JP7555920B2 - Adhesive sheet for device sealing - Google Patents

Description

The present invention relates to an adhesive sheet for device encapsulation, which has an adhesive layer and a release film that have excellent adhesion at room temperature (23°C; the same applies below), and which has excellent releasability of the release film.

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.
The cause of the problem of the deterioration of the light-emitting characteristics is thought to be the infiltration of oxygen, moisture, etc. into the interior of the organic EL element, which deteriorates the electrodes and organic layers. For this reason, it has been proposed to solve this problem by forming a sealant using a pressure-sensitive adhesive layer or adhesive layer with excellent moisture-blocking properties.

For example, Patent Document 1 describes a sheet-like sealing material containing a specific epoxy resin, a specific alicyclic epoxy compound, a thermal cationic polymerization initiator, a photo cationic polymerization initiator, and a specific sensitizer.
A sealing material formed using the sheet-like sealing material described in Patent Document 1 has low oxygen permeability and moisture permeability and has good sealing performance.

JP 2018-95679 A

As described in Patent Document 1, a sheet-shaped sealing material utilizing the reactivity of a cyclic ether group has been suitably used as a material for forming an encapsulant.
However, some of such sheet-like sealing materials have poor application properties at room temperature, and require heating to soften the surface when they are applied to an object to be sealed.
On the other hand, some sheet-like sealing materials that have good application properties at room temperature are inferior in workability during application.
That is, when a sheet-like sealing material (hereinafter sometimes referred to as "adhesive layer") sandwiched between two release films is cut into a predetermined shape, the adhesive layer is deformed by the pressure of the punch blade, and adhesive adheres to the portion (cut surface) of the end of the release film that has not been subjected to the release treatment, making it difficult to peel off the release film efficiently.

The present invention has been made in consideration of the above-mentioned situation, and aims to provide an adhesive sheet for device encapsulation which has an adhesive layer and a release film that have excellent adhesion at room temperature, and in which the release film has excellent releasability.

In order to solve the above problems, the present inventors have conducted extensive research into an adhesive sheet for sealing having two release films and an adhesive layer sandwiched between these release films, the adhesive layer containing a compound having a cyclic ether group.
the result,
(a) an adhesive layer having a storage modulus at 23°C of a predetermined value or less has excellent application properties at room temperature, and (b) an adhesive sheet having an adhesive layer and a release film having a storage modulus at 23°C of a predetermined value or more has excellent releasability of the release film,
Thus, the present invention has been completed.

Thus, according to the present invention, adhesive sheets for device encapsulation as described below in [1] to [10] are provided.

[1] An adhesive sheet for device encapsulation having a first release film and a second release film, and an adhesive layer sandwiched between the first release film and the second release film, the adhesive sheet for device encapsulation satisfying the following requirements (I) and (II):
Requirement (I): The adhesive layer is a layer containing one or more compounds having a cyclic ether group.
Requirement (II): The storage modulus of the adhesive layer at 23° C. is 9.5×10 ⁵ Pa or more and 3.0×10 ⁷ Pa or less.
[2] The adhesive sheet for device encapsulation according to [1], wherein at least one of the compounds having a cyclic ether group is a compound that is liquid at 25°C.
[3] The adhesive sheet for device encapsulation according to [2], wherein the content of the compound having a cyclic ether group that is liquid at 25°C is 53 mass% or more based on the entire adhesive layer.
[4] The adhesive sheet for device encapsulation according to [2] or [3], wherein the content of the compound having a cyclic ether group that is liquid at 25° C. is 65 mass % or less based on the entire adhesive layer.
[5] The adhesive sheet for device encapsulation according to any one of [1] to [4], wherein the adhesive layer further contains a curing agent, and at least one of the curing agents is a thermal cationic polymerization initiator.
[6] The adhesive sheet for device encapsulation according to [5], wherein all of the curing agents are thermal cationic polymerization initiators.
[7] The adhesive sheet for device encapsulation according to [5] or [6], wherein at least one of the compounds having a cyclic ether group is a compound having a glycidyl ether group.
[8] The adhesive sheet for device encapsulation according to any one of [5] to [7], wherein at least one of the compounds having a cyclic ether group is an alicyclic epoxy resin.
[9] The adhesive layer contains a binder resin, and at least one of the binder resins has a glass transition temperature (Tg) of 60° C. or higher. The adhesive sheet for device encapsulation according to any one of [1] to [8].
[10] The adhesive sheet for device encapsulation according to any one of [1] to [9], wherein the layer obtained by curing the adhesive layer has a storage modulus at 90° C. of 1×10 ⁸ Pa or more.
[11] The adhesive sheet for device encapsulation according to any one of [1] to [10], which is used for forming an encapsulant in an optical device.

According to the present invention, an adhesive sheet for device encapsulation is provided which has an adhesive layer and a release film that have excellent adhesion at room temperature, and the release film has excellent releasability.

The adhesive sheet for device encapsulation of the present invention is an adhesive sheet for device encapsulation having a first release film and a second release film, and an adhesive layer sandwiched between the first release film and the second release film, and satisfies the above requirements (I) and (II).

In the present invention, the "first release film" refers to a release film that is peeled off after the "second release film" when the adhesive sheet for device encapsulation is used, and the "second release film" refers to a release film that is peeled off first when the adhesive sheet for device encapsulation is used.
Therefore, when the two release films have different peeling strengths, the "first release film" usually refers to the one of the two release films having the higher peeling strength, and the "second release film" usually refers to the one of the two release films having the lower peeling strength.
The "adhesive layer" is a layer formed by coating a curable adhesive, and has curing and adhesive properties. In other words, the "adhesive layer" is a layer in an uncured state.
In this specification, the “layer obtained by curing the adhesive layer” may be referred to as an “adhesive cured layer.” This adhesive cured layer is used as a sealant.
In the present invention, "curing" refers to a state in which the cohesive strength and storage modulus of the layer are increased by reaction of cyclic ether groups contained in the adhesive layer.

[Adhesive Layer]
(Compound having a cyclic ether group)
The adhesive layer contains one or more compounds having a cyclic ether group (hereinafter, sometimes referred to as "cyclic ether compound (A)").
By curing the adhesive layer containing the cyclic ether compound (A), a sealing material having high adhesive strength and excellent water vapor barrier properties can be formed.

The cyclic ether compound (A) refers to a compound having at least one, preferably two or more, cyclic ether groups in the molecule. In the present invention, the phenoxy resin described below is not included in the cyclic ether compound (A).

The molecular weight of the cyclic ether compound (A) is usually from 100 to 5,000, preferably from 200 to 3,000.
The cyclic ether equivalent of the cyclic ether compound (A) is preferably 50 to 1,000 g/eq, more preferably 100 to 800 g/eq.
By curing an adhesive layer containing a cyclic ether compound (A) having a cyclic ether equivalent within the above range, a sealing material having higher adhesive strength and more excellent moisture blocking properties can be more efficiently formed.
The cyclic ether equivalent in the present invention means a value obtained by dividing the molecular weight by the number of cyclic ether groups.

