Color-shifting effects when printing with triadic inks on multilayer packaging made of transparent polypropylene film

Color reproduction on transparent multilayer films has a wide range of applications in the packaging production. In case of using multi-layer films as decorative or protective elements in packaging production, deviations may occur in color reproduction process due to the pleochroism in multilayer polymeric materials. The purpose of the work is Determination of the conditions of the color effect and measuring the parameters of it in the passing polarized light on film materials with the effect of pleochroism. The object of the study was the model Stoletov pile 77 cm long, 40 cm wide, consisting of 13 layers of polypropylene. Magenta and yellow ink layers were applied to the considered sample in the form of stripes by jet printing UV-curing inks and subsequent photofixation of the examinations was studied. The color difference Δε was calculated by processing photos in the Paint 3D program, followed by the translation of color coordinates from the RGB color space into the Lab system. Subsequently, the δε was calculated between the original sample and the sample placed under the Stoletov pile between two polarized films. The results of the work were the establishment of qualitative and quantitative differences in the color of the translucent layers of CMYK on the multi -layer film of polypropylene in the natural and polarized light, as well as the determination of the maximum calculated difference achieved for yellow with natural and polarized lighting under 12 layers of the Model pile, the maximum difference between the Cian color with the density of filling the halftone dot of the print 50%, reached under 6 layers of the model pile, and the maximum difference between the magenta sample with the density of filling the halftone dot 50%reached under 8 layers of the model pile.