JP7557607B2 - Photocurable resin composition, liquid crystal sealant, liquid crystal display panel using the same, and method for producing the same - Google Patents

Description

The present invention relates to a photocurable resin composition, a liquid crystal sealant, and a liquid crystal display panel using the same and a method for manufacturing the same.

A liquid crystal display panel typically comprises a pair of substrates, a frame-shaped sealing material disposed between the substrates, and liquid crystals filled in the area surrounded by the two substrates and the sealing material. In such liquid crystal display panels, each of the two substrates typically has an alignment film on its surface, which orients the liquid crystal in a desired direction. In conventional liquid crystal display panels, the sealing material is formed by applying a liquid crystal sealant to the outer periphery of the alignment film.

However, in recent years, there has been a demand for narrower frame widths for liquid crystal display panels, and there is also a demand for forming a sealing material on the alignment film of the substrate. Alignment films are often hydrophobic and have fewer hydrophilic functional groups compared to glass substrates and the like. Therefore, when a sealing material is placed on the alignment film, the adhesive strength between the substrate and the sealing material is insufficient, and peeling can occur at the interface between them. As a result, liquid crystal sealing materials containing alkylbenzenesulfonic acid-type titanate coupling agents have been proposed (for example, Patent Document 1).

JP 2014-219589 A

However, the liquid crystal sealant described in Patent Document 1 sometimes does not provide sufficient adhesive strength between the substrate having the alignment film and the sealing member, and there was a need to further increase the adhesive strength between these.

Here, the sealing member is obtained by polymerizing or crosslinking a photocurable and/or thermosetting curable compound. It is therefore conceivable to increase the distance between the crosslinking points of the curable compounds to increase the flexibility of the sealing member and to alleviate the stress applied to the interface between the sealing member and the substrate. However, this method has the problem that moisture easily penetrates through the gaps between the crosslinking points of the curable compounds under high temperature and high humidity conditions because the distance between the crosslinking points is long.

The present invention has been made in consideration of the above problems. Specifically, the object is to provide a photocurable resin composition capable of forming a sealing member having high adhesive strength to a substrate and high moisture resistance, a liquid crystal sealant containing the same, and a liquid crystal display panel and a method for manufacturing the same that use the same.

The present invention provides the following photocurable resin composition and liquid crystal sealant.
[1] A photocurable resin composition comprising a curable compound (A) having an ethylenically unsaturated double bond in the molecule, a photopolymerization initiator (B), organic fine particles (C), and a coupling agent (D), wherein the coupling agent (D) is a coupling agent having at least one chemical structure selected from the group consisting of butadiene rubber, butadiene styrene rubber, acrylic rubber, and silicone rubber.

[2] The photocurable resin composition according to [1], wherein the coupling agent (D) is a silane coupling agent having a butadiene rubber structure.
[3] The photocurable resin composition according to [2], wherein the coupling agent (D) contains an alkoxysilyl group, and the amount of the alkoxysilyl group derived from the coupling agent (D) in the photocurable resin composition 100 is 1.0×10 ^-5 mol or more and 5.0×10 ^-3 mol or less.
[4] The photocurable resin composition according to any one of [1] to [3], wherein the content of the coupling agent (D) is 0.5 to 5 parts by mass per 100 parts by mass of the total amount of the photocurable resin composition.

[5] A photocurable resin composition according to any one of [1] to [4], further comprising at least one latent heat curing agent (E) selected from the group consisting of dihydrazide-based latent heat curing agents, amine adduct-based latent heat curing agents, and polyamine-based latent heat curing agents.

[6] The photocurable resin composition according to any one of [1] to [5], further comprising an inorganic filler (F), wherein the content of the inorganic filler (F) is 5 to 15 parts by mass per 100 parts by mass of the total amount of the photocurable resin composition.
[7] A liquid crystal sealant comprising the photocurable resin composition according to any one of [1] to [6] above.

The present invention provides the following method for manufacturing a liquid crystal display panel.
[8] A method for manufacturing a liquid crystal display panel, comprising the steps of: applying the liquid crystal sealant described in [7] above in a pattern onto at least one of a pair of substrates to form a seal pattern; dripping liquid crystal onto an area surrounded by the seal pattern of the one substrate and/or onto the other substrate while the seal pattern is in an uncured state; overlapping the one substrate and the other substrate via the seal pattern and the liquid crystal; and curing the seal pattern.

[9] The method for manufacturing a liquid crystal display panel according to [8], wherein at least one of the pair of substrates has an alignment film on a surface in contact with the liquid crystal.
[10] The method for manufacturing a liquid crystal display panel according to [8] or [9], wherein the seal pattern is irradiated with light in the step of curing the seal pattern.

[11] The method for manufacturing a liquid crystal display panel according to any one of [8] to [10], wherein in the step of curing the seal pattern, the seal pattern is irradiated with light and then heated.
[12] The method for manufacturing a liquid crystal display panel according to [10] or [11], wherein the light irradiated to the seal pattern includes light in the visible light region.

The present invention provides the following liquid crystal display panel.
[13] A liquid crystal display panel including a pair of substrates, a frame-shaped sealing member disposed between the pair of substrates, and liquid crystal disposed inside the pair of substrates and the sealing member, wherein the frame-shaped sealing member is a cured product of the liquid crystal sealant described in [7].

The photocurable resin composition of the present invention forms a sealing member that has high adhesive strength to the substrate and high moisture resistance.

In this specification, a numerical range expressed using "~" means a range including the numerical values written before and after "~" as the lower and upper limits. In this specification, the amount of each component in a composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition, unless otherwise specified. In the numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In this specification, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

1. Photocurable Resin Composition The photocurable resin composition of the present invention contains a curable compound (A) having an ethylenically unsaturated double bond in the molecule, a photopolymerization initiator (B), organic fine particles (C), and a coupling agent (D).

In conventional photocurable resin compositions (liquid crystal sealants), the substrate and the cured product of the photocurable resin composition (hereinafter also referred to as the "sealing member") are firmly bonded together by covalent bonding between the functional groups present on the substrate surface and the compounds in the photocurable resin composition. However, when the substrate has an alignment film on its surface, the covalent bond is not sufficiently formed, and the adhesive strength between the substrate and the sealing member cannot be sufficiently increased. In addition, when an attempt is made to increase the stress applied to the substrate and the sealing member by reducing the crosslink density of the sealing member and increasing the flexibility of the sealing member, the moisture resistance of the sealing member tends to decrease, which can affect the liquid crystal, etc.

In contrast, in the photocurable resin composition of the present invention, the coupling agent (D) has at least one chemical structure selected from the group consisting of butadiene rubber, butadiene styrene rubber, acrylic rubber, and silicone rubber. When a seal member is formed, such a coupling agent (D) is oriented in large amounts at the interface between the substrate and the seal member. The main causes of peeling between the seal member and the substrate include residual stress generated when the photocurable resin composition (liquid crystal sealant) is cured, and peel stress applied in the direction of peeling between the substrate and the seal member. When the coupling agent (D) is present between the seal member and the substrate, the structure derived from rubber relieves the residual stress and peel stress. On the other hand, the coupling agent (D) exerts its effect with the addition of a small amount. Therefore, the coupling agent (D) is unlikely to affect the crosslink structure and crosslink density of the curable compound (A), and the moisture resistance of the seal member can be maintained at a high level.

