PROCESS FOR PRODUCING POLYESTER FILM

摘要

Molten polyester sheet (2) is solidified by cooling it on the surface of a mobile cooling medium on which water film (7) is formed, and the sheet is stretched at least 4.5-fold in overall stretching ratio in a longitudinal direction through a plurality of stretching steps. Since casting is conducted via the water film, water is absorbed in the surface layer and the interior of the cast sheet, thus facilitating orientation by stretching in the longitudinal direction and lowering the stretching temperature. As a result, stretching with a high stretching ratio can be attained by multi-stage stretching without conducting high-temperature stretching. Thus, this process can accelerate film formation, improve productivity, and provide a film having reduced unevenness in thickness, less surface roughness and excellent abrasion resistance.