JP2002296621A - Liquid crystal display device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate defect of alignment at the step of a storage capacitor part and improve display performance such as contrast in particular. SOLUTION: The direction of the storage capacitor part 5 of a storage capacitor line 4 running across a pixel is directed approximately parallel to the direction rubbing an oriented film 10A with a rubbing cloth in order that the fur of the cloth can rub around the step along the shade of the storage capacitor part 5 so as to align liquid crystal molecules in the pixel around the step of the storage capacitance part 5, which results in an OCB mode liquid crystal display device of high contrast.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display having a high-speed response and a wide-field display performance.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device, a twisted nematic (TN) mode liquid crystal display device using a nematic liquid crystal has been put to practical use, but has disadvantages such as a slow response and a narrow viewing angle. Although an IPS (in-plane driving) mode liquid crystal display device having an excellent wide field of view has been put to practical use, it has disadvantages such as a slow response and a small aperture ratio.

On the other hand, as a display mode having a high response speed and a wide viewing angle, an optical compensation bend mode (hereinafter referred to as an OCB mode) has been proposed (Japanese Patent Application Laid-Open No. 7-84254). This mode will be described with reference to FIG. 8A and 8B, 1 is an array substrate, 2 is a counter substrate,
3 is a scanning signal line, 4 is a storage capacitor line, 5 is a storage capacitor portion in the pixel of the storage capacitor line 4, 6 is a first insulating layer, 7 is a second insulating layer, 8 is a pixel electrode, 9 is a counter electrode, 10A is an alignment film formed on the inner surface of the array substrate 1, 10B is an alignment film formed on the inner surface of the counter substrate 2, 11 is a black matrix, 12
Is a color filter material, 13 is connected to the pixel electrode 8,
A video signal line for providing a video signal, 14 is a semiconductor switch element, and 15 is a liquid crystal.

[0004] The method and operation of the formation will be described below. Forming a conductor made of Al, Ti or the like on the array substrate 1;
The scanning signal line 3 and the storage capacitor line 4 having the storage capacitor unit 5 in the pixel are patterned into the shape shown in FIG. After the first insulating layer 6 is formed on the first electrode group thus formed, an a-Si layer and an n + -type a-Si layer (both in FIG. (Not shown). Further, Al, Ti is formed on predetermined portions of the first insulating layer 6 and the semiconductor switch element 14.
And a second electrode group including the video signal lines 13 is patterned into a predetermined shape.

[0005] Next, a second insulating layer 7 made of SiNx or the like is formed on the array substrate 1A on which the second electrode group is formed. The second insulating layer 7 also serves as a protective film for protecting the semiconductor switch element 14. Further, the pixel electrode 8 is formed of an ITO film.

On the other hand, after the black matrix 11 and the color filter material 12 are formed in a predetermined pattern on the counter substrate 2, the counter electrode 9 is formed of an ITO film.

On the array substrate 1 and the counter substrate 2, alignment films 10A and 10B made of polyimide or the like are formed in order to align the arrangement of molecules of the liquid crystal 15.

By rubbing the surfaces of the array substrate 1 and the counter substrate 2 thus manufactured with a rubbing cloth, the initial alignment direction is determined in a predetermined direction. In the OCB mode liquid crystal display device, the initial alignment direction is substantially parallel to the longitudinal direction of the pixel in order to obtain a wide viewing angle in all directions. As described above, the array substrate 1 and the opposing substrate 2 in which the initial alignment direction of the liquid crystal molecules is determined are attached to each other, and the periphery is adhered with a sealant, and then the liquid crystal 15 is injected and sealed.

From this state, in order to display an image,
For example, as shown in JP-A-10-206822, by applying a voltage pulse of 10 V or more between the pixel electrode 8 and the counter electrode 9, the liquid crystal molecules near the center between the pixel electrode 8 and the counter electrode 9 are formed. Or the liquid crystal molecules containing the twisted alignment rise to generate a transition nucleus in a bend alignment state composed of an arcuately bent alignment region, and propagate this region to bring the entire pixel into a bend alignment state. Next, a normal display signal voltage is turned on and off by the semiconductor switch element 14 and applied between the pixel electrode 8 and the counter electrode 9 to change the degree of the bend alignment state of the liquid crystal molecules. Is displayed by changing the phase difference of.

