MAGNETIC RECORDING MEDIUM
PURPOSE:To improve the dispersibility of ferromagnetic powder in magnetic coating material applied to a substrate and obtain a high S/N by a method wherein the ferromagnetic powder having a high coercive force and a fine needle-shape and fine magnetite powder having a low coercive force are mixed wi...
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Zusammenfassung: | PURPOSE:To improve the dispersibility of ferromagnetic powder in magnetic coating material applied to a substrate and obtain a high S/N by a method wherein the ferromagnetic powder having a high coercive force and a fine needle-shape and fine magnetite powder having a low coercive force are mixed with a specific weight ratio. CONSTITUTION:One of the components of magnetic coating material which is applied to a substrate to form a magnetic layer is fine needle-shaped ferromagnetic powder having a high coercive force. Metal powder, cobalt-coated iron oxide powder, etc., whose long axis length is not larger than 0.2mum and whose coercive force is not less than 1500Oe is used as the ferromagnetic powder. The other component is magnetite powder. Magnetite powder whose average particle diameter is not larger than 0.3mum and whose coercive force is not higher than 150Oe is used as the magnetite powder. The ferromagnetic powder (A) and the magnetite powder (B) are mixed and applied to the substrate with binder so as to have the weight ratio (B)/(A) of a formed magnetic layer 0.03-0.3. With this constitution, the magnetic powder is uniformly dispersed in the magnetic layer and the surface smoothness of the magnetic layer is improved, so that a high S/N can be obtained. |
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