Method for manufacturing magnetic paint, method for manufacturing non-magnetic paint and magnetic recording medium

Abstract

A method for manufacturing magnetic paint or non-magnetic paint, which can produce a magnetic recording medium having excellent surface smoothness by appropriately setting the condition of a dispersion process for improving the dispersibility of the paint, and a magnetic recording medium are provided. The magnetic paint or the non-magnetic paint is produced by performing a dispersion process of a mixed solution, in which a magnetic powder or a non-magnetic powder is mixed into a binder solution containing a binder and a solvent, with a medium dispersion device. The method includes the steps of adjusting the viscosity of the mixed solution to 1,500 cP or less on a BL type viscometer at 20 rpm basis, and performing a dispersion process with the medium dispersion device using dispersion media having an average particle diameter of 0.5 mm or less at a dispersion circumferential speed of 8 to 15 m/s.

What is claimed is:  
     
         1 . A method for manufacturing magnetic paint by performing a dispersion process of a mixed solution, in which a magnetic powder is mixed with a binder solution containing a binder and a solvent, with a medium dispersion device, the method comprising the steps of: 
 adjusting the viscosity of the mixed solution to 1,500 cP or less on a BL type viscometer at 20 rpm basis; and    performing a dispersion process with the medium dispersion device using dispersion media having an average particle diameter of 0.5 mm or less at a dispersion circumferential speed of 8 to 15 m/s.    
     
     
         2 . The method for manufacturing magnetic paint according to  claim 1 , wherein the viscosity is adjusted to 300 cP or less, and subsequently, the dispersion process is performed.  
     
     
         3 . A method for manufacturing non-magnetic paint by performing a dispersion process of a mixed solution, in which a non-magnetic powder is mixed with a binder solution containing a binder and a solvent, with a medium dispersion device, the method comprising the steps of: 
 adjusting the viscosity of the mixed solution to 1,500 cP or less on a BL type viscometer at 20 rpm basis; and    performing a dispersion process with the medium dispersion device using dispersion media having an average particle diameter of 0.5 mm or less at a dispersion circumferential speed of 8 to 15 m/s.    
     
     
         4 . The method for manufacturing non-magnetic paint according to  claim 3 , wherein the viscosity is adjusted to 1,000 cP or less, and subsequently, the dispersion process is performed.  
     
     
         5 . A magnetic recording medium provided with a magnetic layer comprising a coating of the magnetic paint produced by the manufacturing method according to  claim 1  or  claim 2  on a non-magnetic support.  
     
     
         6 . A magnetic recording medium sequentially provided with a non-magnetic layer and a magnetic layer on a non-magnetic support, wherein the non-magnetic layer comprises a coating of the non-magnetic paint produced by the manufacturing method according to  claim 3  or  claim 4 , and the magnetic layer comprises a coating of the magnetic paint produced by the manufacturing method according to  claim 1  or  claim 2.