Adhesive sheet, adhesive sheet with release film, laminate for image display device, image display device, and adhesive sheet for image display device component

Abstract

To provide an adhesive sheet that exhibits excellent adhesion reliability at peripheral edge portions and excellent durability after curing.SOLUTION: The problem is solved by an adhesive sheet formed from a cured product of a resin composition comprising a polymer (A) and a crosslinking agent (B), wherein the polymer (A) includes a polymer composed of a compound having a (meth)acryloyl group accounting for 50 mass% or more of the monomer components, the crosslinking agent (B) contains 50 mass% or more of a crosslinking agent having three or more functional groups, and the content of the crosslinking agent (B) in the resin composition is 10 pts.mass or less relative to 100 pts.mass of the polymer (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet with a release film, a laminate for an image display device, ... and a method for manufacturing the same. The present invention relates to a display device and an adhesive sheet for a component of an image display device. [Background technology]

[0002] In order to improve the visibility of image display devices, the gap between an image display panel such as a liquid crystal display (LCD), a plasma display (PDP), or an electroluminescence display (ELD) and a protective panel or touch panel member placed on the front side (viewing side) of the image display panel is filled with a resin such as an adhesive or glue to suppress reflection of incident light and outgoing light from the displayed image at the air layer interface.

[0003] For example, Patent Document 1 discloses a method for manufacturing a component laminate for an image display device, which has a configuration in which an image display device component is laminated on at least one side of a transparent double-sided adhesive sheet, in which an adhesive sheet that has been slightly hardened by ultraviolet light (hereinafter sometimes referred to as semi-hardened) is attached to the image display device component, and then the adhesive sheet is hardened by irradiating ultraviolet light through the image display device component.

[0004] Furthermore, Patent Document 2 discloses a pressure-sensitive adhesive sheet containing a (meth)acrylic copolymer having an ultraviolet-crosslinkable site, as a pressure-sensitive adhesive sheet useful for displays and touch panels. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4971529 [Patent Document 2] Patent No. 6062740 Summary of the Invention [Problem to be solved by the invention]

[0006] As a requirement for image display devices, there is a strong demand to enlarge the effective display area as much as possible without changing the external dimensions, that is, to narrow the frame. For this reason, there is a demand for adhesive sheets for bonding image display components that can be bonded without air bubbles, even to the peripheral area near the edge of the adhesive sheet, which in the past was located directly below the concealed area and could not be seen.

[0007] Furthermore, in recent years, there has been a demand for high design quality in image display devices, and the shape of the front surface protection panel is changing from flat to those with curved edges or corners, or to designs in which the entire display unit is curved, etc. In the case of curved members or members with curved edges or corners, air bubbles are more likely to occur around the periphery than in flat members.

[0008] The adhesive sheets of Patent Documents 1 and 2 were developed based on a laminated structure using conventional components of an image display device, and no consideration was given to the reliability of adhesion near the peripheral edge of the adhesive sheet, which would have been located directly below the concealed portion and therefore not visible in conventional cases. Furthermore, conventional flexible adhesive sheets can be too flexible and therefore have insufficient shape stability. Such adhesive sheets are unable to maintain their shape over time during storage, resulting in poor handling, or the edge surfaces can be crushed during application, causing the adhesive sheet to easily protrude from the edge. One solution to this problem is to use a pressure-sensitive adhesive sheet that is less flexible and has a certain degree of rigidity, but if the rigidity is made too high, air bubbles are more likely to form around the edges. Therefore, for image display devices with increasingly narrower picture frames, there is a demand for pressure-sensitive adhesive sheets that have an appropriate hardness and excellent bonding reliability at the peripheral edge, which is a trade-off characteristic.

[0009] Furthermore, for some applications such as touch panels, there is a need for films and sheets that are resistant to scratches during the panel production process, i.e., after the adhesive sheet is bonded to other components, and there is a need for adhesive sheets that are highly durable after curing.

[0010] Therefore, against this background, the present invention aims to provide an adhesive sheet having good bonding reliability at the peripheral edge and durability after curing, an adhesive sheet with a release film, a laminate for an image display device, an image display device, and an adhesive sheet for a component of an image display device. [Means for solving the problem]

[0011] That is, the present invention has the following aspects. [1] A pressure-sensitive adhesive sheet comprising a cured product of a resin composition containing a polymer (A) and a crosslinking agent (B), The polymer (A) contains a polymer in which 50 mass % or more of monomer components are compounds having a (meth)acryloyl group, The crosslinking agent (B) contains 50% by mass or more of a trifunctional or higher functional crosslinking agent, The pressure-sensitive adhesive sheet, wherein the content of the crosslinking agent (B) in the resin composition is 10 parts by mass or less per 100 parts by mass of the polymer (A). [2] The pressure-sensitive adhesive sheet according to [1], wherein the gel fraction of the pressure-sensitive adhesive sheet is 30% or more and 80% or less. [3] The pressure-sensitive adhesive sheet according to [1] or [2], wherein the resin composition further contains a polymerization initiator (C). [4] The pressure-sensitive adhesive sheet according to [3], wherein the content of the polymerization initiator (C) is 10 parts by mass or less per 100 parts by mass of the polymer (A). [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the stress relaxation rate (X0) calculated by the following formula (I) from the initial elastic modulus (G0'(0)) 0.1 seconds after applying a 25% strain at a temperature of 70°C to the pressure-sensitive adhesive sheet and the relaxation elastic modulus (G0'(300)) 300 seconds after applying a 25% strain at a temperature of 70°C to the pressure-sensitive adhesive sheet is 0.20 or less. Stress relaxation rate (X0) = (G0'(300) / G0'(0)) (I) [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], which has a glass transition temperature (Tg) defined as the maximum value of Tan δ obtained by dynamic viscoelasticity measurement in shear mode at a frequency of 1 Hz, of -25°C or higher. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], which is curable with active energy rays. [8] The pressure-sensitive adhesive sheet is exposed to an active energy ray having a wavelength of 365 nm with an integrated light intensity of 2000 to 4000 mJ / cm 2 [7] The pressure-sensitive adhesive sheet according to [7], wherein the pressure-sensitive adhesive sheet has a storage shear modulus (G1'(25°C)) of 150 kPa or more at a temperature of 25°C, as determined by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz when irradiated so as to obtain a value of 150 kPa or more. [9] The pressure-sensitive adhesive sheet is exposed to an active energy ray having a wavelength of 365 nm with an integrated light intensity of 2000 to 4000 mJ / cm 2 The pressure-sensitive adhesive sheet according to [7] or [8], wherein the stress relaxation modulus (X1) after curing is 0.22 or more, as calculated by the following formula (II) from the initial elastic modulus (G1'(0)) after curing 0.1 seconds after applying a 25% strain at a temperature of 70°C and the relaxation elastic modulus (G1'(300)) after curing 300 seconds after applying a 25% strain at a temperature of 70°C when irradiated so as to satisfy the following formula: Stress relaxation rate after curing (X1) = (G1'(300) / G1'(0)) (II)

[10] The pressure-sensitive adhesive sheet according to [9], wherein the difference (X1-X0) between the stress relaxation rate (X1) after curing and the stress relaxation rate (X0) is 0.01 or more.

[11] A pressure-sensitive adhesive sheet with a release film, comprising the pressure-sensitive adhesive sheet according to any one of [1] to

[10] and a release film laminated on the pressure-sensitive adhesive sheet.

[12] A laminate for an image display device comprising two image display device components and an adhesive sheet according to any one of [1] to

[10] interposed between the two image display device components, wherein one of the two image display device components is a surface protection panel and the other is a member consisting of one or a combination of two or more members selected from the group consisting of a touch sensor film, an image display panel, a color filter, a polarizing element, and a retardation film.

[13] The laminate for an image display device according to

[12] , wherein the surface protection panel has a frame-shaped concealing portion on the periphery, and the frame has a portion with a width of 3 mm or less.

[14] The laminate for an image display device according to

[12] or

[13] , wherein the surface protection panel has a curved shape.

[15] An image display device comprising the laminate for an image display device according to any one of

[12] to

[14] .

[16] A pressure-sensitive adhesive sheet for use as a component of an image display device, comprising the pressure-sensitive adhesive sheet according to any one of [1] to

[10] . [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an adhesive sheet having good bonding reliability at the peripheral edge and durability after curing, an adhesive sheet with a release film, a laminate for an image display device, an image display device, and an adhesive sheet for a component of an image display device. DETAILED DESCRIPTION OF THE INVENTION

[0013] An example of an embodiment of the present invention will be described in detail below, but the present invention is not limited to the embodiment described below. In the present invention, the term "film" conceptually encompasses sheets, films, and tapes. Furthermore, when the term "panel" is used, such as an image display panel or a protective panel, it encompasses a plate, a sheet, and a film.

[0014] In this specification, when it is written "x to y" (x and y are any numbers), unless otherwise specified, it means "greater than x and less than y", and also means "preferably greater than x" or "preferably smaller than y". Furthermore, when it is stated that the amount is "x or more" (x is any number), it also means that the amount is "preferably greater than x" unless otherwise specified, and when it is stated that the amount is "y or less" (y is any number), it also means that the amount is "preferably smaller than y" unless otherwise specified. Furthermore, "x and / or y (x and y are optional configurations)" means at least one of x and y, and can mean three possibilities: x only, y only, or x and y. In addition, in this specification, "(meth)acrylic" is a comprehensive term that includes acrylic and / or methacrylic, "(meth)acrylate" is a comprehensive term that includes acrylate and / or methacrylate, and "(meth)acryloyl" is a comprehensive term that includes acryloyl and / or methacryloyl. Furthermore, in this specification, the term "main component" refers to a component that has a significant effect on the properties of the material, and the content of the component is usually 50% by mass or more of the entire material, preferably 70% by mass or more, and particularly preferably 90% by mass or more. In the present specification, when numerical ranges are described in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples.

[0015] <<Adhesive sheet>> A pressure-sensitive adhesive sheet according to one embodiment of the present invention (hereinafter, sometimes referred to as "the pressure-sensitive adhesive sheet") comprises a cured product of a resin composition containing a polymer (A) and a crosslinking agent (B), The polymer (A) contains a polymer in which 50 mass% or more of the monomer components are compounds having an acryloyl group, The crosslinking agent (B) contains 50% by mass or more of a trifunctional or higher functional crosslinking agent, The content of the crosslinking agent (B) in the resin composition is 10 parts by mass or less based on 100 parts by mass of the polymer (A). Each component contained in the resin composition will be described in detail below.

[0016] [Polymer (A)] Examples of the polymer (A) include a polymer in which 50% by mass or more of the monomer components are compounds having a (meth)acryloyl group, such as a homopolymer of alkyl (meth)acrylate, or an acrylic polymer obtained by polymerizing an alkyl (meth)acrylate with a monomer component copolymerizable therewith. As the alkyl(meth)acrylate, for example, an alkyl(meth)acrylate (a1) having an alkyl group with 3 to 30 carbon atoms [hereinafter, sometimes referred to as "alkyl(meth)acrylate"] can be used.

[0017] The polymer (A) generally contains 50% by mass or more of an acrylic polymer, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The upper limit is not particularly limited, and may be 100% by mass.

[0018] Examples of the polymer (A) include copolymers of alkyl(meth)acrylate (a1) and at least one copolymerizable monomer selected from the group consisting of a hydroxyl group-containing monomer (a2), a nitrogen-containing monomer (a3), an epoxy group-containing monomer (a4), a vinyl monomer (a5), an alkyl(meth)acrylate monomer (a6) having an alkyl group with 1 or 2 carbon atoms, an alicyclic monomer (a7), a macromonomer (a8), and other copolymerizable monomers (a9) (hereinafter, these may be referred to as "copolymerizable monomers (a2) to (a9)"). Such a polymer (A) usually has structural units derived from the alkyl (meth)acrylate (a1), as well as structural units derived from the copolymerizable monomers (a2) to (a9) contained in the monomer component.

[0019] [Alkyl (meth)acrylate (a1)] The alkyl(meth)acrylate (a1) is a (meth)acrylate having a linear or branched alkyl group with 3 to 30 carbon atoms, and is represented by the following formula (Chemical Formula 1). CH2=C(R 1 )-COO(R 2 )...(Case 1) (In Chemical 1, R 1 represents a hydrogen atom or a methyl group, and R 2 represents a linear or branched alkyl group having 3 to 30 carbon atoms.

[0020] Examples of the alkyl(meth)acrylate represented by the formula (Chemical Formula 1) include linear alkyl(meth)acrylates such as n-propyl(meth)acrylate, i-propyl(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, icosyl(meth)acrylate, henicosyl(meth)acrylate, and behenyl(meth)acrylate; sec-butyl(meth)acrylate; Examples of the branched alkyl (meth)acrylate include isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isobornyl (meth)acrylate, isostearyl (meth)acrylate, isoicosyl (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 may be used alone or in combination of two or more.

