KR20230062825A - variable color adhesive sheet - Google Patents

Abstract

The pressure-sensitive adhesive sheet (S) of the present invention is a variable-color pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer (10) capable of color change. The pressure-sensitive adhesive layer 10 contains a colorant capable of developing color by a first external stimulus, a base polymer, and a polymeric compound, and is curable by a second external stimulus different from the first external stimulus.

Description

variable color adhesive sheet

The present invention relates to a variable color adhesive sheet.

A display panel such as an organic EL panel has a laminated structure including a pixel panel, a cover member, and the like. In the manufacturing process of such a display panel, for example, a transparent adhesive sheet is used for bonding the elements included in the laminated structure.

In addition, as a transparent adhesive sheet disposed on the light output side (image display side) of a pixel panel in a display panel, a colored portion for imparting design, shielding, antireflection, etc. to a predetermined portion of the sheet is formed in advance. It has been proposed to use a pressure-sensitive adhesive sheet. Such an adhesive sheet is described, for example, in Patent Literature 1 below. Patent Literature 1 specifically describes an adhesive sheet having a colored portion containing a carbon black pigment.

Japanese Unexamined Patent Publication No. 2017-203810

However, in the case of using a PSA sheet having pre-formed colored portions in the manufacturing process of the display panel, after bonding the PSA sheet to the adherend, foreign matter and air bubbles between the adherend and the colored portion of the PSA sheet are removed. The presence or absence cannot be properly checked. In bonding of the adhesive sheet in the display panel manufacturing process, it is required to be able to properly inspect the presence or absence of foreign matter and air bubbles between the adherend and the adhesive sheet after the bonding.

On the other hand, from the viewpoint of securing the function of the colored portion provided on the transparent adhesive sheet for display panels, it is required that the diffusion of the colored component in the colored portion over time (ie, bleeding of the colored portion) is suppressed.

The present invention provides a color-changing pressure-sensitive adhesive sheet capable of locally discoloring the pressure-sensitive adhesive layer after bonding to an adherend, and suitable for suppressing spreading of discolored portions of the pressure-sensitive adhesive layer.

The present invention [1] is a color-changing pressure-sensitive adhesive sheet comprising a color-changing pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a colorant capable of developing color in response to a first external stimulus, a base polymer, and a polymerizable compound, and a color-changing pressure-sensitive adhesive sheet capable of being cured by a second external stimulus different from the external stimulus.

In the present invention [2], the pressure-sensitive adhesive layer includes the variable-color pressure-sensitive adhesive sheet according to the above [1], further containing a photopolymerization initiator.

In the present invention [3], the colorant is a compound that develops color by reaction with an acid, and the pressure-sensitive adhesive layer includes the variable color pressure-sensitive adhesive sheet according to [1] or [2] above, further containing a photo-acid generator. do.

In the present invention [4], the colorant is a compound that develops color by reaction with an acid, the pressure-sensitive adhesive layer further contains a photoacid generator and a photopolymerization initiator, and the photopolymerization initiator with respect to the absorbance X of the photoacid generator The variable color adhesive sheet described in [1] above, which has a wavelength region in which the ratio of absorbance Y is 2 or more, within a wavelength range of 300 nm or more and 500 nm or less is included.

In the present invention [5], in any one of [1] to [4], the content of the polymerizable compound in the pressure-sensitive adhesive layer is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the base polymer. and the variable color pressure-sensitive adhesive sheet described above.

In the present invention [6], the pressure-sensitive adhesive layer includes the variable-color pressure-sensitive adhesive sheet according to any one of [1] to [5], wherein the pressure-sensitive adhesive layer has a thickness of 10 μm or more and 300 μm or less.

This invention [7] includes the variable color adhesive sheet according to any one of [1] to [6] above, further comprising a base material disposed on one side of the pressure-sensitive adhesive layer in the thickness direction.

In the variable color pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer contains a colorant capable of developing color in response to a first external stimulus as described above. Therefore, after the color-changing PSA sheet is bonded to the adherend, the color of the PSA layer can be locally discolored by applying a first external stimulus to the portion to be discolored in the PSA layer. In such a color-changing pressure-sensitive adhesive sheet, the presence or absence of foreign substances and air bubbles between the sheet and the adherend can be inspected after bonding and before formation of the discolored portion of the pressure-sensitive adhesive layer.

Further, in the variable color pressure sensitive adhesive sheet, the pressure sensitive adhesive layer contains a base polymer and a polymerizable compound as described above, and is curable by a second external stimulus different from the first external stimulus. Such a color-changing pressure-sensitive adhesive sheet has a region including a portion to be discolored or a discolored portion in the pressure-sensitive adhesive layer (e.g., The entirety of the pressure-sensitive adhesive layer) is suitable for increasing the modulus of elasticity after bonding. Such high modulus of elasticity of the pressure-sensitive adhesive layer is suitable for suppressing the diffusion of the colorant in the pressure-sensitive adhesive layer, and therefore, in the pressure-sensitive adhesive layer having a discolored portion, it is suitable for suppressing the spreading of the discolored portion.

1 is a cross-sectional schematic view of an embodiment of a variable color pressure-sensitive adhesive sheet of the present invention.
Fig. 2 is a schematic cross-sectional view of a modified example of the variable-color PSA sheet of the present invention (where the variable-color PSA sheet is a single-sided PSA sheet with a base material).
3 shows an example of a method of using the variable color pressure-sensitive adhesive sheet of the present invention. Fig. 3A shows a step of preparing a variable color PSA sheet and a member (adhered body), Fig. 3B shows a step of bonding members to each other via the variable color PSA sheet, and Fig. 3C shows a variable color PSA sheet A process of curing the pressure-sensitive adhesive layer is shown, and FIG. 3D shows a process of forming a discolored portion in the pressure-sensitive adhesive layer of the variable color pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet S as an embodiment of the variable-color pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer 10 as shown in FIG. 1 . The adhesive sheet S has a sheet shape with a predetermined thickness and extends in a direction (surface direction) orthogonal to the thickness direction. The adhesive sheet S is, for example, a transparent adhesive sheet disposed on the image display side of a pixel panel in a display panel such as an organic EL panel (having a laminated structure including a pixel panel and a cover member). used

The pressure-sensitive adhesive layer 10 is a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition and having transparency (visible light transmission). The adhesive composition further contains a base polymer, a polymerizable compound, a colorant capable of developing color in response to a first external stimulus, and a photopolymerization initiator in the present embodiment. A portion of the pressure-sensitive adhesive layer 10 subjected to a first external stimulus described later may be discolored. That is, the transparency of the portion of the pressure-sensitive adhesive layer 10 subjected to the first external stimulus can be lowered ex post facto. In addition, the pressure-sensitive adhesive layer 10 can be cured by a second external stimulus described later different from the first external stimulus.

