PURPOSE: To manufacture a longitudinally strengthened polyester film with lesser draw spots by designating the temperature of a monoaxially stretched polyester sheet or film being biaxially stretched and longitudinal and crosswise draw ratios of the sheet or film to spacific values in drawing the sheet or film.
CONSTITUTION: A practically uncrystallized and unoriented polyester sheet or film is stretched longitudinally 1.1 times or more and then biaxially stretched concurrently in longitudinal and crosswise directions. In this method, the longitudinal draw ratio λMC/λTD, is controlled to 1.0W2.0, and longitudinal draw ratio λMD and crosswise draw ratio λTD are each controlled to 2.5 times or more. The concurrent biaxial stretching of the monoaxially stretched film is made at a temperature from Tg (glass transition temperature) -15°C to Tc (crystallization temperaure) or less of the film. Bowing phenomenon can be avoided, and the same thickness of unstretched cast film can be drawn easily into a thin film nearly twice of monoaxial draw ratio.
| JP2009096051 | OPTICAL FILM AND ITS MANUFACTURING METHOD |
| JPH10258459 | PRODUCTION OF BIAXIALLY STRETCHED POLYAMIDE FILM |
SHIYUDOU TADASHI
UENISHI MITSURU
HAYASHI TADASHI
| JPS55113531A | 1980-09-02 | |||
| JP43026110A |