JP7561031B2 - Sealant for organic EL display devices - Google Patents

Description

The present invention relates to a sealant for organic EL display elements that can produce organic EL display elements that have low outgassing properties, excellent coatability, and excellent light extraction efficiency.

Organic electroluminescence (hereinafter also referred to as "organic EL") display elements have a laminate structure in which an organic light-emitting material layer is sandwiched between a pair of opposing electrodes, and 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 in the organic light-emitting material layer to emit light. As such, organic EL display elements are self-luminous, and therefore have the advantages of better visibility than liquid crystal display elements and the like that require a backlight, being able to be made thinner, and being able to be driven by a low DC voltage.

The organic light-emitting material layer and electrodes constituting an organic EL display element have a problem in that their characteristics are easily deteriorated by moisture, oxygen, and the like. Therefore, in order to obtain a practical organic EL display element, it is necessary to isolate the organic light-emitting material layer and electrodes from the atmosphere to extend their life. As a method for isolating the organic light-emitting material layer and electrodes from the atmosphere, the organic EL display element is sealed with a sealant (for example, Patent Document 1). When sealing an organic EL display element with a sealant, a method is usually used in which an inorganic material film called a passivation film is provided on a laminate having an organic light-emitting material layer, and the inorganic material film is sealed with a sealant in order to sufficiently suppress the transmission of moisture, oxygen, and the like.

In recent years, instead of bottom-emission organic EL display elements in which the light emitted from the organic light-emitting material layer is extracted from the substrate surface side on which the light-emitting element is formed, top-emission organic EL display elements in which the light is extracted from the top side of the organic light-emitting layer have been attracting attention. This method has the advantage of being advantageous in terms of long life due to its high aperture ratio and low-voltage drive. In such top-emission organic EL display elements, the top side of the light-emitting layer must be transparent, so the light-emitting element is sealed by laminating a transparent moisture-proof substrate such as glass on the top side of the light-emitting element via a transparent sealing layer (for example, Patent Document 2). However, in top-emission organic EL display elements, even if a transparent moisture-proof substrate or a sealant with sufficiently high transparency is used, there is a problem that the efficiency of extracting the light emitted from the laminate may be poor due to the difference in refractive index between the electrode or passivation film and the sealant. In addition, conventional sealants have problems such as generating outgassing, deteriorating the element, and having poor coatability. Furthermore, in order to reduce damage to the organic EL display element due to heating, a sealant that can be cured at low temperatures is required.

JP 2007-115692 A JP 2009-051980 A

The present invention aims to provide a sealant for organic EL display elements that has low outgassing properties, excellent coatability, and can produce organic EL display elements with excellent light extraction efficiency.

The present invention relates to a sealant for an organic EL display element, which contains a cationic polymerizable compound and a cationic polymerization initiator, and the cationic polymerizable compound is a sealant for an organic EL display element that contains a cycloalkene oxide-type alicyclic epoxy compound, and a compound having a biphenyl skeleton and an epoxy group or an oxetanyl group.
The present invention will be described in detail below.

The present inventors have investigated the use of a cycloalkene oxide-type alicyclic epoxy compound as a cationic polymerizable compound in a sealant for an organic EL display element to improve the coating property and prevent the generation of outgassing. However, although the sealant using such a cycloalkene oxide-type alicyclic epoxy compound has an excellent effect of preventing the generation of outgassing, there is a problem that the light extraction efficiency is reduced due to reflection at the interface between the sealant and the electrode or passivation film due to a large difference in refractive index between the sealant and the electrode or passivation film. Therefore, the present inventors have investigated the use of a combination of the cycloalkene oxide-type alicyclic epoxy compound and a compound having a biphenyl skeleton and an epoxy group or an oxetanyl group as a cationic polymerizable compound. As a result, it has been found that a sealant for an organic EL display element can be obtained that has low outgassing properties and excellent coating properties, and can provide an organic EL display element having excellent light extraction efficiency, and the present invention has been completed.
In addition, when the sealant for an organic EL display element of the present invention is made into a heat-curable sealant by using a thermal cationic polymerization initiator as the cationic polymerization initiator, it can be easily cured at a low temperature of 100° C. or less.

The sealant for an organic EL display element of the present invention contains a cationic polymerizable compound.
The cationic polymerizable compound includes a cycloalkene oxide-type alicyclic epoxy compound. By including the cycloalkene oxide-type alicyclic epoxy compound, the sealant for an organic EL display element of the present invention has low outgassing properties and excellent coatability.

Examples of the above-mentioned cycloalkene oxide type alicyclic epoxy compounds include 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)ether, bis(3,4-epoxycyclohexylmethyl)adipate, 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol, and [(3,4-epoxycyclohexane)-1-yl]methyl methacrylate.

