| 摘要 |
PROBLEM TO BE SOLVED: To provide a back coat preventing a magnetic recording surface from being damaged and reducing increase of a frictional coefficient even in repetitive sliding and reduces electrical resistance which is an another role of the back coat. SOLUTION: In the magnetic recording medium is provided with: an underlayer non-magnetic layer 3 containing non-magnetic powder and a binder on a non-magnetic support 1; and a magnetic layer 2 containing magnetic powder and a binder on the non-magnetic layer 3 and is formed with the back coat 4 on the other side surface of the non-magnetic support 1, wherein the back coat 4 has only carbon black, the carbon black having 40 to 80 nm average particle diameter, the ratio R (=carbon black/a binder) of the carbon black to a binder in the back coat is 1.6 to 2.2 and the back coat 4 contains as the binder,≥50 wt.% urethane resin having 30 to 50°C glass transition temperature Tg in the total binder and contains≥25 wt.% and <50 wt.% nitrocellulose in the total binder. COPYRIGHT: (C)2008,JPO&INPIT
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