Active energy ray-curable adhesive sheet, adhesive sheet with release film, laminate for image display device, image display device, active energy ray-curable adhesive sheet for image display device constituent member, and method for producing active energy ray-curable adhesive sheet

Abstract

To provide an adhesive sheet excellent in adhesive force and mechanical strength.SOLUTION: An active energy ray-curable adhesive sheet is formed from an adhesive composition containing a (meth)acrylic polymer (A), a radically polymerizable compound (B), and a photopolymerization initiator (C). The radically polymerizable compound (B) contains a monofunctional (meth)acrylate (b1) whose homopolymer has a glass transition temperature (Tg) of 0°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable adhesive sheet, an adhesive sheet with a release film, a laminate for an image display device, an image display device, and a method for producing an active energy ray-curable adhesive sheet for a component of an image display device, and more particularly to an active energy ray-curable adhesive sheet, an adhesive sheet with a release film, a laminate for an image display device, an image display device, and a method for producing an active energy ray-curable adhesive sheet for a component of an image display device, which are excellent in both adhesive strength and mechanical strength. [Background technology]

[0002] Image display devices such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs), as well as input devices used in combination with image display devices such as touch panels, are widely used. In the manufacture of these image display devices and input devices, transparent pressure-sensitive adhesive sheets are used to bond optical members, and transparent pressure-sensitive adhesive sheets are also used to bond the image display devices and input devices.

[0003] For example, Patent Document 1 discloses a method for manufacturing a laminate for forming an image display device, which has a configuration in which image display device components are laminated on at least one side of a transparent double-sided adhesive sheet, in which two image display device components are laminated via a photocurable adhesive sheet that has been primarily crosslinked by ultraviolet irradiation, and then the photocurable adhesive sheet is irradiated with ultraviolet light via the image display device components to cause secondary crosslinking and hardening.

[0004] Furthermore, Patent Document 2 discloses that by forming a pressure-sensitive adhesive sheet from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A), a compound (B) having in its molecule a radically polymerizable functional group having a carbon-carbon double bond and a radical-generating group, and an initiator (C) consisting of a compound other than said compound (B), cohesive strength is improved, and reliability and metal corrosion are improved by not generating acid. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 32995 [Patent Document 2] JP 2020-76100 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the adhesive sheets disclosed in Patent Documents 1 and 2 have improved conformability to members having irregularities, in recent years there has been a demand for further improvement in adhesive strength to optical members such as glass. On the other hand, pressure-sensitive adhesive sheets are also required to have mechanical strength from the viewpoint of reliability during production, transportation, and mounting.

[0007] Under these circumstances, an object of the present invention is to provide a pressure-sensitive adhesive sheet that is excellent in adhesive strength and mechanical strength. [Means for solving the problem]

[0008] In view of these circumstances, the present inventors have discovered that an active energy ray-curable adhesive sheet formed from an adhesive composition containing a (meth)acrylic polymer (A), a radically polymerizable compound (B), and a photopolymerization initiator (C), in which the active energy ray-curable adhesive sheet is excellent in adhesive strength and mechanical strength by using, as the radically polymerizable compound (B), a monofunctional (meth)acrylate (b1) having a relatively high glass transition temperature (Tg) when made into a homopolymer, and have completed the present invention.

[0009] That is, the present invention has the following aspects. [1] An active energy ray-curable pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A), a radical-polymerizable compound (B), and a photopolymerization initiator (C), The active energy ray-curable adhesive sheet, wherein the radical polymerizable compound (B) contains a monofunctional (meth)acrylate (b1) having a glass transition temperature (Tg) of 0°C or higher when made into a homopolymer. [2] The active energy ray-curable adhesive sheet according to [1], wherein the monofunctional (meth)acrylate (b1) has a branched structure and / or a cyclic structure. [3] The active energy ray-curable adhesive sheet according to [1] or [2], wherein the boiling point of the monofunctional (meth)acrylate (b1) is 150 to 350°C. [4] The active energy ray-curable adhesive sheet according to any one of [1] to [3], wherein the content of the radical polymerizable compound (B) is 0.5 to 30 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A). [5] The active energy ray-curable adhesive sheet according to any one of [1] to [4], wherein the content of the monofunctional (meth)acrylate (b1) is 40 mass % or more relative to the radical polymerizable compound (B). [6] The active energy ray-curable adhesive sheet according to any one of [1] to [5], wherein the photopolymerization initiator (C) comprises a hydrogen abstraction photopolymerization initiator (c1). [7] The active energy ray-curable adhesive sheet according to any one of [1] to [6], wherein the photopolymerization initiator (C) comprises a hydrogen abstraction type photopolymerization initiator (c1) and a cleavage type photopolymerization initiator (c2). [8] The active energy ray-curable adhesive sheet according to any one of [1] to [7], wherein the content of the photopolymerization initiator (C) is 0.1 to 10 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A). [9] The active energy ray-curable adhesive sheet according to [7], wherein the content ratio (c1 / c2) of the hydrogen abstraction photopolymerization initiator (c1) to the cleavage photopolymerization initiator (c2) is 0.1 to 30.

[10] The active energy ray-curable adhesive sheet according to any one of [1] to [9], wherein the (meth)acrylic polymer (A) is an acrylic polymer having a structural moiety derived from a (meth)acrylate (a1) having an alkyl group with 1 to 15 carbon atoms in the alkyl group, and a structural moiety derived from a polar group-containing monomer (a2).

[11] The active energy ray-curable adhesive sheet according to any one of [1] to

[10] , which has a shear storage modulus (G'(25°C)) of 100 to 800 kPa, as determined by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz.

[12] The active energy ray-curable adhesive sheet according to any one of [1] to

[11] , wherein the active energy ray-curable adhesive sheet has a gel fraction of 30 to 95%.

[13] The active energy ray-curable adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm at an integrated light dose of 2000 to 5000 mJ / cm 2 The active energy ray-curable adhesive sheet according to any one of [1] to

[12] , wherein the adhesive strength to glass at 60°C (P2(60°C)) is 3.5 N / cm or more when irradiated with any irradiation amount within the range.

[14] The active energy ray-curable adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm in an integrated light amount of 2000 to 5000 mJ / cm 2 The active energy ray-curable adhesive sheet according to any one of [1] to

[13] , wherein the ratio (P2(23°C) / P2(60°C)) of the adhesive strength to glass at 23°C (P2(23°C)) to the adhesive strength to glass at 60°C (P2(60°C)) when irradiated with an irradiation amount within the range of

[15] The adhesive strength of the active energy ray-curable adhesive sheet to glass at 60°C (P1(60°C)) is determined by applying an active energy ray having a wavelength of 365 nm to the adhesive sheet in an amount of 2000 to 5000 mJ / cm. 2 The active energy ray-curable adhesive sheet according to any one of [1] to

[14] , wherein the ratio (P2(60°C) / P1(60°C)) of adhesive strength to glass at 60°C (P2(60°C)) when irradiated with any irradiation amount within the range of

[16] The active energy ray-curable adhesive sheet according to any one of [1] to

[15] , which has a strength of 0.2 to 2.5 MPa at 500% elongation measured at a speed of 300 mm / sec in accordance with JIS K 7127.

[17] A pressure-sensitive adhesive sheet with a release film, comprising the active energy ray-curable pressure-sensitive adhesive sheet according to any one of [1] to

[16] and a release film laminated together.

[18] A laminate for an image display device, comprising two image display device components laminated together via the active energy ray-curable adhesive sheet according to any one of [1] to

[16] .

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

[18] .

[20] An active energy ray-curable adhesive sheet for use as a component of an image display device, comprising the active energy ray-curable adhesive sheet according to any one of [1] to

[16] .

