TW202231817A - Color-changeable adhesive sheet - Google Patents

Abstract

An adhesive sheet (S) according to the present invention serving as a color-changeable adhesive sheet includes an adhesive layer (10). The adhesive layer (10) includes a polymer component having a micro-phase separation structure that contains a first phase and a second phase, and a coloring agent capable of producing a color by an external stimulus. The coloring agent is compatible with the first phase and incompatible with the second phase.

Description

Color-changing adhesive sheet

The present invention relates to a color-changing adhesive sheet.

A display panel such as an organic EL panel (Electroluminescence) has a laminated structure including a pixel panel, a cover member, and the like. In the manufacturing process of such a display panel, a transparent adhesive sheet can be used, for example, in order to adhere the elements included in the laminated structure to each other.

In addition, as a transparent adhesive sheet disposed on the light emitting side (image display side) of the pixel panel in the display panel, it is proposed to use a transparent adhesive sheet formed in advance to impart designability, light-shielding property, and anti-reflection property to specific parts of the above-mentioned sheet. Adhesive sheet for other colored parts. Such an adhesive sheet is described in Patent Document 1 below, for example. Patent Document 1 specifically describes an adhesive sheet having a colored portion containing a carbon black pigment. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2017-203810

[Problems to be Solved by Invention]

However, in the production process of the display panel, in the case of using the adhesive sheet with the colored portion formed in advance, after the adhesive sheet is attached to the adherend, it is impossible to properly check the relationship between the adherend and the adhesive sheet. Check for foreign matter and air bubbles between the colored parts. In the process of laminating the adhesive sheet during the manufacturing process of the display panel, it is necessary to be able to properly check whether there is foreign matter or air bubbles between the adherend and the adhesive sheet after lamination.

On the other hand, from the viewpoint of securing the function of the colored portion provided in the transparent adhesive sheet for display panels, it is necessary to suppress the deterioration of the colored portion.

The present invention provides a discolorable adhesive sheet, which can discolor at least a part of an adhesive layer after being attached to an adherend, and is suitable for suppressing deterioration of the discolored part of the adhesive layer. [Technical means to solve problems]

The present invention [1] includes a discolorable adhesive sheet having a discolorable adhesive layer, wherein the adhesive layer includes a polymer component having a microphase-separated structure including a first phase and a second phase ; and a colorant that can be developed by external stimuli; the colorant has compatibility with the first phase described above, and does not have compatibility with the second phase described above.

The present invention [2] includes the color-changing adhesive sheet according to the above [1], wherein the polymer component includes a polymer having a first segment forming the first phase in the molecule, and forming the first segment in the molecule. The second segment of the second phase.

The present invention [3] includes the discolorable adhesive sheet according to the above [2], wherein the polymer is a block polymer, and the block polymer has a first polymer block as the first segment, and the second polymer block as the above-mentioned second segment.

The present invention [4] includes the color-changing adhesive sheet according to the above [2], wherein the polymer is a graft polymer, and the graft polymer has a polymer main chain as the first segment, and a polymer backbone as the first segment. The polymer side chain of the above-mentioned second segment.

The present invention [5] includes the discolorable adhesive sheet according to any one of the above [1] to [4], wherein the mass ratio of the second phase in the polymer component is greater than the mass ratio of the first phase.

The present invention [6] includes the discolorable adhesive sheet according to any one of the above [1] to [5], wherein the colorant is a compound that develops color by a reaction with an acid, and the adhesive layer is Furthermore, a photoacid generator is contained.

The present invention [7] includes the discolorable adhesive sheet according to the above [6], wherein the photoacid generator has compatibility with the first phase and does not have compatibility with the second phase.

The present invention [8] includes the discolorable adhesive sheet according to any one of the above [1] to [7], wherein the adhesive layer is formed by linearly applying the external stimulus to the adhesive layer. The first discoloration width W1 of the inner discoloration area and the second discoloration width W2 of the discolored area after the adhesive layer was heated at 85° C. for 120 hours satisfy 0.5≦W2/W1≦2.

The present invention [9] includes the discolorable adhesive sheet according to any one of the above [1] to [8], wherein the adhesive layer is formed by linearly applying the external stimulus to the adhesive layer. The first discoloration width W1 of the discolored area inside, and the third discoloration width W3 of the discolored area after heat treatment of the adhesive layer at 65°C and 90% relative humidity for 120 hours satisfies 0.5≦W3/W1≦ 2.3. [Effect of invention]

In the color-changing adhesive sheet of the present invention, as described above, the adhesive layer contains a coloring agent capable of developing color by external stimuli. Therefore, after attaching the discolorable adhesive sheet to the adherend, by applying external stimulation to the part to be discolored (at least a part of the adhesive layer) of the adhesive layer, the part can be partially discolored. In the case of such a discolorable adhesive sheet, the presence or absence of foreign matter and air bubbles between the sheet and the adherend can be inspected after lamination and before the discolored portion of the adhesive layer is formed.

Furthermore, in the color-changing adhesive sheet, as described above, the adhesive layer includes a polymer component having a microphase-separated structure including a first phase and a second phase, and the colorant has a phase relative to the first phase. Compatibility, and no compatibility with the second phase. Such a color-changing adhesive sheet is suitable for suppressing the movement (diffusion, etc.) of the colorant developed after the color-changing portion is formed in the adhesive layer (ie, after the colorant is developed by an external stimulus). Deterioration (bleeding, fading, unevenness of color tone, etc.) of the discolored portion is suppressed by suppressing the movement of the developed colorant.

As shown in FIG. 1 , the adhesive sheet S, which is one embodiment of the color-changing adhesive sheet of the present invention, includes an adhesive layer 10 . The adhesive sheet S has a sheet shape with a specific thickness, and extends in a direction (surface direction) orthogonal to the thickness direction. The adhesive sheet S can be used, for example, as a transparent adhesive sheet arranged on the image display side of a pixel panel in display panels such as organic EL panels (having a laminated structure including a pixel panel, a cover member, and the like).

The adhesive layer 10 is a pressure-sensitive adhesive layer formed of an adhesive composition. The adhesive layer 10 has transparency (visible light transmittance). The adhesive layer 10 contains a polymer component and a coloring agent that can be developed by an external stimulus as described below. In such an adhesive layer 10 , the part that is subjected to external stimulation may be discolored. That is, in the adhesive layer 10, the transparency of the part which received external stimulation may fall later.

The polymer component is an adhesive component that exhibits adhesiveness in the adhesive layer 10 . The polymer component exhibits rubber elasticity in the room temperature range. Examples of the polymer component include acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, polysiloxane polymers, polyamide polymers, and Fluoropolymer. From the viewpoint of securing good transparency and adhesiveness of the adhesive layer 10, it is preferable to use an acrylic polymer as a polymer component.

The polymer component has a microphase-separated structure including a first phase and a second phase in the adhesive layer 10 . The first phase is a phase compatible with the colorant. The second phase is a phase incompatible with the colorant. As the microphase separation structure, for example, the spherical structure (island structure) as shown in FIGS. 2A and 2B , the cylindrical structure as shown in FIGS. 2C and 2D , and the spiral as shown in FIGS. 2E and 2F can be exemplified. shape structure (bicontinuous structure), and layered structure as shown in FIG. 2G.

