KR101385460B1 - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, comprising: a first substrate and a second substrate facing each other; A gate line and a data line crossing each other on the first substrate to define a pixel area; A thin film transistor formed at an intersection of the gate line and the data line; A common line formed in parallel with the gate line; A plurality of pixel electrodes connected to the thin film transistors and formed in the pixel area; A plurality of common electrodes branched from the common line to alternate with the pixel electrode; A black matrix formed only on the second substrate so as to correspond to the gate line, the data line, the thin film transistor, the pixel electrode, and the common electrode; And a color filter layer formed on the second substrate so as to correspond to the pixel region, wherein the black matrix is formed to correspond to a portion of the pixel electrode and the common electrode, and has a width narrower than that of the pixel electrode and the common electrode. The edges of the pixel electrode and the common electrode are exposed by the black matrix.

LCD, Transverse Electric Field, IPS, Black Matrix, Luminance, Contrast Ratio

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

1 is a plan view showing a conventional liquid crystal display device

2 is a plan view showing a liquid crystal display device according to a first embodiment of the present invention.

3 is a cross-sectional view of an LCD according to a first exemplary embodiment of the present invention according to II ′ of FIG. 2.

4 is a plan view showing a liquid crystal display device according to a second embodiment of the present invention.

5 is a cross-sectional view illustrating a liquid crystal display according to a second embodiment of the present invention according to II-II ′ of FIG. 4.

6 is a plan view illustrating a liquid crystal display according to a third embodiment of the present invention.

7 is a plan view showing a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a liquid crystal display according to a fourth embodiment of the present invention according to III-III ′ of FIG. 7.

DESCRIPTION OF THE RELATED ART [0002]

110, 210, 410: first substrate

150, 250, 450: second substrate

12, 112, 212, 312, 412: gate line

18, 118, 218, 318, 418: data lines

30, 130, 230, 330, 430: common line

26, 126, 226, 326, 426: pixel electrode

34, 134, 234, 334: common electrode

434: first common electrode

436: second common electrode

52, 152, 252, 352, 452: Black Matrix

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 for improving contrast ratio by lowering luminance in a black state.

As the information society develops, the demand for display devices is increasing in various forms, and in recent years, liquid crystal displays, plasma display panels, and electroluminescent displays have been developed. Various flat panel display devices such as vacuum fluorescent display (Vacuum Fluorescent Display) have been studied, and some of them are already used as display devices in various devices.

Among them, the liquid crystal display device is the most widely used as a substitute for the CRT (Cathode Ray Tube) for the mobile image display device because of the excellent image quality, light weight, thinness, and low power consumption. In addition to the use of the present invention, a variety of applications such as a television, a computer monitor, and the like for receiving and displaying broadcast signals have been developed.

In order for liquid crystal display devices to be used in various parts as a general screen display device, it is important to develop high-quality images such as high definition, high brightness and large area while maintaining the features of light weight, thinness and low power consumption can do.

The liquid crystal display device has various modes depending on the nature of the liquid crystal and the structure of the pattern.

Specifically, the TN method (Twisted Nematic Mode) for arranging the liquid crystal directors to be twisted 90 degrees and then applying voltage to control the liquid crystal directors, and forming two electrodes on one substrate so that the directors of the liquid crystals are twisted in a parallel plane of the alignment layer. In-Plane Switching Mode.

Among these, the transverse electric field type liquid crystal display device is generally composed of a color filter array substrate and a thin film transistor array substrate disposed opposite to each other and having a liquid crystal layer therebetween.

In this case, a black matrix for preventing light leakage and a color filter layer of red, green, and blue for implementing colors on the black matrix are formed on the color filter array substrate.

The thin film transistor array substrate includes a gate line and a data line defining a pixel region, a thin film transistor formed at an intersection point of the gate line and a data line, and a common electrode alternately formed in the pixel region to generate a transverse electric field. And a pixel electrode.

