Adhesives, adhesive sheets, compositions and compounds

Abstract

The present invention provides adhesives, adhesive sheets, compositions, and compounds whose properties can be altered by light irradiation. [Solution] An adhesive containing a compound formed by bonding a photoisomerized molecule to an adhesive polymer. In this adhesive, it is preferable that cyclodextrin is bonded to the adhesive polymer, and that the cyclodextrin encapsulates the photoisomerized molecule. The photoisomerized molecule is preferably a stilbene derivative. The adhesive polymer is preferably an acrylic polymer.

Description

[Technical Field]

[0001] The present invention relates to adhesives, adhesive sheets, compositions, and compounds whose properties can be changed by light irradiation. [Background technology]

[0002] Adhesive sheets have long been widely used, from consumer labels to the bonding of electronic and aerospace components. In particular, in the bonding process of high-priced products, there is a need for materials that can be easily re-peeled at the interface between the desired component and the adhesive layer to prevent yield reduction due to bonding errors.

[0003] Here, Patent Document 1 discloses a photosensitive composite material in which a hardness modifier is mixed with a polymer compound, and the hardness modifier contains a liquid crystal compound and a photoresponsive compound. In this composite material, a stilbene derivative is used as the photoresponsive compound, and through photoisomerization based on irradiation light of different wavelengths, the liquid crystal compound changes into a first photoisomer that transitions the phase structure from a liquid crystal phase to an isotropic phase, and a second photoisomer that transitions the phase structure of the liquid crystal compound from an isotropic phase to a liquid crystal phase, and at least the first photoisomer has transmittance from a range close to the entire visible light range to the entire visible light range. The liquid crystal compound functions as a plasticization modifier for the polymer compound, and in the photosensitive composite material, a tacky mode (soft state) and an adhesive mode (hard state) are reversibly realized. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6961226 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The photosensitive composite material described in Patent Document 1 changes its adhesiveness upon light irradiation, but it requires a liquid crystal compound, and its applications are limited due to the opacity of the liquid crystal compound during the phase separation process.

[0006] This invention has been made in view of the above-mentioned circumstances, and aims to provide adhesives, adhesive sheets, compositions, and compounds whose properties can be changed by light irradiation. [Means for solving the problem]

[0007] To achieve the above objective, firstly, the present invention provides an adhesive containing a compound in which a photoisomerized molecule is bonded to an adhesive polymer (Invention 1).

[0008] In the compound of the above invention (Invention 1), photoisomerized molecules undergo a photoisomerization reaction upon irradiation with light, causing a change in their molecular structure. Due to the structural change of the compound in which these photoisomerized molecules are bonded to the adhesive polymer, the properties of the adhesive, mainly its tackiness and viscoelasticity, change upon irradiation with light. By utilizing this change in properties, for example, it becomes possible to easily re-peel off the adhesive layer at the interface between the desired member and the adhesive layer.

[0009] In the above invention (Invention 1), it is preferable that the compound contains cyclodextrin (Invention 2).

[0010] In the above inventions (Inventions 1 and 2), it is preferable that cyclodextrin is bound to the adhesive polymer, and that the cyclodextrin encapsulates the photoisomerized molecule (Invention 3).

[0011] In the above inventions (Inventions 1 to 3), it is preferable that the photoisomerized molecule is a stilbene derivative (Invention 4).

[0012] In the above inventions (Inventions 1 to 4), it is preferable that the adhesive polymer is an acrylic polymer (Invention 5).

[0013] In the above inventions (Inventions 1 to 5), it is preferable that the adhesive force changes by light irradiation (Invention 6).

[0014] Second, the present invention provides an adhesive sheet having at least an adhesive layer, wherein the adhesive constituting the adhesive layer is the adhesive (Inventions 1 to 6) (Invention 7).

[0015] In the above invention (Invention 7), it may include a base material and the adhesive layer (Invention 8).

[0016] In the above invention (Invention 7), the adhesive sheet may include two release sheets, and the adhesive layer may be sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets (Invention 9).

[0017] Third, the present invention provides a composition containing a photo-isomerizable molecule and cyclodextrin (Invention 10).

[0018] In the above invention (Invention 10), it is preferable to contain an acrylic polymer (Invention 11).

[0019] Fourth, the present invention provides a compound in which a photo-isomerizable molecule and cyclodextrin are bonded to an acrylic polymer (Invention 12).

Advantages of the Invention

[0020] The adhesive, adhesive sheet, composition, and compound according to the present invention can change their properties by light irradiation.

Brief Description of the Drawings

[0021] [Figure 1] It is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view of an adhesive sheet according to another embodiment of the present invention. [[ID=...]]

Mode for Carrying Out the Invention

[0022] Embodiments of the present invention will be described below. [Adhesive] An adhesive according to one embodiment of the present invention contains a compound (hereinafter sometimes referred to as "compound C") formed by bonding a photoisomerized molecule to an adhesive polymer. In compound C, upon irradiation with light, the photoisomerized molecule undergoes a photoisomerization reaction, and its molecular structure changes. For example, in the case of stereoisomers, it changes from the cis isomer to the trans isomer, or from the trans isomer to the cis isomer. Due to the structural change of compound C, to which the photoisomerized molecule that causes such a photoisomerization reaction is bonded to the adhesive polymer, the properties of the adhesive according to this embodiment change upon light irradiation, mainly in terms of tackiness (including the concept of adhesive strength) and viscoelasticity. By utilizing this change in tackiness and viscoelasticity, for example, it becomes possible to easily re-peel off the adhesive layer at the interface between the desired member and the adhesive layer. The adhesive according to the embodiment can exhibit the above effects without requiring a liquid crystal compound.

[0023] In the adhesive according to this embodiment, it is preferable that compound C has cyclodextrin, or that compound C and a compound in which cyclodextrin is bound to an adhesive polymer are used in combination, and of these, it is preferable that compound C has cyclodextrin, and in particular it is preferable that cyclodextrin is bound to the adhesive polymer and that the cyclodextrin encapsulates the photoisomerized molecule. In this case, the cyclodextrin becomes the host molecule and the photoisomerized molecule becomes the guest molecule, and a host-guest interaction is exhibited.

[0024] If compound C of the adhesive according to this embodiment has the above configuration, light irradiation alters the host-guest interaction, and photoisomerization is converted into a bulk volume change. In addition, guest molecules detach from the host molecules, causing aggregation of guest molecules (photoisomerized molecules) and changes in the entanglement of adhesive polymers, resulting in changes in physical properties near the surface of the adhesive. When an adhesive layer made of such an adhesive is irradiated with light, the interfacial adhesion (adhesion) decreases or, conversely, increases only on the surface irradiated with light. Therefore, it becomes possible to peel off the adhesive (layer) from any adherend while leaving it behind by light irradiation.

[0025] The above is further supported by the fact that the adhesive layer made of the adhesive according to this embodiment bends when light is irradiated from one side. Specifically, when compound C containing cyclodextrin is used, the adhesive layer bends in the direction opposite to the side irradiated with light. On the other hand, when compound C without cyclodextrin is used, the adhesive layer bends in the same direction as the side irradiated with light. Thus, with the adhesive layer made of the adhesive according to this embodiment, it is possible to control the bending direction of the adhesive layer due to light irradiation by the presence or absence of cyclodextrin.

[0026] Furthermore, due to the mechanism of action described above, the adhesive according to this embodiment exhibits little change in elastic modulus at high temperatures (e.g., 80°C) before and after light irradiation. Therefore, it does not liquefy even after light irradiation (or during peeling) and can be removed from the desired adherend without leaving any residue.

[0027] In this embodiment, ultraviolet light is preferred as the light used for photoisomerization of the photoisomerized molecule, specifically light with a wavelength of 180 to 400 nm is preferred, light with a wavelength of 200 to 390 nm is particularly preferred, and light with a wavelength of 220 to 380 nm is even more preferred.

[0028] Here, when a stilbene derivative is used as the photoisomerized molecule, the cis-formation (deassociation) and trans-formation (association) of the stilbene derivative can be controlled at the wavelength of the irradiated light described above. This results in changes to the properties of the adhesive according to this embodiment (such as tackiness and viscoelasticity), and the development of peelability from the adherend and adhesion to the adherend can be reversibly controlled.

