Curable composition, sealing agent, frame sealing agent, display panel and method for manufacturing same

Abstract

This curable composition contains a curable compound, a cationic photopolymerization initiator, a tertiary amine, and an inorganic filler. The content of the tertiary amine is 20 parts by mass or more with respect to 100 parts by mass of the photo-cationic polymerization initiator.

Description

TECHNICAL FIELD

[0001] The present application relates to a curable composition, a sealant, a frame sealant, a display panel, and a manufacturing method thereof. BACKGROUND

[0002] In recent years, display devices using display elements such as organic electroluminescence elements (hereinafter, referred to as organic EL elements) have been developed, but display elements are generally likely to be deteriorated by moisture and oxygen in the atmosphere. Therefore, in various display devices, the display element is generally sealed by a sealing layer.

[0003] For example, an organic EL display panel has an element substrate having an organic EL element, a counter substrate, and a sealing layer disposed between them and sealing the organic EL element. Such an organic EL display panel is manufactured by various methods. As one of such manufacturing methods, a dam & fill method is known.

[0004] In the dam & fill method, the organic EL display panel is manufactured, for example, by the following steps: 1) a step of applying a first sealant in a frame shape on the counter substrate; 2) a step of filling a second sealant in a region surrounded by the first sealant to form a sealant layer; 3) a step of irradiating light to the sealant layer; 4) a step of attaching a substrate on which the organic EL element is disposed to the counter substrate having the sealant layer after the light irradiation; and 5) a step of curing the sealant layer by heating (for example, refer to Patent Literature 1).

[0005] In addition, as a frame sealant used in the above method, a sealant containing a polyolefin, an epoxy compound (curable resin A), a thermal curing agent, and a water-absorbing filler is known (for example, refer to Patent Literature 2). In this document, as a thermal curing agent, a thermal cationic initiator is used.

[0006] In addition, as a sealant for an organic EL element, a sealant containing a (meth)acrylic acid-modified epoxy resin-containing photocurable compound and a photocationic polymerization initiator is also known (for example, refer to Patent Literature 3).

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: International Publication No. 2013 / 157059

[0010] Patent Literature 2: International Publication No. 2020 / 149359

[0011] Patent Literature 3: Japanese Patent Application Publication No. 2012-151109 SUMMARY

[0012] Technical problem to be solved by the invention

[0013] However, the sealing agent shown in Patent Literature 2 is cured by heating at 100°C, and thus there is a problem that the element is easily damaged by heating. In order to suppress such damage, low-temperature curability is required for the sealing agent.

[0014] In addition, the sealing agent as described above is also required to have a useable time after light irradiation of a prescribed level or more, that is, to moderately maintain the viscosity low after light irradiation. For example, as described above, after the sealing agent applied to one of the substrates is temporarily cured by irradiation of light, the other substrate is attached, and then the sealing agent is cured by heating. However, the sealing agents shown in Patent Literature 2 and Patent Literature 3 excessively proceed with the curing reaction after the light irradiation and before the attachment of the other substrate, and thus the viscosity easily excessively increases. Therefore, there is a problem that the flowability and tackiness of the sealing agent at the time of attachment are easily impaired, and it is difficult to obtain sufficient adhesive strength. In general, the higher the low-temperature curability, the more the viscosity after light irradiation easily increases, and thus it is desirable to balance these properties.

[0015] Furthermore, from the viewpoint of reducing the moisture permeability of the cured product or improving the shape retention, the frame sealing agent that seals the outer periphery of the element contains a filler. With respect to such a sealing agent, the viscosity after light irradiation increases more, and the flowability and tackiness of the sealing agent at the time of attachment are more easily impaired. Therefore, it is further required to maintain the viscosity low after light irradiation.

[0016] The present invention has been achieved in view of the above circumstances, and provides a curable composition, a sealing agent, a frame sealing agent, a display panel, and a manufacturing method thereof, which can balance low-temperature curability and viscosity stability after light irradiation and impart a cured product having low moisture permeability and high adhesive strength.

[0017] Means for solving the problem

[0018] [1] A curable composition comprising: a curable compound, a photocationic polymerization initiator, a tertiary amine, and an inorganic filler, the content of the tertiary amine being 20 parts by mass or more with respect to 100 parts by mass of the photocationic polymerization initiator.

[0019] [2] The curable composition according to [1], the content of the tertiary amine being 0.5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the curable compound.

[0020] [3] The curable composition according to [1] or [2], the content of the inorganic filler being 20 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the curable compound.

[0021] [4] The curable composition according to any one of [1] to [3], wherein the curable compound comprises an aromatic epoxy compound.

[0022] [5] The curable composition according to any one of [1] to [4], wherein the tertiary amine is a difunctional tertiary amine.

[0023] [6] The curable composition according to any one of [1] to [5], wherein the tertiary amine has an N-O bond.

[0024] [7] The curable composition according to any one of [1] to [6], wherein the tertiary amine has a hindered structure.

[0025] [8] The curable composition according to any one of [1] to [7], wherein, after irradiation of light having a wavelength of 365 nm at an ultraviolet (UV) irradiance of 100 mW / cm 2 for 3000 mJ / cm 2 , the viscosity at 25°C after 60 seconds is 1.0 x 10 4 Pa-s or less.

[0026] [9] A sealant comprising the curable composition according to any one of [1] to [8].

[0027]

[10] A frame sealant comprising the curable composition according to any one of [1] to [8].

