KR20060006154A - Liquid crystal display device and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a liquid crystal display device. According to an exemplary embodiment of the present invention, a liquid crystal display device includes a first substrate on which a thin film transistor is formed, a second substrate facing the first substrate, and the first and second substrates, and has a predetermined pretilt angle. And a twisted nematic (TN) mode liquid crystal layer, wherein the first substrate includes a pixel electrode layer, a reverse signal line for applying an electric field in a direction opposite to the pretilt angle to the liquid crystal layer, and on the pixel electrode layer along the reverse signal line. And a dielectric rib having a dielectric constant different from that of the liquid crystal layer. As a result, the generation of the foreground line caused by the reverse signal line can be suppressed, and the aperture ratio is improved.

Description

Liquid crystal display and its manufacturing method {LIQUID CRYSTAL DISPLAY DEVICE AND METHOD OF MANUFACTURING THE SAME}

1 is a layout view of a thin film transistor substrate according to an embodiment of the present invention,

2 is a cross-sectional view of a liquid crystal panel according to an embodiment of the present invention according to II-II of FIG.

3A and 3B are diagrams illustrating that the dielectric rib of the present invention suppresses generation of foreground lines.

4A to 4C are cross-sectional views illustrating a method of manufacturing a thin film transistor substrate according to an exemplary embodiment of the present invention.

Explanation of Signs of Major Parts of Drawings

171: pixel electrode layer 191: dielectric rib 300: liquid crystal layer

The present invention relates to a liquid crystal display device and a manufacturing method thereof. More particularly, the present invention relates to a liquid crystal display device and a method of manufacturing the same, in which a dielectric rib having a different dielectric constant from a liquid crystal layer is formed on a pixel electrode layer to suppress generation of foreground lines.

The liquid crystal display device includes a thin film transistor substrate on which a thin film transistor is formed, a color filter substrate on which a color filter layer is formed, and a liquid crystal panel on which a liquid crystal layer is positioned. Since the liquid crystal panel is a non-light emitting device, a backlight unit for irradiating light may be disposed on the rear surface of the thin film transistor substrate. Light transmitted from the backlight unit is controlled according to the arrangement of the liquid crystal layer.

In addition, in order to drive each pixel of the liquid crystal panel, a driving circuit, and a data driver and a gate driver for receiving a driving signal from the driving circuit and applying a signal to data lines and gate lines in the display area are provided.

In the TN (twisted nematic) mode liquid crystal layer, which is generally used in large-area high-definition liquid crystal displays, the orientation of liquid crystal molecules is uniaxial orientation of liquid crystal molecules by the uniaxial stretching method of the alignment layer, and free of alignment of the liquid crystal molecules with the alignment layer. It can be expressed as a tilt angle.

The rubbing method used as a means for performing a uniaxial stretching treatment on an alignment film is a simple method of rubbing a substrate coated with a polymer with a cloth.

However, in the case of using such a TN mode liquid crystal layer, some of the gate lines and the data lines form a side electrode electric field with the pixel electrode layer in one pixel, causing the adjacent liquid crystal layer to behave in the opposite direction to the pretilt angle. The gate line and the data line causing the above behavior change depending on the rubbing direction. Specifically, the liquid crystal molecules are arranged in parallel with the electric field, and the liquid crystal layer adjacent to the side electric field formed between the gate line or the data line and the pixel electrode layer is arranged in a direction opposite to the pretilt angle. The liquid crystal layer regions arranged in the opposite direction are called reverse tilt domains or reverse domains. The reverse domain is located parallel to the gate line or the data line. The liquid crystal layer between the liquid crystal layer and the reverse domain, which behaves in the pretilt angle direction, does not control the arrangement of liquid crystal molecules even when an electric field is applied, causing light leakage. This is called a foreground line.

Conventionally, in order to solve this problem, a method of shielding foreground lines using a black matrix on a color filter substrate has been used. The aperture ratio refers to the ratio of the area where information can be displayed in the entire screen area. This method has a problem of lowering the aperture ratio.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a method of manufacturing the same in which the aperture ratio is improved by suppressing generation of foreground lines caused by side electric fields between gate lines or data lines and the pixel electrode layer.

