HIGH CONDUCTIVE WATER-BASED SILVER INK

• US 20110155812A1
• Filed: 09/07/2007
• Published: 06/30/2011
• Est. Priority Date: 09/08/2006
• Status: Active Grant

• Current Assignee: Sun Chemical Corporation
• Original Assignee: Sun Chemical Corporation
• Inventors: Klein, Dave, Rouse, Jason Hayden
• Granted Patent: US 8,709,289 B2
• Time in Patent Office: Days
• US Class Current: 235/492
• CPC Class Codes: C09D 11/52 Electrically conductive inks
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H05K 1/095 for polymer thick films, i.e. having a permanent organic polymeric binder
• CPC Class Codes: Y10T 428/24909 Free metal or mineral containing
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof

Abstract

Disclosed is a conductive composition which can be used to form an aqueous conductive ink with increased conductivity. A film of the dry ink having a thickness of 5 microns or less has a surface roughness of less than 1.5 times the surface roughness of a cellulosic-based substrate which it coats. The aqueous conductive composition contains conductive particles, preferably silver, an anionic wetting agent and a styrene-acrylic copolymer. The composition is highly conductive and requires reduced drying energy. In addition, it may be applied to low cost substrates by high speed printing processes.

Claims

1. A conductive composition which is water-based and when dry, a 5 micron or less layer on a cellulosic substrate has a ratio of surface roughness to substrate roughness of not more than 1.5.

2. The conductive composition of claim 1 having a sheet resistance of not more than 200 milliohm/square when dry and having a thickness of 5 micron or less.

3. The conductive composition of claim 1 having, when dry, a RFID antenna read range of at least 3 meters.

4. The conductive composition of claim 1 further comprising:

(a) conductive particles (b) styrene/(meth)acrylic copolymer

(c) an anionic wetting agent

(d) defoamer and

(e) water.

5. The conductive composition of claim 4, wherein the conductive particles comprise silver.

6. The conductive composition of claim 5, wherein the longest dimension of said silver particles is from about 100 nm and 50 micrometers.

7. The conductive composition of claim 6, wherein the longest dimension of said silver particles is from about 1 to 20 micrometers.

8. The conductive composition of claim 4, wherein the styrene/(meth)acrylic copolymer is a copolymer of styrene and an alkyl (meth)acrylate, optionally partly hydrolyzed or salified.

9. The conductive composition of claim 4, wherein the copolymer to water ratio is about 4 to 1 to 1 to 8.

10. The conductive composition of claim 4 wherein the styrene/(meth)acrylic copolymer comprises a blend with an alkyl (meth)acrylate copolymer.

11. The conductive composition of claim 10 wherein the alkyl moieties comprise at least one of ethyl, propyl, butyl, and hexyl.

12. The conductive composition of claim 4, wherein the anionic wetting agent is selected from the group consisting of alkali sulphosuccinate, alkali sulfosuccinate, and anionic polyacrylate copolymer.

13. The conductive composition of claim 4, wherein the anionic wetting agent is selected from the group consisting of dihexyl sulphosuccinate salt, di-2-ethylhexyl sulfosuccinate salt, and dioctyl sulfosuccinate salt.

14. The conductive composition of claim 4, further comprising at least one solvent selected from the group consisting of alcohols, amines, glycols, acetates, ethers, ketones, aldehydes, and amides.

15. The conductive composition of claim 5, where the silver is about 10 to 90% of the composition, the copolymer is about 2 to 50%, the defoamer is about 0.01 to 4%, and the anionic wetting agent is about 0.01 to 6% by weight.

16. The conductive composition of claim 15, where the silver is about 40 to 75% of the composition, the copolymer is about 2 to 20%, the defoamer is about 0.1 to 2%, and the anionic wetting agent is about 0.1 to 3% by weight.

17. The conductive composition of claim 16, where the silver is about 50 to 70 °

A) of the composition, the copolymer is about 4 to 10%, the defoamer is about 0.2 to 1.5%, and the anionic wetting agent is about 0.5 to 2% by weight.