[0028]

[11] A display panel having: an element substrate on which an element is disposed; an opposing substrate disposed so as to face the element substrate with the element interposed therebetween; and a sealing portion disposed between the element substrate and the opposing substrate for sealing the element, the sealing portion comprising a cured product of the sealant according to [9].

[0029]

[12] A method for manufacturing a display panel, comprising: a step of applying a first sealant in a frame shape along the outer periphery of a display region on the face of either one of an element substrate and an opposing substrate; a step of forming a sealant layer by filling a second sealant in a region surrounded by the first sealant; a step of irradiating light to the sealant layer; a step of adhering one of the substrates to the other via the sealant layer irradiated with light; and a step of curing the sealant layer by heating, at least one of the first sealant and the second sealant being the sealant according to [9].

[0030]

[13] The method for manufacturing a display panel according to

[12] , wherein the first sealant is the sealant according to [9].

[0031] Effects of the Invention

[0032] The present application has been achieved in view of the above-described circumstances, and provides a curable composition, a sealant, a frame sealant, a display panel, and a method for manufacturing the display panel, which can balance low-temperature curability and viscosity stability after light irradiation, and impart a cured product having low moisture permeability and high adhesive strength. DETAILED DESCRIPTION

[0033] As described above, a curable composition having low-temperature curability has a tendency that the viscosity easily increases after light irradiation, and cannot maintain a low viscosity.

[0034] On the contrary, the curable composition of the present application contains a curable compound, a photocationic polymerization initiator, a tertiary amine, and an inorganic filler. Also, in the curable composition of the present application, the content of the tertiary amine is set to be equal to or more than a prescribed amount with respect to the photocationic polymerization initiator. Thus, even if the inorganic filler is contained, low-temperature curability and viscosity stability after light irradiation can be well balanced. The mechanism is not clear, but is presumed as follows.

[0035] With the above-described curable composition, first, when light is irradiated, an acid is generated from the photocationic polymerization initiator. The acid is captured by the tertiary amine in a sufficient amount. Therefore, at the point of time when light is irradiated, the curable compound hardly undergoes curing, and the viscosity of the curable composition after light irradiation is maintained low.

[0036] Thereafter, when the curable composition is heated at a low temperature, the acid captured by the tertiary amine is released, and the curable compound is cured. Therefore, the curable composition is excellent in low-temperature curability.

[0037] Thus, in a case where the curable composition is used for sealing of an optical element in a display panel provided with the optical element, for example, the optical element can be sealed with low moisture permeability and high adhesive strength while suppressing damage of the optical element caused by heat. Hereinafter, the curable composition of one embodiment of the present application will be described specifically.

[0038] 1. Curable composition

[0039] The curable composition of the present embodiment contains a curable compound, a photocationic polymerization initiator, a tertiary amine, and an inorganic filler.

[0040] 1-1. Curable compound

[0041] The curable compound contains a curable compound which is polymerized and cured by an active species generated from the photocationic polymerization initiator. As such a curable compound, an epoxy compound and an oxetane compound can be exemplified, but from the viewpoint of improving heat curability, it is preferable to contain an epoxy compound. The curable compound can contain only one kind of epoxy compound, or can contain two or more kinds.

[0042] In the present specification, an epoxy compound refers to a compound having one or more epoxy groups in a molecule. The number of epoxy groups contained in one molecule of an epoxy compound can be one or more. From the viewpoint of improving the curability, it is preferable that the number of epoxy groups contained in one molecule of an epoxy compound be two or more.

[0043] Examples of the epoxy compound include well-known epoxy compounds such as aromatic epoxy compounds, aliphatic epoxy compounds, and alicyclic epoxy compounds. Among them, from the viewpoint of further reducing the moisture permeability of the cured product, at least one of the epoxy compounds is preferably an aromatic epoxy compound.

[0044] Examples of the aromatic epoxy compound include glycidyl ethers of alcohols (including polyols) containing aromatic rings. Specifically, they include:

[0045] bisphenol type glycidyl ether compounds obtained by the reaction of bisphenols typified by bisphenol A, bisphenol S, bisphenol F, bisphenol AD, and the like, and epichlorohydrin, using diols modified from these aromatic diols with ethylene glycol, propylene glycol, alkanediols, and the like;

[0046] triphenol type glycidyl ether compounds obtained by the reaction of triphenol compounds (e.g., 1,1,1-tris(hydroxyphenyl)methane, 1-[a-methyl-a-(4-hydroxyphenyl)ethyl]-3-[a,a-bis(4-hydroxyphenyl)ethyl]benzene (or 4-[4-[1,1-bis(4-hydroxyphenyl)ethyl]-a,a-dimethylbenzyl]phenol)] and epichlorohydrin;

[0047] novolak type glycidyl ether compounds obtained by the reaction of novolak resins derived from phenol or cresol and formaldehyde, polyphenols typified by polyalkenyl phenol or a copolymer thereof, and the like, and epichlorohydrin;

[0048] glycidyl ether compounds of xylylenephenol resins, and the like.

[0049] Among them, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, and other bisphenol type epoxy compounds, cresol novolak type epoxy compounds, phenol novolak type epoxy compounds, triphenol methane type epoxy compounds, triphenol ethane type epoxy compounds, triphenol type epoxy compounds, dicyclopentadiene type epoxy compounds, diphenyl ether type epoxy compounds, and biphenyl type epoxy compounds are preferable.

