Tdk Electronics Company, Limited

Tdk Corporation

Canon Kabushiki Kaisha

Norifumi Kajimoto

Jun Kamatani

Tetsuo Takahashi

Takayuki Ito

Yosuke Nishide

Hiroyuki Yamada

Naoki Yamada

Hirokazu Miyashita

Yuichi Kubota

Hironobu Iwawaki

Hiroki Ohrui

Satoru Shiobara

Nobutaka Mizuno

Kentaro Ito

Hitoshi Azegami

Masumi Itabashi

Tomona Yamaguchi

Isao Kawata

Yuto Ito

Yoshio Kawakami

Yoneo Matsuzawa

Moe Takahira

Kinji Sasaki

Ikuko Yanagiuchi

In a magnetic recording medium comprising a magnetic layer of a ferromagnetic powder dispersed in a resin binder and a nonmagnetic substrate for the layer, the magnetic layer contains zine aluminate (ZnAl.sub.2 O.sub.4) powder. The ferromagnetic powder is of chromium dioxide (CrO.sub.2) and the ZnAl.sub.2 O.sub.4 content in the magnetic layer is 0.01-1 wt % on the basis of the weight of the ferromagnetic powder.

Magnetic recording medium

A magnetic recording medium comprising a non-magnetic substrate and a magnetic layer thereon containing a ferromagnetic CrO.sub.2 powder dispersed in a resin binder. The magnetic layer contains 0.01-1.0 wt % of Al.sub.2 O.sub.3 powder on the basis of the CrO.sub.2 powder so as to improve wear of magnetic heads.

In a magnetic recording medium having a magnetic recording coat formed on one side of a base and a back coat on the other side, the back coat consists of a dispersion in a binder of an inorgainc pigment powder having an average particle diameter of 0.2 to 0.5 .mu.m and a Mohs hardness of not greater than 6. The binder consists of a specific copolymer, a rubber-like binder, and a polyisocyanate ingredient. The copolymer consists of vinyl chloride, a vinyl alkyl carboxylate, a monomer copolymerizable with vinyl chloride, and a saponified vinyl alkyl carboxylate and has an OH/CH absorption ratio as determined from its infrared absorption spectrum in the range of 0.2 to 0.7.

A magnetic recording medium comprises a substrate coated with a magnetic layer comprising a magnetic powder and a fine titanium oxide powder having a particle diameter of at least 0.4.mu. and at least one other fine hard non-magnetic powder.

A magnetic recording medium comprises a combination of two or more kinds of fine abrasive powders having different true specific gravities in a magnetic layer containing a magnetic powder.

A magnetic tape cassette holding a wound magnetic tape comprising a transparent base film and a magnetic layer having a thickness of 5.mu. or less coated on the base film comprises a hole facing a light source for detecting the tape position, a hole facing a photosenser provided so as to form a light path passing to the hole for light source through which the magnetic tape is passed and a light-shielding filter having a light transmittance in the range between 0.5 and 10 percent placed in the light path.

Magnetic tape cassette

A magnetic recording tape comprises a polyethyleneterephthalate base film coated with a magnetic layer which has an index H given by the equation:

Magnetic recording tape

A magnetic recording medium is prepared by preparing a nitrocellulose-based magnetic composition by kneading a magnetic powder with a mixture of nitrocellulose in a solvent system containing isopropyl alcohol and blending the kneaded mixture with a polyurethane containing unreacted isocyanate groups; coating a substrate with the resulting magnetic composition and allowing the coated substrate to dry. The improvement comprises replacing substantial portions of the isopropyl alcohol from the group consisting of polyurethane resins, polybutadiene resins, butadiene-acrylonitrile copolymers, vinyl chloride-vinyl acetate-vinyl alcohol copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl acetate resins, epoxy resins, phenoxy resins, polyvinyl butyral resins, polyvinyl formal resins and polyester resins.

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Tokyo, Japan

Norifumi Kajimoto