[0029] Ultraviolet irradiation can be performed using high-pressure mercury lamps, Heraeus H lamps, xenon lamps, etc., with an illuminance of 10 to 1000 mW / cm². 2 Preferably, the power is 50-500 mW / cm². 2 It is more preferable that the ultraviolet irradiation time is 1 to 60 minutes, and more preferably 3 to 30 minutes. The distance from the light source is preferably 1 to 1000 mm, particularly preferably 4 to 500 mm, and even more preferably 8 to 100 mm.

[0030] 1. Each ingredient (1) Adhesive polymer The adhesive polymer in the adhesive according to this embodiment is not particularly limited, as long as the desired adhesiveness and desired changes in properties such as adhesiveness and viscoelasticity due to light irradiation can be obtained. Examples of adhesive polymers in this embodiment include acrylic polymers, polyester polymers, polyurethane polymers, silicone polymers, and rubber polymers. Among these, acrylic polymers are preferred because they readily provide the desired adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0031] The acrylic polymer may be uncrosslinked or crosslinked, but from the viewpoint of easily obtaining desired changes in properties such as tackiness and viscoelasticity through light irradiation, the uncrosslinked type is preferred. Furthermore, the acrylic polymer may be non-curable by active energy rays or curable by active energy rays, but from the viewpoint of minimizing the change in elastic modulus at high temperatures before and after light irradiation, the non-curable type is preferred. From the perspective of SDGs, the adhesive polymer may be a material with a high biomass content, a material that can be recycled or reused, or a recycled or reused material. Here, "crosslinking" refers to crosslinking by generally irreversible bonds such as covalent bonds.

[0032] Acrylic polymers are obtained by polymerizing acrylic monomers. Compound C in this embodiment is a compound obtained by bonding a photoisomerized molecule to an adhesive polymer, preferably by adding (grafting) a photoisomerized molecule to the side chain of an acrylic polymer, and particularly preferably by adding (grafting) a photoisomerized molecule and cyclodextrin to the side chain of an acrylic polymer. In this case, copolymerization of an acrylic monomer and a photoisomerized molecule having polymerizable groups is preferred, and particularly preferred copolymerization of an acrylic monomer, a photoisomerized molecule having polymerizable groups, and cyclodextrin having polymerizable groups is preferred.

[0033] In this embodiment, the acrylic monomer is preferably a monofunctional acrylic monomer. This makes it possible to obtain a polymer that does not have a branched structure, and makes it easier to obtain the effect of photoisomerization reaction of photoisomerized molecules.

[0034] The acrylic monomers that constitute the acrylic polymer may be used individually or in combination of two or more types. The acrylic polymer is preferably a (meth)acrylic acid ester polymer.

[0035] (Meth)acrylic acid ester polymers preferably contain alkyl (meth)acrylic acid ester as the acrylic monomer units constituting the polymer. This allows for the expression of desired viscoelasticity and good tackiness. The alkyl group may be linear or branched. In this specification, (meth)acrylic acid refers to both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the concept of "polymer" is also included in the concept of "copolymer".

[0036] From the viewpoint of adhesiveness, alkyl (meth)acrylate esters with 1 to 20 carbon atoms in the alkyl group are preferred. Examples of alkyl (meth)acrylate esters with 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. In particular, from the viewpoint of easily obtaining desired properties such as adhesiveness and viscoelasticity, and changes in desired properties due to light irradiation, alkyl (meth)acrylate esters with 4 to 8 carbon atoms in the alkyl group are preferred, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, or isooctyl (meth)acrylate are especially preferred, and n-butyl acrylate or n-butyl methacrylate are even more preferred. These may be used alone or in combination of two or more.

[0037] The (meth)acrylic acid ester polymer preferably contains 0 to 99.99% by mass of (meth)acrylate alkyl ester as the acrylic monomer units constituting the polymer, more preferably 1 to 99.9% by mass, particularly preferably 3 to 99.5% by mass, even more preferably 6 to 99% by mass, and most preferably 9 to 98.5% by mass. This makes it easier to obtain desired properties such as tackiness and viscoelasticity, as well as desired changes in properties due to light irradiation. In systems using (meth)acrylate alkyl ester and (meth)acrylate alkoxy ester described later, the (meth)acrylate alkyl ester preferably contains 1 to 98% by mass, particularly preferably 4 to 95% by mass, and even more preferably 8 to 92% by mass. This makes it easier to obtain desired properties such as tackiness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0038] (Meth)acrylic acid ester polymers may also preferably contain (meth)acrylic acid alkoxy ester as the acrylic monomer units constituting the polymer. This makes it easier to obtain desired properties such as tackiness and viscoelasticity, as well as desired changes in properties due to light irradiation. Examples of (meth)acrylic acid alkoxy esters include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, and 4-methoxybutyl (meth)acrylate. Among these, 2-methoxyethyl (meth)acrylate is preferred, and 2-methoxyethyl acrylate is particularly preferred, from the viewpoint of easily obtaining desired properties such as tackiness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0039] The (meth)acrylic acid ester polymer preferably contains 0 to 99.99% by mass of (meth)acrylic acid alkoxy ester as the acrylic monomer units constituting the polymer, more preferably 1 to 99.9% by mass, particularly preferably 3 to 99% by mass, even more preferably 6 to 98.5% by mass, and most preferably 8 to 98% by mass. This makes it easier to obtain desired properties such as tackiness and viscoelasticity, as well as desired changes in properties due to light irradiation. In systems using the above-mentioned alkyl (meth)acrylic acid ester and (meth)acrylic acid alkoxy ester in combination, the (meth)acrylic acid alkoxy ester preferably contains 1 to 95% by mass, particularly preferably 3 to 92% by mass, and even more preferably 6 to 90% by mass. This makes it easier to obtain desired properties such as tackiness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0040] The (meth)acrylic acid ester polymer may also contain, as monomer units, reactive group-containing monomers having reactive groups in the molecule, alicyclic structure-containing monomers having alicyclic structures in the molecule, aromatic ring-containing monomers having aromatic rings in the molecule, nitrogen atom-containing monomers having nitrogen atoms in the molecule, as well as vinyl acetate, styrene, etc. These may be used individually or in combination of two or more.

[0041] The (meth)acrylic acid ester polymer preferably contains 1 to 99.99% by mass of acrylic monomers as monomer units constituting the polymer, more preferably 25 to 99.9% by mass, particularly preferably 50 to 99.5% by mass, even more preferably 70 to 98.5% by mass, and most preferably 80 to 98% by mass. This makes it easier to obtain desired properties such as adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0042] The polymerization mode of the (meth)acrylic acid ester polymer may be a random copolymer or a block copolymer.

[0043] (2) Photoisomerizable molecules Photoisomerized molecules undergo a photoisomerization reaction upon irradiation with light, resulting in a change in their molecular structure. In this embodiment, the photoisomerized molecule is preferably a stereoisomer. This facilitates the volume change caused by light irradiation described above. In the case of stereoisomers, it is preferable that the change occurs from the cis isomer to the trans isomer, or from the trans isomer to the cis isomer.

[0044] Examples of photoisomerized molecules in this embodiment include alkylstyrene derivatives, azobenzene derivatives, indigo derivatives, and benzaldehyde derivatives, among which alkylstyrene derivatives are preferred, and stilbene derivatives are particularly preferred. By bonding a stilbene derivative to an adhesive polymer, properties such as adhesiveness and viscoelasticity are easily changed by light irradiation, making it possible to easily re-peel off the adhesive layer at the interface between the desired material and the adhesive layer, or to bend the adhesive layer in a predetermined direction. Furthermore, the host-guest interaction with cyclodextrin is well exhibited, allowing the adhesive (layer) to be peeled off from any adherend while remaining on it by light irradiation, and enabling removal from the desired adherend without residue, even after light irradiation (or during peeling), without liquefaction.

[0045] The stilbene derivative is not particularly limited, as long as it has a stilbene skeleton, is bonded to an adhesive polymer via a desired functional group, and possesses photoisomerization capabilities.