Below, each component in the photocurable resin composition of the present invention is described in detail.

1-1. Curable compound (A)
The curable compound (A) may be any compound having an ethylenically unsaturated double bond in the molecule. The curable compound (A) may be any of a monomer, an oligomer, and a polymer. Examples of the compound (A) include a compound having a (meth)acryloyl group in the molecule. The number of (meth)acryloyl groups per molecule of the compound having a (meth)acryloyl group is one. In this specification, the term "(meth)acryloyl group" means an acryloyl group or a methacryloyl group, or both of these. In addition, the term "(meth)acrylate" means The term (meth)acrylic means either acrylic or methacrylic, or both.

Examples of curable compounds (A) containing one (meth)acryloyl group per molecule include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate.

Examples of the curable compound (A) having two or more (meth)acryloyl groups in one molecule include di(meth)acrylates derived from polyethylene glycol, propylene glycol, polypropylene glycol, etc.; di(meth)acrylates derived from tris(2-hydroxyethyl)isocyanurate; di(meth)acrylates derived from a diol obtained by adding 4 or more moles of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol; di(meth)acrylates derived from a diol obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A; di- or tri(meth)acrylates derived from a triol obtained by adding 3 or more moles of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane; di(meth)acrylates derived from a diol obtained by adding 4 or more moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A; tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate acrylate; trimethylolpropane tri(meth)acrylate or oligomer thereof; pentaerythritol tri(meth)acrylate or oligomer thereof; poly(meth)acrylate of dipentaerythritol; tris(acryloxyethyl)isocyanurate; caprolactone-modified tris(acryloxyethyl)isocyanurate; caprolactone-modified tris(methacryloxyethyl)isocyanurate; poly(meth)acrylate of alkyl-modified dipentaerythritol; poly(meth)acrylate of caprolactone-modified dipentaerythritol; hydroxypivalic acid neopentyl glycol di(meth)acrylate; caprolactone-modified hydroxypivalic acid neopentyl glycol di(meth)acrylate; ethylene oxide-modified phosphate (meth)acrylate; ethylene oxide-modified alkylated phosphate (meth)acrylate; neopentyl glycol, trimethylolpropane, oligo(meth)acrylate of pentaerythritol, and the like.

The curable compound (A) may further have an epoxy group in the molecule. The number of epoxy groups per molecule may be one or more. When the curable compound (A) has not only a (meth)acryloyl group but also an epoxy group in the molecule, the photocurable resin composition can be cured by heat. In other words, it is possible to use photocuring and heat curing in combination. When the photocurable resin composition has photocurability and heat curability, it is possible to cure the photocurable resin composition efficiently in a short time.

An example of a curable compound (A) having a (meth)acryloyl group and an epoxy group in the molecule includes (meth)acrylic acid glycidyl ester obtained by reacting an epoxy compound with (meth)acrylic acid in the presence of a basic catalyst.

The epoxy compound to be reacted with (meth)acrylic acid may be a polyfunctional epoxy compound having two or more epoxy groups in the molecule, and from the viewpoint of suppressing a decrease in the adhesiveness of the cured product of the photocurable resin composition due to an excessive increase in crosslink density, a bifunctional epoxy compound is preferred. Examples of bifunctional epoxy compounds include bisphenol-type epoxy compounds (bisphenol A type, bisphenol F type, 2,2'-diallyl bisphenol A type, bisphenol AD type, hydrogenated bisphenol type, etc.), biphenyl-type epoxy compounds, and naphthalene-type epoxy compounds. Among them, bisphenol-type epoxy compounds of bisphenol A type and bisphenol F type are preferred from the viewpoint of improving the coatability of the photocurable resin composition. The curable compound (A) derived from a bisphenol-type epoxy compound has an advantage of being superior in coatability compared to the curable compound (A) derived from a biphenyl ether type epoxy compound.

The curable compound (A) may contain only one of the above compounds, or may contain two or more of them. In particular, it is preferable that the curable compound (A) contains a compound (A1) having a (meth)acryloyl group and no epoxy group in the molecule, and a compound (A2) having a (meth)acryloyl group and an epoxy group in the molecule. For example, when the photocurable resin composition further contains other curable compounds (e.g., epoxy compounds) described later, the compatibility between the compound (A1) and the epoxy compound may be low. In contrast, when the photocurable resin composition is combined with a compound (A2) having an epoxy group, the compatibility between the curable compound (A) and other resins in the photocurable resin composition is increased. In addition, generally, when the photocurable resin composition is used as a liquid crystal sealant, a hydrophobic compound (e.g., an epoxy compound) is more likely to dissolve into the liquid crystal than a hydrophilic compound, but by combining the compound (A1) and the compound (A2), the dissolution of the epoxy compound into the liquid crystal is more easily suppressed. The content mass ratio of the compound (A2) to the compound (A1) is preferably A2/A1=1/0.4 to 1/1.2, more preferably 1/0.8 to 1/1.2, and even more preferably 1/0.9 to 1/1.1.

The content of the compound (A2) having a (meth)acryloyl group and an epoxy group in the molecule is not particularly limited, but is preferably, for example, 30 mass% or more relative to the total amount of the curable compound (A).

In addition, in any of the above-mentioned curable compounds (A), the weight average molecular weight is preferably about 310 to 1000. The weight average molecular weight of the curable compound (A) can be measured, for example, by gel permeation chromatography (GPC) in terms of polystyrene.

The content of the curable compound (A) is preferably 40 to 80% by mass, more preferably 50 to 75% by mass, based on the total amount of the photocurable resin composition. When the amount of the curable compound (A) is within this range, the strength of the obtained cured product (e.g., a sealing member) is increased, and the adhesion between the substrate and the cured product (sealing member) can be improved.

1-2. Photopolymerization initiator (B)
The photopolymerization initiator is not particularly limited as long as it is a compound capable of radically polymerizing the curable compound (A) by irradiation with light. For example, it may be a self-cleavage type photopolymerization initiator or a hydrogen-withdrawing inorganic type photopolymerization initiator.

Examples of self-cleavage type photopolymerization initiators include alkylphenone compounds (e.g., benzyl dimethyl ketals such as 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF, IRGACURE 651); α-aminoalkylphenones such as 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one (manufactured by BASF, IRGACURE 907); 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF, IRGACURE 184) and the like), acylphosphine oxide compounds (for example, 2,4,6-trimethylbenzoin diphenylphosphine oxide, etc.), titanocene compounds (for example, bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, etc.), acetophenone compounds (for example, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl 4-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, etc.), phenyl glyoxylate compounds (e.g., methylphenyl glyoxyester, etc.), benzoin ether compounds (e.g., benzoin, benzoin methyl ether, benzoin isopropyl ether, etc.), and oxime ester compounds (e.g., 1,2-octanedione-1-[4-(phenylthio)-2-(O-benzoyloxime)] (manufactured by BASF, IRGACURE OXE01), ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime) (manufactured by BASF, IRGACURE OXE02), etc.).

