JPS6289930A - Production of liquid crystal cell - Google Patents

Abstract

PURPOSE:To remarkably reduce the curing time of a sealant by using a photosetting sealant as the sealant for the two inner and outer layers and simultaneously curing the sealants by one's light irradiation. CONSTITUTION:Sealing is carried out in the two inner and outer layer structures, an acrylic photochemical radical polymerization type sealant having excellent liq. crystal resistance is used as the sealant on the inside to be brought into contact with the liq. crystal, and a photochemical cationic polymerization type sealant having an excellent barrier characteristic is used as the sealant on the outside. Both the sealants are cured by one's light irradiation. Consequently, the contrast is not deteriorated and a liq. crystal having high adhesive strength and barrier characteristic can be obtained in a short time.

Description

[Detailed Description of the Invention] [Industrial Application Disassembly] The present invention relates to a method for manufacturing a liquid crystal cell, and more specifically, to a method for manufacturing a liquid crystal cell, and more specifically, a method for manufacturing a liquid crystal cell, in which a liquid crystal enclosing portion is formed by bonding two substrates together at a constant interval. The present invention relates to a sealing method.

[Conventional technology]

Generally, liquid crystal cells used in display devices are made by maintaining a predetermined gap between two glass or plastic substrates using a sealant such as organic epoxy resin or acrylic resin to form a liquid crystal enclosing part. It is manufactured by gluing two pieces together.

As a method for bonding the substrates, a sealant is applied to one substrate by screen printing to form the outer periphery of the cell, and after gluing the other substrate together with a spacer in between, the sealant is applied to one substrate. A curing method is generally employed.

As a special substrate sealing method, proposals regarding two-layer structure sealing in which two different types of sealants are used in two layers, an inner layer and an outer layer, have been proposed in JP-A-57-96317 and JP-A-5. '8-1
No. 17522, JP-A-58-121023, JP-A-5
It is described in JP 7-181527 and the like.

Conventionally, as these sealants, room temperature curing sealants, one-component or two-component epoxy thermosetting sealants, and the like have been used.

Furthermore, in the two-layer structure sealing methods proposed above, thermosetting or room temperature curing sealants are used.

In recent years, various photocurable sealants have been proposed for the purpose of improving the drawbacks of room temperature curing sealants and thermosetting sealants.

Currently proposed photo-curable sealants include an acrylic photo-radical polymerization type that photo-radically polymerizes acrylic and/or methacrylic yarn threads, and an acrylic photo-radical polymerization type that uses aromatic onium salts as polymerization initiators. It can be broadly classified into photo-cationic polymerization type, which involves cationic polymerization of epoxy resin.

[Problem that the invention seeks to solve]

In the general manufacturing method of liquid crystal cells that uses thermosetting or room temperature curing type sealants, some of the sealants are solvent-based and require preliminary drying before bonding the two substrates together. Moreover, both have the problem of long curing time.

Furthermore, all of the sealants used on the outside of the two-layer structure seal described in the prior art documents essentially do not exhibit liquid crystal resistance.

Therefore, if poor adhesion of the inner sealant occurs due to heat over time, etc., the liquid crystal will come into contact with the cured outer sealant, which may cause alignment defects in the liquid crystal or cause liquid crystal drive. The current value may increase.

In a method for manufacturing a liquid crystal cell using a photoradical polymerizable sealant, internal stress is generated in the cured product due to large volumetric shrinkage accompanying polymerization of acrylic or methacrylic monomers, so adhesive strength of the substrates tends to be insufficient.

In addition, in radical polymerization, the polymerization rate is fast, so the structural regularity of the cured product is low, and as a result, the barrier properties are insufficient, and over a long period of moisture resistance, air bubbles are generated in the liquid crystal cell and the liquid crystal is removed from the cell. Leaks are likely to occur.

In the early stages of development, due to inappropriate amounts and types of photoradical initiators, the photoradical initiator and its decomposition products were eluted into the liquid crystal, resulting in poor alignment of the liquid crystal. However, it was almost improved by optimizing the photoradical initiator.

However, insufficient adhesion and poor barrier properties still remain major drawbacks.

On the other hand, the photo-cationic polymerization type sealant almost eliminates the lack of adhesive strength of the photo-radical polymerization type described above and has sufficient adhesive strength.

In addition, compared to the photo-radical polymerization type, it is easy to bring about a slow polymerization rate and structural regularity, and thanks to the contribution of the raw material epoxy resin, a cured product with high barrier properties can be obtained.

Furthermore, even when in contact with a liquid crystal for a long time, only a small amount of components are eluted into the liquid crystal, so that the increase in the liquid crystal driving current value over time is at a level that does not pose any problem.

Therefore, it is thought that the use of photo-cationic polymerizable sealants will become mainstream in the future for liquid crystal cells for normal character display.

