Adhesive sheet

Abstract

Provided is an adhesive sheet capable of temporarily securing an adherend in a releasable manner, which eliminates the need for high-power laser irradiation during peeling and eliminates the need for cleaning the adherend after peeling. The adhesive sheet of the present invention comprises an adhesive layer containing an ultraviolet absorber and / or a photopolymerization initiator, wherein the light transmittance of the adhesive sheet at a wavelength of 355 nm is 60% or less, and the adhesive layer is irradiated with a laser beam of 300 mJ / cm 2 The indentation elastic modulus of the layer at 23°C after ultraviolet irradiation became 25 MPa.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet. Background Art

[0002] When processing various components, such as electronic parts, the following process is typically performed: the component is temporarily fixed to a support using an adhesive sheet, and then the processed component is peeled from the support after processing. For example, Patent Document 1 describes a method in which a substrate (the component to be processed) is temporarily fixed to a support via an adhesive layer and a release layer. After processing, the release layer is destroyed by laser irradiation, and the substrate and adhesive layer are peeled from the support together. The adhesive layer is then removed from the substrate.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 5875850 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, in the above method, the adhesive layer needs to be removed from the component and the non-adhesive surface of the component is cleaned, which is problematic in terms of production cost. In addition, when irradiating with high-power laser, there is also the problem of damaging the component.

[0008] The present invention has been made to solve the above-mentioned conventional problems, and its object is to provide a pressure-sensitive adhesive sheet that can temporarily fix an adherend in a releasable manner, does not require high-power laser irradiation during peeling, and does not require the process of cleaning the adherend after peeling.

[0009] Solutions for solving problems

[0010] The adhesive sheet of the present invention comprises an adhesive layer containing an ultraviolet absorber and / or a photopolymerization initiator, wherein the light transmittance of the adhesive sheet at a wavelength of 355 nm is 60% or less, and the adhesive layer is irradiated with 300 mJ / cm 2 A layer having an indentation elastic modulus of 25 MPa or more at 23°C after ultraviolet exposure.

[0011] In one embodiment, the adhesive layer is composed of an active energy ray-curable adhesive.

[0012] In one embodiment, the molecular weight of the compound constituting the ultraviolet absorber is 1000 or less.

[0013] In one embodiment, the adhesive sheet is attached to a stainless steel plate and irradiated with 300 mJ / cm 2The adhesive strength B at 23°C after ultraviolet exposure was 0.2 N / 20 mm or less.

[0014] In one embodiment, the adhesive sheet is attached to a stainless steel plate and irradiated with 300 mJ / cm 2 The reduction rate of the adhesive strength B at 23° C. after ultraviolet exposure relative to the initial adhesive strength A at 23° C. immediately after the adhesive sheet was attached to the stainless steel plate was 90% or more.

[0015] Effects of the Invention

[0016] According to the present invention, a pressure-sensitive adhesive sheet can be provided that can temporarily secure an adherend in a releasable manner, eliminating the need for high-power laser irradiation during peeling and the need for adherend cleaning after peeling. Furthermore, the pressure-sensitive adhesive sheet of the present invention exhibits releasability not only by low-power laser irradiation but also without the accompanying decomposition of the pressure-sensitive adhesive layer, thereby preventing contamination of the adherend. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 (a) is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. Figure 1 (b) is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to another embodiment of the present invention. DETAILED DESCRIPTION

[0018] A. Overview of PSA Sheet

[0019] Figure 1 (a) is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. The pressure-sensitive adhesive sheet 100 according to this embodiment includes a pressure-sensitive adhesive layer 10. The pressure-sensitive adhesive layer 10 contains an ultraviolet absorber and / or a photopolymerization initiator. Figure 1 (b) is a schematic cross-sectional view of an adhesive sheet according to an embodiment of the present invention. The adhesive sheet 200 of this embodiment further comprises a substrate 20, and an adhesive layer 10 is disposed on at least one side of the substrate 20. Although not shown in the figure, the adhesive sheet of the present invention may be provided with a release liner on the outside of the adhesive layer for the purpose of protecting the adhesive surface until it is used. In addition, the adhesive sheet may further comprise any other appropriate layer as long as the effects of the present invention can be obtained. In one embodiment, the adhesive sheet of the present invention is as follows Figure 1 In another embodiment, the adhesive sheet of the present invention is composed of only one adhesive layer. Figure 1The adhesive layer comprises a substrate and an adhesive layer as shown in (b), and the adhesive layer is directly (i.e., without the aid of other layers) disposed on the substrate. In the present invention, as described later, the adhesive layer can be easily peeled off due to the reduced adhesive strength and deformation associated with the high elastic modulus of the adhesive layer. Therefore, an adhesive sheet can be formed without providing a layer other than the adhesive layer (so-called separation layer) for separating the adherend from the adhesive sheet.

[0020] In the present invention, by making the adhesive layer contain an ultraviolet absorber or a photopolymerization initiator, it is possible to achieve peeling of the adherend based on laser irradiation. In more detail, by irradiating the adhesive layer with laser, the ultraviolet absorber or the photopolymerization initiator is heated and deformed in the adhesive layer, and as a result, peeling properties are exhibited in the portion irradiated with the laser. According to the present invention, the operation as described above can deform the adhesive layer within a small range, so that the adherend can be well peeled when processing a small adherend. If such an adhesive sheet is used, the cleaning of the adherend after peeling can be omitted. In addition, when a small adherend to be peeled and a small adherend not to be peeled are temporarily fixed adjacent to each other, only the small adherend to be peeled can be peeled, and unnecessary detachment of the small adherend can be prevented.

[0021] It is preferred that the adhesive layer is composed of an active energy ray curable adhesive. The adhesive sheet containing the active energy ray curable adhesive reduces the adhesive force of the entire adhesive layer by irradiating active energy rays. After the adhesive layer of the adhesive sheet to which the adherend is attached is irradiated with active energy rays to reduce the adhesive force, it is possible to prevent residual adhesive after peeling by irradiating the laser as described above. If such an adhesive sheet is used, the cleaning of the adherend after peeling can be omitted. In addition, by forming an adhesive layer containing an active energy ray curable adhesive, the laser output power during peeling can be reduced. The adhesive sheet of the present invention exhibits peelability under a low-output laser, so if the adhesive sheet is used, it is possible to reduce damage to the adherend during peeling and prevent the adherend from being damaged. In addition, since peelability can be exhibited by a laser with an output power that does not produce decomposition (thermal decomposition) of the adhesive layer itself, contamination of the adherend caused by decomposition products of the adhesive layer can be prevented. As active energy rays, for example, gamma rays, ultraviolet rays, visible rays, infrared rays (heat rays), radio waves, α rays, β rays, electron rays, plasma streams, ionizing rays, particle beams, etc. can be listed. Ultraviolet rays are preferred.

