JP2021114471A - Sealing sheet - Google Patents

Abstract

To provide a sealing sheet having a sealing agent layer which is excellent in sticking property at normal temperature and is less likely to be deformed in a thermosetting process.SOLUTION: A sealing sheet has a thermosetting sealing agent layer, and satisfies the following requirements (I) to (III). The sealing agent layer contains an epoxy compound, a binder resin and a curing agent. At least one epoxy compound is an epoxy compound which is liquid at 25°C, at least one curing agent is a heat cationic polymerization initiator having a peak top temperature of exothermic peak when differential scanning calorimetry is performed under specific conditions of 120°C or lower. Requirement (I): the sealing agent layer contains one or two or more kinds of epoxy compounds. Requirement (II): storage elastic modulus at 23°C of the sealing agent layer is 1.3×107 Pa or less. Requirement (III): when the temperature of the sealing agent layer is raised from 35°C to 110°C at a rate of 25°C/min and is maintained at 110°C, and complex viscosity of the sealing agent layer after 250 seconds from start of temperature rise is 1×104 Pa s or more.SELECTED DRAWING: None

Description

The present invention relates to a sealing sheet having a sealing agent layer that is excellent in stickability at room temperature (referred to as 23 ° C., the same applies hereinafter) and is not easily deformed in the thermosetting process.

In recent years, organic EL elements have been attracting attention as light emitting elements capable of high-luminance light emission by low-voltage direct current drive.
However, the organic EL element has a problem that the light emitting characteristics such as the light emitting brightness, the light emitting efficiency, and the light emitting uniformity tend to deteriorate with the passage of time.
It is considered that oxygen, water, etc. infiltrate into the inside of the organic EL element and deteriorate the electrode and the organic layer as a cause of the problem of deterioration of the light emitting characteristics. Therefore, it has been practiced to seal the organic EL element with a sealing material to prevent the infiltration of oxygen and moisture.

For example, Patent Document 1 contains a resin component and a curing agent, and the resin component contains a biphenyl skeleton-containing epoxy resin having a weight average molecular weight within a specific range and an alicyclic skeleton having a weight average molecular weight within a specific range. Described is an image display device encapsulant characterized by containing an epoxy resin and a styrene-based oligomer having a weight average molecular weight within a specific range.

WO2018 / 235824

As described in Patent Document 1, a curable sheet-shaped adhesive has been suitably used as a material for forming a sealing material (hereinafter, "sheet-shaped adhesive for forming a sealing material" is referred to as "sealing". Sometimes referred to as "stopping agent layer".)
However, some of the curable sealant layers are inferior in stickability at room temperature, and some need to be heated to soften the surface when sticking to the object to be sealed.
Further, when the encapsulant layer has thermosetting property, the encapsulant layer whose fluidity is enhanced by heating is deformed by an external influence such as vibration in the initial stage of the thermosetting process. In some cases, the sealing performance inherent in the sealing agent layer could not be exhibited.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sealing sheet having a sealing agent layer which is excellent in stickability at room temperature and which is not easily deformed in a thermosetting process.

In order to solve the above problems, the present inventors have diligently studied a sealant layer containing an epoxy compound. As a result, the encapsulant layer that satisfies the requirements for the storage elastic modulus at 23 ° C. and the requirements for the complex viscosity when heated under predetermined conditions is excellent in stickability at room temperature and is not easily deformed in the thermosetting process. It was found that it was a thing, and the present invention was completed.

Thus, according to the present invention, the following sealing sheets [1] to [9] are provided.

[1] A sealing sheet having a thermosetting sealing agent layer.
It is characterized by satisfying the following requirements (I), requirements (II), and requirements (III) .
The encapsulant layer contains an epoxy compound, a binder resin and a curing agent.
At least one of the epoxy compounds is an epoxy compound that is liquid at 25 ° C.
At least one is, the sealing sheet is when subjected to differential scanning calorimetry under the following conditions, the peak top temperature of the exothermic peak is 120 ° C. below the thermal cationic polymerization initiator before Kikata agent.
(Differential scanning calorimetry)
Using a mixture of 0.1 parts by mass of the thermal cationic polymerization initiator, 100 parts by mass of bisphenol A diglycidyl ether, and 0.1 parts by mass of γ-butyrolactone as a measurement sample, the temperature was raised from 30 ° C. to 300 ° C. at 10 ° C./min. Differential scanning calorimetry is performed at speed.
Requirement (I): The encapsulant layer contains one or more epoxy compounds.
Requirements (II): storage modulus at 23 ° C. of the sealant layer is not more than 1.3 × ¹⁰ 7 Pa.
Requirement (III): When the temperature of the sealant layer is raised from 35 ° C. to 110 ° C. at a rate of 25 ° C./min and then maintained at 110 ° C., the complex number of the sealant layer 250 seconds after the start of temperature rise The viscosity is 1 × 10 ⁴ Pa · s or more.
[2] The sealing sheet according to [1], wherein the sealing agent layer satisfies the following requirement (IV).
Requirement (IV): A homogeneous encapsulant layer [encapsulant layer (A) and encapsulant layer (B)] is prepared, and the encapsulant layer (A) is used as a test piece from 0 ° C. to 200 ° C. The differential scanning calorimetry is performed at a heating rate of 10 ° C./min to ° C., and the area [area (α)] of the exothermic peak is determined. Next, the sealant layer (B) was stored in an environment of 23 ° C. and a relative humidity of 50% for 7 days, and then used as a measurement sample, and the difference was made from 0 ° C. to 200 ° C. at a heating rate of 10 ° C./min. Scan calorimetry is performed to determine the area [area (β)] of the exothermic peak. Based on the obtained area value, X calculated from the following formula (1) is 95% or more.

[3] The sealing sheet according to [1] or [2], wherein at least one of the epoxy compounds is an epoxy compound having a glycidyl ether group.
[4] The sealing sheet according to any one of [1] to [3], wherein at least one of the epoxy compounds is an epoxy compound having an alicyclic skeleton.
[5] As at least one of the curing agents, it further contains a thermal cationic polymerization initiator in which the peak top temperature of the exothermic peak exceeds 120 ° C. when the differential scanning calorimetry is performed under the following conditions. , [1] to [4].
(Differential scanning calorimetry)
Using a mixture of 0.1 parts by mass of the thermal cationic polymerization initiator, 100 parts by mass of bisphenol A diglycidyl ether, and 0.1 parts by mass of γ-butyrolactone as a measurement sample, the temperature was raised from 30 ° C. to 300 ° C. at 10 ° C./min. Differential scanning calorimetry is performed at speed.
[6] The sealing sheet according to any one of [1] to [5], wherein all of the curing agents are thermal cationic polymerization initiators.
[7] at least one of the previous fangs Indah resin, the glass transition temperature (Tg) of 60 ° C. or more resins, encapsulating sheet according to any one of [1] to [6].
[8] The sealing according to any one of [1] to [7], wherein the binder resin is one or more resins selected from phenoxy resins, modified olefin resins, and acetal resins. Sheet.
[9] The sealing sheet according to any one of [1] to [8] , which is used for sealing an optical device.

