JPH07301813A - Matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a matrix type liquid crystal display device having improved display quality by simplifying an orientation processing and reducing light leakage by disclination while preventing the degradation of numerical aperture. CONSTITUTION:The matrix type liquid crystal display device is provided with an upper substrate 14, a lower substrate 15, a common electrode 17 at the upper substrate 14 side, many pixel electrodes 19 at the lower substrate 15 side, TFTs connected to respective pixel electrodes and a liquid crystal 21. In this matrix type liquid crystal display device, compensating electrodes 27 are provided at clearance parts between respective pixel electrodes 19 and drain lines 23 and the potential of the common electrode 17 is made to be grounding potentials of respective compensating electrodes. Electric fields in horizontal direction are intensified between respective pixel electrodes 19 and the clearance parts and between the clearance parts and respective drain lines 23 and the electric fields in horizontal direction are effectively weakened between respective pixel electrodes and respective drain lines, and consequently disclinations generated in respective pixel parts are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix type liquid crystal display device using a switching element such as a thin film transistor (TFT).

[0002]

2. Description of the Related Art As a conventional matrix type liquid crystal display device, for example, as shown in FIG. 14, a twisted nematic which is provided with a liquid crystal cell 1 arranged between two polarizers (not shown) and which is driven actively. Type liquid crystal display device (hereinafter, simply referred to as TN-LCD) is known. The liquid crystal cell 1 includes two transparent glass substrates (upper substrate 2 and lower substrate 3) arranged opposite to each other, and a transparent common electrode provided on the lower surface of the upper substrate 2 and covered with an alignment film 4. 5 and
A large number of transparent pixel electrodes 7 arranged in a matrix on the upper surface of the lower substrate 3 and covered with an alignment film 6, and each pixel electrode 7
Thin film transistors (not shown) connected to
Twisted nematic liquid crystal 8 enclosed between both alignment films 4 and 6 and continuously twisted by about 90 ° between them, and the lower substrate 3
Scan lines and signal lines 9 arranged in a matrix on the upper surface side of the pixel electrodes 7 and the pixel electrodes 7 are connected to the scan lines and signal lines 9 via the thin film transistors, respectively.
In this conventional TN-LCD, the liquid crystal in each pixel portion corresponding to each pixel electrode 7 is driven by active matrix. That is, for example, when a signal is input to a scanning line of a certain row and all the thin film transistors connected to the scanning line are turned on, a voltage signal corresponding to image data is input to the signal line 9 of a certain column. Then, a voltage is applied from the signal line 9 through the thin film transistor to each pixel electrode 7 connected to each thin film transistor at the position where the scanning line in the row and the signal line in the column intersect, and this voltage is applied. A voltage is applied to the liquid crystal 8 of each pixel portion between the pixel electrode 7 and the common electrode 5 to which the voltage is applied, whereby the orientation of the liquid crystal molecules in that portion changes, and an optical change accompanying this change. Is visualized by a polarizer (not shown), and a desired display, for example, black and white display is performed.

Such a conventional TN-LCD, in particular, a TN-LC which has a large number of pixel electrodes 7 to enable high-definition display.
In the case of D, the display quality is greatly reduced due to the occurrence of disclination, which is a serious problem. This problem will be specifically described. FIG. 15 shows one of the pixel electrodes 7 when the conventional TN-LCD shown in FIG. 14 is in a normally white mode.
6 shows the display state in one pixel portion when a voltage of about 6 [V] is applied. As shown in FIG. 14, in one pixel unit 10, a normal tilt domain region 10a having the same tilt direction as the pretilt direction is a normal display part, and a reverse tilt domain having a tilt direction opposite to the pretilt direction. The area 10c is an abnormal display portion (shaded area in FIG. 15) that causes light leakage and white spots, and a boundary 10b between the two is a disclination line. In this way, if there is a blank portion in the pixel portion 10, T
The contrast of the entire display portion of the N-LCD is significantly reduced, and the display quality is significantly reduced. As described above, the disclination is determined by the orientation directions (rubbing directions) of the alignment film 4 on the upper substrate 2 side and the alignment film 6 on the lower substrate 3 side (the alignment film 4 side of the liquid crystal 8 and the alignment film). (Inclination direction of liquid crystal molecule long axis at both interfaces on 6 side)
And a direction of a lateral electric field generated between each pixel electrode 7 and each signal line 9 corresponding to the pixel electrode adjacent to the pixel electrode 7 are orthogonal to each other. The reason is that the director of a liquid crystal with a positive dielectric anisotropy Δε (a unit vector in the direction in which the long axis of the liquid crystal molecule is preferentially oriented) is oriented along the local electric field direction, so that the pretilt direction is This is because the directors are oriented at opposite tilt angles on the left and right sides of a place where the directions of the lateral electric fields are orthogonal to each other.

