JPH07294936A - Matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the matrix type liquid crystal display device which improves the contrast to improve the display quality by reducing light leakage due to disclination in the gap part between each picture element electrode and each signal line. CONSTITUTION:The matrix type liquid crystal display device is provided with two substrates facing each other, a common electrode covered with an oriented film, many picture element electrodes 19 which are arranged on the lower substrate like a matrix and are covered with another oriented film, TFTs 20 connected to picture element electrodes, and twisting nematic liquid crystal charged between both oriented films, and picture element electrodes 19 are connected to gate lines 22 and drain lines arranged like a matrix through a drain line 23 and TFTs 20. In this device, the rubbing direction of an arrow A2 of the upper substrate is made approximately perpendicular to drain lines 23, and that of an arrow A1 of the lower substrate is made approximately parallel with drain lines.

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. 9, a matrix-driven twisted nematic is provided with a liquid crystal cell 1 arranged between two polarizers (not shown). 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, a 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, thin film transistors (not shown) connected to each pixel electrode 7, both alignment films 4, Each of the pixel electrodes 7 has a twisted nematic liquid crystal 8 enclosed between 6 and continuously twisted by about 90 ° between them, and scanning lines and signal lines 9 arranged in a matrix on the upper surface side of the lower substrate 3. Are connected to the scanning line and the signal line 9 via the respective thin film transistors. 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. Are visualized by the polarizer, 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 significant deterioration of the display quality due to the occurrence of disclination is a serious problem.
This problem will be specifically described. FIG. 10 (a),
9B shows the pixel electrode 7 when the conventional TN-LCD shown in FIG. 9 is of normally white mode.
1 when a voltage of about 6 [V] is applied to one of the
The display state in each of the two pixel portions is shown. Figure 10
(A) shows that the rubbing direction C ₁ of the alignment film 6 on the lower substrate 3 side is tilted approximately 45 ° clockwise with respect to the horizontal direction in the figure, and the rubbing direction C ₂ of the alignment film 4 on the upper substrate 2 side is set. FIG. 9 is a diagram of a case where the angle is tilted approximately 90 ° clockwise with respect to the rubbing direction C ₁ (the rubbing direction in this case is referred to as a rubbing direction C in the following description). Figure 10
(B) shows that the rubbing direction D ₁ of the alignment film 6 on the lower substrate 3 side is tilted approximately 135 ° clockwise with respect to the horizontal direction in the figure, and the rubbing direction D ₂ of the alignment film 4 on the upper substrate 2 side is set. FIG. 7 is a diagram of a case where the angle is inclined approximately 90 ° clockwise with respect to the rubbing direction D ₁ (the rubbing direction in this case is referred to as a rubbing direction D in the following description). Figure 1
As shown by 0 (a) and (b), the normal display portion 10a of one pixel portion 10 displays black,
Disclination occurs in a part of the disclination, and light leakage occurs at the disclination generation portion, causing white spots. In this way, when the pixel portion 10 has a blank portion,
The contrast of the entire display portion of the TN-LCD is significantly reduced, and the display quality is significantly reduced. Such disclination is caused by the pretilt direction (alignment film 4 of liquid crystal 8) determined by the rubbing direction of each alignment film 4, 6.
Direction of the liquid crystal molecule major axis at both interfaces on the side and the alignment film 6 side), and the direction of the lateral electric field generated between each pixel electrode 7 and each signal line 9 corresponding to the pixel electrode adjacent thereto. Occurs in a place where and are orthogonal. 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. Then, as shown in FIG. 9, the normal tilt domain having the same tilt direction as the pretilt direction is the normal display portion 10a, and the reverse tilt domain having the tilt direction opposite to the pretilt direction is the abnormal display portion (FIG. a) and (b), which are the shaded portions), and the boundary between the two display portions 10a and 10c is the disclination line generation portion.

Generally, the above disclination is likely to occur in a high-definition liquid crystal display device having a small pixel pitch, is likely to occur in an alignment film having a small pretilt angle at both interfaces of the liquid crystal 8, and has a small pretilt angle during high temperature operation. The high temperature operation is more likely to occur than the room temperature operation, and is likely to occur when the lateral electric field is strong.
Particularly, as the pixel pitch becomes smaller, the normal display portion 10a
Since the relative area ratio of the pixel area 10 to the pixel area 10 is reduced, the contrast is further deteriorated. Also, when the pretilt angle becomes smaller, reverse tilt is more likely to occur,
The position where the pretilt direction and the direction of the lateral electric field are orthogonal to each other, that is, the position where the 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. In the conventional TN-LCD, the rubbing directions of the alignment films 4 and 6 of the upper and lower substrates 2 and 3 are the rubbing directions (C) and (D) as shown in FIGS. 10 (a) and 10 (b). .

