JP2000221517A - Sealing material composition for liquid crystal display device and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in characteristics of voltage holding rate by incorporating a specified epoxy resin, hardening agent, polybutadiene maleate, solvent and inorg. filler. SOLUTION: This compsn. contains an epoxy resin containing an orthocresol novolac epoxy resin and dicyclopentadiene epoxy resin, hardening agent, polybutadiene maleate, solvent and inorg. filler. The total amt. of the orthocresol novolac epoxy resin and the dicyclopentadiene epoxy resin is preferably controlled to 60 to 100 pts.wt. to 100 pts.wt. of the whole epoxy resin. The number average mol.wt. of the polybutadiene in the main chain of polybutadiene maleate is preferably 500 to 2,000. The addition ratio of maleic acid anhydride groups to the main chain polybutadiene is preferably 0.3 to 3.2 (mol/mol). The compounding proportion of the polybutadiene maleate is preferably 1 to 10 pts.wt. to 100 pts.wt. of whole epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sealing material composition for a liquid crystal display device and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal display elements have become widespread as flat panel displays because of their features such as light weight, thinness, and low power consumption. The liquid crystal display element is pressure-sealed with a sealing material composition for a liquid crystal display element (hereinafter referred to as a liquid crystal sealing material) using two sheets of glass subjected to an alignment treatment or an outer peripheral portion of a plastic substrate as an adhesive. In recent liquid crystal panels, the effective screen area per unit panel tends to be expanded, but with this, the width of the seal has become narrower than in the past, and a narrower frame has been designed. It is also desired that the adhesive strength per unit is higher than before. Further, as a part of narrowing the frame, a design has been made in which the distance between the seal portion and the display portion is shorter than before. In such a design, if the contaminant leaks from the adjacent seal portion to the display portion, the electrical characteristics of the panel may be degraded and the display quality may be degraded.

At present, a liquid crystal sealing material mainly using an epoxy resin is widely used, and typical examples thereof are Japanese Patent Publication No. 64-5630 and Japanese Patent Publication No. 4-506.
No. 3 publication. The former is an adhesive mainly composed of an epoxy resin having an average molecular weight of 500 or more, a hydrazide compound, a filler and a solvent, and the latter is an adhesive obtained by mixing a silicone component with a thermosetting resin. However, Japanese Patent Publication No. 64
The adhesive described in JP-A-5630 is easily peeled off from the glass substrate by the PCT treatment, which is not preferable in terms of the moisture resistance and the adhesiveness of the panel. In addition,
In the case where the silicone rubber described in Japanese Patent No. 5063 is used, the low molecular weight component derived from silicone is easily released from the cured seal portion, and the voltage holding ratio of the liquid crystal display element is reduced to cause display failure of the panel. It is not preferable because it may cause poor adhesion of an external connection ACF (anisotropic conductive film) used for mounting the panel.

The characteristics required for a liquid crystal sealing material include:
First, strong adhesion under various conditions, and second, the display reliability of the liquid crystal display element is not deteriorated under high temperature or high temperature and high humidity conditions. On the other hand, conventional liquid crystal sealing materials have been used exclusively in combination with a silicone-modified epoxy resin and another epoxy resin (for example, Japanese Patent Publication No. 4-5063, Japanese Patent Application Laid-Open No. 6-73164, Japanese Patent Application Laid-Open No. 6-73164). -75231). The addition of such a flexible component is effective in alleviating the stress of the cured liquid crystal sealing material, but lowers the heat resistance and moisture resistance. Also, the silicone modified epoxy has a broad molecular weight distribution,
Since the low-molecular-weight siloxane component that has not been epoxidized remains, there is a problem that these non-reactive low-molecular-weight components are released from the liquid crystal into and out of the liquid crystal from the cured liquid crystal sealing material.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a sealing material composition for a liquid crystal display element which has excellent moisture adhesion to a glass substrate and does not degrade the voltage holding ratio characteristic indicating the display reliability of the liquid crystal display element. A liquid crystal display device using the same is provided.

