KR19980015423A - Manufacturing method of liquid crystal display device - Google Patents

Abstract

(A) a spacer is sprayed on a first substrate on which an electrode layer and a thin film transistor are formed, and a black matrix, a color filter, and an electrode layer are formed on the first substrate and bonded to a second substrate coated with a sealant, And (b) injecting a polymer / liquid crystal composition containing a photopolymerizable monomer, a liquid crystal monomer, a photopolymerization initiator and a crosslinking agent into the vacant cell, and then irradiating the light. Wherein the mixing ratio of the photo-curing monomer and the liquid crystal monomer in the step (b) is 1:99 to 10:90 by weight, and the temperature during the light irradiation is maintained in the isotropic transition temperature range of the liquid crystal monomer, And a liquid crystal display device. According to the present invention, there is no need for a step of forming an orientation film separately, so that not only the liquid crystal can be oriented very easily, but also the polymer column connecting the upper and lower portions of the cell can be formed, which can contribute to supporting the cell thickness .

Description

Manufacturing method of liquid crystal display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal display device, and more particularly, to a method of manufacturing a liquid crystal display device using a new liquid crystal alignment method using light.

Liquid crystal display (LCD) is less weight and smaller in size than a display device using a cathode ray tube, so that it is easy to carry and does not emit harmful electromagnetic waves to the human body. Accordingly, the demand for liquid crystal displays (LCDs) has been gradually increasing, mainly in portable information terminals and personal computers. Recently, lightweight projection-type liquid crystal TVs capable of providing large-sized high-quality images with small panels have been increasing.

Currently, TN (Twisted Nematic) and STN (Super Twisted Nematic) active matrix thin film transistor liquid crystal display devices are the mainstream in the current information age. However, the TN and STN LCDs show differences in driving and panel structure. In the STN type, a liquid crystal is twisted by 210-270 ° between the upper and lower electrodes of a simple matrix type. In the TFT-TN type, a TFT is formed for each pixel to control pixels, Perform active drive by twisting. Due to the difference of these devices, the STN type is not easy to manufacture and the price is low, but the response response speed is slow and the number of pixels is limited and the display characteristics are not excellent. On the other hand, the TFT-TN type has excellent display characteristics, but is difficult to manufacture and is expensive.

In order to develop an LCD having excellent display characteristics, it is necessary to uniformly control the orientation of the liquid crystal. The term "orientation" refers to a state in which a certain material is partially ordered by external stress or in a linear arrangement of its own arrangement, parallel to one another in a certain direction. In general, the physical properties of liquid crystal are changed by the molecular arrangement, and as a result, the response speed to the external force such as electric field is greatly changed. Therefore, uniform alignment control of the liquid crystal is an important technology in manufacturing the liquid crystal device. Here, it is difficult to uniformly arrange the liquid crystals simply by inserting the liquid crystals into the upper and lower plates.

As a method of aligning the liquid crystal, there is known a method of aligning the liquid crystal by coating an organic polymer material such as polyimide on the surface of the transparent electrode layer to form an alignment film, and rubbing the surface of the alignment film in a physical manner. According to this method, it is possible to orient the liquid crystal in a certain direction by exerting a mechanical force from the outside, but there is a risk that the liquid crystal is contaminated by the dust generated in the rubbing treatment. Particularly, in a thin film transistor There is a problem that the TFT is destroyed.

As another method of aligning the liquid crystal, there is a method of coating the surface of the transparent electrode layer with a polytetrafluoroethylene resin and treating the coated surface thereof, and a method of orienting the liquid crystal by adding lecithin, octadecylmalonic acid or the like to the liquid crystal composition . Among the above methods, there is a problem that it is difficult to increase the size of the electronic method. In the latter method, the physical properties of the liquid crystal are changed by adding a substance such as lecithin to the liquid crystal to lower the electro-optical characteristic. In the case of producing a birefringent liquid crystal cell, There is a problem that adjustment is difficult.

In order to solve such a problem, a method has been proposed in which a transparent electrode layer is coated with a photo-curable material and then light is irradiated thereon to form an alignment layer. However, this method has a disadvantage in that a process of treating the transparent electrode layer with a photo-curable material must be added before injecting the liquid crystal into the cell, and such a process is very complicated and difficult to manufacture.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method of manufacturing a liquid crystal display device capable of easily orienting a liquid crystal without separately performing an alignment film forming process.

1 is a cross-sectional view showing a schematic structure of a liquid crystal display device manufactured according to the present invention,

2 is a cross-sectional view showing a schematic structure of a liquid crystal display completed using a photomask.

