Active energy ray-curable release-type adhesive composition and active energy ray-curable release-type adhesive sheet

Abstract

To provide an adhesive composition having high adhesive strength before active energy ray irradiation and exhibiting excellent releasability and superior stretchability after active energy ray irradiation.SOLUTION: An active energy ray-curable release-type adhesive composition comprises an acrylic resin (A), an active energy ray-curable compound (B), and a crosslinking agent (C), the acrylic resin (A) having a weight-average molecular weight of 1,100,000 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable release-type pressure-sensitive adhesive composition and an active energy ray-curable release-type pressure-sensitive adhesive sheet, and more particularly to an active energy ray-curable release-type pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet used as an adhesive for release-type pressure-sensitive adhesive sheets for temporary surface protection when processing workpieces such as semiconductor wafers, printed circuit boards, processed glass products, metal plates, and plastic plates. [Background technology]

[0002] Conventionally, in the processing steps such as the manufacture of integrated circuits using semiconductor wafers and drilling holes, adhesive sheets for surface protection are used to temporarily protect the surface of the workpiece in order to prevent the workpiece from being soiled or damaged.In recent years, due to the miniaturization of processing technology and the thinning of workpieces, etc., a moderate adhesive strength is required for the workpiece, while after the surface protection role is completed, the adhesive sheet for surface protection needs to be peeled off, and when peeling, it is required to be peeled off with a light force without leaving any adhesive residue.In addition, in recent years, adhesive sheets for surface protection are used not only for semiconductor wafers but also for the processing of various other parts.

[0003] For such adhesive sheets, an active energy ray-curable adhesive composition that can be cured by irradiation with active energy rays and reduce adhesive strength is effective. For example, active energy ray-curable properties are exhibited by (1) blending at least one of a monomer and / or oligomer having an ethylenically unsaturated group with an acrylic resin, or (2) using an ethylenically unsaturated group-containing acrylic resin in which the acrylic resin itself contains an ethylenically unsaturated group.

[0004] In recent years, in the expanding process, which is carried out after processing a workpiece (especially electronic components) and irradiating the pressure-sensitive adhesive sheet with active energy rays to harden (reduce adhesive strength), the pressure-sensitive adhesive layer often cracks during expansion, resulting in adhesion and contamination of the workpiece. Therefore, pressure-sensitive adhesives used in pressure-sensitive adhesive sheets are required to have easy peelability and high extensibility after exposure to active energy rays. For example, Patent Document 1 describes a pressure-sensitive adhesive composition consisting of an elastomeric polymer, an ultraviolet-crosslinkable (meth)acrylic acid ester, a polyisocyanate, and a urethane group-containing ultraviolet-crosslinkable (meth)acrylic acid ester. Patent Document 2 also describes a pressure-sensitive adhesive sheet for processing, which has an intermediate layer between a substrate and an adhesive layer, the intermediate layer consisting primarily of an acrylic polymer with a glass transition temperature of 20°C or higher. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-225779 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-50406 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the pressure-sensitive adhesive composition described in Patent Document 1 was insufficient in expandability and was unsatisfactory. Moreover, the pressure-sensitive adhesive sheet for processing described in Patent Document 2 was designed to be expanded before being irradiated with active energy rays, and the stretchability after being irradiated with active energy rays was unsatisfactory.

[0007] Therefore, under such circumstances, the present invention aims to provide an active energy ray-curable peel-type pressure-sensitive adhesive composition that can give a pressure-sensitive adhesive having good adhesive strength before irradiation with active energy rays, and having good easy releasability and excellent stretchability after irradiation with active energy rays. [Means for solving the problem]

[0008] However, in view of these circumstances, the present inventors have conducted extensive research and have found that by using an acrylic resin having a specific weight-average molecular weight as a pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition can be obtained that has good adhesive strength before irradiation with active energy rays, and good easy releasability and excellent stretchability after irradiation with active energy rays, and have thus completed the present invention.

[0009] That is, the present invention has the following aspects. [1] An active energy ray-curable peel-off pressure-sensitive adhesive composition containing an acrylic resin (A), an active energy ray-curable compound (B), and a crosslinking agent (C), The active energy ray-curable peelable pressure-sensitive adhesive composition, wherein the acrylic resin (A) has a weight-average molecular weight of 1,100,000 or more. [2] The active energy ray-curable peelable pressure-sensitive adhesive composition according to [1], which has a tensile breaking elongation of 500% or more measured under the following conditions: Conditions: A composition consisting of an acrylic resin (A) and a crosslinking agent (C) is applied to a substrate and dried, and a test piece (15 mm wide x 200 μm thick) adjusted to a gel fraction of 65% or more is pulled at a speed of 300 mm / min with a chuck distance of 20 mm. [3] The active energy ray-curable peelable pressure-sensitive adhesive composition according to [1] or [2], wherein the glass transition temperature (Tg) of the acrylic resin (A) is 0°C or lower. [4] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the acrylic resin (A) has a structural unit derived from a carboxy group-containing monomer (a2-1). [5] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the active energy ray-curable compound (B) contains a urethane (meth)acrylate (b). [6] The active energy ray-curable peel-type pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the content of the active energy ray-curable compound (B) is 5 to 100 parts by mass per 100 parts by mass of the acrylic resin (A). [7] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [6], further comprising a photopolymerization initiator (D). [8] An active energy ray-curable peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer crosslinked with the active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [7]. [9] The active energy ray-curable peelable pressure-sensitive adhesive sheet according to [8], wherein the pressure-sensitive adhesive layer is cured and becomes peelable upon irradiation with active energy rays. [Effects of the Invention]

[0010] The active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention has good adhesive strength before being irradiated with active energy rays, and after being irradiated with active energy rays, has easy peelability and extensibility. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below. In this specification, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate. Moreover, the term "acrylic resin" refers to a resin obtained by polymerizing a copolymerization component containing at least one kind of (meth)acrylate monomer. In this specification, the term "film" also includes "tape" and "sheet."

[0012] In this specification, "X and / or Y (X and Y are any configurations)" means at least one of X and Y, and means three possibilities: X only, Y only, and X and Y. When expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less," as well as "preferably larger than X" or "preferably smaller than Y." When expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y." 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 peelable pressure-sensitive adhesive composition according to one embodiment of the present invention (hereinafter sometimes referred to as "the present pressure-sensitive adhesive composition") is mainly used in the pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet, which is generally intended to be peeled off after being attached to a workpiece such as a metal plate, a plastic plate, a semiconductor wafer, etc. The pressure-sensitive adhesive sheet is formed by coating the present pressure-sensitive adhesive composition on a substrate sheet to form a pressure-sensitive adhesive layer, and after being attached to the workpiece, the pressure-sensitive adhesive layer is cured by irradiating it with active energy rays, reducing the adhesive strength, and allowing it to be easily peeled off from the workpiece.

[0014] The present pressure-sensitive adhesive composition contains an acrylic resin (A), an active energy ray-crosslinkable compound (B), and a crosslinking agent (C). Each of the components of the present pressure-sensitive adhesive composition will be described below.

[0015] [Acrylic resin (A)] The acrylic resin (A) used in this embodiment preferably has a structural unit derived from an alkyl (meth)acrylate (a1), a structural unit derived from a functional group-containing monomer (a2), and, if necessary, a structural unit derived from another copolymerizable monomer (a3). Such an acrylic resin (A) is preferably obtained by copolymerizing copolymerization components containing an alkyl (meth)acrylate (a1), a functional group-containing monomer (a2), and, if necessary, other copolymerizable monomers (a3), etc. The content of each monomer relative to the total copolymerization components can be considered to be the content of structural units derived from that monomer in the acrylic resin (A) which is a copolymer. For example, the content of alkyl (meth)acrylate (a1) relative to the total copolymerization components is considered to be the content of structural units derived from alkyl (meth)acrylate (a1) in the acrylic resin (A).

[0016] [Alkyl (meth)acrylate (a1)] The alkyl group of the alkyl (meth)acrylate (a1) has a carbon number of usually 1 to 20, preferably 1 to 12, and more preferably 1 to 8. If the alkyl group has too many carbon atoms, the amount of unreacted residual monomers tends to increase, which tends to cause contamination of the workpiece during peeling.

[0017] Examples of the alkyl (meth)acrylate (a1) include aliphatic alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate; and alicyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. These may be used alone or in combination of two or more. Among the alkyl (meth)acrylates (a1), aliphatic alkyl (meth)acrylates are preferred in terms of copolymerizability, adhesive properties, ease of handling, and ease of raw material availability, and methyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are more preferred, with methyl (meth)acrylate and n-butyl (meth)acrylate being particularly preferred.

