A composition

Abstract

The present invention is directed towards a composition comprising: (a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof; (b) a redox buffer material; and (c) an antioxidant; wherein the redox buffer material is a multivalent metal salt. The present invention is also directed towards a substrate having the composition applied thereon, and the formation of substrate displaying a mark(s) or image(s).

Description

[0001] A COMPOSITION

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to compositions capable of displaying a mark or image of enhanced optical density.

[0004] BACKGROUND

[0005] The use of compositions for variable information printing to produce human and / or machine-readable elements on substrates is known. Following application of such a composition to a substrate, a mark(s) or image(s) can be formed upon exposure of the composition to appropriate radiation.

[0006] An oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is a colourforming compound used in such compositions. The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, decomposes to form colour upon application of radiation to the composition and a mark(s) or image(s) is thus created. However, problems with these currently known compositions exist, in that the mark(s) or image(s) formed is not sufficiently strong and distinct enough.

[0007] Attempts to address this problem have involved the use of components that accelerate the decomposition of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof. However, instead of providing a stronger and more distinct mark(s) or image(s), this has instead resulted in undue colour formation, preventing the formation of any mark(s) or image(s).

[0008] It is therefore desirable to provide a solution that enables the effective formation of a strong and distinct mark(s) or image(s) with enhanced optical density using a composition comprising an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof.

[0009] SUMMARY OF THE INVENTION

[0010] According to a first aspect of the present invention, there is provided a composition comprising: (a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof;

[0011] (b) a redox buffer material; and

[0012] (c) an antioxidant; wherein the redox buffer material is a multivalent metal salt.

[0013] According to a second aspect of the present invention, there is provided a composition comprising:

[0014] (a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof; and

[0015] (b) a redox buffer material; wherein the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, a sulphuric acid multivalent metal salt, and a multivalent metal oxide.

[0016] According to a third aspect of the present invention, there is provided a substrate having a composition applied thereon or incorporated therein, the composition comprising:

[0017] (a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof;

[0018] (b) a redox buffer material; and

[0019] (c) an antioxidant; wherein the redox buffer material is a multivalent metal salt.

[0020] According to a fourth aspect of the present invention, there is provided a substrate having a composition applied thereon or incorporated therein, the composition comprising:

[0021] (a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof; and

[0022] (b) a redox buffer material; wherein the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, a sulphuric acid multivalent metal salt, and a multivalent metal oxide. According to a fifth aspect of the present invention, there is provided a method of forming a substrate according to the third aspect of the present invention, the method comprising applying to or incorporating within a substrate the composition according to the first aspect of the present invention.

[0023] According to a sixth aspect of the present invention, there is provided a method of forming a substrate according to the fourth aspect of the present invention, the method comprising applying to or incorporating within the substrate the composition according to the second aspect of the present invention.

[0024] According to a seventh aspect of the present invention, there is provided a method of forming a mark or image on a substrate according to the third or fourth aspect, the method comprising exposing the composition to radiation to form a mark or image.

[0025] According to an eighth aspect of the present invention, there is provided a use of a redox buffer material in the formation of a mark or image of enhanced optical density on a substrate having a composition applied thereon or incorporated therein, the composition comprising the redox buffer material and an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, wherein the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, a sulphuric acid multivalent metal salt and a multivalent metal oxide.

[0026] According to a ninth aspect of the present invention, there is provided a use of a redox buffer material to control reaction stability and achieve formation of a mark or image, preferably of enhanced optical density, on a substrate having a composition applied thereon or incorporated therein, the composition comprising the redox buffer agent, an antioxidant, and an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, wherein the redox buffer material is a multivalent metal salt.

[0027] DETAILED DESCRIPTION It has been surprisingly and advantageously found that the introduction of a redox buffer material into compositions comprising an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, enables the production of a strong and distinct mark(s) or image(s), i.e., a mark(s) or image(s) of enhanced optical density, upon application of radiation thereto.

[0028] The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, can display complex redox chemistry. Without being bound by theory, the present inventors consider that upon application of radiation, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, decomposes, likely undergoing both oxidation and reduction processes (redox reaction as part of a disproportionation reaction) during the course of its chemical decomposition. The present inventors thus consider the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, to be a Tedox-active’ material. It is overall considered to be a strongly oxidising material for its thermal decomposition. Accordingly, the present inventors consider that the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, undergoes net reduction during its chemical decomposition.

[0029] The present inventors consider that a redox buffer material is able to act as a redox catalyst for the oxidation and reduction processes, i.e. the redox reaction, of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, during its decomposition. The present inventors consider that the redox buffer material serves as a free radical propagator in a disproportionation reaction, cycling between its most favourable oxidation states, without itself necessarily undergoing any permanent oxidation or chemical decomposition to its equivalent oxides (Tedox cycling’).

[0030] Evidence for this is further supported by the fact that it has also been surprisingly and advantageously found by the present inventors that, when present alongside an antioxidant in a composition comprising an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, such as the composition according to the first aspect of the present invention, the redox buffer material detailed herein functions synergistically with the antioxidant to enable the formation of a mark(s) or image(s), preferably of enhanced optical density.

[0031] An antioxidant may be introduced into a composition comprising an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, to accelerate the chemical decomposition of the strongly oxidising oxyanion of a multivalent metal, or oxyacid, or hydrate thereof. However, if the composition did not comprise the redox control material, undue colour formation can occur as the antioxidant and oxyanion of a multivalent metal, or oxyacid, or hydrate thereof undergo a redox reaction - the antioxidant being oxidised and the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, being reduced. The occurrence of this redox reaction may be particularly prevalent in non-oxidising or partially-oxidising atmospheres but will also occur in oxidising atmospheres over time. Such undue colour formation means that it is either not desirable to form a mark(s) or image(s) through specific application of radiation as the composition has already prematurely coloured, or the composition (other than the mark or image) unfavourably colours over time following application of radiation, resulting in an illegible mark or image, or a mark or image of reduced legibility. The redox buffer material detailed herein can act as a redox catalyst and provide a stabilising effect for the composition, controlling reaction stability to prevent the redox reaction between the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and the antioxidant, from occurring unfavourably. The redox buffer material can thus preferably ensure that the chemical decomposition of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof (the mechanism through which colour is formed) takes place only upon specific application of radiation to the composition. Colour formation preferably occurs when the energy threshold required for the initiation of the redox decomposition process is overcome by the application of radiation to the composition. Furthermore, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, preferably demonstrates enhanced reactionsensitivity to the application of radiation. The redox buffer material thus preferably facilitates the formation of a mark(s) or image(s) of enhanced optical density, acting as a redox catalyst. Without being bound by theory, the present inventors consider that the redox buffer material is able to serve as a free radical propagator, cycling between its most favourable oxidation states, without itself necessarily undergoing any permanent oxidation or chemical decomposition to its equivalent oxides (‘redox cycling’). It is thus preferably able to catalyse the decomposition of the redoxactive oxyanion of a multivalent metal, or oxyacid, or hydrate thereof upon application of radiation, as well as buffer both the redox-active oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and antioxidant, when present in the composition, preventing their reaction under ambient conditions.

[0032] By ‘oxidation’ or ‘reduction’ as used herein is meant the transfer of one or more electrons to or from a molecular entity. Reduction is the gain of one or more electrons and oxidation is the removal of one or more electrons.

[0033] The composition according to the first or second aspect of the present invention comprises an oxyanion or oxyacid of a multivalent metal or oxyacid, or hydrate thereof.

[0034] The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, may be any suitable oxyanion of a multivalent metal, or oxyacid, or hydrate thereof (anionic component) present in conjunction with a cationic counterpart. The hydrate may be of the oxyanion of the multivalent metal or corresponding oxyacid of the multivalent metal. The oxyanion of a multivalent metal or oxyacid thereof may also be anhydrous. The use of an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, in compositions is disclosed in US7485403, the content of which is incorporated herein by reference. The anionic component may be an inorganic metal oxyanion compound such as molybdate including di-, tri-, hexa-, hepta-, octa- and deca-molybdates, tungstate, chromate or analogous transition metal compounds also in mixed oxidation states and of mixed inorganic metal oxyanions due to trace elements or any higher concentration ratios. Preferably, the accompanying cationic component is an alkali metal or an alkaline earth metal or ammonium. One example of an oxyanion of a multivalent metal is sodium molybdate. Preferred oxyanions of a multivalent metal are ammonium salts of inorganic metal oxyanion compounds. For example, ammonium paratungstate (APT). Particularly preferred as an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, are ammonium salts of oxyanions of multivalent metals. A particularly preferred oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is ammonium octamolybdate (NH4)4 Mo8O26 or “AOM”, which is a commercially available molybdenum composition with the CAS number 12411 -64- 2.

[0035] Preferably, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is an ammonium salt of an oxyanion of a multivalent metal, such as an ammonium salt of an oxyanion of molybdenum. More preferably, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is ammonium octamolybdate (AOM).

[0036] The composition according to the first or second aspect of the present invention comprises a redox buffer material.

[0037] In the composition according to the first aspect of the present invention, the redox buffer material is a multivalent metal salt.

[0038] The multivalent metal salt may be provided in hydrated or anhydrous form.

[0039] The multivalent metal salt may be an organic or inorganic acid multivalent metal salt, i.e. a multivalent metal salt of an organic or inorganic acid, or a multivalent metal oxide. Preferably, the multivalent metal salt is an organic or inorganic acid multivalent metal salt, and more preferably an organic acid multivalent metal salt.

[0040] Suitable organic acids include, but are not limited to: carboxylic acids such as gluconic acid and acetic acid; oxalic acid; and carbonic acid. Suitable inorganic acids include but are not limited to: sulphuric acid; and phosphoric acid. Preferably, the multivalent metal salt is an organic acid multivalent metal salt.

[0041] Preferably, for the composition according to the first aspect of the present invention, the redox buffer material is selected from a multivalent metal carboxylate, an oxalic acid multivalent metal salt, a carbonic acid multivalent metal salt and a sulphuric acid multivalent metal salt. More preferably, for the composition according to the first aspect of the present invention, the redox buffer material is selected from a multivalent metal carboxylate, an oxalic acid multivalent metal salt and a carbonic acid multivalent metal salt. More preferably, the redox buffer material of the composition according to the first aspect of the present invention is a multivalent metal carboxylate. A carboxylate enhances the redox cycling properties of the multivalent metal due to its electron delocalising properties.

[0042] Suitable examples of multivalent metal carboxylates as referred to herein include but are not limited to: gluconic acid multivalent metal salts; and acetic acid multivalent metal salts. Accordingly, for the composition according to the first aspect of the present invention, the redox buffer material may be selected from a gluconic acid multivalent metal salt, an acetic acid multivalent metal salt, an oxalic acid multivalent metal salt and a carbonic acid multivalent metal salt, preferably a gluconic acid multivalent metal salt, and an acetic acid multivalent metal salt.

[0043] Preferably, the redox buffer material of the composition according to the first aspect of the present invention is a gluonic acid multivalent metal salt.

[0044] The multivalent metal for all the multivalent metal salts detailed above may be any suitable multivalent metal. Suitable examples include, but are not limited to: manganese or iron, preferably manganese. In the context of the present invention, the multivalent metal may have any appropriate oxidation state. Such multivalent metals have advantageous redox cycling properties. For manganese and iron, this is preferably the manganese (II) or iron (II) oxidation state.

[0045] Accordingly, for the composition according to the first aspect of the present invention, the redox buffer material may be selected from an organic or inorganic acid salt of manganese or iron, or a manganese or iron oxide, preferably selected from a manganese or iron carboxylate, an oxalic acid salt of manganese or iron, a carbonic acid salt of manganese or iron, and a sulphuric acid salt of manganese or iron. More preferably, for the composition according to the first aspect of the present invention, the redox buffer material is selected from an organic acid salt of manganese or iron, such as a manganese or iron carboxylate, an oxalic acid salt of manganese or iron, and a carbonic acid salt of manganese or iron.

[0046] More preferably, for the composition according to the first aspect of the present invention, the redox buffer material is a manganese or iron carboxylate. A carboxylate enhances the redox cycling properties of the multivalent metal due to its electron delocalising properties.

[0047] As noted above, manganese or iron carboxylates include, but are not limited to: a gluconic acid salt of manganese or iron, and an acetic acid salt of manganese or iron.

