JP2022170567A - Active energy ray-curable adhesive sheet and display device - Google Patents

Abstract

To provide an active energy ray-curable adhesive sheet having low water vapor permeability, and a display device using the adhesive sheet.SOLUTION: The active energy ray-curable adhesive sheet of the present invention comprises a semi-cured product of an adhesive composition which contains at least a (meth)acrylic polymer, a photopolymerization initiator, and a diene copolymer having (meth)acrylate moieties at both terminals. When the water vapor permeability before curing with active energy rays is X1 and the water vapor permeability after curing with active energy rays is X2, X1 is 200 g/(m2 24 hr) or less and the value of X1/X2 is less than 1.5.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an active energy ray-curable pressure-sensitive adhesive sheet and a display device.

Adhesive sheets are used, for example, for bonding members together, and are widely used in various fields. In recent years, such adhesive sheets have also been used for applications such as display devices such as liquid crystal displays (LCDs) and input devices such as touch panels. Various devices can be easily manufactured with high precision by using adhesive sheets for bonding members such as optical displays constituting a display device or an input device.

An active energy ray-curable adhesive sheet is known as an example of an adhesive sheet (see, for example, Patent Document 1). Such an active energy ray-curable pressure-sensitive adhesive sheet has a property that curing of the active energy ray-curable pressure-sensitive adhesive sheet progresses by irradiation with an active energy ray (that is, by post-curing). Therefore, when the adherends are laminated with the active energy ray-curable pressure-sensitive adhesive sheet and irradiated with an active energy ray, the active energy ray-curable pressure-sensitive adhesive sheet is cured, and the adherends become more firmly. are pasted together.

WO2017/022770

However, although conventional active energy ray-curable pressure-sensitive adhesive sheets often have a desired water vapor transmission rate after post-curing, the initial water vapor transmission rate, that is, the water vapor transmission rate before irradiation with an active energy ray is high. There was a problem. In addition, when a display device or the like equipped with an active energy ray-curable adhesive sheet is irradiated with an active energy ray to post-cure the adhesive sheet, if there is a display bezel or the like, the active energy ray is applied to the adhesive sheet in that portion. Since it does not hit, the post-curing of the part is difficult to progress, and as a result, the water vapor transmission rate of the part becomes insufficient. From this point of view, it can be said that there is an urgent need to develop an active energy ray-curable pressure-sensitive adhesive sheet having a low initial water vapor transmission rate.

The present invention has been made in view of the above, and an object of the present invention is to provide an active energy ray-curable pressure-sensitive adhesive sheet having a low water vapor permeability and a display device using the pressure-sensitive adhesive sheet.

As a result of intensive studies aimed at achieving the above object, the present inventors found that the above object can be achieved by using a diene copolymer having (meth)acrylate moieties at both ends, and completed the present invention. came to.

That is, the present invention includes, for example, the subject matter described in the following sections.
Item 1
A semi-cured adhesive composition comprising at least a (meth)acrylic polymer, a photopolymerization initiator, and a diene copolymer having (meth)acrylate moieties at both ends,
X1 is 200 g/(m ² 24 hr) or less, where X1 is the water vapor transmission rate before curing with active energy rays, and X2 is the water vapor transmission rate after curing with active energy rays;
An active energy ray-curable pressure-sensitive adhesive sheet having a value of X1/X2 of less than 1.5.
Item 2
Item 2. The active energy ray-curable according to Item 1, wherein the pressure-sensitive adhesive composition contains less than 5 parts by mass of a monofunctional acrylic monomer having a molecular weight of less than 1000 per 100 parts by mass of the (meth)acrylic polymer. mold adhesive sheet.
Item 3
The pressure-sensitive adhesive composition contains less than 5 parts by mass of a monofunctional acrylic monomer having an alkyl group having a linear or branched structure with 8 to 24 carbon atoms per 100 parts by mass of the (meth)acrylic polymer. Item 3. The active energy ray-curable pressure-sensitive adhesive sheet according to item 1 or 2.
Item 4
4. The diene copolymer according to any one of Items 1 to 3, wherein the diene copolymer is a polymer having a 1,2-vinyl structure or a polymer having a structure hydrogenated to the 1,2-vinyl structure. Active energy ray-curable adhesive sheet.
Item 5
The diene copolymer has a weight average molecular weight of 1000 to 5000,
Item 5. The active energy ray-curable pressure-sensitive adhesive sheet according to any one of Items 1 to 4, wherein the diene copolymer has a glass transition temperature of 0° C. or lower.
Item 6
Item 6. The active energy ray according to any one of Items 1 to 5, wherein the adhesive composition contains 0.5 to 30 parts by mass of the diene copolymer with respect to 100 parts by mass of the (meth)acrylic polymer. Hardening type adhesive sheet.
Item 7
Item 7. The active energy ray-curable pressure-sensitive adhesive sheet according to any one of items 1 to 6, which has a dielectric constant at 100 kHz after active energy ray curing of 3.5 or less.
Item 8
Used for laminating liquid crystal or organic EL display members,
Item 8. The active energy ray-curable pressure-sensitive adhesive sheet according to any one of Items 1 to 7, wherein the member is glass, a polarizing plate, or a touch sensor.
Item 9
A display device comprising a post-cured product of the active energy ray-curable pressure-sensitive adhesive sheet according to any one of Items 1 to 8 as a pressure-sensitive adhesive layer.

The active energy ray-curable pressure-sensitive adhesive sheet of the present invention has a low water vapor transmission rate.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expressions "contain" and "include" include the concepts of "contain", "include", "substantially consist of" and "consist only of".

1. Active Energy Ray-Curable Adhesive Sheet The active energy ray-curable adhesive sheet of the present invention comprises a (meth)acrylic polymer, a photopolymerization initiator, and a diene copolymer having (meth)acrylate moieties at both ends. A semi-cured product of at least the pressure-sensitive adhesive composition is provided. In the active energy ray-curable pressure-sensitive adhesive sheet of the present invention, X1 is 200 g/(m ² 24 hr), where X1 is the water vapor transmission rate before curing with the active energy ray, and X2 is the water vapor transmission rate after curing with the active energy ray. ) and the value of X1/X2 is less than 1.5. In this specification, curing an active energy ray-curable pressure-sensitive adhesive sheet with an active energy ray may be simply referred to as “post-curing”.

The active energy ray-curable pressure-sensitive adhesive sheet of the present invention has a low water vapor transmission rate even in the initial stage (before post-curing). Therefore, when the active energy ray-curable pressure-sensitive adhesive sheet of the present invention is post-cured, it has a low water vapor transmission rate even at locations not exposed to the active energy ray, resulting in the active energy ray-curable pressure-sensitive adhesive sheet of the present invention. have low water vapor transmission rates even after post-curing.

Hereinafter, the active energy ray-curable adhesive sheet of the present invention is simply referred to as "adhesive sheet".

