A method for providing a developer mix having tribocharge uniformity across varying temperature and humidity conditions is provided. A developer mix used in a dual component development (DCD) system typically is a mixture of toner particles and magnetic carrier particles. Tribocharge uniformity is achieved in the developer mix by performing the step of treating the surface of the magnetic carrier particles with surface additives before the magnetic carrier particles are mixed with the toner particles. Surface additives include but are not limited to silica, titania and alumina.

A two-component developer includes a toner and a carrier. The toner includes a plurality of toner particles. The carrier includes a plurality of carrier particles. Each of the toner particles includes a toner core and a shell layer disposed over the surface of the toner core. The toner has a charge decay constant of at least 0.020 and no greater than 0.050 as measured with the toner particles in an external additive-free state. The carrier has a volume resistivity of at least 1.010.sup.12 .Math.cm.

A developer mix formulation having tribocharge uniformity across varying temperature and humidity conditions is provided. A developer mix used in a dual component development (DCD) system is a mixture of toner particles and magnetic carrier particles. Tribocharge uniformity is achieved in the developer mix by using magnetic carrier particles having surface additives on its surface. Surface additives include but are not limited to silica, titania and alumina.

The present invention relates to a ferrite particle, containing a crystal phase component containing a perovskite crystal represented by the compositional formula: RZrO.sub.3 (provided that R represents an alkaline earth metal element), and having an apparent density in a range represented by the following formula:
1.90Y2.45
provided that Y in the formula is the apparent density (g/cm.sup.3) of the ferrite particle.

A developer mix formulation having tribocharge uniformity across varying temperature and humidity conditions is provided. A developer mix used in a dual component development (DCD) system is a mixture of toner particles and magnetic carrier particles. Tribocharge uniformity is achieved in the developer mix by using magnetic carrier particles having surface additives on its surface. Surface additives include but are not limited to silica, titania and alumina.

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 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 2.0 m or more and 4.5 m or less, and satisfying the following formulas: 6.5log H.sub.10008.5 and 0.80log H.sub.1000/log H.sub.1001.00. 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.

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 m or more and 3.5 m or less, and having a standard deviation Rz of the surface roughness Rz falling in a range represented by the following formula 0.15RzRz0.60Rz. 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.

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.

An electrostatic charge image developer set includes a developer (1) and a developer (2) each containing a toner and a carrier, in which a carrier (1) of the developer (1) includes magnetic particles, a resin coating layer that covers the magnetic particles, and inorganic particles contained in the resin coating layer, a carrier (2) of the developer (2) includes magnetic particles and a resin coating layer that covers the magnetic particles, and a value of A(1)/A(2) is 17 or more and 105 or less, where when an element ratio of a metal and a semimetal that constitute the inorganic particles of the carrier (1) is analyzed by X-ray photoelectron spectroscopy for each of the carrier (1) and the carrier (2), an element ratio on a surface of the carrier (1) is denoted as A(1) and an element ratio on a surface of the carrier (2) is denoted as A(2).