| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyester film which has excellent transparency, good hand cutting properties and good twisting properties and does not lose flexibility of the film even while it is stored and even after it is exposed under a high temperature during processing. SOLUTION: An unstretched laminated film is prepared by laminating a polyester resin layer (B) with a melting point of at least 10°C higher than the melting point of a polyester resin layer (A) on at least one face of the polyester resin layer (A) so as to make the total thickness after stretching to be 1-10μm. This unstretched laminated film is at least monoaxially stretched and then, heat-treated at a temperature not lower than a level lower by 5°C than the melting point of a crystalline polyester resin (C) which constitutes the polyester resin layer (A) and comprises terephthalic acid as a main ingredient, and at the level lower than the melting point of the polyester resin layer (B). The polyester film thus obtained has good tearing characteristics and twisting properties and has flexibility even after it is exposed at a higher temperature. COPYRIGHT: (C)2004,JPO |
