KR100876404B1 - Transverse electric field mode liquid crystal display device - Google Patents

Abstract

The transverse electric field mode liquid crystal display device of the present invention comprises a plurality of gate lines and data lines defining a plurality of pixels, a thin film transistor disposed in each pixel, a pattern formed in the pixel, and formed on the pattern and being substantially parallel to each other. It is composed of at least a pair of electrodes arranged so as to generate a transverse electric field. The electrode has side surfaces facing each other as the common electrode and the pixel electrode, and the height of the electrode is increased by a pattern formed by etching of the gate insulating layer or the protective layer. You will be able to create an electric field.

Description

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

1 is a view showing the structure of a conventional transverse electric field mode liquid crystal display device, in which FIG. 1 (a) is planar and FIG. 1 (b) is a sectional view taken along the line II 'of FIG.

2 is a cross-sectional view showing the structure of a transverse electric field mode liquid crystal display device according to a first embodiment of the present invention.

3 is a cross-sectional view showing the structure of a transverse electric field mode liquid crystal display device according to a second embodiment of the present invention.

4 is a cross-sectional view showing the structure of a transverse electric field mode liquid crystal display device according to a third embodiment of the present invention.

5 is a cross-sectional view showing the structure of a transverse electric field mode liquid crystal display device according to a fourth embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

120,220,320,420: substrate 105,205,305,405: common electrode

107,207,307,407: Pixel electrode 111,211,311,411: Gate electrode

113,213,313,413 Source electrodes 114,214,314,414 Drain electrodes

122,222,322,422: Gate insulating layer 123,223,225,323,423,425: Insulation pattern                 

326,426: metal layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transverse electric field mode liquid crystal display device. In particular, a lower pattern is formed by removing a portion of a gate insulating layer or a protective layer, and then a common electrode and a pixel electrode are formed thereon to form a sloped electrode structure. The present invention relates to a transverse electric field mode liquid crystal display device which can reduce power consumption by increasing the intensity of the transverse electric field generated between the and the pixel electrodes.

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), and VFD (Vacuum Fluorescent Display). Liquid crystal display devices (LCDs) are in the spotlight for reasons of implementation.

Such liquid crystal display devices have various display modes according to the arrangement of liquid crystal molecules. However, TN mode liquid crystal display devices are 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 oriented horizontally with respect to 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 IPS 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.

FIG. 1 is a view showing the structure of a conventional IPS mode liquid crystal display device, in which FIG. 1 (a) is a plan view and FIG. 1 (b) is a sectional view taken along line II ′ of FIG. 1 (a). As shown in FIG. 1A, the 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, the actual liquid crystal panel 1 has N (> n) and M (> m) gate lines 3 and data lines 4, respectively. Are arranged so as to form N × M pixels over the entire liquid crystal panel 1. 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 the middle 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 IPS 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.

The conventional IPS mode liquid crystal display device having the above structure will be described in more detail with reference to the cross-sectional view of FIG.

As shown in FIG. 1B, 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 are formed on the first substrate 20, and a pixel electrode 7 and a data line 4 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.

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 conventional IPS mode liquid crystal display device, the common electrode 5 and the pixel electrode 7 are formed on the first substrate 20 and the gate insulating layer 22 to generate a transverse electric field. Typically, since the common electrode 5 and the pixel electrode 7 are formed to have a thickness of about 1 to 2 μm, a high voltage is applied to the pixel electrode 7 in order to apply a uniform transverse electric field across the entire liquid crystal layer 40. Must be applied). However, in this case, the power consumption of the IPS mode liquid crystal display device is increased, the increase of the power consumption in the liquid crystal display device mainly used in mobile devices such as mobile phones or laptops is a fatal weakness for the convenience of the device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and a part of the gate insulating layer or the protective layer is removed to form a common electrode and a pixel electrode on a tapered pattern to increase the height of the common electrode and the pixel electrode and face each other. An object of the present invention is to provide a transverse electric field mode liquid crystal display device capable of minimizing power consumption.

