| 摘要 |
PURPOSE:To improve dispersibility, wear resistance and running stability by incorporating carbon black having a prescribed average particle size and pulverized powder of a fluoroplastic into a back coat layer. CONSTITUTION:The pulverized powder which contains >=1wt% volatile component consisting of oxygen-contg. groups such as carboxyl group, quinone group and phenol group and has 20-70mum average grain size is used for the carbon black. The carbon black contributes to the improved wettability of itself, accelerated wettability of the pulverized powder of the fluoroplastic and improved dispersibility thereof. The pulverized powder of a tetrafluoroethylene, etc., having 0.08-0.15mum average grain size is used for the fluoroplastic which improves the dispersibility and wettability and is compounded to the carbon black at about 5/1-5/3 per the weight thereof. A cellulosic resin and polyurethane resin are used in combination for the binder resin to improve the wear resistance of the back coat layer. The higher effect is obtd. if an isocyanate compd., nonmagnetic powder such as calcium carbonate powder having >=3 Mohs' hardness and the pulverized powder of the resin are used in combination and the magnetic layer is formed by coating of such mixture. |
