JP7530524B2 - Sheet-shaped curable adhesive and optical component - Google Patents

Description

The present invention relates to a sheet-shaped curable adhesive and optical components, etc.

Conventionally, adhesives cured using cyclic ether group-containing compounds such as epoxy resins have been used in optical applications such as liquid crystal display elements, organic EL (electroluminescence) elements, and micro LED elements.

For example, Patent Document 1 describes an invention relating to an organic electronic device including a substrate having an organic light-emitting element formed thereon and an adhesive film that seals the entire surface of the organic light-emitting element on the substrate. In this case, it is described that the adhesive film includes an adhesive layer, and the adhesive layer includes a photocured product of a photocurable adhesive composition that includes an acrylic polymer, an epoxy resin, and a cationic photopolymerization initiator.

Special table 2015-504580 publication

When an adhesive composition containing a cyclic ether group-containing compound such as an epoxy resin is made into a sheet-shaped curable adhesive, for example, when pressure is applied in the thickness direction, the cyclic ether group-containing compound may seep out from the sheet-shaped curable adhesive, causing so-called bleed-out.
Under these circumstances, there is a demand for sheet-type curable adhesives that can suppress bleed-out.

The sheet-shaped curable adhesive of the present invention is formed from an adhesive composition containing a phenoxy resin having a hydroxyl group and a cyclic ether group-containing compound that is liquid at room temperature, and is adjusted so that the gel fraction is 15% or more.
The present invention provides, for example, an electrically releasing adhesive sheet or the like having the following aspects.
[1] A sheet-like curable adhesive formed from an adhesive composition containing a phenoxy resin (A) having a hydroxyl group and a cyclic ether group-containing compound (B) that is liquid at room temperature, the adhesive having a gel fraction of 15% or more.
[2] The sheet-shaped curable adhesive according to the above [1], wherein the weight average molecular weight of the component (A) is 10,000 to 300,000.
[3] The sheet-shaped curable adhesive according to the above [1] or [2], wherein the glass transition temperature (Tg) of the component (A) is 50°C or higher.
[4] The sheet-shaped curable adhesive according to any one of [1] to [3] above, wherein the viscosity of component (B) at 23°C is 10 to 5,000 mPa·s.
[5] The sheet-shaped curable adhesive according to any one of the above [1] to [4], wherein the component (B) is a homopolymer that, when converted into a homopolymer, has a glass transition temperature (Tg) of 25°C or lower.
[6] The sheet-shaped curable adhesive according to any one of [1] to [5] above, wherein the content of component (B) is 20 to 250 parts by mass per 100 parts by mass of component (A).
[7] The sheet-shaped curable adhesive according to any one of the above [1] to [6], wherein the adhesive composition further comprises a photocationic polymerization initiator (C).
[8] The sheet-form curable adhesive according to any one of the above [1] to [7], wherein the adhesive composition further comprises a crosslinking agent (D) having a functional group capable of reacting with a hydroxyl group.
[9] The sheet-shaped curable adhesive according to the above [8], wherein component (D) comprises an isocyanate-based crosslinking agent (D1).
[10] The sheet-shaped curable adhesive according to the above [8] or [9], wherein the adhesive composition further comprises a crosslinking catalyst (E).
[11] The component (E) contains a metal chelate compound (E1),
The sheet-shaped curable adhesive according to the above-mentioned [10], wherein the metal chelate compound (E1) contains a metal selected from the group consisting of aluminum, bismuth, iron, zirconium, and zinc.
[12] The sheet-shaped curable adhesive according to any one of [1] to [11] above, having a storage modulus at 23°C of 10 MPa or less.
[13] A sheet-like curable adhesive according to any one of [1] to [12] above, for use in optical components.
[14] An optical component comprising a cured product obtained by curing the sheet-shaped curable adhesive according to any one of [1] to [12] above.

The present invention provides a sheet-type curable adhesive that can suppress bleed-out.

The present invention will be described in detail below. Note that the embodiments described below do not limit the present invention, and various modifications can be made within the scope of the present invention.

The numerical ranges described in this specification can be arbitrarily combined with upper and lower limits. For example, when a numerical range is described as "preferably 20 to 120, more preferably 40 to 90," the ranges "20 to 90" and "40 to 120" are also included in the numerical ranges described in this specification. Also, when a numerical range is described as "preferably 20 or more, more preferably 40 or more, and preferably 120 or less, more preferably 90 or less," the ranges "20 to 90" and "40 to 120" are also included in the numerical ranges described in this specification. In addition, when a numerical range described in this specification as "60 to 100," for example, means a range of "60 or more and 100 or less."

In addition, the "active ingredients" of an adhesive composition refer to the components contained in the adhesive composition excluding diluting solvents such as water and organic solvents.

In this specification, the weight average molecular weight (Mw) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

Furthermore, in this specification, the viscosity is a value measured using a rotational viscometer in accordance with JIS Z8803: 2011. Specifically, based on the description of the examples described later, the viscosity is measured using a Brookfield B-type viscometer (analog viscometer RVT) under the following conditions: measurement temperature: 23°C, spindle: No. 5, rotation speed: 20 rpm.

<Sheet-type curable adhesive>
The sheet-form curable adhesive is formed from an adhesive composition containing a phenoxy resin (A) having a hydroxyl group and a cyclic ether group-containing compound (B) that is liquid at room temperature.
In this case, the gel fraction of the sheet-like curable adhesive is 15% or more.
In this specification, the term "sheet-shaped curable adhesive" refers to an adhesive that is non-fluid at room temperature (23° C.) and that is formed into a sheet.
The sheet-like curable adhesive can be formed, for example, by applying an adhesive composition to form a coating film and drying the coating film. In this case, by including a component (A) that has excellent compatibility with component (B) in the adhesive composition and controlling the gel fraction of the resulting sheet-like curable adhesive, it is possible to suppress bleeding out of component (B) from the sheet-like curable adhesive.
The term "bleed out" refers to the phenomenon in which various components contained in the sheet-shaped curable adhesive, such as component (B), seep out onto the surface of the sheet-shaped curable adhesive when the adhesive is stored in a high-temperature and high-humidity environment or a pressurized environment, or when the adhesive is stored for a long period of time in a room temperature environment.

The gel fraction of the sheet-shaped curable adhesive is 15% or more, preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more. By having the gel fraction of the sheet-shaped curable adhesive be 15% or more, it is possible to suppress the bleeding out of the cyclic ether group-containing compound (B). The gel fraction of the sheet-shaped curable adhesive is usually 90% or less, preferably 80% or less, and even more preferably 70% or less. When the content of component (B) in the sheet-shaped curable adhesive layer is increased, the gel fraction of the sheet-shaped curable adhesive tends to decrease, but if the upper limit of the gel fraction of the sheet-shaped curable adhesive is such a value, it becomes easy to include a desired amount of component (B) in the sheet-shaped curable adhesive layer.
In this specification, the "gel fraction" is measured by the method described in the Examples.
The sheet-shaped curable adhesive is used for optical applications such as organic EL (electroluminescence) elements, micro LED elements, etc. That is, the sheet-shaped curable adhesive is preferably used for optical members.

