Pressure-sensitive adhesive sheet and method for manufacturing laminate

Abstract

A purpose of the present invention is to provide a pressure-sensitive adhesive sheet which has excellent impact resistance although being obtained by ultraviolet curing. Another purpose of the present invention is to provide a method for producing a laminate including the pressure-sensitive adhesive sheet. This pressure-sensitive adhesive sheet is a cured object obtained from a pressure-sensitive adhesive composition containing a photopolymerization initiator. The pressure-sensitive adhesive sheet, when examined for dynamic viscoelasticity by a shear method under the conditions of measurement temperatures of from -70°C to 200°C and a frequency of 1 Hz, gives a viscoelasticity chart in which in cases when a lowest temperature at which the loss modulus is maximal is expressed by Ggtemp and a temperature that is the lowest among the temperatures at which the tanδ is maximal and which are higher than the Ggtemp is expressed by Tg and when a temperature that is the lowest among the temperatures at which the ratio between the storage modulus and the loss modulus is minimum and which are in a temperature range of from Tg to 50°C is expressed by GF1temp, a temperature that is the lowest among the temperatures at which the loss tangent is minimal in a range of temperatures higher than the GF1temp is expressed by GF2temp, and the loss tangent at the GF2temp is expressed by GF2tanδ, then the temperature difference between the Ggtemp and the GF1temp is 25.0°C or greater and the GF2tanδ is 0.34 or greater.

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a method for producing a laminate having the pressure-sensitive adhesive sheet. [Background technology]

[0002] Adhesives are used to bond electronic components inside electronic devices such as smartphones and PCs. A typical adhesive bonding method involves first preparing an adhesive sheet with separators on both sides of the adhesive, then cutting the adhesive sheet into the desired shape. One separator is then peeled off from the cut adhesive sheet, and one side of the exposed adhesive is bonded to a first adherend. The other separator is then peeled off, and the other side of the exposed adhesive is bonded to a second adherend. This method generates waste because a portion of the adhesive sheet is discarded after cutting. Furthermore, air bubbles can sometimes form at the bonded surface.

[0003] In response to this, a method has been investigated in which a pressure-sensitive adhesive composition is printed in a desired shape and then bonded to an adherend, without producing a pressure-sensitive adhesive sheet, which can reduce waste generation and prevent air bubbles from forming at the bonding surface.

[0004] For example, Patent Document 1 discloses an invention for providing a radiation-curable pressure-sensitive adhesive composition that allows for fine patterning and exhibits high adhesion to various adherends such as metals and plastics. Patent Document 1 describes a radiation-curable pressure-sensitive adhesive composition that contains 10 to 70% by weight of an aromatic ring-free ethylenically unsaturated monomer, 1 to 10% by weight of a photopolymerization initiator, and 10 to 55% by weight of a crosslinking agent.

[0005] Patent Document 2 discloses an invention for providing a photocurable adhesive composition that, even when irradiated with light in the presence of oxygen, gives a laminate having adhesive strength equivalent to that in the absence of oxygen. Patent Document 2 describes a photocurable adhesive composition that contains (A) a (meth)acrylate oligomer, (B) a monofunctional (meth)acrylic monomer, (C) a difunctional to tetrafunctional (meth)acrylic monomer, (D) a photoinitiator, (E) a tackifier having a softening point of 70 to 150°C, and (F) a liquid plasticizer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-216742 [Patent Document 2] International Publication No. 2016 / 163152 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, the method of printing a pressure-sensitive adhesive composition in a desired shape, forming a pressure-sensitive adhesive sheet, and then laminating the sheet to an adherend without preparing a pressure-sensitive adhesive sheet in advance can reduce waste generation and prevent air bubbles from being introduced into the lamination surface. On the other hand, as a method of curing the pressure-sensitive adhesive composition, ultraviolet curing is desirable from the viewpoints of avoiding heating of the adherend and reducing CO2 emissions, but the pressure-sensitive adhesive sheets obtained by ultraviolet curing have the problem of poor impact resistance.

[0008] An object of the present invention is to provide a pressure-sensitive adhesive sheet that is obtained by ultraviolet curing and yet has excellent impact resistance, and to provide a method for producing a laminate having the pressure-sensitive adhesive sheet. [Means for solving the problem]

[0009] Disclosure 1 provides a pressure-sensitive adhesive sheet that is a cured product of a pressure-sensitive adhesive composition containing a photopolymerization initiator, wherein in a viscoelasticity chart obtained by performing dynamic viscoelasticity measurement using a shear method at a measurement temperature of -70°C to 200°C and a frequency of 1 Hz, when Ggtemp is the temperature at which the loss modulus reaches its maximum on the lowest temperature side and Tg is the lowest temperature at which tanδ reaches its maximum in a range higher than Ggtemp, GF1temp is the lowest temperature in the temperature range from Tg to 50°C at which the ratio of storage modulus to loss modulus is minimum, GF2temp is the lowest temperature at which the loss tangent reaches its minimum in a range higher than GF1temp, and GF2tanδ is the loss tangent at GF2temp, the temperature difference between Ggtemp and GF1temp is 25.0°C or more and GF2tanδ is 0.34 or more. Disclosure 2 is a pressure-sensitive adhesive sheet of Disclosure 1, in which, when GEtemp is the temperature at which the storage modulus becomes a minimum in the region higher than GF2temp in the viscoelasticity chart, or 200°C if there is no temperature at which the storage modulus becomes a minimum in the region higher than GF2temp, GEtanδ is the loss tangent at said GEtemp, and delta tanδ is the value calculated by the formula (GEtanδ-GF2tanδ) / (GEtemp-GF2temp), the delta tanδ is -0.006 or more. Disclosure 3 is the pressure-sensitive adhesive sheet of Disclosure 1 or 2, wherein the temperature difference between the Ggtemp and GF1temp is 50.0°C or more. Disclosure 4 is the pressure-sensitive adhesive sheet of Disclosure 1, 2, or 3, in which the GF2tan δ is 0.50 or greater. The present disclosure 5 is a pressure-sensitive adhesive sheet according to claim 1, 2, 3 or 4, wherein the pressure-sensitive adhesive sheet has a 180° peel adhesive strength to a SUS substrate at 25°C of 6 N / cm or more after being aged for one day in an environment of 25°C and 50% RH. Disclosure 6 is the pressure-sensitive adhesive sheet of Disclosure 1, 2, 3, 4, or 5, wherein the pressure-sensitive adhesive composition contains a nitrogen-containing compound. Disclosure 7 is the pressure-sensitive adhesive sheet of Disclosure 6, wherein the nitrogen-containing compound includes a maleimide derivative. Disclosure 8 is the pressure-sensitive adhesive sheet of Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the pressure-sensitive adhesive composition comprises at least one selected from the group consisting of a hydrogen abstraction photopolymerization initiator and a polymeric photopolymerization initiator. A ninth aspect of the present disclosure is the pressure-sensitive adhesive sheet of the first, second, third, fourth, fifth, sixth, seventh, or eighth aspect of the present disclosure, wherein the pressure-sensitive adhesive composition contains a thermoplastic resin. Disclosure 10 is the PSA sheet of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the PSA composition contains a tackifier. Disclosure 11 is a method for producing a laminate in which the adhesive composition is partially coated on the first adherend, the method comprising the steps of applying the adhesive composition to a first adherend or a separator and exposing the applied adhesive composition to light to form an adhesive sheet according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, and attaching a second adherend to the adhesive sheet, the method for applying the adhesive composition being inkjet printing, screen printing, spray coating, spin coating, gravure offset, or reverse offset printing. The present invention will be described in detail below.

[0010] The present inventors have investigated how to make a pressure-sensitive adhesive sheet obtained by UV-curing a pressure-sensitive adhesive composition exhibit a specific behavior in a viscoelasticity chart obtained by performing dynamic viscoelasticity measurement under specific conditions, and as a result have found that a pressure-sensitive adhesive sheet with excellent impact resistance can be obtained, leading to the completion of the present invention.

