Sealing Material for Liquid Crystal and Method for Producing Same

Abstract

Disclosed is a sealing material for liquid crystals having high adhesion strength and excellent gap-forming power at bonding of panels. Also disclosed are a method for producing such a sealing material and a method for producing a liquid crystal display cell which is improved in productivity, high-speed response and reliability. The sealing material for liquid crystals is produced through a step wherein fine particles (D) having an average particle size of not more than 3 μm are dispersed, using a wet dispersion unit (A), in a reactive resin (C) having an epoxy group and/or a (meth)acryloyl group which resin has been dissolved in a solvent (B) and a following step wherein the solvent (B) is removed.

Description

EXAMPLES

The present invention will be described in further detail referring to examples shown below.

Example 1

After preliminarily mixing 30 parts by weight of an epoxy resin DRGE (manufactured by Nippon Kayaku Co., Ltd.; resorcinol diglycidyl ether multimer), 120 parts by weight of an epoxy acrylate resin R-94100 (manufactured by Nippon Kayaku Co., Ltd.; epoxy acrylate of a bisphenol-F-type epoxy resin), 35 parts by weight of fused and crushed silica (Crystalite 1FF, manufactured by Tatsumori Co., Ltd., average particle size: 1.0 μm), 5 parts by weight of a cross-linked rubber of a core-shell structure (Paralloid EXL-2655, manufactured by Kureha Chemical Industry Co., Ltd., core layer: cross-linked polybutadiene, shell layer: alkyl methacrylate-styrene copolymer, average particle size: 200 nm), and 60 parts by weight of propyleneglycol monomethyl ether as the solvent using a planetary mixer (manufactured by Asada Iron Works Co., Ltd., PVM-50), dispersion treatment was performed using a continuous system sand mill (manufactured by Asada Iron Works Co., Ltd., GMH-L) using media (alumina, diameter: 1 mm). When the dispersion after repeating 20 times of the treatment was sandwiched between glass plates and observed through a microscope, the absence of agglomerates was confirmed. Then, to the dispersion-treated liquid from which the solvent was removed, 1.8 parts by weight of a radical generation type photopolymerization initiator, 3,6-bis (2-methyl-2-morpholinopropionyl)-9-n-octyl carbazole (manufactured by Adeka Corporation, Adeka Optomer N-1414), and 0.5 parts by weight of an aminosilane coupling agent (N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, manufactured by Shin-Etsu Silicone, KBM-603) were added, and after mixing 15 parts by weight of isophthalic acid dihydrazide (trade name: IDH-S, manufactured by Otsuka Chemical Co., Ltd., jet-mill ground grade further pulverized with a jet mill, melting point: 224° C., active hydrogen equivalent: 48.5 g/eq, average particle size 1.3 μm), the mixture was stirred, defoamed and filtered to obtain the sealing material for liquid crystals of the present invention.

Example 2

After preliminarily mixing 30 parts by weight of an epoxy resin DRGE (manufactured by Nippon Kayaku Co., Ltd.; resorcinol diglycidyl ether multimer), 120 parts by weight of an epoxy acrylate resin R-94100 (manufactured by Nippon Kayaku Co., Ltd.; epoxy acrylate of a bisphenol-F-type epoxy resin), 35 parts by weight of alumina (SPC-Al, manufactured by C. I. Kasei Co., Ltd., average particle size 0.05 μm), 5 parts by weight of a cross-linked rubber of a core-shell structure (Paralloid EXL-2655, manufactured by Kureha Chemical Industry Co., Ltd., core layer: cross-linked polybutadiene, shell layer: alkyl methacrylate-styrene copolymer, average particle size: 200 μm), and 60 parts by weight of propyleneglycol monomethyl ether as the solvent using a planetary mixer (manufactured by Asada Iron Works Co., Ltd., PVM-50), dispersion treatment was performed using a continuous system sand mill (manufactured by Asada Iron Works Co., Ltd., GMH-L) using media (alumina, diameter: 1 mm). When the dispersion after repeating 20 times of the treatment was sandwiched between glass plates and observed through a microscope, the absence of agglomerates was confirmed. Then, to the dispersion-treated liquid from which the solvent was removed, 1.8 parts by weight of a radical generation type photopolymerization initiator, 3,6-bis (2-methyl-2-morpholinopropionyl)-9-n-octyl carbazole (manufactured by Adeka Corporation, Adeka Optomer N-1414), and 0.5 parts by weight of an aminosilane coupling agent (N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, manufactured by Shin-Etsu Silicone, KBM-603) were added, and after mixing 15 parts by weight of isophthalic acid dihydrazide (trade name: IDH-S, manufactured by Otsuka Chemical Co., Ltd., jet-mill ground grade further pulverized with a jet mill, melting point: 224° C., active hydrogen equivalent: 48.5 g/eq, average particle size 1.3 μm), the mixture was stirred, defoamed and filtered to obtain the sealing material for liquid crystals of the present invention.

