| 摘要 |
PROBLEM TO BE SOLVED: To secure high productivity in continuous supply of a coated type magnetic recording medium and to suppress remnant magnetization of the whole part of the magnetic recording medium wound around a reel to be the min. by performing demagnetization of the magnetic recording medium under the state of its winding around the reel by applying AC magnetic fields in parallel to the reel surface but in different four directions, respectively. SOLUTION: A demagnetizing device 1 is arranged with z-direction and 1st-4th horizontal direction demagnetizing coils Cz , Cx , Cy , Ca and Cb for generating their respective AC magnetic fields Hz , Hx , Hy , Ha and Hb on 1st and 2nd conveyors 2a and 2b in an L-shaped pattern. The AC magnetic fields Hz is >=2,080 Oe in the perpendicular direction at 50 Hz, and the other AC magnetic fields Hx , Hy , Ha and Hb are >=2,000 Oe in the direction of about 45±3 degrees to each other at 50 Hz. As the magnetic recording medium, a magnetic tape coated with a magnetic coating material on its nonmagnetic film is cut into 1/8 in. and is wound with its length 2,160 m around the reel having a diameter of 11.4 cm, and is demagnetized by the demagnetizing device 1. By this method, the demagnetizing efficiency is enhanced without generating noise of >=-30 dB at a moving speed of 9 m/min of the conveyors 2.
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