Such disclination easily occurs in a high-definition liquid crystal display device having a small pixel pitch,
The alignment film having a small pretilt angle on both interfaces of the liquid crystal 8 is likely to occur, and the pretilt angle is small at the time of high temperature operation. Therefore, the high temperature operation is more likely to occur than the room temperature operation.
Moreover, it tends to occur when the lateral electric field is strong. In particular, as the pixel pitch becomes smaller, the relative area ratio of the normal display section 10a to the pixel section 10 decreases, so that the deterioration of contrast becomes more severe. Further, when the pretilt angle becomes small, reverse tilt is likely to occur, and the position where the pretilt direction and the direction of the lateral electric field are orthogonal to each other, that is, the position where disclination occurs moves inward in the pixel unit 10. Therefore, TN-LCDs, which are required to have high definition and high temperature operation such as when mounted in a car such as an automobile or used in a projector, are more likely to cause disclination, and measures to improve this are strong. Is desired. Conventionally, as a measure for improving light leakage due to disclination, (1) use a high pretilt alignment film (alignment film having a pretilt angle of 5 ° or more),
Alternatively, (2) a light shielding material is provided in accordance with the position where the disclination occurs, so that the light leakage due to the disclination is hidden and reduced.

[0005]

However, in the above method (1), since the position where the disclination occurs is moved outward in the pixel portion, it is easy to hide the light leakage due to the disclination with the light shielding material. Although the effect is great in this respect, there is a problem that it is difficult to uniformly perform the high pretilt alignment. In addition, the method (2) has a problem that the aperture ratio (the ratio of the effective display area to the unit area of the pixel portion) is significantly reduced when the area to be hidden by the light shielding material is increased. The highly demanded high-definition TN-LCD cannot be an effective solution. The present invention has been made in view of the above-mentioned problems of the prior art, and the problem is to simplify the alignment process and prevent the reduction of the aperture ratio, while reducing the light leakage due to the disclination to improve the display quality. An object of the present invention is to provide an improved active matrix type liquid crystal display device.

[0006]

In order to achieve the above object, the invention according to claim 1 is provided with a liquid crystal cell, and the liquid crystal cell includes two substrates arranged to face each other, and both substrates. A common electrode provided on one side and covered with an alignment film, a large number of pixel electrodes arranged in a matrix on the other of the both substrates and covered with an alignment film, and at least one connected to each pixel electrode. A switching element, a liquid crystal enclosed between the both alignment films, and a scanning line and a signal line arranged in a matrix, the scanning line and the signal line corresponding to each pixel electrode, and the switching element. In the matrix type liquid crystal display device connected through the respective electrodes, a compensation electrode is provided in the gap between each pixel electrode and each signal line, and the potential of each compensation electrode is equal to that of the common electrode. Or it is obtained by a ground potential. Preferably, the liquid crystal is a twisted nematic liquid crystal in which the long axis of the liquid crystal molecule is continuously twisted by approximately 90 ° between the both alignment films, and a polarizer is provided on each side of the liquid crystal cell. 2). More preferably,
Each of the switching elements is an amorphous silicon thin film transistor or a polysilicon thin film transistor (claim 3). More preferably, the distance between the pixel electrodes is 0.2 to 4 times the cell gap d of the liquid crystal cell (claim 4). More preferably, each of the pixel electrodes and each of the compensation electrodes are provided in one and the same plane of the substrate (claim 5). Preferably, each of the pixel electrodes, compensation electrodes, and signal lines are provided in the same plane on one side of the substrate (claim 6).

