Powdertech Co., Ltd.

Kanao Kayamoto

Yuji Sato

Toshio Honjo

Issei Shinmura

Hiromichi Kobayashi

Masahiro Ogata

Kazunori Takagi

Takao Sugiura

Tetsuya Uemura

Kouichi Shimizu

Hironori Hojo

Tadashi Harayama

Employed are a resin-coated ferrite carrier for an electrophotographic developer including a ferrite carrier core material having a BET specific surface area of 900 to 5,000 cm/g and an apparent density of 2.30 to 2.80 g/cm, and the electrophotographic developer using this resin-coated ferrite carrier.

Resin-coated ferrite carrier for electrophotographic developer and electrophotographic developer using the resin-coated ferrite 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

Disclosed are a ferrite carrier for electrophotographic developer and an electrophotographic developer using the ferrite carrier, wherein: the ferrite carrier is a composite ferrite composed of Li and Mg; when the composition of the ferrite is calculated as a mixture of a Li ferrite having a stoichiometric composition and a Mg ferrite having a stoichiometric composition, the excessive amount of FeOis less than 5 mol %, or the total excessive amount of LiO and MgO is less than 1 mol %; the content of the elements other than Li, Mg, Fe and O is 2 % by weight or less; and further, the content of Mn in terms of element is 1000 to 9000 ppm.

Ferrite carrier for electrophotographic developer and electrophotographic developer

There are adopted an electrophotographic resin-coated ferrite carrier having a carrier core coated with a resin, wherein a product of an apparent density &#x3c1; (g/cm), average particle size d (&#x3bc;m) and BET specific surface area S (m/g) of the carrier core satisfies the following condition, a method for producing the same, and an electrophotographic developer.4.5&#x2266;&#x3c1;&#xd7;8.5 (20&#x2266;&#x2266;45)

Electrophotographic resin-coated ferrite carrier, method for producing the same, and electrophotographic developer

The present invention provides a method for producing a core material of an electrophotographic ferrite carrier, by charging a raw powder with an average particle size of 20 to 50 &#x3bc;m obtained by preparing raw materials for ferrite into a combustion flame along with a carrier gas for the raw powder, thermal-spraying the powder in atmospheric air to ferritize the powder, subsequently rapidly solidifying the thermal-sprayed particle, and sampling and collecting the particle, wherein the method satisfies the conditions comprising the following (1) to (3): (1) a mixture gas of propane and oxygen is used for the combustion flame for the thermal spraying, and a volumetric ratio of the propane to the oxygen is 1:3.5 to 6.0; (2) the carrier gas for the raw powder is air, nitrogen, oxygen or a mixture gas thereof, and the ratio (a/b) of a charged amount (a) of a raw powder (kg/hr) to a charged amount (b) of the carrier gas (kg/hr) for the raw powder is 4.8 or less; and (3) a flame flow velocity of the combustion flame is 65 to 125 m/sec.

Method for producing core material of electrophotographic ferrite carrier and resin-coated ferrite 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

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 resin-coated carrier for an electrophotographic developer and a process of producing the carrier. The carrier comprises a ferrite core mainly comprising iron oxide, primarily having a spinel structure, and having a volume average particle size of 20 to 45 &#x3bc;m and a resin coat, wherein the carrier has a magnetization of 65 to 80 emu/g in a magnetic field of 1 KOe, the core has an electric current value of 50 to 150 &#x3bc;A and a surface smoothness uniformity of 75% or higher, and the amount of the resin coat is 0.1 to 5.0% by weight based on the core.

Carrier for electrophotographic developer and process of producing the same

A carrier for an electrophotographic developer comprising spherical magnetic core particles which have a volume average particle size of 25 to 45 &mgr;m, an average void size of 10 to 20 &mgr;m, a volume based particle size distribution having less than 1% of 22 &mgr;m or smaller particles, a magnetization of 67 to 88 emu/g in a magnetic field of 1 kOe, and a difference of 10 emu/g or smaller in magnetization in a magnetic field of 1 kOe between scattered particles and remaining particles.

Carrier for electrophotographic developer and electrophotographic developer containing the same

A carrier for an electrophotographic developer which comprises a carrier core and a resin coat having a conducting agent dispersed therein, the resin coat having an inner layer on the carrier core side and an outer layer coating the inner layer, wherein the inner layer contains 7 to 20% by weight of a conducting agent based on the resinous solid content of the inner layer, the outer layer contains 3 to 15% by weight of a conducting agent based on the resinous solid content of the outer layer, and the conducting agent content of the inner layer is greater than that of the outer layer.

A carrier for an electrophotographic developer which is coated with an insulating resin containing a white conducting agent, wherein the white conducting agent includes spherical to lumpy particles of TiO,ZnO,or SnO,having two or more average particle sizes, the particles having thereon a 5 to 50 &angst; thick conducting layer of SnO,having a group V metal or phosphorus in solid solution therein.

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

Ferrite carrier for electrophotographic developer and developer

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

An iron carrier for an electrophotographic developer, the carrier having a mean particle diameter of 25 to 40 .mu.m, a magnetization of at least 160 emu/g at 3000 Oe, an apparent density of 3.0 to 4.2 g/cm.sup.3, a percentage sphericity of at least 80%, and a specific surface area of at least 350 cm.sup.2 /g as determined by an air permeation method; a process for preparing the carrier by a plasma method; and an electrophotographic developer comprising the carrier.

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Kashiwa, Japan

Kanao Kayamoto