From the viewpoint of being able to handle a wide range of applications, from applications requiring thinness such as small and medium-sized displays to applications requiring thickness such as chip sealing of micro LEDs, the thickness of the sheet-shaped curable adhesive is preferably 1 to 200 μm, more preferably 3 to 175 μm, and even more preferably 10 to 150 μm. In this specification, the thickness of the sheet-shaped curable adhesive can be measured in accordance with JIS K7130:1999 using a known thickness meter. When the optical sheet-shaped adhesive has a release material, the thickness of the optical sheet-shaped adhesive is the thickness excluding the thickness of the release material.

The sheet-shaped curable adhesive preferably has a low storage modulus. A low storage modulus makes it easy to apply the sheet-shaped curable adhesive to an adherend even at room temperature without peeling off.
The storage modulus of the sheet-like curable adhesive at 23° C. is preferably 10 MPa or less, and more preferably 5 MPa or less. The storage modulus of the cured product at 23° C. is preferably 0.01 MPa or more, and more preferably 0.05 MPa or more. In this specification, the "storage modulus of the sheet-like curable adhesive at 23° C." is measured by the method described in the Examples.

[Adhesive composition]
The adhesive composition which is the material for forming the sheet-like curable adhesive of the present invention contains a phenoxy resin (A) having a hydroxyl group and a cyclic ether group-containing compound (B) which is liquid at room temperature.
The adhesive composition used in one embodiment of the present invention may further contain a resin other than component (A), a cationic photopolymerization initiator (C), a crosslinking agent (D) having a functional group capable of reacting with a hydroxyl group, a crosslinking catalyst (E), and the like.

In the adhesive composition used in one embodiment of the present invention, the total content of components (A) and (B) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total amount (100% by mass) of the active ingredients of the adhesive composition. The upper limit of the total content of components (A) and (B) is not particularly limited, and may be 100% by mass or less, 99.5% by mass or less, or 99% by mass or less, based on the total amount (100% by mass) of the active ingredients of the adhesive composition.

In the adhesive composition used in one embodiment of the present invention, the total content of components (A), (B), (C), (D), and (E) is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the total amount (100% by mass) of the active ingredients of the adhesive composition. The upper limit of the total content of components (A), (B), (C), (D), and (E) is not particularly limited, and may be 100% by mass or less, 99.5% by mass or less, or 99% by mass or less, based on the total amount (100% by mass) of the active ingredients of the adhesive composition.

(Component (A): Phenoxy resin having a hydroxyl group)
The hydroxyl group-containing phenoxy resin (A) (hereinafter also referred to as "component (A)") has functions such as maintaining the shape of the sheet-form curable adhesive and imparting flexibility.
In addition, since component (A) has excellent compatibility with component (B) described later, it is possible to suppress the bleeding out of component (B) from the sheet-shaped curable adhesive, and to obtain a sheet-shaped curable adhesive having excellent transparency. In addition, since component (A) has excellent heat resistance, it is possible to obtain a sheet-shaped curable adhesive having high heat resistance. Furthermore, since component (A) can provide a sheet-shaped curable adhesive having a high storage modulus after curing, it can be suitably used for sealing applications of organic EL elements where such properties are required.

Component (A) may be a reaction product of an aromatic diol with at least one selected from an aromatic diglycidyl ether compound and an epihalohydrin.

上記一般式（ａ－１）中、Ａは二価の連結基であり、例えば、置換基を有してもよいアルキレン基、置換基を有してもよいシクロアルキレン基、－Ｏ－、またはＳ－等が挙げられる。
前記アルキレン基としては、炭素数１～１０のアルキレン基が好ましい。前記アルキレン基は、具体的には、メチレン基、エチレン基、プロピレン基、イソプロピレン基、ブチレン基等が挙げられる。
また、前記シクロアルキレン基としては、炭素数３～６のシクロアルキレン基が挙げられる。前記シクロアルキレン基は、具体的には、シクロプロピレン基、シクロブチレン基、シクロペンチレン基、シクロへキシレン基等が挙げられる。
前記アルキレン基および前記シクロアルキレン基が置換基を有する場合の置換基としては、特に制限されないが、炭素数６～２０のアリール基（フェニル基、ナフチル基等）、炭素数３～２０のヘテロアリール基（ピロリル基、ピリジル基等）、炭素数１～１０のアルコキシ基（メトキシ基、エトキシ基、プロピルオキシ基等）、ハロゲン原子（フッ素原子、塩素原子、臭素原子、ヨウ素原子等）、ニトロ基、シアノ基等が挙げられる。これらの置換基は１つが置換していても、２以上が組み合わされて置換されていてもよい。
これらの中でも、Ａは、以下に示す二価の連結基が好ましい。

（上記式中、＊は結合位置を示す。） The aromatic diol may be a substituted or unsubstituted compound having two hydroxyl groups on an aromatic ring having 6 to 30 ring carbon atoms.
Examples of the aromatic ring having 3 to 30 ring carbon atoms include a benzene ring, a naphthalene ring, a fluorene ring, an anthracene ring, a phenanthrene ring, a biphenyl ring, and combinations of these rings.
Specifically, the aromatic diol is preferably a compound represented by the following general formula (a-1).

In the above general formula (a-1), A is a divalent linking group, examples of which include an alkylene group which may have a substituent, a cycloalkylene group which may have a substituent, -O-, or S-.
The alkylene group is preferably an alkylene group having a carbon number of 1 to 10. Specific examples of the alkylene group include a methylene group, an ethylene group, a propylene group, an isopropylene group, and a butylene group.
Moreover, the cycloalkylene group includes a cycloalkylene group having a carbon number of 3 to 6. Specific examples of the cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, and a cyclohexylene group.
When the alkylene group and the cycloalkylene group have a substituent, the substituent is not particularly limited, and examples thereof include aryl groups having 6 to 20 carbon atoms (phenyl group, naphthyl group, etc.), heteroaryl groups having 3 to 20 carbon atoms (pyrrolyl group, pyridyl group, etc.), alkoxy groups having 1 to 10 carbon atoms (methoxy group, ethoxy group, propyloxy group, etc.), halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), nitro group, cyano group, etc. One of these substituents may be substituted, or two or more may be substituted in combination.
Among these, A is preferably a divalent linking group shown below.

(In the above formula, * indicates the bond position.)

Specific examples of aromatic diols include, but are not limited to, benzene ring-containing diols such as hydroquinone, 2-bromohydroquinone, resorcinol, and catechol; 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)butane (bisphenol B), 2,2-bis(4-hydroxy-3-methylphenyl)propane (bisphenol C), 1,1-bis(4-hydroxyphenyl)ethane (bisphenol E), bis(4-hydroxyphenyl)methane (bisphenol F), 1,1- Examples of the diols include phenylalkylbenzene ring-containing diols such as bis(4-hydroxyphenyl)cyclohexane (bisphenol Z); phenyloxybenzene ring-containing diols such as bis(4-hydroxyphenyl)ether; phenylthiobenzene ring-containing diols such as bis(4-hydroxyphenyl)sulfide; biphenyl group-containing diols such as 4,4-dihydroxybiphenyl; ketone group-containing diols such as 4,4'-dihydroxydiphenyl ketone; and fluorene group-containing diols such as 9,9'-bis(4-hydroxyphenyl)fluorene.
These aromatic diols may be used alone or in combination of two or more kinds.

