Cnt film and field-emission cold cathode comprising the same

• US 20040104660A1
• Filed: 12/22/2003
• Published: 06/03/2004
• Est. Priority Date: 11/20/2000
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Okada, Yuko, Ito, Fuminori, Okamoto, Akihiko, Tomihari, Yoshinori, Konuma, Kazuo
• Granted Patent: US 7,161,285 B2
• Time in Patent Office: Days
• US Class Current: 313/346R
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: H01J 2201/30469 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 9/025 of field emission cathodes
• CPC Class Codes: Y10S 977/742 Carbon nanotubes, CNTs
• CPC Class Codes: Y10S 977/753 with polymeric or organic binder
• CPC Class Codes: Y10S 977/842 for carbon nanotubes or fullerenes
• CPC Class Codes: Y10S 977/844 Growth by vaporization or dissociation of carbon source using a high-energy heat source, e.g. electric arc, laser, plasma, e-beam
• CPC Class Codes: Y10S 977/939 Electron emitter, e.g. spindt emitter tip coated with nanoparticles

Abstract

A fabrication method for an emitter includes the steps of forming on a glass substrate (10) a CNT film (12) which contains a plurality of carbon nanotubes (CNTs) (12a) and constitutes an emitter electrode (12b), forming a gate electrode (16) via an insulating film (13) on the CNT film (12), forming a plurality of gate openings (17) in the gate electrode (16) and the insulating film (13), and aligning upright the CNTs (12a) in the gate opening (17). The upright alignment generates a stable uniform emission current and provides excellent emission characteristics.

Claims

1. A carbon nanotube (CNT) film comprising CNTs and particulate impurities, characterized in that an area ratio between said CNTS and the particulate impurities in cross section and surface structure is set within a range of 0.5:

99.5 to 40;

60, and that said particulate impurities comprise impurities obtained in conjunction with said CNTs upon fabricating said CNTs.

2. The CNT film according to claim 1, wherein said particulate impurities have a function of a binder material for filling gaps between said CNTs, and another binder material other than said binder material is further added.

3. The CNT film according to claim 2, wherein said another binder material is made of an organic substance.

4. The CNT film according to claim 3, wherein said organic substance is made of a material comprising at least one of acrylic, nitrocellulose, and polyimide resin.

5. The CNT film according to claims 1 to 4, wherein said CNTs and said particulate impurities occupy said CNT film at a filling rate of 70% or more.

6. The CNT film according to any one of claims 2 to 5, wherein said CNT film is formed as a stacked structure of a plurality of layers stacked in sequence, and the content ratio of said CNTs, said particulate impurities, and said another binder material in each of said layers of said stacked structure is set independently of the other layer or layers.

7. The CNT film according to claim 6, wherein as to percentage contents of said CNTs, said particulate impurities and said another binder material, the percentage content of said CNTs is higher in an upper layer whereas the percentage contents of said particulate impurities and said another binder material are higher in a lower layer.

8. The CNT film according to claim 7, wherein the percentage content of CNTs in the uppermost layer is 80 to 90%, the percentage contents of other than CNTs in a layer other than said uppermost layer is 70 to 80%, and the percentage content of said another binder material is 60 to 70% in the lowermost layer.

9. A field emission cold cathode characterized by employing the CNT film according to any one of claims 1 to 8.

10. A fabrication method for fabricating the CNT film according to any one of claims 1 to 8, characterized by patterning said CNTs while preparing a binder material of said particulate impurities and/or said another binder material from a material or materials having an etching rate higher than that of said CNTs.

11. The fabrication method for the CNT film according to claim 10, wherein said binder material and/or said another binder material are left in conjunction with said CNTs in a CNT film area which is left in the step of patterning said CNT film.

12. The fabrication method for the CNT film according to claim 10 or 11, wherein said CNTs and said particulate impurities are obtained in the same step at the same time and used for fabrication.

13. The fabrication method for the CNT film according to claim 10 or 11, wherein said CNTs and said particulate impurities are obtained in different steps and used for fabrication.

16. A method for fabricating the CNT film according to any one of claims 1 to 8, characterized by the step of aligning the surface of said CNT film in the upright direction.

17. A field emission cold cathode characterized by using said CNT film fabricated by the fabrication method for the CNT film according to any one of claims 10 to 16.

18. The field emission cold cathode according to claim 17, wherein said CNT film constitutes an electron emitting surface containing therein said CNTs and said particulate impurities, and said electron emitting surface does not contain particulate impurities having a particle diameter of more than 500 nm.

19. A field emission image display device characterized by the electron emitting cold cathode according to claim 18.

37. A field emission cold cathode characterized by the emitter fabricated by the method for fabricating the emitter according to any one of claims 19 to 36.