[21] A method for producing an active energy ray-curable adhesive sheet according to any one of [1] to

[16] , which comprises curing an adhesive composition containing a (meth)acrylic polymer (A), a radical polymerizable compound (B), and a photopolymerization initiator (C) by irradiation with active energy rays. [Effects of the Invention]

[0010] The active energy ray-curable adhesive sheet of the present invention is excellent in adhesive strength and mechanical strength. In particular, the active energy ray-curable adhesive sheet is excellent in mechanical strength and adhesive strength after being irradiated with active energy rays after being attached to an optical member. Therefore, the active energy ray-curable adhesive sheet of the present invention can be suitably used as an adhesive sheet for an image display device. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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 this specification, 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.

[0012] 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 this specification, "(meth)acrylic" refers to a comprehensive definition of acrylic and methacrylic, "(meth)acrylate" refers to a comprehensive definition of acrylate and methacrylate, and "(meth)acryloyl" refers to a comprehensive definition of acryloyl and methacryloyl. In addition, in this specification, the term "main component" means a component that has a significant effect on the properties of the material, and the content of the component is usually 40% by mass or more of the entire material, preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. In addition, with respect to the numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in one stage can be arbitrarily combined with the upper or lower limit of a numerical range in another stage. Furthermore, 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.

[0013] An active energy ray-curable adhesive sheet according to one embodiment of the present invention (hereinafter, sometimes abbreviated as "the adhesive sheet") is an active energy ray-curable adhesive sheet formed from an adhesive composition containing a (meth)acrylic polymer (A), a radically polymerizable compound (B), and a photopolymerization initiator (C), wherein the radically polymerizable compound (B) contains a monofunctional (meth)acrylate (b1) having a glass transition temperature (Tg) of 0°C or higher when made into a homopolymer. The adhesive sheet is prepared by irradiating an adhesive composition containing a (meth)acrylic polymer (A), a radically polymerizable compound (B) containing a monofunctional (meth)acrylate (b1) having a glass transition temperature (Tg) of 0°C or higher when made into a homopolymer, and a photopolymerization initiator (C) with active energy rays, thereby polymerizing the radically polymerizable compound (B) to form a polymer. Typically, to increase the adhesive strength of a pressure-sensitive adhesive sheet, a (meth)acrylic polymer with a low glass transition temperature (Tg) is used. However, using a (meth)acrylic polymer with a low glass transition temperature (Tg) reduces the mechanical strength. Therefore, to increase the mechanical strength, a (meth)acrylic polymer with a high glass transition temperature (Tg) may be used, but this reduces the adhesive strength, making it difficult to produce a pressure-sensitive adhesive sheet with an excellent balance between adhesive strength and mechanical strength. Therefore, in the present invention, it has been discovered that by incorporating into the radically polymerizable compound (B) a monofunctional (meth)acrylate (b1) that has a glass transition temperature (Tg) of 0°C or higher when made into a homopolymer and using this to make an adhesive sheet, the glass transition temperature (Tg) of the sheet does not unexpectedly become high, and the adhesive force and mechanical strength are excellent. The present pressure-sensitive adhesive sheet will now be described.

[0014] <This adhesive sheet> The pressure-sensitive adhesive sheet has an acrylic pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A). In particular, it is preferred that the (meth)acrylic polymer (A) is used as the main component of the base polymer in the acrylic pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition further contains a radically polymerizable compound (B) and a photopolymerization initiator (C). Furthermore, the pressure-sensitive adhesive composition may further contain other components in addition to the (meth)acrylic polymer (A), the radically polymerizable compound (B), and the photopolymerization initiator (C). The pressure-sensitive adhesive sheet is typically a cured pressure-sensitive adhesive composition. Each component contained in the pressure-sensitive adhesive composition will be described in detail below.

[0015] [(Meth)acrylic polymer (A)] Examples of the (meth)acrylic polymer (A) include a homopolymer of alkyl (meth)acrylate, as well as a copolymer obtained by polymerizing a monomer component copolymerizable therewith. In particular, it is preferable that at least one copolymerization component of the (meth)acrylic polymer (A) has a structural moiety derived from a (meth)acrylate (a1) having an alkyl group with 1 to 15 carbon atoms, and it is more preferable that the (meth)acrylic polymer (A) further has a structural moiety derived from a polar group-containing monomer (a2).

[0016] [(Meth)acrylate (a1) having an alkyl group with 1 to 15 carbon atoms] The alkyl(meth)acrylate (a1) is a linear or branched alkyl(meth)acrylate in which the alkyl group has 1 to 15 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 1 to 15 carbon atoms.

[0017] Examples of the alkyl(meth)acrylate represented by the formula (Chemical Formula 1) include linear alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, 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. ) acrylate; branched alkyl (meth)acrylates such as 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, 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 can be mentioned. These may be used alone or in combination of two or more.

[0018] Among these, linear alkyl (meth)acrylates are preferred from the viewpoint of obtaining flexibility. Furthermore, from the viewpoint of balancing adhesion and flexibility, linear alkyl (meth)acrylates having an alkyl group of 1 to 15 carbon atoms, more preferably 1 to 12, particularly preferably 1 to 9, and especially preferably 1 to 6 carbon atoms are preferred, and examples thereof include 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.

[0019] Among these, branched alkyl(meth)acrylates, i.e., alkyl(meth)acrylates containing a tertiary carbon atom or a quaternary carbon atom in the alkyl group, are preferred because they are more likely to undergo a hydrogen abstraction reaction (described later) upon irradiation with active energy rays, thereby efficiently forming a crosslinked structure. Among these, branched alkyl (meth)acrylates in which the alkyl group has 1 to 15 carbon atoms, more preferably 3 to 13, particularly preferably 5 to 11, and especially preferably 6 to 9 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.

[0020] The proportion of the alkyl (meth)acrylate (a1)-derived structural units relative to the (meth)acrylic polymer (A) is typically 5 to 99% by mass, preferably 30 to 97% by mass, and more preferably 50 to 95% by mass. When the proportion of the alkyl (meth)acrylate (a1)-derived structural units is at or above the lower limit, flexibility tends to be excellent, and conformability to unevenness when the adherend has unevenness tends to be excellent. When the proportion is at or below the upper limit, the effects of the copolymerizable monomer described below are easily obtained, and adhesive strength and cohesive strength tend to be excellent.

[0021] The (meth)acrylic polymer (A) preferably further contains a structural unit derived from a polar group-containing monomer (a2). By containing the structural unit derived from the polar group-containing monomer (a2), the adhesive strength of the pressure-sensitive adhesive sheet to an adherend tends to be improved.

[0022] [Polar group-containing monomer (a2)] Examples of the polar group-containing monomer (a2) include hydroxyl group-containing monomers, carboxyl group-containing monomers, and nitrogen-containing monomers. These may be contained alone or in combination of two or more as structural units in the (meth)acrylic polymer (A). Among these, hydroxyl group-containing monomers and amino group-containing monomers are preferred because they provide excellent adhesive strength to the adhesive sheet.

[0023] (Hydroxyl group-containing monomer) Examples of the hydroxyl group-containing monomer 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 polyoxypropylene glycol; Examples of the hydroxyl group-containing (meth)acrylate include (meth)acrylates having an oxyalkylene structure such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, primary hydroxyl group-containing (meth)acrylates such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, and 4-hydroxyphenyl methacrylate, secondary 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 acrylic polymer (A) has a structural moiety derived from a hydroxyl group-containing monomer, the adhesive strength of the pressure-sensitive adhesive sheet tends to be improved.

[0024] Among the hydroxyl group-containing monomers, preferred are hydroxyalkyl (meth)acrylates having a hydroxyalkyl group having 1 to 10 carbon atoms, more preferably 1 to 6, and particularly preferably 2 to 4 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether, and particularly preferred are primary hydroxyl group-containing (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate.

