WO2023074553A1 - Photocurable adhesive sheet - Google Patents

Abstract

An adhesive sheet (S) serving as a photocurable adhesive sheet according to the present invention includes a base polymer, a photopolymerizable multifunctional compound, and a photo-initiator. The base polymer is a photopolymer and includes a polymer having a photocrosslinking structure.

Description

Photo-curable adhesive sheet

The present invention relates to a photocurable adhesive sheet.

A display panel has a laminated structure including elements such as a pixel panel, a polarizer and a cover glass. In the manufacturing process of the display panel, for example, a transparent adhesive sheet is used for joining the elements included in the laminated structure. A pressure-sensitive adhesive sheet for use in display panels is described, for example, in Patent Document 1 below.

Japanese Patent Application Laid-Open No. 2020-83996

A printed layer colored for decoration or light blocking is provided on the edge of the surface on the pixel panel side of the cover glass for smartphones and tablet devices. The printed layer is provided, for example, over the entire periphery of the edge of the cover glass. This print layer has a predetermined thickness. Therefore, on the pixel panel side of the cover glass, there is a step (printing step) between the surface of the cover glass and the surface of the printed layer. A pressure-sensitive adhesive sheet having a cover glass as an adherend is required to have not only reliability in bonding between adherends but also softness to the extent that it can follow printing steps (step conformability). Insufficient step followability of the adhesive sheet is the cause of the formation of air bubbles along the printed layer between the adhesive sheet and the cover glass, which is attached to the surface of the cover glass on the side of the pixel panel with the printed layer. and is not preferable.

Patent Document 1 describes a photocurable adhesive sheet (photocurable adhesive sheet). This pressure-sensitive adhesive sheet contains an acrylic base polymer having a cross-linked structure with a thermal cross-linking agent such as an isocyanate cross-linking agent, a photopolymerizable polyfunctional compound, and a photopolymerization initiator. According to Patent Document 1, this pressure-sensitive adhesive sheet has step absorbability in a soft state before photocuring, and has excellent adhesion durability after photocuring.

The photocurable adhesive sheet of Patent Document 1 is produced as follows. First, an adhesive composition containing an acrylic base polymer, a photopolymerizable polyfunctional compound, a photopolymerization initiator, a thermal cross-linking agent, and a solvent is applied onto a substrate to form a coating film. be. Next, the coating film on the substrate is dried by heating (drying step). In this step, a relatively large amount of solvent in the coating film is vaporized and removed to the outside of the coating film, thereby drying the coating film. Thereby, an adhesive layer is formed on the substrate. Next, by aging treatment, the cross-linking reaction of the base polymer by the thermal cross-linking agent proceeds in the pressure-sensitive adhesive layer. As described above, a photocurable pressure-sensitive adhesive sheet is formed on the substrate.

However, according to such a manufacturing method, citrus skin-like irregularities are likely to be formed on the surface of the coating film due to evaporation of the solvent in the coating film during the drying process. As a result, it is easy to produce a pressure-sensitive adhesive sheet having a citrus peel surface. The orange peel surface of the transparent pressure-sensitive adhesive sheet is not preferable because it affects the visibility of the display portion of the display panel produced using the pressure-sensitive adhesive sheet.

The present invention provides a photocurable pressure-sensitive adhesive sheet suitable for achieving both step followability and bonding reliability while suppressing the formation of an orange peel surface during manufacturing.

The present invention [1] comprises a base polymer, a photopolymerizable polyfunctional compound, and a photopolymerization initiator, wherein the base polymer is a photopolymer and contains a polymer having a photocrosslinking structure. Includes adhesive sheet.

The present invention [2] is the photocurable adhesive according to [1] above, wherein the content of the photopolymerizable polyfunctional compound is 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the base polymer. Including sheet.

The present invention [3] includes the photocurable pressure-sensitive adhesive sheet according to [1] or [2] above, which further contains an ultraviolet absorber.

The present invention [4] is the light according to [3] above, wherein the photopolymerization initiator has a specific absorbance of 10 or more at a wavelength of 405 nm, and the ultraviolet absorber has a specific absorbance of 5 or less at a wavelength of 405 nm. Includes curable adhesive sheet.

The present invention [5] includes the photocurable pressure-sensitive adhesive sheet according to any one of [1] to [4] above, further comprising an antioxidant.

The present invention [6] includes the photocurable pressure-sensitive adhesive sheet according to any one of [1] to [5] above, which is substantially free of thermal polymerization initiator residue.

In the photocurable pressure-sensitive adhesive sheet of the present invention, as described above, the base polymer is a photopolymer and contains a polymer having a photocrosslinked structure. Such a photocurable pressure-sensitive adhesive sheet is suitable for production from a solvent-free pressure-sensitive adhesive composition. Further, the solvent-free pressure-sensitive adhesive composition does not require a drying step for vaporizing and removing the solvent from the coating film of the composition in the process of producing a pressure-sensitive adhesive sheet from the composition. Unevenness like yuzu skin is less likely to occur. Moreover, the photocurable pressure-sensitive adhesive sheet of the present invention contains a base polymer, a photopolymerizable polyfunctional compound, and a photopolymerization initiator as described above. In such a photocurable adhesive sheet, the adhesive sheet (before photocuring) is used to secure the softness of the adhesive sheet when bonding the adherends together, while the photopolymerizable polyfunctional compound is exposed to light after bonding. The sheet can be made highly elastic by polymerization. Such a photocurable pressure-sensitive adhesive sheet is suitable for achieving both followability to a step on the surface of the adherend when the adherends are joined and bonding reliability after the adherends are joined.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram of one Embodiment of the photocurable adhesive sheet of this invention. An example of the manufacturing method of the photocurable adhesive sheet shown in FIG. 1 is represented. 2A represents the process of forming a coating film of the pressure-sensitive adhesive composition, FIG. 2B represents the process of forming the base pressure-sensitive adhesive sheet, FIG. 2C represents the process of peeling the light release liner, and FIG. Representing the step of applying the post-add component, FIG. 2E represents the step of laminating the light release liner to the sheet. An example of the usage method of the photocurable adhesive sheet shown in FIG. 1 is represented. FIG. 3A shows a step of preparing a photocurable adhesive sheet and two members (adherends), FIG. 3B shows a step of joining the members via the photocurable adhesive sheet, and FIG. It represents a step of photocuring a photocurable adhesive sheet between members. 1 shows the positional relationship between a glass plate and an adhesive sheet in a laminate used for evaluation of conformability to steps in Examples and Comparative Examples.

A pressure-sensitive adhesive sheet S as an embodiment of the photocurable pressure-sensitive adhesive sheet of the present invention, as shown in FIG. . FIG. 1 exemplarily shows a state in which release liners L1 and L2 are attached to both sides of an adhesive sheet S. As shown in FIG. The release liner L1 is arranged on one side of the adhesive sheet S in the thickness direction H. As shown in FIG. A release liner L2 is arranged on the other surface of the adhesive sheet S in the thickness direction H. As shown in FIG. Also, the adhesive sheet S is a transparent adhesive sheet (optical adhesive sheet) that is arranged at a light passage portion of the display panel. Examples of display panels include liquid crystal panels and organic EL panels. A display panel has, for example, a laminated structure including elements such as a pixel panel, a film-like polarizing plate (polarizing film), a touch panel, and a cover glass. The pressure-sensitive adhesive sheet S is used, for example, in the process of manufacturing display panels to bond elements included in a laminated structure.

The adhesive sheet S is a sheet-like pressure-sensitive adhesive. The adhesive sheet S contains a base polymer as a photopolymer, a photopolymerizable polyfunctional compound (first photopolymerizable polyfunctional compound), and a photopolymerization initiator, and has photocurability. The adhesive sheet S may contain a monofunctional monomer as a polymerizable component in addition to the photopolymerizable polyfunctional compound. A photopolymer is a polymer produced by photopolymerization. Photopolymerization is a polymerization method in which the polymerization reaction of polymerizable components proceeds by irradiation with active energy rays such as ultraviolet rays. The term “photocurability” refers to the property of becoming highly elastic when irradiated with active energy rays such as ultraviolet rays.

