KR20070072201A - In plane switching mode liquid crystal display device - Google Patents

Abstract

An IPS(In Plane Switching) mode LCD(Liquid Crystal Display) is provided to form the electric field within a liquid crystal layer in parallel to a substrate completely. Plural gate lines and data lines define plural pixels. A TFT(Thin Film Transistor) is formed at each pixel. The first and second electrodes are substantially arrayed in parallel to each pixel and form the horizontal electric field. The thickness of the first and second electrodes is substantially the same as that of a cell gap. The first and second electrodes are a common electrode(105) and a pixel electrode(107). The first line is electrically connected with the first electrode. The second line is electrically connected with the second electrode and forms the storage capacitance together with the first line. The first and second electrodes are formed by ITO(Indium Tin Oxide) or IZO(Indium Zinc Oxide).

Description

Transverse electric field mode liquid crystal display device {IN PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY DEVICE}

1 is a plan view of a conventional transverse electric field mode liquid crystal display device.

2 is a cross-sectional view taken along line II ′ of FIG. 1.

3 is a plan view of a transverse electric field mode liquid crystal display device according to the present invention.

4 is a cross-sectional view taken along the line II-II ′ of FIG. 2.

Explanation of symbols on the main parts of the drawings

101: liquid crystal panel 103: gate line

104: data line 105: common electrode

107: pixel electrode 110: thin film transistor

116: common line 118: pixel electrode line

120,130: substrate 122: gate insulating layer

124: protective layer 132: black matrix

134: color filter layer 140: liquid crystal layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a transverse electric field mode liquid crystal display device capable of forming an electric field in the liquid crystal layer completely parallel to the substrate to prevent a decrease in luminance due to electric field distortion.

Recently, with the development of various portable electronic devices such as mobile phones, PDAs, and notebook computers, there is a growing demand for flat panel display devices for light and thin applications. Such flat panel displays are being actively researched, such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), FED (Field Emission Display), VFD (Vacuum Fluorescent Display), but mass production technology, ease of driving means, Liquid crystal display devices (LCDs) are in the spotlight for reasons of implementation.

The liquid crystal display device has various display modes according to the arrangement of the liquid crystal molecules. However, the liquid crystal display device of the TN mode is mainly used because of the advantages of easy monochrome display, fast response speed, and low driving voltage. In such a TN mode liquid crystal display device, liquid crystal molecules aligned horizontally with the substrate are almost perpendicular to the substrate when a voltage is applied. Therefore, there is a problem that the viewing angle is narrowed upon application of voltage due to the refractive anisotropy of the liquid crystal molecules.

In order to solve this viewing angle problem, liquid crystal display devices of various modes having wide viewing angle characteristics have recently been proposed, but among them, the liquid crystal display device of the lateral field mode (In Plane Switching Mode) is applied to actual production. It is produced. The transverse electric field mode liquid crystal display device aligns liquid crystal molecules in a plane by forming at least one pair of electrodes arranged in parallel in a pixel to form a transverse electric field substantially parallel to the substrate.

1 is a plan view showing the structure of a conventional transverse electric field mode liquid crystal display device. As shown in FIG. 1, pixels of the liquid crystal panel 1 are defined by gate lines 3 and data lines 4 arranged vertically and horizontally. Although only the (n, m) th pixels are shown in the drawing, in the liquid crystal panel 1, n and m gate lines 3 and data lines 4 are disposed, respectively, and thus the liquid crystal panel 1 is disposed. N x m pixels are formed throughout. The thin film transistor 10 is formed at the intersection of the gate line 3 and the data line 4 in the pixel. The thin film transistor 10 includes a gate electrode 11 to which a scan signal is applied from the gate line 3, and a semiconductor layer formed on the gate electrode 11 and activated as a scan signal is applied to form a channel layer. 12 and a source electrode 13 and a drain electrode 14 formed on the semiconductor layer 12 and to which an image signal is applied through the data line 4. The image signal input from the outside is applied to the liquid crystal layer. do.

In the pixel, a plurality of common electrodes 5 and a pixel electrode 7 are arranged substantially parallel to the data line 4. In addition, a common line 16 connected to the common electrode 5 is disposed in an upper region of the pixel, and a pixel electrode line 18 connected to the pixel electrode 7 is disposed on the common line 16. It overlaps with the common line 16. Storage capacitance is formed in the transverse electric field mode liquid crystal display by overlapping the common line 16 and the pixel electrode line 18.

