| 摘要 |
PROBLEM TO BE SOLVED: To suppress the longitudinal sink of a film to make shrink finish appearance beautiful by specifying a shrinkage factor in hot water with specific temp. in one direction and the max. shrinkage rate in one direction in a dry oven. SOLUTION: A polyester heat-shrinkable film 2 is characterized by that a shrinkage factor in hot water of 75 deg.C in one direction is 0.1-30% and the max. shrinkage rate is 0.1-20%/sec at 100 deg.C and 0.1-30%/sec at 140 deg.C. Therefore, the film is pref. drawn by 3.0-6.0 times finally in one direction and pref. drawn by 1.0-1.8 times in the direction right-angled to this direction. Especially, treatment temp. in drawing in a main direction (main shrinkage direction) is set to Tg+0 deg.C-50 deg.C in preheating and gradually raised at a temp. of Tg-20 deg.C-+30 deg.C in drawing and temp. difference is provided to perform drawing. Further, by cooling the film held to an elongated or tensioned state after drawing while applying stress thereto or further succeedingly cooling the film, pre- and post-treatment characteristics become more well. |
