Vertical alignment liquid crystal display device in which a pixel electrode has slits which divide the pixel electrode into electrode portions

• US 8,068,200 B2
• Filed: 12/19/2005
• Issued: 11/29/2011
• Est. Priority Date: 12/24/2004
• Status: Active Grant

• Current Assignee: Ortus Technology Co., Ltd. (TOPPAN Holdings, Inc.)
• Original Assignee: Casio Computer Company Limited
• Inventors: Mizusako, Ryota, Nakajima, Yasushi, Yamaguchi, Minoru
• Primary Examiner(s): Robinson; Mark
• Assistant Examiner(s): El Shammaa; Mary A
• Application Number:
  US11/311,675
• Publication Number:
  US 20060139541A1
• Time in Patent Office: 2,171 Days
• Field of Search: None
• US Class Current: 349/130
• CPC Class Codes: G02F 1/133707 Structures for producing distorted electric fields, e.g. bumps, protrusions, recesses, slits in pixel electrodes
• CPC Class Codes: G02F 1/133711 by organic films, e.g. polymeric films
• CPC Class Codes: G02F 1/133742 for homeotropic alignment
• CPC Class Codes: G02F 1/1343 Electrodes reflective electrodes G02F1/133553
• CPC Class Codes: G02F 1/13712 the liquid crystal having negative dielectric anisotropy
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 2201/122 having a particular pattern

Abstract

A liquid crystal display device has an opposing substrate on which an opposing electrode is formed, a TFT substrate on which pixel electrodes arranged in matrix, thin film transistors connected to the pixel electrodes respectively, and gate lines and data lines for the thin film transistors are formed, vertical alignment films formed on the opposing inner surfaces of these substrates, and a liquid crystal layer disposed between the vertical alignment films and having negative dielectric anisotropy. Each pixel electrode has a slit formed for separating each pixel into a plurality of sub-pixels by partially eliminating the pixel electrode with a connecting portion left at which adjoining electrode portions of each pixel electrode is connected with each other. The width W₁ of the pixel electrode that runs in a direction in which the slit is formed and width W₂ of the connecting portion have a ratio W₂/W₁ of 0.13 or lower.

Claims

1. A liquid crystal display device comprising:

a first substrate;

a second substrate provided so as to oppose the first substrate; and

a liquid crystal layer containing liquid crystals having a negative dielectric anisotropy, the liquid crystal layer being provided between the first substrate and the second substrate;

wherein the liquid crystal display device further comprises, on a surface of the first substrate facing the liquid crystal layer;

a gate line provided so as to run in a predetermined direction;

a data line provided so as to intersect the gate line;

a TFT corresponding to an intersection between the gate line and the data line, wherein a drain electrode of the TFT is connected to the data line, and a gate electrode of the TFT is connected to the gate line; and

a pixel electrode connected to a source electrode of the TFT;

wherein the pixel electrode comprises;

(i) a plurality of electrode portions, which are formed with a second conductive film, arranged in one line along a data line direction, and (ii) connecting portions electrically connecting the electrode Portions;

wherein the source electrode of the TFT is electrically connected to the pixel electrode at a position of the pixel electrode closer, along the predetermined direction, to a first side of the pixel electrode, wherein the first side of the pixel electrode is near and runs along the data line;

wherein the electrode portions are electrically connected to each other by the connecting portions at positions of the pixel electrode closer, along the predetermined direction, to a second side of the pixel electrode, wherein the second side of the pixel electrode opposes the first side of the pixel electrode; and

wherein slits are provided in the pixel electrode to completely separate sides of the electrode portions at the first side of the pixel electrode;

wherein the liquid crystal display device further comprises an opposing electrode, which is formed with a first conductive film, formed on a surface of the second substrate facing the liquid crystal layer;

wherein when a voltage is applied between the pixel electrode and the opposing electrode, the liquid crystal molecules of the liquid crystal layer are aligned radially so that a center of radial alignment is positioned at each of the electrode portions, which are arranged in one line along the data line direction, in an area where the first and second conductive films are formed; and

wherein the connecting portions electrically connect the electrode portions so that the electrode portions are not separated from each other anywhere between the connecting portions and the second side of the pixel electrode along the predetermined direction.

2. The liquid crystal display device according to claim 1, wherein the source electrode of the TFT is electrically connected to the pixel electrode at a first one of the electrode portions, which is positioned closest to the gate line among the plurality of electrode portions.

3. The liquid crystal display device according to claim 1, wherein the source electrode of the TFT is connected to the pixel electrode along the data line direction, at a side of the pixel electrode at which the gate line is provided.

4. The liquid crystal display device according to claim 1, wherein one said connecting portion is provided between each two adjacent ones of the electrode portions.

5. The liquid crystal display device according to claim 4, wherein the electrode portions and the connecting portions constitute one layer and are formed of one material.

