JPH0726236A - Adhesive for sealing liquid crystal display cell and production of cell - Google Patents

Abstract

PURPOSE:To obtain the subject adhesive which can improve electrical reliability, durability, etc., by compounding an epoxy resin with a specific triazine-based curative, an inorg. filler, and a silane coupling agent. CONSTITUTION:This adhesive is prepd. by compounding an epoxy resin (e.g. a liq. epoxy resin of an epihalohydrin-bisphenol type) with an isocyanuric acid adduct to a 2,4-diamino-6[2'-alkylimidazolyl (1)']ethyl-s-triazine as the curative, an inorg. filler, and a silane coupling agent. A flaky and relatively soft inorg. filler having a large aspect ratio (e.g. mica) is suitable. A liq. crystal display cell with a liq. crystal hardly stained is produced by applying the adhesive to a liq. crystal display cell substrate, sticking another liq. crystal display cell substrate to the adhesive-coated surface of the former substrate at a certain distance, and thermally curing the adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a pair of glass base materials having transparent electrode films arranged opposite to each other, and a peripheral portion is sealed so that the space between the glass base materials can be kept constant, and a liquid crystal is placed in the space. The present invention relates to a solvent-free adhesive for a liquid crystal display cell seal which is used in a liquid crystal display cell filled with and a method for producing a liquid crystal display cell using this adhesive.

[0002]

2. Description of the Related Art Adhesives for seals which have been used for liquid crystal display cells are conventionally inorganic or organic adhesives made of low-melting glass frit, especially epoxy resin adhesives having excellent adhesive strength. An adhesive, and more recently, an ultraviolet curable adhesive or an adhesive that combines ultraviolet curing and heat curing to form a sealant layer has been proposed.

However, in order to obtain the function as a sealant, the inorganic adhesive needs to be treated at a high temperature of about 200 ° C. or higher, and problems such as generation of microcracks are likely to occur, resulting in poor production yield. It was a thing.
On the other hand, among organic adhesives, recently, for the purpose of improving productivity, an adhesive that forms a sealant layer by ultraviolet curing or a combination of ultraviolet curing and heat curing has been proposed. Is not satisfactory in terms of reliability or adhesion to cell substrates.

Therefore, at present, epoxy resin adhesives having a relatively good balance of adhesive strength and the like are widely used,
The formation of a sealant layer using this adhesive is almost entirely screenable.
The printing method is used. Of the epoxy resin adhesives, the two-pack type epoxy resin adhesives require the main component and the curing agent to be weighed and mixed, and the pot life after mixing is about several hours. On the other hand, the one-pack type epoxy resin adhesive requires several hours for curing, and is not suitable for mass production.

In order to eliminate the trouble of the pair of bonded cell base materials being moved and displaced during the bonding of the pair of cell base materials or after the bonding and before the heat curing.
A method is used in which an organic solvent is contained in a sealant, and the organic solvent is removed from the applied adhesive by preliminary drying to increase the apparent viscosity of the adhesive and temporarily fix the pair of glass substrates. ing. Further, for the purpose of preventing the constituent components from seeping out from the adhesive applied on the cell substrate, an organic solvent containing a solid high molecular weight epoxy resin dissolved in an organic solvent at room temperature was contained. Epoxy resin adhesive type is used. However, when an adhesive containing such an organic solvent is used, there are problems such as an adverse effect of the organic solvent remaining in the adhesive on the liquid crystal and instability of printing performance due to evaporation of the organic solvent during printing.

Japanese Patent Publication No. 58-22060 discloses a solventless one-component epoxy resin adhesive.
By selecting a curing agent, both the one-liquid property and the rapid curing property are improved to improve the productivity, and the contamination of the liquid crystal is also prevented, but since it imparts toughness to the adhesive itself, it is also an inorganic glass group. Since liquid butadiene-acrylic copolymer, polyester ether elastomer, or the like is used in order to improve the adhesive strength of the material to the display cell, the conditions of heat resistance and humidity resistance are not sufficiently satisfied.

