KR20070066234A - Liquid crystal display panel, method of manufacturing the same and method of manufacturing alignment film used in the liquid crystal display panel - Google Patents

Abstract

An LCD(Liquid Crystal Display) panel, a manufacturing method thereof and an alignment film manufacturing method used for the same are provided to prevent a defect of a device from generating through the omission of a rubbing process. A TFT(Thin Film Transistor)(120) is formed at a lower substrate. A pixel electrode(140) is electrically connected with the TFT. The first alignment layer(150) is formed on a pixel electrode and constructed by SAMs(Self Assembly Monolayers). An upper substrate(210) is formed oppositely to the lower substrate. A common electrode(220) is formed on the upper substrate. The second alignment layer(250) is formed on the common electrode and constructed by SAMs. A liquid crystal layer(300) is injected between the first and second alignment layers. In the first and second alignment layers, the liquid crystal particles have the pre-tilt angle.

Description

Liquid crystal display panel, manufacturing method thereof and method of manufacturing alignment film used therein {LIQUID CRYSTAL DISPLAY PANEL, METHOD OF MANUFACTURING THE SAME AND METHOD OF MANUFACTURING ALIGNMENT FILM USED IN THE LIQUID CRYSTAL DISPLAY PANEL}

1 is a conceptual diagram illustrating the concept of the present invention.

FIG. 2 is a conceptual diagram illustrating that the liquid crystal molecules of the liquid crystal layer illustrated in FIG. 1 have a pre-tilt angle.

3 is a cross-sectional view illustrating a liquid crystal display panel according to an exemplary embodiment of the present invention.

4 is a conceptual diagram illustrating a method of manufacturing an alignment film according to an embodiment of the present invention.

5 to 7 are cross-sectional views illustrating a method of manufacturing a liquid crystal display panel according to an exemplary embodiment of the present invention.

* Explanation of symbols for main parts of drawings *

30: first alignment layer 40: second alignment layer

60: head 65: body

110: lower substrate 120: thin film transistor

140: pixel electrode 150: first alignment layer

210: upper substrate 220: common electrode

250: second alignment layer 300: liquid crystal layer

500: liquid crystal display panel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel and a method of manufacturing the alignment layer used therein, and more particularly, to a liquid crystal display panel including an alignment layer made of self assembled monolayers (SAMs), a method of manufacturing the alignment layer, and the liquid crystal. A manufacturing method of a display panel is related.

Liquid Crystal Display Apparatus (LCD) is a type of flat panel display, and is a display device that displays an image by using the optical characteristics of the liquid crystal. Such liquid crystal displays are thinner and lighter than other display devices such as CRTs and PDPs, and have low driving voltages and low power consumption, and thus are widely used throughout the industry.

In general, a liquid crystal display device includes a thin film transistor (TFT) for switching each pixel and an array substrate (or TFT substrate) on which pixel electrodes are formed, an opposing substrate (or color filter substrate) on which color filters and a common electrode are formed, and the two substrates. It includes a liquid crystal panel composed of a liquid crystal layer interposed therebetween. The liquid crystal display displays an image by applying a voltage to the liquid crystal layer to control light transmittance.

Various modes have been developed in the liquid crystal display, including a vertically aligned (VA) mode for realizing a wide viewing angle. The liquid crystal panel of the liquid crystal display of the VA mode includes liquid crystal molecules having two substrates vertically aligned on opposite surfaces and a negative type dielectric constant anisotropy interposed between the two substrates. It consists of the liquid crystal layer comprised. In this case, the liquid crystal molecules have a property of homeotropic alignment.

In order to align the liquid crystal, an alignment film is formed on the TFT substrate and the color filter substrate. Many polyimide organic materials are used as the alignment layer. The organic alignment film is subjected to a rubbing process using a rubbing roll after forming and curing the organic polymer film on the substrate by a rotary coating method or a printing coating method. The rubbing process serves to give an alignment direction to the liquid crystal molecules by defining an alignment angle on the surface of the alignment layer.

However, there is a possibility that the thin film transistor (TFT) and the substrate on which various electrodes are formed may be contaminated by the foreign matter adhering to the resin plate during the rubbing process, and dust and static electricity may be generated to cause the TFT element to be disconnected. There is. Further, in order to remove the dust or foreign matter, since a separate washing and drying process is required after the rubbing process, a manufacturing cost increases.