[0021] In one embodiment, the alkyl(meth)acrylate (a1) includes a linear alkyl(meth)acrylate, which is preferable in that flexibility can be obtained. Furthermore, from the viewpoint of balancing adhesion and flexibility, preferred are straight-chain alkyl (meth)acrylates in which the alkyl group has 3 or more carbon atoms, preferably 5 or more, and particularly 7 or more, and 20 or less, more preferably 18 or less, particularly 16 or less, and especially 14 or less, and for example, 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 are preferred.

[0022] In one embodiment, the alkyl(meth)acrylate (a1) includes a branched alkyl(meth)acrylate, i.e., an alkyl(meth)acrylate containing a tertiary carbon atom in the alkyl group. When the alkyl(meth)acrylate includes a branched alkyl(meth)acrylate, a hydrogen abstraction reaction (described later) easily occurs upon irradiation with active energy rays, which is preferable in that a crosslinked structure can be efficiently formed. In the present embodiment, among branched alkyl (meth)acrylates, 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, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, and isobornyl (meth)acrylate are preferred, with 2-ethylhexyl (meth)acrylate and isobornyl (meth)acrylate being more preferred, and 2-ethylhexyl (meth)acrylate being particularly preferred.

[0023] The proportion of the structural units derived from the alkyl (meth)acrylate (a1) relative to the polymer (A) is usually 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, and particularly preferably 20% by mass or more, and is usually 95% by mass or less, preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less. When the proportion of the structural units derived from the alkyl (meth)acrylate (a1) is at least the lower limit, the polymer tends to have excellent flexibility and excellent conformability to unevenness when the adherend has unevenness. When the proportion is at most the upper limit, the effects of the copolymerizable monomers (a2) to (a9), described below, are easily obtained, and the polymer tends to have excellent adhesive strength and cohesive strength.

[0024] In one embodiment, the polymer (A) contains structural units derived from a hydroxyl group-containing monomer (a2) and / or a nitrogen-containing monomer (a3). When the polymer (A) contains structural units derived from a hydroxyl group-containing monomer (a2) and / or a nitrogen-containing monomer (a3), it is possible to provide corrosion resistance, adhesiveness, and resistance to wet heat whitening when the adherend contains a corrosive component such as a metal, which is preferable. That is, in this embodiment, the polymer (A) contains, as a monomer component, a hydroxyl group-containing monomer (a2) and / or a nitrogen-containing monomer (a3).

[0025] [Hydroxyl group-containing monomer (a2)] 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 hydroxy (meth)acrylates such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; diethylene glycol (meth)acrylate; polyethylene glycol (meth)acrylate; polypropylene glycol (meth)acrylate; polytetramethylene glycol (meth)acrylate; polyoxyethylene poly(meth)acrylate; Examples of the hydroxyl group-containing (meth)acrylate include (meth)acrylates having an oxyalkylene structure such as propylene glycol (meth)acrylate, primary hydroxyl group-containing (meth)acrylates such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, secondary hydroxyl group-containing (meth)acrylates such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate, tertiary hydroxyl group-containing (meth)acrylates 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. When the polymer (A) contains a structural unit derived from the hydroxyl group-containing monomer (a2), the adhesive strength of the pressure-sensitive adhesive sheet is improved and whitening under heat and humidity tends to be suppressed. Furthermore, when the resin composition contains a thermal crosslinking agent described later, the structural unit serves as a crosslinking reaction site.

[0026] The number of carbon atoms in the hydroxyalkyl group contained in the hydroxyl group-containing monomer (a2) is preferably 1 or more, more preferably 2 or more, and is preferably 10 or less, even more preferably 6 or less, and particularly preferably 4 or less. For example, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, etc. are preferred, and primary hydroxyl group-containing (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred.

[0027] When the polymer (A) has a structural unit derived from a hydroxyl group-containing monomer (a2), the content thereof is, from the viewpoint of imparting adhesive strength and resistance to wet heat whitening, usually 3% by mass or more, preferably 5% by mass or more, particularly preferably 25% by mass, and usually 30% by mass or less, preferably 25% by mass or less, particularly preferably 20% by mass or less, based on the polymer (A).

[0028] [Nitrogen-containing monomer (a3)] Examples of the nitrogen-containing monomer (a3) ​​include amino group-containing monomers, amide group-containing monomers, isocyanate group-containing monomers, and (meth)acrylonitrile. These may be used alone or in combination of two or more. When the polymer (A) contains a structural unit derived from the nitrogen-containing monomer (a3), it is preferable in that the cohesive strength of the pressure-sensitive adhesive sheet is improved and wet heat whitening can be suppressed. Furthermore, when a hydrogen abstraction polymerization initiator described below is used, the structural unit derived from the nitrogen-containing monomer (a3) ​​has the effect of accelerating the hydrogen abstraction reaction.

[0029] Examples of the amino group-containing monomer include primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; secondary amino group-containing (meth)acrylates such as t-butylaminoethyl (meth)acrylate and t-butylaminopropyl (meth)acrylate; tertiary amino group-containing (meth)acrylates 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.

[0030] 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, Nn-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-ethylmethylacrylamide, 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 a derivative thereof. Among these, (meth)acrylamide is preferred.

[0031] Examples of the isocyanate group-containing monomer include 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof, etc. The isocyanate group may be protected with a blocking agent such as methyl ethyl ketone oxime, 3,5-dimethylpyrazole, 1,2,4-triazole, or diethyl malonate.

[0032] Among these, those having a tertiary nitrogen atom are preferred, as they have a sensitizing effect on the hydrogen abstraction reaction by the hydrogen abstraction polymerization initiator described below, and as a result, can efficiently form a crosslinked structure. Tertiary amino group-containing (meth)acrylates, N,N-dialkyl(meth)acrylamides, N-vinylpyrrolidone, acryloylmorpholine, and the like are particularly preferred.

[0033] When the polymer (A) has a structural unit derived from the nitrogen-containing monomer (a3), the content thereof is, from the viewpoint of imparting cohesive strength and resistance to wet heat whitening, usually 0.1% by mass or more, preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and especially preferably 2% by mass or more, relative to the polymer (A), and is usually 25% by mass or less, preferably 20% by mass or less, particularly preferably 18% by mass or less, and especially preferably 15% by mass or less.

[0034] [Epoxy group-containing monomer (a4)] 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, which may be used alone or in combination of two or more.

[0035] When the polymer (A) has a structural unit derived from the epoxy group-containing monomer (a4), the content thereof is usually 0.1% by mass or more, preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more, relative to the polymer (A), and is usually 15% by mass or less, preferably 13% by mass or less, more preferably 10% by mass or less, and particularly preferably 6% by mass or less.

[0036] [Vinyl monomer (a5)] 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, as well as aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes. These may be used alone or in combination of two or more.

[0037] When the polymer (A) has a constituent moiety derived from the vinyl monomer (a5), the content thereof, from the viewpoint of imparting cohesive strength to the pressure-sensitive adhesive sheet, is usually 1% by mass or more, preferably 5% by mass or more, more preferably 8% by mass or more, and particularly preferably 10% by mass or more, relative to the polymer (A), and is usually 40% by mass or less, preferably 35% by mass or less, more preferably 30% by mass or less, and particularly preferably 25% by mass or less.

[0038] [Alkyl (meth)acrylate monomer (a6) having an alkyl group with 1 or 2 carbon atoms] Examples of the alkyl(meth)acrylate monomer (a6) in which the alkyl group has 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.

[0039] When the polymer (A) has a structural unit derived from an alkyl (meth)acrylate monomer (a6) in which the alkyl group has 1 or 2 carbon atoms, the content thereof is, from the viewpoint of imparting cohesive strength to the pressure-sensitive adhesive sheet, usually 1% by mass or more, preferably 5% by mass or more, particularly preferably 10% by mass or more, and especially preferably 15% by mass or more, relative to the polymer (A), and is usually 60% by mass or less, preferably 55% by mass or less, particularly preferably 50% by mass or less, and especially preferably 45% by mass or less.

[0040] [Alicyclic monomer (a7)] 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, t-butylcyclohexyl (meth)acrylate, adamantyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0041] When the polymer (A) has a structural unit derived from an alicyclic monomer (a7), the content thereof, from the viewpoint of imparting cohesive strength to the pressure-sensitive adhesive sheet, is generally 0.1% by mass or more, preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and especially preferably 2% by mass or more, relative to the polymer (A), and is generally 15% by mass or less, preferably 13% by mass or less, particularly preferably 10% by mass or less, and especially preferably 7% by mass or less.

[0042] [Macromonomer (a8)] The macromonomer (a8) is a monomer that, when polymerized into the polymer (A), can easily increase the number of carbon atoms in the side chain of the polymer (A), for example, to 20 or more. By using the macromonomer (a8) as a monomer component, the polymer (A) can be made into a graft copolymer having structural units (segments) derived from the macromonomer (a8). Furthermore, by changing the blending ratio of the macromonomer (a8) to other monomers, the properties of the main chain and side chains of the graft copolymer can be changed.

[0043] The macromonomer (a8) has a radically polymerizable functional group or a functional group such as a hydroxy group, an isocyanate group, an epoxy group, a carboxy group, an amino group, an amide group, a thiol group, etc. The macromonomer (a8) may have these groups alone or in combination of two or more kinds. Among these, the macromonomer (a8) preferably has a radically polymerizable functional group copolymerizable with other monomers, and may contain one or more radically polymerizable functional groups, but is particularly preferably one radically polymerizable functional group. Furthermore, when the macromonomer (a8) has a functional group, it may contain one or more functional groups, but it is particularly preferred that it contains one functional group.

[0044] The macromonomer (a8) preferably has a skeleton component composed of a polymer or a vinyl polymer. Examples of the backbone component of the macromonomer (a8) include the alkyl(meth)acrylate (a1), the vinyl monomer (a5), the alkyl(meth)acrylate monomer (a6) having an alkyl group with 1 or 2 carbon atoms, and the alicyclic monomer (a7). These may be used alone or in combination of two or more. Among these, it is preferable to use alkyl (meth)acrylates in which the alkyl group has 1 to 8 carbon atoms, alicyclic monomers, and aromatic monomers such as styrene as the backbone component, as this allows for the production of a pressure-sensitive adhesive sheet with excellent cohesive strength. On the other hand, the use of an alkyl(meth)acrylate having 9 to 30 carbon atoms is preferred in that it allows for the production of a pressure-sensitive adhesive sheet with excellent flexibility.

[0045] The number average molecular weight of the macromonomer (a8) is usually 1,000 or more, preferably 1,500 or more, more preferably 2,000 or more, and usually 40,000 or less, preferably 20,000 or less, more preferably 15,000 or less. The number average molecular weight of the macromonomer (a8) is a value calculated as a standard polystyrene as measured by gel permeation chromatography (GPC).

[0046] As the macromonomer (a8), a generally produced one (for example, a macromonomer manufactured by Toagosei Co., Ltd.) can be used as appropriate.

[0047] When polymer (A) has a structural unit derived from macromonomer (a8), its content relative to polymer (A) is usually 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less, more preferably 18% by mass or less. If it is above the lower limit, the phase separation force between the segment containing the structural unit derived from macromonomer (a8) and the segment formed by the other structural units becomes stronger, and the cohesive strength of the pressure-sensitive adhesive sheet tends to be better. If it is below the upper limit, the phase-separated structure tends to collapse easily during lamination, and the unevenness-following ability tends to be better.

[0048] [Other copolymerizable monomers (a9)] Examples of the other copolymerizable monomers (a9) 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, methoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate, and butoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, and phenoxypolyethylene glycol-polypropylene glycol-(meth)acrylate; Aromatic (meth)acrylates such as 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-methacryloyloxybenzophenone, 4-methacryloyloxybenzophenone, Examples include (meth)acrylates having a benzophenone structure such as thacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof, heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, and macromonomers. These may be used alone or in combination of two or more.

[0049] When the polymer (A) has a structural unit derived from another copolymerizable monomer (a9), the content thereof is usually 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, relative to the polymer (A), and is usually 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.

[0050] The method for producing the polymer (A) is not particularly limited, and may be, for example, by polymerizing a monomer component containing an alkyl(meth)acrylate (a1) and, if necessary, at least one selected from the group consisting of copolymerizable monomers (a2) to (a9).

[0051] Examples of the polymerization method include conventionally known methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. Among these, solution polymerization is preferred in that it allows safe and stable production of an acrylic polymer with any monomer composition. Thus, the polymer (A) can be obtained.

[0052] The polymer (A) may have a photoactive moiety, such as a polymerizable carbon-carbon double bond group, introduced into its side chain, which can enhance the crosslinking efficiency of the resin composition and crosslink the resin composition in a shorter time, thereby increasing productivity.

