An electrostatic charge image developing carrier, containing: a magnetic particle; and a resin coating layer that coats the magnetic particle and contains inorganic particles, and the electrostatic charge image developing carrier has a surface of a surface roughness satisfying a ratio B/A of a surface area B to a plan view area A of 1.020 or more and 1.100 or less, the plan view area A and the surface area B being obtained by three-dimensional analysis of the surface, and the magnetic particle has a surface roughness satisfying 0.5 μm≤Sm≤2.5 μm and 0.3 μm≤Ra≤1.2 μm, and Sm represents an average ruggedness interval and Ra represents an arithmetic average surface roughness.

The present invention provides: a ferrite particle containing a crystal phase component containing a perovskite crystal represented by the compositional formula RZrO.sub.3 (where R is an alkaline earth metal element); and an electrophotographic developer carrier core material, an electrophotographic developer carrier, and an electrophotographic developer containing the ferrite particles.

The peak top molecular weight of the tetrahydrofuran-soluble component of the toner, as measured by gel permeation chromatography, is 4,000 or more and 6,500 or less. The tetrahydrofuran-insoluble component of the toner is 10% by weight or more and 30% by weight or less. When the endothermic peak temperature T1 in the heating process and the exothermic peak temperature T2 during the cooling process originating from the ester wax is measured using a differential scanning calorimeter, the value T1-T2 is 15° C. or more and 30° C. or less.

To provide a magnetic core material and carrier for electrophotographic developer, which have small environmental dependence of the electric resistance, can suppress the carrier scattering, and can stably provide good images; a developer contains the carrier; and methods for producing them. The magnetic core material satisfying a value of Formula (1): a+b×10+c+d+e+f, being from 20 to 150, when a fluoride ion amount is denoted by a (ppm), a chloride ion amount is denoted by b (ppm), a bromide ion amount is denoted by c (ppm), a nitrite ion amount is denoted by d (ppm), a nitrate ion amount is denoted by e (ppm), and a sulfate ion amount is denoted by f (ppm), which are measured by a combustion ion chromatography method.

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)

Provided are a magnetic core material for electrophotographic developer and a carrier for electrophotographic developer, which are excellent in charge characteristics and strength and with which a satisfactory image free from defects can be obtained, and a developer containing the carrier. A magnetic core material for electrophotographic developer, having a sulfur component content of from 50 to 700 ppm in terms of a sulfate ion and a BET specific surface area of from 0.06 to 0.25 m.sup.2/g.

Provided are a magnetic core material for electrophotographic developer and a carrier for electrophotographic developer, which are excellent in charging characteristics and strength with low specific gravity and with which a satisfactory image free of defects can be obtained, and a developer containing the carrier. A magnetic core material for electrophotographic developer, having a sulfur component content of from 60 to 800 ppm in terms of a sulfate ion and a pore volume of from 30 to 100 mm.sup.3/g.

To provide a magnetic core material for electrophotographic developer and carrier for electrophotographic developer which have small environmental dependence of the electric resistance, can suppress the carrier scattering, and can stably provide good images; a developer contains the carrier; a method for producing the magnetic core material for electrophotographic developer; a method for producing the carrier for electrophotographic developer, and a method for producing the developer.

The magnetic core material for electrophotographic developer, satisfying a value of Formula (1): a+b10+c+d+e+f, being from 20 to 150, when a fluoride ion amount is denoted by a (ppm), a chloride ion amount is denoted by b (ppm), a bromide ion amount is denoted by c (ppm), a nitrite ion amount is denoted by d (ppm), a nitrate ion amount is denoted by e (ppm), and a sulfate ion amount is denoted by f (ppm), which are measured by a combustion ion chromatography method.

A carrier core material is represented by a composition formula M.sub.XFe.sub.3-XO.sub.4 (where M is at least one type of metal element selected from Mg, Mn, Ca, Ti, Cu, Zn and Ni, 0<X<1), in which part of M and/or Fe is substituted with Sr and formed of ferrite particles, and in the carrier core material, a Sr content is equal to or more than 2500 ppm but equal to or less than 12000 ppm, the amount of Sr eluted with pure water at a temperature of 25 C. is equal to or less than 50 ppm, an apparent density is equal to or more than 1.85 g/cm.sup.3 but equal to or less than 2.25 g/cm.sup.3 and magnetization .sub.1k when a magnetic field of 79.5810.sup.3 A/m (1000 oersteds) is applied is equal to or more than 63 Am.sup.2/kg but equal to or less than 75 Am.sup.2/kg.

A magnetic carrier comprising a magnetic carrier particle having a magnetic carrier particle having a magnetic carrier core particle and a resin coat layer formed on the magnetic carrier core particle surface, and inorganic fine particles A present on a surface of the magnetic carrier particle, wherein each of the inorganic fine particles A has a rectangular parallelepiped particle shape, the inorganic fine particles A have D1 of 10 to 60 nm, the inorganic fine particles A are inorganic particles which have been surface treated with a surface treatment agent or silane coupling agent-treated particles, SP1 of the resin coat layer and SP2 of the surface treatment agent satisfies SP1SP214.00, and the coverage ratio of the magnetic carrier surface by the inorganic fine particles A as measured by ESCA is 5.0 to 20.0 atom %: and a two-component developer comprising at least the magnetic carrier and a toner.