[0048] More preferably, for the composition according to the first aspect of the present invention, the redox buffer material is selected from an organic or inorganic acid salt of manganese, or a manganese oxide, such as manganese carboxylate, an oxalic acid salt of manganese, a carbonic acid salt of manganese and a sulphuric acid salt of manganese.

[0049] More preferably, for the composition according to the first aspect of the present invention, the redox buffer material is selected from a manganese carboxylate, an oxalic acid salt of manganese and a carbonic acid salt of manganese.

[0050] More preferably, for the composition according to the first aspect of the present invention, the redox buffer material is a manganese carboxylate.

[0051] In the composition according to the second aspect of the present invention, the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid metal salt multivalent, a sulphuric acid multivalent metal salt, and a multivalent metal oxide.

[0052] The multivalent metal salt may be provided in hydrated or anhydrous form. Preferably, for the composition according to the second aspect of the present invention, the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt and a carbonic acid multivalent metal salt.

[0053] As for the first aspect of the present invention, for the composition according to the second aspect of the present invention, the multivalent metal of the multivalent metal salt for the options detailed above may be any suitable multivalent metal. Suitable examples include, but are not limited to: manganese or iron, preferably manganese. In the context of the present invention, the multivalent metal may have any appropriate oxidation state. Such multivalent metals have advantageous redox cycling properties. For manganese and iron, this is preferably the manganese (II) or iron (II) oxidation state.

[0054] Accordingly, for the composition according to the second aspect of the present invention, the redox buffer material is preferably selected from a gluconic acid salt of manganese or iron, an acetic acid metal salt of manganese or iron, a carbonic acid salt of manganese or iron, a sulphuric acid salt of manganese or iron, and a manganese or iron oxide, such as a gluconic acid salt of manganese or iron, an acetic acid metal salt of manganese or iron, and a carbonic acid salt of manganese or iron.

[0055] More preferably, for the composition according to the second aspect of the present invention, the redox buffer material is a gluconic acid salt of manganese, an acetic acid metal salt of manganese, a carbonic acid salt of manganese, a sulphuric acid salt of manganese, and a manganese oxide, such as a gluconic acid salt of manganese, an acetic acid metal salt of manganese, and a carbonic acid salt of manganese.

[0056] For both the composition according to the first aspect of the present invention and the composition according to the second aspect of the present invention, the redox buffer material is more preferably a gluconic acid salt of manganese or iron such as a gluconic acid salt of manganese or iron, for example, manganese (II) gluconate or iron (II) gluconate, and most preferably a gluconic acid salt of manganese, for example, manganese (II) gluconate.

[0057] The gluonic acid salt of manganese, for example manganese (II) gluconate may be provided in anhydrous, or in hydrated form (Ci2H22MnOi4 x2H2O).

[0058] The composition according to the first aspect of the present invention comprises an antioxidant.

[0059] By ‘antioxidant’ as used herein, is meant a component that inhibits oxidation or oxidation processes and therefore promotes reduction processes in a redox chemical system that possesses a material with a higher reduction potential than the antioxidant. In the context of the present invention, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, preferably has an intrinsically higher reduction potential than the antioxidant. In the context of the present invention, the antioxidant is a component that will preferably undergo a redox reaction with the strongly oxidising oxyanion of a multivalent metal, or oxyacid, or hydrate thereof. The antioxidant is present in the composition according to the first aspect of the present invention to preferably accelerate the chemical decomposition of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof through redox reaction - oxidation of the antioxidant and reduction of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof.

[0060] In the context of the present invention, the antioxidant and redox buffer material preferably do not possess the same functionality in the composition according to the first aspect of the present invention. These differing functionalities preferably cannot be provided by the same component. The antioxidant and redox buffer material therefore are preferably not the same component.

[0061] For the composition according to the first aspect of the present invention, any suitable antioxidant may be used. Suitable antioxidants include but are not limited to the following: organic acids, organic alcohols, and esters of organic acids. Examples of organic acids include, but are not limited to: tartaric acid; glycolic acid; mandelic acid; oxalic acid; malic acid; malonic acid; tannic acid; citric acid; and ascorbic acid.

[0062] Examples of organic alcohols include, but are not limited to: erythritol; and pentaerythritol.

[0063] Examples of esters of organic acids include, but are not limited to: ascorbyl palmatite; propyl gallate; octyl gallate; and octadecyl gallate.

[0064] Preferably, for the composition according to the first aspect of the present invention, the antioxidant is an organic acid. More preferably, for the composition according to the first aspect of the present invention, the antioxidant is selected from tartaric acid, glycolic acid, mandelic acid, oxalic acid, malic acid, malonic acid, tannic acid, citric acid, and ascorbic acid. More preferably, for the composition according to the first aspect of the present invention, the antioxidant is selected from tartaric acid, glycolic acid and mandelic acid, and most preferably selected from tartaric acid and glycolic acid.

[0065] The composition according to the second aspect of the present invention may not comprise an antioxidant. Preferably, the composition according to the second aspect of the present invention does not comprise an antioxidant as described herein.

[0066] The oxyanion of a multivalent metal or oxyacid, or hydrate thereof, may be present in a composition according to the first or second aspect of the present invention in an amount of from 1 to 70 wt%, such as from 5 to 40 wt%, or even from 10 to 40 wt%, of the composition.

[0067] The oxyanion of a multivalent metal or oxyacid, or hydrate thereof, may be present in a composition according to the first or second aspect of the present invention in an amount of 1 wt% or more, or 5 wt% or more, such as 10 wt% or more, of the composition. The redox buffer material may be present in a composition according to the first aspect or second aspect of the present invention in an amount of from 0.1 to 35 wt%, such as from 0.25 to 35 wt%, or from 0.5 to 35 wt%, or from 0.75 to 35 wt%, or from 1 to 10 wt%, or from 2 to 10 wt% of the composition.

[0068] The redox buffer material may be present in a composition according to the first or second aspect of the present invention in an amount of 0.1 wt% or more, or 0.25 wt% or more, such as 0.5 wt% or more, or 0.75 wt% or more, such as 1 wt% or more, or 2 wt% or more of the composition.

[0069] The antioxidant may be present in a composition according to the first aspect of the present invention in an amount of from 0.1 to 17.5 wt%, such as 0.25 to 17.5 wt%, or from 0.5 to 17.5 wt%, such as from 0.75 to 5 wt%, or from 1 to 5 wt% of the composition.

[0070] The antioxidant may be present in a composition according to the first aspect of the present invention in an amount of 0.1 wt% or more, or 0.25 wt% or more, or 0.5 wt% or more, such as 0.75 wt% or more, or 1 wt% or more, or 2 wt% or more of the composition.

[0071] The composition according to the first or second aspect of the present invention is not a pharmaceutical and / or a medicinal composition.

[0072] For the composition according to the first aspect of the present invention, the redox buffer material and antioxidant may be present at a ratio of from 5:1 to 1 :1 , such as from 2:1 (redox buffer material: antioxidant).

[0073] The composition according to the first or second 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 copolymers, styrene copolymers, styrene-acrylic copolymers, styrene-maleic-acid copolymers and hydrogenated products thereof; vinyl polymers; polyvinyl butyral 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 selected to complement the other components present in the compositions according to the first and second aspects of the present invention.

[0074] The binder may be present in the composition according to the first or second aspect of the present invention in any suitable amount. The composition according to the first or second aspect of the present invention may comprise from 1 to 70 wt%, such as from 5 to 50 wt% and more preferably, from 8 to 40 wt% of binder.

[0075] The composition according to the first or second aspect of the present invention may further comprise a near-infrared radiation absorbing compound. The nearinfrared radiation absorbing compound may be any suitable compound that is capable of absorbing near-infrared (NIR) or mid-infrared radiation, preferably near-infrared radiation. A near-infrared radiation absorbing compound is typically included when near-infrared or mid-infrared radiation, preferably near-infrared radiation, is to be utilised in the formation of the mark or image. More than one near-infrared radiation absorbing compound may be present in the composition according to the first or second aspect of the present invention. Suitable examples of near-infrared radiation absorbing compounds 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 oxide including an inorganic compound of the following formula MxWyOz (where M is at least one element selected from the group consisting of H, He, alkali metal, alkaline earth metal, rare earth element, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, lr, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi and I, W is tungsten, O is oxygen, satisfying 0.001 < x / y < 1 ; and 2.2 < z / y < 3.0. ), 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. The near-infrared radiation absorbing compound may be an inorganic copper salt such as copper (II) hydroxyl phosphate.

[0076] The near-infrared radiation absorbing compound may be present in the composition according to the first or second aspect of the present invention in any suitable amount. The composition according to the first or second aspect of the present invention may comprise from 0.01 to 25 wt%, such as from 0.1 to 15 wt% and more preferably, from 0.25 to 5 wt% of the near-infrared radiation absorbing compound.

[0077] The composition according to the first or second aspect of the present invention may further comprise a solvent. The composition according to the first or second aspect of the present invention may comprise a single solvent or a mixture of solvents. The solvent may be selected from 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, propyl 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. The composition according to the first or second aspect of the present invention may be ‘water-based’ (comprising only water, no organic solvent) or ‘organic solventbased’ (comprising only organic solvent, no water). The solvent may be present in the composition according to the first or second aspect of the present invention in amounts of from 20 to 70 wt%. The amount of solvent includes all solvents present in the composition according to the first or second aspect of the present invention, i.e. includes any solvent of the component materials used to form the compositions. The composition according to the first or second 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. The composition according to the first or second aspect of the present invention may comprise from 0.01 to 10 wt% of additives or combinations thereof.

[0078] Alternatively, i.e. instead of further comprising a binder and / or near-infrared absorbing compound and / or solvent and / or additive as detailed above, the composition according to the first or second aspect of the present invention may further comprise a hot melt adhesive having the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and redox buffer material, and antioxidant when present, admixed therein. Details of hot melt adhesives and compositions formed therefrom and containing an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, are fully disclosed in WO 2022 / 189577, the contents of which is fully incorporated by reference herein.

[0079] Hot melt adhesives are known in the art. A hot melt adhesive is a thermoplastic adhesive material that is solid at ambient temperature, but transitions from the solid state upon application of heat to become molten and able to flow. It returns to the solid state once cooled back to ambient temperature. By the term ‘molten’ in reference to the hot melt adhesive is meant that the hot melt adhesive is able to flow. It may be viscous, but will be able to flow. To become molten, the hot melt adhesive is heated to or above its melting temperature. The melting temperature of the hot melt adhesive is the temperature at which the hot melt adhesive becomes molten and able to flow. It is the temperature at which the hot melt adhesive transitions from a solid state into a viscous flow state. This may sometimes be known in the art as the softening temperature. This melting temperature is effectively the minimum processing temperature of the hot melt adhesive. In the context of the present invention, there is typically a melting temperature range over which the hot melt adhesive becomes molten and is therefore able to flow. This can occur, for example, when a hot melt adhesive comprises more than one thermoplastic polymer, copolymer, oligomer, as discussed below. A hot melt adhesive is thus molten at and above its melting temperature, but is solid at ambient temperature. A hot melt adhesive is tacky when molten. When molten, it can therefore act as an adhesive, or be easily applied to or incorporated within substrate(s). A hot melt adhesive may be tacky when molten and non-tacky when cooled and solid at ambient temperature (typically known in the art as non-pressure sensitive hot melt adhesives), or tacky when molten and remain tacky when cooled and solid at ambient temperature (typically known in the art as pressure sensitive hot melt adhesives).

[0080] By the term "ambient temperature" as used herein is meant a temperature of from 10 to 35 °C, typically 18 to 28 °C. Ambient temperature is encompassed by the broader definition of "ambient conditions", which refers to the normal range of conditions of the surrounding environment to which the composition according to the first or second aspect of the invention is exposed, i.e. the range of temperatures, pressures and atmospheric conditions to which the composition according to the first or second aspect of the present invention is 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.

[0081] Hot melt adhesives, and components thereof, are well known in the art. For example, ‘Sustainable Raw Materials in Hot Melt Adhesives: A Review; Vineeth et al.; Open Journal of Polymer Chemistry; Vol. 10, No. 3; August 2020’ and ‘Basic Study of Evaluation of Thermoplastic Polymers as Hot-Melt Adhesives for Mixed- Substrate Joining; Open Journal of Polymer Chemistry; Col. 6, No. 8; August 2016’ discuss hot melt adhesives.

[0082] In the context of compositions according to the first and second aspects of the present invention, the hot melt adhesive acts as a vehicle for transfer of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof and redox buffer material, as well as the antioxidant when present, to the substrate upon which a mark(s) or image(s) is to be displayed.

