| 摘要 |
A biaxially oriented polyester film for membrane switches which is made of a polyester having at least 80 mol % ethylene 2,6- naphthalenedicarboxylate repeating units and has an endothermic peak having a quantity of endothermic energy of at least 0.4 mJ/mg in the range of 110 to 160 °C. This film is produced by subjecting a biaxially stretched polyester film produced from the polyester by a known method to the following steps (1) and (2) in this order: (1) the step of heating the film in a tension-free state at a temperature between 150 and 180 °C for 1 to 5 hours, and (2) the step of heating the film in the form of cut sheet or roll at a temperature between 80 and 122 °C for 5 to 200 hours. |