Examples of hydrogen abstraction type photopolymerization initiators include benzophenone compounds (e.g., benzophenone, o-benzoyl methylbenzoate-4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 3,3'-dimethyl-4-methoxybenzophenone, etc.), thioxanthone compounds (e.g., thioxanthone, 2-chlorothioxanthone (Tokyo Chemical Industry Co., Ltd.), 1-chloro-4-propoxythioxanthone, 1-chloro-4-ethoxythioxanthone (Lambson Limited, Speedcure CPTX), 2-isopropylxanthone (Lambson Limited, Speedcure CPTX), etc.). ITX), 4-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone (manufactured by Lambson Limited, Speedcure DETX), 2,4-dichlorothioxanthone, etc.), anthraquinone-based compounds (e.g. 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 1-chloroanthraquinone, 2-hydroxyanthraquinone (manufactured by Tokyo Chemical Industry Co., Ltd., 2-hydroxyanthraquinone), 2,6-dihydroxyanthraquinone (manufactured by Tokyo Chemical Industry Co., Ltd., Anthraflavic Acid), 2-hydroxymethylanthraquinone (manufactured by Junsei Chemical Co., Ltd., 2-(Hydroxymethyl)anthraquinone), etc.) and benzyl-based compounds. The photocurable resin composition may contain only one type of photopolymerization initiator (B), or may contain two or more types.

The absorption wavelength of the photopolymerization initiator (B) is not particularly limited, and for example, a photopolymerization initiator (B) that absorbs light with a wavelength of 360 nm or more is preferred. Among them, it is more preferable that the photopolymerization initiator (B) absorbs light in the visible light region, and a photopolymerization initiator (B) that absorbs light with a wavelength of 360 to 430 nm is particularly preferred. In this specification, the "visible light region" refers to the wavelength range of 360 nm to 780 nm.

Examples of photopolymerization initiators (B) that absorb light with wavelengths of 360 nm or more include alkylphenone compounds, acylphosphine oxide compounds, titanocene compounds, oxime ester compounds, thioxanthone compounds, and anthraquinone compounds, with oxime ester compounds being preferred.

The structure of the photopolymerization initiator (B) can be identified by combining high performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC/MS) with NMR or IR measurements.

The molecular weight of the photopolymerization initiator (B) is preferably, for example, 200 or more and 5000 or less. If the molecular weight is 200 or more, when the photocurable resin composition is used as a liquid crystal sealant, the photopolymerization initiator (B) is less likely to dissolve into the liquid crystal. On the other hand, if the molecular weight is 5000 or less, the compatibility with the curable compound (A) is increased, and the curability of the photocurable resin composition is likely to be good. The molecular weight of the photopolymerization initiator (B) is more preferably 230 or more and 3000 or less, and even more preferably 230 or more and 1500 or less.

The molecular weight of the photopolymerization initiator (B) can be determined as the "relative molecular mass" of the molecular structure of the main peak detected when analyzed by high performance liquid chromatography (HPLC).

Specifically, a sample solution is prepared by dissolving the photopolymerization initiator (B) in THF (tetrahydrofuran), and a high performance liquid chromatography (HPLC) measurement is performed. The area percentage of the detected peaks (the ratio of the area of each peak to the total area of all peaks) is then calculated to confirm the presence or absence of a main peak. The main peak is the peak with the highest intensity (the peak with the highest height) among all peaks detected at a detection wavelength characteristic of each compound (for example, 400 nm for thioxanthone compounds). The relative molecular mass corresponding to the peak apex of the detected main peak can be measured by liquid chromatography mass spectrometry (LC/MS).

The amount of photopolymerization initiator (B) is preferably 0.01 to 10% by mass relative to the curable compound (A). When the amount of photopolymerization initiator (B) is 0.01% by mass or more relative to the curable compound (A), the curability of the photocurable resin composition tends to be good. When the content of photopolymerization initiator (B) is 10% by mass or less, when the photocurable resin composition is used as a liquid crystal sealant, the photopolymerization initiator (B) is less likely to dissolve into the liquid crystal. The content of photopolymerization initiator (B) is more preferably 0.1 to 5% by mass relative to the curable compound (A), even more preferably 0.1 to 3% by mass, and particularly preferably 0.1 to 2.5% by mass.

1-3. Organic fine particles (C)
The type of organic fine particles (C) contained in the photocurable resin composition is not particularly limited. Examples of the organic fine particles (C) include silicone particles, acrylic particles, styrene particles such as styrene-divinylbenzene copolymers, and The photocurable resin composition may contain only one type of organic fine particles (C), or may contain two or more types of organic fine particles (C). The average primary particle diameter of the organic fine particles (C) is 0.05 to 1.0 μm. It is preferably 13 μm, more preferably 0.1 to 10 μm, and even more preferably 0.1 to 8 μm.

The shape of the organic fine particles (C) is not particularly limited, but is preferably spherical, and more preferably truly spherical. "Spherical" means that the ratio of the minimum diameter (b) to the maximum diameter (a) of each particle, b/a, is 0.9 to 1.0. The average primary particle size of the organic fine particles (C) can be measured by a microscopic method, specifically, image analysis using an electron microscope. In addition, it is preferable that the surface of the organic fine particles (C) is smooth. If the surface is smooth, the specific surface area decreases, and the amount of organic fine particles (C) that can be added to the photocurable resin composition increases.

The content of the organic fine particles (C) is preferably 0.1 to 30 parts by mass, more preferably 0.3 to 20 parts by mass, and even more preferably 0.3 to 15 parts by mass, relative to 100 parts by mass of the photocurable resin composition. When the amount of the organic fine particles (C) is within this range, the elastic modulus of the photocurable resin composition after photocuring tends to fall within the desired range.

1-4. Coupling agent (D)
The coupling agent (D) may be a compound having at least one chemical structure (hereinafter also referred to as "rubber structure") selected from the group consisting of butadiene rubber, butadiene styrene rubber, acrylic rubber, and silicone rubber, and a group capable of reacting with a functional group present on the substrate surface of the liquid crystal display panel. Examples of the coupling agent (D) include compounds in which an organometallic compound having a group capable of reacting with a functional group present on the substrate surface of the liquid crystal display panel is bonded to the side chain or main chain of the rubber structure.

