Fuji Photo Film Company, Limited

Shigeo Komine

Mikihiko Kato

Kazuhiko Morita

Yasutoshi Okuzawa

Akira Kasuga

Akihiro Matsufuji

Shinichi Kato

Masaaki Fujiyama

Yasuyuki Yamada

Tsutomu Okita

Kiyomi Ejiri

Kazunori Komatsu

Hajime Miyatsuka

Shinobu Iida

Tatsuji Kitamoto

Goro Akashi

Nobuo Tsuji

Nobutaka Yamaguchi

Toshimasa Usami

Tsunehiko Sato

Toshio Kawamata

Noburo Hibino

Sumitaka Tatsuta

Yoshito Mukaida

Koji Sasazawa

Keisuke Yamada

Tomoyuki Kobayashi

Masaaki Igarashi

Katsumi Koyota

Kouji Nakata

A process for the preparation of a magnetic recording medium comprises the steps of subjecting a magnetic recording layer coated on a nonmagnetic support to surface smoothening treatment, the magnetic recording layer comprising a ferromagnetic powder dispersed in a binder, and then grinding both a surface of the magnetic recording layer and a surface of a back layer provided on the support using a specific grinder. The specific grinder is a fixed blade, a diamond wheel or a rotatable blade. A rotatable blade-grinder preferably employable for the grinding procedure comprises a rotatable body having a circular section and one or more blades provided on the periphery of the body.

Process for the preparation of magnetic recording medium

A magnetic recording medium is described, comprising a non-magnetic support having provided thereon, in sequence, an intermediate layer and a magnetic layer coated with a dispersion of ferromagnetic particles in a binder, wherein said intermediate layer contains at least one binder containing at least one of a hydroxyl group and an amino group, and said magnetic layer contains an isocyanate compound.

Magnetic recording medium

A magnetic recording disk comprising a nonmagnetic support and magnetic recording layers provided on both surfaces of said support, said magnetic recording layers comprising a ferromagnetic metal powder dispersed in a binder, which is characterized in that: said disk has a thickness in the range of 20-60 .mu.m and a flexural stiffness in the range of 2.0-200 g.multidot.mm; and each of said magnetic recording layers has a center line average height of not more than 0.03 .mu.m.

Magnetic recording disk

In a magnetic recording medium such as a video tape comprising a nonmagnetic support and a magnetic recording layer provided on the support, said magnetic recording layer comprising a binder and a ferromagnetic powder dispersed therein, the improvement in which:

A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on the support, said magnetic recording layer comprising a binder and a ferromagnetic powder dispersed therein, which is characterized in that said binder is composed of a resin component comprising:

A flexible magnetic disk sheet including a central circular hole is described, having a protective layer on a surface portion surrounding the edge of the central circular hole, comprising the protective layer prepared by coating (a) a compound having an acrylate bond or a methacrylate bond at the end of at least one of a main chain and a side chain of molecules thereof, and (b) a solid lubricating agent, and exposing to radiation thereon for polymerizing and hardening it.

Flexible magnetic disk sheet

A flexible magnetic disk in which the friction between the magnetic sheet of the disk and a positioning member is reduced, the magnetic sheet is positioned properly and without offset each time it is loaded in a reading/reproducing device, and the tracking accuracy and dimensional accuracy are satisfactory. A protective layer is provided around the periphery of a central hole in the magnetic sheet. The protective layer is made of a composition containing a compound which has an acrylic or methacrylic acid ester bond at one or both of a main chain terminal and a side chain thereof. The compound is one which is cured by radiation. The thickness of the protective layer should be 30 microns or less, and the surface irregularity of the protective layer should be 0.03 microns or more represented in terms of a central line average roughness at a cutoff of 2.5 mm.

Flexible magnetic disk

A method for forming protective layer on a surface portion surrounding the edge of a central aperture of a flexible magnetic disc sheet is described, comprising providing a radiation polymerizable composition on a surface portion surrounding the edge of the central aperture of the flexible magnetic disc sheet by screen printing, and hardening the composition by exposure to radiation; a flexible magnetic disc is also described, wherein a protective layer by the foregoing method is provided, with said protective layer having an inner diameter larger than the diameter of the aperture of the disc sheet and an outer diameter smaller than the diameter of the aperture of a jacket enclosing the disc sheet.

Method for forming protective layer on a flexible magnetic disc sheet

In a method of and apparatus for making a magnetic recording medium, a plurality of rod-like orientation magnets are positioned in spaced relation in the movement direction of a non-magnetic substrate so that the magnetic pole facing the non-magnetic substrate is different between adjacent orientation magnets and the orientation magnets are oblique with respect to the substrate movement direction and alternately point reversely. The spaces between the orientation magnets are adjusted so that the intensity of the magnetic field generated in the substrate movement direction between adjacent orientation magnets is 50 Oe or less. A magnetic coating composition is applied onto the non-magnetic substrate, and magnetic grains contained in the composition are randomly orientated by the orientation magnets.

Apparatus for making magnetic recording medium

A flexible magnetic disc sheet is described, which has a central circular hole therein and has a protective layer only on a surface portion surrounding the edge of the central circular hole, the protective layer comprising (a) a radiation polymerized polymer of a compound which is polymerizable and hardenable by radiation and (b) a matting agent.

Flexible magnetic disc sheet

A heat-treating process is disclosed. The process involves cutting a polymer support for a recording medium from a web roll of a long support base into a sheet form. The sheet or sheets in a superposed state are then heat-treated while applying pressure in the range of 1 g/cm.sup.2 to 1 kg/cm.sup.2 at a temperature of 50.degree. C. to 150.degree. C. for a period of time of 15 seconds to 24 hours. The heat treating process avoids conventional problems with respect to thermal shrinkage.

Process for producing a magnetic recording medium having an improved

A flexible magnetic disk sheet having a central circular hole is described, through which an apparatus for reading and writing is engaged, and enclosed in an jacket having a larger central circular hole exposing the hole of the disk sheet within the hole of the jacket, wherein a reinforcing plastic ring containing a solid lubricating agent is provided on the region of the flexible magnetic disk sheet immediately surrounding the central circular hole thereof.

A flexible disk comprises a flexible disk jacket having a central opening and a disk-like magnetic recording medium having a central opening smaller than the central opening of the flexible disk jacket in diameter. The recording medium is accommodated for rotation in the flexible disk jacket so that their central openings are concentrically positioned and the portion of the recording medium surrounding the central opening is exposed through the central opening of the jacket, thereby giving access thereto. The portion of the recording medium surrounding the central opening is provided with a protective layer on one side thereof and a reinforcement ring on the other side thereof. The protective layer is formed of a composition which contains a compound with at least one unsaturated bond per molecule that is polymerizable by ultraviolet rays, and which has been cured by exposure to ultraviolet rays.

Flexible disk

A magnetic recording medium such as a magnetic recording disk or a magnetic recording tape comprising a nonmagnetic support and a magnetic recording layer provided on said support, said magnetic recording layer comprising a nonmagnetic inorganic powder and a ferromagnetic metal powder of a specific surface area in the range of 35-65 m.sup.2 /g dispersed in a binder, which is characterized in that said magnetic recording layer contains an alkyl ester of a fatty acid and an alkoxyalkyl ester of a fatty acid in amounts in the ranges of 5-15 wt. % and 0.5-10 wt. %, respectively, based on the amount of the ferromagnetic metal powder.

Growing community of inventors

Kanagawa, Japan

Shigeo Komine