JP7479843B2 - Sealant for organic EL display devices - Google Patents

Description

The present invention relates to a sealant for organic EL display elements that has excellent inkjet coating properties, low outgassing properties, and adhesion to substrates and inorganic material films, and can produce organic EL display elements that are highly reliable.

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 having 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 that make up an organic EL display element have a problem in that their characteristics are easily deteriorated by moisture, oxygen, etc. 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 lifespan. Patent Document 1 discloses a method of sealing the organic light-emitting material layer and electrodes of an organic EL display element with a laminated film of a silicon nitride film and a resin film formed by a CVD method. Here, the resin film serves to prevent pressure on the organic layer and electrodes due to the internal stress of the silicon nitride film.

One method for forming a resin film is to apply a sealant onto a substrate using an inkjet method, and then harden the sealant. By using such an inkjet application method, a resin film can be formed quickly and uniformly. However, when the sealant is made to have a low viscosity to make it suitable for application by the inkjet method, problems arise such as outgassing and the resulting organic EL display element having poor reliability.

JP 2000-223264 A JP 2005-522891 A JP 2001-307873 A JP 2008-149710 A

In the method of sealing with a silicon nitride film disclosed in Patent Document 1, the organic light-emitting material layer and electrodes may not be completely covered when the silicon nitride film is formed due to unevenness on the surface of the organic EL display element, adhesion of foreign matter, occurrence of cracks due to internal stress, etc. If the coverage with the silicon nitride film is incomplete, moisture will penetrate into the organic light-emitting material layer through the silicon nitride film.
As a method for preventing the infiltration of moisture into an organic light-emitting material layer, Patent Document 2 discloses a method of alternately depositing inorganic material films and resin films, while Patent Documents 3 and 4 disclose methods of forming a resin film on an inorganic material film.
As a method for forming a resin film, there is a method in which a sealant is applied to a substrate by an inkjet method, and then the sealant is cured. By using such an application method using the inkjet method, a resin film can be formed quickly and uniformly. However, when the sealant is made to have a low viscosity so as to be suitable for application by the inkjet method, there are problems such as outgassing and the resulting organic EL display element being inferior in reliability.
An object of the present invention is to provide a sealant for an organic EL display element that has excellent inkjet coatability, low outgassing properties, and adhesion to a substrate or an inorganic material film, and that can provide an organic EL display element that is excellent in reliability.

Invention 1 is a sealant for an organic EL display element, which contains a curable resin and a polymerization initiator, the curable resin contains a compound represented by the following formula (1) and a compound represented by the following formula (2), the content of the compound represented by the following formula (1) is 1.0 to 1.5 times, in terms of weight ratio, the content of the compound represented by the following formula (2), the viscosity of the entire sealant for an organic EL display element at 25°C is 40 mPa·s or less, and the surface tension of the entire sealant for an organic EL display element at 25°C is 15 mN/m or more and 35 mN/m or less.
Invention 2 is a sealant for an organic EL display element, which contains a curable resin and a polymerization initiator, wherein the curable resin contains a compound represented by the following formula (1) and a compound represented by the following formula (2), and the content of the compound represented by the following formula (1) is 1.0 to 1.5 times, in terms of weight ratio, the content of the compound represented by the following formula (2), and the sealant for an organic EL display element is used for coating by an inkjet method.

In formula (1), R ¹ 's are each independently a bond, a linear or branched alkylene group having from 1 to 18 carbon atoms, or a linear or branched alkenylene group having from 2 to 18 carbon atoms; R ² 's are linear or branched alkylene group having from 1 to 18 carbon atoms, or a linear or branched alkenylene group having from 2 to 18 carbon atoms; and n is 0 or 1.

The present invention will be described in detail below. Note that matters common to the sealant for an organic EL display element of the present invention 1 and the sealant for an organic EL display element of the present invention 2 will be described as "sealant for an organic EL display element of the present invention."

