JP2009181091A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an FFS mode liquid crystal display device having properties of an IPS mode allowing a bright display with a large aperture ratio, wherein a seizure phenomenon and flicker are prevented from occurring. <P>SOLUTION: The liquid crystal display device 10A includes first electrodes 21a and second electrodes 21b formed parallel on both sides of clearance regions 20b, and first lower electrodes 18a (third electrodes) and second lower electrodes 18b (fourth electrodes) formed parallel on both sides of clearance regions 21b through an insulating layer 19 from the first electrodes 21a and second electrodes 21b toward a substrate 11, in each pixel on one of a pair of substrates. The first electrodes 21a are formed to overlap with the second lower electrodes 18b, and the second electrodes 21b are formed to overlap with the first lower electrodes 18a respectively in a plan view. The first electrodes 21a are electrically connected to the first lower electrodes 18a, and the second electrodes 21b are electrically connected to the second lower electrodes 18b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a horizontal electric field type liquid crystal display device. More specifically, the present invention is a fringe field switching (Fringe Field Switching) that has the characteristics of an IPS (In-Plane Switching) mode in which the burn-in phenomenon is suppressed and the aperture ratio is large and bright display is possible.
Hereinafter, it is referred to as “FFS”. ) Mode liquid crystal display device.

Liquid crystal display devices include TN (Twisted Nematic) mode and VA (Vertical Alignment).
) Mode, MVA (Multi-domain Vertical Alignment) mode, etc., are often used, but a horizontal electric field type liquid crystal display device having electrodes only on one substrate is also known. The operation principle of the IPS mode liquid crystal display device among the horizontal electric field type liquid crystal display devices will be described with reference to FIGS. 8 and 9 (see Patent Documents 1 and 2 below).

FIG. 8 is a perspective view showing a color filter substrate of a conventional IPS mode liquid crystal display device.
It is a model top view for a pixel. FIG. 9 is a sectional view taken along line IX-IX in FIG.

The IPS mode liquid crystal display device 50 includes an array substrate AR and a color filter substrate CF. In the array substrate AR, a plurality of scanning lines 52 and common wirings 53 are provided in parallel on the surface of the first transparent substrate 51, and a plurality of signal lines 54 are provided in a direction intersecting the scanning lines 52 and common wirings 53. It has been. A common wiring 53 is provided at the center of each pixel.
For example, a comb-like counter electrode (also referred to as “common electrode”) 55 is provided in a strip shape, and a comb-like pixel electrode 56 is also provided so as to sandwich the periphery of the counter electrode 55. The surfaces of the counter electrode 55 and the pixel electrode 56 are, for example, a protective insulating film 57 made of silicon nitride.
And an alignment film 58 made of polyimide or the like.

In addition, near the intersection of the scanning line 52 and the signal line 54, a TFT as a switching element (
Thin Film Transistor (thin film transistor) is formed. This TFT has a scanning line 5
2 and the signal line 54, the semiconductor layer 59 is disposed, and the signal line portion on the semiconductor layer 59 is a TFT.
Source electrode S, the scanning line 12 portion below the semiconductor layer 59 constitutes the gate electrode G, and the conductive layer overlapping with part of the semiconductor layer 59 constitutes the drain electrode D. The electrode D is connected to the pixel electrode 56.

Further, the color filter substrate CF has a color filter layer 61 on the surface of the second transparent substrate 60.
The overcoat layer 62 and the alignment film 63 are provided. Then, the array substrate AR and the color filter substrate CF are opposed so that the pixel electrode 56 and the counter electrode 55 of the array substrate AR and the color filter layer 61 side of the color filter substrate CF are opposed to each other. Next, the liquid crystal LC is sealed between the array substrate AR and the color filter substrate CF, and the polarizing plates 64 and 65 are arranged on the outer sides of the two substrates so that the polarization directions intersect with each other. The liquid crystal display device 50 is formed.