The base polymer is a polymer obtained by photopolymerization of polymerizable components including a monofunctional monomer and a photopolymerizable polyfunctional compound (second photopolymerizable polyfunctional compound). The base polymer is, for example, a partial polymer obtained by photopolymerization of a monofunctional monomer (a mixture of a polymerized monofunctional monomer and an unreacted monofunctional monomer) and a second photopolymerizable polyfunctional compound obtained by photopolymerization. It is a polymer. A monofunctional monomer may be used independently and two or more types may be used together. The second photopolymerizable polyfunctional compound may be used alone, or two or more of them may be used in combination.

Such a base polymer includes a photopolymerized polymer (first photopolymerized polymer) having a photocrosslinked structure. The photocrosslinked structure is a structure in which a linear structure of units derived from a monofunctional monomer is crosslinked by a unit derived from the second photopolymerizable polyfunctional compound. The base polymer may contain a photopolymerized polymer (second photopolymerized polymer) that does not have such a photocrosslinked structure. The second photopolymer polymer is a polymer of monofunctional monomers. Also, the base polymer is preferably an acrylic polymer. The acrylic polymer is a copolymer of polymerizable components containing 50% by mass or more of (meth)acrylic acid ester. "(Meth)acrylic" means acrylic and/or methacrylic.

A monofunctional (meth)acrylic acid ester is preferably used as the monofunctional monomer. As the monofunctional (meth)acrylic acid ester, an alkyl (meth)acrylic acid ester is preferably used, and an alkyl (meth)acrylic acid ester having an alkyl group having 1 to 20 carbon atoms is more preferably used. be done. The (meth)acrylic acid alkyl ester may have a linear or branched alkyl group, or may have a cyclic alkyl group such as an alicyclic alkyl group.

Linear or branched (meth)acrylic acid alkyl esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, ( s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, (meth)acrylic acid Heptyl, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, (meth)acrylic Isodecyl Acid, Undecyl (Meth)acrylate, Dodecyl (Meth)acrylate, Isotridecyl (Meth)acrylate, Tetradecyl (Meth)acrylate, Isotetradecyl (Meth)acrylate, Pentadecyl (Meth)acrylate, (Meth)acrylate cetyl acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate.

Examples of (meth)acrylic acid alkyl esters having an alicyclic alkyl group include, for example, (meth)acrylic acid cycloalkyl esters, (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring, and tricyclic (Meth)acrylic acid esters having the above aliphatic hydrocarbon rings can be mentioned. Cycloalkyl (meth)acrylates include, for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring include isobornyl (meth)acrylate. (Meth)acrylic acid esters having a tricyclic or higher aliphatic hydrocarbon ring include, for example, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate , 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

As the (meth)acrylic acid alkyl ester, an acrylate alkyl ester having an alkyl group having 3 to 15 carbon atoms is preferably used, and more preferably n-butyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. At least one selected from the group consisting of dodecyl is used.

The ratio of the monofunctional monomer in the polymerizable component forming the base polymer is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 60% by mass or more, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the adhesive sheet S. It is preferably 70% by mass or more, particularly preferably 75% by mass or more. The same ratio is, for example, 99% by mass or less.

The polymerizable component may contain, as a monofunctional monomer, a copolymerizable monomer that can be copolymerized with the above monofunctional monomer. Examples of copolymerizable monomers include monomers having a polar group. Polar group-containing monomers include, for example, hydroxyl group-containing monomers, carboxy group-containing monomers, and monomers having a nitrogen atom-containing ring. A polar group-containing monomer is useful for modifying the acrylic polymer, such as ensuring the cohesive strength of the acrylic polymer.

Examples of hydroxy group-containing monomers 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, and 12-hydroxylauryl (meth)acrylate mentioned. As the hydroxy group-containing monomer, preferably at least one selected from the group consisting of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is used.

From the viewpoint of securing the cohesive force of the adhesive sheet S, the proportion of the hydroxy group-containing monomer in the polymerizable component is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. The same ratio is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of adjusting the polarity of the acrylic polymer (related to the compatibility between the various additive components in the adhesive sheet S and the acrylic polymer). is 15% by mass or less.

Carboxy group-containing monomers include, for example, 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 polymerizable component is preferably 1% by mass or more, more preferably 3% by mass, from the viewpoint of ensuring the cohesive force of the adhesive sheet S and ensuring the adhesion of the adhesive sheet S to the adherend. It is at least 5% by mass, more preferably at least 5% by mass. The same ratio is preferably 20% by mass or less, more preferably 10% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of acid corrosion of the adherend.

Examples of monomers having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl -3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N -vinylthiazole, N-vinylisothiazole, and acryloylmorpholine. The monomer having a nitrogen atom-containing ring is preferably at least one selected from the group consisting of N-vinyl-2-pyrrolidone and acryloylmorpholine.

The ratio of the monomer having a nitrogen atom-containing ring in the polymerizable component is preferably 1% by mass or more, more preferably 1% by mass or more, from the viewpoint of ensuring the cohesive force of the adhesive sheet and ensuring the adhesion of the adhesive sheet to the adherend. is 3% by mass or more, more preferably 5% by mass or more. The same ratio is preferably 30% by mass or less 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 and the acrylic polymer in the pressure-sensitive adhesive sheet). More preferably, it is 20% by mass or less.

Examples of the second photopolymerizable polyfunctional compound include polyfunctional monomers and polyfunctional oligomers, preferably polyfunctional oligomers.

Examples of polyfunctional monomers include polyfunctional (meth)acrylates containing two or more ethylenically unsaturated double bonds per molecule. As the polyfunctional monomer, a polyfunctional (meth)acrylate is preferable from the viewpoint of easy introduction of a crosslinked structure by photopolymerization (active energy ray polymerization).

Polyfunctional (meth)acrylates include bifunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates with tetrafunctional or higher functionality.

Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol di (meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, Examples include di(meth)acryloyl isocyanurate and alkylene oxide-modified bisphenol di(meth)acrylate.

Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl) isocyanurate.

Tetrafunctional or higher polyfunctional (meth)acrylates include, for example, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and alkyl-modified dipentaerythritol pentaacrylate. , and dipentaerythritol hexa(meth)acrylate.

The molecular weight of the polyfunctional monomer is preferably 5000 or less, more preferably 3000 or less, still more preferably 2000 or less, particularly preferably 1000 or less, and preferably 200 or more. Such a configuration is preferable from the viewpoint of appropriately adjusting the viscoelasticity (for example, storage modulus and loss tangent) of the base polymer.

Examples of polyfunctional oligomers include urethane acrylate oligomers (oligomers having a urethane skeleton and two or more acryloyl groups), epoxy acrylate oligomers (oligomers having an epoxy skeleton and two or more acryloyl groups), and silicone acrylate oligomers ( oligomers having a siloxane skeleton and two or more acryloyl groups). A urethane acrylate oligomer is preferably used as the polyfunctional oligomer. Commercially available urethane acrylate oligomers include, for example, Artresin UN-333, UN-350, UN-353, UN-5500, and UN-5590 manufactured by Negami Kogyo Co., Ltd.

The weight average molecular weight (Mw) of the polyfunctional oligomer is preferably 20,000 or less, more preferably 15,000 or less, and preferably 5,000 or more. Such a configuration is preferable from the viewpoint of appropriately adjusting the viscoelasticity (for example, storage modulus and loss tangent) of the base polymer. The weight average molecular weight is calculated by measuring with gel permeation chromatography (GPC) and converting to polystyrene.

The proportion of the second photopolymerizable polyfunctional compound in the polymerizable component is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. Such a configuration is preferable for maintaining the sheet shape of the pressure-sensitive adhesive sheet S before photocuring, and therefore preferable for ensuring the handleability of the pressure-sensitive adhesive sheet S. The proportion of the second photopolymerizable polyfunctional compound in the polymerizable component is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. Such a configuration is preferable in order to secure a high degree of softness in the pressure-sensitive adhesive sheet S before photocuring and to realize good step conformability.

The polymerizable component may contain other copolymerizable monomers. Other copolymerizable monomers include, 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. be done. These other copolymerizable monomers may be used alone, or two or more of them may be used in combination.

