| 摘要 |
<p>A biaxially oriented polyester film wherein the ratio R (= IMD/IND) of the peak intensity (IMD) in the lengthwise direction to the peak intensity (IND) in the thicknesswise direction determined at 1615 cm-1 by the laser Raman scattering technique equals or exceeds 6; and a process for the production of a biaxially oriented polyester film which comprises controlling the ratio (A/B) of the maximum thickness (A) of the edge of a cast film to the thickness (B) of the central portion with respect to the width thereof to be within 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 technique to be within the aforementioned range. The biaxially oriented polyester film thus produced has a specific orientation in the lengthwise direction, and therefore has great lengthwise strength and small irregularity in properties, such as thickness or double refraction.</p> |