In the structure shown in FIG. 2A , the first phase M1 is a spherical dispersed phase, and the second phase M2 is a matrix. In the structure shown in FIG. 2B , the first phase M1 is a matrix, and the second phase M2 is a spherical dispersed phase. In the structure shown in FIG. 2C , the first phase M1 is a cylindrical dispersed phase, and the second phase M2 is a matrix. In the structure shown in FIG. 2D , the first phase M1 is a matrix, and the second phase M2 is a cylindrical dispersed phase. In the structure shown in FIG. 2E , the first phase M1 has a three-dimensional network structure, and the second phase M2 is a matrix. In the structure shown in FIG. 2F , the first phase M1 is a matrix, and the second phase M2 has a three-dimensional network structure. In the structure shown in FIG. 2G , the plate-shaped first phase M1 and the plate-shaped second phase M2 are alternately repeated. From the viewpoint of inhibiting the movement of the colorant within the adhesive layer 10, the polymer composition has the microphase separation structure shown in FIG. 2A, FIG. 2C or FIG. 2E.

The polymer component includes a polymer (first polymer) having a first segment forming the first phase and a second segment forming the second phase in the molecule. As a 1st polymer, the block polymer which has a 1st polymer block as a 1st segment, and a 2nd polymer block as a 2nd segment is mentioned, for example. The block polymer can have a plurality of first polymer blocks with different monomer compositions, and can also have a plurality of second polymer blocks with different monomer compositions (in this case, the block polymer is based on the monomer A multi-block copolymer in which the number of types of blocks in the composition is 3 or more). As a 1st polymer, the graft polymer which has a polymer main chain as a 2nd segment, and a polymer side chain as a 1st segment can also be mentioned. The graft polymer can have a plurality of polymer side chains with different monomer compositions, and can also have a plurality of polymer blocks with different monomer compositions in the polymer main chain. The polymer component may contain one type of the first polymer, or may contain a plurality of types of the first polymer. In addition, the polymer component may contain a polymer (second polymer) other than the first polymer. The polymer component may contain one type of the second polymer, or may contain a plurality of types of the second polymer.

The first segment is a segment containing 80% by mass or more of the same monomer composition as the monomer solution determined to have compatibility with the colorant according to the compatibility determination test described in the Examples below (for example, the monomer is selected from from the monomers listed below). The colorant has compatibility with the first phase formed by the first segment. When the colorant has hydrophilicity, the first segment preferably has hydrophilicity. When the colorant is hydrophilic, the first segment is preferably a hard block. The glass transition temperature of the hard block is preferably 0°C or higher, more preferably 30°C or higher, and still more preferably 50°C or higher. When the colorant has hydrophobicity, the first segment preferably has hydrophobicity. When the colorant has hydrophobicity, the first segment is preferably a soft segment. The glass transition temperature of the soft segment is preferably 0°C or lower, more preferably less than 0°C, further preferably -30°C or lower, particularly preferably -50°C or lower.

The second segment is a segment containing 80% by mass or more of the same monomer composition as the monomer solution for which the colorant was judged to be incompatible according to the compatibility judgment test described in the following examples (monomers such as selected from the monomers listed below). The colorant has no compatibility with the second phase formed by such a second segment. When the colorant is hydrophilic, the second segment preferably has hydrophobicity. When the colorant is hydrophilic, the second segment is preferably a soft segment. The glass transition temperature of the soft segment is preferably 0°C or lower, more preferably less than 0°C, further preferably -30°C or lower, particularly preferably -50°C or lower. When the second segment is a soft segment, from the viewpoint of securing the adhesive force of the adhesive layer 10, the mass ratio of the second segment (second phase) in the polymer component is preferably larger than that of the first segment. Mass ratio of segments (phase 1). When the colorant has hydrophobicity, the second segment preferably has hydrophilicity. When the colorant is hydrophobic, the second segment is preferably a hard block. The glass transition temperature of the hard block is preferably 0°C or higher, more preferably 30°C or higher, and still more preferably 50°C or higher.

Regarding the glass transition temperature (Tg) of the polymer (including the segment), the glass transition temperature (theoretical value) calculated based on the following Fox equation can be used. Fox's formula is a relational formula between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of the homopolymer of the monomers constituting the polymer. In the following formula of Fox, Tg represents the glass transition temperature (°C) of the polymer, Wi represents the weight fraction of the monomer i constituting the polymer, and Tgi represents the glass transition temperature of the homopolymer formed from the monomer i (°C). Regarding the glass transition temperature of homopolymers, literature values can be used, for example in "PolymerHandbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7 Introduction to Synthetic Resins for Coatings" (Kitaoka Kyoko). In the third book, Polymer Publications, 1995), the glass transition temperature of various homopolymers is exemplified. On the other hand, the glass transition temperature of the homopolymer of a monomer can also be calculated|required by the method concretely described in Unexamined-Japanese-Patent No. 2007-51271.

Fox's formula 1/(273＋Tg)＝Σ[Wi/(273＋Tgi)]

When an acrylic polymer is used as a polymer component, this acrylic polymer is a copolymer which contains the monomer component of (meth)acrylic-acid alkylester in the ratio of 50 mass % or more, for example. "(Meth)acrylic" means acrylic and/or methacrylic.

As (meth)acrylic-acid alkylester, the (meth)acrylic-acid alkylester which has a C1-C20 linear or branched alkyl group is mentioned, for example. As such alkyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, Isopropyl (meth)acrylate, isobutyl (meth)acrylate, 2nd butyl (meth)acrylate, 3rd butyl (meth)acrylate, pentyl (meth)acrylate, (meth)acrylate Isoamyl acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, Isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate Alkyl ester, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, Pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isopropyl (meth)acrylate Octadecyl, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Alkyl (meth)acrylate may be used alone, or two or more of them may be used in combination. As the alkyl (meth)acrylate forming the hard block, it is preferable to use an alkyl acrylate having an alkyl group having 1 to 5 carbon atoms, and it is more preferable to use a group selected from methyl acrylate, methyl methacrylate, and at least one of the group consisting of n-butyl acrylate. As the alkyl (meth)acrylate forming the soft segment, it is preferable to use an alkyl acrylate having an alkyl group having 7 to 20 carbon atoms, and it is more preferable to use an alkyl acrylate selected from the group consisting of 2-ethylhexyl acrylate, acrylic acid ten At least one of the group consisting of dialkyl ester and octadecyl acrylate.

From the viewpoint of making the adhesive layer 10 appropriately exhibit basic properties such as adhesiveness, the ratio of the alkyl (meth)acrylate in the monomer component is preferably 50% by mass or more, more preferably 60% by mass or more, More preferably, it is 70 mass % or more. This ratio is, for example, 99 mass % or less.

The monomer component may contain a copolymerizable monomer copolymerizable with the alkyl (meth)acrylate. As a copolymerizable monomer, the monomer which has a polar group is mentioned, for example. As a polar group containing monomer, a hydroxyl group containing monomer, the monomer which has a nitrogen atom containing ring, and a carboxyl group containing monomer are mentioned, for example. The polar group-containing monomer contributes to the modification of the acrylic polymer, such as introducing cross-linking points into the acrylic polymer and ensuring the cohesion of the acrylic polymer. In order to modify the acrylic polymer, the polar group-containing monomer may be included in the hard block or in the soft segment.

The copolymerizable monomer preferably contains at least one selected from the group consisting of a hydroxyl group-containing monomer, a monomer having a nitrogen atom-containing ring, and a carboxyl group-containing monomer. It is more preferable that the copolymerizable monomer contains a hydroxyl group-containing monomer and/or a monomer having a nitrogen atom-containing ring.

As a hydroxyl group-containing monomer, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3 (meth)acrylate can be mentioned. -Hydroxypropyl, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, ( 12-hydroxylauryl meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. As the hydroxyl group-containing monomer, 4-hydroxybutyl (meth)acrylate is preferably used, and 2-hydroxybutyl acrylate is more preferably used.

