KR101974162B1 - Self-assembled liquid crystal alignment layer, liquid crystal device using the same and method for manufacturing lcd using the same - Google Patents

Abstract

The present invention relates to a liquid crystal alignment layer and a method of manufacturing a vertically aligned liquid crystal display using the same, and more particularly, to a liquid crystal alignment layer capable of vertically aligning liquid crystal molecules uniformly through hydrogen bonding, And a method for producing the same.
The liquid crystal alignment layer and the liquid crystal display according to the present invention can uniformly arrange the liquid crystal molecules without the conventional polyimide alignment layer by applying the aliphatic organic molecules including the hydrogen bonding unit capable of bonding with the substrate, Can be implemented. In addition, it can realize a higher threshold voltage (Vth) compared to a liquid crystal display device using a conventional polyimide alignment film, and it has an improved level of liquid crystal reaction speed that has a rising time and a pulling time of 2 to 4 times faster Can be implemented.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-aligned liquid crystal alignment layer, a liquid crystal display using the same, and a method of manufacturing the same.

The present invention relates to a self-aligned liquid crystal alignment layer, a liquid crystal display using the same, and a method of manufacturing the same. More particularly, the present invention relates to a self-aligned liquid crystal alignment layer capable of vertically aligning liquid crystal molecules in a liquid crystal layer without a conventional polyimide alignment layer, And a liquid crystal display using the liquid crystal alignment layer and a method of manufacturing the same.

2. Description of the Related Art A liquid crystal display (LCD) is composed of a liquid crystal display panel that displays an image using light transmittance of a liquid crystal and a backlight assembly that provides light. The liquid crystal display panel generally includes a TFT array substrate, a color filter layer substrate facing the array substrate, and a liquid crystal layer interposed between the array substrate and the color filter layer substrate. When an electric field is applied to the liquid crystal layer, the arrangement of the liquid crystal molecules changes according to an electric field formed thereby, and a phase difference of incident light passing through the liquid crystal layer is generated, and light is transmitted to display an image.

In general, an alignment film polymer layer is used to form an initial alignment of liquid crystal molecules in a state where a voltage is not supplied to a display device. Generally, polyimide-based polymers are mainly used, and the polymer solution is printed on the array and the color filter layer substrate in the form of a thin film before the injection of the liquid crystal, followed by heat treatment and firing.

However, the conventional alignment film process requires a separate thin film forming step before liquid crystal injection, and the thin film is subjected to a multi-step drying and curing process, which complicates and takes a long time. In addition, the thickness of the thin film is uneven and problems such as stain are generated. In particular, a polyimide alignment film requires synthesis of a separate monomer in order to improve performance such as contrast ratio and reliability, and its synthesis method also has a complicated problem. Accordingly, it is inevitable to develop a new alignment agent capable of improving display characteristics.

Korean Patent No. 10-0484851 Korean Patent No. 10-0782436 Korean Patent No. 10-1046926

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal alignment layer capable of arranging liquid crystal molecules in a liquid crystal layer through hydrogen bonding without a conventional polyimide alignment layer, and a low cost, high quality A liquid crystal display device and a method of manufacturing the same.

In order to achieve the above object, the present invention provides a TFT array substrate; A color filter substrate; And a liquid crystal layer between the array substrate and the color filter substrate, wherein the organic molecular liquid crystal mixture is prepared by mixing a liquid crystal with an aliphatic organic molecule containing no cyclic group represented by the following formula Step (step 1); Dropping the organic molecular liquid crystal mixture on one side of the array substrate or the color filter substrate (step 2); Attaching the two substrates such that the mixture is positioned between the array substrate and the color filter substrate (step 3); And a step of heat treating the bonded substrate and cooling the bonded substrate to room temperature, wherein hydrogen bonding between the organic molecules and the substrate is performed. The liquid crystal layer may include a liquid crystal and a liquid crystal alignment layer. The substrate may be an ITO substrate or a glass substrate, but is not limited thereto.

[Chemical Formula 1]

In Formula 1,

(여기서 z = 0 ~ 20)일 수 있다.a is selected from the group consisting of a hydroxyl group, an amine group and a carboxylic acid group, and b is

(Where z = 0 to 20).

