KR20030057072A - An in plane switching mode liquid crystal display device and a method of fabricating thereof - Google Patents

Abstract

PURPOSE: A transverse LCD(Liquid Crystal Display) device and a manufacturing method thereof are provided to prevent the degradation of the quality of an LCD by cutting off the light reflected on a chuck. CONSTITUTION: A thin film transistor is placed in each pixel area defined by gate lines and data lines. An opaque metal layer(105a), a transparent metal layer(112a) and a photoresist layer(141) are sequentially placed in the pixel area. Light is irradiated after placing a mask(143) on the substrate to develop the photoresist. The opaque and transparent metals are etched to form a transparent common electrode on the metal layers. A pixel electrode is formed parallel to the common electrode. A protecting layer is formed on a whole substrate(115).

Description

Transverse electric field type liquid crystal display device and manufacturing method therefor {AN IN PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY DEVICE AND A METHOD OF FABRICATING THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transverse electric field type liquid crystal display device, and in particular, an opaque thin metal layer is disposed on at least one of upper and lower portions of a common electrode disposed in a pixel to improve aperture ratio. The present invention relates to a transverse electric field type liquid crystal display device and a method for manufacturing the same, which can prevent screen unevenness caused by light being irradiated to the resist.

Liquid crystal display devices are flat panel display devices, which are mainly applied to portable electronic devices such as notebook computers, PDAs, and mobile phones, as well as high-definition television (HDTV), The range of applications is gradually increasing, such as digital televisions and thin wall-mounted televisions. In general, many kinds of devices such as plasma display panel (PDP), vacuum fluorescent display (VFD) and field emission display (FED) are actively researched as flat panel display devices. The LCD is mainly employed because of advantages such as ease of use, high definition, and the like.

As such LCDs, a twisted nematic mode LCD is mainly used. The TN LCD has a disadvantage in that a viewing angle is narrow. This is due to the refractive anisotropy of the liquid crystal molecules. This phenomenon occurs because liquid crystal molecules oriented horizontally with the substrate are oriented almost perpendicular to the substrate by applying a voltage.

Therefore, in recent years, various studies such as TN LCD equipped with optical compensation plate, multi-domain LCD, and optical alignment LCD have been conducted to improve the viewing angle of LCD, but in reality, the viewing angle could not be effectively improved. In fact, it is very difficult to realize the actual display device.

Currently, among the various types of LCDs proposed to improve the viewing angle, the most popular spot in terms of effect or practicality is the in-plane switching mode, which solves the viewing angle problem by aligning the liquid crystal molecules in a substantially horizontal direction with the substrate. ) LCD.

1 and 2 illustrate the structure of such a transverse electric field LCD. As shown in FIG. 1, in the transverse electric field type LCD, the gate line 1 and the data line 3 are vertically and horizontally arranged to define a pixel area. In an actual LCD, a plurality of such gate lines 1 and data lines 3 are arranged to define a plurality of pixel regions, but in the drawings, only one pixel is illustrated for convenience of description.

In the pixel area, the common line 10 is arranged to be substantially parallel to the gate line 1, and a thin film transistor is disposed at an intersection area of the gate line 1 and the data line 3. . As illustrated in FIG. 2, the TFT is stacked over the entire first gate substrate 5 on which the gate electrode 5 and the gate electrode 5 are formed, formed on a transparent first substrate 15 such as glass. A gate insulating layer 16, a semiconductor layer 7 formed in the region of the gate electrode 5 on the gate insulating layer 16, and a source / drain electrode 9 formed on the semiconductor layer 7. .

In the pixel area, the common electrode 12 and the pixel electrode 14 are arranged in parallel with each other in the extending direction of the data line 3. The common electrode 12 is formed on the first substrate 15 simultaneously with the gate line 1 and the gate electrode 5 to be connected to the common wiring 10, and the pixel electrode 14 is connected to the gate insulating layer 16. It is formed simultaneously with the data line 3 and the source / drain electrodes 9 and connected to the source / drain electrodes 9. In addition, a passivation layer 17 is formed over the entire first substrate 15. Although not shown in the figure, an alignment film for orienting liquid crystal molecules is coated on the protective layer 17.

