SECURITY PRINTING DEVICE AND ITS MANUFACTURING PROCESS

Abstract

A security printing substrate 1 comprises a transparent or translucent polymer substrate 5 having first and second opposing surfaces 5a, 5b and at least one opacifying layer 6a, 6b. The security printing substrate further comprises a first impression 10a of a multi-tonal image disposed on the first and / or second surface of the polymer substrate, the first impression being covered, from the viewpoint of an observer, on at least one side of the security printing substrate by at least one of the opacifying layers 6a, which is disposed continuously over the multi-tonal image, and a second impression 7 of the multi-tonal image formed as a masked work comprising an array of screen elements of a color contrasting with that of the continuous opacifying layer. The second impression is disposed above the continuous opacifying layer from the viewpoint of the observer and aligned with the first impression.When the security printing medium is viewed in reflected light, the second impression dominates the appearance of the multi-tonal image, and when the security printing medium is viewed in transmitted light, the first impression dominates the appearance of the multi-tonal image.