(여기서 z = 4 ~ 20)일 수 있다. 본 발명에 따르면, 상기와 같은 긴 알킬사슬을 포함하는 유기분자를 이용함으로써 기존 폴리이미드 배향막 없이도 강한 수직 배향력을 구현할 수 있고, 이에 따라 액정표시장치의 명암비를 향상시킬 수 있다. More preferably, in Formula 1, b is

(Where z = 4 to 20). According to the present invention, by using organic molecules including long alkyl chains as described above, it is possible to realize a strong vertical orientation force without existing polyimide alignment films, thereby improving the contrast ratio of a liquid crystal display device.

The aliphatic organic molecules may be added in an amount of 0.01 to 10 parts by weight, more preferably 0.1 to 0.5 parts by weight, based on 100 parts by weight of the liquid crystal. When mixed in the above-mentioned range, a uniform liquid crystal alignment layer is formed and excellent black display capability and excellent high-speed response characteristics can be realized.

The heat treatment may be performed at 80 to 120 ° C for 30 to 120 minutes, more preferably at 100 ° C for 60 minutes. When heat treatment is performed in the above range, organic molecules can be uniformly arrayed over the substrate region, and thus a liquid crystal display device free from unevenness of the screen due to uneven orientation can be manufactured.

The aliphatic organic molecule may include at least one selected from the group consisting of octanoic acid, decanoic acid, undecanoic acid, and dodecanoic acid.

The aliphatic organic molecule may be hydrogen bonded to the substrate.

The present invention also relates to a TFT array substrate; A color filter substrate; And a liquid crystal layer interposed between the array substrate and the color filter substrate, wherein a liquid crystal alignment layer is formed between at least one of the array substrate and the color filter substrate and the liquid crystal layer, And the alignment layer is composed of an aliphatic organic molecule containing no cyclic group represented by the above formula (1). The liquid crystal layer may include a liquid crystal and a liquid crystal alignment layer. The liquid crystal alignment layer may orient liquid crystal molecules perpendicular to the substrate.

The present invention also provides a liquid crystal alignment layer made of an aliphatic organic molecule containing no cyclic group represented by the above-mentioned formula (1) as a liquid crystal alignment layer used in a liquid crystal display device. The liquid crystal alignment layer may orient liquid crystal molecules perpendicular to the substrate.

The liquid crystal alignment layer and the liquid crystal display according to the present invention can uniformly arrange the liquid crystal molecules without the conventional polyimide alignment layer by applying the aliphatic organic molecules including the hydrogen bonding unit capable of bonding with the substrate, Can be implemented. In addition, a higher threshold voltage (Vth) can be achieved than a liquid crystal display device using a conventional polyimide alignment layer, and an improved level of liquid crystal reaction speed can be achieved with a rise time and a pulling time of 2 to 4 times faster .

1 is a cross-sectional view of a self-aligned liquid crystal alignment layer and a liquid crystal display using non-covalent hydrogen bonding of an aliphatic organic molecule.
2 is a result of analyzing the black screen area of a liquid crystal display device (Comparative Example and Example 1) in which no voltage is applied in a state that the backlight is turned on, using a DSLR camera.
3 is a graph showing transmittance curves of the liquid crystal display according to the comparative example and the example 1 according to the voltage.
4 is a graph showing a rising time (left side) and a pulling time (right side) of the liquid crystal display device according to Comparative Example (a) and Example 1 (b).
FIG. 5 is a result of analyzing the black screen level of a liquid crystal display device (Comparative Example and Example 2) in which no voltage is applied in a state that the backlight is turned on, using a DSLR camera.
6 is a graph showing a transmittance curve according to the voltage of the liquid crystal display device according to the comparative example and the second embodiment.
7 is a graph showing a rising time (left side) and a pulling time (right side) of the liquid crystal display according to the comparative example (a) and the example 2 (b).

Hereinafter, the present invention will be described in more detail with reference to Examples. The objects, features and advantages of the present invention will be readily understood through the following examples. The present invention is not limited to the embodiments described herein, but may be embodied in other forms. The embodiments described herein are provided to enable those skilled in the art to fully understand the spirit of the present invention. Therefore, the present invention should not be limited by the following examples.

