TWI848192B - Sealing sheet - Google Patents

Abstract

The present invention is a sealing sheet having a curable sealing agent layer, characterized in that the sealing sheet satisfies the following requirements (I), (II), and (III). Requirement (I): The sealing agent layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher. Requirement (II): The sealing agent layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group. Requirement (III): The relative dielectric constant of the cured product of the sealing agent layer is 3.5 or less at 23°C and a frequency of 100kHz. According to the present invention, a sealing sheet having a sealing agent layer that becomes a cured product having low dielectric properties and excellent transparency is provided.

Description

Sealing sheet

The present invention relates to a sealing sheet having a curable sealing agent layer.

In recent years, organic EL elements have attracted attention as light-emitting elements that can emit light with high brightness by low-voltage DC drive. However, organic EL elements have the problem that the light-emitting characteristics such as light-emitting brightness, light-emitting efficiency, and light-emitting uniformity are easily reduced over time. The cause of this problem of reduced light-emitting characteristics is believed to be that oxygen or water penetrates into the interior of the organic EL element, causing the electrode or organic layer to deteriorate, so the organic EL element is sealed with a sealing material to prevent the intrusion of oxygen or water.

For example, Patent Document 1 describes an image display device sealant containing a resin component and a hardener, wherein the resin component contains an epoxy resin containing a biphenyl skeleton having a weight average molecular weight within a specific range, an epoxy resin containing a lipid cyclic skeleton having a weight average molecular weight within a specific range, and a styrene-based oligomer having a weight average molecular weight within a specific range. Patent Document 1 also describes that the image display device sealant has a low dielectric constant because it contains a biphenyl skeleton-containing resin and a styrene-based oligomer. By using the image display device sealant as a sealant in a touch panel, malfunction of the touch panel due to the sealant is unlikely to occur. [Prior Art Document] [Patent Document]

[Patent Document 1] WO2018/235824

[Identify the problem you want to solve]

As described in Patent Document 1, a curable sheet adhesive can be suitably used as a material for forming a sealant (hereinafter referred to as "a sheet adhesive for forming a sealant" as a "sealant layer"). In particular, a sealant layer having a cured product with low dielectric properties is useful as a material for forming a sealant for a touch panel or the like.

The present invention aims to provide a sealing sheet that is more suitable as a material for forming a sealing material for a touch panel or the like (that is, a sealing sheet having a sealing agent layer that becomes a cured product having low dielectric properties and excellent transparency). [Means for solving the problem]

The inventors of the present invention have conducted intensive research on a curable sealant layer in order to solve the above problems. As a result, they have found that a cured product of a sealant layer containing a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher and a compound having an alicyclic skeleton and a cyclic ether group has low dielectric properties and excellent transparency, and thus the present invention has been completed.

Thus, according to the present invention, the following sealing sheets [1] to [7] are provided.

[1] A sealing sheet having a curable sealing agent layer, characterized in that the following requirements (I), (II), and (III) are satisfied. Requirement (I): The sealing agent layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher. Requirement (II): The sealing agent layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group. Requirement (III): The relative permittivity of the cured product of the sealing agent layer at 23°C and a frequency of 100 kHz is 3.5 or less. [2] A sealing sheet as described in [1], wherein the dielectric dissipation factor of the cured product of the sealing agent layer at 23°C and a frequency of 100 kHz is 0.05 or less. [3] A sealing sheet as described in [1] or [2], wherein at least one of the compounds having an alicyclic skeleton and a cyclic ether group is a compound that is liquid at 25°C. [4] A sealing sheet as described in any one of [1] to [3], wherein at least one of the compounds having an alicyclic skeleton and a cyclic ether group is a compound having a glycidyl ether group as a cyclic ether group. [5] A sealing sheet as described in any one of [1] to [4], wherein the total light transmittance of the cured product of the sealing agent layer is 90% or more. [6] A sealing sheet as described in any one of [1] to [5], wherein the haze value of the cured product of the sealing agent layer is less than 1%. [7] A sealing sheet as described in any one of [1] to [6], wherein the b* of the cured product of the sealing agent layer is greater than -1 and less than +1 in the CIE 1976 L*a*b* color space. [Effect of the invention]

According to the present invention, a sealing sheet having a sealing agent layer which becomes a cured product having low dielectric properties and excellent transparency is provided.

[Form for implementing the invention]

The sealing sheet of the present invention is a sealing sheet having a curable sealing agent layer, and is characterized by satisfying the following requirements (I), (II), and (III). Requirement (I): The sealing agent layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher. Requirement (II): The sealing agent layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group. Requirement (III): The relative dielectric constant of the cured product of the sealing agent layer is less than 3.5 at 23°C and a frequency of 100 kHz.

