Encapsulating agent for organic EL display elements

Abstract

An object of the present invention is to provide a sealant for an organic EL display element that is excellent in low outgassing properties and coatability, and that can provide an organic EL display element that is excellent in light extraction efficiency. The present invention provides a sealant for an organic EL display element, which contains a cationic polymerizable compound and a cationic polymerization initiator, wherein the cationic polymerizable compound contains a cycloalkene oxide-type alicyclic epoxy compound and a fluorene-type epoxy compound.

Description

[Technical Field]

[0001] The present invention relates to an encapsulant for organic EL display elements that can be obtained with low outgassing properties, excellent coatability, and excellent light extraction efficiency. [Background technology]

[0002] Organic electroluminescent (hereinafter also referred to as "organic EL") display elements have a laminated structure in which an organic light-emitting material layer is sandwiched between a pair of opposing electrodes. When electrons are injected into this organic light-emitting material layer from one electrode and holes are injected from the other electrode, the electrons and holes combine within the organic light-emitting material layer and emit light. Because organic EL display elements self-emissive, they have advantages over liquid crystal display elements that require a backlight, such as better visibility, the ability to be made thinner, and the ability to be driven by low DC voltage.

[0003] The organic light-emitting material layers and electrodes that constitute organic EL display elements have the problem of being susceptible to degradation of properties due to moisture, oxygen, etc. Therefore, in order to obtain practical organic EL display elements, it is necessary to extend the lifespan by isolating the organic light-emitting material layers and electrodes from the atmosphere. One method of isolating the organic light-emitting material layers and electrodes from the atmosphere is to seal the organic EL display element using a encapsulant (for example, Patent Document 1). When sealing an organic EL display element with an encapsulant, a method is usually used in which an inorganic material film called a passivation film is provided on the laminate having the organic light-emitting material layer, and the inorganic material film is then sealed with an encapsulant, in order to sufficiently suppress the permeation of moisture, oxygen, etc.

[0004] In recent years, top-emission type organic EL display elements, which extract light from the top surface of the organic light-emitting layer, have attracted attention as an alternative to bottom-emission type organic EL display elements, which extract light from the top surface of the organic light-emitting layer from the substrate side on which the light-emitting element is formed. This method has the advantage of a high aperture ratio and low voltage drive, which is advantageous for extending the lifespan. In such top-emission type organic EL display elements, the top surface of the light-emitting layer must be transparent, so it is sealed by laminating a transparent moisture-proof substrate such as glass on the top surface of the light-emitting element via a transparent sealing layer (for example, Patent Document 2). However, in top-emission type organic EL display elements, even when sufficiently transparent materials are used for the transparent moisture-proof substrate and sealing agent, there is a problem that the efficiency of extracting light emitted from the laminate may be inferior due to the refractive index difference between the electrodes, passivation film and sealing agent. In addition, conventional sealing agents have problems such as generating outgassing and degrading the element, or having poor coating properties. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-115692 [Patent Document 2] Japanese Patent Publication No. 2009-051980 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide an encapsulant for organic EL display elements that exhibits low outgassing properties, excellent coatability, and superior light extraction efficiency. [Means for solving the problem]

[0007] The present invention relates to an encapsulant for organic EL display elements containing a cationic polymerizable compound and a cationic polymerization initiator, wherein the cationic polymerizable compound is an encapsulant for organic EL display elements containing a cycloalken oxide type alicyclic epoxy compound and a fluorene type epoxy compound. The present invention will be described in detail below.

[0008] The inventors of the present invention investigated how to improve the applicability and prevent outgassing by using a cycloalken oxide type alicyclic epoxy compound as a cationic polymerizable compound in an organic EL display element encapsulant. However, while encapsulants using such cycloalken oxide type alicyclic epoxy compounds are excellent at preventing outgassing, they have the problem of reduced light extraction efficiency due to reflection at the interface between the electrode / passivation film and the encapsulant because of the large refractive index difference between the electrode / passivation film and the encapsulant. Therefore, the inventors of the present invention investigated using a combination of the cycloalken oxide type alicyclic epoxy compound and a fluorene type epoxy compound as cationic polymerizable compounds. As a result, they found that it is possible to obtain an organic EL display element encapsulant that is excellent in low outgassing and applicability, and that can produce an organic EL display element with excellent light extraction efficiency, thus completing the present invention.

[0009] The encapsulant for organic EL display elements of the present invention contains a cationic polymerizable compound. The above cationic polymerizable compound includes a cycloalkene oxide type alicyclic epoxy compound. By containing the above cycloalkene oxide type alicyclic epoxy compound, the encapsulant for organic EL display elements of the present invention exhibits excellent low outgassing and coating properties.

[0010] Examples of the above-mentioned cycloalkene oxide-type alicyclic epoxy compounds include 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate and bis(3,4-epoxycyclohexylmethyl) ether.

[0011] Among the cycloalken oxide-type alicyclic epoxy compounds mentioned above, commercially available examples include Celoxide 2021P (manufactured by Daicel Corporation).