[0022] The light transmittance of the adhesive sheet of the present invention at a wavelength of 355nm is 60% or less. In the present invention, by reducing the light transmittance, the laser output power during peeling can be reduced. The adhesive sheet of the present invention can show peelability under low-output laser power, so if the adhesive sheet is used, it is possible to reduce damage to the adherend during peeling and prevent the adherend from being damaged. The light transmittance of the adhesive sheet of the present invention at a wavelength of 355nm is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less. If it is within this range, the above-mentioned effect becomes more significant. It should be noted that the light transmittance of the adhesive sheet refers to the light transmittance in the thickness direction of the adhesive sheet, and is the light transmittance measured based on all the constituent layers of the adhesive sheet. In the present invention, the light transmittance of the adhesive sheet at a wavelength of 355nm can be controlled by adjusting the content ratio of the ultraviolet absorber contained in the adhesive layer. In addition, the light transmittance of the adhesive sheet at a wavelength of 355nm can also be controlled by the composition of the base polymer and the photopolymerization initiator constituting the adhesive layer. For example, the light transmittance of the pressure-sensitive adhesive sheet at a wavelength of 355 nm can be controlled by the type and amount of the photopolymerization initiator contained in the pressure-sensitive adhesive layer, particularly by the compatibility between the photopolymerization initiator and the base polymer.

[0023] The visible light transmittance of the adhesive sheet of the present invention is preferably 50% or greater, more preferably 60% or greater, and even more preferably 70% or greater. Within this range, the adhesive sheet can be obtained, allowing the adherend to be peeled off through the adhesive sheet to be clearly identified when the adherend is peeled off by laser irradiation. The higher the visible light transmittance of the adhesive sheet, the more preferred it is, with an upper limit of, for example, 95% (preferably 100%).

[0024] The haze value of the PSA sheet of the present invention is preferably 70% or less, more preferably 65% or less. Within this range, the PSA sheet can be obtained, allowing the adherend to be peeled off through the PSA sheet to be clearly identified when peeling the adherend by laser irradiation. The lower the haze value of the PSA sheet, the more preferred; its lower limit is, for example, 0.1%.

[0025] The initial adhesive force A at 23°C just after the adhesive sheet of the present invention is attached to the stainless steel plate is preferably 0.1N / 20mm~15N / 20mm, more preferably 0.5N / 20mm~10N / 20mm. If it is within this range, an adhesive sheet that can well hold the adherend can be obtained. The adhesive force is measured in accordance with JIS Z 0237:2000. Specifically, the adhesive sheet is attached to a stainless steel plate (arithmetic mean surface roughness Ra: 50±25nm) by reciprocating a 2kg roller once, and after being placed at 23°C for 30 minutes, the adhesive sheet is peeled off and measured under the conditions of a peeling angle of 180° and a peeling speed (tensile speed) of 300mm / min. The adhesive force of the adhesive layer changes due to active energy ray irradiation and laser irradiation. In this specification, "initial adhesive force" refers to the adhesive force before irradiation with active energy rays and laser.

[0026] In one embodiment, the adhesive sheet was attached to a stainless steel plate and irradiated with 300 mJ / cm 2 The adhesive strength B at 23°C after ultraviolet irradiation (also referred to as the adhesive strength B after curing) is preferably 0.2N / 20mm or less, more preferably 0.01N / 20mm to 0.2N / 20mm, and more preferably 0.02N / 20mm to 0.15N / 20mm. If it is within such a range, an adhesive sheet with less residual adhesive can be obtained. The above-mentioned ultraviolet irradiation is performed, for example, using an ultraviolet irradiation device (manufactured by Nitto Seiki Co., Ltd., trade name "UM-810") to irradiate the adhesive layer with ultraviolet rays from a high-pressure mercury lamp (characteristic wavelength: 365nm, cumulative light amount: 300mJ / cm 2 ) and proceed.

[0027] The reduction rate of the post-curing adhesive force (B) relative to the initial adhesive force (A) is preferably 90% or greater, more preferably 95% or greater. Within this range, a PSA sheet with excellent releasability can be obtained. The reduction rate (%) can be calculated using the formula: (initial adhesive force (A) - post-curing adhesive force (B)) / initial adhesive force (A) × 100.

[0028] The thickness of the pressure-sensitive adhesive sheet is preferably 1 μm to 300 μm, more preferably 5 μm to 200 μm.

[0029] B. Adhesive layer

[0030] The thickness of the adhesive layer is preferably 20 μm or less. Within this range, the laser output power during peeling can be further reduced, resulting in an adhesive sheet with excellent peeling performance. The thickness of the adhesive layer is more preferably 10 μm or less, even more preferably 8 μm or less, and even more preferably 1 μm to 8 μm. Within this range, the aforementioned effects become significant.

[0031] The adhesive layer is preferably irradiated with 300 mJ / cm 2 A layer having an indentation elastic modulus of 25 MPa or more at 23°C after ultraviolet irradiation. If an adhesive layer having such an indentation elastic modulus after ultraviolet irradiation is provided, deformation occurs in the adhesive layer by laser irradiation, and as a result, adherends can be peeled off well. In addition, contamination of the adherend during peeling can be prevented. Irradiation 300 mJ / cm 2 The indentation elastic modulus of the adhesive layer after ultraviolet irradiation is more preferably 30 MPa or more, further preferably 40 MPa or more, and particularly preferably 50 MPa or more. 2 The upper limit of the indentation elastic modulus of the pressure-sensitive adhesive layer after ultraviolet exposure is, for example, 500 MPa (preferably 300 MPa). The indentation elastic modulus can be measured by a single indentation method at 23°C, with an indentation speed of 10 nm / s and an indentation depth of 100 nm.

[0032] As described above, the adhesive layer contains an ultraviolet absorber and / or a photopolymerization initiator. Preferably, the adhesive layer is composed of an active energy ray-curable adhesive. The active energy ray-curable adhesive may contain the above-mentioned ultraviolet absorber and / or photopolymerization initiator.

[0033] (UV absorber)

[0034] As the ultraviolet light absorber, as long as it is a compound that absorbs ultraviolet rays (for example, a wavelength of 355nm), any appropriate ultraviolet light absorber can be used. As the ultraviolet light absorber, for example, benzotriazole ultraviolet light absorbers, benzophenone ultraviolet light absorbers, triazine ultraviolet light absorbers, salicylate ultraviolet light absorbers, cyanoacrylate ultraviolet light absorbers, etc. can be listed. Among them, preferably triazine ultraviolet light absorbers or benzotriazole ultraviolet light absorbers, particularly preferably triazine ultraviolet light absorbers. Especially when using acrylic adhesive as adhesive A, from the aspect of high compatibility with the base polymer of this acrylic adhesive, it is possible to preferably use triazine ultraviolet light absorbers. Triazine ultraviolet light absorbers are more preferably composed of a compound with a hydroxyl group, and particularly preferably the ultraviolet light absorber (hydroxyphenyl triazine ultraviolet light absorber) composed of a hydroxyphenyl triazine compound.

