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US 2017/0028764 A1Published application
Method for manufacturing security elements and holograms
AssigneeBASF SE
InventorsMichelle RICHERT, Roland FLEURY, Nikolay A. GRIGORENKO
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Abstract
The present invention relates to a method for forming a surface relief microstructure, especially an optically variable image (an optically variable device) on a transparent or translucent substrate and a product obtainable using the method. A further aspect of the invention is the use for the prevention of counterfeit or reproduction of a document of value and a method of forming a coating showing an angle dependent color change.
Claims15
1:
- A method for forming a surface relief microstructure, especially an optically variable image on a substrate comprising the steps of:
- A) applying a curable composition to at least a portion of a front side of the substrate wherein the substrate is transparent or translucent, and wherein the curable composition comprises:
- a1) an ethylenically unsaturated resin, a monomer or a mixture thereof;
- a2) a photoinitiator selected from the group consisting of a monoacylphosphine oxide compound and a bisacylphosphine oxide compound;
- and
- a3) a metal pigment which is in the form of platelet shaped transition metal particles having a longest dimension of edge length of from 5 nm to 1000 nm, and a thickness of from 1 nm to 100 nm, wherein the metal is Ag;
- B) contacting at least a portion of the curable composition with a surface relief microstructure;
- C) curing the composition with at least one UV lamp, which is arranged on a backside of the transparent or translucent substrate.
5 more elements
2:
- The method according to claim 1, wherein the lamp is a gallium or iron doped medium pressure mercury lamp.
3:
- The method according to claim 1, wherein the curable composition further comprises a second photoinitiator selected from the group consisting of a benzophenone compound, an alpha-hydroxy ketone, alpha-alkoxyketone, and alpha-aminoketone compound.
4:
- The method according to claim 1, wherein the curable composition comprises:
- (a) 5.0 to 0.6% by weight of the photoinitiator;
- (b) 94.9 to 11.9% by weight of the ethylenically unsaturated resin, monomer or mixture thereof;
- and
- (c) 0.1 to 87.5% by weight of the metal pigment,
- wherein the sum of components a) to c) adds up to 100%.
3 more elements
5:
- The method according to claim 1, wherein the shaped transition metal particles comprise hexagonal and/or triangular and/or truncated triangular prisms, which prisms make up more than 20% of a total number of shaped transition metal particles.
6:
- The method according to claim 1, wherein the transparent or translucent substrate is paper or a thermoplastic or crosslinked polymer.
7:
- The method according to claim 10 wherein the transparent or translucent substrate is a thermoplastic polymer selected from the group consisting of polyester, polyvinyl chloride (PVC), polyethylene, polycarbonate, polypropylene and polystyrene.
8:
- The method according to claim 1, wherein the surface relief microstructure is a shim which is a nickel sleeve;
- a nickel plate;
- an etched, or laser imaged metallic drum, or another material mounted on an opaque cylinder or metal cylinder containing an optical variable device (OVD image) on the surface.
9:
- The method according to claim 8, wherein the shim is a nickel plate mounted on an opaque cylinder or metal cylinder and containing the OVD in on the surface.
10:
- The method according to claim 1, wherein the surface relief microstructure is applied over an already existing security element.
11:
- A method for forming a coating showing an angle dependent color change on a substrate comprising the method according to claim 1.
12:
- The method according to claim 1, wherein the surface relief microstructure comprises microstructures having dimensions in the range from about 0.01 microns to about 10 microns.
13:
- The method according to claim 1, wherein the surface relief microstructure comprises microstructures having dimensions in the range from about 0.01 microns to about 1 micron.
14:
- The method according to claim 1, wherein the platelet shaped transition metal particles have a longest dimension of edge length of from 7 nm to 600 nm and a thickness of from 2 inn to 40 nm.
15:
- The method according to claim 1, wherein the platelet shaped transition metal particles have a longest dimension of edge length of from 10 nm to 500 nm and a thickness of from 3 nm to 30 nm.