Fuji Photo Film Company, Limited

Hideaki Kosha

Katsumi Ryoke

Masatoshi Takahashi

Eiichi Tadokoro

Nobutaka Yamaguchi

Kazuko Hanai

Masaaki Fujiyama

Kiyomi Ejiri

Tsutomu Okita

Yasuo Tamai

Tatsuji Kitamoto

Takahito Miyoshi

Akihiro Matsufuji

Masami Suzuki

Takashi Yoneyama

Toshimitu Okutu

Masami Sato

Kouichi Masaki

Toshihiko Miura

Hideomi Watanabe

Takashi Iwasaki

Tadashi Ishikuro

Shin-Ichiro Dezawa

Kazuo Hasumi

A process for preparing a magnetic recording medium by the steps of (a) forming a magnetic layer on one surface of a non-magnetic support and (b) homogeneously dispersing an .alpha.-Al.sub.2 O.sub.3 power having an average particle size of about 0.1 .mu.m or less in a solvent containing a small amount of binder to form a dispersion, mixing the thus-prepared dispersion with a binder to provide a coating composition, and applying the coating composition to the opposite surface of the nonmagnetic support to form a backing layer. The magnetic recording medium has improved wear resistance, a low friction coefficient and excellent electromagnetic properties.

Process for preparing a backing layer of a magnetic recording medium

A magnetic recording medium is described, comprising a non-magnetic support having thereon a magnetic layer containing ferromagnetic particles dispersed in a binder, the ferromagnetic layer containing abrasive agent particles alone or in combination with lubricating agent particles, wherein the weight ratio of (a) the abrasive agent particles which are present, or each of the abrasive agent particles and lubricating agent particles which are present, within 1 .mu.m in a thickness direction from the surface of the magnetic layer to (b) the abrasive agent particles or each of the abrasive agent particles and lubricating agent particles which are present, within the whole magnetic layer is at least 100/(thickness of the magnetic layer -1) % in which the 'thickness of the magnetic layer' represents the thickness in '.mu.m' and is 2 .mu.m or more. A method for preparing a magnetic recording medium comprising: coating on a non-magnetic support a first coating composition having ferromagnetic particles dispersed in a binder, and simultaneously or successively coating thereon a second coating composition having a binder in which there is despersed abrasive agent particles alone or in combination with lubricating agent particles.

Magnetic recording medium and the method for preparing the same

An abrasive tape comprises a flexible substrate and an abrasive layer which is overlaid on the flexible substrate and which contains abrasive grains and a binder. The abrasive grains comprise first abrasive grains, which have a mean grain diameter within the range of 0.07 .mu.m to 0.40 .mu.m and a Mohs hardness within the range of 5 to 7, and second abrasive grains, which have a mean grain diameter within the range of 0.20 .mu.m to 0.60 .mu.m and a Mohs hardness not lower than 8.5.

Abrasive tape

A magnetic recording medium comprising a support having provided on one surface thereof a magnetic layer comprising a binder and ferromagnetic particles dispersed therein, and on the opposite surface thereof a backing layer comprising a binder and non-magnetic particles dispersed therein, wherein at least one of the binders comprises a vinyl chloride copolymer resin having a vinyl chloride unit content of about 70 wt % or more based on the total amount of the binder, a nitrogen content of about from 0.01 to 1 wt % based on the total amount of the binder, and a polymerization degree of about from 250 to 700; and the non-magnetic particles comprises fine carbon particles having a DBP oil absorption of about 150 ml/100 g or more.

Magnetic recording medium

A magnetic recording medium is disclosed, comprising a non-magnetic support having thereon a magnetic layer comprising ferromagnetic fine particles, a binder, and .alpha.-alumina particles having an average size of from about 0.1 to 0.3 .mu.m, provided that the number of .alpha.-alumina particles having a particle size of larger than 0.05 .mu.m is at least equal to the number of .alpha.-alumina particles having a particle size of up to 0.05 .mu.m.

A magnetic recording medium is disclosed which comprises a non-magnetic support having coated thereon a magnetic layer containing a specific amount of a specific acicular Cr.sub.2 O.sub.3 along with alpha-Al.sub.2 O.sub.3, SiC, and/or TiC, which medium shows excellent surface properties and electromagnetic properties, as well as improved running durability.

A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on said support, said magnetic recording layer comprising a ferromagnetic powder dispersed in a binder, characterized in that said magnetic recording layer contains an acicular inorganic powder which has a Mohs' scale of hardness of not less than 5, a length of not longer than 1.0 .mu.m, a thickness of not thicker than 0.1 .mu.m, and an aspect ratio in the range of 5 to 20.

