Abstract: A developing device includes a magnet roll magnetized with plural magnetic poles including a main magnetic pole, a sleeve in a cylindrical shape which is arranged so as to be opposed to an image holding body, and a supporting frame that stably supports the magnet roll in a manner of restraining the magnet roll from rotating in the tangential direction, and supports the sleeve so as to rotate in the tangential direction around the magnet roll. The magnet roll is so arranged that the main magnetic pole is opposed to the image holding body, and a point on the peripheral face where magnetic flux density of the main magnetic pole in the tangential direction at a position along the peripheral face of the magnet roll is zero is set at a position predetermined with respect to a position where the magnet roll comes most closely to the image holding body.

Abstract: An image-forming apparatus comprises: an image carrier; a charging unit; a latent image forming unit; a developing unit that uses a toner maintaining a non-color-developing state when provided with coloring information through exposure to light; a coloring information providing unit that provides the toner image with coloring information by exposing the toner image to light having a predetermined wavelength determined depending on the color not to be developed based on color component information of image data; a transfer unit; a fixing unit; a color-developing unit that develops a color of the toner image provided with the coloring information; and a control unit that controls the coloring information providing unit to expose a background region on the image carrier to light having a predetermined wavelength for preventing color development of the toner.

Abstract: An image-forming apparatus comprises: an image carrier; a charging unit; a latent image forming unit; a developing unit that uses a toner maintaining a non-color-developing state when provided with coloring information through exposure to light; a coloring information providing unit that provides the toner image with coloring information by exposing the toner image to light having a predetermined wavelength determined depending on the color not to be developed based on color component information of image data; a transfer unit; a fixing unit; a color-developing unit that develops a color of the toner image provided with the coloring information; and a control unit that controls the coloring information providing unit to expose a background region on the image carrier to light having a predetermined wavelength for preventing color development of the toner.

Abstract: An image-forming apparatus comprises: an image carrier; a charging unit; a latent image forming unit; a developing unit that uses a toner maintaining a non-color-developing state when provided with coloring information through exposure to light; a coloring information providing unit that provides the toner image with coloring information by exposing the toner image to light having a predetermined wavelength determined depending on the color not to be developed based on color component information of image data; a transfer unit; a fixing unit; a color-developing unit that develops a color of the toner image provided with the coloring information; and a control unit that controls the coloring information providing unit to expose a background region on the image carrier to light having a predetermined wavelength for preventing color development of the toner.

Abstract: An electrophotographic developer is provided for realizing high-quality images and superior reproducibility of laser dots in a low coverage region and reduced unevenness of color in halftone solid images. The electrophotographic developer includes a toner and a carrier. The toner has a shape factor of 140 or less and a volume average particle size distribution GSDv of 1.3 or less. The carrier has a coat resin layer on a core material, the coat resin layer containing a conductive powder. The core material has a dynamic electric resistivity of 1 ?·cm or less under an electric field of 104 V/cm in a form of a magnetic brush. The conductive powder has an electric resistivity of 101 ?·cm or greater and 106 ?·cm or less. The carrier has an electric resistivity in a range between 10 and 1×108 ?·cm. An image forming method is also provided wherein the electrophotographic developer is used for development in a developing stage.

Abstract: An electrophotographic developer is provided for realizing high-quality images and superior reproducibility of laser dots in a low coverage region and reduced unevenness of color in halftone solid images. The electrophotographic developer includes a toner and a carrier. The toner has a shape factor of 140 or less and a volume average particle size distribution GSDv of 1.3 or less. The carrier has a coat resin layer on a core material, the coat resin layer containing a conductive powder. The core material has a dynamic electric resistivity of 1 &OHgr;·cm or less under an electric field of 104 V/cm in a form of a magnetic brush. The conductive powder has an electric resistivity of 101 &OHgr;·cm or greater and 106 &OHgr;·cm or less. The carrier has an electric resistivity in a range between 10 and 1×108 &OHgr;·cm. An image forming method is also provided wherein the electrophotographic developer is used for development in a developing stage.

Abstract: 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.

Abstract: A developing apparatus comprises: a developer support being disposed in the proximity of or in contact with an image support having a surface on which an electrostatic latent image is formed, the developer support having a peripheral surface supported turnably; and a developing bias power supply for supplying a developing bias voltage between the developer support and the image support, wherein a dual component developer including toner and magnetic carriers is supported on the peripheral surface of the developer support to be transported, and the toner is transferred to the image support in an electric field formed at a position where the image support faces the developer support for forming a toner image, and the developer support has a plurality of magnetic poles for attracting almost one layer of the carriers on the peripheral surface of the developer support almost uniformly.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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:.vertline.

Abstract: 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:.vertline.

Abstract: 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.