PROCESS FOR PRODUCTION OF BIAXIALLY ORIENTED POLYESTER FILM

摘要

A process for producing a polyester film which is effectively reduced in the disadvantageous lengthwise and widthwise heat shrinkages inherent in biaxially oriented film and which is excellent in flatness and mechanical characteristics. More specifically, a process for the production of biaxially oriented polyester film which comprises subjecting a biaxially oriented polyester film which has been oriented in the lengthwise and widthwise directions and heat-treated to widthwise relaxation and lengthwise relaxation by a method of shortening the clip intervals, wherein the biaxially oriented polyester film is held under stretching between the widthwise relaxation step and the lengthwise relaxation step.