Magnetic recording medium and method of producing the same

Abstract

A magnetic recording medium, which comprises: a nonmagnetic support; and a magnetic layer comprising a ferromagnetic powder and a binder, wherein an average surface roughness (Ra) at a center of a surface of the magnetic layer measured by using an atomic force microscope (AFM) is 2 nm or less, the maximum height (Rmax) thereof is 50 nm or less, and an arithmetic average of phase difference between a drive signal and a response signal of a probe measured with the atomic force microscope in a tapping mode is from 2 to 20°, and a method of producing the same.

1 - 3 . (canceled) 
   
   
       4 . A method of producing a magnetic recording medium, the method comprising:
 separately dispersing a magnetic solution comprising a ferromagnetic powder and a binder, and an abrasive solution comprising an abrasive; then   mixing the magnetic solution with the abrasive solution to give a coating solution for a magnetic layer; and   applying the coating solution on a nonmagnetic support to form a magnetic layer,   wherein a liquid mixture obtained by mixing the magnetic solution with the abrasive solution is subjected to both of an air-bubbling treatment and an ultrasonication treatment.   
   
   
       5 . The method according to  claim 4 ,
 wherein the air-bubbling treatment is a treatment that is conducted by stirring with a high-speed stirrer having stirring blades at a stirring blade peripheral speed of 10 m/sec or higher for 5 minutes or longer, and then   the ultrasonication treatment is conducted.   
   
   
       6 . The method according to  claim 4 , which further comprises: dispersing a carbon black solution comprising a carbon black with a bead mill; then
 subjecting the obtained dispersion to an air-bubbling treatment followed by an ultrasonication treatment; and then   mixing the dispersion with the magnetic solution and the abrasive solution to thereby give a coating solution for a magnetic layer.   
   
   
       7 - 10 . (canceled)