KR20110076369A

KR20110076369A - Liquid crystal display device and method of fabricating the same

Info

Publication number: KR20110076369A
Application number: KR1020090133063A
Authority: KR
Inventors: 김동국
Original assignee: 엘지디스플레이 주식회사
Priority date: 2009-12-29
Filing date: 2009-12-29
Publication date: 2011-07-06

Abstract

PURPOSE: A liquid crystal display device and manufacturing method thereof are provided to reduce driving voltage and power consumption having viewing angle, contrast ratio, and aperture ratio. CONSTITUTION: A liquid crystal display(100) includes a thin film transistor which is located in a first substrate. A plurality of pixel electrodes(152) is connected to the thin film transistor and is located on the first substrate. A black matrix(162) having an aperture unit is located in the upper part of the thin film transistor. A protective layer(140) covers the black matrix and a color filter layer(164).

Description

Liquid crystal display device and method of fabricating the same

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a wide viewing angle and a high opening ratio.

In recent years, as the society enters the information age, the display field for processing and displaying a large amount of information has been rapidly developed, and the liquid crystal display device as a flat display device having excellent performance of thin, light weight, and low power consumption has been developed. Is replacing the existing Cathode Ray Tube (CRT).

Generally, the driving principle of a liquid crystal display device utilizes the optical anisotropy and polarization properties of a liquid crystal. Since the liquid crystal has a long structure, it has a directionality in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

Accordingly, if the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light is refracted in the molecular arrangement direction of the liquid crystal due to optical anisotropy to express image information.

Currently, an active matrix liquid crystal display device (AM-LCD: abbreviated as an active matrix LCD, abbreviated as a liquid crystal display device) in which a thin film transistor and pixel electrodes connected to the thin film transistor are arranged in a matrix manner has the best resolution and video performance. It is attracting attention.

The liquid crystal display includes a color filter substrate on which a common electrode is formed, an array substrate on which pixel electrodes are formed, and a liquid crystal interposed between the two substrates. In such a liquid crystal display, the common electrode and the pixel electrode are caused by an electric field applied up and down. It is excellent in the characteristics, such as transmittance | permeability and aperture ratio, by the method of driving a liquid crystal.

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

Accordingly, in order to overcome the above disadvantages, an in-plane switching mode liquid crystal display device having excellent viewing angle characteristics has been proposed.

Hereinafter, a general transverse electric field mode liquid crystal display will be described in detail with reference to FIG. 1.

1 is a cross-sectional view of a general transverse electric field mode liquid crystal display device.

As shown, the first and second substrates 1 and 2 are located facing each other, and the liquid crystal layer 3 is interposed between the first and second substrates 1 and 2. The liquid crystal layer 3 includes a plurality of liquid crystal molecules 5. Further, the pixel electrode 7 and the common electrode 9 which are spaced apart from each other are positioned on the first substrate 1. The pixel electrode 7 receives a voltage through a gate line (not shown), a data line (not shown), and a thin film transistor (not shown) formed on the first substrate 1, and the common electrode ( 9 is applied with a voltage through a common wiring (not shown) formed on the first substrate (1). When a voltage is applied to the pixel electrode 7 and the common electrode 9, a horizontal electric field is formed.

First, in the OFF state of the liquid crystal display, no electric field is formed between the pixel electrode 7 and the common electrode 9, and the liquid crystal molecules 5 maintain the initial arrangement and express black color. .

In the ON state, a horizontal electric field is formed between the pixel electrode 7 and the common electrode 9, and liquid crystals are arranged along the horizontal electric field to express a white color.

The transverse electric field mode liquid crystal display has advantages in viewing angle and response speed, but has a disadvantage of low contrast ratio due to light leakage in an off state.

In order to solve the disadvantage of the contrast ratio, a vertical alignment mode liquid crystal display has been proposed. Referring to FIG. 2, which shows a conventional vertical array mode liquid crystal display, first and second substrates 11 and 12 are disposed to face each other, and a liquid crystal layer is disposed between the first and second substrates 11 and 12. (13) is interposed. The liquid crystal layer 13 includes a plurality of liquid crystal molecules 15.

