Patent ID: 7083888
Filing Date: 2006-08-01
Classification: G03G,Y10T

Abstract:
1. An external additive for electrostatically charged image developing toner, comprising spherical hydrophobic fine silica particles having primary particles with a particle diameter of from 0.01 to 5 μm and having been treated with a compound selected from the group consisting of a quaternary ammonium salt compound, a fluoroalkyl-group- containing betaine compound, and a fluoroalkenyl-group- containing betaine compound, said fine silica particles fulfilling the following conditions (i) and (ii): (i) When an organic compound which is liquid at room temperature and has a dielectric constant of from 1 to 40 F/m and fine silica particles are mixed in a weight ratio of 5:1 and shaken, the fine silica particles disperse uniformly in the organic compound; and (ii) The quantity of primary particles remaining as primary particles when methanol is evaporated under heating by means of an evaporator from a dispersion prepared by dispersing the fine silica particles in methanol and thereafter the particles are held at a temperature of 100° C. for 2 hours, represents at least 20% of the quantity of primary particles originally present, wherein said hydrophobic fine silica particles have been obtained by the step (A) of introducing an R