Sealant for display element, cured product thereof, and display device

Abstract

A sealing material for display elements which comprises polymerizable compounds and a curing agent, wherein the polymerizable compounds include ingredient (A), which is a (meth)acrylate having a bi- or higher-functional alicyclic structure, and ingredient (B), which is a (meth)acrylate having a bifunctional chain structure, the content of the ingredient (A) being 60 parts by mass or less per 100 parts by mass of the sum of the ingredients (A) and (B). The sealing material for display elements has a content of ingredient (C), which is a monofunctional (meth)acrylate, of 1 part by mass or less per 100 parts by mass of the polymerizable compounds.

Description

[Technical Field]

[0001] The present invention relates to a sealant for a display element, a cured product thereof, and a display device. [Background technology]

[0002] In the field of display devices, efforts are being made to improve the properties of sealants, and the following will explain this by taking an organic EL display device as an example. Due to their low power consumption, organic EL elements are increasingly being used in displays, lighting devices, etc. Because organic EL elements are susceptible to deterioration due to moisture and oxygen in the atmosphere, they are sealed with various sealing materials before use, and improving the durability of these sealing materials against moisture and oxygen is required for practical use.

[0003] As a method for sealing an organic EL, for example, a method is used in which a first inorganic material film is coated on an organic EL element, a resin layer is formed on the top, and then a second inorganic material film is coated on the top. Examples of the method for coating with the inorganic material film include a method of forming an inorganic material film made of silicon nitride or silicon oxide by a sputtering method or an electron cyclotron resonance (ECR) plasma CVD method.

[0004] A technology using an acrylic resin for the resin layer is described in Patent Document 1 (WO 2019 / 82996). This document describes the use of a combination of an acyclic alkanediol di(meth)acrylate having 6 or more carbon atoms and a cyclic monomer containing a cyclic monofunctional (meth)acrylate and a cyclic bifunctional (meth)acrylate in a sealant for organic electroluminescent display elements. This document claims to provide a sealant that has excellent ejection properties when using an inkjet printer and also has excellent reliability for the resulting organic EL elements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 82996 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors of the present invention have investigated the use of acrylic resins in sealing layers of display devices and found that resin layers made from acrylic resins may have low plasma resistance. As a result, when an inorganic material film is formed on the resin layer by a plasma CVD method or the like, damage to the resin layer may cause pinholes to form in the inorganic material film or the resin layer to peel off from the substrate. Furthermore, when the inventors of the present invention examined the technologies described in the above patent documents, they found that Patent Document 1 had room for improvement in that the cured product had a high glass transition temperature and was therefore not suitable for devices that require flexibility.

[0007] The present invention provides a sealant for display elements that has excellent plasma resistance, and that has both a viscosity that allows stable application by an inkjet method and a low dielectric constant. [Means for solving the problem]

[0008] According to the present invention, there are provided the following sealant for a display element, a cured product, and a display device. [1] A sealant for a display element containing a polymerizable compound and a curing agent, The polymerizable compound comprises the following components (A) and (B): (A) (Meth)acrylate having a bifunctional or higher alicyclic structure (B) (Meth)acrylate having a difunctional chain structure Including, the content of the component (A) is 60 parts by mass or less relative to 100 parts by mass of the total of the components (A) and (B), The sealant for display elements, wherein the content of the component (C): a monofunctional (meth)acrylate in the sealant for display elements is 1 part by mass or less with respect to 100 parts by mass of the polymerizable compound. [2] The sealant for a display element according to [1], wherein the component (A) contains dimethylol-tricyclodecane di(meth)acrylate. [3] The sealant for display elements according to [1] or [2], wherein the component (B) is one or more (meth)acrylates selected from the group consisting of 1,12-dodecanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate. [4] The sealant for a display element according to any one of [1] to [3], which is used for sealing an organic EL display element. [5] A cured product obtained by curing the sealant for a display element according to any one of [1] to [4]. [6] a substrate; a display element disposed on the substrate; a sealing layer that covers the display element; Including, A display device, wherein the sealing layer is formed from a cured product of the sealant for a display element according to any one of [1] to [4]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a sealant for display elements that has excellent plasma resistance, and that has both a viscosity that allows stable application by an inkjet method and a low dielectric constant. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a configuration example of an organic EL display device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by common reference numerals, and descriptions thereof will be omitted where appropriate. In addition, in this embodiment, each component may be used alone or in combination of two or more. Furthermore, the symbol "to" indicating a numerical range means "greater than or equal to" or "less than or equal to," and includes both the upper and lower limits.

