| 摘要 |
<p>The purpose of the present invention is to provide a method for stretching a thermoplastic resin film that is suitable for use particularly in optical applications, that has excellent uniformity of thickness in the longitudinal direction and width direction, and that has minimal scratches such as adhesion scratch or transcription scratch. This purpose is achieved by a method for stretching a film in the longitudinal direction by a difference in circumferential speed between front and rear rollers, wherein infrared rays are emitted to the film by concentration heaters from above the film and below the film, and the film is longitudinally stretched, the longitudinally-directed length of the film surface over which converged infrared rays are emitted from above the film being a, the longitudinally-directed length of the film surface over which converged infrared rays are emitted from below the film being b, the a component and b component overlapping each other, and a and b both being 10 mm to 40 mm.</p> |