6. The liquid crystal display device according to claim 1, wherein W₂/W₁≦

0.13, where a width of each of the electrode portions in the predetermined direction is W₁, and a width of each of the connecting portions in the predetermined direction is W₂.

7. The liquid crystal display device according to claim 1, wherein the pixel electrode comprises three electrode portions.

8. The liquid crystal display device according to claim 1, wherein when a voltage is not applied between the pixel electrode and the opposing electrode, liquid crystal molecules of the liquid crystal layer are aligned perpendicularly to surfaces of the substrates.

9. The liquid crystal display device according to claim 1, wherein the first substrate is formed with a compensating-capacitor electrode positioned to correspond to sides of the electrode portions, and a potential of the compensating-capacitor electrode is set to be equal to a potential of the opposing electrode.

10. The liquid crystal display device according to claim 1, wherein the slits are longer in the predetermined direction than in the data line direction.

11. The liquid crystal display device according to claim 1, wherein the electrode portions are formed so as not to overlap the data line or the gate line.

12. The liquid crystal display device according to claim 1, wherein the pixel electrode is formed such that the electrode portions thereof do not overlap a data line to which another adjacent pixel electrode is connected.

13. The liquid crystal display device according to claim 1, wherein the pixel electrode is formed such that the electrode portions thereof do not overlap a gate line to which another adjacent pixel electrode is connected.

14. The liquid crystal display device according to claim 1, wherein the slits extend in parallel with each other.

15. The liquid crystal display device according to claim 3, wherein a direction along which the drain electrode, the gate electrode, and the source electrode of the TFT are arranged is parallel with the direction along which the electrode portions are arranged.

16. A liquid crystal display device comprising:

a first substrate;

a second substrate provided so as to oppose the first substrate; and

a liquid crystal layer containing liquid crystals having a negative dielectric anisotropy, the liquid crystal layer being provided between the first substrate and the second substrate;

wherein the liquid crystal display device further comprises, on a surface of the first substrate facing the liquid crystal layer;

a gate line provided so as to run in a predetermined direction;

a data line provided so as to intersect the gate line;

a TFT corresponding to an intersection between the gate line and the data line, wherein a drain electrode of the TFT is connected to the data line, and a gate electrode of the TFT is connected to the gate line; and

a pixel electrode connected to a source electrode of the TFT;

wherein the pixel electrode comprises;

(i) a plurality of electrode portions, which are formed with a second conductive film, arranged in one line along a data line direction, and (ii) connecting portions electrically connecting the electrode portions;

wherein the source electrode of the TFT is electrically connected to the pixel electrode at a position of the pixel electrode closer, along the predetermined direction, to a first side of the pixel electrode, wherein the first side of the pixel electrode is near and runs along the data line;

wherein the electrode portions are electrically connected to each other by the connecting portions at positions of the pixel electrode closer, along the predetermined direction, to a second side of the pixel electrode, wherein the second side of the pixel electrode opposes the first side of the pixel electrode; and

wherein slits are provided in the pixel electrode to completely separate sides of the electrode portions at the first side of the pixel electrode;

wherein the liquid crystal display device further comprises an opposing electrode, which is formed with a first conductive film, formed on a surface of the second substrate facing the liquid crystal layer;

wherein when a voltage is applied between the pixel electrode and the opposing electrode, the liquid crystal molecules of the liquid crystal layer are aligned radially so that a center of radial alignment is positioned at each of the electrode portions, which are arranged in one line along the data line direction, in an area where the first and second conductive films are formed;

wherein the source electrode of the TFT is electrically connected to the pixel electrode at a first one of the electrode Portions, which is positioned closest to the gate line among the plurality of electrode portions; and

wherein the first electrode portion is connected to a second one of the electrode portions, which is adjacent to the first electrode portion, at a position of the first electrode portion farthest from the TFT.

17. A liquid crystal display device comprising:

a first substrate;

a second substrate provided so as to oppose the first substrate; and

a liquid crystal layer containing liquid crystals having a negative dielectric anisotropy, the liquid crystal layer being provided between the first substrate and the second substrate;

wherein the liquid crystal display device further comprises, on a surface of the first substrate facing the liquid crystal layer;

a gate line provided so as to run in a predetermined direction;

a data line provided so as to intersect the gate line;

a TFT corresponding to an intersection between the gate line and the data line, wherein a drain electrode of the TFT is connected to the data line, and a gate electrode of the TFT is connected to the gate line; and

a pixel electrode connected to a source electrode of the TFT;

wherein the pixel electrode comprises;

