| 摘要 |
PURPOSE:To prevent the strain, creases, shrinkage spots, etc., of a film at the time of shrinkage by specifying a shrinkage factor after specified heat treatment in one direction and the direction orthogonal to the direction and bringing maximum shrinkage stress at a special temperature in the same direction to a specific value or less. CONSTITUTION:Polyester is composed of polyester or copolymerized polyester consisting of one kind or two kinds or more of dicarboxylic acids and one kind or two kinds or more of a diol component, and a shrinkage factor after treatment for five min in an air oven at 100 deg.C of a polyester film must be brought to 40% or more, preferably 50% or more in either one direction of the longitudinal or cross direction. A shrinkage factor in the direction orthogonal to said direction must be brought to 15% or less, preferably 5% or less. Maximum shrinkage stress at 40-100 deg.C in the same direction must be brought to 50g/mm<2> or below, preferably 30g/mm<2> or below. |
