JPS60120320A - Liquid crystal display element consisting of plastic base plate - Google Patents

Abstract

PURPOSE:To maintain flexibility and high airtightness by sealing the outside circumference of plastic film base plates on which electrodes are formed by plural adhesive agents contg. an adhesive agent consisting essentially of a polymer having a siloxane bond. CONSTITUTION:A liquid crystal display element is constituted of plastic base plates 1, 1', transparent conductive films 2, 2', oriented films 3, 3', a liquid crystal 4 and seal parts 5, 6 formed of an adhesive agent consisting essentially of a polymer having a siloxane bond. Another seal layer 6 is further provided on the inside of the outer seal part 5 in this case. The polymer having the formula I in the molecule (R, R<1> denote hydrogen or >=1 functional group of alkyl group or phenyl group) is preferably used as the above-described silicone adhesive agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a plastic substrate liquid crystal display element.

[Prior art]

A liquid crystal display element has a structure in which a liquid substance is sealed between two transparent upper and lower substrates that have a predetermined electrode pattern. Glass has been used, and its outer periphery has been bonded with epoxy adhesive or low-melting glass solder via a spacer. However, since glass is easily damaged, substrates using flexible plastic films such as polyethylene terephthalate, polycarbonate, and polysulfone have recently been developed, which have improved impact resistance and curved display compared to conventional glass substrates. Advantages such as ease and low cost are cited. Figure 2(a)
and (b) show an example of a liquid crystal display element using this plastic substrate, that is, plastic substrates 1a, la'
A transparent conductive film 2a is formed by a method such as photolithography.
2a' is formed into a predetermined electrode shape, an alignment agent is applied, alignment films 3a and 3a' are applied, and further rubbing is performed, and these substrates 1a and la' are bonded with epoxy resin, acrylic resin, silicone resin, etc. The outer periphery is bonded via a liquid crystal layer 5a, the internal space is filled with liquid crystal 4a, and then the liquid crystal injection port is sealed. However, in the liquid crystal display element configured as described above, when an inflexible adhesive such as an epoxy adhesive is used as the adhesive layer 5a, the adhesive layer and the substrate may not be bonded, or even if bonded, the adhesive layer and the substrate may not be bonded. Because of the large difference in elastic modulus, it is easy to peel off when the display element is bent and used, or when bending stress is applied during the manufacturing process, and therefore liquid crystal leakage and impurities from the outside are likely to occur.

On the other hand, when using a flexible adhesive such as silicone or acrylic, it may not adhere or even if it does adhere, the adhesive itself has high gas permeability, water vapor permeability, and liquid crystal permeability. It is easy for impurities to enter from the outside and for liquid crystal to leak. In this way, in conventionally known liquid crystal display elements, the airtightness of the seal is insufficient, resulting in deterioration over time,
Deterioration is particularly noticeable during high temperature storage and high temperature and high humidity storage.
It was not practically satisfactory.

〔the purpose〕

The present invention is characterized by providing a flexible plastic substrate liquid crystal display element that does not have the drawbacks of the conventional ones.

〔composition〕

According to the present invention, in the liquid crystal display element in which the outer periphery of a plastic substrate forming an electrode is sealed and polymerized, and liquid crystal is injected between the electrodes, the sealing portion is formed of a plurality of adhesive layers, and the plurality of There is provided a plastic substrate liquid crystal display element characterized in that at least one of the adhesive layers is formed of an adhesive whose main component is a polymer having a siloxane bond.

Next, one embodiment of the liquid crystal display element of the present invention will be explained with reference to FIG. 1. 1 and 1' are plastic substrates, 2 and 2' are transparent conductive films, 3 and 3' are alignment films, and 4 is a liquid crystal. Up to this point, it is the same as the conventional one shown in FIG. 1 above. 5,
Reference numeral 6 denotes a sealing portion, which is formed of an adhesive (hereinafter abbreviated as silicone adhesive) whose main component is a polymer having a siloxane bond. In this case, in the seal portion, a separate seal layer 6 is further provided inside the outer peripheral seal portion 5, as shown in FIG.

In the adhesive layer forming the seal portion, the silicone adhesive was the most excellent among sealants for plastic substrate liquid crystal display elements in terms of flexibility, adhesive strength, liquid crystal resistance, and the like. However, water vapor
The gas barrier properties against oxygen and the like and the airtightness of the liquid crystal were not sufficient, and the reliability for practical use could not be satisfied. The inventors believe that such reliability is
It has been found that a dramatic improvement can be achieved by using a multiple seal structure.

As the silicone adhesive, conventionally known adhesives can be used. These silicone adhesives are
A silicone resin, that is, a polymer having the formula in its molecule,
Generally, it is called silicone resin. More specifically, polydimethylsiloxane having the following 9- in the molecule (commercially available products include "Dow Corning 200" and "General Electric 5F
69.5F96.5S4107J, "Toshi Silin 5E1700J, etc." and polymethylphenylsiloxane having the following formula in the molecule (commercially available products include "General Electric 5F1023.5FSR").
82,5R112J, etc.), and polymers having functional groups other than methyl and phenyl groups introduced into the molecule can also be used. Examples of such polymers include polymers with hydroxyl groups introduced (commercially available products include "General Electric 5R-173 and SR-174");
Polymers with alkoxy groups introduced (commercially available products include
General Electric 5R191J), sea
)-) Polymers with introduced Ll groups (-3i-OH) (commercial products include "Dow Corning 340"), polymers with alkyd groups introduced (commercial products include "Dow Corning Silkyd 50") ), polymers with 5i-H groups introduced (commercially available products include Toshi Silicon SE1.700J), etc.Other examples include zodium methyl silicone, polymers with epoxy groups, and fluorosilicone. Can be used.

