Enhanced field emission from carbon nanotubes mixed with particles

• US 20040070326A1
• Filed: 10/07/2003
• Published: 04/15/2004
• Est. Priority Date: 10/09/2002
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Nano-Proprietary, Inc. (Nano Magic, Inc.)
• Inventors: Yaniv, Zvi, Fink, Richard Lee, Mao, Dongsheng
• Granted Patent: US 6,798,127 B2
• Time in Patent Office: Days
• US Class Current: 313/311
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: C23C 18/1204 inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
• CPC Class Codes: C23C 18/127 Preformed particles
• CPC Class Codes: H01J 1/304 Field-emissive cathodes
• CPC Class Codes: H01J 2201/30469 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 2209/0223 Field emission cathodes
• CPC Class Codes: H01J 2329/0455 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 9/025 of field emission cathodes
• CPC Class Codes: Y10S 977/939 Electron emitter, e.g. spindt emitter tip coated with nanoparticles
• CPC Class Codes: Y10S 977/952 Display

Abstract

The present invention is directed toward cathodes and cathode materials comprising carbon nanotubes (CNTs) and particles. The present invention is also directed toward field emission devices comprising a cathode of the present invention, as well as methods for making these cathodes. In some embodiments, the cathode of the present invention is used in a field emission display. The invention also comprises a method of depositing a layer of CNTs and particles onto a substrate to form a cathode of the present invention, as well as a method of controlling the density of CNTs used in this mixed layer in an effort to optimize the field emission properties of the resulting layer for field emission display applications.

Claims

1. A field emission cathode comprising:

a) a substrate; and

b) a field emission cathode material comprising a mixture of carbon nanotubes and particles.

2. The cathode of claim 1, wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, double-wall carbon nanotubes, multi-wall carbon nanotubes, buckytubes, carbon fibrils, chemically-modified carbon nanotubes, derivatized carbon nanotubes, metallic carbon nanotubes, semiconducting carbon nanotubes, metallized carbon nanotubes, and combinations thereof.

3. The cathode of claim 1, wherein the particles are selected from the group consisting of spherical particles, disk-shaped particles, lamellar particles, rod-like particles, metal particles, semiconductor particles, polymeric particles, ceramic particles, dielectric particles, clay particles, fibers, nanoparticles, and combinations thereof.

4. The cathode of claim 1, wherein the cathode material resides on a surface of the substrate as a layer.

5. The cathode of claim 4, wherein the layer of cathode material has a thickness which ranges from about 10 nm to about 1 mm.

6. The cathode of claim 1, wherein nanotubes are present in the cathode material in an amount which ranges from about 0.1 weight percent to about 99 weight percent.

7. The cathode of claim 1, wherein the carbon nanotubes are aligned.

8. The cathode of claim 1, wherein the carbon nanotubes have at least one end trapped between particles.

9. The cathode of claim 1, wherein the carbon nanotubes are trapped within pores in the particles.

10. The cathode of claim 1, wherein the carbon nanotubes are trapped within gaps between the particles.

11. The cathode of claim 1, wherein the particles are lamellar.

12. The cathode of claim 11, wherein the CNTs are trapped between layers within the particles.

13. A field emission display device comprising:

a) an anode assembly; and

b) a cathode assembly, wherein the cathode assembly comprises;

1) a substrate;

2) an electrically conducting layer deposited on the substrate; and

3) a field emission cathode material comprising carbon nanotubes and particles deposited as a layer over the electrically conducting layer.

14. A method comprising the steps of:

a) forming a mixture of carbon nanotubes and particles; and

b) depositing a layer of the mixture of carbon nanotubes and particles onto a substrate to form a cathode.

15. The method of claim 14, wherein the nanotubes are selected from the group consisting of single-wall carbon nanotubes, double-wall carbon nanotubes, multi-wall carbon nanotubes, buckytubes, carbon fibrils, chemically-modified carbon nanotubes, derivatized carbon nanotubes, metallic carbon nanotubes, semiconducting carbon nanotubes, metallized carbon nanotubes, and combinations thereof.

16. The method of claim 14, wherein the particles are selected from the group consisting of spherical particles, disk-shaped particles, lamellar particles, rod-like particles, metal particles, semiconductor particles, polymeric particles, ceramic particles, dielectric particles, clay particles, fibers, nanoparticles, and combinations thereof.

17. The method of claim 14, wherein the step of forming a mixture of carbon nanotubes and particles comprises a milling operation.

18. The method of claim 14, wherein the step of forming a mixture of carbon nanotubes and particles comprises solvent dispersal.

19. The method of claim 14, wherein the mixture of carbon nanotubes and particles is deposited using a method selected from the group consisting of spraying, brushing, electrophoretic deposition, dipping, dispensing, screen printing, ink jet printing, and combinations thereof.

20. The method of claim 19, further comprising a step to remove the solvent from the mixture after depositing the mixture on the substrate.

21. The method of claim 14, further comprising a taping process to activate the cathode.

22. The method of claim 14, further comprising a method of aligning the carbon nanotubes within the layer of carbon nanotubes and particles.

23. The method of claim 14, wherein the particles are lamellar.

24. The method of claim 23, further comprising a method of aligning the carbon nanotubes using a shear force applied to the mixture of the carbon nanotubes and lamellar particles.

25. The method of claim 23, wherein the lamellar particles comprise clay.