JP6378985B2 - Sealant for organic electroluminescence display element - Google Patents

Description

The present invention relates to a sealant for an organic electroluminescence display element that can suppress generation of outgas and has a long pot life after light irradiation.

In recent years, research on organic optical devices using organic thin film elements such as organic electroluminescence (organic EL) display elements and organic thin film solar cell elements has been advanced. The organic thin film element can be easily produced by vacuum deposition, solution coating, or the like, and thus has excellent productivity.

The organic EL display element has a thin film structure in which an organic light emitting material layer is sandwiched between a pair of electrodes facing each other. When electrons are injected from one electrode into the organic light emitting material layer and holes are injected from the other electrode, electrons and holes are combined in the organic light emitting material layer to perform self-light emission. Compared with a liquid crystal display element or the like that requires a backlight, the visibility is better, the thickness can be reduced, and direct current low voltage driving is possible.

However, such an organic EL display element has a problem that when the organic light emitting material layer and the electrode are exposed to the outside air, the light emission characteristics thereof are rapidly deteriorated and the life is shortened. Therefore, for the purpose of improving the stability and durability of the organic EL display element, in the organic EL display element, a sealing technique for shielding the organic light emitting material layer and the electrode from moisture and oxygen in the atmosphere is indispensable. Yes.

Patent Document 1 discloses a method of filling a photocurable sealant between organic EL display element substrates and irradiating light in a top emission organic EL display element or the like. However, such a conventional sealant has a problem in that it may cause an outgas during light irradiation to deteriorate the element.

JP 2001-357773 A

An object of this invention is to provide the sealing agent for organic electroluminescent display elements which can suppress generation | occurrence | production of outgas and has a long pot life after light irradiation.

The present invention is an organic electroluminescence display element sealing agent containing a cationically polymerizable compound and a photocationic polymerization initiator, which is irradiated with light having a wavelength of 365 nm and 50 mW / cm ² for 30 seconds, and then an E type. The time when the viscosity measured at 25 ° C. using a viscometer is 20,000 mPa · s or less is 15 minutes or more, and the time when the viscosity is 300,000 mPa · s or less is 20 minutes or more, The cationic polymerizable compound is a sealing agent for organic electroluminescence display elements containing a compound represented by the following formula (1).

In formula (1), R ^{1 to} R ¹⁸ are a hydrogen atom, a halogen atom, or a hydrocarbon group that may contain an oxygen atom or a halogen atom, and may be the same or different. Also good. X is a bond, an oxygen atom, an alkylene group having 1 to 5 carbon atoms, an oxycarbonyl group, an alkyleneoxycarbonyl group having 2 to 10 carbon atoms, or a secondary amino group.
The present invention is described in detail below.

The photocurable sealant used for sealing the organic EL display element usually contains a curing retarder such as crown ether in order to increase the pot life after light irradiation.
The present inventors thought that this curing retarder was the cause of outgassing when a conventional sealant was used. That is, it was considered that dioxane or the like was generated as outgas by decomposition of the curing retarder with an acid or the like during light irradiation.
Therefore, as a result of intensive studies, the present inventor has been able to suppress the generation of outgas by using a specific cationic polymerizable compound and has a long pot life after light irradiation, and is a sealing agent for organic EL display elements. The inventors have found that can be obtained, and have completed the present invention.
Moreover, the sealing agent for organic EL display elements of the present invention has an appropriate spreadability since the increase in viscosity after light irradiation is gradual.

The sealing agent for organic EL display elements of this invention contains a cationically polymerizable compound.
The cationically polymerizable compound contains a compound represented by the above formula (1) (hereinafter also referred to as “an epoxy compound according to the present invention”). By containing the epoxy compound concerning this invention, the sealing agent for organic EL display elements of this invention can suppress generation | occurrence | production of outgas, and becomes a thing with a long pot life after light irradiation.

The cationic polymerizable compound preferably contains a compound represented by the following formula (2-1) and / or a compound represented by the following formula (2-2) as an epoxy compound according to the present invention. It is more preferable to contain the compound represented by Formula (2-1).

Examples of commercially available epoxy compounds according to the present invention include Celoxide 2021P and Celoxide 8000 (both manufactured by Daicel).

