In-plane switching mode active matrix type liquid crystal display device and method of fabricating the same

• US 6,933,528 B2
• Filed: 04/02/2003
• Issued: 08/23/2005
• Est. Priority Date: 04/04/2002
• Status: Expired due to Term

• Current Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Original Assignee: NEC LCD Technologies Limited (Tianma Microelectronics Company Limited)
• Inventors: Nishida, Shinichi, Itakura, Kunimasa, Matsumoto, Kimikazu
• Primary Examiner(s): Tran, Michael
• Assistant Examiner(s): TRAN, LONG K
• Application Number:
  US10/406,091
• Publication Number:
  US 20040027525A1
• Time in Patent Office: 874 Days
• Field of Search: 257/59, 257/72, 257/222, 257/225, 257/249, 257/291, 257/292, 257/440, 257/443, 349/110, 349/111, 349/139, 349/141, 349/143, 349/147
• US Class Current: 257/59
• 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 1/136218 Shield electrodes
• CPC Class Codes: G02F 2201/40 Arrangements for improving the aperture ratio

Abstract

An in-plane switching mode active matrix type liquid crystal display device includes a first substrate, a second substrate located opposing the first substrate, and a liquid crystal layer sandwiched between the first and second substrates. The first substrate includes a thin film transistor, a pixel electrode, a common electrode, a data line, a scanning line, and a common electrode line. The scanning line and the common electrode line are formed in a common layer in parallel with each other. The common electrode overlaps the data line and the scanning line with an interlayer insulating film existing therebetween. The common electrode line is singly formed at either side about the scanning line. The common electrode is electrically connected to the common electrode line through a contact hole formed throughout the interlayer insulating film, and shields a gap formed between the scanning line and the common electrode line.

Claims

1. An in-plane switching mode active matrix type liquid crystal display device comprising:

(a) a first substrate;

(b) a second substrate located opposing said first substrate; and

(c) a liquid crystal layer sandwiched between said first and second substrates,

wherein said first substrate includes;

(a1) a thin film transistor having a gate electrode, a drain electrode and a source electrode;

(a2) a pixel electrode each associated to a pixel to be driven;

(a3) a common electrode to which a reference voltage is applied;

(a4) a data line;

(a5) a scanning line; and

(a6) a common electrode line,

said gate electrode is electrically connected to said scanning line, said drain electrode is electrically connected to said data line, said source electrode is electrically connected to said pixel electrode, and said common electrode is electrically connected to said common electrode line,

molecular axes of liquid crystal in said liquid crystal layer are rotated in a plane parallel with said first substrate by an electric field substantially parallel with a plane of said first substrate and to be applied between said pixel electrode and said common electrode, to thereby display images,

said scanning line and said common electrode line are formed in a common layer in parallel with each other,

said common electrode overlaps said data line and said scanning line with an interlayer insulating film existing therebetween,

said common electrode line is singly formed at either side about said scanning line,

said common electrode is electrically connected to said common electrode line through a contact hole formed throughout said interlayer insulating film, and

said common electrode shields a gap formed between said scanning line and said common electrode line.

2. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said contact hole is formed in the vicinity of one of two corners defining a diagonal line there across which is obtained, if a rubbing direction is given, by rotating the axis in which the data line extends towards the rubbing direction by an acute angle in a plan view of the pixel.

3. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said liquid crystal display device defines a first sub pixel area to which a first electric field is applied in parallel with a plane of said first substrate between said pixel and common electrodes, and in which said molecular axes of liquid crystal rotate in a first direction in a plane parallel with said first substrate, and a second sub pixel area to which a second electric field is applied in parallel with a plane of said first substrate between said pixel and common electrodes, and in which said molecular axes of liquid crystal rotate in a second direction in a plane parallel with said first substrate, said second direction being different from said first direction.

4. The in-plane switching mode active matrix type liquid crystal, display device as set forth in claim 3, wherein said contact hole is formed at any one of corners at which an extension of said common electrode line towards inside of the picture element, and an extension of said common electrode towards the center of the picture element from said common electrode line form an angle of 90 degrees or greater in a plan view of a pixel.

5. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said common electrode extends beyond said data line by at least 3 micrometers in a width-wise direction thereof.

6. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said common electrode extends beyond said scanning line by at least 1 micrometer in a width-wise direction thereof.

7. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said common electrode is formed in a layer closer to said liquid crystal layer than said pixel electrode, and said common and pixel electrodes are electrically insulated from each other by an interlayer insulating film.

8. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 7, wherein said common electrode is formed in a layer closer to said liquid crystal layer than said pixel electrode, and said common and pixel electrodes cooperate with each other to form an accumulation capacity therebetween.

9. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 7, wherein said pixel electrode and said data line are formed in a common layer.

10. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said pixel electrode is comprised of a plurality of first portions, and a second portion connecting said first portions at ends thereof to one another, and said second portion is located above said common electrode line and cooperates with said common electrode line to form an accumulation capacity therebetween.

11. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 10, wherein said second portion is remote from a scanning line in a next stage by 3 micrometers or greater.

12. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said common electrode is composed of electrically conductive transparent material.

13. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said pixel electrode is composed of electrically conductive transparent material.

14. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said interlayer insulating film is comprised of one of a film composed of organic material, a film composed of transparent inorganic material, and a film having a two-layered structure including a film composed of organic material and a film composed of transparent inorganic material.

15. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 14, wherein said organic material is photosensitive resin.

16. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said interlayer insulating film is comprised of an organic film and an inorganic film, and said organic film is formed above and in the vicinity of said scanning line, said data line, said common electrode line and said thin film transistor.

17. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 16, wherein said organic film is formed only inside of a pattern of said common electrode.

18. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 16, wherein said organic film is composed of photosensitive resin.

19. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said interlayer insulating film is comprised of an organic film and an inorganic film, and said organic film is formed above and in the vicinity of said scanning line, said data line and said thin film transistor.

20. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 19, wherein said organic film is formed only inside of a pattern of said common electrode.

21. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 19, wherein said organic film is composed of photosensitive resin.

22. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said interlayer insulating film is comprised of an organic film and an inorganic film, and said organic film is formed above and in the vicinity of said data line and said thin film transistor.

23. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 22, wherein said organic film is formed only inside of a pattern of said common electrode.

24. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said interlayer insulating film is comprised of an organic film and an inorganic film, and said organic film is formed above and in the vicinity of said data line.

25. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 24, wherein said organic film is formed only inside of a pattern of said common electrode.

26. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 22, wherein said organic film is composed of photosensitive resin.

27. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 24, wherein said organic film is composed of photosensitive resin.

28. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said thin film transistor is formed at an intersection of said scanning and data lines, and said drain electrode is formed directly of said data line.

29. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, further comprising a black matrix layer formed in a matrix.

30. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 29, wherein said black matrix layer has a specific resistance of 1×

10¹⁰ Ω

·

cm or greater.

31. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, further comprising a black matrix layer formed in an isolated pattern only above said thin film transistor for overlapping said thin film transistor.

32. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 31, wherein said black matrix layer has a specific resistance of 1×

10¹⁰ Ω

·

cm or greater.

33. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, further comprising a color layer defining a color filter, said color layer having an edge extending in parallel with said data line.

34. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 33, further comprising color layers defining a color filter, said color layers being arranged in such a manner that adjacent color layers are arranged without a gap therebetween or partially overlap each other.

35. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, further comprising a pillar-shaped pattern formed between said scanning line and said common electrode line for ensuring a gap between said first and second substrates.

36. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein liquid crystal-in said liquid crystal layer has dielectric constant anisotropy Δ

∈

of 9 or greater.

37. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein liquid crystal in said liquid crystal layer has dielectric constant anisotropy Δ

∈

of 11 or greater.

38. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein liquid crystal in said liquid crystal layer has an N/I point of 80 degrees centigrade or higher.

39. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said common electrode is formed above a channel of said thin film transistor with an opening having an end remote from an end of said channel by a predetermined distance.

40. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, further comprising a reverse-rotation preventing structure in a sub pixel area in which all liquid crystal molecules are rotated in the same direction, for preventing liquid crystal molecules from rotating in a direction opposite to said same direction,

said reverse-rotation preventing structure including an auxiliary electrode to which a voltage equal to a voltage of at least one of said pixel electrode and said common electrode is applied such that a direction of a rubbing axis is identical in said sub pixel area with a direction of an electric field generated in said sub pixel area, if said rubbing axis rotates by an acute angle.

41. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said data line is electrically connected around a display area to a first protection circuit formed in the same layer as a layer in which said scanning line is formed, through a contact hole formed throughout an electrically insulating film, and said scanning line is electrically connected around a display area to a second protection circuit formed in the same layer as a layer in which said data line is formed, through a contact hole formed throughout said electrically insulating film.

42. The in-plane switching mode active matrix type liquid crystal display device as set forth in claim 1, wherein said data line is electrically connected around a display area to a first protection circuit formed in the same layer as a layer in which said scanning line is formed, through a contact bole formed throughout an electrically insulating film and further through an electrically conductive pattern formed on a layer formed on said electrically insulating film, and said scanning line is electrically connected around a display area to a second protection circuit formed in the same layer as a layer in which said data line is formed, through a contact hole formed throughout said electrically insulating film and further through an electrically conductive pattern formed on a layer formed on said electrically insulating film.

43. An electronic device including an in-plane switching mode active matrix type liquid crystal display device comprising:

(a) a first substrate;

(b) a second substrate located opposing said first substrate; and

(c) a liquid crystal layer sandwiched between said first and second substrates,

wherein said first substrate includes;

(a1) a thin film transistor having a gate electrode, a drain electrode and a source electrode;

(a2) a pixel electrode each associated to a pixel to be driven;

(a3) a common electrode to which a reference voltage is applied;

(a4) a data line;

(a5) a scanning line; and

(a6) a common electrode line,

said gate electrode is electrically connected to said scanning line, said drain electrode is electrically connected to said data line, said source electrode is electrically connected to said pixel electrode, and said common electrode is electrically connected to said common electrode line,

molecular axes of liquid crystal in said liquid crystal layer are rotated in a plane parallel with said first substrate by an electric field substantially parallel with a plane of said first substrate and to be applied between said pixel electrode and said common electrode, to thereby display images,

said scanning line and said common electrode line are formed in a common layer in parallel with each other,

said common electrode overlaps said data line and said scanning line with an interlayer insulating film existing therebetween,

said common electrode line is singly formed at either side about said scanning line,

said common electrode is electrically connected to said common electrode line through a contact hole formed throughout said interlayer insulating film, and

said common electrode shields a gap formed between said scanning line and said common electrode line.