The second substrate 30 has a black matrix 32 to prevent light from leaking into an image non-display area of the LCD, for example, a TFT area or a region between the pixel and the pixel, and to implement actual colors. A color filter layer 34 is formed, and a liquid crystal is injected between the first substrate 15 and the second substrate 30 to form a liquid crystal layer 20.

In the transverse electric field type liquid crystal display device having the above-described structure, when no voltage is applied between the common electrode 12 and the pixel electrode 14, liquid crystal molecules are formed on the first substrate 15 and the second substrate 30. Although oriented along the alignment direction of the alignment layer (not shown), when a voltage is applied between the common electrode 12 and the pixel electrode 14, an electric field formed between the common electrode 12 and the pixel electrode 14 Accordingly, the liquid crystal molecules are switched so that the liquid crystal molecules are arranged perpendicularly to the extending direction of the common electrode 12 and the pixel electrode 14. In this way, since the liquid crystal molecules in the liquid crystal layer 30 are always switched on the same plane, gray level inversion does not occur in the viewing angle directions in the vertical direction and the left and right directions, thereby improving the viewing angle characteristic.

However, there are disadvantages in the transverse field type LCD as described above. A common electrode and a pixel electrode of a general TN LCD are formed of transparent indium tin oxide (ITO), respectively, and are formed in a pixel region of a first substrate and a second substrate, whereas in a transverse field type LCD, the common electrode and the pixel electrode are opaque metal. It consists of and is arrange | positioned in the pixel. Therefore, the opaque common electrode and the pixel electrode block the light transmission of the pixel region, resulting in a decrease in the aperture ratio of the LCD.

In order to overcome this problem, a transverse field type LCD has been proposed that overcomes the decrease in aperture ratio by forming a common electrode disposed in a pixel with a transparent material such as ITO. However, the transverse field type LCD employing the transparent common electrode as described above may cause the following problems in the manufacturing process. In other words, in order to form a transparent common electrode, a photo process using a mask and a photoresist must be performed. However, a defect of the LCD occurs during the photo process.

FIG. 3 is a diagram illustrating a problem occurring when a transverse field type LCD employing a common transparent electrode is fabricated. In the drawings, the cross-sectional view taken along line B-B 'of FIG.

As shown in the figure, in order to form the common electrode 12, first, a transparent metal layer 12a such as ITO is laminated on the entire first substrate 15, and then the photoresist 41 is stacked thereon. Subsequently, the substrate 15 on which the photoresist 41 is stacked is mounted on the chuck 45 using a vehicle such as a robot arm. A plurality of vacuum holes 47 connected to a vacuum pump (not shown) are formed in the chuck 45 to fix the substrate 15 mounted thereon.

Subsequently, when light such as ultraviolet rays is irradiated from above in a state where the mask 43 is positioned on the substrate 15, light is irradiated only to the photoresist 41 in the region where the common electrode is to be formed. Thereafter, the common electrode 12 may be formed by developing the photoresist 41 and applying an etchant.

On the other hand, the light irradiated onto the substrate 15 through the mask 43 is transparent to the metal layer 12a, so that the entire substrate 15 is transmitted. A part of the transmitted light is reflected by the chuck 45 on which the substrate 15 is mounted, and then proceeds toward the substrate 15 again. At this time, the light reflected toward the substrate 15 proceeds to the photoresist 41 of the region where the common electrode 12 is to be formed, but also to the region where the common electrode 12 is not formed. This means that the photoresist 41 in the undesired area is affected by light. Accordingly, the photoresist 41 of the unwanted region (i.e., the region where the common electrode is not formed) is not completely removed by the developing process during the subsequent development of the photoresist 41, so that the chuck 45 is undesirably eventually. In the direction, the CD (Critical Dimension) different from the normal is deformed.

The metal layer 12a remaining in a region other than the common electrode 12 causes spots on the screen when the LCD is manufactured to produce an image, which acts as a fatal defect in the image quality of the LCD. Therefore, measures for removing staining are necessary.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and when forming a transparent common electrode of a transverse electric field type liquid crystal display device, an opaque metal layer is formed on the upper or lower portion of the transverse electric field type liquid crystal display device to block light reflected by the light during the exposure process. An object of the present invention is to provide a transverse electric field type liquid crystal display device and a method of manufacturing the same, which can prevent the image quality of the liquid crystal display device from deteriorating.