In the present invention, "sealant layer" means "sheet adhesive for forming a sealing material". The cured product of the sealant layer is used as a sealant. The sealant layer is a layer that exhibits non-fluidity at room temperature. The sealant layer can be a thin rectangular shape or a long strip (belt shape).

[Requirement (I)] The sealant layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher (hereinafter referred to as "phenoxy resin (A)").

Phenoxy resins are polymers with a polyaddition structure of aromatic diols and aromatic diglycidyl ethers as the main chain. Phenoxy resins are usually equivalent to high molecular weight epoxy resins with a degree of polymerization of about 100 or more.

The phenoxy resin (A) is important in fully exerting the properties of the compound having an alicyclic skeleton and a cyclic ether group (hereinafter referred to as "cyclic ether group-containing compound (B)"). That is, as described later, in order to reduce the dielectric constant of the cured product of the sealant layer and improve the transparency of the cured product of the sealant layer, it is preferable that the sealant layer contains a large amount of the cyclic ether group-containing compound (B). However, a sealant layer containing a large amount of the cyclic ether group-containing compound (B) may have poor shape retention before curing. In this regard, since the sealant layer of the sealing sheet of the present invention contains the phenoxy resin (A), even when the cyclic ether group-containing compound (B) is contained in a large amount, the shape before curing can be maintained at a certain level over a long period of time.

The glass transition temperature (Tg) of the phenoxy resin (A) is 90°C or higher, preferably 95 to 150°C, and more preferably 100 to 150°C. When the glass transition temperature (Tg) of the phenoxy resin (A) is 90°C or higher, the cured product of the sealant layer has excellent shape retention under high temperature conditions. The glass transition temperature (Tg) of the phenoxy resin (A) can be measured using a differential scanning calorimeter.

The weight average molecular weight (Mw) of the phenoxy resin (A) is generally 10,000 to 200,000, preferably 20,000 to 100,000, and more preferably 30,000 to 80,000. When the weight average molecular weight (Mw) of the phenoxy resin (A) is too small, the sealant layer tends to have difficulty maintaining a certain shape. When the weight average molecular weight (Mw) of the phenoxy resin (A) is too large, the operability of the sealant layer tends to deteriorate. The weight average molecular weight (Mw) of the phenoxy resin (A) can be obtained by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent, and the standard polystyrene conversion value is used.

The epoxy equivalent of the phenoxy resin (A) is preferably 5,000 g/eq or more, more preferably 6,500 g/eq or more. The epoxy equivalent can be measured in accordance with JIS K7236.

Phenoxy resin (A) includes, for example, bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol S type phenoxy resin, bisphenol A type and bisphenol F type copolymerized phenoxy resin, bisphenol E type phenoxy resin, naphthalene type phenoxy resin, novolac type phenoxy resin, biphenyl type phenoxy resin, cyclopentadiene type phenoxy resin, etc. Phenoxy resin (A) can be used alone or in combination of two or more.

The phenoxy resin (A) can be obtained by reacting a difunctional phenol and an epihalohydrin to a high molecular weight, or by reacting a difunctional epoxy resin and a difunctional phenol by addition polymerization. For example, the phenoxy resin (A) can be obtained by reacting a difunctional phenol and an epihalohydrin in an inert solvent at a temperature of 40 to 120°C in the presence of an alkali metal hydroxide. Alternatively, the difunctional epoxy resin and difunctional phenol can be subjected to addition polymerization in an organic solvent such as an amide solvent, ether solvent, ketone solvent, lactone solvent, alcohol solvent, etc., with a boiling point of 120°C or more, in the presence of a catalyst such as an alkali metal compound, an organic phosphorus compound, or a cyclic amine compound, and the reaction solid concentration is heated to 50 to 200°C at a concentration of less than 50% by weight.

Bifunctional phenols are not particularly limited as long as they are compounds with two phenolic hydroxyl groups. For example, hydroquinone, 2-bromohydroquinone, resorcinol, o-cyclopentadienol Monocyclic bifunctional phenols such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, etc.; dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl; dihydroxyphenyl ethers such as bis(4-hydroxyphenyl)ether; and those having a straight-chain alkyl group, branched-chain alkyl group, aryl group, hydroxymethyl group, allyl group, cyclic aliphatic group, halogen (tetrabromobisphenol A, etc.), nitro group, etc. introduced into the aromatic ring of the phenol skeleton; polycyclic bifunctional phenols having a straight-chain alkyl group, branched-chain alkyl group, allyl group, substituted allyl group, cyclic aliphatic group, carbalkoxy group, etc. introduced into the central carbon atom of the bisphenol skeleton; etc.

