| 摘要 |
PROBLEM TO BE SOLVED: To improve still characteristic and recording density by adding very small amount of carbon black and to improve repetitive traveling durability for long time by specifying physical properties of the carbon black, more specifically specifying DBP oil absorption, pH and composition of a soln. in which the carbon black is subjected to impregnation treatment. SOLUTION: Thickness of a magnetic layer is made to be <=0.3 μm and the carbon black treated by a fatty acid is incorporated in the magnetic layer at <=5 wt.% to ferromagnetic metallic powder. Further, the carbon black having 200 to 280 m<2> /g BET surface area and 150 to 200 cc/100g DBP oil absorption is incorporated in the magnetic layer at 0.5 to 2.0 wt.% to the metallic powder. |