[0018] The content of structural units derived from alkyl (meth)acrylate (a1) in the acrylic resin (A) is usually 30 to 99 mass %, preferably 40 to 98 mass %, and more preferably 50 to 97 mass % of all structural units of the acrylic resin (A). If the content is too low, the adhesion and pressure-sensitive adhesive properties before irradiation with active energy rays tend to be easily reduced, while if the content is too high, the cohesive strength of the pressure-sensitive adhesive when made into a pressure-sensitive adhesive tends to be insufficient.

[0019] [Functional group-containing monomer (a2)] Examples of the functional group-containing monomer (a2) include a carboxy group-containing monomer (a2-1), a hydroxy group-containing monomer (a2-2), an amino group-containing monomer, an amide group-containing monomer, a glycidyl group-containing monomer, a sulfonic acid group-containing monomer, and an acetoacetyl group-containing monomer. These functional group-containing monomers can be used alone or in combination of two or more. Among these, the carboxy group-containing monomer (a2-1) and the hydroxy group-containing monomer (a2-2) are preferred.

[0020] The content of the structural units derived from the functional group-containing monomer (a2) in the acrylic resin (A) is usually 50% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less, of all structural units of the acrylic resin (A). When the content is within the above range, storage stability is improved and crosslinking before the drying step can be suppressed, which tends to result in excellent coatability.

[0021] The acrylic resin (A) of this embodiment preferably contains a structural unit derived from a carboxyl group-containing monomer (a2-1). The acrylic resin (A) preferably contains a structural unit derived from a carboxyl group-containing monomer (a2-1), which is advantageous in that it can improve the adhesive properties before irradiation with active energy rays and the stretchability after irradiation with active energy rays.

[0022] Examples of the carboxyl group-containing monomer (a2-1) include (meth)acrylic acid, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxyethyl phthalic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, and cinnamic acid. These can be used alone or in combination of two or more. Among these, (meth)acrylic acid is preferred because it is easily copolymerizable and can easily improve adhesive strength before irradiation with active energy rays.

[0023] When the acrylic resin (A) has a structural unit derived from a carboxy group-containing monomer (a2-1), the content thereof is preferably 0.1 to 30 mass % of all structural units of the acrylic resin (A), from the viewpoint of easily increasing adhesive strength before irradiation with active energy rays, more preferably 0.5 to 20 mass %, even more preferably 1 to 15 mass %, and particularly preferably 1 to 8 mass %. If the content is too low, the adhesive may have insufficient cohesive strength or may have low adhesive strength before irradiation with active energy rays, which may easily cause chipping or breakage.If the content is too high, the glass transition temperature of the acrylic resin (A) may become too high, which may easily reduce adhesion and stretchability to the workpiece.

[0024] Examples of the hydroxyl group-containing monomer (a2-2) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; and hydroxyl group-containing (meth)acrylates such as [4-(hydroxymethyl)cyclohexyl]methyl acrylate, cyclohexanedimethanol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred because they are easily copolymerized, have good crosslinkability with the crosslinking agent (C) described below, and can easily improve stain resistance after irradiation with active energy rays.

[0025] When the acrylic resin (A) has a structural unit derived from a hydroxyl group-containing monomer (a2-2), the content thereof is preferably 30 mass % or less, more preferably 20 mass % or less, and even more preferably 10 mass % or less of the total structural unit of the acrylic resin (A). If the content is too high, the stability of the acrylic resin (A) tends to decrease and the pot life tends to be shortened.

[0026] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0027] When the acrylic resin (A) has structural units derived from amino group-containing monomers, the content thereof is usually 30 mass % or less, preferably 25 mass % or less, and more preferably 20 mass % or less of the total structural units of the acrylic resin (A). If the content is too high, crosslinking will proceed before the drying step, which tends to cause problems with coating properties.

[0028] Examples of the amide group-containing monomer include (meth)acrylamide-based monomers such as methoxydimethylpropanamide, ethoxymethyl(meth)acrylamide, n-butoxymethyl(meth)acrylamide, (meth)acryloylmorpholine, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, (meth)acrylamide, and N-methylol(meth)acrylamide.

[0029] When the acrylic resin (A) has a structural unit derived from an amide group-containing monomer, the content thereof is usually 30 mass % or less, preferably 25 mass % or less, and more preferably 20 mass % or less of the total structural units of the acrylic resin (A). Since amide group-containing monomers tend to have high glass transition temperatures, if the content is too high, the glass transition temperature of the polymer tends to increase, and the adhesive properties before irradiation with active energy rays tend to decrease.

[0030] Examples of the glycidyl group-containing monomer include glycidyl methacrylate and allyl glycidyl methacrylate.

[0031] When the acrylic resin (A) has a structural unit derived from a glycidyl group-containing monomer, the content thereof is usually 20% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less of the total structural units of the acrylic resin (A). If the content is too high, the polymerizability and the stability of the acrylic resin (A) tend to be easily reduced.

[0032] Examples of the sulfonic acid group-containing monomer include olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, 2-acrylamido-2-methylolpropane sulfonic acid, and styrene sulfonic acid or salts thereof.

[0033] When the acrylic resin (A) has a structural unit derived from a sulfonic acid group-containing monomer, the content thereof is usually 10% by mass or less, preferably 5% by mass or less, and more preferably 1% by mass or less, of the total structural units of the acrylic resin (A). If the content is too high, the stability of the acrylic resin (A) may decrease, or crosslinking may proceed before the drying step, which may cause problems with coatability.

[0034] Examples of the acetoacetyl group-containing monomer include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate.

[0035] When the acrylic resin (A) has a structural unit derived from an acetoacetyl group-containing monomer, the content thereof is usually 10% by mass or less, preferably 5% by mass or less, and more preferably 1% by mass or less of the total structural units of the acrylic resin (A). If the content is too high, the polymerizability and adhesive properties tend to be easily reduced.

[0036] [Other copolymerizable monomers (a3)] Examples of the other polymerizable monomer (a3) ​​include unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride, and acrylamido-N-glycolic acid; carboxylic acid vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl stearate, and vinyl benzoate; aromatic ring-containing monomers such as styrene and α-methylstyrene; acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, alkyl vinyl ethers, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, itaconic acid dialkyl esters, fumaric acid dialkyl esters, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyl trimethyl ammonium chloride, and dimethyl allyl vinyl ketone. These may be used alone or in combination of two or more.

[0037] The other polymerizable monomer (a3) ​​may also contain a photocrosslinkable monomer, which generates radicals when exposed to light. Examples of the photocrosslinkable monomer include (meth)acrylate monomers having a benzophenone structure, such as 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof. By using such a photocrosslinkable monomer as a copolymerization component, a photocrosslinkable structural moiety can be formed in the acrylic resin (A).

[0038] When the acrylic resin (A) has structural units derived from other polymerizable monomers (a3), the content thereof is usually 30% by mass or less, preferably 20% by mass or less, of all structural units of the acrylic resin (A). When the other polymerizable monomer (a3) ​​contains a structural unit derived from a photocrosslinkable monomer, the content thereof is usually 10% by mass or less, preferably 5% by mass or less, of all structural units of the acrylic resin (A).

[0039] The acrylic resin (A) is obtained by copolymerizing the copolymerization components containing the alkyl (meth)acrylate (a1), the functional group-containing monomer (a2), and, if necessary, other copolymerizable monomers (a3). Such polymerization methods typically include conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. Among these, solution radical polymerization and bulk polymerization are preferred, and solution radical polymerization is particularly preferred from the viewpoint of stably obtaining the acrylic resin (A).

[0040] In the solution radical polymerization, for example, the copolymerization components and a thermal polymerization initiator are mixed or dropped into an organic solvent, and polymerization is carried out under reflux or generally at 50 to 98° C. for about 0.1 to 20 hours.

[0041] Examples of organic solvents used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol, and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. These can be used alone or in combination of two or more. Among these solvents, it is preferable to use an organic solvent having a boiling point of 80°C or less, since this allows for efficient production of a solventless acrylic resin by distilling off the solvent from the acrylic resin solution obtained by solution polymerization.

[0042] Examples of organic solvents having a boiling point of 80°C or lower include hydrocarbon solvents such as n-hexane (67°C), alcohol solvents such as methanol (65°C), ester solvents such as ethyl acetate (77°C) and methyl acetate (54°C), ketone solvents such as methyl ethyl ketone (80°C) and acetone (56°C), diethyl ether (35°C), methylene chloride (40°C), tetrahydrofuran (66°C), etc. Among these, in terms of versatility and safety, it is preferable to use ethyl acetate, acetone, or methyl acetate, and it is particularly preferable to use ethyl acetate or acetone. The numerical value in parentheses following the name of each organic solvent is the boiling point of the organic solvent.

[0043] The amount of the organic solvent used is usually 10 to 900% by mass relative to 100% by mass of the copolymerization components.

