Abstract: Provided is a novel spherical polymethylsilsesquioxane particle having an unprecedentedly large specific surface area ratio. The spherical polymethylsilsesquioxane particle includes a particle main body containing at least: a network structure formed by silicon atoms (n) and oxygen atoms (n) bonded to the silicon atoms (n); a methyl group bonded to at least one of the silicon atoms (n); and an alkoxyl group bonded to at least one of the silicon atoms (n), wherein the spherical polymethylsilsesquioxane particle satisfies the following expression (1): Expression (1) S1/S2?8.0, in the expression (1), S1 represents a specific surface area (m2/g) measured by a nitrogen adsorption BET one-point method, S2 represents 6/(?×D50) and a unit thereof is (m2/g), ? represents a particle density (g/m3), and D50 represents a volume-based 50% cumulative diameter (m) measured by a laser diffraction/scattering method.

Abstract: Provided are a poly alkylsilsesquioxane fine particle having hydrophobicity and having a small particle diameter, an external additive for toner and a dry toner for electrophotography each using the same, and a method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle. The hydrophobized spherical poly alkylsilsesquioxane fine particle has a mass-based median diameter in a centrifugal sedimentation method within the range of from 0.05 ?m to 0.3 ?m. The fine particle is produced through, for example, at least a process involving: mixing a raw material solution prepared using an alkyl trialkoxysilane with an alkaline aqueous medium to obtain a polycondensation reaction liquid; mixing the polycondensation reaction liquid with an aqueous solution to obtain a fine particle dispersion liquid; and blending a hydrophobizing agent in the fine particle dispersion liquid.

Abstract: Provided are a poly alkylsilsesquioxane fine particle having hydrophobicity and having a small particle diameter, an external additive for toner and a dry toner for electrophotography each using the same, and a method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle. The hydrophobized spherical poly alkylsilsesquioxane fine particle has a mass-based median diameter in a centrifugal sedimentation method within the range of from 0.05 ?m to 0.3 ?m. The fine particle is produced through, for example, at least a process involving: mixing a raw material solution prepared using an alkyl trialkoxysilane with an alkaline aqueous medium to obtain a polycondensation reaction liquid; mixing the polycondensation reaction liquid with an aqueous solution to obtain a fine particle dispersion liquid; and blending a hydrophobizing agent in the fine particle dispersion liquid.