Printing Ink

Abstract

This invention relates to a radiation-curable ink-jet ink having a viscosity of 30 mPas or less at 25° C., the ink comprising: at least two monofunctional (meth)acrylate monomers which comprise a cyclic monofunctional (meth)acrylate monomer and 2-(2-ethoxyethoxy)ethyl acrylate; a monofunctional monomer selected from an N-vinyl amide, and N-acryloyl amine or a mixture thereof; a multifunctional (meth)acrylate monomer; a polymerisable (meth)acrylate oligomer; a radical photoinitiator; and a colouring agent. The ink is preferably used in reel-to-reel printing and in printing where the substrates are stacked.

What is claimed is: 
     
         1 . A radiation-curable ink-jet ink substantially free of water and volatile organic solvents, having a viscosity of 30 mPas or less at 25° C., the ink comprising:
 at least two monofunctional (meth)acrylate monomers which comprise 10 to 25 wt % of a cyclic monofunctional (meth)acrylate monomer and 5 to 15 wt % of 2-(2-ethoxyethoxy)ethyl acrylate; 
 10 to 25 wt % of a monofunctional monomer selected from an N-vinyl amide, an N-acryloyl amine or a mixture thereof; 
 5 to 15 wt % of a multifunctional (meth)acrylate monomer; 
 5 to 35 wt % a polymerisable (meth)acrylate oligomer; 
 a radical photoinitiator; and 
 a colouring agent, wherein the percentages by weight are based on the total weight of the ink. 
 
     
     
         2 . An ink-jet ink as claimed in  claim 1 , wherein the total amount of the at least two monofunctional (meth)acrylate monomers and the at least one monofunctional monomer selected from an N-vinyl amide, an N-acryloyl amine or a mixture thereof is at least 25 wt % based on the total weight of the ink. 
     
     
         3 . An ink-jet ink as claimed in  claim 1 , wherein the cyclic monofunctional (meth)acrylate monomer is selected from phenoxyethyl acrylate (PEA), cyclic trimethylolpropane formal acrylate (CTFA), isobornyl acrylate (IBOA), tetrahydrofurfuryl acrylate (THFA) and mixtures thereof. 
     
     
         4 . An ink-jet ink as claimed in  claim 3 , wherein the cyclic monofunctional (meth)acrylate monomer is phenoxyethyl acrylate (PEA). 
     
     
         5 . An ink-jet ink as claimed in  claim 1 , wherein the monomer selected from an N-vinyl amide, an N-acryloyl amine or a mixture thereof, is selected from N-vinyl caprolactam (NVC), N-vinyl pyrrolidone (NVP), N-acryloylomorpholine (ACMO) and mixtures thereof. 
     
     
         6 . An ink-jet ink as claimed in  claim 1 , wherein the multifunctional (meth)acrylate monomer is a difunctional monomer. 
     
     
         7 . An ink-jet ink as claimed in  claim 1 , wherein the polymerisable (meth)acrylate oligomer is has a molecular weight from 450 to 4,000. 
     
     
         8 . An ink-jet ink as claimed in  claim 1 , wherein the polymerisable (meth)acrylate oligomer has a degree of functionality from 2 to 6. 
     
     
         9 . An ink-jet ink as claimed in  claim 1 , wherein the ink is substantially free of acyclic-hydrocarbon monofunctional (meth)acrylate monomer. 
     
     
         10 . A method of reel-to-reel ink-jet printing, comprising printing the ink-jet ink as claimed in  claim 1  on to a substrate and curing the ink as the substrate is caused to move from a substrate reel to a receiving reel. 
     
     
         11 . A method of ink-jet printing, comprising providing an ink-jet printer with a plurality of substrates, printing the ink-jet ink as claimed in  claim 1  on to a plurality of the substrates, curing the ink on each of the substrates to produce printed substrates, and stacking the printed substrates. 
     
     
         12 . An method as claimed in  claim 11 , wherein the printer contains a substrate-storage facility having a plurality of substrates held therein. 
     
     
         13 . A method as claimed in  claim 11 , wherein the printer is a flat-bed ink-jet printer. 
     
     
         14 . A method as claimed in  claim 10  wherein the substrate is a polyolefin substrate. 
     
     
         15 . A substrate having the ink-jet ink as claimed in  claim 1  printed thereon. 
     
     
         16 . A substrate as claimed in  claim 15 , wherein the substrate is a polyolefin substrate.