Fuji Photo Film Company, Limited

Fujifilm Corporation

Satoshi Matsubaguchi

Hiroaki Takano

Hiroo Inaba

Masaki Suzuki

Ryoichi Yamamoto

Takashi Yamada

Akira Nahara

Yuichiro Murayama

Ayako Matsumoto

Hiroaki Doushita

Masataka Yoshizawa

Tetsuji Nishida

Hiroshi Hashimoto

Naoto Abe

Kiyomi Ejiri

Toshio Tada

Toshiyuki Kitahara

Masato Nagura

Masaaki Nomura

Nobuyoshi Asada

Takeshi Nagata

Akira Manabe

An aspect of the present invention relates to a hexagonal ferrite magnetic powder manufactured by a glass crystallization method as well as having an average plate diameter ranging from 15 to 25 nm, an average plate ratio ranging from 2.0 to 2.8 and a coercive force (Hc) ranging from 159 to 279 kA/m.

Hexagonal ferrite magnetic powder and method of manufacturing the same, and magnetic recording medium and method of manufacturing the same

A binder composition for a magnetic recording medium contains a vinyl copolymer having structural units denoted by each of formulas [1], [2] and [3]. In formula [1], Ris hydrogen, halogen, or methyl, Lis a single bond or a divalent linking group, and Y is an alicyclic group. In formula [2], Ris hydrogen, halogen, or methyl, Lis a single bond or a divalent linking group, and Z is a hydrocarbon group with a carbon number of from 8 to 50. In formula [3], Ris hydrogen, halogen, or methyl, and Lis a single bond or a divalent linking group:   

Binder composition for magnetic recording medium and magnetic recording medium

A binder composition for a magnetic recording medium contains a vinyl copolymer having a structural unit of general formula [1]: wherein Ris H, halogen, or methyl, Lis a single bond or a divalent linking group, and Y is an alicyclic group; a structural unit of general formula [2]: wherein Ris H, halogen, or methyl, Lis a single bond or a divalent linking group, and Z is a hydrocarbon group with a carbon number of from 8 to 50; and a structural unit of general formula [3]: wherein Ris H, halogen, or methyl, and Lis a single bond or a divalent linking group.

Provided is a magnetic recording medium that exhibits excellent electromagnetic characteristics especially in recording and reproducing systems using an MR head, as well as has excellent long-term preservation property. The magnetic recording medium comprises a lower layer comprising a nonmagnetic powder or a ferromagnetic powder and a binder and at least one magnetic layer thereover comprising a ferromagnetic powder and a binder on a support. Said binder comprised in the lower layer and/or magnetic layer comprises a polyurethane, said polyurethane is polyurethane (1) prepared from a chain extending agent, an organic diisocyanate, and a polyester polyol which comprises a dibasic acid component and a diol component, wherein the dibasic acid component comprises an aliphatic dibasic acid component and 70 molar percent or more of the diol component is derived from a diol having an alkyl branched side chain comprising two or more carbon atoms without a ring structure, or said polyurethane is polyurethane (2) prepared from a chain extending agent which comprises an alkyl branched aliphatic diol comprising three or more of total carbon atoms in a branched side chain per molecule, an organic diisocyanate, and a polyester polyol which comprises a dibasic acid component and a diol component, wherein the dibasic acid component comprises an aliphatic dibasic acid component and 70 molar percent or more of the diol component is derived from an alkyl branched aliphatic diol having a branched side chain of which total carbon atoms per molecule is two or more, and magnitude of saturation magnetic flux density (&#x3c6;m) ranges from 150 to 400 G&#xb7;&#x3bc;m.

Magnetic recording medium

A magnetic recording medium comprising a non-magnetic support and a magnetic layer containing a binder and a ferromagnetic metal powder dispersed in the binder, wherein the binder contains a polyurethane resin obtained from a polyester polyol, a chain extender, and an organic diisocyanate, and the magnetic layer has a product &#x3a0; of coercive force Hc (kA/m) in an in-plane, longitudinal direction and magnetic flux &#xd8;m (T&#x3bc;m) in a range of from 400 to 800.

A magnetic recording medium is disclosed, comprising a support having thereon a lower layer containing a nonmagnetic powder or a ferromagnetic powder dispersed in a binder, and at least a magnetic layer containing a ferromagnetic powder dispersed in a binder provided on the lower layer, wherein the binder contains a polyurethane resin obtained from a polyester polyol comprising a specific diol, a chain extending agent and an organic diisocyanate, and the magnetic layer surface has a C/Fe peak ratio of from 7 to 11.

Provision of a highly reliable magnetic recording medium with able to record further high density recording, usable advantageously as a magnetic tape for recording computer data, and having a further improved SNR, and a method for reproducing signals magnetically recorded on a magnetic recording medium to reproduce more desirably magnetic recording such as computer data with high density recording or the like. The magnetic recording medium having, on either side of a flexible nonmagnetic support, a nonmagnetic layer containing a nonmagnetic powder and a binder, and a magnetic layer containing a ferromagnetic powder and a binder, having a thickness in the range of from 0.2 to 0.6 &mgr;m in this order, where a laminated head is used for reproduction. The method for reproducing signals magnetically recorded medium having, on either side of a flexible nonmagnetic support, a nonmagnetic layer containing a nonmagnetic powder and a binder, and a magnetic layer, with a thickness ranging from 0.2 to 0.6 &mgr;m, containing a ferromagnetic powder and a binder in this order, where a laminated head is used as a reproducing head.

