Curable composition, cured film, organic el element and production method of organic el element

Abstract

To provide a curable composition capable of forming a cured film with little generation of outgas.SOLUTION: A curable composition contains a monofunctional oxetane compound (A1) and a polyfunctional compound (A2) which is at least one selected from a group consisting of a polyfunctional oxetane compound and a polyfunctional oxirane compound, and a polymerization initiator. The monofunctional oxetane compound (A1) has a GPC peak area ratio obtained by a specific evaluation of curability with GPC of 5.0% or less. When a cured film obtained by irradiating a coated film formed with the curable composition with an ultraviolet ray with a wavelength of 395 nm in a condition of illuminance of 1,000 mW / cm2 and integrated light quantity of 1,000 mJ / cm2 is heated at 110°C, an outgas amount detected with a headspace method is less than 400 ppm.SELECTED DRAWING: None

Description

[Technical Field]

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

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

[0003] The organic light-emitting layer of an organic EL element is susceptible to deterioration due to contact with moisture and oxygen. For example, there is a concern that moisture may penetrate into the element over a long period of operation, resulting in the formation of non-light-emitting areas (hereinafter also referred to as "dark spots"), or that light-emitting characteristics may be reduced due to contact with moisture and oxygen. Therefore, conventionally, a sealing structure has been provided in an organic EL element to prevent the organic light-emitting layer from coming into contact with moisture and oxygen (see, for example, Patent Documents 1 and 2). Patent Documents 1 and 2 disclose a sealing structure in which a cured film is formed from a curable composition containing organic materials such as a polymerizable compound and a polymerization initiator, and the cured film covers the organic light-emitting layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-26515 [Patent Document 2] International Publication No. 2021 / 010226 Summary of the Invention [Problem to be solved by the invention]

[0005] When an organic EL element is provided with a sealing structure formed from a curable composition, outgassing may easily occur from the sealing structure due to components of the curable composition remaining in the sealing structure (e.g., unreacted polymerizable compound, solvent, etc.) and decomposition products of the polymer obtained by curing the polymerizable compound. Since outgassing from the sealing structure may deteriorate the organic EL element, it is required to minimize outgassing from the sealing structure in the organic EL element.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a curable composition that can form a cured film with little outgassing. [Means for solving the problem]

[0007] According to the present invention, there are provided the following curable composition, cured film, organic EL device, and method for producing the same.

[0008] [1] A curable composition comprising a monofunctional oxetane compound (A1), a polyfunctional compound (A2) which is at least one selected from the group consisting of polyfunctional oxetane compounds and polyfunctional oxirane compounds, and a polymerization initiator, wherein the monofunctional oxetane compound (A1) has a GPC peak area ratio of 5.0% or less as determined by the following curability evaluation using gel permeation chromatography (GPC), and a coating film formed from the curable composition is irradiated with ultraviolet light having a wavelength of 395 nm at an irradiance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2 a curable composition, wherein when the cured film obtained by irradiating the composition under the conditions of (a) above is heated at 110°C, the amount of outgassing detected by a headspace method is less than 400 ppm. Curability evaluation: A coating film formed from a composition containing the compound to be evaluated alone as a polymerizable compound and further containing a polymerization initiator was irradiated with ultraviolet light having a wavelength of 395 nm at an irradiance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2The cured film obtained by irradiating under the above conditions is immersed in tetrahydrofuran, and the tetrahydrofuran solution after the immersion is analyzed by GPC. The total peak area of ​​the GPC chart obtained is defined as the first peak area (S1), and the peak area of ​​the peak derived from the remaining portion of the compound to be evaluated in the GPC chart of the tetrahydrofuran solution is defined as the second peak area (S2). The ratio (S2 / S1) of the second peak area to the first peak area is defined as the GPC peak area ratio.

[0009] [2] A cured film formed using the curable composition according to [1] above. [3] An organic EL element in which an organic light-emitting layer is sealed with the cured film of [2] above. [4] A method for producing an organic EL element, comprising: a step of applying the curable composition according to [1] to a surface of a substrate on which an organic light-emitting layer has been formed, and a step of forming a sealing structure by curing the curable composition by irradiation with radiation. [Effects of the Invention]

[0010] According to the curable composition of the present invention, a cured film that generates little outgassing can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a GPC chart in which the compound represented by formula (1) is used as the evaluation target compound. [Figure 2] 1 is a GPC chart in which the compound represented by formula (2) is used as the evaluation target compound. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] As used herein, 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 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 may also contain 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 composed of a hydrocarbon structure. The term "epoxy group" encompasses both "oxiranyl group" and "oxetanyl group."

[0014] 《Curable composition》 The curable composition of the present disclosure (hereinafter also referred to as "the composition") contains a monofunctional oxetane compound (A1), a polyfunctional compound (A2) that is at least one selected from the group consisting of polyfunctional oxetane compounds and polyfunctional oxirane compounds, and a polymerization initiator. The monofunctional oxetane compound (A1) and the polyfunctional compound (A2) contained in the composition are polymerizable compounds that polymerize in the presence of a polymerization initiator, for example, when exposed to heat or light. Below, each component contained in the composition and other components that may be blended as needed are described in detail, and the physical properties of the composition are also described. Unless otherwise specified, each component may be used alone or in combination of two or more.

[0015] <[A] Polymerizable compound> Monofunctional oxetane compounds (A1) The monofunctional oxetane compound (A1) is a cationically polymerizable compound having one oxetane ring per molecule. The monofunctional oxetane compound (A1) contained in the composition has a GPC peak area ratio of 5.0% or less, as determined by the following curability evaluation using gel permeation chromatography (GPC). Curability evaluation: A coating film formed from a composition containing the compound to be evaluated alone as the polymerizable compound and further containing a polymerization initiator (hereinafter also referred to as the "composition for evaluation") was irradiated with ultraviolet light having a wavelength of 395 nm at an illuminance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2 A cured film is obtained by irradiating under the conditions. The obtained cured film is immersed in tetrahydrofuran (THF), and the tetrahydrofuran solution after immersion is analyzed by GPC. The total peak area of ​​the resulting GPC chart (also referred to as the "cured film GPC chart") is designated as the first peak area (S1). In the cured film GPC chart, the peak area of ​​the peak derived from the remaining portion of the compound to be evaluated is designated as the second peak area (S2). The ratio (S2 / S1) of the second peak area (S2) to the first peak area (S1) is designated as the GPC peak area ratio, and the curability of the compound to be evaluated is evaluated based on the GPC peak area ratio.

[0016] The above-described curability evaluation allows for determining the proportion of the remaining portion of the evaluation target compound that was not polymerized by UV irradiation (i.e., unreacted monomer) relative to the total amount of the evaluation target compound contained in the evaluation composition. The smaller the GPC peak area ratio determined by the above-described curability evaluation, the less unreacted monomer remains in the cured film after UV irradiation of the evaluation composition, and the better the curability of the evaluation target compound. This evaluation method allows for the evaluation of the reactivity (i.e., curability) of a polymerizable compound using a technique that closely resembles the actual process for producing a cured film for an organic EL device or the like from a curable composition.

