Red fluorescent inks for bar code printing

摘要

New ink-jet printing inks provide red printed images with high-intensity fluorescence emission and are capable of printing images that can be used for high density bar code applications (2D bar codes) having high readability. The inks are aqueous and capable of producing machine-readable markings exhibiting fluorescence when exposed to fluorescent-exciting radiation. They exhibit a peak of fluorescence between about 500 nm and about 700 nm and a fluorescent strength of the ink diluted by 100 times of more than about 70 by excitation of ultraviolet radiation. The inks exhibit a peak of absorbance of between about 400 nm and about 600 nm, and an absorbance of the ink diluted by 100 times and measured in 1 mm cell of more than about 0.6. The preferred inks are characterized by a color of the ink diluted by 100 times with water and measured in 1 mm cell is t L*: about 80±10, a*: about 45±20, b*: about 20±35 and a color of the printed image of L*: about 65±10, a*: about 55±10, b*: about 5±20. Compositionally, the preferred inks are comprised of a dye selected from the group consisting of C.I. Acid Red 52, C.I. Acid Red 87 and C.I. Acid Red 92. In some preferred inks, the absorption coefficient to paper is between about 0 mL/m²sec^1/2 and about 130 mL/m²sec^1/2 by the measurement of the Bristow method.