[0083] The hot melt adhesive comprises a thermoplastic polymer, copolymer, oligomer, or mixtures thereof, as a base material. Typically, the hot melt adhesive further comprises a tackifier or resin. The hot melt adhesive typically may also further comprise one or more additive components as described below. Preferably, the hot melt adhesive further comprises a tackifier or resin. Preferably, the hot melt adhesive further comprises one or more additive components.

[0084] The thermoplastic polymer, copolymer, oligomer, or mixture thereof, of the hot melt adhesive may be selected from, but not limited to the following: poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymers; polyethylene acrylate) copolymers; acrylics; polyvinyl butyral; polyolefins such as polybutene, polyethylene, and polypropylene, including low-density (LDPE), medium-density (MDPE) and high-density (HDPE) polyethylene; polyamides such as ethylene diamine and hexamethylene diamine; nylon; polyesters including poly(lactic acid) (PLA), polyethylene terephthlate (PET), polyhydroxyalkanoates (PHA), and poly(glycolic acid) (PGA); polyurethanes; acrylic and styrene-acrylate copolymers; styrene-isoprene-styrene block tri- and copolymers; polystyrenes (PS); polycaprolactones; polycarbonates; fluoropolymers; elastomers; silicone rubbers and polypyrrole, or combinations thereof.

[0085] The thermoplastic polymer, copolymer, or oligomer may be a petro-plastic thermoplastic polymer, copolymer or oligomer, or a bio-plastic thermoplastic polymer, copolymer or oligomer. Preferably, the thermoplastic polymer, copolymer or oligomer is a bio-plastic thermoplastic polymer, copolymer or oligomer. The bio-plastic thermoplastic polymer, copolymer or oligomers encompassed herein include, but are not limited to: poly(lactic acid) (PLA), polyhydroxyalkanoates (PHA), and poly(glycolic acid) (PGA), as well as poly(ethylene-vinyl acetate) or ethylene-vinyl acetate (EVA) copolymers when formed from ethanol derived from sugarcane and / or other natural sources, and polyethylene when formed from sugarcane and / or other natural sources. For the poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymers and polyethylene materials listed herein with respect to the thermoplastic polymer, copolymer, oligomer, or mixtures thereof, both bio-plastic and petro-plastic forms are encompassed.

[0086] As used herein, the prefix ‘petro-plastic’ refers to any material derived from a petrochemical source(s). Such materials are typically recyclable. They are therefore typically manufactured from either virgin or recycled materials, or a combination thereof.

[0087] As used herein, the prefix ‘bio-plastic’ refers to any material derived from a natural and sustainable source. Such materials are typically recyclable, biodegradable and / or compostable, in particular biodegradable and / or compostable. They are therefore typically manufactured from either virgin or recycled materials, or a combination thereof.

[0088] Preferably, the thermoplastic polymer, copolymer, oligomer, or mixture thereof, is recyclable, biodegradable and / or compostable.

[0089] Preferably, the thermoplastic polymer, copolymer, oligomer, or mixture thereof, is selected from polyethylene terephthalate (PET), polyhydroxyalkanoates (PHA), poly(glycolic acid) (PGA), poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymer, low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), and poly(lactic acid) (PLA). More preferably, the thermoplastic polymer, copolymer, oligomer, or mixture thereof, is selected from polyhydroxyalkanoates (PHA), poly(glycolic acid) (PGA), poly(ethylene-vinyl acetate) or ethylene-vinyl acetate (EVA) copolymer, and low- density polyethylene (LDPE). More preferably, the thermoplastic polymer, copolymer, oligomer, or mixture thereof, is selected from a polyhydroxyalkanoates (PHA), poly(glycolic acid) (PGA), and a poly(ethylene-vinyl acetate) or ethylenevinyl acetate (EVA) copolymer. Most preferably, the thermoplastic polymer, copolymer, oligomer is a poly(ethylene-vinyl acetate) or ethylene-vinyl acetate (EVA) copolymer.

[0090] The thermoplastic polymer, copolymer, oligomer, or mixture thereof, may be present in the hot melt adhesive in any suitable amount. The thermoplastic polymer, copolymer, oligomer, or mixture thereof, may be present in an amount of from 20 to 90 %, such as from 30 to 80 %, or from 40 to 75 % of the hot melt adhesive.

[0091] The thermoplastic polymer, copolymer, oligomer, or mixture thereof, may be present in the composition according to the first or second aspect of the present invention in any suitable amount. The thermoplastic polymer, copolymer, oligomer, or mixture thereof, may be present in an amount of from 10 to 90%, such as from 20 to 70%, or even from 25 to 60% of the composition according to the first or second aspect of the invention.

[0092] The hot melt adhesive may further comprise a tackifier or resin. Preferably, the hot melt adhesive comprises a tackifier or resin. More than one tackifier or resin may be present.

[0093] The tackifier or resin may comprise acid, hydroxyl or ester functional groups. Preferably, the tackifier or resin comprises acid or ester functional groups. When the tackifier or resin comprises acid functional groups, the tackifier or resin preferably has an acid group number of 5 to 250, such as 5 to 200.

[0094] Suitable tackifiers or resins include, but are not limited to the following: resins including natural resins such as copal, dammars, mastic and sandarac; petroleum resins; rosins and their derivatives such as rosins, rosin acids, rosin esters and rosin resins - gum rosin, wood rosin or tall oil rosin; hydrogenated rosins such as Foral AX and Foral AX-E rosins from Eastman Chemical Companies; dimerised rosin resins; modified rosin resins; terpenes and modified terpenes; aliphatic, cycloaliphatic, and aromatic resins such as C5 aliphatic resins, C9 aromatic resins, and C5 / C9 aromatic / aliphatic resins; hydrogenated hydrocarbon resins; terpene-phenol resins; polybutenes and polyisobutenes; and combinations thereof. Commercially available examples of tackifers or resins include ‘Piccotac 1020-E Hydrocarbon Resin’, ‘Piccotac 1095-N Hydrocarbon Resin’, ‘Piccotac 9095 Hydrocarbon resin’, ‘Piccotac 8095 Hydrocarbon resin’ available from Eastman Chemcial Companies. Preferably, the tackifier or resin is selected from rosins and their derivatives, hydrogenated rosins, dimerised rosin resins, and modified rosin resins.

[0095] The tackifier or resin may be present in the hot melt adhesive in any suitable amount. Preferably, when present, the tackifier or resin is present in an amount of from 1 to 90 %, such as from 2 to 80 %, or from 5 to 70 %, or 10 to 60 % of the hot melt adhesive.

[0096] The tackifier or resin may be present in composition of the first or second aspect of the present invention in any suitable amount. When present, the tackifier or resin may be present in an amount of from 10 to 90%, 15 to 80%, 20 to 70%, and preferably 25 to 60% of the composition according to the first or second aspect of the present invention.

[0097] The hot melt adhesive may further comprise one or more additive components. Preferably, the hot melt adhesive comprises one or more additive components. Suitable additive components will be well known to a person skilled in the art. These additive components will typically be present to manage the rheological properties, such as viscosity, of the hot melt adhesive, and thus the composition. Examples of suitable additive components include, but are not limited to the following: waxes such as fatty amide waxes, oxidised fischer-tropsch waxes or waxes dervies from both the Fischer-Tropsch and Zigler-Natta processes, water- soluble waxes, polyalkylene wax, mineral waxes such as paraffin and microcrystalline waxes, polyethylene waxes, polyethylene glycol waxes (Carbowax from DOW Chemical Inc.), oxidised polyethylene waxes, bisstearamides such as N, N’-ethylene bisstearamide (Acrawaz from Lonza Inc.), natural and synthetic waxes such as beeswax, soywax, carnuba, ozokerite and ceresin, and silicon waxes; slip additives; lubricants; inhibitors; antioxidants; stabilisers such as Irganox 1010; UV stabilisers and UV absorbers such as the Tinuvin series including Tinuvin 770, 928 326, 1130, (384-2) and 123, and combinations thereof (BASF); adhesion promotors; plasticisers such as glyceryl tribenzoate, alkyl benxoaes and benzoate esters (e.g. Benzoflex 9-88 from Eastman Chemical Corporation), glycols like diethylene glycol, C12-15 alkyl benzoate, C2-C22 alkyl benzoates, alkyl citrates, phthalates, phthalate esters, paraffin oils, and polyisobutylene; light or energy absorbing agents; surfactants; wetting agents such as polyhydroxystearic acid, polyglyceryl-4 isostearate, hexyl laurate, esters like isopropyl myristate, propylene carbonate, isononyl isononanoate, glyceryl behenate / eicosadioate, trihydroxystearin, CI2-15 alkyl benzoate, C2-C22 alkyl benzoates where the alkyl group is straight or branched or mixtures thereof, triethoxycaprylysilane, castor oil; drying promotors; colorants such as pigments; flame retardants; antistatic agents; fillers; tinting agents; viscosity modifiers; fluorescent agents; optical brighteners; oxidising or reducing agents; stabilisers; light stabilising agents such as hindered amines including Tinuvin 292; rheology modifiers such as thickening or thinning agents; matting agents; active clays; anti-settling agents; anti-sagging agents; dispersing agents; surface modification additives; slip additives; levelling agents; fillers; humectants; adhesion promotors; acid or base scavenging agents; retarders; defoamers; surfactants; antifoaming agents; biocides; preservatives; antioxidants such as BHT, phosphites and phosphates; antimicrobial agents; antiviral agents; antibacterial agents; antifungal agents; antimould agents; germicidal agents; sanitising agents; and combinations thereof. Typically, the hot melt adhesive further comprises one or more additive components selected from waxes, plasticisers, antioxidants, UV stabilisers, and fillers, or combinations thereof.

[0098] The one or more additive components may be present in the hot melt adhesive in any suitable amount. Preferably, when present, the one or more additive components are present in an amount of from 0.1 to 35 %, such as from 0.1 to 30 %, or from 0.1 to 25 %, or from 0.1 to 20 % of the hot melt adhesive. The one or more additive components may be present in the composition of the first or second aspect of the present invention in any suitable amount. When present, the one or more additive components may be present in an amount of from 0.1 to 35%, such as 0.1 to 30%, or even 0.1 to 25%, such as 0.1 to 20% of the composition according to the first or second aspect of the present invention.

[0099] The hot melt adhesive may be purchased commercially, or formulated from appropriate starting materials. Hot melt adhesives and components thereof are well known in the art. A skilled person in the art will be easily able to identify suitable hot melt adhesives, or required components such as thermoplastic polymers, oligomers, copolymers, or mixtures thereof, tackifiers or resins, and one of more additive components, depending on the desired properties of the hot melt adhesive in question. Hot melt adhesives and hot melt adhesive materials known in the art, such as those utilised in glue guns and hot glue applicators, are suitable for use in the present invention. Such materials are known by the skilled person.

[0100] Commercially available thermoplastic polymers, copolymers, oligomers, or mixtures thereof suitable for in the hot melt adhesive include, but are not limited to: poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymers available from: ExxonMobil under the tradename ‘Escorene™ Ultra’; Rowak under the tradename ‘Rowalit® 300’; and Evatane as ‘SK functional polymers; Versalis S.p.A Greenflex HN70 from Distrupol; polypropylene from Borealis under the tradename ‘RE 420’; and low-density polyethylene available from Rowak under the tradename ‘Rowalit® H’ and from Lyondell Basell under the tradename ‘Lupolen 1800S’. Commercially available thermoplastic polymers, copolymers, oligomers, or mixtures thereof, for bio-based hot melt adhesives include, but are not limited to: polylactic acid (PLA), known as IngeoTM Biopolymer 3251 D from Nature Works (Minnetonka, MN, USA).