In order to solve this problem, much research is being conducted on the liquid crystal alignment method without rubbing. Examples of processes that do not rub are the Langmuir-Blodgett (LB) method, the micro-shaping method (Grating method), the magnetic field applied surface adsorption method (MOLCA), the optical alignment method and the like.

In the case of the Langmuir-Blodgett (LB) method, a mechanism called Langmuir through is used to make a film, and since only ionic bonds exist between the molecular film and the substrate, it is difficult to form a strong molecular film.

Accordingly, there is a need for a liquid crystal alignment method that forms a robust molecular film between the molecular film and the substrate, does not require a separate device, and is easy to manufacture to reduce costs.

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 panel including a liquid crystal alignment layer that does not require a rubbing process.

Another object of the present invention is to provide a method for producing the alignment layer.

Another object of the present invention is to provide a method of manufacturing the liquid crystal display panel.

According to an exemplary embodiment of the present invention, a liquid crystal display panel includes a lower substrate, a thin film transistor formed on the lower substrate, a pixel electrode electrically connected to the thin film transistor, and a self-assembled monolayer film formed on the pixel electrode. A first alignment layer (SAM), an upper substrate formed to face the lower substrate, a common electrode formed on the upper substrate, a second alignment layer formed on the common electrode, and made of a self-assembled monolayer (SAM) and the first And a liquid crystal layer injected between the first alignment layer and the second alignment layer. The first and second alignment layers may be formed such that the liquid crystal molecules of the liquid crystal layer have a pre-tilt angle. The self-assembled monolayer (SAM) includes a head and a tail. The head is made of, for example, chlorosilane, thiol or alkanoic acid.

According to another aspect of the present invention, there is provided a method of manufacturing an alignment layer, including preparing a solution for forming a self-assembled monolayer (SAM), immersing a substrate in the solution, and chemical reaction between the solution and the surface of the substrate. Forming a self-assembled monolayer (SAM).

According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, the method including: forming a thin film transistor on a lower substrate, forming a pixel electrode electrically connected to the thin film transistor, and opposing the lower substrate. Forming a substrate, forming a common electrode on the upper substrate, preparing a solution for forming a self-assembled monolayer (SAM), dipping the lower substrate on which the pixel electrode is formed, in the solution, Forming a first alignment layer made of a self-assembled monolayer (SAM) through a chemical reaction between a solution and a surface of the pixel electrode, dipping the upper substrate on which the common electrode is formed, in the solution, the solution and the common electrode Forming a second alignment layer made of a self-assembled monolayer (SAM) through a chemical reaction between the surfaces of , And a step of injecting the upper substrate and the liquid crystal layer and the step of combining the lower substrate.

Hereinafter, a liquid crystal display panel according to a preferred embodiment of the present invention, a manufacturing method of an alignment layer used therein, and a manufacturing method of the liquid crystal display panel will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram illustrating the concept of the present invention.

The liquid crystal display panel according to the present invention employs a self assembly monolayer (SAM) as an alignment layer for liquid crystal alignment.

Self-assembled monolayer (SAM) is a simple and flexible system that can control the interfacial properties of metals, metal oxides, and semiconductors. The self-assembled monolayer (SAM) is an organic assembly formed by adsorption of organic molecules present in a solution or gas phase with each other. The adsorbates are spontaneously aligned to form a crystal structure. Since the head of the self-assembled monolayer (SAM) is changeable according to the exposed interface, it is possible to form an organic surface having useful chemical functionality according to the interface. At this time, the molecules forming the film with the surface of the substrate directly bond to form a very strong molecular film. In addition, the thickness of the film is only a few nanometers (nm) to form a very thin and uniform film.

In addition, when forming the film by the self-assembled monolayer (SAM), a separate device is not required, and since the film is not affected by the shape or size of the substrate, the film can be easily formed even on a complex substrate or a substrate having a large area. have.

Referring to FIG. 1, a first alignment layer 30 is formed on a first substrate 10, and a second alignment layer 40 is formed on a second substrate 20.

The first and second substrates 10 and 20 may be made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZO).

The first and second alignment layers 30 and 40 are formed of a self-assembled monolayer (SAM). The head 60 of the self-assembled monolayer (SAM) is chemically bonded to the surfaces of the first and second substrates 10 and 20. The head 60 is made of, for example, chlorosilane, thiol, or alkanoic acid. The body portion 65 includes a plurality of alkyl groups [CH 2] n. At the end (not shown) of the body portion, for example, an aliphatic compound, an aromatic compound, or a material such as benzene may be formed.

