Low VOC, low viscosity UV cationic radiation-cured ink-jet ink system

Ink-jet inks need to be very low in viscosity to transport the ink through the jet nozzle as well as for drop formation and integrity. The objective of this project was to demonstrate UV-cured systems for ink-jet inks and coatings with zero volatile organic compounds and very low viscosity. Cycloaliphatic epoxy systems were selected as binders of choice for this project due to their low viscosity and ability to be cured using UV-cationic photoinitiators. UV-curable coatings and inks with zero VOC and less than 10 cPs viscosities were formulated using exempt solvent acetone and vinyl cyclohexene diepoxide. UV-curable inks with up to 10% black dye were formulated. Rapid cure was achieved through the use of aryl sulfonium salts of hexafluorophosphoric acid. The presence of dye inhibited the reaction, but adequate cure of dyed formulations was achieved by increasing the concentration of the photoinitiator.