Sealant for display elements

Abstract

To provide a sealant for display elements which gives a cured product having a low dielectric constant and excellent flexibility.SOLUTION: The sealant for display elements contains a cationically polymerizable compound, a cationic polymerization initiator, and a polyolefin. The content of the polyolefin is 10 pts.mass or more and 200 pts.mass or less based on 100 pts.mass of the cationically polymerizable compound.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sealing agent for display elements.

Background Art

[0002] Touch panels are used in electronic devices such as mobile phones, smartphones, car navigation systems, and personal computers. Among them, capacitive touch panels are rapidly spreading because of their excellent functionality. In particular, in recent years, the development of display elements such as organic EL display elements equipped with capacitive touch panels has been progressing. As a sealing agent for display elements used in display elements equipped with touch panels, a material having an appropriate viscosity, excellent coatability, and excellent curability is required. As such a sealing agent for display elements, for example, Patent Document 1 discloses an ultraviolet cationic polymerizable compound composition mainly composed of an acrylic compound.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the thinning and enlargement of capacitive touch panels, in order not to reduce the response speed of the touch panel, the sealing agent for display elements is required to have low dielectric properties such as a low dielectric constant and a low dielectric tangent. In addition, as a cationic polymerizable compound used in the sealing agent for display elements, a cationic polymerizable compound such as an epoxy compound is often used because it is hardly inhibited by the reaction with oxygen and has a low curing shrinkage rate. In recent years, with the development of foldable display elements, the sealing agent for display elements is also required to have excellent flexibility after curing. However, conventional sealing agents for display elements using cationic polymerizable compounds have difficulty in achieving both low dielectric properties and excellent flexibility after curing.

[0005] An object of the present invention is to provide a sealant for display elements which has a low dielectric constant when cured and is excellent in flexibility. [Means for solving the problem]

[0006] The present disclosure 1 is a sealant for display elements, which contains a cationic polymerizable compound, a cationic polymerization initiator, and a polyolefin, and the content of the polyolefin per 100 parts by mass of the cationic polymerizable compound is 10 parts by mass or more and 200 parts by mass or less. Disclosure 2 relates to the sealant for display elements of Disclosure 1, wherein the polyolefin has a repeating structure derived from a linear or branched olefin monomer having 4 or more carbon atoms. Disclosure 3 is the sealant for display elements according to Disclosure 1 or 2, wherein the polyolefin does not have a cationically polymerizable group. Disclosure 4 is the sealant for display elements according to Disclosure 1, 2, or 3, in which the cationically polymerizable compound includes a bifunctional or higher functional cationically polymerizable compound having two or more cationically polymerizable groups in one molecule, and the content of the bifunctional or higher functional cationically polymerizable compound in 100 parts by mass of the cationically polymerizable compound is 10 parts by mass or more. Disclosure 5 is the sealant for a display element according to Disclosure 1, 2, 3, or 4, which has a viscosity at 25° C. of 30 mPa·s or less. The present invention will be described in detail below.

[0007] The present inventors have investigated the possibility of further adding a specific amount of polyolefin to a sealant for display elements containing a cationically polymerizable compound and a cationic polymerization initiator, and have found that a sealant for display elements having a low dielectric constant and excellent flexibility in a cured product can be obtained, thereby completing the present invention.

[0008] The sealant for a display element of the present invention contains a cationically polymerizable compound. Examples of the cationic polymerizable compound include epoxy compounds, oxetane compounds, vinyl ether compounds, etc. Among them, the cationic polymerizable compound preferably contains at least one selected from the group consisting of epoxy compounds and oxetane compounds.

[0009] As the epoxy compound, from the viewpoint of coatability and the like, an alicyclic epoxy compound having an alicyclic epoxy group is preferable. Examples of the alicyclic epoxy group include an epoxycyclohexyl group. In addition, as the epoxy compound, from the viewpoints of heat resistance and low dielectric properties of the cured product of the obtained sealing agent for display elements, an epoxy compound having a silicone skeleton is preferable. In particular, as the epoxy compound, an alicyclic epoxy compound having a silicone skeleton is preferable.

