JPH08262446A - Production of liquid crystal display - Google Patents

Abstract

PURPOSE: To provide a means capable of keeping a voltage retention high and reducing a resident DC voltage and orientation dividing by UV irradiation. CONSTITUTION: The oriented films 23 and 26 formed on substrates 21 and 24 are partially irradiated with UV to form a region with the pretilt angle partially differentiated in the pixel in a liq. crystal display. In the production of this display, two substrates 21 and 24 having the oriented films 23 and 26 of polyimide, PVA, etc., with a region with the pretilt angle differentiated in the pixel by UV irradiation are stuck together through a spacer to form a vacant liq. crystal panel, the panel is allowed to stand in a high-humidity atmosphere to increase the moisture concn. in the oriented film, and then a liq. crystal 27 is injected. An ionic substance such as tetraethylammonium tetrafluoroborate is added to the oriented films 23 and 26, a liq. crystal increased in moisture conc. is used, or a liq. crystal added with the ionic substance is used to to produce the same effect. Further, the processes can be combined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device, and in particular, it partially irradiates ultraviolet rays to form a plurality of regions having different alignment states in a pixel and partially adjusts the pretilt angle of liquid crystal molecules. The present invention relates to a method for manufacturing a liquid crystal display device, which is characterized by controlling and improving visual characteristics.

[0002]

2. Description of the Related Art In order to improve the visual characteristics of a liquid crystal display device, in a wide viewing angle liquid crystal display device which realizes, for example, two alignment states in a region having a size of one pixel, there are two types in one pixel. A method using an alignment film is known.

FIG. 5 is a structural explanatory view of a wide viewing angle liquid crystal display device having a plurality of kinds of alignment films in one pixel. In this figure, 1 is a first substrate, 2 is a black matrix,
3 is an electrode, 4 is a first alignment film, 5 is a second alignment film, 6 is a second substrate, 7 is an electrode, 8 is a data bus line, 9 is a first alignment film, and 10 is a second alignment film. The alignment film 11 is a liquid crystal.

In this wide viewing angle liquid crystal display device, a black matrix 2 having an opening in a pixel region, an electrode 3,
First substrate 1 having first alignment film 4 and second alignment film 5
And the second substrate 6 having the electrodes 7, the data bus lines 8, the first alignment film 9 and the second alignment film 10, and the first substrate 1
The second nematic liquid crystal 11 is injected into the gap between the first substrate 1 and the second substrate 6 with the second substrate 6 facing outward with a gap therebetween.

Of the first alignment film 4 and the second alignment film 5 formed on the first substrate 1 by stacking, the second alignment film 5 has an opening in the pixel. Of the first alignment film 9 and the second alignment film 10 which are patterned on the second substrate 6 and are laminated on the second substrate 6, the second alignment film 10 is the first alignment film in the pixel. Second alignment film 5 of the substrate 1 of
Is patterned so as to have an opening at a position not facing the opening.

Then, the first alignment film 4 formed on the first substrate 1 and the second alignment film 5 having an opening are simultaneously rubbed to form a first alignment film formed on the second substrate 6. The alignment film 9 and the second alignment film 10 having an opening are simultaneously rubbed. As a result, the first alignment film 4 exposed from the opening of the second alignment film 5 of the first substrate 1 and the second alignment film 10 of the second substrate in a minute region in a certain pixel, A minute area A is formed.

Further, the first alignment film exposed from the openings of the second alignment film 5 of the first substrate 1 and the second alignment film 10 of the second substrate 6 adjacent to the minute region A. And 9 form a minute region B. This figure shows that the molecules of the liquid crystal 11 in the minute regions A and B are twisted.
The liquid crystal molecules are shown with a circle at the end visible on the front side with respect to the plane of this figure.

In the minute area A, the molecules of the liquid crystal in contact with the first alignment film 4 of the first substrate 1 are oriented in the direction from the right back to the left front, and the pretilt angle is α ₁ Has become. The liquid crystal molecules in the middle portion have an alignment direction substantially parallel to the plane of this figure, and the liquid crystal molecules in contact with the second alignment film 10 of the second substrate 6 go from the left back to the front right. It is oriented and the pretilt angle is α ₂ . . In this case, the angle α ₂ is larger than the angle α ₁ .

