Tackiness agent and / or adhesive agent

Abstract

To provide a tackiness agent and / or an adhesive agent capable of changing physical properties intentionally by an external stimulation.SOLUTION: A tackiness agent and / or an adhesive agent include a component (a) and a component (b) below, in which the component (a) is a polymer (a1) having an intramolecular bond being a reversibly resolvable bond capable of cleaving the bond by an external stimulation and then recoupling, the bond capable of cleaving with a C-C bond or a C-O bond as a terminus and / or a compound (a2) capable of introducing the reversibly resolvable bond to a polymer; and the component (b) is a compound having reactivity to at least one group generated by the cleaving.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive and / or an adhesive, more specifically to a pressure-sensitive adhesive layer capable of exhibiting adhesive properties and / or an adhesive layer capable of exhibiting adhesive properties. [Background technology]

[0002] Among optical devices such as displays, thin, flexible displays, typified by OLEDs, are constructed by laminating multiple optical films or thin-layer devices. Furthermore, devices that require flexibility, such as pressure-sensitive sensors, are constructed by laminating a pressure-sensitive member and a substrate (Patent Document 1). Liquid curing resins, pressure-sensitive adhesives, and adhesives are selected as interlayer fillers in these laminates, and pressure-sensitive adhesives and adhesives (such as pressure-sensitive adhesives) are preferably used from the viewpoints of improving workability, preventing warping due to cure shrinkage, and improving flexibility through stress dispersion.

[0003] The above-mentioned adhesives, etc., have the function of dispersing and alleviating stress generated by bending and folding, particularly in flexible members, and this function is said to be exhibited more efficiently the more flexible the adhesives, etc. (Patent Document 2), and therefore flexible adhesives, etc. are used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-159463 [Patent Document 2] Japanese Patent Publication No. 2020-109177 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, flexible adhesives can deform significantly even with slight stress, which can cause problems during the manufacturing and processing of adhesives, such as glue overflow and glue chipping when cutting with a punching blade, which can lead to process contamination.In addition, such adhesives can cause problems such as glue overflow due to their own weight during storage and glue chipping due to vibration and contact during transportation.

[0006] For this reason, there is a demand for pressure-sensitive adhesive layers and adhesive layers that are easy to handle before sticking or adhering to components, such as during production, processing, storage, and transportation, and that are flexible during use, i.e., after sticking or adhering to components.

[0007] The present invention has been made to solve these problems, and its object is to provide a pressure-sensitive adhesive and / or adhesive whose physical properties can be intentionally changed in response to an external stimulus. [Means for solving the problem]

[0008] The present inventors have made extensive efforts to solve the above problems, and as a result have found that a pressure-sensitive adhesive and adhesive comprising a polymer having a bond that is cleaved by an external stimulus or a compound capable of introducing such a bond into the polymer, and a compound that is reactive with the group generated by the cleavage, can intentionally change physical properties in response to an external stimulus. The present invention was completed based on these findings.

[0009] That is, the present invention provides a pressure-sensitive adhesive and / or adhesive comprising the following components (a) and (b): A pressure-sensitive adhesive and / or adhesive comprising the following components (a) and (b): Component (a): a polymer (a1) having a reversibly decomposable bond that can be cleaved by an external stimulus and then recombined, the reversibly decomposable bond being a C—C bond or a C—O bond at the end of the molecule, and / or a compound (a2) capable of introducing the reversibly decomposable bond into a polymer. Component (b): a compound reactive with at least one of the groups generated by the cleavage

[0010] The component (a) preferably contains the polymer (a1), and the polymer (a1) preferably contains a crosslinking moiety having the reversibly decomposable bond.

[0011] The number of atoms in the linear chain at the crosslinked site is preferably 6 or more.

[0012] It is preferable that the polymer (a1) contains a structure derived from the compound (a2), and the compound (a2) is a polyfunctional compound having the reversibly decomposable bond in its main chain and reactive functional groups at both ends.

[0013] The polyfunctional compound is preferably a di(meth)acrylate compound having a (meth)acryloyl group as the reactive functional group.

[0014] The polyfunctional compound is preferably capable of reacting with light and / or heat having a wavelength of 370 nm or more.

[0015] The reversibly degradable bond is preferably cleavable by light with a wavelength of less than 370 nm.

[0016] The reversibly decomposable bond is preferably —OCC(═O)—.

[0017] The component (b) is preferably a compound that is reactive with either one of the groups generated by the cleavage.

[0018] The component (b) is preferably a compound having a phenolic hydroxyl group.

[0019] The component (b) is preferably a compound having a primary amino group or a secondary amino group.

[0020] The pressure sensitive adhesive and / or adhesive may have a modulus of elasticity reduced in at least a partial region by the external stimulus.

[0021] The pressure-sensitive adhesive and / or adhesive is preferably used for optical purposes.

[0022] The present invention also provides a pressure-sensitive adhesive sheet using the pressure-sensitive adhesive and / or adhesive. [Effects of the Invention]

[0023] The pressure-sensitive adhesive and / or adhesive of the present invention intentionally changes its physical properties in response to an external stimulus. For example, when the flexibility of the pressure-sensitive adhesive and / or adhesive is improved by an external stimulus, the pressure-sensitive adhesive and / or adhesive exhibits excellent handleability before adhesion or bonding to a member, and exhibits excellent flexibility after adhesion or bonding to a member. [Brief explanation of the drawings]

[0024] [Figure 1] 1 shows a schematic cross-sectional view of one embodiment of a pressure-sensitive adhesive sheet or adhesive sheet of the present invention. [Figure 2] FIG. 1 is a plan view showing an embodiment of a pressure-sensitive adhesive layer or adhesive layer of the present invention in which the physical properties of a portion of the layer are changed. [Figure 3] FIG. 2 is a plan view showing another embodiment of the pressure-sensitive adhesive layer or adhesive layer of the present invention, in which the physical properties of a portion of the layer are changed. [Figure 4] FIG. 2 is a plan view showing yet another embodiment of the pressure-sensitive adhesive layer or adhesive layer of the present invention, in which the physical properties of a portion of the layer are changed. DETAILED DESCRIPTION OF THE INVENTION

[0025] [Adhesives, adhesives] In this specification, "adhesion" refers to the property of two surfaces adhering to each other in response to external pressure (e.g., minute pressure) based on the cohesive force of the chemical structure of the composition, and allowing separation if necessary. In contrast, "adhesion" refers to the property of two surfaces being firmly joined together by a chemical reaction (curing) of the composition to produce a cured product, without the intention of separation.

[0026] In addition, in this specification, the form of the "pressure-sensitive adhesive" and "adhesive" is not particularly limited, and may be liquid at room temperature (for example, a solid (paste-like) having fluidity, a pressure-sensitive adhesive composition, an adhesive composition, etc.), or may be solid at room temperature. In addition, the form of the "pressure-sensitive adhesive" and "adhesive" is not particularly limited, and may be sheet-like. In this specification, a "pressure-sensitive adhesive layer" is a sheet-like (layer-like) pressure-sensitive adhesive layer that has no fluidity, and an "adhesive layer" is a sheet-like (layer-like) adhesive layer that has no fluidity.

[0027] The pressure-sensitive adhesive and / or adhesive of the present invention contains at least the following component (a) and component (b): Component (a): a polymer (a1) having a reversibly decomposable bond that can be cleaved by an external stimulus and then recombined, the reversibly decomposable bond being a C—C bond or a C—O bond at the end of the molecule, and / or a compound (a2) capable of introducing the reversibly decomposable bond into a polymer. Component (b): a compound reactive with at least one of the groups generated by the cleavage

[0028] Degradable bonds that are cleaved by the application of an external stimulus are classified into reversibly degradable bonds that can recombine after cleavage, and irreversibly degradable bonds in which the cleavage reaction proceeds irreversibly and does not recombine. In the present invention, the polymer in component (a) is a compound having a reversibly degradable bond. The polymer in component (a) may be referred to as "polymer (a1)," and the compound capable of introducing the reversibly degradable bond into the polymer may be referred to as "compound (a2)." In this specification, "pressure-sensitive adhesive and / or adhesive agent" may be referred to as "pressure-sensitive adhesive, etc."

[0029] The external stimulus that triggers the cleavage reaction of the reversibly decomposable bond is appropriately selected depending on the type of reversibly decomposable bond in component (a), and is not particularly limited, but examples include light and heat. In particular, when polymer (a1) is a thermosetting resin or a photocurable resin such as activated energy ray, from the viewpoint of enabling the thermosetting reaction or photocuring reaction and the cleavage to occur separately, it is preferable that the external stimulus be different from the type of curing when polymer (a1) is curable.

[0030] The light is not particularly limited, but examples thereof include ionizing radiation such as α-rays, β-rays, γ-rays, neutron beams, and electron beams, and active energy rays such as ultraviolet light and visible light. Active energy rays are particularly preferred, and ultraviolet light is more preferred. The light irradiation energy, irradiation time, irradiation method, etc. are not particularly limited. In addition, examples of light sources for irradiating ultraviolet light or visible light include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, and LED lamps.

[0031] Polymer (a1) can be obtained using compound (a2). Polymer (a1) preferably contains a structure derived from compound (a2). Compound (a2) has the reversibly decomposable bond. Examples of compound (a2) include a monomer component, an oligomer component, a crosslinking agent, etc., each having the reversibly decomposable bond. That is, polymer (a1) may contain a structural unit derived from a monomer component and / or an oligomer component having the reversibly decomposable bond, or may contain a structural portion derived from the crosslinking agent. When compound (a2) is a monomer component or an oligomer component, polymer (a1) having the reversibly decomposable bond can be obtained by polymerizing or copolymerizing the monomer component or oligomer component with another monomer component. In this specification, the term "crosslinking agent" refers to a compound capable of forming crosslinks in a resin, and may also be referred to as a "curing agent."

[0032] When compound (a2) is a monomer component or oligomer component, the reversibly decomposable bond may be present in a portion constituting a side chain of polymer (a1) or in a portion constituting the main chain. When present in a portion constituting a side chain, stress is less likely to be applied when the polymer is significantly deformed, and handling properties are maintained in the temperature range of actual use (assumed to be room temperature). On the other hand, when present in a portion constituting the main chain, the molecular weight of the polymer is further reduced after cleavage of the reversibly decomposable bond, which further improves flexibility and allows for significant changes in physical properties.

[0033] From the viewpoint of forming a polymer (a1) by polymerization, crosslinking, or the like, the compound (a2) preferably has a reactive functional group other than the reversibly decomposable bond. When the compound (a2) has two or more reactive functional groups, the compound (a2) functions as a crosslinking agent. When the reactive functional group is a polymerizable functional group, the compound (a2) functions as a monomer component or an oligomer component.