[0011] In the pressure-sensitive adhesive sheet of the present invention, a viscoelasticity chart is obtained by performing dynamic viscoelasticity measurements using a shear method at temperatures from -70°C to 200°C and a frequency of 1 Hz. The temperature at which the loss modulus reaches its maximum on the lowest temperature side is defined as Ggtemp, and the lowest temperature at which tanδ reaches its maximum above Ggtemp is defined as Tg. The lowest temperature at which the ratio of storage modulus to loss modulus is minimum in the temperature range from Tg to 50°C is defined as GF1temp, and the lowest temperature at which the loss tangent reaches its minimum above GF1temp is defined as GF2temp. The loss tangent at GF2temp is defined as GF2tanδ. The lower limit of the temperature difference between Ggtemp and GF1temp is 25.0°C, and the lower limit of GF2tanδ is 0.34. A schematic diagram showing the relationship between Ggtemp, GF1temp, GF2temp, and GF2tanδ on the viscoelasticity chart is shown in Figure 1. When the temperature difference between the Ggtemp and GF1temp is 25.0°C or greater and the GF2tanδ is 0.34 or greater, the pressure-sensitive adhesive sheet of the present invention exhibits excellent impact resistance. The lower limit of the temperature difference between Ggtemp and GF1temp is preferably 40.0°C, and more preferably 50.0°C. There is no particular upper limit that is preferably set for the temperature difference between Ggtemp and GF1temp, but the practical upper limit is 120.0°C. The preferred lower limit of GF2tanδ is 0.50, and although there is no particular preferred upper limit of GF2tanδ, the substantial upper limit is 4.0.

[0012] In the pressure-sensitive adhesive sheet of the present invention, when GEtemp is the temperature at which the storage modulus becomes a minimum in the region higher than GF2temp in the viscoelasticity chart, or 200°C if there is no temperature at which the storage modulus becomes a minimum in the region higher than GF2temp, GEtanδ is the loss tangent at GEtemp, and the value calculated by the formula (GEtanδ-GF2tanδ) / (GEtemp-GF2temp) is deltatanδ, the preferred lower limit of deltatanδ is -0.006. When deltatanδ is -0.006 or greater, the pressure-sensitive adhesive sheet has better impact resistance. A more preferred lower limit of deltatanδ is 0.002. There is no particular preferred upper limit for the delta tan δ, but the substantial upper limit is 0.5.

[0013] Specifically, the viscoelasticity chart can be obtained by performing dynamic viscoelasticity measurement under the following conditions using a dynamic viscoelasticity measuring device, such as MCR-702e (manufactured by Anton Paar). <Condition> Shear method: Measured with twin drive using 8mm parallel plates Measurement temperature -70℃~200℃ Heating rate: 7°C / min Frequency: 1Hz While the temperature is decreasing from 50°C to -70°C at a rate of 10°C / min, the specimen is pre-pressed with 8N and measured from a low temperature as described below in (1) to (6). (1) Heat the specimen at a normal force of 20 N with a strain of 0.005% and measure under these conditions until the torque value falls below 1500 μN m. (2) After (1), the temperature was raised with a normal force of 8 N and a strain of 0.05%, and measurements were taken under these conditions until the torque value became less than 200 μN·m. (3) After (2), raise the temperature with a normal force of 3 N and a strain of 0.5%, and measure under these conditions until the torque value is less than 150 μN m. If the torque value in (3) is 150 μN m or more up to 120°C, proceed to (4). (4) After (3), raise the temperature with a normal force of 1.5 N and a strain of 2%, and measure under these conditions until the torque value is less than 100 μN m. If the torque value in (4) is 100 μN m or more up to 170°C, proceed to (5). (5) After (4), raise the temperature with a normal force of 1 N and a strain of 5%, and measure under these conditions until the torque value is less than 80 μN·m. If the torque value in (5) is 80 μN·m or more up to 190°C or if the thickness is less than 30 μm, proceed to (6). (6) After (5), the temperature is raised with a normal force of 1 N and a strain of 10%, and measurements are taken under these conditions until the temperature reaches 200°C. If the thickness becomes less than 20 μm before the temperature in (6) reaches 200°C, the measurement is terminated. If the storage modulus does not reach a minimum point up to this point, the temperature at 200°C or the end of the measurement is the GEtemp mentioned above.

[0014] The pressure-sensitive adhesive sheet of the present invention has a glass transition temperature of preferably -30°C at its lower limit and 20°C at its upper limit. By having the glass transition temperature in this range, the adhesive sheet can have better adhesion to various substrates. The more preferred upper limit of the glass transition temperature is 10°C. The tan δ peak temperature derived from the above-mentioned viscoelasticity chart can be determined as the glass transition temperature.

[0015] The pressure-sensitive adhesive sheet of the present invention has a 180° peel adhesive strength to a SUS substrate at 25°C of 6 N / cm, preferably at a lower limit thereof, after aging for one day in an environment of 25°C and 50% RH. When the 180° peel adhesive strength to a SUS substrate at 25°C is 6 N / cm or more, the resulting pressure-sensitive adhesive sheet can be suitably used for adhering electronic components and the like that require high adhesiveness. A more preferred lower limit of the 180° peel adhesive strength to a SUS substrate at 25°C is 8 N / cm. There is no particular upper limit to the 180° peel adhesive strength to a SUS substrate at 25° C., but the practical upper limit is 25 N / cm. Specifically, the 180° peel adhesive strength to a SUS substrate at 25° C. can be measured, for example, by the following method. That is, first, the adhesive composition described below was applied to a release PET film, and then the film was exposed to light at a wavelength of 365 nm and an illumination intensity of 20 mW / cm. 2 UV rays with a wavelength of 405 nm and an illuminance of 40 mW / cm 2 The total irradiation amount is 900mJ / cm 2 The film is cured by simultaneous irradiation so that the temperature is maintained at 100°C, yielding a 100 μm-thick cured product (adhesive sheet). The air side of the cured product is then sealed with an easily adhesive polyester film and cut to the specified size to produce a laminated film. The release PET film is then peeled off from the laminated film, and the exposed surface is attached to a SUS substrate and pressed back and forth with a 2 kg roller to obtain a test specimen. The resulting test specimen is then aged for one day at 25°C and 50% RH, after which a 180° peel test is performed at a speed of 300 mm / min using a universal testing machine to measure the 180° peel adhesive strength. Examples of such universal testing machines include the Tensilon RTI-1310 (manufactured by A&D Co., Ltd.).

[0016] The pressure-sensitive adhesive sheet of the present invention is a cured product of a pressure-sensitive adhesive composition containing a photopolymerization initiator. That is, the pressure-sensitive adhesive sheet of the present invention is an ultraviolet-cured product obtained by ultraviolet curing the pressure-sensitive adhesive composition. Since the pressure-sensitive adhesive sheet of the present invention is an ultraviolet-cured product of the pressure-sensitive adhesive composition, it can be said that it is produced using a production process that emits little CO2.

[0017] The pressure-sensitive adhesive composition preferably contains a nitrogen-containing compound, which allows the resulting pressure-sensitive adhesive sheet to have excellent surface curing properties.

[0018] Examples of the nitrogen-containing compound include maleimide derivatives, nitrogen-containing vinyl compounds, etc. Among these, maleimide derivatives are preferred. The reaction system of the maleimide derivative basically proceeds as a hydrogen abstraction (Type II) reaction. Photoradical polymerization by a hydrogen abstraction reaction is less susceptible to oxygen inhibition, and therefore can enhance surface curability. Furthermore, photoradical polymerization by a hydrogen abstraction reaction produces a branched polymer, rather than a linear polymer as in a cleavage (Type I) reaction, and also produces a high cohesive strength. Therefore, by including the maleimide derivative in the pressure-sensitive adhesive composition, it is possible to obtain a pressure-sensitive adhesive sheet that is less susceptible to bleeding due to reduced surface curability and cohesive failure due to reduced surface curability and cohesive strength. In this specification, the term "maleimide derivative" refers to a compound having a maleimide group.