According to the present invention, there is provided a sealing sheet having a sealing agent layer that is excellent in stickability at room temperature and is not easily deformed in the thermosetting process.

The sealing sheet of the present invention is a sealing sheet having a thermosetting sealing agent layer, and is characterized by satisfying the following requirements (I), requirements (II), and requirements (III). Is.
Requirement (I): The encapsulant layer contains one or more epoxy compounds.
Requirements (II): storage modulus at 23 ° C. of the sealant layer is not more than 1.3 × ¹⁰ 7 Pa.
Requirement (III): When the temperature of the sealant layer is raised from 35 ° C. to 110 ° C. at a rate of 25 ° C./min and then maintained at 110 ° C., the complex number of the sealant layer 250 seconds after the start of temperature rise The viscosity is 1 × 10 ⁴ Pa · s or more.

In the present invention, the "sealing agent layer" means a "sheet-like adhesive for forming a sealing material". The cured product of the encapsulant layer is used as an encapsulant.
The encapsulant layer may be strip-shaped or elongated (strip-shaped).

[Requirement (I)]
The encapsulant layer contains one or more epoxy compounds.
When the sealant layer contains an epoxy compound, the sealant layer becomes thermosetting.

The epoxy compound refers to a compound having at least one, preferably two or more epoxy groups in the molecule. In the present invention, the phenoxy resin described later is not included in the epoxy compound.
The epoxy group includes a group containing an oxylan structure such as a glycidyl group, a glycidyl ether group, and an epoxycyclohexyl group.

The molecular weight of the epoxy compound is usually 100 to 5,000, preferably 200 to 3,000.
The epoxy equivalent of the epoxy compound is preferably 50 g / eq or more and 1000 g / eq or less, and more preferably 100 g / eq or more and 800 g / eq or less.
When the epoxy equivalent of the epoxy compound is in the above range, a sealing material (cured product) having high adhesive strength can be formed more efficiently.
The epoxy equivalent in the present invention means a value obtained by dividing the molecular weight by the number of epoxy groups.

The content of the epoxy compound is preferably 55% by mass or more, more preferably 57 to 75% by mass, based on the entire encapsulant layer.
When the content of the epoxy compound is 55% by mass or more with respect to the entire sealing agent layer, a sealing material having high adhesive strength can be formed more efficiently.

Examples of the epoxy compound include an aliphatic epoxy compound (excluding an alicyclic epoxy compound), an aromatic epoxy compound, and an alicyclic epoxy compound.
Examples of the aliphatic epoxy compound include monofunctional epoxy compounds such as glycidyl etherified products of aliphatic alcohols and glycidyl esters of alkylcarboxylic acids;
Examples thereof include polyglycidyl etherified products of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and polyfunctional epoxy compounds such as polyglycidyl esters of aliphatic long-chain polybasic acids.

Representative compounds of these aliphatic epoxy compounds include alkenyl glycidyl ethers such as allyl glycidyl ethers; alkyl glycidyl ethers such as butyl glycidyl ethers, 2-ethylhexyl glycidyl ethers, and C12-13 mixed alkyl glycidyl ethers; 1,4- Butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol tetraglycidyl ether, dipentaerythritol hexaglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol Glycidyl ethers of polyhydric alcohols such as diglycidyl ethers; Polyglycidyl ethers; diglycidyl esters of aliphatic long-chain dibasic acids; monoglycidyl ethers of aliphatic higher alcohols, glycidyl esters of higher fatty acids, epoxidized soybean oil, octyl epoxystearate, butyl epoxy stearate, epoxidized polybutadiene; And so on.

A commercially available product can also be used as the aliphatic epoxy compound. Commercially available products include Denacol EX-121, Denacol EX-171, Denacol EX-192, Denacol EX-211, Denacol EX-212, Denacol EX-313, Denacol EX-314, Denacol EX-321, Denacol EX-411, Denacol EX-421, Denacol EX-512, Denacol EX-521, Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-622, Denacol EX-810, Denacol EX-811, Denacol EX-850, Denacol EX-851, Denacol EX-821, Denacol EX-830, Denacol EX-832, Denacol EX-841, Denacol EX-861, Denacol EX-911, Denacol EX-941, Denacol EX-920, Denacol EX-931 ( Above, manufactured by Nagase ChemteX);
Epolite M-1230, Epolite 40E, Epolite 100E, Epolite 200E, Epolite 400E, Epolite 70P, Epolite 200P, Epolite 400P, Epolite 1500NP, Epolite 1600, Epolite 80MF, Epolite 100MF (all manufactured by Kyoeisha Chemical Co., Ltd.);
ADEKA Glycyrrol ED-503, Adeka Glycyrrol ED-503G, Adeka Glycyrrol ED-506, Adeka Glycyrrol ED-523T (all manufactured by ADEKA);

Examples of the aromatic epoxy compound include phenols having at least one aromatic ring such as phenol, cresol, and butylphenol, or a mono / polyglycidyl etherified product of an alkylene oxide adduct thereof; an epoxy compound having an aromatic heterocycle; and the like. Can be mentioned.

Typical compounds of these aromatic epoxy compounds include bisphenol A, bisphenol F, or glycidyl etherified compounds or epoxy novolac resins obtained by further adding alkylene oxide to these compounds;
Mono / polyglycidyl etherified products of aromatic compounds having two or more phenolic hydroxyl groups such as resorcinol, hydroquinone, and catechol;
A glycidyl etherified product of an aromatic compound having two or more alcoholic hydroxyl groups such as phenyldimethanol, phenyldiethanol, and phenyldibutanol;
Glysidyl ester of a polybasic acid aromatic compound having two or more carboxylic acids such as phthalic acid, terephthalic acid and trimellitic acid, glycidyl ester of benzoic acid, styrene oxide or epoxidized product of divinylbenzene;
Epoxy compounds having a triazine skeleton such as 2,4,6-tri (glycidyloxy) -1,3,5-triazine; and the like.