Examples of the cyclic ether group include an oxirane group (epoxy group), an oxetane group (oxetanyl group), a tetrahydrofuryl group, a tetrahydropyranyl group, etc. Among these, from the viewpoint of forming a sealing material having higher adhesive strength, the cyclic ether group is preferably an oxirane group or an oxetane group, and more preferably an oxirane group.
For the same reason, the cyclic ether compound (A) preferably has two or more oxirane groups or oxetane groups in the molecule, and more preferably has two or more oxirane groups in the molecule.

Examples of compounds having an oxirane group in the molecule include aliphatic epoxy compounds (excluding alicyclic epoxy compounds), aromatic epoxy compounds, and alicyclic epoxy compounds.
Examples of the aliphatic epoxy compounds include monofunctional epoxy compounds such as glycidyl ethers of aliphatic alcohols and glycidyl esters of alkyl carboxylic acids;
Polyfunctional epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts, and polyglycidyl esters of aliphatic long-chain polybasic acids.

Representative compounds of these aliphatic epoxy compounds include alkenyl glycidyl ethers such as allyl glycidyl ether; alkyl glycidyl ethers such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and C12-13 mixed alkyl glycidyl ether; 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, and diglycidyl ether of polyethylene glycol. Examples of such glycidyl ethers include glycidyl ethers of polyhydric alcohols such as diglycidyl ether of polypropylene glycol, polyglycidyl ethers of polyether polyols obtained by adding one or more alkylene oxides to an aliphatic polyhydric alcohol such as propylene glycol, trimethylolpropane, glycerin, etc., diglycidyl esters of aliphatic long-chain dibasic acids, monoglycidyl ethers of aliphatic higher alcohols, glycidyl esters of higher fatty acids, epoxidized soybean oil, epoxy octyl stearate, epoxy butyl stearate, and epoxidized polybutadiene.

Commercially available aliphatic epoxy compounds may also be used, including Denacol EX-121, Denacol EX-171, Denacol EX-192, Denacol EX-211, Denacol EX-212, Denacol EX-313, Denacol EX-314, Denacol EX-321, Denacol EX-411, Denacol EX-421, Denacol EX-512, Denacol EX-521, Denacol EX-611, Denacol EX-612, and Denacol EX-61. 4, Denacol EX-622, Denacol EX-810, Denacol EX-811, Denacol EX-850, Denacol EX-851, Denacol EX-821, Denacol EX-830, Denacol EX-832, Denacol EX-841, Denacol EX-861, Denacol EX-911, Denacol EX-941, Denacol EX-920, Denacol EX-931 (all manufactured by Nagase ChemteX Corporation);
Epolight M-1230, Epolight 40E, Epolight 100E, Epolight 200E, Epolight 400E, Epolight 70P, Epolight 200P, Epolight 400P, Epolight 1500NP, Epolight 1600, Epolight 80MF, Epolight 100MF (all manufactured by Kyoeisha Chemical Co., Ltd.);
Examples of the glycerol are ADEKA GLYCILOR ED-503, ADEKA GLYCILOR ED-503G, ADEKA GLYCILOR ED-506, and ADEKA GLYCILOR ED-523T (all manufactured by ADEKA Corporation).

Examples of the aromatic epoxy compound include mono-/polyglycidyl ethers of phenols having at least one aromatic ring, such as phenol, cresol, and butylphenol, or alkylene oxide adducts thereof; epoxy compounds having an aromatic heterocycle; and the like.
Representative examples of these 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;
Mono/polyglycidyl ethers of aromatic compounds having two or more phenolic hydroxyl groups, such as resorcinol, hydroquinone, catechol, etc.;
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, trimellitic acid, etc., glycidyl esters of benzoic acid, epoxidized products of styrene oxide or divinylbenzene;
Epoxy compounds having a triazine skeleton such as 2,4,6-tri(glycidyloxy)-1,3,5-triazine; and the like.

Commercially available aromatic epoxy compounds may also be used, such as Denacol EX-146, Denacol EX-147, Denacol EX-201, Denacol EX-203, Denacol EX-711, Denacol EX-721, Oncoat EX-1020, Oncoat EX-1030, Oncoat EX-1040, Oncoat EX-1050, Oncoat EX-1051, Oncoat EX-1010, Oncoat EX-1011, and Oncoat 1012 (all manufactured by Nagase ChemteX Corporation);
OGSOL PG-100, OGSOL EG-200, OGSOL EG-210, OGSOL EG-250 (all manufactured by Osaka Gas Chemicals Co., Ltd.);
HP4032, HP4032D, HP4700 (all manufactured by DIC Corporation);
ESN-475V (all manufactured by Nippon Steel Chemical & Material Co., Ltd.);
jER YX8800 (all manufactured by Mitsubishi Chemical Corporation);
MARPROOF G-0105SA, MARPROOF G-0130SP (both manufactured by NOF Corporation);
Epicron N-665, Epicron HP-7200 (both manufactured by DIC Corporation);
EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, XD-1000, NC-3000, EPPN-501H, EPPN-501HY, EPPN-502H, NC-7000L (all manufactured by Nippon Kayaku Co., Ltd.);
ADEKA RESIN EP-4000, ADEKA RESIN EP-4005, ADEKA RESIN EP-4100, ADEKA RESIN EP-4901 (all manufactured by ADEKA Corporation);
TECHMORE VG-3101L (both manufactured by Printec Co., Ltd.);
TEPIC-FL, TEPIC-PAS, TEPIC-UC (all manufactured by Nissan Chemical Industries, Ltd.);

Examples of the alicyclic epoxy compound include polyglycidyl ethers of polyhydric alcohols having at least one alicyclic structure, and cyclohexene oxide- or cyclopentene oxide-containing compounds obtained by epoxidizing cyclohexene- or cyclopentene ring-containing compounds with an oxidizing agent.
Representative examples of these alicyclic epoxy compounds include hydrogenated bisphenol A diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-1-methylcyclohexyl-3,4-epoxy-1-methylhexane carboxylate, 6-methyl-3,4-epoxycyclohexylmethyl-6-methyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexane carboxylate, 3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexane carboxylate, bis(3,4-epoxycyclohexylmethyl) ethyl) adipate, 3,4-epoxy-6-methylcyclohexane carboxylate, methylene bis(3,4-epoxycyclohexane), propane-2,2-diyl-bis(3,4-epoxycyclohexane), 2,2-bis(3,4-epoxycyclohexyl)propane, dicyclopentadiene diepoxide, dicyclopentadiene dimethanol diglycidyl ether, ethylene bis(3,4-epoxycyclohexane carboxylate), dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, 1-epoxyethyl-3,4-epoxycyclohexane, 1,2-epoxy-2-epoxyethylcyclohexane, α-pinene oxide, limonene dioxide, and the like.

