Toda Kogyo Corporation

Unitika Ltd.

Kazuo Fujioka

Hiromitsu Misawa

Koso Aoki

Minoru Kozawa

Eiichi Kurita

Yoji Okano

Naoki Uchida

Yasuhiko Fujii

Toshiyuki Hakata

Shigeru Takaragi

Tetsuro Toda

Sigenori Miyazaki

Yoshiaki Echigo

Keiichi Asami

Haruki Kurokawa

Tsutomu Sakaida

Souichiro Kishimoto

Youzi Okano

Magnetite particles of the present invention have an average particle diameter of 0.05 to 0.50 .mu.m, each of the magnetite particles having a plurality of mountain-shaped protrusions with unsharpened crests on a surface of each magnetite particle, and the number of the mountain-shaped protrusions formed on the surface of each magnetite particle being in the range of 2 to 30 when viewed in projected plan; magnetic iron oxide particles for magnetic toner comprising not less than 60%, in particle number, of the said magnetite particles; and a magnetic toner comprising the said magnetic iron oxide particles and a binder resin. The magnetite particles of the present invention are free from the falling-off from toner particles. The toner particles of the present invention shows a good fluidity and produces visual images having a higher definition upon development of electrostatic latent images.

Magnetic toner particles comprising magnetite particles containing

Magnetic particles for a magnetic toner comprise:

Magnetic particles for magnetic toner and process for producing the same

Magnetite particles of the present invention have an average particle diameter of 0.05 to 0.50 .mu.m, each of the magnetite particles having a plurality of mountain-shaped protrusions with unsharpened crests on a surface of each magnetite particle, and the number of the mountain-shaped protrusions formed on the surface of each magnetite particle being in the range of 2 to 30 when viewed in projected plan; magnetic iron oxide particles for magnetic toner comprising not less than 60%, in number, of the said magnetite particles; and a magnetic toner comprising the said magnetic iron oxide particles and a binder resin. The magnetite particles of the present invention are free from the falling-off from toner particles. The toner particles of the present invention shows a good fluidity and produces visual images having a higher definition upon development of electrostatic latent images.

Magnetite particles, magnetic iron oxide particles, process for the

A magnetic toner containing 100 parts by weight of magnetic Fe.sup.2+ -containing iron oxide particles having an average particle size of 0.05 to 0.30 .mu.m, containing not less than 0.9 atm % and less than 1.7 atm % of silicon, calculated as Si, based on Fe, having a substantially cubic shape each ridge of which has a curved surface, and having a ratio .phi. represented by the following formula of more than 1.0 and less than 1.4:

Magnetic particles for magentic toner and process for producing the same

Disclosed herein is iron oxide particles comprising:

Iron oxide particles and process for producing the same

Spherical magnetic iron oxide particles for a magnetic toner comprise:

Spherical magnetic particles for magnetic toner and process for

The disclosure describes coated granular magnetite particles comprising:

Coated granular magnetite particles and process for producing the same

Magnetic toner particles composed of magnetite core particles containing 0.10 to 1.00 wt % silicon and a hydrous coprecipiate of silica and alumina deposited or adhered on the surfaces of the magnetite core particles. The magnetic toner particles have an area-average diameter of 0.05 to 1.0 .mu.m.

Magnetic particles comprising magnetite core and process for producing

Granular magnetite particles useful as coloring pigments assuming a black color and containing elemental aluminum, 3 to 6 wt %, in the magnetite crystal lattice. The magnetite has a spinel structure with a lattice constant of 8.340 to 8.375 .ANG..

Granular magnetite particles and process for producing the same

A specific magnetic particle powder is described, which is included in magnetic toners used for magnetic image character recognition (MICR). The magnetic particle powder is a magnetite particle and distinguished by the facts that its residual magnetization is of 12 to 20 emu/g, its Fe.sup.2+ content is of 18.5 to 22.5% by weight, its surface is deposited with Si or Al oxide or mixture thereof and its specific surface area is of 3.5 to 9.5 m.sup.2 /g. The magnetic particle powder used as one component of the magnetic toner enables the formation of fine accurate images and the exact detection of the image.

Magnetic particle powder included in magnetic toners for magnetic image

Disclosed herein are spinel-type spherical black iron oxide particles containing 1.5 to 17.0 wt % of Zn, and having a specific surface area of 5 to 15 m.sup.2 /g, a magnetization of not less than 70 emu/g in an external magnetic field of 1 kOe and a coercive force (Hc) of not more than the value obtained from the following expression:

Spinel-type spherical, black iron oxide particles and process for the

Disclosed herein are magnetic particles for a magnetic toner containing a low-molecular binder resin having a weight-average molecular weight of not more than 150,000, said magnetic particles comprising particulate magnetic particles containing iron as the main ingredient and having an oil absorption of not more than 24 ml/100 g and a degree of compaction of not less than 56, and a magnetic toner containing the said magnetic particles.

Magnetic particles for magnetic toner

Disclosed herein is magnetic particles containing iron as the main component which have an average particle diameter of 0.1 to 3.0 .mu.m and a liquid absorption of not more than 18 m.infin..

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Hiroshima, Japan

Kazuo Fujioka