Epoxy resin composition, encapsulant, and image display device

Abstract

This epoxy resin composition comprises an epoxy resin, a styrene-based viscosity adjuster, polyisobutylene and a compatibilizer. The compatibilizer has a diblock structure containing a styrene-derived structure and an olefin-derived structure. The mixing ratio of the compatibilizer is 30-120 parts by mass with respect to 100 parts by mass of the polyisobutylene. The mixing ratio of the compatibilizer is 80-350 parts by mass with respect to 100 parts by mass of the styrene-based viscosity adjuster.

Description

Technical Field

[0001] The present invention relates to an epoxy resin composition, a sealing material, and an image display device.

Background Art

[0002] In recent years, for example, an organic EL display is known as an image display device including an optical element. In such an image display device, the optical element is sealed with a sealing material in order to suppress deterioration of the optical element due to moisture in the atmosphere or the like.

[0003] As a sealing composition for forming such a sealing material, for example, a thermosetting resin composition containing a thermosetting resin (epoxy resin) has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, the sealing material is required to have even lower moisture permeability.

[0006] In order to improve the low moisture permeability, blending polyisobutylene having low moisture permeability with the resin has been considered. However, particularly when the resin is an epoxy resin, there is a problem that a uniform mixture cannot be obtained because the compatibility between the epoxy resin and polyisobutylene is low.

[0007] The present invention provides an epoxy resin composition excellent in compatibility and low moisture permeability, a sealing material containing a cured product of the epoxy resin composition, and an image display device including the sealing material.

Means for Solving the Problems

[0008] The present invention [1] is an epoxy resin composition comprising an epoxy resin, a styrene-based viscosity modifier, polyisobutylene, and a compatibilizer, wherein the compatibilizer has a diblock structure comprising a styrene-derived structure and an olefin-derived structure, the blending ratio of the compatibilizer is 30 parts by mass or more and 120 parts by mass or less per 100 parts by mass of polyisobutylene, and the blending ratio of the compatibilizer is 80 parts by mass or more and 350 parts by mass or less per 100 parts by mass of the styrene-based viscosity modifier.

[0009] The present invention [2] includes a sealing material comprising a cured product of the epoxy resin composition described in [1] above.

[0010] The present invention [3] includes an image display device comprising an optical element and a sealing material described in [2] above for sealing the optical element. [Effects of the Invention]

[0011] The epoxy resin composition of the present invention contains polyisobutylene. Therefore, it exhibits excellent low moisture permeability.

[0012] Furthermore, this epoxy resin composition contains a predetermined proportion of a compatibilizer (a compatibilizer having a diblock structure containing both styrene-derived and olefin-derived structures) relative to both polyisobutylene and a styrene-based viscosity modifier. Therefore, it exhibits excellent compatibility.

[0013] The sealing material of the present invention includes a cured product of the epoxy resin composition of the present invention. Therefore, it has excellent compatibility.

[0014] The image display device of the present invention comprises an optical element and a sealing material of the present invention for sealing the optical element. Therefore, it exhibits excellent low moisture permeability. [Modes for carrying out the invention]

[0015] The epoxy resin composition comprises an epoxy resin, a styrene-based viscosity modifier, polyisobutylene, and a compatibilizer.

[0016] <Epoxy resin> Examples of the epoxy resin include aliphatic epoxy resins, alicyclic epoxy resins, and aromatic epoxy resins.

[0017] [Aliphatic epoxy resin] An aliphatic epoxy resin is a curable resin having an epoxy group and not having an aliphatic ring (alicyclic skeleton) and an aromatic ring.

[0018] Examples of the aliphatic epoxy resin include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether.

[0019] [Alicyclic epoxy resin] An alicyclic epoxy resin is a curable resin having an epoxy group and an aliphatic ring (alicyclic skeleton) and not having an aromatic ring.

[0020] Examples of the alicyclic epoxy resin include glycidyl group-containing alicyclic epoxy resins, glycidyl ether group-containing alicyclic epoxy resins, and epoxy cyclo structure-containing epoxy resins.

[0021] (Glycidyl group-containing alicyclic epoxy resin) A glycidyl group-containing alicyclic epoxy resin has, for example, a glycidyl group bonded to an aliphatic ring. Such a glycidyl group-containing alicyclic epoxy resin is represented by, for example, the following general formula (1).

[0022] [Chemical formula] In formula (1) above, R1 represents a monovalent organic group, and n represents the degree of polymerization. Furthermore, substituents such as alkyl groups may be attached to the carbon atoms constituting the cyclohexane ring.