[0012] (Sealant for display elements) In this embodiment, the sealant for a display element (hereinafter, also referred to simply as "sealant") is a composition used to seal an element, and contains a polymerizable compound and a curing agent. The polymerizable compound contains the following components (A) and (B): (A) (Meth)acrylate having a bifunctional or higher alicyclic structure (B) (Meth)acrylate having a difunctional chain structure The content of component (A) is 60 parts by mass or less per 100 parts by mass of the total of components (A) and (B). The content of component (C): a monofunctional (meth)acrylate in the sealant for display elements is 1 part by mass or less per 100 parts by mass of the polymerizable compound.

[0013] Here, (meth)acrylate means at least one of acrylate and methacrylate, and (meth)acrylic means at least one of acrylic and methacrylic.

[0014] (polymerizable compound) The polymerizable compound may be any compound having a polymerizable functional group, and is preferably a compound having a radically polymerizable functional group. The polymerizable compound contains the above-mentioned components (A) and (B).

[0015] (Component (A)) Component (A) is a (meth)acrylate having a bifunctional or higher functional alicyclic structure. Specifically, component (A) is a (meth)acrylate having an alicyclic structure in its molecular structure and two or more (meth)acrylic groups, and from the viewpoint of improving strength, it is preferably a (meth)acrylate having two (meth)acrylic groups.

[0016] More specifically, component (A) has an alicyclic hydrocarbon structure in its molecular structure, and from the viewpoint of improving heat resistance, the number of carbon atoms in the alicyclic hydrocarbon structure is preferably 4 or more, more preferably 5 or more, even more preferably 6 or more, and is preferably 14 or less, more preferably 12 or less, even more preferably 10 or less. The alicyclic hydrocarbon structure may be a saturated hydrocarbon structure or an unsaturated hydrocarbon structure, but from the viewpoint of improving heat resistance, the alicyclic hydrocarbon structure is preferably a saturated hydrocarbon structure.

[0017] The alicyclic hydrocarbon structure may be a monocyclic hydrocarbon structure, or a polycyclic hydrocarbon structure such as a fused ring hydrocarbon structure or a bridged ring hydrocarbon group structure. Component (A) may contain a group containing such an alicyclic hydrocarbon structure in its molecular structure, and preferably contains a divalent group containing an alicyclic hydrocarbon structure. Specific examples of the monocyclic hydrocarbon group include groups having a cycloalkane structure such as a cyclohexylene group and a cyclohexyl group; and groups having a cycloalkene skeleton such as a cyclodecatrienediyl group and a cyclodecatriene group. Specific examples of the polycyclic hydrocarbon group include groups having a dicyclopentadiene skeleton, such as a tricyclodecanediyl group, a dicyclopentanyl group, and a dicyclopentenyl group; groups having a norbornane skeleton, such as a norbornanediyl group, an isobornanediyl group, a norbornyl group, and an isobornyl group; and groups having an adamantane skeleton, such as an adamantanediyl group and an adamantyl group.

[0018] The cyclic hydrocarbon group in component (A) is preferably a group having a dicyclopentadiene skeleton from the viewpoints of improving plasma resistance and low moisture permeability. Furthermore, from the viewpoint of improving plasma resistance and low moisture permeability, component (A) contains tricyclodecane dimethanol di(meth)acrylate, and is more preferably tricyclodecane dimethanol di(meth)acrylate.

[0019] From the viewpoint of improving heat resistance, the content of component (A) in the sealant is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, relative to 100 parts by mass of the polymerizable compound. Furthermore, from the viewpoint of improving inkjet coating properties, the content of component (A) in the sealant is preferably 60 parts by mass or less, more preferably 58 parts by mass or less, and even more preferably 56 parts by mass or less, relative to 100 parts by mass of the polymerizable compound.

[0020] (Component (B)) Component (B) is a (meth)acrylate having a bifunctional chain structure. Specifically, component (B) is a (meth)acrylate having a chain structure in its molecular structure and two or more (meth)acrylic groups, and from the viewpoint of improving strength, it is preferably a (meth)acrylate having two (meth)acrylic groups. Specific examples of the component (B) include di(meth)acrylates of alkanediols and di(meth)acrylates of (poly)alkylene glycols.

[0021] In component (B), the chain structure may be a linear structure or a branched structure. The chain structure preferably contains a divalent hydrocarbon group having a straight or branched chain, from the viewpoint of improving inkjet coating properties. The number of carbon atoms in the divalent hydrocarbon group is, for example, 1 or more, preferably 2 or more, and more preferably 4 or more, from the viewpoint of easy availability of monomers. Furthermore, from the viewpoint of improving heat resistance, the number of carbon atoms in the divalent hydrocarbon group is preferably 20 or less, and more preferably 14 or less.