[0034] Examples of the polymerizable functional group include a cationically polymerizable group, an anionically polymerizable group, and a radically polymerizable group. Among these, a radically polymerizable group is preferred. Examples of the radically polymerizable group include groups having a radically polymerizable carbon-carbon double bond, such as a (meth)acryloyl group, a vinyl group, a vinyl ether group, and a (meth)allyl group.

[0035] Examples of reactive functional groups other than the polymerizable functional groups include thiol groups, carboxy groups, hydroxy groups, amino groups, epoxy groups, and isocyanate groups, from the viewpoint of achieving an appropriate crosslinking density and ensuring a certain degree of flexibility of the adhesive or the like.

[0036] Furthermore, the number of reactive functional groups in compound (a2) is preferably 2 or more, from the viewpoint of increasing the molecular weight after introduction into polymer (a1) to give the polymer a certain degree of hardness before the application of an external stimulus, while further reducing the molecular weight of the polymer after cleavage to exhibit flexibility. On the other hand, if the number of functional groups is large, crosslinking with many polymers will occur, making it difficult to obtain the effect of cleavage of the reversibly decomposable bond. Therefore, from the viewpoint of ensuring a certain degree of flexibility of the adhesive or the like by maintaining an appropriate crosslink density, the number of functional groups is preferably 4 or less, more preferably 3 or less. In particular, compound (a2) is preferably a polyfunctional compound having the reversibly decomposable bond in its main chain and the reactive functional groups at both ends.

[0037] The reactive functional group is preferably a radically polymerizable group, more preferably a (meth)acryloyl group, i.e., the polyfunctional compound is preferably a di(meth)acrylate compound having a (meth)acryloyl group as the reactive functional group.

[0038] It is preferable that the polymer (a1) contains a structural portion derived from the crosslinking agent. That is, it is preferable that the polymer (a1) contains a crosslinking moiety having the reversibly decomposable bond. In this case, the crosslinking moiety can be cleaved by an external stimulus, which makes it easy to control the crosslink density.

[0039] The number of atoms in the linear chain at the crosslinked site is preferably 6 or more, more preferably 10 or more, and even more preferably 14 or more. When the number of atoms is 6 or more, the polymer has appropriate flexibility before the reversibly decomposable bond is cleaved. From the viewpoint of obtaining an appropriate crosslink density, the number of atoms is, for example, 40 or less, preferably 35 or less.

[0040] The reversibly decomposable bond is a bond that can be cleaved by the external stimulus with a CC bond or a CO bond as a terminal. That is, the reversibly decomposable bond has a CC bond and / or a CO bond, and after cleavage, the terminal becomes a CC bond or a CO bond (on the carbon atom side). The carbon atom on the cleavage side of the CC bond and the CO bond is preferably a tertiary or quaternary carbon atom before cleavage. The bond between C and O in the CO bond may be a single bond (CO) or a double bond (C=O).

[0041] The reversibly decomposable bond is particularly preferably -OCC(=O)-. -OCC(=O)- generates a C-O bond terminal upon cleavage. Both ends of -OCC(=O)- are bonded to other groups, and the above "-OCC(=O)-" contains a symmetrical bond "-C(=O)-CO-".

[0042] -OCC(=O)- is cleaved into -OC and C(=O)- by an external stimulus. It is preferred that -OCC(=O)- generates a radical upon cleavage. That is, it is preferred that -OCC(=O)- is cleaved into -OC· and ·C(=O)- by an external stimulus.

[0043] The reactive functional group in compound (a2) is preferably capable of reacting with light and / or heat. The reversibly decomposable bond is preferably capable of being cleaved by light. When the reactive functional group is photoreactive and the reversibly decomposable bond is capable of being cleaved by light, the peak wavelengths of the light from which the reaction of compound (a2) and the cleavage of the reversibly decomposable bond occur are preferably different, and more preferably in different wavelength ranges, from the viewpoint of preventing the reaction of compound (a2) and the cleavage of the reversibly decomposable bond from occurring simultaneously. Specifically, the reactive functional group in compound (a2) is preferably capable of reacting with light having a wavelength of 370 nm or more (i.e., light including light having a wavelength of 370 nm or more) and / or heat. The reversibly decomposable bond is preferably capable of being cleaved by light having a wavelength of less than 370 nm (i.e., light including light having a wavelength of less than 370 nm).

[0044] Examples of the compound (a2) include the above-mentioned polyfunctional compounds, and among them, di(meth)acrylates having an acetophenone skeleton (sometimes referred to as "compound (a2-1)") are preferred, and di(meth)acrylates having an α-hydroxyacetophenone skeleton are particularly preferred. As the compound (a2-1), compounds represented by the following formula (1), compounds represented by the following formula (2), and compounds represented by the following formula (3) are preferred. [ka]

[0045] In equation (1), two R 1 are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 2 are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group, and may be bonded to each other to form a ring. X represents a direct bond, a divalent hydrocarbon group which may have an ester bond, or a divalent hydrocarbon group which may have an ether bond. Y represents a divalent hydrocarbon group which may have an ester bond or a divalent hydrocarbon group which may have an ether bond. The hydrocarbon group, alkyl group, and aryl group may each have a substituent. m and n each independently represent an integer of 1 or greater.

[0046] [ka]

[0047] In equation (2), two R 1 are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 2 are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group. 2may be bonded to each other to form a ring. X represents a direct bond, a divalent hydrocarbon group which may have an ester bond, or a divalent hydrocarbon group which may have an ether bond. The above hydrocarbon group, alkyl group, and aryl group may each have a substituent. Two m's may be the same or different and represent an integer of 1 or more. L represents a direct bond or a linking group.

[0048] [ka]

[0049] In equation (3), two R 1 are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 2 are the same or different and represent a hydrogen atom, an alkyl group, or an aryl group, and may be bonded to each other to form a ring. X represents a direct bond, a divalent hydrocarbon group which may have an ester bond, or a divalent hydrocarbon group which may have an ether bond. The hydrocarbon group, alkyl group, and aryl group may each have a substituent. m represents an integer of 1 or more. k represents the number of repetitions of the parentheses.

[0050] In formulas (1) to (3), R 1 Examples of the hydrocarbon group having 1 to 4 carbon atoms in the formula include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an s-butyl group, and a t-butyl group.

[0051] In formulas (1) to (3), R 2 The alkyl group in is preferably an alkyl group having 1 to 4 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an s-butyl group, and a t-butyl group. 2 is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably a methyl group.

[0052] In formulas (1) to (3), R 2Examples of the aryl group in the formula (I) include groups having 1 to 3 benzene rings, such as a phenyl group, a naphthyl group, a phenanthrenyl group, an anthracenyl group, etc. Of these, a phenyl group is preferred.

[0053] The Two R's 2 Examples of the ring that can be formed by bonding include hydrocarbon rings such as alicyclic hydrocarbon rings such as a cyclohexyl ring, etc. The number of carbon atoms in the ring is, for example, 3 to 10, and preferably 5 to 8.

[0054] In formulas (1) to (3), the divalent hydrocarbon groups in X and Y which may have an ester bond and the divalent hydrocarbon groups in the divalent hydrocarbon groups which may have an ether bond are preferably alkylene groups having 1 to 6 carbon atoms, more preferably alkylene groups having 2 to 4 carbon atoms. Examples of the alkylene groups include methylene, dimethylene, trimethylene, methylmethylene, and tetramethylene.

[0055] In formulas (1) to (3), m represents the number of repetitions of (-XO) and is an integer of 1 or more, preferably 1 to 10, more preferably 1 to 4, and even more preferably 1 to 2. In formula (1), n ​​represents the number of repetitions of (-YO) and is an integer of 1 or more, preferably 1 to 10, more preferably 1 to 4, and even more preferably 1 to 2.

[0056] In formula (2), L represents a direct bond or a linking group. Examples of the linking group include alkylene groups, divalent groups having a hetero atom such as an ether bond or an ester bond, and groups in which two or more of these are bonded together.

[0057] In formula (3), k is a positive number indicating the number of repetitions of the parentheses, and is preferably 2 or more (for example, 2 to 10), and more preferably 2 to 6.

[0058] The compounds represented by the above formulas (1) to (3) are C(=O)-C(R 2 )2 is cleaved, and the CO bond (C=O) becomes the terminal after cleavage. 2When X is a hydrocarbon group, the C—C bond also becomes an end after cleavage, and when X is a direct bond, the C—O bond (CO) also becomes an end after cleavage.

[0059] Specific examples of the compound (a2) include compounds represented by the following formulas (1-1) to (1-5), compounds represented by the following formulas (2-1) to (2-3), and compounds represented by the following formula (3-1).

[0060] [ka]

[0061] [ka]

[0062] [ka]

[0063] The component (a) may be used alone or in combination of two or more. That is, the adhesive of the present invention may contain either the polymer (a1) or the compound (a2), or both. Furthermore, the polymer (a1) and the compound (a2) may each be used alone or in combination of two or more.

[0064] The content of compound (a2) in the adhesive of the present invention (the total content of one or more selected from the group consisting of compound (a2), structural units derived from compound (a2), and structural moieties derived from compound (a2)) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, relative to 100% by mass of the total amount of the adhesive of the present invention (excluding components that do not remain during layer formation, such as organic solvents), in order to achieve a suitable crosslink density and provide the resin with a suitable flexibility before the application of an external stimulus. The content is preferably 50% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, in order to achieve a suitable crosslink density and provide the resin with a suitable flexibility before the application of an external stimulus.

[0065] Examples of the polymer (a1) include thermoplastic resins, thermosetting resins, and active energy ray-curable resins. Among these, thermoplastic resins and thermosetting resins are preferred. An adhesive containing a thermoplastic resin can exhibit adhesiveness that allows it to adhere to an adherend when subjected to external pressure, for example. An adhesive containing a thermosetting resin can be cured by heating, for example, to adhere to an adherend. Only one type of polymer (a1) can be used, or two or more types can be used.

[0066] The thermosetting resin includes both a resin having thermosetting properties (thermosetting resin) and a resin obtained by curing the thermosetting resin. The thermosetting resin has a thermosetting functional group. The number of thermosetting functional groups in the thermosetting resin is preferably 2 or more (for example, 2 to 4). Examples of the thermosetting resin include phenolic resins, epoxy resins, urethane resins, melamine resins, and alkyd resins. Among these, epoxy resins are particularly preferred.

[0067] Examples of epoxy resins include bisphenol-type epoxy resins, spirocyclic-type epoxy resins, naphthalene-type epoxy resins, biphenyl-type epoxy resins, terpene-type epoxy resins, glycidyl ether-type epoxy resins, glycidyl amine-type epoxy resins, and novolac-type epoxy resins.

[0068] Examples of the bisphenol-type epoxy resins include bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, and tetrabromobisphenol A-type epoxy resins. Examples of the glycidyl ether-type epoxy resins include tris(glycidyloxyphenyl)methane and tetrakis(glycidyloxyphenyl)ethane. Examples of the glycidylamine-type epoxy resins include tetraglycidyldiaminodiphenylmethane. Examples of the novolac-type epoxy resins include cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, α-naphthol novolac-type epoxy resins, and brominated phenol novolac-type epoxy resins.

