JPH09281497A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to embody a wider visual field angle and to attain a good display contrast by providing either of an array substrate and a counter substrate with light shielding layers for shielding the light of the boundaries of varying arraying directions and the regions where the transverse electric fields between pixel electrodes and wirings counter the pretilt of liquid crystal molecules. SOLUTION: The oriented film arranged on the array substrate 100 is subjected to the orientation treatment in the direction (2) in the region A and to the direction (1) in the region B. The oriented film arranged on the counter substrate is also subjected to the orientation treatments respectively in the dotted line directions. The boundaries of the two different orientation regions and the display defective regions based on reverse tilt domains are respectively effectively shielded of light by auxiliary capacitor lines 181. As a result, an excellent display contrast is attained while a high opening rate is maintained. Even more, the light shielding layers are composed of the auxiliary capacitor lines 181, by which the excellent effect is attained without increasing the man- hours of production.

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 having a liquid crystal layer held between a pair of substrates.

[0002]

2. Description of the Related Art In recent years, flat panel displays represented by liquid crystal display devices have been developed with a view to miniaturization, light weight, and low power consumption. 2. Description of the Related Art Conventionally, a general active matrix type liquid crystal display device is a matrix in which a plurality of signal lines and scanning lines are arranged in a matrix on an insulating substrate, and pixel electrodes are arranged near each intersection via a switch element. It includes an array substrate, a counter substrate in which a counter electrode made of a transparent electrode material is arranged on an insulating substrate, and a liquid crystal material sandwiched between these substrates. Then, the signal lines and the scanning lines are respectively drawn out of the display area and are connected to connection pads for electrical connection with an external circuit or the like.

[0003]

However, in recent years,
With the increase in size and definition of such liquid crystal display devices, there is an increasing demand for a wider viewing angle. As a method for improving the viewing angle, a liquid crystal material that can realize a wide viewing angle is used.
Using the optical anisotropic element disclosed in No. 214116,
Alternatively, as disclosed in JP-A-63-106624 and the like, it is known that the arrangement direction of liquid crystal molecules in one display pixel is made different.

Among them, the method of dividing the arrangement direction of the liquid crystal molecules in one display pixel into a plurality of regions and making them different from each other can be dealt with only by a slight process change, and therefore, it is particularly attracting attention. Then, according to the method of dividing the arrangement direction of the liquid crystal molecules in one display pixel into a plurality of regions and making them different, at the boundary portion of the adjacent regions in each display pixel, due to the difference in the arrangement direction of the liquid crystal molecules, Are transmitted, resulting in a decrease in display contrast. From this, Japanese Patent Laid-Open No. 5-17313
No. 8 discloses a technique of shielding the above-mentioned boundary portion that causes a reduction in display contrast by an auxiliary capacitance line arranged in each display pixel.

However, a sufficient display contrast cannot be achieved only by blocking the light from the boundary between adjacent regions. The present invention has been made in view of the above technical problems, and an object thereof is to provide a liquid crystal display device capable of realizing a wide viewing angle and achieving good display contrast. I am trying.

[0006]

According to the first aspect of the present invention,
An array substrate including an active element arranged on one main surface, a pixel electrode electrically connected to the active element, and a wiring electrically connected to the active element and arranged around the pixel electrode And a liquid crystal layer composed of liquid crystal molecules sandwiched between the array substrate and the counter substrate, and a display pixel corresponding to the pixel electrode is configured. In the liquid crystal display device described above, an alignment film is provided on the array substrate and the counter substrate to impart a predetermined pretilt to the liquid crystal molecules of the liquid crystal layer and to define at least two different alignment directions for each display pixel. One of the array substrate and the counter substrate is disposed such that a boundary between the different array directions and a lateral electric field between the pixel electrode and the wiring are the pretilt of the liquid crystal molecules. In the liquid crystal display device comprising the light-shielding layer for shielding the pixel electrode regions against.

