KR102440239B1 - Liquid Crystal Display Device And Method Of Fabricating The Same - Google Patents

Abstract

The present invention relates to a liquid crystal display device and a method for manufacturing the same, and by forming an alignment layer through a UV irradiation process for a self-aligning monomer, the polyimide coating, firing, and rubbing processes can be omitted, and as a result, afterimages are reduced. It is prevented, reliability is improved, manufacturing process is simplified, and manufacturing cost can be reduced.
Furthermore, it is possible to irradiate polarized UV rays using the second polarizing plate disposed inside the second substrate without the wire grid polarizer as an ultraviolet mask, so that the ultraviolet ray polarized through the wire grid polarizer is deformed and generated while passing through the second substrate. It is possible to prevent the misalignment of the orientation, thereby improving the reliability of the orientation.
In addition, by irradiating the polarized UV light through the wire grid polarizer mask, it is possible to omit the mask alignment time and the like, thereby shortening the manufacturing time and reducing the manufacturing cost due to the lifetime of the wire grid polarizer.

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 including an alignment layer formed using an in-cell polarizing plate, and a method for manufacturing the same.

As the era rapidly advances into the information society, the field of display that processes and displays a large amount of information is developing. ) was needed.

Accordingly, a thin film transistor liquid crystal display (TFT-LCD) having excellent color reproducibility and thinness has been developed, which displays an image using the optical anisotropy and polarization properties of liquid crystal molecules.

A liquid crystal display device includes two substrates facing each other and spaced apart from each other, and a liquid crystal layer formed between the two substrates, and a pixel electrode and a first alignment layer, a common electrode and a second alignment layer, respectively, on inner surfaces of the two substrates. These are sequentially formed, and the first and second polarizing layers are respectively formed on the outer surfaces of the two substrates.

However, when using a method in which the pixel electrode and the common electrode are formed to face each other vertically, and the liquid crystal layer is driven by the vertical electric field generated therebetween, there are advantages in characteristics such as transmittance and aperture ratio, There is a disadvantage in that the viewing angle characteristic is not excellent.

In order to overcome this disadvantage, an in-plane switching mode (IPS mode) or a fringe field switching mode using a horizontal electric field generated between a common electrode and a pixel electrode formed on the same substrate: FFS mode) a liquid crystal display device has been proposed.

Meanwhile, in a liquid crystal display device, an alignment layer is used to impart initial directivity to the liquid crystal layer. In general, the alignment layer is completed by coating polyimide (PI) and performing a rubbing process.

By the way, although the alignment layer formed of polyimide can impart initial directionality to the liquid crystal layer, many processes such as cleaning, coating, baking (pre-baking, post-baking), and rubbing must be performed. There is a disadvantage in that the manufacturing cost increases due to consumption of the material, and in particular, foreign substances generated in the rubbing process may cause an afterimage or cause a decrease in reliability.

In order to improve this disadvantage, a self-alignment process in which a liquid crystal layer is formed by mixing a monomer with liquid crystal molecules as a method of forming an alignment layer in which the rubbing process is omitted, and then irradiated with ultraviolet light to form an alignment layer has been proposed. , which will be described with reference to the drawings.

1A to 1D are views for explaining a method of forming an alignment layer by a conventional self-alignment process.

As shown in FIG. 1A , a liquid crystal layer 70 is formed between the first and second substrates 20 and 50 bonded to each other, and the liquid crystal layer 70 includes a liquid crystal molecule 72 and a self-aligning monomer. alignment monomer) 74 , and the liquid crystal molecules 72 have a state in which long axes are randomly arranged.

As shown in FIG. 1B , the liquid crystal layer 70 is formed between the nematic phase and the isotropic phase of the liquid crystal molecules 72 by using a heating device 80 such as a hot plate. It is heated above the transition temperature (Tni) of

As shown in FIG. 1C , a wire grid polarizer 90 is applied to the liquid crystal layer 70 through the second substrate 50 in a state where the liquid crystal molecules 72 are isotropic by heating the liquid crystal layer 70 . ) is used as an ultraviolet mask to irradiate polarized ultraviolet rays.

