Konishiroku Photo Industry Co., Ltd.

Shotaro Watanabe

Makoto Tomono

Goichi Yamakawa

Nobuo Takahashi

Shigeru Uetake

Katsutoshi Tozawa

Takeo Nishimura

Fumio Koizumi

An iron powder developer carrier for electrophotography having at least the outer surface thereof coated with iron oxide. The iron oxide has a particle size of 50 to 200.mu., an apparent density of 1.5 to 2.5 g/cm.sup.3 and a specific surface area of 0.01 to 0.3 m.sup.2 /g. A process for the preparation of iron powder developer carriers for electrophotography, which comprises the steps of subjecting a starting iron powder to a primary calcination treatment in an inert gas atmosphere without using a binder, pulverizing and classifying said calcination product to prepare an intermediate iron powder, reducing the intermediate iron powder in a reducing atmosphere and washing the intermediate iron powder, and subjecting the intermediate iron powder to an oxidizing calcination treatment.

Developing material for electrophotography, process for preparation

An iron powder developing carrier for developing an electrostatic latent image, a manufacturing method thereof, a developer containing said developing carrier and a method of forming a visible image by using said developer. Said iron powder developing carrier has the apparent density from 1.5 to 2.5. Said manufacturing method comprises the steps of sintering a raw iron powder having been ground to particles of not larger than 50 microns in diameter without using any binder agent at the temperature from 900.degree. to 1200.degree. C. to form an sintered body, grinding and classifying said sintered body into an intermediate iron powder having the particle diameter from 50 to 200 microns, then treating said intermediate iron powder to oxidize at the temperature from 280.degree. to 390.degree. C., and adjusting the resultant iron powder so as to have the apparent density from 1.5 to 2.5.

Iron powder developing carrier and the manufacturing method of the same,

A one-component developer for developing a latent electrostatic image which comprises magnetic particles, thermoplastic resins and electric charge controlling dyestuffs as main components and in which the magnetic particles are substantially coated with the electric charge controlling dyestuffs. The resulting toner forms no fringe or ghost and has good duplicativity of halftone images. The toner is made by coating the magnetic particles with the electric charge controlling dyestuffs before mixing the magnetic particles with the resin.

Magnetic toner for developing latent electrostatic images and a process

The present invention is for the improvements of a developer for a one-component latent electrostatic image and the process for the preparation thereof. The present invention is the one which has improved points at issue in the case of using a developer for the conventional conductive one-component latent electrostatic image for a copying machine using a corona discharger and in which particles are prepared by uniformly mixing a magnetic substance in resin and the magnetic substance is substantially exposed on the particle surface by heat treatment and hydrophobic silica fine powders are supported on, or interposed in, said particles; the particles are, as a whole, electrically insulating and given electric charge necessary to form an image by friction of mutual particles; thus even in a copying machine using a corona discharger, good development can be obtained with this developer; and further the present invention is the one which provides a process for the preparation of said particles.

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Machida, Japan

Shotaro Watanabe