| 摘要 |
PURPOSE:To obtain a film of which mechanical strength in longitudinal direction is high by such an arrangement wherein a substantially non-orientation polyethylene terephthalate film is multistage extended under certain conditions, and next, the film is extended laterally, and then it is further extended longitudinally again, and at this time, the product of an extension multiple of each extension shall be made larger than 25 times. CONSTITUTION:A film made of substantially non-oriented polyethylene terephthalate is multi-stage extended so that its non-crystal orientation coefficient becomes 0.6-1.0, and its double refraction rate becomes 0.02-0.1, and next it is extended laterally at an extension multiple of 2.5-4.5 times, and further it is extended longitudinally again at an extension multiple of 1.5-2.5 times and further the product of those multiples of multi-stage extension, lateral extension and longitudinal extension shall be made larger than 25 times. By this arrangement, it is possible to stably manufacture polyethylene terephthalate film of which mechanical strength in the longitudinal direction is high. |
