Patent ID: 8587882

Claim:
An optical layer stack, comprising: a first layer; a second layer; a first spacer part associated with the first layer; and a second spacer part associated with the second layer, wherein the two spacer parts comprise groove and tongue for an engagement in a stacking direction of the optical layer stack and for a shiftability of the first spacer part with respect to the second spacer part in the lateral direction and in the stacking direction the tongue comprises a smaller width than the groove, wherein the first and the second spacer part are connected to each other by means of an adhesive between groove and tongue in order to provide a connection between the first and the second spacer part and a spacing of the first and second layer in stacking direction; and wherein the groove has a bottom which is surrounded by two side walls, and a wall of the groove facing an optical used area is higher than a wall of the groove facing away from the optically used area.