KR100991542B1 - liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device capable of improving the contrast ratio.

Light leakage may occur in a portion of the contact hole not covered by the black matrix, which degrades the contrast ratio of the liquid crystal display device and degrades image quality.

In the liquid crystal display according to the present invention, the drain electrode structure of the portion where the contact hole is formed may be changed so that the region where light leakage occurs is located below the black matrix, thereby blocking light leakage and improving the contrast ratio. Moreover, since the structure of a black matrix is not changed, the fall of an aperture ratio can be prevented.

Description

Liquid crystal display device             

1 is a schematic plan view of a conventional liquid crystal display device.

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

3 is a cross-sectional view taken along line III-III of FIG. 2.

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

FIG. 5 is a cross-sectional view taken along the line IV-IV of FIG. 4. FIG.

<Description of Symbols for Main Parts of Drawings>

112: gate wiring 114: gate electrode

122: active layer 132: data wiring

134: source electrode 136: drain electrode

152: contact hole 162: pixel electrode

192: black matrix

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of improving contrast ratio.

In general, a liquid crystal display device is formed by arranging two substrates having electrodes formed on one surface thereof so that the surfaces on which the two electrodes are formed face each other, injecting a liquid crystal material between the two substrates, and then applying a voltage to the two electrodes. By moving the liquid crystal molecules by an electric field, the device expresses an image by the transmittance of light that varies accordingly.

A liquid crystal display may have various forms. Currently, an active matrix liquid crystal display (AM-LCD) having a thin film transistor and pixel electrodes connected to the thin film transistors arranged in a matrix manner has excellent resolution and video performance. It is most noticed.

The liquid crystal display device has a structure in which pixel electrodes are formed on a lower array substrate, and a common electrode is formed on a color filter substrate, which is an upper substrate, and drives liquid crystal molecules by an electric field perpendicular to a substrate that is vertically stretched. to be. This is excellent in characteristics such as transmittance and aperture ratio, and the common electrode of the upper plate serves as a ground, thereby preventing the destruction of the liquid crystal cell due to static electricity.

The upper substrate of the liquid crystal display device further includes a black matrix to prevent light leakage occurring in portions other than the pixel electrode.

Hereinafter, a conventional liquid crystal display device will be described with reference to the accompanying drawings.                         

1 is a schematic plan view of a conventional liquid crystal display device, wherein the liquid crystal display device includes an upper substrate, a lower substrate, and a liquid crystal layer disposed therebetween. As shown in FIG. 1, a gate wiring 12 and a data wiring 32 are formed on a lower substrate (not shown), and the gate wiring 12 and the data wiring 32 cross each other to form a pixel region P. FIG. ). The thin film transistor T is formed at the intersection of the gate wiring 12 and the data wiring 32. The thin film transistor T includes a gate electrode 14 extending from the gate wiring 12, a source electrode 34 extending from the data wiring 32, and a drain electrode 36 spaced apart from the source electrode 34. Include. In addition, the thin film transistor T includes an active layer 22 between the gate electrode 14 and the source and drain electrodes 34 and 36.

The exposed active layer 22 between the source and drain electrodes 34 and 36 becomes a channel of the thin film transistor T. The wider the channel and the shorter the channel, the better the electrical characteristics of the thin film transistor T. . Therefore, the channel may be formed in a “U” shape so that the width of the channel becomes wider, thereby improving the characteristics of the thin film transistor T.

The source and drain electrodes 34 and 36 are covered with a protective layer (not shown), which has a contact hole 52 exposing the drain electrode 36. Next, the pixel electrode 62 is formed in the pixel area P above the passivation layer, and is connected to the drain electrode 36 through the contact hole 52.

Here, the extension part 22a extending from the active layer 22 protrudes into the pixel region P. The extension part 22a partially overlaps the drain electrode 36 and is partially exposed without overlapping. The extension part 22a serves to prevent the pixel electrode 62 from being cut off at the portion where the contact hole 52 is formed due to the steps of the lower layers. In addition, to prevent the pixel electrode 62 from being disconnected, the contact hole 52 includes one side of the drain electrode 36 and is formed to be positioned on the exposed extension part 22a.