In addition, a commercially available product can also be used as the aromatic epoxy compound. Commercially available products include Denacol EX-146, Denacol EX-147, Denacol EX-201, Denacol EX-203, Denacol EX-711, Denacol EX-721, On-Coat EX-1020, On-Coat EX-1030, On-Coat EX. -1040, On-Coat EX-1050, On-Coat EX-1051, On-Coat EX-1010, On-Coat EX-1011, On-Coat 1012 (all manufactured by Nagase ChemteX Corporation);
Ogsol PG-100, Ogsol EG-200, Ogsol EG-210, Ogsol EG-250 (all manufactured by Osaka Gas Chemical Co., Ltd.);
HP4032, HP4032D, HP4700 (all manufactured by DIC Corporation);
ESN-475V (above, manufactured by Nittetsu Chemical & Materials Co., Ltd.);
JER (formerly Epicoat) YX8800 (all manufactured by Mitsubishi Chemical Corporation);
Maproof G-0105SA, Maproof G-0130SP (above, manufactured by NOF CORPORATION);
Epicron N-665, Epicron HP-7200 (all manufactured by DIC Corporation);
EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, XD-1000, NC-3000, EPPN-501H, EPPN-501HY, EPPN-502H, NC-7000L (all manufactured by Nippon Kayaku Co., Ltd.);
Adeka Resin EP-4000, Adeka Resin EP-4005, Adeka Resin EP-4100, Adeka Resin EP-4901 (all manufactured by ADEKA);
TECHMORE VG-3101L (above, manufactured by Printec):
Examples thereof include TEPIC-FL, TEPIC-PAS, and TEPIC-UC (all manufactured by Nissan Chemical Industries, Ltd.).

The alicyclic epoxy compound includes a polyglycidyl etherified product of a polyhydric alcohol having at least one alicyclic structure, or cyclohexene oxide or cyclopentene obtained by epoxidizing a cyclohexene or cyclopentene ring-containing compound with an oxidizing agent. Examples include oxide-containing compounds.

Typical compounds of these alicyclic epoxy compounds are hydrogenated bisphenol A diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 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), Propane-2,2-Diyl-bis (3,4-Epoxycyclohexane), 2,2-Bis (3,3) 4-epoxycyclohexyl) propane, dicyclopentadiene diepoxyside, ethylenebis (3,4-epoxycyclohexanecarboxylate), dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, 1-epoxyethyl-3 , 4-Epoxycyclohexane, 1,2-epoxy-2-epoxyethylcyclohexane, α-pinenooxide, limonendioxide and the like.

A commercially available product can also be used as the alicyclic epoxy compound. Commercially available products include celoxide 2021P, celoxide 2081, celoxide 2000, celoxide 3000 (above, manufactured by Daicel); Epolite 4000 (manufactured by Kyoeisha Chemical Co., Ltd.); YX8000, YX8034 (above, manufactured by Mitsubishi Chemical Corporation); ADEKA REGIN EP-4088S, ADEKA REGIN EP-4088L, ADEKA REGIN EP-4080E (all manufactured by ADEKA); and the like.

These epoxy compounds may be used alone or in combination of two or more.

At least one of the epoxy compounds is preferably an epoxy compound that is liquid at 25 ° C.
"Liquid at 25 ° C" means having fluidity at 25 ° C. The viscosity of the epoxy compound measured at 25 ° C. and 1.0 rpm using an E-type viscometer is preferably 2 to 10000 mPa · s.
The use of an epoxy compound that is liquid at 25 ° C. facilitates the formation of a sealant layer that meets requirement (II).

When the encapsulant layer contains a liquid epoxy compound at 25 ° C., its content is applied to the entire encapsulant layer from the viewpoint of preventing the encapsulant layer from adhering to unintended objects at the edges. On the other hand, it is preferably 55 to 70% by mass, and more preferably 57 to 65% by mass.
By setting the content of the epoxy compound liquid at 25 ° C. to 55% by mass or more with respect to the entire sealant layer, it becomes easy to form a sealant layer satisfying the requirement (II).

At least one of the epoxy compounds is preferably an epoxy compound having a glycidyl ether group.
Since the glycidyl ether group is not so reactive as the epoxycyclohexyl group or the like, a sealing sheet having better storage stability can be obtained by using an epoxy compound having a glycidyl ether group.

When the encapsulant layer contains an epoxy compound having a glycidyl ether group, the content thereof is preferably 90% by mass or more, more preferably 95 to 100% by mass, based on the total amount of the epoxy compound. ..
By setting the content of the epoxy compound having a glycidyl ether group to 90% by mass or more with respect to the total amount of the epoxy compound, a sealing sheet having better storage stability can be obtained.

At least one of the epoxy compounds is preferably an epoxy compound having an alicyclic skeleton.
By using an epoxy compound having an alicyclic skeleton, the curing reaction by cationic polymerization easily proceeds, the relative permittivity is low, and it becomes easy to form a sealing agent layer having excellent colorless transparency.

When the encapsulant layer contains an epoxy compound having an alicyclic skeleton, the content thereof is preferably 80% by mass or more, more preferably 90 to 100% by mass, based on the total amount of the epoxy compounds. ..
By setting the content of the epoxy compound having an alicyclic skeleton to 80% by mass or more with respect to the total amount of the epoxy compound, the curing reaction by cationic polymerization can easily proceed. Further, it becomes easy to form a sealing agent layer having a low relative permittivity and excellent colorless transparency.

[Requirement (II)]
Storage modulus at 23 ° C. of the sealing agent layer is not more than 1.3 × ¹⁰ 7 Pa.
By storage modulus at 23 ° C. of the sealing agent layer is not more than 1.3 × 10 7 ^Pa, the sealant layer is excellent in sticking resistance at room temperature.
The storage elastic modulus of the sealant layer at 23 ° C. is preferably 1.1 × 10 ⁷ Pa or less, more preferably 1.0 × 10 ⁷ Pa or less.
As long as a constant shape can be maintained, there is no particular lower limit of the storage elastic modulus of the encapsulant layer at 23 ° C., but the storage elastic modulus of the encapsulant layer at 23 ° C. is usually 5.0 × 10 ⁴ Pa or more. Is. From the viewpoint of preventing the sealant layer adheres to the intended product at the end, the storage modulus at 23 ° C. of the sealing agent layer is preferably 3.0 × 10 5 ^Pa or more, More preferably, it is 9.5 × 10 ^{5 Pa or more.}
The storage elastic modulus of the encapsulant layer at 23 ° C. can be measured according to the method described in Examples.

As the amount of the liquid component in the encapsulant layer increases, the storage elastic modulus of the encapsulant layer at 23 ° C. tends to decrease.
Therefore, the encapsulant layer satisfying the requirement (II) can be efficiently formed by adjusting the state (solid, liquid) of the epoxy compound to be used and the content thereof.

