Liquid crystal display device

• US 8,619,227 B2
• Filed: 04/10/2012
• Issued: 12/31/2013
• Est. Priority Date: 12/05/2005
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime, Uochi, Hideki
• Primary Examiner(s): Wong, Tina
• Application Number:
  US13/442,932
• Publication Number:
  US 20120194758A1
• Time in Patent Office: 630 Days
• Field of Search: None
• US Class Current: 349/141
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/134372 for fringe field switching [FFS] where the common electrode is not patterned
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/136209 Light shielding layers, e.g. black matrix, incorporated in the active matrix substrate, e.g. structurally associated with the switching element
• CPC Class Codes: G02F 1/136222 Colour filters incorporated in the active matrix substrate
• CPC Class Codes: G02F 1/136227 Through-hole connection of the pixel electrode to the active element through an insulation layer
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2201/121 common or background
• CPC Class Codes: G02F 2201/123 pixel
• CPC Class Codes: G02F 2201/124 interdigital

Abstract

It is an object of the present invention to apply a sufficient electrical field to a liquid crystal material in a horizontal electrical field liquid crystal display device typified by an FFS type. In a horizontal electrical field liquid crystal display, an electrical field is applied to a liquid crystal material right above a common electrode and a pixel electrode using plural pairs of electrodes rather than one pair of electrodes. One pair of electrodes includes a comb-shaped common electrode and a comb-shaped pixel electrode. Another pair of electrodes includes a common electrode provided in a pixel portion and the comb-shaped pixel electrode.

Claims

1. A liquid crystal display device, comprising:

a substrate;

a gate electrode and a semiconductor layer over the substrate;

a source electrode and a drain electrode over the semiconductor layer;

a first insulating layer over the gate electrode;

a first common electrode over the first insulating layer;

a second insulating layer over the first common electrode;

a second common electrode over the second insulating layer;

a pixel electrode over the second insulating layer, the pixel electrode being electrically connected to one of the source electrode and the drain electrode; and

a liquid crystal material over the pixel electrode and the second common electrode,

wherein a part of the first common electrode overlaps with the second common electrode.

2. The liquid crystal display device according to claim 1, wherein tilting of the liquid crystal material is controlled by an electrical field between the pixel electrode and the first common electrode, and an electrical field between the pixel electrode and the second common electrode.

3. The liquid crystal display device according to claim 1, wherein the semiconductor layer is an amorphous semiconductor layer.

4. The liquid crystal display device according to claim 1,

wherein a reflective electrode is formed over the first insulating layer, and

wherein the reflective electrode is electrically connected to the first common electrode.

5. The liquid crystal display device according to claim 1, wherein the pixel electrode is over the second insulating layer.

6. A liquid crystal display device, comprising:

a substrate;

a gate electrode and a semiconductor layer over the substrate;

a source electrode and a drain electrode over the semiconductor layer;

a first insulating layer over the gate electrode;

a first common electrode over the first insulating layer;

a second insulating layer over the first common electrode;

a second common electrode over the second insulating layer;

a pixel electrode over the second insulating layer, the pixel electrode being electrically connected to one of the source electrode and the drain electrode; and

a liquid crystal material over the pixel electrode and the second common electrode,

wherein a part of the first common electrode overlaps with the second common electrode, and

wherein the first common electrode is a transmissive electrode.

7. The liquid crystal display device according to claim 6, wherein tilting of the liquid crystal material is controlled by an electrical field between the pixel electrode and the first common electrode, and an electrical field between the pixel electrode and the second common electrode.

8. The liquid crystal display device according to claim 6, wherein the semiconductor layer is an amorphous semiconductor layer.

9. The liquid crystal display device according to claim 6,

wherein a reflective electrode is formed over the first insulating layer, and

wherein the reflective electrode is electrically connected to the first common electrode.

10. The liquid crystal display device according to claim 6, wherein the pixel electrode is over the second insulating layer.

11. A liquid crystal display device, comprising:

a substrate;

a gate electrode and a semiconductor layer over the substrate;

a source electrode and a drain electrode over the semiconductor layer;

a first insulating layer over the gate electrode;

a first common electrode over the first insulating layer;

a second insulating layer over the first common electrode;

a second common electrode over the second insulating layer;

a pixel electrode over the second insulating layer, the pixel electrode being electrically connected to one of the source electrode and the drain electrode; and

a liquid crystal material over the pixel electrode and the second common electrode,

wherein a part of the first common electrode overlaps with the second common electrode, and

wherein the second common electrode is comb-shaped.

12. The liquid crystal display device according to claim 11, wherein tilting of the liquid crystal material is controlled by an electrical field between the pixel electrode and the first common electrode, and an electrical field between the pixel electrode and the second common electrode.

13. The liquid crystal display device according to claim 11, wherein the semiconductor layer is an amorphous semiconductor layer.

14. The liquid crystal display device according to claim 11,

wherein a reflective electrode is formed over the first insulating layer, and

wherein the reflective electrode is electrically connected to the first common electrode.

15. The liquid crystal display device according to claim 11, wherein the pixel electrode is over the second insulating layer.