On the other hand, in the minute region B, the liquid crystal molecules in contact with the second alignment film 5 of the first substrate 1 have an alignment direction from the right back to the left front and the pretilt angle is small. It is α ₂ . The liquid crystal molecules in the middle portion have an alignment direction substantially parallel to the plane of this figure, and the liquid crystal molecules in contact with the first alignment film 9 of the second substrate 6 go from the left back to the front right. The orientation is aligned and the pretilt angle is α ₁ . Again, the angle α ₂
Is larger than the angle α ₁ .

When the alignment states of the liquid crystal molecules are made different in the minute regions A and B in the pixel as described above, the contrast ratio can be improved in a wide viewing angle (Japanese Patent Laid-Open No. 5-2100).
(See Japanese Patent Publication No. 99). Further, as an alternative method, a method of controlling the liquid crystal alignment by modifying the surface of the alignment film by ultraviolet irradiation, infrared irradiation, or the like has been considered.

FIG. 6 is a structural explanatory view of a wide-viewing-angle liquid crystal display device in which an alignment film having a partially different alignment state is partially formed in one pixel by irradiation of ultraviolet rays. In this figure, 21 is a first substrate, 22 is a common electrode, 23 is a first alignment film, 2
4 is a second substrate, 25 is a pixel electrode, 26 is a second alignment film, 27 is a liquid crystal, 28 is a first polarizing plate, and 29 is a second polarizing plate.

In this wide viewing angle liquid crystal display device, the first substrate 21 having the common electrode 22 and the first alignment film 23 having the pretilt angle, and the second electrode having the pixel electrode 25 and the pretilt angles α and γ. Second substrate 2 having alignment film 26
4 are arranged so as to face each other with the first substrate 21 and the second substrate 24 on the outside with a gap therebetween.
Twisted nematic liquid crystal 27 is injected into the gap between the substrates 24 to form a liquid crystal display panel, and the upper and lower sides thereof are sandwiched by a first polarizing plate 28 and a second polarizing plate 29.

When manufacturing this wide viewing angle liquid crystal display device,
On the surface of the pixel electrode 25 formed on the second substrate 24, a solution of polyimide having a high pretilt angle α and an imidization ratio of 100% is applied by spin coating, and cured by an oven or the like. The solvent is removed and the second alignment film 26 is formed. This second alignment film 26 is
A mask plate made of quartz that transmits ultraviolet rays is irradiated with ultraviolet rays having a wavelength of 300 nm or less using an exposure mask having an ultraviolet ray blocking material layer such as Cr in a region corresponding to the minute region B.

The fine regions B which have not been irradiated with ultraviolet rays exhibit a high pretilt angle α according to the properties of the polyimide used as the alignment material and by the subsequent rubbing. On the other hand, in the minute area A irradiated with ultraviolet rays, the surface energy of the second alignment film 26 in that area increases, and the pre-tilt angle γ becomes smaller than that in the case of the initial polyimide properties and predetermined rubbing. Thereby, for example, a combination in which the pretilt angle α is 8 degrees, the pretilt angle β is 4 degrees, and the pretilt angle γ is 1 degree can be created.

According to the method for manufacturing a wide-viewing-angle liquid crystal display device in which an alignment film having a partially different alignment state is formed in one pixel by the irradiation of ultraviolet rays, a wide-viewing-angle liquid crystal can be formed by a simple process using one kind of alignment film. A display device can be realized (see Japanese Patent Laid-Open No. 6-222366). However, it is necessary to use an alignment material having a relatively high pretilt angle as the alignment film. This pretilt angle is a parameter that largely depends on the surface energy of the surface of the alignment film.

FIG. 1 is a diagram showing the relationship between the surface energy of the alignment film surface and the pretilt angle. The horizontal axis of this figure shows the surface energy (erg / cm ² ) and the vertical axis shows the pretilt angle (degrees). The liquid crystal used for this measurement was fluorine-based ZLI-4792 (manufactured by Merck), the alignment film was polyimide JALS-214 (manufactured by Japan Synthetic Rubber Co., Ltd.), and the pretilt angle was appropriately changed by changing the number of times of rubbing. This figure shows that the pretilt angle tends to decrease as the surface energy increases. On the other hand, it is known that when the alignment film is irradiated with ultraviolet rays, the surface energy increases and the pretilt angle decreases.

