KR101320493B1 - In plane switching mode liquid crystal display device having high aperture - Google Patents

Abstract

The present invention provides a transverse electric field mode liquid crystal display device having improved aperture ratio. The transverse electric field mode liquid crystal display device according to the present invention includes a plurality of pixels including a plurality of domains defined by gate lines and data lines, and the pixel. A switching element formed therein, a common electrode and a pixel electrode disposed substantially parallel in the pixel to form a transverse electric field, and a data line disposed at both sides to block an electric field by the data line and to form a storage capacitor. It consists of a metal layer and a 2nd metal layer. The common electrode and the pixel electrode are formed of a transparent conductive material on a protective layer made of an organic material, and the outermost common electrode of the pixel overlaps the data line.

Transverse electric field mode, aperture ratio, storage capacity, organic material, outermost common electrode, metal layer

Description

High-aperture-rate transverse electric field mode liquid crystal display device {IN PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY DEVICE HAVING HIGH APERTURE}

1 is a plan view showing the structure of a general transverse electric field mode liquid crystal display device.

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

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

3A is a cross-sectional view showing a pixel structure of a transverse electric field mode liquid crystal display device according to the present invention;

3B is a cross-sectional view showing a structure near a data line of the transverse electric field mode liquid crystal display device according to the present invention;

Description of the Related Art [0002]

105: common electrode 107: pixel electrode

116: gate electrode 117: semiconductor layer

118: source electrode 119: pixel electrode

120,130: substrate 122: gate insulating layer

124: protective layer 132: black matrix

134: color filter layer 140: liquid crystal layer

155: metal layer for electric field interruption 165: metal layer for storage capacity

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transverse electric field mode liquid crystal display device, and more particularly, to a transverse electric field mode liquid crystal display device capable of improving an aperture ratio by arranging electrodes for storage capacitance along the outermost common electrode of a pixel.

2. Description of the Related Art Recently, various portable electronic devices such as a mobile phone, a PDA, and a notebook computer have been developed. Accordingly, there is a growing need for a flat panel display device for a light and small size. 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 element, liquid crystal molecules aligned horizontally with the substrate are oriented substantially 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 IPS mode liquid crystal display device improves the viewing angle characteristic by forming a transverse electric field parallel to the substrate when a voltage is applied and aligning the liquid crystal molecules in a plane.

1 shows an IPS mode liquid crystal display device. As shown in FIG. 1, pixels of a liquid crystal display are defined by gate lines 2 and data lines 3 arranged vertically and horizontally. Although only the (n, m) -th pixel is shown in the figure, n and m of the gate lines 2 and the data lines 3 are disposed in the actual liquid crystal display device, respectively, so that n is distributed throughout the liquid crystal display device. X m pixels are formed.

A thin film transistor 15 is formed at the intersection of the gate line 2 and the data line 3 in the pixel. The thin film transistor 15 includes a gate electrode 16 to which a scan signal is applied from the gate line 2, and a semiconductor layer formed on the gate electrode 16 and activated as a scan signal is applied to form a channel layer. 17 and a source electrode 18 and a drain electrode 19 formed on the semiconductor layer 17 and to which an image signal is applied through the data line 3. 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 3. In addition, a common line 8 connected to the common electrode 5 is disposed in an upper region of the pixel, and a pixel electrode line 9 connected to the pixel electrode 7 is disposed on the common line 9. It overlaps with the said common line 8. A storage capacitance is formed in the transverse electric field mode liquid crystal display device due to the overlap of the common line 8 and the pixel electrode line 9.

In the IPS mode liquid crystal display element configured as described above, the liquid crystal molecules are oriented substantially parallel to the common electrode 5 and the pixel electrode 7. When the thin film transistor 15 is operated to apply a signal to the pixel electrode 7, a transverse electric field substantially parallel to the surface of the liquid crystal display device 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.

The conventional IPS mode liquid crystal display device having the above structure will be described in more detail with reference to FIGS. 2A and 2B. 2A is a cross-sectional view taken along the line II ′ of FIG. 1, and FIG. 2B is a cross-sectional view taken along the line II-II ′ of FIG. 1.

