FORMING METHOD FOR BIAXIAL POLYESTER FILM

摘要

The biaxial drawing polyester film is prepared by drawing with the tenter having the rail of exponential function of formula (1) and (2) : formula (1) , W(1)=W(O)exp(Sx1/V) ; and formula (2), S=V/Lx ln(W(F)/W(O)) : where W(1) is width (m) of the tenter when the drawing length in the tenter is 1; W(O) is width (m) at entrance of drawing range in the tenter; W(F) is width (m) at terminal of drawing range in the tenter; S is latitudinal drawing speed (sec-1); l is distance (m) to any position of drawing range from the entrance in the tenter; V is speed (m/min); L is length (m) between entrance and terminal of drawing range in the tenter. Pref. the latitudinal drawing speed is more than 0.4 sec-1.