Protection element for protecting printed matter, particular for digital printing

摘要

The protection element has an array of individual printing areas printed with different grayscales. A defined portion of the printing areas is printed by color-passers of basic printing inks, such as dark gray, magenta, yellow and black. The remaining portion is printed by gray shading formed from a black ink. The array appears as a composite pattern formed by a scale of different grayscales in a visible part of a spectrum. The printing areas have a different absorption profile in an infrared area of the spectrum.