[0012] The preferred lower limit for the content of the cycloalkene oxide type alicyclic epoxy compound in 100 parts by weight of the total cationic polymerizable compound is 10 parts by weight, and the preferred upper limit is 90 parts by weight. A content of 10 parts by weight or more of the cycloalkene oxide type alicyclic epoxy compound results in an organic EL display element encapsulant that exhibits superior low outgassing and coatability. A content of 90 parts by weight or less of the cycloalkene oxide type alicyclic epoxy compound results in an organic EL display element that exhibits superior light extraction efficiency. A more preferred lower limit for the content of the cycloalkene oxide type alicyclic epoxy compound is 15 parts by weight, a more preferred upper limit is 70 parts by weight, an even more preferred lower limit is 20 parts by weight, an even more preferred upper limit is 65 parts by weight, and a particularly preferred lower limit is 60 parts by weight.

[0013] The above cationic polymerizable compound includes a fluorene-type epoxy compound. By including the above fluorene-type epoxy compound, the encapsulant for organic EL display elements of the present invention has a small refractive index difference with the electrodes and passivation film, and as a result, the resulting organic EL display element has excellent light extraction efficiency.

[0014] The above-mentioned fluorene-type epoxy compound can be any epoxy compound having a fluorene skeleton, and various fluorene-type epoxy compounds can be appropriately selected from viewpoints such as viscosity, refractive index, and photocurability.

[0015] The preferred lower limit for the epoxy equivalent of the above fluorene-type epoxy compound is 200, and the preferred upper limit is 400. Having the epoxy equivalent of the above fluorene-type epoxy compound within this range results in an organic EL display element encapsulant that exhibits superior adhesion, low outgassing, and coatability. In addition, in this specification, the epoxy equivalent of the above fluorene-type epoxy compound means (the molecular weight of the fluorene-type epoxy compound) / (the number of epoxy groups in one molecule of the fluorene-type epoxy compound).

[0016] Examples of commercially available fluorene-type epoxy compounds among the above fluorene-type epoxy compounds include, for example, fluorene-type epoxy compounds manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., fluorene-type epoxy compounds manufactured by Nagase ChemteX Corporation, fluorene-type epoxy compounds manufactured by Osaka Gas Chemical Co., Ltd., and the like. Examples of the fluorene-type epoxy compound manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. include, for example, ESF-300 and the like. Examples of the fluorene-type epoxy compound manufactured by Nagase ChemteX Corporation include, for example, Oncoat EX-1010 and the like. Examples of the fluorene-type epoxy compound manufactured by Osaka Gas Chemical Co., Ltd. include, for example, Ogsoal PG-100, EG-200 and the like. These fluorene-type epoxy compounds may be used alone or in combination of two or more.

[0017] The preferable lower limit of the content of the above fluorene-type epoxy compound in 100 parts by weight of the whole cationic polymerizable compound is 10 parts by weight, and the preferable upper limit is 80 parts by weight. When the content of the fluorene-type epoxy compound is 10 parts by weight or more, the obtained organic EL display element becomes more excellent in light extraction efficiency. When the content of the fluorene-type epoxy compound is 80 parts by weight or less, the obtained sealant for organic EL display elements becomes more excellent in low outgassing property and coating property. The more preferable lower limit of the content of the fluorene-type epoxy compound is 15 parts by weight, the more preferable upper limit is 75 parts by weight, the further preferable lower limit is 20 parts by weight, and the further preferable upper limit is 70 parts by weight. Also, from the viewpoint of making the obtained organic EL display element more excellent in light extraction efficiency, the preferable lower limit of the content of the fluorene-type epoxy compound is 30 parts by weight, the more preferable lower limit is 35 parts by weight, and the further preferable lower limit is 40 parts by weight.

[0018] The above cationic polymerizable compound may include, in addition to the above cycloalkene oxide-type alicyclic epoxy compound and the above fluorene-type epoxy compound, other cationic polymerizable compounds. Examples of the other cationic polymerizable compounds mentioned above include epoxy compounds other than the cycloalkene oxide-type alicyclic epoxy compounds and fluorene-type epoxy compounds mentioned above, oxetane compounds, vinyl ether compounds, and the like.

[0019] Examples of the above-mentioned other epoxy compounds include 1,7-octadiene diepoxide, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, phenyl glycidyl ether, and phenylenedi glycidyl ether.

[0020] Examples of the oxetane compounds mentioned above include 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane, 3-ethyl-3-((3-(triethoxysilyl)propoxy)methyl)oxetane, phenol novolac oxetane, and 1,4-bis(((3-ethyl-3-oxetanyl)methoxy)methyl)benzene.

[0021] Examples of the vinyl ether compounds mentioned above include benzyl vinyl ether, cyclohexanedimethanol monovinyl ether, dicyclopentadiene vinyl ether, 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol divinyl ether, and tripropylene glycol divinyl ether.

[0022] In particular, among the above-mentioned other cationic polymerizable compounds, at least one selected from the group consisting of 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetan, 1,2:7,8-diepoxyoctane, and 1,2:5,6-diepoxycyclooctane is preferred, and 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetan is more preferred.

