US Patent 7871749 Electrophotographic developing agent

A non-magnetic one-component electrophotographic developing agent is provided having improved properties. The electrophotographic developing agent includes parent toner particles comprising a binder resin, a releasing agent, a colorant, and a charge control agent, and an external additive which is added to a surface of the parent toner particles, wherein the binder resin comprises a high viscosity polyester resin having a weight average molecular weight of about 90,000-140,000 and a gel content of less than about 5% and a low viscosity polyester resin having a weight average molecular weight of about 52,000-65,000 and a gel content of less than about 2%. According to an embodiment of the present invention, an electrophotographic developing agent having improved image gloss and fusing property, while ensuring durability may be prepared by using a blended combination of a high viscosity polyester resin and a low viscosity polyester resin.