KR20040004818A - Liquid crystal display - Google Patents

Abstract

PURPOSE: A liquid crystal display is provided to easily restore disordered arrangement of liquid crystal molecules. CONSTITUTION: A liquid crystal display includes upper and lower substrates(300,100), a common electrode(360) formed on the upper substrate, and a pixel electrode(200) formed on the lower substrate. The liquid crystal display further includes an electric field distorting structure(400) formed on the upper or lower substrate, an auxiliary electrode surrounding the pixel electrode, and the first alignment film(380) having the first pre-tilt angle, which is formed on the overall surface of the upper substrate. The liquid crystal display also has the second alignment film(280) that has the second pre-tilt angle smaller than the first pre-tilt angle and is formed on the overall surface of the lower substrate, and a liquid crystal layer formed between the upper and lower substrates.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which a disturbed liquid crystal array is easily restored.

In general, a liquid crystal display device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the two substrates facing each other at a predetermined interval, and the liquid crystal layer is driven by an electric field formed between the two substrates. Is displayed.

One of the liquid crystal displays used in recent years is a twisted nematic (TN) liquid crystal display, in which liquid crystal molecules filled between two substrates are parallel to a substrate and have a constant pitch. It is twisted spirally at (pitch) and is oriented so that the long axis of a liquid crystal molecule may change continuously.

However, the TN liquid crystal display device has a characteristic in that light transmittance of each gray level is changed depending on the viewing angle. In particular, the light transmittance is symmetrically distributed in the left and right directions but asymmetrically distributed in the up and down directions, resulting in gray inversion.

In order to solve the above problems, a method of compensating for the change in light transmittance according to the viewing angle has been proposed by dividing a domain by different liquid crystal driving in one pixel area.

As such, as a representative example of a multi-domain technique of dividing one pixel into several domains, two domain twisted nematic (TDTN) is a technique of forming two regions in which the arrangement of liquid crystals is symmetrical around the center of one pixel region.

Hereinafter, a liquid crystal display according to the related art will be described with reference to the accompanying drawings.

FIG. 1A is a plan view of a conventional liquid crystal display, FIG. 1B is a cross-sectional view of the AA line of FIG. 1A, and FIG. 1C is a view illustrating a liquid crystal driving state when a voltage is applied. Corresponding schematic cross section.

As shown in FIGS. 1A and 1B, a conventional liquid crystal display device has large liquid crystal molecules filled between a lower substrate 10, an upper substrate 30 opposite thereto, and both substrates 10 and 30 (not shown). It is composed of poems.

A gate line 12 and a data line 14 are formed on the lower substrate 10 to cross each other in the vertical and horizontal directions, and a pixel electrode 20 is formed in the pixel area.

The auxiliary electrode 25 is formed on the same layer as the data line 14 and formed at an edge of the pixel electrode 20.

A gate insulating layer 16 is formed between the gate line 12 and the data line 14, and a passivation layer 18 is formed between the data line 14 and the pixel electrode 20.

Although not shown, a thin film transistor including a gate electrode, a semiconductor layer, and a source / drain electrode is formed at an intersection of the gate line 12 and the data line 14.

On the upper substrate 30, a light shielding layer 32 for blocking light leakage to a region outside the pixel region, a color filter layer 34 for implementing color hues (R, G, B) and And the common electrode 36 are formed, respectively.

An organic structure 40 for dividing the liquid crystal alignment of the pixel region is formed on the common electrode 36.

In this case, as can be seen from the electric field formed by the dotted line in FIG. 1B, the fringe field having different directions in one pixel area is formed by the organic structure 40 formed on the common electrode 36. As a result, the liquid crystal alignment becomes different.

Although not shown, a liquid crystal layer is formed between the substrates 10 and 30.

In addition, an alignment film for initial alignment of liquid crystals is formed on the entire surface of both substrates 10 and 30. The alignment film formed on the lower substrate 10 and the alignment film formed on the upper substrate 30 are formed to be deflected by 90 ° to each other, and each alignment film of the upper and lower substrates 30 and 10 is rubbed to have the same pretilt angle with respect to the horizontal plane. . As such, the liquid crystal molecules adjacent to the alignment layer are arranged along the alignment direction of the alignment layer.