[0046] The stilbene derivative before bonding to the adhesive polymer preferably has a polymerizable group and is preferably copolymerized with an acrylic monomer to bond to the adhesive polymer (acrylic polymer). The polymerizable group is not particularly limited as long as it can polymerize with the acryloyl group of the acrylic monomer, but it is preferably a group containing a polymerizable unsaturated double bond, and more preferably an ethylenically unsaturated group. Specifically, it is preferably a (meth)acryloyl group, vinyl group, allyl group, etc., and is particularly preferably a (meth)acryloyl group. The (meth)acryloyl group may also be a functional group derived from (meth)acrylamide. Specifically, the stilbene derivative before bonding to the adhesive polymer is preferably a stilbene (or stilbene derivative) modified with (meth)acrylamide, and is particularly preferably N-(4-styrylphenyl)acrylamide.

[0047] Compound C preferably contains 0.01 to 20% by mass of photoisomerized molecules (especially stilbene derivatives) as monomer units constituting the polymer, more preferably 0.1 to 10% by mass, particularly preferably 0.25 to 8% by mass, even more preferably 0.5 to 5% by mass, and most preferably 0.8 to 2.5% by mass. This makes it easier to obtain desired properties such as adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0048] (3) Cyclodextrin In this specification, "cyclodextrin" may refer to cyclodextrin itself, cyclodextrin having substituents (cyclodextrin derivatives), or cyclodextrin or cyclodextrin derivatives incorporated into a polymer.

[0049] The cyclodextrin may be included in compound C in this embodiment, but it is preferable that it is included in such a way that it encapsulates the photoisomerized molecule, and in particular, it is preferable that it encapsulates the photoisomerized molecule while being bound to the adhesive polymer.

[0050] The cyclodextrin is preferably α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin, and these may have substituents. Among these, β-cyclodextrin is preferred from the viewpoint of more easily obtaining the effects described above, and substituted β-cyclodextrin is particularly preferred.

[0051] The above substituents are obtained by substituting the hydroxyl group of cyclodextrin. Examples of the above substituents include acyl groups, alkyl groups, trityl groups, tosyl groups, trimethylsilane groups, phenyl groups, as well as polyester chains, oxyethylene chains, alkyl chains, ether chains, ester chains, acrylic acid ester chains, etc. Among these, acyl groups are preferred, and acetyl groups are particularly preferred, from the viewpoint of obtaining the aforementioned effects more easily.

[0052] The cyclodextrin before bonding to the adhesive polymer is preferably a polymerizable group (hereinafter sometimes referred to as a "polymerizable cyclodextrin compound"), and is preferably copolymerized with an acrylic monomer to bond to the adhesive polymer (acrylic polymer). The polymerizable group is not particularly limited as long as it can polymerize with the acryloyl group of the acrylic monomer, but it is preferably a group containing a polymerizable unsaturated double bond, and more preferably an ethylenically unsaturated group. Specifically, it is preferably a (meth)acryloyl group, a vinyl group, an allyl group, etc., and is particularly preferably a (meth)acryloyl group. Furthermore, the (meth)acryloyl group may be a functional group derived from (meth)acrylamide. In other words, the cyclodextrin before bonding to the adhesive polymer is preferably a cyclodextrin (or cyclodextrin derivative) modified with (meth)acrylamide.

[0053] In polymerizable cyclodextrin compounds, it is preferable that no hydroxyl groups of cyclodextrin remain, and it is preferable that all hydroxyl groups of cyclodextrin other than those in the polymerizable portion are replaced with acyl groups, particularly acetyl groups.

[0054] It is preferable that the polymerizable cyclodextrin compound has one polymerizable group per cyclodextrin molecule. This makes it possible to create a copolymer of the acrylic monomer and the polymerizable cyclodextrin compound that does not have a branched structure, resulting in excellent solvent solubility.

[0055] From the above viewpoint, it is preferable that the content of polymerizable cyclodextrin compounds having two or more polymerizable groups per molecule in the polymerizable cyclodextrin compound is small. Specifically, it is preferable that it be 0.1% by mass or less, particularly 0.01% by mass or less, and even more preferably 0.001% by mass or less.

[0056] In this embodiment, the polymerizable cyclodextrin compound is preferably the compound represented by the following formula (1). [ka] (R in equation (1) above) 1 R represents a hydrogen atom or a methyl group. 2 '' represents a hydrocarbon containing O, NH, or O, a hydrocarbon containing NH, or a hydrocarbon containing both O and NH. 'CD' represents α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, or their derivatives.

[0057] Examples of the above-mentioned "hydrocarbons containing NH" include, with the right side bonded to CD, -CH2-NH-CH2-, -NH-CH2-O-CH2-, -O-CH2-NH-CH2-, -CH2-NH-CH2-O-, -O-CH2-NH-CH2-O-, -CH2-O-CO-NH-CH2-O-, and -CH2-O-CO-NH-C2H4-O-. Among these, -NH-CH2-O-CH2- is particularly preferred from the viewpoint of being able to more easily obtain the aforementioned effects.

[0058] In formula (1) above, CD is preferably a derivative of β-cyclodextrin, and in particular, the hydroxyl group of cyclodextrin is R 2 It is preferable that the β-cyclodextrin derivative is such that all parts except the bonded portion are substituted with acyl groups, particularly acetyl groups.

[0059] The average molecular weight (Mw) of the polymerizable cyclodextrin compound is preferably 100 to 5000, more preferably 300 to 4000, particularly preferably 600 to 3500, and even more preferably 800 to 3000. This results in superior effects and excellent film strength. The weight-average molecular weight used herein is the value on a standard polystyrene basis, measured by gel permeation chromatography (GPC).

[0060] Furthermore, from the viewpoint of manufacturing and procurement, monomers or dimers are preferred for polymerizable cyclodextrin compounds.

[0061] Compound C preferably contains 0.01 to 50% by mass of polymerizable cyclodextrin compounds as monomer units constituting the polymer, more preferably 0.1 to 25% by mass, particularly preferably 0.25 to 10% by mass, even more preferably 0.5 to 5% by mass, and most preferably 0.8 to 2.5% by mass. This makes it easier to obtain desired properties such as adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0062] (4) Other ingredients The adhesive according to this embodiment may optionally contain various additives commonly used in adhesives, such as crosslinking agents, silane coupling agents, rust inhibitors, ultraviolet absorbers, infrared absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, refractive index adjusters, colorants, fillers, and the like.

[0063] The adhesive according to this embodiment does not need to contain a liquid crystal compound, but it may contain one. The liquid crystal compound content is preferably 10% by mass or less, particularly preferably 5% by mass or less, even more preferably 1% by mass or less, and most preferably 0% by mass.

[0064] 2. Method for producing compound C Compound C in this embodiment is preferably produced by copolymerizing an acrylic monomer with a photoisomerized molecule, and more preferably by copolymerizing an acrylic monomer with a photoisomerized molecule with a polymerizable cyclodextrin compound. The polymerization method may be solution polymerization or solvent-free polymerization. When copolymerizing an acrylic monomer with a photoisomerized molecule, solution polymerization is preferred, and when copolymerizing a photoisomerized molecule with a polymerizable cyclodextrin compound, solvent-free polymerization, particularly bulk polymerization, is preferred.

[0065] In solution polymerization, compound C (a coating solution of compound C) can be produced by polymerizing a mixture of monomers constituting the polymer (acrylic monomer / photoisomerized molecule) in a polymerization solvent using a conventional radical polymerization method, optionally with a polymerization initiator. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more may be used in combination. Examples of polymerization initiators include azo compounds (e.g., azobisisobutyronitrile) and organic peroxides, and two or more may be used in combination.

[0066] In the polymerization process, ultrasonic treatment is also preferred for stirring the monomer mixture. The stirring time by ultrasonic treatment is preferably 5 to 120 minutes. There are no particular restrictions on the ultrasonic irradiation conditions, but it is preferable to use a frequency of 20 to 40 kHz.

[0067] In the case of bulk polymerization, preferably, the photoisomerized molecule and the polymerizable cyclodextrin compound are dissolved in a mixture of one or more acrylic monomers, and the mixture is stirred to obtain a homogeneous solution. It is also preferable to perform ultrasonic treatment during this stirring. The stirring time by ultrasonic treatment is preferably 5 to 120 minutes. There are no particular restrictions on the ultrasonic irradiation conditions, but it is preferable to perform the irradiation at a frequency of 20 to 40 kHz.

