Konica Corporation

Kabushiki Kaisha Toshiba

Tdk Corporation

Konishiroku Photo Industry Co., Ltd.

Kunitsuna Sasaki

Narito Goto

Katsuyuki Takeda

Nobuyuki Sekiguchi

Takahiro Mori

Ryosuke Isobe

Kiyoshi Sawada

Yuki Ando

Hideki Takahashi

Takahiro Hayashi

Takafumi Yanagita

Toshiaki Shibue

Seiichi Tobisawa

Yoshitaka Yasufuku

Masanori Isshiki

Kazumasa Matsumoto

Hisato Kato

Kazuyoshi Imai

Kenji Kumamoto

Ryosuki Isobe

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.

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

A magnetic recording medium is disclosed. The magnetic recording medium is produced by coating the following magnetic paints on a support in the order from the support,

Disclosed is a method of producing a magnetic recording medium which comprises a magnetic layer, comprising a step of kneading a magnetic coating solution containing a ferromagnetic powder and a binder for the magnetic layer under a load of substantial electric power consumption of 0.05 to 0.5 KW per Kg of the ferromagnetic powder in a kneader chamber having an atmospheric water content of not more than 1 g/m.sup.3.

Method of producing magnetic recording medium

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 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 comprises a non-magnetic support and a magnetic layer comprising a ferromagnetic powder having a specific surface area of not less than 55 m.sup.2 /g and at least two kinds of resins each containing repetitive units having a polar group selected from the group consisting of a --SO.sub.3 M group, a --OSO.sub.3 M group, a --COOM group and a --PO(OM').sub.2 group, wherein M is a hydrogen atom or an alkali metal atom, and M' is a hydrogen atom, an alkali metal atom or an alkyl group, and the glass transition points of said two resins are different not less than 60.degree. C. from each other. The recording medium is improved in the dispersibility of the ferromagnetic powder in the magnetic layer and has a satisfactory surface smoothness, high electromagnetic conversion characteristics and a satisfactory running durability.

Magnetic recording medium comprising ferromagnetic powder and polar

There is disclosed a magnetic recording medium having the excellent electromagnetic conversion properties and an improved Young's modulus of a magnetic layer, wherein the magnetic layer contains a binder comprising a polyurethane resin having a polycaprolactone structural unit and a vinyl chloride resin having --SO.sub.3 M, --COOM, --OSO.sub.3 M, ##STR1## wherein M represents hydrogen, lithium, sodium or potassium.

Magnetic recording medium comprising magnetic particles and a

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.

A magnetic recording medium is disclosed which has a magnetic layer comprising a ferromagnetic powder and a specific polyurethane resin as a binder. The polyurethane resin has a weight average molecular weight of not more than 30,000, a glass transition point of not higher than 0.degree. C. and a -SO.sub.3 M group, wherein M is a hydrogen atom or an alkali metal atom, in an amount of not less than 0.35% by weight in terms of sulfur atom. The recording medium is excellent in the dispersibility of the magnetic powder in the binder and has high running stability.

Magnetic recording medium comprising a polyurethane binder resin having

There is disclosed the method of preparing a magnetic recording medium having an improved running durability and the excellent electromagnetic conversion characteristics, wherein the magnetic paint for a magnetic layer is prepared by the steps of:

Production method for magnetic recording medium

A magnetic recording medium is disclosed which comprises a support, and a magnetic layer comprising a specific binder resin, a fatty acid or a fatty acid ester and a magnetic particle. The binder resin comprises a monomer unit of vinyl chloride, a monomer unit having an alkalin metal salt of sulfonic acid or an alkaline salt of phosphoric acid and a monomer unit having an epoxy group. The magnetic recording medium is improved in a dispersibility of magnetic particles, a durability for still picture reproduction, a stability in running and in a S/N ratio of luminance.

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Hino, Japan

Kunitsuna Sasaki