As shown in FIG. 9, in the IPS mode liquid crystal display device 50, when an electric field is formed between the pixel electrode 56 and the counter electrode 55, the liquid crystal that has been aligned in the horizontal direction rotates in the horizontal direction. The amount of incident light transmitted from the backlight can be controlled. This IPS mode liquid crystal display device 50 has the advantages of a wide viewing angle and high contrast. However, since the counter electrode 55 is formed of the same metal material as the common wiring 53 or the scanning line 52, the aperture ratio and the transmission rate are improved. There is a problem that the rate is low. Although not shown, since the pixel electrode 56 and the counter electrode 55 do not overlap in plan view, it is necessary to separately form a storage capacitor in each pixel as in the case of a conventional vertical electric field type liquid crystal display device. There is also a problem that the aperture is lowered by the storage capacitor forming portion.

In order to solve such problems of the IPS mode, an FFS mode liquid crystal display device has been developed (see Patent Documents 3 and 4 below). The operating principle of the FFS mode liquid crystal display device will be described with reference to FIGS.

FIG. 10 is a schematic plan view of one pixel showing a color filter substrate of a conventional FFS mode liquid crystal display device as seen through. 11 is a cross-sectional view taken along line XI-XI in FIG.

The FFS mode liquid crystal display device 70 includes an array substrate AR and a color filter substrate CF. In the array substrate AR, a plurality of scanning lines 72 and common wirings 73 are provided in parallel on the surface of the first transparent substrate 71, and a plurality of signal lines 74 are provided in a direction intersecting the scanning lines 72 and the common wirings 73. It has been. Then, an ITO (Indium Tin Oxi) connected to the common wiring 73 so as to cover each of the regions partitioned by the scanning line 72 and the signal line 74.
A counter electrode 75 made of a transparent material such as de) or IZO (indium zinc oxide) is provided. A pixel electrode 78 made of a transparent material such as ITO, in which a plurality of slits 77 are formed in a stripe shape via an insulating film 76, is provided on the surface of the counter electrode 75. The surfaces of the pixel electrode 78 and the plurality of slits 77 are covered with an alignment film 80.

In the vicinity of the crossing position of the scanning line 72 and the signal line 74, there is a T as a switching element.
FT is formed. In this TFT, a semiconductor layer 79 is disposed on the surface of the scanning line 72, and a part of the signal line 74 is extended so as to cover a part of the surface of the semiconductor layer 79 to constitute a source electrode S. The lower scanning line portion constitutes the gate electrode G, and the conductive layer overlapping with a part of the semiconductor layer 79 constitutes the drain electrode D. The drain electrode D is connected to the pixel electrode 78.

Further, the color filter substrate CF has a color filter layer 83 on the surface of the second transparent substrate 82.
The overcoat layer 84 and the alignment film 85 are provided. Then, the array substrate AR and the color filter substrate CF are opposed so that the pixel electrode 78 and the counter electrode 75 of the array substrate AR and the color filter layer 83 of the color filter substrate CF are opposed to each other. Next, the liquid crystal LC is sealed between the array substrate AR and the color filter substrate,
The FFS mode liquid crystal display device 70 is formed by disposing the polarizing plates 86 and 87 on the outer sides of the two substrates so that the polarization directions are perpendicular to each other.

In the FFS mode liquid crystal display device 70, when an electric field is formed between the pixel electrode 78 and the counter electrode 75, the electric field is directed to the counter electrode 75 on both sides of the pixel electrode 78 as shown in FIG. 11. Therefore, not only the liquid crystal present in the slit 77 but also the liquid crystal present on the pixel electrode 78 can move. Therefore, the FFS mode liquid crystal display device 70 has a feature that it has a wider viewing angle and a higher contrast than the IPS mode liquid crystal display device 50, and further has a high transmittance, thereby enabling bright display. In addition, the FFS mode liquid crystal display device 70 includes:
Since the overlapping area between the pixel electrode 78 and the counter electrode 75 is larger in a plan view than the liquid crystal display device 50 in the IPS mode, there is an advantage in that a larger storage capacity is generated as a secondary, and it is not necessary to separately provide an auxiliary capacity line. To do.
Japanese Patent Laid-Open No. 10-319371 JP 2002-131767 A JP 2002-14363 A JP 2002-244158 A

By the way, it is known that a liquid crystal display device causes a burn-in phenomenon when used for a long time. This phenomenon of image sticking occurs in both the case of the IPS mode liquid crystal display device and the case of the FFS mode liquid crystal display device. However, the FFS as described above
In the liquid crystal display device in the mode, it has been found that the image sticking phenomenon appears greatly as compared with the liquid crystal display device in the conventional IPS mode.

