal energy. "Activation" and like terms used herein in relation to these certain diacetylene compounds, refer to the process by which the non-coloured state of the diacetylene compound is activated, i.e. changes from the unactivated to activated form.

If required, activation of the non-coloured state of the diacetylene compound occurs upon exposure 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 simultaneous exposure of the diacetylene compound to the thermal energy and radiation, or alternatively, the non-coloured state of the diacetylene compound may be activated during the simultaneous exposure of the diacetylene compound to the thermal energy and radiation. If the activation takes place prior to the simultaneous exposure of the diacetylene compound to the thermal energy and radiation, 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 The diacetylene compound may be exposed to the activation temperature using any suitable means. Suitable means include laser excitation through exposure of the diacetylene compound to radiation applied by a laser source(s), i.e. a radiative source. It will be understood by a skilled person that localised positions of the diacetylene compound may be exposed to the activation temperature so as to selectively activate the non-coloured state of the diacetylene compound at these localised positions. The localised positions may overlap each other. Alternatively, the diacetylene compound may be exposed to the activation temperature by flood illumination, or using a conductive thermal energy source such as sources of steam or hot air, a lamps, heat tunnels, LED(s), thermal print heads, thermal conductors, hot liquids or heated substrates. It will be appreciated that the diacetylene compound is exposed to these radiative sources or conductive thermal energy sources for an appropriate amount of time required to activate the non-coloured state of the diacetylene compound. The radiation may be selected from visible light with a wavelength of from 400 to 700 nm, infrared (IR) with a wavelength of from 700 nm to 1 mm, in particular 10600 nm, and near-infrared (NIR) with a wavelength of from 700 to 1600 nm.

In the method according to the first aspect of the present invention, the diacetylene compound may be present in a composition enabling the diacetylene compound to be applied to or incorporated within a substrate. The diacetylene compound may be present in the composition in any suitable amount. Preferably, the composition comprises 0.05 to 40 % of a diacetylene compound, such as from 0.05 to 30 %, and most preferably from 0.05 to 20 % of a diacetylene compound based on the total solid weight of the composition.

The composition comprising the diacetylene compound may further comprise a binder. Suitable examples of binders include, but are not limited to: 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 0 to 60 %, such as from 5 to 50 % and most preferably, from 10 to 45 % of binder based on the total solid weight of the composition.

The composition comprising the diacetylene compound may further comprise a near-infrared (NIR) absorber. 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, reduced or doped inorganic compounds such as reduced indium tin oxide, reduced zinc oxide, reduced tungsten oxide, reduced doped tungsten oxides, 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 to 25 %, such as from 0.005 to 20 % of NIR absorber based on the total solid weight of the coating composition.

The composition comprising the diacetylene compound 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 such as 2-hydroxy-4-methoxybenzophenone; surfactants; wetting agents; drying promoters; colourants such as pigments; tinting agents; fluorescent agents; plasticisers; optical brighteners; oxidising or reducing agents; stabilisers; light stabilising agents such as hindered amines; rheology modifiers such as thickening or thinning agents; humectants; solvents; adhesion promotors; acid or base scavenging agents; wax; retarders; defoamers; antifoamers; biocides; and combinations thereof. Preferably, the composition comprises 0 to 9 %, such as from 0.1 to 8 %, or even from 0.2 to 7 % of additives based on the total solid weight of the composition. The composition comprising the diacetylene compound 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 solvents 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 methoxypropanol, 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%. It will be appreciated that the amount of solvent includes all solvents present in the composition, i.e. includes any solvent of the component materials used to form the composition.

