TRAPEZOIDAL SMOOTH GROOVES FOR VIDEO DISC

摘要

A method of forming a disc having an information recording groove of regular cross-sectional shape by forming a preliminary spiral groove of trapezoidal cross-section in a disc having a relatively flat surface, and then flowing an excess of viscous material on the groove surface of the disc while rotating the disc rapidly and long enough to flow off the excess viscous material so as to leave a continuous coating of viscous material over the surface of the disc, the trapezoidal regions being covered by a coating having a relatively constant radius of curvature.