Toshiba Kikai Kabushiki Kaisha

Hiromu Saijo

Nobuhide Tomura

Koichi Kanazawa

Shigeru Miyazaki

Toshihiro Ozawa

A PVA film successively oriented in two orthogonal directions is prepared by firstly elongating the film in the longitudinal direction by more than 200% while maintaining the water content (Z .times. 100)% at a value of from 10 to 35% and the temperature in a range of from (1.50/Z +20).degree. C to 75.degree. C. The film is then preheated while maintaining its water content at least 7%, and then elongated laterally by more than 200% at a temperature of from 45.degree. to 110.degree. C. Then the film is heat treated at a temperature of 110.degree. to 210.degree. C while permitting the film to shrink by less than 15% in the lateral direction. Finally, the film is cooled to room temperature under tension.

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Sunto, Japan

Hiromu Saijo