[0019] Among the above maleimide derivatives, examples of monofunctional maleimides include N-cyclohexylmaleimide, N-laurylmaleimide, 4-hydroxyphenylmaleimide, N-(4-carboxycyclohexylmethyl)maleimide, N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-methylphenyl)maleimide, N-(2,6-diethylphenyl)maleimide, N-(2-chlorophenyl)maleimide, N-methylmaleimide, and N-ethylmaleimide. Examples of suitable monofunctional maleimides include N-isopropylmaleimide, N-butylmaleimide, N-benzylmaleimide, N-phenylmethylmaleimide, N-(2,4,6-tribromophenyl)maleimide, N-[3-(triethoxysilyl)propyl]maleimide, N-octadecenylmaleimide, N-dodecenylmaleimide, N-(2-methoxyphenyl)maleimide, N-(2,4,6-trichlorophenyl)maleimide, and N-(1-hydroxyphenyl)maleimide. Among these, maleimide derivatives that do not have a structure in which a hydrogen atom is bonded to a heteroatom are preferably selected from the viewpoint of increasing the reaction rate. Furthermore, maleimide derivatives that have a structure in which a hydrogen atom is bonded to a heteroatom may also be used from the viewpoint of improving adhesive strength. Specifically, the monofunctional maleimide is preferably at least one selected from the group consisting of N-cyclohexylmaleimide, 4-hydroxyphenylmaleimide, and N-(4-carboxycyclohexylmethyl)maleimide. Furthermore, examples of the polyfunctional maleimides among the maleimide derivatives include N,N'-methylene bismaleimide, N,N'-trimethylene bismaleimide, N,N'-dodecamethylene bismaleimide, N,N'-(4,4'-diphenylmethane) bismaleimide, 1,4-dimaleimidecyclohexane, isophorone bisurethane bis(N-ethylmaleimide), N,N'-p-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-m-toluylene bismaleimide, and N,N'-4,4'-biphenyl phenylene bismaleimide, N,N'-4,4'-(3,3'-dimethyl-biphenylene) bismaleimide, N,N'-4,4'-(3,3'-dimethyldiphenylmethane) bismaleimide, N,N'-4,4'-(3,3'-diethyldiphenylmethane) bismaleimide, N,N'-4,4'-diphenylpropane bismaleimide, N,N'-4,4'-diphenylether bismaleimide, N,N'-3,3'-diphenylsulfone bismaleimide, and N,N'-4,4'-diphenylsulfone bismaleimide. From the viewpoint of increasing the reaction rate, the above-mentioned monofunctional maleimide and these polyfunctional maleimides may be used in combination as the maleimide derivative. However, since the gel fraction increases, it is not preferable to use a large amount of polyfunctional maleimide in combination.

[0020] The nitrogen-containing vinyl compound is preferably an amide compound having a vinyl group, more preferably a cyclic amide compound having a vinyl group.

[0021] The cyclic amide compound having a vinyl group preferably has a lactam structure, and more preferably is a compound represented by the following formula (1).

[0022] [ka]

[0023] In formula (1), n ​​represents an integer of 2 to 6.

[0024] Examples of the compound represented by the above formula (1) include N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam, etc. Among these, N-vinyl-ε-caprolactam is preferred.

[0025] Among the above-mentioned amide compounds having a vinyl group, examples of compounds other than the above-mentioned cyclic amide compounds having a vinyl group include N-vinylacetamide.

[0026] The preferred lower limit of the content of the nitrogen-containing compound in 100 parts by mass of the pressure-sensitive adhesive composition is 0.4 parts by mass, and the preferred upper limit is 15 parts by mass. When the content of the nitrogen-containing compound is within this range, the resulting pressure-sensitive adhesive sheet has better surface curability and adhesion to various substrates. The more preferred lower limit of the content of the nitrogen-containing compound is 1.5 parts by mass, and the more preferred upper limit is 12 parts by mass.

[0027] The pressure-sensitive adhesive composition preferably contains a (meth)acrylic monomer. By containing the (meth)acrylic monomer, the resulting pressure-sensitive adhesive composition has better curability. In this specification, the term "(meth)acrylic" means acrylic or methacrylic, the term "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group, and the term "(meth)acryloyl" means acryloyl or methacryloyl.

[0028] The (meth)acrylic monomer preferably contains a monofunctional (meth)acrylic monomer from the viewpoint of adhesion to various substrates. In this specification, the term "monofunctional (meth)acrylic monomer" refers to a monomer having one (meth)acryloyl group in one molecule.

[0029] Examples of the monofunctional (meth)acrylic monomer include monofunctional (meth)acrylic acid ester compounds and monofunctional (meth)acrylamide compounds.

[0030] Examples of the monofunctional (meth)acrylic acid ester compound include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-heptyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. , cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, bicyclopentenyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, tetrahydrofurfuryl alcohol acrylic acid polymer ester, ethyl carbitol (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-Octafluoropentyl (meth)acrylate, imido (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxyethyl 2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl phosphate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, 2-(((butylamino)carbonyl)oxy)ethyl (meth)acrylate, (3-propyloxetan-3-yl)methyl (meth)acrylate, (3-butyloxetan-3-yl)methyl (meth)acrylate, (3-ethyloxetan-3-yl)ethyl (meth)acrylate , (3-ethyloxetan-3-yl)propyl (meth)acrylate, (3-ethyloxetan-3-yl)butyl (meth)acrylate, (3-ethyloxetan-3-yl)pentyl (meth)acrylate, (3-ethyloxetan-3-yl)hexyl (meth)acrylate, γ-butyrolactone (meth)acrylate, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-methyl-2-isobutyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-cyclohexyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, and cyclic trimethylolpropane formal acrylate. In this specification, the term "(meth)acrylate" means acrylate or methacrylate.

[0031] Examples of the monofunctional (meth)acrylamide compound include N,N-dimethyl(meth)acrylamide, N-(meth)acryloylmorpholine, N-hydroxyethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N,N-dimethylaminopropyl(meth)acrylamide.

[0032] The preferred lower limit of the content of the monofunctional (meth)acrylic monomer in 100 parts by mass of the pressure-sensitive adhesive composition is 15 parts by mass, and the preferred upper limit is 90 parts by mass. When the content of the monofunctional (meth)acrylic monomer is within this range, the resulting pressure-sensitive adhesive composition has better curability, and the resulting pressure-sensitive adhesive sheet has better adhesion to various substrates. The more preferred lower limit of the content of the monofunctional (meth)acrylic monomer is 20 parts by mass, and the more preferred upper limit is 60 parts by mass.

[0033] The (meth)acrylic monomer may contain a polyfunctional (meth)acrylic monomer, which serves as a cross-linking component.

[0034] Examples of the polyfunctional (meth)acrylic monomer include polyfunctional urethane (meth)acrylates, polyfunctional (meth)acrylic acid ester compounds, and polyfunctional epoxy (meth)acrylates. In this specification, the term "epoxy (meth)acrylate" refers to a compound in which all epoxy groups in an epoxy compound have been reacted with (meth)acrylic acid.

[0035] The polyfunctional urethane (meth)acrylate can be obtained, for example, by reacting an isocyanate compound with a (meth)acrylic acid derivative having a hydroxyl group in the presence of a catalytic amount of a tin compound.

[0036] Examples of isocyanate compounds that can be used as raw materials for the polyfunctional urethane (meth)acrylate include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatephenyl)thiophosphate, tetramethylxylylene diisocyanate, and 1,6,11-undecane triisocyanate.

[0037] Furthermore, as the isocyanate compound serving as a raw material for the polyfunctional urethane (meth)acrylate, a chain-extended isocyanate compound obtained by reacting a polyol with an excess of an isocyanate compound can also be used. Examples of the polyol include ethylene glycol, propylene glycol, glycerin, sorbitol, trimethylolpropane, carbonate diol, polyether diol, polyester diol, and polycaprolactone diol.

[0038] Examples of the (meth)acrylic acid derivative having a hydroxyl group include hydroxyalkyl mono(meth)acrylate, mono(meth)acrylate of a dihydric alcohol, and mono(meth)acrylate or di(meth)acrylate of a trihydric alcohol. Examples of the hydroxyalkyl mono(meth)acrylate include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate. Examples of the dihydric alcohol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol. Examples of the trihydric alcohol include trimethylolethane, trimethylolpropane, and glycerin.

[0039] Examples of the polyfunctional (meth)acrylic acid ester compound include 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-Propanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-added bisphenol A di(meth)acrylate, propylene oxide-added bisphenol A di(meth)acrylate, ethylene oxide-added bisphenol F di(meth)acrylate, dimethylol dicyclopentadiene Di(meth)acrylate, ethylene oxide modified isocyanuric acid di(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, carbonate diol di(meth)acrylate, polyether diol di(meth)acrylate, polyester diol di(meth)acrylate, polycaprolactone diol di(meth)acrylate, polybutadiene diol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, trimethyl Trimethylolpropane tri(meth)acrylate, ethylene oxide-added trimethylolpropane tri(meth)acrylate, propylene oxide-added trimethylolpropane tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, ethylene oxide-added isocyanuric acid tri(meth)acrylate, glycerin tri(meth)acrylate, propylene oxide-added glycerin tri(meth)acrylate , pentaerythritol tri(meth)acrylate, tris(meth)acryloyloxyethyl phosphate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc.

[0040] Examples of the polyfunctional epoxy(meth)acrylate include bisphenol A type epoxy(meth)acrylate, bisphenol F type epoxy(meth)acrylate, bisphenol E type epoxy(meth)acrylate, and caprolactone-modified versions of these.

