COMPOSITION, AND MANUFACTURING METHOD FOR POLARIZING FILM FOR USE THEREWITH

摘要

[Problem] Conventional polarizing films with an aromatic bisazo compound have a low dichroic ratio due to the aromatic bisazo compound not being sufficiently oriented. This is assumed to result from low purity levels of the aromatic bisazo compound. [Solution] A manufacturing method for a polarizing film according to the present invention has a step A and a step B. In step A an aromatic bisazo compound that has a sulfonic acid group, or an aromatic bisazo compound that has a carboxylate group, is refined using reverse-phased chromatography and set so that the purity levels as determined by high-speed liquid chromatography at UV254 nm are 90% or higher. In step B an aqueous solvent having the refined aromatic bisazo compound obtained in step A is flow-cast into a thin film, whereby a polarizing film is obtained.