Tdk Corporation

Eiji Kitaura

Kuniichi Yoda

Kiyoto Fukushima

Shigeru Takamatsu

Yoshio Kawakami

Tsutomu Tsunoda

A magnetic recording medium comprises a light-shielding base in the form of a tape or sheet, and a magnetic layer composed of a magnetic powder of Co-coated .gamma.-Fe.sub.2 O.sub.3 dispersed in a resin binder and applied to the base. The powder has a specific surface area as determined by the BET adsorption method of at least 35 m.sup.2 /g. The light-shielding base portion contiguous to the magnetic layer is a transparent plastic film and the lower base portion is light-shielding. The light-shielding base has a light transmittance of 30% or below. The surface roughness of the base is, in terms of the center-line average surface roughness, 0.012 .mu.m or below.

Magnetic recording medium

In a magnetic recording medium consisting of a base coated with a magnetic coating material, or a dispersion of magnetic particles in a resinous binder, the binder comprises a copolymer composed of vinyl chloride, a vinyl alkylcarboxylate, another monomer copolymerizable with vinyl chloride, and a saponified vinyl alkylcarboxylate and having an OH/CH absorption ratio according to the infrared absorption spectrum of 0.2 to 0.7, a polyurethane resin having in its molecule a --SO.sub.3 M group wherein M represents an alkali metal atom, and a polyurethane resin or polyester resin or both containing no --SO.sub.3 M group wherein M represents an alkali metal atom, and a polyisocyanate.

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Saku, Japan

Eiji Kitaura