The present invention relates to a magnetic recording medium such as a magnetic recording tape. More particularly, it relates to a magnetic recording medium improved in dispersibility and orientability of the magnetic particles, enhanced in surface properties and durability of the magnetic layer and excellent in electro-acoustic properties such as output in a high frequency region and S/N ratio.
In general, a magnetic recording medium comprises a base and a magnetic layer provided on the surface of the base. The magnetic layer is usually formed by applying a magnetic coating composition comprising magnetic particles and a binder onto the surface of the base (e.g. a polyester film). Since the electro-acoustic properties of the magnetic recording medium greatly depend upon the dispersing state of the magnetic particles in the magnetic layer, the magnetic particles are required to be well dispersed in the magnetic layer. However, the magnetic particles are apt to be cohered between or among them, and therefore it is hard to achieve a uniform dispersion of the magnetic particles in the binder. Thus, a magnetic recording medium having satisfactory electro-acoustic properties has not been provided.
In order to prevent the cohesion between or among the magnetic particles and to improve the electro-acoustic properties of a magnetic recording medium, it has been proposed to incorporate dispersing agents such as lecithin, alkylamine salts, fatty acid soaps, resin acid soaps and quaternary ammonium salts into the magnetic layer. However, their dispersing effect on the magnetic particles is still unsatisfactory.