From the viewpoint of introducing a crosslinked structure into the acrylic polymer and securing the cohesive force of the adhesive layer 10, the ratio of the hydroxyl group-containing monomer in the monomer component is preferably 1 mass % or more, more preferably 3 mass % above, more preferably 5 mass % or more. The ratio is preferably 30% by mass or less, more preferably 20% by mass, from the viewpoint of adjusting the polarity of the acrylic polymer (related to the compatibility between the various additive components in the adhesive layer 10 and the acrylic polymer). the following.

As a monomer having a nitrogen atom-containing ring, for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazol, N-vinylpyridine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2 -Pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylpyrrolidine, N-vinyl-3-picolinone, N-ethene yl-2-caprolactam, N-vinyl-1,3-㗁𠯤-2-one, N-vinyl-3,5-𠰌linedione, N-vinylpyrazole, N-vinyl Isoxazole, N-vinylthiazole, and N-vinylisothiazole. As the monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

From the viewpoint of securing the cohesive force of the adhesive layer 10 and securing the adhesive force of the adhesive layer 10 to the adherend, the ratio of the monomer having a nitrogen atom-containing ring in the monomer component is preferably 1 mass % or more, More preferably, it is 3 mass % or more, and still more preferably 5 mass % or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to the compatibility of the various additive components in the adhesive layer 10 with the acrylic polymer), the ratio is preferably 30 mass % or less, more preferably 20 mass % or less.

Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and methacrylic acid. .

From the viewpoint of introducing a cross-linked structure into the acrylic polymer, securing the cohesive force of the adhesive layer 10, and securing the adhesive force of the adhesive layer 10 to the adherend, the ratio of the carboxyl group-containing monomer in the monomer component is preferable It is 1 mass % or more, More preferably, it is 3 mass % or more, More preferably, it is 5 mass % or more. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid, the ratio is preferably 30 mass % or less, more preferably 20 mass % or less.

The monomer component may contain other comonomers. As other copolymerizable monomers, for example, acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, alkoxy group-containing monomers, and Aromatic vinyl compounds.

As an acid anhydride monomer, maleic anhydride and itonic anhydride are mentioned, for example.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (methyl) base) acrylamide propanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

As a phosphoric acid group-containing monomer, 2-hydroxyethyl acryl phosphonate is mentioned, for example.

Examples of epoxy group-containing monomers include epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl (meth)acrylate, and allyl glycidyl ether. , and (meth)acrylic acid glycidyl ether.

As a cyano group-containing monomer, acrylonitrile and methacrylonitrile are mentioned, for example.

As an alkoxy group-containing monomer, (meth)acrylic-acid alkoxyalkyl esters and (meth)acrylic-acid alkoxyalkylene glycol esters are mentioned, for example. Examples of (meth)acrylic acid alkoxyalkyl esters include 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and (meth)acrylic acid. 2-ethoxyethyl ester, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate. As (meth)acrylic-acid alkoxyalkylene glycol ester, (meth)acrylic-acid methoxyethylene glycol, and (meth)acrylic-acid methoxy polypropylene glycol are mentioned, for example. As the hard block-forming alkoxy-containing monomer, 2-methoxyethyl acrylate is preferably used.

As an aromatic vinyl compound, styrene, (alpha)-methylstyrene, and vinyltoluene are mentioned, for example. As olefins, ethylene, butadiene, isoprene, and isobutylene are mentioned, for example. As the aromatic vinyl compound forming the hard block, styrene is preferably used.

Co-monomers may be used alone, or two or more of them may be used in combination.

The polymer component preferably has a polymer selected from methyl methacrylate (MMA), a copolymer of MMA and 4-hydroxybutyl acrylate (4HBA), a polymer of styrene, and a copolymer of styrene and 4HBA At least one of the formed groups serves as a hard block. The polymer component preferably has at least one selected from the group consisting of 2-ethylhexyl acrylate (2EHA) and a copolymer of 2EHA and 4HBA as a soft segment.

The acrylic polymer can be formed by polymerizing the above-mentioned monomer components. As a polymerization method, solution polymerization, block polymerization, and emulsion polymerization are mentioned, for example, Preferably, solution polymerization is mentioned. The acrylic block polymer can be synthesized, for example, in the following manner: after synthesizing the first segment by living polymerization such as RAFT (Reversible Addition-Fragmentation Chain Transfer Polymerization) polymerization in a solution, the first segment is synthesized with a compound used to form the block polymer. The polymerization reaction of the monomer of the second segment and the solution of the first segment is carried out. Alternatively, the acrylic block polymer can also be synthesized as follows: after synthesizing the second segment by living polymerization such as RAFT polymerization in solution, a solution containing the monomer for forming the first segment and the second segment in the polymerization reaction. The acrylic graft polymer can be synthesized, for example, in a solution containing a macromonomer for forming a graft chain (a polymer having a polymerizable double bond at one end) and a monomer for extending the polymer main chain. Polymerization. Alternatively, the acrylic graft polymer can be synthesized, for example, by performing a polymerization reaction (graft polymerization) for extending the side chain of the polymer after synthesizing the main chain of the polymer. As the polymerization initiator, for example, a thermal polymerization initiator can be used. The usage-amount of a polymerization initiator is 0.05 mass part or more with respect to 100 mass parts of monomer components, for example, it is 1 mass part or less.

As a thermal polymerization initiator, an azo polymerization initiator and a peroxide polymerization initiator are mentioned, for example. As an azo polymerization initiator, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis( 2-Methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane)di Hydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methyl) propionamidine) disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride. As a peroxide polymerization initiator, dibenzyl peroxide, 3-butyl peroxymaleate, and lauryl peroxide may, for example, be mentioned.

From the viewpoint of securing the cohesive force of the adhesive layer 10, the weight average molecular weight of the acrylic polymer is preferably 100,000 or more, more preferably 300,000 or more, and still more preferably 500,000 or more. The weight average molecular weight is preferably 5,000,000 or less, more preferably 3,000,000 or less, and still more preferably 2,000,000 or less. The weight average molecular weight of the acrylic polymer can be measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

The glass transition temperature (Tg) of the acrylic polymer is preferably 0°C or lower, more preferably -10°C or lower, and further preferably -20°C or lower. The glass transition temperature is, for example, -80°C or higher.

The adhesive composition may contain a cross-linking agent from the viewpoint of introducing a cross-linked structure into the polymer component. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. joint agent. The crosslinking agent may be used alone, or two or more of them may be used in combination.

As an isocyanate crosslinking agent, for example, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, Hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate. Moreover, as an isocyanate crosslinking agent, the derivative|guide_body of these isocyanates can also be mentioned. As this isocyanate derivative, an isocyanurate modified body and a polyol modified body are mentioned, for example. Examples of commercially available isocyanate crosslinking agents include Coronate L (trimethylolpropane adduct of toluene diisocyanate, manufactured by Tosoh Corporation), Coronate HL (trimethylol hexamethylene diisocyanate). Propane adduct, manufactured by Tosoh), Coronate HX (isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh), and Takenate D110N (trimethylolpropane addition of xylylene diisocyanate) material, manufactured by Mitsui Chemicals).

As an epoxy crosslinking agent, bisphenol A, epichlorohydrin type epoxy resin, vinyl glycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1 ,6-Hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N,N,N',N'-tetraglycidyl-isophthalene Methylamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

From the viewpoint of securing the cohesive force of the adhesive layer 10, the blending amount of the crosslinking agent is, for example, 0.01 part by mass or more, preferably 0.05 part by mass or more, and more preferably 0.07 part by mass with respect to 100 parts by mass of the polymer component. above. From the viewpoint of ensuring good adhesiveness of the adhesive layer 10, the compounding amount of the crosslinking agent is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass relative to 100 parts by mass of the polymer component. parts by mass or less.