In addition, commercially available products can also be used as the alicyclic epoxy compound. Examples of commercially available products include Celoxide 2021P, Celoxide 2081, Celoxide 2000, and Celoxide 3000 (all manufactured by Daicel Corporation); Epolite 4000 (manufactured by Kyoeisha Chemical Co., Ltd.); jER YX8000 and jER YX8034 (manufactured by Mitsubishi Chemical Corporation); ADEKA RESIN EP-4088S, ADEKA RESIN EP-4088L, and ADEKA RESIN EP-4080E (manufactured by ADEKA Corporation); and the like.

Compounds having an oxirane group in the molecule also include epoxy compounds having both an alicyclic structure and an aromatic ring in one molecule. One such compound is Epiclon HP-7200 (manufactured by DIC Corporation).

Among these, from the viewpoint of reducing the dielectric constant of the adhesive cured layer and from the viewpoint of easily forming an adhesive cured layer excellent in colorless transparency, alicyclic epoxy resins are preferred as the compound having an oxirane group. In addition, when the adhesive layer contains a cationic polymerization initiator, alicyclic epoxy resins are preferred from the viewpoint of avoiding excessive slowing down of the cationic polymerization because they have high reactivity in cationic polymerization.
In addition, when a thermal cationic polymerization initiator is used as a curing agent described later, the compound having an oxirane group is preferably a compound having a glycidyl ether group. The cationic polymerization reaction involving the glycidyl ether group tends to proceed relatively gently. Therefore, when the manufacturing process of the adhesive layer includes a process of heating a composition containing components constituting the adhesive layer (for example, a process of heating to 90 ° C or more), the polymerization reaction of the glycidyl ether group is difficult to proceed, and it is easy to maintain the storage modulus of the adhesive layer at 23 ° C. low. The content of the compound having a glycidyl ether group is preferably 70% by mass or more, and preferably 90% by mass or more, based on the total compound having a cyclic ether group. In addition, when the content of the compound having a glycidyl ether group is 90% by mass or more based on the total compound having a cyclic ether group, the storage stability of the adhesive layer can be improved.

Compounds that have an oxetane group in the molecule include 3,7-bis(3-oxetanyl)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, tetraethylene glycol bis(3- and bifunctional aliphatic oxetane compounds such as 1,4-bis(3-ethyl-3-oxetanylmethoxy)butane and 1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane; and monofunctional oxetane compounds such as 3-ethyl-3-[(phenoxy)methyl]oxetane, 3-ethyl-3-(hexyloxymethyl)oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(hydroxymethyl)oxetane and 3-ethyl-3-(chloromethyl)oxetane.

As the compound having an oxetane group in the molecule, commercially available products can be used, such as 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether (all manufactured by Maruzen Petrochemical Co., Ltd.);
ARON OXETANE OXT-121, OXT-221, EXOH, POX, OXA, OXT-101, OXT-211, OXT-212 (all manufactured by Toagosei Co., Ltd.);
Ethanacol OXBP, OXTP (both manufactured by Ube Industries, Ltd.); and the like.

These cyclic ether compounds (A) may be used alone or in combination of two or more.

The content of the cyclic ether compound (A) in the adhesive layer (when two or more types of cyclic ether compounds (A) are contained, the total amount of these) is preferably 53 to 80 mass%, more preferably 57 to 75 mass%, based on the total amount of the adhesive layer.
By setting the content of the cyclic ether compound (A) within the above range, it becomes easier to obtain a cured adhesive layer having a high storage modulus at 90°C.

At least one of the cyclic ether compounds (A) in the adhesive layer is preferably a compound (cyclic ether compound (AL)) that is liquid at 25° C. Here, the term “liquid” refers to one of the aggregate states of a substance, which has a nearly constant volume but does not have a specific shape.
The cyclic ether compound (AL) 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.
By using the cyclic ether compound (AL), it is possible to prevent the storage modulus of the adhesive layer at 23° C. from becoming too high. As a result, it becomes easier to obtain an adhesive layer that has sufficient adhesive strength at room temperature and excellent application properties.

From the viewpoint of adjusting the storage modulus of the adhesive layer at 23°C, the cyclic ether equivalent of the cyclic ether compound (AL) is preferably 150 to 1000 g/eq, more preferably 240 to 900 g/eq.

The content of the cyclic ether compound (AL) in the adhesive layer (the total amount of these compounds when two or more types of compounds are included) is preferably 53% by mass or more, more preferably 57% by mass or more, based on the entire adhesive layer. When the content of the cyclic ether compound (AL) is 53% by mass or more based on the entire adhesive layer, it becomes easier to obtain an adhesive layer that has sufficient adhesive strength at room temperature and excellent adhesion. In addition, it becomes easier to obtain an adhesive cured layer that has a high storage modulus at 90°C.

The content of the cyclic ether compound (AL) in the adhesive layer (the total amount of these compounds when two or more types of compounds are included) is preferably 70% by mass or less, more preferably 68% by mass or less, based on the entire adhesive layer. By having the content of the cyclic ether compound (AL) be 70% by mass or less based on the entire adhesive layer, it becomes easier to obtain an adhesive sheet for device encapsulation that has excellent releasability of the release film.

(Binder resin)
The adhesive layer may contain a binder resin (B). The adhesive layer containing the binder resin (B) has excellent shape retention and handleability.

The weight average molecular weight (Mw) of the binder resin (B) is not particularly limited, but is preferably 10,000 or more, more preferably 10,000 to 150,000, and even more preferably 10,000 to 100,000, in order to provide superior compatibility with the cyclic ether compound (A) and superior shape retention.
The weight average molecular weight (Mw) of the binder resin (B) can be determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

When the adhesive layer contains the binder resin (B), the content of the binder resin (B) (when two or more types of binder resins (B) are contained, the total amount of these) is preferably 20 to 46 mass %, more preferably 23 to 44 mass %, based on the entire adhesive layer.
When the content of the binder resin (B) is within the above range, an adhesive layer having excellent shape retention and sufficient adhesive strength can be easily obtained.

The binder resin (B) is preferably a resin having a glass transition temperature (Tg) of 60° C. or higher, more preferably a resin having a glass transition temperature (Tg) of 90° C. or higher, and even more preferably a resin having a glass transition temperature (Tg) of 110° C. or higher. By using a resin having a glass transition temperature (Tg) of 60° C. or higher, it becomes easy to achieve a storage modulus at 90° C. of 1×10 ⁸ Pa or higher of the adhesive cured product layer.
In addition, since the glass transition temperature (Tg) of the binder resin (B) is 90° C. or higher, even when a large amount of the cyclic ether compound (AL) is contained, it is easy to set the storage modulus of the adhesive layer at 23° C. to a range of 9.5 × 10 ⁵ Pa or higher as described below.
The glass transition temperature (Tg) of the binder resin (B) can be measured in accordance with JIS K 7121 using a differential scanning calorimeter.

