Method for printing paper money, negotiable instruments and the like incorporating marks invisible to the naked eye but automatically revealable in the event of reproduction by photocopying machine

摘要

The method comprises the preparation of a first film 1, 101 having transparent marks 2, 102 on a dark ground 3, 103 and of a second film 5, 11 having the same marks 6, 12 in a medium or dark colour on a transparent ground 7, 13. The first film 1, 101 is then printed using a first ink of predetermined colour and of an intensity such as to produce a printed ground 4, 10 of desired colour and intensity. Finally the second film 5, 11 is printed on the first print 40, 42 using a second ink of the same colour as the first but of a different intensity such as to produce printed marks apparently of the same colour and of the same intensity as the printed ground 4, 10 and therefore not visually distinguishable from the latter, but nevertheless revealable against the said ground in the event of reproduction on a photocopying machine sensitive to the different intensities of the printing inks. (Fig. 5) IMAGE