Curable composition for sealant for organic el display device, cured film for sealant for organic el display device, organic el device, and method for producing organic el device

Abstract

To provide a curable composition for a sealant for an organic EL display device, a cured film for a sealant for an organic EL display device, an organic EL device, and a method for producing an organic EL device, which allow acquisition of a cured film exhibiting favorable inkjet coatability, reduced outgassing, excellent CVD resistance, and high device reliability.SOLUTION: A curable composition for a sealant for an organic EL display device comprises a polymerizable compound, wherein the polymerizable compound includes a monofunctional oxetane compound and a polyfunctional oxetane compound, the monofunctional oxetane compound being 28 mass% or less in the polymerizable compound, a viscosity of the curable composition being 3 mPa s or more and 25 mPa s or less, and a dielectric constant of a cured film formed from the curable composition being 2.8 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curable composition for an encapsulant for an organic EL display element, a cured film for an encapsulant for an organic EL display element, an organic EL element, and a method for producing an organic EL element. [Background technology]

[0002] BACKGROUND ART Organic electroluminescence elements (organic EL elements) are light-emitting elements having a laminated structure including an anode, an organic light-emitting layer, and a cathode, and are widely used in various applications such as display devices and lighting devices.

[0003] The organic light-emitting layer in an organic EL element is susceptible to deterioration due to contact with moisture and oxygen. For example, moisture may penetrate into the element over a long period of operation, resulting in the formation of areas that do not emit light (dark spots), or the light-emitting characteristics may deteriorate due to contact with moisture and oxygen. Therefore, conventionally, organic EL elements have been provided with a sealing structure that seals the organic light-emitting layer, and the sealing structure prevents the organic light-emitting layer from coming into contact with moisture and oxygen.

[0004] The sealing structure of such an organic EL element generally employs a laminate of an inorganic sealing layer / an organic sealing layer / an inorganic sealing layer, and the organic sealing layer is formed, for example, from a curable composition containing a polymerizable compound.

[0005] Oxetane compounds are known as polymerizable compounds, and curable compositions containing polyfunctional oxetane compounds have been proposed (see, for example, Patent Documents 1 and 2). However, the compositions described in Patent Documents 1 and 2 are intended for use as ink compositions and dental materials, respectively, and no consideration has been given to their use as sealants for organic EL display elements. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-238644 [Patent Document 2] European Patent No. 0897710 Summary of the Invention [Problem to be solved by the invention]

[0007] The sealing structure that seals the organic light-emitting layer of an organic EL element may generate outgassing from the sealing structure due to components of the curable composition (e.g., unreacted polymerizable compound, solvent, etc.) remaining in the sealing structure or their decomposition products. The outgassing from the sealing structure may cause deterioration of the organic EL element.

[0008] Furthermore, when an inorganic sealing layer is formed on an organic sealing layer by chemical vapor deposition (CVD) or the like, defects such as wrinkles and cracks may occur in the organic sealing layer depending on the composition of the curable composition that forms the organic sealing layer. When such defects occur in the organic sealing layer, defects such as wrinkles and cracks may also occur in the inorganic sealing layer formed on the organic sealing layer.

[0009] Furthermore, for example, in an organic EL light-emitting device that employs a capacitive touch panel system, a touch sensor is placed on a substrate, but if the dielectric constant of the sealing structure is high, problems such as malfunctions can occur when the touch panel is in use.

[0010] For this reason, the cured film that forms the sealing structure of an organic EL element is required to have low outgassing properties, good CVD resistance, and element reliability. Furthermore, the curable composition that forms the cured film is required to have good coatability (particularly inkjet coatability) so that the coated film does not have unevenness.

[0011] Therefore, an object of the present invention is to provide a curable composition for an encapsulant for an organic EL display element, which can give a cured film having good inkjet coatability, little outgassing, CVD resistance, and good device reliability; a cured film for an encapsulant for an organic EL display element; an organic EL element; and a method for producing an organic EL element. [Means for solving the problem]

[0012] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0013] In one embodiment, the present invention provides A curable composition for an encapsulant for an organic EL display element, comprising a polymerizable compound, the polymerizable compound includes a monofunctional oxetane compound and a polyfunctional oxetane compound, the monofunctional oxetane compound accounts for 28% by mass or less of the polymerizable compound; the viscosity of the curable composition at 25°C is 3 mPa s or more and 25 mPa s or less, A cured film formed from the curable composition has a dielectric constant of 2.8 or less. The present invention relates to a curable composition for use as an encapsulant for an organic EL display element.

[0014] In another embodiment, the present invention provides The present invention also relates to a cured film for use as an encapsulant for an organic EL display device, which is formed using the curable composition, and an organic EL device in which an emitting layer is encapsulated with the cured film.

[0015] In another embodiment, the present invention provides applying the curable composition for an organic EL display element sealant to a surface of a substrate on which an organic light-emitting layer has been formed; a step of forming a sealing structure by irradiating radiation to cure the curable composition. The present invention relates to a method for producing an organic EL element, including the steps of: [Effects of the Invention]

[0016] The curable composition of the present invention contains specific amounts of a monofunctional oxetane compound and a polyfunctional oxetane compound, and has a viscosity and a dielectric constant within specific ranges, thereby enabling the production of a cured film that has good inkjet coatability, little outgassing, and good CVD resistance and device reliability. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0018] Matters related to the embodiments will be described in detail below. In this specification, a numerical range indicated using "to" means that the numerical values ​​before and after "to" are included as the lower and upper limits.

[0019] In this specification, the term "hydrocarbon group" includes chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "chain hydrocarbon group" refers to a linear hydrocarbon group or a branched hydrocarbon group that does not contain a cyclic structure in the main chain and is composed solely of a chain structure. However, the chain hydrocarbon group may be saturated or unsaturated. The term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic hydrocarbon structure as a ring structure and does not contain an aromatic ring structure. However, the alicyclic hydrocarbon group does not necessarily have to be composed solely of an alicyclic hydrocarbon structure, and also includes groups that have a chain structure as part of it. The term "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as a ring structure. However, the aromatic hydrocarbon group does not necessarily have to be composed solely of an aromatic ring structure, and may contain a chain structure or an alicyclic hydrocarbon structure as part of it. The ring structures of the alicyclic hydrocarbon group and the aromatic hydrocarbon group may have a substituent consisting of a hydrocarbon structure.

[0020] The curable composition for use as an encapsulant for an organic EL display element of the present invention will be described below.

[0021] <Curable composition for organic EL display element encapsulant> The curable composition for an encapsulant for an organic EL display element of the present invention contains a polymerizable compound, the polymerizable compound includes a monofunctional oxetane compound and a polyfunctional oxetane compound, the monofunctional oxetane compound accounts for 28% by mass or less of the polymerizable compound; the viscosity of the curable composition at 25°C is 3 mPa s or more and 25 mPa s or less, A cured film formed from the curable composition has a dielectric constant of 2.8 or less.

[0022] <Polymerizable compound> The curable composition for an encapsulant of an organic EL display element of the present invention (hereinafter, also referred to as "the composition") contains a polymerizable compound including a monofunctional oxetane compound and a polyfunctional oxetane compound.

[0023] (Polyfunctional oxetane compounds) The polyfunctional oxetane compound may be a polyfunctional polymerizable compound having two or more oxetanyl groups in one molecule, and its structure is not particularly limited. For example, it is preferable that the compound include a compound represented by the following formula (1): [ka] (In formula (1), R 1 each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms. R 2 represents a divalent organic group.

[0024] Above R 1 Examples of the linear or branched alkyl group having 1 to 5 carbon atoms in the above R include a methyl group, an ethyl group, a propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, a pentyl group, and an i-pentyl group. 1 is preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group.

[0025] Above R 2 Examples of the divalent organic group in the formula (I) include a divalent hydrocarbon group having 1 to 40 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the carbon chain terminal, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a combination thereof.

[0026] Above R 2Examples of the divalent hydrocarbon group having 1 to 40 carbon atoms represented by the formula (I) include a divalent chain hydrocarbon group having 1 to 40 carbon atoms, a divalent alicyclic hydrocarbon group having 3 to 40 carbon atoms, and a divalent aromatic hydrocarbon group having 6 to 40 carbon atoms.

[0027] Above R 2 Examples of the divalent linear hydrocarbon group having 1 to 40 carbon atoms represented by the formula (I) include a divalent linear or branched saturated hydrocarbon group having 1 to 40 carbon atoms, or a divalent linear or branched unsaturated hydrocarbon group having 2 to 40 carbon atoms. Examples of the divalent linear or branched saturated hydrocarbon group having 1 to 40 carbon atoms include alkanediyl groups such as methanediyl, ethanediyl, propanediyl, isopropanediyl, butanediyl, isobutanediyl, pentanediyl, isopentanediyl, hexanediyl, heptanediyl, octanediyl, nonanediyl, and decanediyl. Examples of the divalent linear or branched unsaturated hydrocarbon group having 2 to 40 carbon atoms include alkenediyl groups such as ethenediyl, propenediyl, butenediyl, pentenediyl, and hexenediyl.

[0028] Above R 2Examples of the divalent alicyclic hydrocarbon group having 3 to 40 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of the monocyclic saturated hydrocarbon group include cycloalkanediyl groups such as cyclopropanediyl group, cyclobutanediyl group, cyclopentanediyl group, and cyclohexanediyl group. Examples of the polycyclic saturated hydrocarbon group include bridged alicyclic hydrocarbon groups such as norbornanediyl group, adamantanediyl group, tricyclodecanediyl group, and tetracyclododecanediyl group. Examples of the monocyclic unsaturated hydrocarbon group include monocyclic cycloalkenediyl groups such as cyclopropenediyl group, cyclobutenediyl group, cyclopentenediyl group, and cyclohexenediyl group. Examples of the polycyclic unsaturated hydrocarbon group include polycyclic cycloalkenediyl groups such as norbornenediyl group, tricyclodecenediyl group, and tetracyclododecenediyl group. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms that constitute the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0029] Above R 2 Examples of the divalent aromatic hydrocarbon group having 6 to 40 carbon atoms represented by the formula (I) include arenediyl groups such as a benzenediyl group, a toluenediyl group, a xylenediyl group, a naphthalenediyl group, and an anthracenediyl group; and arenediylalkanediyl groups such as a benzenediylmethanediyl group, a benzenediylethanediyl group, a naphthalenediylmethanediyl group, and an anthracenediylmethanediyl group.

[0030] Examples of heteroatoms constituting the monovalent heteroatom-containing group and divalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0031] Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0032] Examples of the divalent heteroatom-containing group include -CO-, -C(=O)O-, -CS-, -NR'-, -O-, -S-, -SO-, -SO2-, and combinations thereof, where R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0033] Some or all of the hydrogen atoms bonded to atoms constituting the divalent organic group may be substituted with a substituent, such as a halogen atom such as a fluorine atom or an iodine atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an oxo group (=O).