Hereinafter, a conventional liquid crystal display device will be described. 1 is a plan view showing a liquid crystal display device according to the prior art.

In the conventional liquid crystal display, a plurality of gate lines 12 are arranged in one direction with a predetermined interval to define a pixel region on a first substrate (not shown), and a predetermined interval intersects with the gate line 12. And a plurality of data lines 18 are arranged.

In addition, the pixel electrode 26 and the common electrode 34 are alternately formed in each pixel region defined by the intersection of the gate line 12 and the data line 18, thereby generating a transverse electric field, thereby driving the liquid crystal.

In addition, at the intersection of the gate line 12 and the data line 18 to be switched by a signal applied to the gate line 12 to transmit a signal applied to the data line 18 to each pixel electrode 26. A plurality of thin film transistors are formed.

Here, the thin film transistor is formed by protruding from the gate line 12, the gate electrode 12a, the semiconductor layer (not shown) formed on the gate electrode 12a, and the data line 18. A source electrode 18a formed on one side of the upper portion and a drain electrode 20 formed on the other side of the gate electrode 12a at regular intervals from the source electrode 18a are formed.

The common line 30 is formed to be parallel to the gate line 12, and the common electrode 34 is branched from the common line 30. The storage electrode 32 protruding from the common line 30 is formed between the common line 30 and the gate line 12. The storage electrode 32 overlaps the drain electrode 20 and the pixel electrode 26 to form a storage capacitor. Storage capacitors are needed to keep data signals stable.

Although not shown, a gate insulating film is formed on the entire surface of the substrate including the gate line 12 and the gate electrode 12a to insulate the semiconductor layer from the source electrode 18a and the drain electrode 20. The protective film is formed on the entire surface of the substrate including the. In addition, a contact hole 24 is formed in the passivation layer on the drain electrode 20, and the pixel electrode 26 is electrically connected to the drain electrode 20 through the contact hole 24.

As described above, the first substrate on which the thin film transistor is formed is called a thin film transistor array substrate.

In addition, the second substrate corresponding to the first substrate is provided with a black matrix 52 for blocking light in portions other than the pixel region, and red, green, and blue color filter layers (not shown) for expressing color colors. It is. This is called a color filter array substrate.

In the drawing, only the black matrix 52 is illustrated without the color filter layer. In this case, the black matrix 52 is formed at portions corresponding to the gate line 12, the data line 18, and the thin film transistor.

Meanwhile, the pixel electrode 26 is generally formed of a transparent material such as indium tin oxide (ITO) or indium zinc oxide (IZO). Where opaque materials such as the drain electrode 20 and the common line 30 are formed under the pixel electrode 26, light from the lower portion of the first substrate does not pass through the pixel electrode 26. On the other hand, in the position where only the transparent material is under the pixel electrode 26, light from the lower part of the first substrate passes through the pixel electrode 26.

In the liquid crystal display device driven by the transverse electric field as described above, the liquid crystal moves by the transverse electric field generated between the pixel electrode 26 and the common electrode 34. At this time, the liquid crystal positioned on the pixel electrode 26 and the common electrode 34 is not controlled by the transverse electric field. Accordingly, light leakage occurs in the upper portion of the pixel electrode 26, and the luminance of the black state is high, resulting in a low contrast ratio.

The present invention has been made to solve the above problems, in the liquid crystal display device driven by the transverse electric field method to prevent light leakage on the upper pixel electrode to lower the brightness of the black state, thereby increasing the contrast ratio (contrast ratio) It is an object of the present invention to provide a liquid crystal display device.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes a first substrate and a second substrate facing each other, a gate line and a data line defining a pixel region crossing each other on the first substrate, and the gate line and data. A thin film transistor formed at an intersection of the lines, a common line formed in parallel with the gate line, a plurality of pixel electrodes connected to the thin film transistor and formed in a pixel region, and a plurality of branches branched from the common line to alternate with the pixel electrode And a black matrix formed on the second substrate to correspond to the common electrode, the gate line, the data line, the thin film transistor, and the pixel electrode, and a color filter layer formed on the second substrate to correspond to the pixel region. have.

