PRODUCTION METHOD OF OPTICAL FILM

摘要

PROBLEM TO BE SOLVED: To provide a production method of an optical film, by which an optical film having biaxially orientation can be obtained.SOLUTION: The production method of an optical film 1 is carried out by using a multilayer film which is formed of a thermoplastic resin having positive refractive index anisotropy, has a multilayer structure of a plurality of layers stacked in a thickness direction and has a longitudinal direction and a width direction; and the method includes a step of stretching the above multilayer film under the conditions satisfying both of expression (1) 1.2≤x/y≤2.0 and expression (2) y≤100. A multilayer film having 500 or more layers stacked in a thickness direction is used for the above multilayer film. In the expression (1), x represents a thickness (nm) per one layer in the multilayer film; and in expression (1) and expression (2), y represents a thickness (nm) per one layer in the optical film.