[0034] Among these, R 2 From the viewpoints of inkjet coating properties, CVD resistance, and device reliability, it is preferable that the structure does not have a siloxane structure.

[0035] Also, R 2 Preferably, the compound has one or more structures selected from the group consisting of an ether bond and a branched structure, and more preferably has a structure containing both an ether bond and a branched structure. Such a structure is preferable from the viewpoints of reducing outgassing, inkjet coating properties, CVD resistance, and device reliability.

[0036] The polyfunctional oxetane compound preferably contains at least one polyfunctional oxetane compound selected from the group consisting of the following formulae (1-1) to (1-4).

[0037] [ka] (In formula (1-1), R 1 each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms. R 21represents a linear or branched alkanediyl group having 3 to 20 carbon atoms. [ka] (In formula (1-2), R 22 represents a linear or branched alkanediyl group having 3 to 20 carbon atoms. R 23 represents a single bond or a linear or branched alkanediyl group having 1 to 5 carbon atoms. 23 are the same or different from each other. R 1 has the same meaning as the above formula (1-1). [ka] (In formula (1-3), R 24 represents a linear or branched alkanediyl group having 2 to 10 carbon atoms. 24 are the same or different from each other. R 25 represents a single bond or a linear or branched alkanediyl group having 1 to 5 carbon atoms. 25 are the same or different from each other. R 1 has the same meaning as the above formula (1-1). [ka] (In formula (1-4), R 26 represents a linear or branched alkanediyl group having 2 to 10 carbon atoms. 26 are the same or different from each other. R 27 represents an alkyl group having 1 to 4 carbon atoms or an aromatic group having 6 to 20 carbon atoms. 27 are the same or different from each other. X represents an oxygen atom or an alkanediyl group having 1 to 6 carbon atoms. When a plurality of X's are present, the plurality of X's may be the same or different. n represents an integer of 1 to 10. y1 and y2 each independently represent 0 or 1. R 28 represents a single bond or a linear or branched alkanediyl group having 1 to 5 carbon atoms. 28 are the same or different from each other. R 1 has the same meaning as the above formula (1-1).

[0038] R in the above formulas (1-1) and (1-2) 21 , R 22 As the linear or branched alkanediyl group having 3 to 20 carbon atoms, R 2 Among the alkanediyl groups in the above formula (1), those having the corresponding number of carbon atoms can be suitably used. Some or all of the hydrogen atoms bonded to the carbon atoms constituting the alkanediyl group may be substituted with a substituent. Examples of the substituent include R 2 Among these, the substituents that can be possessed by the divalent organic group in R 21 , R 22 As the alkyl group, an alkanediyl group having 6 to 20 carbon atoms and having 1 to 3 branched structures is preferred, and an alkanediyl group having 8 to 15 carbon atoms and having 1 to 2 branched structures is more preferred.

[0039] R in the above formulas (1-1) and (1-2) 1 As the linear or branched alkyl group having 1 to 5 carbon atoms, R 1 A linear or branched alkyl group having 1 to 5 carbon atoms can be suitably used.

[0040] R in the above formula (1-2) 23 In the above, the linear or branched alkanediyl group having 1 to 5 carbon atoms includes the above R 1 It is possible to suitably employ a group in which one hydrogen atom has been removed from a linear or branched alkyl group having 1 to 5 carbon atoms as shown in the formula (I). Of these, a methanediyl group and an ethanediyl group are preferred, with a methanediyl group being more preferred.

[0041] Examples of the polyfunctional oxetane compound represented by the above formula (1-1) include compounds having the following structure.

[0042] [ka]

[0043] Examples of the polyfunctional oxetane compound represented by the above formula (1-2) include compounds having the following structure.

[0044] [ka]

[0045] [ka]

[0046] R in the above formula (1-3) 24 As the linear or branched alkanediyl group having 2 to 10 carbon atoms, R 2 Among the alkanediyl groups in the above formula (1), those having the corresponding number of carbon atoms can be suitably used. Some or all of the hydrogen atoms bonded to the carbon atoms constituting the alkanediyl group may be substituted with a substituent. Examples of the substituent include R 2 The substituents that the divalent organic group in the formula (I) may have can be suitably employed.

[0047] R in the above formula (1-3) 25 In the above formula (1), the linear or branched alkanediyl group having 1 to 5 carbon atoms includes R 1 It is possible to suitably employ a group in which one hydrogen atom has been removed from a linear or branched alkyl group having 1 to 5 carbon atoms as shown in the formula (I). Of these, a methanediyl group and an ethanediyl group are preferred, with a methanediyl group being more preferred.

[0048] R in the above formula (1-3) 1 has the same meaning as the above formula (1-1).

[0049] Examples of the polyfunctional oxetane compound represented by the above formula (1-3) include compounds having the following structure. [ka]

[0050] R in the above formula (1-4) 26 As the linear or branched alkanediyl group having 2 to 10 carbon atoms, R 2 Among the alkanediyl groups in the above formula (1), those having the corresponding number of carbon atoms can be suitably used. Some or all of the hydrogen atoms bonded to the carbon atoms constituting the alkanediyl group may be substituted with a substituent. Examples of the substituent include R 2 Among these, the substituents that can be possessed by the divalent organic group in R 26 As the alkyl group, a linear alkanediyl group having 3 to 5 carbon atoms is preferred.

[0051] R in the above formula (1-4) 27 As the alkyl group having 1 to 4 carbon atoms, R 1 Among the linear or branched alkyl groups having 1 to 5 carbon atoms in the above, those having the corresponding carbon atoms can be suitably used. 27 As the alkyl group, a methyl group is preferred.

[0052] R in the above formula (1-4) 27 In the above, examples of the aromatic group having 6 to 20 carbon atoms include groups in which one hydrogen atom has been removed from the ring portion of an aromatic hydrocarbon ring or a heteroaromatic ring. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, and an anthracene ring. Examples of the heteroaromatic ring include a pyridine ring, a pyridazine ring, a pyrazine ring, a pyrimidine ring, an imidazole ring, and a benzimidazole ring.

[0053] Above R 27In the alkyl group having 1 to 4 carbon atoms and the aromatic group having 6 to 20 carbon atoms, some or all of the hydrogen atoms bonded to the carbon atoms constituting these groups may be substituted with a substituent. 2 The substituents that the divalent organic group in the formula (I) may have can be suitably employed.

[0054] The alkanediyl group having 1 to 6 carbon atoms in X is R 2 Among the alkanediyl groups in the above formula (1), those having the corresponding number of carbon atoms can be suitably used. Some or all of the hydrogen atoms bonded to the carbon atoms constituting the alkanediyl group may be substituted with a substituent. Examples of the substituent include R 2 It is possible to suitably employ a substituent that the divalent organic group in the above formula may have. X is preferably an oxygen atom or an alkanediyl group having 1 to 3 carbon atoms, more preferably an oxygen atom.

[0055] The above n is an integer of 1 to 10, preferably an integer of 1 to 5, more preferably an integer of 1 to 3, and even more preferably 1 or 2.

[0056] R in the above formula (1-4) 28 In the above formula (1), the linear or branched alkanediyl group having 1 to 5 carbon atoms includes R 1 It is possible to suitably employ a group in which one hydrogen atom has been removed from a linear or branched alkyl group having 1 to 5 carbon atoms as shown in the formula (I). Of these, a methanediyl group and an ethanediyl group are preferred, with a methanediyl group being more preferred.

[0057] R in the above formula (1-4) 1 has the same meaning as the above formula (1-1).

[0058] Examples of the polyfunctional oxetane compound represented by the above formula (1-4) include compounds having the following structure.

[0059] [ka]

[0060] Among the polyfunctional oxetane compounds represented by the above formulas (1-1) to (1-4), compounds selected from the group consisting of compounds represented by the above formulas (1-1), (1-2), and (1-4) are preferred, compounds represented by the above formulas (1-1) or (1-2) are more preferred, compounds represented by formula (1-2) are even more preferred, and R 22 It is particularly preferable that the structure has at least one branched structure.

[0061] The dielectric constant of the compound represented by the above formula (1) is preferably 3.0 or less, more preferably 2.8 or less, from the viewpoint of device reliability.

[0062] The content of the compound represented by formula (1) having a dielectric constant of 3.0 or less is preferably 10% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, and even more preferably 30% by mass to 50% by mass, based on the total amount (100% by mass) of the polymerizable compounds contained in the curable composition. By including the compound represented by formula (1) having a dielectric constant of 3.0 or less in the above range, device reliability can be improved, which is preferable.

[0063] The functional group equivalent weight of the polyfunctional oxetane compound is preferably from 120 to 250, more preferably from 130 to 240, and even more preferably from 140 to 230. When the functional group equivalent weight is in the above range, the viscosity and dielectric constant of the oxetane compound fall within the optimum ranges for the composition, which is preferable.

[0064] The content of the polyfunctional oxetane compound is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total amount (100% by mass) of the polymerizable compounds contained in the composition. The upper limit of the content is not particularly limited, but is preferably 99% by mass, more preferably 97% by mass, and even more preferably 95% by mass. A content within the above range is preferred from the viewpoint of device reliability.

[0065] (Monofunctional oxetane compound) The monofunctional oxetane compound is a monofunctional polymerizable compound having one oxetanyl group per molecule. In the present invention, by including a specific amount of the monofunctional oxetane compound, the viscosity of the curable composition can be reduced, the wetting and spreading properties can be improved, and the inkjet coating properties can be excellent. Furthermore, by including a specific amount of the monofunctional oxetane compound, the dielectric constant of the obtained cured film can be reduced.

[0066] The monofunctional oxetane compound may be any compound having one oxetane ring per molecule, and examples thereof include monofunctional oxetane compounds represented by the following formula (2). [ka] (In formula (2), R 3 represents a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms. R 4 represents a monovalent organic group.

[0067] Above R 3 As the linear or branched alkyl group having 1 to 5 carbon atoms, R 1 A linear or branched alkyl group having 1 to 5 carbon atoms can be suitably used.

[0068] Above R 4 The monovalent organic group in the formula (1) is R 2 A monovalent group corresponding to the divalent organic group in the formula (I) can be suitably used.

