Adhesive tape

Abstract

To provide a pressure-sensitive adhesive tape which has excellent pressure-sensitive adhesive force and can achieve both adhesion to an adherend and peelability.SOLUTION: A pressure-sensitive adhesive tape according to an embodiment of the present invention includes a base material and a pressure-sensitive adhesive layer formed of an active energy ray-curable pressure-sensitive adhesive, in which a surface of the pressure-sensitive adhesive layer after irradiation with active energy rays has a microphase-separated structure including an island portion and a sea portion having a storage elastic modulus higher than a storage elastic modulus of the island portion in a storage elastic modulus mapping image obtained using an atomic force microscope.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive tape. [Background technology]

[0002] Adhesive tapes are widely used for the purpose of protecting the surface of adherends and fixing them. For example, in the processing of semiconductor wafers, they are used to properly hold the adherend semiconductor wafer during the back-grinding and dicing processes. In recent years, chips have become increasingly miniaturized and thinner, and adhesive strength is required that can properly hold the semiconductor wafer even when it is ground thin during processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-31620 Summary of the Invention [Problem to be solved by the invention]

[0004] Adhesive tapes with highly adhesive adhesive layers can hold semiconductor wafers during processing. However, processed wafers tend to be thin and easily damaged, which may result in damage when the adhesive tape is removed. Therefore, there is a demand for adhesive tapes with easy release properties that can be easily removed from the substrate after processing. Adhesive tapes using ultraviolet-curable adhesives have been proposed as such adhesive tapes (e.g., Patent Document 1). However, even when such adhesive tapes are used, chips may fly off during dicing due to insufficient adhesive strength, or chips may break during pick-up due to adhesive strength not decreasing sufficiently even after irradiation with active energy rays. [Means for solving the problem]

[0005] 1. An adhesive tape according to an embodiment of the present invention comprises a substrate and an adhesive layer made of an active energy ray-curable adhesive, and the surface of the adhesive layer after irradiation with active energy rays has a microphase-separated structure consisting of island regions and a sea region having a storage modulus higher than that of the island regions, as seen in a storage modulus mapping image obtained using an atomic force microscope. 2. In the pressure-sensitive adhesive tape described in 1 above, the size of the island portions may be 300 nm or less. 3. In the pressure-sensitive adhesive tape according to the above 1 or 2, the active energy ray-curable pressure-sensitive adhesive may be a water-dispersible pressure-sensitive adhesive. 4. In the pressure-sensitive adhesive tape according to any one of the above 1 to 3, the active energy ray-curable pressure-sensitive adhesive may contain a water-dispersible acrylic polymer and an active energy ray-curable resin. 5. In the pressure-sensitive adhesive tape according to the above item 4, the water-dispersible acrylic polymer may be a polymer having a core-shell structure. 6. In the pressure-sensitive adhesive tape according to 4 or 5 above, the water-dispersible acrylic polymer may comprise a shell portion having a glass transition temperature Tg of -10°C or higher and a core portion having a glass transition temperature of less than -10°C. 7. The adhesive tape according to any one of 1 to 6 above may be used in semiconductor wafer processing. [Effects of the Invention]

[0006] According to an embodiment of the present invention, it is possible to provide a pressure-sensitive adhesive tape that has excellent adhesive strength and can achieve both adhesion to an adherend and easy releasability. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a storage modulus mapping image, obtained using an atomic force microscope, of the surface of the pressure-sensitive adhesive layer of a pressure-sensitive adhesive tape according to an embodiment of the present invention after irradiation with active energy rays. [Figure 2] 1 is a schematic cross-sectional view of an adhesive tape according to one embodiment of the present invention. [Figure 3]1 shows a storage modulus mapping image, taken with an atomic force microscope, of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of Example 1 after irradiation with active energy rays. [Figure 4] 1 shows a storage modulus mapping image, taken using an atomic force microscope, of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of Example 2 after irradiation with active energy rays. [Figure 5] 1 shows a storage modulus mapping image, taken with an atomic force microscope, of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of Example 3 after irradiation with active energy rays. [Figure 6] 1 shows a storage modulus mapping image, taken using an atomic force microscope, of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of Example 4 after irradiation with active energy rays. [Figure 7] 1 shows a storage modulus mapping image, obtained using an atomic force microscope, of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of Comparative Example 1 after irradiation with active energy rays. [Figure 8] 1 is a storage modulus mapping image, obtained using an atomic force microscope, of the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of Comparative Example 2 after irradiation with active energy rays. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Overall structure of adhesive tape An adhesive tape according to an embodiment of the present invention comprises a substrate and a pressure-sensitive adhesive layer made of an active energy ray-curable pressure-sensitive adhesive. The surface of this pressure-sensitive adhesive layer after irradiation with active energy rays has a microphase-separated structure (hereinafter also referred to as a sea-island microphase-separated structure) consisting of island regions and a sea region having a storage modulus higher than that of the island regions, as seen in a storage modulus mapping image (hereinafter also referred to as an elastic modulus mapping image) obtained using an atomic force microscope. Figure 1 shows a storage modulus mapping image obtained using an atomic force microscope of the surface of the pressure-sensitive adhesive layer of an adhesive tape according to an embodiment of the present invention after irradiation with active energy rays. An atomic force microscope (AFM) is a microscope that detects atomic forces acting between a probe and a sample. Storage modulus mapping using an AFM can provide information on the distribution of storage modulus within the surface of the pressure-sensitive adhesive layer. As shown in Figure 1, when storage modulus mapping is performed using an AFM on the surface of the pressure-sensitive adhesive layer after irradiation with active energy rays, the island regions are regions with a relatively low storage modulus, and the sea region is regions with a storage modulus higher than that of the island regions. If the elastic modulus mapping image of the pressure-sensitive adhesive layer surface after active energy ray irradiation has such a sea-island structure, the polarity of the pressure-sensitive adhesive that forms a sea portion after active energy ray irradiation tends to be higher than that of the pressure-sensitive adhesive that forms an island portion after active energy ray irradiation. For example, when an active energy ray-curable resin is used as the active energy ray-curable component, the active energy ray-curable resin may be present in a higher amount in the pressure-sensitive adhesive with a higher polarity (i.e., the pressure-sensitive adhesive that forms a sea portion after active energy ray irradiation). Therefore, after active energy ray irradiation, the sea portion, which is the continuous phase, is more easily cured than the island portion, forming a sea that is more elastic than the island portion, and the amount of cure shrinkage of the sea portion may be increased. As a result, a pressure-sensitive adhesive tape that can be easily peeled can be obtained. In this specification, the storage elastic modulus mapping image of the pressure-sensitive adhesive layer surface after active energy ray irradiation using an AFM refers to the result of storage elastic modulus mapping measurement measured under the following conditions. <Storage modulus mapping measurement> An active energy ray irradiation device (for example, Nitto Seiki Co., Ltd., product name "UM-810") was used from the substrate side of the adhesive tape, with an integrated light dose of 460 mJ / cm 2The active energy rays are irradiated so that the cantilever's bending sensitivity and spring constant are calibrated using the AFM in Peak Force QNM mode. The release liner is peeled off from the adhesive tape that has been irradiated with the active energy rays, and elastic modulus mapping is performed under the following conditions to obtain a storage modulus mapping image. Measurement mode Device name: Bruker Atomic Force Microscope, Model Multi Mode 8 Mode: Peak Force QNM Tapping Mode Scan size: 2 μm x 2 μm Scan speed: 1.0Hz Maximum number of samples: 256 x 256 samples / line Peak Force Setpoint: 20nN Peak Force Frequency: 2kHz Modulus Fit Model: JKR (Johnson-Kendall-Roberts) Frequency (Frequency (F)): 70Hz Cantilever Model: 240AC-NA (MikroMasch) Spring Constant: 2N / m

