LIQUID CRYSTAL DISPLAY DEVICE

• US 20100245749A1
• Filed: 06/16/2010
• Published: 09/30/2010
• 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 7,880,836 B2
• Time in Patent Office: Days
• US Class Current: 349/143
• 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; and

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 and a second conductive layer over the first insulating layer in direct contact with the semiconductor layer through openings in the first insulating layer;

a second insulating layer over the first conductive layer and the second 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 one of first conductive layer and the second 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 third conductive layer made from a same film as the first conductive layer and the second conductive layer; and

wherein the third conductive layer is in electrical contact with a fourth conductive layer made of the same film as the gate electrode.

2. 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.

3. A liquid crystal display device according to claim 2, wherein the stripes included in the pixel electrode are in contact through one of their extremities so as to form a comb shape.

4. A liquid crystal display device according to claim 2, wherein the stripes included in the pixel electrode are in contact through their extremities so as to define slits in the pixel electrode.

12. A liquid crystal display device according to claim 1, wherein the semiconductor layer comprises polycrystalline silicon.

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

22. A liquid crystal display device according to claim 1, wherein the first insulating layer comprises nitride.

27. A liquid crystal display device according to claim 1, wherein the first conductive layer and the second conductive layer have a multilayer structure comprising an aluminum layer and a titanium layer.

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

37. A liquid crystal display device according to claim 1, wherein the pixel electrode comprises indium tin oxide.

5. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer; and

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 and a second conductive layer over the first insulating layer in direct contact with the semiconductor layer through openings in the first insulating layer;

a second insulating layer over the first conductive layer and the second 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 one of first conductive layer and the second 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 third conductive layer made from a same film as the first conductive layer and the second conductive layer;

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

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.

6. A liquid crystal display device according to claim 5, wherein the stripes included in the pixel electrode are in contact through one of their extremities so as to form a comb shape.

7. A liquid crystal display device according to claim 5, wherein the stripes included in the pixel electrode are in contact through their extremities so as to define slits in the pixel electrode.

13. A liquid crystal display device according to claim 5, wherein the semiconductor layer comprises polycrystalline silicon.

18. A liquid crystal display device according to claim 5, wherein the gate electrode comprises molybdenum.

23. A liquid crystal display device according to claim 5, wherein the first insulating layer comprises nitride.

28. A liquid crystal display device according to claim 5, wherein the first conductive layer and the second conductive layer have a multilayer structure comprising an aluminum layer and a titanium layer.

33. A liquid crystal display device according to claim 5, wherein the second insulating layer comprises an organic material.

38. A liquid crystal display device according to claim 5, wherein the pixel electrode comprises indium tin oxide.

8. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer; and

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 and a second conductive layer over the first insulating layer in direct contact with the semiconductor layer through openings in the first insulating layer;

a second insulating layer over the first conductive layer and the second 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 one of first conductive layer and the second 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 third conductive layer made from a same film as the first conductive layer and the second conductive layer;

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

wherein the pixel electrode is comb-shaped.

14. A liquid crystal display device according to claim 8, wherein the semiconductor layer comprises polycrystalline silicon.

19. A liquid crystal display device according to claim 8, wherein the gate electrode comprises molybdenum.

24. A liquid crystal display device according to claim 8, wherein the first insulating layer comprises nitride.

29. A liquid crystal display device according to claim 8, wherein the first conductive layer and the second conductive layer have a multilayer structure comprising an aluminum layer and a titanium layer.

34. A liquid crystal display device according to claim 8, wherein the second insulating layer comprises an organic material.

39. A liquid crystal display device according to claim 8, wherein the pixel electrode comprises indium tin oxide.

9. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer; and

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 and a second conductive layer over the first insulating layer in direct contact with the semiconductor layer through openings in the first insulating layer;

a second insulating layer over the first conductive layer and the second 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 one of first conductive layer and the second 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 third conductive layer made from a same film as the first conductive layer and the second conductive layer;

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

wherein the pixel electrode includes a plurality of openings each having a long and narrow shape.

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

wherein openings of a first plurality of openings among the plurality of openings each having a long and narrow shape make a first angle with a scan line;

and

wherein openings of a second plurality of openings among the plurality of openings each having a long and narrow shape make a second angle with the scan line.

15. A liquid crystal display device according to claim 9, wherein the semiconductor layer comprises polycrystalline silicon.

20. A liquid crystal display device according to claim 9, wherein the gate electrode comprises molybdenum.

25. A liquid crystal display device according to claim 9, wherein the first insulating layer comprises nitride.

30. A liquid crystal display device according to claim 9, wherein the first conductive layer and the second conductive layer have a multilayer structure comprising an aluminum layer and a titanium layer.

35. A liquid crystal display device according to claim 9, wherein the second insulating layer comprises an organic material.

40. A liquid crystal display device according to claim 9, wherein the pixel electrode comprises indium tin oxide.

11. A liquid crystal display device comprising:

a thin film transistor comprising;

a gate electrode;

a semiconductor layer; and

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 and a second conductive layer over the first insulating layer in direct contact with the semiconductor layer through openings in the first insulating layer;

a second insulating layer over the first conductive layer and the second 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 one of first conductive layer and the second 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 third conductive layer made from a same film as the first conductive layer and the second conductive layer;

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

wherein the pixel electrode includes a plurality of openings.

16. A liquid crystal display device according to claim 11, wherein the semiconductor layer comprises polycrystalline silicon.

21. A liquid crystal display device according to claim 11, wherein the gate electrode comprises molybdenum.

26. A liquid crystal display device according to claim 11, wherein the first insulating layer comprises nitride.

31. A liquid crystal display device according to claim 11, wherein the first conductive layer and the second conductive layer have a multilayer structure comprising an aluminum layer and a titanium layer.

36. A liquid crystal display device according to claim 11, wherein the second insulating layer comprises an organic material.

41. A liquid crystal display device according to claim 11, wherein the pixel electrode comprises indium tin oxide.