[0069] Specific examples of the monofunctional oxetane compound include 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane, phenoxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-ethyl-3-((3-(triethoxysilyl)propoxy)methyl)oxetane, 3-allyloxyoxetane, 3-ethyl-3-allyloxyoxetane, 3-ethyl-3-acryloyloxymethyloxetane, 3-ethyl-3-methyl Examples include acryloxymethyloxetane, 2-methyl-2-allyl-4-propyloxetane, 3-ethyl-3-(4-acryloyloxybutyloxymethyl)oxetane, 3-ethyl-3-(3-acryloyloxy-2,2-dimethylpropyloxymethyl)oxetane, 3-methyl-3-methoxyoxetane, phenyloxetane, 3-ethyl-3-chloromethyloxetane, 3-ethyl-3-oxetanemethanol, 3-amino-3-dimethyloxetane, and compounds represented by the following formula: [ka]

[0070] The upper limit of the content of the monofunctional oxetane compound is 28% by mass, preferably 23% by mass, more preferably 18% by mass, even more preferably 15% by mass, and particularly preferably 10% by mass, relative to the total amount (100% by mass) of polymerizable compounds contained in the composition. The lower limit of the content is not particularly limited, but is preferably 1% by mass, more preferably 3% by mass, and even more preferably 5% by mass. By keeping the content within the above range, CVD resistance and device reliability are improved.

[0071] (Other polymerizable compounds) The present composition may contain only a monofunctional oxetane compound and a polyfunctional oxetane compound as the polymerizable compound, or may further contain a polymerizable compound other than the monofunctional oxetane compound and the polyfunctional oxetane compound. The other polymerizable compound may be monofunctional or polyfunctional, and examples include monofunctional polymerizable compounds such as monofunctional epoxy compounds and monofunctional vinyl ether compounds, and polyfunctional polymerizable compounds such as polyfunctional epoxy compounds and polyfunctional vinyl ether compounds. These polymerizable compounds may contain an aliphatic hydrocarbon structure, a structure having a divalent heteroatom-containing group between carbon atoms in the aliphatic hydrocarbon structure, an alicyclic structure, an aromatic hydrocarbon structure, a siloxane structure, or other heteroatoms. Among these, an aliphatic hydrocarbon structure, a structure having -O- between carbon atoms in the aliphatic hydrocarbon structure, and an alicyclic structure are preferred. These structures can exhibit good inkjet coating properties and device reliability. Examples of the divalent heteroatom-containing group include R in the above formula (1). 2 When the other polymerizable compound contains a structure other than those described above, the amount of the other polymerizable compound is desirably 20% by mass or less relative to the total amount (100% by mass) of the polymerizable compounds contained in the composition, from the viewpoints of inkjet coating properties and device reliability.

[0072] The monofunctional epoxy compound may be any compound having one oxirane ring per molecule, and specific examples of the monofunctional epoxy compound include cyclohexene oxide, 1-methyl-1,2-epoxycyclohexane, 1,2-epoxy-4-vinylcyclohexane, ethyl glycidyl ether, and butyl glycidyl ether.

[0073] The monofunctional vinyl ether compound may be any compound having one vinyl ether group per molecule, and examples of the monofunctional vinyl ether compound include cyclohexyl vinyl ether, ethylhexyl vinyl ether, and hydroxyethyl vinyl ether.

[0074] The polyfunctional epoxy compound may be any compound having two or more oxirane rings per molecule. Specific examples of polyfunctional epoxy compounds include: 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, 3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate, methylene bis Epoxy group-containing low molecular weight compounds such as (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol, ethylene bis(3,4-epoxycyclohexanecarboxylate), (3,4,3',4'-diepoxy)bicyclohexyl, bis(3,4-epoxycyclohexylmethyl)ether, 1,2-epoxy-1,2-bis(3,4-epoxycyclohexan-1-yl)ethane, 1,2-bis(3,4-epoxycyclohexan-1-yl)ethane, and 2,2-bis(3,4-epoxycyclohexan-1-yl)propane; compounds having two or more alicyclic epoxy groups (preferably 3,4-epoxycyclohexyl groups) in the molecule, such as "X-40-2678," "X-40-2670," "X-40-2720," and "X-22-163A" (all trade names) manufactured by Shin-Etsu Chemical Co., Ltd.; Epoxy group-containing resins such as bisphenol A type epoxy resins, bisphenol E type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol O type epoxy resins, 2,2'-diallyl bisphenol A type epoxy resins, hydrogenated bisphenol type epoxy resins, propylene oxide-added bisphenol A type epoxy resins, resorcinol type epoxy resins, biphenyl type epoxy resins, sulfide type epoxy resins, diphenyl ether type epoxy resins, dicyclopentadiene type epoxy resins, naphthalene type epoxy resins, phenol novolac type epoxy resins, ortho-cresol novolac type epoxy resins, dicyclopentadiene novolac type epoxy resins, biphenyl novolac type epoxy resins, naphthalene phenol novolac type epoxy resins, glycidyl amine type epoxy resins, alkyl polyol type epoxy resins, rubber-modified epoxy resins, glycidyl ester resins, and bisphenol A type episulfide resins; Examples include:

[0075] The polyfunctional vinyl ether compound may be any compound having two or more vinyl ether groups per molecule. Specific examples of the polyfunctional vinyl ether compound include compounds having multiple vinyl ether groups, such as alkanediol divinyl ether, cycloalkanediol divinyl ether, cycloalkane dimethanol divinyl ether, (poly)ethylene glycol divinyl ether, trimethylolpropane divinyl ether, pentaerythritol divinyl ether, trimethylolpropane trivinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, and dipentaerythritol hexavinyl ether, as well as alkylene oxide-modified or caprolactone-modified compounds thereof.

[0076] Among these, the other polymerizable compounds are preferably compounds having one or more 3,4-epoxycyclohexyl groups in the molecule, and for example, the above-mentioned "X-40-2678" manufactured by Shin-Etsu Chemical Co., Ltd. is more preferred.

[0077] The content of the other polymerizable compounds is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on the total amount (100% by mass) of polymerizable compounds contained in the composition. The lower limit of the content is not particularly limited, and the composition may not contain other polymerizable compounds.

[0078] The content of polymerizable compounds in the composition (total amount of monofunctional oxetane compounds, polyfunctional oxetane compounds, and other polymerizable compounds) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of providing a curable composition with good sensitivity and forming a cured film with high sealing effect.

[0079] The curable composition for an encapsulant of an organic EL display element of the present invention preferably contains a polymerization initiator.

[0080] <Polymerization initiator> The polymerization initiator may be any substance that generates a protonic acid or a Lewis acid in response to heat or light. Such a polymerization initiator can be appropriately selected from known thermal cationic polymerization initiators or photocationic polymerization initiators. From the viewpoint of suppressing deterioration of the device, the polymerization initiator is preferably a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include ionic photoacid-generating polymerization initiators and nonionic photoacid-generating polymerization initiators.

[0081] Examples of ionic photoacid-generating cationic photopolymerization initiators include onium salt compounds, halogen-containing compounds, sulfone compounds, sulfonic acid compounds, sulfonimide compounds, and diazomethane compounds. Specific examples of onium salt compounds include those in which the cation moiety is an aromatic sulfonium, aromatic iodonium, aromatic diazonium, aromatic ammonium, or (2,4-cyclopentadien-1-yl)[(1-methylethyl)benzene]-Fe cation and the anion moiety is BF4 - , PF6 - , SbF6 - , [BX4]- , [GaX4] - (X is a phenyl group substituted with two or more fluorine atoms or trifluoromethyl groups), or [PRf6 - ] (Rf is a fluorinated alkyl group).

[0082] As the polymerization initiator, the onium salt compounds mentioned above are preferably used. Among them, the polymerization initiator [BX4] - , [GaX4] - (X is a phenyl group substituted with two or more fluorine atoms or trifluoromethyl groups.) Preferably, X is a pentafluorophenyl group (—CF).

[0083] The cation moiety of the onium tetrakis(fluorinated phenyl)borate is not particularly limited, and specific examples of the cation moiety include sulfonium cations represented by the following formula (3) and formula (4): [ka] (In formulas (3) and (4), R 31 ~R 36 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylthio group having 1 to 6 carbon atoms, an alkylcarbonyloxy group having 1 to 6 carbon atoms, an alkylcarbonylthio group having 1 to 6 carbon atoms, an alkoxycarbonyloxy group having 1 to 6 carbon atoms, or a phenyl group. r1 and r2 are independently 0 or 1.

[0084] In the above formulas (3) and (4), R 31 ~R 36 is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a methoxy group, a methylthio group, a methylcarbonyloxy group, a methylcarbonylthio group, a methoxycarbonyloxy group, or a phenyl group, and more preferably a hydrogen atom or a t-butyl group.

[0085] As the ionic photoacid generating cationic photopolymerization initiator, commercially available products can be used. For example, a cationic moiety represented by the above formula (3) or (4) and [BX4] - Examples of commercially available cationic photopolymerization initiators comprising an anion moiety represented by the following trade names include "CPI-100B," "CPI-110B," "CPI-310B," "CPI-410B," and "ES-1B" (all manufactured by San-Apro Ltd.).

[0086] Furthermore, as the cationic polymerization initiator, an acid generator (specifically, a cationic polymerization initiator in which the central metal of the counter anion is gallium) described in JP 2022-80366 A can also be used. Commercially available cationic polymerization initiators include, for example, CPI-210S ((CF2CF3) n PF (6-n) - as a counter anion (specifically, a triarylsulfonium salt), manufactured by San-Apro Co., Ltd.), and CPI-310FG (a sulfonium salt (specifically, a triarylsulfonium salt) with FG anion as a counter ion, manufactured by San-Apro Co., Ltd.).

[0087] Examples of nonionic photoacid-generating cationic photopolymerization initiators include nitrobenzyl esters, sulfonic acid derivatives, phosphate esters, phenolsulfonate esters, diazonaphthoquinone, N-hydroxyimide sulfonates, and oxime ester-based carboxylic acid esters.

[0088] In the present composition, the content of the polymerization initiator is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the total amount of polymerizable compounds contained in the present composition. By setting the content of the polymerization initiator within this range, the curability of the present composition can be improved, and a cured film with high transparency can be obtained, which is preferable.

[0089] The present composition may contain, in addition to the polymerizable compound and polymerization initiator, a polymerization inhibitor, an antioxidant, a surfactant, and the like.

[0090] <Polymerization inhibitors / antioxidants> The present composition may further contain at least one compound selected from the group consisting of a polymerization inhibitor and an antioxidant. By further containing at least one compound selected from the group consisting of a polymerization inhibitor and an antioxidant, the storage stability of the present composition can be improved.