Examples of the coupling agent (D) include a silane coupling agent in which the organometallic compound is a silane-based compound, a titanate coupling agent in which the organometallic compound is a titanate-based compound, a zirconate coupling agent in which the organometallic compound is a zirconate-based compound, an aluminate coupling agent in which the organometallic compound is a zirconium aluminate-based compound, and an aluminate coupling agent in which the organometallic compound is an aluminate-based compound. Among these, silane coupling agents are particularly preferred in terms of availability and cost. The type of functional group in the organometallic compound that bonds to the metal, i.e., the group that can react with the functional group present on the substrate surface of the liquid crystal display panel, is not particularly limited, and examples thereof include alkoxy groups that can polycondense with OH groups on the substrate surface.

Here, when the coupling agent (D) is a silane coupling agent, the amount of alkoxysilyl groups derived from the coupling agent (D) in 100g of the photocurable resin composition is preferably 1.0×10 ⁻⁵ mol or more and 5.0×10 ⁻³ mol or less, more preferably 2.5×10 ⁻⁵ mol to 1.0×10 ⁻³ mol, and even more preferably 5.0×10 ⁻⁵ mol or more and 8.0×10 ⁻⁴ mol or less. In particular, when the amount of alkoxysilyl groups derived from the coupling agent (D) in 100g of the photocurable resin composition (hereinafter, the unit is also described as "mol/100g") is 5.0×10 ⁻⁵ mol/100g or more, the alkoxysilyl groups form siloxane bonds with OH groups on the substrate surface of the liquid crystal display panel, and the resulting sealing member does not become excessively hard, and it is easy to alleviate residual stresses generated during curing of the photocurable resin composition. Therefore, the adhesive strength between the obtained seal member and the substrate is high. On the other hand, when the amount of alkoxysilyl groups derived from the coupling agent (D) is 8.0× ¹⁰ mol/100 g or less, the cured product of the obtained photocurable resin composition does not become excessively soft, and moisture permeability is not easily deteriorated.

The amount of alkoxysilyl groups derived from the coupling agent (D) in the photocurable resin composition can be calculated from the following formula.
Amount of alkoxysilyl groups={(Amount (g) of coupling agent (D) having alkoxysilyl groups in 100 g of photocurable resin)/(Molecular weight of the coupling agent (D))}×(Number of alkoxysilyl groups in the coupling agent (D))

An example of a silane-based compound, which is an organometallic compound, includes a compound represented by the following structure.

On the other hand, the rubber structure contained in the coupling agent (D) is not particularly limited, and may be any of butadiene rubber, butadiene styrene rubber, acrylic rubber, and silicone rubber, and a single molecule of the coupling agent (D) may contain multiple of these structures. Among these, a coupling agent (D) having a butadiene rubber structure is preferred from the viewpoint of versatility, etc.

The number average molecular weight of the coupling agent (D) is preferably 1000 or more and 1,000,000 or less, and more preferably 2000 or more and 100,000 or less. When the molecular weight of the coupling agent (D) is 1000 or more, the rubber structure portion of the coupling agent (D) becomes sufficiently large, and it becomes easy to sufficiently relieve, for example, the stress applied between the sealing member and the substrate, and the residual stress generated during the curing of the photocurable resin composition. On the other hand, when the molecular weight of the coupling agent (D) is 1,000,000 or less, the coupling agent (D) does not excessively widen the distance between the crosslinking points of the curable compound (A), and the moisture resistance of the sealing member can be improved.

The above number average molecular weight is a value (styrene equivalent value) determined by gel permeation chromatography (GPC) using toluene, tetrahydrofuran, chloroform, etc. as a developing solvent.

Specific examples of the coupling agent (D) include compounds as shown in the following chemical formula, which are obtained by reacting a polybutadiene compound with an organosilane compound.

The coupling agent (D) represented by the above chemical formula contains a repeating unit derived from butadiene having a 2,3-vinyl structure, a repeating unit derived from butadiene having a 1,2-vinyl structure, and a repeating unit in which a silane compound is bonded to the 1,2-vinyl structure. The order of each repeating unit is not particularly limited.

In the above chemical formula, x may be 0 or more, preferably 1 to 40, and more preferably 2 to 20. Furthermore, y may be 1 or more, preferably 1 to 40, and more preferably 2 to 20. z may be 0 or more, preferably 0 to 10, and more preferably 0 to 5. a is an integer from 1 to 3, and more preferably 2 or 3.

R ¹ in the above chemical formula is preferably a substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, examples of which include alkyl groups such as methyl, ethyl, isopropyl, etc.; cycloalkyl groups such as cyclopentyl, etc.; alkenyl groups such as vinyl, etc.; aryl groups such as phenyl, tolyl, etc.; aralkyl groups such as benzyl, 2-phenylethyl, etc.; halogenated alkyl groups such as 3-chloropropyl, etc.; cyanated alkyl groups such as 2-cyanoethyl, etc. Among these, alkyl groups having 1 to 10 carbon atoms or aryl groups having 6 to 10 carbon atoms are preferred, alkyl groups are more preferred, and an ethyl group is particularly preferred.

On the other hand, ^R2 is preferably a substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, examples of which include alkyl groups such as methyl, ethyl, isopropyl, etc.; cycloalkyl groups; alkenyl groups such as allyl; aryl groups such as phenyl and tolyl; aralkyl groups such as benzyl and 2-phenylethyl; halogenated alkyl groups such as 3-chloropropyl; cyanated alkyl groups such as 2-cyanoethyl; alkyl groups containing an ether bond such as methoxyethyl; etc. Among these, alkyl groups having 1 to 10 carbon atoms or aryl groups having 6 to 10 carbon atoms are preferred, alkyl groups are more preferred, and a methyl group is particularly preferred.

The content of the coupling agent (D) is preferably 0.5 to 5 parts by mass, more preferably 1 to 4 parts by mass, and even more preferably 1 to 3 parts by mass, relative to 100 parts by mass of the photocurable resin composition. When the amount of the coupling agent (D) is 1 part by mass or more, the adhesive strength between the sealing member obtained from the photocurable resin composition and the substrate is increased. On the other hand, when the amount of the coupling agent (D) is 5 parts by mass or less, it is less likely to affect the spacing between the crosslinking points of the curable compound (A), and the moisture resistance of the sealing member is improved.

1-5. Latent heat curing agent (E)
The photocurable resin composition preferably further contains a latent heat curing agent (E). The latent heat curing agent (E) is a compound that does not cure the curable compound (A) or other curable compounds described below under normal storage conditions (room temperature, visible light, etc.), but cures these compounds when heat is applied. In other words, when the photocurable resin composition contains the latent heat curing agent (E), the photocurable resin composition becomes heat curable. The latent heat curing agent (E) is preferably, for example, a curable compound containing an epoxy group or a curing agent capable of curing the epoxy-based compound described below (hereinafter also referred to as an "epoxy curing agent").

From the viewpoint of increasing the viscosity stability of the photocurable resin composition and not impairing the moisture resistance of the cured product, the epoxy curing agent preferably has a melting point of 50°C or higher and 250°C or lower, more preferably a melting point of 100°C or higher and 200°C or lower, and even more preferably a melting point of 150°C or higher and 200°C or lower.