The aromatic diglycidyl ether compound includes a compound having two glycidyl groups on a substituted or unsubstituted aromatic ring having 6 to 30 carbon atoms.
The substituted or unsubstituted aromatic ring having 6 to 30 carbon atoms is the same as that described above.
The aromatic diglycidyl compound has a structure in which two hydrogen atoms of the above-mentioned substituted or unsubstituted aromatic ring having 6 to 30 carbon atoms are replaced with glycidyl groups.
Examples of aromatic diglycidyl compounds include bisphenol A diglycidyl ether, bisphenol B diglycidyl ether, bisphenol C diglycidyl ether, bisphenol E diglycidyl ether, bisphenol F diglycidyl ether, etc. These aromatic diglycidyl compounds may be used alone or in combination of two or more kinds.

Examples of epihalohydrins include epichlorohydrin, epibromohydrin, epiiodohydrin, etc. These epihalohydrins may be used alone or in combination of two or more.

The weight average molecular weight of component (A) is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 30,000 or more, and is preferably 300,000 or less, more preferably 200,000 or less, even more preferably 100,000 or less.
In one embodiment, the weight average molecular weight of component (A) is preferably from 10,000 to 300,000, more preferably from 20,000 to 200,000, and even more preferably from 30,000 to 100,000.

The glass transition temperature (Tg) of component (A) is preferably 50°C or higher, and more preferably 60°C or higher. The glass transition temperature (Tg) of component (A) is preferably 200°C or lower, and more preferably 180°C or lower. If the glass transition temperature (Tg) is 50°C or higher, the fluidity of the sheet-shaped curable adhesive decreases, making it possible to further suppress bleeding out, and also to increase the storage modulus of the sheet-shaped curable adhesive after curing.

The content of component (A) is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more, based on the total amount of active ingredients (100% by mass), from the viewpoint of increasing the shape retention of the sheet-like curable adhesive. Furthermore, the content of component (A) is preferably 75% or less, more preferably 65% or less, based on the total mass of the adhesive composition, from the viewpoint of increasing the content of component (B).

The hydroxyl group equivalent (g/eq) of component (A) is typically 50 to 1,000 g/eq, preferably 100 to 750 g/eq, and more preferably 200 to 500 g/eq.

(Resins other than component (A))
The adhesive composition may contain a resin other than component (A). By containing the other resin in the adhesive composition, the physical properties of the sheet-shaped curable adhesive can be adjusted. In this specification, the "other resin" means a resin other than component (A), and the weight average molecular weight thereof is usually 10,000 or more.

Examples of other resins include, but are not limited to, olefin resins, acrylic resins, polyester resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyvinyl chloride, polyamide resins, cellulose-based materials, polyvinyl ethers, polyimide resins, styrene resins, and copolymers containing structural units of these resins. These other resins may be used alone or in combination of two or more.

In addition, the content of other resins is preferably less than 50 parts by mass, more preferably less than 20 parts by mass, more preferably less than 10 parts by mass, and even more preferably less than 5 parts by mass, per 100 parts by mass of the total amount of component (A).

(Component (B): Cyclic Ether Group-Containing Compound That is Liquid at Room Temperature)
The cyclic ether group-containing compound (B) (hereinafter also referred to as “component (B)”), which is liquid at room temperature, imparts the function of a curable adhesive by being contained in the sheet-form curable adhesive.
Because component (B) is liquid at room temperature, the sheet-shaped curable adhesive has excellent room temperature application properties, and when the sheet-shaped curable adhesive contains a photocationic polymerization initiator, the reactivity between cations and the cyclic ether is high during the curing reaction, so that no uncured component (B) remains in the cured product.
In this specification, "being liquid at room temperature" means being in a liquid state having fluidity at 23°C, that is, having a viscosity of 10,000 mPa·s or less at 23°C.

Component (B) is not particularly limited, but examples thereof include a chain alkyl compound containing a cyclic ether group, an alicyclic alkyl compound containing a cyclic ether group, an aromatic compound containing a cyclic ether group, and a polyoxyalkylene compound containing a cyclic ether group.

Examples of the cyclic ether group-containing linear alkyl compound include a reaction product of a substituted or unsubstituted linear alkyl polyol and a cyclic ether group-containing compound.
The linear alkyl polyol is not particularly limited, but examples thereof include alkanediols having 1 to 10 carbon atoms, such as methanediol, ethylene glycol, propylene glycol, 1,4-butanediol, and neopentyl glycol; alkanetriols having 1 to 10 carbon atoms, such as glycerin and trimethylolpropane; and alkanepolyols having 1 to 10 carbon atoms, such as erythritol, pentaerythritol, and sorbitol. Of these, the linear alkyl polyol is preferably an alkyldiol having 1 to 10 carbon atoms, and more preferably ethylene glycol, propylene glycol, or 1,4-butanediol.
When the linear alkyl polyol has a substituent, the substituent is not particularly limited, and examples thereof include an alkoxy group having 1 to 10 carbon atoms (e.g., a methoxy group, an ethoxy group, a propyloxy group), a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), a nitro group, a cyano group, and the like. One of these substituents may be substituted, or two or more may be substituted in combination. The substituents are usually substituted with hydrogen atoms in the alkylene portion of the linear alkyl polyol.
The cyclic ether group-containing compound is not particularly limited, but examples thereof include three-membered cyclic ether group (oxirane)-containing compounds such as epichlorohydrin, epibromohydrin, epiiodohydrin, etc.; and four-membered cyclic ether group (oxetane)-containing compounds such as 3-(chloromethyl)-3-methyloxetane, 3-(bromomethyl)-3-methyloxetane, etc. Of these, the cyclic ether group-containing compound is preferably a three-membered cyclic ether group (oxirane)-containing compound, and more preferably epichlorohydrin or epibromohydrin.

Examples of the cyclic ether group-containing alicyclic alkyl compound include a reaction product of a substituted or unsubstituted cyclic alkyl polyol with a cyclic ether group-containing compound.
The cyclic alkyl polyol is not particularly limited, but includes cycloalkyl diols having 3 to 10 carbon atoms such as 1,2-cyclopropanediol, 1,2-cyclobutanediol, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclopentanediol, 1,3-cyclopentanediol, and hydrogenated bisphenol A; cycloalkane triols having 3 to 10 carbon atoms such as 1,3,5-cyclohexanetriol; and cycloalkane polyols having 3 to 10 carbon atoms such as 1,2,3,4-cyclohexanetetraol. Of these, the alicyclic alkyl compound is preferably a cycloalkyl diol having 3 to 10 carbon atoms, and more preferably hydrogenated bisphenol A.
When the cyclic alkyl polyol has a substituent, the substituent is not particularly limited, and examples thereof include an alkyl group having 1 to 10 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, etc.), an alkoxy group having 1 to 10 carbon atoms (methoxy group, ethoxy group, propyloxy group, etc.), a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), a nitro group, a cyano group, etc. These substituents may be substituted by one or by a combination of two or more. The substituents are usually substituted with hydrogen atoms of the cyclic alkylene portion of the cyclic alkyl polyol.
The cyclic ether group-containing compound is not particularly limited, but examples thereof include three-membered cyclic ether group (oxirane)-containing compounds such as epichlorohydrin, epibromohydrin, epiiodohydrin, etc.; and four-membered cyclic ether group (oxetane)-containing compounds such as 3-(chloromethyl)-3-methyloxetane, 3-(bromomethyl)-3-methyloxetane, etc. Of these, the cyclic ether group-containing compound is preferably a three-membered cyclic ether group (oxirane)-containing compound, and more preferably epichlorohydrin or epibromohydrin.