[0023] When the above-mentioned cationic polymerizable compound includes the above-mentioned other cationic polymerizable compounds, the preferred lower limit of the content of the above-mentioned other cationic polymerizable compounds in 100 parts by weight of the above-mentioned cationic polymerizable compound is 10 parts by weight, and the preferred upper limit is 50 parts by weight. Having the content of the above-mentioned other cationic polymerizable compounds within this range results in a encapsulant for organic EL display elements having superior adhesion and coatability. A more preferred upper limit for the content of the above-mentioned other cationic polymerizable compounds is 45 parts by weight, and an even more preferred upper limit is 40 parts by weight. Furthermore, if the cationic polymerizable compound includes the other cationic polymerizable compounds, the preferred lower limit of the total content of the cycloalken oxide-type alicyclic epoxy compound and the other cationic polymerizable compounds in 100 parts by weight of the cationic polymerizable compound is 20 parts by weight. A total content of 20 parts by weight or more of the cycloalken oxide-type alicyclic epoxy compound and the other cationic polymerizable compounds results in a encapsulant for organic EL display elements with superior coatability. A more preferred lower limit for the total content of the cycloalken oxide-type alicyclic epoxy compound and the other cationic polymerizable compounds is 30 parts by weight, and an even more preferred lower limit is 40 parts by weight.

[0024] The encapsulant for organic EL display elements of the present invention contains a cationic polymerization initiator. Examples of the cationic polymerization initiators mentioned above include thermal cationic polymerization initiators and photocatalytic cationic polymerization initiators.

[0025] The above thermal cationic polymerization initiator has an anionic portion of BF4 - PF6 - SbF6 - , or (BX4) - Examples of sulfonium salts, phosphonium salts, ammonium salts, diazonium salts, iodonium salts, etc., are composed of (wherein X represents a phenyl group substituted with at least two fluorine or trifluoromethyl groups). Among these, sulfonium salts are preferred.

[0026] Examples of the above-mentioned sulfonium salts include triphenylsulfonium tetrafluoroborate and triphenylsulfonium hexafluoroantimonate.

[0027] Examples of the phosphonium salts mentioned above include ethyltriphenylphosphonium hexafluoroantimonate and tetrabutylphosphonium hexafluoroantimonate.

[0028] Examples of the above ammonium salts include dimethylphenyl(4-methoxybenzyl)ammonium hexafluorophosphate, dimethylphenyl(4-methoxybenzyl)ammonium hexafluoroantimonate, dimethylphenyl(4-methoxybenzyl)ammonium tetrakis(pentafluorophenyl)borate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorophosphate, dimethylphenyl(4-methylbenzyl)ammonium hexafluoroantimonate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorotetrakis(pentafluorophenyl)borate, and methylphenyldibenzylammonium hexafluorophosphate. Examples include methylphenyldibenzylammonium hexafluoroantimonate, methylphenyldibenzylammonium tetrakis(pentafluorophenyl)borate, phenyltribenzylammonium tetrakis(pentafluorophenyl)borate, dimethylphenyl(3,4-dimethylbenzyl)ammonium tetrakis(pentafluorophenyl)borate, N,N-dimethyl-N-benzylanilinium hexafluoroantimonate, N,N-diethyl-N-benzylanilinium tetrafluoroborate, N,N-dimethyl-N-benzylpyridinium hexafluoroantimonate, and N,N-diethyl-N-benzylpyridinium trifluoromethanesulfonic acid.

[0029] Examples of commercially available thermal cationic polymerization initiators include those manufactured by Sanshin Chemical Industry Co., Ltd. and those manufactured by King Industries Co., Ltd. Examples of the thermal cationic polymerization initiators manufactured by Sanshin Chemical Industry Co., Ltd. include San-Aid SI-60, San-Aid SI-80, San-Aid SI-B3, San-Aid SI-B3A, and San-Aid SI-B4. Examples of the thermal cationic polymerization initiators manufactured by King Industries include CXC-1612 and CXC-1821.

[0030] The above photo cationic polymerization initiator is not particularly limited as long as it generates a protonic acid or a Lewis acid upon light irradiation, and it may be an ionic photoacid generator type or a non-ionic photoacid generator type.

[0031] As the anion part of the above ionic photoacid generator type photo cationic polymerization initiator, for example, BF4 - , PF6 - , SbF6 - , (BX4) - (However, X represents a phenyl group substituted with at least two or more fluorine or trifluoromethyl groups) and the like can be mentioned. Also, as the above anion part, PF m (C n F 2n+1 ) 6-m - (However, in the formula, m is an integer from 0 to 5, and n is an integer from 1 to 6) and the like can also be mentioned. As the above ionic photoacid generator type photo cationic polymerization initiator, for example, aromatic sulfonium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic ammonium salts, (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe salts, etc. having the above anion part can be mentioned.