[0010]

However, in the case of the above-mentioned liquid crystal display device, the following problems remain.

If there is a step such as a storage capacitor portion inside the pixel, a portion which becomes a shadow of the step when rubbing with a rubbing cloth is generated near the step, and the liquid crystal molecules are not aligned because it is not rubbed. For this reason, when black display is performed, light is leaked from the vicinity of the step, which causes a decrease in contrast.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention devises the structure of an array substrate of an OCB mode liquid crystal display device. Specifically, the following configuration was adopted.

An array substrate on which pixel electrodes, scanning signal lines, video signal lines, storage capacitor lines, and semiconductor switch elements are formed; a counter substrate on which counter electrodes are formed; and a liquid crystal layer sandwiched between the array substrate and the counter substrate In the OCB mode liquid crystal display device provided with the above, the storage capacitor portion in the pixel among the storage capacitor lines is configured not to be orthogonal to the initial alignment direction of the liquid crystal molecules in the liquid crystal layer.

Specifically, of the intersection angles between the storage capacitor portion and the initial alignment direction of the liquid crystal molecules in the liquid crystal layer, the acute angle is 18 ° or more and 75 ° or less.

More specifically, the storage capacitor of each of a pair of adjacent pixels has a substantially line-symmetric structure with respect to a video signal line between the pixels.

Another solution is to provide an array substrate on which pixel electrodes, scanning signal lines, video signal lines, storage capacitor lines, and semiconductor switch elements are formed, a counter substrate on which counter electrodes are formed, and a substrate between the array substrate and the counter substrate. In the OCB mode liquid crystal display device having the liquid crystal layer interposed between the liquid crystal layer and the liquid crystal layer, the storage capacitor portion in the pixel among the storage capacitor lines has a structure substantially parallel to the initial alignment direction of the liquid crystal molecules in the liquid crystal layer.

Still another solution is to provide an array substrate on which pixel electrodes, scanning signal lines, video signal lines, storage capacitor lines, and semiconductor switch elements are formed, a counter substrate on which counter electrodes are formed, and an array substrate and a counter substrate. In an OCB mode liquid crystal display device including a liquid crystal layer sandwiched therebetween, the storage capacitor has a structure having a non-linear portion. Specifically, the non-linear portion of the storage capacitor portion has a structure having at least one bent shape. With such a configuration, it is possible to eliminate poor orientation at the step portion of the storage capacitor portion and improve display performance, particularly contrast.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 shows an OC according to the first embodiment of the present invention.
FIG. 3 is a plan view of one pixel in a B-mode liquid crystal display device.
Hereinafter, components having the same reference numerals as those in FIG. 8 have exactly the same configuration and the same function, and thus description thereof will be omitted. The cross-sectional shape of the liquid crystal display device of the present embodiment is the same as the cross-sectional view of FIG.

First, a conductor made of Al, Ti or the like having a low wiring resistance is formed on the array substrate 1 and the scanning signal lines 3 are formed.
Then, the storage capacitor line 4 having the storage capacitor section 5 in the pixel is patterned into the shape shown in FIG. After the first insulating layer 6 is formed on the first electrode group thus formed, an a-Si layer and an n + -type a-Si layer (both in FIG. (Not shown))
To form Further, a conductor made of Al, Ti, or the like is formed on a predetermined portion of the first insulating layer 6 and the semiconductor switch element 14, and a second electrode group including the video signal line 13 is patterned in a predetermined shape.

Next, a second insulating layer 7 made of SiNx or the like is formed on the array substrate 1 on which the second electrode group is formed. The second insulating layer 7 also serves as a protective film for protecting the semiconductor switch element 14. Further, the pixel electrode 8 is formed of an ITO film.

On the other hand, after the black matrix 11 and the color filter material 12 are formed in a predetermined pattern on the counter substrate 2, the counter electrode 9 is formed of an ITO film.

On these array substrate 1 and counter substrate 2, alignment films 10A and 10B made of polyimide or the like are formed to align the arrangement of molecules of liquid crystal 15.

