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

Abstract

To provide an adhesive having good adhesion before active energy ray irradiation, and after the irradiation, even under exposure to high temperature, having reduced adhesive strength, leaving no adhesive residue, and exhibiting excellent release property without change in wettability.SOLUTION: An active energy ray-curable release-type adhesive composition comprises an acrylic resin (A) and a hydroxyl group-containing hindered amine compound (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable peel-type pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet, and more particularly to an active energy ray-curable peel-type pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet used as a pressure-sensitive adhesive for a peel-type pressure-sensitive adhesive sheet 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 pressure-sensitive adhesive sheets, an active energy ray-curable pressure-sensitive adhesive composition that can be cured by irradiation with active energy rays and reduce adhesive strength is effective, and active energy ray-curability is exhibited, for example, by (1) blending at least one of a monomer and an 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. Among these, ethylenically unsaturated group-containing acrylic resins in which the acrylic resin itself contains an ethylenically unsaturated group have few low-molecular-weight components even after curing by irradiation with active energy rays, and are therefore advantageous in reducing adhesive residue after peeling.

[0004] In recent years, in the manufacturing process of electronic components, components with adhesive tape attached are often exposed to high temperatures. Therefore, adhesive tapes used in the manufacturing process of electronic components are required to have heat resistance so that they can withstand high temperature conditions. Patent Document 1 describes a workpiece processing sheet containing a hindered amine stabilizer in the adhesive layer.

[0005] Furthermore, Patent Document 2 describes that an adhesive in which an ultraviolet absorber or light stabilizer having a molecular weight of a specific value or less is added to a (meth)acrylate polymer having a (meth)acryloyl group in the side chain has excellent weather resistance, heat resistance, and mechanical properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2023 / 171079 [Patent Document 2] Japanese Patent Publication No. 2022-086816 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the techniques disclosed in Patent Documents 1 and 2 above have the problem that sufficient releasability cannot be obtained under high temperature conditions, for example, heat treatment conditions of 175° C. or higher, and are still unsatisfactory. Furthermore, no consideration is given to the change in wettability of the adherend before and after heat treatment.

[0008] Therefore, under such circumstances, the present invention aims to provide an active energy ray-curable peel-type pressure-sensitive adhesive composition that has good adhesive strength before irradiation with active energy rays and excellent heat resistance, and therefore can provide a pressure-sensitive adhesive that has reduced adhesive strength after irradiation with active energy rays even when exposed to high temperatures, leaves no adhesive residue, and has excellent peelability without causing any change in the wettability of the adherend before and after heat treatment. [Means for solving the problem]

[0009] However, the present inventors have conducted extensive research in light of these circumstances, and as a result have found that by using a composition containing an acrylic resin and a specific light stabilizer as a pressure-sensitive adhesive composition, a pressure-sensitive adhesive can be obtained that has good adhesive strength before irradiation with active energy rays, and that the adhesive strength is reduced after irradiation with active energy rays even when exposed to high temperatures, leaves no adhesive residue, and has excellent peelability without causing any change in wettability, thereby completing the present invention.

[0010] That is, the present invention has the following aspects [1] to [8]. [1] An active energy ray-curable peel-off pressure-sensitive adhesive composition comprising an acrylic resin (A) and a hydroxyl group-containing hindered amine compound (B). [2] The active energy ray-curable peelable pressure-sensitive adhesive composition according to [1], wherein the acrylic resin (A) has a structural unit derived from an alkyl group-containing (meth)acrylate (a1) and a structural unit derived from a functional group-containing monomer (a2) other than an amide group. [3] The active energy ray-curable peelable pressure-sensitive adhesive composition according to [1] or [2], wherein the acrylic resin (A) has a structural unit derived from an amide group-containing monomer (a3). [4] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the acrylic resin (A) further has an ethylenically unsaturated group. [5] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the acrylic resin (A) has an ethylenically unsaturated group content of 5 to 250 mmol / 100 g. [6] The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of [1] to [5], further comprising a crosslinking agent (C). [7] [1] [6] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive composition according to any one of [1] to [6] is crosslinked. [8] The pressure-sensitive adhesive sheet according to [7], wherein the pressure-sensitive adhesive layer is cured and becomes peelable upon irradiation with active energy rays. [Effects of the Invention]

[0011] The pressure-sensitive adhesive composition of the present invention has good adhesive strength before irradiation with active energy rays, and can be a pressure-sensitive adhesive having excellent peelability such that the adhesive strength is reduced after irradiation with active energy rays even when exposed to high temperatures, there is no adhesive residue, and there is no change in wettability before and after heat treatment.

[0012] Furthermore, it is presumed that the effects of the present invention are achieved by the fact that the pressure-sensitive adhesive composition of the present invention contains an acrylic resin and a hindered amine compound containing a hydroxyl group, and the hydroxyl group traps radicals in the pressure-sensitive adhesive composition, suppressing the production of a reaction product between the crosslinking agent and the hindered amine compound (B), thereby reducing contamination of the adherend. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments for carrying out the present invention will be specifically described, but the present invention is not limited to these. In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate, respectively. The acrylic resin is a resin obtained by polymerizing a polymerization component containing at least one kind of (meth)acrylate monomer. In the present invention, the term "sheet" is not particularly distinguished from "film" or "tape" and is used to include these terms.

[0014] The pressure-sensitive adhesive composition of the present invention is mainly used in the pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet that is 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 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, thereby reducing the adhesive strength and allowing it to be easily peeled off from the workpiece.

[0015] The pressure-sensitive adhesive composition of the present invention contains an acrylic resin (A) and a hydroxyl group-containing hindered amine compound (B). Each of the components of the pressure-sensitive adhesive composition of the present invention will be described below.

[0016] [Acrylic resin (A)] The acrylic resin (A) used in the present invention is a polymer obtained by polymerizing a copolymerization component (a), which preferably contains an alkyl (meth)acrylate (a1) as a main component and may also contain a functional group-containing monomer (a2), an amide group-containing monomer (a3), and, if necessary, other copolymerizable monomers (a4). The main component is the component that is most abundant in the copolymerization component (a), and typically accounts for 40% by weight or more, preferably 50% by weight or more, of the copolymerization component (a).

[0017] The content of each monomer relative to the total copolymerization component (a) can be considered to be the content of structural units derived from that monomer in all structural units constituting the acrylic resin (A), which is a copolymer. For example, the content of the hydroxyl group-containing monomer (a2-1) relative to the total copolymerization component (a) can be considered to be the content of structural units derived from the hydroxyl group-containing monomer (a2-1) in all structural units constituting the acrylic resin (A). Furthermore, when the pressure-sensitive adhesive composition of the present invention contains two or more acrylic resins (including acrylic resins that do not contain structural units derived from the hydroxyl group-containing monomer (a2-1)) that differ in constituent monomers or their contents, the contents of various monomers such as the hydroxyl group-containing monomer (a2-1) are the contents in the two or more acrylic resins as a whole.

