Liquid crystal display device with wide viewing angle characteristics

• US 5,929,958 A
• Filed: 05/15/1998
• Issued: 07/27/1999
• Est. Priority Date: 03/17/1995
• Status: Expired due to Term

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Yanagawa, Kazuhiko, Ohta, Masuyuki, Kondo, Katsumi, Ashizawa, Keiichiro, Mishima, Yasuyuki, Ohe, Masahito, Ogawa, Kazuhiro, Yanai, Masahiro
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US09/079,360
• Time in Patent Office: 438 Days
• Field of Search: 349/139, 349/141, 349/42, 349/138
• US Class Current: 349/141
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• 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 1/136286 Wiring, e.g. gate line, drain line

Abstract

A liquid crystal display device in which a plurality of pixels are arranged in a matrix shape and a voltage signal waveform is applied to change the optical transmissivity or optical reflectivity of the pixels. A liquid crystal composition layer is disposed between a first substrate and a second substrate. At least one pair of pixel electrodes and counter electrodes are provided for each pixel between a face of the first substrate and a face of the liquid crystal composition layer and an electric field which is generated between the pixel electrode and the counter electrode and which has a component substantially parallel to the face of the first substrate. For each pixel, there are provided a video signal line, a drain electrode, a gate signal line, a gate electrode, a counter voltage signal line, a thin film transistor element, and a capacity element. A counter voltage signal is applied through the counter voltage signal line to the counter electrode. A common bus line which includes a conductive layer having a multi-layered structure, is provided for connecting the counter voltage signal lines of the plural pixels commonly and the counter voltage signal lines are individually led out through the common bus line to counter electrode terminals.

Claims

1. A liquid crystal display device comprising, a plurality of pixels arranged in a matrix shape, and means for applying a voltage signal waveform to change the optical transmissivity or optical reflectivity of said pixels, comprising:

a liquid crystal composition layer having twistable liquid crystal molecules;

a first substrate and a second substrate having said liquid crystal composition layer disposed therebetween, at least one of said first and second substrates being transparent, and at least one polarizing means; and

at least one pair of pixel electrodes and counter electrodes provided for each pixel between a face of said first substrate and a face of said liquid crystal composition layer,

whereby the twisting extent of the liquid crystal molecules of said liquid crystal composition layer is controlled by an electric field which is generated between said pixel electrode and said counter electrode and which has a component substantially parallel to the face of said first substrate,

wherein for each pixel between the face of said first substrate and the face of said liquid crystal composition layer, there are provided a video signal line, a drain electrode, a gate signal line, a gate electrode, a counter voltage signal line, a thin film transistor element, and a capacity element formed by superposing a portion of said pixel electrode over a portion of said counter voltage signal line through a layer insulating film, and

wherein a gate signal is applied through said gate signal line to said gate electrode, a video signal is applied through said video signal line, said drain electrode and said thin film transistor element to said pixel electrode, and a counter voltage signal is applied through said counter voltage signal line to said counter electrode,

wherein the improvement comprises a common bus line for connecting said counter voltage signal lines of said plural pixels commonly,

wherein said counter voltage signal lines are individually led out through said common bus line to counter electrode terminals, and said common bus line includes at least one conductive layer having a multi-layered structure.

2. A liquid crystal display device as set forth in claim 1, wherein said common bus line has the multi-layered structure including a first conductive layer made integral with a counter signal line and a second conductive layer having a resistance lower than a resistance of the first conductive layer.

3. A liquid crystal display device as set forth in claim 2, wherein the first conductive layer made integral with said counter signal line is made of the same material as that of said gate signal line, and the second conductive layer having the lower resistance is made of the same material as that of a conductive layer forming said video signal line.

4. A liquid crystal display device having a plurality of pixels including a plurality of switching elements, comprising:

a pair of substrates;

a liquid crystal layer interposed between said pair of substrates;

an electrode structure which generates an electric field having a component predominately in parallel with at least one of said pair of substrates, said electrode structure including at least one counter electrode and at least one pixel electrode;

at least one counter voltage signal line connected to the at least one counter electrode of the pixels; and

at least one common bus line having a portion connected to at least one end of the at least one counter voltage signal line;

wherein the at least one common bus line has a resistance which is smaller than a resistance of the at least one counter voltage signal line.

5. A liquid crystal display device according to claim 4, wherein the plurality of pixels are arranged in rows and columns, the at least one counter voltage signal line including a plurality of counter voltage signal lines, a respective one of the plurality of counter voltage signal lines being connected to the counter electrodes of the pixels of a respective row, the at least one common bus line having portions thereof connected to at least one end of the plurality of counter voltage signal lines.

6. A liquid crystal display device according to claim 4, wherein the at least one counter electrode and the at least one pixel electrode are provided on one of the pair of substrates.

7. A liquid crystal display device according to claim 4, wherein the at least one common bus line is provided in a non-display region of the liquid crystal display device.

8. A liquid crystal display device according to claim 4, wherein at least one insulating film is formed between the at least one counter voltage signal line and the at least one pixel electrode.

9. A liquid crystal display device according to claim 4, wherein for each pixel there are provided a video signal line and a scanning signal line, the liquid crystal display device further comprising a plurality of driver units including a gate driver unit connected to the scanning signal lines, a drain driver unit connected to the video signal lines and a common driver unit connected to the common bus line.

