| 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 o f film. The optical film particularly, includes a thermoplastic norbornene-bas ed resin with a specified structure formed of a structural unit (I) which impar ts a positive birefringence and a structural unit (II) which imparts a negative birefringence, and which satisfies particular conditions with respect to .DELTA.NI(.lambda.), .DELTA.NII(.lambda.), .DELTA.NI(800) and .DELTA.NII(800 ) wherein .DELTA.NI(.lambda.) and .DELTA.NII(.lambda.) represent the differenc e between a refractive index Nx(.lambda.) in an x axis direction at a waveleng th .lambda., and a refractive index Ny(.lambda.) in a y axis direction, and .DELTA.NI(800) and .DELTA.NII(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. |
