| 摘要 |
PURPOSE:To discriminate surely between true and false and to prevent surely forgery by forming the magnetic recording layer with the upper lower-coercive force magnetic recording layer and the lower high-coercive force magnetic recording layer. CONSTITUTION:The magnetic recording layer 2 consists of the upper low-coercive force magnetic recording layer 2A and the lower high-coercive force magnetic recording layer 2B on a base material 1. After true information is written on the high-coercive force magnetic recording layer 2B, false information is written on the low-coercive force magnetic recording layer 2A. Nevertheless, the recording layer of true information is not affected by the succeeding writing, because the coercive force of the true information recording layer is high. When the cards are read by a conventional reader, the overlap of the true information and the false information is read, and the true information can not be discriminated. After the false information written on the low-coercive force magnetic recording layer 2A is erased, the true information written on the high- coercive force magnetic recording layer 2B is read. Consequently, the true information is never erased by the electric current for the low-coercive force, since the coercive force of the true information recording layer is high.
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