[0044] As the thermal polymerization initiator used in the polymerization reaction, azo-based polymerization initiators and peroxide-based polymerization initiators, which are common radical polymerization initiators, can be used. Examples of azo-based polymerization initiators include 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, (1-phenylethyl)azodiphenylmethane, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), ... ,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), etc., and examples of peroxide polymerization initiators include benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, lauroyl peroxide, t-butyl peroxypivalate, t-hexyl peroxypivalate, t-hexyl peroxyneodecanoate, diisopropyl peroxycarbonate, diisobutyryl peroxide, etc. These can be used alone or in combination of two or more.

[0045] The amount of the thermal polymerization initiator used is usually 0.001 to 10% by mass, preferably 0.1 to 8% by mass, more preferably 0.5 to 6% by mass, even more preferably 1 to 4% by mass, particularly preferably 1.5 to 3% by mass, and most preferably 2 to 2.5% by mass, based on 100% by mass of the copolymerization components. If the amount of the thermal polymerization initiator used is too small, the polymerization rate of the acrylic resin (A) tends to decrease, the amount of residual monomers tends to increase, and the weight-average molecular weight of the acrylic resin (A) tends to increase. If the amount used is too large, the time required for the follow-up heating described below tends to be long, which tends to be unproductive.

[0046] The polymerization temperature in the polymerization reaction is usually 40 to 120° C., but in this embodiment, from the viewpoint of ensuring a stable reaction, it is preferably 50 to 90° C., more preferably 55 to 75° C., and even more preferably 60 to 70° C. If the polymerization temperature is too high, the acrylic resin (A) tends to be easily gelled, and if it is too low, the activity of the thermal polymerization initiator decreases, so that the polymerization rate tends to decrease and the amount of residual monomers tends to increase.

[0047] The polymerization time in the polymerization reaction (the time until the start of the follow-up heating, if follow-up heating is performed as described below) is not particularly limited, but is preferably 0.5 hours or more from the addition of the final thermal polymerization initiator, more preferably 1 hour or more, even more preferably 2 hours or more, and particularly preferably 5 hours or more. The upper limit of the polymerization time is usually 72 hours. The polymerization reaction is preferably carried out while refluxing the solvent, since this facilitates heat removal.

[0048] In the production of the acrylic resin (A), in order to reduce the amount of residual thermal radical initiator, it is preferable to thermally decompose the thermal polymerization initiator by follow-up heating.

[0049] The drive-in heating temperature is preferably higher than the 10-hour half-life temperature of the thermal polymerization initiator, and specifically, is usually 40 to 150°C, and from the viewpoint of suppressing gelation, it is preferably 55 to 130°C, and more preferably 75 to 95°C. If the drive-in heating temperature is too high, the acrylic resin (A) tends to yellow, while if it is too low, the polymerization components and thermal polymerization initiator remain, and the stability over time and thermal stability of the acrylic resin (A) tend to decrease. In this way, an acrylic resin (A) solution can be obtained.

[0050] The weight-average molecular weight (Mw) of the acrylic resin (A) is 1.1 million or more, preferably 1.15 million to 3.0 million, more preferably 1.2 million to 2.7 million, and even more preferably 1.25 million to 2.3 million. If the weight-average molecular weight is too small, the cohesive strength of the resulting pressure-sensitive adhesive layer tends to decrease, and the stretchability after active energy ray curing tends to decrease. On the other hand, if the weight-average molecular weight is too large, the compatibility with the active energy ray-curable compound (B) described below tends to decrease, the solution viscosity increases, and the coatability tends to decrease, and the adhesive strength before active energy ray irradiation tends to decrease. If the weight-average molecular weight is within the above range, in addition to the adhesive properties and stretchability, the adhesive layer also exhibits excellent peelability (lower adhesive strength) after active energy ray irradiation.

[0051] The dispersity of the acrylic resin (A) [weight average molecular weight (Mw) / number average molecular weight (Mn)] is preferably 10 or less, more preferably 7 or less. If the dispersity is too high, the cohesive strength tends to decrease. The lower limit of the dispersity is usually 1.

[0052] The weight-average molecular weight (Mw) of the acrylic resin (A) is a weight-average molecular weight converted into a standard polystyrene molecular weight. The weight-average molecular weight was measured by a high-performance liquid chromatograph (manufactured by Japan Waters, Inc., "Waters2695 (main body)" and "Waters2414 (detector)") using a column: Shodex GPCKF-806L (exclusion limit molecular weight: 2 × 10 7 Separation range: 100 to 2 × 10 7 The molecular weight can be measured by connecting three columns in series (theoretical plate number: 10,000 columns / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm), and the number average molecular weight can be measured in a similar manner. The dispersity can be determined from the measured values ​​of the weight average molecular weight (Mw) and number average molecular weight (Mn).

[0053] The glass transition temperature (Tg) of the acrylic resin (A) is preferably 0° C. or lower, more preferably −70 to −10° C., even more preferably −65 to −15° C., and particularly preferably −60 to −20° C. If the glass transition temperature is too low, the cohesive strength of the pressure-sensitive adhesive layer tends to decrease and the adhesive strength before irradiation with active energy rays tends to decrease, while if the glass transition temperature is too high, the adhesion to the workpiece tends to decrease and the stretchability after irradiation with active energy rays tends to decrease.

[0054] The glass transition temperature (Tg) is a value calculated by applying the glass transition temperature and mass fraction of each of the monomers constituting the acrylic resin (A) to the following Fox formula when the monomers are made into homopolymers.

number

[0055] Here, the glass transition temperature of the homopolymer of the monomers constituting the acrylic resin (A) is usually measured by a differential scanning calorimeter (DSC), and can be measured by a method in accordance with JIS K7121-1987 or JIS K6240.

[0056] When the acrylic resin (A) is formed into a sheet, the tensile elongation at break measured under the following conditions is preferably 500% or more, more preferably 500 to 1000%, even more preferably 550 to 900%, and particularly preferably 550 to 900%. Having the tensile elongation at break within the above range is preferred because it is easy to achieve both adhesive properties and stretchability after irradiation with active energy rays. Conditions: A composition consisting of an acrylic resin (A) and a crosslinking agent (C) is applied to a substrate and dried, and a test piece (15 mm wide x 200 μm thick) adjusted to a gel fraction of 65% by mass or more is pulled at a speed of 300 mm / min with a chuck distance of 20 mm.

[0057] The gel fraction can be calculated from the weights of the test piece before and after immersion by applying a composition consisting of the acrylic resin (A) and the crosslinking agent (C) to a substrate, drying the composition, and aging the composition at 40°C for 7 days. The test piece is then cut into a size of 50 mm x 50 mm, sandwiched between 200 mesh stainless steel meshes, and immersed in ethyl acetate at 23°C for 24 hours. The test piece is then removed and dried, and the weights of the test piece before and after immersion can be calculated. Gel fraction (%) = [Weight of adhesive layer (before immersion) - Weight of SUS mesh] / [Weight of adhesive layer (after immersion) - Weight of SUS mesh] x 100

[0058] To obtain an acrylic resin (A) having such a tensile elongation at break, for example, a method of increasing the weight average molecular weight (Mw) of the acrylic resin (A), a method of reducing the amount of crosslinking agent (C) added, a method of reducing the content of functional group-containing monomer (a2) in the acrylic resin (A), etc., can be mentioned, and by combining these methods, the above-mentioned tensile elongation at break can be obtained. Among them, a method of increasing the weight average molecular weight (Mw) of the acrylic resin is preferred.

[0059] [Active energy ray-curable compound (B)] Examples of the active energy ray-curable compound (B) used in this embodiment include urethane (meth)acrylate compounds (b), monofunctional (meth)acrylate compounds, and polyfunctional (meth)acrylate compounds. Among these, urethane (meth)acrylate compounds (b) are preferred. These compounds may be used alone or in combination of two or more.

[0060] The urethane (meth)acrylate compound (b) may be a urethane (meth)acrylate compound which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1) and a polyvalent isocyanate compound (b2), or a urethane (meth)acrylate compound which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1), a polyvalent isocyanate compound (b2), and a polyol compound (b3), or a urethane (meth)acrylate compound which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1), a polyvalent isocyanate compound (b2), a monofunctional alcohol (b4), and, if necessary, a polyol compound (b3).

[0061] Among these, in the present embodiment, in terms of compatibility with the acrylic resin (A) and adhesive properties and contamination resistance before and after irradiation with active energy rays, a urethane (meth)acrylate compound which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1) and a polyvalent isocyanate compound (b2), or a urethane (meth)acrylate compound which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1), a polyvalent isocyanate compound (b2), and a polyol compound (b3) is preferred, and a urethane (meth)acrylate compound which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1) and a polyvalent isocyanate compound (b2) is particularly preferred. In this embodiment, the urethane (meth)acrylate compound (b) may be used alone or in combination of two or more kinds.