On the other hand, a black matrix 90 is formed on the inner surface of the upper substrate (not shown) facing the lower substrate. The black matrix 90 corresponds to the gate wiring 12, the data wiring 32, and the thin film transistor T, and is formed to cover the edge of the pixel electrode 62. Here, the black matrix 90 is formed to cover a part of the drain electrode 34 and the active layer extension part 22a and a part of the contact hole 52. Therefore, a part of the active layer extension part 22a and the part A of the contact hole 52 positioned in the pixel area P are not covered by the black matrix 90.

The data line 32 and the source and drain electrodes 34 and 36 may be formed of molybdenum (Mo), and such molybdenum may be removed when dry etching the protective layer to form the contact hole 52. Accordingly, as shown in FIG. 1, the drain electrode 36 corresponding to the contact hole 52 is removed. Since the portion is not covered by the black matrix 90, light leaks from this portion when the LCD is driven. do. In addition, a disclination occurs in a portion corresponding to the active layer extension part 22a, but is not covered with the black matrix 90, which causes light leakage.

As such, light leakage occurs in the area A corresponding to the contact hole 52 and the active layer extension portion 22a which are not covered by the black matrix 90, which is the contrast ratio of the liquid crystal display. Decreases the image quality. The black matrix 90 may cover this portion to prevent light leakage, but there is a problem that the aperture ratio is lowered.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a liquid crystal display device which can prevent light leakage and improve the aperture ratio and contrast ratio.

According to an aspect of the present invention, a liquid crystal display device includes: first and second substrates spaced apart from each other; gate wirings and data wirings formed on the inner surface of the first substrate and crossing each other to define pixel regions; A gate electrode connected to the gate wiring, a source electrode connected to the data wiring, a drain electrode spaced apart from the source electrode, and a gate electrode, a source, and a drain formed at an intersection point of the gate wiring and the data wiring; A thin film transistor including an active layer disposed between electrodes, a protective layer including a contact hole covering the thin film transistor and exposing the drain electrode, and a drain layer formed in a pixel area above the protective layer and through the contact hole. A pixel electrode in contact with the second electrode, the inner surface of the second substrate A black matrix exposing a pixel electrode, and a common electrode formed on the black matrix and facing the pixel electrode, wherein the active layer extends into the pixel area and partially overlaps the drain electrode; The contact hole is located in the first extension, the pixel electrode is in top contact with the first extension, and the black matrix covers the first extension.

The contact hole may include one side of the drain electrode.

The exposed active layer between the source and drain electrodes may be a channel of the thin film transistor, and the channel may have a “U” shape.

The source and drain electrodes may be formed of molybdenum, and the drain electrode corresponding to the contact hole may be removed, and the pixel electrode may be in side contact with the drain electrode.

The active layer may further include a second extension part extending below the data line.

Another liquid crystal display device according to the present invention includes first and second substrates spaced apart from each other, and gate wirings and data wirings formed on the inner surface of the first substrate and crossing each other to define pixel regions, and the gate wirings and data wirings. A gate electrode connected to the gate wiring, a source electrode connected to the data wiring, a drain electrode spaced apart from the source electrode, and an active electrode positioned between the gate electrode and the source and drain electrodes A thin film transistor including a layer, a protective layer including a contact hole covering the thin film transistor and exposing the drain electrode, a pixel electrode formed in a pixel area above the protective layer and contacting the drain electrode through the contact hole; It is formed on the inner surface of the second substrate, and exposes the pixel electrode A black matrix and a common electrode formed on the black matrix and facing the pixel electrode, wherein the active layer includes a first extension part extending to the pixel area and partially overlapping the drain electrode; An electrode includes a protrusion corresponding to the first extension, the pixel electrode is in top contact with the first extension, and the contact hole is located in the first extension.

The black matrix may expose the first extension part and the contact hole.

In addition, the contact hole may include one side of the drain electrode.

In example embodiments, the source and drain electrodes may be formed of molybdenum, and the drain electrode corresponding to the contact hole may be removed, and the pixel electrode may be in side contact with the drain electrode.

As described above, according to the present invention, the contrast ratio may be improved by preventing light leakage that may occur in the pixel area, thereby improving the image quality of the liquid crystal display.

Hereinafter, an array substrate for a liquid crystal display device and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic plan view of a liquid crystal display according to a first exemplary embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2.

