| 摘要 |
<p>Patterned security documents are known which have, incorporated into the pattern, a comparison area and a signalling area which tend to blend together without contrasting when perceived by the unaided human eye but photocopied images of which tend to contrast with one another in a photocopy of the original document, so as to identify the photocopy as a counterfeit. This is accomplished by printing lines in the comparison area and signalling area which are beyond the resolution capability of the unaided human eye at normal viewing range, the lines in one but not the other of the two areas being within the resolution capability of a photocopying machine. In accordance with the invention the orientation of the lines in the comparison area is at an angle, preferably about a right angle, to the orientation of the lines in the signalling area and the lines are printed of metallic ink or other suitable reflective substance. Preferably the metallic ink line pattern is applied to a substrate of a relatively light colour. <IMAGE></p> |