38. A flat image display device characterized by the field emission cold cathode according to claim 37.

14. A fabrication method for fabricating a CNT film, comprising the steps of performing arc discharge using a pair of carbon bars opposing each other in a chamber, depositing deposits of CNTs and particulate impurities on each of a top plate, side plates, and a bottom plate within said chamber, and using said deposits to fabricate the CNT film, characterized by:

collecting a top plate deposit and a side plate deposit which are deposited on the top plate and the side plates within said chamber, producing a mixed material by mixing both said collected top plate deposit and said side plate deposit at a predetermined weight ratio, and using said particulate impurities in said mixed material as a material for filling gaps between said CNTs in said mixed material.

15. The fabrication method for the CNT film according to claim 14, wherein contents of said CNTs and particulate impurities are adjusted by using said side plate deposit and said top plate deposit such that an area ratio between said CNTs and said particulate impurities in cross section and surface structure is satisfied within a range of 0.5:

99.5 to 40;

60.

20. A method for fabricating an emitter, comprising the steps of forming on a substrate a CNT film constituting the emitter including a plurality of carbon nanotubes (CNTs);

and

aligning said CNTs on a surface of said CNT film in the upright direction.

21. The method for fabricating the emitter according to claim 20, wherein said CNTs upright aligning step comprises the consecutive steps of adhering an adhesive sheet onto said CNT film and peeling off said adhesive sheet to align said CNTs in the upright direction.

22. The method for fabricating the emitter according to claim 20, further comprising, prior to said CNTs upright aligning step, the steps of forming an electrode on said CNT film with an intervention of an insulating film therebetween and forming a plurality of openings in said electrode and the insulating film, wherein said CNTs upright aligning step aligns said CNTs in said opening in the upright direction.

23. The method for fabricating the emitter according to claim 22, wherein said upright aligning step comprises the consecutive steps of allowing said adhesive sheet to advance into said openings and peeling off said adhesive sheet.

24. The method for fabricating the emitter according to claim 22, further comprising, prior to said insulation film and electrode forming step, the steps of aligning said CNTs on said CNT film surface in the upright direction, and forming a cover film comprising fine particles on said CNT film, wherein said upright aligning step includes the consecutive steps of allowing said adhesive sheet to advance into said openings and peeling off said adhesive sheet to remove at least a part of said cover film.

25. The method for fabricating the emitter according to claim 23 or 24, wherein said upright aligning step using said adhesive sheet is performed under a reduced pressure.

26. The method for fabricating the emitter according to any one of claims 23 to 25, wherein said adhesive sheet has a breathable property.

27. The method for fabricating the emitter according to any one of claims 23 to 26, wherein adhesive projections to be allowed to advance into said plurality of openings are formed on a surface of said adhesive sheet.

28. The method for fabricating the emitter according to claim 27, wherein said adhesive projections are arranged so that said adhesive projections are smaller than said plurality of openings.

29. The method for fabricating the emitter according to any one of claims 23 to 28, wherein said adhesive sheet has an adhesive force of more than 0.002 N/mm and below 0.2 N/mm.

30. A method for fabricating an emitter, comprising the steps of:

forming on a substrate a CNT film constituting the emitter including a plurality of carbon nanotubes (CNTs);

,

aligning the CNTs on said CNT film in the upright direction and forming a protective metal film on said upright aligned CNT film; and

removing said protective metal film by soaking the entire substrate including said protective metal film in an etching solution.

31. The method for fabricating the emitter according to claim 30, further comprising, prior to the step of removing said protective metal film, the steps of forming an electrode on said protective metal film with an intervention of an insulating film therebetween and forming a plurality of openings on said electrode and the insulating film, wherein said protective metal film removing step removes the protective metal film in said opening by etching.

32. The method for fabricating the emitter according to claim 31, further comprising, subsequent to said protective metal film removing step, the steps of replacing said etching solution with water while maintaining said CNT film exposed in said openings under a liquid level, and drying said upright-aligned CNTs in said CNT film by freezing and subliming said water.

33. The method for fabricating the emitter according to claim 31, further comprising, subsequent to said protective metal film removing step, the steps of replacing said etching solution with a super critical fluid while maintaining said CNT film exposed in said opening under a liquid level, and drying said CNT film by transferring removing said super critical fluid into a super critical state and then removing the same.

34. The method for fabricating the emitter according to claim 33, wherein said super critical fluid includes at least one of liquid-state CO₂, N₂, N₂O, xenon and SF₆.

35. The method for fabricating the emitter according to claim 31, further comprising, subsequent to said protective metal film removing step, the consecutive steps of replacing said etching solution with a solution having less surface tension than that of said etching solution while maintaining said CNT film exposed in said opening under a liquid level, and drying said CNT film.

36. The method for fabricating the emitter according to any one of claims 32, 33, and 35, wherein said drying step is performed under a constant pressure and/or at a constant temperature.

39. A flat image display device having an area S (cm²) for one of pixel elements, wherein a count density of upright-aligned CNTs is 1/S (pieces/cm²) or more.