The present inventors considered using 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane, which has excellent curability and low outgassing properties and a relatively low viscosity, as a curable resin for use in a sealant for organic EL display elements. However, although the resulting sealant had excellent curability, there were problems in that it had poor adhesion to substrates and inorganic material films due to cure shrinkage and was unsuitable for inkjet coating. As a result of extensive research, the present inventors considered blending a diepoxy compound having a specific structure as a curable resin in a specific content ratio with the 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane. As a result, they found that it was possible to obtain a sealant for organic EL display elements that had excellent inkjet coating properties, low outgassing properties, and adhesion to substrates and inorganic material films, as well as excellent reliability, and thus completed the present invention.

The sealant for an organic EL display element of the present invention contains a curable resin.
The curable resin contains a compound represented by the formula (1) and a compound represented by the formula (2). By using the compound represented by the formula (1) and the compound represented by the formula (2) in a content ratio described below, the sealant for an organic EL display element of the present invention has excellent inkjet coatability, low outgassing properties, and adhesion to a substrate or an inorganic material film.

In the above formula (1), R ¹ is preferably a linear or branched alkylene group having 1 to 18 carbon atoms, or a linear or branched alkenylene group having 2 to 18 carbon atoms, more preferably a linear or branched alkylene group having 1 to 18 carbon atoms, even more preferably a linear or branched alkylene group having 1 to 3 carbon atoms, and most preferably a methylene group.

In the above formula (1), ^R2 is preferably a linear or branched alkylene group having 1 to 18 carbon atoms, and more preferably a linear or branched alkylene group having 2 to 5 carbon atoms.

In the formula (1), the preferred lower limit of the total number of carbon atoms of ^R1 and ^R2 is 3, and the preferred upper limit is 20. When the total number of carbon atoms of ^R1 and ^R2 is within this range, the resulting sealant for an organic EL display element has low outgassing properties and excellent adhesion to a substrate or an inorganic material film. The more preferred lower limit of the total number of carbon atoms of ^R1 and ^R2 is 4, and the more preferred upper limit is 7.

From the viewpoint of the inkjet coating properties of the resulting sealant for organic EL display elements, it is preferable that n in the above formula (1) is 1.

The lower limit of the boiling point of the compound represented by the formula (1) is preferably 200° C. When the boiling point of the compound represented by the formula (1) is 200° C. or higher, the compound is less likely to volatilize, and the resulting sealant for an organic EL display element has better inkjet coatability. The lower limit of the boiling point of the compound represented by the formula (1) is more preferably 250° C.
In this specification, the boiling point refers to a value measured under a condition of 101 kPa using a method in accordance with JIS K 2233, or a value converted to 101 kPa using a boiling point conversion chart or the like.

Specific examples of the compound represented by the above formula (1) include ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,2,7,8-diepoxyoctane, 1,2,5,6-diepoxyhexane, etc. Among these, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether are preferred, and neopentyl glycol diglycidyl ether is the most preferred, because they are less likely to volatilize and the resulting sealant for organic EL display elements has superior inkjet coating properties.

The content of the compound represented by the above formula (1) is, in weight ratio, 1.0 times the lower limit and 1.5 times the upper limit of the content of the compound represented by the above formula (2). When the content of the compound represented by the above formula (1) is 1.0 times or more the content of the compound represented by the above formula (2), the sealant for organic EL display elements of the present invention has excellent adhesion to the substrate and inorganic material film, and the obtained organic EL display element has excellent reliability. When the content of the compound represented by the above formula (1) is 1.5 times or less the content of the compound represented by the above formula (2), the sealant for organic EL display elements of the present invention has excellent curability and low outgassing properties. The content of the compound represented by the above formula (1) is, in weight ratio, preferably 1.1 times the lower limit and 1.4 times the upper limit of the content of the compound represented by the above formula (2).

The preferred lower limit of the total content of the compound represented by formula (1) and the compound represented by formula (2) in 100 parts by weight of the curable resin is 30 parts by weight. When the total content of the compound represented by formula (1) and the compound represented by formula (2) is 30 parts by weight or more, the resulting sealant for organic EL display elements has excellent inkjet coating properties, low outgassing properties, and adhesion to substrates and inorganic material films. The more preferred lower limit of the total content of the compound represented by formula (1) and the compound represented by formula (2) is 50 parts by weight.
From the viewpoint of low outgassing properties, the preferred upper limit of the total content of the compound represented by the formula (1) and the compound represented by the formula (2) in 100 parts by weight of the curable resin is 80 parts by weight.

