JPH06102518A - Plastic substrate liquid crystal display element - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a liquid crystal display element having excellent adhesiveness, bending resistance, reliability, moisture resistance and solvent resistance as a sealant. [Structure] In a plastic substrate liquid crystal display device configured by laminating substrates made of flexible plastic material, a rubber-like elastic adhesive having self-adhesiveness as a sealant for the outer peripheral portion when the substrates are laminated. A mixture of the agent and the epoxy adhesive is used. Even more preferably,
The rubber-like elastic adhesive is contained in the sealant in an amount of 20 to 80% by weight.

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 constructed by laminating substrates made of flexible plastic material. In particular, it relates to a sealant used for the outer peripheral portion of this liquid crystal display element.

[0002]

2. Description of the Related Art A liquid crystal display device has a structure in which two substrates having a predetermined electrode pattern are opposed to each other, the outer periphery of the substrates is sealed with a sealant, and a liquid crystal substance is sealed between the substrates. Here, the sealing agent is required to have adhesiveness to the substrate, protection to the encapsulated liquid crystal substance, productivity, etc., and epoxy adhesives and the like have been conventionally used.

In recent years, liquid crystal display devices have been made thinner,
There has been a demand for weight reduction, size increase, arbitrary shape, curved surface, and cost reduction. Therefore, the use of a plastic substrate as a substrate for a liquid crystal display element has been studied and is being put to practical use.

FIG. 1 shows an example of a conventional liquid crystal display device using a plastic substrate. In the figure, 1 and 2 are plastic substrates, 3 and 4 are transparent electrodes, 5 and 6 are alignment films, 7 is a sealant for sealing the outer periphery of the liquid crystal display element, and 8 is a sealed liquid crystal part.

The plastic substrate used for such a liquid crystal display device has flexibility, transparency in the visible light region, optical isotropy, surface smoothness and hardness, and a manufacturing process such as liquid crystal display device assembly. Solvent resistance, heat resistance of 100 ° C. or higher, moisture resistance, etc. are required. Particularly, when long-term reliability is required or when it is used under severe conditions such as for automobiles, more excellent moisture permeation resistance and solvent resistance are required.

Therefore, as a plastic substrate, it has been proposed in JP-A-3-252625 to use a composite substrate having a structure in which a protective layer is provided on a base material layer made of a plastic film or sheet.

[0007]

However, since the protective layer provided on the substrate as described in JP-A-3-252625 mentioned above is provided with moisture permeation resistance and solvent resistance, the surface activity is low. Low. Therefore, the conventional sealant has low adhesiveness, and has a problem that it is difficult to bond and seal the substrates. In addition, since the plastic substrate for liquid crystal display element has flexibility, the conventional sealing agent may cause the sealing portion to peel off without following the bending of the liquid crystal display element, or the sealing portion may be cracked to prevent leakage of liquid crystal or moisture. There is a problem in that the liquid crystal display element is intruded and the reliability of the liquid crystal display element is poor.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a liquid crystal display element having excellent adhesiveness, bending resistance, reliability, moisture resistance, and solvent resistance as a sealant. .

[0009]

As a plastic substrate liquid crystal display element according to the present invention, a plastic substrate liquid crystal display element constituted by laminating substrates made of a flexible plastic material is used. It is characterized in that a mixture of a rubber-like elastic adhesive having self-adhesive property and an epoxy adhesive is used as a sealant for the outer peripheral portion.

Although the conventional sealant, for example, an epoxy adhesive alone has the above-mentioned problems, the sealant of the present invention is
It is a mixture of a rubber-like elastic adhesive having self-adhesiveness and an epoxy adhesive, and such a problem is solved.

That is, by mixing a rubber-like elastic adhesive having self-adhesiveness with an epoxy-based adhesive, the self-adhesiveness of the rubber-like elastic adhesive causes the epoxy-based adhesive generated due to a decrease in the activity of the substrate surface. The adhesive strength of the sealant can be improved by assisting the adhesive strength of the adhesive with the adhesive strength. In addition, the flexibility of the sealant can be improved by mixing the rubber-like elastic adhesive and the epoxy adhesive to form the sea-island structure. It is also a sealing agent with excellent reliability, moisture resistance, and solvent resistance.