[0053] Examples of a method for introducing a polymerizable carbon-carbon double bond group into the side chain of the polymer (A) include a method in which a copolymer containing a functional group-containing ethylenically unsaturated monomer such as the above-mentioned hydroxyl group-containing monomer (a2), nitrogen-containing monomer (a3), or epoxy group-containing monomer (a4) is prepared, and then a compound having a polymerizable carbon-carbon double bond group and a functional group reactive with the functional group is subjected to a condensation or addition reaction while maintaining the activity of the polymerizable carbon-carbon double bond group.

[0054] Examples of combinations of these functional groups include an epoxy group (glycidyl group) and a carboxy group, an amino group and a carboxy group, an amino group and an isocyanate group, an epoxy group (glycidyl group) and an amino group, a hydroxyl group and an epoxy group, and a hydroxyl group and an isocyanate group. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferred because of the ease of reaction control. Among these, a combination in which the copolymer has a hydroxyl group and the compound has an isocyanate group is preferred.

[0055] 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.

[0056] From the viewpoint of improving adhesiveness and stress relaxation properties, the content of the compound having a functional group reactive with the functional group and a polymerizable carbon-carbon double bond group is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 1 part by mass or less, and particularly preferably 0.1 parts by mass or less, per 100 parts by mass of polymer (A). The lower limit is usually 0 part by mass.

[0057] The weight average molecular weight (Mw) of the polymer (A) is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 400,000 or more, from the viewpoint of obtaining a resin composition with high cohesive strength. Furthermore, from the viewpoint of ease of handling and uniform stirring, the upper limit of the weight average molecular weight (Mw) of the 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. The lower limit and the upper limit of the weight average molecular weight of the polymer (A) can be arbitrarily combined. The weight average molecular weight of the polymer (A) is a value measured by gel permeation chromatography (GPC) and converted into standard polystyrene.

[0058] [Crosslinking agent (B)] The resin composition contains a crosslinking agent (B) from the viewpoint of promoting the crosslinking reaction. This allows the resin composition to efficiently form a crosslinked structure. Furthermore, when a crosslinked structure is formed in a pressure-sensitive adhesive sheet using the resin composition, a pressure-sensitive adhesive sheet with improved shape stability can be obtained, and storage and handling properties can be improved, and protrusion of the pressure-sensitive adhesive sheet from the edges during lamination can be suppressed. Furthermore, the pressure-sensitive adhesive sheet can obtain good adhesion and cohesion due to the formation of a crosslinked structure.

[0059] From the viewpoint of obtaining a pressure-sensitive adhesive sheet having good durability after curing, the crosslinking agent (B) contains a trifunctional or higher crosslinking agent in an amount of 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The upper limit is not particularly limited, and may be 100% by mass. When the crosslinking agent (B) contains a trifunctional or higher crosslinking agent at a concentration above the lower limit, the polymers (A) are more likely to be strongly crosslinked together during curing, resulting in an adhesive sheet that is highly durable and scratch-resistant after curing.

[0060] The tri- or higher functional crosslinking agent may be tetra- or higher functional, for example, penta- to dodeca-functional. The tri- or higher functional crosslinking agent may contain two or more different types of functional groups. Here, an "N-functional crosslinking agent" refers to a compound having N functional groups in one molecule that can polymerize, bond, or crosslink with other molecules.

[0061] Examples of the crosslinking agent (B) include acrylic crosslinking agents, isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents. In one embodiment, the crosslinking agent (B) includes an isocyanate-based crosslinking agent. When the crosslinking agent (B) includes an isocyanate-based crosslinking agent, this is preferred from the viewpoint that the PSA sheet can be thermally cured even if it does not have active energy ray curability. In another embodiment, the crosslinking agent (B) includes an acrylic crosslinking agent. When the crosslinking agent (B) includes an acrylic crosslinking agent, this is preferable in that the reaction is easily controlled and the pressure-sensitive adhesive sheet has active energy ray curability. In this embodiment, more preferably, the crosslinking agent (B) contains a polyfunctional (meth)acrylate.

[0062] Examples of the polyfunctional (meth)acrylate include polyfunctional (meth)acrylic monomers and polyfunctional (meth)acrylic oligomers having two or more, preferably three or more, (meth)acryloyl groups, which may be used alone or in combination of two or more.

[0063] Examples of the polyfunctional (meth)acrylic monomer include pentanediol di(meth)acrylate, hexadiol 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, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin 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 Tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, prop ... 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, tris(acryloxyethyl) isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate Examples of the hydroxypivalic acid di(meth)acrylate include tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, di(meth)acrylate of hydroxypivalic acid neopentyl glycol ε-caprolactone adduct, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate.

[0064] 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.

[0065] In a specific embodiment, from the viewpoint of imparting appropriate flexibility to the cured product, the crosslinking agent (B) includes a (meth)acrylate monomer and / or oligomer having a glycol structure. In another specific embodiment, from the viewpoint of imparting cohesive strength, the crosslinking agent (B) contains pentaerythritol, an acrylic acid adduct of dipentaerythritol, or an alkoxylated product thereof.

[0066] In the present invention, the content of the crosslinking agent (B) in the resin composition is 10 parts by mass or less, preferably 7.5 parts by mass or less, more preferably 5.0 parts by mass or less, particularly preferably 2.0 parts by mass or less, and extremely preferably 1.5 parts by mass or less, per 100 parts by mass of the polymer (A), in order to maintain the flexibility of the adhesive sheet. Furthermore, from the viewpoint of imparting shape stability to the pressure-sensitive adhesive sheet and durability when made into a laminate for an image display device, the amount is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more. The lower limit and the upper limit of the content of the crosslinking agent (B) can be combined arbitrarily.

[0067] [Polymerization initiator (C)] The resin composition preferably contains a polymerization initiator (C). In this specification, the polymerization initiator (C) is a general term for a compound that is activated by a stimulus such as heat or light to generate anions, cations, radicals, etc. that cause a polymerization initiation reaction. The polymerization initiator is preferably a compound that generates radicals (radical generator, radical polymerization initiator).

[0068] The polymerization initiator (C) may be, for example, a thermal polymerization initiator that is activated by heat, or a photopolymerization initiator that is activated by irradiation with light. The present pressure-sensitive adhesive sheet is a cured product obtained by partially curing (pre-curing) the resin composition, and in one embodiment of the present invention, it is intended to be further cured after lamination with another component. In this case, methods for appropriately controlling the degree of cure in the pre-curing include, for example, using a thermal polymerization initiator and a photopolymerization initiator in combination, performing pre-curing using one curing method to produce a pressure-sensitive adhesive sheet, and then using the other method to impart properties that allow curing after lamination, and a method using only a thermal polymerization initiator or a photopolymerization initiator to control the degree of cure in the pre-curing. In the latter case, it is preferable to use a photopolymerization initiator, as the degree of polymerization can be controlled to some extent by the amount of light irradiation.

[0069] Among the polymerization initiators (C), photopolymerization initiators are preferred. In a particularly preferred embodiment, the polymerization initiator (C) is a polymerization initiator that generates radicals by light (photoradical polymerization initiator).

[0070] Hereinafter, as an example of an embodiment, a case where a photoradical polymerization initiator is used will be described in detail, but as long as the effects of the present invention can be obtained, the polymerization initiator (C) may be changed and / or combined within the above-mentioned range.

[0071] The photoradical polymerization initiators are broadly classified into two types based on the radical generation mechanism. More specifically, they are broadly classified into cleavage-type radical polymerization initiators that can generate radicals by cleaving and decomposing the single bond of the photoradical polymerization initiator itself, and hydrogen abstraction-type radical polymerization initiators that can generate radicals by the excited initiator abstracting hydrogen from a hydrogen donor in the system. These may be used alone or in combination of two or more types. The cleavage type radical polymerization initiator is preferred because it does not cause unsaturation of the polymer (A) and can suppress rigidification, and when a cleavage type radical polymerization initiator is used, it is preferred because it has high photosensitivity. On the other hand, a hydrogen abstraction type radical polymerization initiator is preferred because it can incorporate the polymer (A) into a crosslinked structure by a hydrogen abstraction reaction, and also because the use of a hydrogen abstraction type radical polymerization initiator does not produce photodecomposition products.

[0072] Examples of the hydrogen abstraction type radical polymerization initiator 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-4'-bromobenzophenone, 4-methacryloyloxy Examples of the initiator include intermolecular hydrogen abstraction radical polymerization initiators (c1) such as benzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, and 4-methacryloyloxyethoxy-4'-bromobenzophenone; and intramolecular hydrogen abstraction radical polymerization initiators (c2) such as methylbenzoylformate, methyl benzoylformate, oxyphenylacetic acid-2-(2-oxo-2-phenyl-acetoxy-ethoxy)ethyl ester, and oxyphenylacetic acid-2-(2-hydroxy-ethoxy)ethyl ester. These initiators may be used alone or in combination of two or more.

[0073] Among the intermolecular hydrogen abstraction type radical polymerization initiators (c1), 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, and polymerization initiators having a radically polymerizable functional group with a carbon-carbon double bond in the molecule, such as 4-acryloyloxybenzophenone, 4-methacryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, and 4-methacryloyloxybenzophenone are preferred, with 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-methacryloyloxybenzophenone, and 4-methacryloyloxybenzophenone being more preferred. The polymerization initiators having a radically polymerizable functional group with a carbon-carbon double bond in the molecule are incorporated into the polymer structure after photoreaction, which tends to suppress bleed-out of the polymerization initiator and improve the cohesive strength of the pressure-sensitive adhesive sheet. Furthermore, the intramolecular hydrogen abstraction type radical polymerization initiator (c2) is preferred because it not only functions as a hydrogen donor in the system but also can itself be a starting point for radical generation, and methylbenzoyl formate is more preferred.

[0074] In the present invention, it is preferable that the polymerization initiator (C) contains an intermolecular hydrogen abstraction radical polymerization initiator (c1) and an intramolecular hydrogen abstraction radical polymerization initiator (c2), from the viewpoint of increasing the cohesive strength of the pressure-sensitive adhesive sheet.

[0075] Examples of the cleavage type radical polymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl}-2-methyl-propan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), 2-benzyl-2-dimethylamino-1-(4-mol Examples of suitable amines include 2-(4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-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, and derivatives thereof.

[0076] When the resin composition contains a polymerization initiator (C), the content thereof is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, particularly preferably 2.5 parts by mass or less, and extremely preferably 2.0 parts by mass or less, relative to 100 parts by mass of the polymer (A). The lower limit is usually 0.1 parts by mass.

[0077] When an intermolecular hydrogen abstraction type radical polymerization initiator (c1) and an intramolecular hydrogen abstraction type radical polymerization initiator (c2) are used in combination as the photoinitiator (C), the mass ratio (c2 / c1) thereof is usually 0.5 or more, preferably 1 or more, more preferably 2 or more, and is usually 10 or less, preferably 8 or less, more preferably 6 or less.

[0078] [Monofunctional (meth)acrylate] The resin composition may further contain a monofunctional (meth)acrylate having one (meth)acryloyl group, if necessary. By containing a monofunctional (meth)acrylate having one (meth)acryloyl group, the molecular weight between crosslinking points of the cured product can be increased, which is preferable in that the degree of freedom of movement of the molecular chain is increased and it becomes easier to obtain a cured product with excellent stress relaxation properties.

[0079] Examples of the monofunctional (meth)acrylate include ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, and dodecyl (meth)acrylate. (meth)acrylate, isododecyl (meth)acrylate, tetradecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, cyclononyl (meth)acrylate, cyclodecyl (meth)acrylate, isobornyl (meth)acrylate acrylate, norbornyl (meth)acrylate, adamantyl (meth)acrylate, tricyclodecane dimethanol acrylate, ethoxylated-o-phenylphenol acrylate, 2-hydroxy-o-phenylphenol propyl acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxydiethylene glycol Chole (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, 2-hydroxy-o-phenylphenol propyl acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl tetrahydrophthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxypropyl hydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, etc. benzyl (meth)acrylates;Benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, 2-naphthyl (meth)acrylate, 9-anthracenyl (meth)acrylate, 1-pyrenylmethyl (meth)acrylate, benzyl (meth)acrylate, tricyclodecane dimethanol monoacrylate monocarboxylic acid, dicyclopentanyl acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, trimethylolpropane mono(meth)acrylate, glycerin mono(meth)acrylate, pentaerythritol mono(meth)acrylate, diglycerin mono(meth)acrylate, ditrimethylolpropane mono(meth)acrylate, di Examples include pentaerythritol mono(meth)acrylate, ethoxylated trimethylolpropane mono(meth)acrylate, propoxylated trimethylolpropane mono(meth)acrylate, ethoxylated glycerin mono(meth)acrylate, propoxylated glycerin mono(meth)acrylate, ethoxylated pentaerythritol mono(meth)acrylate, propoxylated pentaerythritol mono(meth)acrylate, ethoxylated ditrimethylolpropane mono(meth)acrylate, propoxylated ditrimethylolpropane mono(meth)acrylate, alkylene oxide-modified diglycerin mono(meth)acrylate, and alkylene oxide-modified dipentaerythritol mono(meth)acrylate, as well as monofunctional oligomers such as monofunctional urethane (meth)acrylate, monofunctional epoxy (meth)acrylate, and monofunctional polyester (meth)acrylate. These may be used alone or in combination of two or more.