[0062] The hydroxyl group-containing (meth)acrylate compound (b1) is preferably one having one hydroxyl group, and examples thereof include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate, 2-hydroxyethyl acryloyl phosphate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, dipropylene glycol (meth)acrylate, fatty acid-modified glycidyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and 2-hydroxy-3-(meth)acrylate. Examples of the hydroxyl group-containing (meth)acrylate compounds include those containing one ethylenically unsaturated group, such as aryloyloxypropyl (meth)acrylate; those containing two ethylenically unsaturated groups, such as glycerin di(meth)acrylate and 2-hydroxy-3-acryloyloxypropyl methacrylate; and those containing three or more ethylenically unsaturated groups, such as pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, and ethylene oxide-modified dipentaerythritol penta(meth)acrylate. These hydroxyl group-containing (meth)acrylate compounds (b1) can be used alone or in combination of two or more.

[0063] Among these, 2-hydroxyethyl acrylate polypropylene glycol monoacrylate is more preferred in that the effects of the present invention can be easily obtained.

[0064] The hydroxyl value of the hydroxyl group-containing (meth)acrylate compound (b1) is preferably 10 to 1000 mgKOH / g, more preferably 20 to 500 mgKOH / g, and particularly preferably 120 to 490 mgKOH / g. When the hydroxyl value is within the above range, it is easy to achieve both easy peelability and stretchability after irradiation with active energy rays.

[0065] Examples of the polyisocyanate compound (b2) include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate, and dicyclohexylmethane-4-isocyanate; alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate; or isocyanurates of these polyisocyanates, adducts with polyhydroxyl compounds such as trimethylolpropane, or polymeric compounds, allophanate polyisocyanates, biuret polyisocyanates, and water-dispersible polyisocyanates.

[0066] Among these, in view of excellent reactivity, versatility and stretchability after irradiation with active energy rays, aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate, aromatic isocyanates such as tolylene diisocyanate and diphenylmethane diisocyanate, alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate and norbornene diisocyanate, and their isocyanurates, Adducts and allophanates with polyhydroxyl compounds are preferred, more preferably isophorone diisocyanate, tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate and their isocyanurates, and adducts and allophanates with polyhydroxyl compounds, and even more preferably isophorone diisocyanate, hexamethylene diisocyanate and their isocyanurates, and adducts and allophanates with polyhydroxyl compounds. Furthermore, dicyclohexylmethane-4,4'-diisocyanate and polyisocyanate-modified (bifunctional) compounds are preferred, as they are particularly effective in achieving the effects of the present invention.

[0067] The isocyanate group content of the polyisocyanate compound (b2) is preferably 1 to 95 mass %, more preferably 5 to 50 mass %, and particularly preferably 15 to 35 mass %. When the isocyanate group content is within the above range, it is easy to achieve both easy peelability and stretchability after irradiation with active energy rays.

[0068] The polyol compound (b3) may be any compound containing two or more hydroxyl groups, and examples thereof include aliphatic polyols, alicyclic polyols, polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, polybutadiene polyols, polyisoprene polyols, (meth)acrylic polyols, polysiloxane polyols, etc. These may be used alone or in combination of two or more.

[0069] Examples of the aliphatic polyols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, dimethylolpropane, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-tetramethylenediol, 1,3-tetramethylenediol, 2-methyl-1,3-trimethylenediol, 1,5-pentamethylenediol, 1, Examples include aliphatic alcohols containing two hydroxyl groups such as 6-hexamethylenediol, 3-methyl-1,5-pentamethylenediol, 2,4-diethyl-1,5-pentamethylenediol, pentaerythritol diacrylate, 1,9-nonanediol, and 2-methyl-1,8-octanediol; sugar alcohols such as xylitol and sorbitol; and aliphatic alcohols containing three or more hydroxyl groups such as glycerin, trimethylolpropane, and trimethylolethane.

[0070] Examples of the alicyclic polyol include cyclohexanediols such as 1,4-cyclohexanediol and cyclohexyldimethanol, hydrogenated bisphenols such as hydrogenated bisphenol A, and tricyclodecane dimethanol.

[0071] Examples of the polyether polyol include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, polypentamethylene glycol, and polyhexamethylene glycol, and random or block copolymers of these polyalkylene glycols.

[0072] Examples of the polyester polyol include a condensation polymer of a polyhydric alcohol and a polycarboxylic acid; a ring-opening polymer of a cyclic ester (lactone); and a reaction product of three components: a polyhydric alcohol, a polycarboxylic acid, and a cyclic ester.

[0073] Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylene diol, 1,3-tetramethylene diol, 2-methyl-1,3-trimethylene diol, 1,5-pentamethylene diol, neopentyl glycol, 1,6-hexamethylene diol, 3-methyl-1,5-pentamethylene diol, 2,4-diethyl-1,5-pentamethylene diol, glycerin, trimethylolpropane, trimethylolethane, cyclohexanediols (such as 1,4-cyclohexanediol), bisphenols (such as bisphenol A), and sugar alcohols (such as xylitol and sorbitol). Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid, and trimellitic acid. Examples of the cyclic ester include propiolactone, β-methyl-δ-valerolactone, and ε-caprolactone.

[0074] Examples of the polycarbonate polyol include a reaction product of a polyhydric alcohol with phosgene, and a ring-opening polymerization product of a cyclic carbonate ester (such as an alkylene carbonate). Examples of the polyhydric alcohol include the polyhydric alcohols exemplified in the description of the polyester polyol, and examples of the alkylene carbonate include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, and hexamethylene carbonate. The polycarbonate polyol may be any compound having a carbonate bond in the molecule and a hydroxyl group at the end, and may have an ester bond in addition to the carbonate bond.

[0075] The polyolefin polyols include those having a homopolymer or copolymer of ethylene, propylene, butene, or the like as a saturated hydrocarbon skeleton and having hydroxyl groups at the molecular terminals.

[0076] The polybutadiene polyol may be a polybutadiene polyol having a butadiene copolymer as a hydrocarbon skeleton and hydroxyl groups at its molecular terminals. The polybutadiene polyol may be a hydrogenated polybutadiene polyol in which all or part of the ethylenically unsaturated groups contained in the polybutadiene polyol structure have been hydrogenated.

[0077] The (meth)acrylic polyols include those having at least two hydroxyl groups in the molecule of a (meth)acrylic acid ester polymer or copolymer, and examples of such (meth)acrylic acid esters include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate.

[0078] Examples of the polysiloxane polyol include dimethylpolysiloxane polyol and methylphenylpolysiloxane polyol.

[0079] Among these, aliphatic polyols and alicyclic polyols are preferably used from the viewpoint of cost, polyester polyols, polyether polyols, and polycarbonate polyols are preferred from the viewpoint of versatility, and polytetramethylene ether glycol is particularly preferred from the viewpoint of ease of achieving the effects of the present invention.

[0080] The weight-average molecular weight of the polyol compound (b3) is preferably 60 to 10,000, more preferably 100 to 5,000, and even more preferably 200 to 4,000. If the weight-average molecular weight of the polyol compound (b3) is too large, the compatibility between the resulting urethane (meth)acrylate compound (b) and the (meth)acrylic resin (A) tends to decrease, and the peelability after irradiation with active energy rays tends to decrease.

[0081] The hydroxyl value of the polyol compound (b3) is preferably 10 to 1000 mgKOH / g, more preferably 20 to 500 mgKOH / g, and particularly preferably 150 to 200 mgKOH / g. When the hydroxyl value is within the above range, it is easy to achieve both easy peelability and stretchability after irradiation with active energy rays.

[0082] The monofunctional alcohol (b4) is not particularly limited, and examples thereof include alcohols containing a linear or branched alkyl group having 1 to 36 carbon atoms, aromatic ring-containing alcohols, alicyclic group-containing alcohols, and heterocycle-containing alcohols, and from the viewpoint of versatility, alcohols containing a linear or branched alkyl group having 1 to 36 carbon atoms are preferred, and alcohols containing a linear or branched alkyl group having 4 to 18 carbon atoms are more preferred. These may be used alone or in combination of two or more.

[0083] The urethane (meth)acrylate compound (b) can be produced by reacting the above-mentioned components by known reaction means, an example of which is shown below. (1) To obtain a urethane (meth)acrylate compound A method of subjecting the hydroxyl group-containing (meth)acrylate compound (b1) to a urethane reaction with a polyisocyanate compound (b2). (2) To obtain a urethane (meth)acrylate compound a method of subjecting the hydroxyl group-containing (meth)acrylate compound (b1), a polyisocyanate compound (b2), and a polyol compound (b3) to a urethane reaction; (3) To obtain a urethane (meth)acrylate compound A method of subjecting the hydroxyl group-containing (meth)acrylate compound (b1), the polyisocyanate compound (b2), the polyol compound (b3), and further the monofunctional alcohol (b4) to a urethane reaction.

