Pressure-sensitive adhesive sheet

Abstract

Provided is a pressure-sensitive adhesive sheet which has excellent impact resistance, is less apt to leave an adhesive residue, and brings about excellent reworkability.　A pressure-sensitive adhesive sheet 1 includes a pressure-sensitive adhesive layer 2 which is a rubber-based pressure-sensitive adhesive layer. When the pressure-sensitive adhesive surface (adhesive surface (X)) of the pressure-sensitive adhesive layer 2 is applied to a stainless-steel plate, and this pressure-sensitive adhesive layer 2 is allowed to stand for 30 minutes in an environment of 23°C and 50% RH and then examined for 180° peeling adhesive force at a pulling speed of 300 mm / min, the peeling adhesive force is 5.5 N / cm or greater. When the pressure-sensitive adhesive surface (X) of the pressure-sensitive adhesive layer 2 is applied to a stainless-steel plate, and this pressure-sensitive adhesive layer 2 is allowed to stand for 24 hours in an environment of 23°C and 50% RH and then examined for dynamic shear bond force under the conditions of a pulling speed of 10 mm / min and a peel angle of 0°, the dynamic shear bond force is 0.35 MPa or greater. When the pressure-sensitive adhesive surface (X) of the pressure-sensitive adhesive layer 2 is applied to a stainless-steel plate, and this pressure-sensitive adhesive layer 2 is allowed to stand for 30 minutes in an environment of 23°C and 50% RH and then examined for 180° peeling adhesive force at a pulling speed of 300 mm / min after supplying 0.5 mL of ethanol to the adhesion interface, then the adhesive force is 2.0 N / cm or less.

Description

adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive sheet.

[0002] In recent years, electronic devices such as home appliances, office automation equipment, mobile phones (e.g., smartphones), digital cameras, and PDAs (Personal Digital Assistants) have become increasingly popular. For example, mobile phones, which are a representative example of mobile devices, tend to have thinner, larger screens for their constituent major components. Typically, the display portion of a mobile device primarily consists of an LCD module and a backlight unit, with various sheet-like components stacked on top of each other to achieve functions such as light emission, reflection, light blocking, and light guidance. Furthermore, recent mobile phones often employ organic electroluminescence displays, which are even more expensive than LCD modules. Adhesive sheets (adhesive tapes) are used to assemble (bond) these components.

[0003] Pressure-sensitive adhesive sheets used in electronic devices are required to have various properties, including high adhesive strength. For example, in addition to having high adhesive strength, they are also required to not peel off even when subjected to impact, and to prevent strong impacts from being applied to the components.

[0004] Incidentally, in recent years, in order to achieve the Sustainable Development Goals (SDGs) adopted at the United Nations Summit in 2015, industrial bonding materials, including PSA sheets, are being required to be easily dismantled (reworkable), i.e., to be able to be easily dismantled at any time and by any method, in order to increase the recycling and reuse rate of the members (adherends) to be bonded.

[0005] As methods for peeling off an adhesive sheet while minimizing damage to the adherend, methods that have been proposed include using ultraviolet light or heat to reduce the adhesive strength and peeling it off, and gripping and pulling part of the adhesive sheet, stretching and deforming the adhesive sheet to peel it off (stretch peeling method, stretch method).

[0006] Furthermore, Patent Document 1 discloses a substrate-attached pressure-sensitive adhesive sheet that can be broken into layers by allowing a solvent to penetrate into the substrate. With this pressure-sensitive adhesive sheet, adherends bonded together by the pressure-sensitive adhesive sheet can be separated by breaking the substrate.

[0007] Chinese Patent No. 112300718

[0008] However, methods using ultraviolet light or heat require the consumer who peels the adhesive sheet to prepare a heating device or ultraviolet irradiation device, making them difficult to adopt. The stretching method requires the adhesive sheet to be provided with a gripping portion for gripping the adhesive sheet, but providing a gripping portion runs counter to the trend toward thinner adhesive sheets, which has been required in recent years due to the trend toward thinner electronic devices. Furthermore, the method disclosed in Patent Document 1 destroys the substrate, but leaves behind a "residue" of the adhesive on the adherend, necessitating the separate removal of the adhesive. For this reason, adhesive sheets are sometimes expected to have impact resistance, meaning they are resistant to peeling even when subjected to impact, and excellent reworkability, meaning they do not leave behind adhesive residue.

[0009] The present invention was conceived under these circumstances, and its object is to provide a pressure-sensitive adhesive sheet that has excellent impact resistance, is less likely to leave adhesive residue, and has excellent reworkability.

[0010] As a result of extensive research to achieve the above object, the present inventors have found that a specific pressure-sensitive adhesive sheet has excellent impact resistance, is less likely to leave adhesive residue, and has excellent reworkability. The present invention was completed based on these findings.

[0011] That is, the present invention provides a PSA sheet comprising a rubber-based pressure-sensitive adhesive layer, wherein the adhesive surface of the rubber-based pressure-sensitive adhesive layer is laminated to a stainless steel plate and left for 30 minutes in an environment of 23°C and 50% RH, and after that, the 180° peel adhesion strength at a tensile speed of 300 mm / min is 5.5 N / cm or more, the adhesive surface of the rubber-based pressure-sensitive adhesive layer is laminated to a stainless steel plate and left for 24 hours in an environment of 23°C and 50% RH, and after that, the dynamic shear adhesion strength measured under conditions of a tensile speed of 10 mm / min and a peel angle of 0° is 0.35 MPa or more, and the 180° peel adhesion strength at a tensile speed of 300 mm / min is 2.0 N / cm or less, when the adhesive surface of the rubber-based pressure-sensitive adhesive layer is laminated to a stainless steel plate and left for 30 minutes in an environment of 23°C and 50% RH, and 0.5 mL of ethanol is supplied to the adhesive interface.

[0012] The rubber-based pressure-sensitive adhesive layer preferably contains a styrene-based rubber as a base polymer.

[0013] The styrene-based rubber preferably contains 5 to 30% by mass of structural units derived from a monovinyl-substituted aromatic compound.

[0014] The styrene-based rubber is preferably a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, the diblock ratio of which is 30% by mass or more.

[0015] The rubber-based pressure-sensitive adhesive layer preferably contains a tackifying resin.

[0016] The hydroxyl value of the tackifier resin is preferably 50 mgKOH / g or more.

[0017] The pressure-sensitive adhesive sheet may further include a coating layer that partially covers the surface of the rubber-based pressure-sensitive adhesive layer.

[0018] The pressure-sensitive adhesive sheet may further include a substrate.

[0019] The substrate is preferably a plastic film or a foam sheet.

[0020] The pressure-sensitive adhesive sheet is preferably used to fix components together in an electric or electronic device.

[0021] The present invention also provides an electric / electronic device comprising the above-mentioned pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive sheet fixes components together using both adhesive surfaces thereof.

[0022] The pressure-sensitive adhesive sheet of the present invention has excellent impact resistance, is less likely to leave adhesive residue, and is excellent in reworkability. Therefore, when used to bond adherends to each other, the sheet is less likely to peel even when subjected to impact, and can be easily peeled off without leaving adhesive residue when desired.

[0023] Fig. 3 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. Fig. 4 is a top view of a pressure-sensitive adhesive sheet according to another embodiment of the present invention. Fig. 5 is a cross-sectional view taken along line III-III' in Fig. 2. Fig. 6 is a front view of an example of a portable electronic device equipped with a pressure-sensitive adhesive sheet. Fig. 7 is an explanatory diagram schematically showing a method for measuring dynamic shear adhesive strength. Fig. 8 is an explanatory diagram schematically showing a method for measuring 180° peel adhesive strength in the presence of ethanol. Fig. 9 is a cross-sectional view of a measurement laminate produced in an adhesive test and a dismantling test.

[0024] [Adhesive Sheet] An adhesive sheet according to one embodiment of the present invention comprises at least a rubber-based adhesive layer. The adhesive sheet has a 180° peel adhesion of 5.5 N / cm or more at a tensile speed of 300 mm / min after laminating the adhesive surface of the rubber-based adhesive layer to a stainless steel plate and leaving it at 23°C and 50% RH for 30 minutes; a dynamic shear adhesion of 0.35 MPa or more after laminating the adhesive surface of the rubber-based adhesive layer to a stainless steel plate and leaving it at 23°C and 50% RH for 24 hours, measured at a tensile speed of 10 mm / min and a peel angle of 0°; and a 180° peel adhesion of 2.0 N / cm or less at a tensile speed of 300 mm / min after laminating the adhesive surface of the rubber-based adhesive layer to a stainless steel plate and leaving it at 23°C and 50% RH for 30 minutes, and supplying 0.5 mL of ethanol to the adhesive interface. In this specification, the rubber-based adhesive layer may be referred to as the "adhesive layer of the present invention."