[0018] [Alkyl (meth)acrylate (a1)] The acrylic resin (A) used in the present invention is a polymer obtained by polymerizing a copolymerization component (a), which contains an alkyl (meth)acrylate (a1) as a main component, and the number of carbon atoms in the alkyl group of the alkyl (meth)acrylate (a1) is preferably 1 to 20, particularly preferably 1 to 12, even more preferably 1 to 8, and especially preferably 1 to 6. When the number of carbon atoms in the alkyl group is within the above range, adhesive residue on the workpiece tends to be even less likely to occur.

[0019] Examples of the alkyl (meth)acrylate (a1) include aliphatic (meth)acrylic acid alkyl esters 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 (meth)acrylic acid alkyl esters 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), methyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred, and methyl (meth)acrylate and n-butyl (meth)acrylate are particularly preferred, in terms of copolymerizability, adhesive properties, ease of handling, and ease of raw material availability.

[0020] The content of alkyl (meth)acrylate (a1) in copolymerization component (a) of acrylic resin (A) is usually 30 to 99 wt %, preferably 40 to 90 wt %, and particularly preferably 50 to 80 wt % of the total copolymerization component (a). When the content is within the above range, the adhesive strength before irradiation with active energy rays is excellent, and the adhesive strength after irradiation with active energy rays is reduced, resulting in further improved releasability.

[0021] [Functional group-containing monomer (a2)] The functional group-containing monomer (a2) is a monomer having a functional group other than an amide group, and examples thereof include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, acetoacetyl group-containing monomers, etc. These functional group-containing monomers can be used alone or in combination of two or more.

[0022] The content of the functional group-containing monomer (a2) in the copolymerization components of the acrylic resin (A) is usually 50% by weight or less, preferably 40% by weight or less, and more preferably 30% by weight or less of the total copolymerization components. If the content is too high, storage stability tends to decrease, crosslinking may occur before the drying step, and problems with coating properties may easily occur. If the content is too low, the amount of ethylenically unsaturated groups introduced tends to decrease, and peelability after irradiation with active energy rays tends to decrease.

[0023] The acrylic resin (A) of the present invention preferably uses a hydroxyl group-containing monomer (a2-1) as the functional group-containing monomer (a2). By using the hydroxyl group-containing monomer (a2-1) as a copolymerization component of the acrylic resin (A), the acrylic resin (A) has a structural moiety derived from the hydroxyl group-containing monomer (a2), i.e., a hydroxyl group. This hydroxyl group serves as a reaction site when introducing an ethylenically unsaturated group (described later) and also serves as a reaction site with the crosslinking agent (C) (described later).

[0024] The hydroxyl group-containing monomer (a2-1) is preferably a hydroxyl group-containing (meth)acrylate monomer, and specific examples thereof include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate, and caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate. Examples of the monomers include oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate, primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate and 3-chloro-2-hydroxypropyl (meth)acrylate, and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate. These may be used alone or in combination of two or more. Among the above hydroxyl group-containing monomers, primary hydroxyl group-containing monomers are preferred because of their excellent reactivity with the ethylenically unsaturated compound and crosslinking agent (C) described below, and 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred.

[0025] The content of the hydroxyl group-containing monomer (a2-1) in the copolymerization components of the acrylic resin (A) is usually 0.1 to 60 wt%, preferably 1 to 50 wt%, more preferably 3 to 40 wt%, and particularly preferably 7 to 30 wt% of the total copolymerization components. If the content is too high, crosslinking tends to proceed before the drying step, which may cause problems with coatability, while if the content is too low, the amount of ethylenically unsaturated groups described below will be reduced, which may result in an insufficient reduction in adhesive strength and an increased susceptibility to contamination of workpieces.

[0026] Examples of the carboxy group-containing monomer include (meth)acrylic acid, (meth)acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamido-N-glycolic acid, cinnamic acid, etc. Among these, (meth)acrylic acid is preferably used in terms of copolymerizability.

[0027] The content of the carboxyl group-containing monomer in the copolymerization components of the acrylic resin (A) is usually 30% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. If the content is too high, the processed material tends to be easily deteriorated, storage stability tends to decrease, and crosslinking tends to proceed before the drying step, causing problems with coatability.

[0028] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0029] The content of the amino group-containing monomer in the copolymerization components of the acrylic resin (A) is usually 30% by weight or less, preferably 25% by weight or less, and more preferably 20% by weight or less, of the total copolymerization components. If the content is too high, crosslinking may proceed before the drying step, which may cause problems with coatability.

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

[0031] The content of the glycidyl group-containing monomer in the copolymerization components of the acrylic resin (A) is usually 120% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. If the content is too high, crosslinking may proceed before the drying step, which may cause problems with coatability.

[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] The content of the sulfonic acid group-containing monomer in the copolymerization components of the acrylic resin (A) is usually 10% by weight or less, preferably 5% by weight or less, and more preferably 1% by weight or less. If the content is too high, 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] The content of the acetoacetyl group-containing monomer in the copolymerization components of the acrylic resin (A) is usually 10% by weight or less, preferably 5% by weight or less, and more preferably 1% by weight or less. If the content is too high, crosslinking may proceed before the drying step, which may cause problems with coatability.

[0036] [Amide group-containing monomer (a3)] The acrylic resin (A) of the present invention preferably uses an amide group-containing monomer (a3) ​​as the copolymerization component (a). Examples of the amide group-containing monomer (a3) ​​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. In particular, (meth)acryloylmorpholine is preferred.

[0037] The content of the amide group-containing monomer (a3) ​​in the copolymerization component (a) of the acrylic resin (A) is usually 1 to 30% by weight, preferably 5 to 25% by weight, and more preferably 8 to 20% by weight of the total copolymerization components. If the content is too low, the effect of improving adhesion to the adherend brought about by the amide group-containing monomer (a3) ​​cannot be exerted, while if the content is too high, the polymer Tg becomes too high, which tends to make the adhesion to the adherend more likely to decrease.

