| 摘要 |
PURPOSE:To produce a polarizing film having excellent moisture resistance, heat resistance and polarization properties, by subjecting a PVA type film to pretreatment consisting of a step of impregnation with an acid catalyst and a step of stretching in water and subjecting the pretreated film to aftertreatment consisting of a step of dry heat stretching and a step of heat-treatment. CONSTITUTION:A PVA type film is subjected to pretreatment consisting of a step of impregnation with an acid catalyst and a step of stretching in water, and then subjected to aftertreatment consisting of the first step of dry heat stretching and the second step of heat-treatment for foming a polyene. In the pretreatment, the step of impregnating with an acid catalyst and the step of stretching in water are carried out in this order or in the reversed order. In case where the step of stretching in water precedes the step of impregnation with an acid catalyst, a step for drying the PVA film to a moderature moisture content can be interposed between both the steps. The PVA type film is preferred to have an average degree of polymerization, of 1,100-2,600. |
