JP2003121874A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device wherein there is little cross- talk among pixels, brightness is favorable in uniformity, and a high quality picture can be obtained. SOLUTION: The liquid crystal display device comprises a 1st substrate formed with data lines D1, D2,...; scanning lines G1, G2,... crossing the data lines; pixel electrodes located at cross positions of the data lines and the scanning lines, transistors for controlling the electricity to the pixel electrodes according to the inputs to the data lines and the scanning lines; common electrodes collocated with the pixel electrodes; common electrode wiring connecting the common electrodes at each line or column; and common wring arranged adjacently to a display area where the pixel electrodes connecting the common electrode wiring, the transistors and the pixels including the common electrodes are arranged, a 2nd substrate arranged in parallel with the 1st substrate, and a liquid crystal held between the 1st substrate and the 2nd substrate. The common wiring comprises contact holes, and a conductive layer to be connected through the contact holes has a ctenoid structure around the contact holes.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device, and more particularly to a wiring in a liquid crystal display device of an in-plane switching mode. FIG. 8 is a view for explaining the structure and operation of an example of a conventional liquid crystal display device using a TN liquid crystal. FIG. 8A is a sectional view of the liquid crystal display device. FIG.
(B) is a perspective view for explaining movement of liquid crystal molecules in the liquid crystal display device. As shown in the cross-sectional view of FIG. 8A, a vertical electric field is formed in a liquid crystal layer 100 in a TN liquid crystal. Here, the vertical direction is a direction perpendicular to the upper substrate 101 or the lower substrate 102. In order to generate a vertical electric field, two electrodes 103 and 104 are formed so as to sandwich the liquid crystal layer 100. That is, the common electrode 103 is formed on a surface of the upper substrate 101 where the substrate 101 and the liquid crystal layer 100 are in contact with each other.
2, a pixel electrode 104 is formed on a surface where the substrate 102 and the liquid crystal layer 100 are in contact with each other. A voltage is applied between these electrodes to generate a vertical electric field in the liquid crystal layer 100. The common electrode 103 is an electrode formed on the entire surface of the upper substrate 101 and common to all pixels of the liquid crystal display device. The pixel electrode 104 is provided individually for each pixel,
This enables different display for each pixel. Since the common electrode 103 and the pixel electrode 104 are formed so as to overlap with the display portion of the pixel, a transparent electrode is used so that the display portion can be seen by a user. As shown in the perspective view of FIG. 8B, the liquid crystal molecules 105 of the TN liquid crystal rise in a direction perpendicular to the substrate 101 or 102 due to the above-described vertical electric field, so that the appearance thereof depends on the direction of the line of sight. Differently, the viewing angle dependency is large. The effective viewing angle of the TN liquid crystal having a contrast of 10 or more is, for example, upper 30 degrees, lower 20 degrees, right and left ±
It is about 45 degrees. FIG. 9 is a schematic equivalent circuit diagram of a pixel of the above-described liquid crystal display device as viewed from above. One pixel 106
Are the liquid crystal layer 100 and the common electrode 1 sandwiching the liquid crystal layer 100.
03, a pixel electrode 104, and a thin film transistor 107 connected to the pixel electrode 104. The source terminal 107S of the thin film transistor 107 is connected to the pixel electrode 104, the drain terminal 107D is connected to the data line D1 arranged in the column direction, and the gate terminal 10S.