[0069] Examples of the thermoplastic resin include polystyrene resins, vinyl acetate resins, polyester resins, polyolefin resins (polyethylene resins, polypropylene resin compositions, etc.), polyimide resins, acrylic resins, etc. Among these, acrylic resins are preferred because they can impart cohesive strength and appropriate flexibility to pressure-sensitive adhesives, etc.

[0070] The design of acrylic resins varies widely depending on the purpose, and it is preferable to appropriately select the monomer type, copolymer composition ratio, molecular weight, molecular weight distribution, crosslinker, and compounding composition ratio depending on the desired values, such as mechanical properties such as flexibility and elastic modulus, thermal properties such as glass transition point, optical properties such as transmittance, haze, and refractive index, and characteristic values ​​specific to adhesives, such as adhesive strength and adhesion.

[0071] An acrylic resin is a resin containing an acrylic monomer (a monomer having a (meth)acryloyl group in the molecule) as a monomer component constituting the resin. That is, the acrylic resin contains a constituent unit derived from an acrylic monomer. The acrylic resin is preferably a polymer containing a (meth)acrylic acid alkyl ester as a monomer component constituting the polymer. In this specification, "(meth)acrylic" refers to "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies to other terms.

[0072] The (meth)acrylic acid alkyl ester as an essential monomer component is preferably a (meth)acrylic acid alkyl ester having a linear or branched alkyl group. The (meth)acrylic acid alkyl ester may be used singly or in combination of two or more.

[0073] The (meth)acrylic acid alkyl ester having a linear or branched alkyl group is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and methyl (meth)acrylate. Examples of the alkyl (meth)acrylate esters include isononyl acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate (stearyl (meth)acrylate), isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0074] As the (meth)acrylic acid alkyl ester having a linear or branched alkyl group, a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 2 or more carbon atoms (preferably 2 to 18, more preferably 3 to 10) is preferred.

[0075] The content of structural units derived from (meth)acrylic acid alkyl esters in the acrylic resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 96% by mass or more, based on 100% by mass of the total amount of monomer components constituting the acrylic resin. The content may be 99% by mass or less, or even 98% by mass or less. Of course, depending on the application and desired properties, the content of structural units derived from (meth)acrylic acid alkyl esters in the acrylic resin may be less than 70% by mass, based on 100% by mass of the total amount of monomer components constituting the acrylic resin.

[0076] The acrylic resin may contain, as a monomer component constituting the resin, the alkyl (meth)acrylate and another monomer (copolymerizable monomer) copolymerizable with the alkyl (meth)acrylate. That is, the acrylic resin may contain a copolymerizable monomer as a constituent unit. Only one type of copolymerizable monomer may be used, or two or more types may be used.

[0077] The copolymerizable monomer can be appropriately selected depending on the reactive functional group when the compound (a2) is a polyfunctional compound. Examples of the copolymerizable monomer include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an epoxy group-containing monomer, a keto group-containing monomer, an alkoxy group-containing monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a vinyl ester monomer, a vinyl ether monomer, an isocyanate group-containing monomer, an aromatic vinyl compound, an alicyclic monomer, an aromatic ring-containing (meth)acrylate, a chlorine-containing monomer, and a nitrogen-containing monomer.

[0078] The content of the structural units derived from copolymerizable monomers in the acrylic resin may be 0.1% by mass or more, or may be 0.3% by mass or more, based on 100% by mass of the total amount of the monomer components constituting the acrylic resin. The content is preferably 30% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, and may even be 1% by mass or less. Of course, depending on the application and desired properties, the content of the structural units derived from copolymerizable monomers in the acrylic resin may be less than 0.1% by mass, based on 100% by mass of the total amount of the monomer components constituting the acrylic resin.

[0079] When the thermosetting resin is contained, the content ratio of the thermosetting resin is not particularly limited. However, in order to impart appropriate initial hardness and hardness after external stimulation to the pressure-sensitive adhesive layer, the content ratio is preferably 3 to 95% by mass, more preferably 5 to 90% by mass, and even more preferably 6 to 85% by mass relative to 100% by mass of the total amount of the pressure-sensitive adhesive of the present invention (excluding components that do not remain during layer formation, such as organic solvents). When the pressure-sensitive adhesive of the present invention contains a thermosetting resin as a base polymer, the content ratio is preferably 50 to 95% by mass, more preferably 60 to 90% by mass, and even more preferably 65 to 85% by mass. When the pressure-sensitive adhesive of the present invention contains a thermoplastic resin as a base polymer, the content ratio is preferably 3 to 80% by mass, more preferably 5 to 50% by mass, and even more preferably 7 to 30% by mass. The amount of the thermosetting resin includes the amounts of the thermosetting resin, its raw material monomer, the crosslinking agent, and structural moieties derived from the crosslinking agent.

[0080] When the thermoplastic resin is contained, the content ratio of the thermoplastic resin is not particularly limited, but is preferably 20 to 97% by mass, more preferably 50 to 95% by mass, and even more preferably 70 to 93% by mass, relative to 100% by mass of the total amount of the adhesive of the present invention (excluding components that do not remain during layer formation, such as organic solvents), in order to impart appropriate initial hardness and hardness after external stimulation to the adhesive layer. When the adhesive of the present invention contains a thermosetting resin as a base polymer, the content ratio is preferably 30% by mass or less, and may be 10% by mass or less, 5% by mass or less, 1% by mass or less, or even 0% by mass. The amount of thermoplastic resin includes the amounts of the thermoplastic resin, its raw material monomer, crosslinking agent, and structural moieties derived from the crosslinking agent.

[0081] The pressure-sensitive adhesives and the like of the present invention contain a compound (b) that is reactive with at least one of the groups generated by cleavage of the reversibly degradable bond. It is preferable that each molecule of component (b) be reactive with one of the two groups generated by cleavage of the reversibly degradable bond. For example, if the reversibly degradable group is -OCC(=O)-, component (b) is reactive with -OC and / or C(=O)-. If a single molecule of component (b) is reactive with both -OC and C(=O)-, component (b) is interposed between -OC and C(=O)-, resulting in a change in physical properties, such as a longer molecular chain, compared to before cleavage of the reversibly degradable bond. On the other hand, if a single molecule of component (b) is reactive with either -OC or C(=O)-, component (b) can block at least one of -OC and C(=O)-, thereby suppressing recombination of the two groups generated by cleavage, making it easier to change physical properties. The component (b) may be used alone or in combination of two or more.

[0082] When polymer (a1) generates radicals upon cleavage, component (b) is preferably a compound having radical scavenging ability (radical scavenger). Examples of the radical scavenger include photoradical polymerization initiators, spin scavengers, antioxidants, polymerization inhibitors, and hydrogen donors.

[0083] From the viewpoint of excellent reactivity with -OC·, component (b) is preferably a compound (b1) having a phenolic hydroxyl group or a compound (b2) having a primary amino group or a secondary amino group. Compound (b1) and compound (b2) may be overlapping compounds.

[0084] Compound (b1) is a compound having a phenol structure, and examples thereof include phenol, hindered phenols, catechol, t-butylcatechol, cresol, naphthol, bisphenols (bisphenol A, bisphenol F, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol S, tetrachlorobisphenol A, tetrabromobisphenol A, etc.), dihydroxynaphthalene, phenol novolac, cresol novolac, bisphenol A novolac, brominated phenol novolac, resorcinol, 4,4'-dihydroxydiphenyl ether, 9,9'-bis(4-hydroxyphenyl)fluorene, 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene, 3,3,3',3'-tetramethyl-1,1'-spirobiindan-6,6'-diol, 3-(4-hydroxyphenyl)-1,1,3-trimethyl-5-indanol, and phenol derivatives such as gallic acid esters. Furthermore, each of the compounds exemplified as compound (b1) may have a substituent.

[0085] Examples of the hindered phenols include phenol derivatives in which a branched alkyl group (preferably an alkyl group containing a quaternary carbon atom) is substituted on the carbon atom adjacent to the carbon atom in the phenol skeleton to which a hydroxy group is bonded, phenol derivatives in which alkyl groups (preferably alkyl groups having 1 to 6 carbon atoms) are substituted on the carbon atoms on both sides of the carbon atom in the phenol skeleton to which a hydroxy group is bonded, and phenol derivatives in which two or more alkyl groups (preferably alkyl groups containing a quaternary carbon atom) are substituted on the benzene ring in the phenol skeleton. Specific examples of the hindered phenols include those sold under the trade names "Irganox1076", "Irganox1135", and "Irganox1520L", 4-(hexyloxy)-2,3,6-trimethylphenol, 2,6-di-tert-butyl-p-cresol, methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2,5-di-tert-amylhydroquinone.

[0086] Compound (b2) may have either a primary amino group or a secondary amino group, or both. The primary amino group and the secondary amino group in compound (b2) have a hydrogen atom bonded to a nitrogen atom, thereby providing radical scavenging ability. Compound (b) is preferably 4,4'-bis(α,α-dimethylbenzyl)diphenylamine.

[0087] From the viewpoint of exhibiting an appropriate recombination-inhibiting effect, the content of component (b) is preferably 10 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 75 parts by mass or more, relative to 100 parts by mass of the total amount of compound (a2) (the total amount of one or more selected from the group consisting of compound (a2), structural units derived from compound (a2), and structural moieties derived from compound (a2)). The content may be, for example, 1000 parts by mass or less, 700 parts by mass or less, or 500 parts by mass or less.

[0088] The adhesive of the present invention may also contain other components in addition to the above-mentioned components, if necessary. Examples of such other components include curing catalysts, crosslinking agents other than the compound (a2), crosslinking accelerators, polymerization initiators, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), oligomers, antioxidants, fillers (metal powders, organic fillers, inorganic fillers, etc.), colorants (pigments, dyes, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, UV absorbers, polymerization inhibitors, granular materials, foil-like materials, flame retardants, silane coupling agents, ion trapping agents, etc. Each of the above other components may be used alone or in combination of two or more.

[0089] The glass transition temperature (Tg) of the pressure-sensitive adhesive or the like of the present invention is preferably 0° C. or lower, more preferably −10° C. or lower, and even more preferably −20° C. or lower. The Tg is preferably −60° C. or higher, more preferably −50° C. or higher. The Tg can be calculated using a dynamic viscoelasticity measurement (DMA) device.

[0090] Hereinafter, preferred embodiments of the pressure-sensitive adhesive of the present invention will be described separately for cases where the pressure-sensitive adhesive is a pressure-sensitive adhesive composition or adhesive composition having fluidity, and for cases where the pressure-sensitive adhesive is a pressure-sensitive adhesive layer or adhesive layer. In this specification, the pressure-sensitive adhesive composition and / or adhesive composition may be referred to as a "pressure-sensitive adhesive composition, etc." In addition, in this specification, the pressure-sensitive adhesive of the present invention that is a pressure-sensitive adhesive layer and / or adhesive layer may be referred to as a "pressure-sensitive adhesive layer, etc."