The liquid crystal layer 50 is injected between the first alignment layer 30 and the second alignment layer 40. The liquid crystal layer 50 is sealed by a sealant (not shown).

In FIG. 1, the liquid crystal molecules of the liquid crystal layer 50 are arranged in a vertical alignment (VA) mode. However, the present invention is not limited thereto. The liquid crystal molecules of the liquid crystal layer 50 may be arranged in a twisted nematic (TN) mode, a mixed twisted nematic (MTN) mode, or a homogeneous alignment mode.

FIG. 2 is a conceptual diagram illustrating that the liquid crystal molecules of the liquid crystal layer illustrated in FIG. 1 have a pre-tilt angle.

Referring to FIG. 1, a first alignment layer 30 is formed on a first substrate 10, and a second alignment layer 40 is formed on a second substrate 20.

The liquid crystal layer 50 is injected between the first alignment layer 30 and the second alignment layer 40. The liquid crystal molecules of the liquid crystal layer 50 may be, for example, a vertical alignment (VA) mode, a twisted nematic (TN) mode, a mixed twisted nematic (MTN), or homogeneous (Homogeneous). Arranged in orientation mode.

The first and second alignment layers 30 and 40 are formed of a self-assembled monolayer (SAM). In this case, the pre-tilt angle may be adjusted according to the type of material forming the self-assembled monolayer (SAM). For example, in the liquid crystal display panel employing the conventional alignment layer, the self-assembled monolayer (SAM) is formed as if the liquid crystal molecules have a pre-tilt angle of 2 to 3 degrees in the twisted nematic (TN) mode. By adjusting the orientation angle of 2 to 3 degrees can maintain the same pre-tilt (pre-tilt) angle. The numerical value of an orientation angle is not limited to this, It can adjust as needed.

3 is a cross-sectional view illustrating a liquid crystal display panel according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the liquid crystal display panel 500 according to the present invention includes a lower substrate 110 and an upper substrate 210 facing the lower substrate.

The thin film transistor 120 is formed on the lower substrate 110. The thin film transistor 120 includes a gate electrode 121, a source electrode 123, and a drain electrode 125 formed on the lower substrate 110. The thin film transistor 120 may further include a semiconductor layer 127 and an impurity semiconductor layer 128 covering the gate electrode 121. A gate insulating layer 130 is formed on the gate electrode 121.

The pixel electrode 140 electrically connected to the thin film transistor 120 is formed on the thin film transistor 120. The pixel electrode 140 is made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZO).

The thin film transistor 120 is formed for each region defined by a plurality of gate lines (not shown) and a plurality of data lines (not shown). The thin film transistor 120 applies or blocks a signal to the pixel electrode 140 according to a signal applied from the gate line (not shown) and the data line (not shown).

An organic insulating layer 170 may be formed on the thin film transistor 120. In this case, the semiconductor device may further include a contact hole 180 for electrically connecting the thin film transistor 120 and the pixel electrode 140. The passivation layer 160 may be formed between the organic insulating layer 170 and the thin film transistor 120.

Meanwhile, the common electrode 220 is formed on the upper substrate 210. The common electrode 220 is made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZO). A black matrix (not shown) that performs a light blocking function and a plurality of color filters (not shown) that express only a desired color may be formed between the upper substrate 210 and the common electrode 220.

A first alignment layer 150 is formed on the pixel electrode 140, and a second alignment layer 250 is formed on the common electrode 220. The first and second alignment layers 150 and 250 are formed of a self-assembled monolayer (SAM). Since the self-assembled monolayer (SAM) has the same structure as that shown in FIGS. 1 and 2, detailed descriptions thereof will be omitted. The head of the self-assembled monolayer SAM is chemically bonded to the surfaces of the pixel electrode 140 and the common electrode 220. The head is made of, for example, chlorosilane, thiol or alkanoic acid.

The liquid crystal layer 300 is injected between the first alignment layer 150 and the second alignment layer 250. The liquid crystal layer 300 is sealed by a sealant (not shown).

The liquid crystal in the liquid crystal layer 300 may be, for example, a vertical alignment (VA) mode, a twisted nematic (TN), a mixed twisted nematic (MTN) mode, or a homogeneous alignment. Arranged in mode.

In this case, the pre-tilt angle of the liquid crystal may be adjusted according to the type of material forming the self-assembled monolayer (SAM).

