UV-curable coatings and methods for applying UV-curable coatings using thermal micro-fluid ejection heads

1. An aqueous ultraviolet-curable fluid composition for use in a micro-fluid ejection device, comprising:

a mixture of polymerizable poly-functional compounds including

a first compound having a high viscosity range of greater than about 150 cps at 25° C.,

a second compound having a medium viscosity range of from about 40 to about 80 cps at 25° C., and

a third compound having a low viscosity range of less than about 4 cps at 25° C., wherein the mixture of polymerizable poly-functional compounds is approximately from about 15 to about 30% by weight of the ultraviolet-curable fluid;

a colorant being from about 2 to about 8% by weight of the ultraviolet-curable fluid for a pigment based colorant and from about 3 to about 6% by weight of the ultraviolet-curable fluid for a dye based colorant;

a photo-initiator being from about 0.1 to about 5% by weight of the ultraviolet-curable fluid, wherein the photo-initiator is substantially soluble in at least one of the polymerizable poly-functional compounds;

a humectant being from about 12 to about 25% by weight of the ultraviolet-curable fluid, wherein the humectant has a boiling point of greater than about 200° C. and a viscosity of less than about 13 cps; and

water being from about 40 to about 50% by weight of the UV curable fluid wherein the fluid composition is substantially devoid of volatile organic carrier fluids.

2. The aqueous ultraviolet-curable fluid composition of claim 1 , wherein the mixture of polymerizable poly-functional compounds comprise;

trimethylolpropane triacrylate as the first compound having a functionality of three and a viscosity of 225 cps at 25° C.;

polyethylene glycol-400 diacrylate as the second compound having a functionality of two and a viscosity of 57 cps at 25° C.; and

N-methyl-2-pyrrolidone as the third compound.

3. The aqueous ultraviolet-curable composition of claim 2 , wherein the mixture of polymerizable poly-functional compounds includes:

trimethylolpropane triacrylate in an amount of 4% by weight of ultraviolet-curable fluid;

polyethylene glycol-400 diacrylate in an amount of 8% by weight of ultraviolet-curable fluid; and

N-methyl-2-pyrrolidone in an amount of 10% by weight of ultraviolet-curable fluid.

4. The aqueous ultraviolet-curable fluid composition of claim 2 , wherein the composition has a viscosity of 3.24 cps at 45° C.

5. The aqueous ultraviolet-curable fluid composition of claim 2 , wherein the composition has a thermal diffusivity value of about 0.12 μm 2 per microsecond.

6. The aqueous ultraviolet-curable fluid composition of claim 2 , wherein the composition has a superheat limit of about 292° C. at a heater interface.

7. The aqueous ultraviolet-curable fluid composition of claim 2 , wherein the composition has a spread factor (D*/d) of about 1.9 on a non-porous substrate, wherein D* represents a spot diameter formed by a fluid droplet on the substrate and d represents a diameter of the fluid droplet prior to impact on the substrate.

8. The aqueous ultraviolet-curable fluid composition of claim 1 , wherein the photo-initiator is substantially soluble in the first compound and present in an amount of about 4% by weight of ultraviolet-curable fluid.

9. The aqueous ultraviolet-curable fluid composition of claim 1 , wherein the humectant comprises diethylene glycol monobutyl ether and is present in an amount of about 20% by weight of the ultraviolet-curable fluid.

10. The aqueous ultraviolet-curable fluid composition of claim 1 , wherein the surfactant is present in an amount of about 1% by weight of the ultraviolet-curable fluid.

11. The aqueous ultraviolet-curable fluid composition of claim 1 , wherein the colorant is a pigment based colorant and present in an amount of about 5% by weight of the ultraviolet-curable fluid.

12. An ultraviolet-curable ink composition comprising:

a mixture of polymerizable poly-functional compounds including

a first compound having a high viscosity range of greater than about 150 cps at 25° C.,

a second compound having a medium viscosity range of from about 40 to about 80 cps at 25° C., and

a third compound having a low viscosity range of less than about 4 cps at 25° C., wherein the mixture of polymerizable poly-functional compounds is approximately from about 15 to about 30% by weight of ultraviolet-curable fluid composition;

a colorant being from about 2 to about 8% by weight of the ultraviolet-curable fluid for a pigment based colorant and from about 3 to about 6% by weight of the ultraviolet-curable fluid for a dye based colorant;

a photo-initiator being from about 0.1 to about 5% by weight of the ultraviolet-curable fluid, wherein the photo-initiator is substantially soluble in at least one of the polymerizable poly-functional compounds;

a humectant being from about 12 to about 25% by weight of the ultraviolet-curable fluid, wherein the humectant has a boiling point of greater than about 200° C. and a viscosity of less than about 13 cps; and

a water being from about 40 to about 50% by weight of the UV curable fluid.

13. The ultraviolet-curable ink composition of claim 12 , wherein the mixture of polymerizable poly-functional compounds includes:

trimethylolpropane triacrylate as the first compound having a functionality of three and aviscosity of 225 cps at 25° C.;

polyethylene glycol-400 diacrylate as the second compound having a functionality of two and a viscosity of 57 cps at 25° C.; and

N-methyl-2-pyrrolidone as the third compound.