KR20070071785A - Liquid crystal display device - Google Patents

Abstract

An in-plane switching LCD(Liquid Crystal Display) is provided to prevent light leakage by using a dynamic alignment layer. A first substrate faces a second substrate. A plurality of gate lines(61) and data lines(64) intersect each other to define a pixel region in the first substrate. A pixel electrode(69) and a common electrode(68) are alternately formed in the pixel region. A plurality of thin film transistors are formed in intersections between gate lines and the data lines. First and second dynamic alignment layers are formed on the first and second substrates. A liquid crystal layer is formed between the first and second substrates. The first and second dynamic alignment layers are aligned in a vertical direction at a black state, and are aligned in a horizontal direction at a white state.

Description

Transverse electric field type liquid crystal display device {Liquid Crystal Display Device}

1 is an exploded perspective view showing a part of a typical TN liquid crystal display device

Figure 2 is a schematic cross-sectional view showing a liquid crystal display device of a typical transverse electric field (IPS)

3A and 3B are diagrams illustrating phase transitions of liquid crystals when voltage on / off is performed in IPS mode.

4a and 4b is a photograph showing a conventional light leakage

5A and 5B are liquid crystal director distribution diagrams in a black state and a white state when the dynamic alignment layer of the present invention is applied.

6A and 6B are perspective views showing liquid crystal alignment in a black state and a white state of the liquid crystal display of the present invention.

7 is a plan view showing a transverse electric field type liquid crystal display device of the present invention.

8 is a structural cross-sectional view taken along lines II ′ and II-II ′;

Explanation of symbols on the main parts of the drawings

60: lower substrate 61: gate line

61a: gate electrode 61b: common wiring

62 gate insulating film 63 active layer

64: data lines 64a and 64b: source and drain electrodes

65: shield 66: contact hole

68 common electrode 69 pixel electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and in particular, to improve brightness and minimize loss of aperture ratio due to bonding margins of upper and lower substrates (In-Plane Switching: IPS). A liquid crystal display device and a manufacturing method thereof.

As the information society develops, the demand for display devices is increasing in various forms.In recent years, liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), and vacuum fluorescent display (VFD) have been developed. Various flat panel display devices have been studied, and some of them are already used as display devices in various devices.

Among them, LCD is the most widely used as a substitute for CRT (Cathode Ray Tube) for the use of mobile image display device because of the excellent image quality, light weight, thinness, and low power consumption, and mobile type such as monitor of notebook computer. In addition, it is being developed in various ways, such as a television for receiving and displaying broadcast signals, and a monitor of a computer.

As described above, although various technical advances have been made in order for the liquid crystal display device to serve as a screen display device in various fields, the task of improving the image quality as the screen display device has many advantages and disadvantages.

Therefore, in order for a liquid crystal display device to be used in various parts as a general screen display device, development of high quality images such as high definition, high brightness, and large area is maintained while maintaining the characteristics of light weight, thinness, and low power consumption. It can be said.

Such a liquid crystal display device may be broadly divided into a liquid crystal panel displaying an image and a driving unit for applying a driving signal to the liquid crystal panel, wherein the liquid crystal panel includes first and second glass substrates having a space and are bonded to each other; It consists of a liquid crystal layer injected between the said 1st, 2nd glass substrate.

The first glass substrate (TFT array substrate) may include a plurality of gate lines arranged in one direction at a predetermined interval, a plurality of data lines arranged at regular intervals in a direction perpendicular to the gate lines, and A plurality of pixel electrodes formed in a matrix form in each pixel region defined by crossing each gate line and data line, and a plurality of thin films that transmit signals of the data line to each pixel electrode by being switched by signals of the gate line The transistor is formed.

The second glass substrate (color filter substrate) includes a black matrix layer for blocking light in portions other than the pixel region, an R, G, B color filter layer for expressing color colors, and a common electrode for implementing an image. Is formed. Of course, the common electrode is formed on the first glass substrate in the transverse electric field type liquid crystal display device.

The first and second glass substrates are bonded by a sealing material having a predetermined space by a spacer and having a liquid crystal injection hole, and a liquid crystal is injected between the two substrates.

In this case, in the liquid crystal injection method, the liquid crystal is injected between the two substrates by osmotic pressure when the liquid crystal injection hole is immersed in the liquid crystal container by maintaining the vacuum state between the two substrates bonded by the reality. When the liquid crystal is injected as described above, the liquid crystal injection hole is sealed with a sealing material.

On the other hand, the driving principle of the liquid crystal display device as described above uses the optical anisotropy and polarization of the liquid crystal.

Since the liquid crystal is thin and long in structure, the liquid crystal has a direction in the arrangement of molecules, and the liquid crystal may be artificially applied to control the direction of the molecular arrangement.

Accordingly, when the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light polarized by optical anisotropy may be arbitrarily modulated to express image information.