[0025] When the (meth)acrylic polymer (A) has a structural unit derived from a hydroxyl group-containing monomer, the content thereof is usually 0.1 to 30 mass%, preferably 1 to 30 mass%, more preferably 3 to 25 mass%, particularly preferably 5 to 20 mass%, and even more preferably 7 to 15 mass%, based on the (meth)acrylic polymer (A).

[0026] (Nitrogen-containing monomers) Examples of the nitrogen-containing monomer include amino group-containing monomers, amide group-containing monomers, and isocyanate group-containing monomers. These may be used alone or in combination of two or more. When the (meth)acrylic polymer (A) has a structural moiety derived from the nitrogen-containing monomer, the cohesive strength of the pressure-sensitive adhesive sheet tends to be improved. Furthermore, when a hydrogen abstraction photopolymerization initiator described below is used, the nitrogen-containing monomer has the effect of promoting a hydrogen abstraction reaction.

[0027] 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; N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylacetamides, and N-vinylcaprolactam.

[0028] 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.

[0029] 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.

[0030] Among these, those having a tertiary nitrogen atom are preferred, from the viewpoint of having a sensitizing effect on the hydrogen abstraction reaction by the hydrogen abstraction photopolymerization initiator described below, and as a result, being able to efficiently form a crosslinked structure. Tertiary amino group-containing (meth)acrylate, N,N-dialkyl(meth)acrylamide, N-vinylpyrrolidone, acryloylmorpholine, etc. are more preferred, and N-vinylpyrrolidone is particularly preferred.

[0031] When the (meth)acrylic polymer (A) has a structural unit derived from a nitrogen-containing monomer, the content thereof is usually 0.1 to 15 mass%, preferably 0.5 to 13 mass%, particularly preferably 1 to 10 mass%, and especially preferably 2 to 9 mass%, relative to the (meth)acrylic polymer (A), from the viewpoint of imparting cohesive strength and resistance to wet heat whitening.

[0032] (Carboxy group-containing monomer) Examples of the carboxyl group-containing monomer include (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, and itaconic acid. These may be used alone or in combination of two or more.

[0033] When the (meth)acrylic polymer (A) has a structural unit derived from a carboxy group-containing monomer, the content thereof is usually 0.1 to 15 mass%, preferably 0.3 to 13 mass%, more preferably 0.5 to 10 mass%, and particularly preferably 1 to 6 mass%, relative to the (meth)acrylic polymer (A).

[0034] The content of the structural unit derived from the polar group-containing monomer (a2) in the (meth)acrylic polymer (A) is usually 0.1 to 30 mass%, preferably 0.3 to 25 mass%, more preferably 0.5 to 20 mass%, and particularly preferably 1 to 15 mass%, based on the (meth)acrylic polymer (A).

[0035] The (meth)acrylic polymer (A) may also contain a monomer other than the (meth)acrylate (a1) having an alkyl group with 1 to 15 carbon atoms and the polar group-containing monomer (a2), such as an epoxy group-containing monomer, a vinyl monomer, an alicyclic monomer, a macromonomer, or another copolymerizable monomer.

[0036] (Epoxy group-containing monomer) Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. These may be used alone or in combination of two or more.

[0037] When the (meth)acrylic polymer (A) has a structural unit derived from an epoxy group-containing monomer, the content thereof is usually 0.1 to 15 mass%, preferably 0.3 to 13 mass%, more preferably 0.5 to 10 mass%, and particularly preferably 1 to 6 mass%, relative to the (meth)acrylic polymer (A).

[0038] (vinyl monomer) Examples of the vinyl monomer 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.

[0039] When the (meth)acrylic polymer (A) has a constituent moiety derived from a vinyl monomer, the content thereof is usually 1 to 40 mass %, preferably 5 to 35 mass %, more preferably 8 to 30 mass %, and particularly preferably 10 to 25 mass %, relative to the (meth)acrylic polymer (A), from the viewpoint of imparting cohesive strength to the pressure-sensitive adhesive sheet.

[0040] (alicyclic monomer) Examples of the alicyclic monomer 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 (meth)acrylic polymer (A) has a structural unit derived from an alicyclic monomer, the content thereof is, from the viewpoint of imparting cohesive strength to the pressure-sensitive adhesive sheet, usually 0.1 to 15 mass%, preferably 0.5 to 13 mass%, particularly preferably 1 to 10 mass%, and especially preferably 2 to 7 mass%, relative to the (meth)acrylic polymer (A).

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

[0043] The macromonomer 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, or a thiol group, and the macromonomer may have these groups alone or in combination of two or more kinds. Among these, the macromonomer preferably has a radically polymerizable functional group that is copolymerizable with other monomers. The macromonomer may have one or more radically polymerizable functional groups, but a macromonomer having only one radically polymerizable functional group is particularly preferred. Furthermore, when the macromonomer 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 preferably has a skeleton component made of an acrylic polymer or a vinyl polymer.

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

[0046] When the (meth)acrylic polymer (A) has a structural unit derived from a macromonomer, the content thereof is usually 1 to 30% by mass, preferably 3 to 20% by mass, and more preferably 5 to 18% by mass, relative to the (meth)acrylic polymer (A). If the content is equal to or greater than the lower limit, the phase separation force between the segment containing the structural unit derived from the macromonomer 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 the content is equal to or less than the upper limit, the phase-separated structure tends to collapse more easily during lamination, and the unevenness-following ability tends to be better.

[0047] (Other copolymerizable monomers) Examples of the other copolymerizable monomers 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, Examples of suitable acrylates include (meth)acrylates having a benzophenone structure such as acryloyloxyethoxybenzophenone, 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.

[0048] When the (meth)acrylic polymer (A) has a structural unit derived from another copolymerizable monomer, the content thereof is usually 1 to 30 mass %, preferably 3 to 20 mass %, and more preferably 5 to 15 mass %, relative to the (meth)acrylic polymer (A).

[0049] The method for producing the (meth)acrylic polymer (A) is not particularly limited, and may be, for example, by polymerizing a (meth)acrylate (a1) having an alkyl group with 1 to 15 carbon atoms and, if necessary, a polar group-containing monomer (a2).

[0050] 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 resin with any monomer composition. In this way, the (meth)acrylic polymer (A) can be obtained.

[0051] The (meth)acrylic polymer (A) may have a photoactive moiety, such as a polymerizable carbon-carbon double bond group, introduced into its side chain, thereby improving the crosslinking efficiency of the pressure-sensitive adhesive composition and enabling the pressure-sensitive adhesive composition to be crosslinked in a shorter time, thereby increasing productivity.

[0052] Examples of a method for introducing a polymerizable carbon-carbon double bond group into the side chain of the (meth)acrylic 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, nitrogen atom-containing monomer, carboxy group-containing monomer, or epoxy group-containing monomer 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.

[0053] 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.

[0054] 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.

[0055] 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 the (meth)acrylic polymer (A). The lower limit is usually 0 part by mass.

[0056] The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 400,000 or more, from the viewpoint of obtaining a pressure-sensitive adhesive composition with high cohesive strength. In addition, the upper limit of the weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is preferably 1.5 million or less, more preferably 1.2 million or less, even more preferably 1.1 million or less, and particularly preferably 1 million or less, from the viewpoints of ease of handling and uniform stirring. The lower limit and upper limit of the weight average molecular weight of the (meth)acrylic polymer (A) can be combined arbitrarily. The weight average molecular weight of the (meth)acrylic polymer (A) is a value calculated as a standard polystyrene as measured by gel permeation chromatography (GPC).

[0057] [Radical polymerizable compound (B)] The pressure-sensitive adhesive composition contains, in addition to the (meth)acrylic polymer (A), a radically polymerizable compound (B), and the radically polymerizable compound (B) contains a monofunctional (meth)acrylate (b1) having a glass transition temperature (Tg) of 0°C or higher when made into a homopolymer. When the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet is irradiated with active energy rays, the radically polymerizable compound (B) becomes a polymer.