[0022] More specifically, the component (B) may include 1,6-hexanediol diacrylate (e.g., A-HD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.), 1,9-nonanediol diacrylate (e.g., A-NOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.; Light Acrylate 1,9ND-A, manufactured by Kyoeisha Chemical Co., Ltd.), 1,10-decanediol diacrylate (e.g., A-DOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.), neopentyl glycol diacrylate (e.g., A-NPG, manufactured by Shin-Nakamura Chemical Co., Ltd.; Light Acrylate NP-A, manufactured by Kyoeisha Chemical Co., Ltd.), ethylene glycol diacrylate (e.g., SR206NS, manufactured by Arkema), triethylene glycol diacrylate (e.g., SR272, manufactured by Arkema), polyethylene glycol diacrylate (e.g., A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.), polypropylene glycol diacrylate (e.g., Examples of suitable dimethacrylates include APG-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.), tripropylene glycol diacrylate (e.g., SR306H (manufactured by Arkema)), 1,3-butanediol dimethacrylate (e.g., BG (manufactured by Shin-Nakamura Chemical Co., Ltd.)), 1,4-butanediol dimethacrylate (e.g., BD (manufactured by Shin-Nakamura Chemical Co., Ltd.)), 1,6-hexanediol dimethacrylate (e.g., HD-N (manufactured by Shin-Nakamura Chemical Co., Ltd.)), 1,9-nonanediol dimethacrylate (e.g., NOD-N (manufactured by Shin-Nakamura Chemical Co., Ltd.) or Light Acrylate 1,9-ND-M (manufactured by Kyoeisha Chemical Co., Ltd.)), 1,10-decanediol dimethacrylate (e.g., DOD-N (manufactured by Shin-Nakamura Chemical Co., Ltd.)), 1,12-dodecanediol dimethacrylate (e.g., SR262 (manufactured by Arkema)), and neopentyl glycol dimethacrylate (e.g., NPG (manufactured by Shin-Nakamura Chemical Co., Ltd.)).

[0023] From the viewpoint of improving the balance between the effects of improved plasma resistance, improved coating stability in the inkjet method, and low dielectric constant, component (B) is one or more (meth)acrylates selected from the group consisting of 1,12-dodecanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate.

[0024] From the viewpoint of improving inkjet coating properties, the content of component (B) in the sealant is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and still more preferably 40 parts by mass or more, relative to 100 parts by mass of the polymerizable compound. Furthermore, from the viewpoint of improving plasma resistance, the content of component (B) in the sealant is, for example, 75 parts by mass or less, preferably 60 parts by mass or less, more preferably 58 parts by mass or less, and even more preferably 56 parts by mass or less, relative to 100 parts by mass of the polymerizable compound.

[0025] Furthermore, the content of component (A) relative to 100 parts by mass of the total of components (A) and (B) is 60 parts by mass or less, preferably 58 parts by mass or less, more preferably 55 parts by mass or less, and even more preferably 50 parts by mass or less, from the viewpoint of improving inkjet coating properties. The lower limit of the content of component (A) relative to 100 parts by mass of the total of components (A) and (B) is more than 0 parts by mass, and from the viewpoint of improving plasma resistance, it is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, even more preferably 30 parts by mass or more, and still more preferably 40 parts by mass or more.

[0026] (Component (C)) Component (C) is a monofunctional (meth)acrylate. Specific examples of component (C) include mono(meth)acrylates having a linear or branched hydrocarbon group in the molecular structure and mono(meth)acrylates having an aromatic hydrocarbon group in the molecular structure. An example of the former is lauryl methacrylate, and an example of the latter is 3-phenoxybenzyl acrylate. From the viewpoint of improving plasma resistance and heat resistance, the sealant for a display element preferably does not contain component (C), that is, the content of component (C) in the sealant for a display element is preferably 0 part by mass relative to 100 parts by mass of the polymerizable compound. From a similar viewpoint, when the sealant for display elements contains component (C), the content of component (C) in the sealant for display elements is more than 0 parts by mass and 1 part by mass or less, preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, and even more preferably 0.01 parts by mass or less, relative to 100 parts by mass of the polymerizable compound.

