Magnetic disc for sound and pictures reproduction - uses magnetic circular films on metallic discs

摘要

The film undergoing the magnetisation process may be applied to both sides of the metallic disc. The film is a mixture of binding material and anisotropic magnetic particles and is applied on the disc in a liquid form. It is spread by centrifugal force, with the disc rotating at high speed. It is magnetised, hardened, ground and then polished. One pair of poles is so arranged that magnetism spreads into the symmetrical plane and forms another even shaped pole pair but of opposite polarity and which converges pointed to the symmetry plane. The distance between the magnetic crests is greater than that of the pole faces and the flux density greates near the poles. The position of the poles is adjustable; during the film application they move toward each other. With this method of film application the reading potential is improved by 50%.