The above object is a TN (twisted) having a predetermined pretilt angle between a first substrate on which a thin film transistor is formed, a second substrate facing the first substrate, and the first and second substrates. A liquid crystal display device comprising a nematic mode liquid crystal layer, wherein the first substrate comprises a pixel electrode layer, a reverse signal line applying an electric field in a direction opposite to the pretilt angle, and the reverse signal line along the reverse signal line. It can be achieved by including a dielectric rib formed on the pixel electrode layer and having a dielectric constant different from that of the liquid crystal layer.

Preferably, the second substrate further includes a color filter layer, and the color filter layer is formed on the second substrate corresponding to the dielectric rib.

Preferably, the first substrate and the second substrate further include polarizing plates having polarization directions perpendicular to each other.

According to another aspect of the present invention, in the method of manufacturing a liquid crystal display device including a TN mode liquid crystal layer positioned above the pixel electrode layer and having a predetermined pretilt angle, a thin film transistor is formed on a substrate material. Forming a protective film on the thin film transistor, forming the pixel electrode layer on the protective film, and forming a dielectric rib on the pixel electrode layer having a dielectric constant different from that of the liquid crystal layer. The dielectric rib may be formed along a reverse signal line applying an electric field in a direction opposite to the pretilt angle to the liquid crystal layer.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. In the following, a film is formed (located) on top of another film, not only when two films are in contact with each other but also when another film is between two layers. It also includes the case where it exists. In the following, the signal line refers to the gate line and the data line together.

1 is a layout view of a thin film transistor substrate according to an embodiment of the present invention, Figure 2 is a cross-sectional view of a liquid crystal panel according to an embodiment of the present invention according to II-II of Figure 1, Figures 3a and 3b is a dielectric of the present invention It is a figure explaining that a rib suppresses generation of a foreground line.

The liquid crystal panel 10 according to the exemplary embodiment of the present invention includes a thin film transistor substrate 100, a color filter substrate 200 facing the thin film transistor substrate, and a liquid crystal layer 300 positioned therebetween.

Although not shown, the LCD further includes a liquid crystal panel 10, a backlight unit positioned on the rear surface of the thin film transistor substrate 100, a driving circuit, an external casing, and the like.

First, the thin film transistor substrate 100 will be described. For convenience, the pixel illustrated in FIG. 1 will be described.

Gate wirings 121a, 121b, 122, and 123 are formed on the first substrate material 110. The gate wirings 121a, 121b, 122, and 123 may be a metal single layer or multiple layers. The gate lines 121a, 121b, 122, and 123 include gate lines 121a and 121b extending in the horizontal direction and gate electrodes 122 of the thin film transistors connected to the gate lines 121a and 121b. Here, the gate pad 123 positioned outside the display area is one end of the gate lines 121a and 121b, and the width thereof is extended for connection with an external circuit.

On the first substrate material 110, a gate insulating film 141 made of silicon nitride (SiNx) or the like covers the gate wirings 121a, 121b, 122, and 123.

A semiconductor layer 142 made of a semiconductor such as amorphous silicon is formed on the gate insulating layer 141 of the gate electrode 122, and n + having a high concentration of silicide or n-type impurities is formed on the semiconductor layer 142. An ohmic contact layer 143 made of a material such as hydrogenated amorphous silicon is formed. The ohmic contact layer 143 is divided into two parts around the gate electrode 122.

Data wires 131a, 131b, 132, 133, and 134 are formed on the ohmic contact layer 143 and the gate insulating layer 141. The data lines 131a, 131b, 132, 133, and 134 may also be a single layer or multiple layers of metal layers. The data wires 131a, 131b, 132, 133, and 134 are formed in the vertical direction and intersect with the gate lines 121a and 121b to define the pixels to define the pixels, and the branches of the data lines 131a and 131b. And separated from the source electrode 132 and the source electrode 132 extending to the upper portion of the ohmic contact layer 143, and the upper portion of the ohmic contact layer 143 opposite to the source electrode 132 with respect to the gate electrode 122. It includes a drain electrode 133 formed in the. Here, the data pad 134 positioned outside the display area is one end of the data lines 131a and 131b, and the width of the data pad 134 is extended for connection with an external circuit.

