Patent attributes
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 ΔNI(λ), ΔNII(λ), ΔNI(800) and ΔNII(800) wherein ΔNI(λ) and ΔNII(λ) represent the difference between a refractive index Nx(λ) in an x axis direction at a wavelength λ, and a refractive index Ny(λ) in a y axis direction, and ΔNI(800) and ΔNII(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.
