AU2014256335B2 - Coating compositions for security elements and holograms - Google Patents

Abstract

The present invention relates to the use of coating compositions, comprising shaped transition metal, especially silver particles and a binder, wherein the ratio of pigment to binder is preferably such that the resulting coating shows an angle dependent colour change, for the production of security elements and holograms. When the coating compositions of the present invention are used in coating a hologram the obtained products show an angle dependent colour change (flip/flop effect), different colours in reflection and transmission, an extremely bright OVD image and extremely strong rainbow effect, high purity and contrast.

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant (s): BASF SE Invention Title: Coating compositions for security elements and holograms The following statement is a full description of this invention, including the best method for performing it know to me/us: 1a Coating Compositions for Security Elements and Holograms The present invention relates to the use of coating compositions, comprising shaped transition metal, especially silver, particles and a binder, wherein the ratio of pigment to binder is preferably such that the resulting coating shows an angle dependent colour 5 change, for the production of security elements and holograms. When the coating compositions of the present invention are used in coating a hologram the obtained products show a an angle dependent colour change (flip/flop effect), different colours in reflection and transmission, an extremely bright OVD image and extremely strong rainbow effect, high purity and contrast. io GB-A-1 , 465,908 (US41 16710) relates to a method for the preparation of particulate metal, such as aluminium, which method comprises depositing a metal coating on a substrate by vapor, electroless or sputter deposition and removing the metal coating from the substrate by dissolving the substrate in a solvent therefor, the thickness of the deposited coating be-ing such that upon dissolution of the substrate the metal is is released as a plurality of metal particles. The metal platelets obtained by the process have a thickness of from 20 to 100 nm, especially 35 to 60 nm. US4321087 discloses a continuous process for preparing finely divided metal particles comprising the steps of: (a) applying a release coating onto at least one side of a continuous carrier sheet in an amount of from 0.75 to 1.50 lbs. of said release coating 20 per side of said carrier sheet, (b) depositing in the form of a thin film, a metal selected from the group consisting of aluminum, chromium, copper, steel, silver and gold, in an amount of from 35 to 45 nm thickness directly onto said release coating, (c) passing said carrier sheet with said release coating and said film of said metal through a solvent for solubilizing said release coating but which is non-reactive with said metal, 25 (d) removing said film of said metal from said carrier sheet in a particulate form to produce the metal particles substantially free of said release coating, and collecting the metal particles in a non-reactive solvent which is non-reactive with said metal, (e) concentrating the metal particles, and (f) breaking the me-tal particles into pigment particles having a particle size diameter between about 25 and 50 microns. 30 W00024946 discloses a process for making flakes comprising: providing a vapor deposition chamber; placing a transport device in the vapor deposition chamber; providing a re-lease coat source and a vacuum deposition source in the vacuum deposition chamber directed toward the transport device, in which the deposition 58789961 (GHMatters) P94035AU.1 LISAW27/10/14 2 source deposits a layer of flake material; applying a vacuum to the chamber, and while the chamber is evacuated, apply-ing-alternate layers of a release coat from the release coat source and a vapor deposited flake layer from the vacuum deposition source to the transport device in sequence to build up a multi-layer sandwich of alternating flake s material layers and intervening release coat layers, the release coat layers comprising a dissolvable material that forms a smooth continuous barrier layer and support surface on which the flake material layers can be formed, so that removal of the sandwich from the evacuated chamber yields a multi-layer sandwich which can be easily separated into flakes of fine particle size by subsequent treatment with a io material that essentially completely dissolves the intervening release coat layers to remove them from the flakes. According to W00024946 another process for making metal flakes is a process of Avery Dennison Corporation for making flakes sold under the designation Metalure@. In this process both sides of a polyester carrier are gravure coated with a solvent is based resin solution. The dried coated web is then transported to a metallizing facility where both sides of the coated sheet are metallized by a thin film of vapor deposited aluminum. The sheet with the thin metal film is then returned to the coating facility where both sides of the aluminum are coated with a second film of the solvent-based resin solution. The dried coated/metal sheet is then transported again to the metallizing 20 facility to apply a second film of vapor deposited aluminum to both sides of the sheet. The resulting multi-layer sheet is then transported for further processing to a facility where the coatings are stripped from the carrier in a solvent such as acetone. The stripping operation breaks the continuous layer into particles con-tained in a slurry. The solvent dissolves the polymer out from between the metal layers in the slurry. The 25 slurry is then subjected to sonic treatment and centrifuging to remove the solvent and the dissolved coating, leaving a cake of concentrated aluminum flakes approximately 65% solids. The cake is then let down in a suitable vehicle and further sized by homogenizing into flakes of controlled size for use in inks, paints, and coatings. Metal flakes produced by this process for use in printable applications such as inks are 30 characterized by a particle size from about 4 to 12 microns and a thickness from about 150 to about 250 angstroms. W0020090613 as well as W003046245 discloses a process for the preparation of flakes having a high aspect ratio in which the flakes have an average particle size from 58789961 (GHMatters) P94035AU. 1 LESAW 27110114 3 about 4 to about 12 microns and a single layer thickness from about 5 to about 500 angstroms. W002/094945 relates to a method for the production of plane-parallel platelets, comprising the steps: 5 a) vapour-deposition, at a pressure below atmospheric pressure, of a separating agent onto a carrier to produce a separating agent layer, b) vapour-deposition, at a pressure below atmospheric pressure, of at least one product layer onto the separating agent layer, and c) dissolution of the separating agent layer in a solvent and production of a suspension io in which the at least one product layer is present in the form of plane-parallel platelets, in which method the separating agent is selected from the group consisting of anthracene, anthraquinone, acetamidophenol, acetylsalicylic acid, camphoric anhydride, benzimidazole, benzene-1 2,4-tricarboxylic acid, biphenyl-2,2-dicarboxylic acid, bis(4-hydroxyphenyl)sulfone, dihydroxyanthraquinone, hydantoin, 3 is hydroxybenzoic acid, 8-hydroxyquinoline-5-sulfonic acid monohydrate, 4 hydroxycoumarin, 7-hydroxycoumarin, 3-hydroxynaphthalene-2-carboxylic acid, isophthalic acid, 4,4-methylene-bis-3-hydroxynaphthalene-2-carboxylic acid, naphthalene- 1 8-dicarboxylic anhydride, phthalimide and its potassium salt, phenolphthalein, phenothiazine, saccharin and its salts, tetra-phenylmethane, 20 triphenylene, triphenylmethanol, and also mixtures of at least two of those substances. The planparall platelets obtained by said process have typically a thickness of 30 to 500 nm and a diameter of from 5 to 50 piri. W006/021528 relates to a process for the production of plane-parallel platelets, comprising the steps: 25 a) vapour-deposition of a separating agent onto a carrier to produce a separating agent layer, b) vapour-deposition of at least one product layer onto the separating agent layer, and c) dissolution of the separating agent layer in a solvent and production of a suspension in which the at least one product layer is present in the form of plane-parallel platelets, 30 wherein 58769961 (GHMatters) P94035.AU.1 LISAW 27/10114 4 the separating agent is selected from the group consisting of anthracene, anthraquinone, acetamidophenol, acetylsalicylic acid, camphoric anhydride, benzimidazole, benzene-1 ,2,4-tricarboxylic acid, biphenyl-2,2-dicarboxylic acid, bis(4 hydroxyphenyl)sulfone, dihydroxyan-thraquinone, hydantoin, 3-hydroxybenzoic acid, 8 5 hydroxyquinoline-5-sulfonic acid mono-hydrate, 4-hydroxycoumarin, 7 hydroxycoumarin, 3-hydroxynaphthalene-2-carboxylic acid, isophthalic acid, 4,4 methylene-bis-3-hydroxynaphthalene-2-carboxylic acid, naphthalene-1 ,8-dicarboxylic anhydride, phthalimide and its potassium salt, phenolphthalein, phenothi-azine, saccharin and its salts, tetraphenylmethane, triphenylene, triphenylmethanol, and also 10 mixtures of at least two of those substances, especially pentaerythritol (C(CH20H)4), trimesic acid (= 1 3,5 bezene tricarboxylic acid), DL-alanine, DL-valine, 2,6 diaminopurine, ascorbic acid, 1 ,3,5-benzenetricarboxylic acid, o-acetylsalicyclic acid, diphenic acid, terephthalic acid, pyrogallol, cyanuric acid, hexamethyltetramine (urotropin), fumaric acid, and 4-acetylbenzoic acid and also mixtures of at least two of is those substances. W007/057328 discloses a process for the production of plane-parallel platelets, comprising the steps: a) deposition of a separating agent I, which is dissolvable in water, onto a carrier to produce a separating agent layer, 20 b) vapour-deposition of a separating agent II, which is not dissolvable in water, onto the separating agent layer of step a), c) vapour-deposition of at least one product layer onto the separating agent layer of step b), and d) vapour-deposition of a separating agent II, which is not dissolvable in water, onto 25 the product layer of step c), e) dissolution of the separating agent layer of step a) in water and production of a suspension in which the at least one product layer is present in the form of plane parallel platelets, the top surface and the bottom surface, but not the side surfaces of which are covered by the separating agent II, and 30 f dissolution of the separating agent layer of steps b) and d) in a solvent and production of a suspension in which the product, comprising at least one layer, is present in the form of plane-parallel platelets. 