Konica Corporation

Kabushiki Kaisha Toshiba

Nobuyuki Sekiguchi

Narito Goto

Katsuyuki Takeda

Kunitsuna Sasaki

Hideki Takahashi

Takahiro Mori

Isamu Michihata

Ryosuke Isobe

Hideki Murata

Masanori Isshiki

Ryosuki Isobe

Syozo Kikugawa

A magnetic recording medium and a manufacturing process thereof are disclosed. The medium comprises a magnetic layer containing a binder, chromium oxide having an average particle size within the range of 0.3 to 0.5 .mu.m and a metal magnetic powder, wherein the binder comprises a polyurethane resin having a polar group selected from the group consisting of --SO.sub.3 M, --OSO.sub.3 M, --COOM, --PO (OM), and --OPO(OM).sub.2 wherein M represents a hydrogen atom or an alkali metal.

Disk type magnetic recording medium and process of manufacturing the same

Disclosed is a magnetic recording medium characterized in that plural magnetic layers are provided on a non-magnetic support, the uppermost layer of the magnetic layers contains a ferromagnetic metallic powder and/or a hexagonal system magnetic powder and a binder, at least one layer other than the uppermost layer contains Co-containing iron oxide and a binder, the film thickness of the uppermost layer is 0.5 .mu.m or less, and the surface of the uppermost layer of the magnetic layers has an R.sub.10z value of the magnetic layer defined below of 50 nm or less, by which electromagnetic conversion characteristics of a magnetic recording medium can be improved.

Magnetic recording medium

A magnetic recording medium having an improved output property over the wide range of wavelength, by controlling the magnetic reluctance and saturated magnetic flux density of the outermost layer and at least one layer other than the outermost layer, as specified in the claims, is disclosed. A magnetic matal powder contained in the outermost layer has an average major axis length of not more than 250 nm and a ratio of the average major axis length divided by an average X-ray measured particle size is less than 12.

The present invention provides a magnetic recording medium comprising a support, lower magnetic layer comprising ferromagnetic powder and nonmagnetic powder dispersed in a binder and an upper magnetic layer which contains ferromagnetic powder dispersed in a binder. The lower layer has a coercive force of not less than 200 Oe, a saturation magnetic flux density in the range of 5-1000 gauss and non magnetic particles with a specific gravity of not less than 2.5. The ferromagnetic powder of the upper layer is a ferromagnetic metal powder containing Fe and Al, and the ratio of non magnetic powder to magnetic powder in the lower magnetic layer is from 50/50 to 99/1.

A magnetic recording medium having magnetic layers on the non-magnetic support. The surface of the non-magnetic support has more than 200 protrusions per mm of the measuring length having more than 0.01 .mu.m height, and protrusions having the height more than 0.30 .mu.m height less than 500 per 400 mm of the measuring length. The protrusions are on the surface of the magnetic layers provided or opposit side of the support or the both sides. These protrusions reduce the surface friction of the medium, resulting the better electro-magnetic properties and the longer life for repeated usages.

A magnetic recording tape of plural magnetic coating layers, which has excellent properties of both the electromagnetic conversion properties, particularly the chromatic output, and the corrosion resistance is disclosed. The top layer contains magnetic metal powder having the weight ratio of Al to Fe being 0.005 to 0.2, and the lower layer has the coercive force of not less than 650 Oe and not more than 1200 Oe.

A magnetic recording tape with plural magnetic layers, having both the electromagnetic conversion properties, particularly the chromatic output, and the corrosion resistance is disclosed. The top layer contains a magnetic metal powder having 0.2-1.5% of water when it is mixed into a magnetic paint and a layer other than the top layer has the coercive force of 500 to 12000 Oe.

A magnetic recording medium is disclosed. The medium comprises a support and provided thereon, a plurality of magnetic layers containing a magnetic powder and a binder, wherein an outermost magnetic layer of said magnetic layers comprises a ferromagnetic metal powder having an average major axis length of not more than 0.25 .mu.m and a crystallite size of not more than 200 .ANG. and carbon black having an average particle diameter of not less than 30 m.mu. in an amount of not more than 1% by weight, said outermost magnetic layer having a thickness of not more than 1 m.mu. and a surface roughness R.sub.10z of not more than 50 nm, and at least one magnetic layer other than said outermost layer comprises a cobalt-containing magnetic iron oxide powder having an average major axis length of not less than 0.25 .mu.m and a crystallite size of not less than 250 .ANG., said magnetic layer having a coercive force of from 500 to 1200 Oe.

Magnetic recording medium comprising multiple magnetic layers with

A magnetic recording medium is disclosed. The medium comprises a non-magnetic support and, provided thereon, plural magnetic layers comprising the uppermost magnetic layer having a thickness of 1.5 .mu.m or less and lower magnetic layers, said plural magnetic layers containing a ferromagnetic powder, a binder and a lubricant, wherein a dynamic friction coefficient of the uppermost layer against a metal pin is 0.25 or less under the condition of a temperature of 20.degree. C. and a relative humidity of 60%, and 0.20 or less under the condition of a temperature of 40.degree. C. and a relative humidity of 20%.

A magnetic recording medium is disclosed, which is improved in electromagnetic conversion properties. The recording medium comprises a support, an uppermost magnetic mayer being provided on the support and one or more lower magnetic layers being provided between the support and the uppermost magnetic layer, in which the uppermost magnetic layer comprises a binder and a hexagonal magnetic powder and has a layer thickness of from 0.1 .mu.m to 1.0 .mu.m, and at least one of the lower magnetic layer comprises a binder having a anionic functional group and a magnetic powder, and has a coercive force of from 500 Oe to 1200 Oe, and the uppermost magnetic layer and the lower layer were formed on the support by wet-on-wet simultaneous multi-layer coating.

Growing community of inventors

Hino, Japan

Nobuyuki Sekiguchi