JP3356273B2 - Liquid crystal display - Google Patents

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 device used for, for example, a television set, a personal computer, a word processor or an OA device.

[0002]

2. Description of the Related Art As a liquid crystal display device described above, a matrix type liquid crystal display device as shown in FIG. 9 is known. This liquid crystal display device has a structure in which a liquid crystal layer 27 is sandwiched between a matrix substrate 28 and a counter substrate 29, and polarizing plates 30 are adhered on both sides. 31 is used as an optical shutter.

FIG. 10 is a plan view of a matrix substrate 28, and FIG. 11 is a plan view of a counter substrate 29. The matrix substrate 28 includes a gate line 32 and a source line 33
Are provided so as to intersect with each other, and a thin film transistor 34 as a switching element is provided near the intersection of each line. Pixel electrodes 35 provided in a matrix
Is the gate line 32 through each thin film transistor 34
And the source line 33. Counter substrate 29
A light-shielding film 37 having an opening 36 corresponding to the pixel electrode 35 and a color filter (not shown) are provided, and a counter electrode 38 is provided on the entire surface. FIG.
Reference numeral 1 denotes the counter substrate 29 viewed from the substrate side. An alignment film (not shown) is formed on the matrix substrate 28 and the counter substrate 29, and the liquid crystal molecules can be aligned in an arbitrary direction by performing a rubbing process.

According to the liquid crystal display device having such a structure, a voltage applied to the liquid crystal layer 27 can be controlled for each pixel by inputting an image signal to the pixel electrode 35 via the thin film transistor 34. When a voltage is applied to the liquid crystal layer 27, the orientation direction of the liquid crystal molecules changes depending on the dielectric anisotropy of the liquid crystal molecules in the liquid crystal layer 27.

The principle of light control of this liquid crystal display device is as follows. The light linearly polarized by the rear polarizer 30 before entering the liquid crystal layer 27 from the backlight 31 is converted into elliptically polarized light, circularly polarized light, or optical rotation depending on the orientation direction of the liquid crystal molecules having the refractive index anisotropy. Cause optical modulation such as
After passing through the liquid crystal layer 27, the light enters the front polarizing plate 30.
The absorption axis component of the light incident on the polarizing plate 30 is absorbed, and the light transmittance changes. By the way, the liquid crystal display device has a TN
(Twisted Nematic) method, STN (S
upper Twisted Nematic) method, E
CB (Electrically Control)
There are many display methods such as a d Birefringence method and a polymer dispersion method. Above all, a liquid crystal display device using the TN method is widely used in television sets, personal computers, word processors, OA devices, and the like. However, in order to further improve contrast and response speed, a non-colored area in the ECB method is used. The liquid crystal display device used has been developed.

[0006] Of the ECB method, in a vertical alignment mode liquid crystal display device, when no voltage is applied, liquid crystal molecules are aligned almost perpendicular to the substrate surface, and a material having a negative dielectric anisotropy is used. To tilt the liquid crystal molecules in the horizontal direction when a voltage is applied. In this mode, since the liquid crystal layer does not use a twisted structure, the response speed is high, and black display is performed using a pair of polarizing plates whose polarization axes are orthogonal to each other without birefringence when no voltage is applied. Therefore, the contrast in the normal direction of the screen is also high. However, in the ECB vertical alignment mode, the transmittance of light has a viewing angle dependency, and improvement of the viewing angle dependency has been an important issue.

Various studies have been made on a method for improving the viewing angle characteristics in the ECB type vertical alignment mode. For example, "SID79 'P845 Level
option of Super-High-image
e-Quality Vertical-Alignment
The "ent-Mode LCD" describes in detail that the viewing angle characteristics can be significantly improved by forming a plurality of regions in which the orientation directions of liquid crystal molecules are different in pixels. As described above, in order to expand the viewing angle characteristics, it is necessary to form a plurality of regions in which the orientation directions of the liquid crystal molecules are different in the pixel by performing orientation division.

[0008] Although the process of the orientation division is not described in this prior art, as the method of the orientation division, for example, "Japan DISPLAY '92"
P591 A Complementary TNL
CD with Wide-Viewing-Angl
e Grayscale ”, a method of forming a resist pattern and performing a rubbing process twice, and“ Japan DISPLAY '92 P886
Wide Viewing Angle Full-
A method of performing rubbing treatment after partially patterning two types of alignment films having different tilt angles of liquid crystal molecules in a pixel as described in “Color TFT LCDs” is known. These are obtained by performing orientation division on the TN mode. However, although the orientation film material and the rubbing direction are different, the present invention can also be applied to the ECB type vertical orientation mode.