[0058] Examples of the radical polymerizable compound (B) include compounds selected from the above-mentioned (meth)acrylates (a1) having an alkyl group with 1 to 15 carbon atoms, polar group-containing monomers (a2), epoxy group-containing monomers, vinyl monomers, alicyclic monomers, macromonomers, and other copolymerizable monomers, which have a glass transition temperature (Tg) of 0° C. or higher when made into a homopolymer. Among these, from the viewpoint of adhesive strength, bulky monomers such as branched, alicyclic, and aromatic monomers are preferred.

[0059] The monofunctional (meth)acrylate (b1) when made into a homopolymer has a glass transition temperature (Tg) of 0° C. or higher, preferably 3° C. or higher, more preferably 5° C. or higher, even more preferably 10° C. or higher, and particularly preferably 15° C. or higher. The upper limit of the glass transition temperature is usually 200° C. By using a monofunctional (meth)acrylate (b1) having a glass transition temperature within the above range, the present pressure-sensitive adhesive sheet tends to have high cohesive strength.

[0060] The boiling point of the monofunctional (meth)acrylate (b1) is usually 150 to 350° C., preferably 180 to 350° C., and more preferably 200 to 350° C. Use of the monofunctional (meth)acrylate (b1) having a boiling point within the above range tends to improve cohesive strength and enable stable production in the manufacturing process.

[0061] Examples of the monofunctional (meth)acrylate (b1) include those having a glass transition temperature (Tg) of 0°C or higher selected from the above-mentioned (meth)acrylates (a1) having an alkyl group with 1 to 15 carbon atoms in the alkyl group, polar group-containing monomers (a2), epoxy group-containing monomers, vinyl monomers, alicyclic monomers, macromonomers, and other copolymerizable monomers. Among these, preferred are cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 1,4-cyclohexanedimethanol monoacrylate, tetrahydrofurfuryl methacrylate, (3-ethyloxetan-3-yl)methyl methacrylate, (2-oxo-1,3-diol), and the like. xolane-4-yl)methyl methacrylate, cyclic trimethylolpropane formal acrylate, 3,3,5-trimethylcyclohexyl acrylate, hydroxyethyl methacrylate, 2-hydroxybutyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, glycerin monomethacrylate, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N-(2-hydroxyethyl)acrylamide, 4-hydroxyphenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and the like. Among these, (meth)acrylates having a branched structure and / or a ring structure are preferred, and isobornyl (meth)acrylate, 1,4-cyclohexanedimethanol monoacrylate, hydroxyethyl methacrylate, N,N-diethylacrylamide, N-(2-hydroxyethyl)acrylamide, and 4-hydroxyphenyl methacrylate are more preferred.

[0062] The content of the monofunctional (meth)acrylate (b1) is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to the radical polymerizable compound (B) from the viewpoint of shape stability of the pressure-sensitive adhesive sheet, etc. The upper limit of the content of the monofunctional (meth)acrylate (b1) is 100% by mass.

[0063] From the viewpoint of shape stability of the pressure-sensitive adhesive sheet, the content of the radically polymerizable compound (B) is preferably 0.5 to 30 parts by mass, more preferably 1 to 30 parts by mass, and even more preferably 3 to 25 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0064] [Photopolymerization initiator (C)] The pressure-sensitive adhesive composition contains a photopolymerization initiator (C). The photopolymerization initiator (C) is a compound that generates radicals when exposed to active energy rays. Photopolymerization initiators are broadly classified into two types based on the radical generation mechanism. More specifically, they are broadly classified into hydrogen abstraction photopolymerization initiators (c1), which can generate radicals by an excited initiator abstracting hydrogen from a hydrogen donor in the system, and cleavage photopolymerization initiators (c2), which can generate radicals by cleaving and decomposing the single bond of the initiator itself. These may be used alone or in combination of two or more types. The hydrogen abstraction photopolymerization initiator (c1) is preferred in that it does not produce photodecomposition products and can incorporate the (meth)acrylic polymer (A) into a crosslinked structure by a hydrogen abstraction reaction. On the other hand, the cleavage-type photopolymerization initiator (c2) is preferred because it has high photosensitivity.

[0065] In this embodiment, the photopolymerization initiator (C) preferably contains a hydrogen abstraction photopolymerization initiator (c1), and more preferably contains a hydrogen abstraction photopolymerization initiator (c1) and a cleavage photopolymerization initiator (c2). The combined use of the hydrogen abstraction photopolymerization initiator (c1) and the cleavage photopolymerization initiator (c2) allows the radical polymerizable compound (B) to be incorporated into a crosslinked structure, resulting in sufficient adhesive strength. Furthermore, a pressure-sensitive adhesive sheet can be obtained that has good adhesive strength not only at room temperature but also at high temperatures, with little change in adhesive strength between room temperature and high temperatures.

[0066] Examples of the hydrogen abstraction photopolymerization initiator (c1) 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-methyl Examples of the photopolymerization initiator include intermolecular hydrogen abstraction photopolymerization initiators such as methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, and 4-methacryloyloxyethoxy-4'-bromobenzophenone; and intramolecular hydrogen abstraction photopolymerization initiators 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 may be used alone or in combination of two or more.

[0067] Among the intermolecular hydrogen abstraction photopolymerization initiators, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, and photopolymerization 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, and 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-methacryloyloxybenzophenone, and 4-methacryloyloxybenzophenone are more preferred. A photopolymerization initiator having a radically polymerizable functional group with a carbon-carbon double bond in its molecule tends to be incorporated into the polymerization structure after photoreaction, thereby suppressing bleed-out of the photopolymerization initiator and improving the cohesive strength of the adhesive sheet. Furthermore, an intramolecular hydrogen abstraction type photopolymerization initiator is preferred because it can act not only as a hydrogen donor in the system but also as a starting point for radical generation, and methylbenzoyl formate is more preferred.

[0068] Examples of the cleavage-type photopolymerization initiator (c2) include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4- α-aminoalkylphenone cleavage-type photopolymerization initiators such as polyethylene glycol (200) di(β-4[4-(2-dimethylamino-2-benzyl)butanoylphenyl]piperazine)propionate, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-( Examples of the photopolymerization initiator include α-hydroxyacetophenone-based cleavage-type photopolymerization initiators such as 4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one and 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl)benzyl}phenyl]-2-methyl-propan-1-one; acylphosphine oxide-based cleavage-type photopolymerization initiators such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide; oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone); methyl phenylglyoxylate; and derivatives thereof. These may be used alone or in combination of two or more. Among these, α-hydroxyacetophenone-based cleavage-type photopolymerization initiators are preferred, with 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenyl-propan-1-one being more preferred.

[0069] The content ratio (c1 / c2) of the hydrogen abstraction photopolymerization initiator (c1) to the cleavage type photopolymerization initiator (c2) is usually 0.1 to 30, preferably 0.5 to 25, more preferably 0.8 to 20, even more preferably 1.1 to 18, and particularly preferably 1.5 to 15. When the content ratio of the hydrogen abstraction photopolymerization initiator (c1) to the cleavage type photopolymerization initiator (c2) is within the above range, it tends to be possible to obtain a pressure-sensitive adhesive sheet that has good adhesive strength not only at room temperature but also at high temperatures, and in which the change in adhesive strength between room temperature and high temperatures is small.

[0070] The content of the photopolymerization initiator (C) is usually 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, more preferably 0.8 to 6 parts by mass or less, and even more preferably 1.0 to 5 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). When two or more types of photopolymerization initiators (C) are used in combination, the above content is the total amount of the photopolymerization initiators (C) used.