[0068] Once a uniform mixture is obtained, it is subjected to heat treatment to form a prepolymer with the desired viscosity, preferably a coatable viscosity. The heating temperature for the heat treatment is preferably 50 to 100°C, and particularly preferably 55 to 90°C. The heating time for the heat treatment is preferably 5 to 30 minutes, and particularly preferably 10 to 20 minutes.

[0069] After applying the above prepolymer to the desired object, the material is heated again to complete polymerization and obtain compound C (an adhesive layer consisting of an adhesive containing compound C). The heating temperature for this heat treatment is preferably 40 to 100°C, and particularly preferably 50 to 80°C. The heating time for this heat treatment is preferably 30 to 1200 minutes, and particularly preferably 180 to 900 minutes. Subsequently, it is preferable to remove residual liquid monomer by heating under reduced pressure, if desired.

[0070] 3. Composition of the adhesive In the adhesive according to this embodiment, compound C may be used alone or in combination of two or more types.

[0071] The content of compound C in the adhesive according to this embodiment is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, particularly preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass. This makes it easier to obtain desired properties such as adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation.

[0072] 4. Physical properties (1) Weight-average molecular weight (Mw) of compound C The weight-average molecular weight (Mw) of compound C is preferably 5,000 to 5 million, more preferably 10,000 to 2.5 million, particularly preferably 50,000 to 2 million, even more preferably 100,000 to 1.5 million, most preferably 150,000 to 1.2 million, and most preferably 180,000 to 1 million. This makes it easier to obtain desired properties such as adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation. The weight-average molecular weight in this specification is the value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0073] (2) Glass transition temperature (Tg) of compound C The glass transition temperature (Tg) of compound C is preferably -100 to 100°C, more preferably -70 to 80°C, particularly preferably -50 to 60°C, and even more preferably -40 to 40°C. This makes it easier to obtain desired properties such as adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation. The method for measuring the glass transition temperature (Tg) in this specification is as shown in the test examples described later.

[0074] (3) Storage modulus G' of the adhesive The storage modulus G'(25) at 25°C of the adhesive according to this embodiment (composed solely of compound C, in which case it is compound C; the same applies hereinafter) is preferably 0.01 to 10 MPa, more preferably 0.02 to 7 MPa, particularly preferably 0.03 to 4 MPa, and even more preferably 0.04 to 2 MPa. As a result, the adhesive layer made of this adhesive can exhibit good film strength and excellent processability. The method for measuring the storage modulus in this specification is as shown in the test examples described later.

[0075] The storage modulus G'(UV25) of the adhesive according to this embodiment at 25°C after irradiation with ultraviolet light under the following conditions is preferably 0.005 to 10 MPa, more preferably 0.007 to 7 MPa, particularly preferably 0.009 to 4 MPa, and even more preferably 0.01 to 2 MPa. As a result, the adhesive layer made of this adhesive can exhibit good film strength even after ultraviolet irradiation (after photoisomerization) and can be peeled off from the adherend without residue.

[0076] <Ultraviolet irradiation conditions> UV wavelength: 365nm Illuminance: 80mW / cm 2 Irradiation time: 120 seconds Distance from light source: 10mm

[0077] The ratio of the storage modulus G'(UV25) of the adhesive at 25°C after UV irradiation to the storage modulus G'(25) of the adhesive at 25°C according to this embodiment (%; (storage modulus G'(UV25) / storage modulus G'(25)) × 100) is preferably 1 to 1000%, more preferably 10 to 800%, particularly preferably 15 to 600%, even more preferably 20 to 400%, and most preferably 25 to 200%. As a result, the adhesive layer made of the adhesive can maintain stable film strength before and after UV irradiation (before and after photoisomerization) and can be peeled off from the adherend without residue.

[0078] The storage modulus G'(80) of the adhesive according to this embodiment at 80°C is preferably 0.001 to 8 MPa, more preferably 0.005 to 4 MPa, particularly preferably 0.010 to 1 MPa, even more preferably 0.015 to 0.5 MPa, and most preferably 0.020 to 0.1 MPa. As a result, the adhesive layer made of this adhesive can exhibit good film strength even at high temperatures.

[0079] For the adhesive according to this embodiment, the storage modulus G'(UV80) of the adhesive at 80°C after irradiation with ultraviolet light under the above conditions is preferably 0.001 to 8 MPa, more preferably 0.004 to 4 MPa, particularly preferably 0.008 to 1 MPa, even more preferably 0.010 to 0.6 MPa, and most preferably 0.012 to 0.2 MPa. As a result, the adhesive layer made of this adhesive can exhibit good film strength even at high temperatures after ultraviolet irradiation and can be peeled off from the adherend without residue.

[0080] The ratio of the storage modulus G'(UV80) of the adhesive at 80°C after UV irradiation to the storage modulus G'(80) of the adhesive according to this embodiment (%; (storage modulus G'(UV80) / storage modulus G'(80)) × 100) is preferably 5 to 2000%, more preferably 10 to 1000%, particularly preferably 20 to 600%, even more preferably 30 to 300%, and most preferably 40 to 170%. As a result, the adhesive layer made of this adhesive can maintain stable film strength before and after UV irradiation (before and after photoisomerization), even at high temperatures.

[0081] [Adhesive sheet] An adhesive sheet according to one embodiment of the present invention comprises at least an adhesive layer, and preferably, a release sheet is laminated on one or both sides of the adhesive layer. A specific configuration of an example of an adhesive sheet according to this embodiment is shown in Figures 1 and 2.

[0082] 1. Structure As shown in Figure 1, the adhesive sheet 1A according to the first embodiment consists of, from bottom to top, a release sheet 12, an adhesive layer 11 laminated on the release surface of the release sheet 12, and a base material 13 laminated on the adhesive layer 11.

[0083] Furthermore, as shown in Figure 2, the adhesive sheet 1B according to the second embodiment consists of two release sheets 12a and 12b, and an adhesive layer 11 sandwiched between the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. In this specification, the release surface of a release sheet refers to the surface of the release sheet that has release properties, and includes both surfaces that have undergone a release treatment and surfaces that exhibit release properties even without a release treatment.

[0084] In both adhesive sheets 1A and 1B, the adhesive layer 11 consists of the adhesive described above. The thickness of the adhesive layer 11 (a value measured in accordance with JIS K7130) is appropriately determined according to the intended use of the adhesive sheets 1A and 1B, but is preferably 1 to 1000 μm, more preferably 5 to 500 μm, particularly preferably 10 to 250 μm, even more preferably 20 to 150 μm, and among those preferably 25 to 100 μm, and especially preferably 30 to 70 μm. This makes it easier to obtain desired properties such as adhesiveness and viscoelasticity, as well as desired changes in properties due to light irradiation. The adhesive layer 11 may be formed as a single layer or as multiple layers laminated together.

[0085] There are no particular restrictions on the base material 13; any base material commonly used for adhesive sheets can be used. Examples include plastic films or laminates thereof, such as polyester films like polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films like polyethylene films and polypropylene films; cellophane; diacetylcellulose films, triacetylcellulose films, acetylcellulose butyrate films; polyvinyl chloride films, polyvinylidene chloride films, polyvinyl alcohol films, ethylene-vinyl acetate copolymer films; polystyrene films, polycarbonate films, polymethylpentene films, polysulfone films, polyetheretherketone films, polyethersulfone films, polyetherimide films, fluororesin films, polyamide films, acrylic resin films, polyurethane resin films, norbornene polymer films, cyclic olefin polymer films, cyclic conjugated diene polymer films, and vinyl alicyclic hydrocarbon polymer films; woven or nonwoven fabrics using fibers such as rayon, acrylic, and polyester; papers such as fine paper, glassine paper, impregnated paper, and coated paper; metal foils such as aluminum and copper; foams such as urethane foam and polyethylene foam; and laminates of two or more of these.

[0086] The base material 13 may be any desired optical component. Examples of optical components include polarizing plates (polarizing films), polarizers, phase difference plates (phase difference films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, and semi-transparent reflective films.

[0087] Furthermore, from an SDG perspective, the base material 13 may be a material with a high biomass content, a material that can be recycled or reused, or a material that has already been recycled or reused.

[0088] The thickness of the substrate 13 varies depending on its type and application, but is generally preferably 10 to 300 μm, particularly preferably 20 to 200 μm, and even more preferably 30 to 100 μm.

[0089] The release sheets 12, 12a, and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 11) is used.

