POLYESTER FILM AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To provide a quality polyester film which is excellent in mechanical strength including tensile properties as represented by Young's modulus and has reduced nonuniformity in thickness. SOLUTION: In a method for producing a polyester film in which a film of a resin containing the polyester as a main component is stretched with the use of a linear motor type simultaneous biaxial tenter, a series of operations in which the film is relaxed after being stretched is repeated 2-10,000 times.