When introducing a cross-linked structure into the polymer component, a cross-linking catalyst may be used in order to efficiently advance the cross-linking reaction. Examples of the crosslinking catalyst include dibutyltin dilaurate, tetra-n-butyl titanate, tetraisopropyl titanate, iron triacetate, and butyl tin oxide, and preferably dibutyl tin dilaurate is used. . The usage-amount of a crosslinking catalyst is 0.0001 mass part or more and 1 mass part or less with respect to 100 mass parts of polymer components, for example.

In the case of using a cross-linking catalyst, a cross-linking inhibitor that can be removed from the adhesive composition afterward can also be formulated in the adhesive composition. When using dibutyltin dilaurate as a crosslinking catalyst, it is preferable to use acetylacetone as a crosslinking inhibitor. In this case, in the adhesive composition, acetylacetone is coordinated to dibutyltin dilaurate, and the crosslinking reaction of the crosslinking agent with respect to the polymer component is suppressed. In the following manufacturing process of the adhesive sheet S, after the adhesive composition is applied on the release film to form a coating film, the acetone acetone can be volatilized by heating at a desired time, so that it can be self-coated. Membrane removal. Thereby, the crosslinking reaction of the crosslinking agent can be advanced.

The compounding quantity of a crosslinking inhibitor is 100 mass parts or more with respect to 100 mass parts of crosslinking catalysts, for example, Preferably it is 1000 mass parts or more. Moreover, this compounding quantity is 5000 mass parts or less, for example.

The colorant has compatibility with the first phase and does not have compatibility with the second phase. The colorant is preferably a compound (color-developing compound) that develops color by reaction with an acid. When the colorant is a color-developing compound, the adhesive composition further contains a photoacid generator.

As a color developing compound, a leuco dye, a triarylmethane dye, a diphenylmethane dye, a fluoran dye, a spiropyran dye, and a rhodamine dye are mentioned, for example. The color-developing compound may be used alone or in combination of two or more.

As a leuco dye, for example, 2'-anilino-6'-(N-ethyl-N-isoamylamino)-3'-methylspiro[phthalide-3,9'- [9H]Dibenzopyran], 3-dibutylamino-6-methyl-7-anilinofluoran, 3-dipropylamino-6-methyl-7-anilinofluoran, 3-Diethylamino-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6- Methyl-7-xylaminofluoran, and 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3- base)-4-azaphthalolide.

As a triarylmethane coloring matter, p,p',p''-tris-dimethylamino triphenylmethane is mentioned, for example. As a diphenylmethane coloring matter, 4, 4- bis- dimethylamino phenyl diphenylmethyl benzyl ether is mentioned, for example. As a fluoran dye, 3-diethylamino-6-methyl-7-chlorofluoran is mentioned, for example. As a spiropyran dye, 3-methylspirodinaphthopyran is mentioned, for example. As a rhodamine coloring matter, rhodamine-B-anilinolactam is mentioned, for example.

From the viewpoint of ensuring good colorability of the adhesive layer 10, as the color-developing compound, it is preferable to use a leuco dye, and it is more preferable to use 2'-anilino-6'-(N-ethyl-N -Isoamylamino)-3'-methylspiro[phthalolactone-3,9'-[9H]dibenzopyran].

The compounding amount of the color-developing compound is preferably 0.5 part by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the polymer component. The compounding amount is preferably 10 parts by mass or less, more preferably 7 parts by mass or less.

The photoacid generator is irradiated with active energy rays as an external stimulus to generate acid. Therefore, an acid is generated from the photoacid generator in the portion of the adhesive layer 10 irradiated with the active energy ray, and the color-developing compound is colored by the acid. From the viewpoint of favorably developing the color-developing compound, the photoacid generator preferably has compatibility with the first phase and does not have compatibility with the second phase. The portion of the adhesive layer 10 irradiated with the active energy rays is colored, for example, in a dark color according to the color development of the color-developing compound. The type of active energy rays is determined according to the type of photoacid generator (specifically, the wavelength of the active energy rays from which the photoacid generator generates acid). Examples of active energy rays include ultraviolet rays, visible light, infrared rays, X-rays, alpha rays, beta rays, and gamma rays. From the viewpoint of the variety of equipment to be used and the ease of handling, as the active energy ray, ultraviolet rays are preferably used.

As a photoacid generator, the onium compound which produces|generates an acid by ultraviolet irradiation is mentioned, for example. The onium compound is provided, for example, in the form of an onium salt of an onium cation and an anion. As an onium cation, iodonium and perium are mentioned, for example. Examples of the anions include Cl ^- , Br ^- , I ^- , ZnCl ₃ ^- , HSO ₃ ^- , BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SbF ₆ ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ HSO ₃ ^- , (C ₆ F ₅ ) ₄ B ^- , and (C ₄ H ₉ ) ₄ B ^- . The photoacid generators may be used alone or in combination of two or more. The adhesive composition preferably contains an onium salt (onium compound) containing perium and C ₄ F ₉ HSO ₃ ^- as a photoacid generator.

The compounding amount of the acid generator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more with respect to 100 parts by mass of the polymer component. The compounding amount is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less.

The compounding amount of the acid generator is, for example, 100 parts by mass or more, preferably 200 parts by mass or more, more preferably 300 parts by mass or more, and still more preferably 330 parts by mass or more, relative to 100 parts by mass of the color-developing compound. The compounding amount is preferably 1000 parts by mass or less, more preferably 700 parts by mass or less, and still more preferably 500 parts by mass or less.

The adhesive composition may also contain other ingredients as needed. As other components, a silane coupling agent, an adhesiveness imparting agent, a plasticizer, a softener, an antioxidant, a surfactant, and an antistatic agent are mentioned, for example.

The adhesive sheet S can be produced by, for example, applying the above-mentioned adhesive composition on a release film (first release film) to form a coating film, and then drying the coating film (in FIG. 1 , indicated by a phantom line). An adhesive sheet S) is arranged on the release film L.

As a release film (release liner), the plastic film which has flexibility is mentioned, for example. As this plastic film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film are mentioned, for example. The thickness of the release film is, for example, 3 μm or more and, for example, 200 μm or less. The surface of the release film is preferably subjected to release treatment.

Examples of the coating method of the adhesive composition include roll coating, touch roll coating, gravure coating, reverse coating, roll brush coating, spray coating, dip roll coating, bar coating, Blade coating, air knife coating, curtain coating, die lip coating, and die nozzle coating. The drying temperature of the coating film is, for example, 50°C to 200°C. The drying time is, for example, 5 seconds to 20 minutes.

When the adhesive composition contains a crosslinking agent, the crosslinking reaction proceeds by aging simultaneously with the above drying or aging after drying. The aging conditions are appropriately set according to the type of the crosslinking agent. The aging temperature is, for example, 20°C to 160°C. The aging time is, for example, 1 minute to 7 days.

Before or after aging, a release film (second release film) may be further laminated on the adhesive layer 10 on the first release film. The second release film is a flexible plastic film with surface release treatment, and the same as that described above for the first release film can be used.

In this way, the adhesive sheet S in which the adhesive surface is protected by the release film can be produced. When using the adhesive sheet S, each release film is peeled from the adhesive sheet S as needed.

From the viewpoint of securing sufficient adhesiveness to the adherend, the thickness of the adhesive layer 10 is preferably 10 μm or more, more preferably 15 μm or more. From the viewpoint of the handleability of the adhesive sheet S, the thickness of the adhesive layer 10 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, and particularly preferably 50 μm or less.

