Novel Method for Coating Magnetic Iron Oxide Particles with Carbon Black

Magnetic particles with finer size, higher coercive force, higher blackness, and lower electrical resistance are required to produce better magnetic tape materials. A new method to coat iron oxide particles with carbon black using an adhesive agent is reported in this paper. Magnetic tapes prepared using the coated particles in the recording layer exhibit improvements in both light transparency and electrical resistance. A decrease in transparency of ∼20% and a reduction in electrical resistance of ∼1 order of magnitude relative to conventionally prepared tapes are achieved when ∼5% of the particle weight is carbon black. Surface smoothness and the orientation ratio are also improved because the dispersibility of these particles in magnetic lacquer is better than that of uncoated magnetic iron oxide particles. Higher electromagnetic performance relative to the conventionally prepared layers is also obtained. TEM photographs indicate that all the carbon black is firmly bound to the surface of the magnetic iron oxide particles in a distinct layer.