JPH1090699A - Hardening type resin composition for sealing of liquid crystal and liquid crystal display panel using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good printing workability and pattern characteristics with high accuracy by allowing a core-shell polymer having each specified core component and shell component to be compatible with a hardening resin compsn. SOLUTION: A core-shell polymer having a core component of rubber-state polymers comprising acrylate or methacrylate polymers having the glass transition temp. lower than room temp. and a shell component of glass-state polymers comprising acrylate or methacrylate polymers having the glass transition temp. higher than the room temp. is made compatible with a hardening resin compsn. By allowing the core-shell polymer to be compatible with a hardening resin compsn., namely, by uniformly dispersing the polymer without dissolving the polymer in the hardening resin compsn and without swelling the surface of polymer particles, the obtd. compsn. shows physical properties with low viscosity and proper thixotropy before the compsn. is applied on a substrate by screen printing. Therefore, good printing workability and pattern characteristics with high accuracy can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a curable resin composition for sealing a liquid crystal cell. More specifically, in the step of manufacturing a liquid crystal cell, the sealing curable resin composition is pseudo-cured by preheating to be transformed into a non-flowable gel, preferably an adhesive gel substance having a surface tackiness, Provision of a liquid crystal cell sealing curable resin composition suitable for an alignment step of aligning upper and lower substrates of a liquid crystal cell at predetermined positions, a method of manufacturing a liquid crystal display panel utilizing characteristics of the sealing curable resin composition, and manufacturing the same The present invention relates to a liquid crystal display panel obtained by the method.

[0002]

2. Description of the Related Art Generally, a sealing resin composition is used for a liquid crystal cell in which two glass plates or plastic plates are bonded with a predetermined gap. Heretofore, a one-part or two-part epoxy-based thermosetting resin composition has been used as the liquid crystal cell sealing resin composition. This epoxy-based thermosetting resin composition was diluted with a solvent for the purpose of improving the workability of screen printing on a substrate and the pattern characteristics. However, since the curable resin composition diluted with the solvent has fluidity, there is a disadvantage that a displacement between the upper and lower substrates is apt to occur during the transfer from the alignment step to the curing step. Therefore, in order to prevent this deviation, a pretreatment for evaporating the solvent to increase the viscosity has been required.

[0003] In recent years, therefore, a curable resin for sealing a liquid crystal cell has been developed in which a photocurable resin composition comprising an acrylic or epoxy resin or a mixture thereof is used. Used as a composition. The advantage of these curable resin compositions for sealing is that by curing by light irradiation or the like, the influence of the temperature at the time of heat curing can be reduced, and the displacement due to thermal expansion of the liquid crystal cell at the time of curing can be suppressed. With this effect, it has become possible to meet the demand for higher definition of the liquid crystal panel. Furthermore, in the case of a photocurable resin composition, single-wafer processing of a liquid crystal cell becomes possible, which can contribute to improvement in productivity of the liquid crystal cell.

The technology of photocurable sealing resin compositions is described in JP-A-56-11832 and JP-A-56-11832.
29779, JP-A-58-44420, JP-A-58-1
05124, JP-A-59-131, JP-A-59-745
27, etc.

[0005]

However, these conventional curable resin compositions for sealing liquid crystal cells have the following problems.

[0006] The curable resin composition for sealing a liquid crystal cell of a solvent-evaporating type typified by a conventionally used epoxy-based heat-curable resin composition is a solvent-evaporating type and therefore can be used even during a coating operation by screen printing. The viscosity increases and the applied amount varies. If volatilization is incomplete, the solvent component elutes into the liquid crystal cell and mixes into the liquid crystal, causing problems such as poor liquid crystal alignment and generation of bubbles.

In the case of a heat-curable resin composition, a long-time high-temperature treatment for curing is required, and a dimensional deviation occurs due to thermal expansion of the substrate. In recent years, the curing conditions have been lowered, but generally still exceed 100 ° C.

When the curable composition for sealing a liquid crystal cell is a photocurable resin composition or a curable resin composition combining light and heat, the above-mentioned misalignment due to thermal expansion can be eliminated.
With respect to the thinned substrate, the vibration deviation due to the deflection of the substrate during the transfer from the alignment step to the curing step becomes large. That is, since the curable resin composition for sealing the liquid crystal cell before curing is in a liquid state, there is no ability to fix the substrate and suppress the displacement, and it is impossible to prevent the displacement. In order to prevent the vibration displacement, the fixing may be temporarily performed with a photocurable resin different from the curable resin composition for sealing. However, there is a disadvantage in that a space for bonding a photo-curable resin for temporary fixing is required on the substrate, and the number of liquid crystal cells produced per substrate is reduced.