The curable resin may contain a polymerizable compound other than the compound represented by formula (1) and the compound represented by formula (2).
Examples of the other polymerizable compounds include epoxy compounds other than the compound represented by formula (1), oxetane compounds other than the compound represented by formula (2), (meth)acrylic compounds, and vinyl ether compounds.
In this specification, the term "(meth)acrylic" means acrylic or methacrylic, the term "(meth)acrylic compound" means a compound having a (meth)acryloyl group, and the term "(meth)acryloyl" means acryloyl or methacryloyl.

Examples of the other epoxy compounds include bisphenol A type epoxy compounds, bisphenol E type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, bisphenol O type epoxy compounds, 2,2'-diallyl bisphenol A type epoxy compounds, alicyclic epoxy compounds, hydrogenated bisphenol type epoxy compounds, propylene oxide-added bisphenol A type epoxy compounds, resorcinol type epoxy compounds, biphenyl type epoxy compounds, sulfide type epoxy compounds, diphenyl ether type epoxy compounds, dicyclopentadiene type epoxy compounds, naphthalene type epoxy compounds, phenol novolac type epoxy compounds, ortho-cresol novolac type epoxy compounds, dicyclopentadiene novolac type epoxy compounds, biphenyl novolac type epoxy compounds, naphthalene phenol novolac type epoxy compounds, glycidyl amine type epoxy compounds, alkyl polyol type epoxy compounds, rubber-modified epoxy compounds, glycidyl ester compounds, and epoxy compounds having a siloxane skeleton. Among these, epoxy compounds having a siloxane skeleton are preferred because the resulting sealant for an organic EL display element has excellent wettability and spreadability on a substrate or an inorganic material film.
Among the above-mentioned epoxy compounds having a siloxane skeleton, commercially available ones include, for example, X-22-169, X-22-163, X-22-343, X-22-2046, X-22-4741, X-22-173DX, and X-22-9002 (all manufactured by Shin-Etsu Chemical Co., Ltd.).
These other epoxy compounds may be used alone or in combination of two or more.

Examples of the other oxetane compounds include 3-(allyloxy)oxetane, phenoxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(phenoxymethyl)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, and oxetane compounds having a siloxane skeleton. Among these, oxetane compounds having a siloxane skeleton are preferred because the resulting sealant for organic EL display elements has excellent wettability and spreadability on substrates and inorganic material films.
These other oxetane compounds may be used alone or in combination of two or more.

Examples of the (meth)acrylic compound include glycidyl (meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, benzyl (meth)acrylate, trimethylolpropane tri(meth)arylate, 1,12-dodecanediol di(meth)acrylate, lauryl (meth)acrylate, and (meth)acrylic compounds having a siloxane skeleton.
Among these, a (meth)acrylic compound having a siloxane skeleton is preferred because the resulting sealant for an organic EL display element has excellent wettability and spreadability on a substrate or an inorganic material film.
Of the above (meth)acrylic compounds having a siloxane skeleton, commercially available ones include, for example, X-22-164, X-22-174DX, X-22-174ASX, X-22-2426, and X-22-2475 (all manufactured by Shin-Etsu Chemical Co., Ltd.).
These (meth)acrylic compounds may be used alone or in combination of two or more kinds.
In this specification, the term "(meth)acrylate" means acrylate or methacrylate.

Examples of the vinyl ether compound 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.
These vinyl ether compounds may be used alone or in combination of two or more kinds.

The sealant for an organic EL display element of the present invention contains a polymerization initiator.
As the polymerization initiator, a photo-cationic polymerization initiator or a thermal cationic polymerization initiator is preferably used. Depending on the type of the other polymerizable compound, a photo-radical polymerization initiator or a thermal radical polymerization initiator is also preferably used.

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.

