| abstract |
(57) Abstract: [PROBLEMS] To manufacture an optical film having excellent optical properties with high productivity by a polycarbonate film casting method. A solvent-containing film of polycarbonate is peeled from a casting support. After that, in the first step, an atmospheric temperature of 15 to 40 ° C. and a tension of 3 to 7 kg per 1 cm 2 in the film conveying direction are conveyed for 2 to 4 minutes. In the second step, the film is sent to the pin tenter. The ambient temperature is Tg-45 to Tg-5 ° C (Tg: glass transition temperature of polycarbonate). Reduce the rail width of the pin tenter from the film width by 2.5 to 7.5%, hold the two edge parts in the width direction of the film with pin clips, and draw a catenary line in the width direction. Transport for 6 minutes. In the third step, the film is sent to the roll suspension type dryer. Atmospheric temperature Tg-10 to Tg ° C., 0.1 per square cm. Transport for 30 to 90 minutes while applying a tension of 4 to 1.5 kg. Cool to room temperature in the fourth step. |