Abstract: A method for manufacturing a surface-treated gas-phase-process silica particle, the method including steps of: adding 1,3-divinyl-1,1,3,3-tetramethyldisilazane to a raw material gas-phase-process silica particle and introducing a vinyldimethylsilyl group on a surface of the raw material gas-phase-process silica particle to obtain a preliminarily treated silica particle; and adding hexamethyldisilazane to the preliminarily treated silica particle and introducing a trimethylsilyl group on a surface of the preliminarily treated silica particle to obtain a surface-treated gas-phase-process silica particle.

Abstract: The invention provides: an electrostatic image-developing toner external additive including granulated silica which is a granulated material of silica powders each having a primary particle size of 5 to 50 nm and a degree of hydrophobization of 50% or more, the granulated silica having a loose bulk density of 150 g/L or more; and a toner including the electrostatic image-developing toner external additive. These provide an electrostatic image-developing toner external additive excellent in handleability and workability and also capable of improving image quality, and a toner using the external additive.

Abstract: There is provided an electrostatic image developing toner less likely to cause image degradation even when used for a long period, by controlling CCA particles present on surfaces of toner particles and thereby keeping an amount of tribocharge generated between the toner and a magnetic carrier or the like constant. A charge control agent composition for external addition for controlling charge amount of toner particles includes: at least two types of carrier particles different in average particle size of primary particles; and a charge control agent (CCA), and an electrostatic image developing toner is constituted of a mixture of toner particles and the aforesaid charge control agent composition for external addition.

Abstract: There is provided an electrostatic image developing toner less likely to cause image degradation even when used for a long period, by controlling CCA particles present on surfaces of toner particles and thereby keeping an amount of tribocharge generated between the toner and a magnetic carrier or the like constant. A charge control agent composition for external addition for controlling charge amount of toner particles includes: at least two types of carrier particles different in average particle size of primary particles; and a charge control agent (CCA), and an electrostatic image developing toner is constituted of a mixture of toner particles and the aforesaid charge control agent composition for external addition.

Abstract: An external additive for electrostatically charged latent image developing toner is provied. The additive includes spherical hydrophobic fine silica particles having primary particles having a particle diameter of from 0.01 to 5 &mgr;m, which fine silica particles fulfill 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.