JPS6283720A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve the adhesion by injecting a liq. sealant consisting of polymerizable acrylic sirup having hydroxyl groups, a multifunctional oligoester compound, a photopolymn. initiator, a photosensitizer and other additives into the gap between substrates and by irradiating active energy beams to cure the sealant and to seal the substrates. CONSTITUTION:The liq. sealant consisting of polymerizable acrylic sirup prepd. from an alkyl (meth)acrylate and a polymerizable unsatd. compound having a hydroxyl group and of a multifunctional oligoester compound having three or more (meth)acryloyloxy groups per one molecule or hurther contg. the photopolymn. initiator, the photosensitizer and other additives is injected into the gap between substrates, and active energy beams are irradiated to cure the sealant and to seal the substrates. Thus, the liq. crystal or a liq. crystal mixture is protected from the external environment contg. moisture, the internal structure is kept airtight, and even when transparent plastic films are used as the substrates, effective sealing can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a liquid crystal display element mounted using an active energy ray-curable encapsulant.

"Prior Art and its Problems" In general, nematic liquid crystals, cholesteric liquid crystals, smectic liquid crystals, electromic materials, and the like are known as liquid crystals that are often used in liquid crystal display devices. In particular, it is known that nematic liquid crystal has a property in which its molecular axes are aligned in the same direction, and that the alignment state of liquid crystal molecules can be changed by changing the intensity of an external electric field, magnetic field, heat, etc. . Usually, a liquid crystal display element has approximately 50
A nematic liquid crystal is sandwiched between two electrode plates, at least one of which is transparent, which are opposed to each other with an interval of .mu.m or less.

Nematic liquid crystals are broadly classified into those having homogeneous alignment, which is aligned parallel to the substrate surface, and homeotropic alignment, which is aligned perpendicular to the substrate surface. In general, in homogeneous alignment, the electrode plate or the insulating film provided on the electrode plate is rubbed in one direction with paper or cloth, and the rubbing directions applied to the two electrode plates cross each other, - generally, they intersect at 906. This is done by stacking the liquid crystals in such a manner as to inject homogeneously aligned nematic liquid crystal into the gap.

In such liquid crystal display elements, glass substrates are generally used as electrode substrates, but recently there has been a movement to use plastic films.

Further, although epoxy sealants are generally used for sealing around the substrate, their use has the following problems.

■ The workable time (pot life) after mixing the hardening agent with the resin is short. However, it takes a long time to reach final hardening after encapsulation, and therefore workability and productivity are poor.

■ Due to lack of flexibility, it is susceptible to soldering heat resistance, thermal shock, and stagnation impact, and has poor airtight reliability.

■ Epoxy encapsulant requires high temperature to cure, so it is difficult to obtain a sufficient rubbing effect (liquid crystal orientation) when sealing around the substrate. In the case of Delastisoku film base meal,
Heat can cause film deformation, discoloration, and deterioration.

In addition, sealants for liquid crystal display elements are required to have excellent long-term moisture resistance and heat resistance to maintain high reliability, and to contain less impurity ions such as Na+ and CL- that degrade circuit function.

On the other hand, the use of active energy ray curing systems that do not require heating during curing has the characteristic that the curing does not occur as long as the active energy rays are applied, and once the active energy rays are irradiated, the curing occurs immediately. ,Productivity,
It is attractive in terms of workability. However, the adhesion is poor,
However, there are drawbacks such as large main shrinkage and poor sealing performance reliability, which has prevented its practical use.

"Means for Solving the Problems" Based on these backgrounds, the present inventors have developed an active energy product that has good adhesion to various substrates and has low shrinkage in order to solve the problems of the above-mentioned epoxy sealants. The present invention was completed by intensively developing a line curing sealant.

"Means for Solving the Problems" That is, the present invention comprises: [A] a hydroxyl group-containing polymerizable acrylic syrup obtained from a (meth)acrylic acid alkyl ester and a hydroxyl group-containing polymerizable unsaturated compound, and [B] A polyfunctional oligoester compound having three or more (meth)acryloyloxy groups per molecule; and, if necessary, a [C] photopolymerization initiator, [D] a photosensitizer, and [E] This book provides a liquid crystal display element characterized in that a liquid sealant consisting of other additives is sealed in a gap between substrates, and then cured and sealed by irradiation with active energy rays.