The reaction-curable polymer having a siloxane bond as described above may be used as it is, or a polymer to which -5i-H groups have been introduced may be used as a curing agent, or a metal salt such as a platinate may be added as a reaction accelerator. The seal of the present invention can be prepared by adding metal oxides such as silica gel or titanium oxide for the purpose of coloring, adjusting viscosity, or improving other properties, blending different types of the above-mentioned polymers, or creating a copolymer structure. It is said to be a drug. In actual use, depending on the type of polymer, it may be a one-part self-crosslinking type or a two-part heating type.

In addition, in the present invention, the adhesive for the outer circumference seal and the adhesive for the inner circumference seal may be of the same type or different types, and in this case, for example, as the adhesive for the outer circumference seal, Using an epoxy group-containing silicone adhesive with high adhesive strength, it can be used as an adhesive for gas barrier seals.
Product reliability can be further improved by using a fluorosilicone adhesive with high properties. In addition, in FIG. 1, the seal part has a double seal structure, but if necessary, third and fourth adhesive layers may be further provided inside the seal formed by the second adhesive layer. It is also possible to form a seal. In such a plurality of sealing adhesive layers, at least one of them is formed of the silicone adhesive layer.

The substrates 1 and 1' may be made of light-transmitting plastics such as polyesters such as polyethylene terephthalate and polybutylene terephthalate, polysulfones, polyethersulfones, polycarbonates, acetyl cellulose, and polymethacrylic acid esters. In this case, polyethylene terephthalate is most preferable in view of the physical properties that influence the reliability of the plastic substrate liquid crystal display element, such as heat resistance, solvent resistance, liquid crystal resistance, gas permeability, and water vapor permeability. Among polyethylene terephthalate films 1-, uniaxially stretched polyethylene terephthalate films are particularly preferred from the viewpoint of optical properties.

〔effect〕

The present invention has the above configuration, and uses a silicone adhesive as a sealing adhesive to improve the disadvantages of conventional products in terms of flexibility, adhesive strength, and liquid crystal resistance. This product improves the poor gas barrier properties and liquid crystal airtightness of silicone adhesive seals by creating a multilayer seal structure. In the case of the present invention, the shortcomings of conventional products are overcome by the simple structure described above, and the product is highly reliable.Moreover, the present invention can be performed by one-time screen printing as in the conventional method without increasing the number of steps. Since it is possible to form a multilayer seal portion by using the above method, the productivity of the product of the present invention is high, and its industrial significance is great.

8- 〔Example〕 Next, the present invention will be explained in more detail with reference to Examples.

Example 1 After forming a predetermined electrode on a uniaxially stretched polyester film with a transparent conductive film by photolithography, an alignment film made of organic titanate, epoxy, and nylon was formed and rubbed. On this substrate, silicone adhesive SE-1700 manufactured by Kurashi Silicone Co., Ltd. was screen printed in the shape shown in FIG. A substrate that had been subjected to a similar orientation treatment and the aforementioned substrate were bonded to each other through a polymer particle spacer with a particle size of 10 μm so that the orientation axes were perpendicular to each other, and an empty cell was prepared by heating at 150° C. for 1 hour. . Then E,
Automotive liquid crystal ZLT-1565 manufactured by Merck was sealed by a vacuum sealing method, and the filling opening was sealed by ultrasonic welding to produce a twisted nematic type liquid crystal display element. This liquid crystal display element showed no visual defects such as alignment deterioration in a high-temperature storage test at 60°C for 1000 hours, and the electro-optical properties such as threshold voltage, contrast ratio, current consumption, and response acceleration varied by ±20% from the initial value. It showed extremely high reliability within Even in a more severe high-temperature test at 80° C., no visual appearance defects occurred for more than 500 hours, and the electro-optical properties showed extremely high reliability with initial value variation within 20%.

Comparative Example 1 In Example 1, a silicone adhesive was printed as shown in FIG. 2, and a liquid crystal display element was produced in the same manner. Although this liquid crystal display element can withstand a high temperature storage test of 60°C for 1000 hours, it has a temperature of about 1
After 00 hours, the alignment deteriorated and it no longer functioned as a liquid crystal display element.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a plan view and a side sectional view of a liquid crystal display element according to the present invention, and FIGS. 2(a) and (b) are a plan view and a side sectional view of a conventional liquid crystal display element. In the figure, ■, 1' is the substrate, 2.2' is the transparent conductive film, 3,
3' is an alignment film, 4 is a liquid crystal, and 5.6 is a silicone adhesive layer. 11- Figure 1' (a) Figure 2 (a) a Figure 1 (b) Figure 2 [b]

Claims (2)

[Claims] (1) In a liquid crystal display element in which the outer periphery of a plastic film substrate forming an electrode is sealed and polymerized, and liquid crystal is injected between the electrodes, the sealing portion is formed of a plurality of adhesive layers, and the plurality of A plastic substrate liquid crystal display element, wherein at least one of the adhesive layers is formed of an adhesive whose main component is a polymer having a siloxane bond. (2) The liquid crystal display element according to claim 1, wherein the sealing portion is constituted by two or more adhesive layers whose main component is a polymer having a siloxane bond.