Examples of the halogenated epoxypropane include epichlorohydrin, epibromohydrin, and epiiodohydrin.

In the present invention, the phenoxy resin (A) may be a commercial product. Examples of the commercial products include YX7200 (glass transition temperature: 150°C), YX6954 (phenoxy resin containing a bisphenol acetophenone skeleton, glass transition temperature: 130°C), and jER1256 (glass transition temperature: 98°C) (all manufactured by Mitsubishi Chemical Corporation).

The content of the phenoxy resin (A) is preferably 30 to 55% by mass, more preferably 35 to 50% by mass, relative to the entire sealant layer. By keeping the content of the phenoxy resin (A) within the above range, it is easy to obtain an improved shape retention of the sealant layer and a sealant layer having low dielectric properties and excellent transparency after curing. In the present invention, "having low dielectric properties" means satisfying requirement (III).

[Requirement (II)] The sealant layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group [cyclic ether group-containing compound (B)]. The compound having an alicyclic skeleton and a cyclic ether group is a compound having an alicyclic skeleton and at least one, preferably two or more, cyclic ether groups in the molecule. In the present invention, the compound having an alicyclic skeleton and a cyclic ether group does not include a phenoxy resin (A). The sealant layer contains the cyclic ether group-containing compound (B), and the cured product of the sealant layer has low dielectric properties and better transparency.

The molecular weight of the cyclic ether group-containing compound (B) is usually 100 to 5,000, preferably 200 to 3,000. The cyclic ether equivalent of the cyclic ether group-containing compound (B) is preferably 50 g/eq or more and 1000 g/eq or less, more preferably 100 g/eq or more and 800 g/eq or less. By hardening the sealant layer having the cyclic ether equivalent of the cyclic ether group-containing compound (B) in the above range, a sealant with high bonding strength can be formed more efficiently. The cyclic ether equivalent of the present invention refers to the value obtained by dividing the molecular weight by the number of cyclic ether groups.

Cyclic ether groups include, for example, oxiranyl groups (epoxy groups), oxetane groups (oxetanyl groups), tetrahydrofuranyl groups, tetrahydropyranyl groups, etc. Among these, the cyclic ether group is preferably an oxiranyl group. In addition, in the present specification, an oxiranyl group includes groups having an oxirane structure such as a glycidyl group, a glycidyl ether group, an epoxyhexyl group, etc.

The cyclic ether group-containing compound (B) is, for example, an epoxide olefin compound such as a polyglycidyl etherified product of a polyol having at least one alicyclic structure, or a cyclohexene oxide or cyclopentene oxide-containing compound obtained by epoxidizing a cyclohexene or cyclopentene ring-containing compound with an oxidizing agent.

Representative compounds of the cyclic ether group-containing compound (B) include hydrogenated bisphenol A diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-1-methylcyclohexyl-3,4-epoxy-1-methylhexanecarboxylate, 6-methyl-3,4-epoxycyclohexylmethyl-6-methyl-3,4-epoxycyclohexanecarboxylate, 3,4- Epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexanecarboxylate, 3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, 3,4-epoxy-6-methylcyclohexanecarboxylate, methylenebis(3,4-epoxycyclohexane) bis(3,4-epoxy cyclohexane)), propan-2,2-diyl-bis(3,4-epoxycyclohexane), 2,2-bis(3,4-epoxycyclohexane)propane, dicyclopentadiene dicyclooxide, ethylene bis(3,4-epoxycyclohexane carboxylate), dioctyl epoxide hexahydrophthalate, di-2-ethylhexyl epoxide hexahydrophthalate, 1-epoxyethyl-3,4-epoxycyclohexane, 1,2-epoxy-2-epoxyethylcyclohexane, α-pinene oxide oxide), limonene oxide, etc.

In addition, the cyclic ether group-containing compound (B) may be a commercial product, such as Celloxide 2021P, Celloxide 2081, Celloxide 2000, Celloxide 3000 (manufactured by Daicel Corporation); Epolight 4000 (manufactured by Kyoei Chemical Co., Ltd.); YX8000, YX8034 (manufactured by Mitsubishi Chemical Corporation); ADEKARESIN EP-4088S, ADEKARESIN EP-4088L, ADEKARESIN EP-4080E (manufactured by ADEKA Corporation); and the like.

The cyclic ether group-containing compound (B) may be used alone or in combination of two or more.

The content of the cyclic ether group-containing compound (B) is preferably 45% by mass or more, and more preferably 55 to 70% by mass, relative to the entire sealant layer. By setting the content of the cyclic ether group-containing compound (B) to be 50% by mass or more relative to the entire sealant layer, a cured sealant layer having a lower dielectric constant and better transparency can be easily obtained.

