| 摘要 |
<p>PURPOSE:To prevent an increase of drop-outs and generation of clogging and to improve traveling durability by incorporating a vinyl chloride/vinyl acetate copolymer, polyester resin and polyisocyanate as a binder into a back layer. CONSTITUTION:The back layer of the magnetic recording medium having a magnetic layer on the surface on one side of a nonmagnetic base and the back layer on the surface of the other side is formed by dispersing nonmagnetic powder into the binder. The vinyl chloride/vinyl acetate copolymer, the polyester resin and polyisocyanate are incorporated into the binder of the back layer. A resin which contains 1 to 15wt.% constituting unit derived from vinyl acetate in the vinyl chloride/vinyl acetate copolymer and has 400 to 500 average degree of polymn. is preferably used. The strength of the back layer degrades and the dispersibility of the nonmagnetic powder degrades if the content is higher than the above-mentioned range. The solubility of the vinyl chloride/vinyl acetate copolymer degrades if the ratio is lower than said range. The back layer which does not increase the drop-outs, has the excellent traveling durability and is improved in hydrolysis resistance is thereby obtd. and the clogging is hardly generated.</p> |