Examples of the first photopolymerizable polyfunctional compound include polyfunctional monomers and polyfunctional oligomers, and polyfunctional monomers are preferably used. Examples of polyfunctional monomers include the polyfunctional monomers described above for the second photopolymerizable polyfunctional compound. Examples of polyfunctional oligomers include the polyfunctional oligomers described above with respect to the second photopolymerizable polyfunctional compound. As the polyfunctional monomer, trifunctional (meth)acrylate is preferably used, more preferably trimethylolpropane tri(meth)acrylate, and still more preferably trimethylolpropane triacrylate (TMPTA).

The content of the first photopolymerizable polyfunctional compound in the adhesive sheet S is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and still more preferably 1 part by mass or more per 100 parts by mass of the base polymer. and preferably 20 parts by mass or less, more preferably 17 parts by mass or less, and even more preferably 15 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet S after photocuring.

Examples of photopolymerization initiators include radical photopolymerization initiators, cationic photopolymerization initiators, and anionic photopolymerization initiators.

Examples of radical photopolymerization initiators include acylphosphine oxide photopolymerization initiators, benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, and aromatic sulfonyl chloride photopolymerization initiators. Polymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators are listed. be done.

Examples of acylphosphine oxide photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenyl Included are phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethan-1-one. mentioned. Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl ) dichloroacetophenone. Examples of α-ketol photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. . Examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzyl. Benzophenone photoinitiators include, for example, benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of ketal photopolymerization initiators include benzyl dimethyl ketal. Thioxanthone photoinitiators include, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

Cationic photopolymerization initiators (photoacid generators) include, for example, onium compounds that generate acid when irradiated with ultraviolet rays. The onium compound is provided, for example, in the form of an onium salt of an onium cation and an anion. Onium cations include, for example, sulfonium and iodonium. 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 ⁻ . Commercially available cationic photopolymerization initiators include, for example, San-Apro CPI-100, CPI-100P, CPI-101A, CPI-200K, CPI-210S, IK-1, IK-2, CPI-310B, and CPI-410S. Examples of commercially available cationic photopolymerization initiators include SP-056, SP-066, SP-130, SP-140, SP-150, SP-170, SP-171, and SP-172 manufactured by ADEKA. is also mentioned.

Examples of anionic photopolymerization initiators (photobase generators) include α-aminoacetophenone compounds, oxime ester compounds, and compounds having biguanide-type cations. Biguanide-type cations include, for example, alkylbiguanidiniums, cycloalkylbiguanidiniums, and cycloalkyl-alkylbiguanidiniums. Examples of anions that form pairs with biguanide cations include borate anions. Examples of commercially available anionic photopolymerization initiators include WPBG-018 (9-anthramethyl N,N'-diethylcarbamate) and WPBG-027 ((E)-1-[3-( 2-hydroxyphenyl)-2-propenoyl]piperidine), WPBG-082 (Guanidium 2-(3-benzoylphenyl)propionate), WPBG-140 (1-(anthraquinon-2-yl)ethylimidazole carboxylate), WPBG- 266 (1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate), WPBG-300 (1,2-dicyclohexyl-4,4,5,5-tetramethyl biguanidinium n-butyltriphenylborate) and WPBG-345 (1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium tetrakis(3-fluorophenyl)borate).

The content of the photopolymerization initiator in the adhesive sheet S is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and still more preferably 0.03 parts by mass or more per 100 parts by mass of the base polymer. It is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, even more preferably 0.1 parts by mass or more, and particularly preferably 0.2 parts by mass or more. Such a configuration is preferable for forming a crosslinked network with a sufficient crosslink density in the adhesive sheet S by a photopolymerization reaction when the adhesive sheet S is irradiated with light, and for significantly changing the viscoelasticity of the adhesive sheet S. . The content of the photopolymerization initiator in the adhesive sheet S is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less per 100 parts by mass of the base polymer. Such a configuration is preferable for suppressing excessive generation of the polymerization initiator when the adhesive sheet S is irradiated with light and for forming a long-distance and continuous crosslinked network by photopolymerization reaction.

The adhesive sheet S may contain other components. Other ingredients include, for example, oligomers, UV absorbers, antioxidants, silane coupling agents, rust inhibitors, rework improvers, isocyanate crosslinkers, and metal deactivators.

When the base polymer is an acrylic polymer, an acrylic oligomer is preferably used as the oligomer. The acrylic oligomer is a copolymer of monomer components containing 50% by mass or more of (meth)acrylic acid ester, and has a weight average molecular weight of, for example, 1,000 or more and 30,000 or less.

The acrylic oligomer is preferably a (meth)acrylic acid alkyl ester having a chain alkyl group (chain alkyl (meth)acrylate) and a (meth)acrylic acid alkyl ester having an alicyclic alkyl group (alicyclic alkyl It is a polymer of monomer components containing (meth)acrylate). Specific examples of these (meth)acrylic acid alkyl esters include, for example, the (meth)acrylic acid alkyl esters described above as the polymerizable component of the acrylic polymer.

As the chain alkyl (meth)acrylate, methyl methacrylate is preferable because it has a high glass transition temperature and excellent compatibility with the base polymer. Preferred alicyclic alkyl (meth)acrylates are dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate. That is, the acrylic oligomer is a monomer component containing methyl methacrylate and at least one selected from the group consisting of dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate. A coalescence is preferred.

The proportion of the alicyclic alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more. The same ratio is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The proportion of chain alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The same ratio is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more.

The acrylic oligomer is obtained by polymerizing the monomer component of the acrylic oligomer. Polymerization methods include, for example, solution polymerization, bulk polymerization, and emulsion polymerization. Acrylic oligomers are preferably formed by solution polymerization. Solvents in solution polymerization include, for example, toluene and ethyl acetate. In the polymerization of the acrylic oligomer, a thermal polymerization initiator may be used, and a chain transfer agent may be used for the purpose of adjusting the molecular weight. Further, in the present embodiment, after the acrylic oligomer is formed, the low-molecular-weight components and the solvent are volatilized and removed from the reaction system such as the reaction solution by heating. Low-molecular-weight components include, for example, unreacted monomers, chain transfer agents, thermal polymerization initiators, and decomposition products (residues) thereof.

Thermal polymerization initiators include, for example, azo polymerization initiators and peroxide polymerization initiators. Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate)dimethyl, 4,4'-azobis-4-cyanovaleric 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'-dimethyleneisobutyramidine) dihydrochloride mentioned. Peroxide polymerization initiators include, for example, dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide.

Chain transfer agents include α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and α-methylstyrene. Dimers are included.

The weight average molecular weight of the oligomer is preferably 1,000 or more, more preferably 1,500 or more, and even more preferably 2,000 or more. The molecular weight is preferably 30,000 or less, more preferably 10,000 or less, still more preferably 8,000 or less. Such a molecular weight range of the oligomer is preferable for ensuring the adhesive strength of the pressure-sensitive adhesive sheet S.

In order to sufficiently increase the adhesive strength of the adhesive sheet S, the content of the oligomer in the adhesive sheet S is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, per 100 parts by mass of the base polymer. More preferably, it is 1 part by mass or more. From the viewpoint of ensuring the transparency of the adhesive sheet S, the content of the oligomer in the adhesive sheet S is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass per 100 parts by mass of the base polymer. parts or less, more preferably 4 parts by mass or less, and particularly preferably 3 parts by mass or less.

Examples of ultraviolet absorbers include triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. As the ultraviolet absorber, a triazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber are preferable because they have high absorbability of ultraviolet rays in the wavelength range of 320 to 370 nm and are excellent in compatibility with acrylic polymers. The ultraviolet absorbers may be used alone, or two or more of them may be used in combination.

Examples of commercially available triazine-based UV absorbers include bisethylhexyloxyphenolmethoxyphenyltriazine (product name “Tinosorb S”, manufactured by BASF), 2-(4,6-bis(2,4-dimethylphenyl)-1, Reaction product of 3,5-triazin-2-yl)-5-hydroxyphenyl and [(alkyloxy)methyl]oxirane (product name "TINUVIN 400", manufactured by BASF), 2-(2,4-dihydroxyphenyl) A reaction product of -4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidate (product name "TINUVIN 405", manufactured by BASF), ( 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (product name “TINUVIN 460”, manufactured by BASF), 2-(4 ,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (product name “TINUVIN 577”, manufactured by BASF), 2-(2-hydroxy-4-[1 -octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (product name "TINUVIN 479", manufactured by BASF), and 2-(4,6-diphenyl- 1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (“ADK STAB LA-46”, manufactured by ADEKA).