[0041] The preferred lower limit of the content of the polyfunctional (meth)acrylic monomer in 100 parts by mass of the pressure-sensitive adhesive composition is 0.5 parts by mass, and the preferred upper limit is 10 parts by mass. When the content of the polyfunctional (meth)acrylic monomer is within this range, the resulting pressure-sensitive adhesive composition has superior cohesive strength, and the resulting pressure-sensitive adhesive sheet has superior adhesion to various substrates. The more preferred lower limit of the content of the polyfunctional (meth)acrylic monomer is 1.5 parts by mass, and the more preferred upper limit is 6 parts by mass.

[0042] The (meth)acrylic monomer preferably contains a monomer capable of acting as a hydrogen donor. The monomer capable of serving as a hydrogen donor is preferably a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond. When the monomer capable of serving as a hydrogen donor is a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond, it can more easily provide hydrogen to a hydrogen abstraction reaction. Of these, the monomer capable of serving as a hydrogen donor is more preferably a monomer having at least one structure selected from the group consisting of an ether bond, a phenoxy group, and an amide bond.

[0043] The (meth)acrylic monomer preferably contains 50% by mass or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond. When the (meth)acrylic monomer contains 50% by mass or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond, the resulting pressure-sensitive adhesive composition has superior surface curability. More preferably, the (meth)acrylic monomer contains 70% by mass or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond. The (meth)acrylic monomer may contain only a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond.

[0044] The pressure-sensitive adhesive composition contains a photopolymerization initiator. The photopolymerization initiator preferably comprises at least one selected from the group consisting of hydrogen abstraction photopolymerization initiators and polymeric photopolymerization initiators. By using at least one selected from the group consisting of hydrogen abstraction photopolymerization initiators and polymeric photopolymerization initiators as the photopolymerization initiator in combination with an amine compound described below, the resulting pressure-sensitive adhesive sheet is less susceptible to bleeding due to reduced surface curability and cohesive failure due to reduced surface curability and cohesive strength.

[0045] The hydrogen abstraction photopolymerization initiator is preferably a benzophenone-based photopolymerization initiator. Examples of the benzophenone-based photopolymerization initiator include benzophenone, 4-chlorobenzophenone, 4,4'-dimethylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, methyl o-benzoylbenzoate, 3,3'-dimethyl-4-methoxybenzophenone, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 4-morpholinobenzophenone, 4,4'-diphenoxybenzophenone, 4-hydroxybenzophenone, 2-carboxybenzophenone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methyl-propionyl)-benzyl)-phenyl)-2-methyl-propan-1-one, 1-(4-(4-benzoylphenylthio)phenyl)-2-tosyl-2-methyl-1-propanone, and 3-ketocoumarin.

[0046] Examples of the polymeric photopolymerization initiator include a polymer of ethyl (2,4,6-trimethylbenzoyl)-phenylphosphonate, polyethylene glycol di(β-4(4-(2-dimethylamino-2-benzyl)butanoylphenyl)piperazine)propionate, and bis(benzophenone-2-carboxylic acid) polyethylene glycol ester.

[0047] Among the above polymeric photopolymerization initiators, commercially available ones include, for example, Omnipol TP, Omnipol 910, and Omnipol 2702 (all manufactured by IGM Resins).

[0048] As the photopolymerization initiator, a cleavage type photopolymerization initiator can also be used. Examples of the cleavage-type photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0049] The preferred lower limit of the content of the photopolymerization initiator in 100 parts by mass of the pressure-sensitive adhesive composition is 1 part by mass, and the preferred upper limit is 15 parts by mass. By having the content of the photopolymerization initiator within this range, the resulting pressure-sensitive adhesive composition has better storage stability and curing properties, and the resulting pressure-sensitive adhesive sheet has better adhesion to various substrates. The more preferred lower limit of the content of the photopolymerization initiator is 3 parts by mass, and the more preferred upper limit is 8 parts by mass.

[0050] The pressure-sensitive adhesive composition preferably contains an amine compound. As described above, by using the amine compound in combination with at least one selected from the group consisting of the hydrogen abstraction photopolymerization initiator and the polymer photopolymerization initiator, the resulting pressure-sensitive adhesive sheet is less susceptible to bleeding due to reduced surface curability and cohesive failure due to reduced surface curability and cohesive strength.

[0051] Examples of the amine compound include (bis-N,N-(4-dimethylaminobenzoyl)oxyethylene-1-yl)-methylamine, bis(2-morpholinoethyl)ether, 1-methyl 10-(1,2,2,6,6-pentamethyl-4-piperidinyl) decanedioate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, and bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate.

[0052] The preferred lower limit of the content of the amine compound in 100 parts by mass of the pressure-sensitive adhesive composition is 0.5 parts by mass, and the preferred upper limit is 5 parts by mass. When the content of the amine compound is 0.5 parts by mass or more, the resulting pressure-sensitive adhesive composition has better surface curing properties. When the content of the amine compound is 5 parts by mass or less, the resulting pressure-sensitive adhesive sheet is less likely to suffer from cohesive failure. A more preferred lower limit of the content of the amine compound is 1.5 parts by mass, and a more preferred upper limit is 3 parts by mass.

[0053] The pressure-sensitive adhesive composition preferably contains a thermoplastic resin. The thermoplastic resin is preferably a compound that does not contain a reactive double bond, or a compound that has a reactive double bond but does not substantially exhibit photoradical polymerization reactivity.

[0054] Examples of the thermoplastic resin include solvent-free acrylic polymers and polymers obtained by drying a polymer dissolved in a solvent. Examples of the solvent-free acrylic polymer include a polymer of at least one monomer selected from (meth)acrylic acid alkyl esters having an alkyl group with 1 to 20 carbon atoms, or a copolymer of the monomer with another copolymerizable monomer. Commercially available solvent-free acrylic polymers include, for example, the ARUFON-UP1000 series, UH2000 series, and UC3000 series (all manufactured by Toagosei Co., Ltd.), the Clarity LA series, and the Clarity LK series (all manufactured by Kuraray Co., Ltd.).

[0055] The preferred lower limit of the content of the thermoplastic resin in 100 parts by mass of the pressure-sensitive adhesive composition is 5 parts by mass, and the preferred upper limit is 45 parts by mass. By having the content of the thermoplastic resin within this range, the viscosity of the resulting pressure-sensitive adhesive composition is improved, a thick coating film can be formed, printability is improved, and a decrease in adhesiveness at high temperatures can be suppressed. The more preferred lower limit of the content of the thermoplastic resin is 10 parts by mass, and the more preferred upper limit is 25 parts by mass.

[0056] The pressure-sensitive adhesive composition may contain a thermosetting resin or a moisture-curing resin, and thus may contain a material that exhibits reactivity to a trigger such as heat or moisture.

[0057] Examples of the thermosetting resin include epoxy resin, phenol resin, urea resin, melamine resin, etc. Among these, epoxy resin is preferred. Examples of the epoxy resin include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, biphenyl type epoxy resins, biphenyl novolac type epoxy resins, biphenol type epoxy resins, naphthalene type epoxy resins, fluorene type epoxy resins, phenol aralkyl type epoxy resins, naphthol aralkyl type epoxy resins, dicyclopentadiene type epoxy resins, anthracene type epoxy resins, epoxy resins having an adamantane skeleton, epoxy resins having a tricyclodecane skeleton, and epoxy resins having a triazine nucleus in the skeleton.

[0058] When the thermosetting resin is used, it is preferable that a thermosetting agent be contained in the pressure-sensitive adhesive composition. Examples of the heat curing agent include cyanate ester compounds (cyanate ester curing agents), phenol compounds (phenol heat curing agents), amine compounds (amine heat curing agents), thiol compounds (thiol heat curing agents), imidazole compounds, phosphine compounds, acid anhydrides, active ester compounds, and dicyandiamide. Furthermore, when an epoxy resin is used as the thermosetting resin, a photocationic polymerization initiator may be added to the pressure-sensitive adhesive composition. This facilitates gradual curing even after the first stage of irradiation with active energy rays. As a result, the resulting pressure-sensitive adhesive sheet has even better initial adhesive strength.

[0059] The photocationic polymerization initiator is not particularly limited as long as it generates a protonic acid or a Lewis acid upon irradiation with light, and may be either an ionic photoacid generating type or a nonionic photoacid generating type.

