Disassembly method and adhesive sheet

Abstract

Provided is a joined body disassembly method that can be applied even to the disassembly of a joined body that contains a member having a relatively low hydrophilicity. This disassembly method achieves both joining reliability and ease of disassembly. Provided is a method for disassembling a joined body wherein the joined body contains: an adhesive sheet having a first adhesive surface, and a first member joined to the first adhesive surface. This method comprises: immersing the joined body in a peeling liquid containing a C1 to C5 lower alcohol as a main component; and disassembling the joined body after this immersion. In a peeling test carried out versus a stainless steel plate as the adherend, the adhesive sheet has a reduction ratio RA of 70% or more for the ethanol peeling force N1 [N / 20 mm] with respect to the normal peeling force N0 [N / 20 mm] in a first-time measurement, and has a reduction ratio RB of 30% or less for the normal peeling force N0S [N / 20 mm] in a second-time measurement with respect to the normal peeling force N0 [N / 20 mm] in the first-time measurement.

Description

Disassembly method and adhesive sheet

[0001] The present invention relates to a method for dismantling a bonded structure including a pressure-sensitive adhesive sheet, and to a pressure-sensitive adhesive sheet. This application claims priority to Japanese Patent Application No. 2023-204737, filed on December 4, 2023, the entire contents of which are incorporated herein by reference.

[0002] Generally, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) are in a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to an adherend when pressure is applied. Utilizing these properties, pressure-sensitive adhesives are widely used in a variety of fields in the form of supported pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer on a support, or in the form of support-less pressure-sensitive adhesive sheets having no support. Furthermore, after use, the pressure-sensitive adhesives are peeled from the adherend by appropriate means, if necessary. Patent documents relating to peeling pressure-sensitive adhesives from adherends include Patent Documents 1 to 3.

[0003] Japanese Patent Application Publication No. 2020-023656 Japanese Patent Application Publication No. 2021-138934 International Publication No. 2022 / 038926

[0004] In recent years, from the perspective of reducing environmental impact and saving resources, it has become common to separate components bonded using adhesives from products after use and reuse them (recycle, reuse, etc.). For example, display devices built into products with display functions, such as smartphones, personal computers (desktop, notebook, tablet, etc.), and televisions, have multilayer structures containing multiple and heterogeneous functional components, such as liquid crystal display devices, organic electroluminescence (EL) display devices, and plasma display panels (PDPs). Because each component contains different materials, there are significant advantages to recycling and reusing them. Furthermore, a technology is known in which a surface protective sheet is adhered to the surface of glass, metal, or organic materials (e.g., PET, PI, etc.) to protect the surface from damage and contamination during processing, transportation, storage, etc., and such a surface protective sheet is removed from the adherend at an appropriate time after the protective purpose has been achieved. Another example of an application requiring the release of adhesive bonding at a desired time is the use of batteries, which are often removed during repair, replacement, product inspection, etc. of components constituting electronic devices.

[0005] However, there is a trade-off between the bonding reliability and ease of disassembly of adhesives, and disassembly of assembled structures requiring high bonding reliability generally tends to be difficult. For example, when disassembling an assembled structure in which rigid bodies are bonded together via an adhesive, it is not possible to deform the adherend members to reduce the peel force, and the force required to release the adhesion across the entire bonded surface tends to be large. Furthermore, the members (adherends) bonded by the adhesive may be hard and brittle or thin, and such members may be damaged by the force applied when the adhesive is peeled off. Under these circumstances, the present inventors proposed in Patent Document 1 a pressure-sensitive adhesive sheet (water-peelable pressure-sensitive adhesive sheet) that can be easily peeled off using water and has improved water resistance reliability during bonding.

[0006] However, since the water-releasable pressure-sensitive adhesive sheet proposed in Patent Document 1 is based on the premise that an aqueous liquid such as water is used to peel the pressure-sensitive adhesive sheet from the adherend, it can be suitably applied to peeling from highly hydrophilic adherends such as glass and silicon wafers, but may not be suitably applied to adherends with low hydrophilicity. If a technology could be provided that achieves both bonding reliability and ease of disassembly for adherends with relatively low hydrophilicity, such as metals and resins, in addition to highly hydrophilic adherends, the range of applicable adherends would be expanded, which would be beneficial.

[0007] The present invention was made in view of the above circumstances, and aims to provide a method for dismantling an assembly that can be applied to dismantling an assembly including components with relatively low hydrophilicity, and that achieves both bonding reliability and ease of dismantling. Another related aim is to provide a pressure-sensitive adhesive sheet that can be easily peeled off from components with relatively low hydrophilicity using an alcoholic liquid.

[0008] This specification provides a method for dismantling an assembly including a pressure-sensitive adhesive sheet having a first adhesive surface and a first member bonded to the first adhesive surface. The dismantling method includes immersing the assembly in a stripping solution containing a lower alcohol having 1 to 5 carbon atoms as a main component, and dismantling the assembly after the immersion. Here, the pressure-sensitive adhesive sheet has a reduction rate R of ethanol peel force N1 [N / 20 mm] relative to normal peel force N0 [N / 20 mm] in the first measurement in the following peel test. Ａ The adhesive sheet has a peel strength of 70% or more when measured twice. Ｓ Reduction rate R of [N / 20mm] ＢThe peel strength may be 30% or less. [Peel Test] (First Measurement) The first adhesive surface of the pressure-sensitive adhesive sheet is attached to a stainless steel plate, placed in an autoclave, and treated at a pressure of 5 atm and a temperature of 50°C for 15 minutes. The sheet is then removed from the autoclave and allowed to stand for 30 minutes in an environment of 23°C and 50% RH. Then, under the same environment, the pressure-sensitive adhesive sheet is peeled from the stainless steel plate using a tensile tester at a peel angle of 180° and a pulling rate of 300 mm / min. During the peeling process, 20 μL of ethanol is dropped onto the location where the pressure-sensitive adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol drop is designated as the normal peel strength N0 [N / 20 mm], and the peel strength observed after the ethanol drop is designated as the ethanol peel strength N1 [N / 20 mm]. (Second Measurement) After drying the adhesive sheet used in the first measurement, the first adhesive surface of the adhesive sheet is attached to a new stainless steel plate, placed in an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50°C, removed from the autoclave and left to stand for 30 minutes in an environment of 23°C and 50% RH, and then peeled from the stainless steel plate using a tensile tester under the same conditions at a peel angle of 180° and a pulling speed of 300 mm / min. During the peeling process, 20 μL of ethanol is dropped at the point where the adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol drop is referred to as the normal peel strength NO. Ｓ [N / 20 mm], and the peel strength observed after dropping ethanol was the ethanol peel strength N1 Ｓ [N / 20mm].

[0009] According to the above disassembly method, the adhesive sheets constituting the laminate have a peel force reduction rate R Ａ By exhibiting a good alcohol removability of 70% or more, the bonded body can be efficiently disassembled by immersion in the stripping solution (e.g., easily disassembled even by immersion in the stripping solution for a relatively short time). ＢA bonded structure having a % or less of alcohol resistance can exhibit a certain level of durability against contact with alcohol under normal conditions of use (i.e., conditions of use in which the bonding by the PSA sheet is expected to be maintained). The disassembly method disclosed herein is useful, for example, as a method for efficiently disassembling such an alcohol-resistant bonded structure.

[0010] In some embodiments, the first member preferably has a contact angle with distilled water of 50 degrees or more. The disassembly method disclosed herein can be preferably carried out in an embodiment for disassembling a bonded structure including such members whose surfaces have relatively low hydrophilicity.

[0011] In some embodiments, the first adhesive surface may be a surface of an acrylic adhesive layer containing an acrylic polymer as a base polymer. The disassembly method disclosed herein can be preferably carried out in an embodiment in which a bonded structure including a PSA sheet having such a configuration is disassembled.

[0012] In some embodiments, the monomer component constituting the acrylic polymer is an alkyl (meth)acrylate having an alkyl group having 10 to 14 carbon atoms ((meth)acrylic acid C １０－１４ That is, the acrylic polymer preferably contains (meth)acrylic acid C １０－１４ The acrylic pressure-sensitive adhesive layer containing such an acrylic polymer is preferably a polymer of a monomer component containing an alkyl ester. Ａ Therefore, a pressure-sensitive adhesive sheet with high adhesion can be suitably realized.

[0013] In some embodiments, the PSA sheet may be a double-sided PSA sheet having a second PSA surface on the surface opposite to the first PSA surface. In such embodiments, the joined structure may further include a second member joined to the second PSA surface. The disassembly method disclosed herein can also be preferably applied to disassembly of such joined structures in which a first member and a second member are joined via a double-sided PSA sheet.

[0014] According to this specification, there is provided a PSA sheet having a first PSA layer constituting a first adhesive surface, a second PSA layer constituting a second adhesive surface that is the surface opposite to the first PSA layer, and a substrate disposed between the first PSA layer and the second PSA layer. In the following peel test, the PSA sheet has a reduction rate R of ethanol peel strength N1 [N / 20 mm] relative to normal peel strength N0 [N / 20 mm]. Ａ The substrate preferably has a weight loss of less than 1% by weight when immersed in ethanol for 10 minutes and then dried. [Peel Test] The first adhesive surface of the pressure-sensitive adhesive sheet is attached to a stainless steel plate, placed in an autoclave and treated at a pressure of 5 atm and a temperature of 50°C for 15 minutes. The sheet is then removed from the autoclave and left to stand in an environment of 23°C and 50% RH for 30 minutes. The pressure-sensitive adhesive sheet is then peeled from the stainless steel plate using a tensile tester at a peel angle of 180° and a pulling rate of 300 mm / min under the same environment. During this peeling process, 20 μL of ethanol is dropped onto the point where the pressure-sensitive adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol drop is designated as the normal peel strength N0 [N / 20 mm], and the peel strength observed after the ethanol drop is designated as the ethanol peel strength N1 [N / 20 mm].

[0015] The peel test corresponds to the first measurement of the peel test in the disassembly method described above.

[0016] The pressure-sensitive adhesive sheet has a structure using a substrate that is substantially insoluble in ethanol, and yet has a peel force reduction rate R Ａ The adhesive sheet exhibits good alcohol removability of 70%. A bonded structure formed using a PSA sheet (substrate-attached double-sided PSA sheet) having such a configuration and properties can be easily disassembled, for example, by immersing it in an alcoholic stripping solution (such as a stripping solution containing a lower alcohol having 1 to 5 carbon atoms as a main component). The PSA sheet can be preferably used, for example, as a component of a bonded structure that is expected to be disassembled by any of the disassembly methods disclosed herein.

[0017] In some embodiments, the PSA sheet preferably has an ethanol absorption rate of 25% by weight or more of the weight of the substrate when the substrate is immersed in ethanol for 10 minutes. When a PSA sheet (substrate-attached double-sided PSA sheet) having a substrate exhibiting a predetermined level of ethanol absorbency is disassembled by immersing the bonded structure including the PSA sheet in, for example, an alcoholic stripping solution (such as a stripping solution containing a lower alcohol having 1 to 5 carbon atoms as the main component), the alcohol absorbency of the substrate can be utilized to efficiently distribute the stripping solution across the bonded structure.

[0018] In some embodiments, the first pressure-sensitive adhesive layer may be an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in an embodiment having the acrylic pressure-sensitive adhesive layer.

[0019] In some embodiments, the monomer component constituting the acrylic polymer is an alkyl (meth)acrylate having an alkyl group having 10 to 14 carbon atoms (hereinafter, referred to as C １０－１４ It is preferable that the acrylic pressure-sensitive adhesive layer contains an acrylic polymer. Ａ Therefore, a pressure-sensitive adhesive sheet with high adhesion can be suitably realized.

[0020] Appropriate combinations of the elements described in this specification may also be included within the scope of the invention for which patent protection is sought by this patent application.

[0021] 1 is a cross-sectional view schematically showing one configuration example of a bonded body including a pressure-sensitive adhesive sheet; FIG. 2 is a cross-sectional view schematically showing another configuration example of a bonded body including a pressure-sensitive adhesive sheet; and FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to an embodiment.

[0022] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0023] In this specification, the "base polymer" of a PSA refers to the main rubbery polymer component contained in the PSA. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, unless otherwise specified, the "main component" refers to a component that accounts for more than 50% by weight.

[0024] In this specification, "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight of an acrylic monomer. The acrylic monomer refers to a monomer derived from a monomer having at least one (meth)acryloyl group per molecule. In addition, in this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Therefore, the concept of acrylic monomer here can include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth)acrylic acid" refers to acrylic acid and methacrylic acid in a comprehensive sense, and "(meth)acrylate" refers to acrylate and methacrylate in a comprehensive sense. The same applies to other similar terms.

[0025] In this specification, "weight" may be read as "mass." For example, "% by weight" may be read as "% by mass," and "parts by weight" may be read as "parts by mass."

[0026] <Characteristics of adhesive sheet> (peel force reduction rate R Ａ The PSA sheet in the technology disclosed herein has a first adhesive surface (typically, the surface of a first PSA layer), and has a peel force reduction rate R (i.e., peel force reduction rate due to ethanol dropping) measured by dropping ethanol on the first adhesive surface during peeling after the first adhesive surface is stuck to a stainless steel plate. Ａ The peel force reduction rate R Ａ can be determined by the above-mentioned peel test (if the first and second measurements are performed in the peel test, from the result of the first measurement). More specifically, the normal peel force N0 [N / 20 mm] and the ethanol peel force N1 [N / 20 mm] are measured by the peel test described in the Examples below, and the obtained values ​​are substituted into the following formula to determine the peel force reduction rate R Ａ is calculated. Ａ [%] = ((N0-N1) / N0) x 100

[0027] Peel force reduction rate R Ａ A PSA sheet having a peel force reduction rate R of 70% or more tends to exhibit good peel force reduction properties with respect to an alcoholic stripping solution (for example, a stripping solution containing a lower alcohol having 1 to 5 carbon atoms as a main component), and can be preferably used as a PSA sheet constituting an assembly that is expected to be dismantled using the dismantling method disclosed herein. An assembly constructed using the above PSA sheet can be efficiently dismantled using the dismantling method disclosed herein. From the viewpoint of shortening the time required for dismantling and reducing the load on the members constituting the assembly during dismantling work, in some embodiments, the peel force reduction rate R Ａ is advantageously 75% or more, preferably 80% or more, more preferably 85% or more, and may be 90% or more, or even 95% or more. Ａ may be 100%, but in some embodiments, it is appropriate that the percentage is less than 100%, and may be 99% or less or 98% or less, from the viewpoint of ease of control of dismantling and peeling operations.