As described above, when the alignment layer employed in the liquid crystal display panel is formed of a self-assembled monolayer (SAM), the rubbing process can be omitted. Therefore, the thin film transistor TFT and various electrodes are formed by foreign substances generated during the rubbing process. There is no risk of contamination of the formed substrate, and it is possible to prevent device defects caused by dust and static electricity. In addition, since a separate washing and drying process for removing the dust or foreign matter is unnecessary, manufacturing costs can be reduced.

4 is a conceptual diagram illustrating a method of manufacturing an alignment film according to an embodiment of the present invention.

Referring to FIG. 4, the method of manufacturing an alignment layer according to the present invention includes preparing a solution for forming a self-assembled monolayer (SAM). The head of the solute of the solution consists of, for example, chlorosilane, thiol or alkanoic acid. The body portion of the solute of the solution contains a plurality of alkyl groups ([CH2] n). At the end of the body portion, for example, an aliphatic compound, an aromatic compound, or a substance such as benzene may be formed.

In this embodiment, octadecyltrichlorosilane (OTS) was used as the solute 70 of the solution for forming a self-assembled monolayer (SAM). The solute 70 includes a head 71 and a body portion 75. The head 71 is composed of chlorosilane, and the body 75 is composed of an alkyl chain having 18 carbon atoms. As a solvent of the solution, toluene or n-hexane was used, for example.

In the method for manufacturing an alignment layer according to the present invention, the self-assembled monolayer (80) is formed by immersing the substrate (10) on which the alignment layer is to be formed in the solution and by chemical reaction between the solution and the surface (15) of the substrate (10). It further comprises the step.

The substrate 10 may be made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZO).

When the substrate 10 is immersed in a solution using the octadecyltrichlorosilane (OTS) as the solute 70, the surface 15 of the substrate 10 made of oxide and the solute 70 are chemically React Thus, chlorine attached to the head 71 of the solute 70 made of chlorosilane is released, and covalent bond with the surface 15 of the substrate 10 made of oxide. An alignment film 80 is formed.

The alignment layer 80 has a high bonding strength because it forms a covalent bond with the surface 15 of the substrate 10. Thus, an extremely durable alignment film is formed.

In this embodiment, the head 71 of the solute 70 is made of chlorosilane, but the present invention is not limited thereto, and the head 71 is, for example, thiol or egg. It may also consist of alkanoic acid.

5 to 7 are cross-sectional views illustrating a method of manufacturing a liquid crystal display panel according to an exemplary embodiment of the present invention.

Referring to FIG. 5, a method of manufacturing a liquid crystal display panel according to the present invention includes forming a thin film transistor 120 on a lower substrate 110. Since the structure of the thin film transistor 120 has the same configuration as that shown in FIG. 3, the same reference numerals are used for the same configuration, and detailed descriptions thereof will be omitted.

The process of forming the thin film transistor 120 includes thin film deposition, photolithography, etching, stripping, and inspection.

The method of manufacturing a liquid crystal display panel according to the present invention further includes applying a pixel electrode 140 electrically connected to the thin film transistor 120 on the thin film transistor 120. The pixel electrode 140 is made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZO). An organic insulating layer 170 may be formed on the thin film transistor 120. In this case, the semiconductor device may further include a contact hole 180 for electrically connecting the thin film transistor 120 and the pixel electrode 140.

Referring to FIG. 6, the method of manufacturing a liquid crystal display panel according to the present invention further includes applying a common electrode 220 on the upper substrate 210. The common electrode 220 is made of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZO).

The method of manufacturing a liquid crystal display panel according to the present invention further includes preparing a solution for forming a self-assembled monolayer (SAM).

As a solute of the solution for forming the self-assembled monolayer (SAM), for example, octadecyltrichlorosilane (OTS) may be used, and as the solvent of the solution, for example, toluene or n-hexane (n-hexane) can be used.

Referring to FIG. 7, a method of manufacturing a liquid crystal display panel according to the present invention includes dipping the lower substrate 110 having the pixel electrode 140 in the solution and between the solution and the surface of the pixel electrode 140. The method may further include forming a first alignment layer 150 formed of a self-assembled monolayer (SAM) through a chemical reaction of.

Since the chemical reaction has already been described with reference to FIG. 4, detailed descriptions thereof will be omitted.

In the method of manufacturing a liquid crystal display panel according to the present invention, a method of manufacturing a liquid crystal display panel may be performed by immersing the upper substrate 210 having the common electrode 220 in the solution and by chemical reaction between the solution and the surface of the common electrode 220. The method may further include forming a second alignment layer 250 formed of the assembled monolayer (SAM).

