US Patent 7144666 Toner used with electrophotography

A toner having toner particles containing a binder resin and a colorant; and a first external additive having 0.1 to 3.0 wt % of large silica particles with an average particle size of 20 to 200 nm; a second external additive having 0.1 to 3.0 wt % of small silica particles with an average particle size of 5 to 20 nm; a third external additive having 0.1 to 2.0 wt % of hydrophobic titanium dioxide microparticles with a resistance of 105 to 1012 Ωcm; and a fourth external additive having at least one of 0.1 to 2.0 wt % of conductive titanium dioxide particles with a resistance of 1 to 105 Ωcm and 0.1 to 2.0 wt % of positively chargeable aluminum oxide particles. Therefore, a thin toner layer with a uniform toner amount is formed on a toner carrier and stable charge distribution and toner flowability are maintained for a long time, thereby resulting in prevention of fog and toner scattering, and improvements in developing efficiency and toner durability.