Ricoh Company, Ltd.

Hisao Kurosu

Shigekazu Enoki

Kazumi Suzuki

Shinichi Namekata

Shingo Sakashita

Masaki Yoshino

Chikara Imai

Osamu Ariizumi

Tatsuya Morita

Tomoko Kino

An anisotropic magnetic material-dispersed resin carrier including: fine magnetic particles; and a binder resin in which at least the fine magnetic particles are dispersed, wherein the anisotropic magnetic material-dispersed resin carrier has a magnetic anisotropy where magnetic fields of the fine magnetic particles are orientated in the same direction, and wherein the anisotropic magnetic material-dispersed resin carrier has a saturation magnetization of 16 emu/g to 30 emu/g, a coercive force of 15 kA/m to 40 kA/m, and a number average particle diameter of 15 &#x3bc;m or more but less than 100 &#x3bc;m.

Anisotropic magnetic material-dispersed resin carrier, electrophotographic developer, and developing device

A developing method including forming a magnetic brush of a two component developer comprising a toner and a magnetic carrier; and developing an electrostatic latent image with the magnetic brush, wherein the ratio (A/A) of the area (A) of the carrier-noncontact portion to the area of the development portion in which the electrostatic latent image can be developed by the magnetic brush is from 0.30 to 0.70, and the ratio (Avc/vs) of the average moving velocity (Avc) of carrier particles contacting the image bearing member to the moving velocity (vs) of the surface of the developer bearing member is from 0.8 to 1.1. Alternatively, it is possible that the ratio (A/A) is not greater than 0.50 and the ratio (Avc/vs) is from 0.3 to 1.1.

Developing method, developing device, and process cartridge and image forming apparatus using the developing device

A developing agent carrying member including magnets is disposed facing an image carrying member, a two-component developing agent containing toner and magnetic carrier is carried in a form of a layer on a surface of the developing agent carrying member, speed difference is generated between the developing agent carrying member and the magnets so as to cause a magnetic brush to flow while forming the magnetic brush on a developing agent layer at least in a facing region where the developing agent carrying member and the image carrying member face one another, and free toner separated from magnetic carrier in a flow of the magnetic brush adheres onto a latent image formed on the image carrying member, whereby developing is performed. A line-shaped latent image is developed with the toner starting from a middle portion thereof in a width direction of the line-shaped latent image.

Method, device and image forming apparatus for developing an image using a two-component developing agent

A method of developing a latent image formed on a surface of an image carrier with toner grains, which constitute a developer together with magnetic carrier grains for supporting the toner grains, by depositing the developer on a developer carrier, which faces the image carrier and accommodates magnetic field forming mechanism, causing the developer carrier to convey the developer to a developing zone formed between the image carrier and the developer carrier, and forming, in the developing zone, a magnet brush including the magnetic carrier grains, which hold the toner grains and gather in a form of brush chains, and free toner grains to be released from the carrier grains, the brush chains of the magnetic carrier grains flow in the developing zone while forming the magnet brush, and, assuming that a potential of the image carrier is Vand that a DC component of a potential of the developer carrier is V, the free toner grains, parted from the magnetic carrier grains flowing, fly at a means flight velocity of 1 m/s or below when V&#x2212;V=400 V holds.

Method and apparatus for developing a latent image using toner grains constituting a developer

In a magnet brush type image developing method of the present invention, at least one position where brush chains formed by magnetic carrier grains rise exists in a portion where an electric field formed between a facing zone where an image carrier and a developer carrier face each other has a strength E(V/m) expressed as:

Method and apparatus of developing a latent image formed on a surface of an image carrier

A two-component developer including toner and magnetic carriers is provided. The two-component developer is characterized in that when a development device including a developer bearing member bearing the two-component developer is operated under a development condition of an image forming apparatus using a quasi-photoconductor in which a 10 &#x3bc;m thick layer of tetrafluoroethylene resin is provided to a conductive material, the number of times of light emission occurring in a magnetic brush formed on the developer bearing member due to partial conduction in the magnetic brush is 10 times or less per second at an observation cross section that is perpendicular relative to a rotation axis of the developer bearing member.

Magnetic carrier, two-component developer, development method, development device and image forming apparatus of electrophotography

The development apparatus develops a latent image formed on a photo-conductor using a developer composed of a toner and a magnetic currier particle. A development sleeve carries the developer on an outer surface thereof so as to transfer the developer to the photo-conductor. A developer application mechanism applies the developer to the outer surface of the development sleeve. A plurality of magnets are provided inside the development sleeve so as to generate a magnetic field so that a magnetic brush is formed by the developer. The magnetic brush is brought into contact with said latent image carrier in a development area where the developer carrier is contiguous to the latent image carrier and the magnetic field between the latent image carrier and the developer separates the toner from the magnetic carrier of the magnetic brush. The wherein the magnetic brush is separated from the latent image carrier outside the development area.

Image forming apparatus having a development apparatus forming a magnetic brush separated from a latent image carrier outside a development area

A developing device of the present invention includes a developing roller provided with a plurality of magnetic poles. The magnetic poles include a main pole and two auxiliary poles positioned at both sides of the main pole for helping the main pole form a magnetic force. The auxiliary poles reduce the half width of the main pole. An AC-biased DC bias for development is applied to the developing roller and disturbs carrier grains close to the developing roller. Images free from various defects including granularity and local omission are achievable with the developing device.

Developing device using a two-ingredient type developer and image forming apparatus using the same

A developing method of the present invention develops a latent image formed on an image carrier with a two-ingredient type developer, which consists of toner grains and magnetic carrier grains for supporting the toner grains. A developer carrier faces the image carrier and accommodates magnetic field forming device therein for causing the developer to deposit on the developer carrier. The developer is conveyed to a developing zone formed between the image carrier and the developer carrier. The latent image is developed by a magnet brush including free toner grains, which part from brush chains formed by the carrier grains when the brush chains start rising on the developer carrier in the developing zone. The method insures a high-density, smooth solid image. A device for practicing the method is also disclosed.

Growing community of inventors

Kanagawa, Japan

Hisao Kurosu