The operation of the conventional liquid crystal display device having such a structure is as follows.

First, when no voltage is applied, the liquid crystal molecules are arranged such that their major axis directions are parallel to the lower substrate 10 and the upper substrate 30, but are continuously twisted by 90 degrees. Therefore, light moves along the long axis direction of the twisted liquid crystal so that the screen shows a white state.

When a voltage is applied, as shown in FIG. 1C, the liquid crystal molecules 50 lying parallel to the lower substrate and the upper substrate stand in a direction perpendicular to the two substrates, so that the screen is black.

In this case, as described above, a fringe field is generated by the organic structure 40 formed on the common electrode 36, so that the liquid crystal molecules 50 may have a first region and a second region around the organic structure 40. At different angles, we compensate for the viewing angle.

On the other hand, such a liquid crystal display device is used in a notebook computer or the like, when the user touches the liquid crystal panel by hand, such as when an unspecific pressure is applied to the liquid crystal panel may be disturbed.

FIG. 2A is a schematic cross-sectional view illustrating a liquid crystal alignment state when a pressure is applied to a conventional liquid crystal display, and FIG. 2B is a schematic cross-sectional view illustrating a liquid crystal alignment state when a pressure is released.

As shown in FIG. 2A, when pressure is applied to the liquid crystal panel, the liquid crystal array is disturbed in a direction opposite to the original liquid crystal array in the first region and the second region, and the screen is momentarily blurred. However, if a certain time passes after the pressure is released, the alignment of the liquid crystal is restored.

However, the restoration is incomplete.

That is, as shown in FIG. 2B, when the pressure is released in the second region in which the alignment direction of the alignment layer formed on the lower substrate and the direction of the electric field are the same as in FIG. The arrangement of the liquid crystal molecules 50 is restored.

However, in the first region where the alignment direction of the alignment layer formed on the lower substrate and the direction of the electric field are different from each other, even if the pressure is released, the liquid crystal molecules 50 cannot be restored in the direction of the original electric field due to the offset action of the alignment layer and the electric field. do.

Accordingly, a problem occurs in that the unevenness occurs in the first region where the alignment direction of the liquid crystal molecules 50 is not restored, thereby lowering the resolution.

On the other hand, as shown in Figure 2a to 2c, the pressure is applied to the liquid crystal panel, the liquid crystal adjacent to the alignment layer during the process of releasing movement is limited by the tilt angle of the alignment layer, the actual movement of the liquid crystal between the upper and lower substrates The portion controlled by the electric field and pressure formed in the portion is the portion between the upper and lower substrates on which the liquid crystal is twisted. That is, the most severely affected part when the pressure is applied to the liquid crystal panel is the central part between the upper and lower substrates where the liquid crystal is nearly 90 °.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device that can be easily restored even if the liquid crystal panel is disturbed due to pressure applied to the liquid crystal panel.

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

FIG. 1B is a cross sectional view along line AA 'of FIG. 1A

Figure 1c is a schematic cross-sectional view corresponding to the line AA 'of Figure 1a when a voltage is applied

2A is a schematic cross-sectional view illustrating a liquid crystal alignment state when a pressure is applied to a conventional liquid crystal display.

2B is a schematic cross-sectional view showing a liquid crystal alignment state when the pressure is released

3A is a plan view of pixels of a liquid crystal display according to an exemplary embodiment of the present invention.

3B is a cross sectional view taken along the line B-B 'in FIG. 3A

4A is a schematic cross-sectional view showing a liquid crystal alignment state when a pressure is applied to the liquid crystal display according to the present invention.

4B is a schematic cross-sectional view showing a liquid crystal alignment state when the pressure is released

5A and 5B relate to a liquid crystal display device according to another exemplary embodiment of the present invention, which is a cross-sectional view corresponding to line BB ′ of FIG. 3A.