On top of the data lines 131a, 131b, 132, 133, and 134 and the semiconductor layer 142 which is not covered, silicon nitride, an a-Si: C: O film deposited by a plasma-enhanced chemical vapor deposition (PECVD) method, or A protective film 151 made of an a-Si: O: F film, an acrylic organic insulating film, and the like is formed. The passivation layer 151 is provided with contact holes 181 and 183 exposing the drain electrode 133 and the data pad 134, respectively, and the contact hole 182 exposing the gate pad 123 together with the gate insulating layer 141. Also formed.                     

The pixel electrode layer 171 is formed on the passivation layer 151. The pixel electrode layer 171 is usually made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

A dielectric rib 191 is formed on the pixel electrode layer 171 along the gate line 121b and the data line 131b. The dielectric rib 191 is formed in contact with the liquid crystal layer 300 at the edge region of the pixel electrode layer 171 and has a rectangular cross section.

Next, the color filter substrate 200 will be described.

Black matrices 221 and 222 are formed on the second substrate material 210. The black matrix 221 positioned on the top of the thin film transistor serves to block direct light irradiation to the thin film transistor. Amorphous silicon thin film transistor is because light leakage current easily flows by light. The black matrix 222 positioned above the data line 131b distinguishes between red, green, and blue filters. The black matrices 221 and 222 may include a photosensitive organic material to which a black pigment is added. As the black pigment, carbon black or titanium oxide is used.

The color filter layer 231 is formed by repeating red, green, and blue filters with the black matrices 221 and 222 as a boundary. The color filter layer 231 serves to impart color to light emitted from the backlight unit (not shown) and passed through the liquid crystal layer 300. The color filter layer 231 generally includes a photosensitive organic material.

An overcoat layer 241 is formed on the black matrices 221 and 222 not covered by the color filter layer 231 and the color filter layer 231. The overcoat layer 241 serves to protect the color filter layer 231 while planarizing the color filter layer 231, and an acrylic epoxy material is generally used.

The common electrode layer 251 is formed on the overcoat layer 241. The common electrode layer 251 is made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The common electrode layer 251 directly applies a voltage to the liquid crystal layer 300 together with the pixel electrode layer 171 of the thin film transistor substrate.

The liquid crystal layer 300 is positioned between the thin film transistor substrate 100 and the color filter substrate 200. The liquid crystal layer 300 is a twist nematic (TN) mode, and the liquid crystal molecules are twisted 90 degrees between the thin film transistor substrate 100 and the color filter substrate 200. Although not shown, the alignment layers rubbed in the direction perpendicular to each other are positioned on the pixel electrode layer 171 and the common electrode layer 251, respectively. In addition, the liquid crystal layer 300 has a predetermined pretilt angle between the alignment layers in the direction of the rubbing.

Hereinafter, the formation position and function of the dielectric rib 191 will be described.

When the alignment layer of the thin film transistor substrate 100 is rubbed at an angle of 135 degrees in the direction shown in FIG. 1, the liquid crystal layer 300 between the data lines 131a and 131b will be taken as an example. Of course, at this time, the alignment layer of the color filter substrate 200 is rubbed in the 45-degree direction to form 90-degree.                     