[0084] The urethanization reaction can be carried out by charging the components into a reactor all at once or separately and carrying out the urethanization reaction by a known reaction means. When producing a urethane (meth)acrylate compound or a urethane (meth)acrylate compound, a method of reacting a polyol compound (b3) with a polyisocyanate compound (b2) in advance to obtain a reaction product, and then reacting the resulting product with a hydroxyl group-containing (meth)acrylate compound (b1) or a monofunctional alcohol (b4) is useful in terms of the stability of the urethanization reaction and the reduction of by-products.

[0085] In the reaction between the hydroxyl group-containing (meth)acrylate compound (b1) and the polyvalent isocyanate compound (b2), it is preferable to use a reaction catalyst in order to promote the reaction.

[0086] Examples of the reaction catalyst include organic metal compounds such as dibutyltin dilaurate, trimethyltin hydroxide, and tetra-n-butyltin; metal salts such as zinc octenoate, tin octenoate, tin octoate, cobalt naphthenate, stannous chloride, and stannic chloride; amine catalysts such as triethylamine, benzyldiethylamine, 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]undecene, N,N,N',N'-tetramethyl-1,3-butanediamine, and N-ethylmorpholine; organic bismuth compounds such as dibutyl bismuth dilaurate and dioctyl bismuth dilaurate; Examples of suitable catalysts include bismuth catalysts such as organic acid bismuth salts, such as bismuth 2-ethylhexanoate, bismuth naphthenate, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth acetate, bismuth bisneodecanoate, bismuth disalicylate, and bismuth digallate; zirconium catalysts, such as inorganic zirconium, organic zirconium, and simple zirconium; and combinations of two or more catalysts, such as zinc 2-ethylhexanoate / zirconium tetraacetylacetonate. Among these, dibutyltin dilaurate and organic bismuth compounds are preferred. These catalysts can be used singly or in combination.

[0087] In the urethanization reaction, organic solvents that do not have a functional group that reacts with an isocyanate group, such as esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatics such as toluene and xylene, can be used.

[0088] The reaction temperature for the urethanization reaction is usually 30 to 90°C, preferably 40 to 80°C, and the reaction time is usually 2 to 10 hours, preferably 3 to 8 hours.

[0089] The urethane-forming reaction is terminated when the content of residual isocyanate groups in the reaction system reaches 0.5% by mass or less, thereby obtaining the urethane (meth)acrylate compound (b).

[0090] The (meth)acryloyl group concentration of the urethane (meth)acrylate compound (b) obtained in this manner is usually 0.01 to 50 mass%, preferably 0.05 to 40 mass%, more preferably 0.1 to 20 mass%, and particularly preferably 0.2 to 10 mass%. By setting the (meth)acryloyl group concentration of the urethane (meth)acrylate compound (b) within the above range, it tends to be possible to obtain a compound with excellent releasability and stretchability after irradiation with active energy rays. The acrylic group concentration is calculated by the following formula, and when two or more types of urethane (meth)acrylate compounds (b) are used, it can be calculated as the sum of the products of the respective weight fractions. Acryloyl group concentration (mass%) = 55 × N(UA) / Mw(UA) N(UA): Number of acryloyl groups in urethane (meth)acrylate Mw(UA): Weight average molecular weight of urethane (meth)acrylate

[0091] Furthermore, from the viewpoint of ease of releasability and stretchability after irradiation with active energy rays, the urethane (meth)acrylate compound (b) preferably has 15 or less ethylenically unsaturated groups, more preferably 2 to 10, and particularly preferably 2 to 5. If the number of ethylenically unsaturated groups is too small, sufficient crosslinking density cannot be obtained and ease of releasability tends to decrease, whereas if the number is too large, stretchability after irradiation with active energy rays tends to decrease.

[0092] The weight-average molecular weight of the urethane (meth)acrylate compound (b) is usually 200 to 10,000, preferably 400 to 5,000, and more preferably 600 to 4,000. If the weight-average molecular weight is too large, the compatibility between the urethane (meth)acrylate compound (b) and the (meth)acrylic resin (A) tends to decrease, resulting in a decrease in adhesive properties before and after irradiation with active energy rays. If the weight-average molecular weight is too small, the cohesive force of the adhesive layer tends to decrease, resulting in a decrease in adhesive properties.

[0093] The weight-average molecular weight is a weight-average molecular weight converted to standard polystyrene molecular weight, and is measured using a high-performance liquid chromatograph (Waters, "ACQUITY APC System") with four columns arranged in series: one ACQUITY APCXT450, one ACQUITY APCXT200, and two ACQUITY APCXT45.

[0094] The viscosity of the urethane (meth)acrylate compound (b) used in this embodiment at 60°C is preferably 50 to 10,000 mPa·s, more preferably 100 to 7,000 mPa·s, and particularly preferably 200 to 4,000 mPa·s. If the viscosity is too low, the cohesive force tends to decrease, and if it is too high, the coatability tends to decrease. The viscosity can be measured using an E-type viscometer.

[0095] The monofunctional (meth)acrylate compound is one other than the urethane (meth)acrylate compound (b), and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, acrylonitrile, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, glycerin mono(meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and the like. meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)-methyl (meth)acrylate, cyclohexanespiro-2-(1,3-dioxolan-4-yl)-methyl (meth)acrylate, 3-ethyl-3-oxetanylmethyl (meth)acrylate, γ-butyrolactone (meth)acrylate, n-butyl (meth)acrylate ) acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, n-stearyl (meth)acrylate, benzyl (meth)acrylate, phenol ethylene oxide modified (n=2) (meth)acrylate, nonylphenol propylene oxide modified (n=2.5) (Meth)acrylate monomers such as half (meth)acrylates of phthalic acid derivatives, such as 2-(meth)acryloyloxyethyl acid phosphate and 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, furfuryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, carbitol (meth)acrylate, benzyl (meth)acrylate, butoxyethyl (meth)acrylate, allyl (meth)acrylate, (meth)acryloylmorpholine, and polyoxyethylene secondary alkyl ether acrylate, 2-hydroxyethyl acrylamide, N-methylol (meth)acrylamide, N-vinylpyrrolidone, 2-vinylpyridine, and vinyl acetate.

[0096] The polyfunctional (meth)acrylate compound is one other than the urethane (meth)acrylate compound (b), and examples thereof include bifunctional (meth)acrylates and trifunctional or higher acrylates. Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, propylene oxide-modified bisphenol A di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, Examples of the diglycidyl acrylate include acrylate, ethoxylated cyclohexanedimethanol di(meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid-modified neopentyl glycol di(meth)acrylate, and isocyanuric acid ethylene oxide-modified diacrylate.

[0097] The tri- or higher functional acrylate is one other than the urethane (meth)acrylate compound (b), and examples thereof include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly(meth)acrylate, isocyanuric acid ethylene oxide modified triacrylate, caprolactone modified dipentaerythritol, and the like. Examples of the dipentaerythritol acrylate include dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tetra(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, and ethoxylated 15-glycerin triacrylate.

[0098] Furthermore, as the active energy ray-curable compound (B), a Michael adduct of acrylic acid or a 2-acryloyloxyethyl dicarboxylic acid monoester can also be used. Examples of such a Michael adduct of acrylic acid include (meth)acrylic acid dimer, (meth)acrylic acid trimer, and (meth)acrylic acid tetramer.

[0099] Examples of the 2-acryloyloxyethyl dicarboxylic acid monoester include carboxylic acids having specific substituents, such as 2-acryloyloxyethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2-acryloyloxyethyl hexahydrophthalic acid monoester, and 2-methacryloyloxyethyl hexahydrophthalic acid monoester. Further examples include oligoester acrylates.

[0100] These active energy ray-curable compounds (B) can be used alone or in combination of two or more.

[0101] In the active energy ray-curable pressure-sensitive adhesive composition of this embodiment, the content of the active energy ray-curable compound (B) is preferably 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, even more preferably 10 to 100 parts by mass, and still more preferably 15 to 80 parts by mass, relative to 100 parts by mass of the (meth)acrylic resin (A). If the content of the active energy ray-curable compound (B) is too low, the peelability after irradiation with active energy rays tends to decrease, while if it is too high, the stretchability before and after irradiation with active energy rays tends to decrease.

[0102] The content of the urethane (meth)acrylate compound (b) in the active energy ray-curable compound (B) is usually 50% by mass or more, preferably 80% by mass or more, with the upper limit being 100% by mass. If the content is too small, the adhesive properties before irradiation with active energy rays tend to decrease, and it becomes difficult to achieve both easy peelability and stretchability after irradiation with active energy rays.