The pixel electrode 17 is positioned on the first substrate 11, and a part of the pixel electrode 17 is removed to form the slit 17. In addition, at least one protrusion 20 is positioned on the second substrate 12, and a common electrode 19 is positioned on the protrusion 20 and the second substrate 12. When voltage is applied to the common electrode 19 and the pixel electrode 17, a vertical electric field is formed to control the liquid crystal molecules 15.

The vertical arrangement mode liquid crystal display device having the above configuration has a high contrast ratio, but has a problem that the viewing angle is limited.

As described above, the transverse electric field mode liquid crystal display has advantages in contrast and the like, but has a disadvantage in contrast ratio, and the vertical array mode liquid crystal display has advantages in contrast ratio but has disadvantages in the viewing angle.

Accordingly, there is a demand for the development of a liquid crystal display device having advantages in view of viewing angle, contrast ratio, aperture ratio, and the like.

An object of the present invention is to provide a liquid crystal display having advantages in terms of viewing angle, contrast ratio and aperture ratio.

In addition, to reduce the driving voltage, to provide a low-power liquid crystal display device.

In order to solve the above problems, the present invention includes a thin film transistor positioned in each of the plurality of pixel regions defined in the first substrate; A plurality of pixel electrodes connected to the thin film transistor and positioned on the first substrate; A black matrix positioned on the thin film transistor, preventing external light from entering the thin film transistor, and having an opening corresponding to the pixel area; A color filter pattern positioned in each of the openings; A protective layer covering the black matrix and the color filter layer; A plurality of common electrodes on the passivation layer and alternately arranged with the plurality of pixel electrodes; A first alignment layer on the plurality of pixel electrodes and the plurality of common electrodes; A second alignment layer on the second substrate and facing the first alignment layer; And a liquid crystal layer positioned between the first and second alignment layers, wherein the liquid crystal layer includes liquid crystal molecules constituting a spiral structure twisted several tens of times, and a spiral axis of the spiral structure is perpendicular to the first and second substrates. One aspect of the present invention is to provide a liquid crystal display device.

The black matrix is characterized by consisting of chromium or black resin.

The black matrix is characterized in that the color filter pattern is overlapped.

The liquid crystal layer includes an RM and a photoinitiator, and UV is irradiated to the liquid crystal layer to have a network structure.

The interval between the pixel electrode and the common electrode is 1 ~ 10㎛.

The interval between the pixel electrode and the common electrode is characterized in that 1 ~ 5㎛.

The pitch of the helical structure is characterized in that 100 ~ 380nm.

In another aspect, the present invention includes the steps of forming a thin film transistor on the first substrate; Forming a black matrix on the first substrate, the black matrix covering the thin film transistor; Forming a color filter layer on the first substrate; Forming a protective layer covering the color filter layer; Forming a plurality of pixel electrodes connected to the thin film transistor and a plurality of common electrodes alternately arranged with the plurality of pixel electrodes on the passivation layer; Forming a first alignment layer on the plurality of pixel electrodes and the plurality of common electrodes; Forming a second alignment layer on the second substrate; Bonding the first and second substrates so that the first and second alignment layers face each other; Injecting a liquid crystal layer between the first and second alignment layers; Irradiating UV to the liquid crystal layer through the second substrate, wherein the liquid crystal layer comprises liquid crystal molecules having a spiral structure twisted several tens of times, RM and a photoinitiator, and the spiral axis of the spiral structure is Provided is a method of manufacturing a liquid crystal display device, characterized in that perpendicular to the first and second substrates.

And covering the thin film transistor and forming a black matrix for blocking light.

The liquid crystal display device of the present invention has an advantage that the viewing angle and contrast ratio are improved by using a liquid crystal having a spiral structure twisted several times and having optical isotropy.

In addition, the liquid crystal display of the present invention has the advantage that the aperture ratio is increased because the color filter layer and the black matrix are formed on one substrate together with the thin film transistor.

