| 摘要 |
PURPOSE:To enable lateral stretching and thermal set whose physical properties are uniform by reducing a bowing phenomenon, by a method wherein at the time of manufacturing of a thermoplastic film which is stretched at least laterally, the film is cooled to a temperature not exceeding the glass transition temperature by providing a cooling process satisfying a specific formula between a lateral stretching process and thermal setting process. CONSTITUTION:At the time of performance of lateral stretching and setting treatment, a film prior to a thermal setting process is cooled to a temperature not exceeding the glass transition temperature and a bowing phenomenon generated with a lateral stretching process is reduced. The lower this cooling temperature is and the bigger a value of a ratio L/W between a length L of a cooling process and a film width W is, the more a reducing effect of the bowing phenomenon is improved, and it is preferable to select the length L of the cooling effect with a formula of L/W>=2.0. Furthermore, the formula of L/W>=3.0 is preferable. In the case where a tenter performing the lateral stretching process and thermal setting process is cut off, since a film is run within atmosphere, it is good that the film is cooled to a temperature not exceeding the glass transition temperature and satisfies L/W>=1.0. |
