PRODUCTION OF BIAXIALLY STRETCHED POLYESTER FILM

摘要

PURPOSE:To obtain an asymmetric polyester film hard to generate a winding habit and a scratch, reduced in the irregularity of anti-curling and excellent in winding habit eliminating properties especially in photographic use. CONSTITUTION:When a biaxially stretched polyester film is produced by stretching an asymmetric polyester multilayered sheet 1 in both of the longitudinal and lateral directions thereof at least once, the surface on a side 3 where the glass transition temp. of a thickness average is high with respect to the surface which makes the thickness of the asymmetric polyester multilayered sheet into two parts is brought into contact with a longitudinally stretching final preheating roll 5 to perform thermal stretching treatment in the longitudinal direction to set a winding habit curl to 135m<-1> or less.