[0050] The epoxy compound can be liquid or solid. From the viewpoint of improving the coatability of the curable composition, an epoxy compound that is liquid is preferred. In addition, from the viewpoint of further reducing the moisture permeability of the cured product, an epoxy compound that is solid is preferred. The softening point of the epoxy compound that is solid is preferably 40°C or higher and 150°C or lower. The softening point can be measured by the ball method prescribed in Japanese Industrial Standards (JIS) K7234.

[0051] The weight average molecular weight of the epoxy compound is preferably 200 or higher and 10,000 or lower, and more preferably 300 or higher and 5,000 or lower. The weight average molecular weight of the epoxy compound is measured by gel permeation chromatography (GPC) and converted to polystyrene.

[0052] As described above, the curable compound can include only one kind of epoxy compound, or two or more kinds. For example, from the viewpoint of more highly balancing the viscosity stability and the permeability of the cured product, a liquid epoxy compound and a solid epoxy compound can be combined. In addition, from the viewpoint of easily balancing the viscosity stability and the permeability of the cured product, a difunctional aromatic epoxy compound and a trifunctional or higher aromatic epoxy compound can be combined.

[0053] For example, in the case of combining a difunctional aromatic epoxy compound and a trifunctional or higher aromatic epoxy compound, the trifunctional or higher aromatic epoxy compound can be, for example, 10% by mass or higher, and preferably 30% by mass or higher and 70% by mass or lower, relative to the total amount of the epoxy compound. If the content of the trifunctional or higher aromatic epoxy compound is 10% by mass or higher, the moisture permeability of the cured product can be further improved. On the other hand, the viscosity of the curable composition after light irradiation tends to increase, but since the acid generated by the photocationic polymerization initiator is trapped by the tertiary amine, excessive increase in the viscosity can be suppressed.

[0054] In addition, the curable compound can include both an epoxy compound and an oxetane compound.

[0055] The content of the epoxy compound relative to the curable compound is preferably 30% by mass or higher, and more preferably 50% by mass or higher, and can be 100% by mass. If the amount of the epoxy compound is 30% by mass or higher, the curability by heating can be further improved.

[0056] The total amount of the curable compound with respect to the curable composition is preferably 20% by mass or more and 90% by mass or less, and more preferably 30% by mass or more and 70% by mass or less. If the amount of the curable compound is 20% by mass or more, the curability is more easily obtained, and the adhesive strength of the cured product is easily further improved. On the other hand, if the amount of the curable compound is 90% by mass or less, the amount of, for example, the inorganic filler relatively increases, and the shape retention of the obtained sealant is easily further improved.

[0057] 1-2. Photocationic polymerization initiator

[0058] The photocationic polymerization initiator is, for example, a photoacid generator that generates an acid by light irradiation.

[0059] The absorption wavelength of the photocationic polymerization initiator is not particularly limited, and, for example, light having an absorption wavelength of 360 nm or more is preferable, and light having an absorption wavelength of 360 nm or more and 430 nm or less is more preferable. If the absorption wavelength of the photocationic polymerization initiator is within the above range, the influence on the optical element is, for example, reduced.

[0060] The photocationic polymerization initiator is not particularly limited, and a publicly known photocationic polymerization initiator can be used.

[0061] Examples of the photocationic polymerization initiator include aromatic sulfonium salts, aromatic selenonium salts, aromatic diazonium salts, aromatic ammonium salts, and the like, in which the anion moiety is BF4 - , (Rf) n PF 6-n - (Rf is an organic group, and n is an integer of 1 to 5), PF6 - , SbF6 - , or BX4 - (X is a phenyl group substituted with at least two or more fluorine groups or trifluoromethyl groups).

[0062] 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, and the like.

[0063] Examples of 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, and bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate.

[0064] Examples of the aromatic diazonium salt include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, and phenyldiazonium tetrakis(pentafluorophenyl)borate.

[0065] Examples of the aromatic ammonium salt include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, and the like.

[0066] Examples of commercially available photocationic polymerization initiators include Irgacure 250, Irgacure 270, and Irgacure 290 (manufactured by BASF), CPI-100P, CPI-101A, CPI-200K, CPI-210S, CPI-310B, and CPI-400PG (manufactured by San-Apro), and SP-150, SP-170, SP-171, SP-056, SP-066, SP-130, SP-140, SP-601, SP-606, and SP-701 (manufactured by ADEKA). Among them, sulfonium salts such as Irgacure 270, Irgacure 290, CPI-100P, CPI-101A, CPI-200K, CPI-210S, CPI-310B, CPI-400PG, SP-150, SP-170, SP-171, SP-056, SP-066, SP-601, SP-606, and SP-701 are preferred.

[0067] The photocationic polymerization initiator may be used alone or in combination of two or more.

[0068] The content of the photocationic polymerization initiator is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, and even more preferably 0.8 to 8 parts by mass, relative to 100 parts by mass of the curable compound. If the content of the photocationic polymerization initiator is 0.1 parts by mass or more, more acid is generated by light irradiation, making it easier to produce a curing reaction during curing by heating. If the content of the photocationic polymerization initiator is 20 parts by mass or less, bleeding can be further reduced, thereby further reducing contamination of optical components, etc.

[0069] 1-3. Tertiary amine

[0070] The tertiary amine traps the acid generated by the photocationic polymerization initiator by light irradiation. Thus, the curing reaction of the curable compound at the time of light irradiation is less likely to occur, and the viscosity of the curable composition after light irradiation can be inhibited from excessively rising.

