Patent ID: 8141908

Claim:
A security device comprising a substrate having a viewing region; a first pattern of a first colour and a second pattern of a second colour on one side of the viewing region; a third pattern of the first colour and a fourth pattern of the second colour on the other side of the viewing region, wherein the first and second patterns on the one side of the viewing region overlap the fourth and third patterns respectively on the other side of the viewing region to define respective first and second overlap regions, whereby a) when each side of the viewing region is viewed in reflected light, the patterns on that side can be distinguished by at least their colours, and b) when the viewing region is viewed in transmitted light, from either side of the substrate, the viewing region is sufficiently transparent that subtractive colour mixing between the overlapped first and fourth patterns of the first overlap region and between the overlapped second and third patterns of the second overlap region results in a perceived single resultant colour being visible for both first and second overlap regions.