DESCRIPTION OF THE REFERENCE NUMERALS

11, 21. Glass substrate 12, 22. Transparent electrode layer

13, 23. Transparent polymer resin layer 14, 24. Liquid crystal

15, 25. Polarizer 16, 26. Analyzer

17. Polymer column

According to an aspect of the present invention, there is provided a liquid crystal display device including: (a) a spacer formed on a first substrate having an electrode layer and a thin film transistor formed thereon and having a black matrix, a color filter and an electrode layer formed thereon, (B) a step of injecting a polymer / liquid crystal composition containing a photopolymerizable monomer, a liquid crystal monomer, a photopolymerization initiator and a cross-linking agent into the open cell, and then irradiating light thereto Wherein the mixing ratio of the photo-curing monomer to the liquid crystal monomer in the step (b) is 1:99 to 10:90 by weight, and the temperature at the time of light irradiation is within the isotropic transition temperature range of the liquid crystal monomer And aligning the liquid crystal. The present invention also provides a method of manufacturing a liquid crystal display device.

In the present invention, a photo-curable monomer and a liquid crystal monomer are mixed at a suitable ratio into a cell, and the photo-curing monomer is successively adsorbed on the surface of the transparent electrode layer by irradiating light in a state where the cell is maintained at a proper temperature Polymerized to cover the surface of the transparent electrode layer, thereby aligning the liquid crystal later. At this time, the alignment state of the liquid crystal is determined depending on factors such as the kind of the photocurable monomer and the liquid crystal monomer used, the mixing ratio of the photocurable monomer and the liquid crystal monomer, the temperature at the time of light irradiation, and the intensity of light.

In the step (b), the intensity of the light is preferably maintained at 1 to 3 mw. If the intensity of light is larger than the above range, the polymerization of the photocurable monomer proceeds too quickly. This is because the photo-curable monomer is polymerized in the liquid crystal before the photo-curable monomer is diffused into the transparent electrode layer so that the polymerization can be performed on the surface of the electrode, so that the liquid crystal can not be aligned as desired.

In the present invention, the photo-curable monomer has a function of aligning the liquid crystal by the surface action with the liquid crystal after being cured, and it is preferable to use an acrylic monomer having excellent transparency. In this case, a crosslinking agent may be further added to improve the physical properties of the photocurable monomer. At this time, the content of the crosslinking agent is 5 to 10% by weight based on the photocurable monomer. As the material which can be used as the crosslinking agent, hexandiol diacrylate, ethoxalated bisphenol A diacrylate or dipentaerythritol pentacrylate can be used.

In the present invention, the mixing ratio of the photo-curing monomer and the liquid crystal monomer is generally 1:99 to 10:90 by weight, preferably 2:98 to 4:10, in some cases, depending on the kind of the photo-curable monomer and the liquid crystal monomer used. : 96 weight ratio. When the content of the photo-curable monomer is larger than the above range, the following phenomenon occurs rather than aligning the liquid crystal on the surface of the transparent electrode layer of the cured polymer. That is, the director of the liquid crystal is twisted or disorderly and discontinuously arranged by a net-like polymer liquid crystal composite having a three-dimensional network structure in which a liquid crystal and a polymer are phase-separated.

The liquid crystal monomer of the present invention is not particularly limited, but it is preferable to use a liquid crystal material having negative dielectric anisotropy. Examples of such compounds include p-methoxybenzylidene-p'-butylaniline and phenyl benzoate.

The temperature at the time of light irradiation is a very important factor for determining whether to cause surface orientation on the transparent electrode layer or random orientation of the liquid crystal and the polymer. In order to achieve the object of the present invention, It is preferable to perform it within the transition temperature range. As described above, the intensity of ultraviolet light is preferably about 1 to 3 mw.

In the step (b), if a light is irradiated using a photomask, a polymer column connecting the upper and lower substrates of the cell can be formed.

FIG. 1 is a cross-sectional view illustrating a schematic structure of a liquid crystal display device manufactured according to the present invention, and FIG. 2 is a schematic cross-sectional view illustrating a structure of a liquid crystal display device having a polymer column. (4) liquid crystal; (5) a polarizing plate; (6) a polarizing plate; and (6) a polarizing plate. (7) represents the polymer column, respectively. Here, the polymer column 7 serves to support the thickness of the cell.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not necessarily limited thereto.

Example 1

A composition obtained by mixing an acrylic resin PN393 (Merck) containing a polymerization initiator and trimethylol propane triacrylate (TMPTA) as a crosslinking agent and a liquid crystal MBBA (p-Methoxybenzylidene-p'-butylaniline) By weight to prepare a polymer / liquid crystal composition.