One of the causes of the image sticking phenomenon is that a step is generated in the FFS mode liquid crystal display device because the upper electrode having a slit is provided on the surface of the insulating film.
That is, since the pixel electrode and the counter electrode are formed on the same plane in the IPS mode liquid crystal display device, the path of the electric force lines from the pixel electrode to the liquid crystal and the path of the electric force lines from the liquid crystal to the counter electrode are symmetric. It becomes. On the other hand, in the FFS mode liquid crystal display device, the path of electric lines of force from the upper electrode to the liquid crystal and the path of electric lines of force from the liquid crystal to the lower electrode are asymmetric.
Since a DC component is generated due to the presence of this asymmetry, the FFS mode liquid crystal display device is
The image sticking phenomenon becomes larger than that of the PS mode liquid crystal display device.

As described above, the IPS mode liquid crystal display device has a feature that the image sticking phenomenon is less than that of the FFS mode liquid crystal display device. However, since the pixel electrode and the counter electrode do not overlap in a plan view, a separate storage capacitor is provided. Therefore, there is a problem that the aperture ratio decreases and the luminance does not increase. In addition, in the liquid crystal display device in the IPS mode, the liquid crystal on the pixel electrode and the counter electrode hardly moves, and this also causes a reduction in luminance.

On the other hand, in the FFS mode liquid crystal display device, since the capacitor is formed where the pixel electrode and the counter electrode overlap in plan view, it is not necessary to separately form a storage capacitor and the aperture can be increased. Brightness can be increased. In addition, since the liquid crystal display device in the FFS mode also drives the liquid crystal in the surface portion and the slit portion of the pixel electrode, the luminance is further improved. However,
In the FFS mode liquid crystal display device, the configuration of the pixel electrode and the counter electrode is asymmetric.
Compared with an S-mode liquid crystal display device, there is a problem that a burn-in phenomenon is likely to occur, and since the storage capacity is not always sufficient, flicker is also likely to occur.

The present invention has been made to solve the problems of the conventional FFS mode liquid crystal display device. That is, an object of the present invention is to provide an FFS mode liquid crystal display device that has the characteristics of an IPS mode in which a burn-in phenomenon and flicker hardly occur and a large aperture ratio and a bright display are possible.

In order to achieve the above object, a liquid crystal display device of the present invention is a liquid crystal display device having a pair of substrates opposed to each other with a liquid crystal layer interposed therebetween, and one of the pair of substrates is driven independently. A plurality of pixels are formed, and in each of the pixels, a first electrode and a second electrode which are formed in parallel with a separation region in between, and an insulating layer is provided on the substrate side from the first electrode and the second electrode. And a third electrode and a fourth electrode formed in parallel with each other across the separation region, wherein the first electrode is one of the third electrode and the fourth electrode, and the second electrode is the first electrode. The first electrode is formed to overlap the other of the third electrode and the fourth electrode in plan view, the first electrode is the other of the third electrode and the fourth electrode, and the second electrode is the third electrode and the fourth electrode. It is characterized by being electrically connected to one of the four electrodes. That.

In the liquid crystal display device of the present invention, the first electrode and the second electrode are formed side by side across the separation region, and correspond to the pixel electrode and the counter electrode of the IPS mode liquid crystal display device. In the present invention, the term “parallel” does not necessarily need to be completely parallel as long as they do not intersect with each other, and is used to include a “<” shape or a zigzag shape.

In the liquid crystal display device of the present invention, the first electrode overlaps one of the third electrode and the fourth electrode, and the second electrode overlaps the other of the third electrode and the second electrode in plan view. In addition, the third electrode is electrically connected to the other of the first electrode and the second electrode, and the fourth electrode is electrically connected to one of the first electrode and the second electrode. . Therefore, in the liquid crystal display device of the present invention, the two pairs of electrodes superimposed in plan view through the insulating film have the same arrangement relationship as in the case of the FFS mode liquid crystal display device, and are adjacent in the same plane. The matching electrode pair has the same arrangement relationship as that of the IPS mode liquid crystal display device.

