| 摘要 |
PURPOSE:To prevent curling from developing and consequently obtain a film with favorable flatness by a method wherein the temperature of cooling rolls are set in two specified steps in a method to cool the thick-gage film, which is made of thermoplastic resin and the thickness after orientation of which lies within the specified range, with the cooling rolls. CONSTITUTION:The temperature of a first cooling roll is set at a temperature comparatively higher than the normal cooling temperature of within the range of Tg-10-Tg-30 deg.C (where Tg is the glass transition temperature of a film) so as to hold down the gradient of the cooling rate of the surface layer of the film, with the side of which the first cooling roll comes into contact. The thickness of the film is 150-1,500mum. The temperature drop in the interior part of the film while being carried by winding on the cooling roll is not so much larger. The temperature of a second cooling roll is set lower than that of the first cooling roll by 10-40 deg.C. As a result, the gradient of the cooling rate of the surface layer of the film, with the side of which the second cooling roll comes into contact, becomes nearly equal to the gradient of the cooling rate of the surface layer of the film in case of the first cooling roll and the densities of the surface layers becomes nearly the same as each other and consequently curling is prevented from developing at the film. |
