Amorphous, fine silica particles, and method for their production and their use

An amorphous fine silica particle made by a flame hydrolysis of a silicon compound, wherein said silica particle having,

• 0.1-0.7 μm of the average particle diameter (median size),
• 5-30 m2/g of the specific surface area by BET,
• less than 40 of the dispersion coefficient (z) shown in the following formula [I], and
• more than 20 μC/m2 of the absolute value of triboelectrostatic charge to the specific surface area by BET.
• Z=Y/2X [I]
• ,where X is a median size, Y is a particle size range which is from 10% to 90% of an accumulative particle size.

A production process of an amorphous fine silica particle by leading a gaseous silicon compound into a flame to be hydrolyzed, the process also comprising,

• setting the flame temperature to be more than melting point of silica,
• setting the silica concentration in the flame to be more than 0.25 kg/Nm3,
• staying the generated silica particle for a short time under the high temperature which is more than melting point of silica, and
• making an amorphous silica particle having 0.1-0.7 μm of the average particle diameter (median size), and 5-30 m2/g of the specific surface area.