In order to achieve the above object, the transverse electric field mode liquid crystal display device according to the present invention comprises a plurality of gate lines and data lines defining a plurality of pixels, a thin film transistor disposed in each pixel, a pattern formed in the pixel, It is formed on the pattern and consists of at least a pair of electrodes arranged substantially parallel to generate a transverse electric field.

The pattern is formed by etching a gate insulating layer or a protective layer, and has a tapered inclined surface. Accordingly, the electrodes formed to have a predetermined thickness from the surface of the pattern, that is, the common electrode and the pixel electrode face each other. In addition, the pattern may be formed of a metal layer and an insulating layer.

The present invention provides an IPS mode liquid crystal display device that can reduce power consumption. In the IPS mode liquid crystal display device, power consumption is related to the transverse electric field generated in the liquid crystal layer. That is, the power consumption of the IPS mode liquid crystal display device is determined according to the magnitude of the voltage applied to generate a uniform transverse electric field throughout the liquid crystal layer. Therefore, in the case of an IPS mode liquid crystal display device in which a uniform lateral electric field is generated in the entire liquid crystal layer only when a high voltage is applied, power consumption increases, and even a low lateral voltage is generated in the entire liquid crystal layer. In the case of the IPS mode liquid crystal display device, power consumption is reduced.

Based on the above point of view, in the present invention, even when a low voltage is applied, power consumption is reduced by increasing the generation region of the transverse electric field, that is, the driving region of the liquid crystal molecules, in the liquid crystal layer. Particularly, in the present invention, the height of the common electrode and the pixel electrode is higher than that of the conventional IPS mode, so that a transverse electric field of a predetermined size is applied to the upper part of the liquid crystal layer, and the inclined surface facing the common electrode and the pixel electrode is formed to be uniform to the lower part of the liquid crystal layer. Allow a magnitude electric field to be applied.

Meanwhile, the present invention is not limited to the IPS mode liquid crystal display device having a specific structure. In general, in the liquid crystal display of the IPS mode, light is transmitted to a region between the common electrode and the pixel electrode. The transmission region depends on the number of formations of the common electrode and the pixel electrode, which is typically represented by a block. For example, in the IPS mode LCD shown in FIG. 1A, three common electrodes and two pixel electrodes are formed, respectively, and four light transmitting regions through which light is transmitted are formed. As such, the IPS mode liquid crystal display device having four transmission regions is generally referred to as a four-block liquid crystal display device. These names are used for convenience of description only and are not intended to limit the specific structure of the liquid crystal display device.

The IPS mode liquid crystal display device of the present invention may be applied to not only 4-block, 6-block or 8-block IPS mode liquid crystal display devices, but also all liquid crystal display devices. In the following description, the IPS mode liquid crystal display device of a specific block is described, but this is for convenience of description and does not limit the structure of the IPS mode liquid crystal display device of the present invention.

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

2 is a view showing the structure of an IPS mode liquid crystal display device according to a first embodiment of the present invention. As shown in the drawing, a thin film transistor, a plurality of common electrodes 105 and a pixel electrode 107 are disposed on the first substrate 120 made of a transparent material such as glass. The thin film transistor includes a gate electrode 111 formed on the first substrate 120, a gate insulating layer 122 formed on the gate electrode, a semiconductor layer 112 formed on the gate insulating layer 122, and the semiconductor layer. The source electrode 113 and the drain electrode 114 formed on the 112 are formed, and the passivation layer 124 is formed on the thin film transistor.

A portion of the gate insulating layer 122 other than the thin film transistor region is etched to form an insulating pattern 123 having a predetermined width on the first substrate 120. As shown in the figure, since the insulating pattern 123 is tapered, the side surface thereof is inclined.

As described above, the common electrode 105 and the pixel electrode 107 are formed on the tapered insulating pattern 123. Since the common electrode 105 and the pixel electrode 107 are not formed only on the upper surface of the insulating pattern 123, but are formed to have a predetermined thickness on the tapered inclined side, the common electrode 105 and the pixel electrode ( 107 completely surrounds the insulating pattern 123. The common electrode 105 and the pixel electrode 107 may be formed by different processes, but it may be formed by the same process to simplify the process. In this case, the common electrode 105 and the pixel electrode 107 are formed by the same process as the source electrode 113 and the drain electrode 114 of the thin film transistor, Cr, Mo, Ta, Cu, Ti, Al or A metal, such as an Al alloy, is deposited by evaporation or sputtering, and then consists of a single layer or a plurality of layers etched using an etchant.

