KR20120119299A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to reduce crosstalk due to a signal of a data line while minimizing lowering of light transmittance. CONSTITUTION: A pixel electrode(PE) and a common electrode(CE) are made of a double layer which has a metal layer and a transparent conductive materials layer on each pixel area on a protective film. The pixel electrode and the common electrode are alternately arranged. A dummy electrode(DmE) is made of a double layer which has a metal layer and a transparent conductive materials layer on a protective film. The dummy electrode is connected to the common electrode. The dummy electrode covers a data line and a shield line.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which image quality can be improved.

In recent years, as the information age has entered, the display field for visually expressing electrical information signals has been rapidly developed, and various flat panel display devices having excellent performance of thinning, light weight, and low power consumption have been developed. Flat Display Device has been developed to quickly replace the existing Cathode Ray Tube (CRT).

Specific examples of such a flat panel display include a liquid crystal display (LCD), an organic light emitting display (OLED), an electrophoretic display (EPD, Electric Paper Display), Plasma Display Panel Device (PDP), Field Emission Display Device (FED), Electroluminescence Display Device (ELD) and Electro-Wetting Display (EWD) Etc. can be mentioned. They commonly have a flat panel display panel that implements an image as an essential component. The flat panel panel has a configuration in which a pair of substrates are faced to each other with a layer of a unique light emitting material or polarizer therebetween. Among them, the liquid crystal display device is a representative example of a flat panel display device, and displays an image by adjusting the light transmittance of the liquid crystal for each pixel by using an electric field.

A typical liquid crystal display device is formed in each of a lower substrate and an upper substrate facing each other, a liquid crystal layer filled between the lower substrate and the upper substrate, and a plurality of pixel regions corresponding to a plurality of pixels, and each liquid crystal cell of the liquid crystal layer for each pixel region. A pixel electrode and a common electrode forming an electric field for changing the direction of?, And a transistor array formed around the plurality of pixel areas to define a plurality of pixel areas and to apply respective pixel voltages to the pixel electrodes of each pixel. .

The transistor array is formed on a lower substrate, the plurality of gate lines and data lines arranged to cross each other and defining a plurality of pixel regions, and a plurality of pixels respectively formed in intersection regions between the gate lines and the data lines and corresponding to the plurality of pixels, respectively. And a plurality of thin film transistors connected to the pixel electrodes of the plurality of transistors, and configured to apply a signal of the data line to the pixel electrode when turned on in response to a signal of the gate line.

At this time, outside the plurality of pixel regions, the liquid crystal cells of the liquid crystal layer are not affected by an electric field between the pixel electrode and the common electrode, and thus may not have a properly controlled direction. As a result, light leakage generated outside the plurality of pixel areas may cause deterioration of image quality. Thus, a general liquid crystal display device further includes a black matrix formed outside the plurality of pixel areas, and light is transmitted only in each pixel area, and blocks light leakage in other areas.

However, even within each pixel region, in some regions adjacent to the data line, the liquid crystal cell may have a properly controlled direction due to interference by signals of the data line (hereinafter referred to as "cross talk"). There is no problem. For this reason, while a signal is applied to the data line, light leakage occurs in some areas adjacent to the data line in each pixel area, so that low luminance cannot be displayed properly, and thus the image quality is degraded. In particular, a signal of a data line should be applied only to a pixel to be scanned, but crosstalk occurs in all pixel regions adjacent to the data line, thereby causing light leakage.

At this time, in order to prevent the crosstalk caused by the signal of the data line, when the black matrix is formed wider, the ratio of the amount of light emitted through each pixel region among the incident light (hereinafter referred to as "light transmittance") As this is lowered, there is a limit in displaying high brightness, which causes a problem of deterioration in image quality.

The present invention is to provide a liquid crystal display device capable of reducing crosstalk due to a signal of a data line while minimizing a decrease in light transmittance.

