| 摘要 |
PURPOSE: To compensate the core set curl generated by a final spool on which the film is wound by heating and stretching the film under specific conditions, thereby forming the curl. CONSTITUTION: Molten polyethylene terephthalate is extruded and is cooled with a cooling drum and is then supplied to the driving rollers 18 of a longitudinal stretching machine 13. The film is then preheated by first IR heaters 20, 21 disposed symmetrically and is thereafter heated to its glass transition temp. or above by the second IR heaters 22, 23 and is stretched. For example, a medium wave heater is used for the heater 22 and a short wave heater for the heater 23. The film is stretched by imparting a temp. gradient of >=10 deg.C to the other surface from one surface of the film and confining the strength in the longitudinal direction of the film to <10N/mm<2> . In succession, the film is passed in cooling water 30 to rapidly stop the longitudinal stretching thereof. As a result, the specified amt. of the longitudinal curl is formed at the film. |
