JP2001100184A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device which does not produce air bubbles in a liquid crystal even for long-term use. SOLUTION: The device is equipped with transparent substrates as an outer casing which are disposed facing each other through the liquid crystal and with a display part consisting of a great number of pixels in a spread direction of the liquid crystal. The amount of carbon dioxide dissolved in the liquid crystal sampled by decomposing the display is specified to <=10 μl per 1 ml of the liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device has a transparent substrate disposed opposite to a liquid crystal interposed therebetween as an envelope, and has a display section comprising a large number of pixels in a direction in which the liquid crystal spreads.

When a shock is applied to such a liquid crystal display device, a phenomenon that bubbles are generated in the liquid crystal is observed.

Although the cause has not been elucidated in detail,
For example, as described in JP-A-8-234188 and JP-A-4-42129, a so-called filter substrate on which a color filter or the like is formed, or a so-called TFT substrate bonded to the filter substrate. It is known to employ a method which is considered to be an adsorption gas release treatment represented by water of hydration by baking the liquid crystal display panel before liquid crystal encapsulation.

[0005]

However, the liquid crystal display device constructed as described above has such an effect that an impact bubble is hardly generated in the liquid crystal, for example, in an environment where an impact is constantly applied to the display surface. The use of No. could not ensure high impact bubble resistance.

The inventors of the present invention have argued that, as described above, the impact bubble resistance is not sufficient because a gas generating potential exists on the opposite substrate or a decomposable gas is generated due to damage due to external factors. Was dissolved into the liquid crystal at normal temperature and normal pressure, and it was confirmed that the amount of dissolved bubbles reached a saturated state and bubbles were generated when an impact was applied to the display surface.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a liquid crystal display device in which bubbles are not generated in liquid crystal even when used for a long time.

[0008]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the liquid crystal display device according to the present invention comprises:
A transparent substrate opposed to the liquid crystal interposed therebetween is used as an envelope, and a display unit including a large number of pixels is provided in a spreading direction of the liquid crystal. Carbon dioxide contained in the liquid crystal obtained by disassembling the liquid crystal is included. Of 10μl per 1ml of liquid crystal
It is characterized by the following.

[0010] Such a liquid crystal display device does not generate bubbles in the liquid crystal even if it is used in an environment where the display surface is constantly impacted, and even if it is generated for several minutes. Disappeared experimentally.

In a liquid crystal display device, the liquid crystal is generally sealed by an organic material layer. Therefore, the gas generation potential for generating bubbles in the liquid crystal is limited to the entire material layer. Will exist.

In other words, even if the gas generation potential in one material layer is lost, it is difficult to suppress the generation of bubbles in the liquid crystal if the gas generation potential exists in another material layer.

However, as a result, when the amount of dissolved carbon dioxide in the liquid crystal is 10 μl or less per 1 ml of the liquid crystal, it is demonstrated that the gas generating potential in the liquid crystal display device is reduced. become.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the liquid crystal display device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the liquid crystal display device according to the present invention.

In FIG. 1, there is a transparent substrate SUB1 on the so-called TFT substrate side. Each pixel region on the liquid crystal side surface of the transparent substrate SUB1 has a pixel electrode I made of a transparent electrode.
TO1 is formed.

The pixel electrode ITO1 defines a pixel region through a thin film transistor TFT driven by the supply of a scanning signal from a gate signal line GT extending in the x direction so as to define the pixel region. A video signal is supplied from a drain signal line (not shown) extending in the y direction.

The pixel electrode ITO is positioned above the thin film transistor TFT via the protective film PSV, and an alignment film ORI is formed on the pixel electrode ITO.
1 is formed.

The alignment film OR11 is a film that comes into direct contact with the liquid crystal LC, and determines the initial alignment direction of the liquid crystal LC.

The TFT substrate thus configured is arranged to face a so-called filter substrate via the liquid crystal LC.

In this filter substrate, a black matrix layer BM is formed on the liquid crystal side surface of the transparent substrate SUB2 so as to define each pixel region.

The black matrix layer BM
A color filter FIL is formed so as to cover the opening, and a flat film OC is formed so as to cover the upper surfaces thereof.

Further, a transparent common electrode ITO2 common to each pixel region is formed on the flat film OC, and an alignment film ORI2 is formed so as to cover the common electrode ITO2.

A liquid crystal LC is interposed between the TFT substrate and the filter substrate thus configured, and a gap between the TFT substrate and the filter substrate is provided in the liquid crystal LC. Is included.

In the liquid crystal LC, the amount of carbon dioxide dissolved therein is 10 μl or less per 1 ml of the liquid crystal.

As described above, the liquid crystal LC in which a limited amount of carbon dioxide is dissolved can be provided with excellent display quality without bubbles even if an impact is applied to the liquid crystal display panel. become.

In the liquid crystal display panel having such a structure, the dissolved amount of CO and CO _{2 in} the liquid crystal was investigated as follows.