Commercially available examples of the above cycloalkene oxide type alicyclic epoxy compounds include Celloxide 2021P (manufactured by Daicel Corporation), TTA26 (manufactured by Sun Chemical Co., Ltd.), EHPE3150 (manufactured by Daicel Corporation), etc.

The preferred lower limit of the content of the cycloalkene oxide type alicyclic epoxy compound in 100 parts by weight of the total of the cationic polymerizable compound is 3 parts by weight, and the preferred upper limit is 45 parts by weight. When the content of the cycloalkene oxide type alicyclic epoxy compound is 3 parts by weight or more, the obtained sealant for organic EL display elements has better curability, low outgassing properties, and coatability. When the content of the cycloalkene oxide type alicyclic epoxy compound is 45 parts by weight or less, the obtained organic EL display element has better light extraction efficiency. The more preferred lower limit of the content of the cycloalkene oxide type alicyclic epoxy compound is 5 parts by weight, the more preferred upper limit is 40 parts by weight, and the even more preferred upper limit is 38 parts by weight.

The cationic polymerizable compound includes a compound having a biphenyl skeleton and an epoxy group or an oxetanyl group. By containing the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group, the sealant for organic EL display elements of the present invention has a small refractive index difference with the electrodes and the passivation film, and as a result, the obtained organic EL display element has excellent light extraction efficiency. In addition, by containing a compound having a biphenyl skeleton and an epoxy group or an oxetanyl group, when the sealant for organic EL display elements of the present invention is used as a heat-curable sealant, it can be easily cured at a low temperature of 100°C or less.

The compound having the biphenyl skeleton and an epoxy group or an oxetanyl group may be an epoxy compound having a biphenyl skeleton or an oxetane compound having a biphenyl skeleton, and various compounds having a biphenyl skeleton and an epoxy group or an oxetanyl group can be appropriately selected from the standpoints of viscosity, refractive index, photocurability, etc.

Specific examples of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group include o-phenylphenol glycidyl ether, a compound represented by the following formula (1), p-phenylphenol glycidyl ether, 4,4-biphenyldiyl bis(glycidyl ether), 4,4'-bis(glycidyloxy)-1,1'-biphenyl, 3,3',5,5'-tetramethyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl, etc. Of these, o-phenylphenol glycidyl ether and the compound represented by the following formula (1) are preferred.
The compound having a biphenyl skeleton and an epoxy group or an oxetanyl group may be used alone or in combination of two or more kinds.

In formula (1), n is the number of repetitions.
The value of n is preferably such that the compound represented by formula (1) satisfies the range of the oxetanyl equivalent described below.

The epoxy equivalent or oxetanyl equivalent of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is preferably 110 in lower limit and 500 in upper limit. When the epoxy equivalent or oxetanyl equivalent of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is within this range, the resulting sealant for organic EL display elements has better adhesion, low outgassing properties, and coatability.
In this specification, the epoxy equivalent or oxetanyl equivalent of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group means (the molecular weight of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group)/(the number of epoxy groups or oxetanyl groups in one molecule of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group).

The preferred lower limit of the molecular weight of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is 200, and the preferred upper limit is 1000. When the molecular weight of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is within this range, the resulting sealant for an organic EL display element has better adhesion, low outgassing properties, and coatability.
In this specification, the "molecular weight" is the molecular weight calculated from the structural formula for compounds with a specific molecular structure, but may be expressed using the weight average molecular weight for compounds with a wide distribution of polymerization degrees and compounds with unspecific modified sites. The "weight average molecular weight" is a value calculated by measuring using tetrahydrofuran as a solvent by gel permeation chromatography (GPC) and converting it into polystyrene. Examples of columns used when measuring the weight average molecular weight calculated in polystyrene terms by GPC include Shodex LF-804 (manufactured by Showa Denko KK).

It is preferable that the compound having the biphenyl skeleton and an epoxy group or an oxetanyl group is liquid at 25° C. When the epoxy equivalent or oxetanyl equivalent of the compound having the biphenyl skeleton and an epoxy group or an oxetanyl group is liquid at 25° C., the resulting sealant for organic EL display elements has excellent coatability.

Commercially available compounds having the above biphenyl skeleton and an epoxy group or an oxetanyl group include, for example, OPP-EP (manufactured by Yokkaichi Synthetic Co., Ltd.) and ETERNACOLL OXBP (manufactured by Ube Industries, Ltd.).

