JP7263813B2 - Adhesive sheet and laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet and a laminate comprising the pressure-sensitive adhesive sheet.

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.

In a display device or an input device, for example, a cover panel made of resin and a layer composed of a touch panel sensor or the like are laminated with an adhesive sheet. have been proposed. For example, Patent Document 1 discloses a (meth)acrylic acid ester polymer containing a (meth)acrylic acid alkyl ester, a reactive functional group-containing monomer having a reactive functional group in the molecule, and N-vinylcarboxylic acid amide, A pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a cross-linking agent (B) has been proposed. It is believed that by using a pressure-sensitive adhesive sheet based on an acrylic polymer having such a specific structure in an input device such as a touch panel, blister resistance and wet heat whitening resistance can be improved. Further, Patent Document 2 discloses an optical pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer that is formed from a pressure-sensitive adhesive composition containing an acrylic polymer with a specific structure and has a predetermined shear storage elastic modulus.

JP 2018-172537 A JP 2012-87240 A

However, when a member such as a cover panel made of resin is adhered with an adhesive sheet, there is a problem that gas generated from the member such as the cover panel (so-called outgas) may cause air bubbles, lifting, peeling, etc. at the adhesion interface. . For example, outgassing can be suppressed by protecting a cover panel or the like to be bonded together with a hard coat layer or the like. However, in this case, there is a problem that the types of members to be pasted together are restricted. In other words, it is difficult to use a conventional adhesive sheet for a member that is likely to generate outgassing and is not protected by a hard coat layer, etc., because the outgassing resistance is inferior. rice field. With the technology disclosed in Patent Document 1 and the like, a certain improvement in blister resistance (outgas resistance) can be expected. However, there was still room for further improvement.

The present invention has been made in view of the above, and an object of the present invention is to provide a pressure-sensitive adhesive sheet having excellent outgas resistance and a laminate comprising the pressure-sensitive adhesive sheet.

As a result of intensive studies aimed at achieving the above objects, the present inventors have found that the above objects can be achieved by using a monofunctional monomer having a cyclic ether structure, and have completed the present invention. .

That is, the present invention includes, for example, the subject matter described in the following sections.
Item 1
A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer contains a crosslinked (meth)acrylic copolymer, a polymerizable monomer having a polymerizable double bond in the molecule, and a photopolymerization initiator,
The crosslinked (meth)acrylic copolymer has a structure in which a crosslinkable (meth)acrylic copolymer is crosslinked with a crosslinking agent,
The pressure-sensitive adhesive sheet, wherein the polymerizable monomer includes a monofunctional monomer having a cyclic ether structure.
Item 2
The pressure-sensitive adhesive sheet according to item 1, wherein the monofunctional monomer having a cyclic ether structure is contained in an amount of 5 to 30 parts by mass with respect to 100 parts by mass of the crosslinkable (meth)acrylic copolymer.
Item 3
Item 3. The adhesive sheet according to Item 1 or 2, wherein the cyclic ether structure is a 4- to 6-membered ring.
Item 4
4. The pressure-sensitive adhesive sheet according to any one of Items 1 to 3, wherein the polymerizable monomer contains a polyfunctional monomer having two or more polymerizable double bonds in the molecule.
Item 5
Item 5. The pressure-sensitive adhesive sheet according to item 4, wherein the polyfunctional monomer has a bisphenol skeleton in the molecule.
Item 6
Item 6. The pressure-sensitive adhesive sheet according to Item 4 or 5, wherein the polyfunctional monomer is contained in an amount of 1 to 15 parts by mass with respect to 100 parts by mass of the crosslinkable (meth)acrylic copolymer.
Item 7
Item 7. The pressure-sensitive adhesive sheet according to any one of items 1 to 6, which is used for bonding with a first member selected from the group consisting of a resin plate, a resin sheet and a resin film.
Item 8
Item 8. The pressure-sensitive adhesive sheet according to Item 7, which is used for bonding the first member and a second member selected from the group consisting of a glass plate, a resin film and a resin plate.
Item 9
A laminate comprising the pressure-sensitive adhesive sheet according to any one of Items 1 to 8 or a cured product thereof.
Item 10
Item 10. The laminate according to Item 9, further comprising the first member, and having a structure in which the first member and a layer of the pressure-sensitive adhesive sheet or a cured product thereof are laminated.

The pressure-sensitive adhesive sheet according to the present invention is excellent in outgassing resistance, and hardly causes air bubbles, lifting and peeling after bonding.

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. Adhesive Sheet The adhesive sheet of the present invention has an adhesive layer. The pressure-sensitive adhesive layer contains a crosslinked (meth)acrylic copolymer, a polymerizable monomer having a polymerizable double bond in the molecule, and a photopolymerization initiator. The combination has a structure in which a crosslinkable (meth)acrylic copolymer is crosslinked with a crosslinking agent, and the polymerizable monomer includes a monofunctional monomer having a cyclic ether structure.

In this specification, "(meth)acryl" means "acryl" or "methacryl", and "(meth)acrylate" means "acrylate" or "methacrylate".

<Crosslinked (meth)acrylic copolymer>
A crosslinked (meth)acrylic copolymer is a polymer having a crosslinked structure formed by reacting a crosslinkable (meth)acrylic copolymer with a crosslinking agent. As such a crosslinked (meth)acrylic copolymer, for example, a wide range of known crosslinked (meth)acrylic copolymers used in adhesive sheets can be applied.

(Crosslinkable (meth)acrylic copolymer)
The crosslinkable (meth)acrylic copolymer can have a structure in which a functional group exhibiting crosslinkability is bonded to the (meth)acrylic copolymer skeleton. The functional group exhibiting cross-linking reactivity is not particularly limited, and examples thereof include a hydroxyl group, a carboxyl group, an amino group, an amide group, an epoxy group, a thiol group, and an isocyanate group. Since the pressure-sensitive adhesive layer is preferably acid-free from the viewpoint that yellowing, corrosion, etc. are less likely to occur, the crosslinkable (meth)acrylic copolymer is also preferably acid-free. Therefore, it is more preferable that the functional group exhibiting cross-linking reactivity does not contain a carboxy group. A particularly preferable functional group exhibiting cross-linking reactivity is a hydroxyl group, and in this case, a cross-linked (meth)acrylic copolymer is easily formed.

The crosslinkable (meth)acrylic copolymer may have, for example, a monomer unit having a functional group exhibiting crosslinkability and a monomer unit having no functional group exhibiting crosslinkability. . In this case, the crosslinkable (meth)acrylic copolymer can be obtained, for example, by copolymerizing a monomer having a functional group exhibiting crosslinkability and a monomer having no functional group exhibiting crosslinkability. can. Hereinafter, a monomer having a functional group exhibiting cross-linking reactivity is referred to as "monomer A", and a monomer not having a functional group exhibiting cross-linking reactivity is referred to as "monomer B".

Examples of the monomer A include hydroxyl group-containing (meth)acrylic monomers and carboxy group-containing (meth)acrylic monomers.