As shown in FIG. 1D, the self-aligning monomer (74 in FIG. 1C) of the liquid crystal layer 70 is polymerized by polarized ultraviolet light, and the first alignment layer 76 is disposed between the first substrate 20 and the liquid crystal layer 70. ) is formed, a second alignment layer 78 is formed between the second substrate 50 and the liquid crystal layer 70, and the liquid crystal molecules 72 are formed by the first and second alignment layers 76 and 78. It has a uniaxial orientation state in which the long axis is aligned along one direction.

However, when polarized UV light is irradiated to the liquid crystal layer 70 using a wire grid polarizer 90 as an UV mask on the second substrate 50 , the polarized UV light is applied to the second substrate 50 . The intensity of polarized UV light is reduced by being reflected from the outer surface of the

In addition, the polarized UV rays are deformed while passing through the second substrate 50, and an orientation shift occurs due to the deformed polarized UV rays. Accordingly, the uniaxial alignment of the liquid crystal molecules 72 is weakened, thereby reducing the quality of the image. become a factor

In addition, the manufacturing time increases depending on the mask alignment time due to the irradiation of polarized UV light through the wire grid polarizer 90, and the wire grid polarizer 90 has a limited life depending on the amount used, so the replacement of the wire grid polarizer 90 Accordingly, there is a problem in that the manufacturing cost increases.

The present invention is proposed to solve this problem, and by arranging an in-cell polarizing plate on the inner surface of the second substrate and irradiating polarized ultraviolet rays through the in-cell polarizing plate to form an alignment layer, the reliability of alignment is increased and manufacturing time is reduced at the same time An object of the present invention is to provide a liquid crystal display device and a method for manufacturing the same, in which manufacturing costs are reduced.

In order to achieve the above object, the present invention provides first and second substrates facing each other and spaced apart from each other, a thin film transistor disposed on the inner surface of the first substrate, a first alignment layer disposed on the thin film transistor, and the first substrate A liquid crystal display comprising a second alignment layer disposed on an inner surface of a second substrate, a second polarizing plate disposed between the second substrate and the second alignment layer, and a liquid crystal layer disposed between the first and second alignment layers; to provide.

Here, each of the first and second alignment layers may be formed of a material in which a self-aligning monomer is polymerized.

In addition, the second polarizer may be a coated polarizer or a wire grid polarizer.

In addition, it may further include a first polarizing plate disposed on the outer surface of the first substrate.

In addition, a black matrix and a color filter layer disposed on the inner surface of the first substrate may be further included.

Meanwhile, the present invention includes the steps of forming a thin film transistor on a first substrate, forming a pixel electrode and a common electrode on the thin film transistor, forming a second polarizing plate on a second substrate, and bonding the first and second substrates to face the pixel electrode and the common electrode and the second polarizing plate of the second substrate; Forming a layer and heating the liquid crystal layer above a transition temperature (Tni) between a nematic phase and an isotropic phase of the liquid crystal molecule, and the self-aligning monomer through the second polarizing plate It provides a method of manufacturing a liquid crystal display device comprising the step of forming first and second alignment layers, respectively, between the first and second substrates and the liquid crystal layer by irradiating ultraviolet rays to the substrate.

In addition, the ultraviolet rays become polarized ultraviolet rays after passing through the second polarizing plate, and the first and second alignment layers may be formed by polymerization of the self-aligning monomers by the polarizing ultraviolet rays, respectively.

Here, the second polarizer may be a coated polarizer or a wire grid polarizer.

The method may further include forming a first polarizing plate on the outer surface of the first substrate.

The method may further include forming a black matrix and a color filter layer on the inner surface of the first substrate.

In the present invention, by irradiating polarized ultraviolet rays to the self-aligning monomer to form an alignment layer, the rubbing process is omitted, and the afterimage caused by foreign substances is prevented and reliability is improved.

