| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method for stably producing an obliquely stretched polyester film to be suitably used for an optical purpose. ! SOLUTION: The production method of a polyester film includes a process of obliquely stretching a film by using a tenter type stretching device, in which both ends in a width direction of the film are gripped with gripping tools and pitches of the gripping tools in a travelling direction of the film are varied in different positions of the gripping tools at both ends. In the velocities of the gripping tools after the film is stretched in the travelling direction by varying pitches of the gripping tools, a ratio (V2/V1) described below is controlled to 1.02 to 1.05, where V1 is a velocity of the gripping tools after the film is stretched on a side where pitches are first varied, and V2 is a velocity of the gripping tools after the film is stretched on the other side where pitches are varied afterward. ! COPYRIGHT: (C)2015,JPO&INPIT |