In this case, since the insulating layer of the thin film transistor is formed to have a thickness of about 0.3 μm, the insulating pattern 123 below the common electrode 105 and the pixel electrode 107 also has a thickness of about 0.3 μm. This means that the height of the common electrode 105 and the pixel electrode 107 of the IPS mode liquid crystal display device according to the present invention is increased by about 0.3 μm, compared to the conventional IPS mode liquid crystal display device. Therefore, when the same voltage as the conventional IPS mode liquid crystal display device is applied, it means that a stronger transverse electric field is applied to the upper part of the liquid crystal layer, that is, near the second substrate on which the color filter layer is formed. In addition, this means that even when a voltage lower than that of the conventional IPS mode liquid crystal display is applied, a transverse electric field is generated near the second substrate.

On the other hand, since the insulating pattern 123 has an inclined side surface, the common electrode 105 and the pixel electrode 107 formed on the insulating pattern 123 also have an inclined side surface. The inclined side surfaces of the common electrode 105 and the pixel electrode 107 face each other, and as a result, a transverse electric field can be smoothly applied to the lower portion of the liquid crystal layer, that is, near the first substrate 120.

As described above, in the IPS mode liquid crystal display device according to the present invention, the common electrode 105 and the pixel electrode 107 are formed on the insulating pattern 123 formed by etching the gate insulating layer 122 to generate a transverse electric field. Since the height of the electrode is increased while the inclined surface of the electrode is opposed, a uniform transverse electric field can be generated over the entire liquid crystal layer even at a low applied voltage. Accordingly, power consumption of the IPS mode liquid crystal display device can be reduced.                     

Meanwhile, although only the structure of the first substrate 120 is illustrated in FIG. 2, the first substrate 120 is bonded to the second substrate on which the color filter layer and the black matrix are formed, and a liquid crystal layer is formed therebetween. .

3 is a view showing the structure of an IPS mode liquid crystal display device according to a second embodiment of the present invention. The IPS mode liquid crystal display device shown in the drawing has the same structure as the IPS mode liquid crystal display device shown in FIG. 2 except for the structures of the common electrode 205 and the pixel electrode 207. Therefore, the description of the same structure will be omitted, and only the common electrode 205 and the pixel electrode 207 will be described.

As shown in the figure, the gate insulating layer 222 and the protective layer 224 of the region except for the thin film transistor region (that is, the region in which the transverse electric field is formed and the screen is displayed) are partially removed and formed as two layers. Insulation patterns 223 and 225 are formed. The insulating patterns 223 and 225 are formed by simultaneously etching the stacked gate insulating layer 222 and the protective layer 224.

Since the insulating patterns 223 and 225 are also tapered, the insulating patterns 223 and 225 have inclined side surfaces, and a common electrode 205 and a pixel electrode 207 are formed thereon. The common electrode 205 and the pixel electrode 207 may be formed by other processes. However, the common electrode 205 and the pixel electrode 207 may be formed by the same process to simplify the process.

Since the gate insulating layer 222 of the thin film transistor is formed to have a thickness of about 0.3 μm and the protective layer 224 is formed to have a thickness of about 0.2 μm, the two-layered insulating patterns 223 and 225 have a thickness of about 0.5 μm. Therefore, the common electrode 205 and the pixel electrode 207 of the IPS mode liquid crystal display device according to the present invention have a thickness about 0.5 μm higher than that of the common electrode and the pixel electrode of the conventional IPS mode liquid crystal display device. Incidentally, the inclined side surfaces of the common electrode 205 and the pixel electrode 207 face each other. Therefore, in the IPS mode liquid crystal display device of the present invention, even a small voltage can generate a uniform transverse electric field across the entire liquid crystal layer.

