Black plate-shaped ferrite composite particles with magnetoplumbite structure and magnetic recording medium using the same

摘要

Black plate-shaped ferrite composite particles with magnetoplumbite structure having an average particle size of 0.01 to 0.2 µm of the present invention, comprise:plate-shaped ferrite particles with magnetoplumbite structure;a coating formed on surface of the plate-shaped ferrite particles with magnetoplumbite structure, comprising at least one of the organosilicon compounds.(1) organosilane compounds obtained by drying or heat-treating an alkoxysilane compounds,(2) polysiloxanes or modified polysiloxanes; or(3) fluoroalkyl organosilane compounds obtained by drying or heat-treating a fluoroalkylsilane compounds; andcarbon black fine particles adhered to the coating, having a particle size of 0.002 to 0.05 µm, the amount of the carbon black fine particles adhered being 0.5 to 10 parts by weight based on 100 parts by weight of the plate-shaped ferrite particles with magnetoplumbite structure.;Such black plate-shaped ferrite composite particles with magnetoplumbite structure are excellent in dispersibility in a vehicle due to fewer carbon black fine particles having fallen off from the surface of each black magnetic composite particle, and have a high blackness and a low volume resistivity.