The type of hydroxyl group-containing (meth)acrylic monomer is not particularly limited as long as it has one or more hydroxyl groups in its molecule. For example, hydroxyl group-containing (meth)acrylic monomers include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 2- Hydroxybutyl (meth) acrylate, 2-hydroxy 3-phenoxypropyl (meth) acrylate, 2,2-dimethyl 2-hydroxyethyl (meth) acrylate, 3-chloro 2-hydroxypropyl (meth) acrylate, 2-hydroxy 3- hydroxyalkyl (meth)acrylates such as phenoxypropyl (meth)acrylate and 8-hydroxyoctyl (meth)acrylate; hydroxyalkyl (meth)acrylamides such as N-hydroxypropyl (meth)acrylamide;

Among these, the hydroxyl group-containing (meth)acrylic monomer is one or more selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and 6-hydroxyhexyl (meth)acrylate. is preferred. In this case, it is easy to obtain a PSA sheet with excellent outgas resistance. A hydroxyl-containing (meth)acrylic monomer can be used individually or in mixture of 2 or more different types.

The type of carboxy group-containing (meth)acrylic monomer is not particularly limited as long as it has one or more carboxy groups in the molecule. For example, carboxy group-containing (meth)acrylic monomers include (meth)acrylic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, citraconic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-( meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxylethyl (meth)acrylate, carboxypolycaprolactone mono(meth)acrylate and the like.

As described above, the monomer A is preferably a hydroxyl group-containing (meth)acrylic monomer because the pressure-sensitive adhesive sheet is preferably acid-free. Monomer A may also be a (meth)acrylic monomer having at least one functional group such as an amino group, an amide group, an epoxy group, a thiol group and an isocyanate group. If the adhesive sheet contains an acid, for example, the content of the monomer having an acid group may be 5% by mass or less with respect to the total mass of the monomers for constituting the crosslinkable (meth)acrylic copolymer. It is preferably 3% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.1% by mass or less.

Examples of the monomer B include (meth)acrylates having linear, branched or cyclic alkyl groups, or (meth)acrylates having an aromatic ring. Specific examples of monomer B include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isopropyl (meth) acrylate, isooctyl (meth) acrylate, 2- Ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl, (meth)acrylate and the like can be mentioned. Monomer B is methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isopropyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) Alkyl (meth)acrylates such as acrylates are preferred. In this case, it is easy to obtain a PSA sheet with excellent outgas resistance. Monomer B can be used alone or in combination of two or more different types.

A crosslinkable (meth)acrylic copolymer can be produced, for example, by polymerizing a monomer A and a monomer B by a known polymerization method. As this polymerization method, for example, solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, or the like can be employed.

In the polymerization for obtaining the crosslinkable (meth)acrylic copolymer, the proportion of the monomer A and the monomer B used is not particularly limited, and can be appropriately set according to the desired crosslinkable (meth)acrylic copolymer. can. For example, 0.5 to 60 parts by mass of the monomer A (monomer having a crosslinkable functional group) can be contained per 100 parts by mass of the total amount of the monomers A and B. In this case, the pressure-sensitive adhesive sheet can have the desired adhesive strength, and deterioration of outgas resistance is less likely to occur. It is preferable that the monomer A is contained in an amount of 1 to 55 parts by mass per 100 parts by mass of the total amount of the monomers A and B.

In the polymerization for obtaining the crosslinkable (meth)acrylic copolymer, polymerizable monomers other than the monomers A and B can be used in combination, if necessary. Examples of such polymerizable monomers include radically polymerizable monomers copolymerizable with monomer A and monomer B other than (meth)acrylate compounds. Specific examples thereof include vinyl acetate and styrene. The amount of the radically polymerizable monomer copolymerizable with Monomer A and Monomer B is preferably 20 parts by mass or less per 100 parts by mass of the total amount of Monomer A and Monomer B, for example.

In the production of the crosslinkable (meth)acrylic copolymer, the proportion (mass ratio) of the monomers A and B used is included in the crosslinkable (meth)acrylic copolymer obtained by the polymerization of the monomers A and B. It corresponds to the mass ratio of a monomer unit having a functional group exhibiting cross-linking reactivity and a monomer unit having no functional group exhibiting cross-linking reactivity.

A solvent may optionally be used in the polymerization method for obtaining the crosslinkable (meth)acrylic copolymer. The type of solvent is not particularly limited, and for example, a wide range of known organic solvents used in polymerization can be used. Examples thereof include ester compounds such as ethyl acetate and butyl acetate; ketones such as acetone and methyl ethyl ketone; hydrocarbons such as hexane; and aromatic compounds such as toluene, xylene and benzene. The amount of the solvent used in the polymerization reaction is not particularly limited.

In the polymerization method for obtaining a crosslinkable (meth)acrylic copolymer, a polymerization initiator can be used as necessary. can do. Examples of polymerization initiators include azobisisobutyronitrile, 2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 1,1′-azobis(cyclohexanecarbonitrile), di-tert-butyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, ammonium persulfate, photopolymerization initiators (Irgacure or Omnilad (registered trademark) series, etc.) and the like.

The concentration of the polymerization initiator is not particularly limited, and can be appropriately adjusted, for example, within a range in which the resulting crosslinkable (meth)acrylic copolymer has a desired molecular weight. For example, 0.01 to 5 parts by mass of the polymerization initiator can be used per 100 parts by mass of the total amount of the monomers A and B.

Polymerization for obtaining a crosslinkable (meth)acrylic copolymer can be carried out, for example, under an inert gas atmosphere such as nitrogen.

The polymerization time and polymerization temperature for obtaining a crosslinkable (meth)acrylic copolymer are also not limited, and can be appropriately set according to the types, amounts and polymerization reactivity of the monomers A and B used. can. For example, the polymerization reaction can be carried out at 20 to 100° C. for 1 to 24 hours.

The weight average molecular weight of the crosslinkable (meth)acrylic copolymer is not particularly limited. 10,000 is more preferable.

In addition, the weight average molecular weight as used in the field of this invention is the polystyrene conversion weight average molecular weight measured by the gel permeation chromatography (GPC) method. The GPC apparatus used in the GPC method is not particularly limited, and commercially available GPC measuring instruments such as LC-2000Plus series manufactured by JASCO Corporation, and RI-2031Plus and UV-2075Plus as detectors can be used. In this case, for example, a GPC column formed by connecting four columns of "Shodex KF801", "Shodex KF803L", "Shodex KF800L" and "Shodex KF800D" manufactured by Showa Denko KK is used. The column temperature can be 40°C. Tetrahydrofuran is used as the eluent, and the measurement is performed at a flow rate of 1.0 ml/min. Normally, a standard polystyrene is used to prepare a calibration curve, and the weight average molecular weight (Mw) can be obtained by polystyrene conversion.

Crosslinkable (meth)acrylic copolymers are so-called random copolymers in which monomer units having crosslinkable functional groups and monomer units not having crosslinkable functional groups are randomly arranged. It can be a polymer. Alternatively, the crosslinkable (meth)acrylic copolymer can have other structures such as block polymers.

(crosslinking agent)
The cross-linking agent is a component for promoting cross-linking of the cross-linkable (meth)acrylic copolymer. In particular, the cross-linking agent can react with functional groups exhibiting cross-linking reactivity in the cross-linkable (meth)acrylic copolymer.

The type of cross-linking agent is not particularly limited, and a wide range of known cross-linking agents can be used. Examples of cross-linking agents include isocyanate cross-linking agents and epoxy cross-linking agents.

The type of isocyanate cross-linking agent is not particularly limited, and a wide range of known compounds can be used. Examples of isocyanate cross-linking agents include polyisocyanates such as tolylene diisocyanate, chlorophenylene diisocyanate, diphenylmethane diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and xylylene diisocyanate; cyclopentylene diisocyanate, cyclohexylene diisocyanate; and aromatic isocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and 4,4′-diphenylmethane diisocyanate. An isocyanate crosslinking agent can be used individually or in mixture of 2 or more different types. Moreover, it is more preferable to use trifunctional derivatives such as adducts, nurates, and burettes obtained from the above diisocyanates as isocyanate cross-linking agents.

