Patent ID: 7452599

Claim:
Fine silica particles having an average particle size of 0.05 to 1 μm, wherein in a measurement of small-angle X-ray scattering, a fractal structure parameter α 1 at length scales ranging from 50 nm to 150 nm and a fractal structure parameter α 2 at length scales ranging from 150 nm to 353 nm satisfy the following formulas (1) and (2): −0.0068 S +2.548≦α 1 ≦−0.0068 S +3.748 (1) −0.0011 S +1.158≦α 2 ≦−0.0011 S +2.058 (2) wherein S is a BET specific surface area (m 2 /g) of the fine silica particles, wherein surfaces of the silica particles are treated with at least one treating agent selected from the group consisting of silylating agents, silicone oils, siloxanes, metal alkoxides, fatty acids and metal salts of the fatty acids.