Security document with micro-prisms

A security document including a substrate of transparent polymeric material, and opacifying layers provided on opposing sides of the substrate, the opacifying layers acting to guide light propagating within the substrate, the substrate being formed with a plurality of micro-prisms for diverting light propagating within the substrate or entering the substrate, each micro-prism including an inclined face at an acute angle with respect to opposing sides of the substrate, the inclined face providing a first interface between the substrate and air, wherein light propagating within the substrate, which is incident on the inclined face at an angle greater than a critical angle, is reflected at the first interface.

A security document including a substrate of transparent polymeric material, and opacifying layers provided on opposing sides of the substrate, the opacifying layer on one side of the substrate only partially covering the substrate to form a window, the opacifying layers acting to guide light propagating within the substrate, wherein the substrate is formed with a plurality of micro-prisms for diverting light propagating within or entering the substrate, wherein the micro-prisms are arranged to direct light incident on the window to propagate along the substrate.