[0071] As the tertiary amine, there are monofunctional tertiary amines having one amino group in the molecule, difunctional tertiary amines having two amino groups, and trifunctional or higher tertiary amines having three or more amino groups. Of these, from the viewpoint of further improving the acid trapping efficiency, difunctional tertiary amines and trifunctional or higher tertiary amines are preferred, and from the viewpoint of more easily maintaining the compatibility with the epoxy compound, difunctional tertiary amines are more preferred.

[0072] From the viewpoint of more easily releasing the trapped acid at the time of heating and further improving the low-temperature curability, the tertiary amine preferably has an N-O bond. That is, difunctional tertiary amines having an N-O bond are preferred.

[0073] In addition, from the viewpoint of more easily releasing the trapped acid at the time of heating and further improving the low-temperature curability, the tertiary amine preferably has a hindered structure. As the hindered structure, for example, a structure having steric hindrance such as 2,2,6,6-tetramethylpiperidine can be exemplified.

[0074] Therefore, the tertiary amine is preferably a difunctional tertiary amine having an N-O bond, more preferably a difunctional tertiary amine having an N-O bond and a hindered structure, and further preferably a tertiary amine having an N-O bond and two 2,2,6,6-tetramethylpiperidine structures in the molecule.

[0075] As such a tertiary amine, compounds represented by formula (1) or (2) can be exemplified.

[0076] [Chemical Formula 1]

[0077] ... (1)

[0078] In formula (1), R 3 represents an alkyl group having a carbon number of 1 to 20. As the straight-chain or branched-chain alkyl group having a carbon number of 1 to 20, for example, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and eicosyl can be exemplified. The two R 3 may be the same as or different from each other.

[0079] [Chemical Formula 2]

[0080] ... (2)

[0081] In formula (2), R 4represents a linear or branched alkyl group having 1 to 20 carbons. As the linear or branched alkyl group having 4 to 20 carbons, for example, there can be mentioned butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and icosyl. Two R 4 may be the same as each other or different from each other.

[0082] R 5 represents an alkylene group having 1 to 8 carbons. As the alkylene group having 1 to 8 carbons, for example, there can be mentioned methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, and octylene.

[0083] Examples of the compound represented by formula (1) include a compound represented by formula (1-1); examples of the compound represented by formula (2) include a compound represented by formula (2-1).

[0084] [Chemical 3]

[0085] (1-1)

[0086] (2-1)

[0087] As the commercially available product of the tertiary amine, for example, there can be mentioned Adekastab LA-81 (manufactured by ADEKA Corporation) and Tinuvin 123 (manufactured by BASF Japan Ltd.).

[0088] The tertiary amine can include only one kind or two or more kinds.

[0089] From the viewpoint of the capturing property of the acid generated from the photocationic polymerization initiator, the content of the tertiary amine is preferably 20 parts by mass or more relative to 100 parts by mass of the photocationic polymerization initiator. If the above content of the tertiary amine is 20 parts by mass or more, the acid can be captured in a large amount, and thus the viscosity increase after light irradiation can be more easily suppressed, and the tackiness can be further improved. From the same viewpoint, the content of the tertiary amine is preferably 60 parts by mass or more, and more preferably 65 parts by mass or more, relative to 100 parts by mass of the photocationic polymerization initiator. The upper limit of the above content of the tertiary amine is not particularly limited, but from the viewpoint of further reducing the tertiary amine remaining as an unreacted component after curing, further reducing the adhesion of the cured product, reducing the moisture permeability of the cured product, and making the physical properties of the cured product more excellent, for example, it can be set to 100 parts by mass or less.

[0090] Further, the content of the tertiary amine is preferably 0.5 parts by mass or more and 20 parts by mass or less, more preferably 1 part by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the curable compound. If the content of the tertiary amine is 0.5 parts by mass or more, more acid can be captured, and thus it is easier to suppress an increase in viscosity after light irradiation, and the tackiness can be further improved. If the content of the tertiary amine is 20 parts by mass or less, the amount of the tertiary amine remaining in an unreacted state after heat curing can be further reduced, and thus the decrease in the properties of the cured product can be further suppressed.

[0091] 1-4. Inorganic filler

[0092] The inorganic filler can have a function of improving the shape retention of the curable composition and reducing the moisture permeability of the cured product.

[0093] Examples of the inorganic filler include calcium carbonate, magnesium carbonate, barium sulfate, magnesium sulfate, aluminum silicate, zirconium silicate, iron oxide, titanium oxide, titanium nitride, alumina other than the above, zinc oxide, silica, potassium titanate, kaolin, talc, glass beads, sericite, activated clay, bentonite, aluminum nitride, and silicon nitride. Among them, silica and talc are preferable.

[0094] The shape of the inorganic filler can be a fixed shape such as a spherical shape, a plate shape, or a needle shape, or can be an amorphous shape. In the case where the inorganic filler is in a spherical shape, the average primary particle diameter of the inorganic filler is preferably 0.1 μm or more and 5 μm or less, more preferably 0.5 μm or more and 3 μm or less, from the viewpoint of the shape retention of the cured product after bonding, the adjustment of the thickness, and the reduction of the moisture permeability. If the average primary particle diameter of the inorganic filler is 5 μm or less, it is easier to reduce the thickness unevenness of the cured product after bonding, and if the average primary particle diameter of the inorganic filler is 0.1 μm or more, the increase in viscosity can be further suppressed. Further, from the viewpoint of adjusting the viscosity (thixotropy) of the curable composition, it is preferable to be in a range smaller than 0.1 μm, for example, 7 nm or more and less than 100 nm. The average primary particle diameter of the inorganic filler can be measured by the laser diffraction method described in JIS Z8825 (2013).

