While cast doing

摘要

PROBLEM TO BE SOLVED: To manufacture a film which is excellent in optical characteristics.;SOLUTION: A dope 21 is cast on a casting drum and a cast film 33 is formed. The cast film 33 is stripped off from the casting drum and a wet film 38 is obtained. At a pin tenter 13, the wet film 38 is subjected to drying treatment. In the drying treatment, an orientation maintaining process for preventing relaxation of orientation of a polymer molecule and a crystallization process for crystallizing the polymer molecule are successively performed. At the orientation maintaining process, temperature of the wet film 38 is adjusted to 30 to ≤40°C by supplying dry wind to the wet film 38 having residual solvent amount ZY of 70 to ≤100 wt.%. Further a temperature changing rate Tv of the wet film 38 is adjusted to -0.6 to 0.6°C/second. At the crystallization process, temperature of the wet film 38 is adjusted to 85 to ≤100°C by supplying dry wind to the wet film 38 having residual solvent amount ZY of 10 to ≤15 wt.%. Further the temperature changing rate Tv of the wet film 38 is adjusted to 0.9 to 2.0°C/sec.;COPYRIGHT: (C)2010,JPO&INPIT