Red fluorescent inks that change properties after being processed

摘要

Ink-jet inks and methods for security and anti counterfeiting utilities are described. The inks are fluorescent with a particular characterizing emission when illuminated with ultraviolet or other interrogating light and then fluoresce with a different characteristic upon illumination with bright light such as from a copying machine. The inks comprise a fluorescent dye, an aqueous liquid vehicle comprising water and organic solvents in sufficient amounts to achieve an ink viscosity and surface tension effective for application of the ink to a substrate in a predetermined pattern by ink-jet printing, wherein the inks are characterized in that after exposing under Xenon lamp of 3,150,000 J/m², the fluorescent strength of the ink diluted 100 times existing between about 500 nm and about 700 nm by excitation of ultraviolet radiation, decreases by at least about 50%. Desirably, the absorbance of the ink is between about 400 nm and about 600 nm and the ink loses fluorescence when subjected to ultraviolet radiation and/or visible radiation. The examples illustrate inks comprised of a dye selected from the group consisting of C.I. Acid Red 52, C.I. Acid Red 87, C.I. Acid Red 92 and C.I. Acid Red 1; water; and organic, polar solvent(s).