[0005]

However, in the conventional TN-LCD, even if the rubbing directions of the alignment films 4 and 6 of the upper and lower substrates 2 and 3 are any of the rubbing directions (C) and (D), Light leakage due to the disclination 10b in the gap portion of the width L (see FIGS. 9 and 10) between each pixel electrode and each signal line 9 (because there is a very bright light leakage). ), There is a problem that the display quality is significantly reduced due to a significant decrease in contrast. This problem will be described with reference to FIGS. 11 and 12. 11A and 11B show the rubbing direction in FIG.
In the rubbing direction C shown in (a), the refractive index anisotropy Δn of the TN liquid crystal 8 and the cell gap d between the alignment films 4 and 6 are set.
(D = 5 μm), the retardation Δnd of the liquid crystal cell is set to 380 nm, and +6 [V] is applied to one pixel electrode 7, and a space having a width L is provided on the right side of the pixel electrode 7. -6 [V] to the signal line 9 (the signal line corresponds to the pixel electrode on the right of the pixel electrode 7)
Is a cross-sectional view of a portion of the liquid crystal 8 centered on the gap when 0 [V] is applied to the common electrode 5. FIG. 11A shows the liquid crystal 8 at the substrate position x near the gap. 11B is a diagram in which the orientation vector diagram of FIG. 11 and the equipotential curve diagram are superimposed, and FIG. 11B is a diagram in which the orientation vector diagram of the liquid crystal 8 at the substrate position x near the gap and the Y value are superimposed. is there. 12 (a) and 12 (b) are shown in FIGS. 11 (a) and 11 (b).
FIG. 11 is a view similar to that of FIG. 10 when the rubbing direction is the rubbing direction D shown in FIG. Note that FIG.
In FIGS. 12A and 12B, the width L of the gap is equal to the cell gap d, and the substrate position x is shown as a ratio to the cell gap d. 11 (a) and 12
In each of the drawings of (a), the director of the liquid crystal stands in most of the area corresponding to the pixel electrode 7 (pixel area) and the area corresponding to the signal line 9, indicating a normal display area for black display. , The disclination in which the orientation is disturbed occurs around the gap of the width L. Further, from FIG. 11B, it can be seen that the peak brightness (Y value) of light leakage due to disclination in the gap is 22.12 (%). Further, it can be seen from FIG. 12B that the brightness (Y value) of the peak in the gap is 33.18 (%). As described above, in the above-described conventional TN-LCD, the rubbing directions of both alignment films 4 and 6 are the rubbing directions (C) and (D), and therefore, the gap portion between each pixel electrode 7 and each signal line 9 is formed. There is a problem that the light leakage due to the disclination at 1 is extremely large and the contrast is significantly reduced. The present invention has been made by paying attention to the above-mentioned problems of the prior art, and the problem is to reduce the light leakage due to disclination in the gap between each pixel electrode and each signal line to reduce the contrast. It is an object of the present invention to provide a matrix type liquid crystal display device which improves the display quality by improving the display quality.

[0006]

In order to achieve the above object, the invention according to claim 1 comprises a pair of polarizers and a liquid crystal cell arranged between the both polarizers, and the liquid crystal cell comprises: Two substrates arranged to face each other, a common electrode provided on one of both substrates and covered with an alignment film, and a large number of substrates arranged in a matrix on the other of the two substrates and covered with an alignment film. A pixel electrode, at least one switching element connected to each pixel electrode, and a twisted nematic liquid crystal that is enclosed between both alignment films and is continuously twisted by approximately 90 ° between both alignment films, Each of the pixel electrodes is
In a matrix type liquid crystal display device in which scanning lines and signal lines arranged in a matrix are connected to each other through each of the elements, the rubbing direction of the alignment film provided on one of the both substrates is set to the direction of the signal lines. It is substantially perpendicular to the extending direction, and the rubbing direction of the alignment film provided on the other of the both substrates is substantially parallel to the extending direction of the signal line. (Claim 1). Of the two polarizers, a reflective type is preferably provided with a reflector outside the polarizer on the pixel electrode side (claim 2). More preferably, the retardation Δnd of the liquid crystal cell, which is the product of the refractive index anisotropy Δn of the liquid crystal and the cell gap d between the alignment films, is 300 nm ≦ Δnd ≦ 550 nm (claim 3). More preferably, each element is an amorphous silicon thin film transistor using amorphous silicon as an active layer or a polysilicon thin film transistor using polysilicon as an active layer (claim 4). More preferably, neither of the substrates has a black stripe for shading between the image electrodes (claim 5).

