| 摘要 |
PURPOSE:To obtain good running stability and running durability even at the time of a high temp. and high humidity by incorporating specific magnetic metal powder and two kinds of carbon blacks into a magnetic layer thereby enhancing the electromagnetic conversion characteristic of the magnetic layer and lowering the specific surface resistance and friction resistance of thereof. CONSTITUTION:The magnetic metal powder having >=40m<2>/g specific surface area in BET value as well as a 1st carbon black (CB) having 50-900m<2>/g specific surface area in BET value and <110ml/100g oil absorption in DBP value and the 2nd CB having 15-80m<2>/g specific surface are in BET value and >=110ml/100g oil absorption in DBP value are incorporated into the magnetic layer. The electromagnetic conversion characteristic of a high level is obtd. by using two kinds of such CBs together with the above-mentioned magnetic metal powder. <=1X10<9>OMEGA/sq specific surface resistance is obtd.; dust is hardly stickable to the magnetic medium and the drop-outs are decreased. The coefft. of friction of the magnetic layer surface is lowered and the excellent running durability is obtd. Since the coefft. of dynamic running durability is low, the powder dislodging at the time of repetitive running is suppressed. The electromagnetic conversion characteristic is not degraded even if the CBs are added at a high ratio and, therefore, the formation of a tape for an 8mm video to the smaller thickness is permitted.
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