[0017] The evaluation composition is prepared, for example, by mixing 100 parts by mass of the compound to be evaluated, 1 part by mass of a polymerization initiator, and 0.1 parts by mass of a surfactant. As the polymerization initiator, any polymerization initiator that can be incorporated into the present composition can be used as appropriate. Furthermore, the evaluation composition may further contain a surfactant in addition to the compound to be evaluated and the polymerization initiator to improve the coatability of the evaluation composition. Similarly, any surfactant that can be incorporated into the present composition can be used as appropriate. To ensure the reliability of the evaluation results, it is recommended that the components incorporated into the evaluation composition, other than the compound to be evaluated, be the same type and amount between the samples being compared.

[0018] A specific embodiment of the curability evaluation is described below. First, a composition for evaluation is prepared, which comprises a monofunctional oxetane compound (A1), which is the compound to be evaluated, a polymerization initiator, and a surfactant. Next, the prepared composition for evaluation is applied to a glass substrate to form a coating film made of the composition for evaluation. Next, ultraviolet light with a wavelength of 395 nm is applied to the coating film on the glass substrate from a UV-LED lamp at an illuminance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2 The composition for evaluation is cured by irradiating the substrate with light under the exposure conditions of 1000 nm to 1000 nm. The exposure conditions are sufficient to fully cure the composition for evaluation. The composition for evaluation is cured under nitrogen atmosphere at 25°C with a dew point of -60°C or less (200 ppm). The cured film obtained by the above curing treatment is then immersed together with the glass substrate in THF. The substrate should be immersed in a sufficient amount of THF so that the cured film on the glass substrate is in even contact with the THF. The immersion time should be sufficient to dissolve the cured film formed on the substrate in THF, for example, 10 to 30 minutes. The tetrahydrofuran solution after immersion is analyzed by GPC to obtain a GPC chart (cured film GPC chart), and the total peak area of ​​the cured film GPC chart is determined as the first peak area (S1). It is believed that the tetrahydrofuran solution after immersion contains unreacted monomer in addition to the polymer component (i.e., the polymer of the monofunctional oxetane compound (A1)), which is the main component of the cured film on the substrate.

[0019] Separately from the evaluation composition, a monomer solution consisting of the monofunctional oxetane compound (A1) and THF was prepared as a standard sample, and a GPC chart (also referred to as a "standard GPC chart") was obtained by GPC analysis of the standard sample. Based on this standard GPC chart, the peak area of ​​the peak in the cured film GPC chart whose elution time coincides with that of the peak appearing in the standard GPC chart was designated as the second peak area (S2). Note that the peak appearing in the standard GPC chart is a peak derived from the monofunctional oxetane compound (A1), which is the compound to be evaluated. The ratio (S2 / S1) of the second peak area (S2) to the first peak area (S1) was calculated as the GPC peak area ratio, thereby parameterizing the curability of the monofunctional oxetane compound (A1). Details of the calculation method for the first peak area (S1) and the second peak area (S2) follow the method described in the Examples below.

[0020] As a specific example, the following formula (1) or (2): [ka] The results of curability evaluation were performed using each of the compounds represented by formula (1) as the evaluation target compound, and are shown in Figures 1 and 2. Figures 1 and 2 each show a cured film GPC chart and a standard GPC chart on a single graph. Figure 1 shows the results when the compound represented by formula (1) above was used as the evaluation target compound, and Figure 2 shows the results when the compound represented by formula (2) above was used as the evaluation target compound. In Figures 1 and 2, the dashed dotted line represents the standard GPC chart, and the solid line represents the cured film GPC chart.

[0021] As shown in Figures 1 and 2, the peaks in the cured film GPC chart are broadened, and a bimodal peak appears at a position (PA in the figure) where the elution time (RT) is 16 to 17 minutes. Furthermore, a bimodal peak appears at position PA, where the elution time (RT) is 16 to 17 minutes, in the standard GPC chart. This indicates that the peak appearing at position PA in the cured film GPC chart is a peak derived from the target compound. The ratio of the peak area at position PA to the total peak area in the cured film GPC chart (GPC peak area ratio) can be used to determine the unreacted monomer ratio of the target compound, i.e., the curability of the target compound. The GPC peak area ratio for each compound was 2.64% for the compound represented by formula (1) and 8.23% for the compound represented by formula (2).

[0022] The monofunctional oxetane compound (A1) incorporated into the composition has a GPC peak area ratio of 5.0% or less as determined by the above-described curability evaluation. If the GPC peak area ratio exceeds 5.0%, the amount of outgassing from the cured film will be too high due to the large amount of unreacted monomer remaining in the cured film. This may cause deterioration of the organic EL device. From the viewpoint of obtaining a cured film with a sufficiently low amount of outgassing, the GPC peak area ratio of the monofunctional oxetane compound (A1) is preferably 4.0% or less, more preferably 3.5% or less, and even more preferably 3.0% or less. Furthermore, from the viewpoint of suppressing problems that may arise due to excessively high reactivity, the GPC peak area ratio of the monofunctional oxetane compound (A1) is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more.

[0023] The structure of the monofunctional oxetane compound (A1) is not particularly limited, as long as the GPC peak area ratio determined by the above-mentioned curability evaluation is 5.0% or less. Examples of the monofunctional oxetane compound (A1) include compounds having one oxetane ring and one or two substituents bonded to the carbon atom at position 3 of the oxetane ring. In terms of being able to obtain a curable composition that has a small amount of outgassing from the cured film and good wetting and spreading properties, a compound having one oxetane ring and two substituents (a first substituent and a second substituent) bonded to the carbon atom at position 3 of the oxetane ring is preferably used as the monofunctional oxetane compound (A1).

[0024] In terms of achieving a good balance between reducing outgassing from the cured film and improving the wettability and spreadability of the curable composition, a compound having a methyl group as the substituent (first substituent) attached to the 3-position of the oxetane ring is preferably used as the monofunctional oxetane compound (A1). The presence of a methyl group at the 3-position of the oxetane ring in the monofunctional oxetane compound (A1) reduces steric hindrance during curing, increasing the reactivity of the monofunctional oxetane compound (A1), compared to, for example, a case in which an ethyl group is attached instead of a methyl group. This is thought to be due to the fact that unreacted monomers in the cured film are reduced by suppressing polymer decomposition in the cured film compared to a case in which a methyl group is not attached to the 3-position of the oxetane ring. This is also thought to be due to the fact that the wettability and spreadability of the composition are ensured by the fact that the presence of a methyl group at the 3-position of the oxetane ring reduces polymer decomposition in the cured film and moderately increases interaction with the substrate to be inkjet-coated and the film formed on the substrate.