<(Meth) acrylic polymer>
The type of (meth)acrylic polymer is not particularly limited, and may be, for example, the same (meth)acrylic polymer used to form a known pressure-sensitive adhesive sheet. In particular, the (meth)acrylic polymer is preferably a polymer in which a cross-linking reaction proceeds with a cross-linking agent described later. is preferred. Examples of crosslinkable functional groups include a carboxy group, a hydroxyl group, a glycidyl group, an amino group, and the like.

One aspect of the (meth)acrylic polymer is a polymer containing a (meth)acrylic ester unit (a) and a monomer unit (b) having a carboxy group and/or a hydroxyl group. "(Meth)acryl" means "acrylic" or "methacryl", "(meth)acrylate" means "acrylate" or "methacrylate", "(meth)allyl" means "allyl" or "metharyl". means.

In addition, the "unit" in the (meth)acrylic ester unit (a) and the monomer unit (b) having a carboxy group and/or a hydroxyl group means a repeating unit constituting a polymer.

(Meth)acrylic ester (a) is a repeating unit derived from a (meth)acrylic ester compound. (Meth)acrylic ester compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, (meth)acrylate, t-butyl acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, ( Examples include n-nonyl meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, and isodecyl (meth)acrylate. Among them, the (meth)acrylic ester compound is preferably a (meth)acrylic ester compound having a linear or branched alkyl group having 4 to 10 carbon atoms, preferably 4 to 8 carbon atoms. The (meth)acrylic ester compound preferably has no hydroxyl group or carboxyl group.

The (meth)acrylic ester unit (a) contained in the (meth)acrylic polymer may be of one type or two or more types.

A monomer unit (b) having a carboxy group is a repeating unit derived from a monomer having a carboxy group. Examples of the monomer having a carboxy group include a wide range of known carboxy group-containing polymerizable monomers, and specific examples include acrylic acid and methacrylic acid.

The hydroxyl group-containing monomer unit (b) is a repeating unit derived from a hydroxyl group-containing monomer. Examples of monomers having a hydroxyl group include a wide range of known hydroxyl group-containing polymerizable monomers, specifically 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate. , 3-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate , polyalkylene glycol mono(meth)acrylate and the like.

The (meth)acrylic polymer may contain both a monomer unit having a carboxy group and a monomer unit having a hydroxyl group as the monomer unit (b), or may contain only one of them. be able to. When the monomer unit (b) contains both a monomer unit having a carboxy group and a monomer unit having a hydroxyl group, the content ratio thereof is not particularly limited, and any content ratio may be desired. of adhesive sheets can be obtained.

In the (meth)acrylic polymer, the content ratio of the (meth)acrylic ester unit (a) and the monomer unit (b) is not particularly limited. For example, the (meth)acrylic polymer may contain 50% by mass or more of the (meth)acrylic ester unit (a) with respect to the total mass of the (meth)acrylic ester unit (a) and the monomer unit (b). It is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more. Further, the content of the (meth)acrylic ester unit (a) with respect to the total mass of the (meth)acrylic ester unit (a) and the monomer unit (b) is preferably 99% by mass or less, more preferably 98% by mass. 98% by mass or less, more preferably 98% by mass or less.

In addition, in the present invention, the content of each structural unit in the (meth)acrylic polymer depends on the amount of the polymerizable monomer derived from the structural unit used when producing the (meth)acrylic polymer. can be considered as matching.

The (meth)acrylic polymer can contain structural units other than the (meth)acrylic ester unit (a) and the monomer unit (b) as long as the effects of the present invention are not impaired. Other structural units include, for example, a wide range of structural units derived from compounds copolymerizable with the (meth)acrylic ester compound. Specific examples of such compounds include (meth)acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylpyrrolidone, vinylpyridine and the like. ) acrylic esters, alkoxyalkyl group-containing (meth)acrylic esters, and the like.

The content of the (meth)acrylic ester unit (a) and the monomer unit (b) is preferably 90% by mass or more, more preferably 95% by mass, based on the total mass of all structural units of the (meth)acrylic polymer. % or more, more preferably 99 mass % or more, and the (meth)acrylic polymer can be composed only of (meth)acrylic ester units (a) and monomer units (b).

In the (meth)acrylic polymer, the arrangement order of each structural unit is not particularly limited, and for example, random copolymers, block copolymers, graft copolymers, etc. can be formed, and production is easy. From the point of view, it is preferably a random copolymer.

The weight average molecular weight of the (meth)acrylic polymer is not particularly limited. For example, the (meth)acrylic polymer preferably has a weight-average molecular weight of 100,000 to 2,000,000, more preferably 200,000 to 1,500,000, because the initial adhesive strength of the adhesive sheet is likely to increase. The weight average molecular weight of the (meth)acrylic polymer means the value before cross-linking with a cross-linking agent described below. The weight average molecular weight of the (meth)acrylic polymer is a value determined based on polystyrene standards, measured under the following conditions by gel permeation chromatography (GPC).
Solvent: Tetrahydrofuran Column: Shodex KF801, KF803L, KF800L, KF800D (connecting four of Showa Denko Co., Ltd.)
Column temperature: 40°C
Sample concentration: 0.5% by mass
Detector: RI-2031plus (manufactured by JASCO)
Pump: RI-2080plus (manufactured by JASCO)
Flow rate (flow rate): 0.8 ml/min
Injection volume: 10 μl
For GPC measurement, 10 samples of standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko KK) Mw = 1320 to 2,500,000 are used as a calibration curve.

The (meth)acrylic polymer contained in the pressure-sensitive adhesive composition may be of only one type, or may be of two or more types.

The method for producing the (meth)acrylic polymer is not particularly limited, and the (meth)acrylic polymer can be obtained, for example, by a production method using a known polymerization method. The (meth)acrylic polymer can also be obtained from commercial products and the like.

<Diene-based copolymer having (meth)acrylate moieties at both ends>
A diene-based copolymer having (meth)acrylate moieties at both ends (hereinafter simply referred to as "diene-based copolymer") is a polymer having a diene-based polymer skeleton (backbone). It is a polymer having (meth)acrylate sites. A (meth)acrylate moiety is, for example, a monovalent group represented by “CH ₂ ═C(CH ₃ )COO—”. It should be noted that the diene-based copolymer is a polymer other than the (meth)acrylic-based polymer, although it is merely a note just to make sure.

Since the pressure-sensitive adhesive sheet of the present invention contains a diene-based copolymer, it has a low water vapor transmission rate before irradiation with active energy rays (before post-curing), and also tends to improve step followability. In addition, the diene copolymer tends to bring about a low dielectric constant to the PSA sheet.