[0010] Examples of the alicyclic epoxy compound having a silicone skeleton include a compound represented by the following formula (1), a compound represented by the following formula (2), etc. Among them, the compound represented by the following formula (1) is preferable.

[0011]

Chemical formula

[0012] In formula (1), R 1 is each independently an alkyl group having 1 to 10 carbon atoms, R 2 is each independently a bond or an alkylene group having 1 to 6 carbon atoms, and n represents an integer of 0 or more and 1000 or less.

[0013]

Chemical formula

[0014] In formula (2), R 3 is each independently an alkyl group having 1 to 10 carbon atoms, R 4is a bond or an alkylene group having 1 to 6 carbon atoms, and R 5 are each independently an alkyl group having 1 to 10 carbon atoms, or a group represented by the following formula (3-1) or (3-2): In formula (2), l represents an integer of 0 to 1000, and m represents an integer of 1 to 100. However, R 5 are all alkyl groups having 1 to 10 carbon atoms, m represents an integer of 2 to 100.

[0015] [ka]

[0016] In formulas (3-1) and (3-2), R 6 represents a bond or an alkylene group having 1 to 6 carbon atoms, and * represents the bonding position.

[0017] Among the above epoxy compounds, examples other than the alicyclic epoxy compounds having a silicone skeleton include 3,4-epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate, 4,4'-bis(1,2-epoxycyclohexane), 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.

[0018] Examples of the oxetane compound 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, and the like. Among them, 3-ethyl-3-(((3-ethyloxetan-3-yl)methoxy)methyl)oxetane and 3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane are preferred.

[0019] 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, tripropylene glycol divinyl ether, and the like.

[0020] Since the cationically polymerizable compound serves as a crosslinking material for improving the film quality of the resulting encapsulant for display elements, it preferably contains a polyfunctional cationically polymerizable compound having two or more cationically polymerizable groups in one molecule. The preferred lower limit of the content of the polyfunctional cationically polymerizable compound in 100 parts by mass of the cationically polymerizable compound is 10 parts by mass. When the content of the polyfunctional cationically polymerizable compound is 10 parts by mass or more, the film quality of the resulting encapsulant for display elements becomes good. A more preferred lower limit of the content of the polyfunctional cationically polymerizable compound is 20 parts by mass. Also, the content of the polyfunctional cationically polymerizable compound in 100 parts by mass of the cationically polymerizable compound may be 100 parts by mass, that is, the cationically polymerizable compound may contain only the polyfunctional cationically polymerizable compound.

[0021] In 100 parts by mass of the encapsulant for a display element of the present invention, the preferable lower limit of the content of the cationic polymerizable compound is 35 parts by mass, and the preferable upper limit is 90 parts by mass. When the content of the cationic polymerizable compound is within this range, the encapsulant for a display element of the present invention has excellent curability and adhesiveness. The more preferable lower limit of the content of the cationic polymerizable compound is 45 parts by mass, and the more preferable upper limit is 75 parts by mass.

[0022] The encapsulant for a display element of the present invention contains a cationic polymerization initiator. As the cationic polymerization initiator, at least one of a photo cationic polymerization initiator and a thermal cationic polymerization initiator is preferably used.

[0023] The photo cationic 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 generator type or a non-ionic photoacid generator type.

[0024] As the anion part of the ionic photoacid generator type photo cationic polymerization initiator, for example, BF4 - , PF6 - , SbF6 - , (BX4) - (wherein X represents a phenyl group substituted with at least two or more fluorine or trifluoromethyl groups) and the like can be mentioned. Further, as the anion part, PF m (C n F 2n+1 ) 6-m - (wherein m is an integer of 0 or more and 5 or less, and n is an integer of 1 or more and 6 or less) and the like can also be mentioned. Examples of the ionic photoacid generator type photo cationic polymerization initiator include aromatic sulfonium salts, aromatic iodonium salts, aromatic diazonium salts, aromatic ammonium salts, (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe salts and the like having the above anion part.