In order to solve such a problem, the present invention is a first substrate and a second substrate facing each other; A liquid crystal layer filled between the first substrate and the second substrate; A gate line and a common line that are alternately and parallel to each other on one surface of the first substrate; A gate insulating layer formed on one surface of the first substrate and covering the gate line and the common line; A data line formed on the gate insulating layer to intersect the gate line to define a plurality of pixel regions; A shield line formed on one surface of the first substrate so as to be parallel to both sides of the data line and connected to the common line; A passivation layer formed on the gate insulating layer to cover the data line; A pixel electrode and a common electrode formed of a double layer of a metal layer and a transparent conductive material layer in each pixel area on the passivation layer; And a dummy electrode formed on the passivation layer as a double layer of the metal layer and the transparent conductive material layer and connected to the common electrode to cover the data line and the shield line. Here, the width of the metal layer is 3㎛ or less, the width of the transparent conductive material layer is more than the width of the metal layer, 4㎛ or less.

As described above, the liquid crystal display according to the present invention includes a pixel electrode and a common electrode having a double layer structure in which a metal layer having a width of 3 μm or less and a transparent conductive material layer of 4 μm or less are laminated, thereby reducing aperture ratio and increasing resistance. While minimizing the increase, it is possible to minimize the difference in luminance characteristics between pixels due to the variation in the width of the metal layer with a process error of 1 μm or less, thereby preventing deterioration in image quality.

In addition, the liquid crystal display according to the present invention includes a dummy electrode having a double layer structure in which a metal layer and a transparent conductive material layer having a wider width than that of the metal layer are stacked, thereby minimizing the aperture ratio loss and further increasing crosstalk due to the data line. Can be reduced, so that image degradation can be minimized.

1 is a plan view illustrating a part of one pixel in a liquid crystal display according to an exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view according to the first embodiment of the present invention in II ′ of FIG. 1.
3 is a cross-sectional view according to a second embodiment of the present invention in II ′ of FIG. 1.
4A and 4B illustrate a liquid crystal display device according to the prior art and a liquid crystal display device according to a first or second embodiment of the present invention, wherein a crosstalk is performed by a data line in a portion of each pixel area adjacent to the data line. It is an image showing generated light leakage.
5 is a graph comparing the results of simulating vertical crosstalk by a data line in the liquid crystal display according to the prior art and the liquid crystal display according to the first or second embodiment of the present invention.

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a plan view illustrating a part of one pixel in a liquid crystal display according to an exemplary embodiment of the present invention. 2 is a cross-sectional view according to the first embodiment of the present invention in FIG. 1 II ′, and FIG. 3 is a cross-sectional view according to the second embodiment of the present invention in FIG. to be.

First, a liquid crystal display according to an exemplary embodiment of the present invention includes a gate line (not shown), a data line DL, a gate line, and a data line intersecting each other such that a plurality of pixel regions corresponding to a plurality of pixels are defined. A thin film transistor (not shown) formed at the intersection of the DL, a common line (not shown) arranged in parallel and alternating with the gate line, and a shield line connected to both sides of the data line DL in parallel with the common line. SL, the pixel electrode PE and the common electrode CE, which are alternately formed in each pixel region, and the common electrode CE, and are connected to the shield line on both sides of the data line DL and the data line DL. The dummy electrode DmE is formed to cover the SL.

The thin film transistor includes a gate electrode connected to the gate line, a source electrode connected to the data line DL, and a drain electrode connected to the pixel electrode PE. The thin film transistor (not shown) is turned on in response to a signal of a gate line, and applies a pixel voltage corresponding to each pixel to the pixel electrode PE when turned on.

The common electrode CE is connected to a common line to receive a common voltage corresponding to all pixels. In this case, since the dummy electrode DmE is connected to the common electrode CE, the common electrode CE receives the common voltage like the common electrode CE.

The liquid crystal display device changes the direction of the liquid crystal cell by using an electric field between the pixel electrode PE and the common electrode CE in each pixel area, and emits light at respective light transmittances. By adjusting the luminance, an image is displayed.