[0025] When the monofunctional oxetane compound (A1) has a first substituent and a second substituent at the 3-position of the oxetane ring, and the first substituent is a methyl group, examples of the second substituent include an alkyl group having 1 to 20 carbon atoms and a monovalent group containing -O- between the carbon-carbon bond of an alkyl group having 2 to 20 carbon atoms. The group exemplified as the second substituent may be linear or branched. When the second substituent is linear, ease of synthesis is easily ensured. Furthermore, when the second substituent is branched, the viscosity of the composition can be easily adjusted within an appropriate range, resulting in better wetting and spreading properties. From the viewpoint of ensuring an appropriate viscosity of the composition, the number of carbon atoms in the second substituent is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. Furthermore, to prevent the viscosity of the composition from becoming too high, the number of carbon atoms in the second substituent is preferably 15 or less, more preferably 12 or less.

[0026] The monofunctional oxetane compound (A1) is attached directly to the oxetane ring or 1 -R 1 -O-(However, R 1 is an alkanediyl group having 1 to 3 carbon atoms, and "* 1 " represents a bond to the oxetane ring.) The monofunctional oxetane compound (A1) may have a linear or branched alkyl group having 6 to 20 carbon atoms bonded via the linear or branched alkyl group. When the monofunctional oxetane compound (A1) has the linear or branched alkyl group, the viscosity of the composition can be easily adjusted within an appropriate range, and the effect of improving the wetting and spreading properties can be further enhanced.

[0027] From the viewpoint of further reducing outgassing, it is preferable that the monofunctional oxetane compound (A1) does not have an ether bond in the moiety other than the oxetane ring. When the monofunctional oxetane compound (A1) does not have an ether bond in the moiety other than the oxetane ring, the outgassing reduction effect can be further enhanced compared to when a compound having an ether bond in the moiety other than the oxetane ring is used. Furthermore, when a compound having no ether bond in the moiety other than the oxetane ring is used, depolymerization and partial scission are less likely to occur in the polymer obtained by polymerization of a polymerizable compound containing the monofunctional oxetane compound (A1), and this is thought to lead to further reduction in outgassing.

[0028] From the viewpoint of ensuring the strength of the cured film, the molecular weight of the monofunctional oxetane compound (A1) is preferably 100 or more, more preferably 120 or more, and even more preferably 140 or more. From the viewpoint of improving the wetting and spreading properties of the composition, the molecular weight of the monofunctional oxetane compound (A1) is preferably 300 or less, more preferably 250 or less, and even more preferably 220 or less.

[0029] Specific examples of the monofunctional oxetane compound (A1) include compounds represented by the following formulae (a-1) to (a-5). [ka]

[0030] In the present composition, the content of the monofunctional oxetane compound (A1) is preferably 20 to 60 mass% based on the total amount of polymerizable compounds contained in the present composition. When the content of the monofunctional oxetane compound (A1) is within the above range, the dielectric constant of the cured film obtained using the present composition can be reduced, outgassing can be sufficiently suppressed, and the wetting and spreading properties of the present composition can be improved. From these perspectives, the content of the monofunctional oxetane compound (A1) is more preferably 25 mass% or more, and even more preferably 30 mass% or more, based on the total amount of polymerizable compounds. Furthermore, from the perspective of improving the curability and other properties of the present composition, the content of the monofunctional oxetane compound (A1) is more preferably 55 mass% or less, and even more preferably 50 mass% or less, based on the total amount of polymerizable compounds.

[0031] ·Multifunctional compound (A2) The polyfunctional compound (A2) is a compound having a total of two or more oxetane rings and / or oxirane rings in one molecule. The polyfunctional compound (A2) is not particularly limited as long as it exhibits cationic polymerizability. The total number of oxetane rings and oxirane rings in one molecule of the polyfunctional compound (A2) is preferably 2 to 4, more preferably 2, from the viewpoint of ensuring good wetting and spreading properties of the composition.

[0032] Specific examples of the polyfunctional compound (A2) include polyfunctional oxetane compounds such as 3,7-bis(3-oxetanyl)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, bis[1-ethyl(3-oxetanyl)]methyl ether, bis(3-ethyl-3-oxetanylmethyl)ether, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, 1,3-bis(3-ethyl-3-oxetanylmethoxy)propane, 1,4- Examples of the bis(3-ethyl-3-oxetanylmethoxy)butane include bis(3-ethyl-3-oxetanylmethoxymethyl)benzene, 1,4-bis(3-ethyl-3-oxetanylmethoxymethyl)benzene, 1,3-bis(3-ethyl-3-oxetanylmethoxymethyl)benzene, 1,2-bis(3-ethyl-3-oxetanylmethoxymethyl)benzene, 4,4'-bis(3-ethyl-3-oxetanylmethoxymethyl)biphenyl, 2,2'-bis(3-ethyl-3-oxetanylmethoxymethyl)biphenyl, 1,6-bis((3-methyloxetan-3-yl)methoxy)hexane, 1,6-bis((3-ethyloxetan-3-yl)methoxy)hexane, a hydrolysis condensate of 3-[(3-ethyloxetan-3-yl)methoxy]propyltrialkoxysilane, and a condensation reaction product of 3-ethyloxetan-3-ylmethanol and a silanetetraol polycondensate.

[0033] Specific examples of polyfunctional oxirane 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, and 3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate. Epoxy group-containing low molecular weight compounds such as methylene bis(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, 2,2-bis(3,4-epoxycyclohexan-1-yl)propane, etc.; Compounds having two or more alicyclic epoxy groups (preferably 3,4-epoxycyclohexyl groups) in the molecule, such as trade names "X-40-2678," "X-40-2670," and "X-40-2720" (all manufactured by Shin-Etsu Chemical Co., Ltd.); Examples of epoxy group-containing resins include 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. Here, the term "alicyclic epoxy group" refers to a group having a ring structure formed by linking two adjacent carbon atoms among the carbon atoms constituting an aliphatic hydrocarbon ring via an ether bond.

[0034] Among the above-mentioned polyfunctional compounds, compounds having a total of two or more oxetane rings in the molecule or a total of two or more alicyclic epoxy groups in the molecule can be preferably used as the polyfunctional compound (A2), in that a curable composition exhibiting excellent curability can be obtained while achieving a low dielectric constant of the resulting cured film.

[0035] In the present composition, the content of the polyfunctional compound (A2) is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the polymerizable compounds, and is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, based on the total amount of the polymerizable compounds.

[0036] While the polyfunctional compound (A2) has high curability, the polyfunctional compound (A2) alone has a high viscosity, and the wettability and spreadability are insufficient, particularly when the curable composition is applied by inkjet coating to form a cured film. Therefore, it has been considered to incorporate a monofunctional oxetane compound to improve the wettability and spreadability of the curable composition. However, monofunctional oxetane compounds tend to be a cause of outgassing from the cured film. In this regard, the present composition contains a specific compound (monofunctional oxetane compound (A1)) as the monofunctional oxetane compound, thereby suppressing outgassing from the cured film and improving the wettability and spreadability.

[0037] Other polymerizable compounds The present composition may contain only the monofunctional oxetane compound (A1) and the polyfunctional compound (A2) as polymerizable compounds. Furthermore, for the purpose of adjusting curability, the present composition may further contain, in addition to the monofunctional oxetane compound (A1) and the polyfunctional compound (A2), a compound different from the monofunctional oxetane compound (A1) and the polyfunctional compound (A2) (hereinafter also referred to as "other polymerizable compounds"). Examples of other polymerizable compounds include monofunctional oxirane compounds.

