Color Reproduction Of Full-color Fluorescent Image And Its Application In Anti-counterfeiting Packaging

Photochromic,a good choice of anti-counterfeiting materials,can achieve anti-fake function and It has a special stimulation for human eyes.Up-conversion nanoparticles(UCNPS)have many advantages such as low toxicity and long life of fluorescent,good light stability and luminescence spectra with narrow,no biological auto-fluorescence interference and the large anti-stokes displacement,the depth of light penetration is strong.Therefore,it is considered as one of the most potential photo luminescent materials and has a broad application prospect in biomedical,solar cells,solid laser,sensors,three-dimensional display,in vivo imaging,security and other fields.In order to expand the application of up-conversion materials in the packaging field,the up-conversion fluorescent ink was prepared by intaglio printing to realize anti-counterfeiting.Fluorescent security elements are mostly displayed as halftone and single color printing.Therefore,color characteristics and full-color imaging of light-emitting inks on rare earth conversion become the focus of this study.In this paper,the up-conversion luminescent materials were prepared into water-based up-conversion fluorescent inks with high intensity,high dispersion and uniform printing,good adhesion and strong adhesion.The application of the material in packaging field was expanded.The effect of dot area ratio on the luminescence performance of fluorescent ink was discussed systematically.Finally,the color fluorescence image combining with the intaglio printing technology was applied to the anti-counterfeiting field by establishing the spectral prediction model and the halftone screening algorithm based on dot enlargement.First of all,the water-borne urethane coated up-conversion phosphor luminescent materials were synthesized by hydrothermal method,and the photogravure printing process was combined to prepare the phosphor luminescent ink for water-borne on-conversion phosphor luminescent inks.Then,the color rendering performance of three-color fluorescent inks was studied.The results show that the three-base-conversion luminescent materials have good dispersion in the aqueous polyurethane system and do not affect the luminescent effect of the three-base-color conversion luminescent materials.Also,the ink has good adhesion,can meet the needs of gravure printing.Secondly,we explored the multicolor reproduction and color control of three-color on-conversion fluorescent ink.And the effect of dot area ratio of overprint color sequence on the reappearance performance of upconversion fluorescent ink was also systematically discussed.The results indicated that the up-conversion fluorescent ink is different from the downconversion material in that there is no fluorescence quenching phenomenon,but under the circumstance of dot superposition,dot expansion could be generated to weaken the fluorescence effect.There is a linear relationship between excitation light power and luminescence intensity of three-color fluorescent ink.Smooth paper surface is conducive to fluorescent ink luminescence.The up-conversion fluorescence spectrum of overprint color blocks is not the direct addition of the fluorescence emission spectrum of the corresponding primary color fluorescent inks.In addition,the change of printing color sequence will have a great impact on the comprehensive performance of multicolor fluorescence emission.Then,we use the above three primary color on the conversion of fluorescent ink,based on the principle of color-light-color imaging to obtain fluorescent color image.The fluorescence spectrum prediction model aims to establish the relationship between the dot area ratio of fluorescent ink and the fluorescence emission spectrum and predict the corresponding spectral output according to the input Chroma value.In this paper,a prediction model of fluorescence spectrum was established by principal component analysis(PCA).The results show that the fluorescence emission spectrum reconstructed by the model is highly consistent with that of the corresponding sample.In the last,periodic function was introduced to improve dot expansion based on am screening algorithm,and the application of fluorescent color image in anti-counterfeiting packaging was explored and designed by using gravure printing technology.Test results show that the optimized halftone algorithm has a positive effect on the improved fluorescence emission.The application potential of fluorescent color image in anticounterfeiting packaging is huge,it not only has good color reproduction effect,can improve the quality of anti-counterfeiting products,and has a good market prospect.