18. The conductive composition of claim 14, wherein the longest dimension of said silver particles is from about 100 nm and 50 micrometers, the styrene/(meth)acrylic copolymer is a copolymer of styrene and an alkyl (meth)acrylate, optionally partly hydrolyzed or salified;

the anionic wetting agent is selected from the group consisting of alkali sulphosuccinate, alkali sulfosuccinate, and anionic polyacrylate copolymer;

the copolymer to water ratio is 4;

1 to 1;

8; and

the composition has a Zahn cup #3 viscosity in the range of about 10 to 40 seconds.

19. The conductive composition of claim 4, having a Zahn cup #3 viscosity in the range of about 10 to 40 seconds.

20. The conductive composition of claim 4, wherein the electrically conductive particles are at least one member of the group consisting of copper, gold, nickel, carbon, graphite, silver alloys, silver coated metal, silver coated glass, silver coated mica, silver coated graphite, nickel coated carbon, and nickel coated graphite.

21. A method of forming a conductive pattern on a substrate comprising applying the conductive composition of claim 1 on a substrate and drying the composition.

22. The method of claim 21, wherein the composition is applied by coating, spraying, painting, or printing.

23. The method of claim 21, wherein said composition is applied by screen, rotary screen, gravure, or letterpress printing.

24. The method of claim 21, wherein said composition is applied by flexographic printing.

25. The method of claim 24, wherein the composition is applied so as to realize graphics with less than about 500 micrometer spacing.

26. The method of claim 24, wherein the composition is applied so as to realize graphics with less than about 300 micrometer spacing.

27. The method of claim 21, wherein said composition is applied in a sufficient amount such that after drying the dried composition has a volume resistivity of about 120 micro-ohms.cm or lower.

28. The method of claim 27, wherein said composition is applied in a sufficient amount such that after drying the dried composition has a volume resistivity of about 60 micro-ohms.cm or lower.

29. The method of claim 21, wherein said composition is applied on said substrate in the form of an antenna.

30. The method of claim 21, wherein said composition is applied on said substrate in the form of an RFID antenna.

31. The method of claim 30, wherein the said composition is applied on said substrate in the form of a RFID antenna designed to operate in the frequency range of at least 800 MHz.

32. The method of claim 31, wherein a RFID integrated circuit chip is connected to said RFID antenna via direct chip attachment, RFID strap attachment, or through space coupling.

33. The method of claim 32, wherein the RFID integrated circuit chip is EPC Class 1 UHF RFID compliant.

34. The method of claim 21, wherein said composition is applied on said substrate to form a printed circuit.

35. The method of claim 21, wherein said substrate is a cellulosic substrate.

36. The method of claim 35, wherein said cellulosic substrate is selected from the group consisting coated paper, uncoated paper, thermal transfer paper, direct thermal paper, coated cardboard, uncoated cardboard, a primed uncoated cardboard, kraft paper, fluted paper, and mottled paper.

37. The method of claim 21, wherein said substrate is a plastic.

38. The method of claim 34, wherein said substrate is selected from the group consisting of a polyester, polyethylene, polypropylene, polyamide, polyimide, polyetherimide, polyurethane, polycarbonate, cellulosic ester (e.g. cellulose acetate etc.), polystyrene and styrenic copolymers.

39. The method of claim 21, wherein the substrate is a metal-oxide coated plastic.

40. An article comprising a substrate in combination with the composition of claim 4.

41. The article of claim 40, wherein the substrate comprises an RFID chip module operating at or above 850 MHz and the composition is in the form of an antenna attached to the module.

42. The article of claim 40, wherein the RFID chip module is attached to the antenna without conductive bonding.

43. The article of claim 40 in which the composition is disposed as an electomagnetic shielding or coating on the substrate.

44. The article of claim 40 in which the composition is disposed in a discontinuous pattern.

45. The article of claim 40 in which the composition is disposed as an initiating layer for electrolytic metal platting.