Examples of the cyclic ether group-containing aromatic compound include a reaction product of a substituted or unsubstituted aromatic polyol with a cyclic ether group-containing compound.
The aromatic polyol is not particularly limited, and examples thereof include the aromatic diols described in the description of component (A) and aromatic triols such as 1,3,5-benzenetriol. Of these, the aromatic polyol is preferably an aromatic diol, more preferably a phenylalkylbenzene ring-containing diol, and further preferably bisphenol A, bisphenol B, bisphenol C, or bisphenol F.
When the aromatic polyol has a substituent, the substituent is not particularly limited, and examples thereof include an alkyl group having 1 to 10 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, an isopropyl group, etc.), an alkoxy group having 1 to 10 carbon atoms (e.g., a methoxy group, an ethoxy group, a propyloxy group, etc.), a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a nitro group, a cyano group, etc. These substituents may be substituted by one or by a combination of two or more. The substituents are usually substituted with hydrogen atoms on the aromatic ring of the aromatic polyol.
The cyclic ether group-containing compound is not particularly limited, but examples thereof include three-membered cyclic ether group (oxirane)-containing compounds such as epichlorohydrin, epibromohydrin, epiiodohydrin, etc.; and four-membered cyclic ether group (oxetane)-containing compounds such as 3-(chloromethyl)-3-methyloxetane, 3-(bromomethyl)-3-methyloxetane, etc. Of these, the cyclic ether group-containing compound is preferably a three-membered cyclic ether group (oxirane)-containing compound, and more preferably epichlorohydrin or epibromohydrin.

Examples of the cyclic ether group-containing polyoxyalkylene compound include reaction products of substituted or unsubstituted (poly)oxyalkylene polyols and cyclic ether group-containing compounds.
Examples of the (poly)oxyalkylene polyol include compounds having an alkanediol having 1 to 10 carbon atoms as a repeating unit, such as (poly)ethylene glycol, (poly)propylene glycol, (poly)butylene glycol, and (poly)oxyethylene (poly)oxypropylene glycol.
When the (poly)oxyalkylene polyol has a substituent, the substituent is not particularly limited, and examples thereof include an alkoxy group having 1 to 10 carbon atoms (e.g., a methoxy group, an ethoxy group, a propyloxy group), a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), a nitro group, a cyano group, and the like. One of these substituents may be substituted, or two or more may be substituted in combination. The aforementioned substituents usually substitute for hydrogen atoms in the alkylene portion of the (poly)oxyalkylene polyol.
The cyclic ether group-containing compound is not particularly limited, but includes three-membered ring cyclic ether group (oxirane)-containing compounds such as epichlorohydrin, epibromohydrin, epiiodohydrin, and aromatic diglycidyl compounds (such as bisphenol A diglycidyl ether, bisphenol B diglycidyl ether, bisphenol C diglycidyl ether, bisphenol E diglycidyl ether, and bisphenol F diglycidyl ether); and four-membered ring cyclic ether group (oxetane)-containing compounds such as 3-(chloromethyl)-3-methyloxetane and 3-(bromomethyl)-3-methyloxetane. Of these, the cyclic ether group-containing compound is preferably a three-membered ring cyclic ether group (oxirane)-containing compound, and more preferably epichlorohydrin, epibromohydrin, or an aromatic diglycidyl compound.
The above-mentioned component (B) may be used alone or in combination of two or more kinds.

The weight average molecular weight of component (B) is appropriately set so that component (B) is liquid at room temperature, and may be, for example, 50 or more, 100 or more, 150 or more, 200 or more, or 300 or more, and may be less than 5,000, 4,000 or less, 3,000 or less, 2,000 or less, 1,000 or less, or 800 or less.

When the component (B) is made into a homopolymer, the glass transition temperature (Tg) of the homopolymer is preferably 25° C. or lower, more preferably 5° C. or lower, and even more preferably −20° C. or lower. When the component (B) is made into a homopolymer, the glass transition temperature (Tg) of the homopolymer is preferably −100° C. or higher, more preferably −80° C. or higher. When the component (B) is made into a homopolymer, the glass transition temperature (Tg) of the homopolymer is 25° C. or lower, which is preferable because the reactivity of the cyclic ether group of the component (B) is high. This is preferable because, for example, when a sheet-shaped curable adhesive is photopolymerized, the reaction proceeds suitably without heating, and the obtained cured product does not contain unreacted component (B) or almost does not contain unreacted component (B).
When the molecular structure of component (B) is sparse and flexible, the glass transition temperature (Tg) of the homopolymer of component (B) tends to be 25° C. or lower. For example, when component (B) has a polyoxyalkylene group, the glass transition temperature (Tg) of the homopolymer can be 25° C. or lower, which is preferable.

The "glass transition temperature (Tg) of the homopolymer when it is made into a homopolymer" means the glass transition temperature (Tg) of the homopolymer (cured product) obtained when component (B) is cured by the following method and measured.
(Preparation of measurement samples)
To 100 parts by mass of the cyclic ether group-containing compound of component (B), 0.5 parts by mass of a thermal cationic polymerization initiator (manufactured by Sanshin Chemical Industry Co., Ltd., product name: SI-B3A) is added. The resulting mixture is poured into a polytetrafluoroethylene mold having a thickness of 1 mm and a size of 20 mm x 20 mm, and cured by heating at 100°C for 60 minutes to obtain a cured product (measurement sample).
(Differential Scanning Calorimetry)
Using a differential scanning calorimeter [manufactured by TA Instruments, product name: DSCQ2000], differential scanning calorimetry is performed by the following method, and then the glass transition temperature is determined. That is, the above measurement sample is crushed, 5 mg is taken, placed in an aluminum pan, the lid is pressed down and sealed, and once held at 120°C for 5 minutes, and then cooled. Then, measurement is performed from 100°C to +120°C at a heating rate of 10°C/min. The temperature at the intersection of the straight line extending the low-temperature side baseline of the obtained curve to the high-temperature side and the tangent drawn at the point where the gradient of the curve of the stepwise change part of the glass transition is maximum is taken as the glass transition temperature (Tg).

The epoxy equivalent of component (B) is preferably 75 g/eq or more, more preferably 150 g/eq or more. The epoxy equivalent of component (B) is preferably 600 g/eq or less, more preferably 500 g/eq or less.

