JP2002350902A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the transition operation of a liquid crystal display device having an OCB(optically compensated birefringence) mode cannot be reliably carried out. SOLUTION: In this liquid crystal display device, it is made possible to apply a transverse electric field equal to or higher than a threshold required for the complete transition of the alignment of liquid crystal molecules of the OCB mode being on a pixel electrode from spray alignment to bend alignment by forming a wiring with an electrically conductive film identical to or different from that of a pixel electrode which is electrically separated from an active element and the pixel electrode on a layer identical to or different from the pixel electrode existing between adjacent pixel electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an OCB (Optically C
In an active matrix type liquid crystal display device in which an active element is connected to a pixel electrode formed of a conductive film for applying a voltage to a liquid crystal layer having an ompensated birefringence (mode), a liquid crystal molecule alignment direction on the pixel electrode is set to an external direction. The present invention relates to a liquid crystal display device for controlling by an electric field from the liquid crystal display.

[0002]

2. Description of the Related Art A conventional OCB (Optically Compensated Bir
efringence) mode in a liquid crystal display device,
The liquid crystal display has a function as a liquid crystal display device after performing the transition operation from the splay alignment to the bend alignment of the liquid crystal molecules, so that the transition operation is completely performed by applying an external voltage immediately before displaying an image. Nucleation is required,
Several configurations have been proposed as a method for forming transition nuclei.

A method for forming a transition nucleus in a conventional OCB mode liquid crystal display device will be described below. FIG. 6 shows a planar structure of a pixel electrode portion of a liquid crystal display device having a conventional configuration. Reference numeral 60 denotes a pixel electrode in an effective screen, and 61 denotes a pixel electrode adjacent to 60. FIG. 7 shows a cross-sectional structure of the pixel electrode portion, and shows a cross section taken along the line AA ′ in FIG. 70 and 71 are adjacent pixel electrodes, and 72 is an active element such as a TFT (Thin Film Transistor) connected to the pixel electrodes. 73 is a liquid crystal layer filled with a liquid crystal material. 74 is a counter electrode.

In order to perform a transition operation of the liquid crystal molecule alignment from the splay alignment to the bend alignment in the OCB mode, a signal level having a potential difference between adjacent pixels 70 and 71 is written and held through an active element. Due to the effect of the horizontal electric field 75 due to the influence of the potential difference, the liquid crystal molecules between the pixel electrodes are transferred from the splay alignment to the bend alignment, and the bend alignment proceeds in the pixel, thereby enabling image display.

[0005]

However, in the conventional pixel configuration, the potential for performing a write / hold operation on each pixel through an active element is limited by the withstand voltage of the active element. Is 20 V, the absolute value of the voltage applied between adjacent pixels is 20 V at the maximum, and when the threshold voltage required for the transition from the splay alignment to the bend alignment is 20 V or more, the transition completely occurs. It may not be performed, which is a major problem of deterioration of image display quality in the OCB mode.

In the present invention, in view of such circumstances, a large transverse electric field for completely changing the liquid crystal molecular alignment on the pixel electrode from the splay alignment to the bend alignment can be obtained, and the complete transfer is realized and the OCB mode is realized. The purpose is to ensure image display quality.

[0007]

In order to solve the above-mentioned problems, a liquid crystal display device according to the present invention is electrically separated from an active element and a pixel electrode in the same layer as the pixel electrode between adjacent pixel electrodes or in a different layer. By forming the wiring with the same conductive film as the pixel electrode or a different conductive film, the liquid crystal molecule alignment on the pixel electrode is more than the threshold value required to completely transfer from splay alignment to bend alignment. A horizontal electric field can be applied.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) First, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 shows a planar structure of a pixel electrode portion of a liquid crystal display device according to Embodiment 1 of the present invention, where 1 is a pixel electrode in an effective screen, 2 is a pixel electrode adjacent to 1, and 3 is a pixel electrode. It is a wiring electrode arranged between the pixel electrodes 1 and 2 adjacent to each other. The wiring electrode 3 is disposed in the same layer on the substrate as the electrodes 1 and 2, and is formed of the same conductive film as the electrodes 1 and 2. FIG. 2 shows a cross-sectional structure of the pixel electrode portion, and shows a cross section taken along line AA ′ in FIG. Reference numerals 20 and 21 denote pixel electrodes adjacent to each other.
2 is a TFT (Thin Film Transisto) connected to the pixel electrode
r), etc .; 23, a liquid crystal layer filled with a liquid crystal material; 24, a counter electrode; 25, a wiring electrode disposed between adjacent pixel electrodes 20 and 21; The direction of the horizontal electric field.