Examples of epoxy crosslinking agents include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol. Diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexanone, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl Ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether and the like.

In obtaining a crosslinked (meth)acrylic copolymer by crosslinking the crosslinkable (meth)acrylic copolymer with a crosslinking agent, the ratio of the crosslinkable (meth)acrylic copolymer and the crosslinking agent is not particularly limited. For example, 0.01 to 5 parts by mass of the cross-linking agent can be used per 100 parts by mass of the crosslinkable (meth)acrylic copolymer. In this case, the adhesive sheet can have desired adhesive strength. It is preferable to use 0.05 to 1 part by mass of the cross-linking agent per 100 parts by mass of the crosslinkable (meth)acrylic copolymer.

When cross-linking the cross-linkable (meth)acrylic copolymer with a cross-linking agent, other components can be used in combination, if necessary. Examples of such other components include silane coupling agents. When a silane coupling agent is used together, the adhesive strength of the adhesive sheet is likely to be improved.

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-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyldialkoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-glycidoxysilane. Propyltriacoxysilane γ-methacryloxypropyltrialkoxysilane, γ-chloropropyltrialkoxysilane, γ-methacryloxypropyldialkoxysilane, γ-mercaptopropyltrialkoxysilane, vinyltrialkoxysilane and the like.

When a silane coupling agent is used in combination in cross-linking the cross-linkable (meth)acrylic copolymer with a cross-linking agent, the amount used is from 0.1 to 0.1 per 100 parts by mass of the cross-linkable (meth)acrylic copolymer. 5 parts by mass can be contained.

<Polymerizable monomer having a polymerizable double bond in the molecule>
In the pressure-sensitive adhesive sheet, the polymerizable monomer having a polymerizable double bond in its molecule includes a monofunctional monomer having a cyclic ether structure. A monofunctional monomer having a cyclic ether structure is a monomer having both a polymerizable double bond and a cyclic ether structure in its molecule. Hereinafter, a polymerizable monomer having a polymerizable double bond in the molecule is referred to as "polymerizable monomer M", and a monofunctional monomer having a cyclic ether structure is referred to as "cyclic ether-containing monomer". do.

(Cyclic ether-containing monomer)
The type of the cyclic ether-containing monomer contained in the polymerizable monomer M is not particularly limited as long as it is a radically polymerizable monomer having a cyclic ether structure in the molecule, and widely known cyclic ether-containing monomers are used. be able to. For example, a cyclic ether-containing monomer can have groups containing cyclic ether structures in side chains.

The cyclic ether structure is not particularly limited as long as it is a 3-membered ring or more, but from the viewpoint of easily improving the outgassing resistance, the cyclic ether structure is more preferably a 4-membered ring or more. That is, the cyclic ether structure is preferably other than a three-membered ring. Among them, the cyclic ether structure is preferably a 4- to 6-membered ring, that is, one or more of a 4-membered ring, a 5-membered ring and a 6-membered ring.

Among the atoms constituting the ring of the cyclic ether structure, the number of oxygen atoms is not particularly limited as long as it is 1 or more. For example, the number of oxygen atoms can be 1 or 2. Among the atoms constituting the ring of the cyclic ether structure, atoms other than the oxygen atom are usually carbon atoms.

The cyclic ether structure is preferably a tetrahydrofuran structure. In this case, the pressure-sensitive adhesive sheet is particularly improved in outgassing resistance.

In the cyclic ether structure, atoms other than oxygen atoms (for example, carbon atoms) constituting the ring may have one or more substituents. The type of the substituent is not particularly limited, and examples thereof include an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and the like. Examples include methyl group, ethyl group, n-propyl group and i-propyl group.

When the cyclic ether structure has the above substituents, the number of substituents, bonding positions, etc. are not particularly limited, and the effect of the present invention is not impaired in any case. Usually, the number of substituents that the cyclic ether structure has is one or two.

Examples of cyclic ether-containing monomers include (meth)acrylic esters having a cyclic ether structure. In this case, for example, it has a structure in which a cyclic ether structure is directly or indirectly bonded to the oxygen atom of the (meth)acrylic ester. When the cyclic ether structure has a structure indirectly bonded to the oxygen atom of the (meth)acrylic ester, for example, a group represented by the following general formula (1) or general formula (2) is an ester oxygen atom and a cyclic It intervenes between ether structures.
—(CH ₂ ) _m — (1)
(In formula (1), m represents an integer of 1 to 5)

In formula (1), m is preferably 1-2. In formula (2), n is preferably 0-4.

Further specific examples of the cyclic ether-containing monomer include the compounds represented by (3-1) to (3-6) below.

The cyclic ether-containing monomer contained in the polymerizable monomer M may be of one kind alone, or may contain two or more different cyclic ether-containing monomers.

The content of the cyclic ether-containing monomer in the adhesive sheet is not particularly limited. From the viewpoint that the pressure-sensitive adhesive sheet has more excellent outgas resistance, the cyclic ether-containing monomer (monofunctional monomer having a cyclic ether structure) in the pressure-sensitive adhesive sheet is It is preferably contained in an amount of 5 to 50 parts by mass.

More specifically, in the pressure-sensitive adhesive sheet, the cyclic ether-containing monomer is more preferably contained in an amount of 7 parts by mass or more with respect to 100 parts by mass of the crosslinkable (meth)acrylic copolymer, and may be contained in an amount of 10 parts by mass or more. Especially preferred. In the adhesive sheet, the cyclic ether-containing monomer is more preferably contained in an amount of 40 parts by mass or less, more preferably 30 parts by mass or less, relative to 100 parts by mass of the crosslinkable (meth)acrylic copolymer. It is particularly preferable to contain 25 parts by mass or less.

The polymerizable monomer M can also contain monofunctional polymerizable monomers other than cyclic ether-containing monomers, as long as the effects of the present invention are not impaired. As such a monofunctional polymerizable monomer, for example, a wide range of known monofunctional polymerizable monomers can be applied. When the polymerizable monomer M contains a monofunctional polymerizable monomer other than a cyclic ether-containing monomer, the content thereof is, for example, 10% by mass or less with respect to the total mass of the polymerizable monomer M, preferably It can be 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.1% by mass or less.

(Polyfunctional monomer)
The polymerizable monomer M also preferably contains a polyfunctional monomer having two or more polymerizable double bonds in its molecule. In this case, the pressure-sensitive adhesive sheet can be easily improved in outgassing resistance, and in addition, it is possible to suppress shrinkage when the pressure-sensitive adhesive sheet is cured. A polyfunctional monomer having two or more polymerizable double bonds in the molecule is hereinafter simply referred to as a "polyfunctional monomer".

The type of polyfunctional monomer is not particularly limited, and for example, a wide range of known polyfunctional monomers used in adhesive sheets can be used. Among them, the polyfunctional monomer preferably has a bisphenol skeleton in the molecule from the viewpoint of more easily suppressing shrinkage when the pressure-sensitive adhesive sheet is cured. More specifically, an alkylene oxide-modified (meth)acrylic ester having a bisphenol skeleton can be used as the polyfunctional monomer. In this case, the alkylene oxide is, for example, ethylene oxide, propylene oxide and the like. The number of alkylene oxide units can be, for example, 1-5.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 4-butylene glycol, 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, di(meth)acrylate ) Tetraethylene glycol acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, diacrylate of bisphenol A diglycidyl ether, tri(meth)acrylate trimethylolpropane, tri(meth)acryl (Meth)acrylic acid esters of polyhydric alcohols such as pentaerythritol acid and pentaerythritol tetra(meth)acrylate; and vinyl methacrylate.