2 and 3, the gate wiring 112 and the gate electrode 114 are formed of a metal-like material on the transparent first substrate 110. The gate wiring 112 is formed in the horizontal direction, and the gate electrode 112 extends from the gate wiring 114.

A gate insulating film 120 made of a silicon nitride film or a silicon oxide film is formed on the gate wiring 112 and the gate electrode 114 to cover them.

Next, an active layer 122 made of pure amorphous silicon is formed on the gate insulating layer 120, and an ohmic contact layer 124 made of amorphous silicon doped with impurities is formed thereon. Meanwhile, first and second extension portions 122a and 122b made of pure amorphous silicon and extending from the active layer 122 are formed.

The data line 132 and the source and drain electrodes 134 and 136 are formed on the ohmic contact layer 124 using a material such as a metal. The data line 132 is formed in the vertical direction, and defines the pixel region P orthogonal to the gate line 112. The source electrode 134 extends from the data line 132, and the drain electrode 136 is separated from the source electrode 134. The source and drain electrodes 136 form a thin film transistor T together with the gate electrode 114 and the active layer 122, and the exposed active layer 122 between the source and drain electrodes 136 is a thin film transistor ( It becomes the channel of T). The source electrode 134 has a “U” shape, and the drain electrode 136 includes a first portion extending in the horizontal direction and a second portion connected to a pixel electrode to be formed later. One end of the drain electrode 136 is surrounded by the source electrode 134 so that the channel of the thin film transistor T has a “U” shape. Since the “U” shape lengthens the length of the channel, the electrical characteristics of the thin film transistor T may be improved.

Here, the first extension part 122a of the active layer protrudes into the pixel region P, but partially overlaps with the drain electrode 136 and is partially exposed without overlapping. In addition, the second extension part 122b extends in the vertical direction and is located under the data line 132. In the present invention, the first extension portion 122a of the active layer and the second portion of the drain electrode 136 are formed to be adjacent to the gate wiring 112.

Next, a passivation layer 150 is formed on the data line 132 and the source and drain electrodes 134 and 136 to cover them, and the passivation layer 150 exposes a portion of the drain electrode 136. ) The contact hole 152 includes one side of the drain electrode 135 to prevent disconnection of the pixel electrode, and is formed to be positioned on the first extension 122a of the active layer. In this case, the protective layer 150 is patterned by a dry etching method to form the contact hole 152. When the drain electrode 136 is formed of molybdenum, the drain electrode 136 is also etched. Accordingly, a part of the drain electrode 136 corresponding to the contact hole 152 is also removed to expose the lower active layer first extension part 122a.

Next, a pixel electrode 162 made of a transparent conductive material is formed in the pixel area P on the passivation layer 150. The pixel electrode 162 is connected to the drain electrode 136 through the contact hole 152 and overlaps the gate wiring 112 of the front end to form a storage capacitor. In this case, since the drain electrode 136 corresponding to the contact hole 152 is removed, the pixel electrode 162 is in side contact with the drain electrode 136.

Meanwhile, a transparent second substrate 190 spaced apart from the first substrate 110 is disposed on the first substrate 110, and a black matrix 192 is formed on an inner surface of the second substrate 190. . The upper portion of the black matrix 192 is made of a transparent conductive material, and a common electrode 194 facing the pixel electrode 162 is formed. Although not shown, a color filter layer is positioned between the black matrix 192 and the common electrode 194, and the color filter layers are sequentially formed of red, green, and blue subcolor filters, and each subcolor filter includes one pixel electrode ( 162).

The black matrix 192 has an opening corresponding to the pixel region P, and corresponds to the gate wiring 112, the data wiring 132, and the thin film transistor T to cover the edge of the pixel electrode 162. Is formed. In addition, since the first extension part 122a and the drain electrode 136 of the active layer are formed adjacent to the gate wiring 112, the black matrix 192 has the same size as before, but the first of the active layer Not only the extension 122a and the drain electrode 136, but also the contact hole 152 positioned on the first extension 122a is covered. Therefore, even if light leakage occurs in the contact hole 152 from which the drain electrode 136 is removed and the portion B where the first extension part 122a of the active layer is located, the light leakage is blocked by the black matrix 192 to prevent the light leakage. . In addition, since the black matrix 192 has the same size as before, it is possible to prevent the aperture ratio from being lowered.