7G is connected to a scanning line G1 wired in the row direction. Here, the column direction means a vertical direction when the liquid crystal display device is viewed from above, and the row direction means a horizontal direction. Since the common electrode 103 is formed on the entire surface of the upper substrate 101 as described above, the common electrodes of all the pixels are in a connected state. FIG. 10 is a view of the entire liquid crystal display device as viewed from above. Display area 10 of this liquid crystal display device
8, the pixels 106 described above are arranged in a matrix. The scanning lines G1 wired in the row direction are connected to all the pixels in the same row, and the scanning lines G2, G3,... Are also connected to all the pixels in the same row. The data lines D1 arranged in the column direction are connected to all the pixels in the same column, and the data lines D2, D3,... Are also connected to the pixels in the same column. Are drawn from the left side of the display area 108 and connected to the gate driver 109, and the data lines D1, D2, D3,... Are drawn from the upper side of the display area 108 and connected to the data driver 110. Have been. The common electrode 103 is drawn out from an end on the side of the display area 108, that is, from the common terminal 103T. On the other hand, instead of the conventional TN liquid crystal,
A liquid crystal of a horizontal electric field type in which the viewing angle dependence of contrast is small has been used. FIG. 11 is a view for explaining the structure and operation of an example of a liquid crystal display device using the liquid crystal of the in-plane switching mode. FIG. 11 (a) is a cross-sectional view of the liquid crystal display device, and FIG. FIG. 4 is a perspective view for explaining movement of liquid crystal molecules in the liquid crystal display device. As shown in the cross-sectional view of FIG. 11A, in a horizontal electric field type liquid crystal, a horizontal electric field is formed in a liquid crystal layer 200. Here, the lateral direction refers to the lower substrate 20.
The direction parallel to 2. In order to generate a horizontal electric field, both the common electrode 203 and the pixel electrode 204
This substrate 202 and the liquid crystal layer 20 on the lower substrate 202
0 is formed on the surface in contact with 0, and a voltage is applied between these electrodes. That is, the common electrode 203 and the pixel electrode 20
4 are formed side by side on the display section of the pixel. As shown in the perspective view of FIG. 11B, the liquid crystal molecules 205 in the liquid crystal of the lateral electric field type rotate only in a plane parallel to the lower substrate 202 by the above-described lateral electric field. The difference in appearance depending on the direction is small, and the viewing angle dependence of the contrast is small. The effective viewing angle of the horizontal electric field type liquid crystal having a contrast of 10 or more is, for example, ± 70 degrees or more in the vertical and horizontal directions. However, if the above-described liquid crystal display device using the in-plane switching mode liquid crystal is constructed using the wiring shown in FIG. 10, the following problems occur. That is, in the TN liquid crystal, the common electrode and the pixel electrode are formed on different substrates, and the common electrode is formed on the entire surface of the upper substrate, so that the common electrode also serves as the common wiring. On the other hand, in the horizontal electric field type liquid crystal, the common electrode and the pixel electrode are formed on the same lower substrate, and the common electrode wiring connected to the common electrode is also formed on the same lower substrate. You. That is, since the common electrode, the pixel electrode, the common electrode wiring, the scanning line, and the data line are all formed on the same lower substrate, in order to secure the light transmittance of the pixel portion having a certain value or more, the conventional method is used. These electrodes and wiring must be made thinner than the TN liquid crystal. In the TN liquid crystal, since the transparent electrode is used for the common electrode and the pixel electrode, there is no relation between the size of the electrode and the aperture ratio of the display area. Metal electrodes are used for the electrodes and the pixel electrodes. Light does not pass through these electrode portions, and a light transmitting region is formed between these two electrodes formed side by side on the lower substrate. Therefore, in the horizontal electric field type liquid crystal, in order to increase the aperture ratio of the display region and increase the transmittance, the two electrodes must be made thinner. As described above, when the electrodes and wiring are made thinner,