[0009] A rubber or an elastomer is dissolved in a curable resin composition for sealing a liquid crystal cell, and a holding force and an adhesion force to a substrate are obtained.
Attempts have been made to improve adhesion, etc., but stringing and high-viscosity compositions have resulted in reduced screen printing workability and coating pattern characteristics, and also have the problem of uneven curing conditions and cured product characteristics. ing.

As described above, each material has advantages and disadvantages, and a curable resin composition for sealing a liquid crystal cell to be used must be selected according to which part of each characteristic is regarded as important.

[0011]

DISCLOSURE OF THE INVENTION As a result of intensive studies, the present invention has revealed that a core component of a rubbery polymer comprising an acrylate or methacrylate polymer having a glass transition point of not higher than room temperature and an acrylate having a glass transition point of not lower than room temperature. Alternatively, these problems have been solved by making a core-shell polymer composed of a shell component of a glassy polymer composed of a methacrylate polymer compatible with the curable resin composition.

Preferably, the core portion of the core-shell polymer is made of an acrylate or methacrylate polymer having a glass transition temperature of -30 ° C. or less, and an acrylate or methacrylate monomer and a C 3 -C 3 carboxyl group. A copolymer having a glass transition temperature of 70 ° C. or higher obtained from a radical polymerizable unsaturated carboxylic acid monomer and a crosslinkable monomer of No. 8 and adding a monovalent or divalent metal cation. Compatibility of a core-shell polymer of copolymer resin particles composed of an ion-crosslinked shell component and having a core component / shell component weight ratio in a range of 10/1 to 1/4 in a curable resin composition. It is characterized by.

The curable resin composition for sealing a liquid crystal cell of the present invention contains any of the following curable resin compositions.

1) A photocurable resin composition containing a curable resin having at least one polymerizable unsaturated bond in its molecule and a photoradical polymerization initiator.

2) A photocurable resin composition containing a curable resin having at least one glycidyl group in its molecule and a cationic photopolymerization initiator.

3) A thermosetting resin composition containing a curable resin having at least one glycidyl group in its molecule and a latent thermosetting agent.

4) A curable resin composition containing a curable resin having at least one or more polymerizable unsaturated bonds in its molecule and a photo-radical polymerization initiator, and at least one or more in its molecule. A photocurable resin composition which is a mixed composition of a curable resin having a glycidyl group and a curable resin composition containing a photocationic polymerization initiator.

5) A curable resin composition containing a curable resin having at least one or more polymerizable unsaturated bonds in its molecule and a photo-radical polymerization initiator; A curable resin composition combining light and heat, which is a mixed composition of a curable resin having a glycidyl group and a curable resin composition containing a latent thermosetting agent.

Further, in the present invention, the sealing curable resin composition for a liquid crystal cell is applied to a glass plate or a plastic plate in a predetermined pattern shape, and then the resin composition is pseudo-cured by preheating to form a non-flowable resin. A liquid crystal cell characterized in that after being denatured into an adhesive substance having surface tackiness, another glass plate or plastic plate is aligned at a predetermined position, and then the resin composition is completely cured by heating or irradiation with ultraviolet light. And a liquid crystal display panel in which liquid crystal is sealed in a liquid crystal cell produced by the production method utilizing the properties of the curable resin composition for a liquid crystal cell.

Here, the curable resin set having a polymerizable unsaturated bond is defined as an ethylenic ester such as a fumarate ester, a maleate ester, an allyl compound, an acrylate ester, a methacrylate ester, a styrene compound and a butadiene compound. It refers to a resin having an unsaturated group, and in the present invention, preferred are urethane-modified or epoxy-modified acrylates or methacrylates. The curable resin group having a glycidyl group refers to a resin generally called an epoxy resin, and is not particularly limited in the present invention as long as it is an existing epoxy resin.

When a core-shell polymer is mixed with a urethane-modified resin, preferably a urethane-modified epoxy resin, the peel strength of adhesion is increased, the change with time in viscosity is small, and the storage stability is excellent, as described in JP-A-6-271827 and JP-A-6-271827.
264045.