Examples of the binder resin (B) include phenoxy resins, polyimide resins, polyamideimide resins, polyvinyl butyral resins, polycarbonate resins, acrylic resins, urethane resins, and modified olefin resins.
These resins may be used alone or in combination of two or more.

The binder resin (B) is preferably at least one selected from the group consisting of phenoxy-based resins and modified olefin-based resins, and is preferably a phenoxy-based resin from the viewpoint of increasing the storage modulus at 90°C of the adhesive cured layer.

Phenoxy resins generally fall under the category of high molecular weight epoxy resins, with a degree of polymerization of approximately 100 or more.

The phenoxy resin preferably has a weight average molecular weight (Mw) of 10,000 to 150,000, and more preferably 10,000 to 100,000. The weight average molecular weight (Mw) of the phenoxy resin can be determined as a standard polystyrene equivalent value by performing gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.
Phenoxy resins, which fall under this category of high molecular weight epoxy resins, are excellent in heat distortion resistance.
The epoxy equivalent of the phenoxy resin is preferably at least 5,000, and more preferably at least 7,000. The epoxy equivalent of the phenoxy resin can be measured in accordance with JIS K7236.

Examples of the phenoxy resin include bisphenol A type, bisphenol F type, bisphenol S type phenoxy resin, copolymer type phenoxy resin of bisphenol A type and bisphenol F type, distilled products thereof, naphthalene type phenoxy resin, novolac type phenoxy resin, biphenyl type phenoxy resin, cyclopentadiene type phenoxy resin, and the like.
These phenoxy resins may be used alone or in combination of two or more.

The phenoxy resin can be obtained by reacting a difunctional phenol with an epihalohydrin to a high molecular weight, or by subjecting a difunctional epoxy resin to a polyaddition reaction with a difunctional phenol.
For example, it can be obtained 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. Alternatively, it can 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 organophosphorus 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. For example, 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, commercially available products can be used as the phenoxy resin. For example, Mitsubishi Chemical Corporation's product names are YX7200 (glass transition temperature: 150°C), YX6954 (phenoxy resin containing a bisphenol acetophenone skeleton, glass transition temperature: 130°C), YL7553, YL6794, YL7213, YL7290, YL7482, and YX8100 (phenoxy resin containing a bisphenol S skeleton), Tohto Kasei Co., Ltd.'s product names are FX280, FX293, and FX293S (phenoxy resin containing a fluorene skeleton), and Mitsubishi Chemical Corporation's products are Examples of such resins include jER1256, jER4250 (glass transition temperature: less than 85° C.), jER4275 (glass transition temperature: 75° C.), and Nippon Steel Chemical & Material Co., Ltd.'s product names: YP-50 (glass transition temperature: 84° C.), YP-50S (all phenoxy resins containing a bisphenol A skeleton), YP-70 (bisphenol A skeleton/bisphenol F skeleton copolymer type phenoxy resin, glass transition temperature: less than 85° C.), ZX-1356-2 (glass transition temperature: 72° C.). For those whose glass transition temperatures are known, the glass transition temperature is shown.

Modified olefin resins are olefin resins with functional groups introduced into them, which are obtained by subjecting a precursor olefin resin to a modification treatment using a modifying agent.

An olefin resin is a polymer containing repeating units derived from an olefin monomer. The olefin resin may be a polymer consisting only of repeating units derived from an olefin monomer, or may be a polymer consisting of repeating units derived from an olefin monomer and repeating units derived from a monomer copolymerizable with the olefin monomer.

The olefin monomer is preferably an α-olefin having 2 to 8 carbon atoms, more preferably ethylene, propylene, 1-butene, isobutylene, or 1-hexene, and further preferably ethylene or propylene. These olefin monomers can be used alone or in combination of two or more.
Examples of monomers copolymerizable with the olefin monomer include vinyl acetate, (meth)acrylic acid esters, styrene, etc. Here, "(meth)acrylic acid" means acrylic acid or methacrylic acid (the same applies below).
These monomers copolymerizable with the olefin monomer may be used alone or in combination of two or more.

Examples of olefin resins include very low density polyethylene (VLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene, polypropylene (PP), ethylene-propylene copolymer, olefin elastomer (TPO), ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid ester copolymer.

The modifying agent used in the modification treatment of the olefin resin is a compound having a functional group in the molecule.
Examples of the functional group include a carboxyl group, a carboxylic anhydride group, a carboxylic ester group, a hydroxyl group, an epoxy group, an amide group, an ammonium group, a nitrile group, an amino group, an imide group, an isocyanate group, an acetyl group, a thiol group, an ether group, a thioether group, a sulfone group, a phosphone group, a nitro group, a urethane group, an alkoxysilyl group, a silanol group, a halogen atom, etc. The compound having a functional group may have two or more types of functional groups in the molecule.

The weight average molecular weight (Mw) of the modified olefin resin is preferably 10,000 to 150,000, and more preferably 30,000 to 100,000.
The weight average molecular weight (Mw) of the modified olefin resin can be determined in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

As the modified olefin resin, an acid-modified olefin resin is preferable. An acid-modified olefin resin is an olefin resin that has been graft-modified with an acid or an acid anhydride. For example, an olefin resin may be reacted with an unsaturated carboxylic acid or an unsaturated carboxylic anhydride (hereinafter sometimes referred to as "unsaturated carboxylic acid, etc.") to introduce a carboxyl group or a carboxylic anhydride group (graft-modified).

Examples of the unsaturated carboxylic acid to be reacted with the olefin resin include unsaturated carboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, and aconitic acid; and unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic acid anhydride, and tetrahydrophthalic anhydride.
These may be used alone or in combination of two or more. Among these, maleic anhydride is preferred because it is easy to obtain a sealing material having higher adhesive strength.

The amount of unsaturated carboxylic acid or the like reacted with the olefin resin is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, and even more preferably 0.2 to 1 part by mass, per 100 parts by mass of the olefin resin. By curing the adhesive layer containing the acid-modified olefin resin obtained in this manner, a sealing material with higher adhesive strength can be formed.

There is no particular limitation on the method of introducing unsaturated carboxylic acid units or unsaturated carboxylic anhydride units into an olefin resin. For example, an olefin resin and an unsaturated carboxylic acid, etc. are reacted by heating and melting them at a temperature equal to or higher than the melting point of the olefin resin in the presence of a radical generator such as an organic peroxide or an azonitrile, or an olefin resin and an unsaturated carboxylic acid, etc. are dissolved in an organic solvent, and then heated and stirred in the presence of a radical generator to react them, thereby graft-copolymerizing an unsaturated carboxylic acid, etc., onto an olefin resin.