Further, as a sealant used in the liquid crystal display element according to the present invention, a rubber-like elastic adhesive is used in the sealant.
It is preferably contained in an amount of 0 to 80% by weight. That is, by setting the rubber-like elastic adhesive to 20% by weight or more,
The moisture permeation resistance of the sealant can be further enhanced. By adjusting the content of the rubber-like elastic adhesive to 80% by weight or less, flexibility, that is, bending resistance can be further enhanced, and moisture resistance and solvent resistance can also be enhanced.

The rubber-like elastic adhesive having self-adhesiveness used in the present invention means an adhesive having adhesiveness and rubber-like elasticity even when cured, that is, a silicone-modified adhesive, a butyl rubber-type adhesive, It is possible to use one or a mixture of two or more kinds of urethane rubber type adhesives, acrylic modified type adhesives and the like, and a mixture of these with a polypropylene glycol resin in order to further improve the rubber-like elasticity. .

As the epoxy adhesive mixed with these, in addition to unmodified epoxy adhesive, epoxy-phenolic adhesive, epoxy-polyamide adhesive, epoxy-nylon adhesive, epoxy-polysulfide adhesive, epoxy-adhesive adhesive One of various modified epoxy adhesives such as silicone-based and nitrile rubber-epoxy-based adhesives, or a mixture of two or more of these unmodified and modified epoxy-based adhesives can be used.

The sealant of the present invention preferably contains no impurities that adversely affect the liquid crystal or the alignment film.

The sealant obtained by mixing the rubber-like elastic adhesive having self-adhesive property and the epoxy adhesive is applied to the outer peripheral portion of the plastic substrate by, for example, screen printing. A transparent electrode and an alignment film are formed on this plastic substrate in advance, and spacers are further scattered. Then, stick the two plastic substrates together,
Cure the sealant. The curing temperature may be a temperature required for each material to dry, cure and crosslink, but the temperature at which the plastic substrate is not deformed becomes the upper limit, and is preferably 130 ° C or lower. Then, after bonding the substrates and curing the sealant, liquid crystal is injected, and the injection port is closed to obtain a plastic substrate liquid crystal display element.

In order to confirm the effects of the present invention, the evaluation of the adhesiveness, flex resistance, reliability, moisture permeability and solvent resistance by the sealing agents of Examples and Comparative Examples described later was conducted as follows. went. In the evaluation, Amorex 7000 manufactured by Teijin Limited was used as the plastic substrate.

First, samples for evaluation of adhesiveness, flex resistance, reliability, and solvent resistance were manufactured as follows. First, a plastic spacer having a diameter of 10 μm is dispersed on a plastic substrate. Subsequently, a 300-mesh screen is used to screen-print the encapsulant on the plastic substrate in a square pattern having a width of 0.5 mm and a side of 35 mm. A plastic substrate of the same shape was attached to the thus prepared substrate, and the sealant was dried and cured to obtain an evaluation sample.

The adhesiveness was evaluated by subjecting the evaluation sample to a tensile tester and measuring the load amount (g) of T-type peeling.

The bending resistance was evaluated by winding the evaluation sample around a cylinder having a diameter of 50 mm and observing the presence or absence of peeling of the substrate.

Regarding reliability, the evaluation sample was tested at a temperature of 60 ° C. and a humidity of 9
After being left under an environmental condition of 0% RH for 500 hours, the above-mentioned adhesion and flex resistance were evaluated, and whether or not both performances were satisfied was evaluated.

The solvent resistance was evaluated by ultrasonic cleaning for 5 minutes while immersing the evaluation sample in each solvent of isopropyl alcohol, acetone, toluene and N-methylpyrrolidone.
It was evaluated by observing the presence or absence of peeling of the substrate.

For moisture vapor resistance, the following samples were prepared in addition to the above-mentioned evaluation samples. First, the plastic substrate is cut into a circle with a diameter of 65 mm, and further 1 cm in the center.
Make a hole in the corner. Then, a plastic spacer having a diameter of 10 μm is dispersed on the substrate. Subsequently, a 300 mesh screen is used to screen-print the encapsulant on the plastic substrate in a square pattern having a width of 0.5 mm and a side of 35 mm so as to surround the central hole. A 40 mm square plastic substrate was attached to the thus prepared substrate, and the sealant was dried and cured to give a moisture vapor resistance evaluation sample.