[0038] [Other copolymerizable monomers (a4)] Examples of the other copolymerizable monomers (a4) include vinyl carboxylic acid ester monomers such as vinyl acetate, vinyl propionate, vinyl stearate, and vinyl benzoate; aromatic ring-containing monomers such as phenyl(meth)acrylate, benzyl(meth)acrylate, phenoxyethyl(meth)acrylate, phenyldiethylene glycol(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, styrene, and α-methylstyrene; biphenyloxy structure-containing (meth)acrylic acid ester monomers such as biphenyloxyethyl(meth)acrylate; 2-methoxyethyl(meth)acrylate, 2-ethoxyethyl(meth)acrylate, and the like. Examples of the monomer include monomers containing an alkoxy group or an oxyalkylene group, such as acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and polypropylene glycol mono(meth)acrylate; acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinylpyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyl trimethylammonium chloride, and dimethyl allyl vinyl ketone. These may be used alone or in combination of two or more.

[0039] The content of the other copolymerizable monomer (a4) in the copolymerization component (a) of the acrylic resin (A) is usually 40% by weight or less, preferably 30% by weight or less, and more preferably 25% by weight or less of the total copolymerization component. If the content of the other copolymerizable monomer (a4) is too high, the adhesive properties tend to be easily reduced.

[0040] In the present invention, a (meth)acrylic resin (A) is produced by polymerizing an alkyl (meth)acrylate (a1), a functional group-containing monomer (a2), an amide group-containing monomer (a3), and other copolymerizable monomers (a4) as copolymerization components (a). 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 is preferred because it allows the acrylic resin (A) to be produced safely and stably with any monomer composition.

[0041] In the solution radical polymerization, for example, copolymerization components (a) such as alkyl(meth)acrylate (a1), functional group-containing monomer (a2), amide group-containing monomer (a3), and, if necessary, other copolymerizable monomers (a4), and a 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.

[0042] Examples of the organic solvent 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. The amount of the organic solvent used is usually 10 to 900 parts by weight per 100 parts by weight of the copolymerization components.

[0043] As the polymerization initiator, a conventional radical polymerization initiator can be used. Specific examples thereof include azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, and peroxide-based polymerization initiators such as benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide and cumene hydroperoxide.

[0044] Furthermore, it is preferable that the acrylic resin (A) has a structural moiety derived from the hydroxyl group-containing monomer (a2-1), i.e., has a hydroxyl group, from the viewpoint of reactivity with the ethylenically unsaturated compound and the crosslinking agent (C), which will be described later. When the acrylic resin (A) has a hydroxyl group, it reacts with the ethylenically unsaturated compound, allowing an ethylenically unsaturated group to be introduced into the acrylic resin (A). Furthermore, a crosslinked structure is formed by the reaction with the crosslinking agent (C), which tends to improve the adhesive strength before irradiation with active energy rays.

[0045] When the acrylic resin (A) has hydroxyl groups, the content of the hydroxyl groups is usually 0.01 to 20% by weight, preferably 0.05 to 10% by weight, and more preferably 0.1 to 5% by weight, relative to the acrylic resin (A). If the hydroxyl group content is too low, the cohesive strength of the adhesive decreases, which tends to cause adhesive residue, while if the hydroxyl group content is too high, the flexibility and adhesive strength of the adhesive decrease, which tends to cause lifting from the workpiece.

[0046] The glass transition temperature (Tg) of the acrylic resin (A) is preferably −60 to 0° C., particularly −55 to −10° C., and further preferably −50 to −30° C. When the glass transition temperature is within the above range, the adhesiveness is excellent and the likelihood of contamination of workpieces is further reduced.

[0047] The glass transition temperature (Tg) is a value calculated by applying the glass transition temperature and weight fraction of each of the monomers constituting the acrylic resin (A) as a homopolymer to the following Fox's formula.

[0048]

number

[0049] Here, the glass transition temperature when the monomers constituting the acrylic resin (A) are made into a homopolymer is usually measured by a differential scanning calorimeter (DSC), and can be measured by a method in accordance with JIS K 7121-1987 or JIS K 6240.

[0050] The weight-average molecular weight of the acrylic resin (A) is usually 100,000 to 2,000,000, preferably 150,000 to 1,500,000, particularly preferably 200,000 to 1,200,000, and especially preferably 300,000 to 1,000,000. If the weight-average molecular weight is equal to or greater than the lower limit, contamination of the workpiece tends to be further reduced. If it is equal to or greater than the upper limit, coating properties tend to be reduced and there is also a tendency for this to be disadvantageous in terms of cost.

[0051] Furthermore, the dispersity (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 20 or less, particularly preferably 10 or less, even more preferably 7 or less, and especially preferably 6 or less. If the dispersity is too high, contamination of the workpiece tends to increase. The lower limit of the dispersity is usually 1.1 in view of production limitations.

[0052] The weight-average molecular weight 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 (Waters Japan, "Waters 2695 (main body)" and "Waters 2414 (detector)") using a Shodex GPC KF-806L column (exclusion limit molecular weight: 2 × 10 7 Separation range: 100 to 2 × 10 7 The number average molecular weight can be measured by using three columns in series (theoretical plate number: 10,000 / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm), and the number average molecular weight can also be obtained in the same way.

[0053] The viscosity of the acrylic resin (A) at 25°C is preferably 5 to 10,000 mPa·s, more preferably 10 to 5,000 mPa·s. If the viscosity is outside this range, the coating properties tend to decrease. The viscosity is measured using an E-type viscometer.

[0054] The acrylic resin (A) may be used as is, but in the present invention, it is preferable that the acrylic resin (A) further contains an ethylenically unsaturated group. When the acrylic resin (A) contains an ethylenically unsaturated group, the ethylenically unsaturated group polymerizes and hardens upon irradiation with active energy rays, resulting in a decrease in adhesive strength. Therefore, when a pressure-sensitive adhesive composition containing the acrylic resin (A) is made into a pressure-sensitive adhesive sheet, easy peelability can be imparted.

[0055] The ethylenically unsaturated group can be introduced into the acrylic resin (A) by reacting the acrylic resin (A) with an ethylenically unsaturated group-containing compound, for example, by the following method: (i) a method of reacting a hydroxyl group of the acrylic resin (A) with an isocyanate group-containing ethylenically unsaturated compound; (ii) a method of reacting a hydroxyl group of the acrylic resin (A) with (meth)acrylic anhydride; (iii) A method of reacting a hydroxyl group of the acrylic resin (A) with an ethylenically unsaturated group-containing carboxylic acid; (iv) A method of reacting a carboxy group of the acrylic resin (A) with a vinyl ether group-containing (meth)acrylic acid ester; Among them, method (i) is preferred from the viewpoint of reactivity. The preferred method (i) will be explained below.