The preferred lower limit of the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group in the total of 100 parts by weight of the cationic polymerizable compound is 30 parts by weight, and the preferred upper limit is 97 parts by weight. When the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is 30 parts by weight or more, the obtained organic EL display element has better light extraction efficiency. When the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is 97 parts by weight or less, the obtained sealant for organic EL display element has better curability, low outgassing properties, and coatability. The more preferred lower limit of the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is 50 parts by weight, the more preferred upper limit is 90 parts by weight, and the even more preferred upper limit is 80 parts by weight.
When the content of the cycloalkene oxide type alicyclic epoxy compound is 1, the ratio of the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group, in terms of weight ratio, is preferably 1 at the lower limit and 20 at the upper limit. By making the ratio of the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group 1 or more, the obtained sealant for an organic EL display element has a more excellent refractive index (light extraction efficiency), and by making it 20 or less, the sealant has a more excellent curability and refractive index. The more preferable lower limit of the ratio of the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is 1.3, the more preferable upper limit is 15, the even more preferable lower limit is 1.4, and the even more preferable upper limit is 10.

The cationic polymerizable compound may contain other cationic polymerizable compounds in addition to the cycloalkene oxide type alicyclic epoxy compound and the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group.
Examples of the other cationically polymerizable compounds include other epoxy compounds other than the cycloalkene oxide type alicyclic epoxy compounds and the compounds having a biphenyl skeleton and an epoxy group or an oxetanyl group, other oxetane compounds, and vinyl ether compounds.

Examples of the other epoxy compounds include fluorene-type epoxy compounds, 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 phenylene diglycidyl ether.

Examples of the other oxetane compounds 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, 1,4-bis(((3-ethyl-3-oxetanyl)methoxy)methyl)benzene, etc.

Examples of the vinyl ether compounds 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, tripropylene glycol divinyl ether, etc.

Among these, the other cationic polymerizable compounds are preferably 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, and more preferably 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane.

When the cationic polymerizable compound contains the other cationic polymerizable compound, the content of the other cationic polymerizable compound in 100 parts by weight of the cationic polymerizable compound is preferably 1 part by weight at the lower limit and 60 parts by weight at the upper limit. By making the content of the other cationic polymerizable compound within this range, the obtained sealant for organic EL display elements has better adhesion and coating properties. The content of the other cationic polymerizable compound is more preferably 10 parts by weight at the lower limit and 50 parts by weight at the upper limit, and even more preferably 15 parts by weight at the lower limit and 40 parts by weight at the upper limit.
In addition, when the cationic polymerizable compound contains the other cationic polymerizable compound, the preferred lower limit of the total content of the cycloalkene oxide type alicyclic epoxy compound and the other cationic polymerizable compound in 100 parts by weight of the cationic polymerizable compound is 20 parts by weight. When the total content of the cycloalkene oxide type alicyclic epoxy compound and the other cationic polymerizable compound is 20 parts by weight or more, the obtained sealant for organic EL display elements has better coatability. The more preferred lower limit of the total content of the cycloalkene oxide type alicyclic epoxy compound and the other cationic polymerizable compound is 25 parts by weight.

The sealant for an organic EL display element of the present invention contains a cationic polymerization initiator.
The cationic polymerization initiator may be a thermal cationic polymerization initiator or a photo cationic polymerization initiator. In particular, when a thermal cationic polymerization initiator is used as the cationic polymerization initiator, the sealant for an organic EL display element of the present invention can be easily cured at a low temperature of 100° C. or less.

Examples of the thermal cationic polymerization initiator include sulfonium salts, phosphonium salts, ammonium salts, diazonium salts, and iodonium salts, whose anion portion is composed of BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , or (BX ₄ ) ⁻ (wherein X represents a phenyl group substituted with at least two or more fluorine atoms or trifluoromethyl groups). Among these, sulfonium salts are preferred.

Examples of the sulfonium salts include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, etc.

Examples of the phosphonium salts include ethyltriphenylphosphonium hexafluoroantimonate, tetrabutylphosphonium hexafluoroantimonate, etc.

The above ammonium salts include, for example, 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. 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 trifluoromethanesulfonate.

Among the above-mentioned thermal cationic polymerization initiators, examples of commercially available ones include thermal cationic polymerization initiators manufactured by Sanshin Chemical Industry Co., Ltd. and thermal cationic polymerization initiators manufactured by King Industries.
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.

The above-mentioned photocationic polymerization initiator is not particularly limited as long as it generates a protonic acid or a Lewis acid upon irradiation with light, and may be an ionic photoacid-generating type or a non-ionic photoacid-generating type.

Examples of the anion moiety of the ionic photoacid generating photocationic polymerization initiator include BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , (BX ₄ ) ⁻ (wherein X represents a phenyl group substituted with at least two fluorine atoms or trifluoromethyl groups), etc. Examples of the anion moiety include PF _m (C _n F _2n+1 ) _6-m ⁻ (wherein m is an integer of 0 to 5, and n is an integer of 1 to 6), etc.
Examples of the ionic photoacid generating type photocationic polymerization initiator include aromatic sulfonium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic ammonium salts, (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe salts, and the like, each of which has the anion moiety.

