Diafoil Company, Ltd.

Diafoil Hoechst Company, Limited

Yoshio Meguro

Chikakazu Kawaguchi

Seiji Sakamoto

Kazuo Endo

Toshifumi Takisawa

Takashi Harada

Masashi Inagaki

Masahiko Fujimoto

Nobuyasu Shudo

Shigeo Utsumi

Kichinojo Tomitaka

Kenji Kato

Kazuyuki Akatsu

Shigeyuki Watanabe

Disclosed herein is a polyethylene terephthalate film for magnetic recording medium, which contains 0.1 to 1.0% by weight based on the film of aggregated silicon oxide particles having an average particle size of 0.03 to 0.2 .mu.m, primary particle of which having an average particle size of 0.005 to 0.05 .mu.m, 0.1 to 1.0% by weight based on the film of aggregated aluminium oxide particles having an average particle size of 0.03 to 0.2 .mu.m, primary particle of which having an average particle size of 0.005 to 0.05 .mu.m and 0.005 to 0.3% by weight based on the film of a crosslinked polymer having an average particle size of 0.2 to 0.8 .mu.m, said film having a center line average surface roughness of 0.003 to 0.015 .mu.m and a sum of F-5 values in both the machine direction and the transverse direction of at least 25.0 kg/mm.sup.2. The film has a flat surface and is excellent in slipperiness, abrasion resistance, scratch resistance and protuberance resistance, which can be used as a base film for high-density magnetic recording medium.

Polyethylene terephthalate film for magnetic recording medium containing

A biaxially oriented polyester film containing a specific calcium carbonate is described. The calcium carbonate contained in the film is specified by its vaterite form, its average particles size of 0.07 to 1.5 .mu.m, and its particle size distribution ratio of not more than 2.00. The biaxially oriented polyester film containing such specific calcium carbonate is excellent in both the running property and wear resistance, and suitable for the use as a base of magnetic recording media.

Polyester film for magnetic recording media

Disclosed herein is a polyester film containing specific fine spherical silica particles. The film of the present invention is especially suitable as a base film for a magnetic recording medium or dielectric for a capacitor. The films of the present invention have the markedly improved properties such as surface properties, electromagnetic properties, electrical properties, etc. due to the excellent dispersibility of the particles in the film.

Polyester films, magnetic recording media and film capacitors produced

Disclosed in this invention is a polyester film for magnetic recording media, containing 0.05 to 5% by weight of inactive inorganic particles (A) having a Mohs hardness of 6 or above and an average particle size of 0.005 to 1.0 .mu.m and 0.01 to 2.0% by weight of inactive particles (B) having an average particle size which is greater than that of the particles (A) and in the range of 0.1 to 3.0 .mu.m, the polyester film having an intrinsic viscosity in the range of 0.52 to 0.65. The polyester film of this invention is excellent in abrasion resistance, scuff resistance and slitting qualities and useful as a base film for magnetic recording media.

Disclosed herein is a polyester film containing specific fine spherical silica particles. The film of the present invention is especially suitable as a base film for a magnetic recording medium or dielectric for a capacitor. The films of the present invention have the markedly improved properties such as surface properties, electromagnetic properties, electrical properties, etc. due to the excellent dispersibliity of the particles in the film.

There is disclosed a polyester film suitable for use in magnetic tapes having the characteristics represented by the following equations: ##EQU1## wherein N.sub.1 is the number of peaks of surface projections per millimeter;

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Machida, Japan

Yoshio Meguro