Jet drop printing process utilizing a radiation curable ink

Claim 1

A jet drop printing process utilizing a radiation curable jet printing ink, comprising: ejecting at high speed from an orifice or orifices a radiation curable ink composition comprising a mixture of (a) 5-80% of a low molecular weight multifunctional ethylenically unsaturated material which will polymerize and cure upon irradiation, (b) 0-90% of a low molecular weight monofunctional ethylenically unsaturated material for viscosity control, cured film flexibility and bond strength, (c) 0-15% of a reactive synergist to promote curing efficiency, (d) 0.2-10% of a solvent dye colorant which does not interfere with the curing efficiency, (e) 0.5-15% of an oil soluble salt to impart conductivity, (f) 0.2-20% of a photoinitiator, and (g) 0-30% of an organic polar solvent compatible with said mixture, said radiation curable ink having a viscosity of less than about 15 centipoise, a resistivity of approximately 50-5000 ohm-cm, and a surface tension of approximately 20-70 dynes/cm so that the stream of said ink composition issuing from said orifice or orifices breaks into droplets, passing said stream of droplets through a charge ring to thereby differentially charge said droplets, selectively deflecting said differentially charged droplets and directing them toward a paper substrate positioned so as to receive a portion of said differentially charged droplets, depositing at least a portion of said droplets in a pattern on said paper substrate, and passing said substrate having said pattern deposited thereon under a radiation source for a sufficient period of time to cure said radiation curable jet printing ink whereby there is formed on said substrate a pattern which is light absorptive at infrared wavelengths, smear resistant and waterproof.