[0007]

The adhesive for liquid crystal display cell seals is used for the orientation and electrical reliability of the liquid crystal filled in the display cell, the mechanical durability of the display cell, the printing performance, and further. It is very important in terms of productivity. The object of the present invention is a solvent-free type which is excellent in heat resistance, moisture resistance, adhesiveness, and other strict characteristics accompanying the expansion of application fields of liquid crystal display elements, and is excellent in productivity improvement against rapid market expansion of liquid crystal display elements. A liquid crystal display cell manufacturing method by a screen printing method, which provides a one-component quick-curing adhesive, and which does not require preliminary drying for evaporating an organic solvent by using the liquid crystal display cell seal adhesive. It is provided.

[0008]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in view of such a situation, they have been identified as a curing agent.
2,4-diamino-6 [2'-alkylimidazolyl (1) '] ethyl-s-triazine / isocyanuric acid adduct represented by the general formula of ## STR3 ## By using epoxysilane or aminosilane as a coupling agent, it has been found that the intended purpose can be achieved, and the present invention has been completed.

[0009]

[Chemical 2] (However, R represents an alkyl group.)

Typical epoxy resins used in the adhesive for liquid crystal display cell seals of the present invention are bisphenol A type diglycidyl ether and phenol novolac type epoxy resin which are liquid at room temperature.

A typical curing agent used in the adhesive for liquid crystal display cell seals of the present invention is 2,4-diamino-
6 [2′-alkylimidazolyl (1) ′] ethyl-s-triazine / isocyanuric acid adduct, the blending ratio of which is 1 part epoxy resin in order to satisfy storage stability, fast curing property and cured product characteristics. 5 to 1 parts by weight of curing agent
It should be added in a proportion of 5 parts by weight. When the compounding ratio of the curing agent is less than 5 parts by weight, the curing speed becomes slow and the productivity is lowered or the reliability is deteriorated due to insufficient curing. Conversely, when it exceeds 15 parts by weight, the unreacted curing agent is cured. It is not preferable because it remains in the product and pollutes the liquid crystal and deteriorates the moisture resistance.

As the inorganic filler used in the liquid crystal display cell seal adhesive of the present invention, those having a large aspect ratio and relatively soft scales such as talc and mica are preferable. Is an inorganic filler having an average particle size of 2 μm or less, an oil absorption of 40 cc / 100 g or more, and a moth hardness of 2 or less. Epoxy resin 1
It is 10 to 40 parts by weight with respect to 00 parts by weight, and if it is less than 10 parts by weight, no effect is seen in printing performance and adhesive performance
If it exceeds 40 parts by weight, the viscosity becomes high and the thixotropic property becomes high, so that printing cannot be performed without using an organic solvent in combination. By using such a filler, it is possible to stabilize the thickness of the screen-printed adhesive layer before bonding the display cells, and the viscosity of the adhesive that affects the resolution of the screen pattern, It is possible to improve printing performance such as thixotropic property and screen removal property. Further, since the tackiness can be imparted to the surface of the adhesive, it is possible to prevent the deviation when the display cells are bonded together, and further, it is possible to alleviate the curing shrinkage and the stress of the adhesive during heat curing,
It also becomes possible to improve the adhesive strength to the cell substrate.

In the production of the liquid crystal display cell seal adhesive of the present invention, the maximum particle size of the filler in the adhesive can be reduced to 5 μm or less by using a three-roll machine and a disperser. And a filler that does not damage the electrode circuit formed in the display cell when screen-printing the adhesive,
For example barium sulfate, barium carbonate, calcium carbonate,
There is no problem even if magnesium carbonate, aluminum silicate or fine powder anhydrous silica is used together.

The silane coupling agent used in the adhesive for a liquid crystal display cell seal of the present invention is epoxysilane or aminosilane, and when combined with the above-mentioned inorganic filler, the moisture resistance and adhesion to the cell substrate are obtained. It has the function of improving power. The amount of the silane coupling agent is 0.5 to 2.0 parts by weight based on 100 parts by weight of the inorganic filler, and 0.2 to 1.0 parts by weight based on 100 parts by weight of the epoxy resin. However, if the compounding amount is less than the above range, the effect of the silane coupling agent is lost, and conversely, if the compounding amount is more than the above range, contamination of the liquid crystal increases, which is not preferable.

In producing the adhesive for liquid crystal display cell seals of the present invention, in order to improve printing performance as necessary, phenylglycidyl ether is used within a range not deteriorating the performance as an adhesive for seals. And butylglycidyl-
There may be used together with a reactive diluent such as tell.