[0095] The specific surface area of the inorganic filler is preferably 0.5 m 2 / g or more and 20 m 2 / g or less. The specific surface area of the inorganic filler is measured by the BET method described in JIS Z8830 (2013).

[0096] The curable composition can contain only one inorganic filler, or two or more. For example, from the viewpoint of adjusting the viscosity (thixotropy) and the shape retention, thickness of the cured product, the curable composition can contain an inorganic filler having a relatively small average primary particle diameter (for example, less than 0.1 μm) and an inorganic filler having a relatively large average primary particle diameter (for example, 0.1 μm or more). The content of the inorganic filler having a relatively small average primary particle diameter is preferably less than the content of the inorganic filler having a relatively large average primary particle diameter.

[0097] The content of the inorganic filler is preferably 10 parts by mass or more and 350 parts by mass or less, relative to 100 parts by mass of the curable compound. If the content of the inorganic filler is 10 parts by mass or more, the shape retention of the cured product is easily further improved, and the moisture permeability is easily further reduced. If the content of the inorganic filler is 350 parts by mass or less, not only the coatability of the curable composition is less likely to be impaired, but also the decrease in the adhesive strength caused by the decrease in the relative amount of the curable compound or the impairment of the flexibility of the cured product is further suppressed. From the same viewpoint, the content of the inorganic filler is more preferably 150 parts by mass or more and 300 parts by mass or less.

[0098] 1-5. Other

[0099] The curable composition can further contain other components in addition to the above-described components. Examples of the other components can further include a photosensitizer, a silane coupling agent, an adhesion promoter, an organic fine particle, a plasticizer, an antioxidant, and an antifoaming agent.

[0100] 1-5-1. Photosensitizer

[0101] The photosensitizer has a function of further improving the polymerization initiation efficiency of the above-described photocationic polymerization initiator and further promoting the curing reaction of the curable compound.

[0102] Examples of the photosensitizer include a thioxanthone-based compound such as 2,4-diethylthioxanthone, 2,2-dimethoxy-1,2-diphenylethan-1-one, benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4-benzoyl-4'-methyl diphenyl sulfide, and 9,10-dibutoxyanthracene. The curable composition can contain only one photosensitizer, or two or more.

[0103] The content of the photosensitizer is, for example, preferably 0.1 part by mass or more and 5 parts by mass or less, and more preferably 0.5 part by mass or more and 2 parts by mass or less, relative to 100 parts by mass of the curable compound. The curable composition can contain only one photosensitizer, or two or more.

[0104] 1-5-2. Silane Coupling Agent

[0105] Examples of the silane coupling agent include vinyltrimethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ- glycidoxypropyltriethoxysilane.

[0106] The content of the silane coupling agent is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 1.0 parts by mass or more and 5.0 parts by mass or less, relative to 100 parts by mass of the curable compound. If the content of the silane coupling agent is 0.1 parts by mass or more, the adhesion strength of the cured product can be further increased. If the content of the silane coupling agent is 10 parts by mass or less, the moisture permeability of the cured product can be further reduced.

[0107] 1-5-3. Common matters

[0108] The total amount of the other components is preferably 0.1% by mass or more and 50% by mass or less, relative to the total amount of the curable composition. If the total amount is 50% by mass or less, the viscosity of the curable composition does not easily increase excessively, and the coatability is not easily impaired.

[0109] 1-6. Physical properties

[0110] The viscosity of the curable composition, which is measured at 25°C and 2.5 rpm using an E-type viscometer, is preferably 50 Pa-s or more and 400 Pa-s or less, more preferably 100 Pa-s or more and 300 Pa-s or less. If the viscosity of the curable composition is 50 Pa-s or more, the shape retention during coating is easily further improved because the viscosity is moderately high. If the viscosity of the curable composition is 400 Pa-s or less, the coatability during coating, for example, by a dispenser, is not easily impaired.

[0111] For the curable composition, light having a wavelength of 365 nm is irradiated at an irradiance of 100 mW / cm 2 The cumulative light amount at the time of irradiation is 3000 mJ / cm 2 The viscosity at 25°C after 60 seconds is preferably 1.0 x 10 4 Pa-s or less, more preferably 1.0 x 10 2 Pa-s or more and 5.0 x 10 3 Pa-s or less. If the viscosity of the curable composition is 1.0 x 10 4 Pa-s or less, the tackiness after light irradiation is maintained, the flowability during lamination is not easily impaired, and the adhesion strength of the cured product can be improved. On the other hand, if the viscosity of the curable composition is 1.0 x 10 2 Pa-s or more, the shape retention of the curable composition after light irradiation can be further improved.

[0112] The viscosity after light irradiation of the above-mentioned viscosity was also measured using an E-type viscometer at 25°C at 2.5 rpm. Specifically, using a bar coater No. 6, a coating film of the curable composition having a thickness of 10 μm was formed on an alkali-free glass having a thickness of 0.7 mm. The coating film was left to stand at room temperature (25°C) for 3 minutes while being subjected to nitrogen purge. Thereafter, for the coating film, ultraviolet rays were irradiated with a metal halide lamp having a wavelength of 365 nm at a UV illuminance of 100 mW / cm2for 60 seconds. 2 The cumulative light amount was 3000 mJ / cm2. 2 After the irradiation, the coating film was scraped off, and the viscosity after 60 seconds was measured in the same manner as described above.