As shown in FIG. 2A, a gate electrode 16 is formed on the first substrate 20, and a gate insulating layer 22 is stacked over the entire first substrate 20. The semiconductor layer 17 is formed on the gate insulating layer 22, and the thin film transistor 15 is formed by forming the source electrode 18 and the drain electrode 19 thereon. In addition, a passivation layer 24 made of an inorganic material such as SiOx or SiNx is formed on the entire first substrate 20.

In addition, a plurality of common electrodes 5 are formed on the first substrate 20, and a pixel electrode 7 and a data line 3 are formed on the gate insulating layer 22 to form the common electrode 5. A transverse electric field is generated between the pixel electrodes 7.

On the second substrate 30, a black matrix 32 and a color filter layer 34 are formed. The black matrix 32 serves to prevent light from leaking into a region where the liquid crystal molecules do not operate. As shown in the figure, the black matrix 32 is formed between the pixel region and the pixel (that is, the gate line and the data line Region). The color filter layer 34 is formed of R (Red), B (Blue), and G (Green) to realize actual colors.

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

As shown in FIG. 2B, common electrodes 5 are formed on both sides of the data line 3. This common electrode (sometimes referred to as the outermost common electrode of a pixel because it is formed at the outermost part of the pixel) is for preventing the transverse electric field formed in the liquid crystal layer 30 in the pixel from being distorted. That is, as a signal is applied to the data line 3, the electric field generated in the data line 3 is shielded to prevent the transverse electric field from being affected.

In the IPS mode liquid crystal display device configured as described above, since an electric field is formed horizontally with the surface of the substrate 20 when a signal is applied, the liquid crystal molecules rotate along the surface of the substrate 20. Therefore, since the viewing angle can be prevented from decreasing due to the refractive anisotropy of the liquid crystal molecules, the viewing angle can be prevented from decreasing.

However, in the IPS mode liquid crystal display device, since the common electrode 5 and the pixel electrode 7 are formed of an opaque metal, there is a problem that the aperture ratio decreases.

An object of the present invention is to provide a transverse electric field mode liquid crystal display device having an improved aperture ratio.

In order to achieve the above object, the transverse electric field mode liquid crystal display device according to the present invention comprises a first substrate; A plurality of pixels defined by gate lines and data lines formed on the first substrate; A thin film transistor formed in the pixel, the gate electrode formed on the first substrate, the gate insulating layer formed on the gate electrode, the semiconductor layer formed on the gate insulating layer, and the source electrode and the drain electrode formed on the semiconductor layer; A protective layer formed on the thin film transistor; A common electrode and a pixel electrode disposed substantially parallel on the passivation layer in the pixel to form a transverse electric field; A first metal layer formed on the first substrate on both sides of the data line to block an electric field by the data line; And a second metal layer having the same width as the first metal layer so as to completely overlap the first metal layer with a gate insulating layer interposed therebetween, wherein the first metal layer and the second metal layer are formed on a different layer from the common electrode. The outermost common electrode of the pixel may be integrally formed with the outermost common electrode of an adjacent pixel so that the outermost common electrode overlaps the data line and covers the first metal layer and the second metal layer.

The common electrode and the pixel electrode are formed of a transparent conductive material on the protective layer, and the protective layer is made of an organic material.

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The reason why the aperture ratio of the IPS mode liquid crystal display device is low is for several reasons as follows. First, the common electrode and the pixel electrode are formed of an opaque metal. Second, the common line and the pixel electrode line forming the storage capacitor are formed of an opaque metal. The common line and the pixel electrode line overlap the storage capacitors to form the storage capacitors. When the width is reduced, the common line and the pixel electrode line do not have sufficient storage capacity. Third, the area between the outermost common electrode of the pixel and the data line is an area blocked by the black matrix and is an area where no actual image is realized. In particular, since the parasitic capacitance is generated between the outermost common electrode and the data line, the outermost common electrode should be separated from the data line by a predetermined distance or more, and the area blocked by the black matrix is increased due to such a spaced arrangement. The aperture ratio is further lowered.