[0006]

The present invention provides an epoxy resin (a) containing an orthocresol novolak type epoxy resin and a dicyclopentadiene type epoxy resin, a curing agent (b), a maleated polybutadiene (c), and a solvent (d). And a sealant composition for a liquid crystal display device, characterized by comprising an inorganic filler (e), and a liquid crystal display device using the same.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Among the epoxy resins used as a main component in the present invention, an orthocresol novolak type epoxy resin is effective in improving heat resistance. However, when used alone, the free volume in a crosslinked structure is reduced. The drawback is that water absorption increases due to the increase, but when a part is replaced with dicyclopentadiene type epoxy resin, the water absorption and moisture permeability can be reduced without impairing heat resistance due to the hydrophobic effect derived from the skeleton. Becomes Furthermore, the addition of maleated polybutadiene to this system further increases the moisture resistance and adhesion,
High adhesion to the glass substrate is maintained even under severe processing such as T. In addition, during the curing reaction, maleic anhydride added to the butadiene chain in a pendant type reacts with the epoxy resin. Since the liquid crystal sealing material is taken into the crosslinked structure, the low molecular weight component derived from butadiene is not released into and out of the sealing portion after the liquid crystal sealing material is cured. From such features, it is possible to greatly improve the moisture adhesion and the voltage holding ratio characteristics of the liquid crystal display element.

The epoxy resin used in the present invention includes an ortho-cresol novolak type epoxy resin and a dicyclopentadiene type epoxy resin. In addition to this, for example, bisphenol A type epoxy resin, alkyl-substituted bisphenol A type epoxy resin, bisphenol F type epoxy resin A resin, an alkyl-substituted bisphenol F type epoxy resin, a bisphenol S type epoxy resin, a glycidylamine type epoxy resin, a phenol novolak type epoxy resin, a biphenyl type epoxy resin, a naphthalene type epoxy resin and the like may be used in combination.

The total amount of the orthocresol novolak type epoxy resin and the dicyclopentadiene type epoxy resin used in the present invention is 60 parts by weight based on 100 parts by weight of the total epoxy resin.
It is preferable to adjust so as to be 100 parts by weight. If the blending amount of the orthocresol novolak type epoxy resin and the dicyclopentadiene type epoxy resin is less than 60 parts by weight, heat resistance and moisture resistance are inferior, and in a high temperature and high humidity environment, the voltage holding characteristic of the liquid crystal display element is deteriorated. Not preferred.

The curing agent used in the present invention includes amine curing agents, imidazole curing agents, hydrazide curing agents such as dicyandiamide and adipic dihydrazide, and acid anhydride curing agents which are generally used as curing agents for epoxy resins. Phenol-based curing agents and the like can be used, and in order to further improve storage stability, these microencapsulated curing agents, adduct-type curing agents, and the like can be used. Further, a curing accelerator can be used in combination with these compounds, and phosphorus-based compounds, imidazole-based compounds, urea-based compounds, dibasic acid compounds, DBU
Salts and the like are generally used.

The maleated polybutadiene used in the present invention is represented by the general formula (1) in which maleic anhydride is added to polybutadiene.

Embedded image A, b, c, and d represent the number of repetitions of each structural unit,
1.8 ≦ a ≦ 10.9, 0.1 ≦ b ≦ 1.0, 4.3 ≦
c ≦ 25.7, 0.2 ≦ d ≦ 2.2, and the number average molecular weight of the main chain polybutadiene and the addition ratio of the maleic anhydride group to the main chain polybutadiene are within the ranges satisfying the following conditions. Any value can be used.

The polybutadiene of the main chain of the maleated polybutadiene used in the present invention has a number average molecular weight of 500 to 20.
00 is preferred. If the molecular weight of the main chain polybutadiene is less than 500, it is difficult to obtain sufficient adhesion to glass by PCT treatment or the like, and if it exceeds 2,000, the maleated polybutadiene is solidified and the workability at the time of blending is deteriorated. Absent.

The addition ratio of the maleic anhydride group to the polybutadiene in the main chain is 0.3 to 3.2 (mol / mo).
1) is preferred. The addition ratio of maleic anhydride groups is 0.3 (mol / mo) to polybutadiene in the main chain.
If it is less than 1), it is difficult to obtain sufficient adhesion to glass by PCT treatment or the like, and if it exceeds 3.2 (mol / mol), the maleated polybutadiene will be solidified and the workability at the time of blending will be deteriorated. Alternatively, the viscosity of the liquid crystal sealing material is extremely increased and the printability is deteriorated, which is not preferable.

The amount of the maleated polybutadiene used in the present invention is 1 to 100 parts by weight of the total epoxy resin.
It is preferably 10 parts by weight. When the addition amount of the maleated polybutadiene is less than 1 part by weight based on the total epoxy resin, it is difficult to obtain the moisture-resistant adhesion of the liquid crystal sealing material,
If the amount is more than 10 parts by weight, the viscosity and the thixotropy of the liquid crystal sealing material are greatly increased, which is not preferable because the screen printability is impaired.