[0032] Examples of the above aromatic sulfonium salts include bis(4-(diphenylsulfonio)phenyl) sulfide bishexafluorophosphate, bis(4-(diphenylsulfonio)phenyl) sulfide bishexafluoroantimonate, bis(4-(diphenylsulfonio)phenyl) sulfide bistetrafluoroborate, bis(4-(diphenylsulfonio)phenyl) sulfide tetrakis(pentafluorophenyl)borate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, diphenyl-4-(phenylthio)phenylsulfonium tetrakis(pentafluorophenyl)borate, triphenylsulfonium hexafluorophosphate, Examples include triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl) sulfide bishexafluorophosphate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl) sulfide bishexafluoroantimonate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl) sulfide bistetrafluoroborate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl) sulfide tetrakis(pentafluorophenyl)borate, and tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate. Among these, triarylsulfonium tetrakis(pentafluorophenyl)borate, such as triphenylsulfonium tetrakis(pentafluorophenyl)borate, is preferred.

[0033] Examples of the above aromatic iodonium salts include diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis(pentafluorophenyl)borate, bis(dodecylphenyl)iodonium hexafluorophosphate, bis(dodecylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluorophosphate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluoroantimonate, 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrafluoroborate, and 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate.

[0034] Examples of the above-mentioned aromatic diazonium salts include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, and phenyldiazonium tetrakis(pentafluorophenyl)borate.

[0035] Examples of the above aromatic ammonium salts include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, 1-benzyl-2-cyanopyridinium tetrafluoroborate, 1-benzyl-2-cyanopyridinium tetrakis(pentafluorophenyl)borate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluorophosphate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluoroantimonate, 1-(naphthylmethyl)-2-cyanopyridinium tetrafluoroborate, and 1-(naphthylmethyl)-2-cyanopyridinium tetrakis(pentafluorophenyl)borate.

[0036] Examples of the above (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe salts include (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) hexafluorophosphate, (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) hexafluoroantimonate, (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) tetrafluoroborate, and (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) tetrakis(pentafluorophenyl)borate.

[0037] Examples of the above-mentioned nonionic photoacid-generating photocationic polymerization initiators include nitrobenzyl esters, sulfonic acid derivatives, phosphate esters, phenolsulfonic acid esters, diazonaphthoquinone, and N-hydroxyimidosulfonate.

[0038] Examples of commercially available photocationic polymerization initiators include those manufactured by Midori Chemical Co., Ltd., Union Carbide Corporation, ADEKA Corporation, 3M Corporation, BASF Corporation, Solvay Corporation, and Sunapro Corporation. Examples of photocationic polymerization initiators manufactured by Midori Chemical Co., Ltd. include DTS-200. Examples of photocationic polymerization initiators from Union Carbide include UVI6990 and UVI6974. Examples of the photocationic polymerization initiators manufactured by ADEKA mentioned above include SP-150 and SP-170. Examples of the 3M photocationic polymerization initiators mentioned above include FC-508 and FC-512. Examples of photocationic polymerization initiators manufactured by BASF include IRGACURE261 and IRGACURE290. Examples of photocationic polymerization initiators from Solvay include PI2074. Examples of photocationic polymerization initiators manufactured by Sunapro include CPI-100P, CPI-200K, and CPI-210S.

[0039] Among the cationic polymerization initiators mentioned above, quaternary ammonium salts in which the counter-anion is borate-based (hereinafter also referred to as "borate-based quaternary ammonium salts") are preferably used. The counter anion of the above borate-based quaternary ammonium salt is BF4 - Alternatively, (BX4)- (where X represents a phenyl group substituted with at least two fluorine or trifluoromethyl groups) is preferable.

[0040] The content of the cationic polymerization initiator is preferably 0.05 parts by weight and preferably 10 parts by weight per 100 parts by weight of the cationic polymerizable compound. This range of cationic polymerization initiator content results in a encapsulant for organic EL display elements with superior curability, storage stability, and moisture resistance of the cured product. A more preferable lower limit for the cationic polymerization initiator content is 0.1 parts by weight and a more preferable upper limit is 5 parts by weight.

[0041] The encapsulant for organic EL display elements of the present invention may contain a thermosetting agent. Examples of the above-mentioned thermosetting agents include hydrazide compounds, imidazole derivatives, acid anhydrides, dicyandiamides, guanidine derivatives, modified aliphatic polyamines, and addition products of epoxy resins with various amines. Examples of the above-mentioned hydrazide compounds include 1,3-bis(hydrazinocarbonoethyl)-5-isopropylhydantoin, sebacate dihydrazide, isophthalic acid dihydrazide, adipic acid dihydrazide, and malonic acid dihydrazide. Examples of the above-mentioned imidazole derivatives include 1-cyanoethyl-2-phenylimidazole, N-(2-(2-methyl-1-imidazolyl)ethyl)urea, 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine, N,N'-bis(2-methyl-1-imidazolylethyl)urea, N,N'-(2-methyl-1-imidazolylethyl)-adipoamide, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2-phenyl-4,5-dihydroxymethylimidazole. Examples of the above-mentioned acid anhydrides include tetrahydrophthalic anhydride and ethylene glycol bis(anhydrotrimellitate). These thermosetting agents may be used individually or in combination of two or more types.