In addition, since the liquid crystal has a network structure through UV irradiation in the state containing the RM and the photoinitiator, the liquid crystal can be quickly recovered to the original spiral structure, thereby preventing an increase in driving voltage.

In addition, since the color filter layer and the black matrix are formed on the lower substrate together with the thin film transistor, UV irradiation is possible in the bonded panel state.

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

The liquid crystal display device of the present invention is characterized by a uniformly standing helix (USH) mode using a flexoelectric effect. The driving principle of the USH mode liquid crystal display device will be described schematically with reference to the drawings.

3 is a view schematically showing a driving principle of the USH mode liquid crystal in the USH mode liquid crystal display according to the present invention.

As shown, the USH-mode liquid crystal has a helical structure in which short pitch chiral nematic liquid crystal molecules are twisted several dozen times in a voltage-free state, and the spiral axis, that is, the spiral axis Parallel to the optical axis. The pitch of the helical structure has a value smaller than the wavelength of visible light, thereby preventing light from being reflected. For example, the pitch of the helical structure is 100-380 nm.

On the other hand, the optical axis is distorted in the voltage applied (ON) state, birefringence is expressed.

4 is a front view of the liquid crystal array structure. The USH mode liquid crystal has a very fast response time because bimesogen liquid crystals are arranged in a structure having polarity. As described above, the USH-mode liquid crystal has a helical structure in which chiral nematic liquid crystal molecules of short pitch are twisted tens of times, and the axis of the helical structure, that is, the helical axis, has a light propagation direction (z direction). Parallel to) It also has the same refractive index in the x and y directions perpendicular to the z direction. (n _x = n _y ), ie, optical isotropic properties in the front viewing angle.

The first and second polarizing plates have polarization axes perpendicular to each other, and light leakage does not occur at the front viewing angle due to the optical isotropy as described above.

Therefore, birefringence is not expressed at the front viewing angle when no voltage is applied, and it has an advantage of obtaining excellent black characteristics.

On the other hand, the USH mode liquid crystal display device is driven in the IPS mode using a horizontal electric field to improve the viewing angle, as described above has the disadvantage of low aperture ratio in the IPS mode. In particular, the USH mode liquid crystal has a structure in which the helical liquid crystal is twisted dozens of times, thereby increasing the driving voltage.

Therefore, an electric field of increased size is required, and the distance between the pixel electrode and the common electrode must be narrowed in the IPS mode. Referring to FIG. 5, which is a graph showing the intensity of the electric field and the relative transmittance in the ISP mode LCD, the transmittance increases as the intensity of the electric field increases.

On the other hand, when the gap between the pixel electrode and the common electrode is narrowed, there is a problem that the aperture ratio decreases. 6 is a cross-sectional view of a liquid crystal display device for solving the problem of a decrease in aperture ratio.

As shown, the liquid crystal display device 100 according to the present invention is spaced apart from the first substrate 110 in which the pixel region P and the switching region S are defined and facing the first substrate 110. The second substrate 180, the thin film transistor Tr positioned on the first substrate 110, the black matrix 162 positioned on the thin film transistor Tr, and the first substrate 110. ) And a plurality of common colors arranged alternately with the color filter layer 164 corresponding to the pixel region P, the plurality of pixel electrodes 152 spaced apart from each other, and the plurality of pixel electrodes 152. A liquid crystal layer positioned between the electrode 154, the first alignment layer 172, the second alignment layer 182 positioned on the second substrate 180, and the first and second alignment layers 172 and 182. 190. Although not shown, seal patterns are formed at edges of the first and second substrates 110 and 180 to prevent leakage of the liquid crystal and form a space into which the liquid crystal layer 190 is injected. In addition, first and second polarizing plates having polarization axes perpendicular to each other are positioned outside the first and second substrates 110 and 180, respectively.

The first substrate 110 is transparent, for example, made of glass.

The gate line 114 extends along the boundary of the pixel region P on the first substrate 110, and the gate electrode 112 is connected to the gate line 114. The gate electrode 112 is positioned in the switching region S defined in the pixel region P. Although not shown, a common wiring is spaced apart from the gate wiring 114 in parallel, and a gate pad is positioned at one end of the gate wiring 114.