[0028] The liquid crystal display panel 4
After cutting the sides, the liquid crystal display panel was slowly opened from one side while tilting the liquid crystal display panel, and the liquid crystal solution was led to the lower part.

This liquid crystal was collected in a 0.3 ml reactive vial. The sampling up to this point was performed in a helium gas atmosphere, and the operation time was set within 4 minutes.

The gas dissolved amount of CO.CO ₂ in the sample liquid crystal was measured using a Hitachi 163 type gas chromatography analyzer.

The columns used consisted of a guard column and an analytical column, each of which was Porapak-T (1.0
m), Active Carbon (2.0 m, 60 /
80 mesh).

Helium gas having a purity of 99.9% or more was flowed as a carrier gas, and the flow rate was 25 ml / min.

The column bath temperature was 90 ° C. and the inlet temperature was 1
80 ° C. The volume of the liquid crystal sample to be injected was 20 μl.

The CO / CO ₂ gas passed through the column is methanated with a Ni catalyst (Metanizer MT-221; manufactured by GL Sciences Co., Ltd .; hydrogen; purity: 99.9% or more) at a temperature of 400 ° C., and a flame ion detector is used. (Detector temperature 180 ° C.).

The peak area corresponding to CO ₂ in the obtained chromatogram was integrated and quantified by an attached data processor. As a calibration gas for quantification, a CO.CO ₂ mixed gas based on helium gas manufactured by Nippon Sanso Corporation was used.

When the amount of carbon dioxide contained in the liquid crystal collected by disassembling the liquid crystal display panel by the above method is set to 10 μl or less per 1 ml of the liquid crystal, it is possible to obtain a liquid crystal without bubbles. .

Here, the amount of dissolved CO ₂ gas can be reduced by vacuum baking the filter substrate after forming the ITO film, and also by changing the conditions of forming the ITO film.

Hereinafter, an embodiment of a method of manufacturing such a liquid crystal display device will be described.

First, as for the filter substrate, the thickness of the filter substrate is set to 0.1 mm.
A black matrix BM is formed on a transparent substrate SUB2 of 7 to 1.0 mm by applying a photosensitive black resin resist, exposing, developing, and firing.

Next, the same steps are repeated using photosensitive red, green and blue resin resists, to obtain a red filter layer FIL (R), a green filter layer FIL (G), and a blue filter layer FIL. (B) is formed.

Further, a flat film OC coated with a resin having a pencil hardness of H or more is formed, and a common electrode ITO2 is formed on the surface of the flat film OC by a low-temperature sputtering method.

Next, regarding the TFT substrate, a thickness of 0.7
Film formation and patterning are repeated on a transparent substrate SUB1 having a thickness of about 1.0 mm, a gate signal line, an insulating film for insulating the gate signal line from a drain signal line to be described later, a semiconductor layer made of a-Si, and a drain signal line To form

The semiconductor layer constitutes an active layer of the thin film transistor TFT in which part of the gate signal line is a gate electrode and part of the insulating film is a gate insulating film, and is formed simultaneously with the drain signal line on the surface thereof. A source electrode and a drain electrode are formed.

Then, after forming the pixel electrode ITO1 connected to the source electrode of the thin film transistor TFT, a protective film PSV is formed covering them.

Thereafter, an alignment film ORI is formed on the surface of each substrate on the liquid crystal side by offset printing and baked.

Further, the orientation film ORI is subjected to an orientation treatment with a cloth in a predetermined direction, and an epoxy adhesive containing a predetermined gap material as a seal material is screen-printed on one of the substrates.

Then, spacers are sprayed on one of the substrates by a spray method, and the other substrate is arranged to face the other substrate. In this case, the spray density of the spacer was set to 150 pieces / mm ² .

Thereafter, the liquid crystal is filled by a vacuum injection method,
The injection part is sealed with an epoxy adhesive.

The liquid crystal display device thus prepared is
As shown in FIG. 2, when a pressing force of 2 kg × 3 seconds was applied using a hard sphere having a diameter of about 1 cm at normal temperature and normal pressure, small bubbles were generated, but the bubbles disappeared after 5 minutes.

Thereafter, the liquid crystal display panel was disassembled and the amount of carbon dioxide dissolved in the liquid crystal was identified.
It was found that about 2 μl was eluted per ml.

[Example 1] As the flat film OC on the filter substrate side opposed to the TFT substrate, V2 manufactured by Nippon Steel Chemical Co., Ltd. was used.
59PA was used.

The composition was applied to a thickness of 2.0 μm after curing, and 500 mj / cm ² (365 nm) using a low-pressure mercury lamp.
After the irradiation, baking was performed at 220 ° C. for 1 hour on a hot plate. An ITO film having a thickness of 1500 ° was formed thereon.

As a process before preparing a liquid crystal display panel, this filter substrate was baked at 230 ° C. for 3 hours at normal pressure.