[0101] Commercially available hot melt adhesives suitable for use in the compositions of the first or second aspect of the present invention include, but are not limited to hot melt adhesives such as those available from Henkel (under the tradename Technomelt, Technomelt Cool, Technomelt Supra, Technomelt Supra Pro, Technomelt Pur, Technomelt PA, Technomelt DA, Easymelt, and EasyFlow), Caswell Adhesives (Premiermelt or Casmelt products), Loctite, Bostik (Kizen, Kizen Force, Kizen ice, Kizen heat, Supergrip, Close TLH 4280E and TLH 2901 E, Protect and Seal TLH 4492E, TLH 2299E, Send TLH 4280E, TLH 4119E, Track TLH 4000E, Show TLH 2211 ELO, TLH 2299E, Hang TLH 2281 E and TLH2211 ELO, and TEF272), DuPont (ELVAX 40W, 150W, 210W, 220W, 240W, 250, 260, 265, 350, 360, 410, 420, 450, 460, 470, 550, 560, 660, 670, 750, 770, 4260, 4310, 4320 and 4355), Repsol (Primeva EVA's P1550M, P18150, P18500, P20020, P2430, P2735, P2870, P28025, P28150, P28400, P28045, P28800, P2850M, P2836M, P33015, P33025, P33045, P33400, P40055 with VA % 15 to 40 and Ebantix EBA's E1715, E1770, E20020, E27150, E33150 EBA (ethylene butyl acrylate) used with Tackifying Agents - Rosin Resins, Polyterpene Resins, Cycloaliphatic Aromatic Resins), Technology Supplied Ltd (‘Proflex 970 Hot Melt Glue Stick’), Tian Tian Adhesive Factory (‘Hot melt glue stick’), Toolstream Ltd (‘Hot melt Glue Stick’, 698462, 652076, 349348, 100024), FPC Corporation (‘Hot Melt Glue’, 501 , 601 , 701 , 702, 707, 708, 7011 , 724) and 3M (Hot Melt Adhesive 3764, 3747, 3748, 3731 , 3738, 3796, 3792, 3762, 3779 and 3789).

[0102] The hot melt adhesive may have any suitable melt flow index (MFI). The hot melt adhesive may have a melt flow index of from 1 to 1000 g / 10 mins, such as from 3 to 900 g / 10 mins or 10 to 900 g / 1 Omins. The melt flow index defines the flowability of the hot melt adhesive when molten at and above its melting temperature.

[0103] Methods of measuring the melt flow index (MFI) of the hot melt adhesive will be well known to a skilled person, and values may be measured according to ISO standard 1133-1 or ASTM D1238. The term melt flow index may be used interchangeably with melt flow rate (MFR) or melt index (Ml) by those in the art. Melt flow index is a measure of the rate of flow of a thermoplastic material such as a hot melt adhesive. It is defined as the mass of the thermoplastic material, in grams, that flows through a capillary of a specific diameter and length in 10 minutes on account of an applied pressure. In the context of the present invention, melt flow index is measured as a value which indicates the relative rate of flow of hot melt adhesives and the way that they behave when being heated to a temperature above ambient temperature that they become molten and are able to flow. The melt flow index of the hot melt adhesive may be roughly inversely proportional to the molecular weight of the thermoplastic polymer, copolymer, oligomer, or mixture thereof, of the hot melt adhesive. Melt flow index can be measured at different temperatures, with different weight loadings and different times, however MFI is commonly measured for 10 minutes, at temperatures of 190 °C and / or 230 °C, and 2.16 kg or 5 kg weight. For example, a standard test uses an MFI apparatus, for example, an Extruson Plastometer for 10 minutes, at 190 °C, and 2.16 kg weight. The applied load provides a shear stress in the apparatus setup.

[0104] The thermoplastic polymer, copolymer, oligomer, or mixture thereof, of the hot melt adhesive may have any suitable molecular weight. Molecular weight can typically be indirectly assessed using MFI measurements, with generally a higher MFI corresponding to a lower molecular weight, and vice versa.

[0105] The melting temperature of the hot melt adhesive, may be from 50 to 200 °C, or from 50 to 160 °C, including from 70 to 150 °C. The melting temperature of the hot melt adhesive is the temperature at which the hot melt adhesive becomes molten and able to flow. It is the temperature at which the hot melt adhesive transitions from a solid state into a viscous flow state. This may sometimes be known in the art as the softening temperature. The melting temperature is effectively the minimum processing temperature of the hot melt adhesive. As discussed above, the melting temperature of the hot melt adhesive may cover a melting temperature range. In the context of the present invention, both end points of any melting temperature range are encompassed by the stated values for the melting temperature of the hot melt adhesive.

[0106] Suitable methods for measuring the melting temperature of the hot melt adhesive will be well known to a skilled person. The melting temperature can be measured using melting point apparatus with a thermometer, differential scanning calorimetry (DSC), or by the known ‘Ring and Ball’ melting temperature measurement method. This may be according to ISO 4625-1 :2020. In the ‘Ring and Ball’ method, a layer of hot melt adhesive layer is placed in a steel ring and cooled. A ball that fits through the ring is placed on top of this hot melt adhesive layer. The whole system is placed in an oil bath, and heated. The melting temperature is determined as the temperature when the ball falls through the hot melt adhesive layer and touches the bottom of the oil bath. Preferably, the melting point of the hot melt adhesive is measured by DSC. This may be according to ISO 11357 - 1 :2016.

[0107] DSC is a technique well known to a skilled person and is a thermoanalysis technique in which differences in the amount of heat energy necessary to change the temperature of a sample of hot melt adhesive and a comparative reference are measured as a function of temperature. The aim is for both the sample of hot melt adhesive and reference to maintain the same temperature so that DSC can determine the endothermic transition as the hot melt adhesive becomes molten and able to flow, i.e. the melting temperature. The underlying principle of DSC is that when the sample of hot melt adhesive undergoes physical transformation, more heat energy will be required to flow to the sample compared to the reference to maintain both at equal temperature. By measuring the difference in heat flow between the sample and reference, DSC is able to determine the amount of heat absorbed during the endothermic transition.

[0108] The hot melt adhesive, and thus a composition according to the first or second aspect of the present invention when formed therefrom, is tacky when molten. The ‘tackiness’ of the hot melt adhesive, and thus the composition, may be measured according to ASTM3121 (‘Rolling Ball Tack’).

[0109] When the thermoplastic polymer, copolymer, oligomer, or mixture thereof, of the hot melt adhesive is a poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymer, the ratio of vinyl acetate to ethylene in the copolymer may be varied. For example, the poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymer may comprise from 1 to 60% of vinyl acetate, such as from 10 to 40%, or even from 15 to 33% of vinyl acetate. The poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymer may comprise 25% or more vinyl acetate. The polyethylene- vinyl acetate) or ethylene-vinyl acetate copolymer may comprise 24% or less vinyl acetate.

[0110] Alteration of the ratio of vinyl acetate to ethylene monomers on the backbone of the poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymer structure may affect properties such as the bonding of the composition to the substrate, and thus the types of substrate to which the composition may be applied or incorporated. For example, if the poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymer comprises a high content of vinyl acetate (25% or greater), the composition is preferably applied to or incorporated within substrates having lower surface energies, such as polymeric films, which require a ‘tackier’ composition. On the other hand, if the poly(ethylene-vinyl acetate) or ethylene-vinyl acetate copolymer comprises a lower content of vinyl acetate (24% or less), the composition is preferably applied to or incorporated within substrates having higher surface energies, including porous or semi-porous substrates such as paper-based substrates including paper, card, cardboard and cartonboard, which require less ‘tacky’ compositions.

[0111] Preferably, the hot melt adhesive forms 20 to 80 %, such as 30 to 70% of the composition according to the first or second aspect of the present invention.

[0112] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and redox buffer material, and antioxidant when present, are admixed within the hot melt adhesive, and homogeneously distributed, dispersed, suspended and incorporated throughout the hot melt adhesive to form the composition according to the first or second aspect of the present invention. The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, redox buffer material, and antioxidant when present, may be introduced into the hot melt adhesive in solid particulate form.

[0113] During formulation of a composition according to the first or second aspect of the present invention using a hot melt adhesive, i.e. incorporation of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and the redox buffer material, or antioxidant when present, into the hot melt adhesive, or during application of the composition to a substrate as detailed below, the hot melt adhesive is required to be molten such that it can flow. This is achieved by heating of the hot melt adhesive, and thus the composition, to or above, preferably above, the melting temperature of the hot melt adhesive. As discussed above, this may encompass a melting temperature range. In order that colour can be formed on the composition following these formulation or application stages through the application of radiation, the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is not reached. Accordingly, in order that a mark(s) or image(s) can be formed on the composition following these formulation or application stages through the application or radiation, during the heating in either of the formulation or application stages, appropriate selection of the hot melt adhesive is necessary. Such selection is dependent upon the relationship between the melting temperature of the hot melt adhesive, and the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof.

[0114] The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, may have a decomposition temperature of from 80 to 700 °C, or from 80 to 500 °C, such as from 100 to 500 °C, such as from 150 to 400 °C, or even from 200 to 300 °C. The decomposition temperature is the temperature at which the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, forms colour. The decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is the temperature at which the compound chemically decomposes. In some literature, this may also be known as the melting temperature.

[0115] The decomposition temperature of ammonium octamolybdate (AOM) is 275 °C.

[0116] The decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, may be measured using differential scanning calorimetry (DSC), or thermogravimetric analysis (TGA). Preferably, the decomposition temperature is measured using DSC. This is a technique well known to a skilled person. DSC is a technique well known to a skilled person and is a thermal analysis technique in which differences in the amount of heat energy necessary to change the temperature of a sample of the oxyanion of a multivalent metal and a comparative reference are measured as a function of temperature. The aim is for both the sample of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and reference to maintain the same temperature so that DSC can determine the endothermic transition as the oxyanion of a multivalent metal decomposes, i.e. the decomposition temperature. The underlying principle of DSC is that when the sample of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, undergoes physical transformation, more heat energy will be required to flow to the sample compared to the reference to maintain both at equal temperature. By measuring the difference in heat flow between the sample and reference, DSC is able to determine the amount of heat absorbed during the endothermic transition.

[0117] The melting temperature of the hot melt adhesive is lower than the temperature at which the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, forms colour, i.e. the melting temperature of the hot melt adhesive is lower than the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof.

[0118] Conversely, the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof is greater than the melting temperature of the hot melt adhesive. Accordingly, the hot melt adhesive, or the composition, may be heated to a temperature at or above, preferably above, the melting temperature of the hot melt adhesive such that the hot melt adhesive becomes molten and suitable for application to a substrate. However, this temperature is below the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof. Accordingly, mark or image formation can be controlled and achieved through the application of radiation to the composition when subsequently required.

[0119] When the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is ammonium molybdate (AOM), the decomposition temperature is higher than the melting temperature of the hot melt adhesive at from 50 to 200 °C, or from 50 or 160 °C, including from 70 to 150 °C, as detailed herein.

[0120] Although the ranges for the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, overlap with those of the melting temperatures of the hot melt adhesive detailed herein, the hot melt adhesive is selected so as to maintain the relationships stated above.

[0121] The melting temperature of the hot melt adhesive is lower than the melting temperature of the redox buffer material, and when present, the antioxidant. Conversely, the melting temperature of the redox buffer material, and when present, the antioxidant, is greater than the melting temperature of the hot melt adhesive. Accordingly, the hot melt adhesive, or the composition, may be heated to a temperature at or above, preferably above, the melting temperature of the hot melt adhesive such that the hot melt adhesive becomes molten and suitable for application to a substrate. However, this temperature is below the melting temperature of the redox buffer material, and when present, the antioxidant. Accordingly, mark or image formation can be controlled and achieved through the application of radiation to the composition when subsequently required.

[0122] The melting temperature of the redox buffer material and antioxidant may be measured using melting point apparatus with a thermometer, differential scanning calorimetry (DSC), or thermogravimetric analysis (TGA).

[0123] Where an antioxidant is present in the composition according to the first aspect of the present invention, the melting temperature of the hot melt adhesive may be from 50 to 150 °C, preferably 50 to 100 °C, such as 50 to 95 °C. Mark or image formation can be controlled and achieved through the application of radiation to the composition when subsequently required.

[0124] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, the present invention encompasses a composition wherein the hot melt adhesive is molten during manufacture, processing and application, as well as a composition wherein the hot melt adhesive is in a solid state (when cooled to ambient temperature) during storage, or following application of the composition to a substrate.

[0125] When the composition according to the first or second aspect of the present invention comprises the hot melt adhesive, the composition may further comprise a near-infrared radiation absorbing compound admixed therein. The nearinfrared radiation absorbing compound is homogeneously distributed, dispersed, suspended and incorporated throughout the hot melt adhesive of the composition. More than one near-infrared radiation absorbing compound may be present. The near-infrared radiation absorbing compound is as described above. The nearinfrared radiation absorbing compound may be present in an amount of from 0.1 to 5 wt% of the composition according to the first or second aspect of the present invention. The infrared radiation absorbing compound may be introduced into the composition in solid particulate form. When present, the infrared radiation absorbing compound may be present in solid particulate form.