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 Rhodia Corporation, 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.
An example of the photocationic polymerization initiator manufactured by Rhodia is PI2074.
Examples of the photocationic polymerization initiator manufactured by San-Apro include CPI-100P, CPI-200K, and CPI-210S.

Examples of the thermal cationic polymerization initiator include sulfonium salts, phosphonium salts, and ammonium 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). Of these, sulfonium salts and ammonium 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 CXC1612 and CXC1821.

Examples of the photoradical polymerization initiator include benzophenone-based compounds, acetophenone-based compounds, acylphosphine oxide-based compounds, titanocene-based compounds, oxime ester-based compounds, benzoin ether-based compounds, benzil, and thioxanthone-based compounds.

Among the above-mentioned photoradical polymerization initiators, examples of commercially available ones include photoradical polymerization initiators manufactured by BASF and photoradical polymerization initiators manufactured by Tokyo Chemical Industry Co., Ltd.
Examples of the photoradical polymerization initiators manufactured by BASF include IRGACURE 184, IRGACURE 369, IRGACURE 379, IRGACURE 651, IRGACURE 819, IRGACURE 907, IRGACURE 2959, IRGACURE OXE01, and Lucirin TPO.
Examples of the photoradical polymerization initiator manufactured by Tokyo Chemical Industry Co., Ltd. include benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether.

Examples of the thermal radical polymerization initiator include azo compounds, organic peroxides, and the like.
Examples of the azo compound include 2,2'-azobis(2,4-dimethylvaleronitrile) and azobisisobutyronitrile.
Examples of the organic peroxide include benzoyl peroxide, ketone peroxide, peroxyketal, hydroperoxide, dialkyl peroxide, peroxy ester, diacyl peroxide, and peroxydicarbonate.

Commercially available examples of the above thermal radical polymerization initiators include VPE-0201, VPE-0401, VPE-0601, VPS-0501, VPS-1001, and V-501 (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

The content of the polymerization initiator is preferably 0.01 parts by weight at the lower limit and 10 parts by weight at the upper limit relative to 100 parts by weight of the curable resin. When the content of the polymerization initiator is 0.01 parts by weight or more, the obtained sealant for organic EL display elements has better curability. When the content of the polymerization initiator is 10 parts by weight or less, the curing reaction of the obtained sealant for organic EL display elements does not become too fast, the workability is better, and the cured product can be made more uniform. A more preferable lower limit of the content of the polymerization initiator is 0.05 parts by weight, and a more preferable upper limit is 5 parts by weight.

The sealant for organic EL display elements of the present invention may contain a sensitizer. The sensitizer has the role of further improving the polymerization initiation efficiency of the polymerization initiator and further promoting the curing reaction of the sealant for organic EL display elements of the present invention.

Examples of the sensitizer include anthracene compounds, thioxanthone compounds, 2,2-dimethoxy-1,2-diphenylethan-1-one, benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, and 4-benzoyl-4'-methyldiphenyl sulfide.
Examples of the anthracene compound include 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, and 9,10-bis(octanoyloxy)anthracene.
The thioxanthone compound includes, for example, 2,4-diethylthioxanthone.

The preferred lower limit of the content of the sensitizer is 0.01 parts by weight and the preferred upper limit is 3 parts by weight relative to 100 parts by weight of the curable resin. When the content of the sensitizer is 0.01 parts by weight or more, the sensitizing effect is more pronounced. When the content of the sensitizer is 3 parts by weight or less, light can be transmitted to deep areas without excessive absorption. A more preferred lower limit of the content of the sensitizer is 0.1 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 further improving the adhesion between the sealant for organic EL display elements of the present invention and the substrate or inorganic material film.

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 at the lower limit and 10 parts by weight at the upper limit relative to 100 parts by weight of the curable resin. By having the content of the silane coupling agent within this range, the effect of improving adhesion while suppressing bleeding out of excess silane coupling agent is excellent. A more preferable lower limit of the content of the silane coupling agent is 0.5 parts by weight, and a more preferable upper limit is 5 parts by weight.

