SUPERFINE SILICA POWDER AND APPLICATION THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a toner external additive excellent in preservable property, electrification characteristic and flowability and to provided a hydrophobized superfine silica powder suitable for the toner external additive.SOLUTION: In one embodiment, there is provided the superfine silica powder having an average particle diameter of 80 nm or more and less than 300 nm, an average sphericity of 0.50 or more and less than 0.80, an average aspect ratio of 1.0 or more and less than 1.50, and a moisture content of 0.05 wt% or more and less than 0.30 wt.%. The specific area is preferably 10.0 m/g or more and less than 150 m/g. In another embodiment, there is provided the superfine silica fine powder which is identical to the above superfine silica powder in the one embodiment except that the surface of superfine silica powder is treated with hexamethyldisilazane. There is also provided a toner external additive for static charge image development containing the superfine silica powder.SELECTED DRAWING: None