METHOD FOR PRODUCING POLARIZING FILM

摘要

Disclosed is a method for producing a polarizing film, wherein a film composed of a polyvinyl alcohol having a high polymerization degree can be processed into a polarizing film having high polarization performance. The method for producing a polarizing film comprises a step wherein a material film, which has a swelling degree of A (%) and is formed from a polyvinyl alcohol having a polymerization degree of not less than 5,000, is wet stretched 2.0-2.9 times, thereby obtaining a stretched film having a swelling degree of B (%).  In this connection, the values A and B satisfy a specific relation.  The method for producing a polarizing film preferably comprises, after the wet stretching step, a step wherein the thus-obtained stretched film is further stretched three or less times in an aqueous boric acid solution.