JP7554179B2 - Sheet-like adhesive, sealing sheet, sealed body of electronic device, and method for manufacturing sealed body of electronic device - Google Patents

Description

The present invention relates to a sheet-like adhesive that is preferably used as a material for forming a cured product that has excellent shape retention under high temperature conditions, an encapsulating sheet having the sheet-like adhesive, an encapsulated electronic device in which an electronic device is encapsulated with the cured product of the sheet-like adhesive, and a method for producing an encapsulated electronic device.

In recent years, organic EL elements have been attracting attention as light-emitting elements capable of emitting high-luminance light when driven by a low-voltage direct current.
However, organic EL elements have a problem in that their light-emitting characteristics, such as light-emitting luminance, light-emitting efficiency, and light-emitting uniformity, tend to deteriorate over time.
It was thought that the cause of this problem of decreased light-emitting characteristics was the infiltration of oxygen, moisture, and the like into the organic EL element, causing deterioration of the electrodes and organic layers. Therefore, a sealant was used to seal the organic EL element to prevent the infiltration of oxygen and moisture.

For example, Patent Document 1 describes a sheet-like sealing material for display elements that contains an epoxy resin having a weight-average molecular weight of 100 to 500, an epoxy resin having a weight-average molecular weight of 800 to 10,000, an epoxy resin having a weight-average molecular weight of 20,000 to 100,000, a specific photocationic polymerization initiator, and a photosensitizer.

JP 2018-159026 A

As described in Patent Document 1, a sheet adhesive containing an epoxy resin has been suitably used as a material for forming a sealing material.
However, according to the investigations of the present inventors, it has been found that a cured product of a sheet-like adhesive containing an epoxy resin may deform under high temperature conditions, and the sealing performance may be significantly reduced.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a sheet-like adhesive that is suitably used as a material for forming a cured product that has excellent shape retention under high temperature conditions, a sealing sheet having the sheet-like adhesive, a sealed electronic device in which an electronic device is sealed with the cured product of the sheet-like adhesive, and a method for manufacturing a sealed electronic device.

In order to solve the above problems, the present inventors conducted extensive research into sheet adhesives containing epoxy resins. As a result, they discovered that by using a phenoxy resin with a high glass transition temperature (Tg) as a binder resin, a cured product with excellent shape retention under high temperature conditions can be obtained, which led to the completion of the present invention.

Thus, according to the present invention, there are provided the following sheet-like adhesives [1] to [5], the sealing sheet [6], the sealed electronic device bodies [7] and [8], and the manufacturing methods for the sealed electronic device bodies [9] and [10].

[1] A sheet-form adhesive comprising the following components (A), (B), and (C):
Component (A): a phenoxy resin having a glass transition temperature (Tg) of 110°C or higher; Component (B): a multifunctional epoxy resin; Component (C): a photocationic polymerization initiator. [2] The sheet adhesive described in [1], wherein at least one of the components (B) is the following component (BL), and the content of the component (BL) is 50 mass% or more based on the entire sheet adhesive.
Component (BL): a multifunctional epoxy resin that is liquid at 25°C. [3] The sheet adhesive according to [1] or [2], further comprising the following component (D):
Component (D): a silane coupling agent having a long-chain spacer group. [4] The sheet-like adhesive according to any one of [1] to [3], which has a storage modulus at 80°C after curing of 500 MPa or more.
[5] The sheet-like adhesive according to any one of [1] to [4], which is used for sealing an electronic device.
[6] An encapsulating sheet having an adhesive layer made of the sheet-like adhesive according to any one of [1] to [5] above, and a functional film.
[7] A sealed electronic device in which an electronic device is sealed with an adhesive cured product layer, the adhesive cured product layer being a cured product of the sheet-like adhesive described in any one of [1] to [5].
[8] The sealed electronic device according to [7], wherein the sealed electronic device is an optical device.
[9] A method for producing a sealed electronic device, comprising the steps of:
Step (b1): A step of irradiating the sheet-like adhesive according to any one of [1] to [5] or the adhesive layer of the encapsulating sheet according to [6] with ultraviolet light to initiate a curing reaction. Step (b2): A step of attaching the sheet-like adhesive or adhesive layer after step (b1) to an electronic device.

The present invention provides a sheet-like adhesive that is suitable for use as a material for forming a cured product that has excellent shape retention under high temperature conditions, a sealing sheet having the sheet-like adhesive, a sealed electronic device in which an electronic device is sealed with the cured product of the sheet-like adhesive, and a method for producing a sealed electronic device.

The present invention will be described in detail below, dividing it into the following sections: 1) sheet-like adhesive, 2) sealing sheet, and 3) electronic device sealing body and its manufacturing method.

1) Sheet Adhesive The sheet adhesive of the present invention contains the following components (A), (B), and (C).
Component (A): a phenoxy resin having a glass transition temperature (Tg) of 110° C. or higher; Component (B): a multifunctional epoxy resin; Component (C): a photocationic polymerization initiator;

A sheet-like adhesive is an adhesive formed into a sheet shape that is non-fluid at room temperature (25°C). In the present invention, the sheet-like adhesive may be in the form of a strip or a long strip (band).