At least one of the cyclic ether group-containing compounds (B) is preferably a compound that is liquid at 25°C. "Liquid at 25°C" means having fluidity at 25°C. The viscosity of the cyclic ether group-containing compound (B) at 25°C and 1.0 rpm measured using an E-type viscometer is preferably 2 to 10000 mPa‧s. By using a cyclic ether group-containing compound (B) that is liquid at 25°C, a sealant layer with better adhesion at room temperature (i.e., 25°C, the same below) can be easily formed.

When the sealant layer contains a cyclic ether group-containing compound (B) that is liquid at 25°C, its content is preferably 55% by mass or more, and more preferably 55 to 70% by mass, relative to the entire sealant layer. By making the content of the epoxy compound that is liquid at 25°C 55% by mass or more relative to the entire sealant layer, it is easy to form a sealant layer with better adhesion at room temperature.

At least one of the cyclic ether group-containing compounds (B) is preferably a compound having a glycidyl ether group as the cyclic ether group. The glycidyl ether group is not as reactive as epoxy epoxyhexyl and the like, so the use of a cyclic ether group-containing compound (B) having a glycidyl ether group makes it easier to obtain a sealing sheet with better storage stability.

When the sealant layer contains a cyclic ether group-containing compound (B) having a glycidyl ether group, its content is preferably 55% by mass or more, and more preferably 55 to 70% by mass, relative to the entire sealant layer. By making the content of the cyclic ether group-containing compound (B) having a glycidyl ether group be 55% by mass or more relative to the entire sealant layer, it is easy to obtain a sealing sheet with better storage stability.

[Requirement (III)] The relative dielectric constant of the cured product of the sealant layer at 23°C and a frequency of 100 kHz (hereinafter referred to as "relative dielectric constant (α)") is 3.5 or less. By using a cured product having a relative dielectric constant (α) of 3.5 or less as a sealant in an electronic device having a touch sensor such as a touch panel, malfunction of the electronic device caused by the sealant can be suppressed. The relative dielectric constant (α) is preferably 3.48 or less, and more preferably 3.47 or less. The lower limit of the relative dielectric constant (α) is not particularly limited, and is usually 2.00 or more.

The test material for the relative dielectric constant (α) is not particularly limited as long as it can fully cure the sealant layer. For example, in the case where the sealant layer has thermosetting properties, a cured product obtained under the curing conditions of 110°C and 1 hour can be used as a measurement sample for the relative dielectric constant (α). The relative dielectric constant (α) can be measured according to the method described in the embodiment.

The cured product of the sealant layer containing a large amount of the cyclic ether group-containing compound (B) tends to have a smaller relative dielectric constant (α). Therefore, the sealant layer satisfying requirement (III) can be formed more efficiently by adjusting the content of the cyclic ether group-containing compound (B).

[Hardener] The sealant layer may contain a hardener. By using a hardener, a sealant layer in which the hardening reaction is performed more efficiently can be obtained. The hardener is not particularly limited as long as it is a hardener that at least initiates the hardening reaction of the cyclic ether group-containing compound (B). Since the hardening reaction can be completed in a shorter time, it is preferable to use a hardener that initiates the hardening reaction by heating. The hardener that initiates the hardening reaction by heating is, for example, a cationic thermal polymerization initiator or a heat-reactive hardener other than these.

Cationic thermal polymerization initiators are compounds that can generate cationic species that initiate polymerization upon heating. Cationic thermal polymerization initiators include, for example, sulfonium salts, quaternary ammonium salts, phosphonium salts, diazonium salts, and iodonium salts.

Examples of the coronium salt include triphenylcoronium tetrafluoroborate, triphenylcoronium hexafluoroantimonate, triphenylcoronium hexafluoroarsenate, triphenyl(4-methoxyphenyl)coronium hexafluoroarsenate, and diphenyl(4-phenylthiophenyl)coronium hexafluoroarsenate.

Commercially available products may be used as cobalt salts. Examples of commercially available products include ADEKAOPTONS SP-150, ADEKAOPTONS SP-170, ADEKAOPTONS CP-66, and ADEKAOPTONS CP-77 (manufactured by Asahi Denka Co., Ltd.), SAN-AID SI-60L, SAN-AID SI-80L, SAN-AID SI-100L, SAN-AID SI-B2A, and SAN-AID SI-B3 (manufactured by Sanshin Chemical Co., Ltd.), CYRACURE UVI-6974 and CYRACURE UVI-6990 (manufactured by Union Carbide Co., Ltd.), UVI-508 and UVI-509 (manufactured by General Electric Co., Ltd.), and FC-508 and FC-509 (manufactured by Minnesota Mining Co., Ltd.). & Manufacturing Co., Ltd.), CD-1010, CD-1011 (the above are manufactured by Thurstomer Co., Ltd.), CI series products (manufactured by Nippon Soda Co., Ltd.), etc.