The diene-based copolymer is preferably a polymer having a 1,2-vinyl structure or a polymer having a structure hydrogenated to the 1,2-vinyl structure. In this case, the water vapor transmission rate of the pressure-sensitive adhesive sheet before post-curing tends to be lower, and the conformability to unevenness is particularly likely to be improved. The 1,2-vinyl structure is, for example, a monovalent group represented by CH ₂ ═CH—, and the hydrogenated structure of the 1,2-vinyl structure is, for example, CH ₃ —CH ₂ — is a monovalent group represented by When the diene-based copolymer is a polymer having a 1,2-vinyl structure or a polymer having a structure hydrogenated to the 1,2-vinyl structure, these structures are, for example, a diene-based copolymer It can have on the side chain of the coalescence.

Among them, it is preferable that the diene-based copolymer has a polybutadiene skeleton and has the (meth)acrylate sites at both ends thereof. As a result, the water vapor transmission rate of the pressure-sensitive adhesive sheet before post-curing is particularly likely to be low, the conformability to irregularities is particularly likely to be improved, and the relative dielectric constant of the pressure-sensitive adhesive sheet can be further reduced.

The (meth)acrylate sites at both ends may be directly bonded to the backbone diene polymer, or may be indirectly bonded via other sites. When the (meth)acrylate site is indirectly bonded via another site, it can be bonded to the diene polymer via a urethane bond, for example. The (meth)acrylate moieties at both ends may be the same or different.

The weight-average molecular weight of the diene-based copolymer is not particularly limited, and can be, for example, 1,000 to 5,000. As a result, the pressure-sensitive adhesive sheet tends to have a low water vapor transmission rate before post-curing, and the conformability to irregularities tends to be improved. The weight-average molecular weight of the diene-based copolymer is measured by gel permeation chromatography (GPC) under the following conditions, and is a value determined based on polystyrene standards, the same conditions as the weight-average molecular weight of the (meth)acrylic polymer. is.

The glass transition temperature of the diene-based copolymer is not particularly limited, and is preferably 0° C. or lower, for example. As a result, the pressure-sensitive adhesive sheet tends to have a lower water vapor transmission rate before post-curing, and tends to improve conformability to unevenness. The glass transition temperature of the diene copolymer can be measured with a differential scanning calorimeter (DSC).

The diene copolymer preferably has a viscosity of, for example, 1,000 to 500,000 mPa·s/45°C. In this case, the initial adhesive strength of the pressure-sensitive adhesive sheet is likely to be increased, the step conformability is particularly likely to be improved, and the relative dielectric constant of the pressure-sensitive adhesive sheet can be further lowered. The viscosity referred to herein is a value measured with a Brookfield viscometer (RB-80L manufactured by TOKI).

The diene-based copolymer contained in the pressure-sensitive adhesive composition may be of only one type, or may be of two or more types.

The method for producing the diene-based copolymer is not particularly limited, and the diene-based copolymer can be obtained, for example, by a production method using a known polymerization method. The diene-based copolymer can be obtained from commercial products, and examples thereof include TE series manufactured by Nippon Soda Co., Ltd.

The content of the diene-based copolymer in the pressure-sensitive adhesive composition is not particularly limited. For example, the adhesive composition preferably contains 0.5 to 30 parts by mass of the diene copolymer with respect to 100 parts by mass of the (meth)acrylic polymer. In this case, the pressure-sensitive adhesive sheet tends to have a lower water vapor transmission rate before post-curing, easily improves step conformability, and can further lower the relative dielectric constant of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive composition more preferably contains 1 part by mass or more of the diene copolymer, more preferably 2 parts by mass or more, and 4 parts by mass or more with respect to 100 parts by mass of the (meth)acrylic polymer. It is particularly preferable to contain 20 parts by mass or less, more preferably 18 parts by mass or less, and particularly preferably 16 parts by mass or less.

<Photoinitiator>
The photopolymerization initiator is a component that plays a role in initiating, for example, the polymerization reaction of the diene-based copolymer by irradiation with active energy rays (that is, post-curing). In the present invention, the term "active energy ray" means an electromagnetic wave or charged particle beam that has an energy quantum, and includes ultraviolet rays, electron beams, visible rays, X-rays, ion beams, and the like. Among them, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.

The type of photopolymerization initiator is not particularly limited, and for example, a wide range of known photopolymerization initiators can be used. Examples of photopolymerization initiators include acetophenone-based initiators, benzoin ether-based initiators, benzophenone-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, and amine-based initiators.

Specific examples of acetophenone-based initiators include diethoxyacetophenone and benzyldimethylketal. Specific examples of benzoin ether-based initiators include benzoin and benzoin methyl ether. Specific examples of benzophenone-based initiators include benzophenone, methyl o-benzoylbenzoate, 2,4,6-trimethylbenzophenone mesityl (phenyl) ketone, 4-methylbenzophenone and the like, and 2,4,6-trimethyl It can also be a mixture of benzophenone mesityl (phenyl) ketone and 4-methylbenzophenone. Specific examples of hydroxyalkylphenone-based initiators include 1-hydroxy-cyclohexyl-phenyl-ketone and the like. Specific examples of thioxanthone-based initiators include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone. Specific examples of amine-based initiators include triethanolamine and ethyl 4-dimethylbenzoate.

The photopolymerization initiator contained in the pressure-sensitive adhesive composition can be used singly or in combination of two or more. A photoinitiator can be obtained from a commercial item etc., for example.

In the pressure-sensitive adhesive composition, the content of the photopolymerization initiator is not particularly limited. selected as appropriate. For example, the adhesive composition may contain 0.05 to 10 parts by mass, preferably 0.1 to 5 parts by mass, of a photopolymerization initiator based on 100 parts by mass of the (meth)acrylic polymer.

<Adhesive composition>
The pressure-sensitive adhesive composition can contain a (meth)acrylic polymer, a diene copolymer, a photopolymerization initiator, and a cross-linking agent.

A cross-linking agent is, for example, a compound having a property of reacting with a (meth)acrylic polymer by heat. Examples of cross-linking agents include isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds. It is preferable to use an isocyanate compound or an epoxy compound as the cross-linking agent in terms of high reactivity with the (meth)acrylic polymer. When the cross-linking agent contains a metal chelate, it is also preferable to use, for example, a known cross-linking retarder in combination.

Examples of isocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the like. Examples of epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diol. glycidyl ether, tetraglycidylxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. mentioned.

The cross-linking agent contained in the pressure-sensitive adhesive composition can be used singly or in combination of two or more. The cross-linking agent can be obtained, for example, from commercial products.

In the adhesive composition, the content of the cross-linking agent is not particularly limited, and can be, for example, 0.01 to 5 parts by mass per 100 parts by mass of the total mass of the (meth)acrylic polymer. In this case, the workability of the pressure-sensitive adhesive sheet to be obtained tends to be enhanced. The content of the cross-linking agent can be 0.05 to 3 parts by weight per 100 parts by weight of the total weight of the crosslinkable (meth)acrylic copolymer.

