KR100510437B1 - Liquid crystal display device and method for forming liquid crystal cell used thereof - Google Patents

Abstract

 Disclosed are a liquid crystal display device capable of improving a wide viewing angle and a method of forming a liquid crystal cell used therein. A liquid crystal display device according to an embodiment of the present invention includes a first substrate and a second substrate having a conductive layer on a surface thereof and spaced apart from each other by a predetermined distance, and a matrix on the first substrate and the second substrate, respectively. A plurality of pixels arranged in a shape, a first alignment layer and a second alignment layer formed on the conductive layers of the first substrate and the second substrate, respectively, and to seal peripheral portions of the first substrate and the second substrate. Sealing means interposed between the first substrate and the second substrate, a plurality of spacers interposed in a space between the first substrate and the second substrate so as to space the first substrate and the second substrate at a predetermined interval; And a first polarizing plate and a second polarizing plate respectively disposed on rear surfaces of the first substrate and the second substrate, and a liquid crystal layer encapsulated in a space between the first substrate and the second substrate, wherein the first substrate Formed on The pixel is composed of two domains coated with alignment layers having different pretilt angles, and each pixel formed on the second substrate is an alignment layer having different pretilt angles. It is characterized by consisting of four domains applied.

Description

Liquid crystal display device and method for forming liquid crystal cell used herein

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a method of forming a pixel used therein, and more particularly, to a liquid crystal display device including a pixel composed of a plurality of domains capable of widening a viewing angle. A method of forming a pixel used.

In response to the demands for personalization of display devices and space saving in the information and information era, a large cathode ray tube (CRT), which has been the dominant display device, has been replaced. Accordingly, various flat panel display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), and an electro-luminescence (EL) have been developed.

Among them, LCD is a display device that combines liquid crystal technology and semiconductor technology that uses the optical properties of liquid crystals whose molecular arrangement is changed by an electric field.

1 is a schematic diagram for explaining the configuration of an LCD.

Specifically, first, a pixel composed of a thin film transistor 12 switched by a signal line and a scan line and a pixel electrode 14 for driving a liquid crystal is formed on a lower glass substrate 10 in a matrix form. Are arranged. The common electrode 24 corresponding to the pixel electrode 14 and a color filter layer 22 corresponding to each pixel electrode are formed on the upper glass substrate 20. Between the lower glass substrate 10 and the upper glass substrate 20, a liquid crystal whose molecular arrangement is changed by an electric field is injected, and a function of polarizing incident light on the rear surface of the pair of glass substrates 10 and 20. Each of the polarizing plates 30 having the same is provided.

When a predetermined voltage is applied to the LCD configured as described above, the liquid crystal molecules and the like are aligned in the rubbing direction of the alignment film surface. The liquid crystal molecules encapsulated between a pair of glass substrates are twisted in a spiral with a constant pitch, and in order to form such a pitch, a lecieric or preferential chiral dopant in the liquid crystal is 0.01 wt% to 8.0 It can be added at a concentration of weight percent (based on the total weight of the liquid crystal layer; the same below).

Twisted Nemtic LCD (TN-LCD) devices, which have recently been widely applied in the field of flat pannel displays, are generally known to have a narrow viewing angle and nonuniformity. The viewing angle of the LCD is mainly determined by the orientation of the liquid crystal molecules located in the middle of the liquid crystal cell. The liquid crystal molecules are formed in a long and thin rod shape, and the long and short axes of the liquid crystal molecules are incident to the polarized light. They work differently. When the LCD is applied at various angles, the long axis of the liquid crystal molecules changes, so gray inversion and a reduction in viewing angle appear.

In order to solve this problem, optical compensation method using retardation film, TN method LCD using non-rubbing and optical orientation using photopolymerization have been reported, but additional processes have been reported. And there are many problems such as an increase in cost, a decrease in yield due to the addition of the material.

Accordingly, the technical problem to be achieved by the present invention is to provide a liquid crystal display device which can widen the viewing angle by solving the conventional problems as described above.

Another object of the present invention is to provide a method of forming a pixel including a plurality of domains used in the liquid crystal display.

