JPH05173120A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which is high in display quality and reliability. CONSTITUTION:Hard coat films 3a-3d are formed on both surfaces of plastic substrates 2a and 2b and SiOx films 4a and 4b are formed by sputtering on the opposite surfaces of the plastic substrates 2a and 2b. Transparent electrode layers 5a and 5b of ITO film and orienting films 6a and 6b are formed in order on the SiOx films 4a and 43b and a liquid crystal layer 8 is interposed between the plastic substrates 2a and 2b. The contact between the plastic substrates 2a and 2b is improved to reduce the cracking of the transparent electrode layers 5a and 5b, and the gas shielding ability of the plastic substrates 2a and 2b is greatly improved to reduce the generation of air bubbles in the liquid crystal layer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used as a display device in OA (Office Automation) equipment such as a notebook type or palmtop type personal computer and a word processor.

[0002]

2. Description of the Related Art In recent years, reflecting the trend of weight reduction and miniaturization of OA equipment such as notebook size or palmtop size, thinning of liquid crystal display devices used as such OA equipment display devices has been achieved. And weight reduction is desired. Therefore, a liquid crystal display device using a plastic substrate has come to be used for OA devices such as a notebook type or palmtop type personal computer and a word processor.

In such a liquid crystal display device, P
A pair of plastic substrates made of ES (Polyether sulphone) is used.
Gas barrier layer made of PVA (Polyvinyl alcohol),
A transparent electrode layer made of an ITO (Indium-tin oxide) film, an alignment film, and the like are formed. Then, a pair of plastic substrates are attached to each other with a sealing material sandwiching the liquid crystal layer, thereby forming a liquid crystal display device.

However, since the plastic substrate made of PES as described above is manufactured by the extrusion molding method, it has a drawback that sufficient surface smoothness cannot be obtained. Therefore, it is well known that such a plastic substrate made of PES is not suitable as a substrate for an STN (Super Twisted Nematic) type liquid crystal display device which requires a highly accurate surface (about 0.01 μm / mm or less).

Therefore, conventionally, by using a molded plastic substrate having a highly accurate surface made of an acrylic resin, an epoxy resin, or the like, the STN type liquid crystal display device can be made compact and lightweight. Is becoming.

[0006]

However, the conventional liquid crystal display device using a plastic substrate made of acrylic resin, epoxy resin, or the like is not sufficient in adhesiveness between the substrates due to the material of the plastic substrate. In the manufacturing process, a wet process using an alkali such as sodium hydroxide at the time of patterning the ITO film, a heat process such as baking of the alignment film, or a high temperature and high humidity (for example, 40 ° C., 95%) after the liquid crystal display device is completed. _When aging or the like is performed in the _RH ) state, there is a risk that cracks may occur in the transparent electrode layer made of the ITO film.

Further, since the plastic substrate has an insufficient gas shielding ability, as described above, aging is performed in a high temperature and high humidity state after completion of the liquid crystal display device, so that a gas is introduced into the liquid crystal layer through the plastic substrate. Has the drawback that air bubbles penetrate into the liquid crystal layer to generate bubbles.

Therefore, conventionally, there is a problem that it is difficult to realize a liquid crystal display device having high display quality and reliability due to the above-mentioned causes.

The present invention has been made in view of the above-mentioned problems of the prior art. By using a plastic substrate, the liquid crystal display device can be made compact and lightweight, and
For example, it is an object of the present invention to improve display quality and reliability in a STN type liquid crystal display device which requires a high-precision surface.

[0010]

In a liquid crystal display device in which a transparent electrode layer is provided on the opposing surfaces of a pair of plastic substrates that are arranged to face each other with a liquid crystal layer sandwiched between them, It is characterized in that a hard coat film made of siloxane is provided, and a SiO _x film is provided on one surface of each of the pair of plastic substrates.

[0011]

According to the above construction, the hard coat film made of siloxane is provided on both surfaces of the plastic substrate on which the liquid crystal layer is mounted, and the SiO _x film is provided on one surface of the plastic substrate. Has been.

Therefore, the adhesion between the plastic substrates is improved, and in the manufacturing process of the liquid crystal display device, for example, a wet treatment using an alkali such as sodium hydroxide at the time of patterning the transparent electrode layer and a heating process such as baking of the alignment film are performed. Even if the liquid crystal display device is subjected to a treatment or is aged at a high temperature and high humidity (for example, 40 ° C., 95% _RH ) after the completion of the liquid crystal display device, the transparent electrode layer is hardly cracked.

Further, even if a plastic substrate having a low gas blocking ability is used, gas intrusion into the liquid crystal layer is suppressed by using the liquid crystal display device having the above-mentioned structure. Even when aging is performed in a high temperature and high humidity state, bubbles generated in the liquid crystal layer are reduced.

[0014]

EXAMPLE An example of the present invention will be described below with reference to FIG. 1, taking a STN type liquid crystal display device as an example.

As shown in FIG. 1, in the liquid crystal display device 1 according to this embodiment, a pair of plastic substrates 2a and 2b made of, for example, polyacrylate are arranged to face each other with a liquid crystal layer 8 in between. Hard coat films 3a, made of siloxane, are formed on the upper and lower surfaces of these plastic substrates 2a, 2b.
3b, 3c and 3d are formed respectively. And
On the hard coat films 3b and 3c on the respective facing surfaces of the plastic substrates 2a and 2b, the SiO _x films 4a and 4b, I are formed.
Transparent electrode layers 5a and 5b made of TO film, alignment films 6a and 6
b are sequentially provided.