[0023] A specific example of a glycidyl group-containing alicyclic epoxy resin represented by the above general formula (1) is the 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol.

[0024] The glycidyl group-containing alicyclic epoxy resin represented by the above general formula (1) can also be a commercially available product. An example of a commercially available glycidyl group-containing alicyclic epoxy resin represented by the above general formula (1) is EHPE3150 (epoxy equivalent 170-190 g / eq., manufactured by Daicel Corporation).

[0025] (Glycidyl ether group-containing alicyclic epoxy resin) A glycidyl ether group-containing alicyclic epoxy resin has glycidyl ether units bonded to an aliphatic ring. Preferably, the glycidyl ether group-containing alicyclic epoxy resin is a polyglycidyl ether-containing alicyclic epoxy resin having multiple glycidyl ether units bonded to an aliphatic ring.

[0026] Examples of glycidyl ether-containing alicyclic epoxy resins include difunctional glycidyl ether-containing alicyclic epoxy resins. Examples of difunctional glycidyl ether-containing alicyclic epoxy resins include hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, and hexahydrophthalate diglycidyl ester.

[0027] (Epoxy cyclostructure-containing epoxy resin) Epoxy cyclo structure-containing epoxy resins have an epoxy cyclo structure that has an epoxy group composed of two adjacent carbon atoms forming an aliphatic ring and one oxygen atom bonded to those two carbon atoms.

[0028] Examples of epoxy resins containing epoxycyclostructures include epoxy resins containing epoxycyclohexane structures (hereinafter referred to as ECH structure-containing epoxy resins).

[0029] Examples of ECH structure-containing epoxy resins include epoxy resins containing one ECH structure as shown in the following chemical formula (2), epoxy resins containing one ECH structure as shown in the following chemical formula (3), epoxy resins containing two ECH structures as shown in the following general formula (4), and modified products thereof.

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] In formula (4) above, X represents a linking group (a divalent group having one or more atoms). R2 represents one atom or substituent selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, an aryl group, a furyl group, and a thienyl group. The two R2s in formula (4) may be the same or different from each other.

[0034] An epoxy resin containing the two ECH structures shown in the general formula (4) above (hereinafter referred to as the ECH structure-containing epoxy resin shown in general formula (4)) has ECH structures (epoxycyclohexyl groups) at both ends of the molecule, and the two epoxycyclohexyl groups are linked via a linking group. The epoxycyclohexyl group is a functional group that includes an epoxy group composed of a cyclohexane ring, two adjacent carbon atoms forming the cyclohexane ring, and one oxygen atom bonded to those two carbon atoms.

[0035] Examples of alkyl groups represented by R2 in the above general formula (4) include linear or branched alkyl groups having 1 to 6 carbon atoms (e.g., methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, etc.).

[0036] Examples of fluoroalkyl groups represented by R2 in the above general formula (4) include linear or branched fluoroalkyl groups having 1 to 6 carbon atoms (e.g., perfluoromethyl group, perfluoroethyl group, perfluoropropyl group, etc.).

[0037] Examples of aryl groups represented by R2 in the above general formula (4) include aryl groups having 6 to 18 carbon atoms (e.g., phenyl group, naphthyl group, etc.).

[0038] Examples of the linking group represented by X in the general formula (4) above include oxygen atoms, sulfur atoms, divalent hydrocarbon groups, polyoxyalkylene groups, carbonyl groups, ether groups, thioether groups, ester groups, carbonate groups, amide groups, and groups formed by linking these groups.

[0039] Examples of divalent hydrocarbon groups include linear or branched alkylene groups having 1 to 20 carbon atoms (e.g., methylene group, methylmethylene group, dimethylmethylene group, ethylene group, propylene group, trimethylene group, butylene group, etc.) and linear or branched unsaturated hydrocarbon groups having 1 to 20 carbon atoms (e.g., propenylene group, methylpropenylene group, butenylene group, etc.).

[0040] Examples of polyoxyalkylene groups include linear or branched polyoxyalkylene groups having 1 to 120 carbon atoms (e.g., polyoxyethylene groups, polyoxypropylene groups, etc.).

[0041] Examples of epoxy resins containing the ECH structure represented by general formula (4) include bis(3,4-epoxycyclohexylmethyl) ether, 1,2-bis(3,4-epoxycyclohexane-1-yl)ethane, 2,2-bis(3,4-epoxycyclohexane-1-yl)propane, 3,4-epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate, and ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl3,4-epoxycyclohexanecarboxylate, with 3,4-epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate being preferred.