On the other hand, in the liquid crystal display device of the horizontal alignment mode in the ECB system, when no voltage is applied, the liquid crystal molecules are aligned almost horizontally with respect to the substrate surface, and a material having a positive dielectric anisotropy is used. Is used to tilt the liquid crystal molecules in the vertical direction when a voltage is applied. Even in this mode, the liquid crystal layer does not use a twisted structure, so that the response speed is high.When a pair of polarizing plates having polarization axes parallel to each other is used, the liquid crystal molecules are uniformly aligned when no voltage is applied. Since display can be performed, the contrast in the normal direction of the screen can be increased. However, even in the ECB type horizontal alignment mode, the transmittance of light has a viewing angle dependency, and improvement of the viewing angle dependency is an important issue.

As a method for improving the viewing angle characteristics in the ECB type horizontal alignment mode, the rubbing process is performed a plurality of times in different directions, as in the ECB vertical alignment mode, so that the alignment direction of the liquid crystal molecules is within one pixel. A method of forming a plurality of different regions and performing orientation division can be applied.

Further, a method for improving the viewing angle characteristics by devising the shape of the electrode is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-160.
No. 041, JP-A-9-160042, and JP-A-9-160061.

All of the techniques disclosed in these publications improve a horizontal electric field method in which a pair of electrodes are formed on the same substrate and liquid crystal molecules are optically modulated by a horizontal electric field component generated between the two electrodes. It can be said that this is an oblique electric field method. That is,
Electrodes are formed on a pair of substrates arranged opposite to each other, an electric field is generated in an oblique direction to the substrate surface, and optical modulation of liquid crystal molecules in the oblique electric field region is used.

FIG. 12 is a sectional view of an electrode structure in the oblique electric field type liquid crystal display device.

Here, the counter electrode 101 and the pixel electrode 10
2 has gap portions 103 and conductor portions 104, and the conductive strip portions 104 of both electrodes are alternately arranged along a direction parallel to the substrate surface. The counter electrode 101 and the pixel electrode 102
When a voltage is applied to the counter electrode 101 and the pixel electrode 1
An oblique electric field is generated in the liquid crystal layer 105 during the period 02. As a result, in the oblique electric field region 106, the orientation direction of the liquid crystal molecules 107 changes according to the direction of the electric field, and optical modulation is obtained.

[0015]

According to the liquid crystal display device in which the alignment is divided in the above-described ECB type vertical alignment mode and ECB type horizontal alignment mode, a plurality of regions having different alignment directions of liquid crystal molecules are formed in the pixel. By doing
The viewing angle characteristics are greatly improved, and excellent performance is obtained.

However, in order to perform the orientation division by the above-described method, it is necessary to add a new process, and an increase in the number of processes and an increase in the number of manufacturing apparatuses are inevitable. In addition, in order to form a divided pattern, it is necessary to apply a resist on the alignment film and perform processes such as exposure, development, and stripping. There is a high risk of adhesion of foreign matter due to permeation, surface deterioration, and further reduction in reliability of the liquid crystal cell due to ionic impurities, and inevitable problems such as a decrease in non-defective product rate and unstable quality. Furthermore, an increase in the rubbing process is indispensable.

As described above, in the conventional liquid crystal display device, although the viewing angle characteristics can be improved, it is very difficult to mass-produce it because the manufacturing cost is greatly increased.

On the other hand, according to the above-described oblique electric field type liquid crystal display device, since an oblique electric field is formed in a symmetrical direction on both sides of the electrode (conductor portion), the liquid crystal molecules are symmetrically formed when a voltage is applied. Can work. Therefore, the viewing angle characteristics can be improved by performing alignment division without forming a plurality of regions having different initial alignment directions of liquid crystal molecules by performing a plurality of rubbing treatments.

However, when utilizing the optical modulation of liquid crystal molecules in such an oblique electric field region, it is difficult to make the direction and intensity distribution of the electric field in the liquid crystal layer uniform.

If the distribution of the direction and intensity of the electric field in the liquid crystal layer is not uniform, the uniformity of the alignment direction of the liquid crystal molecules is impaired, and the optical modulation of the liquid crystal layer partially differs accordingly.
The transmitted light unevenness occurs in the pixel.

As described above, the unevenness of the transmitted light within the pixel is as follows.
In particular, in the case of an enlarged screen of a projection device or the like, it is perceived as rough, and the display quality is significantly reduced.
Further, even in the case of a liquid crystal display device having a high pixel density such that unevenness is not directly recognized, since the density of transmitted light in the pixel occurs, when a black display or a white display is performed at the time of applying a voltage, a part of each pixel is partially displayed. There is a problem that a white display portion or a black display portion remains, respectively, which causes a decrease in contrast and brightness.