By rubbing the surfaces of the array substrate 1 and the counter substrate 2 thus manufactured with a rubbing cloth made of rayon, the initial alignment direction is determined in a predetermined direction. In the OCB mode liquid crystal display device, the initial alignment direction is substantially parallel to the longitudinal direction of the pixel in order to obtain a wide viewing angle in all directions. Therefore, in this embodiment, as shown in FIG. 1, the acute angle θ of the intersection angle between the storage capacitor portion 5 and the initial alignment direction of the liquid crystal molecules in the liquid crystal layer was set to 40 °. As described above, by bringing the storage capacitor portion 5 of the storage capacitor line 4 crossing the pixel close to the direction in which the alignment film 10A is rubbed by the rubbing cloth, the hair of the rubbing cloth follows the shadow caused by the step of the storage capacitor portion 5. As described above, the vicinity of the step is rubbed, so that the vicinity of the step in the pixel by the storage capacitor unit 5 can also be rubbed by the rubbing cloth, and the liquid crystal molecules can be aligned. If the angle θ is smaller than 90 °, the effects of the present invention can be obtained. However, if the angle θ is set to 75 ° or less, a clear effect is exhibited. The smaller the angle θ, the better the orientation, but conversely, the resistance value of the storage capacitor wiring increases. In addition, the minimum angle of θ is naturally limited due to the shape of the pixel.

As described above, the array substrate 1 in which the initial alignment direction of the liquid crystal molecules has been determined is bonded to the counter substrate 2, and the periphery is bonded with a sealant, and then the liquid crystal 15 is injected and sealed.

The semiconductor switch element 14 is connected to the video signal line 13
On / off control is performed by a driving signal input from the scanning signal line 3. And the semiconductor switch element 14
An electric field is generated by a voltage applied between the pixel electrode 8 connected to the counter electrode 9 and the counter electrode 9, the orientation of the liquid crystal 15 is changed, the brightness of each pixel is controlled, and an image is displayed.

Conventionally, light leakage has occurred from the portion of the storage capacitor 5, but light leakage can be reduced by the above configuration. As a result, the contrast of the conventional OCB mode liquid crystal display device was 450, whereas the contrast of the OCB mode liquid crystal display device of the present embodiment was 51%.
5 could be obtained.

As shown in FIG. 2, the shape of the storage capacitor 5 is
If each pixel is substantially line-symmetric with respect to the video signal line 13, the wiring resistance can be reduced, and display defects such as flicker due to wiring delay can be prevented.

Furthermore, when the initial alignment direction of the liquid crystal molecules is determined, if a rubbing cloth made of cotton with a soft waist is used, the hair enters along the step, so that the vicinity of the step is further rubbed and the contrast is improved. It can also be done.

Embodiment 2 Embodiment 2 of the present invention will be described with reference to the drawings.

FIG. 3 shows an OC according to the second embodiment of the present invention.
FIG. 3 is a plan view of one pixel in a B-mode liquid crystal display device.
The present embodiment is an embodiment in which the storage capacitor portion 5 crossing the pixel and the initial alignment direction of the liquid crystal molecules are substantially parallel to each other, which is different from the first embodiment. Hereinafter, components having the same reference numerals as those in FIG. 8 have exactly the same configuration and the same function, and thus description thereof will be omitted.

First, a conductor made of Al, Ti or the like having a low wiring resistance is formed on the array substrate 1 and the scanning signal lines 3 are formed.
Then, the storage capacitor line 4 having the storage capacitor section 5 in the pixel is patterned into the shape shown in FIG. At this time, the storage capacitor line 4 is formed substantially in parallel with the scanning signal line 3 (first embodiment).
Is different from Hereinafter, the method of forming the array substrate 1 and the counter substrate 2 is completely the same as that of (Embodiment 1) up to the step of forming the alignment films 10A and 10B, and thus the description is omitted.

By rubbing the surfaces of the array substrate 1 and the counter substrate 2 thus manufactured with a rubbing cloth, the initial alignment direction is determined in a predetermined direction. The initial orientation direction is substantially parallel to the storage capacitor 5. As described above, by making the storage capacitor portion 5 of the storage capacitor line 4 crossing the pixel substantially parallel to the direction in which the alignment film 10A is rubbed by the rubbing cloth, the hair of the rubbing cloth can be shadowed by the step of the storage capacitor portion 5. Since the vicinity of the step is rubbed along, the vicinity of the step in the pixel by the storage capacitor 5 can also be rubbed by the rubbing cloth, and the liquid crystal molecules can be aligned.

