Konica Corporation

Tdk Corporation

Konishiroku Photo Industry Co., Ltd.

Tkd Corporation

Ryosuke Isobe

Takahiro Mori

Kunitsuna Sasaki

Noboru Koyama

Kiyoshi Sawada

Yuki Ando

Narito Goto

Takafumi Yanagita

Hideaki Wakamatsu

Akihiko Seki

Yasuo Ando

Akira Saitoh

Shu Ishiguro

Hideki Takahashi

Masao Asano

Seiichi Tobisawa

Katsuyuki Takeda

Nobuyuki Sekiguchi

Yasuhisa Yamauchi

Kenji Itozawa

Hiroaki Yamagishi

Disclosed is a magnetic recording medium which comprises a non-magnetic support and a magnetic layer formed thereon and containing at least ferromagnetic metallic powder, and the medium contains an aliphatic acid, wherein average existence ratios of elements in terms of the number of atoms forming the surface of the ferromagnetic metallic powder which is being subjected to orientation treatment in the magnetic layer, are less than 1 of sodium (Na), 40 or less of alkaline earth elements, and 1 to 50 of rare earth elements based on the number of iron (Fe) atom as 100, and the number of carbon atoms of the aliphatic acid being 12 to 24.

Magnetic recording medium comprising a magnetic layer containing

There is disclosed a magnetic recording medium comprising an uppermost layer (magnetic layer containing a ferromagnetic metal powder) and the ferromagnetic metal powder containing Fe, Al and one or more rare earth elements selected from the group consisting of Sm, ND, Y and Pr. The magnetic recording medium has a good electromagnetic converting property and running durability and which is particularly suitable for digital recording media.

Magnetic recording medium

Disclosed is a magnetic recording medium which comprises a non-magnetic support and a layer containing .alpha.-iron oxide powder as a lower layer and a layer containing ferromagnetic powder as an upper layer which are provided on the non-magnetic support in this order from a side of the non-magnetic support, wherein weight ratios of elements in the whole composition of the .alpha.-iron oxide powder are 0.05 to 5 parts by weight of aluminum (Al) atom and 0.05 to 5 parts by weight of silicon (Si) atom based on 100 parts by weight of iron (Fe) atom, and average existence ratios of elements in terms of the number of atoms forming the surface of the .alpha.-iron oxide powder are 40 or less of Al atom and 1 to 60 of Si atom based on the number of Fe atom as 100.

Magnetic recording medium comprising an underlayer containing

A magnetic recording medium comprises a non-magnetic support and provided thereon, in order, a non-magnetic layer containing a non-magnetic powder, and a magnetic layer containing a ferromagnetic metal powder, each layer containing a binder, the crystallite size of the magnetic powder determined according to X-ray measurement being 30 to 120 .ANG. and the dry thickness of the magnetic layer being 0.01 to less than 0.5 .mu.m.

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.

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 is disclosed, which comprises a no-magnetic support having thereon, at least two magnetic layer including a first magnetic layer provided at the farthest position from the support, and a second magnetic layer provided between the first magnetic layer and the support, and a non-magnetic layer provided between the second magnetic layer and the support. In the above, at least one of the magnetic layers comprises a ferromagnetic metal powder. The magnetic layers have a thickness of not thicker than 0.3 .mu.m in total, and the non-magnetic layer has a thickness within the range of from, 0.2 .mu.m to 2.0 .mu.m.

Magnetic recording medium comprising a non magnetic underlayer and two

A magnetic recording medium is disclosed. The medium has a Vickers hardness of said magnetic layer being within a range from 40 to 170, an amount of plastic deformation of said magnetic layer being in a range of 0.3-0.9 .mu.m, and satisfies the relation of (A+200 B).gtoreq.180 wherein A is the value of said Vickers hardness and B is plastic deformation. The magnetic recording medium of the invention provides no contamination of calender rolls caused in the course of manufacturing thereof, and has running stability which is not affected by environmental conditions and which reduces clogging on a magnetic head.

Magnetic recording medium having a magnetic layer with a specified

A magnetic recording medium having plural layers are disclosed. A plastic deformation of an uppermost magnetic layer is from 0.01 to 0.5 .mu.m, and a plastic deformation of the layer other than the uppermost magnetic layer is preferably from 0.01 to 0.6 .mu.m. The uppermost layer preferably has a thickness of less 0.5 .rho.m.

Magnetic recording medium comprising a support and a plurality of layers

A magnetic recording medium having a support and provided thereon, a magnetic layer containing a ferromagnetic metal powder and a binder is disclosed. The ferromagnetic powder comprises an adsorbed moisture of not less than 1.0 weight % and not more than 2.5 weight % of said ferromagnetic metal powder, a pH value of not less than 9.0 and not morer than 11.5, and a specific surface area of not less than 45 m.sup.2 /g measured by a BET method; and the binder comprises at least one polar group selected from the group consisting of: ##STR1## wherein M represents an atom selected from the group consisting of hydrogen, lithium, sodium, and potassium; and M.sup.1 and M.sup.2 represent atoms of hydrogen, lithium, sodium and potassium, and an alkyl group, provided that M.sup.1 and M.sup.2 may be same with or different from each other.

Magnetic recording medium comprising a specified binder resin, specified

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

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

A magnetic recording medium is disclosed. The magnetic recording medium is capable of high density recording; has excellent electromagnetic conversion properties including S/N ratio; whose magnetic powder has good dispersibility and good corrosion resistance; and that has good durability. The magnetic recording medium has a magnetic layer comprising a binder and magnetic metal powder dispersed in the binder. The powder has a specific surface area of not less than 45 m.sup.2 /g, and comprises not less than 90 atomic % of iron atoms, not less than 0.1 atomic % to less than 5 atomic % of aluminum atoms and not less than 0.1 atomic % to less than 10 atomic % of nickel atoms and the aluminum atoms present in the superficial portion of individual particles of the powder are bound with oxygen atoms.

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. The magnetic recording medium is capable of high density recording; has excellent electromagnetic conversion properties including S/N ratio; whose magnetic powder has good dispersibility and good corrosion resistance; and that has good durability. The magnetic recording medium comprises a binder and magnetic metal powder dispersed in the binder and the magnetic metal powder has a specific surface area of not less than 45 m.sup.2 /g, and comprises comprise iron atoms and aluminum atoms in an abundance ratio of from 100:1 to 100:20 in terms of the number of atoms, and abundance ratio of iron atoms to aluminum atoms in the superficial portion of individual particles of the magnetic powder is from 30:70 to 70:30 in terms of the number of atoms.

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Hino, Japan

Ryosuke Isobe