Tdk Corporation

Toru Shimozawa

Masaharu Nishimatsu

Kenji Yokoyama

Masatoshi Nakayama

Kunihiro Ueda

Shigeyo Miyamori

Fumio Maruta

Kazunori Tamazaki

Yoshiaki Saito

Yuichi Kubota

Keiji Koga

In a magnetic recording medium wherein a metal thin film magnetic layer and an overcoat are formed on a nonmagnetic substrate, durability is improved when the overcoat comprises a plasma-polymerized film and a topcoat of an organic fluorine compound; a plasma-polymerized film, a protective carbon film, and a topcoat of an organic fluorine compound; a plasma-polymerized film containing C, F and H; or a plasma-polymerized organometallic film and a fluorine or silicon-containing topcoat. Oxidation of the upper surface of the magnetic layer with a plasma is also effective.

Magnetic recording medium

In a magnetic recording medium wherein a metal thin film magnetic layer and a topcoat layer of an organic fluorine compound are formed on a nonmagnetic substrate, the surface of the magnetic layer is plasma treated or plasma oxidized, enhancing the bond between the adjoining layers. A protective film of carbon may be disposed between the magnetic layer and the topcoat, with the surface of the protective carbon film plasma treated. Instead, a protective film of plasma-polymerized organometallic compound may be used.

In a magnetic recording medium comprising a substrate and a magnetic layer thereon, the magnetic layer is formed by coating a composition of a binder, preferably radiation-curable binder and a plate magnetic material such as hexagonal plate barium or strontium ferrite having an average particle diameter d expressed in .mu.m and an average flakiness R satisfying the following equations: 0.1&lt;d.ltoreq.0.15 and R.gtoreq.280d-22, passing the coating through a magnetic field to orient the magnetic plates, and curing the coating.

A magnetic recording medium comprising a substrate, an optional undercoat layer, and a magnetic layer formed thereon and containing a hexagonal plate magnetic powder, an electroconductive material, and a binder is improved in runnability and recording density by the presence of a fatty acid ester at least on the recording side surface of the magnetic layer, and by providing an electric resistance of up to 5.times.10.sup.9 .OMEGA./cm.sup.2 on the side of the magnetic layer.

In a coating type perpendicular magnetic recording medium intended for digital recording comprising a substrate and a magnetic layer thereon, the magnetic layer is formed from a composition of a binder, preferably radiation-curable binder and plate magnetic material such as hexagonal plate barium or strontium ferrit having an average particle diameter of up to 0.15 .mu.m and a flakiness of at least 6.

Coating type perpendicular magnetic recording medium for digital

A magnetic recording medium comprising a non-magnetic substrate and a coating type magnetic recording layer formed on the substrate, wherein barium ferrite magnetic powder is perpendicularly oriented, characterized in that an undercoating layer comprising a radiation curable binder and carbon black, is provided beneath the magnetic recording layer.

A coating type magnetic recording medium particuarly suitable as a mangetic disk is provided, which comprises a substrate and a magnetic layer of a plate magnetic powder and a binder on the substrate. Selection is made such that the plate magnetic powder has an average particle diameter of up to 0.2 .mu.m and an average flakiness of at least 2, the magnetic layer is up to 1.8 .mu.m thick, and the magnetic recording medium has a coercive force of a value x in Oe and a rectangular ratio Br/Bm of a value y both in a direction perpendicular to the magnetic layer surface, which fall in the range defined by the following equations:

In a magnetic recording medium comprising a substrate and a magnetic layer thereon, the magnetic layer is formed by coating a composition of a binder, preferably radiation-curable binder and a plate magnetic material such as hexagonal plate barium or strontium ferrite having an average particle diameter of up to 0.1 .mu.m and a flakiness of at least 6, passing the coating through a magnetic field to orient the magnetic plates, and curing the coating.

A magnetic recording medium comprising a non-magnetic substrate, a magnetic recording layer formed on one side of the substrate and a back coating layer formed on the other side of the substrate, characterized in that the magnetic recording layer contains a hexagonal system plate crystal magnetic powder having a particle size of at most 0.2 .mu.m, and the back coating layer contains a binder composed of a radiation curable resin and has an electric resistance of at most 10.sup.10 .OMEGA./cm.sup.2.

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Nagano, Japan

Toru Shimozawa