[Requirement (III)]
When the temperature of the sealant layer was raised from 35 ° C. to 110 ° C. at a rate of 25 ° C./min and then maintained at 110 ° C., the complex viscosity of the sealant layer 250 seconds after the start of the temperature rise (hereinafter, this measurement). The complex viscosity under the condition may be described as “complex viscosity (Y)”), which is 1 × 10 ⁴ Pa · s or more.
When the complex viscosity (Y) is 1 × 10 ⁴ Pa · s or more, the curing reaction starts from a relatively early stage of the thermosetting step. Therefore, the sealant layer of the sealing sheet of the present invention cures with almost no state in which the fluidity increases due to the temperature rise, so that it is difficult to be deformed in the thermosetting step.
The complex viscosity (Y) is preferably 1 × 10 ⁴ to 1 × 10 ⁶ Pa · s, and more preferably 1 × 10 ⁵ to 1 × 10 ⁶ Pa · s.
The complex viscosity (Y) can be measured according to the method described in Examples.

The value of complex viscosity (Y) increases as the epoxy compound reacts at lower temperatures.
Therefore, the encapsulant layer satisfying the requirement (III) can be efficiently formed by adjusting the type and amount of the curing agent according to the reactivity of the epoxy compound used.
For example, as will be described later, the value of the complex viscosity (Y) can be increased by using a low temperature reactive thermal cationic polymerization initiator as the curing agent.

[Requirements (IV)]
The encapsulant layer preferably meets the following requirement (IV).
Requirement (IV): A homogeneous encapsulant layer [encapsulant layer (A) and encapsulant layer (B)] is prepared, and the encapsulant layer (A) is used as a test piece from 0 ° C. to 200 ° C. The differential scanning calorimetry is performed at a heating rate of 10 ° C./min to ° C., and the area [area (α)] of the exothermic peak is determined. Next, the sealant layer (B) was stored in an environment of 23 ° C. and a relative humidity of 50% for 7 days, and then used as a measurement sample, and the difference was made from 0 ° C. to 200 ° C. at a heating rate of 10 ° C./min. Scan calorimetry is performed to determine the area [area (β)] of the exothermic peak. Based on the obtained area value, X calculated from the following formula (1) is 95% or more.

Here, the “homogeneous sealant layer” refers to a plurality of sealant layers having substantially the same composition and physical properties. For example, the two sealing agent layers obtained by cutting one sealing agent layer into two correspond to the same quality sealing agent layer [sealing agent layer (A) and sealing agent layer (B)]. do. Further, even if the two sealant layers are collected from different sealant layers instead of the two sealant layers collected from one sealant layer, they are sold as products with the same serial number. The two sealing agent layers collected from the sealing agent layer also correspond to the same quality sealing agent layer [sealing agent layer (A) and sealing agent layer (B)].
The "area of the exothermic peak" means the area of the region surrounded by the baseline and the DSC curve obtained from the portion of the DSC curve other than the exothermic peak.

It is preferable that the sealant layer (A) and the sealant layer (B) are close to the state of the sealant layer immediately after the production of the sealing sheet.
Therefore, the sealant layer (A) and the sealant layer (B) are stored under the condition of -30 to + 10 ° C. after the production of the sealing sheet until the above measurement is performed. It is preferable that the product is stored under the conditions of -15 to + 5 ° C.

As described above, the sealant layer of the sealing sheet of the present invention satisfies the requirement (III).
However, the encapsulant layer satisfying the requirement (III) may undergo a curing reaction at a relatively low temperature, and may be inferior in storage stability.

In this respect, the encapsulant layer satisfying the requirement (IV) has almost no curing reaction even when stored for 7 days in an environment of 23 ° C. and 50% relative humidity, and has excellent storage stability. Excellent.

The encapsulant layer satisfying the requirement (IV) can be efficiently formed by using an epoxy compound having a glycidyl ether group as the epoxy compound or adjusting the amount according to the reactivity of the curing agent. can.

[Curing agent]
The encapsulant layer may contain a curing agent. When the sealant layer contains a curing agent, the curability of the sealant layer is further enhanced.
The curing agent is not particularly limited as long as it initiates the curing reaction, but those that initiate the curing reaction by heating are preferably used.
Examples of the curing agent include a thermal cationic polymerization initiator and other curing agents.
Examples of the curing agent other than the thermal cationic polymerization initiator include tertiary amines such as benzylmethylamine and 2,4,6-trisdimethylaminomethylphenol; 2-methylimidazole, 3-ethyl-4-methylimidazole, and 2-hepta. Examples thereof include imidazole compounds such as decylimidazole; Lewis acids such as boron trifluoride / monoethylamine complex and boron trifluoride / piperazine complex;

As the curing agent, one type can be used alone, or two or more types can be used in combination.
The content of the curing agent is not particularly limited, but is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and further preferably 1 to 5 parts by mass with respect to 100 parts by mass of the epoxy compound. ..

The encapsulant layer preferably contains a thermal cationic polymerization initiator as at least one of the curing agents.
By using the thermal cationic polymerization initiator, it becomes easy to control the curability of the sealant layer near room temperature, and the sealant layer satisfying the requirement (III) can be formed more efficiently.

The thermal cationic polymerization initiator is a compound capable of generating a cationic species that initiates polymerization by heating.
Examples of the thermal cationic polymerization initiator include sulnifoam salt, quaternary ammonium salt, phosphonium salt, diazonium salt, iodonium salt and the like.

Examples of the sulfonium salt include triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroalcinate, tris (4-methoxyphenyl) sulfonium hexafluoroalcinate, and diphenyl (4-phenylthiophenyl) sulfonium. Hexafluoroalcinate, (4-acetoxyphenyl) methyl (2-methylbenzyl) sulfonium tetrakis (pentafluorophenyl) borate, (4-hydroxyphenyl) methyl (4-methylbenzyl) sulfonium tetrakis (pentafluorophenyl) borate, ( Examples thereof include 4-acetoxyphenyl) benzyl (methyl) sulfonium tetrakis (pentafluorophenyl) borate, benzyl (4-hydroxyphenyl) (methyl) sulfonium tetrakis (pentafluorophenyl) borate and the like.

A commercially available product can also be used as the sulfonium salt. Commercially available products include Adeca Opton SP-150, Adeka Opton SP-170, Adeka Opton CP-66, Adeka Opton CP-77 (above, manufactured by Asahi Denka Co., Ltd.), Sun Aid SI-60L, Sun Aid SI-80L, Sun Aid SI-100L, Sun Aid SI. -B2A, Sun Aid SI-B3, Sun Aid SI-B3A, Sun Aid SI-B7 (above, manufactured by Sanshin Chemical Co., Ltd.), CYRACURE UVI-6974, CYRACURE UVI-6990 (above, manufactured by Union Carbide), UVI-508, UVI-509 (above, General Electric), FC-508, FC-509 (above, Minnesota Mining and Manufacturing), CD-1010, CD-1011 (above, Thirstmer), Examples include CI series products (manufactured by Nippon Soda Co., Ltd.).

