JP2001209065A - Wide viewing angle liquid crystal display device and substrate used therefor - Google Patents

Abstract

(57) [Problem] To provide a liquid crystal display device with a wide viewing angle. Another object is to improve image quality. A glass substrate and a side wall formed on the glass substrate and having a side wall of 30 ° to 120 ° with respect to the glass substrate.
A color filter 61 having a depression pattern forming an angle of 90 °, and a depression pattern 81 formed on the color filter 61 along the depression pattern of the color filter 60.
A substrate for a liquid crystal display device, comprising: a common electrode 80 having:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device having a wide viewing angle.

[0002]

2. Description of the Related Art In general, a liquid crystal display device has a structure in which liquid crystal is injected between two substrates and the amount of light transmission is adjusted by adjusting the intensity of an electric field applied thereto.

A vertically oriented twisted nematic (vertic)
all aligned twins-ted nema
A TN (VATN) type liquid crystal display device includes a pair of transparent substrates having a transparent electrode formed on the inner surface, a liquid crystal material between the two transparent substrates, and a light attached to the outer surface of each transparent substrate. It is composed of two polarizing plates for polarizing. When no electric field is applied, the liquid crystal molecules are oriented perpendicular to the two substrates. When an electric field is applied, the liquid crystal molecules filled between the two substrates are fixed at a constant pitch parallel to the substrates.
helically entangled in a helical manner.

[0004]

In the case of a VATN liquid crystal display device, the liquid crystal molecules are oriented perpendicular to the substrate in a state where no electric field is applied, and in a case where an electric field is not applied when a perpendicular polarizing plate is used. Can completely block the light. That is, since the luminance in the off state in the normally black mode is very low, a higher contrast can be obtained as compared with the conventional twisted nematic liquid crystal display device. However, in a state where an electric field is applied, particularly in a state where a gray scale voltage is applied, the light delay (re) depends on the direction in which the liquid crystal display device is viewed as in the normal twisted nematic mode.
There is a problem that the viewing angle is narrow due to a large difference in the target angle.

In order to solve such a problem, an electrode is patterned and a fringe field (fr) is thereby formed.
Various methods for forming multiple regions using an inge field have been proposed. US Patent No. 5,309,264
Lien has presented a method of forming an X-shaped opening in a common electrode, and Histake et al. In US Pat.
No. 690 proposed a method of alternately forming openings in electrodes formed on upper and lower substrates.

However, when a divided orientation is formed using the above-described method, a separate mask is required to pattern the common electrode. Since this affects the liquid crystal material, it is necessary to form a protective film on the color filter, and there is a problem that the tip of the patterned electrode is severely tilted.

A technical problem to be solved by the present invention is to provide a wide viewing angle liquid crystal display device which does not have the above-mentioned problems.

Another technical problem that the present invention seeks to achieve is:
An object of the present invention is to improve the image quality of a wide viewing angle liquid crystal display device.

[0009]

According to the present invention, a common electrode is formed so as to have a depression pattern.

Specifically, a number of pixel electrodes are formed on a first substrate, and formed on a second substrate facing the first substrate so as to be located at a portion corresponding to the pixel electrodes. The common electrode having the depressed pattern is formed.
At this time, the side wall of the depressed pattern is in contact with the first substrate at 30 ° to 1 °.
Make an angle between 20 °.

A storage capacitor electrode and a number of pixel electrodes are formed on the first substrate. A common electrode having a depression pattern located at a portion corresponding to a pixel electrode is formed on a second substrate facing the first substrate. At this time,
When the first substrate is viewed from above, the pixel electrode completely covers the storage capacitor electrode at least in a certain portion.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a thin film transistor substrate for a liquid crystal display according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a liquid crystal display according to a first embodiment of the present invention.

The liquid crystal display device comprises a lower substrate 10, an upper substrate 60 facing the lower substrate 10, and a lower substrate 10 and an upper substrate 6.
The liquid crystal material 90 is injected between 0 and 0 and is vertically aligned with the substrates 10 and 60.