Wiring resistance increases, a voltage drop occurs due to current flowing through the electrodes and wiring, and a current for driving one pixel fluctuates the potential of the electrode of another pixel, causing crosstalk between pixels, There arises a problem that the brightness uniformity is reduced and the image quality is reduced. Furthermore, since the liquid crystal screen has recently become larger, the wiring in the screen becomes longer, and the longer wiring further increases the wiring resistance. As a result, the above problem becomes more prominent. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is an object of the present invention to provide a liquid crystal display device capable of obtaining a high-quality image with less crosstalk between pixels and good luminance uniformity. . According to the present invention, a plurality of data lines, a plurality of scanning lines intersecting these data lines, and a position where the data lines intersect with the scanning lines are arranged. A pixel electrode, a transistor that controls energization to the pixel electrode according to an input from the data line and the scanning line, a common electrode arranged side by side with the pixel electrode, and these common electrodes are connected in a row or a column. A plurality of common electrode wirings, and the pixel electrodes connecting these common electrode wirings;
A first substrate on which a common wiring disposed adjacent to a display region in which a pixel including a transistor and a common electrode is disposed; a second substrate disposed in parallel with the first substrate; In a liquid crystal display device having a liquid crystal sandwiched between the first substrate and the second substrate, a common terminal is connected to one end of the common wiring, a data terminal is connected to one end of the data line, and the scanning is performed. A scanning terminal is connected to both ends of the line, a common wiring connecting from the common terminal to one end of each common electrode wiring includes a contact hole, and at least one of the conductive layers connected by the contact hole has a contact. A liquid crystal display device having a comb-shaped structure around a hole. The structure and operation of a liquid crystal display device using an in-plane switching mode liquid crystal according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a top view of a liquid crystal display device using a horizontal electric field type liquid crystal according to an embodiment of the present invention. Reference numeral 1 denotes a display area of the liquid crystal display device,
In the display area 1, pixels 2 for performing display are arranged in a matrix. The scanning line G1 wired in the row direction is connected to all the pixels in the same row, and the scanning line G1
, G3,... Are similarly connected to all the pixels in the same row. Data line D1 wired in the column direction
Is connected to all the pixels in the same column, and the data line D
, D3,... Are similarly connected to pixels in the same column. The scanning lines G1, G2, G3,...
Are drawn from the left and right sides of. That is, on the left side of the display area 1, the scanning terminals GL1, GL for drawing the scanning lines G1, G2, G3,.
Are provided on the right side of the display area 1 in the same manner as the scanning terminals GR1, GR2, GR3,... For drawing the scanning lines G1, G2, G3,.
Is provided. A scanning terminal G provided on the left side of the display area 1
L1, GL2, GL3,... Are the first gate drivers 3a.
And a scanning terminal G provided on the right side of the display area 1.
R1, GR2, GR3,... Are the second gate drivers 3b.
Is connected to The first gate driver 3a and the second gate driver 3b have the same internal configuration, and simultaneously input the same gate signal from the scanning terminal. The data lines D1, D2, D3,... Are drawn from the upper side of the display area 1. That is, the display area 1
Are connected to the data terminals DT1, DT2,... For drawing out the data lines D1, D2, D3,.
DT3,... Are provided. These data terminals DT
1, DT2, DT3,... Are connected to the data driver 4. The data driver 4 inputs a data signal from a data terminal. FIG. 2 is a schematic equivalent circuit diagram in which the pixel 2 of the liquid crystal display device described above is enlarged. One pixel 2 includes a liquid crystal layer 5, a common electrode 6 sandwiching the liquid crystal layer 5, a pixel electrode 7, and a thin film transistor 8 connected to the pixel electrode 7. Source terminal 8 of thin film transistor 8
S is connected to the pixel electrode 7, the drain terminal 8D is connected to the data line D1 arranged in the column direction, and the gate terminal 8G is connected to the scanning line G1 arranged in the row direction. Here, the column direction means a vertical direction when the liquid crystal display device is viewed from above, and the row direction means a horizontal direction. The common electrode 6 is connected to the common electrode wiring 10 for each row or column. Each common electrode wiring 10 is connected to the common wiring 11 at a portion adjacent to the display area. The common wiring 11 is connected to a common terminal described later. According to the above configuration, the gate signal is supplied to the scanning line G
Since it is input from both ends of 1, G2, G3, ... at the same time,
Compared with a configuration in which input is performed from one side, the length of wiring and the number of pixels in the display area 1 per input terminal are １ ／.