[0007]

According to the liquid crystal display device of the present invention, the rubbing direction of the alignment film provided on one of both substrates is substantially perpendicular to the extending direction of the signal line, and the alignment film provided on the other of both substrates. Since the rubbing direction is substantially parallel to the extending direction of the signal line, light leakage due to disclination in the gap between each pixel electrode and each signal line is reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a part of a matrix type liquid crystal display device according to an embodiment, and FIG. 2 is a vertical sectional view showing a main part of the device. The matrix type liquid crystal display device according to this embodiment is a twisted nematic type reflection type liquid crystal display device (hereinafter, simply referred to as a reflection type TN) which is driven actively and which uses a thin film transistor as a switching element.
-LCD). This reflective TN-LCD is
As shown in FIG. 1 and FIG. 2, a liquid crystal cell 13 disposed between two polarizers 11 and 12 is provided.
Are two transparent glass substrates (upper substrate 14 and lower substrate 15) arranged opposite to each other, a transparent common electrode 17 provided on the lower surface of the upper substrate 14 and covered with an alignment film 16, A large number of transparent pixel electrodes 19 arranged in a matrix on the upper surface of the substrate 15 and covered with an alignment film 18, and thin film transistors connected to the respective pixel electrodes 19 (hereinafter, referred to as
A TFT 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 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 a line, and a reflection plate 24 provided outside the polarizer 12 on the lower substrate 15 side.

Each of the TFTs 20 is an amorphous silicon thin film transistor using amorphous silicon as an active layer, and includes a gate insulating film 25 formed on the upper surface of the lower substrate 15 and a semiconductor formed on the upper surface of the gate insulating film 25. A thin film 20a, a gate electrode 20g formed on the upper surface of the lower substrate 15 at a position corresponding to the central channel region of the semiconductor thin film 20a, and covered with the gate insulating film 25;
It has a drain electrode 20d formed on the drain region of the semiconductor thin film 20a and a source electrode 20s formed on the source region thereof. One gate line (scanning line) 22 corresponding to the gate electrode 20g of each TFT 20
In addition, the drain electrode 20d is connected to one corresponding drain line (signal line) 23, and the source electrode 20s is connected to one corresponding pixel electrode 19. In this way, each pixel electrode 19 is connected to the corresponding gate line 22 and drain line 23 via each TFT 20. Then, a gap portion having a width L is formed between the left and right sides of each pixel electrode 19 and the drain lines 23 on both sides thereof. As the TFT 20, a polysilicon thin film transistor using polysilicon as an active layer may be used.

In the reflective TN-LCD, the TN liquid crystal 21 in each pixel portion corresponding to each pixel electrode 19 is actively driven. That is, for example, when a signal is input to the gate line 22 of a certain row and all the TFTs 20 connected to this gate line 22 are turned on, a voltage signal corresponding to image data is input to the drain line 23 of a certain column. Then, the gate line 22 of the row is
A voltage is applied from the drain line 23 through the TFT 20 to each pixel electrode 19 at a position where the column and the drain line 23 in the column intersect, and between each pixel electrode 19 to which the voltage is applied and the common electrode 17. TN of each pixel unit 26
A voltage is applied to the liquid crystal 21, which changes the orientation of the liquid crystal molecules in that portion, and the optical changes associated with this change are visualized by the polarizers 11 and 12, and a desired display, for example, black and white display is performed. Is configured. Since the TN-LCD of this embodiment is in the normally white mode, the desired display is displayed in black.

The reflection type TN-L according to this embodiment is also provided.
In the CD, as shown in FIG. 1, the drain lines 23 extending in the rubbing direction A ₁ of the alignment film 18 of the lower substrate 15 substantially parallel to the left and right sides of each pixel electrode 19.
Of the alignment film 16 of the upper substrate 14 and the rubbing direction A ₂ of the alignment film 16 of the upper substrate 14 is substantially perpendicular to the extending direction of each drain line 23 (such a rubbing direction will be referred to as rubbing in the following description). Call direction A). In this case, the rubbing direction A ₂ is rotated approximately 90 ° clockwise from the rubbing direction A ₁ .