[0027] From the viewpoint of improving the strength of the cured product, the content of the polymerizable compound in the sealant for display elements is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, still more preferably 90% by mass or more, and even more preferably 93% by mass or more, based on the total composition of the sealant. Furthermore, from the viewpoint of improving the weather resistance of the sealing material, the content of the polymerizable compound in the sealant is preferably 99.9 mass % or less, more preferably 99.5 mass % or less, even more preferably 99 mass % or less, and still more preferably 98 mass % or less, based on the total composition of the sealant.

[0028] (hardening agent) Specific examples of the curing agent include polymerization initiators. From the viewpoint of stably forming a cured product at low temperatures, the polymerization initiator is preferably a photopolymerization initiator, which is a compound that generates radicals or acids upon irradiation with ultraviolet or visible light. Examples of the photopolymerization initiator include acylphosphine oxide initiators, oxyphenylacetic acid ester initiators, benzoylformic acid initiators, and hydroxyphenyl ketone initiators.

[0029] Specific examples of the photopolymerization initiator include benzophenone, Michler's ketone, 4,4'-bis(diethylamino)benzophenone, xanthone, thioxanthone, isopropylxanthone, 2,4-diethylthioxanthone, 2-ethylanthraquinone, acetophenone, 2-hydroxy-2-methyl-4'-isopropylpropiophenone, isopropyl benzoin ether, isobutyl benzoin ether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, camphorquinone, benzanthrone, 4-dimethylaminobenzoin, and the like. Ethyl 4-dimethylaminobenzoate, Isoamyl 4-dimethylaminobenzoate, 4,4'-di(t-butylperoxycarbonyl)benzophenone, 3,4,4'-tri(t-butylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra(t-hexylperoxycarbonyl)benzophenone, 3,3'-di(methoxycarbonyl)-4,4'-di(t-butylperoxycarbonyl)benzophenone, 3,4'-di(methoxycarbonyl)-4,3'- Di(t-butylperoxycarbonyl)benzophenone, 4,4'-di(methoxycarbonyl)-3,3'-di(t-butylperoxycarbonyl)benzophenone, 2-(4'-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(3',4'-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(2',4'-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(2'-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine , 2-(4'-pentyloxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 4-[pN,N-di(ethoxycarbonylmethyl)]-2,6-di(trichloromethyl)-s-triazine, 1,3-bis(trichloromethyl)-5-(2'-chlorophenyl)-s-triazine, 1,3-bis(trichloromethyl)-5-(4'-methoxyphenyl)-s-triazine, 2-(p-dimethylaminostyryl)benzoxazole, 2-(p-dimethylaminostyryl)benzthiazole, 2-mercaptobenzothiazole, 3,3'-Carbonylbis(7-diethylaminocoumarin), 2-(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetrakis(4-ethoxycarbonylphenyl)-1,2'-biimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dibromophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole 2,2'-bis(2,4,6-trichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 3-(2-methyl-2-dimethylaminopropionyl)carbazole, 3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-dodecylcarbazole, bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-fluoropropanol phenyl-1-propanone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-1-propanone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-(dimethylamino)-1-(4-morpholinophenyl)-2-benzyl-1-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4 -(4-morpholinyl)phenyl]-1-butanone, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester, methyl benzoylformate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphinic acid ester, 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyloxime)], 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone-1-(O-acetyloxime), etc.

[0030] Among these, from the viewpoint of improving curability, the photopolymerization initiator is preferably 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-1-propanone, 2,2-dimethoxy-2-phenylacetophenone, The compound is one or more compounds selected from the group consisting of oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester, methyl benzoylformate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphinic acid ester.

[0031] Preferred commercially available photopolymerization initiators include Irgacure 184, Irgacure 651, Irgacure 127, Irgacure 1173, Irgacure 500, Irgacure 2959, Irgacure 754, Irgacure MBF, and Irgacure TPO (all manufactured by BASF), and Omnirad TPO H (manufactured by IGM Resins).

[0032] From the viewpoint of improving curability, the content of the polymerization initiator in the sealant is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and still more preferably 2% by mass or more, based on the total composition of the sealant. In addition, from the viewpoint of suppressing coloration of the sealant, the content of the polymerization initiator in the sealant is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 7% by mass or less, still more preferably 6% by mass or less, and even more preferably 5% by mass or less, based on the total composition of the sealant.

[0033] (Other ingredients) In this embodiment, the sealant may be composed of a polymerizable compound and a curing agent, or may contain other components, such as one or more additives selected from the group consisting of a tackifier, a filler, a curing accelerator, a plasticizer, a surfactant, a heat stabilizer, a flame retardant, an antistatic agent, an antifoaming agent, a leveling agent, and an ultraviolet absorber.