[0071] [Crosslinking agent] The pressure-sensitive adhesive composition may contain a crosslinking agent as needed, as long as the effects of the present invention are not impaired. Examples of the crosslinking agent include crosslinking agents having at least one crosslinkable functional group selected from a (meth)acryloyl group, an epoxy group, an isocyanate group, a carboxyl group, a hydroxyl group, a carbodiimide group, an oxazoline group, an aziridine group, a vinyl group, an amino group, an imino group, and an amide group, and one or more of these may be used in combination. Also included is an embodiment in which the crosslinking agent is chemically bonded to the (meth)acrylic polymer (A). Among these, a crosslinking agent having two or more crosslinkable functional groups is preferred, and a polyfunctional (meth)acrylate is more preferred from the viewpoint of reactivity. However, a crosslinking agent having three or more, or four or more crosslinkable functional groups may be used as needed. The crosslinkable functional group may be protected with a deprotectable protecting group.

[0072] Examples of the polyfunctional (meth)acrylate include 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glucidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-Nonanediol di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxydi(meth)acrylate, bisphenol A polypropoxydi(meth)acrylate, bisphenol F polyethoxydi(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone Modified tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate , polyethylene glycol di(meth)acrylate, tris(acryloxyethyl) isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol hydroxypivalate Examples of the polymerizable monomer include ultraviolet-curable polyfunctional (meth)acrylic monomers such as di(meth)acrylate of ε-caprolactone adduct, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxy tri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate, as well as polyfunctional (meth)acrylic oligomers such as polyester(meth)acrylate, epoxy(meth)acrylate, urethane(meth)acrylate, and polyether(meth)acrylate.

[0073] [Other ingredients] The pressure-sensitive adhesive composition may optionally contain 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 pressure-sensitive adhesive composition may optionally contain 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 pressure-sensitive adhesive composition contains a silane coupling agent.

[0074] [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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] When the pressure-sensitive adhesive composition contains a silane coupling agent, the content thereof is usually 0.005 to 10 parts by mass, preferably 0.01 to 5 parts by mass, and particularly preferably 0.05 to 1 part by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A). When the content is within the above range, adhesive strength and durability tend to be improved.

[0079] [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.

[0080] When the pressure-sensitive adhesive composition contains a plasticizer, the content thereof is not particularly limited and is usually 0.1 to 20 parts by mass, preferably 0.5 to 15 parts by mass, per 100 parts by mass of the (meth)acrylic polymer (A).

[0081] [Tackifier] The pressure-sensitive adhesive 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.

[0082] When the pressure-sensitive adhesive composition contains a tackifier, the content thereof is not particularly limited and is usually 0.1 to 20 parts by mass, preferably 0.5 to 15 parts by mass, per 100 parts by mass of the (meth)acrylic polymer (A).

[0083] [Rust inhibitor] The pressure-sensitive adhesive 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.

[0084] When the pressure-sensitive adhesive composition contains a rust inhibitor, the content thereof is usually 0.01 to 5 parts by mass, and preferably 0.1 to 3 parts by mass or less, per 100 parts by mass of the (meth)acrylic polymer (A).

[0085] <Method of manufacturing the pressure-sensitive adhesive sheet> Next, a method for producing the pressure-sensitive adhesive sheet will be described. However, the following description is an example of a method for producing the present pressure-sensitive adhesive sheet, and the present pressure-sensitive adhesive sheet is not limited to this production method.

[0086] The present pressure-sensitive adhesive sheet can be produced by preparing a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A), a radically polymerizable compound (B), a photopolymerization initiator (C), and other components as needed, forming the pressure-sensitive adhesive composition into a sheet, curing it by crosslinking, i.e., polymerization reaction, and then processing it appropriately as needed.

[0087] The pressure-sensitive adhesive 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, etc.). 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.

[0088] The pressure-sensitive adhesive composition can be formed into a sheet by known methods 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.

[0089] The pressure-sensitive adhesive composition can be cured by irradiation with active energy rays, and the pressure-sensitive adhesive sheet can be produced by irradiating a molded product of the pressure-sensitive adhesive composition, for example, a sheet, with active energy rays. In addition to irradiation with active energy rays, further curing can be achieved by heating.

[0090] 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 photopolymerization initiator (C) and polymerize the photoreactive components such as the (meth)acrylic polymer (A) and the radically polymerizable compound (B). When a hydrogen abstraction type photopolymerization initiator (c1) is used as the photopolymerization initiator (C), a hydrogen abstraction reaction also occurs from the (meth)acrylic polymer (A), and the (meth)acrylic 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 photopolymerization initiator (c1).

[0091] 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.

[0092] 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.

[0093] The amount of active energy ray irradiation (cumulative light amount) is 100 to 10,000 mJ / cm from the viewpoint of curing. 2 is preferred, and more preferably 200 to 5000 mJ / cm 2 , and more preferably 300 to 4000 mJ / cm 2 , especially 400 to 3000 mJ / cm 2 , and even more so, 500 to 2000 mJ / cm 2 It is preferable to carry out the reaction under the following conditions.

[0094] The pressure-sensitive adhesive sheet is preferably pre-cured (primary cured) by irradiation with active energy rays so that it has latent active energy ray curability, in other words, so that it retains active energy ray reactivity. When primary curing is performed by irradiating 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 it is also possible to adjust the degree of active energy ray crosslinking (gel fraction) by using a filter or the like to partially block the active energy rays.

[0095] The present pressure-sensitive adhesive sheet can also be provided as a pressure-sensitive adhesive sheet with a release film, which has a configuration in which a release film is laminated on one or both sides. In particular, from the viewpoint of preventing blocking and adhesion of foreign matter, it is preferable to cover both sides of the pressure-sensitive adhesive sheet with a release film.

[0096] 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.

[0097] As such a release film, any known release film can be used appropriately. As the material 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. Among these, polyester films, and even more particularly polyethylene terephthalate (PET) films, particularly biaxially oriented PET films, are preferred because of their excellent transparency, mechanical strength, heat resistance, flexibility, etc. 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 the main component is provided on the substrate.

[0098] 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.

[0099] In another embodiment of the method for producing the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive 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 heat curing in addition to the above-mentioned curing by irradiation with active energy rays. 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.

[0100] The coating method may be a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing, or bar coating.

[0101] To produce the present pressure-sensitive adhesive sheet using the coating method, for example, the pressure-sensitive adhesive composition can be dissolved in a solvent, coated on the release film, dried, and cured by active energy ray irradiation to form the present pressure-sensitive adhesive sheet. Furthermore, a release film may be laminated, if necessary. In this case, the pressure-sensitive adhesive composition may be coated on a release film, dried, cured by active energy ray irradiation, and a release film may be laminated thereon. Alternatively, the pressure-sensitive adhesive sheet may be formed by coating on a release film, drying, laminating a release film, and then curing by active energy ray irradiation.

[0102] The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive 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.

[0103] 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 (meth)acrylic 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.

[0104] The solvent content in the pressure-sensitive adhesive composition after drying is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

[0105] The drying temperature is usually 40 to 150° C., more preferably 45 to 140° C., even more preferably 50 to 130° C., and particularly preferably 55 to 120° C. Within this temperature range, the solvent can be removed efficiently and relatively safely while suppressing thermal deformation of the release film.

[0106] The drying time is usually 1 to 30 minutes, more preferably 3 to 25 minutes, and even more preferably 5 to 20 minutes. When the drying time is within this range, the solvent can be removed efficiently and sufficiently.

[0107] 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.

[0108] In yet another embodiment of the method for producing the present pressure-sensitive adhesive sheet, a pressure-sensitive adhesive composition may be prepared, coated onto a component of an image display device described below, and the pressure-sensitive adhesive composition may be cured to produce the present pressure-sensitive adhesive sheet, although the method is not limited to this.

