Sony Corporation

Shin-etsu Chemical Co., Ltd.

Toyo Boseki Kabushiki Kaisha

Nippon Polyurethane Industry Co., Ltd.

Yoshinobu Ninomiya

Masashi Somezawa

Akira Hashimoto

Kiyokazu Oiyama

Hiroshi Yoshioka

Ichiro Ono

Masakazu Muroyama

Shin Konishi

Kaoru Nakajima

Mitsuhiro Yoshida

Nobukazu Kotera

Yasuo Yoshinaka

Hideyuki Ohashi

Shinpei Yamamoto

Masayoshi Sugiyama

Masatake Katagiri

Described is a magnetic recording medium comprising a non-magnetic substrate and a magnetic layer formed thereon composed mainly of magnetic powder and a binder, said binder containing a compound represented by a following formula: ##STR1## wherein X represents tertiary amine sulfonate or tertiary amine sulfuric ester, Y represents a monomer having vinyl group which is copolymerizable with vinyl chloride and i, j, k represent polymerization degrees.

Magnetic recording medium

A radiation curable resin which is a polyurethane acrylate having (meth)acryloyloxy groups at the terminal end of the molecule and in the molecular chain thereof, and containing metal sulfonate groups in the molecule in a ratio of 3.0 to 1,500 equivalent/10.sup.6 g of the resin, said polyurethane acrylate being obtained by reaction of

Radiation curable resin

A magnetic recording medium comprising a non-magnetic base and a magnetic layer attached thereto consisting essentially of magnetic powders and a binder. Included within the binder are spherical small sized particles of a benzoguanamine-formaldehyde resin or a benzoguanamine-melamine-formaldehyde resin which serve to improve the running characteristics, reduce the friction coefficient, and improve the strength of the layer.

A magnetic recording medium comprised of a non-magnetic substrate and a magnetic layer formed on one surface of the substrate and consisting essentially of a binder and magnetic powders. As the binder, a thermoplastic polyurethane-urea resin is employed, in which hydrophilic polar groups are introduced. The thermoplastic polyurethane-urea resin contains urethane and urea bonds in the molecule thereof and may be synthesized from a long-chain diol with a molecular weight of about 500 to 5000, a short-chain diol with a molecular weight of about 50 to 500, an organic diisocyanate and an organic diamine. Examples of the thus introduced hydrophilic polar groups are: ##STR1##

A magnetic recording medium has a magnetic layer consisting essentially of a binder and magnetic particles on one surface of a non-magnetic substrate. The thermoplastic polyurethane-urea resin in which unsaturated bonds sensitive to radiation are introduced is used as the binder. The thermoplastic polyurethane-urea resin in which the radiation-sensitive unsaturated bonds are introduced has both urethane and urea bonds in the molecular structure thereof. It is synthesized from long chain diol with a molecular weight of approximately 500 to 5000, a short chain diol with a molecular weight of approximately 50 to 500, an organic diisocyanate, an organic diamine, and a compound containing radiation-sensitive unsaturated double bonds, and cured by radiation. The thermoplastic polyurethane-urea resin in which not only the radiation-sensitive double bonds but also hydrophilic polar groups are introduced may also be used as the binder. These hydrophilic polar groups may for example include --SO.sub.3 M, --OSO.sub.3 M, --COOM, and ##STR1##

The magnetic recording medium comprises a non-magnetic substrate and a magnetic layer formed thereon composed mainly of magnetic powder and a binder. The binder contains a binder component having an absorbed amount of the binder component to a surface of the magnetic powder more than 1.5 mg per square meter of a surface area of the powder measured in 3 weight % solution in methyl ethyl ketone solvent, and the magnetic layer has a pigment volume concentration of the magnetic powder between 60 and 75%. The binder provides an improved strength and high pigment volume concentration of magnetic coating layer, and improved durability of the magnetic recording medium.

A magnetic recording medium having a magnetic layer which is cured by irradiating radiation onto the magnetic layer in which magnetic or magnetizable powder material surface-treated with a silicon compound having a silanol group and/or a silanol-forming group upon hydrolysis and a double-bond sensitive to radiation irradiated is present with a binder. The magnetic recording medium having the aforesaid structure has a sufficient durability.

The thermoplastic polyurethane resin having a molecular weight larger than about 5,000 is obtainable by the polyaddition of a long chain diol (A) having a molecular weight ranging from about 500 to 3,000, an organic diisocyanate (C) and a short chain triol (D) having a molecular weight lower than about 500 and specified structures and, as desired, a short chain diol (B) having a molecular weight ranging from about 50 to 500, in specified ratios. The thermoplastic polyurethane resin provides particularly enhanced heat resistance and solvent resistance with improved dispersibility of a pigment or the like and other resins and favorable compatibility with a solvent or the like.

Thermoplastic polyurethane resins

The magnetic recording medium contains as a binder a thermoplastic polyurethane resin having a molecular weight larger than about 5,000 and produced by the polyaddition of a long chain diol (A) having a molecular weight ranging from about 500 to 3,000, an organic diisocyanate (C) and a short chain triol (D) having a molecular weight lower than about 500 and specified structures and, as desired, a short chain diol (B) having a molecular weight ranging from about 50 to 500, in specified ratios. The binder may contain a nitrocellulose, a vinyl chloride resin, a polyvinyl butyral, a bisphenol A type polyether or a vinyl chloride-hydroxy carboxylate copolymer as a binder component. The binder provides particularly enhanced heat resistance and solvent resistance with improved dispersibility of a pigment or the like and other resins and favorable compatibility with a solvent or the like.

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Miyagi, Japan

Yoshinobu Ninomiya