[0042] Furthermore, commercially available epoxy resins containing the ECH structure shown in the general formula (4) above can also be used. Examples of commercially available epoxy resins containing the ECH structure shown in the general formula (4) above include Celoxide 8010, Celoxide 2021P (epoxy equivalent 128-145 g / eq.), and Celoxide 2081 (all manufactured by Daicel Corporation).

[0043] Preferably, the alicyclic epoxy resin is an epoxy resin containing an epoxycyclo structure. More preferably, the alicyclic epoxy resin is an epoxy resin containing an ECH structure represented by the general formula (4) above.

[0044] The weight-average molecular weight of the alicyclic epoxy resin is, for example, 200 or more, for example, 1000 or less, preferably 500 or less. The weight-average molecular weight (Mw) can be determined by gel permeation chromatography (GPC) using polystyrene as the standard substance (the same applies hereinafter).

[0045] Furthermore, the epoxy equivalent in the alicyclic epoxy resin is, for example, 90 g / eq. or more, preferably 100 g / eq. or more, for example 250 g / eq. or less, preferably 190 g / eq. or less. The epoxy equivalent can be measured in accordance with JIS K7236:2001 (the same applies hereinafter).

[0046] [Aromatic epoxy resin] Aromatic epoxy resins are curable resins that have epoxy groups and aromatic rings, but do not have aliphatic rings (alicyclic skeletons).

[0047] Examples of aromatic epoxy resins include bisphenol-type epoxy resins, diphenyl ether-type epoxy resins, novolac-type epoxy resins (e.g., phenol novolac type, cresol novolac type, biphenyl novolac type, bisphenol novolac type, naphthol novolac type, trisphenol novolac type, and dicyclopentadiene novolac type), biphenyl-type epoxy resins, and naphthalene-type epoxy resins. Preferably, aromatic epoxy resins include bisphenol-type epoxy resins and biphenyl-type epoxy resins.

[0048] Examples of bisphenol-type epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, and bisphenol AD ​​type epoxy resin. Preferably, bisphenol F type epoxy resin is used as the bisphenol-type epoxy resin.

[0049] Furthermore, the aromatic epoxy resin may be solid at room temperature or liquid at room temperature. Preferably, the aromatic epoxy resin is solid at room temperature. "Solid at room temperature" means that it is in a solid state that does not have fluidity at room temperature (23°C), and "liquid at room temperature" means that it is in a liquid state that has fluidity at room temperature (23°C).

[0050] The weight-average molecular weight (Mw) of the aromatic epoxy resin is, for example, 1000 or more, preferably 3000 or more, and also, for example, 10000 or less, preferably 8000 or less.

[0051] Furthermore, the epoxy equivalent in the aromatic epoxy resin is, for example, 1000 g / eq. or more, preferably 5000 g / eq. or more, more preferably 8000 g / eq. or more, and also, for example, 12000 g / eq. or less.

[0052] From the viewpoint of improving low moisture permeability, alicyclic epoxy resins and aromatic epoxy resins are preferred as epoxy resins.

[0053] Epoxy resins can be used alone or in combination of two or more types. Preferably, an alicyclic epoxy resin and an aromatic epoxy resin are used in combination as the epoxy resin.

[0054] When using both alicyclic epoxy resin and aromatic epoxy resin, the blending ratio of the alicyclic epoxy resin is, from the viewpoint of improving low moisture permeability, for example, 20 parts by mass or more, preferably 30 parts by mass or more, and more preferably 35 parts by mass or more, relative to 100 parts by mass of the total amount of alicyclic epoxy resin and aromatic epoxy resin. From the viewpoint of improving low moisture permeability, for example, 60 parts by mass or less, preferably 48 parts by mass or less. The blending ratio of the aromatic epoxy resin is, from the viewpoint of improving low moisture permeability, for example, 40 parts by mass or more, preferably 52 parts by mass or more, relative to 100 parts by mass of the total amount of alicyclic epoxy resin and aromatic epoxy resin. From the viewpoint of improving low moisture permeability, for example, 80 parts by mass or less, preferably 70 parts by mass or less, and more preferably 65 parts by mass or less.