A glass substrate on which a thin film transistor and an ITO electrode were formed, and a glass substrate on which a black matrix, a color filter and an ITO electrode were formed were bonded to each other to form a vacant cell. The polymer / liquid crystal composition was injected into the open cell at room temperature and irradiated with ultraviolet rays (365 nm) at 85 캜 to complete a liquid crystal display panel. A polarizing plate and an analyzer were attached to the panel in a cross state to complete a liquid crystal display.

Observation of the completed cell in the crossed Nicol state of the polarizing microscope revealed a completely black state, and light was transmitted in the state where the electric field was applied to the cell. In this case, depending on the magnitude of the applied voltage, the interference of the transmitted light changes and the color of the light changes.

Example 2

A composition obtained by mixing an acrylic resin PN393 (Merck) containing a polymerization initiator and TMPTA and a liquid crystal MBBA were mixed at a weight ratio of 5:95 to prepare a polymer / liquid crystal composition.

A glass substrate on which a thin film transistor and an ITO electrode were formed, and a glass substrate on which a black matrix, a color filter and an ITO electrode were formed were bonded to each other to form a vacant cell. The polymer / acryl composition was injected into the open cell at room temperature, and ultraviolet rays (365 nm) were irradiated at 85 ° C using a photomask having an aperture ratio of about 50% to complete a liquid crystal display panel. A polarizing plate and an analyzer were attached to the panel in a cross state to complete a liquid crystal display.

The alignment state of the liquid crystal was almost the same as in Example 1, but a polymer column was partially formed in the cell. At this time, there was no correlation between the region where the polymer column was formed and the position of the mask, and the alignment state of the liquid crystal in the region where the light was blocked by the photomask or in the region where the light was directly irradiated was almost the same. This phenomenon can be explained by the fact that the area where light is blocked by the photomask can obtain the same alignment state because the monomer is cured by the light scattered by the liquid crystal or the light reflected from the lower part of the panel.

Example 3-5

The procedure of Example 1 was repeated, except that hexanediol diacrylate, ethoxylated bisphenol A diacrylate, and dipentaacrylate were used instead of TMPTA as a crosslinking agent.

In the case of Example 3-5, the same results as those of Example 1 were obtained.

Comparative Example 1

The procedure of Example 1 was repeated except that ultraviolet ray (365 nm) was irradiated at room temperature.

When the completed cell was observed under the crossed Nicol state of the polarizing microscope, the alignment of the liquid crystal was not uniform, light due to scattering leaks, and the contrast significantly deteriorated.

Comparative Example 2

Except that PN393 (Merck), which is a photocurable monomer containing a photopolymerization initiator, and liquid crystal monomer MBBA were mixed at a weight ratio of 20:80 to form a polymer / liquid crystal composition.

As a result of observing the polymer state of the cell completed with the scanning electron microscope, it was found that the polymer had a three-dimensional net shape. From these facts, it was found that the polymer and the liquid crystal were phase-separated.

According to the present invention, there is no need for a step of forming an orientation film separately, so that not only the liquid crystal can be oriented very easily, but also the polymer column connecting the upper and lower portions of the cell can be formed, which can contribute to supporting the cell thickness .

Claims (6)

(a) Spacers are sprayed onto a first substrate on which an electrode layer and a thin film transistor are formed, and a black matrix, a color filter, and an electrode layer are formed on the first substrate and a second substrate coated with a sealant is formed on the first substrate. And (b) irradiating the hollow cell with a polymer / liquid crystal composition containing a photopolymerizable monomer, a liquid crystal monomer, a photopolymerization initiator and a crosslinking agent, and then irradiating light to the liquid crystal display device As a result, Wherein the mixing ratio of the photo-curable monomer and the liquid crystal monomer in the step (b) is 1:99 to 10:90 by weight, and the liquid crystal is aligned by maintaining the temperature during the light irradiation at the isotropic transition temperature of the liquid crystal monomer A method of manufacturing a liquid crystal display device. The method according to claim 1, wherein the intensity of the light is maintained at 1 to 3 mw in the step (b). The method for manufacturing a liquid crystal display device according to claim 1, wherein the photo-curable monomer is an acrylic resin. The manufacturing method of a liquid crystal display device according to claim 1, wherein in step (b), light is irradiated using a photomask. The method of claim 1, wherein the cross-linking agent is selected from the group consisting of hexanediol diacrylate, ethoxylated bisphenol A diacrylate, and dipentaerythritol acrylate. The method for manufacturing a liquid crystal display device according to claim 1, wherein the content of the crosslinking agent is 5 to 10% by weight based on the photocurable monomer.