Ricoh Company, Ltd.

Naoki Imahashi

Kimitoshi Yamaguchi

Masashi Nagayama

Hiroaki Takahashi

Akihiro Kotsugai

Kousuke Suzuki

Motoharu Tanaka

The present invention is to provide a carrier and a developer, which have fewer occurrences of carrier adhesion and background smear, excellent granularity and longer durability. The carrier comprises the core material particles having magnetism and resin coating layer covering the core material particles, and wherein the weight average particle diameters is in the range of 22 m to 32 m, the proportion of the weight average particle diameters relative to the number average particle diameter is in the range of 1.00 to 1.20, the content of particles having a diameter of 20 m or smaller is 7% by mass, the content of carrier particles having a diameter of 36 m or smaller is in the range of 90% by mass to 100% by mass, and the proportion of the particle density of the core material particles is in the range of 85% to 100% of the true density of the core material particles.

Carrier, developer, image forming method and process cartridge

An object of the present invention is to provide a carrier containing core material particles having magnetism and a coating layer on the surfaces of the core material particles, wherein the core material particles have a magnetization at a magnetic field of 1,000 Oersted of 40 emu/g to 100 emu/g, and the carrier has a weight average particle diameter of 20 &#x3bc;m to 45 &#x3bc;m, a resistance (Log R) of 11 &#x3a9;&#xb7;cm to 17 &#x3a9;&#xb7;cm and a relaxation time &#x3c4; of 150 seconds to 800 seconds.

Carrier, developer and electrophotographic developing method and image forming method

A carrier is provided including a core and a resin layer located overlying the core, wherein the carrier has a weight average particle diameter (Dw) of from 22 to 50 &#x3bc;m, a ratio (Dw/Dp) of the weight average particle diameter (Dw) to a number average particle diameter (Dp) of from 1 to 1.30, a shape factor SF-1 of from 100 to 120, and a shape factor SF-2 of from 100 to 120, and wherein the carrier comprises core particles satisfying the following relationship 0.52&#x3c;(d/D)&#x3c;1.0 in an amount of from 0 to 10,000 ppm by number: wherein D (&#x3bc;m) represents a diameter of a circle having the same area as that of a projected image of a core particle and d (&#x3bc;m) represents a diameter of a circle having the same area as that of a projected image of a maximum hollow present in the core particle.

Electrographic carrier, developer, developing method, image forming apparatus, and process cartridge

The present invention can provide small-diameter core material particles for electro photographic carrier, the particles that can prevent occurrences of carrier adhesions and reduce toner spent, have excellent durability and cause little fluctuations in image density with a narrow particle diameter distribution, and an efficient, cost-effective production method thereof. That is, the core material particles for electro photographic carrier are particles wherein the weight average particle diameter, Dw, is in the range of 22 &#x3bc;m to 32 &#x3bc;m, the ratio of Dw to the number average particle diameter, Dp, satisfies the condition, 1&#x3c;Dw/Dp&#x3c;1.20, the content of particles smaller than 20 &#x3bc;m in diameter is in the range of 0% by mass to 7% by mass and smaller than 36 &#x3bc;m is in the range of 90% by mass to 100% by mass, and the BET specific surface area is in the range of 300 cm/g to 900 cm/g.

Electrophotographic developer and carrier therefor, core material particle for carrier for electrophotographic developer and production method thereof and image forming method

A vibrating sieve for classifying a particulate material, including an oscillator comprising a transducer; and at least two meshes layered together and located in contacting relation to a transducer, wherein a lowermost mesh receiving a vibration from the transducer transmits the vibration to an uppermost mesh to classify the particulate material fed thereon.

Electrophotographic developing carrier, associated apparatus and methodology of classification and application

Electro-photographic images having high picture quality and low carrier adhesion can be obtained using a two-component developer containing a carrier containing (A) a carrier containing a core containing a magnetic material, the core being coated with at least one resin layer; and (B) a toner; wherein the carrier has a weight average particle diameter Dw of 22-32 &#x3bc;m; wherein a content of carrier particles having a diameter smaller than 20 &#x3bc;m is 0-7% by weight based on the weight of the carrier; wherein a content of carrier particles having a diameter smaller than 36 &#x3bc;m is 90-100% by weight based on the weight of the carrier; wherein a weight average particle diameter Dw of the toner is 2-7 &#x3bc;m; and wherein a ratio Dw/Dn of the weight average particle diameter of the toner to the number average particle diameter of the toner is 1.00-1.25.

Developer for use in electrophotography, image forming method and process cartridge

A carrier for use with a toner as a two-component type developer for developing an electrostatic image, comprising spherical magnetic core particles, and a resin layer covering each of said core particles and containing at least two resistance controlling materials having different specific resistances, wherein each of the resistance controlling materials is in the form of particles having a number average particle diameter of no more than 1/10 of a number average particle diameter of the toner.

Carrier for developer for developing electrostatic latent image, developer using same and image forming method using same

The present invention relates to a carrier for electrophotographic developers, a developer containing the carrier, a container for the developer, a image forming apparatus using the developer, an image forming method using the same, and a method of making the carrier.

Carrier for electrophotographic developer

A carrier develops latent electrostatic images in corporation with a toner and one particle of the carrier includes a magnetic particle, and a coating layer covering the magnetic particle. The coating layer includes a crosslinked condensation product of a composition containing (i) an N-alkoxyalkylated polyamide and (ii) at least one resin that is reactive with the alkoxyalkylated polyamide and includes a silicone having a silanol group and/or a hydrolyzable group.

Carrier and developer for developing latent electrostatic images

A process for developing which includes the step of developing a latent electrostatic image on a latent electrostatic image support by a developing agent supplied on a development sleeve, where the developing agent is supplied with a density of 1.3 g/cm to 2.0 g/cm at the closest part between the support and the sleeve, the support is contacted with magnetic brushes formed of the developing agent on the sleeve, so that the magnetic brushes have a width of 2 mm or less at a linearly contacting surface, in a direction where the surface rotates and the developing agent contains toners, and carriers having magnetic core particles and resin layers to cover its surface, the carriers have a weight average particle diameter of 25 &mgr;m to 45 &mgr;m, contain 60 wt % or more of the particles having a diameter of less than 44 &mgr;m, and 7 wt % or less of particles having a diameter of less than 22 &mgr;m.

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Mishima, Japan

Naoki Imahashi