58789961 (GHMaiters) P94035.AU.1 LISAW27110/14 5 The aluminium flakes described in W006/021528 and W007/057328 have an average diameter of at least 2 pm, especially from 2 to 20 pm, more especially from 3 to 15 pm, and most preferred from 5 to 15 pm. The thickness of the aluminium flakes is generally from 10 to 150 nm, especially from 10 to 100 nm, and more especially from 30 to 60 5 nm. W02005/051675 relates to a method for forming a (security) product comprising the steps of: a) providing a sheet of base material, said sheet having an upper and lower surface; b) depositing a metallic ink on at least a portion of the sheet of base material; and io c) forming a diffraction grating on at least a portion of the metallic ink, wherein the optical density of metallic ink when deposited is in the range of 0.2 to 0.8. The average pigment particle diameter is in the range 8-15 pm and the thickness of the pigment particles is in the range 10-50 nm, especially 19-21 nm. W02005/049745 discloses a coating composition for use in coating a diffraction 15 grating, comprising metal pigment particles and a binder wherein the ratio of pigment to binder is sufficiently high as to permit the alignment of the pigment particles to the contours of the diffraction grating. Preferably, the thickness of the pigment particles is less than 50 nm. More preferably, the thickness of pigment particle is less than 35 nm. More preferably still, the thickness of pigment particle is less than 20 nm. Even more 20 preferably still, the thick-ness of pigment particle is in the range 5-18 nm. In one embodiment of W02005/049745, the thickness of the pigment particles is in the range 10-50 nm. In another embodiment, the thickness of pigment particle is in the range 10 30 nm. In another embodiment, the average thickness of pigment particle is 17 nm. In another embodiment, the average thickness of pigment particle is 12.5 nm. 25 Summary In one embodiment, the present invention provides security, or decorative, element, comprising a substrate, which may contain indicia or other visible features in or on its surface, and which contains an optically variable images on it surface, and on at least part of the said substrate surface, a coating 6650718_1 (GHMatters) P94035.AU.1 INNAM 5a comprising platelet shaped transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 600 nm and 6650718_1 (GHMatters) P94035.AU.1 INNAM 6 particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably from 2 to 40 nm and particularly from 4 to 30 nm. Description The present invention provides coating compositions which can show an angle 5 dependent colour change (variation of color as a function of the viewing angle; flip/flop effect) as well as different colours in reflection and transmission, and, when used in printing holograms, results in (security) products which can show an angle dependent colour change (flip/flop effect), different colours in reflection and transmission, an extremely bright OVD image and extremely strong rainbow effect, high purity and/or 10 contrast. The coating compositions comprise shaped transition metal particles (pigment) having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 600 nm and particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably from 2 to 40 nm and particularly from 4 to 30 nm and a binder, wherein is the ratio of pigment to binder is such that the resulting coating shows an angle dependent colour change, i.e. a variation of color as a function of the viewing angle. The layer formed from the shaped transition metal particles exhibits "color shifting", meaning that the layer exhibits a change in color as the layer is viewed at different angles. Said "color shifting" is caused solely by the shaped transition metal particles 20 without the use of additional colorants. The resulting coating shows an angle dependent colour change, if the ratio of binder to shaped transition metal particles (pigment) is below 10: 1, especially below 5:1. The transition metal is selected from the group consisting of Cu, Ag, Au, Zn, Cd, Ti, Cr, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt. The transition metal is preferably Ag. 25 The shaped transition metal particles are typically in the form of nanoplatelets, trigonal and hexagonal nanoprisms, nanostars (branched particles), nanocubes, nanocrescents, nano-disks, nanowires, nanorods, nanohexagons, nanospheroids, nanocylinders, pyramids, vari-ous nanopolyhedra or hollow structures, or they are nanolens-shaped or nanocone-shaped, i.e. they differ from regular spheres. 30 The longest dimension of the edge length of the shaped transition metal particles may vary of from about 15 nm to about 1000 nm, preferably from 15 nm to 600 nm. The 5878961 {OHMatters) P94035.AU.1 LISAW 27/10114 7 thickness of the shaped particles may vary of from about 2 to about 100 nm, preferably from 2 to 30 nm. Preferably, the shaped transition metal particles are in the form of platelets having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 5 600 nm and particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably from 2 to 40 nm and particularly from 4 to 30 nm. More preferred, some of the shaped particles are in the form of trigonal and/or hexagonal prisms. Especially, the shaped particles may be obtained as a mixture of platelets of different shapes in which hexagonal and/or triangular and/or truncated triangular prisms make up more 10 than 20%, preferably more than 30% and in particular more than 50% of the total number of shaped transition metal parti-cles. The shaped particles are advantageously monocrystalline. The aspect ratio (longest dimension of edge length/thickness is at least 1.5, especially in the range of 1.5 to 300, very especially in the range of 1.5 to 125. 15 It is widely known to use in banknotes security elements in the form of strips or threads. Printing the inks (offset, gravure, flexo, ink jet, screen or intaglio inks) of the present invention directly on paper, or other substrates results in a coating showing an angle dependent colour change. This direct printing could replace the security elements in the form of strips or threads used in banknotes, which are made from a 20 transparent film provided with a con-tinuous reflective metal layer, vacuum deposited aluminium on polyester film being the commonest example. The effects obtainable by the coating compositions of the present invention are described on basis of coating compositions, comprising shaped silver particles, but are not limited thereto: 25 The colours in transmission and reflection are dependant on the light-absorption spectrum of the coating and the colour in reflection may be complementary to the colour in transmission in the physical sense. Generally, particles with higher aspect ratio and/or larger linear dimensions provide blue colour in transmission and, depending on pigment to binder ratio, silver, gold, bronze, copper or violet colour in 30 reflection. Particles with lower aspect ratio and/or smaller linear dimensions provide violet, magenta, pink, green or brown colour in transmission and, depending on pigment to binder ratio, various colours in reflection. For example, a blue colour is 58789961 (GHMatters) P94035.AU.1 LISAW 27/10/14 8 provided with silver particles obtained according to Examples 1 (aspect ratio of about 6-7) and 2 (aspect ratio above 10). The coating compositions comprise the shaped transition metal particles and a binder. The binder is a high-molecular-weight organic compound conventionally used in 5 coating compositions. The high molecular weight organic material for the pigmenting of which the pig-ments or pigment compositions according to the invention may be used may be of natural or synthetic origin. High molecular weight organic materials usually have molecular weights of about from 10 3 to 108 g/mol or even more. They may be, for example, natural resins, drying oils, rubber or casein, or natural substances derived 10 therefrom, such as chlorinated rubber, oil-modified alkyd resins, viscose, cellulose ethers or esters, such as ethylcellulose, cellulose acetate, cellulose propionate, cellulose acetobutyrate or nitrocellulose, but especially totally synthetic organic polymers (thermosetting plastics and thermoplastics), as are obtained by polymerisation, polycondensation or polyaddition. From the class of the polymerisation is resins there may be mentioned, especially, polyolefins, such as polyethylene, polypropylene or polyisobutylene, and also substituted polyolefins, such as polymerisation products of vinyl chloride, vinyl acetate, styrene, acrylonitrile, acrylic acid esters, methacry-lic acid esters or butadiene, and also copolymerisation products of the said monomers, such as especially ABS or EVA. 20 Advantageously, the coating composition further comprises a solvent. The binder may comprise any one or more selected from the group comprising nitrocellulose, ethyl cellulose, cellulose acetate, cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), alcohol soluble propionate (ASP), vinyl chloride, vinyl acetate copolymers, vinyl acetate, vinyl, acrylic, polyurethane, polyamide, rosin ester, 25 hydrocarbon, alde-hyde, ketone, urethane, polythyleneterephthalate, terpene phenol, polyolefin, silicone, cellulose, polyamide, polyester and rosin ester resins. An angle dependent colour change can be obtained at a pigment/binder ratio of about 10:1 to about 1 :10, whereas a pigment/binder ratio of > 10: 1 results in silver coloured coatings and a pigment/binder ratio of < 1 :10 results in the loss of visible reflection. 30 The coating composition is preferably a printing ink. The ink according to the present invention comprises, as in the case of an ordinary printing ink, the shaped transition metal particles, a binder, an auxiliary agent, and the like. 5878996,_1 (GHMatlers) P94035AU.1 USAW 27/10/14 9 With respect to the binder resin, a thermoplastic resin may be used, examples of which include, polyethylene based polymers [polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), vinyl chloride-vinyl acetate copolymer, vinyl alcohol-vinyl acetate copolymer, polypropylene (PP), vinyl based polymers [polyvinyl chloride) (PVC), 5 polyvinyl butyral) (PVB), polyvinyl alcohol) (PVA), poly(vinylidene chloride) (PVdC), polyvinyl acetate) (PVAc), polyvinyl formal) (PVF)], polystyrene based polymers [polystyrene (PS), styrene acrylonitrile copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS)], acrylic based polymers [poly(methyl methacrylate) (PMMA), MMA-styrene copolymer], 10 polycarbonate (PC), celluloses [ethyl cellulose (EC), cellulose acetate (CA), propyl cellulose (CP), cellulose acetate butyrate (CAB), cellulose nitrate (CN)], fluorin based polymers [polychlorofluoro-ethylene (PCTFE), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer (FEP), poly(vinylidene fluoride) (PVdF)], urethane based polymers (PU), nylons [type 6, type 66, type 610, type 11], is polyesters (alkyl) [polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexane terephthalate (PCT)], novolac type phenolic resins, or the like. In addition, thermosetting resins such as resol type phenolic resin, a urea resin, a melamine resin, a polyurethane resin, an epoxy resin, an unsaturated polyester and the like, and natural resins such as protein, gum, shellac, copal, starch and rosin may 20 also be used. Furthermore, to the binder, a plasticizer for stabilizing the flexibility and strength of the print film and a solvent for adjusting the viscosity and drying property thereof may be added according to the needs therefor. The solvent may comprise any one or more of an ester, such as n-propyl acetate, iso-propyl acetate, ethyl acetate, butyl acetate; an 25 alcohol, such as ethyl alcohol, industrial methylated spirits, isopropyl alcohol or normal propyl alcohol; a ketone, such as methyl ethyl ketone or acetone; an aromatic hydrocarbon, such as xylene and toluene. A solvent of a low boiling temperature of about 100*C and a petroleum solvent of a high boiling temperature of 250*C or higher, may be used according to the type of the printing method. An alkylbenzene or the like, 30 for example may be used as a solvent of a low boiling temperature. Examples of solvents are ethoxypropanol, methylethylketon, me-thoxypropylacetate, diacetonalcohol etc. Further in addition, an auxiliary agent including a variety of reactive agents for improving drying property, viscosity, and dispersibility, may suitably be added. The 58789961 (GHMatters) P94035.AU.1 LISAW 27110/14 10 auxiliary agents are to adjust the performance of the ink, and for example, a compound that improves the abrasion resistance of the ink surface and a drying agent that accelerates the drying of the ink, and the like may be employed. A photopolymerization-curable resin or an electron beam curable resin wherein a 5 solvent is not used may also be employed as a binder resin that is a principal component of the vehi-cle. The examples thereof include an acrylic resin, and specific examples of acrylic monomers commercially available are shown below. A monofunctional acrylate monomer that may be used includes for example, 2 ethylhexyl acrylate, 2-ethylhexyl-EO adduct acrylate, ethoxydiethylene glycol acrylate, 10 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate caprolactone addduct, 2-phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, nonyl phenol-EO adduct acrylate, (nonyl phenol-EO adduct)-caprolactone adduct acrylate, 2-hydroxy-3-phenoxypropyl acrylate, tetrahydrofurfuryl acrylate, furfuryl alcohol-caprolactone adduct acrylate, acryloyl morpholine, dicyclopentenyl acrylate, is dicyclopentanyl acrylate, dicyclopentenyloxyethyl acrylate, isobornyl acrylate, (4,4 dimethyl-1 ,3-dioxane)-caprolactone adduct acrylate, (3-methyl-5,5-dimethyl-1 3 dioxane)-caprolactone adduct acrylate, and the like. A polyfunctional acrylate monomer that may be used includes hexanediol diacrylate, neo-pentyl glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol 20 diacrylate, neo-pentyl glycol hydroxypivalate diacrylate, (neopentyl glycol hydroxypivalate)-caprolactone adduct diacrylate, (1 ,6-hexanediol diglycidyl ether) acrylic acid adduct, (hydroxypivalalde-hyde-trimethylolpropane acetal) diacrylate, 2,2 bis[4-(acryloyloxydiethoxy)phenyl]propane, 2,2-bis[4 (acryloyloxydiethoxy)phenyl]methane, hydrogenated bisphenol A-ethylene oxide 25 adduct diacrylate, tricyclodecanedimethanol diacrylate, trimethylolpropane triacrylate, pen-taerithritol triacrylate, (trimethylolpropane-propylene oxide) adduct triacrylate, glycerine-propylene oxide adduct triacrylate, a mixture of dipentaerithritol hexaacrylate and pen-taacrylate, esters of dipentaerithritol and lower fatty acid and acrylic acid, dipentaerithritol-caprolactone adduct acrylate, tris(acryloyloxyethyl) isocyanurate, 2 30 acryloyloxyethyl phos-phate, and the like. Inks comprising the above resins are free of solvent and are so constituted as to polymerize in chain reaction upon irradiation by an electron beam or electromagnetic waves. 