[0113] The viscosity after light irradiation of the curable composition can be adjusted by the content of the tertiary amine and the content of the inorganic filler. For example, if the amount of the tertiary amine with respect to the photocationic polymerization initiator is large, the viscosity increase of the curable composition after light irradiation is more easily reduced because more acid generated by the photocationic polymerization initiator by light irradiation can be trapped. On the other hand, the more the content of the inorganic filler, the more easily the viscosity increase after light irradiation becomes large.

[0114] 1-7. Use

[0115] As described above, the curable composition of the present embodiment can be adjusted to a viscosity suitable for lamination after light irradiation, and thus can be used as a sealing agent. That is, the sealing agent contains the above-mentioned curable composition.

[0116] As described later, the sealing agent can be used as a sealing agent or an adhesive for various elements such as an organic EL element, a light emitting diode (LED) element, a liquid crystal element, a semiconductor element, a solar cell element, and the like. For example, the sealing agent can be a sealing agent for sealing a light emitting element such as an organic EL element, a micro LED element, and the like. The sealing agent can be a face sealing agent, or can be a frame sealing agent. For the frame sealing agent, the cured product is required to have higher shape retention, and thus the above-mentioned curable composition is particularly suitable as a frame sealing agent.

[0117] Hereinafter, an example in which the above-mentioned curable composition is used as a sealing agent for a display panel will be described.

[0118] 2. Display panel and method for manufacturing the same

[0119] The display panel of one embodiment of the present application has an element substrate, a counter substrate, and a sealing portion provided between them and sealing an element.

[0120] The element substrate has a substrate and an element. The substrate is a transparent substrate. The material of the transparent substrate can be an inorganic material such as glass, or a plastic such as polycarbonate, polyethylene terephthalate, polyether sulfone, and polymethylmethacrylate (PMMA). The element can be various elements such as an organic EL element, an LED element (including a micro LED), a liquid crystal element, a semiconductor element, and a solar cell element. For example, in the case where the element is an organic EL element, the organic EL element is disposed on the substrate, and has a stacked structure of an anode / emissive layer / cathode.

[0121] The facing substrate is disposed so as to face the element substrate with the element interposed therebetween. The facing substrate can be the same transparent substrate as described above. The facing substrate can also have, for example, a color filter layer.

[0122] The sealing portion includes a frame-shaped first sealing portion disposed so as to surround the outer periphery of the element, and a second sealing portion filled in a region surrounded by the first sealing portion. The first sealing portion is a cured product of a first sealing agent (frame adhesive material). The second sealing portion is a cured product of a second sealing agent (filling adhesive material). At least one of the first sealing agent and the second sealing agent, preferably the first sealing agent, is the curable composition described above.

[0123] The display panel described above can be manufactured by any method. For example, the display panel can be obtained by a manufacturing method including the following steps:

[0124] 1) a step of applying a first sealing agent in a frame shape so as to surround a display region on one of the facing substrate and the element substrate;

[0125] 2) a step of forming a sealing agent layer by filling a second sealing agent in a region surrounded by the first sealing agent applied in a frame shape;

[0126] 3) a step of irradiating light to the sealing agent layer;

[0127] 4) a step of bonding the one substrate to the other substrate via the sealing agent layer on which light has been irradiated; and

[0128] 5) a step of curing the sealing agent layer by heating.

[0129] In the step of 1), the first sealing agent is applied in a frame shape so as to surround the display region on one of the facing substrate and the element substrate, for example, on the facing substrate. The method of application is not particularly limited, and for example, application can be performed by a dispenser or the like.

[0130] In the step of 2), the second sealing agent is filled in a region surrounded by the first sealing agent applied in a frame shape, and a sealing agent layer is formed.

[0131] In the process of 3), the sealant layer is irradiated with light. The light to be irradiated is appropriately selected depending on the kind of the photocationic polymerization initiator in the above-mentioned curable composition as the first sealant, and is preferably light in the visible light region, for example, light having a wavelength of 370 nm or more and 450 nm or less is preferred. The reason for this is that light in this range of wavelength causes relatively little damage to the driving electrode. The irradiation of light can use a publicly known light source that emits ultraviolet light or visible light, for example, a metal halide lamp can be used.

[0132] The amount of light irradiation is preferably an amount in which a moderate degree of tackiness remains in the curable composition after irradiation. For example, in the case of 10 mW / cm 2 or more and 1000 mW / cm 2 or more, it can be set to 1000 mJ / cm 2 or more and 10000 mJ / cm 2 or more.

[0133] By the light irradiation, the curing of the first sealant and the second sealant is started. Further, after the light irradiation is finished, the temperature of the substrate sometimes rises to about 35°C or so, and sometimes it is left in this state. In this way, after the light irradiation, the first sealant and the second sealant are not immediately laminated, but are left in a standby state for a prescribed time, whereby the curing of the first sealant and the second sealant is moderately performed, and a state in which the viscosity is increased is obtained.

[0134] In the process of 4), the facing substrate is laminated to the device substrate via the sealant layer in a state in which the viscosity of the first sealant and the second sealant is moderately increased.

[0135] The lamination is performed in a vacuum chamber, in a manner in which the sealant layer is flattened, by pressing the device substrate and the facing substrate with a press or the like. At this time, since the first sealant having a relatively high viscosity exists in a frame shape around the second sealant, the second sealant can be prevented from flowing out to the outside.

[0136] In the process of 5), the laminated product is heated, and the first sealant and the second sealant are heated to be cured.