[0090] Examples of release sheets 12, 12a, and 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylic acid copolymer film, ethylene-(meth)acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. Crosslinked films of these materials can also be used. Furthermore, laminated films of these materials may also be used. From an SDG perspective, release sheets 12, 12a, and 12b may be made of materials with a high biomass content, materials that can be recycled or reused, or recycled or reused materials.

[0091] It is preferable that the release surfaces of the release sheets 12, 12a, and 12b (especially the surfaces in contact with the adhesive layer 11) are subjected to a release treatment. Examples of release agents used in the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax-based release agents. It is preferable that one of the release sheets 12a and 12b be a heavy-release type with high release force, and the other release sheet be a light-release type with low release force.

[0092] There are no particular restrictions on the thickness of the release sheets 12, 12a, and 12b, but they are generally preferably 20 to 200 μm, and more preferably 30 to 120 μm.

[0093] 2. Manufacturing method To manufacture the above-mentioned adhesive sheet 1A, preferably, the aforementioned compound C coating solution or prepolymer is applied to the release surface of the release sheet 12, and an adhesive layer is formed by heat treatment or the like, and then the base material 13 is laminated onto the adhesive layer. Alternatively, the aforementioned compound C coating solution or prepolymer is applied to one side of the base material 13, and an adhesive layer is formed by heat treatment or the like, and then the release surface of the release sheet 12 is laminated onto the adhesive layer. The conditions for the heat treatment are as described above.

[0094] Furthermore, in order to manufacture the adhesive sheet 1B, the aforementioned compound C coating solution or prepolymer is applied to the release surface of one release sheet 12a (or 12b), and an adhesive layer is formed by heat treatment or the like. Then, the release surface of the other release sheet 12b (or 12a) is laminated onto the adhesive layer.

[0095] For example, methods such as bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating can be used to apply the coating solution or prepolymer of compound C mentioned above.

[0096] 3. Physical properties (1) Adhesive strength In the laminate obtained by bonding two polyethylene terephthalate films via the adhesive layer of the adhesive sheet according to this embodiment, the adhesive strength (initial adhesive strength; IA) measured by the T-type peel method is preferably 0.01 to 50 N / 10 mm, more preferably 0.02 to 40 N / 10 mm, particularly preferably 0.04 to 30 N / 10 mm, even more preferably 0.06 to 20 N / 10 mm, and most preferably 0.08 to 10 N / 10 mm. This provides the desired adhesive durability or good reworkability.

[0097] The adhesive strength (UVA) obtained by the T-type peel method after irradiating one side of the above laminate with ultraviolet light under the following conditions is preferably 0.01 to 50 N / 10 mm, more preferably 0.02 to 40 N / 10 mm, particularly preferably 0.04 to 30 N / 10 mm, even more preferably 0.06 to 15 N / 10 mm, and most preferably 0.07 to 7.5 N / 10 mm. If the lower limit of the adhesive strength is as described above, the adhesive sheet (adhesive layer) can be reused even after ultraviolet irradiation (after photoisomerization). Furthermore, if the upper limit of the adhesive strength is as described above, good reworkability can be obtained even after ultraviolet irradiation (after photoisomerization).

[0098] <Ultraviolet irradiation conditions> UV wavelength: 365nm Illuminance: 80mW / cm 2 Irradiation time: 5 minutes Distance from light source: 10mm

[0099] The ratio (%;{|Adhesion (IA) - Adhesion (UVA)| / Adhesion (IA)}×100) of the absolute change in adhesive strength (UVA) after ultraviolet irradiation to the initial adhesive strength (IA) of the adhesive sheet according to this embodiment is preferably 0.1 to 350%, more preferably 0.5 to 300%, particularly preferably 1 to 200%, even more preferably 2 to 100%, and most preferably 3 to 50%. This makes it possible to control the desired tackiness and peelability from the adherend before and after ultraviolet irradiation (before and after photoisomerization).

[0100] After irradiating the laminate with ultraviolet light under the above conditions, the surface of the adhesive layer from which one of the substrates has peeled off is irradiated with ultraviolet light under the following conditions, and a substrate of the same type as the above substrate is attached to the ultraviolet-irradiated surface of the adhesive layer. When the adhesive strength (RUVA) of the resulting laminate is measured by the T-type peel method, it is preferable that the ratio (%) of the adhesive strength (RUVA) to the initial adhesive strength (IA) is 80% or more. This makes it possible to restore the adhesive strength of the adhesive layer, which has decreased due to ultraviolet irradiation of a predetermined wavelength, by further irradiation of ultraviolet light of a predetermined wavelength.

[0101] <Ultraviolet irradiation conditions> Ultraviolet wavelength: 254nm Illuminance: 80mW / cm 2 Irradiation time: 5 minutes Distance from light source: 10mm

[0102] Herein, the adhesive strength referred to in this specification is the adhesive strength measured by the T-type peel method in accordance with JIS K6854-3:1999, with the measurement sample having a measurement width of 10 mm and measured at a peeling speed of 300 mm / min. Specifically, this is as shown in the test examples described later.

[0103] (2) Haze value The haze value (initial haze value; IH) of the adhesive layer of the adhesive sheet according to this embodiment is preferably 50% or less, preferably 25% or less, particularly preferably 10% or less, even more preferably 5% or less, most preferably 2% or less, and especially preferably 1.5% or less. This results in an adhesive layer with excellent transparency, making it suitable for use in displays and the like. On the other hand, the lower limit of the above haze value (IH) is not particularly limited, but is usually 0% or more, preferably 0.001% or more, preferably 0.01% or more, particularly preferably 0.05% or more, and even more preferably 0.1% or more. Here, the haze value in this specification is the value measured in accordance with JIS K7136:2000.

[0104] In this embodiment, the haze value (UVH) of the adhesive layer of the adhesive sheet after irradiation with ultraviolet light under the above conditions is preferably 50% or less as a lower limit, preferably 25% or less, particularly preferably 10% or less, even more preferably 5% or less, most preferably 2% or less, and especially preferably 1.5% or less as a lower limit and upper limit. As a result, even after ultraviolet irradiation (after photoisomerization), the adhesive layer exhibits excellent transparency and is suitable for use in displays and the like. The adhesive according to this embodiment can achieve this haze value. On the other hand, the lower limit of the haze value (IH) is not particularly limited, but is usually 0% or more, preferably 0.001% or more, preferably 0.01% or more, particularly preferably 0.05% or more, and even more preferably 0.1% or more.

[0105] The ratio (%; (Haze value (UVH) / Haze value (IH)) × 100) of the haze value (UVH) of the adhesive layer of the adhesive sheet according to this embodiment to the haze value (IH) of the adhesive layer after ultraviolet irradiation is preferably 10 to 500%, more preferably 25 to 240%, particularly preferably 50 to 180%, even more preferably 65 to 150%, and most preferably 80 to 120%. This allows the adhesive layer to maintain stable transparency before and after ultraviolet irradiation (before and after photoisomerization). The adhesive according to this embodiment can achieve this ratio.

[0106] (3) Parallel light transmittance The parallel light transmittance (350PT) of the adhesive layer of the adhesive sheet according to this embodiment for light with a wavelength of 350 nm is preferably 0.001 to 50%, more preferably 0.001 to 35%, particularly preferably 0.01 to 20%, even more preferably 0.05 to 10%, and most preferably 0.1 to 5%. This allows the photoisomerization reaction by ultraviolet irradiation to proceed efficiently. The method for measuring parallel light transmittance in this specification is as shown in the test examples described later.

[0107] The parallel light transmittance (400PT) of the adhesive layer of the adhesive sheet according to this embodiment for light with a wavelength of 400 nm is preferably 50% to 100%, more preferably 55% to 96%, particularly preferably 60% to 92%, even more preferably 65% ​​to 88%, and most preferably 70% to 83%. This makes it easier to obtain good transparency of the adhesive sheet in the visible light range.

[0108] The parallel light transmittance (550PT) of the adhesive layer of the adhesive sheet according to this embodiment for light with a wavelength of 550 nm is preferably 50% to 100%, more preferably 55% to 97%, particularly preferably 60% to 94%, even more preferably 65% ​​to 90%, and most preferably 70% to 88%. This makes it easier to obtain good transparency of the adhesive sheet in the visible light range.