The above aromatic sulfonium salts include, for example, 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, and triphenylsulfonium hexafluorophosphate. , 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, tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate, and the like. Of these, triarylsulfonium tetrakis(pentafluorophenyl)borate such as triphenylsulfonium tetrakis(pentafluorophenyl)borate is preferred.

Examples of the 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, 4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrakis(pentafluorophenyl)borate, and the like.

Examples of the aromatic diazonium salts include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, phenyldiazonium tetrakis(pentafluorophenyl)borate, etc.

Examples of the 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, 1-(naphthylmethyl)-2-cyanopyridinium tetrakis(pentafluorophenyl)borate, and the like.

Examples of the (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe salts include, for example, (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, (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) tetrakis(pentafluorophenyl)borate, and the like.

Examples of the above-mentioned nonionic photoacid generating type photocationic polymerization initiators include nitrobenzyl esters, sulfonic acid derivatives, phosphate esters, phenolsulfonic acid esters, diazonaphthoquinone, N-hydroxyimide sulfonates, etc.

Among the above-mentioned photocationic polymerization initiators, commercially available ones include, for example, photocationic polymerization initiators manufactured by Midori Chemical Industry Co., Ltd., photocationic polymerization initiators manufactured by Union Carbide Corporation, photocationic polymerization initiators manufactured by ADEKA Corporation, photocationic polymerization initiators manufactured by 3M Corporation, photocationic polymerization initiators manufactured by BASF Corporation, photocationic polymerization initiators manufactured by Solvay, and photocationic polymerization initiators manufactured by San-Apro Corporation.
An example of the photocationic polymerization initiator manufactured by Midori Kagaku Co., Ltd. is DTS-200.
Examples of the photocationic polymerization initiator manufactured by Union Carbide include UVI6990 and UVI6974.
Examples of the photocationic polymerization initiator manufactured by ADEKA Corporation include SP-150 and SP-170.
Examples of the photocationic polymerization initiator manufactured by 3M include FC-508 and FC-512.
Examples of the photocationic polymerization initiator manufactured by BASF include IRGACURE 261 and IRGACURE 290.
Examples of the photocationic polymerization initiators manufactured by Solvay include PI2074.
Examples of the photocationic polymerization initiator manufactured by San-Apro include CPI-100P, CPI-200K, and CPI-210S.

Among the above-mentioned cationic polymerization initiators, quaternary ammonium salts having a borate-based counter anion (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 preferably BF ₄ ^-- or (BX ₄ )-- (wherein X represents a phenyl group substituted with at least two fluorine atoms or trifluoromethyl groups).

The content of the cationic polymerization initiator is preferably 0.05 parts by weight at the lower limit and 10 parts by weight at the upper limit relative to 100 parts by weight of the cationic polymerizable compound. When the content of the cationic polymerization initiator is within this range, the resulting sealant for organic EL display elements has superior curability, storage stability, and moisture resistance of the cured product. A more preferred lower limit of the content of the cationic polymerization initiator is 0.1 parts by weight, and a more preferred upper limit is 5 parts by weight.

The sealant for an organic EL display element of the present invention may contain a heat curing agent.
Examples of the heat curing agent include hydrazide compounds, imidazole derivatives, acid anhydrides, dicyandiamide, guanidine derivatives, modified aliphatic polyamines, and addition products of various amines and epoxy resins.
Examples of the hydrazide compound include 1,3-bis(hydrazinocarbonoethyl)-5-isopropylhydantoin, sebacic acid dihydrazide, isophthalic acid dihydrazide, adipic acid dihydrazide, and malonic acid dihydrazide.
Examples of the 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)-adipamide, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2-phenyl-4,5-dihydroxymethylimidazole.
Examples of the acid anhydride include tetrahydrophthalic anhydride and ethylene glycol bis(anhydrotrimellitate).
These heat curing agents may be used alone or in combination of two or more kinds.

Among the above heat curing agents, examples of commercially available ones include a heat curing agent manufactured by Otsuka Chemical Co., Ltd. and a heat curing agent manufactured by Ajinomoto Fine-Techno Co., Ltd.
Examples of the heat curing agent manufactured by Otsuka Chemical Co., Ltd. include SDH and ADH.
Examples of the heat curing agents manufactured by Ajinomoto Fine-Techno Co., Inc. include Amicure VDH, Amicure VDH-J, and Amicure UDH.

The content of the heat curing agent is preferably 0.5 parts by weight at the lower limit and 30 parts by weight at the upper limit relative to 100 parts by weight of the cationic polymerizable compound. When the content of the heat curing agent is 0.5 parts by weight or more, the obtained sealant for organic EL display elements has better heat curing properties. When the content of the heat curing agent is 30 parts by weight or less, the obtained sealant for organic EL display elements has better storage stability, and the cured product has better moisture resistance. A more preferred lower limit of the content of the heat curing agent is 1 part by weight, and a more preferred upper limit is 15 parts by weight.