Examples of commercially available benzotriazole-based UV absorbers include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3 -tetramethylbutyl)phenol (product name "TINUVIN 928", manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (product name "TINUVIN PS", manufactured by BASF), 2-( 2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (product name “TINUVIN 900”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)- 6-dodecyl-4-methylphenol (product name “TINUVIN571”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (product name “TINUVIN P”, manufactured by BASF), 2-(2H- benzotriazol-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol (product name "TINUVIN 234", manufactured by BASF), 2-[5-chloro(2H)-benzotriazole-2- yl]-4-methyl-6-(tert-butyl)phenol (product name “TINUVIN 326”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol ( Product name “TINUVIN 328”, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (Product name “TINUVIN 329”, manufactured by BASF), and 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (product name “Sumisorb 250”, manufactured by Sumitomo Chemical).

In the adhesive sheet S, the specific absorbance (first specific absorbance) at a wavelength of 405 nm of the photopolymerization initiator is preferably 10 or more, more preferably 15 or more, and the specific absorbance at a wavelength of 405 nm of the ultraviolet absorber. (Second specific absorbance) is preferably 5 or less, more preferably 3 or less. Such a configuration is preferable from the viewpoint of compatibility between the UV cut function for device protection and the photocurability in the pressure-sensitive adhesive sheet S. Among the above photopolymerization initiators, for example, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide have a first specific absorbance of 15 or more. Among the above UV absorbers, for example, bisethylhexyloxyphenolmethoxyphenyltriazine and 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1, 1,3,3-Tetramethylbutyl)phenol has a second specific absorbance of 3 or less.

The content of the ultraviolet absorber in the adhesive sheet S is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less, or more, per 100 parts by mass of the base polymer. Preferably, it is 2 parts by mass or less. Such a configuration is preferable from the viewpoint of compatibility between the UV cut function for device protection and the photocurability in the pressure-sensitive adhesive sheet S.

Examples of antioxidants include phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, and amine antioxidants. The antioxidants may be used alone, or two or more of them may be used in combination.

As the antioxidant, a phenolic antioxidant is preferably used, and a hindered phenolic antioxidant is more preferably used. Hindered phenol antioxidants include, for example, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (product name "Irganox 1010", manufactured by BASF), octadecyl -3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (product name “Irganox 1076”, manufactured by BASF), 4,6-bis(dodecylthiomethyl)-o-cresol (product name “Irga Nox 1726", manufactured by BASF), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate] (product name "Irganox 245", manufactured by BASF), bis(2, 2,6,6-tetramethyl-4-piperidyl) sebacate (product name “TINUVIN770”, manufactured by BASF), and dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine ethanol (product name "TINUVIN622", manufactured by BASF).

The content of the antioxidant in the pressure-sensitive adhesive sheet S is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less, or more, per 100 parts by mass of the base polymer. Preferably, it is 2 parts by mass or less. Such a configuration is preferable from the viewpoint of achieving both suppression of oxidative deterioration of the adhesive sheet S and photocurability.

Examples of silane coupling agents include silane coupling agents containing epoxy groups. Epoxy group-containing silane coupling agents include, for example, 3-glycidoxydialkyldialkoxysilanes and 3-glycidoxyalkyltrialkoxysilanes. 3-glycidoxydialkyldialkoxysilanes include, for example, 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. 3-glycidoxyalkyltrialkoxysilanes include, for example, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. As the silane coupling agent, 3-glycidoxyalkyltrialkoxysilane is preferably used, and 3-glycidoxypropyltrimethoxysilane is more preferably used. Silane coupling agents may be used alone, or two or more of them may be used in combination. The content of the silane coupling agent in the adhesive sheet S is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 5 parts by mass or less, per 100 parts by mass of the base polymer. More preferably, it is 3 parts by mass or less.

The adhesive sheet S does not substantially contain any residue of the thermal polymerization initiator. The residue of the thermal polymerization initiator includes decomposition products of the thermal polymerization initiator. The proportion of the residue of the thermal polymerization initiator in the adhesive sheet S is preferably 0.005% by mass or less, more preferably 0.001% by mass or less, and particularly preferably 0%.

The thickness of the adhesive sheet S is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesion to the adherend. From the standpoint of handleability and laser processability of the adhesive sheet S, the thickness of the adhesive sheet S is preferably 500 μm or less, more preferably 400 μm or less, more preferably 300 μm or less, more preferably 250 μm or less, more preferably 200 μm or less. , more preferably 150 μm or less, more preferably 135 μm or less, more preferably 100 μm or less, more preferably 75 μm or less, more preferably 50 μm or less.

The haze of the adhesive sheet S is preferably 1% or less, more preferably 0.7% or less, even more preferably 0.5% or less, and particularly preferably 0.4% or less. Such a configuration is preferable for ensuring the transparency required for the pressure-sensitive adhesive sheet S for use in display panels. The haze of the adhesive sheet S is, for example, 0.01% or more. Haze can be measured using a haze meter in accordance with JIS K7136 (2000). Examples of the haze meter include "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and "HM-150 type" manufactured by Murakami Color Research Laboratory.

The total light transmittance of the adhesive sheet S is preferably 90% or higher, more preferably 92% or higher. Such a configuration is preferable for ensuring the transparency required for the pressure-sensitive adhesive sheet S for use in display panels. The total light transmittance of the adhesive sheet S is, for example, 100% or less. The total light transmittance can be measured according to JIS K 7375 (2008).

The gel fraction of the pressure-sensitive adhesive sheet S after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/cm ² is preferably 60% or more and 95% or less. The gel fraction is more preferably 65% or more, still more preferably 68% or more, particularly preferably 70% or more, more preferably 92% or less, still more preferably 90% or less, and even more preferably 88%. % or less, particularly preferably 86% or less. Such a configuration is suitable for suppressing the formation of air bubbles between the adherend and the adhesive sheet S in a state where the adhesive sheet S after photocuring is attached to the adherend. Methods for adjusting the gel fraction after photocuring include, for example, selection of the type of base polymer in the adhesive sheet S, adjustment of the molecular weight, and adjustment of the compounding amount. Methods for adjusting the gel fraction after photocuring include selection of the type of photopolymerizable polyfunctional compound in the pressure-sensitive adhesive sheet S, adjustment of the molecular weight, and adjustment of the compounding amount.

The gel fraction of the adhesive sheet S (before photocuring) is preferably 20% or more and 65% or less. The gel fraction is more preferably 25% or more, still more preferably 30% or more, particularly preferably 35% or more, and more preferably 60% or less, more preferably 58% or less, and more preferably 56%. Below, more preferably 54% or less, more preferably 52% or less, more preferably 50% or less, more preferably 48% or less, more preferably 46% or less. Such a configuration is preferable for suppressing glue dripping during processing of the adhesive sheet S, and also preferable for suppressing deformation of the adhesive sheet S during storage. Methods for adjusting the gel fraction before photocuring include, for example, selection of the type of base polymer in the adhesive sheet S, adjustment of the molecular weight, and adjustment of the compounding amount.

Each of the above gel fractions of the adhesive sheet can be measured as follows. First, about 1 g of adhesive sample is taken from the adhesive sheet. Next, the mass (W ₁ ) of the adhesive sample is measured. Next, the adhesive sample is immersed in 40 g of ethyl acetate in a container for 7 days. Next, all components insoluble in ethyl acetate (insoluble portion) are recovered. The undissolved portion is then dried at 130° C. for 2 hours (removal of ethyl acetate). Next, the mass (W ₂ ) of the undissolved portion is measured. Then, the gel fraction of the adhesive sheet after photocuring is calculated based on the following formula.