With respect to the moisture permeation resistance, this moisture permeation resistance evaluation sample was attached to a moisture permeation cup having a diameter of 60 mm into which calcium chloride was added, and a moisture permeation test method based on JIS-Z-0208 was performed at a temperature of 60 ° C. and a humidity of 90% RH. Performed under environmental conditions, the moisture permeability (g / m ²
・ It was evaluated by measuring 24 hours).

[0025]

Example 1 As a sealing agent, 50% by weight of XN-5A-C manufactured by Mitsui Toatsu Chemicals, Inc. as an epoxy-based adhesive, and a supermarket manufactured by Cemedine Co., Ltd. as a rubber-like elastic adhesive were used. A mixture of 50% by weight of X8008 was used. This sealant was dried and cured at a temperature of 120 ° C. for 1 hour to obtain an evaluation sample of Example 1.

As shown in Table 1, the evaluation results of this sample are as follows: the adhesion is high at 150 (g) and the peeling of the substrate is not observed in the bending resistance, and the reliability is also excellent. The moisture vapor resistance was very small, less than 0.01 (g / m ² · 24 hr), and the solvent resistance was excellent because no peeling was observed for each solvent.

A plastic substrate liquid crystal display device was manufactured using the sealing agent of Example 1. That is, Amorex 7000 manufactured by Teijin Ltd. was used as a substrate, and after the alignment film was formed, a rubbing treatment was performed and then liquid crystal was injected by a vacuum injection method to obtain a plastic substrate liquid crystal display element. When this plastic substrate liquid crystal display element was observed after being left for 500 hours under an environmental condition of 60 ° C. × 90% RH, the display characteristics of the liquid crystal display element were good.

[0028]

Example 2 As the sealing agent, 35% by weight of Araldite AW106 manufactured by Ciba-Geigy as an epoxy-based adhesive, 35% by weight of Araldite HV953U manufactured by Ciba-Geigy as an epoxy-based adhesive curing agent, and a rubber-like elastic adhesive were used. Super X80 manufactured by Cemedine Co., Ltd.
A mixture of 08 and 30% by weight was used. This sealant was dried and cured at a temperature of 120 ° C. for 1 hour to obtain an evaluation sample of Example 2.

As shown in Table 1, the evaluation results of this sample are as follows: the adhesiveness is high at 120 (g), the peeling of the substrate is not observed in the bending resistance, and the reliability is also excellent. The moisture vapor resistance was very small, less than 0.01 (g / m ² · 24 hr), and the solvent resistance was excellent because no peeling was observed for each solvent.

A plastic substrate liquid crystal display device was manufactured using the sealing compound of Example 2. That is, Amorex 7000 manufactured by Teijin Ltd. was used as a substrate, and after the alignment film was formed, a rubbing treatment was performed and then liquid crystal was injected by a vacuum injection method to obtain a plastic substrate liquid crystal display element. When this plastic substrate liquid crystal display element was observed after being left for 500 hours under an environmental condition of 60 ° C. × 90% RH, the display characteristics of the liquid crystal display element were good.

[0031]

[Embodiment 3] As a sealing agent, 35 wt% of Araldite AW106 manufactured by Ciba-Geigy as an epoxy-based adhesive, 35 wt% of Araldite HV953U manufactured by Ciba-Geigy as an epoxy-based adhesive curing agent, and a rubber-like elastic adhesive are used. S-750 manufactured by Cemedine Co., Ltd. as an agent
A mixture of 0% by weight was used. Apply this sealant at a temperature of 12
It was dried and hardened at 0 ° C. for 1 hour to obtain an evaluation sample of Example 3.

As shown in Table 1, the evaluation results of this sample are as follows: the adhesiveness is as high as 100 (g), the peeling of the substrate is not observed in the bending resistance, and the reliability is also excellent. The moisture vapor resistance was very small, less than 0.01 (g / m ² · 24 hr), and the solvent resistance was excellent because no peeling was observed for each solvent.

A plastic substrate liquid crystal display device was manufactured using the sealing agent of Example 3. That is, Amorex 7000 manufactured by Teijin Ltd. was used as a substrate, and after the alignment film was formed, a rubbing treatment was performed and then liquid crystal was injected by a vacuum injection method to obtain a plastic substrate liquid crystal display element. When this plastic substrate liquid crystal display element was observed after being left for 500 hours under an environmental condition of 60 ° C. × 90% RH, the display characteristics of the liquid crystal display element were good.