When there is no dielectric rib 191, the arrangement of the liquid crystal molecules of the liquid crystal layer 300 to which the voltage is applied to the pixel electrode 171 and the common electrode layer 251 is as shown in FIG. 3A. Most of the liquid crystal layer 300 including a portion adjacent to the data line 131a positioned on the left side of the pixel is in the vertical electric field direction 401 between the pixel electrode 171 and the common electrode layer 251, and also in the direction of the pretilt angle. Are arranged. A side electric field 402a is formed between the left data line 131a and the pixel electrode 171, but acts in the same direction as the pretilt angle direction of the liquid crystal molecules. In contrast, the side electric field 402b formed between the data line 131b on the right side and the pixel electrode 171 arranges adjacent liquid crystal molecules in a direction opposite to the pretilt direction. The liquid crystal layers C arranged in the opposite direction are called reverse domains. In this case, the liquid crystal layer A between the liquid crystal layer and the reverse domain arranged in the pretilt direction does not control the arrangement of the liquid crystal molecules even when an electric field is applied, resulting in a foreground line in which light leakage occurs. Although only the data line 131b is given as an example, the foreground line is similarly generated in the liquid crystal layer 300 adjacent to the gate line 121b. As described above, in the present exemplary embodiment, the reverse signal line for generating the foreground line is the data line 131b positioned on the right side of the pixel and the gate line 121b positioned below.

Therefore, the dielectric rib 191 for suppressing the generation of the foreground line is formed along the reverse signal lines 121b and 131b in which the foreground line is generated. 3B is a schematic diagram illustrating that the foreground line generated along the data line 131b is removed by the dielectric rib 191. When the dielectric ribs 191 having a different dielectric constant from the liquid crystal layer 300 are positioned on the pixel electrode layer 171, the existing vertical electric field 401 is distorted to generate a diagonal electric field 403. This diagonal electric field 403 cancels the side electric field 402b between the data line 131b and the pixel electrode layer 171. Therefore, the occurrence of the reverse domain and the foreground line is suppressed.

Since the foreground lines by the reverse signal lines 121b and 131b and the light leakage due to the foreground lines are suppressed, the black matrix region B formed to prevent light leakage is removed, and the color filter layer 231 is positioned instead to increase the aperture ratio.

Here, the thin film transistor substrate 100 and the color filter substrate 200 each have a polarizing plate, the polarization direction is preferably a NW (normally white) mode orthogonal to each other. On the contrary, since the polarization direction is parallel and the NB mode is normally generated in the foreground, the contrast ratio decrease is not large, and thus it is not necessary to cover the black matrix 222.

The above embodiment may be variously modified. For example, the formation position of the dielectric rib 191 may vary depending on the rubbing direction. Specifically, the angle is maintained at 145 degrees and when the rubbing direction is opposite to that of FIG. 1, the reverse signal line becomes the gate line 121a and the data line 131a. The cross-sectional shape of the dielectric rib 191 may be various, such as trapezoidal or semicircle, and may not be continuous. In particular, the present invention can be applied to a multi-domain mode for a wide viewing angle.

Hereinafter, a method of manufacturing the thin film transistor substrate 100 according to the embodiment of the present invention will be described.                     

4A to 4C are cross-sectional views illustrating a method of manufacturing the thin film transistor substrate 100 according to the embodiment of the present invention.

First, a thin film transistor and a data line 131b are formed on the first substrate material 110 as shown in FIG. 4A. The detailed process is as follows.

After depositing a gate metal layer on the first substrate material 110 and patterning it by a photolithography process using a mask, the gate wiring including the gate lines 121a and 121b, the gate electrode 122, the gate pad 123, and the like. (121a, 121b, 122, 123) are formed. Next, three layers of the gate insulating layer 141, the semiconductor layer 142, and the ohmic contact layer 143 are sequentially stacked, and the semiconductor layer 142 and the ohmic contact layer 143 are photo-etched to form an upper portion of the gate electrode 122. An island-shaped semiconductor layer 142 and an ohmic contact layer 143 are formed on the gate insulating layer 141. Next, after depositing the data metal layer, the pattern is patterned by a photolithography process using a mask to be connected to the data lines 131a and 131b and the data lines 131a and 131b that intersect the gate line 121 to form an upper portion of the gate electrode 122. Data lines 131a, 131b, 132, 133, and 134 including a source electrode 132 extending to and a drain electrode 133 facing the same are formed. Subsequently, the ohmic contact layer 143 that is not covered by the data wires 131a, 132b, 133, and 134 is etched to be separated from both sides of the gate electrode 122, and the semiconductor layer 142 is exposed. In order to stabilize the surface of the exposed semiconductor layer 142, it is preferable to perform an oxygen plasma.