Next, the reflection type TN-LCD of the above embodiment.
At the retardation Δnd (T
By changing the product of the refractive index anisotropy Δn of the N liquid crystal 21 and the cell gap d between the alignment films 16 and 18, the disclination 30 (in this embodiment, the rubbing direction is the rubbing direction A). , The abnormality display portion 30 due to disclination is generated on the lower left side of the pixel portion 26 as shown in FIG. 1). here,
The retardation Δnd was changed by fixing the cell gap d and the ordinary light refractive index n ₀ of the TN liquid crystal 21 and appropriately moving the extraordinary light refractive index ne. And the range of changing the retardation Δnd is 3 used in the normal TN liquid crystal.
The range is 00 nm ≦ Δnd ≦ 600 nm.

FIG. 3 shows the relationship between the front Y value and the retardation Δnd in the bright state. In this figure, □ (solid line)
Is the front Y value when 0V is applied to the pixel electrode 19,
(Dashed line) shows the front Y value when 1.5 V is applied to the pixel electrode 19, respectively. 4 shows the relationship between the front Y value and the retardation Δnd in the dark state when 6 V is applied to the pixel electrode 19. As is clear from FIG. 3, the front Y value in the bright state is Δ
The maximum brightness is obtained near nd = 500 nm. On the other hand, as is apparent from FIG. 4, the front Y value in the dark state gradually increases as Δnd increases. As in the case of the reflection type TN-LCD of the above-described embodiment, when it is desired to increase the brightness even if the contrast is sacrificed to some extent, the black stripe cannot be used to reduce the light leakage due to the disclination. Therefore, it is understood from FIGS. 3 and 4 that the retardation Δnd should be limited to approximately 550 nm or less.

FIG. 5 shows the brightness (Y value) of the peak of light leakage due to disclination in the gap of width L between each pixel electrode 19 and each drain line 23. In FIG. 10A, the data in the case of the one embodiment in which the rubbing direction of the both alignment films 16 and 18 is the rubbing direction A is reference numeral A, and the rubbing direction is the rubbing direction C in FIG. 10A. The data in the case of the prior art shown is denoted by reference symbol C, and the data in the case of the conventional technique shown in FIG. 10B in which the rubbing direction is the rubbing direction D is denoted by reference symbol D. As is apparent from FIG. 5, in the case of the above-described embodiment, as shown by the data A, the disclination 30 in the gap portion is obtained.
The peak brightness of light leakage (Y value) is 300 nm
In the entire range of ≦ Δnd ≦ 600 nm, it is much smaller than that of both of the above-described conventional techniques shown by data C and D, respectively. That is, FIG.
In the case of the above-mentioned conventional techniques shown in (a) and (b), since light leakage due to disclination in the gap portion is very large, when black stripes are not used as in a reflective TN-LCD. In the above, the gap portion where very bright light leakage occurs is exposed, and the contrast is significantly lowered, and the display quality is significantly lowered. On the other hand, the reflective TN-L according to the above-described embodiment is used.
According to the CD, the peak brightness (Y value) of light leakage due to disclination is 300 nm ≦ Δnd ≦ 600n
Since it is extremely small in the entire range of m, the contrast is prevented from being lowered and good display quality can be obtained even if the black stripe for light shielding is not used between the pixel electrodes.

The same as this is shown in FIGS. 6 (a) and 6 (b).
11A and 11B and FIGS. 12A and 12B, respectively. FIG. 6 (a),
(B) shows the alignment films 16 and 18 in the TN-LCD of the above-described embodiment in which the rubbing direction is the rubbing direction A.
The cell gap d between them is set to d = 5 [μm], the retardation Δnd is set to 380 nm, and +6 [V] is applied to one pixel electrode 19 shown in FIG. -6 [V] is applied to the drain line 23 (which corresponds to the pixel electrode on the right of the pixel electrode 19) at a position separated by a gap, and 0 [V] is applied to the common electrode 17. FIG. 6A is a cross-sectional view of a portion of the TN liquid crystal 21 centered on the gap when applied, and FIG. 6A shows an alignment vector of the TN liquid crystal 21 at each substrate position x (shown by a ratio with a cell gap). It is the figure which overlapped and showed the figure and the equipotential curve figure, and FIG.6 (b) is TN in each board | substrate position x (it shows by the ratio with a cell gap).
It is the figure which overlapped and showed the orientation vector figure of the liquid crystal 21, and Y value. FIGS. 11 (a) and 11 (b) are diagrams corresponding to FIGS. 6 (a) and 6 (b), respectively, and show data in the case of the conventional technique shown in FIG. 10 (a) where the rubbing direction is the rubbing direction C. Yes, FIGS. 12 (a) and 12 (b) are shown in FIGS. 6 (a) and 6 (b).
10A and 10B are data in the case of the conventional technique shown in FIG. 10B in which the rubbing direction is the rubbing direction D.

