| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical film showing positive wavelength dependency across the entire wavelength region from 400 nm to 800 nm and capable of imparting specified retardation to transmitted light in the above wavelength region with a single sheet of the film. SOLUTION: The optical film contains a thermoplastic norbornene-based resin composed of a structural unit (I) which imparts positive birefringence and a structural unit (II) which imparts negative birefringence in the wavelength region from 400 to 800 nm. The resin has such characteristics that when single polymers comprising the structural unit (I) only and the structural unit (II) only are uniaxially stretched under the same conditions, the difference between the refractive index in the x-axis direction Nx(λ) at a given wavelengthλand the refractive index in the y-axis direction Ny(λ), namely Nx(λ)-Ny(λ), denoted asΔNI(λ) andΔNII(λ), respectively, satisfy the relation ofΔNI(λ)+ΔNII(λ)>0 andΔNI(λ)-ΔNI(800)<ΔNII(800)-ΔNII(λ), wherein each ofΔNI(800) andΔNII(800) represents the difference between the refractive indices in the x-axis direction and in the y-axis direction at 800 nm wavelength. COPYRIGHT: (C)2003,JPO |