[0042] Examples of commercially available thermosetting agents include those manufactured by Otsuka Chemical Co., Ltd. and those manufactured by Ajinomoto Fine Techno Co., Ltd. Examples of thermosetting agents manufactured by Otsuka Chemical Co., Ltd. include SDH and ADH. Examples of the thermosetting agents manufactured by Ajinomoto Fine Techno Co., Ltd. include Amicure VDH, Amicure VDH-J, and Amicure UDH.

[0043] The preferred lower limit for the content of the above-mentioned thermosetting agent is 0.5 parts by weight and the preferred upper limit is 30 parts by weight per 100 parts by weight of the above-mentioned cationic polymerizable compound. When the content of the above-mentioned thermosetting agent is 0.5 parts by weight or more, the resulting encapsulant for organic EL display elements will have superior thermosetting properties. When the content of the above-mentioned thermosetting agent is 30 parts by weight or less, the resulting encapsulant for organic EL display elements will have superior storage stability, and the cured product will have superior moisture resistance. A more preferred lower limit for the content of the above-mentioned thermosetting agent is 1 part by weight and a more preferred upper limit is 15 parts by weight.

[0044] The encapsulant for organic EL display elements of the present invention preferably contains a stabilizer. By containing the above-mentioned stabilizer, the encapsulant for organic EL display elements of the present invention exhibits superior storage stability.

[0045] Aromatic amine compounds are preferably used as the stabilizer mentioned above. Examples of the above-mentioned aromatic amine compounds include benzylamine and aminophenol-type epoxy resins. Examples of the above-mentioned aminophenol-type epoxy resins include triglycidyl-p-aminophenol. Among these, benzylamine is preferred. These stabilizers may be used individually or in combination of two or more.

[0046] The preferred lower limit for the content of the above stabilizer is 0.001 parts by weight and the preferred upper limit is 2 parts by weight per 100 parts by weight of the above cationic polymerizable compound. This range of stabilizer content ensures that the resulting encapsulant for organic EL display elements maintains excellent curability while exhibiting superior storage stability. A more preferred lower limit for the stabilizer content is 0.005 parts by weight and a more preferred upper limit is 1 part by weight.

[0047] The encapsulant for organic EL display elements of the present invention may contain a silane coupling agent. The silane coupling agent serves to improve the adhesion between the encapsulant for organic EL display elements of the present invention and a substrate or the like.

[0048] Examples of the silane coupling agents mentioned above include 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-isocyanatetopropyltrimethoxysilane. These silane coupling agents may be used individually or in combination of two or more.

[0049] The preferred lower limit for the content of the silane coupling agent is 0.1 parts by weight and the preferred upper limit is 10 parts by weight per 100 parts by weight of the cationic polymerizable compound. This range of silane coupling agent content provides superior adhesion while suppressing the bleed-out of excess silane coupling agent. A more preferred lower limit for the silane coupling agent content is 0.5 parts by weight and a more preferred upper limit is 5 parts by weight. Furthermore, from the viewpoint of low outgassing, the preferred upper limit for the content of the silane coupling agent is 0.5 parts by weight, a more preferred upper limit is 0.1 parts by weight, and an even more preferred upper limit is 0.01 parts by weight, per 100 parts by weight of the cationic polymerizable compound.

[0050] The encapsulant for organic EL display elements of the present invention may further contain a surface modifier, to the extent that it does not hinder the objectives of the present invention. By including the above-mentioned surface modifier, the flatness of the coating film of the encapsulant for organic EL display elements of the present invention can be improved. Examples of the surface modifiers mentioned above include surfactants and leveling agents.

[0051] Examples of the surface modifiers mentioned above include silicone-based, acrylic-based, and fluorine-based agents. Examples of commercially available surface modifiers include those manufactured by BIC Chemie Japan and those manufactured by AGC Seimi Chemical. Examples of surface modifiers manufactured by BYK-Chemie Japan include BYK-330, BYK-340, and BYK-345. Examples of surface modifiers manufactured by AGC Seimi Chemical Co., Ltd. include Surflon S-611.

[0052] The encapsulant for organic EL display elements of the present invention may contain a compound or ion exchange resin that reacts with the acid generated in the encapsulant for organic EL display elements in order to improve the durability of the element electrodes, to the extent that it does not hinder the objectives of the present invention.

[0053] Compounds that react with the acid generated above include substances that neutralize the acid, such as alkali metal carbonates or bicarbonates, or alkaline earth metal carbonates or bicarbonates. Specifically, calcium carbonate, calcium bicarbonate, sodium carbonate, sodium bicarbonate, etc., can be used.

[0054] As the ion exchange resin mentioned above, any of the following types can be used: cation exchange type, anion exchange type, or both ion exchange type. However, a cation exchange type or both ion exchange type that can adsorb chloride ions is particularly preferred.

[0055] The encapsulant for organic EL display elements of the present invention may contain a solvent for purposes such as viscosity adjustment, but residual solvent may cause problems such as deterioration of the organic light-emitting material layer or outgassing. Therefore, it is preferable that the encapsulant does not contain a solvent or that the solvent content is 0.05% by weight or less.

[0056] Furthermore, the encapsulant for organic EL display elements of the present invention may optionally contain various known additives such as curing retarders, reinforcing agents, softeners, plasticizers, viscosity modifiers, ultraviolet absorbers, and antioxidants.

