Retardation film and method for production thereof

Abstract

The present invention provides a method for producing a retardation film of a polypropylene resin, the method comprising subjecting a film of a polypropylene resin to longitudinal stretching and transverse stretching which are performed sequentially, wherein the transverse stretching comprises the following steps, and a polypropylene resin retardation film which is obtained by such a method and has both a high axial retardation and a uniform retardation: a step of preheating the film at a preheating temperature which is equal to or higher than the melting point of the polypropylene resin; a step of stretching the preheated film in the transverse direction at a stretching temperature which is lower than the preheating temperature; and a step of heat setting the film stretched in the transverse direction.

Dependencies are inferred from the claim text.