FIG. 2 is an explanatory view of the ultraviolet irradiation time dependency of the pretilt angle. The horizontal axis of this figure is the UV irradiation time (m
in), and the vertical axis represents the pretilt angle (degrees). The liquid crystal used for this measurement is fluorine-based ZLI-4792.
(Manufactured by Merck & Co., Inc.) and the alignment film is polyimide JALS-21.
4 (manufactured by Japan Synthetic Rubber Co., Ltd.), and has an ultraviolet intensity of 8 mW /
cm ² .

According to this explanatory diagram, when the alignment film is irradiated with ultraviolet rays, the pretilt angle sharply decreases from about 8 degrees,
It can be seen that the irradiation decreases for about 10 minutes to almost 0 degree. By applying this property, an ultraviolet irradiation part and a non-irradiation part are provided in a region of one pixel level, fine regions having different pretilt angles are formed, and one or more alignment division states are formed in a relatively simple process. be able to.

[0019]

However, the above-mentioned orientation division method has the following problems. That is, as shown in FIG. 2, when ultraviolet rays are irradiated to increase the surface energy of the alignment film to decrease the pretilt angle, the ultraviolet ray irradiation amount is set to obtain a stable low pretilt angle. Irradiation should be as large as possible, for example 10 minutes or more under these conditions. However, when the irradiation amount of ultraviolet rays is increased, the residual DC voltage is increased.

FIG. 3 is an explanatory diagram of the ultraviolet irradiation time dependency of the residual DC voltage. The horizontal axis of this figure is the UV irradiation time (m
in), and the vertical axis represents the residual DC voltage (V). The liquid crystal used for this measurement is fluorine-based ZLI-4792.
(Manufactured by Merck), and the alignment film is polyimide JALS-
214 (manufactured by Japan Synthetic Rubber Co., Ltd.), ultraviolet intensity is 8 m
It was W / cm ² .

According to this illustration, it can be seen that the residual DC voltage increases as the UV irradiation time becomes longer, and the residual DC voltage reaches 1 V when the UV irradiation time is 10 minutes. An increase in the residual DC voltage causes a burn-in phenomenon that deteriorates the display quality of the liquid crystal panel. Therefore, burn-in is likely to occur in a wide-viewing-angle liquid crystal display device using an alignment film irradiated with ultraviolet rays. It is an object of the present invention to provide a method for manufacturing a liquid crystal display device in which alignment division is performed by ultraviolet irradiation, which can reduce the residual DC voltage while maintaining a high voltage holding ratio.

[0022]

SUMMARY OF THE INVENTION According to the present invention, there is provided a liquid crystal display device in which an alignment film formed on a substrate is partially irradiated with ultraviolet rays to partially form regions having different pretilt angles in a pixel. In the manufacturing method, two substrates having an alignment film having a high hygroscopic property such as polyimide and polyvinyl alcohol in which regions having different pretilt angles are formed by irradiating ultraviolet rays in a pixel are bonded with an adhesive agent through a spacer. A step of injecting a liquid crystal was adopted after bonding by using to form an empty liquid crystal display panel, and then leaving the empty liquid crystal display panel in a high humidity atmosphere to increase the water concentration in the alignment film.

Further, according to the present invention, another manufacturing method of a liquid crystal display device in which a region having different pretilt angles is partially formed in a pixel by partially irradiating an alignment film formed on a substrate with ultraviolet rays. In the method, an alignment film containing an ionic substance such as tetraethylammonium tetrafluoroborate (Et4NBF4) is irradiated with ultraviolet rays to form two regions each having an alignment film in which a region having a different pretilt angle is formed in a pixel. A step of injecting liquid crystal was adopted after the substrates were bonded together with an adhesive using a spacer to form an empty liquid crystal display panel.

