PRODUCTION METHOD OF OPTICAL FILM, OPTICAL FILM, BACKLIGHT UNIT, AND IMAGE DISPLAY DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a production method of an optical film, by which height and pitches of a rugged pattern can be easily controlled in a rugged optical film having refractive index anisotropy in an in-plane direction.SOLUTION: The production method of an optical film aims to produce an optical film having a rugged pattern formed on at least one surface of the film and having refractive index anisotropy in a direction (in-plane direction) parallel to the surface of the optical film. The method includes a stretching step of stretching an unstretched rugged film 100 having a rugged pattern formed on at least one surface thereof so as to impart the refractive index anisotropy to the film. The rugged pattern of the unstretched rugged film 100 includes a plurality of repeated rugged patterns where linear projections and linear recesses are arranged parallel to one another. In the stretching step, the unstretched rugged film 100 is stretched in a direction (MD) along the lines of the rugged pattern while a width of the rugged pattern in the arrangement direction (TD) is fixed to prevent from changing.