According to a second aspect of the present invention, in the alignment film according to the first aspect, the pixel is arranged so that a lateral electric field between the pixel electrode and the wiring minimizes a region against the pretilt of the liquid crystal molecule. A liquid crystal display device is characterized in that the array direction is defined obliquely to the electrodes. A third aspect of the present invention is a liquid crystal display device, wherein the light-shielding layer according to the first aspect is arranged via the pixel electrode and an insulating film.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION First, a phenomenon that causes a reduction in display contrast will be described. As shown in FIG. 3B, one display pixel is divided into two regions, the lower substrate is oriented in the direction indicated by the solid line in the figure, and the upper substrate is oriented in the direction indicated by the dotted line in the figure. When the twisted nematic (TN) liquid crystal is held in a state in which it is twisted by approximately 90 ° between the substrates by performing the alignment treatment in the direction orthogonal to the treatment direction, the liquid crystal molecules are in the alignment state as shown in FIG. . As can be seen from this figure, at the boundary between the regions A and B, light is transmitted when the polarizing plates are arranged orthogonally due to the difference in the alignment state between the regions.

As described above, when one display pixel is divided into a plurality of regions having different orientations, a phenomenon that light is transmitted at the boundary of each region is caused. In addition, each region is affected by the alignment state of liquid crystal molecules and the horizontal electric field generated between the pixel electrodes,
Reverse tilt domain occurs. That is, when no voltage is applied, the liquid crystal molecules are normally aligned between the substrates with a predetermined pretilt angle (θ1) as shown in FIG.

Here, an electric field is applied vertically to the liquid crystal molecules between the substrates, or the pretilt angle (θ
1) larger than [pretilt angle (θ1) + 90 °]
When a gradient electric field having a smaller angle than that shown by dotted lines A and A ′ in the figure is applied, the liquid crystal molecules are aligned from the direction of the gradient electric field as shown in FIG. However, when an inclined electric field having an angle larger than [pretilt angle (θ1) + 90 °] and smaller than [pretilt angle (θ1) + 180 °] shown by dotted lines B and B ′ in the figure is applied to the liquid crystal molecules. , The liquid crystal molecules are aligned according to the direction of the tilt electric field in the direction opposite to the pretilt direction. Further, in the alignment state in which the liquid crystal molecules are not provided with a sufficient pretilt angle (θ1), the alignment state is different from the normal state even without being affected by the tilt electric field.

Thus, even in the same orientation region,
When the reverse tilt domain is generated due to the electric field in the lateral direction or the state of the alignment treatment, light is transmitted in that region as compared with, for example, a region in the normal alignment state.

Therefore, as shown in FIG. 5, the signal lines S and the scanning lines G are arranged in a matrix, and the signal lines S and the scanning lines G are arranged.
A liquid crystal display device using an array substrate in which pixel electrodes E are arranged at the intersections with and through a thin film transistor (TFT) will be described as an example.

In FIGS. 6A to 6D, the solid line arrow indicates the alignment direction on the array substrate side, and the dotted line arrow indicates the alignment direction on the counter substrate. In FIG. 6A, the solid line arrow is along the solid line arrow (1). Liquid crystal display device which has been subjected to the alignment treatment along the solid line arrow (2) after the region A is masked, and the alignment treatment is also performed along the solid line arrow (1) in FIG. After that, the liquid crystal display device in which the region A is masked and the alignment treatment is performed along the solid arrow (2), and in the figure (c), the alignment treatment is performed along the solid arrow (1), The liquid crystal display device in which B is masked and subjected to the alignment treatment along the solid arrow (2) is also subjected to the alignment treatment along the solid arrow (1) in FIG.
Each of the liquid crystal display devices in which the region B is masked and the alignment process is performed along the solid arrow (2) is shown.

From FIGS. 6 (a) to 6 (d), it can be seen that the region in which the reverse tilt domain occurs is small especially in the cases of FIGS. 6 (b) and 6 (d). This is due to the relationship between the influence of the lateral electric field from the signal line S and the scanning line G and the alignment direction of the liquid crystal molecules.

As described above, by forming the specific alignment state, it is possible to minimize the reverse tilt domain region which lowers the display contrast and realize a wide viewing angle.

A liquid crystal display device according to an embodiment of the present invention will be described in detail below with reference to the drawings. 1 is a schematic front view of an array substrate of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of the liquid crystal display device taken along the line AA 'in FIG.

This liquid crystal display device (1) comprises an array substrate (10
0), the counter substrate (500) facing the array substrate (100), and the alignment films (700a) and (700b) between the array substrate (100) and the counter substrate (500), respectively. T retained
A liquid crystal layer (800) made of N liquid crystal and a polarizing plate (9) arranged on the outer surfaces of the substrates (100) and (500) so that their deflection axes are orthogonal to each other.
00a) and (900b).