In addition, according to the present invention, it is possible to irradiate polarized UV rays using an in-cell polarizer disposed on the second substrate without a wire grid polarizer as an ultraviolet mask, thereby improving the reliability of orientation and reducing manufacturing time and manufacturing cost. has

1A to 1D are views for explaining a method of forming an alignment layer by a conventional self-alignment process;
2 is a view showing a liquid crystal display device according to an embodiment of the present invention.
3A to 3G are views for explaining a method of manufacturing a liquid crystal display according to an embodiment of the present invention.

Hereinafter, a liquid crystal display device and a method for manufacturing the same according to the present invention will be described with reference to the accompanying drawings, taking an in-plane switching mode (IPS mode) liquid crystal display device as an example.

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

As shown in FIG. 2 , the liquid crystal display 110 according to the embodiment of the present invention includes first and second substrates 120 and 150 spaced apart from each other facing each other, and first and second substrates 120 , The liquid crystal layer 170 formed between the 150 ) and a backlight unit (not shown) under the first substrate 120 are included.

Specifically, the gate electrode 122 may be formed in each pixel region on the inner surface of the first substrate 120 , and the gate insulating layer 124 may be formed on the entire surface of the first substrate 120 above the gate electrode 122 . .

A semiconductor layer 126 is formed on the gate insulating layer 124 corresponding to the gate electrode 122 , and a source electrode 128 and a drain electrode 130 spaced apart from each other are formed on both ends of the semiconductor layer 126 . can be

Here, the gate electrode 122 , the semiconductor layer 126 , the source electrode 128 , and the drain electrode 130 may constitute the thin film transistor T .

Although not shown, a gate wiring connected to the gate electrode 122 is formed on the upper surface of the first substrate 120 , and a data line connected to the source electrode 128 is formed on the gate insulating layer 124 , and the gate wiring and data lines may cross each other to define a pixel area.

A protective layer 132 is formed on the entire surface of the first substrate 120 on the thin film transistor T, and at the boundary of the pixel region on the protective layer 132, the thin film transistor T, the gate wiring, and the data wiring corresponding to the A black matrix 134 may be formed.

A color filter layer 136 including red, green, and blue color filters corresponding to each pixel area is formed on the black matrix 134 , and the color filter layer 136 and the protective layer 132 connect the drain electrode 130 to each other. It has a drain contact hole that is exposed.

In FIG. 2 , it is exemplified that the black matrix 134 is formed of a different layer from the color filter layer 136 , but in another embodiment, two or more of the red, green, and blue color filters of the color filter layer 136 are overlapped to form a black matrix. (134) can also be used.

A pixel electrode 138 connected to the drain electrode 130 through a drain contact hole and a common electrode 140 spaced apart from the pixel electrode 138 may be formed in each pixel region on the color filter layer 136 . .

The pixel electrode 138 and the common electrode 140 have a bar shape, are made of a metal material or a transparent conductive material, and may be alternately disposed in the pixel area.

In FIG. 2 , it is exemplified that the pixel electrode 138 and the common electrode 140 are formed on the same layer, but in another embodiment, an insulating layer is disposed between the pixel electrode 138 and the common electrode 140 to form a different layer. may be formed.

A first alignment layer 176 may be formed on the pixel electrode 138 and the common electrode 140 .

A second polarizing plate 162 and a second alignment layer 178 may be sequentially formed on the entire inner surface of the second substrate 150 .

A liquid crystal layer 170 including liquid crystal molecules 172 may be formed between the first and second substrates 120 and 150 , and a first polarizing plate 160 may be formed on the outer surface of the first substrate 120 . have.

Here, the first and second alignment layers 176 and 178 may be formed through a UV irradiation process for a self-alignment monomer, respectively.

In addition, the liquid crystal layer 170 is formed by an injection process after bonding the first and second substrates 120 and 150 or by a dispensing process on one of the first and second substrates 120 and 150 . After forming 170, the first and second substrates 120 and 150 may be bonded.

In particular, the second polarizer 162 of the liquid crystal display 110 according to the embodiment of the present invention is an in-cell polarizer disposed between the second substrate 150 and the second alignment layer 178 . can be configured.

