| abstract |
PCT No. PCT/JP95/01702 Sec. 371 Date Apr. 29, 1996 Sec. 102(e) Date Apr. 29, 1996 PCT Filed Aug. 28, 1995 PCT Pub. No. WO96/06722 PCT Pub. Date Mar. 7, 1996A 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 6 or more; 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. |