[0035] Examples of hydroxyphenyltriazine-based ultraviolet absorbers include the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl and [(C10-C16 (mainly C12-C13) alkoxy)methyl]oxirane (trade name "TINUVIN 400", manufactured by BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol), reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidate (trade name "TINUVIN 405", manufactured by BASF), 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (trade name "TINUVIN 460", manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol (trade name "TINUVIN 1577", manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (trade name "Adekastab LA-46", manufactured by ADEKA Co., Ltd.), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (trade name "TINUVIN 479", manufactured by BASF), and the trade name "TINUVIN 477" manufactured by BASF.

[0036] Examples of the benzotriazole-based ultraviolet absorber (benzotriazole-based compound) include 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (trade name "TINUVIN PS", manufactured by BASF), an ester compound of phenylpropionic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy (C7-9 side chain and linear alkyl) (trade name "TINUVIN 384-2", manufactured by BASF), and a mixture of octyl 3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate and 2-ethylhexyl 3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate (trade name "TINUVIN 109", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 900", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 928", manufactured by BASF), methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 reaction product (trade name "TINUVIN 1130", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (trade name "TINUVIN P", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 234", manufactured by BASF), 2-[5-chloro-2H-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (trade name "TINUVIN 326", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-amylphenol (trade name "TINUVIN 328", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 329", manufactured by BASF), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol] (trade name "TINUVIN 360", manufactured by BASF), reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (trade name "TINUVIN 213", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (trade name "TINUVIN 571", manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (trade name "Sumisorb 250", manufactured by Sumitomo Chemical Co., Ltd.), 2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole (trade name "SEESORB 703", manufactured by Shipro Kasei Kaisha, Ltd.), 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidomethyl)phenol (trade name "SEESORB 706", manufactured by Shipro Kasei Kaisha, Ltd.), 2-(4-benzoyloxy-2-hydroxyphenyl)-5-chloro-2H-benzotriazole (trade name "SEESORB 7012BA”), 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol (trade name “KEMISORB 73”, manufactured by Chemipro Kasei Kaisha, Ltd.), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol] (trade name “Adekastab LA-31”, manufactured by Adeka Co., Ltd.), 2-(2H-benzotriazol-2-yl)-p-cellulose (trade name “Adekastab LA-32”, manufactured by Adeka Co., Ltd.), 2-(5-chloro-2H-benzotriazol-2-yl)-6-tert-butyl-4-methylphenol (trade name “Adekastab LA-36”, manufactured by Adeka Co., Ltd.), etc.

[0037] The ultraviolet absorber may be a dye or a pigment. Examples of pigments include azo, phthalocyanine, anthraquinone, lake, perylene, perylone, quinacridone, thioindigo, dioxazine, isoindolinone, and quinophthalone pigments. Examples of dyes include azo, phthalocyanine, anthraquinone, carbonyl, indigo, quinoneimine, methine, quinoline, and nitro dyes.

[0038] The molecular weight of the compound constituting the above-mentioned ultraviolet light absorber is preferably 1000 or less, more preferably 800 or less, and further preferably 600 or less. The ultraviolet light absorber having a molecular weight within the above-mentioned range has excellent compatibility with the base polymer. Therefore, when using the ultraviolet light absorber, deformation occurs only at the laser irradiation site during laser irradiation, and thus it is possible to peel off with very low laser energy. As a result, thermal decomposition of the adhesive layer can be prevented. If such an adhesive layer is formed, an adhesive sheet that is not easily contaminated with the adherend can be obtained. The lower limit of the molecular weight of the compound constituting the ultraviolet light absorber is, for example, 100.

[0039] The maximum absorption wavelength of the ultraviolet absorber is preferably 300 nm to 450 nm, more preferably 320 nm to 400 nm, and even more preferably 330 nm to 380 nm. The difference between the maximum absorption wavelength of the ultraviolet absorber and the maximum absorption wavelength of the photopolymerization initiator is preferably 10 nm or more, more preferably 25 nm or more.

[0040] The content of the ultraviolet absorber is preferably 1 to 50 parts by weight, more preferably 5 to 20 parts by weight, relative to 100 parts by weight of the base polymer in the adhesive layer. Within this range, a PSA sheet can be obtained in which curing of the adhesive layer proceeds well when the adhesive strength of the entire adhesive layer is well reduced by irradiation with active energy rays, and which exhibits good releasability by laser irradiation.

[0041] (Photopolymerization initiator)

[0042] As the photopolymerization initiator, any appropriate initiator can be used. Examples of the photopolymerization initiator include: α-ketoalcohol 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 anisole methyl ether; and benzoyldimethyl ether. Ketal compounds such as acetal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-benzophenone-1,1-propanedione-2-(O-ethoxycarbonyl)oxime; benzophenone compounds such as benzoylbenzoic acid, 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; haloketones; acylphosphine oxides; acylphosphonates, etc. The amount of the photopolymerization initiator used can be set to any appropriate amount.

[0043] In one embodiment, a photopolymerization initiator having a maximum absorption wavelength within a range of 400 nm or less (preferably 380 nm or less, more preferably 340 nm or less) can be used. When such a photopolymerization initiator is used, when the adhesive strength of the entire adhesive layer is reduced by irradiation with active energy rays, a curing reaction of the adhesive occurs preferentially, resulting in an adhesive sheet with particularly low adhesive residue. Furthermore, an adhesive sheet exhibiting excellent releasability upon laser irradiation can be obtained.

[0044] The content of the photopolymerization initiator is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and even more preferably 3 to 15 parts by weight, relative to 100 parts by weight of the base polymer in the adhesive layer. Within this range, curing of the adhesive layer proceeds well when the adhesive strength of the entire adhesive layer is well reduced by irradiation with active energy rays, and the adhesive layer exhibits a large amount of deformation due to laser irradiation, resulting in an adhesive sheet with good releasability.

[0045] As the photopolymerization initiator, a commercially available product can be used. For example, examples of photopolymerization initiators having a maximum absorption wavelength in the range of 400 nm or less include "Irgacure 127," "Irgacure 369," "Irgacure 369E," "Irgacure 379," "Irgacure 379EG," "Irgacure 819," "Irgacure TOP," "Irgacure 784," and "Irgacure OXE01," manufactured by BASF.

[0046] (Active energy ray-curable adhesive)

[0047] In one embodiment, as an active energy ray-curable adhesive, an active energy ray-curable adhesive (A1) comprising a base polymer serving as a masterbatch and an active energy ray-reactive compound (monomer or oligomer) capable of bonding to the base polymer can be used. In another embodiment, an active energy ray-curable adhesive (A2) comprising an active energy ray-reactive polymer as a base polymer can be used. The base polymer preferably has a functional group capable of reacting with a photopolymerization initiator. Examples of the functional group include hydroxyl groups and carboxyl groups.