Examples of the polyfunctional monomer having a bisphenol skeleton in the molecule include bisphenol A diglycidyl ether diacrylate, propoxylated bisphenol A diacrylate, and bisphenol F diglycidyl ether diacrylate.

Commercially available polyfunctional monomers can also be used, for example, trifunctional monomer M310 (trimethylolpropane PO-modified triacrylate) manufactured by Toagosei Co., Ltd. Bifunctional monomer M211B (bisphenol A EO-modified diacrylate) manufactured by Toagosei Co., Ltd., and the like can be mentioned.

In the polyfunctional monomer, the number of polymerizable double bonds in one molecule is not particularly limited as long as it is 2 or more. For example, in a polyfunctional monomer, the number of polymerizable double bonds in one molecule can be two.

The content of the polyfunctional monomer in the pressure-sensitive adhesive sheet is not particularly limited. From the viewpoint of further suppressing the outgassing resistance of the adhesive sheet and the shrinkage after curing, the polyfunctional monomer in the adhesive sheet is 1 to 15 parts per 100 parts by mass of the crosslinkable (meth)acrylic copolymer. It is preferable to include parts by mass.

In the pressure-sensitive adhesive sheet, the content of the polyfunctional monomer is more preferably 3 parts by mass or more, particularly preferably 5 parts by mass or more, based on 100 parts by mass of the crosslinkable (meth)acrylic copolymer. Moreover, in the pressure-sensitive adhesive sheet, it is preferable that the polyfunctional monomer is contained in an amount of 12 parts by mass or less with respect to 100 parts by mass of the crosslinkable (meth)acrylic copolymer.

The polymerizable monomer M can be composed only of a monofunctional monomer and a polyfunctional monomer, or can be composed only of a cyclic ether-containing monomer and a polyfunctional monomer.

<Photoinitiator>
The photopolymerization initiator is a component that causes the polymerization reaction (photopolymerization) to proceed by irradiating the polymerizable monomer M with light. The type of the photopolymerization initiator is not particularly limited as long as it can photopolymerize the polymerizable monomer M, and for example, a wide range of known photopolymerization initiators can be used.

Examples of photopolymerization initiators include, but are not limited to, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl-phenylketone, 2-hydroxy-2-methyl-1-henylpropanone, 1-[4-( 2-hydroxyethoxyl)-phenyl]-2-hydroxy-methylpropanone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methyl-1- Alkylphenone photopolymerization initiators such as propanone, acylphosphine oxide polymerization initiators such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,4,6-trimethylbenzoyl)phenylphosphine oxide, In addition to intramolecular hydrogen abstraction type photopolymerization initiators such as methyl benzoylformate and 4-methylbenzophenone, oxime ester photopolymerization initiators and cationic photopolymerization initiators can be used. A photoinitiator may use only 1 type and can also use 2 or more types together.

In the adhesive sheet, the content of the photopolymerization initiator can be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the polymerizable monomer M. Regarding the content of the photopolymerization initiator, if the crosslinkable (meth)acrylic copolymer is used as a standard, the content of the photopolymerization initiator per 100 parts by mass of the crosslinkable (meth)acrylic copolymer is 0.5 parts by mass. 05 to 5 parts by mass.

<Adhesive layer>
As described above, the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet contains the crosslinked (meth)acrylic copolymer, the polymerizable monomer M, and the photopolymerization initiator. The pressure-sensitive adhesive layer may contain other components such as antistatic agents, antioxidants, preservatives, etc., as long as the effects of the present invention are not impaired. When the pressure-sensitive adhesive layer contains other components, the content thereof is, for example, 10% by mass or less, preferably 5% by mass or less, more preferably 1% by mass or less, particularly preferably 1% by mass or less, based on the total mass of the adhesive layer It can be 0.1% by mass or less.

(Method for Forming Adhesive Layer)
The method of forming the pressure-sensitive adhesive layer is not particularly limited, and for example, widely known methods can be applied. For example, the adhesive layer can be formed using an adhesive composition. The adhesive composition used here can contain the crosslinkable (meth)acrylic copolymer, the crosslinker, the polymerizable monomer M, and a photopolymerization initiator.

Specifically, the adhesive layer is formed by applying the adhesive composition to a substrate to form a coating film of the adhesive composition, and drying (curing) the coating film. , a step of forming an adhesive layer.

The preparation method of the pressure-sensitive adhesive composition is not particularly limited, and the crosslinkable (meth)acrylic copolymer, the crosslinker, the polymerizable monomer M, and the photopolymerization initiator are added at a predetermined mixing ratio. It can be prepared by mixing. The mixing method is also not particularly limited, and for example, a commercially available mixer can be used.

In the pressure-sensitive adhesive composition, the content of each of the crosslinkable (meth)acrylic copolymer, the cross-linking agent, the polymerizable monomer M, and the photopolymerization initiator is appropriately set according to the target pressure-sensitive adhesive sheet. can do. Specifically, the pressure-sensitive adhesive composition is adjusted so that the contents of the crosslinked (meth)acrylic copolymer, the polymerizable monomer M, and the photopolymerization initiator contained in the pressure-sensitive adhesive sheet are each within the ranges described above. The content of each component contained in can be adjusted.

The pressure-sensitive adhesive composition may also contain a solvent as necessary, for example, in order to improve coatability. The solvent is not particularly limited, and examples thereof include ester compounds such as methyl acetate and ethyl acetate; ether compounds such as diethyl ether; ketone compounds such as acetone and methyl ethyl ketone; aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as benzene, toluene and xylene; chlorinated hydrocarbons such as chloroform and 1,2-dichloroethane; alcohols such as methanol, ethanol, isopropyl alcohol and t-butanol. A solvent can be used individually or as a mixture of 2 or more types.

When the pressure-sensitive adhesive composition contains a solvent, it is preferable to use the solvent so that the solid content concentration of the pressure-sensitive adhesive composition is in the range of 10 to 60% by mass, considering the applicability. It is more preferable to use a solvent so that it is in the mass % range.

The method of applying the pressure-sensitive adhesive composition onto the substrate is not particularly limited, and for example, a wide range of known coating methods can be employed. For example, the pressure-sensitive adhesive composition is applied using a commercially available coating device such as a blade coater, air knife coater, roll coater, bar coater, gravure coater, micro gravure coater, rod blade coater, lip coater, die coater, curtain coater, and the like. be able to.

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. For example, the coating amount of the pressure-sensitive adhesive composition can be adjusted so that the thickness of the pressure-sensitive adhesive layer formed after the drying treatment described below is 5 to 1000 μm.

The type of base material for applying the pressure-sensitive adhesive composition is also not particularly limited, and a wide range of base materials used for forming the pressure-sensitive adhesive layer can be used. For example, a release sheet can be mentioned as a base material for applying the pressure-sensitive adhesive composition.

As the release sheet, for example, a so-called separator used for protecting the adhesive layer in a pressure-sensitive adhesive sheet can be used. More specifically, the release sheet may include a resin film having a release layer.

Examples of the resin film in the release sheet include a polyethylene terephthalate film.