[0009] In an elasticity mapping image of the surface of the pressure-sensitive adhesive layer after irradiation with active energy rays, the size of the island portion is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. Furthermore, the size of the island portion is, for example, 50 nm or more. If the island portion size is within the above range, even an aqueous dispersion-type pressure-sensitive adhesive can be mass-produced industrially in a stable manner. In this specification, the island portion size refers to the length of the portion where each island portion has the maximum length, and can be measured by image processing the elasticity mapping image.

[0010] The proportion of island portions on the surface of the pressure-sensitive adhesive layer after irradiation with active energy rays is preferably 10% to 80%, more preferably 10% to 70%, and even more preferably 30% to 70%. When the proportion of island portions is within the above range, a pressure-sensitive adhesive tape can be obtained that properly holds an adherend even after irradiation with active energy rays until peeling, and does not damage the adherend during peeling, even if the adherend is fine and / or thin.

[0011] FIG. 2 is a schematic cross-sectional view of a pressure-sensitive adhesive tape according to an embodiment of the present invention. The pressure-sensitive adhesive tape 100 includes, in this order, a substrate 20 and a pressure-sensitive adhesive layer 10. As described above, the surface of the pressure-sensitive adhesive layer 10 after irradiation with active energy rays has a microphase-separated structure consisting of island regions with a low storage modulus and a sea region with a storage modulus higher than that of the island regions, as seen in a storage modulus mapping image obtained using an atomic force microscope. The microphase-separated structure of the storage modulus of the pressure-sensitive adhesive layer before irradiation with active energy rays may be in any suitable state. The pressure-sensitive adhesive tape according to an embodiment of the present invention may exhibit excellent adhesion to an adherend before irradiation with active energy rays. Furthermore, if the surface of the pressure-sensitive adhesive layer after irradiation with active energy rays has the microphase-separated structure of the sea-island structure, the cure shrinkage of the pressure-sensitive adhesive layer after irradiation with active energy rays is greater, resulting in a pressure-sensitive adhesive tape that can be easily peeled from an adherend. The pressure-sensitive adhesive tape 100 may further include any suitable layer. For example, an intermediate layer (not shown) may be formed between the substrate 20 and the pressure-sensitive adhesive layer 10. When an intermediate layer is included, adhesion to an adherend having an uneven surface can be improved.

[0012] The adhesive strength of the adhesive tape to a Si wafer before irradiation with active energy rays is preferably 2 N / 20 mm or more, more preferably 4 N / 20 mm or more, and even more preferably 5 N / 20 mm or more. If the adhesive strength to a Si wafer before irradiation with active energy rays is within the above range, the tape has sufficient adhesion to the adherend. Furthermore, the adhesive strength to a Si wafer is, for example, 15 N / 20 mm or less. In this specification, the adhesive strength to a Si wafer refers to the adhesive strength measured by the following method. The adhesive tape is cut to a width of 20 mm and a length of 80 mm, and is pressed against the mirror surface of a silicon mirror wafer by rolling a hand roller back and forth once in an atmosphere at 23°C, and allowed to stand at 23°C for 30 minutes. The force required to peel the adhesive tape is then measured by a 90° peel test in an atmosphere at 23°C and 50% RH at a pulling rate of 300 mm / min.

[0013] The adhesive tape has an integrated light intensity of 460mJ / cm 2 The adhesive strength of the adhesive tape to the Si wafer after irradiation with ultraviolet rays is preferably less than 0.25 N / 20 mm, more preferably 0.2 N / 20 mm or less, and even more preferably 0.15 N / 20 mm or less. If the adhesive strength to the Si wafer after irradiation with ultraviolet rays, which are active energy rays, is within the above range, the tape has easy peelability. The smaller the adhesive strength after irradiation with active energy rays (ultraviolet rays), the more preferable. In this specification, the integrated light dose is 460 mJ / cm. 2 The adhesive strength of the adhesive tape to the Si wafer after irradiating with ultraviolet light is the value measured using the following method. The adhesive tape was cut into a width of 20 mm and a length of 80 mm, and pressed onto the mirror surface of a silicon mirror wafer in an atmosphere of 23°C by moving a hand roller back and forth once, and then left at 23°C for 30 minutes. After that, ultraviolet (UV) light was applied to the tape at an integrated light intensity of 460 mJ / cm. 2 The adhesive tape is irradiated from the side of the adhesive tape so that the optical intensity is 365 nm (equivalent to 365 nm). Then, a 90° peel test is carried out in an atmosphere of 23°C and 50% RH at a pulling speed of 300 mm / min to measure the force required to peel the adhesive tape.

[0014] The thickness of the pressure-sensitive adhesive tape according to the embodiment of the present invention can be set to any appropriate thickness, and is preferably 30 μm to 400 μm, more preferably 40 μm to 300 μm, and even more preferably 50 μm to 200 μm.

[0015] A-1. Base material The substrate may be made of any suitable resin. Specific examples of resins constituting the substrate include polyester-based resins such as polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN); polyolefin-based resins such as ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, polyethylene, polypropylene, and ethylene-propylene copolymer; polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyimide, cellulose, fluorine-based resins, polystyrene-based resins such as polyether and polystyrene; polycarbonate, polyethersulfone, and polyetheretherketone. Polyolefin-based resins or polyester-based resins are preferred. Because these resins transmit ultraviolet light, a pressure-sensitive adhesive layer can be formed using a UV-curable pressure-sensitive adhesive to provide a pressure-sensitive adhesive tape with easy peelability.

[0016] The substrate may further contain other components within the range that does not impair the effects of the present invention. Examples of other components include antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, antistatic agents, etc. The types and amounts of other components can be any appropriate amount depending on the purpose.

[0017] The thickness of the substrate is preferably 30 μm to 200 μm, more preferably 40 μm to 180 μm, and even more preferably 45 μm to 180 μm.