[0048] Examples of the base polymer used in the adhesive (A1) include rubber-based polymers such as natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer rubber, reclaimed rubber, butyl rubber, polyisobutylene rubber, and nitrile rubber (NBR); silicone-based polymers; and acrylic polymers. These polymers can be used alone or in combination of two or more. Among them, acrylic polymers are preferred.

[0049] Examples of acrylic polymers include homopolymers or copolymers of hydrocarbon group-containing (meth)acrylates such as alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and aryl (meth)acrylates; and copolymers of such hydrocarbon group-containing (meth)acrylates and other copolymerizable monomers. Examples of alkyl (meth)acrylates include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, amyl, isoamyl, hexyl, heptyl, octyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, undecyl, dodecyl (i.e., lauryl), tridecyl, tetradecyl, hexadecyl, octadecyl, and eicosyl (meth)acrylates. Examples of cycloalkyl (meth)acrylates include cyclopentyl and cyclohexyl (meth)acrylates. Examples of aryl (meth)acrylates include phenyl (meth)acrylate and benzyl (meth)acrylate. The content ratio of the structural unit derived from the hydrocarbon group-containing (meth)acrylate is preferably 40 parts by weight or more, more preferably 60 parts by weight or more, based on 100 parts by weight of the base polymer.

[0050] As the above-mentioned other copolymerizable monomers, for example, monomers containing functional groups such as carboxyl group-containing monomers, acid anhydride monomers, hydroxyl group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, acrylamide and acrylonitrile can be listed. As carboxyl group-containing monomers, for example, acrylic acid, methacrylic acid, (meth) carboxyethyl acrylate, (meth) carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid can be listed. As acid anhydride monomers, for example, maleic anhydride and itaconic anhydride can be listed. As hydroxyl group-containing monomers, for example, 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-hydroxymethylcyclohexyl) methyl (meth) acrylate can be listed. As the glycidyl group-containing monomer, for example, glycidyl (meth)acrylate and methyl glycidyl (meth)acrylate can be listed. As the sulfonic acid group-containing monomer, for example, styrenesulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate and (meth)acryloyloxynaphthalenesulfonic acid can be listed. As the phosphoric acid group-containing monomer, for example, 2-hydroxyethyl acryloyl phosphate can be listed. As acrylamide, for example, N-acryloylmorpholine can be listed. They can be used alone or in combination of two or more. The content ratio of the structural unit derived from the above-mentioned copolymerizable monomer is preferably 60 parts by weight or less, more preferably 40 parts by weight or less relative to 100 parts by weight of the base polymer.

[0051] In order to form a cross-linked structure in its polymer backbone, the acrylic polymer may include a structural unit derived from a multifunctional monomer. As a multifunctional monomer, for example, hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy (meth)acrylate (i.e., poly(meth) glycidyl acrylate), polyester (meth)acrylate, and urethane (meth)acrylate can be listed. One of them can be used alone or in combination of two or more. The content of the structural unit derived from the above-mentioned multifunctional monomer is preferably 40 parts by weight or less, more preferably 30 parts by weight or less relative to 100 parts by weight of the base polymer.

[0052] The weight average molecular weight of the acrylic polymer is preferably 100,000 to 3,000,000, and more preferably 200,000 to 2,000,000. The weight average molecular weight can be measured by GPC (solvent: THF).

[0053] Examples of the active energy ray-reactive compound that can be used in the adhesive (A1) include photoreactive monomers or oligomers containing functional groups having polymerizable carbon-carbon multiple bonds, such as acryloyl, methacryloyl, vinyl, allyl, and ethynyl groups. Specific examples of the photoreactive monomer include esters of (meth)acrylic acid and polyols, such as trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and polyethylene glycol di(meth)acrylate; polyfunctional urethane (meth)acrylates; epoxy (meth)acrylates; and oligoester (meth)acrylates. In addition, monomers such as methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate (2-isocyanatoethyl methacrylate), and m-isopropenyl-α,α-dimethylbenzyl isocyanate can be used. Specific examples of photoreactive oligomers include dimers to pentamers of the above monomers. The molecular weight of the photoreactive oligomer is preferably 100 to 3000.

[0054] Furthermore, as the active energy ray-reactive compound, monomers such as epoxidized butadiene, glycidyl methacrylate, acrylamide, and vinylsiloxane, or oligomers composed of these monomers may be used.

[0055] And then, as above-mentioned active energy ray reactive compound, the mixture of the compound with multiple heterocycles in the organic salts such as onium salt and molecule can be used.For this mixture, by the irradiation of active energy ray (for example, ultraviolet ray, electron beam), organic salt can crack and generate ion, and it can become starting species and cause the ring-opening reaction of heterocycle and form three-dimensional network structure.As above-mentioned organic salt, for example, iodonium salt, phosphonium salt, antimony salt, sulfonium salt, borate etc. can be listed.As the heterocycle in the compound with multiple heterocycles in above-mentioned molecule, oxirane, oxetane, thiirane, aziridine etc. can be listed.

[0056] In the binder (A1), the active energy ray-reactive compound is contained in an amount of preferably 0.1 to 500 parts by weight, more preferably 5 to 300 parts by weight, and even more preferably 40 to 150 parts by weight, based on 100 parts by weight of the base polymer.

[0057] Examples of the active energy ray-reactive polymer (base polymer) contained in the binder (A2) include polymers containing functional groups having carbon-carbon multiple bonds, such as acryloyl, methacryloyl, vinyl, allyl, and ethynyl groups. Specific examples of the active energy ray-reactive polymer include polymers composed of polyfunctional (meth)acrylates; photocationically polymerizable polymers; cinnamoyl group-containing polymers such as polyvinyl cinnamate; diazotized aminophenol novolac resins; and polyacrylamide.

[0058] In one embodiment, an active energy ray-reactive polymer can be used, wherein active energy ray-polymerizable carbon-carbon multiple bonds are introduced into the side chains, main chain, and / or main chain terminals of the acrylic polymer. Examples of methods for introducing radiation-polymerizable carbon-carbon double bonds into acrylic polymers include copolymerizing raw monomers containing a monomer having a predetermined functional group (first functional group) to obtain an acrylic polymer, and then subjecting the acrylic polymer to a condensation reaction or addition reaction with a compound having a predetermined functional group (second functional group) capable of reacting with the first functional group and a radiation-polymerizable carbon-carbon double bond, while maintaining the radiation-polymerizability of the carbon-carbon double bond.