Gel fraction (%) = ( _W2 / _W1 ) x 100

The loss tangent tan δ of the pressure-sensitive adhesive sheet S after curing by light irradiation with an integrated irradiation light amount of 3000 mJ/cm ² preferably has a peak top of 1.5 or more within the range of -40°C to 5°C. The peak top value is more preferably 2 or more, still more preferably 2.5 or more, and particularly preferably 3 or more. Such a configuration is preferable from the viewpoint of low-temperature adhesion reliability of the pressure-sensitive adhesive sheet S. Methods for adjusting the peak top value include, for example, adjusting the composition ratio of the high Tg monomer in the base polymer and adjusting the amount of the high Tg additive added to the pressure-sensitive adhesive sheet S. A method for measuring the loss tangent tan δ is as described later with regard to Examples. The loss tangent of the pressure-sensitive adhesive sheet can be measured using, for example, a dynamic viscoelasticity measuring device (trade name “Advanced Rheometric Expansion System (ARES)”, manufactured by Rheometric Scientific). In the measurement, the measurement mode is shear mode, the measurement temperature range is −50° C. to 150° C., the temperature increase rate is 5° C./min, and the frequency is 1 Hz.

The adhesive sheet S can be manufactured, for example, as follows.

First, a prepolymer composition is prepared (prepolymer composition preparation step). Specifically, first, a mixture (liquid) containing the above-described monofunctional monomer for forming the base polymer and a photopolymerization initiator is prepared. This mixture is solvent-free. Next, by irradiating the mixture with ultraviolet rays, part of the monofunctional monomers in the mixture is photopolymerized to obtain a prepolymer composition (solvent-free prepolymer composition). Light sources for ultraviolet irradiation include, for example, ultraviolet LED lights, black lights, high-pressure mercury lamps, and metal halide lamps. Moreover, in the ultraviolet irradiation, a wavelength cut filter for cutting a part of the wavelength region of the light emitted from the light source may be used as necessary. In the ultraviolet irradiation, the illuminance is, for example, 5 to 200 mW/cm ² , and the integrated irradiation light amount is, for example, 100 to 5000 mJ/cm ² . UV irradiation is preferably continued until the composition has a viscosity of about 15 to 25 Pa·s. This viscosity is a value measured with a Brookfield viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The prepolymer composition contains a photopolymerized product of a monofunctional monomer (second photopolymerized polymer) and a monofunctional monomer that has not undergone polymerization reaction (residual monomer). Also, the prepolymer composition is solvent-free.

Next, a second photopolymerizable polyfunctional compound, a photopolymerization initiator, and optionally other components are added to the prepolymer composition to prepare an adhesive composition (adhesive composition preparation process). Other ingredients include, for example, antioxidants and silane coupling agents. Since the adhesive composition does not contain a solvent, it is a solvent-free adhesive composition.

Next, as shown in FIG. 2A, a coating film 10 is formed between the release liners L1 and L2' (coating film forming step). Specifically, after coating the adhesive composition on the release liner L1 to form the coating film 10, the release liner L2' is adhered onto the coating film 10 on the release liner L1.

The release liners L1 and L2' are each, for example, a flexible plastic film. Examples of such plastic films include polyester films such as polyethylene terephthalate films, polyethylene films, and polypropylene films. The thickness of the release liner is, for example, 3 μm or more and, for example, 200 μm or less. The surface of the release liner is preferably release treated.

Examples of methods for applying the adhesive composition include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, and lip coating. , and die coats.

Next, as shown in FIG. 2B, the coating film 10 between the release liners L1 and L2' is irradiated with ultraviolet rays for photocuring to form a base adhesive sheet 10A (base adhesive sheet forming step). When irradiated with ultraviolet rays, the photopolymerization reaction proceeds in the reaction system containing the above-described residual monomer and the second photopolymerizable polyfunctional compound in the coating film, forming the first photopolymerizable polymer having a photocrosslinked structure.

Next, as shown in FIG. 2C, the release liner L2' is peeled off from the base adhesive sheet 10A (peeling step).

Next, as shown in FIG. 2D, the post-additive component is supplied to the base adhesive sheet 10A (post-additive component supply step). For example, a post-additive component solution (not shown) containing a post-additive component and a solvent is applied to the exposed surface of the base adhesive sheet 10A. The post-addition component contains the first photopolymerizable polyfunctional compound and a photopolymerization initiator, and may contain additives such as ultraviolet absorbers and antioxidants. Next, while permeating the post-addition component from the surface of the base pressure-sensitive adhesive sheet 10A into the base pressure-sensitive adhesive sheet 10A, the solvent is vaporized by heating as necessary. Before this step, the base polymer already has a crosslinked structure to form the base PSA sheet 10A. Therefore, the vaporization of the solvent in this step does not easily form the citrus skin surface on the base adhesive sheet 10A (it is not substantially formed). A photocurable adhesive sheet S is formed by the base adhesive sheet 10A and the post-addition component. The amount of the first photopolymerizable polyfunctional compound added in this step is preferably 0.5 parts by mass or more per 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound. It is more preferably 0.8 parts by mass or more, still more preferably 1 part by mass or more, and is preferably 20 parts by mass or less, more preferably 17 parts by mass or less, and still more preferably 15 parts by mass or less. Such a configuration is suitable for ensuring good bonding reliability in the adhesive sheet S after photocuring.

Next, as shown in FIG. 2E, a release liner L2 is adhered to the adhesive sheet S (lamination step). Release liner L2 includes, for example, the plastic films described above for release liners L1 and L2'.

As described above, the adhesive sheet S whose adhesive surface is covered and protected by the release liners L1 and L2 can be manufactured. The release liners L1 and L2 are peeled off from the adhesive sheet S when the adhesive sheet S is used.

3A to 3C show an example of how to use the adhesive sheet S.

In this method, first, as shown in FIG. 3A, a member 21, a cover glass 22, and an adhesive sheet S are prepared. The member 21 is, for example, a pixel panel for a display panel, a film-like polarizing plate (polarizing film), or a touch panel. The cover glass 22 has a first surface 22a on the member 21 side and a second surface 22b opposite to the first surface 22a. A printing layer 23 for decoration or light shielding is formed on the edge of the first surface 22a. The printed layer 23 is provided, for example, over the entire periphery of the edge of the cover glass 22 . On the member 21 side of the cover glass 22 , there is a step (printing step) between the first surface 22 a and the surface of the printing layer 23 .

Next, as shown in FIG. 3B, one side in the thickness direction H of the member 21 and the other side in the thickness direction H of the cover glass 22 are joined via the adhesive sheet S (joining step).

Next, as shown in FIG. 3C, the adhesive sheet S is photo-cured between members by ultraviolet irradiation (photo-curing step). The ultraviolet irradiation causes the photopolymerization reaction of the first photopolymerizable polyfunctional compound to proceed in the adhesive sheet S, forming a photopolymerized product of the first photopolymerizable polyfunctional compound. Since the photopolymerization reaction proceeds around the base polymer (the first photopolymerization polymer and the second photopolymerization polymer having a photocrosslinking structure), the photopolymerization product of the first photopolymerizable polyfunctional compound interacts with the base polymer. It is formed while forming an interstitial polymer network (IPN). As a result, the adhesive sheet S becomes highly elastic, and the bonding strength between the member 21 and the cover glass 22 increases. Light sources for ultraviolet irradiation include, for example, ultraviolet LED lights, black lights, high-pressure mercury lamps, and metal halide lamps. Moreover, in ultraviolet irradiation, a wavelength cut filter may be used to cut a part of the wavelength region of the light emitted from the light source. In the ultraviolet irradiation, the irradiation integrated light amount is, for example, 50 to 10000 mJ/cm ² .

As described above, the adhesive sheet S contains a first photopolymerized polymer whose base polymer is a photopolymerized product and has a photocrosslinked structure. Such a pressure-sensitive adhesive sheet S can be produced from a solvent-free pressure-sensitive adhesive composition as described above. Further, according to the solvent-free pressure-sensitive adhesive composition, in the process of producing the pressure-sensitive adhesive sheet S from the pressure-sensitive adhesive composition, there is no need for a drying step of evaporating and removing the solvent from the coating film of the composition. On the surface of S, citron skin-like unevenness is less likely to occur.

