JPH021820A - Composition for sealing liquid crystal display element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, particularly super twisted nematic liquid crystals (
A sealing composition for a liquid crystal display element used for manufacturing a liquid crystal display element in which the space between two electrode plates is filled with STN) or ferroelectric liquid crystal, etc., especially when the gap between the electrode plates is as narrow as several μm.
Moreover, the present invention relates to a composition for sealing a liquid crystal display element, which is used when sealing a liquid crystal display element having uniform intervals.

[Prior art and problems to be solved by the invention] Conventionally, sealing compositions used for liquid crystal display elements are:
It contains a main ingredient, a curing agent, a filler, a spacer material, a curing accelerator, a solvent, a viscosity modifier, etc. Conventionally, silica powder or alumina powder has been used as the filler (for example, Publication No. 295029 of 1983).

However, these fillers sometimes contain conductive impurities, and when used as is as a sealing composition for liquid crystal display elements, the electrical insulation between opposing electrode plates may be impaired. In recent years, super twisted nematic liquid crystals (STN), ferroelectric liquid crystals, etc. have been used as liquid crystals for liquid crystal display elements, and liquid crystal display elements using these ferroelectric liquid crystals have a uniform When manufacturing liquid crystal display elements, it is necessary to uniformly control the gap between opposing electrode plates.
It has become an important issue to

In other words, when using ferroelectric liquid crystals, etc., it is necessary to maintain a constant distance between opposing electrode plates of several μm or less, and in order to maintain this distance, conventional sealants using fillers are used. When manufacturing large liquid crystal display elements, after the liquid crystal display element is assembled and the sealant has hardened, the surrounding area is cut along the pattern of the liquid crystal display element and removed (in the process, the surrounding area is removed). There was a problem in that a large force was applied to the sealing part that sealed the opposite i-electrode plate.

In addition, even when using a super twist nematic liquid crystal or a single conventional twist nematic liquid, it has excellent screen printability and strong strength (and the spacing between opposing transparent electrode plates can be formed with high precision). There has been a need for a sealing composition for liquid crystal display elements that can ensure more stable electrical insulation.

Therefore, it is an object of the present invention to bond opposing electrodes of a liquid crystal display element with high strength, to have excellent thixotropy, screen printability, and adhesive retention, and to achieve accurate spacing between transparent electrode plates. An object of the present invention is to provide a composition for sealing a liquid crystal display element, which can be easily formed.

[Means to solve the problem]

As a result of various studies regarding fillers, the present inventors have found that the above object can be achieved by incorporating hexagonal boron nitride as a filler in a sealing composition for a liquid crystal display element.

The present invention has been made based on the above findings, and provides a sealing composition for a liquid crystal display element, which seals around the liquid crystal filled between two transparent electrode plates arranged opposite to each other.
The present invention provides a composition for sealing a liquid crystal display element, which is characterized in that it contains an epoxy resin as a main ingredient, a latent curing agent as a curing agent, and hexagonal boron nitride as a filler.

Further, the composition for sealing a liquid crystal display element as described above, characterized in that the average particle size of hexagonal boron nitride is 3.0 μm or less and the maximum particle size is 5.0 μm or less, and the average particle size of hexagonal boron nitride. The present invention also provides a composition for sealing a liquid crystal display element as described above, which has a diameter of 3.0 μm or less, a maximum particle size of 5.0 μm or less, and a particle diameter of 1.0 μm or less. .

The present invention will be explained in detail below.

The epoxy resin used as the main ingredient in the composition for sealing liquid crystal display elements of the present invention is preferably an epoxy resin having two or more epoxy groups in one molecule, and examples of the epoxy resin include bisphenol A type epoxy Resin, bisphenol F type epoxy resin, dimer acid glycidyl ester type epoxy resin, polyethylene glycol type epoxy resin, polyglycidyl ether of novolac type phenol resin, polyglycidyl polyfunctional phenol type epoxy resin, polyglycidylamine type epoxy resin, chelate structure Examples include epoxy resins having the following. When using the epoxy resin, it is preferable to use the epoxy resin alone or in combination of two or more types, and also include a halide of the epoxy resin, a cycloaliphatic epoxy resin, a polyglycidyl ester type epoxy resin of isocyanuric acid, diglycidyl ether of resorcinol,
Hydantoin type epoxy resins can be used alone or one or more of them can be used in combination with the epoxy resin.