On a lower substrate 10 made of a transparent insulating material such as glass, an indium tin oxide (ITO) is formed.
ide) and IZO (indium zinc oxide)
e) The opening pattern 51 is made of a transparent conductive material such as
Are formed, and each pixel electrode 50 is connected to the switching element 11 and receives an image signal voltage. At this time, a thin film transistor is generally used as the switching element 11, and the thin film transistor is connected to a gate line (not shown) for transmitting a scanning signal and a data line (not shown) for transmitting an image signal. The pixel electrode 50 is turned on (o
n) Turn off. A lower polarizing plate 14 is attached to the lower surface of the lower substrate 10. Here, when the pixel electrode 50 is a reflective liquid crystal display device, it may be made of an opaque material, and in this case, the lower polarizing plate 14 is not necessary.

Similarly, a black matrix 70 for preventing light leakage, a red, green and blue color filter 61 and a transparent conductive material such as ITO or IZO are formed on the lower surface of the upper substrate 60 made of a transparent insulating material such as glass. A common electrode 80 made of a material is formed.

At this time, a depression is formed in the color filter 61. Therefore, the common electrode 80 formed on the color filter 61 is
There is a depression pattern 81 along one depression.

The black matrix 70 is formed not only on the periphery of the pixel area but also on the depression pattern 81 of the common electrode 80. This is to prevent light leakage caused by the depression pattern 81 as described later.

On the other hand, the common electrode 80 has a depression pattern 81.
Is in contact with the black matrix 70. The black matrix 70 may be formed of an organic material, but is generally formed of a conductive material such as chromium. When the black matrix 70 is formed of a conductive material, the black matrix 70 is
, Which acts as a conductive path for transmitting a signal from the common electrode to reduce the common electrode resistance.

The reason why a wide viewing angle can be obtained through such a structure will be described.

When no electric field is applied to the liquid crystal display device, the liquid crystal molecules 90 maintain the state of being vertically arranged on the two substrates 10 and 60, so that the common electrode has the same black state as when there is no depression pattern. .

When an electric field is applied, an electric field perpendicular to the substrates 10, 60 is formed in most places, as shown in FIG. On the other hand, near the depression formed by removing the color filter 61, the common electrode 80 is formed in a bent shape along the color filter pattern. Therefore,
The equipotential surface between the two substrates is not formed parallel to the two substrates 10 and 60 and is bent by the shape of the common electrode 80. As a result, the electric field is not formed perpendicular to the substrates 10 and 60 but in a slightly inclined direction.

Since the liquid crystal has a negative dielectric anisotropy, the alignment direction of the liquid crystal molecules tends to be perpendicular to the direction of the electric field. Therefore, the major axes of the liquid crystal molecules near the depression pattern 81 are twisted while being inclined with respect to the surfaces of the two substrates 10 and 60. As a result, two regions in which the tilt directions of the liquid crystal molecules are opposite to each other with respect to the center line of the depression pattern 81 are generated, and the optical characteristics of the two regions are compensated for each other, so that the viewing angle is widened.

As shown in FIG. 1, when a part of the color filter 61 is removed to form the depression pattern 81 in the common electrode 80, the divided orientation can be formed by a simpler process than a method such as rubbing. In addition, there is an advantage that the arrangement of the liquid crystal molecules can adjust other regions very finely and can be formed in various shapes.

On the other hand, it is also possible to remove only a part of the thickness of the color filter 61 and form the remaining part.

Next, a method of manufacturing a color filter substrate for a liquid crystal display according to an embodiment of the present invention will be described.

First, a metal such as chromium or a black resist is formed on the substrate and patterned to form a black matrix.

Next, a color filter having a groove is formed by applying and patterning a resist of one of red, green, and blue, and then sequentially applying and patterning the other two colors of resist. Complete color filters.

Alternatively, red, green and blue resists are sequentially applied and patterned to form a color filter.
Grooves can be formed in three color filters at a time.

Finally, a transparent conductive material such as ITO is deposited on the black matrix and the color filter to form a common electrode. When the common electrode is formed, the common electrode may be cut off by a step near the groove formed in the color filter. Therefore, it is preferable that the common electrode is thinly deposited twice.