[0091] The polymerization inhibitor is not particularly limited, but examples thereof include hydroquinone, p-methoxyphenol, p-benzoquinone, naphthoquinone, phenanthraquinone, toluquinone, 2,5-diacetoxy-p-benzoquinone, 2,5-dicaproxy-p-benzoquinone, 2,5-acyloxy-p-benzoquinone, 2,5-di-tert-butyl-3-methylphenol, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, p-tert-butylcatechol, mono-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, di-tert-butyl-paracresolhydroquinone monomethyl ether, phenothiazine, alpha naphthol, acetamidine acetate, acetamidine sulfate, phenylhydrazine hydrochloride, Examples of suitable antibacterial agents include hydrazine hydrochloride, trimethylbenzylammonium chloride, laurylpyridinium chloride, cetyltrimethylammonium chloride, phenyltrimethylammonium chloride, trimethylbenzylammonium oxalate, di(trimethylbenzylammonium) oxalate, trimethylbenzylammonium malate, trimethylbenzylammonium tartrate, trimethylbenzylammonium glycolate, phenyl-β-naphthylamine, parabenzylaminophenol, di-β-naphthylparaphenylenediamine, dinitrobenzene, trinitrotoluene, picric acid, cyclohexanone oxime, pyrogallol, tannic acid, resorcinol, triethylamine hydrochloride, dimethylaniline hydrochloride, and dibutylamine hydrochloride.

[0092] When a polymerization inhibitor is blended in the composition, the content of the polymerization inhibitor is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.01 to 3 parts by mass, relative to 100 parts by mass of the total amount of polymerizable compounds contained in the composition. By keeping the content within the above range, it is possible to suppress an increase in viscosity due to unnecessary thermal energy, and gelation or curing reactions, while maintaining the viscosity of the composition within an appropriate range even after long-term distribution or storage, and to exhibit good wetting and spreading properties (and therefore inkjet coatability), which is preferable.

[0093] The antioxidant is used to prevent oxidative deterioration of the curable composition, thereby improving the storage stability of the composition. Examples of the antioxidant include phenolic antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0094] Specific examples of these include phenolic antioxidants such as monophenols such as 2,6-di-tert-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-tert-butyl-p-ethylphenol, and stearyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), and 3,9-bis[1,1-dimethyl-2-{β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]propionate; bisphenols such as 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-tert-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

[0095] Examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate.

[0096] Examples of phosphorus-based antioxidants include diphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, diisodecyl pentaerythritol phosphite, tris(2,4-di-tert-butylphenyl) phosphite, cyclic neopentane tetrayl bis(octadecyl) phosphite, cyclic neopentane tetrayl bis(2,4-di-tert-butylphenyl) phosphite, cyclic neopentane tetrayl bis(2,4-di-tert-butyl-6-methylphenyl) phosphite, and and bis[2-tert-butyl-6-methyl-4-{2-(octadecyloxycarbonyl)ethyl}phenyl]hydrogenphosphite; and oxaphosphaphenanthrene oxides such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-tert-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0097] The antioxidants may be used alone or in combination.

[0098] When an antioxidant is blended in the composition, the content of the antioxidant is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.01 to 3 parts by mass, relative to 100 parts by mass of the total amount of polymerizable compounds contained in the composition. By ensuring that the content is within the above range, it is possible to suppress viscosity increases due to unnecessary thermal energy and gelation or curing reactions, while maintaining the viscosity of the composition within an appropriate range even after long-term distribution or storage, and to exhibit good wetting and spreading properties (and therefore inkjet coatability).

[0099] In addition, in order to improve the storage stability of the present composition, a heat stabilizer such as methylenequinone or 2-dimethylaminomethanol described in JP-A-2020-518952 may be contained in the present composition.

[0100] <Surfactant> A surfactant can be used to further improve the coating properties of the composition (specifically, wetting and spreading properties and reduction of coating unevenness). Examples of surfactants include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants.

[0101] Specific examples of surfactants include fluorine-based surfactants, such as Megafac F-171, F-172, F-173, F-251, F-430, F-554, F-552, and F-563 (manufactured by DIC Corporation); Fluorad FC430 and FC431 (manufactured by Sumitomo 3M); Asahiguard AG710, Surflon S-382, and Surflon S-563 (manufactured by Sumitomo 3M); Examples of suitable acrylic resins include C-101, SC-102, SC-103, SC-104, SC-105, SC-106, and S-611 (manufactured by AGC Seimi Chemical Co., Ltd.); Polyflow No. 75 and No. 95 (manufactured by Kyoeisha Chemical Co., Ltd.); FTX-218 (manufactured by Neos Co., Ltd.); and F-top EF301, EF303, and EF352 (manufactured by Shin-Akita Chemical Co., Ltd.).

[0102] Examples of silicone surfactants include SH200-100cs, SH28PA, SH30PA, SH89PA, SH190, SH8400, SH193, SZ6032, SF8428, DC57, DC190, PAINTAD19, FZ-2101, FZ-77, FZ-2118, L-7001, and L-7002 (manufactured by Dow Corning Toray Co., Ltd.); organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.); and BYK-300, BYK-306, BYK-310, BYK-330, BYK-335, BYK-341, BYK-344, BYK-370, BYK-340, and BYK-345 (manufactured by BYK Japan).

[0103] Examples of nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, and polyethylene glycol distearate.

[0104] When a surfactant is blended in the present composition, the content of the surfactant is preferably 0.01 to 3 parts by mass, more preferably 0.02 to 2 parts by mass, and even more preferably 0.1 to 1.0 part by mass, per 100 parts by mass of the total amount of polymerizable compounds contained in the present composition.

[0105] In addition to the above, other components include, for example, a sensitizer, a softener, a plasticizer, an adhesion aid, an organic solvent, etc. The blending ratio of these components is appropriately selected depending on each component within a range that does not impair the effects of the present disclosure.

[0106] Among the other components, a sensitizer can be used to improve the sensitivity of the cationic polymerization initiator to UV LEDs. The following compounds can be used as the sensitizer. For example, Benzoquinones; 1,4-benzoquinone, 1,2-benzoquinone, etc. Naphthoquinones; 1,4-naphthoquinone, 1,2-naphthoquinone, etc. Anthraquinones: 2-methylanthraquinone, 2-ethylanthraquinone, etc. Anthracene; Anthracene, 9,10-dibutoxyanthracene, 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-bis(acetyloxy)anthracene, 9,10-bis(propionyloxy)anthracene, 9,10-bis(n-butyryloxy)anthracene, 9,10-bis(i-butyryloxy)anthracene, 9,10-bis(n-valeryloxy)anthracene, 9,10-bis(i-valeryloxy)anthracene, 9,10-bis(n-hexanoyloxy)anthracene, 9,10-bis(n-heptanoyloxy)anthracene anthracene, 9,10-bis(n-octanoyloxy)anthracene, 9,10-bis(2-ethylhexanoyloxy)anthracene, 9,10-bis(n-nonanoyloxy)anthracene, 9,10-bis(methoxycarbonyloxy)anthracene, 9,10-bis(ethoxycarbonyloxy)anthracene, 9,10-bis(n-propoxycarbonyloxy)anthracene, 9,10-bis(i-propoxycarbonyloxy)anthracene, 9,10-bis(n-butoxycarbonyloxy)anthracene, 9,10-bis(i-butoxycarbonyloxy)anthracene, 9,10-bis(2-ethylhexyloxycarbonyloxy)anthracene, etc. Thioxanthone; thioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 2,4-diethylthioxanthone, etc. Phenothiazines; phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, N-phenylphenothiazine, etc. Naphthalene; 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 2-methoxynaphthalene, 1,4-dihydroxynaphthalene, and 4-methoxy-1-naphthol, etc. Ketones; dimethoxyacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4'-isopropyl-2-hydroxy-2-methylpropiophenone, and 4-benzoyl-4'-methyldiphenyl sulfide, etc. Carbazoles such as N-phenylcarbazole, N-ethylcarbazole, poly-N-vinylcarbazole, and N-glycidylcarbazole; Chrysene; 1,4-dimethoxychrysene, 1,4-di-α-methylbenzyloxychrysene, etc. Phenanthrene; 9-hydroxyphenanthrene, 9-methoxyphenanthrene, 9-hydroxy-10-methoxyphenanthrene, and 9-hydroxy-10-ethoxyphenanthrene, etc. Examples include xanthone, pyrene, 1,2-benzanthracene, perylene, tetracene, and coronene.

[0107] When a sensitizer is blended in the composition, the content of the sensitizer is preferably 1 to 300 parts by mass, and more preferably 5 to 200 parts by mass, per 100 parts by mass of the polymerization initiator contained in the composition. Using the sensitizer in this range is preferable because it is possible to achieve both high sensitivity and high transparency of the resulting cured film.

[0108] <Organic solvents> An organic solvent may be added to the composition for the purpose of dissolving each component added to the composition. On the other hand, from the viewpoint of enabling the formation of a cured film (particularly an organic sealing layer that protects the organic light-emitting layer of an organic EL device) without heat treatment, it is preferable to minimize the amount of organic solvent used. Specifically, the content of organic solvent in the composition is preferably 0% by mass or more and 3% by mass or less, more preferably 0% by mass or more and 2% by mass or less, and particularly preferably substantially free of organic solvent. Herein, "substantially free of organic solvent" means that the amount of organic solvent contained in the composition is 1% by mass or less, preferably 0.5% by mass or less.

[0109] When an organic solvent is blended into the present composition, the organic solvent used is preferably an organic solvent that can dissolve or disperse each component blended in the present composition and does not react with each component. Specific examples of the organic solvent include alcohols, ketones, esters, ethers, aromatic hydrocarbons, and amides.

[0110] Specific examples of these include alcohols such as methanol, ethanol, isopropanol, butanol, and octanol. Ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Esters include ethyl acetate, butyl acetate, ethyl lactate, γ-butyrolactone, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and methyl-3-methoxypropionate. Ethers include polyoxyethylene lauryl ether, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and diethylene glycol methyl ethyl ether. Aromatic hydrocarbons include benzene, toluene, and xylene. Amides include dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0111] <Preparation of Curable Composition> The present composition can be prepared by mixing the polymerizable compound and polymerization initiator, as well as other components that are blended as necessary.

[0112] <Viscosity of Curable Composition> The viscosity of the composition is 3 mPa·s or more and 25 mPa·s or less. When the viscosity of the composition is 25 mPa·s or less, the composition exhibits good wetting and spreading properties when applied to a substrate by inkjet coating, thereby preventing uneven application due to repelling and the like. Furthermore, when the viscosity of the composition is 3.0 mPa·s or more, the composition can be applied to a substrate with a sufficient film thickness, forming an organic sealing layer that exhibits sufficient sealing effect. The composition is suitable as a curable composition for inkjet coating. The viscosity is preferably 5 mPa·s or more, more preferably 7 mPa·s or more, even more preferably 10 mPa·s or more, and is preferably 23 mPa·s or less, and more preferably 20 mPa·s or less. The viscosity is measured using an E-type viscometer at 25°C and 20 rpm in accordance with JIS K2283. In addition, in the present invention, the curable composition can be heated to reduce its viscosity in order to improve inkjet coating properties.