55789961 {GHMatters) P94035.AU-1 LISAW 27/10/14 11 With respect to inks of ultraviolet-irradiation type among these inks, a photopolymerization initiator, and depending on the needs therefor, a sensitizing agent, and auxiliary agents such as a polymerization inhibitor and a chain transfer agent, and the like may be added thereto. 5 With respect to photo-polymerization initiators, there are, (1) an initiator of direct photolysis type including an arylalkyl ketone, an oxime ketone, an acylphosphine oxide, or the like, (2) an initiator of radical polymerization reaction type including a benzophenone derivative, a thioxanthone derivative, or the like, (3) an initiator of cationic polymerization reaction type including an aryl diazonium salt, an aryl lodinium 10 salt, an aryl sulfonium salt, and an aryl acetophenone salt, or the like, and in addition, (4) an initiator of energy transfer type, (5) an initiator of photoredox type, (6) an initiator of electron transfer type, and the like. With respect to the inks of electron beam-curable type, a photopolymerization initiator is not necessary and a resin of the same type as in the case of the ultraviolet-irradiation type inks can be used, and various kinds of is auxiliary agent may be added thereto according to the needs therefor. The inks comprise a total content of shaped transition metal particles of from 0.1 to 90 % by weight, preferably 0.1-70% by weight based on the total weight of the ink. Preferably, the binder comprises 50% nitrocellulose in conjunction with any above mentioned resin. 20 The composition may additionally comprise a solvent. The solvent may be ester/alcohol blends and preferably normal propyl acetate and ethanol. More preferably, the ester/alcohol blend is in a ratio of between 10: 1 and 40: 1 , even more preferably 20: 1 to 30: 1. The solvent used in the metallic ink may comprise any one or more of an ester, such 25 as n-propyl acetate, iso-propyl acetate, ethyl acetate, butyl acetate; an alcohol, such as ethyl alcohol, industrial methylated spirits, isopropyl alcohol or normal propyl alcohol; a ketone, such as methyl ethyl ketone or acetone; an aromatic hydrocarbon, such as toluene, and water. Preferably, the composition is used in the manufacture of a hologram. Reference is 30 made to W02005/051675 and W02008/061930. The method described therein for forming an optically variable image (an optically variable device) on a substrate comprises the steps of: a) forming an optically variable image (OVI) on a discrete 58789961 (GHMatters) P94035.AU.1 LISAW27 0/14 12 portion of the substrate; and b) depositing a coating composition, especially a metallic ink, comprising platelet shaped transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 600 nm and particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably s from 2 to 40 nm and particularly from 4 to 30 nm and a binder on at least a portion of the OVI. Preferably, step a) comprises al) applying a curable compound to at least a portion of the substrate; a2) contacting at least a portion of the curable compound with OVI forming means; and 10 a3) curing the curable compound. Referring to Fig. I of W008/061930, paper, aluminium, or another opaque substrates (1) is printed with an ultra violet curable lacquer (2) on its lower surface. An optically variable device or other lens or engraved structure is cast (3) into the surface of the lacquer (2) with a clear shim (4) having the optically variable device or other lens or is engraved structure thereon. The optically variable device or other lens or engraved structure image is imparted into the lacquer and instantly cured (6) via an UV lamp disposed through the shim (4) at normal processing speeds through polarizing lens (8), quartz roller (6), and clear polycar-bonate roller (5). The optically variable device or other lens or engraved structure image is a facsimile of the image on the clear shim. 20 Metallic ink (9) is printed (10) over the optically variable device or other lens or engraved structure and causes the optically variable device or other lens or engraved structure to become light reflective. Further colours (11 ) can be subsequently conventionally printed in-line at normal printing process speeds. In an alter-native embodiment, the paper, aluminium, and all manner of other opaque substrate (1) is 25 replaced with a filmic substrate. Such material is substantially transparent and therefore the image is visible from both sides of the surface. The (security) product obtainable by using the above method is new and forms a further subject of the present application. In said embodiment (security) product comprises a substrate, an UV cured lacquer, 30 holographic or other sub-microscopic diffraction gratings engraved into the UV cured lacquer and a metallic coating on the engraved UV cured lacquer on at least portion of the sub-strate. 58789961 (GHMatters) P94035 AU. 1 USAW 27/10/14 13 Referring to Fig. 12 of W008/061930 a film substrate 100, UV cured lacquer 102 and holographic or other sub-microscopic diffraction grating 104 with metallic ink 106 printed over with both first 108 and second surfaces 1 10 viewable. Referring to Fig. 13 of W008/061930 a paper substrate 120, UV cured lacquer 122 s and holographic or other sub-microscopic diffraction grating 124 with metallic ink 126 printed over with the image viewable through the first surface 128 only. In a further preferred embodiment of the present invention a coloured, or metallic ink is deposited on a substrate, on which the optically variable image is formed; before forming the optically variable image on at least a portion of the coloured, or metallic io ink. The substrate may comprise any sheet material. The substrate may be opaque, substan-tially transparent or translucent, wherein the method described in W008/061930 is especially suited for substrates, which are opaque to UV light (non transparent). The substrate may comprise paper, leather, fabric such as silk, cotton, is tyvac, filmic material or metal, such as aluminium. The substrate may be in the form of one or more sheets or a web, The substrate may be mould made, woven, non-woven, cast, calendared, blown, extruded and/or biaxially extruded. The substrate may comprise paper, fabric, man made fibres and polymeric compounds. The substrate may comprise any one or more selected from the group comprising paper, papers 20 made from wood pulp or cotton or synthetic wood free fibres and board. The paper/board may be coated, calendared or machine glazed; coated, uncoated, mould made with cotton or denim content, Tyvac, linen, cotton, silk, leather, po lythyleneterephthalate, polypropylene propafilm, polyvinylchloride, rigid PVC, cellulose, triacetate, acetate polystyrene, polyethylene, nylon, acrylic and polytherimide board. 25 The polythyleneterephthalate substrate may be Melienex type film orientated polypropylene (obtainable from DuPont Films Willimington Delaware product ID Melinex HS-2). The substrates being transparent filmic or non transparent substrates like opaque plastic, paper including but not limited to banknote, voucher, passport, and any other 30 security or fiduciary documents, self adhesive stamp and excise seals, card, tobacco, pharmaceutical, computer software packaging and certificates of authentication, aluminium, and the like. 58789961 (GHMatters) P94035 AU 1 LISAW 27/1014 14 In a preferred embodiment of the present invention the substrate is a non-transparent (o-paque) sheet material, such as, for example, paper. In another preferred embodiment of the present invention the substrate is a transparent sheet material, such as, for example, polythyleneterephthalate. s The forming of an optically variable image on the substrate may comprise depositing a curable compound, or composition on at least a portion of the substrate, The composition, generally a coating or lacquer may be deposited by means of gravure, flexographic, ink jet and screen process printing. The curable lacquer may be cured by actinic radiations, preferably ultraviolet (U.V.) light or electron beam. Preferably, the 10 lacquer is UV cured. UV cur-ing lacquers can be obtained from BASF SE. The lacquers exposed to actinic radiations or electron beam used in the present invention are required to reach a solidified stage when they separate again from the imaging shim in order to keep the record in their upper layer of the sub-microscopic, holographic diffraction grating image or pattern (OVI). Particularly suitable for the is lacquers compositions are chemistries used in the radiation curable indus-tries in industrial coatings and graphic arts. Particularly suitable are compositions containing one or several photo-latent catalysts that will initiate polymerization of the exposed lacquer layer to actinic radiations. Particularly suitable for fast curing and conversion to a solid state are compositions comprising one or several monomers and oligomers 20 sensitive to free-radical polymerization, such as acrylates, methacrylates or monomers or/and oli-gomers, containing at least one ethylenically unsaturated group. Reference is made to pages 8 to 35 of W02008/061930. The UV lacquer may comprise an epoxy-acrylate from the CRAYNOR® Sartomer Europe range (10 to 60%) and one or several acrylates (monofunctional and 25 multifunctional), mo-nomers which are available from Sartomer Europe (20 to 90%) and one, or several photo-initiators (1 to 15%) such as Darocure@ 1173 and a levelling agent such as BYK@361 (0.01 to 1 %) from BYK Chemie. The curable composition is preferably deposited by means of gravure or flexographic printing. 30 The curable composition is preferably curable by means of an ultraviolet (U.V.) light or an electron beam. The curable composition can be coloured. 