| 摘要 |
A process for preparing high tensile strength polyester film especially suitable for manufacturing magnetic recording tapes is disclosed. A raw polyester film is first stretched longitudinally so as to have an index of birefringence of 0.015-0.055, is then further stretched in the same direction at a temperature between 95 DEG C. and 150 DEG C. while the index of birefringence of the film is prevented from exceeding 0.080, is then stretched transversely to 2.5-5 times its width and is further stretched longitudinally and/or transversely to 1.1 times or greater. The product has high tensile strength as well as excellent flatness and slipperiness properties. |
