Patent ID: 9598821
Date: 2017-03-21
CPC Classifications: B32B,B42D,D21H,G02B

Claim:
1. A substrate for security documents comprising one or more paper layers and a polymer layer which is made to adhere to a side of at least one of the paper layers, which polymer layer is substantially transparent in at least one region of the substrate which is not covered by the paper layer or layers so as to form a substantially transparent window in the substrate which is formed and closed by the polymer layer, wherein the polymer layer exhibits in the region of the window (W) a thickness which is greater than a thickness of the polymer layer outside of the region of the window, wherein the thickness of the polymer layer in the region of the window is substantially equal to the added thickness of the paper layer or layers and of the polymer layer outside of the region of the window (W) so that the substrate exhibits a substantially uniform and constant thickness, and wherein the substrate further comprises a micro-optical structure, which is disposed in the region of the window on at least one side of the polymer layer.