LIQUID CRYSTAL DISPLAY DEVICE

• US 20110121307A1
• Filed: 01/21/2011
• Published: 05/26/2011
• 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
• Granted Patent: US 7,999,892 B2
• Time in Patent Office: Days
• US Class Current: 257/66
• 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 1/134309 characterised by their geometrical arrangement
• 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 1/134381 Hybrid switching mode, i.e. for applying an electric field with components parallel and orthogonal to the substrates
• 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 2203/01 transmissive
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body

Abstract

It is an object of the present invention to provide a liquid crystal display device which has a wide viewing angle and less color-shift depending on an angle at which a display screen is seen and can display an image favorably recognized both outdoors in sunlight and dark indoors (or outdoors at night). The liquid crystal display device includes a first portion where display is performed by transmission of light and a second portion where display is performed by reflection of light. Further, a liquid crystal layer includes a liquid crystal molecule which rotates parallel to an electrode plane when a potential difference is generated between two electrodes of a liquid crystal element provided below the liquid crystal layer.

Claims

1. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer comprising polycrystalline silicon;

a gate insulating layer separating the gate electrode and the semiconductor layer;

a first insulating layer over the thin film transistor;

a first conductive layer over the first insulating layer and in direct contact with the semiconductor layer through an opening in the first insulating layer;

a second insulating layer over the first conductive layer;

a common electrode over the second insulating layer;

a third insulating layer over the common electrode; and

a pixel electrode over the third insulating layer,

wherein the pixel electrode is in electrical contact with the first conductive layer through an opening in the third insulating layer and an opening in the second insulating layer;

wherein the common electrode is in electrical contact with a second conductive layer made from a same film as the first conductive layer;

wherein the second conductive layer is in electrical contact with a third conductive layer made of the same film as the gate electrode; and

wherein the common electrode substantially overlaps with the pixel electrode in an optically active region of a pixel.

5. A liquid crystal display device according to claim 1, wherein a region of the common electrode overlaps with the pixel electrode in the optically active region of the pixel, the region of the common electrode having a solid shape.

9. A liquid crystal display device according to claim 1,

wherein the common electrode comprises first conductive stripes;

wherein the pixel electrode comprises second conductive stripes; and

wherein the first conductive stripes and the second conductive stripes substantially do not overlap each other.

13. A liquid crystal display device according to claim 1, wherein the pixel electrode includes a first plurality of parallel and electrically conductive stripes making a first angle with a scan line and a second plurality of parallel and electrically conductive stripes making a second angle with the scan line.

17. A liquid crystal display device according to claim 1, wherein the pixel electrode includes slits.

21. A liquid crystal display device according to claim 1, wherein the pixel electrode is in electrical contact with the first conductive layer through a fourth conductive layer.

25. A liquid crystal display device according to claim 1, wherein the common electrode is a reflective electrode.

29. A liquid crystal display device according to claim 1, wherein the second conductive layer is in direct contact with the third conductive layer.

33. A liquid crystal display device according to claim 1, wherein the pixel electrode and the third conductive layer overlap each other in the pixel.

37. A liquid crystal display device according to claim 1, wherein the common electrode is in electrical contact with the second conductive layer through a fifth conductive layer.

41. A liquid crystal display device according to claim 1, wherein the gate electrode comprises molybdenum.

45. A liquid crystal display device according to claim 1, wherein the first conductive layer and the second conductive layer are made from a same film and have a multilayer structure comprising at least one of an aluminum layer and a titanium layer.

49. A liquid crystal display device according to claim 1, wherein the third insulating layer contains nitride.

52. A liquid crystal display device according to claim 1, wherein the second insulating layer includes an organic material.

