Focusing electrode for field emission displays and method

• US 20020014850A1
• Filed: 07/23/2001
• Published: 02/07/2002
• Est. Priority Date: 05/26/1998
• Status: Active Grant

• Current Assignee: Zhongyi Xia
• Original Assignee: Zhongyi Xia
• Inventors: Xia, Zhongyi
• Granted Patent: US 6,476,548 B2
• Time in Patent Office: Days
• US Class Current: 315/169.1
• CPC Class Codes: H01J 3/022 with microengineered cathode, e.g. Spindt-type

Abstract

A display includes a substrate and an emitter formed on the substrate. A first dielectric layer is formed on the substrate to have a thickness slightly less than a height of the emitter above the planar surface and includes an opening formed about the emitter. The display also includes a conductive extraction grid formed on the first dielectric layer. The extraction grid includes an opening surrounding the emitter. The display further includes a second dielectric layer formed on the extraction grid and a focusing electrode formed on the second dielectric layer. The focusing electrode is electrically coupled to the emitter through an impedance element. The focusing electrode includes an opening formed above the apex. The focusing electrode provides enhanced focusing performance together with reduced circuit complexity, resulting in a superior display.

Claims

1. A field emission display baseplate comprising:

a substrate;

a linear array of emitters formed on the substrate;

a dielectric layer formed on the substrate and including an opening surrounding each of the emitters;

a conductive extraction grid formed on the dielectric layer and including an opening surrounding each of the emitters; and

an oblong focus electrode surrounding the linear array of emitters.

2. The baseplate of claim 1, further comprising a resistor formed on the substrate, the resistor having a first terminal coupled to the emitters and a second terminal that is coupled to a source of electrons.

3. The baseplate of claim 1 wherein the linear array of emitters comprises two or more emitters.

4. The baseplate of claim 1 wherein the linear array of emitters comprises a plurality of emitters arranged in a row having a width of one emitter or more.

5. The baseplate of claim 1 wherein the linear array of emitters comprises a plurality of emitters arranged in a single row having a width of one emitter.

6. The baseplate of claim 1 wherein the linear array of emitters comprises a plurality of emitters arranged in two adjacent rows, wherein the emitters are staggered between the two adjacent rows.

7. The baseplate of claim 1 wherein the substrate comprises silicon.

8. The baseplate of claim 1 wherein the focusing electrode is electrically connected to the emitters.

9. The baseplate of claim 1 wherein the focusing electrode is electrically coupled to the emitters.

10. The baseplate of claim 9, further including an element chosen from the group consisting of:

a bias resistor, a constant current element and a constant voltage drop element, the element electrically coupling the focusing electrode to the emitters.

11. A field emission display baseplate, comprising:

a substrate;

an emitter formed on the substrate;

a dielectric layer formed on the substrate and having an opening formed about the emitter;

a conductive extraction grid formed on the dielectric layer and having an opening formed about the emitter;

a focus electrode formed on the substrate and having an opening formed above the emitter; and

an impedance element electrically coupled between the focus electrode and the emitter.

12. The baseplate of claim 11 wherein the substrate comprises silicon.

13. The baseplate of claim 11 wherein the impedance element is chosen from a group consisting of:

a bias resistor, a constant current element and a constant voltage drop element.

14. The baseplate of claim 11 wherein the focus electrode comprises:

a polysilicon focus electrode; and

a dielectric supporting structure formed on the extraction grid.

15. The baseplate of claim 14 wherein the dielectric supporting structure has a thickness of between five and ten microns.

17. The baseplate of claim 16 wherein the substrate comprises silicon.

18. The baseplate of claim 16 wherein the impedance element comprises a bias resistor.

19. The baseplate of claim 16 wherein the impedance element comprises a constant current element.

20. The baseplate of claim 16 wherein the impedance element comprises a constant voltage drop element.

21. The baseplate of claim 16 wherein the focus electrode comprises:

a polysilicon focus electrode; and

a dielectric supporting structure formed on the extraction grid.