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

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

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

Examples of the iodonium salt include diphenyl iodonium hexafluoroalcinate, bis (4-chlorophenyl) iodonium hexafluoroalcinate, bis (4-bromophenyl) iodonium hexafluoroalcinate, and phenyl (4-methoxyphenyl) iodonium hexafluoroalcinate. Can be mentioned. In addition, as commercial products, UV-9310C (manufactured by Toshiba Silicone), Photoinitiator 2074 (manufactured by Rhone-Poulenc), UVE series products (manufactured by General Electric), FC series products (Minnesota Mining and Manufacturing) (Manufactured by the company) can also be used.

The thermal cationic polymerization initiator may be used alone or in combination of two or more.

The sealant layer is a thermal cationic polymerization initiator (hereinafter, "thermal cationic polymerization initiator (P)") in which the peak top temperature of the exothermic peak becomes 120 ° C. or lower when the differential scanning calorimetry is performed under the following conditions. It is preferable to contain).

(Differential scanning calorimetry measurement conditions)
Using a mixture of 0.1 parts by mass of the thermal cationic polymerization initiator, 100 parts by mass of bisphenol A diglycidyl ether, and 0.1 parts by mass of γ-butyrolactone as a measurement sample, the temperature was raised from 30 ° C. to 300 ° C. at 10 ° C./min. Differential scanning calorimetry is performed at speed.

The thermal cationic polymerization initiator (P) is a low temperature reactive thermal cationic polymerization initiator. Therefore, the encapsulant layer containing the thermal cationic polymerization initiator (P) can easily satisfy the requirement (III). Examples of the thermal cationic polymerization initiator (P) include (4-acetoxyphenyl) methyl (2-methylbenzyl) sulfonium tetrakis (pentafluorophenyl) borate and (4-hydroxyphenyl) methyl (4-methylbenzyl) sulfonium tetrakis (penta). Fluorophenyl) borate, (4-acetoxyphenyl) benzyl (methyl) sulfonium tetrakis (pentafluorophenyl) bolate can be mentioned. Examples of commercially available thermal cationic polymerization initiators (P) include Sun Aid SI-B2A, Sun Aid SI-B3A, and Sun Aid SI-B7 (all manufactured by Sanshin Chemical Co., Ltd.).

When the encapsulant layer contains a thermal cationic polymerization initiator (P), the thermal cationic polymerization initiator having a peak top temperature of more than 120 ° C. when differential scanning calorimetry is performed under the above conditions ( Hereinafter, it may be referred to as “thermal cationic polymerization initiator (Q)”).

The thermal cationic polymerization initiator (Q) is a high temperature reactive thermal cationic polymerization initiator. Therefore, the encapsulant layer containing the thermal cationic polymerization initiator (Q) can easily satisfy the requirement (IV). The peak top temperature of the exothermic peak of the thermal cationic polymerization initiator (Q) is preferably 170 ° C. or lower from the viewpoint of preventing the temperature at the time of curing the encapsulant layer from becoming too high. Examples of the thermal cationic polymerization initiator (Q) include benzyl (4-hydroxyphenyl) (methyl) sulfonium tetrakis (pentafluorophenyl) borate. Moreover, as a commercially available product of the thermal cationic polymerization initiator (Q), Sun Aid SI-B3 (manufactured by Sanshin Kagaku Co., Ltd.) can be mentioned.

When the encapsulant layer contains a thermal cationic polymerization initiator (P) and a thermal cationic polymerization initiator (Q), the weight ratio thereof [thermal cationic polymerization initiator (P): thermal cationic polymerization initiator (Q)]. Is preferably 20:80 to 80:20, more preferably 35:65 to 65:35.
When the weight ratio of the thermal cationic polymerization initiator (P) and the thermal cationic polymerization initiator (Q) is within the above range, it has a sealing agent layer in which the curing reaction starts from a relatively early stage of the thermal curing step. Moreover, it is possible to efficiently obtain a sealing sheet having excellent storage stability.

In the sealing sheet of the present invention, it is preferable that all of the curing agents contained in the sealing agent layer are thermal cationic polymerization initiators.
If a curing agent other than the thermal cationic polymerization initiator is used, the encapsulant layer may be colored or the transparency of the encapsulant layer may be lowered.
On the other hand, when a thermal cationic polymerization initiator is used, such a problem is unlikely to occur. Therefore, since all the curing agents contained in the encapsulant layer are thermal cationic polymerization initiators, a sealing agent having excellent colorless transparency. Layers can be formed efficiently.

[Binder resin]
The sealant layer may contain a binder resin. The sealant layer containing the binder resin has excellent shape retention and handleability.
The weight average molecular weight (Mw) of the binder resin is not particularly limited, but is preferably 10,000 or more, more preferably 10,000 to 1, because it is excellent in compatibility with the epoxy compound and also excellent in shape retention. ,,000,000, more preferably 10,000-800,000.
The weight average molecular weight (Mw) of the binder resin can be determined as a standard polystyrene-equivalent value by performing gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

When the encapsulant layer contains a binder resin, the content of the binder resin (the total amount of these when two or more kinds of binder resins are contained) is preferably 20 to 43 mass with respect to the entire encapsulant layer. %, More preferably 23-40% by mass.
When the content of the binder resin is within the above range, it becomes easy to obtain a sealing agent layer having excellent shape retention and sufficient adhesive strength.

The glass transition temperature (Tg) of the binder resin is not particularly limited, but is preferably 60 ° C. or higher, more preferably 90 ° C. or higher, and even more preferably 110 ° C. or higher.
When the glass transition temperature (Tg) of the binder resin is 60 ° C. or higher, it is easy to increase the storage elastic modulus of the cured product of the adhesive layer. Further, when the glass transition temperature (Tg) of the binder resin is 90 ° C. or higher, the encapsulant layer having excellent shape retention can be efficiently formed.

Examples of the binder resin include phenoxy resins, modified olefin resins, acetal resins and the like.
Among these, a phenoxy resin is preferable as the binder resin because a sealing agent layer having excellent shape retention can be easily obtained.

The phenoxy resin generally corresponds to a high molecular weight epoxy resin and has a degree of polymerization of about 100 or more.
The epoxy equivalent of the phenoxy resin is preferably 5,000 or more, more preferably 7,000 or more. The value of epoxy equivalent can be measured according to JIS K7236.