Then, according to the liquid crystal display device of the present invention, a capacitance is formed by each of the two pairs of electrode pairs that overlap with each other through the insulating film in a plan view, and these capacitances are connected in parallel. Therefore, in the liquid crystal display device of the present invention, as a result, a larger storage capacitor is formed than in the conventional FFS mode liquid crystal display device, so that a liquid crystal display device with less flicker can be obtained.
In addition, according to the liquid crystal display device of the present invention, the liquid crystal can be driven in the FFS mode in all the electrodes, so that bright display is possible, and the symmetry of the electrodes is intermediate between the IPS mode and the FFS mode. The occurrence of a direct current component is reduced, and the image sticking phenomenon is also improved. As described above, according to the liquid crystal display device of the present invention, it becomes an FFS mode liquid crystal display device having the characteristics of the IPS mode in which a burn-in phenomenon and flicker hardly occur and the aperture ratio is large and bright display is possible.

In the liquid crystal display device according to this aspect, it is preferable that at least one of the third electrode and the fourth electrode is formed of a transparent conductive material.

According to the liquid crystal display device of this aspect, since at least one of the third electrode and the fourth electrode is made of a transparent conductive material, the light from the backlight is not particularly shielded. A device is obtained. In the present invention, it is preferable that both the third electrode and the fourth electrode are formed of a transparent conductive material. Further, the first electrode and the second electrode can be formed of a metal material, but are bright. In order to obtain a display, it is preferable to form the transparent conductive material. As the transparent conductive material, a known material such as ITO or IZO can be used.

In the liquid crystal display device according to this aspect, the first electrode, the second electrode, and the third electrode
The electrode and the fourth electrode are preferably formed in a comb shape.

According to the liquid crystal display device of this aspect, since the region where the liquid crystal is driven within one pixel and the region where it is difficult to drive are subdivided, the liquid crystal is apparently driven uniformly within one pixel. ,
Display image quality is improved.

In the liquid crystal display device according to this aspect, the first electrode, the second electrode, and the third electrode
The electrode and the fourth electrode are preferably formed in a comb-teeth shape extending along a scanning line or a signal line formed on the one substrate.

According to the liquid crystal display device of this aspect, the FFS can be effectively performed in the vicinity of the switching element.
Since the structure and the IPS structure can be formed, the aperture ratio can be increased without waste.

In the liquid crystal display device according to this aspect, the third electrode and the fourth electrode may be wider than the first electrode and the second electrode, respectively.

According to the liquid crystal display device of this aspect, since the characteristics of the FFS mode liquid crystal display device appear strongly, a high applied voltage is required, but since a good fringe field effect occurs in all the electrodes, a brighter display A liquid crystal display device can be obtained. In addition, when manufacturing the liquid crystal display device of such an aspect, the tolerance for mask displacement is increased, which makes it easier to manufacture.

In the liquid crystal display device according to this aspect, the third electrode and the fourth electrode may have the same width as the first electrode and the second electrode, respectively.

According to the liquid crystal display device of this aspect, the tolerance for mask displacement at the time of manufacture is reduced, but the applied voltage may be low, and a fringe field is generated in all the electrodes. Is obtained.

In the liquid crystal display device according to this aspect, the third electrode and the fourth electrode may be narrower than the first electrode and the second electrode, respectively.

According to the liquid crystal display device of this aspect, since the characteristics of the IPS mode liquid crystal display device appear strongly, the brightness becomes dark, but the applied voltage can be small. In addition, when manufacturing the liquid crystal display device of such an aspect, the tolerance for mask displacement is increased, which makes it easier to manufacture.

In the liquid crystal display device according to this aspect, it is preferable that the third electrode and the fourth electrode are formed on the surface of the planarization film formed for each pixel.

If a flattening film is formed for each pixel, each electrode formed on the surface of the flattening film is flattened by unevenness due to the presence of, for example, a switching element, etc., so that the cell gap is made uniform. . Therefore, according to the liquid crystal display device of this aspect, a liquid crystal display device with good display image quality can be obtained.

