Patent ID: 6090898
Filing Date: 2000-07-18
Classification: C08J,Y10T

Abstract:
A polyester film, having at least one surface portion and a central portion, comprising a non-liquid crystal polyester (A) and a copolyester (B), said copolyester (B) containing mesogen groups in the main chain to form a phase separated structure in said non-liquid crystal polyester (A), said copolyester (B) having dispersed domains, wherein forms of said dispersed domains satisfy the following formulae (1) and (2):0.02<(I/J)<50 (1)K<1/2.times.S[I, J] (2)where I, J and K are form indicators expressing the average form of the plurality of domains existing in the film: I is the average length of said dispersed domains of said copolyester (B) in the machine direction of the film; J, the average length of said dispersed domains of said copolyester (B) in the transverse direction; and K, the average length of said dispersed domains of said copolyester (B) in the normal direction: and S is a function for selection the shorter value of the lengths I and J; if I>J, S means J, and if I<J, S means I.