| 摘要 |
PURPOSE:To obtain a medium having good characteristics and little dropout by successively forming first, second and third magnetic layers on a nonmagnetic supporting body in a manner that the sum of film thickness of the second and third magnetic layers is <=0.7mum and the coercive force of the ferromagnetic powder in the third magnetic layer is 1.2 - 2.5 times as much as that of the first magnetic layer. CONSTITUTION:In each magnetic layer on the magnetic supporting body, ferro magnetic powder is dispersed in a binder resin. These layers are formed in a manner that the sum of film thickness of the second and third magnetic layers is 0.7 - 0.2 mum, the second layer is made thin on the first layer, and the first magnetic layers is 0.5 - 4mum thick. As for the ferromagnetic powder, Co-contg. gamma-Fe2O3, etc., is used, and the ferromagnetic powder in the third layer is selected so that it has coercive force 1.2 - 2.5 times as much as that of the ferromagnetic powder in the first magnetic layer. As for the binder resin, modi fied vinyl chloride resin, etc., is used and kneaded to prepare the magnetic coating material, which is then applied on the supporting body, oriented in a magnetic field before dried, subjected to surface smoothening treatment and then cut into a desired shape to obtain the product. |
