KR101232506B1 - Liquid Crystal Display - Google Patents

Abstract

The present invention relates to a liquid crystal display device capable of improving the response speed of the liquid crystal.

This liquid crystal display device comprises an alignment film for orienting liquid crystals; The alignment layer is a material of the liquid crystal structure is bonded to at least one of the main chain and side chain of the alignment material.

Description

Liquid Crystal Display

1 is a schematic view showing a conventional liquid crystal display.

2 is a view showing an alignment layer provided in a conventional liquid crystal display.

3 is a schematic view of a liquid crystal display according to the present invention;

4 schematically illustrates another liquid crystal display according to the present invention;

5 is a view showing an alignment layer provided in the liquid crystal display according to the present invention.

6a and 6b are views for explaining the movement of the liquid crystal molecules by the alignment film according to the present invention.

<Explanation of symbols for the main parts of the drawings>

24, 103, 240: liquid crystal 1, 101: alignment film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of improving the response speed of liquid crystals.

The liquid crystal display displays an image by adjusting the light transmittance of the liquid crystal having dielectric anisotropy using an electric field. To this end, the liquid crystal display includes a liquid crystal display panel (hereinafter referred to as a liquid crystal panel) for displaying an image through a liquid crystal cell matrix, and a driving circuit for driving the liquid crystal panel.

Referring to FIG. 1, a conventional liquid crystal panel includes a color filter substrate 10 and a thin film transistor substrate 20 bonded to each other and a liquid crystal 24 filled in a liquid crystal space provided between two substrates 10 and 20. It consists of.

The color filter substrate 10 includes a black matrix 4, a color filter 6, and a common electrode 8 sequentially formed on the upper substrate 2. The black matrix 4 is formed in a matrix form on the upper substrate 2. This black matrix 4 divides the area of the upper substrate 2 into a plurality of cell areas in which the color filter 6 is to be formed, and prevents light interference and external light reflection between adjacent cells. The color filter 6 is formed to be divided into red (R), green (G), and blue (B) in the cell region divided by the black matrix (4) to transmit red, green, and blue light, respectively. The common electrode 8 supplies a common voltage Vcom which is a reference when driving the liquid crystal 24 to the transparent conductive layer coated on the color filter 6. In addition, an overcoat layer (not shown) may be further formed between the color filter 6 and the common electrode 8 to planarize the color filter 6.

The thin film transistor substrate 20 includes a thin film transistor 18 and a pixel electrode 22 formed in each cell region defined by the intersection of the gate line 14 and the data line 16 on the lower substrate 12. The thin film transistor 18 supplies the data signal from the data line 16 to the pixel electrode 22 in response to the gate signal from the gate line 12. The pixel electrode 22 formed of the transparent conductive layer supplies a data signal from the thin film transistor 18 to drive the liquid crystal 24.

Meanwhile, the common electrode 8 described above may not be formed on the color filter substrate 10 as shown in FIG. 1, but may be formed to be parallel to the pixel electrode 22 of the thin film transistor substrate 20.

The liquid crystal 24 having dielectric anisotropy is rotated according to the electric field formed by the data signal of the pixel electrode 22 and the common voltage Vcom of the common electrode 8 to adjust the light transmittance so that gray scales are realized.

Such a liquid crystal display has a problem in that, when the response speed of the liquid crystal is slow, a phenomenon in which moving parts of the image appear to bleed on the display screen occurs. In order to solve this problem, many studies have been studied, such as improving the driving circuit and driving method of the liquid crystal display. In addition, development of the liquid crystal composition which can improve the response characteristic of a liquid crystal is also progressing. However, there is a limit in improving the response speed of the liquid crystal by changing the driving circuit and the driving method or the liquid crystal composition. Therefore, on the other side, there is a need to develop a method for improving the response speed.

On the other hand, the liquid crystal display device must orient the liquid crystal molecules 24 uniformly to align the liquid crystal molecules 24 in a predetermined direction. Accordingly, the liquid crystal display device includes an alignment layer 1 on the color filter substrate 10 and the thin film transistor substrate 20 as shown in FIG. 2 so that the liquid crystal molecules 24 are uniformly aligned. An alignment regulating force (Anchoring Energy) is applied between the alignment film 1 and the liquid crystal molecules 24 so that the liquid crystal 24 is uniformly aligned. The liquid crystal molecules 24 oriented in the alignment layer 1 are driven in response to an electric field applied between the common electrode and the pixel electrode. At this time, the liquid crystal molecules 24 react to the applied voltage over several to several tens of ms, and this response speed responding to the voltage application is called a rising time. One of several factors influencing the rising time of the liquid crystal molecules 24 is presumably due to the alignment regulating force between the alignment film 1 and the liquid crystal molecules 24 and the physical force to maintain the initial stop state.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of improving the response speed of the liquid crystal.