[0059] Examples of combinations of the first and second functional groups include carboxyl and epoxy, epoxy and carboxyl, carboxyl and aziridine, aziridine and carboxyl, hydroxyl and isocyanate, and isocyanate and hydroxyl. Among these combinations, from the perspective of ease of reaction tracking, preferred are combinations of hydroxyl and isocyanate, and combinations of isocyanate and hydroxyl. Furthermore, the technical difficulty of producing polymers with highly reactive isocyanate groups is high. From the perspective of ease of producing or obtaining acrylic polymers, it is more preferred that the first functional group on the acrylic polymer side be a hydroxyl group and the second functional group be an isocyanate. Examples of isocyanate compounds having both a radiation-polymerizable carbon-carbon double bond and an isocyanate as a second functional group include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. The acrylic polymer having a first functional group preferably contains a structural unit derived from the above-mentioned hydroxyl group-containing monomer, and further preferably contains a structural unit derived from an ether compound such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether.

[0060] The said adhesive (A2) may further contain the said active energy ray reactive compound (monomer or oligomer).

[0061] The active energy ray-curable adhesive may contain an ultraviolet absorber and / or a photopolymerization initiator. The details of the ultraviolet absorber and photopolymerization initiator used are as described above.

[0062] In one embodiment, the active energy ray-curable adhesive may include a photosensitizer.

[0063] In one embodiment, the above-mentioned photosensitizer can be used in combination with the above-mentioned photopolymerization initiator. The photosensitizer transfers the energy obtained by absorbing light by itself to the photopolymerization initiator, thereby generating free radicals from the photopolymerization initiator, and therefore, polymerization can be performed using light on the long wavelength side where the photopolymerization initiator itself has no absorption peak. Therefore, by containing a photosensitizer, the difference between the absorption wavelength of the above-mentioned ultraviolet absorber and the wavelength at which free radicals can be generated by the photopolymerization initiator can be increased. As a result, the photopolymerization of the adhesive layer and the peeling based on the ultraviolet absorber can be performed without affecting each other. In one embodiment, 2,2-dimethoxy-1,2-diphenylethane-1-one (for example, BASF, trade name "Irgacure 651") as a photopolymerization initiator can be used in combination with a photosensitizer. As such a photosensitizer, the trade name "UVS-581" manufactured by Kawasaki Chemicals, Ltd., 9,10-diethoxyanthracene (for example, Kawasaki Chemicals, Ltd., trade name "UVS1101") and the like can be listed.

[0064] Other examples of the above-mentioned photosensitizers include 9,10-dibutoxyanthracene (e.g., Kawasaki Chemicals, trade name "UVS-1331"), 2-isopropylthioxanthone, benzophenone, thioxanthone derivatives, and 4,4'-bis(dimethylamino)benzophenone. Examples of thioxanthone derivatives include ethoxycarbonylthioxanthone and isopropylthioxanthone.

[0065] The content of the photosensitizer is preferably 0.01 to 2 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the base polymer.

[0066] The active energy ray-curable adhesive preferably contains a crosslinking agent. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, and amine crosslinking agents.

[0067] The content of the cross-linking agent is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight, based on 100 parts by weight of the base polymer of the adhesive.

[0068] In one embodiment, an isocyanate-based crosslinking agent is preferably used. An isocyanate-based crosslinking agent is preferred because it can react with various functional groups. Specific examples of the isocyanate crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic isocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate; and isocyanate adducts such as trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industries, Ltd., trade name "CORONATE L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industries, Ltd., trade name "Coronate HL"), and isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industries, Ltd., trade name "Coronate HX"). It is preferable to use a cross-linking agent having three or more isocyanate groups.

[0069] The active energy ray-curable adhesive may further contain any appropriate additives as needed. Examples of the additives include active energy ray polymerization accelerators, free radical scavengers, tackifiers, plasticizers (e.g., trimellitate plasticizers, pyromellitate plasticizers, etc.), pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, release regulators, softeners, surfactants, flame retardants, and antioxidants.

[0070] C.Substrate

[0071] The substrate may be made of any suitable resin. Examples of such resins include polyolefin resins such as polyethylene resins, polypropylene resins, polybutene resins, and polymethylpentene resins; polyurethane resins, polyester resins, polyimide resins, polyetherketone resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, fluorine resins, silicone resins, cellulose resins, and ionomer resins. Among these, polyolefin resins are preferred.

[0072] The thickness of the substrate is preferably 2 μm to 300 μm, more preferably 2 μm to 100 μm, and even more preferably 2 μm to 50 μm.

[0073] The light transmittance of the substrate at a wavelength of 355 nm is preferably 70% or higher, more preferably 80% or higher, further preferably 90% or higher, and particularly preferably 95% or higher. The upper limit of the total light transmittance of the substrate is, for example, 98% (preferably 99%).

[0074] D. Method for manufacturing adhesive sheet

[0075] The adhesive sheet can be manufactured by any appropriate method. For example, the adhesive sheet can be obtained by applying the adhesive to a substrate or a release liner. As the coating method, various methods such as rod coating, air knife coating, gravure coating, gravure reverse coating, reverse roller coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing can be adopted. Alternatively, a method in which an adhesive layer is formed on a release liner and then attached to a substrate can be adopted.

[0076] E. How to use the adhesive sheet

[0077] The adhesive sheet of the present invention can be used when temporarily fixing any appropriate workpiece (such as an electronic component) when processing the workpiece. As a method of using the adhesive sheet of the present invention, for example, a method of using it in the following manner can be cited: (i) attaching the workpiece to the adhesive sheet and fixing it; (ii) processing the workpiece; (iii) irradiating the entire adhesive layer of the adhesive sheet with active energy rays (such as ultraviolet rays) to reduce the adhesive force of the adhesive sheet; (iv) irradiating the portion where it is desired to exhibit peelability with a laser to peel the workpiece. According to this method, the workpiece can be peeled off by falling off naturally. In addition, when temporarily fixing multiple workpieces, only a part of them can be peeled off. If the adhesive sheet of the present invention is used, the adhesive force can be reduced to the extent that it will fall off naturally, so even very small workpieces (such as 50 μm square) can be peeled off separately.

[0078] Example

[0079] The present invention is described in detail below by way of examples, but the present invention is not limited to these examples. The test and evaluation methods in the examples are as follows. In addition, unless otherwise specified, "parts" and "%" are by weight.

[0080] (1) Transmittance at 355nm wavelength

[0081] The PET separator film of the PSA sheet was peeled off and attached to a large glass slide (manufactured by Matsunami Glass, trade name "S9111") using a hand roller. The measurement was performed with the PET separator film on the other side peeled off. Specifically, the transmittance of the PSA sheet itself at a wavelength of 355 nm was measured using a spectrophotometer (trade name "Spectrophotometer U-4100" manufactured by Hitachi High-Tech Corporation) on the large glass slide.