Each of the gate electrode 112, the gate wiring 114, the common wiring, and the gate pad may have a single layer structure made of a low resistance metal material such as aluminum, an aluminum alloy, copper, or a copper alloy. Or it may have a double layer structure consisting of a lower layer of molybdenum-titanium alloy (MoTi) and the upper layer of copper, or a triple layer structure of MoTi, copper, MoTi.

A gate insulating layer 116 is disposed to cover the gate electrode 112, the gate line 114, the common line, and the gate pad. The gate insulating layer 116 may be made of an inorganic insulating material such as silicon oxide or silicon nitride.

The semiconductor layer 120 is positioned in the switching region S on the gate insulating layer 116. That is, the semiconductor layer 120 overlaps the gate electrode 112. The semiconductor layer 120 includes an active layer 120a made of pure amorphous silicon and an ohmic contact layer 120b formed on the active layer 120b and made of impurity amorphous silicon.

In addition, the data line 130 extends along the boundary of the pixel region P on the gate insulating layer 116. The data line 130 crosses the gate line 114 to define the pixel area P.

In addition, the source electrode 132 and the drain electrode 134 are spaced apart from each other on the semiconductor layer 120. The source electrode 132 is connected to the data line 130. A central portion of the active layer 120a is exposed to a space between the source electrode 132 and the drain electrode 134.

The gate electrode 112, the gate insulating layer 116, the semiconductor layer 120, the source electrode 132, and the drain electrode 134 constitute the thin film transistor Tr as a switching element. The thin film transistor Tr is connected to the gate line 114 and the data line 130 through the gate electrode 112 and the source electrode 132, respectively.

Although not shown, a data pad is positioned at one end of the data line 130.

Each of the data line 130, the source electrode 132, the drain electrode 134, and the data pad may have a single layer structure made of a low resistance metal material such as aluminum, an aluminum alloy, copper, or a copper alloy. Or it may have a double layer structure consisting of a lower layer of molybdenum-titanium alloy (MoTi) and the upper layer of copper, or a triple layer structure of MoTi, copper, MoTi.

The first passivation layer 140 is formed to cover the data line 130, the source electrode 132, the drain electrode 134, and the data pad.

The first passivation layer 140 may be made of an inorganic insulating material such as silicon oxide or silicon nitride. The first protective layer 140 may be made of an organic insulating material such as benzocyclobutene (BCB) or photo acryl.

The black matrix 156 is positioned on the first passivation layer 140 and is disposed to cover the thin film transistor Tr to prevent light from being irradiated onto the active layer 120a. The black matrix 156 is made of a metal material such as chromium or black resin. In addition, the black matrix 162 is positioned corresponding to the gate line 114 and the data line 130, thereby preventing light leakage around the gate line 114 and the data line 130. . The black matrix 162 has an opening corresponding to the pixel area P. FIG. That is, the black matrix 162 has a lattice shape, and the opening of the lattice shape corresponds to the pixel area P.

In addition, the color filter layer 164 is disposed to cover the first passivation layer 140 and correspond to the pixel area P. FIG. For example, the color filter layer 164 includes a red color filter 164a, a green color filter 164b, and a blue color filter 164c. Each of the red, green, and blue color filters 164a, 164b, and 164c is positioned in the opening of the black matrix 162.

As described above, in the present invention, since the color filter layer 164 and the black matrix 162 are formed on the first substrate 110 like the thin film transistor Tr, the aperture ratio can be improved.

That is, when the color filter layer 164 and the black matrix 162 are formed on the second substrate 180 which is the upper substrate, and the second substrate 180 and the first substrate 110 are aligned, the margin is considered. Since it should be, opening ratio falls. However, in the present invention, since the color filter layer 164, the black matrix 162, and the thin film transistor Tr are formed on the first substrate 110, the bonding margin does not need to be considered, and thus the aperture ratio is improved.

A second protective layer 170 made of an organic insulating material such as photo-acryl is disposed on the black matrix 162 and the color filter layer 164. The second passivation layer 170 serves to planarize the step difference caused by the black matrix 162 and the color filter layer 164.