[0056] In the above method (i), the hydroxyl group derived from the hydroxyl group-containing monomer (a2-1) contained in the acrylic resin (A) reacts with the isocyanate group of the isocyanate group-containing ethylenically unsaturated compound, and an ethylenically unsaturated group-containing acrylic resin can be obtained in which an ethylenically unsaturated group containing an ethylenically unsaturated bond and a urethane bond is introduced into the acrylic resin (A).

[0057] [Isocyanate group-containing ethylenically unsaturated compounds] The isocyanate group-containing ethylenically unsaturated compound is a monomer having an isocyanate group and a polymerizable ethylenically unsaturated group. Examples of the isocyanate group-containing ethylenically unsaturated compound include 2-(meth)acryloyloxyethyl isocyanate, 3-(meth)acryloyloxy-n-propyl isocyanate, 2-(meth)acryloyloxyisopropyl isocyanate, 4-(meth)acryloyloxy-n-butyl isocyanate, 2-(meth)acryloyloxy-tert-butyl isocyanate, 2-(meth)acryloyloxybutyl-4-isocyanate, 2-(meth)acryloyloxybutyl-3-isocyanate, 2-(meth)acryloyloxybutyl-2-isocyanate, and 2-(meth)acryloyloxybutyl-1-isocyanate. Examples of the isocyanate include 5-(meth)acryloyloxy-n-pentyl isocyanate, 6-(meth)acryloyloxy-n-hexyl isocyanate, 7-(meth)acryloyloxy-n-heptyl isocyanate, 2-(isocyanatoethyloxy)ethyl (meth)acrylate, 3-(meth)acryloyloxyphenyl isocyanate, 4-(meth)acryloyloxyphenyl isocyanate, 1,1-bis((meth)acryloyloxymethyl)methyl isocyanate, 1,1-bis((meth)acryloyloxymethyl)ethyl isocyanate, and 2'-pentenoyl-4-oxyphenyl isocyanate. These may be used alone or in combination of two or more. Among these compounds, (meth)acrylate monomers are particularly preferred from the viewpoints of ease of synthesis and availability of raw materials, and 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, 2-(isocyanatoethyloxy)ethyl methacrylate, 2-(isocyanatoethyloxy)ethyl acrylate, and 1,1-bis(acryloyloxymethyl)ethyl isocyanate are more preferred.

[0058] The proportion of the acrylic resin (A) and the isocyanate group-containing ethylenically unsaturated compound used in the reaction between them is appropriately set in consideration of the ratio between hydroxyl groups and isocyanate groups, and varies depending on the types of the two compounds. However, the proportion of the isocyanate group-containing ethylenically unsaturated compound is usually 10 to 100 mol %, preferably 20 to 97 mol %, and particularly preferably 30 to 95 mol %, per 100 mol % of the hydroxyl group-containing monomer (a2-1) in the acrylic resin (A).

[0059] The reaction of the two compounds may be carried out in the presence of a reaction catalyst, and the reaction rate can be adjusted by the amount of the reaction catalyst added. As the reaction catalyst, a known reaction catalyst can be used. Specific examples of the reaction catalyst include dibutyltin dilaurate, copper naphthenate, cobalt naphthenate, zinc naphthenate, triethylamine, 1,4-diazabicyclo[2.2.2]octane, zirconium acetylacetonate, titanium diisopropoxybis(ethylacetoacetate), and a mixture of bismuth tris(2-ethylhexanoate) and 2-ethylhexanoic acid. One selected from these reaction catalysts can be used alone, or two or more can be used in combination.

[0060] The reaction temperature when reacting the two compounds is preferably 25 to 100° C., more preferably 30 to 60° C. The reaction time is preferably 30 minutes to 50 hours, more preferably 3 hours to 20 hours.

[0061] When reacting the two compounds, a polymerization inhibitor may be added to the reaction system as needed. A commonly used polymerization inhibitor can be used, such as a phenolic compound or a hydroquinone compound. Specific examples of the polymerization inhibitor include hydroquinone, methoxyhydroquinone, catechol, p-tert-butylcatechol, cresol, and 2,6-di-tert-butyl-4-methylphenol (BHT). In addition, when reacting the two compounds, known additives may be added depending on the purpose.

[0062] The addition reaction rate between the hydroxyl groups derived from the hydroxyl group-containing monomer (a2-1) in the acrylic resin (A) and the isocyanate groups of the isocyanate group-containing ethylenically unsaturated compound, i.e., the urethane conversion rate, is preferably 5 to 99%, more preferably 10 to 90%. If the urethane conversion rate is too low, the adhesive strength after irradiation with active energy rays such as ultraviolet rays tends to be difficult to sufficiently reduce, while if the urethane conversion rate is too high, the urethane reaction tends to be incomplete, leaving unreacted isocyanate group-containing ethylenically unsaturated compound.

[0063] The urethane conversion rate can be calculated, for example, from the ratio of the amount (mol) of isocyanate groups in the isocyanate group-containing ethylenically unsaturated compound to the amount (mol) of hydroxyl groups in the acrylic resin (A). It is determined that 100% of the isocyanate groups have reacted by confirming the disappearance of the peak of the isocyanate groups by IR measurement. Another method for calculating the urethane conversion rate is to calculate it from the ratio of the integral values ​​of the structure derived from the hydroxyl group-containing monomer (a2-1) before and after the urethane conversion reaction, as determined by 1H-NMR measurement.

[0064] The above describes the method (i), which is a preferred embodiment for introducing an ethylenically unsaturated group into the acrylic resin (A). However, in the methods (ii) to (iv), an ethylenically unsaturated group can also be introduced into the acrylic resin (A) by following a conventional method.

[0065] When the acrylic resin (A) has an ethylenically unsaturated group, the content of the ethylenically unsaturated group is usually 5 to 250 mmol / 100 g, preferably 30 to 200 mmol / 100 g, and more preferably 50 to 160 mmol / 100 g. If the content of the ethylenically unsaturated group is too low, the releasability upon irradiation with active energy rays tends to decrease, while if the content of the ethylenically unsaturated group is too high, the adhesive strength before irradiation with active energy rays tends to decrease.

[0066] The content of the ethylenically unsaturated group can be calculated from the following formula. Ethylenically unsaturated group content (mmol / 100g) = Hydroxyl groups (mmol) contained in 100 g of acrylic resin (A) before the addition of ethylenically unsaturated groups × addition reaction rate (%) / weight (g) of 100 g of acrylic resin (A) after the addition of ethylenically unsaturated groups × 100

[0067] When the acrylic resin (A) has an ethylenically unsaturated group, the glass transition temperature (Tg) is preferably −65 to 0° C., particularly −60 to −10° C., further preferably −55 to −20° C., and especially preferably −50 to −30° C. If the glass transition temperature is within the above range, the adhesiveness is excellent and contamination of the workpiece can be reduced. The glass transition temperature (Tg) can be calculated by the method described above.