[0082] (2) Haze value

[0083] The haze value was measured using a haze meter (trade name "HAZE METER HM-150," manufactured by Murakami Color Research Laboratory) by placing a large glass slide (trade name "S9111," manufactured by Matsunami Glass) so that incident light was perpendicular to the surface of the slide. The PET separator film of the PSA sheet was then peeled off and applied to the large glass slide after haze measurement using a hand roller. The haze value was then measured again with the PET separator film removed from the other side. The haze value of the PSA sheet was determined by subtracting the haze value of the glass slide alone from the obtained haze value.

[0084] (3) Indentation elastic modulus

[0085] The PET separator of the adhesive sheet was peeled off and attached to a large glass slide (S9111, manufactured by Matsunami Glass Co., Ltd.) using a hand roller. Ultraviolet rays (specific wavelength: 365 nm, cumulative light intensity: 350 mJ / cm) from a high-pressure mercury lamp were irradiated onto the entire surface of the glass slide using an ultraviolet irradiation device (UM-810, manufactured by Nitto Seiki Co., Ltd.). 2 The PET separator on the other side was then peeled off to expose the adhesive layer. The indentation modulus was measured using a Hysitron TriboIndenter TI-950. The measurement was performed using a single indentation method at 23°C, an indentation speed of 10 nm / s, and an indentation depth of 100 nm.

[0086] (4) Adhesion

[0087] The PET separator of the adhesive sheet was peeled off, and a 25 μm thick PET sheet (Lumirror S10 manufactured by Toray Industries, Inc.) was laminated. The PET separator on the other side was then peeled off, and the sheet was laminated to SUS304 using a 2 kg roller reciprocating once. The adhesive strength was measured according to JIS Z0237:2000 (peel angle 180°, peel speed (tensile speed) 300 mm / min, measurement temperature: 23°C) and was used as the initial adhesive strength.

[0088] After the adhesive sheet was attached to the SUS304 in the same manner, the entire surface was irradiated with ultraviolet light (specific wavelength: 365 nm, cumulative light intensity: 300 mJ / cm) from a high-pressure mercury lamp using an ultraviolet irradiation device (Nitto Seiki, trade name "UM-810") from the adhesive sheet side. 2 ) and then the adhesive strength was measured in the same manner as above and the adhesive strength after curing was determined.

[0089] The reduction rate of adhesive force was calculated by reduction rate [%] = (initial adhesive force - adhesive force after curing) / initial adhesive force × 100.

[0090] (5) Laser peeling

[0091] The PET separator of the adhesive sheet was peeled off and attached to a large slide glass (S9111, manufactured by Matsunami Glass Co., Ltd.) using a hand roller. The PET separator on the other side was then peeled off, and a 100 μm square silicon chip was attached to the adhesive surface.

[0092] Using an ultraviolet irradiation device (Nitto Seiki, trade name "UM-810"), the entire surface of the slide glass was irradiated with ultraviolet rays from a high-pressure mercury lamp (specific wavelength: 365 nm, cumulative light intensity: 350 mJ / cm 2 ).

[0093] In the irradiated area: Under the conditions of output power of 0.2W, 0.1W, and 0.05W, a laser with a wavelength of 355nm was irradiated only at the target component position from the large slide side (1 plus per chip). The case where it fell off naturally was recorded as qualified (0), and the case where it did not fall off naturally was recorded as unqualified (×).

[0094] In the case of natural fall, the laser irradiation site was observed from the adhesive layer side using a laser microscope to observe the morphology of the adhesive layer surface. In Table 1, the situation where the adhesive decomposed due to laser irradiation and part or all of the adhesive layer disappeared was recorded as concave, and the situation where no change was observed was recorded as smooth. When the surface of the adhesive layer is smooth, it is possible to prevent contamination of the adherend. On the other hand, the concave state of the adhesive layer surface indicates that the adhesive layer itself has undergone thermal decomposition. In such a state, there is concern about contamination of the adherend.

[0095] [Production Example 1] Preparation of Acrylic Polymer I

[0096] 100 parts by weight of 2-methoxyethyl acrylate, 27 parts by weight of acryloylmorpholine, and 22 parts by weight of 2-hydroxyethyl acrylate were mixed to prepare a monomer composition.

[0097] Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer. 500 parts by weight of toluene, 149 parts by weight of the monomer composition, and 0.3 parts by weight of benzoyl peroxide (BPO) were added under a nitrogen atmosphere and stirred at 60°C for 5 hours. The mixture was then cooled to room temperature, and 24 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to add NCO groups to the terminal OH groups of the side chains of 2-hydroxyethyl acrylate in the copolymer, thereby obtaining an acrylic polymer solution I containing an acrylic polymer I having a terminal carbon-carbon double bond.

[0098] [Production Example 2] Preparation of Acrylic Polymer II

[0099] 100 parts by weight of butyl acrylate, 78 parts by weight of ethyl acrylate, and 40 parts by weight of hydroxyethyl acrylate were mixed to prepare a monomer composition.

[0100] Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer, and 507 parts by weight of toluene, 218 parts by weight of the above-mentioned monomer composition, and 1.2 parts by weight of benzoyl peroxide (BPO) were added under a nitrogen atmosphere, followed by stirring at 60°C for 5 hours. The mixture was then cooled to room temperature, and 42.6 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to add NCO groups to the terminal OH groups of the side chains of 2-hydroxyethyl acrylate in the copolymer, thereby obtaining an acrylic polymer solution II containing an acrylic polymer II having a terminal carbon-carbon double bond.

[0101] [Production Example 3] Preparation of Acrylic Polymer III

[0102] 90 parts by weight of lauryl methacrylate and 10 parts by weight of 2-hydroxyethyl methacrylate were mixed to prepare a monomer composition.

[0103] Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer. 43 parts by weight of toluene, 100 parts by weight of the monomer composition, and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were added under a nitrogen atmosphere and stirred at 60°C for 4 hours. The mixture was then cooled to room temperature, and 9 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to add NCO groups to the terminal OH groups of the side chains of 2-hydroxyethyl acrylate in the copolymer, thereby obtaining an acrylic polymer solution III containing an acrylic polymer III having a terminal carbon-carbon double bond.

[0104] [Production Example 4] Preparation of Acrylic Polymer IV

[0105] 100 parts by weight of 2-ethylhexyl acrylate, 25.5 parts by weight of acryloylmorpholine, and 18.5 parts by weight of hydroxyethyl acrylate were mixed to prepare a monomer composition.

[0106] Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer, and 60 parts by weight of toluene, 144 parts by weight of the above-mentioned monomer composition, and 0.3 parts by weight of benzoyl peroxide (BPO) were added under a nitrogen atmosphere, followed by stirring at 60°C for 4 hours. The mixture was then cooled to room temperature, and 12 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to add NCO groups to the terminal OH groups of the side chains of 2-hydroxyethyl acrylate in the copolymer, thereby obtaining an acrylic polymer solution IV containing an acrylic polymer IV having a terminal carbon-carbon double bond.