In order to achieve the above object, a method of manufacturing a transverse electric field type liquid crystal display device according to a first aspect of the present invention comprises the steps of laminating an opaque metal, a transparent metal and a photoresist on a substrate, and after placing a mask on the substrate Irradiating light to develop the photoresist and etching the opaque metal and the transparent metal to form a transparent common electrode on the gate electrode, the opaque metal layer and the opaque metal layer, and the gate over the substrate on which the gate electrode and the common electrode are formed. Forming a semiconductor layer in the gate electrode region on the gate insulating layer after laminating an insulating layer, forming a source / drain electrode and a pixel electrode on the semiconductor layer and the gate insulating layer, respectively, and protecting the entire substrate Laminating the layers.

In addition, according to the second aspect of the present invention, there is provided a method of manufacturing a transverse electric field type liquid crystal display device by laminating a transparent metal, an opaque metal, and a photoresist on a substrate, and placing a mask on the substrate to irradiate light. Developing a resist and etching a transparent metal and an opaque metal to form a gate electrode, a transparent common electrode, and an opaque metal layer disposed on the common electrode; removing the opaque metal layer disposed on the common electrode; And depositing a gate insulating layer over the entire substrate on which the common electrode is formed, and forming a semiconductor layer in the gate electrode region on the gate insulating layer, and source / drain electrodes and pixel electrodes on the semiconductor layer and the gate insulating layer, respectively. Forming and laminating a protective layer over the entire substrate.

The transverse electric field liquid crystal display device fabricated by the above method comprises a substrate, a plurality of gate lines and data lines arranged vertically and horizontally on the substrate, and defining a plurality of pixel regions, and substantially parallel to the gate lines in the pixel region. A common line arranged in parallel, a thin film transistor disposed in each pixel region, and at least one pair of pixels arranged in substantially parallel to the data lines in the pixel region to apply an electric field substantially parallel to the substrate as a signal is applied thereto. An electrode, a transparent common electrode, and an opaque metal layer disposed under the common electrode.

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

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

3 is a view showing that light is reflected on a chuck of an exposure apparatus during a manufacturing process of a conventional transverse electric field type liquid crystal display device so that light is irradiated to a photoresist layer in an unwanted region.

4 is a view showing a method of manufacturing a transverse electric field type liquid crystal display device according to an embodiment of the present invention.

5 is a view showing a method of manufacturing a transverse electric field type liquid crystal display device according to another embodiment of the present invention.

6 is a view showing another structure of the liquid crystal display device manufactured according to the transverse electric field type liquid crystal display device manufacturing method of the present invention.

** Explanation of symbols for main parts of drawings **

105,205,305: gate electrodes 107,207,307: semiconductor layer

109,209,309 Source / drain electrodes 112,212,312 Common electrodes

114,214,314: pixel electrode 115,215,315: substrate

116,216,316: gate insulating layer 117,217,317: protective layer

118,218,318: opaque metal layer

In the present invention, when the transparent common electrode of the transverse electric field type LCD is formed, the light irradiated to the photoresist is reflected by the chuck on which the substrate is mounted and is irradiated to the photoresist applied to a region other than the common electrode, thereby causing a poor image quality of the LCD. prevent. To this end, in the present invention, an opaque metal layer is formed below or above the common electrode to prevent the light irradiated onto the substrate from being transmitted to the chuck.

When the metal layer is formed on the common electrode, the metal layer is removed by an etching process, so that only the transparent common electrode remains in the final LCD. However, when the metal layer is formed below the common electrode, the metal layer cannot be removed, and thus remains in the final manufactured LCD. In this case, the aperture ratio decreases due to the metal layer, but since the thickness of the metal layer is much smaller than that of the general IPS LCD, the aperture ratio improvement effect in the thickness direction exists. In other words, when the opaque metal layer is formed under the transparent common electrode, the aperture ratio may be improved as compared with the general IPS LCD.

While the pixel electrode of the transverse electric field type LCD is formed in the same layer as the source / drain electrode of the TFT, the common electrode can be formed in any layer. For example, it may be formed on the same layer as the gate electrode of the TFT, may be formed on the same layer as the pixel electrode, or may be formed on the protective layer. In all such cases, by forming an opaque metal layer on the upper or lower portion of the common electrode as described above, it is possible to prevent image quality defects due to light reflection by the chuck.

Hereinafter, a manufacturing method and a structure of a transverse electric field LCD according to the present invention with reference to the accompanying drawings will be described in detail.