[0018] A-2.Adhesive layer The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape according to an embodiment of the present invention is formed from an active energy ray-curable pressure-sensitive adhesive. Representative examples of active energy ray-curable pressure-sensitive adhesives include ultraviolet-curable pressure-sensitive adhesives. The active energy ray-curable pressure-sensitive adhesive is preferably a water-dispersible pressure-sensitive adhesive. A pressure-sensitive adhesive containing a water-dispersible acrylic polymer, an active energy ray-curable resin, and a photopolymerization initiator is preferably used as the water-dispersible pressure-sensitive adhesive. Use of such a pressure-sensitive adhesive can provide excellent adhesive strength and excellent adhesion to an adherend. Furthermore, after irradiation with active energy rays, the surface of the pressure-sensitive adhesive layer has a microphase-separated structure with a sea-island structure in an elastic modulus mapping image, and a water-dispersible pressure-sensitive adhesive can be provided that can achieve both adhesion and easy releasability. Furthermore, despite being a water-based pressure-sensitive adhesive composition, such a pressure-sensitive adhesive has excellent adhesive strength and can achieve both adhesion to an adherend and easy releasability. Therefore, a pressure-sensitive adhesive that can reduce the amount of solvent used, thereby reducing the environmental impact, and that can be used suitably in semiconductor wafer processing can be provided.

[0019] A-2-1. Water-dispersible acrylic polymer A water-dispersible acrylic polymer (hereinafter also referred to as an acrylic polymer) can be obtained by emulsion polymerization of any appropriate monomer component in water. That is, the water-dispersible acrylic polymer is an emulsion of an acrylic polymer. The average particle size of the acrylic polymer emulsion is preferably 80 nm to 400 nm, more preferably 100 nm to 300 nm, and even more preferably 100 nm to 200 nm. In this specification, the average particle size of the water-dispersible acrylic polymer refers to the volume-based median diameter (D50) measured by a laser diffraction / scattering method.

[0020] In one embodiment, the water-dispersible acrylic polymer is preferably a polymer having a core-shell structure (hereinafter also referred to as a core-shell polymer). Use of a water-dispersible acrylic polymer that is a core-shell polymer can provide a PSA that has superior adhesive strength before irradiation with active energy rays and can achieve both adhesion to an adherend and easy releasability.

[0021] The water-dispersible acrylic polymer that is a core-shell polymer can be obtained by emulsion polymerization of any appropriate monomer components in a stepwise manner, for example, by emulsion polymerization of a monomer composition that forms a core portion by any appropriate method, and then emulsion polymerization of a monomer composition that forms a shell portion in the presence of the polymer particles that become the core portion, which is called seed polymerization.

[0022] The water-dispersible acrylic polymer, which is a core-shell polymer, preferably has a core ratio of 5% by weight or more, more preferably 10% by weight or more. When the weight ratio of the core part to the shell part is within the above range, it is possible to provide a water-dispersible PSA composition that has excellent adhesive strength and can achieve both adhesion to an adherend and easy releasability.

[0023] The core-shell polymer preferably comprises a shell portion having a glass transition temperature Tg of −10° C. or higher and a core portion having a glass transition temperature Tg of less than −10° C. Use of such a core-shell polymer makes it possible to obtain a pressure-sensitive adhesive tape that has excellent adhesive strength before irradiation with active energy rays and that can be peeled off from an adherend without damaging the adherend after irradiation with active energy rays.

[0024] The glass transition temperature Tg of the shell portion is preferably -10°C or higher, more preferably -5°C or higher, and even more preferably 0°C or higher. The glass transition temperature Tg of the shell portion is, for example, 50°C or lower. The glass transition temperature Tg of the core portion is preferably less than -10°C, more preferably -20°C or lower, even more preferably -30°C or lower, and particularly preferably -35°C or lower. The glass transition temperature Tg of the core portion is, for example, -60°C or higher. When the glass transition temperatures Tg of the core portion and the shell portion are within the above ranges, a pressure-sensitive adhesive tape can be provided that has good adhesiveness before irradiation with active energy rays and good releasability after irradiation with active energy rays.

[0025] In this specification, the glass transition temperature of a water-dispersible acrylic polymer refers to a theoretical value calculated by the Fox equation from the monomer units constituting each polymer and their proportions. The theoretical glass transition temperature calculated by the Fox equation can be consistent with the measured glass transition temperature determined by methods such as differential scanning calorimetry (DSC) or dynamic viscoelasticity measurement. As described below, when the theoretical value cannot be calculated, the measured glass transition temperature can be used.

[0026] The Fox equation, as shown below, is a relational expression between the Tg of an acrylic polymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers that make up the acrylic polymer. 1 / Tg=Σ(Wi / Tgi) (In the formula, Tg is the glass transition temperature (unit: K) of the acrylic polymer, Wi is the weight fraction of monomer i in the acrylic polymer (copolymerization ratio by weight), and Tgi is the glass transition temperature (unit: K) of the homopolymer of monomer i.)

[0027] The glass transition temperature of the homopolymer used to calculate Tg can be any value described in any appropriate document. For example, for the monomers listed below, the following values ​​are used as the glass transition temperatures of the homopolymers of the monomers: 2-Ethylhexyl acrylate -70℃ Methyl methacrylate 8℃ Acrylic acid 106℃ 2-Acryloyloxyethyl succinate -40℃ 4-Hydroxybutyl acrylate -40℃ N-Acryloylmorpholine 145℃

[0028] For the glass transition temperatures of homopolymers of monomers other than those exemplified above, the values ​​described in, for example, "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) can be used. When multiple values ​​are listed, the highest value is used.

[0029] For monomers for which the glass transition temperature of the homopolymer is not listed in the Polymer Handbook, the value obtained by the measurement method described in JP 2007-51271 A can be used. Specifically, 100 parts by weight of the monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as the polymerization solvent were charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and the mixture was stirred for 1 hour while passing nitrogen gas through. After removing oxygen from the polymerization system in this manner, the temperature was raised to 63°C and the reaction was continued for 10 hours. The mixture was then cooled to room temperature to obtain a homopolymer solution with a solids concentration of 33% by weight. This homopolymer solution was then cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) approximately 2 mm thick. This test sample was punched out into a disk with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics). Viscoelasticity was measured in shear mode at a temperature range of -70°C to 150°C and a heating rate of 5°C / min. The peak top temperature of tan δ was taken as the Tg of the homopolymer.

[0030] A-2-2. Monomer component The composition of the monomer composition used to form the core and shell portions can be adjusted to form core or shell portions having any appropriate glass transition temperature. For example, monomers may be selected based on the Fox formula above so as to form core or shell portions having a designed glass transition temperature Tg, and then emulsion polymerized.

[0031] Any suitable acrylic monomer can be used as the monomer component. A typical monomer component is a (meth)acrylic acid alkyl ester. Specific examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and (meth) Examples of (meth)acrylic acid C1-20 alkyl esters include nonyl acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more. In this specification, (meth)acrylic refers to acrylic and / or methacrylic.

