Tailored ink for piston driven electrostatic liquid drop modulator

1. An ink composition comprising water, a solvent, a solvent-soluble dye, and a surfactant, wherein said ink exhibits a stable liquid microemulsion phase at a first temperature and a second temperature higher than the first temperature, wherein the first temperature is about 22° C. and the second temperature is between about 22° C. and about 60° C., and has a conductivity of at most about 200 μS/cm and a dielectric constant of at least about 60.

2. An ink composition according to claim 1 , wherein said ink has a conductivity of at most about 10 μS/cm and a dielectric constant of at least about 70.

3. An ink composition according to claim 1 , wherein the first temperature is about 22° C. and the second temperature is about 60° C.

4. An ink composition according to claim 1 , wherein the solvent has a high dielectric constant and is selected from the group consisting of 1-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, N-acetylethanolamide, N-ethylformamide, N-butylacetamide, formamide, N-propylpropanamide, N-ethylacetaniide, N-methylpropanamide, and N-methylformamide.

5. An ink composition according to claim 4 , wherein the solvent is 1-methyl-2-pyrrolidinone.

6. An ink composition according to claim 1 , wherein the surfactant has an Hydrophile-Lipophile Balance (HLB) value of from about 8 to about 19.

7. An ink composition according to claim 1 wherein the surfactant is selected from the group consisting of a polyoxyethylene alkyl ether, an ethoxylated alkyl phenol, a propyleneoxide-b-ethylene oxide, and a polyethylene glycol with secondary alcohols.

8. An ink composition according to claim 1 further comprising a humectant selected from the group consisting of tetramethylene sulfone, ethylene glycol, diethylene glycol, glycerol, 1-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, pentanol, benzyl alcohol, 1,2-pentanediol, 1,5-pentanediol, and high molecular weight diols and polyols.

9. An ink composition according to claim 1 , wherein the water is present in an amount of from about 60 to about 95 percent by weight.

10. An ink composition according to claim 1 , wherein the solvent is present in an amount of from about 2 to about 10 percent by weight.

11. An ink composition according to claim 1 , wherein the surfactant is present in an amount of from about 1 to about 10 percent by weight.

12. An ink composition according to claim 1 , wherein the solvent-soluble dye is present in an amount of from about 1 to about 10 percent by weight.

13. An ink composition according to claim 1 , wherein the water, the solvent, and the surfactant are present in relative amounts of about 85 percent by weight water, about 10 percent by weight solvent, and about 5 percent by weight surfactant.

14. An ink composition according to claim 1 , wherein the ink composition further comprises a humectant and the water, the solvent, the surfactant, and the humectant are present in relative amounts of about 80 percent by weight water, about 10 percent by weight solvent, about 5 percent by weight surfactant, and about 5 percent by weight humectant.

15. A method of making an ink composition for use in a microelectromechanical system-based fluid ejector comprising:

providing a solution comprising a solvent, a solvent-soluble dye, and a surfactant; and

adding said solution to water under conditions effective to produce an ink composition which exhibits a stable liquid microemulsion phase at a first temperature and a second temperature higher than the first temperature wherein the first temperature is about 22° C. and the second temperature is between about 22° C. and about 60° C., and has a conductivity of at most about 200 μS/cm and a dielectric constant of at least about 60.

16. A method of making an ink composition for use in a microelectromechanical system-based fluid ejector comprising:

providing a solution or dispersion comprising a dye or a pigment; and

adding to said solution or dispersion an additive which comprises a material that enhances dielectric permittivity and/or reduces conductivity under conditions effective to produce an ink composition having a conductivity of at most about 200 μS/cm and a dielectric constant of at least about 60.

17. A method according to claim 16 , wherein said additive is a co-solvent selected from the group consisting of ethylene glycol, diethylene glycol, glycerol, 1-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, N-acetyl ethanolainide, N-ethyl formamide, N-butylacetamide, formamide, N-propylpropanamide, N-ethylacetamide, N-methylpropanamide, and N-methylformamide.

18. A method according to claim 16 , wherein said additive is in the form of a particle and comprises a material selected from the group consisting of latex, titanium dioxide, alumina, and silica.

19. A method according to claim 16 , wherein said solution or dispersion is aqueous and said additive is a buffer selected from the group consisting of cyclohexylaminopropanesulfonic acid (CAPS), hydroxyethylpiperazine ethanesulfonic acid (HEPES), and hydroxyethylpiperazine propanesulfonic acid (HEPPS).

20. A method according to claim 16 , wherein said solution or dispersion is aqueous and said additive is diglycine or triglycine.

21. A method according to claim 16 , wherein said solution or dispersion is non-aqueous and said additive is selected from the group consisting of lecithin, lanolin, and linolenic acid.

22. A method according to claim 16 , wherein said additive is present in the ink composition in an amount from about 0.05 to about 25 percent by weight.

23. A method according to claim 16 , wherein said pigment is carbon black or a color pigment.

24. A method according to claim 16 , wherein said solution or dispersion further comprises a surfactant.