The haze of the adhesive layer 10 (the haze before an external stimulus is applied to the adhesive layer 10 ) is preferably 3% or less, more preferably 2% or less, and more preferably 1% or less. Such a configuration is suitable for inspecting the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after the adhesive sheet S is attached to the adherend. The haze of the adhesive layer 10 can be measured using a haze meter in accordance with JIS K7136 (2000). As a haze meter, "NDH2000" by Nippon Denshoku Kogyo Co., Ltd., and "HM-150 type" by Murakami Color Technology Laboratory Co., Ltd. can be mentioned, for example.

The average transmittance of the adhesive layer 10 at a wavelength of 400 to 700 nm (the average transmittance before applying external stimulation to the adhesive layer 10 ) is preferably 80% or more, more preferably 85% or more, and more preferably 90% above. Such a configuration is suitable for inspecting the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after the adhesive sheet S is attached to the adherend.

The adhesive force exhibited by the adhesive sheet S on the stainless steel plate in the peeling test at 23° C., peeling angle 180° and peeling speed (stretching speed) 300 mm/min after being attached to the glass plate is for example It is 1 N/25 mm or more and, for example, 50 N/25 mm or less.

In the adhesive sheet S, the first discoloration width W1 of the discolored region in the adhesive layer 10 is formed by linearly applying an external stimulus to the adhesive layer 10, and the adhesive layer is further heated at 85°C. 10. The second discoloration width W2 of the discolored region after heat treatment for 120 hours satisfies the following formula (1).

0.5≦W2/W1≦2・・・(1)

Such a configuration is suitable for suppressing deterioration (bleeding, fading, uneven color tone, etc.) of the discolored portion formed in the adhesive layer 10 , and thus contributes to maintaining the functional properties of the discolored portion.

The first discoloration width W1 of the discolored region in the adhesive layer 10 is formed by applying an external stimulus linearly to the adhesive layer 10, and further, the adhesive layer 10 is subjected to The third discoloration width W3 of the discolored region after the 120-hour heat treatment satisfies the following formula (2).

0.5≦W3/W1≦2.3・・・(2)

Such a configuration is suitable for suppressing deterioration (bleeding, fading, uneven color tone, etc.) of the discolored portion formed in the adhesive layer 10 , and thus contributes to maintaining the functional properties of the discolored portion.

As shown in FIG. 3 , the adhesive sheet S may be a single-sided adhesive sheet having a base material 20 in addition to the adhesive layer 10 . In this case, specifically, the adhesive sheet S is provided with the adhesive layer 10 and the base material 20 arrange|positioned at one surface side of the thickness direction. Preferably, the substrate 20 is in contact with one surface in the thickness direction of the adhesive layer 10 .

The base material 20 is an element that functions as a transparent support. The substrate 20 is, for example, a flexible plastic film. As a constituent material of the plastic film, for example, polyolefin, polyester, polyamide, polyimide, polyvinyl chloride, polyvinylidene chloride, cellulose, polystyrene, and polycarbonate may be mentioned. As the polyolefin, for example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene /vinyl acetate copolymer, ethylene/ethyl acrylate copolymer, and ethylene/vinyl alcohol copolymer. As polyester, for example, polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate may be mentioned. As the polyamide, for example, polyamide 6, polyamide 6,6, and partially aromatic polyamide may be mentioned. Regarding the base material 20, from the viewpoint of taking into account both its transparency and mechanical strength, the plastic material of the base material 20 is preferably polyester, more preferably polyethylene terephthalate.

The base material 20 has transparency. The haze of the base material 20 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. The haze of the base material 20 can be measured using a haze meter according to JIS K7136 (2000).

The surface of the substrate 20 on the side of the adhesive layer 10 may be subjected to physical treatment, chemical treatment, or primer treatment for improving the adhesion with the adhesive layer 10 . As a physical treatment, corona treatment and plasma treatment are mentioned, for example. As a chemical treatment, an acid treatment and an alkali treatment are mentioned, for example.

From the viewpoint of securing the strength of the base material 20 to function as a support, the thickness of the base material 20 is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 20 μm or more. Moreover, from the viewpoint of realizing moderate flexibility of the adhesive sheet S, the thickness of the base material 20 is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

The adhesive sheet S shown in FIG. 3 can be manufactured by the same method as the above-mentioned manufacturing method of an adhesive sheet except that the base material 20 is used instead of the 1st peeling film, for example.

4A to 4C show an example of a method of using the adhesive sheet S. As shown in FIG. The method includes a preparation step, a bonding step, and a discolored portion forming step.

First, in a preparation process, as shown to FIG. 4A, the adhesive sheet S, the 1st member 31, and the 2nd member 32 are prepared. The first member 31 is, for example, a display panel such as an organic EL panel. The first member 31 may be other electronic devices and optical devices. The second member 32 is, for example, a transparent base material. As a transparent base material, a transparent plastic base material and a transparent glass base material are mentioned.

Next, in a joining process, as shown to FIG. 4B, the 1st member 31 and the 2nd member 32 are joined via the adhesive sheet S. Thereby, the laminated body Z is obtained. In the laminated body Z, the adhesive sheet S is arrange|positioned so that the thickness direction one surface of the 1st member 31 may contact, and the 2nd member 32 may be arrange|positioned so that the thickness direction surface contact of this adhesive sheet S may be carried out.

After the bonding step, the presence or absence of foreign matter and air bubbles between the members 31 and 32 and the adhesive sheet S is inspected as necessary.

Next, in the step of forming the discolored portion, as shown in FIG. 4C , an external stimulus is applied to the adhesive layer 10 in the laminate Z to form the discolored portion 11 in the adhesive layer 10 . Specifically, the adhesive layer 10 is irradiated with active energy rays as an external stimulus through a mask pattern (not shown) for shielding a specific area of the adhesive layer 10 from the side of the transparent second member 32 . Thereby, the part of the adhesive layer 10 that is not covered by the mask pattern is discolored.

As a light source for active energy ray irradiation in this step, an ultraviolet LED (Light Emitting Diode, light emitting diode) lamp, a high pressure mercury lamp, and a metal halide lamp are mentioned, for example. In addition, in the irradiation of active energy rays in this step, a wavelength cutoff filter may be used as needed, which is used to cut off a part of the wavelength region of the active energy rays emitted from the light source.

In this step, in the portion of the adhesive layer 10 irradiated with active energy rays, an acid is generated by the photoacid generator, and the color-developing compound is colored by the reaction with the acid. Thereby, the discolored portion 11 is formed in the adhesive layer 10 .

For example, the adhesive sheet S can be used for bonding between members in the above-described manner. When the first member 31 is a display panel such as an organic EL panel, by providing the discolored portion 11 in a pattern shape corresponding to (ie, opposite to) the metal wiring formed on the pixel panel included in the panel, the metal wiring can be suppressed. External light reflection from wiring.

In the adhesive sheet S, as described above, the adhesive layer 10 contains a coloring agent that can be developed by external stimulation. Therefore, after the adhesive sheet S is attached to the adherend (in the present embodiment, the members 31 and 32), the adhesive layer 10 can be made to be discolored by applying an external stimulus to the portion to be discolored in the adhesive layer 10. Local discoloration. The adhesive sheet S that can form the discolored portion 11 in the adhesive layer 10 after being attached to the adherend can be inspected between the adhesive sheet S and the adherend after lamination and before the discolored portion 11 of the adhesive layer 10 is formed Whether there are foreign objects and air bubbles.