In addition, according to the present invention, another method of manufacturing a liquid crystal display device in which regions having different pretilt angles are partially formed in a pixel by partially irradiating an alignment film formed on a substrate with ultraviolet rays. In the method, an empty liquid crystal display panel is obtained by bonding two substrates, each of which has an alignment film in which regions having different pretilt angles are partially formed in a pixel by irradiating ultraviolet rays, with an adhesive agent through a spacer. After forming
A process of injecting liquid crystal having a high water concentration into this empty liquid crystal display panel is adopted.

In addition, according to the present invention, another liquid crystal display device is formed in which a region having a different pretilt angle is partially formed in a pixel by partially irradiating an alignment film formed on a substrate with ultraviolet rays. In the method, an empty liquid crystal display panel is obtained by bonding two substrates, each of which has an alignment film in which regions having different pretilt angles are partially formed in a pixel by irradiating ultraviolet rays, with an adhesive agent through a spacer. After forming
A step of injecting a liquid crystal added with an ionic substance such as tetraethylammonium tetrafluoroborate (Et4NBF4) into the empty liquid crystal display panel was adopted.

Further, it is possible to employ a step of combining any two or more of the above steps.

[0027]

The inventors of the present invention, as a method of preventing an increase in residual DC voltage, which is a problem of the alignment-divided liquid crystal display device of the ultraviolet irradiation type, increase the moisture concentration in the alignment film surface or in the liquid crystal, and It was considered to reduce the residual DC voltage while keeping the voltage holding ratio high by facilitating the movement.

FIG. 4 is an explanatory diagram of the UV irradiation time dependency of the residual DC voltage. The horizontal axis of this figure is the UV irradiation time (m
in), and the vertical axis represents the residual DC voltage (V). The liquid crystal used for this measurement is fluorine-based ZLI-4792.
(Manufactured by Merck), and the alignment film is polyimide JALS-
214 (manufactured by Japan Synthetic Rubber Co., Ltd.), ultraviolet intensity is 8 m
It was W / cm ² .

According to this explanatory diagram, when the humidification treatment is not performed, as described above, the residual DC voltage is about 1 V when the ultraviolet rays are irradiated for 10 minutes, whereas the alignment film is subjected to the humidification treatment. In that case, it is about 0.2 V even when the ultraviolet ray is irradiated for 10 minutes, and it can be seen that it can be greatly reduced.

The phenomenon of decreasing the residual DC voltage also occurs by increasing the water concentration in the liquid crystal. It was also found that the residual DC voltage can be reduced by mixing an ionic substance such as tetraethylammonium tetrafluoroborate (Et4NBF4) in the alignment film or the liquid crystal. According to the present invention, the characteristics and reliability of the alignment-divided liquid crystal display device by ultraviolet irradiation can be improved, and a wide viewing angle and high gradation liquid crystal display device required in the future can be realized.

[0031]

【Example】

(First Embodiment) An embodiment of the present invention will be described below. IT
After forming an alignment film made of polyimide on the glass substrate on which the O electrode is formed, two glass substrates are placed, the alignment film is placed inside, spacers are scattered, and a certain gap is kept with a gap between them. An empty liquid crystal display panel is formed by sealing with a sealant.

This empty liquid crystal display panel is set to a relative humidity of 100.
%, The liquid crystal is vacuum-injected after being left in a high humidity tank for a certain period of time. At this time, the residual DC voltage can be controlled by changing the time for which the empty liquid crystal display panel is left in the high humidity tank. With this method, the residual DC voltage can be reduced.

Instead of the alignment film made of polyimide in this embodiment, a highly hygroscopic alignment film such as polyvinyl alcohol can be used. In addition, in this example, tetraethylammonium tetrafluoroborate (Et
4NBF4) or the like, an alignment film added with an ionic substance is used, and ultraviolet rays are radiated on the alignment film to partially form regions having different pretilt angles in the pixel, and then liquid crystal is injected to obtain almost the same as in this embodiment. The same effect of reducing the residual DC voltage can be obtained.

(Second Embodiment) When a liquid crystal (ZLI-4792: manufactured by Merck & Co., Inc.) having a high water content is injected into an empty liquid crystal display panel, the residual DC voltage is almost the same as in the first embodiment. Can be reduced. (Third embodiment) A liquid crystal (ZLI-
4792: manufactured by Merck & Co.), when injecting a liquid crystal mixed with an ionic substance such as tetraethylammonium tetrafluoroborate (Et4NBF4) into the same, the residual DC voltage can be reduced almost in the same manner as in the first embodiment. .

