Adhesive sheet and layered product

Abstract

Provided is an adhesive sheet which is used for bonding adherends having different expansion / contraction rates to each other, and which is unlikely to peel from an adherend even in an environment in which temperature changes occur or in a high temperature environment.　This adhesive sheet is used for bonding a pair of adherends having different expansion / contraction rates to each other, and comprises an adhesive layer obtained from an adhesive composition. The adhesive composition contains at least a main agent, which contains a (meth)acrylic polymer, and a silane coupling agent. The adhesive layer has a gel fraction of 80% or more and has a residual stress of 3.0-10.0 kPa 60 seconds after applying a twisting shear force of 15% at 105ºC.

Description

Pressure-sensitive adhesive sheet and laminate

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a laminate.

[0002] In recent years, pressure-sensitive adhesive sheets are materials formed with a pressure-sensitive adhesive layer containing, for example, an acrylic polymer as a main component, and are used for bonding various optical components such as touch panels and liquid crystal displays (LCDs), as well as for use in automobile sunroofs and large building windows.

[0003] Such pressure-sensitive adhesive sheets have been widely studied, and various means have been proposed for improving not only adhesive strength but also various other performances. For example, Patent Document 1 proposes a pressure-sensitive adhesive sheet with a release liner, which comprises a pressure-sensitive adhesive sheet having a substrate and a pressure-sensitive adhesive layer, and a release liner disposed on the pressure-sensitive adhesive layer, and is said to be capable of easily escaping air when attached to an adherend during use, allowing for good adhesion.

[0004] On the other hand, a pair of adherends having different linear expansion coefficients (expansion coefficients) may be bonded together using a pressure-sensitive adhesive sheet. For example, a laminate is known in which a glass substrate and a resin substrate are bonded together with a pressure-sensitive adhesive sheet. It is also known that such a laminate can be used for various purposes, such as sunroofs for automobiles and large windows for buildings.

[0005] JP 2011-094057 A

[0006] However, laminates in which adherends with different expansion and contraction rates are bonded together with a conventional pressure-sensitive adhesive sheet have a problem in that, due to the difference in the expansion and contraction rates between the adherends, peeling occurs, for example, at the edges of the adherends, in environments where temperature changes occur or high temperatures occur. This problem becomes more pronounced as the adherends become larger; for example, the thicker the adherend, the more likely it is that peeling will occur in environments where temperature changes occur or high temperatures occur. From this perspective, there has been a demand for a pressure-sensitive adhesive sheet that is less likely to peel when adherends with different expansion and contraction rates are bonded together, even when placed in environments where temperature changes and high temperatures occur.

[0007] The present invention has been made in view of the above, and aims to provide an adhesive sheet that, when adherends with different expansion and contraction rates are bonded together, is less likely to peel from the adherends, even in environments where temperature changes occur or in high-temperature environments.

[0008] As a result of extensive research into achieving the above object, the present inventors have discovered that the above object can be achieved by using a pressure-sensitive adhesive layer having specific physical properties, and have thus completed the present invention.

[0009] That is, the present invention encompasses, for example, the subject matter described in the following items: Item 1: A pressure-sensitive adhesive sheet used to bond a pair of adherends having different expansion and contraction rates together, comprising a pressure-sensitive adhesive layer obtained from a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition containing at least a main agent including a (meth)acrylic polymer and a silane coupling agent, the pressure-sensitive adhesive layer having a gel fraction of 80% or more, the pressure-sensitive adhesive layer having a residual stress of 3.0 kPa or more and 10.0 kPa or less 60 seconds after application of a 15% torsional shear stress at 105°C, and satisfying the following formula (1): |(X1-X2)|≧0.1% (1) (wherein, when one of the pair of adherends is adherend A and the other is adherend B, X1 is the expansion and contraction rate (%) when adherend A is heated from 23°C to 110°C, and X2 is the expansion and contraction rate (%) when adherend B is heated from 23°C to 110°C). Item 2. The pressure-sensitive adhesive sheet according to Item 1, wherein the pressure-sensitive adhesive composition contains a monofunctional monomer having a ring structure. Item 3. The pressure-sensitive adhesive sheet according to Item 1 or 2, wherein the pressure-sensitive adhesive composition contains 0.05 parts by mass or more and 5 parts by mass or less of the silane coupling agent per 100 parts by mass of the base agent. Item 4. The pressure-sensitive adhesive sheet according to any one of Items 1 to 3, wherein the pressure-sensitive adhesive composition is solvent-free, and the pressure-sensitive adhesive layer has a crosslinked structure formed by a polyfunctional monomer. Item 5. The pressure-sensitive adhesive sheet according to any one of Items 1 to 4, wherein the pressure-sensitive adhesive composition contains an acrylic tackifier. Item 6. The pressure-sensitive adhesive sheet according to any one of Items 1 to 5, wherein the thickness is 75 μm or more. Item 7. The pressure-sensitive adhesive sheet according to any one of Items 1 to 6, wherein the thickness of the adherend A or the adherend B, which has a higher stretchability, is 2 mm or more. Item 8. The pressure-sensitive adhesive sheet according to any one of Items 1 to 7, wherein the adherend A and the adherend B both have a total light transmittance of 50% or more. Item 9. The pressure-sensitive adhesive sheet according to Item 8, which is for use in car windows, building windows, or door windows. Item 10. A laminate comprising the pressure-sensitive adhesive sheet according to any one of Items 1 to 9 and a pair of adherends having different stretch rates.

[0010] The pressure-sensitive adhesive sheet according to the present invention is used to bond adherends having different expansion and contraction rates together, and is unlikely to peel from the adherend even in environments where temperature changes occur or in high-temperature environments.

[0011]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0012] The pressure-sensitive adhesive sheet of the present invention is used to bond adherends having different expansion and contraction rates, and includes a pressure-sensitive adhesive layer obtained from a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition contains at least a base agent containing a (meth)acrylic polymer and a silane coupling agent, and the pressure-sensitive adhesive layer has a gel fraction of 80% or more, and the pressure-sensitive adhesive layer has a residual stress of 3.0 kPa or more and 10.0 kPa or less 60 seconds after application of a 15% torsional shear stress at 105°C. Additionally, the pressure-sensitive adhesive sheet of the present invention satisfies the following formula (1): |(X1-X2)|≧0.1% (1) (wherein, when one of the pair of adherends is adherend A and the other is adherend B, X1 is the expansion and contraction rate (%) of adherend A when heated from 23°C to 110°C, and X2 is the expansion and contraction rate (%) of adherend B when heated from 23°C to 110°C).

[0013] The pressure-sensitive adhesive sheet of the present invention is used to bond adherends having different expansion and contraction rates together, and is unlikely to peel from the adherend even in environments where temperature changes occur or in high-temperature environments.

[0014] As described above, the pressure-sensitive adhesive sheet of the present invention comprises a pressure-sensitive adhesive layer obtained from a pressure-sensitive adhesive composition. For example, when the pressure-sensitive adhesive composition is an active energy ray-curable type as described below, the pressure-sensitive adhesive layer can be formed by irradiating the pressure-sensitive adhesive with active energy rays to cure it.

[0015] The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains at least a base agent containing a (meth)acrylic polymer and a silane coupling agent.

[0016] (Base agent containing (meth)acrylic polymer) The base agent containing a (meth)acrylic polymer contains at least a (meth)acrylic polymer and is the main component of the pressure-sensitive adhesive composition. The base agent containing a (meth)acrylic polymer may consist of only a (meth)acrylic polymer, or may contain a (meth)acrylic polymer and a monofunctional monomer described below. When the base agent containing a (meth)acrylic polymer contains a (meth)acrylic polymer and a monofunctional monomer, the base agent becomes a monomer solution of the (meth)acrylic polymer, which is a so-called syrup.