In recent years, active matrix driving, which has been developed for LCD televisions, has a TPT (Th1n Film Transi...
stor) to fix the opening degree of the liquid crystal shutter for 1.6 milliseconds, which is one scan time of the television.

In this method, charge is accumulated in a capacitor whose dielectric is the liquid crystal layer between the upper and lower substrates, and this is used to drive the VJ.
This method is common, but the use of a photo-cationic polymerizable sealant lowers the electrical resistance of the liquid crystal around the cured sealant,
The time constant of a portion of the capacitor becomes small, and an appropriate opening degree of the liquid crystal shutter cannot be maintained during one television scan.

As a result, a phenomenon occurred in which the contrast in this area decreased.

For these reasons, there has been a strong desire to develop a sealing process that does not reduce contrast even when driven by an active matrix, provides high adhesive strength and barrier properties, and can complete sealing in a short time.

The present invention provides a sealing method that can easily and quickly produce high-quality liquid crystal cells with high adhesive strength and barrier properties comparable to photo-cationic polymerization sealants, without reducing contrast even in active matrix drive. Its purpose is to provide.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the present inventors have developed a two-layer structure for sealing, an inner and an outer layer, in the process of sealing the upper and lower substrates to manufacture a liquid crystal cell. An acrylic photoradical polymerization type sealant with good liquid crystal resistance is used as the adhesive, and a photocationic polymerization type sealant with good adhesive and barrier properties is used as the outer sealant. The inventors have discovered that by curing both of the two, even in an active matrix driven liquid crystal cell, a liquid crystal cell with high adhesive strength and barrier properties can be obtained in a short time without deterioration of contrast, and the present invention has been completed. .

In the process of sealing two substrates constituting a liquid crystal cell, the present invention uses an acrylic photoradical polymerization type sealing agent as a sealing agent that forms the inner periphery of the cell that contacts the liquid crystal. This method of manufacturing a liquid crystal cell is characterized in that an epoxy photo-cationically polymerizable sealant is used as a sealant forming the outer periphery of the cell, and both sealants are simultaneously cured by light irradiation.

In the present invention, the acrylic radical photopolymerizable sealant is one whose main component is an acrylic ester and/or a methacrylic ester, and a photoradical initiator and other additives. It can be used without any particular restriction as long as it has a small amount of eluate.

On the other hand, an epoxy photo-cationically polymerizable sealing agent has an epoxy resin as its main component, and contains an aromatic onium salt as a photoinitiator and other additives.

Preferably, these photocurable sealants are solvent-free and do not require precure during curing.

There are no particular restrictions on the method of applying the sealant to the substrate, but screen printing is generally used.

The inner and outer two-layer structure sealing of the present invention involves printing an epoxy photo-cationic polymerization type sealant that forms the outer periphery of the cell on one substrate, and acrylic photo-radical polymerization type sealing that forms the inner periphery of the cell on the other substrate. It is formed by printing a sealing agent, pasting it together so that both adhesives are in contact with each other, and then irradiating it with light.

As a light source for light irradiation, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, etc. are used.

Note that the sealing process of the present invention is not only used for sealing the sides of a liquid crystal cell, but can also be employed as a method for sealing a liquid crystal injection hole of a liquid crystal cell.

[For production]

The present invention is a method for manufacturing a liquid crystal cell that employs two-layer sealing, in which both the inner and outer layers are photocurable sealants, and these sealants are cured by - times of light irradiation. By curing at the same time, the curing time of the sealant can be significantly shortened compared to conventional liquid crystal cell manufacturing methods that employ two-layer sealing using room-temperature curing or thermosetting sealants.

In addition, by using an acrylic photo-radical polymerizable sealant as the sealant on the inner periphery that contacts the liquid crystal, in active matrix drive liquid crystal cells, the epoxy photo-cationically polymerizable sealant is applied to the side that contacts the liquid crystal. Contrast defects that occur in other cases do not occur.

Furthermore, adhesive strength and barrier properties are ensured by employing an epoxy photo-cationic polymerizable sealant as the outer peripheral adhesive.

〔Example〕

The present invention will be specifically explained by giving examples.

However, the scope of the present invention is not limited in any way by the following examples.

In addition, parts expressing quantities in Examples are based on weight.

(1) Preparation of photoradical polymerizable sealant Liquid 1 with a molecular weight of approximately 1500 and having acrylic groups at both ends
．． 2-Polybutadiene (TEA-1000/Nippon Soda 0
Chrysanthemum brand name): 29 parts, epoxy whose main component is diglycidyl ether bisphenol A acrylate <sp
.