The adhesive composition can also contain a silane coupling agent. The type of silane coupling agent is not particularly limited, and for example, a wide range of known compounds can be used. Silane coupling agents include, for example, γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyldialkoxysilane, γ- Aminopropyltriethoxysilane, γ-Aminopropyltrimethoxysilane, γ-Glycidoxypropyltriacoxysilane, γ-Methacryloxypropyltrialkoxysilane, γ-Chloropropyltrialkoxysilane, γ-Methacryloxypropyldialkoxysilane , γ-mercaptopropyltrialkoxysilane, vinyltrialkoxysilane, and the like. The silane coupling agent may also be an oligomer of various alkoxysiloxanes. All of these silane coupling agents are commercially available.

When the pressure-sensitive adhesive composition contains a silane coupling agent, the content can be 0.1 to 5 parts by mass per 100 parts by mass of the (meth)acrylic polymer. Silane coupling agents may be used alone or in combination of two or more.

The pressure-sensitive adhesive composition can contain a solvent from the viewpoint of improving coatability. Examples of solvents include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichlorethylene, tetrachloroethylene, and dichloropropane; methanol, ethanol, Alcohols such as propanol, isopropyl alcohol, butanol, isobutyl alcohol and diacetone alcohol; Ethers such as diethyl ether, diisopropyl ether, dioxane and tetrahydrofuran; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone and cyclohexanone; Methyl acetate , Esters such as ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Polyols such as glycol monomethyl ether acetate and derivatives thereof are included.

When the pressure-sensitive adhesive composition contains a solvent, its content is not particularly limited, for example, with respect to 100 parts by mass of the (meth)acrylic polymer, it can be 25 to 500 parts by mass, and 30 to 400 parts by mass. is more preferable. Also, the content of the solvent is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, relative to the total mass of the pressure-sensitive adhesive composition. One type of solvent may be used alone, or two or more types may be used in combination. When two or more types are used in combination, the total mass is preferably within the above range.

The pressure-sensitive adhesive composition can contain various additives for pressure-sensitive adhesives other than those described above as long as the effects of the present invention are not impaired. Such additives can be selected from, for example, plasticizers, antioxidants, metal corrosion inhibitors, tackifiers, ultraviolet absorbers, light stabilizers such as hindered amine compounds, and the like, as required. Dyes and pigments may also be added for the purpose of coloring.

A polymerizable monomer can be mentioned as another component contained in the pressure-sensitive adhesive composition. Examples of polymerizable monomers include polyfunctional polymerizable monomers and monofunctional monomers. Hereinafter, the polymerizable monomer is referred to as "polymerizable monomer M". Although it is merely a remark just to make sure, the polymerizable monomer M means a component other than the diene-based copolymer. The type of the polymerizable monomer M is not particularly limited, and for example, a wide range of known polyfunctional polymerizable monomers and monofunctional monomers used for producing pressure-sensitive adhesive sheets can be used.

However, in the present invention, as described above, the pressure-sensitive adhesive composition preferably does not contain the specific polymerizable monomers described below in that the water vapor transmission rate before post-curing of the pressure-sensitive adhesive sheet tends to be lower. Even if the specific polymerizable monomer is included, it is preferable that the amount used is small. The specific polymerizable monomer mentioned here specifically includes a monofunctional acrylic monomer having a molecular weight of less than 1000, and even if this is included, the content is 100 parts by mass of the (meth)acrylic polymer. It is preferably less than 5 parts by mass, more preferably 1 part by mass or less, still more preferably 0.1 parts by mass or less, and particularly preferably 0.05 parts by mass or less. It is particularly preferred that the pressure-sensitive adhesive composition does not contain a monofunctional acrylic monomer having a molecular weight of less than 1,000.

Other examples of specific polymerizable monomers include monofunctional acrylic monomers having an alkyl group having a linear or branched structure with 8 to 24 carbon atoms. is preferably less than 5 parts by mass, more preferably 1 part by mass or less, further preferably 0.1 part by mass or less per 100 parts by mass of the (meth)acrylic polymer, and 0.05 mass parts Part or less is particularly preferred. It is particularly preferable that the adhesive composition does not contain a monofunctional acrylic monomer having an alkyl group having a linear or branched structure with 8 to 24 carbon atoms.

It is also preferable that the pressure-sensitive adhesive composition does not contain both monofunctional acrylic monomers having a molecular weight of less than 1000 and monofunctional acrylic monomers having an alkyl group having a linear or branched structure with 8 to 24 carbon atoms.

Therefore, when the pressure-sensitive adhesive composition contains a polymerizable monomer M, the polymerizable monomer M is a monofunctional acrylic monomer having a molecular weight of less than 1000 and a linear or It is most preferable to exclude monofunctional acrylic monomers having alkyl groups with branched structures. If the polymerizable monomer M is other than a monofunctional acrylic monomer having a molecular weight of less than 1000 and a monofunctional acrylic monomer having an alkyl group having a linear or branched structure with 8 to 24 carbon atoms, the content The amount is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the (meth)acrylic polymer. It is also preferable that the adhesive composition does not contain the polymerizable monomer M.

The method for preparing the pressure-sensitive adhesive composition is not particularly limited. For example, a (meth) acrylic polymer synthesized in advance, a photopolymerization initiator, a diene-based copolymer having (meth) acrylate sites at both ends, and optionally other components (e.g., a cross-linking agent, A silane coupling agent, a solvent, etc.) can be mixed in a predetermined ratio to prepare a pressure-sensitive adhesive composition. In this case, the (meth)acrylic polymer can be used in the form of a solution or dispersion. When the (meth)acrylic polymer is a solution or dispersion, the solution or dispersion may contain the solvent. The solution or dispersion of the (meth)acrylic polymer having a functional group can have a solid content concentration of, for example, 1 to 50% by mass.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention comprises a layered semi-cured material formed from the pressure-sensitive adhesive composition. Such a semi-cured product functions as an adhesive sheet as well as an adhesive layer.

The semi-cured product includes at least a cured product of a (meth)acrylic polymer, the photopolymerization initiator, and the diene copolymer (diene copolymer having (meth)acrylate sites at both ends). The cured product of the (meth)acrylic polymer is, for example, a crosslinked polymer produced by the reaction of the (meth)acrylic polymer and the crosslinking agent. However, the semi-cured product may contain unreacted (meth)acrylic polymer and cross-linking agent. The method for forming the semi-cured product will be described later in <Method for Producing Adhesive Sheet>.

The pressure-sensitive adhesive sheet of the present invention may be formed only of the semi-cured material, or may have a layer other than the semi-cured material. Hereinafter, the semi-cured material may be referred to as "adhesive layer".