Next, the relationship between the form of the depression pattern and the image quality of the liquid crystal display device will be examined.

FIGS. 2 and 3 are cross-sectional views of a liquid crystal display according to a first embodiment of the present invention, in which the side walls of the depressed pattern formed in the color filter form 90 ° with respect to the substrate. It is a figure which shows an equipotential surface and a light transmittance curve in the case of making 45 degrees.

In the case of FIG. 2, the equipotential surface has a sharp bend only in the lower part of the depression pattern of the common electrode 80 and the upper part of the opening 51 of the pixel electrode 50. Therefore, the light transmittance also changes abruptly only at the portion where the depression pattern and the opening are present.
Therefore, if only the portion where the depression pattern is formed is blocked, no texture appears. But,
In the case of FIG. 3, the equipotential surface has a sharp bend not only at the lower part of the depression pattern of the common electrode 80 and at the upper part of the opening 51 of the pixel electrode 50 but also around the depression pattern. The light transmittance also rapidly changes not only in the portion where the depression pattern and the opening are present but also in the periphery of the depression pattern. Therefore, a texture appears at the periphery T of the depression pattern.

As can be inferred from the above, the smaller the angle between the side wall of the depression pattern and the substrate, the more the texture spreads to the periphery of the depression pattern. Therefore, the larger the angle between the side wall of the depression pattern and the substrate, the better. Here, the angle between the side wall of the depression pattern and the substrate is the angle measured from the side where the color filters 61 are packed. This angle may exceed 90 °. But this angle is 12
If the angle is 0 ° or more, there is a high possibility that the common electrode 80 formed of a material such as ITO is cut at the depression pattern portion.

In FIG. 3, even when the angle between the side wall of the depression pattern and the substrate is 45 °, the texture T appears around the depression pattern, but the display quality is not so much reduced. Further, it can be adjusted to some extent by changing the width of the depression pattern, the width of the opening of the pixel electrode, and the like. Therefore, the lower limit of the angle between the side wall and the substrate is about 30 °.

Next, a liquid crystal display according to a second embodiment of the present invention will be described.

FIG. 4 is a plan view of a liquid crystal display according to a second embodiment of the present invention, FIG. 5 is a cross-sectional view taken along the line IV-IV ′ of FIG. 4, and FIG. 6 explains the effect of the present invention. FIG. 6 is a cross-sectional view for comparison with FIG.

A gate line 20 is formed laterally on the lower insulating substrate 10. The gate electrode 20 has a gate electrode 2
1 is formed in the form of a protrusion. Two common electrode lines 22 and 25 are formed on the insulating substrate 10 alongside the gate line 20. The two common electrode lines 22 and 25 are connected to each other by two storage capacitor electrodes 23 and 24 formed in the vertical direction. At this time, the common electrode lines 22, 25
May be three or more, or may be formed by a single line. The gate line 20, the gate electrode 21, the common electrode lines 22, 25, and the storage capacitor electrodes 23, 24 are formed of a metal such as aluminum or chromium. At this time, they may be formed as a single layer, or may be formed as a double layer formed by continuously laminating a chromium layer and an aluminum layer. In addition, the gate wiring and the common wiring can be formed using various metals.

Silicon nitride (SiN) is formed on the gate line 20, the common electrode lines 22, 25, and the storage capacitor electrodes 23, 24.
A gate insulating film 31 made of x) or the like is formed.

A data line 40 is formed on the gate insulating film 31 in the vertical direction. The data line 40 has a source electrode 41 formed as a branch.
, A drain electrode 42 is formed. The data line 40, the source electrode 41, and the drain electrode 42 are formed of a material such as chromium and aluminum similarly to the gate wiring. In addition, it can be formed in a single layer or multiple layers.

Under the source electrode 41 and the drain electrode 42, a semiconductor layer (not shown) used as a channel portion of the thin film transistor and the source and drain electrodes 4 are formed.
A contact layer (not shown) is formed to reduce the contact resistance between the semiconductor layers 1 and 42 and the semiconductor layer. The semiconductor layer is usually formed using amorphous silicon, and the contact layer is formed using amorphous silicon doped at a high concentration as an n-type impurity.