Hereinafter, the steps after the bonding of the array substrate 1 and the counter substrate 2 are completely the same as those of the first embodiment, and therefore the description thereof is omitted.

Conventionally, light leakage has occurred from the storage capacitor section 5, but light leakage can be reduced by the above configuration. As a result, the contrast of the conventional OCB mode liquid crystal display device was 450, whereas the contrast of the OCB mode liquid crystal display device of the present embodiment was 53%.
0 could be obtained.

In this embodiment, the scanning signal lines 3 are arranged in the horizontal direction on the display screen of the liquid crystal display device. However, as shown in FIG. 4, the horizontal scanning type liquid crystal display in which the scanning signal lines 3 are arranged in the vertical direction. Similar effects can be obtained as a device.

Further, when the initial alignment direction of the liquid crystal molecules is determined, if a rubbing cloth made of cotton with a soft waist is used, the hair enters along the step and the vicinity of the step is further rubbed to improve the contrast. It can also be done.

(Embodiment 3) Embodiment 3 of the present invention will be described with reference to the drawings.

FIG. 5 shows an OC according to the third embodiment of the present invention.
FIG. 3 is a plan view of one pixel in a B-mode liquid crystal display device.
This embodiment is an embodiment in which a non-linear portion is provided in the storage capacitor portion 5, and is different from (Embodiment 1) and (Embodiment 2) in this point. Hereinafter, the components having the same numbers as those in FIG. 8 have exactly the same configuration and the same function, and thus the description thereof will be omitted.

First, a conductor made of Al, Ti or the like having a small wiring resistance is formed on the array substrate 1 and the scanning signal line 3 is formed.
Then, the storage capacitor line 4 having the storage capacitor section 5 in the pixel is patterned into the shape shown in FIG. Hereinafter, the method for forming the array substrate 1 and the opposing substrate 2 is completely the same as that of (Embodiment 1) up to the step of forming the alignment films 10A and 10B, and thus the description is omitted.

By rubbing the surfaces of the array substrate 1 and the counter substrate 2 thus manufactured with a rubbing cloth, the initial alignment direction is determined in a predetermined direction. The initial alignment direction is substantially parallel to the longitudinal direction of the pixel. In this case, since the storage capacitor portion 5 has the bent portion, each bent portion of the storage capacitor portion 5 approaches parallel to the direction in which the alignment film 10A is rubbed by the rubbing cloth. Therefore, as in the first embodiment, the hair of the rubbing cloth is
Since the vicinity of the step is rubbed along the shadow caused by the step, the vicinity of the step in the pixel by the storage capacitor unit 5 can also be rubbed by the rubbing cloth, and the liquid crystal molecules can be aligned.

Hereinafter, the steps after the bonding of the array substrate 1 and the counter substrate 2 are exactly the same as those in the first embodiment, and therefore the description thereof is omitted.

Conventionally, light leakage has occurred from the portion of the storage capacitor 5, but light leakage can be reduced by the above configuration. As a result, the contrast of the conventional OCB mode liquid crystal display device was 450, whereas the contrast of the OCB mode liquid crystal display device of the present embodiment was 52.
0 could be obtained.

In this embodiment, the bent portion is provided on one side of the storage capacitor portion 5 as shown in FIG. 5, but the bent portions are provided on both sides of the storage capacitor portion 5 as shown in FIG. Thereby, the contrast can be further improved. Further, by bending the storage capacitor section 5 itself as shown in FIG. 7, the contrast can be improved without lowering the aperture ratio.

Further, when the initial alignment direction of the liquid crystal molecules is determined, if a rubbing cloth made of cotton with a soft waist is used, the hair enters along the step, so that the vicinity of the step is further rubbed and the contrast is improved. It can also be done.

[0047]

As described above, the OCB according to the present invention is used.
The mode liquid crystal display device has the following effects.