[0080] When a monofunctional (meth)acrylate is contained, the content thereof is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, and particularly preferably 6 parts by mass or more, per 100 parts by mass of polymer (A), from the viewpoint of adjusting the crosslinking density and imparting appropriate flexibility to the cured product. The upper limit is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0081] [Other ingredients] The resin composition may contain, as needed, various additives such as silane coupling agents, ultraviolet absorbers, plasticizers, tackifiers, antioxidants, light stabilizers, metal deactivators, antiaging agents, moisture absorbers, rust inhibitors, and inorganic particles as "other components" as long as the effects of the present invention are not impaired. Furthermore, the resin composition may contain, as needed, reaction catalysts such as tertiary amine compounds, quaternary ammonium compounds, and tin laurate compounds. These may be used alone or in combination of two or more. These may be used alone or in combination of two or more. Of these, it is preferable that the resin composition contains a silane coupling agent.

[0082] [Silane coupling agents] Silane coupling agents are organosilicon compounds containing, in their structure, at least one reactive functional group and at least one alkoxy group bonded to a silicon atom. Examples of the reactive functional group include epoxy groups, (meth)acryloyl groups, mercapto groups, hydroxyl groups, carboxy groups, amino groups, amide groups, and isocyanate groups. Among these, epoxy groups and mercapto groups are preferred in terms of balance of durability.

[0083] The alkoxy group bonded to the silicon atom preferably contains an alkoxy group having 1 to 8 carbon atoms from the viewpoint of durability and storage stability, and is particularly preferably a methoxy group or an ethoxy group. The silane coupling agent may have an organic substituent other than the reactive functional group and the alkoxy group bonded to the silicon atom, such as an alkyl group or a phenyl group.

[0084] Examples of the silane coupling agent include monomeric epoxy group-containing silane coupling agents, which are silane compounds such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and silane coupling agents in which a part of the silane compound is hydrolyzed and condensed, or in which the silane compound is polymerized with methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, Oligomeric epoxy group-containing silane coupling agents which are silane compounds obtained by co-condensation of alkyl group-containing silane compounds such as ethyltrimethoxysilane; monomeric mercapto group-containing silane coupling agents which are silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethyldimethoxysilane, and silane coupling agents in which a part of the silane compounds is hydrolyzed and condensed, or silanes in which the silane compounds are ... oligomeric mercapto group-containing silane coupling agents, which are silane compounds obtained by co-condensation of alkyl group-containing silane compounds such as methyltrimethoxysilane and ethyltrimethoxysilane; (meth)acryloyl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane and 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane; amino group-containing silane coupling agents such as methyl silane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane; and vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane. These may be used alone or in combination of two or more.

[0085] Among these, epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents are preferably used because of their excellent durability, and among these, epoxy group-containing silane coupling agents are particularly preferred.

[0086] When the resin composition contains a silane coupling agent, the content thereof is usually 0.005 parts by mass or more, preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and usually 10 parts by mass or less, preferably 5 parts by mass or less, particularly preferably 1 part by mass or less, relative to 100 parts by mass of the polymer (A). When the content is within the above range, adhesive strength and durability tend to be improved.

[0087] [Plasticizer] The plasticizer may be at least one selected from the group consisting of, but not limited to, polyisobutylene, polyisoprene, polybutadiene, amorphous polyolefins and copolymers thereof, silicones, polyacrylates, oligomeric polyurethanes, ethylene propylene copolymers, and the like, and any combinations or mixtures thereof. Among these, polyisobutylene is preferred. The polyisobutylene plasticizer may be, for example, one selected from the OPPANOLB series, which is commercially available from BASF under the trade name OPPANOL.

[0088] When the resin composition contains a plasticizer, the content thereof is not particularly limited and is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and usually 20 parts by mass or less, preferably 15 parts by mass or less, per 100 parts by mass of polymer (A).

[0089] [Tackifier] The resin composition may contain a tackifier to improve the adhesive strength of the pressure-sensitive adhesive sheet. 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), coumaran-indene resins, petroleum-based 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.

[0090] When the resin composition contains a tackifier, the content thereof is not particularly limited and is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and usually 20 parts by mass or less, preferably 15 parts by mass or less, per 100 parts by mass of polymer (A).

[0091] [Rust inhibitor] The resin composition may contain a rust inhibitor to prevent corrosion when the adherend contains a corrosive portion such as a metal wiring. Examples of the rust inhibitor include triazoles and benzotriazoles.

[0092] When the resin composition contains a rust inhibitor, the content thereof is usually 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and usually 5 parts by mass or less, preferably 3 parts by mass or less, per 100 parts by mass of polymer (A).

[0093] <<Viscoelastic properties of adhesive sheets>> <Shear storage modulus (G0' (25℃))> In one embodiment, the pressure-sensitive adhesive sheet has a shear storage modulus (G0'(25°C)) at a temperature of 25°C, obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz, of 100 kPa or more.

[0094] PSA sheets that satisfy the above shear storage modulus (G0' (25°C)) tend to have excellent shape stability. From this viewpoint, the shear storage modulus (G0'(25°C)) is preferably 120 kPa or more, more preferably 150 kPa or more, even more preferably 200 kPa or more, particularly preferably 250 kPa or more, and of these, 300 kPa or more is preferred, and 400 kPa or more is most preferred. On the other hand, from the viewpoint of ensuring the stress relaxation properties of the pressure-sensitive adhesive sheet, the shear storage modulus (G0'(25°C)) is preferably 1000 kPa or less, more preferably 900 kPa or less, even more preferably 750 kPa or less, and particularly preferably 500 kPa or less. The lower and upper limits of the shear storage modulus (G0'(25°C)) can be combined in any desired manner.

[0095] The shear storage modulus (G0'(25°C)) is measured, for example, as follows. This pressure-sensitive adhesive sheet is repeatedly laminated to a thickness of 0.7 to 1.2 mm (for example, 0.8 mm), and then punched out to a diameter of 8 mm. The resulting sample is subjected to dynamic viscoelasticity measurement using a rheometer under the following conditions: measurement jig: 8 mm diameter parallel plates, frequency: 1 Hz, measurement temperature: -50 to 150°C, heating rate: 5°C / min, and the shear storage modulus (G'(25°C)) at a temperature of 25°C is read.

[0096] In measuring the shear storage modulus (G'(25°C)), it is necessary to avoid fluctuations in the measurement results due to the influence of the measuring jig. The shear storage modulus (G'(25°C)) is a value measured after adjusting the thickness to the range of 0.7 to 1.2 mm, which allows the shear storage modulus (G'(25°C)) to be accurately measured without being influenced by the measuring jig. Note that "adjusted to a thickness of 0.7 to 1.2 mm" means that if the thickness of the PSA sheet used as a measurement sample is less than this range, the thickness of the measurement sample is adjusted to this range by stacking several sheets, etc. The same applies when the thickness of the measurement sample is specified in other tests in this specification.

[0097] Examples of methods for adjusting the shear storage modulus (G0'(25°C)) within the above range include, but are not limited to, methods of adjusting the composition and molecular weight of the polymer (A), the type and content of the crosslinking agent (B) and the polymerization initiator (C), and methods of adjusting the amount of active energy ray irradiation.

[0098] <Initial elastic modulus (G0'(0))> In one embodiment, the pressure-sensitive adhesive sheet has an initial elastic modulus (G0'(0)) of 5 kPa or more 0.1 seconds after a strain of 25% is applied to the pressure-sensitive adhesive sheet at a temperature of 70°C. By satisfying the above initial elastic modulus (G0'(0)), it is possible to obtain a pressure-sensitive adhesive sheet with a desirable cohesive force. Such a pressure-sensitive adhesive sheet tends to have excellent shape stability. From the viewpoint of suppressing the phenomenon of adhesive overflow, the initial elastic modulus is preferably 10 kPa or more, more preferably 15 kPa or more, and even more preferably 20 kPa or more. Furthermore, when the adherend has irregularities, from the viewpoint of filling in the surface irregularities during lamination, the initial modulus of elasticity (G0'(0)) is preferably 100 kPa or less, more preferably 60 kPa or less, and even more preferably 40 kPa or less. The lower limit and upper limit of the initial modulus of elasticity (G0'(0)) can be arbitrarily combined.

[0099] <Relaxation modulus (G0'(300))> In one embodiment, the pressure-sensitive adhesive sheet has a relaxation modulus (G0'(300)) of 0.1 to 20 kPa 300 seconds after a 25% strain is applied to the pressure-sensitive adhesive sheet at a temperature of 70°C.

[0100] By satisfying the relaxation modulus (G0'(300)), a pressure-sensitive adhesive sheet with desirable cohesive strength can be obtained. Such pressure-sensitive adhesive sheets tend to have excellent shape stability. In order to prevent the adhesive from spilling out, the relaxation modulus (G0'(300)) is preferably 0.2 kPa or more, more preferably 0.5 kPa or more, and even more preferably 1 kPa or more. In order to maintain a suitable flexibility and ensure wettability to the adherend, the relaxation modulus (G0'(300)) is preferably 15 kPa or less, more preferably 10 kPa or less, and even more preferably 5 kPa or less. The lower and upper limits of the relaxation modulus (G0'(300)) can be arbitrarily combined.

[0101] The initial elastic modulus (G0'(0)) and the relaxed elastic modulus (G0'(300)) are measured, for example, as follows. The pressure-sensitive adhesive sheets are repeatedly laminated to a thickness of 0.7 to 1.2 mm (for example, approximately 0.8 mm), and then punched out to a diameter of 25 mm. A rheometer is used to apply a 25% strain at 70°C to the obtained sample, and the elastic modulus is read after 0.1 seconds and 300 seconds.

[0102] Examples of methods for adjusting the initial modulus (G0'(0)) and the relaxation modulus (G0'(300)) include, but are not limited to, methods for adjusting the composition and molecular weight of the polymer (A), the type and content of the crosslinking agent (B) and the polymerization initiator (C), and methods for adjusting the amount of active energy ray irradiation.

[0103] <Stress relaxation rate (X0)> In laminates that require precision lamination, such as laminates for image display devices, when laminating components together, it is common to perform finish lamination by pressure treatment or heat and pressure treatment using an autoclave or the like. (Hereinafter, pressure treatment and heat and pressure treatment may be collectively referred to as "pressure treatment, etc.") Then, bubbles may occur at the peripheral edge after the completion of the pressure treatment, etc., or after the start of product use. One of the main causes of the formation of such bubbles is thought to be that air present in an apparatus such as an autoclave oven used for the pressure treatment, etc., during the laminating step, becomes high pressure inside the apparatus and enters between the laminating member and the pressure-sensitive adhesive sheet. Conventionally, such bubbles would not be visible on the outside because the peripheral edges of displays are covered by a concealing layer such as a printed layer or a bezel. However, in recent years, with the demand for narrower picture frames and frameless designs for displays, the peripheral edges have become narrower, and there has been a strong demand for improved resistance to bubbles at the peripheral edges of pressure-sensitive adhesive sheets.

[0104] In view of the above, in one embodiment of the present invention, the pressure-sensitive adhesive sheet has a stress relaxation rate (X0) of 0.20 or less, calculated using the following formula (I) from the initial elastic modulus (G0'(0)) 0.1 seconds after applying a 25% strain at a temperature of 70°C and the relaxation elastic modulus (G0'(300)) 300 seconds after applying a 25% strain at a temperature of 70°C: Stress relaxation rate (X0) = (G0'(300) / G0'(0)) (I)

[0105] From the viewpoint of improving the resistance to foaming at the peripheral edge of the pressure-sensitive adhesive sheet, the stress relaxation rate (X0) is preferably 0.15 or less, more preferably 0.1 or less, and even more preferably 0.05 or less. On the other hand, from the viewpoint of suppressing adhesive extrusion, the stress relaxation rate (X0) is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, particularly preferably 0.04 or more, and most preferably 0.10 or more. The lower limit and upper limit of the stress relaxation rate (X0) can be combined arbitrarily.

[0106] By setting the stress relaxation rate (X0) to the above lower limit or higher, a pressure-sensitive adhesive sheet with excellent stress relaxation properties can be provided. Because such a pressure-sensitive adhesive sheet is flexible, it is excellent in absorbing foreign matter and defects that can be the starting point for foaming, and it is also easy to diffuse the air that is absorbed during lamination of components. As a result, it is possible to reduce or eliminate air bubbles remaining at the peripheral edge of the pressure-sensitive adhesive sheet.

