Vertical alignment liquid crystal display device

• US 20060139541A1
• Filed: 12/19/2005
• Published: 06/29/2006
• 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: Yamaguchi, Minoru, Mizusako, Ryota, Nakajima, Yasushi
• Granted Patent: US 8,068,200 B2
• Time in Patent Office: Days
• 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 pair of substrates opposing to each other with a predetermined gap therebetween;

at least one opposing electrode formed on an inner surface of one substrate of the pair of substrates;

a plurality of pixel electrodes arranged in a matrix of a row direction and a column direction on an inner surface of the other substrate of the pair of substrates, each defining a pixel in an area where each faces the opposing electrode, and each having at least one slit for separating each into a plurality of electrode portions to divide each pixel into a plurality of sub-pixels, which slit is formed by eliminating a part of each pixel electrode so as to leave un-eliminated a connecting portion which has a predetermined width, at which adjoining electrode portions of each pixel electrode are connected with each other, and whose width is formed so as to be smaller than ⅕

of a width of each pixel electrode which width runs in a direction in which the slit is formed;

a plurality of thin film transistors formed on the inner surface of the other substrate so as to correspond to the plurality of pixel electrodes respectively, and connected to the corresponding pixel electrodes respectively;

a plurality of gate lines and data lines formed on the inner surface of the other substrate between rows and columns of the plurality of pixel electrodes respectively, for supplying a gate signal and a data signal to the thin film transistors on the corresponding rows and columns;

vertical alignment films formed on the inner surfaces of the one and the other substrates respectively, so as to cover the pixel electrodes and the opposing electrode; and

a liquid crystal layer filled in the gap between the pair of substrates and having a negative dielectric anisotropy.

2. The liquid crystal display device according to claim 1, wherein

a width W₁ as the width of the pixel electrode that runs in a direction in which the slit is formed and a width W₂ as the width of the connecting portion at which adjoining electrode portions of each pixel electrode are connected with each other are set to values which satisfy

W₂/W₁≦

0.1 3.

3. The liquid crystal display device according to claim 1, wherein

a width of the slit of each pixel electrode is 4.0 μ

m or smaller.

4. The liquid crystal display device according to claim 1, wherein

each of the plurality of pixel electrodes is formed in an elongated shape having shorter sides and longer sides, has the thin film transistor connected to one end of one of the shorter sides thereof, and is provided with the at least one slit which extends in a direction parallel with the shorter sides for separating the pixel electrode into the plurality of electrode portions.

5. The liquid crystal display device according to claim 1, wherein

each of the plurality of separated electrode portions of the pixel electrode is formed in substantially a shape of a square.

6. A liquid crystal display device, comprising:

a pair of substrates opposing to each other with a predetermined gap therebetween;

at least one opposing electrode formed on an inner surface of one substrate of the pair of substrates;

a plurality of pixel electrodes arranged in a matrix of a row direction and a column direction on an inner surface of the other substrate of the pair of substrates, each defining a pixel in an area where each faces the opposing electrode, and each having at least one slit for separating each into a plurality of electrode portions to divide each pixel into a plurality of sub-pixels, which slit is formed by eliminating a part of each pixel electrode so as to leave un-eliminated a connecting portion which has a predetermined width, at which adjoining electrode portions of each pixel electrode are connected with each other, and which is formed at a position off a center of a width of each pixel electrode which width runs in a direction in which the slit is formed, toward one side of the width of the pixel electrode;

a plurality of thin film transistors formed on the inner surface of the other substrate so as to correspond to the plurality of pixel electrodes respectively, and connected to the corresponding pixel electrodes respectively;

a plurality of gate lines and data lines formed on the inner surface of the other substrate between rows and columns of the plurality of pixel electrodes respectively, for supplying a gate signal and a data signal to the thin film transistors on the corresponding rows and columns;

vertical alignment films formed on the inner surfaces of the one and the other substrates respectively, so as to cover the pixel electrodes and the opposing electrode; and

a liquid crystal layer filled in the gap between the pair of substrates and having a negative dielectric anisotropy.

7. The liquid crystal display device according to claim 6, wherein

each of the plurality of pixel electrodes is formed in an elongated shape having shorter sides and longer sides, has the thin film transistor connected to one end of one of the shorter sides thereof, is provided with the at least one slit which extends in a direction parallel with the shorter sides for separating the pixel electrode into the plurality of electrode portions, and has the connecting portion at which the plurality of electrode portions are connected with each other formed at the longer side that is opposite to the longer side to which the thin film transistor is closer.

8. The liquid crystal display device according to claim 7, wherein

each of the plurality of pixel electrodes has an elongated shape whose longer sides are substantially three times larger than the shorter sides, and is provided with at least two slits for separating the pixel electrode into at least three or more electrode portions in a direction of the longer sides, with connecting portions of the respective slits formed at opposite longer sides of the pixel electrode alternately.

9. The liquid crystal display device according to claim 6, wherein

each of the plurality of pixel electrodes is formed in substantially a shape of a rectangle having shorter sides and longer sides, has the thin film transistor connected at one end of one shorter side thereof, and is provided with a plurality of slits for separating the pixel electrode into a plurality of electrode portions which are arranged in two columns and two rows, with connecting portions at which adjoining electrode portions are connected with each other being formed between each of the plurality of electrode portions and its adjoining electrode portion in a same column and between each of the plurality of electrode portions and its adjoining electrode portion in a same row.