[0032] The monomer composition may further include any other suitable monomer copolymerizable with the (meth)acrylic acid alkyl ester. For example, carboxyl group-containing monomers such as acrylic acid and methacrylic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; hydroxyl group-containing monomers such as hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; sulfonic acid group-containing monomers such as styrene sulfonic acid and allyl sulfonic acid; (N-substituted) amide monomers such as diacetone acrylamide, (meth)acrylamide, and N,N-dimethyl (meth)acrylamide; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate; (meth)acrylic alkoxyalkyl (meth)acrylate monomers such as methoxyethyl acetate; maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide; itaconimide monomers such as N-methylitaconimide and N-ethylitaconimide; succinimide monomers; vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, and methylvinylpyrrolidone; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate; acrylic ester monomers having a heterocycle, halogen atom, silicon atom, or the like, such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; olefin-based monomers such as isoprene, butadiene, and isobutylene; and vinyl ether monomers such as vinyl ether.By including these monomer components, it is possible to improve cohesive strength, heat resistance, crosslinkability, etc. These monomer components may be used alone or in combination of two or more.

[0033] In one embodiment, it is preferable to use an amide group-containing monomer as the monomer component constituting the shell part.Specific examples of the amide group-containing monomer include acrylamide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide;N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam-based monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. Preferred are N-(meth)acryloylmorpholine, N,N-diethyl(meth)acrylamide, and N-isopropylacrylamide, and more preferred is N-acryloylmorpholine. The use of an amide group-containing monomer as the monomer used in the polymerization of the shell portion can improve the initial adhesive strength of the pressure-sensitive adhesive layer. The content of the amide group-containing monomer in all the monomers constituting the shell portion is, for example, 0.01 to 10% by weight, and preferably 0.1 to 7% by weight.

[0034] In one embodiment, the acrylic polymer is preferably a polymer obtained by polymerizing a monomer composition containing a carboxyl group-containing monomer represented by formula (1) as a monomer component. When the acrylic polymer is a core-shell polymer, the carboxyl group-containing monomer represented by formula (1) may be contained only in the monomer composition used for polymerization of the core portion, or only in the monomer composition used for polymerization of the shell portion, or may be contained in both the monomer composition used for polymerization of the core portion and the monomer composition used for polymerization of the shell portion. The carboxyl group-containing monomer may be used alone or in combination of two or more types. [ka] (In the formula, R 1 represents a hydrogen atom or a methyl group, and R 2 represents a divalent hydrocarbon group, x represents an integer of 1 to 20, and y represents 0 or 1).

[0035] R 1 represents a hydrogen atom or a methyl group. x is an integer of 1 to 20, preferably an integer of 1 to 10, and more preferably an integer of 1 to 8. y is 0 or 1. R 2 represents a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include saturated aliphatic hydrocarbon groups such as alkylene groups, saturated alicyclic hydrocarbon groups such as cycloalkylene groups, aromatic hydrocarbon groups such as phenylene groups, unsaturated aliphatic hydrocarbon groups, and unsaturated alicyclic hydrocarbon groups. Preferably, R 2 is a linear or branched alkylene group or cycloalkylene group, more preferably a linear or branched alkylene group or cycloalkylene group having 1 to 20 carbon atoms, and even more preferably a linear or branched alkylene group or cycloalkylene group having 1 to 10 carbon atoms. 2 When is a divalent hydrocarbon group as described above, a pressure-sensitive adhesive having excellent dispersion stability and coatability can be obtained.

[0036] Specific examples of the carboxyl group-containing monomer represented by formula (1) include 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, ω-carboxy-polycaprolactone (n≒2) monoacrylate, and 2-methacryloyloxyethyl hexahydrophthalic acid.

[0037] The carboxyl group-containing monomer represented by formula (1) may be a commercially available product, such as "HOA-MS," "Light Ester HO-MS(N)," or "Light Acrylate HOA-HH(N)" manufactured by Kyoeisha Chemical Co., Ltd., or "Aronix M-5300" manufactured by Toagosei Co., Ltd.

[0038] The content of the carboxyl group-containing monomer represented by formula (1) is preferably 3 to 30 parts by weight, more preferably 4 to 25 parts by weight, even more preferably 4 to 20 parts by weight, and particularly preferably 6 to 15 parts by weight, relative to 100 parts by weight of the monomer components (in the case of a core-shell polymer, the monomer components used in polymerization of the core portion or the monomer components used in polymerization of the shell portion). If the content of the carboxyl group-containing monomer represented by formula (1) is within the above range, a PSA having excellent dispersion stability and coatability can be obtained.

[0039] A-2-3.Surfactants Any appropriate surfactant can be used as the surfactant. Preferably, a reactive surfactant can be used. The reactive surfactant not only functions as a surfactant but also has a radically polymerizable functional group in the molecule (e.g., a radically reactive group such as an ethenyl group, a propenyl group, an allyl group, or an allyl ether group). The use of a reactive surfactant can reduce contamination of an adherend caused by a pressure-sensitive adhesive using a water-dispersible acrylic polymer and can improve the adhesive strength of the pressure-sensitive adhesive composition before radiation irradiation treatment. In addition, the water resistance of a pressure-sensitive adhesive tape (e.g., a pressure-sensitive adhesive layer) using the pressure-sensitive adhesive composition can be improved, and peeling of the pressure-sensitive adhesive tape can be suppressed even when water is splashed on it during processing.

[0040] Examples of reactive surfactants include surfactants in which a radically polymerizable functional group (radical reactive group) such as a propenyl group or an allyl ether group has been introduced into any suitable surfactant (e.g., anionic surfactants, nonionic surfactants, etc.). Reactive surfactants have a radically polymerizable functional group associated with an ethylenically unsaturated double bond, and can reduce the saturated water absorption of the pressure-sensitive adhesive layer formed compared to non-reactive surfactants. Furthermore, from the viewpoints of the stability of the aqueous dispersion and the durability of the pressure-sensitive adhesive layer, the reactive surfactants preferably used may be used alone or in combination of two or more.

[0041] Specific examples of anionic surfactants include higher fatty acid salts such as sodium oleate; alkylarylsulfonates such as sodium dodecylbenzenesulfonate; alkylsulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate; polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate; polyoxyethylene alkylaryl ether sulfate salts such as sodium polyoxyethylene nonylphenyl ether sulfate; alkylsulfosuccinate salts and derivatives thereof such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, and sodium polyoxyethylene lauryl sulfosuccinate; and polyoxyethylene distyrenated phenyl ether sulfate salts. Specific examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, and sorbitan trioleate; polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate; polyoxyethylene higher fatty acid esters such as polyoxyethylene monolaurate and polyoxyethylene monostearate; glycerin higher fatty acid esters such as oleic acid monoglyceride and stearic acid monoglyceride; polyoxyethylene-polyoxypropylene block copolymers, and polyoxyethylene distyrenated phenyl ether.