[0055] The blending ratio of the epoxy resin is, from the viewpoint of improving low moisture permeability, for example, 30 parts by mass or more, preferably 40 parts by mass or more, and from the viewpoint of improving low moisture permeability, for example, 70 parts by mass or less, preferably 63 parts by mass or less, more preferably 58 parts by mass or less, relative to 100 parts by mass of the total amount of epoxy resin, styrene viscosity modifier, polyisobutylene, and compatibilizer.

[0056] <Styrene-based viscosity modifier> Styrene-based viscosity modifiers are components that impart tackiness to epoxy resin compositions.

[0057] Examples of styrene-based viscosity modifiers include styrene polymers, α-methylstyrene polymers, and styrene-α-styrene copolymers.

[0058] Styrene-based viscosity modifiers can also be commercially available. Examples of commercially available styrene-based viscosity modifiers include the FTR series (e.g., FTR-8120, FTR-8100, both manufactured by Mitsui Chemicals, Inc.).

[0059] The weight-average molecular weight (Mw) of the styrene-based viscosity modifier is, for example, 1000 or more, preferably 1200 or more, and more preferably 1300 or more, from the viewpoint of improving low moisture permeability, and also, for example, 2000 or less, preferably 1500 or less.

[0060] Styrene-based viscosity modifiers can be used alone or in combination of two or more types.

[0061] The blending ratio of the styrene-based viscosity modifier is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, per 100 parts by mass of epoxy resin, from the viewpoint of improving low moisture permeability, and for example, 20 parts by mass or less, preferably 15 parts by mass or less, from the viewpoint of improving low moisture permeability.

[0062] Furthermore, the blending ratio of the styrene-based viscosity modifier is, from the viewpoint of improving low moisture permeability, for example, 1.0 part by mass or more, preferably 5.0 parts by mass, and from the viewpoint of improving low moisture permeability, for example, 10 parts by mass or less, preferably 7.8 parts by mass or less, relative to 100 parts by mass of the total amount of epoxy resin, styrene-based viscosity modifier, polyisobutylene, and compatibilizer.

[0063] <Polyisobutylene> Polyisobutylene is a component that imparts low moisture permeability to epoxy resin compositions.

[0064] The weight-average molecular weight of polyisobutylene is, for example, 10,000 or more, preferably 30,000 or more, and more preferably 45,000 or more, from the viewpoint of improving low moisture permeability, and also, for example, 100,000 or less, preferably 70,000 or less, and more preferably 50,000 or less.

[0065] The proportion of polyisobutylene added is, for example, 15 parts by mass or more, preferably 25 parts by mass or more, and more preferably 35 parts by mass or more, per 100 parts by mass of epoxy resin, from the viewpoint of improving low moisture permeability, and for example, 50 parts by mass or less.

[0066] Furthermore, the proportion of polyisobutylene added is, from the viewpoint of improving low moisture permeability, for example, 100 parts by mass or more, preferably 120 parts by mass or more, more preferably 200 parts by mass or more, and even more preferably 250 parts by mass or more, per 100 parts by mass of styrene-based viscosity modifier. Also, from the viewpoint of improving low moisture permeability, for example, 600 parts by mass or less, preferably 450 parts by mass or less, and more preferably 350 parts by mass or less.

[0067] Furthermore, the proportion of polyisobutylene added is, from the viewpoint of improving low moisture permeability, for example, 10 parts by mass or more, preferably 15 parts by mass or more, and from the viewpoint of improving low moisture permeability, for example, 40 parts by mass or less, preferably 30 parts by mass or less, more preferably 25 parts by mass or less, relative to 100 parts by mass of the total amount of epoxy resin, styrene viscosity modifier, polyisobutylene, and compatibilizer.

[0068] <Compatibilizer> Compatibilizers are components used to improve compatibility (specifically, compatibility between styrene-based viscosity modifiers (epoxy resins) and polyisobutylene).

[0069] The compatibilizer has a diblock structure containing both a styrene-derived structure and an olefin-derived structure. If the compatibilizer has a diblock structure containing both a styrene-derived structure and an olefin-derived structure, the compatibility between the styrene-based viscosity modifier (epoxy resin) and polyisobutylene can be improved.

[0070] Examples of such compatibilizers include the hydrogenated styrene-isoprene block copolymer represented by the following formula (5). [ka] In formula (5) above, l and m represent the degree of polymerization.