Example 3

After preliminarily mixing 20 parts by weight of an epoxy resin RE-203 (manufactured by Nippon Kayaku Co., Ltd.; diglycidyl ether of ethylene oxide-added bisphenol S), 80 parts by weight of an epoxy acrylate resin R-94100 (manufactured by Nippon Kayaku Co., Ltd.; epoxy acrylate of a bisphenol-F-type epoxy resin), 25 parts by weight of titanium black pigment (Titanium Black 13R, manufactured by Mitsubishi Materials Corporation, average particle size 73 μm), 5.8 parts by weight of a cross-linked rubber of a core-shell structure (Paralloid EXL-2655, manufactured by Kureha Chemical Industry Co., Ltd., core layer: cross-linked polybutadiene, shell layer: alkyl methacrylate-styrene copolymer, average particle size: 200 μm), and 60 parts by weight of propyleneglycol monomethyl ether as the solvent using a planetary mixer (manufactured by Asada Iron Works Co., Ltd., PVM-50), dispersion treatment was performed using a continuous system sand mill (manufactured by Asada Iron Works Co., Ltd., GMH-L) using media (alumina, diameter: 1 mm). When the dispersion after repeating 20 times of the treatment was sandwiched between glass plates and observed through a microscope, the absence of agglomerates was confirmed. Then, to the dispersion-treated liquid from which the solvent was removed, 3.6 parts by weight of a radical generation type photopolymerization initiator, 3,6-bis (2-methyl-2-morpholinopropionyl)-9-n-octyl carbazole (manufactured by Adeka Corporation, Adeka Optomer N-1414), and 0.2 parts by weight of an aminosilane coupling agent (N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, manufactured by Shin-Etsu Silicone, KBM-603) were added, and after mixing 13.5 parts by weight of adipic acid dihydrazide (trade name: ADH-S, manufactured by Otsuka Chemical Co., Ltd., jet-mill ground grade further pulverized with a jet mill, melting point: 190° C., active hydrogen equivalent: 43.5 g/eq, average particle size 1.3 μm), the mixture was stirred, defoamed and filtered to obtain the sealing material for liquid crystals of the present invention.

Comparative Example 1

After preliminarily mixing 30 parts by weight of an epoxy resin DRGE (manufactured by Nippon Kayaku Co., Ltd.; resorcinol diglycidyl ether multimer), 120 parts by weight of an epoxy acrylate resin R-94100 (manufactured by Nippon Kayaku Co., Ltd.; epoxy acrylate of a bisphenol-F-type epoxy resin), 35 parts by weight of fused and crushed silica (Crystalite 1FF, manufactured by Tatsumori Co., Ltd., average particle size: 1.0 μm), and 5 parts by weight of a cross-linked rubber of a core-shell structure (Paralloid EXL-2655, manufactured by Kureha Chemical Industry Co., Ltd., core layer: cross-linked polybutadiene, shell layer: alkyl methacrylate-styrene copolymer, average particle size: 200 nm), using a planetary mixer, dispersion treatment was performed using a three-roll mill (manufactured by Noritake Co., Ltd.). When the dispersion after repeating 20 times of the treatment was sandwiched between glass plates and observed through a microscope, minute agglomerates were found. Then, to the dispersion-treated liquid, 1.8 parts by weight of a radical generation type photopolymerization initiator, 3,6-bis (2-methyl-2-morpholinopropionyl)-9-n-octyl carbazole (manufactured by Adeka Corporation, Adeka Optomer N-1414), and 0.5 parts by weight of an aminosilane coupling agent (N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, manufactured by Shin-Etsu Silicone, KBM-603) were added, and after mixing 15 parts by weight of isophthalic acid dihydrazide (trade name: IDH-S, manufactured by Otsuka Chemical Co., Ltd., jet-mill ground grade further pulverized with a jet mill, melting point: 224° C., active hydrogen equivalent: 48.5 g/eq, average particle size 1.3 μm), the mixture was stirred, defoamed and filtered to obtain the sealing material for liquid crystals.