[0109] The ratio of the parallel light transmittance (400PT) of light at a wavelength of 400 nm to the parallel light transmittance (350PT) of light at a wavelength of 350 nm in the adhesive layer of the adhesive sheet according to this embodiment ((parallel light transmittance (400PT) / parallel light transmittance (350PT)) × 100) is preferably 1.2 to 1 million, more preferably 2 to 800,000, particularly preferably 5 to 600,000, even more preferably 10 to 400,000, and most preferably 15 to 200,000. This achieves both easy peelability due to photoisomerization reaction and transparency of the adhesive sheet.

[0110] 4. Uses of adhesive sheets The adhesive layer of the adhesive sheet according to this embodiment can be peeled off without residue from one adherend while leaving the adhesive layer on the other adherend by light irradiation. Therefore, it can be preferably used, for example, in applications where expensive components need to be bonded in a repositionable manner. Furthermore, since the adhesive layer of the adhesive sheet according to this embodiment can maintain high transparency before and after light irradiation, it can be preferably used in applications where optical components or the like are bonded. Accordingly, the adhesive sheet according to this embodiment can be preferably used in the manufacture of displays and the like.

[0111] [Composition] A composition according to one embodiment of the present invention preferably contains a photoisomerized molecule and cyclodextrin, and further preferably contains an acrylic polymer. In this composition, the photoisomerized molecule undergoes photoisomerization upon light irradiation, and the host-guest interaction between the photoisomerized molecule and cyclodextrin changes, resulting in a change in properties. In particular, the inclusion of an acrylic polymer may cause changes in desired properties such as tackiness and viscoelasticity. The composition according to this embodiment can be used, for example, in the above-mentioned adhesive and adhesive sheet, but is not limited thereto.

[0112] [Compound] A compound according to one embodiment of the present invention is formed by bonding a photoisomerized molecule and a cyclodextrin to an acrylic polymer. In this compound, photoisomerization occurs upon light irradiation, and the host-guest interaction between the photoisomerized molecule and the cyclodextrin changes, resulting in a change in properties. In particular, if the acrylic polymer is adhesive, changes in desired properties such as adhesiveness and viscoelasticity may occur. The compound according to this embodiment can be used, for example, in the above-mentioned adhesives and adhesive sheets, but is not limited thereto.

[0113] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0114] For example, the release sheet 12 in adhesive sheet 1A may be omitted, and either the release sheets 12a or 12b in adhesive sheet 1B may be omitted.

[0115] In this specification, when "X~Y" (where X and Y are any numbers) is written, unless otherwise specified, it includes the meaning of "greater than or equal to X and less than or equal to Y," as well as "preferably greater than X" or "preferably less than Y." Similarly, when "greater than or equal to X" (where X is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "less than or equal to Y" (where Y is any number) is written, unless otherwise specified, it also includes the meaning of "preferably less than Y." [Examples]

[0116] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0117] [Manufacturing Example 1] 4-aminostilbene (2 g) and triethylamine (1.5 mL) were dissolved in 50 mL of diethyl ether. Under a nitrogen atmosphere, acryloyl chloride (0.8 mL) dissolved in diethyl ether (15 mL) was added dropwise to this solution while stirring at 0°C. The reaction mixture was allowed to return to room temperature and stirred for 2 hours. The reaction mixture was washed with water and then vacuum-dried to obtain N-(4-styrylphenyl)acrylamide.

[0118] [Manufacturing Example 2] As a polymerizable cyclodextrin compound, a polymerizable β-cyclodextrin compound (CD) represented by the following formula (2) was prepared using the same procedure as in Production Example 6 of International Publication No. 2018 / 159791. [ka] (In formula (2), Ac represents an acetyl group.)

[0119] The molecular weight of the polymerizable β-cyclodextrin compound (CD) was measured using the method described later, and it was found to be 2059 (Mw).

[0120] [Example 1] One part by mass of N-(4-styrylphenyl)acrylamide (stilbene modified with acrylamide; Sti) prepared in Production Example 1 and one part by mass of polymerizable β-cyclodextrin compound (CD) prepared in Production Example 2 were dissolved in 98 parts by mass of n-butyl methacrylate as an acrylic monomer, and the mixture was sonicated at 50°C for 60 minutes. This solution was heated in an oil bath at 75°C for 15 minutes to form a prepolymer.

[0121] When the viscosity of the above solution approached that of glycerol, the solution was applied between the release surfaces of two release sheets (a heavily release sheet R1, which was a polyethylene terephthalate film with one side released with a silicone-based release agent, and a lightly release sheet R2, which was a polyethylene terephthalate film with one side released with a silicone-based release agent). Then, the mixture was heated at 65°C for 12 hours to complete polymerization. Next, one of the release sheets R2 was peeled off and dried under reduced pressure at 80°C for 12 hours to remove a small amount of residual liquid monomer, forming an adhesive layer consisting of compound C. Release sheet R2 was then laminated onto the adhesive layer to obtain an adhesive sheet. The thickness of the adhesive layer was 40 μm. The thickness of the adhesive layer was measured in accordance with JIS K7130 using a constant-pressure thickness gauge (Teclock Co., Ltd., product name "PG-02") (the same applies hereafter).

[0122] Furthermore, regarding the peeling force of release sheet R1 and release sheet R2 in the obtained adhesive sheet, it was confirmed that release sheet R1 has a greater peeling force than release sheet R2.

[0123] [Examples 2-6] An adhesive sheet was manufactured in the same manner as in Example 1, except that the type and amount of acrylic monomer and the thickness of the adhesive layer were changed as shown in Table 1.

[0124] [Example 7] Compound C was prepared by copolymerizing 1 part by mass of N-(4-styrylphenyl)acrylamide (stilbene modified with acrylamide; Sti) prepared in Production Example 1 with 99 parts by mass of n-butyl methacrylate as an acrylic monomer by solution polymerization. Specifically, N-(4-styrylphenyl)acrylamide, n-butyl methacrylate, and azobisisobutyronitrile (AIBN) as a polymerization initiator were dissolved in toluene, sonicated for 5 minutes, and then stirred at 80°C for 24 hours under a nitrogen atmosphere. AIBN was then added to the solution and stirred at 90°C for 12 hours under a nitrogen atmosphere. Subsequently, the solution was added dropwise to ice-cooled methanol to obtain a pale yellow crude product. This crude product was washed three times alternately with chloroform and methanol and dried at 70°C for 12 hours to obtain compound C (coating solution).

[0125] The obtained compound C coating solution was applied to the release-treated surface of a heavy-peel type release sheet R1 using a coater. Then, it was heated at 90°C for 1 minute to form an adhesive layer consisting of compound C. Next, the adhesive layer on the release sheet R1 obtained above and a light-peel type release sheet R2 were bonded together so that the release-treated surface of the release sheet R2 was in contact with the coating layer, thereby producing an adhesive sheet having an adhesive layer with a thickness of 20 μm, i.e., an adhesive sheet consisting of release sheet R1 / adhesive layer (thickness: 20 μm) / release sheet R2.

[0126] [Example 8] An adhesive sheet was manufactured in the same manner as in Example 7, except that the type and amount of acrylic monomer were changed as shown in Table 1.

[0127] [Comparative Example 1] A (meth)acrylic acid ester polymer was prepared by copolymerizing 20 parts by mass of n-butyl acrylate, 40 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of methyl methacrylate, and 10 parts by mass of 4-hydroxybutyl acrylate by solution polymerization.

[0128] 100 parts by mass (based on solid content; the same applies hereafter) of the (meth)acrylic acid ester polymer obtained above was mixed with 0.2 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, product name "Takenate D-110N"), stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

[0129] The coating solution of the adhesive composition obtained above was applied to the release surface of a heavy-peel type release sheet R1 using a coater. Then, it was heated at 90°C for 1 minute to form a coating layer. Next, the coating layer on the release sheet R1 obtained above and a light-peel type release sheet R2 were bonded together so that the release surface of the release sheet R2 was in contact with the coating layer, and cured for 7 days under conditions of 23°C and 50% RH to produce an adhesive sheet having an adhesive layer with a thickness of 50 μm, i.e., an adhesive sheet consisting of release sheet R1 / adhesive layer (thickness: 50 μm) / release sheet R2.

