Tdk Corporation

Konica Corporation

Kazuyuki Shimazaki

Kaoru Kawasaki

Akihiko Seki

Takahiro Mori

Akira Saitoh

Eizo Tsunoda

Hisato Kato

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

A mixture containing a magnetic powder, a binder, and an organic solvent is kneaded by passing it through a twin-shaft continuous kneader while the shearing force applied to the mixture is varied by changing the set angle of paddles used. The temperature of the mixture is controlled to be higher than Tg and lower than the boiling point of the organic solvent when it passes through the maximum shearing force zone, and to be lower than the temperature of the mixture upon its passage through the maximum shearing force zone, preferably lower than Tg when it passes through zones other than the maximum shearing force zone. There is obtained a magnetic recording medium which has improved dispersion of magnetic powder and excellent electromagnetic properties as well as a low coefficient of friction and improved transport stability.

Method for preparing magnetic recording medium

Growing community of inventors

Saku, Japan

Kazuyuki Shimazaki