A multilayered polymer film includes a first set of optical layers and a second set of optical layers. The first set of optical layers is made from a polyester which is often birefringent. The polyesters of the first set of optical layers typically have a composition in which 70-100 mol % of the carboxylate...http://www.google.es/patents/US7459204?utm_source=gb-gplus-sharePatente US7459204 - Modified copolyesters and improved multilayer reflective films
Modified copolyesters and improved multilayer reflective films