[0130] [Comparative Examples 2-4] Adhesive sheets were manufactured in the same manner as in Comparative Example 1, except that the type and amount of acrylic monomer, the amount of crosslinking agent, and the thickness of the adhesive layer were changed as shown in Table 1. In Comparative Examples 2 and 3, 10 parts by mass of ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester A-9300-1CL") (H1) was added as an ultraviolet-curable component, and 1 part by mass of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide was added as a photopolymerization initiator. In Comparative Example 3, an additional 15 parts by mass of silicone filler (manufactured by Momentive, product name "Tospar 145") was added. In Comparative Example 4, 10 parts by mass of pentaerythritol triacrylate (triester 37%) (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name "A-TMM-3L") (H2) was used as the UV-curable component, and 1 part by mass of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide was used as the photopolymerization initiator.

[0131] Here, Table 1 shows the respective formulations (in terms of solid content) of the adhesive composition when (meth)acrylic acid ester polymer is present in 100 parts by mass (in terms of solid content). Details of the abbreviations and other terms listed in Table 1 are as follows. [Compound C / (meth)acrylic acid ester polymer] Sti:N-(4-styrylphenyl)acrylamide CD: Polymerizable β-cyclodextrin compound produced in Production Example 1 BMA: n-butyl methacrylate MEA: 2-methoxyethyl acrylate BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate MMA: Methyl methacrylate 4HBA: 4-hydroxybutyl acrylate [UV curable component] H1: ε-Caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester A-9300-1CL") H2: Pentaerythritol triacrylate (37% triester) (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product name "A-TMM-3L")

[0132] [Test Example 1] (Measurement of weight-average molecular weight (Mw)) The weight-average molecular weight (Mw) of the polymerizable β-cyclodextrin compound produced in Production Example 1, compound C produced in Examples 1-8, and (meth)acrylic acid ester polymers prepared in Comparative Examples 1-4 was measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement) and converted to polystyrene equivalent. The results are shown in Table 1.

[0133] <Measurement conditions> • GPC measuring device: Tosoh Corporation, HLC-8020 • GPC column (passes through in the following order): Manufactured by Tosoh Corporation TSK Guard Column HXL-H TSK gel GMHXL (x2) TSK gel G2000HXL • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0134] [Test Example 2] (Measurement of glass transition temperature (Tg)) The glass transition temperature (Tg) of Compound C prepared in Examples 1-8 and the (meth)acrylic acid ester polymers prepared in Comparative Examples 1-4 was determined by measurement using a differential scanning calorimetry system (TA Instruments Japan Co., Ltd., product name "DSC Q2000"). Specifically, 4 mg of the polymer sample was taken, placed in an aluminum pan, and sealed with a lid. The sample was heated and cooled in a dry nitrogen atmosphere from -70°C to 70°C at a heating / cooling rate of 10°C / min. A DSC curve was created using the data from the second heating. The glass transition temperature (Tg) was defined as the temperature at the intersection of a straight line extending the baseline on the low-temperature side of the obtained DSC curve toward the high-temperature side and a tangent line drawn at the point where the slope of the curve representing the stepwise transition of the glass transition is maximum. The results are shown in Table 1.

[0135] Example 3 (Measurement of Storage Elastic Modulus) The adhesive layers of the adhesive sheets produced in the examples and comparative examples were laminated in multiple layers to form a laminate with a thickness of about 0.5 mm. A cylinder (height 0.5 mm) with a diameter of 8 mm was punched out from the obtained laminate of the adhesive layers and used as a sample.

[0136] For the above sample, in accordance with JIS K7244-1, using a viscoelasticity measuring device (manufactured by Anton paar, product name "MCR302"), the dynamic viscoelasticity was measured under the following conditions, and the storage elastic modulus G'(25) at 25°C and the storage elastic modulus G'(80) at 80°C were observed. The results are shown in Table 2. Measurement frequency: 1 Hz Measurement temperature range: -20 to 150°C

[0137] A band-pass filter was installed in the light source of a xenon UV lamp (manufactured by Asahi Spectra Co., Ltd., product name "MAX-301") to extract monochromatic light (ultraviolet light) with a wavelength of 365 nm. The adhesive layers of the adhesive sheets produced in the examples and comparative examples were irradiated with ultraviolet light (UV) under the following conditions through the release sheet R1. For the adhesive layer after the above ultraviolet irradiation, the storage elastic modulus G'(UV25) at 25°C and the storage elastic modulus G'(UV80) at 80°C were observed in the same manner as above. The results are shown in Table 2.

[0138] <UV Irradiation Conditions> · Use a high-pressure mercury lamp · Illuminance: 80 mW / cm 2 · Irradiation time: 5 minutes · Distance from the light source: 10 mm · Use "UVPF-A1" manufactured by Eye Graphics Co., Ltd. as the UV illuminometer

[0139] The ratio of the storage modulus G'(UV25) of the adhesive after UV irradiation to the storage modulus G'(25) of the adhesive obtained above at 25°C (%; (storage modulus G'(UV25) / storage modulus G'(25)) × 100), and the ratio of the storage modulus G'(UV80) of the adhesive after UV irradiation to the storage modulus G'(80) of the adhesive at 80°C (%; (storage modulus G'(UV80) / storage modulus G'(80)) × 100) were calculated. The results for each are shown in Table 2.

[0140] [Test Example 4] (Measurement of haze value) The adhesive layers of the adhesive sheets manufactured in the examples and comparative examples were bonded to glass, and these were used as measurement samples. After background measurements were performed on the glass, the haze value (%; IH) of the measurement samples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SH7000") in accordance with JIS K7136:2000. The results are shown in Table 2.

[0141] The adhesive layer of the adhesive sheets manufactured in the examples and comparative examples was irradiated with ultraviolet light on one side under the same conditions as in Test Example 3. The haze value (%; UVH) of the adhesive layer after UV irradiation was measured in the same manner as described above. The results are shown in Table 2.

[0142] The ratio of the haze value (UVH) of the adhesive layer after UV irradiation to the haze value (IH) of the adhesive layer obtained above (%; (Haze value (UVH) / Haze value (IH)) × 100) was calculated. The results are shown in Table 2.

[0143] [Test Example 5] (Measurement of parallel light transmittance) The parallel light transmittance of the adhesive layer in the adhesive sheets manufactured in the examples and comparative examples was blank-calibrated using a UV-Vis spectrophotometer (JASCO Corporation, product name "V-650"), and the parallel light transmittance at wavelengths of 350 nm (350PT), 400 nm (400PT), and 550 nm (550PT) was derived. The results are shown in Table 2.

[0144] The ratio (%; (absorbance (400PT) / absorbance (350PT)) × 100) of the absorbance of the adhesive layer obtained above at a wavelength of 400 nm to the absorbance of light at a wavelength of 350 nm (350PT) was calculated. The results are shown in Table 2.

[0145] [Test Example 6] (Measurement of Adhesion) The release sheet R2 of the adhesive sheets manufactured in the examples and comparative examples was peeled off, and a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4360", with an easy-adhesion layer, thickness: 100 μm, base material A) was laminated to the exposed adhesive layer surface (surface A). Next, the release sheet R1 was peeled off, and a PET film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4360", with an easy-adhesion layer, thickness: 100 μm, base material B) was laminated to the exposed adhesive layer surface (surface B), obtaining a laminate of PET film (base material A) / adhesive layer / PET film (base material B). The obtained laminate was cut into rectangles with a width of 10 mm and a length of 50 mm, and these were used as samples.

[0146] Under conditions of 23°C and 50% RH, both PET films were peeled from the adhesive layer using a tensile testing machine (Orientec Co., Ltd., product name "Tensilon") in accordance with the T-type peel method of JIS K6854-3:1999 at a peeling speed of 300 mm / min, and the adhesive strength (IA; N / 10 mm) was measured. The results are shown in Table 2.

[0147] One side of the above sample was irradiated with ultraviolet light under the same conditions as in Test Example 3. The adhesive strength (UVA; N / 10mm) was then measured using the same method as described above. Note that this adhesive strength measurement was performed regardless of whether substrate A or substrate B peeled off from the adhesive layer. The results are shown in Table 2.

[0148] The ratio (%;{|Adhesion (IA) - Adhesion (UVA)| / Adhesion (IA)}×100) of the absolute change in adhesion (UVA) after UV irradiation to the initial adhesion (IA) of the adhesive sheet obtained above was calculated. The results are shown in Table 2.