[0091] (adhesive layer, adhesive layer) Figure 1 is a cross-sectional view showing one embodiment of the pressure-sensitive adhesive layer etc. of the present invention. The pressure-sensitive adhesive layer or adhesive layer 1 shown in Figure 1 is laminated on the release-treated surface of a release liner 2 to form a pressure-sensitive adhesive sheet or adhesive sheet 10 with a release liner.

[0092] The pressure-sensitive adhesive layer etc. preferably contains at least the polymer (a1) and the component (b). The polymer (a1) may be used singly or in combination of two or more.

[0093] The pressure-sensitive adhesive layer etc. may contain other components in addition to the above-mentioned components. Examples of the other components include those exemplified and explained as other components that may be contained in the pressure-sensitive adhesive etc. of the present invention. Only one type of the other components may be used, or two or more types may be used.

[0094] The content of polymer (a1) in the pressure-sensitive adhesive layer, etc., is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 80% by mass or more, based on 100% by mass of the total amount of the pressure-sensitive adhesive layer, etc. A content of 30% by mass or more facilitates imparting adhesiveness to the pressure-sensitive adhesive layer, etc. The content is preferably 99.5% by mass or less, more preferably 99% by mass or less. A content of 99.5% by mass or less facilitates composition design by blending a crosslinking agent or component (b). When compound (a2) is a monomer component or oligomer component, the content includes the amount of compound (a2) and the amount of structural units derived from compound (a2). The amount of polymer (a1) includes the amount of polymer (a1), its raw material monomer, crosslinking agent, and structural moieties derived from the crosslinking agent.

[0095] The proportion of the crosslinking agent and / or structural moieties derived from the crosslinking agent in the pressure-sensitive adhesive layer, etc. is preferably 0.1 to 20 mass %, more preferably 0.3 to 10 mass %, and even more preferably 0.4 to 8 mass %, relative to 100 mass % of the total amount of polymer (a1). When compound (a2) is a crosslinking agent, the above content includes the amount of compound (a2) and the amount of structural moieties derived from compound (a2).

[0096] In the pressure-sensitive adhesive layer etc. of the present invention, the polymer (a1) preferably forms a network structure. A network structure refers to a state in which molecules are entangled with each other, or a state in which molecular chains form long molecules via some kind of bond. That is, the polymer (a1) is preferably a polymer in which a network structure is formed by bonds or entanglement of molecules. A pressure-sensitive adhesive layer etc. having such a configuration forms a network structure by bonds or entanglement of polymers with each other, and can have appropriate hardness. When the degradable bonds are decomposed by an external stimulus, the polymer structure is shredded and flexibility is improved.

[0097] The term "molecular entanglement" refers to a state in which polymers form a network structure without covalent bonds. To form such an entangled structure, it is preferable to contain different types of polymers that are unlikely to undergo crosslinking reactions with each other. From the viewpoint of ease of preparation, it is preferable to form an entangled structure between thermoplastic resins or between a thermosetting resin and a thermoplastic resin. This structure is suitable for a pressure-sensitive adhesive layer that is relatively flexible before the application of an external stimulus because it does not involve covalent bonds.

[0098] The state in which the molecular chains form a long molecule via some kind of bond indicates a polymer formed from a single polymer. To form such a long molecule, it is preferable to contain a single polymer, and it is preferable to contain the above-mentioned thermosetting resin. In this configuration, since the molecular chains are covalently bonded to a long length, a relatively hard adhesive layer can be formed, and since the number of sites that are cleaved by an external stimulus increases, it is suitable for an adhesive layer that has a greater difference in flexibility before and after the external stimulus.

[0099] The pressure-sensitive adhesive layer etc. of the present invention changes in physical properties of at least a part of its region in response to an external stimulus. Examples of the physical properties include mechanical strength (hardness, breaking characteristics, etc.), adhesiveness, optical properties (transparency, total light transmittance, haze, etc.), and solvent affinity (gel fraction, swelling degree, etc.). Examples of the hardness include elastic modulus such as shear storage modulus, Young's modulus, etc. Examples of changes in the physical properties include a decrease in hardness (improvement in flexibility), an increase in breaking elongation, a decrease in breaking stress, an improvement in adhesive strength, an improvement in transparency, a decrease in haze, and L * a * b * These include changes in various values ​​of the physical properties, a decrease in the gel fraction, an increase in the degree of swelling, etc. It is preferable that the above physical properties do not return to their original state after the change (for example, that which has decreased does not increase).

[0100] The pressure-sensitive adhesive layer etc. of the present invention preferably has a property that the hardness of at least a part of the region is reduced by an external stimulus. It is preferable that the hardness does not increase after the reduction. Such a pressure-sensitive adhesive layer etc. does not increase in hardness when the pressure-sensitive adhesive layer etc. is adhered or bonded to a member, and flexibility is maintained.

[0101] The pressure-sensitive adhesive layer etc. of the present invention preferably has a shear storage modulus (G') reduced in at least a portion of its area by an external stimulus (particularly, light irradiation). The flexibility of such a pressure-sensitive adhesive layer etc. is improved by the external stimulus. Furthermore, it is preferable that the shear storage modulus (G') does not increase after the reduction.

[0102] The adhesive layer etc. of the present invention has a shear storage modulus (G') of 1.0 × 10 at -20°C before application of an external stimulus. 3 ~1.0×10 8 Pa, more preferably 1.0×10 4 ~1.0×10 7 Pa, more preferably 1.0 × 10 4 ~1.0×10 6 Pa, particularly preferably 2.0 × 10 4 ~1.0×10 5The pressure-sensitive adhesive layer and the like having the above shear storage modulus have an appropriate hardness even in a low-temperature environment before application of an external stimulus, and are excellent in handleability.

[0103] The adhesive layer etc. of the present invention has a shear storage modulus (G') of 1.0 × 10 at 25°C before application of an external stimulus. 3 ~1.0×10 8 Pa, more preferably 1.0×10 4 ~1.0×10 7 Pa, more preferably 1.0 × 10 4 ~1.0×10 6 Pa, particularly preferably 2.0 × 10 4 ~1.0×10 5 The pressure-sensitive adhesive layer and the like having the above shear storage modulus have an appropriate hardness before the application of an external stimulus, and are excellent in handleability.

[0104] The adhesive layer etc. of the present invention has a shear storage modulus (G') at 60°C before application of an external stimulus of 1.0 x 10 3 ~5.0×10 7 Pa, more preferably 7.0×10 3 ~1.0×10 6 Pa, more preferably 1.0 × 10 4 ~1.0×10 5 The pressure-sensitive adhesive layer etc. having the above shear storage modulus has an appropriate hardness before the application of an external stimulus even when the temperature is slightly elevated due to the environment, and is excellent in handleability.

[0105] The adhesive layer etc. of the present invention has a shear storage modulus (G') of 1.0 × 10 at -20°C after application of an external stimulus. 3 ~1.0×10 8 Pa, more preferably 1.0×10 4 ~1.0×10 7 Pa, more preferably 1.0 × 10 4 ~1.0×10 6 Pa, particularly preferably 2.0 × 10 4 ~1.0×10 5When the shear storage modulus is within the above range, after application of an external stimulus, the flexibility is excellent even in a low-temperature environment, and the ability to conform to unevenness and adhesion are excellent.

[0106] The adhesive layer etc. of the present invention has a shear storage modulus (G') at 25°C after application of an external stimulus of 1.0 x 10 2 ~5.0×10 6 Pa, more preferably 1.0×10 3 ~5.0×10 5 Pa, more preferably 3.0 × 10 3 ~1.0×10 5 Pa, particularly preferably 5.0 × 10 3 ~7.0×10 4 When the shear storage modulus is within the above range, the pressure-sensitive adhesive layer etc. of the present invention has superior flexibility after application of an external stimulus, and superior step-following ability, adhesion and the like.

[0107] The pressure-sensitive adhesive layer etc. of the present invention has a shear storage modulus (G') at 60°C after application of an external stimulus of 1.0 x 10 2 ~1.0×10 6 Pa, more preferably 5.0×10 2 ~3.0×10 5 Pa, more preferably 1.0 × 10 3 ~1.0×10 5 Pa, particularly preferably 2.0 × 10 3 ~8.0×10 4 When the shear storage modulus is within the above range, after application of an external stimulus, for example, when the temperature is slightly elevated due to the environment, the flexibility is excellent, and the ability to conform to unevenness and adhesion are also excellent.

[0108] The pressure-sensitive adhesive layer etc. of the present invention preferably has a ratio of the shear storage modulus (G') at -20°C before application of an external stimulus to the shear storage modulus (G') at -20°C after application of an external stimulus [after application of an external stimulus / before application of an external stimulus] (sometimes referred to as the "shear storage modulus (G') ratio (-20°C)") of 0.99 or less (e.g., 0.01 to 0.99), more preferably 0.98 or less (e.g., 0.05 to 0.98), even more preferably 0.95 or less (e.g., 0.1 to 0.95), and particularly preferably 0.9 or less (e.g., 0.2 to 0.9). In this case, the flexibility, step-following ability, and adhesion of the pressure-sensitive adhesive layer etc. in a low-temperature environment tend to change more significantly before and after application of an external stimulus.

[0109] The pressure-sensitive adhesive layer etc. of the present invention preferably has a ratio of the shear storage modulus (G') at 25°C before application of an external stimulus to the shear storage modulus (G') at 25°C after application of an external stimulus [after application of external stimulus / before application of external stimulus] (sometimes referred to as the "shear storage modulus (G') ratio (25°C)") of 0.9 or less (e.g., 0.01 to 0.9), more preferably 0.8 or less (e.g., 0.05 to 0.8), and even more preferably 0.7 or less (e.g., 0.1 to 0.7). In this case, the flexibility, step-following ability, and adhesion of the pressure-sensitive adhesive layer etc. at around 25°C tend to change more significantly before and after application of an external stimulus.

[0110] The pressure-sensitive adhesive layer etc. of the present invention preferably has a ratio of the shear storage modulus (G') at 60°C before application of an external stimulus to the shear storage modulus (G') at 60°C after application of an external stimulus [after application of an external stimulus / before application of an external stimulus] (sometimes referred to as the "shear storage modulus (G') ratio (60°C)") of less than 0.95 (e.g., 0.01 or more and less than 0.95), more preferably 0.8 or less (e.g., 0.05 to 0.8), even more preferably 0.7 or less (e.g., 0.1 to 0.7), and particularly preferably 0.6 or less (e.g., 0.2 to 0.6). In this case, the flexibility, step-following ability, and adhesion of the pressure-sensitive adhesive layer etc. in a high-temperature environment tend to change more significantly before and after application of an external stimulus.