Examples of epoxy curing agents include dihydrazide-based thermal latent curing agents, amine adduct-based thermal latent curing agents, polyamine-based thermal latent curing agents, dicyandiamide-based thermal latent curing agents, imidazole-based thermal latent curing agents, etc. The photocurable resin composition may contain only one of these, or may contain two or more of them.

Examples of dihydrazide-based thermal latent curing agents include adipic acid dihydrazide, 1,3-bis(hydrazinocarboethyl)-5-isopropylhydantoin, 7,11-octadecadiene-1,18-dicarbohydrazide, dodecanedioic acid dihydrazide, and sebacic acid dihydrazide, etc.

Amine adduct-based heat-latent curing agents are heat-latent curing agents consisting of an addition compound obtained by reacting an amine compound having catalytic activity with any compound. Commercially available examples of amine adduct-based heat-latent curing agents include Amicure PN-40, Amicure PN-23, Amicure PN-31, Amicure PN-H, Amicure MY-24, and Amicure MY-H (all manufactured by Ajinomoto Fine-Techno Co., Ltd.).

Polyamine-based thermally latent curing agents are thermally latent curing agents having a polymer structure obtained by reacting an amine with an epoxy resin, and examples of commercially available products include ADEKA HARDENER EH4339S and ADEKA HARDENER EH4357S (both manufactured by ADEKA Corporation).

Examples of dicyandiamide-based thermal latent curing agents include dicyandiamide, etc.

Examples of imidazole-based thermal latent curing agents include 2,4-diamino-6-[2'-ethylimidazolyl-(1')]-ethyltriazine and 2-phenylimidazole.

Among the above, dihydrazide-based latent heat curing agents, amine adduct-based latent heat curing agents, and polyamine-based latent heat curing agents are preferred from the viewpoints of availability, compatibility with other components, etc. The latent heat curing agent (C) may contain only one type of epoxy curing agent, or may contain two or more types.

The amount of latent heat curing agent (E) is preferably 3 to 30 parts by mass, more preferably 3 to 20 parts by mass, and even more preferably 5 to 20 parts by mass, per 100 parts by mass of the total amount of the photocurable resin composition. The photocurable resin composition may be a one-component curable resin composition. One-component curable resin compositions have excellent workability because there is no need to mix the base agent and the curing agent when using them.

1-6. Inorganic filler (F)
The photocurable resin composition may further contain an inorganic filler (F) as necessary. When the photocurable resin composition contains the inorganic filler (F), the viscosity of the photocurable resin composition, the strength of the cured product, the linear expansion property, etc. tend to be good.

Examples of inorganic fillers (F) include calcium carbonate, magnesium carbonate, barium sulfate, magnesium sulfate, aluminum silicate, zirconium silicate, iron oxide, titanium oxide, titanium nitride, aluminum oxide (alumina), zinc oxide, silicon dioxide, potassium titanate, kaolin, talc, glass beads, sericite activated clay, bentonite, aluminum nitride, silicon nitride, etc. Among these, silicon dioxide and talc are preferred.

The shape of the inorganic filler (F) may be regular, such as spherical, plate-like, or needle-like, or may be irregular. When the inorganic filler (F) is spherical, the average primary particle size of the inorganic filler (F) is preferably 1.5 μm or less, and the specific surface area is more preferably 0.5 to 20 m ² /g. The average primary particle size of the inorganic filler (F) can be measured by the laser diffraction method described in JIS Z8825-1. The specific surface area of the filler can be measured by the BET method described in JIS Z8830.

The amount of inorganic filler (F) is preferably 5 to 15 parts by mass relative to 100 parts by mass of the total amount of the photocurable resin composition. When the amount of inorganic filler (F) is 5 parts by mass or more, the moisture resistance of the cured product (sealing member) of the photocurable resin composition is likely to be increased, and when it is 10 parts by mass or less, the coating stability of the photocurable resin composition is unlikely to be impaired. The content of inorganic filler (F) is more preferably 5 to 10 parts by mass relative to the photocurable resin composition.

1-7. Other Curable Compounds The photocurable resin composition may further contain a thermosetting compound. However, the thermosetting compound is a compound different from the above-mentioned curable compound (A).

Examples of thermosetting compounds include epoxy compounds having an epoxy group in the molecule. The epoxy compound may be any of a monomer, oligomer, or polymer. When the photocurable resin composition contains an epoxy compound, the display characteristics of the resulting liquid crystal panel are improved, and the moisture resistance of the cured product (sealing member) is also improved.

It is particularly preferable that the epoxy compound has an aromatic ring. The weight average molecular weight of the epoxy compound is preferably 500 to 10,000, and more preferably 1,000 to 5,000. The weight average molecular weight of the epoxy compound is measured in terms of polystyrene by gel permeation chromatography (GPC).

Examples of aromatic epoxy compounds include aromatic diols such as bisphenol A, bisphenol S, bisphenol F, bisphenol AD, etc., and diols obtained by modifying these aromatic diols with ethylene glycol, propylene glycol, alkylene glycol, etc., and aromatic polyhydric glycidyl ether compounds obtained by reacting epichlorohydrin with epichlorohydrin; novolac resins derived from phenol or cresol and formaldehyde, polyphenols such as polyalkenylphenols and their copolymers, etc., and novolac-type polyhydric glycidyl ether compounds obtained by reacting epichlorohydrin with epichlorohydrin; glycidyl ether compounds of xylylene phenol resins, etc. Among these, cresol novolac type epoxy compounds, phenol novolac type epoxy compounds, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, triphenol methane type epoxy compounds, triphenol ethane type epoxy compounds, trisphenol type epoxy compounds, dicyclopentadiene type epoxy compounds, diphenyl ether type epoxy compounds, and biphenyl type epoxy compounds are preferred. The photocurable resin composition may contain only one type of epoxy compound, or may contain two or more types of epoxy compounds.

The epoxy compound may be liquid or solid. From the viewpoint of increasing the moisture resistance of the cured product, a solid epoxy compound is preferred. The softening point of a solid epoxy compound is preferably 40°C or higher and 150°C or lower. The softening point can be measured by the ring and ball method specified in JIS K7234.

The content of the thermosetting compound is preferably 3 to 20 parts by mass per 100 parts by mass of the photocurable resin composition. When the amount of the thermosetting compound is 3 parts by mass or more, it is easy to effectively improve the moisture resistance of the cured product (sealing member) of the photocurable resin composition. When the content of the thermosetting compound is 20 parts by mass or less, the photocurable resin composition is less likely to experience excessive viscosity increase. The amount of the thermosetting compound is more preferably 3 to 15 parts by mass, and even more preferably 4 to 15 parts by mass per 100 parts by mass of the photocurable resin composition.

The content of the thermosetting compound is preferably 3.8 to 50 parts by mass, more preferably 5 to 30 parts by mass, per 100 parts by mass of the curable compound (A). When the content of the thermosetting compound relative to the curable compound (A) is 3.8 parts by mass or more, the moisture resistance of the cured product and the adhesive strength to the glass substrate are further improved. On the other hand, when the content is 50 parts by mass or less, compatibility with the curable compound (A) during production is likely to be good.

