Patent ID: 6494490
Filing Date: 2002-12-17
Classification: B41M

Abstract:
In a process for producing a photoluminescent printed polychromatic image (8) invisible under illumination in visible light and visible under illumination by at least one source (14) of invisible light, comprising:choosing or producing by subtractive synthesis an original polychromatic image (1), visible in visible light, producing and recording at least one set of at least three images, known as filtered images (6a, 6b, 6c), by filtering the original image (1), printing separately one after the other and one above the other at least one set of at least three images, known as printed images (8a, 8b, 8c), by using and reproducing respectively one of the filtered images (6a, 6b, 6c), with a printing composition containing a photoluminescent pigment, the different photoluminescent pigments of the different printed images of the same set emitting, under illumination by at least one source (14) of invisible light, colors capable of forming all the colors of the visible spectrum by additive synthesis; the improvement comprising: producing filtered images, known as monochromatic filtered images (6a, 6b, 6c), by filtering the original image (1) in a spectral pass-band lower than or equal to 15 nm centred on a wavelength, known as the filtering wavelength, chosen from the wavelengths of at least three fundamental colors, the different filtering wavelengths of the monochromatic filtered images being distinct in pairs and being such as to enable all the colors of the visible spectrum to be formed by additive synthesis, each of these filtering wavelengths being at least approximately equal to a wavelength of an emission peak of a photoluminescent pigment under illumination by at least one source (14) of invisible light, and printing each printed image, known as the monochromatic printed image (8a, 8b, 8c), by using and reproducing one of the monochromatic filtered images (6a, 6b, 6c) with a printing composition containing a photoluminescent pigment having an emission peak wavelength under illumination by at least one source (14) of invisible light, which is at least approximately equal to the filtering wavelength used for obtaining the said monochromatic filtered image (6a, 6b, 6c).