Next, as shown in FIG. 4B, the passivation layer 151 is formed and the pixel electrode layer 171 is formed. The pixel electrode layer 171 is in contact with the drain electrode 133 through the contact hole 181. The pixel electrode layer 171 is formed by depositing a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) by sputtering or the like.

Finally, as shown in FIG. 4C, a dielectric rib 191 is formed on the pixel electrode layer 171. The dielectric rib 191 is positioned in the edge region of the pixel electrode layer 171 and is formed along the reverse signal lines 121b and 131b. This process is described in detail as follows. When the dielectric rib 191 is a negative photosensitive resin, the dielectric rib 191 is first coated, and then only a portion where the dielectric rib 191 is to be formed is irradiated with ultraviolet rays using a mask. Subsequently, when developed, the region not irradiated with ultraviolet rays is dissolved and removed by the developer.

Looking at the manufacturing method of the color filter substrate 200 as follows.

First, black matrices 221 and 222 are formed on the second substrate material 210. The black matrices 221 and 222 may be made of a photosensitive material to which black pigments are added, and are completed by applying, developing and baking. In this case, since the black matrix 222 formed on the reverse signal lines 121b and 131b of the thin film transistor substrate 100 does not need to consider the foreground line, the black matrix 222 is narrowly formed so as to cover only the reverse signal lines 121b and 131b. Thereafter, the color filter layer 231 is formed, and the color filter layer 231 is alternately formed with red, green, and blue filters for each pixel. Conventionally, the color filter layer 231 is also formed in the region B where the black matrix 222 that prevents light leakage due to the foreground line is to be located.

When the color filter layer 231 is completed, the overcoat layer 241 is formed to planarize the color filter layer 231 and protect the color filter layer 231. When the common electrode layer 251 is deposited on the overcoat layer 241 by sputtering or the like, the color filter substrate 200 is completed.

In forming the thin film transistor substrate 100 and the color filter substrate 200, a process of forming an alignment layer on the pixel electrode layer 171 and the common electrode layer 251 is added. The alignment direction of each alignment film is 90 degrees mutually. The reverse signal lines 121b and 131b change according to the rubbing direction of the alignment layer, and thus the position of formation of the dielectric rib 191 also changes.

According to the present invention, the area that is shielded by the black matrix 222 due to the foreground line, that is, the portion where the dielectric rib 191 is positioned in the embodiment of the present invention becomes a pixel area, thereby improving the aperture ratio.

As described above, according to the present invention, there is provided a liquid crystal display device and a method of manufacturing the same, in which generation of foreground lines due to side electric fields between signal lines and pixel electrode layers is suppressed.

Claims (4)

A twisted nematic (TN) mode liquid crystal having a predetermined pretilt angle between the first substrate on which the thin film transistor is formed, the second substrate facing the first substrate, and the first and second substrates. A liquid crystal display comprising a layer, The first substrate, A pixel electrode layer, A reverse signal line for applying an electric field opposite to the pretilt angle to the liquid crystal layer; And a dielectric rib formed on the pixel electrode layer along the reverse signal line and having a dielectric constant different from that of the liquid crystal layer. The method of claim 1, The second substrate further includes a color filter layer, And the color filter layer is formed on the second substrate corresponding to the dielectric rib. The method of claim 1, And the first and second substrates further include polarizing plates having polarization directions perpendicular to each other. In the manufacturing method of a liquid crystal display device comprising a TN mode liquid crystal layer positioned on the pixel electrode layer and having a predetermined pretilt angle, Forming a thin film transistor on the substrate material; Forming a passivation layer on the thin film transistor; Forming the pixel electrode layer on the passivation layer; Forming a dielectric rib on the pixel electrode layer having a dielectric constant different from that of the liquid crystal layer; And the dielectric rib is formed along a reverse signal line applying an electric field in a direction opposite to the pretilt angle to the liquid crystal layer.

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