| 摘要 |
PROBLEM TO BE SOLVED: To avoid shifts in tracking and deterioration of a planarity during long-term use at high temp. and high humidity by maintaining the rate of dimensional change and intrasurface anisotropy the level lower than a prescribed level at high temp. and high humidity. SOLUTION: This polyester film has 0.1% or lower rate of dimensional change and 0.05% or lower as intrasurface anisotropy at 80 deg.C in 30 min and 0.2% or lower rate of dimensional change and 0.1% or lower intrasurface anisotropy at 80 deg.C and at 80% RH for 30 min. A polyester resin forming the polyester film is a linear polyester using an arom. dicarboxylic acid as the principal acid component and an aliphatic glycol as the principal glycol component. The arom. dicarboxylic acid is, e.g. terephthalic acid, naphthalenedicarboxylic acid or isophthalic acid. The aliphatic glycol is, e.g. a 2-10C polyethylene glycol such as ethylene glycol or diethylene glycol. |
