| 摘要 |
PURPOSE:To improve running property and durability by incorporating bar- shaped calcium carbonate having >=5 anisotropic ratio into a back layer formed by laminating successively a non-magnetic substrate and back layer. CONSTITUTION:A magnetic layer is provided on one surface of the non-magnetic substrate of a magnetic recording medium. The magnetic layer consists of a binder and ferromagnetic material and may contain further a filler, polishing material, lubricating agent, dispersant, etc. The back layer is provided on the surface on which the magnetic layer is not provided. The bar-shaped calcium carbonate having >=5 anisotropic ratio is incorporated into the back layer. The calcium carbonate having the anisotropic ratio in a 5-30 range is preferably used and the calcium carbonate having <=2mum, more preferably 0.5-2mum length in the long axis direction is used. The anisotropic ratio refers to the ratio between the length in the long axis direction of the crystal and the length in the short axis direction and the content of the bar-shaped calcium carbonate in the back layer is preferably in a 50-350pts.wt. range by the total weight of the binder.
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