Adhesive tape

Abstract

To provide a pressure-sensitive adhesive tape which suppresses the surface contamination of an adherend with foreign matter and is excellent in antistatic performance.SOLUTION: An adhesive tape according to an embodiment of the present invention includes a base material; and an adhesive layer formed of an active energy ray-curable adhesive containing a (meth) acrylic polymer having a radiation-polymerizable carbon-carbon double bond, an ionic liquid, and a photopolymerization initiator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, the circuit width of semiconductor circuits has become narrower and more three-dimensional, resulting in the formation of more complex and delicate circuits. Direct bonding (hybrid bonding), which directly bonds wafers together, is being considered as a method for achieving three-dimensional semiconductors (Patent Document 1). Furthermore, optical components that form camera lenses, such as CMOS (Complementary Metal Oxide Semiconductor) image sensors and infrared cut filters, are becoming increasingly sophisticated, and minute particles such as dust can cause a decrease in functionality. Therefore, optical components that form camera lenses are often stored with protective adhesive tape attached to their surfaces until use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-180273 [Patent Document 2] Patent No. 5773379 Summary of the Invention [Problem to be solved by the invention]

[0004] When performing direct bonding, the surface of the wafer to be bonded must be less contaminated to prevent defects. Adhesive tape is usually applied to the wafer surface to protect the circuit surface until bonding. However, even when adhesive tape is applied, foreign matter may adhere to the circuit surface after the adhesive tape is removed, requiring an additional cleaning process. Depending on the type and size of the foreign matter, it may not be sufficiently removed even after a cleaning process. Furthermore, delicate and complex circuit surfaces may be damaged by electrostatic discharge when the adhesive tape is removed. Therefore, adhesive tapes with excellent antistatic properties are required. However, when antistatic agents are used, the antistatic agent may contaminate the adherend. Therefore, adhesive tapes that suppress surface contamination of the adherend by foreign matter and have excellent antistatic properties are required.

[0005] Even in stacked CMOS image sensors (e.g., Patent Document 2), when the adhesive tape for surface protection is peeled off, foreign matter may adhere to the surface to which the adhesive tape was attached, requiring a subsequent cleaning process. Infrared cut filters may also be shipped in a state where they are placed on the adhesive tape. Once shipped, the product remains in the buyer's possession, making it difficult to clean the product after the adhesive tape is peeled off. Therefore, the size of foreign matter that can be allowed to adhere after the adhesive tape is peeled off is becoming smaller every year, and there is a demand for adhesive tapes that further suppress surface contamination of adherends by foreign matter. Furthermore, depending on the components used in optical elements, adhesive tapes may be required to have excellent antistatic properties. [Means for solving the problem]

[0006] 1. An adhesive tape according to an embodiment of the present invention comprises a substrate; and an adhesive layer formed from an active energy ray-curable adhesive containing a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond, an ionic liquid, and a photopolymerization initiator. 2. In the pressure-sensitive adhesive tape described in 1 above, the active energy ray-curable pressure-sensitive adhesive may have a gel fraction of 97.5% or more after irradiation with active energy rays. 3. In the pressure-sensitive adhesive tape according to 1 or 2 above, the cation of the ionic liquid may have an amino group. 4. In the pressure-sensitive adhesive tape according to any one of the above 1 to 3, the anion of the ionic liquid may have a sulfonic acid group. 5. In the pressure-sensitive adhesive tape according to any one of 1 to 4 above, the surface resistivity of the pressure-sensitive adhesive layer before irradiation with active energy rays is 5×10 11 It may be □ / Ω or less. 6. In the pressure-sensitive adhesive tape according to any one of the above items 1 to 5, the active energy ray-curable pressure-sensitive adhesive may further contain polyalkylene glycol. 7. In the pressure-sensitive adhesive tape according to 6 above, the polyalkylene glycol may be at least one selected from the group consisting of polyethylene glycol and polypropylene glycol. 8. In the pressure-sensitive adhesive tape according to any one of the above items 1 to 7, the substrate may have a light transmittance of 60% or more at a wavelength of 365 nm. 9. In the pressure-sensitive adhesive tape according to any one of the above items 1 to 8, the photopolymerization initiator may have an absorption coefficient in methanol at a wavelength of 365 nm of 80 ml / g·cm or more. 10. In the pressure-sensitive adhesive tape according to any one of 1 to 9 above, the content of the photopolymerization initiator may be 0.5 parts by weight or less based on 100 parts by weight of the (meth)acrylic polymer. 11. In the pressure-sensitive adhesive tape according to any one of the above items 1 to 10, the substrate may be a polyethylene terephthalate film. 12. In the pressure-sensitive adhesive tape according to any one of 1 to 11 above, a release liner having a light release layer may be further laminated to the pressure-sensitive adhesive layer, and the thickness of the light release layer may be 0.06 μm or less. 13. In the pressure-sensitive adhesive tape according to the above item 12, the amount of Si on the surface of the pressure-sensitive adhesive layer after the release liner has been peeled off, as determined by X-ray photoelectron spectroscopy, may be 1.0 atm % or less. 14. The pressure-sensitive adhesive tape according to any one of 1 to 13 above may have a tape peeling test in which the number of particles of 0.30 μm or larger is 50 or less. 15. The pressure-sensitive adhesive tape according to any one of 1 to 14 above may have a particle count of 1,500 or less that is 0.15 μm or more and less than 0.30 μm in size in a tape peeling test. 16. The adhesive tape according to any one of 1 to 15 above may be used to protect the circuit surface of a semiconductor wafer. 17. The pressure-sensitive adhesive tape according to any one of 1 to 15 above may be used for protecting the surfaces of optical products and optical glass products. [Effects of the Invention]

[0007] According to an embodiment of the present invention, a pressure-sensitive adhesive tape can be provided which is capable of suppressing surface contamination of an adherend by foreign matter and also has excellent antistatic properties. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive tape according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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 formed from an active energy ray-curable pressure-sensitive adhesive containing a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond (hereinafter also referred to as an acrylic polymer having a radiation-polymerizable carbon-carbon double bond), an ionic liquid, and a photopolymerization initiator. FIG. 1 is a schematic cross-sectional view of an adhesive tape according to an embodiment of the present invention. An adhesive tape 100 according to an embodiment of the present invention comprises a substrate 10 and a pressure-sensitive adhesive layer 20. In practical use, a release liner can be temporarily attached to the pressure-sensitive adhesive layer 20 in a releasable manner until use. The pressure-sensitive adhesive layer 20 is formed from an active energy ray-curable pressure-sensitive adhesive containing a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond, an ionic liquid, and a photopolymerization initiator. A pressure-sensitive adhesive layer formed from such an active energy ray-curable pressure-sensitive adhesive can suppress surface contamination caused by foreign matter adhering to the surface of an adherend. Such foreign matter may include not only external dust and the like, but also components derived from the adhesive constituting the pressure-sensitive adhesive layer. Representative examples of active energy ray-curable adhesives include adhesives using a polymer having a radiation-polymerizable carbon-carbon double bond, whose base polymer can be cured by irradiation with active energy rays, and adhesives using an active energy ray-curable oligomer, etc. When a polymer having a radiation-polymerizable carbon-carbon double bond is used, the molecular weight of the polymer increases, which is thought to reduce adhesion of foreign matter to the adherend. However, even when an adhesive containing a polymer having a radiation-polymerizable carbon-carbon double bond is used, contamination of the adherend due to the adhesive layer may occur. In the pressure-sensitive adhesive tape according to an embodiment of the present invention, the active energy ray-curable adhesive constituting the adhesive layer contains an ionic liquid. The inclusion of an ionic liquid can further prevent adhesion of foreign matter originating from the adhesive constituting the adhesive layer to the adherend surface. Furthermore, the ionic liquid also functions as an antistatic component, thereby improving the antistatic properties of the adhesive tape. Note that "(meth)acrylic" refers to acrylic and / or methacrylic.

