Patent ID: 8362104

Claim:
Digital printing ink comprising pigments having a maximum particle size not more than 1 micron and lacking organic solvent, wherein the digital printing ink is produced by a method comprising: (a) dispersing pigments in a mixture comprising polymerizable monomers and oligomers, which includes polyol acrylate; (b) diluting the mixture with monofunctional and multifunctional acrylic monomers until a viscosity of between 10 and 30 centipoises is achieved, between 10% and 25% of total acrylic monomers are monofunctional acrylic monomers, isobornyl acrylate is among the monofunctional acrylic monomers, between 50% and 90% of total acrylic monomers are multifunctional acrylic monomers, and bifunctional and trifunctional acrylic monomers are among the multifunctional acrylic monomers; (c) introducing a photoinitiator system, which starts polymerization of the monomers and oligomers by irradiation with ultraviolet light, to the diluted mixture; and (d) filtering to retain particles bigger than 1 micron, thereby obtaining the digital printing ink lacking organic solvent as a result.