[0007]

In the liquid crystal display device according to the first aspect, the compensating electrode is provided in the gap between each pixel electrode and each signal line, and the potential of each compensating electrode is set to the same potential as the common electrode or the ground potential. Thereby, the lateral electric field is strengthened between the pixel electrodes and the gaps, and between the gaps and the signal lines, effectively weakening the lateral electric field between the pixel electrodes and the signal lines, As a result, the disclination generated in each pixel portion is reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a vertical cross-sectional view showing a main part of an active matrix type liquid crystal display device according to an embodiment, and is a plan view showing a part of a large number of pixels, which is a cross-sectional view taken along the line AA of FIG. is there. An active matrix type liquid crystal display device according to this embodiment uses a thin film transistor as a switching element, and an active driven transmission type twisted nematic type liquid crystal display device (hereinafter, simply referred to as TN-
LCD). As shown in FIGS. 1 and 2, this TN-LCD includes a liquid crystal cell 13 arranged between two polarizers 11 and 12, and the liquid crystal cell 13 is composed of two liquid crystal cells 13 arranged to face each other. A transparent glass substrate (upper substrate 14 and lower substrate 15), a transparent common electrode 17 provided on the lower surface side of the upper substrate 14 and covered with an alignment film 16, and a lower substrate 1
5, a large number of transparent pixel electrodes 19 arranged in a matrix and covered with an alignment film 18, and each pixel electrode 19
Thin film transistors (hereinafter, simply referred to as T
FT) 20, a twisted nematic liquid crystal (hereinafter, simply referred to as TN liquid crystal) 21 enclosed between both alignment films 16 and 18 and continuously twisted by about 90 ° between them, and a matrix shape on the upper surface of the lower substrate 15. It has a large number of gate lines (scanning lines) 22 and drain lines (signal lines) 23 arranged in the.

On the upper surface of the upper substrate 14, color filters 24 of red (R), green (G) and blue (B) are alternately arranged corresponding to the pixel electrodes 19.
And a large number of black matrices 25 that respectively cover the entire periphery of each pixel electrode 19. The common electrode 17 is formed on the lower surfaces of the color filter 24 and each black matrix 25. In FIG. 2, a portion corresponding to each pixel electrode 19 and not shielded by each black matrix 25 is each pixel portion 26. In this embodiment, each black matrix 25 has such a size as to block light which adversely affects the image display such as light leakage due to disclination (see the chain double-dashed line in FIG. 2) to a necessary minimum. It has become.

On the other hand, a compensation electrode 27 is provided on the upper surface of the lower substrate 15 in a gap (a gap having a width L) between each pixel electrode 19 and each drain line 23. The same voltage as that of the common electrode 17 is applied to each compensation electrode 27. In this embodiment, each compensation electrode 27
Is a ground electrode to which the same potential of 0 [V] as the common electrode is applied.

Each compensation electrode 27 is provided in the same plane as each pixel electrode 19 (that is, the upper surface of the lower substrate 15) and covered with the alignment film 18. On the other hand, each drain line 23 is provided at a position above each compensation electrode 27 (a height position different from each compensation electrode 27) and the alignment film 1 is provided.
It is covered with 8. In addition, each of the gate lines 22 is
Although not shown in FIG. 1, the alignment film 18 is provided so as not to contact the drain lines 23.

Each of the TFTs 20 is an amorphous silicon thin film transistor using amorphous silicon as an active layer, and the gate electrode 20g of each TFT 20 corresponds to one gate line 22 and the drain electrode 20 thereof.
The drain electrode 23 corresponding to d is connected to the pixel electrode 19 corresponding to the source electrode 20s. In this way, each pixel electrode 19 is connected to the corresponding gate line 22 and drain line 23 and each T
They are respectively connected via the FT20. A polysilicon thin film transistor using polysilicon as an active layer may be used as each TFT 20.