[0103] The content of monofunctional (meth)acrylates and polyfunctional (meth)acrylates other than the urethane (meth)acrylate compound (b) in the active energy ray-curable compound (B) is usually less than 50% by mass, preferably less than 20% by mass, with the lower limit being 0% by mass. If the content is too high, the stretchability after irradiation with active energy rays tends to decrease.

[0104] [Crosslinking agent (C)] The pressure-sensitive adhesive composition further contains a crosslinking agent (C). Examples of the crosslinking agent (C) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, and amine-based crosslinking agents. Among these, it is preferable to use an isocyanate-based crosslinking agent in terms of improving the adhesion of the peel-type pressure-sensitive adhesive sheet to the substrate sheet and in terms of reactivity with the acrylic resin (A). These crosslinking agents (C) may be used alone or in combination of two or more.

[0105] Examples of the isocyanate-based crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hexamethylene diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, and biuret and isocyanurate forms of these polyisocyanate compounds. Among these, in terms of chemical resistance and reactivity with functional groups, the isocyanurate of hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, adduct of 2,6-tolylene diisocyanate and trimethylolpropane, isocyanurates of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, and adduct of tetramethylxylylene diisocyanate and trimethylolpropane are preferred.

[0106] Examples of the epoxy crosslinking agent include bisphenol A-epichlorohydrin type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, 1,3'-bis(N,N-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-m-xylylenediamine.

[0107] Examples of the aziridine-based crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide).

[0108] Examples of the oxazoline-based crosslinking agent include 2,2'-bis(2-oxazoline), 1,2-bis(2-oxazolin-2-yl)ethane, 1,4-bis(2-oxazolin-2-yl)butane, 1,8-bis(2-oxazolin-2-yl)butane, 1,4-bis(2-oxazolin-2-yl)cyclohexane, 1,2-bis(2-oxazolin-2-yl)benzene, and 1,3-bis(2-oxazolin-2-yl) Examples include bisoxazoline compounds containing aliphatic or aromatic groups such as benzene, and polymers of one or more addition-polymerizable oxazolines such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

[0109] Examples of the melamine-based crosslinking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins.

[0110] Examples of the aldehyde crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleic dialdehyde, glutaric dialdehyde, formaldehyde, acetaldehyde, and benzaldehyde.

[0111] Examples of the amine-based crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resins, and polyamides.

[0112] The content of the crosslinking agent (C) is usually 0.1 to 30 parts by mass, preferably 0.2 to 20 parts by mass, and more preferably 0.3 to 15 parts by mass, relative to 100 parts by mass of the acrylic resin (A). If the amount of crosslinking agent (C) is too small, the cohesive strength of the adhesive layer tends to decrease, and the adhesive properties tend to decrease. If the amount of crosslinking agent (C) is too large, the adhesive properties before irradiation with active energy rays tend to decrease, and the stretchability after irradiation with active energy rays tends to decrease.

[0113] [Photopolymerization initiator (D)] The present pressure-sensitive adhesive composition preferably contains a photopolymerization initiator (D). The photopolymerization initiator (D) used in this embodiment may be any one that generates radicals by the action of light. When the acrylic resin (A) has the photocrosslinkable structural moiety, the photopolymerization initiator (D) may not be contained.

[0114] Examples of the photopolymerization initiator (D) include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, Acetophenones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer; benzoins such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, and 4-benzoyl-4'-methyl-diphenyl sulfide , 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, (4-benzoylbenzyl)trimethylammonium chloride and other benzophenones; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1 thioxanthones such as 2-chloro-4-propoxythioxanthone and 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one mesochloride; and acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.Among these, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, etc. are preferred because they do not sublimate even when heated and are stable. These photopolymerization initiators (D) can be used alone or in combination of two or more.

[0115] Examples of auxiliary agents for the photopolymerization initiator (D) include triethanolamine, triisopropanolamine, and 4,4'-dimethylaminobenzophenone (Michler's ketone). It is also possible to use in combination with 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, etc. These auxiliary agents can also be used alone or in combination of two or more.

[0116] The content of the photopolymerization initiator (D) is preferably 0.1 to 20 parts by mass, particularly preferably 0.5 to 15 parts by mass, and especially preferably 1 to 10 parts by mass, relative to 100 parts by mass of the active energy ray-curable compound (B). If the content of the photopolymerization initiator (D) is too low, the peelability after irradiation with active energy rays tends to be easily reduced, while if it is too high, the contamination resistance of the workpiece after irradiation with active energy rays tends to be reduced.

[0117] [Other ingredients] The present pressure-sensitive adhesive composition may further contain additives such as antistatic agents, antioxidants, plasticizers, fillers, pigments, diluents, antioxidants, UV absorbers, and UV stabilizers, provided that the effects of the present invention are not impaired. These additives may be used alone or in combination of two or more. Antioxidants are particularly effective in maintaining the stability of the pressure-sensitive adhesive layer. When an antioxidant is added, its content is not particularly limited, but is preferably 0.01 to 5 mass% of the pressure-sensitive adhesive composition. In addition to the additives, the pressure-sensitive adhesive composition of the present invention may also contain small amounts of impurities contained in the raw materials used to produce the components of the pressure-sensitive adhesive composition.

[0118] Furthermore, since the present pressure-sensitive adhesive composition has reduced contamination resistance on the workpiece after irradiation with active energy rays, it is preferable that the pressure-sensitive adhesive composition does not contain a tackifying resin such as a terpene-based resin, a rosin-based resin, a chroman-based resin, a phenol-based resin, a styrene-based resin, or a petroleum-based resin.

[0119] [Active energy ray-curable peelable pressure-sensitive adhesive composition] Thus, the present pressure-sensitive adhesive composition is obtained by mixing the acrylic resin (A), the active energy ray-curable compound (B), and the crosslinking agent (C) with optional components such as the photopolymerization initiator (D) and other components, as needed.

[0120] The present pressure-sensitive adhesive composition is crosslinked by the crosslinking agent (C) and is therefore suitable for use as a pressure-sensitive adhesive layer in an active energy ray-curable peel-type pressure-sensitive adhesive sheet. After this active energy ray-curable peel-type pressure-sensitive adhesive sheet is attached to a workpiece, the pressure-sensitive adhesive layer is cured by irradiating the sheet with active energy rays, resulting in a decrease in adhesive strength and thus exhibiting releasability. Taking advantage of this property, the sheet is used to temporarily protect the surface of various workpieces when processing the workpieces. The active energy ray-curable peelable pressure-sensitive adhesive sheet will be described below.

[0121] Examples of workpieces that can be protected by the active energy ray-curable peelable pressure-sensitive adhesive sheet include semiconductor wafers, printed circuit boards, processed glass products, metal plates, and plastic plates.

[0122] The active energy ray-curable peelable adhesive sheet typically comprises a substrate sheet, an adhesive layer comprising the present adhesive composition, and a release film. To prepare such an active energy ray-curable peelable adhesive sheet, the present adhesive composition is first applied directly onto a release film or a substrate sheet, either as is or after adjusting the concentration with an appropriate organic solvent. The composition is then dried, for example, by heat treatment at 80 to 105°C for 0.5 to 10 minutes, and then attached to a substrate sheet or a release film to obtain a peelable adhesive sheet. To balance the adhesive properties, the composition may be further aged after drying.

[0123] Examples of the substrate sheet include sheets made of at least one synthetic resin selected from the group consisting of: polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymer; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyethylene fluoride resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyethylene fluoride; polyamides such as nylon 6 and nylon 6,6; vinyl polymers such as polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; cellulose resins such as cellulose triacetate and cellophane; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; polystyrene; polycarbonate; polyarylate; and polyimide; and woven and nonwoven fabrics made of metal foils such as aluminum, copper, and iron, paper such as fine paper and glassine paper, glass fiber, natural fibers, synthetic fibers, etc. These substrate sheets can be used as a single layer or as a multi-layered body in which two or more types are laminated together. Among these, sheets made of synthetic resins are preferred from the viewpoint of weight reduction and the like.

[0124] Furthermore, as the release film, for example, various synthetic resin sheets, paper, woven fabrics, nonwoven fabrics, etc. exemplified above as the base material sheets can be used which have been subjected to a release treatment.

[0125] The method for applying the pressure-sensitive adhesive composition is not particularly limited as long as it is a common coating method, and examples thereof include roll coating, die coating, gravure coating, comma coating, and screen printing.

[0126] As the active energy rays, generally, light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X-rays and gamma rays, as well as electron beams, proton beams, neutron beams, etc. can be used. However, it is advantageous to use ultraviolet rays in terms of curing speed, ease of availability of irradiation equipment, cost, etc.