[0028] (Peeling force reduction rate R ＢIn some embodiments of the technology disclosed herein, the pressure-sensitive adhesive sheet has a peel strength of N / 20 mm [N / 20 mm] at the first measurement in the above-mentioned peel test. Ｓ Reduction rate (normal peel force reduction rate) R [N / 20 mm] Ｂ The normal peel force reduction rate R is suitably, for example, 70% or less. Ｂ More specifically, the peel strength is measured by the peel test described in the Examples below, and the peel strength is measured by the normal peel strength N0 [N / 20 mm] and the normal peel strength N0 Ｓ The normal peel force reduction rate R is calculated by measuring the peel force reduction rate R and substituting the obtained value into the following formula. Ｂ [%] = ((N0-N0 Ｓ ) / N0) x 100

[0029] The normal peel force reduction rate R Ｂ can be understood as an index showing the degree to which the normal peel strength of a PSA sheet peeled (ethanol peeled) from an adherend (stainless steel plate) in a mode in which ethanol is supplied to the interface between the first PSA layer and the adherend, is reduced compared to the normal peel strength of the PSA sheet at the beginning (before the ethanol was supplied). For example, in a PSA sheet having a first PSA layer that dissolves too easily in ethanol or a first PSA layer that swells excessively on contact with ethanol and the cohesiveness of the surface portion is significantly reduced, the PSA constituting the first PSA layer may be lost due to elution into ethanol or remaining on the adherend surface, or the surface smoothness of the first PSA layer may be impaired, resulting in a lower normal peel strength N0 at the second measurement than the normal peel strength N0 at the first measurement. Ｓ The normal peel strength reduction rate R of the adhesive sheet is significantly reduced, and in severe cases, it becomes impossible to attach the adhesive sheet to a new adherend (stainless steel plate) even if a second measurement is performed. ＢNot being too high can be advantageous from the viewpoint of increasing the durability of the assembled body against contact with alcohol under normal conditions of use of an assembled body including the PSA sheet (i.e., conditions of use in which the adhesive sheet is expected to maintain its bonding). It is also preferable from the viewpoint of increasing the reusability (re-attachability) of an adhesive sheet separated from an adherend using an alcoholic stripping solution. For example, in an assembled body in which a first member and a second member are joined via an adhesive sheet, if the disassembly method disclosed herein is applied to separate the first member and the adhesive sheet, and the separated adhesive sheet (which may maintain the bonding between the second adhesive surface and the second member) is used to construct a new assembled body, the normal peel force reduction rate R Ｂ It can be advantageous for the

[0030] In some embodiments, the normal peel force reduction ratio R Ｂ is advantageously 50% or less, preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, and may be 15% or less, 10% or less, 9.0% or less, or 8.0% or less, or may be 7.0% or less, 5.0% or less, or 3.0% or less. Ｂ is typically 0% or more (e.g., more than 0%), and from a practical viewpoint, for example, taking into consideration the balance with other performances and characteristics, it may be 0.5% or more, 1.0% or more, 1.5% or more, or 2.0% or more.

[0031] (Normal Peel Force N0) In the technology disclosed herein, the normal peel force N0 of the PSA sheet is not particularly limited and may be, for example, 0.2 N / 20 mm or more. In some embodiments, from the viewpoint of bonding reliability during normal use, the normal peel force N0 is preferably 0.5 N / 20 mm or more, more preferably 0.7 N / 20 mm or more, and more preferably 1.2 N / 20 mm or more (e.g., 1.5 N / 20 mm or more), and may be 2.0 N / 20 mm or more, 3.0 N / 20 mm or more, 4.0 N / 20 mm or more, 5.0 N / 20 mm or more, or 6.0 N / 20 mm or more. A PSA sheet or a bonded body including such a PSA sheet with a higher normal peel force N0 has a peel force reduction rate R Ａ Furthermore, in some embodiments, from a practical standpoint, for example, in consideration of the balance with other performance and characteristics, the normal peel strength N0 of the PSA sheet may be, for example, 50 N / 20 mm or less, 40 N / 20 mm or less, 30 N / 20 mm or less, 25 N / 20 mm or less, 20 N / 20 mm or less, or 15 N / 20 mm or less.

[0032] The above description regarding the upper and lower limits of the normal peel strength N0 of the PSA sheet (normal peel strength N0 at the time of the first measurement) is based on the normal peel strength N0 at the time of the second measurement. Ｓ Upper and lower limits may also be applied.

[0033] (Ethanol Peeling Force N1) In the technology disclosed herein, the ethanol peeling force N1 of the PSA sheet is calculated by multiplying the peeling force reduction rate R ＡThe ethanol peeling force N1 may be, but is not particularly limited to, any force that satisfies the above condition. From the viewpoint of ease of disassembly and peeling using an alcoholic stripping solution, in some embodiments, the ethanol peeling force N1 is, for example, suitably 1.5 N / 20 mm or less, advantageously 1.0 N / 20 mm or less, preferably less than 1.0 N / 20 mm, more preferably 0.8 N / 20 mm or less, may be 0.5 N / 20 mm or less, may be 0.4 N / 20 mm or less, or may be 0.3 N / 20 mm or less. The ethanol peeling force N1 may be 0 N / 20 mm or more, and from the viewpoint of ease of control of disassembly and peeling operations, in some embodiments, it is suitable to be more than 0 N / 20 mm, for example, 0.01 N / 20 mm or more, or may be 0.05 N / 20 mm or more.

[0034] The above description regarding the upper and lower limits of the ethanol peel strength N1 of the PSA sheet (the ethanol peel strength N1 at the time of the first measurement) is based on the ethanol peel strength N2 at the time of the second measurement. Ｓ Upper and lower limits may also be applied.

[0035] (Peeling force reduction rate R ＡＳ In some aspects of the technology disclosed herein, the pressure-sensitive adhesive sheet has a normal peel strength of N0 at the second measurement in the above-mentioned peel test. Ｓ Ethanol peeling force N1 against [N / 20 mm] Ｓ Reduction rate of [N / 20 mm] (i.e., reduction rate of peel force due to dropping of ethanol in the second measurement) R ＡＳ It is appropriate that the peel force reduction rate R is, for example, 55% or less. Ａ More specifically, the peel strength is determined by the peel test described in the Examples below. Ｓ [N / 20 mm] and ethanol peeling force N1 Ｓ The peel force reduction rate R is calculated by measuring [N / 20 mm] and substituting the obtained value into the following formula: ＡＳ [%] = ((NO Ｓ -N1 Ｓ ) / N0 Ｓ ) x 100

[0036] Peel force reduction rate R ＡＳIn an embodiment in which the PSA sheet is peeled from an adherend using an alcoholic stripping solution and then reused (for example, by attaching the PSA sheet to a new adherend), the PSA sheet in which the peel force reduction rate R is suppressed can exhibit good alcohol removability even during the reuse. This makes it possible to preferably achieve both bonding reliability during the reuse and ease of disassembly and peeling. In some embodiments, the peel force reduction rate R ＡＳ is advantageously 70% or more, preferably 75% or more or 80% or more, more preferably 85% or more, and may be 90% or more, or even 95% or more. ＡＳ may be 100%, and in some embodiments may suitably be less than 100%, and may be 99% or less or 98% or less.

[0037] The stainless steel plate (SUS430BA plate) used as the adherend in the peel test described above has a contact angle with distilled water of about 80 degrees on the surface to which the PSA sheet is attached, and a contact angle with ethanol of about 10 degrees. The same applies to the stainless steel plates (SUS430BA plates) used as the adherend in the peel test and the first member of the joined body in the examples described below.

[0038] <Conjugate Comprising Pressure-Sensitive Adhesive Sheet> This specification provides a conjugate (which may also be understood as a member with a pressure-sensitive adhesive sheet) comprising at least the pressure-sensitive adhesive sheet and a first member bonded to the first adhesive surface of the pressure-sensitive adhesive sheet. Ａ A pressure-sensitive adhesive sheet in which the thickness of the adhesive sheet is within any of the above ranges can be preferably used as a component of such a bonded structure.

[0039] The PSA sheet included in the bonded structure may be, for example, a substrateless PSA sheet consisting solely of a PSA layer. A substrateless PSA sheet is typically a double-sided PSA sheet (substrateless double-sided PSA sheet) in which one surface of the PSA layer serves as a first adhesive surface and the other surface (the surface opposite the first adhesive surface) of the PSA layer serves as a second adhesive surface. As shown in FIG. 1 , the substrateless double-sided PSA sheet can be configured as a bonded structure 100 in which a first member 61 and a second member 62 are bonded via the PSA sheet 1 by bonding the first adhesive surface 11a of the PSA sheet 1 (the PSA layer 11) to a first member 61 and the second adhesive surface 11b to a second member 62. Therefore, the first member can be understood as an adherend to which the first adhesive surface of the PSA sheet is attached. Similarly, the second member can be understood as an adherend to which the second adhesive surface of the PSA sheet is attached. Before use, the adhesive sheet may be in a form in which each of the first adhesive surface and the second adhesive surface is protected by a release liner (typically, a release liner in which at least the side that contacts the adhesive surface is a release surface).

[0040] The PSA sheet included in the above-mentioned bonded structure may be a substrate-attached double-sided PSA sheet having a first PSA layer 11 on a first surface 20a of a substrate 20 and a second PSA layer 12 on a second surface 20b (the side opposite to the first surface), as in the PSA sheet 2 included in the bonded structure of the embodiment shown in Fig. 2 . The PSA sheet 2 can be configured by bonding the first PSA surface 11a, which is the surface of the first PSA layer 11, to a first member 61 and bonding the second PSA surface 12a, which is the surface of the second PSA layer 12, to a second member 62, thereby forming a bonded structure 200 in which the first member 61 and the second member 62 are bonded via the PSA sheet 2. Before use, the PSA sheet 2 can be a component of a PSA sheet with release liner 50 in which the first PSA surface 11a and the second PSA surface 12a are protected by release liners 31, 32 (typically, release liners in which at least the side that contacts the PSA surface serves as a release surface), as shown in Fig. 3 . For example, a sheet-like substrate (liner substrate) configured so that one side serves as a release surface by providing a release layer made of a release treatment agent on that side can be preferably used as release liners 31, 32. Alternatively, release liner 32 can be omitted, and release liner 31 having release surfaces on both sides can be used, which can be superimposed on PSA sheet 2 and wound spirally to form a PSA sheet with release liner in a form (roll form) in which second PSA surface 12 a is protected by being in contact with the back surface of release liner 31.

[0041] The release liner is not particularly limited, and examples thereof include release liners in which the surface of a liner substrate such as a resin film or paper has been release-treated, and release liners made of low-adhesion materials such as fluorine-based polymers (e.g., polytetrafluoroethylene) and polyolefin-based resins (e.g., polyethylene and polypropylene). For the release treatment, for example, a silicone-based or long-chain alkyl-based release treating agent can be used. In some embodiments, a release-treated resin film can be preferably used as the release liner.

[0042] Furthermore, the PSA sheet included in the bonded structure disclosed herein may be a single-sided PSA sheet having a PSA layer on a first surface of a substrate, the surface of the PSA layer forming a first adhesive surface, or a single-sided PSA sheet having a first PSA layer on a first surface of a first substrate, a second PSA layer on a second surface of the first substrate, and a second substrate bonded to the surface of the second PSA layer (the surface opposite to the first substrate). By bonding the first adhesive surface of such a single-sided PSA sheet to a first member, a bonded structure (adhesive-attached member) including the first member and the single-sided PSA sheet can be formed.

[0043] In the embodiment shown in Figures 1 and 2, the first member, second member, and adhesive sheet constituting the bonded structure are all configured in a layered, sheet-like, or plate-like shape, and the bonded structure has the form of a laminated structure (laminate). However, the shapes of the first member, second member, and adhesive sheet do not have to be layered, sheet-like, or plate-like, and can have various shapes. For example, the first member only needs to have a surface that bonds with the first adhesive surface of the adhesive sheet, and may have various three-dimensional member shapes, such as complex shapes or curved shapes, based on the application and purpose of use. The adhesive sheet can also have various shapes to match the surface shapes of the first member and second member.

[0044] In this specification, the terms "member" and "members" in the terms "first member" and "second member" are used to mean constituent elements of a joined body, and are not particularly limited other than that meaning. For example, the first member and the second member may each be an independent article or part, or each may be a member constituting a different article.

[0045] Furthermore, the bonded structure may include other members or components in addition to the first and second members. For example, if the first member is part of a product such as an electronic device, the bonded structure may be composed of multiple members or components.

[0046] The materials of the first member and the second member are not particularly limited. The material constituting at least the surface of each member may be, for example, a metal material such as stainless steel (SUS) or aluminum; glass such as an alkali glass plate or alkali-free glass; or a resin material such as an acrylic resin, an ABS resin, a polycarbonate resin, or a polystyrene resin. The surface to which the first adhesive surface or the second adhesive surface is bonded may be a painted surface with a paint such as an acrylic, polyester, alkyd, melamine, urethane, acid-epoxy crosslinked, or a composite of these (e.g., an acrylic-melamine, an alkyd-melamine), or a plated surface such as a zinc-plated steel plate.

[0047] In some embodiments, the surface of the first component to which the first adhesive surface is bonded may have a contact angle with distilled water (hereinafter also referred to as a water contact angle) of, for example, 30 degrees or more or 40 degrees or more. In some preferred embodiments, the water contact angle of the bonding surface is 50 degrees or more, and may be 60 degrees or more (e.g., more than 60 degrees), 70 degrees or more, 75 degrees or more, or 80 degrees or more. According to the technology disclosed herein, even in a bonded structure in which the first adhesive surface of the adhesive sheet is bonded to such a surface with relatively low hydrophilicity, it is possible to preferably achieve both bonding reliability and ease of disassembly.

[0048] Furthermore, the water contact angle of the surface of the first component is suitably 150 degrees or less, advantageously 120 degrees or less, and preferably 100 degrees or less (e.g., 90 degrees or less). The technology disclosed herein can also be implemented in an embodiment in which the water contact angle of the surface is, for example, 75 degrees or less, 65 degrees or less, 55 degrees or less, 45 degrees or less, 35 degrees or less, 25 degrees or less, or 15 degrees or less. The lower limit of the water contact angle is, in principle, 0 degrees. In some embodiments, the water contact angle of the surface can be, for example, more than 0 degrees, 1 degree or more, 3 degrees or more, or 5 degrees or more.