58. An electronic appliance including a liquid crystal display device according to claim 1.

2. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer comprising polycrystalline silicon;

a gate insulating layer separating the gate electrode and the semiconductor layer;

a first insulating layer over the thin film transistor;

a first conductive layer over the first insulating layer and in direct contact with the semiconductor layer through an opening in the first insulating layer;

a second insulating layer including an organic material over the first conductive layer;

a common electrode over the second insulating layer;

a third insulating layer containing nitride over the common electrode; and

a pixel electrode over the third insulating layer,

wherein the pixel electrode is in electrical contact with the first conductive layer through an opening in the third insulating layer and an opening in the second insulating layer;

wherein the common electrode is in electrical contact with a second conductive layer made from a same film as the first conductive layer;

wherein the second conductive layer is in electrical contact with a third conductive layer made of the same film as the gate electrode; and

wherein the common electrode substantially overlaps with the pixel electrode in an optically active region of a pixel.

6. A liquid crystal display device according to claim 2, wherein a region of the common electrode overlaps with the pixel electrode in the optically active region of the pixel, the region of the common electrode having a solid shape.

10. A liquid crystal display device according to claim 2,

wherein the common electrode comprises first conductive stripes;

wherein the pixel electrode comprises second conductive stripes; and

wherein the first conductive stripes and the second conductive stripes substantially do not overlap each other.

14. A liquid crystal display device according to claim 2, wherein the pixel electrode includes a first plurality of parallel and electrically conductive stripes making a first angle with a scan line and a second plurality of parallel and electrically conductive stripes making a second angle with the scan line.

18. A liquid crystal display device according to claim 2, wherein the pixel electrode includes slits.

22. A liquid crystal display device according to claim 2, wherein the pixel electrode is in electrical contact with the first conductive layer through a fourth conductive layer.

26. A liquid crystal display device according to claim 2, wherein the common electrode is a reflective electrode.

30. A liquid crystal display device according to claim 2, wherein the second conductive layer is in direct contact with the third conductive layer.

34. A liquid crystal display device according to claim 2, wherein the pixel electrode and the third conductive layer overlap each other in the pixel.

38. A liquid crystal display device according to claim 2, wherein the common electrode is in electrical contact with the second conductive layer through a fifth conductive layer.

42. A liquid crystal display device according to claim 2, wherein the gate electrode comprises molybdenum.

46. A liquid crystal display device according to claim 2, wherein the first conductive layer and the second conductive layer are made from a same film and have a multilayer structure comprising at least one of an aluminum layer and a titanium layer.

55. A liquid crystal display device according to claim 2, wherein the first insulating layer comprises nitride.

56. A liquid crystal display device according to claim 2, wherein the pixel electrode comprises indium tin oxide.

59. An electronic appliance including a liquid crystal display device according to claim 2.

3. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer comprising polycrystalline silicon;

a gate insulating layer separating the gate electrode and the semiconductor layer;

a first insulating layer comprising nitride over the thin film transistor;

a first conductive layer over the first insulating layer and in direct contact with the semiconductor layer through an opening in the first insulating layer;

a second insulating layer over the first conductive layer;

a common electrode over the second insulating layer;

a third insulating layer over the common electrode; and

a pixel electrode over the third insulating layer,

wherein the pixel electrode is in electrical contact with the first conductive layer through an opening in the third insulating layer and an opening in the second insulating layer;

wherein the common electrode is in electrical contact with a second conductive layer made from a same film as the first conductive layer;

wherein the second conductive layer is in electrical contact with a third conductive layer made of the same film as the gate electrode; and

wherein the common electrode substantially overlaps with the pixel electrode in an optically active region of a pixel.

7. A liquid crystal display device according to claim 3, wherein a region of the common electrode overlaps with the pixel electrode in the optically active region of the pixel, the region of the common electrode having a solid shape.

11. A liquid crystal display device according to claim 3,

wherein the common electrode comprises first conductive stripes;

wherein the pixel electrode comprises second conductive stripes; and

wherein the first conductive stripes and the second conductive stripes substantially do not overlap each other.

15. A liquid crystal display device according to claim 3, wherein the pixel electrode includes a first plurality of parallel and electrically conductive stripes making a first angle with a scan line and a second plurality of parallel and electrically conductive stripes making a second angle with the scan line.

