ADDITIVE FOR MAGNETIC RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To obtain an additive which can give high-density magnetic recording media excellent in running performances and durability by using a crosslinked polymer prepared by polymerizing a monomer containing a crosslinking monomer (e.g. divinylbenzene) and having a specified particle diameter. SOLUTION: This additive comprises crosslinked polymer particles obtained by polymerizing a crosslinking monomer (A) with a polymerizable monomer (B) and having a mean particle diameter of 0.01-5μm. Component A is e.g. divinylbenzene or ethylene glycol dimethacrylate having at least two polymerizable double bonds (e.g. nonconjugated vinyl compound or a polyacrylate compound). Component B is desirably an aromatic monovinyl compound or (meth)acrylic ester. The content of component A in the crosslinked polymer particles is below 10%, desirably below 3%. Usually, 1-5wt.% crosslinked polymer particles are added to a magnetic powder, and the obtained mixture is used to form the magnetic layer of a magnetic recording medium. This additive makes the surface of the magnetic layer irregular and improves its slipperiness and durability.