Patent ID: 7214339
Filing Date: 2007-05-08
Classification: B29C,B29K,G11B,Y10T

Abstract:
1. A method for producing a polyester film, comprising: (a) stretching and relaxing the polyester film using a linear motor driven simultaneously biaxially stretching tenter oven; and (b) repeating step (a) from 3 to less than 10000 times, wherein stretching is performed at an area stretching ratio of from 1.05 to 5 times, and wherein relaxing is performed at a relaxation rate of from 0.1 to 80% based on machine direction length and transverse direction length reached immediately before relaxation, and wherein said polyester film is made of a resin mainly composed of a polyester, and wherein a total area stretching ratio of 25 to 150 times is achieved.