1-8. Other Compounds The photocurable resin composition of the present invention may further contain additives such as a thermal radical polymerization initiator, a silane coupling agent other than the above-mentioned coupling agent (D), an ion trapping agent, an ion exchange agent, a leveling agent, a pigment, a dye, a sensitizer, a plasticizer, and an antifoaming agent, as necessary.

Examples of silane coupling agents include vinyltrimethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, etc. The content of the silane coupling agent is preferably 0.01 to 5 parts by mass per 100 parts by mass of the curable compound (A). When the content of the silane coupling agent is 0.01 part by mass or more, the cured product of the photocurable resin composition is more likely to be improved.

The photocurable resin composition of the present invention may further contain spacers, etc. for adjusting the gap of the liquid crystal display panel.

The total amount of other components is preferably 1 to 50 parts by mass per 100 parts by mass of the total amount of the photocurable resin composition. If the total amount of other components is 50 parts by mass or less, the viscosity of the photocurable resin composition is unlikely to increase excessively, and the coating stability of the photocurable resin composition is unlikely to be impaired.

The viscosity of the photocurable resin composition of the present invention as measured with an E-type viscometer at 25° C. and 2.5 rpm is preferably 200 to 450 Pa·s, and more preferably 300 to 400 Pa·s. When the viscosity is within the above range, the photocurable resin composition can be easily applied with a dispenser.

The photocurable resin composition of the present invention can be used as a sealant as described above. The photocurable resin composition is particularly suitable as a display element sealant used to seal display elements such as liquid crystal display elements, organic EL elements, and LED elements. In addition, the photocurable resin composition of the present invention is highly suitable as a liquid crystal sealant for the liquid crystal dropping method because it is unlikely to contaminate the liquid crystal.

2. Liquid crystal display panel and its manufacturing method The liquid crystal display panel of the present invention includes a pair of substrates (a display substrate and an opposing substrate) each having an alignment film, a frame-shaped seal member disposed between the alignment films of the pair of substrates, and a liquid crystal layer filled in the space surrounded by the seal member between the pair of substrates. The seal member is a cured product of the above-mentioned photocurable resin composition (liquid crystal sealant).

The display substrate and the counter substrate are both transparent substrates. The material of the transparent substrate may be an inorganic material such as glass, or a plastic such as polycarbonate, polyethylene terephthalate, polyethersulfone, or PMMA.

A matrix-shaped TFT, a color filter, a black matrix, etc. may be arranged on the surface of the display substrate or the counter substrate. An alignment film is further arranged on the surface of the display substrate or the counter substrate. The alignment film contains a known organic alignment agent or an inorganic alignment agent.

As mentioned above, the sealing material obtained from a general liquid crystal sealant may have low adhesion to these alignment films. In contrast, the above-mentioned photocurable resin composition (liquid crystal sealant) has an alkoxy group that reacts with the substrate surface, and therefore the coupling agent (D) present near the interface with the substrate has a rubber structure in its molecular structure, which can alleviate the residual stress that occurs in the sealant when cured at the particularly fragile interface between the substrate and the sealant, and absorb the stress applied from the outside to the liquid crystal display panel. Therefore, even if the sealant is placed in the area where the alignment film is formed, peeling is unlikely to occur at these interfaces. Therefore, the liquid crystal display panel of the present invention can achieve a narrow frame.

The liquid crystal display panel is manufactured using the liquid crystal sealant of the present invention. There are generally two methods for manufacturing liquid crystal display panels: the liquid crystal dropping method and the liquid crystal injection method. It is preferable that the liquid crystal display panel of the present invention is manufactured by the liquid crystal dropping method.

The manufacturing method for liquid crystal display panels using the liquid crystal dropping method is as follows:
1) A step of applying the above-mentioned liquid crystal sealant in a pattern shape (frame shape) on the alignment film of one of a pair of substrates each having an alignment film to form a seal pattern;
2) dropping liquid crystal onto one of the substrates in an area surrounded by the seal pattern or onto the other substrate while the seal pattern is in an uncured state;
3) superposing one substrate and the other substrate via the seal pattern and the liquid crystal;
4) curing the seal pattern.

In step 1), the liquid crystal sealant is applied to the desired shape. There are no particular restrictions on the application method, and any general method can be used. At this time, there are no particular restrictions on the width of the seal pattern to be formed, but the above-mentioned liquid crystal sealant has high adhesive strength with the substrate. Therefore, it is possible to make the width of the sealant approximately 0.3 mm to 0.6 mm.

In step 2), the seal pattern being uncured means that the curing reaction of the liquid crystal sealant has not progressed to the gel point. For this reason, in step 2), the seal pattern may be semi-cured by irradiating it with light or heating in order to suppress dissolution of the liquid crystal sealant into the liquid crystal. One substrate and the other substrate are a display substrate or a counter substrate, respectively. In addition, when liquid crystal is dropped onto the other substrate in step 2), the liquid crystal is dropped so that it fits inside the seal pattern when the two substrates are superimposed in step 3).

In step 4), curing by light irradiation alone may be performed, but curing by heating may also be performed after curing by light irradiation. Curing by light irradiation allows the liquid crystal sealant to be cured in a short time, thereby suppressing dissolution into the liquid crystal. Combining curing by light irradiation and curing by heating reduces damage to the liquid crystal layer caused by light compared to curing by light irradiation alone.

The light to be irradiated is selected appropriately depending on the type of photopolymerization initiator (B) in the above-mentioned liquid crystal sealant (photocurable resin composition), but light in the visible light region is preferred, for example light with a wavelength of 370 to 450 nm. This is because light of the above wavelengths causes relatively little damage to the liquid crystal material and driving electrodes. For the light irradiation, known light sources that emit ultraviolet light or visible light can be used. When irradiating visible light, high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, xenon lamps, fluorescent lamps, etc. can be used.

The light irradiation energy may be sufficient as long as the curable compound (A) can be cured. The light curing time depends on the composition of the liquid crystal sealant, but is, for example, about 10 minutes.

The heat curing temperature depends on the composition of the liquid crystal sealant, but is, for example, 120°C, and the heat curing time is approximately 2 hours.

The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited in any way by these examples, and the embodiments can be modified without departing from the spirit of the present invention.

1. Preparation of Materials 1-1. Preparation of Curable Compound (A) The following curable compounds (A-1) to (A-4) were prepared.
Curable compound (A-1): Methacrylic-modified bisphenol F-type epoxy resin prepared in Synthesis Example 1 below. Curable compound (A-2): Acrylic resin (Light Acrylate 14EG-A, manufactured by Kyoei Chemical Co., Ltd.).
Curable compound (A-3): acrylic resin prepared in Synthesis Example 2 below. Curable compound (A-4): methacrylic-modified bisphenol F epoxy resin prepared in Synthesis Example 3 below.

