Security devices and methods of manufacture thereof

Abstract

A method of manufacturing an image element array for a security device is disclosed. The method comprises: (a) providing a metallised substrate web comprising a substrate having a first metal layer thereon on a first surface of the substrate, the first metal layer being soluble in a first etchant substance; (b) applying a first photosensitive resist layer to the first metal layer; (c) exposing the first photosensitive resist layer to radiation of a wavelength to which the resist layer is responsive through a patterned mask, by conveying the substrate web along a transport path and, during the exposure, moving the patterned mask alongside the substrate web along at least a portion of the transport path at substantially the same speed as the substrate web, such that there is substantially no relative movement between the mask and the substrate web, wherein the patterned mask comprises first pattern elements in which the mask is substantially opaque to the radiation and second pattern elements in which the mask is substantially transparent to the radiation, whereupon the exposed second pattern elements of the first photosensitive resist layer react resulting in increased solubility by a second etchant substance, the non-exposed first pattern elements remaining relatively insoluble by the second etchant substance; and (d) applying the first and second etchant substances to the substrate web whereupon the second pattern elements of both the first resist layer and the first metal layer are dissolved, the remaining first pattern elements of the first metal layer forming an image element array.