| 摘要 |
PURPOSE:To obtain a film without bowing and with the unified material in its lateral direction by making a specific lateral-draw and heat treatment on a longitudinally uniaxially oriented polyester film. CONSTITUTION:At the time when the longitudinally uniaxially oriented polyester film is made by the lateral-draw, it is laterally draw in the region of Tg-Tm-20 deg.C by raising the temperature in the draw-range divided into two or more and then made by thermosetting. In the division less than two stages, the draw becomes uneven and the draw-breakage of film is likely to take place. It is preferably that the lateral draw magnification is made up to 50-90% of the lateral draw magnification, at least, in a two stages temperature zone within the range of the temperature of Tg-Tg+100 deg.C, and then the lateral draw is made within the temperature ranging from the temperature higher than pre-stage draw temperature to the temperature of Tm-20 deg.C. The thermosetting is made preferably for 3-30sec within the range of temperature of Tm-60 deg.C-Tm-20 deg.C in view of the characteristics of biaxial oriented polyester. The width relaxation in thermosetting should be done as required, and the rate of relaxation is preferably 3-15%. |