[Component (A)]
The sheet adhesive of the present invention contains, as component (A), a phenoxy resin having a glass transition temperature (Tg) of 110° C. or higher (hereinafter sometimes referred to as “phenoxy resin (A)”).

Phenoxy resin is a polymer whose main chain is a polyaddition structure of aromatic diol and aromatic diglycidyl ether. Phenoxy resin generally corresponds to a high molecular weight epoxy resin, and refers to one with a degree of polymerization of about 100 or more.

When the sheet adhesive contains phenoxy resin (A), the cured product of the sheet adhesive has excellent shape retention even under high temperature conditions.

The phenoxy resin (A) is also important in that it allows the properties of the component (B) to be fully exhibited.
That is, as described below, from the viewpoint of the tackiness of the sheet adhesive and the shape retention of the cured product of the sheet adhesive under high temperature conditions, it is preferable that the sheet adhesive contain a large amount of component (B).
However, sheet adhesives containing a large amount of component (B) have the problem that they tend to be poor in shape retention.
In particular, since a sheet adhesive containing component (C) may require a certain amount of time for the curing reaction to be completed, when such a sheet adhesive contains a large amount of component (B), it was necessary to improve the shape retention.
In this regard, the sheet adhesive of the present invention contains the phenoxy resin (A) and is therefore able to maintain a constant shape for a long period of time even when it contains a large amount of component (B).

The glass transition temperature (Tg) of the phenoxy resin (A) is 110°C or higher, preferably 120 to 180°C, and more preferably 140 to 165°C.
The phenoxy resin (A) having a glass transition temperature (Tg) of 110° C. or higher allows the sheet adhesive to maintain a constant shape for a long period of time. Furthermore, the cured product of the sheet adhesive exhibits excellent shape retention even under high temperature conditions.
The glass transition temperature (Tg) of the phenoxy resin (A) can be measured in accordance with JIS K 7121 using a differential scanning calorimeter.

The weight average molecular weight (Mw) of the phenoxy resin (A) is usually 10,000 to 200,000, preferably 20,000 to 100,000, and more preferably 30,000 to 80,000.
If the weight average molecular weight (Mw) of the phenoxy resin (A) is too small, the sheet adhesive tends to have difficulty in maintaining a constant shape, whereas if the weight average molecular weight (Mw) of the phenoxy resin (A) is too large, the sheet adhesive tends to have poor handleability.
The weight average molecular weight (Mw) of the phenoxy resin (A) can be determined in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

The epoxy equivalent of the phenoxy resin (A) is preferably 5,000 g/eq or more, more preferably 7,000 g/eq or more. The epoxy equivalent value can be measured in accordance with JIS K7236.

Examples of the phenoxy resin (A) include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol S type phenoxy resin, copolymer type phenoxy resin of bisphenol A type and bisphenol F type, bisphenol E type phenoxy resin, naphthalene type phenoxy resin, novolac type phenoxy resin, biphenyl type phenoxy resin, and cyclopentadiene type phenoxy resin.
These phenoxy resins (A) can be used alone or in combination of two or more.

The phenoxy resin (A) can be obtained by a method of reacting a difunctional phenol with an epihalohydrin to a high molecular weight, or by a method of subjecting a difunctional epoxy resin with a difunctional phenol to a polyaddition reaction.
The phenoxy resin (A) can be obtained, for example, by reacting a bifunctional phenol with an epihalohydrin in the presence of an alkali metal hydroxide in an inert solvent at a temperature of 40 to 120° C. The phenoxy resin (A) can also be obtained by subjecting a bifunctional epoxy resin and a bifunctional phenol to a polyaddition reaction in the presence of a catalyst such as an alkali metal compound, an organic phosphorus compound, a cyclic amine compound, or the like in an organic solvent having a boiling point of 120° C. or higher, such as an amide solvent, an ether solvent, a ketone solvent, a lactone solvent, or an alcohol solvent, by heating to 50 to 200° C. at a reaction solids concentration of 50% by weight or less.

The bifunctional phenols are not particularly limited as long as they are compounds having two phenolic hydroxyl groups. Examples of bifunctional phenols include monocyclic bifunctional phenols such as hydroquinone, 2-bromohydroquinone, resorcinol, and catechol; bisphenols such as bisphenol A, bisphenol F, bisphenol AD, and bisphenol S; dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl; dihydroxyphenyl ethers such as bis(4-hydroxyphenyl)ether; and those in which a linear alkyl group, a branched alkyl group, an aryl group, a methylol group, an allyl group, a cyclic aliphatic group, a halogen (such as tetrabromobisphenol A), or a nitro group has been introduced into the aromatic ring of the phenol skeleton; and polycyclic bifunctional phenols in which a linear alkyl group, a branched alkyl group, an allyl group, an allyl group with a substituent, a cyclic aliphatic group, or an alkoxycarbonyl group has been introduced into the carbon atom in the center of the bisphenol skeleton.

Examples of epihalohydrins include epichlorohydrin, epibromohydrin, and epiiodohydrin.

In addition, in the present invention, a commercially available product can be used as the phenoxy resin (A). Examples of commercially available phenoxy resins (A) include YX7200 (glass transition temperature: 150°C) and YX6954 (phenoxy resin containing a bisphenolacetophenone skeleton, glass transition temperature: 130°C) manufactured by Mitsubishi Chemical Corporation.