A protective film 32 made of an inorganic insulator such as silicon nitride or an organic insulator such as a resin is formed on the data lines 40 and the like. The protective film 32 has a drain electrode 4
A contact hole (not shown) for exposing 2 is formed.

On the protective film 32, a pixel electrode 50 having an opening pattern 51 is formed. The pixel electrode 50 is I
It is formed using a transparent conductor such as TO or IZO or an opaque conductor such as aluminum (Al) having excellent light reflection characteristics. The opening pattern 51 formed in the pixel electrode 50 includes a horizontal opening formed in the horizontal direction at a position bisecting the pixel electrode 50 vertically and a diagonal direction formed in the upper and lower portions of the bisected pixel electrode 50. Hatched openings. At this time, the upper and lower hatched openings are perpendicular to each other. This is to uniformly disperse the directions of the fringe fields in four directions. That is, the liquid crystal tilt direction is dispersed in four directions in a small area divided by the opening pattern 51 and a depression pattern 81 described later. At this time, the angle formed by the upper and lower oblique line openings is
It may slightly fluctuate around 90 degrees (vertical). That is,
The angle formed by the upper and lower oblique line openings may vary between 85 degrees and 95 degrees.

At this time, the storage capacitor electrodes 23 and 24 are formed so as to be completely covered by the pixel electrodes 50 at portions A, B, C and D when the liquid crystal display device is viewed from above.

A black matrix 70 for preventing light from leaking is formed on the upper insulating substrate 60. Red, green, and blue color filters 61 having depressions are formed on the black matrix 70. On the color filter 61, a common electrode 80 having a depression pattern 81 of the color filter 61 is formed. At this time, the depression pattern 81 is formed by the depression of the color filter 61. The common electrode 80 is formed of a transparent conductor such as ITO or IZO.

The depression pattern 81 of the common electrode 80 has a diagonal opening of the pixel electrode 50 interposed therebetween, and includes a refraction portion which overlaps with the diagonal line and the side of the pixel electrode 50. At this time, the bending portions are classified into a vertical bending portion and a horizontal bending portion. The pixel electrode 50 completely covers the storage capacitor electrodes 23 and 24 below the portion (A, B, C, D) of the pixel electrode 50 that overlaps the vertical refraction portion.
This can prevent the appearance of texture lines.

Next, the reason why the occurrence of texture can be prevented in the liquid crystal display device according to the present invention will be described with reference to FIGS.

First, the cause of the occurrence of texture in the liquid crystal display device will be examined with reference to FIG.

FIG. 6 shows the common electrode 800 and the pixel electrode 50.
The shape of the lines of electric force and the liquid crystal molecules arranged by the electric field lines when an electric field is applied between 0 and 0 are shown. As shown in FIG. 6, a strong electric field is formed between the storage capacitor electrodes 230 and 240 and the pixel electrode. Such an electric field affects the electric field around the pixel region. Such an effect is particularly significant in the portion (A, B, C, D) of the common electrode 800 where the depression pattern 81 is formed. For this reason, a fringe field which is inclined in a direction opposite to the center of the pixel region is formed around the pixel region. Therefore,
The arrangement direction of the liquid crystal molecules is reversed at a portion (T) between the peripheral portion and the central portion of the pixel region. This part (T) appears as a texture on the screen.

The reason why the occurrence of texture in the liquid crystal display device according to the present invention can be prevented will be described with reference to FIG.

In FIG. 5, the pixel electrode 50 is connected to the storage capacitor electrode 2.
3, 24 are completely covered. Therefore, the lines of electric force formed between the pixel electrode 50 and the storage capacitor electrodes 23 and 24 are mostly connected to the lower surface of the pixel electrode 50. As a result, the electric field formed between the storage capacitor electrodes 23 and 24 does not affect the liquid crystal molecules. The fringe field, which is not affected by the storage capacitor electrodes 23 and 24, maintains a certain direction in the pixel region, and changes its inclination direction to a point where the pixel region has escaped (a portion blocked by the black matrix). Eventually, a portion (T) where the alignment direction of the liquid crystal molecules is reversed also appears in a portion that has escaped from the pixel region. Since this part is blocked by the black matrix, no texture appears on the screen.