In the method according to the first aspect of the present invention, the diacetylene compound may be present in a composition further comprising at least one additional compound capable of forming colour through a transition from a non-coloured state to a coloured state(s) through exposure of the additional compound to an additional stimulus. The at least one additional compound may be present in the composition in any suitable amount. The suitable additional stimulus will be dependent upon the additional compound selected and include, but are not limited to: appropriately selected thermal energy and/or radiation. Examples of suitable additional compounds include, but are not limited to the following: a pyrazole (thio)semicarbazone compound capable of transitioning from a non-coloured state to a coloured state upon exposure to either thermal energy or radiation; a pyrazole (thio)semicarbazone compound capable of transitioning from a non-coloured state to a coloured state upon exposure to either thermal energy or radiation, the pyrazole (thio)semicarbazone being accompanied by an acid- or base-generating agent; a keto acid compound capable of transiting from a non-coloured state to a coloured state upon exposure to radiation and an accompanying acid-generating agent; a leuco dye (including but not limited to halochromic, thermochromic and photochromic leuco dyes) capable of transitioning from a non-coloured state to a coloured state upon exposure to radiation and an accompanying acid-generating agent; and a compound formed from a salicylic aldehyde or salicylic ketone compound capable of transitioning from a non-coloured state to a coloured state upon exposure to radiation and an accompanying base-generating agent. The acid-generating agent or base-generating agent are present to facilitate a pH change by generating acid or base respectively upon exposure to either thermal energy or radiation, causing the at least one additional compound to form colour, i.e. transition from a non-coloured state to a coloured state.

By the term "pyrazole (thio)semicarbazone compound" is meant a compound having a pyrazole group and a (thio) semicarbazone group. By the term "keto acid compound" is meant a compound having a carboxylic acid group and a ketone group. In some instances, the ketone group is hydrated. By the term a "compound formed from a salicylic aldehyde or salicylic ketone" is meant a compound formed from a parent salicylic aldehyde or salicylic ketone compound (aldehyde or ketone derivatives of salicylic acid). Preferably, the compound formed from a salicylic aldehyde or salicylic ketone compound is a compound formed from the condensation reaction of a linked primary diamine and two independently selected salicylic aldehyde or salicylic ketone compounds. By the term "linked primary diamine" is meant a compound comprising two primary amine groups joined by a carbon chain of 0 to 20 carbon atoms, preferably 0 to 10 carbon atoms, more preferably 0 to 8 carbon atoms, and most preferably 0 to 6 carbon atoms. More preferably, the compound formed from a salicylic aldehyde or salicylic ketone compound is a compound formed from the condensation reaction of hydrazine and two independently selected salicylic aldehyde or salicylic ketone compounds.

Preferably, the coloured state of the additional compound will be different to those of the first and second coloured states of the diacetylene compound. Preferably, the coloured state of the additional compound is yellow. The coloured state of the additional compound will preferably be stable under ambient conditions.

According to a second aspect of the present invention, there is provided a substrate comprising a diacetylene compound having a stable non-coloured or coloured state on or within the substrate, the stable non-coloured or coloured state of the diacetylene compound obtainable by simultaneously exposing to both thermal energy and radiation, the non-coloured state or, if formed the first coloured state of a diacetylene compound having non-coloured, first coloured and second coloured states and the diacetylene compound being capable of transitioning from the non-coloured state to the first or second coloured state and from the first coloured state to the second coloured state and applied on or incorporated within the substrate, wherein the radiation has a wavelength of 400 nm or less, and the thermal energy is selected to:

(i) form a stable non-coloured state; or

(ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or

(iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state; wherein in (ii) and (iii), the resulting second coloured state is stable.

It will therefore be appreciated that as a result of simultaneous exposure of a diacetylene compound having non-coloured, first coloured and second coloured states and applied to or incorporated within the substrate, to thermal energy and radiation, a stable non-coloured or second coloured state may be developed at localised positions on the substrate. The substrate may thus display a single coloured image (if, at localised positions, the diacetylene compound is in the second coloured state) or a multi-coloured image (if, at localised positions, the diacetylene compound is in the first coloured state and if, at other localised positions, the diacetylene compound is in the second coloured state). It will be appreciated that the diacetylene compound is not applied on or incorporated within the substrate having stable non-coloured or coloured states. Reference to the diacetylene compound as it is applied to or incorporated within the substrate, is to the diacetylene compound prior to its simultaneous exposure to both thermal energy and radiation, i.e. to a diacetylene compound having non coloured, first coloured and second coloured states and being applied to or incorporated within the substrate. The simultaneous exposure of this diacetylene compound to thermal energy and radiation to form a diacetylene compound having stable non-coloured or coloured states at localised positions takes places only once this diacetylene compound having non-coloured, first coloured and second coloured states has been applied to or incorporated within the substrate.