In order to achieve the above object, the liquid crystal display device according to the present invention comprises an alignment film for orienting the liquid crystal; The alignment layer is a material of the liquid crystal structure is bonded to at least one of the main chain and side chain of the alignment material.

The material of the liquid crystalline structure is driven with the same directivity in the same electric field as the liquid crystal.

The liquid crystal display includes a gate line, a data line crossing the gate line to define a pixel region, a thin film transistor formed at an intersection of the gate line and the data line, a pixel electrode connected to the thin film transistor, and a horizontal line with the pixel electrode. A thin film transistor substrate including a common electrode forming an electric field is provided, and the alignment layer is formed on the thin film transistor substrate.

In addition, the liquid crystal display includes a color filter substrate which is formed to face the thin film transistor substrate and includes a black matrix that separates cell regions and a color filter formed in the divided cell regions, and the alignment layer includes the color filter. Formed on the substrate.

Another liquid crystal display device includes a thin film transistor including a gate line, a data line crossing the gate line to define a pixel area, a thin film transistor formed at an intersection of the gate line and the data line, and a pixel electrode connected to the thin film transistor. A substrate; A black matrix formed to face the thin film transistor substrate and separating a cell region, a color filter formed in the divided cell region, and a common electrode formed on the color filter in front of the pixel electrode to form a vertical electric field with the pixel electrode; And a color filter substrate, wherein the alignment layer is formed on at least one of the thin film transistor substrate and the color filter substrate.

Other objects and features of the present invention in addition to the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 3 to 6B.

The liquid crystal display device displays an image by adjusting the light transmittance of the liquid crystal using an electric field. Such liquid crystal displays are classified into vertical electric field types and horizontal electric field types according to the direction of the electric field for driving the liquid crystal.

In a vertical field type liquid crystal display device, a common electrode formed on an upper substrate and a pixel electrode formed on a lower substrate are disposed to face each other to drive a liquid crystal by a vertical electric field formed therebetween.

In a horizontal field type liquid crystal display, a liquid crystal is driven by a horizontal electric field between a pixel electrode and a common electrode arranged side by side on a lower substrate.

Referring to FIG. 3, the vertical field type liquid crystal display includes a color filter substrate 110 and a thin film transistor substrate 120 bonded to each other and liquid crystal molecules 124 injected between the two substrates 110 and 120. It is composed.

The color filter substrate 110 includes a black matrix 104, a color filter 106, and a common electrode 108 sequentially formed on the upper substrate 102. The black matrix 104 is formed in a matrix form on the upper substrate 102. The black matrix 104 divides an area of the upper substrate 102 into a plurality of cell areas in which the color filter 106 is to be formed, and prevents light interference and external light reflection between adjacent cells. The color filter 106 is formed to be divided into red (R), green (G), and blue (B) in the cell region divided by the black matrix 104 to transmit red, green, and blue light, respectively. The common electrode 108 supplies a common voltage Vcom which is a reference when driving the liquid crystal 103 to the transparent conductive layer coated on the color filter 106. In addition, an overcoat layer (not shown) may be further formed between the color filter 106 and the common electrode 108 to planarize the color filter 106.

The thin film transistor substrate 120 includes a thin film transistor 118 and a pixel electrode 122 formed in each cell region defined by the intersection of the gate line 114 and the data line 116 in the lower substrate 112. The thin film transistor 118 supplies the data signal from the data line 116 to the pixel electrode 122 in response to the gate signal from the gate line 112. A vertical electric field is formed between the pixel electrode 122 supplied with the data signal through the thin film transistor 118 and the common electrode 108 supplied with the common voltage Vcom. By the vertical electric field, the liquid crystal molecules 103 arranged between the thin film transistor substrate 250 and the color filter substrate 260 are driven by dielectric anisotropy. According to the driving degree of the liquid crystal molecules 103, the light transmittance passing through the pixel region is changed to implement an image.

Referring to FIG. 4, a horizontal field type liquid crystal display device includes a thin film transistor substrate 120 and a color filter substrate 110 bonded to each other and liquid crystal molecules filled in a liquid crystal space provided between the two substrates 120 and 110. 240).

The color filter substrate 260 is an overcoat layer 236 for planarizing the black matrix 232 sequentially formed on the upper substrate 211, the upper substrate 211 on which the color filter 234 and the black matrix 232 are formed. It includes.

The thin film transistor substrate 250 includes a thin film transistor 230 formed in each cell region defined by the intersection of the gate line 202 and the data line 204 in the lower substrate 201, and a pixel electrode formed to form a horizontal electric field in the cell region. 222 and the common electrode 224, and a common line 226 connected to the common electrode 224.

