Adhesive composition, adhesive sheet, adhesive sheet with release film, laminate for image display device, image display device, and adhesive sheet for organic el display device

Abstract

A pressure-sensitive adhesive composition for adhering an optical member, the pressure-sensitive adhesive composition containing a (meth) acrylic polymer (A) and a photoinitiator (B), the photoinitiator (B) containing a photoinitiator (b1) that is a compound containing a radical-polymerizable functional group having a carbon-carbon double bond and a radical-generating group in the molecule, and the molar absorption coefficient at 405 nm is 30 (L / mol.cm) or more.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive sheet using the same, an adhesive sheet with a release film, a laminate for an image display device, an image display device, and an adhesive sheet for an organic EL display device.

[0002] This application claims priority based on Japanese Patent Application No. 2023-049998 filed in Japan on March 27, 2023, the contents of which are incorporated herein by reference. Background Art

[0003] In recent years, in order to improve the visual recognition of image display devices, the following operations have been carried out: using resins such as adhesives and bonding agents, the gaps between the image display panel of a liquid crystal display (LCD), plasma display (PDP) or electroluminescent display (ELD) and optical components such as a protective panel and touch panel components arranged on the front surface side (visual recognition side) thereof are filled, thereby suppressing the reflection of incident light and outgoing light from the displayed image at the air layer interface.

[0004] For example, Patent Document 1 discloses a method for manufacturing a laminated body for an image display device having a structure in which components constituting an image display device are laminated on at least one side of a transparent double-sided adhesive sheet. The method comprises a method in which an adhesive sheet that has been once cross-linked by ultraviolet light is affixed to the components constituting the image display device, and then the adhesive sheet is irradiated with ultraviolet light through the components constituting the image display device to cause secondary curing.

[0005] Patent Document 2 discloses a pressure-sensitive adhesive sheet containing a (meth)acrylic copolymer having an ultraviolet-crosslinkable moiety as a pressure-sensitive adhesive sheet useful for display and touch panels.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 4971529

[0009] Patent Document 2: Japanese Patent No. 6062740 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] Adhesive sheets that form a crosslinked structure upon UV irradiation often contain a photoinitiator that generates free radicals upon UV irradiation. However, in recent years, there has been a growing demand for adhesive sheets that cure efficiently with relatively low energy, specifically those that cure with energy rays at longer wavelengths (e.g., active energy rays with wavelengths longer than 380 nm), particularly visible light, to save energy and protect components.

[0012] Furthermore, in recent years, with the demand for power saving, weight reduction, and thickness reduction of image display devices, organic EL has become increasingly popular as image display panels, replacing conventional liquid crystal panels.

[0013] In image display devices such as organic EL display devices, components within the image display devices may be degraded by ultraviolet rays. To suppress degradation due to ultraviolet rays, there is a strong demand for adhesive sheets that cure with visible light.

[0014] In addition, in the case of an adhesive sheet that is adhered to an adherend such as a component of an image display device and then irradiated with light through the component to achieve secondary curing, if the sandwiched component has ultraviolet light absorptivity, there is a problem that the light required for curing the adhesive sheet cannot reach it. Therefore, the adhesive sheet used in the image display device of this structure needs to be an adhesive sheet that is cured using visible light.

[0015] Therefore, photocurable adhesive sheets using photoinitiators that absorb in the long-wavelength ultraviolet and visible regions, such as α-aminoacetophenone-based and acylphosphine oxide-based photoinitiators, have been developed. However, these cleavage-type photoinitiators generate offgassing products such as benzaldehyde as photodecomposition products, making them less environmentally friendly.

[0016] On the other hand, hydrogen-abstracting photoinitiators such as thioxanthone and anthraquinone, which do not produce photodecomposition products, have absorption in the ultraviolet and visible light regions in the long-wavelength region. However, compared with substances such as benzophenone that do not absorb in the long-wavelength region, they lack hydrogen-abstracting ability and cannot achieve sufficient curing sensitivity.

[0017] An object of the present invention is to provide an adhesive composition for bonding optical components, an adhesive sheet for bonding optical components, an adhesive sheet with a release film, and a laminate for image display devices, an image display device, and an adhesive sheet for organic EL display devices obtained using the same, which are capable of being cured by energy rays on the longer wavelength side (e.g., active energy rays with a wavelength longer than 380 nm, particularly active energy rays with a wavelength of 405 nm) and produce fewer photodecomposition products.

[0018] Solutions for solving problems

[0019] One embodiment of the present invention includes the following aspects.

[0020] [1] An adhesive composition for bonding optical members.

[0021] Containing a (meth)acrylic polymer (A) and a photoinitiator (B),

[0022] The photoinitiator (B) includes a photoinitiator (b1), which is a compound containing a radical polymerizable functional group having a carbon-carbon double bond and a radical generating group in the molecule, and has a molar absorption coefficient at 405 nm of 30 (L / mol·cm) or more.

[0023] [2] The adhesive composition according to [1], wherein the photoinitiator (b1) comprises at least one selected from the group consisting of a hydrogen abstraction photoinitiator and an intramolecular cleavage photoinitiator, wherein the hydrogen abstraction photoinitiator is a hydrogen abstraction photoinitiator having a structure in which the free radical generating group is excited by irradiation with active energy rays, undergoes a hydrogen abstraction reaction, and thereby generates free radicals; and the intramolecular cleavage photoinitiator is an intramolecular cleavage photoinitiator in which the free radical generating group is excited by irradiation with active energy rays, undergoes cleavage within the molecule, and thereby generates free radicals.

[0024] [3] The adhesive composition according to [1] or [2], wherein the photoinitiator (b1) is a hydrogen-abstraction-type photoinitiator having a (meth)acryloyl group as the radical-polymerizable functional group and having the following structure: the radical-generating group is excited by irradiation with active energy rays, undergoes a hydrogen-abstraction reaction, and thereby generates a radical structure.

[0025] [4] The adhesive composition according to any one of [1] to [3], wherein the free radical generating group in the photoinitiator (b1) comprises at least one structure selected from the group consisting of a benzoin structure, a benzil ketal structure, an acylphosphine oxide structure, an α-aminoacetophenone structure, an α-hydroxyacetophenone structure, a benzophenone structure, a thioxanthone structure, an anthraquinone structure, a phenyl glyoxylate structure, and an oxime ester structure.

[0026] [5] The adhesive composition according to any one of [1] to [4], wherein the radical-generating group in the photoinitiator (b1) has a thioxanthone structure.

[0027] [6] The adhesive composition according to any one of [1] to [5], wherein the content of the photoinitiator (B) is 0.01 parts by mass or more per 100 parts by mass of the (meth)acrylic polymer (A).

[0028] [7] The adhesive composition according to any one of [1] to [6], wherein the content of the photoinitiator (b1) in the photoinitiator (B) is 30% by mass or more relative to the total mass of the photoinitiator (B).

[0029] [8] The adhesive composition according to any one of [1] to [7], wherein the (meth)acrylic polymer (A) comprises at least one structural unit selected from the group consisting of a structural unit derived from an alkyl (meth)acrylate (m1), a structural unit derived from a hydroxyl-containing monomer (a2), and a structural unit derived from a nitrogen-containing monomer (a3), wherein the alkyl (meth)acrylate (m1) has a linear or branched alkyl group having 3 to 30 carbon atoms.

[0030] [9] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to [8].

[0031]

[10] The pressure-sensitive adhesive sheet according to [9], wherein the gel fraction (X0) is 20% or more.

[0032]

[11] The adhesive sheet according to [9] or

[10] , wherein the adhesive sheet is active energy ray-curable and has a cumulative light intensity of 2000 to 4000 mJ / cm 2 When the pressure-sensitive adhesive sheet is irradiated with active energy rays having a wavelength of 405 nm at any irradiation dose within this range, the gel fraction (X1) is 30% or more.

[0033]

[12] The adhesive sheet according to any one of [9] to

[11] , wherein the difference (X1-X0) between the gel fraction (X1) and the gel fraction (X0) is 10% or more.

[0034]

[13] The pressure-sensitive adhesive sheet according to any one of [9] to

[12] , which is used for bonding optical components.

[0035]

[14] A pressure-sensitive adhesive sheet with a release film, comprising a laminate of the pressure-sensitive adhesive sheet according to any one of [9] to

[13] and a release film.

[0036]

[15] A laminate for an image display device, comprising two optical members laminated via the pressure-sensitive adhesive sheet according to any one of [9] to

[13] .

[0037]

[16] An image display device comprising the laminate for an image display device according to

[15] .

[0038]

[17] A pressure-sensitive adhesive sheet for an organic EL display device, comprising the pressure-sensitive adhesive sheet according to any one of [9] to

[13] .

[0039] Effects of the Invention

[0040] The adhesive composition of the present invention can be cured by energy rays on the longer wavelength side (for example, energy rays with a longer wavelength than 380 nm, especially active energy rays of 405 nm), and has a small amount of photodecomposition products. Therefore, it can be suitably used in adhesive sheets used for bonding optical components, especially adhesive sheets for organic EL display devices. DETAILED DESCRIPTION

[0041] Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiment described below.

[0042] It should be noted that, in the present invention, the "film" conceptually includes sheets, films, and tapes.

[0043] In addition, when the term "panel" is used, such as an image display panel, a protective panel, etc., it includes a plate body, a sheet, and a film.

[0044] In the present invention, "x to y" (x and y are arbitrary numbers) includes "x or more and y or less" and "preferably greater than x" or "preferably less than y" unless otherwise specified.

[0045] In addition, when “x or more” (x is an arbitrary number) is expressed, it includes the meaning of “preferably greater than x” unless otherwise specified, and when “y or less” (y is an arbitrary number) is expressed, it includes the meaning of “preferably less than y” unless otherwise specified.

[0046] Furthermore, “x and / or y (x and y are arbitrary components)” means at least one of x and y, and means three types: only x, only y, or x and y.

[0047] In the present invention, “(meth)acrylic” includes acrylic and methacrylic, “(meth)acrylate” includes acrylate and methacrylate, and “(meth)acryloyl” includes acryloyl and methacryloyl.

[0048] The "(meth)acrylic polymer" refers to a copolymer having a structural unit derived from a (meth)acrylic monomer. The (meth)acrylic polymer may further have a structural unit derived from a monomer other than the (meth)acrylic monomer (for example, styrene).

[0049] <<Adhesive Composition>>

[0050] The adhesive composition for bonding optical components described in the present invention (hereinafter referred to as the "present adhesive composition") is characterized in that it contains a (meth)acrylic polymer (A) and a photoinitiator (B), and the aforementioned photoinitiator (B) includes a photoinitiator (b1), and the photoinitiator (b1) is a compound containing a free radical polymerizable functional group having a carbon-carbon double bond and a free radical generating group in the molecule, and has a molar absorption coefficient at 405 nm of 30 (L / mol·cm) or more.

[0051] Hereinafter, each component contained in this adhesive composition will be described in detail.

[0052] <(Meth)acrylic polymer (A)>

[0053] Examples of the (meth)acrylic polymer (A) contained in the present adhesive composition include, in addition to homopolymers of alkyl (meth)acrylates, copolymers obtained by polymerizing monomer components copolymerizable therewith.

[0054] Among them, the (meth)acrylic polymer preferably contains two or more copolymerization components, and at least one of the copolymerization components is an alkyl (meth)acrylate having an alkyl group with 3 to 30 carbon atoms.

[0055] More specifically, examples of the (meth)acrylic polymer (A) include copolymers formed from a (meth)acrylic acid alkyl ester having an alkyl group with 3 to 30 carbon atoms and a monomer component copolymerizable with the (meth)acrylic acid alkyl ester, which includes at least one monomer selected from the group consisting of (a1) a carboxyl group-containing monomer, (a2) a hydroxyl group-containing monomer, (a3) ​​a nitrogen-containing monomer, (a4) an epoxy group-containing monomer, (a5) a vinyl monomer, (a6) an alkyl (meth)acrylic acid ester monomer having an alkyl group with 1 or 2 carbon atoms, (a7) an alicyclic monomer, and (a8) other copolymerizable monomers.