Further, a resin having two or more glycidyl groups, which is a reaction product of the epoxy resin and an oligomer having a functional method, can also be used, and in that case, it can be used by mixing with the various epoxy resins. Examples of the oligomer include liquid rubbers having carboxyl groups as terminal groups, liquid rubbers having amine groups as terminal groups, and the like.

The latent curing agent used as a curing agent in the sealing composition for a liquid crystal display element of the present invention is a curing agent that can be stored stably at room temperature for a certain period of time and rapidly hardens when exposed to heat, light, pressure, etc. Examples of the latent curing agent include a one-component composition mixed with an epoxy resin.

In addition, known curing agents include, for example, guanidine compounds such as dicyandiamide, phenol resins such as phenol novolak resin, bisphenol resins, phenol compounds, imidazoles, triazine m1), 4.4-
Diaminodiphenylsulfone, acid hydrazide compound,
Examples include N,N-dialkyl urea derivatives and boron trifluoride complexes, and these curing agents can be used alone or in a mixture of 2fif or more.

Among the above curing agents, phenol resin-based curing agents, guanamine compounds, and curing agents that are reaction products of bisphenol A type epoxy resin and bisphenol A and have hydroxyl groups at both end groups have excellent storage stability at room temperature and adhesive properties. High strength,
It can be preferably used as a curing agent in the composition for sealing a liquid crystal display element of the present invention.

In addition, there are other photocurable curing agents that cure with visible light and ultraviolet light. Examples of photocurable curing agents include Lewis acid salts of aromatic diazonium, Lewis acid salts of diallyliodonium, and triallylsulfonium. Examples include Lewis acid salts.

Furthermore, examples of the curing accelerator to be added to the curing agent include tertiary amines, imidazoles, and aromatic amines.

The hexagonal boron nitride blended as a filler in the sealing composition for a liquid crystal display element of the present invention preferably maintains insulation properties, and the hexagonal boron nitride includes:
It is preferable that the powder be a high-purity fine powder containing almost no impurities exhibiting hygroscopicity or hydration reactivity, as well as conductive impurities.

The hexagonal boron nitride can impart thixotropy to the composition for sealing a liquid crystal display element, thereby improving screen printability. No matter what form of hexagonal boron nitride is added to the sealing composition for the liquid crystal display element, it is possible to impart thixotropy to the sealing composition for the liquid crystal display element.

The hexagonal boron nitride compounded in the main ingredient and curing agent of the sealing composition for a liquid crystal display element of the present invention preferably has an average particle size of less than 10.0 μm; When it is less than 1, it is easy to form a structure that imparts thixotropy, and the screen printability is excellent, and the fluidity during curing of the composition for sealing a liquid crystal display element can be reduced.

Furthermore, when the above-mentioned boron nitride is added as a filler to a sealing composition for a liquid crystal display element, the strength of the sealing composition for a liquid crystal display element can be improved. Therefore, even when it is necessary to uniformly adjust the gap between two transparent electrode plates in an extremely narrow dimension of 1 to 3 μm, such as in a liquid crystal display element using ferroelectric liquid crystal,
By using the hexagonal boron nitride, the strength of the sealing composition for a liquid crystal display element can be improved, and there is no possibility that the transparent electrode plates will peel off from each other even in the process of cutting the liquid crystal display element into a predetermined pattern. There is no such thing.

Furthermore, when manufacturing a liquid crystal display element using ferroelectric liquid crystal as the liquid crystal, the average particle diameter of hexagonal boron nitride is 3.
．． It is preferable that the particle size is 0 μm or less and the maximum particle size is 5.0 μm or less, and more preferably that the primary particle size is 1.0 μm or less. For example, super twisted nematic liquid crystal (STN) or other liquid crystals When filling the space between the transparent electrode plates of a display element, it is sufficient that the average particle diameter is adjusted to a size smaller than the gap formed between the two transparent electrode plates.