[0017] The (meth)acrylic polymer may be, for example, a wide variety of known acrylic polymers used to form pressure-sensitive adhesive sheets. For example, the (meth)acrylic polymer may be a polymer of a (meth)acrylic acid ester. That is, the (meth)acrylic polymer is a polymer having a (meth)acrylic acid ester unit.

[0018] Examples of the (meth)acrylic acid ester include (meth)acrylates having a linear or branched alkyl group, (meth)acrylates having a ring structure in the side chain, and (meth)acrylates having a hydroxyl group in the side chain.

[0019] In a (meth)acrylate having a linear or branched alkyl group, the alkyl group may have, for example, 1 to 20 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 2 to 14 carbon atoms, and even more preferably 3 to 12 carbon atoms.

[0020] Specific examples of (meth)acrylates having a linear or branched alkyl group 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, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate.

[0021] The (meth)acrylate having a ring structure in the side chain is preferably a (meth)acrylic monomer having an alicyclic or aromatic ring in the side chain, more preferably a (meth)acrylic monomer having an alicyclic ring. Examples of the alicyclic ring include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, norbornene, norbornadiene, dicyclopentane, isobornyl, tetrahydrofuran, and tetrahydropyran. The alicyclic ring may have a spiro structure. Examples of the aromatic ring include benzene, naphthalene, anthracene, pyridine, furan, benzofuran, pyrrole, thiophene, imidazole, and oxazole. Among these, the ring structure is preferably an alicyclic ring, more preferably at least one selected from cyclohexane, dicyclopentane, isobornyl, and benzene, and particularly preferably cyclohexane or isobornyl. The above-mentioned ring structure may further have a substituent. Examples of the substituent include substitutable substituents selected from a halogen atom, a halogenated alkyl group, an alkyl group, an alkenyl group, an acyl group, a hydroxy group, a hydroxyalkyl group, an alkoxy group, an aryl group, a heteroaryl group, an alicyclic group, a cyano group, an epoxy group, an oxetanyl group, a mercapto group, an amino group, and a (meth)acryloyl group.

[0022] The (meth)acrylate having a ring structure in the side chain preferably has a structure in which a monovalent group having a ring structure is bonded to an ester oxygen of the (meth)acrylate, and in this case, the monovalent group having a ring structure preferably has 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms, and even more preferably 4 to 8 carbon atoms.

[0023] Specific examples of (meth)acrylates having a ring structure in the side chain include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, O-phenylphenoxyethyl (meth)acrylate, etc. Among these, the (meth)acrylate having a ring structure in the side chain is preferably at least one selected from the group consisting of cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, in that peeling between the adherend and the PSA sheet is less likely to occur even in temperature-changing and high-temperature environments.

[0024] Examples of the (meth)acrylate having a hydroxyl group in the side chain include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (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-phenoxypropyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and polyalkylene glycol mono(meth)acrylate.

[0025] The (meth)acrylic polymer may have a monomer unit other than the above-mentioned (meth)acrylic acid ester, and examples thereof include a carboxyl group-containing (meth)acrylate unit such as (meth)acrylic acid, a glycidyl group-containing (meth)acrylate unit, an amino group-containing (meth)acrylate, and other monomer units based on (meth)acrylamide, allylamine, etc.

[0026] In order to prevent peeling of the adhesive sheet from the adherend even under temperature-changing and high-temperature conditions, the (meth)acrylic polymer is preferably a polymer of monomers containing at least one selected from the group consisting of (meth)acrylates having a linear or branched alkyl group, (meth)acrylates having a ring structure in the side chain, and (meth)acrylates having a hydroxyl group in the side chain. That is, the (meth)acrylic polymer preferably contains at least one monomer unit selected from the group consisting of (meth)acrylate units having a linear or branched alkyl group, (meth)acrylate units having a ring structure in the side chain, and (meth)acrylate units having a hydroxyl group in the side chain. In particular, the (meth)acrylic polymer preferably contains at least (meth)acrylate units having a linear or branched alkyl group.

[0027] The (meth)acrylic polymer preferably contains 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more of (meth)acrylate units having a linear or branched alkyl group, and more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

[0028] The (meth)acrylic polymer preferably contains 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more of a (meth)acrylate having a ring structure in a side chain, and more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less.

[0029] The (meth)acrylic polymer preferably contains 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more of (meth)acrylate units having a hydroxyl group in a side chain, and more preferably 50% by mass or less, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less.

[0030] The (meth)acrylic polymer may contain other monomer units than those described above, as long as the effects of the present invention are not impaired. The content of the other monomer units in the (meth)acrylic polymer may be 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0031] The ratio (molar ratio) of each structural unit in the (meth)acrylic polymer can be considered to be the same as the molar ratio of each monomer used in producing the polymer.

[0032] The (meth)acrylic polymer may be composed of only one type of monomer unit selected from the group consisting of a (meth)acrylate unit having a linear or branched alkyl group, a (meth)acrylate unit having a ring structure in the side chain, and a (meth)acrylate unit having a hydroxyl group in the side chain.

[0033] The weight-average molecular weight of the (meth)acrylic polymer is preferably greater than 10,000, more preferably 100,000 or more, and even more preferably 200,000 or more. The weight-average molecular weight of the (meth)acrylic polymer is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,200,000 or less.

[0034] The weight-average molecular weight referred to in the present invention refers to the weight-average molecular weight measured in terms of polystyrene by gel permeation chromatography (GPC). There are no particular limitations on the GPC apparatus used in the GPC method, and commercially available GPC measuring instruments, such as the LC-2000Plus series manufactured by JASCO Corporation, and detectors such as the RI-2031Plus and UV-2075Plus, can be used. In this case, for example, a GPC column consisting of four columns connected together, namely, "Shodex KF801," "Shodex KF803L," "Shodex KF800L," and "Shodex KF800D" manufactured by Showa Denko K.K., can be used. The column temperature can be set to 40°C. Tetrahydrofuran is used as the eluent, and measurements are performed at a flow rate of 1.0 ml / min. Typically, a calibration curve is prepared using standard polystyrene, and the weight-average molecular weight (Mw) can be obtained in terms of polystyrene.

[0035] The (meth)acrylic polymer can be produced by a known method. For example, a (meth)acrylic polymer can be produced by polymerizing a monomer mixture for forming each structural unit by a known polymerization method. The (meth)acrylic polymer may be a partially polymerized product, that is, a state in which a portion of the monomers used in the polymerization remains unpolymerized, that is, the above-mentioned syrup state. In this case, it is clear that the monomers contained in the syrup are a portion of the monomers used in the polymerization of the (meth)acrylic polymer. As the polymerization method, for example, solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc. can be used. The acrylic polymer can also be obtained from a commercially available product, etc.

[0036] In the PSA composition, the base agent can be in the form of a syrup (in the form of a partial polymer of a (meth)acrylic polymer) as described above, i.e., the base agent can be a monofunctional monomer solution of the (meth)acrylic polymer. In the case of such a monofunctional monomer solution, the polymer fraction (the proportion of the polymer content relative to the total mass of the polymer and the monofunctional monomer) can be, for example, 1 to 50 mass%, preferably 5 to 30 mass%. The base agent may consist only of the (meth)acrylic polymer and the monofunctional monomer.

[0037] The type of monofunctional monomer is not particularly limited, and examples thereof include various monomers used to form the (meth)acrylic polymer, namely, the above-mentioned (meth)acrylic acid esters, specifically, (meth)acrylates having a linear or branched alkyl group, (meth)acrylates having a ring structure in the side chain, (meth)acrylates having a hydroxyl group in the side chain, etc. The content ratios of the (meth)acrylates having a linear or branched alkyl group, (meth)acrylates having a ring structure in the side chain, and (meth)acrylates having a hydroxyl group in the side chain contained in the monofunctional monomer can be set to the same ranges as the content ratios of the (meth)acrylate units having a linear or branched alkyl group, (meth)acrylate units having a ring structure in the side chain, and (meth)acrylate units having a hydroxyl group in the side chain contained in the (meth)acrylic polymer, respectively.