The hydroxyl group-containing polymerizable acrylic syrup (hereinafter abbreviated as acrylic syrup) [A] obtained from the (meth)acrylic acid alkyl ester and the hydroxyl group-containing polymerizable unsaturated compound used in the present invention is the (meth)acrylic acid alkyl ester. and a polymerizable unsaturated compound containing a hydroxyl group, usually in a ratio of 99:1 to 70:30, preferably 97:3 to 85:1.
It can be easily obtained by partially polymerizing in bulk at a weight ratio of 5 to 5 to form a slag. Alternatively, it is also possible to sufficiently polymerize these by solution polymerization, suspension polymerization, emulsion polymerization, etc., and then dilute and dissolve in a polymerizable vinyl monomer such as (meth)acrylic acid acrylic ester to obtain acrylic syrup. be.

The (meth)acrylic acid alkyl ester used here is a (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 8 carbon atoms, such as ethyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylate, Examples include propyl acrylate, each of which may be used alone or in combination of two or more types of Fi, among which methyl methacrylate is particularly preferably used.

Examples of polymerizable unsaturated compounds containing hydroxyl groups include β-hydroxyethyl (meth)acrylate and β-hydroxypropyl (meth)acrylate, which are obtained by partial esterification of polyhydric alcohols and (meth)acrylic acid. 1,6-hexanediol mono(meth)acrylate, neointylglycol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, trimethylolzolo-9(meth)acrylate and K d metaerythritol ( There are also meth)acrylates and the like obtained from the addition reaction of butylglycidyl ether, persatic acid glycidyl ester or phenylglycidyl ether with (meth)acrylic acid.

Here, a polyfunctional oligoester compound having three or more (meth)acryloyloxy groups per molecule [
Typical examples of polyfunctional oligoester [B] (hereinafter abbreviated as polyfunctional oligoester [B]) include trimethylo-/I/7'rono-en tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. ) acrylate, dipentaerythritol tri(meth)
Acrylate, metaerythritol tetra (meth)
Acrylate, dipentaerythritol penta(meth)
There are acrylates, dipentaerythritol trisa(meth)acrylates, etc., all of which are preferred in carrying out the present invention, and mixed compositions (hereinafter abbreviated as mixed compositions) containing one type or a combination of esters [B]. )teeth,
It is possible to obtain sealing properties with excellent adhesion to the substrate, flexibility, moisture resistance, curability, workability, etc., and the mixing ratio is usually [A:l:CB]=zo: so~
The range is 70:30, especially [A]: [B]
The range of =25 near 5 to 55:45 is particularly good for adhesion, hardness,
It is preferable because it has excellent moisture resistance.

The above-described mixed composition can provide sealing properties with excellent adhesion to the substrate, flexibility, moisture resistance, curability, and workability. This mixed composition may be used as it is as a liquid sealant, but if necessary, a photopolymerization initiator [C]
, a photosensitizer [D], and other additives [E) may be added thereto for use as a sealant. Further, it is also possible to use an organic solvent to adjust the viscosity to be suitable for the injection/coating method of the sealant.

Examples of the photopolymerization initiator [C] used here include hahensoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzophenone, anthraquinone, benzyl methyl ketal, hydroxycyclohexyl phenyl ketone, azobis-2,4
-dimethylvaleronitrile, etc., and the above mixed composition 1
It is usually used in an amount of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight. Further, a photosensitizer CDI having a polymerizable unsaturated bond such as dimethylamine ethyl (meth)acrylate or diethylaminoethyl (meth)acrylate can be used in combination. The amount of the photosensitizer ("D) used is as follows.
The amount is usually 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, based on 00M parts.

Furthermore, other additives [E) include silicone-based, fluorine-based, high-boiling aromatic hydrocarbon-based, and polycarbonate-based to further improve antifoaming properties and stability. known leveling agents and antifoaming agents such as amine salts of phosphoric acid or polyphosphoric acid; polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether or phenothiazine; and quaternary ammonium chlorides such as pendyltrimethylammonyl chloride. , diethylhydroxyamine, nitrile compound, benzothiazole, 4-amino-2,2,6,6-titramethylpiveridine, bis-
Storage stabilizers such as (1,2,2,6,6-bentamethyl-4-piperidinyl)ce,-N-cate and organic acids such as lactic acid, citric acid, citric acid, tartaric acid, benzoic acid, etc. , the amount of such additives used is usually in the mixed composition 1
The amount is within the range of 2 parts by weight or less per 00 ift parts.

It goes without saying that two or more of these photopolymerization initiator [C], photosensitizer [D], and other additives CEI may be used in combination.

As described above, the curing of the liquid sealant obtained by further adding [C], [D], and [:E:] to the mixed composition consisting of [A] and CB'll is performed using active energy. This is done by irradiation with radiation, such as ultraviolet rays, gamma rays, electron beams, etc. Among these, in the case of ultraviolet curing, for example, xenon lamps, low-pressure, medium-pressure and high-pressure water lamps, IST lamps, Metal 7 to Ridelande, etc. can be used as light sources, and in particular ultraviolet rays with a wavelength of 200 to 400 nm can be used. It is preferable to use as a king.