[0038] The monofunctional oxirane compound may be any compound having one oxirane ring per molecule, and specific examples of the monofunctional oxirane compound include cyclohexene oxide, 1-methyl-1,2-epoxycyclohexane, 1,2-epoxy-4-vinylcyclohexane, ethyl glycidyl ether, and butyl glycidyl ether.

[0039] However, monofunctional oxirane compounds tend to cause outgassing from the cured film. Therefore, it is preferable that the composition does not contain a monofunctional oxirane compound, or contains only a small amount of the monofunctional oxirane compound. Specifically, the content of the monofunctional oxirane compound is preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, based on the total amount of polymerizable compounds contained in the composition.

[0040] <[B] 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.

[0041] 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] - (X is a phenyl group substituted with two or more fluorine or trifluoromethyl groups), or [PRf6 - ] (Rf is a fluorinated alkyl group).

[0042] As the polymerization initiator, the onium salt compounds mentioned above are preferably used. Among them, the polymerization initiator is preferably [PF k (C p F 2p+1 ) 6-k ] - It is preferable that the compound contains an onium fluorinated alkylfluorophosphate having an anion moiety represented by the formula (wherein k is an integer of 3 to 5, and p is an integer of 1 to 3). k (C p F 2p+1 ) 6-k ] - The anion part represented by (C pF 2p+1 ) is 1 or more and has a fluorocarbon chain, so it acts as a relatively strong acid. This is thought to enhance cationic polymerization performance and improve curability.

[0043] The cation moiety of the onium fluorinated alkylfluorophosphate is not particularly limited, and specific examples of the cation moiety include sulfonium cations represented by the following formula (4) or (5). [ka] (In formula (4) and formula (5), R 11 ~R 16 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 each independently 0 or 1.

[0044] In the above formulas (4) and (5), R 11 ~R 16 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.

[0045] Specific examples of the ionic photoacid generating cationic photopolymerization initiator include a compound having a cationic moiety represented by the above formula (4) or (5) and [PF k (C p F 2p+1 ) 6-k ] - Specific examples of onium salts comprising an anion moiety represented by the formula (I) include the cationic polymerization initiators described in JP-A-2018-36533, such as those under the trade names "CPI-210S" and "CPI-410S" (both manufactured by San-Apro Co., Ltd.).

[0046] 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.

[0047] In the present composition, the content of the polymerization initiator is usually 0.1 to 10 parts by mass per 100 parts by mass of the total amount of polymerizable compounds contained in the present composition. The content of the polymerization initiator is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the total amount of polymerizable compounds. By setting the content of the polymerization initiator within the above range, the curability of the present composition can be improved, and a cured film with high transparency can be obtained.

[0048] <Other ingredients> In addition to the polymerizable compound and polymerization initiator described above, the present composition may further contain components other than the polymerizable compound and polymerization initiator (hereinafter also referred to as "other components"). Examples of other components include a polymerization inhibitor, an antioxidant, and a surfactant.

[0049] Polymerization inhibitor / antioxidant The present composition may further contain at least one compound selected from the group consisting of a polymerization inhibitor and an antioxidant (hereinafter also referred to as "compound (C)"). When the present composition further contains compound (C), the storage stability of the present composition can be improved.

[0050] 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, and phenylhydrazine hydrochloride. , 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.

[0051] 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 ensuring that the content is within the above range, it is possible to maintain the viscosity of the composition within an appropriate range even after long-term distribution or storage, while suppressing viscosity increases due to unnecessary thermal energy and gelation or curing reactions, and to ensure good wetting and spreading properties (and therefore inkjet coatability).

[0052] 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.

[0053] 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]2,4,8,10-tetraoxaspiro[5,5]un. bisphenols such as decane; and polymeric phenols 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, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid), 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.

[0054] Examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate. 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.

[0055] The antioxidants may be used alone or in combination of two or more, such as a phenolic / sulfur or phenolic / phosphorus antioxidant. Also, commercially available phenolic antioxidants (e.g., IRGANOX 1010 (trade name) manufactured by BASF Japan) and commercially available phosphorus-based antioxidants (e.g., IRGAFOS 168 (trade name) manufactured by BASF Japan) may be used alone or in combination.

[0056] 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 ensure good wetting and spreading properties (and also inkjet coatability).

[0057] In addition, in order to improve the storage stability of the composition, in addition to the above-mentioned compound (C), a heat stabilizer such as methylenequinone or 2-dimethylaminomethanol described in JP-A-2020-518952 may be contained in the composition.

[0058] Surfactants A surfactant can be used to further improve the coating properties of the composition (specifically, the wetting and spreading properties and the reduction of coating unevenness). Examples of surfactants include fluorine-based surfactants (including fluorine-containing nonionic surfactants), silicone-based surfactants, and nonionic surfactants.

[0059] Specific examples of surfactants include fluorine-based surfactants, such as Megafac F-171, F-172, F-173, F-251, F-430, F-554, and F-563 (manufactured by DIC Corporation); Fluorad FC430 and FC431 (manufactured by Sumitomo 3M Limited); Asahiguard AG710, Surflon S-382, SC-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 Corporation); and F-top EF301, EF303, and EF352 (manufactured by Shin-Akita Chemical Co., Ltd.).

[0060] 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).

[0061] 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.

[0062] 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 part by mass, per 100 parts by mass of the total amount of polymerizable compounds contained in the present composition.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] <Preparation of Curable Composition> The composition can be prepared by mixing a polymerizable compound, a polymerization initiator, and other components that are blended as necessary. From the viewpoint of obtaining a curable composition with good sensitivity and forming a cured film with high sealing effect, the content of the polymerizable compound in the composition is preferably 80 parts by mass or more, more preferably 85 parts by mass or more, and even more preferably 90 parts by mass or more, relative to 100 parts by mass of the total amount of the composition.

[0068] <Viscosity of Curable Composition> The viscosity of the composition, measured using an E-type viscometer at 25°C and 20 rpm, is preferably in the range of 1.0 to 40.0 mPa·s. When the viscosity of the composition is 40.0 mPa·s or less, the composition exhibits better wetting and spreading properties when applied to a substrate by inkjet coating, thereby preventing uneven application due to repelling and the like. When the viscosity of the composition is 1.0 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.

[0069] From the viewpoint of obtaining a curable composition with excellent inkjet coatability, the viscosity of the composition is more preferably 30.0 mPa·s or less, even more preferably 20.0 mPa·s or less, and particularly preferably 10.0 mPa·s or less. Furthermore, from the viewpoint of stable inkjet ejection and ensuring a sufficient film thickness, the viscosity of the composition is more preferably 2.0 mPa·s or more, even more preferably 5.0 mPa·s or more. In this specification, the viscosity of the curable composition is a value measured in accordance with JIS K 2283:2000. Details of the measurement method follow the method described in the Examples below.