[0038] (Silane Coupling Agent) Examples of the silane coupling agent include mercapto-based silane coupling agents containing a mercapto group, epoxy-based silane coupling agents containing an epoxy group, vinyl-based silane coupling agents containing a vinyl group, and isocyanurate-based silane coupling agents. Commercially available silane coupling agents can also be used. Examples of commercially available silane coupling agents include KBM-802, X-12-1056ES, KBM-402, KBM-403, KBM-5103, KBM-502, KBM-503, and KBM-9659 manufactured by Shin-Etsu Chemical Co., Ltd. By including a silane coupling agent in the pressure-sensitive adhesive composition, the adhesion between the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition and the adherend can be further improved.

[0039] When the pressure-sensitive adhesive composition contains a silane coupling agent, its content ratio is not particularly limited.In order to prevent peeling between the adherend and the pressure-sensitive adhesive sheet even under temperature change and high temperature environments, the content ratio of the silane coupling agent is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.15 parts by mass or more, particularly preferably 0.2 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, particularly preferably 1 part by mass or less, relative to 100 parts by mass of the main agent.

[0040] <Tackifier> The PSA composition may further contain a tackifier. By containing a tackifier in the PSA composition, the PSA layer formed from the PSA composition tends to have better adhesion to the adherend.

[0041] The type of tackifier is not particularly limited, and for example, a wide range of tackifiers used in known pressure-sensitive adhesive sheets can be applied.

[0042] Among these, the tackifier is preferably an acrylic tackifier, that is, the pressure-sensitive adhesive composition preferably contains an acrylic tackifier.

[0043] Examples of the acrylic tackifier include resins having a glass transition temperature of 20° C. or higher. The glass transition temperature of the acrylic tackifier is preferably 30° C. or higher, more preferably 40° C. or higher, and even more preferably 50° C. or higher, and is preferably 200° C. or lower, more preferably 180° C. or lower, and even more preferably 150° C. or lower. By adjusting the glass transition temperature of the acrylic tackifier to fall within the above range, the adhesion of the pressure-sensitive adhesive sheet to the adherend can be improved.

[0044] The structural units contained in the acrylic tackifier may include a monomer unit having an alicyclic ring. When the acrylic tackifier includes a monomer unit having an alicyclic ring, the number of carbon atoms constituting the alicyclic ring is preferably 6 or more. Examples of alicyclic rings having 6 or more carbon atoms include cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, norbornene, norbornadiene, isobornyl, and dicyclopentane. Examples of preferred monomers having an alicyclic ring include isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyl (meth)acrylate.

[0045] The acrylic tackifier can contain alkyl(meth)acrylate units in place of or in addition to the alicyclic monomer units. Examples of alkyl(meth)acrylates include alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, isobutyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, lauryl(meth)acrylate, cetyl(meth)acrylate, stearyl(meth)acrylate, and behenyl(meth)acrylate. Of these, it is preferable that the acrylic tackifier contain methyl(meth)acrylate.

[0046] The acrylic tackifier is preferably a copolymer containing both an alicyclic monomer unit and an alkyl(meth)acrylate unit. In order to easily improve the adhesion between the pressure-sensitive adhesive sheet and the adherend, the content of the alkyl(meth)acrylate unit relative to the total mass of the acrylic tackifier is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less.

[0047] The acrylic tackifier may contain other monomer units as needed. The other monomers may be any monomers copolymerizable with the alkyl (meth)acrylates, such as (meth)acrylonitrile, vinyl acetate, vinyl chloride, and ethyl vinyl ether. The content of the other monomer units in the acrylic tackifier is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0048] The weight-average molecular weight of the tackifier is preferably 3,000 or more, more preferably 3,200 or more, and even more preferably 3,500 or more. The weight-average molecular weight of the tackifier may be 20,000 or less, more preferably 15,000 or less, and even more preferably 10,000 or less. The weight-average molecular weight of the tackifier is measured by gel permeation chromatography (GPC) and converted using a calibration curve prepared using standard polystyrenes with known molecular weights. Such resins may be commercially available or may be synthesized by known methods.

[0049] The content of the tackifier in the pressure-sensitive adhesive composition is not particularly limited. In order to easily improve the adhesion of the pressure-sensitive adhesive sheet to the adherend, the content of the tackifier is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of the main agent.

[0050] The tackifier may be formed solely from an acrylic tackifier, or may contain components other than the acrylic tackifier. The tackifier contained in the pressure-sensitive adhesive composition may be one type alone or two or more types.

[0051] <Polyfunctional Monomer> The PSA composition may contain a polyfunctional monomer. Examples of such polyfunctional monomers include compounds having two or more polymerizable double bonds in the molecule. The polyfunctional monomer has two or more polymerizable double bonds (e.g., radically polymerizable double bonds), preferably two or more but less than five, and more preferably two or more but less than four. When the PSA composition contains a polyfunctional monomer, it can react with the monomer in the syrup to form, for example, a crosslinked polymer. That is, when the PSA composition contains a polyfunctional monomer, the resulting PSA layer can have a crosslinked structure due to the polyfunctional monomer.

[0052] When the pressure-sensitive adhesive composition contains a polyfunctional monomer, the pressure-sensitive adhesive sheet obtained is particularly resistant to peeling from the adherend even when placed in an environment of changing temperature or in a high-temperature environment.

[0053] Examples of polyfunctional monomers include bifunctional monomers (monomers having two polymerizable double bonds), such as polyethylene glycol diacrylate, polypropylene diacrylate, alkyl diacrylate, polytetramethylene glycol diacrylate, polypropylene glycol diacrylate, dioxane diacrylate, tricyclodecanol diacrylate, and fluorene diacrylate. Examples of polyfunctional monomers include trifunctional or higher functional monomers, such as alkoxylated trimethylolpropane triacrylate, alkoxylated glycerin triacrylate, caprolactone-modified isocyanurate triacrylate, pentaerythritol acrylate, alkoxylated pentaerythritol acrylate, (alkoxylated) pentaerythritol acrylate, (alkoxylated) ditrimethylolpropane acrylate, (alkoxylated) dipentaerythritol acrylate, and (ethoxylated) polyglycerin acrylate.

[0054] The polyfunctional monomer may have a bisphenol skeleton in one molecule, such as a diacrylate of bisphenol A diglycidyl ether, a diacrylate of propoxylated bisphenol A, or a diacrylate of bisphenol F diglycidyl ether.

[0055] Commercially available polyfunctional monomers include, for example, "A-200" (polyethylene glycol #200 diacrylate), "A-400" (polyethylene glycol #400 diacrylate), and "A-600" (polyethylene glycol #600 diacrylate) from the NK Ester series, which are bifunctional polyethylene glycol acrylates manufactured by Shin-Nakamura Chemical Co., Ltd., the trifunctional monomer A-TMPT ((alkoxylated) trimethylolpropane acrylate), the trifunctional monomer M310 (trimethylolpropane PO-modified triacrylate) and the trifunctional monomer M321 (trimethylolpropane propylene oxide-modified triacrylate) manufactured by Toagosei Co., Ltd., the bifunctional monomer M211B (bisphenol A EO-modified diacrylate) and M240 (polyethylene glycol diacrylate), and the tetrafunctional monomer M-408 (ditrimethylolpropane tetraacrylate), all manufactured by Toagosei Co., Ltd. Other commercially available polyfunctional monomers include, for example, A-DOG, A-DCP, A-9300, and A-9200YN manufactured by Shin-Nakamura Chemical Co., Ltd., FA-731A manufactured by Hitachi Chemical Co., Ltd., and AOMA manufactured by Nippon Shokubai.