Hereinafter, the best embodiment of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies a liquid crystal display device for embodying the technical idea of the present invention, and is not intended to identify the present invention as this liquid crystal display device, but claims The present invention can be equally applied to other embodiments included in the scope. In addition, in each drawing used for the description in this specification, each layer and each member are displayed at different scales so that each layer and each member can be recognized on the drawing. However, it is not necessarily displayed in proportion to the actual dimensions.

FIG. 1 is a schematic plan view for one pixel, which is seen through the color filter substrate of the liquid crystal display device according to the first embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is II of FIG.
It is sectional drawing along the I-III line. FIG. 4 is a schematic plan view for one pixel, seeing through the color filter substrate of the liquid crystal display device according to the second embodiment. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a schematic plan view of one pixel that is seen through the color filter substrate of the liquid crystal display device according to the third embodiment. 7 is a cross-sectional view taken along line VII-VII in FIG.

[First Embodiment]
The liquid crystal display device 10A according to the first embodiment includes an array substrate (first substrate) AR and a color filter substrate (second substrate) CF. The array substrate AR is a first substrate such as a glass substrate.
A plurality of scanning lines 12 and signal lines 13 are arranged in a matrix on the surface of the display area of the transparent substrate 11.
Are crossed in a state where they are insulated from each other by the gate insulating film 14, and a common wiring (not shown) is formed at the peripheral portion of the display region. Each region surrounded by the scanning lines 12 and the signal lines 13 forms each pixel (also referred to as “sub-pixel”). Further, for example, a TFT is formed as a switching element for each pixel on the first transparent substrate 11, and the entire surface of the first transparent substrate 11 including the TFT is made of, for example, a silicon nitride layer or a silicon oxide layer. Covered with a passivation film 15.

A planarizing film 16 made of an organic material is formed on the surface of the passivation film 15, and a first contact hole 17 is formed in the planarizing film 16 and the passivation film 15 at a position corresponding to the drain electrode D of the TFT. Is formed. On the surface of the planarizing film 16, a pair of comb-shaped first lower electrode 18a and second lower electrode 18b extending along the signal line 13 with the separation region 20a interposed between the respective pixels are provided. Is formed. The first lower electrode 18a corresponds to the third electrode of the present invention, and the second lower electrode 18b corresponds to the fourth electrode of the present invention. One of the pair of the first lower electrode 18a and the second lower electrode 18b may be made of a metal material such as aluminum, but at least one of the first lower electrode 18a and the second lower electrode 18b is made of ITO or the like in order to increase the aperture ratio. It is preferably made of a transparent conductive material such as IZO.

The first lower electrode 18a is electrically connected to the drain electrode D of the TFT through the first contact hole 17, and the second lower electrode 18b is connected to the display region through the second lower electrode of the adjacent pixel. It is electrically connected to the common wiring formed at the peripheral edge. Therefore, in the liquid crystal display device 10A of the first embodiment, the first lower electrode 18a functions as a pixel electrode, and the second
The lower electrode 18b functions as a counter electrode.

Further, an insulating film 19 made of a silicon nitride layer or a silicon oxide layer is formed over the entire surface of the first transparent substrate 11 on which the first lower electrode 18a and the second lower electrode 18b are formed. On the surface of the insulating film 19, the signal lines 1 are connected to each other with a separation region 20 b interposed therebetween.
3 are formed so as to overlap the second lower electrode 18b and the first lower electrode 18a in a plan view, respectively. . The first electrode 21a and the second electrode 21b are preferably formed of a transparent conductive material such as ITO or IZO in order to increase the aperture ratio and enable bright display.
It can also be formed of a metal material such as aluminum.

Further, here, the first lower electrode 18a and the second lower electrode 18b are formed so that the width thereof is wider than the widths of the first electrode 21a and the second electrode 21b. With this configuration,
The first electrode 21a and the second electrode 21b are formed on the surface of the insulating film 19 by photolithography.
Since the tolerance of the positional deviation of the mask when forming is increased, the manufacturing is facilitated. In addition,
In particular, the widths of the first lower electrode 18a and the second lower electrode 18b are changed to each other and the first electrode 2 is changed.
There is no advantage in changing the widths of 1a and the second electrode 21b. For this reason, the first lower electrode 18a and the second lower electrode 18b have substantially the same width as each other, and the first electrode 21
The widths of a and the second electrode 21b may be formed so as to be substantially the same.

