Thin aluminium flakes

Abstract

The present invention relates to aluminium flakes having a thickness between 7 and 9 nm, coating compositions containing them and the use of the coating compositions for forming (security) products. When the compositions of the present invention are used in coating a hologram the obtained products show an extremely bright OVD image and extremely strong rainbow effect, high purity and contrast.

1 . An aluminium flake having a thickness above 5 nm and below 10 nm. 
     
     
         2 . The aluminium flake according to  claim 1  having a thickness between 7 and 9 nm. 
     
     
         3 . The aluminium flake according to  claim 1 , wherein the mean particle diameter D 50  of the aluminum particles is in the range of 8.0 to 15.0 μm. 
     
     
         4 . A coating composition, comprising the aluminium flakes according to  claim 1 . 
     
     
         5 . The coating composition according to  claim 4 , comprising the aluminium flakes according to  claim 1  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. 
     
     
         6 . The coating composition according to  claim 5 , wherein the composition further comprises a solvent. 
     
     
         7 . The coating composition according to  claim 6 , wherein the solvent comprises any one or more of the group comprising an ester, a ketone, an alcohol, an aromatic hydrocarbon and water. 
     
     
         8 . The coating composition according to  claim 6 , wherein the binder comprises 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, hydrocarbon, aldehyde, ketone, urethane, polythyleneterephthalate, terpene phenol, polyolefin, silicone, cellulose, polyamide, polyester and rosin ester resins. 
     
     
         9 . The composition as claimed  claim 4  for use in coating an optically variable image (hologram). 
     
     
         10 . A metallic ink comprising the aluminium flakes according to  claim 1  and a binder. 
     
     
         11 . The metallic ink of  claim 10 , wherein the ratio of pigment to binder is sufficiently high to permit the alignment of the pigment particles to the contours of a diffraction grating 
     
     
         12 . A method for forming an optically variable image (an optically variable device) on a substrate comprising the steps of:
 a) forming an optically variable image (OVI) on a discrete portion of the substrate; and   b) depositing the metallic ink according to  claim 11  on at least a portion of the diffraction grating.   
     
     
         13 . The method according to  claim 12 , comprising the steps of:
 a) applying a curable compound to at least a portion of the substrate;   b) contacting at least a portion of the curable compound with OVI forming means;   c) curing the curable compound and   d) depositing the metallic ink on at least a portion of the cured compound, said metallic ink comprise an aluminium flake having a thickness of 5 nm to 10 nm and a binder.   
     
     
         14 . A (security) product obtainable by using the method as claimed in  claim 12 . 
     
     
         15 . 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,   (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 the metallic ink according to  claim 11  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   (g) applying a heat activated adhesive onto the layer obtained in step e), or f).   
     
     
         16 . A method of labeling an article of manufacture, the method comprising the steps of:
 contacting the heat activated adhesive layer of the hot stamping foil obtained according to  claim 15  with said article; hot stamping said hot stamping foil to 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.