Modified copolyesters and improved multilayer reflective films

摘要

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 subunits are first carboxylate subunits and 0-30 mol % are comonomer carboxylate subunits and 70 to 100 mol % of the glycol subunits are first glycol subunits and 0 to 30 mol % of the glycol subunits are comonomer glycol subunits, where at least 0.5 mol % of the combined carboxylate and glycol subunits are comonomer carboxylate or comonomer glycol subunits. The second set of optical layers comprise copolyesters wherein 0.01 to 2.5 mol % of the combined carboxylate and glycol subunits are carboxylate subunits derived from compounds having three or more carboxylate or ester functionalities, glycol subunits derived from compounds having three or more hydroxyl functionalities, or combinations thereof. The multilayered polymer film may be used to form, for example, a reflective polarizer or a mirror.