The first electrode 21 a passes through the first contact hole 17 and passes through the drain electrode D of the TFT.
Are electrically connected to the first lower electrode 18a.
The second electrode 21b is electrically connected to the second lower electrode 18b through the second contact hole 23. Therefore, in the liquid crystal display device 10A of the first embodiment, the first electrode 21a functions as a pixel electrode, and the second electrode 21b functions as a counter electrode. The electrode overlapping with the first electrode 21a functioning as the pixel electrode in plan view is the second lower electrode 18b functioning as the counter electrode, and the electrode overlapping with the second electrode 21b functioning as the counter electrode in plan view is The first lower electrode 18a that functions as a pixel electrode is required.

For this reason, the pair of the first electrode 21a and the second lower electrode 18b and the pair of the second electrode 21b and the first lower electrode 18a, which are overlapped in plan view, are mutually in the FFS mode liquid crystal display device. The arrangement relationship is the same as in the case. In addition, a pair composed of the first electrode 21a and the second electrode 21b adjacent to each other on the same plane and a pair composed of the first lower electrode 18a and the second lower electrode 18b are the same as in the case of an IPS mode liquid crystal display device. The same arrangement relationship is obtained. The first electrode 21a
Which of the first electrode 21b and the second electrode 21b is to be a pixel electrode, and the first lower electrode 1
It is arbitrary which of 8a and the second lower electrode 18b is to be the pixel electrode. However, the electrode pairs that overlap with each other through the insulating film 19 in a plan view need to be a pair of a pixel electrode and a counter electrode, and an electrode pair that is adjacent in the same plane also has a pair of a pixel electrode and a counter electrode. It is necessary to be. Furthermore, including the surfaces of the first electrode 21a and the second electrode 21b,
A first alignment film 24 is formed over the entire display area.

Further, as shown in FIG. 1, the color filter substrate CF is formed on the surface of the second transparent substrate 25 such as a glass substrate on the scanning line 12, the signal line 13, and the first contact hole 1 of the array substrate AR.
7. The light-shielding film 26 covers the second contact hole 23 and the position corresponding to the TFT.
Is formed. Further, a color filter layer 27 of a predetermined color is formed on the surface of the second transparent substrate 25 surrounded by the light shielding film 26. Further, the light shielding film 26 and the color filter layer 2
An overcoat layer 28 is formed so as to cover the surface of 7. A second alignment film 29 is formed on the surface of the overcoat layer 28.

The first electrode 21a and the second electrode 21b of the array substrate AR and the color filter substrate C
The array substrate AR and the color filter substrate CF are opposed to each other so that the F color filter layer 27 faces each other, and the liquid crystal 30 is sealed therebetween. Further, the first polarizing plate 31 and the backlight device (not shown) are arranged outside the array substrate AR, and the second polarizing plate 32 is arranged outside the color filter substrate CF, and the liquid crystal according to the first embodiment. The display device 10A is completed.

The liquid crystal display device 10A of the first embodiment operates as follows. In the liquid crystal display device 10A, the first electrode 21a and the first lower electrode 18a function as pixel electrodes, and the second electrode 21b and the second lower electrode 18b operate as counter electrodes. The first electrode 21a and the second lower electrode 18b overlap with each other via the insulating film 19 in plan view, and the second electrode 21b and the first electrode
The lower electrode 18a overlaps with the insulating film 19 in plan view. Therefore, when the liquid crystal display device 10A is activated, an electric field E1 is generated between the first electrode 21a and the second electrode 21b, as shown in FIG. 3, and the first electrode 21a and the second lower electrode 18b. An electric field E2 is applied between the two. Further, an electric field E3 in the direction opposite to the electric field E2 is applied between the first lower electrode 18a and the second electrode 21b.