[0056] (1) Among the above-mentioned copolymerizable monomers (a1) to (a8), the following copolymerizable monomers (a1), (a2) or (a3) ​​are particularly preferred.

[0057] (2) In addition, it is particularly preferred that the copolymerizable monomer (a1) is not contained and that any of the copolymerizable monomers (a2) or (a3) ​​is contained. By containing any of the copolymerizable monomers (a2) or (a3), it is possible to achieve both corrosion resistance when the adherend contains a corrosive component such as a metal, adhesion, and resistance to wet heat whitening. In addition, from the viewpoint of improving aggregability, it is particularly preferred to contain both the copolymerizable monomers (a2) and (a3).

[0058] (3) Furthermore, among the copolymerizable monomers (a3), those having a tertiary nitrogen atom are preferred from the viewpoint of having a sensitizing effect on the hydrogen abstraction reaction described later and, as a result, enabling efficient crosslinking.

[0059] (4) Among the above-mentioned alkyl (meth)acrylates, those containing a tertiary carbon atom in the alkyl group are preferred. By using such an alkyl (meth)acrylate, hydrogen abstraction reaction occurs more easily during light irradiation, and as a result, crosslinking is easily and efficiently formed.

[0060] The alkyl (meth)acrylate is preferably a linear or branched alkyl (meth)acrylate having an alkyl group with 3 to 30 carbon atoms, and is represented by the following formula (m1) (hereinafter also referred to as polymerizable monomer (m1)).

[0061] CH2=C(R 1 )-COO(R 2 )···Formula (m1)

[0062] (In formula (m1), R 1 represents a hydrogen atom or a methyl group, R 2 represents a linear or branched alkyl group having 3 to 30 carbon atoms.

[0063] Examples of the (meth)acrylic acid alkyl ester represented by formula (m1) include n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, eicosyl (meth)acrylate, heneicosyl (meth)acrylate, and behenyl (meth)acrylate. Branched-chain alkyl esters; branched-chain alkyl (meth)acrylates such as sec-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, isoeicosyl (meth)acrylate, butyloctyl (meth)acrylate, isomyristyl (meth)acrylate, isocetyl (meth)acrylate, hexyldecyl (meth)acrylate, isostearyl (meth)acrylate, octyldecyl (meth)acrylate, octyldodecyl (meth)acrylate, and isobehenyl (meth)acrylate. These can be used alone or in combination of two or more.

[0064] Among these, linear alkyl (meth)acrylates are preferred from the perspective of achieving flexibility. Furthermore, from the perspective of achieving a balance between adhesiveness and flexibility, alkyl (meth)acrylates having an alkyl group with 3 to 20 carbon atoms, further 5 to 18 carbon atoms, particularly 6 to 16 carbon atoms, and particularly 7 to 14 carbon atoms are preferred. Examples of these are n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, decyl (meth)acrylate, and lauryl (meth)acrylate.

[0065] Among these, branched alkyl (meth)acrylates are preferably used from the viewpoint that the hydrogen abstraction reaction described later readily occurs upon light irradiation, thereby enabling efficient formation of a cross-linked structure. Among these, branched alkyl (meth)acrylates having an alkyl group with 3 to 20 carbon atoms, further 5 to 18 carbon atoms, particularly 6 to 16 carbon atoms, and particularly 7 to 14 carbon atoms are preferred. For example, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate are preferred.

[0066] With respect to 100% by mass of all structural units constituting the (meth) acrylic acid polymer (A), the ratio of the structural units derived from the above-mentioned (meth) acrylic acid alkyl ester is preferably 5% by mass or more and 95% by mass or less, more preferably 10% by mass or more and 90% by mass or less, further preferably 15% by mass or more and 85% by mass or less, particularly preferably 20% by mass or more and 80% by mass or less. If the ratio of the structural units derived from the (meth) acrylic acid alkyl ester is above the aforementioned lower limit, there is a tendency for excellent flexibility, and there is a tendency for excellent concave-convex followability when the adherend has concave-convex. If it is below the aforementioned upper limit, there is a tendency for the effect of the copolymerizable monomers described later, adhesive strength, and excellent cohesive force to be easily obtained.

[0067] The lower limit and upper limit of the content of the structural unit derived from the aforementioned alkyl (meth)acrylate may be arbitrarily combined.

[0068] Examples of the carboxyl group-containing monomer (a1) include (meth)acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxypropylphthalic acid, 2-(meth)acryloyloxyethylmaleic acid, 2-(meth)acryloyloxypropylmaleic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, and itaconic acid. These may be used alone or in combination of two or more.

[0069] Examples of the hydroxyl group-containing monomer (a2) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, polytetramethylene glycol (meth)acrylate, and polyoxyethylene polyoxyethylene. (Meth)acrylates having an oxyalkylene structure, such as propylene glycol (meth)acrylate; (meth)acrylates containing a primary hydroxyl group, such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid; (meth)acrylates containing a secondary hydroxyl group, such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; (meth)acrylates containing a tertiary hydroxyl group, such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate; and vinyl ethers, such as 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether. These may be used alone or in combination of two or more.

[0070] The hydroxyl group-containing monomer (a2) improves the adhesive strength of the PSA sheet and suppresses whitening due to moisture and heat. In addition, when the PSA composition contains a thermal crosslinking agent described below, it serves as a reaction site for crosslinking.

[0071] Among the aforementioned hydroxyl-containing monomers (a2), preferred are hydroxyl-containing monomers having a hydroxyalkyl group having 1 to 10 carbon atoms, further 1 to 6 carbon atoms, and particularly 2 to 4 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether. Particularly preferred are (meth)acrylates containing a primary hydroxyl group, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate.

[0072] The content of the structural unit derived from the hydroxyl group-containing monomer (a2) in the (meth)acrylic polymer (A) is preferably 3 to 30% by mass, more preferably 5 to 25% by mass, and particularly preferably 7 to 20% by mass, based on the total structural units of the (meth)acrylic polymer (A), from the viewpoint of imparting adhesive strength and resistance to whitening by moist heat.

[0073] As the above-mentioned nitrogen-containing monomer (a3), for example, in addition to amino-containing monomers, amide-containing monomers, and isocyanate-containing monomers, (meth) acrylonitrile and the like can also be listed. Utilizing nitrogen-containing monomers (a3) ​​can improve the cohesive force of the adhesive sheet and can suppress wet heat whitening. These can be one or a combination of two or more. In addition, the nitrogen-containing monomer (a3) ​​has the effect of promoting the hydrogen abstraction reaction described later.

[0074] Regarding the aforementioned amino-containing monomer as the aforementioned nitrogen-containing monomer, for example, there can be listed (meth)acrylates containing primary amino groups such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; (meth)acrylates containing secondary amino groups such as tert-butylaminoethyl (meth)acrylate and tert-butylaminopropyl (meth)acrylate; (meth)acrylates containing tertiary amino groups such as ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminopropylacrylamide; and monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylacetamides, and N-vinylcaprolactam.

[0075] Examples of the amide group-containing monomer include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-n-butyl(meth)acrylamide, diacetone(meth)acrylamide, and N,N'-methylenebis(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-ethylmethacrylamide, and N,N-diallyl(meth)acrylamide; hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide; maleimide or its derivatives;

[0076] Examples of the isocyanate group-containing monomer include 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof. The isocyanate group can be protected with a blocking agent such as methyl ethyl ketone oxime, 3,5-dimethylpyrazole, 1,2,4-triazole, or diethyl malonate.

[0077] Among these, from the viewpoint of having a sensitizing effect on the hydrogen abstraction reaction described later and, as a result, being able to effectively form a cross-linked structure, those having a tertiary nitrogen atom are preferred. For example, (meth)acrylates containing a tertiary amino group, N,N-dialkyl(meth)acrylamides, N-vinylpyrrolidone, acryloylmorpholine, and the like are particularly preferred.

[0078] The content of the structural unit derived from the nitrogen-containing monomer (a3) ​​in the (meth)acrylic polymer (A) is preferably 0.1 to 15% by mass, more preferably 0.5 to 13% by mass, particularly preferably 1 to 10% by mass, and even more preferably 2 to 7% by mass, based on the total structural units of the (meth)acrylic polymer (A), from the viewpoint of imparting cohesive strength and resistance to whitening by moist heat.

[0079] Examples of the epoxy group-containing monomer (a4) include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether.

[0080] Examples of the vinyl monomer (a5) include compounds having a vinyl group in the molecule. Examples of such compounds include vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl laurate, and vinyl stearate; and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes. These may be one or a combination of two or more. These may be used alone or in combination of two or more.

[0081] Examples of the (meth)acrylic acid alkyl ester monomer (a6) having an alkyl group with 1 or 2 carbon atoms include methyl (meth)acrylate and ethyl (meth)acrylate, which may be used alone or in combination of two or more.

[0082] The content of the structural units derived from the comonomer (a6) in the (meth)acrylic polymer (A) is preferably 0.1 to 15% by mass, more preferably 0.5 to 13% by mass, particularly preferably 1 to 10% by mass, and even more preferably 2 to 7% by mass, relative to the total structural units of the (meth)acrylic polymer (A), from the viewpoint of imparting cohesive strength to the PSA sheet.

[0083] Examples of the alicyclic monomer (a7) include cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, and adamantyl (meth)acrylate. These may be used alone or in combination of two or more.

[0084] The content of the structural units derived from the comonomer (a7) in the (meth)acrylic polymer (A) is preferably 0.1 to 15% by mass, more preferably 0.5 to 13% by mass, particularly preferably 1 to 10% by mass, and even more preferably 2 to 7% by mass, relative to the total structural units of the (meth)acrylic polymer (A), from the viewpoint of imparting cohesive strength to the PSA sheet.

[0085] Examples of the other copolymerizable monomers (a8) include (meth)acrylates having an alkoxyalkylene glycol skeleton, such as methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, butoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, butoxypolypropylene glycol (meth)acrylate, methoxypolytetramethylene glycol (meth)acrylate, butoxypolytetramethylene glycol (meth)acrylate, methoxypolyoxyethylenepolyoxypropylene glycol (meth)acrylate, and butoxypolyoxyethylenepolyoxypropylene glycol (meth)acrylate; and (meth)acrylates having an alkoxyalkylene glycol skeleton, such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, phenoxypolyethylene glycol-polypropylene glycol-(meth)acrylate, and nonylphenol ethylene oxide adduct (meth)acrylate. 4-Acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof; (meth)acrylates containing heterocyclic rings such as tetrahydrofurfuryl (meth)acrylate; macromonomers, etc. These can be used alone or in combination of two or more.

[0086] The content of the structural units derived from the copolymerizable monomer (a8) in the (meth)acrylic polymer (A) is preferably from 1% by mass to 30% by mass, more preferably from 3% by mass to 20% by mass, and even more preferably from 5% by mass to 15% by mass, relative to the total structural units constituting the (meth)acrylic polymer (A). The lower and upper limits of the above content may be arbitrarily combined.

[0087] The side chains of the (meth)acrylic polymer (A) may be introduced with photoactive sites, such as polymerizable carbon-carbon double bond groups, thereby increasing the crosslinking efficiency of the adhesive composition, enabling the adhesive composition to be crosslinked in a shorter time and improving productivity.

[0088] Examples of methods for introducing polymerizable carbon-carbon double bond groups into the side chains of the (meth)acrylic polymer (A) include preparing a copolymer comprising the hydroxyl group-containing monomer (a2) and an ethylenically unsaturated monomer containing a functional group, and then subjecting a compound having a functional group capable of reacting with these functional groups and a polymerizable carbon-carbon double bond group to a condensation or addition reaction while maintaining the activity of the polymerizable carbon-carbon double bond group.