[0068] Furthermore, when the acrylic resin (A) has an ethylenically unsaturated group, the weight-average molecular weight is usually 100,000 to 2,000,000, preferably 150,000 to 1,500,000, particularly preferably 200,000 to 1,200,000, and especially preferably 300,000 to 1,000,000. If the weight-average molecular weight is equal to or greater than the lower limit, contamination of workpieces can be further reduced, but if it is too large, coatability tends to decrease and there is also a tendency for it to be disadvantageous in terms of cost.

[0069] Furthermore, when the acrylic resin (A) has an ethylenically unsaturated group, the polydispersity (weight average molecular weight / number average molecular weight) is preferably 20 or less, particularly preferably 15 or less, even more preferably 10 or less, and especially preferably 7 or less. If the polydispersity is too high, contamination of the workpiece tends to increase. The lower limit of the polydispersity is usually 1.1 in view of production limitations.

[0070] When the acrylic resin (A) has an ethylenically unsaturated group, the weight average molecular weight and dispersity can be measured by the above-mentioned methods.

[0071] When the acrylic resin (A) has an ethylenically unsaturated group, the viscosity at 25°C is preferably 5 to 10,000 mPa·s, more preferably 500 to 5,000 mPa·s. If the viscosity is outside the above range, the coatability tends to decrease. The viscosity is measured using an E-type viscometer.

[0072] Furthermore, even when the acrylic resin (A) has an ethylenically unsaturated group, it is preferable that the acrylic resin (A) has a structural moiety derived from the hydroxyl group-containing monomer (a2-1), i.e., that the acrylic resin (A) has a hydroxyl group, from the viewpoint of reactivity with the crosslinking agent (C) described later.

[0073] When the acrylic resin (A) has an ethylenically unsaturated group, the hydroxyl group content is usually 0.01 to 10% by weight, preferably 0.05 to 8% by weight, and more preferably 1 to 5% by weight. If the hydroxyl group content is too low, the cohesive strength of the adhesive decreases, which tends to cause adhesive residue, while if the hydroxyl group content is too high, the flexibility and adhesive strength of the adhesive decrease, which tends to cause lifting from the workpiece.

[0074] [Hydroxyl group-containing hindered amine compound (B)] The pressure-sensitive adhesive composition of the present invention contains a hydroxyl group-containing hindered amine compound (B). Examples of the hydroxyl group-containing hindered amine compound (B) include the N-OR type hindered amine light stabilizer 2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine and the NR type bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate. 2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine is preferred due to its excellent hydroxyl group reactivity.

[0075] The content of the hydroxyl group-containing hindered amine compound (B) used in the present invention is usually preferably 1 to 10 parts by weight, and particularly preferably 3 to 7 parts by weight, per 100 parts by weight of the acrylic resin (A). When the content is within the above range, the amount of radicals trapped is sufficient, the effect of improving heat resistance is exerted, and the generation of reaction products between the crosslinking agent and the hydroxyl group-containing hindered amine compound (B) is suppressed, thereby reducing contamination of the adherend.

[0076] The hydroxyl group-containing hindered amine compound (B) may be used alone or in combination of two or more thereof. Other hydroxyl group-free hindered amine compounds may also be contained.

[0077] [Crosslinking agent (C)] The resin composition of the present invention preferably further contains a crosslinking agent (C) to improve adhesive strength before irradiation with active energy rays. As described above, the crosslinking agent (C) reacts with functional groups in the acrylic resin (A) to form a crosslinked structure, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, amine-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, isocyanate-based crosslinking agents are preferred in terms of improving adhesion to the adherend and reactivity with the acrylic resin (A).

[0078] The isocyanate crosslinking agent contains at least two isocyanate groups, and examples thereof include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and biuret and isocyanurate forms thereof, as well as adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, aromatic polyisocyanates and adducts of aromatic polyisocyanates and trimethylolpropane are preferred in terms of chemical resistance and reactivity with functional groups, and adducts of tolylene diisocyanate and trimethylolpropane are particularly preferred.

[0079] Examples of the epoxy crosslinking agent include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.

[0080] Examples of the aziridine crosslinking agent include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine, and trimethylolpropane tri-β-(2-methylaziridine)propionate.

[0081] Examples of the melamine-based crosslinking agent include melamine; methylolmelamine derivatives such as amino group-containing methylolmelamine obtained by condensing melamine with formaldehyde, imino group-containing methylolmelamine, and hexamethylolmelamine; and alkylated methylolmelamines such as partially or completely alkylated methylolmelamine and imino group-containing partially or completely alkylated methylolmelamine obtained by reacting a methylolmelamine derivative with a lower alcohol such as methyl alcohol or butyl alcohol to partially or completely etherify it.

[0082] Examples of the aldehyde crosslinking agent include aldehyde compounds that liberate aldehyde in an aqueous solution, such as formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde, glyoxal, glutaraldehyde, dialdehyde starch, hexamethylenetetramine, 1,4-dioxane-2,3-diol, 1,3-bis(hydroxymethyl)-2-imidazolidine, dimethylol urea, N-methylol acrylamide, urea formalin resin, and melamine formalin resin, as well as aromatic aldehyde compounds such as benzaldehyde, 2-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, and m-hydroxybenzaldehyde.

[0083] Examples of the amine-based crosslinking agent include 4,4'-methylene-bis(2-chloroaniline), modified 4,4'-methylene-bis(2-chloroaniline), and diethyltoluenediamine.

[0084] The metal chelate crosslinking agent may be, for example, a chelate compound whose metal atom is aluminum, zirconium, titanium, zinc, iron, tin, etc., and aluminum chelate compounds are preferred from the viewpoint of performance. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethyl acetoacetate, diisopropoxyaluminum monolauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, diisopropoxyaluminum monoisostearyl acetoacetate, etc.

[0085] The crosslinking agent (C) may be used alone or in combination of two or more kinds.

[0086] The content of the crosslinking agent (C) is usually preferably 0.01 to 20 parts by weight, particularly preferably 0.2 to 10 parts by weight, and even more preferably 0.2 to 3 parts by weight, per 100 parts by weight of the acrylic resin (A). If the amount of crosslinking agent (C) is too small, the cohesive strength of the adhesive will decrease, which will tend to cause adhesive residue, while if the amount is too large, the flexibility and adhesive strength of the adhesive will decrease, which will tend to cause lifting from the workpiece.