16. A liquid crystal display device, comprising:

a substrate;

a gate electrode and a semiconductor layer over the substrate;

a source electrode and a drain electrode over the semiconductor layer;

a first insulating layer over the gate electrode;

a first common electrode over the first insulating layer;

a second insulating layer over the first common electrode;

a second common electrode over the second insulating layer;

a pixel electrode over the second insulating layer, the pixel electrode being electrically connected to one of the source electrode and the drain electrode; and

a liquid crystal material over the pixel electrode and the second common electrode,

wherein a part of the first common electrode overlaps with the second common electrode, and

wherein the first common electrode is a transmissive electrode, and

wherein the second common electrode is comb-shaped.

17. The liquid crystal display device according to claim 16, wherein tilting of the liquid crystal material is controlled by an electrical field between the pixel electrode and the first common electrode, and an electrical field between the pixel electrode and the second common electrode.

18. The liquid crystal display device according to claim 16, wherein the semiconductor layer is an amorphous semiconductor layer.

19. The liquid crystal display device according to claim 16,

wherein a reflective electrode is formed over the first insulating layer, and

wherein the reflective electrode is electrically connected to the first common electrode.

20. The liquid crystal display device according to claim 16, wherein the pixel electrode is over the second insulating layer.

21. A liquid crystal display device comprising:

a substrate;

a gate electrode and a semiconductor layer over the substrate;

a first insulating layer over the gate electrode;

a source electrode and a drain electrode over and electrically connected to the semiconductor layer, wherein each of the source electrode and the drain electrode comprises a first metal;

a conductive layer comprising a second metal over and in contact with the first insulating layer, wherein the second metal is the same as the first metal;

a first transparent conductive layer under and in contact with the conductive layer, wherein the first transparent conductive layer is over and in contact with the first insulating layer;

a second insulating layer over the first transparent conductive layer;

a second transparent conductive layer over the second insulating layer, the second transparent conductive layer having a slit; and

a liquid crystal layer over the second transparent conductive layer, wherein the first transparent conductive layer and the second transparent conductive layer overlap with each other.

22. The liquid crystal display device according to claim 21,

wherein the first transparent conductive layer is a first common electrode, and

wherein the second transparent conductive layer is a pixel electrode.

23. The liquid crystal display device according to claim 21, wherein the second transparent conductive layer is electrically connected to one of the source electrode and the drain electrode.

24. The liquid crystal display device according to claim 21, further comprising:

a third transparent conductive layer having a slit over and in contact with a surface,

wherein the second transparent conductive layer is over and in contact with the surface.

25. The liquid crystal display device according to claim 21, wherein the gate electrode is provided over the semiconductor layer.

26. The liquid crystal display device according to claim 21, wherein the gate electrode is provided under the semiconductor layer.

27. The liquid crystal display device according to claim 21, wherein the semiconductor layer comprises amorphous silicon.

28. The liquid crystal display device according to claim 21, wherein the second transparent conductive layer is a second common electrode.

29. The liquid crystal display device according to claim 21, wherein the second insulating layer is provided over the semiconductor layer.

30. The liquid crystal display device according to claim 21, wherein a part of the first transparent conductive layer and the second transparent conductive layer overlap with each other.

31. The liquid crystal display device according to claim 21, wherein the slit has a comb-shape.

32. The liquid crystal display device according to claim 21, wherein the first metal and the second metal are molybdenum.

33. A mobile computer comprising:

a display portion comprising the liquid crystal display device according to claim 21.

34. An electronic book comprising:

a display portion comprising the liquid crystal display device according to claim 21.

35. A liquid crystal display device comprising:

a gate electrode;

a first insulating layer over the gate electrode;

a conductive layer comprising a metal over and in contact with the first insulating layer;

a first transparent conductive layer under and in contact with the conductive layer, wherein the first transparent conductive layer is over and in contact with the first insulating layer;

a second insulating layer over the first transparent conductive layer;

a second transparent conductive layer over the second insulating layer, the second transparent conductive layer having a slit; and

a liquid crystal layer over the second transparent conductive layer, wherein the first transparent conductive layer and the second transparent conductive layer overlap with each other.

36. The liquid crystal display device according to claim 35, further comprising:

a source electrode and a drain electrode, wherein each of the source electrode and the drain electrode comprises a first metal,

wherein the conductive layer comprises a second metal, and

wherein the second metal is the same as the first metal.

37. The liquid crystal display device according to claim 35,

wherein the first transparent conductive layer is a first common electrode, and

wherein the second transparent conductive layer is a pixel electrode.

38. The liquid crystal display device according to claim 36, wherein the second transparent conductive layer is electrically connected to one of the source electrode and the drain electrode.

39. The liquid crystal display device according to claim 35, further comprising:

a third transparent conductive layer having a slit over and in contact with a surface,

wherein the second transparent conductive layer is over and in contact with the surface.

40. The liquid crystal display device according to claim 35, wherein a part of the first transparent conductive layer and the second transparent conductive layer overlap with each other.

41. The liquid crystal display device according to claim 35, wherein the slit has a comb-shape.

42. A mobile computer comprising:

a display portion comprising the liquid crystal display device according to claim 35.

43. An electronic book comprising:

a display portion comprising the liquid crystal display device according to claim 35.