KR20030058165A - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device capable of stabilizing a liquid crystal domain, comprising: a gate wiring and a data wiring defining a first pixel and a second substrate, each unit pixel region crossing each other on the first substrate; A thin film transistor connected to the data line and configured to switch a video signal on the gate line, a pixel electrode connected to the thin film transistor and having a rectangular shape to transmit light, and a lower portion of the second substrate; And a black matrix formed on the substrate, a color filter corresponding to each pixel area, and a common electrode formed under the color filter.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of stabilizing the liquid crystal domain.

Recently, display devices are also required to be lighter and thinner in accordance with lighter and thinner personal computers, televisions, and the like, and according to such demands, flat panel displays such as liquid crystal displays (LCDs) instead of cathode ray tubes (CRTs) are required. Is being developed and put into practical use in various fields.

A liquid crystal display (hereinafter, LCD) applies an electric field to liquid crystal molecules having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to adjust the amount of light transmitted through the substrate to obtain a desired image signal. It is a display device. Such LCDs are typical of portable flat panel display devices. Among them, TFT-LCDs using thin film transistors (TFTs) as switching elements are mainly used.

The LCD has a structure in which a pixel electrode is formed on a lower substrate and a common electrode is formed on an upper substrate, and the liquid crystal molecules are driven by an electric field perpendicular to the substrate applied between the two electrodes.

At this time, since the liquid crystal molecules are rod-shaped, the refractive index and the dielectric constant of the long axis and the short axis are different from each other. Accordingly, the refractive indices are different depending on the direction in which the liquid crystal molecules are viewed, resulting in a difference in viewing angle between the front and the side views of the screen. Therefore, in order to solve this problem, conventionally, a slit is formed on the upper plate even in one unit pixel, and the liquid crystal driving electrode of the lower plate is formed in a slit shape, thereby forming a double domain when forming an electric field. That is, when the electric field is formed between the pixel electrode and the common electrode, the direction in which the liquid crystal molecules are distorted is changed to compensate for the anisotropy of the long and short axes of the liquid crystal molecules.

Hereinafter, a liquid crystal display of a conventional vertical alignment mode will be briefly described with reference to the accompanying drawings.

As shown in FIG. 1, on the array substrate 10 of the conventional liquid crystal display device, a plurality of gate lines 11 transmitting scan signals and a plurality of data intersecting the gate lines 11 transmit image signals. A switching element 13 formed in an area surrounded by the line 12 and the gate line 11 and the data line 12 and connected to the respective gate lines and the data lines, and connected to the switching element 13. And a pixel electrode 15 which responds to the operation of the switching element. In this case, the pixel electrode 15 is a pixel electrode patterned to have a plurality of slits 15a, and forms an electric field to drive the liquid crystal. 25 is a low dielectric film formed on the common electrode described below.

Next, as shown in FIG. 2, in the conventional color filter substrate 20 for a liquid crystal display, the black matrix 21 has an opening 21a at a portion corresponding to the pixel electrode 15 of FIG. 1. And a color filter 22 having red, green, and blue colors, so that one color corresponds to one opening 21a. Although not shown, the color filter substrate forms a transparent common electrode on the entire surface of the substrate, and a protrusion-like low dielectric film 25 corresponding to each of the pixel electrodes 15 is formed on the common electrode between the slit 15a patterns.

3 is a cross-sectional view when the array substrate 10 and the color filter substrate 20 are disposed, which corresponds to a cross section taken along the line VV ′ of FIGS. 1 and 2. Here, the drawings are described with reference to the pixel electrode formed on the array substrate, the common electrode formed on the color filter substrate, and the liquid crystal alignment, and the rest of the configuration is omitted.

As shown, a pixel electrode 15 having a slit 15a shape is provided on an array substrate (not shown), and a projection shape is formed on a common electrode 24 on a color filter substrate (not shown) opposite thereto. A low dielectric film 25 having a structure is formed. In this case, the low dielectric film 25 on the color filter substrate is formed at an intermediate position between the slits 15a formed on the pixel electrode 15, and the liquid crystal layer 30 vertically aligned between the array substrate and the color filter substrate. Is interposed. The liquid crystal layer 30 is arranged in the liquid crystal molecules perpendicular to the substrate under the influence of the vertical alignment layer. At this time, some liquid crystal molecules are arranged in a vertical direction with respect to the surface under the influence of the low dielectric film 25.

On the other hand, when a predetermined voltage is applied between the pixel electrode 15 and the common electrode 24, as shown in FIG. A normal electric field is formed, and the electric field is distorted by the slit 15a pattern, so that the liquid crystal molecules are arranged perpendicular to the electric field. As a result, a multi-domain that is symmetrical with respect to the vertex of the low dielectric film 24 is formed.

However, the conventional liquid crystal display has the following problems.