As the acid-modified olefin resin, commercially available products can be used. Examples of commercially available products include Admer (registered trademark) (manufactured by Mitsui Chemicals, Inc.), Unistall (registered trademark) (manufactured by Mitsui Chemicals, Inc.), BondyRam (manufactured by Polyram Corporation), orevac (registered trademark) (manufactured by ARKEMA Corporation), and Modic (registered trademark) (manufactured by Mitsubishi Chemical Corporation).

[Hardening agent]
The adhesive layer may contain a curing agent. When the adhesive layer contains a curing agent, the curing property of the adhesive layer is further enhanced.
The curing agent is not particularly limited as long as it initiates a curing reaction. However, from the viewpoint that it may be difficult or should be avoided to cure the adhesive layer by energy rays such as ultraviolet rays, and from the viewpoint that there is no need to introduce an energy ray irradiation device, a curing agent that initiates a curing reaction by heating is preferably used.
The curing agent may be a thermal cationic polymerization initiator or other curing agents.
Examples of curing agents other than the thermal cationic polymerization initiator include tertiary amines such as benzylmethylamine and 2,4,6-trisdimethylaminomethylphenol; imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-heptadecylimidazole; and Lewis acids such as boron trifluoride-monoethylamine complex and boron trifluoride-piperazine complex.

The curing agent may be used alone or in combination of two or more kinds.
When the adhesive layer contains a curing agent, the content of the curing agent is not particularly limited, but is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the cyclic ether compound (A).

The adhesive layer preferably contains a thermal cationic polymerization initiator as at least one type of curing agent.
By using a thermal cationic polymerization initiator, the curing property of the adhesive layer can be controlled more accurately.

A thermal cationic polymerization initiator is a compound that can generate cationic species that initiate polymerization upon heating.
Examples of the thermal cationic polymerization initiator include sulfonium salts, quaternary ammonium salts, phosphonium salts, diazonium salts, and iodonium salts.

Examples of sulfonium salts include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroarsinate, tris(4-methoxyphenyl)sulfonium hexafluoroarsinate, diphenyl(4-phenylthiophenyl)sulfonium hexafluoroarsinate, (4-acetoxyphenyl)methyl(2-methylbenzyl)sulfonium tetrakis(pentafluorophenyl)borate, (4-hydroxyphenyl)methyl(4-methylbenzyl)sulfonium tetrakis(pentafluorophenyl)borate, (4-acetoxyphenyl)benzyl(methyl)sulfonium tetrakis(pentafluorophenyl)borate, and benzyl(4-hydroxyphenyl)(methyl)sulfonium tetrakis(pentafluorophenyl)borate.

Commercially available sulfonium salts can also be used. Commercially available products include ADEKAOPTON SP-150, ADEKAOPTON SP-170, ADEKAOPTON CP-66, ADEKAOPTON CP-77 (all manufactured by Asahi Denka Co., Ltd.), SAN-AID SI-60L, SAN-AID SI-80L, SAN-AID SI-100L, SAN-AID SI-B2A, SAN-AID SI-B7, SAN-AID SI-B3A, SAN-AID SI-B3 (all manufactured by Sanshin Chemical Co., Ltd.), CYRACURE UVI-6974, CYRACURE Examples of such products include UVI-6990 (manufactured by Union Carbide), UVI-508, UVI-509 (manufactured by General Electric Company), FC-508, FC-509 (manufactured by Minnesota Mining and Manufacturing Company), CD-1010, CD-1011 (manufactured by Thirstomer Corporation), and CI series products (manufactured by Nippon Soda Co., Ltd.).

Examples of quaternary ammonium salts include tetrabutylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium hydrogen sulfate, tetraethylammonium tetrafluoroborate, tetraethylammonium p-toluenesulfonate, N,N-dimethyl-N-benzylanilinium hexafluoroantimonate, N,N-dimethyl-N-benzylanilinium tetrafluoroborate, N,N-dimethyl-N-benzylpyridinium hexafluoroantimonate, N,N-diethyl-N-benzyltrifluoromethanesulfonate, N,N-dimethyl-N-(4-methoxybenzyl)pyridinium hexafluoroantimonate, and N,N-diethyl-N-(4-methoxybenzyl)toluidinium hexafluoroantimonate.

Examples of phosphonium salts include ethyltriphenylphosphonium hexafluoroantimonate, tetrabutylphosphonium hexafluoroantimonate, etc.

Examples of diazonium salts include AMERICURE (manufactured by American Can Co., Ltd.) and ULTRASET (manufactured by Asahi Denka Co., Ltd.).

Examples of iodonium salts include diphenyliodonium hexafluoroarsinate, bis(4-chlorophenyl)iodonium hexafluoroarsinate, bis(4-bromophenyl)iodonium hexafluoroarsinate, phenyl(4-methoxyphenyl)iodonium hexafluoroarsinate, etc. Commercially available products that can be used include UV-9310C (manufactured by Toshiba Silicone Co., Ltd.), Photoinitiator 2074 (manufactured by Rhone-Poulenc), UVE series products (manufactured by General Electric Co.), and FC series products (manufactured by Minnesota Mining and Manufacturing Co., Ltd.).

Thermal cationic polymerization initiators can be used alone or in combination of two or more.

In the device encapsulation adhesive sheet of the present invention, all of the curing agents contained in the adhesive layer are preferably thermal cationic polymerization initiators.
If a curing agent other than a thermal cationic polymerization initiator is used, the adhesive layer may be discolored or the transparency of the adhesive layer may decrease.
On the other hand, when a thermal cationic polymerization initiator is used, such problems are unlikely to occur, and therefore, by using a thermal cationic polymerization initiator as all of the curing agents contained in the adhesive layer, an adhesive layer having excellent colorlessness and transparency can be efficiently formed.

(Silane coupling agent)
The adhesive layer may contain a silane coupling agent. By curing the adhesive layer containing the silane coupling agent, a sealing material having superior wet heat durability can be formed.

As the silane coupling agent, a known silane coupling agent can be used. Among them, an organosilicon compound having at least one alkoxysilyl group in the molecule is preferred.