[0042] As the reactive surfactant, commercially available products may be used. Specific examples of anionic reactive surfactants include alkyl ether reactive surfactants such as "Aqualon KH-05," "Aqualon KH-10," and "Aqualon KH-20" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "ADEKA REASOAP SR-10N" and "ADEKA REASOAP SR-20N" manufactured by Asahi Denka Kogyo Co., Ltd., and "Latemul PD-104" manufactured by Kao Corporation; sulfosuccinate ester reactive surfactants such as "Latemul S-120," "Latemul S-120A," "Latemul S-180P," and "Latemul S-180A" manufactured by Kao Corporation, and "Eleminol JS-20" manufactured by Sanyo Chemical Industry Co., Ltd.; and "Aqualon H-2855A," "Aqualon H-3855B," "Aqualon H-3855C," "Aqualon H-3856," "Aqualon HS-05," "Aqualon HS-10," "Aqualon HS-20," and "Aqualon H" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. alkylphenyl ether or alkylphenyl ester reactive surfactants such as "ADEKA REASOAP SDX-30," "AQUALON BC-05," "AQUALON BC-10," "AQUALON BC-20," and "ADEKA REASOAP SDX-222," "ADEKA REASOAP SDX-223," "ADEKA REASOAP SDX-232," "ADEKA REASOAP SDX-233," "ADEKA REASOAP SDX-259," "ADEKA REASOAP SE-10N," and "ADEKA REASOAP SE-20N," manufactured by Asahi Denka Kogyo Co., Ltd.; (meth)acrylate sulfate ester reactive surfactants such as "ANTOX MS-60" and "ANTOX MS-2N," manufactured by Nippon Nyukazai Co., Ltd., and "ELEMINOL RS-30," manufactured by Sanyo Chemical Industries, Ltd.; and phosphate ester reactive surfactants such as "H-3330PL," manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and "ADEKA REASOAP PP-70," manufactured by Asahi Denka Kogyo Co., Ltd.Specific examples of nonionic reactive surfactants include alkyl ether reactive surfactants such as those manufactured by Asahi Denka Kogyo Co., Ltd. under the trade names "ADEKA REASOAP ER-10," "ADEKA REASOAP ER-20," "ADEKA REASOAP ER-30," and "ADEKA REASOAP ER-40," and those manufactured by Kao Corporation under the trade names "LATEMUL PD-420," "LATEMUL PD-430," and "LATEMUL PD-450"; alkyl phenyl ether or alkyl phenyl ester reactive surfactants such as those manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. under the trade names "AQUALON RN-10," "AQUALON RN-20," "AQUALON RN-30," and "AQUALON RN-50," and those manufactured by Asahi Denka Kogyo Co., Ltd. under the trade names "ADEKA REASOAP NE-10," "ADEKA REASOAP NE-20," "ADEKA REASOAP NE-30," and "ADEKA REASOAP NE-40"; and (meth)acrylate sulfate ester reactive surfactants such as those manufactured by Nippon Nyukazai Co., Ltd. under the trade names "RMA-564," "RMA-568," and "RMA-1114."

[0043] As the reactive surfactant, an anionic reactive surfactant is preferably used. Anionic reactive surfactants often have excellent polymerization stability and are preferred from the viewpoints of particle stability and appearance. Anionic reactive surfactants and nonionic reactive surfactants may be used in combination.

[0044] In one embodiment, the reactive surfactant is preferably SO4 2- The concentration of ions is 100 μg / g or less. The reactive surfactant is preferably an ammonium salt type surfactant. In an embodiment of the present invention, the adhesive tape may be an adhesive tape used in the processing of semiconductor wafers. Therefore, impurity ions contained in the adhesive may be a problem. Therefore, it is preferable that the adhesive contains as few impurity ions as possible. SO4 2- If the ion concentration is within the above range and an ammonium salt surfactant is used, the adverse effects of impurity ions can be suppressed. Note that any appropriate method can be used to reduce or remove impurity ions, such as an ion exchange resin method, a membrane separation method, or a method of precipitating and filtering impurities using alcohol.

[0045] The reactive surfactant is used in any appropriate amount. The reactive surfactant is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, per 100 parts by weight of the monomer composition. If the reactive surfactant content exceeds 5 parts by weight per 100 parts by weight of the monomer composition, when the pressure-sensitive adhesive composition is used in an adhesive tape for processing semiconductor wafers, small pieces of the device may peel off from the adhesive tape during the dicing process or a subsequent process. Furthermore, if the reactive surfactant content is less than 0.1 part by weight per 100 parts by weight of the monomer composition, a stable emulsified state may not be maintained.

[0046] In addition, a reactive surfactant and a surfactant not having a radical polymerizable functional group may be used in combination. Examples of surfactants not having a radical polymerizable functional group include anionic surfactants and nonionic anionic surfactants such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, and sodium polyoxyethylene alkyl sulfosuccinate; and nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene polyoxypropylene block polymer. These surfactants may be used alone or in combination of two or more.

[0047] A-2-4. Polymerization method for water-dispersible acrylic polymer The water-dispersible acrylic polymer can be polymerized by any suitable method. For example, water such as ion-exchanged water, a monomer composition, a surfactant, a polymerization initiator, and optional additives can be added to a reaction vessel and mixed, followed by emulsion polymerization to obtain a water-dispersible acrylic polymer. When the water-dispersible acrylic polymer is a core-shell polymer, for example, a monomer composition containing a monomer that forms the core portion, water, a surfactant, a polymerization initiator, and optional additives can be added to a reaction vessel and mixed, followed by emulsion polymerization to form polymer particles that will become the core portion. Next, a monomer composition containing a monomer that forms the shell portion, water, a surfactant, a polymerization initiator, and optional additives can be added to a reaction vessel and mixed, followed by emulsion polymerization to form the shell portion, thereby obtaining a water-dispersible acrylic polymer that is a core-shell polymer. Examples of optional additives include chain transfer agents and silane coupling agents.

[0048] Any suitable polymerization initiator can be used as the polymerization initiator. For example, azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine) are used; persulfates such as potassium persulfate and ammonium persulfate are used; benzoyl persulfate is used; and peroxide-based polymerization initiators such as peroxide, t-butyl hydroperoxide, and hydrogen peroxide; and redox-based initiators formed by combining a peroxide with a reducing agent (for example, a combination of a peroxide and ascorbic acid (e.g., a combination of aqueous hydrogen peroxide and ascorbic acid), a combination of a peroxide and an iron (II) salt (e.g., a combination of aqueous hydrogen peroxide and an iron (II) salt), a combination of a persulfate and sodium hydrogen sulfite, etc.). Only one type of polymerization initiator may be used, or two or more types may be used in combination.

[0049] The polymerization initiator can be used in any appropriate amount depending on the type of polymerization initiator used, the composition of the monomer composition, etc. The content of the polymerization initiator is, for example, 0.01 to 1 part by weight, and preferably 0.02 to 0.5 parts by weight, per 100 parts by weight of the monomer composition.