The sealant for organic EL display elements of the present invention preferably contains a stabilizer. By containing the above-mentioned stabilizer, the sealant for organic EL display elements of the present invention has better storage stability.

As the stabilizer, an aromatic amine compound is preferably used.
Examples of the aromatic amine compound include benzylamine and aminophenol type epoxy resins.
The aminophenol type epoxy resin includes triglycidyl-p-aminophenol and the like.
Of these, benzylamine is preferred.
These stabilizers may be used alone or in combination of two or more kinds.

The content of the stabilizer is preferably 0.001 parts by weight at the lower limit and 2 parts by weight at the upper limit relative to 100 parts by weight of the cationic polymerizable compound. When the content of the stabilizer is within this range, the resulting sealant for organic EL display elements has excellent storage stability while maintaining excellent curability. A more preferred lower limit of the content of the stabilizer is 0.005 parts by weight, and a more preferred upper limit is 1 part by weight.

The sealant for organic EL display elements of the present invention may contain a silane coupling agent. The silane coupling agent has the role of improving adhesion between the sealant for organic EL display elements of the present invention and a substrate, etc.

Examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, etc. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 0.1 parts by weight and 10 parts by weight, based on 100 parts by weight of the cationic polymerizable compound.By the content of the silane coupling agent being within this range, the effect of improving adhesion is superior while suppressing the bleeding out of excess silane coupling agent.The more preferred lower limit of the content of the silane coupling agent is 0.5 parts by weight and the more preferred upper limit is 5 parts by weight.
From the viewpoint of low outgassing, the content of the silane coupling agent is preferably at most 0.5 parts by weight, more preferably at most 0.1 parts by weight, and even more preferably at most 0.01 parts by weight, relative to 100 parts by weight of the cationic polymerizable compound.

The sealant for an organic EL display element of the present invention may further contain a surface modifier within a range that does not impair the object of the present invention. By containing the above-mentioned surface modifier, the flatness of the coating film of the sealant for an organic EL display element of the present invention can be improved.
Examples of the surface modifier include a surfactant and a leveling agent.

Examples of the surface modifier include silicone-based, acrylic-based, and fluorine-based ones.
Among the above surface modifiers, commercially available ones include, for example, surface modifiers manufactured by BYK Japan KK and surface modifiers manufactured by AGC Seimi Chemical Co., Ltd.
Examples of the surface modifiers manufactured by BYK Japan include BYK-330, BYK-340, and BYK-345.
An example of the surface modifier manufactured by AGC Seimi Chemical Co., Ltd. is Surflon S-611.

The sealant 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 sealant for organic EL display elements in order to improve the durability of the element electrodes, within a range that does not impair the object of the present invention.

Examples of compounds that react with the generated acid include substances that neutralize the acid, such as carbonates or bicarbonates of alkali metals, or carbonates or bicarbonates of alkaline earth metals. Specific examples include calcium carbonate, calcium bicarbonate, sodium carbonate, and sodium bicarbonate.

The above-mentioned ion exchange resin can be of the cation exchange type, anion exchange type, or amphoteric ion exchange type, but the cation exchange type or amphoteric ion exchange type, which can adsorb chloride ions, is particularly preferred.

The sealant for organic EL display elements of the present invention may contain a solvent for the purpose of adjusting viscosity, etc., but since residual solvent may cause problems such as deterioration of the organic light-emitting material layer or generation of outgassing, it is preferable that the sealant does not contain a solvent or that the solvent content is 0.05% by weight or less.

In addition, the sealant for organic EL display elements of the present invention may contain various known additives such as curing retarders, reinforcing agents, softeners, plasticizers, viscosity adjusters, UV absorbers, and antioxidants, as necessary.

The sealant for organic EL display devices of the present invention has a viscosity of preferably 2000 mPa·s as measured at 25° C. and 2.5 rpm using an E-type viscometer. When the viscosity is 2000 mPa·s or less, the sealant for organic EL display devices obtained has excellent coatability. The more preferred upper limit of the viscosity is 1500 mPa·s, and the even more preferred upper limit is 1000 mPa·s.
The lower limit of the viscosity is preferably 10 mPa·s.
The viscosity can be measured, for example, using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer with a CP1 cone plate.