[0025] The pressure-sensitive adhesive sheet of the present invention may be a so-called "substrate-less" pressure-sensitive adhesive sheet that does not have a substrate (substrate layer), or may be a pressure-sensitive adhesive sheet that has a substrate. In this specification, a "substrate-less" pressure-sensitive adhesive sheet may be referred to as a "substrate-less pressure-sensitive adhesive sheet," and a pressure-sensitive adhesive sheet that has a substrate may be referred to as a "substrate-attached pressure-sensitive adhesive sheet." Examples of the substrate-less pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet consisting only of the pressure-sensitive adhesive layer of the present invention, and a double-sided pressure-sensitive adhesive sheet consisting of the pressure-sensitive adhesive layer of the present invention and another pressure-sensitive adhesive layer (a pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer of the present invention). Examples of the substrate-attached pressure-sensitive adhesive sheet include a pressure-sensitive adhesive sheet comprising a substrate and the pressure-sensitive adhesive layer of the present invention provided on at least one side of the substrate. Examples include a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on one side of the substrate, a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on both sides of the substrate, and a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer of the present invention on one side of the substrate and another pressure-sensitive adhesive layer on the other side. The above-mentioned "substrate (substrate layer)" refers to a support, and is the part that is attached to an adherend together with the pressure-sensitive adhesive layer when the pressure-sensitive adhesive sheet of the present invention is used (applied) to an adherend. The release liner that is peeled off when the pressure-sensitive adhesive sheet is used (applied) is not included in the above-mentioned substrate.

[0026] Fig. 1 is a cross-sectional view showing one embodiment of a pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive sheet 1 shown in Fig. 1 is a substrate-less double-sided pressure-sensitive adhesive sheet consisting of a single pressure-sensitive adhesive layer 2 that is the pressure-sensitive adhesive layer of the present invention, and release liners 3 and 4 are provided on both pressure-sensitive adhesive surfaces, respectively.

[0027] (Pressure-sensitive adhesive layer of the present invention) The pressure-sensitive adhesive sheet of the present invention may include only one pressure-sensitive adhesive layer of the present invention, or may include two or more pressure-sensitive adhesive layers of the present invention. When the pressure-sensitive adhesive sheet of the present invention includes two or more pressure-sensitive adhesive layers of the present invention, the multiple pressure-sensitive adhesive layers of the present invention may be the same pressure-sensitive adhesive layer, or may be pressure-sensitive adhesive layers different in composition, thickness, physical properties, etc.

[0028] The adhesive surface of the pressure-sensitive adhesive layer of the present invention is laminated to a stainless steel plate and left for 30 minutes under an environment of 23°C and 50% RH. The 180° peel adhesion at a tensile speed of 300 mm / min is 5.5 N / cm or more, preferably 6.0 N / cm or more, more preferably 6.5 N / cm or more, even more preferably 9.0 N / cm or more, and particularly preferably 10.0 N / cm or more. A peel adhesion of 5.5 N / mm or more indicates excellent adhesion to the adherend. The peel adhesion is, for example, 50.0 N / cm or less. When the pressure-sensitive adhesive sheet of the present invention is a substrateless type pressure-sensitive adhesive sheet, it is preferable to measure the adhesive surface opposite the adhesive surface from which the peel adhesion is measured by backing it with a plastic film such as a PET film. Detailed methods are as shown in the examples. Furthermore, when a coating layer, described below, partially covers the surface (adhesive surface) of the pressure-sensitive adhesive layer of the present invention, the 180° peel adhesion is the adhesive strength when the coating layer is present.

[0029] The peel adhesive strength can be adjusted by appropriately selecting the type (styrene content, diblock ratio, etc.) and content of the base polymer in the adhesive layer, and the type (softening point, etc.) and content of the tackifier resin.

[0030] In this specification, the adhesive surface of the pressure-sensitive adhesive layer of the present invention having the above peel adhesive strength may be referred to as "adhesive surface (X)".

[0031] The adhesive surface (adhesive surface (X)) of the pressure-sensitive adhesive layer of the present invention is bonded to a stainless steel plate and left to stand for 24 hours in an environment of 23°C and 50% RH. After this, the dynamic shear adhesive strength measured under conditions of a pulling rate of 10 mm / min and a peel angle of 0° is 0.35 MPa or more, preferably 0.4 MPa or more, more preferably 0.5 MPa or more, and even more preferably 1.0 MPa or more. When the dynamic shear adhesive strength is 0.35 MPa or more, it is possible to maintain the state in which the pressure-sensitive adhesive sheet is bonded to the adherend. Furthermore, when the 180° peel adhesive strength is 5.5 N / cm or more and the dynamic shear adhesive strength is 0.35 MPa or more, the pressure-sensitive adhesive sheet is unlikely to peel even when an impact is applied while it is bonded to the adherend, and has excellent impact resistance. The dynamic shear adhesive strength is, for example, 10.0 MPa or less. When the pressure-sensitive adhesive sheet of the present invention is a substrateless type pressure-sensitive adhesive sheet, it is preferable to measure the pressure-sensitive adhesive surface opposite to the pressure-sensitive adhesive surface for measuring the dynamic shear adhesive strength by backing it with a thin metallic film such as stainless steel foil.Details of the method are as shown in the examples.When it is a double-sided pressure-sensitive adhesive sheet, it is preferable that the dynamic shear adhesive strength of both pressure-sensitive adhesive surfaces of the pressure-sensitive adhesive sheet is within the above range.When it has a coating layer described below that partially covers the surface (adhesive surface (X)) of the pressure-sensitive adhesive layer of the present invention, the dynamic shear adhesive strength is the adhesive strength when the coating layer is present.

[0032] The dynamic shear adhesive strength can be adjusted by appropriately selecting the type and content of the base polymer in the pressure-sensitive adhesive layer, and the type (hydroxyl value, etc.) and content of the tackifier resin.

[0033] When the adhesive surface (adhesive surface (X)) of the pressure-sensitive adhesive layer of the present invention is laminated to a stainless steel plate and left for 30 minutes in an environment of 23°C and 50% RH, and 0.5 mL of ethanol is supplied to the adhesive interface, the 180° peel adhesion at a tensile speed of 300 mm / min from this state is 2.0 N / cm or less, preferably 1.0 N / cm or less, and more preferably 0.5 N / cm or less. When the peel adhesion is 2.0 N / mm or less, the pressure-sensitive adhesive sheet can be easily peeled from the adherend with ethanol and is less likely to leave adhesive residue. The peel adhesion may be 0 N / cm. When the pressure-sensitive adhesive sheet of the present invention is a substrateless type pressure-sensitive adhesive sheet, it is preferable to measure the adhesive surface opposite the adhesive surface where the peel adhesion is measured by backing it with a plastic film such as a PET film. Detailed methods are as shown in the examples. When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable that the peel adhesion of both adhesive surfaces of the pressure-sensitive adhesive sheet be within the above range. Furthermore, when a coating layer described below is provided to partially cover the surface (adhesive surface (X)) of the pressure-sensitive adhesive layer of the present invention, the above 180° peel adhesive strength is the adhesive strength in a state in which the coating layer is provided.

[0034] The peel adhesive strength in the presence of ethanol can be adjusted by appropriately selecting the type and content of the base polymer in the adhesive layer, the type and content of the tackifier resin, etc. It can also be adjusted by the formation, pattern, and area ratio of the coating layer described below.

[0035] As the stainless steel plate, a SUS304 plate such as a SUS304BA plate can be used. The thickness of the adherend should be such that it does not bend during measurement, for example, 0.3 to 0.5 mm, preferably 0.4 mm. "SUS304" is an austenitic stainless steel containing 18% Cr and 8% Ni.

[0036] The pressure-sensitive adhesive layer of the present invention has a weight average molecular weight Mw of the pressure-sensitive adhesive after an aging test at 80°C for 4 weeks. Ｈ (Mw after aging Ｈ ) the weight average molecular weight Mw of the pressure sensitive adhesive before the aging test Ｈ (Mw before aging Ｈ ) to [after aging w Ｈ / Before aging Mw Ｈ ](「Mw Ｈ The Mw retention rate (sometimes referred to as "retention rate") is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, particularly preferably 85% or more, and may even be 100%. Ｈ The closer the retention rate is to 100%, the higher the quality stability of the PSA sheet tends to be. Alternatively, taking into consideration the balance with other adhesive properties and economic efficiency, from a practical standpoint, Mw Ｈ The retention rate may be less than 100% (for example, 99% or less). Ｈ The retention rate can be adjusted by appropriately selecting, for example, the type and content of the base polymer, the type and content of the tackifier resin, the type and content of the antioxidant, and the like.

[0037] The aging test is carried out by storing a pressure-sensitive adhesive sheet of the present invention, in which a release liner is attached to the adhesive surface (adhesive surface (X)) of the pressure-sensitive adhesive layer, in an atmospheric atmosphere at 80°C for 4 weeks. Ｈ is the following Mw Ｈ It can be calculated by a measurement method.

