Patent ID: 8114212

Claim:
Powdery silica composite particles comprising silica composite particles obtained by a surface treatment step of adding acid or alkali to a reactant solution comprising: core silica particles of 5 to 200 nm in average particle size; alkoxysilane; a phosphonium salt ionic liquid represented by the following general formula (I): wherein R 1 , R 2 , and R 3 respectively represent a linear or branched alkyl group having 1 to 5 carbon atoms, R 4 represents a linear or branched alkyl group having 1 to 5 carbon atoms, n represents an integer of 1 to 8, and X represents an anionic group; and a reaction solvent such that the alkoxysilane is hydrolyzed, thereby surface-treating the core silica particles; wherein the silica composite particles comprise the phosphonium salt ionic liquid represented by the general formula (1) at a content of 1% by weight or higher in terms of the P atom.