The amount of hexagonal boron nitride added to the sealing composition for liquid crystal display elements is not particularly limited, but in order to improve the fluidity of the sealing composition for liquid crystal display elements, it is necessary to The amount is preferably 10ffl1% or less of the total weight of the resin, including the weight of the resin, its curing agent, and curing accelerator.

The composition for sealing a liquid crystal display element of the present invention may contain additives other than those mentioned above that are used in ordinary epoxy resins, such as thickeners, reinforcing agents, dyes, pigments, organic solvents, extenders, and coupling agents. etc. can be added within a range that does not impede the effects of the present invention.

Further, the material between the transparent electrode plates forming the transparent electrode plates of the liquid crystal display element to which the sealing composition for a liquid crystal display element of the present invention is applied is not particularly limited, but such materials include: For example, in addition to glass, polyethylene terephthalate (PET), polyether sulfone (PE5)
, a transparent plastic film such as polymethyl meccrylate (PMMA).

The above-mentioned transparent electrode plate can be obtained by forming a transparent electrode film made of indium tin oxide (ITO), tin oxide (SnO□), etc. between the transparent electrode plates by a known method such as metal vapor deposition, sputtering, or screen printing. can.

〔Example〕

Hereinafter, the present invention will be explained based on the following examples.

In the following examples, "parts" and "%" respectively represent "parts by weight" and "% by weight" unless otherwise specified.

[! ] tA of the composition for sealing liquid crystal display elements! ! Examples 1 to 6 are compositions for sealing liquid crystal display elements containing the filler used in the present invention, and Comparative Examples 1 to 2 are compositions for sealing liquid crystal display elements containing conventional fillers.
Examples 1 to 3 shown in Table 1 as shown in Table 1 and Table 2
The compositions for sealing liquid crystal display elements of Comparative Examples 1 and 2 were prepared as follows.

Epicoat 1001 (
60 parts of Bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy), 40 parts of Adeka Resin EP-4000 (propylene oxide-adducted core diol epoxy resin, manufactured by Jishuka), and light phase phenol novolak H- as a curing agent.
13 (Meisho Kasei, phenol novolac resin) 28 parts,
As curing accelerators, 1 part of CUREZOL 2B-4MZ (manufactured by Shikoku Kasei, imidazole compound), 2 parts of KBM-403 (manufactured by Shin-Etsu Chemical, silane coupling agent), and the filler and methylcarpitol (solvent) shown in Table 1 were used, respectively. After adding a predetermined amount, the mixture was kneaded using three rolls to prepare an epoxy resin composition.

Next, epoxy resin compositions (Examples 4 to 5) having compositions different from the above-mentioned epoxy resin compositions were prepared. First, 70 parts of Epicoat 828 as the main epoxy resin,
Epicor) 871 (manufactured by Yuka Shell Epoxy, polymerized fatty acid polyglycidyl ester) 30 parts, DI as a hardening agent
CY-7 (manufactured by Yuka Shell Epoxy, dicyandiamide)
5 parts, 2 parts of Curesol lB2MZ (manufactured by Shikoku Kasei Co., Ltd., imidazole compound) as a curing accelerator, and predetermined amounts of fillers shown in Table 2 were added, and further KBM-403 (
After adding 2 parts of silane coupling agent (manufactured by Shin-Etsu Chemical) and 20 parts of methylcarpitol as a solvent, the mixture was kneaded with three rolls to prepare an epoxy resin composition.

Next, 0.1% of each epoxy resin composition is added to each of the above epoxy resin compositions with an alumina spacer adjusted to a predetermined particle size so as to ensure a predetermined thickness between the transparent electrode plates. &+1 compositions (Examples 1 to 6 and Comparative Examples 1 to 2) for sealing liquid crystal display elements were prepared.

In addition, an alignment film made of a polyimide film of glass on which ITO was vapor-deposited was formed as a transparent electrode plate, and the composition for sealing the liquid crystal display element shown in Table 1 was screen-printed around the surface of the film, and the sealing composition for the liquid crystal display element shown in Table 1 was screen printed on the periphery of the surface of the glass film on which ITO was vapor-deposited. After screen printing, the sealing composition was pre-cured at 90°C for 30 minutes, and the other transparent electrode plate was placed on top of this, and pressure was applied at 180°C.
'C for 120 minutes to form a seal portion for each liquid crystal display element. Liquid crystal (for example, E-44 (manufactured by BDH), ZLI-4003 (manufactured by Merck & Co., Ltd.)) is injected between the two opposing transparent electrode plates obtained in this manner and sealed, thereby creating a liquid crystal display. I got the element.

