INK COMPOSITION FOR MAKING A CONDUCTIVE SILVER STRUCTURE

• US 20150004325A1
• Filed: 12/20/2012
• Published: 01/01/2015
• Est. Priority Date: 12/23/2011
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois
• Original Assignee: Board of Trustees of The University of Illinois
• Inventors: Lewis, Jennifer A., Walker, Steven B.
• Granted Patent: US 9,469,773 B2
• Time in Patent Office: Days
• US Class Current: 427/469
• CPC Class Codes: B05D 1/005 Spin coating
• CPC Class Codes: B05D 1/04 involving the use of an electrostatic field B05D1/025 and B05D1/14 take precedence
• CPC Class Codes: B05D 1/18 performed by dipping
• CPC Class Codes: C09D 11/52 Electrically conductive inks
• CPC Class Codes: C23C 18/161 from plating step, e.g. inkjet
• CPC Class Codes: C23C 18/168 Control of temperature, e.g. temperature of bath, substrate
• CPC Class Codes: C23C 18/1692 Heat-treatment
• CPC Class Codes: C23C 18/42 Coating with noble metals
• CPC Class Codes: C23C 18/44 using reducing agents
• CPC Class Codes: C23C 26/02 applying molten material to the substrate

Abstract

An ink composition for making a conductive silver structure comprises a silver salt and a complex of (a) a complexing agent and a short chain carboxylic acid or (b) a complexing agent and a salt of a short chain carboxylic acid, according to one embodiment. A method for making a silver structure entails combining a silver salt and a complexing agent, and then adding a short chain carboxylic acid or a salt of the short chain carboxylic acid to the combined silver salt and a complexing agent to form an ink composition. A concentration of the complexing agent in the ink composition is reduced to form a concentrated formulation, and the silver salt is reduced to form a conductive silver structure, where the concentrated formulation and the conductive silver structure are formed at a temperature of about 120° C. or less.

Claims

1. An ink composition for making a conductive silver structure, the ink composition comprising:

a silver salt; and

a complex of (a) a complexing agent and a short chain carboxylic acid or (b) a complexing agent and a salt of a short chain carboxylic acid.

2. The ink composition of claim 1, wherein the short chain carboxylic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, pentanoic acid, and butyric acid.

3. The ink composition of claim 2, wherein the short chain carboxylic acid is formic acid.

4. The ink composition of claim 1, wherein the complexing agent is selected from the group consisting of an alkyl amine and ammonia.

5. The ink composition of claim 4, wherein the alkyl amine is selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, and amylamine.

6. The ink composition of claim 1, wherein the silver salt is selected from the group consisting of silver acetate, silver formate, silver carbonate, silver fluoride, silver nitrate, silver nitrite, silver chloride, silver bromide, silver iodide, silver phosphate, and silver oxide.

7. The ink composition of claim 1, further comprising methylenediamine or ethylenediamine.

8. The ink composition of claim 1, further comprising a solvent selected from the group consisting of ethanol, butanol, propylene glycol, water, and combinations thereof.

9. The ink composition of claim 1, further comprising elemental silver, wherein the elemental silver is formed by reduction of a portion of the silver salt.

10. The ink composition of claim 9, wherein the ink composition has a viscosity of between about 1 mPa·

s and about 10⁶ mPa·

s under low shear conditions.

11. The ink composition of claim 1, wherein the silver salt is silver acetate,

wherein the complexing agent is selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, amylamine, and ammonia, and

wherein the short chain carboxylic acid is formic acid.

12. The ink composition of claim 11, further comprising ethylenediamine.

13. The ink composition of claim 11, further comprising a solvent selected from the group consisting of ethanol, butanol, propylene glycol, water, and combinations thereof.

14. An ink composition for making a conductive silver structure, the ink composition comprising:

a silver salt;

a complexing agent for dissolving the silver salt, the complexing agent not being a reducing agent for the silver salt; and

an acid for complexing with the complexing agent and reducing the silver salt;

wherein each of the complexing agent and the acid has a boiling point of about 120°

C. or less.

15. The ink composition of claim 14, further comprising a solvent having a boiling point of about 120°

C. or less.

16. A method of making a conductive silver structure, the method comprising:

combining a silver salt and a complexing agent;

adding a short chain carboxylic acid or a salt of the short chain carboxylic acid to the combined silver salt and complexing agent to form an ink composition;

reducing a concentration of the complexing agent in the ink composition to form a concentrated formulation; and

reducing the silver salt to form a conductive silver structure,

wherein the concentrated formulation and the conductive silver structure are formed at a temperature of about 120°

C. or less.

17. The method of claim 16, wherein the temperature is about 90°

C. or less.

18. The method of claim 16, wherein the short chain carboxylic acid or the salt of the short chain carboxylic acid is not added until after the silver salt is dissolved in the complexing agent.

19. The method of claim 16, further comprising depositing the ink composition onto a substrate.

20. The method of claim 19, wherein the ink composition is deposited onto the substrate by a method selected from the group consisting of spray processing, dip coating, spin coating, inkjet printing and e-jet printing.

21. The method of claim 16, further comprising depositing the concentrated formulation onto a substrate.

22. The method of claim 21, wherein the concentrated formulation is deposited onto the substrate by a method selected from the group consisting of screen printing, roll-to-roll processing, and direct ink writing.

23. The method of claim 16, wherein the conductive silver structure comprises a resistivity of about 2×

10<sup>−

5</sup> Ω

cm or less.