[0038] <Mw Ｈ Measurement method> Weight average molecular weight Mw Ｈ is the weight average molecular weight calculated from the molecular weight distribution curve obtained by GPC measurement in the region where the molecular weight in terms of polystyrene is 10,000 or more. On the other hand, the weight average molecular weight calculated for the entire molecular weight distribution curve (i.e., including the region where the molecular weight in terms of polystyrene is less than 10,000) is the weight average molecular weight Mw ＴThe sample for GPC measurement is prepared by dissolving the adhesive collected from the adhesive layer in tetrahydrofuran (THF) to prepare a 0.1% by mass solution, leaving the solution to stand overnight, and then filtering the solution through a 0.45 μm membrane filter to obtain a filtrate. GPC measurement can be performed under the following conditions or conditions that provide equivalent results. Analytical device: Tosoh Corporation, model number "HLC-8120GPC" Column: TSKgel Super HZM-H / HZ4000 / HZ3000 / HZ2000 Column size: 6.0 mm ID × 150 mm Eluent: THF Flow rate: 0.6 mL / min Detector: Differential refractometer (RI) Column temperature: 40°C Injection volume: 20 μL Standard sample: Polystyrene

[0039] The susceptibility of the pressure-sensitive adhesive layer of the present invention to aging can be evaluated in a short period of time by measuring the oxidation induction time using a chemiluminescence method. Chemiluminescence is a technique for detecting extremely weak light emitted when excited carbonyl and singlet oxygen, which are produced by a bimolecular reaction of peroxy radicals generated by stimuli such as light or heat, return from an excited state to a ground state. The oxidation induction time is the time until a rapid increase in luminescence is observed, and can be the time until the luminescence intensity is observed at 10,000 times per second. A CL-Spectrometer chemiluminescence spectrometer (model number "CLA-FS4", manufactured by Tohoku Electronics Co., Ltd.) can be used as an evaluation device. The oxidation induction time can be obtained by spraying nitrogen at 100 mL / min onto a 20 mm diameter sample in a 150°C atmosphere for 60 minutes, then switching to oxygen at 100 mL / min and measuring the time until the luminescence intensity is observed at 10,000 times per second. The oxidation induction time is preferably 5 minutes or longer, more preferably 10 minutes or longer.

[0040] The pressure-sensitive adhesive layer of the present invention is a rubber-based pressure-sensitive adhesive layer in which the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is a rubber-based pressure-sensitive adhesive. The rubber-based pressure-sensitive adhesive may be either a natural rubber-based pressure-sensitive adhesive or a synthetic rubber-based pressure-sensitive adhesive.

[0041] The pressure-sensitive adhesive layer of the present invention contains a rubber-based resin as a base polymer that exhibits adhesiveness. In this specification, the term "base polymer" refers to a main component of the polymer components in the pressure-sensitive adhesive that constitutes the pressure-sensitive adhesive layer, for example, a polymer component that accounts for more than 50 mass %.

[0042] The content of the base polymer in the pressure-sensitive adhesive layer of the present invention is preferably 60% by mass or more, and may be 70% by mass or more, 80% by mass or more, or 90% by mass or more, relative to 100% by mass of the total amount of the pressure-sensitive adhesive layer, and the content is preferably 99% by mass or less, and may be 95% by mass or less, 90% by mass or less, 80% by mass or less, or 70% by mass or less.

[0043] The rubber-based resin serving as the base polymer in the pressure-sensitive adhesive layer of the present invention is not particularly limited, but examples thereof include natural rubber; olefin-based rubbers such as isoprene rubber, polyisobutylene rubber, butyl rubber, and ethylene-propylene rubber; styrene-based rubbers such as styrene-butadiene rubber, styrene-isoprene rubber, styrene-ethylene-propylene-styrene rubber, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, and styrene-ethylene-propylene block copolymer; reclaimed rubber; and modified products thereof. Furthermore, when the rubber-based resin is a copolymer, it may be either a block copolymer or a random copolymer. Among these, styrene-based rubber is preferred as the base polymer. Only one type of the base polymer may be used, or two or more types may be used.

[0044] The styrene-based rubber contains a structural unit derived from a monovinyl-substituted aromatic compound. The content of the monovinyl-substituted aromatic compound is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 17% by mass or more, even more preferably 20% by mass or more, and particularly preferably 22% by mass or more, relative to 100% by mass of the total amount of the monomer components constituting the styrene-based rubber. The content is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less. When the content is within the above range, the hardness of the pressure-sensitive adhesive layer becomes appropriate and the adhesion to the adherend becomes better. The content of the monovinyl-substituted aromatic compound is １ It can be measured by H-NMR (nuclear magnetic resonance spectroscopy). In this specification, the content ratio of the monovinyl-substituted aromatic compound may be referred to as the "styrene content."

[0045] The styrene-based rubber is preferably a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound. The block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound has at least one segment (A segment) whose main monomer is a monovinyl-substituted aromatic compound and at least one segment (B segment) whose main monomer is a conjugated diene compound. Generally, the glass transition temperature of the A segment is higher than that of the B segment. Examples of the block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound include a triblock copolymer (A-B-A triblock copolymer) having an A segment (hard segment) at each end of a B segment (soft segment), and a diblock copolymer (A-B diblock copolymer) consisting of one A segment and one B segment. The "main monomer" refers to a monomer component that accounts for more than 50% by mass of the total amount (100% by mass) of the monomer components constituting the segment.

[0046] The proportion of the structural units derived from the monovinyl-substituted aromatic compound in the A segment (hard segment) is preferably 70% by mass or more (e.g., 70 to 100% by mass), more preferably 90% by mass or more, relative to 100% by mass of the total amount of the A segment. Furthermore, the proportion of the structural units derived from the conjugated diene compound in the B segment (soft segment) is preferably 70% by mass or more (e.g., 70 to 100% by mass), more preferably 90% by mass or more, relative to 100% by mass of the total amount of the B segment.

[0047] The block copolymer may be in the form of a diblock copolymer, a triblock copolymer, a radial copolymer, or a mixture thereof. In the triblock copolymer or the radial copolymer, it is preferable that the A segment is located at the end of the polymer chain. This is because the A segments located at the end of the polymer chain tend to gather together to form domains, which form a pseudo-crosslinked structure and improve the cohesion of the PSA.

[0048] The block copolymer preferably has a diblock content of 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 60% by mass or more. A diblock content of 30% by mass or more provides superior adhesion to adherends. From the viewpoints of superior reworkability and reduced adhesive residue, the diblock content is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and particularly preferably 75% by mass or less (e.g., 70% by mass or less).

[0049] The diblock copolymer ratio is determined by the following method. Specifically, the block copolymer is dissolved in tetrahydrofuran (THF), and high-performance liquid chromatography is performed using two GS5000H and two G4000H liquid chromatography columns manufactured by Tosoh Corporation, each connected in series for a total of four columns, at a temperature of 40°C and a flow rate of 1 mL / min, using THF as the mobile phase. The peak area corresponding to the diblock copolymer is measured from the resulting chart. The diblock copolymer ratio is then determined by calculating the percentage of the peak area corresponding to the diblock copolymer relative to the total peak area.

[0050] The block copolymer preferably has a styrene content of 15% or more and a diblock ratio of 30% by mass or more, which provides excellent adhesion to adherends, better reworkability, and less adhesive residue.

[0051] Examples of the monovinyl-substituted aromatic compound include styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-isobutylstyrene, p-t-butylstyrene, chloromethylstyrene, etc. One or more of the monovinyl-substituted aromatic compounds may be used.

[0052] Examples of the conjugated diene compound include 1,3-butadiene, isoprene, etc. One type of the conjugated diene compound may be used alone, or two or more types may be used together.

[0053] Among the block copolymers of the monovinyl-substituted aromatic compound and the conjugated diene compound, styrene-based block copolymers in which the monovinyl-substituted aromatic compound has an A segment (styrene block) containing styrene are preferred.

[0054] As the styrene-based block copolymer, a copolymer containing isoprene as a conjugated diene compound (styrene-isoprene block copolymer) or a copolymer containing 1,3-butadiene as a conjugated diene compound (styrene-butadiene block copolymer) is preferred.

[0055] The content of the styrene-based block copolymer in the styrene-based rubber (particularly the total content of the styrene-isoprene block copolymer and / or the styrene-butadiene block copolymer) is preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more, relative to 100% by weight of the total amount of the styrene-based rubber.

[0056] The pressure-sensitive adhesive layer of the present invention preferably contains a tackifier resin. When the pressure-sensitive adhesive layer of the present invention contains a tackifier resin, the pressure-sensitive adhesive sheet has better interfacial adhesion to the adherend. The above-mentioned tackifier resin may be used alone or in combination of two or more types.

[0057] Examples of the tackifying resin include phenol-based tackifying resins, terpene-based tackifying resins, rosin-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, and ketone-based tackifying resins.

[0058] Examples of the phenolic tackifying resin include terpene phenolic resins, hydrogenated terpene phenolic resins, alkylphenolic resins, and rosin phenolic resins. The terpene phenolic resins are polymers containing terpene residues and phenolic residues, such as copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and phenol-modified terpene homopolymers or copolymers. Examples of terpenes constituting the terpene phenolic resins include monoterpenes such as α-pinene, β-pinene, and limonene (d-isomer, l-isomer, d / l-isomer (dipentene)). The hydrogenated terpene phenolic resins are resins having a hydrogenated structure of the terpene phenolic resins. The alkylphenolic resins are resins (oil-based phenolic resins) obtained from alkylphenols and formaldehyde. Examples of the alkylphenolic resins include novolac and resol types. The rosin phenolic resins are phenol-modified rosins or various rosin derivatives described below. The rosin phenol resin can be obtained, for example, by adding phenol to rosins or various rosin derivatives described below in the presence of an acid catalyst and then thermally polymerizing the resulting mixture.

[0059] Examples of the terpene-based tackifying resin include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. The terpene polymer may be a homopolymer of one type of terpene, or a copolymer of two or more types of terpenes. Examples of homopolymers of one type of terpene include α-pinene polymer, β-pinene polymer, and dipentene polymer. The modified terpene-based tackifying resin is a modified terpene resin (modified terpene resin) obtained by modifying the terpene resin. Examples of the modified terpene resin include styrene-modified terpene resin and hydrogenated terpene resin.

