| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain an electrostatic developing agent which has an excellent flow property, caking resistance and cleanability and is stable and uniform in electrostatic chargeability by incorporating non-crystalline spherical silica particulates having a specified specific surface area and a specific grain size distribution. SOLUTION: The electrostatic developing agent is obtained by adding the non-crystalline spherical silica particulates to toner particles. The specific surface area of the spherical silica particulates is 5 to 50 m2/g, more preferably 10 to 30 m2/g. The grain size distribution thereof is 5 to 1000 nm, more preferably 20 to 300 nm. The spherical silica particulates are prepared by subjecting alkoxysilane and/or its partial hydrolysis condensate to combustion decomposition in a flame. This alkoxysilane is preferably tetramethoxysilane or methyl trimethoxysilane. The spherical silica particulates do not substantially contain chlorine and the content of metal impurities exclusive of silicon is preferably <=5 ppm.</p> |