[0049] The above description regarding the water contact angle of the first member can also be applied to the water contact angle of the second member in a bonded structure including a first member and a second member. In some embodiments, the water contact angle of at least the bonding surface of the first member is preferably 50 degrees or more (e.g., 50 degrees or more and 100 degrees or less), and more preferably 60 degrees or more, 65 degrees or more, 70 degrees or more, or 80 degrees or more.

[0050] In some embodiments, the surface of the first component to which the first adhesive surface is bonded may have a contact angle with ethanol (hereinafter also referred to as the ethanol contact angle), for example, of 60 degrees or less, preferably 50 degrees or less. In some preferred embodiments, the ethanol contact angle of the surface is 40 degrees or less, more preferably 30 degrees or less (e.g., 25 degrees or less), and may be 20 degrees or less or 15 degrees or less. When the ethanol contact angle of the component surface is small, the alcohol liquid tends to spread easily along the surface, which tends to improve dismantling ability by immersion in an alcoholic stripping solution. In principle, the lower limit of the ethanol contact angle is 0 degrees. In some embodiments, the ethanol contact angle of the surface may be, for example, greater than 0 degrees, 1 degree or more, 3 degrees or more, or 5 degrees or more.

[0051] The above description regarding the contact angle of ethanol on the first member can also be applied to the contact angle of ethanol on the second member in an assembly including a second member in addition to the first member.

[0052] The contact angles of the bonding surfaces with respect to ethanol and distilled water are measured as follows. Specifically, measurements are performed by the sessile drop method using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DMo-501 model," control box "DMC-2," and control / analysis software "FAMAS (version 5.0.30)") in an environment of 23°C and 50% RH. The amount of ethanol dropped when measuring the contact angle with ethanol and the amount of distilled water dropped when measuring the contact angle with distilled water are each 2 μL, and the contact angles are calculated by the Θ / 2 method from images taken 5 seconds after the drops were dropped (performed with N5).

[0053] In some embodiments, the bonded structure has a configuration in which a first member and a second member are bonded via an adhesive sheet, and both the first member and the second member are rigid. When disassembling a bonded structure in which both the first member and the second member are rigid, it is not possible to deform the adherend (increase the peel angle) to reduce the peel force. Therefore, a considerable amount of force is required to release the adhesion across the entire bonded surface (e.g., the bonded surface between the first member and the first adhesive surface), making it difficult to disassemble manually. The disassembly method disclosed herein allows efficient separation of the first member and the second member, even in a bonded structure with such a configuration (e.g., after immersion in an alcoholic stripping solution for a relatively short period of time). The materials of the first member and the second member may be the same or different. Rigid materials that can be used for the first member and the second member include metal materials (e.g., stainless steel, aluminum, etc.), glass, hard resin, and ceramic materials.

[0054] Here, "rigid body" refers to an object that has a rigidity and size that is not substantially deformed by human force, and in this specification, refers to an object that cannot be deformed by human force (based on the standard of an average adult male) from the joined state to a level that improves disassembly when disassembling a joined body. Although not particularly limited, the term "rigid body" in this specification refers to an object that has a tensile modulus of elasticity of 1 x 10 １０ Pa or more; and bending rigidity is 0.01 Pa m ３ or more;

[0055] The tensile modulus refers to the tensile modulus measured in accordance with JIS K7161. More specifically, it is measured by the following method. [Tensile Test] A test specimen is prepared by cutting a measurement object into a strip of 10 mm width. This test specimen is stretched in accordance with JIS K7161 under the following conditions to obtain a stress-strain curve. (Stretching Conditions) Measurement temperature: 25°C Tensile speed: 300 mm / min Chuck distance: 50 mm As the tensile tester, a universal tension-compression tester (device name "Tension-Compression Tester, TCM-1kNB", manufactured by Minebea Co., Ltd.) or an equivalent can be used. The tensile modulus can be determined from the linear regression of the stress-strain curve. In addition, the bending rigidity value D [Pa m ３ ] is expressed by the formula: D = Eh, where h [m] is the thickness of the material, ν is the Poisson's ratio of the material, and E [Pa] is the tensile modulus of elasticity. ３ / 12(1-ν ２ ) ;

[0056] The thickness of the glass (e.g., glass plate), metal material (e.g., metal plate), or ceramic material (e.g., ceramic plate) that can be used as the first member and / or the second member is not particularly limited and may be, for example, approximately 0.1 mm or more, or approximately 0.5 mm or more. Glass, metal materials, and ceramic materials having thicknesses within the above ranges can have rigid body properties, which makes it advantageous to apply the technology disclosed herein. The maximum thickness of the glass, metal material, and ceramic material is not particularly limited and may be approximately 30 cm or less, approximately 10 cm or less, approximately 1 cm or less, approximately 5 mm or less, or approximately 2 mm or less.

[0057] Furthermore, the resin material (typically a plastic material) that can be used for the first member and / or the second member has a tensile modulus of elasticity of 1×10 １０ Pa or more; and a bending rigidity of 0.01 Pa m ３A material satisfying at least one of the above conditions is used. Examples of the resin material include polyester resin, acrylic resin, ABS resin, polycarbonate resin, polystyrene resin, polyimide resin, etc. Although not particularly limited, the thickness of the resin material is, for example, approximately 1 mm or more, and may be approximately 2 mm or more, 3 mm or more, 5 mm or more, or 1 cm or more. Resin materials having a thickness within the above range may have rigid body properties, and therefore the application of the technology disclosed herein is highly advantageous. The maximum thickness of the resin material is not particularly limited and may be approximately 30 cm or less, approximately 10 cm or less, or approximately 1 cm or less.

[0058] <Adhesive Layer> The adhesive sheet in the technology disclosed herein includes at least an adhesive layer (first adhesive layer) constituting the first adhesive surface of the adhesive sheet. The type of adhesive constituting the first adhesive layer is not particularly limited. The adhesive may be, for example, an adhesive comprising one or more adhesives selected from various known adhesives such as acrylic adhesives, rubber adhesives (natural rubber-based, synthetic rubber-based, and mixtures thereof), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluorine-based adhesives. Here, an acrylic adhesive refers to an adhesive containing an acrylic polymer as the main component (base polymer). The same applies to rubber adhesives and other adhesives.

[0059] [Acrylic Pressure-Sensitive Adhesive] In some embodiments, an acrylic pressure-sensitive adhesive may be preferably used as a constituent material of the pressure-sensitive adhesive. Acrylic pressure-sensitive adhesives have a high degree of freedom in designing physical properties and characteristics, and are suitable for realizing a pressure-sensitive adhesive sheet that can be used to form an assembly that combines reliable bonding and easy disassembly.

[0060] (Acrylic Polymer) The acrylic polymer that is the base polymer of the acrylic pressure-sensitive adhesive in the technology disclosed herein may be, for example, an acrylic polymer composed of a monomer component containing a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal. Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having a carbon number of X to Y at the ester terminal will be referred to as "(meth)acrylic acid C Ｘ－Ｙ In some embodiments, (meth)acrylic acid C in the monomer components constituting the acrylic polymer may be expressed as "alkyl ester." １－２０ The content of the alkyl ester is suitably 50% by weight or more, preferably 65% ​​by weight or more or 70% by weight or more, and may be 75% by weight or more, 80% by weight or more, or 85% by weight or more, in order to easily balance the properties. １－２０ The content of the alkyl ester may be 100% by weight, or from the viewpoint of the cohesiveness of the PSA and the adhesion to polar adherends, it may be, for example, 99.9% by weight or less, 99% by weight or less, 98% by weight or less, or 95% by weight or less. １－２０ The alkyl esters can be used alone or in combination of two or more.

[0061] In some embodiments, the monomer components constituting the acrylic polymer include one or more (meth)acrylic acids C ４－２０ It is preferable that the (meth)acrylic acid C contains one or more alkyl esters. ４－１８ The technology disclosed herein can be preferably practiced in a mode in which an assembled body including a PSA sheet provided with a PSA layer containing such an acrylic polymer as a base polymer is disassembled, or in the form of a substrate-attached double-sided PSA sheet having the PSA layer.

[0062] In this specification, "monomer components constituting an acrylic polymer" or "monomer components of an acrylic polymer" refer to monomer components constituting an acrylic polymer contained in a pressure-sensitive adhesive (layer). The monomer components may be contained in the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive (layer) as unreacted monomers (i.e., in the form of raw material monomers in which the polymerizable functional groups are unreacted), in the form of polymers (i.e., as monomer units), or in both of these forms.

[0063] In some embodiments, the monomer component constituting the acrylic polymer is (meth)acrylic acid C １０－１４ It is preferable that the acrylic polymer contains an alkyl ester. An acrylic pressure-sensitive adhesive layer containing such an acrylic polymer is likely to provide good alcohol peelability. The reason for this is, but is not limited to, the C content of the acrylic polymer. １０－１４ The alkyl side chains impart a suitable degree of hydrophobicity to the surface of the acrylic pressure-sensitive adhesive layer, which makes it easier for the alcoholic stripping solution to wet and spread along the surface, which is thought to contribute to improved alcohol stripping properties. １０－１４ Specific examples of alkyl esters include decyl acrylate, lauryl acrylate (LA), tetradecyl acrylate, decyl methacrylate, lauryl methacrylate, and tetradecyl methacrylate. (Meth)acrylic acid C １０－１４ The alkyl esters can be used alone or in combination of two or more.

[0064] (Meth)acrylic acid C in the monomer components of acrylic polymer １０－１４The content of the alkyl ester may be, for example, 1% by weight or more, and from the viewpoint of the alcohol strippability and the like, is preferably 3% by weight or more or 5% by weight or more, more preferably 10% by weight or more or 15% by weight or more, and may be 20% by weight or more, 25% by weight or more, 30% by weight or more, 40% by weight or more, 45% by weight or more, or even 50% by weight or more. １０－１４ The content of the alkyl ester may be, for example, 95% by weight or less, 90% by weight or less, or 80% by weight or less. In some embodiments, in consideration of the balance between alcohol strippability and other properties, the content of the (meth)acrylic acid C in the monomer component may be １０－１４ The alkyl ester content is suitably 75% by weight or less, advantageously 70% by weight or less, preferably 65% ​​by weight or less, and may be 60% by weight or less, 55% by weight or less, 50% by weight or less, or even less than 50% by weight (e.g., 45% by weight or less, 40% by weight or less, or 35% by weight or less).

[0065] In some embodiments, the monomer component constituting the acrylic polymer is (meth)acrylic acid C ４－９ (Meth)acrylic acid C may contain alkyl esters. ４－９ Alkyl esters (e.g., acrylic acid C ４－９ (Meth)acrylic acid C (alkyl ester) can be useful for improving the flexibility of the adhesive and improving adhesive performance (for example, normal peel strength). ４－９ Specific examples of alkyl esters include butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and isononyl (meth)acrylate. ４－９The alkyl esters can be used alone or in combination of two or more. For example, the monomer component preferably contains either or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

[0066] (Meth)acrylic acid C in the monomer components of acrylic polymer ４－９ The content of the alkyl ester may be, for example, 1% by weight or more, and from the viewpoint of obtaining a higher use effect, it is preferably 5% by weight or more or 10% by weight or more, more preferably 20% by weight or more, and may be 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, or 60% by weight or more. ４－９ The content of alkyl ester may be, for example, 95% by weight or less, and from the viewpoint of easily obtaining good alcohol strippability, it is advantageous to be 90% by weight or less, and it is preferably 85% by weight or less, or it may be 80% by weight or less, or 75% by weight or less, or it may be 70% by weight or less.

[0067] In some embodiments, the monomer component constituting the acrylic polymer is one or more (meth)acrylic acid C ４－９ alkyl ester and one or more (meth)acrylic acids C １０－１４ In order to facilitate obtaining good alcohol strippability, in some embodiments, the (meth)acrylic acid C alkyl ester may be contained in combination with the acrylic polymer. ４－９ (Meth)acrylic acid C to alkyl ester １０－１４ The weight-based content ratio of alkyl ester (C １０－１４ / C ４－９ ) is preferably 0.1 or more, more preferably 0.3 or more. １０－１４ / C ４－９) may be 0.5 or more, 0.8 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.8 or more, or 2.0 or more. In some embodiments, taking into consideration the balance of adhesive performance, the content ratio (C １０－１４ / C ４－９ ) is preferably 10 or less, more preferably 5.0 or less, may be 4.0 or less, or may be 3.0 or less.

[0068] The monomer components constituting the acrylic polymer may contain, in addition to the (meth)acrylic acid alkyl ester, other monomers (copolymerizable monomers) copolymerizable with the (meth)acrylic acid alkyl ester, as necessary. Examples of copolymerizable monomers that can be used include monomers having polar groups (e.g., nitrogen-containing rings, hydroxyl groups, carboxyl groups, etc.) and monomers whose homopolymer glass transition temperatures are relatively high (e.g., 10°C or higher). Monomers having polar groups can be useful for introducing crosslinking points into the acrylic polymer or for increasing the cohesive strength of the adhesive. The copolymerizable monomers can be used alone or in combination of two or more.

[0069] Non-limiting examples of copolymerizable monomers include monomers having a nitrogen atom-containing ring, hydroxyl group-containing monomers, carboxy group-containing monomers, acid anhydride group-containing monomers, monomers containing sulfonic acid groups or phosphoric acid groups, epoxy group-containing monomers, cyano group-containing monomers, isocyanate group-containing monomers, amide group-containing monomers, amino group-containing monomers, monomers having a succinimide skeleton, maleimides, aminoalkyl (meth)acrylates, alkoxy group-containing monomers, alkoxysilyl group-containing monomers, vinyl esters, vinyl ethers, aromatic vinyl compounds, olefins, (meth)acrylic acid esters having an alicyclic hydrocarbon group, (meth)acrylic acid esters having an aromatic hydrocarbon group, as well as heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from terpene compound derivative alcohols.

[0070] Examples of monomers having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine. , N-vinylmorpholine, N-(meth)acryloylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyridazine, and the like (for example, lactams such as N-vinyl-2-caprolactam).

[0071] Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

[0072] Examples of the (meth)acrylic acid ester having an alicyclic hydrocarbon group include (meth)acrylates containing an alicyclic hydrocarbon group, such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.