The operation by the electric field E1 applied between the first electrode 21a and the second electrode 21b is the same as that of the conventional IPS mode liquid crystal display device 50 shown in FIGS. The first
The operation by the electric field E2 applied between the electrode 21a and the second lower electrode 18b and the operation by the electric field E3 applied between the first lower electrode 18a and the second electrode 21b are shown in FIGS. This is the same as the case of the conventional FFS mode liquid crystal display device 70 shown in FIG. Accordingly, the liquid crystal display device 10A of the first embodiment operates as an IPS mode liquid crystal display device between the first electrode 21a and the second electrode 21b, and the first electrode 21a and the second lower electrode 18b The liquid crystal display device of the FFS mode is operated between the second electrode 21b and the first lower electrode 18a.

Accordingly, the liquid crystal display device 10A of the first embodiment includes the first electrode 21a and the second lower electrode 18.
b and the second electrode 21b and the first lower electrode 18a are overlapped with each other through the insulating film 19 in a plan view, so that a capacitance is formed in each of the two electrode pairs that overlap in the plan view. Are connected in parallel. Therefore, in the liquid crystal display device 10A of the first embodiment, as a result, a larger storage capacitor is formed than in the conventional FFS mode liquid crystal display device, so that it is not necessary to separately form a storage capacitor and flicker occurs. A small number of liquid crystal display devices 10A can be obtained.

In addition, since the liquid crystals on the surfaces of the first electrode 21a and the second electrode 21b are driven like an FFS mode liquid crystal display device, the luminance is higher than that of the IPS mode liquid crystal display device.
In addition, since the symmetry of the electrode is an intermediate configuration between the IPS mode and the FFS mode, the generation of a DC component is reduced, and the image sticking phenomenon is also improved. Therefore, according to the liquid crystal display device 10A of the first embodiment, a bright display liquid crystal display device having both advantages of the IPS mode and the FFS mode can be obtained.

The liquid crystal display device 10A of the first embodiment is formed so that the widths of the first lower electrode 18a and the second lower electrode 18b are wider than the widths of the first electrode 21a and the second electrode 21b. Therefore, the characteristics of the FFS mode are enhanced, and the applied voltage is higher than that of the conventional IPS mode liquid crystal display device, but a bright display is possible. Further, in the liquid crystal display device 10A of the first embodiment, the first to fourth electrodes 21a, 21b, 18a and 18 are used.
Although an example in which b is a comb-teeth shape extending along the signal line 13 has been shown, the same effect can be obtained by a comb-teeth shape extending along the scanning line 12.

[Second Embodiment]
Next, a liquid crystal display device 10B according to a second embodiment will be described with reference to FIGS. In addition,
4 and 5, the same components as those of the liquid crystal display device 10A according to the first embodiment shown in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted. Also, the cross-sectional view of the portion corresponding to the II-II line in FIG. 1 in FIG.

The liquid crystal display device 10B of the second embodiment is different from the liquid crystal display device 10A of the first embodiment in that the width of the first lower electrode 18a and the second lower electrode 18b is the first electrode 21a and The second electrode 21b is substantially the same as the width of the second electrode 21b. According to the liquid crystal display device 10B of the second embodiment having such a configuration, the tolerance for mask displacement when the first electrode 21a and the second electrode 21b are formed by photolithography is reduced, but the applied voltage is Even if it is low, a fringe field is generated in all electrodes, so that a bright display liquid crystal display device 10B can be obtained.

[Third Embodiment]
Next, a liquid crystal display device 10C according to a third embodiment will be described with reference to FIGS. In addition,
6 and 7, the same components as those of the liquid crystal display device 10A of the first embodiment shown in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted. Further, the cross-sectional view of the portion corresponding to the line II-II in FIG. 1 in FIG. 6 is the same as FIG.

The configuration of the liquid crystal display device 10C of the third embodiment is different from that of the liquid crystal display device 10A of the first embodiment in that the widths of the first lower electrode 18a and the second lower electrode 18b are reversed. This is that the width is made narrower than the widths of 21a and the second electrode 21b. According to the liquid crystal display device 10C of the third embodiment having such a configuration, since the characteristics of the IPS mode liquid crystal display device appear strongly, the brightness becomes dark, but the applied voltage can be small. Moreover, the first electrode 2
Since the tolerance for mask misalignment when the 1a and the second electrode 21b are formed by the photolithography method is increased, it is easy to manufacture.