Is equivalent to Therefore, since the wiring resistance and capacitance of the scanning line can be reduced to half, the signal delay of the scanning line can be reduced, and the generation of a DC voltage and the variation in luminance in the pixel due to the signal delay can be suppressed. it can. Further, it is possible to increase the aperture ratio in the display area 1 by reducing the wiring width of the scanning line by an amount corresponding to the reduction in the wiring resistance. Further, a lower cost wiring process having a relatively high specific resistance can be used, and as a result, the cost of the liquid crystal display device can be reduced. FIG. 3 is a diagram showing a position of a liquid crystal injection port in the liquid crystal display device shown in FIG. Liquid crystal inlet 9
Are provided on the lower side of the display area 1 where no terminal row of scanning terminals or data terminals is provided. In the horizontal electric field type liquid crystal display device according to the present embodiment, the rubbing direction is approximately 20 ± with respect to the direction perpendicular to the electric field formed between the common electrode 6 and the pixel electrode 5.
10 degrees. Here, the rubbing direction indicates the initial alignment direction of the liquid crystal, and is determined by rubbing the substrate surface in a certain direction with a cloth or the like. The rubbing angle with respect to the pixel electrode 5 and the common electrode 6 is set large when importance is placed on the light transmittance, and small when importance is placed on the response speed. If the injection port 9 is provided at the above position, the liquid crystal is injected along the rubbing direction, so that the injection time is shorter than when the liquid crystal is injected from other positions. Further, since the injection port 9 is provided on a side where no terminal is provided and there is sufficient space, a plurality of injection ports can be provided,
This also shortens the injection time. FIG. 4 shows the display area 1 and the scanning terminals GL1, GL2, GL3,... Provided on the left side of the display area 1 and the scanning terminal GR1 provided on the right side in the liquid crystal display device shown in FIG. , GR2, GR3,... And data terminals DT1, DT2, DT3,. These terminals are divided into a plurality of blocks. For example, among the scanning terminals provided on the left side of the display area 1, the scanning terminals GL1, GL2, GL3 form the first block BL1, and the scanning terminals GL4, GL
5, GL6 forms the second block BL2. At both ends of a row of terminals forming these blocks, common terminals COM1, COM2, COM3,... Are provided. That is, the common terminal COM is provided above the scanning terminal GL1.
1 and a common terminal COM immediately below the scanning terminal GL3.
2 and a common terminal COM above the scanning terminal GL4.
3 and a common terminal COM immediately below the scanning terminal GL6.
4 are provided. The common terminals COM2 and COM3 are connected to a common electrode line in the display area 1 through a common line. Details of the common wiring will be described later. The configuration after the scanning terminal GL7 is similar to that described above. The same applies to the scanning terminals GR1, GR2, GR3,... Provided on the right side of the display area 1 and the data terminals DT1, DT2, DT3,. According to the above configuration, since the common terminal is provided for each block of the scanning terminal and the data terminal, the resistance of the common wiring can be reduced as compared with the case where the common terminal is at the end of the side. In addition, crosstalk between pixels and variations in luminance can be suppressed. FIG. 5 is a diagram showing a detailed configuration of the common terminals COM2 and COM3 provided at the boundary between the blocks BL1 and BL2 of the scanning terminals on the left side of the display area 1 shown in FIG. The wiring from the common terminal to the common electrode wiring in the display area is defined as a common wiring. Since the distance of the common wiring differs depending on the position of the common electrode wiring, the length of the wiring differs and the wiring resistance also differs. In order to make the wiring resistance to all common electrode wiring ends uniform,
Wiring resistance is adjusted by passing through three conductive layers stacked in the thickness direction of the liquid crystal display device. That is, when the distance is short and the wiring is short, the wiring is not directly connected but is passed through a plurality of conductive layers to increase the wiring resistance. The conductive layer is formed on the first substrate closest to the lower substrate.
A second layer is overlaid on the layer, and a third layer is overlaid thereon. An insulating film is provided between these conductive layers. The first layer is mainly provided with scanning lines, and the second layer is mainly provided with data lines. The third layer covers the contact hole on the first layer and the contact hole on the second layer at the same time in the region shown in FIG. 5, and is provided so as to connect them. The method of manufacturing this contact hole is the third method.