[0010] In the pressure-sensitive adhesive tape according to an embodiment of the present invention, the number of particles of 0.30 μm or larger in tape peeling evaluation is preferably 50 or less, more preferably 45 or less, and even more preferably 35 or less. The fewer the number of particles of 0.30 μm or larger, the better, and it may even be 0. Particles of 0.30 μm or larger can cause problems in optical applications. Examples of particles of 0.30 μm or larger include clumps derived from the pressure-sensitive adhesive. Furthermore, the number of particles of 0.15 μm or larger but less than 0.30 μm in tape peeling evaluation is preferably 1,500 or less, more preferably 1,400 or less, and even more preferably 1,000 or less. The fewer the number of particles of 0.15 μm or larger but less than 0.30 μm, the better, and it may even be 0. 0.15 μm may be the minimum size measurable with a general particle measuring device. When the number of particles of 0.30 μm or more and / or the number of particles of 0.15 μm or more are within the above ranges, adhesion of foreign matter to the adherend is suppressed, and a pressure-sensitive adhesive tape in which surface contamination of the adherend by foreign matter is suppressed can be obtained. In this specification, tape peel evaluation refers to the number of particles on the wafer surface measured by the following evaluation method. <Tape peeling evaluation> The adhesive tape is cut into a 25cm x 25cm piece to be used as a sample. The sample is then attached to a 6-inch mirror wafer. It is then left to stand at 23°C for 2 hours. Next, it is irradiated with active energy rays (ultraviolet rays) using a UV irradiation device for the dicing process (for example, Nitto Seiki Co., Ltd., product name UM-810). When the absorption coefficient of the photopolymerization initiator contained in the adhesive layer at a wavelength of 365 nm in methanol is 80 ml / g cm or more, the cumulative light intensity of the active energy rays is 460 mJ / cm. 2 If the absorption coefficient of the photopolymerization initiator in methanol at a wavelength of 365 nm is less than 80 ml / g cm, the cumulative light dose is 700 mJ / cm. 2 The adhesive tape is then peeled off from the wafer surface, and particle count on the wafer surface is measured using a wafer surface inspection device (e.g., Takano Corporation, product name "WM-7S"). The absorption coefficient of the photopolymerization initiator in methanol at a wavelength of 365 nm will be described later.

[0011] The pressure-sensitive adhesive tape may further include any appropriate layer other than the substrate and the pressure-sensitive adhesive layer. For example, it may further include an intermediate layer and an antistatic layer. The provision of an intermediate layer can improve adhesion to an adherend with a highly uneven surface. The intermediate layer can be formed of any appropriate material. It may be molded from a resin such as an ethylene-vinyl acetate resin, or may be formed by curing an ultraviolet-curable acrylic resin by irradiating it with ultraviolet light, or may be formed using a composition containing an acrylic resin and an ultraviolet-curable oligomer. Using a composition containing an acrylic resin and an ultraviolet-curable oligomer can better absorb unevenness on the adherend surface during lamination. The intermediate layer may also be formed using any appropriate adhesive (an adhesive that is not ultraviolet-curable). The provision of an antistatic layer can further prevent electrostatic damage to semiconductor elements due to static electricity when the pressure-sensitive adhesive tape is peeled off.

[0012] The thickness of the pressure-sensitive adhesive tape can be set in any appropriate range, preferably 10 μm to 500 μm, more preferably 50 μm to 400 μm, and even more preferably 60 μm to 300 μm.

[0013] B. Base material The substrate can be made of any suitable resin. Specific examples of resins constituting the substrate include polyester-based resins such as polyethylene terephthalate (PET), 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; and polyethersulfone. Polyethylene terephthalate, ethylene-vinyl acetate copolymer, polyolefin-based resins, and laminated films thereof are preferably used. When a laminated film is used, films formed from these resins can be laminated in any suitable order and number. Using these resins makes it possible to obtain a tape suitable for processes such as backgrinding and dicing. Furthermore, if there is no problem in terms of application, using a soft substrate such as an ethylene-vinyl acetate copolymer or a polyolefin resin can disperse stress during peeling, thereby suppressing the occurrence of cohesive failure in the pressure-sensitive adhesive layer and reducing the number of foreign matter particles generated.

[0014] 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, and heat stabilizers. The types and amounts of other components can be any appropriate amount depending on the purpose.

[0015] The substrate preferably has a light transmittance of 60% or more, more preferably 70% or more, at a wavelength of 365 nm. When the light transmittance at 365 nm is within the above range, both the visibility of the pressure-sensitive adhesive tape when attached to an adherend and easy peeling of the pressure-sensitive adhesive layer by irradiation with active energy rays can be achieved. When the light transmittance at a wavelength of 365 nm is less than 60%, the visibility is improved, but the pressure-sensitive adhesive layer may not be sufficiently cured.

[0016] The light transmittance of the substrate at a wavelength of 365 nm can be adjusted by any appropriate method. For example, the light transmittance can be adjusted by adding any appropriate material, such as a colorant, to the material constituting the substrate, or by providing a colored layer on any appropriate surface of the substrate. Any appropriate colorant can be used. For example, phthalocyanine pigments can be used. Only one colorant can be used, or two or more colorants can be used in combination. In addition, one surface of the substrate (the surface on which the adhesive layer of the resulting adhesive tape is not laminated) can be provided with an uneven surface, such as a matte finish, to reduce transparency and thereby improve visibility.

[0017] The substrate may further include any appropriate other layer. Specific examples include an easy-adhesion layer, an antistatic layer, and the like. The easy-adhesion layer and the antistatic layer may contain any appropriate antiblocking agent. When the substrate has a light transmittance of 60% or more at a wavelength of 365 nm, the light transmittance may be adjusted by adding a colorant or the like to the other layer. Examples of colorants or the like to be added to the other layer include those that can be added to the material forming the substrate.

[0018] The thickness of the substrate can be set to any appropriate value, and is preferably 10 μm to 200 μm, and more preferably 20 μm to 150 μm.

[0019] C.Adhesive layer The pressure-sensitive adhesive layer is formed from an active energy ray-curable pressure-sensitive adhesive containing a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond, an ionic liquid, and a photopolymerization initiator. Forming a pressure-sensitive adhesive layer using such a pressure-sensitive adhesive can provide a pressure-sensitive adhesive tape that has excellent antistatic properties and can suppress surface contamination of the adherend by foreign matter. Using a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond as the base polymer can suppress low-molecular-weight components derived from the pressure-sensitive adhesive. However, even with the use of such a base polymer, there is still room for improvement in the contamination of the adherend surface by foreign matter. The pressure-sensitive adhesive of an embodiment of the present invention uses an ionic liquid in combination with a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond. The ionic liquid contained in the pressure-sensitive adhesive tends to precipitate on the surface of the pressure-sensitive adhesive layer that is formed. Using a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond in combination with an ionic liquid can cause the ionic liquid to be unevenly distributed at the interface with the adherend, making it easier to peel the pressure-sensitive adhesive tape from the adherend. Furthermore, if the ionic liquid is unevenly distributed on the surface of the pressure-sensitive adhesive, adhesion of foreign matter originating from the pressure-sensitive adhesive layer can also be suppressed.