In the present invention, the aperture ratio is improved by fabricating an IPS mode liquid crystal display device in view of the above factors. First, the aperture ratio is improved by forming the common electrode and the pixel electrode with a transparent conductive material. Second, the width of the common line and the pixel electrode line is minimized. To this end, in the present invention, a separate storage capacitor is secured to reduce the size of the storage capacitor generated by the common line and the pixel electrode line. As a result, the width of the common line and the pixel electrode line can be reduced. Third, the non-display area blocked by the black matrix is minimized by minimizing the separation between the outermost common electrode of the pixel and the data line. To this end, in the present invention, the protective layer is formed of an organic material to minimize parasitic capacitance generated between the outermost common electrode and the data line, and thus overlap the outermost common electrode and the data line.

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

3A and 3B are cross-sectional views showing the structure of an IPS mode liquid crystal display device according to the present invention. At this time, since the planar structure of the IPS mode liquid crystal display device according to the present invention is substantially similar to that shown in FIG. 1, the planar structure will be described with reference to FIG. 1. 3A and 3B are cross-sectional views taken along lines II ′ and II-II ′ of FIG. 1, and FIG. 3A is a cross-sectional view illustrating a pixel structure, and FIG. 3B is a cross-sectional view illustrating a structure near a data line.

As shown in FIGS. 3A and 3B, a gate electrode 116 is formed on the first substrate 120, and a gate insulating layer 22 is stacked on the entire first substrate 120. The semiconductor layer 117 is formed on the gate insulating layer 122, and a source electrode 118 and a drain electrode 119 are formed thereon. In addition, a protective layer 124 is formed over the entire first substrate 20. The protective layer 124 is formed by stacking an organic material such as Benzo Cyclo Butene (BCB) or photo acryl.

In addition, a common electrode 105 and a pixel electrode 107 made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) are disposed on the protective layer 124 to be substantially parallel to the first substrate. A transverse electric field parallel to 120 is formed. In this case, the outermost common electrode 105b of the pixel overlaps the data line 103. As shown in FIG. 3B, the outermost common electrode 105b of the corresponding pixel is formed integrally with the outermost common electrode 105b of the substantially adjacent pixel to overlap the data line 103. As such, by overlapping the outermost common electrode 105b and the data line 103, an image non-display area generated by the outermost common electrode 105b and the data line 103 can be minimized.

On the other hand, the parasitic capacitance due to the overlap of the outermost common electrode 105b and the data line 103 is small enough to be negligible. In general, since organic materials such as BCB and photoacryl have a lower dielectric constant than inorganic materials, even when the outermost common electrode 105b and the data line 103 overlap, the parasitic capacitance is formed to be negligible. Furthermore, when the organic material is used, since the protective layer 122 can be formed thicker than the inorganic material, the parasitic capacitance is further reduced, resulting in overlapping the outermost common electrode 105b and the data line 103. Even if the failure is caused by the parasitic capacity.

The field blocking metal layer 155 caused by the data line 103 is formed on the first substrate 120 on both sides of the data line 103. The electric field blocking metal layer 155 blocks an electric field generated by the data line 103 to prevent distortion of the transverse electric field formed by the common electrodes 105a and 105b and the pixel electrode 107. In this case, the metal layer 155 may be formed of the same metal by the same process as the gate electrode 116 of the thin film transistor.

In addition, the electric field by the data line 103 is not only blocked by the metal layer 155 but also by the outermost common electrode 105b formed on the protective layer 124. Of course, since the electric field blocking by the outermost common electrode 105b is small, there is some electric field blocking effect, so that the width of the electric field blocking metal layer 155 is changed to a conventional electric field blocking metal layer (of course, In this case, the outermost common electrode serves as an electric field cutoff).                     

A storage capacitor metal layer 165 is disposed on the gate insulating layer 122 on the field blocking metal layer 155 to overlap the field blocking metal layer 155. At this time, since the storage capacitor metal layer 165 is disposed along the electric field blocking metal layer 155, the opening ratio reduction phenomenon due to the storage capacitor metal layer 165 does not occur.

As shown in FIG. 1, the storage capacitance of the IPS mode liquid crystal display device is generally formed by a common line connected to the common electrodes 105a and 105b and a pixel electrode line connected to the pixel electrode 107. In this case, the common line and the pixel electrode line of the IPS mode liquid crystal display device according to the present invention are also formed on the first substrate 120 and the gate insulating layer 122 in the same manner as the common line and the pixel electrode line of the conventional IPS mode liquid crystal display device. . In this case, the common line and the pixel electrode line are electrically connected to the common electrodes 105a and 105b and the pixel electrode 107 through contact holes formed in the gate insulation 122 and the protection layer 124, respectively. Will be.

