| 摘要 |
<p>PURPOSE:To prevent the forgery of printed matter such as securities or an ID card by forming a colorant layer developing a color by short-time heating and discoloring by long-time heating on an arbitrary support in a shape of a character, a mark or a figure. CONSTITUTION:A support for forming a colorant layer may be composed of arbitrary material quality but a sheet like article having 10 - 1,000mum thickness such as paper, a plastic sheet or a plastic card is usually selected. Since it is necessary that the colorant layer develops a color when the real layer of printed matter is judged and can keep a developed color state for a time sufficient to judge, one developing a color within a short time by heating is used. Further, it is necessary to erase the developed color by long-time heating in order to erase the color if desired after judgement to restore the colorant layer to the state before judgement. As a colorant, a mixture of a leuco dye and a certain kind of a compound (color developing and erasing agent) can be used. The colorant layer is formed, for example, by dissolving or dispersing the color developing and erasing agent, the leuco dye and a resin binder in water or an org. solvent and printing a support with the obtained solution or dispersion.</p> |