[0073] Examples of the carboxy group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0074] When such a copolymerizable monomer is used, its amount (or the total amount when multiple types of copolymerizable monomers are used) is not particularly limited and can be, for example, 0.01% by weight or more of the monomer components. From the viewpoint of better demonstrating the effect of using the copolymerizable monomer, the amount of the copolymerizable monomer used may be 0.1% by weight or more, or even 0.5% by weight or more of the total monomer components. Furthermore, from the viewpoint of easily balancing the adhesive properties, the amount of the copolymerizable monomer used is suitably 60% by weight or less of the total monomer components, and may be 50% by weight or less, or may be 40% by weight or less.

[0075] In some embodiments, the monomer component constituting the acrylic polymer may contain a nitrogen atom-containing monomer. Use of a nitrogen atom-containing monomer can better achieve both good alcohol releasability and normal release force. Examples of the nitrogen atom-containing monomer include those having nitrogen-containing functional groups (such as nitrogen atom-containing rings, amide groups, and amino groups) exemplified above. Suitable examples of nitrogen atom-containing monomers include monomers having nitrogen atom-containing rings. Examples include N-vinyl cyclic amides, and among these, N-vinyl-2-pyrrolidone (NVP) is preferred. The nitrogen atom-containing monomers may be used alone or in combination of two or more. The content of the nitrogen atom-containing monomer (preferably the nitrogen atom-containing ring-containing monomer) in the monomer component may be, for example, 0.5 wt % or more. From the viewpoint of achieving better use effects, 1 wt % or more is appropriate, 3 wt % or more is advantageous, 5 wt % or more is preferable, and it may also be 7 wt % or more, 8 wt % or more, or 9 wt % or more. Furthermore, from the viewpoint of avoiding the pressure-sensitive adhesive layer from becoming excessively hydrophilic, the content of the monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring) in the monomer component is suitably 40% by weight or less, preferably 30% by weight or less, and may also be 25% by weight or less, 20% by weight or less, 15% by weight or less, or 12% by weight or less.

[0076] In some preferred embodiments, the monomer component constituting the acrylic polymer is (meth)acrylic acid C １０－１４ In this embodiment, the ratio of (meth)acrylic acid C to the monomer having a nitrogen atom (preferably the monomer having a nitrogen atom-containing ring) in the monomer components of the acrylic polymer is 1:1 or more. １０－１４ The weight-based content ratio of alkyl ester (C １０－１４ / N-containing monomer) is preferably 1 or more (for example, 3 or more), may be 5 or more, or may be 10 or more. １０－１４ / N-containing monomer) is preferably 10,000 or less, may be 5,000 or less, may be 3,000 or less, or may be 2,000 or less. １０－１４ / N-containing monomer) may be 1000 or less, 500 or less, 200 or less, 80 or less, 40 or less, or 20 or less.

[0077] (Meth)acrylic acid C １０－１４ In some embodiments in which an alkyl ester and a monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring) are used in combination, (meth)acrylic acid C １０－１４ The total content of the alkyl ester and the monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring) is preferably 8% by weight or more or 10% by weight or more, more preferably 15% by weight or more or 20% by weight or more, and may be 25% by weight or more, 30% by weight or more, or 35% by weight or more. １０－１４ The total content of the alkyl ester and the monomer having a nitrogen atom (preferably the monomer having a nitrogen atom-containing ring) may be, for example, 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, or 50% by weight or less.

[0078] In some embodiments, the monomer component constituting the acrylic polymer may contain a hydroxyl group-containing monomer. The hydroxyl group-containing monomer may be useful for adjusting the cohesive strength of the PSA and the degree of crosslinking (e.g., crosslinking with an isocyanate crosslinker). Examples of the hydroxyl group-containing monomer include those exemplified above, and preferred examples include 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA). The hydroxyl group-containing monomer may be used alone or in combination of two or more. When a hydroxyl group-containing monomer is used, the amount used is not particularly limited. For example, the content of the hydroxyl group-containing monomer in the monomer component may be 0.5 wt % or more, 1 wt % or more, 3 wt % or more, or 5 wt % or more. In some embodiments, from the viewpoint of preventing a decrease in alcohol removability due to excessive hydrophilicity of the pressure-sensitive adhesive layer, the content of the hydroxyl group-containing monomer in the monomer component is suitably 30% by weight or less, preferably 25% by weight or less or 20% by weight or less, more preferably 15% by weight or less, or may be 12% by weight or less, 10% by weight or less, or may be 8% by weight or less. The technology disclosed herein can be preferably implemented in an embodiment in which the content of the hydroxyl group-containing monomer in the monomer component is less than 5% by weight, less than 1% by weight, or less than 0.1% by weight.

[0079] In some embodiments, the monomer component constituting the acrylic polymer may contain an alicyclic hydrocarbon group-containing (meth)acrylate. When an alicyclic hydrocarbon group-containing (meth)acrylate is used, the amount used is not particularly limited and can be, for example, 1 wt% or more, or 5 wt% or more of the monomer component. In some embodiments, from the viewpoint of the flexibility of the PSA, the content of the alicyclic hydrocarbon group-containing (meth)acrylate in the monomer component is suitably 30 wt% or less, preferably 20 wt% or less or 15 wt% or less, and may be 10 wt% or less. The technology disclosed herein can be preferably implemented in an embodiment in which the content of the alicyclic hydrocarbon group-containing (meth)acrylate in the monomer component is less than 5 wt%, less than 1 wt%, or less than 0.1 wt%.

[0080] In some embodiments, the content of the carboxyl group-containing monomer in the monomer component of the acrylic polymer is suitably less than 10 wt%, and preferably less than 3 wt% or less than 1 wt% (e.g., less than 0.1 wt%). Limiting the amount of the carboxyl group-containing monomer used in this manner can be advantageous from the viewpoint of avoiding a decrease in alcohol releasability due to excessive hydrophilization of the pressure-sensitive adhesive layer. The carboxyl group-containing monomer may not be substantially used as a monomer component of the acrylic polymer. Here, "substantially not using a carboxyl group-containing monomer" means that the carboxyl group-containing monomer is not used at least intentionally.

[0081] The composition of the monomer components constituting the acrylic polymer can be set so that the glass transition temperature Tg, calculated based on the composition of the monomer components using the Fox formula, is −75° C. or higher and 10° C. or lower. In some embodiments, from the viewpoint of adhesive strength and the like, the Tg is suitably 0° C. or lower, preferably −10° C. or lower, and may be −20° C. or lower, −30° C. or lower, or −40° C. or lower. Furthermore, from the viewpoint of cohesion and the like, the Tg may be, for example, −60° C. or higher, −50° C. or higher, or −45° C. or higher.

[0082] Here, the Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below: 1 / Tg = Σ(Wi / Tgi) In the Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio by weight), and Tgi represents the glass transition temperature of a homopolymer of monomer i (unit: K). The glass transition temperature of the homopolymer used to calculate Tg is determined from known sources, specifically, values ​​found in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989). When multiple values ​​are found in this document, the highest value is used.

[0083] The PSA layer in the technology disclosed herein can be formed using a PSA composition containing the monomer components of the above-described composition in the form of a polymer, an unpolymer (i.e., a form in which the polymerizable functional group is unreacted), or a mixture thereof. The PSA composition can be in various forms, such as an aqueous dispersion PSA composition in which the PSA (adhesive component) is dispersed in water, a solvent-based PSA composition in which the PSA is contained in an organic solvent, an active energy ray-curable PSA composition prepared to form a PSA upon curing with active energy rays such as ultraviolet light or radiation, or a hot-melt PSA composition that is applied in a heated, molten state and forms a PSA upon cooling to near room temperature. PSA compositions according to some embodiments are solvent-based or solventless PSA compositions. Solvent-free PSA compositions include active energy ray-curable PSA compositions and hot-melt PSA compositions. From the viewpoint of ease of control of alcohol peelability, etc., the PSA sheet in the technology disclosed herein can preferably be one in which the PSA layer constituting the first adhesive surface is formed from a solvent-based PSA composition or an active energy ray (typically ultraviolet curing)-curable PSA composition.

[0084] For polymerization, known or conventional thermal polymerization initiators or photopolymerization initiators can be used depending on the polymerization method, polymerization mode, etc. The thermal polymerization initiator is not particularly limited, but examples of usable initiators include azo-based polymerization initiators, peroxide-based initiators, redox-based initiators formed by combining peroxides with reducing agents, and substituted ethane-based initiators. The photopolymerization initiator is not particularly limited, but examples of usable initiators include ketal-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. The polymerization initiators can be used alone or in appropriate combinations of two or more. The amount of such a thermal polymerization initiator or photopolymerization initiator used is not particularly limited and may be a normal amount depending on the polymerization method, polymerization mode, etc. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, e.g., about 0.01 to 1 part by weight) of the polymerization initiator can be used per 100 parts by weight of the monomer to be polymerized.

[0085] In the polymerization, various conventionally known chain transfer agents (which may also be understood as molecular weight regulators or polymerization degree regulators) can be used as needed. Examples of chain transfer agents that can be used include mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol. Alternatively, chain transfer agents that do not contain sulfur atoms (non-sulfur chain transfer agents) may be used. The chain transfer agents can be used alone or in combination of two or more. When a chain transfer agent is used, the amount used can be, for example, approximately 0.01 to 1 part by weight per 100 parts by weight of the monomer components. The synthesis of an acrylic polymer in the technology disclosed herein can also be preferably carried out in an embodiment in which a chain transfer agent is not used.

[0086] The molecular weight of the acrylic polymer obtained by appropriately employing the above-mentioned various polymerization methods is not particularly limited and can be set within an appropriate range depending on the required performance. The weight average molecular weight (Mw) of the acrylic polymer is, for example, about 10 × 10 ４ From the viewpoint of achieving a good balance between cohesive strength and adhesive strength, ４ The acrylic polymer according to some embodiments preferably has a viscosity of about 50×10 ４ The upper limit of the Mw of the acrylic polymer is approximately 500 × 10 ４ Less than (for example, approximately 150 x 10 ４ The Mw can be approximately 75×10 ４ Here, Mw refers to a value calculated in terms of standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, a model named "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) may be used.

[0087] The pressure-sensitive adhesive composition according to some embodiments may be an active energy ray-curable pressure-sensitive adhesive composition. In this specification, "active energy rays" refers to energy rays having energy capable of inducing chemical reactions such as polymerization reactions, crosslinking reactions, and decomposition of initiators. Examples of active energy rays include light such as ultraviolet rays, visible light, and infrared rays, and radioactive rays such as α-rays, β-rays, γ-rays, electron beams, neutron beams, and X-rays. A suitable example of an active energy ray-curable pressure-sensitive adhesive composition is a photocurable pressure-sensitive adhesive composition. Photocurable pressure-sensitive adhesive compositions have the advantage that even thick pressure-sensitive adhesive layers can be easily formed. Among these, ultraviolet-curable pressure-sensitive adhesive compositions are preferred.

[0088] The photocurable pressure-sensitive adhesive composition typically contains at least a portion of the monomer components of the composition (which may be a portion of the type of monomer or a portion of the amount) in the form of a polymer. The polymerization method for forming the polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately adopted. For example, thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization (typically carried out in the presence of a thermal polymerization initiator); photopolymerization carried out by irradiation with light such as ultraviolet light (typically carried out in the presence of a photopolymerization initiator); radiation polymerization carried out by irradiation with radiation such as beta rays and gamma rays; etc. can be appropriately adopted. Among these, photopolymerization is preferred.

[0089] Photocurable pressure-sensitive adhesive compositions according to some preferred embodiments contain a partial polymer of a monomer component (e.g., an acrylic partial polymer). Such a partial polymer is typically a mixture of a polymer derived from the monomer component and an unreacted monomer, and preferably exhibits a syrup-like (viscous liquid) state. Hereinafter, a partial polymer of this nature may be referred to as a "monomer syrup" or simply as a "syrup." The polymerization method used for partially polymerizing the monomer component is not particularly limited, and various polymerization methods such as those described above can be appropriately selected and used. From the viewpoints of efficiency and simplicity, a photopolymerization method is preferably employed. Photopolymerization allows the polymerization conversion rate of the monomer component (monomer conversion) to be easily controlled by changing polymerization conditions such as the light irradiation dose (light amount).

[0090] The polymerization conversion rate of the monomer mixture in the partial polymer is not particularly limited. The polymerization conversion rate can be, for example, about 70% by weight or less, and from the viewpoint of ease of preparation and coatability of the pressure-sensitive adhesive composition containing the partial polymer, it is suitably about 50% by weight or less, and preferably about 40% by weight or less. The lower limit of the polymerization conversion rate is not particularly limited, but is typically about 1% by weight or more, and suitably about 5% by weight or more.

[0091] The pressure-sensitive adhesive composition containing the partial polymer may contain other components (e.g., photopolymerization initiators, crosslinking agents, polyfunctional monomers, acrylic oligomers, tackifying resins, silane coupling agents, etc.) that are used as needed. The method for blending such other components is not particularly limited, and for example, the other components may be contained in the monomer mixture in advance, or may be added to the partial polymer.

[0092] The PSA composition according to some embodiments may be a solvent-based PSA composition. A solvent-based PSA composition typically contains a solution polymer of a monomer component and additives used as needed. The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents (e.g., toluene, ethyl acetate, etc.). Solution polymerization produces a polymerization reaction liquid in the form of a polymer of a monomer component (typically, a polymer with a polymerization conversion rate of the monomer component of 80% by weight or more, preferably 90% by weight or more) dissolved in the polymerization solvent. The solvent-based PSA composition disclosed herein can be preferably produced using the polymerization reaction liquid.

[0093] (Polyfunctional Monomer) A polyfunctional monomer may be used in the pressure-sensitive adhesive composition as needed. The polyfunctional monomer may be useful for purposes such as adjusting the cohesive strength of the pressure-sensitive adhesive. The polyfunctional monomer may form a crosslinked structure by reacting the ethylenically unsaturated group with light (e.g., ultraviolet) irradiation or the like. For example, a polyfunctional monomer may be preferably used as a component to be blended into a photocurable pressure-sensitive adhesive composition. As the polyfunctional monomer, a compound having two or more ethylenically unsaturated groups may be used. The polyfunctional monomer may be used alone or in combination of two or more.

