An optical body includes a substrate and a cholesteric liquid crystal layer disposed on the substrate. The cholesteric liquid crystal layer has a non-uniform pitch along a thickness direction of the layer and comprises a crosslinked polymer material that substantially fixes the cholesteric liquid crystal...http://www.google.de/patents/US7277141?utm_source=gb-gplus-sharePatent US7277141 - Optical bodies containing cholesteric liquid crystal material and methods of manufacture