In this embodiment, as shown in FIG. 2, the alignment treatment direction (rubbing direction of the alignment film 18) A ₁ of the lower substrate 15 is set to about 45 clockwise with respect to the horizontal direction in the figure.
The upper substrate 14 is oriented so that the alignment treatment direction (rubbing direction of the alignment film 16) A ₂ of the upper substrate 14 is inclined approximately 90 ° clockwise with respect to the alignment treatment direction A ₁ . In the following description, such an alignment treatment direction of the upper and lower substrates 14 and 15 will be referred to as a rubbing direction A. In this embodiment, since the rubbing direction A is the alignment treatment direction of the upper and lower substrates 14 and 15, the disclination is as shown in FIG.
As shown by the two-dot chain line in FIG.

Further, as shown in FIG. 2, each compensation electrode 27 has a part of the peripheral edge of each pixel electrode 19, that is, the right side edge, the left side edge and the lower side in the gap of the width L. It extends along the edge. Further, all the compensation electrodes 27 corresponding to the pixel portions 26 are continuously formed as shown in FIG.

Further, in the TN-LCD according to the above embodiment, the TN liquid crystal 21 of each pixel portion corresponding to each pixel electrode 19 is provided.
Are to be actively driven. That is,
For example, a signal is input to the gate line 22 of a certain row and all the TFTs 2 connected to this gate line 22
When the voltage signal according to the image data is input to the drain line 23 of a certain column with 0 turned on, each pixel electrode at the position where the gate line 22 of the row and the drain line 23 of the column intersect A voltage is applied from the drain line 23 to the TFT 19 via the TFT 20, and a voltage is applied to the TN liquid crystal 21 of each pixel section between each pixel electrode 19 to which the voltage is applied and the common electrode 17, and thereby the voltage is applied. The alignment of the liquid crystal molecules in the part is changed, and the optical change accompanying this change is visualized by the polarizers 11 and 12, and a desired image is displayed in color.

In the TN-LCD according to the above-described embodiment, the compensation electrode 27 is provided in the gap portion of the width L between each pixel electrode 19 and each drain line 23, and each compensation electrode 27 is the same as the common electrode 17. Due to the configuration in which the voltage of 0 [V] is applied, the lateral electric field becomes strong between the pixel electrodes 19 and the gaps and between the gaps and the drain lines 23. The lateral electric field between the electrode 19 and each drain line 23 is weakened, thereby reducing the disclination generated in each pixel unit 26.

The reduction of the disclination will be described with reference to FIGS. 3 to 10.
3A and 3B, in the above embodiment, the cell gap d between the alignment films 16 and 18 is about d = 5 [μm], the width L of the gap is L = d, and , +6 [V] is applied to one pixel electrode 19 shown in FIGS. 1 and 2, and the drain line 23 (the drain line is the pixel electrode 1 is provided on the right side of the pixel electrode 19 at a position separated by the gap of the width L).
9 corresponding to the pixel electrode on the right of 9) -6
FIG. 3A is a cross-sectional view of a portion of the TN liquid crystal 21 centering on the gap when [V] is applied to the common substrate 17 and the compensation electrode 27, respectively.
FIG. 3 is a diagram in which an alignment vector diagram of the liquid crystal 21 and an equipotential curve diagram are superimposed, and FIG. 3B is a diagram in which the alignment vector diagram of the TN liquid crystal 21 and the Y value (Y value transmittance curve) are superimposed. On the other hand, FIGS. 4A and 4B show the case where the disclination countermeasure of providing the compensation electrode 27 as in the above-described embodiment is not applied and the other conditions are shown in FIGS. )
3 (a) and 3 (b) in the same case as in FIG.
It is a figure similar to.