[0113] <Dielectric constant of cured film obtained from curable composition> The dielectric constant of the cured film obtained by curing the composition is 2.8 or less, preferably 2.79 or less. The dielectric constant is measured by using a UV-LED lamp with a wavelength of 395 nm for the composition at an illuminance of 1000 mW / cm. 2 And the cumulative light intensity is 3000mJ / cm 2 This is the dielectric constant at a frequency of 100 kHz of the cured film obtained by irradiating ultraviolet light under the conditions of (a) to (c). Details of the method for measuring the dielectric constant of the cured film are as described in the Examples below. Having the dielectric constant of the cured film fall within the above range is preferable from the viewpoint of device reliability.

[0114] <Indentation Elastic Modulus of Cured Film Obtained from Curable Composition> The indentation modulus of a cured film formed from the curable composition is preferably 1.0 GPa or more, more preferably 1.2 GPa or more, and even more preferably 1.5 GPa or more. The indentation modulus within this range is preferred from the viewpoint of CVD resistance.

[0115] <Uses of the curable composition> Although the present composition is intended for use as an encapsulant for organic electroluminescent (EL) display devices, its properties also enable its use as a material for filling holes in HID (Hole-in-a-Display-Area) structures and for forming planarizing films. Furthermore, the present composition can also be used as a material for forming a coating layer to protect wiring at the bent portions of flexible displays or at the bends where wiring extends from the display area to the outside. Examples of coating layers for bent portions include the microcoating layer described in International Publication No. 2016 / 09925. The microcoating layer can be formed by slit coating or inkjet coating. The present composition is useful in that it can be applied to both coating methods. The present composition is particularly useful as a composition for forming an encapsulated structure, i.e., an encapsulant for organic EL devices, by thin film encapsulation (TFE) of organic electroluminescent devices (organic EL devices).

[0116] <Other embodiments> In another embodiment, the present invention provides A curable composition for an encapsulant for an organic EL display element, comprising a polymerizable compound, the polymerizable compound contains a polyfunctional oxetane compound and does not contain a monofunctional oxetane compound, or the polymerizable compound contains a monofunctional oxetane compound in an amount of 28 mass% or less; the viscosity of the curable composition is 3 mPa s or more and 25 mPa s or less, The present invention relates to a curable composition for use as a sealant for an organic EL display element, wherein the dielectric constant of a cured film formed from the curable composition is 2.8 or less.

[0117] <Cured film and organic EL element> The cured film of the present disclosure (hereinafter also referred to as "the present cured film") is formed from the above-mentioned curable composition, and has little outgassing, excellent CVD resistance, and excellent device reliability. In the organic EL device of the present invention, the light-emitting layer is sealed with the cured film.

[0118] <<Method for manufacturing organic EL elements>> The present cured film and an organic EL device in which the organic light-emitting layer is sealed with the present cured film can be produced using the present composition by a method including the following steps 1 and 2. (Step 1) A step of applying the present composition to the surface of a substrate on which an organic light-emitting layer is formed. (Step 2) A step of forming a sealing structure by curing the composition by irradiating it with radiation. Each step will be described in detail below.

[0119] [Process 1: Coating process] In this process, the present composition is applied to the light-emitting layer-forming surface of a substrate on which an organic light-emitting layer has been formed, thereby forming a coating film made of the present composition on the light-emitting layer-forming surface. The substrate to which the present composition is applied has a laminate formed thereon, including various layers such as an anode layer, a hole injection layer, a hole transport layer, an electron injection layer, and a cathode layer in addition to the organic light-emitting layer, and this laminate constitutes an organic EL device. The light-emitting layer-forming surface to which the present composition is applied may be covered with an inorganic film (inorganic sealing layer). Examples of inorganic materials constituting the inorganic film include silicon nitride (SiNx) and silicon oxide (SiOx). In this case, a thin-film sealing layer including an organic sealing layer and an inorganic sealing layer is formed on the organic light-emitting layer as a sealing structure.

[0120] Examples of methods for applying the present composition include spraying, roll coating, spin coating, slit die coating, bar coating, and inkjet coating. Of these, inkjet coating is preferred from the viewpoints of throughput and thinning. The present composition exhibits excellent curability despite its low viscosity and suppresses the occurrence of coating unevenness, making it suitable for inkjet coating.

[0121] [Process 2: Curing process] In this step, the coating film formed in step 1 is irradiated with radiation to cure the coating film, thereby obtaining a cured film. Examples of radiation include charged particle beams such as ultraviolet light, far ultraviolet light, visible light, X-rays, and electron beams. Among these, ultraviolet light is preferred, and for example, ultraviolet light with a wavelength of 350 to 400 nm can be preferably used as the irradiation light. The radiation exposure dose is 0.05 to 10 J / m 2 This makes it possible to obtain an organic EL device coated with an organic sealing layer made of the present composition. The thickness of the cured film is usually 0.5 to 15 μm. The organic sealing layer formed from the present composition may be further coated with an inorganic film. Examples of inorganic materials that constitute the inorganic film include silicon nitride (SiNx) and silicon oxide (SiOx).

[0122] In the organic EL device of the present disclosure manufactured by the method including the above-described steps 1 and 2, the organic light-emitting layer is sealed with an organic sealing layer made of the present composition. Therefore, the organic EL device of the present disclosure can sufficiently prevent moisture from penetrating into the organic light-emitting layer, thereby suppressing moisture-related problems, specifically the occurrence of dark spots and deterioration of light-emitting properties such as brightness and luminous efficiency. Furthermore, the organic EL device of the present disclosure generates little outgas from the organic sealing layer, and the dielectric constant of the organic sealing layer is sufficiently low. Such an organic EL device of the present disclosure is useful, for example, as an organic EL lighting device or an organic EL display device. [Example]

[0123] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0124] The dielectric constants of the polyfunctional oxetane compounds obtained in the following synthesis examples were measured by the following method. <Method for measuring the dielectric constant of polyfunctional oxetane compounds> A curable composition was prepared by adding 100 parts by mass of a polyfunctional oxetane compound, 1 part by mass of (D-1) as a polymerization initiator, 0.1 parts by mass of (E-1) as a polymerization inhibitor, and 1 part by mass of (F-1) as a surfactant. Each curable composition was applied to a substrate, which had ITO vapor-deposited to a thickness of 30 nm on non-alkali glass, using a spin coater so that the cured thickness would be 8 μm. Next, an LED UV lamp was used to apply 395 nm ultraviolet light at 3000 mJ / cm. 2 A cured film was produced by irradiating the sample. A UniJet E110Z HD (Type U395A-455, manufactured by Ushio Inc.) was used as the LED UV lamp. Aluminum was then vapor-deposited to a thickness of 50 nm on the resin surface of the cured film to produce a test piece for dielectric constant measurement. The dielectric constant of the resulting test piece was measured at 25°C and 100 kHz using a dielectric constant measurement device. A 4284A LCR meter (manufactured by Hewlett-Packard) was used as the dielectric constant measurement device.

[0125] [Synthesis Example 1] Synthesis of polyfunctional oxetane compound (A-1) A 2 L eggplant-shaped flask containing a stir bar was charged with 94.7 g of 3-methyl-3-oxetanemethanol, 930 mL of dichloromethane, 113 g of triethylamine, and 7.6 g of 1-methylimidazole, and the mixture was cooled to an internal temperature of 10°C or below. At the same temperature, 177 g of tosyl chloride was added in portions and stirred for 30 minutes. The reaction was continued overnight at room temperature under a nitrogen atmosphere. The mixture was then diluted with approximately 1000 mL of dichloromethane and washed sequentially with 2 M hydrochloric acid, saturated aqueous NaHCO3, and ion-exchanged water. The organic layer was then dried over anhydrous magnesium sulfate and concentrated under reduced pressure using a rotary evaporator. The resulting residue was dried under reduced pressure to obtain 216 g of crude solid compound (1a). The crude product was used directly in the subsequent reaction. In the formula, "Ts" refers to a p-toluenesulfonyl group. [ka]

[0126] A 3 L eggplant-shaped flask containing a stir bar was charged with 216 g of compound (1a), 106 g of lithium bromide monohydrate, and 2200 mL of acetone. The mixture was allowed to react for 2.5 hours under reflux conditions under a nitrogen atmosphere. The insoluble matter was then removed by filtration through Celite, and the mixture was concentrated under reduced pressure at 200 Torr on a rotary evaporator until no more acetone was distilled. 1.5 L of diisopropyl ether was added to the resulting residue, and the insoluble matter was removed by filtration through Celite. The mixture was then concentrated under reduced pressure at 180 Torr on a rotary evaporator until no more solvent was distilled. Most of the solvent was then removed by atmospheric distillation using a Wittmer column. Further vacuum distillation was performed at 20-21 Torr / 70°C to obtain 125 g of compound (1b). [ka]

[0127] A 1 L eggplant-shaped flask equipped with a stir bar, a thermometer, a Dimroth condenser, and a dropping funnel, and purged with nitrogen, was charged with 11.8 g of 1,7-heptanediol and 200 mL of dimethylformamide (DMF). Then, 12 g of sodium hydride (oil-based) was added in an ice bath and stirred for 30 minutes under a nitrogen atmosphere. A solution of compound (1b) dissolved in 200 mL of DMF was then added dropwise over 20 minutes, ensuring the internal temperature did not exceed 10°C, and the mixture was stirred at 80°C for 3 hours under a nitrogen atmosphere. The reaction solution was then cooled to below 10°C, and 100 mL of ion-exchanged water was added. The mixture was then stirred at room temperature for 30 minutes. The resulting solution was extracted three times with a 3:1 (volume ratio) mixed solvent of hexane and ethyl acetate. The resulting organic layer was further extracted three times with ion-exchanged water. The organic layer was concentrated under reduced pressure using a rotary evaporator, and the resulting residue was purified using a silica gel column to obtain 29.0 g of compound (A-1). The resulting compound (A-1) had a dielectric constant of 2.87 and a functional group equivalent weight of 150.22. [ka]

[0128] [Synthesis Example 2] Synthesis of polyfunctional oxetane compound (A-2) 29.3 g of compound (A-2) represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that 1,7-heptanediol was replaced with 1,8-octanediol. The dielectric constant of the obtained compound (A-2) was 2.84, and the functional group equivalent weight was 157.235. [ka]

[0129] [Synthesis Example 3] Synthesis of polyfunctional oxetane compound (A-3) 31.7 g of compound (A-3) represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that 1,7-heptanediol was replaced with 1,9-nonanediol. The dielectric constant of the obtained compound (A-3) was 2.8, and the functional group equivalent weight was 164.245. [ka]

[0130] [Synthesis Example 4] Synthesis of polyfunctional oxetane compound (A-4) 31.2 g of compound (A-4) represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that 1,7-heptanediol was replaced with 1,10-decanediol. The dielectric constant of the obtained compound (A-4) was 2.76, and the functional group equivalent weight was 171.26. [ka]