The sealing agent for organic EL display elements of the present invention contains other cationic polymerizable compounds such as bisphenol A type epoxy resin and bisphenol F type epoxy resin as the cationic polymerizable compound as long as the object of the present invention is not impaired. However, from the viewpoint of suppressing outgassing, it is preferable that no other cationically polymerizable compound is contained.

When it contains the said other cationically polymerizable compound, the minimum with preferable content of the epoxy compound concerning this invention in 100 weight part of the whole cationically polymerizable compound is 60 weight part. When the content of the epoxy compound according to the present invention is less than 60 parts by weight, the effect of suppressing outgas may not be sufficiently exhibited. The minimum with more preferable content of the epoxy compound concerning this invention is 70 weight part.

The sealing agent for organic EL display elements of this invention contains a photocationic polymerization initiator.
The photocationic polymerization initiator is not particularly limited as long as it generates a protonic acid or a Lewis acid by light irradiation, and may be an ionic photoacid generating type or a nonionic photoacid generating type. May be.

Examples of the ionic photoacid-generating photocationic polymerization initiator include sulfonium borate, sulfonium phosphate, sulfonium antimonate, iodonium borate, iodonium phosphate, iodonium antimonate, diazonium borate, diazonium phosphate. Type, diazonium antimonate type, ammonium borate type, ammonium phosphate type, ammonium antimonate type, etc., specifically, the cation moiety is aromatic sulfonium, aromatic iodonium, aromatic diazonium, aromatic ammonium, or a (2,4-cyclopentadiene-1-yl) ((1-methylethyl) benzene) -Fe cation, anion moiety is _{^{BF 4 -, PF 6 -,}} SbF 6 -, Is (BX ₄₎ - ^(where, X is representative of at least two or more fluorine or phenyl group substituted by trifluoromethyl group) onium salts, and the like composed. Of these, sulfonium borate-based photocationic polymerization initiators are preferably used because of their excellent transparency.

Examples of the aromatic sulfonium salt include bis (4- (diphenylsulfonio) phenyl) sulfide bishexafluorophosphate, bis (4- (diphenylsulfonio) phenyl) sulfide bishexafluoroantimonate, and bis (4- ( Diphenylsulfonio) phenyl) sulfide bistetrafluoroborate, bis (4- (diphenylsulfonio) phenyl) sulfide tetrakis (pentafluorophenyl) borate, diphenyl-4- (phenylthio) phenylsulfonium hexafluorophosphate, diphenyl-4- ( Phenylthio) phenylsulfonium hexafluoroantimonate, diphenyl-4- (phenylthio) phenylsulfonium tetrafluoroborate, diphenyl-4- (phenylthio) Phenylsulfonium tetrakis (pentafluorophenyl) borate, triphenylsulfonium hexafluorophosphate, 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 ( - (2-hydroxyethoxy)) phenylsulfonio) phenyl) sulfide tetrakis (pentafluorophenyl) borate, and the like.

Examples of the aromatic iodonium salt 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 hexa Fluorophosphate, 4-methylphenyl-4- (1-methylethyl) Such as phenyl iodonium hexafluoroantimonate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrakis (pentafluorophenyl) borate Can be mentioned.

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

Examples of the aromatic ammonium salt include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, 1-benzyl-2-cyanopyridinium tetrafluoroborate, and 1-benzyl. 2-cyanopyridinium tetrakis (pentafluorophenyl) borate, 1- (naphthylmethyl) -2-cyanopyridinium hexafluorophosphate, 1- (naphthylmethyl) -2-cyanopyridinium hexafluoroantimonate, 1- (naphthylmethyl) Examples include 2-cyanopyridinium tetrafluoroborate and 1- (naphthylmethyl) -2-cyanopyridinium tetrakis (pentafluorophenyl) borate.

Examples of the (2,4-cyclopentadien-1-yl) ((1-methylethyl) benzene) -Fe salt include (2,4-cyclopentadien-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-cyclopentadien-1-yl) ((1-methylethyl) benzene) -Fe (II) tetrakis (penta Fluorophenyl) borate and the like.

