Patent ID: 9660119
Date: 2017-05-23
CPC Classifications: B29D,B32B,C08G,C08J,C08L,H01L,Y02E,Y10T

Claim:
1. A polyester film, having a stress heat resistant coefficient f(125) that satisfies the following Equation (1) and a wet thermo retention represented by the following Equation (2) of 30% or higher: wherein, in Equation (1), f(125) is a value obtained by substituting t=125° C. in an approximation represented by f(t); t represents a temperature (° C.) at a time of heat treatment (thermo processing); f(t) represents a stress heat resistant coefficient f at a thermo temperature t and represents an approximation to a straight line obtained by linear approximation by a least squares method of values plotted from a relationship between the thermo temperature t and a logarithm (log T(t)) of time T at which a rupture stress is 50% when the thermo temperature t is 150° C., 160° C., 170° C., or 180° C.; T(150) is a time (hr) at which the maximum stress in a tensile test after thermo processing at 150° C. and 0% RH is 50% of the maximum stress in a tensile test before thermo processing; T(160) is a time (hr) at which the maximum stress in a tensile test after thermo processing at 160° C. and 0% RH is 50% of the maximum stress in a tensile test before thermo processing; T(170) is a time (hr) at which the maximum stress in a tensile test after thermo processing at 170° C. and 0% RH is 50% of the maximum stress in a tensile test before thermo processing; T(180) is a time (hr) at which the maximum stress in a tensile test after thermo processing at 180° C. and 0% RH is 50% of the maximum stress in a tensile test before thermo processing; and S(120) represents a breaking elongation (%) after aging for 100 hours at 120° C. and 100% RH, and S(0) represents a breaking elongation (%) before aging at 120° C. and 100% RH.