As shown in FIGS. 2 and 3, the liquid crystal display according to the first and second embodiments of the present invention may include a first substrate (Sb) and a second substrate (Su), which face each other. The liquid crystal layer (LC) filled between the first substrate Sb and the second substrate Su, and alternately and parallel to each other on one surface of the first substrate Sb facing the liquid crystal layer LC On the gate line (not shown), the common line (not shown) and the first substrate (Sb) to be formed, the shield line (SL) which is formed in parallel to both sides of the data line (DL) in connection with the common line A gate insulating film GI formed on one surface of the first substrate Sb to cover the gate line, the common line, and the shield line SL, and the gate line on the gate insulating film GI to define a plurality of pixel regions. On the data line DL and the gate insulating layer GI formed to intersect with each other and cover the data line DL and cover the data line DL. In each pixel area PA, a double layer of a metal layer (Me) and a transparent conductive material layer (TC) is formed, and the pixel electrode PE and the common electrode CE which alternate with each other, and A double layer of a metal layer (Me) and a transparent conductive material layer (TC) is formed on the passivation layer, and is connected to the common electrode CE to connect the data line DL and the data line DL. ) Includes dummy electrodes DmE covering shield lines SL at both sides.

The liquid crystal display is formed on one surface of the second substrate Su, except for the plurality of pixel areas PA, and blocks the black matrix BM and the second substrate Su that block light leakage. A color filter CF is formed in the pixel region and transmits light of a wavelength region representing a predetermined color.

The shield line SL is connected to the common line CL and is formed in parallel with the data line DL at positions spaced at predetermined intervals on both sides of the data line DL. The shield line SL is disposed to intersect the data line DL and the pixel area PA while having the same voltage level as that of the common line CL, and is provided by the data line DL to which a predetermined signal is applied. Reduced influence of the generated electric field on the liquid crystal cell in the pixel region. Accordingly, the occurrence of cross talk due to the signal of the data line DL may be reduced.

The pixel electrode PE and the common electrode CE have a comb teeth alternate with each other in each pixel area, and are formed of a double layer of a metal layer Me and a transparent conductive material layer TC. In this case, the transparent conductive material layer TC has a width EW1 that is wider by an additional width than the metal layer Me. That is, the width EW1 of the transparent conductive material layer TC is larger than the width EW2 of the metal layer Me. At this time, the width difference EW1-EW2 between the two layers is equal to or greater than 0 μm, and the width of the metal layer Me It is less than the process error for the width. Here, the widths of the transparent conductive material layer TC and the metal layer Me may be in a direction in which the data lines DL are arranged side by side (generally in a horizontal direction) or in a direction in which the data line DL intersects therein (generally vertical). Direction).

In other words, the transparent conductive material layer TC may have the same width as the metal layer Me, and may have a width that is as large as a process error or less with respect to the width of the metal layer Me.

In particular, the width of the metal layer Me constituting the pixel electrode PE and the common electrode CE is 3 μm in order to increase the ratio (hereinafter, referred to as “opening ratio”) of the area in which the light is substantially emitted. It can be determined as follows. At this time, the process error with respect to the width EW2 of the metal layer Me is known to be 0.5 μm per side, that is, 1 μm or less as a whole, and the width EW1 of the transparent conductive material layer TC is represented by the metal layer ( It may be determined to be 4 μm or less, adding 0.5 μm or less to both sides of the width EW2 of Me).

The dummy electrode DmE is connected to the common electrode CE to cover the data line DL and the shield line SL. In this case, like the common electrode CE and the pixel electrode CE, the dummy electrode DmE is formed of a double layer of the metal layer Me and the transparent conductive material layer TC on the passivation layer Passi. The dummy electrode DmE is connected to at least one of the common line CL and the shield line SL through a contact hole (not shown) passing through the gate insulating layer GI and the passivation layer Passi. Extends from

Like the shield line SL, the dummy electrode DmE is disposed to intersect the data line DL and the pixel area PA while maintaining the same voltage level as that of the common electrode CE, thereby applying a predetermined signal. The electric field generated between the data line DL and the common electrode CE or the pixel electrode PE in the pixel area PA, or between the black matrix BM is reduced. Accordingly, the occurrence of cross talk due to the signal of the data line DL may be reduced.