[0094] Examples of the ethylenically unsaturated group contained in the polyfunctional monomer include, but are not limited to, an acryloyl group, a methacryloyl group, a vinyl group, and an allyl group. From the viewpoint of photoreactivity, preferred ethylenically unsaturated groups include an acryloyl group and a methacryloyl group. Among them, an acryloyl group is preferred.

[0095] Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyldiol (meth)acrylate, and hexyldiol di(meth)acrylate. Suitable examples include trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0096] The amount of the polyfunctional monomer used is suitably in the range of, for example, about 0.01 to 3.0 parts by weight per 100 parts by weight of the base polymer (acrylic polymer) or its monomer components. From the viewpoint of achieving a good balance between alcohol removability, dismantling ability of the bonded body, and bonding reliability during normal use, in some embodiments, the amount of the polyfunctional monomer used per 100 parts by weight of the base polymer or its monomer components is suitably 2.0 parts by weight or less, advantageously 1.5 parts by weight or less, preferably 1.0 part by weight or less, and may also be 0.7 parts by weight or less, 0.5 parts by weight or less, or 0.3 parts by weight or less.

[0097] (Acrylic Oligomer) The acrylic pressure-sensitive adhesive disclosed herein may contain an acrylic oligomer from the viewpoint of improving cohesive strength, adhesiveness, etc. As the acrylic oligomer, it is preferable to use a polymer having a Tg higher than that of the acrylic polymer. For example, in an embodiment in which ultraviolet irradiation is used when forming a pressure-sensitive adhesive (layer) from the pressure-sensitive adhesive composition, an acrylic oligomer is preferable because it is less likely to cause polymerization inhibition.

[0098] Suitable examples of acrylic oligomers include homopolymers of dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), as well as copolymers of DCPMA and methyl methacrylate (MMA), copolymers of DCPMA and IBXMA, copolymers of ADA and MMA, copolymers of CHMA and isobutyl methacrylate (IBMA), copolymers of CHMA and IBXMA, copolymers of CHMA and acryloylmorpholine (ACMO), copolymers of CHMA and diethylacrylamide (DEAA), and copolymers of CHMA and AA. The acrylic oligomers can be used alone or in combination of two or more.

[0099] The Mw of the acrylic oligomer can typically be from about 1,000 to less than about 30,000, preferably from about 1,500 to less than about 10,000, and more preferably from about 2,000 to less than about 5,000. When the Mw is within the above range, the effect of improving cohesion and adhesion to adjacent surfaces is easily achieved. The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and calculated as a value equivalent to standard polystyrene. Specifically, the measurement is performed using a Tosoh HPLC 8020 with two TSKgel GMH-H (20) columns at a flow rate of about 0.5 mL / min in tetrahydrofuran solvent.

[0100] When an acrylic oligomer is contained in an acrylic pressure-sensitive adhesive, the content thereof can be, for example, 0.01 parts by weight or more relative to 100 parts by weight of the base polymer or its monomer component, and from the viewpoint of obtaining a higher effect, it is advantageous to set it to 0.1 parts by weight or more, and preferably to set it to 0.5 parts by weight or more, and it may be 1.0 parts by weight or more, or 1.5 parts by weight or more. From the viewpoint of the flexibility of the pressure-sensitive adhesive, compatibility with the base polymer, etc., the content of the acrylic oligomer relative to 100 parts by weight of the base polymer or its monomer component is, for example, suitably less than 30 parts by weight, and may be 20 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less.

[0101] (Crosslinking Agent) The pressure-sensitive adhesive composition disclosed herein can contain a crosslinking agent as needed. The type of crosslinking agent is not particularly limited, and can be selected from conventionally known crosslinking agents, for example, depending on the composition of the pressure-sensitive adhesive composition, so that the crosslinking agent exerts an appropriate crosslinking function within the pressure-sensitive adhesive. Examples of crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These can be used alone or in combination of two or more.

[0102] The content of the crosslinking agent (the total amount when two or more crosslinking agents are included) is not particularly limited. From the viewpoint of realizing a PSA that exhibits well-balanced adhesive properties such as adhesive strength and cohesive strength, the content of the crosslinking agent is suitably approximately 5 parts by weight or less, preferably approximately 0.001 to 5 parts by weight, more preferably approximately 0.001 to 4 parts by weight, and even more preferably approximately 0.001 to 3 parts by weight, per 100 parts by weight of the acrylic polymer or the monomer components constituting the acrylic polymer. Alternatively, the PSA composition may be a PSA composition that does not contain the above-mentioned crosslinking agent. For example, when a photocurable PSA composition is used as the PSA composition disclosed herein, the PSA composition may be substantially free of a crosslinking agent such as an isocyanate-based crosslinking agent. Here, the PSA composition being substantially free of a crosslinking agent (typically an isocyanate-based crosslinking agent) means that the amount of crosslinking agent per 100 parts by weight of the monomer components is less than 0.05 parts by weight (e.g., less than 0.01 parts by weight).

[0103] A crosslinking catalyst may be used to more effectively promote the crosslinking reaction. Furthermore, the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive may contain a crosslinking retarder (e.g., a compound that generates keto-enol tautomerism) if desired. The amounts of the crosslinking catalyst and crosslinking retarder used are not limited to a specific range, and appropriate amounts are used depending on the purpose, etc.

[0104] [Polyester-Based Pressure-Sensitive Adhesive] In some other embodiments of the technology disclosed herein, a pressure-sensitive adhesive containing a polyester-based polymer can be preferably used as a constituent material of the pressure-sensitive adhesive layer.

[0105] (Polyester-based polymer) A polyester-based polymer is typically contained in the pressure-sensitive adhesive layer as a base polymer. In this specification, the polyester-based polymer refers to a polymer obtained by polycondensation of a polycarboxylic acid and a polyol.

[0106] The polycarboxylic acid used in the synthesis of the polyester polymer may be any of aromatic polycarboxylic acids, alicyclic polycarboxylic acids, aliphatic polycarboxylic acids, and unsaturated polycarboxylic acids. Any of dicarboxylic acids containing two carboxyl groups in one molecule, tricarboxylic acids (tricarboxylic acids) containing three carboxyl groups, and tetracarboxylic or higher polycarboxylic acids containing four or more carboxyl groups may be used.

[0107] Specific examples of polycarboxylic acids include aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, norbornanedicarboxylic acid, and adamantanedicarboxylic acid; Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as carboxylic acid, succinic acid, glutaric acid, dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, thiodipropionic acid, and diglycolic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, and citraconic acid; trivalent or higher polycarboxylic acids such as trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, and trimesic acid; dimer acids and trimer acids obtained by dimerizing or trimerizing fatty acids such as oleic acid; and derivatives thereof. These may be used alone or in combination of two or more. The derivatives of the polycarboxylic acids include derivatives such as carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters.

[0108] As the polycarboxylic acid, an aromatic polycarboxylic acid (typically an aromatic dicarboxylic acid) is preferably used. The use of an aromatic polycarboxylic acid tends to easily prevent the penetration of polar chemicals and the like. In addition, the cohesive strength of the adhesive tends to be increased, and the holding power tends to be improved. Suitable examples include isophthalic acid, terephthalic acid, and orthophthalic acid, with isophthalic acid being more preferred. These can be used alone or in combination of two or more. For example, isophthalic acid and terephthalic acid can be used in combination.

[0109] The molar ratio of aromatic carboxylic acid to the total number of moles of polycarboxylic acid in the monomer component of polyester polymer is not particularly limited, but is suitably about 1 mol% or more. From the viewpoint of durability and holding power against polar chemicals, etc., it is preferably about 10 mol% or more, more preferably about 30 mol% or more, even more preferably about 40 mol% or more, for example, it may be about 50 mol% or more, or even about 60 mol% or more. In addition, the molar ratio of the aromatic carboxylic acid is suitably about 95 mol% or less, and from the viewpoint of adhesive properties such as peel strength, it is preferably about 85 mol% or less, more preferably about 80 mol% or less, even more preferably about 75 mol% or less (for example, 70 mol% or less). The molar ratio of the aromatic carboxylic acid may be about 65 mol% or less (for example, about 55 mol% or less).

[0110] Furthermore, as the polycarboxylic acid, an aliphatic polycarboxylic acid (typically an aliphatic dicarboxylic acid) is also preferably used. Suitable examples include dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid, of which adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid are more preferred, and adipic acid and sebacic acid are even more preferred.

[0111] The molar ratio of aliphatic carboxylic acid in the total number of moles of polycarboxylic acid in the monomer component of polyester polymer is not particularly limited, but is suitably about 1 mol% or more, and from the viewpoint of adhesive properties such as peel strength, it is preferably about 10 mol% or more, more preferably about 15 mol% or more, even more preferably about 20 mol% or more, particularly preferably about 25 mol% or more, and may be about 35 mol% or more (for example, about 50 mol% or more).In addition, the molar ratio of the above-mentioned aliphatic carboxylic acid is suitably about 90 mol% or less, and from the viewpoint of durability against polar chemicals, etc., it is preferably about 70 mol% or less, more preferably about 60 mol% or less, for example, it may be about 50 mol% or less, or may be about 40 mol% or less.

[0112] From the viewpoint of obtaining a glass transition temperature (Tg) suitable for the adhesive, it is preferable to use an aliphatic polycarboxylic acid (typically an aliphatic dicarboxylic acid) in combination with an aromatic polycarboxylic acid (typically an aromatic dicarboxylic acid). Ａ and aromatic polycarboxylic acid C Ｂ The molar ratio (C Ａ : C Ｂ ) is suitably about 1:49 to 49:1, and may be about 5:45 to 45:5. In a preferred embodiment, the molar ratio (C Ａ : C Ｂ ) is approximately 5:45 to 40:10, more preferably approximately 10:40 to 35:15 (e.g., approximately 15:35 to 30:20), and may be, for example, approximately 5:45 to 25:25 or approximately 10:40 to 20:30 (e.g., approximately 15:35 to 20:30).

[0113] Furthermore, it is preferable that the polycarboxylic acid is mainly composed of a dicarboxylic acid. In some embodiments, in the monomer components of the polyester polymer, the proportion of dicarboxylic acids in the total amount of polycarboxylic acids is suitably about 90 mol% or more, preferably about 95 mol% or more, more preferably about 98 mol% or more, even more preferably about 99 mol% or more (e.g., 99 to 100 mol%), and typically 99.9 mol% or more (in other words, the polycarboxylic acid is substantially composed of dicarboxylic acids). The proportion of trivalent or higher polycarboxylic acids in the total amount of the polycarboxylic acids is suitably about 10 mol% or less, preferably about 5 mol% or less, more preferably about 3 mol% or less, even more preferably about 1 mol% or less, and particularly preferably about 0.1 mol% or less (in other words, the polycarboxylic acid is substantially free of trivalent or higher polycarboxylic acids).

[0114] The polyol used in the synthesis of the polyester polymer disclosed herein may be any of aliphatic polyols, alicyclic polyols, aromatic polyols, and unsaturated polyols. Any of diols containing two hydroxy groups in one molecule, triols containing three hydroxy groups, and tetrahydric or higher polyols containing four or more hydroxy groups may be used.

[0115] Specific examples of the polyol include aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, and 1,8-octanediol; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and the like. Alicyclic diols such as cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and their ethylene oxide and propylene oxide adducts; dimer diol; trivalent or higher polyols such as pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, and adamantanetriol. These can be used alone or in combination of two or more.

[0116] As the polyol, aliphatic polyols (typically aliphatic diols) and alicyclic polyols (typically alicyclic diols) are preferred, with aliphatic polyols being more preferred. By combining these polyols (preferably aliphatic diols) with the above-mentioned polycarboxylic acids (preferably polycarboxylic acids containing aromatic dicarboxylic acids), a polyester-based polymer with excellent adhesive properties can be preferably obtained. Suitable examples include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. From the viewpoint of reactivity, etc., ethylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol are more preferred. These may be used alone or in combination of two or more. For example, a combination of ethylene glycol, 2,2-dimethyl-1,3-propanediol, and 1,6-hexanediol may be mentioned.

[0117] The molar proportion of aliphatic polyols and alicyclic polyols (preferably the molar proportion of aliphatic polyols) in the total number of moles of polyols in the monomer components of the polyester polymer is not particularly limited, but is suitably about 50 mol% or more, and from the viewpoint of obtaining good adhesive properties, is preferably about 70 mol% or more, more preferably about 80 mol% or more, even more preferably about 90 mol% or more, and particularly preferably about 95 mol% or more (e.g., 99 to 100 mol%). Furthermore, the molar proportion of the aliphatic polyols and alicyclic polyols (preferably the molar proportion of aliphatic polyols) may be, for example, about 95 mol% or less.

[0118] Furthermore, it is preferable that the polyol is mainly composed of a diol. In some embodiments, the proportion of diols in the total amount of polyols in the monomer components of the polyester-based polymer is suitably about 90 mol% or more, preferably about 95 mol% or more, more preferably about 98 mol% or more, even more preferably about 99 mol% or more (e.g., 99 to 100 mol%), and typically 99.9 mol% or more (in other words, the polyol is substantially composed of diols). The proportion of trihydric or higher polyols in the total amount of polyols is suitably about 10 mol% or less, preferably about 5 mol% or less, more preferably about 3 mol% or less, even more preferably about 1 mol% or less, and particularly preferably about 0.1 mol% or less (in other words, the polyol is substantially free of trihydric or higher polyols).

[0119] The polyester polymer may be substantially composed of the polycarboxylic acid and polyol described above. However, for the purpose of introducing desired functional groups or adjusting molecular weight, other copolymerization components (e.g., monocarboxylic acids or alcohols) other than the polycarboxylic acid and polyol may be copolymerized within a range that does not impair the effects of the technology disclosed herein. The proportion of the other copolymerization components is, for example, approximately less than 3 mol%, typically approximately less than 1 mol% (even less than 0.1 mol%). The technology disclosed herein can also be preferably implemented in an embodiment in which the monomer components of the polyester polymer do not substantially contain the other copolymerization components.

[0120] The method for obtaining the polyester polymer disclosed herein is not particularly limited, and any polymerization method known as a synthetic method for polyester polymers can be appropriately employed. From the viewpoints of polymerization efficiency, molecular weight control, and the like, it is appropriate to blend the monomer raw material used in the synthesis of the polyester polymer so that 1 equivalent or more (e.g., 1 to 2 equivalents) of polyol is blended per equivalent of polycarboxylic acid. In a preferred embodiment, the blending amount of polyol per equivalent of polycarboxylic acid is more than 1 equivalent and 1.8 equivalents or less (e.g., 1.2 to 1.7 equivalents).