Further, in the liquid crystal display device as described above, the common electrode is branched from the common line to surround the outside of the pixel area, and is formed between the pixel electrode connected to the first common electrode. The second common electrode is formed, and the black matrix is further formed on the second common electrode.

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

2 is a plan view illustrating a liquid crystal display device according to a first embodiment of the present invention, and FIG. 3 is a cross-sectional view illustrating a liquid crystal display device according to a first embodiment of the present invention according to II ′ of FIG. 2.

First, the liquid crystal display according to the first exemplary embodiment of the present invention includes a first substrate 110 and a second substrate 150 facing each other, and a gate crossing each other on the first substrate 110 to define a pixel region. A thin film transistor formed at an intersection of the line 112 and the data line 118, the gate line 112 and the data line 118, the common line 130 formed in parallel with the gate line 112, A plurality of pixel electrodes 126 connected to the thin film transistor and formed in the pixel region, a plurality of common electrodes 134 branched from the common line 130 and alternately formed with the pixel electrode 126, and a gate line 112. ), A black matrix 152 formed on the second substrate 150 to correspond to the data line 118, the thin film transistor, and the pixel electrode 126, and a black matrix 152 formed on the second substrate 150 to correspond to the pixel region. It is configured to include a color filter layer 154.

The black matrix 152 is formed to prevent light from passing through portions other than the pixel region, which is an area displaying the screen, and is formed to correspond to the gate line 112, the data line 118, and the thin film transistor. In addition, the present invention is driven by a transverse electric field generated between the pixel electrode 126 and the common electrode 134, the pixel is formed of a transparent metal such as indium tin oxide (ITO), indium zinc oxide (IZO) The black matrix 152 is formed to correspond to the pixel electrode 126 in order to prevent light leakage due to the liquid crystal not moving above the electrode 126.

The thin film transistor protrudes from the gate line 112, the semiconductor layer 116 formed over the gate electrode 112a, and the data line 118 protrudes from the gate electrode 112a. A source electrode 118a formed on one side and a drain electrode 120 formed on the other side of the gate electrode 112a at regular intervals from the source electrode 118a are formed.

The storage electrode 132 protruding from the common line 130 is formed between the common line 130 and the gate line 112. The storage electrode 132 overlaps the drain electrode 120 and the pixel electrode 126 to form a storage capacitor. Storage capacitors are needed to keep data signals stable.

A gate insulating film is formed on the entire surface of the first substrate 114 including the gate line 112 and the gate electrode 112a to insulate the semiconductor layer 116 from the source electrode 118a and the drain electrode. The passivation layer 122 is formed on the entire surface of the first substrate 114 including the 120. In addition, a contact hole 124 is formed in the passivation layer 122 on the drain electrode 120, and the pixel electrode 126 is electrically connected to the drain electrode 120 through the contact hole 124.

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

4 is a plan view showing a liquid crystal display device according to a second embodiment of the present invention, and FIG. 5 is a cross-sectional view showing a liquid crystal display device according to a second embodiment of the present invention according to II-II 'of FIG. 4.

The liquid crystal display according to the second exemplary embodiment of the present invention includes a first substrate 210 and a second substrate 250 facing each other, and a gate line intersecting each other on the first substrate 210 to define a pixel region. 212 and the data line 218, the thin film transistor formed at the intersection of the gate line 212 and the data line 218, the common line 230 formed in parallel with the gate line 212, and the thin film transistor. A plurality of pixel electrodes 226 connected to the plurality of pixel electrodes 226 formed in the pixel region, a plurality of common electrodes 234 branched from the common line 230, and alternately formed with the pixel electrodes 226, a gate line 212, The black matrix 252 is formed on the second substrate 250 to correspond to the data line 218, the entire region of the thin film transistor, and a part of the pixel electrode 226, and the second substrate 250 to correspond to the pixel region. It is configured to include a color filter layer 254 formed on the).

