An optical film is provided which includes a disperse phase of polymeric particles disposed within a continuous birefringent matrix. The film is oriented, typically by stretching, in one or more directions. The size and shape of the disperse phase particles, the volume fraction of the disperse phase,...http://www.google.es/patents/US5783120?utm_source=gb-gplus-sharePatente US5783120 - Method for making an optical film