[0107] [Production Example 5] Preparation of Acrylic Polymer V

[0108] 70 parts by weight of ethyl acrylate, 30 parts by weight of 2-hydroxyethyl acrylate, 5 parts by weight of methyl methacrylate, and 4 parts by weight of hydroxyethyl acrylate were mixed to prepare a monomer composition.

[0109] Next, nitrogen gas was introduced into a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer, and 295 parts by weight of toluene, 109 parts by weight of the above-mentioned monomer composition, and 0.2 parts by weight of benzoyl peroxide (BPO) were added under a nitrogen atmosphere. The mixture was stirred at 60° C. for 4 hours to obtain an acrylic polymer solution V containing an acrylic polymer V having a weight-average molecular weight of 500,000.

[0110] [Example 1]

[0111] (Preparation of Adhesive)

[0112] To 100 parts by weight of an acrylic polymer solution I containing an acrylic polymer I were added 3 parts by weight of a crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industries, Ltd.) and 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 369" manufactured by BASF) to obtain an adhesive (1).

[0113] (Adhesive Sheet)

[0114] The adhesive (1) was applied to the silicone-treated surface of a PET separator (thickness: 38 μm), and then heated at 130° C. for 2 minutes to form an adhesive layer with a thickness of 5 μm.

[0115] A PET release film was laminated onto the adhesive layer using a hand roller to obtain an adhesive sheet with a release film.

[0116] The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0117] [Example 2]

[0118] A PSA sheet with a separator was obtained in the same manner as in Example 1 except that the amount of the photopolymerization initiator (manufactured by BASF, trade name "Irgacure 369") added was 10 parts by weight. The obtained PSA sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0119] [Example 3]

[0120] (Preparation of Adhesive)

[0121] To an acrylic polymer solution I containing 100 parts by weight of an acrylic polymer I were added 3 parts by weight of a crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.), 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 369" manufactured by BASF), and 5 parts by weight of an ultraviolet absorber (trade name "KEMISORB111" manufactured by CHEMIPRO KASEI, molecular weight: 244.2) to obtain an adhesive (3).

[0122] (Adhesive Sheet)

[0123] The adhesive (3) was applied to the silicone-treated surface of a PET separator (thickness: 38 μm), and then heated at 130° C. for 2 minutes to form an adhesive layer with a thickness of 5 μm.

[0124] A PET release film was laminated onto the adhesive layer using a hand roller to obtain an adhesive sheet with a release film.

[0125] The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0126] [Example 4]

[0127] A PSA sheet with a separator was obtained in the same manner as in Example 3, except that the amount of the UV absorber (manufactured by Chemipro Kasei, trade name "KEMISORB111", molecular weight: 244.2) was changed to 20 parts by weight. The obtained PSA sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0128] [Example 5]

[0129] A PSA sheet with a separator was obtained in the same manner as in Example 3, except that 5 parts by weight of a UV absorber (trade name "KEMISORB 71" manufactured by Chemipro Kasei, molecular weight: 225.3) was used instead of 5 parts by weight of the UV absorber (trade name "KEMISORB 111" manufactured by Chemipro Kasei, molecular weight: 244.2). The obtained PSA sheet with a separator was subjected to the above-described evaluation. The results are shown in Table 1.

[0130] [Example 6]

[0131] A PSA sheet with a separator was obtained in the same manner as in Example 3, except that 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 907" manufactured by BASF) was used instead of 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 369" manufactured by BASF), and 5 parts by weight of a UV absorber (trade name "Tinuvin 405" manufactured by BASF Japan, molecular weight: 583.8) was used instead of 5 parts by weight of a UV absorber (trade name "KEMISORB111" manufactured by CHEMIPRO KASEI, molecular weight: 244.2). The obtained PSA sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0132] [Example 7]

[0133] A PSA sheet with a separator was obtained in the same manner as in Example 3, except that 10 parts by weight of a photopolymerization initiator (BASF, trade name "Irgacure 907") was used instead of 3 parts by weight of a photopolymerization initiator (BASF, trade name "Irgacure 369"), and 5 parts by weight of a UV absorber (BASF Japan, trade name "Tinuvin 405," molecular weight: 583.8) was used instead of 5 parts by weight of a UV absorber (CHEMIPRO KASEI, trade name "KEMISORB111," molecular weight: 244.2). The obtained PSA sheet with a separator was subjected to the above-described evaluation. The results are shown in Table 1.

[0134] [Example 8]

[0135] A PSA sheet with a separator was obtained in the same manner as in Example 3, except that 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 127" manufactured by BASF) was used instead of 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 369" manufactured by BASF), and 5 parts by weight of a UV absorber (trade name "Tinuvin 405" manufactured by BASF Japan, molecular weight: 583.8) was used instead of 5 parts by weight of a UV absorber (trade name "KEMISORB 111" manufactured by CHEMIPRO KASEI, molecular weight: 244.2). The obtained PSA sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0136] [Example 9]

[0137] A PSA sheet with a separator was obtained in the same manner as in Example 3, except that 5 parts by weight of a UV absorber (trade name "Tinuvin PS" manufactured by BASF Japan, molecular weight: 267.3) was used instead of 5 parts by weight of a UV absorber (trade name "KEMISORB111" manufactured by CHEMIPRO KASEI, molecular weight: 244.2). The obtained PSA sheet with a separator was subjected to the above-described evaluation. The results are shown in Table 1.

[0138] [Example 10]

[0139] A PSA sheet with a separator was obtained in the same manner as in Example 3, except that the crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.) was added in an amount of 0.5 parts by weight and 5 parts by weight of a UV absorber (trade name "Tinuvin PS" manufactured by BASF Japan, molecular weight: 267.3) was used in place of 5 parts by weight of the UV absorber (trade name "KEMISORB111" manufactured by Chemipro Kasei, molecular weight: 244.2). The obtained PSA sheet with a separator was subjected to the above-described evaluation. The results are shown in Table 1.

[0140] [Example 11]

[0141] (Preparation of Adhesive)

[0142] To an acrylic polymer solution II containing 100 parts by weight of an acrylic polymer II were added 3 parts by weight of a crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industries, Ltd.), 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 369" manufactured by BASF), and 5 parts by weight of an ultraviolet absorber (trade name "Tinuvin PS" manufactured by BASF, molecular weight: 267.3) to obtain an adhesive (11).

[0143] (Adhesive Sheet)

[0144] The adhesive (11) was applied to the silicone-treated surface of a PET separator (thickness: 38 μm), and then heated at 130° C. for 2 minutes to form an adhesive layer with a thickness of 5 μm.

[0145] A PET release film was laminated onto the adhesive layer using a hand roller to obtain an adhesive sheet with a release film.