The release layer is a layer formed on at least one side of the resin film, and has a release force smaller than the adhesive force of the adhesive layer, and is formed so that the release sheet can be easily peeled off. layer. For such a release layer, for example, a wide range of known components that are used as a release layer in pressure-sensitive adhesive sheets can be applied. For example, a known silicone material can be used to form the release layer.

When the release sheet is used as the substrate, the pressure-sensitive adhesive composition can be applied to the release layer surface of the release sheet to form a coating film of the pressure-sensitive adhesive composition.

After coating the pressure-sensitive adhesive composition on a base material such as the release sheet to form a coating film, a drying process is performed to form a pressure-sensitive adhesive layer on the base material. By this drying treatment, the reaction between the crosslinkable (meth)acrylic copolymer contained in the pressure-sensitive adhesive composition and the crosslinker proceeds, and the crosslinkable (meth)acrylic copolymer is crosslinked with the crosslinker. , the crosslinked (meth)acrylic copolymer is formed.

The conditions for the drying treatment are not particularly limited, and for example, a wide range of conventional drying methods for coating films of pressure-sensitive adhesive compositions can be employed. Such drying treatment can be performed using, for example, a known heating device. The heating temperature can be, for example, 50 to 200.degree. C., preferably 60 to 150.degree. The heating time may be set so that the solvent volatilizes and the residual solvent concentration in the adhesive layer is, for example, 1000 ppm or less. It is preferable to appropriately set the time within about 1 to 30 minutes.

By the drying treatment, an adhesive layer containing the crosslinked (meth)acrylic copolymer, the polymerizable monomer M, and the photopolymerization initiator is formed. In other words, in the drying process, the cross-linking reaction of the cross-linkable (meth)acrylic copolymer mainly progresses and the curing progresses, but the polymerizable monomer M has not yet been polymerized. In other words, it can be said that the pressure-sensitive adhesive layer is in a state in which the pressure-sensitive adhesive composition is semi-cured. As a reminder, the cross-linking reaction of the cross-linkable (meth)acrylic copolymer is not necessarily completed by the drying treatment, and the cross-linking reaction may proceed even by the aging treatment described below.

A protective layer for protecting the adhesive layer can be attached to the pressure-sensitive adhesive layer thus formed. In this case, the protective layer is attached to the surface of the pressure-sensitive adhesive layer opposite to the substrate. As the protective layer, for example, a release sheet can be used as described above. As for the release sheet as the protective layer, a resin film or the like having a release layer can be exemplified as in the case of the base material. As the resin film, for example, a polyethylene terephthalate film or the like can be used as described above, and the release layer can be formed of, for example, a known silicone material.

When both the substrate and the protective layer are release sheets (first release sheet and second release sheet, respectively), the release force of the release layer of the release sheet (first release sheet) as the substrate, It is preferably different from the adhesive strength of the release layer of the release sheet (second release sheet) for forming the protective layer. In other words, when both the substrate and the protective layer are release sheets, it is preferable that the release sheets have different release forces. In this case, when peeling off the release sheets, it becomes easy to selectively peel off only one of the release sheets, and it is easy to suppress the phenomenon of so-called separation.

A desired pressure-sensitive adhesive sheet can be obtained by forming a pressure-sensitive adhesive layer and, if necessary, forming a protective layer as described above, and then appropriately performing an aging treatment. By this aging treatment, as described above, the cross-linking reaction of the cross-linkable (meth)acrylic copolymer proceeds, and the curing proceeds further.

The method of aging treatment is not particularly limited, and for example, a method of leaving the pressure-sensitive adhesive sheet in an atmosphere of 15 to 50° C. can be mentioned. The aging time can be appropriately set depending on the temperature, and can be, for example, 1 to 10 days.

<Structure of Adhesive Sheet>
In the pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be appropriately set according to the intended use. For example, when the pressure-sensitive adhesive sheet is used for bonding members such as a resin cover panel in an input device or the like, the thickness of the pressure-sensitive adhesive layer can be 5 to 1000 μm. The pressure-sensitive adhesive sheet may be either a single-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive sheet, and is usually a double-sided pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet may be formed of only the pressure-sensitive adhesive layer, or may have other layers as necessary. Other layers can be formed on one side or both sides of the adhesive layer. Other layers include the aforementioned release sheet. When release sheets are formed on both sides of the pressure-sensitive adhesive layer, as described above, both release sheets (first release sheet and second release sheet) can have different release forces. When the two release sheets have different peel strengths, for example, when peeling off the release sheets, it becomes easier to selectively peel off only one of the release sheets, and the phenomenon of so-called separation can be easily suppressed.

For example, in the above-described method for forming an adhesive layer, when a release sheet is used as the base material and a release sheet is used as the protective layer, an adhesive sheet having release sheets on both sides of the adhesive layer (release layer You can directly get the adhesive sheet with After forming the pressure-sensitive adhesive layer, separate release sheets may be provided on both sides of the layer to obtain a pressure-sensitive adhesive sheet with a release layer.

When the pressure-sensitive adhesive sheet has release sheets, these release sheets can function as so-called separators in the pressure-sensitive adhesive sheet.

When the pressure-sensitive adhesive sheet includes a release sheet, the thickness of the release sheet is not particularly limited. For example, the thickness of the release sheet can be 20-300 μm, preferably 30-150 μm. The release sheets on both sides of the pressure-sensitive adhesive layer may have different thicknesses.

<How to use the adhesive sheet>
The pressure-sensitive adhesive sheet can be widely used for bonding members (adherends) such as substrates and films to each other.

For example, by interposing a pressure-sensitive adhesive sheet between a pair of adherends and bonding the adherends together with the pressure-sensitive adhesive sheet to form a laminate, the adherends can be bonded together with the pressure-sensitive adhesive sheet. In particular, the durability can be maximized by irradiating the active energy ray to the laminate after adhering the adherends with the pressure-sensitive adhesive sheet. When the adhesive sheet includes a release sheet, the adhesive sheet is interposed between the pair of adherends with the release sheet removed.

As described above, since the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet exists in a state in which the pressure-sensitive adhesive composition is semi-cured, the active energy ray is applied to the pressure-sensitive adhesive layer, whereby the polymerizability present in the pressure-sensitive adhesive layer A polymerization reaction of the monomer M takes place with a photopolymerization initiator. As a result, the curing of the pressure-sensitive adhesive layer proceeds further, and the adherends are adhered to each other more firmly due to the curing of the pressure-sensitive adhesive layer.

By curing the adhesive layer, a polymer of the polymerizable monomer M (hereinafter referred to as "polymer M") is generated in the adhesive layer. This polymer M has a structural unit derived from a cyclic ether-containing monomer in its structural units, and by having this, the pressure-sensitive adhesive sheet exhibits excellent outgassing resistance. As a result, even if a gas component (outgas) is generated from the adherend before, during, or after the polymerization reaction of the polymerizable monomer M, the pressure-sensitive adhesive layer is hardly affected by the outgas. Even after the adhesive layer is cured, air bubbles, floating and peeling are less likely to occur.

Here, the active energy rays include 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. 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 integrated amount of active energy ray irradiation is, for example, 500 to 5000 mJ/cm ² , preferably 1000 to 4000 mJ/cm ² , more preferably 1500 to 3000 mJ/cm ² .

The method of irradiating the active energy ray is also not particularly limited. For example, the entire surface of the laminate can be irradiated with the active energy ray. From this point of view, at least one of the adherends is preferably transparent. For the irradiation of active energy rays, for example, a known active energy ray irradiation device can be used.