Quaternary ammonium salts, such as 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, hexafluoroantimonate), N,N-diethyl-N-benzyl trifluoromethanesulfonate, N,N-dimethyl-N-(4-methoxybenzyl)pyridinium hexafluoroantimonate, N,N-diethyl-N-(4-methoxybenzyl) toluidinium hexafluoroantimonate, etc.

Examples of the phosphonium salt include ethyltriphenylphosphonium hexafluoroantiphonate and tetrabutylphosphonium hexafluoroantiphonate.

Examples of the diazonium salt include AMERICURE (manufactured by America Can Co., Ltd.) and ULTRASET (manufactured by Asahi Denka Co., Ltd.).

Iodine salts include, for example, diphenyl iodine hexafluoroarsenate, bis(4-chlorophenyl)iodine hexafluoroarsenate, bis(4-bromophenyl)iodine hexafluoroarsenate, phenyl(4-methoxyphenyl)iodine hexafluoroarsenate, etc. Commercially available products such as UV-9310C (manufactured by Toshiba Silicone Co., Ltd.), Photoinitiator 2074 (manufactured by Rhône-Poulenc Co., Ltd.), UVE series products (manufactured by General Electric Co., Ltd.), and FC series products (manufactured by Minnesota Mining & Manufacturing Co., Ltd.) can also be used.

Examples of heat-reactive curing agents other than cationic thermal polymerization initiators include amine compounds such as benzylmethylamine and 2,4,6-tris-dimethylaminomethylphenol; imidazole compounds such as 2-methylimidazole, 3-ethyl-4-methylimidazole, and 2-heptadecylimidazole; Lewis acids such as boron trifluoride-monoethylamine complex and boron trifluoride-piperazine complex; and the like.

The hardener may be used alone or in combination of two or more. The content of the hardener 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 group-containing compound (B).

[Silane coupling agent] The sealant layer may also contain a silane coupling agent. By using a silane coupling agent, it is easy to obtain a sealant layer with better wet heat durability.

The silane coupling agent may be a known silane coupling agent. Among them, an organic silicon compound having at least one alkoxysilyl group in the molecule is preferred. Silane coupling agents, such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, etc., silane coupling agents having (meth)acryl groups; vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, diethoxymethylvinylsilane, trichlorovinylsilane, vinyltris(2-methoxyethoxy)silane, etc., silane coupling agents having vinyl groups; Silane coupling agents having epoxy groups, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 8-glycidoxyoctyltrimethoxysilane, etc.; Silane coupling agents having styryl groups, such as p-styryltrimethoxysilane, p-styryltriethoxysilane, etc.;

Silane coupling agents having amino groups, 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-dimethylbutylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride; Silane coupling agents having urea groups, such as 3-ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane; Silane coupling agents having halogen atoms such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane; Silane coupling agents having halogen groups such as 3-butylpropylmethyldimethoxysilane and 3-butylpropyltrimethoxysilane; Silane coupling agents having sulfide groups such as bis(trimethoxysilylpropyl) tetrasulfide and bis(triethoxysilylpropyl) tetrasulfide; Silane coupling agents having isocyanate groups such as 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane; 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; etc. These silane coupling agents can be used alone or in combination of two or more.

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

[Other ingredients] The sealant layer may contain other ingredients within the scope that does not hinder the effect of the present invention. Other ingredients include additives such as ultraviolet absorbers, antistatic agents, light stabilizers, antioxidants, resin stabilizers, fillers, pigments, extenders, softeners, etc. These can be used alone or in combination of two or more. When the sealant layer contains such additives, their content can be appropriately determined according to the purpose.

[Sealing agent layer] The thickness of the sealing agent layer is usually 1 to 50 μm, preferably 1 to 25 μm, and more preferably 5 to 25 μm. The sealing agent layer having a thickness within the above range is suitable for use as a material for forming a sealing material. The thickness of the sealing agent layer can be measured using a known thickness gauge in accordance with JIS K 7130 (1999).

The method for forming the sealant layer is not particularly limited. For example, the sealant layer can be formed using a casting process. When the sealant layer is produced by a casting process, a sealant composition containing components constituting the sealant layer can be prepared, and the obtained sealant composition can be applied to a substrate or a peeling layer surface of a peeling film that has been subjected to a peeling treatment using a known method, and the obtained coating is dried to form a sealant layer.