The content of the phenoxy resin (A) is preferably 15 to 47% by mass, and more preferably 25 to 45% by mass, based on the total mass of the sheet-like adhesive.
By ensuring that the content of the phenoxy resin (A) is within the above range, the shape retention and adhesiveness of the sheet adhesive, as well as the shape retention of the cured product under high temperature conditions, are maintained in a well-balanced manner.

[Component (B)]
The sheet adhesive of the present invention contains a polyfunctional epoxy resin (hereinafter sometimes referred to as polyfunctional epoxy resin (B)) as component (B).
"Multifunctional" means having two or more epoxy groups in the molecule.

The weight average molecular weight (Mw) of the polyfunctional epoxy resin (B) is preferably 100 to 5,000, more preferably 200 to 4,000.
The weight average molecular weight (Mw) of the polyfunctional epoxy resin (B) can be determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

The epoxy equivalent of the multifunctional epoxy resin (B) is preferably 100 g/eq or more and 500 g/eq or less, more preferably 115 g/eq or more and 300 g/eq or less. By curing a sheet-like adhesive containing a multifunctional epoxy resin (B) having an epoxy equivalent of 100 g/eq or more and 500 g/eq or less, a cured product with excellent adhesive strength can be obtained.

The content of the polyfunctional epoxy resin (B) is preferably 50% by mass or more, more preferably 52 to 70% by mass, and even more preferably 55 to 68% by mass, based on the total mass of the sheet-like adhesive.
By ensuring that the content of the polyfunctional epoxy resin (B) is within the above range, the shape retention and tackiness of the sheet-like adhesive, as well as the shape retention of the cured product under high temperature conditions, are maintained in a well-balanced manner.

Examples of polyfunctional epoxy resins (B) include aliphatic epoxy compounds (excluding alicyclic epoxy compounds), aromatic epoxy compounds, alicyclic epoxy compounds, etc.

Examples of aliphatic epoxy compounds include 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, tetraglycidyl ether of sorbitol, hexaglycidyl ether of dipentaerythritol, diglycidyl ether of polyethylene glycol, diglycidyl ether of polypropylene glycol, dicyclopentadiene dimethanol diglycidyl ether, etc.

Examples of aromatic epoxy compounds include glycidyl ethers of bisphenol A, bisphenol F, or compounds obtained by further adding alkylene oxide to these compounds, and epoxy novolac resins; polyglycidyl ethers of aromatic compounds having two or more phenolic hydroxyl groups, such as resorcinol, hydroquinone, and catechol; glycidyl ethers of aromatic compounds having two or more alcoholic hydroxyl groups, such as phenyldimethanol, phenyldiethanol, and phenyldibutanol; glycidyl esters of polybasic aromatic compounds having two or more carboxylic acids, such as phthalic acid, terephthalic acid, and trimellitic acid; and the like.

Examples of alicyclic epoxy compounds include polyglycidyl ethers of polyhydric alcohols having at least one alicyclic structure, such as hydrogenated bisphenol A, and cycloalkene oxide compounds such as cyclohexene oxide and cyclopentene oxide-containing compounds obtained by epoxidizing cyclohexene or cyclopentene ring-containing compounds with an oxidizing agent.

These polyfunctional epoxy resins (B) may be used alone or in combination of two or more. It is preferable that the polyfunctional epoxy resin (B) contains an alicyclic epoxy compound from the viewpoint of preventing coloration of the sheet adhesive.

At least one of the polyfunctional epoxy resins (B) is preferably the following component (BL).
Component (BL): A polyfunctional epoxy resin that is liquid at 25°C (hereinafter, may be referred to as liquid polyfunctional epoxy resin (BL)).
"Liquid at 25° C." means that it has fluidity at 25° C. The liquid polyfunctional epoxy resin (BL) preferably has a viscosity of 2 to 10,000 mPa·s as measured at 25° C. and 1.0 rpm using an E-type viscometer.

Sheet adhesives containing component (A) tend to have poor adhesion, but the sheet adhesive of the present invention contains the liquid multifunctional epoxy resin (BL) and therefore has sufficient adhesion.
In addition to the above effects, the liquid multifunctional epoxy resin (BL) forms a cured product with a high crosslink density and also tends to further enhance the shape retention of the cured product under high temperature conditions, so the sheet adhesive of the present invention is preferably used as a material for forming a cured product that has excellent shape retention under high temperature conditions.

The content of the liquid polyfunctional epoxy resin (BL) is preferably 50% by mass or more, more preferably 52 to 70% by mass, and even more preferably 55 to 68% by mass, based on the total mass of the sheet adhesive.
When the amount of the liquid polyfunctional epoxy compound (BL) is 50 mass % or more based on the total amount of the sheet adhesive, a sheet adhesive having superior adhesion can be efficiently obtained.