The structure of the pressure-sensitive adhesive sheet is not particularly limited as long as it has the pressure-sensitive adhesive layer. The adhesive sheet may be a single-sided adhesive sheet or a double-sided adhesive sheet. When the pressure-sensitive adhesive sheet is a single-sided pressure-sensitive adhesive sheet, it may be a multilayer sheet in which a semi-cured product (adhesive layer) is laminated on a support. Further, another layer may be provided between the support and the pressure-sensitive adhesive layer. When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, a single-layer pressure-sensitive adhesive sheet consisting of a semi-cured product (adhesive layer), a multi-layer pressure-sensitive adhesive sheet obtained by laminating multiple pressure-sensitive adhesive layers, and other adhesive sheets between the pressure-sensitive adhesive layers A multi-layer pressure-sensitive adhesive sheet obtained by laminating pressure-sensitive adhesive layers, and a multi-layer pressure-sensitive adhesive sheet obtained by laminating a support between pressure-sensitive adhesive layers are exemplified. When the double-sided pressure-sensitive adhesive sheet has a support, it is preferable to use a transparent support as the support. Such a double-sided pressure-sensitive adhesive sheet is excellent in transparency as a whole pressure-sensitive adhesive sheet, and therefore can be suitably used for bonding optical members.

Examples of the support include plastic films such as polystyrene, styrene-acrylic copolymers, acrylic resins, polyethylene terephthalate, polycarbonate, polyetheretherketone, and triacetylcellulose; optical films such as antireflection films and electromagnetic wave shielding films; is mentioned.

The pressure-sensitive adhesive layer may be covered with a release sheet, in which case a pressure-sensitive adhesive sheet with a release sheet is provided. Therefore, the pressure-sensitive adhesive sheet of the present invention can be used to form a pressure-sensitive adhesive sheet with a release sheet. As the release sheet, a release laminated sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity substrate. is mentioned. Papers and polymer films are used as the base material for the release sheet in the release laminated sheet.

As the release agent constituting the release agent layer, for example, a general-purpose addition-type or condensation-type silicone-based release agent or a compound containing a long-chain alkyl group is used. In particular, an addition-type silicone-based release agent having high reactivity is preferably used. Specific examples of silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone Co., Ltd., and KS-3600, KS-774 and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. is mentioned. Further, the silicone-based release agent may contain a silicone resin which is an organosilicon compound having _SiO2 units and ( _CH3 )3SiO1 _/2 units or _CH2 =CH( _CH3 ) _{SiO1 /2} units. preferable. Specific examples of silicone resins include BY24-843, SD-7292, SHR-1404, etc. manufactured by Dow Corning Toray Silicone Co., Ltd., and KS-3800, X92-183, etc. manufactured by Shin-Etsu Chemical Co., Ltd.

When the pressure-sensitive adhesive layer has release sheets on both sides, the release sheets may have different releasability. When the releasability from one side and the releasability from the other are different, it becomes easy to peel off only the release sheet with higher releasability first.

The thickness of the pressure-sensitive adhesive layer is not particularly limited because it can be appropriately set according to the application. For example, the thickness of the adhesive layer is preferably 10-1000 μm, more preferably 20-500 μm, even more preferably 100-400 μm. In particular, the thickness of the pressure-sensitive adhesive layer means the total thickness of each layer when the pressure-sensitive adhesive layer has a multi-layered structure.

In the pressure-sensitive adhesive sheet, X1 is 200 g/(m ² 24 hr) or less, where X1 is the water vapor transmission rate before curing with active energy rays, and X2 is the water vapor transmission rate after curing with active energy rays, and X1/X2. is less than 1.5. In this specification, the water vapor transmission rate of the adhesive sheet means the water vapor transmission rate when the thickness of the adhesive sheet is converted to 100 μm.

When X1 is 200 g/(m ² ·24 hr) or less and the value of X1/X2 is less than 1.5, the pressure-sensitive adhesive sheet of the present invention has a low water vapor transmission rate even before post-curing.

Here, in the "curing by active energy rays" for measuring X2, the irradiation conditions for the active energy rays are a wavelength of 355 nm, an illuminance of 120 mW/ ^cm2 , and an integrated amount of light of 3000 mJ/ ^cm2 . As an illuminometer, "UV-PFA1" manufactured by Eye Graphics Co., Ltd. is used. Under these irradiation conditions, ECS-4011GX/N manufactured by iGraphics Co., Ltd. was used as an ultraviolet irradiator, and a high-pressure mercury lamp H04-L41 and a heat ray cut filter were attached to this. Hereinafter, this irradiation condition is referred to as "irradiation condition A".

X1 is preferably 195 g/(m ² ·24 hr) or less, more preferably 190 g/(m ² ·24 hr) or less. The value of X1/X2 is preferably 1.4 or less, more preferably 1.3 or less, even more preferably 1.2 or less. The lower limit of X1/X2 is 1, for example.

The pressure-sensitive adhesive sheet contains at least a (meth)acrylic polymer crosslinked structure, the photopolymerization initiator, and the diene copolymer. becomes small, and the value of X1/X2 can also show a small value.

Therefore, even if there is a part of the adhesive sheet that is not exposed to the active energy ray when the adhesive sheet is post-cured, the water vapor transmission rate of that part is sufficiently low, and the water vapor transmission rate of the post-cured part is higher than the water vapor transmission rate of the post-cured part. , and as a result, the pressure-sensitive adhesive sheet can have a low water vapor transmission rate. As a result, when the pressure-sensitive adhesive sheet is applied to an electronic device such as a display device (for example, an organic EL light-emitting element), damage to the device due to water vapor can be suppressed.

If the pressure-sensitive adhesive sheet does not contain a monofunctional acrylic monomer having a molecular weight of less than 1000 and/or a monofunctional acrylic monomer having an alkyl group having a linear or branched structure with 8 to 24 carbon atoms, especially X1 becomes smaller, that is, the water vapor transmission rate tends to become lower. Although this is not intended to be a restrictive interpretation, when the adhesive sheet contains these monofunctional acrylic monomers, the monomer has a kind of plasticizing effect. If there is a portion not exposed to the active energy ray, the plasticizing effect of the monofunctional acrylic monomer acts on this portion. It is presumed that this increases the water vapor transmission rate of this portion.

The dielectric constant at 100 kHz after the adhesive sheet is cured under the irradiation condition A is, for example, 3.5 or less. Since the pressure-sensitive adhesive sheet has such a low dielectric constant, for example, the pressure-sensitive adhesive sheet of the present invention is suitable for use in various applications such as display devices such as liquid crystal or organic EL. Easier to prevent it from working.

The relative permittivity of the pressure-sensitive adhesive sheet after curing with active energy rays can be controlled, for example, by adjusting the type and content of the diene-based copolymer. The relative permittivity of the pressure-sensitive adhesive sheet after curing with active energy rays is a value measured under an environment of 100 KHz frequency, 23° C. and 50% RH, and is calculated by the method specified in JIS C 2138.