[0025] Examples of the aromatic sulfonium salt include bis(4-(diphenylsulfonio)phenyl)sulfide bis(hexafluorophosphate), bis(4-(diphenylsulfonio)phenyl)sulfide bis(hexafluoroantimonate), bis(4-(diphenylsulfonio)phenyl)sulfide bis(tetrafluoroborate), 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 bis(hexafluorophosphate), bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bis(hexafluoroantimonate), bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bis(tetrafluoroborate), bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide tetrakis(pentafluorophenyl)borate, tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate, and the like.

[0026] 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)phenyl iodonium hexafluorophosphate, 4-methylphenyl-4-(1-methylethyl)phenyl iodonium hexafluoroantimonate, 4-methylphenyl-4-(1-methylethyl)phenyl iodonium tetrafluoroborate, 4-methylphenyl-4-(1-methylethyl)phenyl iodonium tetrakis(pentafluorophenyl)borate, and the like.

[0027] Examples of the aromatic diazonium salt include phenyl diazonium hexafluorophosphate, phenyl diazonium hexafluoroantimonate, phenyl diazonium tetrafluoroborate, phenyl diazonium tetrakis(pentafluorophenyl)borate, and the like.

[0028] Examples of the aromatic ammonium salt 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.

[0029] 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-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe(II) hexafluoroantimonate, (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe(II) tetrafluoroborate, and (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe(II) tetrakis(pentafluorophenyl)borate.

[0030] Examples of the nonionic photoacid-generating cationic photopolymerization initiator include nitrobenzyl esters, sulfonic acid derivatives, phosphate esters, phenolsulfonic acid esters, diazonaphthoquinone, and N-hydroxyimide sulfonates.

[0031] Among the above-mentioned cationic photopolymerization initiators, commercially available ones include, for example, cationic photopolymerization initiators manufactured by Midori Chemical Industry Co., Ltd., cationic photopolymerization initiators manufactured by Union Carbide Corporation, cationic photopolymerization initiators manufactured by ADEKA Corporation, cationic photopolymerization initiators manufactured by 3M Corporation, cationic photopolymerization initiators manufactured by BASF Corporation, cationic photopolymerization initiators manufactured by Solvay Chemical Industries, Ltd., and cationic photopolymerization initiators manufactured by San-Apro Corporation. Examples of the cationic photopolymerization initiators manufactured by Midori Chemical Co., Ltd. include DTS-200. Examples of the cationic photopolymerization initiators manufactured by Union Carbide include UVI6990 and UVI6974. Examples of the cationic photopolymerization initiators manufactured by ADEKA Corporation include SP-150 and SP-170. Examples of the cationic photopolymerization initiator manufactured by 3M include FC-508 and FC-512. Examples of the above-mentioned photo cationic polymerization initiator manufactured by BASF include IRGACURE 261, IRGACURE 290, etc. Examples of the above-mentioned photo cationic polymerization initiator manufactured by Solvay include PI2074, etc. Examples of the above-mentioned photo cationic polymerization initiator manufactured by San-Apro include CPI-100P, CPI-200K, CPI-210S, CPI-410B, CPI-410S, etc.

[0032] Examples of the above-mentioned thermal cationic polymerization initiator include sulfonium salts, phosphonium salts, ammonium salts, etc., in which the anionic part is BF4 - , PF6 - , SbF6 - , or (BX4) - (wherein X represents a phenyl group substituted with at least two or more fluorine or trifluoromethyl groups). Among them, sulfonium salts and ammonium salts are preferred.

[0033] Examples of the above-mentioned sulfonium salts include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, etc.

[0034] Examples of the above-mentioned phosphonium salts include ethyltriphenylphosphonium hexafluoroantimonate, tetrabutylphosphonium hexafluoroantimonate, etc.

