Fuji Photo Film Company, Limited

Toshihiko Miura

Kouichi Masaki

Shinji Saito

Hiroo Inaba

Hiroaki Araki

Hiroshi Ogawa

Masaaki Fujiyama

Masatoshi Takahashi

Kiyomi Ejiri

Katsumi Ryoke

Masaki Suzuki

Hiroaki Takano

Yasuyuki Tanaka

Yasuo Tamai

Naoyoshi Chino

Nobuo Yamazaki

Michihiro Shibata

Kenichi Masuyama

Yutaka Kakuishi

Kazuaki Taga

Hideaki Kosha

Kazuo Kato

Takamitsu Asai

Youichi Hayata

Kunihiko Honda

Noboru Zinbo

Takashi Suda

Kideaki Kosha

Koyotaka Fukino

Junji Yazawa

Tatsuya Oguri

Jun-ichi Nakamikawa

A ferromagnetic metal powder for magnetic recording containing iron as the main constituent and MAl O (wherein M is a transition metal), wherein the coercive force (Hc) thereof is from 135 to 240 kA/m, the saturation magnetization (&sgr;s) is from 100 to 150 A&middot;m /kg, the average major axis length of the particles thereof is from 30 to 80 nm, the average acicular ratio of the particles is from 4.0 to 8.0, and the variation coefficient of the major axis lengths is from 3 to 25%. A magnetic recording medium having on a support a non-magnetic layer and at least a magnetic layer containing the above-described ferromagnetic metal powder, said medium has good short wavelength output and good S/N.

Magnetic recording medium

Provided is a magnetic recording medium with a total thickness equal to or less than 8 &mgr;m having good electromagnetic characteristics and good repeat running durability in which the dropping of powder onto the running path and tape edge deformation are prevented and a magnetic recording medium with a total thickness equal to or less than 8 &mgr;m having good electromagnetic characteristics, good repeat running durability, and good dimensional stability. A magnetic recording medium having on one surface of a nonmagnetic support a lower layer comprising an inorganic powder and a binder and an upper magnetic layer comprising a ferromagnetic powder and a binder in that order, and having on the other surface thereof a backcoat layer, wherein: said nonmagnetic support comprises inorganic powder particles with a mean primary particle diameter in a range of from 40 to 200 nm; the number of particles of said inorganic powder in the cross-section of said nonmagnetic support is in a range of from 10 to 200/100 &mgr;m , said nonmagnetic support exhibits a coercivity in a range of from 159 to 239 kA/m; and the overall thickness is equal to or less than 8 &mgr;m. A magnetic recording medium having on one surface of a nonmagnetic support a lower layer comprising an inorganic powder and a binder and an upper magnetic layer comprising a ferromagnetic powder and a binder in that order, and having on the other surface thereof a backcoat layer, wherein: said nonmagnetic support comprises inorganic powder particles with a mean primary particle diameter in a range of from 10 to 200 nm; the number of particles of said inorganic powder in the cross-section of said nonmagnetic support is in the range of from 10 to 200/100 &mgr;m , the amount of curl d in the direction of width of said magnetic recording medium is equal to or higher than 0.4 mm and equal to or less than 1.0 mm in the direction of protrusion of the magnetic layer at a width of 6.35 mm; and the overall thickness is equal to or less than 8 &mgr;m.

Magnetic recording medium comprising a non-magnetic layer having inorganic particles of specific size and distribution

A ferromagnetic metal powder comprises: a metal portion comprising Fe; and an oxide layer around the metal portion, wherein the oxide layer comprises an iron oxide having magnetism such that the saturation magnetization is from 50 to 95 A.m /kg.

Ferromagnetic metal powder and magnetic recording medium using the same

An optical information recording disc is composed a transparent substrate, an information recording layer, a metallic light-reflecting layer, a light-shielding layer, and an ink-printable layer, in order. The light-shielding layer is prepared essentially from a binder polymer and zinc sulfide particles, so that an ink, particularly an aqueous ink solution, applied onto the ink-printable layer gives a clear ink image with almost no blur.

Optical information recording medium

A magnetic recording medium is disclosed, which comprises a nonmagnetic support having thereon a magnetic layer containing at least ferromagnetic metal particles, wherein said ferromagnetic metal particles have a coercive force of from 1,700 to 3,000 Oe, an average long axis length of from 30 to 80 nm, an average acicular ratio of from 2.0 to 5.0, and a crystallinity of from 30 to 100%.

A magnetic recording medium comprising a nonmagnetic support having provided thereon at least a magnetic layer containing ferromagnetic metal particles, wherein the magnetic layer has a coercive force of 2,000 to 3,000 Oe and a Bm of 3,800 to 5,500 G, the ferromagnetic metal particles has an average major axis length of 0.05 to 0.12 .mu.m and an average aspect ratio of 4.0 to 10.0, the average number of crystallites constituting the ferromagnetic metal particles per particle is from 2.0 to 5.0, and the crystallites has an average aspect ratio of 1.0 to 2.0.