[0089] As the combination of these functional groups, there can be listed epoxy (glycidyl) and carboxyl, amino and carboxyl, amino and isocyanate, epoxy (glycidyl) and amino, hydroxyl and epoxy, hydroxyl and isocyanate, etc. Among these functional group combinations, from the ease of reaction control, the combination of hydroxyl and isocyanate is preferred. Among them, the combination of the copolymer having a hydroxyl group and the aforementioned compound having an isocyanate group is suitable.

[0090] Examples of the isocyanate compound having a polymerizable carbon-carbon double bond group include the above-mentioned 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof.

[0091] Regarding the content of the compound having a functional group capable of reacting with a functional group and a polymerizable carbon-carbon double bond group, from the viewpoint of improving adhesion and stress relaxation properties, it is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, further preferably 1 part by mass or less, and particularly preferably 0.1 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). It should be noted that the lower limit is usually 0 parts by mass. Specifically, it is preferably 0 parts by mass or more and 10 parts by mass or less, more preferably 0 parts by mass or more and 5 parts by mass or less, further preferably 0 parts by mass or more and 1 part by mass or less, and particularly preferably 0 parts by mass or more and 0.1 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0092] From the viewpoint of obtaining the present pressure-sensitive adhesive composition having high cohesive strength, the weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 400,000 or more.

[0093] From the viewpoint of handling properties and uniform stirring properties, the upper limit of the weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 1.5 million or less, more preferably 1.2 million or less, even more preferably 1.1 million or less, and particularly preferably 1 million or less. Specifically, the weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 200,000 or more and 1.5 million or less, more preferably 300,000 or more and 1.2 million or less, even more preferably 400,000 or more and 1.1 million or less, and particularly preferably 400,000 or more and 1,000,000 or less.

[0094] The lower limit and upper limit of the weight average molecular weight of the (meth)acrylic polymer (A) may be arbitrarily combined.

[0095] The weight average molecular weight of the (meth)acrylic polymer (A) is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC).

[0096] The method for producing the (meth)acrylic polymer (A) is not particularly limited, but for example, a method of polymerizing a monomer mixture of an alkyl (meth)acrylate having an alkyl group having 3 to 30 carbon atoms and, if necessary, one or more copolymerizable monomers selected from (a1) to (a8) can be used.

[0097] <Photoinitiator (B)>

[0098] The adhesive composition contains a photoinitiator (b1) as a photoinitiator (B). The photoinitiator (b1) is a compound containing a free radical polymerizable functional group having a carbon-carbon double bond and a free radical generating group in the molecule, and has a molar absorption coefficient at 405 nm of 30 (L / mol·cm) or more.

[0099] Here, the "radical-generating group" refers to a group that generates a radical capable of initiating a polymerization reaction when excited by active energy rays.

[0100] A photoinitiator is a compound that generates free radicals using active energy rays.

[0101] Photoinitiators are broadly classified into two types based on their free radical generation mechanism. More specifically, they are categorized as cleavage-type photoinitiators, where single bonds in the initiator itself are broken to generate free radicals, and hydrogen abstraction-type photoinitiators, where the excited initiator abstracts hydrogen from a hydrogen donor in the system to generate free radicals.

[0102] α-Aminoacetophenone-based and acylphosphine oxide-based photoinitiators are primarily used as photoinitiators with high sensitivity to long-wavelength light. However, these are cleavage-type photoinitiators, and therefore generate offgassing products such as benzaldehyde as photodecomposition products. Therefore, improvements are strongly desired.

[0103] In addition, hydrogen-abstracting photoinitiators such as thioxanthone and anthraquinone, which are currently known as photoinitiators that are sensitive to light in the long wavelength region, do not generate photodecomposition products. However, compared with substances such as benzophenone that do not absorb in the long wavelength region, they lack hydrogen-abstracting ability and cannot achieve sufficient curing sensitivity, thus limiting their use.

[0104] In light of this situation, the present inventors have conducted intensive studies and have consequently discovered that by using a photoinitiator (b1) which is a compound containing a radically polymerizable functional group having a carbon-carbon double bond and a radical-generating group in its molecule and having a molar absorption coefficient of 30 (L / mol·cm) or more at 405 nm, the generation of decomposition products can be suppressed and the curing reaction of the (meth)acrylic polymer (A) can be favorably performed, and curing can be performed by energy rays on the long wavelength side, for example, energy rays with a wavelength of 405 nm. This has led to the completion of the present invention.

[0105] The photoinitiator (b1) contains a free radical polymerizable functional group having a carbon-carbon double bond within the molecule. This structure allows the photoinitiator to be incorporated into the polymerized structure after the photoreaction, thereby suppressing the production of decomposition products derived from the photoinitiator. Furthermore, this is preferred from the perspective of suppressing photoinitiator exudation and improving the cohesive force of the adhesive sheet.

[0106] Examples of the radical polymerizable functional group possessed by the photoinitiator (b1) include a (meth)acryloyl group and an allyl group. Among these, a (meth)acryloyl group is preferred, and an acryloyl group is more preferred, due to its high reactivity.

[0107] The number of radical polymerizable functional groups possessed by the photoinitiator (b1) may be one or two or more, but is preferably one.

[0108] The photoinitiator (b1) has a radical-generating group in its molecule, and thus can be activated by irradiation with active energy rays to generate radicals, which serve as starting points for the curing reaction.

[0109] As free radical-generating groups, groups derived from known photoradical generators can be used. Examples include groups having structures that undergo photolysis upon irradiation with active energy rays, such as acylphosphine oxide structures, α-aminoacetophenone structures, and α-hydroxyacetophenone structures; groups having structures that undergo hydrogen abstraction reactions upon irradiation with active energy rays, such as benzophenone structures, thioxanthone structures, anthraquinone structures, and phenylglyoxylate structures, to generate free radicals; and groups having oxime ester structures. Of these, structures that undergo hydrogen abstraction reactions upon irradiation with active energy rays are preferred from the perspective of suppressing the generation of decomposition products. Groups having thioxanthone structures are particularly preferred from the perspective of adjusting the molar absorption coefficient at 405 nm, as described below.

[0110] By including a group having a hydrogen abstraction structure as a radical generating group, the photoinitiator (b1) functions as a hydrogen abstraction type photoinitiator.

[0111] Conventional hydrogen-abstraction photoinitiators having a benzophenone structure, a thioxanthone structure, an anthraquinone structure, a phenylglyoxylate structure, and the like generally have low efficiency in abstracting hydrogen from a hydrogen donor using light in the long wavelength region, making it difficult to proceed with the curing reaction of the (meth)acrylic polymer (A). However, by using a photoinitiator containing the aforementioned hydrogen-abstraction structure as a free radical-generating group and a radically polymerizable functional group having a carbon-carbon double bond within the molecule, and having a molar absorption coefficient of 30 (L / mol·cm) or greater at 405 nm, it has been unexpectedly discovered that the curing reaction of the (meth)acrylic polymer (A) proceeds well, and curing occurs using energy rays on the long wavelength side, for example, energy rays with a wavelength of 405 nm.

[0112] A hydrogen abstraction-type photoinitiator is preferred because it does not generate photodecomposition products like cleavage-type photoinitiators. Furthermore, since the (meth)acrylic polymer (A) also undergoes a hydrogen abstraction reaction, the (meth)acrylic polymer (A) is incorporated into the crosslinked structure, and thus a crosslinked structure with many crosslinking sites is easily formed. From this perspective, a hydrogen abstraction-type photoinitiator is also preferred.

[0113] A photoinitiator containing a radically polymerizable functional group having a carbon-carbon double bond in the molecule bonds to the carbon-carbon double bonds of the (meth)acrylic polymer (A) and the polyfunctional (meth)acrylate (C) during the photocuring reaction and is incorporated into the crosslinked structure. This is also preferred from this viewpoint because it can prevent the bleeding and migration of the photoinitiator.

[0114] The photoinitiator (b1) has a molar absorption coefficient of 30 (L / mol·cm) or greater at 405 nm, resulting in excellent sensitivity to long-wavelength active energy rays. Therefore, the use of photoinitiator (b1) can provide an adhesive composition that can be cured by relatively long-wavelength active energy rays (e.g., active energy rays at 405 nm, which is a longer wavelength than 380 nm). From this perspective, the molar absorption coefficient is preferably 40 (L / mol·cm) or greater, more preferably 50 (L / mol·cm) or greater, further preferably 60 (L / mol·cm) or greater, and particularly preferably 70 (L / mol·cm) or greater.

[0115] It should be noted that, from the viewpoint of internal (or deep) curing properties, the upper limit of the molar absorption coefficient is preferably 1.0×10 6 (L / mol·cm) or less, more preferably 5.0×10 5 (L / mol·cm) or less, more preferably 1.0×10 5 (L / mol·cm) or less, particularly preferably 5.0×10 4 (L / mol·cm) or less.

[0116] The lower limit and upper limit of the molar absorption coefficient can be arbitrarily combined. Specifically, the molar absorption coefficient is preferably greater than 40 (L / mol·cm) and less than 1.0×10 6 (L / mol·cm) or less, more preferably 50 (L / mol·cm) or more and 5.0×10 5 (L / mol·cm) or less, more preferably 60 (L / mol·cm) or more and 1.0×10 5 (L / mol·cm) or less, particularly preferably 70 (L / mol·cm) or more and 5.0×10 4 (L / mol·cm) or less.

[0117] The molar absorption coefficient of the photoinitiator (b1) at 405 nm can be calculated by dissolving the photoinitiator (b1) at a predetermined concentration in chloroform or the like, measuring the absorbance at 405 nm using a UV-visible spectrophotometer, and calculating the molar absorption coefficient using the following formula based on the absorbance obtained.

[0118] A = εLc (A represents absorbance, ε represents molar absorption coefficient (L / mol·cm), c represents the molar concentration of photoinitiator (b1) (mol / L), and L represents optical path length (cm))

