Konica Corporation

Yuki Ando

Takahiro Mori

Ryosuke Isobe

Kunitsuna Sasaki

Kiyoshi Sawada

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

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:

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Hino, Japan

Yuki Ando