In the transverse electric field mode liquid crystal display device configured as described above, the liquid crystal molecules are aligned substantially in parallel with the common electrode 5 and the pixel electrode 7. When the thin film transistor 10 is operated to apply a signal to the pixel electrode 7, a transverse electric field substantially parallel to the liquid crystal panel 1 is generated between the common electrode 5 and the pixel electrode 7. Since the liquid crystal molecules rotate on the same plane along the transverse electric field, gray level inversion due to the refractive anisotropy of the liquid crystal molecules can be prevented.

A conventional transverse electric field mode liquid crystal display device having the above-described structure will be described in more detail with reference to FIG.

As shown in FIG. 2, a gate electrode 11 is formed on the first substrate 20, and a gate insulating layer 22 is stacked over the entire first substrate 20. The semiconductor layer 12 is formed on the gate insulating layer 22, and the source electrode 13 and the drain electrode 14 are formed thereon. In addition, a passivation layer 24 is formed on the entire first substrate 20.

In addition, a plurality of common electrodes 5 made of metal are formed on the first substrate 20, and pixel electrodes 7 and data lines 4 made of metal are formed on the gate insulating layer 22. The transverse electric field E is generated between the common electrode 5 and the pixel electrode 7.

The black matrix 32 and the color filter layer 34 are formed on the second substrate 30. The black matrix 32 is to prevent light leakage into an area where the liquid crystal molecules do not operate. As shown in the drawing, the black matrix 32 is formed between the region of the thin film transistor 10 and between the pixel and the pixel (ie, the gate line and the data line). Area). The color filter layer 34 is composed of R (Red), B (Blue), and G (Green) to realize actual colors.

The liquid crystal layer 40 is formed between the first substrate 20 and the second substrate 30 to complete the liquid crystal panel 1.

As described above, in the transverse electric field mode liquid crystal display device, the transverse electric field E is formed inside the liquid crystal layer 40 by the common electrode 5 and the pixel electrode 7 formed on the substrate 20 and the gate insulating layer 22, respectively. ) Is generated to drive the liquid crystal molecules inside the liquid crystal layer 40 in parallel with the surface of the substrate.

However, the following problem occurs in the transverse electric field mode liquid crystal display device having the above structure. As shown in FIG. 2, the common electrode 5 and the pixel electrode 7 are formed on the first substrate 20 and the gate insulating layer 22, respectively. Therefore, the transverse electric field E formed between the actual common electrode 5 and the pixel electrode 7 does not become completely parallel to the substrate 20. That is, the electric field of the common electrode 5 and the pixel electrode 7 and its side surfaces, that is, the region A in the drawing, is not completely parallel to the surface of the substrate 20. Therefore, in the region A, since the liquid crystal molecules arranged along the electric field E are arranged at an angle, not completely parallel to the surface of the substrate 20, light leakage occurs in the region A, resulting in image quality. This causes a decrease. In addition, since the light transmittance in the area A is lowered, there is a problem that the luminance of the entire liquid crystal display element is lowered.

The present invention is to solve the above problems, the common electrode and the pixel electrode to form a transverse electric field is formed almost the same as the cell gap of the liquid crystal panel transverse electric field mode that can prevent light leakage phenomenon and prevent the brightness is lowered It is an object to provide a liquid crystal display device.

In order to achieve the above object, the transverse electric field mode liquid crystal display device according to the present invention includes a plurality of gate lines and data lines defining a plurality of pixels, a thin film transistor formed in each pixel, and substantially parallel to each pixel. Arranged to form a transverse electric field, the thickness being comprised of at least one first electrode and a second electrode that are substantially equal to the cell gap.

The first electrode and the second electrode are made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), and the first electrode is formed through the first contact hole formed in the protective layer and the gate insulating layer. The second electrode is connected to the first line and is connected to the second line through the second contact hole formed in the passivation layer to form a storage capacitor between the first line and the second line.

