Tokyo Shibaura Denki Kabushiki Kaisha

Tokyo Shibaura Electric Co., Ltd.

Kabushiki Kaisha Toshiba

Konica Corporation

Toshihiko Oguchi

Tsutomu Kubo

Ichiyoshi Saito

Hirohisa Kato

Hajime Takeuchi

Moriyasu Wada

Tsutomu Uehara

Hirotaka Yokoyama

Yukio Suzuki

Akio Ishizawa

Tsuyoshi Ueno

Isao Suzuki

Hiroshi Endo

Seiichi Tobisawa

Tadashi Ido

Masaru Hayashi

Hiromi Yoshida

Toshiharu Nakagawa

Toshio Fukaya

Shigeo Iiri

Masashi Awa

Naoyuki Hirate

Toshimitsu Asano

Yoshiyasu Koike

Minori Murano

Ken-ichi Furuhata

Michiyasu Takagi

Yuji Doki

A magnetic recording medium comprises a non-magnetic base material, a lower magnetic layer containing a magnetic powder for recording in a long wavelength range, and an upper magnetic layer containing a magnetic powder for recording in a short wavelength range. By adding a small particle abrasive with a median diameter in the range from 0.05 to 0.3 .mu.m to the upper magnetic layer and by properly selecting the type and amount of a resin binder contained in the upper magnetic layer, a satisfactory abrasion effect can be obtained. This effect can be obtained, even if the abrasive with a small particle diameter is used without necessity of increase of the amount thereof. In addition, by using this abrasive, even if the upper magnetic layer is thin, the surfaces of the upper magnetic layer and the lower magnetic layer can be smoothened. Therefore, an excellent magnetic recording medium having high recording and reproduction characteristics in a wide wavelength range and high running durability can be provided. In particular, the recording and reproduction characteristics in a short wavelength range can be improved. A hexagonal ferrite powder can be used as a magnetic powder for recording in a short wavelength range.

Magnetic recording medium having two magnetic layers comprising magnetic

A magnetic recording medium comprises a non-magnetic base material; a lower magnetic layer containing a magnetic powder for recording in a long wavelength range and a resin binder; an upper magnetic layer containing a magnetic powder for recording in a short wavelength range and a resin binder; and an intermediate layer disposed between the two magnetic layers. By properly selecting the type and amount of resin binder contained in the upper magnetic layer and by disposing the intermediate layer whose main component is a resin binder, dispersion property of the magnetic powder in the upper magnetic layer can highly be improved, and thin and smooth magnetic layers can be obtained. Thus, the recording medium provides excellent reproduction characteristics in the wide wavelength range and has excellent running durability. In particular, the reproduction characteristics in a short wavelength range can be improved. A hexagonal ferrite powder is suitably used as the magnetic powder for recording in the short wavelength range. As the resin binder for the intermediate layer, a polyisocyanate compound whose molecular weight is 1,000 or less is particularly effective.

Magnetic records medium having multiple magnetic layers for recording in

A magnetic recording medium is disclosed comprising a substrate coated with a mixture which consists essentially of (1) hexagonal plate-like shaped, ferrite magnetic powder particles having an average particle diameter of 0.2 .mu.m or less and (2) a binder resin having an active hydrogen equivalent of 2000 or more. This magnetic recording medium displays no flocculation of the hexagonal system ferrite magnetic powder, and has excellent dispersion properties and perpendicular orientation ability. Further, smoothness on the coating film is good, and S/N properties are noticeably improved.

Magnetic recording medium

Disclosed is a magnetic recording medium, characterized in that 5 to 100 parts by weight of hexagonal ferrite particles having an average particle diameter of 0.01 to 0.2 .mu.m and 100 parts by weight of ferromagnetic particles having a saturation magnetization of 72 to 220 emu/g and an average particle diameter larger than that of the hexagonal ferrite particles are dispersed in a resinous binder.

Magnetic recording media having ferromagnetic and ferrite particles in

To manufacture a perpendicular magnetic recording medium, a nonmagnetic substrate having a coating layer of a binder with magnetic particles dispersed therein is passed through a magnetic field in a direction substantially perpendicular thereto, and a perpendicular orientation of the magnetic particles is performed as the substrate passes through an upstream region of the magnetic field. A viscosity of the coating layer is increased in a downstream region of the magnetic field, thereby restricting further movement of the magnetic particles in the coating layer before the nonmagnetic substrate is removed from the magnetic field.