Therefore, in order to ensure display quality and display performance, it is necessary to form a more uniform electric field. For example, a horizontal distance (gap) is formed between a pair of substrate surfaces.
The electrode may be formed by expanding the thickness sufficiently from the thickness of the liquid crystal layer.

However, when the distance between the electrodes is increased, the electric field is reduced, so that a higher driving voltage must be applied between the electrodes, which causes an increase in power consumption and an increase in cost for increasing the withstand voltage of the driver. Inevitable.

As described above, in the oblique electric field type liquid crystal display device, it is essentially difficult to achieve both improvement in display quality and display performance and reduction in power consumption and cost.

The present invention has been made to solve such problems of the prior art, and forms a plurality of regions in each pixel having different alignment directions of liquid crystal molecules by a method capable of mass production, thereby providing a visual field. It is an object of the present invention to provide a liquid crystal display device capable of improving angular characteristics, contrast, and response speed, reducing power consumption, and reducing manufacturing costs.

[0026]

According to the present invention, there is provided a liquid crystal display device , comprising: a first substrate having a first electrode;
Liquid in a gap with a second substrate having a second electrode opposed to the second substrate.
A liquid crystal display device in which a plurality of pixels are arranged in a matrix by sandwiching a liquid crystal layer having crystal molecules , wherein each pixel has
In addition, the first electrode has two crossing directions.
A first gap portion is provided, and the second electrode is
Along the two intersecting directions so as not to overlap with the gap 1
A second gap portion is provided, wherein the first electrode and the
When a voltage is applied to the second electrode, the first gap and
And near the periphery of each of the second gaps ,
An electric field in an oblique direction is formed for each of the first substrate and the second substrate, and the first gap and the second electric field are formed .
In addition to the vicinity of each peripheral edge portion of the second gap portion , the first
A vertical electric field is formed for each of the substrate and the second substrate , thereby achieving the above object.

When a voltage is applied to the first electrode and the second electrode, the first gap and the second gap are applied.
The oblique direction electric current formed near each peripheral edge of the
Depending on the field, the first gap and the second gap
The liquid crystal molecules in the vicinity of each peripheral part tilt in a predetermined direction,
Thereby, the first gap portion and the second gap portion
The configuration may be such that the tilt direction of the liquid crystal molecules other than those near the respective peripheral portions is controlled.

When the liquid crystal molecules in the liquid crystal layer have negative dielectric anisotropy and no voltage is applied to the first and second electrodes, the first substrate and the second
It may be configured that will be oriented substantially perpendicular to the substrate.

When the liquid crystal molecules in the liquid crystal layer have a positive dielectric anisotropy and no voltage is applied to the first electrode and the second electrode, the first substrate and the second
It may be configured that will be oriented generally horizontally relative to the substrate.

[0030]

[0031]

The width of the first gap and the width of the second gap are each provided so as to be larger than the interval between the first electrode and the second electrode. Is also good. Previous
The first gap and the second gap are respectively
It may be provided along two orthogonal directions.

Hereinafter, the operation of the present invention will be described.

In the present invention, the gaps between the electrodes on both substrates are arranged in each pixel so that they do not overlap each other, and when a voltage is applied, the substrate is placed on the liquid crystal layer near the periphery of each gap. Since an electric field is formed in an oblique direction with respect to the plane, the liquid crystal molecules are inclined in a certain direction in the liquid crystal layer near the peripheral edge of the gap due to the oblique electric field. Further, since the directions of the electric field in the oblique direction are different between one side and the other side across the gap, a plurality of regions having different alignment directions are formed in each pixel.

When a voltage is applied, the liquid crystal molecules are inclined in a predetermined direction with respect to the substrate surface by an oblique electric field near the periphery of the gap. An electric field perpendicular to the substrate surface is formed in the liquid crystal layer portion sandwiched between the two electrodes except for the vicinity of the peripheral portion of each gap portion. Even in this portion, the peripheral portion of the gap portion is formed due to the elasticity of the liquid crystal molecules. Under the influence of the tilt direction of the nearby liquid crystal molecules, the tilt direction of the liquid crystal molecules is controlled and optically modulated. Therefore, a wide symmetrical viewing angle characteristic can be obtained, and a uniform electric field can be given in the vertical direction to the substrate in the overlapping portion of the pixel electrode and the counter electrode, which is the most area of the pixel, and the To prevent display unevenness from occurring, thereby obtaining extremely excellent optical characteristics.

