PREVENTING UNAUTHORIZED COPYING OF DOCUMENTS

摘要

A document (1) carries indicia and at least one copy protection device (2). The copy protection device (2) comprises a marking separate from the indicia and defined by a pair of inks (3; 4-8) which present a continuous, substantially plain coloured area when viewed and illuminated under visible light, the presence of the different inks being substantially undetectable when the area is subjected to visible colour separation scanning. When the area is scanned at and/or illuminated under at least one wavelength outside the visible wavelength range a pattern is generated which is detectable, whereby the presence of this combination of properties indicates that a copying process should not be carried out.