Fuji Xerox Co., Ltd.

Tsuneo Noami

Takeshi Sumikawa

Nobumasa Furuya

Kazuo Maruyama

Kiyoshi Horie

Toshiro Yamamoto

Koji Adachi

Toru Okamoto

Koji Masuda

Yoshihiko Fujimura

Koichi Saitoh

Tadakazu Edure

Hiroh Soga

Yuji Suemitsu

Taku Aoshima

Kouji Adachi

Kazuo Marugama

Furuya Nobumasa

Toshirou Yamamoto

A multi-color image formation apparatus and method of its use prevent deterioration of stability due to a recharging process in one cycle of multi-color image formation and also effectively avoid color mixing in the toner image previously formed. The multi-color image formation apparatus includes an electrostatic latent image formation member, a first electrostatic latent image formation device for forming a first electrostatic latent image on the electrostatic latent image formation member, a first developer for developing the first electrostatic latent image with a first toner, a second electrostatic latent image formation device for forming a second electrostatic latent image on the electrostatic latent image formation member, and a second developer for developing the second electrostatic latent image with a second toner. The second electrostatic latent image formation device reduces the absolute value of the potential of an image portion of the electrostatic latent image and also reduces the absolute value of the potential of the common area of background portions of the first and second electrostatic latent images.

Multi-color image formation apparatus and method for preventing the

The development apparatus of this invention includes a developer supporting body consisting of a rotatable non-magnetic sleeve and a magnet roll fixedly installed within the rotatable non-magnetic sleeve. The development method involves the following steps: a latent image formed on a latent image supporting body is developed or made visible with a two-component developer carried on the developer supporting body in a non-contact manner; a horizontal magnetic field which is orientated in the circumferential direction of the developer supporting body is applied to the developer in an effective development area on the developer supporting body, the effective development area facing the latent image supporting body; and a developer movement promotion magnetic field is applied locally to a part of the effective development area on the developer supporting body so that the developer is expelled from that part of the effective development area and that chains of carrier of the developer in the developer expelled region are slid in the circumferential direction of the developer supporting body. This development method ensures a sufficiently high development performance during the multicolor image forming process without disturbing the toner image formed.

Development method and apparatus and multicolor image forming apparatus

A color image recording apparatus according to the present invention comprises a light-sensitive drum, a first developing device for developing a first electrostatic latent image on the drum surface as a first toner image, a second developing device for developing a second electrostatic latent image as a second toner image on the drum surface along with the first toner image, and a developing bias voltage source for applying a developing bias voltage to the second developer device comprising a DC component and an AC component of a predetermined period, wherein the AC component has a waveform such that the time for the voltage to change from a value such that an electric field making toner move toward the electrostatic latent image is maximum to a value such that the electric field becomes minimum is set to be at least 1/2 of the predetermined period of the AC component. According to a method of the present invention a first toner is electrostatically attracted to an electrostatic latent image on the surface of a light-sensitive drum, and then a second toner is electrostatically attracted to the electrostatic latent image on the drum surface by applying a periodic AC electric field in which the time during which the electric field develops the electrostatic latent image with the second toner exceeds the time during which the electric field does not develop the electrostatic latent image with the second toner. The developed first and second toner images are then simultaneously transfered to a copy sheet.

Color image recording method and apparatus

A first negative or positive latent electrostatic image is formed on a latent image bearing body with a first writing device, and developed with a monochromatic toner. A second latent image of the type different than the first latent image is formed by a second writing device after setting the background voltage of the second image to have an absolute value larger than the first image, and then developed with one or two color toners selected from three color toners of respective multi-color developing units. A plurality of multi-color toner images may be formed in respective rotation cycles of the latent image bearing body. A monochromatic toner image may be formed in the same rotation cycle as one of the multi-color toner images. Finally, a plurality of toner images thus produced are transferred onto a recording sheet at once after polarities of the plurality of toner images have been arranged into the same polarity.

Color image forming apparatus and method

There is disclosed a dual component developing device for developing an electrostatic latent image formed on a latent image carrier. The system comprises a rotatable nonmagnetic sleeve, a magnetic roll mounted inside the sleeve, and a developer-limiting member made from a nonmagnetic material. The magnetic roll has neighboring magnetic poles which have the same polarity and repel each other. The limiting member is disposed opposite to the repelling magnetic poles and between the position at which the magnetic force produced by the repelling pole located on the upstream side as viewed in the direction of movement of developer is maximal and the position at which the magnetic forces produced between the repelling poles is minimal. Thus, the developing device is capable of forming a thin film of the developer without aging. The amount of the transferred developer depends to a lesser extent on the spacing between the sleeve and the limiting member.

Developing magnetic roller having repulsive magnetic poles and

In a color recording apparatus, charges are applied to a latent electrostatic image carrier by a scorotron having a grid after development of a first latent electrostatic image on the carrier with a first color toner. Thereafter, a second electrostatic latent image is formed and developed with a second color toner. If the charges given by the scorotron have the same polarity as a charging polarity of the first color toner, a potential of the grid is set to be equal to a non-image portion potential of the first latent electrostatic image, or set to have a polarity opposite to that of an image portion potential of the first latent electrostatic image assuming that the non-image portion potential is regarded as 0 V as a reference potential. If the charges given by the scorotron have a polarity opposite to the charging polarity of the first color toner, a potential of the grid is set to have a polarity opposite to that of the non-image portion potential image assuming that the image portion potential is regarded as 0 V as a reference potential.

Color recording apparatus

An image forming method of the present invention comprises: a first toner image formation process for forming a first toner image by forming, on a latent image carrier, a first latent image which corresponds to a first image and developing the first latent image by a first toner charged to one polarity through a development process selected from normal and reverse development process selected from normal and reverse development processes so as to correspond to the polarity of the first toner; a second toner image formation process for forming a second toner image by forming, on the latent image carrier, a second latent image which correspond to a second image and developing the second latent image by a second toner charged to the other polarity by the other development process while applying a developing bias; and a transfer treatment process for simultaneously transferring said first and second toner images to a transfer medium; wherein said developing bias VB2 satisfies the following equations:

Image recording method

Image recording method of the present invention comprises the steps of forming electrostatic latent image on a latent image carrier by a latent image forming means, developing the formed electrostatic latent image with toner, and transferring the visualized toner image to a transfer material after repeating at least the developing step plural times, wherein double-element developer formed from mixing toner and magnetic carrier with its density of 4.0 g/cm.sup.3 or less is used in at least the second and the succeeding developing steps among the plural times of the developing steps.

Electrophotographic image recording method

A latent color image developing system for copying a document having a first color images and second color images develops the first color images with a first color developer and the second color images with a second color developer. The second color developer includes a toner and a magnetic carrier having a density of less than 4.0 g/cm.sup.3 and a particle size in the range of 30-50 microns. A developer roll is used having a main developing pole with a flux density of more than 500 gauss in a nip region proximate a photosensitive member having latent electrostatic images to be developed.

Latent image color developing system

In electrostatic latent image developing process capable of effecting either positive or negative reproduction a magnetic toner of a high resistivity is controlled to form a magnetic brush having a potential insufficient for development. The toner chain constituting the brush is separated under the influence of an electric field between the developing roll and the image carrier, to produce toner particles having one polarity continuing with the developing roll, and particles of the opposite polarity transferred to the carrier.

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Kanagawa, Japan

Tsuneo Noami