| 摘要 |
<p>A method of producing a certificate on a substrate which is difficult to reproduce using color copiers including the steps of printing a first portion of the certificate in a first color and printing the second portion of the certificate in a second color, wherein the first and second portions have substantial color contrast in the original and, when reproduced using conventional color copiers, have substantially the same color. Preferably, the step of printing the second portion includes printing with a fluorescent ink.</p> |
