JPH08152640A - Production of liquid crystal display device - Google Patents

Abstract

PURPOSE: To improve the visual field angle characteristic of a liquid crystal display device by applying an emulsion of a hydrophobic high polymer material and a hydrophilic high polymer material on a substrate, then curing this coating by heating and rubbing the coating. CONSTITUTION: Electrodes 2 are formed on a substrate 1. Next, the hydrophobic high polymer material and the hydrophilic high polymer material are mixed. The emulsion of the hydrophobic high polymer material and a hydrophilic high polymer material is then applied approximately over the entire surface of the substrate 1 formed with the electrodes 2. The emulsion 3 applied on the substrate 1 is thereafter heated by a hot air circulation system or far IR radiation system. Finally, two sheets of the formed substrates 1 are prepd. and after spacer members 4 are evenly sprayed on the one substrate 1, the other substrate 1 is stuck thereto and liquid crystals are injected between two sheets of the substrates. The liquid crystal display device is completed by sealing an injection port.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a personal computer, a word processor,
The present invention relates to a method for manufacturing a liquid crystal display device used for a display device such as a small television.

[0002]

2. Description of the Related Art A conventional method of manufacturing a liquid crystal display device is shown in FIG.
The explanation is based on (a). Transparent substrates 1 and 2 such as glass
Transparent electrode 3 such as ITO (Indium-Tin-Oxygen),
4 is formed, alignment films 5 and 6 made of a polyimide resin or the like are formed on the electrodes 3 and 4, and two substrates 1 and 2 are arranged so that the alignment films 5 and 6 face each other. It was manufactured by injecting the liquid crystal 7 between the substrates 1 and 2.

On the outside of the substrates 1 and 2, there are provided polarizing plates 8 and 9 which allow only light in a predetermined vibration direction to pass therethrough.

The alignment films 5 and 6 are butyl cellosolve,
A polyimide varnish in which about 10% by weight of a solvent such as n-methyl-2-pyrrolidone or γ-butyrolactone is dissolved is applied to substrates 1 and 2 on which electrodes 3 and 4 are formed by spin coating or flexographic printing. Method, and heat-treat (bak) this polyimide varnish at about 150 to 230 ° C., and then the length of the hair is 0.5.
It was formed by rubbing by rubbing in a certain direction with a buff cloth of about 5 mm.

In the liquid crystal display device thus formed, as shown in FIG. 4A, the liquid crystal 7 is controlled in the rubbing direction of the alignment films 5 and 6 when no potential difference is generated between the electrodes 3 and 4. Are oriented in a certain direction. At this time, light incident from the substrate 2 side only enters the liquid crystal layer 7 that matches the polarization axis of the polarizing plate 9, and the polarization plane of the incident light is rotated as the liquid crystal molecules 7 rotate. The rotated light has a polarization axis in the same direction as the other polarizing plate 8 and is transmitted. At this time, the liquid crystal display device displays white.

On the other hand, as shown in FIG.
When a potential difference is generated between the electrodes 3 and 4, the liquid crystal molecules 7
Are arranged substantially perpendicular to the electrodes 3 and 4 due to their own dielectric anisotropy. Therefore, the light incident on the liquid crystal layer 7 from the substrate 2 side is not rotated because the liquid crystal molecules 7 do not rotate,
It is absorbed because it does not match the polarization axis of the polarizing plate 8. Therefore, there is no light emitted from the liquid crystal display device and a black display is obtained. Black-and-white display is performed by such a method.

[0007]

However, in the above-described conventional method for manufacturing a liquid crystal display device, when the alignment films 5 and 6 are formed, a polyimide varnish obtained by dissolving only polyimide in a solvent is formed on the entire surfaces of the substrates 1 and 2. After uniformly coating and curing, the entire surface is rubbed in a certain direction to form fine grooves, so that liquid crystal molecules 7 are spread over the entire surfaces of the substrates 1 and 2 in a region where no potential difference is generated between the electrodes 3 and 4. Alignment is performed with a uniform pretilt angle, and depending on the angle at which the liquid crystal display device is viewed, there are problems in that some directions may not be well viewed, and sometimes black and white may appear reversed. That is, the liquid crystal display device manufactured by the conventional liquid crystal display device manufacturing method has a viewing angle characteristic of about 25 degrees in the upper direction and 10 in the lower direction.
There was a problem that the viewing angle dependency was extremely strong at about 40 degrees in the horizontal direction and about 40 degrees in the horizontal direction.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the conventional method, and provides a method of manufacturing a liquid crystal display device in which the viewing angle dependence of the liquid crystal display device is eliminated. To aim.