First, referring to FIG. 6A, the pixel electrode 19
Portion (pixel portion 26) and drain line 23 corresponding to
The director of the TN liquid crystal 21 stands up in most of the area corresponding to (1) to indicate a normal display area of black display, but the alignment is disturbed around the gap of width L. That is, disclination occurs at a position slightly inside the region of the drain line 23 from the gap. Further, from FIG. 6B, the retardation Δnd is set to 380
In the case of nm, the peak position (Y value) of light leakage due to disclination in the gap is 2.50 (%).
It turns out that it is a degree. On the other hand, as shown in FIG.
From (b), it can be seen that the peak (Y value) of light leakage due to disclination in the gap is 22.12 (%). Similarly, from FIG. 12B, the peak (Y value) of light leakage due to disclination in the gap is 33.
It turns out that it is 18 (%). FIG. 6B and FIG.
Comparing (b) and FIG. 12 (b), respectively,
It can be seen that when the retardation Δnd is 380 nm, the peak of the light leakage (Y value) due to the disclination in the gap is much smaller in the case of the above-mentioned one example than in the cases of the above-mentioned respective prior arts.

Next, FIG. 7 shows a modification of the above embodiment. In the TN-LCD according to this modification, the lower substrate 1
The rubbing direction B ₁ of the alignment film 18 of _No. 5 is substantially perpendicular to each drain line 23, and the rubbing direction B ₂ of the alignment film 16 of the upper substrate 14 is substantially parallel to each drain line 23 (such rubbing direction is , Referred to as rubbing direction B in the following description). In this case, rubbing direction B
₂ is rotated approximately 90 ° clockwise from the rubbing direction B ₁ . In addition, in FIG. 5, the data of this modified example is indicated by a symbol B. Further, the same data as in FIGS. 6 (a) and 6 (b) for this modification is shown in FIG. 8 (a),
Each is shown in (b). As is clear from FIG. 5, in the case of this modification as well, as shown by data B, the peak brightness (Y value) of light leakage due to disclination in the gap portion is 300 nm ≦. Δnd ≦
In the entire range of 600 nm, it is sufficiently smaller than either of the above-mentioned conventional techniques shown by data C and D, respectively. Further, from FIG. 8B, when the retardation Δnd is set to 380 nm, the disclination in the gap portion (in this modified example, the rubbing direction is set to the rubbing direction B, an abnormal display due to the disclination is displayed). As shown in FIG.
It can be seen that the peak position (Y value) of light leakage due to (generated on the lower left side of 6) is about 11.81 (%).
Therefore, also in the case of this modified example, it can be seen that the peak (Y value) of light leakage due to the disclination in the gap portion is sufficiently smaller than that in each of the above-mentioned related arts.

Although the above embodiment is a reflection type matrix liquid crystal display device, the present invention is not limited to this and can be applied to a transmission type matrix liquid crystal display device. Even in this case, since the brightness of the peak of light leakage due to disclination in the gap is very small as described above, it is not necessary to hide the gap with a black stripe to reduce the light leakage. A black stripe may be provided only in the peripheral portion of the portion 26 to reduce light leakage due to the disclination 3. Therefore, due to the black stripe, the shielded area is small and a bright display can be obtained.

In the above-mentioned embodiment, the pixel electrode 1
Even when the voltage applied to 9 is -6 [V] and the voltage applied to the drain line 23 corresponding to the pixel electrode on the right side is +6 [V], the same result as above is obtained due to the symmetry of the voltage. can get.

Further, in the above-described embodiment, as shown in FIG. 1, 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 and the pixel electrode 19, respectively. Further, in the above-described embodiment, as shown in FIG. 2, each pixel electrode 19 has one TF.
Although it is connected to the corresponding gate line 22 and drain line 23 via T20, each pixel electrode 19 is connected to the corresponding gate line 22 and drain line 23 via two TFTs respectively. You may comprise. Further, the pixel electrodes may be arranged in a mosaic pattern and the drain lines (signal lines) may be formed in a zigzag pattern. In that case, the rubbing direction of the alignment film may be perpendicular to the extending direction of the signal lines. It should be parallel.