[0126] When a hot melt adhesive is utilised, the composition according to the first or second aspect of the present invention does not comprise a solvent or water. There is no water or solvent present in either the hot melt adhesive or the composition according to the first or second aspect of the present invention.

[0127] When a hot melt adhesive is utilised, for the formation of the composition according to the first or second aspect of the present invention, the hot melt adhesive is heated to or above its melting temperature such that it becomes molten (said melting temperature of the hot melt adhesive being lower than the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof) and the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and redox buffer material, as well as antioxidant where used, is brought into contact, introduced and admixed into the molten hot melt adhesive. If a nearinfrared radiation absorbing compound is utilised, it is also introduced in this manner. Alternatively, the hot melt adhesive and oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and redox buffer material, as well as the antioxidant when used, are brought into contact, heated to or above the melting temperature of the hot melt adhesive (said melting temperature of the hot melt adhesive being lower than the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof), and the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and redox buffer material, as well as the antioxidant when used, is then admixed into the molten hot melt adhesive. If a near-infrared radiation absorbing compound is utilised, it is also introduced in this manner.

[0128] The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, redox buffer material and if present, the antioxidant, and the infrared radiation absorbing compound, are preferably introduced into the composition in solid particulate form.

[0129] When a hot melt adhesive is utilised, in the method of formation of the composition according to the first or second aspect of the present invention, the hot melt adhesive is heated to or above its melting temperature such that the hot melt adhesive becomes molten and able to flow. The melting temperature of the hot melt adhesive is as discussed above for the composition of the first or second aspect of the present invention. Preferably, the hot melt adhesive is heated to from 50 to 200 °C, or from 50 to 160 °C, such as from 70 to 150 °C.

[0130] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, as discussed above, during the formation of the composition according to the first or second aspect of the present invention, the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is not reached. The decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is as described above.

[0131] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, the heating of the hot melt adhesive in the formation of the composition according to the first or second aspect of the present invention may be achieved by any means. Suitable heating apparatus include hot melt guns and applicators, extrusion and moulding equipment, injection, blow moulding, calendaring, rotational moulding, thermoforming and hot- melt coaters. Manufacture of the composition according to the first or second aspect of the present invention can be achieved using standard thermoplastic processing machinery, for example, equipment such as that used for extruding, blending, mixing, pulverising and moulding including injection and blow moulding and other typical equipment of different sizes and specifications can be used for calendaring, rotational moulding, thermoforming and hot-melt coating. This can include processing using liquid or solid masterbatches and in solid forms such as sticks, blocks, lumps, rods, balls, beads, pellets, granules and powders. Once the composition according to the first or second aspect of the present invention has been formed and when the hot melt adhesive is molten, the composition can be directly applied to or incorporated within a substrate. The composition according to the first or second aspect of the present invention will then cool to ambient temperature and solidify on the substrate as the hot melt adhesive cools, transitioning back to a solid state. Alternatively, once the composition according to the first or second aspect of the present invention has been formed, the composition can be allowed to cool to ambient temperature and solidify such that the hot melt adhesive transitions back to the solid state. The composition according to the first or second aspect of the present invention as a whole is then in a solid state. The composition according to the first or second aspect of the present invention can then be stored or transported in the solid state, and when needed, re-heated to the melting temperature of the hot melt adhesive (selected so as to be below the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof) in order that the hot melt adhesive becomes molten and the composition according to the first or second aspect of the present invention may be applied to or incorporated within a substrate.

[0132] When a hot melt adhesive is utilised in a composition according to the first aspect of the present invention, preferably the melting temperature of the hot melt adhesive utilised is less than 100 °C, such as less than 100 °C and greater than 50 °C. The temperature to which the hot melt is heated in the production of the composition as discussed above is less than 100 °C, such as less than 100 °C and greater than 50 °C. Preferably, when a hot melt adhesive is utilised, the composition is a composition according to the second aspect of the present invention, comprising an oxyanion of a multivalent metal, an oxyacid, or a hydrate thereof, and the redox buffer material defined therein.

[0133] Preferably, the composition according to the first or second aspect of the present invention further comprises a binder and / or near-infrared absorbing compound and / or solvent and / or additive as detailed above. Preferably, the composition according to the first or second aspect of the present invention does not comprise a hot melt adhesive.

[0134] The composition according to the first or second aspect of the present invention is a radiation-reactive composition, such as a laser-reactive composition, i.e. capable of forming a mark or image upon application of radiation to the composition, preferably using a non-contact source, for example, from a laser source(s). The composition according to the first or second aspect of the present invention is suitable as an ink composition. The composition according to the first or second aspect of the present invention is suitable for the formation of a mark(s) or image(s) on substrates.

[0135] The composition according to the first or second aspect of the present invention may be applied to or incorporated within any suitable substrate.

[0136] Thus, according to a third and fourth aspects of the present invention, there is provided a substrate comprising the composition according to the first or second aspect of the present invention applied thereon or incorporated therein.

[0137] Examples of suitable substrates of the third or fourth aspect of the present invention to which the composition according to the first or second aspect of the present invention may be applied or incorporated include, but are not limited to, those formed of the following substrate materials: polymers and recycled polymer materials such as polyhydroxyalkanoates (PHA), poly(glycolic acid) (PGA), polyethylene terephthalate (PET), polyethylene vinyl -acetate) or ethylene-vinyl acetate copolymers, 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 such as tinplate; textiles; paper-based substrates including paper, card, carton, paperboard, cartonboard, corrugated paper, corrugated card, corrugated carton, corrugated paperboard, cardboard, corrugated cartonboard, folding carton and equivalent recycled analogues, or combinations thereof; ceramics; foodstuffs and pharmaceutical preparations; or combinations thereof, e.g. polymer lined paper or polymer impregnated paper. Suitable substrates include multi-layer substrates formed from the materials and substrates listed above. The polymer and recycled polymer materials may be in the form of polymer film substrates. The polymer and recycled polymer materials may be metallised. By metallised is meant that the material is coated with a thin layer of metal, for example, aluminium. In these cases, the polymer and recycled polymer material may be a metallised polymer film. Such films may be used as a barrier layer, for example, in multi-layer substrate constructions.

[0138] The substrate according to the third or fourth aspect of the present invention may comprise a single or multiple layers of the composition according to the first or second aspect of the present invention applied thereto or incorporated therein.

[0139] When the composition according to the first or second aspect of the present invention comprises hot melt adhesive, the substrate according to the third or fourth aspect of the present invention encompasses substrates having a composition applied thereto or incorporated therein, wherein the composition has just been applied and is molten, i.e. prior to it cooling to ambient temperature. Substrates are also encompassed having a composition according to the first or second aspect of the present invention applied thereto or incorporated therein, wherein the composition is solid at ambient temperature. This composition may be tacky or non-tacky at ambient temperature. The composition according to the first or second aspects of the present invention and the substrate according to the third or fourth aspects of the present invention to which the composition according to the first or second aspects has been applied or incorporated, may be suitable for end use as labels (adhesive or wraparound), and / or in fast-moving consumer goods; packaging such as disposable packaging including food and hot or cold beverage containers; hygiene and personal care product packaging such as shampoo bottles; cosmetic product packaging; decorative metal products; blister pack packaging; laminated pouches; medical and diagnostic devices and associated packaging.

[0140] The composition according to the first or second aspects of the present invention and the substrate according to the third or fourth aspects of the present invention to which the composition according to the first or second aspects has been applied or incorporated, may find particular use in the packaging industry. The substrate according to the third or fourth aspect of the present invention may be articles such as packaging products including, but not limited to paper-based and containers boxes including cardboard and cartonboard boxes and the like, paperbased tubes including cardboard tubes and the like, plastic bottles, plastic packaging paper-based bottles, plastic lids, glass bottles, aluminium cans and lids, steel cans and lids, wrap around labels, stretch sleeves, shrink sleeves, and self-adhesive labels. Preferably, the substrate according to the third or fourth aspect of the present invention is a packaging product. Packaging products include lids and containers such as food and / or beverage containers or containers of pharmaceuticals or non-consumable personal care and household products. Suitable examples of containers include boxes, pouches, bottles such as beverage bottles, the blister packaging typically used in the pharmaceutical and tobacco or vaping industries, and clamshell packaging typically used in the food industry. Such substrates are typically formed of plastic, cardboard, or paper, preferably plastic. Substrates include the substrates as described herein having additional components associated therewith, such as plastic bottles having plastic lids associated therewith. A plastic substrate also includes plastic substrates as described herein having additional non-plastic components associated therewith, such as for example, a metal, aluminium foil, or paper sealing layer (lidding) in blister packaging. A plastic substrate also includes the plastic substrate, with any associated closure, pump, cap, spout, handle, lid, or cover. The substrates according to the third or fourth aspect of the present invention may be used to store, transport, and distribute goods such as pharmaceuticals, food and drink and non-consumable personal care and household products.

[0141] For the third or fourth aspect of the present invention, the substrate may be a multi-layer substrate construction. Such multi-layer substrate constructions may comprise multiple layers of differing substrate materials bonded together. The composition according to the first or second aspect of the present invention may be applied thereto. Alternatively, or additionally, such multi-layer substrate constructions may comprise the composition according to the first or second aspect of the present invention present, at least, between two layers of substrate material. Such constructions are substrates having the composition according to the first or second aspect of the present invention incorporated therein. This may be known in the art as a ‘laminate construction’. The multi-layer substrate construction may be considered to comprise a plurality of discrete layers. The substrate material layers may be formed of the same substrate materials as detailed above for substrates.

[0142] By ‘a substrate comprising the composition incorporated therein’ or like terms used herein, this preferably refers to a multi-layer substrate construction as described herein, comprising the composition according to the first or second aspect of the present invention present, at least, between two layers of substrate material.

[0143] The multi-layer substrate constructions may comprise two or more layers of substrate materials. The two or more layers of substrate material may be the same or different. This may be in terms of material type, colour, thickness and / or transparency. Where one or all of the layers of substrate material is a polymer film, one or more of the two or more layers may be metallised. For example, to act as a barrier layer. Where one or all of the two or more layers of substrate material is a polymer film, one or more of the layers of substrate material may be ‘heat-sealed’ plastic material. Such material is typically formed through processing, e.g. melting, of the plastic material itself.

[0144] Where the multi-layer substrate constructions comprise the composition according to the first or second aspect of the present invention present, at least, between two layers of substrate material, preferably at least one of the layers of substrate material is transparent or translucent, preferably transparent. The mark or image formed in the composition according to the first or second aspect of the present invention can thus be seen therethrough.

[0145] The first or second composition according to the present invention may be present in the multi-layer substrate constructions as single or multiple layers, i.e. once or multiple times. This may be at the same position of the multi-layer substrate construction, or between differing substrate material layers. The multi-layer substrate constructions may comprise two or more layers of the composition according to the first or second aspect of the present invention.

[0146] Typically, in the context of the present invention, the multi-layer substrate constructions correspond to laminated film packaging. Typically, the multi-layer substrate constructions are plastic pouches, plastic boxes or plastic bottles, preferably plastic pouches. Preferably, the substrate material layers are in the form of polymeric film.

[0147] The multi-layer substrate constructions may further comprise one or more additional layers. Such additional layers may be selected from, but are not limited to: thermal insulating layers; protective layers; adhesion promoting layers; adhesive layers; barrier layers including metal foils or coated plastic materials; quenching layers; and light stabilisers; or combinations thereof. The positioning of the one or more additional layer in the multi-layer substrate construction may differ depending on the type of one or more additional layer utilised and its function within the multi-layer substrate construction. Preferably, the multi-layer substrate constructions comprise an adhesive layer and / or barrier layer. Preferably, the multi-layer substrate constructions comprise the composition according to the first or second aspect of the present invention and an adhesive positioned between two layers of substrate material.

[0148] Preferably, the multi-layer substrate constructions comprise, in the following order: substrate material; the composition according to the first or second aspect of the present invention; an adhesive; and a layer of substrate material.

[0149] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, the composition may be tacky at ambient temperature, and two substrate material layers may be bonded together by the composition in a multi-layer substrate construction. No additional adhesive layer may be necessary.