4 is a view showing a method of manufacturing a transverse electric field LCD according to an embodiment of the present invention. First, as shown in FIG. 4A, an opaque metal layer 105a such as Al, Al alloy, Mo, etc., a transparent metal layer 112a such as ITO or Indium Zinc Oxide (IZO) is formed on a transparent substrate 115 such as glass. And a photoresist layer 141 are laminated. Subsequently, the substrate on which the opaque metal layer 105a, the transparent metal layer 112a, and the photoresist layer 141 are stacked is transported and mounted on the chuck 145 using a robot arm (not shown), and then the substrate ( 115) Light such as ultraviolet rays is irradiated in a state where the mask 143 is positioned above.

The mask 143 is composed of a transmission region through which light passes and a non-transmission region through which light is blocked. The mask 143 is aligned so that the transmission region is positioned in a region where a gate electrode or a common electrode is to be formed. Light is irradiated to the photoresist layer 141 through the transmission region of the mask 143. At this time, the light irradiated to the photoresist layer 141 passes through the photoresist layer 141 and the transparent metal layer 112a, but is blocked by the opaque metal layer 105a and does not reach the chuck 145. Therefore, there is no light reflected by the chuck 145, and eventually light is irradiated only to the photoresist layer 141 in the desired region (i.e., the region corresponding to the transmissive region of the mask 143).

Subsequently, although not shown in the drawings, a developer is applied to the photoresist layer 141 to which light is irradiated to remove the photoresist layer 141 that is not irradiated with light, and then opaque metal layer 105a and transparent by an etchant. The metal layer 112a is etched to form the opaque metal patterns 105 and 118 and the transparent metal pattern 112 as shown in FIG. 4 (b). In this case, the opaque metal pattern 105 is a gate electrode, and a transparent metal layer is removed thereon by an etching process, but the transparent electrode 112 serving as a common electrode remains on the opaque metal pattern 118.

As described above, the gate insulating layer 116 such as SiNx or SiOx is formed on the entire substrate 115 on which the gate electrode 105 and the common electrode 112 are formed, and then the gate is formed. The semiconductor layer 107, the source / drain electrodes 109, and the pixel electrodes 114 are formed in the electrode 105 region. The semiconductor layer 107 may be made of polycrystalline silicon, but is preferably formed by laminating and etching amorphous silicon by a chemical vapor deposition (CVD) method. Although not shown in the figure, an n ⁺ amorphous silicon is stacked on the semiconductor layer 107 or an ohmic contact layer doped with n ⁺ impurities is formed on the semiconductor layer 107. The source / drain electrodes 109 and the pixel electrodes 114 are formed by laminating metals such as Al, Al alloys, Cr, Ti, and the like and then performing photoetching.

Subsequently, as shown in FIG. 4 (d), the TFT array substrate, which is the lower panel of the LCD, is completed by laminating the protective layer 117 over the entire substrate 115. The protective layer 117 is made of an inorganic material such as SiNx or SiOx, but may be formed of an organic material such as benzocyclobutene (BCB) or photoacryl to improve the planarization of the film and to improve the aperture ratio. It can also be configured as.

Although not shown in the drawings, the TFT array substrate formed as described above is bonded to the color filter substrate on which the color filter and the black matrix are formed with the liquid crystal layer interposed therebetween to produce a transverse electric field type LCD.

In the transverse electric field type liquid crystal display device fabricated by the above process, when forming the common electrode 112 made of transparent ITO, an opaque metal layer is positioned below the reflection by the chuck of the exposure equipment that may occur during light irradiation. Can be prevented. However, in the transverse field type LCD manufactured by the above method, as illustrated in FIG. 4D, an opaque metal layer 118 is positioned below the transparent common electrode 112. In general, when the common electrode of the transverse electric field type LCD is formed of an opaque metal, the reduction of the aperture ratio depends mainly on the width of the opaque common electrode, but also the thickness of the common electrode. Since the width of the opaque metal layer 118 shown in FIG. 4D is almost the same as that of the upper common electrode, the improvement of the opening ratio due to the width of the metal layer 118 is difficult to expect. However, since the thickness of the metal layer 105b can be formed much smaller than the thickness of the opaque common electrode, the effect of improving the aperture ratio in the thickness direction can be obtained. In other words, in the transverse electric field type LCD formed by the above method, a predetermined aperture ratio effect can be obtained and the image quality can be prevented from being lowered.