Synthesis Example 1 Synthesis of Curable Compound (A- 1 ) 160 g of liquid bisphenol F type epoxy resin (Epotohto YDF-8170C, manufactured by Tohto Kasei Co., Ltd., epoxy equivalent 160 g/eq), 0.1 g of polymerization inhibitor (p-methoxyphenol), 0.2 g of catalyst (triethanolamine), and 43.0 g of methacrylic acid were charged into a flask, and reacted for 5 hours while feeding dry air and stirring under reflux at 90° C. The obtained resin was washed 20 times with ultrapure water to obtain a curable compound (A- 1 ) (methacrylic acid modified bisphenol F type epoxy resin (partially modified methacrylated product)).

[Synthesis Example 2] Synthesis of curable compound (A-3) 116 g of 2-hydroxyethyl acrylate, 0.1 g of a polymerization inhibitor (p-methoxyphenol), and 100 g of succinic anhydride were charged into a flask, and dry air was pumped in and the mixture was reacted for 5 hours while refluxing and stirring at 90°C. Subsequently, 170 g of bisphenol A diglycidyl ether was added, and the mixture was reacted for 5 hours while refluxing and stirring at 90°C. The obtained resin was washed 20 times with ultrapure water to obtain a curable compound (A-3).

Synthesis Example 3 Synthesis of Curable Compound (A-4) 160 g of liquid bisphenol F type epoxy resin (Epotohto YDF-8170C, manufactured by Tohto Kasei Co., Ltd., epoxy equivalent 160 g/eq), 0.1 g of polymerization inhibitor (p-methoxyphenol), 0.2 g of catalyst (triethanolamine), and 81.7 g of methacrylic acid were charged into a flask, and reacted for 5 hours while feeding dry air and stirring under reflux at 90° C. The obtained resin was washed 20 times with ultrapure water to obtain a curable compound (A-4) (methacrylic acid modified bisphenol F type epoxy resin (95 mol% partially modified methacrylate)).

1-2. Preparation of Photopolymerization Initiator (B) As the photopolymerization initiator (B), IRGACURE OXE01, manufactured by BASF Japan, was prepared.

1-3. Preparation of Organic Fine Particles (C) As organic fine particles (C), fine particle polymer F351, manufactured by Aica Kogyo Co., Ltd., was prepared.

（上記化学式において、Ｒはアルキル基）
・カップリング剤（Ｄ－２）：シランカップリング剤（ＫＢＭ－４０３、信越シリコーン社製、分子量：２３６、アルコキシシリル基数：１） 1-4. Preparation of Coupling Agent (D) The following coupling agents (D-1) and (D-2) were prepared.
Coupling agent (D-1): A commercially available silane coupling agent represented by the following chemical formula (average molecular weight: 6000, number of alkoxysilyl groups: 1)

(In the above formula, R is an alkyl group.)
Coupling agent (D-2): Silane coupling agent (KBM-403, manufactured by Shin-Etsu Silicones, molecular weight: 236, number of alkoxysilyl groups: 1)

1-5. Preparation of Latent Heat Curing Agent (E) The following latent heat curing agents (E-1) and (E-2) were prepared.
Latent heat curing agent (E-1): adipic dihydrazide (ADH, manufactured by Nippon Kasei Co., Ltd., melting point 177 to 184°C)
Latent heat curing agent (E-2): Modified polyamine (EH-5030S, manufactured by ADEKA Corporation)

1-6. Preparation of Inorganic Filler (F) As the inorganic filler (F), silica particles (S-100, manufactured by Nippon Shokubai Kagaku Co., Ltd.) were prepared.

1-7. Preparation of other compounds The following compounds were also prepared.
Epoxy resin: YL983U, manufactured by Mitsubishi Chemical Corporation Polyisoprene rubber 1: UC-102, manufactured by Kuraray Co., Ltd. (weight average molecular weight: 17,000)
Polyisoprene rubber 2: UC-203M, manufactured by Kuraray Co., Ltd. (weight average molecular weight: 35,000)
Polybutadiene rubber: LBR-361, manufactured by Kuraray Co., Ltd. (weight average molecular weight: 5,500)
Polystyrene butadiene rubber: Ricon 100, manufactured by Cray Valley (weight average molecular weight: 4,500)

2. Preparation of resin composition 2-1. Example 1
8 parts by mass of epoxy resin, 54 parts by mass of the curable compound (A-1) obtained in Synthesis Example 1, 2 parts by mass of curable compound (A-2) (polyethylene glycol diacrylate), 5 parts by mass of the curable compound (A-3) obtained in Synthesis Example 2, 5 parts by mass of the curable compound (A-4) obtained in Synthesis Example 3, 1 part by mass of photopolymerization initiator (B), 12 parts by mass of organic fine particles (C), 2 parts by mass of coupling agent (D-1), 5 parts by mass of latent heat curing agent (E-1) (adipic acid dihydrazide), and 6 parts by mass of inorganic filler (F) (silica particles) were thoroughly mixed using a three-roll mill to obtain a uniform composition, thereby obtaining a photocurable resin composition.

2-2. Examples 2 to 4 and Comparative Examples 1 to 5
Photocurable resin compositions were prepared in the same manner as in Example 1, except that the compositions were changed as shown in Table 1.

3. Evaluation The amount of alkoxysilyl groups in the photocurable resin compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were evaluated by the following methods in terms of compatibility, adhesive strength, and moisture permeability. The results are shown in Table 1.

3-1. Amount of alkoxysilyl groups in photocurable resin composition The amount of alkoxysilyl groups (mol/100 g) in 100 g of photocurable resin composition was determined as follows.
Amount of alkoxysilyl groups (mol/100 g)={(Amount of coupling agent (D) having an alkoxysilyl group in 100 g of photocurable resin (g))/(Molecular weight of the coupling agent (D))}×(Number of alkoxysilyl groups in the coupling agent (D))

As described above, the photocurable resin composition was mixed uniformly using a triple roll and placed in a container and left to stand for 10 minutes. Thereafter, the presence or absence of separation was visually checked and judged according to the following criteria.
○: No separation ×: Separation observed

3-3. Adhesion strength test The obtained photocurable resin composition was applied in a frame shape on one of a pair of substrates (40 mm x 45 mm glass substrate (RT-DM88-PIN, EHC)) on which a transparent electrode and an alignment film had been formed in advance, using a dispenser (Shot Master, Musashi Engineering Co., Ltd.) to form a seal pattern. The seal pattern was formed in a 38 mm x 38 mm rectangular shape with a cross-sectional area of 2500 μm ² (corresponding to a frame width of 0.5 mm). Note that the frame width of the seal material for recent liquid crystal displays is as narrow as 1.8 mm and generally about 8 mm, and this test is a severe condition for an adhesion strength test with an extremely narrow line width. One glass substrate on which the seal pattern was formed and the other glass substrate were bonded together under reduced pressure so that the orientation of the alignment film was perpendicular to each other, and then the substrate was opened to the atmosphere. The two bonded glass substrates were then held in a light-shielding box for one minute. Thereafter, the plate was irradiated with light including visible light (light having a wavelength of 370 to 450 nm) at 3000 mJ/ ^cm2 , and then heated at 120°C for 1 hour to cure the photocurable resin composition, thereby obtaining a test piece.