[0034] Next, the properties of the sealant will be described. The glass transition temperature (Tg) of the cured product of the sealant is 50° C. or higher, preferably 60° C. or higher, and more preferably 70° C. or higher, from the viewpoint of improving the heat resistance of the sealant material. From the viewpoint of improving flexibility, the Tg of the cured product of the sealant is less than 200°C, preferably 190°C or less, and more preferably 180°C or less.

[0035] Specifically, the Tg of the sealant is measured by the following method: First, the uncured sealant is sandwiched between PET films using a 100 μm thick Teflon® sheet as a mold, and is irradiated with a UV-LED having a wavelength of 395 nm at an illuminance of 1000 mW / cm. 2 , cumulative light intensity 1500mJ / cm 2 The resulting composition is cured under the following conditions: The resulting cured product is cut with a cutter into a measurement sample measuring 10 mm wide x 40 mm long. The Tg of the cured product was measured using a dynamic viscoelasticity measuring device "DMS6100" by applying a frequency of 1 Hz to a measurement sample of the cured product in air while raising the temperature from room temperature to 250°C at a rate of 5°C / min, measuring tanδ, and the temperature at the peak top of tanδ was taken as Tg.

[0036] The properties of the sealant are not limited, but the sealant is preferably liquid from the viewpoint of improving the flexibility and plasma resistance of the sealing material and from the viewpoint of being suitable for forming a cured material by a coating method such as an inkjet method.

[0037] In addition, in the embodiment, from the viewpoint of stably forming a sealing material such as a resin film, the sealant is preferably a sealant used for coating, more preferably a sealant used for coating by an inkjet method.

[0038] The viscosity of the sealant measured at 25°C and 20 rpm using an E-type viscometer is preferably 5 mPa·s or more, more preferably 8 mPa·s or more, and even more preferably 10 mPa·s or more, from the viewpoint of improving inkjet ejection properties. From the viewpoint of improving inkjet ejection properties, the viscosity of the sealant is preferably 30 mPa·s or less, more preferably less than 30.0 mPa·s, even more preferably 28.5 mPa·s or less, and even more preferably 27 mPa·s or less.

[0039] From the viewpoint of improving the sealing properties of the sealant, the dielectric constant of the cured product of the sealant is preferably less than 3.5, more preferably 3.4 or less, even more preferably 3.3 or less, even more preferably 3.2 or less, and even more preferably 3.1 or less. The dielectric constant of the cured sealant can be set to, for example, 1.0 or more. Here, the dielectric constant of the cured sealant is 1000mW / cm irradiance with a UV-LED of 395nm wavelength. 2 , cumulative light intensity 1500mJ / cm 2 The dielectric constant is measured at a frequency of 100 kHz for a cured product obtained by curing the curable composition under the conditions above.

[0040] Next, a method for producing the sealant will be described. The method for producing the sealant is not limited, and may include, for example, mixing a polymerizable compound, a curing agent, and other appropriate components, such as various additives added as needed. Examples of methods for mixing the components include a method in which the components are uniformly kneaded using various known kneading machines, such as a planetary mixer, a homodisper, a universal mixer, a Banbury mixer, a kneader, a two-roll mill, a three-roll mill, or an extruder, either alone or in combination, at room temperature or under heating, under normal pressure, reduced pressure, increased pressure, or in an inert gas stream.

[0041] The resulting sealant can also be used to form a sealing material. For example, the sealant may be applied to a substrate and then dried. Known methods such as inkjet printing, screen printing, and dispenser application can be used for application. Drying can be performed, for example, by heating to a temperature at which the polymerizable compound does not polymerize. The shape of the resulting sealing material is not limited, and it can be, for example, a film or layer.

[0042] The sealing material is, for example, a cured product obtained by curing the sealing agent in this embodiment, and more specifically, a photocured product of the sealing agent. Examples of methods for photocuring the sealant include methods of curing the sealant by irradiating it with light using a light source such as a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an excimer laser, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, a sodium lamp, a halogen lamp, a xenon lamp, an LED lamp, a fluorescent lamp, sunlight, or an electron beam irradiation device.

[0043] In this embodiment, the polymerizable compound contains components (A) and (B) in specific ratios, and the content of component (C) is within a specific range. Therefore, by using a sealant containing such a polymerizable compound and a curing agent, it is possible to obtain a sealant that has excellent plasma resistance, a viscosity that allows stable application by an inkjet method, and a low dielectric constant. By using a resin layer obtained from such a polymerizable compound as a sealant, it is possible to obtain, for example, a display device with excellent reliability.

