BigPatents India

A security element ( 2, 4) for insertion in or application to a security document, whereupon said element is visually recognisable from both sides of the security document (1), structured in various layers, and comprising two interference elements (I1, I2) having a colour-varying effect, a metal reflecting layer (R) disposed therebetween, and, optionally, diffraction structures (8). The colour-varying effect and/or the optical diffracting effects of one or two sides of the security element (2,4) can be perceived according to the arrangement of the layers (I1, R, I2 ) and the optionally provided diffraction structures (8) on a transparent substrate (S). The security element is particularly suitable for use as a double-sided window thread (4) and as a label or transfer element (2) above a hole (3) in the security document (1). (FIG.1).