The base polymer is an adhesive component for expressing adhesiveness in the adhesive layer 10 . The base polymer exhibits rubber elasticity in the room temperature region. Examples of the base polymer include acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluoropolymers. From the viewpoint of ensuring good transparency and adhesiveness of the pressure-sensitive adhesive layer 10, an acrylic polymer is preferably used as the base polymer.

The content of the base polymer in the pressure-sensitive adhesive layer 10 is preferably 50% by mass or more, more preferably 60% by mass or more, from the viewpoint of appropriately expressing the function of the base polymer in the pressure-sensitive adhesive layer 10. More preferably, it is 70 mass % or more.

An acrylic polymer is, for example, a polymer obtained by polymerizing a monomer component containing an alkyl (meth)acrylate in a proportion of 50% by mass or more. "(meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As an alkyl (meth)acrylate, the (meth)acrylic acid alkylester which has a linear or branched C1-C20 alkyl group is mentioned, for example. Examples of such alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, and (meth)acrylate. ) Isobutyl acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, (meth) Heptyl acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, (meth)acrylic acid Isodecyl, (meth)acrylate undecyl, (meth)acrylate dodecyl, (meth)acrylate isotridecyl, (meth)acrylate tetradecyl, (meth)acrylate isotetradecyl, (meth)acrylate pentadecyl, (meth)acrylate hexadecyl acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. (meth)acrylic-acid alkyl ester may be used independently, and 2 or more types may be used together. As the (meth)acrylic acid alkyl ester, preferably, an alkyl acrylate ester having an alkyl group of 1 to 12 carbon atoms is used, more preferably, methyl acrylate and an alkyl acrylate ester having an alkyl group of 2 to 12 carbon atoms are used together , More preferably, methyl acrylate and 2-ethylhexyl acrylate are used together.

The proportion of (meth)acrylic acid alkyl ester in the monomer component is preferably 50% by mass or more, more preferably 60% by mass or more, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the pressure-sensitive adhesive layer 10 , More preferably, it is 70 mass % or more. The ratio is, for example, 99% by mass or less.

The monomer component may also contain a copolymerizable monomer copolymerizable with (meth)acrylic acid alkyl ester. As a copolymerizable monomer, the monomer which has a polar group is mentioned, for example. Examples of the polar group-containing monomer include a hydroxyl group-containing monomer, a monomer having a nitrogen atom-containing ring, and a carboxy group-containing monomer. The polar group-containing monomer is useful for modifying the acrylic polymer, such as introducing a crosslinking point into the acrylic polymer and securing cohesive force of the acrylic polymer.

The copolymerizable monomer preferably includes 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. More preferably, the copolymerizable monomer includes a hydroxyl group-containing monomer and/or a monomer having a nitrogen atom-containing ring.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, ( 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, 2-hydroxyethyl (meth)acrylate is preferably used, and 2-hydroxyethyl acrylate is more preferably used.

The ratio of the hydroxyl group-containing monomer in the monomer component is preferably 1% by mass or more, more preferably 3% by mass or more, from the viewpoint of introduction of a crosslinked structure into the acrylic polymer and securing of cohesive force in the pressure-sensitive adhesive layer 10. It is mass % or more, More preferably, it is 5 mass % or more. The ratio is preferably from the viewpoint of adjusting the viscosity of the polymerization reaction solution during polymerization of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to compatibility between various additive components in the pressure-sensitive adhesive layer 10 and the acrylic polymer). is 30% by mass or less, more preferably 20% by mass or less.

Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, and N- Vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylphy Peridine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazine- 2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, and N-vinylisothiazole. As a monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

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

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

The ratio of the carboxyl group-containing monomer in the monomer component is determined from the viewpoints of introducing a crosslinked structure into the acrylic polymer, securing cohesive force in the pressure-sensitive adhesive layer 10, and securing adherence to the adherend in the pressure-sensitive adhesive layer 10. In , it is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more. The ratio is preferably 30% by mass or less, more preferably 20% by mass or less, 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 monomer component may contain other copolymerizable monomers. Examples of other copolymerizable monomers include acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, amide group-containing monomers, monomers having a succinimide skeleton, maleimides, Itaconimides, alkoxy group-containing monomers, vinyl esters, vinyl ethers, and aromatic vinyl compounds.

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

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, and sulfonic acid. propyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

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

As the epoxy group-containing monomer, for example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl (meth)acrylate, allyl glycidyl ether, and glycidyl (meth)acrylate ether.

Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

Examples of the amide group-containing monomer include N-vinylcarboxylic acid amides such as (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N-alkyl (meth)acrylamide, and N-vinylacetamide. , N-hydroxyalkyl (meth)acrylamide, N-alkoxyalkyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, and N-(meth)acryloylmorpholine. . Examples of N,N-dialkyl (meth)acrylamide include N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and N,N-dipropyl (meth)acrylamide. acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl) (meth)acrylamide, and N,N-di(t-butyl) (meth)acrylamide. can Examples of N-alkyl (meth)acrylamides include N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, and N-n-butyl (meth)acrylamide. amides. As N-hydroxyalkyl (meth)acrylamide, for example, N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1 -Hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, and N-(4-hydroxybutyl) (meth)acrylamide. Examples of N-alkoxyalkyl (meth)acrylamide include N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide. can

Examples of the monomer having a succinimide skeleton include N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyloxymethylenesuccinimide. ) acryloyl-8-oxyhexamethylene succinimide.

As maleimides, N-cyclohexyl maleimide, N-isopropyl maleimide, N-lauryl maleimide, and N-phenyl maleimide are mentioned, for example.

Examples of itaconimides include N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, and N-2-ethylhexyl itaconimide. imide, N-cyclohexylitaconimide, and N-laurylitaconimide.

Examples of the alkoxy group-containing monomer include alkoxyalkyl (meth)acrylates and alkoxyalkylene glycols (meth)acrylates. Examples of alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and propoxyethyl (meth)acrylate. , butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate. Examples of the alkoxyalkylene glycols (meth)acrylates include methoxyethylene glycol (meth)acrylates and methoxypolypropylene glycol (meth)acrylates.

Examples of vinyl esters include vinyl acetate and vinyl propionate.

Examples of vinyl ethers include methyl vinyl ether and ethyl vinyl ether.

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.

A copolymerizable monomer may be used independently and two or more types may be used together.

An acrylic polymer can be formed by polymerizing the above-mentioned monomer components. Examples of the polymerization method include solution polymerization, bulk polymerization, and emulsion polymerization, preferably solution polymerization. In solution polymerization, a reaction solution is prepared by blending a monomer component and a polymerization initiator in a solvent, for example, and then the reaction solution is heated. Then, an acrylic polymer solution containing an acrylic polymer can be obtained by undergoing a polymerization reaction of the monomer component in the reaction solution. As a polymerization initiator, a thermal polymerization initiator is used, for example. The usage amount of the polymerization initiator is, for example, 0.05 part by mass or more, and, for example, 1 part by mass or less, based on 100 parts by mass of the monomer component.