[0035] Examples of the ammonium salts include dimethylphenyl(4-methoxybenzyl)ammonium hexafluorophosphate, dimethylphenyl(4-methoxybenzyl)ammonium hexafluoroantimonate, dimethylphenyl(4-methoxybenzyl)ammonium tetrakis(pentafluorophenyl)borate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorophosphate, dimethylphenyl(4-methylbenzyl)ammonium hexafluoroantimonate, dimethylphenyl(4-methylbenzyl)ammonium hexafluorotetrakis(pentafluorophenyl)borate, and methylphenyldibenzylammonium hexafluorophosphate. , 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, N,N-diethyl-N-benzylpyridinium trifluoromethanesulfonate, and the like.

[0036] Among the above-mentioned thermal cationic polymerization initiators, commercially available ones include, for example, 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.

[0037] The preferable lower limit of the content of the cationic polymerization initiator with respect to 100 parts by mass of the cationic polymerizable compound is 0.01 part by mass, and the preferable upper limit is 10 parts by mass. When the content of the cationic polymerization initiator is 0.01 part by mass or more, the obtained encapsulant for display elements becomes excellent in curability. When the content of the cationic polymerization initiator is 10 parts by mass or less, the curing reaction of the obtained encapsulant for display elements does not become too fast, the workability becomes excellent, and the cured product can be made more uniform. The more preferable lower limit of the content of the cationic polymerization initiator is 0.05 part by mass, and the more preferable upper limit is 5 parts by mass.

[0038] The encapsulant for display elements of the present invention contains a polyolefin. By containing the polyolefin, the cured product of the encapsulant for display elements of the present invention has a low dielectric constant and is excellent in flexibility.

[0039] From the viewpoint of making the obtained encapsulant for display elements excellent in low dielectric characteristics after curing, the polyolefin preferably does not have a cationic polymerizable group. Specifically, the cationic polymerizable group means an epoxy group, an oxetanyl group, a vinyl ether group, etc.

[0040] Specific examples of the polyolefin include polyethylene, polypropylene, polybutene, polyisobutylene, polybutadiene, and copolymers of olefin monomers derived therefrom. Among them, the polyolefin preferably has a repeating structure derived from a linear or branched olefin monomer having 4 or more carbon atoms, more preferably polybutene or polyisobutylene, and even more preferably polybutene.

[0041] The preferable lower limit of the weight average molecular weight of the polyolefin is 300, and the preferable upper limit is 980. When the weight average molecular weight of the polyolefin is within this range, the obtained encapsulant for display elements becomes excellent in coatability and flexibility after curing. The more preferable upper limit of the weight average molecular weight of the polyolefin is 430. In the present specification, the above-mentioned "weight average molecular weight" is a value obtained by measurement using tetrahydrofuran as a solvent in gel permeation chromatography (GPC) and converted to polystyrene equivalent. Examples of the column used for measuring the weight average molecular weight in terms of polystyrene by GPC include Shodex LF-804 (manufactured by Showa Denko K.K.).

[0042] The lower limit of the content of the above-mentioned polyolefin with respect to 100 parts by mass of the above-mentioned cationically polymerizable compound is 10 parts by mass, and the upper limit is 200 parts by mass. When the content of the above-mentioned polyolefin is 10 parts by mass or more, the obtained sealing agent for display elements becomes excellent in low dielectric constant characteristics after curing. When the content of the above-mentioned polyolefin is 200 parts by mass or less, the obtained sealing agent for display elements becomes excellent in coatability, and low dielectric constant characteristics and flexibility after curing. The preferable lower limit of the content of the above-mentioned polyolefin is 30 parts by mass, the preferable upper limit is 150 parts by mass, and the more preferable upper limit is 130 parts by mass.

[0043] The sealing agent for display elements of the present invention may contain a sensitizer. The above-mentioned sensitizer has a role of further improving the polymerization initiation efficiency of the above-mentioned cationic polymerization initiator and further promoting the curing reaction of the sealing agent for display elements of the present invention.

[0044] Examples of the above-mentioned sensitizer include thioxanthone-based compounds, 2,2-dimethoxy-1,2-diphenylethane-1-one, benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and the like. Examples of the above-mentioned thioxanthone-based compounds include 2,4-diethylthioxanthone.