16. A field emission display baseplate, comprising:

a substrate;

an emitter formed on the substrate, the emitter being electrically coupled to a first node;

a dielectric layer formed on the substrate and having an opening formed about the emitter;

a conductive extraction grid formed on the dielectric layer and having an opening formed about the emitter;

a focus electrode formed on the substrate and having an opening formed above the emitter, the focus electrode being electrically coupled to the first node;

an impedance element electrically coupled between the focus electrode and the emitter; and

a current source coupled to the first node.

22. The baseplate of claim 22 wherein the dielectric supporting structure has a thickness of between five and ten microns.

24. The display of claim 23 wherein the focus electrode comprises:

a polysilicon focusing electrode; and

a dielectric supporting structure formed between the extraction grid and the polysilicon focusing electrode.

25. The display of claim 23 wherein the dielectric supporting structure has a thickness of between five and ten microns.

26. The display of claim 23 wherein the focusing electrode is electrically connected to the emitter.

27. The display of claim 23 wherein the substrate comprises silicon.

28. The display of claim 23, further comprising an impedance element coupled between the focus electrode and the emitter.

29. The display of claim 28 wherein the impedance element is chosen from a group consisting of:

a bias resistor, a constant current element and a constant voltage drop element.

23. A field emission display comprising:

a baseplate comprising;

a substrate;

an emitter formed on the substrate;

a dielectric layer formed on the substrate and having an opening formed about the emitter;

a conductive extraction grid formed on the dielectric layer and having an opening formed about the emitter; and

a focusing electrode formed on the substrate and having an opening formed above the emitter such that the focusing electrode physically confines electrons emitted from the emitter; and

a faceplate comprising;

a transparent insulating viewing layer;

a transparent conductive layer formed on the transparent viewing layer; and

a cathodoluminescent layer formed on the transparent conductive layer, the faceplate positioned with the cathodoluminescent layer towards the substrate.

30. A field emission display comprising:

a baseplate comprising;

a substrate;

a linear array of emitters formed on the substrate;

a dielectric layer formed on the substrate and including an opening surrounding each of the emitters;

a conductive extraction grid formed on the dielectric layer and including an opening surrounding each of the emitters; and

a focus electrode including an oblong opening surrounding the emitters, the focus electrode being electrically coupled to the emitters; and

a faceplate comprising;

a transparent insulating viewing layer;

a transparent conductive layer formed on the transparent insulating viewing layer; and

a cathodoluminescent layer formed on the transparent conductive layer, wherein the faceplate is positioned with the cathodoluminescent layer adjacent the substrate.

31. The display of claim 30 wherein the focus electrode is electrically connected to the emitters.

32. The display of claim 30 wherein the substrate comprises silicon.

33. The display of claim 30, further comprising an impedance element coupled between the focus electrode and the emitters.

34. The display of claim 30 wherein the impedance element is chosen from a group consisting of:

a bias resistor, a constant current element and a constant voltage drop element.

35. The display of claim 30 wherein the emitters comprise a linear array of emitters arranged in a row having a width of two emitters or less.

36. The baseplate of claim 30 wherein the emitters comprise a linear array of emitters arranged in a single row having a width of one emitter.

37. The display of claim 30 wherein the focus electrode comprises:

a polysilicon focus electrode; and

a dielectric supporting structure formed on the extraction grid.