The adhesive sheet S contains a base polymer, a first photopolymerizable polyfunctional compound, and a photopolymerization initiator, as described above. In such a pressure-sensitive adhesive sheet S, while ensuring the softness of the pressure-sensitive adhesive sheet S at the time of bonding between adherends by the pressure-sensitive adhesive sheet S (before photocuring), after bonding, the first photopolymerizable polyfunctional compound is exposed to light. The adhesive sheet S can be made highly elastic by polymerization. Such a pressure-sensitive adhesive sheet S is suitable for achieving both conformability to a step on the surface of the adherend when the adherends are joined and bonding reliability after the adherends are joined.

As described above, the adhesive sheet S is suitable for achieving both step followability and bonding reliability while suppressing the formation of the citrus peel surface during manufacturing.

The present invention will be specifically described below with reference to examples. However, the invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, parameters, etc. described below are the corresponding compounding amounts ( content), physical properties, parameters, etc., upper limits (values defined as “less than” or “less than”) or lower limits (values defined as “greater than” or “greater than”).

<Preparation of acrylic oligomer>
First, 60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), and a chain A mixture containing 3.5 parts by mass of α-thioglycerol as a transfer agent and 100 parts by mass of toluene as a polymerization solvent was stirred at 70° C. for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of 2,2′-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator is added to the mixture to prepare a reaction solution, which is then heated at 70° C. for 2 hours under a nitrogen atmosphere. , and then reacted at 80° C. for 2 hours (polymerization reaction). Next, by heating the reaction solution at 130° C., the toluene, the chain transfer agent and the unreacted monomer were volatilized and removed. As a result, an acrylic oligomer (solid form) was obtained. The weight average molecular weight of this acrylic oligomer was 5,100.

<Preparation of prepolymer composition>
In a flask, 71 parts by mass of n-butyl acrylate (BA), 13 parts by mass of N-vinyl-2-pyrrolidone (NVP), 13 parts by mass of 4-hydroxybutyl acrylate (4HBA), and acryloylmorpholine ( ACMO) 3 parts by weight of the monomer mixture, the first photopolymerization initiator (product name "Irgacure 184", 1-hydroxy-cyclohexyl-phenyl-ketone, manufactured by BASF) 0.031 parts by weight, the second photopolymerization After adding 0.031 parts by mass of an initiator (product name “Irgacure 651”, 2,2-dimethoxy-1,2-diphenylethan-1-one, manufactured by BASF), the mixture was exposed to ultraviolet light under a nitrogen atmosphere. A part of the monomer components in the mixture was polymerized to obtain a prepolymer composition. UV irradiation was continued until the viscosity of the composition reached about 20 Pa·s. This viscosity is a value measured with a Brookfield viscometer under the conditions of rotor No. 5, rotor speed of 10 rpm, and temperature of 30°C. The resulting prepolymer composition contains a photopolymer (photopolymer P1a) and a monomer component (residual monomer) that has not undergone a polymerization reaction.

<Preparation of adhesive composition>
Next, 100 parts by mass of the prepolymer composition, 3 parts by mass of the above acrylic oligomer, and 0.6 mass of urethane acrylate oligomer (product name "UN-350", manufactured by Negami Kogyo Co., Ltd.) as the second photopolymerizable polyfunctional compound part, a third photopolymerization initiator (product name “Irgacure 819”, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by BASF) 0.4 parts by mass, and an antioxidant (product name “Irga Nox 1010", manufactured by BASF) 0.5 parts by mass, a rust inhibitor (product name "BT-120", manufactured by Johoku Chemical Industry Co., Ltd.) 0.2 parts by mass, and a silane coupling agent (product name "KBM-403", Shin-Etsu Chemical Co., Ltd.) was mixed with 0.3 parts by mass to obtain an adhesive composition C1.

<Preparation of base adhesive sheet>
Next, the pressure-sensitive adhesive composition C1 was applied onto the release-treated surface of the first release liner (product name “DIAFOIL MRF”, thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. formed. Next, the release-treated surface of the second release liner (product name: "Diafoil MRE", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was laminated onto the coating film on the first release liner. rice field. Next, the coating film between the release liners was irradiated with ultraviolet rays from the second release liner side, and the coating film was photocured to form a pressure-sensitive adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light (manufactured by Toshiba) was used as a light source, the illuminance was set at 6.5 mW/cm ² , and the irradiation integrated light amount was set at 1500 mJ/cm ² . In the ultraviolet irradiation step, the photopolymerization reaction proceeds in the system containing the residual monomer and the second photopolymerizable polyfunctional compound in the coating film to form a photopolymerization polymer P1b having a photocrosslinking structure. Moreover, since the photopolymerization reaction proceeds around the photopolymerization polymer P1a, the photopolymerization polymer P1b is formed around the photopolymerization polymer P1a. The adhesive layer formed in this step contains the photopolymerization polymer P1a and the photopolymerization polymer P1b as the base polymer P1. As described above, a base PSA sheet with a double-sided release liner (first release liner/base PSA sheet (thickness: 100 μm)/second release liner) was produced.

[Example 1]
<Preparation of post-addition component solution>
First, 5.8 parts by mass of a polyfunctional acrylate monomer (product name “Viscoat #295”, trimethylolpropane triacrylate (TMPTA), manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a first photopolymerizable polyfunctional compound, and a third 0.3 parts by mass of a photopolymerization initiator (product name “Irgacure 819”, manufactured by BASF), 7 parts by mass of an ultraviolet absorber (product name “Tinosorb S”, manufactured by BASF), and 94.2 parts by mass of ethyl acetate as a solvent were mixed to prepare a post-addition component solution (anything other than the solvent in the solution is a post-addition component). Table 1 shows the composition of the post-addition component solution. In Table 1, the unit of the blending amount of each component is relative "parts by mass".

<Preparation of photocurable adhesive sheet>
Next, after peeling off the second release liner from the double-sided release liner-attached base PSA sheet, the post additive component solution was applied to a thickness of 20 μm on the exposed surface of the base PSA sheet thus exposed (coating treatment). . A bar coater RDS No. 10 manufactured by RD SPECIALTIES was used for coating. Next, it was dried in a dryer at 110° C. for 60 seconds. By coating treatment and drying treatment, the post-addition component (polyfunctional acrylate monomer as the first photopolymerizable polyfunctional compound, the third photopolymerization initiator, the ultraviolet absorber) is permeated into the base adhesive sheet, and the solvent is removed. vaporized. The base pressure-sensitive adhesive sheet changed into a photocurable pressure-sensitive adhesive sheet due to the permeation of the post-addition component. In this example, 1 part by mass of the first photopolymerizable polyfunctional compound per 100 parts by mass of the prepolymer composition and the second photopolymerizable polyfunctional compound (i.e., 100 parts by mass of the base polymer) was added to the base adhesive sheet (parts by mass of the first photopolymerizable polyfunctional compound per 100 parts by mass of the base polymer are shown in Tables 2 and 3). Next, on the photocurable adhesive sheet on the first release liner, the release-treated surface of a third release liner (product name: "DIAFOIL MRE", thickness: 75 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side. pasted together.

As described above, a photocurable pressure-sensitive adhesive sheet with a double-sided release liner (first release liner/photocurable pressure-sensitive adhesive sheet (thickness: 100 μm)/third release liner) of Example 1 was produced.

[Examples 2 to 6]
Photocurable pressure-sensitive adhesive sheets with double-sided release liner of Examples 2 to 6 were prepared in the same manner as the photocurable pressure-sensitive adhesive sheet with double-sided release liner of Example 1, except that the composition of the post-additive component solution was changed to the composition shown in Table 1. An adhesive sheet was produced.

[Examples 7 to 10]
The photocurable pressure-sensitive adhesive sheet with a double-sided release liner of Example 1 was used, except that the composition of the post-additive component solution was changed to the composition shown in Table 1, and that the coating treatment and the subsequent drying treatment were performed twice. Photocurable pressure-sensitive adhesive sheets with a double-sided release liner of Examples 7 to 10 were prepared in the same manner.