The diacetylene compound may be present in a composition as detailed above to enable the diacetylene compound to be applied to or incorporated within the substrate. Preferably, the diacetylene compound applied to or incorporated within the substrate is present in a composition.

The substrate may further comprise at least one additional compound capable of forming colour through a transition from a non-coloured state to a coloured state(s). Preferably, the coloured state of the additional compound will be different to those of the first and second coloured states of the diacetylene compound. The additional compound may be applied to or incorporated within the substrate. The at least one additional compound may be present in any suitable amount.

Examples of suitable substrates to which a diacetylene compound having non coloured, first coloured and second coloured states may be applied to 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. The polymer and recycled polymer materials may be in the form of polymer film substrates.

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

Preferably, the substrate to which the diacetylene compound having non coloured, first-coloured and second coloured-states may be applied or incorporated is a polymer film substrate. Preferably, the substrate is colourless (i.e. opaque or transparent), off-white or white.

It will be appreciated by a skilled person that the substrate to which a diacetylene compound having non-coloured, first coloured and second coloured state is 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. The polymers and recycled polymer materials may be in the form of polymer film substrates.

Preferably, the substrate comprises one or more additional adhesive layers. 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 additional adhesive layer may cover all, substantially all, or part of the surface area of an exterior surface of the substrate. When a diacetylene compound having non-coloured, first coloured and second coloured states is applied to the substrate, the additional adhesive layer is preferably on an exterior surface of the substrate other than that to which the diacetylene compound is applied.

It will be appreciated that the substrate may further comprise one or more additional layers such that the substrate is a multi-layered product. Suitable additional layers may be selected from, but are not limited to: thermal insulating layers, protective layers, primer layers, adhesion promoting layers and radiation blocking layers such as UV blocking/absorbing layers, quenching layers or hindered amine light stabilisers or combinations thereof. Suitable additional layers may also include an additional layer comprising an at least one additional compound as discussed above. The at least one additional compound may be present in this additional layer in any suitable amount. It will be appreciated that the layer structure of the multi-layered product will vary depending upon intended use, and that the thickness of the layers will vary dependent upon their composition.

When the substrate is a multi-layered product, it will be appreciated by a skilled person that this multi-layered product may itself be applied to a further substrate in the manner discussed above.

The substrate to which the diacetylene compound having non-coloured, first coloured and second coloured states is applied to or incorporated within may be suitable for end use as labels and/or in, for example, fast-moving consumer goods; packaging such as disposable packaging including food and hot or cold beverage containers; hygiene and personal care product packaging such as shampoo bottles; cosmetic product packaging; medical and diagnostic devices and associated packaging; and outdoor products such as signage.

A diacetylene compound having non-coloured, first coloured and second coloured states may be applied to the substrate by any suitable method. Preferably, the diacetylene compound having non-coloured, first coloured and second coloured states is applied to the substrate as a composition. Methods of applying the diacetylene compound 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 diacetylene compound may be applied to all, substantially all or part of the surface area of the substrate.

A diacetylene compound having non-coloured, first coloured and second coloured states may be applied on the substrate to any suitable coat weight. Preferably, the diacetylene compound is applied to a coat weight of from 0.01 to 100 gsm (grams per square metre), such as from 0.01 to 50 gsm, or even from 0.01 to 30 gsm. Most preferably, the diacetylene compound is applied to a coat weight of from 0.01 to 20 gsm.

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 diacetylene compound applied thereto, and comparing the two weights.

A diacetylene compound having non-coloured, first coloured and second coloured states may be applied on the substrate as a single layer or as part of a multi-layer system. The diacetylene compound may be applied on the substrate as an undercoat or an overcoat, on top of a primer or as a primer layer. The diacetylene compound may be applied to the substrate once or multiple times. The diacetylene compound may be applied to at least part or all of an exterior surface of the substrate. A diacetylene compound having non-coloured, first coloured and second coloured states may be incorporated within the substrate by any suitable method. Preferably, the diacetylene compound having non-coloured, first coloured and second coloured states is incorporated within the substrate as a composition. Methods of incorporating the diacetylene compound 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.