[0071] In the compatibilizer, the proportion of units having a styrene-derived structure is, for example, 30 mol% or more, preferably 40 mol% or more, and for example, 70 mol% or less, preferably 60 mol% or less, relative to the total amount of units having a styrene-derived structure and units having an olefin-derived structure. Similarly, the proportion of units having an olefin-derived structure is, for example, 30 mol% or more, preferably 40 mol% or more, and for example, 70 mol% or less, preferably 60 mol% or less, relative to the total amount of units having a styrene-derived structure and units having an olefin-derived structure.

[0072] More preferably, in the compatibilizer, the proportion of units having a styrene-derived structure and the proportion of units having an olefin-derived structure are the same. That is, the proportion of units having a styrene-derived structure is 50 mol% of the total amount of units having a styrene-derived structure and units having an olefin-derived structure, and the proportion of units having an olefin-derived structure is 50 mol%. It is preferable that the proportion of units having a styrene-derived structure in the compatibilizer is 0.5 to 10 with respect to the molecular chain of the styrene-based viscosity modifier.

[0073] Commercially available compatibilizers can also be used. An example of a commercially available compatibilizer is Septon 1020 (manufactured by Kuraray Co., Ltd.).

[0074] Compatibilizers can be used alone or in combination of two or more types.

[0075] The proportion of the compatibilizer is 30 parts by mass or more, preferably 40 parts by mass or more, and 120 parts by mass or less, preferably 90 parts by mass or less, and more preferably 70 parts by mass or less, per 100 parts by mass of polyisobutylene.

[0076] If the blending ratio of the compatibilizer to 100 parts by mass of polyisobutylene is above the lower limit mentioned above, the compatibility (specifically, the compatibility between the styrene-based viscosity modifier (epoxy resin) and polyisobutylene) and low moisture permeability can be improved.

[0077] On the other hand, if the blending ratio of the compatibilizer to 100 parts by mass of polyisobutylene is below the above lower limit, the above-mentioned compatibility and low water permeability will decrease.

[0078] Furthermore, if the blending ratio of the compatibilizer to 100 parts by mass of polyisobutylene is below the above upper limit, the low moisture permeability can be improved.

[0079] On the other hand, if the blending ratio of the compatibilizer to 100 parts by mass of polyisobutylene exceeds the above upper limit, the low moisture permeability decreases.

[0080] Furthermore, the blending ratio of the compatibilizer is 80 parts by mass or more, preferably 120 parts by mass or more, and 350 parts by mass or less, preferably 250 parts by mass or less, and more preferably 200 parts by mass or less, per 100 parts by mass of the styrene-based viscosity modifier.

[0081] If the blending ratio of the compatibilizer to 100 parts by mass of the styrene-based viscosity modifier is above the lower limit mentioned above, the low moisture permeability can be improved.

[0082] On the other hand, if the mixing ratio of the compatibilizer to 100 parts by mass of the styrene-based viscosity modifier is below the above lower limit, the low water permeability will decrease.

[0083] Furthermore, if the blending ratio of the compatibilizer to 100 parts by mass of the styrene-based viscosity modifier is below the above upper limit, the compatibility (specifically, the compatibility between the styrene-based viscosity modifier (epoxy resin) and polyisobutylene) and low moisture permeability can be improved.

[0084] On the other hand, if the blending ratio of the compatibilizer to 100 parts by mass of the styrene-based viscosity modifier exceeds the above upper limit, the compatibility and low water permeability will decrease.

[0085] Furthermore, the proportion of the compatibilizer added is, for example, 5 parts by mass or more, preferably 8 parts by mass or more, and for example, 25 parts by mass or less, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less, based on 100 parts by mass of the total amount of epoxy resin, styrene viscosity modifier, polyisobutylene, and compatibilizer.

[0086] <Additives> The epoxy resin composition may contain additives in appropriate proportions as needed.

[0087] Examples of additives include polymerization initiators, other viscosity modifiers, leveling agents, silane coupling agents, fillers, sensitizers, antioxidants, anti-aging agents, plasticizers, UV absorbers, preservatives, and antimicrobial agents.

[0088] Additives can be used individually or in combination of two or more types.

[0089] [Polymerization initiator] Examples of polymerization initiators include thermal cationic polymerization initiators and photocationic polymerization initiators. A thermal cationic polymerization initiator is preferred as the polymerization initiator.

[0090] A thermal cationic polymerization initiator is a thermal acid generator that produces acid (cations) upon heating.

[0091] As a thermal cationic polymerization initiator, known thermal cationic polymerization initiators can be used. For example, AsF 6- SbF 6- , PF 6- BF 4- , B(C6F5)4 - CF3SO3 - Examples of salts that use the following as counter anions include sulfonium salts, phosphonium salts, quaternary ammonium salts, diazonium salts, and iodonium salts.