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

Examples of the surface conditioner include silicone-based and fluorine-based ones.
Among the above surface conditioners, commercially available ones include, for example, BYK-340, BYK-345 (both manufactured by BYK Japan KK), Surflon S-611 (manufactured by AGC Seimi Chemical Co., Ltd.), and the like.

The content of the surface conditioner is preferably 0.01 parts by weight at the lower limit and 5 parts by weight at the upper limit relative to 100 parts by weight of the curable resin. By having the content of the surface conditioner within this range, the surface tension of the entire sealant for organic EL display elements of the present invention can be more easily adjusted. A more preferred lower limit of the content of the surface conditioner is 0.1 parts by weight, and a more preferred upper limit is 3 parts by weight.

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 the generation of outgassing, it is preferable that the solvent content is 0.05% by weight or less, and it is most preferable that the sealant does not contain any solvent.

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

Methods for producing the sealant for organic EL display elements of the present invention include, for example, a method in which a curable resin, a polymerization initiator, and additives such as a silane coupling agent, which are added as necessary, are mixed using a mixer such as a homodisper, homomixer, universal mixer, planetary mixer, kneader, or three-roll mixer.

The sealant for an organic EL display element of the present invention 1 has an upper limit of viscosity at 25° C. of 40 mPa·s. By having the viscosity of 40 mPa·s or less, the sealant for an organic EL display element of the present invention 1 has excellent inkjet coatability. The preferred upper limit of the viscosity of the sealant for an organic EL display element of the present invention 1 is 20 mPa·s.
The lower limit of the viscosity of the sealant for an organic EL display element of the first invention is preferably 5 mPa·s.
In this specification, the viscosity refers to a value measured using an E-type viscometer at 25° C. and 100 rpm.

The sealant for an organic EL display element of the present invention 2 preferably has an upper limit of 40 mPa·s in viscosity at 25° C. When the viscosity is 40 mPa·s or less, the sealant for an organic EL display element of the present invention 2 has better inkjet coatability. The sealant for an organic EL display element of the present invention 2 more preferably has an upper limit of 20 mPa·s in viscosity.
The lower limit of the viscosity of the sealant for an organic EL display element of the second invention is preferably 5 mPa·s.

The sealant for an organic EL display element of the present invention 1 has a surface tension at 25° C. of 15 mN/m at a lower limit and 35 mN/m at an upper limit. When the surface tension is within this range, the sealant for an organic EL display element of the present invention 1 has excellent inkjet coatability. The surface tension of the sealant for an organic EL display element of the present invention 1 is preferably 20 mN/m at a lower limit and 30 mN/m at an upper limit, more preferably 22 mN/m at a lower limit and 28 mN/m at an upper limit.
The surface tension can be measured at 25° C. using a dynamic wettability tester.

The sealant for organic EL display elements of the present invention 2 has a surface tension at 25°C of preferably 15 mN/m at the lower limit and 35 mN/m at the upper limit. With the surface tension in this range, the sealant for organic EL display elements of the present invention 2 has superior inkjet coating properties. The more preferred lower limit of the surface tension of the sealant for organic EL display elements of the present invention 2 is 20 mN/m, the more preferred upper limit is 30 mN/m, the even more preferred lower limit is 22 mN/m, and the even more preferred upper limit is 28 mN/m.

The total light transmittance of the cured product of the sealant for organic EL display devices of the present invention for light having a wavelength of 380 nm or more and 800 nm or less is preferably 80%. When the total light transmittance is 80% or more, the resulting organic EL display device has more excellent optical properties. The more preferable lower limit of the total light transmittance is 85%.
The total light transmittance can be measured using, for example, a spectrometer such as AUTOMATIC HAZE METER MODEL TC-III DPK (manufactured by Tokyo Denshoku Co., Ltd.) The cured product used for measuring the light transmittance and the moisture permeability and water content described below can be obtained by irradiating the cured product with 3000 mJ/ ^cm2 ultraviolet light having a wavelength of 365 nm using a light source such as an LED lamp.