Method and apparatus for perpendicular magnetic recording medium

Disclosed is a magnetic recording medium comprising substrate and a resinous composition containing magnetic particles of uniaxially-anisotropic hexagonal crystals having particle diameters of 0.01.about.0.3 .mu.m and coated on said substrate; the ratio of remanent magnetization to saturation magnetization on the magnetization curve corrected to demagnetizing field which is measured in a direction vertical to the surface of the recording medium, ranging from 0.3 to 0.7. This magnetic recording medium requires no orientation treatment for its production.

Magnetic recording media

Barium-ferrite series powders are prepared from an alkaline aqueous solution containing a prescribed ratio of ions of the metals equal to those contained in the powder. In the first stage, the alkaline aqueous solution is heated at a constant volume at 150.degree. to 300.degree. C. to precipitate a precursor of the barium-ferrite series powder. Then, the precursor is baked at 700.degree. to 1,000.degree. C. to crystallize the precursor.

Method of producing barium-ferrite series powder

A coated powder comprising a transition metal or compound thereof prepared by the process which comprises coating the surface of a powdered transition metal or compound there with a free radical polymerizable monomer having an e value of (-)0.8 to (+)0.8 and then subjecting the resulting coated powder to free-radical polymerization conditions.

Polymer coated transition metal powder as electrostatic image toner

An apparatus for forming a cloud of magnetic toner particles has a rotatable magnet roller with a number of magnetic poles disposed within a non-magnetic cylindrical sleeve. Magnetic toner particles are supplied from a hopper onto the sleeve. A magnetic bar is disposed above the sleeve. The rotation of the magnet roller causes the sleeve to carry magnetic toner particles thereon. When the magnetic toner particles carried approach to the magnetic bar, those become in a cloudy state.

Apparatus for forming a cloud of toner particles

A magnetic brush apparatus is provided with a hopper for supplying powdered one-component magnetic developer to a cylindrical sleeve housing a rotating magnet roller with a number of magnetic poles. The powdered magnetic toner supplied onto the sleeve surface is formed into a magnetic brush on the sleeve surface under control of alternating magnetic field generated by the magnet roller. The magnet brush is carried around the sleeve surface with rotation of the magnet roller. Outside the sleeve surface a predetermined distance is positioned a magnetic member which may be attached to the tip end of a doctor blade. The magnetic member disturbs the alternating magnetic field on the sleeve surface, thereby restricting the height of the powdered developer passing between the end of the magnetic member and the sleeve surface.

Magnetic brush apparatus for electrostatic printing system

This invention is concerned with a method for forming spherical particles of thermoplastic material, characterized by the step of blowing a stream of gas having thermoplastic particles dispersed therein from a peripheral region into a jet of pressurized hot gas to form the thermoplastic particles into uniform spherical particles. It also provides apparatus for carrying out the foregoing method which includes means for discharging a jet of pressurized hot gas from an outlet port and means for ejecting a stream of gas having thermoplastic particles dispersed therein from the periphery of the outlet port toward the jet of pressurized hot gas.

Method and apparatus for forming spherical particles of thermoplastic

Toner for electrostatic image development, comprising a toner body powder which contains a thermoplastic resin binder having a first reactive functional group and a micro powder which has a second reactive functional group capable of a curing reaction with the first reactive functional group. Owing to the curing reaction between the first and second reactive functional groups, the micro powder particles are bonded on the particles of the toner body powder. Thus the toner is powder particles with non-adhesive surfaces and possesses a good preservation stability. Over a long time after its manufacture the toner can provide clear developed images.

Toner for electrostatic image development

A device develops an electrostatically charged image formed on a photoelectroconductive layer with toner particles bearing a residual magnetization. The toner particles are provided on a vessel and in an alternating magnetic field to be rotated and repeatedly rebounded while charged, so as to be attracted onto the charged image.

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Kawasaki, Japan

Toshihiko Oguchi