Explanation of symbols for the main parts of drawings

100: lower substrate 120: gate line

140: data line 160: gate insulating film

180: protective film 200: pixel electrode

280: second alignment layer 300: upper substrate

320: light shielding layer 340: color filter layer

360: common electrode 205, 365: field induction window

380: First alignment layer 400: Organic structure

500: liquid crystal molecules

In order to achieve the above object, the present invention provides a lower substrate and an upper substrate, a common electrode formed on the upper substrate, a pixel electrode formed on the lower substrate, and an electric field distortion formed on the upper substrate or the lower substrate. Structure, an auxiliary electrode formed to surround the pixel electrode, a first alignment layer formed on the entire surface of the upper substrate to have a first pretilt angle, and a first pretilt angle of the first alignment layer on the entire lower substrate. A liquid crystal display device comprising a second alignment film formed to have a smaller second pretilt angle and a liquid crystal layer formed between both substrates is provided.

The field distortion structure may be an organic structure formed on the common electrode, an electric field induction window formed on the common electrode, or the electric field distortion structure may be an electric field induction window formed on the pixel electrode.

In addition, the first pretilt angle is preferably 4 ° to 7 °.

Preferably, the second pretilt angle is 0 ° to 2 °.

The thin film transistor may be further formed on the lower substrate in a gate line and a data line crossing the gate line and the data line, and an intersection region of the gate line and the data line.

The auxiliary electrode may be formed on the same layer as the gate line or on the same layer as the data line.

In the upper substrate, a light blocking layer and a color filter layer may be further formed below the common electrode.

Preferably, an overcoat layer is further formed between the color filter layer and the common electrode.

In addition, the present invention for achieving the above object is a lower substrate and an upper substrate, a light shielding layer formed on the upper substrate, a color filter layer formed on the light shielding layer, a common electrode formed on the color filter layer, the common An organic structure formed on the electrode, a first alignment layer formed on the entire surface of the upper substrate to have a first pretilt angle, a gate line and a data line formed vertically and horizontally on the lower substrate to define a pixel region, and the gate A thin film transistor formed at an intersection region of a line and a data line, a pixel electrode formed at the pixel region, an auxiliary electrode formed to surround the pixel electrode, and an entire surface of the lower substrate than a first pretilt angle of the first alignment layer. A second alignment layer formed to have a small second pretilt angle and a liquid crystal layer formed between the both substrates. To provide a liquid crystal display device is configured.

Preferably, the first pretilt angle is 4 ° to 7 °.

Preferably, the second pretilt angle is 0 ° to 2 °.

That is, in the present invention, even when pressure is applied to the liquid crystal panel, the pretilt angle of the alignment layer of the lower substrate is made smaller than the pretilt angle of the alignment layer of the upper substrate, thereby reducing the canceling effect between the electric field and the alignment layer and smoothly aligning the liquid crystal. It is to restore.

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

3A is a plan view of one pixel of the liquid crystal display according to the exemplary embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along the line B-b 'of FIG. 3A.

As shown in FIGS. 3A and 3B, a gate line 120 and a data line 140 are formed on the lower substrate 100 to cross each other in a vertical direction to define a pixel region, and a pixel electrode 200 is formed in the pixel region. Formed.

The auxiliary electrode 250 is formed on the same layer as the data line 140 and overlaps the pixel electrode at the edge of the pixel electrode 200.

In this case, the auxiliary electrode 250 may be formed on the same layer as the gate line 120 or may not be overlapped with the pixel electrode 200.

A gate insulating layer 160 is formed between the gate line 120 and the data line 140, and a passivation layer 180 is formed between the data line 140 and the pixel electrode 200.

The gate insulating layer 160 and the passivation layer 180 may be formed of a material such as SiNx, SiOx, BenzoCycloButene (BCB), acrylic resin, polyamide compound, or the like.

Although not shown, a thin film transistor including a gate electrode, a semiconductor layer, and a source / drain electrode is formed at an intersection of the gate line 120 and the data line 140.