In the sealant for organic EL display devices of the present invention, the refractive index of the cured product at 25° C. at the sodium D line is preferably 1.55 at its lower limit. By setting the refractive index within this range, the difference in refractive index between the electrode and the passivation film is small, and as a result, the organic EL display device obtained has excellent light extraction efficiency. The more preferable lower limit of the refractive index is 1.56.
The "refractive index at the sodium D line" can be measured using an Abbe refractometer.
The cured product for measuring the refractive index may be, for example, a measuring piece having a length of 20 mm, a width of 10 mm, and a thickness of 0.5 to 1 mm. The cured product for measuring the refractive index may be obtained by heating at 100°C for 30 minutes if it is a thermosetting sealant, or by irradiating it with ultraviolet light at ^about 2000 mJ/cm2 and then heating it at 100°C for 30 minutes if it is a photothermosetting sealant.

The sealant for an organic EL display device of the present invention is particularly suitably used as an in-plane sealant for covering and sealing a laminate having an organic light-emitting material layer.
The sealant for an organic EL display element of the present invention is suitably used for sealing a top-emission type organic EL display element.

A method for sealing an organic EL display element using the sealant for organic EL display elements of the present invention may include, for example, a method having a step of applying the sealant for organic EL display elements of the present invention to a substrate surface of the organic EL display element by printing, a dispensing method, an inkjet method, or the like, and a step of curing the applied sealant for organic EL display elements by heating and/or light irradiation.

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

When the above-mentioned sealant for organic EL display elements is cured by heating, it is preferable to heat it at 50°C or higher and 120°C or lower in order to sufficiently cure the sealant while reducing damage to the laminate having the organic light-emitting material layer.

When the sealant for an organic EL display element of the present invention is cured by light irradiation, the sealant for an organic EL display element of the present invention can be suitably cured by irradiating it with light having a wavelength of 300 nm or more and 400 nm or less and an integrated light amount of 300 mJ/ ^cm2 or more and 3,000 mJ/ ^cm2 or less.

Examples of light sources used for the 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, electron beam irradiation devices, etc. These light sources may be used alone or in combination of two or more.
These light sources are appropriately selected in accordance with the absorption wavelength of the cationic photopolymerization initiator.

Means for irradiating the sealant for organic EL display elements of the present invention with light include, for example, simultaneous irradiation from various light sources, sequential irradiation with a time lag, a combination of simultaneous irradiation and sequential irradiation, etc., and any irradiation means may be used.

The cured product obtained by the step of curing the sealant for an organic EL display element by heating and/or light irradiation may be further covered with an inorganic material film.
The inorganic material constituting the inorganic material film may be a conventionally known material, such as silicon nitride (SiN _x ) or silicon oxide (SiO _x ). The inorganic material film may be a single layer or a laminate of multiple layers. The laminate may be coated with the inorganic material film and a resin film composed of the sealant for an organic EL display element of the present invention, which are alternately arranged.

The method for producing the organic EL display element may include a step of bonding a substrate coated with the sealant for an organic EL display element of the present invention (hereinafter also referred to as "one substrate") to another substrate.
The substrate to which the sealant for an organic EL display element of the present invention is applied (hereinafter also referred to as "one substrate") may be a substrate on which a laminate having an organic light-emitting material layer is formed, or a substrate on which such a laminate is not formed.
When the one substrate is a substrate on which the laminate is not formed, the sealant for an organic EL display element 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 the one substrate. That is, the sealant may be applied to the entire surface of the area where the laminate will be located when the other substrate is bonded to the one substrate, or a sealant portion having a closed pattern may be formed in a shape that completely fits the area where the laminate will be located when the other substrate is bonded to the one substrate.
Also, as a method for sealing the organic EL display element, a so-called dam-fill sealing method may be used. 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 part. Next, the sealant for organic EL display element of the present invention is applied inside the applied curable paste, and the opposing sealing substrate is bonded while the sealant is prevented from protruding by the curable paste on the periphery. Then, a method may be used in which the curable paste on the periphery and the sealant for organic EL display element of the present invention that has been pressed inward are cured by heating and/or light irradiation.

The step of curing the sealant for an organic EL display element by heating and/or light irradiation may be carried out before the step of bonding the one substrate to the other substrate, or may be carried out after the step of bonding the one substrate to the other substrate.
When the step of curing the sealant for an organic EL display element by heating and/or light irradiation is carried out before the step of bonding the one substrate and the other substrate, the sealant for an organic EL display element of the present invention preferably has a pot life of 1 minute or more from heating and/or light irradiation until the curing reaction progresses and adhesion becomes impossible. By having the pot life of 1 minute or more, it is possible to obtain a higher adhesive strength without excessive curing progress before bonding the one substrate and the other substrate.

In the step of bonding the one substrate to the other substrate, the method for bonding the one substrate to the other substrate is not particularly limited, but it is preferable to bond the substrate to the other substrate in a reduced pressure atmosphere.
The preferred lower limit of the degree of vacuum under the reduced pressure atmosphere is 0.01 kPa, and the preferred upper limit is 10 kPa. When the degree of vacuum under the reduced pressure atmosphere is within this range, air bubbles in the sealant for an organic EL display element of the present invention can be more efficiently removed when the one substrate and the other substrate are bonded together, without spending a long time to achieve a vacuum state due to the airtightness of a vacuum device or the capacity of a vacuum pump.