[0045] The content of the above sensitizer preferably has a lower limit of 0.01 parts by mass and an upper limit of 3 parts by mass with respect to 100 parts by mass of the above cationic polymerizable compound. When the content of the sensitizer is 0.01 parts by mass or more, the sensitizing effect is more exerted. When the content of the sensitizer is 3 parts by mass or less, light can be transmitted to a deep part without excessive absorption. A more preferable lower limit of the content of the sensitizer is 0.1 parts by mass, and a more preferable upper limit is 1 part by mass.

[0046] The encapsulant for a display element of the present invention may contain a thermosetting agent as long as it does not inhibit the object of the present invention. Examples of the above thermosetting agent include hydrazide compounds, imidazole derivatives, acid anhydrides, dicyandiamide, guanidine derivatives, modified aliphatic polyamines, addition products of various amines and epoxy resins, and the like. Examples of the above hydrazide compounds include 1,3-bis(hydrazinocarbonoethyl)-5-isopropylhydantoin, sebacic acid dihydrazide, isophthalic acid dihydrazide, adipic acid dihydrazide, malonic acid dihydrazide, and the like. Examples of the above 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, 2-phenyl-4,5-dihydroxymethylimidazole, and the like. Examples of the above acid anhydrides include tetrahydrophthalic anhydride, ethylene glycol bis(anhydrotrimellitate), and the like. These thermosetting agents may be used alone or in combination of two or more.

[0047] Examples of commercially available products among the above thermosetting agents include thermosetting agents manufactured by Otsuka Chemical Co., Ltd., thermosetting agents manufactured by Ajinomoto Fine-Techno Co., Inc., and the like. Examples of the thermosetting agent manufactured by the above-mentioned Otsuka Chemical Co., Ltd. include SDH, ADH, etc. Examples of the thermosetting agent manufactured by the above-mentioned Ajinomoto Fine-Techno Co., Inc. include Amicure VDH, Amicure VDH-J, Amicure UDH, etc.

[0048] The content of the above thermosetting agent preferably has a lower limit of 0.5 parts by mass and an upper limit of 30 parts by mass with respect to 100 parts by mass of the above cationic polymerizable compound. When the content of the above thermosetting agent is within this range, the obtained encapsulant for display elements will have excellent thermosetting properties while maintaining excellent storage stability. A more preferable lower limit of the content of the above thermosetting agent is 1 part by mass, and a more preferable upper limit is 15 parts by mass.

[0049] The encapsulant for display elements of the present invention may further contain a silane coupling agent. The above silane coupling agent has the role of improving the adhesiveness between the encapsulant for display elements of the present invention and a substrate or the like.

[0050] Examples of the above silane coupling agent include 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, etc. These silane compounds may be used alone or in combination of two or more.

[0051] The content of the above silane coupling agent preferably has a lower limit of 0.1 part by mass and an upper limit of 10 parts by mass with respect to 100 parts by mass of the above cationic polymerizable compound. When the content of the above silane coupling agent is within this range, while suppressing bleed-out due to excess silane coupling agent, the adhesiveness of the obtained encapsulant for display elements will be excellent due to the improved effect. A more preferable lower limit of the content of the above silane coupling agent is 0.5 part by mass, and a more preferable upper limit is 5 parts by mass.

[0052] The encapsulant for display elements of the present invention may contain a curing retardant. By containing the above-mentioned curing retardant, the pot life of the obtained encapsulant for display elements can be extended.

[0053] Examples of the above-mentioned curing retardant include polyether compounds and the like. Examples of the above-mentioned polyether compound include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, crown ether compounds and the like. Among them, crown ether compounds are preferred.

[0054] The content of the above-mentioned curing retardant preferably has a lower limit of 0.05 parts by mass and an upper limit of 5.0 parts by mass with respect to 100 parts by mass of the cationic polymerizable compound. When the content of the above-mentioned curing retardant is within this range, the generation of outgas when curing the obtained encapsulant for display elements can be suppressed, and the delay effect can be more exerted. A more preferable lower limit of the content of the above-mentioned curing retardant is 0.1 parts by mass, and a more preferable upper limit is 3.0 parts by mass.