[0092] Polymerization initiators can be used alone or in combination of two or more types.

[0093] The mixing ratio of the polymerization initiator is, for example, 1 part by mass or more, preferably 2 parts by mass or more, and for example, 5 parts by mass or less, per 100 parts by mass of epoxy resin.

[0094] Furthermore, the blending ratio of the polymerization initiator is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and for example, 5.0 parts by mass or less, preferably 2.0 parts by mass or less, based on 100 parts by mass of the total amount of epoxy resin, styrene viscosity modifier, polyisobutylene, and compatibilizer.

[0095] [Other viscosity modifiers] Other viscosity modifiers are viscosity modifiers other than the styrene-based viscosity modifiers described above. Specifically, examples of other viscosity modifiers include petroleum resins, terpene resins, phenolic resins, and rosin resins. Petroleum resins are preferred as other viscosity modifiers.

[0096] Other viscosity modifiers can also be commercially available. For example, QTN-1500 (petroleum resin, manufactured by Nippon Zeon Co., Ltd.) is one such commercially available viscosity modifier.

[0097] Other viscosity modifiers can be used alone or in combination of two or more types.

[0098] The proportion of other viscosity modifiers is, for example, 10 parts by mass or more, preferably 15 parts by mass or more, and for example, 30 parts by mass or less, preferably 20 parts by mass or less, based on 100 parts by mass of the total amount of epoxy resin, styrene-based viscosity modifier, polyisobutylene, and compatibilizer.

[0099] [Leveling agent] Leveling agents are components used to improve the flatness of encapsulants obtained using epoxy resin compositions.

[0100] Examples of leveling agents include silicone-based leveling agents, acrylic-based leveling agents, and fluorine-based leveling agents. Silicone-based leveling agents are preferred as leveling agents.

[0101] Leveling agents can be used alone or in combination of two or more types.

[0102] The blending ratio of the leveling agent is, for example, 0.1 parts by mass or more, and for example, 1.0 part by mass or less, preferably 0.5 parts by mass or less, based on 100 parts by mass of the total amount of epoxy resin, styrene viscosity modifier, polyisobutylene, and compatibilizer.

[0103] [Silane coupling agent] Examples of silane coupling agents include silane compounds having an epoxy group, silane compounds having a carboxyl group, silane compounds having a methacryloyl group, silane compounds having an acid anhydride group, and silane compounds having an isocyanate group. Preferably, silane compounds having an epoxy group are used as silane coupling agents.

[0104] Silane coupling agents can be used alone or in combination of two or more types.

[0105] The proportion of the silane coupling agent is, for example, 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and for example, 3.0 parts by mass or less, preferably 1.0 part by mass or less, based on 100 parts by mass of the total amount of epoxy resin, styrene viscosity modifier, polyisobutylene, and compatibilizer.

[0106] [Filling material] Examples of fillers include silica, alumina, oxides (e.g., titanium oxide, magnesium oxide), and hydroxides (e.g., aluminum hydroxide, magnesium hydroxide). Silica is preferred as a filler.

[0107] The fillers can be used individually or in combination of two or more types.

[0108] The proportion of the filler is, for example, 5 parts by mass or more, preferably 10 parts by mass or more, and for example, 50 parts by mass or less, preferably 30 parts by mass or less, based on 100 parts by mass of the total amount of epoxy resin, styrene viscosity modifier, polyisobutylene, and compatibilizer.

[0109] <Preparation of epoxy resin composition> To prepare an epoxy resin composition, epoxy resin, a styrene-based viscosity modifier, polyisobutylene, a compatibilizer, and additives as needed are mixed. In particular, when a polymerization initiator is included, the other components are mixed first, and then the polymerization initiator is added. This prepares the epoxy resin composition.

[0110] Furthermore, the epoxy resin composition can be diluted with a known organic solvent. In other words, the epoxy resin composition can be prepared as a varnish for epoxy resin compositions.

[0111] When an epoxy resin composition is diluted with a known organic solvent (e.g., methyl ethyl ketone and toluene), the solid content concentration of the varnish of the epoxy resin composition is, for example, 10% by mass or more, and for example, 50% by mass or less.

[0112] Such epoxy resin compositions exhibit excellent compatibility (specifically, compatibility between styrene-based viscosity modifiers (epoxy resins) and polyisobutylene) and low moisture permeability. Therefore, they can be suitably used as encapsulating materials for sealing optical elements.