[0056] The content of the polyfunctional monomer in the pressure-sensitive adhesive composition is not particularly limited. In order to particularly prevent peeling between the adherend and the pressure-sensitive adhesive sheet even under temperature change and high temperature conditions, the content of the polyfunctional monomer is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.15 parts by mass or more, particularly preferably 0.2 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, even more preferably 1 part by mass or less, and particularly preferably 0.6 parts by mass or less, relative to 100 parts by mass of the main agent. When the content of the polyfunctional monomer is within the above range, it becomes easy to control the residual stress 60 seconds after application of a 15% torsional shear stress at 105°C within the desired range.

[0057] The polyfunctional monomer contained in the pressure-sensitive adhesive composition may be one type alone or two or more types.

[0058] <Additional Monofunctional Monomer> The PSA composition may contain an additional monofunctional monomer. As described above, when the base agent is a syrup (e.g., a partial polymer), the base agent contains a (meth)acrylic polymer and a portion of the monomer (monofunctional monomer) used to polymerize the polymer. In addition to this, the PSA composition may further contain an additional monofunctional monomer. Therefore, in this specification, "monofunctional monomer" refers to a monomer derived from a partial polymer of a (meth)acrylic polymer, while "additional monofunctional monomer" may refer to a monomer other than the monomer derived from a partial polymer of a (meth)acrylic polymer. The additional monofunctional monomer may be the same type as or a different type from the monomer derived from the partial polymer of a (meth)acrylic polymer.

[0059] The type of additional monofunctional monomer is not particularly limited, and examples thereof include a wide range of known monofunctional monomers used in PSA sheets. Among these, the additional monofunctional monomer preferably has a ring structure. That is, the PSA composition preferably contains a monofunctional monomer having a ring structure. In this case, the resulting PSA sheet is likely to be prevented from peeling from the adherend even when placed in a temperature-changing environment or a high-temperature environment.

[0060] The monofunctional monomer having a ring structure is more preferably a (meth)acrylate having a ring structure in a side chain. In the (meth)acrylate having a ring structure in a side chain, the number of carbon atoms in the ring structure is preferably 3 or more, more preferably 4 or more, even more preferably 5 or more, even more preferably 6 or more, and is preferably 18 or less, more preferably 14 or less, even more preferably 12 or less, and particularly preferably 11 or less.

[0061] Specific examples of the additional monofunctional monomer include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, O-phenylphenoxyethyl (meth)acrylate, etc. Among these, the additional monofunctional monomer is preferably at least one selected from the group consisting of dicyclopentanyl (meth)acrylate and isobornyl (meth)acrylate, in that peeling between the adherend and the PSA sheet is less likely to occur even in temperature-changing and high-temperature environments.

[0062] The content of the additional monofunctional monomer in the pressure-sensitive adhesive composition is not particularly limited. In order to easily improve the adhesion of the pressure-sensitive adhesive sheet to the adherend, the content of the additional monofunctional monomer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more, relative to 100 parts by mass of the main agent, and is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0063] The additional monofunctional monomer contained in the pressure-sensitive adhesive composition may be one type alone or two or more types.

[0064] <Photopolymerization initiator> The pressure-sensitive adhesive composition may further contain a photopolymerization initiator. The photopolymerization initiator initiates polymerization of the polyfunctional monomer when irradiated with active energy rays. In this specification, "active energy rays" refers to electromagnetic waves or charged particle rays that have an energy quantum, and examples thereof include ultraviolet rays, electron beams, visible light, X-rays, and ion beams. Among these, ultraviolet rays or electron beams are preferred from the viewpoint of versatility, and ultraviolet rays are particularly preferred.

[0065] The type of photopolymerization initiator is not particularly limited, and a wide range of known photopolymerization initiators can be used. Examples of the photopolymerization initiator include acetophenone-based photopolymerization initiators such as 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4-(2-hydroxyethoxyl)-phenyl]-2-hydroxy-methylpropanone, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methyl-1-propanone; acylphosphine oxide-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,4,6-trimethylbenzoyl)phenylphosphine oxide; intramolecular hydrogen abstraction photopolymerization initiators such as methyl benzoylformate and 4-methylbenzophenone; and oil-soluble polymerization initiators such as oxime ester-based photopolymerization initiators and cationic photopolymerization initiators. Among these, the photopolymerization initiator is preferably at least one selected from the group consisting of acetophenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and oxime ester-based photopolymerization initiators.

[0066] Commercially available acetophenone-based photopolymerization initiators include EsacureOne (oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenylpropanone], photoinitiator manufactured by IGM Resins B.V.), Omnirad 651 (2,2-dimethoxy-2-phenylacetophenone, manufactured by IGM Resins B.V.), Omnirad 184 (1-hydroxycyclohexylphenyl ketone, manufactured by IGM Resins B.V.), and Omnirad 1173 (2-hydroxy-2-methyl-1-phenylpropanone, manufactured by IGM Resins B.V.). Commercially available acylphosphine oxide-based photopolymerization initiators include Omnirad 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM RESINS BV) and Omnirad TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, manufactured by IGM RESINS BV).

[0067] In the pressure-sensitive adhesive composition, the content ratio of the photopolymerization initiator is not particularly limited, and for example, it is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the main agent, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 1.5 parts by mass or less.

[0068] <Pressure-Sensitive Adhesive Composition> The pressure-sensitive adhesive composition contains at least the (meth)acrylic polymer and a silane coupling agent, and may also contain, as necessary, one or more selected from the group consisting of a tackifier, a polyfunctional monomer, a monofunctional monomer, and a photopolymerization initiator. The pressure-sensitive adhesive composition may contain other components to the extent that the effects of the present invention are not impaired. Examples of other components include crosslinkers, solvents, plasticizers, antioxidants, metal corrosion inhibitors, UV absorbers, and light stabilizers. Dyes or pigments may also be added for coloring purposes.

[0069] The crosslinking agent can be appropriately selected, for example, taking into consideration the reactivity with the crosslinkable functional group of the (meth)acrylic polymer, and can be a wide variety of known crosslinking agents contained in pressure-sensitive adhesive sheets. Specific examples of the crosslinking agent can be selected from known crosslinking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds. Of these, it is preferable that the crosslinking agent contains at least one selected from isocyanate compounds, epoxy compounds, and metal chelate compounds.

[0070] When the PSA composition contains a solvent, the solvent is a solvent other than a polymerizable monomer (i.e., excluding monofunctional monomers, additional monofunctional monomers, and polyfunctional monomers), and examples thereof include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; alcohols such as methanol, ethanol, 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; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; and polyols and derivatives thereof such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate.

[0071] The pressure-sensitive adhesive composition is preferably a solvent-free type. In this case, the pressure-sensitive adhesive composition preferably contains a polyfunctional monomer. That is, the pressure-sensitive adhesive composition is a solvent-free type, and the pressure-sensitive adhesive layer preferably has a crosslinked structure due to the polyfunctional monomer. The method for preparing the pressure-sensitive adhesive composition is not particularly limited, and for example, known methods can be widely adopted.

[0072] The pressure-sensitive adhesive composition is preferably a so-called active energy ray-curable pressure-sensitive adhesive composition that has the property of being cured by irradiation with active energy rays. In this case, the pressure-sensitive adhesive composition contains a photopolymerization initiator and components whose polymerization is initiated by the photopolymerization initiator (for example, the above-mentioned monofunctional monomer, additional monofunctional monomer, and polyfunctional monomer).

[0073] (Adhesive Sheet) The adhesive sheet of the present invention is obtained by forming the above-mentioned adhesive composition into a sheet, that is, it has an adhesive layer containing a cured product of the adhesive composition.

[0074] The pressure-sensitive adhesive layer can be formed by curing the pressure-sensitive adhesive composition. The method for curing the pressure-sensitive adhesive composition is not particularly limited, and for example, any known method can be widely used. Specifically, the method can include a step of applying the pressure-sensitive adhesive composition to a substrate to form a coating film, and a step of irradiating the coating film with active energy rays to obtain a cured product of the pressure-sensitive adhesive composition. This allows the pressure-sensitive adhesive layer to be formed by curing the pressure-sensitive adhesive composition.

