| 摘要 |
<p>PURPOSE:A highly stable, black marking agent which is capable of being easily eliminated or decolorized, prepared by mixing red and blue components which are pH indicators with a yellow component which is an acid dye. CONSTITUTION:A marking agent comprising a red pigment, a blue pigment, a yellow pigment and an aqueous medium, wherein said red pigment and blue pigment are pH indicators which develop colors in an alkaline range, said yellow pigment is an acid dye and said aqueous medium is an alkaline medium. The indicators which are used are preferably dyes which are colorless or pale yellow in a neutralacidic range and red and blue in an alkaline range, and which have a carboxyl group and/or a sulfonic group in their structures. As the yellow pigment, an acid dye which has a carboxyl group and/or sulfonic group in its structure is preferably used.</p> |