The sealant for organic EL display devices of the present invention preferably has a transmittance of 85% or more at 400 nm after irradiating the cured product with ultraviolet light for 100 hours at an optical path length of 20 μm. The transmittance of 85% or more after irradiating with ultraviolet light for 100 hours results in high transparency, small light emission loss, and excellent color reproducibility. The lower limit of the transmittance after irradiating with ultraviolet light for 100 hours is more preferably 90%, and even more preferably 95%.
As the light source for irradiating the ultraviolet light, for example, a xenon lamp, a carbon arc lamp, or other conventionally known light source can be used.

The sealant for organic EL display elements of the present invention preferably has a moisture permeability of 100 g/m2 or less at a thickness of 100 μm, measured by exposing the cured product to an environment of 85° C. and 85% RH for 24 hours in accordance with JIS Z ^0208. By having the moisture permeability of 100 g/m2 or ^less , the effect of preventing deterioration of the organic light-emitting material layer due to moisture in the cured product becomes superior, and the obtained organic EL display element has superior reliability.

The sealant for organic EL display devices of the present invention preferably has a moisture content of less than 0.5% when the cured product is exposed to an environment of 85° C. and 85% RH for 24 hours. When the moisture content of the cured product is less than 0.5%, the effect of preventing deterioration of the organic light-emitting material layer due to moisture in the cured product is more excellent, and the obtained organic EL display device has better reliability. The more preferable upper limit of the moisture content of the cured product is 0.3%.
The water content can be measured, for example, by the Karl Fischer method in accordance with JIS K 7251 or by measuring the weight increase after water absorption in accordance with JIS K 7209-2.

A method for manufacturing an organic EL display element using the sealant for organic EL display elements of the present invention includes, for example, a method having a step of applying the sealant for organic EL display elements of the present invention to a substrate by an inkjet method, and a step of curing the applied sealant for organic EL display elements by light irradiation and/or heating.

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 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 light irradiation and/or heating 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 made 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.

The step of curing the sealant for an organic EL display element by light irradiation and/or heating 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 light irradiation and/or heating 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 light irradiation and/or heating 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 excellent inkjet coating properties, low outgassing properties, and adhesion to substrates and inorganic material films, and can produce organic EL display elements that are highly reliable.

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

(Examples 1 to 7, Comparative Examples 1 to 6)
According to the compounding ratios shown in Tables 1 and 2, each material was uniformly stirred and mixed at a stirring speed of 3000 rpm using a Homo Disper type stirring mixer (manufactured by Primix Corporation, "Homo Disper L Type") to prepare each of the sealants for organic EL display elements of Examples 1 to 7 and Comparative Examples 1 to 6.
For each of the sealants for organic EL display elements obtained in the examples and comparative examples, the viscosity was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., "VISCOMETER TV-22") at 25°C and 100 rpm, and the surface tension was measured using a dynamic wettability tester (manufactured by Rhesca Corporation, "WET-6100 Model") at 25°C. These are shown in Tables 1 and 2.

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

(1) Inkjet Coating Property (1-1) Inkjet Discharge Property Each of the sealants for organic EL display elements obtained in the Examples and Comparative Examples was applied, using an inkjet discharge device (Microjet Corporation, "NanoPrinter500"), in a droplet amount of 30 picoliters onto alkali-cleaned alkali-free glass (Asahi Glass Company, Limited, "AN100") at a speed of 5 m/s and a pitch of 500 μm, in a total of 1,000 droplets.
The inkjet dischargeability was evaluated as follows: when the number of droplets that could not be coated was 0, it was marked as "◎", when the number of droplets that could not be coated was 1 or more and less than 5, it was marked as "◯", when the number of droplets that could not be coated was 5 or more and less than 20, it was marked as "△", and when the number of droplets that could not be coated was 20 or more, it was marked as "X".