[0075] The PSA composition can be applied using a known coating device, such as a blade coater, air knife coater, roll coater, bar coater, gravure coater, microgravure coater, rod blade coater, lip coater, die coater, or curtain coater.

[0076] The substrate used for coating the pressure-sensitive adhesive composition is not particularly limited. For example, the pressure-sensitive adhesive composition can be coated onto various substrates such as resin substrates and glass substrates. When the substrate has a release sheet as described below, the pressure-sensitive adhesive composition can also be coated onto this release sheet. The pressure-sensitive adhesive composition can also be directly coated onto the member to be adhered. The thickness of the pressure-sensitive adhesive composition after coating is not particularly limited, and can be appropriately set depending on the desired thickness of the pressure-sensitive adhesive layer (or pressure-sensitive adhesive sheet). After forming the coating film, the coating film may be subjected to a heating treatment or a drying treatment, if necessary.

[0077] The step of irradiating the coating film with active energy rays can be, for example, a step similar to a known method. In this step, the photopolymerization initiator in the pressure-sensitive adhesive composition generates radicals due to the active energy rays, and the polymerizable components in the pressure-sensitive adhesive composition (e.g., monomers, polyfunctional monomers, etc. in the pressure-sensitive adhesive composition) initiate and progress a polymerization reaction due to the generated radicals, thereby forming a polymerized and cured product. This allows the formation of a pressure-sensitive adhesive layer and improving adhesive strength.

[0078] Examples of active energy rays include ultraviolet rays, electron beams, visible light, X-rays, and ion beams, and can be appropriately selected depending on the photopolymerization initiator contained in the pressure-sensitive adhesive composition. Among these, ultraviolet rays or electron beams are preferred from the viewpoint of versatility, and ultraviolet rays are particularly preferred. Examples of light sources that can be used for ultraviolet rays include chemical lamps, high-pressure mercury lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, carbon arcs, xenon arcs, and electrodeless ultraviolet lamps. The irradiation output of ultraviolet rays is such that the cumulative light amount is 100 to 10,000 mJ / cm. ２ It is preferable to set the value to 200 to 5000 mJ / cm ２ In the step of irradiating the coating film with active energy rays, the active energy rays may be irradiated in two stages.

[0079] The cured product formed as described above can be used as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive layer may consist of only the cured product of the pressure-sensitive adhesive, or may contain other components in addition to the cured product of the pressure-sensitive adhesive.

[0080] The pressure-sensitive adhesive sheet of the present invention may include other layers as long as it includes the pressure-sensitive adhesive layer, or may be formed only with the pressure-sensitive adhesive layer. That is, the pressure-sensitive adhesive sheet preferably consists of only the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer has, for example, a single-layer structure.

[0081] The pressure-sensitive adhesive layer has a gel fraction of 80% or more. If the gel fraction of the pressure-sensitive adhesive layer is less than 80%, peeling between the adherend and the pressure-sensitive adhesive sheet is likely to occur when placed in a temperature-changing environment or a high-temperature environment. The gel fraction of the pressure-sensitive adhesive layer is preferably 82% or more, more preferably 84% or more, and is preferably 98% or less, more preferably 95% or less.

[0082] The gel fraction of the pressure-sensitive adhesive layer is a value measured by the following method. First, approximately 0.1 g of the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) is collected in a sample bottle, 30 ml of ethyl acetate is added, and the mixture is shaken for 24 hours. The contents of the sample bottle are then filtered through a 200-mesh stainless steel wire mesh, and the residue on the wire mesh is dried at 120°C for 1 hour to measure the dry mass (g). The gel fraction is calculated from the obtained dry mass using the following formula: Gel fraction (mass%) = (dry mass / collected mass of pressure-sensitive adhesive sheet) x 100...Equation 11.

[0083] The pressure-sensitive adhesive layer has a residual stress of 3.0 kPa or more and 10.0 kPa or less 60 seconds after application of a 15% torsional shear stress at 105° C. Hereinafter, the residual stress 60 seconds after application of a 15% torsional shear stress at 105° C. will be simply referred to as "residual stress after 60 seconds."

[0084] If the residual stress of the pressure-sensitive adhesive layer after 60 seconds is less than 3.0 kPa or exceeds 10.0 kPa, peeling between the adherend and the pressure-sensitive adhesive sheet is likely to occur when placed in a temperature-changing environment or a high-temperature environment. The residual stress of the pressure-sensitive adhesive layer after 60 seconds is preferably 3.5 kPa or more, and is preferably 9 kPa or less, more preferably 8 kPa or less, and even more preferably 7 kPa or less.

[0085] The residual stress after 60 seconds of the pressure-sensitive adhesive layer can be measured using a laminated sheet of the pressure-sensitive adhesive layer laminated to a thickness of 1000 μm. Specifically, the laminated sheet is pressurized in an autoclave at 30°C and 0.5 MPa for 10 minutes to obtain a measurement sample. The obtained measurement sample is subjected to a torsional strain of 15% while being held at a constant temperature of 105°C using an Anton Paar MCR301 with a probe diameter of 8 mm. The torsional strain is then applied to the obtained measurement sample, and the shear stress is read 1 minute after the load. This shear stress is the residual stress after 60 seconds of the pressure-sensitive adhesive layer.

[0086] The thickness of the pressure-sensitive adhesive layer is preferably 75 μm or more. In this case, peeling between the adherend and the pressure-sensitive adhesive sheet tends to be difficult even in environments with high temperature changes and warm environments. The thickness of the pressure-sensitive adhesive layer is more preferably 80 μm or more, even more preferably 90 μm or more, and particularly preferably 100 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 400 μm or less.

[0087] The pressure-sensitive adhesive sheet of the present invention may also be a pressure-sensitive adhesive sheet provided with a substrate such as a release sheet on one or both sides. That is, the present invention also encompasses a pressure-sensitive adhesive sheet with a release sheet that includes a pressure-sensitive adhesive sheet and a release sheet.

[0088] Examples of the release sheet include a release laminate 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. Paper or a polymer film is used as the release sheet substrate in the release laminate sheet. Examples of the release agent that constitutes the release agent layer include general-purpose addition-type or condensation-type silicone-based release agents and long-chain alkyl group-containing compounds. Commercially available release laminate sheets may also be used. Examples include a heavy-duty separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films, and a light-duty separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films.

[0089] The pressure-sensitive adhesive sheet of the present invention is used to bond a pair of adherends having different stretch rates. When one of the pair of adherends is adherend A and the other is adherend B, the following formula (1) |(X1-X2)|≧0.1% (1) is satisfied. In formula (1), X1 is the stretch rate (%) of adherend A when heated from 23°C to 110°C, and X2 is the stretch rate (%) of adherend B when heated from 23°C to 110°C. When the stretch rate is x, x is a value calculated by {(length of adherend at 110°C - length of adherend at 23°C before heating) / length of adherend at 23°C before heating} × 100 (%). The length of the adherend refers, for example, to the length in the MD or TD direction of the adherend.

[0090] In addition, in formula (1), there may be a directionality in the stretch rate between adherend A and adherend B (the stretch rate may differ depending on the direction). In such cases, the stretch rates in the directions in which the rate of change in stretch rate when heated from 23°C to 110°C is large will be adopted as the values ​​of X1 and X2, respectively.

[0091] By bonding adherends A and B that satisfy formula (1) with the pressure-sensitive adhesive sheet of the present invention, peeling between the adherends and the pressure-sensitive adhesive sheet is less likely to occur even when placed in a temperature-changing environment or a high-temperature environment.

[0092] In formula (1), |(X1-X2)| ≧ 0.1% is preferable, |(X1-X2)| ≧ 0.15% is more preferable, and |(X1-X2)| ≧ 0.2% is even more preferable. The upper limit of |(X1-X2)| is preferably 1%.

