| 摘要 |
PURPOSE:To improve the mechanical properties of stretched films by a method in which a polysulfone resin film is subjected to a zone-stretching process under a condition that the temperature of the film, which is calculated in terms of a specific formula, is within the range from temperatures lower than the secon dary transition temperature of polysulfone resin to the secondary transition temperature. CONSTITUTION:A polysulfone resin film 2 is subjected to a zone-stretching process under a condition that the temperature (t deg.C) of the film, which is calculated by the formula (1), is within the range from a temperature 25 deg.C lower than the secondary transition temperature of the resin to the secondary transition temperature (less in hereinafter Tg) of the resin. In the formula (1), t0 is initial temperature ( deg.C) of the film, t1 is heating temperature ( deg.C), tau is heating time (hour) of the film, and a is thickness (m) of the film. The stretched film so obtained has extremely high molecular orientation bacause it is heated and stretched at Tg or within a specific temperature range slightly lower than Tg, and the molecular orientation is fixed without relaxation because of the narrow heating zone. Stretched film having excellent thickness accuracy can thus be obtained. |
