PRODUCTION OF PHASE DIFFERENCE FILM

摘要

PROBLEM TO BE SOLVED: To stably produce a phase difference film showing uniform retardation which does not produce color irregularity in a liquid crystal display device by subjecting a cast film to primary stretching in a specified temp. range and then subjecting the film to secondary stretching in a specified temp. range. SOLUTION: A thermoplastic resin film produced by soln. casting method is subjected to primary stretching in a temp. range from Tg (glass transition temp.) to Tg+30 deg.C, and further subjected to secondary stretching in a temp. range from Tg-10 deg.C to Tg+20 deg.C. The primary stretching is carried out at a rather high temp. where relaxation of stress is dominant so that the residual phase difference intrinsic to the flow-cast film and that undesirable film shape such as flares can be corrected. The obtd. film has no residual stress and made flat. By subjecting the film thus corrected to secondary stretching at a rather low temp. where the occurrence of phase difference is dominant than stress relaxation, uniform phase difference can be added to the film.