| 摘要 |
PURPOSE:To eliminate the possibility of letting out a secret, by a method wherein a negative pattern formed by an ink layer remaining in an ink sheet is perfectly decomposed so that its shape is destroyed. CONSTITUTION:A heat roller 38 rotatably abuts on an ink sheet 10 in the width direction thereof. The ink sheet 10 is held between the heat roller 38 and a roller 40 under pressure. In the heat roller 38 with a built-in heat source, the periphery abutting on an ink layer 14 of the ink sheet 10 is heated up to a temperature enough to melt or sublimate the ink layer 14 due to the heat of the heat source. Therefore, the ink layer 14 melts when the ink sheet 10 abuts against the heat roller 38 ; moreover, an ink is scattered thereabouts as if smashed because the ink sheet 10 is depressed. In this manner, a negative pattern 34 formed clearly in the ink layer 14 is blurred and decomposed at last.
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