878996 1 (GHMatters) P94035.AUA LISAW27/10/14 15 The metallic ink may be applied to the substrate by means of conventional printing press such as gravure, rotogravure, flexographic, lithographic, offset, letterpress intaglio and/or screen process, or other printing process. in order that the hologram is clearly visible on both the first and second surface of a s clear filmic substrate and the first surface of a paper substrate, preferably, the metallic pigment particles are printed in such a way as to align themselves such that they follow and conform to the contours of the diffraction grating. To accomplish this alignment of metal pigment particles to the contours of the diffraction grating the ink (coating composition) preferably has a very low binder, a low io pigment content and a medium pigment to binder ratio and/or very thin pigment particles. A filmic substrate is printed conventionally with a number of coloured inks, using, for example, a Cerutti R950 printer (available from Cerrutti UK Long Hanborough Oxon.). The sub-strate is then printed with an ultra violet curable lacquer. An OVI is cast into 15 the surface of the curable composition with a shim having the OVI thereon, the holographic image is imparted into the lacquer and instantly cured via a UV lamp, becoming a facsimile of the OVI disposed on the shim. A metallic ink is printed over the OVI and causes the OVI to become light reflective, the OVI is visible on the first surface of a paper or other non-filmic substrate and both sides of the filmic substrate. 20 In another embodiment, the UV curable composition is replaced with an electronic beam curable composition and the UV lamp replaced with an electron beam emitting device. The ink preferably comprises low solids, high viscosity binders. Preferably, the pigment to binder ratio is in the range of 10 : 1 to 1: 10 by weight. More preferably, the pigment 25 to binder ratio is by weight in the range of 6 : 1 to 1 : 6, and even more preferably 4 : 1 to 1 : 4. Most preferably the pigment to binder ratio is from 3 : 1 to 1 : 3. The metal pigment content by weight of the composition may be less than 90%. Preferably the pigment content by weight of the composition is less than 70%, more preferably in the range of 0.1 % to 90%, even more preferably in the range 0.1 % to 30 70%. The binder may comprise any one or more selected from the group comprising nitro cellulose, vinyl chloride, vinyl acetate copolymers, vinyl, acrylic, urethane, 58789961 (GHMatters) P94035AU1 LISAW27/10114 16 polythyleneterephthalate, terpene phenol, polyolefin, silicone, cellulose, polyamide, polyester, rosin ester resins. The preferred binder is 50% nitrocellulose (ID nitrocellulose DHL120/170 and nitrocellulose DLX30/50 supplied by Nobel Industries) 50% polyurethane (ID Neorez U335 supplied by Avecia). The solvents may be 5 ester/alcohol blends and preferably normal propyl acetate and ethanol in a ratio of 20: 1 to 30: 1. The compositions of the present invention can be applied to holograms for use on substrates such as (security products), including banknotes, credit cards, identification documents like passports, identification cards, drivers licenses, or other verification 10 documents, pharmaceutical apparel, software, compact discs, tobacco packaging and other products or packaging prone to counterfeiting or forgery, to protect them from fraudulent conversion, diversion or imitation. Preferably, when the substrate carrying the metallised image or pattern is subsequently over-laid onto printed pictures and/or text, or the substrate is pre-printed is with pictures and/or text and the metallised image or pattern is deposited thereon those pre-printed features are visible through the substrate and/or the metallic composition coated diffraction grating or image. The coating compositions may be deposited on a diffraction grating disposed on a sub strate such as a substantially transparent, translucent, or opaque substrate. The 20 substrate may comprise paper, filmic material or metal, such as aluminium. The substrate may comprise polymeric compounds. The substrate may comprise papers made from wood pulp or cotton or synthetic wood-free fibres. The diffraction grating may be formed using any methods known to the skilled man such as those described in US4,913,858, US5,164,227, W02005/051675 and 25 W02008/061930. The coating composition may be applied to the substrate by means of conventional printing press such as gravure, rotogravure, flexographic, lithographic, offset, letterpress intaglio and/or screen process, or other printing process. Preferably, when the substrate carrying the enhanced diffractive image or pattern is 30 subsequently over-laid onto printed pictures and/or text, or the substrate is pre-printed with pictures and/or text and the enhanced diffractive image or pattern is deposited 58789961 (GHMatters) P94035 AU LISAW 27/10114 17 thereon, those printed features are visible through the substrate and/or the metallic ink coated diffraction grating or image. By varying the film-weight and density of the deposited metallic ink, the transmission of light through the enhanced image can be adjusted to provide a desirable range of s visual effects. The composition may further comprise modifying additives, for example colorants and/or suitable solvent (s). Preferably, the resin maintains adhesion of the composition to the surface of the diffraction grating. io Specific additives can be added to the composition to modify its chemicals and/or physical properties. Polychromatic effects can be achieved by the introduction of (colored) inorganic and/or organic pigments and/or solvent soluble dyestuffs into the ink, to achieve a range of coloured shades. By addition of a dye the transmission colour can be influenced. By the addition of fluorescent, or phosphorescent materials 15 the transmission and/or the reflection colour can be influenced. Suitable colored pigments especially include organic pigments selected from the group consisting of azo, azomethine, methine, anthraquinone, phthalocyanine, perinone, pery-lene, diketopyrrolopyrrole, thioindigo, dioxazine iminoisoindoline, dioxazine, iminoisoindoli-none, quinacridone, flavanthrone, indanthrone, anthrapyrimidine and 20 quinophthalone pigments, or a mixture or solid solution thereof; especially a dioxazine, diketopyrrolopyrrole, quinacridone, phthalocyanine, indanthrone or iminoisoindolinone pigment, or a mixture or solid solution thereof. Colored organic pigments of particular interest include C.I. Pigment Red 202, C.I. Pigment Red 122, C.I. Pigment Red 179, C.i. Pigment Red 170, C.I. Pigment Red 144, 25 C.1. Pigment Red 177, C.1. Pigment Red 254, C.1. Pigment Red 255, C.,1. Pigment Red 264, C.1. Pigment Brown 23, C.1. Pigment Yellow 109, C.1. Pigment Yellow 110, C.1. Pigment Yellow 147, C.1. Pigment Orange 61 , C.I. Pigment Orange 71 , C.I. Pigment Orange 73, C.I. Pigment Orange 48, C.I. Pigment Orange 49, C.I. Pigment Blue 15, C.I. Pigment Blue 60, C.I. Pigment Violet 23, C.I. Pigment Violet 37, C.I. Pigment Violet 30 19, C.I. Pigment Green 7, C.I. Pigment Green 36, the 2,9-dichloro-quinacridone in platelet form described in WO08/055807, or a mixture or solid solution thereof. 58789961 (GHMatters} P94035,AU.1 LISAW 27/10114 18 Plateletlike organic pigments, such as plateletlike quinacridones, phthalocyanine, fluororubine, dioxazines, red perylenes or diketopyrrolopyrroles can advantageously be used. Suitable colored pigments also include conventional inorganic pigments; especially s those selected from the group consisting of metal oxides, antimony yellow, lead chromate, lead chromate sulfate, lead molybdate, ultramarine blue, cobalt blue, manganese blue, chrome oxide green, hydrated chrome oxide green, cobalt green and metal sulfides, such as cerium or cadmium sulfide, cadmium sulfoselenides, zinc ferrite, bismuth vanadate, Prussian blue, Fe30 4 , carbon black and mixed metal oxides, io Examples of dyes, which can be used to color the curable composition, are selected from the group consisting of azo, azomethine, methine, anthraquinone, phthalocyanine, dioxaz-ine, flavanthrone, indanthrone, anthrapyrimidine and metal complex dyes. Monoazo dyes, cobalt complex dyes, chrome complex dyes, anthraquinone dyes and copper phthalocyanine dyes are preferred. 15 It is possible to generate striking colour effects by combining shaped, especially plateletlike and spherical silver particles having a diameter in the range of from 3 to 40 nm. Refer-ence is made to Example 7 of the present application. Hence, in a preferred embodiment of the present invention the coating composition comprises besides platelet-like transition metal (silver) particles spherical transition 20 metall (silver) particles having a diameter in the range of from 3 to 40 nm, wherein up to 40 % of the transition metal (silver) particles can be spherical. The binder resins may be initially dissolved in the appropriate solvent(s) to form liquid varnishes. These varnishes can then be blended together with the metallic pigment and/or other components by means of a high-speed blender to produce the 25 composition. In accordance with a further aspect of the present invention, there is provided a metallic ink comprising shaped transition metal particles (pigment) and a binder. The ratio of pigment to binder is sufficiently high as to permit the alignment of the metal particles to the contours of a diffraction grating. 30 The shaped transition metal particles may be prepared by any means known to the skilled man. For example, US2008/0295646 describes a thermal method of preparing metal, in particular silver nanoprisms having a unimodal size distribution and a 58789961 (GHMatters} P94035AU.1 LISAW 27/10/14 19 predetermined thickness in the form of a colloidal suspension. A photochemical method of preparing silver nanoprisms of controlled edge length through wavelength modulation is described in W02004/089813. W02006/099312 describes the synthesis of gold nanoprisms. Silica-coated silver prisms which can be dispersed in a variety of s organic solvents are described in C. Xue et al., Adv. Mater. 19, 2007, 4071. W02009056401 describes nano-shaped transition metal particles, in particular nanoplate-lets, characterized by a surface plasmon resonance in the near infrared (NIR) range and their preparation. These particles are used as IR absorbers in heat shielding architectural, automotive glazing or agricultural films, laser welding, laser io printing, security printing and near infrared curing of coatings. The shaped transition metal particles may be prepared by any means known to the person skilled in the art. Reference is, for example, made to W02010/108837. The method of manufacturing shaped transition metal particles, selected from the group consisting of Cu, Ag, Au, Zn, Cd, Ti, Cr, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt, is comprises the steps of first a) generating isotropic spherical metal nanoparticles by mixing a solution of reducing agent with an aqueous mixture comprising a transition metal salt in a concentration of higher than 2 mmol per liter and a polymeric dispersant and/or capping agent, and b) inducing controlled agglomeration of said isotropic nanoparticles by treatment with a peroxide, leading to formation of platelet-shaped 20 metallic nano- or micro-particles. The transition metal is preferably Ag, Cu, Pd or Au, more preferably Ag. The shaped particles may also be made from two of the above-mentioned transition metals to form core-shell or alloy type particles, for example as described in W007103536. Suitable examples of silver salts of mono-, di-, tri- or polycarboxylic acids include silver 25 salts of acetic acid, propionic acid, 4-cyclohexyl butyric acid, oxalic acid, malonic acid, succinic acid, malic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, citric acid and polyacrylic acid. Suitable examples of silver salts of sulfonic or polysulfonic acids include silver salts of methane sulfonic acid, trifluormethane sulfonic acid, vinyl sulfonic acid, benzene 30 sulfonic acid, toluene sulfonic acid, styrene sulfonic acid and sulfonated polystyrene. Suitable examples of silver salts of P-containing acids include silver salts of phosphoric acid, metaphosphoric acid, phosphorous acid, pyrophosphoric acid, hypophosphoric 58789961 (GHMatters) P94035AU.1 LISAW 2711O14 20 acid and organo-substituted derivatives thereof, phenol-phosphate resins, polyacrylic phosphates and phosphonates. Preferred silver(l) salts are AgNO 3 , Ag 2 0, AgCl0 4 , Ag 2