[0070] <Wetting and spreading> This composition has good wetting and spreading properties when applied to a substrate. Specifically, an evaluation substrate made of a glass substrate coated with SiNx was subjected to inkjet ejection at a pitch of 50 μm × 50 μm using an inkjet head equipped with 20 nozzles aligned in a line perpendicular to the scanning direction, to draw a line pattern with a width of 1000 μm. After leaving the substrate for 3 minutes, the line pattern was exposed to ultraviolet light with a wavelength of 395 nm at an illuminance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2 When the composition is cured by exposure under the above conditions, the line pattern width is 1500 μm or more. This composition is particularly suitable as a curable composition for inkjet coating. The line pattern width measured in the evaluation of wetting and spreading properties is a measurement value when the curable composition is cured under the conditions of a nitrogen atmosphere, 25°C, and a dew point of -60°C or less (200 ppm).

[0071] <Amount of outgassing from cured film> This composition is applied to a coating film formed from the curable composition by irradiating ultraviolet light with a wavelength of 395 nm at an irradiance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2 When the cured film obtained by irradiating under the above conditions is heated at 110°C, the outgassing amount detected by headspace analysis is preferably less than 400 ppm and not more than 250 ppm. Here, the outgassing from the cured film mainly includes components derived from unreacted monomers (especially monofunctional monomers) of the polymerizable compounds contained in the curable composition that did not react during the formation of the cured film, and components derived from decomposition products resulting from depolymerization or partial cleavage due to acid components remaining in the film after polymerization. The monofunctional oxetane compound (A1) contained in this composition is highly reactive to radiation and is also resistant to decomposition, which is believed to enable the achievement of low outgassing amounts within the above range. Furthermore, this composition, which can form cured films with sufficiently low outgassing amounts, is suitable as a cured film material for organic EL devices. Details of the method for measuring the outgassing amount of the cured film are described in the Examples section below.

[0072] <Dielectric constant of cured film> By curing this composition, a cured film with a sufficiently low dielectric constant can be obtained. Specifically, this composition is exposed to an illuminance of 1000 mW / cm. 2 And the cumulative light intensity is 3000mJ / cm 2 The dielectric constant at a frequency of 100 kHz of the cured film obtained by irradiating ultraviolet light with a wavelength of 395 nm under the above conditions is preferably 2.8 or less. The dielectric constant of the cured film obtained under these conditions is more preferably 2.7 or less, and even more preferably 2.6 or less. For example, in an organic EL light-emitting device employing a touch panel system, a touch sensor is disposed on the substrate. However, if the dielectric constant of the sealing structure is high, there is a concern that inconveniences such as malfunctions may occur during use of the touch panel. Therefore, the sealing structure provided in the organic EL element is required to have a low dielectric constant. In this regard, the present composition allows for the production of a cured film with a sufficiently low dielectric constant. Note that details of the method for measuring the dielectric constant of the cured film are as described in the Examples below.

[0073] <Cured film and organic EL element> The cured film of the present disclosure (hereinafter also referred to as the "cured film") is formed from the curable composition prepared as described above. The composition has good wetting and spreading properties, and can give a cured film with a low outgassing amount and a low dielectric constant. The composition can be used as various materials, for example, sealing structures for organic EL devices, microlenses, antireflection films, diffraction gratings for AR devices, and the like. The composition can also be used as a material for filling holes in HID (Hole-In-A-Display-Area) structures and forming planarizing films.

[0074] Furthermore, the present composition can form a cured film with low moisture permeability, which can prevent the intrusion of foreign matter and has excellent bending resistance. Therefore, the composition can also be used as a material for forming a coating layer that protects wiring at the bent portion of a flexible display or at the bend portion where wiring extends from the display unit 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 either of these coating methods. The present composition is particularly useful as a composition for forming an encapsulating structure, i.e., an encapsulant for an organic EL element, by performing thin film encapsulation (TFE) on an organic electroluminescence element (organic EL element).

[0075] 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.

[0076] [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 that constitute the inorganic film include silicon nitride (SiNx) and silicon oxide (SiOx). In this case, a thin-film sealing layer comprising an organic sealing layer and an inorganic sealing layer is formed on the organic light-emitting layer as a sealing structure.

[0077] 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.

[0078] [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).

[0079] 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.

[0080] The present disclosure described above in detail includes the following aspects. [Aspect 1] A curable composition comprising a monofunctional oxetane compound (A1), a polyfunctional compound (A2) which is at least one selected from the group consisting of polyfunctional oxetane compounds and polyfunctional oxirane compounds, and a polymerization initiator, wherein the monofunctional oxetane compound (A1) has a GPC peak area ratio of 5.0% or less as determined by the following curability evaluation using gel permeation chromatography (GPC), and a coating film formed from the curable composition is irradiated with ultraviolet light having a wavelength of 395 nm at an irradiance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2 a curable composition, wherein when the cured film obtained by irradiating the composition under the conditions of (a) above is heated at 110°C, the amount of outgassing detected by a headspace method is less than 400 ppm. Curability evaluation: A coating film formed from a composition containing the compound to be evaluated alone as a polymerizable compound and further containing a polymerization initiator was irradiated with ultraviolet light having a wavelength of 395 nm at an irradiance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2The cured film obtained by irradiating under the above conditions is immersed in tetrahydrofuran, and the tetrahydrofuran solution after the immersion is analyzed by GPC. The total peak area of ​​the GPC chart obtained is defined as the first peak area (S1), and the peak area of ​​the peak derived from the remaining portion of the compound to be evaluated in the GPC chart of the tetrahydrofuran solution is defined as the second peak area (S2). The ratio (S2 / S1) of the second peak area to the first peak area is defined as the GPC peak area ratio. [Aspect 2] An evaluation substrate made of a glass substrate coated with SiNx was subjected to inkjet ejection at a pitch of 50 μm × 50 μm using an inkjet head equipped with 20 nozzles aligned in a direction perpendicular to the scanning direction, to draw a line pattern with a width of 1000 μm. After leaving the substrate for 3 minutes, ultraviolet light with a wavelength of 395 nm was applied to the line pattern at an illuminance of 1000 mW / cm. 2 And the cumulative light intensity is 1000mJ / cm 2 The curable composition according to [Aspect 1], wherein when cured by exposure under the conditions of [Aspect 2], the line pattern width is 1500 μm or more. [Embodiment 3] The curable composition according to [Embodiment 1] or [Embodiment 2], which has a viscosity at 25°C of 1.0 to 40.0 mPa·s. [Aspect 4] The curable composition according to any one of [Aspect 1] to [Aspect 3], wherein the monofunctional oxetane compound (A1) has two substituents at the 3-position of the oxetane ring. [Aspect 5] The curable composition according to any one of [Aspect 1] to [Aspect 4], wherein the monofunctional oxetane compound (A1) has a methyl group bonded to the 3-position of the oxetane ring. [Aspect 6] The curable composition according to any one of [Aspect 1] to [Aspect 5], wherein the monofunctional oxetane compound (A1) does not have an ether bond in the portion excluding the oxetane ring. [Embodiment 7] The monofunctional oxetane compound (A1) is attached directly or 1 -R 1 -O-(However, R 1 is an alkanediyl group having 1 to 3 carbon atoms, and "* 1The curable composition according to any one of [Aspect 1] to [Aspect 6], wherein the curable composition has a linear or branched alkyl group having 6 to 20 carbon atoms bonded via a bond (" represents a bond to the oxetane ring). [Aspect 8] The curable composition according to any one of [Aspect 1] to [Aspect 7], wherein the content of the monofunctional oxetane compound (A1) is 20 to 60 mass % based on the total amount of polymerizable compounds contained in the curable composition. [Aspect 9] Illuminance 1000mW / cm 2 And the cumulative light intensity is 3000mJ / cm 2 The curable composition according to any one of [Aspect 1] to [Aspect 8], wherein the curable composition is irradiated with ultraviolet light having a wavelength of 395 nm under the conditions of (a) to (c), and the resulting cured film has a dielectric constant of 2.8 or less at a frequency of 100 kHz. [Aspect 10] The curable composition according to any one of [Aspect 1] to [Aspect 9], which is for inkjet application. [Embodiment 11] The curable composition according to any one of [Embodiment 1] to [Embodiment 10], which is used to form a sealing structure that seals the organic light-emitting layer of an organic EL device. [Embodiment 12] A cured film formed using the curable composition according to any one of [Embodiment 1] to [Embodiment 11]. [Embodiment 13] An organic EL device in which an organic light-emitting layer is sealed with the cured film according to [Embodiment 12]. [Aspect 14] A method for producing an organic EL device, comprising the steps of: applying the curable composition according to any one of [Aspects 1] to [Aspect 11] to a surface of a substrate on which an organic light-emitting layer has been formed, and forming a sealing structure by irradiating the curable composition with radiation to cure the curable composition. [Aspect 15] The method for producing an organic EL device according to [Aspect 14], wherein the curable composition is applied by inkjet coating. [Example]