[0119] Specific examples of the photoinitiator (b1) include 1-(meth)acryloyloxythioxanthone, 2-(meth)acryloyloxythioxanthone, 3-(meth)acryloyloxythioxanthone, 4-(meth)acryloyloxythioxanthone, 1-(2-(meth)acryloyloxyethoxy)thioxanthone, 2-(2-(meth)acryloyloxyethoxy)thioxanthone, 3-(2-(meth)acryloyloxyethoxy)thioxanthone, 4-(2-(meth)acryloyloxyethoxy)thioxanthone, 1-(3-(meth)acryloyloxypropoxy)thioxanthone, 2-(3-(meth)acryloyloxypropoxy)thioxanthone, 3-(3-(meth)acryloyloxypropoxy)thioxanthone, 4-(3-(meth)acryloyloxyethoxy)thioxanthone, oxypropoxy) thioxanthone, 1-(4-(meth)acryloyloxybutoxy) thioxanthone, 2-(4-(meth)acryloyloxybutoxy) thioxanthone, 3-(4-(meth)acryloyloxybutoxy) thioxanthone, 4-(4-(meth)acryloyloxybutoxy) thioxanthone, 2-(2-(meth)acryloyloxyethoxy)-2-oxoethyl thioxanthone-1-carboxylate, 2-(2-(meth)acryloyloxyethoxy)-2-oxoethyl thioxanthone-2-carboxylate, 2-(2-(meth)acryloyloxyethoxy)-2-oxoethyl thioxanthone-3-carboxylate, 2-(2-(meth)acryloyloxyethoxy)-2-oxoethyl thioxanthone-4-carboxylate, 2-(2-(meth)acryloyloxyethoxy)-2-oxoethyl thioxanthone-1-carboxylate 2-(3-(meth)acryloyloxypropoxy)-2-oxoethyl thioxanthone-2-carboxylate, 2-(3-(meth)acryloyloxypropoxy)-2-oxoethyl thioxanthone-3-carboxylate, 2-(3-(meth)acryloyloxypropoxy)-2-oxoethyl thioxanthone-4-carboxylate, 2-(4-(meth)acryloyloxybutoxy)-2-oxoethyl thioxanthone-1-carboxylate, 2-(4-(meth)acryloyloxybutoxy)-2-oxoethyl thioxanthone-2-carboxylate, 2-(4-(meth)acryloyloxybutoxy)-2-oxoethyl thioxanthone-3-carboxylate, 2-(3-(meth)acryloyloxypropoxy)-2-oxoethyl thioxanthone-4-carboxylate 2-Hydroxy-3-(2-(meth)acryloyloxyethoxy)propyl thioxanthone-3-carboxylate, 2-Hydroxy-3-(2-(meth)acryloyloxyethoxy)propyl thioxanthone-4-carboxylate, 2-Hydroxy-3-(3-(meth)acryloyloxypropoxy)propyl thioxanthone-1-carboxylate, 2-Hydroxy-3-(2-(meth)acryloyloxyethoxy)propyl thioxanthone-2-carboxylate, 2-Hydroxy-3-(2-(meth)acryloyloxyethoxy)propyl thioxanthone-3-carboxylate, 2-Hydroxy-3-(2-(meth)acryloyloxyethoxy)propyl thioxanthone-4-carboxylate, 2-Hydroxy-3-(3-(meth)acryloyloxypropoxy)propyl thioxanthone-2-carboxylate, 2-Hydroxy-3-(3-(meth)acryloyloxypropoxy)propyl thioxanthone-3-carboxylate,2-Hydroxy-3-(3-(meth)acryloyloxypropoxy)propyl thioxanthone-4-carboxylate, 2-Hydroxy-3-(4-(meth)acryloyloxybutoxy)propyl thioxanthone-1-carboxylate, 2-Hydroxy-3-(4-(meth)acryloyloxybutoxy)propyl thioxanthone-2-carboxylate, 2-Hydroxy-3-(4-(meth)acryloyloxybutoxy)propyl thioxanthone-3-carboxylate, 2-Hydroxy-3-(4-(meth)acryloyloxybutoxy)propyl thioxanthone-4-carboxylate, 1-(2-hydroxy-3-(meth)acryloyloxypropoxy)thioxanthone, 2-(2-hydroxy-3-(meth)acryloyloxypropoxy)thioxanthone, 3-(2-hydroxy-3-(meth)acryloyloxy 2-(meth)acryloyloxypropyl)thioxanthone, 4-(2-hydroxy-3-(meth)acryloyloxypropoxy)thioxanthone, 2-hydroxy-3-(meth)acryloyloxypropyl thioxanthone-1-carboxylate, 2-hydroxy-3-(meth)acryloyloxypropyl thioxanthone-2-carboxylate, 2-hydroxy-3-(meth)acryloyloxypropyl thioxanthone-3-carboxylate, 2-hydroxy-3-(meth)acryloyloxypropyl thioxanthone-4-carboxylate, 2-(meth)acryloyloxyethyl thioxanthone-1-carboxylate, 2-(meth)acryloyloxyethyl thioxanthone-2-carboxylate, 2-(meth)acryloyloxyethyl thioxanthone-3-carboxylate, 2-(meth)acryloyloxyethyl thioxanthone-4-carboxylate, 3-(meth)acryloyloxyethyl thioxanthone-1-carboxylate ) acryloyloxypropyl ester, 3-(meth)acryloyloxypropyl thioxanthone-2-carboxylate, 3-(meth)acryloyloxypropyl thioxanthone-3-carboxylate, 3-(meth)acryloyloxypropyl thioxanthone-4-carboxylate, 4-(meth)acryloyloxybutyl thioxanthone-1-carboxylate, 4-(meth)acryloyloxybutyl thioxanthone-2-carboxylate, 4-(meth)acryloyloxybutyl thioxanthone-3-carboxylate, 4-(meth)acryloyloxybutyl thioxanthone-4-carboxylate, 1-(3-(meth)acryloyloxy-1-oxopropoxy)thioxanthone, 2-(3-(meth)acryloyloxy-1-oxopropoxy)thioxanthone, 3-(3-(meth)acryloyloxy-1-oxopropoxy)thioxanthone , 4-(3-(meth)acryloyloxy-1-oxopropoxy)thioxanthone, 1-(4-(meth)acryloyloxy-1-oxobutoxy)thioxanthone, 2-(4-(meth)acryloyloxy-1-oxobutoxy)thioxanthone, 3-(4-(meth)acryloyloxy-1-oxobutoxy)thioxanthone, 4-(4-(meth)acryloyloxy-1-oxobutoxy)thioxanthone, 1-(5-(meth)acryloyloxy-1-oxopentyloxy)thioxanthone, 2-(5-(meth)acryloyloxy-1-oxopentyloxy)thioxanthone, 3-(5-(meth)acryloyloxy-1-oxopentyloxy)thioxanthone, 4-(5-(meth)acryloyloxy-1-oxopentyloxy)thioxanthone,1-[2-(2-(meth)acryloyloxyethoxy)-2-oxoethoxy]thioxanthone, 2-[2-(2-(meth)acryloyloxyethoxy)-2-oxoethoxy]thioxanthone, 3-[2-(2-(meth)acryloyloxyethoxy)-2-oxoethoxy]thioxanthone, 4-[2-(2-(meth)acryloyloxyethoxy)-2-oxoethoxy]thioxanthone, 1-[2-(3-(meth)acryloyloxypropoxy)-2-oxoethoxy]thioxanthone, 2-[2-(3-(meth)acryloyloxypropoxy)-2-oxoethoxy]thioxanthone, 3-[2-(3-(meth)acryloyloxypropoxy)-2 -oxyethoxy] thioxanthone, 4-[2-(3-(meth)acryloyloxypropoxy)-2-oxoethoxy] thioxanthone, 1-[2-(4-(meth)acryloyloxybutoxy)-2-oxoethoxy] thioxanthone, 2-[2-(4-(meth)acryloyloxybutoxy)-2-oxoethoxy] thioxanthone, 3-[2-(4-(meth)acryloyloxybutoxy)-2-oxoethoxy] thioxanthone, 4-[2-(4-(meth)acryloyloxybutoxy)-2-oxoethoxy] thioxanthone, 1-[2-(2-hydroxy-3-(meth)acryloyloxypropoxy)-2-oxoethoxy] thioxanthone, 2-[2-(2 -hydroxy-3-(meth)acryloyloxypropoxy)-2-oxoethoxy]thioxanthone, 3-[2-(2-hydroxy-3-(meth)acryloyloxypropoxy)-2-oxoethoxy]thioxanthone, 4-[2-(2-hydroxy-3-(meth)acryloyloxypropoxy)-2-oxoethoxy]thioxanthone, 1-[(2-(meth)acryloyloxyethoxy)carbonyloxy]thioxanthone, 2-[(2-(meth)acryloyloxyethoxy)carbonyloxy]thioxanthone, 3-[(2-(meth)acryloyloxyethoxy)carbonyloxy]thioxanthone, 4-[(2-(meth)acryloyloxyethoxy)carbonyloxy]thioxanthone, 1-[(3 -(meth)acryloyloxypropoxy)carbonyloxy]thioxanthone, 2-[(3-(meth)acryloyloxypropoxy)carbonyloxy]thioxanthone, 3-[(3-(meth)acryloyloxypropoxy)carbonyloxy]thioxanthone, 4-[(3-(meth)acryloyloxypropoxy)carbonyloxy]thioxanthone, 1-[(4-(meth)acryloyloxybutoxy)carbonyloxy]thioxanthone, 2-[(4-(meth)acryloyloxybutoxy)carbonyloxy]thioxanthone, 3-[(4-(meth)acryloyloxybutoxy)carbonyloxy]thioxanthone, 4-[(4-(meth)acryloyloxybutoxy)carbonyloxy]thioxanthone and derivatives thereof. The photoinitiator (b1) can be used alone or in combination of two or more.

[0120] In the present invention, the content of the photoinitiator (B) is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, particularly preferably 0.08 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic polymer (A). The upper limit is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. If the content of the photoinitiator (B) is at least the lower limit, poor curing tends to be prevented. If it is at most the upper limit, bleed-out of the photoinitiator (B) tends to be suppressed, and problems such as embrittlement and coloration tend to be easily suppressed.

[0121] The content of the photoinitiator (b1) in the present adhesive composition is preferably 0.05 parts by mass or more relative to 100 parts by mass of the (meth) acrylic polymer (A), more preferably 0.1 parts by mass or more, and further preferably 0.2 parts by mass or more. In addition, with respect to the upper limit, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, further preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less. If the content of the photoinitiator (b1) is above the aforementioned lower limit, there is a tendency to prevent poor curing. If it is below the aforementioned upper limit, there is a tendency to suppress the exudation of the photoinitiator (b1) and easily suppress the problems of embrittlement and coloring. In addition, when it is above the aforementioned upper limit, the residual concentration that is not completely consumed after light irradiation also becomes larger, which sometimes becomes the cause of product degradation caused by the unexpected curing reaction in an environment such as exposure to severe ultraviolet rays. The lower limit and upper limit of the content of the photoinitiator (b1) can be arbitrarily combined. Specifically, the content of the photoinitiator (b1) in the present adhesive composition is preferably 0.05 parts by mass or more and 10 parts by mass or less, more preferably 0.1 parts by mass or more and 8 parts by mass or less, and even more preferably 0.2 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0122] The adhesive composition may contain a photoinitiator (b2) other than the photoinitiator (b1) as a photoinitiator (B) as long as the effects of the present invention are not impaired. The photoinitiator (b2) is a compound that does not contain a free radical polymerizable functional group having a carbon-carbon double bond, or a compound that has a free radical generating group in the molecule and has a molar absorption coefficient of not less than 30 (L / mol·cm) at 405 nm. The photoinitiator (b2) may be either a hydrogen abstraction type photoinitiator or a cleavage type photoinitiator, and may be used alone or as a mixture of the two. In addition, one type or a combination of two or more types may be used.

[0123] Hydrogen abstraction type photoinitiators are broadly classified into intermolecular hydrogen abstraction type photoinitiators that abstract hydrogen from other molecules and intramolecular hydrogen abstraction type photoinitiators that also undergo hydrogen abstraction reactions within the same molecule.

[0124] Examples of the hydrogen abstraction type photoinitiator as the photoinitiator (b2) include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, methyl 2-benzoylbenzoate, 4-[(4-methylphenyl)thio]benzophenone, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy- Intermolecular hydrogen abstraction photoinitiators such as 4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, and 4-methacryloyloxyethoxy-4'-bromobenzophenone; and intramolecular hydrogen abstraction photoinitiators such as methyl benzoylformate, 2-(2-oxo-2-phenyl-acetoxy-ethoxy)ethyl oxyphenylacetate, and 2-(2-hydroxy-ethoxy)ethyl oxyphenylacetate.

[0125] Among these, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, etc., which contain a radically polymerizable functional group having a carbon-carbon double bond in the molecule, are preferred from the viewpoint that they are incorporated into the polymerized structure after the photoreaction, thereby suppressing the bleeding of the photoinitiator and improving the cohesive strength of the PSA sheet.

[0126] In addition, intramolecular hydrogen abstraction type photoinitiators such as methyl benzoylformate, 2-(2-oxo-2-phenyl-acetoxy-ethoxy)ethyl oxyphenylacetate, and 2-(2-hydroxy-ethoxy)ethyl oxyphenylacetate are not only hydrogen donors in the system, but can also serve as starting points for the generation of free radicals themselves, and are therefore preferred from this point of view.

[0127] Furthermore, as the photoinitiator (b2), a cleavage-type photoinitiator may be used to the extent that the photodecomposition product does not affect the quality. From the viewpoint of having high photosensitivity, a cleavage-type photoinitiator is preferred.