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

The phenoxy resin can be obtained by a method of reacting a bifunctional phenol and epihalohydrin to a high molecular weight, or by a double addition reaction of a bifunctional epoxy resin and a bifunctional phenol.
For example, it can be obtained by reacting bifunctional phenols and epihalohydrin in the presence of an alkali metal hydroxide in an inert solvent at a temperature of 40 to 120 ° C. Further, the bifunctional epoxy resin and the bifunctional phenols are mixed with an amide solvent or an ether solvent having a boiling point of 120 ° C. or higher in the presence of a catalyst such as an alkali metal compound, an organic phosphorus compound or a cyclic amine compound. It can also be obtained by performing a heavy addition reaction by heating to 50 to 200 ° C. at a reaction solid content concentration of 50% by weight or less in an organic solvent such as a ketone solvent, a lactone solvent, or an alcohol solvent.

The bifunctional phenols are not particularly limited as long as they are compounds having two phenolic hydroxyl groups. For example, monocyclic bifunctional phenols such as hydroquinone, 2-bromohydroquinone, resorcinol, and catechol, bisphenols such as bisphenol A, bisphenol F, bisphenol AD, and bisphenol S, and dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl. Dihydroxyphenyl ethers such as bis (4-hydroxyphenyl) ethers; and linear alkyl groups, branched alkyl groups, aryl groups, methylol groups, allyl groups, cyclic aliphatic groups, halogens (allyl groups) on the aromatic rings of these phenol skeletons. Tetrabromobisphenol A, etc.), nitro group, etc. introduced, linear alkyl group, branched alkyl group, allyl group, allyl group with substituent, cyclic aliphatic group in the carbon atom in the center of these bisphenol skeletons Polycyclic bifunctional phenols into which a group, an alkoxycarbonyl group, etc. have been introduced; and the like can be mentioned.

Examples of epichlorohydrin include epichlorohydrin, epibrom hydrin, epiiodohydrin and the like.

Further, in the present invention, a commercially available product can also be used as the phenoxy resin. For example, product names manufactured by Mitsubishi Chemical Co., Ltd .: YX7200, YL7553, YL6794, YL7213, YL7290, YL7482, product names manufactured by Mitsubishi Chemical Co., Ltd .: YX8100 (bisphenol S skeleton-containing phenoxy resin), product names manufactured by Toto Kasei Co., Ltd .: FX280, FX293, FX293S (fluorene skeleton-containing phenoxy resin), product names manufactured by Mitsubishi Chemical Co., Ltd .: jER1256, jER4250, product names manufactured by Nittetsu Chemical & Materials Co., Ltd .: YP-50, YP-50S (all bisphenol A skeleton-containing phenoxy resin) ), Product name: YX6954 (bisphenol acetophenone skeleton-containing phenoxy resin) manufactured by Mitsubishi Chemical Co., Ltd., product name: ZX-1356-2 manufactured by Nittetsu Chemical & Materials Co., Ltd. and the like.

〔Silane coupling agent〕
The encapsulant layer may contain a silane coupling agent. By containing the silane coupling agent, it becomes easier to obtain a sealing agent layer having better moist heat durability.

As the silane coupling agent, a known silane coupling agent can be used. Of these, an organosilicon compound having at least one alkoxysilyl group in the molecule is preferable.
Examples of the silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltri. Silane coupling agent having a (meth) acryloyl group such as methoxysilane; vinyl group such as vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, diethoxymethylvinylsilane, trichlorovinylsilane, vinyltris (2-methoxyethoxy) silane Silane coupling agent with;
2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 8-glycid Silane coupling agent having an epoxy group such as xioctyltrimethoxysilane;
Silane coupling agent having a styryl group such as p-styryltrimethoxysilane and p-styryltriethoxysilane;

N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane , 3-Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N -(Vinylbenzyl) -2-aminoethyl-3-aminopropyl Asilane coupling agent having an amino group such as a hydrochloride of trimethoxysilane;
A silane coupling agent having a ureido group such as 3-ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane;
Silane coupling agent having halogen atoms such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane;
A silane coupling agent having a mercapto group such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane;
Silane coupling agent having a sulfide group such as bis (trimethoxysilylpropyl) tetrasulfide and bis (triethoxysilylpropyl) tetrasulfide;
Silane coupling agent having an isocyanate group such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane;
A silane coupling agent having an allyl group such as allyltrichlorosilane, allyltriethoxysilane, and allyltrimethoxysilane;
Examples thereof include silane coupling agents having a hydroxyl group such as 3-hydroxypropyltrimethoxysilane and 3-hydroxypropyltriethoxysilane; and the like.
These silane coupling agents may be used alone or in combination of two or more.

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

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

[Encapsulant layer]
The thickness of the encapsulant layer is usually 1 to 50 μm, preferably 1 to 25 μm, and more preferably 5 to 25 μm. The encapsulant layer having a thickness within the above range is suitably used as a material for forming the encapsulant.
The thickness of the sealant layer can be measured according to JIS K 7130 (1999) using a known thickness gauge.

The method for forming the sealant layer is not particularly limited. For example, the encapsulant layer can be formed using the casting method.
When the encapsulant layer is produced by the casting method, a encapsulant composition containing the components constituting the encapsulant layer is prepared, and the obtained encapsulant composition is used as a base by a known method. A sealing agent layer can be formed by applying a coating to the peeled layer surface of the material or the peeling film and drying the obtained coating film.

The encapsulant composition may contain a solvent.
As the solvent, 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; n-pentane, n-hexane and n- An aliphatic hydrocarbon solvent such as heptane; an alicyclic hydrocarbon solvent such as cyclopentane, cyclohexane, and methylcyclohexane; and the like can be mentioned.
These solvents may be used alone or in combination of two or more.
The content of the solvent can be appropriately determined in consideration of coatability and the like.

Examples of the method for applying the encapsulant composition include a spin coating method, a spray coating method, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, and a gravure coating method.

Examples of the method for drying the coating film include conventionally known drying methods such as hot air drying, hot roll drying, and infrared irradiation.
The conditions for drying the coating film are, for example, 80 to 150 ° C. for 30 seconds to 5 minutes.

The sealant layer is thermosetting. That is, by heating the encapsulant layer, at least the epoxy groups of the epoxy compound react and the encapsulant layer is cured.

The conditions for thermosetting the sealant layer are not particularly limited.
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 storage elastic modulus of the cured sealant layer obtained by curing the sealant layer at 90 ° C. is preferably 1 × 10 ⁸ Pa or more, and more preferably 1 × 10 ⁹ to 1 × 10 ¹¹ Pa. be. A sealant cured product layer having a storage elastic modulus of 1 × 10 ⁸ Pa or more at 90 ° C. is more suitable as a sealing material because it has excellent sealing properties. Further, in the step carried out for manufacturing the device encapsulant after the sealant cured product layer is formed, the sealant cured product layer is easily prevented from being broken or peeled off.