SO

4 , CH 3 C0 2 Ag, mono-, di- or tris ilver citrate, Ch SOsAg, CFsSOsAg, wherein AgN03, CH3C02Ag and Ag 2 0 are more s preferred. Examples of suitable gold salts are KAu(CN) 2 ; Aul; AuBr; AuCl; R'C0 2 Au, wherein R' has the same meaning, as described for R'C0 2 Ag; HAuCl 4 ; AuBr 3 ; AuBr 4 K; AuBr 4 Na; AuC ; AuCI 4 K; AuCl 4 Li; AuCl 4 Na and mixtures thereof, wherein HAuC 4 is preferred. Examples of suitable copper salts are Cu(NOs) 2 ; KCu(CN) 2 ; copper(II)acetylacetonate; 10 Cu(R'C0 2

)

2 , wherein R 1 has the same meaning, as described for R 1 0 2 Ag; Cu(C104) 2 ; CuBr, CuBr 2 , CuCI, CuC1 2 , Cul, CuSO 4 and mixtures thereof. The dispersant may be any polymer which prevents agglomeration or aggregation of the spherical and shaped particles. The dispersant may be a non-ionic, anionic or cationic polymer having a weight average molecular weight of from 500 to 2,000,000 15 g/mol, preferably from 1500 to 1 ,000,000, which forms a solution or emulsion in the aqueous mixture. Typically, the polymers may contain polar groups. Suitable polymeric dispersants often possess a two-component structure comprising a polymeric chain and an anchoring group. The particular combination of these leads to their effectiveness. 20 Suitable commercially available polymeric dispersants are, for example, EFKA* 4046, 4047, 4060, 4300, 4330, 4580, 4585, 8512, Disperbyk* 161 , 162, 163, 164, 165, 166, 168, 169, 170, 2000, 2001 , 2050, 2090, 2091 , 2095, 2096, 2105, 2150, Ajinomoto Fine Techno's PB* 71 1 , 821 , 822, 823, 824, 827, Lubrizol's Solsperse* 24000, 31845, 32500, 32550, 32600, 33500, 34750, 36000, 36600, 37500, 39000,41090, 25 44000, 53095, ALBRITECT* CP30 (a copolymer of acrylic acid and acrylphosphonate) and combinations thereof. Preference is given to polymers derived from hydroxyalkyl(meth)acrylates and/or polyglycol (meth)acrylates, such as hydroxyethyl and hydroxypropyl (meth)acrylate, polyethylene glycol (meth)acrylates, (meth)acrylates having amine functionality, for 30 example, N-[3-(dimethylamino)propyl](meth)acrylamide or 2-(N,N dimethylamino)ethyl(meth)acrylate. 5878996_1 (GHMatters) P94035.AU1 LISAW 27/10/14 21 In particular, non-ionic copolymer dispersants having amine functionality are preferred. Such dispersants are commercially available, for example as EFKA@ 4300, EFKA@ 4580 or EFKA 4585, The polymeric dispersants may be used alone or in admixture of two or more. s Suitable reducing agents may be selected from the group consisting of boranes and complexes thereof, metal boranates, hydrides, aluminates, aldehydes, carboxylic acids, hydra-zines, hydrosulfites, stannanes, stannates, silanes, phosphines, phosphites and siloxanes. Preference is given to sodium borohydride, borane complexes with sulfides and 10 amines, hydrazine and ascorbic acid. Examples of suitable peroxides are selected from the group consisting of H202, d Csalkyl peroxyacids, e.g. peracetic acid, acetyl cyclohexane sulfonyl peroxide, diisopropyl peroxy-dicarbonate, tert-amyl perneodecanoate, tert-butyl perneodecanoate, tert-butyl perpivalate, tert-amylperpivalate, bis(2,4 15 dichlorobenzoyl)peroxide, diisononanoyl peroxide, didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, bis(2-methylbenzoyl)peroxide, disuccinic acid peroxide, diacetyl peroxide, dibenzoyl peroxide, tert-butyl per-2-ethylhexanoate, bis(4 chlorobenzoyl)-peroxide, tert-butyl perisobutyrate, tert-butyl permaleinate, 1 ,1-bis(tert butylperoxy)3,5,5-trimethylcyclohexane, 1 ,1 -bis(tert-butylperoxy)cyclohexane, tert 20 butyl peroxy isopropylcarbonate, tert-butyl perisononaoate, 2,5-dimethylhexane 2,5 dibenzoate, tert-butyl peracetate, tert-amyl perbenzoate, tert-butyl perbenzoate, 2,2 bis(tert-butylperoxy)butane, 2,2 bis(tert-butylperoxy) propane, dicumyl peroxide, 2,5 dimethylhexane-2,5-di-tert-butylperoxide, 3-tert-butylperoxy 3-phenylphthalide, di-tert amyl peroxide, a,a'-bis(tert-butylperoxyisopropyl)benzene, 3,5-bis (t-butylperoxy)3,5 25 dimethyl 1 2-dioxolane, di-tert-butylperoxide, 2,5-dimethylhexyne-2,5-di-tert butylperoxide and 3,3,6,6,9,9-hexamethyl-1 ,2,4,5-tetraoxacyclononane, wherein H202 is preferred. Optionally, the mixture of step a) of the present invention contains a capping agent. If present, the capping agent is typically used in a concentration up to 1 M, preferably 30 from 0.001 to 100 mM. Examples of suitable capping agents include mono- and polycarboxylic acids (e.g. citric acid, ethylenediamine tetraacetic acid, propionic acid) and salts thereof (e.g. 58789961 (GHMaUers) P94035.AU.1 USAW27/10/14 22 sodium citrate, sodium salts of ethylenediamine tetraacetic acid, sodium propionate), sulphur-containing compounds, such as thiols (e.g. mercaptoethanol, dithiothreitol, mercaptopolyethylenegly-col), linear and cyclic disulfides (e.g. cystamine, mercaptoethanol disulfide, cyclo-dithiothreitol), xanthates (e.g. sodium s ethylxanthogenate), dithiocarbamates (e.g. diethyl-ammonium salt of diethyldithiocarbamic acid) and the like, amines (e.g. ammonia, amino-ethanol, methylamine) and aminocarboxylic acids (e.g. aminoacetic acid, 2-aminopropionic acid, 3-aminopropionic acid). The process of platelet-shaped particles manufacture is preferably carried out by 10 dissolving or dispersing the transition metal salt in water in concentration of >0.2 % by weight in the presence of a dispersant and optionally at least one of abovementioned water-soluble capping agents and dissolving or dispersing the reducing agent and optionally at least one of abovementioned water-soluble capping agents in water. The resulting solutions or disper-sions are held at a temperature of less than 20*C, is preferably they are cooled down to 5*C or less, e.g. about 0 to 50C. These two solutions are mixed either by addition of one solution to another, or, preferably, they are mixed by pumping both solutions into a mixing chamber, said chamber having additional outlet to collect the resulting dispersion of spherical nanoparticles. The simplest example of such a mixing chamber is a three-way connec-tor of any shape. 20 Upon completion of the metal salt reduction, the >20% by weight solution of hydrogen peroxide in water is slowly added to the dispersion of spherical metal nanoparticles with stirring until the desired spectral profile of reaction mixture is achieved. The step of peroxide addition may be performed at a temperature of from about 0*C to about 100*C. Preferably, the peroxide is added at a temperature of from 20 to 70*C, more 25 preferably from 30 to 600C. The as prepared platelet-shaped metal particles are isolated by any means, known to a person skilled in the art, e.g. reversible agglomeration using appropriate surface-modifying agents and/or by centrifugation and/or by extraction with organic solvent. The shaped particles may show NIR absorption, which characteristic might represent 30 an additional security feature. The coating composition, especially metallic ink of the present invention can also be used in the production of a hot stamping foil. 58789961 (GHMatters) P94035,AU-1 LISAW 27/10/14 23 Accordingly, the present invention is also directed to a method of producing a hot stamping foil comprising the steps of: (a) coating a carrier with a release coating, (b) applying a coating of a hard lacquer onto the release coating, 5 (c) applying an ultraviolet primer coating onto the coating of the hard lacquer, (d) contacting at least a portion of the ultraviolet primer coating with optically variable image (optically variable device) forming means; (e) depositing a coating composition comprising platelet shaped transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm, io preferably from 15 nm to 600 nm and particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably from 2 to 40 nm and particularly from 4 to 30 nm and a binder, especially a printing ink to the UV primer holding the transferred optically variable device either as a whole or in partial areas, (f) optionally printing subsequently process colours, and is (g) applying a heat activated adhesive onto the layer obtained in step e), or f). Examples of the release compound are silica, microcrystalline wax, rice wax, oricuri wax, stearic acid esters, polyglycols, and metallic salts of fatty acids. Examples of the coating of the hard lacquer are polymethylmethacrylate, styrene acryloni-trile, polyethyleneterephthalate, nitrocellulose, or mixtures thereof. The coating 20 of the hard lacquer affixed to said release coating has in general a thickness in the range 0.25 microns to 9 microns and has a glass transition temperature of at least 70 *C. Examples of the adhesive compound are vinyl alcohol, polyacrylates, polyalkacrylates, vinyl resins, polyvinyl acetate, cellulose resins, polyacrylamides, and ethylene/vinyl 25 acetate copolymers. Under the present invention a carrier film substrate having the thickness on the order of 12 microns to 75 microns and formed of a suitable plastic material such as a polyester, oriented polypropylene or other suitable material is coated with a release coating such as a microcrystalline wax or a partially saponified montan wax or other 58789961 (GHMatters) P94035.AU.1 LISAW 27/10/14 24 wax based coatings having a thickness in the range of 0.025 microns to 5 microns and then has a coating of hard lacquer applied over the release coating in a thickness in the range of 0.25 microns to 10 microns. The hard lacquer coating may be applied by a gravure roller following which is dried an ultraviolet primer coating having the thickness 5 in a range of 0.3 microns to 9 microns is then applied by means of a gravure roller. An optically variable device is contacted by the embossing shim having an optically variable device thereon and is transferred into the surface of the UV lacquer and cured by UV light. A layer of the vacuum metallic ink is applied to the UV primer holding the transferred optically variable device either as a whole or in partial areas. Subsequent io process colours can be gravure printed. The hot stamping foil obtained in the above process can be used to label an article of manufacture. The method of labeling the article of manufacture comprises the steps of: con-tacting the heat activated adhesive layer of the hot stamping