The electric field distortion for forming the multi-domain is symmetrically by the low dielectric film 24 and the slit 15a pattern. However, when the liquid crystal display device having the above structure is driven using the existing asymmetric switching element 13, Inconsistency in the electric field distortion caused by the asymmetrical portion of the switching element 13 occurred.

That is, FIG. 5 shows a micrograph in halftone, and it can be seen that an inconsistency in the liquid crystal domain occurs due to an inconsistency in the electric field distortion phenomenon around the switching element 13.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of forming a stable multi-domain by forming a switching element on the gate wiring.

1 is a layout diagram of a conventional array substrate for a liquid crystal display device.

2 is a layout diagram of a conventional color filter substrate for a liquid crystal display device.

3 and 4 are cross-sectional views of the combination of Figs.

5 is a micrograph in halftone.

6 is a layout diagram illustrating a liquid crystal display device according to an exemplary embodiment of the present invention.

7, 8A, 9A, 10, and 11 are layout views illustrating various embodiments using the structure of FIG. 6.

8B is a sectional view of FIG. 8A.

9B is a sectional view of FIG. 9A;

Explanation of symbols on the main parts of the drawings

30 array board 31 gate wiring

34 semiconductor layer 40 data wiring

41 source electrode 42 drain electrode

45: contact hole 47: protective layer

50: pixel electrode 50a: uneven portion

51, 52, 90: Slit pattern 54: Peripheral electrode

60: liquid crystal layer 70: color filter substrate

72: black matrix 72a: opening

73: color filter 74: overcoat film

75 common electrode 80 slit or low dielectric film

82, 92: low dielectric film T: thin film transistor

According to an aspect of the present invention, there is provided a liquid crystal display device including: a first wiring, a second wiring, a gate wiring and a data wiring crossing each other on the first substrate to define respective unit pixel regions; A thin film transistor connected to the thin film transistor formed on the gate line to switch a video signal, a pixel electrode connected to the thin film transistor, and configured to have a rectangular shape for transmitting light, and a black matrix formed under the second substrate; And a color filter corresponding to each pixel area and a common electrode formed under the color filter.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

6 is a layout for explaining a liquid crystal display according to an exemplary embodiment of the present invention, and FIGS. 7, 8A, 9A, 10, and 11 are layouts for describing various embodiments using the structure of FIG. 6. 8B is a sectional view of FIG. 8A, and FIG. 9B is a sectional view of FIG. 9A.

First, as shown in FIG. 6, an array substrate 30 for a liquid crystal display device, which is a transparent glass substrate, is provided. A plurality of gate wirings 31 are formed on the substrate 30 in the horizontal direction, and one side of the gate wiring 31 is concave without forming a gate electrode extending from the gate wiring 31 as before. do. Next, although not shown in the figure, an insulating film is formed over the entire surface of the substrate 30 on which the gate wiring 31 is formed.

Next, a semiconductor layer 34 that defines a thin film transistor formation region is formed on the insulating film. The semiconductor layer 34 generally forms an amorphous silicon film, and then performs an ohmic contact with a subsequent data line and an etch preventing role during formation of an extended drain and source electrode in the data line. Is doped to include an ohmic contact layer 34b formed on the surface of the amorphous silicon film.

Next, a plurality of data lines 40 are formed on the semiconductor layer 34 and the insulating layer (not shown) to cross the gate lines 31 in the vertical direction to define respective pixel regions, and the data lines 40 are formed. The thin film transistor T is formed by overlapping the source electrode 41 and the drain electrode 42 opposite to the source electrode 41 on the gate wiring 31. That is, the thin film transistor T is formed on the gate wiring 31. As a result, a region through which light is transmitted from the pixel electrode to be formed later can be formed into a quadrangular shape, and the stability of the liquid crystal domain due to the electric field can be imparted by suppressing a mismatch in electric field distortion caused by a conventional thin film transistor. .

Subsequently, a protective film (not shown) is formed on the entire structure in which the data line 40 and the thin film transistor T are formed. Next, a predetermined portion of the passivation layer is etched to form a contact hole 45 partially exposing the drain electrode 42.

Then, a pixel electrode 50 made of a transparent conductive material is formed in the pixel area on the passivation layer (not shown). The pixel electrode 50 is formed at the lower end of the pixel electrode 50 to partially overlap with the drain electrode 42 and is connected to the thin film transistor T through the contact hole 45. A region through which light is transmitted by the backlight (not shown) is formed in a square shape.

Next, as shown in FIG. 7, in the color filter substrate 70 for the liquid crystal display device, the black matrix 72 includes the pixel of FIG. 6 for the purpose of preventing light leakage from the edge of the pixel electrode 50. A color filter 73 having an opening 72a in a portion corresponding to the electrode 50 is formed over the entire surface of the substrate and has a color of red, green, and blue so that one color corresponds to one opening 72a. Formed. At this time, the opening 72a has a rectangular shape like the pixel electrode 50. Next, although not shown, the transparent common electrode is formed on the entire surface of the color filter substrate.