[Component (C)]
The sheet adhesive of the present invention contains a cationic photopolymerization initiator as component (C).
A sheet adhesive containing a photocationic polymerization initiator has excellent versatility.
In other words, since sheet adhesives containing photoradical polymerization initiators tend to complete their curing reaction in a short period of time, the method of using sheet adhesives containing photoradical polymerization initiators is usually limited to attaching the sheet adhesive to an object and then irradiating the sheet adhesive with light to cure it.
On the other hand, the sheet adhesive of the present invention, which contains a photocationic polymerization initiator, requires a certain amount of time for the curing reaction to be completed, and therefore is not limited to use in which the sheet adhesive is attached to an object and then cured; the sheet adhesive may be attached to an object after the curing reaction has been initiated.

In addition, the characteristic that it takes a certain amount of time for the curing reaction to be completed may cause a problem that the sheet adhesive may deform before the curing reaction is completed, making it impossible to fix the object at the intended position. In particular, sheet adhesives containing a liquid multifunctional epoxy resin (BL) tend to have high fluidity, making them prone to this problem.
In this regard, the sheet adhesive of the present invention, even when it contains a liquid multifunctional epoxy resin (BL), contains a phenoxy resin (A) with a high Tg, and therefore is able to maintain a certain shape until the curing reaction is complete, and to fix the object in the desired position.

A photocationic polymerization initiator is a compound that generates cationic species when irradiated with ultraviolet light, initiating the curing reaction of a cationic curable compound. It consists of a cationic portion that absorbs ultraviolet light and an anionic portion that serves as a source of acid generation.

Examples of photocationic polymerization initiators include sulfonium salt compounds, iodonium salt compounds, phosphonium salt compounds, ammonium salt compounds, antimony salt compounds, diazonium salt compounds, selenium salt compounds, oxonium salt compounds, and bromine salt compounds. Among these, sulfonium salt compounds are preferred because of their excellent compatibility with other components, and aromatic sulfonium salt compounds having an aromatic group are more preferred.

Sulfonium salt compounds include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 4,4'-bis[diphenylsulfonio]diphenylsulfide-bishexafluorophosphate, 4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide-bishexafluoroantimonate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluorophosphate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluorophosphate, -isopropylthioxanthone hexafluoroantimonate, 7-[di(p-toluyl)sulfonio]-2-isopropyltetrakis(pentafluorophenyl)borate, phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluorophosphate, phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluoroantimonate, 4-tert-butylphenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluorophosphate, 4-tert-butylphenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide 4-(4-(2-chlorobenzoyl)phenylthio)phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate, 4,4',4''-tetrakis(pentafluorophenyl)borate, 4-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate, 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, 4-{4-(2-chlorobenzoyl)phenylthio}phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate, thiophenyldiphenylsulfonium hexafluoroantimonate halide, 4,4',4''-tetrakis(pentafluorophenyl)borate, tris(β-hydroxyethoxyphenyl)sulfonium hexafluoroantimonate, 4,4'-bis[diphenylsulfonio]diphenylsulfide-bishexafluoroantimonate, diphenyl[4-(phenylthio)phenyl]sulfonium trifluorotrispentafluoroethylphosphate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium tris[(trifluoromethyl)sulfonyl]methanide, and salts in which the cation moiety is 4-(phenylthio)phenyldiphenylsulfonium and the anion moiety is a phosphorus-based anion to which fluorine and a perfluoroalkyl group are added.

Examples of iodonium salt compounds include diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di(4-nonylphenyl)iodonium hexafluorophosphate, (tricumyl)iodonium tetrakis(pentafluorophenyl)borate, etc.

Examples of phosphonium salt compounds include tri-n-butyl(2,5-dihydroxyphenyl)phosphonium bromide and hexadecyltributylphosphonium chloride.

Examples of ammonium salt compounds include benzyltrimethylammonium chloride, phenyltributylammonium chloride, and benzyltrimethylammonium bromide.

Examples of antimonate compounds include triphenylsulfonium hexafluoroantimonate, p-(phenylthio)phenyl diphenylsulfonium hexafluoroantimonate, 4-chlorophenyl diphenylsulfonium hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluoroantimonate, and diaryliodonium hexafluoroantimonate.

These photocationic polymerization initiators can be used alone or in combination of two or more.

In addition, commercially available products can be used as the photocationic polymerization initiator. Commercially available products include Cyracure UVI-6970, Cyracure UVI-6974, Cyracure UVI-6990, and Cyracure UVI-950 (all manufactured by Union Carbide Corporation), Irgacure 250, Irgacure 261, and Irgacure 264 (all manufactured by Chiba Specialty Chemicals), SP-150, SP-151, SP-170, and Optomer SP-171 (all manufactured by ADEKA Corporation), CG-24-61 (manufactured by Chiba Specialty Chemicals), and DAICAT. II (manufactured by Daicel), UVAC1590, UVAC1591 (manufactured by Daicel-Cytec), CI-2064, CI-2639, CI-2624, CI-2481, CI-2734, CI-2855, CI-2823, CI-2758, CIT-1682 (manufactured by Nippon Soda Co., Ltd.), PI-2074 (manufactured by Rhodia), FFC509 (manufactured by 3M), BBI-102, BBI-101, BBI-103, MPI-103, TPS-103, MDS -103, DTS-103, NAT-103, NDS-103 (all manufactured by Midori Chemical Industry Co., Ltd.), CD-1010, CD-1011, CD-1012 (manufactured by Sartomer Co., Ltd.), CPI-100P, CPI-101A, CPI-200K, CPI-310B (all manufactured by San-Apro Co., Ltd.), San-Aid SI-60, San-Aid SI-80, San-Aid SI-100, San-Aid SI-110, San-Aid SI-150 (all manufactured by Sanshin Chemical Industry Co., Ltd.), and the like.