[0149] [Test Example 7] (Evaluation of peeling morphology after UV irradiation) In the sample prepared in Test Example 6, ultraviolet light was irradiated through substrate A onto surface A of the adhesive layer under the same conditions as in Test Example 3. After the ultraviolet irradiation, the sample was peeled off at 10 mm / min using the T-peel method, as in Test Example 6. This was repeated three times. The state of the peel interface and adhesive layer on the peeled sample was observed, and the "failure mode during adhesive layer peeling" was evaluated according to the following criteria. The results are shown in Table 3. Interfacial delamination: The failure mode was interfacial delamination in all three cases. Cohesive failure: The failure mode was cohesive failure in all three trials.

[0150] The delamination interface in the sample after the above delamination was observed, and the "substrate from which the adhesive layer has been removed" was evaluated according to the following criteria. The results are shown in Table 3. A: In all three cases, the adhesive layer peeled off from substrate A, and no residue of the adhesive layer remained on substrate A. B: In all three attempts, the adhesive layer peeled off from substrate B, and no residue of the adhesive layer remained on substrate B. A or B: Although the peeling did not occur from the same substrate in all three instances, the adhesive layer peeled from either substrate A or substrate B, and no residue of the adhesive layer remained on the substrate. A and B: Residue from the adhesive layer remained on both substrate A and substrate B.

[0151] [Test Example 8] (Evaluation of selective peelability of substrates) Based on the evaluation results of the "failure mode during adhesive layer peeling" and the "substrate from which the adhesive layer has peeled" in Test Example 7, the ease of selective peeling of the substrate was judged according to the following criteria, to determine whether the peeling interface with respect to the direction of ultraviolet irradiation is always constant when the adherends bonded to both sides of the adhesive layer are made of the same material. The results are shown in Table 3. ○: The "failure mode during adhesive layer peeling" was "interfacial peeling," and the evaluation result of the "substrate from which the adhesive layer has peeled off" was either "A" or "B." △: The "failure mode during adhesive layer peeling" was "interfacial peeling," and the evaluation result for the "substrate from which the adhesive layer has peeled off" was "A or B." ×: The "failure mode during adhesive layer peeling" was "cohesive failure," or the evaluation result of the "substrate from which the adhesive layer has peeled off" was "A and B."

[0152] [Test Example 9] (Evaluation of adhesive strength recovery after easy peeling) For adhesive sheets that received a ○ or △ evaluation for substrate selective peelability in Test Example 8, ultraviolet light with a wavelength of 254 nm was irradiated onto the surface of the adhesive layer from which the substrate (substrate A or substrate B) had peeled off, in the same manner as in Test Example 3. Subsequently, the adhesive layer was re-laminated to a PET film (Toyobo Co., Ltd., product name "Cosmoshine A4360", with an easy-adhesion layer, thickness: 100 μm) as the substrate, and heated at 80°C for 30 minutes. The resulting laminate was measured for adhesive strength (RUVA; N / 10 mm) using the T-peel method, in the same manner as in Test Example 6. The ratio (%; (adhesion strength (RUVA) / adhesive strength (IA)) × 100) of the measured adhesive strength (RUVA) to the initial adhesive strength (IA) measured in Test Example 6 was calculated, and the adhesive strength recovery after easy peeling was evaluated according to the following criteria. The results are shown in Table 2. ○: 80% or more ×: Less than 80%

[0153] [Test Example 10] (Evaluation of re-adhesion after easy peeling) For adhesive sheets that received a ○ or △ rating for substrate selective peelability in Test Example 8, ultraviolet light with a wavelength of 254 nm was irradiated onto the surface of the adhesive layer from which the substrate (substrate A or substrate B) had peeled off, using the same method as in Test Example 3. Subsequently, the adhesive layer was re-laminated to a PET film (Toyobo Co., Ltd., product name "Cosmoshine A4360", with an easy-adhesion layer, thickness: 100 μm) as the substrate, and heated at 80°C for 30 minutes. The re-laminated substrate was then manually peeled off the resulting laminate, and the re-adhesion after peeling was evaluated according to the following criteria. The results are shown in Table 3. ○: The re-bonded substrate could not be easily peeled off. ×: The re-bonded substrate could be easily peeled off.

[0154] [Test Example 11] (Evaluation of contamination potential of the adherend) For the substrate samples after peeling in Test Example 7, the presence or absence of adhesive residue was visually confirmed, and the residue was wiped off with an ethanol-impregnated paper wiper (manufactured by Nippon Paper Crecia Co., Ltd., product name "Kimwipes"), and the adhesion to the substrate was evaluated according to the following criteria. The results are shown in Table 3. ○: No visible residue was found on the peeled substrate. △: Some residue was observed on the peeled substrate, but it could be easily removed by wiping with a paper wiper. ×: Significant residue remained on the peeled substrate or both substrates, and it was difficult to remove with a paper wiper.

[0155] [Test Example 12] (Evaluation of Visibility) PET film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4360", with easy-adhesion layer, thickness: 100 μm) was laminated to both sides of the adhesive layer of the adhesive sheets manufactured in the examples and comparative examples to obtain the first sample (before UV irradiation). One side of this first sample was irradiated with ultraviolet light under the same conditions as in Test Example 3, and this was designated as the second sample (after UV irradiation).

[0156] A piece of paper printed with "aiueo" in 10.5pt font was placed on a desk, and the first and second samples described above were positioned 20 cm directly above it. The legibility of the printed content (characters) on the paper on the desk was visually checked by looking through the samples, and the legibility was evaluated according to the following criteria. The results are shown in Table 3. ○: The characters were easily legible in all samples. △: The characters were legible in at least one of the samples. ×: The text was illegible in all samples.

[0157] [Table 1]

[0158] [Table 2]

[0159] [Table 3]

[0160] As can be seen from Tables 2 and 3, the adhesive layer (adhesive) of the adhesive sheet manufactured in the examples changed properties upon ultraviolet irradiation. Furthermore, the adhesive layer could be selectively and easily peeled off from one substrate by ultraviolet irradiation, and the peeled adhesive layer could be reattached to the substrate by ultraviolet irradiation at a predetermined wavelength. In addition, when peeled off from the substrate after ultraviolet irradiation, no adhesive residue remained on the substrate, preventing contamination. Moreover, the adhesive layer exhibited high transparency before and after ultraviolet irradiation, and the visibility of objects transmitted through the adhesive layer was excellent. [Industrial applicability]

[0161] The adhesive and adhesive sheet according to the present invention can be peeled off from one adherend without leaving any residue while leaving the adhesive layer on the other adherend, and can maintain high transparency before and after light irradiation. Therefore, they can be preferably used, for example, in applications such as bonding optical components and manufacturing displays. Furthermore, the composition and compound according to the present invention can be used, as an example, in the above-mentioned adhesive and adhesive sheet. [Explanation of Symbols]

[0162] 1A, 1B... Adhesive sheets 11…Adhesive layer 12, 12a, 12b… Release sheets 13...Base material

Claims

1. An adhesive containing a compound formed by the bonding of a photoisomerized molecule to an adhesive polymer.

2. The adhesive according to claim 1, characterized in that the compound has cyclodextrin.

3. The adhesive according to claim 1, characterized in that a cyclodextrin is bound to the adhesive polymer, and the cyclodextrin encapsulates the photoisomerized molecule.

4. The adhesive according to claim 1, characterized in that the photoisomerized molecule is a stilbene derivative.

5. The adhesive according to claim 1, characterized in that the adhesive polymer is an acrylic polymer.

6. The adhesive according to claim 1, characterized in that its adhesive strength changes upon light irradiation.

7. An adhesive sheet having at least an adhesive layer, The adhesive constituting the adhesive layer is the adhesive described in any one of claims 1 to 6. An adhesive sheet characterized by the following features.

8. The adhesive sheet according to claim 7, characterized by comprising a base material and the adhesive layer.

9. The adhesive sheet comprises two release sheets. The adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the two release sheets. The adhesive sheet according to feature 7.

10. A composition containing a photoisomerized molecule and cyclodextrin.

11. The composition according to claim 10, characterized by containing an acrylic polymer.

12. A compound formed by bonding an acrylic polymer with a photoisomerized molecule and cyclodextrin.

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