Konishiroku Photo Industry Co., Ltd.

Konica Corporation

Kenji Itozawa

Issei Nakamura

Takahiro Mori

Noboru Koyama

Ryosuke Isobe

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 comprising a support and a magnetic layer on said support. Said magnetic layer is a unitary magnetic layer comprising iron oxide powder having cobalt adsorbed on the surface thereof. The average grain size of said powder is not more than 0.5.mu., the ratio of the major axis to the minor axis (acicular ratio) of said powder is from 1.3 to 4.5 and the coercive force of said powder is from 500 to 800 Oe.

Magnetic recording medium

A magnetic recording medium containing iron carbide is disclosed. Iron carbide shows electric conductivity and low light transmission. Therefor an antistatic property and light shielding ability of the medium are improved. Iron carbide is contained in the magnetic layer of the medium in combined with the other ferromagnetic materials such as Co-adhered-.gamma.-Fe.sub.2 O.sub.3 or hexagonal ferrite. An amount of iron carbide in the magnetic layer is within the range of from 1.5 to 15% of the magnetic layer by volume.

Magnetic recording medium containing iron carbide

A magnetic recording medium comprising a support and a magnetic layer on said support. Said magnetic layer is a unitary magnetic layer comprising ferromagnetic metallic powder. The average grain size of said ferromagnetic powder is not more than 0.5.mu., the ratio of the major axis to the minor axis (acicular ratio) of said powders is from 1.3 to 4.5 and the coercive force of said powders is from 550 to 800 Oe.

A magnetic recording medium comprising a support and a magnetic layer on said support. The magnetic layer is a unitary magnetic layer comprising ferromagnetic metallic powder. The average grain size of said ferromagnetic powder is not more than 0.5.mu., the ratio of the major axis to the minor axis (acicular ratio) of said powders is from 1.3 to 4.5, and the coercive force of said powder is from 1350 Oe to 1600 Oe.

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Hachioji, Japan

Kenji Itozawa