[0127] The cumulative irradiation dose of the ultraviolet rays is usually 50 to 3000 mJ / cm 2 and preferably 100 to 1000 mJ / cm 2 The irradiation time varies depending on the type of light source, the distance between the light source and the adhesive layer, the thickness of the adhesive layer, and other conditions, but is usually a few seconds, and in some cases may be a very short time of less than one second.

[0128] The adhesive strength of the active energy ray-curable peelable adhesive sheet varies depending on the type of substrate sheet, the type of workpiece, etc., but the 180-degree peel strength before irradiation with active energy rays is usually 1 N / 25 mm or more, and preferably 3 N / 25 mm or more.

[0129] The active energy ray-curable peelable pressure-sensitive adhesive sheet generally has a peel strength lower after irradiation with active energy rays than that before irradiation with active energy rays. The 180-degree peel strength of the peelable pressure-sensitive adhesive sheet after irradiation with active energy rays is usually 1 N / 25 mm or less, and preferably 0.5 N / 25 mm or less.

[0130] The elongation of the active energy ray-curable release sheet after irradiation with active energy rays is usually 45% or more, preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more, with the upper limit usually being 200%.

[0131] The elongation of the active energy ray-curable release sheet after irradiation with active energy rays was measured by irradiating a sheet piece having a sheet structure of light release PET / adhesive layer / heavy release PET with an adhesive layer thickness of 100 μm and a width of 15 mm with an 80 W high-pressure mercury lamp at an integrated irradiation dose of 1000 mJ / cm. 2 After irradiation, the adhesive layer alone is removed from the sheet piece and pulled under conditions of a chuck distance of 20 mm and a pulling speed of 30 mm / min, and the adhesive strength can be calculated from the displacement when the adhesive layer breaks.

[0132] A peelable adhesive sheet using this adhesive composition as an adhesive layer can be attached to a workpiece to temporarily protect the surface of the workpiece, and then irradiated with active energy rays, whereby the adhesive layer hardens and the adhesive strength decreases, allowing the sheet to be easily peeled off from the workpiece. [Example]

[0133] The present invention will be described in more detail below with reference to 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" refers to parts by mass.

[0134] [Production of acrylic resin (A-1)] A reactor equipped with a temperature controller, thermometer, stirrer, dropping funnel, and reflux condenser was charged with 65 parts of n-butyl acrylate (a1), 30 parts of methyl acrylate (a1), 5 parts of acrylic acid (a2), 100 parts of ethyl acetate, and 0.0125 parts of 2,2'-azobisisobutyronitrile (AIBN (thermal polymerization initiator)) as a polymerization catalyst. The mixture was heated with stirring, and the reaction started when the internal temperature reached its peak. The mixture was then added dropwise over 1 hour. Next, 1.75 hours after the start of the reaction, 30 parts of ethyl acetate were added dropwise over 1 hour. 3.25 hours after the start of the reaction, ethyl acetate and 60 ppm of polymerization inhibitor (MEHQ) were added to terminate the reaction, yielding an acrylic resin (A-1) solution.

[0135] [Acrylic resin (A-2)] In a reactor equipped with a temperature controller, thermometer, stirrer, dropping funnel, and reflux condenser, 95 parts of n-butyl acrylate (a1), 5 parts of acrylic acid (a2), 15 parts of ethyl acetate, 40 parts of acetone, and 0.0125 parts of AIBN were charged, and the temperature was raised with stirring. The reaction started when the internal temperature reached its peak top. 0.5 hours after the start of the reaction, a mixture of 33 parts of ethyl acetate and 0.125 parts of AIBN was added dropwise over 1 hour, and then 1.75 hours after the start of the reaction, 25 parts of ethyl acetate was added dropwise over 1 hour. 3.25 hours after the start of the reaction, ethyl acetate and 60 ppm of polymerization inhibitor (MEHQ) were added to terminate the reaction, and an acrylic resin (A-2) solution was obtained.

[0136] [Acrylic resin (A'-1)] A reactor equipped with a temperature controller, thermometer, stirrer, dropping funnel, and reflux condenser was charged with 66 parts of ethyl acetate and heated to reflux while stirring. Once the internal temperature stabilized, a mixture of 70 parts of n-butyl acrylate (a1), 20 parts of methyl methacrylate (a1), 9.9 parts of acrylic acid (a2), 0.1 parts of 2-hydroxyethyl methacrylate (a2), 4 parts of ethyl acetate, and 0.035 parts of AIBN was added dropwise over 2 hours and allowed to react under reflux. Next, 22 parts of ethyl acetate and 0.04 parts of AIBN were added 3 hours after the start of the reaction, and then 8 parts of ethyl acetate and 0.04 parts of AIBN were added 5 hours after the start of the reaction. The reaction was terminated 7 hours after the start of the reaction, yielding an acrylic resin (A'-1) solution.

[0137] [Acrylic resin (A'-2)] A reactor equipped with a temperature controller, thermometer, stirrer, dropping funnel, and reflux condenser was charged with 90 parts of ethyl acetate and 0.07 parts of AIBN, and the temperature was raised to reflux with stirring. Once the internal temperature stabilized, a mixture of 70 parts of n-butyl acrylate (a1), 25 parts of methyl acrylate (a1), and 5 parts of acrylic acid (a2) as copolymerization components was added dropwise over 2 hours and reacted under reflux. Next, 3 hours after the start of the reaction, 8 parts of ethyl acetate and 0.05 parts of AIBN were added, and then 5 hours after the start of the reaction, 8 parts of ethyl acetate and 0.03 parts of AIBN were added. The reaction was terminated 7 hours after the start of the reaction, yielding an acrylic resin (A'-2) solution.

[0138] [Physical Properties of Acrylic Resins (A-1), (A-2), (A'-1), and (A'-2)] The copolymerization components and physical properties of the acrylic resins (A-1), (A-2), (A'-1), and (A'-2) obtained above are shown in Table 1. The weight average molecular weight and glass transition temperature were measured as follows.

[0139] (Measurement of weight average molecular weight) The weight-average molecular weight (Mw) of the acrylic resin (A) is the weight-average molecular weight converted into the molecular weight of standard polystyrene. The weight-average molecular weight was measured by a high-performance liquid chromatograph (manufactured by Japan Waters, Inc., "Waters2695 (main body)" and "Waters2414 (detector)") using a Shodex GPCKF-806L column (molecular weight exclusion limit: 2 × 10 7 Separation range: 100 to 2 × 10 7 The measurement was carried out using three columns connected in series (theoretical plate number: 10,000 plates / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm).

[0140] (Measurement of glass transition temperature) The glass transition temperature (Tg) was calculated by applying the glass transition temperature and mass fraction of each of the monomers constituting the acrylic resin (A) as a homopolymer to the following Fox's formula.

number

[0141] [Table 1]

[0142] [Preparation of acrylic resin sheet] A composition prepared by blending the acrylic resins (A-1), (A-2), (A'-1), and (A'-2) obtained above and the crosslinking agent (C-1) described below as shown in Table 2 below was applied to a heavy release film ("SP-PET3803-BU" manufactured by Mitsui Chemicals Tohcello Inc.), dried at 100°C for 5 minutes, and then attached to a light release film ("SP-PET3801-BU" manufactured by Mitsui Chemicals Tohcello Inc.) and aged at 40°C for 3 days to adjust the gel fraction to 65% or more, thereby obtaining an acrylic resin sheet (acrylic resin layer thickness: 200 μm).

[0143] (Measurement of tensile elongation at break of acrylic resin sheet) The release film was peeled off from a 15 mm wide test piece of the acrylic resin sheet obtained above, leaving only the acrylic resin layer, and then the composition was applied to a substrate and dried using a precision universal testing machine (Shimadzu Corporation's "Autograph AG-X"), and the test piece (15 mm wide x 200 μm thick) adjusted to a gel fraction of 65% or more was measured for tensile elongation at break (%) at a speed of 300 mm / min with a chuck distance of 20 mm. The results are shown in Table 2 below.

