Systems and Methods For Printing Patterns Using Near Infrared Upconverting Inks

A system for generating a security pattern on a substrate without post-processing after printing, comprising:

• a. an upconverting ink for converting NIR excitation to shorter wavelength luminescence, wherein the upconverting ink comprises 0.1-15 wt % Tm and Er-based nanocrystals, wherein the nanocrystals are capped with ligand, and wherein the ink is formed by mixing the nanocrystals with a polymer in a solvent capable of dissolving the polymer and a co-solvent for controlling ink print quality;
• wherein the co-solvent constitutes 0.1 to 50 vol % of the solvent;
• b. an ink printer for printing the upconverting ink onto the substrate in a coded color pattern, wherein the coded color pattern comprises primary and secondary colors, wherein the secondary colors are produced by controlling overlap of two or three of the primary colors;
• and
• c. a material coating the coded color pattern to block one or more spectrums of light while passing NIR light;
• d. wherein the security pattern is produced or stabilized without using post-processing, such as photo-masking photolithography, chemical development, or heat treatment;
• e. wherein an excitation power density is set corresponding to the coded color pattern for revealing the security pattern, wherein a change in the excitation power density results in a shift in hue of the coded color pattern;
• f. wherein the coded color pattern is exposed to NIR light at the set excitation power density to reveal the security pattern from the coded color pattern;
• wherein the coded color pattern depends on the excitation power density, and the overlap of two or three of the primary colors, whereby the coded color pattern can only be produced using the excitation power density corresponding specifically to the coded color pattern of the one or more color compositions.

A system for generating security patterns on a substrate without post-processing after printing, comprising:

• a. an upconverting ink having at least 0.1-15 wt % Tm and Er-based nanocrystals capped with a ligand, and wherein the ink is formed by mixing the nanocrystals with a polymer in a solvent capable of dissolving the polymer and a co-solvent for controlling ink print quality, wherein the co-solvent constitutes 0.1 to 50 vol % of the solvent, wherein the upconverting ink converts NIR excitation to shorter wavelength luminescence and;
• b. an ink printer for directly depositing the ink onto the substrate in a coded color pattern of one or more color compositions, wherein the coded color pattern is indiscernible under ambient light and discernable with an excitation power density, wherein the coded color pattern comprises primary and secondary colors forming one or more color compositions, wherein the secondary colors are produced by controlling overlap of two or three of the primary colors;
• and
• c. a material coating the coded color pattern to block one or more spectrums of light while passing NIR light;
• d. wherein the security pattern is produced or stabilized without using post-processing, such as photo-masking photolithography, chemical development, or heat treatment;
• e. wherein the coded color pattern is exposed to NIR light having the corresponding excitation power density to decode the coded color pattern for revealing the security pattern, wherein the coded color pattern depends on the excitation power density, and the overlap of two or three of the primary colors, whereby the coded color pattern can only be produced using the excitation power density corresponding specifically to the coded color pattern of the one or more color compositions;
• and
• f. wherein the coded color pattern is viewed from the security pattern.