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Magnetic recording medium and method of manufacturing the same

  • US 8,535,817 B2
  • Filed: 08/26/2010
  • Issued: 09/17/2013
  • Est. Priority Date: 08/27/2009
  • Status: Active Grant
First Claim
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1. A magnetic recording medium comprising a nonmagnetic layer containing a nonmagnetic powder and a binder and a magnetic layer containing a ferromagnetic powder and a binder in this order on a nonmagnetic support, whereinthe magnetic layer comprises a nonmagnetic powder of which coefficient of variation CV of a particle size distribution as denoted by the following formula (1):


  • CV(%)=σ



    ×

    100 



    (1)is less than 20 percent,the nonmagnetic powder contained in the magnetic layer is silica powder,the magnetic layer further comprises an inorganic powder other than the silica powder, with a Mohs'"'"' hardness of equal to or higher than 6,the magnetic layer contains no carbon black, andthe magnetic layer has a thickness being equal to or less than 0.1 μ

    m and falling within a range of 1.1≦

    φ

    /t≦

    8.0, wherein σ

    denotes the standard deviation of the particle diameter, φ

    denotes the average particle diameter of the nonmagnetic powder comprised in the magnetic layer expressed in μ

    m, and t denotes the thickness of the magnetic layer expressed in μ

    m.

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