[0055] The encapsulant for display elements of the present invention may further contain a surface modifier within a range that does not inhibit the object of the present invention. By containing the above-mentioned surface modifier, the flatness of the coating film of the encapsulant for display elements of the present invention can be improved. Examples of the above-mentioned surface modifier include surfactants and leveling agents.

[0056] Examples of the above-mentioned surface modifier include silicone-based, acrylic-based, fluorine-based and the like. Examples of commercially available products among the above-mentioned surface modifiers include surface modifiers manufactured by BYK-Chemie Japan Co., Ltd., surface modifiers manufactured by AGC Seimi Chemical Co., Ltd., and the like. Examples of the surface modifier manufactured by BYK-Chemie Japan Co., Ltd. include BYK-340, BYK-345 and the like. Examples of the surface modifier manufactured by AGC Seimi Chemical Co., Ltd. include Surfron S-611 and the like.

[0057] The encapsulant for a display element of the present invention may contain a compound or an ion exchange resin that reacts with an acid generated in the encapsulant, as long as the object of the present invention is not inhibited.

[0058] Examples of the compound that reacts with the acid generated in the above composition include substances that neutralize the acid, such as carbonates or bicarbonates of alkali metals or alkaline earth metals. Specifically, for example, calcium carbonate, calcium bicarbonate, sodium carbonate, sodium bicarbonate, etc. are used.

[0059] As the above ion exchange resin, any of cation exchange type, anion exchange type, and amphoteric ion exchange type can be used, but cation exchange type or amphoteric ion exchange type that can adsorb chloride ions is particularly preferred.

[0060] In addition, the encapsulant for a display element of the present invention may contain various known additives such as a reinforcing agent, a softening agent, a plasticizer, a viscosity modifier, an ultraviolet absorber, an antioxidant, etc., if necessary.

[0061] As a method for producing the encapsulant for a display element of the present invention, for example, a method of mixing a cationically polymerizable compound, a cationic polymerization initiator, a polyolefin, and additives such as a silane coupling agent added as necessary using a mixer such as a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, a three-roll mill, etc. can be mentioned.

[0062] The encapsulant for a display element of the present invention can be suitably used for coating by an inkjet method. The above inkjet method may be a non-heated inkjet method or a heated inkjet method. In this specification, the above "non-heated inkjet method" is a method of inkjet coating at a coating head temperature of less than 28°C, and the above "heated inkjet method" is a method of inkjet coating at a coating head temperature of 28°C or more.

[0063] In the above-described thermal inkjet method, an inkjet coating head equipped with a heating mechanism is used. Since the inkjet coating head is equipped with a heating mechanism, the viscosity and surface tension can be reduced when discharging the sealing agent for display elements.

[0064] Examples of the inkjet coating head equipped with the above heating mechanism include the KM1024 series manufactured by Konica Minolta and the SG1024 series manufactured by Fujifilm Dimatix.

[0065] When the sealing agent for display elements of the present invention is used for coating by the above thermal inkjet method, the heating temperature of the coating head is preferably in the range of 28°C or higher and 80°C or lower. When the heating temperature of the coating head is within this range, the viscosity increase of the sealing agent for display elements over time is further suppressed, and the discharge stability is further improved.

[0066] The sealing agent for display elements of the present invention preferably has an upper limit of viscosity at 25°C of 30 mPa·s. When the viscosity at 25°C is 30 mPa·s or less, the obtained sealing agent for display elements is excellent in coatability (especially inkjet coatability). A more preferable upper limit of the viscosity at 25°C of the sealing agent for display elements of the present invention is 25 mPa·s. Also, from the viewpoint of shape retention after coating, etc., the preferable lower limit of the viscosity at 25°C of the sealing agent for display elements of the present invention is 8 mPa·s, and a more preferable lower limit is 10 mPa·s. In this specification, the above "viscosity" means a value measured using an E-type viscometer under the condition of 100 rpm. Examples of the above E-type viscometer include VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.), and a CP1 type cone plate can be used.