(i) a plurality of electrode portions, which are formed with a second conductive film, arranged in one line along a data line direction, and (ii) connecting portions electrically connecting the electrode portions;

wherein the source electrode of the TFT is electrically connected to the pixel electrode at a position of the pixel electrode closer, along the predetermined direction, to a first side of the pixel electrode, wherein the first side of the pixel electrode is near and runs along the data line;

wherein the electrode portions are electrically connected to each other by the connecting portions at positions of the pixel electrode closer, along the predetermined direction, to a second side of the pixel electrode, wherein the second side of the pixel electrode opposes the first side of the pixel electrode; and

wherein slits are provided in the pixel electrode to completely separate sides of the electrode portions at the first side of the pixel electrode;

wherein the liquid crystal display device further comprises an opposing electrode, which is formed with a first conductive film, formed on a surface of the second substrate facing the liquid crystal layer;

wherein when a voltage is applied between the pixel electrode and the opposing electrode, the liquid crystal molecules of the liquid crystal layer are aligned radially so that a center of radial alignment is positioned at each of the electrode portions, which are arranged in one line along the data line direction, in an area where the first and second conductive films are formed; and

wherein each of the electrode portions has a rectangular shape with a same area.

18. A liquid crystal display device comprising:

a first substrate;

a second substrate provided so as to oppose the first substrate; and

a liquid crystal layer containing liquid crystals having a negative dielectric anisotropy, the liquid crystal layer being provided between the first substrate and the second substrate;

wherein the liquid crystal display device further comprises, on a surface of the first substrate facing the liquid crystal layer;

a gate line provided so as to run in a predetermined direction;

a data line provided so as to intersect the gate line;

a TFT corresponding to an intersection between the gate line and the data line, wherein a drain electrode of the TFT is connected to the data line, and a gate electrode of the TFT is connected to the gate line; and

a pixel electrode connected to a source electrode of the TFT;

wherein the pixel electrode comprises;

(i) a plurality of electrode portions, which are formed with a second conductive film, arranged in one line along a data line direction, and (ii) connecting portions electrically connecting the electrode Portions;

wherein the source electrode of the TFT is electrically connected to the pixel electrode at a position of the pixel electrode closer, along the predetermined direction, to a first side of the pixel electrode, wherein the first side of the pixel electrode is near and runs along the data line;

wherein the electrode portions are electrically connected to each other by the connecting portions at positions of the pixel electrode closer, along the predetermined direction, to a second side of the pixel electrode, wherein the second side of the pixel electrode opposes the first side of the pixel electrode; and

wherein slits are provided in the pixel electrode to completely separate sides of the electrode portions at the first side of the pixel electrode;

wherein the liquid crystal display device further comprises an opposing electrode, which is formed with a first conductive film, formed on a surface of the second substrate facing the liquid crystal layer;

wherein when a voltage is applied between the pixel electrode and the opposing electrode, the liquid crystal molecules of the liquid crystal layer are aligned radially so that a center of radial alignment is positioned at each of the electrode portions, which are arranged in one line along the data line direction, in an area where the first and second conductive films are formed; and

wherein the pixel electrode has a straight side formed by one side of each of the electrode portions and one side of each of the connecting portions.

19. A liquid crystal display device comprising:

a first substrate;

a second substrate provided so as to oppose the first substrate; and

a liquid crystal layer containing liquid crystals having a negative dielectric anisotropy, the liquid crystal layer being provided between the first substrate and the second substrate;

wherein the liquid crystal display device further comprises, on a surface of the first substrate facing the liquid crystal layer;

a gate line provided so as to run in a predetermined direction;

a data line provided so as to intersect the gate line;

a TFT corresponding to an intersection between the gate line and the data line, wherein a drain electrode of the TFT is connected to the data line, and a gate electrode of the TFT is connected to the gate line; and

a pixel electrode connected to a source electrode of the TFT;

wherein the pixel electrode comprises;

(i) a plurality of electrode portions, which are formed with a second conductive film, arranged in one line along a data line direction, and (ii) connecting portions electrically connecting the electrode portions;

wherein the source electrode of the TFT is electrically connected to the pixel electrode at a position of the pixel electrode closer, along the predetermined direction, to a first side of the pixel electrode, wherein the first side of the pixel electrode is near and runs along the data line;

wherein the electrode portions are electrically connected to each other by the connecting portions at positions of the pixel electrode closer, along the predetermined direction, to a second side of the pixel electrode, wherein the second side of the pixel electrode opposes the first side of the pixel electrode; and

wherein slits are provided in the pixel electrode to completely separate sides of the electrode portions at the first side of the pixel electrode;

wherein the liquid crystal display device further comprises an opposing electrode, which is formed with a first conductive film, formed on a surface of the second substrate facing the liquid crystal layer;

wherein when a voltage is applied between the pixel electrode and the opposing electrode, the liquid crystal molecules of the liquid crystal layer are aligned radially so that a center of radial alignment is positioned at each of the electrode portions, which are arranged in one line along the data line direction, in an area where the first and second conductive films are formed; and

wherein the connecting portions are arranged such that sides of the electrode portions at the second side of the pixel electrode are connected with each other such that the second side of the pixel electrode is straight.