The present invention provides a transverse electric field mode liquid crystal display without distortion of the transverse electric field. In other words, there is provided a transverse electric field mode liquid crystal display device which forms a transverse electric field substantially parallel to the surface of the substrate over the entire liquid crystal layer and over the entire substrate. To this end, in the present invention, the thickness of the common electrode and the pixel electrode forming the transverse electric field is increased as compared with the related art. Conventionally, since an electric field is formed between the common electrode arranged in parallel and the upper surface of the pixel electrode, the electric field of the surface and the side of the electrode is inclined, but in the present invention, the thickness of the common electrode and the pixel electrode is increased to increase the thickness between the side of the electrode. Since the electric field is formed at, the distortion of the electric field can be prevented.

Hereinafter, the transverse electric field mode liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a view showing a transverse electric field mode liquid crystal display device according to the present invention;

As shown in FIG. 3, the transverse electric field mode liquid crystal display device according to the present invention includes a plurality of gate lines 103 and data lines 104 arranged vertically and horizontally to define a plurality of pixels, and a gate line in the pixels. 103 and the thin film transistor 110 disposed at the intersection of the data line 104 and the common electrode 105 and the pixel which are disposed substantially parallel in the pixel to form a transverse electric field substantially parallel to the surface of the substrate. It consists of an electrode 107.

The thin film transistor 110 is formed on the gate electrode 111 to which the scan signal is applied from the gate line 103, and is formed on the gate electrode 111 to be activated as the scan signal is applied through the gate line 103. A source electrode 113 and a drain electrode 114 for forming a semiconductor layer 112 forming a layer and an image signal formed on the semiconductor layer 112 and applied through the data line 104 to the pixel electrode 107. It is composed of

The common line 116 electrically connected to the common electrode 105 and the pixel electrode line 118 electrically connected to the pixel electrode 107 are disposed in the pixel. In this case, the common line 116 and the pixel electrode line 118 are disposed with different layers, that is, insulating layers, to form a storage capacitor.

In addition, the common electrode 105 is connected to the common line 116 through the first contact hole 117 and the pixel electrode 107 is connected to the pixel electrode line 118 through the second contact hole 119. . In the drawing, although each pixel electrode 107 is formed separately and connected to the pixel electrode line 118 through two second contact holes 119, each pixel electrode 107 is integrally formed to form a single one. It may be connected to the pixel electrode line 118 by the second contact hole 119. In addition, only one first contact hole 117 may be formed or a plurality of first contact holes 117 may be formed.

In the transverse electric field mode liquid crystal display device configured as described above, the liquid crystal molecules are arranged substantially parallel to the common electrode 105 and the pixel electrode 107. When the thin film transistor 110 operates to apply a signal to the pixel electrode 107, a transverse electric field substantially parallel to the liquid crystal panel 101 is generated between the common electrode 105 and the pixel electrode 107. Since the liquid crystal molecules rotate on the same plane along the transverse electric field, gray level inversion due to the refractive anisotropy of the liquid crystal molecules can be prevented.

4 is a cross-sectional view taken along the line II-II ′ of FIG. 3, and the lateral field mode liquid crystal display device according to the present invention will be described in more detail with reference to this.

As shown in FIG. 4, the gate electrode 111 is formed on the first substrate 120, and the gate insulating layer 122 is stacked on the entire first substrate 120. The semiconductor layer 112 is formed on the gate insulating layer 122, and a source electrode 113 and a drain electrode 114 are formed thereon. In addition, a passivation layer 24 is formed on the entire first substrate 120.

The data line 104 is formed on the gate insulating layer 122, and a plurality of common electrodes 105 and pixel electrodes are formed on the passivation layer 124, so that the common electrode 105 and the pixel electrode ( A transverse electric field E occurs between 107. In this case, the common electrode 105 and the pixel electrode 107 are formed by stacking and patterning a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), respectively. It is formed almost the same as the cell gap. That is, the common electrode 105 and the pixel electrode 107 are formed to have a few μm.

Although not shown in the drawing, a common electrode line 116 is formed on the first substrate 120 to be common through the first contact hole 117 formed in the gate insulating layer 122 and the protective layer 124. It is electrically connected with the electrode 105. In addition, on the gate insulating layer 122, the pixel electrode line 118 is electrically connected to the pixel electrode 118 through the second contact hole 119 formed in the protective layer 124 and input through the thin film transistor 110. The resulting image signal is applied to the pixel electrode 118. As such, the gate insulating layer 122 is positioned between the common line 116 and the pixel electrode 118 to form a storage capacitor.