Examples of the photo-radical polymerization initiator include acetophenone compounds, benzoin compounds, benzoin alkyl ethers, benzophenone compounds, thioxanthone compounds, benzyl and acylphosphine oxide compounds. Examples of the cationic photopolymerization initiator include triallylsulfonium salts.

Examples of the latent thermal polymerization initiator include dicyanamide, imidazole derivatives, N-alkyl urea derivatives,
N-alkylthiourea derivatives, N-aminopiperazines,
Examples include phenylenediamine, melamine, guanamine, and boron trifluoride complex compounds. Particularly preferred is a latent thermal polymerization initiator of the microcapsule type obtained by blocking an imidazole derivative with an isocyanate compound.

The core shell polymer in the present invention is:
A powder composed of a core component of a rubber-like polymer composed of an acrylate or methacrylate-based polymer having a glass transition point of not higher than room temperature, and a shell component of a glassy polymer composed of an acrylate or methacrylate-based polymer having a glass transition point of not lower than room temperature Refers to a copolymer.

The core component comprises a monofunctional (meth) acrylate compound having an alkoxyl group having 4 to 8 carbon atoms, and a polyhydric alcohol (meth) acrylate such as di (meth) acrylate such as ethylene glycol diacrylate and butylene glycol dimethacrylate. A) bifunctional monomers having functional groups with different polymerization rates in one molecule for cross-linking a copolymer monomer such as an acrylate compound or an aromatic divinyl compound such as divinylbenzene with a shell component, for example, allyl (meth) acrylate And diallyl maleate.

After emulsion polymerization of the core component, monomers having a glass transition point of a cured product such as styrene, divinyltoluene and methyl methacrylate having a glass transition point of room temperature or higher as a shell component, or these monomers and ethyl (meth) acrylate, butyl (meth) 1) Carbon number 1 such as acrylate
A mixed monomer having a glass transition point of room temperature or higher and a core component / shell component weight ratio of 10/1 to 1/4. A core-shell polymer of a copolymer particle having a two-layer structure is obtained.

Here, depending on the shell component, when the core-shell polymer is mixed with the curable resin composition, the shell component may be dissolved or swelled. ) Unsaturated monocarboxylic acids such as acrylic acid, crotonic acid and cinnamic acid, and unsaturated dicarboxylic acid monomers having 3 to 8 carbon atoms and having a dicarboxyl group such as maleic acid, itaconic acid, fumaric acid and maleic anhydride or anhydrides Monocarboxylic acid monomer, monoethyl maleate, monobutyl maleate, monoethyl fumarate, monoester of unsaturated dicarboxylic acid, such as monoethyl itaconate, is added to the above-mentioned shell component and copolymerized to form a carboxylic acid group on the shell component. Is preferably introduced.

Further, when a mono- or divalent metal cation, for example, a metal cation such as potassium, sodium, lithium, calcium, zinc, tin or the like is added to the carboxylic acid group of the shell component, ionic crosslinkability is exhibited. Solvent resistance to dissolution or swelling in a solvent or liquid resin can be improved. Furthermore, if the resin is preheated at a temperature lower than the temperature at which the resin is heat-cured by utilizing the reversible reactivity of the ionic cross-linking, it becomes easy to obtain a pseudo-curability that changes to a non-flowable gel-like material.

[0029]

In the present invention, the core-shell polymer is made compatible with the curable resin composition, that is, the polymer is uniformly dispersed without dissolving in the resin and swelling the surface of the polymer particles. The following effects were obtained.

Since the physical properties before application of screen printing to the substrate are low in viscosity and have appropriate thixotropic properties, good printing workability and highly accurate pattern characteristics can be obtained. In addition, after application, the composition is more likely to be transformed into a non-flowable gel under the conditions of a short time and a low temperature preheating as compared with the conventional solvent-dilutable type curable resin composition for sealing a liquid crystal cell. Further, if the pseudo-cured gel material is given a surface tackiness, the substrate holding force is further improved.

In order to improve the pattern characteristics of screen printing, it is not necessary to dilute the curable resin composition for sealing a liquid crystal cell with a solvent to reduce the viscosity. Eliminates unevenness in properties or variations in the amount of coating. Further, it is possible to improve the quality and reliability of the liquid crystal cell, such as preventing the solvent from being mixed into the liquid crystal when the solvent emission is incomplete.

