Powdertech Co., Ltd.

Minolta Camera Kabushiki Kaisha

Toshio Honjo

Koji Aga

Yuji Sato

Hiromichi Kobayashi

Kanao Kayamoto

Tsuyoshi Itagoshi

Masahiro Ogata

Tetsuya Uemura

Issei Shinmura

Tomoyuki Suwa

Toshiyuki Fukumoto

Kouichi Shimizu

Norio Takei

Ichiro Demizu

Yukio Tanigami

Toru Iwata

Yuji Shintani

Kazunori Takagi

Etsuaki Urano

Shinobu Nakasawa

Yasuhiko Kataoka

Nobutaka Torii

Yoshifumi Imamura

Miyoko Ito

Kazuhiro Itadaki

Osamu Doi

Shinichi Matsuda

Tadashi Harayama

Hironori Hojo

A ferrite core material for a resin-filled type carrier, and a resin-filled type carrier which is used as an electrophotographic developer by mixing a toner, sufficiently secure the image density, have no carrier adhesion and can maintain high-quality images over a long period, and an electrophotographic developer using the carrier, are provided. A ferrite core material for a resin-filled type carrier characterized in a void fraction of 10 to 60%, a resin-filled type carrier filled in the carrier core material with a resin, and an electrophotographic developer composed of the resin-filled type carrier and a toner, are provided.

Ferrite core material for resin-filled type carrier, resin-filled type carrier, and electrophotographic developer using the carrier

An object of the present invention is to provide a resin-coated ferrite carrier comprising a carrier core material having a small particle size, a high sphericity and surface uniformity, and a low standard deviation, a process for producing the carrier, and an electrophotographic developer comprising the resin-coated ferrite carrier and having a high image quality and excellent durability. For achieving the above object, there is provided a resin-coated carrier for an electrophotographic developer characterized by comprising spherical ferrite particles having an average particle size of 20 to 50 &#x3bc;m, a surface uniformity of 90% or more, an average sphericity of 1 to 1.3 and a sphericity standard deviation of 0.15 or less, a process for producing the carrier, and an electrophotographic developer comprising the resin-coated carrier.

Resin-coated carrier for electrophotographic developer and process for producing the same, and electrophotographic developer comprising the resin-coated carrier

A spherical resin-coated ferrite carrier for an electrophotographic developer which can maintain a stable resistance and chargeability, a favorable charge rising property because of an excellent fluidity, and has a suitable durability, its production method which is excellent in economic efficiency and production stability, and an electrophotographic developer using the resin-coated ferrite carrier, are provided. A resin-coated ferrite carrier for an electrophotographic developer which is a spherical resin-coated ferrite carrier, wherein a carrier core material thereof has an irregular surface to improve the adhesive strength to a resin coat, and wherein the irregularity of the surface takes a finely streaked wrinkle pattern, its production method, and an electrophotographic developer using the resin-coated ferrite carrier, are employed.

Resin-coated ferrite carrier for electrophotographic developer, its production method, and electrophotographic developer using the resin-coated ferrite carrier

It is contemplated to provide irregular shaped ferrite carrier which has a lower resistance, a high specific surface area, a low specific gravity and a longer operational life, and an electrophotographic developer comprising the ferrite carrier which prevents the toner scattering, has a high image density, and is responsive to high-speed and color imaging. The irregular shaped ferrite carrier is characterized in that the carrier particles are irregular shaped, and 40 percent by number or more of the particles have a rock candy sugar shape and/or an oyster shell shape, and that the shape factor (SF-1=R/S&#xd7;&#x3c0;/4&#xd7;100, wherein R is a maximum length and S is a projected area.) is 140 to 250, and the distribution width (&#x3b4;) is 60 or less.

Irregular shaped ferrite carrier and electrophotographic developer using the ferrite carrier

A carrier for an electrophotographic developer which is used as an electrophotographic developer in a mixture with a toner and which secures sufficiently the image density and can maintain high-quality images for a long period, and an electrophotographic developer using the carrier, are provided. A resin-filled ferrite carrier for electrophotographic developer obtained by filling, with a resin, avoid of a porous ferrite core whose void continues from the surface to reach the interior of the core, the carrier comprising a plurality of three-dimensional laminate structures in which resin layers and ferrite layers are alternately present, and an electrophotographic developer including the carrier and a toner, are employed.