Comparative Example 2

After preliminarily mixing 30 parts by weight of an epoxy resin DRGE (manufactured by Nippon Kayaku Co., Ltd.; resorcinol diglycidyl ether multimer), 120 parts by weight of an epoxy acrylate resin R-94100 (manufactured by Nippon Kayaku Co., Ltd.; epoxy acrylate of a bisphenol-F-type epoxy resin), 35 parts by weight of alumina (SPC-Al, manufactured by C. I. Kasei Co., Ltd., average particle size 0.05 μm), and 5 parts by weight of a cross-linked rubber of a core-shell structure (Paralloid EXL-2655, manufactured by Kureha Chemical Industry Co., Ltd., core layer: cross-linked polybutadiene, shell layer: alkyl methacrylate-styrene copolymer, average particle size: 200 nm), using a planetary mixer, dispersion treatment was performed using a three-roll mill (manufactured by Noritake Co., Ltd.). When the dispersion after repeating 20 times of the treatment was sandwiched between glass plates and observed through a microscope, the minute agglomerates were found. Then, to the dispersion-treated liquid, 1.8 parts by weight of a radical generation type photopolymerization initiator, 3,6-bis (2-methyl-2-morpholinopropionyl)-9-n-octyl carbazole (manufactured by Adeka Corporation, Adeka Optomer N-1414), and 0.5 parts by weight of an aminosilane coupling agent (N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, manufactured by Shin-Etsu Silicone, KBM-603) were added, and after mixing 15 parts by weight of isophthalic acid dihydrazide (trade name: IDH-S, manufactured by Otsuka Chemical Co., Ltd., jet-mill ground grade further pulverized with a jet mill, melting point: 224° C., active hydrogen equivalent: 48.5 g/eq, average particle size 1.3 μm), the mixture was stirred, defoamed and filtered to obtain the sealing material for liquid crystals.

Test Examples

Vertical Adhesive Strength

To 100 g of the obtained sealing material for liquid crystals, 1 g of glass fibers having a diameter of 5 μm was added as a spacer, and mixed and stirred. The sealing material was applied onto a glass substrate (15 mm×30 mm×0.7 mm thick) using a needle at room temperature, the glass substrate was bonded to another glass substrate so as to intersect and weakly pressed, and fixed using a binder clip. After irradiating 3000 mJ/cm² of ultraviolet beams from a UV irradiator, the substrate was placed in an oven at 120° C. for 1 hour to cure. The diameter of the bonded surface was measured with a microscope to calculate the area of the bonded surface. The diameter of the sample for measurement was made to be within the range between 0.8 μm and 1.2 μm. The sample for measurement was fixed with a jig, the stretching speed was set to about 20 mm/min, and the facing substrate was stretched in the vertical direction to measure the peeling strength. The vertical adhesive strength was calculated using the following equation.

Vertical adhesive strength (MPa)=Peeling strength (N)/Sealing area (mm²)

The measurements were performed 10 times, and the mean value was taken as the vertical adhesive strength of the sealing material.

The results of examples and comparative examples are shown in Table 1.

Gap Formation Test

To 100 g of the obtained sealing material for liquid crystals, 1 g of glass fibers was added as a spacer, and mixed and stirred. The sealing material was applied onto a glass substrate (15 mm×30 mm×0.7 mm thick) using a needle at room temperature, the glass substrate was bonded to another glass substrate so as to intersect and weakly pressed, and fixed using a binder clip. After irradiating 3000 mJ/cm² of ultraviolet beams from a UV irradiator, the substrate was placed in an oven at 120° C. for 1 hour to cure, the bonded surface was observed through a microscope. When the sealing material was collapsed to the diameter of the spacer and a desired gap was formed, the spacer contacts the glass substrate and was clearly visible (evaluated as ◯); however, when the sealing material was not collapsed to the diameter of the spacer and a desired gap was not formed, the spacer was invisible (evaluated as X).

