| 摘要 |
PURPOSE:To improve the traveling durability of the titled medium without deteriorating the electromagnetic characteristic by dispersing carbon black having specified mean primary particle diameter, an inorg. pigment having specified mean primary particle diameter and 2-4 Mohs' hardness, and an inorg. pigment having specified mean primary particle diameter and 5-7 Mohs' hardness in a binder to form a backcoat layer. CONSTITUTION:Carbon black having 10-30mmu mean primary particle diameter is used and a light shielding property is provided by the carbon black especially when a magnetic layer having an insufficient light shielding property such as a Co-coated gamma-Fe2O3 dispersion layer is formed on a transparent carrier of polyester, etc. The content of the carbon black in the whole inorg. pigment powder is regulated to about 30-80wt%. The inorg. pigment having 2-4 Mohs' hardness is selected from CaCO3, MgCO3, etc., and the mean primary particle diameter is adjusted to 0.03-0.1mu. The inorg. pigment having 5-7 Mohs' hardness is selected from TiO2, SiO2, alpha-Fe2O3, etc., and the mean primary particle diameter is controlled to 0.03-0.1mu.
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