Dainippon Ink and Chemicals, Incorporated

Katsunori Ohba

Toshiro Kogawara

Shinji Amaya

Takeshi Isonaka

Masanobu Nakamura

Hideki Gambayashi

Katsuyuki Ogura

The present invention provides a carrier for electrophotography, which is capable of charging the toner in the developer very rapidly to a target electrostatic charge and at the same time, is capable of maintaining the target electrostatic charge during printing, so that the chemical fogging related to the slow charging rate can be eliminated and the image density related to the maintenance of the electrostatic charge can be preserved during printing. The charging rate and the charge maintenance of the electrophotographic carrier can be preserved if the carrier composed of magnetic core particles and the resin coat satisfies the following equation (B)>&lsqb;(&minus;19.4)&times;(A)&plus;31&rsqb;, wherein (A) represents a carbon content (weight %) of the carrier and (B) represents a ratio of the square root of the number of emitted photoelectrons ((CPS) ) and the photon energy (eV).

Electrophotographic carrier, developer using the same, and developing method

Developer for electrostatic image development

The present invention relates to a developer for electrostatic image development comprising: a toner for electrostatic image development which comprises a resin and a colorant; and a carrier formed by a carrier core material and a resin layer including a resistance control agent which is formed on the surface of the carrier core material, wherein the resin layer of the carrier has a concentration gradient of the resistance control agent toward the thickness direction of the resin layer, a concentration of the resistance control agent is the highest in the vicinity of the carrier core material, and is gradually lowered toward the surface of the resin layer, and the resistance control agent is present on the surface of the resin layer, as well as relates to an image forming method, wherein it comprises a step of developing an electrostatic image at a developing speed of 20 m/min or higher, by means of employing the developer for electrostatic image development. The developer for electrostatic image development of the invention exhibits a stable development and transfer behavior without any variation of triboelectric charging performance, electric resistance, or the like, even when used as a two-component developer, and in addition, affords a printed image with high image quality and high grade without any fogging.

Developer for electrostatic image development and image forming method using the same

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Oyama, Japan

Katsunori Ohba