In order to achieve the above technical problem, the present invention, the first substrate and the second substrate having a conductive layer on its surface, spaced apart from each other by a predetermined interval; A plurality of pixels arranged in a matrix form on the first substrate and on the second substrate; First and second alignment layers formed on the conductive layers of the first substrate and the second substrate, respectively; Sealing means interposed between the first substrate and the second substrate to seal a peripheral portion of the first substrate and the second substrate; A plurality of spacers interposed in a space between the first substrate and the second substrate to space the first substrate and the second substrate at a predetermined interval; First and second polarizing plates disposed on rear surfaces of the first substrate and the second substrate, respectively; And a liquid crystal layer encapsulated in a space between the first substrate and the second substrate, wherein each pixel formed on the first substrate is coated with two alignment layers having different pretilt angles. (two domains), and each pixel formed on the second substrate is formed of four domains (four domains) coated with an alignment layer having a different pretilt angle. to provide.

In the present invention, the liquid crystal layer is made of liquid crystal doped with a positive dielectric anisotropy and doped with a photopolymerized dopant.

In the present invention, the photopolymerized dopant is any one selected from the group consisting of cinnamate derivatives, acrylate derivatives, and coumarin derivatives, and the concentration of the photopolymerized dopant is 0 wt. % To 5% by weight.

In the present invention, the first alignment layer and the second alignment layer are formed of polyimide.

In order to achieve the above technical problem, the present invention also includes a first substrate and a second substrate having a conductive layer on the surface thereof and spaced apart from each other by a predetermined interval; First and second alignment layers formed on the conductive layers of the first substrate and the second substrate, respectively; Sealing means interposed between the first substrate and the second substrate to seal a peripheral portion of the first substrate and the second substrate; A plurality of spacers interposed in a space between the first substrate and the second substrate to space the first substrate and the second substrate at a predetermined interval; First and second polarizing plates disposed on rear surfaces of the first substrate and the second substrate, respectively; And a liquid crystal layer enclosed in a space between the first substrate and the second substrate, the liquid crystal layer comprising four different domains.

In the present invention, the first alignment layer and the second alignment layer have a pretilt angle of 0.5 ° to 3 °.

In the present invention, the liquid crystal layer is made of liquid crystal doped with a positive dielectric anisotropy and doped with a photopolymerized dopant.

In the present invention, the photopolymerized dopant is any one selected from the group consisting of cinnamate derivatives, acrylate derivatives, and coumarin derivatives, and the concentration of the photopolymerized dopant is 0 wt. % To 5% by weight.

In the present invention, the first alignment layer and the second alignment layer are formed of polyimide.

In order to achieve the above another technical problem, the present invention, (a) applying an alignment film on the substrate formed electrode; (b) first rubbing the alignment layer in a predetermined direction; And (c) forming a second rubbed region on the first rubbed alignment layer in a direction opposite to the first rubbing direction.

In the present invention, the step (c) may include: (c1) applying a photosensitive film to the entire surface of the alignment film primarily rubbed in the predetermined direction; (c2) patterning the photoresist to form a photoresist pattern that exposes a predetermined region of the alignment layer; (c3) second rubbing a predetermined region of the exposed alignment layer in a direction opposite to the first rubbing direction; (c4) removing the photoresist pattern.

In the present invention, the alignment film is formed of a polyimide film.

In order to achieve the above technical problem, the present invention also, (a) alternately applying an alignment film having a different pretilt angle on the substrate on which the electrode is formed in a stripe shape; (b) first rubbing the alignment layer in the same direction as the coating direction; (c) forming a striped photoresist pattern on the primary rubbed alignment layer, the stripes being perpendicular to the coating direction; (d) second rubbing the alignment layer in the same direction as the photosensitive layer pattern; And (e) removing the photoresist pattern.

In the present invention, the alignment film is formed of a polyimide film.