The gel fraction of the adhesive sheet is not particularly limited. The gel fraction of the pressure-sensitive adhesive sheet (before irradiation under irradiation condition A) is, for example, 35% or more, preferably 40% or more, more preferably 45% or more, and particularly preferably 50% or more, and the upper limit is, for example, , 70%. Further, the gel fraction after curing the adhesive sheet under the irradiation condition A is, for example, 55% or more, preferably 60% or more, more preferably 65% or more, and particularly preferably 70% or more. For example, 95%.

A gel fraction is a value measured by the following method. First, about 0.1 g of the adhesive sheet is collected in a sample bottle, 30 ml of ethyl acetate is added, and shaken for 24 hours. Thereafter, the contents of the sample bottle are filtered through a 150-mesh stainless wire mesh, and the residue on the wire mesh is dried at 100° C. for 1 hour to measure the dry mass (g). The gel fraction is calculated from the obtained dry mass by the following formula 1.
Gel fraction (% by mass) = (dry mass/collected mass of adhesive sheet) x 100 Equation 1

The haze of the adhesive sheet of the present invention is not particularly limited. For example, the haze after storing the pressure-sensitive adhesive sheet of the present invention for 10 days in a dry environment at 85°C and after storing it for 10 days in an environment at 60°C and a relative humidity of 95% is 1% or less, preferably 0.5% or less.

In addition, the haze of the pressure-sensitive adhesive sheet of the present invention after a durability test by exposure to ultraviolet light is 1% or less, preferably 0.5% or less. The durability test by ultraviolet exposure referred to here is a treatment in which the adhesive sheet is irradiated for 4 hours at an illuminance of 0.63 mW/cm ² in an environment of 60° C., and then stored for 4 hours under dew condensation conditions at 50° C. Do a total of 12 times.

The total light transmittance of the adhesive sheet of the present invention is not particularly limited. For example, the total light transmittance (JIS K 7361-1: 1997) is 85% or more, preferably 90% or more. Further, the pressure-sensitive adhesive sheet of the present invention has a total light transmittance of 85% or more, preferably 90% or more after the durability test by ultraviolet exposure described above.

The b ^* value of the adhesive sheet of the present invention is not particularly limited. For example, after the pressure-sensitive adhesive sheet of the present invention is stored for 10 days in an environment of 85°C, and after storage for 10 days in an environment of 60°C and a relative humidity of 95%, the b ^* value is 1 or less, preferably 0.5 or less. In addition, the b ^* value of the pressure-sensitive adhesive sheet of the present invention after the above-described durability test by exposure to ultraviolet rays is 1 or less, preferably 0.5 or less.

By having the optical properties (haze, total light transmittance, b ^* value) as described above, the pressure-sensitive adhesive sheet of the present invention can satisfy the transparency required when the pressure-sensitive adhesive sheet is used as an optical member. It is suitable for optical applications because it is also excellent in humidity clouding resistance.

2. Method for Producing Adhesive Sheet The method for producing the adhesive sheet of the present invention is not particularly limited, and for example, a wide range of known methods for producing active energy ray-curable adhesive sheets can be employed. For example, the pressure-sensitive adhesive sheet of the present invention can be obtained by a production method including a step of applying a pressure-sensitive adhesive composition to form a coating film, and a step of curing the coating film to obtain a semi-cured product.

A method for forming a coating film of the pressure-sensitive adhesive composition is not particularly limited, and for example, a wide range of known coating methods can be employed. For example, a coating film can be formed using a commercially available coating device such as a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a micro gravure coater, a rod blade coater, a lip coater, a die coater, and a curtain coater. . The coating amount of the adhesive composition is not particularly limited, and can be appropriately set according to the thickness of the adhesive layer of the intended adhesive sheet. The coating can be formed on any suitable substrate, for example, the coating can be formed on a release sheet.

The method of curing the coating film to obtain a semi-cured product is not particularly limited. In the present invention, the semi-cured product is preferably formed by heating the coating film. The heating conditions are not particularly limited, for example, the coating film can be heated under conditions of 50 ° C. or higher and 150 ° C. or lower, and the heating time is appropriately determined according to the heating temperature and the target residual solvent concentration of the adhesive layer. It can be set, for example, from 1 to 30 minutes. For the heat treatment, a known heating device such as a heating furnace or an infrared lamp can be used. After the heat treatment, if necessary, the semi-cured product can be aged under a predetermined environment.

The semi-cured material obtained as described above becomes the adhesive layer of the adhesive sheet. When the pressure-sensitive adhesive composition contains a volatile matter such as a solvent, it evaporates during the process of forming a semi-cured product. As described above, the semi-cured product comprises a crosslinked polymer produced by the reaction of the (meth)acrylic polymer and the crosslinking agent, the photopolymerization initiator, and the diene copolymer ((meth) a diene-based copolymer having an acrylate site). However, the semi-cured product may contain unreacted (meth)acrylic polymer and cross-linking agent. In addition, the photopolymerization initiator and the diene-based copolymer may be consumed during the process of forming the semi-cured product. The photopolymerization initiator and the diene copolymer remaining in the semi-cured product are respectively 95% by mass or more with respect to the photopolymerization initiator and the diene copolymer contained in the pressure-sensitive adhesive composition. and preferably 99% by mass or more.

A semi-cured product (adhesive layer) is formed as described above, and the adhesive sheet of the present invention can be obtained. If necessary, the semi-cured material (adhesive layer) may be protected on one side or both sides with a release sheet or the like. For example, the aforementioned adhesive sheet with a release sheet is provided.

(How to use the adhesive sheet)
The pressure-sensitive adhesive sheet of the present invention contains the photopolymerization initiator and the diene-based copolymer in the semi-cured product, and therefore has active energy ray curability. Therefore, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet can be brought into contact with the surface of the adherend, and in this state, the pressure-sensitive adhesive layer can be post-cured, particularly completely cured, by irradiating the active energy ray. Adheres to the body.

There is no particular limitation on the active energy ray employed for post-curing, and from the viewpoint of versatility, ultraviolet rays or electron beams are preferred, and ultraviolet rays are particularly preferred. As the ultraviolet light source, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an extra-high pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp, or the like can be used. As the electron beam, for example, an electron beam emitted from various electron beam accelerators such as a Cockroftwald accelerator, a Van de Clough accelerator, a resonance transformer accelerator, an insulating core transformer accelerator, a linear accelerator, a dynamitron accelerator, and a high frequency accelerator can be used.

The irradiation conditions of the active energy ray are also not particularly limited, and can be appropriately set depending on the wavelength. For example, the irradiation output of ultraviolet rays is preferably such that the integrated light quantity is 100 mJ/cm ² or more and 10000 mJ/cm ² or less, more preferably 500 mJ/cm ² or more and 5000 mJ/cm ² or less.

Since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is in a semi-cured state, the pressure-sensitive adhesive layer can conform to unevenness even if the adherend has a stepped portion before the irradiation with the active energy ray. In this way, after laminating the adhesive sheet and allowing it to follow the irregularities, the adhesive layer is completely cured with active energy rays, thereby increasing the cohesive force of the adhesive layer and improving the adhesiveness to the adherend. do.

