| 摘要 |
PURPOSE:To reduce dispersion time, to decrease the amt. of the resin to be adsorbed to nonmagnetic powder and to make smaller the coefft. of friction by dispersing the nonmagnetic powder into a binder soln. at a low ratio and coating the soln. on the surface of a nonmagnetic base on the side opposite from the surface on which a magnetic layer is provided then subjecting the surface to a highly smoothing treatment. CONSTITUTION:The coating liquid is prepd. by combining 1 or >=2 kinds of nonmagnetic inorg. powders such as carbon black, graphite, CaCO3, BaSO4, ZnO and TiO2 and dispersing the same into the binder resin soln. and such coating liquid is coated on the surface of the base on the side opposite from the surface on which the magnetic layer such as magnetic tape or magnetic sheet is provided. The kneading time for the inorg. powder and resin soln. in a ball mill is made half the kneading time of the conventional practice or below to obtain the low dispersed and kneaded matter in the stage of the preparing the above-mentioned coating liquid. The kneaded matter is filtered with a filter having average 3mu grain size by which the paint for the back coat layer is obtd. Such paint is coated on the base and after drying, the surface is treated with a super calender roll by which the back coat layer having the surface roughness within the 0.25-0.35 range of the average roughness of the 'surface roughness' specified in JIS B6001 + point surface roughness RZ is obtd. The magnetic recording medium having the small coefft. of friction, excellent video S/N and good running stability is thus obtd. |