[0107] The stress relaxation modulus (X0) can be adjusted by adjusting the initial modulus (G0'(0)) and the relaxation modulus (G0'(300)). Examples of methods for adjusting the stress relaxation modulus (X0) include, similar to adjusting the initial modulus (G0'(0)) and the relaxation modulus (G0'(300)), adjusting the composition and molecular weight of the polymer (A) and the type and content of the crosslinking agent (B) and the polymerization initiator (C), as well as adjusting the amount of active energy ray irradiation. However, the method is not limited to these.

[0108] <Glass transition temperature (Tg0)> In one embodiment, the present pressure-sensitive adhesive sheet has the following properties. The glass transition temperature (Tg0) defined by the maximum value of Tan δ obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is -25°C or higher.

[0109] By providing the above properties, a pressure-sensitive adhesive sheet with excellent shape stability tends to be obtained. From this viewpoint, the glass transition temperature (Tg0) is preferably -20°C or higher, more preferably -15°C or higher, even more preferably -10°C or higher, particularly preferably -5°C or higher, and most preferably 0°C or higher. On the other hand, from the viewpoint of obtaining appropriate flexibility and stress relaxation property, the upper limit is preferably 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower, particularly preferably 20°C or lower, and of these, 5°C or lower is preferred. The lower limit and upper limit of the glass transition temperature (Tg0) can be combined arbitrarily.

[0110] The glass transition temperature (Tg0) can be obtained by reading the temperature at which the loss tangent (Tanδ) becomes maximum, i.e., the peak temperature, from the dynamic viscoelasticity spectrum data in the shear mode obtained by the same method as in the measurement of the shear storage modulus (G0'(25°C)) at 25°C described above. In the case where a plurality of maximum values ​​exist in the viscoelasticity spectrum, the "peak temperature" refers to the temperature at which the largest maximum value is obtained.

[0111] Examples of methods for adjusting the glass transition temperature (Tg0) within the above range include, but are not limited to, adjusting the composition and molecular weight of the polymer (A), the type and content of the crosslinking agent (B) and the polymerization initiator (C), and adjusting the amount of active energy ray irradiation.

[0112] <Gel fraction> In one embodiment, the pressure-sensitive adhesive sheet has a gel fraction of preferably 30% or more, more preferably 40% or more, and even more preferably 45% or more. On the other hand, from the viewpoint of obtaining stress relaxation properties, the gel fraction is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. The lower and upper limits of the gel fraction can be combined arbitrarily. A pressure-sensitive adhesive sheet that satisfies the above physical properties tends to have an appropriate cohesive force and excellent shape stability.

[0113] The gel fraction is measured, for example, as follows. The adhesive sheet, the mass of which has been measured in advance, and a 150-mesh SUS wire mesh are prepared. The adhesive sheet is then wrapped in the SUS (stainless steel) wire mesh and immersed in ethyl acetate at 23°C for 24 hours. It is then dried at 70°C for 4.5 hours, and the mass of the sheet and the SUS wire mesh is measured. The mass of the insoluble adhesive sheet remaining in the wire mesh (mass after immersion) is calculated by subtracting the mass of the SUS wire mesh from the mass of the adhesive sheet before immersion in ethyl acetate (mass before immersion). The gel fraction (%) is then calculated as the percentage of the mass of the insoluble adhesive sheet remaining in the wire mesh (mass after immersion) relative to the mass of the adhesive sheet before immersion in ethyl acetate (mass before immersion).

[0114] Examples of methods for adjusting the gel fraction within the above range include, but are not limited to, adjusting the composition and molecular weight of the polymer (A), the type and content of the crosslinking agent (B) and the polymerization initiator (C), and adjusting the amount of active energy ray irradiation.

[0115] <Adhesive strength> In one embodiment, the pressure-sensitive adhesive sheet has an adhesive strength to soda-lime glass of 2 N / cm or more at a temperature of 23° C. and a peeling speed of 60 mm / min.

[0116] An adhesive strength of 2 N / cm or more prevents peeling of the adhesive sheet edge surface, and excellent bonding reliability can be obtained at the peripheral edge. From this viewpoint, the adhesive strength is preferably 4 N / cm or more, more preferably 6 N / cm or more, and even more preferably 12 N / cm or more. There is no particular upper limit to the adhesive strength, but from the viewpoint of reworkability, it is usually 50 N / cm, preferably 30 N / cm.

[0117] The adhesive strength is measured, for example, as follows. A 100 μm thick polyethylene terephthalate (PET) film was laminated to the adhesive layer of the adhesive sheet, and the other side was roll-pressed onto soda lime glass to form a laminate. The laminate was then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to form a finished laminate, which was used as a sample for adhesive strength measurement. The adhesive strength was determined by peeling this sample at a peel angle of 180° and a peel rate of 60 mm / min under an environment of 23°C and 50% RH.

[0118] In one embodiment, the pressure-sensitive adhesive sheet is preferably active energy ray-curable. Here, the term "active energy ray-curable" means that the pressure-sensitive adhesive sheet has the property of being curable by active energy rays, in other words, that there is room for curing by active energy rays.

[0119] The pressure-sensitive adhesive sheet according to the present invention is a cured product of a resin composition, and in one embodiment, exhibits the property of being further cured (curable) by heat and / or active energy rays. The curable nature of this pressure-sensitive adhesive sheet allows it to be cured (secondary cured) after being attached to an adherend, thereby providing a pressure-sensitive adhesive sheet with excellent cohesive strength, durability, etc. after curing.

[0120] <<Properties after curing>> In the following, when the pressure-sensitive adhesive sheet has curing properties, the properties after curing will be described in detail.

[0121] <Curing method for evaluating various properties after curing> In this specification, when evaluating various properties of the pressure-sensitive adhesive sheet after curing, the pressure-sensitive adhesive sheet after curing to be subjected to evaluation can be obtained by curing the pressure-sensitive adhesive sheet in the following manner.

[0122] When the pressure-sensitive adhesive sheet is active energy ray-curable, the pressure-sensitive adhesive sheet after curing is cured by irradiating the pressure-sensitive adhesive sheet with active energy rays having a wavelength of 365 nm with an integrated light dose of 2000 to 4000 mJ / cm. 2 This can be obtained by irradiating the light so that When the present pressure-sensitive adhesive sheet is thermosetting, the cured pressure-sensitive adhesive sheet can be obtained, for example, by heating the present pressure-sensitive adhesive sheet at 70 to 90° C. for 80 to 160 minutes. Depending on the evaluation item, the curing may be carried out after laminating the pressure-sensitive adhesive sheet to a specific substrate or backing film before curing, as will be described in detail in the Examples below.

[0123] <Stress relaxation rate after curing (X1)> In one embodiment, the cured pressure-sensitive adhesive sheet preferably has the following property: The stress relaxation modulus (X1) after curing is 0.22 or greater, as calculated using the following formula (II) from the initial elastic modulus (G1'(0)) 0.1 seconds after applying a 25% strain at 70°C to the cured pressure-sensitive adhesive sheet and the relaxation modulus (G1'(300)) 300 seconds after applying a 25% strain at 70°C to the pressure-sensitive adhesive sheet: Stress relaxation rate (X1) = (G1'(300) / G1'(0)) (II)

[0124] An adhesive sheet having the above stress relaxation rate (X1) has excellent resistance to deformation, and therefore tends to be less susceptible to dents or indentations when made into a laminate for an image display device, and to exhibit excellent durability. From the viewpoint of obtaining excellent durability, the stress relaxation rate (X1) is preferably 0.25 or more, more preferably 0.30 or more, even more preferably 0.35 or more, particularly preferably 0.45 or more, and extremely preferably 0.50 or more. On the other hand, from the viewpoint of obtaining stress relaxation properties, the stress relaxation rate (X1) is preferably 1.00 or less, more preferably 0.80 or less, and even more preferably 0.70 or less. The lower limit and upper limit of the stress relaxation rate (X1) can be arbitrarily combined.

[0125] <Initial modulus of elasticity after curing (G1'(0))> In one embodiment, the adhesive sheet after curing has an initial elastic modulus (G1'(0)) of 10 kPa or more 0.1 seconds after applying a 25% strain to the adhesive sheet after curing at a temperature of 70°C. An adhesive sheet having the above initial elastic modulus (G1'(0)) after curing has high cohesive strength, and therefore tends to exhibit excellent durability against dents and indentations when made into a laminate for an image display device. From the viewpoint of obtaining excellent durability, the initial elastic modulus (G1'(0)) after curing is preferably 15 kPa or more, more preferably 20 kPa or more, and even more preferably 25 kPa or more. On the other hand, from the viewpoint of obtaining stress relaxation properties, the initial elastic modulus after curing (G1'(0)) is preferably 200 kPa or less, more preferably 100 kPa or less, even more preferably 70 kPa or less, and particularly preferably 35 kPa or less. The lower limit and upper limit of the initial elastic modulus after curing (G1'(0)) can be arbitrarily combined. The method for measuring the initial modulus of elasticity after curing (G1'(0)) is the same as the method for measuring the initial modulus of elasticity (G0'0)).

[0126] <Relaxation modulus after curing (G1'(300))> In one embodiment, the cured pressure-sensitive adhesive sheet has a post-curing relaxation modulus (G1'(300)) of 1 to 200 kPa 300 seconds after a 25% strain is applied to the cured pressure-sensitive adhesive sheet at a temperature of 70°C. An adhesive sheet having the above-mentioned relaxation modulus after curing (G1'(300)) has high cohesive strength, and therefore tends to exhibit excellent durability against dents and indentations when made into a laminate for an image display device. From the viewpoint of obtaining excellent durability, the relaxation modulus (G1'(300)) after curing is preferably 2 kPa or more, more preferably 3 kPa or more, even more preferably 5 kPa or more, and particularly preferably 8 kPa or more. On the other hand, from the viewpoint of obtaining stress relaxation properties, the relaxation modulus after curing (G1'(300)) is preferably 200 kPa or less, more preferably 100 kPa or less, even more preferably 50 kPa or less, particularly preferably 20 kPa or less, and even more preferably 15 kPa or less, and most preferably 10 kPa or less. The lower limit and upper limit of the relaxation modulus after curing (G1'(300)) can be arbitrarily combined. The method for measuring the relaxation modulus of elasticity after curing (G1'(300)) is the same as that for measuring the relaxation modulus of elasticity (G0'(300)).

[0127] <Difference in stress relaxation rate before and after curing> In one embodiment, the pressure-sensitive adhesive sheet has a difference (X1-X0) between the stress relaxation rate (X1) after curing and the stress relaxation rate (X0) of 0.01 or more. A pressure-sensitive adhesive sheet comprising the (X1-X0) tends to be able to provide a high level of resistance to foaming at the peripheral edge and durability against dents and indentations when made into a laminate for image display. From this viewpoint, the value of (X1-X0) is preferably 0.02 or more, more preferably 0.10 or more, and even more preferably 0.20 or more.

[0128] <Shear storage modulus after curing (G1' (25℃))> In one embodiment, the pressure-sensitive adhesive sheet after curing has a shear storage modulus (G1'(25°C)) at 25°C of 150 kPa or more, as determined by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz. A pressure-sensitive adhesive sheet having the above-mentioned shear storage modulus (G1' (25°C)) after curing tends to have a high cohesive force after being irradiated with active energy rays.

[0129] In order to obtain a high cohesive force, the shear storage modulus (G1' (25°C)) after curing is preferably 160 kPa or more, more preferably 180 kPa or more, and even more preferably 200 kPa or more. On the other hand, from the viewpoint of obtaining stress relaxation properties, the shear storage modulus (G1'(25°C)) after curing is preferably 1000 kPa or less, more preferably 900 kPa or less, even more preferably 800 kPa or less, particularly preferably 750 kPa or less, and most preferably 500 kPa or less. The lower limit and upper limit of the shear storage modulus (G1'(25°C)) after curing can be combined in any desired manner. The method for measuring the shear storage modulus after curing (G1'(25°C)) is the same as that for measuring the shear storage modulus at 25°C (G0'(25°C)).

[0130] <Glass transition temperature after curing (Tg1)> In one embodiment, the pressure-sensitive adhesive sheet after curing has a glass transition temperature (Tg1) of −25° C. or higher, which is defined as the maximum value of Tan δ obtained by dynamic viscoelasticity measurement in shear mode at a frequency of 1 Hz. A pressure-sensitive adhesive sheet having this property tends to have high cohesive strength after being irradiated with active energy rays. From the viewpoint of obtaining high cohesive strength, the glass transition temperature (Tg1) after curing is preferably −23° C. or higher, more preferably −20° C. or higher, even more preferably −10° C. or higher, particularly preferably −5° C. or higher, and most preferably 0° C. or higher. On the other hand, from the viewpoint of obtaining stress relaxation properties, the glass transition temperature (Tg1) after curing is preferably 60° C. or lower, more preferably 40° C. or lower, even more preferably 30° C. or lower, and even more preferably 20° C. or lower, particularly preferably 5° C. or lower. The lower limit and upper limit of the glass transition temperature (Tg1) can be combined in any desired manner.