Accordingly, in the process of forming the first and second alignment layers 176 and 178, the ultraviolet rays irradiated from the outside of the second substrate 150 can be polarized into linearly polarized ultraviolet rays through the second polarizing plate 162 without a separate wire or a polarizing plate mask. there will be

And, as the polarized UV light transmitted through the second polarizing plate 162 is irradiated, the self-aligning monomer is polymerized to form the first and second alignment layers 176 and 178,

Therefore, it is possible to irradiate polarized UV rays using the second polarizing plate 162 disposed inside the second substrate 150 without the wire grid polarizer (90 in FIG. 1C) as an ultraviolet mask, and thus the wire grid polarizer (90 in FIG. 1C) can be used to irradiate the polarized UV rays. 90), it is possible to prevent the distortion of the orientation caused by the deformation while passing through the second substrate (50 in FIG. 1D), thereby improving the reliability of the orientation.

In addition, it is possible to reduce the manufacturing cost according to the life of the wire grid polarizer (FIG. 1C 90).

In the liquid crystal display 110 as described above, when the thin film transistor T is turned on according to the gate voltage of the gate wiring, the data voltage of the data wiring is transferred to the pixel electrode 138 through the thin film transistor T. ) is approved.

A horizontal electric field is generated between the pixel electrode 138 to which the data voltage is applied and the common electrode 140 to which the common voltage is applied, and the liquid crystal molecules 172 of the liquid crystal layer 170 are rearranged according to the generated horizontal electric field. display the image.

In particular, by forming the first and second alignment layers 176 and 178 through the UV irradiation process for the self-aligning monomer, the polyimide coating, firing, and rubbing processes can be omitted, and as a result, afterimage is prevented and reliability. This is improved, the manufacturing process is simplified and the manufacturing cost is reduced.

A method of manufacturing a liquid crystal display including an alignment layer formed using such an in-cell polarizing plate will be described with reference to the drawings.

3A to 3G are diagrams for explaining a method of manufacturing a liquid crystal display according to an exemplary embodiment of the present invention, which will be described with reference to FIG. 2 .

As shown in FIG. 3A , a gate electrode 122 , a gate insulating layer 124 , a semiconductor layer 126 , a source electrode 128 , and a drain electrode 130 are sequentially formed on the first substrate 120 . Thus, the thin film transistor T is completed, and the protective layer 132 may be formed on the thin film transistor T.

In addition, the black matrix 134 and the color filter layer 136 may be formed on the protective layer 132 , and the pixel electrode 138 and the common electrode 140 may be formed on the color filter layer 136 .

As shown in FIG. 3B , a second polarizing plate 162 may be formed on the second substrate 150 . Here, the second polarizer 162 is an in-cell polarizer and is disposed to face the first substrate 120 when the first and second substrates 120 and 150 are adhered.

That is, an in-cell type second polarizing plate 162 is formed on the entire inner surface of the second substrate 150 .

Here, the in-cell type second polarizing plate 162 may be formed by a coating method.

For example, the in-cell-type second polarizing plate 162 may be an E (extraordinary) type in the form of a disc made of a supramolecular complex or a plurality of organic compounds, and may be of an E (extraordinary) type. It may have a parallel optical axis, an absorption axis perpendicular to the optical axis, and a transmission axis parallel to the optical axis.

In addition, the in-cell type second polarizing plate 162 is made of a transparent substrate and a metal wire formed on the transparent substrate, and reflects a polarization component parallel to the metal wire W (S polarization) and a perpendicular polarization component (P polarization). ) may be a transmissive wire grid polarizer.

As shown in FIG. 3C , the first and second substrates 120 and 150 are bonded so that the second polarizing plate 162 formed on the second substrate 150 faces the first substrate 120 , and the first And a liquid crystal layer 170 is formed between the second substrates 120 and 150 in a mixture of the liquid crystal molecules 172 and the self-alignment monomer 174 .