foil obtained according to the above process with said article; hot stamping said hot stamping foil to is cause said heat activated adhesive layer to adhere to said article; and removing the carrier of said hot stamping foil from said hard lacquer layer. The optically variable device (OVD) is, for example, an diffractive optical variable image (DOVI). The term "diffractive optical variable image" as used herein may refer to any type of holograms including, for example, but not limited to a multiple plane 20 hologram (e.g., 2-dimensional hologram, 3-dimensional hologram, etc.), a stereogram, and a grating image (e.g., dot-matrix, pixelgram, exelgram, kinegram, etc.). Examples of an optically variable image or device are holograms or diffraction gratings, moire grating, etc. These optical microstructured images are composed of a series of structured surfaces. These surfaces may have straight or curved profiles, with constant 25 or random spacing, and may even vary from microns to millimetres in dimension. Patterns may be circular, linear, or have no uniform pattern. For example a Fresnel lens has a micro-structured surface on one side and a pano surface on the other. The microstructured surface consists of a series of grooves with changing slope angles as the distance from the optical axis increases. The draft facets located between the slope 30 facets usually do not affect the optical performance of the Fresnel lens. Another aspect of the present invention is directed to a decorative, or security element, especially a security element which displays a more evident visual colour change and which can easily be checked by the "man on the street". 58789961 (GHMatters) P94035.AUA LISAW 27/10/14 25 Accordingly, the present invention relates to a security element, especially for a document of value, right, identity, for a security label or a branded good, comprising a substrate, which may contain indicia or other visible features in or on its surface, and on at least part of the said substrate surface, a coating comprising platelet shaped 5 transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm, preferably from 15 nm to 600 nm and particularly from 20 nm to 500 nm, and a thickness of from 2 nm to 100 nm, preferably from 2 to 40 nm and particularly from 4 to 30 nm. Preferably, the coating shows an angle dependent colour change. The colour change io is a "simple message of authenticity", which can be checked by the unaided human eye. At least part of a substrate is coated with a layer, comprising the platelet shaped transition metal particles. The coating comprising the platelet shaped transition metal particles can have a form, The form may be, for example, a symbol, a stripe, a 1s geometric form, a fancy emblem, a writing, an alphanumeric character, a depiction of an object, or a part thereof. The security element of the present invention can be used for the prevention of counterfeit or reproduction, on a document of value, right, identity, a security label or a branded good. Using coating compositions resulting in different colour flop the security 20 element according to invention can be so constructed that two adjacent portions of a coating show different colours depending on the viewing angles. In a preferred embodiment the first surface portion shows a first colour at a first viewing angle, while the second surface portion shows a second colour at the first viewing angle. At a second viewing angle the first surface portion shows the second colour and 25 the second surface portion shows the first colour. Preferably the colours used exhibit a high colour contrast. A method of producing the security element, comprises the steps of a) providing a substrate having a surface, which surface may contain indicia or other visible features; 30 b) applying, on top of at least part of the said substrate surface a coating, comprising the platelet shaped transition metal particles and a curable transparent binder, and (c) curing said coating layer. 58789961 (GHMalters) P9403S.AU.1 USAW 27/10/14 26 As decribed above, the surface of the substrate may have an OVI on its surface, or a layer on the substrate may have an OVI on its surface. The coating, comprising the platelet shaped transition metal particles and a curable transparent binder, is applied on top of at least part of the said OVI. 5 An object of value, right, identity, security label, branded good, can be tested for authenticity by checking whether a colour change in dependence from the viewing angle is present. Various aspects and features of the present invention will be further discussed in terms of the examples. The following examples are intended to illustrate various aspects and io features of the present invention, but not to limited the scope of the present invention. Examples Example 1 20 g of the copolymer prepared according to Example 2 from WO 2004/045755 A2 (40 w/w dispersion in water), 20 g of ethyleneglycol and 6 g of MPEG-5000-thiol are is dissolved in 1950 ml of de-ionized water in a thermostated 10 1 reactor, equipped with an efficient stirrer. After cooling to -1 *C, 10.2 g (60 mmol) of AgNO3 are added and the obtained solution is gently stirred for 15 min. 4.54 g (120 mmol) of NaBhU are dissolved in 1 I of de-ionized water in a separate vessel and cooled to 0"C. This solution is rapidly added in one portion to the above solution of AgNO3 with vigorous 20 stirring (500 rpm). The reaction mixture is vigorously stirred (500 rpm) for 5 min at 00C and then warmed up to 200C with gentle stirring over 1 h. 150 ml of H202 (50% w/w solution in water) is added at a rate of 3 ml/min to the mixture with vigorous stirring (350 rpm) to obtain a dark-blue dispersion of silver plate-lets. Water is evaporated to the volume of 200 ml, and the residual dispersion is centrifuged 25 at 8000 G for 30 min. The supernatant is decanted; the precipitate is rinsed with de ionized water (2x40 ml) and re-dispersed in 200 ml of I ,4-dioxan under ultra sonication. The dispersion is centrifuged at 8000 G, the supernatant is discarded and the precipitate is re-dispersed in EtOAc to obtain a dispersion of 6.3 g of silver platelets. 30 Example 2 Two solutions are prepared: 58789961 (GHMatters) P94035.AU.1 LISAW 27110/14 27 Solution A: 7 g of the copolymer prepared according to Example 2 from WO 20041045755 A2 (40% w/w dispersion in water) and 1.2 g of MPEG-5000-thiol are dissolved in 20 ml of de-ionized water and cooled to 0*C. Then, a solution of 2.04 g (12 mmol) of AgNCb in 23 ml of de-ionized water is added with stirring, and the resulting 5 mixture is cooled to 0*C. Solution B: 0.908 g (24 mmol) of NaBH 4 and 0.07 ml (ca. 1.15 mmol) of 28% w/w ammonia solution in water are dissolved in 49 ml of de-ionized water and cooled to 00C. Synthesis: Solutions A and B are pumped with equal flow rates (30 ml/min) into a io three-way connector (inner diameter of the inlets 1 mm). The resulting dispersion of spherical Ag particles is continuously drained from the third outlet (inner diameter 3 mm) of connector into a 1 I round-bottom flask, pre-cooled to 0*C, containing 0.05 ml of TEGO Foamex 1488 de-foamer and stirred for 10 min at this temperature. The mixture is then heated to 45*C and treated with 20 ml of H202 (50% w/w solution in is water) at a rate of 0.6 ml/min with vigorous stirring to obtain a dark-blue dispersion of silver platelets. The dispersion is centrifuged at 8000 G for 30 min, followed by decanting the supernatant and rinsing the precipitate with de-ionized water (2x40 imL). The precipitate is re-dispersed in 200 ml of 1 ,4-dioxan under ultra-sonication. The dispersion is centrifuged at 8000 G, the supernatant is discarded and the precipitate is 20 re-dispersed in EtOAc to obtain a dispersion of 1.23 g of silver platelets. Fig. 1 is a Transmission Electron Micrograph (TEM) of the irregularly-shaped silver platelets obtained in Example 2. Example 3 Two solutions are prepared: 25 Solution A: 8 g of the copolymer prepared according to Example 2 from WO 2004/045755 A2 (40% w/w dispersion in water) and 1.2 g of MPEG-5000-thiol are dissolved in 20 ml of de-ionized water and cooled to 0*C. Then, a solution of 2.04 g (12 mmol) of AgNO3 in 23 ml of de-ionized water is added with stirring, and the resulting mixture is cooled to 0*C. 30 Solution B: 0.908 g (24 mmol) of NaBH 4 and 0.07 ml (ca. 1.15 mmol) of 28% w/w ammonia solution in water are dissolved in 49 ml of de-ionized water and cooled to 00C. 58789961 (GHMatters) P94035.AU.1 LISAW27/1014 28 Synthesis: Solutions A and B are pumped with equal flow rates (30 ml/min) into a three-way connector (inner diameter of the inlets 1 mm). The resulting dispersion of spherical Ag par-tides is continuously drained from the third outlet (inner diameter 3 mm) of connector into a 1 1 round-bottom flask, pre-cooled to 0*C, containing 0.05 ml 5 of TEGO Foamex 1488 de-foamer and stirred for 10 min at this temperature. The mixture is then heated to 45*C and treated with 20 ml of H202 (50% w/w solution in water) at a rate of 0.6 ml/min with vigorous stirring to obtain a dark-blue dispersion of silver platelets. The dispersion is centrifuged at 8000 G for 30 min, followed by decanting the supernatant and rinsing the precipitate with de-ionized water (2x40 imL). 