[0060] Examples of the ionic photoacid-generating photocationic polymerization initiator include the following: The cation moiety is an aromatic sulfonium, aromatic iodonium, aromatic diazonium, aromatic ammonium, or (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe cation, and the anion moiety is BF4- , PF6 - , SbF6 - , or (BX4) - The X represents a phenyl group substituted with at least two fluorine or trifluoromethyl groups.

[0061] Examples of the aromatic sulfonium salt include bis(4-(diphenylsulfonio)phenyl)sulfide bishexafluorophosphate, bis(4-(diphenylsulfonio)phenyl)sulfide bishexafluoroantimonate, bis(4-(diphenylsulfonio)phenyl)sulfide bistetrafluoroborate, bis(4-(diphenylsulfonio)phenyl)sulfide tetrakis(pentafluorophenyl)borate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, and diphenyl-4-(phenylthio)phenylsulfonium tetrakis(pentafluorophenyl)borate. , triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bishexafluorophosphate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bishexafluoroantimonate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bistetrafluoroborate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide tetrakis(pentafluorophenyl)borate, and the like.

[0062] Examples of the aromatic diazonium salt include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, and phenyldiazonium tetrakis(pentafluorophenyl)borate.

[0063] Examples of the aromatic ammonium salt include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, 1-benzyl-2-cyanopyridinium tetrafluoroborate, 1-benzyl-2-cyanopyridinium tetrakis(pentafluorophenyl)borate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluorophosphate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluoroantimonate, 1-(naphthylmethyl)-2-cyanopyridinium tetrafluoroborate, and 1-(naphthylmethyl)-2-cyanopyridinium tetrakis(pentafluorophenyl)borate.

[0064] Examples of the (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe salt include (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe(II) hexafluorophosphate, (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe(II) hexafluoroantimonate, (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe(II) tetrafluoroborate, and (2,4-cyclopentadien-1-yl)((1-methylethyl)benzene)-Fe(II) tetrakis(pentafluorophenyl)borate.

[0065] Examples of the nonionic photoacid-generating cationic photopolymerization initiator include nitrobenzyl esters, sulfonic acid derivatives, phosphate esters, phenolsulfonic acid esters, diazonaphthoquinone, and N-hydroxyimidesulfonates.

[0066] The above cationic photopolymerization initiators may be used alone or in combination of two or more. The content of the cationic photopolymerization initiator is preferably 0.1 parts by mass at the lower limit and 10 parts by mass at the upper limit relative to 100 parts by mass of the epoxy resin.

[0067] Examples of the moisture-curing resin include moisture-curing urethane resins and resins having crosslinkable silyl groups. Among these, moisture-curing urethane resins are preferred. Moisture-curing urethane resins have a urethane bond and an isocyanate group, and the isocyanate group in the molecule reacts with moisture to cure. The isocyanate group is preferably located at the end of the molecule. The moisture-curable urethane resin may have a radical-reactive functional group. The moisture-curable urethane resin can be obtained by reacting a polyol compound having two or more hydroxyl groups in one molecule with a polyisocyanate compound having two or more isocyanate groups in one molecule.

[0068] When the moisture-curable resin is used, it is preferable to add a moisture-curing accelerator to the pressure-sensitive adhesive composition in order to improve the curing rate during moisture curing. Examples of the moisture-curing accelerator include compounds having a morpholine skeleton, compounds having a piperidine skeleton, and compounds having a piperazine skeleton.

[0069] The pressure-sensitive adhesive composition preferably contains a tackifier. Examples of the tackifier include rosin-based resins and terpene-based resins.

[0070] Examples of the rosin-based resin include rosin diol. The rosin diol is not particularly limited as long as it is a rosin-modified diol having two rosin skeletons and two hydroxyl groups in the molecule. Diols having a rosin component in the molecule are called rosin polyols, and these include polyether types such as polypropylene glycol (PPG) in which the skeleton excluding the rosin component is polyether, and polyester types such as condensation polyester polyols, lactone polyester polyols, and polycarbonate diols. Examples of the rosin diol include rosin esters obtained by reacting rosin with polyhydric alcohols, epoxy-modified rosin esters obtained by reacting rosin with epoxy compounds, and modified rosins having hydroxyl groups, such as polyethers having a rosin skeleton, etc. These can be produced by conventionally known methods.

[0071] Examples of the rosin component include pimaric acid-type resin acids such as abietic acid and its derivatives, such as dehydroabietic acid, dihydroabietic acid, tetrahydroabietic acid, diabietic acid, neoabietic acid, and levopimaric acid; hydrogenated rosins obtained by hydrogenating these; and disproportionated rosins obtained by disproportionating these.

[0072] Commercially available examples of the rosin-based resins include Pine Crystal D-6011, Pine Crystal KE-615-3, Pine Crystal KR-614, Pine Crystal KE-100, Pine Crystal KE-311, Pine Crystal KE-359, Pine Crystal KE-604, and Pine Crystal D-6250 (all manufactured by Arakawa Chemical Industries, Ltd.).

[0073] Examples of the terpene resin include terpene phenol resin. The terpene phenol resin is a copolymer of phenol and a terpene resin, which is an essential oil component obtained from natural products such as pine resin and orange peel, and also includes partially hydrogenated terpene phenol resins in which at least a portion of the copolymer is hydrogenated, and fully hydrogenated terpene phenol resins in which the copolymer is completely hydrogenated. Here, the fully hydrogenated terpene phenolic resin is a terpene resin obtained by substantially completely hydrogenating a terpene phenolic resin, and the partially hydrogenated terpene phenolic resin is a terpene resin obtained by partially hydrogenating a terpene phenolic resin. The terpene phenolic resin has a terpene-derived double bond and an aromatic ring double bond derived from a phenol. Therefore, the fully hydrogenated terpene phenolic resin means a resin in which both the terpene moiety and the phenol moiety are completely or almost completely hydrogenated, and the partially hydrogenated terpene phenolic resin means a resin in which the degree of hydrogenation of these moieties is partial rather than complete. The hydrogenation method and reaction format are not particularly limited. Among the above terpene phenol-based resins, commercially available ones include, for example, YS Polystar NH (fully hydrogenated terpene phenol-based resin) manufactured by Yasuhara Chemical Co., Ltd.

[0074] The preferred lower limit of the tackifier content per 100 parts by mass of the PSA composition is 5 parts by mass, and the preferred upper limit is 50 parts by mass. By ensuring that the tackifier content is within this range, the resulting PSA sheet will have better adhesion to various substrates. The more preferred lower limit of the tackifier content is 15 parts by mass, and the more preferred upper limit is 35 parts by mass.

[0075] The pressure-sensitive adhesive composition may contain a plasticizer. Examples of the plasticizer include organic acid esters, organic phosphates, and organic phosphites.

[0076] Examples of the organic acid ester include monobasic organic acid esters and polybasic organic acid esters. Examples of the monobasic organic acid ester include glycol esters obtained by reacting a monobasic organic acid such as butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptyl acid, n-octylic acid, 2-ethylhexyl acid, pelargonic acid (n-nonylic acid), or decylic acid with a glycol such as triethylene glycol, tetraethylene glycol, or tripropylene glycol. Examples of the polybasic organic acid ester include ester compounds obtained by reacting a polybasic organic acid such as adipic acid, sebacic acid, or azelaic acid with an alcohol having a linear or branched structure and 4 to 8 carbon atoms.

[0077] Specific examples of the organic acid esters include triethylene glycol di-2-ethylbutyrate (3GH), triethylene glycol di-2-ethylhexanoate (3GO), triethylene glycol dicaprylate, triethylene glycol di-n-octanoate, and triethylene glycol di-n-heptanoate (3G7). Other examples include tetraethylene glycol di-n-heptanoate (4G7), tetraethylene glycol di-2-ethylhexanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol di-2-ethylbutyrate, and 1,3-propylene glycol di-2-ethylbutyrate. Further examples include 1,4-butylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylhexanoate, and dipropylene glycol di-2-ethylbutyrate. Other examples include triethylene glycol di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate (4GH), diethylene glycol dicaprylate, dihexyl adipate (DHA), dioctyl adipate, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, etc. Other examples include oil-modified sebacic acid alkyd, a mixture of a phosphate ester and an adipate ester, and a mixed adipate ester made from an alkyl alcohol having 4 to 9 carbon atoms and a cyclic alcohol having 4 to 9 carbon atoms.