The liquid crystal molecules in the liquid crystal layer may have a negative dielectric anisotropy and may be oriented substantially perpendicular to the substrate surface when no voltage is applied. It is also possible to adopt a configuration that has dielectric anisotropy and is oriented substantially horizontally with respect to the substrate surface when no voltage is applied. In any case, when a voltage is applied, the liquid crystal molecules are tilted in a predetermined direction with respect to the substrate surface due to an oblique electric field in the vicinity of the peripheral edge of the gap, and most of the area of the pixel according to the tilt direction. Liquid crystal molecules that are given a uniform electric field in the direction perpendicular to the substrate at the overlap between the pixel electrode and the counter electrode are controlled in the tilt direction, so that the uniform alignment direction can be easily controlled. Can be.

In the present invention, the gaps between the electrodes on one substrate and the gaps between the electrodes on the other substrate are alternately arranged in each pixel along a direction parallel to the substrate surface. Accordingly, a plurality of regions having different orientations are alternately formed in each pixel by an electric field oblique to the substrate surface.

Further, in the present invention, since the gap between the electrodes on each substrate has portions along each of two directions intersecting each other in each pixel, each pixel has a portion with respect to the substrate surface. Thus, oblique electric fields are formed in four directions.

Further, in the present invention, since the width of the electrode gap on each substrate is larger than the distance between the electrodes on both substrates, the width of the electric field in the oblique direction with respect to the substrate surface is reduced. The component (in the direction parallel to the substrate surface) increases.

[0040]

Embodiments of the present invention will be described below.

(Embodiment 1) The liquid crystal display device of Embodiment 1 has a liquid crystal layer sandwiched between a matrix substrate and a counter substrate and polarizers on both sides, similarly to the conventional liquid crystal display device shown in FIG. And a light source, a so-called backlight, is arranged on the back surface of the liquid crystal display device and used as an optical shutter.

FIG. 1 is a plan view of a matrix substrate according to the first embodiment, FIG. 2 is a plan view of a counter substrate, and FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG.

In this matrix substrate, a gate line 1 and a source line 7 are provided to intersect each other, and a thin film transistor 4 as a switching element is provided near an intersection of each line. The pixel electrodes 10 provided in a matrix have a gap 15 in each pixel, and are connected to the gate line 1 and the source line 7 via each thin film transistor 4. The opposing substrate is provided with a light-shielding film 13 having an opening 12 corresponding to the pixel electrode 10 and a color filter (not shown), and an opposing electrode 14 is provided on the entire surface excluding the gap 16. Note that FIG.
Shows the counter substrate viewed from the substrate side. An alignment film (not shown) for vertically aligning liquid crystal molecules when no voltage is applied is formed on the matrix substrate and the counter substrate, and this alignment film is not subjected to a rubbing process.

As shown in FIG. 3, the thin film transistor 4 is provided with a gate electrode 2 branched from a gate line 1 and a gate insulating film 3 provided thereon. An a-Si layer 5 is provided on the gate insulating film 3 so as to overlap the gate electrode 2.
N ⁺ -a-Si layers 6a and 6b are provided. The source line 7 is formed on the n ⁺ -a-Si layer 6a.
A source electrode 8 branching from n ⁺ -a-Si
The drain electrode 8 is provided on the layer 6b. A pixel electrode 10 is provided so as to partially overlap the drain electrode 8, and a protective film 11 is provided so as to cover the pixel electrode 10.

This liquid crystal display device can be manufactured, for example, as follows.

First, on the matrix substrate, a Ta film is formed by a sputtering method and patterned by a photolithography method to form a gate line 1 and a gate electrode 2 branched from the gate line 1.

On top of that, SiN _{x was formed} by PE-CVD.
A gate insulating film 4 made of and an a-Si film and an n ⁺ -a-Si film doped with P are continuously formed, and the a-Si layer 5 and the n ⁺ -a-Si layers 6a and 6b are formed. The patterning is performed while leaving the portion where the thin film transistor 4 is formed.

Next, a Ti film is formed by a sputtering method and patterned by a photolithography method to form a source line 7, a source electrode 8 and a drain electrode 9 branched from the source line 7. In this case, n ⁺ -a-Si layer 6a by using the same resist pattern, by etching the 6b, n ⁺ -a-Si layer 6a protruding from the source electrode 8 and drain electrode 9, 6b
Is removed.

Subsequently, an ITO film is formed by a sputtering method, and is patterned to form a gap 1 in each pixel.
5 is formed. In this embodiment, a gap 15 in the direction along the gate line 1 is formed at a center of the pixel electrode 10 with a width of 5 μm.