Such liquid crystals may be classified into positive liquid crystals having positive dielectric anisotropy and negative liquid crystals having negative dielectric anisotropy according to an electrical specific classification. The liquid crystal molecules arranged in parallel and having negative dielectric anisotropy are arranged perpendicularly to the direction in which the electric field is applied and the major axis of the liquid crystal molecules.

1 is an exploded perspective view illustrating a part of a general TN liquid crystal display device.

As shown in FIG. 1, the lower substrate 1 and the upper substrate 2 bonded to each other with a predetermined space, and the liquid crystal layer 3 injected between the lower substrate 1 and the upper substrate 2 are composed of. It is.

More specifically, the lower substrate 1 has a plurality of gate lines 4 arranged in one direction at regular intervals to define the pixel region P, and in a direction perpendicular to the gate lines 4. A plurality of data lines 5 are arranged at regular intervals, and a pixel electrode 6 is formed in each pixel region P where the gate line 4 and the data line 5 intersect, and each gate line The thin film transistor T is formed at the portion where (4) and the data line 5 intersect.

The upper substrate 2 includes a black matrix layer 7 for blocking light in portions other than the pixel region P, an R, G, and B color filter layer 8 for expressing color colors, and an image. The common electrode 9 is formed to implement the.

The thin film transistor T may include a gate electrode protruding from the gate line 4, a gate insulating film (not shown) formed on the front surface, an active layer formed on the gate insulating film above the gate electrode, and the data. And a source electrode protruding from the line 5 and a drain electrode to face the source electrode.

The pixel electrode 6 uses a transparent conductive metal having a relatively high light transmittance, such as indium-tin-oxide (ITO).

In the liquid crystal display device configured as described above, the liquid crystal layer 3 positioned on the pixel electrode 6 is aligned by a signal applied from the thin film transistor T, and the liquid crystal layer 3 is aligned with the alignment degree of the liquid crystal layer 3. Accordingly, the image can be expressed by controlling the amount of light passing through the liquid crystal layer 3.

As described above, the liquid crystal panel drives the liquid crystal by an electric field applied up and down, and has excellent characteristics such as transmittance and aperture ratio, and the common electrode 9 of the upper substrate 2 serves as a ground to discharge static electricity. It is possible to prevent the destruction of the liquid crystal cell.

However, the liquid crystal drive by the electric field applied up-down has a disadvantage that the viewing angle characteristics are not excellent.

Accordingly, in order to overcome the above disadvantages, a new technology, that is, a liquid crystal display device of a transverse electric field method (IPS), has been proposed.

Hereinafter, a general liquid crystal display device of a transverse electric field method (IPS) will be described.

2 is a schematic cross-sectional view of a liquid crystal display device of a general transverse electric field method (IPS).

As shown in FIG. 2, an upper substrate having a pixel electrode 12 and a common electrode 13 formed on the same plane on the lower substrate 11 and having a predetermined space and bonded to the lower substrate 11. The liquid crystal layer 14 formed between the parts 15 is operated by the transverse electric field between the pixel electrode 12 and the common electrode 13 on the lower substrate 11.

3A and 3B are diagrams illustrating phase transitions of liquid crystals when voltages are turned on and off in the IPS mode.

That is, FIG. 3A shows an off state in which no transverse electric field is applied to the pixel electrode 12 or the common electrode 13, so that the phase change of the liquid crystal layer 14 does not occur. For example, the pixel electrode 12 and the common electrode 13 are basically shifted by 45 ° in the horizontal direction.

FIG. 3B is an on state in which a transverse electric field is applied to the pixel electrode 12 and the common electrode 13, and a phase shift of the liquid crystal layer 14 occurs, and is about 45 ° compared to the off state of FIG. 3A. It can be seen that the horizontal direction of the pixel electrode 12 and the common electrode 13 and the twist direction of the liquid crystal have a twist angle.

As described above, in the liquid crystal display of the IPS, both the pixel electrode 12 and the common electrode 13 exist on the same plane.

An advantage of the transverse electric field method is that a wide viewing angle is possible.

That is, when the liquid crystal display device is viewed from the front, the liquid crystal display device may be visible in the about 70 ° direction in the up / down / left / right directions.

In addition, there is an advantage that the manufacturing process is simpler and the color shift according to the viewing angle is smaller than that of the liquid crystal display device.

However, since the common electrode 13 and the pixel electrode 12 are present on the same substrate, there is a disadvantage in that transmittance and aperture ratio due to light are reduced.

In addition, there is a disadvantage in that the response time due to the driving voltage must be improved and the cell gap is made uniform because the misalign margin of the cell gap is small.

That is, the transverse electric field type liquid crystal display device has the advantages and disadvantages as described above can be selected according to the user's use.