A drain contact hole 142 exposing a part of the drain electrode 134 is formed through the second protective layer 170 and the first protective layer 140. In addition, a data pad contact hole (not shown) for exposing the data pad through the second protective layer 170, the first protective layer 140, the second protective layer 170, and the first protective layer 170. A gate pad contact hole (not shown) for exposing the gate pad is formed through the first protective layer 140 and the gate insulating layer 116.

The plurality of pixel electrodes 152 are positioned on the second passivation layer 170. The pixel electrode 152 contacts the drain electrode 134 through the drain contact hole 142 and is spaced apart from each other.

In addition, the plurality of common electrodes 154 arranged alternately with the plurality of pixel electrodes 152 are disposed on the second passivation layer 170. The common electrode 154 is connected to the common wiring (not shown).

Each of the pixel electrode 152 and the common electrode 154 may be made of a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO). Is done.

An interval between the pixel electrode 152 and the common electrode 154 may be 1 to 10 μm. Preferably it may be 1 ~ 5㎛. In the present invention, the distance between the pixel electrode 152 and the common electrode 154 is narrowed to enhance the intensity of the electric field.

Although not shown, a gate pad electrode connected to the gate pad through the gate pad contact hole and a data pad electrode connected to the data pad through the data pad contact hole are positioned on the second passivation layer 170. .

A first alignment layer 172 is disposed to cover the pixel electrode 152 and the common electrode 154 and to initially arrange the liquid crystal molecules in the liquid crystal layer 190.

The second substrate 180 is transparent, for example, made of glass.

The second alignment layer 182 facing the first alignment layer 172 is positioned on the second substrate 180 to determine the initial arrangement of the liquid crystal molecules.

The liquid crystal layer 190 is positioned between the first and second alignment layers 172 and 182. The liquid crystal molecules of the liquid crystal layer 190 have a helical structure in which chiral nematic liquid crystal molecules of short pitch are twisted dozens of times, and the axis of the helical structure, that is, the spiral axis is parallel to the optical axis. Has an array. The optical axis is perpendicular to the first and second substrates.

As described above, the liquid crystal molecules of the liquid crystal layer 190 have a spiral structure that is twisted several tens of times, and the twisted structure is unwinded by application of a voltage. However, when the maximum applied voltage is applied, the helical structure is released beyond the limit and may not be restored to its original state. That is, at such a limit value, a higher driving voltage is required to restore the liquid crystal molecules to their original state, which causes a problem of increased power consumption.

In order to solve this problem, it is necessary to give the network structure to the liquid crystal molecules, RM (reactive mesogen) and photo-initiator (photo-initiator) is added to the liquid crystal layer 190 and irradiated with UV. That is, when RM having a photoactive group is added and UV is irradiated, photoreaction occurs by the photoinitiator and the liquid crystal layer 190 has a network structure.

Therefore, even when a voltage higher than the threshold value is applied, the liquid crystal molecules are easily restored to the original spiral structure, and an increase in driving voltage can be prevented.

7 is a schematic cross-sectional view of a liquid crystal display according to another exemplary embodiment of the present invention.

As illustrated, the liquid crystal display 200 according to the present invention is spaced apart from the first substrate 210 in which the pixel region P and the switching region S are defined, and face the first substrate 210. A second substrate 280, a liquid crystal layer 290 positioned between the first and second substrates 210 and 280, a thin film transistor Tr positioned on the first substrate 210, and The black matrix 262 positioned on the thin film transistor Tr, the color filter layer 264 on the first substrate 210 and corresponding to the pixel area P, and a plurality of spaced apart from each other. Pixel electrodes 252, a plurality of common electrodes 254 arranged alternately with the plurality of pixel electrodes 252, a first alignment layer 272, and a second alignment layer positioned on the second substrate 280. 282 and a liquid crystal layer 290 positioned between the first and second alignment layers 272 and 282. Although not shown, seal patterns are formed at edges of the first and second substrates 210 and 280 to prevent leakage of the liquid crystal and form a space into which the liquid crystal layer 290 is injected. In addition, first and second polarizing plates having polarization axes perpendicular to each other are positioned outside the first and second substrates 210 and 280, respectively.