Examples of the nonionic photoacid-generating photocationic polymerization initiator include nitrobenzyl ester, sulfonic acid derivative, phosphoric acid ester, phenolsulfonic acid ester, diazonaphthoquinone, N-hydroxyimide sulfonate and the like.

Examples of commercially available photocationic polymerization initiators include, for example, DTS-200 (manufactured by Midori Chemical Co., Ltd.), UVI6990, UVI6974 (all manufactured by Union Carbide), SP-150, SP-170 (all ADEKA), FC-508, FC-512 (all manufactured by 3M), IRGACURE 290 (BASF), PI 2074 (Rhodia), and the like.

The content of the cationic photopolymerization initiator is preferably 0.01 parts by weight and preferably 10 parts by weight with respect to 100 parts by weight of the cationic polymerizable compound. When the content of the cationic photopolymerization initiator is less than 0.01 parts by weight, the polymerization reaction of the cationically polymerizable compound may not proceed sufficiently or may become too slow. When the content of the cationic polymerization initiator exceeds 10 parts by weight, the viscosity rapidly increases after light irradiation, the spreadability is deteriorated, the pot life is shortened and the workability is decreased, and the obtained sealing agent The cured product may be non-uniform. The more preferable lower limit of the content of the photocationic polymerization initiator is 0.1 parts by weight, the more preferable upper limit is 5 parts by weight, the still more preferable lower limit is 0.5 parts by weight, and the still more preferable upper limit is 3 parts by weight.

It is preferable that the sealing agent for organic EL display elements of this invention does not contain a curing retarder from the viewpoint of suppressing generation of outgas. Even if it does not contain this hardening retarder, the sealing agent for organic EL display elements of this invention has a long pot life after light irradiation, and has a moderate expansibility.

The sealing agent for organic EL display elements of the present invention may contain a sensitizer as long as the object of the present invention is not impaired. The sensitizer has a role of further improving the polymerization initiation efficiency of the cationic polymerization initiator and further promoting the curing reaction of the curable resin composition of the present invention.

Examples of the sensitizer include thioxanthone compounds such as 2,4-diethylthioxanthone, 2,2-dimethoxy-1,2-diphenylethane-1-one, benzophenone, 2,4-dichlorobenzophenone, o- Examples include methyl benzoylbenzoate, 4,4′-bis (dimethylamino) benzophenone, 4-benzoyl-4′methyldiphenyl sulfide.

The content of the sensitizer is preferably 0.05 parts by weight and preferably 3 parts by weight with respect to 100 parts by weight of the cationic polymerizable compound. When the content of the sensitizer is less than 0.05 parts by weight, the sensitizing effect may not be sufficiently obtained. When the content of the sensitizer exceeds 3 parts by weight, absorption may be excessively increased and light may not be transmitted to the deep part. The minimum with more preferable content of the said sensitizer is 0.1 weight part, and a more preferable upper limit is 1 weight part.

The sealing agent for organic EL display elements of the present invention preferably contains a stabilizer for the purpose of improving storage stability.
Examples of the stabilizer include amine compounds and aminophenol type epoxy resins.

The content of the stabilizer is preferably 0.001 part by weight and preferably 2 parts by weight with respect to 100 parts by weight of the cationic polymerizable compound. When the content of the stabilizer is less than 0.001 part by weight, effects such as improving the storage stability of the obtained sealing agent for organic EL display elements may not be sufficiently exhibited. When content of the said stabilizer exceeds 2 weight part, hardening of sealing agent may be inhibited. The minimum with more preferable content of the said stabilizer is 0.05 weight part, and a more preferable upper limit is 1 weight part.

The sealing agent for organic EL display elements of the present invention may contain a silane coupling agent. The said silane coupling agent has a role which improves the adhesiveness of the sealing agent for organic EL display elements of this invention, a board | substrate, etc.

Examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-isocyanatopropyltrimethoxysilane. These silane coupling agents may be used independently and 2 or more types may be used together.

The content of the silane coupling agent is preferably 0.1 parts by weight and preferably 10 parts by weight with respect to 100 parts by weight of the cationic polymerizable compound. When the content of the silane coupling agent is less than 0.1 parts by weight, the effect of improving the adhesiveness of the obtained sealing agent for organic EL display elements may not be sufficiently exhibited. When content of the said silane coupling agent exceeds 10 weight part, an excess silane coupling agent may bleed out. The minimum with more preferable content of the said silane coupling agent is 0.5 weight part, and a more preferable upper limit is 5 weight part.