The liquid crystal display according to the first exemplary embodiment of the present invention includes an upper substrate in which pixels consisting of two domains coated with alignment layers having different pretilt angles are arranged in a matrix form, and each other. By providing a lower substrate in which pixels consisting of four domains coated with an alignment film having different pretilt angles are arranged in a matrix, the alignment direction of liquid crystal molecules positioned inside the liquid crystal layer is varied. Can be mad. On the other hand, the liquid crystal display device according to the second embodiment of the present invention is composed of four regions in which the alignment directions of liquid crystal molecules inside the liquid crystal layer bulk are different. Accordingly, the liquid crystal display device according to the present invention can realize the wide viewing angle characteristic because the liquid crystal molecules can reflect the back light in various directions.

Hereinafter, a liquid crystal display device and a method of forming a pixel having a plurality of domains according to the present invention will be described in detail with reference to the accompanying drawings.

First embodiment

2 is a cross-sectional view of a liquid crystal display device according to a first exemplary embodiment of the present invention, and FIGS. 3A to 3D are three-dimensional views of a unit liquid crystal cell of the liquid crystal display device shown in FIG. 2.

In FIG. 2, reference numerals “40a” and “40b” denote upper and lower substrates, respectively, “42a” and “42b” denote common electrode layers and pixel electrode layers, and “44a” and “44b” denote first alignment layers, respectively. And "46" represents a liquid crystal layer, and "48a" and "48b" represent a first polarizing plate and a second polarizing plate, respectively.

Referring to FIG. 2, a pixel composed of a thin film transistor (not shown) switched by a signal line and a scanning line and a pixel electrode (not shown) for driving a liquid crystal is formed on a lower substrate 40b. The pixel electrode layers 42b arranged in the upper and lower sides are formed, and a second alignment layer 44b, for example, polyimide, for arranging liquid crystals in a predetermined direction is coated thereon.

A color filter layer (not shown) and a common electrode layer 42a corresponding to the pixels arranged in the matrix form are formed on the upper substrate 40a which is spaced apart from the lower substrate 40b so as to face each other. For example, polyimide is applied to the first alignment layer 44a for arranging the liquid crystals in a predetermined direction.

Although not shown, a seal agent is printed between the upper substrate 40a and the lower substrate 40b to seal the periphery of the two substrates. The upper substrate 40a and the lower substrate are printed. Between the 40b, a plurality of spacers are further formed to space the predetermined distance between the upper substrate 40a and the lower substrate 40b.

First and second polarizing plates 48a and 48b for polarizing incident light are respectively attached to the rear surfaces of the upper substrate 40a and the lower substrate 40b.

Meanwhile, a liquid crystal layer 46 is formed between the upper and lower substrates 40a and 40b facing each other at a predetermined interval, and the liquid crystal layer 46 has a positive dielectric anisotropy (+). And a liquid crystal doped with a photopolymerized dopant.

The photopolymerized dopant is any one selected from the group consisting of cinnamate derivatives, acrylate derivatives, and coumarin derivatives, based on the total weight of the liquid crystal layer 46. Used at a concentration of weight percent.

A process of preparing a mixture of the nematic liquid crystal and the photopolymerized dopant and encapsulating the liquid crystal layer 46 is as follows.

(1) First, 2 wt% of vinyl 4-methoxy-cinnamate, for example, photocurable, is doped into the nematic liquid crystal as a dopant.

(2) The nematic liquid crystal doped with 2 wt% of the vinyl 4-methoxy-cinnamate at a temperature higher than or equal to the clearing temperature of the nematic liquid crystal is encapsulated in the liquid crystal layer 46. .

(3) After liquid crystal encapsulation, the liquid crystal layer 46 is irradiated with ultraviolet rays at about 5 J / cm 2 for about 10 minutes. At this time, the ultraviolet light can be obtained by using a high-pressure mercury lamp having a light intensity of 10 ㎽ / ㎠, linearly polarized and has a wavelength of 320nm. And voltage is applied at 5-20 volts (V), and it irradiates at the temperature more than the clearing temperature of the said nematic liquid crystal.

3A to 3D are three-dimensional views of the unit liquid crystal cell of the liquid crystal display device according to the first embodiment of the present invention.