[0128] Examples of the cleavage-type photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)benzyl] ] phenyl}-2-methyl-propane-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-( 4-morpholinyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide, 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyl oxime), 1-(O-acetyl oxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone, 1-[4-[[4-(2-hydroxyethoxy)phenyl]thio]phenyl]-1,2-propanedione 2-(O-acetyl oxime), 1-[1-(4-benzoylphenyl)-1H-indol-3-yl]-1,2-octanedione 2-(O-acetyl oxime), and derivatives thereof.

[0129] The content of the photoinitiator (b2) in the present adhesive composition is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, further preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). The lower limit is usually 0 parts by mass. Specifically, the content of the photoinitiator (b2) in the present adhesive composition is preferably 0 parts by mass or more and 5 parts by mass or less, more preferably 0.1 parts by mass or more and 4 parts by mass or less, further preferably 0.5 parts by mass or more and 3 parts by mass or less, and particularly preferably 1 part by mass or more and 2 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0130] In the present invention, from the viewpoint of achieving the effects of the present invention, the content of the photoinitiator (b1) in the photoinitiator (B) is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, relative to the total mass of the photoinitiator (B). Furthermore, the total amount of the photoinitiator (B) is preferably the photoinitiator (b1).

[0131] <Multifunctional (meth)acrylate (C)>

[0132] From the viewpoint of promoting cross-linking reaction, this adhesive composition preferably contains multifunctional (meth)acrylate (C). Thus, for example, even with the same light exposure, this adhesive composition can quickly form a cross-linked structure. In addition, if the adhesive sheet obtained using this adhesive composition forms a cross-linked structure, it can prevent the paste from overflowing when stored or rolled into a roll, and good adhesion and cohesion can be obtained.

[0133] However, when the acrylic polymer (A) can undergo a hydrogen abstraction reaction due to the action of a photoinitiator (B) or the like, and a sufficient cross-linking structure is formed at least within the acrylic polymer (A) or between acrylic polymers (A), it is not necessarily necessary to contain a polyfunctional (meth)acrylate (C).

[0134] Examples of the polyfunctional (meth)acrylate (C) include (meth)acrylic monomers and (meth)acrylic oligomers having two or more functional groups, etc. These can be used alone or in combination of two or more.

[0135] Examples of the (meth)acrylic monomer having two or more functional groups include pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, heptanediol di(meth)acrylate, octanediol di(meth)acrylate, nonanediol di(meth)acrylate, decanediol di(meth)acrylate, undecanediol di(meth)acrylate, dodecanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, glycerol di(meth)acrylate, and neopentyl glycol di(meth)acrylate. acrylate, glyceryl glycidyl ether di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A polypropoxy di(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone modified tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tri(acryloyloxy) ethyl) isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, di(meth)acrylate of ε-caprolactone adduct of hydroxypivalic acid neopentyl glycol, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, di(trimethylolpropane) tetra(meth)acrylate, and the like.

[0136] Examples of the polyfunctional (meth)acrylic oligomer include polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, urethane (meth)acrylate oligomers, and polyether (meth)acrylate oligomers.

[0137] Among these, from the viewpoint of imparting appropriate flexibility to the cured product, (meth)acrylate monomers and oligomers having a diol structure are preferred.

[0138] From the viewpoint of being able to impart shape stability to the adhesive sheet and durability when made into a laminate for an image display device, the content of the multifunctional (meth)acrylate (C) in the present adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more relative to 100 parts by mass of the (meth)acrylic polymer (A). In addition, from the viewpoint of maintaining the flexibility of the adhesive sheet, the upper limit is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and particularly preferably 10 parts by mass or less.

[0139] The lower limit and upper limit of the content of the polyfunctional (meth)acrylate (C) may be arbitrarily combined. The content of the polyfunctional (meth)acrylate (C) in the present adhesive composition is preferably from 0.1 parts by mass to 20 parts by mass, more preferably from 0.5 parts by mass to 15 parts by mass, further preferably from 1 part by mass to 12 parts by mass, and particularly preferably from 1 part by mass to 10 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0140] Furthermore, from the viewpoint of further increasing the crosslinking density and improving long-term reliability, a thermal crosslinking agent may be used in combination with the polyfunctional (meth)acrylate (C).

[0141] Examples of the thermal crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents. Among these, isocyanate crosslinking agents are preferably used due to their excellent reactivity with the (meth)acrylic polymer (A).

[0142] <Other ingredients>

[0143] The present adhesive composition may contain various additives as needed as "other components" such as silane coupling agents, plasticizers, tackifying resins, antioxidants, light stabilizers, metal inert agents, antioxidants, hygroscopic agents, rust inhibitors, ultraviolet absorbers, inorganic particles, etc., within the range not impairing the effects of the present invention.

[0144] Furthermore, a reaction catalyst such as a tertiary amine compound, a quaternary ammonium compound, or a tin laurate compound may be appropriately contained as needed.

[0145] These can be used alone or in combination of two or more.

[0146] [Silane coupling agent]

[0147] Silane coupling agents are organosilicon compounds containing one or more reactive functional groups and one or more alkoxy groups bonded to silicon atoms in their structures. Examples of the reactive functional groups include epoxy groups, (meth)acryloyl groups, mercapto groups, hydroxyl groups, carboxyl groups, amino groups, amide groups, and isocyanate groups. Among these, epoxy groups and mercapto groups are preferred from the perspective of durability balance.

[0148] As the aforementioned alkoxy group bonded to a silicon atom, from the viewpoint of durability and storage stability, an alkoxy group having 1 to 8 carbon atoms is preferred, and a methoxy group and an ethoxy group are particularly preferred. It should be noted that the silane coupling agent may have an organic substituent other than the reactive functional group and the alkoxy group bonded to a silicon atom, such as an alkyl group, a phenyl group, etc.

[0149] Examples of the silane coupling agent used in the present invention include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, which are monomeric silane compounds containing epoxy groups; a portion of the aforementioned silane compound undergoes hydrolysis and polycondensation, or the aforementioned silane compound reacts with methyltriethoxysilane, ethyltriethoxysilane, or methyltriethoxysilane. Silane coupling agents containing epoxy groups and belonging to oligomers of silane compounds, which are formed by co-condensation of silane compounds containing alkyl groups such as trimethoxysilane and ethyltrimethoxysilane; silane coupling agents containing mercapto groups and belonging to monomers of silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethyldimethoxysilane; silane coupling agents containing mercapto groups and belonging to monomers of silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethyldimethoxysilane; hydrolysis and polycondensation of part of the above-mentioned silane compounds or the above-mentioned silane compounds with methyltriethoxysilane, ethyltriethoxysilane Silane coupling agents containing mercapto groups, which are oligomers of silane compounds and are formed by the co-condensation of silane compounds containing alkyl groups such as methyltrimethoxysilane and ethyltrimethoxysilane; silane coupling agents containing (meth)acryloyl groups such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane and 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropyl Silane coupling agents containing amino groups such as methyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; silane coupling agents containing isocyanate groups such as 3-isocyanatopropyltriethoxysilane; silane coupling agents containing vinyl groups such as vinyltrimethoxysilane and vinyltriethoxysilane.

[0150] These may be used alone or in combination of two or more.

[0151] Among these, epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents are preferably used from the viewpoint of excellent durability, and epoxy group-containing silane coupling agents are particularly preferred.

[0152] The content of the silane coupling agent in the present adhesive composition is preferably 0.005 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and particularly preferably 0.05 to 1 part by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A). When this content is above the lower limit, durability tends to be improved, while when it is below the upper limit, durability tends to be improved.

[0153] [Plasticizer]

[0154] The present PSA composition may contain a plasticizer in order to impart flexibility to the PSA sheet.

[0155] Examples of plasticizers are not limited and include, for example, those selected from the group consisting of polyisobutylene, polyisoprene, polybutadiene, amorphous polyolefins and copolymers thereof, silicones, polyacrylates, oligomeric polyurethanes, ethylene-propylene copolymers, and any combinations or mixtures thereof.

[0156] Among these, the plasticizer is preferably polyisobutylene. Examples of polyisobutylene plasticizers that can be used in this specification include those marketed under the trade name OPPANOL by BASF, and in particular those selected from the OPPANOL B series.

[0157] From the perspective of environmental protection, the volatile organic compound (VOC) value of the plasticizer used is preferably as small as possible. When measured by thermogravimetric analysis, it is preferably less than 1000 ppm, more preferably less than 800 ppm, further preferably less than 600 ppm, and most preferably less than 400 ppm.

[0158] The content of the plasticizer in the present adhesive composition is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0159] [Thickener]

[0160] The present adhesive composition may contain a tackifier in order to improve the adhesive strength of the adhesive sheet.

[0161] Examples of tackifiers include terpene resins such as polyterpenes (e.g., α-pinene resins, β-pinene resins, and limonene resins) and aromatic modified polyterpene resins (e.g., phenol-modified polyterpene resins), 2,3-dihydrobenzofuran-indene resins, and petroleum resins such as C5 hydrocarbon resins, C9 hydrocarbon resins, C5 / C9 hydrocarbon resins, and dicyclopentadiene resins; and rosins such as modified rosin, hydrogenated rosin, polymerized rosin, and rosin esters.

[0162] The content of the tackifier in the present pressure-sensitive adhesive composition is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0163] [Rust inhibitor]

[0164] The adhesive composition may contain a rust inhibitor in order to prevent corrosion when the adherend includes a corrosive portion such as metal wiring.

[0165] Examples of the rust preventive include triazoles and benzotriazoles.

[0166] The content of the rust inhibitor in the present adhesive composition is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0167] [Ultraviolet absorber]

[0168] The present adhesive composition may contain an ultraviolet absorber. By including an ultraviolet absorber, degradation of the adhesive sheet itself and the adherend due to ultraviolet rays can be suppressed.

[0169] When the present adhesive composition contains an ultraviolet absorber, it is preferable to cure the composition by light having a wavelength other than the absorption wavelength of the ultraviolet absorber in order to photocure the composition.

[0170] Examples of the ultraviolet absorber include benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, triazine ultraviolet absorbers, salicylic acid ultraviolet absorbers, and cyanoacrylate ultraviolet absorbers. These ultraviolet absorbers may be used alone or in combination of two or more.

[0171] Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfonyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfonyloxybenzophenone trihydrate, 2,2'-dihydroxy-4-methoxy Benzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfonyloxybenzophenone sodium, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, etc.

[0172] Examples of the benzotriazole-based ultraviolet absorber include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-3,5-diisopropylphenyl)phenylbenzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, and 2-(2-hydroxy-3 ,5-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-di-tert-pentylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-4-octyloxyphenyl)benzotriazole, 2,2'-methylenebis(4-isopropylphenyl-6-benzotriazolephenyl), 2,2'-p-phenylenebis(1,3-benzoxazin-4-one, 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidemethyl)-5-methylphenyl]benzotriazole, etc.

[0173] Examples of the triazine-based ultraviolet absorber include 2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-ethoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-propoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-butoxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-hexyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, and 2-(2-hydroxy-4-octyloxyphenyl)-4,6-diphenyl-1,3,5-triazine. 6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-dodecyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2-(2-hydroxy-4-benzyloxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3-5-triazine, 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3 ,5-triazine, 2-[4-[(2-hydroxy-3-dodecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-tridecyloxypropyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2-[4-[(2-hydroxy-3-(2'-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy s-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-nonyloxy-2-hydroxypropyloxy)-5-α-isopropylphenyl]-s-triazine, 2,4-bis(2,4-dimethylphenyl)-6-[2-hydroxy-4-(3-decyloxy-2-hydroxypropyloxy)-5-α-isopropylphenyl]-s-triazine, 2-(2-hydroxy-4-acryloyloxyethoxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, and the like.

[0174] Examples of the salicylic acid-based ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate.

[0175] Examples of the cyanoacrylate-based ultraviolet absorber include 2-ethylhexyl 2-cyano-3,3'-diphenylacrylate and ethyl 2-cyano-3,3'-diphenylacrylate.