The common line 226 is formed in parallel with the gate line 202 with the cell region interposed therebetween, and supplies a reference voltage for driving the liquid crystal molecules 240 to the common electrode 224.

The thin film transistor 230 supplies the data signal from the data line 204 to the pixel electrode 222 in response to the gate signal from the gate line 202. A horizontal electric field is formed between the pixel electrode 222 supplied with the data signal through the thin film transistor 230 and the common electrode 224 supplied with the reference voltage through the common line 226. The horizontal electric field causes the liquid crystal molecules 240 arranged between the thin film transistor substrate 250 and the color filter substrate 260 to rotate by dielectric anisotropy. According to the degree of rotation of the liquid crystal molecules 240, the light transmittance passing through the pixel region is changed, thereby realizing an image.

In the above-described vertical field or horizontal field type liquid crystal display, the liquid crystal molecules 103 or 240 must be uniformly aligned. Accordingly, the vertical field type or the horizontal field type liquid crystal display according to the exemplary embodiment of the present invention has a color filter substrate 110 or 260 and a thin film transistor substrate as shown in FIG. 5 to uniformly align the molecules of the liquid crystal 103 or 240. 120 or 250 is provided with an alignment film 101.

Referring to FIG. 5, an alignment layer 101 according to an exemplary embodiment of the present invention is formed by bonding a material (X) having a dielectric anisotropy to at least one of a side chain and a main chain of an alignment material.

The alignment film 101 according to the embodiment of the present invention includes the liquid crystal structure material X, and thus, the liquid crystal structure material X in the alignment film 101 in which the liquid crystal molecules 103 or 240 are aligned. It has a property to react to the voltage applied to the liquid crystal display device.

The force by which the alignment film 101 reacts by the applied voltage acts as a torque for the initial deformation of the liquid crystal 103 or 240. The torque of the alignment layer 101 improves the response speed of the liquid crystal molecules 103 or 240 driven by the applied voltage.

6A and 6B, the response speed improvement of the liquid crystal molecules 103 or 240 will be described in detail. For reference, FIGS. 6A and 6B illustrate the horizontal field type liquid crystal display shown in FIG. 4.

Referring to FIG. 6A, liquid crystal molecules are uniformly aligned with the alignment layer before voltage is applied to the liquid crystal display.

When the voltage is applied to the liquid crystal display, the liquid crystal molecules 240 are driven by the voltage. However, as shown in FIG. 6B, the liquid crystal structure X in the alignment layer also has a force to react. This force acts as a torque for the initial deformation of the liquid crystal molecules 240 to improve the response speed of the liquid crystal molecules 240.

Although the principle for improving the response speed is not shown in the vertical field type liquid crystal display device, the same applies to the vertical field type liquid crystal display device shown in FIG. 3.

The alignment layer 101 according to the first embodiment of the present invention is formed by bonding a material (X) having a liquid crystalline structure to the side chain of [Formula 3], which is an alignment material, as shown in [Formula 1].

In addition, the alignment layer 101 according to the second embodiment of the present invention is formed by bonding a material (X) having a liquid crystalline structure to the main chain of [Formula 3], which is an alignment material, as shown in [Formula 2].

As the alignment material for bonding the material (X) of the liquid crystal structure, various polyimide materials may be used as well as [Formula 3].

[Structural formula 1]

[Formula 2]

[Structural Formula 3]

An example of the substance (X) of the liquid crystalline structure mentioned above is [Formula 4].

[Structural Formula 4]

(페닐기) 또는,

(사이클로 헥실기) 또는,

(다이옥산기) 또는,

또는,

또는 상기 구조 중 어느 하나가 포함된 성분 또는 구성성분이 별도로 없는 단순한 결합등의 구조로 구성된다.(예를 들면

구조 등)R ¹ in [Formula 4] And R ² At least one of them is coupled to the main chain or side chain of the alignment material. And R ¹ and R ² is a structure composed of an alkyl chain or alkenyl chain (alkenyl chain) or a simple bond without a separate component. And in [Formula 4], A ¹ , A ² , A ³ and A ⁴ are

(Phenyl group) or,

(Cyclohexyl group) or,

(Dioxane group) or,

or,

Or a simple bond or the like which does not have any component or component included in any of the above structures.

Structure etc.)

In addition, Z ¹ , Z ² in [Formula 4] And Z ³ is —C≡C— or —CF ₂ O— or —C _n H _2n — or —C _n H _2n-x — or —CO ₂ — or a component comprising one of the above structures or It consists of a structure such as a simple bond without any components.

The alignment layer 101 according to the present invention described above is formed on at least one of the color filter substrate 110 and the thin film transistor substrate 120 of the vertical field type liquid crystal display shown in FIG. 3.

