HIGHLY DISPERSIBLE, HIGHLY HYDROPHOBIC SPHERICAL SILICA FINE POWDER, METHOD FOR PRODUCING THE POWDER, AND USE

摘要

PPROBLEM TO BE SOLVED: To provide a highly hydrophobic spherical silica fine powder prepared by treating a spherical silica powder having a BET specific surface area of 10-50 mSP2/SP/g to make it highly hydrophobic and highly dispersible and to provide an external toner additive which eliminates image defects due to particles buried in the surface of a toner and imparts a stabilized printability improving effect. PSOLUTION: The highly dispersible, highly hydrophobic spherical silica fine powder is prepared by hydrophobizing a spherical silica powder having a BET specific surface area of 10-50 mSP2/SP/g with hexamethyldisilazane and has a degree of hydrophobicity of 65% or higher (as measured by a methanol titration method) and a loose bulk density of 0.25 g/cmSP3/SPor higher. A method for producing the silica fine powder comprises floating a spherical silica powder in a gas, spraying it with a specified amount of water, and spraying it further with a specified amount of hexamethyldisilazane. The external toner additive for developing a charge pattern comprises the highly dispersible, highly hydrophobic spherical silica fine powder. PCOPYRIGHT: (C)2004,JPO