From the equipotential curve diagram of FIG. 3A, from the pixel electrode 19 (+6 [V]) to the drain line 23 (-6).
The lateral electric field to [V]) can be seen. Further, in the same figure, the director of the liquid crystal stands up in most of the portion corresponding to the pixel electrode 19 (pixel portion 26) and the portion corresponding to the drain line 23, showing a normal display portion for black display. Disorder of orientation is seen around the gap of width L. That is, disclination is generated at a position slightly inside the area of the pixel electrode 19 from the gap.
In the case of FIG. 3A, as compared with the case of FIG. 4A, the compensating electrode 27 having an equipotential curve in the gap portion.
You can clearly see that they are concentrated at both ends. In the case of one embodiment, the peak brightness of light leakage due to disclination in the area corresponding to each pixel electrode 19 (in each pixel portion 26) (hereinafter, simply referred to as Y value).
Is 10.87 (%) (see FIG. 3 (b)) and smaller than the Y value (13.40 (%)) in the case of FIG. 4 (b). On the other hand, comparing FIG. 3 (b) with FIG. 4 (b), in the case of the embodiment shown in FIG. 3 (b), the disorder of the orientation in the gap portion is shown in FIG. 4 (b). Is larger than the case. However, there is no particular problem if the gaps having the disordered orientation are blocked by the black matrix 25.

Next, in FIGS. 5A and 5B, in the above embodiment, the width L of the gap portion is L = 2d, and other conditions are as shown in FIGS. 3A and 3B. It is a figure which shows the data at the time of making it the same as the case. 6 (a) and 6 (b) are the same as in the case of FIGS. 4 (a) and 4 (b) above, except that the measures for disclination are not applied, and FIGS.
It is a figure which shows the data at the time of making width L of the said gap part L = 2d like the case of (b). Also in the case of FIG. 5A, it is clearly seen that the equipotential curves are concentrated at both ends of the compensation electrode 27 in the gap, as compared with the case of FIG. 6A. In the case of the embodiment shown in FIG. 5B, Y in the region corresponding to each pixel electrode 19
The value is 10.73 (%) and smaller than the Y value (14.45 (%)) in the case of FIG. 6 (b). As described above, also in the case of FIG. 5A, the disclination generated in each pixel unit 26 is reduced. Also, in the case of the embodiment shown in FIG. 5B, the disorder of the orientation in the gap is larger than that in the case of FIG. 6B.
If the black matrix 25 shields each of the gaps in which the orientation is disturbed, there is no particular problem.

Next, in FIGS. 7A and 7B, in the above embodiment, the width L of the gap portion is L = 4d, and other conditions are as shown in FIGS. 3A and 3B. It is a figure which shows the data at the time of making it the same as the case. 8 (a) and 8 (b) are the same as in the case of FIGS. 4 (a) and 4 (b) above, except that the measures for disclination are not applied, and FIGS.
It is a figure which shows the data at the time of making the width L of the said gap part L = 4d like the case of (b). Also in the case of FIG. 7A, it can be clearly seen that the equipotential curves are concentrated on both ends of the compensation electrode 27 in the gap, as compared with the case of FIG. 8A. In the case of the embodiment shown in FIG. 7B, Y in the region corresponding to each pixel electrode 19
The value is 10.73 (%) and smaller than the Y value (14.45 (%)) in the case of FIG. 8B. Thus, also in the case of FIG. 7A, the disclination generated in each pixel unit 26 is reduced. Also, in the case of the embodiment shown in FIG. 7B, the disturbance of the orientation in the gap is larger than that in the case of FIG. 8B.
If the black matrix 25 shields each of the gaps in which the orientation is disturbed, there is no particular problem.