[0121] The polyester polymer in the technology disclosed herein can be obtained by polycondensation of a polycarboxylic acid and a polyol, similar to general polyesters. More specifically, a polyester polymer can be synthesized by proceeding with the reaction between a carboxyl group of a polycarboxylic acid and a hydroxyl group of a polyol, typically while removing water (produced water) produced by the reaction from the reaction system. Methods for removing the produced water from the reaction system include a method of blowing an inert gas into the reaction system and removing the produced water together with the inert gas from the reaction system, and a method of distilling the produced water from the reaction system under reduced pressure (reduced pressure method). The reduced pressure method is preferably used because it is suitable for shortening the synthesis time and improving productivity.

[0122] The reaction temperature during the above reaction (including esterification and polycondensation), and the degree of vacuum (pressure within the reaction system) when a reduced pressure method is employed, can be appropriately set so as to efficiently obtain a polyester polymer with the desired properties (e.g., molecular weight). While not particularly limited, the reaction temperature is typically set to 180°C to 260°C, for example, 200°C to 220°C. Setting the reaction temperature within the above range ensures a good reaction rate, improves productivity, and facilitates the prevention or suppression of deterioration of the resulting polyester polymer. While not particularly limited, the degree of vacuum is typically set to 10 kPa or less (typically 10 kPa to 0.1 kPa), for example, 4 kPa to 0.1 kPa. Setting the pressure within the reaction system within the above range allows the water produced by the reaction to be efficiently distilled out of the system, making it easier to maintain a good reaction rate. Furthermore, when the reaction temperature is relatively high, setting the pressure within the reaction system to at least the above lower limit facilitates the prevention of the raw materials, polycarboxylic acid and polyol, from distilling out of the system. From the viewpoint of maintaining a stable pressure in the reaction system, it is usually appropriate to set the pressure in the reaction system to 0.1 kPa or more.

[0123] In the above reaction, as in the synthesis of general polyesters, a known or conventional catalyst can be used in an appropriate amount for esterification and condensation. Examples of such catalysts include various metal compounds such as titanium-based, germanium-based, antimony-based, tin-based, and zinc-based compounds; strong acids such as p-toluenesulfonic acid and sulfuric acid; and the like. Among these, titanium-based metal compounds (titanium compounds) are preferred. Specific examples of such titanium compounds include titanium tetraalkoxides such as titanium tetrabutoxide, titanium tetraisopropoxide, titanium tetrapropoxide, and titanium tetraethoxide; alkyl titanates such as tetraisopropyl titanate, tetrabutyl titanate, octaalkyltrititanate, and hexaalkylditanate; and titanium acetate.

[0124] In the above process of synthesizing a polyester polymer by the reaction of a polycarboxylic acid with a polyol, a solvent may or may not be used. The synthesis can be carried out substantially without using an organic solvent (meaning, for example, that an organic solvent is intentionally used as a reaction solvent during the reaction is excluded). Synthesizing a polyester polymer substantially without using an organic solvent and preparing a polyester pressure-sensitive adhesive using such a polyester polymer are preferable because they meet the demand for reducing the use of organic solvents in the production process.

[0125] In the above reaction, since there is generally a correlation between the molecular weight of the polyester polymer synthesized and the viscosity of the reaction system, this can be utilized to control the molecular weight of the polyester polymer. For example, by continuously or intermittently measuring (monitoring) the torque of the stirrer and the viscosity of the reaction system during the reaction, it is possible to synthesize a polyester polymer having a target molecular weight with high accuracy.

[0126] Although not particularly limited, in some embodiments, a polyester polymer having a hydroxyl value of less than 30 mgKOH / g (e.g., less than 15 mgKOH / g) can be used as the base polymer of the polyester-based PSA. The hydroxyl value of the polyester-based polymer is preferably less than 12 mgKOH / g, more preferably less than 10 mgKOH / g, and may be, for example, less than 8 mgKOH / g or less than 5 mgKOH / g. The lower limit of the hydroxyl value is 0 mgKOH / g or more (typically more than 0 mgKOH / g, e.g., 1 mgKOH / g or more). The hydroxyl value of the polyester-based polymer can be measured in accordance with JIS K0070:1992. If a nominal value of the hydroxyl value is provided by a manufacturer, etc., that value can be used.

[0127] Furthermore, although not particularly limited, in some embodiments, a polyester polymer having an acid value of less than 10 mgKOH / g can be used as the base polymer of the polyester PSA. The acid value of the polyester polymer is preferably less than 5 mgKOH / g, more preferably less than 3 mgKOH / g, and even more preferably less than 2 mgKOH / g, and may be, for example, less than 1 mgKOH / g. The lower limit of the acid value is 0 mgKOH / g. The hydroxyl value of the polyester polymer may be 0 mgKOH / g or may be greater than 0 mgKOH / g. The acid value of the polyester polymer can be measured in accordance with JIS K0070:1992. When a nominal value of the hydroxyl value is provided by a manufacturer or the like, that value can be used.

[0128] Although not particularly limited, from the viewpoint of bonding reliability with an adherend during use of the PSA sheet, the Tg of the polyester-based polymer is advantageously about 15°C or less, preferably about 0°C or less, more preferably about -10°C or less, even more preferably about -15°C or less, and may be, for example, about -20°C or less. From the viewpoint of the cohesive strength of the PSA layer, the Tg of the polyester-based polymer is usually about -80°C or more, preferably about -60°C or more, more preferably about -40°C or more, and even more preferably about -30°C or more (for example, -20°C or more). The Tg of the polyester-based polymer can be adjusted by appropriately changing the monomer composition (i.e., the types and amount ratios of monomers used in synthesizing the polymer). In the technology disclosed herein, the base polymer of the PSA layer can be any of high Tg (e.g., Tg of −20°C or higher, typically −20°C to 15°C) polyester polymers, medium Tg (e.g., Tg of −40°C or higher but less than −20°C), and low Tg (e.g., Tg of less than −40°C, typically −80°C or higher but less than −40°C). Among these, medium Tg and high Tg polyester polymers are preferred. The Tg of the polyester polymer can be measured using a commercially available differential scanning calorimeter (e.g., TSA Instruments, model "DSC Q20"). Measurement conditions include a shear strain frequency of 1 Hz, a temperature range of −90°C to 100°C, and a heating rate of 10°C / min. If the nominal hydroxyl value is provided by the manufacturer, this value can be used.

[0129] The number average molecular weight (Mn) of the polyester-based polymer is not particularly limited and may be, for example, approximately 5,000 or more. Here, Mn refers to a value calculated in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As a GPC device, for example, a model named "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used. From the viewpoint of durability against polar chemicals and the like, for example, cohesive strength, retention strength, etc., the Mn of the polyester-based polymer is preferably approximately 7,000 or more, more preferably approximately 9,000 or more, and may be, for example, approximately 12,000 or more, approximately 15,000 or more, or approximately 18,000 or more (for example, approximately 24,000 or more). The Mn of the polyester-based polymer is usually approximately 10 × 10 ４ It is appropriate that the thickness is equal to or less than 5×10 ４ Less than or equal to 3×10 ４ or less, for example, approximately 2×10 ４ It may be less than or equal to about 1.5×10 ４ It may be the following:

[0130] (Crosslinking agent) The pressure-sensitive adhesive composition used to form the polyester-based pressure-sensitive adhesive layer preferably contains a crosslinking agent as an optional component. The pressure-sensitive adhesive layer in the technology disclosed herein may contain the crosslinking agent in the form after crosslinking reaction, the form before crosslinking reaction, the form after partial crosslinking reaction, or an intermediate or composite form thereof. The crosslinking agent is usually contained in the pressure-sensitive adhesive layer exclusively in the form after crosslinking reaction. Note that the crosslinking agent used to crosslink the polyester-based polymer may also function as a chain extender.

[0131] The type of crosslinking agent is not particularly limited, and can be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agents can be used alone or in combination of two or more. Among these, isocyanate-based crosslinking agents are preferred.

[0132] As the isocyanate-based crosslinking agent, a polyfunctional isocyanate (a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent can be used alone or in combination of two or more.

[0133] Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0134] Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0135] Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0136] A preferred example of the polyfunctional isocyanate is a polyfunctional isocyanate having an average of three or more isocyanate groups per molecule. Such a trifunctional or higher isocyanate may be a multimer (e.g., a dimer or trimer) of a bifunctional or trifunctional or higher isocyanate, a derivative (e.g., an addition reaction product of a polyhydric alcohol with two or more molecules of a polyfunctional isocyanate), a polymer, or the like. Examples of polyfunctional isocyanates include a dimer or trimer of diphenylmethane diisocyanate, an isocyanurate of hexamethylene diisocyanate (a trimer adduct of an isocyanurate structure), a reaction product of trimethylolpropane and tolylene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and the like. Examples of commercially available products of such polyfunctional isocyanates include those manufactured by Asahi Kasei Chemicals Corporation under the trade name "Duranate TPA-100"; those manufactured by Tosoh Corporation under the trade names "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096"; and those manufactured by Mitsui Chemicals, Inc. under the trade names "Takenate D110N," "Takenate D120N," "Takenate D140N," and "Takenate D160N."

[0137] In embodiments in which an isocyanate-based crosslinking agent is used, the amount used is not particularly limited. The amount of the isocyanate-based crosslinking agent used can be, for example, approximately 0.5 parts by weight or more and approximately 10 parts by weight or less per 100 parts by weight of the polyester-based polymer. From the viewpoint of durability against polar chemicals, etc., the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the polyester-based polymer is usually approximately 1 part by weight or more, and preferably approximately 1.5 parts by weight or more (for example, approximately 3 parts by weight or more). Furthermore, the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the polyester-based polymer is usually approximately 8 parts by weight or less, and preferably approximately 5 parts by weight or less.

[0138] The total amount of crosslinking agent used is not particularly limited, and can be selected, for example, from a range of about 0.005 parts by weight or more (e.g., 0.01 parts by weight or more, typically 0.1 parts by weight or more) to about 10 parts by weight or less (e.g., about 8 parts by weight or less, preferably about 5 parts by weight or less) relative to 100 parts by weight of the base polymer.

[0139] (Crosslinking Catalyst) In order to more effectively proceed with the crosslinking reaction, a crosslinking catalyst can be used in addition to the above crosslinking agent. Examples of the crosslinking catalyst include zirconium-containing compounds (zirconium-based catalysts) such as zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethylacetoacetate, and zirconium octylate compounds; tin (Sn)-containing compounds (tin-based catalysts) such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, trimethyltin hydroxide, and butyltin oxide; aluminum sec-butoxide, aluminum sec-butoxide, and the like. Examples of the organometallic catalyst include aluminum-containing compounds (aluminum-based catalysts) such as aluminum trisacetylacetonate, aluminum bisethylacetoacetate, and aluminum trisethylacetoacetate; iron-containing compounds (iron-based catalysts) such as ferric naphthem; and titanium-containing compounds (titanium-based catalysts) such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, titanium acetylacetonate, titanium tetraacetylacetonate, and titanium ethylacetoacetate. The crosslinking catalysts can be used alone or in combination of two or more.

[0140] The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used can be, for example, about 0.001 parts by weight or more, suitably about 0.01 parts by weight or more, or may be about 0.05 parts by weight or more (for example, 0.10 parts by weight or more) relative to 100 parts by weight of the polyester-based polymer. Furthermore, the amount of the crosslinking catalyst used can be, for example, about 3 parts by weight or less, suitably about 1 part by weight or less, or may be about 0.3 parts by weight or less, relative to 100 parts by weight of the polyester-based polymer.

[0141] (Hydrolysis stabilizer) The pressure-sensitive adhesive composition used to form the polyester-based pressure-sensitive adhesive layer may contain a hydrolysis stabilizer (also called a hydrolysis inhibitor). By adding a hydrolysis stabilizer, hydrolysis reactions in the pressure-sensitive adhesive are suppressed, making it easier to obtain good durability of adhesive performance. The hydrolysis stabilizer is not particularly limited, and known or conventional hydrolysis stabilizers can be used. Examples include oxazoline group-containing compounds, epoxy group-containing compounds, and carbodiimide group-containing compounds. Of these, carbodiimide group-containing compounds are preferred. The hydrolysis stabilizers can be used alone or in combination of two or more.

[0142] Examples of carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and monofunctional cyclic carbodiimides. Here, a monofunctional cyclic carbodiimide refers to a compound having one carbodiimide group within its molecular structure, in which the first nitrogen atom and the second nitrogen atom of the carbodiimide group are bonded via a linking group composed of an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. The linking group may contain a heteroatom or a substituent. Suitable examples of carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, and monofunctional cyclic carbodiimides.

[0143] The amount of hydrolysis stabilizer (preferably a carbodiimide group-containing compound) used is not particularly limited, but is suitably about 0.05 parts by weight or more, preferably about 0.1 parts by weight or more, for example, about 0.3 parts by weight or more, per 100 parts by weight of polyester polymer so that the effect of the hydrolysis stabilizer is preferably exhibited. The upper limit of the amount of hydrolysis stabilizer used is suitably about 5 parts by weight or less, preferably about 3 parts by weight or less, for example, 1 part by weight or less, per 100 parts by weight of polyester polymer.

[0144] [Other Components] (Tackifier Resin) The adhesive (e.g., acrylic adhesive, polyester adhesive, etc.) in the technology disclosed herein may contain a tackifier resin. Examples of tackifier resins include rosin-based tackifier resins, rosin derivative tackifier resins, petroleum-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, and ketone-based tackifier resins. These can be used alone or in combination of two or more. Among these, one or more selected from rosin-based tackifier resins, rosin derivative tackifier resins, and terpene phenol resins can be preferably used. For example, a tackifier resin (preferably a rosin derivative tackifier resin) having a softening point of 80°C or higher (e.g., 120°C or higher and 180°C or lower) can be preferably used.

[0145] When a tackifier resin is used, the amount used is suitably 1 part by weight or more per 100 parts by weight of the monomer components constituting the base polymer of the PSA to optimally exert its effects; from the viewpoint of obtaining even greater effects, the amount may be 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, or 25 parts by weight or more. Furthermore, the amount of tackifier resin used per 100 parts by weight of the monomer components may be, for example, 50 parts by weight or less or 30 parts by weight or less. The PSA in the technology disclosed herein may use less than 1 part by weight of tackifier resin per 100 parts by weight of the monomer components, or may be substantially free of tackifier resin.