[Comparative Example 1]
First, 64.5 parts by mass of n-butyl acrylate (BA) and 6.0 parts by mass of cyclohexyl acrylate (CHA) were mixed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube. , N-vinyl-2-pyrrolidone (NVP) 9.6 parts by mass, 4-hydroxybutyl acrylate (4HBA) 14.9 parts by mass, isostearyl acrylate 5.0 parts by mass, and a thermal polymerization initiator 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a, 0.065 parts by mass of α-thioglycerol as a chain transfer agent, and 233 parts by mass of ethyl acetate as a polymerization solvent in nitrogen The mixture was reacted at 56° C. for 5 hours and then at 70° C. for 3 hours (polymerization reaction) while stirring under an atmosphere. Thus, a polymer solution containing an acrylic polymer was obtained.

Next, in the polymer solution, per 100 parts by mass of the acrylic polymer, 0.1 parts by mass of an isocyanate cross-linking agent (product name "Takenate D110N", trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals) and a polyfunctional acrylate monomer 4.7 parts by mass of dipentaerythritol hexaacrylate (DPHA), 5 parts by mass of the acrylic oligomer, the first photopolymerization initiator (product name "Irgacure 184", manufactured by BASF) 0.2 parts by mass, and a silane cup 0.3 parts by mass of a ring agent (product name “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed to obtain an adhesive composition C2.

Next, the pressure-sensitive adhesive composition C2 was applied onto the release-treated surface of the first release liner (product name “Diafoil MRF”, thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. formed. Next, the coating film on the first release liner was dried by heating at 100° C. for 3 minutes to form a pressure-sensitive adhesive layer with a thickness of 100 μm. Next, the release-treated surface of a second release liner (product name: "Diafoil MRE", thickness: 75 μm, manufactured by Mitsubishi Chemical Corporation) whose one side was release-treated was attached to the pressure-sensitive adhesive layer on the first release liner. . After that, aging treatment was performed at 25° C. for 3 days, and the cross-linking reaction of the acrylic polymer with the isocyanate cross-linking agent was allowed to proceed in the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer thus formed contains, as a base polymer P2, an acrylic polymer having a thermally crosslinked structure with an isocyanate crosslinking agent.

As described above, a pressure-sensitive adhesive sheet with a double-sided release liner (first release liner/adhesive sheet (thickness: 100 μm)/second release liner) of Comparative Example 1 was produced.

[Comparative Example 2]
<Preparation of adhesive composition>
First, 110 parts by mass of the prepolymer composition, 0.4 parts by mass of a third photopolymerization initiator (product name "Irgacure 819", manufactured by BASF), 5.8 parts by mass of the acrylic oligomer, and a urethane acrylate oligomer ( Product name "UN-350", manufactured by Neagari Kogyo Co., Ltd.) 1.1 parts by mass, antioxidant (product name "Irganox 1010", manufactured by BASF) 0.5 parts by mass, rust inhibitor (product name "BT-120" , Johoku Chemical Co., Ltd.) 0.2 parts by mass, a silane coupling agent (product name “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass, and a polyfunctional acrylate monomer (product name “Viscoat #295” , manufactured by Osaka Organic Chemical Industry Co., Ltd.) and 2 parts by mass were mixed to obtain an adhesive composition C3.

<Preparation of adhesive sheet>
Next, the pressure-sensitive adhesive composition C3 was applied onto the release-treated surface of the first release liner (product name “Diafoil MRF”, thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side to form a coating film. formed. Next, the release-treated surface of a second release liner (product name: "Diafoil MRE", thickness: 38 µm, manufactured by Mitsubishi Chemical Corporation) having a release-treated surface on one side was laminated onto the coating film on the first release liner. rice field. Next, the coating film between the release liners was irradiated with ultraviolet rays from the second release liner side, and the coating film was photocured to form a pressure-sensitive adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light (manufactured by Toshiba) was used as a light source, the illuminance was set to 5 mW/cm ² , and the irradiation integrated light amount was set to 1500 mJ/cm ² . In the ultraviolet irradiation step, a photopolymerization reaction proceeds around the photopolymerization polymer P1a in the coating film to form a photopolymerization polymer P3b having a photocrosslinking structure. The pressure-sensitive adhesive layer formed in this step contains the photopolymerization polymer P1a and the photopolymerization polymer P3b as the base polymer P3.

As described above, a pressure-sensitive adhesive sheet with a double-sided release liner (first release liner/adhesive sheet (thickness: 100 μm)/second release liner) of Comparative Example 2 was produced.

[Comparative Example 3]
A pressure-sensitive adhesive sheet with a double-sided release liner of Comparative Example 3 was prepared in the same manner as the pressure-sensitive adhesive sheet with a double-sided release liner of Comparative Example 2 except for the following. In the preparation of the pressure-sensitive adhesive composition C3, the blending amount of the polyfunctional acrylate monomer (product name “Viscoat #295”, manufactured by Osaka Organic Chemical Industry Co., Ltd.) was changed from 2 parts by weight to 0.04 parts by weight. In the ultraviolet irradiation step, a photopolymerization reaction proceeds around the photopolymerization polymer P1a in the coating film to form a photopolymerization polymer P4b having a photocrosslinking structure. The pressure-sensitive adhesive layer formed in the same process contains a photopolymerization polymer P1a and a photopolymerization polymer P4b as a base polymer P4.

As described above, a pressure-sensitive adhesive sheet with a double-sided release liner (first release liner/adhesive sheet (thickness: 100 μm)/second release liner) of Comparative Example 3 was produced.
nothing.

<Specific absorbance>
The specific absorbance at a wavelength of 405 nm was examined for the third photopolymerization initiator (product name: "Irgacure 819", manufactured by BASF) and the ultraviolet absorber (product name: "Tinosorb S", manufactured by BASF). Specifically, first, an ethyl acetate solution of a sample (third photopolymerization initiator or ultraviolet absorber) having a predetermined concentration was prepared as a sample solution. Next, the absorption spectrum of the sample solution was measured with a spectrophotometer (product name “U4100”, manufactured by Hitachi High-Technologies Corporation). In this measurement, the temperature condition was 23° C., the measurement cell length was 10 mm, and the measurement range wavelength was 300 to 500 nm. Then, in the spectrophotometer, the absorbance (vertical axis) of the measured absorption spectrum was converted to specific absorbance (the specific absorbance is the absorbance when the sample concentration is 1 mg/mL and the measurement cell length is 1 cm). . The specific absorbance E1 of the third photopolymerization initiator (product name “Irgacure 819”) at a wavelength of 405 nm was 18.2 (cm ⁻¹ ). The specific absorbance E2 of the ultraviolet absorber (product name “Tinosorb S”) at a wavelength of 405 nm was 3.4 (cm ⁻¹ ).

<Surface texture>
The surface properties (presence or absence of orange peel) of each pressure-sensitive adhesive sheet of Examples 1 to 10 and Comparative Examples 1 to 3 were examined as follows.

First, a first sample sheet (200 mm x 200 mm) was cut out from the pressure-sensitive adhesive sheet with a double-sided release liner. Next, the first sample sheet was placed between the projection screen and the light source (the projection screen was placed in a posture that spreads vertically and horizontally, and the light source is perpendicular to the screen plane of the projection screen). 800 mm apart in the direction). Specifically, the first sample sheet was placed at a position 400 mm away from the light source, with the sheet surface inclined at an angle of 45 degrees with respect to the screen surface. The light source was then turned on to illuminate the first sample sheet toward the projection screen. Next, the projected image (transmitted image) formed on the projection screen by the light emitted from the light source and transmitted through the first sample sheet was observed (specifically, the presence and degree of orange peel was examined). The surface properties of the adhesive sheet were evaluated as "good" when a uniform transmission image without unevenness in brightness was observed, and as "bad" when there was unevenness in brightness due to orange peel in the transmission image. bottom. The results are shown in Tables 2 and 3.

〈Followability over bumps〉
The level difference followability of each adhesive sheet of Examples 1 to 10 and Comparative Examples 1 to 3 was examined as follows.