[0150] However, preferably for the multi-layer substrate constructions described herein, the compositions of the first or second aspects of the present invention do not comprise hot melt adhesive. Preferably, for the multi-layer substrate constructions described herein, the compositions of the first or second aspects of the present invention further comprise a binder and / or near-infrared absorbing compound and / or solvent and / or additive as detailed above.

[0151] For the multi-layer substrate constructions, the substrate material layers may typically, individually, have a thickness of from 8 to 100 pm. Any layer of composition according to the first or second aspect of the present invention in the multi-layer substrate construction may have the coat weight as described herein for application to a substrate. The multi-layer substrate constructions may typically have an overall thickness of 500 pm or less, such as 200 pm or less. Any one or more additional layer in the multi-layer substrate construction may have a thickness of 100 pm or less.

[0152] When the multi-layer substrate constructions comprise the composition according to the first or second aspect of the present invention present, at least, between two layers of substrate material, the composition according to the first or second aspect of the present invention between the two layers of substrate material is preferably not exposed to an oxidising atmosphere, it being contained between the layers of substrate material.

[0153] In the context of the present invention, the substrates according to the third or fourth aspect of the present invention encompasses substrates which do not display a mark or image, i.e. have the composition according to the first or second aspect of the present invention applied thereon but prior to the application of radiation to form a mark or image thereon, as well as encompassing substrates which display a mark or image, i.e. have the composition according to the first or second aspect of the present invention applied thereon and have had radiation applied thereto.

[0154] For the multi-layer substrate constructions, any mark or image formed, is formed using the composition according to the first or second aspect of the present invention and thus, when the multi-layer substrate constructions comprise the composition according to the first or second aspect of the present invention present, at least, between two layers of substrate material, the mark or image is formed ‘within’ or ‘incorporated within’ the multi-layer substrate construction. The multi-layer substrate construction displays a mark or image.

[0155] According to a fifth aspect of the present invention, there is provided a method of forming a substrate according to the third or fourth aspects of the present invention, the method comprising applying to or incorporating within a substrate the composition according to the first or second aspect of the present invention respectively.

[0156] The composition according to the first or second aspect of the present invention may be applied to or incorporated within the substrate by any suitable method. Methods of applying the composition to a substrate, or a substrate material layer in a multi-layer substrate construction, 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, pad printing, offset printing and meyer bar coating. For when hot melt adhesive is utilised in a composition according to the first or second aspect of the present invention, suitable application methods include, but are not limited to: hot melt guns and applicators, extrusion, injection moulding, and moulding equipment and coaters.

[0157] The composition according to the first or second aspect of the present invention may be applied to at least a portion of the substrate or a substrate material layer in a multi-layer substrate construction.

[0158] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, for the methods of forming the substrate according to the third or fourth aspect, the composition is applied to the substrate, or a substrate material layer in a multi-layer substrate construction, when molten and may be allowed to cool to ambient temperature and solidify. By allowing the composition according to the first or second aspect of the present invention to cool to ambient temperature and solidify following application to the substrate, or a substrate material layer in a multi-layer substrate construction, the hot melt adhesive of the composition transitions to a solid state. When the hot melt adhesive used is non-tacky at ambient temperature, as a result of this cooling, the composition according to the first or second aspect of the present invention solidifies and becomes resistant to removal during any subsequent handling, storage or use of the substrate. Typically, the time taken for the composition according to the first or second aspect of the present invention to cool and solidify in this instance depends on the volume of the composition applied, i.e. the coat weight, but typically this is from 0.1 to 100 seconds, such as from 1 to 10 seconds at ambient temperature.

[0159] The composition according to the first or second aspect of the present invention may be applied on a substrate, or a substrate material layer in the multi-layer substrate construction, to any suitable coat weight dependent upon both the substrate to which the composition is applied and the application method. Typically, the composition according to the first or second aspect of the present invention may be applied to a coat weight of from 0.1 to 50 gsm (grams per square metre), such as from 0.1 to 25 gsm, or from 0.1 to 15 gsm. If the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, the composition may be applied to a coat weight of from 0.1 to 1000 gsm, such as from 0.1 to 500 gsm, or from 0.1 to 250 gsm, and more preferably from 0.1 to 150 gsm.

[0160] 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 difference between the two weights. All coat weights are per individual layer of the composition according to the first or second aspect of the present invention that is applied to the substrate.

[0161] The composition according to the first or second aspect of the present invention may be applied to the substrate, or a substrate material layer in a multi-layer substrate construction, as a single layer or as multiple layers.

[0162] The composition according to the first or second aspect of the present invention may be applied to at least part, or all, of a surface of the substrate, or a surface of a substrate material layer in a multi-layer substrate construction.

[0163] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, in order for the application of the composition to the substrate, or substrate material layer for a multi-layer substrate construction, to take place when the hot melt adhesive is molten, the composition must have been heated to or above the melting temperature of the hot melt adhesive (but below the melting decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and melting temperature of the redox buffer material and where present, antioxidant). This may be directly following production of the composition whilst the hot melt adhesive is molten, or following storage of the composition such that the composition is heated to or above the melting temperature of the hot melt adhesive therein (but below the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and melting temperature of the redox buffer material, and where present, antioxidant) in order that the hot melt adhesive becomes molten for application to the substrate, or substrate material layer for a multi-layer substrate construction. Suitable methods for heating the composition will be well known to a skilled person, and include typical industrial thermoplastic processing and application equipment such as that used for extruding, moulding, injection, blow moulding, calendaring, rotational moulding, thermoforming, hot-melt coating, glue guns and hot glue applicators. As the composition is not heated to the decomposition temperature of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, or the melting temperature of redox buffer material and where present, antioxidant, a mark or image formation may be facilitated by the subsequent application of radiation.

[0164] The application of the composition according to the first or second aspect of the present invention to a substrate, or substrate material layer of a multi-layer substrate construction, enables the substrate to display a mark or image. Accordingly, the substrate according to the third or fourth aspect of the present invention encompasses the substrate having the composition applied thereto or incorporated therein prior to the application of radiation, i.e., not displaying a mark(s) or image(s) thereon, as well as the substrate having the composition applied thereto or incorporated therein after the application of radiation such that the substrate displays a mark(s) or image(s) thereon.

[0165] Thus, according to a sixth aspect of the present invention, there is provided a method of forming a mark or image on a substrate according to the third or fourth aspect of the present invention having a composition according to the first or second aspect of the present invention applied thereon or incorporated therein, the method comprising exposing the composition to radiation to form a mark or image.

[0166] The mark or image is formed by the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof. The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, forms colour upon application of the radiation thereto. By ‘colour’ as used herein is meant colours, tints, shades and hues of the visible light colour spectrum, i.e. red, orange, yellow, blue, green and violet, in addition to black, brown, turquoise, purple, pink, cyan, magenta, white and all mixtures thereof. All primary, secondary, tertiary, quaternary and quinary colours are encompassed, i.e. the colour formed may be a primary, secondary, tertiary, quaternary or quinary colour. In the context of the 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 black, brown, turquoise, purple, pink, cyan, white and magenta. In the context of the present invention, if the composition according to the first or second aspect of the present invention inherently has a colour (before any radiation is applied thereto), the colour, and thus the mark or image, formed upon application of radiation to the composition according to the first or second aspect of the present invention is different to, or has a stronger optical density than, the colour that the composition according to the first or second aspect of the present invention may have upon formulation, storage, or application to a substrate prior to the application of radiation thereto.

[0167] The oxyanion of a multivalent metal is a colour forming compound and thus in turn, a mark or image-forming compound, particularly suitable for forming marks or images displaying variable information.

[0168] The composition according to the first or second aspect of the present invention prior to application of radiation may have any colour. Alternatively, the composition according to the first or second aspect of the present invention prior to the application of radiation may be colourless.

[0169] The composition according to the first or second aspect of the present invention prior to the application of radiation may be transparent or opaque.

[0170] In the context of the present invention, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, preferably does not form colour until controlled and specific application of radiation to the composition. In some instances, typically when the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, may display some colour prior to the application of radiation to the composition. This may be as a result of temperatures reached during processing, manufacture or application of the composition according to the first or second aspect of the present invention to a substrate. However, even in this case, the desired mark or image may still be formed through the application of radiation to the composition as application of the radiation causes the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, to display colour of a much stronger optical density than the ‘background’ colour formed such that an effective and contrasting mark or image is still formed. Preferably, prior to the application of radiation to the composition according to first and second aspects of the present invention, and in the part(s) of the composition to which radiation is not applied, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, does not display colour. Preferably, the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, only displays colour in the part(s) of the composition according to the first or second aspect of the present invention to which radiation has been applied, i.e. the part(s) of the composition that have been exposed to radiation.

[0171] The term "mark or image" incorporates but is not limited to: marks such as words or text, logos, graphics, figures, pictures, symbols, codes, linear barcodes, 2- dimensional Datamatrix, QR (quick response) codes, Digimarc codes and text, microtext and text including alphanumeric fonts and symbol fonts and characters. In the context of the present invention, it is the manipulation of the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof (‘colour-forming compound’), that facilitates the formation of a mark or image. The mark or image formed will be human and / or machine readable, and can be used for coding and marking, tagging tracking and tracing, and late-stage customisation or personalisation purposes. The code can be composed of for example alphanumeric text or symbol fonts to indicate expiry dates and / or batch or lot codes. The code may also be graphical and for example, capable of being scanned or verified with a device such as a barcode scanner, verifier or using a smartphone camera or app. The mark or image formed is typically used to display variable information on the substrate. In the context of the present invention, the mark or image will be a contrasting mark or image. By "contrasting mark or image" is meant that the mark or image formed is easily discernible from the ‘background’ of the composition according to the first or second aspect of the present invention, i.e. the part of the composition which has not been exposed to radiation, or the colour of the substrate if visible through the composition following application to the substrate.

[0172] In the context of the present invention, the mark or image formed is strong and distinct. The mark or image preferably has enhanced optical density.

[0173] The optical density of the mark or image may be evaluated, for example, by measurement of an absolute optical density black (ODB) value, an optical density magenta (ODM) value, an optical density cyan (ODC) value, or an optical density yellow (ODY) colour. ODB values are suitable for evaluation of a mark(s) or image(s) that is black in colour, or a shade or tint thereof. ODM values are suitable for evaluation of a mark(s) or image(s) that is red in colour, or a shade or tint thereof. ODC values are suitable for evaluation of a mark(s) or image(s) that is blue in colour, or a shade or tint thereof. ODY values are suitable for evaluation of a mark(s) or image(s) that is yellow in colour, or a shade or tint thereof. In the context of ODB, ODM, ODC and ODY values, the higher the value, the stronger the colour formed. The absolute ODB, ODM, ODC and ODY value quantifies the optical density on the respective black, magenta, cyan or yellow colour scale from low to high values, where ODB, ODM, ODC and ODY values can be made using a standard instrument densitometer and X-Rite eXact or SpectroEye or TechKon SpectroDens spectrophotometer. A strong and distinct image preferably has an absolute ODB, ODC, ODM or ODY value of 0.4 or more, such as 0.7 or more, or even 1.0 or more.

[0174] In the context of the present invention, when the oxyanion of multivalent metal, or oxyacid or hydrate thereof, is an ammonium salt of an oxyanion of a multivalent metal, such as an ammonium salt of an oxyanion of molybdenum, such as ammonium octamolybdate (AOM), the colour and / or image formed when an oxyanion of a multivalent metal, or oxyacid or hydrate thereof is utilised as the colour-forming compound will typically be black in colour, or a shade or tint thereof, including greyscale depending on the density of the black colour formed by the radiation. In such cases, other than being visually identifiable, the effective formation of colour or an image may be demonstrated, as noted above, by a measured absolute optical density (ODB) black value. This measures the density of the black colour of the mark or image. In the context of ODB values, the higher the value, the darker the black colour formed. For the present invention, preferably an ODB value of 0.4 or more, such as 0.7 or more, or even 1 .0 or more is desired. This quantifies the optical density on the black colour scale from low to high values, where ODB measurements can be made using a standard instrument densitometer and an X-Rite eXact or SpectroEye or TechKon SpectroDens spectrophotometer. Such a value demonstrates effective formation of a mark or image of ‘enhanced optical density’ by the compositions according to the first or second aspect of the present invention upon exposure to radiation.