As a thermal polymerization initiator, an azo polymerization initiator and a peroxide polymerization initiator are mentioned, for example. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, and 2,2'-azobis(2-methylpropionic acid). ) dimethyl, 4,4'-azobis-4-cyanovalerian acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2' -azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, and 2,2 '-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride. As a peroxide polymerization initiator, dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide are mentioned, for example.

The weight average molecular weight of the acrylic polymer is preferably 100000 or more, more preferably 300000 or more, still more preferably 500000 or more, from the viewpoint of securing the cohesive force in the pressure-sensitive adhesive layer 10. The same weight average molecular weight is preferably 5000000 or less, more preferably 3000000 or less, still more preferably 2000000 or less. The weight average molecular weight of the acrylic polymer is measured by a gel permeation chromatograph (GPC) and calculated in terms of polystyrene.

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

Regarding the glass transition temperature (Tg) of the polymer, a glass transition temperature (theoretical value) obtained based on the following formula of Fox can be used. Fox's formula is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of monomers constituting the polymer. In Fox's formula below, Tg represents the glass transition temperature (°C) of a polymer, Wi represents the weight fraction of monomer i constituting the polymer, and Tgi represents the glass transition temperature of a homopolymer formed from monomer i. (°C) is shown. For the glass transition temperature of the homopolymer, literature values can be used, for example, "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7 Synthesis for Paints" Introduction to resins” (Kyojo Kitaoka, Polymer Publishing Society, 1995) lists the glass transition temperatures of various homopolymers. On the other hand, about the glass transition temperature of the homopolymer of a monomer, it is also possible to obtain|require by the method specifically described in Unexamined-Japanese-Patent No. 2007-51271.

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

The adhesive composition may contain a crosslinking agent from the viewpoint of introducing a crosslinked structure into the base polymer. 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. A crosslinking agent may be used independently and two or more types may be used together.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate. nate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthaline diisocyanate, triphenylmethane triisocyanate , and polymethylene polyphenyl isocyanate. Moreover, derivatives of these isocyanates are also mentioned as an isocyanate crosslinking agent. As the said isocyanate derivative, an isocyanurate modified body and a polyol modified body are mentioned, for example. As a commercially available isocyanate crosslinking agent, for example, Coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), Coronate HL (of hexamethylene diisocyanate) Trimethylolpropane adduct, manufactured by Tosoh), Coronate HX (isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh), and Takenate D110N (trimethyl of xylylene diisocyanate) All-propane adducts, manufactured by Mitsui Chemicals) are exemplified.

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6- Hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamineglycidylamine, N,N,N',N'-tetraglycidyl-m-xyl relendiamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

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 base polymer, from the viewpoint of securing the cohesive force of the pressure-sensitive adhesive layer 10. More than that. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive layer 10, the compounding amount of the crosslinking agent relative to 100 parts by mass of the base polymer is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass. is less than

When a crosslinking structure is introduced into the base polymer, a crosslinking catalyst may be used to effectively advance the crosslinking reaction. Examples of the crosslinking catalyst include dibutyltin dilaurate, tetra-n-butyl titanate, tetraisopropyl titanate, ferric nasem, and butyltin oxide, and preferably both Dibutyltin iraurate is used. The amount of the crosslinking catalyst used is, for example, 0.0001 part by mass or more and 1 part by mass or less with respect to 100 parts by mass of the base polymer.

When a crosslinking catalyst is used, a crosslinking inhibitor that can be removed posthumously from the adhesive composition may be incorporated into the adhesive composition. When dibutyltin dilaurate is used as a crosslinking catalyst, acetylacetone is preferably used as a crosslinking inhibitor. In this case, in the adhesive composition, acetylacetone is coordinated with dibutyltin dilaurate, and the crosslinking reaction of the crosslinking agent with respect to the base polymer is suppressed. In the manufacturing process of the adhesive sheet S described later, after the adhesive composition is applied on the peeling film to form a coating film, acetylacetone can be volatilized and removed from the coating film by heating at a desired timing. Thereby, the crosslinking reaction of the crosslinking agent can be advanced.

The blending amount of the crosslinking inhibitor is, for example, 100 parts by mass or more, preferably 1000 parts by mass or more, based on 100 parts by mass of the crosslinking catalyst. Moreover, the compounding quantity of copper is 5000 mass parts or less, for example.

A polymerizable compound is a compound having a polymerizable functional group. The polymerizable functional group has an ethylenically unsaturated double bond. As a polymerizable functional group, a (meth)acryloyl group, a vinyl group, and a propenyl group are mentioned, for example. Examples of the polymerizable compound include a monomer having one polymerizable functional group (monofunctional monomer) and a monomer having a plurality of polymerizable functional groups (polyfunctional monomer). Moreover, as a polymeric compound, the compound which has a (meth)acryloyl group as a polymerizable functional group is used from a reactive viewpoint. A (meth)acryloyl group means an acryloyl group and/or a methacryloyl group. A polymeric compound may be used independently, and 2 or more types may be used together.

Examples of the monofunctional monomer include ethyl (meth)acrylate, n-butyl (meth)acrylate, ter-butyl (meth)acrylate, isobutyl methacrylate, 2-ethylhexyl (meth)acrylate, Isodecyl (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, Stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, Cyclopentenyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate Latex, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol (meth)acrylate, trifluoroethyl (meth)acrylate, methacryloxyoxyethyl acid phosphate, 2-hydroxyethyl methacrylic acid phosphate, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, acryloylmo polyne, morpholinoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and N,N-dimethylaminoethyl (meth)acrylate. .

Examples of the polyfunctional monomer include bifunctional monomers, trifunctional monomers, and tetrafunctional or higher functional monomers.

Examples of the difunctional monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate. Methacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate ) acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, di(meth)acryloyl isocyanurate, and alkylene oxide-modified bisphenol di(meth)acrylate can be heard

As a trifunctional monomer, trimethylolpropane tri (meth)acrylate, pentaerythritol tri (meth)acrylate, and tris (acryloyloxyethyl) isocyanurate are mentioned, for example.

Examples of the tetrafunctional or higher functional monomer include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and alkyl modified dipentaerythritol pentaacrylate, dipentaerythritol hexa(meth)acrylate, and isocyanuric acid EO modified di- and triacrylates.