First, a second sample sheet (75 mm x 45 mm) was cut out from the pressure-sensitive adhesive sheet with a double-sided release liner. Next, the third or second release liner was peeled off from the adhesive sheet of the second sample sheet, and the exposed surface of the adhesive sheet thus exposed was attached to the center of a PET film (thickness: 125 µm, 100 mm x 50 mm). . In the bonding, a roll laminator was used, the pressure between rolls was set to 0.2 MPa, and the feed rate was set to 100 mm/min (the same applies to bonding described later). Next, the first release liner is peeled off from the adhesive sheet on the PET film, and the exposed surface of the adhesive sheet thus exposed is attached to a glass plate with a printed layer (thickness 500 μm, length 100 mm×width 50 mm). , to obtain a laminate. FIG. 4 shows the positional relationship between the glass plate 41 and the adhesive sheet 42 in the laminate. A printing layer 43 (thickness: 45 μm, black ink) is formed on one side of the glass plate 41 in the thickness direction along the entire edge of the glass plate 41 . The printed layer 43 is formed within a range of 15 mm inward from each end of the glass plate 41 in the length direction D1, and is formed within a range of 5 mm inward from each end of the glass plate 41 in the width direction D2. there is The adhesive sheet 42 is attached to the center of one side of the glass plate 41 in the thickness direction, and is in contact with the printed layer 43 over the entire circumference of the edge of the sheet. That is, the printed layer 43 on the glass plate 41 is sandwiched between the glass plate 41 and the adhesive sheet 42 within a range of 2.5 mm outward from the inner edge of the same layer.

Next, the laminate was autoclaved for 30 minutes under conditions of 50°C and 0.5 MPa. After that, the vicinity of the inner edge of the printed layer in the laminate was observed. Specifically, using a digital microscope, the inside of the inner edge of the printed layer (the area where the adhesive sheet should be brought into close contact with the glass plate) was observed from the PET film side of the laminate at an observation magnification of 20. Then, with respect to the conformability of the pressure-sensitive adhesive sheet to unevenness, when no air bubbles were observed in the observation range, it was evaluated as "good", and when air bubbles were observed, it was evaluated as "bad". The results are shown in Tables 2 and 3.

<Joining reliability>
The bonding reliability of each pressure-sensitive adhesive sheet of Examples 1-10 and Comparative Examples 1-3 was examined as follows.

First, the same laminate as that used for the evaluation of the step followability was prepared. Next, the laminate was autoclaved under conditions of 50° C. and 0.5 MPa for 30 minutes. Next, the adhesive sheet in the laminate was irradiated with ultraviolet rays from the glass plate side to photocure the adhesive sheet. In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set at 300 mW/cm ² , and the irradiation integrated light amount was set at 3000 mJ/cm ² . Next, the laminate was allowed to stand under conditions of 23° C. and 50% relative humidity for 24 hours. The laminate was then stored under conditions of 85° C. and 85% relative humidity for 300 hours. After that, the adhesive sheet in the laminate was observed along the edges with a magnifying glass. Then, regarding the bonding reliability of the adhesive sheet, the case where there is substantially no peeling or foaming at the edge of the adhesive sheet is evaluated as "good", and the case where there is peeling or foaming at the edge of the adhesive sheet (i.e., "good") ”) was evaluated as “bad”. The results are shown in Tables 2 and 3.

<Adhesive force>
For each adhesive sheet in Examples 1 to 10 and Comparative Examples 1 to 3, the adhesive force F1 was measured by the following first peel test, and the adhesive force F2 was measured by the following second peel test.

[First peel test]
First, a test piece was produced for each adhesive sheet. In preparing the test piece, first, the third or second release liner was peeled off from the adhesive sheet, and a PET film (thickness: 50 μm) was attached to the exposed surface of the adhesive sheet exposed by this. Release liner/adhesive sheet/PET film) was obtained. Next, a test piece (width 10 mm×length 100 mm) was cut out from the laminated film. Next, under an environment of 23° C. and a relative humidity of 50%, the first release liner was peeled off from the adhesive sheet of the test piece, and the exposed surface of the adhesive sheet thus exposed was placed on an alkali glass plate ( A laminated body (alkali glass plate/adhesive sheet/PET film) was obtained by bonding to the air side of soda plate glass (manufactured by Matsunami Glass Industry). The air surface is the exposed surface of the alkali glass plate (the surface opposite to the surface in contact with the molten metal) when the alkali glass plate flows over the molten metal in the manufacturing process of the alkali glass plate. In the bonding, the test piece was press-bonded to the alkali glass plate by reciprocating a 2-kg roller once (the same applies to the bonding described below). Next, the laminate was autoclaved (heated and pressurized). In the autoclave treatment, the temperature was 50° C., the pressure was 0.5 MPa, and the treatment time was 15 minutes. Next, the adhesive sheet in the laminate was irradiated with ultraviolet rays from the side of the alkali glass plate (photocuring treatment). In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set to 300 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . Next, the laminate was allowed to stand in an environment of 23° C. and 50% relative humidity for 30 minutes. Next, under the environment of 23° C. and relative humidity of 50%, a peel test was carried out by peeling the test piece from the alkaline glass plate to measure the peel strength. A tensile tester (Product name: TCM-1kNB, manufactured by Minebea Co., Ltd.) was used for this measurement. In this measurement, the peel angle of the test piece to the adherend was set at 180°, the tensile speed of the test piece was set at 300 mm/min, and the peel length was set at 50 mm (measurement conditions of the peel test). The measured peel strength is shown in Tables 2 and 3 as adhesive force F1 (N/10 mm) to an alkali glass plate produced by the float method.

[Second peel test]
First, a test piece was produced for each adhesive sheet. In preparing the test piece, first, the third or second release liner was peeled off from the adhesive sheet, and a PET film (thickness: 50 μm) was attached to the exposed surface of the adhesive sheet exposed by this. Release liner/adhesive sheet/PET film) was obtained. Next, a test piece (width 10 mm×length 100 mm) was cut out from the laminated film. Next, the pressure-sensitive adhesive sheet in the test piece was irradiated with ultraviolet rays from the side of the first release liner (photocuring treatment). In the ultraviolet irradiation, a metal halide lamp was used as a light source, the illuminance was set to 300 mW/cm ² , and the irradiation integrated light amount was set to 3000 mJ/cm ² . Next, under an environment of 23° C. and a relative humidity of 50%, the first release liner was peeled off from the adhesive sheet of the test piece, and the exposed surface of the adhesive sheet thus exposed was placed on an alkali glass plate ( A laminate (alkali glass plate/adhesive sheet/PET film) was obtained. Next, the laminate was autoclaved (heated and pressurized). In the autoclave treatment, the temperature was 50° C., the pressure was 0.5 MPa, and the treatment time was 15 minutes. Next, the laminate was allowed to stand for 30 minutes in an environment of 23° C. and 50% relative humidity. Next, under the environment of 23° C. and relative humidity of 50%, a peel test was carried out by peeling the test piece from the alkaline glass plate to measure the peel strength. The measured peel strength is shown in Tables 2 and 3 as adhesive force F2 (N/10 mm) to an alkali glass plate produced by the float method. Tables 2 and 3 also show the ratio of the adhesive force F2 to the adhesive force F1.

The photocurable pressure-sensitive adhesive sheet of the present invention is used, for example, in the manufacturing process of display panels to bond elements included in the laminated structure of the panels.

S adhesive sheet (photocurable adhesive sheet)
H thickness direction L1, L2 release liner 21 member 22 cover glass 23 printed layer

Claims (6)

1. a base polymer;
   a photopolymerizable polyfunctional compound;
   and a photopolymerization initiator,
   A photocurable pressure-sensitive adhesive sheet, wherein the base polymer is a photopolymer and contains a polymer having a photocrosslinking structure.
2. The photocurable pressure-sensitive adhesive sheet according to claim 1, wherein the content of the photopolymerizable polyfunctional compound is 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the base polymer.
3. The photocurable adhesive sheet according to claim 1, further comprising an ultraviolet absorber.
4. The photocurable pressure-sensitive adhesive sheet according to claim 3, wherein the photopolymerization initiator has a specific absorbance of 10 or more at a wavelength of 405 nm, and the ultraviolet absorber has a specific absorbance of 5 or less at a wavelength of 405 nm.
5. The photocurable pressure-sensitive adhesive sheet according to claim 1, further comprising an antioxidant.
6. The photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which does not substantially contain a residue of a thermal polymerization initiator.

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