By using the pressure-sensitive adhesive sheet as described above, it is possible to obtain a laminate in which the adherend and the post-cured pressure-sensitive adhesive sheet are laminated. Therefore, the laminate contains the post-cured product of the active energy ray-curable pressure-sensitive adhesive sheet as the pressure-sensitive adhesive layer.

The type of the adherend in the laminate is not particularly limited, and examples thereof include various optical members. Examples of the optical member include constituent members in optical products such as touch panels and image display devices, and specific examples include members for liquid crystal or organic EL displays. Liquid crystal or organic EL display members specifically include glass, polarizing plates, and touch sensors.

Since the pressure-sensitive adhesive sheet of the present invention has a low water vapor permeability before irradiation with active energy rays, even if there is a portion that is not exposed to the active energy ray, the water vapor permeability of the portion is low and the dielectric constant can be adjusted to be low. From the viewpoint that it is possible, it is preferably used for lamination of members for liquid crystal or organic EL displays. Since the pressure-sensitive adhesive sheet can form a pressure-sensitive adhesive layer having a low water vapor transmission rate, it can suppress damage to the device due to water vapor when applied to an electronic device such as a display device. Therefore, a display device or the like is suitable as the laminate.

The pressure-sensitive adhesive sheet of the present invention can be applied to various uses that require a pressure-sensitive adhesive sheet, in addition to the above liquid crystal or organic EL displays.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the embodiments of these examples.

(Production example 1)
2-Ethylhexyl methacrylate (2-EHMA), 2-ethylhexyl acrylate (2-EHA), and 2-hydroxyethyl methacrylate (2-HEMA) were blended at a mass ratio of 70:20:10 to form a radical polymerization initiator. 2,2′-azobis(2,4-dimethylvaleronitrile) was dissolved in the solution as . The solution was heated to 60°C for random copolymerization to obtain a (meth)acrylic polymer having a weight average molecular weight (Mw) of 450,000 and a glass transition temperature (Tg) of -20°C.

(Each component of the adhesive composition)
Each component contained in the adhesive composition used in each example and comparative example was as follows.
<(Meth) acrylic polymer>
The (meth)acrylic polymer obtained in Production Example 1 was used as the (meth)acrylic polymer.

<Diene-based copolymer>
Either of the following two types of diene-based copolymer was used.
・"TEAI-1000" manufactured by Nippon Soda Co., Ltd. (Mw1000, Tg-14°C)
・"TE-2000" manufactured by Nippon Soda Co., Ltd. (Mw2000, Tg-9°C)

<Crosslinking agent>
A xylene diisocyanate compound (“D-110N” manufactured by Mitsui Chemicals, Inc.) was used as a cross-linking agent.

<Silane coupling agent>
The silane coupling agent used was "X-41-1810" manufactured by Shin-Etsu Chemical.

<Photoinitiator>
One of the following two photopolymerization initiators was used.
・ Omnirad 184 (IGM resin)
・Esacure TZT (IGM resin)

<Monofunctional acrylic monomer>
Either of the following two kinds of monofunctional acrylic monomers was used.
- Isostearyl acrylate (ISTA manufactured by Osaka Organic Chemical Industry Co., Ltd. (abbreviated as ISTA), molecular weight 324)
- Isobornyl acrylate (IBXA manufactured by Osaka Organic Chemical Industry Co., Ltd. (abbreviated as IBXA), molecular weight 208)

<Polymonofunctional monomer>
A trifunctional monomer M321 (trimethylolpropane propylene oxide-modified triacrylate, molecular weight 546) manufactured by Toagosei Co., Ltd. was used as the polymonofunctional monomer.

(Example 1)
A pressure-sensitive adhesive composition was prepared according to the formulation conditions shown in Table 1. Specifically, 100 parts by mass of the (meth)acrylic polymer obtained in Production Example 1 (in terms of polymer components), a diene copolymer (“TEAI-1000” manufactured by Nippon Soda Co., Ltd.) 1 part by mass, and a cross-linking agent 0.2 parts by mass, 0.2 parts by mass of a silane coupling agent, 0.4 parts by mass of a photopolymerization initiator (Omnirad 184), and ethyl acetate as a solvent (E) so that the solid content concentration is 46% by mass were mixed to obtain an adhesive composition.

A 100 μm-thick polyethylene terephthalate film (first release sheet, manufactured by Oji F-Tex Co., Ltd.: 100RL-07(2)) having a release layer treated with a silicone-based release agent is applied to the pressure-sensitive adhesive composition. It was applied uniformly with an applicator so that the coating amount after drying was 200 μm/m ² . For coating, a doctor blade YD type manufactured by Yoshimitsu Seiki Co., Ltd. was used, and the coating was heated at 100° C. for 3 minutes in an air circulating constant temperature oven. Thus, an adhesive layer was formed on the surface of the first release sheet. A second release sheet (manufactured by Oji F-Tex Co., Ltd.: 50RL-07(L)) with a thickness of 50 μm is attached to the surface of this adhesive layer, and the semi-cured product (adhesive layer) has a difference in peel strength. A pressure-sensitive adhesive sheet with a release sheet having a configuration of first release film/adhesive sheet (adhesive layer)/second release film sandwiched between a pair of release films was obtained. The pressure-sensitive adhesive sheet was subjected to an aging treatment of standing for 7 days under the conditions of 23° C. and 50% relative humidity. The thickness of the adhesive sheet was 200 µm.

(Examples 2 to 9, Comparative Examples 1 to 4)
A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1, except that the types and amounts of the components of the pressure-sensitive adhesive composition were changed to those shown in Table 1. The thickness of each adhesive sheet was as shown in Table 1.

(Evaluation method)
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated as follows.
<Water vapor transmission rate (before post-curing)>
The water vapor transmission rate of the adhesive sheet before post-curing was calculated by the cup method based on JISZ0208-1976. Using an 80 μm tack film (TD80ULM (manufactured by Fujifilm) as a base material, the surface exposed by peeling off the light release film of the pressure-sensitive adhesive sheet is attached to the base material, and then the heavy release film of the pressure-sensitive adhesive sheet is peeled off. The laminate is used to measure the water vapor transmission rate (X1).When setting the laminate in the cup, the outside of the cup is the tack film, and the inside is the adhesive layer of the adhesive sheet. The measurement was performed in the presence of 5 g of calcium chloride in an environment of 40° C. and 90% RH, and the laminate was stored in this environment for 24 hours. The water vapor transmission rate per sheet of 100 μm was calculated.