[0078] The organic phosphate or organic phosphite ester may be a compound obtained by a condensation reaction between phosphoric acid or phosphorous acid and an alcohol, and among these, a compound obtained by a condensation reaction between an alcohol having 1 to 12 carbon atoms and phosphoric acid or phosphorous acid is preferred. Examples of the alcohol having 1 to 12 carbon atoms include methanol, ethanol, butanol, hexanol, 2-ethylbutanol, heptanol, octanol, 2-ethylhexanol, decanol, dodecanol, butoxyethanol, butoxyethoxyethanol, and benzyl alcohol. Examples of the organic phosphate ester or organic phosphite ester include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, tri(2-ethylhexyl) phosphate, tri(butoxyethyl) phosphate, tri(2-ethylhexyl) phosphite, isodecylphenyl phosphate, and triisopropyl phosphate.

[0079] The pressure-sensitive adhesive composition may contain an antifoaming agent. Examples of the antifoaming agent include silicone-based antifoaming agents, acrylic polymer-based antifoaming agents, vinyl ether polymer-based antifoaming agents, and olefin polymer-based antifoaming agents.

[0080] The pressure-sensitive adhesive composition may further contain various known additives such as a crosslinking agent, a viscosity modifier, a silane coupling agent, a sensitizer, a heat curing agent, a cure retarder, an antioxidant, a storage stabilizer, a dispersant, and a filler, within the scope of not impairing the object of the present invention. Furthermore, from the viewpoint of preventing a decrease in ultraviolet reactivity, it is preferable that the pressure-sensitive adhesive composition be substantially free of organic solvents, and specifically, it is preferable that the content of organic solvents per 100 mass parts of the pressure-sensitive adhesive composition be 1.5 mass parts or less.

[0081] Examples of methods for preparing the pressure-sensitive adhesive composition include a method of using a mixer to mix the nitrogen-containing compound, the (meth)acrylic monomer, the photopolymerization initiator, a thermoplastic resin, additives added as needed, etc. Examples of the mixer include a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, and a three-roll mill.

[0082] The viscosity of the pressure-sensitive adhesive composition at 25°C is preferably 5 mPa·s at its lower limit and 250,000 mPa·s at its upper limit. Having the viscosity in this range makes the pressure-sensitive adhesive composition more suitable for printing. The viscosity is more preferably 100 mPa·s at its lower limit and 150,000 mPa·s at its upper limit. The viscosity can be measured, for example, using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer, using an appropriate cone plate depending on the viscosity range of the pressure-sensitive adhesive composition, under conditions of 25°C and 10 rpm.

[0083] The pressure-sensitive adhesive sheet of the present invention is formed by irradiating the pressure-sensitive adhesive composition with ultraviolet light to cure it. The pressure-sensitive adhesive sheet of the present invention may be formed on a substrate (separator) and be transferable to an adherend, or may be formed directly on the adherend. When the pressure-sensitive adhesive sheet of the present invention is formed directly on the adherend, the number of times of lamination can be minimized and air bubbles can be prevented from being introduced at the interface during lamination. On the other hand, when the pressure-sensitive adhesive sheet of the present invention is formed on a substrate (separator), the pressure-sensitive adhesive sheet is placed on the adherend by transfer, which has the advantage of fewer constraints on application.

[0084] The thickness of the pressure-sensitive adhesive sheet of the present invention is preferably 30 μm or more, more preferably 50 μm or more. By having the thickness of the pressure-sensitive adhesive layer of 30 μm or more, sufficient adhesion can be obtained. Furthermore, in order to accommodate the trend toward thinner electronic devices, the thickness of the pressure-sensitive adhesive layer is preferably 1000 μm or less, more preferably 500 μm or less.

[0085] The present invention also includes a method for producing a laminate, which includes the steps of applying the pressure-sensitive adhesive composition to a first adherend or a separator and exposing the composition to light to form the pressure-sensitive adhesive sheet of the present invention, and attaching a second adherend to the pressure-sensitive adhesive layer, the method for applying the pressure-sensitive adhesive composition being inkjet printing, screen printing, spray coating, spin coating, gravure offset, or reverse offset printing, and in which the pressure-sensitive adhesive composition is partially applied to the first adherend. When the pressure-sensitive adhesive sheet of the present invention is formed on the separator, the step of transferring the obtained pressure-sensitive adhesive sheet to the first adherend is performed, followed by the step of attaching the second adherend to the pressure-sensitive adhesive layer.

[0086] Examples of the material for the first adherend and the second adherend include metals such as stainless steel and aluminum, and resins. [Effects of the Invention]

[0087] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that is obtained by ultraviolet curing and yet has excellent impact resistance. Furthermore, according to the present invention, it is possible to provide a method for producing a laminate having the pressure-sensitive adhesive sheet. [Brief explanation of the drawings]

[0088] [Figure 1] FIG. 1 is a schematic diagram showing the relationship between Ggtemp, GF1temp, GF2temp, and GF2tanδ in a viscoelasticity chart. DETAILED DESCRIPTION OF THE INVENTION

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0090] ( Reference example 1~ 5, 7-10, 15-17, Examples 6, 11-14, 18, Comparative Examples 1 to 7) (1) Preparation of adhesive composition According to the compounding ratios shown in Tables 1 to 3, the materials except for the crosslinking agent were mixed in a planetary mixer (Thinky Corporation, "Awatori Rentaro") to obtain pressure-sensitive adhesive compositions. Details of the materials indicated by abbreviations in the table are as follows: (nitrogen-containing compounds) CHMI: N-cyclohexylmaleimide (Nippon Shokubai Co., Ltd.) NVC: N-vinyl-ε-caprolactam (Tokyo Chemical Industry Co., Ltd.) ((Meth)acrylic monomer) CBA: Ethyl carbitol acrylate (Osaka Organic Chemical Industry Co., Ltd., "Viscoat #190", containing ether bonds) MEDOL-10: (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (Osaka Organic Chemical Industry, Ltd., contains an ether bond) IDAA: Isodecyl acrylate (Osaka Organic Chemical Industry Co., Ltd.) IBOA: Isobornyl acrylate (Nippon Shokubai Co., Ltd.) Viscoat #216: 2-butylcarbamoyloxyethyl acrylate (Osaka Organic Chemical Industry, containing amide bond) 4-HBA: 4-hydroxybutyl acrylate (Mitsubishi Chemical Corporation) UA-160TM: Polyether-based multifunctional urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) AB-6: Acrylic compound with an acryloyl group at one end (manufactured by Toagosei Co., Ltd.) HPVM-L1253: An olefin-based compound with a methacryloyl group at one end (Kraton Polymer Japan) (Photopolymerization initiator) Omnirad 184: 1-hydroxycyclohexyl phenyl ketone (IGM Resins, cleavage-type photoinitiator) Omnirad TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by IGM Resins, cleavage-type photoinitiator) Esacure TZT: A mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (manufactured by IGM Resins, a hydrogen abstraction photoinitiator) Esacure 3644: 3-ketocoumarin (IGM Resins, hydrogen abstraction photoinitiator) Omnipol TP: Ethyl (2,4,6-trimethylbenzoyl)-phenylphosphinate polymer (IGM Resins, polymeric photoinitiator) Omnipol 910: Polyethylene glycol di(β-4(4-(2-dimethylamino-2-benzyl)butanoylphenyl)piperazine)propionate (IGM Resins, polymeric photoinitiator) Omnipol 2702: Bis(benzophenone-2-carboxylic acid) polyethylene glycol ester (IGM Resins, polymeric photoinitiator) (thermoplastic resin) LA2140: Acrylic block copolymer (Kuraray) LK9333: Acrylic block copolymer (manufactured by Kuraray) Acrylic polymer A: synthesized by the method described below Acrylic polymer B: Synthesized by the method described below (tackifier) KE-359: Rosin resin (manufactured by Arakawa Chemical Industries, Ltd.) (Crosslinking agent) Millionate MR: Polymeric MDI (manufactured by Tosoh Corporation) Coronate L: Toluene diisocyanate (manufactured by Tosoh Corporation) (amine compounds) ADK STAB LA-52: Tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate Eversorb 93: Mixture of bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 1-methyl 10-(1,2,2,6,6-pentamethyl-4-piperidinyl) decanedioate (Antifoaming agent) KS-66: An oil compound type defoamer made by blending silicon oil with finely powdered silica (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0091] (Acrylic polymer A) A 2-L separable flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser was charged with 50 parts by weight of ethyl acetate as the polymerization solvent. After heating to reflux, 0.4 parts by weight of 2,2'-azobis(isobutyronitrile) was added as a polymerization initiator. 77 parts by weight of butyl acrylate, 17 parts by weight of 2-ethylhexyl acrylate, 0.01 parts by weight of 2-hydroxyethyl acrylate, 6 parts by weight of acrylic acid, and 0.15 parts by weight of 1-thioglycerol as a chain transfer agent were mixed and added dropwise to the separable flask using a dropping funnel over 2 hours. The time when the dropping began was defined as the polymerization initiation time. The polymerization reaction was carried out at 60°C for 6 hours from the initiation of polymerization to obtain an acrylic polymer solution. The resulting solution was heated and dried to obtain Acrylic Polymer A.