Thereafter, a protective film 11 made of SiN _x is formed by the PE-CVD method to complete the matrix substrate.

Next, the counter substrate is formed of a C having an opening 12.
A color filter (not shown) was formed on the light-shielding film 13 made of r, and a counter electrode 14 made of ITO having a gap 16 in each pixel was formed thereon. In this embodiment, the gap 16 in the direction along the gate line 1 is formed with a width of 5 μm at two locations above and below the opening 12 corresponding to the outer shape of the pixel electrode 10. This counter substrate may be manufactured before the matrix substrate described above.

An alignment film (not shown) is formed by printing on both the matrix substrate and the counter substrate prepared as described above, and the substrates are bonded together. In this embodiment, the distance between the pixel electrode 10 and the counter electrode 14 is set to 4 μm with a spacer interposed between the matrix substrate and the counter substrate. Rubbing was not performed because it was not necessary.

Finally, a liquid crystal having a negative dielectric anisotropy is injected into a gap between the two substrates, the injection port is sealed, and a polarizing plate is bonded on both sides, whereby the liquid crystal display device of this embodiment is completed. Complete.

At this time, by arranging the absorption axes of the pair of polarizers at right angles to each other and at an angle of 45 ° to the gate line, that is, at an angle of 45 ° to the screen, the light is not vertically applied when no voltage is applied. , And a normally black display is obtained. Thus, black display can be performed in a state where there is no birefringence when no voltage is applied, so that the contrast in the normal direction of the screen can be increased.
Further, since the liquid crystal layer does not use a twist structure, the response speed can be increased.

The tilt direction of the liquid crystal molecules when a voltage is applied to the obtained liquid crystal display device will be described with reference to FIG. 4, which is a cross-sectional view of a portion corresponding to line BB 'in FIG.

In this liquid crystal display device, a gap 15 having a width of 5 μm is provided at the center of the pixel electrode 10, and a gap 16 having a width of 5 μm is provided at both ends of the counter electrode 14.
Is set to be larger than the distance between the pixel electrode 10 and the counter electrode 14, so that when a voltage is applied between the electrodes, the electric field 17 near the ends a and b (peripheral edge of the gap) of the electrodes. Is distorted.

Since a liquid crystal having a negative dielectric anisotropy is used as a liquid crystal, when a voltage is applied to liquid crystal molecules which are oriented in a direction substantially perpendicular to the substrate when no voltage is applied, FIG. In the region A in the middle, since the electric field direction is formed obliquely in the region a corresponding to the end,
A torque is applied to the liquid crystal molecules to incline to the left (upper side of the screen) so as to be orthogonal to the electric field direction.

On the other hand, in a region between the pixel electrode 10 and the counter electrode 14 other than the vicinity of the periphery of the gap, which corresponds to most of the region A, the direction of the electric field is perpendicular to the substrate. The tilt direction of the torque acting on the liquid crystal molecules initially aligned substantially perpendicular to the substrate is not affected by the local oblique electric field. However, under the influence of the elastic force between the liquid crystal molecules exerted by the liquid crystal molecules tilting counterclockwise in the region a, the liquid crystal molecules similarly tilt counterclockwise in the region where there is only a vertical electric field, It was confirmed that the torque at this time depends on the electric field strength in the vertical direction.

In the region B, a torque for tilting the liquid crystal molecules clockwise (downward on the screen) acts on the liquid crystal molecules according to the same principle.

As a result, the alignment direction of the liquid crystal molecules can be controlled over the entire surface of the pixel, and the alignment direction of the liquid crystal molecules is vertically divided with respect to the screen within one pixel. Therefore, a vertically symmetric viewing angle characteristic with respect to the screen was obtained.

The present invention relates to a method disclosed in Japanese Patent Application Laid-Open No. 9-160041.
JP-A-9-160042 and JP-A-9-10042
It does not utilize optical modulation of liquid crystal molecules in an oblique electric field region as in JP-A-60061. The gap between the electrodes forms an oblique electric field in the vicinity of the periphery of the gap, and in most regions of the pixel other than the vicinity of the periphery, the pixel electrode and the counter electrode are opposed to each other on the substrate surface. An electric field is generated in a direction perpendicular to the electric field. Therefore, it is not preferable that the ratio of the gap between the electrodes in the pixel is too large, or the ratio of the overlap between the pixel electrode and the counter electrode in the pixel is too small.

In the first embodiment, the gap between the pixel electrode and the counter electrode is formed in the direction along the gate line. However, the gap may be formed in the direction along the source line. Other directions may be used as long as the parts are alternately arranged along the substrate plane.