The solvent used in the present invention is used for the purpose of adjusting the viscosity of the liquid crystal sealing material and for uniformly mixing the components. The type of the solvent is not particularly limited, and examples thereof include n-hexane, n-decane, and cyclohexane. Hydrocarbon solvents, aromatic hydrocarbon solvents such as benzene, toluene and xylene, ester solvents such as butyl acetate, benzyl acetate, methyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, methyl cellosolve acetate And polyhydric alcohols such as ethylene glycol, diethylene glycol and diglyme, and derivatives thereof, and the like, alone or in combination of two or more. The amount of the solvent added is 2 to 2 of all components from the viewpoint of printability and the like.
Preferably, it is 50% by weight.

The inorganic filler used in the present invention includes, for example, carbonates, sulfates, alumina, amorphous or spherical silica of various metals, titanium oxide, potassium titanate and the like. Alumina and silica are preferably used alone or in combination of two or more. Further, the addition amount of the inorganic filler is preferably 3 to 50% by weight based on the whole composition from the viewpoint of workability such as printability.

In the materialization of the liquid crystal sealing material of the present invention,
In addition to the above components of the liquid crystal sealing material composition, a coupling agent, an antifoaming agent, a leveling agent, etc. may be added. When adjusting the liquid crystal sealing material, three components are required to uniformly mix each component. It is preferable to knead sufficiently using a roll or the like.

As a method for manufacturing a liquid crystal display element using the liquid crystal sealing material of the present invention, there are the following methods.
First, a seal pattern is formed on one of the glass substrates on which a liquid crystal alignment layer is formed by a process such as screen printing, and after preliminarily dried by a drier or the like, the other substrate is bonded, and pressure is applied as necessary. And further heat-cured in a drying oven or the like. It is appropriate that the preliminary drying is usually performed at 50 to 120 ° C. for 5 to 60 minutes, and the heat curing is generally performed at 100 to 200 ° C. for about 60 to 180 minutes. Further, in order to maintain the gap between the two substrates, the liquid crystal sealing material may contain 1 to 3% of spherical silica having a predetermined diameter and 5 to 8 μm in diameter as a rod-shaped spacer. Inject liquid crystal into the bonded substrate and apply UV
The injection port is sealed with a cured resin or the like to form a liquid crystal display element.

[0019]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

The evaluation of the liquid crystal sealing material obtained in the examples was performed by the following test piece preparation and evaluation method. (1) Preparation and pretreatment of tensile adhesion test piece A spherical silica spacer with a diameter of 5 μm was used for the liquid crystal sealing material.
%, And a test piece for a tensile test was prepared in the following manner. (Screen printing) Using a 300-mesh plate, a central part of a non-alkali glass substrate (OA-2, 20 mm × 25 mm, manufactured by Nippon Electric Glass Co., Ltd.) that had been subjected to a cleaning process was 0.3 mm in width and 1 cm in length. The pattern of the liquid crystal sealing material was screen-printed. (Preliminary drying) The above substrate was heated at 90 ° C./30 in a hot air dryer.
Minutes. (Lamination / Heat Curing) Next, an alkali-free glass substrate (OA-2, manufactured by NEC Corporation, pre-cleaned)
20 mm x 25 mm) is bonded to the pre-dried substrate, and then pressed in a hot air drier under a pressure of 1 kg / cm2.
The specimen was cured by heating at 0 ° C. for 120 minutes. (PCT treatment) The cured test piece was placed in a pressure cooker, treated for 24 hours at 125 ° C./100% RH / 2.3 atm, and then heated and dried at 100 ° C. for 30 minutes. .

(2) Test Method for Tensile Adhesive Strength As a means for evaluating the adhesive strength among the necessary properties of a liquid crystal sealing material, a pressure cooker (PCT) treatment is performed on a pair of glass substrates bonded with the liquid crystal sealing material. Since the method of measuring the tensile strength is the most effective, the PCT
Fixing jigs were adhered to both sides of the treated test piece and the untreated test piece, and pulled up and down by Tensilon to measure the load.