This array substrate (100) comprises 600 scanning lines (12) made of molybdenum-tungsten (Mo-W) alloy on an insulating substrate (101) made of glass having a thickness of 0.7 mm.
1) and the substantially H-shaped auxiliary capacitance line (181) are arranged substantially parallel to each other, and are orthogonal to the scanning line (121) (800
× 3) Signal line (111) made of aluminum (Al)
Is arranged.

A TFT (131) having the scanning line (111) as a gate electrode and the signal line (121) as a drain electrode is arranged near the intersection of the signal line (111) and the scanning line (121). Has been done. This TFT (131) is made of amorphous silicon (a-Si: a) on the scanning line (121) via an insulating film (123).
H) The semiconductor layer (125) composed of a thin film is arranged, and the semiconductor layer
A channel protective film (127) self-aligned with the scanning line (111) is disposed on the (125). Then, each TFT (1
A drain electrode and a source electrode (135) are electrically connected to the semiconductor layer (125) of (31) through a low resistance semiconductor layer (129) made of an n + type a-Si: H thin film. The source electrode (135) is a pixel electrode (14) made of ITO.
1) electrically connected to the pixel electrode (141) and auxiliary capacitance line
It is opposed to (181) via the insulating film (123), and an auxiliary capacitance (Cs) is formed in this region. This TFT (131) is
Amorphous silicon (a-S) is used as the semiconductor layer (125).
Although the i: H) thin film is used as an example, the semiconductor layer may be made of polysilicon (p-Si) or a compound semiconductor.

The array substrate (100) is an insulating substrate.
Triangular rubbing marks (211a) and (211b) of about 1 mm square are formed at the corners of (101) in the same step as the formation of the scanning line (121) and can be visually identified. The rubbing marks (211a) and (211b) may be formed in the same step as the signal line (111) and the like as long as they can be visually identified. Then, it may be removed after the alignment treatment is completed.

Opposing substrate (500) of this liquid crystal display device (1)
Is a TFT (131), a scanning line (121) and a pixel electrode (141), a light blocking film (511) for blocking a gap between the signal line (111) and the pixel electrode (141), a color filter layer (521) and ITO.
The counter electrode (531) is composed of.

Then, the array substrate (1
00) As shown in FIG. 1 (b), the alignment film (700a) arranged above is first subjected to alignment treatment so that the pretilt angle (θ1) becomes 4 ° in the direction of the solid arrow (1) in the figure. It Thereafter, the region B is masked, and an alignment treatment is performed so that the pretilt angle (θ1) becomes 4 ° in the direction of the solid arrow (2) in the figure.
Then, by removing the mask, the alignment treatment is performed in the area A in the direction of the solid arrow (2) in the drawing and in the area B in the direction of the solid arrow (1) in the drawing. Also,
The alignment film (700b) arranged on the counter substrate (500) is also shown in FIG.
(B) Orientation treatment is performed in the direction of the middle dotted line arrow. Here, the alignment treatment as shown in FIG. 5D is made so that the region in which the lateral electric field opposes the pretilt of the liquid crystal molecules is most reduced. (1
The reason for this is that performing the first alignment treatment from the downstream side of 31) reduces the alignment treatment defects.

Liquid crystal display device configured as described above
In (1), in the display pixel formed corresponding to each pixel electrode (141), the liquid crystal molecules of the TN liquid crystal are twisted and aligned by about 90 ° between the substrates (100) and (500), and two different alignments are provided. It will have an area.

However, even in the liquid crystal display device (1) which has been subjected to the alignment treatment as described above, a reverse tilt domain occurs in the shaded area in FIG. 1 (b). Therefore, according to the liquid crystal display device (1) of this embodiment, the H-shaped auxiliary capacitance line (1
By 81), the reverse tilt domain is shielded from light. That is, in the main wiring portion (183) of the auxiliary capacitance line (181), the area A
To prevent light leakage at the boundary between the area B and the area B. Further, the auxiliary capacitance line (181) includes first to fourth branch wiring portions (extending from the main wiring portion (181) along the outer shape of the pixel electrode (141) in order to secure a sufficient auxiliary capacitance (Cs). 185a), (185b), (187a),
(187b).

The first branch wiring (185a) is connected to the pixel electrode (1
By setting the overlap length Δ1 with the pixel electrode (141) to 5 μm, the third branch wiring (187a) similarly causes the display defect due to the reverse tilt domain generated in the region B to overlap with the pixel electrode (141). Is set to 5 μm to block light.
The second branch wiring (185b) and the fourth branch wiring (187b) are set to have an overlapping length Δ2 of 3 μm with the pixel electrode (141) so as to make up for the shortage of the auxiliary capacitance set as described above. ing. In addition, the main wiring part (183) of the auxiliary capacitance line (181)
Corner portions (184a) and (184b) are provided to shield the reverse tilt domain from occurring near the boundary between the regions A and B, respectively.