[0081] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified.

[0082] 1. Synthesis of compounds and evaluation of curability [Synthesis Example 1] Synthesis of Oxetane 1 A 500 mL four-neck flask equipped with a thermometer, dropping funnel, and Dimroth condenser was charged with 113 g of a 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 (1a). [ka]

[0083] A 2 L four-neck flask containing 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 of 10°C or below under a nitrogen atmosphere. Next, a solution of 129 g of crude compound (1a) dissolved in 1343 mL of anhydrous tetrahydrofuran (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 thin-layer chromatography (TLC), the flask was cooled to an internal temperature of 10°C or below. The four-neck flask containing the reaction mixture was equipped with a stirrer blade and a three-one motor, 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. Insoluble matter was filtered through Celite, and the resulting solution was concentrated under reduced pressure using a rotary evaporator, and the THF was removed. The residue was dissolved in ethyl acetate and washed successively with 1M HCl, saturated aqueous NaHCO3, and ion-exchanged water. The organic layer was concentrated under reduced pressure using a rotary evaporator. The resulting residue was purified using a silica gel column to obtain 59.5 g of compound (1b). [ka]

[0084] 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 (1b) and 168 mL of anhydrous THF. The flask was cooled to an internal temperature of 10°C or below under a nitrogen atmosphere. Next, 136 mL of 1.6 M butyllithium hexane solution was added dropwise to the four-neck flask over 90 minutes so that 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 so that the internal temperature did not exceed 10°C, followed by stirring overnight at room temperature. The mixture was then stirred for an additional 3 hours at an internal temperature of 55°C, after which 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 the THF and hexane. The residue was dissolved in ethyl acetate and washed with ion-exchanged water, and the organic layer was then concentrated under reduced pressure using a rotary evaporator. The resulting residue was purified using a silica gel column to obtain 37.7 g of oxetane 1 represented by the following formula: [ka]

[0085] -Curing evaluation A composition for evaluating monomer curability (hereinafter also simply referred to as the "evaluation composition") was prepared by mixing, in an atmospheric environment, 100 parts by mass of Oxetane 1, 1 part by mass of a cationic photopolymerization initiator represented by chemical formula (I2-1) described in paragraph 0127 of JP2018-036533A, and 0.1 parts by mass of a fluorine-containing nonionic surfactant ("F554" manufactured by DIC Corporation). Next, the evaluation composition was applied to an alkali-free glass substrate using a spin coater under conditions of a nitrogen atmosphere, 25°C, and a dew point of -60°C or less (200 ppm) so that the cured thickness would be 8 μm. After applying the evaluation composition, a UV-LED lamp was used to irradiate the substrate with 395 nm ultraviolet light at an illuminance of 1000 mW / cm under the same conditions as when the composition was applied. 2 , cumulative light intensity 1000mJ / cm2 The composition for evaluation was cured by irradiating under the exposure conditions of 1000 W / m². The UV-LED lamp used was a UniJet E110Z HD (Type U395A-455, manufactured by Ushio Inc.). The cured film and the substrate were then immersed in THF for a time sufficient for the cured film to dissolve in THF, to obtain a cured film solution. When immersing the cured film, the entire substrate on which the cured film was formed was immersed in THF. Separately, a compound of the same type as the monomer used in preparing the evaluation composition was dissolved in THF to prepare a monomer solution. The molecular weight distributions of the resulting cured film solution and monomer solution were measured by GPC. A GPC device, "HLC-8320GPC" (Tosoh Technosystems), was used. The area ratio (peak area ratio) of the peak in the GPC chart of the cured film solution (cured film GPC chart) whose elution time matched that of the GPC chart of the monomer solution (standard GPC chart) to the total peak area was calculated to be 2.38%.

[0086] [Synthesis Example 2] Synthesis of Oxetane 2 A 1-L four-neck flask equipped with a stirrer, a thermometer, a dropping funnel, and a Dimroth condenser and purged with argon was charged with 11.0 g of 3-methyl-3-oxetanemethanol and 150 mL of anhydrous tetrahydrofuran. 48 mL of n-butyllithium was added dropwise with stirring at an internal temperature of 5°C under an argon atmosphere, and the mixture was stirred for 1 hour. Next, 22.6 g of paratoluenesulfonyl chloride dissolved in 100 mL of anhydrous tetrahydrofuran was added dropwise with stirring, and the mixture was stirred for 1 hour. The reaction solution was added in small portions to 300 g of ice water to quench the reaction. After extraction with dichloromethane, the organic layer was dried over magnesium sulfate and concentrated to obtain 29.53 g of crude compound (2a). In the formula, "Ts" represents a p-toluenesulfonyl group. [ka]

[0087] A 1L four-neck flask equipped with a stirrer, a thermometer, a dropping funnel, and a Dimroth condenser, and purged with argon, was charged with 150 mL of anhydrous dimethyl sulfoxide. 4.43 g of sodium hydride was added dropwise under stirring at an internal temperature of 20°C under an argon atmosphere, and the mixture was stirred for 30 minutes. Next, 14.4 g of 2-ethyl-1-hexanol dissolved in 40 mL of anhydrous dimethyl sulfoxide was added dropwise under stirring and the mixture was stirred for 1 hour. 25.81 g of compound (2a) dissolved in 40 mL of anhydrous dimethyl sulfoxide was added dropwise under stirring and the mixture was stirred for 1 hour. The reaction solution was added portionwise to 500 g of ice water to quench the reaction. Extraction was performed with isopropyl ether, and the organic layer was dried and concentrated over magnesium sulfate. The resulting crude product was distilled at 82°C and 0.3 kPa, followed by silica gel column purification to obtain oxetane 2, represented by the following formula: [ka]

[0088] -Curing evaluation A composition for evaluation was prepared in the same manner as in Synthesis Example 1, except that Oxetane 2 was used instead of Oxetane 1. The curability of Oxetane 2 was evaluated by GPC measurement. The GPC peak area ratio was calculated from the GPC chart of the cured film and was found to be 2.64% (FIG. 1).