[0131] [Synthesis Example 5] Synthesis of polyfunctional oxetane compound (A-5) A 2 L eggplant-shaped flask containing a stir bar was charged with 108 g of 3-ethyl-3-oxetanemethanol, 930 mL of dichloromethane, 112.6 g of triethylamine, and 7.6 g of 1-methylimidazole, and the mixture was cooled to an internal temperature of 10 °C or below. At the same temperature, 177 g of tosyl chloride was added in portions and stirred for 30 minutes. The reaction was continued overnight at room temperature under a nitrogen atmosphere. The mixture was then diluted with approximately 1000 mL of dichloromethane and washed sequentially with 2 M hydrochloric acid, saturated aqueous NaHCO3, and ion-exchanged water. The organic layer was then dried over anhydrous magnesium sulfate and concentrated under reduced pressure on a rotary evaporator. The resulting residue was dried under reduced pressure to yield 228 g of crude solid compound (5a). The crude product was used directly in the next reaction. [ka]

[0132] A 3 L eggplant-shaped flask containing a stir bar was charged with 228 g of compound (5a), 106 g of lithium bromide monohydrate, and 2200 mL of acetone. The mixture was allowed to react under reflux for 2.5 hours under a nitrogen atmosphere. The insoluble matter was then removed by filtration through Celite, and the mixture was concentrated under reduced pressure at 200 Torr on a rotary evaporator until no more acetone was distilled. 1.5 L of diisopropyl ether was added to the resulting residue, and the insoluble matter was removed by filtration through Celite. The mixture was then concentrated under reduced pressure at 180 Torr on a rotary evaporator until no more solvent was distilled. Most of the solvent was then removed by atmospheric distillation using a Wittmer column. Further vacuum distillation was carried out at 20-21 Torr / 80°C, yielding 136 g of compound (5b). [ka]

[0133] A 1 L eggplant-shaped flask equipped with a stirrer, a thermometer, a Dimroth condenser, and a dropping funnel, and purged with nitrogen, was charged with 11.8 g of 1,8-octanediol and 200 mL of DMF. Then, 12 g of sodium hydride (oil-based) was added in an ice bath and stirred for 30 minutes under a nitrogen atmosphere. A solution of compound (5b) dissolved in 200 mL of DMF was then added dropwise over 20 minutes, ensuring the internal temperature did not exceed 10°C, and the mixture was stirred at 80°C for 3 hours under a nitrogen atmosphere. The reaction solution was then cooled to below 10°C, and 100 mL of ion-exchanged water was added, followed by stirring at room temperature for 30 minutes. The resulting solution was extracted three times with a mixed solvent of hexane and ethyl acetate (3:1 by volume). The resulting organic layer was further extracted three times with ion-exchanged water. The organic layer was concentrated under reduced pressure using a rotary evaporator, and the resulting residue was purified using a silica gel column to obtain 33.2 g of compound (A-5). The resulting compound (A-5) had a dielectric constant of 2.76 and a functional group equivalent weight of 171.26. [ka]

[0134] [Synthesis Example 6] Synthesis of polyfunctional oxetane compound (A-6) 34.1 g of compound (A-6) represented by the following formula was obtained in the same manner as in Synthesis Example 5, except that 1,8-octanediol was replaced with 1,9-nonanediol. The dielectric constant of the obtained compound (A-6) was 2.73, and the functional group equivalent weight was 178.275. [ka]

[0135] [Synthesis Example 7] Synthesis of polyfunctional oxetane compound (A-7) A 2 L eggplant-shaped flask containing a stir bar was charged with 81.7 g of 3-oxetanemethanol, 930 mL of dichloromethane, 113 g of triethylamine, and 7.6 g of 1-methylimidazole, and the mixture was cooled to an internal temperature of 10°C or below. At the same temperature, 177 g of tosyl chloride was added in portions and stirred for 30 minutes. The reaction was continued overnight at room temperature under a nitrogen atmosphere. The mixture was then diluted with approximately 1000 mL of dichloromethane and washed sequentially with 2 M hydrochloric acid, saturated aqueous NaHCO3, and ion-exchanged water. The organic layer was then dried over anhydrous magnesium sulfate and concentrated under reduced pressure using a rotary evaporator. The resulting residue was dried under reduced pressure to obtain 204 g of crude solid compound (7a). The crude product was used directly in the next reaction. [ka]

[0136] A 3 L eggplant-shaped flask containing a stir bar was charged with 204 g of compound (7a), 106 g of lithium bromide monohydrate, and 2200 mL of acetone. The mixture was allowed to react for 2.5 hours under reflux conditions under a nitrogen atmosphere. The insoluble matter was then removed by filtration through Celite, and the mixture was concentrated under reduced pressure at 200 Torr on a rotary evaporator until no more acetone was distilled. 1.5 L of diisopropyl ether was added to the resulting residue, and the insoluble matter was removed by filtration through Celite. The mixture was then concentrated under reduced pressure at 180 Torr on a rotary evaporator until no more solvent was distilled. Most of the solvent was then removed by atmospheric distillation using a Wittmer column. Further vacuum distillation was performed at 20-21 Torr / 60°C to obtain 115 g of compound (7b). [ka]

[0137] A 1-L eggplant-shaped flask equipped with a stirrer, a thermometer, a Dimroth condenser, and a dropping funnel, and purged with nitrogen, was charged with 14.6 g of 1,8-octanediol and 200 mL of DMF. Then, 12 g of sodium hydride (oil-based) was added in an ice bath and stirred for 30 minutes under a nitrogen atmosphere. A solution of compound (7b) dissolved in 200 mL of DMF was then added dropwise over 20 minutes, ensuring the internal temperature did not exceed 10°C, and the mixture was stirred at 80°C for 3 hours under a nitrogen atmosphere. The reaction solution was then cooled to below 10°C, and 100 mL of ion-exchanged water was added. The mixture was then stirred at room temperature for 30 minutes. The resulting solution was extracted three times with a 3:1 (volume ratio) mixed solvent of hexane and ethyl acetate. The resulting organic layer was further extracted three times with ion-exchanged water. The organic layer was concentrated under reduced pressure using a rotary evaporator, and the resulting residue was purified using a silica gel column to obtain 27.1 g of compound (A-7). The resulting compound (A-7) had a dielectric constant of 2.91 and a functional group equivalent weight of 143.205. [ka]

[0138] [Synthesis Example 8] Synthesis of polyfunctional oxetane compound (A-8) 28.8 g of compound (A-8) represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that 1,7-heptanediol was replaced with 1,2-heptanediol. The dielectric constant of the obtained compound (A-8) was 2.87, and the functional group equivalent weight was 150.22. [ka]

[0139] [Synthesis Example 9] Synthesis of polyfunctional oxetane compound (A-9) 28.8 g of compound (A-9) represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that 1,7-heptanediol was replaced with 2-methyl-2-propyl-1,3-propanediol. The dielectric constant of the obtained compound (A-9) was 2.87, and the functional group equivalent weight was 150.22. [ka]

[0140] [Synthesis Example 10] Synthesis of polyfunctional oxetane compound (A-10) 31.0 g of compound (A-10) represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that 1,7-heptanediol was replaced with 2,4-diethyl-1,5-pentanediol (DL-, meso-mixture). The dielectric constant of the obtained compound (A-10) was 2.73, and the functional group equivalent weight was 164.245. [ka]

[0141] [Synthesis Example 11] Synthesis of polyfunctional oxetane compound (A-11) 31.4 g of compound (A-11) represented by the following formula was obtained in the same manner as in Synthesis Example 5, except that 1,8-octanediol was replaced with 1,2-heptanediol. The dielectric constant of the obtained compound (A-11) was 2.80, and the functional group equivalent weight was 164.245. [ka]

[0142] [Synthesis Example 12] Synthesis of polyfunctional oxetane compound (A-12) A 3L eggplant-shaped flask containing a stir bar was charged with 160.3 g of 2,4-diethyl-1,5-pentanediol, 1600 mL of dichloromethane, and 242.9 g of triethylamine, and the mixture was cooled to an internal temperature of below 10°C. At the same temperature, 381.3 g of tosyl chloride was added in portions and stirred for 30 minutes. The mixture was then stirred overnight at room temperature under a nitrogen atmosphere. The mixture was diluted with 1000 mL of dichloromethane and washed sequentially with 2 mol / L hydrochloric acid, saturated aqueous sodium bicarbonate, and ion-exchanged water. The organic layer was dried over anhydrous magnesium sulfate and concentrated under reduced pressure on a rotary evaporator. The resulting residue was dried under reduced pressure to obtain 377.4 g of solid. Next, the solid obtained above, 230.2 g of lithium bromide monohydrate, and 2000 mL of acetone were added to a 3L eggplant-shaped flask containing a stir bar, and the mixture was allowed to react under reflux for 2 hours. Insoluble matter was removed by filtration through Celite, and the mixture was concentrated under reduced pressure on a rotary evaporator until acetone no longer distilled. The resulting residue was mixed with 1500 mL of diisopropyl ether, washed with ion-exchanged water, and the organic layer was dried over anhydrous magnesium sulfate and concentrated under reduced pressure using a rotary evaporator. The resulting residue was then distilled under reduced pressure to obtain 231.7 g of compound (12a). [ka]

[0143] In a 2 L four-neck flask equipped with a stirrer, a thermometer, and a Dimroth condenser and purged with nitrogen, 71.5 g of compound (12a), 131 g of triphenylphosphine, and 600 mL of DMF were added and stirred for 15 hours at an internal temperature of 130° C. under a nitrogen atmosphere. After cooling to room temperature, the reaction solution was added dropwise to toluene, and the precipitated solid was collected and dried under reduced pressure to obtain 194 g of compound (12b) as an isomer mixture. [ka]

[0144] A 3L four-neck flask equipped with a stirring blade, a three-one motor, and a thermometer was charged with 102g of 3-methyl-3-oxetanemethanol, 1.58g of 2,2,6,6-tetramethylpiperidine-1-oxyl, and 2L of dichloromethane, and cooled to an internal temperature of 10°C or below. Next, 200g of sodium hypochlorite pentahydrate was added in portions so that the internal temperature did not exceed 10°C, and the mixture was stirred at the same temperature for another 3 hours. The reaction mixture was then poured into 2L of ion-exchanged water and stirred. The organic layer was separated and washed sequentially with 10% aqueous sodium thiosulfate, 2% aqueous sodium hydroxide, and ion-exchanged water. The organic layer was concentrated under reduced pressure using a rotary evaporator. The resulting residue was then distilled under reduced pressure to obtain 86.5g of compound (12c). [ka]