The liquid crystal layer LC is formed of a liquid crystal cell having a predetermined initial alignment direction, and the liquid crystal cell rotates in a direction corresponding to an electric field between the pixel electrode PE and the common electrode CE, and selectively transmits light.

The color filter CF is formed in each of a plurality of pixel areas on one surface of the second substrate Su, and transmits light of a wavelength region corresponding to a predetermined color corresponding to each of the plurality of pixels. For example, the color filter CF may be formed of a dye or a fluorescent material that transmits light corresponding to any one color of red, green, and blue (RGB) corresponding to each pixel area.

2, in the pixel electrode PE, the common electrode CE, and the dummy electrode DmE, the transparent conductive material layer TC may be formed of a metal layer Me. It consists of a double layer structure disposed below. That is, the transparent conductive material layer TC has a first width EW1 and is formed on the passivation layer Passi, and the metal layer Me has a second width EW2 smaller than the first width EW1 and has transparency. It is formed on the dielectric material layer TC.

In contrast, as shown in FIG. 3, in the pixel electrode PE, the common electrode CE, and the dummy electrode DmE, the transparent conductive material layer TC may be formed of a metal layer. Me) consists of a double layer structure arranged on top. That is, the metal layer Me has a second width EW2 and is formed on the passivation layer Passi, and the transparent conductive material layer TC has a first width EW1 larger than the metal layer Me, and the metal layer ( Me) is formed on the passivation layer (Passi) to cover.

As described above, according to the first and second embodiments of the present invention, the pixel electrode PE and the common electrode CE formed in each pixel area PA have a metal layer Me having a second width EW2 and A double layer structure of the transparent conductive material layer TC having a first width EW1 greater than the second width EW2 is formed. In this case, the second width EW2 of the metal layer Me is determined to be 3 μm or less in order to maximize the aperture ratio of each pixel area PA. In addition, the first width EW1 of the transparent conductive material layer TC is a second width EW2 of the metal layer Me, that is, 3 μm or more, and the metal layer Me varies due to a process error (1 μm). Is determined to be the maximum width, ie 4 μm or less. In addition, since the transparent conductive material layer TC is stacked together with the metal layer Me having a low resistance, it is not necessary to consider the high resistance, and thus has a thickness of 200 kPa or less, which shows a transmittance of about 97.3% or more.

Unlike the first and second embodiments of the present invention, in the case where the pixel electrode PE and the common electrode CE are made of only the transparent conductive material layer TC, a metal layer having the same width due to the characteristics of the material having transparency The light transmittance of each pixel region can be improved rather than that of the pixel region. However, as ITO, IZO, ITZO, etc., which are mainly selected as transparent conductive materials, have a high resistance of about 200 μΩ · cm, they should be formed with a width of about 4 μm or more and a thickness of 500 μs or more, so that the light transmittance of each pixel region is rather increased. There are limitations to the improvement. In addition, the transparent conductive material may be patterned only by a photolithography method, and thus may not be formed as a fine electrode having a width of 3 μm or less, and thus the area occupied by the pixel electrode PE and the common electrode CE in each pixel area. There is a drawback to limiting this.

On the other hand, when the pixel electrode PE and the common electrode CE are formed of only the metal layer Me, there is no limitation in the pattern process, and thus the fine electrode having a width of about 3 μm or less may be formed using a dry etching method or the like. There are advantages to it.

However, due to mask misalignment, shaking, or deviation in etching, a process error with respect to the electrode width is generally generated. At this time, the process error is known to be about 0.4㎛ 0.5㎛.