In producing the adhesive for liquid crystal display cell seals of the present invention, three adhesives prepared in advance by blending a prescribed amount of the above-mentioned epoxy resin, epoxy curing agent, filler and silane coupling agent are used. Kneading using a roll machine
It may be pulverized and prepared so that the maximum particle size of the solid matter in the adhesive is 5 μm or less in consideration of the thickness of the adhesive for sealing.

In manufacturing the liquid crystal display cell of the present invention, a predetermined amount of a spacer for obtaining a predetermined display cell interval is mixed with the liquid crystal display cell seal adhesive, and then the predetermined adhesive is applied. In order to obtain the thickness and width of the layer, this is screen-printed on the display cell substrate, or a predetermined adhesive layer is screen-printed to have a predetermined thickness and width of the adhesive layer. After sprinkling a predetermined amount of a spacer having a particle diameter of No. 1 on the other side, the other display cell base material is immediately attached thereto, and a pair of cell base materials are fixed by a predetermined method so as not to shift. Then, the cell base material is heated to a temperature of 115 to 1
15 to 20 minutes at 25 ° C., further 120 to 1 temperature
Heat at 50 ° C. for 20-30 minutes, or 12
A liquid crystal cell is obtained by heating and curing at a temperature of 0 to 150 ° C. for 20 to 40 minutes.

[0018]

【Example】

(Example 1) 100 parts of epibis type liquid epoxy resin [trade name: Epicron 850, manufactured by Dainippon Ink and Chemicals, Inc.]
2,4-diamino-6 [2'-methylimidazolyl (1) '] ethyl-s-triazine / isocyanuric acid adduct 10 parts as a curing agent, talc 30 as a scale-like inorganic filler
Parts, 0.5 parts of epoxysilane as a silane coupling agent [trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.] and thixotropic agent [trade name: Aerosil # 30]
0, manufactured by Nippon Aerosil Co., Ltd.], and the mixture was uniformly kneaded using a three-roll mill until the particle size became 5 μm or less, to prepare an epoxy resin one-component solventless adhesive. The viscosity of this product at 25 ° C. measured by an E-type viscometer was 500 poise, and the performance evaluation results were as shown in Table 1.

Next, a spacer (particle diameter: 8 μm) is added to the obtained adhesive and mixed, and a pattern (length 40 mm, width 90 mm, width 1 mm) is screen-printed on the cell base material that has been subjected to an alignment treatment in advance. ) Was printed. Another pair of cells was attached to each other, held so that the distance between the cells was about 10 μm, heated at a temperature of 120 ° C. for 10 minutes, and further heated at a temperature of 150 ° C. for 30 minutes. The obtained liquid crystal sealing cell was filled with an ester type liquid crystal and the mouth was sealed to manufacture a liquid crystal display cell. The performance evaluation results of the obtained liquid crystal cell are as shown in Table 1.

(Example 2) 75 parts of the same epibis type liquid epoxy resin as used in Example 1 and phenol novolac type liquid epoxy resin [trade name: Epicoat 152,
Manufactured by Yuka Shell Epoxy Co., Ltd.] to 20 parts of 2,4-diamino-6 [2′-methylimidazolyl (1) ′] as a curing agent.
Ethyl-s-triazine / isocyanuric acid adduct 10
Parts, 20 parts of mica and 30 parts of barium sulfate as a scale-like inorganic filler, 1 part of the same epoxy silane as used in Example 1 as a silane coupling agent, and 5 parts of butyl glycidyl ether having an average molecular weight of 130 as a reactive diluent. Also, 2 parts of the same thixotropic agent as used in Example 1 was added and mixed, and this mixture was uniformly kneaded using a three-roll mill until the particle size became 5 μm or less, and the epoxy resin 1 liquid solventless type An adhesive was prepared. The initial viscosity of this product was 450 poise, and the results of its performance evaluation test were as shown in Table 1.

Then, the obtained adhesive was used to bond the paired cells in the same manner as in Example 1 and heated at a temperature of 120 ° C. for 40 minutes. A liquid crystal display cell was manufactured by filling the obtained liquid crystal sealing cell with an ester type liquid crystal and sealing the mouth. When the performance evaluation test of this liquid crystal display cell was conducted, the results were as shown in Table 1.

