Patent ID: 7611815

Claim:
An external additive for a toner for electrophotography, comprising: oxide fine particles which contain silicon, wherein the oxide fine particles have a primary particle diameter of 50 nm to 170 nm in number average, a standard deviation σ of a particle size distribution of the primary particle diameter satisfies a relation of: R/4≦σ≦R, in which the R expresses the primary particle diameter, the oxide fine particles are substantially spherical having a circularity SF1 of 100 to 130 and a circularity SF2 of 100 to 125, the circularity SF1 is defined as an equation (1) and the circularity SF2 is defined as an equation (2); SF 1=( L 2 /A )×(π/4)×100 equation (1) SF 2=( P 2 /A )×(1/4π)×100 equation (2) wherein “L” expresses the absolute maximum length of the oxide fine particles; “A” expresses a projected area of the oxide fine particles; and “P” expresses a maximum perimeter of the oxide fine particles; further comprising hydrophobed inorganic fine particles having an average particle diameter of primary particles of 1 to 100 nm.