Examples of the silane coupling agent include silane coupling agents having a (meth)acryloyl group, such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and 8-methacryloxyoctyltrimethoxysilane;
Silane coupling agents having a vinyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, diethoxymethylvinylsilane, trichlorovinylsilane, vinyltris(2-methoxyethoxy)silane, and 7-octenyltrimethoxysilane;
Silane coupling agents having an epoxy group, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 8-glycidoxyoctyltrimethoxysilane;
Silane coupling agents having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane;

Silane coupling agents having an amino group, such as N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, and N-(2-aminoethyl)-8-aminooctyltrimethoxysilane;
Silane coupling agents having a ureido group, such as 3-ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane;
Silane coupling agents having a halogen atom, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane;
silane coupling agents having a mercapto group, such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane;
Silane coupling agents having a sulfide group, such as bis(trimethoxysilylpropyl)tetrasulfide and bis(triethoxysilylpropyl)tetrasulfide;
Silane coupling agents having an isocyanate group, such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane;
silane coupling agents having an allyl group, such as allyltrichlorosilane, allyltriethoxysilane, and allyltrimethoxysilane;
Silane coupling agents having a hydroxyl group, such as 3-hydroxypropyltrimethoxysilane and 3-hydroxypropyltriethoxysilane; and the like.
Among these, from the viewpoint of improving the adhesion of the adhesive layer to the adherend, it is preferable to use a long-chain spacer type silane coupling agent having a linear alkyl group having 6 or more carbon atoms. Examples of long-chain spacer type silane coupling agents having a linear alkyl group having 6 or more carbon atoms include 8-methacryloxyoctyltrimethoxysilane, 7-octenyltrimethoxysilane, 8-glycidoxyoctyltrimethoxysilane, N-(2-aminoethyl)-8-aminooctyltrimethoxysilane, etc., and it is preferable to use 8-glycidoxyoctyltrimethoxysilane.
These silane coupling agents can be used alone or in combination of two or more.

When the adhesive layer contains a silane coupling agent, the content of the silane coupling agent in the entire adhesive layer is preferably 0.01 to 5 mass%, more preferably 0.05 to 1 mass%.

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

(Adhesive Layer)
The shape, size, etc. of the adhesive layer are not particularly limited. The adhesive layer may be in the form of a strip or a long strip. In this specification, the term "long strip" refers to a shape having a length of 5 times or more than the width, preferably 10 times or more, specifically a film shape having a length that can be wound into a roll for storage or transportation. The upper limit of the ratio of the length to the width of the film is not particularly limited, but may be, for example, 100,000 times or less.

The thickness of the adhesive layer is usually 1 to 50 μm, preferably 1 to 25 μm, and more preferably 5 to 25 μm. An adhesive layer having a thickness within the above range is suitably used as a material for forming a sealing material.
The thickness of the adhesive layer can be measured using a known thickness meter in accordance with JIS K 7130 (1999).

The adhesive layer may have a single layer structure, or may have a multi-layer structure (a plurality of adhesive layers laminated together).
The adhesive layer may be one having homogeneous components, or one having heterogeneous components (for example, in the adhesive layer having the above-mentioned multi-layer structure, both components are mixed at the interface between the two adhesive layers, resulting in an apparent single-layer structure).

The storage modulus of the adhesive layer at 23° C. is 9.5×10 ⁵ Pa or more and 3.0×10 ⁷ Pa or less, and preferably 9.9×10 ⁵ Pa or more and 2.0×10 ⁷ Pa or less. In addition, since the pressure applied when attaching the adhesive layer to an object to be sealed can be reduced, the storage modulus of the adhesive layer at 23° C. is preferably 1.3×10 ⁷ Pa or less, more preferably 1.1×10 ⁷ Pa or less, and even more preferably 1.0×10 ⁷ Pa or less.

When the adhesive layer has a storage modulus of 9.5 × 10 ⁵ Pa or more at 23°C, a punch blade can be pressed into the adhesive sheet for device encapsulation without significantly deforming the adhesive layer when cutting the adhesive sheet for device encapsulation into a predetermined shape, which prevents the adhesive from adhering to the untreated portions of the edge of the release film, and allows the release film to be peeled off efficiently.
An adhesive layer having a storage modulus of 9.5×10 ⁵ Pa or more at 23° C. can be easily obtained by using, for example, a cyclic ether compound (A) having a large cyclic ether equivalent. In addition, the storage modulus of the adhesive layer at 23° C. can be reduced by reducing the content of the cyclic ether compound (AL) in the adhesive layer. Furthermore, by using a relatively rigid resin such as a phenoxy resin, an adhesive layer having a storage modulus of 9.5×10 ⁵ Pa or more at 23° C. can be easily obtained even when the content of the cyclic ether compound (AL) in the adhesive layer is high.

When the storage modulus of the adhesive layer at 23° C. is 3.0×10 ⁷ Pa or less, the adhesive layer has sufficient adhesive strength at room temperature and excellent application properties.
An adhesive layer having a storage modulus of 3.0×10 ⁷ Pa or less at 23° C. can be easily obtained, for example, by increasing the amount of the cyclic ether compound (AL). Furthermore, as described above, when the adhesive layer contains a thermal cationic polymerization initiator, the storage modulus of the adhesive layer at 23° C. can be easily reduced to 3.0×10 ⁷ Pa or less by using the cyclic ether compound (A) as a compound having a glycidyl ether group.
The storage modulus of the adhesive layer can be measured using a known dynamic viscoelasticity measuring device.
Specifically, it can be measured by the method described in the Examples.

The adhesive layer has a curing property. That is, by subjecting the adhesive layer to a predetermined curing treatment, the cyclic ether group in the cyclic ether compound (A) reacts, and the adhesive layer is cured to become an adhesive cured product layer.
The curing treatment may be a heat treatment, a light irradiation treatment, etc. These may be appropriately determined depending on the properties of the adhesive layer.

The storage modulus of the adhesive cured layer at 90° C. is preferably 1×10 ⁸ Pa or more, and more preferably 1×10 ⁹ to 1×10 ¹¹ Pa. An adhesive cured layer having a storage modulus of 1×10 ⁸ Pa or more at 90° C. is excellent in sealing properties and is therefore more suitable as a sealing material. Furthermore, in a process carried out for producing a device sealing body after the formation of the adhesive cured layer, damage and peeling of the adhesive cured layer are easily prevented.
The storage modulus of the cured adhesive layer can be measured using a known dynamic viscoelasticity measuring device.
Specifically, it can be measured by the method described in the Examples.

The adhesive cured layer has excellent adhesive strength. When a 180° peel test is performed under conditions of a temperature of 23°C and a relative humidity of 50%, the adhesive strength of the adhesive cured layer is usually 1 to 20 N/25 mm, preferably 2.5 to 15 N/25 mm. This 180° peel test can be performed, for example, in accordance with the adhesive strength measurement method described in JIS Z0237:2009 under conditions of a temperature of 23°C and a relative humidity of 50%.