From the viewpoint of the rapid curability of the pressure-sensitive adhesive layer 10, as the polymerizable compound, preferably a polyfunctional monomer is used, more preferably a trifunctional monomer or a tetrafunctional or higher functional monomer is used. As the trifunctional monomer for the polymerizable compound, trimethylolpropane tri(meth)acrylate is preferably used, and trimethylolpropane triacrylate is more preferably used. As the tetrafunctional or higher functional monomer for the polymerizable compound, dipentaerythritol hexa(meth)acrylate is preferably used, and dipentaerythritol hexaacrylate is more preferably used.

The blending amount of the polymerizable compound is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, with respect to 100 parts by mass of the base polymer, from the viewpoint of ensuring sufficient hardness in the pressure-sensitive adhesive layer 10 after curing. Preferably it is 9 parts by mass or more, particularly preferably 10 parts by mass or more. From the viewpoint of ensuring sufficient adhesive strength in the pressure-sensitive adhesive layer 10 after curing, the blending amount of the polymerizable compound relative to 100 parts by mass of the base polymer is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, still more preferably It is 43 parts by mass or less.

A photopolymerization initiator initiates a polymerization reaction of a polymerizable compound. Examples of the photopolymerization initiator include benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, and benzophenone photopolymerization initiator. , ketal photopolymerization initiators, thioxanthone photopolymerization initiators, and acylphosphine oxide photopolymerization initiators.

The colorant is preferably a compound that develops color by reaction with an acid (color-developing compound). When the colorant is a color-developing compound, the adhesive composition further contains an acid 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. A color developing compound may be used independently, and 2 or more types may be used together.

Examples of the leuco dye include 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-[9H]xanthene]; 3-Dibutylamino-6-methyl-7-anilinofluoran, 3-dipropylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran , 3-dimethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, and 3-(4-diethylamino-2-ethoxyphenyl )-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide.

Examples of the triarylmethane dye include p,p',p"-tris-dimethylaminotriphenylmethane. Examples of the diphenylmethane dye include 4,4-bis- Dimethylaminophenylbenzhydrylbenzyl ether.Examples of the fluoran dye include 3-diethylamino-6-methyl-7-chlorofluorane.As the spiropyran dye, Examples of the rhodamine pigment include 3-methylspirodinaphthopyran, and rhodamine-B-anilinolactam.

From the viewpoint of ensuring good colorability in the pressure-sensitive adhesive layer 10, the color-developing compound is preferably a leuco dye, more preferably 2'-anilino-6'-(N-ethyl-N-isopentylamino)- 3'-methylspiro[phthalide-3,9'-[9H]xanthene] is used.

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

As the acid generator, a photoacid generator that generates an acid when irradiated with active energy rays is preferably used. In this case, the portion of the pressure-sensitive adhesive layer 10 that has been irradiated with active energy rays as the first external stimulus can be discolored. Specifically, in a portion of the pressure-sensitive adhesive layer 10 irradiated with active energy rays, an acid is generated from a photoacid generator, and the color-developing compound develops color with the acid. The portion of the pressure-sensitive adhesive layer 10 that has been irradiated with active energy rays is colored dark, for example, according to the color development of the color-developing compound. The type of active energy ray as the first external stimulus is determined by the type of photoacid generator (specifically, the wavelength of the active energy ray at which the photoacid generator generates acid). Examples of active energy rays include ultraviolet rays, visible light, infrared rays, X-rays, α-rays, β-rays, and γ-rays. From the viewpoint of diversity of use equipment and ease of handling, ultraviolet rays are preferably used as the active energy ray.

As the photoacid generator, for example, an onium compound that generates an acid by ultraviolet irradiation (first external stimulus) is exemplified. The onium compound is provided in the form of, for example, an onium salt of an onium cation and an anion. As an onium cation, iodonium and sulfonium are mentioned, for example. Examples of 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 ^- . A photoacid generator may be used independently, or two or more types may be used together. The adhesive composition preferably contains an onium salt (onium compound) composed of sulfonium and C ₄ F ₉ HSO ₃ ^- as a photoacid generator.

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

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

The adhesive composition may contain other components as needed. Examples of other components include silane coupling agents, tackifiers, plasticizers, softeners, antioxidants, surfactants, and antistatic agents.

The adhesive sheet S can be produced, for example, by applying the above-described adhesive composition onto a release film (first release film) to form a coating film, and then drying the coating film (in FIG. 1, The adhesive sheet S is arrange|positioned on the peeling film L shown by a phantom line).

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

As a method of applying the adhesive composition, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. The drying temperature of the coating film is, for example, 50°C to 200°C. Drying time is 5 seconds - 20 minutes, for example.

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

Moreover, you may laminate|stack a peeling film (2nd peeling film) further on the adhesive layer 10 on the 1st peeling film before or after aging. The second release film is a flexible plastic film subjected to surface release treatment, and the same one as described above for the first release film can be used.

As described above, the adhesive sheet S in which the adhesive face is covered and protected by the release film can be manufactured. Each peeling film is peeled off from the adhesive sheet S as needed when using the adhesive sheet S.

The thickness of the pressure-sensitive adhesive layer 10 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesiveness to the adherend. From the standpoint of the handleability of the PSA sheet S, the thickness of the PSA layer 10 is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

The haze of the pressure-sensitive adhesive layer 10 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. Such a structure is suitable for inspecting the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after bonding the adhesive sheet S to the adherend. The haze of the adhesive layer 10 can be measured using a haze meter based on JIS K7136 (2000). As a haze meter, "NDH2000" by Nippon Denshoku Kogyo Co., Ltd. and "HM-150 type|mold" by Murakami Color Technology Laboratory Co., Ltd. are mentioned, for example.

The average transmittance of the pressure-sensitive adhesive layer 10 at a wavelength of 400 to 700 nm (average transmittance before applying the first and second external stimuli to the pressure-sensitive adhesive layer 10) is preferably 80% or more, more preferably 85% or more. , more preferably 90% or more. Such a structure is suitable for inspecting the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after bonding the adhesive sheet S to the adherend.

After the pressure-sensitive adhesive sheet S is bonded to the glass plate, the adhesive strength to the stainless plate in a peeling test under peeling conditions of 23°C, a peeling angle of 180°, and a peeling speed of 300 mm/min is, for example, 1 N/min. It is 25 mm or more and, for example, 50 N/25 mm or less.

The shear storage modulus (first shear storage modulus) at 25° C. of the pressure-sensitive adhesive layer 10 (before curing) is preferably 0.1 ×10 ⁵ Pa or more, more preferably 0.2 × 10 ⁵ Pa or more, still more preferably 0.3 × 10 ⁵ Pa or more. The first shear storage modulus is preferably 10×10 ⁵ Pa or less, more preferably 5×10 ⁵ Pa or less, and still more preferably 3×10 ⁵ Pa or less.