[Encapsulation sheet]
The sealing sheet of the present invention has the above-mentioned sealing agent layer.
The sealing sheet of the present invention may have a base material, a release film, a functional film, or the like in addition to the sealing agent layer.

As the base material, a resin film can usually be used.
The resin components of the resin film include polyimide, polyamide, polyamideimide, polyphenylene ether, polyetherketone, polyetheretherketone, polyolefin, polyester, polycarbonate, polysulfone, polyethersulfone, polyphenylene sulfide, polyallylate, acrylic resin, and cyclo. Examples thereof include olefin-based polymers, aromatic-based polymers, and polyurethane-based polymers.
The thickness of the base material is not particularly limited, but is preferably 10 to 500 μm, more preferably 10 to 300 μm, and even more preferably 15 to 200 μm.

The release film functions as a support in the manufacturing process of the sealing sheet, and also functions as a protective sheet for the sealing agent layer until the sealing sheet is used.
When the sealing sheet of the present invention is used, the release film is usually peeled off.

As the release film, a conventionally known one can be used. For example, a base material for a release film having a release layer peeled with a release agent can be mentioned.
As the base material for the release film, paper base materials such as glassin paper, coated paper, and high-quality paper; laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper base materials; polyethylene terephthalate resin, polybutylene terephthalate resin, etc. Plastic films such as polyethylene naphthalate resin, polypropylene resin, and polyethylene resin; and the like.

Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.
The thickness of the release film is not particularly limited, but is usually about 20 to 250 μm.

When the sealing sheet of the present invention has a release film, it may have two release films in total, one on each side of the sealant layer, or only on one side of the sealant layer. It may have a release film.

Examples of the functional film include a conductive film, a gas barrier film, an antireflection film, a retardation film, a viewing angle improving film, a brightness improving film and the like. Among these, for example, examples of the gas barrier film include a film having a film of a metal or an inorganic compound.
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 suitably used as a material for forming a sealing material for an electronic device. Among the electronic devices, light-related devices such as light emitting devices, light receiving devices, and display devices are preferable.
Examples of optical-related devices include organic EL elements such as organic EL displays and organic EL lighting; liquid crystal elements such as liquid crystal displays; electronic paper elements; solar cell elements; light emitting diodes; and the like.

The method for 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 the sealant layer of the sealing sheet of the present invention to the target electronic device and then curing the sealant layer by the above method.

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

[Compounds used in Examples or Comparative Examples]
-Epoxy compound (A1): Hydrogenated bisphenol A type epoxy resin [manufactured by Mitsubishi Chemical Co., Ltd., trade name: YX8000, epoxy equivalent: 205 g / eq]
-Epoxy compound (A2): 3', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate [manufactured by Daicel, trade name: seroxide 2021P, epoxy equivalent: 128 to 145 g / eq]
-Phenoxy resin (B1): (manufactured by Mitsubishi Chemical Corporation, product name: YX7200B35, glass transition temperature (Tg): 150 ° C.)
-Thermal cationic polymerization initiator (C1): (4-hydroxyphenyl) methyl (4-methylbenzyl) sulfonium tetrakis (pentafluorophenyl) borate (manufactured by Sanshin Chemical Co., Ltd., trade name: Sun Aid SI-B7)
-Thermal cationic polymerization initiator (C2): benzyl (4-hydroxyphenyl) (methyl) sulfonium tetrakis (pentafluorophenyl) borate (manufactured by Sanshin Chemical Co., Ltd., trade name: Sun Aid SI-B3)
-Silane coupling agent (D1): 8-glycidoxyoctyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBM4803)

[Evaluation of reactivity of thermal cationic polymerization initiator]
Using a mixture of 0.1 parts by mass of the thermal cationic polymerization initiator (C1), 100 parts by mass of bisphenol A diglycidyl ether (manufactured by Mitsubishi Chemical Co., Ltd., jER828) and 0.1 parts by mass of γ-butyrolactone as a measurement sample, 30 to 30 to The peak top temperature of the exothermic peak when the differential scanning calorimetry is performed at a heating rate of 10 ° C./min up to 300 ° C. is 105 ° C.
On the other hand, when the thermal cationic polymerization initiator (C2) is used instead of the thermal cationic polymerization initiator (C1), the peak top temperature of the exothermic peak at this time is 140 ° C.

[Example 1]
170 parts by mass of epoxy compound (A1), 100 parts by mass of phenoxy resin (B1), 1.5 parts by mass of thermal cationic polymerization initiator (C1), 1.5 parts by mass of thermal cationic polymerization initiator (C2), silane coupling agent (D1) 0.2 parts by mass was dissolved in methyl ethyl ketone to prepare a coating solution.
This coating liquid is applied onto the peeling surface of the release film (first release film, manufactured by Lintec Corporation, trade name: SP-PET752150), and the obtained coating film is dried at 100 ° C. for 2 minutes to increase the thickness. A 15 μm sealant layer was formed. A release-treated surface of another release film (second release film, manufactured by Lintec Corporation, trade name: SP-PET381130) was bonded onto this sealant layer to obtain a seal sheet.

[Examples 2 and 3, Comparative Examples 1 and 2]
A sealing sheet was obtained in the same manner as in Example 1 except that the type and amount of each component constituting the sealing agent layer were changed to those shown in Table 1.

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

[Measurement of storage elastic modulus of sealant layer at 23 ° C]
The sealant layers of the sealing sheets obtained in Examples and Comparative Examples were laminated at 23 ° C. using a laminator to obtain a test piece having a thickness of about 1 mm.
The obtained test piece was -20 using a dynamic viscoelasticity measuring device (manufactured by Antonio Par, trade name: Physica MCR301) under the conditions of frequency 1 Hz, strain 1%, and heating rate 3 ° C./min. The storage elastic modulus was measured in the range of ~ 150 ° C. The measurement results at 23 ° C. are shown in Table 1.

[Evaluation of suitability for attaching the sealant layer to the object to be sealed]
The sealing sheets obtained in Examples and Comparative Examples were cut to obtain test pieces having a width of 50 mm and a length of 150 mm. The sealant layer exposed by peeling off the second release film of the obtained test piece was placed on a non-alkali glass plate under the conditions of a temperature of 23 ° C. and a relative humidity of 50%, and further, using a pressure-bonding roll, 0. A pressure of 5 MPa was applied. The state of floating of the sealant layer from the non-alkali glass plate was observed, and the one without floating was evaluated as A, and the one with floating was evaluated as B.