The sealing agent for organic EL display elements of the present invention may contain a surface modifier as long as the object of the present invention is not impaired. By containing the surface modifier, the flatness of the coating film can be imparted to the organic EL display element sealant of the present invention.
Examples of the surface modifier include surfactants and leveling agents.

Examples of the surfactant and the leveling agent include silicon-based, acrylic-based, and fluorine-based ones.
Examples of commercially available surfactants and leveling agents include BYK-345, BYK-340 (all manufactured by Big Chemie Japan), and Surflon S-611 (manufactured by AGC Seimi Chemical). Can be mentioned.

The encapsulant for organic EL display elements of the present invention reacts with the acid generated in the encapsulant for organic EL display elements in order to improve the durability of the element electrode within a range not impairing the object of the present invention. A compound or an ion exchange resin may be contained.

Examples of the compound that reacts with the generated acid include substances that neutralize the acid, for example, alkali metal carbonates or bicarbonates, or alkaline earth metal carbonates or bicarbonates. Specifically, for example, calcium carbonate, calcium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate and the like are used.

As the ion exchange resin, any of a cation exchange type, an anion exchange type, and a both ion exchange type can be used, and in particular, a cation exchange type or a both ion exchange type capable of adsorbing chloride ions. Is preferred.

Moreover, the sealing agent for organic EL display elements of the present invention is a reinforcing agent, a softening agent, a plasticizer, a viscosity modifier, an ultraviolet absorber, and an antioxidant as necessary, as long as the object of the present invention is not impaired. Various known additives such as these may be contained.

Examples of the method for producing the sealing agent for organic EL display elements of the present invention include a cationically polymerizable compound using a mixer such as a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, or a three roll. And a method of mixing a thermal cationic polymerization initiator and / or a thermosetting agent and an additive such as a silane coupling agent added if necessary.

The sealing agent for organic EL display elements of the present invention uses an E-type viscometer, and the lower limit of the viscosity at 25 ° C. is 50 mPa · s, and the upper limit is 8000 mPa · s. When the viscosity is less than 50 mPa · s, the obtained sealing agent for organic EL display elements of the present invention is inferior in applicability or composition unevenness occurs and the cured product is inferior in transparency. Or When the said viscosity exceeds 8000 mPa * s, the sealing agent for organic EL display elements of this invention obtained will be inferior to applicability | paintability. The preferable lower limit of the viscosity is 70 mPa · s, the preferable upper limit is 3000 mPa · s, the more preferable lower limit is 100 mPa · s, and the more preferable upper limit is 1000 mPa · s.
The viscosity is, for example, a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer, and a rotational speed of 1 to 100 rpm as appropriate from the optimum torque number in each viscosity region using CP1 cone plate. Can be measured by selecting.

As described above, the encapsulant for an organic EL display element of the present invention has a moderate pot life since it has a moderate increase in viscosity after light irradiation.
Specifically, the sealant for an organic EL display element of the present invention has a viscosity measured at 25 ° C. using an E-type viscometer after irradiation with light having a wavelength of 365 nm and 50 mW / cm ² for 30 seconds. It is preferable that the time that is 10,000 mPa · s or less is 15 minutes or more and the time that the viscosity is 300,000 mPa · s or less is 20 minutes or more. That is, when the viscosity after 15 minutes from light irradiation is 20,000 mPa · s or less, it has appropriate spreadability, and after 20 minutes from light irradiation, the viscosity is 300,000 mPa · s or less. And sufficient time can be taken for the panel bonding process etc. of an organic EL display element.

ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of outgas can be suppressed and the sealing agent for organic electroluminescent display elements with a long pot life after light irradiation can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
As a cationically polymerizable compound, 100 parts by weight of a compound represented by the above formula (2-1) (manufactured by Daicel, “Celoxide 2021P”), and a cationic photopolymerization initiator, a sulfonium borate photocationic polymerization initiator ( For organic EL display elements, 1 part by weight of Midori Chemical Co., Ltd., “DTS-200”) is uniformly stirred and mixed at a stirring speed of 3000 rpm using a stirring mixer (“AR-250”, manufactured by Shinky Corporation). A sealant was prepared.