[0087] [Other ingredients] The pressure-sensitive adhesive composition of the present invention may preferably further contain, for example, an ethylenically unsaturated compound in terms of releasability after irradiation with active energy rays, provided that the effects of the present invention are not impaired. The pressure-sensitive adhesive composition may also contain additives such as antistatic agents, polymerization inhibitors, plasticizers, fillers, pigments, diluents, antioxidants, UV absorbers, UV stabilizers, tackifier resins, and photopolymerization initiators. These additives may be used alone or in combination. Polymerization inhibitors are particularly effective in maintaining the stability of the pressure-sensitive adhesive layer. When a polymerization inhibitor is added, its content is not particularly limited, but is preferably 0.01 to 5 wt %. In addition to the additives, the pressure-sensitive adhesive composition may contain small amounts of impurities contained in the raw materials used to produce the components of the pressure-sensitive adhesive composition.

[0088] [Adhesive composition] Thus, the pressure-sensitive adhesive composition of the present invention can be obtained by mixing the acrylic resin (A), the hydroxyl group-containing hindered amine compound (B), preferably the crosslinking agent (C), and, if necessary, other components. The content of the acrylic resin (A) in the entire pressure-sensitive adhesive composition is usually 50% by weight or more, preferably 60% by weight or more, and particularly preferably 70% by weight or more. If the content is too low, it becomes difficult to obtain the effects of the present invention.

[0089] The pressure-sensitive adhesive composition of the present invention is preferably used as a pressure-sensitive adhesive sheet for temporarily protecting the surface of a workpiece when processing the workpiece, such as an electronic substrate, a semiconductor wafer, a processed glass product, a metal plate, a plastic plate, etc. The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive composition is crosslinked. The pressure-sensitive adhesive sheet will now be described.

[0090] [Adhesive sheet] The pressure-sensitive adhesive sheet of the present invention typically comprises a substrate sheet, a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of the present invention, and a release film. To prepare such a pressure-sensitive adhesive sheet, the pressure-sensitive adhesive composition of the present invention 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. This 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 pressure-sensitive adhesive sheet. Furthermore, to balance the adhesive properties, further aging may be performed after drying.

[0091] 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, etc.

[0092] Furthermore, as the release film, for example, various synthetic resin sheets, paper, woven fabrics, nonwoven fabrics, etc. exemplified above as the base sheet can be used which have been subjected to a release treatment.

[0093] The method for applying the pressure-sensitive adhesive composition is not particularly limited as long as it is a common application method, and examples thereof include roll coating, die coating, gravure coating, comma coating, and screen printing.

[0094] The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is generally preferably 4 to 200 μm, and more preferably 5 to 100 μm.

[0095] The aging conditions are typically a temperature of room temperature (23°C) to 70°C, and a time of 1 to 30 days. Specifically, the aging may be performed under conditions such as 1 to 20 days at 23°C, 3 to 10 days at 23°C, or 1 to 7 days at 40°C.

[0096] The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is preferably 10 to 99% by weight, particularly preferably 20 to 97% by weight, and even more preferably 40 to 95% by weight, from the viewpoint of adhesiveness. If the gel fraction is too low, the adhesive strength to the workpiece tends to decrease, while if the gel fraction is too high, the adhesive strength to the workpiece tends to decrease.

[0097] The gel fraction is a measure of the degree of crosslinking (degree of hardening) and is calculated, for example, by the following method: The pressure-sensitive adhesive sheet is attached to a SUS mesh sheet (200 mesh), the pressure-sensitive adhesive sheet is wrapped, and then the sheet is immersed in ethyl acetate in a sealed container for 24 hours. The gel fraction is calculated from the change in weight of the pressure-sensitive adhesive layer before and after immersion in ethyl acetate using the following formula. Gel fraction (wt%) = weight (g) of adhesive layer after immersion in ethyl acetate / Weight of adhesive layer before immersion in ethyl acetate (g) x 100

[0098] The gel fraction of the pressure-sensitive adhesive layer can be adjusted to fall within the above range by adjusting the type and amount of the crosslinking agent (C), for example.

[0099] By irradiating the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention with active energy rays, the ethylenically unsaturated groups contained in the pressure-sensitive adhesive layer are polymerized, the pressure-sensitive adhesive layer is hardened, and the adhesive strength is reduced, thereby enabling peeling.

[0100] As the active energy ray, 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, ultraviolet rays are preferred in terms of curing speed, ease of availability of irradiation equipment, cost, etc.

[0101] The cumulative dose of ultraviolet light is usually 50 to 3000 mJ / cm2 , preferably 100 to 1,000 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 several seconds, and in some cases may be a fraction of a second.

[0102] The adhesive strength of the pressure-sensitive adhesive sheet varies depending on the type of substrate sheet, the type of workpiece, etc., but is preferably 3.0 N / 25 mm or more, more preferably 4.0 N / 25 mm or more, before irradiation with active energy rays. The upper limit of the adhesive strength before irradiation with active energy rays is usually 100 N / 25 mm. The adhesive strength after irradiation with active energy rays is preferably 0.3 N / 25 mm or less, and more preferably 0.1 N / 25 mm or less.

[0103] The pressure-sensitive adhesive sheet of the present invention is also heated at 175°C for 1 hour and then irradiated with ultraviolet light (cumulative irradiation dose 250 mJ / cm 2 ) is preferably 0.5 N / 25 mm or less, and more preferably 0.2 N / 25 mm or less.

[0104] Furthermore, the pressure-sensitive adhesive sheet of the present invention is heated at 200°C for 1 hour, and then irradiated with ultraviolet light (cumulative irradiation dose 250 mJ / cm 2 ) is preferably 0.7 N / 25 mm or less, and more preferably 0.4 N / 25 mm or less.

[0105] The pressure-sensitive adhesive composition of the present invention is useful as a peel-type pressure-sensitive adhesive sheet, for example, by laminating a pressure-sensitive adhesive sheet using the composition as a pressure-sensitive adhesive layer to a workpiece, temporarily protecting the surface of the workpiece, and then irradiating it with active energy rays, which hardens the pressure-sensitive adhesive layer and reduces the adhesive strength, allowing it to be easily peeled off from the workpiece.Furthermore, since the pressure-sensitive adhesive sheet of the present invention has excellent heat resistance, even if it is subjected to a heating process at, for example, 175°C or higher, particularly 200°C or higher after being attached to the surface of the workpiece, subsequent irradiation with active energy rays reduces the adhesive strength, leaves no adhesive residue, and exhibits excellent peelability without causing any change in wettability. [Example]

[0106] 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. Note that "%" and "parts" below are based on weight.

