Fuji Photo Film Company, Limited

Fujifilm Corporation

Tdk Corporation

Hitoshi Noguchi

Shinji Saito

Nobuo Yamazaki

Hiroshi Ogawa

Hiroo Inaba

Takeshi Harasawa

Junichi Nakamikawa

Yasushi Endo

Masatoshi Takahashi

Hiroshi Hashimoto

Osamu Shimizu

Hideaki Shiga

Kazuhiro Niitsuma

Takeshi Kakuta

Kazuhiko Maejima

Hiroaki Doushita

Ayako Matsumoto

Kazuo Kato

Mitsuyoshi Kawai

Junichi Nakamigawa

Makoto Yoshida

Masahi Aonuma

Shinji Saitoh

The magnetic signal reproduction system comprises a magnetic recording medium comprising a magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support; and a reproduction head, wherein a number of protrusions equal to or greater than 10 nm in height on the magnetic layer surface, as measured by an atomic force microscope, ranges from 50 to 2500/10,000 &#x3bc;m, a quantity of lubricant on the magnetic layer surface, denoted as a surface lubricant index, ranges from 0.5 to 5.0, a surface abrasive occupancy of the magnetic layer ranges from 2 to 20 percent, and the reproduction head is a magnetoresistive magnetic head comprising a spin-valve layer.

Magnetic recording medium and magnetic signal reproduction method

Magnetic signal reproduction system employing a spin-valve MR head developed for high-density recording and a spin-valve MR head and magnetic signal reproduction method for reproducing magnetic signals in which a spin-valve MR head is employed

Provided is a magnetic recording medium exhibiting good electromagnetic characteristics in high-density recording The magnetic recording medium employed for magnetically recording signals with a track width equal to or less than 2.0 &#x3bc;m and reproducing the magnetically recorded signals, wherein said magnetic recording medium comprises a magnetic layer comprising a hexagonal ferrite ferromagnetic powder and a binder or comprises a nonmagnetic layer comprise a nonmagnetic powder and a binder and a magnetic layer comprising a hexagonal ferrite ferromagnetic powder and a binder in this order on a nonmagnetic support. Said magnetic layer has a thickness equal to or less than 0.2 &#x3bc;m, and said hexagonal ferrite ferromagnetic powder has an average plate diameter being 1/30 or less of the magnetically recorded track width as well as &#xbd; or less of the thickness of the magnetic layer.

Magnetic recording medium

A magnetic disc medium comprising: a magnetic sheet in the form of a disk; a case encasing the magnetic sheet so as to be capable of rotating; and a nonwoven liner fastened on an inner face of the case so as to face the magnetic sheet, wherein the magnetic sheet comprises a support, a substantially nonmagnetic lower layer, and a magnetic layer containing hexagonal ferrite powder dispersed in a binder and having central plane average surface roughness of from 1 nm to 4 nm, and the liner comprises polyethylene terephthalate in an amount of 20% by weight or more.

Magnetic disc medium

A magnetic recording and reproduction method comprising recording or reproducing a track of a rotating magnetic disk by means of a magnetic head, wherein the magnetic disk comprises a support and a magnetic layer containing ferromagnetic powder and a binder; the track has a breadth of 2 &#x3bc;m or less; and a frictional force between the magnetic layer and the magnetic head at innermost peripheral area of a recording region of the magnetic disk is 30 mN or less, a frictional force between the magnetic layer and a magnetic head at outermost peripheral area of a recording region of the magnetic disk is 20 mN or less, and a ratio of the frictional force at the innermost peripheral area to the frictional force at the outermost peripheral area is from 1.0 to 4.0.

Magnetic recording and reproduction method

A magnetic disk medium having on a support a magnetic layer containing hexagonal ferrite powder dispersed in a binder, with the support having a thickness of 20 &#x3bc;m to 80 &#x3bc;m and the magnetic disk medium having an inside diameter X of 2 mm to 10 mm, an outside diameter Y of 20 mm to 50 mm, an X/Y ratio satisfying the relation 0.05&#x2266;X/Y&#x2266;0.20 and a curl quantity of 1 mm or below, which is suitable for use in small-diameter portable computer equipment and video recorders, and besides, can attain a recording capacity of at least several hundred megabytes.

Magnetic disk medium

A magnetic recording medium is disclosed, comprising a support having provided thereon a substantially nonmagnetic lower layer by coating a lower layer coating solution comprising a nonmagnetic powder dispersed in a binder and drying, and a layer having a thickness of from 0.01 to 0.15 &#x3bc;m by coating a magnetic layer coating solution comprising a ferromagnetic metal powder or a hexagonal ferrite powder dispersed in a binder, wherein the magnetic layer contains diamond particles having an average particle size of from 1/5 to 2 times the thickness of the magnetic layer in an amount of from 0.1 to 5.0 mass % based on the ferromagnetic metal powder.