However, it is also true that the maximum aperture ratio improvement effect cannot be obtained in the transverse electric field type LCD manufactured by this method. Therefore, there is a need for a method of manufacturing a transverse electric field LCD that can prevent degradation of image quality and at the same time obtain the maximum aperture ratio improvement effect, which is illustrated in FIG.

The manufacturing method shown in FIG. 5 is very similar to the method shown in FIG. Therefore, the detailed description thereof will be omitted and specific manufacturing methods will be described based only on the differences.

As shown in FIG. 5A, a metal is stacked and etched on a transparent substrate 215 such as glass to form a gate electrode 205. Thereafter, the ITO 212a, the opaque metal layer 218a, and the photoresist layer 241 are formed over the entire substrate 215 on which the gate electrode 205 is formed, and then a mask 243 is placed on the substrate 215. Irradiate light such as ultraviolet rays in the positioned state.

The process differs from the process of FIG. 4A in that the opaque metal layer and ITO are successively formed in FIG. 4A, whereas in this embodiment, the gate electrode 205 is first formed, and then ITO (ITO) is formed on the substrate. That is, the transparent metal layer 212a and the opaque metal layer 218a are sequentially formed. That is, the timing of forming the gate electrode and the stacking order of the transparent metal layer 212a and the opaque metal layer 218a are different. As described above, even when the stacking order of the transparent metal layer 212a and the opaque metal layer 218a is different, the irradiated light is blocked by the opaque electrode 218a and thus does not reach the chuck of the exposure apparatus. The same effect as in the previous method can be obtained.

Subsequently, when the photoresist development process and the metal layer etching process are performed, as shown in FIG. 5B, the transparent common electrode 212 and the opaque metal layer 218 thereon are formed on the substrate 215. Is formed. Subsequently, as shown in FIG. 5C, the opaque metal layer 218 on the common electrode 212 is removed, and the gate electrode 205 is formed after the gate insulating layer 216 is formed over the entire substrate 215. TFTs of the transverse electric field type LCD by forming the semiconductor layer 207 and the source / drain electrodes in the region), and then laminating the protective layer 217 over the entire substrate 215 as shown in FIG. Complete the array substrate.

As described above, in this embodiment, the opaque metal layer 218 is formed on the transparent common electrode 212 to block ultraviolet rays, but since the metal layer 218 is finally removed, the opaque metal layer in the finished LCD 218 will not remain. Therefore, light is irradiated onto the photoresist of an undesired area to prevent degradation of the image quality of the LCD and at the same time to maximize the aperture ratio improvement effect.

Meanwhile, in the above embodiments, a transparent common electrode made of ITO is formed on the same layer as the substrate, that is, the gate electrode. However, the present invention is not limited to the transverse electric field LCD of this specific structure, but can be applied to the transverse electric field LCD of all structures.

For example, the present invention may be applied to a transverse field type LCD having a structure in which the common electrode 312 is formed on the passivation layer 317, as shown in FIGS. 6A and 6B. 6 (a) illustrates the formation of the opaque metal layer 318 under the transparent common electrode 312, and FIG. 6 (b) illustrates the formation of the opaque metal layer 318 on the transparent common electrode 312. Drawing.

In addition, the common electrode and the pixel electrode can also be applied to a transverse electric field LCD formed on the protective layer. FIG. 7 illustrates a transverse electric field LCD having such a structure. FIG. 7A illustrates an LCD in which an opaque metal layer 418 is formed under a transparent common electrode 412. FIG. 7B illustrates an opaque display. A metal layer is formed on the transparent common electrode 412 to show the LCD is removed. In this case, reference numeral 414 denotes a pixel electrode, which is formed on the passivation layer 417.

In addition, although not shown in the drawings, the present invention may be applied to a transverse field type LCD having a common electrode formed on the same layer as the pixel electrode. In this case, the opaque metal layer may be made of a metal different from the pixel electrode, but it is preferable that the opaque metal layer is made of the same material as the pixel electrode and formed by the same process.

Therefore, the method and structure to which the present invention is applied are not limited to the transverse electric field type liquid crystal display device having a specific structure but may be applied to the liquid crystal display device having all possible structures. Therefore, the scope of the present invention should not be determined by the above detailed description, but should be determined by the appended claims.