The liquid crystal display 100 of the present invention will be described with reference to FIG. The liquid crystal display device 100 includes a liquid crystal layer 130 between the color filter substrate 110 and the TFT array substrate 120. A liquid crystal alignment layer including aliphatic organic molecules is formed between the liquid crystal layer 130 of the liquid crystal display device 100 and the substrates 110 and 120. The liquid crystal alignment layer is a novel self-aligned liquid crystal alignment layer containing an aliphatic organic molecule 140 containing no cyclic group. The aliphatic organic molecules constituting the liquid crystal alignment layer have a hydrogen bonding unit 141 for bonding with the substrate at one end (a portion) and a liquid-crystalline molecule capable of interacting with the liquid crystal molecules of the liquid crystal layer at the other end There is a flexible alkyl group 142. Particularly, the aliphatic organic molecule is characterized in that it does not contain a ring group. When the aliphatic organic molecules are mixed with the host liquid crystal and injected into the liquid crystal display device, one end (a portion) of the aliphatic organic molecules undergoes hydrogen bonding with the ITO transparent electrode or glass of the substrate to fix the organic molecules to the substrate , And the other end (b part) interacts with the liquid crystal molecules to vertically align the liquid crystal molecules, thereby making it possible to manufacture a self-aligned vertical alignment layer.

Example 1: Preparation of a liquid crystal display device containing octanoic acid

Preparation of liquid crystal mixture

Octanoic acid, an aliphatic organic molecule, was added to 100 parts by weight of a host liquid crystal having a dielectric anisotropy (DELTA epsilon) of -3.3 at a concentration of about 0.2 parts by weight. Was stirred for about 10 minutes at a temperature of 70 캜 so that octanoic acid could be completely dissolved and mixed in the host liquid crystal.

Manufacturing of Liquid Crystal Display

Next, an octanoic acid liquid crystal mixture was evenly dropped on a lower TFT array substrate having a pixel electrode (ITO) or an upper color filter substrate having a common electrode (common ITO), and the two substrates were bonded together using a sealant. After the cementation, the liquid crystal display cell was heat-treated in a high-temperature oven at 100 ° C for about 1 hour. Thereafter, the solution was gradually cooled to room temperature to cause octanoic acid molecules to be bonded to the substrate by non-covalent hydrogen bonding, and liquid crystal molecules were vertically aligned by octanoic acid molecules to form a liquid crystal alignment layer.

Example 2: Preparation of liquid crystal display device containing decanoic acid

Preparation of liquid crystal mixture

To 100 parts by weight of a host liquid crystal having a dielectric anisotropy (DELTA epsilon) of -3.3 was added decanoic acid, an aliphatic organic molecule, at a concentration of about 0.2 parts by weight. The mixture was stirred at 70 DEG C for about 10 minutes so that decanoic acid could be completely dissolved and mixed in the host liquid crystal.

Manufacturing of Liquid Crystal Display

Next, the decanoic acid liquid crystal mixture was evenly dropped on a lower TFT array substrate having a pixel electrode (ITO) or an upper color filter substrate having a common electrode (common ITO), and the two substrates were bonded together using a sealant. After the cementation, the liquid crystal display cell was heat-treated in a high-temperature oven at 100 ° C for about 1 hour. Thereafter, the solution was gradually cooled to room temperature to cause the decanoic acid molecules to be bonded to the substrate by non-covalent hydrogen bonding, and at the same time, the liquid crystal molecules were vertically aligned by decanoic acid molecules to form a liquid crystal alignment layer.

Comparative Example

A lower TFT array substrate having a pixel electrode (ITO) or an upper color filter substrate having a common electrode (common ITO) was coated with 5 g of polyimide with N-methyl-2-pyrrolidone and gamma The polyimide solution dissolved in 100 mL of the mixed solution of gamma-butyrolactone was uniformly dispersed using a spin coater. The coated TFT array substrate or the upper color filter substrate having the common electrode was soft baked at 120 DEG C for 5 minutes using a hot plate and hard baked at 230 DEG C for 30 minutes using an oven (hard baking) to form a PI alignment film having a thickness of about 100 nm. Thereafter, the host liquid crystal having a dielectric anisotropy (??) Of -3.3 was evenly dropped on the substrate, and the two substrates were bonded together using a sealant. After the cementation, the liquid crystal display cell was heat-treated in a high-temperature oven at a temperature of 100 ° C for about 1 hour, and cooled to room temperature to prepare a liquid crystal display device.

EXPERIMENTAL EXAMPLE 1: Analysis of Orientation Force and Electro-optical Characteristics of Liquid Crystal Display

The alignment properties and the electro-optical characteristics of the liquid crystal display device manufactured according to Example 1 were measured. As a result of comparing the degree of black display on the OV where no voltage was applied to the liquid crystal device, the new liquid crystal display cell manufactured according to Example 1 showed a liquid crystal display cell (comparative example) to which the conventional polyimide alignment film was applied, And a black screen was realized without light leakage throughout the screen (FIG. 2).