[0044] Furthermore, the sealant obtained in this embodiment is suitable for use in sealing, for example, display elements, preferably organic EL display elements. According to this embodiment, a sealant having excellent plasma resistance, which can be stably applied by an inkjet method during the formation of a resin layer, and which has an effectively reduced dielectric constant can be obtained. Therefore, for example, damage to display elements during the manufacturing process of a display device can be effectively suppressed, and the manufacturing stability of the display device can also be improved. Below, an example of the configuration of a display device will be given, taking an organic EL display device as an example.

[0045] (Organic EL display device) In this embodiment, the organic EL display device has a layer formed of a cured product of the sealant. By protecting the organic EL element with a resin layer obtained by curing the sealant of this embodiment, it is possible to sufficiently prevent moisture from penetrating into the organic EL element, thereby maintaining high performance and durability of the organic EL element.

[0046] The organic EL display device may have either a top emission structure or a bottom emission structure. The organic EL element is preferably disposed on a substrate and is pre-coated with an inorganic material film so as to cover the region including the organic EL element before being protected by the resin layer obtained by curing the sealant of the present embodiment.

[0047] Fig. 1 is a cross-sectional view showing an example of the configuration of an organic EL display device according to this embodiment. The display device 100 shown in Fig. 1 is an organic EL display device, and includes a substrate (base layer 50), a display element (light-emitting element 10) disposed on the base layer 50, and a sealing layer 22 (which may be an overcoat layer 22 or a barrier layer 22) that covers the light-emitting element 10. The sealing layer 22 is made of, for example, a cured product of the sealant according to this embodiment. The light-emitting element 10 is specifically an organic EL display element. 1 , the display device 100 has, as layers located closer to the observation side than the light-emitting element 10, a barrier layer 21 (which may be a touch panel layer 21 or a surface protective layer 21), a sealing layer 22 (which may be an overcoat layer 22 or a barrier layer 22), a planarization layer 23 (which may be the sealing layer 23), and a barrier layer 24. The planarization layer 23 is provided on the base layer 50 so as to cover the light-emitting element 10, and the barrier layer 24 is provided on the surface of the planarization layer 23. The sealing layer 22 is provided on the base layer 50 so as to cover the planarization layer 23 and the barrier layer 24. The barrier layer 21 is provided on the sealing layer 22.

[0048] The material of the base layer 50 is not limited, and various materials can be used, such as a glass substrate, a silicon substrate, a plastic substrate, etc. A TFT substrate having a plurality of TFTs (thin film transistors) and a planarization layer on a substrate can also be used.

[0049] The inorganic material constituting the barrier layer 24, i.e., the inorganic material film, is, for example, silicon nitride (SiN x ), silicon oxide (SiO x ), aluminum oxide (Al2O3), etc. The inorganic material film may be a single layer or a laminate of multiple types of layers. Methods for covering the light emitting element 10 with an inorganic material film include, for example, sputtering and electron cyclotron resonance (ECR) plasma CVD when the inorganic material film is made of silicon nitride or silicon oxide.

[0050] Of these, the sputtering method can be carried out using, for example, argon, nitrogen, or the like, alone or in combination, as a carrier gas, under conditions of room temperature, power of 50 to 1000 W, and pressure of 0.001 to 0.1 Torr. The ECR plasma CVD method can be carried out using, for example, a mixed gas of SiH4 and O2 or a mixed gas of SiH4 and N2 under conditions of a temperature of 30°C to 100°C, a pressure of 10 mTorr to 1 Torr, a frequency of 2.45 GHz, and a power of 10 to 1000 W. The thickness of the inorganic material film formed on the light emitting element 10 is not limited, but from the viewpoint of improving sealing performance and flexibility, it is, for example, 0.01 to 10 μm, and preferably 0.1 to 5 μm.

[0051] Examples of a method for protecting the light emitting element 10 with a resin layer obtained by curing the sealant of this embodiment, such as the sealing layer 22, include a method of applying the sealant onto the light emitting element 10 and curing it. As the application method, an inkjet method is preferably used. The thickness of the resin layer is not limited, but from the viewpoint of improving sealing performance and flexibility, it is, for example, 0.1 to 50 μm, and preferably 1 to 20 μm.

