| 摘要 |
PURPOSE:To enhance dimensional stability and better plane properties to prevent unevenness of thickness by slowly cooling down to room temperature after imparting to a reinforced PET film finished in heat treatment a specified amount of limpness to the progressing direction of film at a specified temperature. CONSTITUTION:A film, not oriented substantially, consisting mainly of polyethylene terephthalate is oriented by 3.0-5.0 times at 80-130 deg.C in length and breadth to make a biaxial oriented film. Next, the same is biaxially oriented simultaneously by 1.0-2.0 times at 110-180 deg.C in length and breadth while both ends are being grasped with clips. Then the same is heat-treated at 160-240 deg.C. After that, 0.1-2% limpness is imparted to the progressing direction of film (longitudinal direction) at a temperature of 80-130 deg.C and the film is slowly cooled down to room temperature at 3-20 deg.C/sec to be wound up. Polyethylene terephthalate (PET) is a polymer, a copolymer or a mixture comprising ethylene terephthalate unit more than 70mol% of molecular constitution. The melting point of polymer is more than 250 deg.C, preferably more than 255 deg.C. |