[0057] The encapsulant for organic EL display elements of the present invention has a preferred upper limit of viscosity of 250 Pa·s, as measured using an E-type viscometer under conditions of 25°C and 2.5 rpm. A viscosity of 250 Pa·s or less results in an encapsulant for organic EL display elements with excellent coatability. A preferred upper limit of viscosity is 100 Pa·s, and a more preferred upper limit is 10 Pa·s. Furthermore, the preferred lower limit of the viscosity is 5 mPa·s. The viscosity described above can be measured, for example, using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer, with the CP1 cone plate.

[0058] The encapsulant for organic EL display elements of the present invention has a preferred lower limit of 1.55 for the refractive index of sodium D lines at 25°C in the cured product. Having the refractive index within this range results in a small refractive index difference with the electrodes and passivation film, and as a result, the resulting organic EL display element exhibits excellent light extraction efficiency. A more preferred lower limit for the refractive index is 1.56. The "refractive index of sodium D line" mentioned above can be measured using an Abbe refractometer. Furthermore, as the cured material used to measure the refractive index, for example, a measuring piece approximately 20 mm in length, 10 mm in width, and 0.5 to 1 mm in thickness is used. If the cured material used to measure the refractive index is a thermosetting sealant, it can be obtained by heating at 100°C for 30 minutes, and if it is a photothermosetting sealant, it can be obtained at 2000 mJ / cm². 2 It can be obtained by irradiating it with a certain amount of ultraviolet light and then heating it at 100°C for 30 minutes.

[0059] The encapsulant for organic EL display elements of the present invention is particularly suitable for use as an in-plane encapsulant for coating and sealing a laminate having an organic light-emitting material layer. Furthermore, the encapsulant for organic EL display elements of the present invention is suitably used for encapsulating top-emission type organic EL display elements.

[0060] A method for encapsulating an organic EL display element using the encapsulant for organic EL display elements of the present invention includes, for example, a step of applying the encapsulant for organic EL display elements of the present invention to a substrate by printing, dispensing, or inkjet, and a step of curing the applied encapsulant for organic EL display elements by heating and / or light irradiation.

[0061] In the step of applying the encapsulant for organic EL display elements of the present invention to a substrate, the encapsulant for organic EL display elements of the present invention may be applied to the entire surface of the substrate or to a part of the substrate. The shape of the encapsulated portion of the encapsulant for organic EL display elements of the present invention formed by application is not particularly limited as long as it can protect the laminate having the organic light-emitting material layer from the outside air. It may be a shape that completely covers the laminate, or a closed pattern may be formed around the periphery of the laminate, or a pattern with a partial opening may be formed around the periphery of the laminate.

[0062] When curing the above-mentioned encapsulant for organic EL display elements by heating, it is preferable to heat it at a temperature of 50°C to 120°C from the viewpoint of sufficiently curing it while reducing damage to the laminate having the organic light-emitting material layer.

[0063] When curing the encapsulant for organic EL display elements of the present invention by light irradiation, the encapsulant for organic EL display elements of the present invention is subjected to a wavelength of 300 nm to 400 nm and a light intensity of 300 mJ / cm². 2 More than 3000mJ / cm 2 The following cumulative light intensity can be used to achieve suitable curing.

[0064] Examples of light sources used for the above-mentioned light irradiation include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, excimer lasers, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, sodium lamps, halogen lamps, xenon lamps, LED lamps, fluorescent lamps, sunlight, and electron beam irradiation devices. These light sources may be used individually or in combination of two or more types. These light sources are appropriately selected to match the absorption wavelength of the photocationic polymerization initiator.

[0065] Examples of light irradiation methods for the encapsulant for the organic EL display element of the present invention include simultaneous irradiation with various light sources, sequential irradiation with time differences, and combined irradiation of simultaneous and sequential irradiation, and any of these irradiation methods may be used.

[0066] The cured product obtained by the process of curing the above-mentioned encapsulant for organic EL display elements by heating and / or light irradiation may be further coated with an inorganic material film. The inorganic material constituting the above inorganic material film can be one of conventionally known materials, for example, silicon nitride (SiN x ) and silicon dioxide (SiO x Examples include the following. The inorganic material film may consist of a single layer or may be a laminate of multiple layers. Alternatively, the laminate may be coated by alternately repeating the inorganic material film and a resin film consisting of the encapsulant for the organic EL display element of the present invention.

