| 摘要 |
PURPOSE:To give a surface roughness of necessary minimum to secure video characteristic and to improve the wear resistance of a magnetic recording medium, by installing a back coat layer containing barium sulfate or calcium carbonate and zinc oxide powders of <=1mu in mean grain size to the back of a base. CONSTITUTION:A back coat layer containing barium sulfate and/or calcium carbonate having a mean grain size of <=1mu and zinc oxide powder having a mean grain size of <=1mu, is installed to the back of a base, the main surface of which has a magnetic layer. The mixing ratio of the barium sulfate and/or calcium carbonate, zinc oxide powder, and carbon black to the material forming the back coat layer is usually set at 30-80wt% of the total weight of the material. Moreover, it is desirable to set the mixing ratio of the zinc oxide powder at 10-70wt% of the total weight of the barium sulfate and/or calcium carbonate. The back coat layer is fomred by applying a coating material prepared by mixing and dispersing barium sulfate and/or calcium carbonate and zinc oxide powders into a binder to the back of a base, to the main surface of which a magnetic layer is formed in advance. The applying thickness is usually set at 0.3- 3.0mu. |