FIG. 3 shows an equivalent circuit of a substrate on which the pixel electrodes are arranged. Reference numeral 30 denotes a pixel electrode, 31 denotes an active element connected to the pixel electrode, and 32 denotes a scan connected to the pixel electrode. 33, a signal electrode connected to supply a signal to the electrode 31, a driving circuit connected to 32, a driving circuit connected to 32, and a driving circuit connected to 33, and 36 between the adjacent pixel electrodes. This figure shows the arranged wiring electrodes, which are electrically separated from the elements shown in the above-mentioned items 30 to 35, and have means for applying a voltage from outside.

In order to perform a transition operation from the splay alignment to the bend alignment in the OCB mode, the signal level at the pixel electrode 30 is written and held through the active element 31 in order to perform the transition operation. At this time, the potential is changed at the same time to apply a horizontal electric field between 30 and 36, thereby executing the transition. As an example, when a signal level of 5 V is written and held on the pixel electrode 30 and a voltage of 30 V is applied to the 36 wirings, a voltage of 25 V is applied as an absolute value between the 30 and 36 electrodes, and the splay alignment is bent. When the threshold voltage required for the transition to the orientation is 20 V, the transition is completely performed. At this time, the absolute value of the voltage applied at 36 can be set to a voltage at which the transition can be completely performed without being limited by the withstand voltage of the active element and the drive circuit. In addition,
The threshold of the voltage required for the transition is determined by the space between the electrodes, the shape of the electrodes, the composition of the liquid crystal material, and the alignment state. Becomes possible.

Further, the wiring 36 may be set to a common potential between the pixels, or may be set arbitrarily for each pixel. Further, there is no limitation on the shape and the arrangement location between adjacent pixels.
The active elements connected to the pixel electrodes were made of a material such as single crystal silicon, amorphous silicon, or polycrystalline silicon.
Either a TFT configuration or a diode configuration may be used.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows a planar structure of a pixel electrode portion of the liquid crystal display device according to the second embodiment of the present invention, where 40 is a pixel electrode in an effective screen, 41 is a pixel electrode adjacent to 40, and 42 is 40
And 41 are wiring electrodes arranged in another layer between adjacent pixel electrodes. The wiring electrode 42 is disposed on a different layer on the substrate from the substrates 40 and 41, and is formed of a conductive film different from the substrates 40 and 41. FIG. 5 shows a cross-sectional structure of the pixel electrode portion, and shows a cross section taken along line AA ′ in FIG.
Reference numerals 50 and 51 denote pixel electrodes adjacent to each other; 52, an active element such as a TFT (Thin Film Transistor) connected to the pixel electrode; 53, a liquid crystal layer filled with a liquid crystal material; 51 is a wiring electrode arranged in another layer between adjacent pixel electrodes, 56 is an interlayer insulating film between the above 55 and the pixel electrode, and 57 is a horizontal electric field direction between the pixel electrode and the wiring electrode. The equivalent circuit of the substrate on which the pixel electrodes are arranged is the same as that of the first embodiment shown in FIG.

The operation for shifting the liquid crystal molecule alignment from the splay alignment to the bend alignment in the OCB mode is the same as that of the first embodiment.
, The lateral electric field 57 that affects the liquid crystal molecules with respect to the voltage applied between 50 and 55 is smaller than in the first embodiment. However, since the voltage can be arbitrarily applied to 55, the effect for executing the transfer remains unchanged.

Further, if it is another layer between adjacent pixels, the shape and
There is no restriction on the location. Furthermore, since the wiring electrode 42 in FIG. 4 is arranged in a different layer from the pixel electrode, it may overlap the pixel electrode in a plan view. Further, the wiring electrode 42 in FIG. 4 may be formed of the same conductive film as the adjacent pixel electrodes 40 and 41.

[0015]

As is apparent from the above description, the liquid crystal display device of the present invention is provided on the same layer as the pixel electrode between adjacent pixel electrodes or on a different layer from the active element and the pixel electrode. By forming wiring with the same conductive film as the pixel electrode or a different conductive film,
The effective effect of enabling the application of a horizontal electric field equal to or greater than the threshold required to completely change the OCB mode liquid crystal molecule alignment from the splay alignment to the bend alignment on the pixel electrode can be obtained, which is of great industrial value. .

[Brief description of the drawings]

FIG. 1 is a plan structural view of a pixel electrode portion of a liquid crystal display device according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional structural view of a pixel electrode portion of the liquid crystal display device in Embodiment 1.

FIG. 3 is an equivalent circuit diagram of a substrate on which a pixel electrode is arranged in the liquid crystal display device in Embodiment 1.

FIG. 4 is a plan structural view of a pixel electrode portion of a liquid crystal display device according to Embodiment 2 of the present invention.

FIG. 5 is a cross-sectional structure diagram of a pixel electrode portion of a liquid crystal display device in Embodiment 2.