Since the pressure-sensitive adhesive sheet has excellent outgas resistance, it is particularly suitable for applications in which air bubbles or the like are likely to occur due to outgassing from an adherend.

Specifically, the pressure-sensitive adhesive sheet can be used for bonding with one type of first member selected from the group consisting of a resin plate, a resin sheet and a resin film. The first member can be obtained, for example, by a known manufacturing method, or can be obtained from commercial products. When the first member is a resin plate, it can be obtained, for example, by casting, or by various molding methods such as injection molding. The first member may be molded into various shapes other than a plate, sheet, and film depending on the purpose of use of the pressure-sensitive adhesive sheet.

The thickness of the first member is not particularly limited, and can be appropriately set according to the application to which the pressure-sensitive adhesive sheet is applied. For example, when the first member is a resin plate, its thickness can be usually 1 mm or more.

The resin for forming the first member such as a resin plate is not particularly limited, and examples thereof include acrylic resins such as polymethyl methacrylate, polycarbonate resins, and styrene resins such as polystyrene. The resin may contain two or more different resins, for example, a composite material containing an acrylic resin and a polycarbonate resin. Among them, the pressure-sensitive adhesive sheet is preferably used for bonding polymethyl methacrylate resin plates and polycarbonate resin plates, and particularly preferably used for bonding polycarbonate resin plates. That is, when bonding is performed using an adhesive sheet, one of the adherends can be a resin plate of polycarbonate resin or the like.

Polycarbonate resin is known as a material that easily generates outgas compared to acrylic resin and the like. For this reason, in order to suppress the problem of outgassing, conventional efforts have been made to provide a hard coat layer on a polycarbonate resin plate. Even a polycarbonate resin plate can suppress the influence of outgassing. Outgassing may occur, for example, at the time of irradiation with active energy rays during bonding, or may occur gradually over time after bonding.

The pressure-sensitive adhesive sheet is more preferably used for bonding the first member and one type of second member selected from the group consisting of a resin plate, a resin sheet and a resin film.

Since the pressure-sensitive adhesive sheet has excellent outgas resistance and is particularly suitable for bonding polycarbonate resin plates as adherends, it is suitable for applications such as display devices such as liquid crystal displays (LCDs) and input devices such as touch panels. It can be used particularly preferably. Examples of constituent members of the touch panel include an ITO film in which an ITO film is provided on a transparent resin film, an ITO glass in which an ITO film is provided on the surface of a glass plate, and a transparent conductive film in which a transparent resin film is coated with a conductive polymer. , hard coat films, anti-fingerprint films, and the like. Examples of constituent members of the image display device include antireflection films, oriented films, polarizing films, retardation films, brightness enhancement films and the like used in liquid crystal display devices.

2. Laminate The laminate of the present invention comprises the pressure-sensitive adhesive sheet described above or a cured product thereof. When the pressure-sensitive adhesive sheet includes a release sheet, it exists in the laminate with the release sheet peeled off. That is, it can be said that the laminate includes the pressure-sensitive adhesive layer.

In the laminate, if the adhesive layer is in a semi-cured state as described above (that is, if the polymerizable monomer M is present in the adhesive layer), the laminate includes an adhesive sheet. On the other hand, in the laminate, if the adhesive layer is further cured by irradiation with active energy rays as described above, the laminate comprises a cured adhesive sheet.

The laminate can further include other layers, such as the first member. When the laminate includes the first member, the laminate has a structure in which the first member and a layer of the pressure-sensitive adhesive sheet or its cured product are laminated. The first member is the same as the first member described in the section <Method of Using Adhesive Sheet>. Therefore, for example, a polycarbonate resin plate can be used as the first member.

In addition to the first member such as a polycarbonate resin plate, the laminate can further include other layers such as a substrate layer. In this case, the laminate can have a structure in which the substrate layer, the pressure-sensitive adhesive sheet or its cured product, and the first member are laminated in this order.

Examples of the substrate layer include an ITO substrate, a glass substrate, a metal substrate, a resin substrate, paper, cloth, and non-woven fabric.

When the laminate comprises a cured product of an adhesive sheet, for example, a laminate comprising an adhesive sheet before curing (that is, an adhesive layer in a semi-cured state) is manufactured, and this laminate is irradiated with an active energy ray. By doing so, a laminate comprising a cured adhesive sheet can be obtained.

Since the laminate is excellent in outgassing resistance, it can be particularly preferably used for applications such as display devices such as liquid crystal displays (LCD) and input devices such as touch panels.

The method for producing the laminate is not particularly limited. For example, after the adhesive layer of the adhesive sheet described above is laminated to the adherend in a semi-cured state, the adhesive layer is post-cured by irradiating an active energy ray. a step of allowing Specifically, the method for producing a laminate includes a step 1 of laminating an adherend on at least one side of an adhesive sheet, and irradiating the adhesive layer of the adhesive sheet with an active energy ray. has a step 2 of post-curing the . That is, the method for manufacturing a laminate can include the step of forming the pressure-sensitive adhesive layer described above.

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.

(Synthesis example 1)
<Production of crosslinkable (meth)acrylic copolymer (a-1)>
Butyl acrylate (BA) was prepared as monomer B (monomer having no functional group exhibiting cross-linking reactivity), and 2-hydroxyethyl acrylate (2HEA) was prepared as monomer A (monomer having functional group exhibiting cross-linking reactivity). , 75% by weight of BA and 25% by weight of 2HEA were prepared. After mixing this monomer mixture and an ethyl acetate solution of 2,2′-azobis(2,4-dimethylvaleronitrile) as a radical polymerization initiator to obtain a mixture, the mixture is heated to 60° C. and randomly Copolymerization was carried out to obtain a crosslinkable (meth)acrylic copolymer (a-1). The weight average molecular weight of the crosslinkable (meth)acrylic copolymer (a-1) was 580,000.

In addition, the weight average molecular weight was measured by gel permeation chromatography (GPC) and calculated based on polystyrene standards. Measurement conditions for gel permeation chromatography (GPC) are as follows.
Solvent: tetrahydrofuran Column: Shodex KF801, KF803L, KF800L, KF800D (4 columns manufactured by Showa Denko Co., Ltd. were connected and used)
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
Calibration curve: standard polystyrene Shodex standard Polystyrene (manufactured by Showa Denko) Mw = 1320 to 2,500,000 A calibration curve of 10 samples was used.

(Synthesis Example 2-1)
With reference to the aforementioned Patent Document 1, 60% by mass of 2-ethylhexyl acrylate (2EHA), 5% by mass of 4-acryloylmorpholine, 15% by mass of isobornyl acrylate, 5% by mass of N-vinylacetamide and 15% by mass of 2-hydroxyethyl acrylate. % by mass was copolymerized by a solution polymerization method to prepare a crosslinkable (meth)acrylic copolymer (b-1). The molecular weight of this crosslinkable (meth)acrylic copolymer (b-1) was a weight average molecular weight (Mw) of 510,000.

(Synthesis Example 2-2)
A crosslinkable acrylic copolymer was prepared as follows according to the method described in Example 1 of Patent Document 2 mentioned above. 2-ethylhexyl acrylate (2EHA) 63 parts by mass, N-vinyl-2-pyrrolidone (NVP) 15 parts by mass, methyl methacrylate (MMA) 9 parts by mass, 2-hydroxyethyl acrylate (2HEA) 13 parts by mass, radical polymerization initiation 2,2′-azobis(2,4-dimethylvaleronitrile) was dissolved in ethyl acetate as a reagent. The solution was heated to 65° C. for random copolymerization to obtain a crosslinkable acrylic copolymer (b-2). The weight average molecular weight of the crosslinkable acrylic copolymer (B-2) was 780,000.

