JP2796573B2 - Liquid crystal display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal display device using a polymer film substrate.

[Problems to be solved by conventional technology and invention]

Generally, a vacuum encapsulation method utilizing a pressure difference is used for injecting liquid crystal into a liquid crystal cell. This vacuum sealing method
Set the cell and liquid crystal in the vacuum bell jar, depressurize the inside of the bell jar until the degree of vacuum becomes 0.1 torr or less, immerse the cell inlet into the liquid crystal, return the inside of the bell jar to atmospheric pressure, and inject the liquid crystal. The way to do it.

On the other hand, in recent years, polymer film substrates such as polyester, polyethylene terephthalate, and polyether sulfone have become popular as liquid crystal cell constituent substrates in view of thinning, weight reduction, ease of processing, and cost reduction of liquid crystal display elements. Has been used for

However, since the polymer film substrate has higher gas permeability than the glass substrate, when injecting liquid crystal using the vacuum encapsulation method as described above, the liquid crystal is enclosed in the cell when returning the bell jar to atmospheric pressure. This causes a problem that gas leaks from the substrate surface before the formation and bubbles are generated. If the liquid crystal cell is a small cell such as a clock display, the liquid crystal is sealed before the gas leaks from the substrate surface and no bubbles are generated, and even if it occurs, the bubbles diffuse and disappear after one day Resulting in. However, the larger the cell, the larger the bubble, and the bubble does not disappear even when the cell is left.

Since generation of such bubbles causes deterioration of display quality of the liquid crystal display device, some proposals have been made so far to prevent generation of bubbles.

For example, JP-A-61-69027 and JP-A-61-69028 disclose that a polymer film surface is coated with a low-permeability organic film in order to improve the gas permeability of the polymer film substrate. A technique for improving gas barrier properties by laminating another organic film or the like has been proposed. However, the methods of organic film coating and organic film bonding can solve the problems such as generation of air bubbles at the time of thermal shock of cells, mixing of air bubbles at the time of high-temperature and high-humidity storage test, and increase of current value. The injected bubble (the generation of bubbles due to transmission from the substrate surface during liquid crystal injection) is not improved.

Japanese Patent Publication No. 62-124124 discloses that an insulating oxide film is formed between a polymer film substrate and a transparent conductive film to improve the adhesion of the transparent conductive film or improve the permeability of moisture and various gases. A technology to do this has been proposed. However, in this method, a plurality of films are formed only on one side of the polymer film substrate, and there is a problem that curl is generated due to heat in a manufacturing process and productivity is reduced.

The present invention has been made in order to solve the above-mentioned problems of the prior art. Even if the liquid crystal cell is enlarged, the generation of bubbles due to leakage from the substrate surface generated at the time of liquid crystal injection is extremely small and the display quality is reduced. An object is to provide an excellent liquid crystal display device using a polymer film substrate.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, at least one or more of the constituent substrates having a transparent conductive film on the inner surface thereof is composed of a polymer film substrate, and a liquid crystal cell having liquid crystal sealed between the substrates is provided. in configured liquid crystal display device, the polymer film metal oxide coating having a film thickness of at least 200Å on the outer surface of the substrate is formed, oxygen permeability of the polymer film substrate ^{1cc / m 2 / 24hour / latom} / A liquid crystal display device having a temperature of 20 ° C. or lower is provided.

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view schematically showing one configuration example of a liquid crystal display device according to the present invention. In the figure, reference numerals 1 and 1 'denote polymer film substrates, for example, uniaxially or biaxially stretched polyethylene terephthalate film, polysulfone film, polyethersulfone film, polycarbonate film, cellulose triacetate film and the like. The polymer film substrates 1 and 1 'may use the above-described film alone or may be a composite substrate provided with an undercoat layer, a protective film and the like in order to improve adhesion. Transparent conductive films (ITO films) 2 and 2 'for display electrodes are formed on the inner surfaces of the polymer film substrates 1 and 1', and alignment films 4 and 4 'are further formed thereon. is there. Gas barrier layers 3, 3 'made of metal oxide and having a thickness of 200 mm or more on the outer surfaces of the polymer film substrates 1, 1'.
There is formed, the oxygen permeation amount are set to be ^{1cc / m 2 / 24hour / latom} / 20 ℃ or less. The constituent material of the gas barrier layer _{3,3 ', SiO 2, SnO 2} , In 2 O 3, ITO, TiO 2, Al
Metal oxides such as ₂ O ₃ , ZnO, and Ta ₂ O ₅ are used. The thickness of the gas barrier layers 3, 3 'is set to an appropriate value of 200 ° or more in consideration of the transmittance of the material used. If the thickness is smaller than 200 °, sufficient gas barrier properties cannot be obtained. On one surface, the transparent conductive films 2, 2 'and the alignment films 4, 4'
A pair of polymer film substrates 1, 1 ', on which the gas barrier layers 3, 3' are formed on the other surface, are formed by dispersing a gap agent 5 between the two substrates and then printing a sealing material 5 around the substrates. And then pasted together. Then, the liquid crystal 7 is sealed in the space formed by the above-described vacuum sealing method, and a liquid crystal display device is configured.