In the first to third embodiments, the first lower electrode 18a and the second lower electrode 1 are used.
Although the example in which both 8b and the first electrode 21a and the second electrode 21b are comb-shaped has been shown, these comb-shaped portions do not necessarily have to be linear. That is, these comb-like portions do not necessarily have to be completely parallel as long as they do not intersect with each other, and may be bent, for example, in a “<” shape or a zigzag shape. With such a configuration, the viewing angle dependency of the display image quality of the obtained liquid crystal display device is reduced.

FIG. 3 is a schematic plan view of one pixel that is seen through a color filter substrate of the liquid crystal display device according to the first embodiment. It is sectional drawing along the II-II line of FIG. It is sectional drawing along the III-III line of FIG. FIG. 6 is a schematic plan view for one pixel that is seen through a color filter substrate of a liquid crystal display device according to a second embodiment. It is sectional drawing along the VV line of FIG. FIG. 10 is a schematic plan view of one pixel that is seen through a color filter substrate of a liquid crystal display device according to a third embodiment. It is sectional drawing along the VII-VII line of FIG. FIG. 10 is a schematic plan view of one pixel that is seen through a color filter substrate of a conventional IPS mode liquid crystal display device. It is sectional drawing in alignment with IX-IX of FIG. FIG. 10 is a schematic plan view of one pixel that is seen through a color filter substrate of a conventional FFS mode liquid crystal display device. It is sectional drawing along the XII-XII line of a figure.

Explanation of symbols

10A to 10C: liquid crystal display device 11: first transparent substrate 12: scanning line 13: signal line
14: Gate insulating film 15: Passivation film 16: Planarization film 17: First contact hole 18a: First lower electrode (third electrode) 18b: Second lower electrode (fourth electrode) 1
9: Insulating film 20a, 20b: Separation region 21a: First electrode 21b: Second electrode 23:
Second contact hole 24: first alignment film 25: second transparent substrate 26: light shielding film
27: Color filter layer 28: Overcoat layer 29: Second alignment film 30: Liquid crystal
31: First polarizing plate 32: Second polarizing plate

Claims (8)

In a liquid crystal display device having a pair of substrates disposed opposite to each other with a liquid crystal layer interposed therebetween,
A plurality of independently driven pixels are formed on one of the pair of substrates,
In each of the pixels, the first electrode and the second electrode that are formed in parallel with the separation region interposed therebetween, and the separation region is sandwiched between the first electrode and the second electrode on the substrate side through an insulating layer. A third electrode and a fourth electrode formed side by side in parallel,
The first electrode is formed so as to overlap with one of the third electrode and the fourth electrode, and the second electrode overlaps with the other of the third electrode and the fourth electrode in plan view,
The liquid crystal display device, wherein the first electrode is electrically connected to the other of the third electrode and the fourth electrode, and the second electrode is electrically connected to one of the third electrode and the fourth electrode. . The liquid crystal display device according to claim 1, wherein at least one of the third electrode and the fourth electrode is formed of a transparent conductive material. The liquid crystal display device according to claim 1, wherein the first electrode and the second electrode, and the third electrode and the fourth electrode are formed in a comb shape. The first electrode and the second electrode, and the third electrode and the fourth electrode are each formed in a comb shape extending along a scanning line or a signal line formed on the one substrate. The liquid crystal display device according to claim 4. 2. The liquid crystal display device according to claim 1, wherein the third electrode and the fourth electrode are wider than the first electrode and the second electrode, respectively. The liquid crystal display device according to claim 1, wherein the third electrode and the fourth electrode have the same width as the first electrode and the second electrode, respectively. The liquid crystal display device according to claim 1, wherein the third electrode and the fourth electrode are narrower than the first electrode and the second electrode, respectively. The liquid crystal display device according to claim 1, wherein the third electrode and the fourth electrode are formed on a surface of a planarizing film formed in each pixel.

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