10 The precipitate is re-dispersed in 200 ml of 1 4-dioxan under ultra-sonication. The dispersion is centrifuged at 8000 G, the supernatant is discarded and the precipitate is re-dispersed in EtOAc to obtain a dispersion of 1.23 g of silver platelets. Example 4 Two solutions are prepared: is Solution A: 10 g of the copolymer prepared according to Example 2 from W02004/045755 (40% w/w dispersion in water) and 1.0 g of MPEG-5000-thiol are dissolved in 16 ml of de-ionized water and cooled to 0*C. Then, a solution of 1.70 g (10 mmol) of AgNCb in 23 ml of de-ionized water is added with stirring, and the resulting mixture is cooled to 0*C. 20 Solution B: 0.756 g (20 mmol) of NaBhU and 0.067 ml (1.0 mmol) of ethylenediamine are dissolved in 50 ml of de-ionized water and cooled to 0*C. Synthesis: Solutions A and B are pumped with equal flow rates (30 ml/min) into a three-way connector (inner diameter of the inlets 1 mm). The resulting dispersion of spherical silver particles is continuously drained from the third outlet (inner diameter 3 25 mm) of connector into a 1 I round-bottom flask, pre-cooled to 0*C, containing 0.05 ml of TEGO Foamex 1488 defoamer and stirred for 10 min at this temperature. The mixture is then heated to 40'C and treated with 20 ml of H202 (50% w/w solution in water) at a rate of 0.5 ml/min with vigorous stirring to obtain a violet dispersion of silver platelets. The dispersion is centrifuged at 10000 G for 30 min, followed by decanting 30 the supernatant and rinsing the precipitate with de-ionized water (2x40 imL). The precipitate is re-dispersed in 200 ml of 1 ,4-dioxan under ultra-sonication. The dispersion is centrifuged at 10000 G, the supernatant is discarded and the precipitate 5878996_1 (GHMalters) P94035.AU.1 LISAW 27/10/14 29 is re-dispersed in ethyl acetate (EtOAc) to obtain a dispersion of 1.02 g of silver platelets. Example 5 Two solutions are prepared: 9 Solution A: 10 g of the copolymer prepared according to Example 2 from WO 2004/045755 (40% w/w dispersion in water) and 1.0 g of MPEG-5000-thiol are dissolved in 16 ml of de-ionized water and cooled to 00C. Then, a solution of 1.70 g (10 mmol) of AgNCb in 23 ml of de-ionized water is added with stirring, and the resulting mixture is cooled to 0*C. io Solution B: 0.756 g (20 mmol) of NaBhU and 43 mg of polyethylene mine (Typical Mr 600, Typical M, 800) are dissolved in 50 ml of de-ionized water and cooled to 0 C. Synthesis: Solutions A and B are pumped with equal flow rates (30 ml/min) into a three-way connector (inner diameter of the inlets 1 mm). The resulting dispersion of spherical Ag particles is continuously drained from the third outlet (inner diameter 3 15 mm) of connector into a 1 I round-bottom flask, pre-cooled to 0*C, containing 0.06 ml of TEGO Foamex 1488 defoamer and stirred for 10 min at this temperature. The mixture is then heated to 40*C and treated with 8.5 ml of H202 (50% w/w solution in water) at a rate of 0.5 ml/min with vigorous stirring to obtain a magenta-colored dispersion of silver platelets. The dispersion is centrifuged at 10000 G for 30 min, 20 followed by decanting the supernatant and rinsing the precipitate with de-ionized water (2x40 imL). The precipitate is re-dispersed in 200 ml of 1 ,4-dioxan under ultra sonication. The dispersion is centrifuged at 10000 G, the supernatant is discarded and the precipitate is re-dispersed in EtOAc to obtain a dispersion of 1.02 g of silver platelets. 2S Example 6 Two solutions are prepared: Solution A: 7 g of the copolymer prepared according to Example 2 from WO 2004/045755 A2 (40% w/w dispersion in water) and 1.2 g of MPEG-5000-thiol are dissolved in 19 ml of 58789961 (GHMatters} P94035 AU.1 LISAW 27/10114 30 de-ionized water and cooled to 00C. Then, a solution of 2.04 g (12 mmol) of AgNCb in 23 ml of de-ionized water is added with stirring, and the resulting mixture is cooled to 00C. Solution B: 0.908 g (24 mmol) of NaBH 4 and 0.07 ml (ca. 1 .15 mmol) of 28% w/w s ammonia solution in water are dissolved in 49 ml of de-ionized water and cooled to 0*C. Synthesis: Solutions A and B are pumped with equal flow rates (30 ml/min) into a three-way connector (inner diameter of the inlets 1 mm). The resulting dispersion of spherical Ag particles is continuously drained from the third outlet (inner diameter 3 10 mm) of connector into a 1 I round-bottom flask, pre-cooled to 0*C, containing 0.06 ml of TEGO Foamex 1488 de- foamer and stirred for 10 min at this temperature. The mixture is then ultra-filtered 3 times (300000 polyethersulfone membrane, 5 bar), the residue is diluted with 1 -methoxy-2- propanol (Dowanol) and the mixture is evaporated to the final weight of 6.5 g to provide 20% w/w dispersion of spherical silver 15 nanoparticles in Dowanol. Example 7 Varnish preparation: 7.15g of nitrocellulose (DHM 10-25 IPA (Nobel Enterprises, UK)) are slowly added to 92.85g of ethyl acetate (99-100% rein, Brenntag) in a 250m1_ glass bottle and gently stirred until complete dissolution at room temperature. Solid 20 content measurements are then performed and quantity of ethyl acetate is adjusted to achieve a value of 10% solid content in the varnish preparation. General procedure for metallic ink preparation: 3 g silver pigment dispersion (0.6g of the silver particles obtained in Examples 1 -6 in 2.4 g ethylacetate) are added to the above varnish in such a proportion as to adjust the pigment to binder ratio to the values indicated in 25 Table 1 . The obtained dispersion is stirred with a Dispermat at 800rpm for 10 minutes affording a metallic ink which is printed by a handcoater (HC2, 12 micron wet film thickness) on contrast paper and a transparent PES film. Table 1 : Visual effects obtained with coatings, containing silver particles obtained according to Examples 1 to 6 of the present application. 30 58789961 (GHMatters) P94035.AU.1 LISAW 27/10114 31 Silver Silver particles Pigment / Reflection Color Transmission Dispersion ob-tained in Binder Color Ex. Ratio 1 1") 3:1.1 Gold/Copper Blue 2 2" 3:1.1 Gold/Copper Blue 3 3" 3:1.1 Gold/Copper Blue 4 47) 1:1.4 Gold/Bronze Violet 5 5" 1:1.4 Greenish Gold Magenta 6 6" 1:3.4 Yellowish Brown Yellowish Brown 7 - - 2:1 Violet Green 8 1" 1:0.1 Silver Opaque 1 )ca. 20% w/w Ag in ethyl acetate. 2) ca. 20% w/w Ag in Dowanol. 3) Mixture of the silver particles obtained in Example 1 and 6 in a ratio of 4: 1 ; ca. 20% s w/w Ag in ethyl acetate. The obtained products show depending on the viewing angle a colour flop from gold to blue or green to violet or gold to magenta, gold to violet (depending among others on the type of silver particles) above Black and White Leneta-Cards. Example 8 10 Preparation of UV-curable inks: silver particles obtained in Examples 1 to 6 are mixed with BASF SE UV varnish (1-methyl-i ,2-ethanediyl)bis[oxy(methyl-2,1-ethanediyl)] diacrylate and poly(oxy-1 ,2-ethanedlyl), oc-hydroxy-[(1 -oxo-2-propen-1 -yl)oxy]-, ether with 2-ethyl-2-(hydroxymethyl)-1 3- and propanediol (3:1 ), Phosphite N, oligo[2 hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone], oxybis(methyl-2,1 is ethanediyl)diacrylate, and tertiary amine derivate) in such a proportion as to adjust the pigment to binder ratio to the values indicated in Table 1. Solvent is evaporated at 85*C in an oven, and the resulting ink is stirred with a Dispermat at 800rpm for 10 minutes to afford metallic UV-curable inks, which are printed by a handcoater (HC2, 12 micron film thickness) on transparent PES film and cured at 40m/min, 160Watt/crri2. 20 Example 9 The silver pigment dispersions (3.4 g of dispersion) as shown in Table 1 are mixed with nitrocellulose, n-propylacetate and Dowanol PM (0.25g nitrocellulose, 2.75g n propylacetate, 2.0 g Dowanol PM) to make a coating composition with a pigment to binder ratio shown in Table 1. The coatings are printed on an RK proofer press over an 25 aluminium foil, and white coated paper provided with a holographic image by applying 58789961 (GHMalters) P94035.AU.1 LISAW 27/10/14 32 a clean UV curable varnish (1-methyl-1 ,2-ethanediyl)bis[oxy(methyl-2, 1 -ethanediyl)] diacrylate and poly(oxy-1 ,2-ethanediyl), oc-hydroxy-[(1 -oxo-2-propen-1 -yl)oxy]-, ether with 2-ethyl-2-(hydroxymethyl)--1 3- and propanediol (3:1 ), Phosphite N, oligo[2 hydroxy-2-methyl-1 -[4-(1 -methylvinyl)phenyl]propanone], oxybis(methyl-2,1 s ethanediyl)diacrylate, and tertiary amine derivate) onto the corona treated substrate and embossing by using a shim and exposing to UV light. The obtained products are characterized by an extremely bright OVD image and extremely strong rainbow effect, high purity and contrast and show depending on the viewing angle a colour flop from gold to blue or green to violet or gold to magenta, gold io to violet (depending among others on the type of silver particles). Example 10 Varnish preparation: 10g of nitrocellulose (DHM 3/5 IPA (Nobel Enterprises, UK)) are slowly added to 90.00g of ethyl acetate (99-100% rein, Brenntag) in a 250ml_ glass bottle and gently stirred until complete dissolution at room temperature. Solid content is measurer-ments are then performed and quantity of ethyl acetate is adjusted to achieve a value of 7% solid content in the varnish preparation. General procedure for metallic ink preparation: 28.6 g silver pigment dispersion (16.3 g of the silver particles obtained in ethylacetate) are added to the above varnish in such a proportion as to adjust 1 :1 the pigment to binder ratio. The obtained dispersion is stirred with a 20 Dispermat at 800 rpm for 10 minutes affording a metallic ink which is printed by gravure with a 100% to 5% step wedge cylinder, 701/cm screen on transparent PES and BOPP film. The ink weight printed on film corresponds to Table 1: All colour measurements in remission/transmission are effected using a spectrophometer Konica Minolta CM-512M3 (3 angles measurements at 250, 450 and 25 750) circular illumination over Black&White Leneta cards on the printed surface. Step wedge Geometry L* C* h* 100% PES on black 250 15.3 6.2 68.9 450 10.8 0.9 105.5 750 8.5 1.9 263.6 PES on white 250 14.6 10.5 310.9 450 11.0 13.1 295.8 | 750 7.3 11.6 291.6 587899_1 (GHMatters) P94035.AU.1 LISAW27/1014 33 Step wedge Geometry L* C* h* 75% PES on black 250 13.5 2.9 78.5 450 10.4 1.6 190.9 750 6.2 3.6 263.6 PES on white 250 17.8 27.5 293.7 450 14.8 29.2 292.0 75* 0 9.8 25.4 291.9 The obtained prints show depending on the viewing angle a colour flop from gold and blue above Black and White Leneta-Cards. Step wedge Geometry L* C* h 100% BOPP on black 250 15.3 6.2 68.9 450 10.8 0.9 105.5 750 8.5 1.9 263.6 BOPP on white 250 15.5 17.5 302.7 450 11.8 19.7 295.0 75* 07.2_ 15.8| 292.0 Step wedge 75% | Geometry L* C* h" BOPP on black 250 13.5 3 2.9 78.5 _ 450 10.4 1.6 190.9 | 750 6.2 | 3.6 263.6 BOPP on white 250 17.8 27.5 293.7 450 14.8 ] 29.2 292.0 750 9.8 25.4 291.9 It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the io common general knowledge in the art, in Australia or any other country. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to is preclude the presence or addition of further features in various embodiments of the invention. 20 58789961 (GHMatters) P94035.AU.1 LISAW 27/10/14