[0145] A 2 L four-neck flask equipped with a stirrer, a thermometer, and a dropping funnel, and purged with nitrogen, was charged with 162 g of compound (12b), 56.1 g of potassium t-butoxide, and 1 L of anhydrous THF. The mixture was stirred at room temperature for 1 hour under a nitrogen atmosphere. The reaction solution was then cooled to below 10°C, and a solution of 42.0 g of compound (12c) in 100 mL of anhydrous THF was added dropwise over 40 minutes, ensuring the internal temperature did not exceed 10°C. The mixture was then stirred at room temperature for 4 hours. 500 mL of ion-exchanged water was then added, and the insoluble matter was filtered. The resulting solution was concentrated under reduced pressure on a rotary evaporator to remove most of the THF. The residue was extracted twice with diisopropyl ether, washed with ion-exchanged water, and concentrated under reduced pressure on a rotary evaporator. The resulting residue was purified using a silica gel column to obtain 44.6 g of compound (12d) as an isomer mixture. [ka]

[0146] 4.40 g of activated carbon containing 5% palladium, 44.0 g of compound (12d), and 500 mL of ethyl acetate were sequentially added to a 1 L autoclave, and the reaction system was purged with hydrogen. The initial hydrogen pressure was then adjusted to 1.0 MPa, and the mixture was vigorously stirred at room temperature for 3 hours. The reaction solution was then suction filtered through a glass filter lined with Celite, and the filtrate was concentrated under reduced pressure using a rotary evaporator. The resulting residue was purified using a silica gel column to obtain 43.7 g of compound (A-12) as an isomer mixture. The dielectric constant of the resulting compound (A-12) was 2.73, and the functional group equivalent weight was 148.245. [ka]

[0147] [Synthesis Example 13] Synthesis of polyfunctional oxetane compound (A-13) 38.1 g of compound (A-13) was obtained in the same manner as in Synthesis Example 12, except that 3-methyl-3-oxetanemethanol was replaced with 3-ethyl-3-oxetanemethanol. The dielectric constant of the obtained compound (A-13) was 2.66, and the functional group equivalent weight was 162.275. [ka]

[0148] [Synthesis Example 14] Synthesis of polyfunctional oxetane compound (A-14) 41.6 g of compound (A-14) was obtained in the same manner as in Synthesis Example 12, except that compound (12a) was replaced with 1,6-dibromohexane. The dielectric constant of the obtained compound (A-14) was 2.92, and the functional group equivalent weight was 113.18. [ka]

[0149] [Synthesis Example 15] Synthesis of monofunctional oxetane compound (A2-2) A 500 mL four-neck flask equipped with a thermometer, dropping funnel, and Dimroth condenser was charged with 113 g of 20% sodium ethoxide ethanol solution and 50.9 mL of ethanol. 54.6 g of diethyl methylmalonate was added dropwise over 40 minutes while stirring at an internal temperature of 40-50°C. The mixture was then stirred for 30 minutes at an internal temperature of 50°C under a nitrogen atmosphere. Next, 101 g of 1-bromononane was added dropwise over 10 minutes at the same temperature, followed by stirring under reflux for 3 hours. After cooling to room temperature, insoluble matter was filtered through Celite. The resulting solution was concentrated under reduced pressure on a rotary evaporator to remove ethanol. Approximately 1000 mL of ethyl acetate and 800 mL of ion-exchanged water were added to the residue, and the mixture was separated. The organic layer was dried over anhydrous magnesium sulfate and concentrated under reduced pressure on a rotary evaporator. The resulting residue was dried under reduced pressure to obtain 129 g of crude compound (15a). [ka]

[0150] A 2 L four-neck flask equipped with a stirrer, a thermometer, a dropping funnel, and a Dimroth condenser, and purged with nitrogen, was charged with 19.1 g of lithium aluminum hydride and 192 mL of anhydrous tetrahydrofuran (THF). The flask was cooled to an internal temperature below 10 °C under a nitrogen atmosphere. Next, a solution of 129 g of crude compound (15a) in 1343 mL of anhydrous THF was added over 20 minutes to avoid vigorous reaction, followed by stirring under reflux for 1 hour. After confirming completion of the reaction by TLC, the flask was cooled to an internal temperature below 10 °C. A stirring blade and a three-one motor were attached, and saturated aqueous sodium sulfate was carefully added until the reaction mixture turned from gray to white to decompose the excess lithium aluminum hydride and terminate the reaction. The insoluble matter was filtered through Celite, and the resulting solution was concentrated under reduced pressure on a rotary evaporator, and the THF was removed. The residue was dissolved in ethyl acetate and washed sequentially with 1 M HCl, saturated aqueous NaHCO3, and ion-exchanged water. The organic layer was then concentrated under reduced pressure on a rotary evaporator. The resulting residue was purified using a silica gel column to obtain 59.5 g of compound (15b). [ka]

[0151] A 2L four-neck flask equipped with a stirring blade, a three-one motor, a thermometer, and a dropping funnel, and purged with nitrogen, was charged with 59.5 g of compound (15b) and 168 mL of anhydrous THF under a nitrogen atmosphere. Next, 136 mL of 1.6 M butyllithium hexane solution was added dropwise over 90 minutes, ensuring the internal temperature did not exceed 10°C, and the mixture was stirred at room temperature for an additional 1 hour. The reaction mixture was then cooled to an internal temperature of 10°C or below, and a solution of 37.7 g of tosyl chloride dissolved in 567 mL of anhydrous THF was added dropwise over 15 minutes, followed by stirring at room temperature for 90 minutes. The reaction mixture was then cooled to an internal temperature of 10°C or below, and 136 mL of 1.6 M butyllithium hexane solution was added dropwise over 15 minutes, ensuring the internal temperature did not exceed 10°C, followed by stirring overnight at room temperature. After stirring for an additional 3 hours at an internal temperature of 55°C, the reaction was quenched by adding methanol. The insoluble matter was filtered through Celite, and the resulting solution was concentrated under reduced pressure using a rotary evaporator to remove THF and hexane. The residue was dissolved in ethyl acetate and washed with ion-exchanged water, and the organic layer was concentrated under reduced pressure using a rotary evaporator. The resulting residue was purified using a silica gel column to obtain 37.7 g of a monofunctional oxetane compound (A2-2) represented by the following formula: [ka]

[0152] <Preparation of Curable Composition> The components used in preparing the curable compositions of the Examples and Comparative Examples are shown below.

[0153] (Polyfunctional oxetane compounds) (A-1) to (A-14): Compounds (A-1) to (A-14) synthesized in the above Synthesis Examples 1 to 14 (A-15): OXT-221 (3,3'-(oxybis(methylene))bis(3-ethyloxetane), manufactured by Toagosei Co., Ltd.), dielectric constant: 3.07

[0154] (Monofunctional oxetane compound) (A2-1): OXT-212 (3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane, manufactured by Toagosei Co., Ltd.) (A2-2): Compound (A2-2) obtained in Synthesis Example 15 above

[0155] (Multifunctional epoxy compound) (B1-1): X-22-163A (polysiloxane having epoxy structure-containing groups at both ends, manufactured by Shin-Etsu Chemical Co., Ltd.) (B1-2): X-40-2678 (Shin-Etsu Chemical Co., Ltd.)

[0156] (Polymerization initiator) (D-1): CPI-410B (sulfonium borate, manufactured by San-Apro Co., Ltd.) (D-2): CPI-310FG (triarylsulfonium salt with FG anion as a counter ion, manufactured by San-Apro Co., Ltd.)

[0157] (polymerization inhibitor) (E-1): 2,5-di-t-butylhydroquinone (Fujifilm Wako Pure Chemical Industries, Ltd.)

[0158] (surfactant) (F-1): Megafac F-563 (fluorine oligomer, manufactured by DIC Corporation)

[0159] (sensitizer) (G-1): UVS-1331 (manufactured by Air Water Performance Chemicals Inc.)

[0160] [Example 1] A curable composition was prepared by adding 40 parts by mass of (A-1) and 45 parts by mass of (A-15) as polyfunctional oxetane compounds, 15 parts by mass of (A2-1) as a monofunctional oxetane compound, 1 part by mass of (D-1) as a polymerization initiator, 0.1 part by mass of (E-1) as a polymerization inhibitor, and 1 part by mass of (F-1) as a surfactant.

[0161] [Examples 2 to 20, Comparative Examples 1 to 4] Curable compositions of Examples 2 to 20 and Comparative Examples 1 to 4 were prepared in the same manner as in Example 1, except that the compositions were changed as shown in Tables 1 and 2.

[0162] The viscosity, indentation modulus, and dielectric constant of the curable compositions prepared in Examples 1 to 20 and Comparative Examples 1 to 4 were measured by the methods described below. The measurement results are shown in Tables 1 and 2.

[0163] <Viscosity> The viscosity (mPa·s) of each curable composition was measured at 25°C and 20 rpm using an E-type viscometer (RE-85L (cone rotor type: 1°34' x R24), manufactured by Toki Sangyo Co., Ltd.).

[0164] <Dielectric constant> Each curable composition was applied to a substrate, which had ITO vapor-deposited to a thickness of 30 nm on non-alkali glass, using a spin coater so that the cured thickness would be 8 μm. Next, an LED UV lamp was used to apply 395 nm ultraviolet light at 3000 mJ / cm. 2 A cured film was produced by irradiating the sample. A UniJet E110Z HD (Type U395A-455, manufactured by Ushio Inc.) was used as the LED UV lamp. Aluminum was then vapor-deposited to a thickness of 50 nm on the resin surface of the cured film to produce a test piece for dielectric constant measurement. The dielectric constant of the resulting test piece was measured at 25°C and 100 kHz using a dielectric constant measurement device. A 4284A LCR meter (manufactured by Hewlett-Packard) was used as the dielectric constant measurement device.

[0165] <Indentation elastic modulus> Each curable composition was applied to a thickness of 8 μm using a spin coater, and then irradiated with ultraviolet light having a wavelength of 395 nm at 3000 mJ / cm using an LED lamp. 2 After the coating was cured by irradiation, the indentation modulus (GPa) was measured using a Fischer Picodentor HM500 measuring device.

[0166] [evaluation] For the curable compositions prepared in Examples 1 to 20 and Comparative Examples 1 to 4, the following items were evaluated by the methods described below. The evaluation results are shown in Tables 1 and 2.

[0167] <Outgas> The outgas generated during heating of the cured films of each curable composition obtained in the examples and comparative examples was measured by gas chromatography using the headspace method as shown below. First, each curable composition was coated to a thickness of 8 μm using a spin coater. Next, after irradiating ultraviolet light with a wavelength of 395 nm from an LED lamp at 3000 mJ / cm 2 to cure the coating film, the cured film was placed in a headspace vial, the vial was sealed, and heated at 110 °C for 30 minutes to measure the amount of generated gas (ppm) by the headspace method.