The viscosity of component (B) at 23°C is preferably 10 mPa·s or more. In addition, since component (B) is liquid at room temperature and has fluidity, the upper limit of the viscosity of component (B) at 23°C is usually 10,000 mPa·s or less, and in the case where the sheet-shaped curable adhesive contains a cationic polymerization initiator, from the viewpoint of increasing the reactivity of the cation with the cyclic ether during the curing reaction, it is preferably 5,000 mPa·s or less, more preferably 3,000 mPa·s or less, and even more preferably 1,000 mPa·s or less. In one embodiment, the viscosity of component (B) at 23°C is preferably 10 to 5,000 mPa·s, and more preferably 10 to 1,000 mPa·s.

The content of component (B) is preferably 40 parts by mass or more, and more preferably 50 parts by mass or more, per 100 parts by mass of component (A). The content of component (B) is preferably 200 parts by mass or less, and more preferably 150 parts by mass or less, per 100 parts by mass of component (A). In one embodiment, the content of component (B) is preferably 40 to 200 parts by mass, and more preferably 50 to 150 parts by mass, per 100 parts by mass of component (A).

(Component (C): Photocationic Polymerization Initiator)
The adhesive composition preferably further contains a photocationic polymerization initiator (C) (hereinafter also referred to as "component (C)"). Component (C) has the function of favorably progressing the polymerization reaction of component (B) etc. when the sheet-shaped curable adhesive is used, and the function of improving the storage stability of the sheet-shaped curable adhesive. Component (C) generates cationic species by light irradiation and initiates the polymerization reaction of component (B) etc.

Component (C) is not particularly limited, but examples thereof include sulfonium salt compounds, iodonium salt compounds, phosphonium salt compounds, ammonium salt compounds, diazonium salt compounds, selenium salt compounds, oxonium salt compounds, and bromine salt compounds.

Examples of sulfonium salt compounds include, but are not limited to, 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 4,4'-bis[diphenylsulfonio]diphenylsulfide-bishexafluorophosphate, etc.

The iodonium salt compound is not particularly limited, but examples thereof include diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di(4-nonylphenyl)iodonium hexafluorophosphate, (tricumyl)iodonium tetrakis(pentafluorophenyl)borate, and the like.
Examples include:

Examples of phosphonium salt compounds include, but are not limited to, tri-n-butyl(2,5-dihydroxyphenyl)phosphonium bromide, hexadecyltributylphosphonium chloride, etc.

The ammonium salt compound is not particularly limited, but examples thereof include benzyltrimethylammonium chloride, phenyltributylammonium chloride, and benzyltrimethylammonium bromide.
The above-mentioned component (C) may be used alone or in combination of two or more kinds.

The content of component (C) is preferably 0.1% by mass or more, and more preferably 0.3% by mass or more, based on the total amount (100% by mass) of the active ingredients of the adhesive composition. The upper limit of the content of component (C) is preferably 3% by mass or less, and more preferably 2% by mass or less.

(Component (D): Crosslinking agent having a functional group capable of reacting with a hydroxyl group)
The adhesive composition preferably further contains a crosslinking agent (D) (hereinafter also referred to as "component (D)") having a functional group capable of reacting with a hydroxyl group. Component (D) has the function of reacting with the hydroxyl group of component (A) to form a crosslinked structure when the sheet-like curable adhesive is formed. This makes it possible to increase the gel fraction of the obtained sheet-like curable adhesive and effectively suppress bleeding out.

Examples of the crosslinking agent (D) having a functional group capable of reacting with a hydroxyl group include an isocyanate-based crosslinking agent (D1) and an acid anhydride crosslinking agent (D2). Of these, the crosslinking agent (D) having a functional group capable of reacting with a hydroxyl group preferably includes an isocyanate-based crosslinking agent (D1) from the viewpoint of high reactivity with a hydroxyl group and selectivity of the molecular skeleton. In this specification, the term "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in the molecule.

The isocyanate-based crosslinking agent (D1) is not particularly limited, but examples thereof include aromatic isocyanates such as phenylene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, and naphthalene diisocyanate; aliphatic isocyanates such as pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and hydrogenated products of the aromatic isocyanates; dimers (biurets), trimers (isocyanurates), and pentamers of these; and trimethylolpropane (TMP) adducts of these.

Of these, the isocyanate-based crosslinking agent (D1) is preferably tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), or a dimer (biuret), trimer (isocyanurate), or pentamer thereof, and more preferably tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), or a dimer (biuret), trimer (isocyanurate), or pentamer thereof.
The above-mentioned isocyanate-based crosslinking agents (D1) may be used alone or in combination of two or more kinds.

Examples of the crosslinking agent (D2) which is an acid anhydride include phthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, pyromellitic anhydride, trimellitic anhydride, methylnadic anhydride, 1,3,3a,4,5,9b-hexahydro-5(tetrahydro-2,5-dioxo-3-furanyl)naphtho[1,2-c]furan-1,3-dione (TDA-100), 1,2,3,4-butanetetracarboxylic dianhydride (BT-100), hydrogenated pyromellitic anhydride (HPMDA), hydrogenated trimellitic anhydride (HTMAn), etc. The above-mentioned crosslinking agents (D2) which are acid anhydrides may be used alone or in combination of two or more kinds.
Furthermore, one or more of the above-mentioned isocyanate-based crosslinking agents (D1) and one or more of the above-mentioned acid anhydride crosslinking agents (D2) may be used in combination.

The content of component (D) is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of component (A). The content of component (D) is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of component (A).

(Component (E): Crosslinking catalyst)
The adhesive composition preferably further contains a crosslinking catalyst (E) (hereinafter also referred to as "component (E)"). Component (E) has the function of promoting the crosslinking reaction between the hydroxyl group of component (A) and the functional group capable of reacting with the hydroxyl group of component (D) when forming the sheet-like curable adhesive. The hydroxyl group of component (A) is preferably derived from an aromatic diglycidyl ether compound or epihalohydrin, and is therefore a secondary hydroxyl group, which tends to have low reactivity due to steric hindrance. By promoting the crosslinking reaction between component (A) and component (D) by allowing component (E) to coexist, a crosslinked structure can be suitably formed. As a result, the gel fraction of the obtained sheet-like curable adhesive can be increased, and bleeding out can be suppressed.

Component (E) is not particularly limited, but examples thereof include metal chelate compounds, metal alkoxides, etc. Of these, it is preferable that component (E) contains a metal chelate compound (E1).

The metal chelate compound (E1) contains a metal and a ligand. In this case, the metal chelate compound (E1) preferably contains a metal selected from the group consisting of aluminum, bismuth, iron, zirconium, and zinc, more preferably contains a metal selected from the group consisting of iron, zirconium, and zinc, and even more preferably contains iron and/or zinc. It is preferable that component (E) contains these metals because the crosslinking reaction rate of components (A) and (D) is increased.

Examples of ligands include β-diketones such as acetylacetone, hexane-2,4-dione, heptane-2,4-dione, heptane-3,5-dione, 5-methyl-hexane-2,4-dione, octane-2,4-dione, 6-methylheptane-2,4-dione, and 2,6-dimethylheptane-3,5-dione; and β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, sec-butyl acetoacetate, tert-butyl acetoacetate, methyl propionylacetate, and ethyl propionylacetate.

