Patent ID: 7790361
Filing Date: 2010-09-07
Classification: B41M,B42D,G03H

Abstract:
1. A method of producing a security document or device comprising a substrate and an optically diffractive device, the method comprising the steps of: applying a coating to an area of a surface on at least one side of the substrate; and irradiating an area of the coating with a patterned laser beam bearing the pattern of a desired diffractive device to ablate selected portions of the coating and thereby form an optically diffractive structure in said coating, wherein the substrate comprises a transparent plastic film and the coating comprises a transparent coating, in the absence of a reflective or opacifying layer at least during said step of irradiating, wherein said step of irradiating comprises directly exposing the coating to said patterned laser beam at a surface thereof so that at least one portion of the transparent coating is ablated its full thickness without ablating the substrate, and wherein laser ablation of the transparent coating with the patterned laser beam forms a diffractive microstructure in the transparent coating which is encoded with complex data, and the resulting optically diffractive device is a numerical-type diffractive optical element.