A hidden image security device and method

Abstract

A method for producing an optical device, preferably a security device, including the steps of: forming a planar relief structure on a substantially planar first surface of a substrate, preferably a transparent substrate, the planar relief structure having a first alignment direction and including a plurality of relief structure elements each having the same height; and applying a liquid crystal polymer (LCP) layer onto the planar relief structure such that the LCP layer is aligned with the relief structure, wherein the LCP layer includes at least one or more first LCP regions having a first height and one or more second LCP regions having a second height above the substantially planar first surface of the substrate, wherein the second height is different to the first height, and an optical device formed by such a method.

Description

technical field [0001] The invention relates generally to the field of optical security devices such as are used on banknotes. Background technique [0002] It is well known that many banknotes around the world, as well as other security documents, carry optical devices that act as security elements. Some optical security elements produce optical effects that vary depending on whether the optical security element is viewed through a decoding screen or not. Therefore, the incorporation of such optical security elements into security documents acts as a deterrent to counterfeit documents. [0003] Nonetheless, unscrupulous forgery gangs have become more organized and technologically capable, and the high rewards (despite the risks) from forgery have become easier to recognize. In recent years, attempts to imitate genuine components have become increasingly successful. The problem is exacerbated by the fact that the process by which members of the public authenticate banknot...

AI Technical Summary

Problems solved by technology

Forming liquid crystal layers onto non-planar surfaces is relatively difficult for at least two reasons

First, it can be difficult to produce non-planar surfaces that include relief structures with height differences sufficient to produce different optical effects

Second, specialized equipment may be required in order to apply the liquid crystal layer correctly (eg, in sufficient registration) to the non-planar surface

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