[0111] The pressure-sensitive adhesive layer etc. of the present invention preferably has a lower Young's modulus after application of an external stimulus than before application of an external stimulus. Such a pressure-sensitive adhesive layer etc. has excellent handleability before application of the external stimulus, and has excellent flexibility, impact resistance, and resistance to shape deformation at high speeds after application of the external stimulus.

[0112] The pressure-sensitive adhesive layer etc. of the present invention preferably has a Young's modulus (E1) of 200 MPa or less (e.g., 0.03 to 200 MPa) before application of an external stimulus. Furthermore, the pressure-sensitive adhesive layer etc. preferably has a Young's modulus (E2) of 150 MPa or less (e.g., 0.001 to 150 MPa), more preferably 100 MPa or less, after application of an external stimulus. A pressure-sensitive adhesive layer etc. having the above Young's modulus has an appropriate hardness before application of an external stimulus, and is superior in workability in production, processing, storage, transportation, and the like. Furthermore, a pressure-sensitive adhesive layer having the above Young's modulus has excellent flexibility after application of an external stimulus, and is superior in step-following ability, adhesion, and the like.

[0113] The pressure-sensitive adhesive layer etc. of the present invention preferably has a ratio of Young's modulus (E1) before application of an external stimulus to Young's modulus (E2) after application of an external stimulus [Young's modulus (E2) / Young's modulus (E1)] (sometimes referred to as "Young's modulus ratio") of 0.97 or less (e.g., 0.1 to 0.97), more preferably 0.8 or less (e.g., 0.2 to 0.8), and even more preferably 0.7 or less (e.g., 0.3 to 0.7). In this case, the pressure-sensitive adhesive layer etc. has excellent flexibility before and after application of an external stimulus, excellent resistance to minute deformation, and more excellent impact resistance, resistance to shape deformation at high speeds, step-following ability, adhesion, etc.

[0114] The pressure-sensitive adhesive layer etc. of the present invention preferably has a higher breaking elongation after application of an external stimulus than the breaking elongation before application of an external stimulus. Such a pressure-sensitive adhesive layer etc. has excellent handleability before application of the external stimulus, and has excellent resistance to minute deformation, impact resistance, and resistance to shape deformation at high speeds after application of the external stimulus.

[0115] The pressure-sensitive adhesive layer etc. of the present invention preferably has a breaking elongation (B1) before application of an external stimulus of 100 to 2000%, more preferably 100 to 1000%, even more preferably 120 to 900%, and particularly preferably 150 to 850%. A pressure-sensitive adhesive layer etc. having the above breaking elongation (B1) has appropriate hardness before application of an external stimulus and is superior in handleability.

[0116] The pressure-sensitive adhesive layer etc. of the present invention preferably has a breaking elongation (B2) after application of an external stimulus of 100 to 1300%, more preferably 130 to 1100%, and even more preferably 160 to 1000%. A pressure-sensitive adhesive layer etc. having the above breaking elongation (B2) after application of an external stimulus has excellent flexibility, excellent resistance to minute deformation, and excellent impact resistance and resistance to shape deformation in the high-speed range.

[0117] The pressure-sensitive adhesive layer etc. of the present invention preferably has a ratio of the breaking elongation (B1) before application of an external stimulus to the breaking elongation (B2) after application of an external stimulus [breaking elongation (B2) / breaking elongation (B1)] (sometimes referred to as the "breaking elongation ratio") of more than 1.1 (e.g., more than 1.1 and not more than 5.0), more preferably 1.2 or more (e.g., 1.2 to 3.0), and even more preferably 1.3 or more (e.g., 1.3 to 2.5). In this case, the pressure-sensitive adhesive layer etc. has excellent flexibility before and after application of an external stimulus, excellent resistance to minute deformation, and excellent impact resistance and resistance to shape deformation at high speeds.

[0118] The pressure-sensitive adhesive layer etc. of the present invention preferably satisfies one or more of the following: the shear storage modulus (G') ratio (-20°C) is 0.95 or less, the shear storage modulus (G') ratio (25°C) is 0.93 or less, the shear storage modulus (G') ratio (60°C) is 0.90 or less, the Young's modulus ratio is less than 1, and the breaking elongation ratio is 1.3 or more. In this case, it can be said that the physical properties of the pressure-sensitive adhesive layer etc. are intentionally changed by an external stimulus.

[0119] The thickness of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is, for example, about 5 to 250 μm, more preferably 7 to 200 μm, even more preferably 10 to 100 μm, and particularly preferably 10 to 50 μm.

[0120] <Pressure-sensitive adhesive composition, adhesive composition> The pressure-sensitive adhesive layer of the present invention is formed from a pressure-sensitive adhesive composition. The adhesive layer is also formed from an adhesive composition. The pressure-sensitive adhesive composition etc. preferably contains at least a base polymer and / or its raw material monomer. In particular, it is preferable to contain a base polymer from the viewpoint of ensuring that the resulting pressure-sensitive adhesive layer etc. exhibits adhesiveness. The base polymer is polymer (a1) and / or other polymers (i.e., polymers without reversibly decomposable bonds). When the base polymer is one of the other polymers, the pressure-sensitive adhesive composition etc. further contains compound (a2). Only one type of base polymer may be used, or two or more types may be used. The pressure-sensitive adhesive composition etc. may or may not contain component (b).

[0121] When the base polymer is the other polymer, the pressure-sensitive adhesive composition or the like further contains a compound (a2). In this case, the pressure-sensitive adhesive composition or the like may further contain a monomer component (sometimes referred to as "monomer component (c)") reactive with the compound (a2). The compound (a2) is reactive with the other polymer and / or the monomer component (c). When the compound (a2) is reactive with the other polymer, the other polymer reacts with the compound (a2) in the pressure-sensitive adhesive layer or the like by heat or light irradiation to form, for example, a polymer chain, and the polymer chain and the other polymer bond to form a network structure, thereby obtaining a pressure-sensitive adhesive layer or the like containing the polymer (a1). When the compound (a2) and the monomer component (c) are contained, the compound (a) reacts with the monomer component (c) in the pressure-sensitive adhesive layer or the like by heat or light irradiation to form, for example, a polymer chain, and the polymer chain and the other polymer become entangled to form a network structure, thereby obtaining a pressure-sensitive adhesive layer or the like containing the polymer (a1). Only one type of monomer component (c) may be used, or two or more types may be used.

[0122] When the PSA composition or the like contains the raw material monomer, the compound (a2) is incorporated into the base polymer when the raw material monomer is polymerized to form the polymer (a1). Alternatively, the raw material monomer is polymerized to form the other polymer, which is then reacted with the compound (a2) to form the polymer (a1).

[0123] The pressure-sensitive adhesive compositions and the like mainly include (i) pressure-sensitive adhesive compositions and the like containing polymer (a1), (ii) pressure-sensitive adhesive compositions and the like containing polymer (a1) and the other polymers described above, (iii) pressure-sensitive adhesive compositions and the like containing the other polymers described above, compound (a2), and, if necessary, monomer component (c), and (iv) pressure-sensitive adhesive compositions and the like containing compound (a2), and, if necessary, monomer component (c).

[0124] Thus, polymer (a1) may be a reaction product of the other polymer, compound (a2), and monomer (c), or may be a polymer containing the other polymer and a reaction product of the other polymer and compound (a2) (particularly, entangled). When the base polymer is polymer (a1), the pressure-sensitive adhesive layer, etc. may contain unreacted compound (a2) and / or unreacted monomer (c).

[0125] The pressure-sensitive adhesive composition may contain other components in addition to the above-mentioned components. Examples of the other components include those exemplified and explained as other components that may be contained in the pressure-sensitive adhesive layer of the present invention, as well as solvents such as organic solvents. Only one of the other components may be used, or two or more of the other components may be used.

[0126] <Release liner> The release liner protects the adhesive surface and / or bonding surface that comes into contact with the pressure-sensitive adhesive layer of the present invention until it is used, and is peeled off when the pressure-sensitive adhesive layer is used.

[0127] Examples of the substrate for the release liner include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, polyimide films, and fluororesin films. Crosslinked films of these films are also included. Furthermore, laminated films of these films may also be used.

[0128] The release surface of the release liner (particularly the surface that comes into contact with the pressure-sensitive adhesive layer, etc.) is preferably subjected to a release treatment. Examples of release agents used for the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0129] The thickness of the release liner is not particularly limited, but is, for example, about 20 to 150 μm.

[0130] One embodiment of the method for producing a pressure-sensitive adhesive layer or the like of the present invention will be described below. For example, the pressure-sensitive adhesive sheet or adhesive sheet 10 with a release liner shown in Figure 1 can be produced by the following method. A pressure-sensitive adhesive composition or the like that forms a pressure-sensitive adhesive layer or the like 1 is applied to a base layer or the release-treated surface of a release liner 2 that has been subjected to a release treatment to form a coating layer, and then the coating layer is solidified by heating to remove the solvent or thermal curing, or by curing with light irradiation, thereby producing a pressure-sensitive adhesive layer or the like. When light irradiation is performed, it is performed after a separate release liner is laminated onto the coating layer.

[0131] The pressure-sensitive adhesive composition, etc. may be in any form as long as the effects of the present invention are not impaired. For example, the pressure-sensitive adhesive composition, etc. may be an emulsion type, a solvent type (solution type), a hot-melt type, a photopolymerization type, etc. Among these, emulsion type, solvent type, and photopolymerization type are preferred because they facilitate the production of pressure-sensitive adhesive layers, etc., with excellent productivity. That is, the pressure-sensitive adhesive layer, etc. of the present invention preferably contains an emulsion polymer, a solvent-type polymer, or a photopolymerization polymer as the base polymer. Furthermore, the pressure-sensitive adhesive layer, etc. of the present invention containing a photopolymerization polymer is preferably a solvent-free pressure-sensitive adhesive layer. Such a pressure-sensitive adhesive layer can be produced from a solvent-free pressure-sensitive adhesive composition. A solvent-free pressure-sensitive adhesive composition does not require a step of volatilizing and removing the solvent from the coating film of the composition during the process of producing the pressure-sensitive adhesive layer, etc. from the composition. Therefore, the pressure-sensitive adhesive layer, etc. is suitable for reducing environmental impact. A photopolymerization polymer is a polymer formed by a polymerization method in which a polymerization reaction of a polymerizable component is promoted by irradiation with active energy rays, such as ultraviolet light.

[0132] When the pressure-sensitive adhesive composition contains polymer (a1), the pressure-sensitive adhesive layer is formed by heating when solidifying the coating layer. When the pressure-sensitive adhesive composition contains the other polymer and / or raw material monomer and compound (a2), the raw material monomer is polymerized as needed by heating or light irradiation when solidifying the coating layer, and compound (a2) forms a bond with a polymer of the raw material monomer or the other polymer, forming polymer (a1) and simultaneously forming the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer may then be heated or irradiated with light, or if polymer (a1) is a curable resin, may be cured.