Magnetic recording medium and method for reproducing magnetic recording

Provided is a magnetic recording medium having good electromagnetic characteristics, particularly both improved high-density recording characteristics and good durability, and particularly a C/N ratio that is markedly improved in the high-density recording region. A magnetic recording medium comprising a nonmagnetic lower layer and a magnetic layer provided in this order on a support wherein said magnetic layer comprises a ferromagnetic metal powder or a ferromagnetic hexagonal ferrite powder and a binder and has a coercive force equal to or higher than 143 kA/m. Said magnetic recording medium is a medium for recording signals having a surface recording density ranging from 0.2 to 2 Gbit/inch ; said support has a thickness equal to or less than 5.5 &mgr;m and a Young's modulus in the MD direction equal to or higher than 11,000 Mpa; and said support has on the reverse surface from said magnetic layer a backcoat layer, said backcoat layer having not fewer than 200 and not more than 1,000 protrusions having a height equal to or higher than 50 nm per 10,000 &mgr;m .

Magnetic recording medium comprising a backcoat layer having specific protrusions

A magnetic recording tape is described, which comprises a plastic support having provided thereon a magnetic layer comprising a ferromagnetic metal powder dispersed in a binder, wherein the magnetic layer has the product P of the coercivity Hc (Oe) in the in-plane machine direction of the tape and the magnetic flux &phgr;m (G&middot;cm) of from 100 to 160.

Magnetic recording tape with controlled Hc and magnetic flux/unit area value and controlled Cl/Fe intensity

A magnetic recording medium is disclosed, comprising a nonmagnetic support having thereon at least two coating layers which comprise:

A magnetic recording medium comprises a non-magnetic substrate, a lower coating layer, which is overlaid upon the non-magnetic substrate and primarily contains a binder and inorganic particles dispersed in the binder, and a magnetic layer, which is overlaid upon the lower coating layer and is constituted of at least a single layer. The magnetic layer contains at least a binder and ferromagnetic metal particles dispersed in the binder. The thickness of the magnetic layer falls within the range of 0.05 .mu.m to 0.5 .mu.m. The surface roughness of a top magnetic layer is at most 3 nm. The lower coating layer contains a fatty acid. An increase in the number of small protrusions, which have a height of at least 30 nm, does not occur substantially on the surface of the magnetic layer after the magnetic recording medium has been stored for seven days under environmental conditions of a temperature of 60.degree. C. and a relative humidity of 90%.

A magnetic recording medium is disclosed, comprising a magnetic layer mainly comprising a ferromagnetic powder and a binder resin formed on at least one side of a non-magnetic support, wherein said magnetic layer has a thickness of from 0.05 .mu.m to 0.8 .mu.m, said ferromagnetic powder has an average long axis length of from 0.05 .mu.m to 0.20 .mu.m, and said binder resin comprises a polyurethane having a radius of gyration from 5 to 25 nm in cyclohexanone.

Magnetic recording medium containing magnetic powder and a polyurethane

A cleaning medium for magnetic recording devices comprises a non-magnetic substrate and a lower coating layer, which is overlaid upon the non-magnetic substrate and primarily contains a binder and non-magnetic inorganic particles dispersed in the binder. The cleaning medium also comprises a cleaning layer, which is overlaid upon the lower coating layer and contains a binder and inorganic particles dispersed in the binder, the inorganic particles at least containing ferromagnetic particles. The thickness of the cleaning layer falls within the range of 0.05 .mu.m to 1.0 .mu.m, and the squareness ratio of the cleaning layer falls within the range of 0.6 to 0.98. The cleaning medium yields little wear of magnetic heads, has good cleaning characteristics, and is capable of trueing up the shape of an end of a cleaned magnetic head into a sharp shape, such that the compatibility of the magnetic head with both of a metal evaporated tape and a metal powder tape in coming into close and uniform contact with the tapes may be kept good.

Cleaning medium for magnetic recording devices, in which the cleaning

A magnetic recording medium prepared by a process which comprises providing a nonmagnetic layer comprising a nonmagnetic powder and a binder on a nonmagnetic support, and then providing one or more magnetic layers containing at least a ferromagnetic powder and a binder on the nonmagnetic layer while the nonmagnetic layer is wet, wherein the thickness of the magnetic layer is from 0.07 to 0.20 .mu.m, the magnetic layer comprises a resin curable by a polyisocyanate as a binder, the nonmagnetic layer is a layer cured by a polyisocyanate, and the ratio N/Fe in the magnetic layer is from 0.010 to 0.090 as determined by an X-ray photoelectric spectrophotometer; and a magnetic recording medium comprising a nonmagnetic support having thereon a lower nonmagnetic layer comprising a nonmagnetic powder and a binder, and further thereon a magnetic layer comprising at least a ferromagnetic metal powder and a binder, wherein the magnetic layer has a thickness of from 0.07 to 0.20 .mu.m, the magnetic layer has a maximum magnetic flux density Bm of from 3,700 to 6,000 G as measured in an external magnetic field of 10 kOe, the magnetic layer has a coercive force Hc of from 2,000 to 3,000 Oe, the magnetic layer has a center line surface roughness Ra of from 1.0 to 3.0 nm, and the nonmagnetic support has a center line surface roughness of from 0.5 to 7.0 nm on the side thereof to which the lower non layer is provided.

A magnetic recording medium comprising a nonmagnetic substrate having thereon a magnetic layer, wherein the magnetic layer is a metal thin film comprising mainly a composition represented by the formula: (Co.sub.100-x Pd.sub.x).sub.100-y Cr.sub.y or [(Co..sub.100-x Pd.sub.x).sub.100-y Cr.sub.y ].sub.100-z O.sub.z wherein x, y and z are atomic percents, and 10.ltoreq.x 40, 5.ltoreq.y.ltoreq.25 and 0.5.ltoreq.z.ltoreq.15. The present medium can be produced at low costs, and has excellent perpendicular magnetic anisotropy.

Growing community of inventors

Kanagawa, Japan

Satoshi Matsubaguchi