A diacetylene compound having non-coloured, first coloured and second coloured states may be incorporated within a substrate to any suitable weight percentage of the total solid weight of the substrate. Preferably, the substrate comprises 0.1 to 30% of the diacetylene compound incorporated within based on the total solid weight of the substrate. More preferably, the substrate comprises 0.15 to 20% of the diacetylene compound incorporated within based on the total solid weight of the substrate. Most preferably, the substrate comprises 0.15 to 15% of the diacetylene compound incorporated within based on the total solid weight of the substrate.

It will be appreciated that the one or more additional layers discussed above in relation to the substrate may be applied to the substrate in the same manner as described herein in relation to the diacetylene compound.

As discussed above, the application or incorporation of a diacetylene compound having non-coloured, first coloured and second coloured states on or within a substrate and the subsequent simultaneous exposure to both thermal energy and radiation of the non-coloured or, if formed, first coloured state of the diacetylene compound enables the formation of a stable non-coloured or second coloured state of the diacetylene compound at localised positions. This enables the formation of a single-coloured image (if localised positions of the diacetylene compound are in the second coloured state), or a multi-coloured image (if localised positions of the diacetylene compound are in the first coloured state and other localised positions of the diacetylene compound are in the second coloured state), on or within the substrate.

Thus, according to a third aspect of the present invention there is provided a method of forming an image on or within a substrate comprising applying to or incorporating within a substrate a diacetylene compound having a non-coloured, first coloured and second coloured state, the diacetylene compound being capable of transitioning from the non-coloured state to the first or second coloured state and from the fist coloured state to a second coloured state, the method comprising simultaneously exposing to both thermal energy and radiation, the non-coloured state or, if formed, the first coloured state of the diacetylene compound applied on or incorporated within the substrate as required to selectively provide a stable non-coloured or second coloured state at localised positions and thereby create an image on or within the substrate, wherein the radiation has a wavelength of 400 nm or less, and the thermal energy is selected to:

(i) form a stable non-coloured state; or

(ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or

(iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state; wherein in (ii) and (iii), the resulting second coloured state is stable.

It will be appreciated by a skilled person that the diacetylene compound is in the non-coloured state upon application to or incorporation within the substrate. It will further be appreciated that a first coloured state of the diacteylene compound must be formed prior to (iii) taking place. This first coloured state may be formed either by effecting a transition from the non-coloured state (either unactivated or activated) to the first coloured state through the simultaneous exposure of the diacetylene compound to both selected thermal energy and radiation, or otherwise, such as through exposure of the non-coloured state of the diacetylene compound to a stimulus such as radiation to effect a transition from the non-coloured state (either unactivated or activated) to the first coloured state.

It will be appreciated that the diacetylene compound is exposed to different combinations of thermal energy and radiation to facilitate each of (i) to (iii) as required to selectively provide a stable non-coloured or second coloured state at localised positions. As discussed above, it is the thermal energy that enables the different transitions (i) to (iii). After this simultaneous exposure to thermal energy and radiation, the diacetylene compound applied on or incorporated within the substrate may thus be in the stable non-coloured or second coloured state at localised positions of the diacetylene compound such that the substrate can display 1 colour (if localised positions are in the second coloured state) or 2 colours (if localised positions of the diacetylene compound are in the first coloured state and other localised positions of the diacetylene compound are in the second coloured state) to show a single- or multi-coloured image.

In the method of forming an image according to the present invention, as discussed above, the exposure of the diacetylene compound to the thermal energy and radiation may be at localised positions of the diacetylene compound using a laser source(s), by flood illumination using a lamp; a diode bar; or LED(s), or using a conductive thermal energy source as required.

As discussed above, it will be appreciated that the method of forming an image on a substrate may further comprise the step of activating the non-coloured state of a diacetylene compound through exposure of the diacetylene compound to an activation temperature.

