Diafoil Company, Ltd.

Kazuyuki Akatsu

Shigeo Utsumi

Kazuo Endo

Narihiro Masuda

Chikakazu Kawaguchi

Masashi Inagaki

Toshifumi Takisawa

Yoshinori Sato

Satoshi Otonari

Kichinojo Tomitaka

Yoshio Meguro

Masahiko Fujimoto

Kenji Kato

Nobuyasu Shudo

Shigeyuki Watanabe

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.

Polyester films, magnetic recording media and film capacitors produced

Disclosed herein is a magnetic card comprising a monoaxially or biaxially stretched minute-cellular polyester film which has an apparent density of 0.4 to 1.3 g/cm.sup.3 and an opacifying power of 0.2 or more and a magnetic layer applied on at least one surface of said film. By using the polyester film containing small air bubbles as the base material of the magnetic card, flexibility, flatness and punching property, which were insufficient in a magnetic card using a conventional polyester film, are improved.

Magnetic card

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Yokohama, Japan

Kazuyuki Akatsu