[0060] Examples of the rosin-based tackifying resin include rosins and rosin derivative resins. Examples of the rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, or the like. Examples of the rosin derivative resin include derivatives of the rosins. Examples of the rosin derivative resin include rosin esters, such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; unsaturated fatty acid-modified rosins obtained by modifying rosin esters with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups of rosins or the various rosin derivatives described above; and metal salts of rosins or the various rosin derivatives described above. Specific examples of the rosin esters include methyl esters, triethylene glycol esters, glycerin esters, and pentaerythritol esters of unmodified or modified rosin.

[0061] Examples of the hydrocarbon tackifying resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, petroleum resins such as aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.) and aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0062] Among the tackifying resins, from the viewpoint of superior adhesion to adherends and impact resistance, phenol-based tackifying resins, terpene-based tackifying resins, and hydrocarbon-based tackifying resins are preferred, more preferably terpene-phenol-based tackifying resins, terpene-based tackifying resins, and petroleum resins, even more preferably terpene-phenol-based tackifying resins and terpene-based tackifying resins, and particularly preferably terpene-phenol-based tackifying resins.

[0063] The softening point of the tackifier resin is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, even more preferably 130°C or higher, and particularly preferably 140°C or higher. When the softening point is 100°C or higher, the cohesive strength is higher and high adhesive strength is easily achieved. The softening point is, for example, 160°C or lower.

[0064] The hydroxyl value of the tackifier resin is not particularly limited, but is preferably 50 mgKOH / g or more, more preferably 60 mgKOH / g or more, even more preferably 70 mgKOH / g or more, even more preferably 80 mgKOH / g or more, and particularly preferably 100 mgKOH / g or more. When the hydroxyl value is 50 mgKOH / g or more (particularly 80 mgKOH / g or more), the dynamic shear adhesive strength of the pressure-sensitive adhesive layer of the present invention tends to be high, resulting in better impact resistance. The hydroxyl value is, for example, 300 mgKOH / g or less, preferably 250 mgKOH / g or less, more preferably 200 mgKOH / g or less. Terpene phenol-based tackifier resins having a hydroxyl value within the above range are particularly preferred. The hydroxyl value of the tackifier resin can be measured by potentiometric titration according to JIS K0070:1992.

[0065] The content of the tackifier resin in the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is preferably 1 to 60 parts by mass, more preferably 2 to 50 parts by mass, and even more preferably 5 to 40 parts by mass, per 100 parts by mass of the total base polymer. When the content is 1 part by mass or more, the adhesiveness to the adherend and dynamic shear adhesive strength tend to be higher. When the content is 60 parts by mass or less, the reworkability is excellent and adhesive residue is less likely to occur. In particular, the proportion of the terpene phenol-based tackifier resin relative to 100% by mass of the total tackifier resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of reducing the dynamic shear adhesive strength and facilitating rework with less adhesive residue. Furthermore, the total proportion of the petroleum resin and the terpene-based resin may be within the above range.

[0066] The pressure-sensitive adhesive layer of the present invention may further contain, as necessary, additives such as crosslinking agents, crosslinking accelerators, antiaging agents, antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, UV absorbers, polymerization inhibitors, foil-like materials, rust inhibitors, colorants, oligomers, etc., within the range that does not impair the effects of the present invention. Only one of the above additives may be used, or two or more thereof may be used.

[0067] When the pressure-sensitive adhesive layer of the present invention contains an antioxidant, the antioxidant can be used in combination with a rubber-based resin and a tackifying resin, thereby increasing the Mw Ｈ The anti-aging agent may be used alone or in combination with two or more other types thereof.

[0068] The antioxidant preferably contains a radical scavenger (radical trapping agent). Examples of the radical scavenger include conventional or commonly used agents used in the technical field of rubber-based resins, such as phenolic antioxidants, hindered amine antioxidants, and aromatic amine antioxidants. The radical scavengers may be used alone or in combination of two or more.

[0069] As the antiaging agent, for example, it is effective to use a radical scavenger and a sulfur-based antioxidant in combination. Alternatively, a phosphorus-based antioxidant may be used as the antiaging agent. A higher effect can be achieved by using a radical scavenger (e.g., a phenol-based antioxidant) in combination with a sulfur-based antioxidant and a phosphorus-based antioxidant.

[0070] Among these, phenolic antioxidants are preferred as the radical scavengers. Examples of the phenolic antioxidants include monophenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol and 2,6-di-t-butyl-4-ethylphenol; 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol); 4,4'-thiobis(3-methyl-6 bisphenol-based antioxidants such as 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, and 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane.

[0071] The phenol-based antioxidant may be a hindered phenol-based antioxidant, such as pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 4,6-bis(dodecylthiomethyl)-o-cresol, 4-[[4,6-bis(octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-t-butylphenol, triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, polycondensation product of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensation product), and the like.

[0072] The content of the radical scavenger (e.g., a phenolic antioxidant) is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the total amount of the base polymer. Ｈ The content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, from the viewpoint of suppressing a decrease in the cohesiveness of the PSA before aging.

[0073] The sulfur-based antioxidant continuously functions as a peroxide decomposer that decomposes and / or converts peroxides that may be generated in the adhesive layer into stable compounds, thereby reducing the Mw Ｈ This can contribute to improving the retention rate (and thus improving the quality stability of the PSA sheet). In a PSA layer containing a rubber-based resin and a phenol-based tackifying resin (e.g., a terpene phenol resin), the use of a sulfur-based antioxidant is particularly effective.

[0074] Examples of the sulfur-based antioxidant include thioether-based antioxidants having a thioether structure in the molecule. Examples of the sulfur-based antioxidant include 2,2-bis({[3-(dodecylthio)propionyl]oxy}methyl)propanediyl bis[3-(dodecylthio)propionate, bis[2-methyl-4-(3-n-dodecylthiopropionyloxy)-5-t-butylphenyl]sulfide, 3-dodecylsulfanylpropanoic acid=2-t-butyl-4-[(5-t-butyl-4-hydroxy-2-methylphenyl)sulfanyl]-5-methylphenyl, dilauryl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, and pentaerythritol tetralaurylthiopropionate. One or more of the sulfur-based antioxidants may be used.

[0075] The sulfur-based antioxidant is preferably a sulfur-based antioxidant having a structure that does not contain an aromatic ring (for example, a thioether-based antioxidant). ２ —OC(O)—CH ２ CH ２ -S-CH ２ Thioether antioxidants having one or more (for example, three or four) "-" structures are more preferred.

[0076] The number of thioetheric sulfur atoms contained in one molecule of the thioetheric antioxidant may be 1 or 2 or more. From the viewpoint of the durability of the effect, a thioetheric antioxidant containing two or more (e.g., 2 to 4) thioetheric sulfur atoms in one molecule is preferred.

[0077] The content of the sulfur-based antioxidant is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the total amount of the base polymer. ＨFrom the viewpoint of suppressing a decrease in the cohesion of the PSA before aging, the content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less.

[0078] The phosphorus-based antioxidant functions as a peroxide decomposer that decomposes or converts peroxides that may be generated in the adhesive layer into stable compounds, thereby reducing the Mw Ｈ This can contribute to improving the retention rate (and thus improving the quality stability of the PSA sheet). Examples of the phosphorus-based antioxidant include tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite, triphenyl phosphite, distearyl pentaerythritol diphosphite, etc. One type of the phosphorus-based antioxidant may be used alone, or two or more types may be used in combination.

[0079] The content of the phosphorus-based antioxidant is, for example, 0.05 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the total amount of the base polymer. Ｈ From the viewpoint of suppressing a decrease in the cohesiveness of the PSA before aging, the content is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 7 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0080] As the antioxidant, a sulfur-based antioxidant (e.g., a thioether-based antioxidant) and a phosphorus-based antioxidant may be used in combination. In this case, the Mw Ｈ This can effectively improve the retention rate.

[0081] When the pressure-sensitive adhesive layer of the present invention contains an oligomer, the interfacial adhesion of the pressure-sensitive adhesive sheet to the adherend is superior. The weight-average molecular weight of the oligomer is preferably 2,500 to 10,000, more preferably 3,000 to 8,000. The weight-average molecular weight can be determined in polystyrene equivalent terms by GPC. For example, it can be measured under the following conditions using a high-speed GPC device "HPLC-8120GPC" manufactured by Tosoh Corporation. Column: TSKgel Super HZM-H / HZ4000 / HZ3000 / HZ2000 Solvent: Tetrahydrofuran Flow rate: 0.6 ml / min

[0082] The oligomer is preferably an acrylic oligomer constituted by an acrylic monomer as an essential monomer component. The acrylic oligomer preferably contains a (meth)acrylic acid ester having an alicyclic hydrocarbon group as a constituent unit. The acrylic monomer contained as the constituent unit may be of only one type or two or more types.

[0083] In one embodiment, the acrylic oligomer preferably contains a (meth)acrylic acid alkyl ester as a structural unit. The (meth)acrylic acid alkyl ester is preferably methyl methacrylate (MMA). The proportion of the (meth)acrylic acid alkyl ester in all monomer components constituting the acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more. The proportion is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. The acrylic oligomer may also contain, as a structural unit, a monomer copolymerizable with the (meth)acrylic acid alkyl ester.