The first substrate 210 is transparent, for example, made of glass.

The gate line 214 extends along the boundary of the pixel region P on the first substrate 210, and the gate electrode 212 is connected to the gate line 214. The gate electrode 212 is positioned in the switching region S defined in the pixel region P. Although not shown, a common wiring is spaced apart from the gate wiring 214 in parallel, and a gate pad is positioned at one end of the gate wiring 214.

Each of the gate electrode 212, the gate wiring 214, the common wiring, and the gate pad may have a single layer structure made of a low resistance metal material such as aluminum, an aluminum alloy, copper, or a copper alloy. Or it may have a double layer structure consisting of a lower layer of molybdenum-titanium alloy (MoTi) and the upper layer of copper, or a triple layer structure of MoTi, copper, MoTi.

A gate insulating layer 216 is disposed to cover the gate electrode 212, the gate wiring 214, the common wiring, and the gate pad. The gate insulating layer 216 may be made of an inorganic insulating material such as silicon oxide or silicon nitride.

The semiconductor layer 220 is positioned in the switching region S on the gate insulating layer 216. That is, the semiconductor layer 220 overlaps the gate electrode 212. The semiconductor layer 220 includes an active layer 120a made of pure amorphous silicon and an ohmic contact layer 220b formed of impurity amorphous silicon on the active layer 220b.

The data line 230 extends along the boundary of the pixel region P on the gate insulating layer 216. The data line 230 crosses the gate line 214 to define the pixel area P.

In addition, the source electrode 232 and the drain electrode 234 are spaced apart from each other on the semiconductor layer 220. The source electrode 232 is connected to the data line 230. A central portion of the active layer 220a is exposed to a space between the source electrode 232 and the drain electrode 234.

The gate electrode 212, the gate insulating layer 216, the semiconductor layer 220, the source electrode 232, and the drain electrode 234 constitute the thin film transistor Tr as a switching element. The thin film transistor Tr is connected to the gate line 214 and the data line 230 through the gate electrode 212 and the source electrode 232, respectively.

Although not shown, a data pad is positioned at one end of the data line 230.

Each of the data line 230, the source electrode 232, the drain electrode 234, and the data pad may have a single layer structure including a low resistance metal material such as aluminum, an aluminum alloy, copper, or a copper alloy. Or it may have a double layer structure consisting of a lower layer of molybdenum-titanium alloy (MoTi) and the upper layer of copper, or a triple layer structure of MoTi, copper, MoTi.

The first passivation layer 240 is formed to cover the data line 230, the source electrode 232, the drain electrode 234, and the data pad. The first passivation layer 240 includes a drain contact hole 242 exposing a portion of the drain electrode 234. The first passivation layer 240 may be made of an inorganic insulating material such as silicon oxide or silicon nitride. The first protective layer 240 may be made of an organic insulating material such as benzocyclobutene (BCB) or photo acryl.

The color filter layer 264 is disposed to cover the first passivation layer 240 and correspond to the pixel region P and the thin film transistor Tr. For example, the color filter layer 264 includes a red color filter 264a, a green color filter 264b, and a blue color filter 264c. Each of the red, green, and blue color filters 264a, 264b, and 264c is positioned for each pixel region P, and the boundary of the pixel region P, that is, the thin film transistor Tr and the data line 230, is positioned. And the color filter patterns 264a, 264b, and 264c positioned in the adjacent pixel region P corresponding to the gate wiring 214. For example, the red color filter pattern 264a and the green color filter pattern 264b of the neighboring pixel region P overlap each other at positions corresponding to the thin film transistor Tr and the data line 230. The overlapped color filter patterns 264a and 264b prevent light from entering the thin film transistor Tr and at the same time prevent light leakage around the data line 230. That is, the overlapped color filter patterns 264a and 264b serve as light blocking means like the black matrix.

