POLYESTER FILM AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To obtain a polyester film of high quality excellent in rigidity, tenacity and heat shrinkage characteristics and reduced in thickness irregularity and surface defect and a method for producing the same. SOLUTION: In a method for producing a polyester film by biaxially stretching a film comprising a resin based on polyester at the same time by using a simultaneous biaxial tenter of a linear motor system, micro-stretching operation setting the area draw ratio of the film to 1.0005-3.0 times is continuously repeated three times or more to obtain the polyester film.