That is, it is possible to obtain a high-quality OCB mode liquid crystal display device in which no light leaks inside the pixel during black display.

As described above, it is possible to provide a liquid crystal display device capable of obtaining a high contrast with a high response speed and a wide viewing angle, so that the industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a plan view of one pixel in an OCB mode liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a plan view of two pixels in the OCB mode liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is a plan view of one pixel in an OCB mode liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a horizontal scanning OCB according to the second embodiment of the present invention.
Plan view of one pixel in mode liquid crystal display device

FIG. 5 is a plan view of one pixel in an OCB mode liquid crystal display device according to Embodiment 3 of the present invention.

FIG. 6 is a plan view of one pixel in an OCB mode liquid crystal display device according to Embodiment 3 of the present invention.

FIG. 7 is a plan view of one pixel in an OCB mode liquid crystal display device according to Embodiment 3 of the present invention.

8 (a) is a plan view of one pixel in a conventional OCB mode liquid crystal display device, and FIG. 8 (b) is a cross-sectional view of a configuration in a conventional OCB mode liquid crystal display device, showing a cross section along AA in FIG. 8 (a). Figure

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Array substrate 2 Counter substrate 3 Scan signal line 4 Storage capacitance line 5 Storage capacitance part 6 First insulating layer 7 Second insulating layer 8 Pixel electrode 9 Counter electrode 10A, 10B Alignment film 11 Black matrix 12 Color filter material 13 Video signal line 14 Semiconductor switch element 15 Liquid crystal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/30 349 G09F 9/30 349Z (72) Inventor Kazuhiro Nishiyama 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Within Denki Sangyo Co., Ltd. (72) Kenji Nakao, 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Daiichi Suzuki 1006, Kadoma Kadoma, Kadoma, Osaka Pref. (Reference) 2H088 HA03 HA08 HA12 HA14 JA05 MA02 MA07 2H090 KA05 LA15 MA06 MB03 2H092 GA14 JA24 JB22 JB31 JB51 JB61 NA25 PA02 PA08 QA07 5C094 BA03 BA43 CA19 DA15 EA04 EA07 FB16 FB19 JA09

Claims (8)

[Claims] 1. An array substrate on which pixel electrodes, scanning signal lines, video signal lines, storage capacitor lines, and semiconductor switch elements are formed, a counter substrate on which counter electrodes are formed, and sandwiched between the array substrate and the counter substrate. OCB with liquid crystal layer
In the mode liquid crystal display device, a storage capacitor portion in a pixel of the storage capacitor line is not orthogonal to an initial alignment direction of liquid crystal molecules in the liquid crystal layer. 2. The liquid crystal according to claim 1, wherein an acute angle of an intersection angle between the storage capacitor portion and an initial alignment direction of liquid crystal molecules of the liquid crystal layer is 75 ° or less. Display device. 3. The storage capacitor section of each of the adjacent pixels is substantially line-symmetric with respect to a video signal line disposed between the pixels. Liquid crystal display device. 4. An array substrate on which pixel electrodes, scanning signal lines, video signal lines, storage capacitor lines, and semiconductor switch elements are formed, a counter substrate on which counter electrodes are formed, and sandwiched between the array substrate and the counter substrate. OCB with liquid crystal layer
In the mode liquid crystal display device, a storage capacitor portion in a pixel of the storage capacitor line is substantially parallel to an initial alignment direction of liquid crystal molecules in the liquid crystal layer. 5. An array substrate on which pixel electrodes, scanning signal lines, video signal lines, storage capacitor lines, and semiconductor switch elements are formed, a counter substrate on which counter electrodes are formed, and sandwiched between the array substrate and the counter substrate. OCB with liquid crystal layer
In the mode liquid crystal display device, the storage capacitor portion has a non-linear portion. 6. The liquid crystal display device according to claim 5, wherein the non-linear portion of the storage capacitor portion has at least one bent shape. 7. The liquid crystal display device according to claim 1, wherein the storage capacitance line is formed of an Al alloy. 8. The liquid crystal display device according to claim 1, wherein a material of the rubbing cloth in the alignment treatment for determining the initial alignment of the liquid crystal molecules in the liquid crystal layer is cotton. Method.