Fluoropolymer binders for carbon nanotube-based transparent conductive coatings

• US 20060113510A1
• Filed: 08/11/2005
• Published: 06/01/2006
• Est. Priority Date: 08/11/2004
• Status: Active Grant

• Current Assignee: Eikos, Inc.
• Original Assignee: Eikos, Inc.
• Inventors: Arthur, David J., Luo, Jiazhong, Glatkowski, Paul J.
• Granted Patent: US 7,378,040 B2
• Time in Patent Office: Days
• US Class Current: 252/500
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: C08J 2367/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds; C08J2367/06 takes precedence
• CPC Class Codes: C08J 2427/12 containing fluorine atoms
• CPC Class Codes: C08J 7/0423 with at least one layer of inorganic material and at least one layer of a composition containing a polymer binder
• CPC Class Codes: C08J 7/043 Improving the adhesiveness of the coatings per se, e.g. forming primers adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50
• CPC Class Codes: C08J 7/044 Forming conductive coatings; Forming coatings having anti-static properties
• CPC Class Codes: C08J 7/046 Forming abrasion-resistant coatings; Forming surface-hardening coatings
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor

Abstract

This invention relates to flexible, transparent and conductive coatings and films formed using carbon nanotubes (CNT) and, in particular, single wall carbon nanotubes, with polymer binders. Preferably, coatings and films are formed from carbon nanotubes applied to transparent substrates forming one or multiple conductive layers at nanometer level of thickness. Polymer binders are applied to the CNT network coating having an open structure to provide protection through infiltration. This provides for enhancement of properties such as moisture resistance, thermal resistance, abrasion resistance and interfacial adhesion. Polymers may be thermoplastics or thermosets, or a combination thereof. Polymers may also be insulative or inherently electrical conductive, or any combination of both. Polymers may comprise single or multiple layers as a basecoat underneath a CNT coating, or a topcoat above a CNT coating, or combination of the basecoat and the topcoat forming a sandwich structure. A fluoropolymer containing binder, which is a solution of one fluoropolymer or a blend of fluoropolymers, which may be formulated with additives, is applied onto a carbon nanotube-based transparent conductive coating at nanometer level of thickness on a clear substrate such as PET and glass. The fluoropolymers or blend can be either semi-crystalline (with low level of crystallinity) or amorphous, preferably to be amorphous with low refraction index. Binder coating thickness can be adjusted by changing binder concentration, coating speed and/or other process conditions. This binder coating significantly improves optical transparency, and also maintain or increases conductivity of the CNT-based coating. With other benefits such as abrasion, thermal and moisture resistance, this binder coating and the resulting products is used for display and electronic applications.

Claims

1. A conductive coating or film comprised of carbon nanotubes and a fluoromonomer or fluoropolymer binder.

2. The coating or film of claim 1, wherein the carbon nanotubes are less than 3.5 nm in diameter.

3. The coating or film of claim 1, wherein the carbon nanotubes are single-walled carbon nanotubes.

4. The coating or film of claim 1, wherein the fluoromonomer or fluoropolymer binder is selected from the group consisting of crystalline and semicrystalline fluoromonomers and fluoropolymers, amorphous fluoromonomers and fluoropolymers, fluoroplastics, fluoroelastomers, fluoroacrylates, fluorourethanes, terfluoromonomers and terfluoropolymers, perfluoro carbon-based monomers and polymers, fluoro-containing thermoplastics, thermosets and elastomers, blends of one or more different fluoromonomers and fluoropolymers, and combinations thereof.

5. The coating or film of claim 1, wherein the fluoromonomer or fluoropolymer binder is selected from the group consisting of polyvinylidene fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, Teflon AF™

, SIFEL 611™

, 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole, Cytop™

, tetrafluoroethylene and co-polymers of tetrafluoroethylene, FluoroPel PFC™

, and combination thereof.

6. The coating or film of claim 1, which is optically transparent.

7. The coating or film of claim 6, which has a transmittance value to light at 550 nm of greater than 75%.

8. The coating or film of claim 7, wherein the transmittance value is greater than 90%.

9. The coating or film of claim 6, which has a transmittance value to light at 550 nm of greater than the corresponding transmittance value of the coating or film without said binder.

10. The coating or film of claim 9, wherein the transmittance value is at least 5% greater than the corresponding transmittance value of the coating or film without said binder.

11. The coating or film of claim 1, which has a sheet resistance of from 10⁻

1 to 10⁴Ω

/□

.

12. The coating or film of claim 11, wherein the sheet resistance is from 10¹ to 10³Ω

/□

.

13. The coating or film of claim 11, wherein the sheet resistance is up to 10% less than the corresponding sheet resistance of the coating or film without said binder.

14. The coating or film of claim 11, wherein the sheet resistance is up to 50% less than the corresponding sheet resistance of the coating or film without said binder.

15. The coating or film of claim 1, wherein the fluoropolymer binder further contains an additive.

16. The coating or film of claim 1, wherein the additive is selected from the group consisting of silanes, fluorosilanes, siloxanes, and metal alkoxides, and combinations thereof.

17. A method of forming a conductive coating or film comprising applying to a substrate a layer of carbon nanotubes and a layer of a fluoropolymer.

18. The method of claim 17, wherein the coating or film is optically transparent.

19. The method of claim 18, wherein the coating or film has a transmittance value to light at 550 nm of greater than 65%.

20. The method of claim 18, wherein the transmittance value is greater than 90%.

21. The method of claim 18, wherein the transmittance value to light at 550 nm is greater than the corresponding transmittance value of the coating or film without said binder.

22. The method of claim 18, wherein the transmittance value is up to 5% greater than the corresponding transmittance value of the coating or film without said binder.

23. The method of claim 22, wherein the transmittance value is up to 50% greater than the corresponding transmittance value of the coating or film without said binder.

24. A method of increasing the conductivity of a conductive film comprising:

applying a layer of carbon nanotubes to a surface to form a conductive film;

applying another layer of material to said carbon nanotube layer that compresses said carbon nanotubes and increases sheet conductivity across a surface of said conductive film.

25. The method of claim 24, wherein the another layer contains a fluoropolymer or fluoromonomer binder.