| 摘要 |
PURPOSE:To simultaneously manufacture a plurality of very thin films by a method wherein a plurality of unstretched films made of thermoplastic resin, the glass transition temperature of which is below the specified value, are piled up one another under the condition that liquid the boiling point of which lies within a specified range, is held between the films, and, after that, stretched in longitudinal and lateral directions at a specified temperature and heat-treated and finally separated from one another. CONSTITUTION:A plurality of unstretched films are simultaneously obtained by extruding thermoplatic resin, the glass transition temperature (Tg) of which is 130 deg.C, or lower, through a die with a plurality of slits. The resultant films are piled up one another under the condition that liquid, the boiling point (Bp) of which is 100 deg.C or above and 150 deg.C or below, is held between the films. Further, the films are longitudinally stretched and, after that, laterally stretched at a temperature, which is above Tg of the thermoplastic resin and below Bp of the liquid +30 deg.C, Furthermore, the resultant films are heat-treated and cooled and, after the edge parts of the films are cut off, they are separated from one another. Thus, a plurality of stretched films made of the same polymer are simultaneously manufactured under the state that the breakages caused during stretching and separation operation are decreased. |