Next, in FIGS. 9A and 9B, in the above embodiment, the width L of the gap portion is set to L = 0.2d, and other conditions are shown in FIGS. 3A and 3B. It is a figure which shows the data at the time of making it the same as the case of FIG. 10 (a), (b)
9A and 9B are the same as in the case of FIG. 4A and FIG.
As in the case of (a) and (b), the width L of the gap is set to L =
It is a figure which shows the data at the time of being set to 0.2d. Figure 9
In the case of (a), the equipotential curve is concentrated on both ends of the compensation electrode 27 in the gap because the width of the gap is narrower than in the case of FIG. 10 (a). However, in the case of the embodiment shown in FIG. 9B, the Y value in the region corresponding to each pixel electrode 19 is 1
The value is 1.36 (%) and is slightly smaller than the Y value (11.39 (%)) in the case of FIG. 10 (b). Thus, also in the case of FIG. 9A, the disclination generated in each pixel unit 26 is slightly reduced.
In the case of the embodiment shown in FIG. 9B, the disorder of the orientation in the gap is almost the same as that in the case of FIG. 10B.

Thus, the TN-L according to the above embodiment
According to C, when the width L of the gap is L = d (the case shown in FIG. 3), when L = 2d (the case of FIG. 5),
When L = 4d (in the case of FIG. 7) and L = 0.2d
In any of the above cases (in the case of FIG. 9), the equipotential curves concentrate on both ends of each compensation electrode 27, so that between each pixel electrode 19 and the above gap, and between this gap and each drain. Between the lines 23, the lateral electric field becomes stronger,
The lateral electric field between each pixel electrode 19 and each drain line 23 is effectively weakened, whereby the disclination generated in each pixel portion 26 is reduced, and the light leakage due to the disclination is reduced. Therefore, according to the one embodiment, as in the conventional technique, as a measure for improving light leakage due to disclination, a high pretilt alignment film (pretilt angle of 5 ° is difficult to align.
It is not necessary to use the above alignment film) or provide a light-shielding material such as black summatris according to the position where the disclination occurs to hide the light leakage due to the disclination (that is, the black matrix 255 is
It is enough to block the light that adversely affects the image display such as light leakage due to the disclination), so that the orientation process can be simplified and the aperture ratio can be prevented from decreasing. Light leakage can be reduced and display quality can be improved. As a result, the T that requires high-definition and high-temperature operation such as when mounted on a car such as an automobile or used for a projector
A high-definition TN-LCD that can be effectively used as an N-LCD and that requires a high aperture ratio at the same time.
Can also be used effectively.

Further, according to the above embodiment, as described above, by weakening the lateral electric field, each pixel unit 2
In addition to reducing the disclination generated in 6 to reduce the light leakage due to the disclination, the light that adversely affects the image display such as the light leakage due to the disclination is blocked to the minimum necessary. Since the black matrix 25 of a certain size is provided so as to cover the entire peripheral portion of each pixel electrode 19, a large decrease in the aperture ratio is prevented and light leakage due to disclination is further reduced. be able to.

Further, according to the above embodiment, each pixel unit 2
Since all of the compensation electrodes 27 corresponding to 6 are continuously formed as shown in FIG. 2, the manufacturing is facilitated and the cost is reduced.

Next, a first modified example of the above embodiment is shown in FIG.
It will be described based on 1. In the above-mentioned embodiment, as shown in FIG. 1, each compensation electrode 27 is provided in the same plane as each pixel electrode 19 (that is, the upper surface of the lower substrate 15), and each drain line 23 is more than each compensation electrode 27. It is provided at an upper position (a height position different from each compensation electrode 27). On the other hand, in this modification, each drain line 23 is provided in the same plane as each pixel electrode 19 and each compensation electrode 27, that is, on the upper surface of the lower substrate 15. The other structure is the same as that of the above-mentioned one embodiment.

Next, another modification of the above-described embodiment is shown in FIG.
2 and FIGS. 13A and 13B. 12 and FIGS. 13A and 13B show the upper and lower substrates 1 respectively.
The orientation processing directions of 4, 15 and the position where disclination occurs in each pixel portion 26 in each case are shown. In the second modified example shown in FIG. 12, the alignment treatment direction B ₁ of the lower substrate 15 is substantially parallel to the drain line 23, and the alignment treatment direction B ₂ of the upper substrate 14 is clockwise with respect to the alignment treatment direction B ₁ . The disclination occurs on the lower left side of each pixel portion 26 because it is tilted by approximately 90 °. Also in the case of this modification, as in the case of the above-described embodiment, by providing the compensation electrode 27 in each of the gap portions having the width L, the disclination in each pixel portion 26 can be reduced. .