The content of the photocationic polymerization initiator is typically 0.1 to 10 parts by mass, preferably 0.3 to 8 parts by mass, and more preferably 0.5 to 6 parts by mass, per 100 parts by mass of component (B).

[Component (D)]
The sheet adhesive of the present invention preferably contains, as component (D), a silane coupling agent having a long-chain spacer group (hereinafter sometimes referred to as "silane coupling agent (D)").
The cured product of the sheet adhesive containing the silane coupling agent (D) exhibits superior adhesive strength.

A silane coupling agent is a silane compound having a silicon atom, a functional group, and a hydrolyzable group bonded to the silicon atom.

The long-chain spacer group refers to a divalent group that connects a silicon atom and a functional group, and has three or more atoms constituting the main chain.
The number of atoms constituting the main chain is preferably 3 to 12, and more preferably 6 to 10.
Examples of the long-chain spacer group include polymethylene groups such as a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, a nonamethylene group, a decamethylene group, an undecamethylene group, and a dodecamethylene group.

The functional group refers to a group that is reactive with other compounds (mainly organic compounds).
Examples of the functional group include a vinyl group, an allyl group, an epoxy group, a glycidoxy group, a 3,4-epoxycyclohexyl group, an amino group, a substituted amino group, an acryl group, a methacryl group, a mercapto group, an isocyanate group, and a group having an acid anhydride structure.
Among these, groups having a cyclic ether structure, such as an epoxy group, a glycidoxy group, or a 3,4-epoxycyclohexyl group, are preferred as the functional group, since they tend to give a cured product that has excellent shape retention even under high temperature conditions.

Examples of "hydrolyzable groups" include alkoxy groups such as methoxy and ethoxy groups; halogen atoms such as chlorine and bromine atoms; and the like.

Examples of silane coupling agents (D) include compounds represented by the following formula:

R ¹ represents a functional group, and R ² represents an alkyl group having 1 to 5 carbon atoms. A plurality of R ² may be the same or different. x represents an integer of 6 or more.
Examples of the functional group of R ¹ include those mentioned above. Examples of the alkyl group having 1 to 5 carbon atoms of R ² include a methyl group, an ethyl group, and the like.
x is an integer of 3 or more, preferably an integer of 3 to 12, and more preferably an integer of 6 to 10.

Specific examples of the silane coupling agent (D) include 8-glycidoxyoctyltrimethoxysilane, 8-glycidoxyoctyltriethoxysilane, 8-acryloyloxyoctyltrimethoxysilane, 8-acryloyloxyoctyltriethoxysilane, 8-methacryloyloxyoctyltrimethoxysilane, 8-methacryloyloxyoctyltriethoxysilane, 8-vinyloctyltrimethoxysilane, and 8-vinyloctyltriethoxysilane.
The silane coupling agent (D) can be used alone or in combination of two or more kinds.

When the sheet adhesive contains a silane coupling agent (D), the content of the silane coupling agent (D) is preferably 0.01 to 5 parts by mass, more preferably 0.02 to 3 parts by mass, per 100 parts by mass of the (B) component.

[Other ingredients]
The sheet adhesive of the present invention may contain other components as long as the effects of the present invention are not impaired.
Examples of other components include additives such as silane coupling agents other than the silane coupling agent (D), ultraviolet absorbers, antistatic agents, light stabilizers, antioxidants, resin stabilizers, fillers, pigments, extenders, and softeners.
These may be used alone or in combination of two or more.
When the sheet adhesive of the present invention contains these additives, the content thereof can be appropriately determined depending on the purpose.

[Sheet adhesive]
The thickness of the sheet adhesive of the present invention is usually 1 to 50 μm, preferably 2 to 40 μm, and more preferably 5 to 30 μm. A sheet adhesive having a thickness within the above range is suitably used as a material for forming an encapsulant.
The thickness of the sheet-like adhesive can be measured using a known thickness meter in accordance with JIS K 7130 (1999). In addition, when the sheet-like adhesive has a release film as described below, the thickness of the sheet-like adhesive does not include the thickness of the release film.

From the standpoint of protection from the external environment, it is preferable that the sheet-like adhesive of the present invention has a release film on at least one side, and it may have a release film on both sides.

Note that the sheet adhesive of the present invention having a release film on at least one side represents the state before use, and when using the sheet adhesive of the present invention, the release film is usually peeled off and removed. When the sheet adhesive has release films on both sides, the release film with the lower release strength is usually peeled off and removed first.

As the release film, a resin film can usually be used.
Examples of the resin component of the resin film include polyimide, polyamide, polyamideimide, polyphenylene ether, polyether ketone, polyether ether ketone, polyolefin, polyester, polycarbonate, polysulfone, polyether sulfone, polyphenylene sulfide, polyarylate, acrylic resin, cycloolefin polymer, aromatic polymer, polyurethane polymer, etc. Among these, polyester resin is preferable.

