Fuji Xerox Co., Ltd.

Takuto Tanaka

Yasuki Yamauchi

Toru Teshigawara

Toshiaki Sagara

Haruyuki Nanba

Jun Abe

Nobumasa Furuya

Shigeru Inaba

Koichiro Shinohara

Haruyuki Namba

Takahide Inoue

Satoru Hirosaki

Toshie Gotoh

In a developing device for visualizing an electrostatic latent image using two-component developer containing toner and magnetic carrier, excellent development will be performed and deterioration of the developer will be prevented. A developer carrier opposite to an image carrier having an electrostatic latent image formed thereon is prepared by forming a thin layer of aluminum with a thickness of 3 .mu.m or less on the peripheral surface of a roll-shaped member made of ferrite, and the surface roughness Rz of the peripheral surface of the foregoing ferrite roll is set to 50 .mu.m or less. N-poles and S-poles are alternately magnetized at a 50-to-250-.mu.m pitch along the peripheral surface of this ferrite roll. These magnetic poles can be magnetized to have uniform intensity because the peripheral surface of the roll has been smoothly finished, and a developer layer having only substantially one layer of the carrier uniformly attracted is formed on the peripheral surface. On the other hand, a magnetic recording layer is provided on a roll-shaped conductive substrate, and its surface may be finished so as to satisfy relation of Rz.ltoreq.50 .mu.m. At this time, the thickness of the magnetic recording layer is desirably set to 200 .mu.m or less.

Developing device using two-component developer

An image forming apparatus and an image forming method in which a latent image is formed by scanning the surface of an image bearing body with a laser light blinking in accordance with pulse-width modulation based on an image signal. Output-control-wave generating device generates an output control wave having a peak for a write time of each picture element. The output control wave is turned on and off by a gate circuit with timing determined by an exposure control signal generated by exposure control device. A signal output by the gate circuit is converted by a V/I converter into a driving current wave for controlling radiation of a laser light by an exposure unit. In this way, exposure energy produced by the exposure unit can be concentrated on an exposure time duration of each picture element, allowing the amount of mutual interference among picture elements to be reduced.

Image forming apparatus and image forming method that concentrates

In a color image forming apparatus, charging, exposure and development are repeated thereby a plurality of color component toner images are formed in superposing on an image carrier and then transferred collectively to an image receptor. As a charging device used in image forming cycle of at least the second color or later, a corona charging device having a discharge electrode and a grid is used. An electrode power source applying at least AC voltage is connected to the discharge electrode, and a grid power source applying AC voltage in nearly the same phase as that of the AC voltage applied to the discharge electrode is connected to the grid, and frequency or peak-to-peak amplitude of the AC voltage from the grid power source is set to optimum range.

Color image forming apparatus

In a color image forming apparatus, a screen of each of electrostatic latent images to be formed by an exposing device has a parallel lines structure, and phases of the electrostatic latent images each having the parallel lines structure for at least two different colors are made different from each other. Accordingly, the color image forming apparatus can totally solve the problem caused by the rise in potential of exposed portions by toner charges and the dielectric property of toner layers and the problem caused by the toner shielding effect to thereby allow faithful reproduction of a highlight area important for a good halftone image, especially a high-quality color image.

A color-image forming apparatus includes: an electrostatic latent image holder; electrostatic latent image forming unit for forming a plurality of electrostatic latent images on the image holder; a scanning unit for scanning the electrostatic latent image holder periodically at predetermined timings; developing devices for developing each of the plurality of electrostatic latent images by toners of each of different colors respectively, and forming thus developed toner image on the image holder; a simultaneously transferring device for simultaneously transferring the plurality of toner images onto a transfer medium; fixing device for fixing the toner image on the transfer medium; and timing-setting unit for setting a timing at which said scanning means starts scanning at each of slow scanning pitches in the direction of fast scanning for each of the plurality of colors; wherein the timings which are allotted to each of the colors are different each other so that the starting position of the scanning of each color at each of slow scanning pitches in the direction of the fast scanning is successively shifted at a predetermined distance.

Growing community of inventors

Nakai-machi, Japan

Takuto Tanaka