[0020] C-1. (Meth)acrylic polymers having radiation-polymerizable carbon-carbon double bonds As described above, a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond is used as the base polymer. Specifically, a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond introduced into a side chain and / or terminal is used. More specifically, an acrylic polymer having a polymerizable carbon-carbon double bond introduced into a (meth)acrylic polymer is used. The use of an acrylic polymer makes it easy to adjust the storage modulus and tensile modulus of the pressure-sensitive adhesive layer, and also makes it possible to obtain a pressure-sensitive adhesive tape having an excellent balance between adhesive strength and releasability. Furthermore, contamination of the adherend surface due to components derived from the pressure-sensitive adhesive can be reduced. One type of (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond may be used alone, or two or more types may be used in combination.

[0021] Any suitable acrylic polymer can be used as the acrylic polymer. Examples of the acrylic polymer include a polymer obtained by polymerizing a monomer composition containing one or more esters of acrylic acid or methacrylic acid having a linear or branched alkyl group with a functional group-containing monomer. Use of a functional group-containing monomer can produce a polymer into which a radiation-polymerizable carbon-carbon double bond can be easily introduced.

[0022] The linear or branched alkyl group is preferably an alkyl group having 30 or less carbon atoms, more preferably an alkyl group having 1 to 20 carbon atoms, and even more preferably an alkyl group having 4 to 18 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a heptyl group, a cyclohexyl group, a 2-ethylhexyl group, an octyl group, an isooctyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, an undecyl group, a lauryl group, a tridecyl group, a tetradecyl group, a stearyl group, an octadecyl group, and a dodecyl group.

[0023] The monomer composition may contain any other suitable monomer. Examples of the other monomer include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth)acrylate, 2-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-hydroxypropyl (meth)acrylate. Examples of functional group-containing monomers include hydroxyl group-containing monomers such as (hydroxymethylcyclohexyl)-methyl acrylate, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphate group-containing monomers such as 2-hydroxyethylacryloylphosphate. As described above, the inclusion of a functional group-containing monomer allows for the production of an acrylic polymer in which polymerizable carbon-carbon double bonds are easily introduced. The content of the functional group-containing monomer is preferably 4 to 30 parts by weight, and more preferably 6 to 20 parts by weight, per 100 parts by weight of the total of all monomer components.

[0024] The weight-average molecular weight of the acrylic polymer is preferably 100,000 or more, more preferably 300,000 or more, even more preferably 500,000 or more, and particularly preferably 600,000 to 3,000,000. Within these ranges, bleeding of low molecular weight components is suppressed, and a pressure-sensitive adhesive tape that is inhibited from contaminating the adherend due to foreign matter can be obtained. The molecular weight distribution (weight-average molecular weight / number-average molecular weight) of the acrylic polymer is preferably 1 to 20, more preferably 3 to 10. Use of an acrylic polymer with a narrow molecular weight distribution can prevent bleeding of low molecular weight components, and a pressure-sensitive adhesive tape with low contamination can be obtained. The weight-average molecular weight and number-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene equivalent).

[0025] Acrylic polymers having polymerizable carbon-carbon double bonds can be obtained by any suitable method. For example, they can be obtained by reacting (e.g., condensation reaction, addition reaction) a polymer obtained by any suitable polymerization method with a compound having a polymerizable carbon-carbon double bond. Specifically, when using an acrylic polymer, an acrylic polymer (copolymer) having structural units derived from a monomer having any suitable functional group is polymerized in any suitable solvent, and then the functional group of the acrylic polymer is reacted with a compound having a polymerizable carbon-carbon double bond that can react with the functional group to obtain an acrylic polymer having a polymerizable carbon-carbon double bond. The amount of the compound having a polymerizable carbon-carbon double bond to be reacted is preferably 4 to 30 parts by weight, more preferably 4 to 20 parts by weight, per 100 parts by weight of the acrylic polymer. Any suitable solvent can be used, including, for example, various organic solvents such as ethyl acetate, methyl methyl ketone, and toluene.

[0026] When reacting a resin with a compound having a polymerizable carbon-carbon double bond as described above, it is preferable that the resin and the compound having a polymerizable carbon-carbon double bond each have a functional group capable of reacting with each other. Examples of functional group combinations include a carboxyl group / epoxy group, a carboxyl group / aziridine group, and a hydroxyl group / isocyanate group. Among these functional group combinations, a combination of a hydroxyl group and an isocyanate group is preferred because it is easy to track the reaction.

[0027] Examples of compounds having a polymerizable carbon-carbon double bond include 2-isocyanatoethyl methacrylate, methacryloisocyanate, 2-methacryloyloxyethyl isocyanate (2-isocyanatoethyl methacrylate), and m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0028] C-2. Photopolymerization initiator Any suitable initiator can be used as the photopolymerization initiator. Examples of the photopolymerization initiator include acylphosphine oxide photoinitiators 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-hydroxycyclohexylphenyl ketone; methoxyacetophenone, Acetophenone compounds such as 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; ketal compounds such as benzil dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; 1-phenone-1,1-propanedione-2-( Photoactive oxime compounds such as 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 acylphosphonate, and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropane-1. Preferably, 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropane-1 can be used. One type of photopolymerization initiator may be used alone, or two or more types may be used in combination.

[0029] In one embodiment, the photopolymerization initiator preferably has an absorption coefficient at a wavelength of 365 nm in methanol of 80 ml / g cm or more, more preferably 90 ml / g cm or more, and even more preferably 100 ml / g cm or more. The absorption coefficient at a wavelength of 365 nm is 800 ml / g cm or less. When the absorption coefficient of the photopolymerization initiator is within the above range, the pressure-sensitive adhesive layer can be efficiently cured and easily peeled upon irradiation with active energy rays, and cohesive failure can be suppressed. Furthermore, even when a substrate with excellent visibility (e.g., a substrate with a light transmittance at a wavelength of 365 nm of 60% or more) is used, the pressure-sensitive adhesive layer can be efficiently cured and cohesive failure can be suppressed. Herein, the absorption coefficient at a wavelength of 365 nm in methanol can be measured by any appropriate method.

[0030] Commercially available photoinitiators with an absorption coefficient of 80 ml / g cm or greater at 365 nm in methanol may be used, such as Omnirad 184 (88.6 ml / g cm), Omnirad 127D (107 ml / g cm), and Omnirad 651 (361 ml / g cm).

[0031] The photopolymerization initiator is used in any appropriate amount. The content of the photopolymerization initiator is preferably 0.50 parts by weight or less, more preferably 0.45 parts by weight or less, and even more preferably 0.40 parts by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond. The content of the photopolymerization initiator is preferably 0.20 parts by weight or more. When the content of the photopolymerization initiator is within the above range, the content of decomposition products that may be formed in the pressure-sensitive adhesive layer after irradiation with active energy rays can be reduced. As a result, contamination of the adherend surface by foreign matter can be suppressed.