[0109] Furthermore, the present pressure-sensitive adhesive sheet may be a single-layer pressure-sensitive adhesive sheet consisting of only an acrylic pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, or may be a multi-layer pressure-sensitive adhesive sheet in which other acrylic pressure-sensitive adhesive layers 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 consisting of an outermost layer, an innermost layer, and an intermediate layer, and particularly preferably at least three layers in which the outermost layer and the innermost layer are acrylic pressure-sensitive adhesive layers. By using such a layer structure, the functions of the outer and inner layers and the intermediate layer can be adjusted, and a pressure-sensitive adhesive sheet with a good balance of adhesive strength, cohesive strength, mechanical strength, etc. can be obtained.

[0110] When the pressure-sensitive adhesive sheet has at least three layers, i.e., 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 pressure-sensitive adhesive composition containing (meth)acrylic polymers (A) of different compositions, particularly containing (meth)acrylic 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. The outermost layer and the innermost layer may be formed from a pressure-sensitive adhesive composition containing (meth)acrylic polymers (A) of different compositions, particularly containing (meth)acrylic polymers (A) of different compositions as main components, but are preferably formed from a pressure-sensitive adhesive composition containing (meth)acrylic polymers (A) of the same composition.

[0111] Furthermore, when the pressure-sensitive adhesive sheet has at least three layers, the outermost and innermost layers of which are acrylic pressure-sensitive adhesive layers, the ratio of the total thickness of the outermost and innermost layers to the total thickness is preferably 5 to 70%, more preferably 10 to 60%, and particularly preferably 20 to 45%. By setting the thicknesses of the outermost and innermost layers within these ranges, a pressure-sensitive adhesive sheet can be obtained that is excellent in durability and lamination suitability, such as resistance to foaming at the peripheral edge, resistance to adhesive extrusion, and level difference absorbency.

[0112] The pressure-sensitive adhesive sheet thus obtained is to be attached to an adherend for use. In addition, the pressure-sensitive adhesive sheet can be further cured (secondary cured) by irradiating it with active energy rays in order to increase its adhesive strength to the adherend for use.

[0113] The pressure-sensitive adhesive sheet 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 pressure-sensitive adhesive sheet is preferably 10% or less, more preferably 5% or less, and particularly preferably 3% or less.

[0114] The gel fraction of the present pressure-sensitive adhesive sheet is preferably 30 to 95%, more preferably 40 to 85%, even more preferably 45 to 70%, and particularly preferably 47 to 65%. In addition, this adhesive sheet is exposed to active energy rays with a wavelength of 365 nm with an integrated light intensity of 2000 to 5000 mJ / cm 2 When irradiated at any irradiation dose within this range, the gel fraction is preferably 40 to 90%, more preferably 45 to 90%, even more preferably 50 to 85%, and particularly preferably 55 to 80%. The gel fraction is measured by wrapping a sample in a 150-mesh SUS wire mesh and immersing it in ethyl acetate for 24 hours. The sample is then dried at 70°C for 4.5 hours, and the mass of the PSA sheet is measured before and after immersion in ethyl acetate. The difference between the two masses is taken as the mass of the insoluble PSA sheet remaining in the wire mesh. The gel fraction (%) can be calculated as the mass percentage of the insoluble PSA sheet remaining in the wire mesh relative to the mass of the PSA sheet before immersion in ethyl acetate.

[0115] The shear storage modulus (G'(25°C)) of the present pressure-sensitive adhesive sheet is preferably 100 to 800 kPa, more preferably 120 to 700 kPa, even more preferably 140 to 600 kPa, and particularly preferably 160 to 500 kPa. In addition, this adhesive sheet is exposed to active energy rays with a wavelength of 365 nm with an integrated light intensity of 2000 to 5000 mJ / cm2 When irradiated at any irradiation dose within the range, the shear storage modulus at 25°C (G'(25°C)) is preferably 100 to 800 kPa, more preferably 120 to 700 kPa, even more preferably 140 to 600 kPa, and particularly preferably 160 to 550 kPa. The shear storage modulus can be calculated by performing dynamic viscoelasticity measurement using a rheometer viscoelasticity measuring device ("DHR-2" manufactured by TA Instruments) under the following conditions: measurement jig: 8 mm diameter parallel plates, frequency: 1 Hz, measurement temperature: -10 to 150°C, and heating rate: 5°C / min.

[0116] The adhesive strength of this pressure-sensitive adhesive sheet to glass at 23°C (P1(23°C)) is preferably 5 N / cm or more, more preferably 7 N / cm or more, even more preferably 9 N / cm or more, and particularly preferably 10 N / cm or more. The adhesive strength to glass at 60° C. (P1(60° C.)) is preferably 3 N / cm or more, more preferably 3.5 N / cm or more, and even more preferably 4 N / cm or more.

[0117] The ratio (P1(23°C) / P1(60°C)) of the adhesive strength to glass at 23°C (P1(23°C)) to the adhesive strength to glass at 60°C (P1(60°C)) is preferably 0.5 to 2.9, more preferably 0.6 to 2.7, even more preferably 0.7 to 2.5, and particularly preferably 0.7 to 2.3. The smaller this value, the less likely the adhesive strength is to decrease.

[0118] This adhesive sheet is exposed to active energy rays with a wavelength of 365 nm with an integrated light intensity of 2000 to 5000 mJ / cm 2 When irradiated with any irradiation amount within the range, the adhesive strength to glass at 23°C (P2(23°C)) is preferably 5 N / cm or more, particularly preferably 6 N / cm or more, more preferably 8 N / cm or more, even more preferably 9 N / cm or more, and particularly preferably 10 N / cm or more. In addition, this adhesive sheet is exposed to active energy rays with a wavelength of 365 nm with an integrated light intensity of 2000 to 5000 mJ / cm2 When irradiated with any of the irradiation amounts within the range, the adhesive strength to glass at 60°C (P2(60°C)) is preferably 3.5 N / cm or more, more preferably 4 N / cm or more, even more preferably 4.5 N / cm or more, particularly preferably 5 N / cm or more, and especially preferably 5.5 N / cm or more.

[0119] The ratio (P2(23°C) / P2(60°C)) of the adhesive strength to glass at 23°C (P2(23°C)) to the adhesive strength to glass at 60°C (P2(60°C)) is preferably 0.5 to 3.0, more preferably 0.5 to 2.5, even more preferably 0.6 to 2.0, and particularly preferably 0.7 to 1.7. The smaller this value, the less likely the adhesive strength is to decrease.

[0120] In addition, the adhesive strength of the adhesive sheet to glass at 23°C (P1 (23°C)) is determined by applying an active energy ray having a wavelength of 365 nm to the adhesive sheet at an integrated light intensity of 2000 to 5000 mJ / cm. 2 When irradiated at any irradiation dose within this range, the ratio (P2(23°C) / P1(23°C)) of adhesive strength to glass at 23°C (P2(23°C)) is preferably 0.5 to 1.5, more preferably 0.6 to 1.4, and even more preferably 0.7 to 1.3. The larger this value, the less likely the adhesive strength is to decrease before and after curing.

[0121] Furthermore, the adhesive strength of the adhesive sheet to glass at 60°C (P1 (60°C)) is determined by applying an active energy ray having a wavelength of 365 nm to the adhesive sheet at an integrated light intensity of 2000 to 5000 mJ / cm. 2 When irradiated with any irradiation amount within this range, the ratio (P2(60°C) / P1(60°C)) of adhesive strength to glass at 60°C (P2(60°C)) is preferably 0.6 to 1.5, more preferably 0.7 to 1.4, and even more preferably 0.8 to 1.3. The larger this value, the less likely the adhesive strength is to decrease before and after curing.

[0122] The strength of this pressure-sensitive adhesive sheet at 500% elongation measured in accordance with JIS K 7127 at a rate of 300 mm / sec is preferably 0.2 to 2.5 MPa, more preferably 0.2 to 2.0 MPa, and even more preferably 0.3 to 1.5 MPa.