(3) How to make a liquid crystal display element for voltage holding ratio test and pretreatment 1% of a 5 μm diameter spherical silica spacer was mixed with the liquid crystal sealing material obtained in the embodiment, and the voltage holding ratio by the liquid crystal sealing material was used. Since the most effective method is to measure the voltage holding ratio in the vicinity of the liquid crystal sealing material in order to confirm the effect on
Using the pattern of the ITO conductive film 3 described above, a liquid crystal display element was manufactured in the following manner. (Screen printing) An alignment film was formed using a 300-mesh plate, and a pattern of a liquid crystal sealing material 1 having a line width of 0.3 mm was screen-printed on the outer peripheral portion of the lower substrate of the glass substrate provided with the ITO conductive film 3 in FIG. . At this time, the formation position of the ITO conductive film 3 was set at a distance of 3 mm from the inside of the liquid crystal sealing material 1 application portion. (Preliminary drying) The above substrate was heated at 90 ° C./30 in a hot air dryer.
Minutes. (Lamination / Heat-curing) The orientation direction of the upper substrate of the glass substrate with the ITO conductive film 3 of FIG. 1 facing the lower substrate on which the orientation film is formed is the orientation direction of the substrate on which the liquid crystal sealing material is printed. To 90 degrees,
160 ° C. in a hot air dryer with a pressure of 1 kg / cm ²
Heat curing for 120 minutes to obtain an empty liquid crystal cell. (Liquid crystal injection / sealing) Fluorine-based liquid crystal (ZLI-4792, manufactured by Merck) was injected into the above liquid crystal cell, and the injection port was sealed with an acrylic UV-curable resin sealing material 2 to obtain 10 test liquid crystals. A display element was manufactured. (Wet heat treatment) Five test liquid crystal display elements described above were put into a pressure cooker, and the temperature was 125 ° C / 100% RH / 2.
After performing the treatment under the condition of 3 atm for 24 hours, heating and drying were performed at 100 ° C. for 30 minutes. Further, the other five test liquid crystal display elements were placed in a dryer at 150 ° C. and subjected to heat treatment.
After 240 hours, it was taken out and returned to room temperature.

(4) Test Method of Voltage Holding Ratio After preparing a test liquid crystal display element as described above, the voltage holding ratio of the pretreated liquid crystal display element was measured by a voltage holding ratio measuring device (VHR-, manufactured by Toyo Technica Co., Ltd.). Measured according to 1).

(Example 1) As an epoxy resin, an ortho-cresol novolak type epoxy resin (epoxy equivalent:
196) 40 parts by weight, dicyclopentadiene type epoxy resin (epoxy equivalent: 250) 20 parts by weight, naphthalene type epoxy resin (epoxy equivalent: 150) 40 parts by weight,
10 parts by weight of adipic dihydrazide as a curing agent, 3 parts by weight of a maleated polybutadiene resin, 5 parts by weight of amorphous silica as an inorganic filler, 60 parts by weight of spherical silica, and 13 parts by weight of ethyl carbitol as a solvent were mixed by stirring. The mixture was sufficiently kneaded with this roll to obtain a liquid crystal sealing material. Table 1 shows the results of the evaluation of the voltage holding ratio of the liquid crystal display element using the obtained liquid crystal sealing material and the tensile adhesive force of the liquid crystal sealing material. The number average molecular weight of the main chain measured by GPC of the maleated polybutadiene used here was 2,000, and the addition ratio of the maleic anhydride group to the polybutadiene of the main chain measured by titration with potassium hydroxide was 3. 2 (mol / mol).

Example 2 As an epoxy resin, bisphenol A type epoxy resin (epoxy equivalent: 190) 4
0 parts by weight, 40 parts by weight of orthocresol novolak type epoxy resin (epoxy equivalent: 196), 20 parts by weight of dicyclopentadiene type epoxy resin (epoxy equivalent: 250), 15 parts by weight of dicyandiamide as a curing agent, 5 parts by weight of maleated polybutadiene resin Then, 5 parts by weight of amorphous silica as an inorganic filler, 60 parts by weight of alumina, and 20 parts by weight of methyl carbitol as a solvent were stirred and mixed, and further kneaded sufficiently with three rolls to obtain a liquid crystal sealing material. Evaluation was performed in the same manner as in Example 1, and the results are as shown in Table 1.
The GPC of the maleated polybutadiene used here
The number average molecular weight of the main chain measured by the method described above was 1000, and the addition ratio of maleic anhydride groups to polybutadiene in the main chain measured by titration with potassium hydroxide was 1.6.
(Mol / mol).

