Abstract: There is disclosed a two-component developing agent for use in an mage formation based on electrophotography, which has high developability even at a high speed printing and good developability in the case of the image formation for a long period of time. The two-component developing agent includes a carrier comprising a magnetic particle and an insulating toner. A surface of the magnetic particle is coated with at least a resin. A mean particle size of the magnetic particle is between 30 and 90 &mgr;m and an aggregation degree of said carrier is between 2 and 15%.

Abstract: A carrier for an electrophotographic developer which has a flowability index F1, represented by formula (1), of 63 to 75 sec/(50·cm3) and a flowability index F2, represented by formula (2), of 30 to 100 Oe·g/cm3:

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.

Abstract: 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.

Abstract: 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.

Abstract: 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 TiO2 ZnO2 or SnO2 having two or more average particle sizes, the particles having thereon a 5 to 50 Å thick conducting layer of SnO2 having a group V metal or phosphorus in solid solution therein.

Abstract: A resin-coated carrier for an electrophotographic developer which comprises a carrier core coated with an acryl-modified silicone resin the silicone resin of which has a methyl group and other organic groups, the molar ratio of the methyl group to the total organic groups inclusive of the methyl group [methyl group/(methyl group+other organic groups)]being 64 mol % or higher and lower than 70 mol %, and the acrylic resin to silicone resin weight ratio ranging from 2/8 to 4/6.

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

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

Abstract: A ferrite carrier for electrophotographic developers which is represented by formula:(MnO).sub.x (MgO).sub.y (Fe.sub.2 O.sub.3).sub.zwherein x+y+z=100 mol %, and part of MnO, MgO and/or Fe.sub.2 O.sub.3 is substituted with SnO.sub.2, and has a saturation magnetization of 20 to 43 emu/g.

Abstract: 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.

Abstract: A ferrite carrier for electrophotographic developers which comprises a Mn-Mg ferrite having the general formula(MnO).sub.x (MgO).sub.y (Fe.sub.2 O.sub.3).sub.zwherein x+y+z=100 mol % and SrO is substituted for a part of MnO, MgO and/or Fe.sub.2 O.sub.3.

Abstract: 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 <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.

Abstract: 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.

Abstract: A ferrite carrier for electrophotographic developers which comprises a lithium-based ferrite having the general formula(Li.sub.2 O).sub.x (Fe.sub.2 O.sub.3).sub.100-xwherein x is not more than 16.7 mole % and a part of Li.sub.2 O and/or Fe.sub.2 O.sub.3 is substituted with at least one member selected from the group consisting of alkaline earth metal oxides.

Abstract: 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.

Abstract: This invention relates to a carrier for developing electrostatic latent images comprising;carrier core particles having specified physical properties such as mean particle size, a bulk density, ratio of small particles, surface area index and the like, andresin-coating layers formed of specified components at specified content by a sintering process so that the layer resin may have specified physical properties such as ratio of integrated intensity and the like.