[0137] The heating temperature is a temperature at which the sealant layer is cured, and from the viewpoint of reducing damage to the device by heat, it is preferably a low temperature, for example, a temperature lower than 100°C, and is preferably 40°C or more and 90°C or less, and more preferably 60°C or more and 85°C or less. The heating time also depends on the heating temperature, and is, for example, 60 minutes or more and 120 minutes or less.

[0138] In the above embodiment, in step 3), when irradiated with light, acid is generated by the photocationic polymerization initiator. However, since the acid is trapped by the tertiary amine, the viscosity does not increase excessively and can be maintained at a low level. Therefore, even for curable compositions containing inorganic fillers, fluidity and tack are not easily impaired during lamination in step 4). Furthermore, in step 5), the acid trapped by the tertiary amine is released by heating, allowing the curable compound to cure at low temperatures. As a result, sufficient adhesive strength can be achieved even for curable compositions containing inorganic fillers.

[0139] Furthermore, while the above embodiment illustrates the use of the curable composition primarily as a sealant for organic EL devices, the present invention is not limited thereto and can also be used as a sealant or adhesive for various devices such as LED devices (including micro-LEDs), liquid crystal devices, semiconductor devices, and solar cell devices, as well as an interlayer filler for touch panels. Furthermore, the curable composition can also be used as a sealant or adhesive applied to non-translucent substrates, such as printed circuit boards used in smart antennas for electric vehicles or substrates with under-wiring light shielding used in dye-sensitized solar cells.

[0140] Example

[0141] The present invention will be further described below with reference to Examples and Comparative Examples, but the technical scope of the present invention is not limited thereto.

[0142] 1. Material Preparation

[0143] 1-1. Curable compound (A)

[0144] Curable compound (A-1): Aromatic trifunctional epoxy compound (VG3101L, 2-(glycidyloxyphenyl)propylphenyl-1,1-bis(glycidyloxyphenyl)ethane, manufactured by Printec Co., Ltd., solid)

[0145] Curable compound (A-2): Bisphenol F epoxy resin (YL983U, manufactured by Mitsubishi Chemical Corporation, bifunctional, liquid)

[0146] 1-2. Photocationic polymerization initiator (B)

[0147] CPI-210S (manufactured by San-Apro)

[0148] [Chemistry 4]

[0149]

[0150] 1-3. Tertiary amine (C)

[0151] • a compound represented by the following formula (Tinuvin 123 manufactured by BASF Japan Ltd.)

[0152] [Chemical 5]

[0153]

[0154] 1-4. Inorganic filler (D)

[0155] • Inorganic filler (D-1): spherical silica (Sansil SP07M manufactured by Tokuyama Corp., average particle diameter 0.7 μm)

[0156] • Inorganic filler (D-2): finely powdered silica (HM-30S manufactured by Tokuyama Corp., average particle diameter 7 nm)

[0157] 1-5. Photosensitizer (E)

[0158] • UVS-1331 (manufactured by Air Water Inc.)

[0159] 1-6. Silane coupling agent (F)

[0160] • KBM403 (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0161] 2. Preparation of curable composition

[0162] (Example 1)

[0163] A curable composition was obtained by mixing 100 parts by mass of the curable compound (A-1), 200 parts by mass of the curable compound (A-2), 15 parts by mass of the photocationic polymerization initiator (B), 5 parts by mass of the tertiary amine (C), 500 parts by mass of the inorganic filler (D-1), 20 parts by mass of the inorganic filler (D-2), 5 parts by mass of the photosensitizer (E), and 30 parts by mass of the silane coupling agent (F) using a roll mixer.

[0164] (Example 2, Comparative Example 1)

[0165] The blending amounts of the respective components were changed as shown in Table 1, and otherwise, a curable composition was obtained in the same manner as in Example 1.

[0166] 3. Evaluation

[0167] For the curable compositions obtained in Examples 1 to 2 and Comparative Example 1, (1) viscosity, (2) tackiness after light irradiation, (3) moisture permeation amount, and (4) adhesive strength were evaluated by the following methods.

[0168] (1) Viscosity (before light irradiation, after light irradiation)

[0169] The viscosity of the obtained curable composition was measured at 25°C using a cone and plate viscometer method according to JIS K5600-2-3 (2014) with an E-type viscometer (TVE-35L viscometer, manufactured by Tokimec, Inc., rotor name: 3° x R9.7). The rotational speed of the cone at the time of measurement was set to 2.5 rpm.

[0170] Next, a 10-μm-thick coating film of the curable composition was formed on 0.7-mm-thick non-alkali glass using a bar coater No. 6. The coating film was left to stand for 3 minutes at room temperature (25°C) while being subjected to nitrogen purge. Thereafter, the coating film was irradiated with ultraviolet rays (light of 365-nm wavelength, UV illuminance: 100 mW / cm 2 , cumulative light amount: 3000 mJ / cm 2 , for 60 seconds, and the viscosity at that time was measured in the same manner as described above.

[0171] (2) Stickiness after light irradiation

[0172] A 10-μm-thick coating film of the obtained curable composition was formed on 0.7-mm-thick non-alkali glass using a bar coater No. 6. The coating film was left to stand for 3 minutes at room temperature (25°C) while being subjected to nitrogen purge. Thereafter, the coating film was irradiated with ultraviolet rays (light of 365-nm wavelength, UV illuminance: 100 mW / cm 2 , cumulative light amount: 3000 mJ / cm 2 ). Next, the coating film was touched with a hand wearing a protective glove, and the stickiness was confirmed. Then, the case where stickiness was present was set to "Yes", and the case where no stickiness was present was set to "No".

