| 摘要 |
PURPOSE:To enhance the gas barrier property, mechanical strength, electromagnetic conversion characteristics, etc., of a biaxially oriented polyester film, by forming a specific structure of polyester film having a thickwise refractive index ratio of 0.935-0.975 and an intrinsic viscosity of 0.3-1.4. CONSTITUTION:A biaxially oriented polyester film having a thickwise refractive index ratio of 0.935-0.975 and an intrinsic viscosity of 0.3-1.4 is obtained from a polyester containing at least 85mol% repeating unit of formula I (where X is a halogen selected from F, Cl, and Br or a 1-3C alkyl, l and m are each an integer of 1-2, p is an integer of 2-6, and q is an integer of 2-4). For example, pellets of polyethylenebis alpha,beta-(2-chlorophenoxy)ethane-4,4'-dicarboxylate are supplied to a extruder, extruded through a slit die at 270-310 deg.C after being melted, cooled, and then subjected to a biaxial stretching process. |