Furthermore, in the adhesive sheet S, as described above, the adhesive layer 10 includes a polymer component having a microphase-separated structure including a first phase and a second phase, and the color-developing compound as a colorant has a Compatibility of the first phase, and no compatibility with the second phase. In such an adhesive sheet S, after the discolored portion is formed on the adhesive layer 10 (that is, after the color-developing compound is colored by an external stimulus), the color-developing compound tends to stay in the region of the first phase. , which is suitable for inhibiting the movement (diffusion, etc.) of the color-developing compound in the adhesive layer 10 . Deterioration (bleeding, fading, uneven color tone, etc.) of the discolored part is suppressed by suppressing the movement of the color-developing compound.

As described above, the adhesive sheet S can discolor at least a part of the adhesive layer 10 after being attached to the adherend, and is suitable for suppressing deterioration of the discolored part of the adhesive layer 10 . Suppressing the deterioration of the discolored portion of the adhesive layer 10 helps to maintain the functional properties of the discolored portion, such as designability, light-shielding property, and anti-reflection property. [Example]

Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to an Example. In addition, the specific numerical values such as the compounding amount (content), physical property value, parameter, etc. described below can be replaced by the upper limit of the compounding amount (content), physical property value, parameter, etc. corresponding to the compounding amount (content), physical property value, parameter, etc. described in the above-mentioned "Embodiment" (defined as "under" or "under" value) or lower limit (defined as "above" or "over" value).

[Example 1] <Preparation of polymer components> In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, 95 parts by mass of styrene, 5 parts by mass of 4-hydroxybutyl acrylate (4HBA), and trithiocarbonic acid as a chain transfer agent: 1.45 parts by mass of bis{4-[ethyl-(2-acetoxyethyl)aminocarboxy]benzyl}ester, 2,2'-azobis(isobutyric acid) as a polymerization initiator A mixture of 0.12 parts by mass of dimethyl ester and 36 parts by mass of anisole as a solvent was stirred at 130° C. for 7 hours under a nitrogen atmosphere (polymerization reaction). Thereby, a copolymer of styrene and 4HBA (styrene-4HBA copolymer) was obtained. The weight average molecular weight (Mw) of the copolymer was 26,000.

Next, in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, 70 parts by mass of 2-ethylhexyl acrylate (2EHA) and 30 parts by mass of the above-mentioned styrene-4HBA copolymer (solid A mixture of 0.04 parts by mass of dimethyl 2,2'-azobis(isobutyrate) as a polymerization initiator, and 57 parts by mass of ethyl acetate as a solvent was heated at 75°C under nitrogen It was stirred under atmosphere for 7 hours (polymerization reaction). Thereby, a polymer solution (polymer solution P ₁ ) containing the acrylic block polymer was obtained. The weight average molecular weight (Mw) _of the acrylic block polymer in the polymer solution P1 was 86,000. Further, the acrylic block polymer has a styrene-4HBA copolymer block (first polymer block) as a hard block (first segment) and a 2EHA block as a soft segment (second segment) segment (2nd polymer block).

<Preparation of adhesive composition> To the polymer solution P1 containing the acrylic block polymer, an isocyanate crosslinking agent (commercial product) was added as a crosslinking agent per ₁₀₀ parts by mass of the acrylic block polymer (polymer component). Name "Takenate D110N", a 75% ethyl acetate solution of a trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals Co., Ltd.) 0.25 parts by mass (in terms of solid content), as a crosslinking catalyst Dibutyltin dilaurate (trade name "OL-1", 1 mass % ethyl acetate solution, manufactured by Tokyo Fine Chemical Co., Ltd.) 0.01 mass part (solid content conversion amount), as a crosslinking inhibitor (for crosslinking contact 3 parts by mass of acetone acetone as a ligand of the medium, and a leuco dye (trade name "S-205", 2'-anilino-6'-(N-ethyl-N-iso) as a color-developing compound Amylamino)-3'-methylspiro[phthalolactone-3,9'-[9H]dibenzopyran], manufactured by Yamada Chemical Industry Co., Ltd.) 2 parts by mass, and a photoacid generator (trade name "SP-056", onium salt of perionium and C ₄ F ₉ HSO ₃ ^- , manufactured by ADEKA Corporation) 7 parts by mass were mixed to prepare an adhesive composition.

<Formation of the adhesive layer> A coating film was formed by coating the adhesive composition on the release-treated surface of a 38 μm-thick base film (trade name “MRF#38”, polyester film, manufactured by Mitsubishi Plastics Corporation) that had undergone release treatment on one side. Next, the coating film was dried by heating at 132° C. for 3 minutes. Thereby, an adhesive layer with a thickness of 25 μm was formed on the base film. Next, the release-treated surface of a release film with a thickness of 38 μm (trade name “MRE #38”, polyester film, manufactured by Mitsubishi Plastics Corporation), which has been released on one side, is attached to the adhesive on the base film. Floor. Thereafter, aging treatment was performed at 60° C. for 24 hours to allow the crosslinking reaction in the adhesive layer to proceed. The adhesive sheet of Example 1 was produced in the above-described manner. About the composition of the polymer component and the adhesive layer in the adhesive sheet of Example 1, the unit is shown in Table 1 as part by mass (the same applies to the following Examples and Comparative Examples).

[Example 2] In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, a 75 parts by mass of 2-ethylhexyl acrylate (2EHA) and methyl methacrylate (MMA) were prepared in a reaction vessel. Monomer (trade name "AA-6", manufactured by Toagosei Co., Ltd.) 20 parts by mass, 4-hydroxybutyl acrylate (4HBA) 5 parts by mass, 2,2'-azobisisobutyronitrile as a polymerization initiator A mixture of 0.2 parts by mass of (AIBN), 80 parts by mass of ethyl acetate as a solvent, and 50 parts by mass of methyl ethyl ketone was stirred at 60° C. for 7 hours under a nitrogen atmosphere (polymerization reaction). Thereby, a polymer solution (polymer solution P ₂ ) containing an acrylic acid graft polymer was obtained. _The weight average molecular weight (Mw) of the acrylic graft polymer in the polymer solution P2 was 350,000. In addition, the acrylic graft polymer has a polymer main chain as a soft segment (second segment) containing the main component 2EHA, and a polymer side chain as a hard block (first segment) containing the main component MMA . Then, the adhesive sheet of Example 2 was produced in the same manner as the adhesive sheet of Example 1, except that the polymer solution P ₂ was used instead of the polymer solution P ₁ in preparing the adhesive composition.

[Comparative Example 1] In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, 63 parts by mass of 2-ethylhexyl acrylate (2EHA) and 9 parts by mass of methyl methacrylate (MMA) were prepared parts, 13 parts by mass of 2-hydroxyethyl acrylate (HEA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 2,2'-azobisisobutyronitrile ( A mixture of 0.2 parts by mass of AIBN) and 233 parts by mass of ethyl acetate as a solvent was stirred at 60° C. for 7 hours under a nitrogen atmosphere (polymerization reaction). Thereby, the polymer solution (polymer solution _P3 ) containing an acrylic polymer was obtained. The weight average molecular weight (Mw) of the acrylic polymer in the polymer solution _P3 was 1.2 million. In addition, the acrylic polymer is a random copolymer. Then, the adhesive sheet of Comparative Example 1 was produced in the same manner as the adhesive sheet of Example 1, except that the polymer solution P ₃ was used instead of the polymer solution P ₁ in preparing the adhesive composition.

<Presence or absence of microphase separation structure> The presence or absence of a microphase-separated structure was confirmed as follows with respect to the adhesive layer of each of the adhesive sheets of Examples 1, 2 and Comparative Example 1. First, a sample for transmission electron microscope (TEM) observation is produced. Specifically, the adhesive layer was dyed and then rapidly frozen, and a thin slice was cut out from the adhesive layer using an ultramicrotome (manufactured by Leica). Then, with respect to this sheet, observation and imaging were performed using a transmission electron microscope (trade name "HT7820", manufactured by Hitachi High-Technologies Corporation). Next, the obtained TEM image is analyzed and binarized by image analysis software.