[0175] Assessment of undue coloration of the composition according to the first or second aspect of the present invention on which a mark or image is, or is to be, formed may be evaluated by measurement of a AE value. This assessment is particularly relevant for the composition according to the first aspect of the present invention comprising an antioxidant, as discussed herein. The AE value represents the measurable difference in L*a*b* colour to determine if any coloration of the composition according to the first or second aspect of the present invention has occurred, other than the desired formation of a mark or image. A sample of the ‘background’ of an imaged or unimaged composition according to the first or second aspect of the present invention is compared with a white background. AE may be measured using the below standard mathematical formula, on a X-rite eXact spectrophotometer (L = L*, a = a* and b = b*).

[0176] AE measurements may be made on a white background. AE allows for the quantification of the visual perception between two colours. A low AE demonstrates that there is no visual difference, i.e. no undue colour formation or unfavourable coloration. The AE measurement may be less than 5. Such a AE measurement provides a good indication that there is no visual perception of a difference between the two.

[0177] The radiation may be applied to the composition according to the first or second aspect of the present invention at localised positions of the composition to selectively form a mark or image. A human and / or machine-readable mark or image is formed.

[0178] "Radiation" and like terms 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 (p) radiation, neutron radiation and plasma. The wavelength ranges of the different regions of the electromagnetic spectrum are known to a skilled person. For completeness, by the term "near-infrared radiation" is meant radiation in the near-infrared region of the electromagnetic spectrum, and having a wavelength of from 780nm to 2500nm, preferably 780 nm to 1600 nm. Typically, the near-infrared radiation is applied at wavelengths of 780 nm to 1600 nm when using commercially available fibre lasers. By the term "mid-infrared radiation" is meant radiation in the mid-infrared region of the electromagnetic spectrum, and having a wavelength of from 2500nm to 50000 nm, preferably 9000 to 12000 nm, or 9300 nm, 9600 nm, 10200 nm or 10600 nm, or more preferably 10600 nm. Typically, the mid-infrared radiation is applied at wavelengths of 9000 to 12000 nm such as 9300 nm, 9600 nm, 10200 nm or 10600 nm, preferably 10600 nm using commercially available CO2 lasers.

[0179] The radiation may be selected from ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, 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 nearinfrared (NIR) radiation with a wavelength of from 700 to 1600 nm. Preferably, the radiation is selected from ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, infrared (IR) radiation with a wavelength of from 9000 to 12000 nm, infrared (IR) radiation with a wavelength of from 700 nm to 1 mm, and near-infrared (NIR) radiation with a wavelength of from 700 to 1600 nm such as 950 to 1100 nm. More preferably, the radiation is selected from ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, and infrared (IR) radiation with a wavelength of from 9000 to 12000 nm, such as 9300, 9600, 10200 or 10600 nm. More preferably, the radiation is selected from ultraviolet (UV) radiation with a wavelength of from 10 to 400 nm, and infrared (IR) radiation with a wavelength of 10600 nm.

[0180] Preferably, the infrared radiation with a wavelength of from 9000 to 12000 nm, such as 9300, 9600, 10300 or 10600 nm, is applied using a CO2 laser,

[0181] When the composition according to the first or second aspect of the present invention comprises a hot melt adhesive, the radiation is applied to the composition after it has cooled and solidified at ambient temperature, typically with the composition applied on or incorporated in the substrate.

[0182] The radiation may be applied to the composition according to the first or second aspect of the present invention by any suitable means. Preferably, the radiation is applied to the composition according to the first or second aspect of the present invention using non-contact means or source. By ‘non-contact’ is meant a means or source that is not in contact with the composition according to the first or second aspect of the present invention or substrate according to the third or fourth aspect of the present invention when delivering the radiation thereto. Suitable means include laser excitation through application of radiation to the composition according to the first or second aspect of the present invention by a laser source(s). Preferably, the radiation is applied to the composition according to the first or second aspect of the present invention using a laser source(s). By the term "laser source(s)" and like terms used herein is meant any suitable commercial or non-commercial laser source(s). Suitable examples include, but are not limited to a fibre laser, fibre-coupled laser diode array, CO2 laser, laser diode array or direct diode laser for providing radiation, including near-infrared or mid-infrared radiation. It will be understood by a skilled person that the radiation may be applied to the composition according to the first or second aspect of the present invention at localised positions to selectively facilitate the formation of colour, and thus a mark or image at these localised positions in the composition. These localised positions may overlap with each other. It will also be understood by a skilled person that the radiation is applied to the composition according to the first or second aspect of the present invention for an appropriate amount of time required to facilitate the formation of image. Typically, the time required to deliver sufficient radiation will depend upon the means used to apply radiation and the method of application. For example, in one embodiment, the radiation may be applied to the composition for less than 120 seconds or for less than 60 seconds, such as for less than 20 seconds, or even less than 10 or 5 seconds.

[0183] When applied using a laser source(s), the radiation dosage applied 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 / cm2. For example, where a laser source(s) is used to apply the radiation, the fluence (amount of energy delivered per unit area) may affect the optical density of the image formed. In the context of the present invention, the fluence is dependent upon the power of the means used to apply the radiation (wattage), and the time for which the radiation is applied to a particular localised position on the substrate, which may 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 image formed will have lower optical density (lower ODB), and where the fluence is high (e.g. higher power and / or longer irradiation times), the image formed will have a higher optical density (higher ODB) and be of higher contrast with the ‘background’ or unimaged parts, of the composition. In the context of the present invention, fluence values may range from 0.01 to 50 J / cm2, such as from 0.1 to 25 J / cm2, and even from 0.5 to 10 J / cm2. Preferably, the radiation is applied to the composition according to the first or second aspect of the present invention at localised positions of the composition in order to form the desired mark or image. Essentially, upon application of the radiation, a colour is formed at the areas of the composition according to the first or second aspect of the present invention on the substrate to which the radiation is applied. The oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, undergoes a reaction (chemical decomposition) to form colour. A human and / or machine readable mark or image is thus generated.

[0184] 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 and tautomers thereof.

[0185] All of the features contained herein may be combined with any of the above aspects and in any combination.

[0186] 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.

[0187] EXAMPLES

[0188] Example 1

[0189] A composition according to the first aspect of the present invention comprising an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, a redox buffer material, and an antioxidant was prepared according to Table 1.

[0190] Table 1

[0191] Example 2

[0192] A composition according to the second aspect of the present invention comprising an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, and a redox buffer was prepared according to Table 2.

[0193] Table 2

[0194] Comparative Example 1

[0195] A comparative composition comprising only an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof and antioxidant, but no redox buffer material, was prepared according to Table 3. Table 3

[0196] Comparative Example 2

[0197] A comparative composition comprising only an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, but no redox buffer material, was prepared according to Table 4.

[0198] Table 4

[0199] Evaluation 1 The compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were separately applied to 50 pm white PET film at a coat weight of 4 gsm with an RK K control coater.

[0200] Radiation was applied to each of the compositions using a 10.6 pm CO2 laser to form a black mark. Absolute ODB and AE measurements were obtained using an X-rite eXact spectrometer (an average of 10 measurements was taken). AE measurements were obtained 1 hour, and 24 hours, after application of the composition to the PET film, and after the application of the radiation. Absolute ODB measurements were obtained 1 hour after application of the composition to the PET film, and after application of the radiation. The samples were kept under ambient conditions. Results are shown in Table 5 below.

[0201] Table 5 When Example 2 and Comparative Example 2 are compared, it can be seen that the presence of the redox buffer in Example 2 enables a 43% increase in optical density of the mark formed relative to Comparative Example 2.

[0202] When Example 1 and Comparative Example 2 are compared, it can be seen that the presence of the redox buffer and antioxidant in Example 1 enables a 50% increase in optical density of the mark formed relative to Comparative Example 2.

[0203] When Example 1 and Comparative Example 1 are compared, it can be seen that the presence of the redox buffer in Example 1 prevents unfavourable coloration of the composition occurring over time. The mark of Example 1 remains strong and distinct. Evaluation 2

[0204] The compositions of Examples 1 and 2 and Comparative Examples 1 and 2 were separately applied to 50 pm white PET film at a coat weight of 4 gsm with an RK K control coater.

[0205] Each composition on the PET film was overprinted with Novacote SF716A+CA336 adhesive (an adhesive layer) at a coat weight of 2 gsm with a RK K control coater.

[0206] A 20 pm transparent OPP film was then laminated over the adhesive layer with Cheminstruments LL-100 laboratory laminator to form multi-layer substrate constructions.

[0207] Radiation was applied to the composition of each multi-layer substrate construction using a 10.6 pm CO2 laser to form a black mark.

[0208] Absolute ODB and AE measurements were obtained using an X-rite eXact spectrometer (an average of 10 measurements was taken). AE measurements were obtained 1 hour after application of the composition to the PET film and formation of the multi-layer substrate construction, and after application of radiation. Absolute ODB measurements were obtained 1 hour after application of the composition to the PET film and formation of the multi-layer substrate construction, and after application of the radiation. The samples were kept under ambient conditions. Results are shown in Table 6 below.

[0209] Table 6 When Example 1 and Comparative Example 1 are compared, it can be seen that the presence of the redox buffer in Example 1 prevents unfavourable coloration of the composition occurring. The mark of Example 1 is strong and distinct compared to that of Comparative Example 1 .

[0210] When Example 2 and Comparative Example 2 are compared, it can be seen that the presence of the redox buffer in Example 2 enables a 52% increase in optical density of the mark formed relative to Comparative Example 2.

[0211] Example 3

[0212] A composition according to the second aspect of the present invention comprising an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof and a redox buffer material was prepared according to Table 7.

[0213] Table 7

[0214] Comparative Example 3

[0215] A comparative composition comprising an oxyanion of a multivalent meal, or oxyacid, or hydrate thereof, but no redox buffer material, was prepared according to Table 8.

[0216] Table 8

[0217] Evaluation 3

[0218] The compositions of Example 3 and Comparative Example 3 were separately applied to a 50 pm transparent PET film at a coat weight of 6 gsm with a RK K control coater.

[0219] Radiation was applied to each of the compositions using a 10.6 pm CO2 laser to form a black mark.

[0220] Absolute ODB measurements were obtained using an X-rite eXact spectrometer (an average of 10 measurements was taken). Absolute ODB measurements were obtained 1 hour after application of the composition to the PET film, and after application of the radiation. The Samples were kept under ambient conditions. Results are shown in Table 9 below.

[0221] Table 9

[0222] When Example 3 and Comparative Example 3 are compared, it can be seen that the presence of the redox buffer in Example 3 enables a 20% increase in optical density of the mark formed relative to Comparative Example 3.

[0223] EMBODIMENTS

[0224] 1. A composition comprising:

[0225] (a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof; (b) a redox buffer material; and

[0226] (c) an antioxidant; wherein the redox buffer material is a multivalent metal salt. A composition comprising:

[0227] (a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof; and

[0228] (b) a redox buffer material; wherein the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, a sulphuric acid metal salt, and a multivalent metal oxide. The composition according to embodiment 1 or 2, wherein the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is an ammonium salt of an oxyanion of a multivalent metal, preferably an ammonium salt of an oxyanion of molybdenum, and more preferably ammonium octamolybdate (AOM). The composition according to embodiment 1 , or embodiment 3 when dependent upon embodiment 1 , wherein the redox buffer material is selected from an organic or inorganic acid multivalent metal salt, or a multivalent metal oxide, preferably selected from an organic or inorganic acid multivalent metal salt, and more preferably from an organic acid multivalent metal salt. The composition according to embodiment 1 , or embodiment 3 or 4 when dependent upon claim 1 , wherein the redox buffer material is selected from a multivalent metal carboxylate, an oxalic acid multivalent metal salt, a carbonic acid multivalent metal salt and a sulphuric acid multivalent metal salt, more preferably selected from a multivalent metal carboxylate, an oxalic acid multivalent metal salt and a carbonic acid multivalent metal salt, and more preferably a multivalent metal carboxylate. The composition according to embodiment 1 , or embodiment 3, 4 or 5 when dependent upon embodiment 1 , wherein the redox buffer material is selected from an organic or inorganic acid salt of manganese or iron, or a manganese or iron oxide, preferably an organic or inorganic acid salt of manganese or iron, and more preferably an organic acid salt of manganese or iron. The composition according to embodiment 6 when dependent thereon, wherein the redox buffer material is selected from a manganese or iron carboxylate, an oxalic acid salt of manganese or iron, a carbonic acid salt of manganese or iron, and a sulphuric acid salt of manganese or iron, preferably selected from a manganese or iron carboxylate, an oxalic acid salt of manganese or iron and a carbonic acid salt of manganese or iron, and more preferably a manganese or iron carboxylate. The composition according to embodiment 6 or 7, wherein the redox buffer material is selected from an organic or inorganic acid salt of manganese or a manganese oxide, preferably an organic or inorganic acid salt of manganese, and more preferably an organic acid salt of manganese. The composition according to any of embodiments 6 to 8, wherein the redox buffer material is selected from a manganese carboxylate, an oxalic acid salt of manganese, a carbonic acid salt of manganese and a sulphuric acid salt of manganese, preferably selected from a manganese carboxylate, an oxalic acid salt of manganese and a carbonic acid salt of manganese, and more preferably a manganese carboxylate. The composition according to embodiment 1 , or any of embodiments 3 to 5 when dependent upon embodiment 1 , wherein the redox buffer material is a metal carboxylate, preferably a gluconic acid metal salt. The composition according to embodiment 2, or embodiment 3 when dependent upon embodiment 2, wherein the redox buffer material is selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, and a sulphuric acid multivalent metal salt, preferably selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, and a carbonic acid multivalent metal salt. The composition according to embodiment 2, or embodiment 3 or 11 when dependent upon embodiment 2, wherein the redox buffer material is selected from a gluconic acid salt of manganese or iron, an acetic acid salt of manganese or iron, a carbonic acid salt of manganese or iron, a sulphuric acid salt of manganese or iron, and a manganese or iron oxide, preferably selected from a gluconic acid salt of manganese or iron, an acetic acid salt of manganese or iron, a carbonic acid salt of manganese or iron, and a sulphuric acid salt of manganese or iron, and more preferably selected from a gluconic acid salt of manganese or iron, an acetic acid salt of manganese or iron, and a carbonic acid salt of manganese or iron. The composition according to embodiment 2, or any of embodiments 3, 11 or 12, wherein the redox buffer material is selected from a gluconic acid salt of manganese, an acetic acid salt of manganese, a carbonic acid salt of manganese, a sulphuric acid salt of manganese, and a manganese oxide, preferably selected from a gluconic acid salt of manganese, an acetic acid salt of manganese, a carbonic acid salt of manganese, and a sulphuric acid salt of manganese, and more preferably selected from a gluconic acid salt of manganese, an acetic acid salt of manganese, and a carbonic acid salt of manganese. The composition according to any of embodiments 1 to 13, wherein the redox buffer material is a gluconic acid salt of manganese or iron, preferably a gluconic acid salt of manganese, and more preferably manganese (II) gluconate. 15. The composition according to embodiment 1 , or any of embodiments 3 to 10 or 14 when dependent upon embodiment 1 , wherein the antioxidant is selected from an organic acid, organic alcohol, and esters of organic acids.

[0229] 16. The composition according to embodiment 15, embodiment 1 , or any of embodiments 3 to 10 or 14 when dependent upon claim 1 , wherein the antioxidant is an organic acid, preferably selected from tartaric acid, glycolic acid and mandelic acid, and more preferably selected from tartaric acid and glycolic acid.

[0230] 17. The composition according to embodiment 1 , or any of embodiments 3 to 16 where dependent thereon, wherein the ratio of the redox buffer material to antioxidant is from 5:1 to 1 :1 .

[0231] 18. A substrate comprising the composition of any of embodiments 1 to 17 applied thereon or incorporated therein.

[0232] 19. The substrate according to embodiment 18, wherein the substrate is a multi-layer substrate construction having the composition of any of embodiments 1 to 17 incorporated therein.

[0233] 20. The composition or substrate according to any of embodiments 1 to 19, wherein the composition displays a mark or image.

[0234] 21. A method of forming a substrate according to embodiment 18 or 19, the method comprising applying to a substrate or a substrate material of a multi-layer substrate construction, the composition of any of embodiments 1 to 17.

[0235] 22. A method of displaying a mark or image on a substrate according to embodiment 18 or 19, the method comprising exposing the composition to radiation, preferably using a laser source(s), to form a mark or image, and preferably wherein the radiation is applied at localised positions of the composition to selectively develop the mark or image. 23. Use of a redox buffer material in the formation of a mark or image of enhanced optical density on a substrate having the composition according to embodiment 2, or any of embodiments 11 , 12 or 14 where dependent thereon applied thereon, the composition comprising the redox buffer material and an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, wherein the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, a sulphuric acid multivalent metal salt, and a multivalent metal oxide.

[0236] 24. Use of a redox buffer material to control reaction stability and achieve formation of a mark or image on a substrate, preferably of enhanced optical density, having a composition according to embodiment 1 , or any of embodiments 3 to 16 where dependent thereon applied thereon.

Claims

CLAIMS1. A composition comprising:(a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof; and(b) a redox buffer material; wherein the redox buffer material is a multivalent metal salt selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, a sulphuric acid metal salt, and a multivalent metal oxide.

2. The composition according to claim 1 , wherein the redox buffer material is selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, a carbonic acid multivalent metal salt, and a sulphuric acid multivalent metal salt, preferably selected from a gluconic acid salt of manganese or iron, an acetic acid multivalent metal salt, and a carbonic acid multivalent metal salt.

3. The composition according to claim 1 or 2, wherein the redox buffer material is selected from a gluconic acid salt of manganese or iron, an acetic acid salt of manganese or iron, a carbonic acid salt of manganese or iron, a sulphuric acid salt of manganese or iron, and a manganese or iron oxide, preferably selected from a gluconic acid salt of manganese or iron, an acetic acid salt of manganese or iron, a carbonic acid salt of manganese or iron, and a sulphuric acid salt of manganese or iron, and more preferably selected from a gluconic acid salt of manganese or iron, an acetic acid salt of manganese or iron, and a carbonic acid salt of manganese or iron.

4. The composition according to any of claims 1 to 3, wherein the redox buffer material is selected from a gluconic acid salt of manganese, an acetic acid salt of manganese, a carbonic acid salt of manganese, a sulphuric acid salt of manganese, and a manganese oxide, preferablyselected from a gluconic acid salt of manganese, an acetic acid salt of manganese, a carbonic acid salt of manganese, and a sulphuric acid salt of manganese, and more preferably selected from a gluconic acid salt of manganese, an acetic acid salt of manganese, and a carbonic acid salt of manganese.

5. A composition comprising:(a) an oxyanion of a multivalent metal, or oxyacid, or hydrate thereof;(b) a redox buffer material; and(c) an antioxidant; wherein the redox buffer material is a multivalent metal salt.

6. The composition according to claim 5, wherein the redox buffer material is selected from an organic or inorganic acid multivalent metal salt, or a multivalent metal oxide, preferably selected from an organic or inorganic acid multivalent metal salt, and more preferably from an organic acid multivalent metal salt.

7. The composition according to claim 5 or 6, wherein the redox buffer material is selected from a multivalent metal carboxylate, an oxalic acid multivalent metal salt, a carbonic acid multivalent metal salt and a sulphuric acid multivalent metal salt, more preferably selected from a multivalent metal carboxylate, an oxalic acid multivalent metal salt and a carbonic acid multivalent metal salt, and more preferably a multivalent metal carboxylate.

8. The composition according any of claims 5 to 7, wherein the redox buffer material is selected from an organic or inorganic acid salt of manganese or iron, or a manganese or iron oxide, preferably an organic or inorganic acid salt of manganese or iron, and more preferably an organic acid salt of manganese or iron.

9. The composition according to claim 8, wherein the redox buffer material is selected from a manganese or iron carboxylate, an oxalic acid salt of manganese or iron, a carbonic acid salt of manganese or iron, and a sulphuric acid salt of manganese or iron, preferably selected from a manganese or iron carboxylate, an oxalic acid salt of manganese or iron and a carbonic acid salt of manganese or iron, and more preferably a manganese or iron carboxylate.

10. The composition according to claim 8 or 9, wherein the redox buffer material is selected from an organic or inorganic acid salt of manganese or a manganese oxide, preferably an organic or inorganic acid salt of manganese, and more preferably an organic acid salt of manganese.

11. The composition according to any of claims 8 to 10, wherein the redox buffer material is selected from a manganese carboxylate, an oxalic acid salt of manganese, a carbonic acid salt of manganese, and a sulphuric acid salt of manganese, preferably selected from a manganese carboxylate, an oxalic acid salt of manganese and a carbonic acid salt of manganese, and more preferably a manganese carboxylate.

12. The composition according to 5 to 7, wherein the redox buffer material is a multivalent metal carboxylate, preferably a gluconic acid metal salt.

13. The composition according to any of claims 5 to 12, wherein the antioxidant is selected from an organic acid, organic alcohol, and esters of organic acids.

14. The composition according to any of claims 5 to 13, wherein the antioxidant is an organic acid, preferably selected from tartaric acid, glycolic acid and mandelic acid, and more preferably selected from tartaric acid and glycolic acid.

15. The composition according to any of claims 5 to 14, wherein the ratio of the redox buffer material to antioxidant is from 5:1 to 1 :1 .

16. The composition according to any of claims 5 to 15, wherein the antioxidant is present in an amount of 0.1 wt% or more, preferably 0.25 wt% or more, more preferably 0.5 wt% or more, more preferably 0.75 wt% or more, more preferably 1 wt% or more, and more preferably 2 wt% or more of the composition.

17. The composition according to any of claims 5 to 16, wherein the antioxidant is present in an amount of from 0.1 to 17.5 wt%, preferably from 0.25 to 17.5 wt%, more preferably from 0.5 to 17.5 wt%, more preferably from 0.75 to 5 wt%, and more preferably from 1 to 5 wt% of the composition.

18. The composition according to any preceding claim, wherein the oxyanion of a multivalent metal or oxyacid, or hydrate thereof is present in an amount of from 1 to 70 wt%, preferably from 5 to 40 wt%, and more preferably from 10 to 40 wt%, of the composition.

19. The composition according to any preceding claim, wherein the oxyanion of a multivalent metal or oxyacid, or hydrate thereof is present in an amount of 1 wt% or more, preferably 5 wt% or more, more preferably 10 wt% or more, of the composition.

20. The composition according to any preceding claim, wherein the redox buffer material is present in an amount of 0.1 wt% or more, preferably 0.25 wt% or more, more preferably 0.5 wt% or more, more preferably 0.75 wt% or more, more preferably 1 wt% or more, and more preferably 2 wt% or more of the composition.

21. The composition according to any preceding claim, wherein the redox buffer material is present in an amount of from 0.1 to 35 wt%, preferably from 0.25 to 35 wt%, more preferably from 0.5 to 35 wt%, more preferably from 0.75 to 35 wt%, more preferably from 1 to 10 wt%, and more preferably from 2 to 10 wt% of the composition.

22. The composition according to any preceding claim, wherein the oxyanion of a multivalent metal, or oxyacid, or hydrate thereof, is an ammonium salt of an oxyanion of a multivalent metal, preferably an ammonium salt of an oxyanion of molybdenum, and more preferably ammonium octamolybdate (AOM).

23. The composition according to any preceding claim, wherein the redox buffer material is a gluconic acid salt of manganese or iron, preferably a gluconic acid salt of manganese, and more preferably manganese (II) gluconate.

24. A substrate comprising the composition of any of claims 1 to 23 applied thereon or incorporated therein.

25. The substrate according to claim 24, wherein the substrate is a multi-layer substrate construction having the composition of any of claims 1 to 23 incorporated therein.

26. The composition or substrate according to any of claims 1 to 25, wherein the composition displays a mark or image.

27. The substrate according to claim 24 or 25, wherein the composition applied thereon or incorporated therein displays a mark or image.

28. A method of forming a substrate according to claim 24 or 25, the method comprising applying to a substrate or a substrate material of a multi-layer substrate construction, the composition of any of claims 1 to 23.

29. A method of displaying a mark or image on a substrate according to claim 24 or 25, the method comprising exposing the composition to radiation, preferably using a laser source(s), to form a mark or image, and preferably wherein the radiation is applied at localised positions of the composition to selectively develop the mark or image.

30. Use of a redox buffer material in the formation of a mark or image of enhanced optical density on a substrate having the composition according to any of claims 1 to 4, or claims 18 to 23 where dependent thereon, applied thereon or incorporated therein.

31. Use of a redox buffer material to control reaction stability and achieve formation of a mark or image, preferably of enhanced optional density, on a substrate having a composition according to any of claims 5 to 17, or claims 18 to 23 where dependent thereon, applied thereon or incorporated therein.

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