THERMOPLASTIC NORBORNENE RESIN BASED OPTICAL FILM

摘要

An optical film is provided, which displays a positive wavelength dependency across the entire wavelength region from 400 to 800 nm, and is capable of imparting a specified retardation to transmitted light with a single sheet of film. The optical film particularly, includes a thermoplastic norbornene-based resin with a specified structure formed of a structural unit (I) which imparts a positive birefringence and a structural unit (II) which imparts a negative birefringence, and which satisfies particular conditions with respect to DeltaNI(lambda), DeltaNII(lambda), DeltaNI(800) and DeltaNII(800) wherein DeltaNI(lambda) and DeltaNII(lambda) represent the difference between a refractive index Nx(lambda) in an x axis direction at a wavelength lambda, and a refractive index Ny(lambda) in a y axis direction, and DeltaNI(800) and DeltaNII(800) represent the difference in refractive indexes at a wavelength of 800 nm, and the x axis represents the stretching direction and the y axis represents the in-plane direction perpendicular to the x direction.