Spacers having diameters of 5 μm and 2 μm were observed, respectively.

The results of examples and comparative examples are shown in Table 1.

	TABLE 1
				Comparative	Comparative
	Example 1	Example 2	Example 3	Example 1	Example 2
Vertical adhesive	17	20	20	3	3
strength (MPa)
Gap formation test
5 μm	◯	◯	◯	X	X
2 μm	◯	◯	◯	X	X

As is obvious from Table 1, Examples 1 to 3 produced by the producing method of the present invention excel in adhesive strength and gap-forming ability; however, Comparative Examples 1 and 2 produced by different methods are significantly inferior is these required properties even though the compositions are identical. This is considered because the inorganic filler and the rubber particles, which are dispersed components, are not homogeneously dispersed. .

INDUSTRIAL APPLICABILITY

The sealing material for liquid crystals of the present invention excels in workability for applying to the substrates and bonding property, and excels in adhesive strength and gap-forming ability. By using the sealing material for liquid crystals of the present invention in the liquid crystal dropping method, a liquid crystal display cell having improved high-speed response and reliability can be produced.

Claims

1. A sealing material for liquid crystals produced by homogeneously dispersing fine particles (D) having an average particle size of not more than 3 μm in a reactive resin (C) having an epoxy group and/or a (meth)acryloyl group dissolved in a solvent (B) using a wet dispersion unit (A) in which a dispersion vessel (a) contains media (b) as dispersing media and a rapidly rotating stirrer (c) disperses agglomerated particles by allowing the media to collide each other in a high-speed rotating field; and then removing the solvent (B).

2. The sealing material for liquid crystals according to claim 1, wherein the wet dispersion unit (A) is of a continuous processing system.

3. The sealing material for liquid crystals according to claim 1 or 2, wherein said media (b) has a diameter of 0.1 to 5 mm each, and is made of any material selected from alumina, zirconia, zirconia-reinforced alumina, and silicon nitride.

4. The sealing material for liquid crystals according to any of claims 1 to 3, wherein the fine particles (D) has an average particle size of not more than 0.3 μm.

5. The sealing material for liquid crystals according to any of claims 1 to 4, wherein the fine particles (D) are inorganic fine particles (D-1).

6. The sealing material for liquid crystals according to claim 5, wherein the inorganic fine particles (D-1) are made of silica and/or alumina and/or titanium black pigment.

7. The sealing material for liquid crystals according to any of claims 1 to 6, wherein the fine particles (D) are organic fine particles (D-2).

8. The sealing material for liquid crystals according to claim 7, wherein the organic fine particles (D-2) are cross-linked rubber fine particles.

9. The sealing material for liquid crystals according to claim 8, wherein the cross-linked rubber fine particles are cross-linked rubber fine particles having a core-shell structure.

10. The sealing material for liquid crystals according to any of claims 1 to 9, which is obtained by further adding any one or more of additives selected from the group consisting of a curing agent, a curing promoter, a photopolymerization initiator, a polymerization inhibitor, a coupling agent, an ion scavenger, and an antioxidant, and then dispersing, and/or adding one or more of said additives after removing the solvent (B).

11. A method for producing a sealing material for liquid crystals, characterized by comprising homogeneously dispersing fine particles (D) having an average particle size of not more than 3 μm in a reactive resin (C) having an epoxy group and/or a (meth)acryloyl group dissolved in a solvent (B) using a wet dispersion unit (A) in which a dispersion vessel (a) contains media (b) as dispersing media and a rapidly rotating stirrer (c) disperses agglomerated particles by allowing the media to collide each other in a high-speed rotating field; and then removing the solvent (B).

12. A liquid crystal display cell sealed with a cured product of the sealing material for liquid crystals according to any of claims 1 to 10.

13. A method for producing a liquid crystal display cell composed of two substrates, characterized by comprising adding a liquid crystal dropwise inside the weir of the sealing material for liquid crystals according to any of claims 1 to 10 formed on one substrate, bonding the other substrate, and then curing the sealing material by light and/or heat.

14. A method for producing a liquid crystal display cell composed of two substrates, characterized by comprising bonding two substrates with the sealing material for liquid crystals according to any of claims 1 to 10, curing the sealing material by light and/or heat to form a cell, injecting a liquid crystal, and then sealing an injecting port with an end sealing material.