STRONGLY NEGATIVE CHARGE GRANTED, HYDROPHOBIC, AND SPHERICAL SILICA FINE PARTICLE, METHOD FOR PRODUCING THE PARTICLE, AND CHARGE CONTROL AGENT OBTAINED BY USING THE PARTICLE FOR DEVELOPING ELECTROSTATIC CHARGE IMAGE

摘要

PROBLEM TO BE SOLVED: To provide a strongly negative charge granted, hydrophobic, and spherical silica fine particle which imparts desired negative charge polarity and an electric charge quantity to a toner and keeps such the imparted state stably over a long period of time.SOLUTION: The strongly negative charge granted, hydrophobic, and spherical silica fine particle is a spherical hydrophobic silica fine particle having 0.005-0.030 micron volume-based median diameter of primary particles, 3 or smaller value of a particle size distribution (D90/D10) and 0.8-1 average degree of roundness.