In the present invention, since the contact hole where the light leakage occurs and the corresponding extension of the active layer are located under the black matrix without changing the structure and size of the black matrix, the reduction of the aperture ratio is prevented and the contrast ratio is about 5%. You can improve the degree.

4 is a schematic plan view of a liquid crystal display according to a second exemplary embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along line IV-IV of FIG. 4.                     

As shown in FIGS. 4 and 5, the gate wiring 212 and the gate electrode 214 are formed of an opaque conductive material such as metal on the transparent first substrate 210. The gate wiring 212 is formed in the horizontal direction, and the gate electrode 212 extends from the gate wiring 214. In addition, a protrusion 214a extending from the gate electrode 214 is formed on the first substrate 210.

A gate insulating film 220 made of a silicon nitride film or a silicon oxide film is formed on the gate wiring 212 and the gate electrode 214 to cover them.

Next, an active layer 222 made of pure amorphous silicon is formed on the gate insulating layer 220, and an ohmic contact layer 224 made of amorphous silicon doped with impurities is formed thereon. Meanwhile, first and second extension portions 222a and 222b made of pure amorphous silicon and extending from the active layer 222 are formed.

The data line 232 and the source and drain electrodes 234 and 236 are formed of an opaque conductive material such as metal on the ohmic contact layer 224. The data line 232 is formed in the vertical direction and defines the pixel region P orthogonal to the gate line 212. The source electrode 234 extends from the data line 232, and the drain electrode 236 is separated from the source electrode 234 on the gate electrode 214. The source and drain electrodes 236 form a thin film transistor T together with the gate electrode 214 and the active layer 222, and the exposed active layer 222 between the source and drain electrodes 236 is a thin film transistor ( It becomes the channel of T). The source electrode 234 has a “U” shape, and the drain electrode 236 includes a first portion extending in the horizontal direction and a second portion connected to a pixel electrode to be formed later. One end of the drain electrode 236 is surrounded by the source electrode 234 so that the channel of the thin film transistor T has a “U” shape. The “U” shape increases the width of the channel, thereby improving the electrical characteristics of the thin film transistor T.

Here, the first extension part 222a of the active layer protrudes into the pixel area P. The first extension part 222a overlaps the protrusion part 214a of the lower gate electrode and is positioned on the protrusion part 214a. In addition, the first extension part 222a partially overlaps the drain electrode 236 and is partially exposed without overlapping. Meanwhile, the second extension part 222b extends in the vertical direction and is located under the data line 232.

Next, a passivation layer 250 is formed on the data line 232 and the source and drain electrodes 234 and 236 to cover them, and the passivation layer 250 exposes a portion of the drain electrode 236. ) The contact hole 252 includes one side of the drain electrode 235 to prevent disconnection of the pixel electrode, and is formed to be positioned on the first extension part 222a of the active layer. In this case, the protective layer 250 is patterned by a dry etching method to form the contact hole 252. When the drain electrode 236 is formed of molybdenum, the drain electrode 236 is also etched. Accordingly, a portion of the drain electrode 236 corresponding to the contact hole 252 is also removed to expose the lower active layer first extension part 222a.

Next, a pixel electrode 262 made of a transparent conductive material is formed in the pixel area P above the passivation layer 250. The pixel electrode 262 is connected to the drain electrode 236 through the contact hole 252, and overlaps the gate wiring 212 at the front end to form a storage capacitor. In this case, since the drain electrode 236 corresponding to the contact hole 252 is removed, the pixel electrode 262 is in side contact with the drain electrode 236.

Meanwhile, a transparent second substrate 290 is spaced apart from the first substrate 210 on the first substrate 210, and a black matrix 292 is formed on an inner surface of the second substrate 290. . The common electrode 294 formed of a transparent conductive material and facing the pixel electrode 262 is formed on the black matrix 292. Although not shown, a color filter layer is positioned between the black matrix 292 and the common electrode 294. The color filter layer includes red, green, and blue sub-color filters sequentially formed, and each sub-color filter includes one pixel electrode ( 262).

The black matrix 292 has an opening corresponding to the pixel region P, and corresponds to the gate wiring 212, the data wiring 232, and the thin film transistor T to cover the edge of the pixel electrode 262. Is formed. Here, the black matrix 292 has the same size as before, and a portion of the first extension part 222a and the contact hole 252 of the active layer is exposed without being covered by the black matrix 292.