In the adhesive layer of the adhesive sheet of Example 1, as shown in FIG. 5 , a microphase-separated structure was confirmed. The microphase separation structure of the adhesive layer is the spherical structure shown in FIG. 2A . Specifically, in the adhesive layer, benzene as a hard block (first segment) is dispersed in a matrix (second phase) formed by the 2EHA block as a soft segment (second segment) The dispersed phase formed by ethylene-4HBA copolymer blocks.

In the adhesive layer of the adhesive sheet of Example 2, as shown in FIG. 6 , a microphase-separated structure was confirmed. The microphase separation structure of the adhesive layer is the spherical structure shown in FIG. 2A . Specifically, in the adhesive layer, in the matrix (second phase) formed by the polymer main chain which is the soft segment (second segment) containing the main components 2EHA and 4HBA, as the main component is dispersed The dispersed phase formed by the polymer side chains of the hard block (first segment) of MMA and 4HBA.

In the adhesive layer of Comparative Example 1, as shown in FIG. 7, the microphase separation structure was not confirmed.

<Compatibility Judgment Test> For each of the color-developing compounds and photoacid generators used in Examples 1, 2 and Comparative Example 1, the compatibility with various monomers was investigated.

Specifically, first, styrene, 4-hydroxybutyl acrylate (4HBA), methyl methacrylate (MMA), acrylic acid, N-vinyl-2-pyrrolidone (NVP), 2-methoxy acrylate were prepared Each solution of methyl ethyl ester (2MEA), methyl acrylate, 2-ethylhexyl acrylate (2EHA), lauryl acrylate (dodecyl acrylate), and stearyl acrylate (octadecyl acrylate) as a monomer solution. As a monomer solution, a mixed solution of 95 mass % of styrene and 5 mass % of 4HBA was also prepared.

Next, in a 50 mL spiral tube, a mixture (the ratio of the compound C: 2.5 mass %) containing 7.8 g of the monomer solution and 0.2 g of the compound C (color developing compound or photoacid generator) was stirred. The stirring system uses a magnetic stirrer. During stirring, the temperature was set to 25° C., the rotational speed of the stirrer was set to 500 rpm, and the stirring time was set to 5 minutes. After the stirring, it was visually confirmed whether or not the compound C was dissolved in the monomer solution by such stirring without turbidity or precipitation. The color-developing compound and the photoacid generator were dissolved in each solution of styrene, 4HBA, MMA, acrylic acid, NVP, 2MEA, and methyl acrylate, and a mixed solution of 95% by mass of styrene and 5% by mass of 4HBA. Cloudiness or precipitation occurred (compound C showed compatibility). On the other hand, the color-developing compound and the photoacid generator were not dissolved in each solution of 2EHA, lauryl acrylate, and stearyl acrylate, respectively, resulting in cloudiness or precipitation (compound C did not show compatibility).

Then, it was determined that the segment containing 80% by mass or more of the same monomer composition as the monomer solution in which the compound C exhibited the above-mentioned compatibility was formed in a microphase-separated structure by the polymer component having the segment phase is compatible. In addition, it was determined that the segment containing 80% by mass or more of the same monomer composition as the monomer solution in which the compound C did not exhibit the above-mentioned compatibility was formed in the microphase separation by the polymer component having the segment. The phases within the structure are not compatible. That is, the color-developing compound and the photoacid generator used in Examples 1, 2 and Comparative Example 1 were formed in a microphase-separated structure with respect to the hard block (HS) containing 95% by mass of styrene and 5% by mass of 4HBA, respectively. The inner phase (the first phase in Example 1) is compatible (in the HS in Example 1, the ratio of the monomer (styrene, 4HBA) that compound C shows compatibility is 80% by mass or more ). The color-developing compounds and photoacid generators used in Examples 1, 2 and Comparative Example 1 respectively form a phase in a microphase-separated structure with respect to HS containing MMA as a main component (the first phase in Example 2) Compatibility (in the HS in Example 2, the ratio of the monomers (MMA, 4HBA) showing compatibility in Compound C is 80% by mass or more). In addition, the color developing compounds and the photoacid generators used in Examples 1, 2 and Comparative Example 1 were respectively used for the phase in which the soft segment (SS) containing 2EHA as the main component was formed in the microphase separation structure (Example). The second phase in 1 and 2) has no compatibility (in SS in Examples 1 and 2, the ratio of the monomer (2EHA) for which compound C does not show compatibility is 80% by mass or more).

＜Haze＞ About the adhesive layer of each of the adhesive sheets of Examples 1, 2 and Comparative Example 1, the haze was examined as follows. First, a sample for haze measurement is prepared. Specifically, after peeling the release film (MRE#38) from the adhesive sheet, the adhesive layer side of the sheet (substrate film, adhesive layer) was attached to Eagle glass (thickness 0.55 mm, Matsunami Glass Co., Ltd.). manufacture), the substrate film (MRF #38) was peeled from the adhesive layer on Eagle glass. Thereby, the sample for haze measurement (1st sample for measurement) was produced. Next, the haze of the adhesive layer in the sample was measured using a haze measuring apparatus (trade name "HZ-1", manufactured by Suka Testing Machine Co., Ltd.) (first haze measurement). In this measurement, the sample for measurement is installed in the apparatus so that light is irradiated to the sample for measurement from the Eagle glass side of the sample for measurement. In addition, in this measurement, the measurement result obtained by measuring only Eagle glass under the same conditions was used as a reference line. The haze (before UV (ultraviolet) irradiation) of the adhesive layer obtained in this way is shown in Table 1.

On the other hand, with respect to each of the adhesive sheets of Examples 1 and 2 and Comparative Example 1, the haze after UV irradiation was examined as follows.

First, the same sample as the above-mentioned first measurement sample is prepared. Next, the sample is irradiated with ultraviolet rays. Specifically, for the adhesive sheet (adhesive layer) in the sample, in an environment of 23° C. and a relative humidity of 50%, ultraviolet rays were irradiated through the glass from the Eagle glass side (by the UV irradiation, the adhesive layer was The leuco pigment reacts with the photoacid generator). In this UV irradiation, a UV-LED lamp with a wavelength of 365 nm in a UV-LED irradiation device (model "QEL-350-RU6W-CW-MY") manufactured by Quark Technology was used as a light source, and the cumulative light intensity of irradiation was set to 8000 mJ/cm ² (the cumulative light intensity of irradiation within the wavelength range of 320 to 390 nm). In the above-described manner, a sample for measurement (second sample for measurement) was prepared.

Next, with respect to the second measurement sample, the haze of the adhesive layer in the sample was measured using a haze measuring apparatus (trade name "HZ-1", manufactured by Suka Testing Machine Co., Ltd.) (second haze measurement). Regarding the specific measurement method and conditions, the second haze measurement is the same as the above-mentioned first haze measurement. The haze (after UV irradiation) of the adhesive layer obtained in this way is shown in Table 1.

<Durability test> Regarding the adhesive layer of each of the adhesive sheets of Examples 1, 2 and Comparative Example 1, the degree of suppression of exudation of the discolored portion formed was investigated as follows.

First, for each of the adhesive sheets of Examples 1, 2 and Comparative Example 1, a plurality of adhesive sheets were prepared.