[0089] [Comparative Synthesis Example 1] Synthesis of Oxetane 3 48.2 g of oxetane 3 represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that diethyl methylmalonate was replaced with diethyl ethylmalonate and 1-bromononane was replaced with 1-bromo-3-ethylheptane. [ka]

[0090] -Curing evaluation A composition for evaluation was prepared in the same manner as in Synthesis Example 1, except that Oxetane 3 was used instead of Oxetane 1, and the curability of Oxetane 3 was evaluated. The GPC peak area ratio was calculated in the same manner as in Synthesis Example 1 and was found to be 5.66%.

[0091] [Comparative Synthesis Example 2] Synthesis of Oxetane 4 37.6 g of oxetane 4 represented by the following formula was obtained in the same manner as in Synthesis Example 1, except that diethyl methylmalonate was replaced with diethyl malonate and 1-bromononane was replaced with 1-bromododecane. [ka]

[0092] -Curing evaluation A composition for evaluation was prepared in the same manner as in Synthesis Example 1, except that Oxetane 4 was used instead of Oxetane 1, and the curability of Oxetane 4 was evaluated. The GPC peak area ratio was calculated in the same manner as in Synthesis Example 1 and was found to be 1.39%.

[0093] 2. Preparation of Curable Composition The components used to prepare the curable compositions are as follows: <Polymerizable compound> Monofunctional oxetane compounds A1-1: Oxetane 1 obtained in Synthesis Example 1 (GPC peak area ratio: 2.38%) A1-2: Oxetane 2 obtained in Synthesis Example 2 (GPC peak area ratio: 2.64%) A1-3: Oxetane 3 obtained by Comparative Synthesis Example 1 (GPC peak area ratio: 5.66%) A1-4: Oxetane 4 obtained by Comparative Synthesis Example 2 (GPC peak area ratio: 1.39%) A1-5: 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane ("OXT-212" manufactured by Toagosei Co., Ltd.) [ka]

[0094] A composition for evaluation was prepared in the same manner as in Synthesis Example 1, except that OXT-212 was used instead of Oxetane 1, and the curability of OXT-212 was evaluated. The GPC peak area ratio was calculated in the same manner as in Synthesis Example 1 and was found to be 8.23% (Figure 2).

[0095] ·Multifunctional compound (A2) A2-1: 3,3'-(oxybismethylene)bis(3-ethyloxetane) ("OXT-221" manufactured by Toagosei Co., Ltd.) A2-2: 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (Daicel Corporation "Celloxide 2021P")

[0096] <Polymerization initiator> B-1: A photocationic polymerization initiator represented by chemical formula (I2-1) described in paragraph 0127 of JP 2018-036533 A <Antioxidants> C-1: Pentaerythritol tetrakis(3-3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid (BASF "Irganox 1010") <Surfactants> D-1: Fluorine-containing nonionic surfactant (DIC "F554")

[0097] [Example 1] A curable composition was prepared by mixing, under atmospheric conditions, 40 parts by mass of Oxetane 1 as a monofunctional oxetane compound, 50 parts by mass of OXT-221 and 10 parts by mass of Celloxide 2021P as polyfunctional compounds (A2), 1 part by mass of a photocationic polymerization initiator represented by chemical formula (I2-1) described in paragraph 0127 of JP2018-036533A as a polymerization initiator, 0.1 parts by mass of Irganox1010 as an antioxidant, and 0.1 parts by mass of F554 as a surfactant.

[0098] [Example 2 and Comparative Examples 1 to 3] Curable compositions were prepared in the same manner as in Example 1, except that the type and amount of the polymerizable compound were changed as shown in Table 1.

[0099] 3. Evaluation The curable compositions of Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated by the following methods. The evaluation results are shown in Table 1.

[0100] <Viscosity> The viscosity (mPa·s) of the curable composition was measured at 25°C and 20 rpm using an E-type viscometer (RE-85L (cone rotor type: 1°34' × R24) manufactured by Toki Sangyo Co., Ltd.) in accordance with JIS K 2283:2000.

[0101] <Evaluation of inkjet coating wettability> An evaluation substrate was prepared by depositing a 100 nm thick SiNx film on a glass substrate. Using 20 adjacent nozzles of an inkjet head SE-128AA (manufactured by FUJIFILM Dimatix) attached to a piezo inkjet printer nanoprinter 1500 (manufactured by Microjet), the curable composition was ink-jet ejected at a 50 μm x 50 μm pitch onto the evaluation substrate. After a further 3 minutes, a line pattern 1000 μm wide x 3 cm long was drawn using a 395 nm LED lamp at an illuminance of 1000 mW / cm. 2 , cumulative light intensity 1000mJ / cm 2 The ink was irradiated with light to cure the line pattern. The droplet volume per drop was calculated from the ink mass when 100,000 drops were ejected per nozzle and the density of the curable composition, and the waveform of the inkjet head was changed so that one drop was 12 pL. The line pattern width obtained was measured using an optical microscope and evaluated according to the following criteria. ○: Line pattern width is 1500 μm or more △: Line pattern width is 1000 μm or more and less than 1500 μm ×: Line pattern width is less than 1000 μm

[0102] <Dielectric constant of cured film> In a nitrogen-substituted glove box at 25°C and a dew point of -60°C or less (200 ppm), the curable composition was applied to a substrate, which had been prepared by vapor-depositing ITO to a thickness of 30 nm on non-alkali glass, using a spin coater so that the cured thickness would be 8 μm. Next, a UV-LED lamp was used to apply ultraviolet light of 395 nm at an illuminance of 1000 mW / cm. 2 , cumulative light intensity 1000mJ / cm 2 The curable composition was cured by irradiation under the following conditions. A UniJet E110Z HD (Type U395A-455, manufactured by Ushio Inc.) was used as the UV-LED lamp. Aluminum was then vapor-deposited to a thickness of 50 nm on the surface of the cured film to prepare a test piece for dielectric constant measurement. The dielectric constant of the obtained test piece was measured using a dielectric constant measurement device at 25°C and 100 kHz. A 4284A LCR meter (manufactured by Hewlett-Packard) was used as the dielectric constant measurement device.