[0131] The method for measuring the glass transition temperature (Tg1) after curing is the same as that for measuring the glass transition temperature (Tg0).

[0132] <Gel fraction after curing> In one embodiment, the pressure-sensitive adhesive sheet after curing has a gel fraction of 35% or more. A pressure-sensitive adhesive sheet having the above-described gel fraction after curing has high cohesive strength, and when made into a laminate for an image display device, can exhibit excellent durability. From the viewpoint of obtaining excellent durability, the gel fraction after curing is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more. On the other hand, from the viewpoint of obtaining an appropriate stress relaxation property, the gel fraction after curing is preferably 95% or less, and more preferably 90% or less. The lower and upper limits of the gel fraction can be combined arbitrarily.

[0133] The method for measuring the gel fraction after curing is the same as that for measuring the gel fraction.

[0134] <Adhesive strength after curing> In one embodiment, the pressure-sensitive adhesive sheet after curing has an adhesive strength to soda-lime glass of 2 N / cm or more at a temperature of 23° C. and a peeling rate of 60 mm / min. A pressure-sensitive adhesive sheet having the above adhesive strength tends to exhibit excellent reliability without peeling even when used as a laminate for an image display device. From this viewpoint, the adhesive strength after curing is preferably 3 N / cm or more, more preferably 8 N / cm or more, and even more preferably 12 N / cm or more. The upper limit of the adhesive strength after curing is not particularly limited, but from the viewpoint of reworkability, it is usually 50 N / cm, preferably 30 N / cm.

[0135] The adhesive strength after curing is measured, for example, as follows. The adhesive sheet is laminated to a 100 μm thick polyethylene terephthalate (PET) film as a backing film, and the other side is roll-pressed onto soda lime glass, followed by autoclaving (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) for final adhesion. The integrated light intensity at a wavelength of 365 nm is then 2000-4000 mJ / cm. 2 The adhesive sheet is irradiated with active energy rays through the backing film so as to cure the adhesive sheet, thereby preparing a sample for measuring adhesive strength. The adhesive strength after curing is determined by the peel force (N / cm) when this sample is peeled at a peel angle of 180° and a peel rate of 60 mm / min in an environment of 23°C and 50% RH.

[0136] <<Manufacturing method of the present pressure-sensitive adhesive sheet>> Next, a method for producing the pressure-sensitive adhesive sheet will be described. However, the following description is merely an example of a method for producing the present pressure-sensitive adhesive sheet, and the present pressure-sensitive adhesive sheet is not limited to sheets produced by this production method.

[0137] The present pressure-sensitive adhesive sheet can be produced by preparing a resin composition containing a polymer (A), preferably a crosslinking agent (B), a polymerization initiator (C), and other components as necessary, molding the pressure-sensitive adhesive composition into a sheet, curing it by crosslinking, i.e., polymerization, and then processing it appropriately as necessary.

[0138] The resin composition can be prepared by kneading the raw materials using a temperature-controllable kneader (for example, a single-screw extruder, a twin-screw extruder, a planetary mixer, a twin-screw mixer, a pressure kneader, or the like). When kneading various raw materials, various additives such as silane coupling agents and antioxidants may be blended together with the resin in advance and then fed to the kneader, or all materials may be melt-mixed in advance and then fed, or a master batch in which only the additives are concentrated in the resin may be prepared and then fed.

[0139] The resin composition can be formed into a sheet by any known method, such as wet lamination, dry lamination, extrusion casting using a T-die, extrusion lamination, calendaring, inflation, injection molding, and liquid injection curing. Among these, when producing a sheet, wet lamination, extrusion casting, and extrusion lamination are preferred.

[0140] The resin composition can be cured by irradiating it with active energy rays, and the pressure-sensitive adhesive sheet can be produced by irradiating a molded product of the resin composition, for example, a sheet, with active energy rays. In addition to irradiating it with active energy rays, further curing can be achieved by heating.

[0141] Furthermore, the irradiation energy, irradiation time, irradiation method, etc. of the active energy ray are not particularly limited as long as they can activate the polymerization initiator (C) and polymerize the photoreactive component such as the (meth)acrylic acid ester compound. When a hydrogen abstraction type radical polymerization initiator is used as the polymerization initiator (C), a hydrogen abstraction reaction also occurs from the polymer (A), and the polymer (A) is incorporated into the crosslinked structure, thereby forming a crosslinked structure with many crosslinking points. Therefore, the present pressure-sensitive adhesive sheet is preferably one that is cured using a hydrogen abstraction type radical polymerization initiator.

[0142] Examples of the active energy rays in the active energy ray irradiation include light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, and visible light rays, as well as ionizing radiation such as X-rays, α-rays, β-rays, γ-rays, electron beams, proton beams, and neutron beams. Among these, ultraviolet rays are preferred from the viewpoints of suppressing damage to optical device components and controlling reactions. Furthermore, ultraviolet rays are preferred from the viewpoints of curing speed, ease of obtaining an irradiation device, cost, and the like.

[0143] Examples of light sources for ultraviolet 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 LED lamps, all of which emit light in the wavelength range of 150 to 450 nm. Of these, it is preferable to use high-pressure mercury lamps, metal halide lamps, and LED lamps.

[0144] The amount of active energy ray irradiation (cumulative amount of light) is preferably 100 mJ / m from the viewpoint of curing. 2 or more, more preferably 200 mJ / cm 2 More preferably, 300 mJ / cm 2 More than 400 mJ / cm, particularly preferably 400 mJ / cm 2 or more, most preferably 500 mJ / cm 2 or more, and preferably 10,000 mJ / cm 2 Less than or equal to 5000 mJ / cm 2 or less, more preferably 4000 mJ / cm 2 Below 3000 mJ / cm, particularly preferably 2 Below 2000 mJ / cm, most preferably 2000 mJ / cm 2 The following is the result.

[0145] The present pressure-sensitive adhesive sheet is preferably pre-cured by irradiation with active energy rays so as to have latent active energy ray curability, in other words, so as to retain active energy ray reactivity. When pre-curing is performed by irradiation with active energy rays, the degree of active energy ray crosslinking (gel fraction) can be adjusted by controlling the amount of active energy ray irradiation, but the degree of active energy ray crosslinking (gel fraction) can also be adjusted by using a filter or the like to partially block the active energy rays.

[0146] The present pressure-sensitive adhesive sheet can also be provided as a pressure-sensitive adhesive sheet with a release film laminated on one or both sides. In particular, from the viewpoint of preventing blocking and adhesion of foreign matter, it is preferable to coat both sides of the present pressure-sensitive adhesive sheet with a release film.

[0147] When release films are provided on both sides of the pressure-sensitive adhesive sheet, it is preferable to use a laminate structure in which a light release film with a relatively low release strength is laminated with a heavy release film with a relatively high release strength. When using an adhesive sheet with release films on both sides, first, one release film (light release film) is peeled off to expose one side of the adhesive sheet, and then the sheet is bonded to an image display device component (referred to as the first component), and the other release film (heavy release film) is peeled off to expose the other side of the adhesive sheet, and another image display device component (referred to as the second component) is bonded to the other side.

[0148] As such a release film, any known release film can be used appropriately. As the substrate for the release film, for example, a film such as a polyester film, a polyolefin film, a polycarbonate film, a polystyrene film, an acrylic film, a triacetyl cellulose film, or a fluororesin film that has been subjected to a release treatment by coating with a release agent such as a silicone resin, or release paper, etc. can be appropriately selected and used. Of these, polyester film is preferred, polyethylene terephthalate (PET) film is more preferred, and biaxially stretched PET film is particularly preferred because of its excellent transparency, mechanical strength, heat resistance, flexibility, and the like. A release film can be used in which a release layer formed by curing a curable silicone-based release agent containing a silicone resin as a main component is provided on the substrate.

[0149] The thickness of the release film is not particularly limited, but from the viewpoint of processability and handling, it is preferably 10 to 250 μm, more preferably 25 to 200 μm, and particularly preferably 35 to 190 μm.

[0150] In another embodiment of the method for producing the pressure-sensitive adhesive sheet, the resin composition can be dissolved in an appropriate solvent and then coated using various coating techniques. When a coating method is used, the present pressure-sensitive adhesive sheet can be obtained by pre-curing using heat in addition to the above-mentioned active energy ray irradiation. Furthermore, when a coating method is used, the thickness of the present pressure-sensitive adhesive sheet can be adjusted by the coating thickness and the solids concentration of the coating liquid.

[0151] The coating method may be a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing, or bar coating.

[0152] To produce the present pressure-sensitive adhesive sheet using the coating method, for example, the resin composition is dissolved in a solvent, then coated on the release film, dried, and pre-cured by irradiating with active energy rays to form the present pressure-sensitive adhesive sheet. Furthermore, a release film may be laminated, if necessary. In this case, the composition may be coated on a release film, dried, pre-cured by irradiating with active energy rays, and then a release film may be laminated thereon. Alternatively, the composition may be coated on a release film, dried, and then a release film may be laminated thereon, and then pre-cured by irradiating with active energy rays to form the present pressure-sensitive adhesive sheet.

[0153] The solvent is not particularly limited as long as it dissolves the resin composition, and examples thereof 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 propyl alcohol. These can be used alone or in combination of two or more. Among these, ethyl acetate, acetone, methyl ethyl ketone, and toluene are preferred in terms of solubility, drying properties, cost, and the like, and ethyl acetate is particularly preferred.

[0154] In terms of drying property, the content of the solvent is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 400 parts by mass or less, and particularly preferably 300 parts by mass or less, relative to 100 parts by mass of the polymer (A), while it is preferably 1 part by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, and particularly preferably 150 parts by mass or more.

[0155] The solvent content in the resin composition after drying is preferably 1% by mass or less. It is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and most preferably 0.5% by mass or less. The content is preferably 0% by mass.

[0156] The drying temperature is usually 40° C. or higher, preferably 45° C. or higher, more preferably 50° C. or higher, and particularly preferably 55° C. or higher, and is usually 150° C. or lower, preferably 140° C. or lower, more preferably 130° C. or lower, and particularly preferably 120° C. or lower. Within this temperature range, the solvent can be removed efficiently and relatively safely while suppressing thermal deformation of the release film.

[0157] The drying time is usually 1 minute or more, preferably 3 minutes or more, more preferably 3 minutes or more, and usually 30 minutes or less, preferably 25 minutes or less, more preferably 20 minutes or less. Within this time range, the solvent can be removed efficiently and sufficiently.

[0158] Drying methods include, for example, drying with a dryer, drying with a heated roll, drying by blowing hot air onto the film, etc. Among these, using a dryer is preferred because it allows for uniform and easy drying. These methods can be used alone or in combination of two or more.

[0159] In yet another embodiment of the method for producing the present pressure-sensitive adhesive sheet, a resin composition may be prepared, coated onto a component of an image display device described below, and the resin composition may be pre-cured to produce the present pressure-sensitive adhesive sheet, although the method is not limited to this.

[0160] Furthermore, the present pressure-sensitive adhesive sheet may be a single-layer pressure-sensitive adhesive sheet consisting of only a pressure-sensitive adhesive layer formed from a resin composition, or may be a multi-layer pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers formed from the resin composition or other pressure-sensitive adhesive layers are laminated. Among these, the layer structure of the present pressure-sensitive adhesive sheet is preferably at least two layers, more preferably at least three layers: an outermost layer, an innermost layer, and an intermediate layer, and particularly preferably the outermost layer, the innermost layer, and the intermediate layer are at least three layers formed from the resin composition. By using such a layer structure, the pressure-sensitive adhesive sheet tends to be less likely to be indented or dented even when localized pressure is applied.

[0161] When the pressure-sensitive adhesive sheet has at least three layers, namely, a top layer, a bottom layer, and an intermediate layer, the top layer and the bottom layer (hereinafter also referred to as "top and bottom layers") and the intermediate layer (the layer sandwiched between the top layer and the bottom layer) are preferably formed from a resin composition containing polymers (A) of different compositions, particularly containing polymers (A) of different compositions as the main component. Such a layer configuration is advantageous in that trade-off properties such as stress relaxation and shape retention can be functionally separated for each layer. Furthermore, the outermost layer and the innermost layer may be formed from a resin composition containing polymers (A) of different compositions, particularly polymers (A) of different compositions as the main component, but are preferably formed from a resin composition containing polymers (A) of the same composition.

