Fuji Xerox Co., Ltd.

Takeshi Sumikawa

Nobumasa Furuya

Tsuneo Noami

Kazuo Maruyama

Kiyoshi Horie

Koji Adachi

Isao Ito

Toshiro Yamamoto

Toru Okamoto

Hideaki Tanaka

Shigehito Ando

Tadakazu Edure

Tomoo Kobayashi

Kei Hirata

Shinji Sasahara

Shigeo Ohno

Hiroh Soga

Taku Aoshima

Michiaki Takahashi

Tomoyoshi Chihara

Masashi Ogasawara

Kouji Adachi

Takeshi Nagao

Tsuneo Naomi

Kazuo Marugama

Furuya Nobumasa

Toshirou Yamamoto

An image recording apparatus includes an image carrying part, a developing part and an image transferring part. The image carrying part has a surface on which an electrostatic latent image is formed. The developing part develops the electrostatic image into a toner image by selectively applying toner to the surface of the image carrying part. The image transferring part transfers the toner image onto a recording sheet or an intermediate image transferring part. Fine particles are uniformly formed on the surface of the image carrying part, and a portion of the fine particles is transferred from the image carrying part with the toner image. The fine particles are smaller in diameter than the toner particles.

Image recording apparatus and method with improved image transfer characteristics

A developing apparatus uses a dual-component developer containing a magnetic carrier and toner electrically attracted to the magnetic carrier for selectively transferring the toner to an electrostatic latent image formed on an image support for visualizing the latent image. The developing apparatus includes a developer transport member facing the image support and having a peripheral surface for supporting and transporting the developer. A toner excess supplying member supplies excess toner to the developer supported on the developer transport member. An excess toner separator separates toner having a small adhesion force to the carrier from the developer to which excessive toner is applied.

Developing apparatus comprising excessive toner separation means

A dual-component magnetic brush developing device using a dual-component developer containing magnetic carriers and toner electrically attracted to the magnetic carriers. The dual-component magnetic brush developing device comprises: a magnetic field generation member being formed with a plurality of magnetic poles almost equally spaced from each other on a peripheral surface; a developer transport member being supported outside the magnetic field generation member for circumferential rotation and moving together with the magnetic field generation member at least in a developing area facing the image carrier in the proximity thereof; toner supply means for supplying an excess of new toner to magnetic carriers supported on the developer transport member and passing through the developing area; magnetic field reduction unit for reducing a magnetic field strength in the vicinity of a surface of the developer transport member by an agitation section for agitating the developer to which the excessive toner is supplied; and excessive toner separation unit being disposed downstream from the agitation section in a circumferential rotation direction of the developer transport member for separating excessive toner from the magnetic carriers supported on the developer transport member.

Dual-component magnetic brush developing device

In a color image forming apparatus, as the second and subsequent development processes of the simultaneously transfer type, a non-contact type AC field double-element development is employed, and an absolute value of the difference between the maximum bias which provides the maximum toner developing electric field in the direction to the side of the latent image carrier and the average value of the developing bias is set larger than an absolute value of the difference between the minimum bias voltage which provides the minimum toner developing electric field in the direction to the side of the latent image carrier and the average value of the developing bias, while the bias voltage region located between the maximum bias voltage and the average bias voltage is set to a ratio of from 0.25 to 0.45 for one period of the AC voltage, and the frequency of the bias voltage is set from 4 kHz to 10 kHz.

Color image recording method for transferring a multi-colored image to

A developing device, which has a developer carrying member forming a magnetic brush of a two-component developer and is capable of carrying out a development while it is not in contact with an electrostatic latent image retaining member, is improved so as to reproduce an image at a sufficient image density.

Device for developing an electrostatic image on an image member

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

Composite image recording apparatus

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.

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Kanagawa, Japan

Takeshi Sumikawa