A liquid crystal display according to a third embodiment of the present invention will be described.

FIG. 7 is a plan view of a liquid crystal display according to a third embodiment of the present invention.

The basic structure of the liquid crystal display according to the third embodiment, such as wiring and thin film transistors, is the same as that of the second embodiment. However, the opening pattern 5 of the pixel electrode 50
1, the shape of the depression pattern 81 of the common electrode is different from the planar area shape of the storage capacitor electrode 24 and the common electrode line 25.

The opening pattern 51 includes a horizontal opening formed in the horizontal direction and a vertical opening formed in the vertical direction. The depression pattern 81 includes a peripheral portion formed so as to overlap the vicinity of the pixel electrode 50 and a horizontal portion formed between the two horizontal openings.

The opening pattern 51 and the depression pattern 81 overlap and divide the pixel electrode 50 into a number of small areas. Each small area forms a polygon whose two longest sides are parallel to each other. This is to shorten the response time of the liquid crystal molecules. That is, a fringe field (fringe field) formed by the opening pattern 51 and the depression pattern 81.
By d), the direction in which the liquid crystal molecules are arranged becomes parallel to each other. In this case, the response time is shortened because the operation of the liquid crystal molecules is completed only by one-step operation.

Also in the liquid crystal display device according to the second embodiment, the small area divided by the opening pattern 51 and the depression pattern is a polygon in which the two longest sides are parallel.

The common electrode line 25 is formed as a single line extending in the horizontal direction, but may be formed in a plurality. The common electrode line 25 overlaps the horizontal portion of the depression pattern 81. The storage capacitor electrode 24 is formed side by side with the left and right sides of the pixel electrode 50, and is covered by the pixel electrode 50. This is to prevent the occurrence of texture as in the second embodiment.

Finally, a liquid crystal display according to a fourth embodiment of the present invention will be described with reference to FIG.

The liquid crystal display device according to the fourth embodiment also has an opening pattern 51 of the pixel electrode 50 and a depression pattern 8 of the common electrode.
Only the pattern 1 and the planar shapes of the storage capacitor electrode 24 and the common electrode line 25 are different from the second and third embodiments.

The opening pattern 51 in the fourth embodiment is formed by several X-shapes. The depression pattern 81 includes a peripheral portion and a lateral portion, and is formed in a form that isolates each of the X-shaped opening patterns 51.

The common electrode line 25 is formed by a single line extending in the lateral direction, but may be formed by a plurality. The common electrode line 25 overlaps one of the lateral portions of the depression pattern 81. The storage capacitor electrode 24 is formed side by side with the left and right sides of the pixel electrode 50, and is covered by the pixel electrode 50.

[0063]

As described in the embodiments of the present invention, when a groove is formed in a color filter to form a divided alignment liquid crystal display device, the viewing angle of the liquid crystal display device can be increased by a simple process, and the response speed can be increased. It is possible to obtain a liquid crystal display device with high speed and excellent image quality.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display according to a first embodiment of the present invention.

FIG. 2 shows an equipotential surface and a light transmittance curve (90 °) in the first embodiment of the present invention.

FIG. 3 shows an equipotential surface and a light transmittance curve (45 °) in the first embodiment of the present invention.

FIG. 4 is a plan view of a liquid crystal display according to a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line IV-IV ′ of FIG. 4;

FIG. 6 is a cross-sectional view for explaining the effect of the present invention, and is a drawing corresponding to FIG.

FIG. 7 is a plan view of a liquid crystal display according to a third embodiment of the present invention.

FIG. 8 is a plan view of a liquid crystal display according to a fourth embodiment of the present invention.