In this case, the pre-tilt angle may be adjusted according to the type of the material forming the first and second alignment layers 150 and 250 made of the self-assembled monolayer (SAM).

The method of manufacturing a liquid crystal display panel according to the present invention further includes combining the lower substrate 110 on which the first alignment layer 150 is formed and the upper substrate 210 on which the second alignment layer 250 is formed. .

The liquid crystal layer 300 is injected between the first alignment layer 150 and the second alignment layer 250. The liquid crystal layer 300 is sealed by a sealant (not shown). The liquid crystal in the liquid crystal layer 300 may be, for example, a vertical alignment (VA) mode, a twisted nematic (TN), a mixed twisted nematic (MTN) mode, or a homogeneous alignment. Arranged in mode.

As described above, according to the present invention, since the alignment layer employed in the liquid crystal display panel is formed of a self-assembled monolayer (SAM), the number of steps can be reduced by omitting the rubbing process.

In addition, the thin film transistor TFT and the substrate on which the various electrodes are formed may not be contaminated by the foreign matter generated during the rubbing process, and device defects due to dust and static electricity may be prevented.

In addition, since a separate washing and drying process for removing the dust or foreign matter is unnecessary, manufacturing costs can be reduced.

In addition, since the self-assembled monolayer (SAM) is not affected by the shape or size of the substrate, it is possible to form a thin and uniform alignment layer even on a complicated substrate, and to facilitate large area.

While the invention has been described with reference to the examples, those skilled in the art may variously modify and change the invention without departing from the spirit and scope of the invention as set forth in the claims below. You will understand.

Claims (14)

Lower substrate; A thin film transistor formed on the lower substrate; A pixel electrode electrically connected to the thin film transistor; A first alignment layer formed on the pixel electrode and formed of a self-assembled monolayer (SAM); An upper substrate formed to face the lower substrate; A common electrode formed on the upper substrate; A second alignment layer formed on the common electrode and formed of a self-assembled monolayer (SAM); And And a liquid crystal layer injected between the first alignment layer and the second alignment layer. The liquid crystal display panel of claim 1, wherein the first and second alignment layers are formed such that liquid crystal molecules of the liquid crystal layer have a pre-tilt angle. The liquid crystal display panel of claim 1, wherein the self-assembled monolayer (SAM) comprises a head and a tail, and the head is chlorosilane. The liquid crystal display panel according to claim 3, wherein the tail portion is an alkyl chain having 18 alkoxy groups bonded thereto. The liquid crystal display panel of claim 1, wherein the self-assembled monolayer (SAM) comprises a head and a tail, and the head is thiol or alkanoic acid. The liquid crystal display panel of claim 1, further comprising an organic insulating layer formed between the pixel electrode and the thin film transistor and a contact hole for electrically connecting the pixel electrode and the thin film transistor. Preparing a solution for forming a self-assembled monolayer (SAM); Dipping the substrate in the solution; And Forming a self-assembled monolayer (SAM) through a chemical reaction between the solution and the surface of the substrate. 8. The method of claim 7, wherein the solute of the solution is octadecyltrichlorosilane. The method of claim 7, wherein the solvent of the solution is toluene or n-hexane. The method of claim 7, further comprising forming a thin film transistor on the substrate and applying a transparent electrode on the thin film transistor before the dipping of the substrate in the solution. Forming a thin film transistor on the lower substrate; Forming a pixel electrode electrically connected to the thin film transistor; Forming an upper substrate opposite the lower substrate; Forming a common electrode on the upper substrate; Preparing a solution for forming a self-assembled monolayer (SAM); Dipping the lower substrate on which the pixel electrode is formed in the solution; Forming a first alignment layer made of a self-assembled monolayer (SAM) through a chemical reaction between the solution and the surface of the pixel electrode; Dipping the upper substrate in which the common electrode is formed in the solution; Forming a second alignment layer made of a self-assembled monolayer (SAM) through a chemical reaction between the solution and the surface of the common electrode; Combining the upper substrate and the lower substrate; And A liquid crystal display panel manufacturing method comprising the step of injecting a liquid crystal layer. The method of claim 11, wherein the first and second alignment layers are formed such that the liquid crystal molecules of the liquid crystal layer have a pre-tilt angle. 12. The method of claim 11, wherein the solute of the solution is octadecyltrichlorosilane. The method of claim 11, wherein the solvent of the solution is toluene or n-hexane.

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