Method of producing a magnetic recording medium comprising a substrate supporting a film of discrete magnetic particles in a plastics binder matrix

摘要

Discrete magnetic particles are formed in situ in a plastics binder matrix by forming a coating liquid by dispersing a nickel hypophosphite solution in a plastics binder and binder solvent, such as polyvinyl alcohol in water or polyester urethane polymer in an organic solvent, coating a substrate with the coating liquid and exposing the coating to a radiant energy source, such as x-rays or an electron beam. Thereafter the area exposed to radiation is developed by contact with a solution including ions of at least one of cobalt, nickel and iron and a reducing agent, such as a hypophosphite ion, to produce a magnetic recording medium comprising discrete magnetic particles dispersed within the plastics binder in the area exposed tothe radiant energy while the unexposed areas do not contain magnetic particles.