As described above, since the transverse electric field type liquid crystal display device of the present invention uses a transparent material such as ITO as a common electrode, the aperture ratio of the liquid crystal display device is greatly improved. In addition, in the present invention, when forming the common electrode, by forming an opaque metal layer on the upper or lower portion of the common electrode to block the light traveling to the chuck of the exposure equipment during the exposure process, the light reflected by the chuck is a photo of the area where the unwanted Irradiation to the resist layer makes it possible to prevent the formation of unwanted metal layers in the pixel region.

Claims (16)

Forming a plurality of gate lines and data lines defining pixel regions on the substrate and thin film transistors disposed in the pixel regions, respectively; Sequentially forming an opaque metal, a transparent metal, and a photoresist in each pixel region on the substrate; Placing a mask on the substrate and irradiating light to develop photoresist and etching the opaque metal and the transparent metal to form a transparent common electrode on the opaque metal layer and the opaque metal layer arranged substantially parallel to the data line. step; And And forming a protective layer over the entire substrate after forming the pixel electrodes arranged in parallel with the common electrode. The method of claim 1, wherein the forming of the thin film transistor comprises: Forming a gate electrode on the substrate; Forming a gate insulating layer over the entire substrate on which the gate electrode is formed; Forming a semiconductor layer in a gate electrode region on the gate insulating layer; And Forming a source / drain electrode on the semiconductor layer. The method of claim 1, wherein the transparent metal layer is formed of a material selected from the group consisting of indium tin oxide (ITO) and indium zinc oxide (IZO). The method of claim 1, wherein the step of laminating the opaque metal and the transparent metal, Depositing an opaque metal on the substrate; And Laminating a transparent metal on the opaque metal. The method of claim 4, wherein forming the gate electrode of the thin film transistor comprises etching the opaque metal. The method of claim 1, wherein the step of laminating the opaque metal and the transparent metal, Depositing an opaque metal on the gate insulating layer; And Laminating a transparent metal on the opaque metal. 7. The method of claim 6, wherein forming the source / drain electrodes of the thin film transistor comprises etching the opaque metal. The method of claim 1, wherein the step of laminating the opaque metal and the transparent metal, Depositing an opaque metal on the protective layer; And Laminating a transparent metal on the opaque metal. Forming a plurality of gate lines and data lines defining pixel regions on the substrate and thin film transistors disposed in the pixel regions, respectively; Stacking a transparent metal, an opaque metal and a photoresist in each pixel area on the substrate; After placing a mask on the substrate, light is irradiated to develop a photoresist, and the transparent metal and the opaque metal are etched to form a transparent common electrode arranged substantially parallel to the data line and an opaque metal layer disposed on the common electrode. Doing; Removing the opaque metal layer disposed on the common electrode; And Forming a pixel electrode arranged substantially parallel to the common electrode, and then laminating a protective layer over the entire substrate. Board; A plurality of gate lines and data lines arranged vertically and horizontally on the substrate to define a plurality of pixel regions; A common line arranged substantially parallel to a gate line in the pixel area; A thin film transistor disposed in each pixel region; At least a pair of pixel electrodes and a transparent common electrode arranged in substantially parallel to the data lines in the pixel area and applying an electric field substantially parallel to the substrate as a signal is applied; And A transverse electric field liquid crystal display device comprising an opaque metal layer disposed under the common electrode. The method of claim 10, wherein the thin film transistor, A gate electrode formed on the substrate; A gate insulating layer stacked over the entire substrate on which the gate electrode is formed; A semiconductor layer formed in the gate electrode area on the gate insulating layer; A source / drain electrode formed on the semiconductor layer; And And a protective layer stacked over the entire substrate. The liquid crystal display of claim 10, wherein the common electrode is made of a material selected from the group consisting of ITO and IZO, and is connected to the common line. 12. The liquid crystal display device according to claim 11, wherein the pixel electrode is disposed on the gate insulating layer. The liquid crystal display of claim 11, wherein the pixel electrode is disposed on the passivation layer. The liquid crystal display device of claim 11, wherein the opaque metal layer and the common electrode are disposed on the gate insulating layer. The liquid crystal display device of claim 11, wherein the opaque metal layer and the common electrode are disposed on the passivation layer.