HIGHLY HYDROPHOBIC SPHERICAL SOL-GEL SILICA FINE PARTICLE, METHOD FOR PRODUCING THE SAME, TONER EXTERNAL ADDITIVE FOR ELECTROSTATIC CHARGE IMAGE DEVELOPMENT COMPOSED OF THE FINE PARTICLE, AND DEVELOPER USING THE TONER EXTERNAL ADDITIVE

摘要

PPROBLEM TO BE SOLVED: To provide highly hydrophobic spherical sol-gel silica fine particles; a method for producing the same; a toner external additive for electrostatic charge image development, which is excellent in flowability of a toner, caking resistance, fixability, cleaning property, environmental stability of the electrified charge amount, or the like and useful for an electrophotographic method, and to provide a developer containing the toner additive. PSOLUTION: The method for producing the highly hydrophobic spherical sol-gel silica fine particles having a hydrophobicity of 50 and comprising primary particles having an average particle diameter of 0.01-5 m includes: a process for obtaining heat treated spherical sol-gel silica fine particles having a hydrophobicity of 50 by heat treating hydrophobic spherical sol-gel silica fine particles having a hydrophobicity of 50 and comprising primary particles having an average particle diameter of 0.01-5 m, which are obtained by making hydrophilic spherical sol-gel silica fine particles, obtained by the hydrolysis condensation of hydrocarbyloxysilane, hydrophobic; and a process for making the heat treated spherical sol-gel silica fine particles hydrophobic. The silica fine particles obtained by the method is also provided. The toner external additive comprises the silica fine particles, and the developer contains the toner external additive. PCOPYRIGHT: (C)2007,JPO&INPIT