| 摘要 |
A copy-protected printed product has a zone which is printed using at least two different printing screens 1, 2 using screen printing technology, but using the same colour. The printing screens 1, 2 differ in their screen angle from zero to 5 degree, in the percentage of the size of the screen points by 1 to 3 percentage points, and in the number of screen points along one side of a square centimetre by zero to 20. A warning symbol is printed in one screen 1. It is located in a zone which is printed with the other screen 2. Within the above screen limiting values, the warning symbol on the original is invisible, but appears clearly on a copy. A film for a printing machine has the different screens 1, 2 in order to image an indicator 3 for identifying copies. In a method for the automatic classification of a sheet as a copy, in one zone of an original an imprint with two screens in the same colour is made, their screen geometry being set to differ from each other within the abovementioned limits. <IMAGE> |