(Embodiment 2) In the liquid crystal display device of Embodiment 2, a pixel electrode 18 having a gap 20 as shown in FIG. 5 is provided on a matrix substrate, and a gap 21 as shown in FIG. A liquid crystal display device similar to that of the first embodiment was manufactured except that a counter electrode 19 having the following structure was provided. Gap 20,
The width of 21 was 5 μm, and the overlap width of the pixel electrode 18 and the counter electrode 19 was 20 μm. The gap portions 20 and 21 have portions along each of two directions orthogonal to each other, here, a portion along the gate line 1 and a portion along the source line 7. The gaps 20 of the pixel electrode 18 and the gaps 21 of the counter electrode 19 are alternately arranged in a direction along the substrate surface.

The principle of operation when a voltage is applied to the obtained liquid crystal display device is the same as that of the first embodiment. In this case, the inclination direction of the liquid crystal molecules in the portion corresponding to the line CC ′ in FIG. This will be described with reference to FIG. 7 which is a sectional view.

In this liquid crystal display device, the width of the gaps 20 and 21 is set to be larger than the distance between the pixel electrode 18 and the counter electrode 19, so that when a voltage is applied between the electrodes, the ends of the electrodes are closed. The electric field 22 is distorted near the (peripheral edge of the gap). Since a liquid crystal having a negative dielectric anisotropy is used as the liquid crystal, when a voltage is applied to the liquid crystal molecules that are aligned in the vertical direction when no voltage is applied, the liquid crystal molecules in the region A in FIG. The liquid crystal molecules tilt to the right, and in the region B of FIG. 7, the liquid crystal molecules tilt to the left. Thereby, the gap portions 20 and 21 of the electrode
Are obtained on both sides of the substrate. In the second embodiment, the gaps 20 and 21 of the electrodes are provided.
Are provided along two directions orthogonal to each other,
The inclination directions of the liquid crystal molecules are four directions of up, down, left and right, respectively.
It was divided into different types of regions, and the viewing angle characteristics symmetrical with respect to the screen were obtained.

In the second embodiment, the gaps between the electrodes are formed in two directions orthogonal to each other. However, the gaps may be formed in two directions intersecting at other angles.
It may be formed along the direction more than the direction.

In the first and second embodiments, an example in which the present invention is applied to a liquid crystal display device in a vertical alignment mode has been described. In the third embodiment, the present invention is applied to a liquid crystal display device in a horizontal alignment mode. An example of application will be described.

(Embodiment 3) In Embodiment 3,
An alignment film is formed by printing on both the matrix substrate and the counter substrate manufactured in the same manner as in the first embodiment, and the two substrates are bonded to each other. In this embodiment, the distance between the pixel electrode and the counter electrode is set to 4 μm with a spacer interposed between the matrix substrate and the counter substrate. The rubbing treatment was performed once in the direction orthogonal to the gap between the pixel electrodes on the matrix substrate, and once in the direction orthogonal to the gap between the counter electrodes on the counter substrate.

Then, a liquid crystal having a positive dielectric anisotropy is injected into a gap between the two substrates, the injection port is sealed, and a polarizing plate is bonded on both sides to manufacture the liquid crystal display device of the present embodiment. did.

At this time, by arranging the absorption axes of the pair of polarizing plates parallel to each other and arranging them at an angle of 45 ° with respect to the gate line, that is, at an angle of 45 ° with respect to the screen, light is not horizontally applied in the horizontal alignment. Is normally birefringent in the liquid crystal layer and is cut off. Accordingly, black display can be performed in a state where the liquid crystal molecules are uniform when no voltage is applied, so that the contrast in the normal direction of the screen can be increased. Further, since the liquid crystal layer does not use a twist structure, the response speed can be increased.

The tilt direction of liquid crystal molecules when a voltage is applied to the obtained liquid crystal display device will be described with reference to FIG. 8, which shows a portion where a pixel electrode and a counter electrode face each other.

In this liquid crystal display device, a gap 215 having a width of 5 μm is provided at the center of the pixel electrode 210 and the opposite electrode 214 is formed.
Has a gap 216 with a width of 5 μm at both ends.
Since the widths of the electrodes 15 and 216 are set to be larger than the distance between the pixel electrode 210 and the counter electrode 214, when a voltage is applied between the electrodes, the ends a and b of the electrodes (peripheries of the gaps)
The electric field 217 is distorted in the vicinity.

