According to the present invention, there is provided a carrier core material that is formed of ferrite particles in which 48 to 52 mass % of Fe, 16 to 22 mass % of Mn, 1.0 to 3.5 mass % of Mg and 0.05 to 0.5 mass % of Ca are included, and when an electrical resistance value with an applied voltage of 500 V in an environment (in an L/L environment) in which the temperature is 10° C. and the relative humidity is 35% is R.sub.L (Ω.Math.cm), and an electrical resistance value with an applied voltage of 500 V in an environment (in an H/H environment) in which the temperature is 30° C. and the relative humidity is 70% is R.sub.H (Ω.Math.cm), formula (1) below is satisfied.
0.1≤(log R.sub.L−log R.sub.H)≤0.3  (1)

An object of the present invention is to provide a ferrite particle having a low apparent density, filling a specified volume with a low weight with various properties maintained in a controllable state, a ferrite carrier core material composed of the ferrite particle, and a ferrite carrier using the ferrite core material and an electrophotographic developer. To achieve the object, the ferrite particle having the outer shell structure containing the Ti oxide for the ferrite carrier core material, and the ferrite carrier using the ferrite particle as the ferrite carrier core material and the electrophotographic developer are employed.

An object of the present invention is to provide ferrite particles for supporting a catalyst having a small apparent density, various properties are maintained in a controllable state and a specified volume is filled with a small weight, and a catalyst using the ferrite particles for supporting a catalyst. To achieve the object, ferrite particles for supporting a catalyst provided with an outer shell structure containing Ti oxide, a catalyst using the ferrite particles for supporting a catalyst are employed.

An electrostatic charge image developing carrier includes: magnetic particles; and a resin layer coating the magnetic particles and containing inorganic particles, in which an exposed area ratio of the magnetic particles is 0.1% or more and 4.0% or less, an average particle diameter of the inorganic particles is 5 nm or more and 90 nm or less, and a ratio B/A of a surface area B of the electrostatic charge image developing carrier to a plan view area A of the electrostatic charge image developing carrier is 1.020 or more and 1.100 or less when a surface of the electrostatic charge image developing carrier is three-dimensionally analyzed.

A developing device includes a developing container, a first stirring conveyance member, a second stirring conveyance member, and a developer carrying member. The developing container includes a first conveyance chamber and a second conveyance chamber that are arranged mutually side by side, and contains a two-component developer including a carrier and a toner. The first stirring conveyance member stirs and conveys the developer present in the first conveyance chamber in a first direction. The second stirring conveyance member stirs and conveys the developer present in the second conveyance chamber in a second direction. The developing container includes a toner replenishment portion that directly feeds a replenishment toner into the developer present in the first conveyance chamber from an upstream side of the first conveyance chamber with respect to the first direction. The carrier satisfies 0.73≤FR×AD/shape factor≤2.10.

In a carrier core material according to the present invention, the volume moment mean D [4, 3] of O. Bluntness measured with an injection type image analysis particle size distribution meter is equal to or greater than 65% and equal to or less than 80%, and the volume moment mean D [4, 3] of ISO Roundness is equal to or greater than 80% and equal to or less than 86%. In this way, it is possible to suppress development memory and carrier adherence.

A carrier for developing an electrostatic image includes a magnetic particle and a resin layer with which the magnetic particle is coated and which contains silica particles having an average particle diameter of 50 nm or more and 200 nm or less. In the carrier, a silicon element ratio Si1 in a region in which a distance from a surface of the resin layer in a direction toward an inside is 0.1 μm or more and 0.2 μm or less and a silicon element ratio Si2 in a region in which a distance from a surface of the magnetic particle in a direction toward the surface of the resin layer is 0.0 μm or more and 0.1 μm or less satisfy formula 1-1 and formula 2-1 below.

0.005≤Si1≤2  Formula 1-1

1≤Si1/Si2≤1000  Formula 2-1

Provided is a two-component developer for electrostatic charge image development including: toner particles containing toner base particles and an external additive disposed on a surface of the toner base particles; and carrier particles having a core material particle and a shell portion disposed on a surface of the core material particle, wherein the external additive contains inorganic particles surface-modified with a surface modifier represented by the following Formula (1); and a value of an iron element content (atomic %) measured by X-ray photoelectron spectroscopy (XPS) on a surface of the carrier particles satisfies the following Expression (1),

(R.sub.1).sub.4-n—Si—(X).sub.n  Formula (1):

4.0≤{A.sub.Fe/(A.sub.c+A.sub.o+A.sub.Fe)}×100≤15.0  Expression (1):

An electrostatic image developing carrier includes core particles provided by dispersing a magnetic powder in a resin and resin cover layers covering the core particles, wherein the resin cover layers have a surface coverage of 96 area % or more, the resin cover layers include 10 mass % or more and 50 mass % or less of inorganic particles relative to a total mass of the resin cover layers, and the inorganic particles in surfaces of the carrier have a surface exposure ratio of 6 atomic % or more and 15 atomic % or less determined by X-ray photoelectron spectroscopy.

The present invention relates to a ferrite particle containing a crystal phase component containing a perovskite crystal represented by a compositional formula: RZrO.sub.3 (provided that R represents an alkaline earth metal element), having a surface roughness Rz of 0.8 .Math.m or more and 3.5 .Math.m or less, and having a standard deviation Rzσ of the surface roughness Rz falling in a range represented by the following formula 0.15 × Rz ≤ Rzσ ≤ 0.60 × Rz. The ferrite particle can be used as an electrophotographic developer carrier core material. In addition, an electrophotographic developer carrier and an electrophotographic developer can be obtained.