The sealant composition may also contain a solvent. The solvent may be, for example, an aromatic hydrocarbon solvent such as benzene, toluene, etc.; an ester solvent such as ethyl acetate, butyl acetate, etc.; a ketone solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.; an aliphatic hydrocarbon solvent such as n-pentane, n-hexane, n-heptane, etc.; an aliphatic cyclopentane, cyclohexane, methylcyclohexane, etc.; etc. These solvents may be used alone or in combination of two or more. The content of the solvent may be appropriately determined in consideration of the coating properties, etc.

The method of applying the sealant composition includes, for example, a rotary coating method, a spray coating method, a rod coating method, a knife coating method, a roller coating method, a scraper coating method, a nozzle coating method, a gravure coating method, and the like.

The method for drying the coating film is a known drying method such as hot air drying, hot roller drying, infrared irradiation, etc. The conditions for drying the coating film are, for example, 80 to 150°C and 30 seconds to 5 minutes.

When the sealant layer has a thermosetting property, by heating the sealant layer, at least the cyclic ether group of the cyclic ether group-containing compound (B) reacts, thereby curing the sealant layer.

There are no particular restrictions on the conditions for heat-hardening the sealant layer. The heating temperature is usually 80 to 200°C, preferably 90 to 150°C. The heating time is usually 30 minutes to 12 hours, preferably 1 to 6 hours.

The dielectric loss factor of the cured product of the sealant layer at 23°C and a frequency of 100kHz (hereinafter referred to as "dielectric loss factor (β)") is preferably 0.05 or less, more preferably 0.045 or less, and even more preferably 0.040 or less. The lower limit of the dielectric loss factor (β) is not particularly limited, but is usually 0.0001 or more. When the dielectric loss factor (β) is 0.05 or less, heat generation or signal attenuation can be suppressed. The dielectric loss factor (β) can be measured according to the method described in the embodiment. Since the sealant layer of the sealing sheet of the present invention contains a cyclic ether group-containing compound (B), the cured product tends to have a reduced dielectric loss factor.

The total light transmittance of the cured product of the sealant layer is preferably 90% or more, more preferably 91% or more. The upper limit of the total light transmittance is not particularly limited, and is usually 100% or less. By using a cured product with a total light transmittance of 90% or more as a sealant in a display device such as a touch panel, an electronic device with better visibility can be obtained. The total light transmittance can be measured according to the method described in the embodiment. Since the sealant layer of the sealing sheet of the present invention contains a cyclic ether group-containing compound (B), the cured product tends to have an increased total light transmittance.

The haze value of the cured product of the sealant layer is preferably 1% or less, more preferably 0.9% or less, and particularly preferably 0.4% or less. The lower limit of the haze value is not particularly limited, and is usually 0% or more. By using a cured product with a haze value of 1% or less as a sealant in a display device such as a touch panel, an electronic device with better visibility can be obtained. The haze value can be measured according to the method described in the embodiment. Since the sealant layer of the sealing sheet of the present invention contains a cyclic ether group-containing compound (B), the cured product tends to have a reduced haze value.

The b* value of the cured product of the sealant layer in the CIE 1976 L*a*b* color space is preferably greater than -1 and less than +1. By using a cured product having a b* value within the above range as a sealant in a display device such as a touch panel, an electronic device with better visibility can be obtained. The b* value can be measured according to the method described in the embodiment. The sealant layer of the sealing sheet of the present invention has a tendency to have a b* value close to 0 because it contains a cyclic ether group-containing compound (B).

[Sealing sheet] The sealing sheet of the present invention has the above-mentioned sealing agent layer. In addition to the sealing agent layer, the sealing sheet of the present invention may also have a substrate, a release film, a functional film, etc.

Resin films can usually be used as substrates. The resin components of the resin films are, for example, polyimide, polyamide, polyamide-imide, polyphenylene ether, polyether ketone, polyether ether ketone, polyolefin, polyester, polycarbonate, polysulfone, polyether sulfone, polyphenylene sulfide, polyacrylate, acrylic resin, cycloolefin polymer, aromatic polymer, polyurethane polymer, liquid crystal polymer film, etc. The thickness of the substrate is not particularly limited, preferably 10 to 500 μm, more preferably 10 to 300 μm, and even more preferably 15 to 200 μm.

The peeling film acts as a support in the manufacturing step of the sealing sheet, and acts as a protective sheet for the sealant layer until the sealing sheet is used. In addition, when using the sealing sheet of the present invention, the peeling film is usually peeled off and removed.