[0067] The method for manufacturing the above-described organic EL display element may include a step of bonding a substrate coated with the encapsulant for organic EL display elements of the present invention (hereinafter also referred to as "one substrate") to the other substrate. The substrate to which the encapsulant for the organic EL display element of the present invention is applied (hereinafter also referred to as "one of the substrates") may be a substrate on which a laminate having an organic light-emitting material layer is formed, or it may be a substrate on which the laminate is not formed. If one of the above-mentioned substrates is a substrate on which the laminate is not formed, the encapsulant for organic EL display elements of the present invention may be applied to the one substrate so as to protect the laminate from the outside air when the other substrate is bonded to it. That is, it may be applied to the entire area where the laminate will be located when the other substrate is bonded, or a closed pattern of encapsulant may be formed in a shape that completely covers the area where the laminate will be located when the other substrate is bonded. Furthermore, a so-called dam-fill sealing method may be used as a method for sealing the above-mentioned organic EL display element. That is, first, a curable paste is applied to the substrate of the organic EL display element so as to surround the periphery of the display portion. Next, the sealing agent for organic EL display elements of the present invention is applied to the inside of the applied curable paste, and the opposing sealing substrates are bonded together while preventing the sealing agent from overflowing with the curable paste at the periphery. After that, a method may be used in which the curable paste at the periphery and the sealing agent for organic EL display elements of the present invention that has been pushed inward is cured by heating and / or light irradiation.

[0068] The step of curing the above-mentioned encapsulant for the organic EL display element by heating and / or light irradiation may be performed before the step of bonding one substrate to the other substrate, or after the step of bonding one substrate to the other substrate. When the step of curing the above-mentioned encapsulant for organic EL display elements by heating and / or light irradiation is performed before the step of bonding one substrate to the other substrate, it is preferable that the encapsulant for organic EL display elements of the present invention has a pot life of 1 minute or more from the time of heating and / or light irradiation until the curing reaction progresses to the point where adhesion becomes impossible. By having a pot life of 1 minute or more, it is possible to obtain higher adhesive strength without the curing progressing too much before bonding one substrate to the other substrate.

[0069] In the step of bonding one substrate to the other substrate, the method of bonding the two substrates is not particularly limited, but it is preferable to bond them under a reduced pressure atmosphere. The preferred lower limit of the vacuum under the above-mentioned reduced pressure atmosphere is 0.01 kPa, and the preferred upper limit is 10 kPa. Having the vacuum under the above-mentioned reduced pressure atmosphere within this range allows for more efficient removal of air bubbles in the encapsulant for the organic EL display element of the present invention when bonding one substrate to the other, without requiring a long time to achieve a vacuum state due to the airtightness of the vacuum device or the capacity of the vacuum pump. [Effects of the Invention]

[0070] According to the present invention, it is possible to provide an organic EL display element encapsulant that has excellent low outgassing properties and coatability, and excellent light extraction efficiency. [Modes for carrying out the invention]

[0071] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0072] (Examples 1-14, Comparative Examples 1-3) According to the mixing ratios listed in Tables 1-3, each material was stirred and mixed using a stirring mixer at a stirring speed of 2000 rpm to prepare the encapsulants for organic EL display elements in Examples 1-14 and Comparative Examples 1-3. An AR-250 (manufactured by Shinky Co., Ltd.) was used as the stirring mixer.

[0073] <Rating> The following evaluations were performed on each encapsulant for organic EL display elements obtained in the examples and comparative examples. The results are shown in Tables 1 to 3.

[0074] (1) Viscosity The viscosity of each encapsulant for organic EL display elements obtained in the examples and comparative examples was measured using an E-type viscometer at 25°C and 2.5 rpm. A VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) was used as the E-type viscometer. Furthermore, since the encapsulant for organic EL display elements obtained in Comparative Example 2 was solid at 25°C, it was not possible to measure its viscosity.

[0075] (2) Storage stability For each encapsulant for organic EL display elements obtained in the examples and comparative examples, the initial viscosity immediately after manufacturing and the viscosity after storage at 25°C for one week were measured using an E-type viscometer at 25°C. The viscosity change rate was derived as (viscosity after storage at 25°C for one week) / (initial viscosity). A VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) was used as the E-type viscometer. Storage stability was evaluated using the following criteria: a viscosity change rate of less than 1.2 was rated "◎", a rate between 1.2 and 1.5 was rated "○", a rate between 1.5 and 2.0 was rated "△", and a rate of 2.0 or higher was rated "×". Furthermore, since the encapsulant for organic EL display elements obtained in Comparative Example 2 was solid at 25°C, it was not possible to evaluate its storage stability.

[0076] (3) Spreadability To 100 parts by weight of each organic EL display element encapsulant obtained in the examples and comparative examples, 0.3 parts by weight of polymer beads with an average particle size of 10 μm was added and uniformly dispersed using a planetary stirring device. Micropearl SP (manufactured by Sekisui Chemical Co., Ltd.) was used as the polymer beads. Two glass substrates measuring 5 cm in length and 5 cm in width were prepared, and 0.1 mL of the obtained dispersion was placed in the center of one glass substrate, with the other glass substrate placed on top. A 100 g weight was placed on the other glass substrate to spread the encapsulant, and after being left on a 60°C hot plate for 10 minutes, the weight was removed and the diameter of the wetted area between the glass substrates was measured. The applicability was evaluated as follows: "◎" if the diameter was 30 mm or more, "○" if it was 25 mm or more but less than 30 mm, "△" if it was 20 mm or more but less than 25 mm, and "×" if it was less than 20 mm.