The pressure-sensitive adhesive layer 10 of the pressure-sensitive adhesive sheet S preferably has a wavelength region in which the ratio of the absorbance Y of the photopolymerization initiator to the absorbance X of the photoacid generator is 2 or more within a wavelength range of 300 nm or more and 500 nm or less. The ratio is preferably 3 or more, more preferably 10 or more, still more preferably 50 or more, and particularly preferably 100 or more. The same ratio is, for example, 1 million or less.

As shown in FIG. 2 , the PSA sheet S may be a single-sided PSA sheet with a base material including a base material 20 in addition to the PSA layer 10 . In this case, the pressure-sensitive adhesive sheet S specifically includes the pressure-sensitive adhesive layer 10 and the base material 20 disposed on one side in the thickness direction. Preferably, the substrate 20 contacts one side of the pressure-sensitive adhesive layer 10 in the thickness direction.

The substrate 20 is an element that functions as a transparent support. The substrate 20 is, for example, a plastic film having flexibility. Examples of the constituent material of the plastic film include polyolefin, polyester, polyamide, polyimide, polyvinyl chloride, polyvinylidene chloride, cellulose, polystyrene, and polycarbonate. Examples of the polyolefin include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene/vinyl acetate copolymer, and ethylene. • Ethyl acrylate copolymer, and ethylene/vinyl alcohol copolymer. As polyester, polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate are mentioned, for example. Examples of the polyamide include polyamide 6, polyamide 6 and 6, and partially aromatic polyamide. In the base material 20, from the viewpoint of achieving both transparency and mechanical strength, the plastic material of the base material 20 is preferably polyester, more preferably polyethylene terephthalate.

The substrate 20 has transparency. The haze of the substrate 20 is preferably 3% or less, more preferably 2% or less, still more preferably 1% or less. The haze of the substrate 20 can be measured using a haze meter in accordance with JIS K7136 (2000).

The surface of the base material 20 on the side of the pressure-sensitive adhesive layer 10 may be subjected to physical treatment, chemical treatment, or undercoating treatment for enhancing adhesion to the pressure-sensitive adhesive layer 10 . As a physical treatment, a corona treatment and a plasma treatment are mentioned, for example. Examples of chemical treatment include acid treatment and alkali treatment.

The thickness of the substrate 20 is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more, from the viewpoint of securing strength for the substrate 20 to function as a support. Further, from the viewpoint of realizing appropriate flexibility in the adhesive sheet S, the thickness of the substrate 20 is preferably 200 μm or less, more preferably 150 μm or less, still more preferably 100 μm or less.

The PSA sheet S shown in FIG. 2 can be manufactured, for example, by the same method as the PSA sheet manufacturing method described above, except that the substrate 20 is used instead of the first peeling film.

3A to 3D show an example of a method of using the pressure-sensitive adhesive sheet S. This method includes a preparation process, a bonding process, a curing process, and a discoloration portion forming process.

First, in the preparation step, as shown in Fig. 3A, the adhesive sheet S, the first member 31, and the second 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 another electronic device or an optical device. The second member 32 is, for example, a transparent substrate. As a transparent base material, a transparent plastic base material and a transparent glass base material are mentioned.

Next, in the joining step, as shown in Fig. 3B, the first member 31 and the second member 32 are joined with the adhesive sheet S interposed therebetween. In this way, the layered product Z is obtained. In the layered body Z, the adhesive sheet S is disposed so as to contact one surface of the first member 31 in the thickness direction, and the second member 32 is disposed on one side of the adhesive sheet S in the thickness direction. It is placed so as to contact the surface.

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

Next, in the curing step, as shown in FIG. 3C , a second external stimulus is applied to the pressure-sensitive adhesive layer 10 in the layered product Z (when the above test is performed, the layered product Z that has passed the test) to cure the pressure-sensitive adhesive layer 10. In this embodiment, the second external stimulus is active energy ray irradiation. This active energy ray is irradiated to the pressure-sensitive adhesive layer 10 from the side of the transparent second member 32 . As a light source for active energy ray irradiation in this process, an ultraviolet LED light, a high pressure mercury lamp, and a metal halide lamp are mentioned, for example. In the active energy ray irradiation in this step, a wavelength cut filter for cutting a part of the wavelength region in the active energy ray emitted from the light source may be used as needed.

The active energy ray as the second external stimulus has a different wavelength range from the active energy ray as the first external stimulus. In the present embodiment, the active energy ray as the second external stimulus has a wavelength that does not substantially generate acid in the acid generator. The lower limit of the wavelength range of the active energy ray is preferably 365 nm, more preferably 370 nm, still more preferably 375 nm, still more preferably 380 nm, still more preferably 385 nm, still more preferably 390 nm, particularly preferably It is 395 nm. In the present embodiment, preferably, a photopolymerization initiator that initiates a polymerization reaction of a polymerizable compound by receiving active energy ray irradiation of such a wavelength is incorporated into the pressure-sensitive adhesive layer 10 .

In this step, in the pressure-sensitive adhesive layer 10 subjected to active energy ray irradiation, the polymerization reaction of the polymerizable compound is started by the photopolymerization initiator, and the polymerization reaction proceeds. As a result, the modulus of elasticity of the pressure-sensitive adhesive layer 10 increases.

As described above, the pressure-sensitive adhesive layer 10 preferably has a wavelength range (wavelength range R) in which the ratio of the absorbance Y of the photopolymerization initiator to the absorbance X of the photoacid generator is 2 or more within a wavelength range of 300 nm or more and 500 nm or less. do. The ratio (Y/X) in the wavelength range R is preferably 3 or more, more preferably 10 or more, still more preferably 100 or more. Preferably, at least a part of the wavelength of the active energy ray irradiated as the second external stimulus is within the wavelength range R. More preferably, all of the wavelengths of the active energy ray irradiated as the second external stimulus are within the wavelength range R. A configuration in which an active energy ray having a wavelength within such a wavelength range is applied to the pressure-sensitive adhesive layer 10 as a second external stimulus causes the pressure-sensitive adhesive layer 10 to be cured while suppressing discoloration in the pressure-sensitive adhesive layer 10. suitable for curing In the curing step, from the viewpoint of curing the pressure-sensitive adhesive layer 10 while suppressing discoloration in the pressure-sensitive adhesive layer 10, the ratio of the absorbance Y of the photopolymerization initiator to the absorbance X of the photoacid generator is preferably larger. .

The shear storage modulus (second shear storage modulus) at 25° C. of the pressure-sensitive adhesive layer 10 after curing, as shown by dynamic viscoelasticity measurement under conditions of a frequency of 1 Hz and a heating rate of 5° C./min, is preferably 0.2 × 10 ⁵ Pa or more, more preferably 2×10 ⁵ Pa or more, still more preferably 5×10 ⁵ Pa or more. The second shear storage modulus is preferably 100×10 ⁵ Pa or less, more preferably 50×10 ⁵ Pa or less, and still more preferably 25×10 ⁵ Pa or less. The ratio of the second shear storage modulus to the first shear storage modulus is preferably 2 or more, more preferably 5 or more, still more preferably 10 or more. The ratio is preferably 300 or less, more preferably 250 or less, still more preferably 100 or less, still more preferably 50 or less, and particularly preferably 30 or less.