A known peeling film can be used. For example, a peeling film substrate having a peeling layer treated with a peeling agent. The peeling film substrate includes, for example, a paper substrate such as glass paper, coated paper, or high-quality paper; laminated paper with thermoplastic resins such as polyethylene laminated on these paper substrates; plastic films such as polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polypropylene resin, and polyethylene resin; etc.

The stripping agent is, for example, a rubber elastomer such as a silicone resin, an olefin resin, an isoprene resin, a butadiene resin, a long-chain alkyl resin, an alkyd resin, a fluorine resin, etc. The thickness of the stripping film is not particularly limited, but is generally about 20 to 250 μm.

When the sealing sheet of the present invention has a release film, there may be two release films, one on each side of the sealing agent layer, or there may be a release film on only one side of the sealing agent layer.

Functional films include, for example, conductive films, gas barrier films, anti-reflection films, phase difference films, viewing angle enhancement films, brightness enhancement films, etc. Among these, for example, gas barrier films are thin films with metal or inorganic compound films. The thickness of the functional film is not particularly limited, but is usually 5 to 200 μm, preferably 10 to 100 μm.

The sealant layer of the sealing sheet of the present invention is suitable for use as a material for forming a sealant of an electronic device. The sealant layer of the sealing sheet of the present invention provides a cured product with low dielectric properties. Due to the production of this property, the electronic device is preferably a touch sensor having a touch panel. In addition, the sealant layer of the sealing sheet of the present invention provides a cured product with excellent transparency. Due to the production of this property, the electronic device is preferably an electronic device requiring light transmittance. Electronic devices requiring light transmittance include, for example, organic EL elements such as organic EL displays and organic EL lighting; liquid crystal elements such as liquid crystal displays; electronic book elements; solar cell elements; light-emitting diodes; etc.

The method of sealing an electronic device using the sealing sheet of the present invention is not particularly limited. For example, the electronic device can be sealed by attaching a sealing agent layer of the sealing sheet of the present invention to the target electronic device and then curing the sealing agent layer by the above method. [Example]

The present invention is described in more detail with the following examples, but the present invention is not limited to the following examples.

[Compounds used in Examples or Comparative Examples] ‧Phenoxy resin (A1): (Mitsubishi Chemical Co., Ltd., trade name: YX6954BH30, glass transition temperature (Tg): 130°C, epoxy equivalent: 10,000 to 16,000 g/eq) ‧Phenoxy resin (A2): (Mitsubishi Chemical Co., Ltd., trade name: 1256B40, glass transition temperature (Tg): 98°C, epoxy equivalent: 6,700 to 8,000 g/eq) ‧Phenoxy resin (A3): (Mitsubishi Chemical Co., Ltd., trade name: YX8100BH30, glass transition temperature (Tg): 150°C) ‧Compounds with cyclic ether groups (B1): Hydrogenated bisphenol A epoxy resin [Mitsubishi Chemical Co., Ltd., trade name: YX8034, cyclic ether equivalent: 270 g/eq, having an alicyclic skeleton and glycidyl ether groups, and being a liquid compound at 25°C] ‧Compounds with cyclic ether groups (B2): Hydrogenated bisphenol A epoxy resin [Mitsubishi Chemical Co., Ltd., trade name: YX8000, cyclic ether equivalent: 205 g/eq, having an alicyclic skeleton and glycidyl ether groups, and being a liquid compound at 25°C] ‧Compound with cyclic ether group (BX1): Bisphenol A type epoxy resin [Mitsubishi Chemical Co., Ltd., trade name: jER828, cyclic ether equivalent: 189g/eq, a compound having an aromatic skeleton and a glycidyl ether group, liquid at 25°C] ‧Cationic thermal polymerization initiator (C1): (Sanshin Chemical Co., Ltd., trade name: SAN-AID SI-B3) ‧Silane coupling agent (D1): 8-glycidoxyoctyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., trade name: KBM4803)

[Example 1] 100 parts by mass of phenoxy resin (A1), 150 parts by mass of compound having a cyclic ether group (B1), 3.3 parts by mass of cationic thermal polymerization initiator (C1), and 0.2 parts by mass of silane coupling agent (D1) were dissolved in methyl ethyl ketone to prepare a coating liquid. This coating liquid was applied to the peeling treatment surface of a peeling film (the first peeling film, manufactured by Lintech, trade name: SP-PET752150), and the obtained coating film was dried at 100°C for 2 minutes to form a sealant layer with a thickness of 15 μm. The peeling-treated surface of a peeling film (the second peeling film, manufactured by Lintech, trade name: SP-PET381130) is laminated onto the sealant layer to obtain a sealing sheet.

