| 摘要 |
PURPOSE:To obtain a high video S/N and increase in drop-out by providing a magnetic layer on one side of a non-magnetic base, providing a backing layer on the other surface, and incorporating carbon black having respectively a specified value of average primary particle sizes therein. CONSTITUTION:The carbon black to be incorporated in a magnetic layer is satisfactory if the carbon black has <=30mmu average primary particle size, which is preferably 5-25mmu and more preferably 10-20mmu. If the size is larger than said sizes, the electromagnetic converting characteristic is poor and if the size is too small, difficulty arises in terms of dispersibility. The carbon black to be incorporated into the backing layer has 50-150mmu average primary particle size, which is preferably 70-120mmu, and more preferably 80-110mmu. If the particle size is smaller than said sizes, the traveling durability is poor. On the other hand, if the size it too large, the coating film has poor smoothness and the ruggedness is liable to be transferred onto the surface of the magnetic layer, thus resulting in the deteriorated electromagnetic conversion characteristic. Total amt. of <=30mmu carbon black to be incorporated in 100pts.wt. the magnetic material is preferably 1-20pts.wt., more preferably 3-15pts.wt. |