Next, by irradiating ultraviolet rays to the adhesive layer of the adhesive sheet through a photomask having a linear opening, a linear discolored portion is formed in the adhesive layer. The photomask is formed by a dry film photoresist arranged on the side surface of the base film in the adhesive sheet, and the line width of the opening of the photomask is about 200 μm (the line width of the opening of each photomask is different) . In the ultraviolet irradiation, a UV-LED lamp with a wavelength of 365 nm in the UV-LED irradiation device (model "QEL-350-RU6W-CW-MY") manufactured by Quark Technology was used as the light source, and the mask and the substrate were separated. The film was irradiated with ultraviolet rays to the adhesive layer, and the cumulative light intensity of irradiation was set to 2000 mJ/cm ² (the cumulative light intensity of irradiation in the range of wavelength 320 to 390 nm).

Next, the line width of the linear discolored portion formed in the adhesive layer was measured (measurement of the initial line width). Specifically, first, the linear discolored portion formed in the adhesive layer was observed with a digital microscope (trade name "VHX-900", manufactured by KEYENCE Corporation), and a portion including the discolored portion and its vicinity were photographed at a magnification of 50 times. area. Next, the captured image is binarized by the image analysis software. Next, in the image after the binarization process, the line width (W1) of the linearly discolored portion is measured.

Next, the adhesive sheet in which the linear discoloration portion was formed in the adhesive layer was heat-treated at 85° C. for 120 hours (1st durability test).

Next, the line width of the linear discolored portion in the adhesive layer of the adhesive sheet was measured. The specific measurement method is the same as that described above for the determination of the initial line width. The line width W1 of the linear discolored portion before the first durability test, the line width W2 of the linear discolored portion after the first durability test, and the amount of change from the line width W1 to the line width W2 (|W2-W1| ), and the rate of change of the line width W2 with respect to the line width W1 (W2/W1) are shown in Table 1.

On the other hand, with respect to the adhesive layers of the adhesive sheets of Examples 1, 2 and Comparative Example 1, the second durability test was carried out instead of the first durability test, and the investigation was carried out in the same manner as described above. The degree of oozing inhibition of the formed linear discolored portion. In the second durability test, the adhesive sheet on which the linear discoloration portion was formed in the adhesive layer was subjected to heat treatment at 65° C. and a relative humidity of 90% for 120 hours. The line width W1 of the linear discolored portion before the second durability test, the line width W3 of the linear discolored portion after the second durability test, and the amount of change from the line width W1 to the line width W3 (|W3-W1| ), and the rate of change of the line width W3 with respect to the line width W1 (W3/W1) are shown in Table 1.

Regarding the amount of change (|W2-W1|) and the rate of change (W2/W1) of the line width of the linear discolored portion after the first durability test, the adhesive sheets of Examples 1 and 2 were smaller than those of Comparative Example 1. Sheet. Regarding the amount of change (|W3-W1|) and the rate of change (W3/W1) of the line width of the linear discolored portion after the second durability test, the adhesive sheets of Examples 1 and 2 were also smaller than those of Comparative Example 1. Adhesive sheet. That is, in each of the adhesive sheets of Examples 1 and 2, as compared with the adhesive sheet of Comparative Example 1, the change (deterioration) of the discolored portion of the adhesive layer was suppressed.

[Table 1] Example 1 Example 2 Comparative Example 1 polymer composition Styrene 28.5 (HS principal component) ― ― MMA ― 20 (HS principal component) 9 4HBA 1.5 5 ― HEA ― ― 13 NVP ― ― 15 2EHA 70 (SS principal component) 75 (SS principal component) 63 Chromogenic compounds ( leuco pigments) 2 2 2 Photoacid generator (SP-056) 7 7 7 Crosslinker ( Isocyanate Crosslinker) 0.25 0.25 0.25 Cross-linking catalyst ( dibutyltin dilaurate) 0.01 0.01 0.01 Crosslinking inhibitor ( acetone acetone) 3 3 3 Haze of the adhesive layer (%) Before UV irradiation 1.0 2.7 0.5 After UV irradiation 1.0 2.2 0.6 The first durability test (85 ℃, 120 h) W1(μm) 360.0 291.1 340.0 W2(μm) 342.2 300.0 708.9 |W2 －W1| 17.8 8.9 368.9 W2/W1 0.95 1.03 2.09 The second durability test (65 ℃, 90%RH, 120 h) W1(μm) 302.2 240.0 360.0 W3(μm) 302.2 266.7 853.4 |W3 －W1| 0 26.7 493.4 W3/W1 1.00 1.11 2.37

10: Adhesive layer 11: Discoloration part 20: Substrate 31: Component 1 32: Component 2 L: release film M1: Phase 1 M2: Phase 2 S: Adhesive sheet (color-changing adhesive sheet) Z: Laminate

FIG. 1 is a schematic cross-sectional view of one embodiment of the color-changing adhesive sheet of the present invention. FIG. 2 is a schematic view of an example of a microphase-separated structure in an adhesive layer. 2A and 2B show a spherical structure, FIGS. 2C and 2D show a cylindrical structure, FIGS. 2E and 2F show a spiral structure, and FIG. 2G shows a layered structure. 3 is a schematic cross-sectional view of a modification of the color-changing adhesive sheet of the present invention (when the color-changing adhesive sheet is a single-sided adhesive sheet with a base material). FIG. 4 shows an example of a method of using the color-changing adhesive sheet of the present invention. FIG. 4A shows the step of preparing the color-changing adhesive sheet and the member (adhered body), and FIG. 4B shows the step of joining the members to each other via the color-changing adhesive sheet. FIG. 4C shows the step of forming the discolored portion on the adhesive layer of the discolorable adhesive sheet. FIG. 5 is a TEM image of the adhesive layer of Example 1. FIG. FIG. 6 is a TEM image of the adhesive layer of Example 2. FIG. FIG. 7 is a TEM image of the adhesive layer of Comparative Example 1. FIG.

10: Adhesive layer

L: release film

S: Adhesive sheet (color-changing adhesive sheet)

Claims (9)

A color-changing adhesive sheet, which is provided with a color-changing adhesive layer, and The above-mentioned adhesive layer includes: a polymer component, which has a microphase-separated structure including a first phase and a second phase; and a coloring agent, which can be colored by external stimulation; The colorant has compatibility with the first phase and does not have compatibility with the second phase. The color-changing adhesive sheet according to claim 1, wherein the polymer component comprises a polymer having a first segment forming the first phase and a second segment forming the second phase in the molecule. The color-changing adhesive sheet according to claim 2, wherein the polymer is a block polymer, and the block polymer has a first polymer block as the first segment and a first polymer block as the second segment. 2 polymer blocks. The color-changing adhesive sheet according to claim 2, wherein the polymer is a graft polymer, and the graft polymer has a polymer main chain as the second segment and a polymer side as the first segment chain. The color-changing adhesive sheet according to claim 1, wherein the mass ratio of the second phase in the polymer component is greater than the mass ratio of the first phase. The color-changing adhesive sheet according to any one of claims 1 to 5, wherein the colorant is a compound that develops color by reaction with an acid, and The above-mentioned adhesive layer further contains a photoacid generator. The color-changing adhesive sheet according to claim 6, wherein the photoacid generator has compatibility with the first phase, and does not have compatibility with the second phase. The discolorable adhesive sheet according to any one of claims 1 to 5, wherein the first discoloration width W1, And the 2nd discoloration width W2 of the said discoloration area|region after heat-processing this adhesive bond layer at 85 degreeC for 120 hours satisfy|fills 0.5≦W2/W1≦2. The discolorable adhesive sheet according to any one of claims 1 to 5, wherein the first discoloration width W1, And further, the 3rd discoloration width W3 of the said discoloration area|region after heat-processing this adhesive layer at 65 degreeC and 90% of relative humidity for 120 hours satisfies 0.5≦W3/W1≦2.3.

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