[0052] In the display device 100, it is preferable to further laminate an inorganic material film (barrier layer 24) on the resin layer described above in order to enhance the effect of protecting the light emitting element 10 from moisture and oxygen in the atmosphere. The inorganic material and formation method constituting the inorganic material film laminated on the resin layer are the same as those for the inorganic material film covering the light emitting element 10 described above. The thickness of the inorganic material film formed on the resin layer is not limited, but from the viewpoint of improving sealing performance and flexibility, it is, for example, 0.01 to 10 μm, and preferably 0.1 to 5 μm.

[0053] In the display device 100, a barrier layer 24 and a sealing layer 22 are provided on the light emitting element 10, and the sealing layer 22 is made of a resin layer obtained by curing the sealant of this embodiment, so that a highly reliable display device 100 can be obtained. Specifically, even when a plasma treatment step is performed when forming the barrier layer 24 on the sealing layer 22, damage to the barrier layer 24 can be suppressed. In addition, for example, SiN x It is also possible to prevent pinholes from occurring in the barrier layer 24, which is a film. [Example]

[0054] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these. First, the materials used in the following examples are listed.

[0055] (polymerizable compound) (A) Alicyclic UV curing resin 1: Dimethylol-tricyclodecane diacrylate, Light Acrylate DCP-A, manufactured by Kyoeisha Chemical Co., Ltd. UV curing resin 2: Dimethylol-tricyclodecane dimethacrylate, Light Acrylate DCP-M, manufactured by Kyoeisha Chemical Co., Ltd. (B) Chain-like UV-curable resin 3: 1,12-dodecanediol dimethacrylate, SR262, manufactured by Arkema UV curable resin 4: 1,9-nonanediol diacrylate, Light Acrylate 1,9ND-A, manufactured by Kyoeisha Chemical Co., Ltd. UV curable resin 5: 1,9-nonanediol dimethacrylate, Light Acrylate 1,9ND-M, manufactured by Kyoeisha Chemical Co., Ltd. UV curing resin 6: Triethylene glycol diacrylate, SR272, manufactured by Arkema UV curing resin 7: Tripropylene glycol diacrylate, SR306H, manufactured by Arkema

[0056] (C)-1: Linear monofunctional UV curing resin 8: Lauryl methacrylate, Light Acrylate L, manufactured by Kyoeisha Chemical Co., Ltd. (C)-2: Aromatic monofunctional UV curing resin 9: 3-phenoxybenzyl acrylate, Light Acrylate POB-A, manufactured by Kyoeisha Chemical Co., Ltd.

[0057] (Polymerization initiator) UV radical initiator 1: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, Omnirad TPO H, IGM Resins

[0058] (Examples 1 to 5, Comparative Examples 1 to 4) The components were blended to obtain the formulation shown in Table 1, to obtain a liquid curable composition as a sealant. The properties of the sealant obtained in each example or its cured product were measured by the following methods. The measurement results are shown in Table 1.

[0059] (viscosity) The viscosity of the curable composition obtained in each example was measured at 25°C and 20 rpm using an E-type viscometer (LV DV-II+ Pro, manufactured by Brookfield Corporation). A viscosity measurement value of less than 30 mPa s was deemed to be acceptable.

[0060] (glass transition temperature) First, a cured sealant was obtained by the following procedure: A 100 μm thick Teflon® sheet was used as a mold, and the uncured sealant was sandwiched between PET films, and then irradiated with a UV-LED having a wavelength of 395 nm at an illuminance of 1000 mW / cm. 2 , cumulative light intensity 1500mJ / cm 2 The mixture was cured under the conditions of 1 to 3, to obtain a cured product. The resulting cured product was cut with a cutter into a measurement sample measuring 10 mm in width and 40 mm in length. Then, using a dynamic viscoelasticity measuring device "DMS6100," tan δ was measured by applying a frequency of 1 Hz to the cured product sample in air while raising the temperature from room temperature to 250°C at a rate of 5°C / min. The temperature at the peak top of the obtained tan δ was taken as Tg.

[0061] (Dielectric constant) A coating film for obtaining a cured product for measuring the dielectric constant was prepared as follows. The resulting sealant was loaded into an inkjet cartridge DMC-11610 (manufactured by Fujifilm Dimatix). The inkjet cartridge was then set into an inkjet device DMP-2831 (manufactured by Fujifilm Dimatix). After adjusting the discharge conditions, the sealant was applied to a 5 cm x 5 cm area on a substrate consisting of non-alkali glass with aluminum vapor-deposited to a thickness of 100 nm, so that the cured thickness would be 10 μm. The resulting coating was placed in a box at room temperature (25°C) for 5 minutes under nitrogen flow, and then irradiated with ultraviolet light at a wavelength of 395 nm at an irradiance of 1000 mW / cm. 2 , cumulative light intensity 1500mJ / cm 2 The coating was irradiated under the conditions of 100° C. to 120° C. to form a cured film. After that, aluminum was vapor-deposited onto the inkjet-coated surface to a thickness of 100 nm, and the dielectric constant was measured at 100 kHz using the automatic balancing bridge method with an LCR meter HP4284A (Agilent Technologies). A dielectric constant measurement value of less than 3.5 was deemed to be acceptable.

