| 摘要 |
PROBLEM TO BE SOLVED: To provide a composite non-magnetic particle powder for a non-magnetic underlayer of a magnetic recording medium, the powder having low volume resistivity and low-soluble sodium salt and soluble sulfate contents, and to provide a magnetic recording medium having low surface electrical resistance, satisfactory surface smoothness, generating less dropouts and having proper preservation property of a tape, even if the non-magnetic underlayer is made thin. SOLUTION: The composite non-magnetic particle powder for the non-magnetic underlayer of the magnetic recording medium is provided where the surfaces of particles of hematite particle powder or iron hydroxide-containing particle powder are coated with a surface modifier and carbon black adheres to the coating, wherein the composite non-magnetic particle powder contains 150 ppm or lower soluble sodium salt content expressed in terms of Na and 150 ppm or lower soluble sulfate content, expressed in terms of SO<SB>4</SB>. The magnetic recording medium is formed, by using the composite non-magnetic particle powder as the composite non-magnetic particle powder for the non-magnetic underlayer of the magnetic recording medium. COPYRIGHT: (C)2008,JPO&INPIT
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