Sealing with such a liquid sealant is performed by applying the liquid sealant along the edge of at least one of the substrates by screen printing or the like.
It can be formed by stacking two substrates and then curing the sealant by irradiation with active energy rays. In addition, a suitable sweeper material such as lath fibers, glass beads, plastic beads, etc. may be dispersed in the sealant, and these sweeper materials may be disposed within the liquid crystal layer. You can also leave it there.

Although irradiation with active energy rays can be carried out in the atmosphere, curability can be further improved and preferable results can be obtained when irradiation is carried out in a stream of an inert gas, such as nitrogen or argon.

Substrates for the liquid crystal display element used in the present invention include powder glass, quartz glass, soda glass with 5102 coating, transparent plastic films such as polyethylene terephthalate (RET) film, polypropylene film,
Polycarbonate film, 41J vinyl chloride film, etc. are subject to strict regulations. Particularly in the electronics industry, which places emphasis on mass production, using a transparent plastic film as a substrate and shortening the sealing curing time is a major advantage, leading to immediate line automation. It is effective to use this sealant.

The liquid crystal used in the present invention is not particularly limited, and includes, for example, nematic liquid crystal such as azoxy liquid crystal, thick basic liquid crystal, azo liquid crystal, biphenyl liquid crystal, taphenyl liquid crystal, phenylcyclohexane liquid crystal, ester liquid crystal, etc. There are type liquid crystals and mixtures thereof.

"Effects of the Invention" The liquid encapsulant used in the present invention is colorless and transparent, has a low curing temperature, protects liquid crystals and liquid crystal mixtures from the external environment such as moisture, and maintains the airtightness of the internal structure. A liquid crystal display element having effective sealing properties can also be provided when a film is used as a substrate.

The liquid crystal display element of the present invention can be used in display elements of various devices by combining polarizers such as circular or linear polarizing plates, or reflective plates.

Examples include display elements such as liquid crystal televisions, electronic computers, wristwatches, thin plastic liquid crystal televisions, thin plastic electronic computers, thin plastic watches, and thin plastic displays.

"Examples" The present invention will be described below with reference to Examples and Comparative Examples, but the invention is not limited to these Examples in view of the gist of the invention. Note that all parts and parts in the examples are based on weight.

Example 1 95 parts of methyl methacrylate, 5 parts of β-hydroxyethyl methacrylate, and 0.6 parts of n-dodecyl mercaptan were placed in a four-bottle flask equipped with a condenser and a stirrer, and a reaction was carried out at 95°C under a nitrogen stream for 8 hours. When the viscosity reached 8 poise, 50 ppm of hydroquinone was added as a polymerization inhibitor and the mixture was cooled to obtain acrylic syrup [A-11].

Next, to 95 parts of this acrylic syrup [''A-1], 5 parts of trimethylol derono I trimethacrylate,
Add 95 parts of hexaacrylate to cyintererythritol, and further add 10 parts of Ilga Cure Hiro 184 (photopolymerization initiator manufactured by Iggy Co., Ltd.) and Toshi Silicone 5H5.
After adding 0.003 part of 500C antifoaming agent manufactured by Toshi Silicon Co., Ltd., it was diluted with methyl isobutyl ketone until the polymerization component content became 90% to obtain a liquid sealant (1).

As shown in Figure-1, the substrate 1.1 is colorless transparent PET.
Using a film, tin oxide is selectively vacuum-deposited on the inside as a transparent electrode 2.2, and then ladder-type siloxane having phenyl groups and MaS (
An alignment film 3.3 is prepared by forming a film having a 1:1 composition of OEt) 3 hydrolyzate and subjecting the film to a rubbing treatment. Then, apply liquid sealant (1) to the peripheral area of the substrate with the alignment film side of
), and then irradiated with ultraviolet rays for 10 seconds using a high-pressure mercury lamp manufactured by Toshiba Corporation with an output of 2 kW to form a sealing layer 5, and then injecting Schiff liquid crystal mixture 4 to finally seal the injection port. do. Furthermore, substrate 1. A liquid crystal display element was obtained by attaching a Hυ polarizing plate 6.6 to the outside of 1-, , so that the polarization axes differed by 90 degrees.

The liquid crystal display element thus created was heated to 80°C and the relative temperature was 90°C.
% for 500 hours, and the presence or absence of whitening or clouding was visually observed to evaluate the moisture resistance of the device. The results are shown in Table-1.