(1-2) Wetting and spreading property Each of the organic EL display element sealants obtained in the examples and comparative examples was applied on alkali-cleaned non-alkali glass (Asahi Glass Co., Ltd., "AN100") in a droplet volume of 30 picoliters using an inkjet discharge device (Microjet Co., Ltd., "NanoPrinter500"). The application conditions were a height of 0.5 mm from the substrate, a pitch of 800 μm, and a frequency of 20 kHz. The diameter of the droplets on the non-alkali glass 10 minutes after application was measured, and the wetting and spreading property was evaluated as follows: "◎" when the diameter of the droplets was 180 μm or more, "○" when the diameter of the droplets was 150 μm or more and less than 180 μm, "△" when the diameter of the droplets was 120 μm or more and less than 150 μm, and "×" when the diameter of the droplets was less than 120 μm.

(2) Low Outgassing Property The amount of outgassing generated when the cured product of each of the sealants for organic EL display elements obtained in the Examples and Comparative Examples was heated was measured by gas chromatography using the headspace method described below.
First, 100 mg of each sealant for organic EL display elements was applied to a thickness of 300 μm using an applicator, and then the sealant was cured by irradiating it with ultraviolet light having a wavelength of 365 nm from an LED lamp at 3000 mJ/cm ^2. Next, the obtained sealant cured product was placed in a headspace vial, the vial was sealed, and the product was heated at 100° C. for 30 minutes, and the generated gas was measured by the headspace method.
The low outgassing property was evaluated as follows: when the generated gas was less than 400 ppm, it was marked as "◎", when it was 400 ppm or more but less than 600 ppm, it was marked as "◯", when it was 600 ppm or more but less than 800 ppm, it was marked as "△", and when it was 800 ppm or more, it was marked as "X".

(3) Adhesion to inorganic material film Each of the sealants for organic EL display devices obtained in the Examples and Comparative Examples was applied to a glass substrate on which a silicon nitride film having a thickness of 300 nm had been formed in advance, to a thickness of 10 μm, using a spin coater. Next, the sealant for organic EL display devices was irradiated with ultraviolet light having a wavelength of 365 nm at 3000 mJ/ ^cm2 from an LED lamp, and further heated at 100° C. for 30 minutes to harden the sealant for organic EL display devices, thereby obtaining a resin film.
The resin film thus formed was subjected to a cross-cut test with a cut interval of 1 mm according to JIS K 5600-5-6. The adhesion to the inorganic material film was evaluated as follows: peeling of 5% or less in the cross-cut test was indicated as "◎", peeling of more than 5% and less than 35% was indicated as "◯", peeling of more than 35% and less than 65% was indicated as "△", and peeling of more than 65% was indicated as "×".

(4) Reliability of organic EL display element (4-1) Preparation of substrate on which laminate having organic light-emitting material layer is arranged A glass substrate (length 25 mm, width 25 mm, thickness 0.7 mm) on which an ITO electrode is formed to a thickness of 1000 Å was used as a substrate. The above substrate was ultrasonically cleaned with acetone, an alkaline aqueous solution, ion-exchanged water, and isopropyl alcohol for 15 minutes each, and then cleaned with boiled isopropyl alcohol for 10 minutes, and further immediately before treatment was performed with a UV-ozone cleaner (manufactured by Japan Laser Electronics Co., Ltd., "NL-UV253").
Next, this substrate was fixed to a substrate holder of a vacuum deposition apparatus, 200 mg of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) was placed in an unglazed crucible, and 200 mg of tris(8-quinolinolato)aluminum (Alq ₃ ) was placed in another unglazed crucible, and the pressure inside the vacuum chamber was reduced to 1×10 ^-4 Pa. Thereafter, the crucible containing α-NPD was heated, and α-NPD was deposited on the substrate at a deposition rate of 15 Å/s to form a hole transport layer with a thickness of 600 Å. Next, the crucible containing Alq ₃ was heated, and an organic light-emitting material layer with a thickness of 600 Å was formed at a deposition rate of 15 Å/s. Thereafter, the substrate on which the hole transport layer and the organic light-emitting material layer were formed was transferred to another vacuum deposition apparatus, and 200 mg of lithium fluoride was placed in a tungsten resistance heating boat in this vacuum deposition apparatus, and 1.0 g of aluminum wire was placed in another tungsten boat. Thereafter, the pressure in the deposition chamber of the vacuum deposition apparatus was reduced to 2×10 ⁻⁴ Pa, and lithium fluoride was deposited to a thickness of 5 Å at a deposition rate of 0.2 Å/s, and then aluminum was deposited to a thickness of 1000 Å at a rate of 20 Å/s. The pressure in the deposition chamber was returned to normal pressure with nitrogen, and the substrate on which the laminate having the organic light-emitting material layer of 10 mm×10 mm was disposed was taken out.