[0050] The chain transfer agent can be used, for example, to adjust the molecular weight of the water-dispersible acrylic polymer. Any appropriate chain transfer agent can be used. Specific examples include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol. The chain transfer agent may be used alone or in combination of two or more. The content of the chain transfer agent is usually 0.001 to 0.5 parts by weight per 100 parts by weight of the monomer composition.

[0051] The water-dispersible acrylic polymer can be obtained by emulsion polymerization of a monomer composition, a reactive surfactant, a polymerization initiator, and optional additives such as a chain transfer agent. Therefore, the water-dispersible acrylic polymer can be prepared in the form of an emulsion. Any appropriate method can be used for emulsion polymerization. Specific examples include emulsion polymerization methods using a general batch charging method (bulk polymerization method), a monomer dropping method, and a monomer emulsion dropping method. When adding monomers or the like by dropping, the addition can be continuous or divided into portions. The polymerization temperature can be set to any appropriate value depending on the type of polymerization initiator, for example, in the range of 5°C to 100°C. It is also preferable to add aqueous ammonia, various water-soluble amines, or an aqueous alkali solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution to the solution of the water-dispersible acrylic polymer obtained by emulsion polymerization to adjust the pH to, for example, 6 to 11, preferably 7 to 10.

[0052] The gel fraction of the water-dispersible acrylic polymer is preferably 50% by weight or more, more preferably 70% by weight or more. If the gel fraction of the water-dispersible acrylic polymer is less than 50% by weight, the adhesive strength after irradiation with active energy rays is less likely to decrease, and the adherend is more likely to be contaminated by the sol component. The gel fraction of the water-dispersible acrylic polymer is, for example, 99% by weight or less. The gel fraction of the water-dispersible acrylic polymer can be determined by any appropriate method. For example, the gel fraction can be determined as the content insoluble in a solvent such as ethyl acetate. Specifically, the gel fraction is determined as the weight fraction (unit: wt%) of the insoluble component after immersing the water-dispersible acrylic polymer in ethyl acetate at 23°C for 7 days relative to the sample before immersion.

[0053] A-3. Active energy ray curable resin As the active energy ray-curable resin, any appropriate resin that can be cured by active energy rays such as ultraviolet rays can be used. Preferably, an ultraviolet-curable resin is used. As the ultraviolet-curable resin, for example, an ultraviolet-curable monomer and / or oligomer can be used. Examples of ultraviolet-curable monomers include urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Examples of ultraviolet-curable oligomers include urethane-based oligomers, polyether-based oligomers, polyester-based oligomers, polycarbonate-based oligomers, and polybutadiene-based oligomers. The oligomer preferably has a molecular weight of about 100 to 30,000. The monomer and oligomer may be used alone or in combination of two or more. The active energy ray-curable resin may be emulsified using any appropriate surfactant or self-emulsifying urethane (meth)acrylate, as needed. By emulsifying, the water-dispersible pressure-sensitive adhesive can be easily prepared.

[0054] Commercially available active energy ray-curable resins may be used. Examples include UBE's trade name "ETERNACOLL UW-9102," DIC's trade name "HYDRAN Exp UV-100S," Arakawa Chemical Industries, Ltd.'s trade names "BEAMSET EM-90" and "BEAMSET EM-94," Daicel-Allnex's trade names "UCECOAT7655," "UCECOAT7200," and "UCECOAT7773," and Fujifilm Wako Pure Chemical Industries, Ltd.'s trade names "FOM-03006" and "FOM-03009." From the viewpoint of compatibility with the water-dispersible acrylic polymer, an aqueous resin (aqueous dispersion of resin) may be appropriately selected and used.

[0055] The active energy ray-curable resin can be used in any appropriate amount depending on the type of water-dispersible acrylic polymer, etc. For example, the amount is preferably 5 to 200 parts by weight, more preferably 20 to 150 parts by weight, and even more preferably 50 to 150 parts by weight, relative to 100 parts by weight of the water-dispersible acrylic polymer.

[0056] A-4. Photopolymerization initiator Any suitable initiator can be used as the photopolymerization initiator. Examples of the photopolymerization initiator include acylphosphine oxide photopolymerization initiators such as ethyl 2,4,6-trimethylbenzylphenylphosphinate and (2,4,6-trimethylbenzoyl)phenylphosphine oxide; α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenylketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; and benzyl dimethyl ketal. aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphonates; and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropane-1. The photopolymerization initiator may be used alone or in combination of two or more. Preferably, a photopolymerization initiator that is liquid at room temperature (e.g., 23°C) is used because it can be dissolved (compatible) in the water-dispersed acrylic polymer solution.

[0057] As the photopolymerization initiator, commercially available products may be used, for example, trade names of Omnirad 500, Omnirad TPO-L, Omnirad MBF, Omnirad 1173, etc., manufactured by IGM Resins, may be mentioned.

[0058] The photopolymerization initiator can be used in any appropriate amount. The content of the photopolymerization initiator is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight, relative to 100 parts by weight of the water-dispersible acrylic polymer. If the content of the photopolymerization initiator is less than 0.5 parts by weight, the composition may not be sufficiently cured when irradiated with active energy rays. If the content of the photopolymerization initiator is more than 20 parts by weight, the storage stability of the water-dispersible pressure-sensitive adhesive composition may be reduced.

[0059] A-5. Crosslinking agent In one embodiment, the pressure-sensitive adhesive composition may further contain a crosslinking agent. The gel fraction of the pressure-sensitive adhesive composition can be adjusted by using a crosslinking agent. Any appropriate crosslinking agent can be used. Examples of the crosslinking agent include bifunctional or higher epoxy crosslinking agents, isocyanate crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine resin crosslinking agents, metal chelate crosslinking agents, peroxide crosslinking agents, and hydrazine crosslinking agents. Only one crosslinking agent may be used, or two or more crosslinking agents may be used in combination.

[0060] Specifically, examples of the crosslinking agent include epoxy-based crosslinking agents such as N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, and 1,6-hexanediol diglycidyl ether; isocyanate-based crosslinking agents (blocked isocyanate-based crosslinking agents, etc.) such as tolylene diisocyanate (blocked); carbodiimide-based crosslinking agents such as "Carbodilite V-01 (manufactured by Nisseibo Co., Ltd.)"; epoxy-based crosslinking agents such as polyethylene glycol diglycidyl ether and polyglycerol polyglycidyl ether; and water-dispersible isocyanate-based crosslinking agents such as "Elastron BN-69 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)." oxazoline-based crosslinking agents such as trade name "Epocross WS-500 (manufactured by Nippon Shokubai Co., Ltd.)"; aziridine-based crosslinking agents such as trade name "ChemiTite PZ-33 (manufactured by Nippon Shokubai Co., Ltd.)"; hydrophilic-treated carbodiimide-based crosslinking agents such as trade names "Carbodilite V-02" and "Carbodilite V-04 (manufactured by Nisshinbo Co., Ltd.)"; crosslinking agents containing an active methylol group or an active alkoxymethyl group, such as an active methylol group such as hexamethylol melamine, or an active alkoxymethyl group such as hexamethoxymethyl melamine; metal chelate-based crosslinking agents such as trade name "Orgatix AI135 (manufactured by Matsumoto Pharmaceutical Industries Co., Ltd.)"; and hydrazine-based crosslinking agents such as adipic acid dihydrazide and phthalic acid dihydrazide.