As described above, in the present invention, the color filter layer 264 and the overlapped color filter patterns 264a, 264b, and 264c serving as light blocking means are formed on the first substrate 210 as the thin film transistor Tr. As a result, the aperture ratio can be improved.

That is, when the color filter layer is formed on the second substrate 280 which is the upper substrate, and the second substrate 280 and the first substrate 210 are aligned, a margin must be taken into consideration, so that the aperture ratio is lowered. However, in the present invention, since the color filter layer 280 is formed on the first substrate 210 together with the thin film transistor Tr, and the color filter pattern is superimposed and used as a black matrix, the bonding margin does not have to be considered, and thus the aperture ratio This is improved.

The third protective layer 270 made of an inorganic insulating material such as silicon oxide or silicon nitride is disposed on the color filter layer 264.

In the liquid crystal display shown in FIG. 6, the third protective layer 170 is made of an organic insulating material. However, when the third protective layer 170 is made of an organic insulating material, a problem arises in that the transmittance is lowered. In addition, when a defect occurs in the third protective layer 170 made of the organic insulating material, repair is difficult, thereby lowering the yield. Therefore, in the present embodiment, the third protective layer 270 is formed of an inorganic insulating material.

A drain contact hole 242 exposing a portion of the drain electrode 234 is formed through the second protective layer 270 and the first protective layer 240. In addition, a data pad contact hole (not shown) for exposing the data pad through the second protective layer 270, the first protective layer 240, the second protective layer 270, and the second protective layer 270. A gate pad contact hole (not shown) for exposing the gate pad is formed through the first protective layer 240 and the gate insulating layer 216.

The plurality of pixel electrodes 252 is positioned on the second passivation layer 270. The pixel electrode 252 is in contact with the drain electrode 234 through the drain contact hole 242 and is spaced apart from each other.

In addition, the plurality of common electrodes 254 arranged alternately with the plurality of pixel electrodes 252 are disposed on the second passivation layer 270. The common electrode 254 is connected to the common wiring (not shown).

Each of the pixel electrode 252 and the common electrode 254 may be formed of a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO). Is done.

An interval between the pixel electrode 252 and the common electrode 254 may be 1 to 10 μm. Preferably it may be 1 ~ 5㎛. In the present invention, the distance between the pixel electrode 252 and the common electrode 254 is narrowed to enhance the intensity of the electric field.

Although not shown, a gate pad electrode connected to the gate pad through the gate pad contact hole and a data pad electrode connected to the data pad through the data pad contact hole are disposed on the second passivation layer 270. .

A first alignment layer 272 is disposed to cover the pixel electrode 252 and the common electrode 254 and to initially arrange the liquid crystal molecules in the liquid crystal layer 290.

The second substrate 280 is transparent, for example, made of glass.

A second alignment layer 282 facing the first alignment layer 272 is positioned on the second substrate 280 to determine an initial arrangement of liquid crystal molecules.

The liquid crystal layer 290 is positioned between the first and second alignment layers 272 and 282. The liquid crystal molecules of the liquid crystal layer 190 have a helical structure in which chiral nematic liquid crystal molecules of short pitch are twisted dozens of times, and the axis of the helical structure, that is, the spiral axis is parallel to the optical axis. Has an array.

As described above, the liquid crystal molecules of the liquid crystal layer 290 have a spiral structure that is twisted several tens of times, and the twisted structure is unwinded by application of a voltage. However, when the maximum applied voltage is applied, the helical structure is released beyond the limit and may not be restored to its original state. That is, at such a limit value, a higher driving voltage is required to restore the liquid crystal molecules to their original state, which causes a problem of increased power consumption.

In order to solve this problem, it is necessary to give a network structure to the liquid crystal molecules, RM (reactive mesogen) and photo-initiator (photo-initiator) is added to the liquid crystal layer 290 and irradiated with UV. That is, when RM having a photoactive group is added and UV is irradiated, photoreaction occurs by the photoinitiator and the liquid crystal layer 290 has a network structure.

A method of manufacturing a liquid crystal display according to an embodiment of the present invention is as follows.

