| 摘要 |
PURPOSE:To enable a confidential text or an ID number to be read only when X rays or the like are used, by providing a copying sheet comprising a carbon transfer sheet having a carbon ink layer and a carbon receiving sheet for forming ink images which can be read only on a video system using soft X rays or supersoft X rays. CONSTITUTION:A mixture of 40 parts of calcium tungstate and 10 parts of liquid paraffin is kneaded by a triple roll mill, and then 5 parts of paraffin wax and 1 part of carnauba wax are added to the kneaded mixture, followed by agitating sufficiently while heating to 100 deg.C to prepare a carbon ink. While heating the carbon ink to 90 deg.C, the ink is applied to a copying paper by a carbon printing press to obtain a carbon transfer sheet. On the other hand, a carbon receiving sheet is obtained by subjecting a woodfree paper to printing and embossing. When the surface of the carbon receiving sheet printed with concealed characters which can not be read at all by the naked dyes is set on a SOFTEX video system, the characters can be clearly read. |