A flexible magnetic recording medium to which data is transferred by being brought into intimate contact with a master carrier which has a land/groove pattern corresponding to the data and also has a surface whose Moh's hardness is 6 to 10. The magnetic recording medium includes a substrate, a non-magnetic layer, and a magnetic layer. The non-magnetic layer and the magnetic layer are coated on the substrate in the recited order. The magnetic layer contains an abrasive comprising diamond particles whose average particle size is 0.03 to 0.5 &mgr;m. The diamond particle content of the abrasive is in a range of 0.1 to 5 wt % of ferromagnetic powder contained in the magnetic layer.

Flexible magnetic recording medium

Provided is a magnetic recording medium ensuring an adequate S/N even in high density magnetic recording, and tending not to electrostatically damage MR heads during recording and reproduction employing MR heads. A magnetic recording medium comprising a nonmagnetic layer comprising a nonmagnetic powder and a binder and a magnetic layer comprising a ferromagnetic metal powder or a ferromagnetic hexagonal ferrite powder and a binder in this order on at least one side of a nonmagnetic support, wherein said nonmagnetic layer comprises 10 to 50 mass parts of carbon black with a mean particle diameter of 10 to 30 nm per 100 mass parts of said nonmagnetic powder, said magnetic layer has a thickness equal to or less than 0.2 &mgr;m, the standard deviation b of the average intensity a of elements due to said ferromagnetic powder as determined by electron-beam microanalysis is 0.03&lE;b/a&lE;0.4, and said magnetic layer has a center surface average roughness Ra equal to or less than 5 nm and a ten-point average roughness Rz equal to or less than 50 nm.

Provided are a method of magnetic recording and reproducing capable of permitting high density recording on magnetic recording media even under the condition of high data transfer rates and yielding adequate recording and reproduction characteristics when an MR head is used in reproduction, and a magnetic recording medium capable of being used in this magnetic recording and reproducing method. The magnetic recording and reproducing method is a method for reproducing a signal magnetically recorded on a magnetic recording medium with a magnetoresistive (MR) head. The magnetic recording medium comprises a substantially nonmagnetic lower layer and a magnetic layer comprising a hexagonal ferrite ferromagnetic powder and a binder in this order on at least one side of a nonmagnetic support, in which said hexagonal ferrite ferromagnetic powder has a mean plate diameter ranging from 15 to 40 nm and a mean plate thickness ranging from 4 to 15 nm, and said magnetic layer has a coercive force Hc ranging from 143.3 to 318.4 kA/m, and said signal magnetically recorded has a maximum recording frequency ranging from 10 to 80 MHz.

Magnetic recording and reproducing method and magnetic recording medium employed for the same

A magnetic recording medium comprising: a nonmagnetic support; and at least one magnetic layer comprising a ferromagnetic hexagonal ferrite powder and a binder, wherein the magnetic layer comprises diamond particles having an average particle size of 0.03 to 0.5 &mgr;m in a ratio of 0.1 to 5% by weight to the ferromagnetic hexagonal ferrite powder, the ferrite hexagonal ferrite powder has an average tabular diameter of 5 to 40 nm, and the binder is at least one of: (i) a binder comprising from 0.2 to 0.7 meq/g of at least one polar group selected from &mdash;SO M, &mdash;OSO M, &mdash;PO(OM) , &mdash;OPO(OM) and &mdash;COOM, wherein M represents a hydrogen atom, an alkali metal or ammonium, and (ii) a binder comprising from 0.5 to 5 meq/g of at least one polar group selected from &mdash;CONR R , &mdash;NR R and &mdash;N R R R wherein R , R and R each independently represents a hydrogen atom or an alkyl group.

A magnetic recording medium in the form of a disc comprising a polyethylene naphthalate support having provided thereon a magnetic layer comprising ferromagnetic metal fine powder or ferromagnetic hexagonal ferrite fine powder dispersed in a binder, wherein the central plane average surface roughness of the magnetic layer of the magnetic recording medium is 5 nm or less, the thickness variation rate of the disc is 3% or less, and the total thickness of the disc X &mgr;m and the outside diameter of the disc Y mm satisfy the relationship of 0.3&lE;Y/X&lE;0.8.

Magnetic recording medium in the form of a disc

A magnetic recording medium is disclosed, comprising a support having provided thereon a magnetic layer containing a ferromagnetic powder and a binder as main components, wherein the ferromagnetic powder is a hexagonal ferrite powder having an average tabular diameter of from 15 to 40 nm, the perpendicular factor of squareness ratio SQ of the magnetic layer is from 0.1 to 0.55, the specific surface area and the total pore volume per weight of the magnetic layer by a nitrogen adsorption method are from 0.1 to 50 m /g and from 0.001 to 1 ml/g, respectively, and the magnetic layer thickness is from 0.02 to 0.3 &mgr;m.

A magnetic recording and reproducing method comprising recording and reproducing a signal with a magnetic head in a track width (A) of less than 5 &mgr;m on a magnetic recording medium comprising a support having provided thereon a magnetic layer containing at least a ferromagnetic powder, an abrasive and a binder, wherein the average longer size (B) of the abrasive particle(s) which are present on the magnetic layer surface is &frac13; or less of the track width (A).

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Kanagawa, Japan

Hitoshi Noguchi