[0107] [Production of acrylic resin (A-1)] A four-necked round-bottom flask equipped with a reflux condenser, stirrer, nitrogen gas inlet, and thermometer was charged with 65 parts of ethyl acetate. The internal temperature was raised to the boiling point to initiate the reaction. 70 parts of the prepared 2-ethylhexyl acrylate (2EHA), 10 parts of acryloylmorpholine (ACMO), 17 parts of 2-hydroxyethyl acrylate (HEA), and 0.045 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator were added dropwise over 2 hours. After reacting for one hour, 3 parts of 2-hydroxyethyl acrylate (HEA) and 7.5 parts of ethyl acetate solution were added and the reaction was continued at reflux for 0.5 hours. 7.5 parts of an ethyl acetate solution containing 1% AIBN were added and the reaction was continued at reflux for 2 hours. 30 parts of an ethyl acetate solution containing 0.3% AIBN were added again and the reaction was continued at reflux for 2 hours. The reaction was then stopped and the mixture was diluted with ethyl acetate to obtain an acrylic resin (A1) solution.

[0108] To the acrylic resin (A1) solution obtained above, 2-methacryloyloxyethyl isocyanate (hereinafter referred to as "MOI") (manufactured by Resonac) and dibutyltin dilaurate as a urethanization catalyst were added appropriately, and the mixture was allowed to react at 50°C for 18 hours. After that, 0.02 parts of MEHQ was added to obtain an ethylenically unsaturated group-containing acrylic resin (A-1) solution (solid content 45.9%, viscosity 4900 mPa·s / 25°C, acrylic resin (A-1): weight average molecular weight (Mw) 780,000, dispersity (Mw / Mn) 5.5). The urethanization rate of HEA by MOI was 90 mol%, and the ethylenically unsaturated group content was 125 mmol / 100 g.

[0109] [Table 1]

[0110] [Hydroxyl group-containing hindered amine compound (B)] Tinuvin 152 (2,4-bis[N-butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, manufactured by BASF) [Other hindered amine compounds] Tinuvin 123 (chemical compound: Decanedicarboxylic acid bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl) ester, reaction product with 1,1-dimethylethyl hydroperoxide and octane, manufactured by BASF) LA-68 (compound name: 1,2,3,4-butanetetracarboxylic acid tetramethyl ester, reaction product with 2,2,6,6-tetramethyl-4-piperidinol and β,β,β',β'-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol, manufactured by ADEKA Corporation)

[0111] [Crosslinking agent (C)] The following crosslinking agent (C-1) was prepared. Takenate D101E (adduct of tolylene diisocyanate and trimethylolpropane, manufactured by Mitsui Chemicals)

[0112] [Photopolymerization initiator] The following photopolymerization initiators were prepared: Omnirad127 (2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one, manufactured by IGM Resins)

[0113] <Examples 1 to 6 and Comparative Examples 1 to 5> To 100 parts of the acrylic resin prepared as described above, a hindered amine compound, a crosslinking agent (C), and a photopolymerization initiator were added and mixed as shown in Table 2 below, and this was then adjusted with ethyl acetate to a solids concentration (resin content) of 30% by weight to obtain a pressure-sensitive adhesive composition solution.

[0114] [Table 2]

[0115] The adhesive composition solution obtained above was used to prepare an adhesive sheet as described below, and the adhesive strength was measured and evaluated. The evaluation results are shown in Table 3.

[0116] <Adhesive sheet (S1) (for gel fraction measurement)> The pressure-sensitive adhesive composition solution obtained above was applied to a heavy release 38 μm polyester release sheet (manufactured by Mitsui Chemicals Tocello Inc.: Lumirror (registered trademark) SP03-38BU) so that the thickness after drying would be 25 μm, and after drying at 100°C for 5 minutes, this was laminated to a light release 38 μm polyester release sheet (manufactured by Mitsui Chemicals Tocello Inc.: Lumirror (registered trademark) SP01-38BU) and aged in an environment of 40°C for 3 days to obtain a pressure-sensitive adhesive sheet (S1) for gel fraction measurement.

[0117] <Adhesive sheet (S2) (for measuring adhesive strength)> The pressure-sensitive adhesive composition solution obtained above was applied to a polyimide film (film thickness 50 μm) ("Kapton 200H" manufactured by DuPont-Toray Co., Ltd.) so that the thickness after drying would be 25 μm. After drying at 100°C for 5 minutes, the film was laminated to a 38 μm polyester release sheet with a light release property (Lumirror (registered trademark) SP01-38BU manufactured by Mitsui Chemicals Tocello Co., Ltd.) and aged for 3 days in an environment of 40°C to obtain a pressure-sensitive adhesive sheet (S2) for measuring adhesive strength.

[0118] [Gel fraction] The pressure-sensitive adhesive sheet (S1) was cut to 40 mm x 40 mm, and the light-release 38 μm polyester-based release sheet was peeled off. The pressure-sensitive adhesive layer was then attached to a 50 mm x 100 mm SUS mesh sheet (200 mesh). Next, the heavy-release 38 μm polyester-based release sheet was peeled off, and the SUS mesh sheet was folded back from the center in the longitudinal direction to encase the sample. The sample was then immersed in a sealed container containing 250 g of ethyl acetate for 24 hours. The gel fraction was calculated from the change in weight of the pressure-sensitive adhesive layer before and after immersion in ethyl acetate using the following formula. Gel fraction (%) = (weight (g) of adhesive layer after immersion in ethyl acetate) / Weight of adhesive layer before immersion in ethyl acetate (g) × 100

[0119] [Adhesive strength before irradiation with active energy rays] A 25 mm x 100 mm test piece was prepared from the pressure-sensitive adhesive sheet (S2), and the 38 μm polyester release sheet with a light release property was peeled off. The test piece was then pressed onto an alkali-free glass plate (manufactured by Corning, Eagle XG) using a 2 kg rubber roller, which was rolled back and forth twice under pressure in an atmosphere of 23°C and 50% RH. After leaving the test piece to stand in the same atmosphere for 30 minutes, the 180-degree peel strength (N / 25 mm) was measured at a peel speed of 300 mm / min.

[0120] [Adhesive strength after exposure to active energy rays (high-pressure mercury lamp)] A 25mm x 100mm test piece was prepared from the pressure-sensitive adhesive sheet (S2), the 38μm polyester release sheet was peeled off, and the piece was pressed against an alkali-free glass plate (Corning Eagle XG) using a 2kg rubber roller, which was rolled back and forth twice under pressure at 23°C and 50%RH, and then allowed to stand for 30 minutes in the same atmosphere. Subsequently, an 80W high-pressure mercury lamp was used to irradiate the non-alkali-free glass plate side with ultraviolet light (cumulative exposure dose 250mJ / cm2), and the piece was allowed to stand for 30 minutes under 23°C and 50%RH, after which the 180° peel strength (N / 25mm) was measured at a peel rate of 300mm / min.