After the array substrate 30 and the color filter substrate 70 of the liquid crystal display device thus formed are bonded together, a liquid crystal layer is injected therebetween to form a liquid crystal cell.

Hereinafter, various embodiments using a multi-domain technology capable of forming two regions having different arrangement directions of liquid crystal molecules using the liquid crystal display of the present invention having the structures shown in FIGS. 6 and 7 will be described. . Here, the same structure is shown with the same code | symbol.

First, as shown in FIG. 8A, the pixel electrode 50 further includes a slit 52 extending in the vertical direction. In addition, the peripheral electrode 54 is formed under the slit 52 of the pixel electrode 50, for example, on the same layer as the data line 40 so as to overlap the pixel electrode with a width a of about 2 μm. . The peripheral electrode 54 serves to reinforce the fringe field when driving the liquid crystal layer. The peripheral electrode 54 is made of an opaque conductive material, and is made of a material such as aluminum or an aluminum alloy having a relatively low specific resistance. Can be. Although not shown in the drawing, the peripheral electrode 54 is connected to the common electrode and simultaneously receives a common voltage. Since an insulating film (not shown) is formed between the peripheral electrode 54 and the pixel electrode 50, it can be used as a storage electrode for maintaining the cell voltage. When the electric field is formed using the pixel electrode 50 on the array substrate 30 configured as described above and the common electrode (not shown) of FIG. 7, the thin film transistor T is symmetrical and thus stability of the liquid crystal domain due to the electric field. Is given.

FIG. 8B is a cross-sectional view of the liquid crystal display of FIG. 8A taken along the line A-A '.

As illustrated, a gate insulating film (not shown) and a semiconductor layer (not shown) are formed on the array substrate 30, and a peripheral electrode spaced apart from the data line 40 and the data line by a predetermined distance thereon. 54) is formed. A protective layer 47 made of an organic insulating material such as BCB or photo acrylate is formed on the data line 40 and the peripheral electrode 54, and a transparent conductive material is formed on the protective layer 47. The pixel electrode 50 is formed with predetermined slits 52. In this case, the peripheral electrode 54 is partially overlapped with the predetermined width a under the slit 52 of the pixel electrode 50. The protective layer 47 may be formed of silicon oxide (SiO ₂ ) or silicon nitride (SiNx).

Next, the color filter substrate 70 is disposed on the pixel electrode 50 at regular intervals, and a black matrix 72 is formed below the color filter substrate 70, and the black matrix 72 is a pixel. The edge of the electrode 50 is covered. Next, red, green, and blue color filters 73 are formed under the black matrix 72, and an overcoat layer 74 is formed under the black matrix 72. A transparent common electrode 75 is formed below the overcoat layer 74.

Next, the liquid crystal layer 60 is positioned between the pixel electrode 50 and the common electrode 75.

In the liquid crystal display, the slit 52 is formed on the pixel electrode 50, and when a voltage is applied to the common electrode 75 and the pixel electrode 50, a fringe field is formed between the two electrodes. do. At this time, when the liquid crystal molecules of the liquid crystal layer 60 have different arrangements around the slit pattern 52 due to the square pixel electrode 70, stability of the liquid crystal domain is provided, thereby rubbing twice. Even if it is not abnormal, it is possible to form multi-domains having different alignment directions of the liquid crystal molecules. The liquid crystal layer 60 may use a liquid crystal having a positive or negative dielectric anisotropy, and may include a chiral dopant. The above embodiment is preferably applied to the TN mode, it may be applied to the VA mode.

In addition, as shown in FIG. 9A, a slit or a low dielectric film 80 is formed at portions corresponding to the pixel electrodes 50 on the common electrode on the color filter substrate (not shown), and the peripheral electrode 54 is formed. An upper portion of the data line 40 is formed to partially overlap the edge of the pixel electrode 50. In this case, the slit or low dielectric film 80 may be formed to extend in the lower left direction from the upper right portion of the pixel electrode 50, or may be formed to extend in the lower right direction from the upper left portion of the pixel electrode 50. It may also be formed in parallel with the data line 40. In addition, when an electric field is formed using the pixel electrode 50 on the array substrate 30 and the common electrode (not shown) of FIG. 7, the thin film transistor T has a symmetry, and thus stability of the liquid crystal domain due to an electric field. Is given. The low dielectric film 80 may be formed in various shapes such as Ｘ, ╋, double wire.

FIG. 9B is a cross-sectional view of the liquid crystal display of FIG. 9A taken along the line B-B '.