Carrier for electrophotographic developer, and electrophotographic developer using the same

A resin-coated ferrite carrier having a uniform resin coating and emitting no offensive odors, etc., its production method, and an electrophotographic developer which comprises the resin-coated ferrite carrier, is excellent in the charge stability and image quality stability over a long period, causes less fogging of image or carrier adhesion, is favorable in the image density and environmental dependency, and can fully respond to high-speed and full-color imaging, are provided. The resin-coated ferrite carrier for the electrophotographic developer is characterized in that the surface of ferrite particles is coated with a mixed resin of a tetrafluoroethylene-hexafluoropropylene copolymer or a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer and a polyamideimide resin, and that the mixed resin contains a silicon oxide.

A ferrite carrier for the electrophotographic developer containing 40 to 500 ppm of zirconium; a method for preparing a ferrite carrier for the electrophotographic developer, comprising the steps for weighing, mixing, and pulverizing ferrite raw materials, and for granulating, drying, and firing the obtained slurry; wherein a zirconium raw material is added so that the zirconium content after firing becomes 40 to 500 ppm; and an electrophotographic developer using the ferrite carrier.

Ferrite carrier for electrophotographic developer and method for preparing the same, and electrophotographic developer using the same

A carrier for an electrophotographic developer comprising a carrier core coated with a silicone resin containing a quaternary ammonium salt as a catalyst.

Carrier for electrophotographic development and electrophotographic

A carrier for an electrophotographic developer comprising a carrier core coated with a silicone resin containing a crosslinking agent having a phenyl group.

A ferrite carrier for electrophotographic developers which is represented by formula:

Ferrite carrier for electrophotographic developer and

A method for regenerating a carrier coated with a silicone resin or a resin containing a silane coupling agent in an electrophotographic developer comprising the carrier and a toner, which comprises separating the developer into the carrier and the toner, immersing the separated carrier in an aqueous alkali solution, and stirring the mixture to remove the toner component adhered to the carrier surface and the coating resin.

Regeneration of carrier and electrophotographic developer containing

A ferrite carrier for electrophotographic developers which comprises a Mn-Mg ferrite having the general formula

Ferrite carrier for electrophotographic developer and developer

This invention provides a ferrite carrier for an electrophotographic developer characterized in that a core material is ferrite particle composed of 17.0 to 29.0 mol % of Li.sub.2 O and 71.0 to 83.0 mol % of Fe.sub.2 O.sub.3, exhibits a resistance of 2.5.times.10.sup.8 to 2.5.times.10.sup.9 .OMEGA. when a voltage of 250 V is applied, satisfies the relationship: a.sub.1 -a.sub.2 .ltoreq.1.5 when the resistance (R.sub.1) of the ferrite particle exhibited when a voltage of 250 V is applied thereto is taken as a.sub.1 .times.10.sup.b .OMEGA. and the resistance (R.sub.2) thereof exhibited when a voltage of 1000 V is applied thereto is taken as a.sub.2 .times.10.sup.b .OMEGA. (with the proviso that 1.0.ltoreq.a.sub.1 &lt;10, 0.1.ltoreq.a.sub.2, and b is an integer of 6 to 9), and the carrier prepared by coating the ferrite particle with a resin exhibits a resistance of 1.0.times.10.sup.9 to 1.0.times.10.sup.15 .OMEGA. when a voltage 250 V is applied thereto, and has a true specific gravity of 4.70 or below.

Ferrite carrier for electrophotographic developer and developer using

This invention provides a method for manufacturing a resin-coated carrier for an electrophotographic developer comprising the steps of coating the surface of a carrier core which is a dielectric material, with a resin which is also a dielectric material and then baking the thus obtained resin coated carrier core by means of microwave heating under the conditions that a thickness of the resin-coated carrier layer to be baked is in the range of from 5 to 25 mm, the number of revolution of agitating blade for agitating the microwave is in the range of from 20 to 40 rpm and an irradiation time is in the range of from 30 seconds to 10 minutes, to obtain the resin-coated carrier. The resin-coated carriers are characterized by having an excellent durability, excellent resistance to the environment, as well as excellent producibility and economy.

Method for manufacturing a resin-coated carrier for an

A ferrite carrier for electrophotographic developers which comprises a lithium-based ferrite having the general formula

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Kashiwa, Japan

Toshio Honjo