Next, in the discoloration portion forming step, as shown in FIG. 3D, a first external stimulus is applied to the adhesive layer 10 in the layered product Z to form the discoloration portion 11 in the adhesive layer 10. form Specifically, from the side of the transparent second member 32, a mask pattern (not shown) for masking a predetermined area in the pressure-sensitive adhesive layer 10 is interposed, and the pressure-sensitive adhesive layer 10 acts as a first external stimulus. An active energy ray (first active energy ray) is irradiated. As a result, the portion of the pressure-sensitive adhesive layer 10 not masked by the mask pattern is discolored.

As a light source for active energy ray irradiation in this process, an ultraviolet LED light, a high pressure mercury lamp, and a metal halide lamp are mentioned, for example. In the active energy ray irradiation in this step, a wavelength cut filter for cutting a part of the wavelength region in the active energy ray emitted from the light source may be used as needed.

The first active energy ray has a different wavelength range from the above-described active energy ray (second active energy ray) serving as the second external stimulus. The wavelength range of the first active energy ray preferably includes at least a range smaller than the wavelength range of the second active energy ray (wavelength range on the shorter wavelength side) (the wavelength range of the first active energy ray is equal to the wavelength of the second active energy ray). ranges and overlapping ranges). When the first active energy ray has a lower limit in the wavelength range, or when a lower limit is provided in the wavelength range of the first active energy ray using, for example, a wavelength cut filter, the lower limit of the wavelength range of the first active energy ray is , preferably 300 nm, more preferably 305 nm, even more preferably 310 nm, still more preferably 315 nm, still more preferably 320 nm, still more preferably 325 nm, and particularly preferably 330 nm. Alternatively, light with a wavelength of less than 300 nm may be contained in the first active energy ray. As a light source of such light, a high pressure mercury lamp and a metal halide lamp are mentioned, for example. When the first active energy ray has an upper limit on the wavelength range, or when an upper limit is provided on the wavelength range of the first active energy ray using, for example, a wavelength cut filter, the upper limit of the wavelength range of the first active energy ray is , preferably 400 nm, more preferably 395 nm, even more preferably 390 nm, even more preferably 385 nm, still more preferably 380 nm, still more preferably 375 nm, and particularly preferably 370 nm. In the present embodiment, preferably, a photoacid generator that generates an acid by being irradiated with an active energy ray of such a wavelength is blended into the pressure-sensitive adhesive layer 10 .

In this step, acid is generated from the photoacid generator in the portion of the pressure-sensitive adhesive layer 10 that has been irradiated with the first active energy ray, and the color-developing compound develops color by reaction with the acid. As a result, the discoloration portion 11 is formed in the pressure-sensitive adhesive layer 10 . Such discoloration part formation process may be performed before a hardening process.

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

As described above, the pressure-sensitive adhesive sheet S contains a colorant capable of developing color in response to a first external stimulus. Therefore, after bonding the adhesive sheet S to the adherend (members 31 and 32 in this embodiment), by applying a first external stimulus to the portion to be discolored in the adhesive layer 10, The pressure-sensitive adhesive layer 10 may be locally discolored. In the PSA sheet S capable of forming the discoloration portion 11 on the PSA layer 10 after bonding to an adherend, after bonding and before formation of the discoloration portion 11 of the PSA layer 10, the PSA sheet S ) and the adherend, the presence or absence of foreign matter and air bubbles can be inspected.

In the PSA sheet S, the PSA layer 10 contains a base polymer and a polymeric compound as described above, and is curable by a second external stimulus different from the first external stimulus. Such an adhesive sheet S secures the softness (low elastic modulus) of the adhesive layer 10 suitable for bonding to an adherend at the time of bonding, and in the adhesive layer 10, the discoloration scheduled portion or discolored portion 11 ) It is suitable for increasing the modulus of elasticity after pasting the region (for example, the whole of the pressure-sensitive adhesive layer 10) containing. Such high modulus of elasticity of the pressure-sensitive adhesive layer 10 is suitable for suppressing the diffusion of the colorant in the pressure-sensitive adhesive layer 10, and therefore suitable for suppressing the spreading of the discolored portion 11 of the pressure-sensitive adhesive layer 10. do.

As described above, the second shear storage modulus of the pressure-sensitive adhesive layer 10 after curing is preferably 0.2×10 ⁵ Pa or more, more preferably 2×10 ⁵ Pa or more, still more preferably 5×10 ⁵ Pa More than that. Such a configuration is suitable for suppressing the spreading of the discolored portion 11 formed on the pressure-sensitive adhesive layer 10 .

The ratio of the second shear storage modulus to the first shear storage modulus of the pressure-sensitive adhesive layer 10 before curing is, as described above, preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, It is also preferably 100 or less, more preferably 50 or less, still more preferably 30 or less. Such a structure is suitable for balancing the bonding force by the adhesive sheet S (the pressure-sensitive adhesive layer 10) in the bonding process described above and the suppression of the spreading of the discolored portion 11.

Example

The present invention will be described in detail by showing examples below, but the present invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, and parameters described below are the compounding amounts (content), physical property values, and parameters corresponding to them described in the above-mentioned “Specific Content for Carrying Out the Invention”. It can be substituted with the upper limit (numerical value defined as "below" or "less than") or the lower limit (numerical value defined as "greater than" or "exceeding") of the same.

[Example 1]

<Preparation of base polymer>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet pipe, 63 parts by mass of 2-ethylhexyl acrylate (2EHA), 9 parts by mass of methyl methacrylate (MMA), and 2-hydroxy acrylate 13 parts by mass of ethyl (HEA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 0.2 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and a solvent A mixture containing 233 parts by mass of ethyl acetate as the mixture was stirred at 60°C for 7 hours in a nitrogen atmosphere (polymerization reaction). In this way, a polymer solution containing an acrylic polymer was obtained. The weight average molecular weight (Mw) of the acrylic polymer in this polymer solution was 1.2 million.