[0032] C-3. Ionic Liquids Any appropriate ionic liquid can be used as the ionic liquid. Specifically, a molten salt (room-temperature molten salt) composed of a pair of anion and cation and liquid at 25°C can be used. If the active energy ray-curable pressure-sensitive adhesive contains an ionic liquid, the ionic liquid can be unevenly distributed on the surface of the pressure-sensitive adhesive layer facing the adherend in the pressure-sensitive adhesive layer formed. As a result, contamination of the adherend surface by foreign matter originating from the pressure-sensitive adhesive tape can be suppressed. The ionic liquid can also function as an antistatic agent. Therefore, it can impart antistatic properties to the pressure-sensitive adhesive tape. Only one type of ionic liquid can be used, or two or more types can be used in combination.

[0033] The anion of the ionic liquid is, for example, polyoxyethylene(2)-ethylhexyl sulfate, (FSO2)2N - , (CF3SO2)2N - , (CF3CF2SO2)2N - , (CF3SO2)3C - , Br - , AlCl4 - , Al2Cl7 - , NO3 - , BF4 - , PF6 - , CH3COO - , CF3COO - , CF3CF2CF2COO - , CF3SO3 - , CF3(CF2)3SO3 - , AsF6 - , SbF6 - , and F(HF) n - Among these, examples of anions include anions having a sulfonic acid group with 10 or more carbon atoms, such as polyoxyethylene (2)-ethylhexyl sulfate, and PF6 - and (CF3SO2)2N - Preferred are fluorine-containing anions such as: When these anions are used, the ionic liquid tends to precipitate more easily on the surface of the pressure-sensitive adhesive layer, and the number of particles can be reduced.

[0034] Any appropriate cation can be used as the cation of the ionic liquid. Specific examples include imidazolium-based cations, ammonium-based cations, pyrrolidinium-based cations, and pyridinium-based cations. Cations having an amino group, such as ethylaminoethyl cation, are preferred. The use of these cations allows for easy mobility within the pressure-sensitive adhesive layer due to the small molecular weight of the cation, and can also improve antistatic properties.

[0035] Examples of imidazolium cations include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-nonyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, and 1-dodecyl-3-methylimidazolium cation. imidazolium cation, 1-tridecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1-pentadecyl-3-methylimidazolium cation, 1-hexadecyl-3-methylimidazolium cation, 1-heptadecyl-3-methylimidazolium cation, 1-octadecyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, 1-benzyl-3-methylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, and 1,3-bis(dodecyl)imidazolium cation.

[0036] Examples of pyridinium cations include 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, and 1-octyl-4-methylpyridinium cation.

[0037] Examples of pyrrolidinium cations include 1-ethyl-1-methylpyrrolidinium cation and 1-butyl-1-methylpyrrolidinium cation.

[0038] Examples of ammonium-based cations include tetraethylammonium cation, tetrabutylammonium cation, methyltrioctylammonium cation, tetradecitrihexylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethylacrylate cation.

[0039] The ionic liquid is preferably a cation having an amino group and an anion having a sulfonic acid group with 10 or more carbon atoms, or PF6 - and (CF3SO2)2N - Specifically, a compound containing a 1-butyl-3-methylpyridinium cation and (CF3SO2)2N - Ionic liquid containing 1-butyl-3-methylimidazolium cation and PF6 - and an ionic liquid containing an ethylethanolammonium cation and polyoxyethylene (2)-2-ethylhexyl ether sulfate. Use of these ionic liquids can provide a pressure-sensitive adhesive tape that can further inhibit contamination of the adherend surface due to adhesion of foreign matter and can exhibit better antistatic properties.

[0040] Commercially available ionic liquids may be used, including, for example, those manufactured by Nippon Carlit Co., Ltd. under the trade names CIL-312, CIL-625, CIL-635, and CIL-R50, and those manufactured by Nippon Nyukazai Co., Ltd. under the trade name AS-100.

[0041] The content of the ionic liquid is preferably 1.0 to 3.0 parts by weight, more preferably 1.3 to 2.6 parts by weight, and even more preferably 1.6 to 2.2 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond. When the content of the ionic liquid is within the above range, it is possible to provide a pressure-sensitive adhesive tape that can further suppress contamination of the adherend surface due to adhesion of foreign matter and can exhibit better antistatic performance.

[0042] C-4. Polyalkylene glycol The active energy ray-curable adhesive preferably further contains polyalkylene glycol. If the active energy ray-curable adhesive further contains polyalkylene glycol, components contained in the adhesive layer, such as ionic liquid, can move within the adhesive layer even after irradiation with active energy rays. As a result, the deterioration of the antistatic performance of the adhesive layer after irradiation with active energy rays can be suppressed. Only one type of polyalkylene glycol may be used, or two or more types may be used in combination.

[0043] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene glycol-propylene glycol copolymers. Polyethylene glycol and polypropylene glycol are preferred. The use of these polyalkylene glycols can result in uneven distribution on the surface of the adhesive layer facing the adherend, similar to ionic liquids. As a result, contamination of the adherend surface by foreign matter originating from the adhesive tape can be suppressed. Even the addition of a small amount can improve the mobility of the ionic liquid, which can be effective in preventing static electricity on the adhesive surface, particularly after UV curing. Alternatively, a polyalkylene glycol derivative may be used instead of polyalkylene glycol. When using a polyalkylene glycol derivative, one that is liquid at 0°C can be used.

[0044] The number average molecular weight of the polyalkylene glycol can be set to any appropriate value. For polyethylene glycol, the number average molecular weight of the polyalkylene glycol is preferably 200 to 600. For polypropylene glycol, the number average molecular weight is preferably 200 to 4200, more preferably 400 to 000, and even more preferably 600 to 2000. When the number average molecular weight of the polyalkylene glycol is within the above range, the polyalkylene glycol can be unevenly distributed on the surface of the pressure-sensitive adhesive layer facing the adherend. As a result, contamination of the adherend surface by foreign matter originating from the pressure-sensitive adhesive tape can be suppressed.

[0045] The content of the polyalkylene glycol is preferably 0.05 to 0.35 parts by weight, more preferably 0.15 to 0.25 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond. When the content of the polyalkylene glycol is within the above range, it is possible to obtain a pressure-sensitive adhesive tape that can suppress the generation of foreign matter and exhibit excellent antistatic properties even after irradiation with active energy rays.

[0046] C-5. Additives The PSA may contain any suitable additives as needed, such as crosslinkers, catalysts (e.g., platinum catalysts), tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, UV absorbers, light stabilizers, release modifiers, softeners, surfactants, flame retardants, and solvents.

[0047] In one embodiment, the PSA further comprises a crosslinking agent. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and chelate-based crosslinking agents. The content of the crosslinking agent is preferably 0.2 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, and even more preferably 0.5 to 4 parts by weight, relative to 100 parts by weight of the base polymer contained in the PSA. When the content of the crosslinking agent is within the above range, adhesion of foreign matter originating from the PSA to the surface of the adherend can be suppressed.

[0048] In one embodiment, an isocyanate-based crosslinking agent is preferably used. Isocyanate-based crosslinking agents are preferred because they can react with a variety of functional groups. When an isocyanate-based crosslinking agent is used as the crosslinking agent and the content of the crosslinking agent is within the above range, contamination of the adherend surface by foreign matter originating from the pressure-sensitive adhesive layer can be further suppressed.

