Konica Corporation

Tdk Corporation

Hisato Kato

Takahiro Mori

Kimio Ozawa

Narito Goto

Noboru Koyama

Kaoru Kawasaki

Akihiro Maezawa

Takahiro Hayashi

Kunitsuna Sasaki

Akihiko Seki

Akira Saitoh

Kazumasa Matsumoto

Hiroaki Yamagishi

Hiromichi Enomoto

Kazuyoshi Imai

Kazuyuki Shimazaki

This invention concerns a method for producing a magnetic recording medium by passing a magnetic coating material comprising a ferromagnetic powder and a binder resin through an ultrasonic treating device under the operating conditions of 10 to 200 kHz of frequency of oscillation and 10 to 100 .mu.m of amplitude of ultrasonic wave thereby effecting ultrasonic treatment of the magnetic coating material and coating the treated magnetic coating material on a substrate either directly or through an undercoating layer, characterized in that the ultrasonic treating device comprises an ultrasonic treating tank adapted to effect ultrasonic wave treatment of the magnetic coating material by passing the material therethrough, an ultrasonic wave horn inserted into the ultrasonic treating tank and provided with an operating end surface capable of exerting an ultrasonic oscillation on the magnetic coating material, and an ultrasonic wave oscillator connected to a basal part side of the ultrasonic wave horn, an operating depth H defined by the distance from the operating end surface of the ultrasonic wave horn to a bottom wall surface of the ultrasonic treating tank opposed to the operating end surface is set at a magnitude in the range of 2 to 40 mm, and the magnetic coating material to be coated on the substrate is subjected to tile ultrasonic treatment.

Method for production of magnetic recording medium

Disclosed is a magnetic recording medium comprising a non-magnetic support having thereon a plurality of layers, wherein an outermost layer is a magnetic layer having a thickness of less than 0.5 .mu.m, and layers other than the outermost layer contain two or more kinds of non-magnetic powder having different average particle sizes. The magnetic recording medium has high durability in running under high temperature and high humidity.

Magnetic recording medium having a magnetic layer containing magnetic

Disclosed are a magnetic recording medium which comprises a non-magnetic support, one or more coating layers provided on the non-magnetic support and an upper layer of the coating layers being a magnetic layer containing ferromagnetic metallic powder with the total thickness of the coating layers being 0.5 to 2.5 .mu.m, wherein the magnetic layer has a surface roughness Ra of 1.0 to 4.6 nm and a surface roughness R10z of 8.0 to 35.0 nm, which satisfy the relations of:

Magnetic recording medium having a magnetic layer with specified limits

Disclosed is a magnetic recording medium which comprises;

Magnetic recording medium comprising a conductive underlayer containing

A magnetic disc is disclosed, which comprises a disc-shaped magnetic recording medium having a magnetic layer comprising a ferromagnetic powder and a binder and a case having a liner of a nonwoven fabric comprising a polyester fiber or a polyacrylonitrile fiber in a ratio of not less than 30% by weight. The binder of the magnetic recording medium comprises a modified polyurethane resin containing a a polar group selected from the group consisting of a -SO.sub.3 M group, a --OSO.sub.3 M group, a --COOM group, a --PO(OM).sub.2 group and a --OPO(OM).sub.2 group, in which M is a hydrogen atom or a alkali metal atom, or a hydroxyl group provided that the polar group may form an intramolecular salt.

Magnetic disc assembly comprising a disc having a magnetic layer with a

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Hino, Japan

Hisato Kato