The alignment layer 101 according to the present invention is formed on the thin film transistor substrate 250 of the horizontal field type liquid crystal display shown in FIG. 4. In addition, the alignment layer 101 according to the present invention may be formed on the color filter substrate 260 of the vertical field type liquid crystal display illustrated in FIG. 4, or an alignment layer formed of an alignment material to which the liquid crystal material (X) is not bonded may be formed. have.

The dielectric anisotropy of the material (X) of the liquid crystalline structure included in the alignment layer 101 of the present invention is the same as that of the liquid crystal molecules 103 or 240 oriented by the alignment layer 101. It has dielectric anisotropy of. That is, if the liquid crystal molecules 103 or 240 have a positive dielectric anisotropy, the material X of the liquid crystal structure also has a positive dielectric anisotropy or the molecules of the liquid crystal 103 or 240 are negative (-). If the dielectric constant anisotropy of), the material (X) of the liquid crystal structure also has a negative dielectric anisotropy. The reason why the liquid crystal material (X) and the liquid crystal molecules 103 or 240 have the same dielectric anisotropy is that the liquid crystal material (X) and the liquid crystal molecules 103 or 240 are moved in the same direction by an electric field. Is to give power. In other words, the material (X) of the liquid crystal structure is intended to receive a force to move in the same direction as the driving direction of the liquid crystal molecules 103 or 240 with respect to the electric field. When the liquid crystal structure X and the liquid crystal molecules 103 or 240 are driven in the same direction, the rotational torque of the liquid crystal structure X affects the driving of the liquid crystal molecules 103 or 240 so that the liquid crystal The response speed of the molecules 103 or 240 can be increased.

In addition, the alignment layer 101 according to the present invention is not limited to a specific mode of the liquid crystal display, but may be in in-plane switching (“IPS”) mode, twisted nematic (“TN”). It can be applied to a mode, a vertical alignment mode (hereinafter referred to as a "VA") mode, and the like. In the VA mode, since a liquid crystal having negative dielectric anisotropy is generally included, the liquid crystal structure of the alignment layer according to the exemplary embodiment of the present invention also has negative dielectric anisotropy.

In general, since the pretilt of the alignment film is set to 3 ° or less in the IPS mode and 5 ° to 10 ° in the TN mode, the pretilt value of the alignment film of the present invention is set according to the above requirements.

As described above, the liquid crystal display according to the present invention applies an alignment film in which a material having a liquid crystal structure is bonded to a side chain or a main chain of an existing alignment material, thereby aligning the liquid crystal together with the liquid crystal when a voltage is applied. The alignment film having a structure also has a property of reacting to an applied voltage, thereby increasing the initial response speed of the liquid crystal.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

Liquid crystal molecules filled in the liquid crystal space; An alignment layer formed of an alignment material and a material of a liquid crystalline structure to align the liquid crystal molecules; The material of the liquid crystal structure, Is bonded to at least one of the main chain and side chain of the alignment material, has the same dielectric anisotropy as the liquid crystal molecules, And a rotational torque of the material of the liquid crystalline structure to move in the same direction as the driving direction of the liquid crystal molecules. The method of claim 1, The oriented material is formed of a polyimide material, Liquid crystal display device characterized in that the material of the liquid crystalline structure is of the formula: Formula 1 　　

In the above formula, R1 'and "R2" are "alkyl" or "alkenyl"; A 1 to A 4 are each independently any one selected from the group consisting of phenyl, cyclohexyl, 1,3-dioxanyl, 1,3-pyrimidinyl and pyridinyl; Z1 to Z3 are each independently selected from the group consisting of -C≡C-, -CF ₂ O-, -CH _2- , and -CO _2- . The method of claim 1, A gate line, a data line crossing the gate line to define a pixel region, a thin film transistor formed at an intersection of the gate line and the data line, a pixel electrode connected to the thin film transistor, and a common electric field forming a horizontal electric field with the pixel electrode A thin film transistor substrate including an electrode, And the alignment layer is formed on the thin film transistor substrate. The method of claim 3, wherein A color filter substrate formed to face the thin film transistor substrate and including a black matrix separating cell regions and a color filter formed in the divided cell regions; And the alignment layer is formed on the color filter substrate. The method of claim 1, A thin film transistor substrate including a gate line, a data line crossing the gate line to define a pixel region, a thin film transistor formed at an intersection of the gate line and the data line, and a pixel electrode connected to the thin film transistor; A black matrix formed to face the thin film transistor substrate and separating a cell region, a color filter formed in the divided cell region, and a common electrode formed on the color filter in front of the pixel electrode to form a vertical electric field with the pixel electrode; Equipped with a color filter substrate And the alignment layer is formed on at least one of the thin film transistor substrate and the color filter substrate.

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