Further, in the third modified example shown in FIG. 13A, the alignment treatment direction C ₁ of the lower substrate 15 is tilted clockwise by approximately 135 ° with respect to the horizontal direction in FIG.
Since the alignment treatment direction C ₂ of _No. 4 is tilted approximately 90 ° clockwise with respect to the alignment treatment direction C ₁ , disclination occurs on the lower left side of each pixel portion 26. In the fourth modification shown in FIG. 13B, the alignment treatment direction D ₁ of the lower substrate 15 is substantially perpendicular to the drain line 23, and the alignment treatment direction D ₂ of the upper substrate 14 is the alignment treatment direction D _1. Since it is tilted clockwise by about 90 °, disclination occurs on the upper left side of each pixel unit 26. Also in these modified examples, as in the case of the above-described one embodiment, by providing the compensation electrode 27 in each of the gap portions having the width L, the disclination in each pixel portion 26 can be reduced. it can.

Further, in the above-mentioned embodiment, the transmissive twisted nematic liquid crystal display device driven by the active matrix is shown, but the present invention is not limited to this, and the reflective twisted nematic liquid crystal display device is shown. It is also applicable to devices. Further, although the liquid crystal display device of the above-described embodiment is for color display, the present invention is not limited to this, and can be applied to a liquid crystal display device for monochrome display.

Further, in the above-described embodiment, as shown in FIG. 2, the drain electrode 20d of each TFT 20 is connected to the drain line (signal line) 23, and the source electrode 20s thereof is connected to the pixel electrode 19, respectively. The source electrode 20s and the drain electrode 20d may be connected to the signal line 23 and the pixel electrode 19, respectively. Further, in the above-described one embodiment, as shown in FIG. 2, each pixel electrode 19 is connected to the corresponding gate line 22 and drain line 23 through one TFT 20, but each pixel electrode 19 is connected. May be connected to the corresponding gate line 22 and drain line 23 via the two TFTs.

As the switching element, a non-linear element such as MIM (metal-insulating film-metal) may be used instead of the thin film transistor 20.

[0031]

As described above, according to the matrix type liquid crystal display device of the present invention (the invention according to claim 1), the compensation electrode is provided in the gap between each pixel electrode and each signal line. Moreover, since the potential of each compensation electrode is set to the same potential as the common electrode or the ground potential, the lateral electric field becomes strong between the pixel electrode and the gap portion and between the gap portion and each signal line, which is effective. Further, the lateral electric field between each pixel electrode and each signal line is weakened, thereby reducing the disclination generated in each pixel portion. Therefore, it is possible to reduce the light leakage due to disclination and improve the display quality while simplifying the alignment process and preventing the aperture ratio from decreasing.

[Brief description of drawings]

1 is a vertical cross-sectional view showing a main part of an active matrix type liquid crystal display device according to an embodiment of the present invention.
It is sectional drawing which follows the AA line.

FIG. 2 is a plan view showing a part of a large number of pixels of the liquid crystal display device shown in FIG.

FIG. 3A is a diagram in which an alignment vector diagram of a liquid crystal and an equipotential curve diagram are overlapped when the width L of the gap portion is L = d in the liquid crystal display device according to the embodiment.
FIG. 7B is a diagram in which the alignment vector diagram of the liquid crystal and the Y value when L = d is overlapped in the same device.

FIG. 4 (a) is an alignment vector diagram and an equipotential curve diagram of the liquid crystal when the width L of the gap is L = d in the case where no measure for disclination is applied (conventional liquid crystal display device). It is the figure which piled up. FIG. 7B is a diagram in which the alignment vector diagram of the liquid crystal and the Y value when L = d is overlapped in the same device.