When the release film has a release agent layer, examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, fluorine-based resins, etc.

The thickness of the release film is usually 10 to 300 μm, preferably 10 to 200 μm, and more preferably 15 to 100 μm.

The method for producing the sheet adhesive of the present invention is not particularly limited. For example, it can be produced using a casting method.

The method for producing a sheet-type adhesive by the casting method involves applying the adhesive composition to a release film using a known method, and then drying the resulting coating to obtain a sheet-type adhesive with a release film.

The adhesive composition can be prepared by mixing and stirring the above-mentioned components (A), (B), and (C), and, if desired, other components, by a known method.
When a solvent is used in preparing the adhesive composition, the viscosity of the adhesive composition can be appropriately adjusted by the amount of the solvent used.

Examples of the solvent include aliphatic hydrocarbon solvents such as n-hexane and n-heptane; aromatic hydrocarbon solvents such as toluene and xylene; halogenated hydrocarbon solvents such as dichloromethane, ethylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, and monochlorobenzene;
Examples of the solvent include alcohol-based solvents such as methanol, ethanol, propanol, butanol, and propylene glycol monomethyl ether; ketone-based solvents such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; ester-based solvents such as ethyl acetate and butyl acetate; cellosolve-based solvents such as ethyl cellosolve; and ether-based solvents such as 1,3-dioxolane.
These solvents may be used alone or in combination of two or more.
The content of the solvent can be appropriately determined taking into consideration the coatability, film thickness, and the like.

The release film used in the production of the sheet adhesive functions as a support during the manufacturing process of the sheet adhesive, and also functions as a release film for the above-mentioned sheet adhesive until the sheet adhesive is used.

Methods for applying the adhesive composition include, for example, spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

Methods for drying the coating of the adhesive composition include conventionally known drying methods such as hot air drying, heated roll drying, and infrared irradiation.
The coating film is dried, for example, at 80 to 150° C. for 30 seconds to 5 minutes.

The sheet adhesive of the present invention can be cured by exposure to ultraviolet light.
Specific examples of the ultraviolet light source include light sources such as ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arc lamps, black light fluorescent lamps, metal halide lamps, etc. The wavelength of the ultraviolet light to be irradiated may be in the wavelength range of 190 to 380 nm.
The type, dose, and duration of irradiation of ultraviolet light can be appropriately determined depending on the components of the sheet adhesive to be irradiated and the content of each component.
The irradiation illuminance is preferably about 20 to 1000 mW/cm ² , and the light quantity is preferably about 50 to 3000 mJ/cm ² .

The storage modulus at 80° C. of the cured product of the sheet-like adhesive of the present invention is preferably 500 MPa or more, more preferably 800 to 3000 MPa, and even more preferably 1200 to 2500 MPa.
A cured product having a storage modulus of 500 MPa or more at 80° C. is unlikely to deform even under high-temperature conditions, and therefore such a cured product can be preferably used as a sealing material whose performance is hardly deteriorated even under high-temperature conditions.
The storage modulus at 80° C. of the cured product can be measured by the method described in the examples.

Because of the above-mentioned properties, the sheet adhesive of the present invention is suitable for use as a material for forming a sealant for electronic devices.
Examples of the electronic device include various elements constituting the sealing body of the electronic device described below, such as an organic EL element, a liquid crystal element, and an electronic paper element.

2) Encapsulating Sheet The encapsulating sheet of the present invention has an adhesive layer made of the sheet-like adhesive of the present invention and a functional film.

Examples of the functional film include a conductive film, a gas barrier film, an anti-reflection film, a retardation film, a viewing angle improving film, and a brightness improving film. Among these, for example, the gas barrier film includes a film having a metal or inorganic compound film, and a film having a metal film is preferred. Examples of the metal used include aluminum, zinc, copper, and the like, and among these, aluminum is preferred.
The thickness of the functional film used in the present invention is not particularly limited, but is usually 5 to 200 μm, preferably 10 to 100 μm.
When the functional film is a film having a metal or inorganic compound film, the functional film may have low transmittance of ultraviolet light. Such a functional film usually has a transmittance of 60% or less for ultraviolet light having a wavelength of 365 nm. When the functional film has low transmittance of ultraviolet light, the advantage of the manufacturing method (β) described below becomes prominent. From this viewpoint, when manufacturing an electronic device sealed body using the manufacturing method (β), the transmittance of the functional film for ultraviolet light having a wavelength of 365 nm is preferably 55% or less, more preferably 50% or less.

The encapsulating sheet of the present invention may have at least the functional film and an adhesive layer made of the sheet-like adhesive of the present invention.
The functional film may have one layer or two or more layers, and the adhesive layer may have one layer or two or more layers.
When the functional film is a gas barrier film having a metal or inorganic compound film and a resin film, in order to prevent water vapor that has entered from the end of the resin film from migrating to the sealed device, it is preferable that the adhesive layer is provided on a side closer to the metal or inorganic compound film than the resin film, and that the adhesive layer and the resin film are separated by the metal or inorganic compound film.