[Complex viscosity of encapsulant layer during temperature rise process]
The sealant layers of the sealing sheets obtained in Examples and Comparative Examples were laminated under the conditions of 23 ° C. and 50% relative humidity to obtain a test piece having a thickness of about 1 mm.
The obtained test piece was subjected to a frequency of 1 Hz, a strain of 0.1%, and a heating rate of 25 ° C./min (110 ° C.) using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, trade name: ARES). The complex viscosity was measured in the range of 35 to 110 ° C. under the condition of (maintaining 110 ° C. after reaching).
Table 1 shows the complex viscosities of the test pieces 250 seconds after the start of temperature rise.

[Evaluation of shape retention of sealant layer in thermosetting process]
The sealing agent layer exposed by peeling off the second release film of the sealing sheet obtained in Examples and Comparative Examples was attached to a non-alkali glass plate, and then cut into a size of width 50 mm × length 50 mm. And obtained a test piece.
The sealant layer exposed by peeling the first release film from the test piece was placed on a non-alkali glass plate under the conditions of a temperature of 23 ° C. and a relative humidity of 50%, and further, using a pressure-bonding roll, a pressure of 0.5 MPa. Was added to obtain a laminate.
Then, the laminate was heat-pressed under the conditions of 0.5 MPa and 110 ° C. The case where no deformation was observed in the sealant layer of the laminate after hot pressing was evaluated as A, and the case where the area of the sealant layer was expanded and deformed was evaluated as B.

[Evaluation of storage stability of sealant layer]
Two sealing sheets obtained in Examples and Comparative Examples were prepared.
Using the sealant layer of one of the sealing sheets as the test piece A, differential scanning calorimetry (device used: DSC Q2000 manufactured by TA Instruments) was performed at a heating rate of 10 ° C./min from 0 ° C. to 200 ° C. The peak area [area (α)] of the exothermic peak was determined.
The other sealing sheet is stored for 7 days in an environment of 23 ° C. and 50% relative humidity, and the differential scanning calorimetry is similarly performed using the sealing agent layer of the sealing sheet as test piece B to generate heat. The peak area [area (β)] of the peak was determined.
The ratio of the area (β) to the area (α) was evaluated as A when the ratio was 95% or more, and B when the ratio was less than 95%.

The following can be seen from Table 1.
The sealing agent layer of the sealing sheet obtained in Examples 1 to 3 is excellent in stickability at 23 ° C. and is not easily deformed in the thermosetting process.
On the other hand, the sealing agent layer of the sealing sheet obtained in Comparative Example 1 does not contain the thermal cationic polymerization initiator having low temperature reactivity, and therefore does not satisfy the requirement (III) of the present invention. Therefore, it becomes easy to fluidize in the thermosetting process and is inferior in shape retention.
Further, the sealing agent layer of the sealing sheet obtained in Comparative Example 2 does not satisfy the requirement (II) of the present invention. Therefore, it is inferior in stickability at 23 ° C.
Further, the sealing agent layer of the sealing sheet obtained in Comparative Example 2 contains a thermal cationic polymerization initiator having low temperature reactivity and does not contain an epoxy compound having a glycidyl ether group. Therefore, this sealing sheet is inferior in storage stability.

Claims (9)

A sealing sheet having a thermosetting sealing agent layer.
It is characterized by satisfying the following requirements (I), requirements (II), and requirements (III) .
The encapsulant layer contains an epoxy compound, a binder resin and a curing agent.
At least one of the epoxy compounds is an epoxy compound that is liquid at 25 ° C.
At least one is, the sealing sheet is when subjected to differential scanning calorimetry under the following conditions, the peak top temperature of the exothermic peak is 120 ° C. below the thermal cationic polymerization initiator before Kikata agent.
(Differential scanning calorimetry)
Using a mixture of 0.1 parts by mass of the thermal cationic polymerization initiator, 100 parts by mass of bisphenol A diglycidyl ether, and 0.1 parts by mass of γ-butyrolactone as a measurement sample, the temperature was raised from 30 ° C. to 300 ° C. at 10 ° C./min. Differential scanning calorimetry is performed at speed.
Requirement (I): The encapsulant layer contains one or more epoxy compounds.
Requirements (II): storage modulus at 23 ° C. of the sealant layer is not more than 1.3 × ¹⁰ 7 Pa.
Requirement (III): When the temperature of the sealant layer is raised from 35 ° C. to 110 ° C. at a rate of 25 ° C./min and then maintained at 110 ° C., the complex number of the sealant layer 250 seconds after the start of temperature rise The viscosity is 1 × 10 ⁴ Pa · s or more. The sealing sheet according to claim 1, wherein the sealing agent layer satisfies the following requirement (IV).
Requirement (IV): A homogeneous encapsulant layer [encapsulant layer (A) and encapsulant layer (B)] is prepared, and the encapsulant layer (A) is used as a test piece from 0 ° C. to 200 ° C. The differential scanning calorimetry is performed at a heating rate of 10 ° C./min to ° C., and the area [area (α)] of the exothermic peak is determined. Next, the sealant layer (B) was stored in an environment of 23 ° C. and a relative humidity of 50% for 7 days, and then used as a measurement sample, and the difference was made from 0 ° C. to 200 ° C. at a heating rate of 10 ° C./min. Scan calorimetry is performed to determine the area [area (β)] of the exothermic peak. Based on the obtained area value, X calculated from the following formula (1) is 95% or more.

The sealing sheet according to claim 1 or 2, wherein at least one of the epoxy compounds is an epoxy compound having a glycidyl ether group. The sealing sheet according to any one of claims 1 to 3, wherein at least one of the epoxy compounds is an epoxy compound having an alicyclic skeleton. Claimed as at least one of the curing agents, further containing a thermal cationic polymerization initiator having a peak top temperature of an exothermic peak exceeding 120 ° C. when differential scanning calorimetry is performed under the following conditions. The sealing sheet according to any one of 1 to 4.
(Differential scanning calorimetry)
Using a mixture of 0.1 parts by mass of the thermal cationic polymerization initiator, 100 parts by mass of bisphenol A diglycidyl ether, and 0.1 parts by mass of γ-butyrolactone as a measurement sample, the temperature was raised from 30 ° C. to 300 ° C. at 10 ° C./min. Differential scanning calorimetry is performed at speed. The sealing sheet according to any one of claims 1 to 5, wherein all of the curing agents are thermal cationic polymerization initiators. At least one front fangs Indah resin, the glass transition temperature (Tg) of 60 ° C. or more resins, encapsulating sheet according to claim 1. The sealing sheet according to any one of claims 1 to 7, wherein the binder resin is one or more resins selected from a phenoxy resin, a modified olefin resin, and an acetal resin. The sealing sheet according to any one of claims 1 to 8 , which is used for sealing an optical device.