To effectively utilize the full width of a biaxially stretched polyester film in consideration of the orienting property of the film and to reduce cost by cutting the film having a specified difference in the orientation angle between the central and edge parts, in such a way that the difference in the angle of orientation between both edges is reduced to a specified value or smaller and then carrying out heat treatment.
A biaxially stretched polyester film having 30° or higher difference in the angle of orientation between the central and edge parts in the width direction after film formation is cut into two or more, in such a way that the difference in the angle of orientation between both edges is reduced to 25° or smaller, and then heat treatment is carried out at 60-200°C under 0.01-60 kg/cm2 tension in conveyance before coating with photographic constituent layers, including a photosensitive layer and after coating with an undercoat layer. The polyester film undergoes 0.01 g/cm3 or smaller density change, a birefrigence change of 0.005 or smaller and an elastic modulus change of 0.75-1.2 in the longitudinal direction before and after the heat treatment.
| JP4591992 | Biaxially stretched polypropylene film |
| JP5148841 | Fine roughened polypropylene film |
| JPS63315222 | SHRINKABLE STYRENE RESIN FILM |
EZURE HIDETOSHI
HOSOI YUJI