44. A method of fabricating an in-plane switching mode active matrix type liquid crystal display device comprising:

(a) a first substrate;

(b) a second substrate located opposing said first substrate; and

(c) a liquid crystal layer sandwiched between said first and second substrates,

wherein said first substrate includes;

(a1) a thin film transistor having a gate electrode, a drain electrode and a source electrode;

(a2) a pixel electrode each associated to a pixel to be driven;

(a3) a common electrode to which a reference voltage is applied;

(a4) a data line;

(a5) a scanning line; and

(a6) a common electrode line,

said gate electrode is electrically connected to said scanning line, said drain electrode is electrically connected to said data line, said source electrode is electrically connected to said pixel electrode, and said common electrode is electrically connected to said common electrode line,

molecular axes of liquid crystal in said liquid crystal layer are rotated in a plane parallel with said first substrate by an electric field substantially parallel with a plane of said first substrate and to be applied between said pixel electrode and said common electrode, to thereby display images,

said method comprising the steps of;

(a) forming said scanning line and said common electrode line in a common layer in parallel with each other wherein said common electrode line is singly formed at either side about said scanning line;

(b) forming an interlayer insulating firm over said data line and said scanning line;

(c) forming a contact hole throughout said interlayer insulating film; and

(d) forming said common electrode on said interlayer insulating film such that said common electrode is electrically connected to said common electrode line through said contact hole and said common electrode shields a gap formed between said scanning line and said common electrode line.

45. The method as set forth in claim 44, further comprising the step of forming said pixel electrode and said data line in a common layer.

46. The method as set forth in claim 44, further comprising the step of forming said pixel electrode comprised of a plurality of first portions, and a second portion connecting said first portions at ends thereof to one another, wherein said second portion is located above said common electrode line and cooperates with said common electrode line to form an accumulation capacity therebetween.

47. The method as set forth in claim 44, further comprising the step of forming said interlayer insulating film so as to have a two-layered structure including an organic film and an inorganic film.

48. The method as set forth in claim 44, further comprising the step of forming said interlayer insulating film so as to have a two-layered structure including an organic film and an inorganic film wherein and said organic film is formed above and in the vicinity of said scanning line, said data line, said common electrode line and said thin film transistor.

49. The method as set forth in claim 44, further comprising the step of forming said interlayer insulating film so as to have a two-layered structure including an organic film and an inorganic film wherein and said organic film is formed above and in the vicinity of said scanning line, said data line and said thin film transistor.

50. The method as set forth in claim 44, further comprising the step of forming said interlayer insulating film so as to have a two-layered structure including an organic film and an inorganic film wherein and said organic film is formed above and in the vicinity of said data line and said thin film transistor.

51. The method as set forth in claim 44, further comprising the step of forming said interlayer insulating film so as to have a two-layered structure including an organic film and an inorganic film wherein and said organic film is formed above and in the vicinity of said data line.

52. The method as set forth in claim 44, further comprising the step of forming a black matrix layer in an isolated pattern only above said thin film transistor for overlapping said thin film transistor.

53. The method as set forth in claim 44, further comprising the step of forming a color layer defining a color filter such that said color layer has an edge extending in parallel with said data line.

54. The method as set forth in claim 44, further comprising the step of forming color layers defining a color filter such that said color layers are arranged in such a manner that adjacent color layers are arranged without a gap therebetween or partially overlap each other.

55. The method as set forth in claim 44, further comprising the step of forming a pillar-shaped pattern on at least one of said first and second substrates between said scanning line and said common electrode line for ensuring a gap between said first and second substrates.

56. The method as set forth in claim 44, further comprising the step of forming said common electrode above a channel of said thin film transistor with an opening having an end remote from an end of said channel by a predetermined distance.

57. The method as set forth in claim 44, further comprising the step of electrically connecting said data line around a display area to a first protection circuit formed in the same layer as a layer in which said scanning line is formed, through a contact hole formed throughout an electrically insulating film, and further electrically connecting said scanning line around a display area to a second protection circuit formed in the same layer as a layer in which said data line is formed, through a contact hole formed throughout said electrically insulating film.

58. The method as set forth in claim 44, further comprising the step of electrically connecting said data line around a display area to a first protection circuit formed in the same layer as a layer in which said scanning line is formed, through a contact hole formed throughout an electrically insulating film and further through an electrically conductive pattern formed on a layer formed on said electrically insulating film, and further electrically connecting said scanning line around a display area to a second protection circuit formed in the same layer as a layer in which said data line is formed, through a contact hole formed throughout said electrically insulating film and further through an electrically conductive pattern formed on a layer formed on said electrically insulating film.