Further, the liquid crystal layer 8 between the alignment films 6a and 6b.
Is sealed by a sealing material 9 provided on the peripheral edge of each of the facing surfaces of the plastic substrates 2a and 2b.
The dimension between the plastic substrates 2a and 2b is kept constant by the spacers 7 ...
Further, polarizing plates 10a and 10b are attached on the hard coat films 3a and 3b on the surfaces opposite to the facing surfaces of the plastic substrates 2a and 2b, respectively.

The manufacturing process of the liquid crystal display device 1 having the above structure will be described below.

First, two plastic substrates 2a and 2b are dipped in a solution in which a siloxane-based hard coating agent is dissolved, and then the plastic substrates 2a and 2b are pulled up, so that both surfaces of the plastic substrates 2a and 2b are removed. Hard coat film 3a, 3b, 3 made of siloxane
c · 3d is formed with a film thickness of 2 to 3 μm. Then, the plastic substrate 2 on which the hard coat films 3b and 3c are formed
on one surface of a · 2b, respectively SiO _x film 4a · 4b having a thickness 100~1000Å formed by sputtering or the like, further, these on SiO _x film 4a · 4b, a thickness 500~3000Å by sputtering or the like By forming an ITO film and patterning the ITO film into a predetermined shape by etching or the like, the transparent electrode layers 5a and 5b are formed.
To form.

Next, alignment films 6a and 6b are formed on the surfaces of the plastic substrates 2a and 2b on which the transparent electrode layers 5a and 5b are formed by firing or the like. Then, seal printing is performed on the peripheral portions of the plastic substrates 2a and 2b to form the sealing material 9, and then the spacers 7 are scattered to form the transparent electrode layers 5a and 5b on the respective plastic substrates 2a and 2b. Plastic substrate 2a
Stick 2b together.

Next, a liquid crystal material is injected and sealed between the plastic substrates 2a and 2b to form a liquid crystal layer 8. After that, by attaching polarizing plates 10a and 10b to the opposite surfaces of the plastic substrates 2a and 2b, respectively, the STN having a twist angle of 240 degrees and a cell gap of 6 μm is formed.
The liquid crystal display device 1 of the mold is manufactured.

Regarding the liquid crystal display device 1 and the conventional liquid crystal display device produced as described above, high temperature and high humidity (40
° C., after aging at _RH 95%), O ₂ transmission amount of the liquid crystal layer, and H ₂ O permeation amount was measured, respectively, O ₂
And the gas shielding ability against H ₂ O were compared. The measurement results are shown in Table 1.

[0022]

[Table 1]

As is clear from Table 1 above, the liquid crystal display device 1 of this embodiment has a very high gas shielding ability as compared with the conventional liquid crystal display device, and almost no bubbles are present in the liquid crystal layer 8. It turned out that it did not occur.

As described above, the liquid crystal display device 1 of this embodiment
Has hard coat films 3a, 3b, 3c, and 3d made of siloxane formed on both surfaces of the plastic substrates 2a and 2b, and further, SiO _x films 4a and 4b are formed on opposite sides of the plastic substrates 2a and 2b. After that, the transparent electrode layer 5
a * 5b is formed.

As a result, the plastic substrates 2a and 2b
In order to improve the adhesiveness between the layers, in the manufacturing process of the liquid crystal display device 1, a wet process using an alkali such as sodium hydroxide during the patterning of the transparent electrode layers 5a and 5b and a heat process such as baking of the alignment film are performed. Or high temperature and high humidity after completion of the liquid crystal display device (for example, 40 ° C, 95%
% _RH ), it is possible to reduce cracks in the transparent electrode layers 5a and 5b which are likely to occur when aging or the like is performed.

Further, since the gas shielding ability of the plastic substrates 2a and 2b is remarkably improved, even if the aging is performed at high temperature and high humidity as described above after completion of the liquid crystal display device, almost no bubbles are generated in the liquid crystal layer 8. .. Therefore,
In the STN type liquid crystal display device that requires a high-precision surface, not only downsizing and weight reduction but also improvement in display quality and reliability can be realized.

In this embodiment, the STN type liquid crystal display device has been described as an example, but the present invention can be applied to a liquid crystal display device adopting another driving method.

[0028]

As described above, in the liquid crystal display device of the present invention, the hard coat film made of siloxane is provided on both surfaces of the pair of plastic substrates.
SiO 2 is formed on one surface of each of the pair of plastic substrates.
The x film is provided.

Therefore, the adhesion between the plastic substrates is improved, the generation of cracks in the transparent electrode layer can be prevented, and the gas shielding ability of the plastic substrate is significantly improved, so that the generation of bubbles in the liquid crystal layer is reduced. Can be made Therefore, for example, in a STN type liquid crystal display device that requires a high-precision surface, downsizing /
It is possible to reduce the weight and improve the display quality and reliability.

[Brief description of drawings]

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

[Explanation of symbols]

1 liquid crystal display device 2a · 2b plastic substrates 3a · 3b hard coat film 4a · 4b SiO _x film 5a · 5b transparent electrode layer 8 liquid crystal layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Makoto Iwamoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Kyohei Isohata 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka (72) Inventor Yasuyuki Nagano 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Prefecture

Claims (1)

[Claims] 1. A liquid crystal display device in which a transparent electrode layer is provided on the opposing surfaces of a pair of plastic substrates that are arranged so as to face each other with a liquid crystal layer in between, and both surfaces of the pair of plastic substrates are made of siloxane. A hard coat film is provided,
SiO 2 is formed on one surface of each of the pair of plastic substrates.
A liquid crystal display device characterized by being provided with an _x film.