[0146] (Surfactant) The adhesive may contain a surfactant. As the surfactant, known nonionic surfactants, anionic surfactants, cationic surfactants, etc. can be used. Of these, nonionic surfactants are preferred. The surfactants can be used alone or in combination of two or more.

[0147] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monooleate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate; polyoxyethylene glyceryl ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; and the like.

[0148] Examples of anionic surfactants include alkyl sulfates such as lauryl sulfate and octadecyl sulfate; fatty acid salts; alkyl benzene sulfonates such as nonyl benzene sulfonate and dodecyl benzene sulfonate; naphthalene sulfonates such as dodecyl naphthalene sulfonate; alkyl diphenyl ether disulfonates such as dodecyl diphenyl ether disulfonates; polyoxyethylene alkyl ether sulfates such as polyoxyethylene octadecyl ether sulfate and polyoxyethylene lauryl ether sulfate; polyoxyethylene alkyl phenyl ether sulfates such as polyoxyethylene lauryl phenyl ether sulfate; polyoxyethylene styrenated phenyl ether sulfate; sulfosuccinates such as lauryl sulfosuccinate and polyoxyethylene lauryl sulfosuccinate; polyoxyethylene alkyl ether phosphates; polyoxyethylene alkyl ether acetates; etc. When the anionic surfactant forms a salt, this salt can be, for example, a metal salt (preferably a monovalent metal salt) such as sodium salt, potassium salt, calcium salt, magnesium salt, etc., ammonium salt, amine salt, etc.

[0149] The content of the surfactant in the PSA is not particularly limited and can be set so as to adequately exhibit the effects of the surfactant. In some embodiments, the content of the surfactant can be, for example, 0.05 parts by weight or more, and may be 0.1 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, or 1.5 parts by weight or more, relative to 100 parts by weight of the monomer components constituting the base polymer. In some embodiments, the amount of surfactant used is suitably 3 parts by weight or less, preferably 2 parts by weight or less, and more preferably less than 1 part by weight or less than 0.5 parts by weight, relative to 100 parts by weight of the monomer components constituting the base polymer. The technology disclosed herein can be preferably implemented in an embodiment in which the content of the surfactant in the PSA is limited to less than 0.3 parts by weight (i.e., 0 parts by weight or more and less than 0.3 parts by weight), less than 0.1 parts by weight, or less than 0.01 parts by weight, relative to 100 parts by weight of the monomer components constituting the base polymer, or in which the PSA is substantially free of surfactant.

[0150] (Other Optional Components) The adhesives disclosed herein may contain, as necessary, various additives commonly used in the field of adhesives, such as viscosity adjusters (e.g., thickeners), pH adjusters, leveling agents, plasticizers, silane coupling agents, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antioxidants, etc. As for such various additives, conventionally known ones can be used in the usual way, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

[0151] In some embodiments, the adhesive constituting the first adhesive layer may have a limited amount of components other than the base polymer (e.g., an acrylic polymer) in the adhesive. The amount of components other than the base polymer in the adhesive is suitably, for example, 30 wt % or less of the total weight of the adhesive, and preferably 15 wt % or less, 12 wt % or less, or 10 wt % or less. An adhesive with a limited amount of components other than the base polymer is more likely to satisfy predetermined optical properties (e.g., transparency) and may be suitable for optical applications. In some embodiments, the amount of components other than the base polymer in the adhesive may be 5 wt % or less, 3 wt % or less, or 2 wt % or less. For example, an adhesive formed from a photocurable adhesive composition may preferably have a configuration in which the amount of components other than the base polymer is limited in this way.

[0152] [Formation of Pressure-Sensitive Adhesive Layer] The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein may be a cured layer of a pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer can be formed by applying (e.g., coating) the pressure-sensitive adhesive composition to a suitable surface and then appropriately curing the composition. For pressure-sensitive adhesive compositions using a partial polymer of a monomer component (acrylic polymer syrup), the curing treatment typically involves a final copolymerization reaction. That is, the partial polymer is subjected to a further copolymerization reaction to form a fully polymerized product. When two or more curing treatments (drying, crosslinking, polymerization, etc.) are performed, these can be performed simultaneously or in multiple stages. For example, when a photocurable pressure-sensitive adhesive composition requires drying (e.g., a photocurable pressure-sensitive adhesive composition in which a partial polymer of a monomer component is dissolved in an organic solvent), the composition can be dried before photocuring. For solvent-based pressure-sensitive adhesive compositions or aqueous dispersion-based pressure-sensitive adhesive compositions, the curing treatment typically involves drying (heat drying), and further treatments such as crosslinking can be performed as needed.

[0153] The pressure-sensitive adhesive composition can be applied using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater or spray coater.

[0154] [Thickness of Pressure-Sensitive Adhesive Layer] The thickness of the pressure-sensitive adhesive layer is not particularly limited and may be, for example, about 3 μm to 2000 μm. From the viewpoint of adhesion to the adherend, such as conformability to unevenness, in some embodiments, the thickness of the pressure-sensitive adhesive layer is advantageously 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. Furthermore, from the viewpoint of preventing the occurrence of adhesive residue due to cohesive failure of the pressure-sensitive adhesive layer, in some embodiments, the thickness of the pressure-sensitive adhesive layer is usually 500 μm or less, preferably 200 μm or less, more preferably 100 μm or less, and may be 50 μm or less, or may be 30 μm or less.

[0155] [First Pressure-Sensitive Adhesive Layer and Second Pressure-Sensitive Adhesive Layer] When the pressure-sensitive adhesive sheet disclosed herein has a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer (for example, a substrate-attached double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer on the first surface of the substrate and a second pressure-sensitive adhesive layer on the second surface of the substrate), the pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer (first pressure-sensitive adhesive) and the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer (second pressure-sensitive adhesive) may have the same composition or different compositions. Furthermore, the configuration (thickness, etc.) and various properties of the first pressure-sensitive adhesive layer may be the same as or different from the configuration and various properties of the second pressure-sensitive adhesive layer. For example, the peel force reduction rate R Ａ The peel force reduction rate R of the second pressure-sensitive adhesive layer Ａ may be approximately the same, higher, or lower (for example, less than 70%, less than 50%). From the viewpoint of ease of manufacturing the PSA sheet, in some embodiments, it is preferable to form the first PSA layer and the second PSA layer using the same PSA composition. Furthermore, the thickness of the second PSA layer may be greater than, smaller than, or the same as the thickness of the first PSA layer. In some embodiments, it is preferable that the thicknesses of the first PSA layer and the second PSA layer are the same.

[0156] <Substrate> The pressure-sensitive adhesive sheet in the technology disclosed herein may include a substrate. Examples of the substrate include various resin films such as polyolefin film, polyester film, polyvinyl chloride film, etc.; foam sheets made of foams such as polyurethane foam, polyethylene foam, polychloroprene foam, etc.; woven and nonwoven fabrics made by single or mixed spinning of various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.), and fiber aggregates such as paper (washi paper, fine paper, kraft paper, crepe paper); metal foils such as aluminum foil, copper foil, and stainless steel (SUS); etc. The substrate may have a composite structure of these. Examples of composite substrates include laminated substrates (multilayer substrates) made of a structure in which metal foil and the above-mentioned resin film are laminated, and resin sheets reinforced with inorganic fibers such as glass cloth.

[0157] In some embodiments, the substrate can preferably include a base film that is an independently shape-retaining (self-supporting or independent) resin film. Here, "resin film" refers to a resin film that has a non-porous structure and typically contains substantially no air bubbles (void-free). Therefore, the resin film is a concept that is distinct from foam films and nonwoven fabrics. The resin film may have a single-layer structure or a multi-layer structure of two or more layers (e.g., a three-layer structure). The resin film may be a transparent film. Transparent resin films are suitable for optical applications.

[0158] Suitable examples of resin materials constituting the resin film include polyester resins, polyphenylene sulfide (PPS) resins, polyolefin resins, and polyimide resins. Specific examples of resin films that can be preferably used as the substrate layer include polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, PPS film, polyether ether ketone (PEEK) film, transparent polyimide (CPI) film, polypropylene (PP) film, and triacetyl cellulose (TAC) film. Preferred examples from the standpoint of strength include PET film, PEN film, PPS film, PEEK film, and CPI film. Preferred examples from the standpoints of availability, dimensional stability, optical properties, and the like include PET film, CPI film, and TAC film. The resin film may contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and antiblocking agents, as needed. The amount of additives added is not particularly limited and can be appropriately determined depending on the application.

[0159] In some other embodiments, a substrate including a porous layer can be preferably used as the substrate. Examples of the porous layer include the foam sheet (particularly a foam sheet with an open cell structure) and a fibrous assembly. The substrate including the porous layer may be a substrate consisting of one or more porous layers, or may be a substrate having a non-porous layer (e.g., a resin film) in addition to a porous layer.

[0160] The substrate may have an auxiliary layer in addition to the porous layer or non-porous layer described above. Examples of the auxiliary layer include a decorative layer such as a printed layer, an undercoat layer, a release layer, etc. The surface of the substrate facing the pressure-sensitive adhesive layer may be subjected to a conventionally known surface treatment, such as corona treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer (primer), antistatic treatment, or release treatment, as needed.

[0161] The thickness of the substrate is not particularly limited. The thickness of the substrate may be, for example, 1 μm or more, 10 μm or more, 20 μm or more, or 30 μm or more, and may be, for example, 5 mm or less, 2 mm or less, or 1 mm or less. In some embodiments in which the substrate includes a porous layer such as a foam sheet, the thickness of the substrate may be, for example, 50 μm or more, 100 μm or more, 200 μm or more, or 300 μm or more. In some embodiments in which the substrate is made of a resin film, the thickness of the substrate may be, for example, 500 μm or less, 250 μm or less, or 100 μm or less.

[0162] When the PSA sheet in the technology disclosed herein has a substrate (e.g., a substrate disposed between a first PSA layer and a second PSA layer), the substrate is preferably substantially insoluble in ethanol. More specifically, the weight loss rate of the substrate when immersed in ethanol for 10 minutes and then dried (hereinafter referred to as the "weight loss rate due to ethanol immersion" or simply the "weight loss rate") is preferably less than 1 wt%. PSA sheets having an ethanol-insoluble substrate are preferred because they are less likely to experience problems such as dissolution or deformation of the substrate due to contact with an alcoholic solvent during normal use. Furthermore, when disassembling an assembly including such a PSA sheet, it is preferable that the substrate be ethanol-insoluble from the viewpoints of reusability of the PSA sheet after disassembly and ease of separation (e.g., peeling) of the PSA sheet from disassembled components to which the PSA sheet is bonded. The weight loss rate of the substrate due to ethanol immersion is measured by the following method. [Method for Measuring Weight Loss Rate Due to Ethanol Immersion] 1. The substrate to be measured is cut to a size of 20 mm x 20 mm to prepare a sample. 2. Measure the initial weight (W0) of the sample. 3. Completely immerse the sample in 50 mL of ethanol at 25°C. 4. After 10 minutes of immersion, remove the sample that has absorbed the ethanol from the ethanol. Measure the weight (W2) of the sample after drying it at 130°C for 30 minutes. 5. Calculate the weight loss rate of the substrate due to ethanol immersion using the following formula: Weight loss [%] = ((W0 - W2) / W0) x 100

[0163] In some embodiments, the substrate can preferably be one that can absorb a certain amount of ethanol after a relatively short period of immersion in ethanol. Here, the concept of a substrate absorbing ethanol encompasses absorption due to ethanol entering voids in the substrate (e.g., within the pores of a substrate having a porous layer) and absorption due to swelling of the constituent materials of the substrate with ethanol. For example, it is preferable that the amount of ethanol absorbed when the substrate is immersed in ethanol for 10 minutes (hereinafter simply referred to as "ethanol absorption amount") is 25 wt% or more of the weight of the substrate. More specifically, the amount of ethanol absorbed by a substrate is measured by the following method. [Method for Measuring Ethanol Absorption Amount] 1. The substrate to be measured is cut into a size of 20 mm x 20 mm to prepare a sample. 2. The initial weight (W0) of the sample is measured. 3. The sample is completely immersed in 50 mL of ethanol at 25°C. 4. After 10 minutes of immersion, the ethanol-absorbed sample is gently pulled vertically out of the ethanol and the weight (W1) of the sample at the time of ethanol absorption is quickly measured. 5. Calculate the amount of ethanol absorbed by the substrate using the following formula: Ethanol absorption [%] = ((W1 - W0) / W0) x 100

[0164] When an assembly including a substrate with an ethanol absorption capacity of 25% by weight or more is immersed in an alcoholic stripping solution, for example, a PSA sheet having a substrate with an ethanol absorption capacity of 25% by weight or more can utilize the alcohol absorbency of the substrate to efficiently distribute the stripping solution across the assembly. For example, the stripping solution can be efficiently introduced from the end face (outer edge) of the assembly to the interior (inward in the surface direction). This can shorten the immersion time in the stripping solution (and ultimately the time required to dismantle the assembly) in the disassembly method disclosed herein. For dismantling relatively large assembly (having a long distance from the outer edge to the center), it is particularly useful to shorten the immersion time by utilizing the alcohol absorbency of the substrate in this way. Note that in a PSA sheet having a substrate on which a PSA layer constituting the adhesive surface is provided (e.g., a double-sided PSA sheet with a substrate), the adhesive surface can exhibit good alcohol releasability (e.g., a peel force reduction rate R of 70% or more). Ａ), the PSA layer tends to have good peelability from a substrate that has absorbed alcohol. Ａ When dismantling an assembly in which the adhesive surface of the PSA sheet is bonded to a member, a PSA sheet (e.g., a double-sided PSA sheet with a substrate) exhibiting the above formula (1) can be immersed in an alcoholic stripping solution to allow the stripping solution to act on the interface between the adhesive surface and the member and / or the interface between the PSA layer constituting the adhesive surface and the substrate, thereby enabling efficient dismantling of the assembly. Note that, in the technology disclosed herein, in an embodiment in which the PSA sheet has a substrate, dismantling of the assembly (e.g., separation of the PSA sheet from the first member) or alcohol stripping may proceed between the member and the PSA layer (adhesive surface), or between the substrate and the PSA layer, or may proceed in a combined or intermediate manner.

