A two-component developer includes a toner and a carrier. The toner is a positively chargeable toner that is positively charged by friction with the carrier. The toner includes a plurality of toner particles each including a toner mother particle and a plurality of first resin particles. An anionic surfactant having higher negative chargeability than the first resin particles is present on surfaces of the first resin particles. The carrier includes a plurality of carrier particles each including a carrier mother particle and a plurality of second resin particles. A cationic surfactant having higher positive chargeability than the second resin particles is present on surfaces of the second resin particles. The first resin particles have a zeta potential lower than 0 mV at a pH of 5. The second resin particles have a zeta potential higher than 0 mV at a pH of 5.

A carrier core material is provided that is formed with ferrite particles which can uniformly adhere a coupling agent to the entire surface. A carrier core material is formed with ferrite particles, and the powder pH of the ferrite particles is equal to or more than 9. Here, the ferrite particles are preferably formed of Mn ferrite or MnMg ferrite. The ferrite particles preferably contain 45 wt % or more but 65 wt % or less of Fe, 15 wt % or more but 30 wt % or less of Mn and 5 wt % or less of Mg.

A developer mix used in a dual component development (DCD) system is a mixture of toner particles and magnetic carrier particles, wherein the magnetic carrier particle is surface treated with a hydrophobized titania particle. The surface treatment with a hydrophobized titania particle may be selected from either a spherical, disk, or spindle shaped. Tribocharge of the toner and the toner charge stability across cartridge life or environments may be suitably modified by selecting a preferred size and shape of the hydrophobized titania.

A magnetic carrier comprising: a magnetic material-dispersed resin carrier core material; and a resin coating layer on the surface of the magnetic material-dispersed resin carrier core material, wherein the magnetic material-dispersed resin carrier core material contains a core material particle containing a magnetic material and a binder resin, and a primer compound having an amino group, the resin coating layer contains a coating resin A, which is a polymer of monomers including at least a (meth)acrylic acid ester having an alicyclic hydrocarbon group, and the content of the primer compound in the magnetic material-dispersed resin carrier core material and the content of the resin coating layer are in specific range.

The two-component developer constituted of a toner and carriers, wherein the toner contains a crystalline polyester resin, constituted of a linear saturated aliphatic polyester unit, dispersed in an amorphous polyester resin obtained by polymerizing a bivalent alcohol component monomer and a dicarboxylic acid as an acid component monomer; wherein the carriers have a magnetic property and have core particles covered with a covering layer containing at least a binder resin and aminopropyltriethoxysilane; and

wherein an image of the magnetic carriers photographed by a scanning electron microscope shows the following features:
a percentage of a total area of high-brightness parts derived from a metal oxide on the one magnetic carrier particle to a total projected area is 3.0% by area at the maximum and 80% by piece in the magnetic carriers at the minimum and
an average percentage of the total area of the high-brightness parts derived from the metal oxide on the magnetic carrier particle to the total projected area of the magnetic carriers is 3.0% by area at the maximum.

A developer mix used in a dual component development (DCD) system is a mixture of toner particles and magnetic carrier particles, wherein the magnetic carrier particle is surface treated with a hydrophobized titania particle. The surface treatment with a hydrophobized titania particle may be selected from either a spherical, disk, or spindle shaped. Tribocharge of the toner and the toner charge stability across cartridge life or environments may be suitably modified by selecting a preferred size and shape of the hydrophobized titania.

Methacrylate resins of at least one bio-based methacrylate monomer, where the monomer includes a rosin or isosorbide moiety obtained from natural sources, can be used in toner, carrier coating or both.

There is provided a resin-filled ferrite carrier for an electrophotographic developer, in which a void of a porous ferrite particle used as a ferrite carrier core material is filled with silicone resin, wherein a true specific gravity (Y) of the porous ferrite particle filled with the silicone resin and a Si/Fe value (X) measured by fluorescent X-ray elemental analysis satisfy the following inequality (1):
350XY4.83100X(1).

A magnetic carrier comprising:a magnetic material-dispersed resin carrier core material; and a resin coating layer on the surface of the magnetic material-dispersed resin carrier core material, wherein the magnetic material-dispersed resin carrier core material contains a core material particle containing a magnetic material and a binder resin, and a primer compound having an amino group, the resin coating layer contains a coating resin A, which is a polymer of monomers including at least a (meth)acrylic acid ester having an alicyclic hydrocarbon group, and the content of the primer compound in the magnetic material-dispersed resin carrier core material and the content of the resin coating layer are in specific range.

(Meth)acrylate resins of at least one bio-based (meth)acrylate monomer, where the monomer includes a rosin or isosorbide moiety obtained from natural sources, can be used in toner, carrier coating or both.