[0067] The encapsulant for a display element of the present invention preferably has a surface tension at 25°C with a lower limit of 15 mN / m and an upper limit of 35 mN / m. When the surface tension at 25°C is within this range, it can be more suitably applied by the inkjet method. A more preferable lower limit of the surface tension at 25°C is 20 mN / m, and an even more preferable lower limit is 22 mN / m. Also, a more preferable upper limit of the surface tension at 25°C is 30 mN / m, and an even more preferable upper limit is 28 mN / m. Note that the above surface tension means a value measured by the Wilhelmy method using a dynamic wettability tester. Examples of the dynamic wettability tester include the WET-6100 type (manufactured by Resca).

[0068] When containing the above photo cationic polymerization initiator, the encapsulant for a display element of the present invention can be suitably cured by irradiating light with a wavelength of 300 nm or more and 400 nm or less and an integrated light quantity of 300 mJ / cm 2 or more and 3000 mJ / cm 2 or less.

[0069] Examples of the light source used for the above 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 according to the absorption wavelength of the above photo cationic polymerization initiator.

[0070] Examples of the means for irradiating light onto the encapsulant for a display element of the present invention include simultaneous irradiation of various light sources, sequential irradiation with a time difference, combined irradiation of simultaneous irradiation and sequential irradiation, etc., and any irradiation means may be used.

[0071] The display element sealant of the present invention has a dielectric constant of a cured product measured at 25°C and 100 kHz of preferably 3.0. Since the dielectric constant of the cured product is 3.0 or less, the display element sealant of the present invention can be suitably used in organic EL display devices equipped with a touch panel. The upper limit of the dielectric constant of the cured product is more preferably 2.8, and even more preferably 2.7. There is no particular preferred lower limit for the dielectric constant of the cured product, but the substantial lower limit is 2.2. The "dielectric constant" can be measured using a dielectric constant measuring device. The cured product for measuring the dielectric constant is prepared by applying a sealant for display elements to a glass substrate to a thickness of 8 μm, and in the case of a photocurable sealant, applying a 395 nm wavelength LED UV lamp at an illuminance of 1000 mW / cm. 2 In the case of a thermosetting sealant, it can be obtained by heating at 100°C for 60 minutes. [Effects of the Invention]

[0072] According to the present invention, it is possible to provide a sealant for display elements which has a low dielectric constant when cured and is excellent in flexibility. DETAILED DESCRIPTION OF THE INVENTION

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0074] (Examples 1 to 12, Comparative Examples 1 to 6) Each of the curable resin compositions of Examples 1 to 12 and Comparative Examples 1 to 6 was prepared by stirring and mixing the materials using a stirring mixer according to the compounding ratios shown in Tables 1 and 2. The stirring mixer used was a THINKY MIXER ARE-310.

[0075] <Evaluation> The sealants for display elements obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Tables 1 and 2.

[0076] (viscosity) For each of the obtained encapsulants for display elements, using an E-type viscometer and a CP1-type cone plate, the viscosity at 25 °C and 100 rpm was measured. As the E-type viscometer, VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) was used.