[0049] 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 3 μm to 500 μm, more preferably 4 μm to 400 μm, and even more preferably 5 μm to 350 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, it can exert sufficient adhesive strength to the adherend. When the pressure-sensitive adhesive tape includes an intermediate layer as another layer, the thickness of the pressure-sensitive adhesive layer refers to the total thickness of the pressure-sensitive adhesive layer and the intermediate layer.

[0050] The surface resistivity of the pressure-sensitive adhesive layer before irradiation with active energy rays is preferably 5×10 11 The surface resistivity before irradiation with active energy rays is, for example, 1×10 10 When the surface resistivity of the pressure-sensitive adhesive layer before irradiation with active energy rays is within the above range, a pressure-sensitive adhesive tape with excellent antistatic properties can be obtained.

[0051] The surface resistivity of the pressure-sensitive adhesive layer after irradiation with active energy rays is preferably 1×10 12 If the surface resistivity of the pressure-sensitive adhesive layer before irradiation with active energy rays is within the above range, peel electrification when the pressure-sensitive adhesive tape is peeled off from the adherend can be suppressed, and when the adherend is a wafer, for example, electrostatic breakdown of the circuit can be suppressed.

[0052] The gel fraction of the pressure-sensitive adhesive layer after irradiation with active energy rays is preferably 97.5% or more, more preferably 98% or more. If the gel fraction of the pressure-sensitive adhesive layer after irradiation with active energy rays is within the above range, adhesion of foreign matter originating from the pressure-sensitive adhesive layer to the surface of the adherend can be suppressed. The gel fraction of the pressure-sensitive adhesive layer after irradiation with active energy rays may vary depending on the components contained in the pressure-sensitive adhesive, and is, for example, 99.0% or less. In this specification, the gel fraction of the pressure-sensitive adhesive layer after irradiation with active energy rays refers to a value measured by the following method. <Gel fraction after irradiation with active energy rays> Using a UV irradiation device (for example, Nitto Seiki Co., Ltd., product name "UM-810"), the adhesive tape with a release liner laminated was irradiated with a cumulative light intensity of 460 mJ / cm from the adhesive layer side of the adhesive tape, while the adhesive tape without a release liner was purged with nitrogen. 2 The active energy rays are irradiated so that the gel fraction is 0.1 g. Next, a sample of approximately 0.1 g is collected from the adhesive layer of the irradiated adhesive tape and its weight is measured. The collected sample is wrapped in a Teflon (registered trademark) porous film and left in toluene at room temperature (e.g., 23°C) for one week. The sample is then removed from the Teflon (registered trademark) porous film, heated in an oven at 120°C for one hour to dry the toluene, and its weight is measured. The gel fraction is calculated from the measured weight using the following formula. Gel fraction (%) = weight of sample after immersion in toluene (g) / weight of sample before immersion in toluene (g)

[0053] The Si content of the surface of the pressure-sensitive adhesive layer after the release liner has been peeled off, as determined by X-ray photoelectron spectroscopy, is preferably 3.5 atm% or less, more preferably 1.0 atm% or less, and even more preferably 0.5 atm% or less. As described above, in practice, pressure-sensitive adhesive tapes are stored with a release liner laminated on the surface of the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer until use. During storage, components such as the release agent may migrate from the surface of the release liner to the surface of the pressure-sensitive adhesive layer. Such migration of additives from the surface of the release liner to the surface of the pressure-sensitive adhesive layer can also contribute to contamination of the surface of the adherend. If the Si content of the surface of the pressure-sensitive adhesive layer after the release liner has been peeled off is within the above range, contamination due to adhesion of foreign matter to the surface of the adherend can be reduced.

[0054] The pressure-sensitive adhesive layer may have any appropriate adhesive strength. The adhesive strength of the pressure-sensitive adhesive layer to a silicon wafer before UV irradiation is preferably 0.50 N / 20 mm to 40 N / 20 mm, more preferably 1.00 N / 20 mm to 35 N / 20 mm, and even more preferably 1.5 N / 20 mm to 30 N / 20 mm. In this specification, the adhesive strength of the pressure-sensitive adhesive layer refers to a value measured by cutting a pressure-sensitive adhesive tape to a width of 20 mm and a length of 80 mm, pressing the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape against the mirror surface of a silicon mirror wafer by moving a 2 kg roller back and forth once in an atmosphere at 23°C, leaving it at 23°C for 30 minutes, and then conducting a 180° peel test in an atmosphere at 23°C and 50% RH at a pulling rate of 300 mm / min.

[0055] The adhesive strength of the adhesive layer to a silicon wafer after UV irradiation is preferably 0.001 N / 20 mm to 1.000 N / 20 mm, more preferably 0.005 N / 20 mm to 0.850 N / 20 mm, and even more preferably 0.005 N / 20 mm to 0.800 N / 20 mm. The adhesive strength after UV irradiation is measured by cutting the adhesive tape to a width of 20 mm and a length of 80 mm, pressing the adhesive layer against the mirror surface of a silicon mirror wafer by rolling a 2 kg roller back and forth once in an atmosphere at 23°C, leaving it at 23°C for 30 minutes, and then irradiating the adhesive tape with UV light to a silicon wafer with an integrated light dose of 460 mJ / cm when the absorption coefficient of the photopolymerization initiator at a wavelength of 365 nm in methanol is 80 ml / g cm or more. 2 (wavelength 365 nm) (If the absorption coefficient of the photoinitiator in methanol at a wavelength of 365 nm is less than 80 ml / g cm, the cumulative light dose is 700 mJ / cm 2 ) and then a 180° peel test is carried out under conditions of 23°C, 50% RH atmosphere, and a pulling speed of 300 mm / min.

[0056] D. Release liner As described above, the pressure-sensitive adhesive tape can be stored until practical use in a state where a release liner is attached to the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer. The release liner typically has a substrate film and a light release layer. Any appropriate release agent can be used as the release agent constituting the light release layer. Examples of release agents include silicone-based release agents, fluorine-based release agents, and long-chain alkyl acrylate-based release agents.

[0057] Any suitable substrate can be used as the substrate film, and examples thereof include plastic (eg, polyethylene terephthalate (PET), polyethylene, polypropylene) films, nonwoven fabrics, and paper.

[0058] The light release layer can be formed by applying a composition containing the release agent to the substrate film. The thickness of the light release layer is preferably 0.06 μm or less, more preferably 0.03 μm to 0.06 μm. When the thickness of the light release layer is within the above range, migration of the release agent from the release liner to the surface of the pressure-sensitive adhesive layer is suppressed, and as a result, contamination of the adherend surface by foreign matter originating from the pressure-sensitive adhesive tape can be suppressed.

[0059] E. Adhesive tape manufacturing method The pressure-sensitive adhesive tape can be produced by any appropriate method. In one embodiment, the pressure-sensitive adhesive tape can be produced, for example, by forming a pressure-sensitive adhesive layer on a substrate. The pressure-sensitive adhesive layer may be formed by coating the substrate with the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer, or by forming the layers on any appropriate release liner and then transferring them. Various coating methods can be used, including 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. Alternatively, a method may be used in which a pressure-sensitive adhesive layer is separately formed on a release liner and then bonded to the substrate.

