SURFACE-HYDROPHOBIZED SPHERICAL SILICA FINE PARTICLE, METHOD FOR PRODUCING THE SAME, AND TONER EXTERNAL ADDITIVE, OBTAINED BY USING THE PARTICLE, FOR DEVELOPING ELECTROSTATIC CHARGE IMAGE

摘要

PROBLEM TO BE SOLVED: To provide a surface-hydrophobized spherical silica fine particle capable of making excellent the environmental stability of the electric charge quantity of a toner, a method for producing the surface-hydrophobized spherical silica fine particle, and a toner external additive for developing an electrostatic charge image, which additive is obtained by using the surface-hydrophobized spherical silica fine particle.SOLUTION: The surface-hydrophobized spherical silica fine particle is characterized in that the average particle diameter of primary particles is 0.01-5μm in terms of a volume-based median diameter and at least a part of the surface thereof is hydrophobized. The water content-retaining amount of the surface-hydrophobized spherical silica fine particle is 5-10 mass% of the dead weight thereof after left standing for three days under a 25°C/50%RH condition. Even after left standing for two days under a high-temperature and high-humidity(32°C/80%RH) condition or after left standing for two days under a low-temperature and low-humidity (10°C/10%RH) condition, fluctuations of the water content-retaining amount are within ±3% (±3 points) of the 5-10 mass% being the water content-retaining amount thereof.