The black matrix 132 and the color filter layer 134 are formed on the second substrate 130. The black matrix 132 is to prevent light leakage into an area in which the liquid crystal molecules do not operate. As shown in the drawing, the black matrix 132 is between the region of the thin film transistor 110 and the pixel and the pixel (ie, the gate line and the data line). Area). The color filter layer 134 is composed of R (Red), B (Blue), and G (Green) to realize actual colors.

The liquid crystal layer 140 is formed between the first substrate 120 and the second substrate 130 to complete the liquid crystal panel 101.

As described above, in the present invention, since the common electrode 105 and the pixel electrode 107 forming the transverse electric field E are formed to have almost the same thickness as the cell gap, when an image signal is applied to the pixel electrode 107, A transverse electric field E that is completely horizontal to the surface of the substrate 120 is formed over the entire liquid crystal layer 140. Furthermore, in the present invention, since the common electrode 105 and the pixel electrode 107 are formed on the same layer (that is, a protective layer), the horizontal electric field E can be applied to the liquid crystal layer 140. Therefore, when the liquid crystal molecules are arranged along the transverse electric field E, the liquid crystal molecules are completely horizontal to the surface of the substrate 120 to remove light leakage. In addition, since the liquid crystal molecules are arranged in the same direction over the entire liquid crystal layer in accordance with the applied image signal, the light transmittance can be prevented from being lowered.

On the other hand, in the above description of the present invention, the transverse electric field mode liquid crystal display device having a specific structure has been described, but is not limited to this structure of the present invention. For example, arrangement of various numbers of common electrodes and pixel electrodes in a pixel will be included in the present invention. In addition, although the common electrode and the pixel electrode are arranged in a straight line in the above description, the present invention also includes a structure in which the pixel is divided into a plurality of domains by being bent one or more times (ie, zigzag) to improve the viewing angle characteristic. It must be. In addition, the common electrode and the pixel electrode may be formed of an opaque metal instead of only a transparent conductive material.

Accordingly, the scope of the present invention should be determined not by the detailed description of the invention but by the appended claims.

As described above, in the present invention, since the common electrode and the pixel electrode are formed at substantially the same height as the cell gap in the same layer, a transverse electric field substantially parallel to the surface of the substrate is formed over the entire liquid crystal layer. Therefore, it is possible to effectively prevent light leakage and luminance decrease due to distortion of the electric field. Furthermore, in the present invention, since the common electrode and the pixel electrode are formed of a transparent conductive material, luminance can be further improved.

Claims (10)

A plurality of gate lines and data lines defining a plurality of pixels; A thin film transistor formed in each pixel; And A transverse electric field mode liquid crystal display device comprising at least one first electrode and a second electrode which are arranged substantially parallel to each pixel to form a transverse electric field, the thickness of which is substantially equal to the cell gap. The transverse electric field mode liquid crystal display device of claim 1, wherein each of the first electrode and the second electrode comprises a common electrode and a pixel electrode. The method of claim 1, A first line electrically connected to the first electrode; And And a second line electrically connected to the second electrode to form a first line and a storage capacitance. The method of claim 1, wherein the thin film transistor, A gate electrode formed on the first substrate; A gate insulating layer formed over the entire first substrate; A semiconductor layer formed on the gate insulating layer; A source electrode and a drain electrode formed on the semiconductor layer; And And a protective layer formed on the source electrode and the drain electrode. The transverse electric field mode liquid crystal display device of claim 4, wherein the first electrode and the second electrode are formed on a protective layer. The transverse electric field mode liquid crystal display device of claim 5, wherein the first electrode and the second electrode are made of a transparent conductive material. The transverse electric field mode liquid crystal display device of claim 6, wherein the first electrode and the second electrode are made of indium tin oxide (ITO) or indium zinc oxide (IZO). The transverse electric field liquid crystal display device of claim 4, wherein the first line is formed on a first substrate, and the second line is formed on a gate insulating layer. The method of claim 8, wherein the first line is connected to the first electrode through a first contact hole formed in the protective layer and the gate insulating layer, and the second line is connected to the second electrode through a second contact hole formed in the protective layer. Transverse electric field mode liquid crystal display device characterized in that. The method of claim 1, A black matrix formed on the second substrate; A color filter layer formed on the second substrate; And A transverse electric field mode liquid crystal display device comprising a liquid crystal layer formed between a first substrate and a second substrate.

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