It will therefore be appreciated by a skilled person that the simultaneous exposure of the diacetylene compound to the thermal energy and radiation, and if necessary, an activation temperature as detailed above, whether at localised positions, through flood illumination or using a conductive thermal energy source as appropriate and as discussed above, will create an image on the substrate as a stable non-coloured or second coloured state of the diacetylene compound may be selectively developed at localised positions to create the image. It will be understood by a skilled person that these localised positions may overlap each other.

It will further be understood by a skilled person that the exposure of the diacetylene compound to the thermal energy and radiation, and if necessary an activation temperature at localised positions, through flood illumination or using a conductive thermal energy source as appropriate and discussed above, will be conducted in the appropriate order required to selectively form the a stable non coloured or second coloured state of the diacetylene compound at localised positions as required to form the desired image. A skilled person will appreciate that the order in which the diacetylene compound is exposed to the thermal energy and radiation and if necessary an activation temperature will be dependent upon the diacetylene compound utilised and the image that is desired.

It will further be understood by a skilled person that if an at least one additional compound is present as discussed above, exposure of the composition or substrate to the thermal energy and radiation, and if necessary the activation temperature, and additional stimulus at localised position will be conducted in the appropriate order as required to selectively form a stable non-coloured or second coloured state of the diacetylene compound and the coloured state of the additional compound at localised positions as required to form the desired image. It will be appreciated that simultaneous thermal energy and radiation, and if necessary the activation temperature, and the additional stimulus may be applied to the composition or substrate at the same localised position. For example, where the coloured state of the additional compound is different in colour to the second coloured state of the diacetylene compound, in order to form a colour resulting from the mixture of the colours of a coloured state of the diacetylene compound and a coloured state of the at least one additional compound, the same localised position of the composition or substrate may be exposed to (a) radiation and thermal energy to effect (ii) or (iii) and form the second coloured state of the diacetylene compound, and (b) the additional stimulus to form the coloured state of the additional compound, the resulting colour at that localised position being a mixture of the colour of the second coloured state of the diacetylene compound and the coloured state of the additional compound.

According to a fourth aspect of the present invention, there is provided a use of a diacetylene compound having a stable non-coloured or coloured state for the formation of an image on or within a substrate, the stable non-coloured or coloured state of the diacetylene compound obtainable by simultaneously exposing to both thermal energy and radiation, the non-coloured state or, if formed, the first coloured state of a diacetylene compound having a non coloured, first coloured and second coloured state and being capable of transitioning from the non-coloured state to the first or second coloured state and from the first coloured state to the second coloured state and applied to or incorporated within the substrate, wherein the radiation has a wavelength of 400 nm or less, and the thermal energy is selected to:

(i) form a stable non-coloured state; or

(ii) effect a transition from the non-coloured state of the diacetylene compound to the second coloured state; or

(iii) effect a transition from the first coloured state of the diacetylene compound to the second coloured state; wherein in (ii) and (iii), the resulting second coloured state is stable.

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 how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the following experimental data.

Examples Example 1

N1 -N22-ditetradecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was simultaneously exposed to a 15 watt UV 254 nm germicidal lamp and positioned over a precision hotplate with a temperature of 120 °C (close to but lower than the melting point of N1-N22- ditetradecyldocosa-10,12-diynediamide (123 °C)) with vacuum seal to ensure good thermal contact, for a period of 99 seconds. The composition applied on the PET film formed a red colour only where it was exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye. This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from the non-coloured state to the second coloured state (ii) and the resulting stable second coloured state.

Table 1

Example 2

N1 -N22-ditetradecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was simultaneously exposed to a 15 watt UV 254 nm germicidal lamp and positioned over a precision hotplate with a temperature of 125 °C (greater than the melting point of N1 -N22- ditetradecyldocosa-10,12-diynediamide (123 °C)) with vacuum seal to ensure good thermal contact, for a period of 99 seconds. The composition applied on the PET film remained colourless only where it was exposed to the ultraviolet radiation. The colourless area was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the colourless area was maintained, and there was no measurable change to visual appearance seen by the human eye. This is an example of the simultaneous exposure to thermal energy and radiation enabling the formation of a stable non-coloured state (i).

