| 摘要 |
PROBLEM TO BE SOLVED: To provide hydrophobic spherical silica fine particles which can impart flowability, caking resistance and satisfactory electrostatic charges to a toner, which has a small particle diameter, high flowability, high dispersibility and low cohesiveness and thus are useful as a toner external additive. SOLUTION: The hydrophobic spherical silica fine particles are prepared by a hydrophobic treatment process comprising a step of introducing an R<SP>1</SP>SiO<SB>3/2</SB>unit (wherein, R<SP>1</SP>is a substituted or non-substituted monovalent hydrocarbon group of 1-20C) on the surface of a hydrophilic spherical silica fine particle practically consisting of an SiO<SB>2</SB>unit obtained by hydrolyzing and condensing a tetrafunctional silane compound and/or its partial hydrolysis-condensation product and then a step of introducing an R<SP>2</SP><SB>3</SB>SiO<SB>1/2</SB>unit (wherein, R<SP>2</SP>may be the same or different and is a substituted or non-substituted 1-20C monovalent hydrocarbon group). The hydrophobic spherical silica fine particles have a basic flowability energy of 500 mJ or less and a particle diameter of 0.005-0.09μm. COPYRIGHT: (C)2009,JPO&INPIT
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