[0060] F. Applications of adhesive tape The pressure-sensitive adhesive tape according to the embodiment of the present invention can be suitably used for protecting the circuit surface of a semiconductor wafer in a semiconductor processing step. As described above, the pressure-sensitive adhesive tape according to the embodiment of the present invention has excellent antistatic properties and can suppress surface contamination of an adherend by foreign matter. Therefore, adhesion of foreign matter to the circuit surface can be suppressed, and electrostatic breakdown of the circuit due to peeling electrification can also be suppressed.

[0061] In one embodiment, the pressure-sensitive adhesive tape of the present invention can be suitably used for surface protection of optical products and optical glass products. In optical products and optical glass products, adhesion of foreign matter to the surface and surface scratches can affect properties such as refractive index, potentially preventing the desired performance from being achieved. Furthermore, cleaning the product after shipping can be difficult. Using the pressure-sensitive adhesive tape of the present invention as a surface protection tape for optical products and optical glass products not only protects the surface of the optical product and optical glass product from scratches and dirt until use, but also prevents surface contamination of the optical product and optical glass product due to foreign matter originating from the surface protection tape after the surface protection tape is peeled off. [Example]

[0062] 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.

[0063] [Production Example 1] Production of base polymer A polymerization experiment was conducted using a 1 L round-bottom separable flask equipped with a separable cover, separatory funnel, thermometer, nitrogen inlet tube, Liebig condenser, vacuum seal, stirring rod, and stirring blade. 100 parts by weight of butyl acrylate (BA), 80 parts by weight of ethyl acrylate (EA), 40 parts by weight of 2-hydroxyethyl acrylate (HEA), 0.2 parts by weight of benzoyl peroxide, and 500 parts by weight of toluene were added to the polymerization apparatus. Polymerization was then carried out for 6 hours at 61 °C in a nitrogen stream. Next, 41 parts by weight of a compound containing a radiation-polymerizable carbon-carbon double bond (manufactured by Showa Denko K.K., product name "Karenzu MOI") was added to the polymerization apparatus and allowed to react for 24 hours at 50 °C to yield Polymer A (base polymer) with a weight-average molecular weight of 700,000 and double bonds introduced into the side chains.

[0064] [Manufacturing Example 2] Preparation of release liner A light release layer-forming composition (a liquid prepared from 100 parts by weight of "KS-776L" (Shin-Etsu Silicones), 2 parts by weight of "CAT-PLR-1" (Shin-Etsu Silicones), 1 part by weight of "CAT-PLR-2" (Shin-Etsu Silicones), 2215 parts by weight of n-hexane, 2215 parts by weight of n-heptane, and 5 parts by weight of "CAT-PL-50T" (Shin-Etsu Silicones)) was applied to a polyethylene terephthalate (PET) substrate film (manufactured by Toray Industries, Inc., trade name "Lumirror S-105", thickness 38 μm) using a bar coater to a dry thickness of 0.05 μm, and then dried at 130°C to obtain a release liner.

[0065] [Manufacturing Example 3] Preparation of substrate A 1.5 μm thick urethane-based adhesion-enhancing treatment layer was formed by gravure printing on a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., product name "Lumirror S-105," thickness 50 μm) to obtain release liner B. The urethane-based adhesion-enhancing treatment layer contained phthalocyanine copper at a concentration that gave a light transmittance of 70% at a wavelength of 365 nm.

[0066] [Example 1] 100 parts by weight of the base polymer obtained in Production Example 1, 3 parts by weight of a crosslinking agent (manufactured by Mitsui Chemical Co., Ltd., trade name "Takenate D-101A"), 0.3 parts by weight of a photopolymerization initiator 1 (manufactured by IGM Resins, trade name "omnirad 127D", extinction coefficient in methanol at 365 nm: 107 ml / g cm), 0.3 parts by weight of an ionic liquid 1 (manufactured by Nippon Carlit Co., Ltd., trade name "CIL312", cation: 1-butyl-3-methylpyridinium cation, anion: (CFSO)N - 2 parts by weight of PEG-1400 PEG-1400 PEG-1400 copolymer, and 0.2 parts by weight of polyalkylene glycol 1 (polypropylene glycol (PPG), manufactured by NOF Corporation, trade name "UNIOL D-1200") were mixed together, and ethyl acetate was appropriately added to obtain a pressure-sensitive adhesive solution. The resulting adhesive solution was applied to the release liner prepared in Production Example 2 and dried for 2 minutes at 120°C to form an adhesive layer with a thickness of 10 µm. Next, the substrate prepared in Production Example 3 was attached to the side of the adhesive layer not covered with the release liner, and aging treatment was performed at 50°C for 48 hours to obtain an adhesive tape.

[0067] [Example 2] An adhesive tape was obtained in the same manner as in Example 1, except that a commercially available release liner (manufactured by Mitsubishi Plastics, Inc., product name "MRF38", thickness 38 μm) was used instead of the release liner produced in Production Example 2.

[0068] [Example 3] An adhesive solution was obtained in the same manner as in Example 1, except for not adding polyalkylene glycol 1. An adhesive tape was obtained in the same manner as in Example 1, except for using the obtained adhesive solution.

[0069] [Example 4] An adhesive tape was obtained in the same manner as in Example 1, except that polyalkylene glycol 1 was replaced with 0.2 parts by weight of polyethylene glycol (PEG) (manufactured by Sanyo Chemical Industries, Ltd., trade name "PEG-200").

[0070] [Example 5] Instead of ionic liquid 1, ionic liquid 2 (manufactured by Nippon Carlit Co., Ltd., trade name "CIL625", cation: 1-butyl-3-methylimidazolium cation, anion: PF6 - An adhesive tape was obtained in the same manner as in Example 1, except that 1.6 parts by weight of the hydroxybenzoate was used.

[0071] [Example 6] An adhesive tape was obtained in the same manner as in Example 1, except that 2.0 parts by weight of ionic liquid 3 (manufactured by Nippon Nyukazai Co., Ltd., trade name "Aminoion AS100", anion: ethylethanolammonium cation, anion: polyoxyethylene (2)-2-ethylhexyl ether sulfate ester) was used instead of ionic liquid 1.

[0072] [Example 7] An adhesive tape was obtained in the same manner as in Example 6, except that polyalkylene glycol 1 was replaced with 0.2 parts by weight of polyethylene glycol (PEG) (manufactured by Sanyo Chemical Industries, Ltd., trade name "PEG-200").

[0073] [Example 8] An adhesive solution was obtained in the same manner as in Example 1, except for not adding polyalkylene glycol 1. An adhesive tape was obtained in the same manner as in Example 6, except for using the obtained adhesive solution.

[0074] [Example 9] An adhesive tape was obtained in the same manner as in Example 1, except that 0.3 parts by weight of photopolymerization initiator 2 (manufactured by IGM Resins, trade name "omnirad2959", extinction coefficient in methanol at 365 nm: 48.9 ml / g cm) was used instead of photopolymerization initiator 1.

[0075] [Example 10] An adhesive tape was obtained in the same manner as in Example 6, except that 0.3 parts by weight of photopolymerization initiator 2 (manufactured by IGM Resins, trade name "omnirad2959", extinction coefficient in methanol at 365 nm: 48.9 ml / g cm) was used instead of photopolymerization initiator 1.