10. A liquid crystal display device according to claim 9, further comprising a timing controller connected with the plurality of driver units.

11. A liquid crystal display device according to claim 4, wherein the at least one common bus line includes portions extending in parallel in a row direction of the pixels.

12. A liquid crystal display device according to claim 11, wherein the at least one common bus line is provided in a non-display region of the liquid crystal display device.

13. A liquid crystal display device according to claim 11, wherein the portions of the at least one common bus line extending in parallel in the row direction of the pixels are formed of the same material as a video signal line.

14. A liquid crystal display device according to claim 4, wherein the at least one common bus line includes portions extending in parallel to the row direction of the plurality of pixels and portions extending in parallel to the column direction of the plurality of pixels.

15. A liquid crystal display device according to claim 14, wherein the at least one common bus line has portions provided in regions other than a region where video signal lines are connected to a drain driver unit.

16. A liquid crystal display device according to claim 14, wherein the at least one common bus line includes portions connected together in a drain driver unit.

17. A liquid crystal display device according to claim 14, wherein the portions of the at least one common bus line extending in parallel with the row direction of the plurality of pixels are formed of the same material as a video signal line, and the portions of the at least one common bus line extending in parallel with the column direction are formed of the same material as a scanning signal line.

18. A liquid crystal display device according to claim 17, wherein the at least one common bus line has portions connected to both ends of the at least one counter voltage signal line.

19. A liquid crystal display device according to claim 14, wherein the portion of the at least one common bus line connected to at least one end of the counter voltage signal line is electrically connected through at least one contact hole.

20. A liquid crystal display device having a plurality of pixels including a plurality of switching elements, comprising:

a pair of substrates;

a liquid crystal layer interposed between said pair of substrates;

an electrode structure which generates an electric field having a component predominantly in parallel with at least one of said pair of said substrates, said electrode structure including at least one counter electrode and at least one pixel electrode;

at least one counter voltage signal line connected to the at least one counter electrode of the pixels; and

at least one common bus line having a portion connected to the at least one end of the at least one counter voltage signal line;

wherein the at least one common bus line includes a multi-layer structure having at least one conductive layer.

21. A liquid crystal display device according to claim 20, wherein the at least one common bus line includes a first conductive layer made integral with the at least one counter voltage signal line and a second conductive layer having a resistance lower than a resistance of the first conductive layer.

22. A liquid crystal display device according to claim 21, wherein the second conductive layer is made of the same material as that of a conductive layer forming a video signal line.

23. A liquid crystal display device according to claim 20, wherein for each pixel there are provided a video signal line and a scanning signal line, the liquid crystal display device further comprising a plurality of driver units including a gate driver unit connected to the scanning signal lines, a drain driver unit connected to the video signal lines and a common driver unit connected to the common bus line.

24. A liquid crystal display device according to claim 23, further comprising a timing controller connected with the plurality of driver units.

25. A liquid crystal display device according to claim 20, wherein the at least one common bus line includes portions extending in parallel in a row direction of the pixels.

26. A liquid crystal display device according to claim 25, wherein the at least one common bus line is provided in a non-display region of the liquid crystal display device.

27. A liquid crystal display device according to claim 25, wherein the portions of the at least one common bus line extending in parallel in the row direction of the pixels are formed of the same material as a video signal line.

28. A liquid crystal display device according to claim 20, wherein the at least one common bus line includes portions extending in parallel to the row direction of the plurality of pixels and portions extending in parallel to the column direction of the plurality of pixels.

29. A liquid crystal display device according to claim 28, wherein the at least one common bus line has portions provided in regions other than a region where video signal lines are connected to a drain driver unit.

30. A liquid crystal display device according to claim 28, wherein the at least one common bus line includes portions connected together in a drain driver unit.

31. A liquid crystal display device according to claim 28, wherein the portions of the at least one common bus line extending in parallel with the row direction of the plurality of pixels are formed of the same material as a video signal line, and the portions of the at least one common bus line extending in parallel with the column direction are formed of the same material as a scanning signal line.

32. A liquid crystal display device according to claim 28, wherein the portion of the at least one common bus line connected to at least one end of the counter voltage signal line is electrically connected through at least one contact hole.

33. A liquid crystal display device having a plurality of pixels including a plurality of switching elements, comprising:

a pair of substrates;

a liquid crystal layer interposed between said pair of substrates;

an electrode structure which generates an electric field having a component predominantly in parallel with at least one of said pair of said substrates, said electrode structure including at least one counter electrode and at least one pixel electrode;

at least one counter voltage signal line connected to the at least one counter electrode of the pixels;

at least one common bus line having a portion connected to the at least one end of the at least one counter voltage signal line; and

at least one dummy signal line formed of the same material and having the same thickness as the at least one common bus line being arranged in at least one region of the liquid crystal display device other than a region having the at least one common bus line arranged therein.

34. A liquid crystal display device according to claim 33, wherein for each pixel, there are provided a video signal line and a scanning signal line and the at least one dummy signal line is formed of the same material and having the same thickness as the scanning signal line.

35. A liquid crystal display device according to claim 33, wherein for each pixel, there are provided a video signal line and a scanning signal line, and the at least one dummy signal line is formed of the same material and the same thickness as the video signal line.