[0162] Furthermore, when the pressure-sensitive adhesive sheet has at least three layers (surface layer / intermediate layer / backmost layer) consisting of a surface layer, a backmost layer, and an intermediate layer, the surface layer and the backmost layer (the surfaces to be attached to the components of the image display device) are preferably high Tg layers. The intermediate layer sandwiched between the surface layer and the backmost layer is preferably a low Tg layer. Furthermore, the high Tg layers used for the surface layer and the backmost layer may have different glass transition temperatures (Tg), but it is preferable that the surface layer and the backmost layer have the same glass transition temperature, and it is particularly preferable that the surface layer and the backmost layer are pressure-sensitive adhesive layers formed from the same resin composition.

[0163] The high Tg layer refers to a layer having a maximum value (glass transition temperature) of loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in the shear mode described above of usually −25° C. or higher, preferably −10° C. or higher, and particularly preferably 0° C. or higher. The upper limit of the glass transition temperature of the high Tg layer is usually 60° C. or lower, preferably 40° C. or lower, more preferably 30° C. or lower, and even more preferably 20° C. or lower. The low Tg layer is a layer whose maximum value (glass transition temperature) of loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in the shear mode is lower than that of the high Tg layer, and whose glass transition temperature is usually 20° C. or lower, preferably 15° C. or lower, more preferably 10° C. or lower, even more preferably 8° C. or lower, particularly preferably 5° C. or lower, and most preferably 0° C. or lower. The lower limit of the glass transition temperature of the low Tg layer is usually −80° C., preferably −60° C. or higher, more preferably −50° C. or higher, and even more preferably −40° C. or higher.

[0164] Furthermore, when the pressure-sensitive adhesive sheet has at least three layers, namely, a surface layer, a back layer, and an intermediate layer, the ratio of the sum of the thicknesses of the surface layer and the back layer to the total thickness is preferably 5% or more, more preferably 10% or more, particularly preferably 20% or more, and is preferably 70% or less, more preferably 60% or less, particularly preferably 45% or less. By setting the thicknesses of the surface layer and the back layer within the above ranges, a pressure-sensitive adhesive sheet can be obtained that has excellent adhesion suitability and durability, such as resistance to foaming at the peripheral edge, resistance to adhesive extrusion, and level difference absorbency.

[0165] The pressure-sensitive adhesive sheet thus obtained is an optically transparent pressure-sensitive adhesive sheet. Here, "optically transparent" means that the total light transmittance is 80% or more, preferably 85% or more, and more preferably 90% or more. The haze value of the present pressure-sensitive adhesive sheet is preferably 10% or less, more preferably 5% or less, and particularly preferably 3% or less.

[0166] The thickness of the present pressure-sensitive adhesive sheet is preferably 50 μm or more, more preferably 60 μm or more, and particularly preferably 70 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, and particularly preferably 300 μm or less.

[0167] Furthermore, the pressure-sensitive adhesive sheet may be embossed or processed to have various irregularities (such as conical, pyramidal, or hemispherical shapes) as needed. Furthermore, in order to improve adhesion to various components, the surface may be subjected to various surface treatments such as corona treatment, plasma treatment, and primer treatment.

[0168] <Preferred uses of this adhesive sheet> In one embodiment, the pressure-sensitive adhesive sheet is suitable for use in bonding optical members. Specifically, the pressure-sensitive adhesive sheet is suitable for use in bonding members constituting a display, particularly members used in manufacturing a display, and is suitable for use as a pressure-sensitive adhesive sheet for bonding an image display device component such as an image display panel and a protective panel or touch panel disposed on the front side (viewing side) of the image display panel, or a component constituting the image display device component. The image display device components can be the same as those described below.

[0169] <<Laminate for image display device>> A laminate for an image display device according to one example of an embodiment of the present invention (hereinafter, sometimes referred to as "the present laminate for an image display device") is a laminate for an image display device having a configuration in which two components of the image display device are laminated with the present pressure-sensitive adhesive sheet interposed therebetween. The present laminate for an image display device is preferably a laminate for an image display device having a configuration in which two components of the image display device are laminated with the present pressure-sensitive adhesive sheet interposed therebetween.

[0170] Of the components of the laminate for an image display device, the pressure-sensitive adhesive sheet has been described above, and the components other than the pressure-sensitive adhesive sheet will be described below.

[0171] <Image display device components> Examples of image display device components that make up the present laminate for image display devices include flat panel image display device components, curved image display device components, and flexible image display device components. Examples of such image display device components include image display panels such as liquid crystal displays and organic electroluminescence (EL) displays, surface protection panels (surface protection films), polarizing plates, polarizing elements, retardation films, color filters, barrier films, viewing angle compensation films, brightness enhancement films, contrast enhancement films, diffusion films, semi-transparent reflective films, electrode films, transparent conductive films, metal mesh films, and touch sensor films. Any one of these may be used alone or in combination. Examples include a surface protection panel combined with other image display device components, or a surface protection panel combined with other image display device components.

[0172] It is preferable that one of the two image display device components is a surface protection panel, and the other is a component consisting of one or a combination of two or more components selected from the group consisting of a touch sensor film, an image display panel, a color filter, a polarizing element, and a retardation film, and it is more preferable that the surface protection panel has a frame-shaped concealing portion on its periphery, and the frame has a portion with a width of 3 mm or less. With this configuration, the effects of the present invention can be particularly enjoyed.

[0173] <Method of manufacturing the laminate for the image display device> The method for manufacturing the present laminate for an image display device is not particularly limited, and as described above, for example, the resin composition may be applied to a component of the image display device to form an adhesive sheet, or an adhesive sheet with a release film may be formed in advance and then laminated to the component of the image display device.

[0174] <<Image display devices>> An image display device according to an embodiment of the present invention (hereinafter, sometimes referred to as "the image display device") is an image display device incorporating a laminate for an image display device having a configuration in which two components of the image display device are bonded together via the pressure-sensitive adhesive sheet. For example, there can be mentioned an image display device having a structure in which a laminate for an image display device having a configuration in which two components of the image display device are bonded together via the pressure-sensitive adhesive sheet is combined with other components of the image display device. In this case, examples of "other components of the image display device" include FPC cables, reflective sheets, light guide plates and light sources, diffusion films, prism sheets, liquid crystal panels, organic EL panels, anti-reflection films, color filters, polarizing plates, retardation plates, glass substrates, surface protection films, and composites of these components. Specific examples of the image display device include liquid crystal displays, organic EL displays, inorganic EL displays, electronic paper, plasma displays, and microelectromechanical system (MEMS) displays used in personal computers, mobile terminals, game consoles, televisions (TVs), car navigation systems, touch panels, pen tablets, etc. [Example]

[0175] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0176] <<Various evaluation conditions>> The pressure-sensitive adhesive sheets with release films prepared in Examples 1 to 5 and Comparative Example 1 described below were used to carry out the following various evaluations.

[0177] [Holding force] The pressure-sensitive adhesive sheets with release films prepared in the Examples and Comparative Examples were cut to 40 mm × 100 mm, the release film on one side was removed, and a PET film (Diafoil S-100, manufactured by Mitsubishi Chemical Corporation, thickness 50 μm) was attached as a backing film using a hand roller. This was then cut into strips 20 mm wide × 100 mm long to prepare test specimens. Next, the remaining release film was peeled off, and one end of the specimen in the longitudinal direction was attached to a SUS plate (120 mm × 50 mm × 1.2 mm thick) with a hand roller so that the adhesion area was 20 mm × 20 mm. Next, the test piece was cured for 15 minutes in an atmosphere of 70°C, and a 500 g weight was attached vertically to the other end of the test piece (the unattached part). After leaving it for 24 hours, the length (mm) of the downward shift of the adhesion position between the SUS plate and the backing PET film was measured.

[0178] [Shear storage modulus (G') at 25°C] The release film on one side of the pressure-sensitive adhesive sheets with release film produced in the Examples and Comparative Examples was removed, and the sheets were repeatedly laminated with a hand roller to a thickness of approximately 0.8 mm, and then punched out into 8 mm diameter circles to prepare samples. The resulting samples were placed in a rheometer (TA Instruments "DHR-2") and subjected to dynamic viscoelasticity measurements under the following conditions: measurement jig: 8 mm diameter parallel plates, frequency: 1 Hz, measurement temperature: -50 to 150°C, and heating rate: 5°C / min, and the shear storage modulus (G') at 25°C was read.

[0179] [Glass transition temperature] The release film on one side of the pressure-sensitive adhesive sheets with release film prepared in the Examples and Comparative Examples was removed, and the sheets were repeatedly laminated with a hand roller to a thickness of approximately 0.8 mm, and then punched out into 8 mm diameter circles to prepare samples. The resulting samples were placed in a rheometer (TA Instruments "DHR-2") and subjected to dynamic viscoelasticity measurements under the following conditions: measurement jig: 8 mm diameter parallel plates, frequency: 1 Hz, measurement temperature: -50 to 150°C, and heating rate: 5°C / min. The glass transition temperature (Tg), defined as the maximum value of Tan δ obtained by dynamic viscoelasticity measurements in shear mode at a frequency of 1 Hz, was then determined.

[0180] [Stress relaxation rate] The release film on one side of the adhesive sheets with release film produced in the examples and comparative examples was removed, and the sheets were repeatedly laminated with a hand roller to adjust the thickness to approximately 0.8 mm, and then punched out into a circle with a diameter of 25 mm to prepare a sample. A 25% strain was applied to the obtained sample using a viscoelasticity measuring device (TA Instruments "DHR2"), and the storage modulus after 0.1 seconds was measured as the initial modulus (G'(0)). A 25% strain was also applied to the sample at 70°C, and the storage modulus after 300 seconds was measured as the relaxation modulus (G'(300)). The values ​​of the initial modulus (G'(0)) and the relaxation modulus (G'(300)) were substituted into the following formula (I) to determine the stress relaxation rate (X). Stress relaxation rate (X)=(G'(300) / G'(0))...(I)

[0181] [Creep strain] The release film was removed from each of the pressure-sensitive adhesive sheet laminates produced in the Examples and Comparative Examples. Multiple layers of the sheet were laminated to form a laminate with a thickness of 1.0 mm. A cylindrical body with a diameter of 8 mm (height of 1.0 mm) was punched out from the obtained laminate of adhesive sheets (adhesive layers), and this was used as a sample. The creep strain (Y0) of the sample was measured using a viscoelasticity measuring device (manufactured by TA Instruments, product name "DHR2") under the following measurement conditions. That is, the creep strain (Y0) [%] was calculated from the strain value when a shear stress of 10 kPa was applied for 175 seconds at a temperature of 25°C using the following formula. Creep strain [%] = (strain value when shear stress is applied for 175 seconds / thickness of adhesive sheet (adhesive layer)) x 100

[0182] [Recovery rate] The recovery rate is the creep strain value (Y 175 ) and the strain after 175 seconds (Y 175 ) [%] was calculated. Strain after 175 seconds (Y0) [%] = (strain value 175 seconds after releasing shear stress / thickness of adhesive sheet (adhesive layer)) × 100 Then, the creep strain (Y0) [%] and the strain after 175 seconds (Y 175 ) [%], the recovery rate [%] was calculated using the following formula. Recovery rate [%]=[{(Y0)-Y(Y 175 )} / (Y0)]×100

[0183] [Adhesive strength] (Sample production) The release film on one side of the adhesive sheets with release film prepared in the Examples and Comparative Examples was removed, and a PET film (Cosmoshine A4300, manufactured by Toyobo Co., Ltd., 100 μm thick) was applied as a backing film using a hand roller. This was cut into strips 10 mm wide x 150 mm long, and the remaining release film was peeled off, revealing the adhesive sheet surface, which was then applied to the surface of soda-lime glass using a hand roller. The resulting laminate was autoclaved (60°C, gauge pressure 0.2 MPa, 20 minutes) for finish application to prepare a sample for adhesive strength measurement. (Adhesion measurement) The obtained adhesive strength measurement sample was pulled at an angle of 180° at a peeling rate of 60 mm / min under conditions of 23°C and 50% RH, and the adhesive sheet together with the backing film was peeled off from the soda lime glass, and the tensile strength (N / cm) was measured with a load cell to determine the adhesive strength. When evaluating the adhesive strength of the cured adhesive sheet, after preparing the sample, the adhesive sheet was irradiated with light through the backing film to cure the adhesive sheet, and then the adhesive strength was measured.

[0184] [Total light transmittance and haze value] (Sample production) The adhesive sheets with release films prepared in the examples and comparative examples were cut to a length of 100 mm and a width of 70 mm, and then the release films were peeled off one by one. Soda lime glass (82 mm x 53 mm x 0.5 mm thick) was roll-laminated to both the front and back sides of the adhesive sheet, and any excess double-sided adhesive sheet protruding from the glass was cut off. The laminated product was then autoclaved (60°C, gauge pressure 0.2 MPa, 20 minutes) to prepare a sample for measuring optical properties.

