Abstract: The present invention is directed to a process for producing a biaxially oriented polyester film which comprises: subjecting a polyester film to simultaneous biaxial stretching in a stretching apparatus constructed to simultaneously stretch the film in the lengthwise and widthwise directions thereof; and subsequently subjecting the film to successive biaxial stretching in the lengthwise and widthwise directions thereof in the same apparatus as mentioned above. With this process, a film can be efficiently formed, without film breaking, which film is small in thickness and greatly strong in its lengthwise and widthwise directions.

Abstract: The present invention is directed to a process for producing a biaxially oriented polyester film which comprises: subjecting a polyester film to simultaneous biaxial stretching in a stretching apparatus constructed to simultaneously stretch the film in the lengthwise and widthwise directions thereof: and subsequently subjecting the film to successive biaxial stretching in the lengthwise and widthwise directions thereof in the same apparatus as mentioned above. With this process, a film can be efficiently formed, without film breaking, which film is small in thickness and greatly strong in its lengthwise and widthwise directions.

Abstract: A heat-sensitive mimeograph stencil having a uniform shape of openings, which have an excellent balance of retention and permeation of printing ink is disclosed.The heat-sensitive mimeograph stencil includes a polyester film and a porous support made of polyester fibers, which is laminated on the polyester film, wherein the porous support constitutes a network having fused points formed by fusion of the fibers, and that membranes spanning the fibers are formed at some of the fused points, the membranes having thicknesses smaller than average diameter of the fibers. By virtue of this structure, the printed matter obtained by mimeographing using the stencil has high quality and is free from backside transcription. Further, the mimeograph stencil is excellent in ease of transportation.

Abstract: A biaxially oriented polyester film wherein the ratio (=I.sub.MD /I.sub.ND) of the peak intensity (I.sub.MD) in the longitudinal direction to the peak intensity (I.sub.ND) in the thickness direction determined at 1615 cm.sup.-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.

Abstract: A thermoplastic resin film wherein the variation in thickness of the film in the longitudinal direction is not more than 5% and the ratio "Pw1/PwT" of the sum of spectral intensities of wave-number components present in the wave-number range of 0.15 to 0.45 (1/m) (Pw1) to the sum of spectral intensities of the full wave-number range (PwT) determined when a wave form of the variation in thickness is subjected to analysis of Fourier transformation is not more than 0.20, and wherein the variation in thickness of the film in the longitudinal direction is not more than 5% and the ratio "Pw2/PwT" of the sum of spectral intensities of wave-number components present in the wave-number range of 1.00 to 2.00 (1/m) (Pw2) to the sum of spectral intensities of the full wave-number range (PwT) is not more than 0.15. In such a film, the uniformity in thickness can remarkably improved, and snaking and wrinkles in post processing can be prevented.