A light shielding layer 320 is formed on the upper substrate 300 to block light leakage to an area outside the pixel area. The color filter layer 340 and the common electrode 360 are sequentially formed on the light blocking layer 320 to implement color hues R, G, and B.

In this case, an overcoat layer may be additionally formed between the color filter layer 340 and the common electrode 360 to protect the color filter layer 340 and to planarize the substrate.

In addition, an organic structure 400 for dividing the liquid crystal alignment of the pixel region is formed on the common electrode 360.

It is preferable that the dielectric constant of the organic structure 400 is equal to or smaller than that of the liquid crystal. In addition, the organic structure 400 is preferably made of a photosensitive material, more preferably made of acrylic resin (photoacrylate) or BCB (BenzoCycloButene).

The first alignment layer 280 and the second alignment layer 380 are formed on the front surfaces of the upper substrate 300 and the lower substrate 100, respectively.

In this case, the pretilt angle θ ₁ of the first alignment layer 380 is greater than the pretilt angle θ ₂ of the second alignment layer 280.

Preferred pretilt angles range from θ ₁ to 4 ° to 7 ° and θ ₂ to 0 ° to 2 °.

The first and second alignment layers 380 and 280 are formed by rubbing alignment treatment using a material such as a polyamide or polyimide compound, polyvinylalcohol (PVA), polyamic acid, or the like. Can be.

In addition, the first and second alignment layers 380 and 280 may be formed by photo-alignment using a photoreactive material such as polyvinylcinnamate (PVCN), polysiloxanecinnamate (PSCN), or cellulosecinnamate (CelCN) -based compound. The light alignment treatment simultaneously determines the pretilt angle and the alignment direction by at least one light irradiation, wherein the light irradiation preferably uses light in the ultraviolet region. Any of polarized light, linearly polarized light, and partially polarized light may be used.

Although not shown, a liquid crystal layer is formed between the substrates 100 and 300. The liquid crystal molecules constituting the liquid crystal layer are twisted nematic (TN) type having a positive dielectric anisotropy.

The operation of the liquid crystal display according to the present invention having such a structure is as follows.

First, when no voltage is applied, the liquid crystal molecules are arranged such that their major axes are parallel to the lower substrate 100 and the upper substrate 300, but are continuously twisted by 90 °. Therefore, light moves along the long axis direction of the twisted liquid crystal so that the screen shows a white state.

When a voltage is applied, as shown in FIG. 3C, the liquid crystal molecules 500 lying parallel to the lower substrate 100 and the upper substrate 300 stand in a direction perpendicular to the two substrates, so that the screen is black. Indicates.

In this case, as described above, the fringe field is generated by the organic structure 400 formed on the common electrode 360, so that the liquid crystal molecules 500 may have a first region and a second region with the organic structure 400 as a boundary. Compensate the viewing angle by forming different orientation directions at.

On the other hand, Figure 4a is a schematic cross-sectional view showing a liquid crystal alignment state when the pressure is applied to the liquid crystal display according to the present invention, Figure 4b is a schematic cross-sectional view showing a liquid crystal alignment state when the pressure is released, it is disturbed by the external pressure The state in which the liquid crystal alignment is restored to the original state will be described below.

As shown in FIG. 4A, when pressure is applied to the liquid crystal panel, the liquid crystal array is disturbed in a direction opposite to the original liquid crystal alignment direction in the first region and the second region, and the screen is momentarily blurred.

However, if a certain time passes after the pressure is released, the alignment direction of the liquid crystal is restored to the original state.

That is, as shown in FIG. 4B, in the second region in which the alignment direction of the alignment layer formed on the lower substrate 100 and the direction of the electric field are identical to each other in the pixel region, when the pressure is released as in the conventional case, mutually reinforcing action of the alignment layer and the electric field is performed. By doing so, the arrangement of the liquid crystal molecules 500 in the direction of the electric field of Winrae is restored.