[Action]

In the present invention, the metal oxide film is formed on the outer surface of the polymer film substrate, the oxygen permeability of ^{1cc / m 2 / 24hour / latom} / 20
Since the temperature is below ℃, the generation of injection bubbles during liquid crystal injection is effectively prevented even if the cell is enlarged, and the film is not concentrated on one side of the polymer film substrate. This prevents the occurrence of curl due to the above. Therefore, the above-mentioned problem is solved, and a liquid crystal display device which is excellent in display quality and can be enlarged can be provided.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

Example 1 As a substrate 1, 1 ', the oxygen permeation amount was 12 cc / m ² / 24hour / latom /
Using a uniaxially stretched polyethylene terephthalate film at 20 ° C, ITO films (display electrode films) 2, 2 'each having a thickness of 500 mm are formed on one surface of the substrate 1, 1' by DC sputtering, and the other surface is formed. An ITO film (gas barrier layer) 3, 3 'having a thickness of 300 mm was formed thereon by the same method. Thereby, the oxygen permeation amount was 0.7 cc / m ² / 24hour / latom / 20 ° C. Then 2,
Only the 2 ′ ITO film was processed by photolithography,
A display electrode for 0 × 160 dots was used. Further, after forming alignment films 4, 4 'using an alignment agent (trade name: HL-1110; manufactured by Hitachi Chemical Co., Ltd.), rubbing treatment was performed to set the twist angle between the upper and lower electrodes to 220 °. Next, 150 to 200 plastic beads having an average particle size of 6.2 μm / m as a gap agent 5 were formed on one substrate.
Dispersed with a dispersion density of m ² . Then, a sealing material 6 made of a flexible epoxy adhesive is printed on the other substrate, the two substrates are bonded together, and the sealing material 6 is cured at 80 ° C. for 90 minutes.
A liquid crystal cell having an effective display area of 55 mm × 60 mm was obtained. A chiral nematic-containing smectic liquid crystal 7 was injected into the liquid crystal cell by a vacuum sealing method. At this time, the vacuum reach is 0.05 to
rr. Immediately after the injection, one bubble having a diameter of 0.5 mmφ was generated around the sealing material 6, but disappeared one day later.

Example 2 As a substrate 1, 1 ', the oxygen transmission rate was 11 cc / m ² / 24hour / 1atom /
Using a uniaxially stretched polyethylene terephthalate film at 20 ° C, ITO films (display electrode films) 2, 2 'each having a thickness of 500 mm are formed on one surface of the substrate 1, 1' by DC sputtering, and the other surface is formed. The thickness is 50 by the same DC sputtering method.
0 ° SiO ₂ films (gas barrier layers) 3, 3 ′ were formed, respectively. As a result, the oxygen transmission rate is 0.9 cc / m ² / 24hour / 1atom /
The temperature reached 20 ° C. Next, the ITO films 2, 2 'were processed by a photolithography method to form display electrodes for 640 × 400 dots. Further, after forming alignment films 4, 4 'using an alignment agent (trade name: HL-1110; manufactured by Hitachi Chemical Co., Ltd.), rubbing treatment was performed to set the twist angle between the upper and lower electrodes to 220 °. Next, plastic beads having an average particle diameter of 6.2 μm as a gap agent 5 were dispersed on one substrate at a dispersion density of 150 to 200 beads / mm ² . Then, a sealing material 6 made of a flexible epoxy adhesive is printed on the other substrate, the two substrates are bonded together, and the sealing material 6 is cured at 80 ° C. for 90 minutes, and the effective display area is 250 mm × 150 mm. A liquid crystal cell was obtained. A chiral nematic-containing smectic liquid crystal 7 was injected into the liquid crystal cell by a vacuum sealing method. At this time, the degree of vacuum reached was 0.03 torr. Immediately after injection 1mmφ in diameter
Two large bubbles were generated around the sealing material 6, but disappeared one day later.

Comparative Example Oxygen permeation rate of 12 cc / m ² / 24hour / latom /
Using a uniaxially stretched polyethylene terephthalate film at 20 ° C., an ITO film (display electrode film) 2, 2 ′ having a thickness of 500 ° was formed on one surface of the substrate 1, 1 ′ by a DC sputtering method. No gas barrier layer was formed on the surface. Thereafter, a liquid crystal cell was prepared in the same manner as in Example 2, and liquid crystal was injected by a vacuum sealing method. Immediately after the injection, four bubbles having a diameter of 5 mm were generated, and when left for one day, the size of the bubbles became small, but they did not disappear.

〔The invention's effect〕

According to the present invention, it is possible to provide a high-quality liquid crystal display device in which generation of bubbles during liquid crystal encapsulation is extremely small even when the cell is enlarged.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the configuration of a liquid crystal display device according to the present invention. 1,1 'polymer film substrate 2,2' transparent electrode film 3,3 'gas barrier layer 4,4' alignment film 5 gap agent 6 sealing material 7 liquid crystal

Claims (1)

(57) [Claims] 1. A liquid crystal display device comprising a liquid crystal cell in which at least one or more of the constituent substrates having a transparent conductive film on the inner surface is made of a polymer film substrate and a liquid crystal is sealed between the substrates. A metal oxide film having a thickness of 200 ° or more is formed on the outer surface of the polymer film substrate, and the oxygen permeation amount of the polymer film substrate is 1 cc / m ² / 24hou.
A liquid crystal display device having a temperature of r / latom / 20 ° C or lower.