| 摘要 |
PURPOSE:To obtain a high-elasticity film which is high in the elasticity modulus in a longitudinal direction, not fibrillated easily in a lateral direction and, suitable for example, for a recording tape even under unstretched state, by molding liquid crystalline polyester composed of a polyethylene terephthalate copolymer modified with p-hydroxybenzoic acid into a filmy state, while applying a specific draft thereto. CONSTITUTION:Polyester is composed of polyethylene-terephthalate-type copolymer polyester modified with p-hydroxybenzoic acid. The title film is a highly- elastic polyester film having the tensile strength of at least 8kg/mm<2> in a longitudinal direction, the tensile modulus of at least 400kg/mm<2> in the longitudinal direction, and the tensile strength of at least 2kg/mm<2> in a lateral direction under a state of an unstretched film as it has been manufactured into a film while applying draft to the polyester, which has been melted and extruded. In the case where a ratio of the ingredient of the p-hydroxybenzoic acid in a liquid crystalline polyester is too little, a highly-elastic film is hard to obtain and on the one hand, in the case where the same is too much, a uniform film is hard to obtain. Therefore, it is preferable that the ratio is 29.4-43.0mol% and especially 30.7-38.0mol%. |