However, in the transverse type liquid crystal display, the following problems occur due to the initial rubbing characteristics of the alignment layer that is horizontally aligned.

4A and 4B are photographs showing conventional light leakage.

As shown in FIGS. 4A and 4B, the conventional transverse electric field type liquid crystal display device is implemented in a normally black mode, and the initial rubbing direction of the alignment layer is made in the same direction as the absorption axis of one of the upper and lower polarizing plates having transmission axes perpendicular to each other. . The ordering parameters in the polarizer absorption axis direction are reduced due to the unevenness of the alignment, the influence of the stepped portion, and the like, causing light leakage in the black.

Thus, as shown, partially bright pixels are seen, thereby degrading the user's sense of vision.

The present invention has been made to solve the above problems,

Thus, as shown in the figure, the pixels are observed to be partially bright, thereby reducing the user's sense of vision. A transverse electric field system suitable for solving the aperture ratio reduction and luminance reduction problems caused by the bonding margin of the upper and lower substrates. A liquid crystal display device and a method of manufacturing the same are provided.

In order to achieve the above object, a transverse electric field type liquid crystal display device includes a first and a second substrate facing each other, and a plurality of gate lines and data crossing each other on the first substrate to define pixel regions. A line, a pixel electrode and a common electrode alternately formed in the pixel region, a plurality of thin film transistors formed at an intersection of the gate line and the data line, and first and second portions formed on the first substrate and the second substrate. It is characterized by including a liquid crystal layer formed between the dynamic alignment layer and the first and second substrates.

The first and second dynamic alignment layers are oriented in the vertical direction in the black state, and in the horizontal direction in the white state.

The first and second dynamic alignment layers include side chains and liquid crystal molecules in the side chains.

The liquid crystal molecules have positive dielectric anisotropy.

Hereinafter, a transverse electric field type liquid crystal display device and a manufacturing method thereof according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

In the transverse electric field type liquid crystal display device of the present invention, the alignment films formed on the arrays of the first and second substrates are formed by using the dynamic alignment films, and the corresponding liquid crystals are provided by the positive liquid crystals provided in the dynamic alignment film side chains in the black state and the white state, respectively. It is to have an orientation of.

The transverse type liquid crystal display device of the present invention described below is a liquid crystal display device of normally black mode driving in which an initial state is implemented in a black state and a white state is applied when a voltage is applied.

5A and 5B are liquid crystal director distribution diagrams in a black state and a white state when the dynamic alignment layer of the present invention is applied, and FIGS. 6A and 6B illustrate liquid crystal alignment in a black state and a white state of a liquid crystal display of the present invention. Perspective view.

When the alignment layer (not shown) formed on the first substrate 100 and the second substrate 200 is configured as a dynamic alignment layer, as shown in FIGS. 5A and 6A, the alignment layer is aligned in a vertical direction in a black state. To be oriented.

In addition, as shown in FIGS. 5B and 6B, the dynamic alignment layer is laid down in a horizontal direction when a horizontal electric field is applied by a liquid crystal having positive dielectric anisotropy provided at the end of the side chain, indicating a normal white state.

As such, the alignment layer is used as the dynamic alignment layer because the alignment layer is initially vertically aligned by the alignment layers of the liquid crystals, and thus exhibits a lower light leakage than the black light leakage in the transverse electric field mode.

When a horizontal electric field is applied, a transverse electric field is generated, and the liquid crystal and the alignment layer may be arranged by the formed electric field to form gray and white.

As such, the dynamic alignment layer to which the liquid crystal having positive dielectric anisotropy is applied is driven from the vertical alignment to the horizontal alignment by the applied horizontal electric field, thereby inducing the liquid crystal directors horizontally, thereby reducing the driving voltage and improving the transmittance. Can be represented.

As described above, the reason for using the dynamic alignment layer having different initial alignment characteristics according to the black state (no voltage applied) and the white state (voltage applied state) in the present invention is that the first and second substrates of the transverse electric field type liquid crystal display device are used. The first polarizing plate 310 and the second polarizing plate 320 formed on the back surface of the (100, 200) are each made to have a transmission axis in a direction perpendicular to each other, on the contrary, the first and second substrates (100, 200) This is because light leakage occurs in the initial state (black state) because the alignment films formed on the image are rubbed in an inclined state at an angle of 45 ° to each other.

7 is a plan view illustrating a transverse electric field type liquid crystal display device of the present invention, and FIG. 8 is a cross-sectional view of the structure taken along lines II ′ and II ′.

In the transverse electric field type liquid crystal display according to the present invention, as illustrated in FIGS. 7 and 8, the gate line 61 and the data line 64 vertically intersect to define a pixel area on the transparent lower substrate 60. The thin film transistor T is formed in an area where the gate line 61 and the data line 64 cross each other.