When the adhesive sheet for device encapsulation of the present invention is used to form an encapsulant in a light-related device such as a light-emitting device, a light-receiving device, or a display device, the adhesive cured layer is preferably excellent in colorless transparency. The total light transmittance of the adhesive cured layer having a thickness of 15 μm is preferably 85% or more, more preferably 90% or more. There is no particular upper limit for the total light transmittance, but it is usually 99% or less.
The total light transmittance can be measured in accordance with JIS K7361-1:1997.

The water vapor transmission rate of the cured adhesive layer is usually 0.1 to 200 g·m ⁻² ·day ⁻¹ , and preferably 1 to 150 g·m ⁻² ·day ⁻¹ .
The water vapor transmission rate can be measured using a known gas transmission rate measuring device.

[Release film]
The adhesive sheet for device encapsulation of the present invention has a first release film and a second release film.
When using the adhesive sheet for device encapsulation of the present invention, the release film is usually peeled off and removed. At this time, the second release film is peeled off and removed before the first release film. Since the second release film can be peeled off and removed efficiently, it is preferable that the release strength of the second release film is lower than that of the first release film.
In the following description, there is no distinction between the "first release film" and the "second release film", and they may simply be referred to as "release films".

The release film functions as a support during the manufacturing process of the device encapsulation adhesive sheet, and also functions as a protective sheet for the adhesive layer until the device encapsulation adhesive sheet is used.

Any known release film can be used. For example, a release film having a release layer on a substrate for the release film can be used. The release layer can be formed using a known release agent.

Examples of substrates for release films include paper substrates such as glassine paper, coated paper, and fine paper; laminated paper obtained by laminating a thermoplastic resin such as polyethylene to these paper substrates; and plastic films such as polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polypropylene resin, and polyethylene resin.
Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.
The thickness of the release film is not particularly limited, but is usually about 20 to 250 μm.

[Adhesive sheet for device encapsulation]
The adhesive sheet for device encapsulation of the present invention comprises the first release film and the second release film, and the adhesive layer sandwiched between these release films.
The adhesive sheet for device encapsulation of the present invention may have a three-layer structure of a first release film/adhesive layer/second release film.

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

When the adhesive sheet for device encapsulation is produced by a casting method, it can be produced, for example, by the following method.
Two release films having a release layer (release film (A) and release film (B)) and a coating liquid containing components constituting the adhesive layer are prepared. The coating liquid is applied to the release layer surface of the release film (A) using a known method, and the resulting coating film is dried to form an adhesive layer. Next, the release film (B) is layered on the adhesive layer so that the release layer surface of the release film (B) is in contact with the adhesive layer, thereby obtaining an adhesive sheet for device encapsulation.

When preparing a coating liquid by diluting the components constituting the adhesive layer, examples of the solvent used in preparing the coating liquid include aromatic hydrocarbon solvents such as benzene and toluene; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as n-pentane, n-hexane and n-heptane; alicyclic hydrocarbon solvents such as cyclopentane, cyclohexane and methylcyclohexane; and the like.
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 and the like.

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

Methods for volatilizing the solvent in the coating film and drying the coating film include conventionally known drying methods such as hot air drying, heated roll drying, and infrared irradiation.
Conditions for drying the coating film are, for example, 30 seconds to 5 minutes at 80 to 150° C., and more preferably 1 to 4 minutes at 90 to 120° C. By drying the coating film at 90° C. or higher, it is easy to dry the coating film even in a drying time of 5 minutes or less, and productivity is excellent.

There are no particular limitations on the method for producing a device encapsulation body using the device encapsulation adhesive sheet of the present invention. For example, the following steps (a1) to (a5) and steps (b1) to (b5) can be carried out to encapsulate an object to be encapsulated (a device) and produce a device encapsulation body.

Step (a1): The second release film of the device encapsulation adhesive sheet is peeled off and removed to obtain an intermediate for device encapsulation.
Step (a2): The adhesive layer exposed by carrying out step (a1) is attached to an object to be encapsulated (device).
Step (a3): The first release film is further peeled and removed from the device encapsulating intermediate body.
Step (a4): The adhesive layer exposed by carrying out step (a3) is attached to a substrate (a glass plate, a gas barrier film, etc.).
Step (a5): The adhesive layer is cured by a predetermined means to form a cured adhesive layer.

Step (b1): The second release film of the device encapsulation adhesive sheet is peeled off and removed to obtain an intermediate for device encapsulation.
Step (b2): The adhesive layer exposed by carrying out step (b1) is attached to a substrate (a glass plate, a gas barrier film, etc.).
Step (b3): The first release film is further peeled and removed from the device encapsulating intermediate body.
Step (b4): The adhesive layer exposed by carrying out step (b3) is attached to an object to be encapsulated (device).
Step (b5): The adhesive layer is cured by a predetermined means to form a cured adhesive layer.

In the above-mentioned method for producing a sealed device, in step (a2) or step (b2), the attachment of the adhesive layer to the sealed object or substrate is preferably performed in a room temperature (15 to 35°C, the same below) environment from the viewpoint of ease of operation and productivity. Similarly, step (b4) is also preferably performed in a room temperature environment.

In the adhesive sheet for device encapsulation of the present invention, when cutting into a predetermined shape, a punch blade can be pressed into the adhesive sheet for device encapsulation without significantly deforming the adhesive layer, which prevents the adhesive from adhering to the non-release-treated portions of the edge of the release film, allowing the release film to be peeled off efficiently.
Furthermore, the adhesive cured product layer formed using the adhesive layer constituting the device encapsulation adhesive sheet of the present invention has excellent adhesive strength and water vapor barrier properties, and therefore the device encapsulation adhesive sheet of the present invention is suitably used as a material for forming an encapsulant in a device encapsulation body.

The device encapsulation body is not particularly limited. Examples of the device encapsulation body include light-related devices such as light-emitting devices, light-receiving devices, and display devices. When the adhesive layer has high light transmittance, the adhesive sheet for device encapsulation of the present invention is preferably used as a material for forming the encapsulant in the light-related device encapsulation body. Specific examples of these include organic EL devices such as organic EL displays and organic EL lighting; liquid crystal displays; electronic paper; solar cells such as inorganic solar cells and organic thin-film solar cells; and the like.

When the adhesive cured layer obtained from the adhesive layer constituting the device encapsulation adhesive sheet of the present invention is transparent, the device encapsulation adhesive sheet of the present invention is suitably used as a material for forming an encapsulant in devices such as organic EL displays, organic EL lighting, liquid crystal displays, and electronic paper.