As the storage capacitor metal layer 165 is formed to form the storage capacitor, a desired amount of storage capacity can be secured even if the storage capacitor formed by the common line and the pixel electrode line is reduced. In other words, the storage capacitance formed by the common line and the pixel electrode line is designed to be smaller than before. Therefore, in the IPS mode liquid crystal display device of the present invention, the width of the common line and the pixel electrode line can be reduced as compared with the conventional IPS mode liquid crystal display device. As a result, the aperture ratio is improved by the degree of reduction of the common line and the pixel electrode line. You will get the effect.

Meanwhile, 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 a region where the liquid crystal molecules do not operate. The black matrix 132 is mainly formed between the thin film transistor region and the pixel and the pixel (ie, the gate line and the data line region). The color filter layer 134 is composed of R (Red), B (Blue), and G (Green) to realize actual colors. Although not shown, an overcoat layer may be formed on the color filter layer 134 to protect the color filter layer 134 and to planarize the second substrate 130. A liquid crystal layer is formed between the first substrate 120 and the second substrate 130 to complete the IPS mode liquid crystal display device.

In addition, this invention is not limited only to a specific structure. The IPS mode of the planar structure shown in FIG. 1, that is, the common electrode and the pixel electrode are bent at a predetermined angle so that the pixels are divided into two domains. The present invention may be applied to a liquid crystal display device. In addition, the present invention may be applied not only to a three subpixel structure having subpixels of R, G, and B, but also to a 4-subpixel IPS mode liquid crystal display device having subpixels of R, G, B, and W (White). .

In the IPS mode liquid crystal display device of the present invention, the following effects can be obtained.

First, since the common electrode and the pixel electrode disposed in the pixel are formed of a transparent conductive material, the aperture ratio can be improved.

Second, since the protective layer is formed of an organic insulating film, since the outermost common electrode of the pixel is overlapped with the data line, the aperture ratio can be improved.

Third, since the electric field of the data line is blocked by the outermost common electrode of the pixel and the field blocking metal layer, the transverse electric field applied to the liquid crystal layer by the data line can be effectively prevented from being distorted.

Fourth, since the storage capacitor metal layer is disposed along the field blocking metal layer to form additional storage capacitance, the width of the common line and the pixel electrode line can be reduced, thereby improving the aperture ratio.

Claims (11)

A first substrate; A plurality of pixels defined by gate lines and data lines formed on the first substrate; A thin film transistor formed in the pixel, the gate electrode formed on the first substrate, the gate insulating layer formed on the gate electrode, the semiconductor layer formed on the gate insulating layer, and the source electrode and the drain electrode formed on the semiconductor layer; A protective layer formed on the thin film transistor; A common electrode and a pixel electrode disposed substantially parallel on the passivation layer in the pixel to form a transverse electric field; A first metal layer formed on the first substrate on both sides of the data line to block an electric field by the data line; And A second metal layer having a same width as the first metal layer so as to completely overlap the first metal layer with a gate insulating layer interposed therebetween, The first metal layer and the second metal layer are formed on a layer different from the common electrode, and the outermost common electrode of the pixel is integrally formed with the outermost common electrode of the adjacent pixel so that the outermost common electrode overlaps the data line. And transverse electric field mode liquid crystal display device covering the first metal layer and the second metal layer. delete delete The transverse electric field mode liquid crystal display device of claim 1, wherein the common electrode and the pixel electrode are made of a transparent conductive material. The transverse electric field mode liquid crystal display device of claim 4, wherein the conductive material comprises indium tin oxide (ITO) and indium zinc oxide (IZO). The transverse electric field mode liquid crystal display device of claim 1, wherein the protective layer is formed of an organic material. delete The transverse electric field mode liquid crystal display device of claim 1, wherein the common electrode and the pixel electrode are bent at least once in the pixel so that the pixel includes a plurality of domains. delete delete The method of claim 1, A second substrate; And The transverse electric field mode liquid crystal display device further comprising a black matrix formed on the second substrate.

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