Ricoh Company, Ltd.

Tohoku Ricoh Co., Ltd.

Fuchio Takeda

Toshio Kaneko

Kazuo Kobayashi

Hiroyuki Matsushiro

Yoshihiro Ogata

Toshihiko Takaya

Koji Sakamoto

Kunihiko Tomita

Atsushi Ohta

Shuichi Endoh

Yasuo Hirano

Kazuo Nojima

Hachiro Tosaka

Akito Yoshimaru

Atsushi Shinozaki

Kazuhiro Nishido

Takeo Wada

Yasutaka Nakamura

A stencil printer of the present invention includes a print drum and a pressing member. After a cut stencil or master has been wrapped around the print drum, the pressing member presses a paper or similar recording medium against the master. As a result, ink fed to the print drum oozes out to the paper and prints a desired image thereon. When the pressing member presses the paper against the master, an electric field is formed between the pressing member and the print drum in the direction in which the ink migrates from the drum to the paper. The printer is capable of adjusting image density without varying a mechanical pressure to act on the drum or varying the print speed.

Stencil printer having an electric field between the print drum and the

A developing device for an image forming apparatus and capable of maintaining desirable image quality by reducing a change in the charged state of the surface of a developing roller and a change in the amount of charge to deposit on a developer. An insulating layer constitutes the surface of the developing roller and is made of a material more than 50 percent of which constitutes a non-polar high molecule. This prevents a toner from filming the surface of the roller. The insulating layer is implemented by a material substantially the same as the toner in charge series, so that the toner is frictionally charged by a member other than the developing roller. A discharge brush is held in contact with the roller and made of a material substantially identical with the toner in charge series, thereby preventing the toner from being frictionally charged by the brush even when the toner films the roller. Further, the insulating layer is constituted by a material in which a non-polar high molecule and a polar high molecule are mixed in a suitable ratio. As a result, a space charge is scarcely stored in the surface of the roller, thereby preventing a charge from being injected into the roller surface.

Developing device for an image forming apparatus

A one-component magnetic toner with high resistivity for use in electrophotography for developing latent electrostatic images to visible toner images by contact development, includes a coloring agent, a binder resin, and a magnetic material which contains a bivalent metal and a trivalent iron with the molar ratio of the bivalent metal to the trivalent iron being 1/3 or less.

One-component magnetic toner for use in electrophotography

An image forming apparatus capable of preventing a toner from depositing on non-charged part of an image carrier just after the start of an image forming operation even when implemented with a contact reversal development system and a contact charging system. A charge power source assigned to a charging roller feeds a current great enough to prevent toner deposition on the non-charged part of the image carrier to a constant voltage generation circuit which is connected to the image carrier.

Image forming apparatus

A developing device for use in an image forming apparatus and having a developing roller, developing sleeve or similar developer carrier for supplying a one-component developer, or toner, to a latent image which is electrostatically formed on an image carrier such as a photoconductive element. A dielectric layer forming part of the developer carrier and closely related to the fluctuation of developing characteristic has a frequency characteristic which is confined in a predetermined range. Hence, the device is operable in a desirable manner by confining the fluctuation of developing characteristic ascribable to that of developing linear speed in a predetermined range without resorting to the actual measurement of a response characteristic of a developer carrier.

Developer carrier with a dielectric layer having a frequency

A developer carrier is used in a dry-type image developing device employing a one-component developer in an electrophotographic copier or an electrostatic recording apparatus. The developer carrier has a resin coating layer including an electrically conductive filler dispersed therein which is made of a material having a volume resistivity of at most 100 .OMEGA.cm. With this arrangement, the range in which the resistance of the surface layer varies under the ambient condition of varying temperature and humidity is small, producing a copy of stable image quality free from a smeared or contaminated background.

Developer carrier containing electrically conductive filler present in a

A developing device including a developing roller which has a resilient support layer and a dielectric layer provided on the support layer and developing an electrostatic latent image formed on a photoconductive drum through the roller by using a single-component developer, i.e. toner. The variation of development characteristics ascribable to the developing roller is suppressed by providing a resilient material which constitutes the support layer with a resistance value less than a predetermined value that is mostly determined by a relationship between the resistance value and the developing time. Further, a method is described for producing a developing roller for the developing device.

Developing device with a developing roller and using a single-component

A developing device includes a developing sleeve driven to rotate for transporting a film of charged developer as carried thereon past a developing station where the film of developer is applied to an electrostatic latent image to have it developed. Also provided is a sponge roller pressed against and driven to rotate in the same rotating direction as that of the developing sleeve, so that the developer is supplied to the developing sleeve at one side of the contact between the developing sleeve and the sponge roller and any residual developer on the developing sleeve is removed at the other side of the contact. Preferably, a desired voltage difference is established between the developing sleeve and the sponge roller. Furthermore, the sponge roller is preferably so structured to have a sufficient conductivity level at least at its outer peripheral surface thereby allowing the residual charge on the developing sleeve to be discharged sufficiently.

Thin film developing device

An electrostatic latent image developing apparatus supplies toner to a latent image carrier such as a drum-shaped photosensitive body to visualize a latent image formed thereon. The toner is supplied by a rotating drum-shaped toner carrier having a portion confronting the photosensitive body adjacent thereto and another portion held in contact with toner contained in a toner container. The toner is electrostatically attracted to the toner carrier and transferred therefrom to the photosensitive body. The toner on the toner carrier is regulated into a thin toner layer by a toner layer regulating member that is resiliently held in sliding contact with the toner carrier. To prevent toner deposits from being attached to the toner layer regulating member, the toner layer regulating member is made of a material adapted to wear with the attached toner. In order to provide the toner layer regulating member with an ability to triboelectrically charge toner, whether chargeable to a polarity (-) or (+), or to control the amount of electricity on toner chargeable to a polarity (-) or (+) and prevent toner deposits from being attached to the toner layer regulating member, another material to control the amount of electricity on toner is mixed in the material which can be worn with the attached toner.

Electrostatic latent image developing apparatus

A developing apparatus is disclosed, in which a developing roller composed of an insulating layer, a dielectric layer and an electrically conductive substrate is made in contact with a photosensitive member to develope a latent image on the member. The dielectric layer is formed of a material whose resistivity-specific dielectricity characteristics satisfies a certain condition which is suitable for medial tone development or binary tone development.

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Tokyo, Japan

Fuchio Takeda