[0176] Among these, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and triazine-based UV absorbers are preferred from the perspective of effectively suppressing UV degradation of the PSA sheet itself and adherends. Among these, triazine-based UV absorbers containing a triazine structure are more preferred from the perspective of excellent heat resistance.

[0177] From the perspective of improving light resistance reliability, the content of the UV absorber in the present adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1.5 parts by mass or more, particularly preferably 3 parts by mass or more, and most preferably 5 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic polymer (A). On the other hand, from the perspective of suppressing bleed-out and improving yellowing resistance, the content of the UV absorber is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less, particularly preferably 8 parts by mass or less, and most preferably 7 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0178] The method for preparing the present adhesive composition is not particularly limited. For example, the present adhesive composition can be prepared by mixing a (meth)acrylic polymer (A) and a photoinitiator (b1), and, if necessary, other components such as a photoinitiator (b2), a polyfunctional (meth)acrylate (C), and a silane coupling agent in predetermined amounts.

[0179] The pressure-sensitive adhesive composition obtained in this manner can be suitably used in a pressure-sensitive adhesive sheet, particularly a pressure-sensitive adhesive sheet for bonding optical members.

[0180] This adhesive composition can be in a slurry form. The slurry component in this case can be composed of an acrylic polymer and a monomer component. In one example, this slurry component can be formed by so-called partial polymerization, or it can be prepared by adding monomers to a polymer formed by complete polymerization or a partially polymerized polymer of the monomers constituting the (meth)acrylic polymer (A). That is, if a predetermined monomer composition is partially polymerized, a part of the monomers will polymerize to form an oligomer or a polymer, while a part of the monomers will remain, thereby forming a slurry component. In addition, in another example, a slurry can also be prepared by adding monomer components to a partially polymerized or completely polymerized polymer.

[0181] Therefore, the monomer units constituting the (meth)acrylic polymer (A) in this specification may refer to monomers existing in the form of oligomers or polymers in the components of the acrylic polymer, or monomers contained in the syrup component before polymerization.

[0182] <<Adhesive Sheet>>

[0183] The pressure-sensitive adhesive sheet for laminating an optical member of the present invention (hereinafter also referred to as "the present pressure-sensitive adhesive sheet") is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the present pressure-sensitive adhesive composition. The present pressure-sensitive adhesive sheet is particularly useful as a pressure-sensitive adhesive sheet for organic EL display devices.

[0184] The present adhesive sheet may be a single-layer sheet consisting solely of an adhesive layer formed from the present adhesive composition (hereinafter also referred to as "present adhesive layer"), or a multilayer sheet in which a plurality of present adhesive layers are laminated.

[0185] <Physical Properties of the PSA Sheet>

[0186] The present pressure-sensitive adhesive sheet may have the following physical properties.

[0187] [Gel fraction (X0)]

[0188] The gel fraction (X0) of the present adhesive sheet is preferably 20% or greater. If the gel fraction of the present adhesive sheet is above the lower limit, it is easy to fully maintain its shape. From this viewpoint, the gel fraction (X0) is more preferably 25% or greater, further preferably 30% or greater, and particularly preferably 35% or greater.

[0189] From the viewpoint of achieving flexibility, the gel fraction (X0) of the present pressure-sensitive adhesive sheet is preferably 70% or less, more preferably 60% or less, further preferably 55% or less, and particularly preferably 50% or less.

[0190] The lower and upper limits of the gel fraction (X0) may be arbitrarily combined. Specifically, the gel fraction (X0) of the present adhesive sheet is preferably 20% to 70%, more preferably 25% to 60%, further preferably 30% to 55%, and particularly preferably 35% to 50%.

[0191] The gel fraction (X0) serves as a criterion for the degree of crosslinking (degree of curing), and can be measured under the measurement conditions described in the examples below.

[0192] The present adhesive sheet is preferably active energy ray-curable. Here, "active energy ray-curable adhesive sheet" means that the adhesive sheet has the property of being curable by active energy rays, in other words, the adhesive sheet has room for curing by active energy rays.

[0193] The adhesive sheet may be formed by curing the adhesive composition to a state where it can be cured with active energy rays (hereinafter referred to as "primary cure"), or by crosslinking the adhesive composition with a thermal crosslinking agent (primary cure) and then curing with active energy rays. The adhesive sheet in the primary cured state can be cured by irradiation with active energy rays before or after being attached to the adherend (hereinafter referred to as "secondary cure").

[0194] When the PSA sheet is active energy ray-curable, "gel fraction X0" refers to the gel fraction of the PSA sheet after primary curing.

[0195] The primary curing of the present PSA sheet may be performed by heat or active energy ray. However, from the viewpoint of easily controlling the gel fraction (X0) within a predetermined range, the primary curing by active energy ray irradiation is preferred.

[0196] The active energy ray used in the primary curing is preferably an active energy ray having a wavelength longer than 380 nm, and particularly preferably an active energy ray having a wavelength longer than 400 nm.

[0197] When the adhesive sheet is cured once with active energy rays, for example, the cumulative irradiation dose at 405 nm is preferably 10 to 4000 mJ / cm 2 The active energy ray irradiation is preferably performed at a dose of 50 mJ / cm 2 Above and 3500mJ / cm 2 Less than 100 mJ / cm 2 Above and 3000mJ / cm 2 Below, particularly preferably 200 mJ / cm 2 Above and 2500mJ / cm 2 Below, more preferably 300mJ / cm 2 Above and 2000mJ / cm 2 If the irradiation dose is within the above range, it is preferred because there is a tendency for the curing degree to be adjusted while leaving room for curing.

[0198] In addition, when the active energy ray is irradiated from both sides, the active energy ray irradiation amount is the sum of the cumulative energy on one side and the cumulative energy on the other side.

[0199] [Gel fraction (X1)]

[0200] When the adhesive sheet is active energy ray curable, the cumulative light intensity is 2000 to 4000 mJ / cm 2 When the pressure-sensitive adhesive sheet is irradiated with active energy rays having a wavelength of 405 nm at any irradiation dose within this range (after secondary curing), the gel fraction (X1) is preferably 30% or greater, more preferably 40% or greater, even more preferably 50% or greater, and particularly preferably 60% or greater. Specifically, the gel fraction (X1) is preferably 30% or greater and 100% or less, more preferably 40% or greater and 90% or less, even more preferably 50% or greater and 80% or less, and particularly preferably 60% or greater and 70% or less.

[0201] When the gel fraction (X1) after the secondary curing is 30% or more, the durability of the laminate for an image display device obtained using the present pressure-sensitive adhesive sheet becomes excellent.

[0202] In addition, the difference (X1-X0) between the gel fraction (X1) after the aforementioned secondary curing and the gel fraction (X0) before irradiation with active energy rays (before secondary curing), i.e., the primary cured state, is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. Specifically, the difference (X1-X0) is preferably 10% or more and 50% or less, more preferably 15% or more and 45% or less, and even more preferably 20% or more and 40% or less. By making the difference (X1-X0) % 10 or more, it is possible to balance the adhesion of the adhesive sheet to the components of the image display device and the durability of the laminated body for the image display device after pasting at a higher level.

[0203] The gel fraction (X1) can be measured by the method described in the examples below.

[0204] [Adhesion]

[0205] When the adhesive sheet is active energy ray curable, the adhesive sheet is attached to soda lime glass and the accumulated light intensity is 2000 to 4000 mJ / cm 2 When irradiated with active energy rays having a wavelength of 405 nm at any exposure dose within this range, the adhesive strength at a peel angle of 180° and a peel rate of 60 mm / min relative to soda-lime glass is preferably 5.0 N / cm or greater, more preferably 6.0 N / cm or greater, and even more preferably 7.0 N / cm or greater. Specifically, the adhesive strength is preferably 5.0 N / cm or greater and 10.0 N / cm or less, more preferably 6.0 N / cm or greater and 9.0 N / cm or less, and even more preferably 7.0 N / cm or greater and 8.0 N / cm or less. By achieving an adhesive strength of 5.0 N / cm or greater, the durability of a laminated body for an image display device obtained using this adhesive sheet is improved.

[0206] In the measurement of the adhesive strength, the peeling mode when peeling the present adhesive sheet from the component sheet is preferably interfacial peeling.

[0207] Image display components used in image display devices are often expensive. When adhesive wear occurs during the component bonding process, reworkability is required, ensuring that the adhesive sheet can be peeled off without leaving any adhesive residue. Specifically, it is necessary to prevent the adhesive sheet from remaining on the component surface during peeling, a phenomenon known as "stripping." By adopting an interfacial peeling mode, an adhesive sheet with excellent reworkability is achieved without contaminating the product.

[0208] The peeling mode of the PSA sheet can be determined by, for example, visually observing the adherend after the adhesion test to confirm the presence of adhesive residue. More specifically, the presence of adhesive residue at a level that can be visually observed can be determined as cohesive failure.

[0209] [Chroma]

[0210] The chromaticity (b*) of the present adhesive sheet is preferably 4.0 or less, more preferably 3.0 or less, even more preferably 2.5 or less, particularly preferably 2.0 or less, even more preferably 1.5 or less, and most preferably 1.0 or less. Specifically, the chromaticity (b*) is preferably 0 or more and 4.0 or less, more preferably 0 or more and 3.0 or less, even more preferably 0.1 or more and 2.5 or less, particularly preferably 0.3 or more and 2.0 or less, even more preferably 0.5 or more and 1.5 or less, and most preferably 0.8 or more and 1.0 or less.

[0211] The adhesive sheet has transparency in visual observation, and transparency indicates that the components are uniformly compatible. By making the adhesive sheet transparent, the visual recognizability of the image display surface is not impaired, and an excellent appearance can be obtained. It should be noted that transparency in visual observation specifically refers to: the total light transmittance of the adhesive sheet measured in accordance with JIS K7361-1 (ISO-13468-1) is 50% or more, and the haze value measured in accordance with JIS K7136 (ISO-14782) is 10% or less.

[0212] [Total light transmittance, haze]

[0213] The total light transmittance of this adhesive sheet, as measured in accordance with JIS K7361-1 (ISO-13468-1), is preferably 80% or higher, more preferably 85% or higher, and even more preferably 90% or higher. Specifically, the total light transmittance is preferably 80% or higher and 100% or lower, more preferably 85% or higher and 100% or lower, and even more preferably 90% or higher and 100% or lower. When the total light transmittance of this adhesive sheet is above the aforementioned lower limit, it can be suitably used as an adhesive sheet for image display devices.

[0214] The haze of this adhesive sheet, as measured in accordance with JIS K7136 (ISO-14782), is preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. Specifically, the haze is preferably 0% or more and 1.0% or less, more preferably 0% or more and 0.8% or less, and even more preferably 0% or more and 0.5% or less. By having a haze of 1.0% or less, this adhesive sheet can be suitably used as an adhesive sheet for image display devices.

[0215] The haze can be measured using a haze meter.

[0216] In order to set the haze of the present pressure-sensitive adhesive sheet within the aforementioned range, the present pressure-sensitive adhesive sheet preferably does not contain particles such as organic particles.

[0217] <Thickness>

[0218] The thickness of the present adhesive sheet is not particularly limited. If it is 10 μm or more, the handling property is good. If it is 1000 μm or less, it can contribute to the thinning of the present adhesive sheet. From this viewpoint, the thickness of the present adhesive sheet is preferably 10 μm or more, more preferably 15 μm or more, further preferably 20 μm or more, and particularly preferably 25 μm or more. On the other hand, with regard to the upper limit, it is preferably 1000 μm or less, more preferably 500 μm or less, further preferably 400 μm or less, particularly preferably 300 μm or less, and especially preferably 250 μm or less. Specifically, the thickness of the adhesive sheet is preferably 10 μm or more and 1000 μm or less, more preferably 15 μm or more and 500 μm or less, further preferably 20 μm or more and 300 μm or less, and particularly preferably 25 μm or more and 250 μm or less.