The content of component (E) is preferably 0.001 parts by mass or more, and more preferably 0.005 parts by mass or more, per 100 parts by mass of component (A). The content of component (E) is preferably 3 parts by mass or less, and more preferably 1 part by mass or less, per 100 parts by mass of component (A).

The content ratio of component (E) to component (D) [(E)/(D)] is preferably 0.001 or more, more preferably 0.003 or more. The content ratio of component (E) to component (D) [(E)/(D)] is preferably 1 or less, more preferably 0.5 or less.

(Additives)
The adhesive composition may contain additives.
The additives are not particularly limited, and examples thereof include silane coupling agents, ultraviolet absorbers, antistatic agents, light stabilizers, antioxidants, resin stabilizers, fillers, pigments, extenders, softeners, etc. These additives may be used alone or in combination of two or more.

(solvent)
The adhesive composition may contain a solvent. The solvent has the function of imparting fluidity to the adhesive composition, which makes it possible to suitably form a sheet-shaped curable adhesive from the adhesive composition.

Examples of the solvent include, but are not limited to, 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. These solvents may be used alone or in combination of two or more.

The solvent content can be determined appropriately taking into account the composition of the adhesive composition and the manufacturing conditions of the sheet-form curable adhesive.

[Release material]
The sheet-shaped curable adhesive of the present invention may be sandwiched between two release materials. The release material has a function of preventing unintentional adhesion to other members before use, a function of improving handling, etc. When used, the release material is peeled off from the sheet-shaped curable adhesive to adhere to various members.
The release material may include a release substrate and a release agent layer laminated on one or both sides of the release substrate, or the release substrate itself may have releasability and may not have a release agent layer.
Examples of the release substrate include resin films formed from resins such as polyimide, polyamide, polyamideimide, polyphenylene ether, polyether ketone, polyether ether ketone, polyolefin, polyester, polycarbonate, polysulfone, polyether sulfone, polyphenylene sulfide, polyarylate, acrylic resins, cycloolefin polymers, aromatic polymers, and polyurethane polymers. Among these, polyester resins are preferred.
An example of a release substrate having releasability is a resin film made of a fluorine-based resin or the like.
Examples of the release agent layer include layers formed as coatings of resins such as 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 material is not particularly limited, but is preferably 5 to 300 μm, more preferably 10 to 200 μm, and even more preferably 15 to 100 μm.

[Method of producing sheet-shaped curable adhesive]
A sheet-form curable adhesive is formed from the adhesive composition described above.
The method for forming the sheet-like curable adhesive is not particularly limited, but may be, for example, a method in which the adhesive composition is applied to a support and the resulting coating film is dried. In this case, the support is preferably a release material.

Methods for applying the adhesive composition include, but are not limited to, spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, etc.

The drying method is not particularly limited, but examples thereof include hot air drying, hot roll drying, infrared irradiation, and the like.
The drying temperature is not particularly limited, but is preferably from 80 to 150°C, more preferably from 85 to 120°C, and even more preferably from 90 to 110°C.
The drying time is preferably from 30 seconds to 5 minutes, more preferably from 45 seconds to 4 minutes, and even more preferably from 1 to 3 minutes.

The shape retention of the sheet-form curable adhesive is improved by causing at least a portion of the cyclic ether functional groups of component (B) contained in the adhesive composition to undergo a polymerization reaction.
Furthermore, when the adhesive composition contains component (D), the crosslinking reaction between components (A) and (D) improves the shape retention of the sheet-like curable adhesive and increases the gel fraction. In this case, when the adhesive composition further contains component (E), the crosslinking reaction is accelerated and the time required for gelation can be shortened, thereby reducing production costs.
These reactions can be accelerated by the heat involved in drying the formation reactions.

<Optical components>
The sheet-shaped curable adhesive is preferably used for an optical member. Therefore, according to one aspect of the present invention, there is provided an optical member including a cured product obtained by curing the sheet-shaped curable adhesive.

The curing method is not particularly limited, and may be photocuring, heat curing, or a combination of these. From the viewpoint of shortening the time required for the curing process, and from the viewpoint of being able to cure the sheet-shaped curable adhesive without heating and being suitable for use in devices such as organic EL elements that should be avoided at high temperatures, photocuring is preferred as the curing method. The sheet-shaped curable adhesive contains a cyclic ether group-containing compound (B) that is liquid at room temperature, and therefore has high reactivity in the photocuring reaction.

Photocuring is usually carried out by irradiating the sheet-shaped curable adhesive with ultraviolet light.
Examples of ultraviolet light sources include ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arc lamps, black light fluorescent lamps, and metal halide lamps.
The wavelength of the ultraviolet light is preferably, for example, 190 to 380 nm.
The irradiation illuminance is preferably, for example, 20 to 1000 mW/cm ² .
The amount of irradiation light is preferably, for example, 50 to 3000 mJ/ ^cm2 .

Heat curing is usually carried out by heating the sheet-shaped curable adhesive.
The heating temperature is, for example, preferably from 80 to 200°C, and more preferably from 90 to 190°C.
The heating time is, for example, preferably 30 minutes to 12 hours, and more preferably 1 to 6 hours.

The cured product obtained by curing the sheet-shaped curable adhesive preferably has a high storage modulus. A high storage modulus can provide effects such as the sheet-shaped curable adhesive being less likely to soften even at high temperatures and less likely to lose adhesiveness due to temperature changes.
The storage modulus of the cured product at 100° C. is preferably at least 1×10 ⁵ Pa, more preferably at least 2×10 ⁵ Pa, and even more preferably at least 5×10 ⁵ Pa. There is no particular upper limit to the storage modulus of the cured product at 100° C., but it is usually not more than 2×10 ⁷ Pa. In this specification, the "storage modulus of the cured product at 100° C." is measured in accordance with JIS K7244-6 using a viscoelasticity measuring device (product name: MCR302, manufactured by Anton Paar) by the torsional shear method as follows.

(Preparation of measurement samples)
The sheet-shaped curable adhesive is layered to obtain a laminate having a thickness of 0.5 mm. The laminate of the sheet-shaped curable adhesive is irradiated with UV light to cure the laminate made of the sheet-shaped curable adhesive. After UV irradiation, the laminate is heated at 100° C. for 60 minutes to promote the curing reaction, and a cured product of the sheet-shaped curable adhesive (laminate) is obtained.
The UV irradiation is performed using a high pressure mercury lamp manufactured by iGraphics Co., Ltd. under the conditions of an illuminance of 200 mW/cm ² and an integrated light quantity of 1000 mJ/cm ^2. The actinometer used is "UVPF-A1" manufactured by iGraphics Co., Ltd.
The cured sheet-like curable adhesive (laminate) was punched out into a cylindrical body with a diameter of 8 mm (height of 0.5 mm) to be used as a measurement sample.
(Measurement of storage shear modulus)
Using the obtained measurement sample, the storage modulus of the cured product at 100° C. is measured under conditions of a frequency of 1 Hz, a test start temperature of −20° C., a test end temperature of +150° C., and a heating rate of 3° C./min.