[0076] [Example 11] A substrate having a light transmittance of 60% was produced in the same manner as in Production Example 3, except that phthalocyanine copper was added to the urethane-based easy-adhesion treatment layer at a concentration such that the light transmittance at a wavelength of 365 nm was 60%. A pressure-sensitive adhesive tape was obtained in the same manner as in Example 6, except that the obtained substrate was used.

[0077] [Table 1]

[0078] (Comparative Example 1) 80 parts by weight of butyl acrylate (BA), 15 parts by weight of acrylonitrile, and 5 parts by weight of acrylic acid were copolymerized in ethyl acetate by a conventional method to obtain a solution containing an acrylic copolymer with a number average molecular weight of 800,000. To this solution, 10 parts by weight of diol-type polypropylene glycol with a molecular weight of 3,000 and 3 parts by weight of a polyisocyanate compound (manufactured by Mitsui Chemical Co., Ltd., trade name "Takenate D-101A") were added to obtain an acrylic pressure-sensitive adhesive solution. The obtained acrylic adhesive solution was applied to a corona-treated 50 μm polyethylene terephthalate (PET) substrate (manufactured by Toray Industries, Inc., product name "Lumirror S-105") and heated at 80°C for 3 minutes to obtain an adhesive tape.

[0079] (Comparative Example 2) 75 parts by weight of methyl acrylate, 10 parts by weight of methoxyethyl acrylate, 5 parts by weight of N-vinylpyrrolidone, and 10 parts by weight of 2-hydroxyethyl acrylate were copolymerized in ethyl acetate by a conventional method to obtain a solution containing an acrylic polymer with a weight-average molecular weight of 650,000. Next, 12 parts by weight of a compound having a radiation-polymerizable carbon-carbon double bond (manufactured by Showa Denko K.K., trade name "Karenzu MOI") was added to the solution containing the acrylic polymer, and a double-bond-introduced acrylic polymer solution with a weight-average molecular weight of 650,000 was obtained by a conventional method. Next, 70 parts by weight of an ultraviolet-curable oligomer obtained by reacting pentaerythritol triacrylate and diisocyanate with the double bond-introduced acrylic polymer solution were added, along with 3 parts by weight of a photopolymerization initiator (manufactured by IGM Resins, trade name "Omnirad 651", extinction coefficient in methanol at 365 nm: 361 ml / g cm), 2 parts by weight of a polyisocyanate compound (manufactured by Mitsui Chemical Co., Ltd., trade name "Takenate D-101A"), and 10 parts by weight of polypropylene glycol with a number-average molecular weight of 2000, to obtain an acrylic adhesive solution. The obtained acrylic adhesive solution was applied to a corona-treated 50 μm polyethylene terephthalate (PET) substrate (manufactured by Toray Industries, Inc., product name "Lumirror S-105") and heated at 80°C for 3 minutes to obtain an adhesive tape.

[0080] (Comparative Example 3) 30 parts by weight of 2-ethylhexyl acrylate, 70 parts by weight of methyl acrylate, 10 parts by weight of acrylic acid, and 0.2 parts by weight of benzoyl peroxide were added and polymerized at 60°C for 6 hours under a nitrogen atmosphere, yielding a solution containing an acrylic polymer with a weight-average molecular weight of 1.1 million. A mixture of 100 parts by weight of the obtained acrylic polymer, 50 parts by weight of UV Oligomer 1 (manufactured by Mitsubishi Chemical Corporation, trade name: Shikou UV-1700TL), 45 parts by weight of UV Oligomer 2 (manufactured by Mitsubishi Chemical Corporation, trade name: Shikou UV-3000TL), 15 parts by weight of tackifier (manufactured by Yasuhara Chemical Co., Ltd., trade name: M-G125), 0.2 parts by weight of light release agent (manufactured by Toho Chemical Industry Co., Ltd., trade name: Phosphanol RL-210), 4.5 parts by weight of ionic liquid (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Elexcel AS-110, cation: 1-ethyl-3-methylimidazolium, anion: bis(fluorosulfonyl)imide), and a photopolymerization initiator (manufactured by IGM Resins BV, trade name: Omnirad An adhesive solution was obtained by mixing 3 parts by weight of 2959 (absorption coefficient in methanol at 365 nm: 48.9 ml / g cm), 5 parts by weight of a polyisocyanate compound (manufactured by Mitsui Chemical Co., Ltd., trade name "Takenate D-101A"), and toluene. The obtained adhesive solution was applied to a corona-treated 50 μm polyethylene terephthalate (PET) substrate (manufactured by Toray Industries, Inc., product name "Lumirror S-105") and heated at 80° C. for 3 minutes to obtain an adhesive tape.

[0081] Comparative Example 4 80 parts by weight of 2-ethylhexyl acrylate, 20 parts by weight of methyl acrylate, 10 parts by weight of acrylic acid, and 0.2 parts by weight of benzoyl peroxide were added and polymerized at 60°C for 6 hours under a nitrogen atmosphere to obtain a solution of an acrylic polymer with a weight-average molecular weight of 1.1 million. A mixture of 100 parts by weight of this polymer, 50 parts by weight of UV oligomer (manufactured by Mitsubishi Chemical, product name "UV-1700TL"), and an ionic liquid (manufactured by Japan Carlit Co., Ltd., product name "CIL-312", cation: 1-butyl-3-methylpyridinium cation, anion: (CFSO)N) was added. -0.1 parts by weight of methylcellulose), 3 parts by weight of a photopolymerization initiator (manufactured by IGM Resins BV, trade name "omnirad 2959", extinction coefficient in methanol at 365 nm: 48.9 ml / g cm), and 5 parts by weight of a polyisocyanate compound (manufactured by Mitsui Chemical Co., Ltd., trade name "Takenate D-101A") were added to obtain an adhesive solution. The obtained adhesive solution was applied to a corona-treated 50 μm polyethylene terephthalate (PET) substrate (manufactured by Toray Industries, Inc., product name "Lumirror S-105") and heated at 80° C. for 3 minutes to obtain an adhesive tape.

[0082] (Comparative Example 5) 75 parts by weight of 2-ethylhexyl acrylate, 25 parts by weight of N-acryloylmorpholine, 3 parts by weight of acrylic acid, 0.1 parts by weight of hydroxyethyl acrylate, and 0.2 parts by weight of 2,2'-azobisisobutyronitrile were copolymerized in ethyl acetate by a conventional method to obtain a polymer solution containing a polymer with a weight-average molecular weight of 1.2 million. To the resulting polymer solution, 2 parts by weight of a light release agent (manufactured by Daiichi Kogyo Seiyaku, trade name "Epane 710"), 7 parts by weight of an ionic liquid (manufactured by Nippon Nyukazai Co., Ltd., trade name "Aminoion AS100", cation: ethylethanolammonium cation, anion: polyoxyethylene (2)-2-ethylhexyl ether sulfate ester), and 4 parts by weight of a polyisocyanate compound (manufactured by Mitsui Chemical Co., Ltd., trade name "Takenate D-101A") were added to obtain a pressure-sensitive adhesive solution. The obtained adhesive solution was applied to a corona-treated 50 μm polyethylene terephthalate (PET) substrate (manufactured by Toray Industries, Inc., product name "Lumirror S-105") and heated at 80° C. for 3 minutes to obtain an adhesive tape.

[0083] <Evaluation> The pressure-sensitive adhesive tapes obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Table 2.