[0113] More specifically, the sealing material includes the cured product of the epoxy resin composition described above.

[0114] If the epoxy resin composition contains a thermal cationic polymerization initiator, the epoxy resin composition is cured by heating it.

[0115] The heating conditions include a curing temperature of, for example, 60°C or higher, and for example, 100°C or lower. The heating time is, for example, 1 minute or more, and for example, 60 minutes or less.

[0116] The cured product of the epoxy resin composition is preferably transparent. Specifically, the total light transmittance (in accordance with JIS K 7361-1) of the cured product of the epoxy resin composition is, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and also, for example, 100% or less.

[0117] Since the sealing material contains the cured product of the epoxy resin composition described above, it exhibits excellent low moisture permeability.

[0118] <Image display device> The image display device comprises an optical element and the sealing material that seals the optical element. Because the image display device includes the sealing material, it has excellent low moisture permeability.

[0119] <Effects and Effects> The epoxy resin composition contains polyisobutylene. Therefore, it exhibits excellent low moisture permeability.

[0120] Furthermore, this epoxy resin composition contains a predetermined proportion of a compatibilizer (a compatibilizer having a diblock structure containing both styrene-derived and olefin-derived structures) relative to both polyisobutylene and a styrene-based viscosity modifier. Therefore, it exhibits excellent compatibility.

[0121] More specifically, the compatibilizer possesses both a structure similar to that of a styrene-based viscosity modifier and a structure similar to that of polyisobutylene.

[0122] Furthermore, the compatibilizer has a diblock structure in which the styrene-derived structure and the olefin-derived structure are combined.

[0123] Therefore, the compatibility between styrene-based viscosity modifiers and epoxy resins that have excellent compatibility with them, and polyisobutylene is improved.

[0124] On the other hand, if the compatibilizer contains styrene-derived structures and olefin-derived structures, but these do not have a diblock structure, for example, if it is a block copolymer consisting of a styrene-derived structure, an olefin-derived structure, and a styrene-derived structure, the distance between the styrene-derived structures at both ends is limited by chemical bonds. Therefore, unless a styrene-based viscosity modifier is adjacent to both ends, the compatibility will not improve.

[0125] In contrast, the compatibilizer in this epoxy resin composition has a styrene-derived structure at one end and an olefin-derived structure at the other end, thus reliably improving compatibility.

[0126] Since the sealing material contains the cured product of the epoxy resin composition described above, it exhibits excellent low moisture permeability. [Examples]

[0127] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts" and "%" are based on mass. Furthermore, specific numerical values ​​such as blending ratios (content), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than") of the blending ratios (content), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0128] <Details of ingredients> The trade names and abbreviations of the components used in each example and comparative example are described in detail below. CEL2021P: 3,4-Epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate, an epoxy resin containing the ECH structure shown in the above general formula (4), trade name "Celoxide 2021P", molecular weight: 252.3, epoxy equivalent: 128~145 g / eq., manufactured by Daicel Corporation. jER-4005P: Room temperature solid bisphenol F type epoxy resin, weight-average molecular weight 7582, epoxy equivalent 10000 g / eq., product name "jER4005P", manufactured by Mitsubishi Chemical Corporation. XY-6954B35: Room temperature solid biphenyl-type epoxy resin, weight-average molecular weight 36,691, epoxy equivalent 10,000 g / eq., trade name "XY-6954B35", manufactured by Mitsubishi Chemical Corporation. FTR-8120: Styrene-based viscosity modifier, weight-average molecular weight 1420, manufactured by Mitsui Chemicals, Inc. FTR-8100: Styrene-based viscosity modifier, weight-average molecular weight 1420, manufactured by Mitsui Chemicals, Inc. TETRAX-3T: Polyisobutylene, trade name "Tetrax Grade 3T", weight-average molecular weight 49000, manufactured by ENEOS Corporation. TETRAX-6T: Polyisobutylene, trade name "Tetrax Grade 6T", weight-average molecular weight 80,000, manufactured by ENEOS Corporation. Septon-1020: Compatibilizer, hydrogenated styrene-isoprene block copolymer (percentage of units with styrene-derived structure: 50%, percentage of units with olefin-derived structure: 50%), manufactured by Kuraray Co., Ltd. ToughTec M1943: Compatibilizer, polystyrene-polybutadiene-polystyrene block copolymer, manufactured by Asahi Kasei Corporation. CXC-1733: Thermal cationic polymerization initiator, manufactured by Kusumoto Chemical Co., Ltd. QTN-1500: Other viscosity modifiers, petroleum resin, manufactured by Nippon Zeon Co., Ltd. BYK-302: Silicone-based leveling agent, manufactured by Big Chemie. KBM-403:3-Glycidoxypropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. X12-967C: Silane coupling agent containing acid anhydride, manufactured by Shin-Etsu Chemical Co., Ltd. KBM-4803: Silane compound containing an epoxy group, manufactured by Shin-Etsu Chemical Co., Ltd. EP4088L: Epoxy resin with a dicyclopentadiene skeleton, manufactured by ADEKA. SC-2050MB: Filler, silica, manufactured by Admatex Co., Ltd.