[0077] (4) Curability For each encapsulant for organic EL display elements obtained in the examples and comparative examples, the reaction rate of epoxy groups (decrease rate of peaks derived from epoxy groups) was measured using an infrared spectrometer after curing by heating at 100°C for 30 minutes. For the encapsulant for organic EL display elements obtained in Example 13, ultraviolet light at a wavelength of 365 nm was applied using a UV-LED at a rate of 1500 mJ / cm². 2 After irradiation, the material was heated at 90°C for 30 minutes to cure. A UMA600 infrared spectrometer (manufactured by Agilent Technologies) was used. The curing properties were evaluated as follows: "◎" if the reaction rate of the epoxy group was 90% or higher, "○" if it was 80% or higher but less than 90%, "△" if it was 60% or higher but less than 80%, and "×" if it was less than 60%.

[0078] (5) Refractive index and light extraction efficiency A mold was prepared by cutting a 1 mm thick silicone rubber sheet into a rectangle 20 mm long and 10 mm wide. This mold was placed on a release PET film, and the encapsulants for each organic EL display element obtained in the examples and comparative examples were filled into the mold. Then, another release PET film was used to cover the mold, ensuring no air bubbles remained, and a laminate was obtained. The obtained laminate was sandwiched between two glass plates and fixed in place. The encapsulant was cured by heating in a 100°C oven for 30 minutes. After that, the PET film was peeled off to remove the cured encapsulant from the silicone rubber sheet, and a test piece 10 mm long, 20 mm wide, and 1 mm thick was obtained. For the encapsulant for organic EL display elements obtained in Example 13, ultraviolet light at a wavelength of 365 nm was applied at a rate of 1500 mJ / cm using a UV-LED. 2 After irradiation, the specimens were heated at 90°C for 30 minutes to cure them. The refractive index of the sodium D line at 25°C was measured on the obtained specimens using an Abbe refractometer. The Abbe refractometer used was the NAR-4T (manufactured by Atago). Furthermore, considering the refractive index difference with the electrodes and passivation film, the light extraction efficiency was evaluated as follows: "○" if the refractive index was 1.55 or higher, "△" if it was between 1.53 and 1.55, and "×" if it was less than 1.53.

[0079] (6) Low outgassing Each encapsulant for organic EL display elements obtained in the examples and comparative examples was weighed out at a dose of 300 mg and sealed in a vial, and then cured by heating at 100°C for 30 minutes. For the encapsulant for organic EL display elements obtained in Example 13, ultraviolet light with a wavelength of 365 nm was applied at a rate of 1500 mJ / cm using a UV-LED. 2 After irradiation, the vial was heated at 90°C for 30 minutes to cure. Furthermore, the vial was heated in a constant temperature oven at 85°C for 100 hours, and the amount of vaporized components in the vial was measured using a gas chromatograph-mass spectrometer. A JMS-Q1050 (manufactured by JEOL Ltd.) was used as the gas chromatograph-mass spectrometer. Low outgassing properties were evaluated as follows: "○" if the amount of vaporized components was less than 50 ppm, "△" if it was between 50 ppm and less than 100 ppm, and "×" if it was 100 ppm or more.

[0080] [Table 1]

[0081] [Table 2]

[0082] [Table 3] [Industrial applicability]

[0083] According to the present invention, it is possible to provide an organic EL display element encapsulant that has excellent low outgassing properties and coatability, and excellent light extraction efficiency.

Claims

1. An encapsulant for organic EL display elements containing a cationic polymerizable compound and a cationic polymerization initiator, The cationic polymerizable compound comprises a cycloalken oxide type alicyclic epoxy compound and a fluorene type epoxy compound. The content of the fluorene-type epoxy compound is 30 parts by weight or more and 75 parts by weight or less in 100 parts by weight of the total cationic polymerizable compound. The cationic polymerization initiator includes a salt in which the counteranion is borate-based. A encapsulant for organic EL display elements characterized by the following features.

2. The encapsulant for an organic EL display element according to claim 1, wherein the content of the cycloalken oxide type alicyclic epoxy compound is 10 parts by weight or more and 70 parts by weight or less in 100 parts by weight of the total cationic polymerizable compound, and the content of the fluorene type epoxy compound is 30 parts by weight or more and 75 parts by weight or less.

3. The encapsulant for organic EL display elements according to claim 1 or 2, wherein the cationic polymerizable compound comprises, in addition to the cycloalken oxide type alicyclic epoxy compound and the fluorene type epoxy compound, other cationic polymerizable compounds.

4. The encapsulant for organic EL display elements according to claim 3, comprising at least one selected from the group consisting of 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, 1,2:7,8-diepoxyoctane, and 1,2:5,6-diepoxycyclooctane as the other cationic polymerizable compound.

5. The encapsulant for organic EL display elements according to claim 4, comprising 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane as the other cationic polymerizable compound.

6. The encapsulant for organic EL display elements according to claim 3, 4, or 5, wherein the content of the other cationic polymerizable compounds in 100 parts by weight of the cationic polymerizable compound is 10 parts by weight or more and 50 parts by weight or less.

7. The encapsulant for organic EL display elements according to claim 1, 2, 3, 4, 5, or 6, wherein the cationic polymerization initiator comprises a quaternary ammonium salt in which the counter anion is borate-based.

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