In the second embodiment of the present invention, the contact hole 252 from which the drain electrode 236 is removed and the portion C where the first extension part 222a of the active layer is located are not covered with the black matrix 292. Since the gate electrode protrusion 214a made of an opaque conductive material is formed to correspond to this portion C as a light blocking layer, even if light leakage occurs in this portion C, it is blocked by the protrusion 214a and is not visible. . When the light leakage portion C is blocked by the black matrix 292 on the second substrate 290, the area of the black matrix 292 should be larger than the actual light leakage region C in consideration of the bonding margin. Therefore, the aperture ratio is further lowered. However, as in the second embodiment of the present invention, when the light leakage region is covered by the gate electrode protrusion 214a, the area of the protrusion 214a may be formed so as to correspond only to the light leakage region C, and thus the black matrix 292 It is possible to prevent lowering of the aperture ratio than in the case of). In the present invention, a case in which the protrusion 214a is connected to the gate electrode 214 has been described. However, the protrusion 214a may be formed in a pattern separated from the gate electrode 214 to serve as a light blocking layer. .

As described above, in the present invention, light leakage can be prevented to improve the contrast ratio, and a decrease in the aperture ratio can be prevented.

The present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit of the present invention.

In the liquid crystal display according to the present invention, the light leakage may be located under the black matrix to block light leakage and improve the contrast ratio. Moreover, since the structure of a black matrix is not changed, the fall of an aperture ratio can be prevented. In the present invention, a stable and improved production yield can be obtained by forming a channel of the thin film transistor in a “U” shape.

Claims (11)

First and second substrates spaced apart from each other; Gate wirings and data wirings formed on an inner surface of the first substrate and crossing each other to define a pixel region; A gate electrode connected to the gate wiring, a source electrode connected to the data wiring, a drain electrode spaced apart from the source electrode, and a gate electrode, a source, and a drain formed at an intersection point of the gate wiring and the data wiring; A thin film transistor including an active layer between the electrodes; A protective layer covering the thin film transistor and including a contact hole exposing the drain electrode; A pixel electrode formed in the pixel area above the protective layer and contacting the drain electrode through the contact hole; A black matrix formed on an inner surface of the second substrate and exposing the pixel electrode; And A common electrode formed on the black matrix and facing the pixel electrode Including; The active layer includes a first extension part extending to the pixel area and partially overlapping the drain electrode, wherein the contact hole is located in the first extension part. The pixel electrode is in top contact with the first extension part, And the black matrix covers the first extension part. The method of claim 1, The contact hole includes a side surface of the drain electrode. The method of claim 1, The exposed active layer between the source and drain electrodes becomes a channel of the thin film transistor, and the channel has a “U” shape. The method of claim 1, And the source and drain electrodes are formed of molybdenum, and the drain electrode corresponding to the contact hole is removed. The method of claim 4, wherein And the pixel electrode is in side contact with the drain electrode. The method of claim 1, The active layer further includes a second extension part extending below the data line. First and second substrates spaced apart from each other; Gate wirings and data wirings formed on an inner surface of the first substrate and crossing each other to define a pixel region; A gate electrode connected to the gate wiring, a source electrode connected to the data wiring, a drain electrode spaced apart from the source electrode, and a gate electrode, a source, and a drain formed at an intersection point of the gate wiring and the data wiring; A thin film transistor including an active layer between the electrodes; A protective layer covering the thin film transistor and including a contact hole exposing the drain electrode; A pixel electrode formed in the pixel area above the protective layer and contacting the drain electrode through the contact hole; A black matrix formed on an inner surface of the second substrate and exposing the pixel electrode; And A common electrode formed on the black matrix and facing the pixel electrode Including; The active layer includes a first extension part extending to the pixel area and partially overlapping the drain electrode; The electrode includes a protrusion corresponding to the first extension portion, The pixel electrode is in top contact with the first extension part, And the contact hole is located in the first extension part. The method of claim 7, wherein The black matrix liquid crystal display exposes the first extension part and the contact hole. The method of claim 7, wherein The contact hole includes a side surface of the drain electrode. The method of claim 7, wherein And the source and drain electrodes are formed of molybdenum, and the drain electrode corresponding to the contact hole is removed. The method of claim 10, And the pixel electrode is in side contact with the drain electrode.

Images