The encapsulating sheet of the present invention may further have other layers.
Examples of other layers include a primer layer that improves adhesion at the interface between the adhesive layer and the functional film, a functional coating layer or a protective film that is provided on the side of the functional film that does not have an adhesive layer, and an antistatic layer or a stress relaxation layer that can be formed on both sides of the functional film.

The thickness of the sealing sheet of the present invention is usually 6 to 270 μm. The thickness of the sealing sheet does not include members such as a release film and a protective film that are peeled off and removed before use.

The encapsulating sheet of the present invention can be produced, for example, by bonding the sheet-like adhesive of the present invention to a functional film.

3) Sealed Electronic Device The sealed electronic device of the present invention is an electronic device sealed with an adhesive cured product layer that is a cured product of the sheet-like adhesive of the present invention.

The electronic devices include those described above.
The adhesive cured product layer is formed by curing the sheet-like adhesive of the present invention. The adhesive cured product layer may be formed by curing the adhesive layer of the encapsulating sheet of the present invention.

The cured product of the sheet-like adhesive of the present invention can easily be made colorless and transparent. Because of this characteristic, it is preferable that the encapsulated body of the electronic device is an optical device such as a light-emitting device, a light-receiving device, or a display device.
Examples of light-related devices include organic EL displays, organic EL lighting, liquid crystal displays, electronic paper, etc. The encapsulated body of the electronic device is more preferably a display device such as an organic EL display, a liquid crystal display, or electronic paper.

The sealed electronic device can be manufactured by the manufacturing method (α) having the following steps (a1) and (a2) or the manufacturing method (β) having the following steps (b1) and (b2).

[Production method (α)]
Step (a1): A step of attaching the sheet-like adhesive of the present invention or the adhesive layer of the encapsulating sheet of the present invention to an electronic device to produce a laminate. Step (a2): A step of irradiating the sheet-like adhesive or the adhesive layer in the laminate obtained in step (a1) with ultraviolet light.

The production method (α) involves attaching a sheet-like adhesive to an electronic device and then initiating a curing reaction of the sheet-like adhesive.
After the curing reaction started in step (a2) is completed, a known process is carried out to produce the desired sealed electronic device.
The production method (α) is preferably used when producing sealed electronic devices with good productivity.

[Production method (β)]
Step (b1): A step of irradiating the sheet-like adhesive of the present invention or the adhesive layer of the encapsulating sheet of the present invention with ultraviolet light to initiate a curing reaction. Step (b2): A step of attaching the sheet-like adhesive or adhesive layer after step (b1) to an electronic device before the curing reaction is completed.

In the production method (β), after the curing reaction of the sheet-shaped adhesive is initiated, the sheet-shaped adhesive is attached to an electronic device before the curing reaction is completed.
After the step (b2) and after the curing reaction started in the step (b1) is completed, a known step can be carried out to produce the desired sealed electronic device.
The sheet adhesive of the present invention initiates a curing reaction by the cationic photopolymerization initiator, and requires a certain amount of time until the curing reaction is completed. Therefore, the production method (β) can be used to produce an encapsulated electronic device.
The manufacturing method (β) is preferably used in cases where there is a risk of the electronic device being damaged by ultraviolet light irradiation, or where the encapsulating sheet is located outside the adhesive layer (on the side distal to the electronic device to which it is attached) and where a layer having ultraviolet light blocking properties is present as a layer such as a functional film.

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

[Compounds used in the Examples and Comparative Examples]
Phenoxy resin (A1): (manufactured by Mitsubishi Chemical Corporation, product name: YX7200B35, glass transition temperature: 150° C.)
Phenoxy resin (A2): (manufactured by Mitsubishi Chemical Corporation, product name: YX6954BH30, glass transition temperature: 130° C.)
Phenoxy resin (X): (manufactured by Mitsubishi Chemical Corporation, product name: 4250, glass transition temperature: 78° C.)
Liquid multifunctional epoxy resin (BL1): Hydrogenated bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: YX8000, epoxy equivalent: 205 g/eq)
Liquid multifunctional epoxy resin (BL2): 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (manufactured by Daicel Corporation, product name: Celloxide 2021P, epoxy equivalent: 128 to 145 g/eq)
Photocationic polymerization initiator (C1): 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate (manufactured by San-Apro Co., Ltd., product name: CPI-100P)
Photocationic polymerization initiator (C2): a salt in which the cationic moiety is 4-(phenylthio)phenyldiphenylsulfonium and the anionic moiety is a phosphorus-based anion to which fluorine and a perfluoroalkyl group are added (manufactured by San-Apro Co., Ltd., product name: CPI-200K)
Silane coupling agent (D1): 8-glycidoxyoctyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM4803)

Example 1
100 parts by mass of a phenoxy resin (A1) (calculated as an active ingredient excluding the solvent, the same applies below), 170 parts by mass of a liquid multifunctional epoxy resin (BL1), 5 parts by mass of a photocationic polymerization initiator (C1), and 0.1 parts by mass of a silane coupling agent (D1) were diluted with methyl ethyl ketone to prepare a resin composition (1) having an active ingredient concentration of 50%.
This resin composition (1) was coated on the release-treated surface of a release film (manufactured by Lintec Corporation, product name: SP-PET752150), and the resulting coating was dried at 100° C. for 2 minutes to form a sheet adhesive having a thickness of 20 μm. The release-treated surface of another release film (manufactured by Lintec Corporation, product name: SP-PET381031) was attached to the sheet adhesive to produce a sheet adhesive with release film (1).