[0168] <Inkjet coating property> For an evaluation substrate on which SiNx was formed to a film thickness of 100 nm on a glass substrate, inkjet ejection of each curable composition was performed from an inkjet head of a piezo-type inkjet printer at a pitch of 50 μm × 50 μm to produce a coating film with a size of 10 cm square. Further, after 5 minutes, it was irradiated with a 395 nm LED lamp at an exposure amount of 3000 mJ / cm 2 to cure the coating film. At that time, the voltage conditions of the inkjet head were changed so that the film thickness of the cured film became 8 μm, and the amount of one drop of the ejected ink dot was adjusted. The obtained cured film was evaluated according to the following criteria. ○: No coating film unevenness was observed visually. △: Coating film unevenness due to partial film thickness change was observed visually. ×: Uncoated areas were observed visually.

[0169] <CVD resistance> Each curable composition was coated on a non-alkali glass using a spin coater so that the thickness after curing became 8 μm. Next, ultraviolet light with a wavelength of 395 nm was irradiated from an LED UV lamp at 3000 mJ / cm 2The coating film was cured by irradiating it with light. The LED UV lamp used was a UniJet E110Z HD (Type U395A-455, manufactured by Ushio Inc.). Then, a 100 nm thick inorganic sealing layer (SiNx film) was formed on the organic sealing layer by RF sputtering using a SiNx target, and the surface was observed using an SEM. ◯: No wrinkles on the surface of the inorganic sealing layer. △: There are some wrinkles on the surface of the inorganic sealing layer. ×: Wrinkles are observed on the entire surface of the inorganic sealing layer.

[0170] <Element reliability> A plurality of array substrates were prepared, each having a glass substrate (OA-10, manufactured by Nippon Electric Glass Co., Ltd.) with an array of ITO transparent electrodes and a 3-μm-thick planarization layer with contact holes that exposed only a portion of the ITO transparent electrodes. An Al film with a thickness of 100 nm was formed on the planarization layer by DC sputtering using an Al target. An ITO film with a thickness of 20 nm was formed on the Al film by DC magnetron reactive sputtering using an ITO target. The substrates thus formed had an anode layer consisting of an Al film and an ITO film. A resist material (Optomer NN803, manufactured by JSR Corporation) was used to form a coating on the anode layer, followed by a series of processes including i-line irradiation (wavelength 365 nm), development, running water rinsing, air drying, and heat treatment, forming a pixel-defining layer with a 2-mm square opening region in part of the anode layer. The substrates with the anode layer and pixel-defining layer formed thereon were transferred to a vacuum deposition chamber, and the deposition chamber was heated to 1E. -4After evacuating the chamber to 100 Pa, a hole-injecting molybdenum oxide (MoOx) film was deposited on the substrate by resistance heating deposition at a deposition rate of 0.004-0.005 nm / sec using a deposition mask with a predetermined pattern, forming a hole-injecting layer with a thickness of 1 nm. A hole-transporting layer with a thickness of 35 nm was formed on the hole-injecting layer by resistance heating deposition of 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD) using a deposition mask with a predetermined pattern under the same evacuation conditions as the hole-injecting layer. The deposition rate was 0.2-0.3 nm / sec. A green light-emitting material, tris(8-quinolinolato)aluminum, an aluminum chelate complex, was deposited on the hole-transporting layer by resistance heating deposition under the same conditions as the hole-transporting layer, forming a 35 nm light-emitting layer. The film formation rate was 0.5 nm / sec or less. A film of lithium fluoride was formed on the light-emitting layer by resistance heating vapor deposition under the same exhaust conditions as for the hole injection layer, forming an electron injection layer with a thickness of 0.8 nm. The film formation rate was 0.004 nm / sec or less. Subsequently, magnesium and Ag were simultaneously formed on the electron injection layer by resistance heating vapor deposition under the same exhaust conditions as for the hole injection layer, forming a first cathode layer with a thickness of 5 nm. The film formation rate was 0.5 nm / sec or less. Subsequently, the substrate was transferred to another film formation chamber (sputtering chamber), and a second cathode layer with a thickness of 100 nm was formed on the first cathode layer by RF sputtering using an ITO target. In this manner, a substrate on which an organic EL device for evaluation was formed was obtained. A thin film sealing layer was formed on the substrate on which the organic EL element was formed by the following procedure. The substrate on which the organic EL element was formed was transferred to a film formation chamber (sputtering chamber), and an inorganic sealing layer (SiNx film) with a thickness of 100 nm was formed on the cathode layer by RF sputtering using a SiNx target. Next, the organic EL element was transferred to a glove box substituted with N2, and each curable composition was ejected in a predetermined pattern using a piezo-type inkjet printer, and then an exposure dose of 3000 mJ / cm2 was used using a UniJet E110ZHD 395 nm LED lamp manufactured by Ushio Inc. 2The organic EL device was then irradiated with light at 1000 W ... 2 The appearance of the light emitted from the light-emitting part (non-lighting part: dark spot) was observed and evaluated based on the following criteria. ◯: No dark spots with a diameter of 0.1 mm or more are observed within the 2 mm square light-emitting area. △: One or two dark spots with a diameter of 0.1 mm or more are observed within a 2 mm square light-emitting area. ×: Three or more dark spots with a diameter of 0.1 mm or more are observed within a 2 mm square light-emitting area.

[0171] [Table 1]

[0172] [Table 2]

[0173] As shown in Tables 1 and 2, the curable compositions of Examples 1 to 20 were able to form cured films with excellent inkjet coatability, reduced outgassing, and excellent CVD resistance and device reliability. On the other hand, the comparative examples were inferior to the examples in terms of inkjet coatability, outgassing, CVD resistance, and device reliability.

Claims

1. A curable composition for an organic EL display element sealant, comprising a polymerizable compound, the polymerizable compound includes a monofunctional oxetane compound and a polyfunctional oxetane compound, the monofunctional oxetane compound accounts for 28% by mass or less of the polymerizable compound; The viscosity of the curable composition is 3 mPa s or more and 25 mPa s or less, a cured film formed from the curable composition has a dielectric constant of 2.8 or less; A curable composition for use as an encapsulant for organic EL display elements.

2. 2. The curable composition for use as an encapsulant for an organic EL display element according to claim 1, wherein a cured film formed from the curable composition has an indentation modulus of elasticity of 1.0 GPa or more when indented with an indenter.

3. The curable composition for an encapsulant for an organic EL display element according to claim 1 , wherein the polyfunctional oxetane compound comprises a compound represented by the following formula (1): 【Chemistry 1】 (In formula (1), R １ each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms. R ２ represents a divalent organic group.

4. The curable composition for an encapsulant for an organic EL display element according to claim 3 , wherein the compound represented by formula (1) has a dielectric constant of 3.0 or less.

5. The curable composition for an encapsulant for an organic EL display element according to claim 4 , wherein the compound represented by formula (1) is contained in the polymerizable compound in an amount of 10% by mass to 90% by mass.

6. In the formula (1), R １ The curable composition for an organic EL display element sealant according to claim 3 , wherein is a methyl group.

7. In the formula (1), R ２ The curable composition for an organic EL display element sealant according to claim 3 , wherein the curable composition does not have a siloxane structure.

8. In the formula (1), R ２ The curable composition for an encapsulant for an organic EL display element according to claim 3 , wherein the alkyl group has one or more structures selected from the group consisting of an ether bond and a branched structure.

9. 2. The curable composition for an encapsulant for an organic EL display element according to claim 1, wherein the polyfunctional oxetane compound comprises at least one compound selected from the group consisting of compounds represented by the following formulas (1-1), (1-2), (1-3), and (1-4): 【Chemistry 2】 (In formula (1-1), R １ each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms. R ２１ represents a linear or branched alkanediyl group having 3 to 20 carbon atoms. 【Transformation 3】 (In formula (1-2), R ２２ represents a linear or branched alkanediyl group having 3 to 20 carbon atoms. R ２３ represents a single bond or a linear or branched alkanediyl group having 1 to 5 carbon atoms. ２３ are the same or different from each other. R １ has the same meaning as the above formula (1-1). 【Chemistry 4】 (In formula (1-3), R ２４ represents a linear or branched alkanediyl group having 2 to 10 carbon atoms. ２４ are the same or different from each other. R ２５ represents a single bond or a linear or branched alkanediyl group having 1 to 5 carbon atoms. ２５ are the same or different from each other. R １ has the same meaning as the above formula (1-1). 【Transformation 5】 (In formula (1-4), R ２６ represents a linear or branched alkanediyl group having 2 to 10 carbon atoms. ２６ are the same or different from each other. R ２７ represents an alkyl group having 1 to 4 carbon atoms or an aromatic group having 6 to 20 carbon atoms. ２７ are the same or different from each other. X represents an oxygen atom or an alkanediyl group having 1 to 6 carbon atoms. When a plurality of X's are present, the plurality of X's may be the same or different. n represents an integer of 1 to 10. y1 and y2 each independently represent 0 or 1. R ２８ represents a single bond or a linear or branched alkanediyl group having 1 to 5 carbon atoms. ２８ are the same or different from each other. R １ has the same meaning as the above formula (1-1).

10. R in the formula (1-1) ２１ , R in formula (1-2) ２２ The curable composition for an encapsulant for an organic EL display element according to claim 9, wherein is an alkanediyl group having 3 to 20 carbon atoms and having a branched structure with 1 to 3 atoms.

11. 11. The curable composition for an organic EL display element sealant according to claim 1, wherein the polyfunctional oxetane compound has a functional group equivalent weight of 120 or more and 250 or less.

12. The curable composition for an organic EL display element sealant according to any one of claims 1 to 10, wherein the polymerizable compound includes a compound having one or more 3,4-epoxycyclohexyl groups in the molecule.

13. The curable composition for an organic EL display element sealant according to any one of claims 1 to 10, further comprising a surfactant.

14. The curable composition for an organic EL display element sealant according to any one of claims 1 to 10, further comprising a polymerization inhibitor or an antioxidant.

15. The curable composition for use as a sealant for an organic EL display element according to any one of claims 1 to 10, which is a sealant for an organic EL element to be inkjet coated.

16. A cured film for use as an encapsulant for an organic EL display element, formed using the curable composition for use as an encapsulant for an organic EL display element according to any one of claims 1 to 10.

17. An organic EL element having an organic light-emitting layer sealed with the cured film for an organic EL display element sealant according to claim 16.

18. a step of applying the curable composition for an organic EL display element sealant according to any one of claims 1 to 10 to a surface of a substrate on which an organic light-emitting layer has been formed, a step of forming a sealing structure by irradiating radiation to cure the curable composition. A method for manufacturing an organic EL element, comprising:

19. The method for producing an organic EL element according to claim 18 , wherein the curable composition for an organic EL display element sealant is applied to the surface on which the light-emitting layer is to be formed by inkjet coating.

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