| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyester film and a manufacturing method for the same, which is excellent in hydrolysis resistance, while heat resistance under dry thermo-condition is excellent and mechanical strength is stably maintained.SOLUTION: In a polyester film satisfying a stress heat resistance index f(125) ≥3, a wet thermo-retention (=100×S(120)/S(0)) is 30% or more. [f(125): t=125 degree C is substituted into an approximation formula f(t) ; t: thermo-temperature [degree C]; f(t): the approximation formula of a straight line obtained by linear approximation of a plotted value from a relation of the thermo-temperature and a logarithm logT(t) of time T when rupture stress is 50%, when t=150, 160, 170 and 180, using a least square method, T(t): time (hr) when a maximum stress in a pulling test after thermo-processing (temperature t, 0% RH) becomes 50% before thermo-processing, S(120): rupture elongation (%) after 100 hours at 120 degree C, 100% RH, S(0): rupture elongation (%) before that]. |
