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.

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.

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.

A positively chargeable toner includes toner particles each including a toner base particle and an external additive. The toner base particle contains, at least, a binder resin, a colorant, and a release agent. The external additive includes an inorganic particle and a resin particle. The resin particle contains a cationic surfactant, has a volume average particle size of 40 nm or more but 110 nm or less, and has a hardness of 1 N or higher when measured with a probe displacement of 40 nm. Where SP1 is a difference between an SP value of the release agent and an SP value of the resin particle, and SP2 is a difference between an SP value of the binder resin and the SP value of the resin particle, 0.8SP11.1 (cal/cm.sup.3).sup.1/2 and 1.3SP21.6 (cal/cm.sup.3).sup.1/2 are satisfied.