1507 (trade name of Showa Kobunshi Zen): 40 parts, trimethylolpropane triacrylate (8-TMPT, Shin-Nakamura Chemical (trade name of barrel)) = 10 parts, photoradical polymerization initiator (Irgacure 65 Tochihakaigi Co., Ltd.) Product name):
1 part, silane coupling agent with acrylic group (KB
M530/Shin-Etsu Silicone-〇Product name): 1
．． After thoroughly mixing 5 parts and 12 parts of amorphous silica Aerosil (i1380/Nippon Aerosil (trade name of Muga)), they were further kneaded with three paint rollers to obtain a photoradical polymerizable sealant [A]. .

(2) Preparation of epoxy photocationic polymerizable sealant Epoxidized 1,2-polybutadiene (13F-100
50 parts, alicyclic epoxy resin (Bakelite ERL-4)
299.:3- (trade name of Nion Carhide Corporation) = 50 parts, photocationic polymerization initiator triphenylsulfonium tetrafluoroborate (50% soluble in propylene carbonate &): 5 parts, silane cup with epoxy group Ring agent (trade name of KBM 403, Shin-Etsu Silicone ■): 1.5 parts and Aerosil #380: 10 parts were mixed well, kneaded with three paint rollers, and epoxy photocationic polymerization sealant C was prepared.
B) was obtained.

(3) Manufacturing sample 1 of liquid crystal cell and liquid crystal display The photoradical polymerizable sealing agent (A ) was applied by screen printing to form the inner periphery of the liquid crystal cell.

On the other glass substrate, the epoxy photocationically polymerizable sealant CB) produced above was applied by screen printing in a manner slightly larger than the applied shape of (A) to form the outer periphery of the liquid crystal cell. .

Then, the CA] coated with two glass substrates becomes the CB.
), and then irradiated with light for 3.5 seconds using a high-pressure mercury lamp (80W/cm) at an irradiation distance of lQcm to harden the sealant and obtain a liquid crystal cell. Ta.

Liquid crystal was injected into the liquid crystal cell by a vacuum method, and the liquid crystal injection hole was sealed with a sealing material to obtain a liquid crystal display. An active matrix liquid crystal display equipped with TPT was produced in a similar manner.

Comparative sample 1 An acrylic photoradical polymerization sealant (A) was applied to one side of the same glass substrate as sample 1 by screen printing to form a liquid crystal cell, one of the substrates was glued together, and a high-pressure mercury lamp was used. (80W/cm) Irradiation distance: 10cm
A liquid crystal cell was obtained by irradiating light for 3.5 seconds, and a liquid crystal display was obtained by filling and sealing the liquid crystal by a vacuum method. An active matrix liquid crystal display was produced in the same manner.

Comparative Sample 2 A liquid crystal display was prepared in the same manner as Comparative Sample 1 except that the epoxy photo-cationic polymerizable sealant CBI was used in place of the acrylic photo-radical polymerizable sealant (A) of Comparative Sample 1. did.

Comparative Sample 3 In place of the acrylic photoradical polymerizable sealant (A) of Comparative Example 1, 50 parts of the above-produced sealant (A) and [13
): 50 parts were mixed well and kneaded with three paint rollers to obtain a liquid crystal display in exactly the same manner as Comparative Sample 1, except that an acrylic photoradical and epoxy photocation mixed type sealant (C) was used. The body was created.

(4) Evaluation of samples For the liquid crystal displays of the samples prepared above and comparative samples, evaluate the initial contrast properties in the active matrix, high temperature and high temperature durability, rate of change in liquid crystal cell drive current value after high and high temperature aging, and cold and heat cycle resistance. did.

The evaluation results are shown in Table 1.

〔Effect of the invention〕

As shown in Table 1, in the method for manufacturing a liquid crystal cell of the present invention, a liquid crystal cell with high quality and high durability can be produced compared to the conventional single-layer structure sealing using only a photocurable sealant. Can be manufactured.

In addition, compared to two-layer sealing using conventional thermosetting sealants, curing is completed in an extremely short time, significantly reducing the time required for the sealant curing process in the liquid crystal cell manufacturing process. As a result, the liquid crystal cell manufacturing process can be streamlined.

The present invention provides a streamlined method for manufacturing a liquid crystal cell that is suitable for manufacturing a liquid crystal cell, particularly a cell for an active matrix drive liquid crystal display, and has extremely great industrial significance.

Patent applicant (430) Nippon Soda Co., Ltd. Epson Corporation

Claims (1)

[Claims] (1) In the process of sealing the two substrates that make up the liquid crystal cell, an acrylic photoradical polymerization type sealant is used as a sealant to form the inner periphery of the cell that comes into contact with the liquid crystal. A method for manufacturing a liquid crystal cell, characterized in that an epoxy photocationically polymerizable sealant is used as a sealant forming the outer periphery, and both sealants are simultaneously cured by light irradiation.