19. A liquid crystal display device according to claim 3, wherein the pixel electrode includes slits.

23. A liquid crystal display device according to claim 3, wherein the pixel electrode is in electrical contact with the first conductive layer through a fourth conductive layer.

27. A liquid crystal display device according to claim 3, wherein the common electrode is a reflective electrode.

31. A liquid crystal display device according to claim 3, wherein the second conductive layer is in direct contact with the third conductive layer.

35. A liquid crystal display device according to claim 3, wherein the pixel electrode and the third conductive layer overlap each other in the pixel.

39. A liquid crystal display device according to claim 3, wherein the common electrode is in electrical contact with the second conductive layer through a fifth conductive layer.

43. A liquid crystal display device according to claim 3, wherein the gate electrode comprises molybdenum.

47. A liquid crystal display device according to claim 3, wherein the first conductive layer and the second conductive layer are made from a same film and have a multilayer structure comprising at least one of an aluminum layer and a titanium layer.

50. A liquid crystal display device according to claim 3, wherein the third insulating layer contains nitride.

53. A liquid crystal display device according to claim 3, wherein the second insulating layer includes an organic material.

57. A liquid crystal display device according to claim 3, wherein the pixel electrode comprises indium tin oxide.

60. An electronic appliance including a liquid crystal display device according to claim 3.

4. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer comprising polycrystalline silicon;

a gate insulating layer separating the gate electrode and the semiconductor layer;

a first insulating layer over the thin film transistor;

a first conductive layer over the first insulating layer and in direct contact with the semiconductor layer through an opening in the first insulating layer;

a second insulating layer over the first conductive layer;

a common electrode over the second insulating layer;

a third insulating layer over the common electrode; and

a pixel electrode comprising indium tin oxide over the third insulating layer,

wherein the pixel electrode is in electrical contact with the first conductive layer through an opening in the third insulating layer and an opening in the second insulating layer;

wherein the common electrode is in electrical contact with a second conductive layer made from a same film as the first conductive layer;

wherein the second conductive layer is in electrical contact with a third conductive layer made of the same film as the gate electrode; and

wherein the common electrode substantially overlaps with the pixel electrode in an optically active region of a pixel.

8. A liquid crystal display device according to claim 4, wherein a region of the common electrode overlaps with the pixel electrode in the optically active region of the pixel, the region of the common electrode having a solid shape.

12. A liquid crystal display device according to claim 4,

wherein the common electrode comprises first conductive stripes;

wherein the pixel electrode comprises second conductive stripes; and

wherein the first conductive stripes and the second conductive stripes substantially do not overlap each other.

16. A liquid crystal display device according to claim 4, wherein the pixel electrode includes a first plurality of parallel and electrically conductive stripes making a first angle with a scan line and a second plurality of parallel and electrically conductive stripes making a second angle with the scan line.

20. A liquid crystal display device according to claim 4, wherein the pixel electrode includes slits.

24. A liquid crystal display device according to claim 4, wherein the pixel electrode is in electrical contact with the first conductive layer through a fourth conductive layer.

28. A liquid crystal display device according to claim 4, wherein the common electrode is a reflective electrode.

32. A liquid crystal display device according to claim 4, wherein the second conductive layer is in direct contact with the third conductive layer.

36. A liquid crystal display device according to claim 4, wherein the pixel electrode and the third conductive layer overlap each other in the pixel.

40. A liquid crystal display device according to claim 4, wherein the common electrode is in electrical contact with the second conductive layer through a fifth conductive layer.

44. A liquid crystal display device according to claim 4, wherein the gate electrode comprises molybdenum.

48. A liquid crystal display device according to claim 4, wherein the first conductive layer and the second conductive layer are made from a same film and have a multilayer structure comprising at least one of an aluminum layer and a titanium layer.

51. A liquid crystal display device according to claim 4, wherein the third insulating layer contains nitride.

54. A liquid crystal display device according to claim 4, wherein the second insulating layer includes an organic material.

61. An electronic appliance including a liquid crystal display device according to claim 4.