(Example 1)
<Preparation of adhesive composition (A-1)>
Per 100 parts by mass of the crosslinkable acrylic copolymer (a-1) produced in Synthesis Example 1, 0.2 parts by mass of a tolylene diisocyanate compound (Coronate L-55E, manufactured by Tosoh Corporation) as a cross-linking agent, and a silane cup. 0.30 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403) as a ring agent, and 3-ethyl-3-oxetanylmethyl acrylate (Osaka Organic Chemical Industry Co., Ltd.) as a cyclic ether-containing monomer. OXE-10) 25 parts by mass, 12 parts by mass of bisphenol A ethylene oxide-modified diacrylate (manufactured by Toagosei Co., Ltd., Aronix M211B) as a polyfunctional monomer, and bis(2,4) as a photopolymerization initiator. ,6-Trimethylbenzoyl) phenylphosphine oxide (BASF Japan, IRGACURE819) was added in an amount of 1.0 parts by mass, and ethyl acetate was added as a solvent so that the solid content concentration was 35% by mass. to obtain a pressure-sensitive adhesive composition (A-1).

<Preparation of adhesive layer (A-1)>
Next, as the first release sheet, a polyethylene terephthalate film having a thickness of 100 μm provided with an easy-adhesive layer treated with a silicone-based release agent (heavy separator film, manufactured by Teijin DuPont Films, release-treated polyethylene terephthalate film ) was prepared. The pressure-sensitive adhesive composition (A-1) is evenly applied to the easy-adhesive layer side surface of the first release sheet with an applicator so that the coating thickness after drying is 150 μm, and the pressure-sensitive adhesive After preparing a coating film of the composition (A-1), it is dried for 3 minutes in an air circulation type constant temperature oven at 90 ° C. to form an adhesive layer (A-1) on the surface of the first release sheet. bottom.

Next, prepare a second release sheet having a thickness of 75 μm (light separator film, manufactured by Teijin DuPont Films, release-treated polyethylene terephthalate film) that has been subjected to a release treatment with higher release properties than the first release sheet. bottom. This second release sheet was attached onto the adhesive layer (A-1) formed on the surface of the first release sheet. As a result, the first release sheet/adhesive layer (A-1)/second release sheet configuration in which the adhesive layer (A-1) is sandwiched between a pair of release sheets having different peeling strengths is released. A pressure-sensitive adhesive sheet with a sheet was obtained. This pressure-sensitive adhesive sheet with a release sheet was left to stand for 7 days under the conditions of 23° C. and 50% relative humidity for aging treatment.

(Example 2)
The same method as in Example 1 except that 3-ethyl-3-oxetanylmethyl methacrylate (OXE-30, manufactured by Osaka Organic Chemical Industry Co., Ltd.) was used instead of 3-ethyl-3-oxetanylmethyl acrylate as a cyclic ether-containing monomer. to obtain a pressure-sensitive adhesive sheet with a release sheet.

(Example 3)
Tetrahydrofurfuryl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat # 150) 20 parts by weight instead of 25 parts by weight of 3-ethyl-3-oxetanylmethyl acrylate as a cyclic ether-containing monomer, and bisphenol as a polyfunctional monomer A A pressure-sensitive adhesive sheet with a release sheet was prepared in the same manner as in Example 1, except that 6 parts by mass of bisphenol FEO-modified diacrylate (manufactured by Toagosei Co., Ltd., Aronix M208) was used instead of 12 parts by mass of ethylene oxide-modified diacrylate. Obtained.

(Example 4)
Adhesive with a release sheet in the same manner as in Example 3 except that an acrylate having a tetrahydrofurfuryl structure (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat #150D) was used instead of tetrahydrofurfuryl acrylate as a cyclic ether-containing monomer. got a sheet.

(Example 5)
(2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., MEDOL-10) instead of 25 parts by mass of 3-ethyl-3-oxetanylmethyl acrylate as a cyclic ether-containing monomer Using 10 parts by mass, bisphenol A EO (3.8) adduct diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat #700HV) instead of 12 parts by mass of bisphenol A ethylene oxide-modified diacrylate as a multifunctional monomer A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1, except that 10 parts by mass was used.

(Example 6)
(2-Methyl-2-ethyl-1,3-dioxolan-4-yl) 10 parts by mass of cyclic trimethylolpropane formal acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat #200) was used instead of 10 parts by mass of methyl acrylate. A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 5.

(Comparative example 1)
A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1, except that the monofunctional monomer having a cyclic ether structure, the polyfunctional monomer and the photopolymerization initiator were not used.
(Comparative example 2)
A pressure-sensitive adhesive sheet with a release sheet was prepared in the same manner as in Example 1 except that isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., ISTA) was used instead of 3-ethyl-3-oxetanylmethyl acrylate as a monofunctional monomer. got

(Comparative Example 3)
To 100 parts by mass of the crosslinkable (meth)acrylic copolymer (b-1) produced in Synthesis Example 2-1, 0.15 mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., BHS8515) as a cross-linking agent and 0.30 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403) as a silane coupling agent so that the solid content concentration is 35% by mass. Methyl ethyl ketone was added as a solvent to obtain an adhesive composition (B-1). Then, in the method for producing the adhesive layer (A-1) of Example 1, the adhesive layer of Example 1 except that the adhesive composition (A-1) was changed to the adhesive composition (B-1) A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in the production method of (A-1). This pressure-sensitive adhesive sheet with a release sheet had a pressure-sensitive adhesive layer (B-1).

(Comparative Example 4)
For 100 parts by mass of the crosslinkable (meth)acrylic copolymer (b-2) produced in Synthesis Example 2-2, 0.3 mass of an isocyanate-based cross-linking agent (Takenate D110N, manufactured by Mitsui Chemicals, Inc.) as a cross-linking agent. part, 0.2 parts by mass of a polyol obtained by adding propylene oxide to ethylenediamine as a crosslinking accelerator (EDP-300, manufactured by Adeka Co., Ltd.), and 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., 0.15 weight of KBM-403) was added, and ethyl acetate was added as a solvent so that the solid content concentration was 30% by mass to obtain an adhesive composition (B-1). Next, in the method for producing the adhesive layer (A-1) of Example 1, the adhesive composition (A-1) was changed to the adhesive composition (B-2), and the drying treatment was performed at 60 ° C. The pressure-sensitive adhesive layer of Example 1 (A-1 ) to obtain a pressure-sensitive adhesive sheet with a release sheet. This pressure-sensitive adhesive sheet with a release sheet had a pressure-sensitive adhesive layer (B-2).