At this time, after bonding the first and second substrates 120 and 150 , the liquid crystal layer 170 is formed by an injection process of a mixture of the liquid crystal molecules 172 and the self-aligning monomer 174 , or the first and second substrates After forming the liquid crystal layer 170 by a dropping process of a mixture of the liquid crystal molecules 172 and the self-aligning monomer 174 on one of 120 and 150, the first and second substrates 120 and 150 are attached to each other. can

As shown in FIG. 3D , the liquid crystal layer 170 is formed between the nematic phase and the isotropic phase of the liquid crystal molecules 172 by using a heating device 180 such as a hot plate. It is heated above the transition temperature (Tni) of Accordingly, the liquid crystal molecules 172 become isotropic.

This is because when polarized UV light is irradiated to the liquid crystal layer 170 in a state in which the liquid crystal molecules 172 are in a nematic phase, the polarized UV light is not properly transmitted to the self-aligning monomer 174 due to the refractive index anisotropy of the liquid crystal layer 170. Since the layer is not formed, it is to transfer the liquid crystal molecules 172 to an isotropic phase before irradiating polarized UV rays.

As shown in FIG. 3E , ultraviolet light is applied to the liquid crystal layer 170 through the second substrate 150 of the first and second substrates 120 and 150 bonded in a state in which the liquid crystal molecules 172 are transferred in an isotropic phase. (UV) irradiation.

Here, the ultraviolet rays can be polarized as linearly polarized light by the second polarizing plate 162 disposed inside the second substrate 150 . A polymerization reaction occurs in the self-aligned monomer 174 by the polarized UV light.

In this case, since the black matrix 134 and the color filter layer 136 are formed on the first substrate 120 , ultraviolet rays can be irradiated to the liquid crystal layer 170 through the second substrate 150 .

In particular, since ultraviolet rays passing through the second substrate are directly polarized with linear polarization by the second polarizing plate disposed inside the second substrate and then directly incident on the liquid crystal layer without passing through another optical medium, a wire grid polarizer (Fig. 1c 90), the linearly polarized ultraviolet ray is deformed while passing through the second substrate, thereby preventing misalignment of the orientation.

In addition, it is possible to omit the mask alignment time due to polarized UV irradiation through the wire grid polarizer (FIG. 1C 90), thereby shortening the manufacturing time and reducing the manufacturing cost due to the life of the wire grid polarizer (FIG. 1C 90). do.

As shown in FIG. 3f , a first alignment layer 176 is formed between the first substrate 120 and the liquid crystal layer 170 by polymerization of the self-aligning monomer 174 according to irradiation with polarized ultraviolet rays, and the second substrate A second alignment layer 178 is formed between 150 and the liquid crystal layer 170 , and the liquid crystal layer 170 is formed by the liquid crystal molecules 172 by the initial orientation of the first and second alignment layers 176 and 178 . ) has a uniaxial orientation state in which the long axis is aligned along one direction in a plane parallel to the first and second substrates 120 and 150 .

As shown in FIG. 3G , the liquid crystal display 110 is completed by forming the first polarization layer 160 on the outer surface of the first substrate 120 .

As described above, in the liquid crystal display 110 and the method for manufacturing the same according to the embodiment of the present invention, the first and second alignment layers 176 and 178 are formed through the UV irradiation process for the self-aligned monomer, so that the polyimide coating, firing, and rubbing processes can be omitted, and as a result, afterimages are prevented, reliability is improved, manufacturing processes are simplified, and manufacturing costs are reduced.

In particular, it is possible to irradiate polarized UV rays using the second polarizing plate 162 disposed inside the second substrate 150 without the wire grid polarizing plate (90 in FIG. 1C) as an ultraviolet mask, so that the wire grid polarizing plate (90 in FIG. 1C) can be used to irradiate the polarized UV rays. 90), it is possible to prevent the distortion of the orientation caused by the deformation while passing through the second substrate (50 in FIG. 1D), thereby improving the reliability of the orientation.

In addition, it is possible to reduce the manufacturing time due to polarized UV irradiation through the wire grid polarizer (FIG. 1C 90) and the manufacturing cost according to the lifetime of the wire grid polarizer (FIG. 1C 90).