<Preparation of adhesive composition>

To the above-described polymer solution containing an acrylic polymer, 11.1 parts by mass of dipentaerythritol hexaacrylate (DPHA) (manufactured by Daicel Allnex) as a polymerizable compound per 100 parts by mass of the acrylic polymer (base polymer), and a photopolymerization initiator ( Trade name "Omnirad 819", bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM Resins BV) 0.1 parts by mass, and a leuco dye as a chromogenic compound (trade name "S-205", 2'-anyl 2.2 parts by mass of rhino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-[9H]xanthen], manufactured by Yamada Chemical Industry Co., Ltd., and photoacid generation agent (trade name "Sp-056", an onium salt of sulfonium and C ₄ F ₉ HSO ₃ ^- manufactured by ADEKA) 7.8 parts by mass and an isocyanate crosslinking agent as a crosslinking agent (trade name "Takenate D110N", xylylene diiso 75% ethyl acetate solution of trimethylolpropane adduct of cyanate, manufactured by Mitsui Chemicals) 0.25 parts by mass (solid content equivalent) and dibutyltin dilaurate (trade name "OL-1") as a crosslinking catalyst , 1% by mass ethyl acetate solution, manufactured by Tokyo Fine Chemical Co., Ltd.) 0.01 parts by mass (in terms of solid content) and 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for crosslinking catalyst) were added and mixed to prepare an adhesive composition.

<Formation of pressure-sensitive adhesive layer>

On a polyethylene terephthalate film (base film) having a thickness of 38 μm, the surface of which was subjected to release treatment, the adhesive composition was applied with a fountain roll to form a coating film. Next, this coating film was dried by heating at 132°C for 3 minutes. In this way, an adhesive layer having a thickness of 25 μm was formed on the base film. Next, the release-treated surface of the separator (a polyethylene terephthalate film having a thickness of 38 µm and subjected to release treatment on one side) was bonded to the pressure-sensitive adhesive layer on the base film. Thereafter, aging treatment was performed at 60°C for 24 hours to promote crosslinking reaction in the pressure-sensitive adhesive layer.

In the above manner, the pressure-sensitive adhesive sheet of Example 1 was produced. The composition of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of Example 1 is shown in Table 1 in parts by mass (the same applies to Examples and Comparative Examples later).

[Examples 2 to 5 and Comparative Example 1]

Except for the following, each PSA sheet of Examples 2 to 5 and Comparative Example 1 was produced in the same manner as the PSA sheet of Example 1.

In the production process of each PSA sheet of Examples 2 to 5, in preparing the PSA composition, each component was blended in the compounding amount shown in Table 1. In the preparation of the adhesive composition in the production process of the adhesive sheet in Examples 4 and 5, trimethylolpropane triacrylate (TMPTA) (manufactured by Osaka Organic Chemical Industry Co., Ltd.) was used as the polymerizable compound instead of DPHA. In addition, in the production process of the PSA sheet of Comparative Example 1, in preparing the PSA composition, each component was blended in the blending amount shown in Table 1 (a polymerizable compound and a photopolymerization initiator were not blended).

<Light transmittance>

The average transmittance at a wavelength of 400 to 700 nm was investigated as follows for the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet in Examples 1 to 5 and Comparative Example 1.

First, the adhesive sheet was bonded to eagle glass (thickness: 0.55 mm, manufactured by Matsunami Glass Co., Ltd.) to prepare a measurement sample (first measurement sample). Next, the average transmittance at a wavelength of 400 to 700 nm was measured for the sample for measurement using a spectrophotometer U4150 manufactured by Hitachi High-Technologies Co., Ltd. (first transmittance measurement). In this measurement, the total light transmittance of the sample for measurement at a wavelength of 400 to 700 nm was measured at a pitch of 1 nm. In addition, in this measurement, the transmittance spectrum obtained by measuring only the eagle glass under the same conditions was used as a baseline. Table 1 shows the measured average transmittance T1 (average transmittance at a wavelength of 400 to 700 nm before UV irradiation) of the pressure-sensitive adhesive layer.

On the other hand, the average transmittance at a wavelength of 400 to 700 nm after UV irradiation was investigated for each of the PSA sheets of Examples 1 to 5 and Comparative Example 1 as follows.

First, a sample similar to the first measurement sample described above was produced. Next, the sample was irradiated with ultraviolet rays. Specifically, the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) in the sample was irradiated with ultraviolet rays from the eagle glass side through the glass in an environment of 23°C and 50% relative humidity (by the UV irradiation, the pressure-sensitive adhesive layer The leuco dye and the photoacid generator in the reaction were reacted). In this UV irradiation, a UV-LED lamp with a wavelength of 365 nm in a UV-LED irradiation device manufactured by Quark Technology (model number "QEL-350-RU6W-CW-MY") was used as a light source, and the cumulative irradiation light amount was 8000 mJ/ It was set as cm ² (the cumulative amount of irradiation light in the range of wavelength 320 to 390 nm). As described above, a measurement sample (second measurement sample) was prepared.

Next, the average transmittance at a wavelength of 400 to 700 nm was measured for the second measurement sample using a spectrophotometer U4150 manufactured by Hitachi High-Technologies Corporation (second transmittance measurement). Regarding the specific measurement method and conditions, the second transmittance measurement is the same as the first transmittance measurement described above. Table 1 shows the measured average transmittance T2 (average transmittance at a wavelength of 400 to 700 nm after UV irradiation) of the pressure-sensitive adhesive layer. Table 1 also shows the ratio of average transmittance T2 to average transmittance T1 described above.

<Shear storage modulus of pressure-sensitive adhesive layer (before curing treatment)>

The shear storage modulus of the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet of Examples 1 to 5 and Comparative Example 1 was investigated by dynamic viscoelasticity measurement (first measurement).

The sample for the 1st measurement was produced as follows. First, for each pressure-sensitive adhesive layer to be measured, 60 pressure-sensitive adhesive layers (thickness: 25 µm) were laminated to obtain laminated pressure-sensitive adhesive layers (thickness: 1.5 mm). Next, the laminated pressure-sensitive adhesive layer was punched to obtain a cylindrical pellet (thickness: 1.5 mm, diameter: 7.9 mm) as a first measurement sample.

For the dynamic viscoelasticity measurement, a dynamic viscoelasticity measuring device (trade name "ARES", manufactured by Rheometrics) was used. Specifically, after fixing a sample for measurement to a jig of a parallel plate having a diameter of 7.9 mm, measurement of dynamic viscoelasticity was performed with the device described above. In this measurement, the measurement mode was the shear mode, the measurement temperature range was -70°C to 250°C, the temperature increase rate was 5°C/min, and the frequency was 1 Hz. Table 1 shows the shear storage modulus (E1) of the pressure-sensitive adhesive layer (before curing treatment) at 25°C.

<Shear storage modulus of pressure-sensitive adhesive layer (after curing treatment)>

The shear storage modulus of the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of Examples 1 to 5 and Comparative Example 1 after the curing treatment was measured by dynamic viscoelasticity measurement (second measurement).