[0123] The thickness of the present pressure-sensitive adhesive sheet is preferably 50 to 1000 μm, more preferably 60 to 500 μm, and particularly preferably 75 to 300 μm.

[0124] 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.

[0125] <Preferred uses of this adhesive sheet> The pressure-sensitive adhesive sheet is suitable for use in bonding optical components. Specifically, it is suitable for use in bonding components constituting a display, particularly components used in manufacturing a display, and is suitable for use as a pressure-sensitive adhesive sheet for bonding an image display panel and components constituting the image display device, such as a protective panel or touch panel, disposed on the front side (viewing side) of the image display panel, or components constituting the image display device components. The image display device components can be the same as those described below.

[0126] <<Laminate for image display device>> A laminate for an image display device according to one 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 image display device components are laminated via the present pressure-sensitive adhesive sheet.

[0127] Of the components of the present laminate for an image display device, the present pressure-sensitive adhesive sheet has been described above, and the components other than the pressure-sensitive adhesive sheet will be described below.

[0128] <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 liquid crystal displays, organic electroluminescence (EL) displays, surface protection panels (surface protection films), polarizing plates, polarizers, 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.

[0129] 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 of the group consisting of a touch sensor, an image display panel, a color filter, a polarizing film, 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.

[0130] The present laminate for an image display device is preferably fixed in a curved state. Since the present pressure-sensitive adhesive sheet also has excellent reliability in laminating to curved parts, the above-mentioned configuration allows the effects of the present invention to be particularly enjoyed.

[0131] <Method of manufacturing the laminate for the image display device> The method for producing the present laminate for an image display device is not particularly limited, and as described above, for example, the adhesive 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.

[0132] <<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]

[0133] 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. In the examples, "parts" and "%" refer to mass standards.

[0134] <Ingredients> First, the (meth)acrylic polymer (A) and the pressure-sensitive adhesive composition prepared in the examples and comparative examples will be described in detail.

[0135] <(Meth)acrylic polymer (A)> Acrylic polymer (A-1): Random copolymer of 46 parts 2-ethylhexyl acrylate, 45 parts methyl acrylate, and 9 parts N-vinylpyrrolidone

[0136] <Radical polymerizable compound (B)> Monofunctional monomer (B-1): Isobornyl acrylate (IBXA) (Tg: 97°C, boiling point: 246°C) Monofunctional monomer (B-2): Isobornyl methacrylate (IBXMA) (Tg: 180°C, boiling point: 258°C) Monofunctional monomer (B-3): 1,4-cyclohexanedimethanol monoacrylate (CHDMMA) (Tg: 18°C, boiling point: 311°C) Monofunctional monomer (B-4): hydroxyethyl methacrylate (HEMA) (Tg: 55°C, boiling point: 250°C) Monofunctional monomer (B-5): N,N-diethylacrylamide (DEAA) (Tg: 81°C, boiling point: 190°C) Monofunctional monomer (B-6): N-(2-hydroxyethyl)acrylamide (HEAA) (Tg: 98°C, boiling point: 328°C) Monofunctional monomer (B-7): 4-hydroxyphenyl methacrylate (PHOH) (Tg: 149°C, boiling point: 320°C)

[0137] <Photopolymerization initiator (C)> [Hydrogen abstraction photoinitiator (c1)] Photopolymerization initiator (C-1): A mixture of 4-methylbenzophenone and 2,4,6-trimethylbenzophenone (Ezacure TZT, manufactured by IGM) Photopolymerization initiator (C-2): 4-methylbenzophenone (MBP) [Cleavage-type photopolymerization initiation (c2)] Photopolymerization initiator (C-3): 1-hydroxycyclohexyl phenyl ketone (IGM "Omnirad184")

[0138] [Examples 1 to 10, Comparative Example 1] The raw materials of the adhesive composition and ethyl acetate as a solvent were mixed uniformly according to the formulation shown in Table 1 below to obtain an adhesive composition solution (solid content concentration: 40% by mass).

[0139] The pressure-sensitive adhesive composition solution was coated onto a release film (a silicone release-treated polyester film manufactured by Mitsubishi Chemical Corporation, thickness 100 μm) so that the thickness after drying would be 60 μm. After coating, the film was placed in a dryer heated to 90° C. and held for 10 minutes to volatilize and dry the solvent contained in the pressure-sensitive adhesive composition. Furthermore, a release film (a silicone release-treated polyester film manufactured by Mitsubishi Chemical Corporation, thickness 75 μm) was laminated on the surface of the adhesive composition from which the solvent had been dried to form a laminate, and the adhesive composition was irradiated with ultraviolet light through the release film using a high-pressure mercury lamp (wavelength 365 nm) (primary curing) (see Table 2 for the accumulated light amount), to obtain an adhesive sheet with a release film. The pressure-sensitive adhesive sheets obtained in the examples and comparative examples were pressure-sensitive adhesive sheets having active energy ray curability, that is, pressure-sensitive adhesive sheets that were cured by irradiation with active energy rays.

[0140] [Table 1]

[0141] The pressure-sensitive adhesive sheets with release films obtained above were evaluated as follows, and the results are shown in Tables 2 and 3 below.

[0142] <Gel fraction> The release films were removed from the pressure-sensitive adhesive sheets with release films produced in the Examples and Comparative Examples, and these were used as samples. The sample was wrapped in a 150-mesh SUS wire mesh and immersed in ethyl acetate for 24 hours. It was then dried at 70°C for 4.5 hours, and the mass of the pressure-sensitive adhesive sheet was measured before and after immersion in ethyl acetate. The difference between the two masses was taken as the mass of the insoluble pressure-sensitive adhesive sheet remaining in the wire mesh. The mass percentage of the insoluble pressure-sensitive adhesive sheet remaining in the wire mesh relative to the mass of the pressure-sensitive adhesive sheet before immersion in ethyl acetate was calculated as the gel fraction (%).

[0143] In addition, the pressure-sensitive adhesive sheets with release films obtained in the examples and comparative examples were exposed to an accumulated light intensity of 3000 mJ / cm of active energy rays with a wavelength of 365 nm using a high-pressure mercury lamp (wavelength 365 nm). 2 The adhesive sheet was irradiated with light through the release film to cure the adhesive sheet (secondary curing). Using this cured pressure-sensitive adhesive sheet, the gel fraction after curing was measured in the same manner as the gel fraction before light irradiation.

[0144] <Shear storage modulus (G'), loss tangent (Tanδ), glass transition temperature (Tg)> 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 obtained samples were placed in a rheometer viscoelasticity measuring device (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: -10 to 150°C, and heating rate: 5°C / min, and the shear storage modulus (G') values ​​from 25 to 150°C and the loss tangent (Tan δ) values ​​from 25 to 150°C were read. Furthermore, from the obtained temperature dispersion data of dynamic viscoelasticity, the temperature at the maximum point of the loss tangent (tan δ) was read as the glass transition temperature (Tg).

[0145] In addition, the pressure-sensitive adhesive sheets with release films obtained in the examples and comparative examples were exposed to an accumulated light intensity of 3000 mJ / cm of active energy rays with a wavelength of 365 nm using a high-pressure mercury lamp (wavelength 365 nm).2 The adhesive sheet was irradiated with light through the release film to cure the adhesive sheet (secondary curing). Using the cured pressure-sensitive adhesive sheet, the storage shear modulus (G'), loss tangent (Tan δ), and glass transition temperature (Tg) after curing were measured in the same manner as before light irradiation.

