| 摘要 |
PROBLEM TO BE SOLVED: To stably produce a phase difference plate having uniform retardation in the plane direction with high productivity even when the film is not uniform in its thickness, by stretching a thermoplastic resin film in such a manner that a thick part has a higher average temp. in the thickness direction than in a thin part. SOLUTION: A thermoplastic resin film is uniaxially or biaxially stretched at a temp. in the range from Tg-30 deg.C to Tg+60 deg.C, wherein Tg is the glass transition temp., in such a manner that a thick part has a higher average temp. in the thickness direction than in a thin part. As for the thermoplastic resin, a thermoplastic resin showing double refraction by stretching is used. For example, a cellulose resin or a vinyl chloride resin is used. The thickness of the film is detected by using a non-contact thickness meter using laser, radiation, ultrasonics or the like. The film temp. is controlled by using a heater which uses hot air blow, microwaves or far IR rays. |