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]
Cyclic ether compound (AL1): hydrogenated bisphenol A glycidyl ether epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: YX8000, liquid at 25°C, epoxy equivalent: 205 g/eq)
Cyclic ether compound (AL2): hydrogenated bisphenol A glycidyl ether epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: YX8034, liquid at 25°C, epoxy equivalent: 270 g/eq)
Binder resin (B1): (phenoxy resin, manufactured by Mitsubishi Chemical Corporation, product name: YX7200B35, glass transition temperature (Tg): 150° C.)
Curing agent (C1): Thermal cationic polymerization initiator: benzyl (4-hydroxyphenyl) (methyl) sulfonium tetrakis (pentafluorophenyl) borate (manufactured by Sanshin Chemical Industry Co., Ltd., product name: San-Aid SI-B3)
Curing agent (C2): Imidazole-based curing agent (manufactured by Shikoku Chemical Industry Co., Ltd., product name: Curesol 2E4MZ)
Silane coupling agent (D1): 8-glycidoxyoctyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM4803)
Release film (E1): manufactured by Lintec Corporation, product name: SP-PET752150
Release film (E2): manufactured by Lintec Corporation, product name: SP-PET381130

Example 1
A coating liquid was prepared by dissolving 130 parts by mass of a cyclic ether compound (AL1), 100 parts by mass of a binder resin (B1), 3.8 parts by mass of a curing agent (C1), and 0.2 parts by mass of a silane coupling agent (D1) in methyl ethyl ketone.
This coating liquid was applied onto the release-treated surface of a release film (E1) (first release film), and the resulting coating was dried for 2 minutes at 100° C. to form an adhesive layer having a thickness of 15 μm. The release-treated surface of a release film (E2) (second release film) was attached onto this adhesive layer to obtain an adhesive sheet for device encapsulation.

[Example 2, Comparative Examples 1 and 2]
An adhesive sheet for device encapsulation was obtained in the same manner as in Example 1, except that the types and amounts of each component constituting the adhesive layer were changed to those shown in Table 1.

The following tests were conducted on the adhesive sheets for device encapsulation obtained in Examples 1 and 2 and Comparative Examples 1 and 2. The results are shown in Table 1.

(1) Storage Modulus of Adhesive Layer The adhesive layer of the adhesive sheet for device encapsulation obtained in the Examples or Comparative Examples was laminated using a laminator at 23° C. to a thickness of approximately 1 mm, and the resulting laminate was used as a measurement sample to measure its storage modulus.
That is, the storage modulus of this measurement sample was measured in the temperature range of -20 to +150°C using a storage modulus measuring device (manufactured by Anton Paar, product name: Physica MCR301) under conditions of a frequency of 1 Hz, a strain of 1%, and a heating rate of 3°C/min. The measurement results at 23°C are shown in Table 1.

(2) Storage Modulus of Cured Adhesive Layer The adhesive layers of the device encapsulation adhesive sheets obtained in the Examples and Comparative Examples were laminated to a thickness of 200 μm at 23° C. using a laminator, and the resulting laminate was heated at 110° C. for 1 hour to obtain a cured product. This cured product was used as a measurement sample to measure its storage modulus.
That is, the storage modulus of this measurement sample was measured in the temperature range of -20°C to +150°C using a storage modulus measuring device (manufactured by TA Instruments, product name: DMAQ800) under conditions of a frequency of 11 Hz, an amplitude of 5 μm, and a temperature rise rate of 3°C/min. The measurement results at 90°C are shown in Table 1.

(3) Evaluation of the suitability of the adhesive layer for application to the object to be sealed The adhesive sheets for device sealing obtained in the Examples and Comparative Examples were cut to obtain test pieces with a width of 50 mm and a length of 150 mm. The second release film of the obtained test pieces was peeled off to expose the adhesive layer, which was then placed on alkali-free glass at a temperature of 23° C. and a relative humidity of 50%, and a pressure of 0.5 MPa was applied using a pressure roller. The state of the adhesive layer lifting from the alkali-free glass was observed, and those that did not lift were rated as A, and those that did lift were rated as B.

(4) Evaluation of Cutting Processability of Adhesive Sheet for Device Encapsulation The adhesive sheets for device encapsulation obtained in the Examples and Comparative Examples were cut into a size of 150 mm length and 165 mm width using an air-type sample cutting device.
Specifically, a punching blade of the above size was pressed into the device encapsulation adhesive sheet from the second release film side to cut the device encapsulation adhesive sheet into test pieces.
The second release film of the obtained test piece was peeled off and removed. At this time, a test piece in which the adhesive layer did not peel off from the first release film was rated as A, and a test piece in which the adhesive layer adhered to the end of the second release film and peeled off from the first release film was rated as B.

The following can be seen from Table 1.
The adhesive layers of the device encapsulation adhesive sheets obtained in Examples 1 and 2 have excellent adhesion at 23°C.
Furthermore, these adhesive sheets for device encapsulation also have excellent cutting processability, allowing the release film to be efficiently peeled off and removed.
On the other hand, the adhesive layer of the device encapsulation adhesive sheet obtained in Comparative Example 1 has excellent adhesion at 23°C, but because the storage modulus of the adhesive layer at 23°C is too low, this device encapsulation adhesive sheet has poor cutting processability.
Moreover, the adhesive layer of the device encapsulation adhesive sheet obtained in Comparative Example 2 has an excessively high storage modulus at 23° C., and therefore has poor application properties.

Claims (7)

An adhesive sheet for device encapsulation having a first release film and a second release film, and an adhesive layer sandwiched between the first release film and the second release film, the adhesive sheet for device encapsulation satisfying the following requirements (I) , (II) , (III), (IV), and (V) .
Requirement (I): The adhesive layer is a layer containing one or more compounds having a cyclic ether group that are liquid at 25°C .
Requirement (II): The storage modulus of the adhesive layer at 23° C. is 9.5×10 ⁵ Pa or more and 3.0×10 ⁷ Pa or less.
Requirement (III): The layer obtained by curing the adhesive layer has a storage modulus at 90° C. of 1×10 ⁸ Pa or more.
Requirement (IV): The adhesive layer is a layer containing 53% by mass or more of a compound having a cyclic ether group that is liquid at 25° C. based on the entire adhesive layer.
Requirement (V): The adhesive layer is a layer containing a binder resin having a glass transition temperature of 90° C. or higher. 2 . The adhesive sheet for device encapsulation according to claim 1 , wherein the content of the compound having a cyclic ether group that is liquid at 25° C. is 65% by mass or less based on the entire adhesive layer. 3. The adhesive sheet for device encapsulation according to claim 1, wherein the adhesive layer further contains a curing agent, at least one of which is a thermal cationic polymerization initiator. 4. The adhesive sheet for device encapsulation according to claim 3 , wherein all of the curing agents are thermal cationic polymerization initiators. 5. The adhesive sheet for device encapsulation according to claim 3 , wherein at least one of the compounds having a cyclic ether group is a compound having a glycidyl ether group. The adhesive sheet for device encapsulation according to claim 3 , wherein at least one of the compounds having a cyclic ether group is an alicyclic epoxy resin. The adhesive sheet for device encapsulation according to any one of claims 1 to 6 , which is used for forming an encapsulant in an optical device.