In the liquid crystal display according to the second embodiment, all parts except for the position where the black matrix is formed are the same as in the case of the first embodiment, and description thereof will be omitted. That is, in the liquid crystal display according to the second embodiment, the black matrix 252 is formed to correspond to the entire region of the gate line 212, the data line 218, and the thin film transistor, and is formed in a portion of the pixel electrode 226. It is characterized in that it is formed to correspond.

In the liquid crystal display device according to the first embodiment, the black matrix is formed to correspond to the entire region of the pixel electrode, so that the effect of lowering the luminance in the black state can be maximized, while the luminance in the white state is also lowered, so that the overall luminance is lowered. Is concerned.

In contrast, in the liquid crystal display according to the second exemplary embodiment, the black matrix 252 is formed to correspond to a partial region of the pixel electrode 226 with a width narrower than that of the pixel electrode 226 so that the luminance of the black state is increased. The lowering effect can be prevented while reducing the overall luminance.

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

6 is a plan view of a liquid crystal display according to a third exemplary embodiment of the present invention.

In the liquid crystal display according to the third exemplary embodiment of the present invention, the gate line 312, the data line 318, the thin film transistor, the common line 330, the common electrode 334, and the pixel electrode 326 are implemented in the first embodiment. It is formed in the same structure as the liquid crystal display according to the example.

However, as in the second embodiment, the black matrix 352 is formed to correspond to the entire region of the gate line 312, the data line 318, and the thin film transistor, and is formed to correspond to a partial region of the pixel electrode 326. There is a characteristic in point. That is, as shown in FIG. 6, stripes are patterned in a direction parallel to the gate line 312 on the second substrate (not shown) corresponding to the pixel electrode 326 of the first substrate (not shown). The black matrix 352 is formed to have.

In the second and third embodiments, the black matrix is formed to correspond to a partial region of the pixel electrode. The present invention is not limited to the case where the black matrix is formed in the form described in the second and third embodiments, and includes all cases in which the black matrix is formed to correspond to a partial region of the pixel electrode. For example, the black matrix may be formed to have a plurality of stripes in a direction parallel to the data line so as to correspond to one pixel electrode of the first substrate.

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

7 is a plan view illustrating a liquid crystal display device according to a fourth embodiment of the present invention, and FIG. 8 is a cross-sectional view showing a liquid crystal display device according to a fourth embodiment of the present invention according to III-III ′ of FIG. 7.

In the liquid crystal display according to the fourth exemplary embodiment of the present invention, the first substrate 410 and the second substrate 450 facing each other, and the gate line crossing the first substrate 410 and defining pixel regions intersecting with each other. 412 and the data line 418, the thin film transistor formed at the intersection of the gate line 412 and the data line 418, the common line 430 formed in parallel with the gate line 412, and the thin film A plurality of pixel electrodes 426 connected to the transistor and formed in the pixel region, a first common electrode 434 formed from a common line 430 to surround the pixel region, and a first common electrode 434. A second common electrode 436 connected to the plurality of pixel electrodes 426, a gate line 412, a data line 418, a thin film transistor, a pixel electrode 426, and a second common electrode ( A black matrix 452 formed on the second substrate 450 to correspond to 434, and a pixel And a color filter layer 454 formed on the second substrate 450 to correspond to the region.

In the liquid crystal display according to the fourth exemplary embodiment, parts except for the first and second common electrodes 434 and 436 and the black matrix 452 are the same as in the first exemplary embodiment, and thus a detailed description thereof will be omitted. That is, in the liquid crystal display according to the fourth exemplary embodiment, the common electrode is branched from the common line 430 and connected to the first common electrode 434 and the first common electrode 434 formed to surround the outside of the pixel area. The second common electrode 436 is formed between the plurality of pixel electrodes 426 and the black matrix 452 is further formed on the second substrate 450 to correspond to the second common electrode 452. It is characteristic in that it becomes.