(Examples 2 to 5, Comparative Examples 1 and 2)
Each material described in Table 1 was stirred and mixed in the same manner as in Example 1 in accordance with the mixing ratio described in Table 1, and the organic EL display element seals of Examples 2 to 5 and Comparative Examples 1 and 2 were mixed. A stop agent was prepared.

<Evaluation>
The following evaluation was performed about each sealing agent for organic EL display elements obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Initial viscosity About each sealing agent for organic EL display elements obtained in Examples and Comparative Examples, using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., “VISCOMETER TV-22”) at 25 ° C. The viscosity (initial viscosity) was measured.

(2) Each of the organic EL display element sealants obtained in the delayed curable examples and comparative examples was applied onto a glass substrate, and an ultraviolet irradiation device (manufactured by Oak Co., “JL-4300-3S” was applied to the substrate. )) Was irradiated with ultraviolet rays at 1500 mJ / cm ² . After 20 minutes, the curability was confirmed (when the viscosity was greatly increased, the viscosity was measured in the same manner as “(1) Initial viscosity”), and then heated in an oven at 100 ° C. for 15 minutes to confirm the curability. . As a result, the case where it was uncured and not hardened after 20 minutes of ultraviolet irradiation and was cured after heating at 100 ° C. was marked with “O”, and the viscosity increased to 300,000 mPa · s or more after 20 minutes of ultraviolet irradiation. And when it is cured after heating at 100 ° C., or when it is uncured without significant thickening after 20 minutes of ultraviolet irradiation, and the cured state after heating at 100 ° C. is incomplete. Delayed curability was evaluated as “C” when “Δ” was cured within 20 minutes of ultraviolet irradiation or when it was uncured after heating at 100 ° C.

(3) Viscosity after light irradiation (after 15 minutes and after 20 minutes) Each sealing agent for organic EL display elements obtained in Examples and Comparative Examples was applied on a glass substrate, and an ultraviolet irradiation device was applied to the substrate. (Oak Co., Ltd., “JL-4300-3S”) was irradiated with ultraviolet light having a wavelength of 365 nm and 50 mW / cm ² for 30 seconds. The viscosity at 25 ° C. was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., “VISCOMETER TV-22”) 15 minutes and 20 minutes after the irradiation with ultraviolet rays.

(4) Outgas prevention properties Each sealing agent for organic EL display element obtained in Examples and Comparative Examples was weighed and sealed in a vial, 300 mg, and then irradiated with an ultraviolet irradiation device (manufactured by Oak Co., "JL-4300 −3S ”) was irradiated with ultraviolet rays at 1500 mJ / cm ² , and the vaporized components in the vial were measured using a gas chromatograph mass spectrometer (manufactured by JEOL Ltd.,“ JMS-Q1050 ”).
The outgassing prevention property was evaluated as “◯” when the vaporized component amount was less than 50 ppm, “Δ” when it was 50 ppm or more and less than 100 ppm, and “X” when it was 100 ppm or more.

ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of outgas can be suppressed and the sealing agent for organic electroluminescent display elements with a long pot life after light irradiation can be provided.

Claims (3)

A sealing agent for an organic electroluminescence display element comprising a cationically polymerizable compound and a photocationic polymerization initiator,
After irradiating light with a wavelength of 365 nm and 50 mW / cm ² for 30 seconds, using an E-type viscometer, the time when the viscosity measured at 25 ° C. is 20,000 mPa · s or less is 15 minutes or more, and The time during which the viscosity is 300,000 mPa · s or less is 20 minutes or more,
The cationic polymerizable compound contains a compound represented by the following formula (2-1) ,
The encapsulant for organic electroluminescence display elements, wherein the cationic photopolymerization initiator is a sulfonium borate-based cationic photopolymerization initiator.

2. The encapsulant for an organic electroluminescence display element according to claim 1 , wherein the content of the cationic photopolymerization initiator is 0.01 to 10 parts by weight with respect to 100 parts by weight of the cationic polymerizable compound. The encapsulant for organic electroluminescence display elements according to claim 1, which does not contain a curing retarder.