Formed from the layer to the underlying substrate, stopping at the first conductive layer encountered. That is, if there is a second layer immediately below the contact hole formed from the third layer, the formation of the contact hole stops at the second layer, and the third layer and the second layer are connected. If the conductive layer is not provided at the position of the second layer but is provided in the first layer, the contact hole reaches the first layer, and the third layer and the first layer are connected. In FIG. 5, common terminals COM2 and C
The common wiring from OM3 is connected at the side of display area 1 (point P1 in the figure). DIS1 to DIS5 in the figure
Is a pixel. Here, the path of the common wiring from the point P1 to the pixel DIS3 closest to the point P1 will be described. First, the contact holes c1 to c4 are reached from the point P1 via the conductive layer S0 provided in the first layer. The contact holes c1 to c4 reach the third layer, the third layer reaches the other conductive layer S3 in the first layer via the contact holes c5 to c8, and reaches the pixel DIS3 via the conductive layer S3. . Further, as another route, the conductive layer S0 reaches the third layer via the contact holes c1 to c4, and the third layer reaches the second layer via the contact holes e1 to e8. From contact hole e
There is also a route that reaches the third layer again via 9 to e16, reaches the conductive layer S3 from the third layer via the contact holes c5 to c8, and reaches the pixel DIS3 via the conductive layer S3. Next, the path from the point P1 to the pixel DIS2 farther from the pixel DIS3 will be described. First, a route via only the first and third layers will be described. From the point P1 to the contact holes c1 to c4 via the conductive layer S0,
The contact holes c1 to c4 reach the third layer, the third layer reaches the conductive layer S2 in the first layer via the contact holes c9 to c18, and reaches the pixel DIS2 via the conductive layer S2. . That is, while the number of contact holes at the time of returning from the third layer to the first layer in the path to the pixel DIS3 is four, c5 to c8, the number of contact holes from the third layer in the path to the pixel DIS2 is The number of contact holes when returning to the first layer is 10 from c9 to c18, so that the resistance due to the contact holes is reduced. Similarly, in the case of the farther pixel DIS1, the third
The number of contact holes returning from the layer to the first layer is c19 to
The number is further increased to 12 of c30. That is, the number of contact holes provided in parallel on the way is changed according to the distance from the terminal to the pixel, thereby making the resistance of the entire wiring uniform. It should be noted that there is a route from the first layer to the second layer via the third layer, and from the second layer to the first layer again via the third layer. The number of contact holes has been changed. Further, when the common wiring length is long, the wiring resistance can be reduced by making the wiring thick. FIG. 6 is a modified example of the common wiring shown in FIG. In this example, the second conductive layer is wider than in the example shown in FIG. For example, contact hole e
Since the conductive layer below 23 and e24 is wide and this portion can contribute to conduction, the resistance of the path to the pixel DIS2 can be further reduced. FIG. 7 is an enlarged view of the periphery of a contact hole provided in the middle of the common wiring shown in FIG. 5 or FIG. In the configuration shown in FIG. 5 or FIG. 6, a contact hole is provided in the common wiring between the common terminal and the common electrode wiring, and the wiring resistance is adjusted to make the wiring resistance to each common electrode wiring end uniform. Is what you do. At this time, as one of means for adjusting the wiring resistance in the direction of decreasing the resistance, there is a method of making the shape of the conductive layer around the contact hole into a comb shape. With such a shape, the distance between the contact holes becomes shorter. Therefore, for example, even if a conductive layer having a relatively high specific resistance is used as the third layer S14 in FIG. 7, the wiring distance in the third layer S14 is reduced. It is possible to make adjustments in the direction in which the wiring resistance becomes shorter and the wiring resistance decreases. According to the present invention, a high-quality image with little crosstalk between pixels and good luminance uniformity can be obtained.