The alignment films formed on each of the filter substrate and the TFT substrate are RN-SE721 manufactured by Nissan Chemical Industries, Ltd.
0 was used.

The coating was performed so that the film thickness became 0.1 μm, and the film was temporarily baked on a hot plate at 90 ° C. for 15 minutes, and then baked at 230 ° C. for 1 hour.

An aqueous solution of Sekisui Plastic Spacer Micropearl SP-205 (average particle size: 5.0 μm) was sprayed on this with a sprayer, and baked at 150 ° C. for 1 hour. The spray density of the spacers was set to 150 pieces / mm ² .

Furthermore, a sealing material pattern was formed by screen printing a Mitsui Chemicals sealing material Struct Bond XN-21S which had been kneaded and defoamed with class fibers having an average particle size of 5.0 μm.

After heating at 80 ° C. for about 30 minutes, the filter substrate and the TFT substrate were overlaid and baked at 200 ° C. for 6 hours.

The liquid crystal display panel having the above-mentioned structure is described in 1.
Vacuum to 0 × 10 ³ Pa or less and bake for 12 hours 20
C. Annealed. A liquid crystal ZL14792 made by Merck was sealed in a liquid crystal display panel, the sealing opening was closed with 3026B made by Three Bond, and cured by irradiating light with a low-pressure mercury lamp having an illuminance of 100 mW / cm ² (365 nm) to 5000 mJ / cm ² .

As a result of the bubble test of the liquid crystal display panel thus constructed, it was confirmed that the bubble nuclei disappeared after leaving for 2 minutes.

Thereafter, the liquid crystal display panel was disassembled and the amount of carbon dioxide dissolved in the liquid crystal was identified.
About 2 μm was eluted per 1 ml of the liquid crystal.

Example 2 The evacuation before filling the liquid crystal was performed by about 1
Except for the time of 200 ° C., a liquid crystal display panel completely identical to the example was prepared.

As a result of the bubble test of this liquid crystal display panel, 1
The bubble nuclei disappeared after standing for 5 minutes.

In this case, substantially the same effect as in Example 1 was obtained although the bubble disappearance time was prolonged.

Thereafter, when the liquid crystal display panel was disassembled and the amount of carbon dioxide dissolved in the liquid crystal was identified,
About 1 μ was eluted per 1 ml of the liquid crystal.

Comparative Example A liquid crystal display panel was prepared in exactly the same manner as in Example 1, except that no pretreatment was performed at the time of assembling the liquid crystal display panel.

As a result of the bubble test of this liquid crystal display panel, the bubble nuclei did not disappear even after being left for about one week, but rather grew.

Thereafter, the liquid crystal display panel was disassembled and the amount of carbon dioxide dissolved in the liquid crystal was identified.
About 20 μ was eluted per 1 ml of the liquid crystal.

[0069]

As is apparent from the above description,
According to the liquid crystal display device of the present invention, it is possible to obtain a liquid crystal display device that does not generate bubbles in the liquid crystal even when used for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a view illustrating a method of applying a shock to the liquid crystal display device before measuring the amount of carbon dioxide contained in the liquid crystal of the liquid crystal display device according to the present invention.

[Explanation of symbols]

SUB: Glass substrate, PSV: Protective film, TFT
Thin film transistor, ITO1, pixel electrode, ORI
Alignment film, LC: liquid crystal, SP: spacer, OC: flat film, ITO2: common electrode, FIL: filter layer,
BM: Black matrix.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Teruo Kitamura 3300 Hayano, Mobara-shi, Chiba Prefecture Within Hitachi, Ltd. Display Group (72) Inventor Akira Ishii 3681-Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd. (72 ) Inventor Toshio Sato 3681 Hayano Mobara-shi, Chiba F-term in Hitachi Device Engineering Co., Ltd. PA08 PA12 PA19 QA09 QA11 QA14 QA16 RA05 TA04 TA06 TA09 TA13

Claims (6)

[Claims] 1. A liquid crystal device comprising: a transparent substrate opposed to a liquid crystal interposed liquid crystal as an envelope; and a display unit comprising a large number of pixels in a spreading direction of the liquid crystal. Wherein the dissolved amount of carbon dioxide contained in the liquid crystal is 10 μl or less per 1 ml of liquid crystal. 2. The fixing device according to claim 1, wherein the fixing of the other transparent substrate to the one transparent substrate is performed using a sealing material formed so as to surround the display unit, also serving as sealing of the liquid crystal. Liquid crystal display. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal is in contact with an alignment film formed on each of the transparent substrates. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is in a twisted nematic display mode. 5. The liquid crystal display device according to claim 1, wherein the transparent substrate has a thickness of 0.9 mm or less. 6. The liquid crystal display device according to claim 1, wherein the dissolved amount of carbon dioxide in the liquid crystal is 90% or less of the saturation solubility.