FLEXIBLE MAGNETIC RECORDING CARRIER PROVIDED WITH REAR LAYER

PURPOSE: To prepare a dispersion liquid to form a back layer which shows no decrease in gloss or increase in roughness, nor decrease in mechanical characteristics such as wear resistance by completing dispersion under specified technical conditions and then maintaining the stable state. CONSTITUTION: The magnetic recording carrier consists of a nonmagnetic base tape, a magnetic layer formed on the principal surface of the base tape, and a back coating layer comprising a polymer binder, nonmagnetic filler and supporting pigment. The back layer contains 15 to 40vol.% precipitated silica to the whole volume. The precipitated silica contains 98 to 99.5 % SiO2 and has pH=5 to 7 and 90 to 650m /g specific surface area. The surface of the silicate is covered with a polyurethane by 0.05 to 0.25g/m coating amt. This polyurethane has 40000 to 120000 average mol.wt. Mw and contains 10 to 100mg equiv. phosphate groups per 1kg of polyurethane.