10. The liquid crystal display device according to claim 9, wherein

the connecting portion at which, of the plurality of electrode portions, the electrode portion to which the thin film transistor is connected and the other electrode portion adjoining this electrode portion are connected with each other is formed at one shorter side of the pixel electrode other than one longer side thereof that is closer to the thin film transistor.

11. The liquid crystal display device according to claim 6, wherein

each of the plurality of electrode portions into which each pixel electrode is separated is formed in substantially a shape of a square.

12. The liquid crystal display device according to claim 6, further comprising

a compensating-capacitor electrode formed between a surface of the other substrate on which the plurality of pixel electrodes are provided and the pixel electrodes, so as to correspond to a circumference of each of the plurality of pixel electrode and so as to partially overlap with the circumference of the pixel electrode while being insulated from the pixel electrode, for forming a compensating capacity between itself and the pixel electrode and for forming a region of an electric field having a predetermined value between itself and the opposing electrode.

13. The liquid crystal display device according to claim 6, further comprising

an auxiliary electrode formed between a surface of the other substrate and the plurality of pixel electrodes, so as to correspond to the slit of each of the plurality of pixel electrodes and so as to face the opposing electrode on the one substrate, for forming an electric field having a predetermined value between itself and the opposing electrode.

14. The liquid crystal display device according to claim 6, further comprising:

a compensating-capacitor electrode formed between a surface of the other substrate on which the plurality of pixel electrodes are provided and the pixel electrodes, so as to correspond to a circumference of each of the plurality of pixel electrode and so as to partially overlap with the circumference of the pixel electrode while being insulated from the pixel electrode, for forming a compensating capacity between itself and the pixel electrode and for forming a region of an electric field having a predetermined value between itself and the opposing electrode; and

an auxiliary electrode formed between the surface of the other substrate and the plurality of pixel electrodes, integrally with the compensating-capacitor electrode, so as to correspond to the slit of each of the plurality of pixel electrodes, for forming an electric field having a predetermined value between itself and the opposing electrode on the one substrate.

15. A liquid crystal display device, comprising:

a pair of substrates opposing to each other with a predetermined gap therebetween;

at least one opposing electrode formed on an inner surface of one substrate of the pair of substrates;

a plurality of pixel electrodes arranged in a matrix of a row direction and a column direction on an inner surface of the other substrate of the pair of substrates, each defining a pixel in an area where each faces the opposing electrode, and each having at least one slit for separating each into a plurality of electrode portions to divide each pixel into a plurality of sub-pixels having a shape of substantially a square, which slit is formed by eliminating a part of each pixel electrode so as to leave un-eliminated a connecting portion which has a predetermined width, and at which adjoining electrode portions of each pixel electrode are connected with each other;

a plurality of thin film transistors formed on the inner surface of the other substrate so as to correspond to the plurality of pixel electrodes respectively, and connected to the corresponding pixel electrodes respectively;

a plurality of gate lines and data lines formed on the inner surface of the other substrate between rows and columns of the plurality of pixel electrodes respectively, for supplying a gate signal and a data signal to the thin film transistors on the corresponding rows and columns;

vertical alignment films formed on the inner surfaces of the one and the other substrates respectively, so as to cover the pixel electrodes and the opposing electrode;

a liquid crystal layer filled in the gap between the pair of substrates and having a negative dielectric anisotropy; and

an auxiliary electrode formed between a surface of the other substrate on which the plurality of pixel electrodes are provided and these pixel electrodes, so as to correspond to a circumference of each of the plurality of pixel electrodes and the slit while being insulated from each pixel electrode, for forming a region between itself and the opposing electrode in which region an electric field having a predetermined value is generated.

16. The liquid crystal display device according to claim 15, wherein

each of the plurality of pixel electrodes is formed in an elongated shape having shorter sides and longer sides, has the thin film transistor connected to one end of one of the shorter sides thereof, is provided with the at least one slit which extends in a direction parallel with the shorter sides for separating the pixel electrode into the plurality of electrode portions, and has the connecting portion at which the plurality of electrode portions are connected with each other formed at the longer side that is opposite to the longer side to which the thin film transistor is closer.

17. The liquid crystal display device according to claim 15, wherein

the auxiliary electrode is formed along the circumference of each pixel electrode and along edges of the electrode portions which are separated by the slit, so as to partially overlap with the circumference and the electrode portions.

18. The liquid crystal display device according to claim 17, wherein the auxiliary electrode is provided with a compensating-capacitor electrode for forming a compensating capacity between itself and the opposing electrode.

19. The liquid crystal display device according to claim 15, wherein

an electric potential of the auxiliary electrode is set to substantially a same value as an electric potential of the opposing electrode.

20. The liquid crystal display device according to claim 15, further comprising

protrusions formed on the inner surface of the one substrate on which the opposing electrode is formed, at positions corresponding to a center of the respective electrode portions which are separated by the slit of each of the plurality of pixel electrode on the other substrate.