| 摘要 |
PURPOSE:To obtain a recording medium having high C/N, less drop-outs and high reliability by forming ferromagnetic powder of ferromagnetic iron oxide contg. specific ratios of cobalt and bivalent iron, incorporating a specific polyurethane resin as a binder therein and specifying the surface resistivities of a magnetic layer and back layer. CONSTITUTION:The ferromagnetic powder used in the magnetic recording medium formed by providing the magnetic layer contg. the ferromagnetic powder and binder on one face and providing the back layer on the other face is formed of the ferromagnetic iron oxide contg. 1-10wt% cobalt by the weight of the iron oxide and 1-10wt% bivalent iron by the weight of tervalent iron. The magnetic layer contains the polyurethane resin contg. 1-100equiv./10<5>g carboxyl group at 15wt% of the total binder weight as the binder. The surface resistivity on the surface of the magnetic layer is specified to <=10<11>OMEGA and the surface resistivity on the surface of the back layer to <=5X10<6>OMEGA. The particle size of the ferromagnetic powder is specified to about 0.01-1mu length, the ratio of the major axis/axial width to about 1/1-50/1 and the specific surface area of the ferromagnetic powder to about 30-50m<2>/g. The excellent C/N is thereby provided to the medium and the drop-outs are extremely decreased.
|