As a result of measurement of a voltage-transmittance curve according to a voltage, the cell according to the first embodiment has a VT shape shifted to the right compared to the conventional cell (comparative example), and has a higher threshold voltage Vth ) (Fig. 3). This means that the new orientation material exhibits better vertical orientation power compared to the conventional one. From this, it can be seen that a high contrast ratio can be obtained because the luminance in the black state is low at the same voltage.

As a result of measuring the liquid crystal reaction time (response time) of the liquid crystal display, the rising time (T _on ) and the falling time (T _off ) of the conventional liquid crystal display ) Is 41 ms. In the case of the new liquid crystal display device according to the first embodiment, the rising time is 49 ms and the polling time is 27 ms, which realizes an improved level of high-speed liquid crystal reaction rate (Fig. 4).

EXPERIMENTAL EXAMPLE 2: Analysis of Orientation Force and Electro-optical Properties of Liquid Crystal Display

The alignment properties and the electro-optical characteristics of the liquid crystal display device manufactured according to Example 2 were measured. As a result of comparing the degree of black display on the OV where no voltage was applied to the liquid crystal device, the new liquid crystal display cell manufactured according to Example 2 has a liquid crystal display cell (comparative example) and a conventional liquid crystal display cell And exhibited a vertical orientation at an equivalent level and realized a black screen without light leakage throughout the screen (Fig. 5).

As a result of measuring the voltage-transmittance curve according to the voltage, the cell according to the second embodiment has a VT shape shifted to the right compared to the conventional cell (comparative example), and has a higher threshold voltage Vth ) (Fig. 6). This means that the new orientation material exhibits better vertical orientation power compared to the conventional one. From this, it can be seen that a high contrast ratio can be obtained because the luminance in the black state is low at the same voltage.

As a result of measuring the liquid crystal reaction time (response time) of the liquid crystal display, the rising time (T _on ) and the falling time (T _off ) of the conventional liquid crystal display ) Was 41 ms. In the case of the new liquid crystal display device according to the second embodiment, the rising time is 21 ms and the polling time is 27 ms. As with the liquid crystal display device according to the first embodiment, (Fig. 7). Fig.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

100: liquid crystal display
110: color filter substrate 111: substrate
112: color filter 113: common electrode
120: TFT array substrate 121: substrate
122: insulating film 123: pixel electrode
124: data line 130: liquid crystal
140: organic molecule 141: hydrogen bonding unit
142: alkyl group 150: short
160: Sealant

Claims (10)

A TFT array substrate;
A color filter substrate; And
A liquid crystal layer between the array substrate and the color filter substrate;
A liquid crystal display device manufacturing method characterized in that a substrate and a liquid crystal layer are directly bonded to each other,
(Step 1) of preparing an organic molecule-liquid crystal mixture by mixing a liquid crystal with at least one aliphatic organic molecule selected from the group consisting of octanoic acid, decanoic acid, undecanoic acid and dodecanoic acid;
Dropping the organic molecule-liquid crystal mixture on one side of the array substrate or the color filter substrate (step 2);
Attaching the two substrates such that the mixture is positioned between the array substrate and the color filter substrate (step 3); And
A step of heat treating the bonded substrate and cooling the bonded substrate to a normal temperature (step 4); and hydrogen bonding between the organic molecules and the substrate.
The method according to claim 1,
Wherein the aliphatic organic molecules are added in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the liquid crystal.
The method according to claim 1,
Wherein the heat treatment is performed at 80 to 120 DEG C for 30 to 120 minutes.
delete The method according to claim 1,
Wherein the aliphatic organic molecules are hydrogen bonded to the substrate.
A TFT array substrate;
A color filter substrate; And
And a liquid crystal layer interposed between the array substrate and the color filter substrate;
A liquid crystal display device characterized in that a substrate and a liquid crystal layer are directly bonded to each other,
A liquid crystal alignment layer is formed between at least one of the array substrate and the color filter substrate and the liquid crystal layer,
Wherein the liquid crystal alignment layer comprises at least one aliphatic organic molecule selected from the group consisting of octanoic acid, decanoic acid, undecanoic acid and dodecanoic acid.
delete The method of claim 6,
Wherein the liquid crystal alignment layer vertically aligns the liquid crystal molecules in the liquid crystal layer.
delete delete

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