Each hexahedron shown in FIGS. 3A to 3D shows a unit liquid crystal cell (corresponding to one pixel) of the liquid crystal display device according to the first embodiment of the present invention, wherein the top surface of the hexahedron is the first alignment layer. An area corresponding to one pixel in (44a of FIG. 2), an area corresponding to one pixel in the second alignment layer (44b in FIG. 2), and a lower surface of the hexahedron, and an inside of the hexahedron in the liquid crystal layer Corresponds to part of (46 in FIG. 2).

Here, "arrow" indicates the rubbing direction of the polyimide film (44a and 44b in FIG. 2), and "high" means that the pretilt angle of the polyimide film (44a and 44b in FIG. 2) is large, and "low" means poly The pretilt angles of the mid film (44a, 44b in FIG. 2) are small. As shown in FIGS. 3A to 3D, each pixel formed on the upper substrate 40a of FIG. 2 is coated with two regions of a polyimide film 44a of FIG. 2 having different pretilt angles. (two domains), and each pixel formed on the lower substrate 40b of FIG. 2 includes four regions coated with a polyimide film (44b of FIG. 2) having different pretilt angles. four domains).

4A to 4E are cross-sectional views illustrating a method of forming a two-domain pixel having two regions having different pretilt angles among the unit liquid crystal cells shown in FIGS. 3A to 3D. admit.

Referring to FIG. 4A, an alignment film 52 is formed by, for example, applying a polyimide film onto a substrate 50 on which an electrode is formed.

Referring to FIG. 4B, the entire surface of the alignment layer 52 is rubbed in a selected direction to form a first rubbed alignment layer 52a.

Referring to FIG. 4C, after the photoresist is coated on the alignment layer 52a on which the entire surface is primarily rubbed, the photoresist layer is exposed and developed to expose a portion of the primary rubbed alignment layer 52a. 54).

Referring to FIG. 4D, the exposed region of the primary rubbed alignment layer 52a is rubbed in a direction opposite to the primary rubbing direction, thereby rubbing the alignment layer 52b in a direction opposite to the primary rubbed region 52a. ).

Referring to FIG. 4E, a two-domain pixel having two regions having different pretilt angles is completed by removing the photoresist pattern 54 (FIG. 4D).

5A through 5D are plan views illustrating a method of forming a four-domain pixel having four regions having different pretilt angles among the unit liquid crystal cells illustrated in FIGS. 3A through 3D. admit.

Referring to FIG. 5A, an alignment film 54 is formed by, for example, applying a polyimide film onto a substrate of a liquid crystal display device on which electrodes are formed, and then heat-processing at an appropriate temperature.

In this case, the alignment layer 54 is applied in a stripe shape having the same width as shown, and alternate alignment layers 54 having different pretilt angles are alternately applied like A-B-A-B. Next, primary rubbing is performed by rubbing the entire surface of the alignment layer 54 along the stripes in the direction of the arrow.

Referring to FIG. 5B, a photosensitive film is coated on the first rubbed alignment layer 54, followed by exposure and development to expose a portion of the alignment layer 54 and is patterned to be orthogonal to the stripes of the alignment layer 54. Pattern 56 is formed.

Referring to FIG. 5C, the second rubbing is performed by rubbing the exposed region of the alignment layer in the same direction as the photosensitive layer pattern 56. In this way, the alignment layer under the photoresist pattern 56 remains in a rubbed state, for example, as shown in FIG. 5A, and the alignment film 54a in the portion where the photoresist pattern 56 is not formed is As shown in FIG. 5C, rubbing in the opposite direction, that is, in the longitudinal direction.

Referring to FIG. 5D, when the photosensitive film pattern (56 of FIG. 5C) is removed, the alignment layer patterns 54a and 54b as illustrated may be obtained. Since the alignment layer patterns 54a and 54b are rubbed in opposite directions, and the alignment layers rubbed in the same direction are alternately formed of polyimide films having different pretilt angles, they are divided into four regions. In this way, a four-domain pixel consisting of four regions having different pretilt angles is completed.

Subsequently, a four-domain pixel having a substrate on which two-domain pixels are formed having the different pretilt angles and four regions having different pretilt angles are formed. After bonding the substrate on which the pixels) are formed at a predetermined interval, the mixture of the nematic liquid crystal and the photopolymerized dopant is sealed in the space between the two substrates, and according to the first embodiment of the present invention according to a conventional manufacturing process. The liquid crystal display device according to the present invention is completed.