Example 3 Ortho-cresol novolak type epoxy resin (epoxy equivalent: 1) as epoxy resin
96) 60 parts by weight, 40 parts by weight of dicyclopentadiene-type epoxy resin (epoxy equivalent 250), 4 parts by weight of maleated polybutadiene resin, 10 parts by weight of adipic dihydrazide as a curing agent, amorphous silica 5 as an inorganic filler
Parts by weight, 20 parts by weight of spherical silica, and 13 parts by weight of ethyl carbitol as a solvent were stirred and mixed, and further sufficiently kneaded with three rolls to obtain a liquid crystal sealing material. Evaluation was performed in the same manner as in Example 1, and the results are as shown in Table 1. The number average molecular weight of the main chain of the maleated polybutadiene used herein measured by GPC was 1,000, and the addition ratio of maleic anhydride groups to polybutadiene in the main chain measured by titration with potassium hydroxide was 0.1. 35 (mol /
mol).

(Comparative Example 1) Bisphenol A type epoxy resin (epoxy equivalent: 240) 10 as an epoxy resin
0 parts by weight, 15 parts by weight of dicyandiamide as a curing agent, 5 parts by weight of amorphous silica as an inorganic filler, 60 parts by weight of spherical silica, and 20 parts by weight of methyl carbitol as a solvent are stirred and mixed, and further sufficiently kneaded with three rolls. Thus, a liquid crystal sealing material was obtained. Evaluation was performed in the same manner as in Example 1, and the results are as shown in Table 1.

Comparative Example 2 100 parts by weight of an orthocresol novolak type epoxy resin (epoxy equivalent: 196) as an epoxy resin, 10 parts by weight of adipic dihydrazide as a curing agent, 5 parts by weight of amorphous silica as an inorganic filler, spherical 60 parts by weight of silica and 13 parts by weight of ethyl carbitol as a solvent were stirred and mixed, and further sufficiently kneaded with three rolls to obtain a liquid crystal sealing material. Evaluation was performed in the same manner as in Example 1, and the results are as shown in Table 1.

(Comparative Example 3) As an epoxy resin, a glycidylamine type epoxy resin (epoxy equivalent: 120) 5
0 parts by weight, 50 parts by weight of bisphenol A type epoxy resin (epoxy equivalent: 240), 15 parts by weight of dicyandiamide as a curing agent, 5 parts by weight of amorphous silica as an inorganic filler, 60 parts by weight of alumina, 20 parts by weight of methyl carbitol as a solvent The parts were stirred and mixed, and further sufficiently kneaded with three rolls to obtain a liquid crystal sealing material. Evaluation was performed in the same manner as in Example 1, and the results are as shown in Table 1.

[0030]

[Table 1]

In each of the examples of the present invention, the tensile adhesion after the humidifying treatment was maintained at a high value and the moisture resistance and adhesion were good as compared with the comparative example, and the voltage holding ratio was also high.
It was shown that the display reliability was good with little deterioration.

[0032]

The sealing material composition for a liquid crystal display device of the present invention and the liquid crystal display device using the same have excellent moisture resistance adhesion to a glass substrate, and have low reliability of the liquid crystal display device with little deterioration of the voltage holding ratio. An excellent liquid crystal display device can be provided.

[Brief description of the drawings]

FIG. 1 is a liquid crystal display device for a voltage holding ratio test used in the present invention.

[Explanation of symbols]

 1: liquid crystal sealing material 2: sealing material 3: conductive film

Claims (6)

[Claims] 1. An epoxy resin containing (a) an orthocresol novolak type epoxy resin and a dicyclopentadiene type epoxy resin, (b) a curing agent, (c) a maleated polybutadiene, (d) a solvent, and (e) an inorganic filler. And a sealing material composition for a liquid crystal display element. 2. The sealing material composition for a liquid crystal display device according to claim 1, wherein the total amount of the ortho-cresol novolak epoxy resin and the dicyclopentadiene epoxy resin is 60 to 100 parts by weight based on 100 parts by weight of the total epoxy resin. object. 3. The sealing material composition for a liquid crystal display element according to claim 1, wherein the polybutadiene in the main chain of the maleated polybutadiene has a number average molecular weight of 500 to 2,000. 4. A maleated polybutadiene having a maleic anhydride group addition ratio of 0.3 to polybutadiene in the main chain.
4 to 3.2 (mol / mol).
The sealing material composition for a liquid crystal display element according to the above. 5. The sealing material composition for a liquid crystal display device according to claim 1, wherein the amount of the maleated polybutadiene is 1 to 10 parts by weight based on 100 parts by weight of the total epoxy resin. 6. A liquid crystal display device using the sealing material composition for a liquid crystal display device according to claim 1.