[0034]

Example 4 An evaluation sample of Example 4 was prepared in the same manner as in Example 2 except that the mixing ratio of the adhesive used in Example 2 was changed. That is, in Example 4, 5% by weight of the epoxy adhesive main agent, 5% by weight of the epoxy adhesive curing agent,
A rubber-like elastic adhesive was used as a sealant having a mixing ratio of 90% by weight.

As shown in Table 1, the evaluation results of this sample are as follows: the adhesion is high at 120 (g), the peeling of the substrate is not observed in the bending resistance, and the reliability is also excellent. The moisture vapor resistance was excellent because it was a small value of 0.03 (g / m ² · 24 hr), and the solvent resistance was also excellent because no peeling was observed for each solvent.

A plastic substrate liquid crystal display device was manufactured using the sealing compound of Example 4. That is, Amorex 7000 manufactured by Teijin Ltd. was used as a substrate, and after the alignment film was formed, a rubbing treatment was performed and then liquid crystal was injected by a vacuum injection method to obtain a plastic substrate liquid crystal display element. When this plastic substrate liquid crystal display element was observed after being left for 300 hours under an environmental condition of 60 ° C. × 90% RH, the display characteristics of the liquid crystal display element were good. However, after this was left for 500 hours under the environmental condition of 60 ° C. × 90% RH, a part of the surrounding sealing part did not display due to the intrusion of water.

[0037]

Comparative Example 1 Only the epoxy adhesive used in Example 2 was used as the sealant. That is, as the sealant, an epoxy-based adhesive main agent (Araldite AW1 manufactured by Ciba Geigy)
06) 50% by weight and 50% by weight of an epoxy adhesive hardening agent (Araldite HV953U manufactured by Ciba-Geigy) were used.

As a result of the evaluation, as shown in Table 1, the moisture permeation resistance is very small, less than 0.01 (g / m ² · 24 hr), and peeling is observed in each solvent even in the solvent resistance. However, the adhesiveness is very low and inferior at 50 (g), and in terms of bending resistance, the encapsulant does not follow the bending of the substrate and peels off, resulting in bad results and of course poor reliability. Met.

[0039]

[Comparative Example 2] The rubber-like elastic adhesive used in Example 2 (Super X8008 manufactured by Cemedine Co., Ltd.) was used as the sealant.
We used only one.

As shown in Table 1, the evaluation results for this were as follows: the adhesiveness was 150 (g), which was high and excellent, and no peeling of the substrate was observed in bending resistance, and the reliability was also excellent. The moisture resistance was 0.80 (g / m ² · 24 hr), which was a large value and inferior. Further, regarding the solvent resistance, peeling was not observed with respect to isopropyl alcohol and it was excellent, but peeling occurred with respect to acetone, toluene, and N-methylpyrrolidone, and it was inferior.

[0041]

[Table 1]

[0042]

The liquid crystal display device using the plastic substrate of the present invention uses a mixture of a rubber-like elastic adhesive having self-adhesive property and an epoxy adhesive as a sealant, more preferably in the sealant. 20 to 8 of rubber-like elastic adhesive
By containing 0% by weight, it is possible to obtain a liquid crystal display element having excellent adhesiveness as a sealant, bending resistance, reliability, moisture permeation resistance, and solvent resistance.

[Brief description of drawings]

[Figure 1] Plastic substrate liquid crystal display device

[Explanation of symbols]

 1, 2 Plastic substrate 3, 4 Transparent electrode 5, 6 Alignment film 7 Sealant 8 Liquid crystal part

Claims (2)

[Claims] 1. A plastic substrate liquid crystal display device constituted by laminating substrates made of flexible plastic material, wherein a rubber-like elastic material having self-adhesiveness is used as a sealant for an outer peripheral portion when the substrates are laminated. A plastic substrate liquid crystal display device comprising a mixture of a mold adhesive and an epoxy adhesive. 2. A rubber-like elastic adhesive containing 20 to 8 in a sealant.
The plastic substrate liquid crystal display device according to claim 1, wherein the liquid crystal display device contains 0% by weight.