[0084] In one embodiment, the acrylic oligomer preferably contains a functional group-containing monomer as a constituent unit. The functional group-containing monomer is preferably a polar group-containing monomer, more preferably a carboxy group-containing monomer. The proportion of the functional group-containing monomer in all monomer components constituting the acrylic oligomer is preferably 3% by mass or more, more preferably 4% by mass or more. The proportion is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. The acrylic oligomer may also contain, as a constituent unit, a monomer copolymerizable with the functional group-containing monomer.

[0085] The thickness of the pressure-sensitive adhesive layer of the present invention is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. Even when the thickness is as thin as 200 μm or less, the pressure-sensitive adhesive layer of the present invention has excellent adhesion to the adherend and impact resistance. The thickness is not particularly limited, but from the viewpoint of achieving even better adhesion to the adherend and impact resistance, it is preferably 6 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. Furthermore, when the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet with a substrate, the total thickness of the pressure-sensitive adhesive layer on one side is preferably within the above range.

[0086] The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet of the present invention may be in any form, for example, an emulsion type, a solvent type (solution type), an active energy ray curable type, a hot melt type (hot melt type), etc. Among these, a solvent type or an active energy ray curable type pressure-sensitive adhesive layer is preferred because it is easy to obtain a pressure-sensitive adhesive layer with excellent productivity.

[0087] Examples of the active energy rays include ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams, as well as ultraviolet rays, and ultraviolet rays are particularly preferred. That is, the active energy ray-curable pressure-sensitive adhesive layer is preferably an ultraviolet-curable pressure-sensitive adhesive layer.

[0088] The pressure-sensitive adhesive layer of the present invention can be produced, for example, by applying (coating) a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer onto a release liner and drying and curing the resulting pressure-sensitive adhesive composition layer, or by applying (coating) the pressure-sensitive adhesive composition onto a release liner and irradiating the resulting pressure-sensitive adhesive composition layer with active energy rays to cure it. If necessary, the resulting pressure-sensitive adhesive layer may be further dried by heating.

[0089] (Substrate) The substrate is an element that functions as a support in the pressure-sensitive adhesive sheet. The substrate may be a single layer, or may be a laminate of substrates of the same or different types.

[0090] Examples of the substrate include plastic substrates (e.g., plastic films), porous materials such as paper, cloth, and nonwoven fabric, nets, and foam sheets. As the substrate, plastic substrates (particularly plastic films) and foam sheets are preferred.

[0091] Examples of resins constituting the plastic substrate include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, very low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, and ethylene-hexene copolymer; polyurethane resins; rubber resins (natural rubber, synthetic rubber, mixtures thereof, etc.); polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyether ether ketone; polyetherimide; polyamides such as aramid and wholly aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; and silicone resin. Only one of the above resins may be used, or two or more may be used.

[0092] Of the above substrates, a PET substrate is preferred from the viewpoint that it is suitable for thinning and can be easily produced with high smoothness.

[0093] The foam sheet is not particularly limited, but is preferably a plastic foam. The plastic material (including rubber material) for forming the plastic foam is not particularly limited and can be appropriately selected from known plastic materials. Only one type of plastic material may be used, or two or more types may be used.

[0094] Specifically, examples of plastic foams include olefin-based resin foams such as polyethylene foam, polypropylene foam, ethylene-propylene copolymer foam, and ethylene-vinyl acetate copolymer foam; polyester-based resin foams such as polyethylene terephthalate foam, polyethylene naphthalate foam, and polybutylene terephthalate foam; polyvinyl chloride-based resin foams such as polyvinyl chloride foam; vinyl acetate-based resin foam; polyphenylene sulfide resin foam; amide-based resin foams such as polyamide (nylon) resin foam and wholly aromatic polyamide (aramid) resin foam; polyimide-based resin foam; polyether ether ketone (PEEK) foam; styrene-based resin foams such as polystyrene foam; and urethane-based resin foams such as polyurethane resin foam. Rubber-based resin foams may also be used as plastic foams.

[0095] Among these, olefin resin foams are preferred because of their excellent chemical resistance, solvent resistance, moisture permeability resistance, elasticity, and processability, and polyethylene foams, polypropylene foams, and the like are particularly preferred.

[0096] The foam sheet has an expansion ratio of, for example, 1.5 to 30 cc / g, preferably 2.5 to 25.0 cc / g, from the viewpoint of excellent sealing properties, cushioning properties, elasticity, processability, and waterproofing. In this specification, the expansion ratio of the foam sheet is defined as the reciprocal of the apparent density measured in accordance with JIS K6767.

[0097] From the viewpoint of excellent sealing properties, cushioning properties, elasticity, processability, and waterproofing, the elongation of the foam sheet is, for example, 100 to 600%, preferably 400 to 550%, in the MD direction, and, for example, 100 to 500%, preferably 150 to 450%, in the CD direction. In this specification, the elongation of the foam sheet is measured in accordance with JIS K6767.

[0098] From the viewpoint of excellent sealing properties, cushioning properties, elasticity, processability, and waterproofing, the tensile strength of the foamed sheet is, for example, 0.5 to 15 MPa, preferably 1.0 to 10.0 MPa in the MD direction, and, for example, 0.5 to 13.0 MPa, preferably 1.0 to 9.0 MPa in the CD direction. In this specification, the tensile strength of the foamed sheet is measured in accordance with JIS K6767.

[0099] From the viewpoint of excellent sealing properties, cushioning properties, elasticity, processability, and waterproofing, the compression hardness of the foamed sheet is, for example, 5 to 150 kPa, preferably 12 to 120 kPa, when the substrate is placed on a flat plate and compressed to 25% of its original thickness. In this specification, the compression hardness of the foamed sheet is measured in accordance with JIS K6767.

[0100] The thickness of the foamed sheet can be appropriately selected depending on the strength, flexibility, purpose of use, etc., and is, for example, about 50 to 240 μm, preferably about 80 to 200 μm, and more preferably about 100 to 150 μm. The foamed sheet may have a single-layer structure or a laminated structure.

[0101] The substrate may contain various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants (pigments or dyes), dispersants (surfactants, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, etc. The blending ratio of the various additives is about less than 30% by mass (for example, less than 20% by mass, typically less than 10% by mass) relative to 100% by mass of the total mass of the substrate.

[0102] The substrate may include an auxiliary layer, such as a colored layer, a reflective layer, an undercoat layer, or an antistatic layer, provided on the surface of the substrate.

[0103] The surface of the substrate may be subjected to surface treatments such as physical treatments such as corona discharge treatment, plasma treatment, sand matting treatment, ozone exposure treatment, flame exposure treatment, high-voltage shock exposure treatment, and ionizing radiation treatment; chemical treatments such as chromic acid treatment; and adhesion-enhancing treatments using a coating agent (primer), for the purpose of improving adhesion and retention with the pressure-sensitive adhesive layer. The surface treatment for improving adhesion is preferably applied to the entire surface of the substrate.

[0104] The thickness of the substrate is not particularly limited, but is preferably 5 μm or more, and more preferably 10 μm or more. A thickness of 5 μm or more provides superior reworkability. The thickness is not particularly limited, but may be, for example, 240 μm or less, 200 μm or less, or 150 μm or less.

[0105] (Coating layer) The pressure-sensitive adhesive sheet of the present invention may further comprise a coating layer that partially covers the surface (adhesive surface (X)) of the pressure-sensitive adhesive layer of the present invention. By providing such a coating layer, when ethanol is added during rework, the surface of the coating layer acts as a flow path for ethanol, making it easier for the ethanol to spread to areas not covered by the coating layer, making rework easier and reducing the likelihood of adhesive residue.

[0106] Fig. 2 is a top view showing one embodiment of the pressure-sensitive adhesive sheet of the present invention having a coating layer, and Fig. 3 is a cross-sectional view taken along line III-III' in Fig. 2. The pressure-sensitive adhesive sheet 1 shown in Figs. 2 and 3 has a pressure-sensitive adhesive layer 2, which is the pressure-sensitive adhesive layer of the present invention, formed on the release-treated surface of a release liner 4 as shown in Fig. 1. A coating layer 5 is partially disposed on the surface of the pressure-sensitive adhesive layer 2. In other words, the surface (adhesive surface) of the pressure-sensitive adhesive layer 2 is partially covered by the coating layer 5. When the pressure-sensitive adhesive sheet 1 is bonded to an adherend, the coating layer 5 exhibits no or low adhesiveness to the pressure-sensitive adhesive sheet 1 and the adherend. Therefore, when ethanol is added to the interface between the adherend and the pressure-sensitive adhesive sheet during rework, the surface of the coating layer 5 serves as a flow path for the ethanol, resulting in excellent reworkability and less adhesive residue.

[0107] The thickness of the coating layer is not particularly limited, but is preferably less than 3 μm, more preferably 2 μm or less, and even more preferably less than 2 μm. If the thickness is less than 3 μm, ethanol can easily penetrate and the adhesive surface of the pressure-sensitive adhesive sheet becomes smooth. In addition, the adhesiveness to the adherend and the appearance are also good. The thickness of the coating layer can be measured by observing the cross section of the pressure-sensitive adhesive sheet with a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0108] From the viewpoint of excellent smoothness of the adhesive surface of the pressure-sensitive adhesive layer, the thickness of the coating layer is preferably equal to or thinner than the thickness of the pressure-sensitive adhesive layer of the present invention. For example, the ratio of the thickness of the coating layer to the thickness of the pressure-sensitive adhesive layer of the present invention [coating layer / pressure-sensitive adhesive layer of the present invention] is preferably 0.75 or less, more preferably 0.70 or less, even more preferably 0.5 or less, and particularly preferably 0.4 or less.

