| 摘要 |
PURPOSE:To obtain efficiently a film having excellent optical isotropy by forming a heat treating raw material in providing a groove having a specific width and a specific depth at least on one end in the film cross section in a film width direction. CONSTITUTION:In the film cross section in a film width direction, a heat treating raw material 1 is formed which has a groove 2 at a width W of (10/100).L or more with respect to the width S of the film and a depth T of (1/10) or more with respect to the film thickness D of the film at least on one end thereof. For the resin constituting of this heat treating raw material, thermoplastic resin is used, however, it is preferred to employ fluorocarbon resin, engineering plastics, and aromatic polyester resin. By heat-treating afore- mentioned raw material, a film can be obtained which is excellent in its optical isotropy. |