[0061] The content of the crosslinking agent is, for example, 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, and more preferably 0.1 to 3 parts by weight, relative to 100 parts by weight of the water-dispersible acrylic polymer. As described above, the water-dispersible PSA composition may not contain a crosslinking agent (i.e., the content of the crosslinking agent may be 0 part by weight).

[0062] A-6. Additives The PSA may contain any suitable additives as needed. Examples of the additives include catalysts (e.g., platinum catalysts), tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, UV absorbers, light stabilizers, release modifiers, softeners, flame retardants, solvents, etc. The additives are used in any suitable amount depending on the purpose.

[0063] The thickness of the pressure-sensitive adhesive layer can be set to any appropriate value. The thickness of the pressure-sensitive adhesive layer is preferably 2 μm to 200 μm, more preferably 3 μm to 150 μm, and even more preferably 5 μm to 100 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, it can exert sufficient adhesive strength to the adherend.

[0064] B. Manufacturing method of adhesive tape The pressure-sensitive adhesive tape of the embodiment of the present invention can be produced by any appropriate method. For example, it can be obtained by applying a pressure-sensitive adhesive to a release liner, drying it, forming a pressure-sensitive adhesive layer on the release liner, and then transferring the pressure-sensitive adhesive layer to a substrate. Alternatively, the pressure-sensitive adhesive tape can be obtained by applying a pressure-sensitive adhesive to a substrate and drying it. As a method for applying the pressure-sensitive adhesive, various methods can be used, such as bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing. As a drying method, any appropriate method can be used.

[0065] C. Applications of adhesive tape The pressure-sensitive adhesive tape according to the embodiment of the present invention can be suitably used in the manufacturing process of semiconductor wafers. For example, it can be used as a dicing tape, a backgrinding tape, or the like. As described above, the pressure-sensitive adhesive tape according to the embodiment of the present invention properly holds the adherend before irradiation with active energy rays, and after irradiation with active energy rays, the pressure-sensitive adhesive tape can be peeled off without damaging the adherend, even if the adherend is fine and / or thin. Therefore, it can also be suitably used in the processing of thinner semiconductor wafers with complex structures. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0067] [Synthesis Example 1] Synthesis of acrylic polymer A In a reaction vessel equipped with a condenser, nitrogen inlet, thermometer, and stirrer, 180 parts by weight of water, 62 parts by weight of 2-ethylhexyl acrylate (2EHA), 23 parts by weight of methyl methacrylate (MMA), 10 parts by weight of a carboxyl group-containing monomer (HOA-MS) (2-acryloyloxyethyl succinic acid, manufactured by Kyoeisha Chemical Co., Ltd., trade name "HOA-MS"), 5 parts by weight of 4-hydroxybutyl acrylate (4HBA) (manufactured by Osaka Organic Chemical Industry Co., Ltd., product name "4-HBA"), and 3 parts by weight of a reactive surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon HS-1025") were mixed and emulsified using a homomixer. The atmosphere was then replaced with nitrogen for 1 hour while stirring. The internal bath temperature during the polymerization was then maintained at 60°C. To this was added 0.04 parts by weight of a water-soluble azo initiator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "VA-057") to initiate polymerization, followed by heating for 2 hours to produce a core portion. Next, 90 parts by weight of water, 35 parts by weight of 2EHA, 45 parts by weight of MMA, 10 parts by weight of HOA-MS, 5 parts by weight of HBA, 5 parts by weight of acryloylmorpholine (ACMO), and 1 part by weight of a reactive surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd., product name "Aqualon HS-1025") were mixed and stirred with a homomixer to prepare a shell monomer emulsion. 0.2 parts by weight of a water-soluble azo initiator (Fujifilm Wako Pure Chemical Industries, Ltd., product name "VA-057") was added to the aqueous dispersion of core particles. After a 10-minute induction period, the emulsified shell monomer emulsion was added over 2 hours, and then the mixture was allowed to age for another 2 hours to produce core-shell water-dispersed acrylic polymer A.

[0068] [Synthesis Examples 2 to 4] Synthesis of acrylic polymers B to D Core-shell water-dispersible acrylic polymers B to D were obtained in the same manner as in Synthesis Example 1, except that the monomer compositions of the core and shell parts were changed as shown in Table 1.

[0069] [Synthesis Example 5] Synthesis of acrylic polymer E A reaction vessel equipped with a condenser, nitrogen inlet, thermometer, and stirrer was charged with 180 parts by weight of water, 47.5 parts by weight of 2EHA, 35 parts by weight of MMA, 10 parts by weight of HOA-MS, 5 parts by weight of 4HBA, 2.5 parts by weight of ACMO, and 2 parts by weight of a reactive surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon KH-1025"), and emulsified by stirring with a homomixer. The atmosphere was then purged with nitrogen for 1 hour while stirring. The internal bath temperature during the polymerization was then controlled at 60°C. Next, 0.1 parts by weight of a water-soluble azo initiator (Fujifilm Wako Pure Chemical Industries, Ltd., trade name "VA-057") was added to initiate polymerization, and the mixture was heated for 5 hours to synthesize water-dispersible acrylic polymer E.

[0070] [Table 1]

[0071] [Example 1] 100 parts by weight of acrylic polymer, 100 parts by weight of UV-curable resin (manufactured by UBE, trade name "ETERNACOLL UW-9102"), 0.2 parts by weight of crosslinker (manufactured by Nisshinbo Chemical Inc., trade name "Carbodilite V-04"), and 3 parts by weight of photopolymerization initiator (manufactured by IGM Resins B.V., trade name "Omnirad TPO-L") were added and mixed, and then neutralized with 10% aqueous ammonia to prepare an aqueous dispersion. The resulting adhesive solution was coated onto the silicone release-treated surface of a polyester film (thickness: 38 μm) that had been treated with a silicone release agent, so that the dry thickness would be 20 μm. The coating was then dried at 125°C for 3 minutes to form an adhesive layer. Next, a polyolefin (PO) film (thickness: 80 μm) that had been surface-oxidized by corona discharge was bonded to the adhesive layer surface, transferring the adhesive layer and producing an adhesive tape.

[0072] [Example 2] An adhesive tape was obtained in the same manner as in Example 1, except that the core-shell type water-dispersible acrylic polymer B was used instead of the core-shell type water-dispersible acrylic polymer A, and no crosslinking agent was added.

