High refractive index coatings and their use in the protection of surface relief structures
AssigneeSecurency International Pty Ltd
InventorsPhei Lok, Gary Fairless Power, Odisea Batistatos
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Abstract
High refractive index coatings having metal oxide particles are disclosed. Dispersions of metal oxide particles in solvent are also disclosed. These find use in the protection of surface relief structures. In some disclosed embodiments, the coatings or dispersions contain UV-curable resins. The coatings and dispersions find application in the field of security devices and documents and tokens incorporating security devices.
Claims21
-33. (canceled)
A security device comprising:
- (a) a substrate;
- and
- (b) a transparent protective coating, wherein
- (i) the substrate has a surface relief structure and the coating is applied to the surface relief structure, said coating having a refractive index greater than the refractive index of the surface relief structure, or
- (ii) the coating forms all or part of a surface relief structure;
- wherein, for each alternative, said coating comprises particles of at least one metal oxide which have a primary crystallite size from 1 to 100 nm.
A dispersion comprising particles of one or more metal oxides, at least one organic solvent and at least one transparent varnish, wherein the particles of metal oxide have a primary crystallite size from 1 to 100 nm.
A method of protecting a surface relief structure, said method comprising the following steps:
- (a) providing a dispersion comprising metal oxide particles having a primary crystallite size from 1 to 100 nm in an organic solvent,
- (b) applying said dispersion to a surface relief structure, and
- (c) removing the solvent so as to form a transparent coating,
- wherein the coating has a refractive index greater than the refractive index of the surface relief structure.
Dependencies are inferred from the claim text.