[0092] (Acrylic polymer B) A 2-L separable flask equipped with a thermometer, stirrer, nitrogen inlet, and condenser was charged with 80 parts by weight of ethyl acetate as the polymerization solvent. After heating to reflux, 0.1 parts by weight of 2,2'-azobis(isobutyronitrile) was added as a polymerization initiator. 18 parts by weight of 2-ethylhexyl acrylate, 79 parts by weight of n-heptyl acrylate, 0.2 parts by weight of 2-hydroxyethyl acrylate, 3 parts by weight of acrylic acid, and 0.05 parts by weight of dodecanethiol as a chain transfer agent were mixed and added dropwise to the separable flask using a dropping funnel over 2 hours. The time when the dropping began was defined as the polymerization initiation time. The polymerization reaction was carried out at 80°C for 6 hours from the initiation of polymerization to obtain an acrylic polymer solution. The resulting solution was heated and dried to obtain Acrylic Polymer B.

[0093] (2) Preparation of adhesive sheet ( Reference example 1~4 、 7, 9 , 10, 15-17, Examples 6, 11-14, 18, Comparative Example 2) The obtained pressure-sensitive adhesive composition was applied to the inner treated surface of a release PET film (manufactured by Nippa Corporation, "1-C", thickness 38 μm) using an applicator to a thickness of 100 μm. Reference example 2, 3, 7, 9 、 16, 17 , and Examples 12 and 13For these adhesive compositions, a crosslinking agent was mixed into the adhesive composition before coating to the content shown in Tables 1 to 3. Next, without sealing the coated surface, the adhesive composition was cured in an atmospheric environment using a batch-type UV LED curing device at a wavelength of 365 nm and an illuminance of 20 mW / cm. 2 UV rays with a wavelength of 405 nm and an illuminance of 40 mW / cm 2 The total irradiation amount is 900mJ / cm 2 The adhesive composition was cured to obtain an adhesive sheet by simultaneously irradiating the two UV LEDs at the same time so that the curing temperature was 100°C or higher. The batch-type UV LED curing device used was an M UVBA (manufactured by ITEC Co., Ltd.). The air side of the adhesive sheet was then sealed with a PET sheet ("1-E" manufactured by Nippa Co., Ltd., thickness 50 μm) that had been release-treated on one side, to obtain a laminate including the adhesive sheet. The pressure-sensitive adhesive sheet obtained by this method is formed by irradiating the pressure-sensitive adhesive composition only with ultraviolet light without heating it, and therefore can be said to have an excellent effect in reducing CO2 emissions. Furthermore, the pressure-sensitive adhesive sheet obtained by this method without using acrylic polymers A and B, which are produced by heating, can be said to have an excellent effect in reducing CO2 emissions.

[0094] ( Reference example 5, 8, Comparative Example 1) The obtained pressure-sensitive adhesive composition was applied to the inner treated surface of a release PET film (manufactured by Nippa Corporation, "1-C", thickness 38 μm) using an applicator to a thickness of 100 μm. Reference example For the adhesive compositions according to Comparative Example 1 and Comparative Example 5, a crosslinking agent was mixed into the adhesive composition before coating to the content shown in Tables 1 and 3. Next, the surface facing the atmosphere was sealed with a release PET film (Nippa Corporation's "1-E", thickness 50 μm). In this sealed state, a batch-type UV LED curing device was used to cure the adhesive composition with a wavelength of 365 nm and an illuminance of 4 mW / cm. 2 UV rays with a wavelength of 405 nm and an illuminance of 4 mW / cm 2 The total irradiation amount is 1500mJ / cm 2 The pressure-sensitive adhesive composition was cured by simultaneously irradiating the two layers so that a laminate including the pressure-sensitive adhesive sheet was obtained. The pressure-sensitive adhesive sheet obtained by this method is also formed by irradiating the pressure-sensitive adhesive composition only with ultraviolet light without heating it, and therefore can be said to have an excellent effect in reducing CO2 emissions. Furthermore, the pressure-sensitive adhesive sheet obtained by this method without using acrylic polymers A and B, which are produced by heating, can be said to have an excellent effect in reducing CO2 emissions.

[0095] (Comparative Examples 3 to 7) A 2-L separable flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser was charged with 70 parts by mass of ethyl acetate and 40 parts by mass of acetone as polymerization solvents, heated to reflux, and then 0.05 parts by mass of 2,2'-azobis(isobutyronitrile) was added as a polymerization initiator. The resulting pressure-sensitive adhesive composition was then added dropwise to the separable flask over 2 hours using a dropping funnel. The time when the dropping began was taken as the polymerization initiation time, and the polymerization reaction was carried out at 60°C for 6 hours from the initiation of polymerization, yielding a polymer solution. The resulting polymer solution was mixed with a crosslinking agent in the amounts shown in Table 3, and then coated using an applicator onto a release PET film (Nippa Corporation, "1-C", thickness 38 μm) so that the thickness after drying would be 100 μm, yielding an adhesive sheet. Drying was carried out at 40°C for 20 minutes, at 60°C for 20 minutes, and at 110°C for 10 minutes, in that order. The air side of the adhesive sheet was then sealed with a PET sheet (Nippa Corporation, "1-E", thickness 50 μm) that had been release-treated on one side, yielding a laminate including the adhesive sheet. It should be noted that the pressure-sensitive adhesive sheet obtained by this method is formed by heating the pressure-sensitive adhesive composition, and therefore is inferior in terms of the effect of reducing CO2 emissions.

[0096] (3) Dynamic viscoelasticity measurement Both release PET films were peeled from the resulting laminate containing the pressure-sensitive adhesive sheet, and dynamic viscoelasticity measurements were performed on the pressure-sensitive adhesive sheet under the following conditions to obtain a viscoelasticity chart. The dynamic viscoelasticity measurement device used was an MCR-702e (manufactured by Anton Paar) or similar. From the resulting viscoelasticity chart, Ggtemp, GF1temp, the temperature difference between Ggtemp and GF1temp, GF2temp, GF2tanδ, GEtemp, GEtanδ, and delta tanδ were calculated. The tanδ peak temperature calculated from the resulting viscoelasticity chart was also determined as the glass transition temperature (Tg). The results are shown in Tables 1 to 3. <Condition> Shear method: Measured with twin drive using 8mm parallel plates Measurement temperature -70℃~200℃ Heating rate: 7°C / min Frequency: 1Hz While the temperature is decreasing from 50°C to -70°C at a rate of 10°C / min, pre-pressure is applied at 8N, and measurements are taken from the low temperature as described below in (3-1) to (3-6). (3-1) Heat the specimen at a normal force of 20 N with a strain of 0.005% and measure under these conditions until the torque value becomes less than 1500 μN m. (3-2) After (3-1), the temperature is increased with a normal force of 8 N and a strain of 0.05%, and measurements are taken under these conditions until the torque value becomes less than 200 μN·m. (3-3) After (3-2), raise the temperature with a normal force of 3N and a strain of 0.5%, and measure under these conditions until the torque value is less than 150μN·m. If the torque value in (3-3) is 150μN·m or more up to 120℃, proceed to (3-4). (3-4) After (3-3), raise the temperature with a normal force of 1.5 N and a strain of 2%, and measure under these conditions until the torque value is less than 100 μN m. If the torque value in (3-4) is 100 μN m or more up to 170°C, proceed to (3-5). (3-5) After (3-4), raise the temperature with a normal force of 1 N and a strain of 5%, and measure under these conditions until the torque value is less than 80 μN m. If the torque value in (3-5) is 80 μN m or more up to 190 °C or if the thickness is less than 30 μm, proceed to (3-6). (3-6) After (3-5), the temperature is raised with a normal force of 1 N and a strain of 10%, and measurements are taken under these conditions until the temperature reaches 200°C. If the thickness becomes less than 20 μm before the temperature in (3-6) reaches 200°C, the measurement is terminated. If the storage modulus does not reach a minimum point up to this point, the temperature at 200°C or the end of the measurement is the GEtemp mentioned above.