[0009]

In order to achieve the above object, in the method of manufacturing a liquid crystal display device according to the present invention, liquid crystal is injected between two substrates each having an electrode and an alignment film formed thereon. In the method for manufacturing a liquid crystal display device, the alignment film is formed by applying an emulsion composed of a hydrophobic polymer material and a hydrophilic polymer material onto the two substrates on which the electrodes are formed, and curing the emulsion. This cured film is formed by rubbing.

[0010]

When the alignment film is formed of two kinds of materials that do not dissolve each other as described above, two kinds of regions can be formed in the alignment film in which liquid crystal molecules can be maintained at different pretilt angles. as a result,
Due to the anisotropy of the refractive index of the liquid crystal molecules, the angle of light transmission will be different for each region, reducing the viewing angle dependence,
The viewing angle characteristics of the liquid crystal display device can be improved.

[0011]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 1A to 1E are process diagrams showing an embodiment of a method for manufacturing a liquid crystal display device according to the present invention.

First, an electrode 2 is formed on a substrate 1 as shown in FIG. As the substrate 1, non-alkali glass containing no alkali component is used. This is because when the substrate 1 contains an alkaline component, when the electrode 2 formed on the substrate 1 is a transparent conductive film, the electric characteristics of the transparent conductive film may be deteriorated or clouding may occur. The electrode 2 is composed of, for example, a transparent conductive film such as ITO, and has a thickness of 50 to 150 by a vapor deposition method or a sputtering method.
It is formed to about nm. Although not shown, in the case of an active matrix liquid crystal display device, the electrode 2 is formed after the electrode 2 is formed or before the electrode 2 is formed.
A switching thin film transistor for controlling the application of voltage to the gate electrode is formed.

Next, as shown in FIG. 2B, a hydrophobic polymer material and a hydrophilic polymer material are mixed. This hydrophobic polymer material includes HDDA, NPGDA, TPGDA, M
There are acrylate monomers such as ANDA and TMPTA, oligoester acrylate, urethane acrylate, epoxy acrylate, polyamic acid, and polyimide resin. Further, examples of the hydrophilic polymer material include gelatin and PVA (polyvinyl alcohol). The hydrophobic polymer material and the hydrophilic polymer material are sampled at a ratio of 1: 1 and put into the micro homogenizer 10 and mixed with stirring. This stirring and mixing was carried out at 3000 rpm for 5
Do about a minute. Further, it is desirable that the hydrophobic polymer material and the hydrophilic polymer material are stirred and mixed, and then degassed in vacuum or left standing under normal pressure. Thus, by stirring and mixing the hydrophobic polymer material and the hydrophilic polymer material with the micro homogenizer 10, an emulsion (emulsion) in which the hydrophobic polymer material and the hydrophilic polymer material are emulsified and dispersed can be obtained. .

Next, as shown in FIG. 1C, an emulsion of a hydrophobic polymer material and a hydrophilic polymer material is applied to substantially the entire surface of the substrate 1 on which the electrode 2 is formed. That is, the emulsion 3 of the hydrophobic polymer material and the hydrophilic polymer material is dropped on the substrate 1 and the substrate 1 is rotated at a high speed by a spin coating method, or the emulsion is dropped on an anilox roll to form a rubber plate. It is performed by a flexographic printing method or the like in which the substrate 1 is applied through the attached plate cylinder. In the case of applying by the spin coating method, the emulsion is scattered around the substrate 1 and the utilization rate is reduced. Therefore, the flexographic printing method is preferably used in the mass production process. In any case, it is applied uniformly so as to have a thickness of about 0.05 to 1 μm.

Next, as shown in FIG. 1D, the emulsion 3 applied on the substrate 1 is heated by a hot air circulation system or a far infrared radiation system. The emulsion 3 is cured by maintaining the temperature of about 140 ° C. for about 1 hour. Then, the cured polymer material 3 is rubbed in a certain direction with a buff cloth made of fibers such as rayon or nylon having a length of hair of 0.5 to 5 mm to form fine grooves on the surface of the polymer material. A rubbing process is performed to form the alignment film 3.

