BIAXIAL ORIENTIERTER POLYESTERFILM UND DESSEN HERSTELLUNGSVERFAHREN

摘要

A biaxially oriented polyester film wherein the ratio (=IMD /IND) of the peak intensity (IMD) in the longitudinal direction to the peak intensity (IND) in the thickness direction determined at 1615 cm<-1> by laser Raman scattering method is not less than 6; and a process for production of a biaxially oriented polyester film which comprises the steps of controlling the ratio (A/B) of the maximum thickness (A) of the edge portion of a cast film to the thickness (B) of the central portion in the transverse direction thereof in the range of 2 to 6, biaxially stretching the cast film, and controlling the peak intensity ratio of the biaxially oriented film determined by the laser Raman scattering method in the above-described range. The biaxially oriented polyester film thus produced has a specific orientation in the longitudinal direction, and therefore has great strength in the longitudinal direction and small irregularity in properties such as thickness or birefringence.