The sample for the second measurement (cylindrical pellets obtained by punching the laminated pressure-sensitive adhesive layer having a thickness of 1.5 mm) was subjected to ultraviolet irradiation (curing treatment) for each of the 60 pressure-sensitive adhesive layers before lamination, and the first It was produced in the same way as the sample for measurement. In the curing treatment, specifically, ultraviolet irradiation was performed on each pressure-sensitive adhesive layer before lamination in an environment of 23°C and a relative humidity of 50%. In this ultraviolet irradiation, a UV-LED lamp with a wavelength of 405 nm in a UV-LED irradiation device manufactured by Quark Technology (model number "QEL-350-RU6W-CW-MY") was used as a light source, and the cumulative irradiation light amount was 2000 mJ/ It was set as cm ² (the cumulative amount of irradiated light in a wavelength range of 395 to 445 nm).

The second measurement was performed under the same apparatus and conditions as the first measurement. Table 1 shows the shear storage modulus (E2) of the pressure-sensitive adhesive layer (after curing) at 25°C, 65°C, and 85°C.

<Evaluation of suppression of spreading of discolored parts>

With respect to the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet in Examples 1 to 5 and Comparative Example 1, the degree of blurring suppression of the formed discolored portion was investigated as follows.

First, a plurality of PSA sheets were prepared for each PSA sheet in Examples 1 to 5 and Comparative Example 1.

Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was irradiated with ultraviolet light in an environment at 23° C. and a relative humidity of 50% (the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet in Examples 1 to 5 was cured by the ultraviolet light irradiation). In this ultraviolet irradiation, a UV-LED lamp with a wavelength of 405 nm in a UV-LED irradiation device manufactured by Quark Technologies (model number "QEL-350-RU6W-CW-MY") was used as a light source, and the pressure-sensitive adhesive layer was applied over the base film. Ultraviolet rays were irradiated, and the cumulative irradiation light amount was set to 2000 mJ/cm ² (the irradiation integrated amount in the range of 395 to 445 nm) (this ultraviolet irradiation condition is the curing treatment in the sample preparation process of the second measurement are the same as the UV irradiation conditions of).

Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was irradiated with ultraviolet light through a photomask having linear openings to form linear discolored portions in the pressure-sensitive adhesive layer. The photomask is formed of a dry film photoresist disposed on the base film-side surface of the adhesive sheet, and the line width of the opening of the photomask is about 250 to 280 μm (the line width of the opening differs for each photomask). In the ultraviolet irradiation, a UV-LED lamp with a wavelength of 365 nm in a UV-LED irradiation device manufactured by Quark Technology (model number "QEL-350-RU6W-CW-MY") was used as a light source, and an adhesive was applied over a photomask and base film. The layer was irradiated with ultraviolet rays, and the cumulative amount of irradiation light was 2000 mJ/cm ² (the integrated amount of irradiation light in the range of wavelength 320 to 390 nm).

Next, the line width of the linear discoloration portion formed on the pressure-sensitive adhesive layer was measured (measurement of initial line width). Specifically, first, the linear discoloration portion formed on the pressure-sensitive adhesive layer was observed with a digital microscope (trade name "VHX-900", manufactured by KEYENCE), and the area including a part of the discoloration portion and its vicinity was magnified 50 times. was filmed with Next, the captured image was binarized by image analysis software. Next, in the image after the binarization process, the line width (W1) of the linear discoloration portion was measured.

Next, the pressure-sensitive adhesive sheet in which linear discoloration portions were formed in the pressure-sensitive adhesive layer was subjected to heat treatment at 85°C for 120 hours (first durability test).

Next, the line width of the linear discolored portion in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was measured. A specific measurement method is the same as the measurement method described above regarding the measurement of the initial line width. Table 1 shows the line width W1 of the linear discoloration portion before the first durability test, the line width W2 of the linear discoloration portion after the first durability test, and the increase rate (W2/W1) of the line width W2 relative to the line width W1.

In addition, with respect to the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet of Examples 1 to 5 and Comparative Example 1, except that the second durability test was performed instead of the first durability test, the same method as described above was performed, and the spread of the formed linear discoloration portion was suppressed. investigated the extent of In the second durability test, the pressure-sensitive adhesive sheet in which linear discoloration portions were formed in the pressure-sensitive adhesive layer was subjected to heat treatment at 65°C and 90% relative humidity for 120 hours. Table 1 shows the line width W1 of the linear discoloration portion before the second durability test, the line width W3 of the linear discoloration portion after the second durability test, and the increase rate (W3/W1) of the line width W3 relative to the line width W1.

[evaluation]

The rate of increase in line width (W2/W1) of the linear discoloration portion after the first durability test was smaller in each of the PSA sheets of Examples 1 to 5 than that of the PSA sheet in Comparative Example 1. The rate of increase in line width (W3/W1) of the linear discoloration portion after the second durability test was also smaller in the PSA sheets of Examples 1 to 5 than in the PSA sheet in Comparative Example 1. That is, in each of the PSA sheets of Examples 1 to 5, the bleeding of the discolored portion of the PSA layer was suppressed more than the PSA sheet in Comparative Example 1.

The embodiment described above is an illustration of the present invention, and the present invention should not be interpreted limitedly by the embodiment. Modifications of the present invention obvious to those skilled in the art in the art are included in the scope of the later claims.

The variable-color adhesive sheet of the present invention is used, for example, in the manufacturing process of a display panel for bonding elements included in a laminated structure of a display panel.

S Adhesive Sheet (Variable Color Adhesive Sheet)
10 adhesive layer
11 discoloration part
20 entries
31 first member
32 Second member

Claims (7)

A color changeable pressure-sensitive adhesive sheet having a color-changeable pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer,
A color changeable pressure-sensitive adhesive sheet containing a colorant capable of developing color in response to a first external stimulus, a base polymer, and a polymerizable compound, and curable by a second external stimulus different from the first external stimulus. According to claim 1,
The pressure-sensitive adhesive layer further contains a photopolymerization initiator, the variable color pressure-sensitive adhesive sheet. According to claim 1,
The coloring agent is a compound that develops color by reaction with an acid,
The pressure-sensitive adhesive layer further contains a photo-acid generator, the variable color pressure-sensitive adhesive sheet. According to claim 1,
The coloring agent is a compound that develops color by reaction with an acid,
The pressure-sensitive adhesive layer further contains a photoacid generator and a photopolymerization initiator,
A variable color pressure-sensitive adhesive sheet having a wavelength range in which the ratio of the absorbance Y of the photopolymerization initiator to the absorbance X of the photoacid generator is 2 or more within a wavelength range of 300 nm or more and 500 nm or less. According to claim 1,
The content of the polymerizable compound in the pressure-sensitive adhesive layer is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the base polymer. According to claim 1,
The pressure-sensitive adhesive layer has a thickness of 10 μm or more and 300 μm or less. According to claim 1,
The variable color pressure-sensitive adhesive sheet further comprising a base material disposed on one side of the pressure-sensitive adhesive layer in the thickness direction.

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