<Outgas resistance evaluation>
(Test Example 1-1)
Using the pressure-sensitive adhesive sheets with release sheets produced in Examples 1 to 6 and Comparative Example 2, outgas resistance was evaluated as follows. In the pressure-sensitive adhesive sheet with a release sheet, the second release sheet, which is a light separator film, is peeled off to expose the pressure-sensitive adhesive layer, and a polycarbonate resin plate with a thickness of 1 mm (Teijin's pan It was attached to a light sheet PC-1151). Next, the first release sheet, which is a heavy separator film, was peeled off, and a glass plate having a size of 100 mm×200 mm was adhered to the entire surface of the exposed pressure-sensitive adhesive layer as a second member. Thus, a laminate sample composed of polycarbonate resin plate/adhesive layer/glass plate was obtained. After treating the laminate sample in an autoclave at 40 ° C. and 0.5 MPa for 30 minutes, ultraviolet rays were irradiated from the glass plate side so that the integrated light amount was 3000 mJ / cm ² , and a test with a size of 100 mm × 200 mm was performed. Got a sample. The test sample was placed in an environment of 85° C. and relative humidity of 85%, and after 2 hours and 100 hours, the test sample was visually observed, and air bubbles, floating and peeling were evaluated according to the following three criteria. .
⊚: No air bubbles, lifting or peeling was observed after 2 hours or 100 hours.
◯: Fine air bubbles were observed after 2 hours, but no air bubbles, floating and peeling were observed after 100 hours.
x: Bubbles, floating and peeling were observed both after 2 hours and after 100 hours.

(Test Example 1-2)
As the adhesive sheet with a release sheet, the same as in Test Example 1-1 except that the adhesive sheet with a release sheet prepared in Comparative Examples 1, 3 and 4 was used, and the laminate sample was not irradiated with ultraviolet rays. A test sample was obtained in the method. The test sample was visually observed, and air bubbles, floating and peeling were evaluated according to the same criteria as in Test Example 1-1.

(Test Example 2-1)
Using the pressure-sensitive adhesive sheets with release sheets produced in Examples 1 to 6 and Comparative Example 2, outgas resistance was evaluated as follows. In the adhesive sheet with a release sheet, the second release sheet, which is a light separator film, is peeled off to expose the adhesive layer, and a hard-coated polycarbonate resin plate with a thickness of 1 mm as the first member (Mitsubishi Gas It was attached to the side of Iupilon Sheet MR-58U manufactured by Kagaku Co., Ltd. on which the hard coat layer was not attached. Next, the first release sheet, which is a heavy separator film, was peeled off, and a glass plate having a size of 100 mm×200 mm was adhered to the entire surface of the exposed pressure-sensitive adhesive layer as a second member. Thus, a laminate sample composed of polycarbonate resin plate/adhesive layer/glass plate was obtained. After treating the laminate sample in an autoclave at 40 ° C. and 0.5 MPa for 30 minutes, ultraviolet rays were irradiated from the glass plate side so that the integrated light amount was 3000 mJ / cm ² , and a test with a size of 100 mm × 200 mm was performed. Got a sample. The test sample was placed in an environment of 85° C. and relative humidity of 85%, and after 2 hours and 100 hours, the test sample was visually observed, and air bubbles, floating and peeling were evaluated according to the following three criteria. .
⊚: No air bubbles, lifting or peeling was observed after 2 hours or 100 hours.
◯: Fine air bubbles were observed after 2 hours, but no air bubbles, floating and peeling were observed after 100 hours.
x: Bubbles, floating and peeling were observed both after 2 hours and after 100 hours.

(Test example 2-2)
As the adhesive sheet with a release sheet, the same as in Test Example 2-1 except that the adhesive sheet with a release sheet prepared in Comparative Examples 1, 3 and 4 was used, and the laminate sample was not irradiated with ultraviolet rays. A test sample was obtained in the method. The test sample was visually observed, and air bubbles, floating and peeling were evaluated according to the same criteria as in Test Example 2-1.

(Test Example 3-1)
Using the pressure-sensitive adhesive sheets with release sheets produced in Examples 1 to 6 and Comparative Example 2, outgas resistance was evaluated as follows. In the pressure-sensitive adhesive sheet with a release sheet, the second release sheet, which is a light separator film, is peeled off to expose the pressure-sensitive adhesive layer, and a 125 μm thick ITO film (manufactured by Oike Kogyo Co., Ltd.) is applied to the pressure-sensitive adhesive layer as a second member. KB300) was pasted together. Next, the first release sheet, which is a heavy separator film, is peeled off, and an acrylic resin plate made of polymethyl methacrylate (PMMA) having a size of 100 mm × 200 mm and a thickness of 1 mm is used as the first member for the exposed adhesive layer. (Acrylite MR-200, manufactured by Mitsubishi Rayon Co., Ltd.) was adhered to the entire surface. As a result, a laminate sample composed of a polymethyl methacrylate resin plate/adhesive layer/ITO film was obtained. After treating the laminate sample in an autoclave at 40 ° C. and 0.5 MPa for 30 minutes, ultraviolet rays were irradiated from the glass plate side so that the integrated light amount was 3000 mJ / cm ² , and a test with a size of 100 mm × 200 mm was performed. Got a sample. The test sample was placed in an environment of 85° C. and relative humidity of 85%, and after 2 hours and 100 hours, the test sample was visually observed, and air bubbles, floating and peeling were evaluated according to the following three criteria. .
⊚: No air bubbles, lifting or peeling was observed after 2 hours or 100 hours.
◯: Fine air bubbles were observed after 2 hours, but no air bubbles, floating and peeling were observed after 100 hours.
x: Bubbles, floating and peeling were observed both after 2 hours and after 100 hours.

(Test Example 3-2)
As the adhesive sheet with a release sheet, the same as in Test Example 3-1 except that the adhesive sheet with a release sheet prepared in Comparative Examples 1, 3 and 4 was used, and the laminate sample was not irradiated with ultraviolet rays. A test sample was obtained in the method. The test sample was visually observed, and air bubbles, floating and peeling were evaluated according to the same criteria as in Test Example 3-1.

(Evaluation results)
Table 1 shows the evaluation results of outgas resistance. From the comparison of the pressure-sensitive adhesive sheets obtained in Examples 1-6 and the pressure-sensitive adhesive sheets obtained in Comparative Examples 1-4, the pressure-sensitive adhesive sheets obtained in Examples 1-6 have excellent outgas resistance, especially the hard coat It was found to have excellent outgassing resistance even for a polycarbonate film having no layer.

Claims (8)

A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer contains a crosslinked (meth)acrylic copolymer, a polymerizable monomer having a polymerizable double bond in the molecule, and a photopolymerization initiator,
The crosslinked (meth)acrylic copolymer has a structure in which a crosslinkable (meth)acrylic copolymer is crosslinked with a crosslinking agent,
The polymerizable monomer includes a monofunctional monomer having a cyclic ether structure and a polyfunctional monomer having two or more polymerizable double bonds in the molecule,
The pressure-sensitive adhesive sheet , wherein the polyfunctional monomer has a bisphenol skeleton in its molecule . 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the monofunctional monomer having a cyclic ether structure is contained in an amount of 5 to 30 parts by mass with respect to 100 parts by mass of the crosslinkable (meth)acrylic copolymer. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein said cyclic ether structure is a 4- to 6-membered ring. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3 , wherein the polyfunctional monomer is contained in an amount of 1 to 15 parts by mass with respect to 100 parts by mass of the crosslinkable (meth)acrylic copolymer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4 , which is used for bonding with a first member selected from the group consisting of resin plates, resin sheets and resin films. The pressure-sensitive adhesive sheet according to claim 5 , which is used for bonding the first member and a second member selected from the group consisting of a glass plate, a resin film and a resin plate. A laminate comprising the adhesive sheet according to any one of claims 1 to 6 or a cured product thereof. 8. The laminate according to claim 7 , further comprising the first member, and having a structure in which the first member and a layer of the pressure-sensitive adhesive sheet or a cured product thereof are laminated.