As illustrated in FIGS. 7 and 8, the black matrix 452 is formed to correspond to the entire region of the gate line 412, the data line 418, and the thin film transistor, and the second common electrode 436 and the pixel electrode are formed. Corresponding to 426 is formed in a narrower width. However, the present invention is not limited to this case, and may be formed to correspond to the entire areas of the second common electrode 436 and the pixel electrode 426. In addition, the second common electrode 436 and the pixel electrode 426 may be formed to have stripes in parallel with the gate line 412 or in parallel with the data line 418.

The pixel electrode 426 and the second common electrode 436 are formed of a transparent metal such as indium tin oxide (ITO) or indium zinc oxide (IZO) in the same layer. The second common electrode is electrically connected to the first common electrode 434 through the contact hole 438.

In the first to fourth embodiments, the pixel electrode is formed in parallel with the data line. However, the present invention is not limited thereto, and the pixel electrode is formed to be bent once in one pixel area. It may be formed in the shape of bending once in the same direction. In addition, the pixel electrode and the common electrode may be formed to be bent several times in one pixel area.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, Will be apparent to those of ordinary skill in the art.

The liquid crystal display device according to the present invention as described above has the following effects.

First, by forming a black matrix on the second substrate so as to correspond to the pixel electrode or the common electrode formed of a transparent material on the first substrate, light leakage to the upper portion of the pixel electrode or the common electrode may be prevented.

Second, the brightness in the black state is reduced by reducing the light leakage, thereby increasing the contrast ratio.

Third, compared with the case where the pixel electrode and the common electrode are formed of an opaque metal to prevent light leakage, there is an effect of reducing the cost. That is, in the case of forming the pixel electrode and the common electrode as an opaque metal, it is more expensive than the transparent metal, but in the case of the present invention, the object of the present invention can be achieved at a low cost by additionally forming a black matrix. .

Claims (12)

A first substrate and a second substrate facing each other; A gate line and a data line crossing each other on the first substrate to define a pixel region; A thin film transistor formed at an intersection of the gate line and the data line; A common line formed in parallel with the gate line; A plurality of pixel electrodes connected to the thin film transistors and formed in the pixel area; A plurality of common electrodes branched from the common line to alternate with the pixel electrode; A black matrix formed only on the second substrate so as to correspond to the gate line, the data line, the thin film transistor, the pixel electrode, and the common electrode; A color filter layer formed on the second substrate to correspond to the pixel region; The black matrix is formed to correspond to a portion of the pixel electrode and the common electrode, and is formed to have a width narrower than that of the pixel electrode and the common electrode, and edges of the pixel electrode and the common electrode are exposed by the black matrix. Liquid crystal display device characterized in that. The method of claim 1, The pixel electrode is formed of a transparent metal. delete The method of claim 1, And the black matrix is formed to correspond to an entire area of the gate line, the data line, and the thin film transistor. delete The method of claim 1, The black matrix formed to correspond to a partial region of the pixel electrode, And a stripe pattern in a direction parallel to the gate line or in a direction parallel to the data line. The method of claim 1, The common electrode may include a first common electrode branched from the common line to surround the pixel area, and a second common electrode connected to the first common electrode and formed between the pixel electrodes. and, The black matrix is formed to correspond to a portion of the second common electrode, and is formed to have a width narrower than that of the second common electrode, and an edge of the second common electrode is exposed by the black matrix. A liquid crystal display device. The method of claim 7, wherein The pixel electrode and the second common electrode are formed of a transparent metal. delete The method of claim 7, wherein And the black matrix is formed to correspond to an entire area of the gate line, the data line, and the thin film transistor. delete The method of claim 7, wherein The black matrix formed to correspond to a partial region of the second common electrode, And a stripe pattern in a direction parallel to the gate line or in a direction parallel to the data line.

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