[0219] <Method for producing the present adhesive sheet>

[0220] Next, the method for producing the present pressure-sensitive adhesive sheet will be described.

[0221] However, the following description is an example of a method for producing the present PSA sheet, and the present PSA sheet is not limited to a PSA sheet produced by this production method.

[0222] The present adhesive sheet can be produced, for example, by preparing the present adhesive composition, molding the present adhesive composition into a sheet, subjecting it to crosslinking, i.e., polymerization, to curing, and then performing appropriate processing as needed. Alternatively, the present adhesive composition can be prepared, applied to a component constituting an image display device, and cured to form the present adhesive sheet.

[0223] When preparing the adhesive composition, the aforementioned raw materials can be mixed using a propeller stirrer or a kneader (eg, a single-screw extruder, a twin-screw extruder, a planetary mixer, a twin-shaft mixer, a pressure kneader, etc.).

[0224] It should be noted that when mixing various raw materials, various additives such as silane coupling agents and antioxidants can be mixed with the resin in advance (blended) and then supplied to a stirrer or kneader. Alternatively, all materials can be melt-mixed in advance and then supplied. Alternatively, a masterbatch can be prepared by concentrating only the additives in the resin and then supplied.

[0225] As a method for forming the present adhesive composition into a sheet, known methods can be used, such as wet lamination, dry lamination, extrusion casting using a T-die, extrusion lamination, calendaring, blow molding, injection molding, liquid injection curing, etc. Among them, wet lamination, extrusion casting, and extrusion lamination are preferred for producing a sheet.

[0226] The present adhesive composition can be cured by irradiation with active energy rays. The present adhesive sheet can be produced by irradiating a molded article of the present adhesive composition, such as a sheet, with active energy rays. In addition to irradiation with active energy rays, heating can also be used to further achieve curing.

[0227] The irradiation energy, irradiation time, irradiation method, etc. of the active energy ray are not particularly limited as long as the photopolymerization initiator can be activated to polymerize the monomer components.

[0228] As the active energy ray in the above-mentioned active energy ray irradiation, for example, light such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, visible rays, X-rays, α rays, β rays, γ rays, electron beams, proton beams, neutron rays and other ionizing radiations can be listed. Among them, from the viewpoint of suppressing damage to the components constituting the image display device and easily controlling the reaction, ultraviolet rays or visible rays are suitable. In addition, from the viewpoints of curing speed, ease of obtaining an irradiation device, price, etc., curing using ultraviolet ray irradiation or visible light irradiation is also advantageous. Among them, from the viewpoint of preventing curing inhibition caused by ultraviolet absorbers, it is preferred to cure using visible rays, for example, active energy rays of 405nm.

[0229] Examples of light sources for active energy ray irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, low-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, and LEDs that emit light in the wavelength range of 150 to 450 nm.

[0230] The active energy ray irradiation dose (cumulative light dose) is preferably 10 to 6000 mJ / cm from the viewpoint of curing.2 , more preferably 50 mJ / cm 2 ~5500mJ / cm 2 , more preferably 100mJ / cm 2 ~5000mJ / cm 2 , particularly preferably 200 mJ / cm 2 ~4000mJ / cm 2 , especially preferably 300mJ / cm 2 ~3000mJ / cm 2 .

[0231] As another embodiment of the method for producing the present adhesive sheet, the adhesive composition may be dissolved in a suitable solvent and applied using various coating methods. Note that, when the adhesive composition is in a slurry form, it may be applied without using a solvent.

[0232] When using a coating method, in addition to the curing by active energy ray irradiation, the present adhesive sheet can also be obtained by thermal curing. During coating, the thickness of the present adhesive sheet can be adjusted by the coating thickness and the solid content concentration of the coating liquid.

[0233] For example, after the adhesive composition is dissolved in a solvent, it can be applied to a release film and dried, solidified by active energy ray irradiation, thereby forming this adhesive sheet. And then, the release film can be stacked as needed. In this case, it can be applied to a release film and dried, solidified by active energy ray irradiation, and a release film is stacked thereon. In addition, it can also be applied to a release film and dried, after the release film is stacked, solidified by active energy ray irradiation, thereby forming this adhesive sheet.

[0234] The solvent is not particularly limited as long as it dissolves the adhesive composition. Examples include ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl acetoacetate, and ethyl acetoacetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic solvents such as toluene and xylene; and alcohol solvents such as methanol, ethanol, and propanol. These solvents may be used alone or in combination of two or more. Of these, ethyl acetate, acetone, methyl ethyl ketone, and toluene are preferred from the perspectives of solubility, drying properties, and price, with ethyl acetate being particularly suitable.

[0235] The amount of the solvent used is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, further preferably 400 parts by mass or less, and particularly preferably 300 parts by mass or less, based on 100 parts by mass of the (meth)acrylic polymer (A), from the perspective of drying properties. On the other hand, it is preferably 1 part by mass or more, more preferably 50 parts by mass or more, further preferably 100 parts by mass or more, and particularly preferably 150 parts by mass or more.

[0236] As the coating method, for example, a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing, or bar coating can be used.

[0237] The solvent content in the dried adhesive composition is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

[0238] The drying temperature is generally 40 to 150° C., more preferably 45 to 140° C., further preferably 50 to 130° C., and particularly preferably 55 to 120° C. Within this temperature range, thermal deformation of the release film can be suppressed and the solvent can be removed efficiently and relatively stably.

[0239] The drying time is usually 1 to 30 minutes, more preferably 3 to 25 minutes, and even more preferably 5 to 20 minutes. Within the above time range, the solvent can be removed efficiently and sufficiently.

[0240] Examples of drying methods include drying with a dryer, a hot roller, and drying by blowing hot air onto the film. Among these, a dryer is preferred from the perspective of uniform and easy drying. These methods may be used alone or in combination of two or more.

[0241] <<Adhesive Sheet with Release Film>>

[0242] The present PSA sheet may be provided as a PSA sheet with a release film (PSA sheet laminate) by laminating a release film on one or both sides of the PSA layer (PSA sheet) formed from the present PSA composition.

[0243] When release films are provided on both sides of the adhesive sheet, it is preferred to form a laminate structure comprising a light release film having a relatively low release force and a heavy release film having a relatively high release force. When using an adhesive sheet with release films provided on both sides, the release film (light release film) on one side is first peeled off to expose one side of the adhesive sheet, and then the adhesive sheet is attached to a component constituting an image display device (the first component). The release film (heavy release film) on the other side is then peeled off, and another component constituting an image display device (the second component) is attached to the other side of the exposed adhesive sheet.

[0244] As the release film, a known release film can be used appropriately.

[0245] As materials for release films, for example, films such as polyester films, polyolefin films, polycarbonate films, polystyrene films, acrylic films, cellulose triacetate films, and fluororesin films, coated with a release agent such as a silicone resin and then subjected to release treatment, and release paper, etc. are suitably selected. Among these, polyester films, and more particularly polyethylene terephthalate (PET) films, particularly biaxially stretched PET films, are preferred due to their excellent transparency, mechanical strength, heat resistance, and flexibility. Release films can be used in which a release layer formed by curing a curable silicone-based release agent primarily composed of a silicone resin is provided on such substrates.

[0246] The thickness of the release film is not particularly limited, but is preferably 10 to 250 μm, more preferably 25 to 200 μm, and even more preferably 35 to 190 μm, from the viewpoint of processability and handling properties.

[0247] <Preferred Applications of the PSA Sheet>

[0248] This adhesive sheet is suitable for bonding optical components. Specifically, it is suitable for bonding components constituting displays, especially components used in display manufacturing. It is used as an adhesive sheet for bonding image display panels to image display device components such as protective panels and touch panels disposed on the front surface (visual recognition side) of the image display panel, or components constituting the aforementioned image display device components.

[0249] In addition, as components of the image display device, the same components as those described later can be used.

[0250] <<Laminated body for image display device>>

[0251] An image display device laminate (hereinafter sometimes referred to as the "present image display device laminate") in one embodiment of the present invention is a laminate having a structure in which two image display device components are laminated with the present adhesive sheet interposed therebetween. The present image display device laminate is preferably a laminate having a structure in which two image display device components are laminated with the present adhesive sheet interposed therebetween.

[0252] Among the components of the laminate for the image display device, the pressure-sensitive adhesive sheet is as described above, and the components other than the pressure-sensitive adhesive sheet will be described below.

[0253] <Image Display Device Constituent Members>

[0254] As the image display device constituent member constituting the laminate for the present image display device, for example, a flat-panel image display device constituent member and a flexible image display device constituent member can be listed. As such an image display device constituent member, for example, a flexible display such as a liquid crystal display, an organic electroluminescent (EL) display, a cover lens (cover film), a polarizing plate, a polarizer, a phase difference film, a barrier film, a viewing angle compensation film, a brightness enhancement film, a contrast improvement film, a diffusion film, a semi-transmitting reflective film, an electrode film, a transparent conductive film, a metal mesh film, a touch sensor film, etc. can be listed. Any one of these or two of the two can be used in combination. For example, a combination of a flexible display and other image display device constituent members, a combination of a cover lens and other image display device constituent members can be listed.

[0255] It should be noted that a flexible image display device component is a bendable component used in an image display device having a curved surface, and is a component that can be repeatedly bent. Particularly preferred are components that can be fixed into a curved shape with a curvature radius of 25 mm or greater, and particularly components that can withstand bending with a curvature radius of less than 25 mm, and more preferably, components that can withstand bending with a curvature radius of less than 3 mm.

[0256] In the above-mentioned structure, examples of the member constituting the image display device constituent member include a resin sheet and glass.

[0257] Examples of the material of the resin sheet include polyester resins, cycloolefin resins, cellulose triacetate resins, polymethyl methacrylate resins, polyurethanes, epoxy resins, polyimide resins, and aramid resins. These resins may be a single resin or two or more resins. Among these, a resin sheet containing as a main component at least one resin selected from the group consisting of polyester resins, cycloolefin resins, cellulose triacetate resins, polymethyl methacrylate resins, epoxy resins, polyimide resins, aramid resins, and polyurethane resins is preferred.

[0258] Here, the "main component" refers to the component that accounts for the largest weight ratio among the components constituting the components of the image display device, specifically, the component that accounts for more than 50 mass% of the resin composition (resin sheet) that forms the components of the image display device, further preferably accounts for more than 55 mass%, and particularly preferably accounts for more than 60 mass%.

[0259] <Method for Manufacturing the Laminated Body for Image Display Device>

[0260] There are no particular restrictions on the method for producing the laminate for the image display device. As described above, for example, the adhesive composition can be applied to the image display device components to form an adhesive sheet, or an adhesive sheet with a release film can be pre-formed and then attached to the image display device components.

[0261] <<Image Display Device>>

[0262] An image display device according to an example embodiment of the present invention (hereinafter sometimes referred to as the "present image display device") is an image display device incorporating an image display device laminate having a structure in which two image display device components are adhered to each other with the present adhesive sheet sandwiched therebetween. For example, the present image display device can be formed by laminating the image display device laminate having a structure in which two image display device components are adhered to each other with the present adhesive sheet sandwiched therebetween with another image display device component.

[0263] Example

[0264] Hereinafter, an example of an embodiment of the present invention will be described in detail, but the present invention is not limited to the embodiment described below.

[0265] First, the raw materials of the adhesive compositions prepared in Examples are described in detail.

[0266] <(Meth)acrylic polymer (A)>

[0267] (Meth)acrylic polymer (A-1): an acrylic copolymer (weight-average molecular weight: approximately 700,000) randomly copolymerized with 67 parts by mass of 2-ethylhexyl acrylate, 5 parts by mass of methyl acrylate, 10 parts by mass of ethyl acrylate, 4 parts by mass of 4-hydroxybutyl acrylate, and 14 parts by mass of hydroxyethyl acrylate.