(Comparative Example 1) 90 parts of the same epibis type liquid epoxy resin as used in Example 1 was added with 2, as a curing agent.
4-diamino-6 [2'-methylimidazolyl (1) '] ethyl-s-triazine / isocyanuric acid adduct 10 parts, non-scaly talc as an inorganic filler 40 parts and barium sulfate 20 parts, silane coupling agent As amino silane [brand name: KBE903, Shin-Etsu Chemical Co., Ltd.
2 parts, 10 parts of phenylglycidyl ether having an average molecular weight of 155 as a reactive diluent, and 1 part of the same thixotropic agent used in Example 1 were added and mixed,
This mixture was uniformly kneaded using a three-roll mill until the particle size became 5 μm or less, to prepare an epoxy resin one-component solventless adhesive. The viscosity of this product at 25 ° C. measured by an E-type viscometer was 350 poise, and the results of the performance evaluation test were as shown in Table 1.

Then, a liquid crystal display cell was manufactured by using the obtained adhesive agent in the same manner as in Example 1 and a performance evaluation test was conducted. The results are shown in Table 1. .

COMPARATIVE EXAMPLE 2 100 parts of the same epibis type liquid epoxy resin as used in Example 1 was added to 2,4-diamino-6 [2'-methylimidazolyl (1) '] as a curing agent.
Ethyl-s-triazine / isocyanuric acid adduct 15
Parts, 15 parts of barium sulfate as an inorganic filler and 40 parts of amorphous fused silica, and 1 part of the same thixotropic agent as used in Example 1 are mixed and uniformly kneaded using a three-roll mill, An epoxy resin one-component solventless adhesive containing no silane coupling agent was prepared. The viscosity of this product was 500 poise, and the performance evaluation test was conducted. The results are shown in Table 1.

Then, a liquid crystal display cell was manufactured by using the above-mentioned adhesive obtained in the same manner as in Example 1 and a performance evaluation test was conducted. The results are shown in Table 1.

Comparative Example 3 90 parts of the same epibis type liquid epoxy resin as used in Example 1 and 10 parts of epibis type solid epoxy resin [trade name: Epicoat 1004, manufactured by Yuka Shell Epoxy Co., Ltd.], 2,4-diamino-6 [2'-methylimidazolyl (1) '] ethyl-s as a curing agent
10 parts of triazine / isocyanuric acid adduct, 20 parts of barium sulphate and 40 parts of talc as inorganic filler, 0.5 parts of the same epoxy silane as used in Example 1 as silane coupling agent, used in Example 1 1 part of the same thixotropic agent as described above and 20 parts of butyl cellosolve as a solvent were added and mixed, and this mixture was uniformly kneaded by a three-roll mill to produce a solvent-type epoxy resin one-component adhesive. The viscosity of this product was 450 poise, and the results of its performance evaluation test were as shown in Table 1.

Then, a spacer is added to the obtained adhesive and mixed, and a pattern (length 40 mm, width 90 mm, width 90 mm, width 90 mm,
Width 1 mm) was printed. Another cell preheated by heating at a temperature of 50 to 60 ° C. for 1 hour was attached to the cell, and the cell spacing was about 10 μm while being pressurized.
After heating at a temperature of 150 ° C for 30 minutes, the temperature is further increased to 15
Heated at 0 ° C. for 30 minutes. The obtained liquid crystal sealing cell was filled with biphenyl-based liquid crystal and the mouth was sealed to manufacture a liquid crystal display cell, and the performance evaluation test was conducted. The results are shown in Table 1.

(Comparative Example 4) 70 parts of the same epibis type liquid epoxy resin and liquid butadiene as used in Example 1
Acrylonitrile copolymer [trade name: HIKA-CTBN
1300X13, manufactured by Ube Industries, Ltd., and 10 parts of 2,4-diamino-6 [2'-methylimidazolyl] as a curing agent.
(1) ′] 10 parts of ethyl-s-triazine / isocyanuric acid adduct, 30 parts of talc as an inorganic filler and reactive diluent [trade name: Epomic R-098, manufactured by Mitsui Petrochemical Epoxy Co., Ltd.] 20 parts Was added, mixed uniformly while heating, and cooled to room temperature, and then thixotropic agent [trade name: Aerosil # 200, Nippon Aerosil Co., Ltd.
Manufacture] 0.5 part was added and uniformly kneaded using a three-roll mill to produce an epoxy resin one-component solventless adhesive containing no silane coupling agent. The viscosity of this product was 300 poise, and a performance evaluation test was conducted. The results are shown in Table 1.