[0146] <Adhesion to glass> The release film on one side of the adhesive sheet with release film prepared in the Examples and Comparative Examples was removed, and a PET film (Mitsubishi Chemical Corporation, Diafilm S-100, thickness 50 μm) was attached 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, and the exposed adhesive surface was attached to soda-lime glass using a hand roller to prepare an adhesive strength measurement sample. The obtained adhesive strength measurement sample was peeled from the soda-lime glass together with the backing film while being pulled at an angle of 180° at 23 ° C. and 60 ° C. at a peeling rate of 60 mm / min, and the tensile strength (N / cm) was measured using a load cell, and the adhesive strength to glass at 23 ° C. (P1 (23 ° C.)) and the adhesive strength to glass at 60 ° C. (P1 (60 ° C.)) were determined.

[0147] From the adhesive strength to glass measured above, the ratio of the adhesive strength to glass at 23°C to the adhesive strength to glass at 60°C (P1(23°C) / P1(60°C)) was calculated.

[0148] In addition, the pressure-sensitive adhesive sheets with release films obtained in the examples and comparative examples were exposed to an accumulated light intensity of 3000 mJ / cm of active energy rays with a wavelength of 365 nm using a high-pressure mercury lamp (wavelength 365 nm). 2 The adhesive sheet was irradiated with light through the release film to cure the adhesive sheet (secondary curing). Using this cured adhesive sheet, the adhesive strength to glass at 23°C (P2(23°C)) and the adhesive strength to glass at 60°C (P2(60°C)) after curing were determined in the same manner as the adhesive strength to glass before light irradiation.

[0149] From the adhesive strength to glass measured above, the ratio of the adhesive strength to glass at 23°C to the adhesive strength to glass at 60°C (P2(23°C) / P2(60°C)) was calculated.

[0150] In addition, from the adhesive strength to glass measured above, the ratio of the adhesive strength to glass of the adhesive sheet (secondary curing) at 23°C to the adhesive strength of the adhesive sheet (primary curing) at 23°C (P2(23°C) / P1(60°C)), and the ratio of the adhesive strength to glass of the adhesive sheet (secondary curing) at 60°C to the adhesive strength of the adhesive sheet (primary curing) at 60°C (P2(60°C) / P1(60°C)) were calculated.

[0151] <Strength at 500% elongation> The release films were removed from the pressure-sensitive adhesive sheets with release films prepared in the Examples and Comparative Examples, and these were used as samples. The tensile strength of each sample was measured at a speed of 300 mm / sec in accordance with JIS K 7127 (1999).

[0152] In addition, the pressure-sensitive adhesive sheets with release films obtained in the examples and comparative examples were exposed to an accumulated light intensity of 3000 mJ / cm of active energy rays with a wavelength of 365 nm using a high-pressure mercury lamp (wavelength 365 nm). 2 The adhesive sheet was irradiated with light through the release film to cure the adhesive sheet. Using this cured pressure-sensitive adhesive sheet, the tensile strength after curing was measured in the same manner as the tensile strength before light irradiation.

[0153] [Table 2]

[0154] [Table 3]

[0155] Even when the active energy ray-curable adhesive sheets of the Examples were formulated with a monomer having a high glass transition temperature, the glass transition temperature of the adhesive sheets did not rise too much, and the sheets had excellent mechanical strength and adhesive strength even after being irradiated with active energy rays after application, providing an excellent balance between mechanical strength and adhesive strength. On the other hand, the active energy ray-curable adhesive sheet of Comparative Example 1, which did not contain a radical polymerizable compound (monofunctional monomer), had poor mechanical strength and did not have a sufficient balance between mechanical strength and adhesive strength, and therefore could not achieve the object of the present invention. [Industrial Applicability]

[0156] The pressure-sensitive adhesive sheet of the present invention has excellent adhesive strength and mechanical strength, and can therefore be suitably used as a pressure-sensitive adhesive sheet for image display devices.

Claims

1. An active energy ray-curable pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A), a radical-polymerizable compound (B), and a photopolymerization initiator (C), The active energy ray-curable pressure-sensitive adhesive sheet, wherein the radical polymerizable compound (B) contains a monofunctional (meth)acrylate (b1) having a glass transition temperature (Tg) of 0°C or higher when made into a homopolymer.

2. The active energy ray-curable pressure-sensitive adhesive sheet according to claim 1 , wherein the monofunctional (meth)acrylate (b1) has a branched structure and / or a cyclic structure.

3. The active energy ray-curable adhesive sheet according to claim 1 or 2, wherein the monofunctional (meth)acrylate (b1) has a boiling point of 150 to 350°C.

4. 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the content of the radical polymerizable compound (B) is 0.5 to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A).

5. The active energy ray-curable pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the content of the monofunctional (meth)acrylate (b1) is 40 mass % or more relative to the radical polymerizable compound (B).

6. The active energy ray-curable pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the photopolymerization initiator (C) comprises a hydrogen abstraction photopolymerization initiator (c1).

7. The active energy ray-curable pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the photopolymerization initiator (C) comprises a hydrogen abstraction photopolymerization initiator (c1) and a cleavage photopolymerization initiator (c2).

8. 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the content of the photopolymerization initiator (C) is 0.1 to 10 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A).

9. The active energy ray-curable adhesive sheet according to claim 7, wherein the content ratio (c1 / c2) of the hydrogen abstraction type photopolymerization initiator (c1) to the cleavage type photopolymerization initiator (c2) is 0.1 to 30.

10. 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the (meth)acrylic polymer (A) is an acrylic polymer having a structural moiety derived from a (meth)acrylate (a1) having an alkyl group with 1 to 15 carbon atoms in the alkyl group, and a structural moiety derived from a polar group-containing monomer (a2).

11. 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the shear storage modulus (G'(25°C)) obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz is 100 to 800 kPa.

12. 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the active energy ray-curable adhesive sheet has a gel fraction of 30 to 95%.

13. The active energy ray-curable adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm in an integrated light amount of 2000 to 5000 mJ / cm 2 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the adhesive strength to glass at 60°C (P2(60°C)) is 3.5 N / cm or more when irradiated with any of the irradiation amounts within the range of 1.

14. The active energy ray-curable adhesive sheet is irradiated with active energy rays having a wavelength of 365 nm in an integrated light amount of 2000 to 5000 mJ / cm 2 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the ratio (P2(23°C) / P2(60°C)) of the adhesive strength to glass at 23°C (P2(23°C)) to the adhesive strength to glass at 60°C (P2(60°C)) when irradiated with any irradiation amount within the range of

15. The adhesive strength of the active energy ray-curable adhesive sheet to glass at 60°C (P1 (60°C)) is determined by applying an active energy ray having a wavelength of 365 nm to the adhesive sheet in an amount of 2000 to 5000 mJ / cm. 2 3. The active energy ray-curable adhesive sheet according to claim 1, wherein the ratio (P2(60°C) / P1(60°C)) of adhesive strength to glass at 60°C (P2(60°C)) when irradiated with any irradiation amount within the range of

16. 3. The active energy ray-curable pressure-sensitive adhesive sheet according to claim 1, wherein the strength at 500% elongation measured in accordance with JIS K 7127 at a rate of 300 mm / sec is 0.2 to 2.5 MPa.

17. 3. A pressure-sensitive adhesive sheet with a release film, comprising the active energy ray-curable pressure-sensitive adhesive sheet according to claim 1 or 2 laminated with a release film.

18. A laminate for an image display device, comprising two image display device components laminated together with the active energy ray-curable adhesive sheet according to claim 1 or 2 interposed therebetween.

19. An image display device comprising the laminate for an image display device according to claim 18.

20. An active energy ray-curable adhesive sheet for use as a component of an image display device, comprising the active energy ray-curable adhesive sheet according to claim 1 or 2.

21. 3. The method for producing an active energy ray-curable pressure-sensitive adhesive sheet according to claim 1 or 2, wherein a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A), a radically polymerizable compound (B), and a photopolymerization initiator (C) is cured by exposure to active energy rays.

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