FIELD: electrical engineering.
SUBSTANCE: printed security feature provided onto a printable substrate, which printed security feature includes a printed area, consisting of a plurality of adjacent rectilinear and/or curvilinear elements printed with a given spatial frequency. Rectilinear and/or curvilinear elements are printed with at least first and second inks, which exhibit the same or substantially the same optical appearance when illuminated with visible white light, such that the printed security feature produces a first graphical representation when illuminated with visible white light, at least first ink being an ink which responds to non-visible light excitation by producing a characteristic optical response differentiating the first ink from the second ink. Security feature produces a second graphical representation when illuminated with non-visible light, which second graphical representation exhibits a distinctive two-dimensional graphic element, which is revealed only when the security feature is illuminated with non-visible light. Inside boundaries of the distinctive two-dimensional graphic element, a part of the rectilinear and/or curvilinear elements is printed with a combination of the first and second inks, the rectilinear and/or curvilinear elements being subdivided, within said part, into first and second juxtaposed sections, which are respectively printed using first ink and using second ink. Outside the boundaries of the distinctive two-dimensional graphic element, portions of the rectilinear and/or curvilinear elements are printed with only one of the at least first and second inks. At least first and second inks are printed in register one with respect to the other, so that the boundaries of the distinctive two-dimensional graphic element are not visible when the printed security feature is illuminated with visible white light, and the distinctive two-dimensional graphic element only becomes visible when the security feature is illuminated with non-visible light.
EFFECT: printed security feature is provided on a printable substrate.
23 cl, 16 dwg
