| 摘要 |
PURPOSE:To improve durability, dimensional stability by providing a transfer ink layer on one side face of a biaxially oriented polyester film having specific thickness, longitudinal F5 value, critical viscosity. CONSTITUTION:A transfer ink layer is provided on one side face of a biaxially oriented polyester film having 1-10 of mum of thickness, 9-13kg/mm<2> of longitudinal F5 value, and 0.63-0.90 of critical viscosity. Polyester chip having high molecular weight is so dried and melted that the critical viscosity of the film becomes 0.63 or more, extruded in a sheet state from a slitlike die, solidified by cooling by a casting drum to form an unoriented sheet. The sheet is longitudinally oriented high magnification at a high temperature in multiple states, i.e., heated to 80-130 deg.C in two or a plurality of zones, so oriented that the total magnification becomes 3 to 7 times by the peripheral speed difference between the rolls, then laterally oriented 3.0-4.5 times at 90-120 deg.C, and then heat treated at 200 deg.C or higher to obtain a film. |