In addition, when the pressure is released even in the first region where the alignment direction of the alignment layer formed on the lower substrate 200 and the direction of the electric field are different from each other, the liquid crystal is restored by the action of the alignment layer having the high pretilt angle formed on the upper substrate. As a reinforcing action, the liquid crystal molecules 500 are restored to the original state as in the second region.

In this way, the pretilt angle of the alignment film formed on the upper substrate is made relatively larger than the pretilt angle of the alignment film formed on the lower substrate so that the alignment film formed on the upper substrate reinforces the direction of the electric field. This is to restore the original.

5A and 5B illustrate a liquid crystal display device according to another exemplary embodiment, which is a cross-sectional view corresponding to line A-A of FIG. 3A.

According to another exemplary embodiment of the present invention illustrated in FIG. 5A, the liquid crystal display device is a method of distorting an electric field for domain division, and does not form an organic structure on the common electrode 360 as illustrated in FIG. 3B. The electric field guide window 365 is formed in the common electrode 360. In addition, the components including the alignment layer 380 are the same as in the above-described embodiment, and accordingly, the same reference numerals are given.

In the liquid crystal display according to the exemplary embodiment illustrated in FIG. 5B, the organic material structure is not formed on the common electrode 360, but the field induction window 205 is formed in the pixel electrode 200. . In addition, the components including the alignment layer are the same as in the above-described embodiment, and therefore are given the same reference numerals.

The various embodiments of the present invention described above relate to a liquid crystal display device in which one pixel is divided into two domains, but the technical idea of the present invention may be applied even when divided into three or more domains.

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

By completely restoring the liquid crystal alignment defect after the screen touch, the unevenness of the screen can be prevented.

Claims (14)

A lower substrate and an upper substrate; A common electrode formed on the upper substrate; A pixel electrode formed on the lower substrate; An electric field distortion structure formed on the upper substrate or the lower substrate; An auxiliary electrode formed to surround the pixel electrode; A first alignment layer formed on the entire surface of the upper substrate to have a first pretilt angle; A second alignment layer formed on the entire surface of the lower substrate to have a second pretilt angle smaller than the first pretilt angle of the first alignment layer; And And a liquid crystal layer formed between the substrates. The method of claim 1, And the field distortion structure is an organic structure formed on the common electrode. The method of claim 1, And the field distortion structure is an electric field induction window formed in the common electrode. The method of claim 1, And the field distortion structure is an electric field induction window formed in the pixel electrode. The method according to any one of claims 1 to 4, The first pretilt angle is 4 ° to 7 ° characterized in that the liquid crystal display device. The method according to any one of claims 1 to 4, And the second pretilt angle is between 0 ° and 2 °. The method according to any one of claims 1 to 4, A gate line and a data line intersected longitudinally and horizontally with each other on the lower substrate; And a thin film transistor further formed at an intersection region of the gate line and the data line. The method of claim 7, wherein And the auxiliary electrode is formed on the same layer as the gate line. The method of claim 7, wherein And the auxiliary electrode is formed on the same layer as the data line. The method according to any one of claims 1 to 4, The upper substrate further includes a light blocking layer and a color filter layer under the common electrode. The method of claim 10, And an overcoat layer between the color filter layer and the common electrode. A lower substrate and an upper substrate; A light blocking layer formed on the upper substrate; A color filter layer formed on the light blocking layer; A common electrode formed on the color filter layer; An organic structure formed on the common electrode; A first alignment layer formed on the entire surface of the upper substrate to have a first pretilt angle; A gate line and a data line intersecting vertically and horizontally on the lower substrate to define a pixel area; A thin film transistor formed at an intersection of the gate line and the data line; A pixel electrode formed in the pixel region; An auxiliary electrode formed to surround the pixel electrode; A second alignment layer formed on the entire surface of the lower substrate to have a second pretilt angle smaller than the first pretilt angle of the first alignment layer; And And a liquid crystal layer formed between the substrates. The method of claim 12, The first pretilt angle is 4 ° to 7 ° characterized in that the liquid crystal display device. The method of claim 12, And the second pretilt angle is between 0 ° and 2 °.