| 摘要 |
PURPOSE: To obtain an improved polyethylene terephthalate photographic film base having superior dimensional stability, optical transparency and mechanical strength and capable of finishing by cutting, shredding or perforating technique due to restricted breaking resistance while suppressing the occurrence of dust. CONSTITUTION: Melted polyethylene terephthalate resin is cast on a casting surface, the resultant film is successively subjected to orientation by stretching in the longitudinal direction in a stretching ratio of 2.0-4.0, widening by stretching in the transverse direction in a stretching ratio of 2.0-4.0, heat setting at about 200-250 deg.C under restraint and rebound prevention by shrinking the width by 2-20% to obtain a film having an index of plane double refraction of 0.12-0.149 and the objective polyethylene terephthalate film base is produced. |