Claims (20)

[Claims] A substrate formed on the substrate and having a side wall with respect to the substrate;
A substrate for a liquid crystal display device, comprising: a color filter having a depression pattern forming an angle of not less than 120 ° and not more than 120 °; and a common electrode formed on the color filter. 2. The liquid crystal display according to claim 1, further comprising a black matrix formed on the substrate, wherein a part of the black matrix is formed to overlap the depression pattern. Equipment substrate. 3. A first substrate, a plurality of pixel electrodes formed on the first substrate, a second substrate disposed to face the first substrate, and a second substrate disposed on the second substrate. The side wall is formed at a position corresponding to the pixel electrode so that the side wall is at least 30 ° with respect to the first substrate.
A common electrode having a depression pattern forming an angle of less than or equal to °,
A liquid crystal display device comprising: 4. A color filter having a depression pattern formed between the second substrate and the common electrode, wherein the depression pattern of the common electrode is formed by the depression pattern of the color filter. The liquid crystal display device according to claim 3. 5. The liquid crystal display device according to claim 3, further comprising a black matrix formed on the second substrate and partially overlapping a depression pattern of the common electrode. 6. The liquid crystal display according to claim 5, wherein the depression pattern portion of the common electrode is in contact with the black matrix. 7. The storage device of claim 1, further comprising a storage capacitor electrode formed on the first substrate, wherein the pixel electrode completely covers the storage capacitor electrode with at least a predetermined portion when the first substrate is viewed from above. ing,
The liquid crystal display device according to claim 3. 8. The pixel electrode according to claim 7, wherein the predetermined portion where the pixel electrode completely covers the storage capacitor electrode is a portion where a side of the pixel electrode overlaps a depression pattern formed on the common electrode. The liquid crystal display device as described in the above. 9. The liquid crystal display device according to claim 7, wherein the storage capacitor electrodes are located one each on the left and right of the pixel electrode. 10. The liquid crystal display device according to claim 7, wherein said storage capacitor electrode is a branch of a common electrode line. 11. The liquid crystal display device according to claim 7, wherein said common electrode line overlaps with said depression pattern. 12. The pixel electrode has an opening pattern.
A liquid crystal display device according to claim 7. 13. An opening pattern of the pixel electrode is formed in a horizontal direction at a position where the pixel electrode is vertically divided into two portions, and is formed in a diagonal direction at upper and lower portions of the bisected pixel electrode. The upper and lower diagonal openings are perpendicular to each other, and the depression pattern of the common electrode is diagonal with the diagonal openings of the opening pattern interposed therebetween. And a refraction portion overlapping the portion and a side of the pixel electrode.
3. The liquid crystal display device according to 2. 14. A certain portion where the pixel electrode completely covers the branch electrode of the common electrode is a portion where a refraction portion of the depression pattern overlaps a vertical side of the pixel electrode.
The liquid crystal display device according to claim 13. 15. An opening pattern of the pixel electrode and a depression pattern of the common electrode overlap to divide the pixel electrode into a number of small areas, and the small areas are polygons having two longest sides parallel to each other. 2. The method according to claim 1, wherein
3. The liquid crystal display device according to 2. 16. The small area is classified into a first small area having two longest sides in a first direction and a second small area having a second direction, and the first direction and the second direction are different from each other. 85 ゜ or more 9
16. The liquid crystal display device according to claim 15, wherein the angle is less than 5 [deg.]. 17. The liquid crystal display device according to claim 16, wherein said first direction is a direction oblique to a side of said pixel electrode. 18. The device according to claim 1, wherein the first direction is parallel to one of upper and lower sides or left and right sides of the pixel electrode.
7. The liquid crystal display device according to 6. 19. A first substrate, a storage capacitor electrode formed on the first substrate, a number of pixel electrodes formed on the first substrate, and arranged facing the first substrate. And a common electrode formed on the second substrate and having a depression pattern at a position corresponding to the pixel electrode. When the first substrate is viewed from above, the pixel electrode is A liquid crystal display device in which a storage capacitor electrode is completely covered by at least a certain portion. 20. The pixel electrode according to claim 19, wherein the predetermined portion where the pixel electrode completely covers the storage capacitor electrode is a portion where a side of the pixel electrode overlaps a depression pattern formed on the common electrode. The liquid crystal display device as described in the above.