[0093] Of the adherend A and the adherend B, the one that has a higher expansion / contraction rate when heated from 23°C to 110°C preferably has a thickness of 2 mm or more. In this case, the pressure-sensitive adhesive sheet of the present invention can also be suitably used for applications such as sunroofs for automobiles and large windows for buildings. The thickness of the adherend A and the adherend B can be, for example, 100 mm or less.

[0094] It is preferable that the total light transmittance of both the adherend A and the adherend B is 50% or more. In this case, the pressure-sensitive adhesive sheet of the present invention is suitable for applications requiring high transparency, and can be particularly suitably used for applications such as sunroofs for automobiles and large windows for buildings.

[0095] The combination of materials for the adherend A and the adherend B is not particularly limited, and various combinations can be used as long as they satisfy the formula (1). For example, if the adherend having a larger expansion / contraction rate (%) when heated from 23°C to 110°C is polycarbonate, examples of the adherend having a smaller expansion / contraction rate (%) when heated from 23°C to 110°C include glass, stretched polyethylene terephthalate, cycloolefin polymer film, TAC film, and ITO-deposited film.

[0096] The pressure-sensitive adhesive sheet of the present invention can be used in various applications for bonding adherends together, and is particularly suitable for automobile windows and sunroofs, windows for building materials, and door windows. In particular, the pressure-sensitive adhesive sheet of the present invention is resistant to peeling between the adherend and the pressure-sensitive adhesive sheet even under temperature changes and high-temperature conditions, and is therefore suitable for applications such as automobile sunroofs and large building windows.

[0097] The pressure-sensitive adhesive sheet of the present invention can be used to form a laminate by bonding adherends together. That is, the present invention encompasses a laminate comprising the pressure-sensitive adhesive sheet and a pair of adherends having different stretch rates.

[0098] One embodiment of the laminate is a laminate obtained by laminating, in this order, the adherend A, the pressure-sensitive adhesive sheet of the present invention, and the adherend B. In this case, the pressure-sensitive adhesive sheet of the present invention is directly attached to the adherend A and the adherend B.

[0099] Because the laminate includes the pressure-sensitive adhesive sheet of the present invention, peeling between the adherend and the pressure-sensitive adhesive sheet is unlikely to occur even when placed in a temperature-changing environment or a high-temperature environment, despite the different expansion and contraction rates of adherend A and adherend B. For example, even if the adherend with the greater expansion and contraction rate has a thickness exceeding 2 mm, peeling of the pressure-sensitive adhesive sheet in the laminate is unlikely to occur.

[0100] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in each embodiment of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as described in this specification.

[0101] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0102] The following monomers (monofunctional monomers) were prepared for producing the "main component containing a (meth)acrylic polymer" used in each example: 2EHA: 2-ethylhexyl acrylate, BA: butyl acrylate, 4HBA: 4-hydroxybutyl acrylate, IBXA: isobornyl acrylate, and CHMA: cyclohexyl methacrylate.

[0103] In addition, the following "multifunctional monomers," "additional monofunctional monomers," "silane coupling agents," and "photopolymerization initiators" used in each example were prepared.

[0104] (Polyfunctional Monomers) A-200: Bifunctional Monomer (Polyethylene Glycol #200 Diacrylate, Shin-Nakamura Chemical Co., Ltd., NK Ester A-200 (registered trademark)) A-600: Bifunctional Monomer (Polyethylene Glycol #200 Diacrylate, Shin-Nakamura Chemical Co., Ltd., NK Ester A-600 (registered trademark))

[0105] (Additional monofunctional monomers) IBXA: isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) DCPA: dicyclopentanyl acrylate (manufactured by Resonac Co., Ltd.)

[0106] (Silane coupling agent) KBM-9659 ("KBM-9659" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd.) KBM-403 ("KBM-403" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd.)

[0107] (Photopolymerization initiator) Esacure One (registered trademark) (manufactured by IGM Resins B.V., Esacure One (registered trademark))

[0108] (Production Example 1: Production of Tackifier a) 250 g of methyl methacrylate, 250 g of isobornyl methacrylate, 20 g of n-dodecyl mercaptan, 500 g of ethyl acetate, and 200 g of methyl ethyl ketone were added to a 2 L flask equipped with a stirrer, a nitrogen inlet tube, a cooling tube, and a thermometer. After 60 minutes of nitrogen substitution at a nitrogen flow rate of 300 ml / min, the nitrogen flow rate was reduced to 100 ml / min, and the temperature was raised to 70 ° C. in a water bath and the heating was stopped. 2 g of AIBN was added, and the mixture was reacted for 3 hours while controlling the heat generation, and then 3 g of AIBN was added, and the mixture was reacted for 4 hours, after which it was cooled to 30 ° C. Finally, the mixture was dried at 100 ° C. for 5 hours to remove the solvent, and an acrylic tackifier a (referred to as tackifier resin a in Table 1) having a weight average molecular weight of 6,000 and a glass transition temperature of 85 ° C. was obtained.

[0109] (Production Example 2: Production of tackifier b) An acrylic tackifier b (referred to as tackifying resin b in Table 1) having a weight average molecular weight of 8,000 and a glass transition temperature of 95°C was obtained in the same manner as in Production Example 1, except that the ingredients were changed to 200 g of methyl methacrylate, 300 g of isobornyl methacrylate, and 15 g of n-dodecyl mercaptan.

[0110] (Production Example 3: Production of tackifier c) An acrylic tackifier c (referred to as tackifying resin c in Table 1) having a weight average molecular weight of 6,000 and a glass transition temperature of 95°C was obtained in the same manner as in Production Example 1, except that 250 g of dicyclopentanyl methacrylate was used instead of 250 g of isobornyl methacrylate.

[0111] The tackifiers obtained in Production Examples 1 to 3 were dried at 100° C. for 5 hours to remove the solvent before use in each example.

[0112] Example 1 Production of a Main Component Containing a (Meth)acrylic Polymer A (meth)acrylic polymer (syrup) was synthesized according to the main component composition containing a (meth)acrylic polymer shown in Table 1. Specifically, 100 parts by mass of a monomer mixture consisting of 2EHA, 4HBA, and IBXA (mass ratio 65:30:5) prepared in the amounts shown in Table 1 and 0.06 parts by mass of n-dodecyl mercaptan were added to a 2-L flask equipped with a stirrer, a nitrogen inlet tube, a condenser, and a thermometer, and nitrogen substitution was performed for 60 minutes at a nitrogen flow rate of 300 ml / min. Thereafter, the nitrogen flow rate was reduced to 100 ml / min, the mixture was heated to 65°C in a water bath, 0.15 g of AIBN was added, and the mixture was allowed to react for 30 minutes while controlling the heat generation, and then cooled to room temperature. Additional monomer was added to the flask so as to achieve the monomer ratio of the aforementioned mass ratio, and the solids concentration was adjusted to 20%. In this manner, a (meth)acrylic polymer syrup (a solution in which a (meth)acrylic polymer is dissolved in a monofunctional monomer) having a solid content of 20% by mass and a weight-average molecular weight of 900,000 was obtained as the main component.

[0113] <Preparation of Pressure-Sensitive Adhesive Composition> Next, a pressure-sensitive adhesive layer was obtained from a pressure-sensitive adhesive composition prepared according to the pressure-sensitive adhesive composition preparation conditions shown in Table 1. First, as shown in Table 1, 6 parts by mass of tackifier a (tackifying resin a) obtained in Preparation Example 1, 0.2 parts by mass of A-200 as a polyfunctional monomer, 5 parts by mass of IBXA as an additional monofunctional monomer (referred to as "monofunctional monomer" in Table 1), 0.3 parts by mass of KBM-9659 as a silane coupling agent, and 0.3 parts by mass of Esacure One as a photopolymerization initiator were added relative to 100 parts by mass of the total amount of the base resin, and the mixture was stirred and degassed to obtain Pressure-Sensitive Adhesive Composition 1.

