US Patent 7223451 Polycarbonate-based oriented film and retardation film

A uniaxially or biaxially oriented film which is made from a specific polycarbonate having a fluorene ring and a glass transition temperature of 165° C. or higher and which has a heat shrinkage factor when it is heated at 90° C. for 500 hours of 0.1% or less, and a ratio of retardation R(450) within the film plane at a wavelength of 450 nm to retardation R(550) within the film plane at a wavelength of 550 nm of 1 to 1.06. This film can be used in a high-quality liquid crystal display device such as a vertical alignment liquid crystal display device and is useful as a retardation film which almost solves a frame problem.