METHOD OF PRODUCING MAGNETIC DISKS HAVING SIGNALS

摘要

A method of producing many duplicate magnetic disks from a master disk at high speed using a simple device while preventing the demagnetization of the master disk. The disk for duplication has a magnetic layer including magnetic powder such as hexagonal ferrite crystals, a majority of which has the easy axis substantially perpendicular to the disk surface rather than along the tracks. The disk is placed in a manner that its magnetic layer is in contact with the magnetic layer of the master disk in which signals are recorded with magnetization along the tracks. The alternating magnetic field is applied over the disks in nearly a vertical direction, so that the signals of the master disk are transferred to the disk for duplication.