Fuji Photo Film Company, Limited

Koichi Yamauchi

Hiroo Inaba

Yasuyuki Yamada

Akihiro Matsufuji

Nobuo Tsuji

Takeshi Kakuta

Hiroshi Ogawa

Yasuyuki Tanaka

Shinichi Funabashi

Masatoshi Kiyama

A magnetic recording medium comprising a nonmagnetic support having provided thereon a magnetic layer comprising a ferromagnetic powder dispersed in a binder, wherein said ferromagnetic powder has a specific surface area of 40 m.sup.2 /g or more as measured by the BET method; said magnetic layer further comprises carbon black having an average particle diameter of from about 20 to 120 m.mu.; and said binder comprises the combination of (1) a vinyl chloride resin containing a phosphate ester group represented by ##STR1## wherein M.sub.1 and M.sub.2, which may be the same or different, each represents Na, K, Li, H, N.sym.R.sub.3, or N.sym.HR.sub.2 wherein R represents an alkyl group or a hydrogen atom, and (2) at least one resin other than said vinyl chloride resin containing at least one of --SO.sub.3 M, --OSO.sub.2 M, --COOM, and ##STR2## wherein M, M.sub.1, and M.sub.2, which may be the same or different, each represents Na, K, Li, H, N.sup.4 .sym. R.sub.3, or N.sup..sym. HR.sub.2 wherein R represents an alkyl group or a hydrogen atom; provided that the weight ratio of said resin other than said vinyl chloride resin to said vinyl chloride resin is from about 0.4 to 2.5.

Magnetic recording medium containing ferro magnetic powder, polar group

A magnetic recording medium comprising a nonmagnetic support having provided thereon a magnetic layer comprising a ferromagnetic powder dispersed in a binder, wherein said ferromagnetic powder has a specific surface area of 40 m.sup.2 /g or more as measured by the BET method; said magnetic layer further comprises Al.sub.2 O.sub.3 particles having an average particle diameter of from about 0.1 to 0.5 .mu.m; and said binder comprises the combination of (1) a vinyl chloride resin containing a phosphate ester group represented by ##STR1## wherein M.sub.1 and M.sub.2, which may be the same or different, each represents Na, K, Li, H, N.sym.R.sub.3, or N.sym.HR.sub.2 wherein R represents an alkyl group or a hydrogen atom, and (2) at least one resin other than said vinyl chloride resin containing at least one of --SO.sub.3 M, --OSO.sub.2 M, --COOM, and ##STR2## wherein M, M.sub.1, and M.sub.2, which may be the same or different, each represents Na, K, Li, H, N.sym.R.sub.3, or N.sym.HR.sub.2 wherein R represents an alkyl group or a hydrogen atom; provided that the weight ratio of said resin other than said vinyl chloride resin to said vinyl chloride resin is from about 0.4 to 2.5.

Magnetic recording medium

A magnetic recording medium exhibiting good still durability and good running properties is disclosed, which comprises a non-magnetic support having thereon a first magnetic layer and a second magnetic layer in sequence, the first and second magnetic layers containing ferromagnetic powder and a binder, wherein a fatty acid ester (A) having the following structure is contained in the first magnetic layer and a fatty acid ester (B) having the following structure is contained in the second magnetic layer: ##STR1##

A magnetic recording medium which comprises a non-magnetic support having thereon a magnetic recording layer containing a ferromagnetic fine powder and a binder as main components is disclosed. The magnetic recording layer containing as the binder (1) a vinyl chloride-vinyl acetate-maleic acid copolymer which has a mean polymerization degree of about 300 to about 400 and a maleic acid fraction of about 0.6 to about 1.5 wt %, (2) a polyurethane resin which has a number average molecular weight of 40,000 to 100,000 and is prepared from (i) a mixture of polyneopentyladipate having a mean molecular weight of 500 to 2,500 and polybutyleneadipate having a mean molecular weight of 500 to 2,500 with a mixing ratio of the former to the latter of from 2/8 to 9/1 by weight and (ii) diphenylmethane diisocyanate, and optionally (3) a low molecular weight polyisocyanate compound.

The present invention relates to a magnetic recording medium excellent in S/N ratio and abrasion resistance, which comprises a non-magnetic support and a magnetic recording layer coated thereon, consisting of a ferromagnetic fine powder and a binder, in which the binder contains (1) nitrocellulose having an average polymerization degree of 50 to 300 and a nitrification degree of 10.7 to 13 and (2) a polyurethane resin having a number average molecular weight of 40,000 to 100,000, obtained from diphenylmethane diisocyanate and a mixture of polyneopentyl adipate having an average molecular weight of 800 to 2000 and polybutylene adipate having an average molecular weight of 800 to 2000 in a mixing proportion by weight of 2/8 to 9/1.

Growing community of inventors

Kanagawa, Japan

Koichi Yamauchi