Liquid crystal display device configured as described above
According to (1), in each alignment process, first, the region where the lateral electric field between the signal line (111) or the scanning line (121) and the pixel electrode (141) is opposed to the pretilt of the liquid crystal molecule is reduced most. Therefore, the display failure itself based on the reverse tilt domain is reduced.

Moreover, the boundary between two different alignment regions and the display defect region based on the reverse tilt domain are
Each is efficiently shielded from light by the auxiliary capacitance line (181). For these reasons, the liquid crystal display device of this embodiment
According to (1), excellent display contrast can be achieved while maintaining a high aperture ratio. Moreover, by constructing the light shielding layer with the auxiliary capacitance line (181), the number of manufacturing steps does not increase, and the auxiliary capacitance line (181) itself does not include the signal line (111) or the scanning line.
Since it is formed along the outer shape of the pixel electrode (141) so as to shield and alleviate the lateral electric field between the (121) and the pixel electrode (141), a further excellent effect can be achieved.

Naturally, each display pixel has 2 pixels.
Since it has three different orientation regions, a wide viewing angle can be achieved. In this embodiment, the auxiliary capacitance line (181) shields the display defect region based on the boundary between two different alignment regions and the reverse tilt domain.
The light shielding layer (511) on the opposite substrate (500) side may be used, but considering the alignment accuracy with the array substrate (100), it is preferable to use the array substrate (100), especially for shielding the lateral electric field. If this is alleviated, it is desirable to use the auxiliary capacitance line (181). Further, when the scanning line (121) is used as the auxiliary capacitance line, the scanning line (121) may be used. Further, in this embodiment, the case where two different alignment regions are formed in each display pixel is taken as an example, but a plurality of alignment regions may be formed.

[0029]

According to the present invention, it is possible to obtain a liquid crystal display device which can realize a wide viewing angle and can achieve a good display contrast.

[Brief description of drawings]

1A and 1B show a liquid crystal display device according to an embodiment of the present invention. FIG. 1A is a schematic front view of an array substrate, and FIG. 1B is a view showing its alignment direction. .

FIG. 2 is a schematic perspective view of the liquid crystal display device taken along the line AA ′ in FIG.

FIG. 3 is a diagram illustrating an array state of the liquid crystal display device when no voltage is applied.

FIG. 4 is a diagram illustrating an array state of the liquid crystal display device when a voltage is applied.

FIG. 5 is a schematic configuration diagram of an array substrate.

FIG. 6 is a diagram for explaining a display defect area based on a reverse tilt domain.

[Explanation of symbols]

 (1) ... Liquid crystal display (100) ... Array substrate (111) ... Signal line (121) ... Scan line (131) ... TFT (141) ... Pixel electrode (500) ... Counter substrate (800) ... Liquid crystal layer

Claims (3)

[Claims] 1. An active element arranged on one main surface, a pixel electrode electrically connected to the active element, and a wiring electrically connected to the active element and arranged around the pixel electrode. Corresponding to the pixel electrode, including an array substrate provided with, a counter substrate arranged to face the array substrate, and a liquid crystal layer composed of liquid crystal molecules sandwiched between the array substrate and the counter substrate. In the liquid crystal display device including the display pixels, the liquid crystal molecules of the liquid crystal layer are given a predetermined pretilt on the array substrate and the counter substrate, and at least two different arrangement directions are provided for each display pixel. An alignment film for defining is arranged, and one of the array substrate and the counter substrate has a boundary in the different arrangement direction and a lateral electric field between the pixel electrode and the wiring that is a liquid crystal molecule. The liquid crystal display device comprising the light-shielding layer for shielding the pixel electrode regions against the serial pretilt. 2. The alignment film according to claim 1, wherein the lateral direction electric field between the pixel electrode and the wiring is oblique to the pixel electrode so as to minimize a region where the lateral electric field is opposed to the pretilt of the liquid crystal molecule. A liquid crystal display device characterized in that the arrangement direction is defined in the. 3. A liquid crystal display device, wherein the light-shielding layer according to claim 1 is arranged via the pixel electrode and an insulating film.