[0268] <Photoinitiator (B)>

[0269] Photoinitiator (b1-1): a photoinitiator represented by the following formula 2-1, containing a radical polymerizable functional group having a carbon-carbon double bond and a thioxanthone structure as a radical generating group in the molecule (molar absorption coefficient at a wavelength of 405 nm: 1.7×10 3 L / mol·cm)

[0270]

[0271] Photoinitiator (b1-2): a photoinitiator represented by the following formula 2-2, containing a radical polymerizable functional group having a carbon-carbon double bond and a thioxanthone structure as a radical generating group in the molecule (molar absorption coefficient at a wavelength of 405 nm: 5.9×10 3 L / mol·cm)

[0272]

[0273] Photoinitiator (b2-1): 2,4-diethylthioxanthone ("Omnirad DETX" manufactured by IGM, molar absorption coefficient at a wavelength of 405 nm: 3.3 × 10 3 L / mol·cm)

[0274] Photoinitiator (b2-2): 4-methacryloyloxybenzophenone (manufactured by MCC UNITEC, molar absorption coefficient at a wavelength of 405 nm: 0 L / mol·cm)

[0275] [Example 1]

[0276] 100 parts by mass of the (meth)acrylic polymer (A-1) and 0.3 parts by mass of the photoinitiator (b1-1) were uniformly mixed to prepare an adhesive composition.

[0277] The adhesive composition was spread into a sheet on a 100 μm thick release film (PET film manufactured by Mitsubishi Chemical Corporation) subjected to a silicone release treatment so as to have a thickness of 50 μm.

[0278] Next, a 75 μm thick release film (PET film manufactured by Mitsubishi Chemical Corporation) treated with silicone release was laminated on the sheet-like PSA composition to form a laminate, thereby obtaining a PSA sheet with a release film consisting of release film / PSA sheet / release film.

[0279] Next, a high-pressure mercury lamp was used to measure the cumulative light intensity around a wavelength of 405 nm using an ultraviolet integrated light meter "UIT-250" (manufactured by Ushio Inc.) and a light receiver "UVD-C405" (manufactured by Ushio Inc.) through a polyethylene terephthalate film ("O700E100" manufactured by Mitsubishi Chemical Corporation) that intercepts UV light, so that the cumulative light intensity at a wavelength of 405 nm reached 1000 mJ / cm on both surfaces of the pressure-sensitive adhesive sheet with the release film. 2 The adhesive sheet is semi-cured by irradiating light in a manner of

[0280] The obtained release film-attached pressure-sensitive adhesive sheet has active energy ray-curable properties.

[0281] [Examples 2-3, Comparative Examples 1-2]

[0282] A PSA sheet with a release film was prepared in the same manner as in Example 1 except that the PSA composition was changed to the ratio shown in Table 1.

[0283] [Physical property measurement and evaluation]

[0284] The following various measurements and evaluations were performed on the PSA sheets produced in Examples and Comparative Examples. The evaluation results are summarized in Table 1.

[0285] <Gel Fraction>

[0286] For the adhesive sheets with release films produced in the Examples and Comparative Examples, approximately 0.1 g of the adhesive sheet was extracted from the sheet after peeling off the release film. The extracted adhesive sheet was placed in a pre-made bag of SUS mesh (#150) weighing X (g). The bag was sealed to prepare the sample, and the mass Y (g) of the sample was measured. After the sample was immersed in ethyl acetate and stored at 23°C in a dark place for 24 hours, it was removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate. The mass Z (g) of the dried sample was measured. Based on the measured masses, the gel fraction (X0) after primary curing was calculated using the following formula.

[0287] Gel fraction (%) = [(ZX) / (YX)] × 100

[0288] In addition, for the pressure-sensitive adhesive sheets with release films produced in the examples and comparative examples, a high-pressure mercury lamp was used through a polyethylene terephthalate film ("O700E100" manufactured by Mitsubishi Chemical Corporation) that intercepts UV light (the transmittance at a wavelength of 380 nm was 0.7% and the transmittance at a wavelength of 405 nm was 87%), and the integrated light intensity near a wavelength of 405 nm was measured using an ultraviolet integrated light meter "UIT-250" (manufactured by Ushio Inc.) and a light receiver "UVD-C405" (manufactured by Ushio Inc.). The integrated light intensity was 3000 mJ / cm 2 The adhesive sheet was irradiated with light in a manner of , and cured. The cured adhesive sheet was used in the same manner as the gel fraction (X0) to calculate the gel fraction (X1) after secondary curing.

[0289] <Chroma>

[0290] The release films of the adhesive sheets with release films produced in the Examples and Comparative Examples were removed, and the two exposed adhesive surfaces were sandwiched between two sheets of soda-lime glass (0.55 mm thick) to prepare adhesive samples. The chromaticity (b*) of the adhesive samples was measured using a spectrophotometer "SC-T" (Suga Test Instruments) according to JIS K7103, under D65 illuminant and a 10° field of view.

[0291] <Adhesion>

[0292] The release films on one side of the release film-attached PSA sheets produced in Examples and Comparative Examples were peeled off, and a 100 μm thick polyethylene terephthalate film (“COSMOSHINE A4300” manufactured by TOYOBO CO., LTD.) was attached as a liner film to prepare a laminate.

[0293] The laminate was cut into pieces 150 mm long and 10 mm wide. The remaining release film was then peeled off, and the exposed adhesive surface was brought into contact with soda-lime glass. The adhesive sheets were then roller-bonded by reciprocating a roller once. The resulting laminate was aged at 60°C for 30 minutes for final bonding. The laminate was then subjected to UV light interception using a high-pressure mercury lamp (with a transmittance of 0.7% at 380 nm and 87% at 405 nm) through a polyethylene terephthalate film ("O700E100" manufactured by Mitsubishi Chemical Corporation) that intercepts UV light. The cumulative light intensity near a wavelength of 405 nm was measured using an ultraviolet integrated light meter "UIT-250" (manufactured by Ushio Inc.) and a light receiver "UVD-C405" (manufactured by Ushio Inc.). The total light intensity was 3000 mJ / cm3 at the wavelength of 405 nm. 2 The adhesive sheet was cured by irradiating light in a manner of 10° C. and aged at 23° C. for 15 hours to prepare a sample for adhesive strength measurement.

[0294] When the adhesive strength measurement sample was peeled off at a peeling angle of 180° and a peeling speed of 60 mm / min under an environment of 23° C. and 40% RH, the peeling force (N / cm) to the glass was measured to determine the adhesive strength (P1).

[0295] The peeling mode when peeling the adhesive sheet produced in the example from the glass was interfacial peeling. In addition, when the peeling mode was cohesive failure, it is recorded as "(cohesive failure)" in the table.

[0296] [Table 1]

[0297]

[0298] As shown in Table 1, the adhesive sheets of Examples 1 to 3 obtained using a photoinitiator containing a radically polymerizable functional group having a carbon-carbon double bond and a radical-generating group in the molecule and having a molar absorption coefficient of 30 (L / mol·cm) or greater at 405 nm exhibited sufficient curability with respect to light having a wavelength of 405 nm and also exhibited low chromaticity (b*) values, indicating suitable results.

[0299] On the other hand, the adhesive sheet of Comparative Example 1 used a photoinitiator containing no radical polymerizable functional group having a carbon-carbon double bond, and although the molar absorption coefficient at a wavelength of 405 nm was sufficiently large, the curing properties to light at a wavelength of 405 nm were poor.

[0300] In addition, the adhesive sheet of Comparative Example 2 uses a photoinitiator that contains a free radical polymerizable functional group having a carbon-carbon double bond and a free radical generating group in the molecule, but has a molar absorption coefficient of less than 30 (L / mol·cm) at 405 nm. The molar absorption coefficient at a wavelength of 405 nm is small, and the curing properties with respect to light of a wavelength of 405 nm are poor.

[0301] Industrial applicability

[0302] The adhesive composition of the present invention can be cured by energy rays on the longer wavelength side (for example, energy rays with a longer wavelength than 380 nm, especially active energy rays of 405 nm), and has a small amount of photodecomposition products, and can be suitably used in adhesive sheets used for bonding optical components, especially adhesive sheets for organic EL display devices.

Claims

1. An adhesive composition for bonding optical components. Containing a (meth)acrylic polymer (A) and a photoinitiator (B), The photoinitiator (B) includes a photoinitiator (b1), which is a compound containing a free radical polymerizable functional group having a carbon-carbon double bond and a free radical generating group in the molecule, and has a molar absorption coefficient at 405 nm of 30 (L / mol·cm) or more.

2. The adhesive composition according to claim 1, wherein The photoinitiator (b1) comprises at least one selected from the group consisting of hydrogen abstraction type photoinitiators and intramolecular cleavage type photoinitiators, The hydrogen abstraction type photoinitiator has the following structure: the free radical generating group is excited by the irradiation of active energy rays, undergoes a hydrogen abstraction reaction, and thus generates a free radical structure. The intramolecular cleavage-type photoinitiator is an intramolecular cleavage-type photoinitiator in which the radical-generating group is excited by irradiation with active energy rays and cleaved within the molecule to generate free radicals.

3. The adhesive composition according to claim 1, wherein The photoinitiator (b1) is a hydrogen abstraction type photoinitiator in which the radical polymerizable functional group is a (meth)acryloyl group and has a structure in which the radical generating group is excited by irradiation with active energy rays to undergo a hydrogen abstraction reaction, thereby generating radicals.

4. The adhesive composition according to claim 1, wherein The free radical generating group in the photoinitiator (b1) comprises at least one structure selected from the group consisting of a benzoin structure, a benzil ketal structure, an acylphosphine oxide structure, an α-aminoacetophenone structure, an α-hydroxyacetophenone structure, a benzophenone structure, a thioxanthone structure, an anthraquinone structure, a phenyl glyoxylate structure, and an oxime ester structure.

5. The adhesive composition according to claim 1, wherein The free radical generating group in the photoinitiator (b1) has a thioxanthone structure.

6. The adhesive composition according to claim 1, wherein The content of the photoinitiator (B) is 0.01 parts by mass or more relative to 100 parts by mass of the (meth)acrylic polymer (A).

7. The adhesive composition according to claim 1, wherein The content of the photoinitiator (b1) in the photoinitiator (B) is 30% by mass or more relative to the total mass of the photoinitiator (B).

8. The adhesive composition according to claim 1, wherein The (meth)acrylic polymer (A) comprises at least one structural unit selected from the group consisting of a structural unit derived from an alkyl (meth)acrylate (m1), a structural unit derived from a hydroxyl group-containing monomer (a2), and a structural unit derived from a nitrogen-containing monomer (a3), wherein the alkyl (meth)acrylate (m1) has a linear or branched alkyl group having 3 to 30 carbon atoms. 9 . A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 . 10 . The pressure-sensitive adhesive sheet according to claim 9 , wherein the gel fraction (X0) is 20% or more. The adhesive sheet according to claim 10 , wherein The adhesive sheet has active energy ray curing properties and the cumulative light intensity is 2000 to 4000 mJ / cm 2 When the pressure-sensitive adhesive sheet is irradiated with active energy rays having a wavelength of 405 nm at any irradiation dose within this range, the gel fraction (X1) is 30% or more.

12. The adhesive sheet according to claim 11, wherein The difference (X1-X0) between the gel fraction (X1) and the gel fraction (X0) is 10% or more. The pressure-sensitive adhesive sheet according to claim 9, which is used for bonding optical components. 14 . A pressure-sensitive adhesive sheet with a release film, comprising a laminate of the pressure-sensitive adhesive sheet according to claim 9 and a release film. 15 . A laminate for an image display device, comprising a structure in which two optical members are laminated with the pressure-sensitive adhesive sheet according to claim 9 interposed therebetween. 16 . An image display device comprising the laminate for an image display device according to claim 15 . 17 . An adhesive sheet for an organic EL display device, comprising the adhesive sheet according to claim 9 .

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