In addition, when applied to optical components, the sheet-shaped curable adhesive is applied to the optical component after the attached release material is peeled off. In this case, the sheet-shaped curable adhesive of this embodiment has excellent room temperature application properties and therefore excellent workability. Then, by curing the sheet-shaped curable adhesive to form a cured product, it can function, for example, as a sealing layer for the optical component.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring the weight average molecular weight (Mw), viscosity, and glass transition temperature (Tg) are described below.

[Weight average molecular weight (Mw)]
The weight average molecular weight (Mw) of the phenoxy resin, which is component (A), was measured as a polystyrene equivalent value by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[viscosity]
The viscosity of the epoxy resin constituting component (B) was measured using a rotational viscometer in accordance with JIS Z8803: 2011. Specifically, a Brookfield B-type viscometer (analog viscometer RVT) was used under the following conditions: measurement temperature: 23°C, spindle: No. 5, and rotation speed: 20 rpm.

[Glass transition temperature (Tg)]
The glass transition temperature (Tg) of the cured product of the epoxy resin constituting component (B) was measured by the following method.
(Preparation of measurement samples)
To 100 parts by mass of each epoxy resin, 0.5 parts by mass of a thermal cationic polymerization initiator (manufactured by Sanshin Chemical Industry Co., Ltd., product name: SI-B3A) was added. The resulting mixture was poured into a polytetrafluoroethylene mold having a thickness of 1 mm and a size of 20 mm x 20 mm, and cured by heating at 100°C for 60 minutes to obtain a cured product (measurement sample).
(Differential Scanning Calorimetry)
Using a differential scanning calorimeter [manufactured by TA Instruments, product name: DSCQ2000], differential scanning calorimetry was performed by the following method, and then the glass transition temperature was determined. That is, the above-mentioned measurement sample was crushed, 5 mg was taken, placed in an aluminum pan, the lid was pressed down and sealed, and once held at 120°C for 5 minutes, and then cooled. Then, the temperature was measured from -100°C to +120°C at a heating rate of 10°C/min. The temperature at the intersection of the straight line extending the baseline on the low temperature side of the obtained curve to the high temperature side and the tangent drawn at the point where the gradient of the curve of the stepwise change part of the glass transition is maximum was taken as the glass transition temperature (Tg).

[Gelation completion time, gel fraction]
The time required for the produced adhesive composition to completely gel was evaluated as the gelation completion time.
Specifically, first, the gel fraction of the sheet-shaped curable adhesive immediately after production was measured. Next, the sheet-shaped curable adhesive was stored in an environment of 23°C and 50% relative humidity, and the gel fraction was measured every day. The number of days until the rate of change represented by the following formula fell within ±5% was evaluated as the gelation completion time. If there was no substantial change in the gel fraction value from immediately after application until 14 days later, it was determined that the reaction had not progressed.

The gel fraction was measured by the following method.
That is, the sheet-shaped curable adhesive with release liner was cut to a size of 80 mm x 80 mm. The release liner on both sides of the cut sheet with release liner was removed to prepare a test piece.
In the measurement, the test piece was wrapped in a polyester mesh (product name: Tetoron mesh #200) and weighed on a precision balance, and the mass of the mesh alone was subtracted to calculate the mass (mass of the test piece before immersion).
Next, the test piece wrapped in the mesh was immersed in methyl ethyl ketone (MEK) at 23° C. for 3 days, and then removed and dried in an oven at 100° C. for 2 hours. After immersion, the test piece was wrapped in a polyester mesh (product name: Tetron mesh #200) and weighed on a precision balance, and the mass of the mesh alone was subtracted to calculate the gel fraction (mass of the test piece after immersion). The gel fraction was calculated using the following formula.

The gel fraction of the sheet-shaped curable adhesive was the gel fraction at the time when gelation was complete. If it was determined that the reaction was not progressing, the gel fraction 14 days after preparation was used as the gel fraction of the sheet-shaped curable adhesive.

[Compounds used]
The following compounds were prepared:
(1) Phenoxy resin (A)
YP70 (a reaction product of biphenyl-containing diol and bisphenol diglycidyl ether, glass transition temperature (Tg): 70° C., Mw: 55,000, hydroxyl equivalent = 270 g/eq, manufactured by Nippon Steel Chemical & Material Co., Ltd.)
(2) Cyclic Ether Group-Containing Compound (B)
YX7400 (reaction product of butylene glycol and bisphenol A diglycidyl ether, properties at 23°C: liquid, epoxy equivalent: 440 g/eq, glass transition temperature (Tg) when homopolymerized: -69°C, viscosity (23°C): 200 mPa, manufactured by Mitsubishi Chemical Corporation)
YX8000 (hydrogenated bisphenol A type epoxy resin, properties at 23°C: liquid, epoxy equivalent: 205 g/eq, glass transition temperature (Tg) when homopolymerized: 96.4°C, viscosity (23°C): 2000 mPa, manufactured by Mitsubishi Chemical Corporation)
(3) Photocationic Polymerization Initiator (C)
CPI-100P (4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, manufactured by San-Apro Co., Ltd.)
(4) Crosslinking agent (D)
・BHS-8515 (tolylene diisocyanate (TDI)-based crosslinking agent, manufactured by Toyochem Co., Ltd.)
・Coronate HX (isocyanurate-modified hexamethylene diisocyanate (HDI) isocyanate-based crosslinking agent (triisocyanate), manufactured by Tosoh Corporation)
(5) Crosslinking catalyst (E)
Tris(2,4-pentanedionato)iron(III) (iron (Fe) chelate compound, manufactured by Tokyo Chemical Industry Co., Ltd.)
K-KAT-4205 (zirconium (Zr) chelate compound, manufactured by Kusumoto Chemicals Co., Ltd.)
K-KAT-635 (zinc (Zn) chelate compound, manufactured by Kusumoto Chemicals Co., Ltd.)
K-KAT-640 (bismuth (Bi) chelate compound, manufactured by Kusumoto Chemicals Co., Ltd.)
K-KAT-5218 (aluminum (Al) chelate compound, manufactured by Kusumoto Chemicals Co., Ltd.)

[Example 1]
(Preparation of Adhesive Composition)
An adhesive composition was prepared by diluting 100 parts by mass (effective component ratio) of YP70 as the phenoxy resin (A), 65 parts by mass (effective component ratio) of YX7400 as the cyclic ether group-containing compound (B), 1.2 parts by mass (effective component ratio) of CPI-100P as the photocationic polymerization initiator (C), and 0.01 parts by mass (effective component ratio) of tris(2,4-pentanedionato)iron(III) as the crosslinking catalyst (E) with methyl ethyl ketone to a concentration of the active components of 50% by mass.

(Production of sheet-shaped curable adhesive)
The prepared adhesive composition was applied onto the release-treated surface of a release material, SP-PET752150 (manufactured by Lintec Corporation). The resulting coating was left to stand for 2 minutes while blowing air in an environment of 100°C to dry, thereby producing a sheet-like curable adhesive having a thickness of 25 μm. Next, the release-treated surface of a release material, SP-PET381031 (manufactured by Lintec Corporation), was attached to the surface of the sheet-like curable adhesive that did not have a release material, thereby producing a sheet-like curable adhesive with a release material.