[0133] When the pressure-sensitive adhesive composition contains component (b), the pressure-sensitive adhesive layer of the present invention can be produced by the above method. On the other hand, when the pressure-sensitive adhesive composition does not contain component (b), a separately prepared composition containing component (b) can be applied to the pressure-sensitive adhesive layer or coating layer formed by the above method, allowing it to impregnate (penetrate) into the pressure-sensitive adhesive layer, and then the solvent contained in the composition can be removed by heating, thereby producing the pressure-sensitive adhesive layer of the present invention (post-addition). More specifically, for example, component (b) can be impregnated only at targeted locations where physical properties are to be changed using a known or conventional coating method such as inkjet printing, thereby forming regions with different physical properties within the surface. Note that the above impregnation may be performed even when the pressure-sensitive adhesive composition contains component (b).

[0134] The composition containing the component (b) is preferably in a liquid state at the time of impregnation. The composition containing the component (b) preferably contains a solvent such as an organic solvent in addition to the component (b).

[0135] In this manner, a pressure-sensitive adhesive sheet with a release liner or adhesive sheet 10 shown in FIG. 1 is obtained.

[0136] The application of the pressure-sensitive adhesive layer etc. of the present invention is not particularly limited, and it can be used for any application. The pressure-sensitive adhesive layer etc. of the present invention can be used, for example, for optical applications, i.e., for bonding to optical components. The pressure-sensitive adhesive layer etc. of the present invention is used, for example, in optical components such as electrical and electronic devices, when attaching (mounting) various members or components to predetermined locations (e.g., housings, etc.). Note that "electrical and electronic devices" refers to devices that fall into at least either electrical or electronic categories. Examples of the electrical and electronic devices include image display devices such as liquid crystal displays, electroluminescence displays, and plasma displays, as well as portable electronic devices. Examples of the image display devices include image display devices in the portable electronic devices, and displays (roll displays) inside and outside vehicles such as trains and buses.

[0137] Examples of the portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including eyeglasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. as accessories, and earwear devices attached to the ears like earphones), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, e-books, in-car information devices, portable radios, portable televisions, portable printers, portable scanners, and portable modems. Note that in this specification, "portable" does not simply mean being portable, but rather means having a level of portability that allows an individual (average adult) to carry it relatively easily.

[0138] The physical properties of the adhesive layer, etc. of the present invention can be intentionally changed by an external stimulus. For example, the hardness can be reduced by an external stimulus. Such an adhesive layer, etc. of the present invention has excellent handleability before adhesion or bonding to a member, and excellent flexibility after adhesion or bonding to a member, during production, processing, storage, transportation, etc. Therefore, for example, when cutting with a punching blade, glue extrusion and glue chipping, and process contamination caused by these, can be prevented. Furthermore, glue extrusion due to its own weight is unlikely to occur during storage, and glue chipping due to vibration or contact is unlikely to occur during transportation. Furthermore, after adhesion or bonding to a member, for example, when used by laminating it to a member, excellent flexibility can be achieved, thereby providing excellent adhesion (adhesive strength), adhesive strength, bendability, foldability, flex resistance, etc. Furthermore, the adhesive layer, etc. of the present invention can reduce stress by an external stimulus, thereby allowing the adhesion and adhesive strength to be varied.

[0139] Therefore, the pressure-sensitive adhesive layer etc. of the present invention is preferably used for bonding components (particularly between components) in electrical and electronic devices that are used by folding, for example, electrical and electronic devices having a foldable image display device (flexible display) (particularly, a foldable image display device (foldable display)).

[0140] Furthermore, by applying an external stimulus to a partial region of the pressure-sensitive adhesive layer etc. of the present invention, a pressure-sensitive adhesive layer etc. having a region with partially different physical properties can be obtained. For example, when the elastic modulus is reduced by an external stimulus, a pressure-sensitive adhesive layer etc. having a reduced elastic modulus in at least a partial region can be obtained by the external stimulus.

[0141] 2 and 3 show embodiments of a pressure-sensitive adhesive layer or the like having regions with partially different physical properties. The pressure-sensitive adhesive layer or the like shown in FIG. 2 has one edge 11 and the other edge 12 that are parallel to each other in a plan view. The pressure-sensitive adhesive layer or the like includes an external stimulus application region 21 and two external stimulus non-application regions 22. In the pressure-sensitive adhesive layer or the like, the external stimulus non-application region 22, the external stimulus application region 21, and the external stimulus non-application region 22 are arranged in this order along the one edge 11 and the other edge 12. Note that in FIG. 2, the boundary 31 between the external stimulus non-application region 22 and the external stimulus application region 21 is drawn with a solid line, but in reality, the boundary 31 may not be visually observable, and a clear boundary may not even exist. The external stimulus application region 21 is arranged continuously from the one edge 11 to the other edge 12.

[0142] A boundary region (not shown) is provided near one edge 11 of the boundary 31. The two boundary regions each include the boundary 31 in a plan view. The boundary region is continuously disposed from one edge 11 to the other edge 12. In each of the two boundary regions, the concentration of the (b) component (or a structure derived from the (b) component) may gradually decrease as it progresses in the direction from the external stimulus applied region 21 toward the external stimulus not applied region 22.

[0143] Preferably, the external stimulus application region 21 is a relatively soft part, and the external stimulus non-application region 22 is a relatively hard part. According to the adhesive layer etc. shown in FIG. 2 , by providing the external stimulus application region 21, which is a soft part, in the region (bending part) that is used by folding, it is preferably used for foldable applications, and it is possible to achieve both durability and impact resistance in the bending part. Furthermore, the combination of the external stimulus application region 21, which is a soft part, and the external stimulus non-application region 22, which is a hard part, provides excellent adhesiveness to the adherend of the external stimulus non-application region 22, and high reliability when attached to the adherend. Furthermore, by having a boundary region, the adhesive layer etc. and the adherend are less likely to bend suddenly when used by folding, and are therefore excellent in durability.

[0144] 3 includes, in plan view, an external stimulus not yet applied region 22 and an external stimulus applied region 21 formed in the center of the external stimulus not yet applied region 22. In the above-mentioned adhesive layer, the external stimulus not yet applied region 22 is arranged in a frame shape around the external stimulus applied region 21. Other than the shapes of the external stimulus not yet applied region 22 and the external stimulus applied region 21, it is the same as FIG.

[0145] The adhesive layer etc. shown in Figure 4 has one edge 11 and the other edge 12 that are parallel to each other in a plan view. The adhesive layer etc. includes an external stimulus not applied region 22 and two external stimulus applied regions 21. In the adhesive layer etc., the external stimulus applied region 21, the external stimulus not applied region 22, and the external stimulus applied region 21 are arranged in this order along the one edge 11 and the other edge 12. The external stimulus applied region 21 and the external stimulus not applied region 22 are arranged continuously from the one edge 11 to the other edge 12. This is the same as Figure 2 except that the positions of the external stimulus not applied region 22 and the external stimulus applied region 21 are reversed.

[0146] Figures 2 and 4 show an example in which the external stimulus application area 21 is arranged continuously in a straight line from one edge 11 to the other edge 12, but the external stimulus application area 21 does not have to be formed continuously from one edge 11 to the other edge 12, and may also have a curved or bent shape, and its shape is not particularly limited.

[0147] The shape of the external stimulus application region 21 is not particularly limited, and may be linear (straight, curved, curved, etc.) or nonlinear, such as a ring, circle, star, polygon, etc., when viewed from above. The shape can be appropriately adjusted to provide excellent conformability to an adherend having a complex shape and excellent durability of the adherend.

[0148] The hardness of the plurality of external stimulus application regions 21 may be the same or different. The hardness of the plurality of external stimulus non-application regions 22 may be the same or different.

[0149] A pressure-sensitive adhesive layer having an external stimulus-applied region and an external stimulus-unapplied region can be produced by impregnating the pressure-sensitive adhesive layer with the above-mentioned component (b). A composition containing the above-mentioned component (b) is applied to a region of a pressure-sensitive adhesive layer or the like to which no external stimulus has been applied, which will be the external stimulus-applied region, to impregnate the pressure-sensitive adhesive layer or the like with component (b). An external stimulus is then applied to an area including the impregnated region, thereby forming the external stimulus-applied region. Alternatively, the external stimulus can be applied only to a region of a pressure-sensitive adhesive layer or the like containing component (b) to which no external stimulus has been applied, to form the external stimulus-applied region. For example, when the external stimulus is an active energy ray, the external stimulus-applied region can be formed by photomasking the region other than the region to be the external stimulus-applied region and irradiating only the region to be the external stimulus-applied region with active energy ray.

[0150] [Adhesive sheets, adhesive sheets] A pressure-sensitive adhesive sheet and / or adhesive sheet can be obtained using the pressure-sensitive adhesive layer etc. of the present invention. In this specification, the pressure-sensitive adhesive sheet and / or adhesive sheet may be referred to as a "pressure-sensitive adhesive sheet etc." The pressure-sensitive adhesive sheet etc. may be a so-called "substrate-less type" pressure-sensitive adhesive sheet etc. that does not have a substrate (substrate layer), or may be a type of pressure-sensitive adhesive sheet etc. that has a substrate. In this specification, a "substrate-less type" pressure-sensitive adhesive sheet etc. may be referred to as a "substrate-less pressure-sensitive adhesive sheet etc.", and a type of pressure-sensitive adhesive sheet etc. that has a substrate may be referred to as a "substrate-attached pressure-sensitive adhesive sheet etc." Examples of the substrate-less pressure-sensitive adhesive sheet etc. include a double-sided pressure-sensitive adhesive sheet etc. that consists only of the pressure-sensitive adhesive layer etc. of the present invention, and a double-sided pressure-sensitive adhesive sheet etc. that consists of the pressure-sensitive adhesive layer etc. of the present invention and another pressure-sensitive adhesive layer etc. (a pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer etc. of the present invention). The substrate-attached PSA sheet or the like is a PSA sheet or the like comprising a substrate and the PSA layer or the like of the present invention formed on at least one surface of the substrate, and examples thereof include a single-sided PSA sheet or the like having the PSA layer or the like of the present invention on one side of the substrate, a double-sided PSA sheet or the like having the PSA layer or the like of the present invention on both sides of the substrate, and a double-sided PSA sheet or the like having the PSA layer or the like of the present invention on one side of the substrate and another PSA layer or the like on the other side. The "substrate (substrate layer)" mentioned above refers to a support, and is the part that is attached to the adherend together with the PSA layer or the like when the PSA sheet or the like is used (attached) to the adherend. A release liner that is peeled off when the PSA sheet or the like is used (attached) is not included in the substrate.

