A carrier for electrophotographic image formation includes carrier particles. Each of the carrier particles includes a core particle and a coating layer covering the core particle. The coating layer includes diantimony pentoxide-containing particles.

The present invention relates to a carrier including: a magnetic core material; and a resin coating layer coating a surface of the magnetic core material, in which the resin coating layer contains a binder resin, and fluorine element-containing resin particles dispersed in the binder resin, the resin coating layer has a coefficient of variation of a film thickness of 25% or less, and the resin coating layer has an average value of the number of the fluorine element-containing resin particles being 3 particles/μm.sup.2 or more and 350 particles/μm.sup.2 or less per unit area in a cross section of the resin coating layer, and has a coefficient of variation thereof being 20% or less.

The present invention relates to a ferrite particle containing a crystal phase component containing a perovskite-type crystal represented by a composition formula of RZrO3 (wherein R is an alkaline earth metal element), and a Mg content of 0.45 mass % or less. The present invention also relates to a carrier core material for an electrophotographic developer, containing the ferrite particle; a carrier for an electrophotographic developer, containing the ferrite particle and a resin coating layer provided on a surface of the ferrite particle; and an electrophotographic developer containing the carrier for an electrophotographic developer and a toner.

A carrier for electrostatic image development includes: a core material; and a coating resin layer that contains inorganic particles and covers the core material. The content of the inorganic particles is 10% by mass or more and 60% by mass or less based on the total mass of the coating resin layer. The volume average diameter D (μm) of the inorganic particles and the thickness T (μm) of the coating resin layer satisfy the following relational expression (1): 0.007≤D/T≤0.24.

A carrier for developing an electrostatic charge image includes magnetic particles and a resin coating layer covering the magnetic particles, the resin coating layer containing inorganic particles. The ratio M1/M2 is 0.8 or more and 1.2 or less, where M1 is the concentration of the inorganic particles in the resin coating layer within a distance of 300 nm from the carrier surface, and M2 is that within a distance of 300 nm from the surface of the resin coating layer closer to the magnetic particle, and the percentage surface exposure of the magnetic particles is 0% by area or more and 5% by area or less. A cavity lies at least in part between the resin coating layer and a surface of the magnetic particles, and the average width, or the average length parallel to the thickness of the resin coating layer, of the cavity is 50 nm or more and 500 nm or less.

A carrier for developing an electrostatic charge image includes magnetic particles and a resin coating layer covering the magnetic particles, the resin coating layer containing inorganic particles. The ratio M1/M2 is 0.8 or more and 1.2 or less, where M1 is the concentration of the inorganic particles in the resin coating layer within a distance of 300 nm from the carrier surface, and M2 is that within a distance of 300 nm from the surface of the resin coating layer closer to the magnetic particle, and the percentage surface exposure of the magnetic particles is 0% by area or more and 5% by area or less. A cavity lies at least in part between the resin coating layer and a surface of the magnetic particles, and the average width, or the average length parallel to the thickness of the resin coating layer, of the cavity is 50 nm or more and 500 nm or less.

A method for producing a carrier for developing an electrostatic charge image, the method includes: adding a coating liquid containing a resin, conductive particles, and a solvent and magnetic particles to a mixer having a stirring blade, and mixing the coating liquid and the magnetic particles to obtain a mixture; and evaporating and drying the solvent from the mixture to produce a carrier having a resin coating layer on surfaces of the magnetic particles, wherein a viscosity μ of the coating liquid when being added to the mixer is more than 60 mPa.Math.s and 1,000 mPa.Math.s or less, and a value of a ratio μ/W of the viscosity μ(mPa.Math.s) to an amount W (parts by mass) of the resin coating layer with respect to 100 parts by mass of the magnetic particles in the carrier is 20 or more and 500 or less.

A method for producing a carrier for developing an electrostatic charge image, the method includes: adding a coating liquid containing a resin, conductive particles, and a solvent and magnetic particles to a mixer having a stirring blade, and mixing the coating liquid and the magnetic particles to obtain a mixture; and evaporating and drying the solvent from the mixture to produce a carrier having a resin coating layer on surfaces of the magnetic particles, wherein a viscosity μ of the coating liquid when being added to the mixer is more than 60 mPa.Math.s and 1,000 mPa.Math.s or less, and a value of a ratio μ/W of the viscosity μ(mPa.Math.s) to an amount W (parts by mass) of the resin coating layer with respect to 100 parts by mass of the magnetic particles in the carrier is 20 or more and 500 or less.

A two-component developer 100 includes a carrier 200 and a toner 300. The carrier 200 satisfies the relationships 100≤α≤220 and 300≤β≤480 when a voltage is applied in 1 V steps by a bridge resistance measurement method, where α (V) is a carrier voltage value obtained when a current value flowing through the carrier 200 reaches 1.0.sup.−7 (A), and β (V) is a carrier voltage value obtained when the current value reaches 1.0.sup.−5 (A).

A toner includes a toner particle containing a binder resin containing a crystalline polyester. In differential scanning calorimetry (DSC), the toner is heated to 180° C. at a rate of 10° C./min, then cooled to 25° C. at a rate of 10° C./min and successively from 25° C. to 15° C. at a rate of 3° C./min, and heated again to 180° C. at a rate of 10° C./min. As a result, an exothermic amount P1 when the toner is cooled from 80° C. to 40° C. is 1.00 J/g or less, an exothermic amount P2 when the toner is cooled from 25° C. to 15° C. is 0.10 J/g or more, and when a sum of endothermic amounts P3 (J/g) when the toner is heated again from 40° C. to 180° C. and a sum of exothermic amounts P4 (J/g) when the toner is cooled from 180° C. to 40° C. satisfies 2.0 ≤ P3-P4 ≤ 10.0.