[0129] <Preparation of epoxy resin composition> Example 1~ 6. Example 8~ Example 11, and Comparative Examples 1-1 6 Based on the formulations described in Tables 1 to 3, epoxy resin compositions were prepared by blending each component. Specifically, first, all components except the polymerization initiator were blended in a flask. Next, 50 parts by mass of methyl ethyl ketone and 50 parts by mass of toluene were added and dissolved by stirring at room temperature. Then, the polymerization initiator was added and stirred at room temperature. This prepared a varnish of the epoxy resin composition.

[0130] <Rating> [compatibility] The varnish state of the epoxy resin compositions in each example and comparative example was observed visually. Compatibility was evaluated based on the following criteria. The results are shown in Tables 1 to 3. {standard} ○: The varnish of the epoxy resin composition was transparent. ×: In the epoxy resin varnish, turbidity and / or aggregates were observed.

[0131] [Coating properties] The epoxy resin varnishes of each example and comparative example were applied to a PET film (release-treated PET film (product name: PET75x1H-ASI5, manufactured by Nippa Co., Ltd., thickness: 75 μm, base film)) using a coating machine, and then dried in a nitrogen-purged oven at 80°C for 3 minutes to form a coating film (thickness: 15 μm). The coating properties were evaluated based on the following criteria. The results are shown in Tables 1 to 3. {standard} ○: No coating streaks and / or defects were observed. ×: Coating streaks and / or imperfections were observed.

[0132] [Peelability] The peelability was evaluated based on the following criteria. The results are shown in Tables 1 to 3. {standard} ○: The resin alone could be removed from the PET film. ×: The resin could not be removed from the PET film on its own, or the resin film was damaged due to scratches, holes, etc.

[0133] [Low moisture permeability] In the peelability evaluation, the peeled coating film was subjected to a 24-hour moisture permeability test in a constant temperature and humidity chamber at 60°C and 95% RH, in accordance with the JIS Z 0208 moisture permeability test (cup method), and the moisture permeability was measured. Lower moisture permeability is considered to indicate superior low moisture permeability. The results are shown in Tables 1 to 3. In the coating performance evaluation, coating films that could not be peeled off are indicated as "unmeasurable" in Tables 2 and 3. Furthermore, even if the coating film could not be peeled off, if there were small holes and / or cracks, moisture permeability could not be measured and was indicated as "unmeasurable".

[0134] [Table 1]

[0135] [Table 2]

[0136] [Table 3]

[0137] The above invention is provided as an illustrative embodiment of the present invention, but this is merely illustrative and should not be interpreted restrictively. Modifications of the present invention that are obvious to those skilled in the art are included in the claims below. [Industrial applicability]

[0138] The epoxy resin composition, encapsulant, and image display device of the present invention can be suitably used, for example, in the manufacture of organic EL displays.

Claims

1. It contains epoxy resin, a styrene-based viscosity modifier, polyisobutylene, and a compatibilizer. The compatibilizer has a diblock structure comprising a styrene-derived structure and an olefin-derived structure. The proportion of the compatibilizer is 30 parts by mass or more and 120 parts by mass or less per 100 parts by mass of polyisobutylene. The blending ratio of the aforementioned compatibilizer is 80 parts by mass or more and 350 parts by mass or less per 100 parts by mass of the styrene-based viscosity modifier. The aforementioned polyisobutylene consists solely of polyisobutylene having a weight-average molecular weight of 49,000 or less. The epoxy resin is an epoxy resin composition comprising an alicyclic epoxy resin and an aromatic epoxy resin.

2. A sealing material comprising a cured product of the epoxy resin composition described in claim 1.

3. An image display device comprising an optical element and a sealing material according to claim 2 for sealing the optical element.

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