[0173] (3) Moisture permeation amount

[0174] The obtained curable composition was applied to release paper at a thickness of 100 μm using an applicator. Thereafter, the applied curable composition was put into a container for nitrogen replacement, and after nitrogen purge was performed for 5 minutes, light of 3000 mJ / cm 2 (wavelength of 365-nm light corrected by a sensor) was irradiated, and further, the curable composition was cured by heating at 120°C for 1 hour, to thereby produce a film formed of a cured product.

[0175] Two pieces of the cured film were placed on an aluminum cup in which calcium chloride (anhydrous) was enclosed as a moisture absorbent, and further, an aluminum ring was placed and screw-fastened, and the initial weight of the entire aluminum cup was measured. Thereafter, the aluminum cup was put in a thermostat set at 60°C and 90% Rh, and after 24 hours, the aluminum cup was taken out, and the weight was measured. The obtained weight value was substituted into the following calculation formula, and the moisture permeation amount was calculated.

[0176] Moisture permeation amount (g / m 2 24h) = (weight after test - weight before test) x film thickness / (film area x 100)

[0177] If the moisture permeation amount is 50 g / m 2 or less, it is judged to be good, and if it exceeds 50 g / m 2 , it is judged to be poor.

[0178] (4) Adhesive strength

[0179] On an alkali-free glass of 25 mm x 45 mm x 0.7 mm, the obtained curable composition was coated in a circular shape using a silk screen. The seal pattern was set to a circular shape with a diameter of 1 mm. Subsequently, on the coated film of the curable composition, light with a wavelength of 365 nm was irradiated at an irradiation intensity of 100 mW / cm 2 After irradiation for 30 seconds from one of the alkali-free glass sides, a pair of 0.7 mm thick alkali-free glasses were attached, and a sample of a laminate was obtained by heating using an oven at 80°C for 60 minutes.

[0180] Then, after the obtained sample was left to stand in a constant temperature room at 23°C for 24 hours, the stress at that time was measured by stretching in a direction parallel to the surface at a speed of 2 mm / minute using a tensile tester (model 210 tensile tester manufactured by Intesco).

[0181] The evaluation results of the curable compositions of Examples 1 to 2 and Comparative Example 1 are shown in Table 1.

[0182] [Table 1]

[0183]

[0184] As shown in Table 1, it was found that the curable composition of Comparative Example 1 which did not contain a tertiary amine did not have tackiness after light irradiation, and the adhesive strength of the cured product was also low.

[0185] On the other hand, it was found that the curable compositions of Examples 1 and 2 which contained a tertiary amine in an amount of 0.1% by mass or more had tackiness after light irradiation. In addition, it was found that the adhesive strength of the cured product was also high.

[0186] From these results, it was found that even if an inorganic filler is contained, by using a photo cationic polymerization initiator in combination with a tertiary amine in an amount of 0.1% by mass or more, it is possible to keep the viscosity after light irradiation low, and the low-temperature curability is also excellent.

[0187] This application claims priority based on Japanese Patent Application No. 2023-54118 filed on March 29, 2023. The content described in the specification of this application is incorporated into the specification of the present application in its entirety.

[0188] Industrial applicability

[0189] According to the present application, it is possible to provide a curable composition which can balance low-temperature curability and stability of viscosity after light irradiation, and impart a cured product having low moisture permeability and high adhesive strength.

Claims

1. A curable composition comprising: a curable compound, a photocationic polymerization initiator, a tertiary amine, and an inorganic filler, The content of the tertiary amine is 20 parts by mass or more relative to 100 parts by mass of the photocationic polymerization initiator.

2. The curable composition according to claim 1, wherein The content of the tertiary amine is 0.5 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the curable compound.

3. The curable composition according to claim 1, wherein The content of the inorganic filler is 20 parts by mass or more and 400 parts by mass or less relative to 100 parts by mass of the curable compound.

4. The curable composition according to claim 1, wherein The curable compound includes an aromatic epoxy compound.

5. The curable composition according to claim 1, wherein The tertiary amine is a difunctional tertiary amine.

6. The curable composition according to claim 1, wherein The tertiary amine has an N-O bond.

7. The curable composition according to claim 1, wherein The tertiary amine has a hindered structure.

8. The curable composition according to claim 1, wherein The wavelength of 365nm was UV irradiated at 100mW / cm 2 Irradiation cumulative light dose 3000mJ / cm 2 After 60 seconds, the viscosity at 25°C was 1.0×10 4 Pa·s or less. 9 . A sealant comprising the curable composition according to claim 1 . 10 . A frame sealant comprising the curable composition according to claim 1 .

11. A display panel comprising: a component substrate configured with components; an opposing substrate disposed opposite to the element substrate with the element interposed therebetween; and A sealing portion is disposed between the element substrate and the opposing substrate and is used to seal the element. The sealing portion includes a cured product of the sealant according to claim 9 .

12. A method for manufacturing a display panel, comprising: a step of applying a first sealant in a frame shape along the periphery of the display area on a surface of either the element substrate or the counter substrate; a step of filling a second sealant in a region surrounded by the first sealant to form a sealant layer; a step of irradiating the sealant layer with light; a step of bonding one substrate to the other substrate via the sealant layer irradiated with light; and a step of heating the sealant layer to cure it, At least one of the first sealant and the second sealant is the sealant according to claim 9 .

13. The method for manufacturing a display panel according to claim 12, wherein: The first sealant is the sealant according to claim 9.

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