The surface condition of the alignment film 3 is schematically shown in FIG. Since the alignment film 3 is formed of a hydrophobic polymer material and a hydrophilic polymer material, the alignment film 3 subjected to the rubbing treatment also contains a hydrophobic polymer material in the region 3b made of the hydrophilic polymer material. The minute regions 3a to be formed become an alignment film which is randomly scattered. In this case, the region 3a made of the hydrophobic polymer material keeps the liquid crystal molecules at a high pretilt angle, and the region 3b made of the hydrophilic polymer material keeps the liquid crystal molecules at a low pretilt angle. Region 3a made of hydrophobic polymer material
Is preferably formed to have a diameter of 10 to 100 μm. When the diameter of the region 3b made of the hydrophobic polymer material is 10 μm or less, the region where the liquid crystal molecules have a uniform pretilt angle becomes too small to induce light scattering, and good display cannot be performed. Further, when the diameter of the region 3b made of the hydrophobic polymer material is 100 μm or more, the liquid crystal molecules in one pixel are all aligned with a uniform pretilt angle, so that the viewing angle dependency becomes strong.

Finally, as shown in FIG. 1 (e), two substrates 1 formed as described above are prepared, and one of the substrates 1 has a spherical or rod-shaped polymer system having a diameter of about 5 μm. Alternatively, after the glass-based spacer members 4 are uniformly dispersed, the other substrate 1 is attached, liquid crystal is injected between the two substrates, and the injection port is sealed to complete the process.

FIG. 3A is a sectional view of a liquid crystal display device manufactured by the manufacturing method of the present invention. 3 in FIG. 3 (a)
Is an alignment film, and the alignment film 3 is interspersed with regions 3a made of a hydrophobic polymer material and regions 3b made of a hydrophilic polymer material. Further, in relation to the facing alignment film 3 ′, the regions 3a and 3 formed of the hydrophobic polymer material are also formed.
Regions 3b and 3b 'formed of a'and a hydrophilic polymer material
There is no regularity with. In addition, in FIG. 3A, reference numerals 4 and 4 ′ are polarizing plates. In this case, the region 3a formed of the hydrophobic polymer material maintains the liquid crystal molecules 4 at a high pretilt angle, and the region 3c formed of the hydrophilic polymer material maintains the liquid crystal molecules 4 at a low pretilt angle. . Therefore, since the pretilt angle of the liquid crystal molecule 5 is different for each fine region, the angle of light transmission is different due to the refractive index anisotropy of the liquid crystal molecule, and the viewing angle dependence of the liquid crystal display device is weakened, and thus the viewing angle. The characteristics are improved.

FIG. 3B shows a state in which a potential difference is generated between the electrodes 2, 2 '. In this state, the liquid crystal molecules 5 are aligned perpendicularly to the electrodes 2 and 2'to display black, and in this state of black display, it is the same as the conventional device.

According to the above-mentioned embodiment, when the present inventor made a prototype of a liquid crystal display device and measured the viewing angle characteristics, the vertical and horizontal directions were 40 degrees, and a liquid crystal display device having excellent viewing angle characteristics was obtained. It was confirmed.

[0021]

As described above, according to the method of manufacturing a liquid crystal display device of the present invention, an emulsion of a hydrophobic polymer material and a hydrophilic polymer material is applied onto a substrate and then cured by heating. By rubbing the film, an alignment film is formed, so that minute regions with different pretilt angles of liquid crystal molecules can be formed randomly, and the viewing angle dependence of the liquid crystal display device is weakened, improving the viewing angle characteristics of the liquid crystal display device. Can be made.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for manufacturing a liquid crystal display device according to the present invention.

FIG. 2 is a diagram showing a surface state of an alignment film manufactured by a method for manufacturing a liquid crystal display device according to the present invention.

FIG. 3 is a diagram showing a relationship between an alignment film manufactured by a method for manufacturing a liquid crystal display device according to the present invention and a pretilt angle of liquid crystal molecules.

FIG. 4 is a diagram showing a relationship between an alignment film manufactured by a conventional manufacturing method and a pretilt angle of liquid crystal molecules.

[Explanation of symbols]

1, 1 '... substrate, 2 and 2' ... electrode, 3 and 3 '.
..Alignment films

Claims (1)

[Claims] 1. A method of manufacturing a liquid crystal display device comprising injecting a liquid crystal between two substrates each having an electrode and an alignment film formed thereon, wherein the alignment film comprises a hydrophobic polymer material and a hydrophilic polymer material. A method for manufacturing a liquid crystal display device, comprising: applying an emulsion comprising the above to two substrates having the electrodes formed thereon and curing the same, and then subjecting the cured film to a rubbing treatment.