In describing the present invention, a color filter on thin film transistor (COT) type liquid crystal display 110 in which a thin film transistor T and a color filter layer 136 are sequentially formed on the first substrate 120 as an example. However, in another embodiment, a liquid crystal display device of a thin film transistor on color filter (TOC) type in which a color filter layer and a thin film transistor are sequentially formed on a first substrate, or red and green without forming a color filter layer on a display panel In a field sequential color mode (FSC mode) liquid crystal display device that sequentially emits a blue light source to display a color, an alignment film is formed through polarized UV irradiation by an in-cell polarizing plate formed inside the second substrate. can

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below. You will understand that it can be done.

110: liquid crystal display 120: first substrate
122: gate electrode 124: gate insulating film
126: semiconductor layer 128: source electrode
130: drain electrode 132: protective layer
134: black matrix 136: color filter layer
138: pixel electrode 140: common electrode
150: second substrate 160: first polarizing plate
162: second polarizing plate 170: liquid crystal layer
176: first alignment layer 178: second alignment layer

Claims (12)

first and second substrates facing each other and spaced apart;
a thin film transistor disposed on the inner surface of the first substrate;
a first alignment layer disposed on the thin film transistor;
a second alignment layer disposed on the inner surface of the second substrate;
a second polarizing plate disposed between the second substrate and the second alignment layer;
a liquid crystal layer disposed between the first and second alignment layers
including,
The second polarizing plate is in contact with the second alignment layer,
The first and second alignment layers heat the liquid crystal layer including liquid crystal molecules and a self-aligning monomer to a transition temperature (Tni) or higher between a nematic phase and an isotropic phase of the liquid crystal molecules. A liquid crystal display formed between the first and second substrates and the liquid crystal layer by irradiating polarized UV rays to the self-aligning monomer of the liquid crystal layer through the second polarizing plate in a state in which the liquid crystal molecules are transferred to the isotropic phase Device.
delete The method of claim 1,
The second polarizer is a coating type polarizer or a wire grid polarizer (Wire Grid Polarizer) liquid crystal display.
4. The method of claim 3,
The liquid crystal display device further comprising a first polarizing plate disposed on the outer surface of the first substrate.
4. The method of claim 3
The liquid crystal display device further comprising a black matrix and a color filter layer disposed on the inner surface of the first substrate.
forming a thin film transistor on the first substrate;
forming a pixel electrode and a common electrode on the thin film transistor;
forming a second polarizing plate on the second substrate;
bonding the first and second substrates to face the pixel electrode and the common electrode of the first substrate and a second polarizing plate of the second substrate;
forming a liquid crystal layer between the first and second substrates using a mixture of liquid crystal molecules and a self-aligning monomer;
heating the liquid crystal layer above a transition temperature (Tni) between a nematic phase and an isotropic phase of the liquid crystal molecules;
In a state in which the liquid crystal molecules are transferred to the isotropic phase, first and second alignment layers are respectively formed between the first and second substrates and the liquid crystal layer by irradiating polarized UV rays to the self-aligning monomer through the second polarizing plate. step to form
A method of manufacturing a liquid crystal display comprising a.
7. The method of claim 6,
The ultraviolet rays become the polarized ultraviolet rays after passing through the second polarizing plate,
The first and second alignment layers are each formed by polymerization of the self-aligning monomer by the polarized UV rays.
8. The method of claim 7,
The second polarizing plate is a coating-type polarizing plate or a wire grid polarizer (Wire Grid Polarizer) manufacturing method of a liquid crystal display device.
9. The method of claim 8,
The method of manufacturing a liquid crystal display device further comprising the step of forming a first polarizing plate on the outer surface of the first substrate.
9. The method of claim 8,
and forming a black matrix and a color filter layer on the inner surface of the first substrate. The method of claim 1,
The liquid crystal molecules of the liquid crystal layer have a uniaxial alignment state in which long axes are aligned along one direction in a plane parallel to the first and second substrates.
12. The method of claim 11,
The liquid crystal molecules having the uniaxial alignment state overlap the thin film transistor.

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