Also, by combining any two or more of the above-mentioned steps, the residual DC voltage can be reduced in the same manner as in the first embodiment.

[0036]

As described above, according to the present invention,
By adding a relatively simple process, it is possible to improve the characteristics and reliability of the alignment-divided liquid crystal display device by ultraviolet irradiation, and this greatly contributes to the technical field of the liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a surface energy of an alignment film surface and a pretilt angle.

FIG. 2 is an explanatory diagram of ultraviolet irradiation time dependency of a pretilt angle.

FIG. 3 is an explanatory diagram of the UV irradiation time dependency of the residual DC voltage.

FIG. 4 is an explanatory diagram of UV irradiation time dependency of residual DC voltage.

FIG. 5 is a configuration explanatory view of a wide viewing angle liquid crystal display device having a plurality of kinds of alignment films in one pixel.

FIG. 6 is a structural explanatory view of a wide viewing angle liquid crystal display device in which an alignment film having a partially different alignment state is partially formed in one pixel by irradiation of ultraviolet rays.

[Explanation of symbols]

 1 First Substrate 2 Black Matrix 3 Electrode 4 First Alignment Film 5 Second Alignment Film 6 Second Substrate 7 Electrode 8 Data Bus Line 9 First Alignment Film 10 Second Alignment Film 11 Liquid Crystal 22 Common Electrode 23 First Alignment Film 21 First Substrate 25 Pixel Electrode 26 Second Alignment Film 24 Second Substrate 27 Liquid Crystal 28 First Polarizing Plate 29 Second Polarizing Plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shun Tsuki 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Yoji Suzuki, 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (6)

[Claims] 1. A method for manufacturing a liquid crystal display device, wherein a region having a different pretilt angle is partially formed in a pixel by partially irradiating an alignment film formed on a substrate with ultraviolet light. After two substrates, each having an alignment film in which a region having a different pretilt angle is formed in a pixel, are bonded together with an adhesive via a spacer to form an empty liquid crystal display panel, the empty liquid crystal display is displayed. A method for manufacturing a liquid crystal display device, which comprises leaving a panel in a high-humidity atmosphere to increase the water content in an alignment film and injecting liquid crystal. 2. The method for manufacturing a liquid crystal display device according to claim 2, wherein an alignment film having high hygroscopicity such as polyimide or polyvinyl alcohol is used as the alignment film. 3. A method for manufacturing a liquid crystal display device, wherein a region having a different pretilt angle is partially formed in a pixel by partially irradiating an alignment film formed on a substrate with ultraviolet rays. Ultraviolet rays are radiated to an alignment film added with an ionic substance such as a rate, and two substrates having an alignment film in which a region having a different pretilt angle is partially formed in a pixel are attached using an adhesive agent through a spacer. A method for manufacturing a liquid crystal display device, which comprises forming an empty liquid crystal display panel together and then injecting liquid crystal. 4. A method of manufacturing a liquid crystal display device, wherein a region having a different pretilt angle is partially formed in a pixel by partially irradiating an ultraviolet ray on an alignment film formed on a substrate. After two substrates, each having an alignment film in which a region having a different pretilt angle is formed in a pixel, are bonded together with an adhesive via a spacer to form an empty liquid crystal display panel, the empty liquid crystal display is displayed. A method of manufacturing a liquid crystal display device, which comprises injecting liquid crystal having an increased water concentration into a panel. 5. A method of manufacturing a liquid crystal display device, wherein a region having a different pretilt angle is partially formed in a pixel by partially irradiating an alignment film formed on a substrate with ultraviolet light, After two substrates, each having an alignment film in which a region having a different pretilt angle is formed in a pixel, are bonded together with an adhesive via a spacer to form an empty liquid crystal display panel, the empty liquid crystal display is displayed. A method for manufacturing a liquid crystal display device, which comprises injecting a liquid crystal containing an ionic substance such as tetraethylammonium tetrafluoroborate into a panel. 6. Any one of claims 1 to 5
A method for manufacturing a liquid crystal display device, characterized by combining two or more.