[0109] The coating layer 5 presents a predetermined pattern (coating layer pattern) on the adhesive surface of the pressure-sensitive adhesive layer 2. In the embodiment shown in Fig. 2, the coating layer 5 presents a grid pattern. Specifically, the grid pattern of the coating layer 5 is composed of a first stripe pattern portion 51 and a second stripe pattern portion 52 arranged so as to intersect with the first stripe pattern portion 51 on the adhesive surface of the pressure-sensitive adhesive layer 2.

[0110] In the pressure-sensitive adhesive sheet of the present invention, the area ratio of the coating layer-free portion on the surface of the pressure-sensitive adhesive layer of the present invention is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. When the area ratio is 70% or more, the adhesiveness to the adherend is superior. From the viewpoint of superior ethanol penetration during rework, the area ratio is preferably 90% or less, more preferably 85% or less.

[0111] The coating layer is preferably a resin layer. Examples of resins constituting the coating layer include polyurethane resins, phenolic resins, epoxy resins, polyamide resins, urea-melamine resins, silicone resins, polysilazane resins, fluorine-based resins, phenoxy resins, methacrylic resins, acrylic resins, acrylic-urethane resins, acrylic-styrene resins, polyarylate resins, polyester resins, polyolefin resins, polystyrene resins, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyvinyl acetate, polyvinylidene chloride, polycarbonate, celluloses, and polyacetal. These resins may be any type, such as thermosetting resins, ultraviolet-curing resins, electron beam-curing resins, and two-component resins. The above resins may be used alone or in combination of two or more.

[0112] The coating layer may contain various additives, such as a filler, an antioxidant, an antioxidant, an ultraviolet absorber, a crosslinking agent, a lubricant, a colorant (pigment, dye, etc.), an antistatic agent, a flowability adjuster (thixotropic agent, thickener, etc.), and a film-forming aid, as needed.

[0113] The coating layer is typically non-adhesive or weakly adhesive, which preferably allows for good ethanol penetration. The coating layer is attached to a stainless steel plate and left for 30 minutes in an environment of 23°C and 50% RH, and the 180° peel adhesion at a tensile speed of 300 mm / min is preferably less than 6 N / cm, more preferably 2 N / cm or less. The 180° peel adhesion of the coating layer can be measured by preparing a sample whose entire surface is covered with the coating layer, and measuring the sample in the same manner as the 180° peel adhesion of the pressure-sensitive adhesive layer of the present invention described above.

[0114] The method for disposing the coating layer on the surface of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but the following method can be used, for example. Specifically, a coating layer-forming composition is prepared by dissolving or dispersing it in an appropriate solvent, as necessary. Next, using an appropriate method from among various known or commonly used printing methods, the composition is applied to the release-treated surface of a release support (e.g., a release liner) and cured. The release support surface on which the coating layer has been formed is then brought into contact with the surface of the pressure-sensitive adhesive layer of the present invention, thereby transferring the coating layer to the surface of the pressure-sensitive adhesive layer of the present invention. In this way, a coating layer can be partially disposed on the surface (adhesive surface) of the pressure-sensitive adhesive layer of the present invention. For example, a desired coating layer pattern, such as a grid pattern, can be preferably formed by using methods such as offset printing, silk screen printing, relief printing, flexographic printing, gravure printing, and inkjet printing. Alternatively, a similar configuration can be obtained by further forming the pressure-sensitive adhesive layer of the present invention on the surface of the coating layer formed on the release support so as to cover the coating layer. In this case, the formed pressure-sensitive adhesive layer is then transferred to the surface of a support such as another release liner or substrate.

[0115] (Adhesive Sheet) The adhesive sheet of the present invention may have a release liner attached to the surface (adhesive surface) of the adhesive layer until use. When the adhesive sheet is a double-sided adhesive sheet, each adhesive surface on both sides may be protected by two release liners, or may be protected by a single release liner with release surfaces on both sides in a form wound into a roll (rolled body). The release liner is used as a protective material for the adhesive layer and is peeled off when the sheet is attached to an adherend. It should be noted that the release liner is not necessarily provided.

[0116] The release liner can be a conventional release paper, and is not particularly limited. Examples include substrates with a release treatment layer, low-adhesion substrates made of fluoropolymers, and low-adhesion substrates made of non-polar polymers. Examples of substrates with a release treatment layer include plastic films and papers surface-treated with release agents such as silicone-based, long-chain alkyl-based, fluorine-based, and molybdenum sulfide-based release agents. Examples of fluorine-based polymers in the low-adhesion substrates made of fluoropolymers include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymers, and chlorofluoroethylene-vinylidene fluoride copolymers. Examples of non-polar polymers include olefin-based resins (e.g., polyethylene, polypropylene, etc.). The release liner can be formed by known or conventional methods. The thickness of the release liner is also not particularly limited.

[0117] The pressure-sensitive adhesive sheet of the present invention can be easily peeled and recovered from the adherend with little adhesive residue using alcohol. The alcohol used for the peeling may be alcohol itself, a mixed solvent containing alcohol as the main component, or a mixture of these containing a small amount of additives as needed. As the alcohol, monohydric lower alcohols having 1 to 4 carbon atoms are preferred, with methanol, ethanol, isopropyl alcohol, etc. being particularly preferred. Among these, ethanol is preferred from the standpoint of safety, etc. One or more of the above alcohols may be used.

[0118] The pressure-sensitive adhesive sheet is preferably for attaching electrical and electronic components, that is, for use by being attached to components included in electrical and electronic devices. The pressure-sensitive adhesive sheet is particularly preferably used for applications in which components included in electrical and electronic devices are attached to each of the two adhesive surfaces of the double-sided pressure-sensitive adhesive sheet, i.e., for fixing components together in electrical and electronic devices. The double-sided pressure-sensitive adhesive sheet may be used for either fixing or temporarily fixing the components together.

[0119] The term "electrical and electronic devices" refers to devices that fall into at least either an electrical device or an electronic device. Examples of the electrical and electronic devices include image display devices such as liquid crystal displays, electroluminescence displays, and plasma displays, as well as portable electronic devices.

[0120] Examples of the portable electronic device include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including eyeglasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. as accessories, earwear devices attached to the ears like earphones), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, e-books, in-car information devices, portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, "portable" does not simply mean being portable, but also means having a level of portability that allows an individual (average adult) to carry it relatively easily. The pressure-sensitive adhesive sheet is used, for example, so that the pressure-sensitive adhesive layer adheres to components of the portable electronic device.

[0121] The pressure-sensitive adhesive sheet of the present invention may be used to bond at least one adhesive surface to a metal plate such as a stainless steel plate. In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used to bond a battery in an electric / electronic device (particularly, a portable electronic device) to the housing of the electric / electronic device, from the viewpoints of excellent impact resistance, little adhesive residue, and excellent reworkability.

[0122] Figure 4 schematically shows an example of a portable electronic device (smartphone) in which the above-mentioned pressure-sensitive adhesive sheet is used to bond a battery and a housing. As shown in Figure 4, a battery (heat-generating element) 8 is built into a housing 7 of the portable electronic device 6. The portable electronic device 6 is also configured with a pressure-sensitive adhesive sheet 1 made of the pressure-sensitive adhesive layer of the present invention. In this configuration example, the pressure-sensitive adhesive sheet 1 has the form of a double-sided pressure-sensitive adhesive sheet that fixes the components constituting the portable electronic device 6, specifically the housing 7 and the battery 8. The portable electronic device 6 is also equipped with a touch panel 9 whose display unit also functions as an input unit.

[0123] The pressure-sensitive adhesive sheet of the present invention can also be used to bond components (particularly between components) in electrical and electronic devices that are used by folding, such as electrical and electronic devices having a foldable image display device (flexible display) (particularly, a foldable image display device (foldable display)).

[0124] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Note that the number of blended parts (parts by mass) all refers to the number of blended parts of each component described.

[0125] Example 1 (Preparation of Pressure-Sensitive Adhesive Composition) 100 parts by mass of a styrene-isoprene block copolymer (trade name "Quintac 3520", manufactured by Zeon Corporation), 10 parts by mass of a terpene phenol resin (trade name "YS Polystar T145", manufactured by Yasuhara Chemical Co., Ltd.), 2 parts by mass of an antioxidant (trade name "Irgafos 168", manufactured by BASF Corporation) and 1 part by mass of an antioxidant (trade name "Irganox 565", manufactured by BASF Corporation), 0.75 parts by mass of an isocyanate-based crosslinking agent (trade name "Takenate D101E", manufactured by Mitsui Chemicals, Inc.), and toluene as a solvent were stirred and mixed to prepare a pressure-sensitive adhesive composition having a solids concentration of 35% by mass.

