Patent ID: 8101330

Claim:
A two component developer comprising a toner and a carrier, wherein carrier particles of the carrier comprise magnetic material powder dispersed in a phenol-formaldehyde resin, and have an average shape coefficient SF-1 of 1.0 to 1.2 and an average shape coefficient SF-2 of 1.1 to 2.5, and a volume based median diameter of from 10 to 100 μm; the toner comprises colored particles and external additive particles, wherein the external additive particles comprise a complex oxide containing silicon atoms and at least one of titanium atoms and aluminum atoms, and (R 1 )/(R 2 ) is less than 1, wherein (R 1 ) is an average existing ratio of the silicon atoms in an entirety of the external additive particles defined as a value obtained from a weight of silicon atoms in the entirety of the external additive particles divided by the total weight of the silicon atoms, the titanium atoms and the aluminum atoms in the entirety of the external additive particles, and (R 2 ) is a surface existing ratio of the silicon atoms in a surface of the external additive particles defined as a value obtained from a weight of silicon atoms in the surface divided by the total weight of the silicon atoms, the titanium atoms and the aluminum atoms in the surface.