38. The display of claim 37 wherein the dielectric supporting structure has a thickness of one micron or less.

40. The computer system of claim 39 wherein the focus electrode is electrically coupled to the emitters.

41. The computer system of claim 39 wherein the emitters are arranged in two adjacent rows.

42. The computer system of claim 39 wherein the emitters are staggered between two adjacent rows.

39. A computer system comprising:

a central processing unit;

a memory device coupled to the central processing unit, the memory device storing instructions and data for use by the central processing unit;

an input interface; and

a display comprising;

a baseplate comprising;

a substrate;

a linear array of emitters formed on a surface of the substrate;

a dielectric layer formed on the substrate, the dielectric layer having an opening surrounding each of the emitters;

a conductive extraction grid formed on the dielectric layer, the extraction grid substantially in a plane defined by tips of the emitters and having an opening surrounding a tip of a respective one of the emitters; and

an oblong focus electrode surrounding the emitters; and

a faceplate comprising;

a transparent insulating viewing surface;

a transparent conductor formed on the transparent viewing surface; and

a cathodoluminescent layer formed on the conductive transparent layer.

43. A method of operating a field emission display comprising:

emitting electrons from a first emitter; and

focusing the stream of electrons emitted from the first emitter with a first focus electrode that is electrically coupled to the first emitter and that physically confines the stream of electrons.

44. The method of claim 43, further comprising setting the voltage on the first focus electrode to be a function of a first bias current through the first emitter.

45. The method of claim 43, further comprising setting a voltage on the first focus electrode to be equal to a voltage on the first emitter.

46. The method of claim 45, further comprising steps of:

emitting electrons from a second emitter; and

focusing the electrons emitted from the second emitter with a second focus electrode that is electrically coupled to the second emitter and that physically confines the stream of electrons from the second emitter.

47. The method of claim 46, further comprising setting the voltage on the second focus electrode to be equal to a voltage on the second emitter.

49. The method of claim 48 wherein returning a current including the intercepted portion of the emitted electrons to the emitter comprises returning a current including the intercepted portion of the emitted electrons to the emitter via an impedance element.

50. The method of claim 48 wherein intercepting a portion of the emitted electrons comprises intercepting a portion of the emitted electrons by the focus electrode.

51. The method of claim 48, further comprising setting a voltage on the focus electrode to be equal to the emitter voltage minus the current including the intercepted portion of the emitted electrons times the impedance element impedance.

52. The method of claim 48 wherein:

returning a current including the intercepted portion of the emitted electrons to the emitter comprises returning a current including the intercepted portion of the emitted electrons to the emitter via an impedance element; and

intercepting a portion of the emitted electrons comprises intercepting a portion of the emitted electrons by the focus electrode, and the method further comprises;

setting a voltage on the focus electrode to be equal to the emitter voltage minus the current including the intercepted portion of the emitted electrons times the impedance element impedance.

48. A method for operating a field emission display, comprising:

supplying electrons to an emitter from a current source;

emitting the electrons from the emitter;

focusing the emitted electrons by a focus electrode;

intercepting a portion of the emitted electrons;

returning the intercepted portion of the emitted electrons to the emitter; and

accelerating a non-intercepted portion of the emitted electrons towards a faceplate.

53. A method of operating a field emission display, the method comprising:

emitting electrons from an emitter;

focusing the emitted electrons with a focus electrode;

intercepting a portion of the emitted electrons;

returning the intercepted portion of the emitted electrons to the emitter through an impedance element; and

accelerating a non-intercepted portion of the emitted electrons towards a faceplate.

54. The method of claim 53 wherein intercepting a portion of the emitted electrons comprises intercepting a portion of the emitted electrons with the focus electrode.

55. The method of claim 53 wherein returning a current including the intercepted portion of the emitted electrons comprises returning a current including the intercepted portion of the emitted electrons to the emitter via a resistor.

56. The method of claim 53 wherein returning a current including the intercepted portion of the emitted electrons comprises returning a current including the intercepted portion of the emitted electrons to the emitter via a constant current element.

57. The method of claim 53 wherein returning a current including the intercepted portion of the emitted electrons comprises returning a current including the intercepted portion of the emitted electrons to the emitter via a constant voltage drop element.

58. The method of claim 53, further comprising setting a bias voltage on the focus electrode to be equal to the emitter voltage minus the current including the intercepted portion of the emitted electrons times the impedance element impedance.

59. The method of claim 53, further comprising supplying electrons to the emitter from a current source.