Then, using the above-mentioned adhesive obtained,
A liquid crystal display cell was manufactured by the same method as in Example 1 and a performance evaluation test was conducted. The results are shown in Table 1.

Comparative Example 5 100 parts of the same epibis type liquid epoxy resin as used in Example 1 was added to 2,4-diamino-6 [2'-methylimidazolyl (1) '] as a curing agent.
Ethyl-s-triazine / isocyanuric acid adduct 10
Parts, sericite as an inorganic filler (average particle size 1.5
μm, Mohs hardness 3.5) 10 parts, spherical synthetic quartz (high-purity synthetic silica, average particle size 0.4 μm) 40 parts, 0.5 part of the same epoxy silane as used in Example 1 as a silane coupling agent. Then, 1 part of the same thixotropic agent as used in Example 1 was added and mixed, and this mixture was uniformly kneaded with a three-roll mill to produce a solvent-free epoxy resin one-component adhesive. The viscosity of this product was 400 poise, and the results of its performance evaluation test were as shown in Table 1.

Then, using the above obtained adhesive,
A liquid crystal display cell was manufactured by the same method as in Example 1 and a performance evaluation test was conducted. The results are shown in Table 1.

[0032]

[Table 1]

The epoxy resin adhesive and the liquid crystal cell thus obtained were evaluated and tested according to the following test standards and conditions. Pot life The time until the initial viscosity becomes 1.5 times after being left at a temperature of 25 ° C. Printability (screen printing) A 1 mm pattern was printed using a 225 mesh screen on a glass slide degreased with methanol-water, and after curing, a line (line magnification) was applied using a microscope (10x5x). The meandering state was visually judged. ○: Almost no line meandering △: Line meandering Bleeding during curing 1mm pattern 225 on the copper plate chemically treated on the surface
After printing using a mesh screen and heating and curing at a temperature of 120 ° C. for 15 minutes, the state of bleeding around the line was visually judged. ◯: Almost no bleeding Δ: Many bleeding Manufacturing time The time from the printing of the sealant to the end of curing. The Tg sealing agent was heated and cured at a temperature of 150 ° C. for 30 minutes, and then the endothermic inflection point was measured by the DSC method. Liquid Crystal Contamination At a temperature of 60 ° C. and a humidity of 90% RH, display disorder was observed in a liquid crystal display cell left for 500 hours. ◯: No display disorder Δ: Display disorder Disappearance test Knife test after leaving for 500 hours at a temperature of 60 ° C. and a humidity of 90% RH. ◯: Glass breakage (good adhesion) Δ: Peeling occurred

[0034]

The adhesive for liquid crystal display cell seals of the present invention can further improve the electrical reliability and mechanical durability of the display cell. Further, the liquid crystal display cell manufactured using the adhesive of the present invention has very little liquid crystal contamination,
Its productivity is dramatically increased.

Claims (3)

[Claims] 1. A 2,4-diamino-6 [2′-alkylimidazolyl group represented by the general formula of Chemical Formula 1 as a curing agent.
(1) '] An adhesive for liquid crystal display cell seals, which contains an ethyl-s-triazine / isocyanuric acid adduct, an inorganic filler and a silane coupling agent as essential components. [Chemical 1] (However, R represents an alkyl group.) 2. The adhesive for liquid crystal display cell seals according to claim 1, wherein a scale-like inorganic filler is used as the inorganic filler. 3. Epoxy resin, 2,4-diamino-6
[2'-Alkylimidazolyl (1) '] ethyl-s-triazine-isocyanuric acid adduct, an inorganic filler and a silane coupling agent as a main component for a liquid crystal display cell seal adhesive on a liquid crystal cell substrate. Apply it to the part where the other display cell base material is to be adhered, and bond the other liquid crystal display cell base material at a fixed interval to this base material surface and heat the liquid crystal display cell seal adhesive. A method for producing a liquid crystal display cell, which comprises curing.