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

[0022]

As described above, according to the matrix type liquid crystal display device of the present invention (the invention according to claim 1), the rubbing direction of the alignment film provided on one of the two substrates is set to the signal line. Since it is almost perpendicular to the extending direction and the rubbing direction of the alignment film provided on the other side of both substrates is substantially parallel to the extending direction of the signal line, there is a gap between each pixel electrode and each signal line. Light leakage due to disclination is reduced. Therefore, light leakage due to disclination in the gap between each pixel electrode and each signal line can be reduced, which improves the contrast and improves the display quality.

[Brief description of drawings]

FIG. 1 is a plan view showing a part of a reflective matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a main part of the liquid crystal display device shown in FIG.

FIG. 3 is a graph showing a front Y value in a bright state.

FIG. 4 is a graph showing a front Y value in a dark state.

FIG. 5 is a graph showing the brightness (Y value) of the peak of light leakage due to disclination in the gap.

6A is a diagram in which an alignment vector diagram of liquid crystal and an equipotential curve diagram are overlapped and shown in the case of the liquid crystal display device shown in FIG. FIG. 7B is a diagram in which the orientation vector diagram of the liquid crystal and the Y value are overlapped and shown in the case of the same device.

FIG. 7 is an explanatory diagram showing a modified example of the liquid crystal display device shown in FIG.

8A is a diagram of FIG. 6 in the case of the modification shown in FIG.
It is a figure similar to (a). FIG. 6B is a view similar to FIG. 6B in the case of the modified example.

FIG. 9 is an explanatory diagram for explaining the occurrence of disclination in the conventional liquid crystal display device.

10A is an explanatory diagram showing a conventional example when the rubbing direction is the rubbing direction C in the liquid crystal display device shown in FIG. (B) is an explanatory view showing a conventional example when the rubbing direction is the rubbing direction D in the same apparatus.

11A is a view similar to FIG. 6A, and FIG.
It is a figure in the case of the prior art example shown to (a). (B) is FIG.
It is a figure similar to (b), and is a figure in the case of the prior art example shown to Fig.10 (a).

12A is a view similar to FIG. 6A, and FIG.
It is a figure in the case of the prior art example shown to (b). (B) is FIG.
It is a figure similar to (b), and is a figure in the case of the prior art example shown in FIG.10 (b).

[Description of Reference Signs] 11, 12 Polarizer 13 Liquid Crystal Cell 14 Upper Substrate (One Substrate) 15 Lower Substrate (Other Substrate) 16, 18 Alignment Film 17 Common Electrode 19 Pixel Electrode 20 Thin Film Transistor (Switching Element) 21 Twisted Nettic Liquid crystal (liquid crystal) 22 Gate line (scanning line) 23 Drain line (signal line)

Claims (5)

[Claims] 1. A pair of polarizers, and a liquid crystal cell disposed between the both polarizers, the liquid crystal cell being provided on two substrates arranged to face each other, and provided on one of the two substrates. A common electrode covered with an alignment film, a number of pixel electrodes arranged in a matrix on the other of the two substrates and covered with the alignment film, and at least one switching element connected to each pixel electrode. , A twisted nematic liquid crystal enclosed between the two alignment films and continuously twisted by approximately 90 ° between the two alignment films, wherein each pixel electrode has a scanning line and a signal line arranged in a matrix, and In a matrix type liquid crystal display device connected through each switching element, the rubbing direction of the alignment film provided on one of the substrates is substantially perpendicular to the extending direction of the signal line, and A matrix type liquid crystal display device, wherein a rubbing direction of the alignment film provided on the other side of the substrate is substantially parallel to an extending direction of the signal line. 2. The matrix type liquid crystal display device according to claim 1, wherein, of the both polarizers, a reflective plate is provided outside the polarizer on the pixel electrode side. 3. The retardation Δnd of the liquid crystal cell, which is the product of the refractive index anisotropy Δn of the liquid crystal and the cell gap d between the alignment films, is 300 nm ≦ Δnd ≦ 550 nm. The matrix type liquid crystal display device according to claim 1. 4. Each of the elements is an amorphous silicon thin film transistor using amorphous silicon as an active layer or a polysilicon thin film transistor using polysilicon as an active layer.
The matrix liquid crystal display device according to any one of 1. 5. The matrix type liquid crystal display device according to claim 1, wherein neither of the substrates has a black stripe for shading between the picture electrodes.