5A is a view showing a case where the width L of the gap portion is L = 2d in the liquid crystal display device according to the embodiment.
It is a figure similar to (a). (B) is the same device, L
4 is a diagram similar to FIG. 3B in the case where = 2d.

6A is a view similar to FIG. 4A in the case where the width L of the gap portion is L = 2d in the conventional liquid crystal display device. FIG. 4B is a view similar to FIG. 4B when L = 2d in the same device.

FIG. 7A is a diagram illustrating a case where the width L of the gap portion is L = 4d in the liquid crystal display device according to the embodiment.
It is a figure similar to (a). (B) is the same device, L
4 is a diagram similar to FIG. 3B in the case of setting = 4d.

FIG. 8A is a view similar to FIG. 4A in the case where the width L of the gap portion is L = 4d in the conventional liquid crystal display device. FIG. 4B is a view similar to FIG. 4B when L = 4d in the same device.

9A is a diagram similar to FIG. 3A in the case where the width L of the gap portion is L = 0.2d in the liquid crystal display device according to the embodiment. (B) is the same device,
It is a figure similar to FIG.3 (b) at the time of being L = 0.2d.

10A is a conventional liquid crystal display device, and FIG. 4A when the width L of the gap is L = 0.2d.
It is a figure similar to. (B) is the same apparatus, L = 0.
FIG. 5 is a view similar to FIG. 4B in the case of 2d.

11 is a vertical cross-sectional view showing a first modification of the embodiment shown in FIG.

FIG. 12 is a diagram showing a second modification of the embodiment, and is an explanatory diagram showing the alignment processing direction of the upper and lower substrates and the disclination generation position in the pixel portion.

13A is a diagram showing a third modification of the embodiment, and is an explanatory diagram similar to FIG. 12. FIG. (B) is a figure which shows the 4th modification and is an explanatory view similar to FIG.

FIG. 14 is an explanatory diagram for explaining the occurrence of disclination in the conventional liquid crystal display device.

FIG. 15 is an explanatory diagram showing a state where disclination occurs in one pixel in the conventional liquid crystal display device.

[Explanation of symbols]

 13 liquid crystal cell 14 upper substrate 15 lower substrate 16 and 18 alignment film 17 common electrode 19 pixel electrode 20 thin film transistor (switching element) 21 twisted nematic liquid crystal (liquid crystal) 22 gate line (scanning line) 23 drain line (signal line) 27 compensation electrode

Claims (6)

[Claims] 1. A liquid crystal cell comprising: two substrates arranged to face each other; a common electrode provided on one of the two substrates and covered with an alignment film; On the other hand, a large number of pixel electrodes arranged in a matrix and covered with an alignment film, at least one switching element connected to each pixel electrode, a liquid crystal enclosed between the alignment films, and a matrix. A matrix-type liquid crystal display device, comprising: arranged scanning lines and signal lines, wherein each pixel electrode is connected to the corresponding scanning line and signal line via each of the switching elements. A matrix type liquid crystal display characterized in that a compensating electrode is provided in a gap between the signal line and each signal line, and the potential of each compensating electrode is set to the same potential as the common electrode or the ground potential. Location. 2. The liquid crystal is a twisted nematic liquid crystal in which the long axis of the liquid crystal molecule is continuously twisted by approximately 90 ° between the both alignment films, and a polarizer is provided on each side of the liquid crystal cell. The liquid crystal display device according to claim 1. 3. The liquid crystal display device according to claim 1, wherein each of the switching elements is an amorphous silicon thin film transistor or a polysilicon thin film transistor. 4. The liquid crystal display device according to claim 1, wherein the distance between the pixel electrodes is 0.2 to 4 times the cell gap d of the liquid crystal cell. 5. The liquid crystal display device according to claim 1, wherein the pixel electrodes and the compensation electrodes are provided in the same plane on one side of the substrate. 6. The liquid crystal display device according to claim 1, wherein the pixel electrodes, the compensation electrodes, and the signal lines are provided on one of the same planes of the substrate.