Claims (10)

1. Security, or decorative, element, comprising a substrate, which may contain indicia or other visible features in or on its surface, and which contains an optically variable image on its surface and on at least part of the said substrate surface, a 5 coating comprising platelet shaped transition metal particles having a longest dimension of edge length of from 15 nm to 1000 nm and a thickness of from 2 nm to 100 nm.

2. The element according to claim 1, wherein the longest dimension of edge length is from 15 nm to 600 nm. 10

3. The element according to claim 1 or claim 2, wherein the longest dimension of edge length is from 20 nm to 500 nm.

4. The element according to any one of claims 1 to 3, wherein the thickness is from 2 to 40 nm.

5. The element according to any one of claims 1 to 4, wherein the thickness is 15 from 4 to 30 nm.

6. The element, according to any one of claims 1 to 5, wherein the metal is selected from the group consisting of Cu, Ag, Au, Zn, Cd, Ti, Cr, Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt.

7. The element according to claim 6, wherein the metal is Ag. 20

8. The element, according to claim 6 or claim 7, wherein the shaped transition metal particles having a longest dimension of edge length of from 15 to 1000 nm and a thickness of 2 to 100 nm and comprising hexagonal and/or triangular and/or truncated triangular prisms, which prisms make up more than 20% of the total number of shaped transition metal particles. 25

9. The element, according to any one of claims 1 to 8, wherein the binder comprises any one or more selected from the group comprising nitrocellulose, ethyl cellulose, cellulose acetate, cellulose acetate propionate (CAP), cellulose acetate bu tyrate (CAB), alcohol soluble propionate (ASP), vinyl chloride, vinyl acetate copoly mers, vinyl acetate, vinyl, acrylic, polyurethane, polyamide, rosin ester, hydrocarbon, 6650718_1 (GHMatters) P94035.AU.1 INNAM 35 aldehyde, ketone, urethane, polythyleneterephthalate, terpene phenol, polyolefin, silicone, cellulose, polyamide, polyester and rosin ester resins.

10. Use of the element according to any one of claims 1 to 9, for the prevention of counterfeit or reproduction, on a document of value, right, identity, a security label or a 5 branded good. 6650718_1 (GHMatters) P94035.AU.1 INNAM