Example 3

N1 -N22-didodecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was simultaneously exposed to a 15 watt UV 254 nm germicidal lamp and positioned over a precision hotplate with a temperature of 117 °C (close to but lower than the melting point of N1-N22-didodecyldocosa- 10,12-diynediamide (120 °C)) with vacuum seal to ensure good thermal contact, for a period of 99 seconds. The composition applied on the PET film formed a red colour only where it was exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from the non-coloured state to the second coloured state (ii) and the resulting stable second coloured state.

Example 4

N1 -N22-didodecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was simultaneously exposed to a 15 watt UV 254 nm germicidal lamp positioned over a precision hotplate with a temperature of 125 °C (greater than the melting point of N1-N22-didodecyldocosa-10,12- diynediamide (120 °C)) with vacuum seal to ensure good thermal contact, for a period of 99 seconds. The composition applied on the PET film remained colourless only where it was exposed to the ultraviolet radiation. The colourless area was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the colourless area was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation enabling the formation of a stable non-coloured state (i).

Example 5

N1 -N22-ditetradecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was heated to activate the non- coloured state of the diacetylene compound for 1 minute at 120 °C, cooled to ambient temperature, and exposed to a 30 watt UV germicidal lamp for 1 minute to generate a blue colour (the first coloured state of the diacetylene compound). The film was then simultaneously exposed to a 15 watt UV germicidal lamp positioned over a precision hotplate with a temperature of 120 °C ( close to but lower than the melting point (123 °C) of N1-N22-ditetradecyldocoa-10,12- diynediamide) with vacuum seal to ensure good thermal contact, for a period of 99 seconds. The composition applied on the PET film formed a red colour only in areas where the blue colour had been exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from a first coloured state to the second coloured state (iii) and the resulting stable second coloured state.

Example 6

N1 -N22-didodecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was simultaneously exposed to a 15 watt UV 254 nm germicidal lamp positioned over a precision hotplate with a temperature of 115 °C (close to but lower than the melting point of N1-N22-didodecyldocosa- 10,12-diynediamide (120 °C)) with vacuum seal to ensure good thermal contact, for a period of 99 seconds. The composition applied on the PET film formed a red colour only where it was exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye. This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from the non-coloured state to the second coloured state (ii) and the resulting stable second coloured state.

Example 7

N1 -N22-dicyclopropyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was exposed to 30 watt UV 254 nm germicidal lamp for 10 seconds to generate a blue colour (the first coloured state of the diacetylene compound). The film was then simultaneously exposed to a 30 watt UV 254 nm germicidal lamp positioned over a precision hotplate with a temperature of 150 °C (equal to the melting point (150-155 °C) of N1-N22- dicyclopropyldocosa-10,12-diynediamide, or close to but lower than the melting point (150-155 °C) of N1-N22-dicyclopropyldocosa-10,12-diynediamide) with vacuum seal to ensure good thermal contact, for a period of 60 seconds. The composition applied on the PET film formed a red colour only in areas where the blue colour had been exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from a first coloured state to a second coloured state (iii) and the resulting stable second coloured state.

The process of Example 7 was repeated with the precision hotplate set at a temperature of 160 °C and then with the precision hotplate set at a temperature of 170 °C. The same result was obtained for each repetition: the red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

Example 8 N1 -N22-dihexyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was heated at 100 °C to activate the non coloured state of the diacetylene compound, cooled to ambient temperature, and exposed to a 30 watt 254 nm germicidal lamp for 10 seconds to generate a blue colour (the first coloured state of the diacetylene compound). The film was then simultaneously exposed to a 30 watt UV 254 nm germicidal lamp positioned over a precision hotplate with a temperature of 150 °C (greater than the melting point (105-107 °C) of but lower than the decomposition temperature ( >200 °C) of N1 - N22-dihexyldocosa-10,12-diynediamide) with vacuum seal to ensure good thermal contact, for a period of 60 seconds. The composition applied on the PET film formed a red colour only in areas where the blue colour had been exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from a first coloured state to a second coloured state (iii) and the resulting stable second coloured state.