The time to gelation completion and gel separation were also measured.

[Examples 2 to 6, Comparative Examples 1 to 2]
A sheet-shaped curable adhesive with a release liner was produced in the same manner as in Example 1, except that the compounds used and the amounts added were changed as shown in Table 1 below.
The gelation completion time and gel fraction were measured using the above method. Note that, since the gel fraction value of the sheet-shaped curable adhesive produced in Comparative Examples 1 and 2 did not change substantially from immediately after application until 14 days later, it was determined that the reaction had not progressed. For this reason, in Comparative Examples 1 and 2, the gel fraction after 14 days was taken as the gel fraction of the sheet-shaped curable adhesive.

The adhesive compositions or sheet-like curable adhesives with release liner produced in Examples 1 to 6 and Comparative Examples 1 and 2 were measured and evaluated for bleed-out resistance, storage modulus (23°C), and room temperature application. Each measurement and evaluation was performed after the sheet-like curable adhesives were produced and stored in an environment of 23°C and a relative humidity of 50% until the gelation completion time had elapsed (14 days for Comparative Examples 1 and 2).

[Bleed-out resistance]
Using a sheet-like curable adhesive with a release material, multiple sheets were laminated at 23° C. using a laminator so that the thickness of the sheet-like curable adhesive was about 1 mm, and the resulting laminate was cut into a circle with a diameter of 8 mm. The release materials on both sides were peeled off to expose the adhesive layer, which was used as a test piece.
The bleed-out resistance was evaluated using a dynamic viscoelasticity measuring device (manufactured by Anton Paar, product name: Physica MCR301). First, a cylindrical measuring tool having the same cross-sectional shape (diameter 8 mm) as the test piece was closely attached to the upper surface of the test piece so as to overlap it. Next, a load of 1 N was applied to the test piece in the vertical direction from above. After 20 minutes, the test piece was visually observed and the bleed-out resistance was evaluated according to the following criteria. The results obtained are shown in Table 2 below.
A: No seepage of the sheet-shaped curable adhesive component from the test piece outside the outer periphery of the measuring jig was observed, and the bleed-out resistance was excellent. F: Seepage of the sheet-shaped curable adhesive component from the test piece outside the outer periphery of the measuring jig was observed, and the bleed-out resistance was poor.

[Storage modulus (23°C)]
Using a sheet-like curable adhesive with a release material, multiple sheets were laminated at 23° C. using a laminator so that the thickness of the sheet-like curable adhesive was about 1 mm, and the resulting laminate was cut into a circle with a diameter of 8 mm. The release materials on both sides were peeled off to expose the adhesive layer, which was used as a test piece.
Using a dynamic viscoelasticity measuring device (manufactured by Anton Paar, product name: Physica MCR301), the storage modulus was measured in the range of -20 to 150°C 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 2 below.

[Applicability at room temperature]
The sheet-shaped curable adhesive with release material was cut to a size of 25 mm wide and 150 mm long to obtain a test piece. Next, the release material on one side of the test piece was peeled off to expose the sheet-shaped curable adhesive, which was then placed on a glass plate 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 lift between the sheet-shaped curable adhesive and the glass plate was visually observed and evaluated according to the following criteria. The results obtained are shown in Table 2 below.
A: No floating occurred. F: Floating occurred.

From the results in Table 2, the sheet-shaped curable adhesives prepared in Examples 1 to 6 were found to have excellent bleed-out resistance. On the other hand, the sheet-shaped curable adhesives prepared in Comparative Examples 1 and 2 were found to have lower bleed-out resistance than Examples 1 to 6.

Claims (16)

The adhesive composition is formed from a phenoxy resin having a hydroxyl group (A), a cyclic ether group-containing compound (B) that is liquid at room temperature, and an isocyanate-based crosslinking agent (D1),
The component (B) includes a homopolymer having a glass transition temperature (Tg) of 25° C. or lower,
A sheet-form curable adhesive having a gel fraction of 15% or more. The sheet-like curable adhesive according to claim 1, wherein the adhesive composition further contains a photocationic polymerization initiator (C). The sheet-like curable adhesive according to claim 1, wherein the adhesive composition further comprises a crosslinking catalyst (E). The component (E) contains a metal chelate compound (E1),
4. The sheet-form curable adhesive according to claim 3, wherein the metal chelate compound (E1) comprises a metal selected from the group consisting of aluminum, bismuth, iron, zirconium, and zinc. The adhesive composition is formed from a phenoxy resin having a hydroxyl group (A), a cyclic ether group-containing compound (B) that is liquid at room temperature, an isocyanate-based crosslinking agent (D1), and a metal chelate compound (E1),
the metal chelate compound (E1) contains a metal selected from the group consisting of aluminum, bismuth, iron, zirconium, and zinc;
A sheet-form curable adhesive having a gel fraction of 15% or more. The sheet-like curable adhesive according to claim 5, wherein the component (B) includes a homopolymer that, when made into a homopolymer, has a glass transition temperature (Tg) of 25°C or less. The sheet-like curable adhesive according to claim 5, wherein the adhesive composition further contains a photocationic polymerization initiator (C). The adhesive composition is formed from a phenoxy resin having a hydroxyl group (A), a cyclic ether group-containing compound (B) that is liquid at room temperature, a photocationic polymerization initiator (C), an isocyanate-based crosslinking agent (D1), and a crosslinking catalyst (E),
The component (B) includes a homopolymer having a glass transition temperature (Tg) of 25° C. or lower,
A sheet-form curable adhesive having a gel fraction of 15% or more . The adhesive composition is formed from a phenoxy resin having a hydroxyl group (A), a cyclic ether group-containing compound (B) that is liquid at room temperature, a photocationic polymerization initiator (C), an isocyanate-based crosslinking agent (D1), and a crosslinking catalyst (E),
The component (E) contains a metal chelate compound (E1),
the metal chelate compound (E1) contains a metal selected from the group consisting of aluminum, bismuth, iron, zirconium, and zinc;
A sheet-form curable adhesive having a gel fraction of 15% or more . The sheet-like curable adhesive according to any one of claims 1 to 9 , wherein the weight average molecular weight of component (A) is 10,000 to 300,000. The sheet-like curable adhesive according to any one of claims 1 to 9 , wherein the glass transition temperature (Tg) of the component (A) is 50°C or higher. The sheet-like curable adhesive according to any one of claims 1 to 9 , wherein component (B) has a viscosity at 23°C of 10 to 5,000 mPa·s. The sheet-like curable adhesive according to any one of claims 1 to 9 , wherein the content of component (B) is 20 to 250 parts by mass per 100 parts by mass of component (A). The sheet-shaped curable adhesive according to any one of claims 1 to 9 , having a storage modulus at 23°C of 10 MPa or less. The sheet-shaped curable adhesive according to any one of claims 1 to 9 , which is used for optical members. An optical component comprising a cured product obtained by curing the sheet-like curable adhesive according to any one of claims 1 to 9 .