[0103] <Outgassing> In a nitrogen-substituted glove box at 25°C and a dew point of -60°C or less (200 ppm), the curable composition was applied to a 6-inch silicon wafer using a spin coater so that the thickness after curing would be 8 μm. Next, a UV-LED lamp was used to apply ultraviolet light of 395 nm at an illuminance of 1000 mW / cm. 2 , cumulative light intensity 1000mJ / cm 2 The curable composition was cured by irradiation under the following conditions: As the UV-LED lamp, a UniJet E110Z HD (Type U395A-455, manufactured by Ushio Inc.) was used. A 6-inch silicon wafer was then cut into 1 cm x 5 cm pieces for each cured film to prepare test specimens for outgassing measurement. The test specimens were placed in headspace vials, sealed, and heated at 110°C for 30 minutes. The generated gas was measured using the headspace method. Using 1 μL of a 400 ppm solution of toluene diluted with methanol as a reference substance, the mass per unit area was calculated from the mass of toluene and the peak area of ​​toluene. The mass of gas generated from the test specimen was then calculated from the total peak area of ​​the gas generated from the test specimen and the mass per unit area calculated from toluene. Finally, the amount of outgassing was calculated by calculating the ratio of the mass of gas generated from the test specimen to the mass of the film on the test specimen. A GCMS-QP2010plus (Shimadzu Corporation) was used as the outgassing measurement device. ◎: Gas generated is less than 250 ppm ○: The amount of gas generated is 250 ppm or more and less than 400 ppm △: The amount of gas generated is between 400 ppm and 800 ppm ×: The gas generated is 800 ppm or more In the above evaluation, if the amount of gas generated from the cured film is less than 400 ppm ("◎" or "◯"), it can be said that the film is practical.

[0104] [Table 1]

[0105] As shown in Table 1, Examples 1 and 2, which used a monofunctional oxetane compound (A1) having a GPC peak area ratio of 5.0% or less as the polymerizable compound, showed a sufficiently low amount of outgassing from the cured film compared to Comparative Examples 1 to 3. Furthermore, the curable compositions of Examples 1 and 2 had a moderately low viscosity and excellent inkjet coating wettability and spreadability. Furthermore, the cured films obtained from the curable compositions of Examples 1 and 2 also had a low dielectric constant.

[0106] In Comparative Examples 1 and 3, a monofunctional oxetane compound having a GPC peak area ratio of more than 5.0% was used instead of the monofunctional oxetane compound (A1) having a GPC peak area ratio of 5.0% or less, which is thought to have resulted in a large amount of unreacted monomer remaining in the cured film after UV irradiation and a large amount of outgassing caused by the unreacted monomer. Furthermore, the monofunctional oxetane compound (A1-4) used in Comparative Example 2 has little steric hindrance and is highly reactive upon UV irradiation, but the polymer formed upon UV irradiation is easily decomposed, which is thought to have resulted in a large amount of outgassing caused by polymer decomposition products.

Claims

1. a monofunctional oxetane compound (A1); a polyfunctional compound (A2) which is at least one selected from the group consisting of polyfunctional oxetane compounds and polyfunctional oxirane compounds; a polymerization initiator; A curable composition comprising: The monofunctional oxetane compound (A1) has a GPC peak area ratio of 5.0% or less as determined by the following curability evaluation using gel permeation chromatography (GPC), The coating film formed from the curable composition was irradiated with ultraviolet light having a wavelength of 395 nm at an illuminance of 1000 mW / cm ２ And the cumulative light amount is 1000 mJ / cm ２ a curable composition, wherein when the cured film obtained by irradiating the composition under the conditions of (a) to (c) is heated at 110°C, the amount of outgassing detected by a headspace method is less than 400 ppm. Curability evaluation: A coating film formed from a composition containing the compound to be evaluated alone as the polymerizable compound and further containing a polymerization initiator was irradiated with ultraviolet light having a wavelength of 395 nm at an illuminance of 1000 mW / cm. ２ And the cumulative light amount is 1000 mJ / cm ２ a cured film obtained by irradiating under the above conditions is immersed in tetrahydrofuran, and the tetrahydrofuran solution after the immersion is analyzed by GPC. The total peak area in a GPC chart obtained is defined as a first peak area (S1), and the peak area of ​​a peak derived from the remaining portion of the compound to be evaluated in the GPC chart of the tetrahydrofuran solution is defined as a second peak area (S2). The ratio (S2 / S1) of the second peak area to the first peak area is defined as the GPC peak area ratio.

2. An evaluation substrate made of a glass substrate coated with SiNx was subjected to inkjet ejection at a pitch of 50 μm × 50 μm using an inkjet head equipped with 20 nozzles arranged in a row in a direction perpendicular to the scanning direction, to draw a line pattern with a width of 1000 μm. After leaving the substrate for 3 minutes, ultraviolet light with a wavelength of 395 nm was applied to the line pattern at an illuminance of 1000 mW / cm. ２ And the cumulative light amount is 1000 mJ / cm ２ 2. The curable composition according to claim 1, wherein the curable composition has a line pattern width of 1500 μm or more when cured by exposure under the conditions of

3. The curable composition according to claim 1, having a viscosity at 25°C of 1.0 to 40.0 mPa·s.

4. The curable composition according to claim 1 , wherein the monofunctional oxetane compound (A1) has two substituents at the 3-position of the oxetane ring.

5. The curable composition according to claim 1 , wherein the monofunctional oxetane compound (A1) has a methyl group bonded to the 3-position of the oxetane ring.

6. The curable composition according to claim 1 , wherein the monofunctional oxetane compound (A1) does not have an ether bond in a portion other than the oxetane ring.

7. The monofunctional oxetane compound (A1) is bonded directly to the oxetane ring or １ -R １ -O- (where R １ is an alkanediyl group having 1 to 3 carbon atoms, and "* １ The curable composition according to claim 1, wherein the alkyl group is a straight-chain or branched alkyl group having 6 to 20 carbon atoms and is bonded to the oxetane ring via a bond (

8. 2. The curable composition according to claim 1, wherein the content of the monofunctional oxetane compound (A1) is 20 to 60 mass % based on the total amount of the polymerizable compounds contained in the curable composition.

9. Illuminance 1000mW / cm ２ And the cumulative light intensity is 3000 mJ / cm ２ 2. The curable composition according to claim 1, wherein the curable composition is irradiated with ultraviolet light having a wavelength of 395 nm under the conditions of (a) to (c), and the cured film obtained has a dielectric constant of 2.8 or less at a frequency of 100 kHz.

10. The curable composition of claim 1 , which is for inkjet application.

11. The curable composition according to claim 1 , which is used to form a sealing structure for sealing an organic light-emitting layer of an organic EL element.

12. A cured film formed using the curable composition according to any one of claims 1 to 11.

13. An organic EL device having an organic light-emitting layer sealed with the cured film according to claim 12.

14. a step of applying the curable composition according to any one of claims 1 to 11 to a surface of a substrate on which an organic light-emitting layer has been formed, the surface having the light-emitting layer formed thereon; forming a sealing structure by curing the curable composition by irradiating with radiation; A method for manufacturing an organic EL element, comprising:

15. The method for producing an organic EL element according to claim 14 , wherein the curable composition is applied by inkjet coating.

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