According to the present invention, it is possible to provide a sealant for organic EL display elements that has low outgassing properties, excellent coatability, and can produce organic EL display elements with excellent light extraction efficiency.

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

(Examples 1 to 5, 7, 8 , Reference Example 6 , Comparative Examples 1 to 4)
Each material was stirred and mixed at a stirring speed of 2000 rpm using a stirring mixer according to the compounding ratios shown in Tables 1 and 2 to prepare sealants for organic EL display elements in Examples 1 to 5, 7, and 8 , Reference Example 6 , and Comparative Examples 1 to 4. An AR-250 (manufactured by Thinky Corporation) was used as the stirring mixer.

<Evaluation>
The sealants for organic EL display elements obtained in the Examples , Reference Examples , and Comparative Examples were evaluated as follows. The results are shown in Tables 1 and 2.

(1) Viscosity The viscosity of each of the sealants for organic EL display elements obtained in the Examples , Reference Examples , and Comparative Examples was measured at 25° C. and 2.5 rpm using an E-type viscometer. The E-type viscometer used was a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.).

(2) Coating property: 0.3 parts by weight of polymer beads having an average particle size of 10 μm was added to 100 parts by weight of each sealant for organic EL display elements obtained in the Examples , Reference Examples , and Comparative Examples, and uniformly dispersed using a planetary stirrer. Micropearl SP (manufactured by Sekisui Chemical Co., Ltd.) was used as the polymer beads. Two glass substrates each having a length of 5 cm and a width of 5 cm were prepared, and 0.1 mL of the obtained dispersion was placed at the center of one of the glass substrates, and the diameter that spread after 30 seconds was measured.
The coatability was evaluated as follows: when the diameter was 5.5 mm or more, it was marked "◎", when it was 5.0 mm or more and less than 5.5 mm, it was marked "◯", when it was 4.5 mm or more and less than 5.0 mm, it was marked "△", and when it was less than 4.5 mm, it was marked "X".

(3) Curability The reaction rate when each of the sealants for an organic EL display element obtained in the Examples , Reference Examples , and Comparative Examples was cured was determined.
For the sealants for organic EL display elements obtained in Examples 1 to 4 , 8 , Reference Example 6 , and Comparative Examples 1 to 4, reaction calorimetry was performed using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science Corporation, "DSC6220"), and the reaction rate was calculated using the following calculation formula (I). In calculation formula (I), H ₀ is the reaction heat amount when the sealant for organic EL display elements, which has been heat-cured at 100°C for 30 minutes, is heated to 40°C to 200°C at a heating rate of 10°C/min using an aluminum sample pan under a nitrogen gas atmosphere. In addition, in calculation formula (I), H ₁ is the reaction heat amount when the sealant for organic EL display elements, which has been heat-cured at 100°C for 30 minutes, is heated to 40°C to 200°C at a heating rate of 10°C/min.
(H ₀ −H ₁ )/H ₀ (I)
For the sealants for organic EL display elements obtained in Examples 5 and 7, reaction calorimetry was performed when irradiated with active energy rays and when the temperature was increased using a Photo-DSC (a combination of "DSC Q100" and a light source device "Qseries PCA" manufactured by TA Instruments), and the reaction rate was calculated using the following calculation formula (II). In calculation formula (II), H ₂ is the total heat generation amount from before the irradiation of active energy rays to the end of the temperature increase when irradiating active energy rays with an illuminance of 3.7 W/cm ² and an integrated light amount of 1.5 J/cm ² at 25° C. in a nitrogen atmosphere using a high-pressure mercury lamp (without a cut filter) and increasing the temperature to 40° C. to 200° C. at a temperature increase rate of 10° C./min immediately after the irradiation. The integrated light amount was measured using UV-351 (manufactured by ORC Corporation) as the integrated light amount at a wavelength of 351 nm. In addition, in the calculation formula (II), _H3 is the amount of heat generated (H3) from cooling to 25°C to the completion of heating to 200°C when, immediately after irradiation with active energy rays under the above conditions, the temperature is raised to 100°C at a heating rate of 20°C/min, held at 100°C for 30 minutes, cooled to 25°C at 10°C/min, and then heated to 200°C at a heating rate of ₁₀ °C/min.
(H ₂ -H ₃ )/H ₂ (II)
The curability was evaluated as follows: a reaction rate of 90% or more was marked "◎", a reaction rate of 80% or more but less than 90% was marked "◯", a reaction rate of 60% or more but less than 80% was marked "△", and a reaction rate of less than 60% was marked "X".