Since a liquid crystal having a positive dielectric anisotropy is used as the liquid crystal, when a voltage is applied to the liquid crystal molecules which are oriented substantially horizontally with respect to the substrate when no voltage is applied, FIG. In the region A in the middle, since the electric field direction is formed obliquely in the region a corresponding to the end,
A torque acts on the liquid crystal molecules 218 (region a) to incline rightward (downward on the screen) so as to be orthogonal to the electric field direction.

On the other hand, the pixel electrode 210 and the counter electrode 214 other than near the periphery of the gap, which correspond to most of the region A,
In the region between the two, the direction of the electric field is perpendicular to the substrate, and the tilt direction of the torque acting on the liquid crystal molecules that are initially aligned almost horizontally to the substrate surface is locally oblique. Unaffected by directional electric field. However, under the influence of the elastic force between the liquid crystal molecules exerted by the liquid crystal molecules 218 tilted clockwise in the region a, the liquid crystal molecules 218 similarly tilt clockwise in the region where there is only an electric field in the vertical direction. However, it was confirmed that the torque at this time depends on the electric field strength in the vertical direction.

Also in the region B, a torque for tilting the liquid crystal molecules 218 counterclockwise (upward on the screen) acts on the liquid crystal molecules 218 according to the same principle.

As a result, the alignment direction of the liquid crystal molecules can be controlled over the entire surface of the pixel, and the alignment direction of the liquid crystal molecules is vertically divided with respect to the screen within one pixel. Therefore, a vertically symmetric viewing angle characteristic with respect to the screen was obtained.

In the third embodiment, the gap between the pixel electrode and the counter electrode is formed in the direction along the gate line. However, the gap may be formed in the direction along the source line. Other directions may be used as long as the parts are alternately arranged along the substrate plane. Further, as in the second embodiment, the gaps between the electrodes may be formed in two directions perpendicular to each other. In this case, the rubbing direction is set at 45 ° with respect to the direction of the gaps between the electrodes.

As described above, the region for forming the oblique electric field is formed only in the vicinity of the periphery of the gap between the pixel electrode and the counter electrode, and is sandwiched between the pixel electrode and the counter electrode by the tilt direction of the liquid crystal molecules in this portion. In the region where the electric field is vertical, the tilt direction of the liquid crystal molecules is controlled, and the alignment direction can be controlled over the entire surface of the pixel.

This is because liquid crystal molecules having a negative dielectric anisotropy which are vertically aligned when no voltage is applied or liquid crystal molecules having a positive dielectric anisotropy which are horizontally aligned when no voltage is applied. When an electric field is applied vertically,
Utilizing an extremely characteristic phenomenon that the tilt direction of the liquid crystal molecules in the portion other than the vicinity of the periphery can be easily controlled by the action of the elastic force exerted by the liquid crystal molecules in the vicinity of the periphery of the gap. Is achieved by:

As a result, a wide symmetrical viewing angle characteristic can be obtained, and a uniform electric field in the vertical direction can be applied to the substrate in the overlapping portion between the pixel electrode and the counter electrode, which is the most area of the pixel. Therefore, it is possible to prevent unevenness occurring in the pixel, and to obtain extremely excellent optical characteristics.

In the region where the electric field is distorted in the peripheral portion of the gap between the electrodes, the alignment state of the liquid crystal is different from the other portions. However, in the case of a normally black mode liquid crystal display device which performs black display when no voltage is applied, Since no voltage is applied at the time of black display, there is no influence of electric field distortion, and a good black display can be obtained. Further, if a light-shielding film is formed in this portion, it is possible to completely prevent the influence on the display performance.

The present invention is not limited to the above embodiment. The shape of the pixel electrode and the shape of the counter electrode may generate an oblique electric field near the peripheral edge of the gap, and may cause the electric field in both directions other than the peripheral edge of the gap. Any shape may be used in combination so long as a vertical electric field is generated in the portion sandwiched between the electrodes and the shape of the liquid crystal molecules can be divided into a plurality of different regions in a tilt direction. The portion and the gap between the opposing electrodes may have a curved shape.

In the above-described embodiment, the normally black mode liquid crystal display device that performs black display when no voltage is applied has been described. However, the present invention is applied to a normally white mode liquid crystal display device that performs white display when no voltage is applied. It is also possible.

In the above embodiment, a liquid crystal display device using a thin film transistor as a switching element has been described. However, if a plurality of pixels are formed in a matrix, a two-terminal element such as an MIM may be used. The present invention can be applied to a liquid crystal display device that has been used or a simple matrix type liquid crystal display device.

