MAGNETIC RECORDING MEDIUM AND IT PRODUCTION

摘要

PROBLEM TO BE SOLVED: To prevent malfunction and to obtain stable reproduced signals by magnetizing a magnetic layer so as to be balanced with noise at the time of reading while applying a DC bias magnetic field, thereby diminishing the output of the noise from the card edge. SOLUTION: This medium 1 has a magnetic layer 3 having 1500 to 5000Oe coercive force on a nonmagnetic substrate 2. the layer 3 is magnetized by a CD magnetic field after completely demagnetized by an AC magnetic field. The intensity of magnetization is controlled to be balanced with the pulse noise produced on the edge at the time of reading while a DC bias magnetic field is applied. The intensity may be changeda little according to the reading rate, the DC bias magnetic field to be applied, and kinds of a reading device, and is preferably 1-30% of the saturation magnetization of the layer 3. For example, when information is read out at 1000m/sec while 100G bias magnetic field is applied, the layer is magnetized by a DC magnetic field of about 1.5kG. The noise from the card edge is thereby diminished.