[0151] When the pressure-sensitive adhesive sheet of the present invention is a substrate-attached pressure-sensitive adhesive sheet, the substrate is not particularly limited, and examples thereof include various optical films such as plastic films, anti-reflection (AR) films, anti-glare (AG) films, polarizing plates, and retardation plates. Examples of the substrate include porous materials such as paper, cloth, and nonwoven fabrics, nets, foam sheets, and metal foils. Examples of materials for the plastic film include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymers, and cyclic olefin polymers such as "Arton" (a cyclic olefin polymer, manufactured by JSR Corporation) and "Zeonor" (a cyclic olefin polymer, manufactured by Zeon Corporation). These plastic materials may be used alone or in combination.

[0152] The thickness of the substrate is not particularly limited, but is preferably 10 to 150 μm, more preferably 15 to 125 μm, and even more preferably 25 to 100 μm. The substrate may have either a single layer or multiple layers. The surface of the substrate may be appropriately subjected to a known or commonly used surface treatment, such as a physical treatment such as a corona discharge treatment or a plasma treatment, or a chemical treatment such as a primer treatment.

[0153] The pressure-sensitive adhesive sheet etc. may have a release liner provided on the surface (adhesive surface or adhesive surface) of the pressure-sensitive adhesive layer etc. until use. When the pressure-sensitive adhesive sheet etc. is a double-sided pressure-sensitive adhesive sheet etc., each adhesive surface or adhesive surface may be protected by two release liners, or may be protected by a single release liner with release surfaces on both sides in a rolled form (rolled body). The release liner is used as a protective material for the pressure-sensitive adhesive layer etc., and is peeled off when the pressure-sensitive adhesive sheet etc. is attached to the adherend. When the pressure-sensitive adhesive sheet etc. is a substrate-less pressure-sensitive adhesive sheet etc., the release liner also serves as a support for the pressure-sensitive adhesive layer etc. It is not necessary to provide a release liner.

[0154] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. [Example]

[0155] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The numerical values ​​of each component shown in Table 1 are in parts by mass.

[0156] Example 1 (Preparation of acrylic prepolymer solution) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 5 parts by mass of n-butyl acrylate (BA), 95 parts by mass of n-octyl acrylate (NOAA), 0.25 parts by mass of a photopolymerization initiator (trade name "Omnirad 819", manufactured by IGM Resins Italia Srl), and 0.05 parts by mass of a photopolymerization initiator (trade name "Omnirad 184", manufactured by IGM Resins Italia Srl) were added, and then nitrogen gas was introduced and substituted with nitrogen for about 20 minutes while stirring. Thereafter, nitrogen gas was introduced at 5 mW / cm. 2 The reaction rate was adjusted to 5 to 15%, and an acrylic prepolymer solution was obtained.

[0157] (Formation of adhesive sheet) To the acrylic prepolymer solution, 0.5 parts by mass of a photodegradable compound (1) represented by the above formula (1-1) as a crosslinking agent and 2 parts by mass of t-butylcatechol (TBC) (polymerization inhibitor (1)) as a polymerization inhibitor were added and stirred to prepare a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was applied to the release-treated surface of a release liner (trade name "MRE38", manufactured by Mitsubishi Chemical Corporation, a polyethylene terephthalate film with one side treated for release, thickness 38 μm) to form a pressure-sensitive adhesive composition layer, and the release-treated surface of a release liner (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation) was laminated onto the pressure-sensitive adhesive composition layer. Next, the pressure-sensitive adhesive composition was illuminated with a black light at 2.5 mW / cm. 2 The cumulative amount of ultraviolet light is 2400mJ / cm 2 Polymerization was carried out by irradiating the polymer until the temperature reached a temperature of 1000° C., thereby producing an adhesive sheet (thickness: 50 μm) containing the polymer (a1) and (b) components.

[0158] Example 2 A pressure-sensitive adhesive sheet containing polymers (a1) and (b) was prepared in the same manner as in Example 1, except that the amount of photodegradable compound (1) was 1 part by mass.

[0159] Example 3 A pressure-sensitive adhesive sheet containing polymers (a1) and (b) was prepared in the same manner as in Example 1, except that the amount of photodegradable compound (1) added was 2 parts by mass.

[0160] Example 4 A pressure-sensitive adhesive sheet containing polymer (a1) was prepared in the same manner as in Example 3, except that the polymerization inhibitor (1) was not blended. A solution prepared by dissolving 4 parts by mass of polymerization inhibitor (1) in 36 parts by mass of ethyl acetate was then applied to the entire surface of the obtained pressure-sensitive adhesive sheet to impregnate the sheet with the solution, and after 5 minutes had elapsed, the sheet was dried at 80°C for 5 minutes to prepare a pressure-sensitive adhesive sheet containing polymers (a1) and (b).

[0161] Comparative Example 1 An adhesive sheet was produced in the same manner as in Example 3, except that nonanediol diacrylate (NDDA) was used as the crosslinking agent instead of the photodegradable compound (1) and the polymerization inhibitor (1) was not used.

[0162] Comparative Example 2 A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the polymerization inhibitor (1) was not used.

[0163] Comparative Example 3 A pressure-sensitive adhesive sheet was produced in the same manner as in Example 2, except that the polymerization inhibitor (1) was not used.

[0164] Comparative Example 4 A pressure-sensitive adhesive sheet was produced in the same manner as in Example 3, except that the polymerization inhibitor (1) was not used.

[0165] Comparative Example 5 A pressure-sensitive adhesive sheet was produced in the same manner as in Example 3, except that nonanediol diacrylate (NDDA) was used as the crosslinking agent instead of the photodegradable compound (1).

[0166] Example 5 An adhesive sheet containing the polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 1 part by mass of the photodegradable compound (2) represented by the above formula (1-4) was used as the crosslinking agent instead of 0.5 parts by mass of the photodegradable compound (1).

[0167] Example 6 An adhesive sheet containing the polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 0.45 parts by mass of the photodegradable compound (3) represented by the above formula (1-2) was used as the crosslinking agent instead of 0.5 parts by mass of the photodegradable compound (1).

[0168] Example 7 An adhesive sheet was prepared in the same manner as in Example 1, except that 0.7 parts by mass of the photodegradable compound (4) represented by the above formula (2-2) was used as the crosslinking agent instead of 0.5 parts by mass of the photodegradable compound (1).

[0169] Example 8 An adhesive sheet containing the polymers (a1) and (b) was prepared in the same manner as in Example 1, except that 0.84 parts by mass of the photodegradable compound (5) represented by the above formula (3) (k = 2 to 5) was used as the crosslinking agent instead of 0.5 parts by mass of the photodegradable compound (1).

[0170] Example 9 An adhesive sheet containing the polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 0.6 parts by mass of the photodegradable compound (6) represented by the above formula (1-3) was used as the crosslinking agent instead of 0.5 parts by mass of the photodegradable compound (1).

[0171] Example 10 An adhesive sheet containing the polymers (a1) and (b) was prepared in the same manner as in Example 1, except that 1.25 parts by mass of the photodegradable compound (7) represented by the above formula (2-3) was used as the crosslinking agent instead of 0.5 parts by mass of the photodegradable compound (1).

[0172] Example 11 An adhesive sheet containing polymers (a1) and (b) was prepared in the same manner as in Example 1, except that 4.7 parts by mass of a polymerization inhibitor (2) under the trade name "Irganox 1135" (manufactured by BASF Japan Ltd., a compound represented by the formula below) was used instead of 2 parts by mass of the polymerization inhibitor (1). [ka]

[0173] Example 12 An adhesive sheet containing polymers (a1) and (b) was prepared in the same manner as in Example 1, except that 6.4 parts by mass of a polymerization inhibitor (3) under the trade name "Irganox 1076" (manufactured by BASF Japan Ltd., a compound represented by the formula below) was used instead of 2 parts by mass of the polymerization inhibitor (1). [ka]

[0174] Example 13 An adhesive sheet containing polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 2 parts by mass of butyl gallate (a compound represented by the following formula) was used as polymerization inhibitor (4) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0175] Example 14 An adhesive sheet containing polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 3.5 parts by mass of methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (a compound represented by the following formula) was used as polymerization inhibitor (5) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0176] Example 15 An adhesive sheet containing polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 3 parts by mass of 2,5-di-tert-amylhydroquinone (a compound represented by the formula below) was used as polymerization inhibitor (6) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0177] Example 16 An adhesive sheet containing polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 2.8 parts by mass of 2,6-di-tert-butyl-p-cresol (a compound represented by the following formula) was used as polymerization inhibitor (7) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0178] Example 17 An adhesive sheet containing polymers (a1) and (b) was prepared in the same manner as in Example 1, except that 2.8 parts by mass of 4-(hexyloxy)-2,3,6-trimethylphenol (a compound represented by the formula below) was used as polymerization inhibitor (8) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0179] Example 18 An adhesive sheet containing polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 2.7 parts by mass of 2,5-di-tert-butylhydroquinone (a compound represented by the formula below) was used as polymerization inhibitor (9) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0180] Example 19 An adhesive sheet containing polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 2 parts by mass of tert-butylhydroquinone (a compound represented by the following formula) was used as polymerization inhibitor (10) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0181] Example 20 An adhesive sheet containing polymer (a1) and (b) components was prepared in the same manner as in Example 1, except that 4.9 parts by mass of 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (a compound represented by the formula below) was used as polymerization inhibitor (11) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0182] Example 21 A pressure-sensitive adhesive sheet containing polymers (a1) and (b) was prepared in the same manner as in Example 1, except that 4.1 parts by mass of dodecyl gallate (a compound represented by the following formula) was used as polymerization inhibitor (12) instead of 2 parts by mass of polymerization inhibitor (1). [ka]

[0183] Example 22 (Preparation of emulsion-based polymer solution) A monomer emulsion was prepared by blending 67 parts by mass of 2-ethylhexyl acrylate (2EHA), 30 parts by mass of n-butyl acrylate (BA), 3 parts by mass of acrylic acid (AA), 3.6 parts by mass of the photodegradable compound (1) represented by the above formula (1-1), 0.02 parts by mass of 1-dodecyl mercaptan (1-LSH) as a chain transfer agent, 2.7 parts by mass of an emulsifier (trade name "Aqualon KH-10", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and 53 parts by mass of ion-exchanged water in a container and then stirring and mixing. Next, 0.3 parts by mass of an emulsifier (trade name "Aqualon KH-10", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 50 parts by mass of ion-exchanged water were added to a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and the atmosphere was replaced with nitrogen at room temperature (25°C) for 1 hour while stirring. Thereafter, 0.1 parts by mass of a polymerization initiator (trade name "VA-057", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and the temperature was raised to 60°C. Next, the monomer emulsion was added dropwise to the reaction vessel over 3 hours, and polymerization was carried out for 3 hours with stirring while maintaining the liquid temperature in the reaction vessel at around 60° C. Thereafter, the mixture was cooled to room temperature, and the pH was adjusted to 7 with 10% aqueous ammonia to obtain an emulsion polymer solution with a solid content of 50% by mass.

