| 摘要 |
PURPOSE:To enhance the dimensional stability of film by a method wherein a roll-film is aged under specified conditions and, after that, rewound and aged again. CONSTITUTION:Polyester film, which is biaxially stretched by publicly known methods and conditions, and is thermoset and wound in a roll, is firstly retained for 24hr or longer in an atmosphere having the temperature range of 40-90 deg.C. Next, the roll subjected to the above-mentioned retention treatment is rewound so that the portion, which occupies the surface layer part of the roll at first, occupies the core part of the rewound roll and the portion, which occupies the core part of the roll at first, occupies the surface layer part of the rewound roll and again retained for 24hr or longer in an atmosphere having the temperature range of 40-90 deg.C. The humidity of the atmosphere is preferably as high as possible unless dew condenses on the film. Due to the above-mentioned retention treatment, the polyester film, the rate of dimensional change of which at comparatively low temperature is remarkably reduced, can be obtained. Especially, the rate of longitudinal dimensional change is small and its scattering becomes small. |