[0114] <Production of Pressure-Sensitive Adhesive Sheet> The obtained pressure-sensitive adhesive composition 1 was applied to a 100 μm thick polyester film (release sheet) coated with a silicone release agent to a thickness of 300 μm, and the coated film was then laminated with a 75 μm thick polyester film (release sheet) coated with a silicone release agent. After that, the coated film was exposed to a chemical lamp at an illuminance of 5 mW / cm. ２ , cumulative illuminance 750 mJ / cm ２ Further, a high-pressure mercury lamp was used to irradiate the sample with an illuminance of 200 mW / cm２ , cumulative illuminance 2000 mJ / cm ２ A pressure-sensitive adhesive layer was formed by irradiating the film so as to obtain a pressure-sensitive adhesive sheet 1 having release sheets on both sides.

[0115] <Preparation of Laminate> Adherend A was a 5 mm thick polycarbonate plate ("PC-1600" manufactured by Takiron C.I.) cut into a 15 cm square, and adherend B was a 1 mm thick float glass (manufactured by Hiraoka Glass Industry Co., Ltd.) cut into a 15 cm square. Adherend A was pre-annealed by placing it in a 95°C dryer for 6 hours, and then one side of the annealed adherend A was corona treated. This corona treatment was carried out using a CORONA GENERATOR AGF-B10 (manufactured by Kasuga Electric Works) at an output of 0.14 kW, a speed of 5 m / min, and four treatments. Next, one of the polyester films bonded to the pressure-sensitive adhesive sheet 1 was peeled off, and the corona-treated surface of the adherend A was bonded to the exposed pressure-sensitive adhesive layer. Thereafter, the other polyester film of the pressure-sensitive adhesive sheet was peeled off, and adherend B was attached to the exposed pressure-sensitive adhesive layer to obtain a laminate. This laminate was pressure-bonded in an autoclave at a pressure of 0.5 kPa and a temperature of 30°C for 30 minutes, and then allowed to stand at room temperature for 1 day to produce a laminate for evaluation.

[0116] (Example 2) <Production of base agent containing (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a base agent in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the base agent composition was changed to the conditions shown in Table 1.

[0117] <Preparation of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 2 was obtained in the same manner as in the preparation of the pressure-sensitive adhesive composition of Example 1, except that the preparation conditions for the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0118] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 2 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that Pressure-Sensitive Adhesive Composition 2 was applied to a thickness of 175 μm instead of Pressure-Sensitive Adhesive Composition 1.

[0119] <Preparation of Laminate> A laminate was obtained in the same manner as in the preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to the pressure-sensitive adhesive sheet 2 and the adherend A was changed to a polycarbonate plate having a thickness of 3 mm.

[0120] (Example 3) <Production of (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0121] <Production of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 3 was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0122] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 3 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that Pressure-Sensitive Adhesive Composition 3 was applied in place of Pressure-Sensitive Adhesive Composition 1 to a thickness of 250 μm.

[0123] <Preparation of Laminate> A laminate was obtained in the same manner as in preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to pressure-sensitive adhesive sheet 3.

[0124] (Example 4) <Production of (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0125] <Production of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 4 was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0126] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 4 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that the obtained pressure-sensitive adhesive composition 4 was used instead of the pressure-sensitive adhesive composition 1.

[0127] <Preparation of Laminate> A laminate was obtained in the same manner as in the preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to pressure-sensitive adhesive sheet 4, the adherend A was changed to a polycarbonate plate having a thickness of 3 mm, and the adherend B was changed to a polyethylene terephthalate film ("A4360" manufactured by Toyobo) having a thickness of 0.1 mm. In preparing this laminate, the polyethylene terephthalate film and the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) were attached to each other so that the easily adhesive surface of the polyethylene terephthalate film was in contact with each other.

[0128] (Example 5) <Production of (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0129] <Production of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 5 was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0130] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 5 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that Pressure-Sensitive Adhesive Composition 5 was applied to a thickness of 100 μm instead of Pressure-Sensitive Adhesive Composition 1.

[0131] <Preparation of Laminate> A laminate was obtained in the same manner as in preparation of the laminate in Example 1, except that adhesive sheet 1 was changed to adhesive sheet 5, adherend A was changed to a polycarbonate plate having a thickness of 2 mm (Mitsubishi Gas Chemical Company, MRS58TB), and adherend B was changed to a heat-shielding film having a thickness of 0.05 mm (Geomatec Corporation, "ITO vapor-deposited film"). In preparing this laminate, the adhesive sheet and adhesive layer were attached together so that the ITO surface of the heat-shielding film was in contact with each other.

[0132] (Example 6) <Production of (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0133] <Production of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 6 was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0134] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 6 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that Pressure-Sensitive Adhesive Composition 6 was applied to a thickness of 150 μm instead of Pressure-Sensitive Adhesive Composition 1.

[0135] <Preparation of Laminate> A laminate was obtained in the same manner as in the preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to the pressure-sensitive adhesive sheet 6 and the adherend A was changed to a polycarbonate plate having a thickness of 1 mm (manufactured by Teijin, "PC1151").

[0136] (Example 7) <Production of (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0137] <Production of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 7 was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0138] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 7 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that, instead of Pressure-Sensitive Adhesive Composition 1, Pressure-Sensitive Adhesive Composition 7 was applied to a thickness of 50 μm, and the 75 μm thick polyester film (release sheet) coated with a silicone release agent was changed to a 50 μm thick polyester film (release sheet) coated with a silicone release agent.

[0139] <Preparation of Laminate> A laminate was obtained in the same manner as in the preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to the pressure-sensitive adhesive sheet 7 and the adherend A was changed to a polycarbonate plate having a thickness of 2 mm (Mitsubishi Gas Chemical Company, MRS58TB).

[0140] Comparative Example 1 Production of (meth)acrylic polymer A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0141] <Production of Pressure-Sensitive Adhesive Composition> A pressure-sensitive adhesive composition 1a was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0142] <Production of Pressure-Sensitive Adhesive Sheet> A pressure-sensitive adhesive sheet 1a was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that pressure-sensitive adhesive composition 1a was applied in place of pressure-sensitive adhesive composition 1 so as to have a thickness of 250 μm.

[0143] <Preparation of Laminate> A laminate was obtained in the same manner as in preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to the pressure-sensitive adhesive sheet 1a.

[0144] (Comparative Example 2) <Production of (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0145] <Production of Pressure-Sensitive Adhesive Composition> A pressure-sensitive adhesive composition 2a was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0146] <Production of Pressure-Sensitive Adhesive Sheet> A pressure-sensitive adhesive sheet 2a was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that the pressure-sensitive adhesive composition 2a obtained was used instead of the pressure-sensitive adhesive composition 1.

[0147] <Preparation of Laminate> A laminate was obtained in the same manner as in preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to pressure-sensitive adhesive sheet 2a and the adherend B was changed to a polyethylene terephthalate film having a thickness of 0.1 mm ("A4360" manufactured by Toyobo Co., Ltd.). In preparing this laminate, the polyethylene terephthalate film and the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) were attached together so that the easily adhesive surface of the polyethylene terephthalate film was in contact with the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer).

[0148] (Comparative Example 3) <Production of (meth)acrylic polymer> A syrup of a meth)acrylic polymer was obtained as a main component in the same manner as in the production of a (meth)acrylic polymer in Example 1, except that the main component composition was changed to the conditions shown in Table 1.

[0149] <Production of Pressure-Sensitive Adhesive Composition> A pressure-sensitive adhesive composition 3a was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0150] <Production of Pressure-Sensitive Adhesive Sheet> A pressure-sensitive adhesive sheet 3a was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that pressure-sensitive adhesive composition 3a was applied to a thickness of 175 μm instead of pressure-sensitive adhesive composition 1.

[0151] <Preparation of Laminate> A laminate was obtained in the same manner as in the preparation of the laminate in Example 1, except that the pressure-sensitive adhesive sheet 1 was changed to pressure-sensitive adhesive sheet 3a and the adherend A was changed to a polycarbonate plate having a thickness of 3 mm.