[0184] (Formation of adhesive sheet) To the emulsion polymer solution, 0.5 parts by mass of a thickener (trade name "ADEKA NOL UH-450VF" manufactured by ADEKA Corporation) and 5 parts by mass of a polymerization inhibitor (1) were added per 100 parts by mass of the acrylic polymer, and the mixture was stirred and mixed to obtain a pressure-sensitive adhesive composition (solution). This pressure-sensitive adhesive composition (solution) was applied using an applicator to the release-treated surface of a release liner (trade name "CA1" manufactured by Fujiko Co., Ltd., polyethylene terephthalate film with one side treated for release, thickness 50 μm). After heating and drying at 130°C for 3 minutes, the release-treated surface of a release liner (trade name "MRE38" manufactured by Mitsubishi Chemical Corporation, polyethylene terephthalate film with one side treated for release, thickness 38 μm) was attached to produce a pressure-sensitive adhesive sheet (thickness 18 μm) containing polymers (a1) and (b).

[0185] Example 23 (Preparation of Solvent-Based Polymer Solutions) A reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas inlet tube was charged with 99 parts by mass of 2-ethylhexyl acrylate (2EHA), 1 part by mass of 4-hydroxybutyl acrylate (4HBA), 1 part by mass of the photodegradable compound (1) represented by the above formula (1-1), and 236 parts by mass of ethyl acetate, and the mixture was purged with nitrogen at room temperature (25°C) for 1 hour with stirring. 0.2 parts by mass of azobisisobutyronitrile (AIBN) was then added as a polymerization initiator, and the mixture was heated to 60°C and reacted for 4 hours, then heated to 70°C and reacted for 2 hours to prepare a solvent-based polymer solution.

[0186] (Formation of adhesive sheet) To the solvent-based polymer solution, 10 parts by mass of polymerization inhibitor (1) was added per 100 parts by mass of acrylic polymer, and the mixture was stirred and mixed to obtain a pressure-sensitive adhesive composition (solution). This pressure-sensitive adhesive composition (solution) was applied using an applicator to the release-treated surface of a release liner (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation, polyethylene terephthalate film with one side treated for release, thickness 38 μm). After heating and drying at 130°C for 3 minutes, the release-treated surface of a release liner (trade name "MRE38", manufactured by Mitsubishi Chemical Corporation, polyethylene terephthalate film with one side treated for release, thickness 38 μm) was attached to produce a pressure-sensitive adhesive sheet (thickness 18 μm) containing polymers (a1) and (b).

[0187] <Evaluation> The pressure-sensitive adhesive sheets produced in the examples and comparative examples were evaluated as follows before and after UV irradiation. The results are shown in the table below. UV irradiation was carried out by the following method.

[0188] (UV irradiation) For the pressure-sensitive adhesive sheets obtained in Examples 1 to 4, 21 to 23, and the Comparative Example, a UV-LED irradiation device manufactured by Quark Technology (model number "QEL-350-RU6W-CW-MY") was used, and a UV-LED lamp with a wavelength of 340 nm was used as the light source. The cumulative irradiation light amount in the wavelength range of 320 to 390 nm was 20 J / cm. 2 The pressure-sensitive adhesive sheets obtained in Examples 5 to 20 were irradiated with ultraviolet light containing light with a wavelength of 370 nm or less using a high-pressure mercury lamp at an integrated irradiation dose of 10 J / cm. 2 The entire surface of the pressure-sensitive adhesive sheet was irradiated with ultraviolet light.

[0189] (1) Shear storage modulus and glass transition temperature The pressure-sensitive adhesive sheets were laminated to prepare a measurement sample approximately 1.0 mm thick, and dynamic viscoelasticity measurements were performed under the following conditions using an Advanced Rheometric Expansion System (ARES) manufactured by Rheometric Scientific Corp. The shear storage modulus and glass transition temperature (Tg) at -20°C, 25°C, and 60°C were calculated. (Measurement conditions) Deformation mode: Torsion Measurement frequency: 1Hz Heating rate: 5°C / min Measurement temperature: -70~150℃ Shape: Parallel plate 8.0mmφ

[0190] (2) Tensile test The 50 μm thick PSA sheet obtained by laminating as needed was cut into 50 mm × 30 mm pieces, and the release liner was removed to prepare a 30 mm long strip sample. The top and bottom 10 mm portions of this were fixed in the chuck of a tension / compression testing machine (product name "Autograph AGS-50NX", manufactured by Shimadzu Corporation), and a tensile test was performed under the conditions of a chuck distance of 10 mm and a tensile speed of 300 mm / min.

[0191] (3) Young's modulus E From the spectrum obtained in the tensile test, the change in stress σ with respect to strain ε in the elastic deformation region (E=Δσ / Δε) was calculated.

[0192] (4) Breaking elongation The strain at break in the tensile test was taken as the breaking elongation (%).

[0193] [Table 1]

[0194] [Table 2]

[0195] [Table 3]

[0196] [Table 4]

[0197] [Table 5]

[0198] As shown in Tables 1 to 5, the pressure-sensitive adhesive sheets of the examples were exposed to ultraviolet light, and their Young's modulus and shear storage modulus decreased compared to before exposure, and their elongation at break increased, resulting in changes in their physical properties. Therefore, it was determined that the pressure-sensitive adhesive sheets of the examples were usable as pressure-sensitive adhesive sheets that were superior in handleability before exposure to ultraviolet light compared to after exposure to ultraviolet light, and superior in flexibility after exposure to ultraviolet light.

[0199] Variations of the invention according to the present disclosure are described below. [Appendix 1] A pressure-sensitive adhesive and / or adhesive containing the following components (a) and (b): Component (a): a polymer (a1) having a reversibly decomposable bond that can be cleaved by an external stimulus and then recombined, the reversibly decomposable bond being a C—C bond or a C—O bond at the end of the molecule, and / or a compound (a2) capable of introducing the reversibly decomposable bond into a polymer. Component (b): a compound reactive with at least one of the groups generated by the cleavage [Appendix 2] The pressure-sensitive adhesive and / or adhesive according to Appendix 1, wherein the component (a) comprises the polymer (a1), and the polymer (a1) comprises a crosslinking moiety having the reversibly degradable bond. [Appendix 3] The pressure-sensitive adhesive and / or adhesive according to Appendix 2, wherein the number of atoms in the linear chain at the crosslinked site is 6 or more. [Appendix 4] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 3, wherein the polymer (a1) contains a structure derived from the compound (a2), and the compound (a2) is a polyfunctional compound having the reversibly decomposable bond in its main chain and reactive functional groups at both ends. [Appendix 5] The pressure-sensitive adhesive and / or adhesive according to Appendix 4, wherein the polyfunctional compound is a di(meth)acrylate compound having a (meth)acryloyl group as the reactive functional group. [Appendix 6] The pressure-sensitive adhesive and / or adhesive according to Appendix 4 or 5, wherein the polyfunctional compound is capable of reacting with light and / or heat having a wavelength of 370 nm or more. [Appendix 7] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 6, wherein the reversibly degradable bond can be cleaved by light with a wavelength of less than 370 nm. [Appendix 8] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 7, wherein the reversibly decomposable bond is -OCC(=O)-. [Appendix 9] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 8, wherein the component (b) is a compound reactive with either one of the groups generated by the cleavage. [Appendix 10] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 9, wherein the component (b) is a compound having a phenolic hydroxyl group. [Appendix 11] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 9, wherein the component (b) is a compound having a primary amino group or a secondary amino group. [Appendix 12] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 11, wherein the modulus of elasticity in at least a partial region is reduced by the external stimulus. [Appendix 13] The pressure-sensitive adhesive and / or adhesive according to any one of Appendices 1 to 12, which is used for optical applications. [Appendix 14] An adhesive sheet using the adhesive and / or bonding agent according to any one of Appendices 1 to 13. [Explanation of symbols]

[0200] 1. Pressure sensitive adhesive layer or adhesive layer 2 Release liner 10. Adhesive sheet or adhesive sheet with release liner 11 One Edge 12 Other edge 21 External Stimulation Area 22 Area without external stimulation 31 Boundary

Claims

1. A pressure-sensitive adhesive and / or adhesive comprising the following components (a) and (b): Component (a): a polymer (a1) having a reversibly decomposable bond that can be cleaved by an external stimulus and then recombined, the reversibly decomposable bond being a C—C bond or a C—O bond at the end of the molecule, and / or a compound (a2) capable of introducing the reversibly decomposable bond into a polymer. Component (b): a compound reactive with at least one of the groups generated by the cleavage

2. The pressure-sensitive adhesive and / or adhesive according to claim 1 , wherein the component (a) comprises the polymer (a1), and the polymer (a1) comprises a crosslinking moiety having the reversibly degradable bond.

3. The pressure-sensitive adhesive and / or adhesive according to claim 2 , wherein the number of atoms in the linear chain at the crosslinked site is 6 or more.

4. The pressure-sensitive adhesive and / or adhesive according to claim 1 or 2, wherein the polymer (a1) contains a structure derived from the compound (a2), and the compound (a2) is a polyfunctional compound having the reversibly decomposable bond in its main chain and reactive functional groups at both ends.

5. The pressure-sensitive adhesive and / or adhesive according to claim 4 , wherein the polyfunctional compound is a di(meth)acrylate compound having a (meth)acryloyl group as the reactive functional group.

6. The pressure-sensitive adhesive and / or adhesive according to claim 4 , wherein the polyfunctional compound is capable of reacting with light and / or heat having a wavelength of 370 nm or more.

7. The pressure-sensitive adhesive and / or adhesive according to claim 1 or 2, wherein the reversibly degradable bond can be cleaved by light with a wavelength of less than 370 nm.

8. The pressure-sensitive adhesive and / or adhesive according to claim 1 or 2, wherein the reversibly decomposable bond is -O-C-C(=O)-.

9. The pressure-sensitive adhesive and / or adhesive according to claim 1 or 2, wherein the component (b) is a compound reactive with either one of the groups generated by the cleavage.

10. 3. The pressure-sensitive adhesive and / or adhesive according to claim 1, wherein the component (b) is a compound having a phenolic hydroxyl group.

11. 3. The pressure-sensitive adhesive and / or adhesive according to claim 1, wherein the component (b) is a compound having a primary amino group or a secondary amino group.

12. The pressure-sensitive adhesive and / or adhesive according to claim 1 or 2, wherein the modulus of elasticity of at least a portion of the region is reduced by the external stimulus.

13. The pressure-sensitive adhesive and / or adhesive according to claim 1 or 2, which is used for optical purposes.

14. A pressure-sensitive adhesive sheet using the pressure-sensitive adhesive and / or adhesive according to claim 1 or 2.

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