[0062] (Damage to the organic EL element) As an index of the plasma resistance of the sealant, damage to the organic EL element during the plasma treatment step was evaluated by the following method. The sealant obtained in each example was introduced into an inkjet cartridge DMC-11610 (manufactured by Fujifilm Dimatix Co., Ltd.), and the inkjet cartridge was set into an inkjet device DMP-2831 (manufactured by Fujifilm Dimatix Co., Ltd.). After adjusting the discharge state, the sealant was applied to a glass substrate in a size of 15 mm x 15 mm so that the thickness after curing would be 10 μm. The resulting coating was placed in a box at room temperature (25°C) for 5 minutes under nitrogen flow, and then irradiated with ultraviolet light of 395 nm at 1500 mW / cm 2 The coating was irradiated with light at 1000 kJ / min for 1 second to form a cured film.

[0063] The sample on which the cured film was formed was subjected to plasma treatment for 1 minute under the conditions of a 2500 W ICP power supply, a 300 W RF power supply, a DC bias of 200 V, an argon (Ar) flow rate of 50 sccm, and a pressure of 10 mtorr. Then, SiN x Using a target, an inorganic sealing layer (SiN x A film was formed. On the other hand, an OLED element was deposited on the opposing substrate, and the substrate on which the inorganic sealing layer was formed was attached to obtain a sample for evaluation.

[0064] A reliability test was carried out on the samples obtained in each example at 85°C. Specifically, the light-emitting area ratio (%) of the samples obtained in each example after storage at 85°C for 100 hours was determined using the following method. That is, the light-emitting area in the initial state and after storage for 100 hours was calculated using Motic Images Plus software (Shimadzu Rika Co., Ltd.), and the light-emitting area ratio was determined. A light-emitting area ratio of 50% or more was considered to be acceptable.

[0065] [Table 1]

[0066] As can be seen from Table 1, the sealants obtained in each example were excellent in the effect of suppressing damage to organic EL elements due to plasma irradiation. Furthermore, the sealants obtained in each example were excellent in the balance of the properties of viscosity, dielectric constant, and Tg.

[0067] This application claims priority based on Japanese Patent Application No. 2020-157660, filed on September 18, 2020, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0068] 10 Light-emitting element 21 Barrier layer, touch panel layer or surface protection layer 22 Sealing layer, overcoat layer, or barrier layer 23 Planarization or sealing layer 24 Barrier layer 50 Base material layer 100 display device

Claims

1. A sealant for a display element, comprising a polymerizable compound and a curing agent, The polymerizable compound comprises the following components (A) and (B): (A) (Meth)acrylate having a bifunctional or higher alicyclic structure (B) (Meth)acrylate having a difunctional chain structure Including, the content of the component (A) is 30 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the total of the components (A) and (B), the content of the component (C): monofunctional (meth)acrylate in the sealant for a display element is 0 parts by mass relative to 100 parts by mass of the polymerizable compound, A sealant for display elements, in which the content of the polymerizable compound in the sealant for display elements is 80% by mass or more with respect to the total composition of the sealant for display elements (however, this excludes sealants for display elements which contain, as non-volatile components, at least high-refractive-index particles having core particles and a surface-treated layer that coats the core particles and is formed from a coupling agent, a (meth)acrylate having two or more ethylenically unsaturated groups and having an alicyclic structure, an aromatic ring structure, or a combination thereof, and a polymerization initiator, and in which the content of the non-volatile components is more than 95% by mass and 100% by mass or less).

2. 2. The sealant for a display element according to claim 1, wherein the component (A) contains dimethylol-tricyclodecane di(meth)acrylate.

3. 3. The sealant for a display element according to claim 1, wherein the component (B) is one or more (meth)acrylates selected from the group consisting of 1,12-dodecanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate.

4. The sealant for a display element according to claim 1 , which is used for sealing an organic EL display element.

5. A cured product obtained by curing the sealant for a display element according to claim 1 .

6. A substrate; a display element disposed on the substrate; a sealing layer that covers the display element; Including, A display device, wherein the sealing layer is formed from a cured product of the sealant for display elements according to claim 1 .

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