Since the polymer having the core-shell structure is dispersed, a sea-island structure is formed in the cured product, and the effect of stress relaxation is exhibited, and the adhesive strength is improved. In addition, since it is a dispersion type from an initial state as compared with a conventional rubber melting type or the like, there is no variation in physical properties of a cured product due to curing conditions and cured portions.

[0033]

EXAMPLES Tables 1, 2, 3 and 4 show examples of the composition of the curable resin composition for sealing a liquid crystal cell of the present invention. Example 1 is a resin composition having a glycidyl group, which is a photocurable type.
Examples 4 to 6 show the thermosetting types. Also,
Examples 7 to 10 show photocurable taps, which are resin compositions having unsaturated bonds. Examples 11 to 18 show photocurable types of a mixed system of a resin composition having a glycidyl group and a resin composition having an unsaturated bond, and Examples 19 to 26 show a combined type using light and heat. As comparative examples, cases where the core-shell polymer was not added are shown as comparative examples 1 to 8.

The curable resin compositions for sealing liquid crystal cells of Examples and Comparative Examples were applied to glass substrates of liquid crystal panels, and the following evaluations were made. The results are also shown in Tables 1 to 4.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

Coating workability: The curable resin composition for sealing a liquid crystal cell was screen-printed on a glass substrate, and the linearity of the pattern immediately after printing and the occurrence of sink marks were observed.
Judgment criteria were as follows. ○ ・ ・ ・ ・ ・ ・ No case × ・ ・ ・ ・ ・ ・ Sink marks, cuts, etc. occur

Panel holding force before curing: The glass substrate, for which the above-mentioned coating workability has been confirmed, is preheated to quasi-cure the curable resin composition for sealing the liquid crystal cell to be transformed into a non-flowable adhesive substance, and then to another glass. It was bonded to the substrate. The presence / absence of displacement of the upper and lower glass substrates when the bonded glass substrates were pressed with a finger was examined. The criteria were as follows. ○ ・ ・ ・ ・ No deviation × ・ ・ ・ ・ Deviation

Substrate adhesion after curing: The glass substrate bonded by the above-mentioned panel holding force before curing was irradiated with ultraviolet rays or heated to completely cure the curable resin composition for a liquid crystal cell.
Next, when scribing (dividing the glass substrate into the size of the display panel), it was confirmed whether or not the cured portion of the curable resin composition for sealing a liquid crystal cell had peeled off. The criteria were as follows. ○ ・ ・ ・ ・ No peeling △ ・ ・ ・ ・ Partial lifting occurs at corners × ・ ・ ・ ・ Glass substrate peeled into two

Reliability test result: After performing a reliability test in which the display panel produced by the above-mentioned substrate adhesion after curing was exposed for 1000 hours in an environment of a temperature of 60 ° C. and a humidity of 95%, electrical characteristics (specific resistance, voltage holding ratio) were obtained. Was examined for changes. The criteria were as follows. ○ ・ ・ ・ ・ Change rate of electrical characteristics is 10 compared to before the reliability test
Within% △ ・ ・ ・ ・ ・ ・ Change rate of electrical characteristics is 30 compared to before the reliability test
% ×: The rate of change in electrical characteristics is 30 compared to before the reliability test
%that's all

[0043]

EFFECT OF THE INVENTION Since it has a low viscosity and a suitable thixotropic property, good printing workability and high-precision pattern characteristics can be obtained, and after coating, a conventional solvent-dilutable sealing curable resin composition is applied. It is easy to be transformed into a non-flowable gel under the condition of preheating at a low temperature in a shorter time than in the case of.

Further, since solvent dilution for improving the pattern characteristics of screen printing is unnecessary, unevenness in workability or variation in coating amount due to thickening during the screen printing operation can be eliminated, and the liquid crystal in the case where the solvent scatter is incomplete is eliminated. It is possible to improve the quality and reliability of the liquid crystal cell, such as prevention of solvent mixing.

In addition, since the polymer having the core-shell structure is dispersed, a sea-island structure is formed in the cured product, and this structure exerts a stress relaxation effect, thereby improving the adhesive force between the panel substrates.