[0144] (Measurement of gel fraction of acrylic resin sheet) The adhesive layer alone was removed from a 50mm x 50mm test piece of the resulting adhesive sheet for tensile evaluation, sandwiched between 200-mesh stainless steel sheets, immersed in ethyl acetate, and left to stand at 23°C for 24 hours. After standing, the piece was removed and the ethyl acetate was completely evaporated using a dryer. The gel fraction (%) was calculated from the weight before and after immersion using the following formula. The results are shown in Table 2 below. Gel fraction (%) = [Weight of adhesive layer (before immersion) - Weight of SUS mesh] / [Weight of adhesive layer (after immersion) - Weight of SUS mesh] x 100

[0145] [Table 2]

[0146] [Production of active energy ray-curable compounds (B-1) to (B-9)] (Production of urethane (meth)acrylate (b-1)) A four-neck flask equipped with a temperature controller, a thermometer, a stirrer, a water-cooled condenser, and a nitrogen gas inlet was charged with 39.9 parts of 2-hydroxypropyl acrylate (b1) (manufactured by Osaka Organic Chemicals), 60.1 parts of a polyisocyanate modified product (isocyanate group content: 21.0%) (manufactured by Tosoh Corporation) (b2), 0.04 parts of 2,6-di-tert-butylcresol (BHT) as a polymerization inhibitor, and 0.02 parts of dibutyltin dilaurate (DBTL), a tin compound, as a reaction catalyst, and reacted at 60°C. The reaction was terminated when the residual isocyanate groups reached 0.3 mass% or less, yielding a mixture of urethane acrylate (b-1) (6 ethylenically unsaturated groups, weight-average molecular weight 2400, acryloyl group concentration 6.9 mass%) in which the ratio of (b1):(b2) was 3:1 (mol). The copolymerization components and physical properties of the resulting urethane (meth)acrylate (b-1) are shown in Table 3 below.

[0147] (Production of urethane (meth)acrylates (b-2) to (b-8)) Solutions of urethane (meth)acrylates (b-2) to (b-8) were obtained in the same manner as in the production of urethane (meth)acrylate (b-1), except that the monomer composition was changed as shown in Table 3 below. The copolymerization components, physical properties, etc. of the obtained urethane (meth)acrylates (b-2) to (b-8) are shown in Table 3 below.

[0148] [Table 3]

[0149] The urethane (meth)acrylates (b-1) to (b-8) obtained above were blended as shown in Table 4 below to prepare active energy ray-curable compounds (B-1) to (B-9).

[0150] [Table 4]

[0151] [Crosslinking agent (C)] The following crosslinking agent (C) was prepared: Isocyanate crosslinking agent (C-1): Trimethylolpropane adduct of tolylene diisocyanate (Tosoh Corporation: Coronate L-55E)

[0152] [Photopolymerization initiator (D)] The following photopolymerization initiator (D) was prepared. Photopolymerization initiator (D-1): 1-hydroxycyclohexyl phenyl ketone (OMNIRAD184 manufactured by IGM Resins)

[0153] [Examples 1 to 9, Comparative Examples 1 to 3] To 100 parts of the acrylic resin (A) prepared as described above, an active energy ray-curable compound (B), a crosslinking agent (C), and a photopolymerization initiator (D) were added and mixed as shown in Tables 5 and 6 below, and this was adjusted with ethyl acetate to a solids concentration (resin content) of 30 mass % to obtain a pressure-sensitive adhesive composition solution.

[0154] [Preparation of Peelable Pressure-Sensitive Adhesive Sheet] The adhesive composition solution obtained above was applied to a polyethylene terephthalate film (film thickness 38 μm) (manufactured by Toray Industries, Inc., "T60 Lumirror") as a substrate using an applicator, and then dried at 100°C for 5 minutes. After cooling to room temperature, the film was attached to a release film (manufactured by Mitsui Chemicals Tocello, Inc., "SP-PET3801-BU") and aged at 40°C for 3 days to obtain a peel-away adhesive sheet (adhesive layer thickness 25 μm). The resulting peelable pressure-sensitive adhesive sheets were subjected to the following measurements and evaluations, and the results are shown in Tables 5 and 6 below.

[0155] (Adhesive strength before exposure to active energy rays) A 25mm x 100mm test piece was prepared from the peel-off adhesive sheet obtained above, and after peeling off the release film, it was pressed onto a stainless steel plate (SUS304BA plate) by rolling a 2kg rubber roller back and forth twice in an atmosphere of 23°C and 50% relative humidity. After leaving it to stand in the same atmosphere for 30 minutes, the 180-degree peel strength (N / 25mm) was measured at a peel speed of 300mm / min and evaluated according to the following criteria. [Evaluation criteria] 〇:3N / 25mm or more △: 1N / 25mm or more, less than 3N / 25mm ×: Less than 1N / 25mm

[0156] (Adhesive strength after exposure to active energy rays) A 25 mm x 100 mm test piece was prepared from the peel-type pressure-sensitive adhesive sheet obtained above, and after peeling off the release film, it was pressed onto a stainless steel plate (SUS304BA plate) by rolling a 2 kg rubber roller back and forth twice in an atmosphere of 23°C and 50% relative humidity, and then left to stand for 30 minutes in an atmosphere of 23°C and 50% relative humidity. After that, it was irradiated with ultraviolet light (cumulative irradiation dose 180 mJ / cm) from a height of 18 cm at a conveyor speed of 51.0 m / min using one 80 W high-pressure mercury lamp. 2 After leaving the sample to stand for 30 minutes in an atmosphere of 23°C and 50% relative humidity, the 180° peel strength (N / 25 mm) was measured at a peel rate of 300 mm / min. [Evaluation criteria] ○: Less than 0.6N / 25mm △: 0.6N / 25mm or more, less than 1.0N / 25mm ×:1.0N / 25mm or more

[0157] (Elongation of peel-off pressure-sensitive adhesive sheet) [Preparation of sheet for evaluation of breaking elongation] In the preparation of the peel-type pressure-sensitive adhesive sheet, coating, drying, and aging were carried out in the same manner as in the preparation of the peel-type pressure-sensitive adhesive sheet, except that the substrate was changed to a heavy-release film (SP-PET3803BU) and the thickness of the pressure-sensitive adhesive layer was changed to 100 μm. Then, the sheet was irradiated with ultraviolet light (cumulative irradiation dose 1000 mJ / cm ) from a height of 18 cm at a conveyor speed of 9.2 m / min using one 80 W high-pressure mercury lamp. 2 ) to obtain a sheet for evaluation of breaking elongation.

[0158] (Elongation at break after irradiation with active energy rays) A 15 mm wide test piece was prepared from the sheet for evaluating breaking elongation obtained above, and the release film was peeled off from the test piece to leave only the adhesive layer. The breaking elongation was measured when the test piece was pulled at a chuck distance of 20 mm and a pulling speed of 30 mm / min using a precision universal testing machine (Shimadzu Corporation, "Autograph AG-X"), and evaluated according to the following criteria. [Evaluation criteria] ◎: 100% or more 〇: 50% or more, less than 100% △: 30% or more, less than 50% ×: Less than 30%

[0159] [Table 5]

[0160] [Table 6]

[0161] The sheets produced using the active energy ray-curable peelable pressure-sensitive adhesive compositions containing the acrylic resins having weight-average molecular weights of a specific amount or more in Examples 1 to 9 had good adhesive strength before active energy ray irradiation, good releasability after active energy ray irradiation, and also excellent elongation. On the other hand, the sheets produced using the active energy ray-curable peelable pressure-sensitive adhesive compositions containing acrylic resins having weight-average molecular weights of not more than a specific amount in Comparative Examples 1 to 3 were not excellent in any of the adhesive strength before active energy ray irradiation, the releasability after active energy ray irradiation, and the elongation. [Industrial Applicability]

[0162] The pressure-sensitive adhesive composition of the present invention can be suitably used as a pressure-sensitive adhesive sheet for temporary surface protection when processing electronic substrates, semiconductor wafers, processed glass products, metal plates, plastic plates, and the like.

Claims

1. An active energy ray-curable peel-off pressure-sensitive adhesive composition comprising an acrylic resin (A), an active energy ray-curable compound (B), and a crosslinking agent (C), The active energy ray-curable peelable pressure-sensitive adhesive composition, wherein the acrylic resin (A) has a weight-average molecular weight of 1,100,000 or more.

2. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, which has a tensile breaking elongation of 500% or more measured under the following conditions: Conditions: A composition consisting of an acrylic resin (A) and a crosslinking agent (C) is applied to a substrate and dried, and a test piece (width 15 mm x thickness 200 μm) adjusted to a gel fraction of 65% by mass or more is pulled at a speed of 300 mm / min with a chuck distance of 20 mm.

3. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic resin (A) has a glass transition temperature (Tg) of 0°C or lower.

4. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic resin (A) has a structural unit derived from a carboxy group-containing monomer (a2-1).

5. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the active energy ray-curable compound (B) contains a urethane (meth)acrylate (b).

6. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the content of the active energy ray-curable compound (B) is 5 to 100 parts by mass per 100 parts by mass of the acrylic resin (A).

7. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, further comprising a photopolymerization initiator (D).

8. An active energy ray-curable peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of claims 1 to 7 is crosslinked.

9. The active energy ray-curable peelable pressure-sensitive adhesive sheet according to claim 8, wherein the pressure-sensitive adhesive layer is cured and becomes peelable upon irradiation with active energy rays.

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