[0085]

As described in detail above, according to the present invention,
By forming a gap at the time of patterning the pixel electrode and the counter electrode, it is possible to control the tilt direction of the liquid crystal molecules in each pixel to perform alignment division. Risks such as adhesion of foreign substances due to penetration of the developing solution and stripping solution, deterioration of the surface, and a decrease in the reliability of the liquid crystal cell due to ionic impurities, and problems such as a decrease in non-defective products and unstable quality. Absent. Further, since an alignment treatment step such as a rubbing treatment is not required, it is possible to prevent the occurrence of a defect relating to this step.

As a result, the viewing angle characteristics depending on the tilt direction of the liquid crystal molecules are canceled out by a pair of regions where the tilt directions are opposed to each other, so that the display device has a symmetrical wide viewing angle characteristic, and has a high contrast and a high response speed. In addition, it is possible to obtain a liquid crystal display device having excellent display performance in which display quality is not degraded due to display unevenness, roughness, and the like, and which has no increase in power consumption and is excellent in mass productivity.

[Brief description of the drawings]

FIG. 1 is a plan view of a matrix substrate according to a first embodiment.

FIG. 2 is a plan view of a counter substrate according to the first embodiment.

FIG. 3 is a cross-sectional view taken along the line A-A 'of FIG.

FIG. 4 is a cross-sectional view of a portion corresponding to line BB ′ in FIG. 1;

FIG. 5 is a plan view of a matrix substrate according to a second embodiment.

FIG. 6 is a plan view of a counter substrate according to a second embodiment.

FIG. 7 is a sectional view taken along line C-C 'of FIG.

FIG. 8 is a cross-sectional view illustrating a portion where a pixel electrode and a counter electrode face each other according to a third embodiment.

FIG. 9 is a sectional view showing a conventional liquid crystal display device.

FIG. 10 is a plan view of a conventional matrix substrate.

FIG. 11 is a plan view of a conventional counter substrate.

FIG. 12 is a cross-sectional view showing an electrode structure in a conventional liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Gate line 2 Gate electrode 3 Gate insulating film 4 Thin film transistor 5 a-Si layer 6a, 6bn ⁺ -a-Si layer 7 Source line 8 Source electrode 9 Drain electrode 10, 18, 210 Pixel electrode 11 Protective film 12 Opening 13 Light-shielding film 14, 19, 214 Counter electrode 15, 16, 20, 21, 215, 216 Gap 17, 22, 217 Electric field 218 Liquid crystal molecules

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/1343 G02F 1/1337

Claims (6)

(57) [Claims] A first substrate having a first electrode;
A liquid crystal display device in which a liquid crystal layer having liquid crystal molecules is sandwiched in a gap between a second substrate having a second electrode facing a first electrode and a plurality of pixels arranged in a matrix. Te, Oite in each pixel, wherein the first electrode, two-way crossing
A first gap portion is provided along the direction, and the second electrode is
Are intersecting with each other so as not to overlap with the first gap.
A second gap is provided along the direction, and a voltage is applied to the first electrode and the second electrode.
And the first gap and the second gap, respectively.
The first substrate and the second substrate near the peripheral edge of the first substrate;
Electric field in an oblique direction is formed for each plate, the
In addition to the vicinity of the respective peripheral portions of the first gap portion and the second gap portion , the first substrate and the second substrate
Electric field in the vertical direction is formed for each liquid crystal display device. 2. When a voltage is applied to the first electrode and the second electrode, the first gap and the second
The oblique direction formed near each peripheral edge of the gap
The first gap and the second gap by an electric field
Of the liquid crystal molecules in the vicinity of the respective peripheral portions of the first gap portion and the second gap portion are tilted in a predetermined direction.
Each of the tilt direction of the liquid crystal molecules other than near the periphery is controlled, the liquid crystal display device according to claim 1 of The inter. 3. When the liquid crystal molecules in the liquid crystal layer have a negative dielectric anisotropy, and when no voltage is applied to the first electrode and the second electrode , the first liquid crystal layer has a negative dielectric anisotropy . Substrate and the second
Ru is oriented substantially perpendicular to the second substrate, the liquid crystal display device according to claim 1 or claim 2. 4. A liquid crystal molecules of the liquid crystal layer has a positive dielectric anisotropy, when applying no electric <br/> pressure to the first electrode and the second electrode, the first Substrate and the second
Ru is oriented substantially horizontally with respect to the second substrate, the liquid crystal display device according to claim 1 or claim 2. 5. The width of the first gap and the width of the second gap are respectively equal to the width of the first electrode and the width of the second electrode.
The liquid crystal display device according to any one of claims 1 to 4 , wherein the liquid crystal display device is provided so as to be larger than an interval between the two. 6. The first gap and the second gap.
The parts are respectively provided along two orthogonal directions.
The liquid crystal display device according to claim 1.