[Examples 2 to 3, Comparative Examples 1 and 2] Except for changing the types and amounts of the components constituting the sealant layer to those described in Table 1, the rest is the same as Example 1 to obtain a sealing sheet.

The following tests were conducted on the sealing sheets obtained in Examples 1 to 3 and Comparative Examples 1 and 2. The results are shown in Table 1.

[Relative dielectric constant, dielectric loss factor] The sealing sheet obtained in the embodiment or comparative example was heated at 110°C for 1 hour to cure the sealant layer. The peeling film was peeled off from the cured sealing sheet to obtain a test sample. For the obtained test sample, the relative dielectric constant and dielectric loss factor at 23°C and 100kHz were measured using an LF impedance analyzer (manufactured by Agilent Technologies, HP4192A) by the automatic balancing bridge method.

[Total light transmittance] One peeling film of the sealing sheet obtained in the embodiment or comparative example was peeled off to expose the sealant layer. The exposed sealant layer was bonded to alkali-free glass at 23°C using a laminating press to obtain a laminate. The obtained laminate was heated at 110°C for 1 hour to cure the sealant, and then one peeling film was peeled off to obtain a test sample. For the obtained test sample, the total light transmittance (%) was measured using a haze meter (NDH-2000, manufactured by Nippon Denshoku Industries) in accordance with JIS K7361:1997.

[Haze value] The same test sample as used in the total light transmittance was prepared. The haze value (%) of the obtained test sample was measured using a haze meter (NDH-2000 manufactured by Nippon Denshoku Industries) in accordance with JIS K7136:2000.

[Color measurement] The same test sample as used in the total light transmittance was prepared. For the obtained test sample, the color value b* specified in the CIE 1976 L*a*b* color system was measured using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3200) in accordance with JIS Z 8729-1994.

[Table 1] Embodiment Comparison Example 1 2 3 1 2 Composition (mass) Phenoxy resin (A1) 100 - - - - Phenoxy resin (A2) - 100 100 100 - Phenoxy resin (A3) - - - - 100 Compounds with cyclic ether groups (B1) - - 150 - - Compounds with cyclic ether groups (B2) 150 150 - - - Compounds with cyclic ether groups (BX1) - - - 150 150 Cationic thermal polymerization initiator (C1) 3.3 3.3 3.3 3.3 3.3 Silane coupling agent (D1) 0.2 0.2 0.2 0.2 0.2 Relative dielectric constant 3.47 3.46 3.50 3.77 3.89 Dielectric loss factor 0.032 0.038 0.039 0.042 0.030 Total light transmittance (%) 91 91 91 91 91 Fog value (%) 0.4 0.4 0.4 0.5 0.5 b* value 0.3 0.2 0.2 0.2 0.3

The following can be seen from Table 1. The sealant layer of the sealing sheet obtained in Examples 1 to 3 contains a large amount of a compound having an alicyclic skeleton and a cyclic ether group [cyclic ether group-containing compound (B)], so its cured product has low dielectric properties and excellent transparency. On the other hand, in Comparative Examples 1 and 2, where a compound having an aromatic skeleton and a cyclic ether group is used instead of the cyclic ether group-containing compound (B), the cured product of the sealant layer of the sealing sheet obtained has an increased dielectric constant.

without.

without.

Claims (7)

A sealing sheet having a curable sealing agent layer, which satisfies the following requirements (I), (II), and (III), wherein the sealing agent layer contains a phenoxy resin having a glass transition temperature (Tg) of 90°C or higher, the sealing agent layer contains one or more compounds having an alicyclic skeleton and a cyclic ether group, and the sealing agent layer has a relative dielectric constant of 3.5 or less at 23°C and a frequency of 100kHz, wherein the content of the compound having an alicyclic skeleton and a cyclic ether group is 55-70% by mass relative to the entire sealing agent layer. A sealing sheet as described in claim 1, wherein the dielectric loss factor of the cured sealant layer is less than 0.05 at 23°C and a frequency of 100kHz. A sealing sheet as described in claim 1 or 2, wherein at least one of the compounds having an alicyclic skeleton and a cyclic ether group is a liquid compound at 25°C. The sealing sheet as described in claim 1 or 2, wherein at least one of the compounds having an alicyclic skeleton and a cyclic ether group is a compound having a glycidyl ether group as a cyclic ether group. A sealing sheet as described in claim 1 or 2, wherein the total light transmittance of the cured sealant layer is 90% or more. A sealing sheet as described in claim 1 or 2, wherein the haze value of the cured product of the sealant layer is less than 1%. A sealing sheet as described in claim 1 or 2, wherein the cured product of the sealant layer has a b* value of greater than -1 and less than +1 in the CIE 1976 L*a*b* color space.