If the pixel electrode PE and the common electrode CE have a width of 4 μm or more, a process error of about 0.4 μm to 0.5 μm is only 0.125 or less with respect to the total width (4 μm or more). Even if the width of the electrode varies with the process error, the visibility due to the difference in aperture ratio between the entire pixel regions appears low.

However, when the pixel electrode PE and the common electrode CE are fine electrodes having a width of about 3 μm or less, a process error of about 0.4 μm to 0.5 μm is about 0.134 or more with respect to the total width (3 μm or less). Because of the ratio, when the width of the electrode varies with the process error, the visibility due to the difference in aperture ratio between the entire pixel regions appears very high. That is, due to a large difference in aperture ratio between each pixel region due to the difference in width between the pixel electrode PE and the common electrode CE, a difference in luminance characteristics between pixels may be recognized as a stain, resulting in deterioration of image quality. .

Accordingly, according to the first and second embodiments of the present invention, the pixel electrode PE and the common electrode CE are formed in a double layer structure in which a metal layer Me and a transparent conductive material layer TC are stacked. The metal layer Me having a width of 3 μm or less minimizes the reduction of the opening ratio due to the area occupied by the electrode and minimizes the increase in resistance, and the transparent conductive material layer TC of 4 μm or less of the metal layer Me Differences in luminance characteristics between pixels due to variations in process errors of 1 탆 or less in width can be minimized, and deterioration in image quality can be prevented.

In addition, since the transparent conductive material layer TC has a thickness of 200 μs or less, the transparent conductive material layer TC not only exhibits light transmittance of 97.3% or more, but also the transparent conductive material layer TC and the metal layer Me at least on one side of the transparent conductive material layer TC. Since a part of the width difference (EW1-EW2) between the?) Is not covered by the metal layer Me, light can be transmitted therethrough, thereby minimizing the reduction of the aperture ratio.

In addition, according to the first and second embodiments of the present invention, the dummy electrode DmE, like the pixel electrode PE and the common electrode CE, has a double layer structure of a metal layer Me and a transparent conductive material layer TC. Is made of. In this case, the metal layer Me constituting the dummy electrode DmE is formed to have a width that can cover both the data line DL and the shield line SL on both sides of the data line DL, excluding a plurality of pixel regions. Blocks light transmission in that area of the rest. In addition, the transparent conductive material layer TC constituting the dummy electrode DmE has a width wider than that of the metal layer Me stacked together, so that a portion of the transparent conductive material layer TC invades the pixel area. By the transparent conductive material layer TC of the dummy electrode DmE, a horizontal electric field generated between the data line DL to which a signal is applied and the pixel electrode PE adjacent thereto may be reduced.

That is, the transparent conductive material layer TC of the dummy electrode DmE has a width wider than that of the metal layer Me and the black matrix BM of the dummy electrode DmE, and is partially formed in the pixel area PA. The crosstalk caused by the data line DL may be further reduced.

4A and 4B illustrate a liquid crystal display device according to the prior art and a liquid crystal display device according to a first or second embodiment of the present invention, wherein a crosstalk is performed by a data line in a portion of each pixel area adjacent to the data line. It is an image showing generated light leakage. 5 is a graph comparing the results of simulating vertical crosstalk by a data line in the liquid crystal display according to the prior art and the liquid crystal display according to the first or second embodiment of the present invention.

In the liquid crystal display according to the related art, since the dummy electrode formed of the metal layer includes a dummy electrode, if the dummy electrode has a width that invades the pixel area, the aperture ratio is inevitably reduced. It is formed wide enough to cover only the lines and shield lines.

On the other hand, according to the first and second embodiments of the present invention, the dummy electrode DmE formed of the double layer structure of the metal layer Me and the transparent conductive material layer TC includes the dummy electrode DmE, thereby minimizing the reduction of the aperture ratio. The transparent conductive material layer TC of DmE may have a width invading in the pixel area, thereby reducing crosstalk due to the data line DL.