[0152] Evaluation method (Tg of tackifier) ​​A DSC600 manufactured by Hitachi High-Tech Science was used to measure the glass transition temperature of the tackifier. 5 mg of alumina was used as a reference, and approximately 5 mg of a solvent-removed tackifier resin was placed in a 5 mm diameter aluminum sample pan, and the temperature was raised from 0°C to 150°C at a heating rate of 10°C / min in an environment with a nitrogen flow rate of 50 ml / min. The inflection point at which the specific heat changed was read as the glass transition temperature of the tackifier resin.

[0153] (Gel Fraction) Approximately 0.1 g of the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) was collected in a sample bottle, 30 ml of ethyl acetate was added, and the mixture was shaken for 24 hours. The contents of the sample bottle were then filtered through a 200-mesh stainless steel wire mesh, and the residue on the wire mesh was dried for 1 hour at 120° C. to measure the dry mass (g). The gel fraction was calculated from the obtained dry mass using the following formula: Gel fraction (mass %) = (dry mass / collected mass of pressure-sensitive adhesive sheet) × 100...Equation 11.

[0154] <Residual Stress After 60 Seconds> First, a laminated sheet having a thickness of 1000 μm was prepared by laminating multiple pressure-sensitive adhesive layers formed from each pressure-sensitive adhesive composition. The laminated sheet was then pressurized in an autoclave at 30°C and 0.5 MPa for 10 minutes to obtain a measurement sample. The obtained measurement sample was subjected to a 15% torsional strain load using an Anton Paar MCR301 with a probe diameter of 8 mm and an initial heating temperature of 105°C for 2 minutes. Then, while the temperature was maintained at 105°C, a 15% torsional strain load was applied, and the shear stress was measured 1 minute after the load. This shear stress was defined as the residual stress after 60 seconds of the pressure-sensitive adhesive layer. The residual stress after 60 seconds refers to the residual stress after 60 seconds of applying a 15% torsional shear stress at 105°C.

[0155] <Measurement of Elasticity of Adherend> The elasticity of adherend A and adherend B was measured using a Hitachi High-Tech Science TMA7100. The adherends were placed in an environment with a nitrogen flow rate of 200 ml / min and heated from 23°C to 150°C at a heating rate of 20°C / min. The elasticity was measured when the sample temperature reached 110°C, and this was used as the elasticity of the adherend (X1 and X2). For adherends with a thickness of more than 1 mm, a 1 cm square sample was prepared and measured in compression mode. Films were cut to 5 mm x 40 mm and then measured in tension mode.

[0156] <High-Low Temperature Cycle Test> The laminates prepared in the examples and comparative examples were placed in a thermal shock tester ES-57L manufactured by Hitachi Air Conditioning SE. The ambient temperature inside the test chamber was changed from -20°C to 85°C and then back to -20°C, and this cycle was repeated. The test was conducted for one hour per cycle, and the test was terminated after 72 hours. After the test, the laminates were visually inspected and evaluated according to the following criteria. <Evaluation Criteria> ◯: Peeling from the edge was less than 2 mm, and no bubbles or the like were observed. Peeling was extremely likely to occur even with temperature changes. △: Peeling from the edge was 2 mm or more but less than 5 mm, and no bubbles were observed. Peeling was likely to occur even with temperature changes. ×: Peeling from the edge was 5 mm or more, or bubbles were observed, and peeling was likely to occur with temperature changes.

[0157] <Boiling test> The laminates produced in the examples and comparative examples were placed in a boiling water bath and held in this state for 2 hours, after which the laminates were removed and visually inspected and evaluated according to the following criteria. ◯: Peeling from the edge was less than 2 mm, no air bubbles or the like were generated, and peeling between the adherend and the pressure-sensitive adhesive sheet was extremely unlikely to occur even in a high-temperature environment. △: Peeling from the edge was 2 mm or more but less than 5 mm, no air bubbles or the like were generated, and peeling between the adherend and the pressure-sensitive adhesive sheet was unlikely to occur even in a high-temperature environment. ×: Peeling from the edge was 5 mm or more, or air bubbles were observed, and peeling was more likely to occur in a high-temperature environment.

[0158] Evaluation Results Table 1 shows the (meth)acrylic polymer composition and pressure-sensitive adhesive composition preparation conditions used in producing the pressure-sensitive adhesive sheets obtained in each of the Examples and Comparative Examples, as well as the measurement results of the thickness, gel fraction, and residual stress after 60 seconds (residual stress after 60 seconds of application of a 15% torsional shear stress at 105°C) of the resulting pressure-sensitive adhesive sheets.

[0159] Table 1 also shows the evaluation results (results of high-temperature-low-temperature cycle tests and boiling tests) of laminates obtained using the pressure-sensitive adhesive sheets obtained in each Example and Comparative Example and adherends A and B. Table 1 also shows the expansion / contraction ratios (2%) and thicknesses of adherends A and B when heated from 23°C to 110°C, as well as the value of |(X1-X2)| in equation (1). X1 represents the expansion / contraction ratio (%) of adherend A when heated from 23°C to 110°C, and X2 represents the expansion / contraction ratio (%) of adherend B when heated from 23°C to 110°C.

[0160] In addition, in the preparation conditions of the pressure-sensitive adhesive composition in Table 1, a blank column means that the raw material was not used.

[0161]

[0046] As can be seen from Table 1, the pressure-sensitive adhesive sheets obtained in the examples were resistant to peeling even when adherends with different expansion and contraction coefficients were bonded together, and the adhesion between the adherend and the pressure-sensitive adhesive sheet was good even when placed in a high-temperature environment, making the pressure-sensitive adhesive sheet resistant to peeling and particularly suppressing peeling at the edges. Therefore, it was demonstrated that a pressure-sensitive adhesive sheet that is resistant to peeling even when temperature changes and in a high-temperature environment are obtained by providing the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition containing at least a (meth)acrylic polymer and a silane coupling agent, and by having the gel fraction and residual stress after 60 seconds within the specified ranges.

[0162]

Claims

1. An adhesive sheet used for bonding a pair of adherends having different expansion and contraction rates, comprising an adhesive layer obtained from an adhesive composition, said adhesive composition containing at least a base agent including a (meth)acrylic polymer and a silane coupling agent, said adhesive layer having a gel fraction of 80% or more, said adhesive layer having a residual stress 60 seconds after application of a 15% torsional shear stress at 105°C of 3.0 kPa or more and 10.0 kPa or less, and satisfying the following formula (1): |(X1-X2)|≧0.1%...(1) (wherein, when one of the pair of adherends is adherend A and the other is adherend B, X1 is the expansion and contraction rate (%) when adherend A is heated from 23°C to 110°C, and X2 is the expansion and contraction rate (%) when adherend B is heated from 23°C to 110°C).

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive composition contains a monofunctional monomer having a ring structure.

3. The adhesive sheet according to claim 1 or 2, wherein the adhesive composition contains 0.05 parts by mass or more and 5 parts by mass or less of the silane coupling agent per 100 parts by mass of the base agent.

4. The adhesive sheet according to claim 1 or 2, wherein the adhesive composition is a solvent-free adhesive, and the adhesive layer has a crosslinked structure formed by a polyfunctional monomer.

5. The adhesive sheet according to claim 1 or 2, wherein the adhesive composition contains an acrylic tackifier.

6. The pressure-sensitive adhesive sheet according to claim 1 or 2, having a thickness of 75 μm or more.

7. An adhesive sheet according to claim 1 or 2, wherein the adherend having the higher elasticity between the adherend A and the adherend B has a thickness of 2 mm or more.

8. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein both of the adherend A and the adherend B have a total light transmittance of 50% or more.

9. The pressure-sensitive adhesive sheet according to claim 8, which is for use as a car window, a building window, or a door window.

10. A laminate comprising the pressure-sensitive adhesive sheet according to claim 1 or 2 and a pair of adherends having different elasticity rates.

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