A magnetic recording medium comprising a non-magnetic support having provided thereon a magnetic layer being provided on one surface of the support and a backing layer being provided on the surface of the support opposite to said magnetic layer, the backing layer contains binder and non-magnetic particles comprised of (i) corbon black having an average particle size of 0.1 to 1.0 .mu.m and (ii) particles of abrasives having a Mohs' hardness of at least 6 and an average particle size of 1 .mu.m or less, with the non-magnetic particles in said backing layer being used in an amount of 40 to 300 parts by weight per 100 parts by weight of binder.

A magnetic recording medium comprises a non-magnetic support having provided thereon a magnetic layer containing magnetic particles dispersed in a binder. The magnetic layer contains acicular Cr.sub.2 O.sub.3 having an average length in the long axis of 1.0 .mu.m or less, an average length in the short axis of 0.1 .mu.m or less and an acicular ratio (long axis/short axis) of from 5/1 to 20/1 in an amount of from 1 to 20 wt % based on the total weight of the magnetic particles. The binder comprises at least one material selected from the group consisting of polyurethane having a glass transition temperature (Tg) of from 0.degree. to 95.degree. C. or containing a metal sulfonate group, or a vinyl chloride resin containing a metal sulfonate group.

A magnetic recording medium is described, comprising a magnetic layer coated on one side of a non-magnetic support and a backing layer coated on the opposite side of the non-magnetic support, wherein the backing layer is provided after the magnetic layer has been subjected to calendering treatment and the backing layer comprises (i) non-magnetic particles including carbon black particles having an average particle diameter of from 0.1 to 1 .mu.m and (ii) a binder composition comprising from 50 to 95 wt % of a resin having a 100% modulus at 150 kg/cm.sup.2 or less based on the total weight of the binder composition, and the weight ratio of non-magnetic particles to binder composition contained in the backing layer is from 300/100 to 40/100.

A magnetic recording medium is described, comprising a non-magnetic support having provided thereon a magnetic layer being provided on one surface of the support and a backing layer being provided on the surface of the support opposite to said magnetic layer, the backing layer containing (A) a binder comprised of resin having a 100% modulus of 150 kg/cm.sup.2 or less present in an amount of 50 to 95 wt % based on the total weight amount of binder and (B) non-magnetic particles comprised of (i) carbon black having an average particle size of more than 0.1 .mu.m to 1.0 .mu.m, and (ii) carbon black having an average particle size of 0.01 .mu.m to 0.1 .mu.m in a weight ratio of carbon black (i)/carbon black (ii) of 95/5 to 5/95, with the non-magnetic particles in the backing layer being present in an amount of 40 to 300 parts by weight per 100 parts by weight of the total binder.

A magnetic recording medium is described, comprising a non-magnetic support having a magnetic layer and a backing layer which is provided on the surface of the support opposite to the magnetic layer, the backing layer containing (a) non-magnetic particles comprising carbon black having an average particle diameter of 0.1 to 1.0 .mu.m, (b) a binder comprising (i) a resin having 150 kg/cm.sup.2 or less of 100% modulus in an amount of at least 50 wt % based on the total amount of binder, and (ii) a diphenyl methane diisocyanate type hardening agent, with the amount of non-magnetic particles to total contained in the backing layer being 40 to 300 parts by weight of non-magnetic particles per 100 parts by weight of binder.

A magnetic recording medium comprising a non-magnetic support having provided thereon a magnetic layer on one side and a backing layer on the other side, wherein the backing layer contains (1) non-magnetic powders containing carbon black having an average particle diameter of from 0.1 to 1 .mu.m; (2) two or more binders wherein (a) at least one of the binders is a resin having a 100% modulus of from 15 to 150 kg/cm.sup.2 in an amount of from 50 to 95 wt % based on the total amount of the binders in the backing layer, and (b) the rest binder(s) is/are a resin other than the resin having a 100% modulus of from 15 to 150 kg/cm.sup.2, and the weight ratio of all the non-magnetic powders to all the binders in the backing layer is from 300:100 to 40:100; and (3) a polyisocyanate in an amount of from 15 to 40 wt % based on the total amount of the binders in the backing layer.

A process for preparing cobalt-modified ferromagnetic iron oxide by modifying ferromagnetic .gamma.-Fe.sub.2 O.sub.3 particles with cobalt, wherein prior to cobalt modification treatment, the ferromagnetic .gamma.-Fe.sub.2 O.sub.3 is heat treated at a temperature in the range of from about -200.degree. C. to +30.degree. C. of the critical temperature at which partial transition of .gamma.-Fe.sub.2 O.sub.3 into .alpha.-Fe.sub.2 O.sub.3 occurs and which reduces the saturation magnetization to 99% of the saturation magnetization measured before the heat treatment, and the atomic ratio of Fe.sup.++ /Fe.sup.+++ after the cobalt modification is 0.00 to 0.10.

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Kanagawa, Japan

Hideaki Kosha