[0121] [Adhesive strength after heating at 175°C and before exposure to active energy rays] A 25mm x 100mm test piece was prepared from the pressure-sensitive adhesive sheet (S2), and the 38μm polyester release sheet was peeled off. The test piece was then pressed onto an alkali-free glass plate (Corning Eagle XG) at 23°C and 50%RH using a 2kg rubber roller, which was then rolled back and forth twice. The test piece was then heat-treated at 175°C for 1 hour. The stainless steel plate with the heat-treated pressure-sensitive adhesive sheet attached was then left to stand for 1 hour at 23°C and 50% relative humidity, after which the 180° peel strength (N / 25mm) was measured at a peel speed of 300mm / min. The results were evaluated as follows: 〇 9.0N / 25mm or more × Less than 9.0N / 25mm

[0122] [Adhesive strength after heating to 175°C and exposure to active energy rays] A 25mm x 100mm test piece was prepared from the pressure-sensitive adhesive sheet (S2), and the 38μm polyester release sheet was peeled off. The test piece was then pressed against an alkali-free glass plate (Corning Eagle XG) at 23°C and 50%RH using a 2kg rubber roller, which was then rolled back and forth twice. The test piece was then heat-treated at 175°C for 1 hour. The stainless steel plate with the heat-treated pressure-sensitive adhesive sheet attached was then left to stand for 1 hour at 23°C and 50%RH. After that, it was irradiated with ultraviolet light from the alkali-free glass plate side using an 80W high-pressure mercury lamp (total exposure dose: 250mJ / cm2). After standing for 30 minutes at 23°C and 50%RH, the 180° peel strength (N / 25mm) was measured at a peel rate of 300mm / min. Evaluation was performed as follows. 〇 0.20N / 25mm or less × Greater than 0.20N / 25mm

[0123] [Adhesive strength after heating at 200°C and before exposure to active energy rays] A 25mm x 100mm test piece was prepared from the pressure-sensitive adhesive sheet (S2), and the 38μm polyester release sheet was peeled off. The test piece was then pressed onto an alkali-free glass plate (Corning Eagle XG) at 23°C and 50%RH using a 2kg rubber roller, which was then rolled back and forth twice. The test piece was then heat-treated at 150°C for 1 hour. The stainless steel plate with the heat-treated pressure-sensitive adhesive sheet attached was then left to stand for 1 hour at 23°C and 50% relative humidity, after which the 180° peel strength (N / 25mm) was measured at a peel speed of 300mm / min. Evaluation was performed as follows: 〇 5.0N / 25mm or more × Less than 5.0N / 25mm

[0124] [Adhesive strength after heating at 200°C and exposure to active energy rays] A 25mm x 100mm test piece was prepared from the pressure-sensitive adhesive sheet (S2). The 38μm polyester release sheet was peeled off and the test piece was pressed against an alkali-free glass plate (Corning Eagle XG) at 23°C and 50%RH using a 2kg rubber roller, which was then rolled back and forth twice. The test piece was then heat-treated at 150°C for 1 hour. The stainless steel plate with the heat-treated pressure-sensitive adhesive sheet attached was then left to stand for 1 hour at 23°C and 50%RH. After that, it was irradiated with ultraviolet light from the alkali-free glass plate side using an 80W high-pressure mercury lamp (total exposure dose: 250mJ / cm2). After standing for 30 minutes at 23°C and 50%RH, the 180° peel strength (N / 25mm) was measured at a peel rate of 300mm / min. Evaluation was performed as follows. 〇 0.40N / 25mm or less × Greater than 0.40N / 25mm

[0125] [Dyne pen evaluation before heating, after heating at 175°C or after heating at 200°C and after irradiation with active energy rays] A dyne pen (test pen) is a product used to check wettability and easily evaluate surface energy values ​​(dyne level). The dyne pen was increased in increments of 2 starting from 30 mN / m, and a line was drawn to find the range in which the adhesive repelled within 2 seconds. The glass surface, which was the adherend, was held at 32 mN / m and repelled at 34 mN / m, so the surface energy of the glass was determined to be between 32 mN / m and 34 mN / m. Assuming that the change in surface energy would be small if the adherend was not contaminated, the glass after UV irradiation was evaluated as follows. Note that if there was any adhesive residue or adhesive marks visible to the naked eye, it was determined that the adherend was contaminated, and no evaluation was made with the dyne pen, resulting in an X rating. ○ 30mN / m or more and 36mN / m or less ×: More than 36mN / m, or there is residual glue or adhesive marks

[0126] [Table 3]

[0127] [Table 4]

[0128] [Table 5]

[0129] In Examples 1 to 6, the adhesive strength before and after UV irradiation was satisfactory, and the evaluation using a dyne pen showed that there was little change in surface energy. On the other hand, in Comparative Examples 1 to 3, the adhesive strength did not decrease sufficiently after heating and UV irradiation at 175°C and 200°C, and adhesive residue and marks were observed on the glass after peeling. Tinuvin 123 is the same N-OR type hindered amine light stabilizer as Tinuvin 152, so it is expected to have the same ability to trap radicals generated by heat. However, because it does not have a hydroxyl group and is not incorporated into the polymer, it segregates at the substrate interface or adherend interface during heating and is unable to disperse evenly in the adhesive, which is thought to be why it did not exert its full effect. Furthermore, in Comparative Examples 4 and 5, a change in surface energy was observed in evaluation with a dyne pen after heating and UV irradiation at 200°C. It is possible that the hindered amine compound (B) migrated to the adherend interface due to heating, contaminating the adherend. [Industrial Applicability]

[0130] 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-type pressure-sensitive adhesive composition comprising an acrylic resin (A) and a hydroxyl group-containing hindered amine compound (B).

2. 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 an alkyl group-containing (meth)acrylate (a1) and a structural unit derived from a functional group-containing monomer (a2) other than an amide group.

3. 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 an amide group-containing monomer (a3).

4. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic resin (A) further has an ethylenically unsaturated group.

5. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the acrylic resin (A) has an ethylenically unsaturated group content of 5 to 250 mmol / 100 g.

6. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1 , further comprising a crosslinking agent (C).

7. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive composition according to any one of claims 1 to 6 is crosslinked.

8. The pressure-sensitive adhesive sheet according to claim 7 , wherein the pressure-sensitive adhesive layer is cured and becomes peelable by irradiation with active energy rays.

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