[0126] (Preparation of Pressure-Sensitive Adhesive Sheet) The pressure-sensitive adhesive composition was applied to a release-treated layer of a 75 μm-thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) one side of which had been release-treated with silicone, so that the pressure-sensitive adhesive layer was 50 μm thick, and dried at 110° C. for 2 minutes to form a pressure-sensitive adhesive layer. A release-treated layer of a 38 μm-thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) one side of which had been release-treated with silicone was then superimposed on the pressure-sensitive adhesive layer to prepare the double-sided pressure-sensitive adhesive sheet of Example 1. The oxidation induction time of the double-sided pressure-sensitive adhesive sheet (oxidation induction time measured by the chemiluminescence method described above) was 33 minutes.

[0127] Examples 2 to 6, 9 to 11, Comparative Examples 1 to 10 The pressure-sensitive adhesive compositions and double-sided pressure-sensitive adhesive sheets of each example were prepared in the same manner as in Example 1, except that the formulation of the pressure-sensitive adhesive composition was changed as shown in Table 1 or Table 2.

[0128] The pressure-sensitive adhesive composition prepared in Example 6 was applied to the release-treated layer of a 75 μm-thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) one side of which had been release-treated with silicone, so that the pressure-sensitive adhesive layer would be 50 μm thick, and the applied layer was dried at 110° C. for 2 minutes to form a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer obtained above was then bonded to both sides of a 12 μm-thick PET film (product name "Lumirror S10#12", manufactured by Toray Industries, Inc.), to produce the double-sided pressure-sensitive adhesive sheet of Example 7.

[0129] Example 8 (Formation of Coating Layer) A coating layer-forming material (urethane-based: two-component mixed curing ink) was applied by gravure printing onto the release-treated layer of a 75 μm-thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) whose one side had been release-treated with silicone, to form a coating layer (application thickness: approximately 1.5 μm, transparent) having a grid pattern. In this way, a coating layer-forming release film was obtained in which the coating layer was partially formed on the release-treated layer of the release liner.

[0130] (Preparation of Pressure-Sensitive Adhesive Composition) 100 parts by mass of a styrene-isoprene block copolymer (trade name "Quintac 3520", manufactured by Zeon Corporation), 30 parts by mass of a terpene phenol resin (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd.), 2 parts by mass of an antioxidant (trade name "Irgafos 168", manufactured by BASF Corporation, a phosphorus-based antioxidant) and 1 part by mass of an antioxidant (trade name "Irganox 565", manufactured by BASF Corporation, a phenol-based antioxidant), 0.75 parts by mass of an isocyanate-based crosslinking agent (trade name "Takenate D101E", manufactured by Mitsui Chemicals, Inc.), and toluene as a solvent were stirred and mixed to prepare a pressure-sensitive adhesive composition having a solids concentration of 35% by mass.

[0131] (Preparation of adhesive sheet) The adhesive composition was applied to a release-treated layer of a 75 μm thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) with one side treated with silicone for release, so that the adhesive layer had a thickness of 50 μm, and dried at 110 ° C. for 2 minutes to form an adhesive layer. A release-treated layer of a 38 μm thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) with one side treated with silicone for release was then superimposed on the adhesive layer. Then, a 75 μm thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) with one side treated with silicone for release was peeled off and then replaced with the coating layer-forming release film obtained above, thereby producing a double-sided adhesive sheet of Example 8 in which the coating layer was formed in a grid pattern on one adhesive surface of the adhesive layer.

[0132] Example 11 The pressure-sensitive adhesive composition prepared in Example 6 was applied to the release-treated layer of a 75 μm-thick polyethylene terephthalate film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) whose one side had been treated with silicone for release, so that the thickness of the pressure-sensitive adhesive layer was 25 μm, and the film was dried at 110° C. for 2 minutes to form a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer obtained above was then bonded to both sides of a 100 μm-thick black polyethylene foam substrate (product name "Volara XL-HN#03001W Shorikuro", manufactured by Sekisui Chemical Co., Ltd., expansion ratio: 2.9 cc / g, elongation: 480% (MD direction), 195% (CD direction), tensile strength: 9.5 MPa (MD direction), 8.7 MPa (CD direction), compression hardness: 64 kPa (at 25% compression)), to prepare the double-sided pressure-sensitive adhesive sheet of Example 12.

[0133] The components shown in Tables 1 and 2 are as follows: <Base polymer> Quintac 3520: trade name "Quintac 3520", manufactured by Zeon Corporation, styrene-isoprene block copolymer, styrene content 15% by mass, diblock ratio 78% by mass Quintac 3270: trade name "Quintac 3270", manufactured by Zeon Corporation, styrene-isoprene block copolymer, styrene content 24% by mass, diblock ratio 67% by mass Quintac 3280: trade name "Quintac 3280", manufactured by Zeon Corporation, styrene-isoprene block copolymer, styrene content 25% by mass, diblock ratio 17% by mass

[0134] <Oligomer> This acrylic oligomer was produced by the following method. 60 parts by mass of dicyclopentanyl methacrylate and 40 parts by mass of methyl methacrylate as monomer components, 3.5 parts by mass of α-thioglycerol as a chain transfer agent, and 100 parts by mass of toluene as a polymerization solvent were mixed and stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of AIBN was added as a thermal polymerization initiator, and the mixture was reacted at 70°C for 2 hours, and then the temperature was raised to 80°C and the mixture was reacted for 2 hours. Thereafter, the reaction solution was heated to 130°C, and the toluene, chain transfer agent, and unreacted monomer were dried and removed to obtain a solid acrylic oligomer (weight average molecular weight 5100).

[0135] <Tackifying Resins> YS Polystar U130: trade name "YS Polystar U130", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 130°C, hydroxyl value 30 mgKOH / g YS Polystar T145: trade name "YS Polystar T145", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 145°C, hydroxyl value 60 mgKOH / g YS Polystar S145: trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 145°C, hydroxyl value 100 mgKOH / g YS Polystar K125: trade name "YS Polystar K125", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 125°C, hydroxyl value 200 mgKOH / g PX1150N: Trade name "YS Resin PX1150N", manufactured by Yasuhara Chemical Co., Ltd., a mixture of terpene resin and petroleum resin, softening point 115°C, hydroxyl value less than 1 mgKOH / g

[0136] <Evaluation> The pressure-sensitive adhesive sheets obtained in the examples and comparative examples were evaluated as follows, and the results are shown in the table.

[0137] (1) 180° Peel Adhesion Strength Under a measurement environment of 23°C and 50% RH, the release liners on both sides of the PSA sheets prepared in the Examples and Comparative Examples were peeled off, and a 25 μm thick PET film treated with a primer (product name "N-200NT", manufactured by 3M Innovative Properties Company) was attached to one adhesive surface of the PSA sheet as a backing, and the sheet was cut to a size of 25 mm wide and 100 mm long to prepare a measurement sample. For the prepared measurement sample, the exposed adhesive surface of the measurement sample was pressed against the surface of a stainless steel plate (SUS304BA plate) by rolling a 2 kg roller back and forth three times under an environment of 23°C and 50% RH. The sheet was then left in the same environment for 30 minutes. Then, using a universal tension and compression tester, the 180° peel strength (peel adhesive strength) [N / cm] was measured under environmental conditions of a tension speed of 300 mm / min, a peel angle of 180°, 23°C, and 50% RH, and the average value of n = 3 was used as the measurement result. A tensile tester (product name "AG-X", manufactured by Shimadzu Corporation) was used as the universal tension and compression tester.

[0138] (2) Dynamic Shear Adhesion Strength Measurement samples were prepared by cutting the pressure-sensitive adhesive sheets prepared in the Examples and Comparative Examples to a size of 25 mm x 25 mm. Under an environment of 23°C and 50% RH, one adhesive surface of the measurement sample was placed on a stainless steel plate (SUS304BA plate), and the other adhesive surface was placed on the surface of a backing material (SUS304 liner, 0.1 mm thick), and pressure-bonded by rolling three times with a 2 kg roller. After leaving this under the same environment for 24 hours, the dynamic shear adhesive strength was measured using a tensile tester at a pulling rate of 10 mm / min and a peel angle of 0°. Specifically, as shown in FIG. 5, one adhesive surface 10a of the measurement sample 10 was bonded to a stainless steel plate 21, and the other adhesive surface 10b of the measurement sample 10 was bonded to a backing material 22 and pressure-bonded. This was pulled at the above-mentioned speed in the direction of the arrow in FIG. 5 (i.e., the shear direction), and the peel strength per 25 mm x 25 mm was measured. The dynamic shear adhesive strength [MPa] was calculated from the obtained values, and the maximum value for n = 2 was used as the measurement result. A universal tension / compression tester (product name "TG-1kN", manufactured by Minebea Co., Ltd.) was used as the tensile tester.