[0146] The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0147] [Example 12]

[0148] (Preparation of Adhesive)

[0149] To an acrylic polymer solution III containing 100 parts by weight of acrylic polymer III were added 5 parts by weight of a crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.), 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 369" manufactured by BASF), and 5 parts by weight of an ultraviolet absorber (trade name "Tinuvin PS" manufactured by BASF, molecular weight: 267.3) to obtain an adhesive (12).

[0150] (Adhesive Sheet)

[0151] The adhesive (12) was applied to the silicone-treated surface of a PET separator (thickness: 38 μm), and then heated at 130° C. for 2 minutes to form an adhesive layer with a thickness of 5 μm.

[0152] A PET release film was laminated onto the adhesive layer using a hand roller to obtain an adhesive sheet with a release film.

[0153] The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0154] [Example 13]

[0155] A PSA sheet with a separator was obtained in the same manner as in Example 12, except that 5 parts by weight of a crosslinking agent (trade name "Coronate HX" from Nippon Polyurethane Industries, Ltd.) was used instead of 5 parts by weight of a crosslinking agent (trade name "Coronate L" from Nippon Polyurethane Industries, Ltd.). The resulting PSA sheet with a separator was subjected to the aforementioned evaluation. The results are shown in Table 1.

[0156] [Comparative Example 1]

[0157] A pressure-sensitive adhesive sheet with a separator was obtained in the same manner as in Example 12 except that no ultraviolet absorber was added. The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0158] [Comparative Example 2]

[0159] (Preparation of Adhesive)

[0160] To an acrylic polymer solution I containing 100 parts by weight of an acrylic polymer I were added 5 parts by weight of a crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industries, Ltd.), 10 parts by weight of a photopolymerization initiator (trade name "Irgacure 651" manufactured by BASF), and 5 parts by weight of an ultraviolet absorber (trade name "Tinuvin 405" manufactured by BASF Japan, molecular weight: 583.8) to obtain an adhesive (C2).

[0161] (Adhesive Sheet)

[0162] The adhesive (C2) was applied to the silicone-treated surface of a PET separator (thickness: 38 μm), and then heated at 130° C. for 2 minutes to form an adhesive layer with a thickness of 5 μm.

[0163] A PET release film was laminated onto the adhesive layer using a hand roller to obtain an adhesive sheet with a release film.

[0164] The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0165] [Comparative Example 3]

[0166] (Preparation of Adhesive)

[0167] To 100 parts by weight of acrylic polymer solution IV containing acrylic polymer IV were added 3 parts by weight of a crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.), 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 369" manufactured by BASF), and 5 parts by weight of an ultraviolet absorber (trade name "Tinuvin 477" manufactured by BASF Japan, molecular weight: 583.8) to obtain an adhesive (C3).

[0168] (Adhesive Sheet)

[0169] The adhesive (C3) was applied to the silicone-treated surface of a PET separator (thickness: 38 μm), and then heated at 130° C. for 2 minutes to form an adhesive layer with a thickness of 5 μm.

[0170] A PET release film was laminated onto the adhesive layer using a hand roller to obtain an adhesive sheet with a release film.

[0171] The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0172] [Comparative Example 4]

[0173] A PSA sheet with a separator was obtained in the same manner as in Comparative Example 3, except that 5 parts by weight of a UV absorber (trade name "Tinuvin PS" manufactured by BASF Japan, molecular weight: 267.3) was used instead of 5 parts by weight of a UV absorber (trade name "Tinuvin 477" manufactured by BASF Japan, molecular weight: 583.8). The obtained PSA sheet with a separator was subjected to the above-described evaluation. The results are shown in Table 1.

[0174] [Comparative Example 5]

[0175] (Preparation of Adhesive)

[0176] To 100 parts by weight of acrylic polymer solution V containing acrylic polymer V were added 4 parts by weight of a crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.) and 20 parts by weight of an ultraviolet absorber (trade name "Tinuvin 477" manufactured by BASF Japan, molecular weight: 583.8) to obtain an adhesive (C5).

[0177] (Adhesive Sheet)

[0178] The adhesive (C5) was applied to the silicone-treated surface of a PET separator (thickness: 38 μm), and then heated at 130° C. for 2 minutes to form an adhesive layer with a thickness of 5 μm.

[0179] A PET release film was laminated onto the adhesive layer using a hand roller to obtain an adhesive sheet with a release film.

[0180] The obtained pressure-sensitive adhesive sheet with a separator was subjected to the above-mentioned evaluation. The results are shown in Table 1.

[0181] [Table 1]

[0182]

[0183] As shown in Table 1, the adhesive sheet exhibits excellent releasability when irradiated with a low-power laser (0.2 W or less) when its transmittance at a wavelength of 355 nm is 60% or less. Furthermore, the adhesive sheet of the present invention exhibits releasability without residual unevenness (i.e., without decomposition of the adhesive layer) by adjusting the intensity of the irradiated laser.

[0184] Description of Reference Numerals

[0185] 10 Adhesive layer

[0186] 20 substrate

[0187] 100, 200 adhesive sheets

Claims

1. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising a UV absorber and a photopolymerization initiator, The adhesive sheet has a light transmittance of 0.9% or more and 28.9% or less at a wavelength of 355 nm. The adhesive layer was irradiated with 300 mJ / cm 2 The layer has an indentation elastic modulus of 25 MPa or more at 23°C after exposure to ultraviolet rays. The ultraviolet absorber is a benzotriazole ultraviolet absorber, The content ratio of the ultraviolet absorber is 5 parts by weight or more and less than 20 parts by weight relative to 100 parts by weight of the base polymer. The adhesive layer is composed of an active energy ray-curable adhesive. The active energy ray-curable adhesive comprises, as a base polymer, an acrylic polymer serving as a masterbatch and an active energy ray-reactive compound capable of bonding to the acrylic polymer, or an active energy ray-reactive polymer having active energy ray-polymerizable carbon-carbon multiple bonds introduced into the side chain, main chain, and / or main chain terminal of the acrylic polymer. The initial adhesive force A at 23° C. immediately after the pressure-sensitive adhesive sheet is attached to a stainless steel plate is 0.8 N / 20 mm or more and less than 10 N / 20 mm.

2. The adhesive sheet according to claim 1, wherein The molecular weight of the compound constituting the ultraviolet absorber is 1,000 or less.

3. The adhesive sheet according to claim 1 or 2, wherein The adhesive sheet was attached to a stainless steel plate and irradiated with 300 mJ / cm 2 The adhesive strength B at 23°C after ultraviolet exposure was 0.2 N / 20 mm or less.

4. The adhesive sheet according to any one of claims 1 to 3, wherein The adhesive sheet was attached to a stainless steel plate and irradiated with 300 mJ / cm 2 The reduction rate of the adhesive strength B at 23° C. after ultraviolet exposure relative to the initial adhesive strength A at 23° C. immediately after the adhesive sheet was attached to the stainless steel plate was 90% or more.

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