(■) Performance test of sealing composition for liquid crystal display elements The following gap formation test was performed on each of the above liquid crystal display elements.
A seal portion strength test and a print pattern retention test were conducted, and the test results are shown in Table 3.

<Gap formation test> Measure the thickness at five arbitrary points on the liquid crystal display element, and
If both points formed a predetermined thickness, 0.4 points formed a predetermined thickness, it was evaluated as Δ, and if two or more points did not form a predetermined thickness, it was evaluated as ×.

<Seal strength test>f&, 1, in which the liquid crystal display element was cut into a predetermined pattern.
Pressure test was carried out at 20±2° C. for 8 hours. As a result, the strength of each seal portion was evaluated as ◯ if there was no peeling on the opposing transparent electrode, Δ if there was peeling in a part, and × if the whole was peeled off.

Pattern retention test> Compare the applied width of the sealing composition for liquid crystal display elements by printing before heat curing and the applied width after heat curing, and check whether there is no sagging and no change in the applied width. The pattern retainability of each pattern was evaluated as ○ for the state, Δ for the state where there was some flow and bleeding, and × for the state where the entire coat ran and the shape of the coating width was not maintained.

(III) Results From the results of the gap formation, seal strength, and pattern retention tests shown in Table 3, the following was found.

■The sealing compositions for liquid crystal display elements used in Examples 1 to 6 above had a gap of 2 μm between each transparent electrode plate, and
Regardless of the thickness of 5 μm, the gap is uniformly formed, each gap shape is good, and the adhesive strength of the sealing part is high so that the transparent electrodes cannot be separated from each other, and it is also suitable for sealing liquid crystal display elements. The pattern retention of the composition is also good.

On the other hand, Comparative Example 1.2 is inferior in the above-mentioned gap forming ability, and furthermore, peeling occurs between the transparent electrode plates, and pattern retention is also poor.

(2) Among the above Examples 1 to 6, the composition for sealing a liquid crystal display element used in Example 3 had a maximum particle size of hexagonal boron nitride as a filler of 9.0 μm and an average particle size of 5.0 μm.
0 μm primary particle size is 3.0 p m, which is larger than the 2 μm gap between one transparent electrode plate, so the gap forming ability and the 2 μm gap between the transparent 7it electrode plates are Although the strength of the seal portion is slightly inferior, the above-mentioned performances are still excellent overall when compared with Comparative Example 1.2.

■Furthermore, the composition for sealing a liquid crystal display element used in Example 5 among Examples 1 to 6 above has a maximum particle size of 20 μm of hexagonal boron nitride as a filler, which is significantly higher than in other Examples. The gap between the transparent electrode plates is 2μ.
Although the gap forming ability, sealing strength, and pattern characteristics of the liquid crystal display element of M are slightly inferior to those of other examples, the average particle diameter and the -order particle diameter are both small (because they were prepared, Comparative Example 1.2 All of the above performances are excellent overall.

[Effects of the Invention] The sealing composition of the liquid crystal display element of the present invention can bond the opposing electrodes of the liquid crystal display element with high strength, has excellent thixotropy, and has excellent screen printability and pattern retention. Therefore, the interval between the transparent electrode plates can be formed with high precision.

Patent applicant: Ube Industries Co., Ltd. Ube Chemical Industry Co., Ltd.

Claims (3)

[Claims] (1) A sealing composition for a liquid crystal display element that seals around the liquid crystal filled between two transparent electrode plates arranged opposite to each other, which includes an epoxy resin as a main ingredient and a latent curing agent as a curing agent. and hexagonal boron nitride as a filler. (2) The average particle diameter of the hexagonal boron nitride is 3.0 μm
The composition for sealing a liquid crystal display element according to claim 1, wherein the composition has a maximum particle diameter of 5.0 μm or less. (3) The primary particle diameter of the hexagonal boron nitride is 1.0 μm
The composition for sealing a liquid crystal display element according to claim 2, which is as follows.