Further, if the injection port is provided at a position where the liquid crystal can be injected along the rubbing direction, the liquid crystal is injected along the rubbing direction, so that the injection time of the liquid crystal is shortened. Further, if the wiring resistance of the common wiring from the common terminal to each common electrode wiring is made uniform, crosstalk and luminance uniformity are improved. Also, if the common terminal is provided for each block, the series resistance between the common electrode wiring and the common wiring is reduced, so that crosstalk is reduced. Also, by changing the thickness of the common wiring according to the length of the wiring and making the wiring resistance of the common wiring to each pixel uniform, the luminance uniformity is improved. In addition, by changing the number of contact holes in the middle of the wiring according to the length of the wiring and making the wiring resistance of the common wiring to each pixel uniform, crosstalk and brightness uniformity are improved. In the embodiment, the number of contact holes is used for adjusting the uniformity of the common wiring resistance.
Similarly, the resistance of the common wiring can be made uniform by changing the area or the perimeter of the contact hole. Also, if the shape around the contact hole is made to be a comb shape, it becomes possible to adjust in the direction in which the wiring resistance becomes low,
Since an appropriate wiring resistance can be set, the wiring resistance to each pixel can be made uniform, and crosstalk and luminance uniformity are improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a liquid crystal display device using an in-plane switching mode liquid crystal according to an embodiment of the present invention. FIG. 2 is a schematic equivalent circuit diagram in which a pixel of the liquid crystal display device is enlarged. FIG. 3 is a diagram showing a position of a liquid crystal injection port in a liquid crystal display device. FIG. 4 is a diagram showing a detailed configuration of a boundary portion between a display region and a terminal in the liquid crystal display device. FIG. 5 is a diagram showing a detailed configuration of a common wiring from a common terminal to a pixel. FIG. 6 is a diagram showing a modification of a common wiring from a common terminal to a pixel. FIG. 7 is an enlarged view of the periphery of a contact hole provided in the middle of a common wiring. FIG. 8 is a diagram showing a liquid crystal display device using a conventional TN liquid crystal. FIG. 9 is a schematic equivalent circuit diagram of a pixel of a conventional liquid crystal display device. FIG. 10 is a diagram of the entire conventional liquid crystal display device as viewed from above. 11 is a diagram showing a liquid crystal display device using a liquid crystal of an in-plane switching method. [Description of References] 1 display area 2 pixel 3a first gate driver 3b second gate driver 4 data driver 5 liquid crystal layer 6 common electrode 7 Pixel electrode 8 Thin film transistor 8S Source terminal 8D Drain terminal 8G Gate terminal 9 Injection 10 Common electrode wiring 11 Common wiring 100 Liquid crystal layer 101 Upper substrate 102 Lower substrate 103 Common electrode 104 Pixel electrode 105 Liquid crystal molecules 106 Pixel 107 Thin film transistor 108 Display area 200 Liquid crystal layer 201 Upper substrate 202 Lower substrate 203 Common electrode 204 Pixel electrode 205 Liquid crystal molecule 206 Pixel

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Seiichi Matsumoto             NEC Corporation 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation             In the formula company (72) Inventor Tamura Fumichi             NEC Corporation 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation             In the formula company F term (reference) 2H092 GA14 GA24 GA29 JA46 NA01

Claims (1)

Claims: 1. A plurality of data lines, a plurality of scanning lines intersecting with the data lines, a pixel electrode disposed at a position where the data lines intersect with the scanning lines, A transistor for controlling energization of the pixel electrode in accordance with an input from a data line and a scanning line; a common electrode arranged side by side with the pixel electrode; and a plurality of common electrode wirings connecting these common electrodes in one row or one column A first substrate formed with a common line connected to a display region in which pixels including the pixel electrode, the transistor, and the common electrode are arranged, the common line connecting these common electrode lines; In a liquid crystal display device having a second substrate arranged in parallel with one substrate, and a liquid crystal sandwiched between the first substrate and the second substrate, a common terminal is connected to one end of the common wiring. A data terminal is connected to one end of the data line, a scanning terminal is connected to both ends of the scanning line, and a common wiring connecting from the common terminal to one end of each common electrode wiring includes a contact hole. A liquid crystal display device, wherein at least one of the conductive layers connected by the contact hole has a comb-shaped structure around the contact hole.