(4) Refractive index and light extraction efficiency A mold was prepared by cutting out a silicone rubber sheet having a thickness of 1 mm into a rectangle having a length of 20 mm and a width of 10 mm. This mold was placed on a release PET film, and the mold was filled with each of the sealants for organic EL display elements obtained in the Examples, Reference Examples , and Comparative Examples. The mold was then covered with another release PET film to prevent air bubbles from remaining in the mold, to obtain a laminate. The obtained laminate was sandwiched and fixed between two glass plates, and the sealant was cured. The sealants for organic EL display elements obtained in Examples 1 to 4 , 8 , Reference Example 6 , and Comparative Examples 1 to 4 were cured by heating at 100°C for 30 minutes, and the sealants for organic EL display elements obtained in Examples 5 and 7 were cured by irradiating them with ultraviolet light having a wavelength of 365 nm at 1500 mJ/ ^cm2 using a UV-LED, and then heating at 90°C for 30 minutes. The PET film was then peeled off to remove the cured sealant from the silicone rubber sheet, yielding a test piece measuring 10 mm in length, 20 mm in width, and 1 mm in thickness. The refractive index of the sodium D line at 25° C. was measured for the test piece using an Abbe refractometer. An NAR-4T (manufactured by Atago Co., Ltd.) was used as the Abbe refractometer.
In addition, taking into consideration the refractive index difference with the electrodes and passivation film, the light extraction efficiency was evaluated as follows: a refractive index of 1.56 or more was marked "○", a refractive index of 1.54 or more but less than 1.56 was marked "△", and a refractive index of less than 1.54 was marked "×".

(5) Low outgassing Each of the sealants for organic EL display elements obtained in the Examples , Reference Examples , and Comparative Examples was weighed out and filled in a vial in an amount of 300 mg, and then cured. The sealants for organic EL display elements obtained in Examples 1 to 4 , 8 , Reference Example 6 , and Comparative Examples 1 to 4 were heated at 100°C for 30 minutes to be cured, and the sealants for organic EL display elements obtained in Examples 5 and 7 were irradiated with 1500 mJ/ ^cm2 ultraviolet light having a wavelength of 365 nm using a UV-LED, and then heated at 90°C for 30 minutes to be cured. Furthermore, the vial was heated in a thermostatic oven at 85°C for 100 hours, and the amount of vaporized components in the vial was measured using a gas chromatograph mass spectrometer. As the gas chromatograph mass spectrometer, JMS-Q1050 (manufactured by JEOL Ltd.) was used.
The low outgassing property was evaluated as follows: if the amount of vaporized components was less than 50 ppm, it was marked "◯", if it was 50 ppm or more and less than 100 ppm, it was marked "Δ", and if it was 100 ppm or more, it was marked "X".

According to the present invention, it is possible to provide a sealant for organic EL display elements that has low outgassing properties, excellent coatability, and can produce organic EL display elements with excellent light extraction efficiency.

Claims (6)

A sealant for an organic EL display element, comprising a cationic polymerizable compound and a cationic polymerization initiator,
The cationic polymerizable compound includes a cycloalkene oxide type alicyclic epoxy compound and a compound having a biphenyl skeleton and an epoxy group or an oxetanyl group,
the content of the cycloalkene oxide-type alicyclic epoxy compound is 3 parts by weight or more and 40 parts by weight or less, and the content of the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group is 60 parts by weight or more and 97 parts by weight or less, in 100 parts by weight of the cationic polymerizable compound;
The sealant for an organic EL display element has a viscosity measured using an E-type viscometer at 25° C. and 2.5 rpm of 10 mPa·s or more and 1000 mPa·s or less,
The sealant for an organic electroluminescence display element, wherein a refractive index at 25° C. of a cured product of the sealant for an organic electroluminescence display element is 1.56 or more for sodium D ray. The sealant for an organic electroluminescence display element according to claim 1 , wherein the cationic polymerizable compound contains, in addition to the cycloalkene oxide type alicyclic epoxy compound and the compound having a biphenyl skeleton and an epoxy group or an oxetanyl group, another cationic polymerizable compound. The sealant for an organic EL display element according to claim 2, wherein the other cationically polymerizable compound comprises 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. 4. The sealant for an organic EL display element according to claim 3 , wherein the other cationically polymerizable compound comprises 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane. 5. The sealant for an organic EL display element according to claim 2, 3 or 4 , wherein the content of the other cationic polymerizable compound is 10 parts by weight or more and 50 parts by weight or less in 100 parts by weight of the cationic polymerizable compound. 6. The sealant for an organic EL display element according to claim 1, 2, 3, 4 or 5 , wherein the cationic polymerization initiator contains a quaternary ammonium salt whose counter anion is a borate type.