Biaxially oriented polyester film of specific thickness for film condensation processing

摘要

Biaxially oriented polyester film of thickness below 12 mu m has a specific shrinkage properties. Biaxially oriented polyester film of thickness below 12 mu m has a widthwise shrinkage at 200 deg C in % S200(TD) of at most 5%, a temperature at which shrinkage begins Ts(TD) of at least 160 deg C, a lengthwise shrinkage at 200 deg C in % S200(MD) of 2-5 %, a shrinkage ratio Ns220/Ns160 of at least 4.5, where Ns220 is the shrinkage force at 220 deg C and Ns160 is the shrinkage force at 160 deg C, a sheet fixation peak of at least 210 deg C and a sheet density of 1.39-1.41 g/cm<3> An independent claim is also included for the production of the above film by stretching sequentially in the length and width directions, then finally thermofixing, whereby the relaxation speed is below 20% and the maximum temperature is above 210 deg C.