Tdk Corporation

Kazunori Tamazaki

Yuichi Kubota

Masaharu Nishimatsu

Keiji Koga

Tsutomu Aoyama

Toru Shimozawa

Hitoshi Azegami

Osamu Inoue

Akio Watanabe

Shigeru Shimada

Kazuhiro Kuroda

Keiko Tsuchiya

Shigeharu Watase

This invention concerns a magnetic recording medium which comprises a nonmagnetic support, a magnetic layer provided on one surface of the nonmagnetic support and a backcoat layer provided on the other surface of the nonmagnetic support, wherein the nonmagnetic support is provided with such physical properties as Young's moduluses in the longitudinal direction and the lateral direction thereof in the range of 1300-1600 kg/cm.sup.2, respectively, and a breaking elongation in the range of 3-10% and said magnetic recording medium is provided on the magnetic layer side thereof with a convex cupping the magnitude of which is in the range of 0.02-0.20 mm at a width of 3.8 mm. The magnetic recording medium, therefore, realizes perfect head touch even when the thickness of the nonmagnetic support and the thickness of the whole medium are small. Even when the magnetic recording medium is exposed to the mechanical influences and physical influences of aging, it suffers extremely small change in the form (such as, for example, the cupping value) and therefore conserves the head touch and other factors in highly satisfactory state. It suffers occurrence of dropout or head stain only sparingly.

Magnetic recording medium

A magnetic recording medium whose magnetic layer formed on a base comprises a magnetic powder and a binder which contains a tertiary amine and uses 1,4-cyclohexanedimethanol as a chain extender. The magnetic powder is preferably of CrO.sub.2. The medium is made by mixing and dispersing the magnetic powder in a binder which consists of a reaction product of (A) a polyester which is a reaction product of a diol selected from among ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, and 1,6-hexanediol, and adipic acid, (B) a chain extender consisting of 1,4-cyclohexanedimethanol, (C) an aliphatic or aromatic diisocyanate in an amount substantially equal to the combined molar amount of the polyester and the chain extender, and (D) a tertiary amine, and applying the resulting magnetic coating material to a base.

A magnetic recording medium wherein a magnetic layer containing a particulate magnetic material and a binder is formed on a substrate exhibits improved performance as magnetic recording tape, disk, and sheet when the particulate magnetic material comprises particles having iron carbide at least on the surface thereof and optional oxide particles, and the particulate magnetic material contains 5 to 90% by weight of iron carbide in the form of Fe.sub.n C.

A magnetic recording medium comprising a substrate, an optional undercoat layer, and a magnetic layer formed thereon and containing a hexagonal plate magnetic powder, an electroconductive material, and a binder is improved in runnability and recording density by the presence of a fatty acid ester at least on the recording side surface of the magnetic layer, and by providing an electric resistance of up to 5.times.10.sup.9 .OMEGA./cm.sup.2 on the side of the magnetic layer.

A magnetic recording medium comprising a non-magnetic substrate and a coating type magnetic recording layer formed on the substrate, wherein barium ferrite magnetic powder is perpendicularly oriented, characterized in that an undercoating layer comprising a radiation curable binder and carbon black, is provided beneath the magnetic recording layer.

A magnetic sheet comprising a disk-shaped substrate and a magnetic layer is loaded in a magnetic sheet operating device, typically electronic camera comprising a magnetic head for performing recording and reproducing operations on the sheet while rotating the sheet. The magnetic layer is formed from a composition comprising a magnetic powder and a binder having a specified complex elastic modulus.

Magnetic sheet

A magnetic recording medium comprising fine ferromagnetic particles as the main component and a binder composed of a mixture of a radiation sensitive soft resin, a radiation sensitive modified resin and a partially saponified vinyl chloride-vinyl acetate copolymer containing at least 0.5% by weight of maleic acid, said binder being cross-linked and polymerized by radiation.

Growing community of inventors

Saku, Japan

Kazunori Tamazaki