Powdertech Co., Ltd.

Issei Shinmura

Kanao Kayamoto

Yuji Sato

Hiromichi Kobayashi

Toshio Honjo

Tsuyoshi Itagoshi

Koji Aga

Tetsuya Igarashi

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

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

There are adopted: a carrier core material for an electrophotographic developer, including Mg, Ti and Fe as main components, and containing Fe, Mg and Ti in contents of 52 to 66% by weight, 3 to 12% by weight and 0.2 to 12% by weight, respectively; an electrophotographic developer carrier prepared by coating with a resin the surface of the carrier core material; and an electrophotographic developer using the carrier.

Carrier core material for electrophotographic developer, carrier and electrophotographic developer using the 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 carrier core material containing at least one metal oxide (MO) having a melting point of not higher than 1000&#xb0; C. and at least one metal oxide (MO) having a melting point of not lower than 1800&#xb0; C., wherein the metal (M) for constituting the metal oxide (MO) has an electrical resistivity of not less than 10&#x3a9;&#xb7;cm. Also disclosed is a two-component developing agent comprising a coated carrier, which comprises the carrier core material coated with a resin, and toner particles. Further disclosed is an image forming method comprising developing an electrostatic latent image formed on a photosensitive member with the two-component developing agent using an alternating electric field. The carrier core material and the coated carrier have high magnetization and are free from occurrence of leakage of electric charge over a wide range of electric field from low electric field to high electric field. According to the two-component developing agent, an excellent image can be formed.

Carrier core material, coated carrier, and two-component developing agent for electrophotography

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 core material for an electrophotographic developing agent, which comprises 100 parts by weight of a ferrite component represented by a formula (A) and 0.1 to 5.0 parts by weight of ZrOthat is present in the ferrite component without forming a solid solution, and which has a magnetization, at 1000(10/4&#x3c0;&#xb7;A/m), of 65 to 85 Am/kg and an electrical resistance, at an applied voltage of 1000 V, of 10to 10&#x3a9;.(MnO)(MgO)(FeO)&#x2003;&#x2003;(A)wherein x, y and z are each expressed in % by mol and are numbers satisfying the conditions of 40&#x2266;x&#x2266;60, 0.1&#x2266;y&#x2266;10 and x+y+z=100. Also disclosed is a two-component developing agent comprising a coated carrier, which is obtained by coating the above carrier core material with a resin, and toner particles. Further disclosed is an image forming method comprising developing an electrostatic latent image formed by the use of an alternating electric field, with the two-component developing agent. The carrier core material and the coated carrier have high magnetization and high resistance. According to the two-component developing agent of the invention, an excellent image can be formed.

Carrier core material, coated carrier, two-component developing agent for electrophotography, and image forming method

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.

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Kashiwa, Japan

Issei Shinmura