Second embodiment

6 is a cross-sectional view of a liquid crystal display device according to a second embodiment of the present invention, and FIG. 7 is a cross-sectional view showing a liquid crystal layer 66 of the liquid crystal display device shown in FIG.

In Fig. 6, reference numerals “60a” and “60b” denote upper and lower substrates, respectively, “62a” and “62b” denote common and pixel electrode layers, respectively, and “64a” and “64b” denote first alignment layers, respectively. And "66" represents a liquid crystal layer, and "68a" and "68b" represent a first alignment plate and a second polarizing plate, respectively.

Referring to FIG. 6, a pixel composed of a thin film transistor (not shown) switched by a signal line and a scanning line and a pixel electrode (not shown) for driving a liquid crystal is formed on a lower substrate 60b. The pixel electrode layer 62b is arranged so that the second alignment layer 64b, for example polyimide, for arranging the liquid crystals in a predetermined direction is coated so as to have a pretilt angle of 0.5 ° to 3 °.

A color filter layer (not shown) and a common electrode layer 62a corresponding to the pixels arranged in the matrix form are formed on the upper substrate 60a which is spaced apart from the lower substrate 60b so as to face each other. The first alignment film 64a, for example, polyimide, for arranging the liquid crystals in a predetermined direction, is coated so as to have a pretilt angle of 0.5 ° to 3 °. In addition, the first alignment layer 64a and the second alignment layer 64b are both rubbed in one direction.

Although not shown, a seal agent is printed between the upper substrate 60a and the lower substrate 60b to seal the periphery of the two substrates. The upper substrate 60a and the lower substrate 60b are printed. In addition, a plurality of spacers are formed between the upper substrates 60a and the lower substrates 60b to space apart a predetermined interval.

First and second polarizing plates 68a and 68b for polarizing incident light are respectively attached to the rear surfaces of the upper and lower substrates 60a and 60b, respectively.

Meanwhile, a liquid crystal layer 66 is formed between the upper substrate 60a and the lower substrate 60b facing each other at a predetermined interval, and the liquid crystal layer 66 has positive dielectric anisotropy and is photopolymerized. It consists of a liquid crystal doped with a dopant.

The photopolymerized dopant is any one selected from the group consisting of cinnamate derivatives, acrylate derivatives, and coumarin derivatives, with a concentration of 0 wt% to 5 wt% based on the total weight of the liquid crystal layer. Used as.

The process of preparing a mixture of the nematic liquid crystal and the photopolymerized dopant and encapsulating the liquid crystal layer 66 is the same as described in the first embodiment.

FIG. 7 shows a liquid crystal layer 66 of the liquid crystal display device according to the second embodiment of the present invention shown in FIG.

As shown in FIG. 7, the liquid crystal layer 66 of the liquid crystal display according to the second exemplary embodiment of the present invention may have four different domains A, B, C, and D formed in a bulk. It is a pure nematic liquid crystal consisting of), and does not contain a chiral dopant (chiral dopant). Since the pretilt angles of the first alignment layer 64a and the second alignment layer 64b are small, and the liquid crystal layer 66 does not contain a chiral dopant, two twist directions and two rising directions of the liquid crystal molecules are provided. (two rising directions) appear with the same probability. The arrow of FIG. 7 shows the twist direction of the liquid crystal at the time of electric field application. At this time, photopolymerization in the bulk allows the four different domains (A, B, C, D) to exist stably, and a threshold voltage at which a twist effect occurs. Decrease).

As described above, in the liquid crystal display according to the first exemplary embodiment of the present invention, pixels of two domains coated with alignment layers having different pretilt angles are arranged in a matrix form. A liquid crystal molecule positioned inside the liquid crystal layer by having an upper substrate and a lower substrate composed of four domains having four domains coated with alignment layers having different pretilt angles arranged in a matrix form. The orientation direction of these can be varied. On the other hand, the liquid crystal display device according to the second embodiment of the present invention is composed of four regions in which the alignment directions of liquid crystal molecules are different on the bulk inside the liquid crystal layer. Accordingly, the liquid crystal display device according to the present invention can realize the wide viewing angle characteristic because the liquid crystal molecules can reflect the back light in various directions.