First, a thin film transistor, a black matrix, a color filter layer, a pixel electrode, a common electrode, and a first alignment layer are formed on a first substrate. The black matrix may be formed of chromium or black resin as shown in FIG. 6, or may have a configuration in which color filter patterns are overlapped as shown in FIG. 7.

Next, a second alignment film is formed on the second substrate.

Next, a seal pattern is formed at an edge of at least one of the first and second substrates, and the first and second substrates are bonded to each other.

Next, liquid crystal molecules are injected between the first and second substrates to form a liquid crystal layer. At this time, the liquid crystal layer is a USH mode liquid crystal.

On the other hand, in order to reduce the driving voltage, RM and a photoinitiator may be added to the liquid crystal layer.

As described above, when RM and a photoinitiator are added to the liquid crystal layer, the liquid crystal molecules have a network structure by irradiating UV through the second substrate. At this time, since the color filter layer and the black matrix are formed on the first substrate together with the thin film transistor, the UV irradiation process is easily performed.

As in the related art, when the color filter layer and the black matrix are formed on the second substrate which is the upper substrate, the UV irradiation process may not be performed. That is, since the color filter and the black matrix are positioned on the second substrate, which is the upper substrate, UV is blocked, and since the thin film transistor, the gate wiring, the data wiring, etc. are located on the first substrate, which is the lower substrate, the UV is blocked.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

2 is a cross-sectional view of a general vertical array mode liquid crystal display device.

4 is a front view of the liquid crystal array structure.

5 is a graph showing the relationship between the electric field intensity and the relative transmittance in the ISP mode liquid crystal display.

6 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

7 is a schematic cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

Claims

A thin film transistor positioned in each of the plurality of pixel regions defined in the first substrate;

A plurality of pixel electrodes connected to the thin film transistor and positioned on the first substrate;

A black matrix positioned on the thin film transistor, preventing external light from entering the thin film transistor, and having an opening corresponding to the pixel area;

A color filter pattern positioned in each of the openings;

A protective layer covering the black matrix and the color filter layer;

A plurality of common electrodes on the passivation layer and alternately arranged with the plurality of pixel electrodes;

A first alignment layer on the plurality of pixel electrodes and the plurality of common electrodes;

A second alignment layer on the second substrate and facing the first alignment layer;

A liquid crystal layer positioned between the first and second alignment layers,

The liquid crystal layer includes liquid crystal molecules constituting a spiral structure twisted tens of times, and the spiral axis of the spiral structure is perpendicular to the first and second substrates.

The method of claim 1,

And the black matrix is made of chromium or black resin.

The method of claim 1,

And the black matrix is formed by overlapping the color filter patterns.

The method of claim 1,

The liquid crystal layer comprises an RM and a photoinitiator, characterized in that the liquid crystal layer is UV irradiated to have a network structure.

The method of claim 1,

And a distance between the pixel electrode and the common electrode is 1 to 10 μm.

The method of claim 1,

And a gap between the pixel electrode and the common electrode is 1 to 5 μm.

The method of claim 1,

Liquid crystal display device characterized in that the pitch of the spiral structure is 100 ~ 380nm.

Forming a thin film transistor on the first substrate;

Forming a black matrix on the first substrate, the black matrix covering the thin film transistor;

Forming a color filter layer on the first substrate;

Forming a protective layer covering the color filter layer;

Forming a plurality of pixel electrodes connected to the thin film transistor and a plurality of common electrodes alternately arranged with the plurality of pixel electrodes on the passivation layer;

Forming a first alignment layer on the plurality of pixel electrodes and the plurality of common electrodes;

Forming a second alignment layer on the second substrate;

Bonding the first and second substrates so that the first and second alignment layers face each other;

Injecting a liquid crystal layer between the first and second alignment layers;

Irradiating UV to the liquid crystal layer through the second substrate;

The liquid crystal layer includes a liquid crystal molecule having a spiral structure twisted tens of times, RM and a photoinitiator, wherein the spiral axis of the spiral structure is perpendicular to the first and second substrates.

The method of claim 8,

And forming a black matrix covering the thin film transistor to block light.