FIG. 6 is a plan structural view of a pixel electrode portion of a liquid crystal display device having a conventional configuration.

FIG. 7 is a sectional structural view of a pixel electrode portion of a liquid crystal display device having a conventional configuration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pixel electrode in effective screen 2 Pixel electrode adjacent to 1 3 Wiring electrode arranged between adjacent pixel electrodes 20 Pixel electrode 21 in effective screen 21 Pixel electrode adjacent to 20 22 TFT (Thin) connected to pixel electrode Film Transisto
23) Active elements such as r) 23 Liquid crystal layer 24 Counter electrode 25 Wiring electrode arranged between adjacent pixel electrodes 26 Lateral electric field direction between pixel electrodes and wiring electrode 30 Pixel electrode 31 30 Active element connected to 30 32 Scanning electrode 33 Driving circuit connected to signal electrode 34 32 35 Driving circuit connected to 33 33 Wiring electrode arranged between adjacent pixel electrodes 40 Pixel electrode 41 in the effective screen 41 Pixel electrode adjacent to 40 42 Between adjacent pixel electrodes Wiring electrode arranged in the pixel 50 Pixel electrode in the effective screen 51 Pixel electrode adjacent to 50 52 TFT (Thin Film Transistor) connected to the pixel electrode
r) etc. 53 Liquid crystal layer 54 Counter electrode 55 Wiring electrode 56 arranged between adjacent pixel electrodes 56 Interlayer insulating film between 50 and 55 57 Lateral electric field direction between pixel electrode and wiring electrode 60 Pixel in effective screen Pixel electrode adjacent to electrode 61 60 70 Pixel electrode 71 in the effective screen 71 Pixel electrode adjacent to 70 72 TFT (Thin Film Transistor) connected to the pixel electrode
r) etc. 73 Liquid crystal layer 74 Counter electrode 75 Horizontal electric field direction between pixels

Claims (13)

[Claims] [Claim 1] Optically Compensated Birefring (OCB)
In an active matrix type liquid crystal display device in which an active element is connected to a pixel electrode formed of a conductive film for applying a voltage to a liquid crystal layer having a mode, the same layer between adjacent pixel electrodes is used. A liquid crystal display device characterized in that wiring is formed in the same conductive film as a pixel electrode on a layer of a liquid crystal display. 2. The liquid crystal display device according to claim 1, wherein in the liquid crystal display device, a wiring formed between the pixel electrodes is arranged in a horizontal direction with respect to an image display direction. 3. The liquid crystal display device according to claim 1, wherein in the liquid crystal display device, a wiring formed between the pixel electrodes is arranged in a direction perpendicular to an image display direction. 4. The liquid crystal display according to claim 1, wherein in the liquid crystal display device, wirings formed between the pixel electrodes are arranged simultaneously in a horizontal direction and a vertical direction with respect to an image display direction. Display device. 5. In the liquid crystal display device, a wiring formed between the pixel electrodes is electrically separated from the active elements and the pixel electrodes on a substrate on which the active elements are formed. 2. The liquid crystal display device according to claim 1, further comprising means for applying the voltage. 6. A wiring formed between the pixel electrode and a layer of a different layer from the pixel electrode with a conductive film different from the pixel electrode, and the wiring is an active element on a substrate on which an active element is formed. And a means electrically isolated from the pixel electrode and capable of externally applying a voltage. 7. The liquid crystal display device according to claim 6, wherein a wiring formed between the pixel electrodes is arranged in a horizontal direction with respect to an image display direction. 8. The liquid crystal display device according to claim 6, wherein a wiring formed between the pixel electrodes is arranged in a direction perpendicular to an image display direction. 9. The liquid crystal display device according to claim 6, wherein wirings formed between the pixel electrodes are simultaneously arranged in a horizontal direction and a vertical direction with respect to an image display direction. Liquid crystal display. 10. A wiring is formed between the pixel electrode and a layer of a layer different from the pixel electrode by using the same conductive film as the pixel electrode, and the wiring is active on a substrate on which an active element is formed. A liquid crystal display device, which is electrically separated from an element and a pixel electrode, and includes a unit capable of externally applying a voltage. 11. The liquid crystal display device according to claim 10, wherein a wiring formed between the pixel electrodes is arranged in a horizontal direction with respect to an image display direction.
The liquid crystal display device as described in the above. 12. The liquid crystal display device according to claim 10, wherein a wiring formed between the pixel electrodes is arranged in a direction perpendicular to an image display direction.
The liquid crystal display device as described in the above. 13. The liquid crystal display device according to claim 10, wherein wirings formed between the pixel electrodes are arranged simultaneously in a horizontal direction and a vertical direction with respect to an image display direction. Liquid crystal display.