[0084] <Silicone transfer amount (Si amount)> The release liner was peeled from the adhesive layer of the adhesive tape. Next, the adhesive surface where the release liner had been attached was measured by X-ray photoelectron spectroscopy using ESCA (Electron Spectroscopy for Chemical Analysis) to determine the Si ratio (atomic %) on the adhesive layer surface. For the measurement, a Shimadzu ESCA device "KRATOS ULTRA2" was used. The X-ray source was monochromatic Al Kα (5 mA, 75 W, Resolution 40), the photoelectron take-off angle was 90°, and the analysis area was 1.1 mmφ. Qualitative analysis was performed by wide scan measurement, and the detected elements were then measured by narrow scan measurement.

[0085] <Number of particles> The adhesive tape was cut into a 25cm x 25cm sample. The sample was then attached to a 6-inch mirror wafer. It was then left to stand at 23°C for 2 hours. Next, it was irradiated with active energy rays (ultraviolet rays) using a UV irradiation device for dicing processes (manufactured by Nitto Seiki Co., Ltd., product name UM-810). When the absorption coefficient of the photopolymerization initiator contained in the adhesive layer at a wavelength of 365 nm in methanol is 80 ml / g cm or more, the cumulative light intensity of the active energy rays is 460 mJ / cm. 2 If the absorption coefficient of the photopolymerization initiator in methanol at a wavelength of 365 nm is less than 80 ml / g cm, the cumulative light dose is 700 mJ / cm. 2 The adhesive tape was then peeled off from the wafer surface, and the number of particles on the wafer surface was measured using a wafer surface inspection device (manufactured by Takano Corporation, product name "WM-7S") to count the number of particles of 0.15 μm or more and less than 0.30 μm, and the number of particles of 0.30 μm or more.

[0086] <Gel fraction> The release liner was peeled off from the adhesive tape, and a UV irradiation device (manufactured by Nitto Seiki Co., Ltd., product name "UM-810") was used to expose the adhesive layer side of the adhesive tape to an integrated light dose of 460 mJ / cm. 2The active energy rays were irradiated so that the gel fraction was 0.1 g. Next, a sample of approximately 0.1 g was collected from the adhesive layer of the adhesive tape after ultraviolet irradiation, and its weight was measured. The collected sample was wrapped in a Teflon (registered trademark) porous film and left in toluene for one week. The sample was then removed from the Teflon (registered trademark) porous film, heated in an oven at 120°C for one hour to dry the toluene, and its weight was measured. The gel fraction was calculated from the measured weight using the following formula. Gel fraction (%) = weight of sample after immersion in toluene (g) / weight of sample before immersion in toluene (g)

[0087] <Surface resistivity> The surface resistivity of the adhesive layer surface of the adhesive tape was measured using a resistivity meter (manufactured by Mitsubishi Chemical Corporation, product name "Hiresta MCP-HT450") under conditions of 23°C, 55% RH, and an applied voltage of 100 V for 30 seconds. Separately, the release liner was peeled off from the adhesive tape, and a UV irradiation device (manufactured by Nitto Seiki Co., Ltd., product name "UM-810") was used to measure the surface resistivity of the adhesive layer surface of the adhesive tape at an integrated light intensity of 460 mJ / cm. 2 The pressure-sensitive adhesive layer after irradiation with active energy rays was also similarly measured for surface resistivity.

[0088] <Light transmittance> The transmittance of the film used as the substrate was measured in the wavelength range of 200 nm to 800 nm using a total light measuring device (Shimadzu Corporation, product name "UV-2550"), and the light transmittance at a wavelength of 365 nm was calculated.

[0089] <Thickness of light release layer> The release liners used in the examples and comparative examples were embedded in epoxy resin. The embedded release liners were cut, and 10 random points on the cut surface were observed and measured using a transmission electron microscope, and the average value was calculated. Note that portions where the light release layer was extremely thin were not used as points for measuring the thickness.

[0090] [Table 2]

[0091] The pressure-sensitive adhesive tapes of the examples of the present invention had appropriate surface resistivity even after irradiation with active energy rays. In addition, the transfer of Si to the pressure-sensitive adhesive layer surface was suppressed, and the adhesion of foreign matter to the adherend surface was also suppressed. [Industrial Applicability]

[0092] The pressure-sensitive adhesive tape according to the embodiment of the present invention is suitable for use in protecting the circuit surface of a semiconductor wafer, as well as for protecting the surfaces of optical products and optical glass products. [Explanation of symbols]

[0093] 10 Base material 20 adhesive layer 100 adhesive tape

Claims

1. An adhesive tape comprising: a substrate; and an adhesive layer formed of an active energy ray-curable adhesive containing a (meth)acrylic polymer having a radiation-polymerizable carbon-carbon double bond, an ionic liquid, and a photopolymerization initiator.

2. The pressure-sensitive adhesive tape according to claim 1 , wherein the active energy ray-curable pressure-sensitive adhesive has a gel fraction of 97.5% or more after irradiation with active energy rays.

3. The pressure-sensitive adhesive tape according to claim 1 , wherein the cation of the ionic liquid has an amino group.

4. The pressure-sensitive adhesive tape according to claim 1 , wherein the anion of the ionic liquid has a sulfonic acid group.

5. The surface resistivity of the pressure-sensitive adhesive layer before irradiation with active energy rays is 5×10 １１ The pressure-sensitive adhesive tape according to claim 1, having a resistance of □ / Ω or less.

6. The pressure-sensitive adhesive tape according to claim 1 , wherein the active energy ray-curable pressure-sensitive adhesive further comprises polyalkylene glycol.

7. The pressure-sensitive adhesive tape according to claim 6 , wherein the polyalkylene glycol is at least one selected from the group consisting of polyethylene glycol and polypropylene glycol.

8. The pressure-sensitive adhesive tape according to claim 1 , wherein the substrate has a light transmittance of 60% or more for a light beam with a wavelength of 365 nm.

9. 9. The pressure-sensitive adhesive tape according to claim 8, wherein the photopolymerization initiator has an absorption coefficient in methanol at a wavelength of 365 nm of 80 ml / g cm or more.

10. The pressure-sensitive adhesive tape according to claim 1 , wherein the content of the photopolymerization initiator is 0.5 parts by weight or less based on 100 parts by weight of the (meth)acrylic polymer.

11. The pressure-sensitive adhesive tape according to claim 1 , wherein the substrate is a polyethylene terephthalate film.

12. The pressure-sensitive adhesive tape according to claim 1 , wherein a release liner having a light release layer is further laminated on the pressure-sensitive adhesive layer, and the light release layer has a thickness of 0.06 μm or less.

13. The pressure-sensitive adhesive tape according to claim 12 , wherein the amount of Si on the surface of the pressure-sensitive adhesive layer after the release liner has been peeled off is 1.0 atm % or less as determined by X-ray photoelectron spectroscopy.

14. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the number of particles of 0.30 μm or more is 50 or less in a tape peeling test.

15. The pressure-sensitive adhesive tape according to claim 14, wherein the number of particles having a size of 0.15 μm or more and less than 0.30 μm is 1,500 or less in a tape peeling test.

16. The pressure-sensitive adhesive tape according to claim 1 , which is used to protect the circuit surface of a semiconductor wafer.

17. The pressure-sensitive adhesive tape according to claim 1 , which is used for protecting the surface of an optical product or an optical glass product.

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