[0077] (Low dielectric constant of cured product) On a glass substrate with an aluminum electrode vapor-deposited thereon, the obtained encapsulant for display elements was applied using a spin coater under the conditions of 900 rpm and 20 seconds to obtain a coating film with a thickness of 8 μm. Next, the obtained coating film was irradiated with ultraviolet light having a wavelength of 395 nm and an illuminance of 1000 mW / cm 2 for 1 second under dry air using an LED UV lamp to obtain a laminate having a cured film of the encapsulant for display elements. As the LED UV lamp, the SQ series (manufactured by Quark Technology Co., Ltd.) was used. Thereafter, an aluminum electrode was formed on the surface of the cured film using a vacuum deposition apparatus (manufactured by ULVAC, "VPC-410") to fabricate a test piece for dielectric constant measurement. For the obtained test piece, the dielectric constant was measured at 25 °C and 100 kHz using a dielectric constant measurement apparatus. As the dielectric constant measurement apparatus, a 1260-type impedance analyzer (manufactured by Solartron) and a 1296-type dielectric constant measurement interface (manufactured by Solartron) were used. Regarding the encapsulants for display elements obtained in Examples 1 to 9 and Comparative Examples 3 to 5, taking the dielectric constant of the test piece obtained using the encapsulant for display elements obtained in Examples 1 to 9 and Comparative Examples 3 to 5 as A1, and the dielectric constant of the test piece obtained using the encapsulant for display elements obtained in Comparative Example 1 as B1, the dielectric constant reduction rate was calculated by the following formula. Dielectric constant reduction rate (%) = ((B1 - A1) ÷ B1) × 100 Also, regarding the encapsulants for display elements obtained in Examples 10 to 12 and Comparative Example 6, taking the dielectric constant of the test piece obtained using the encapsulant for display elements obtained in Examples 10 to 12 and Comparative Example 6 as A2, and the dielectric constant of the test piece obtained using the encapsulant for display elements obtained in Comparative Example 2 as B2, the dielectric constant reduction rate was calculated by the following formula. Dielectric constant reduction rate (%) = ((B2 - A2) ÷ B2) × 100 The low dielectric properties of the cured product were evaluated from the obtained rate of decrease in dielectric constant according to the following criteria. A: When the dielectric constant decrease rate is 3% or more B: When the dielectric constant decrease rate is less than 3%

[0078] (Flexibility of the cured product) The sealant for display elements thus obtained was applied to a 100 μm-thick PET film using a spin coater at 900 rpm for 20 seconds to obtain a coating film having a thickness of 8 μm. The coating film was then irradiated with an LED UV lamp at a wavelength of 395 nm and an illuminance of 1000 mW / cm. 2 A laminate having a cured film of the sealant for display devices was obtained by irradiating the laminate with ultraviolet light for 1 second. The resulting laminate was subjected to a bending test 10,000 times using a tabletop durability tester (YUASA SYSTEM, "DLDM111LHA"), in which the laminate was bent 10,000 times with the cured film facing outward so that the bending radius was 1.0 mm. In addition, a similarly obtained laminate was subjected to a bending test 10,000 times with the bending radius changed to 0.5 mm. The laminate after the bending test was checked, and the flexibility of the cured product was evaluated according to the following criteria. AA: When no cracks or wrinkles occur in the cured film in bending tests with bending radii of 1.0 mm and 0.5 mm A: In a bending test with a bending radius of 1.0 mm, no cracks or wrinkles occurred in the cured film, but in a bending test with a bending radius of 0.5 mm, cracks or wrinkles occurred in the cured film. B: When wrinkles appear on the cured film during a bending test with a bending radius of 1.0 mm C: When cracks occur in the cured film during a bending test with a bending radius of 1.0 mm

[0079] [Table 1]

[0080] [Table 2] [Industrial Applicability]

[0081] According to the present invention, it is possible to provide a sealing agent for a display element in which the cured product has a low dielectric constant and excellent flexibility.

Claims

1. A sealing agent for a display element, comprising a cationically polymerizable compound, a cationic polymerization initiator, and a polyolefin, wherein the content of the polyolefin is 10 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the cationically polymerizable compound.

2. The sealing agent for a display element according to claim 1, wherein the polyolefin has a repeating structure derived from a linear or branched olefin monomer having 4 or more carbon atoms.

3. The sealing agent for a display element according to claim 1 or 2, wherein the polyolefin does not have a cationically polymerizable group.

4. The cationically polymerizable compound includes a polyfunctional cationically polymerizable compound having two or more cationically polymerizable groups in one molecule, and the content of the polyfunctional cationically polymerizable compound is 10 parts by mass or more in 100 parts by mass of the cationically polymerizable compound. The sealing agent for a display element according to claim 1 or 2.

5. The sealing agent for a display element according to claim 1 or 2, having a viscosity at 25°C of 30 mPa·s or less.

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