[0139] (3) 180° Peel Adhesion (with Ethanol) Under a measurement environment of 23°C and 50% RH, the release liners on both sides of the PSA sheets prepared in the Examples and Comparative Examples were peeled off, and a 25 μm thick PET film treated with a primer (product name "N-200NT", manufactured by 3M Innovative Properties Company) was attached to one adhesive surface of the PSA sheet as a backing, and the sheet was cut to a size of 25 mm wide and 100 mm long to prepare a measurement sample. For the prepared measurement sample, under an environment of 23°C and 50% RH, the exposed adhesive surface of the measurement sample was pressed against the surface of a stainless steel plate (SUS304BA plate) by rolling a 2 kg roller back and forth three times. This was left in the same environment for 30 minutes. Then, using a universal tension and compression tester, 0.5 mL of ethanol (trade name "Special Grade Ethanol," concentration: 99.5%, manufactured by Kishida Chemical Co., Ltd.) was dropped onto the adhesive interface between the measurement sample and the stainless steel plate (the 25 mm-wide side of the measurement sample). Immediately after the drop, the 180° peel strength (peel adhesive strength) [N / cm] was measured under environmental conditions of a tensile speed of 300 mm / min, a peel angle of 180°, 23°C, and 50% RH. Specifically, as shown in FIG. 6 , one adhesive surface of the measurement sample 11 was bonded to a stainless steel plate 21, and the other adhesive surface of the measurement sample 11 was bonded to a backing material 23 and pressure-bonded. Then, 0.5 mL of ethanol 31 was supplied to the peel interface on the 25 mm-wide side of the measurement sample. Immediately after the supply, the measurement sample 11 was peeled by pulling in the direction of the arrow shown in FIG. 6 at the above-mentioned speed. The peel strength in the stable state at this time was measured, and the average value of n = 3 was used as the measurement result. A tensile testing machine (product name "AG-X", manufactured by Shimadzu Corporation) was used as the universal tension and compression testing machine.

[0140] (4) Adhesion Test Under a measurement environment of 23°C and 50% RH, a 30 mm x 80 mm measurement sample was cut out from the pressure-sensitive adhesive sheet prepared in the Examples and Comparative Examples. Under an environment of 23°C and 50% RH, one adhesive surface of the measurement sample was attached to the surface of a 30 mm x 80 mm stainless steel plate (SUS304BA plate), and then the other exposed adhesive surface of the measurement sample was attached to the surface of a 30 mm x 100 mm stainless steel plate (SUS304BA plate), and pressure-bonded by three reciprocating strokes using a 2 kg roller. This was left in the same environment for 30 minutes. A measurement laminate was prepared. In the measurement laminate, one end of the two stainless steel plates and the measurement sample were aligned. Then, a 500 g load was hung from the other end of the stainless steel plate extending in the planar direction, 10 mm from the other end, to confirm adhesion. 7, one adhesive surface of the measurement sample 12 was attached to a 30 mm × 80 mm stainless steel plate 24, and the other adhesive surface was attached to a 30 mm × 100 mm stainless steel plate 25, and a load 32 (500 g) was hung from the sample. If no peeling occurred in the measurement laminate after 5 minutes, the adhesiveness was determined to be good.

[0141] (5) Dismantling Test A 300 g load was suspended from the measurement laminate shown in Figure 7 as the load 32. 0.3 mL of ethanol (product name "Special Grade Ethanol", concentration: 99.5%, manufactured by Kishida Chemical Co., Ltd.) was then dropped onto the interface 33 on the other end side of the measurement sample 12 and the stainless steel plate 25, and the time until the stainless steel plate 25 dismantled and fell was measured. Note that if the time was less than 5 minutes, the dismantling was judged to be good.

[0142] (6) Adhesive residue After the above dismantling test, the adhesive surface of the dismantled stainless steel plate was visually inspected, and if no remaining adhesive was found, it was evaluated as "none." Note that "*" in the table indicates that the stainless steel plate was not dismantled after 5 minutes in the above dismantling test, and therefore adhesive residue was not evaluated.

[0143]

[0144]

[0145] As shown in Table 1, the PSA sheets of the Examples were evaluated as having excellent adhesion to adherends, being easily reworkable with alcohol, and not leaving much adhesive residue. Furthermore, the PSA sheets were evaluated as having high dynamic shear adhesive strength and excellent impact resistance. On the other hand, when the 180° peel adhesive strength was less than 5.5 N / cm (Comparative Examples 1, 2, and 4), the PSA sheets were evaluated as having poor adhesion to adherends. When the dynamic shear adhesive strength was less than 0.35 MPa (Comparative Examples 1 to 3), the PSA sheets were evaluated as having poor impact resistance. Furthermore, when the 180° peel adhesive strength (with ethanol) exceeded 2.0 N / cm (Comparative Examples 5 to 10), the PSA sheets were evaluated as having poor reworkability.

[0146] Variations of the invention according to the present disclosure are described below. [Appendix 1] A pressure-sensitive adhesive sheet comprising a rubber-based pressure-sensitive adhesive layer, wherein the adhesive surface of the rubber-based pressure-sensitive adhesive layer is bonded to a stainless steel plate and left for 30 minutes in an environment of 23°C and 50% RH, and after that, the 180° peel adhesion strength at a tensile speed of 300 mm / min is 5.5 N / cm or more, the dynamic shear adhesion strength at a tensile speed of 10 mm / min and a peel angle of 0° is 0.35 MPa or more, and the adhesive surface of the rubber-based pressure-sensitive adhesive layer is bonded to a stainless steel plate and left for 30 minutes in an environment of 23°C and 50% RH, and after 0.5 mL of ethanol is supplied to the adhesive interface, the 180° peel adhesion strength at a tensile speed of 300 mm / min is 2.0 N / cm or less. [Appendix 2] The pressure-sensitive adhesive sheet according to Appendix 1, wherein the rubber-based pressure-sensitive adhesive layer comprises a styrene-based rubber as a base polymer. [Appendix 3] The pressure-sensitive adhesive sheet according to Appendix 2, wherein the styrene-based rubber comprises 5 to 30% by mass of a structural unit derived from a monovinyl-substituted aromatic compound. [Appendix 4] The pressure-sensitive adhesive sheet according to Appendix 2 or 3, wherein the styrene-based rubber is a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, with a diblock copolymer ratio of 30% by mass or more. [Appendix 5] The pressure-sensitive adhesive sheet according to any one of Appendixes 1 to 4, wherein the rubber-based pressure-sensitive adhesive layer comprises a tackifier resin. [Appendix 6] The pressure-sensitive adhesive sheet according to Appendix 5, wherein the tackifier resin has a hydroxyl value of 50 mgKOH / g or more. [Appendix 7] The pressure-sensitive adhesive sheet according to any one of Appendixes 1 to 6, further comprising a coating layer partially covering the surface of the rubber-based pressure-sensitive adhesive layer. [Appendix 8] The pressure-sensitive adhesive sheet according to any one of Appendixes 1 to 7, further comprising a substrate. [Appendix 9] The pressure-sensitive adhesive sheet according to Appendix 8, wherein the substrate is a plastic film or a foam sheet. [Appendix 10] The pressure-sensitive adhesive sheet according to any one of Appendices 1 to 9, which is used to fasten components together in an electrical / electronic device. [Appendix 11] An electrical / electronic device comprising the pressure-sensitive adhesive sheet according to Appendices 10, wherein the pressure-sensitive adhesive sheet fastens components together using both adhesive surfaces.

[0147] REFERENCE SIGNS LIST 1 adhesive sheet 2 adhesive layer 3, 4 release liner 5 coating layer 51 first stripe pattern portion 52 second stripe pattern portion 6 portable electronic device 7 housing 8 battery 9 touch panel 10, 11, 12 measurement sample 10a, 10b adhesive surface 21, 24, 25 stainless steel plate 22, 23 backing material 31 ethanol 32 interface

Claims

A rubber-based adhesive layer is provided, the adhesive surface of the rubber-based pressure-sensitive adhesive layer is attached to a stainless steel plate and left to stand for 30 minutes in an environment of 23°C and 50% RH, after which the 180° peel adhesive strength at a pulling rate of 300 mm / min is 5.5 N / cm or more, the adhesive surface of the rubber-based pressure-sensitive adhesive layer is attached to a stainless steel plate, and the resulting sheet is left to stand for 24 hours in an environment of 23°C and 50% RH, after which the dynamic shear adhesive strength measured under conditions of a pulling rate of 10 mm / min and a peel angle of 0° is 0.35 MPa or more; A pressure-sensitive adhesive sheet in which the adhesive surface of the rubber-based pressure-sensitive adhesive layer is attached to a stainless steel plate, and the sheet is left for 30 minutes in an environment of 23°C and 50% RH, and 0.5 mL of ethanol is supplied to the adhesive interface, and the 180° peel adhesive strength at a tensile speed of 300 mm / min from this state is 2.0 N / cm or less. 　 The pressure-sensitive adhesive sheet according to claim 1 , wherein the rubber-based pressure-sensitive adhesive layer contains a styrene-based rubber as a base polymer. 　 The pressure-sensitive adhesive sheet according to claim 2 , wherein the styrene-based rubber contains 5% by mass or more of structural units derived from a monovinyl-substituted aromatic compound. 　 The pressure-sensitive adhesive sheet according to claim 2 , wherein the styrene-based rubber is a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, the diblock copolymer having a diblock content of 30% by mass or more. 　 The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the rubber-based pressure-sensitive adhesive layer contains a tackifying resin. 　 The pressure-sensitive adhesive sheet according to claim 5 , wherein the tackifier resin has a hydroxyl value of 50 mgKOH / g or more. 　 The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, further comprising a coating layer that partially covers the surface of the rubber-based pressure-sensitive adhesive layer. 　 The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, further comprising a substrate. 　 The pressure-sensitive adhesive sheet according to claim 8, wherein the substrate is a plastic film or a foam sheet. 　 The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, which is used to fix components together in an electric or electronic device. 　 An electrical / electronic device comprising the adhesive sheet according to claim 10, wherein the adhesive sheet fixes components together with both adhesive surfaces thereof.

Images