As illustrated, a gate insulating film (not shown) and a semiconductor layer (not shown) are formed on the array substrate 30, and data lines 40 spaced at regular intervals are formed thereon. A passivation layer 47 made of an organic insulating material such as BCB is formed on the data line 40, and a peripheral electrode 54 partially overlapping the data line 40 is formed on the passivation layer 47. .

An inorganic insulating film 55 is formed on the substrate on which the peripheral electrode 54 is formed, and a pixel electrode 50 partially overlapping the peripheral electrode 54 is formed thereon.

Next, the color filter substrate 70 is disposed on the array substrate 30 at a predetermined interval, and a black matrix 72 is formed below the color filter substrate 70, and the black matrix 72 is a pixel. The edge of the electrode 50 is covered. Next, red, green, and blue color filters 73 are formed under the black matrix 72, and an overcoat layer 74 is formed under the black matrix 72, and a transparent common electrode 75 is formed under the black matrix 72. have. Subsequently, a low dielectric layer 80 corresponding to the pixel electrode 50 is formed on the common electrode 75. In this case, the slits may be formed in the common electrode 75 instead of the low dielectric film 80 to form a multi-domain. Next, the liquid crystal layer 60 is positioned between the pixel electrode 50 and the common electrode 75. The liquid crystal layer 60 may use a liquid crystal having a positive or negative dielectric anisotropy, and may include a chiral dopant. In addition, the above embodiment is preferably applied to the TN mode, and is applicable to the VA mode.

Next, as shown in FIG. 10, a plurality of slit patterns 90 are formed to sequentially separate one side and the other side of the pixel electrode 50 of the array substrate 30. The slit pattern 90 extends in a direction parallel to the gate line 31, and a peripheral electrode 54 is formed under the pixel electrode to partially overlap the slit pattern 90.

Here, reference numeral 92 denotes a plurality of low-k dielectric films formed on the common electrode of the color filter substrate to correspond to the pixel electrodes 50 and is used for forming a multi-domain.

The low dielectric film 92 may be formed in various shapes. In addition, the above embodiment is preferably applied to the VA mode, it is also applicable to the TN mode.

Subsequently, as illustrated in FIG. 11, the pixel electrode 50 on the array substrate 30 of the liquid crystal display device is a pixel electrode patterned to have a plurality of slits 51, and is disposed below the pixel electrode 50. The peripheral electrode 54 partially overlapping the pixel electrode 50 is formed.

Here, reference numeral 82 denotes a low-k dielectric film formed corresponding to the slit 51 pattern of the pixel electrode 50 on the common electrode of the color filter substrate, and is used for forming a multi-domain. The slit 51 may be formed of a low dielectric film, the low dielectric film 82 may be a slit, and the shape of the slit 51 may be modified into various shapes. In addition, the above embodiment is preferably applied to the VA mode, it is also applicable to the TN mode.

In the liquid crystal display according to the present invention, the thin film transistor T is formed on the gate wiring 31 to use the pixel electrode 50 and the common electrode (not shown) on the array substrate 30. Therefore, when the electric field is formed, the thin film transistor T portion is symmetrical to impart stability of the liquid crystal domain due to the symmetrical pixel shape.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The liquid crystal display of the present invention described above has the following effects.

The thin film transistor T is formed on the gate wiring on the array substrate for a liquid crystal display device of the present invention to form the pixel electrode in a square shape. As a result, when the electric field is formed using the pixel electrode on the array substrate and the common electrode (not shown) on the color filter substrate, the thin film transistor T has a symmetry, thereby improving stability of the liquid crystal domain due to symmetrical pixel shapes. It can be given.

Claims (12)

A first substrate and a second substrate, Gate wiring and data wiring crossing each other on the first substrate to define respective unit pixel regions; A thin film transistor connected to the data line and formed on the gate line to switch a video signal; A pixel electrode connected to the thin film transistor and formed such that an area through which light passes has a rectangular shape; A black matrix formed under the second substrate; A color filter corresponding to each pixel region; And a common electrode formed under the color filter. The method of claim 1, And a slit on the pixel electrode. The method of claim 2, And a peripheral electrode formed to partially overlap the pixel electrode under the slit of the pixel electrode. The method of claim 3, wherein And the peripheral electrode is formed on the same layer as the data line. The method of claim 1, The common electrode further comprises an opening. The method of claim 1, And a low dielectric film on the common electrode. The method according to claim 5 or 6, And a peripheral electrode formed under the pixel electrode to partially overlap the edge of the pixel electrode. The method of claim 7, wherein And the peripheral electrode is formed on the data line. The method of claim 1, And the pixel electrode has a plurality of slit patterns in which one side part and the other side part are separated in sequence. The method of claim 9, And a peripheral electrode formed under the pixel electrode to partially overlap the slit pattern. The method of claim 10, And the peripheral electrode is formed on the same layer as the gate line. The method of claim 11, And a low dielectric film formed on the common electrode to be disposed between the slit patterns.