In addition, liquid sealant (1) was used in the same P as that used above.
It was coated on the ET film so that the thickness after curing was 50 μm, and then it was similarly irradiated with ultraviolet rays and cured, and then JI
An adhesion test was conducted according to SK-5400. The results are shown in Table-1.

Example 2 90 parts of methyl methacrylate, 10 parts of propyl acrylate, n
- 0.6 m of dodecyl mercaptan was charged, the reaction was carried out at 95°C under a nitrogen stream, the reaction was continued for 8 hours, and the viscosity was 8.
Hydroquinone 50 as a polymerization inhibitor at the time of poise
Acrylic syrup after cooling with addition of ppm [A-2]
I got it.

In the next step, add 3 parts of trimethylol derono I to 3 parts of this acrylic syrup CA-2135, di(
After adding 62 parts of phtaerythritol trimethacrylate and further adding 5 parts of benzoin methyl ether as a photopolymerization initiator, the mixture was diluted with methyl isobutyl ketone until the polymerization component content was 88%, and liquid sealant Ql)
I got it. A liquid crystal display element was obtained in exactly the same manner as in Example 1 except for using this sealant. was tested. The results are shown in Table IK.

Examples 3 to 6 Acrylic board (Example 3) in place of the PET film
Four types of liquid crystals were prepared in exactly the same manner as in Example 1, except that a polyethylene plate (Example 4), a polyvinyl chloride plate (Example 5), and a polyderopylene cargenate plate (Example 6) were used. A display element was created. Moisture resistance and adhesion were then tested in the same manner. The results are shown in Table-1.

Comparative Example 1 Epiclon 860 [Dainippon Ink & Chemicals Co., Ltd. J!] was used instead of the liquid sealant (1). J epoxy resin] and Epiclon B-655 (the company's epoxy resin curing agent) at 1:1.
A liquid crystal display element was prepared in the same manner as in Example 1, except that an acid anhydride-curing type epoxy sealant mixed at a weight ratio of 1 was used, and the mixture was heated and cured at 200° C. for 1 hour. Moisture resistance and adhesion were then tested in the same manner. Display the results -
Shown in 1.

Comparative Example 2 In place of the liquid sealant (1), 1 portion of Epiclon 860 and Epiclon B-015 (an epoxy resin curing agent made by the same company) was used.
A liquid crystal display element was prepared in the same manner as in Example 1, except that an amine-curing type epoxy sealant mixed at an IT ratio of :l was used and cured at room temperature for 24 hours. Moisture resistance and adhesion were then tested in the same manner. The results are shown in Table-1.

Comparative Example 3 A liquid sealant was obtained in the same manner as in Example 1 except that 100 parts of methyl methacrylate was used instead of 95 parts of methyl methacrylate and 5 parts of β-hydroxyethyl methacrylate.
Next, a liquid crystal display element was produced in the same manner except that the ultraviolet irradiation time was changed to 30 seconds. Moisture resistance and adhesion were then tested in the same manner. The results are shown in Table-1.

Comparative Example 4 Acrylic syrup [A-1: 195 parts of acrylic syrup (A-1) alone instead of 95 parts of trimethylol, 5 parts of 4-trimethacrylate, and 95 parts of dipentaerythritol hexaacrylate A liquid crystal display element was obtained in the same manner as in Example 1, except that the UV irradiation time was 30 seconds.Then, moisture resistance and adhesion were tested in the same manner.The results are shown in Table 1.

Table-1 *1) Curing conditions: All except Comparative Examples 1 and 2 were UV cured.

*2) Moisture resistance ◎: No change ○: Slightly cloudy Δ
: Cloudy X: Whitening Qin 3) Adhesion ◎: 100/100 0: 99/1
00~90/100Δ: 89A00~50,40
0 X: 49/100 or less.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display element. 1.1 ... Substrate, 2.2 ... Transparent electrode, -(1
) -jin) -(1)
-(2)3.3...Alignment film, 4...Liquid crystal, 5...
・Seal layer, 6.6...Polarizing plate. -Q) -(2)

Claims (1)

[Scope of Claims] [A] A polymerizable acrylic syrup containing a hydroxyl group obtained from a (meth)acrylic acid alkyl ester and a polymerizable unsaturated compound containing a hydroxyl group, and [B] 3 or more (meth)acrylic syrups per molecule. A liquid seal consisting of a polyfunctional oligoester compound having an acryloyloxy group, and further, if necessary, [C] a photopolymerization initiator, [D] a photosensitizer, and [E] other additives. 1. A liquid crystal display element, characterized in that the agent is sealed in a gap between substrates, and then cured and sealed by irradiation with active energy rays.