[0073] [Example 3] An adhesive tape was obtained in the same manner as in Example 2, except that 50 parts by weight of UW-9102 and 50 parts by weight of UV-W300 (manufactured by Mitsubishi Chemical Corporation, product name "Shikou UV-W300") were used as the UV-curable resin.

[0074] [Example 4] An adhesive tape was obtained in the same manner as in Example 1, except that core-shell type water-dispersible acrylic polymer C was used instead of core-shell type water-dispersible acrylic polymer A, no crosslinking agent was added, and 1 part by weight of a thickener (manufactured by San Nopco Limited, trade name "SN Thickener 612") and 1 part by weight of a leveling agent (manufactured by Daiichi Kogyosha Pharmaceutical Co., Ltd., trade name "Neocol SW-C") were added.

[0075] (Comparative Example 1) An adhesive tape was obtained in the same manner as in Example 2, except that the core-shell type water-dispersible acrylic polymer D was used instead of the core-shell type water-dispersible acrylic polymer B.

[0076] (Comparative Example 2) An adhesive tape was obtained in the same manner as in Example 3, except that the water-dispersible acrylic polymer E was used instead of the core-shell water-dispersible acrylic polymer C.

[0077] <Evaluation> The water-dispersible acrylic polymers used in the examples and comparative examples and the resulting pressure-sensitive adhesive tapes were evaluated as follows. The results are shown in Table 2. 1. Glass transition temperature The glass transition temperatures of the water-dispersible acrylic polymers obtained in Synthesis Examples 1 to 5 were calculated using the following Fox formula. 1 / Tg=Σ(Wi / Tgi) (In the formula, Tg is the glass transition temperature (unit: K) of the acrylic polymer, Wi is the weight fraction of monomer i in the acrylic polymer (copolymerization ratio by weight), and Tgi is the glass transition temperature (unit: K) of the homopolymer of monomer i.) The glass transition temperatures of the homopolymers of the monomers were as follows: 2-Ethylhexyl acrylate -70℃ Methyl methacrylate 8℃ Acrylic acid 106℃ 2-Acryloyloxyethyl succinate -40℃ 4-Hydroxybutyl acrylate -40℃ N-Acryloylmorpholine 145℃

[0078] 2. Storage Modulus Mapping Measurement The adhesive tape substrate was exposed to an active energy ray irradiation device (manufactured by Nitto Seiki Co., Ltd., product name "UM-810") with an integrated light dose of 460 mJ / cm 2 The active energy rays were irradiated so that the cantilever's warpage sensitivity and spring constant were calibrated using an atomic force microscope (AFM) in Peak Force QNM mode. The release liner was peeled off from the pressure-sensitive adhesive tape irradiated with the active energy rays, and elastic modulus mapping was performed under the following conditions to obtain a storage elastic modulus mapping image. Mapping images of the pressure-sensitive adhesive tapes of the examples and comparative examples are shown in Figures 3 to 8. Measurement mode Device name: Bruker Atomic Force Microscope, Model MultiMode 8 Mode: Peak Force QNM Tapping Mode Scan size: 2 μm x 2 μm Scan speed: 1.0Hz Maximum number of samples: 256 x 256 samples / line Peak Force Setpoint: 20nN Peak Force Frequency: 2kHz Modulus Fit Model: JKR (Johnson-Kendall-Roberts) Frequency (Frequency (F)): 70Hz Cantilever Model: 240AC-NA (MikroMasch) Spring Constant: 2N / m

[0079] 3. Adhesive strength The obtained adhesive tape was cut into a width of 20 mm and a length of 80 mm, and pressed against the mirror surface of a silicon mirror wafer (manufactured by Shin-Etsu Hando Co., Ltd.) by rolling a hand roller back and forth once in an atmosphere of 23° C., and left for 30 minutes at 23° C. Thereafter, the force required to peel the adhesive tape was measured under conditions of 23° C., 50% RH atmosphere, 90° peeling, and a pulling speed of 300 mm / min, and this was taken as the pre-UV adhesive strength. In addition, adhesive tape was pressed onto a silicon mirror wafer in the same manner and left at 23°C for 30 minutes. Then, ultraviolet (UV) light (integrated light intensity: 460 mJ / cm 2 The adhesive tape was irradiated with UV light (equivalent to 365 nm). The force required to peel the adhesive tape was then measured under conditions of 23°C, 50% RH, 90° peeling, and a pulling speed of 300 mm / min, and this was taken as the post-UV adhesive strength.

[0080] 4. Size and proportion of islands The obtained storage modulus mapping image was binarized using free software (ImageJ). Ten randomly selected islands were measured from the storage modulus mapping image, and the size was calculated as the average island size. The island size was defined as the maximum length of each island. The proportion of the island in the mapping image was calculated from the binarized image.

[0081] [Table 2]

[0082] The pressure-sensitive adhesive tapes of the Examples of the present invention had a microphase-separated structure, which was a sea-island structure, on the surface of the pressure-sensitive adhesive layer after irradiation with active energy rays. The pressure-sensitive adhesive tapes of the Examples of the present invention had high adhesive strength before irradiation with active energy rays, and the adhesive strength was sufficiently reduced after irradiation with ultraviolet rays, and were able to achieve both adhesion to an adherend and easy releasability. [Industrial Applicability]

[0083] The pressure-sensitive adhesive tape according to the embodiment of the present invention can be suitably used for processing semiconductor wafers. [Explanation of symbols]

[0084] 10 adhesive layer 20 Base material 100 adhesive tape

Claims

1. The adhesive sheet has a substrate and a pressure-sensitive adhesive layer made of an active energy ray-curable pressure-sensitive adhesive, A pressure-sensitive adhesive tape, wherein the surface of the pressure-sensitive adhesive layer after irradiation with active energy rays has a microphase-separated structure consisting of island portions and sea portions having a storage elastic modulus higher than that of the island portions, in a storage elastic modulus mapping image obtained using an atomic force microscope.

2. The pressure-sensitive adhesive tape according to claim 1 , wherein the island portions have a size of 300 nm or less.

3. The pressure-sensitive adhesive tape according to claim 1 , wherein the active energy ray-curable pressure-sensitive adhesive is a water-dispersible pressure-sensitive adhesive.

4. The pressure-sensitive adhesive tape according to claim 3 , wherein the active energy ray-curable pressure-sensitive adhesive comprises a water-dispersible acrylic polymer and an active energy ray-curable resin.

5. The pressure-sensitive adhesive tape according to claim 4 , wherein the water-dispersible acrylic polymer is a polymer having a core-shell structure.

6. The pressure-sensitive adhesive tape according to claim 5, wherein the water-dispersible acrylic polymer comprises a shell portion having a glass transition temperature Tg of -10°C or higher and a core portion having a glass transition temperature Tg of less than -10°C.

7. The adhesive tape according to claim 1 , which is used in semiconductor wafer processing.

Images