Example 2
A sheet-like adhesive (2) with a release film was prepared in the same manner as in Example 1, except that 120 parts by mass of a liquid multifunctional epoxy resin (BL2) was used instead of the liquid multifunctional epoxy resin (BL1) in Example 1.

Example 3
A sheet-like adhesive (3) with a release film was prepared in the same manner as in Example 1, except that in Example 1, 3 parts by mass of a cationic photopolymerization initiator (C2) was used instead of the cationic photopolymerization initiator (C1).

Example 4
A sheet-like adhesive (4) with a release film was prepared in the same manner as in Example 1, except that 100 parts by mass of phenoxy resin (A2) was used instead of the phenoxy resin (A1) in Example 1.

Example 5
A sheet-like adhesive (5) with a release film was prepared in the same manner as in Example 1, except that the content of the liquid multifunctional epoxy resin (BL1) in Example 1 was changed to 100 parts by mass.

Comparative Example 1
A sheet-like adhesive (6) with a release film was prepared in the same manner as in Example 1, except that 100 parts by mass of the phenoxy resin (X) was used instead of the phenoxy resin (A1) in Example 1.

The following tests were carried out on the sheet-like adhesives with release films (1) to (6) obtained in Examples 1 to 5 and Comparative Example 1. The results are shown in Table 1.

(Evaluation of the adhesion of sheet adhesives)
The sheet-like adhesive obtained in each of the Examples and Comparative Examples was laminated onto glass at 23° C. and a pressure of 0.2 MPa using a laminator.
By visual observation, the samples with no peeled areas were rated as ◯, and the samples with at least some peeled areas were rated as ×.

(Storage Modulus of Cured Sheet Adhesive)
The sheet-like adhesive obtained in the Examples or Comparative Examples was laminated using a laminator at 23°C and a pressure of 0.2 MPa to obtain a laminate having a thickness of 200 μm. This laminate was irradiated with ultraviolet light using a high-pressure mercury lamp manufactured by I-Graphics Co., Ltd. under conditions of an illuminance of 200 mW/ ^cm2 and an accumulated light quantity of 2000 mJ/ ^cm2 . The actinometer used was "UVPF-A1" manufactured by I-Graphics Co., Ltd. Thereafter, in order to promote the reaction, the laminate was heated at 100°C for 2 hours.
The laminate after the curing reaction was used as a sample, and the storage modulus was measured in tension mode with a storage modulus measuring device (manufactured by TA Instruments, product name: DMAQ800) under conditions of a frequency of 1 Hz and an amplitude of 5 μm. The temperature was raised at a rate of 3° C./min, and measurements were performed in the range of −20 to 150° C. The measurement results at 80° C. are shown in Table 1.

The following can be seen from Table 1.
The cured products of the sheet-like adhesives (1) to (5) obtained in Examples 1 to 5 are excellent in shape retention even under high temperature conditions.
Comparing Examples 1 to 5 with Comparative Example 1, it is clear that the glass transition temperature of the phenoxy resin affects the shape retention of the cured product under high temperature conditions.
Furthermore, when comparing Examples 1 to 4 with Example 5, it can be seen that by including a large amount of liquid multifunctional epoxy resin (BL), both the adhesion of the sheet adhesive and the shape retention of the cured product under high temperature conditions are improved.

Claims (8)

A sheet-like adhesive comprising the following components (A), (B), and (C), wherein the content of the following component (A) is 15 to 47 mass % and the content of the following component (B) is 52 to 70 mass % relative to the entirety of the sheet-like adhesive:
Component (A): a phenoxy resin having a glass transition temperature (Tg) of 130 to 180°C; Component (B): a multifunctional epoxy resin, at least one of which is Component (BL): a multifunctional epoxy resin that is liquid at 25°C, and the content of Component (BL) is 52 to 70 mass% based on the entire sheet-like adhesive; Component (C): a photocationic polymerization initiator. The sheet adhesive according to claim 1 , further comprising the following component (D):
Component (D): Silane coupling agent having a long-chain spacer group 3. The sheet adhesive according to claim 1, which has a storage modulus at 80°C after curing of 500 MPa or more. The sheet adhesive according to any one of claims 1 to 3 , which is used for sealing electronic devices. An encapsulating sheet comprising an adhesive layer made of the sheet-like adhesive according to any one of claims 1 to 4 and a functional film. A sealed electronic device comprising an electronic device sealed with a cured adhesive layer, the cured adhesive layer being a cured product of the sheet-like adhesive according to any one of claims 1 to 4 . The encapsulated electronic device according to claim 6 , wherein the encapsulated electronic device is an optical device. A method for producing a sealed electronic device, comprising the steps of:
Step (b1): A step of irradiating the sheet-like adhesive according to any one of claims 1 to 4 or the adhesive layer of the encapsulating sheet according to claim 6 with ultraviolet light to initiate a curing reaction. Step (b2): A step of attaching the sheet-like adhesive or the adhesive layer after step (b1) to an electronic device.