An indentation tester (Model 210, manufactured by Intesco) was pressed vertically into the corner of the seal member of the obtained test piece at a distance of 4.5 mm from the corner, at a speed of 5 mm/min, and the stress at which the seal peeled off was measured. The adhesive strength was calculated by dividing the stress by the line width of the seal member. The adhesive strength was evaluated as follows.
◯: 15 N/mm or more △: 10 N/mm or more but less than 15 N/mm ×: Less than 10 N/mm

3-4. Moisture permeability measurement The moisture permeability of the photocurable resin composition was measured by a moisture permeability cup method in accordance with JIS: Z0208. Specifically, the above-mentioned photocurable resin composition was applied to a release paper in a film thickness of 100 μm using an applicator. The release paper on which the coating film of the photocurable resin composition was formed was irradiated with ultraviolet light ^at 3 J/cm2. After that, it was kept in a hot air drying oven at 120°C for 60 minutes, and then removed and cooled. Then, the coating film was peeled off from the release paper to obtain a film with a film thickness of 100 μm.

From the obtained 100 μm film, an aluminum cup was prepared by a method conforming to JIS: Z0208, and left in a high-temperature, high-humidity chamber at 60° C. and 90% RH for 24 hours. Then, from the mass before and after leaving in the high-temperature, high-humidity chamber, the moisture permeability was calculated by the following formula.
Moisture permeability (g/ ^m2 ·100 μm·24 h)=[weight of aluminum cup after standing for 24 h (g)−weight of aluminum cup before standing (g)]/film area ( ^m2 )
The moisture permeability was evaluated according to the following criteria.
〇: Less than 100g/ ^m2 , 100μm, 24h △: 100g/ ^m2 , 100μm, 24h or more and less than 130g/ ^m2 , 100μm, 24h ×: 130g/ ^m2 , 100μm, 24h or more

As shown in Table 1, the photocurable resin composition containing the coupling agent (D-1) having a butadiene rubber structure had high adhesive strength with the substrate and low moisture permeability (Examples 1 to 6). In contrast, when the coupling agent did not have a rubber structure, the adhesive strength did not increase (Comparative Example 1). In addition, when various rubbers were added instead of the coupling agent, the adhesive strength did not increase sufficiently and the moisture permeability increased (Comparative Examples 2 to 5). It is believed that the difference between the Examples and Comparative Examples is evident because the adhesive strength test was evaluated at a width narrower than the width of the frame of the conventional sealing material. Furthermore, when the coupling agent without a rubber structure and the rubber were added separately, the adhesive strength decreased and the moisture permeability was also high (Comparative Examples 6 and 7). Furthermore, even if the amount of the coupling agent without a rubber structure was increased or decreased, it was difficult to achieve both adhesive strength and reduced moisture permeability (Comparative Examples 8 and 9). It is believed that in Comparative Example 9, although the amount of alkoxysilyl groups was high, the adhesive strength was low because there was no structure (rubber structure) that relieves stress.

This application claims priority from Japanese Patent Application No. 2021-030188, filed February 26, 2021. The entire contents of said application specification are incorporated herein by reference.

The photocurable resin composition of the present invention forms a sealing member that has high adhesive strength to the substrate and high moisture resistance. Therefore, the photocurable resin composition is very useful as a sealing agent for various display elements.

Claims (11)

A curable compound (A) having an ethylenically unsaturated double bond in the molecule,
A photopolymerization initiator (B),
Organic fine particles (C), and a coupling agent (D),
A photocurable resin composition comprising:
The curable compound (A) includes a compound (A1) having a (meth)acryloyl group and no epoxy group in the molecule, and a compound (A2) having a (meth)acryloyl group and an epoxy group in the molecule,
the coupling agent (D) is a coupling agent having at least one chemical structure selected from the group consisting of butadiene rubber, butadiene styrene rubber, acrylic rubber, and silicone rubber;
the amount of the curable compound (A) is 40 to 80% by mass based on the total amount of the photocurable resin composition,
the amount of the photopolymerization initiator (B) is 0.01 to 10% by mass based on the amount of the curable compound (A);
the amount of the organic fine particles (C) is 0.1 to 30 parts by mass per 100 parts by mass of the total amount of the photocurable resin composition,
the amount of the coupling agent (D) is 0.5 to 5 parts by mass per 100 parts by mass of the total amount of the photocurable resin composition;
the coupling agent (D) contains an alkoxysilyl group,
the amount of the alkoxysilyl group derived from the coupling agent (D) in 100 g of the photocurable resin composition is 1.0×10 ⁻⁵ mol or more and 8.0×10 ⁻⁴ mol or less;
Photocurable resin composition. The coupling agent (D) is a silane coupling agent having a butadiene rubber structure.
The photocurable resin composition according to claim 1. Further containing at least one latent heat curing agent (E) selected from the group consisting of dihydrazide-based latent heat curing agents, amine adduct-based latent heat curing agents, and polyamine-based latent heat curing agents;
The photocurable resin composition according to claim 1 or 2 . Further containing an inorganic filler (F),
The content of the inorganic filler (F) is 5 to 15 parts by mass based on 100 parts by mass of the total amount of the photocurable resin composition.
The photocurable resin composition according to any one of claims 1 to 3 . A liquid crystal sealant comprising the photocurable resin composition according to any one of claims 1 to 4 . A step of applying the liquid crystal sealant according to claim 5 in a pattern on at least one of a pair of substrates to form a seal pattern;
dropping liquid crystal onto an area surrounded by the seal pattern of one of the substrates and/or onto the other substrate while the seal pattern is in an uncured state;
a step of overlapping the one substrate and the other substrate with the seal pattern and the liquid crystal interposed therebetween;
curing the seal pattern;
Including,
A method for manufacturing a liquid crystal display panel. At least one of the pair of substrates has an alignment film on a surface in contact with the liquid crystal.
The method for manufacturing the liquid crystal display panel according to claim 6 . In the step of curing the seal pattern,
Irradiating the seal pattern with light;
A method for manufacturing the liquid crystal display panel according to claim 6 or 7 . In the step of curing the seal pattern,
The seal pattern is irradiated with light and then heated.
A method for manufacturing the liquid crystal display panel according to any one of claims 6 to 8 . The light irradiated to the seal pattern includes light in the visible light region.
The method for manufacturing the liquid crystal display panel according to claim 8 or 9 . A liquid crystal display panel including a pair of substrates, a frame-shaped seal member disposed between the pair of substrates, and liquid crystal disposed inside the pair of substrates and the seal member,
The frame-shaped sealing member is a cured product of the liquid crystal sealant according to claim 5 .
LCD display panel.