In this case, the thin film transistor T may include a gate electrode 61a occupying one region of the gate line 61, a gate insulating layer 62 formed on the entire surface of the lower substrate 60 including the gate electrode 61a, and The active layer 63 is formed on the gate insulating layer 62 above the gate electrode 61a, and is separated from the source electrode 64a and the source electrode 64a which protrude from the data line 64 at regular intervals. It is composed of the formed drain electrode 64b.

In addition, a common wiring 61b is formed on the same layer as the gate line 61, and the common wiring 61b is formed to cross the pixel area in parallel with the gate line 61.

The passivation layer 65 is formed on the entire lower substrate 60 including the data line 64, and the contact hole 66 is formed in the drain electrode 64b. At this time, the protective film 65 is formed of a silicon nitride film.

On the passivation layer 65 of the pixel region, the common electrode 67 and the pixel electrode 68 are alternately arranged in parallel with a predetermined interval.

In this case, a plurality of common electrodes 67 are arranged in a pixel area parallel to the data line 64, and the pixel electrodes 68 are connected to the drain electrode 64b of the thin film transistor through the contact hole 66. have.

The common electrode 67 and the pixel electrode 68 are formed of a transparent conductive film.

Although not shown in the drawing, the upper substrate corresponding to the lower substrate configured as described above has a color filter layer formed at a portion corresponding to the pixel region in order to realize color, and serves to distinguish between the color filter layers and to block light. In order to do this, a black matrix layer is formed.

In this case, the black matrix layer is formed on the gate line 61, the data line 64, the peripheral area including the data line 64 and the common electrode 67 adjacent to each other, and a portion corresponding to the thin film transistor.

Liquid crystals positioned between the common electrode 67 and the pixel electrode 68 are arranged in the same direction by a transverse electric field distributed between the common electrode 67 and the pixel electrode 68 to form one domain.

Reference numeral 69 denotes a storage electrode, and forms a storage on common structure.

When the common electrode 67 and the pixel electrode 68 are formed of a transparent conductive film, the overall brightness of the liquid crystal display device can be improved.

However, if the black matrix layer is also formed on the upper portion of the data line 64 and the peripheral region as described above, the upper and lower substrates must be designed in consideration of the bonding margin when bonding the upper and lower substrates. As the size of the substrate is gradually increasing, there is a concern that the luminance decreases due to the bonding margin of the upper and lower substrates around the data line 64.

In other words, the black matrix layer should be formed not only in the data line 64 but also in a portion corresponding to the data line 64 and the common electrode 67 adjacent thereto, so that the aperture ratio loss and the luminance decrease due to the bonding margin are concerned.

In addition, since the protective film formed of the silicon nitride film is formed to be relatively thin, approximately 0.3 [mu] m, the problem of deterioration in image quality due to the crosstalk and parasitic capacitance of the data line and the common electrode also occurs.

Therefore, in order to compensate for the problem of deterioration in image quality due to crosstalk between the data line and the common electrode, a low dielectric constant organic insulating film is flattened to have a thickness of approximately 3 μm instead of forming a protective film with a silicon nitride film on the entire surface of the lower substrate. It is formed and used.

The first and second dynamic alignment layers are oriented in the vertical direction in the black state, and in the horizontal direction in the white state.

The first and second dynamic alignment layers include side chains and liquid crystal molecules in the side chains.

The liquid crystal molecules have positive dielectric anisotropy.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the above embodiments, but should be defined by the claims.

As described above, the transverse electric field type liquid crystal display device and the method of manufacturing the same have the following effects.

By using the dynamic alignment film, in the initial state, the initial pretilt angle is oriented in the vertical direction, thereby maintaining the vertical alignment state, preventing light leakage due to the initial rubbing characteristics, and in the white state where voltage is applied. By the liquid crystal having a positive dielectric provided in the chain, the normal white state can be exhibited by the dynamic alignment layer oriented in the same direction together with the liquid crystals oriented in the horizontal direction along the horizontal electric field.

Claims (5)

First and second substrates opposed to each other; A plurality of gate lines and data lines crossing each other on the first substrate to define pixel regions; A pixel electrode and a common electrode which are alternately formed in the pixel area; A plurality of thin film transistors formed at intersections of the gate lines and the data lines; First and second dynamic alignment layers formed on the first substrate and the second substrate; And And a liquid crystal layer formed between the first and second substrates. The method of claim 1, And the first and second dynamic alignment layers are aligned in a vertical direction in a black state and in a horizontal direction in a white state. The method of claim 1, And said first and second dynamic alignment layers comprise side chains and liquid crystal molecules in said side chains. The method of claim 3, wherein The liquid crystal molecules have a positive dielectric anisotropy, characterized in that the transverse field-type liquid crystal display device. According to claim 1, And the first and second dynamic alignment layers have a vertical alignment in an initial state.

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