A magnetic recording medium having improved electromagnetic characteristics and running properties is disclosed. The magnetic recording medium comprises a non-magnetic support having thereon a plurality of magnetic layers consisting of two or more layers composed of a first lower magnetic layer and a second upper magnetic layer, provided on said support by either co-coating the lower magnetic layer and the upper magnetic layer in the wet state, or coating the lower magnetic layer and then the upper magnetic layer while the lower magnetic layer is still in the wet state; wherein the cobalt-modified iron oxide is employed as the ferromagnetic powder contained in the lower magnetic layer, ferromagnetic metal is employed as the ferromagnetic powder contained in the upper magnetic layer, both the ferromagnetic powder contained in the lower magnetic layer and the ferromagnetic powder contained in the upper magnetic layer having an average major axis length of 0.25 .mu.m or less and an average acicular ratio of 10 or less, a difference in the average major axis length between the ferromagnetic powder contained in the lower magnetic layer and that contained in the upper magnetic layer of 0.08 .mu.m or less, and a difference in the average acicular ratio between the ferromagnetic powder contained in the lower layer and that contained in the upper layer of 4 or less.

Disclosed is a magnetic recording medium comprising at least two layers comprising at least one lower non-magnetic layer containing at least a non-magnetic particle and a binder on a non-magnetic support, and at least one upper magnetic layer containing at least a ferromagnetic particle and a binder on the lower non-magnetic layer, wherein a mean total thickness d of the upper magnetic layer is more than 0.01 .mu.m to less than 0.3 .mu.m, and a standard deviation .sigma. of the total thickness of the upper magnetic layer and the mean total thickness d of the upper magnetic layer satisfy the relationship of 0.05.ltoreq..sigma./d.ltoreq.0.5.

A magnetic recording medium is disclosed, comprising a nonmagnetic support having thereon a lower nonmagnetic layer comprising nonmagnetic particles dispersed in a binder and further having on the lower layer an upper magnetic layer comprising ferromagnetic metal particles comprising alpha iron crystals dispersed in a binder, wherein said upper magnetic layer has diffraction dots attributable to the ferromagnetic metal particles present on the magnetic layer surface when analyzed by reflection high-energy electron diffraction, the number of said diffraction dots is from 5 to 15 when counted in a 100.degree. range on a circular arc of diffraction dots caused by diffraction on a (211) plane of said ferromagnetic metal particles present on the magnetic layer surface.

A magnetic recording medium having well-balanced properties with respect to head abrasion characteristics, head cleaning characteristics and drop out characteristics is disclosed, which comprises a non-magnetic support having thereon a magnetic layer containing a ferromagnetic powder and a binder, wherein the magnetic layer has been brought into contact with a carbon steel alloy or super hard alloy made from powders having a Mohs' hardness of at lease 6 and rubbed therewith. A process of producing the magnetic recording medium is also disclosed.

Magnetic recording medium kubbed with a super hard alloy blade

A magnetic recording medium comprising a non-magnetic support having thereon a plurality of magnetic layers each comprising a ferromagnetic powder dispersed in a binder, wherein the layer located within a thickness of 0.5 .mu.m from an uppermost surface of said plurality of magnetic layers and a layer located within a thickness of 0.5 .mu.m above the adjacent non-magnetic support have a higher packing density of ferromagnetic powder than an interlayer interposed therebetween. In a preferred embodiment, the interlayer consists of two layers and there are provided on the non-magnetic support a 1st magnetic layer, a 2nd magnetic layer, a 3rd magnetic layer and a 4th magnetic layer in this order from the non-magnetic support; the sum of the thickness of said 3rd magnetic layer and said 4th magnetic layer being not more than 3.5 .mu.m.

A magnetic recording medium is disclosed, which comprises a non-magnetic support having on one surface of the support a backing layer containing carbon black and a binder and on the opposite surface of the support a magnetic recording layer containing a ferromagnetic power and a binder, the ferromagnetic powder being oriented in the magnetic recording layer such that the ratio of the number of diffraction points N(220)/N(113) measured at the surface region of the magnetic layer by high energy electron diffraction is at most 1.65; and the squareness ratio Br/Bm of the magnetic layer is from 0.830 to 0.860 at 25.degree. C. The medium has excellent running durability, S/N ratio, and dropout properties.

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

A method for measuring the thickness of a multi-layer magnetic recording medium which provides a high accuracy and which can be used for continuous on-line monitoring of product thickness. First, first and second magnetic layers are simultaneously coated onto a running nonmagnetic support to form the recording medium. The first and second magnetic layers are made of materials having different responses to fluorescent X-rays. Then, the thickness of at least one of said first and second layers is measured by exposing the recording medium to fluorescent X-rays.

Method for measuring thickness of magnetic recording medium

A magnetic recording medium is described, comprising a non-magnetic support having provided thereon a magnetic layer comprising a binder having dispersed therein a ferromagnetic powder, in which said magnetic layer contains surface-coated inorganic particles having a Mohs hardness of 5 or more as an abrasive, said coated inorganic particles being present in a larger proportion in the vicinity of the surface of the magnetic layer. The magnetic recording medium has improved electromagnetic characteristics and improved running durability.

Growing community of inventors

Kanagawa, Japan

Toshihiko Miura