(4-2) Coating with Inorganic Material Film A A mask having an opening of 13 mm×13 mm was placed on the substrate on which the obtained laminate was placed so as to cover the entire laminate, and an inorganic material film A was formed by plasma CVD.
The plasma CVD method was performed using _SiH4 gas and nitrogen gas as source gases, with flow rates of _SiH4 gas 10 sccm and nitrogen gas 200 sccm, RF power 10 W (frequency 2.45 GHz), chamber temperature 100° C., and chamber pressure 0.9 Torr.
The thickness of the formed inorganic material film A was about 1 μm.

(4-3) Formation of Resin Protective Film Each of the sealants for organic EL display elements obtained in the Examples and Comparative Examples was applied in a pattern onto the obtained substrate using an inkjet discharge device (Microjet Corporation, "NanoPrinter 300").
Thereafter, the sealant for organic EL display elements was cured by irradiating it with ultraviolet light having a wavelength of 365 nm at 3000 mJ/cm ² using an LED lamp to form a resin protective film.

(4-4) After forming a coating resin protective film using inorganic material film B, a mask having an opening of 12 mm x 12 mm was placed so as to cover the entire resin protective film, and inorganic material film B was formed by a plasma CVD method to obtain an organic EL display element.
The plasma CVD method was carried out under the same conditions as in "(4-2) Coating with inorganic material film A" above.
The thickness of the formed inorganic material film B was about 1 μm.

(4-5) Observation of the light-emitting state of the organic EL display element The obtained organic EL display element was exposed to an environment of a temperature of 85° C. and a humidity of 85% for 100 hours, and then a voltage of 3 V was applied to visually observe the light-emitting state of the organic EL display element (presence or absence of dark spots and peripheral quenching of pixels). The reliability of the organic EL display element was evaluated as follows: "◎" indicates that there was no dark spot or peripheral quenching and the element emitted light uniformly; "○" indicates that there was no dark spot or peripheral quenching but a slight decrease in luminance was observed; "△" indicates that there was dark spot or peripheral quenching; and "×" indicates that the non-light-emitting portion was significantly enlarged.

According to the present invention, it is possible to provide a sealant for organic EL display elements that has excellent inkjet coating properties, low outgassing properties, and adhesion to substrates and inorganic material films, and can produce organic EL display elements that are highly reliable.

Claims (3)

A sealant for an organic EL display element, comprising a curable resin and a polymerization initiator,
The curable resin contains a compound represented by the following formula (1), a compound represented by the following formula (2) , and an epoxy compound having a siloxane skeleton ,
The content of the compound represented by the following formula (1) is 1.0 times or more and 1.5 times or less in weight ratio to the content of the compound represented by the following formula (2),
the viscosity of the entire sealant for an organic EL display element at 25° C. is 40 mPa·s or less, and the surface tension of the entire sealant for an organic EL display element at 25° C. is 15 mN/m or more and 35 mN/m or less,
A sealant for an organic electroluminescence display device, characterized in that it is used for application by an inkjet method.

In formula (1), R ¹ 's are each independently a bond, a linear or branched alkylene group having from 1 to 18 carbon atoms, or a linear or branched alkenylene group having from 2 to 18 carbon atoms; R ² 's are linear or branched alkylene group having from 1 to 18 carbon atoms, or a linear or branched alkenylene group having from 2 to 18 carbon atoms; and n is 0 or 1.

The sealant for organic EL display elements according to claim 1, wherein the total content of the compound represented by formula (1) and the compound represented by formula (2) in 100 parts by weight of the curable resin is 30 parts by weight or more. 3. The sealant for an organic electroluminescence display element according to claim 1, wherein the total number of carbon atoms in ^R1 and ^R2 is 7 or less.