4 is a view showing the structure of an IPS mode liquid crystal display device according to a third embodiment of the present invention. As shown in the figure, in the IPS mode liquid crystal display device of this embodiment, the common electrode 305 and the pixel electrode 307 are formed on the patterns 323 and 326 formed on the first substrate 320. In this case, the first pattern 323 is formed by etching the gate insulating layer 322 of the thin film transistor, and the second pattern 326 is a metal layer. That is, the IPS mode liquid crystal display device of this embodiment has the same structure as the liquid crystal display device shown in FIG. 2 except for the metal layer 326. The height of the common electrode 305 and the pixel electrode 307 is increased by the metal layer 236 than the height of the common electrode and the pixel electrode shown in FIG. 2, so that a uniform transverse electric field is applied to the entire liquid crystal layer even with a smaller voltage. It can be formed. In addition, since the metal layer 326 is in electrical contact with the common electrode 305 and the pixel electrode 307, the signal is not blocked even when the common electrode 305 and the pixel electrode 307 are disconnected. It can be prevented from occurring.

Although the IPS mode liquid crystal display device of the structure of this embodiment appears to have a more complicated structure than the IPS mode liquid crystal display device shown in Fig. 2, the actual manufacturing process is simple. That is, since the metal layer 326 is made of the same metal as the source electrode 313 and the drain electrode 314 of the thin film transistor, the metal layer 326 can be formed during the thin film transistor process.

5 is a diagram illustrating a structure of an IPS mode liquid crystal display device according to a fourth exemplary embodiment of the present invention. In the IPS mode liquid crystal display device shown in FIG. 4, the metal layers 426 are formed on the insulating patterns 423 and 425. The higher common electrode 405 and the pixel electrode 407 are formed. At this time, the same effect as in FIG. 4 can be obtained.

Meanwhile, although the metal layer is formed under the insulating layer in the patterns of FIGS. 4 and 5, the metal layer may be formed under the insulating layer and the insulating layer may be formed thereon. That is, a metal layer may be formed on the first substrate, and an insulating layer may be formed thereon. At this time, the metal layer is preferably formed by the same process as the gate electrode of the thin film transistor for simplicity of the process.

As described above, in the IPS mode liquid crystal display device of the present invention, a portion of the insulating layer of the image display area is removed to form a tapered insulating pattern, and a common electrode and a pixel electrode are formed by laminating metal on the insulating pattern. Therefore, the heights of the common electrode and the pixel electrode increase and the inclined side surfaces face each other. As a result, even when a voltage smaller than the voltage applied by the conventional IPS mode liquid crystal display device is applied, a uniform transverse electric field is generated over the entire liquid crystal layer, thereby reducing power consumption of the IPS mode liquid crystal display device.

Claims (17)

A plurality of gate lines and data lines formed on the substrate to define a plurality of pixels; A gate electrode formed in each pixel, a plurality of gate insulating layers formed on a substrate, parallel to each other along the data lines in the pixels at a predetermined width, and a semiconductor layer formed on the gate insulating layer over the gate electrodes; A thin film transistor comprising a source electrode and a drain electrode formed on the semiconductor layer, and a protective layer formed on the source electrode and the drain electrode; A metal layer formed on the plurality of gate insulating layers formed in the pixel in parallel with the data lines; And At least one pair of common and pixel electrodes formed on the metal layer and on the side of the gate insulating layer and the metal layer to form an electric field substantially parallel to the substrate, And the common electrode and the pixel electrode are electrically connected to each other to transmit a signal when a break occurs in the common electrode or the pixel electrode. The transverse electric field mode liquid crystal display of claim 1, wherein the gate insulating layer and the metal layer thereon are tapered. delete delete delete delete delete The transverse electric field mode liquid crystal display device of claim 1, wherein the metal layer is formed of the same metal as the source electrode and the drain electrode of the thin film transistor. The transverse electric field mode liquid crystal display device of claim 1, wherein the protective layer is formed between the gate insulating layer and the metal layer. delete delete delete delete delete delete delete delete

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