Sony Corporation

Shin-Etsu Chemical Co., Ltd.

Kunio Kobayashi

Hiroshi Yoshioka

Yoshio Inoue

Minoru Takamizawa

Masashi Somezawa

Yoshiaki Hisagen

Kaoru Nakajima

Shigeo Kimura

Isao Kubota

Toshimi Miyao

A magnetic recording medium having a non-magnetic substrate, a first magnetic layer composed mainly of magnetic powder and binder and formed on the non-magnetic substrate, and a second magnetic layer composed mainly of magnetic powder and binder and formed on the first magnetic layer is disclosed. In this case, the magnetic powder of the first magnetic layer is made of ferro-magnetic metal powder which has a specific surface area of 20 to 40 m.sup.2 /g measured according to BET adsorption method, the first magnetic layer has coercive force H.sub.c1 of 800 to 1500 Oe, residual magnetic flux density of 3000 to 5000 Gausses and a thickness of more than 2.mu., while the magnetic powders of the second magnetic layer is made of ferro-magnetic metal powder which has a specific surface area of 40 to 150 m.sup.2 /g measured according to BET adsorption method, the second magnetic layer has coercive force H.sub.c2 of 1000 to 2500 Oe, residual magnetic flux density of 2000 to 3000 Gausses and a thickness 0.1 to 2.mu., and the coercive forces H.sub.c1 and H.sub.c2 are selected to satisfy H.sub.c1 .ltoreq.H.sub.c2 .

Magnetic recording medium

A magnetic recording medium carrying a magnetic layer thereon, the magnetic layer primarily composed of binder and magnetic powder, wherein the binder is composed of an acrylic compound having a plurality of unsaturated bonds in its molecule and a thermoplastic resin in a weight ratio of 80:20 to 20:80, and is hardened under irradiation.

The invention provides a novel diorganopolysiloxane compound composed of dimethysiloxane units, methyl (2-perfluoroalkylethyl)siloxane units and methyl acyloxyalkylsiloxane units. The novel diorganopolysiloxane compounds of the invention have excellent lubricating properties so that they are useful as an additive ingredient in various materials such as coating compositions, magnetic layer of recording tapes and the like where lubricity or mold releasability is essential.

Novel diorganopolysiloxane compounds

A magnetic recording medium having a layer containing as a lubricant one or more organo-polysiloxane compounds having the following formula (I): ##STR1## (wherein each of A.sub.1 and A.sub.2 is independently --CH.sub.3, --CH.sub.2 --CH.sub.2 --(CF.sub.2).sub.q --CF.sub.3 or --R.sub.1 OCOR.sub.2 ; R.sub.1 is a divalent hydrocarbon residue having 1 to 5 carbon atoms; R.sub.2 is a monovalent hydrocarbon residue having from 7 to 21 carbon atoms; each of l, m and n is independently O or an integer ranging from 1 to 200; and each of p and q is independently O or an integer ranging from 1 to 12; provided that when at least one of the groups A.sub.1 and A.sub.2 is the group --R.sub.1 OCOR.sub.2, each l, m and n may be O and that, when each group A.sub.1 and A.sub.2 is one of the groups other than the group --R.sub.1 OCOR.sub.2, each l and m may be O and n is an integer ranging from 1 to 200).

A magnetic recording medium having low friction coefficient and superior in aging characteristics is disclosed. The magnetic recording medium is provided with a lubricant which is strongly bonded to the magnetic recording medium by a bombardment of an electron beam. In one embodiment, the lubricant containing a molecular chain having a lubricating property, and a double bond sensitive to dissociation products such as free radicals are coated on a magnetic layer and then electron beam irradiates the magnetic layer. A radical reaction then occurs causing a covalent bond of the lubricant to the magnetic recording layer.

Growing community of inventors

Miyagi, Japan

Kunio Kobayashi