| 摘要 |
PURPOSE:To obviate degradation of surface smoothness, running stability and wear resistance even after long-term traveling by adding and using specific alumina hydrate to and for a back coating layer. CONSTITUTION:The back coating layer contains the alumina hydrate expressed by the general formula Al2O3.xH2O (x is 2.9-0.1). the alumina hydrate to be used is transition alumina of x-Al2O3, k-Al2O3, boehmite, rho-Al2O3, gamma-Al2O3 and theta-Al2O3 having hexagonal planar crystal structure of the mixture composed thereof. The particle sizes of the alumina expressed by the general formula Al2O3.xH2O are about <=2mum, more preferably <=1mum and the alumina having 0.3-1.0mum particle size is usually used. The magnetic recording medium which has the excellent surface smoothness, running stability and wear resistance, obviates the degradation thereof even after long-term running and obviates the degradation of the magnetic characteristics is obtd.
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