Thus, comparing FIG. 4A and FIG. 4B, crosses in the liquid crystal display device according to the first and second embodiments of the present invention, rather than light leaked due to crosstalk in the conventional liquid crystal display device (shown in blue squares). You can see that the light leaking out due to the torque (marked in blue squares) is smaller.

In addition, as shown in FIG. 5, in the conventional liquid crystal display device (indicated by "Ref" in FIG. 5), the light leakage due to crosstalk is represented by 4.79%, whereas the first or the second embodiment of the present invention In the liquid crystal display according to the second embodiment (indicated as “an embodiment of the present invention” in FIG. 5), light leakage due to crosstalk is found to be 4.55% which is 0.24% lower than that of the related art.

As described above, according to the first and second embodiments of the present invention, the dummy electrode DmE is formed in a double layer structure of the metal layer Me and the transparent conductive material layer TC. In this case, the transparent conductive material layer TC of the dummy electrode DmE may have a metal layer Me of the dummy electrode DmE having a width covering both the data line DL and the shield line SL on both sides of the data line DL. Since the crosstalk due to the data line DL can be reduced as compared with the related art, as the width is larger than the width and is partially invaded in the pixel area, the deterioration of image quality can be minimized. In addition, similar to the pixel electrode PE and the common electrode CE, the transparent conductive material layer TC of the dummy electrode DmE has a thickness of 200 μs or less, indicating a light transmittance of 97.3% or more, thereby reducing crosstalk. In addition, the aperture ratio loss can be minimized.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes may be made without departing from the technical spirit of the present invention.

Sb: Lower substrate SL: Shield line
GI: Gate Insulation Passi: Protective Layer
DL: data line PE: pixel electrode
CE: common electrode DmE: dummy electrode
Su: Upper board BM: Black matrix
CF: color filter

Claims (10)

A first substrate and a second substrate facing each other;
A liquid crystal layer filled between the first substrate and the second substrate;
A gate line and a common line that are alternately and parallel to each other on one surface of the first substrate;
A gate insulating layer formed on one surface of the first substrate and covering the gate line and the common line;
A data line formed on the gate insulating layer to intersect the gate line to define a plurality of pixel regions;
A shield line formed on one surface of the first substrate so as to be parallel to both sides of the data line and connected to the common line;
A passivation layer formed on the gate insulating layer to cover the data line;
A pixel electrode and a common electrode formed of a double layer of a metal layer and a transparent conductive material layer in each pixel area on the passivation layer; And
And a dummy electrode formed on the passivation layer as a double layer of the metal layer and the transparent conductive material layer and connected to the common electrode to cover the data line and the shield line. The method of claim 1,
The width of the transparent conductive material layer is larger than the width of the metal layer. The method of claim 2,
A width difference between the transparent conductive material layer and the metal layer is greater than or equal to 0 μm and less than or equal to a process error with respect to the width of the metal layer. The method of claim 3,
The process error is 1㎛ liquid crystal display device. The method of claim 2,
The metal layer has a width of 3 μm or less,
The width of the transparent conductive material layer is greater than the width of the metal layer, less than 4㎛ liquid crystal display device. The method of claim 2,
The thickness of the transparent conductive material layer is less than 200Å. The method according to any one of claims 2 to 6,
The transparent conductive material layer is formed on the protective film,
The metal layer is formed on the transparent conductive material layer. The method according to any one of claims 2 to 6,
The metal layer is formed on the protective film,
And the transparent conductive material layer is formed to cover the metal layer on the passivation layer. The method of claim 2,
It further comprises a black matrix formed on a surface of the second substrate except for the plurality of pixel areas, and blocks the light leakage,
And a portion of the black matrix corresponding to the data line has the same width as the dummy electrode. The method of claim 2,
And the common electrode is connected to the common line through a contact hole passing through the passivation layer and the gate insulating layer.

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