| 摘要 |
PURPOSE:To obtain polyester film of high Young's modulus and strength, by orienting polyester extruded from a slit by specific rates in a machine-axial direction and in a direction rectangular to it at temperatures higher than the softening point. CONSTITUTION:In preparation of polyester film, polyester is melt-extruded from a slit and the width is elongated by 1.5 times or more in a machine-axial direction and in a direction rectangular to it and the area is magnified by three times or more. The clearance of the slit is freely selected according to the thickness of the film. According to the abovementioned method, the melt film-forming process gives useful polyester film with an excellent mechanical property not only with regard to a film machine-axial direction but also to a direction rectangular to it from polyester which forms molten material with optical anisotropy. |
