Hitachi Maxell, Limited

Masaya Funahashi

Akira Miyake

Teruhisa Miyata

Kenichi Inoue

Kunio Mizushima

Kohji Norimatsu

Mikio Kishimoto

Hajime Doi

Shoichi Sakamoto

Fujio Matsumoto

Hitoshi Nagatani

Tomizo Taniguchi

A magnetic recording medium suitable for high density recording having improved erasing characteristics is produced by a method comprising the steps of forming an under coat layer containing an electrically conductive material on at least one surface of a substrate, applying a magnetic paint containing hexagonal system ferrite magnetic powder on the under coat layer and drying the applied magnetic paint to form a magnetic layer having a thickness of not larger than 0.7 .mu.m.

Magnetic recording medium

A magnetic recording medium improved in durability over a wide range of temperature which comprises a substrate and a magnetic layer comprising magnetic powder and a resinous binder formed on the substrate, characterized in that the magnetic layer further comprises a monovalent alcohol ester of a fatty acid and a straight chain saturated fatty acid ester of not less than 28 carbon atoms in a weight proportion of 99:1 to 1:99 in a combined amount of 0.1 to 20 percent by weight based on the weight of the magnetic powder.

A magnetic recording disc having a high durability and good electromagnetic conversion characteristics which comprises a non-magnetic support and a magnetic layer provided on at least one surface of the support, wherein the magnetic layer comprises magnetic powder, a resinous binder, polishing particles and a lubricating agent, characterized in that the polishing particles have a Mohs' scale of hardness of not less than 7 and an average particle size of 0.25 r to 0.75 r (r being the thickness (.mu.m) of the magnetic layer) and the lubricating agent is a fatty acid ester having a melting point of not higher than 10.degree. C.

A recording disc cartridge comprising a recording disc containing, at least in its surface layer, at least one compound selected from the group consisting of an aliphatic acid and its salt and derivative, a case in which the recording disc is rotatively contained, and a liner comprising polyester fiber which is interposed between the case and the recording disc with facing the disc, which has good durability and less drop out.

Recording disc cartridge

A magnetic recording medium improved in durability at an elevated temperature which comprises a substrate and a magnetic layer comprising magnetic powder and a resinous binder formed on the substrate, characterized in that the magnetic layer further comprises an ester of a polyvalent alcohol with a fatty acid in an amount of 0.01 to 40 parts by weight to one part by weight of the magnetic powder.

A magnetic recording disc having a high durability and being rotatively driven with small starting torque which comprises a non-magnetic support and a magnetic layer provided on at least one surface of the support, the magnetic layer comprising magnetic powder, a resinous binder, (a) an ester of an unsaturated fatty acid of 8 to 18 carbon atoms with a monovalent or polyvalent, saturated or unsaturated alcohol of not more than 18 carbon atoms optionally substituted with at least one alkoxy group having not more than 8 carbon atoms and (b) a fatty acid ester of the formula: ##STR1## wherein R.sub.1 is a saturated or unsaturated aliphatic hydrocarbon group having 8 to 18 carbon atoms, R.sub.2 is an alkyl group having not more than 18 carbon atoms and n is an integer of 1 or more, the combined amount of the unsaturated fatty acid ester (a) and the fatty acid ester (b) being not less than 5 parts by weight to 100 parts by weight of the magnetic powder.

A magnetic disc comprising a non-magnetic substrate, an undercoat coated on the surfaces of the substrate and a magnetic layer containing magnetic powder dispersed in a binder coated on the undercoat, characterized in that the undercoat has a thickness of from 0.5 to 10.0 .mu.m and such a porosity that a lubricant is contained therein in an amount of from 30 to 200 mg/cm.sup.3, which provides good surface lubricity and improved durability.

Magnetic disc

A magnetic recording medium which comprises a substrate and a magnetic layer comprising a magnetic powder, a resinous binder, a lubricant and optionally a non-magnetic abrasive being formed on at least one surface of the substrate, characterized in that the lubricant comprises an ester of an unsaturated higher fatty acid with an alcohol having 6 to 16 carbon atoms, which has improved wear resistance in a wide temperature range.

A magnetic recording medium which comprises a substrate and a magnetic layer comprising magnetic powder and a resinous binder formed on the substrate, characterized in that the magnetic layer further comprises a lubricant and an unsaturated fatty acid ester, which is improved in durability.

Growing community of inventors

Osaka, Japan

Masaya Funahashi