Claims (11)

[Claims] 1. A core component of a rubbery polymer composed of an acrylate or methacrylate polymer having a glass transition point of room temperature or lower, and a shell of a glassy polymer composed of an acrylate or methacrylate polymer having a glass transition point of room temperature or higher. A curable resin composition for sealing a liquid crystal cell, wherein a core-shell polymer comprising components is made compatible with the curable resin composition. 2. A core component comprising an acrylate or methacrylate polymer having a glass transition temperature of -30 ° C. or lower in a core portion, a radical polymerizable polymer having an acrylate or methacrylate monomer and a carboxyl group having 3 to 8 carbon atoms. A shell made of a copolymer having a glass transition temperature of 70 ° C. or higher obtained from an unsaturated carboxylic acid monomer and a crosslinkable monomer, and ion-crosslinked by adding a monovalent or divalent metal cation. And a core-shell polymer composed of copolymer resin particles having a core component / shell component weight ratio in the range of 10/1 to 1/4, wherein the core-shell polymer is compatible with the curable resin composition. The curable resin composition for sealing a liquid crystal cell according to claim 1. 3. The curable resin composition for sealing a liquid crystal cell according to claim 1 or 2, wherein the curable resin having at least one or more polymerizable unsaturated bonds in a molecule and a photo radical. A photo-curable liquid crystal cell sealing resin composition containing a polymerization initiator and exhibiting a pseudo-curable behavior of being modified into a non-flowable gel by preheating before a curing reaction by ultraviolet irradiation. . 4. The curable resin composition for sealing a liquid crystal cell according to claim 1, wherein the curable resin having at least one glycidyl group in a molecule and a cationic photopolymerization initiator. A photo-curable liquid crystal cell sealing resin composition, which contains a pseudo-curable behavior that changes into a non-flowable gel by preheating before a curing reaction by ultraviolet irradiation. 5. The curable resin composition for sealing a liquid crystal cell according to claim 1 or 2, wherein the curable resin having at least one glycidyl group in a molecule and a latent thermosetting agent. A heat-curable liquid crystal cell sealing resin composition characterized by exhibiting a pseudo-curable behavior of being modified into a non-flowable gel by preheating at a temperature below the temperature at which the latent curing agent causes a curing reaction. Stuff. 6. The curable resin composition for sealing a liquid crystal cell according to claim 1 or 2, wherein the curable resin having at least one polymerizable unsaturated bond in a molecule and a photo radical. Contains a polymerization initiator, and further contains a curable resin having at least one glycidyl group in the molecule and a cationic photopolymerization initiator, and becomes a non-fluid gel by preheating before the curing reaction by ultraviolet irradiation. A photocurable resin composition for sealing a liquid crystal cell, which exhibits a denaturing pseudo-curable behavior. 7. The curable resin composition for sealing a liquid crystal cell according to claim 1 or 2, wherein the curable resin having at least one or more polymerizable unsaturated bond in a molecule and a photo-radical. Contains a polymerization initiator, and further contains a curable resin having at least one glycidyl group in the molecule and a latent heat curing agent, and is either pre-heated before curing reaction by ultraviolet irradiation or cured by the latent curing agent. A resin composition for sealing a liquid crystal cell which is curable in combination with light and heat, which exhibits a pseudo-curing behavior that changes into a non-flowable gel by preheating below a reaction temperature. 8. The liquid crystal sealing curable resin composition according to claim 1 or 2 is applied to a glass plate or a plastic plate in a predetermined pattern shape, and then the resin composition is pseudo-cured by preheating. Liquid crystal, wherein the liquid composition is completely cured by heating or ultraviolet irradiation after aligning another glass plate or a plastic plate at a predetermined position after being transformed into a non-flowable gel-like substance. Cell manufacturing method. 9. A curable resin composition for sealing a liquid crystal according to claim 1 or 2 is applied to a glass plate or a plastic plate in a predetermined pattern shape, and then the resin composition is pseudo-cured by preheating. After being transformed into a non-flowable tacky adhesive material having a surface tackiness, another glass plate or plastic plate is aligned at a predetermined position, and then the resin composition is completely cured by heating or irradiation with ultraviolet rays. A method for manufacturing a liquid crystal cell, comprising: 10. A liquid crystal display panel in which a cell is formed by laminating a substrate with the resin composition for sealing a liquid crystal cell according to claim 1 or 2, and a liquid crystal is sealed in the cell. 11. A liquid crystal display panel, wherein liquid crystal is sealed in a liquid crystal cell manufactured by using the manufacturing method according to claim 8.