The process of Example 8 was repeated with the precision hotplate set at a temperature of 160 °C and then with the precision hotplate set at a temperature of 170 °C. The same result was obtained for each repetition: the red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

Example 9

N1 -N22-dioctyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was heated at 100 °C to activate the non-coloured state of the diacetylene compound, cooled to ambient temperature, and exposed to a 30 watt 254 nm germicidal lamp for 10 seconds to generate a blue colour (the first coloured state of the diacetylene compound). The film was then simultaneously exposed to a 30 watt UV 254 nm germicidal lamp positioned over a precision hotplate with a temperature of 130 °C (greater than the melting point (103-105 °C) but lower than the decomposition temperature (>200 °C) of N1 - N22-dioctyldocosa-10,12-diynediamide) with vacuum seal to ensure good thermal contact, for a period of 60 seconds. The composition applied on the PET film formed a red colour only in areas where the blue colour had been exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from a first coloured state to a second coloured state (iii) and the resulting stable second coloured state.

The process of Example 9 was repeated with the precision hotplate set at a temperature of 150 °C, then with the precision hotplate set at a temperature of 160 °C, and then with the precision hotplate set at a temperature of 170 °C. The same result was obtained for each repetition: the red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

Example 10

N1 -N22-didecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was heated at 100 °C to activate the non coloured state of the diacetylene compound, cooled to ambient temperature, and exposed to a 30 watt 254 nm germicidal lamp for 10 seconds to generate a blue colour (the first coloured state of the diacetylene compound). The film was then simultaneously exposed to a 30 watt UV 254 nm germicidal lamp positioned over a precision hotplate with a temperature of 130 °C (greater than the melting point (122-124 °C) but lower than the decomposition temperature (>200 °C) of N1 - N22-didecyldocosa-10,12-diynediamide) with vacuum seal to ensure good thermal contact, for a period of 60 seconds. The composition applied on the PET film formed a red colour only in areas where the blue colour had been exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from a first coloured state to a second coloured state (iii) and the resulting stable second coloured state.

The process of Example 10 was repeated with the precision hotplate set at a temperature of 150 °C, then with the precision hotplate set at a temperature of 160 °C, and then with the precision hotplate set at a temperature of 170 °C. The same result was obtained for each repetition: the red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

Example 11

N1 -N22-dihexadecyldocosa-10,12-diynediamide was formulated into a composition as detailed in Table 1 , and applied to a polyethylene terephthalate (PET) film using a 16 pm K-bar. The film was heated at 100 °C to activate the non-coloured state of the diacetylene compound, cooled to ambient temperature, and exposed to a 30 watt 254 nm germicidal lamp for 10 seconds to generate a blue colour (the first coloured state of the diacetylene compound). The film was then simultaneously exposed to a 30 watt UV 254 nm germicidal lamp positioned over a precision hotplate with a temperature of 130 °C (greater than the melting point (112-114 °C) but lower than the decomposition temperature (>200 °C) of N1 -N22-dihexadecyldocosa-10,12-diynediamide) with vacuum seal to ensure good thermal contact, for a period of 60 seconds. The composition applied on the PET film formed a red colour only in areas where the blue colour had been exposed to the ultraviolet radiation. The red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

This is an example of the simultaneous exposure to thermal energy and radiation effecting a transition from a first coloured state to a second coloured state (iii) and the resulting stable second coloured state. The process of Example 11 was repeated with the precision hotplate set at a temperature of 150 °C, then with the precision hotplate set at a temperature of 160 °C, and then with the precision hotplate set at a temperature of 170 °C. The same result was obtained for each repetition: the red colour was stable for at least 24 hours under an accelerated solar radiation source (osram ultra vitalux 240V 300W UVA/UVB bulb), i.e. the red colour was maintained, and there was no measurable change to visual appearance seen by the human eye.

The melting points detailed in the examples were measured using melting point tubes (capillary method). The decomposition temperatures detailed in the examples were measured using differential scanning calorimetry (DSC).