PURPOSE: To improve traveling durability without increasing the coefft. of friction, by providing a coating layer wherein filler powder is kneaded and dispersed in a binder consisting of a phenoxy resin, polyol and polyisocyanate compd. on the substrate surface on the side opposite from a magnetic recording layer.
CONSTITUTION: A phenoxy resin has the structure shown in the formula I , and contributes to the provision of heat resistance, toughness and blocking resistance. Polyols of polyester type and polyether types are used, and the mol. wt. thereof is 300W5,000, more preferably 600W4,000 in terms of reactivity with polyisocyanate. The filler for the back layer is inorg. powder such as SiO2, CaCO3, Al2O3, Fe2O3, TiO2, MnO, ZnO, CaO in addition to carbon black powder, graphite, tungsten disulfide, molybdenum disulfide, and boron nitride. Fatty acids of ≥12 carbon atoms and ester compds. thereof, and further silicone and paraffin wax are usable as a lubricant in order to decrease the coefft. of friction of the back layer and to improve travelling property and durability.
MIYOSHI TAKAHITO
OKUTSU TOSHIMITSU
FUJIYAMA MASAAKI