[0185] (Measurement of total light transmittance and haze value) The haze value was measured based on JIS K7136:2000. That is, the diffuse transmittance and total luminous transmittance were measured using a haze meter photometer ("HAZE METER NDH-5000" manufactured by Nippon Denshoku Kogyo Co., Ltd.). The haze value was calculated by substituting the obtained diffuse transmittance (DT) and total luminous transmittance (TT) values ​​into the following formula. [Formula] Haze value = (DT / TT) x 100 [%]

[0186] [Chromaticity] The optical property measurement samples prepared for total light transmittance and haze value were used, and a simultaneous photometric spectrophotometer ("SC-P" manufactured by Suga Test Instruments Co., Ltd.) was used. * a * b * Lightness L defined by the color system * , chromaticity a * and chromaticity b * was measured.

[0187] [Gel fraction] For the adhesive sheets with release film prepared in the Examples and Comparative Examples, approximately 0.1 g of adhesive sheet pieces were collected from the adhesive sheets after peeling off the release film. The collected adhesive sheet pieces were wrapped in a SUS mesh (#150) bag with a mass (X) and the bag was closed to prepare a sample, and the mass (Y) of the sample was measured. The sample was immersed in ethyl acetate and stored in a dark place at 23°C for 24 hours, then removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate, and the mass (Z) of the dried sample was measured. The gel fraction was calculated from each measured mass using the following formula: Gel fraction (%) = [(ZX) / (YX)] × 100

[0188] [Various evaluations of adhesive sheets after curing] The pressure-sensitive adhesive sheets with release films prepared in the examples and comparative examples, or the evaluation samples described below, were irradiated with active energy rays having a wavelength of 365 nm at an integrated light intensity of 3000 mJ / cm using a metal halide lamp. 2 The pressure-sensitive adhesive sheet was irradiated with light through a release film or a backing film so as to cure the pressure-sensitive adhesive sheet, or a sample for evaluation after curing was prepared. To evaluate the storage shear modulus (G') at 25°C, glass transition temperature, stress relaxation rate, gel fraction, creep strain, and recovery rate, the adhesive sheet with release film was cured and then samples for measuring various items were prepared and evaluated. In the evaluation of adhesive strength, total light transmittance, haze value, and chromaticity, a sample for measurement was prepared, cured by irradiating light, and then adhesive strength was measured. For holding power, shear storage modulus (G') at 25°C, glass transition temperature, stress relaxation rate, creep strain, recovery rate, and gel fraction, the adhesive sheet with release film was cured by light irradiation and then an evaluation sample was prepared.

[0189] Prior to the examples, the following raw materials were prepared.

[0190] <Polymer (A)> (A-1): In a 2L flask equipped with a condenser, 40.0 parts of ethyl acetate (boiling point 77 ° C.) was added as a polymerization solvent, 0.01 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN) as a polymerization initiator, 5.5 parts of 2-ethylhexyl acrylate (2EHA), 2.5 parts of methyl acrylate (MA), 1.5 parts of N,N-dimethylacrylamide (DMAA), and 0.5 parts of methyl methacrylate (MMA). The mixture was heated to reflux in the flask, and then 10 parts of ethyl acetate, 0.17 parts of ADVN, 49.5 parts of 2EHA, 22.5 parts of MA, 13.5 parts of DMAA, and 4.5 parts of MMA were added dropwise over 3 hours. After 45 minutes of addition, 12 parts of ethyl acetate and 0.13 parts of ADVN were added dropwise over 1 hour, followed by a 3.2-hour reaction to obtain a solution of acrylic resin (A-1). The polymerization solvent was then degassed to obtain acrylic resin (A-1). The weight-average molecular weight (Mw) of the acrylic resin (A-1) was 400,000, the polydispersity index (PDI) was 3.9, and the glass transition temperature based on dynamic viscoelasticity was 2°C.

[0191] <Crosslinking agent (B)> (B-1): Polypropylene glycol diacrylate (bifunctional, "APG400" manufactured by Shin-Nakamura Chemical Co., Ltd.) (B-2): Pentaerythritol triacrylate and tetraacrylate mixture (3-4 functional groups, "ATMM3L" manufactured by Shin-Nakamura Chemical Co., Ltd.) (B-3): Dipentaerythritol polyacrylate (5-6 functional groups, "A9550" manufactured by Shin-Nakamura Chemical Co., Ltd.) (B-4): Urethane acrylate (hexafunctional, Asia Industries Co., Ltd. "RUA-071") (B-5): A mixture of tripentaerythritol acrylate, mono- and dipentaerythritol acrylate, and polypentaerythritol acrylate (6 to 10 functional groups, "Viscoat #802" manufactured by Osaka Organic Chemical Industry Co., Ltd.) (B-6): Urethane acrylate (10 functional groups, Asia Industries Co., Ltd. "RUA-066VE") <Polymerization initiator (C)> (C-1): Methyl benzoyl formate (IGM "Omnirad MBF") (C-2): 4-Metharyloyloxybenzophenone ("MBP" manufactured by Shinryo Corporation)

[0192] <Other ingredients (D)> (D-1) Silane coupling agent: 3-glycidyloxypropyltrimethoxysilane (Shin-Etsu Chemical "KBM403" manufactured by

[0193] Example 1 A resin composition was prepared by uniformly mixing 100 parts by mass of polymer (A-1), 1.5 parts by mass of crosslinking agent (B-2), 1.05 parts by mass of polymerization initiator (C-1), 0.45 parts by mass of polymerization initiator (C-2), and 0.2 parts by mass of silane coupling agent.

[0194] Next, the resin composition was spread in a sheet shape to a thickness of 150 μm on a silicone release-treated release film (PET film manufactured by Mitsubishi Chemical Corporation) having a thickness of 100 μm, and a silicone release-treated release film (PET film manufactured by Mitsubishi Chemical Corporation) having a thickness of 75 μm was laminated on the sheet-like resin composition. Then, using a high-pressure mercury lamp, the integrated light intensity of the wavelength of 365 nm was 1250 mJ / cm 2 Both surfaces of the sheet-shaped resin composition were irradiated with active energy rays through the release film to pre-cure, thereby obtaining a pressure-sensitive adhesive sheet with a release film consisting of release film / pressure-sensitive adhesive sheet / release film. The pressure-sensitive adhesive sheet of Example 1 was an active energy ray-curable pressure-sensitive adhesive sheet that was cured by irradiation with active energy rays.

[0195] <Examples 2 to 5 and Comparative Example 1> A pressure-sensitive adhesive sheet with a release film was prepared in the same manner as in Example 1, except that the formulation and integrated light amount were changed as shown in Table 1 below. Similarly to Example 1, the pressure-sensitive adhesive sheets of Examples 2 to 5 and Comparative Example 1 were pressure-sensitive adhesive sheets having active energy ray curability, that is, pressure-sensitive adhesive sheets that are cured by irradiation with active energy rays.

[0196] [Table 1]

[0197] [Physical property measurement and evaluation] The pressure-sensitive adhesive sheets produced in the examples and comparative examples were subjected to the measurements and evaluations of the various properties described above. The evaluation results of the pressure-sensitive adhesive sheets are shown in Table 2 below. In addition, the integrated light intensity was further increased to 3000 mJ / cm for the adhesive sheets produced in the examples and comparative examples. 2 The various properties were measured and evaluated when the resin was irradiated with ultraviolet light so that the cured product was cured. The evaluation results after curing are shown in Table 3 below.

[0198] [Table 2]

[0199] [Table 3]

[0200] As can be seen from Tables 2 and 3, all of the pressure-sensitive adhesive sheets of Examples 1 to 5 had sufficient adhesive strength, with an adhesive strength of 10 N / cm or more before curing. Furthermore, all of the pressure-sensitive adhesive sheets of the Examples had a holding strength of 1 mm or less, indicating excellent shape stability. Furthermore, the pressure-sensitive adhesive sheets of Examples 1 to 5 all had a shear storage modulus (G1' (25°C) after curing of 150 kPa or more, and a stress relaxation modulus (X1) that was also equal to or greater than that of the comparative example, demonstrating that they had excellent resistance to deformation due to stress. Furthermore, the adhesive sheets of the examples are superior to those of Comparative Example 1 in creep strain and have a good recovery rate, and therefore are found to have good resistance to deformation due to long-term stress. Furthermore, all of the pressure-sensitive adhesive sheets of the examples had a chromaticity of b * was less than 0.5.

[0201] As described above, according to the present invention, it is possible to provide an adhesive sheet having good bonding reliability at the peripheral edge and durability after curing, an adhesive sheet with a release film, a laminate for an image display device, an image display device, and an adhesive sheet for a component of an image display device. [Industrial Applicability]

[0202] The pressure-sensitive adhesive sheet of the present invention has excellent lamination properties and can be laminated without air bubbles up to the peripheral edge near the edge of the pressure-sensitive adhesive sheet, and therefore can be suitably used as a pressure-sensitive adhesive sheet for image display devices, particularly image display devices with narrow frame designs or frameless designs. Furthermore, since the adhesive sheet of the present invention has good resistance to deformation due to stress after curing, it is possible to provide a laminate for an image display device, an image display device, and an adhesive sheet for a component of an image display device that exhibit excellent durability against dents and indentations when subjected to repeated use or impacts such as being dropped.

Claims

1. A pressure-sensitive adhesive sheet comprising a cured product of a resin composition containing a polymer (A) and a crosslinking agent (B), The polymer (A) contains a polymer in which 50 mass% or more of monomer components are compounds having a (meth)acryloyl group, The crosslinking agent (B) contains 50% by mass or more of a trifunctional or higher functional crosslinking agent, The pressure-sensitive adhesive sheet, wherein the content of the crosslinking agent (B) in the resin composition is 10 parts by mass or less per 100 parts by mass of the polymer (A).

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive sheet has a gel fraction of 30% or more and 80% or less.

3. The pressure-sensitive adhesive sheet according to claim 1 , wherein the resin composition further contains a polymerization initiator (C).

4. The pressure-sensitive adhesive sheet according to claim 3 , wherein the content of the polymerization initiator (C) is 10 parts by mass or less relative to 100 parts by mass of the polymer (A).

5. The pressure-sensitive adhesive sheet was subjected to a strain of 25% at a temperature of 70°C, and the initial elastic modulus (G 0 '(0)) and the relaxation modulus (G 0 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the stress relaxation rate (X0) calculated from the tensile strength (Tg) of the sheet (300) by the following formula (I) is 0.20 or less: Stress relaxation rate (X0) = (G 0 '(300) / G 0 '(0))...(I)

6. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the glass transition temperature (Tg) defined as the maximum value of Tan δ obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is −25° C. or higher.

7. The pressure-sensitive adhesive sheet according to claim 1 , which is curable with active energy rays.

8. The pressure-sensitive adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm in an integrated light amount of 2000 to 4000 mJ / cm 2 When irradiated so as to be 1 The pressure-sensitive adhesive sheet according to claim 7, wherein the value of tensile strength (MPa) is 150 kPa or more.

9. The pressure-sensitive adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm in an integrated light amount of 2000 to 4000 mJ / cm 2 When irradiated so as to obtain the initial elastic modulus (G 1 '(0)) and the relaxation modulus (G 1 8. The pressure-sensitive adhesive sheet according to claim 7, wherein the stress relaxation rate (X1) after curing calculated from the above-mentioned formula (II) is 0.22 or more: Stress relaxation rate after curing (X1) = (G 1 '(300) / G 1 '(0))...(II)

10. The pressure-sensitive adhesive sheet according to claim 9, wherein the difference (X1-X0) between the stress relaxation rate (X1) after curing and the stress relaxation rate (X0) is 0.01 or more.

11. A pressure-sensitive adhesive sheet with a release film, comprising the pressure-sensitive adhesive sheet according to claim 1 and a release film laminated on the pressure-sensitive adhesive sheet.

12. A laminate for an image display device comprising two image display device components and the adhesive sheet according to claim 1 interposed between the two image display device components, wherein one of the two image display device components is a surface protection panel and the other is a member consisting of any one or a combination of two or more members selected from the group consisting of a touch sensor film, an image display panel, a color filter, a polarizing element and a retardation film.

13. 13. The laminate for an image display device according to claim 12, wherein the surface protection panel has a frame-shaped concealing portion on its periphery, and the frame has a portion with a width of 3 mm or less.

14. The laminate for an image display device according to claim 12 , wherein the surface protection panel has a curved shape.

15. An image display device comprising the laminate for an image display device according to claim 12 or 14.

16. A pressure-sensitive adhesive sheet for use as a component of an image display device, comprising the pressure-sensitive adhesive sheet according to claim 1.

Images