HYDROPHOBIC SILICA FINE PARTICLES AND ELECTROPHOTOGRAPHIC TONER COMPOSITION

摘要

Provided are silica microparticles having a fine primary particle size suitable for an external toner additive, the microparticles including no bulky agglomerated particles responsible for a decrease in dispersibility into toner and fluidity of toner. The microparticles are capable of preventing detachment from toner, and are superior in effects of imparting uniform dispersibility and fluidity, thereby preventing a white point on printed images from occurring. The silica microparticles are characterized in that the silica microparticles are produced using hexamethyl disilazane or organo-polysiloxane by carrying out hydrophobization of hydrophilic silica microparticles having an average primary particle size of from 20 to 100 nm produced by a gas phase method, and that a ratio of agglomerated particles having a particle size of 1.5 µm or more is less than a predetermined value by determining using laser diffractometry by a volume-based particle size measurement of the particle.