Process for producing multi-layered magnetic recording media

Details Process for producing multi-layered magnetic recording media Process for producing multi-layered magnetic recording media

1990-12-06

1991-12-03

Pianalio, Bernard

Coating processes

Magnetic base or coating

Magnetic coating

428900, H01F 1002

Patent

active

050699342

ABSTRACT:
A multi-layer coating method by which multi-layered magnetic recording media having good recording characteristics can be produced consistently at high speed with multiple thin layers being coated simultaneously while insuring effective prevention of unwanted phenomena such as color unevenness and longitudinal streaks. A plurality of organic solvent based dispersions that are non-Newtonian fluids having fine particles dispersed therein are simultaneously applied in superposition onto a continuously running nonmagnetic support using an extrusion type applicator head. The coating operation is performed in such a manner that the Reynolds number as determined by the average of the kinetic viscosity coefficients of the dispersions, the coating speed and the equivalent diameter during coating is adjusted to 400 or below, and that, at the same time, the yield stress of at least the dispersion for the topmost layer is adjusted to 10 dyne/cm.sup.2 or more. Further, the coating operation is performed in such a way that the ratio of .eta..sub.T to .eta..sub.H is adjusted to 50 or above, where .eta..sub.H is the viscosity of the dispersions at the rate of shear that is exerted upon the dispersions when they are applied using an extrusion type applicator head, and .eta..sub.T is the viscosity of the dispersions at the shear rate for the time period defined by the end of application and the entrance into the subsequent drying zone.

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