Abstract: 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 cm2/g and an apparent density of 2.30 to 2.80 g/cm3, and the electrophotographic developer using this resin-coated ferrite carrier.

Abstract: There are adopted an electrophotographic resin-coated ferrite carrier having a carrier core coated with a resin, wherein a product of an apparent density ? (g/cm3), average particle size d (?m) and BET specific surface area S (m2/g) of the carrier core satisfies the following condition, a method for producing the same, and an electrophotographic developer. 4.5??×d×S?8.

Abstract: 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 ?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.

Abstract: 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.

Abstract: Objects of the present invention are to provide a carrier core material for an electrophotographic developer having a true spherical shape and excellent strength, and a controllable true density and/or apparent density, and a method for manufacturing the carrier core material, a carrier and a method for manufacturing the carrier, and an electrophotographic developer using the carrier. In order to achieve the objects, there are employed a carrier core material for an electrophotographic developer, containing 3 to 100% by number of hollow particles having an iron content of 36 to 78% by weight, and a carrier for an electrophotographic developer, obtained by coating a resin on a surface of the carrier core material, and methods for manufacturing these, and an electrophotographic developer using the carrier.

Abstract: 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.

Abstract: 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.

Abstract: A carrier core material containing at least one metal oxide (MLO) having a melting point of not higher than 1000° C. and at least one metal oxide (MHO) having a melting point of not lower than 1800° C., wherein the metal (MH) for constituting the metal oxide (MHO) has an electrical resistivity of not less than 10?5 ?·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.

Abstract: 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.

Abstract: 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.

Abstract: 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 cm2/g and an apparent density of 2.30 to 2.80 g/cm3, and the electrophotographic developer using this resin-coated ferrite carrier.

Abstract: 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 ?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.

Abstract: There are adopted an electrophotographic resin-coated ferrite carrier having a carrier core coated with a resin, wherein a product of an apparent density ? (g/cm3), average particle size d (?m) and BET specific surface area S (m2/g) of the carrier core satisfies the following condition, a method for producing the same, and an electrophotographic developer. 4.5??×d×S?8.

Abstract: 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 ZrO2 that is present in the ferrite component without forming a solid solution, and which has a magnetization, at 1000(103/4?·A/m), of 65 to 85 Am2/kg and an electrical resistance, at an applied voltage of 1000 V, of 105 to 109 ?. (MnO)x(MgO)y(Fe2O3)z??(A) wherein x, y and z are each expressed in % by mol and are numbers satisfying the conditions of 40?x?60, 0.1?y?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.

Abstract: 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 ?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 ?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.

Abstract: 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.

Abstract: A carrier core material containing at least one metal oxide (MLO) having a melting point of not higher than 1000° C. and at least one metal oxide (MHO) having a melting point of not lower than 1800° C., wherein the metal (MH) for constituting the metal oxide (MHO) has an electrical resistivity of not less than 10−5 &OHgr;·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.

Abstract: Disclosed is 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 ZrO2 that is present in the ferrite component without forming a solid solution, and which has a magnetization, at 1000(103/4&pgr;·A/m), of 65 to 85 Am2/kg and an electrical resistance, at an applied voltage of 1000 V, of 105 to 109 &OHgr;.

Abstract: 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 &mgr;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 &mgr;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.

Abstract: 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.