[0097] <Evaluation> Reference example, Example 、 and 、 The pressure-sensitive adhesive sheets obtained in the comparative examples were evaluated as follows, and the results are shown in Tables 1 to 3.

[0098] (180° peel adhesive strength) The resulting laminate including the pressure-sensitive adhesive sheet was cut into a width of 75 mm and a length of 125 mm, and one of the release PET films was peeled off and transferred to the inner treated surface of an easy-adhesion polyester film ("Cosmoshine A4100" manufactured by Toyobo Co., Ltd.), which was then cut into a width of 25 mm and a length of 200 mm (adhesion surface 25 mm x 125 mm) to obtain a laminate film. The other release PET film was then peeled off from the laminate film, and the exposed surface was attached to a SUS 304-BA substrate with a width of 80 mm, a length of 125 mm, and a thickness of 1 mm. The resulting film was then pressed back and forth with a 2 kg roller to obtain a test specimen. The obtained test pieces were cured for one day in an environment of 25°C and 50% RH, and then the 180° peel adhesive strength was measured by performing a 180° peel at a speed of 300 mm / min using a universal testing machine (A&D Co., Ltd., "Tensilon RTI-1310").

[0099] (shock resistance) The resulting laminate, including the adhesive sheet, was cut into a 25mm x 25mm piece, and both release PET films were peeled off. A 40mm x 40mm x 3mm SUS substrate with a 20mm x 20mm x 3mm hole in the center was then bonded to a 25mm x 25mm x 3mm SUS substrate via the adhesive sheet to obtain a laminate. The resulting laminate was then compressed at 62N using a universal testing machine (A&D Co., Ltd., "Tensilon RTI-1310") to prepare test specimens. The center of the test specimen was impacted by gravity dropping a 16mm diameter, 5kg weight from a height of 51mm using a drop weight tester (IMATEK Co., Ltd., "IM1C-15"). From the spectrum of ms vs. N, the area of ​​the first peak (amount of energy) was calculated as the impact absorption rate ΔE (J). The maximum point was taken as the peak force (impact resistance test force (N)). The impact resistance was evaluated according to the following criteria. ◎: When ΔE exceeds 0.345J or when peak force exceeds 1.60N ○: ΔE is 0.120 J or more and 0.345 J or less, and the peak force is 1.20 N or more and 1.60 N or less ×: ΔE is less than 0.120 J and the peak force is 1.20 N or more and 1.60 N or less, or ΔE is 0.120 J or more and 0.345 J or less and the peak force is less than 1.20 N ××: ΔE is less than 0.120 J and the peak force is less than 1.20 N

[0100] [Table 1]

[0101] [Table 2]

[0102] [Table 3] [Industrial Applicability]

[0103] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that is obtained by ultraviolet curing and yet has excellent impact resistance. Furthermore, according to the present invention, it is possible to provide a method for producing a laminate having the pressure-sensitive adhesive sheet.

Claims

1. A pressure-sensitive adhesive sheet that is a cured product of a pressure-sensitive adhesive composition that contains a monofunctional (meth)acrylic monomer, at least one of a polyfunctional (meth)acrylic monomer and a crosslinking agent, a tackifier, and a photopolymerization initiator, the monofunctional (meth)acrylic monomer comprises at least one selected from the group consisting of a monofunctional (meth)acrylic acid ester compound and a monofunctional (meth)acrylamide compound, and the content of the monofunctional (meth)acrylic monomer per 100 parts by mass of the pressure-sensitive adhesive composition is 15 parts by mass or more and 90 parts by mass or less; the polyfunctional (meth)acrylic monomer includes at least one selected from the group consisting of a polyfunctional urethane (meth)acrylate, a polyfunctional (meth)acrylic acid ester compound, and a polyfunctional epoxy (meth)acrylate; the tackifier comprises at least one selected from the group consisting of a rosin-based resin and a terpene-based resin, and the content of the tackifier in 100 parts by mass of the PSA composition is 5 parts by mass or more and 50 parts by mass or less; In a viscoelasticity chart obtained by performing dynamic viscoelasticity measurement under the conditions of a shear method, a measurement temperature of -70°C to 200°C, and a frequency of 1 Hz, When the temperature at which the loss modulus reaches its maximum value on the lowest temperature side is defined as Ggtemp, and the lowest temperature among the temperatures at which tanδ reaches its maximum value in a region higher than Ggtemp is defined as Tg, the lowest temperature in the temperature region from Tg to 50°C among the temperatures at which the ratio of the storage modulus to the loss modulus is minimum is defined as GF1temp, and the lowest temperature among the temperatures at which the loss tangent reaches its minimum value in a region higher than GF1temp is defined as GF2temp, and the loss tangent at GF2temp is defined as GF2tanδ, The temperature difference between the Ggtemp and the GF1temp is 50.0°C or more, The GF2 tan δ is 0.34 or more. A pressure-sensitive adhesive sheet characterized by:

2. A pressure-sensitive adhesive sheet that is a cured product of a pressure-sensitive adhesive composition that contains a monofunctional (meth)acrylic monomer, at least one of a polyfunctional (meth)acrylic monomer and a crosslinking agent, a tackifier, and a photopolymerization initiator, the monofunctional (meth)acrylic monomer comprises at least one selected from the group consisting of a monofunctional (meth)acrylic acid ester compound and a monofunctional (meth)acrylamide compound, and the content of the monofunctional (meth)acrylic monomer per 100 parts by mass of the pressure-sensitive adhesive composition is 15 parts by mass or more and 90 parts by mass or less; the polyfunctional (meth)acrylic monomer includes at least one selected from the group consisting of a polyfunctional urethane (meth)acrylate, a polyfunctional (meth)acrylic acid ester compound, and a polyfunctional epoxy (meth)acrylate; the tackifier comprises at least one selected from the group consisting of a rosin-based resin and a terpene-based resin, and the content of the tackifier in 100 parts by mass of the PSA composition is 5 parts by mass or more and 50 parts by mass or less; In a viscoelasticity chart obtained by performing dynamic viscoelasticity measurement under the conditions of a shear method, a measurement temperature of -70°C to 200°C, and a frequency of 1 Hz, When the temperature at which the loss modulus reaches its maximum value on the lowest temperature side is defined as Ggtemp, and the lowest temperature among the temperatures at which tanδ reaches its maximum value in a region higher than Ggtemp is defined as Tg, the lowest temperature in the temperature region from Tg to 50°C among the temperatures at which the ratio of the storage modulus to the loss modulus is minimum is defined as GF1temp, and the lowest temperature among the temperatures at which the loss tangent reaches its minimum value in a region higher than GF1temp is defined as GF2temp, and the loss tangent at GF2temp is defined as GF2tanδ, The temperature difference between the Ggtemp and the GF1temp is 25.0°C or more, The GF2 tan δ is 0.34 or more, After aging for one day in an environment of 25°C and 50% RH, the 180° peel adhesive strength of the pressure-sensitive adhesive sheet to a SUS substrate at 25°C is 6 N / cm or more. A pressure-sensitive adhesive sheet characterized by:

3. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein, in the viscoelasticity chart, GEtemp is the temperature at which the storage modulus becomes a minimum in the region higher than GF2temp, or 200°C if there is no temperature at which the storage modulus becomes a minimum in the region higher than GF2temp, the loss tangent at said GEtemp is GEtanδ, and the value calculated by the formula (GEtanδ-GF2tanδ) / (GEtemp-GF2temp) is delta tanδ, and said delta tanδ is -0.006 or more.

4. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the GF2 tan δ is 0.50 or more.

5. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive composition contains a nitrogen-containing compound.

6. The pressure-sensitive adhesive sheet according to claim 5 , wherein the nitrogen-containing compound includes a maleimide derivative.

7. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive composition comprises at least one selected from the group consisting of a hydrogen abstraction photopolymerization initiator and a polymeric photopolymerization initiator.

8. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive composition contains a thermoplastic resin.

9. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the content of the tackifier in 100 parts by mass of the pressure-sensitive adhesive composition is 5 parts by mass or more and 50 parts by mass or less.

10. a step of forming the pressure-sensitive adhesive sheet according to claim 1 or 2 by applying the pressure-sensitive adhesive composition to a first adherend or a separator and exposing the composition to light; and a step of attaching a second adherend to the pressure-sensitive adhesive sheet, The method for applying the pressure-sensitive adhesive composition is inkjet printing, screen printing, spray coating, spin coating, gravure offset, or reverse offset printing, and the pressure-sensitive adhesive composition is partially applied onto the first adherend or the separator.

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