The present invention has been described in detail with reference to specific embodiments, but the present invention is not limited thereto, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention.

 1 is a perspective view illustrating an example of a general liquid crystal display device.

2 is a cross-sectional view illustrating a liquid crystal display device according to a first embodiment of the present invention.

3A to 3D are perspective views three-dimensionally showing a unit liquid crystal cell of the liquid crystal display shown in FIG. 2.

4A through 4E are cross-sectional views illustrating a method of forming a two-domain pixel of two region among the unit liquid crystal cells illustrated in FIGS. 3A through 3D.

5A through 5D are plan views illustrating a method of forming a four-domain pixel including four regions among the unit liquid crystal cells illustrated in FIGS. 3A through 3D.

6 is a cross-sectional view illustrating a liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view of the liquid crystal layer 66 of the liquid crystal display shown in FIG.

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

40a: upper substrate 40b: lower substrate

42a: common electrode layer 42b: pixel electrode layer

44a, 44b: first alignment layer and second alignment layer 46: liquid crystal layer

48a, 48b: a first polarizing plate and a second polarizing plate

Claims (9)

A first substrate and a second substrate having a conductive layer on the surface thereof and spaced apart from each other by a predetermined interval; A plurality of pixels arranged in a matrix form on the first substrate and on the second substrate; First and second alignment layers formed on the conductive layers of the first substrate and the second substrate, respectively; Sealing means interposed between the first substrate and the second substrate to seal a peripheral portion of the first substrate and the second substrate; A plurality of spacers interposed in a space between the first substrate and the second substrate to space the first substrate and the second substrate at a predetermined interval; First and second polarizing plates disposed on rear surfaces of the first substrate and the second substrate, respectively; And A liquid crystal layer encapsulated in a space between the first substrate and the second substrate, Each pixel formed on the first substrate is composed of two domains coated with an alignment layer having a different pretilt angle, and each pixel formed on the second substrate has a different pretilt angle. A liquid crystal display device comprising four domains coated with an alignment film having a pretilt angle. The method of claim 1, wherein the liquid crystal layer, A liquid crystal display device characterized in that the dielectric anisotropy is positive (+) and consists of a liquid crystal doped with a photopolymerized dopant. The liquid crystal display device of claim 2, wherein the photopolymerized dopant is any one selected from the group consisting of cinnamate derivatives, acrylate derivatives, and coumarin derivatives. The liquid crystal display of claim 2, wherein the concentration of the photopolymerized dopant is 0 wt% to 5 wt%. The method of claim 1, wherein the first alignment layer and the second alignment layer, A liquid crystal display device, characterized in that formed of polyimide. (a) applying an alignment film on the substrate on which the electrode is formed; (b) first rubbing the alignment layer in a predetermined direction; And (c) forming a second rubbed region in the first rubbed alignment layer in a direction opposite to the first rubbing direction,  Step (c) is, (c1) applying a photosensitive film to the entire surface of the alignment film primarily rubbed in the predetermined direction; (c2) patterning the photoresist to form a photoresist pattern that exposes a predetermined region of the alignment layer; (c3) second rubbing a predetermined region of the exposed alignment layer in a direction opposite to the first rubbing direction; And and (c4) removing the photosensitive film pattern. The method of claim 6, wherein the alignment layer, It forms with the polyimide membrane, The liquid crystal cell formation method characterized by the above-mentioned. (a) alternately applying an alignment film having different pretilt angles in a stripe shape on the substrate on which the electrode is formed; (b) first rubbing the alignment layer in the same direction as the coating direction; (c) forming a striped photoresist pattern on the primary rubbed alignment layer, the stripes being perpendicular to the coating direction; (d) second rubbing the alignment layer in the same direction as the photosensitive layer pattern; And (e) removing the photosensitive film pattern. The method of claim 8, wherein the alignment layer, It forms with a polyimide film, The liquid crystal cell formation method characterized by the above-mentioned.

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