<Water vapor transmission rate (after post-curing)>
The water vapor transmission rate of the pressure-sensitive adhesive sheet after post-curing was calculated by the cup method based on JISZ0208-1976. The pair of release sheets of the pressure-sensitive adhesive sheet with a release sheet was peeled off, and the pressure-sensitive adhesive sheet was post-cured by irradiation with active energy rays under the same conditions as the irradiation condition A described above. On one side of the post-cured pressure-sensitive adhesive sheet, an 80 μm tack film (TD80ULM (manufactured by Fujifilm) as a substrate was laminated to prepare a laminate, and the water vapor transmission rate was measured. The laminate was set in a cup. In doing so, the outer side of the cup was the tack film and the inner side was the adhesive layer of the adhesive sheet.The measurement environment was 40 ° C. and 90% RH, and stored for 24 hours in the presence of 5 g of calcium chloride under this environment. Then, from the change in the mass of the laminate before and after storage, the water vapor transmission rate per 100 μm of the adhesive sheet was calculated.The irradiation condition in irradiation condition A was a wavelength of 355 nm and an illuminance of 120 mW/cm ² , and the integrated light amount was 3000 mJ/cm ^2. The illuminance meter used was "UV-PFA1" manufactured by Eye Graphics Co., Ltd. Under this irradiation condition A, ECS-4011GX/N manufactured by Eye Graphics Co., Ltd. was used as the ultraviolet irradiator. , and a high-pressure mercury lamp H04-L41 and a heat ray cut filter were attached to it.

<Adhesive strength to glass (initial adhesive strength)>
A PET film (“A4300 #100” manufactured by Toyobo Co., Ltd.) is used as a backing material, and an adhesive sheet (before post-curing) is applied to a glass plate (soda glass manufactured by Hiraoka Special Glass Co., Ltd., 1.1 mm thick) with a 2 kg load roll. pasted together. After leaving this at 25 ° C. for 24 hours, using a tensile tester (model: RTC-1210, manufactured by A & D), according to JIS Z 0237, at a tensile speed of 300 mm / min (and 3000 mm / min) When peeled at 180 degrees The peel strength was measured and taken as the initial adhesive strength (X1) of the adhesive sheet.

<Adhesive strength to glass (after post-curing)>
A PET film (“A4300 #100” manufactured by Toyobo Co., Ltd.) is used as a backing material, and an adhesive sheet (before post-curing) is applied to a glass plate (soda glass manufactured by Hiraoka Special Glass Co., Ltd., 1.1 mm thick) with a 2 kg load roll. After lamination, the pressure-sensitive adhesive sheet was irradiated with an active energy ray from the backing material side under the same conditions as the above irradiation condition A, and post-cured. After leaving the adhesive sheet after this post-curing at 25 ° C. for 24 hours, using a tensile tester (model: RTC-1210, manufactured by A&D), a tensile speed of 300 mm / min (and 3000 mm / min) according to JIS Z 0237. The peel strength at the time of 180 degree peeling was measured and defined as the adhesive strength (X2) of the adhesive sheet after post-curing. The irradiation conditions in irradiation condition A were a wavelength of 355 nm, an illuminance of 120 mW/cm ² , and an integrated amount of light of 3000 mJ/cm ² . The illuminance meter used was "UV-PFA1" manufactured by Eye Graphics. Under this irradiation condition A, ECS-4011GX/N manufactured by iGraphics Co., Ltd. was used as an ultraviolet irradiator, and a high pressure mercury lamp H04-L41 and a heat ray cut filter were attached to this.

<Gel fraction>
About 0.1 g of the pressure-sensitive adhesive sheet (before or after post-curing) was collected in a sample bottle, added with 30 ml of ethyl acetate, and shaken for 24 hours. After that, the contents of the sample bottle are filtered through a 150-mesh stainless steel wire mesh, and the residue on the wire mesh is dried at 100 ° C. for 1 hour to measure the dry mass (g). 1 to determine the gel fraction. The post-curing of the pressure-sensitive adhesive sheet in the measurement of the gel fraction was performed under the irradiation condition A described above.

<Dielectric constant>
The post-cured pressure-sensitive adhesive sheet was sandwiched between two copper foils and autoclaved (40° C., 0.5 MPa, 30 min). After that, it was measured based on JIS C 2138 with a permittivity measurement system (manufactured by Toyo Technica Co., Ltd., model 1260). The frequency was 100 kHz, the dielectric constant was calculated by the method specified in JIS C 2138 under the environment of 23° C. and 50% RH.

Table 1 shows the production conditions and evaluation results of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples. All of the pressure-sensitive adhesive sheets obtained in Examples had a low water vapor transmission rate before post-curing (that is, in a semi-cured state), a low relative dielectric constant, and high transparency and step conformability. was excellent. On the other hand, the pressure-sensitive adhesive sheets obtained in Comparative Examples are produced from a pressure-sensitive adhesive composition that does not contain a diene copolymer, and furthermore, contain a monofunctional acrylic monomer and/or a polymonofunctional monomer. It had a high water vapor transmission rate before post-curing (that is, in a semi-cured state).

Claims (9)

A semi-cured adhesive composition comprising at least a (meth)acrylic polymer, a photopolymerization initiator, and a diene copolymer having (meth)acrylate moieties at both ends,
X1 is 200 g/(m ² 24 hr) or less, where X1 is the water vapor transmission rate before curing with active energy rays, and X2 is the water vapor transmission rate after curing with active energy rays;
An active energy ray-curable pressure-sensitive adhesive sheet having a value of X1/X2 of less than 1.5. The active energy ray according to claim 1, wherein the pressure-sensitive adhesive composition contains less than 5 parts by mass of a monofunctional acrylic monomer having a molecular weight of less than 1000 per 100 parts by mass of the (meth)acrylic polymer. Hardening type adhesive sheet. The pressure-sensitive adhesive composition contains less than 5 parts by mass of a monofunctional acrylic monomer having an alkyl group having a linear or branched structure with 8 to 24 carbon atoms per 100 parts by mass of the (meth)acrylic polymer. The active energy ray-curable pressure-sensitive adhesive sheet according to claim 1 or 2. 4. The diene copolymer according to any one of claims 1 to 3, wherein the diene copolymer is a polymer having a 1,2-vinyl structure or a polymer having a structure hydrogenated to the 1,2-vinyl structure. active energy ray-curable adhesive sheet. The diene copolymer has a weight average molecular weight of 1000 to 5000,
The active energy ray-curable pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the diene copolymer has a glass transition temperature of 0°C or lower. The adhesive composition contains 0.5 to 30 parts by mass of the diene copolymer with respect to 100 masses of the (meth)acrylic polymer, the active energy according to any one of claims 1 to 5. Line curing adhesive sheet. The active energy ray-curable pressure-sensitive adhesive sheet according to any one of claims 1 to 6, having a dielectric constant at 100 kHz after active energy ray curing of 3.5 or less. Used for laminating liquid crystal or organic EL display members,
The active energy ray-curable pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the member is glass, a polarizing plate, or a touch sensor. A display device comprising a post-cured product of the active energy ray-curable pressure-sensitive adhesive sheet according to any one of claims 1 to 8 as a pressure-sensitive adhesive layer.