[0165] In some embodiments, the ethanol absorption amount of the substrate may be, for example, 50 wt % or more, 75 wt % or more, 100 wt % or more, 150 wt % or more, or 200 wt % or more. The upper limit of the ethanol absorption amount of the substrate is not particularly limited. In some embodiments, from the viewpoint of preventing an excessive decrease in the strength of the substrate and preventing an increase in the weight of the bonded body due to immersion in the stripping solution, the ethanol absorption amount of the substrate is, for example, suitably 2000 wt % or less, preferably 1500 wt % or less, 1000 wt % or less, or 800 wt % or less, and may be 700 wt % or less, 600 wt % or less, 500 wt % or less, or 400 wt % or less.

[0166] <Method for Dismantling a Joint> This specification provides a method for dismantling a joint including a pressure-sensitive adhesive sheet having a first adhesive surface and a first member bonded to the first adhesive surface. The dismantling method includes immersing the joint in an alcoholic stripping solution and dismantling the joint after the immersion. The pressure-sensitive adhesive sheet has a peel force reduction rate R ＡThe disassembly method allows the bonded structure to be efficiently disassembled. Furthermore, by using an alcoholic stripper instead of water, even a bonded structure in which a pressure-sensitive adhesive sheet is bonded to a member for which the peel force reduction effect of water stripping is unlikely to be achieved (e.g., a member with a relatively large water contact angle on the surface) can be suitably disassembled. Furthermore, compared to disassembly methods using water, the process of removing the stripper after disassembly tends to be shorter or simpler. The pressure-sensitive adhesive sheet constituting the bonded structure may be, for example, any of the pressure-sensitive adhesive sheets described in this specification.

[0167] The alcoholic stripper may be an alcohol or a mixed solvent mainly containing alcohol, optionally containing a small amount of additives. As the alcohol, a monohydric lower alcohol having 1 to 5 carbon atoms is preferably used. Among these, ethanol is preferred from the viewpoints of safety, versatility, etc.

[0168] The solvent other than the alcohol constituting the mixed solvent may be water or a lower ketone (e.g., acetone) that is uniformly miscible with the alcohol. The additive may be a known surfactant. From the viewpoint of avoiding contamination of the members that constitute the bonded structure, a stripper solution that is substantially free of additives may be preferably used in some embodiments.

[0169] From the viewpoints of ease of disassembly of the bonded structure and removability of the stripper solution (e.g., volatilization), in some embodiments, the alcohol content in the stripper solution is advantageously 60 wt % or more, preferably 70 wt % or more, or may be 80 wt % or more, 90 wt % or more, 95 wt % or more, or may be 98 wt % or more. The alcohol content in the stripper solution may be 100 wt %, or from the viewpoints of cost and availability, may be 99.9 wt % or less, 99.5 wt % or less, or 99 wt % or less, or may be 95 wt % or less, or may be 90 wt % or less.

[0170] The time for immersing the bonded body in the alcoholic stripping solution can be appropriately set so as to enable proper disassembly of the bonded body (preferably, disassembly in a manner that avoids damage or deformation of the components). From the viewpoint of shortening the time required for disassembly (the time from the start of immersion in the stripping solution to the completion of separation of at least one component), in some embodiments, the immersion time of the bonded body in the stripping solution is suitably 3 hours or less, preferably 1 hour or less, more preferably 30 minutes or less, and may be 20 minutes or less or 15 minutes or less. Furthermore, in some embodiments, the immersion time may be, for example, 30 seconds or more, or may be 1 minute or more, or may be 3 minutes or more, or 5 minutes or more. The appropriate immersion time may vary depending on the shape and size (bonding area) of the bonded body. For example, the immersion time may be preferably applied as the immersion time when disassembling a bonded body configured such that a flat-plate-shaped first component and a flat-plate-shaped second component are bonded by a 100 mm x 50 mm adhesive sheet (a double-sided adhesive sheet without a substrate or with a substrate).

[0171] The immersion of the bonded body in the stripper solution may be carried out at room temperature (about 15°C to 30°C, for example, about 25°C), or at a temperature higher or lower than room temperature. Immersion at a temperature higher than room temperature can be advantageous from the viewpoint of promoting the effect of immersion. From the viewpoint of avoiding excessive volatilization of the stripper solution, in some embodiments, the temperature higher than room temperature is suitably, for example, 60°C or lower, and may be 50°C or lower, or 40°C or lower.

[0172] After immersion of the bonded body in the stripping solution, the operation of disassembling the bonded body (which can be understood as an operation of separating at least some of the components of the bonded body from the other parts) may be performed after removal from the stripping solution or may be performed in the stripping solution. From the viewpoints of workability during the disassembly operation and suppressing contamination of the stripping solution, in some embodiments, it is preferable to perform the disassembly operation of the bonded body after removal from the stripping solution. Note that, in the disassembly method disclosed herein, the bonded body may be naturally disassembled (without application of external force) while immersed in the stripping solution. However, in some embodiments, from the viewpoint of controlling the timing of disassembly, it is preferable to perform the disassembly operation by applying an external force to the bonded body after immersion in the stripping solution (after removal from the stripping solution).

[0173] In some embodiments, disassembly of the bonded structure performed after immersion in the stripping solution may include separating the first PSA layer constituting the first adhesive surface from a member adjacent to the first PSA layer. The member adjacent to the first PSA layer may be a member (adherend) bonded to the first adhesive surface of the PSA sheet before disassembly, or may be a member adjacent to the back surface of the first PSA layer (the surface opposite the first PSA surface). The member adjacent to the back surface of the first PSA layer may be, for example, a second member in a bonded structure in which a first member and a second member are bonded via a first PSA layer (a substrate-less double-sided PSA sheet), or may be a substrate in a substrate-attached PSA sheet. Therefore, when the disassembly method disclosed herein is applied to disassemble an assembly including a substrate-attached PSA sheet having a first PSA layer on the substrate, the disassembly of the assembly after immersion in the stripping solution may be carried out in a manner that first separates the first member and the first PSA layer, or in a manner that first separates the first PSA layer and the member adjacent to its back surface (e.g., the second member or the substrate of the PSA sheet), or in a combination or intermediate manner of these. Furthermore, when disassembling an assembly in which the substrate-attached PSA sheet is a substrate-attached double-sided PSA sheet, and the first adhesive surface of the substrate-attached double-sided PSA sheet is bonded to a first member and the second adhesive surface is bonded to a second member, the disassembly of the assembly after immersion in a stripping solution may be carried out in a manner that first separates the first member and the first PSA layer, or in a manner that first separates the first PSA layer and the substrate adjacent to its back surface, or in a manner that first separates the second member and the second PSA layer, or in a manner that first separates the second PSA layer and the substrate adjacent to its back surface, or in a combination or intermediate manner of these. Ａ In any of the above-described embodiments, when the peel force reduction rate R is 70% or more, the effect of facilitating disassembly of the bonded body by immersion in the stripping solution can be exhibited. Ａ By having a surface roughness of 70% or more, even in an embodiment in which the initial separation after immersion in the stripping solution occurs at a location other than the interface between the first member and the first pressure-sensitive adhesive layer, the first member and the first pressure-sensitive adhesive layer can be easily separated at an appropriate timing thereafter.

[0174] When the bonded structure to be disassembled using the disassembly method disclosed herein includes a PSA sheet having a substrate (e.g., a substrate disposed between a first PSA layer and a second PSA layer), the substrate can preferably absorb a certain amount of the stripper solution (e.g., ethanol) used in the disassembly method after a relatively short immersion period. This allows, for example, when a bonded structure including a member and the PSA sheet bonded to the member is immersed in the stripper solution, the stripper solution absorbency of the substrate can be utilized to efficiently distribute the stripper solution across the bonded structure. For example, the stripper solution can be efficiently introduced from the edge (outer edge) of the bonded structure to the interior (inward in the surface direction). This can shorten the immersion time in the stripper solution (and thus the time required to disassemble the bonded structure) in the disassembly method disclosed herein. In some embodiments, the amount of stripper solution absorbed by the substrate when immersed in the stripper solution for 10 minutes (hereinafter also referred to as the "stripping solution absorption amount") is preferably 25% by weight or more of the substrate. The removal solution absorption amount of the substrate is measured in the same manner as the above-described method for measuring the ethanol absorption amount, except that the removal solution (which may be ethanol) used for disassembling the bonded structure is used instead of ethanol. The upper limit of the removal solution absorption amount of the substrate can be any of the upper limits exemplified in the above-described description of the ethanol absorption amount. Similarly, the lower limit of the removal solution absorption amount of the substrate can be any of the lower limits exemplified in the above-described description of the ethanol absorption amount.

[0175] In some embodiments of the disassembly method disclosed herein, the substrate included in the bonded structure disassembled using the disassembly method is preferably substantially insoluble in the stripping solution (e.g., ethanol) used in the disassembly method. For example, the weight loss rate of the substrate when immersed in the stripping solution for 10 minutes and then dried (hereinafter also referred to as the "weight loss rate due to stripping solution immersion") is preferably less than 1 wt%. This can be advantageous from the viewpoints of reusability of the PSA sheet after disassembly and ease of separation (e.g., peeling) of the PSA sheet from the disassembled components to which the PSA sheet is bonded. The weight loss rate of the substrate due to immersion in the stripping solution is measured in the same manner as the above-described method for measuring the weight loss rate due to ethanol immersion, except that the stripping solution (which may be ethanol) used to disassemble the bonded structure is used instead of ethanol. The upper limit of the weight loss rate of the substrate due to immersion in the stripping solution can be any of the upper limits exemplified in the above-described description of the weight loss rate due to ethanol immersion. Similarly, as the lower limit of the weight loss rate of the substrate due to immersion in the stripping liquid, any of the lower limit values ​​exemplified in the above description of the weight loss rate due to immersion in ethanol can be used.

[0176] <Applications> Taking advantage of the feature of combining bonding reliability with alcohol-based stripping ability (and thus ease of disassembly using an alcohol-based stripping solution), the PSA sheet in the technology disclosed herein can be used for applications such as fixing, joining, molding, decorating, protecting, and supporting components that constitute various mobile devices (portable devices), automobiles, home appliances, etc. Examples of materials that constitute at least the surface of the above-mentioned components include the same materials as those that constitute at least the surface of the first component or second component described above.

[0177] An example of a preferred application is optical applications. The technology disclosed herein can be preferably implemented as a method for dismantling an optical pressure-sensitive adhesive sheet used for bonding optical members (for bonding optical members) or for manufacturing a product using the optical member (optical product), and as a method for dismantling a bonded structure including the pressure-sensitive adhesive sheet.

[0178] The optical member refers to a member having optical properties (for example, polarization, light refraction, light scattering, light reflectivity, light transmittance, light absorption, light diffraction, optical rotation, visibility, etc.). The optical member is not particularly limited as long as it is a member having optical properties, but examples thereof include components constituting devices (optical devices) such as display devices (image display devices) and input devices, or components used in these devices, such as polarizing plates, wavelength plates, retardation plates, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflection films, hard coat (HC) films, impact absorbing films, antifouling films, photochromic films, light control films, transparent conductive films (ITO films), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and further components in which these are laminated (these may be collectively referred to as "functional films"). The above "plate" and "film" respectively include plate-like, film-like, sheet-like and other forms. For example, "polarizing film" includes "polarizing plate", "polarizing sheet", and the like.

[0179] Examples of the display device include a liquid crystal display device, an organic EL display device, a PDP, and electronic paper. The technology disclosed herein is particularly suitable for devices that include expensive components, such as foldable display devices and in-vehicle display devices. The display device also includes a display device that allows input, such as a touch panel. Since there is a strong demand for the display device to be recyclable and reusable, applying the technology disclosed herein is particularly beneficial.

[0180] The optical member is not particularly limited, and examples thereof include members (e.g., sheet-like, film-like, or plate-like members) made of glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal thin film, etc. In this specification, the term "optical member" also includes members (such as design films, decorative films, and surface protection films) that serve to decorate or protect a display device or input device while maintaining its visibility.

[0181] Other examples of applications of the bonded structure disclosed herein, and products, devices, and structures including the bonded structure, include fixing protective panels (lenses) that protect display sections for electronic devices, fixing decorative panels for displays (e.g., television displays), fixing batteries for electronic devices, and fixing circuit boards (glass core substrates, organic resin substrates, etc.) for integrated circuit (IC) devices in electronic devices. For example, the bonded structure can be preferably used in electronic devices (preferably portable electronic devices) that require high adhesive reliability from the pressure-sensitive adhesive sheet when joining components, while also requiring smooth removal of component parts during repair, replacement, inspection, recycling, etc. For example, mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear types worn on the wrist like a wristwatch, modular types worn on a part of the body with a clip or strap, eyewear types including glasses (monocular and binocular types, including head-mounted types), clothing types attached to shirts, socks, hats, etc. as accessories, earwear types attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), In portable electronic devices such as portable game devices, electronic dictionaries, electronic organizers, e-books, in-car information devices, portable radios, portable televisions, portable printers, portable scanners, and portable modems, the display device can be preferably used for fixing protective panels (lenses) that protect the display unit, fixing key module components, fixing rim sheets, fixing decorative panels, fixing batteries, fixing circuit boards, fixing various other components (various panel components, buttons, lighting equipment components, internal camera components, heat dissipation materials, graphite sheets), fixing display materials (including various marks) such as logos (designed characters) and various designs. The display device can also be a component of electronic devices such as desktop computers, displays, and televisions (liquid crystal, plasma, organic electroluminescence, etc.). 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.

[0182] The matters disclosed in this specification include the following: [1] A method for dismantling an assembly including a pressure-sensitive adhesive sheet having a first adhesive surface and a first member bonded to the first adhesive surface, the method comprising: immersing the assembly in a stripping solution containing a lower alcohol having 1 to 5 carbon atoms as a main component; and dismantling the assembly after the immersion, wherein the pressure-sensitive adhesive sheet has a reduction rate R of ethanol peel force N1 [N / 20 mm] relative to normal peel force N0 [N / 20 mm] in the first measurement in the following peel test. Ａ is 70% or more, and the normal peel force N0 [N / 20 mm] at the time of the first measurement is Ｓ Reduction rate R of [N / 20mm] Ｂ Disassembly method, in which the peel strength is 30% or less. [Peel Test] (First Measurement) The first adhesive surface of the pressure-sensitive adhesive sheet is attached to a stainless steel plate, placed in an autoclave and treated at a pressure of 5 atm and a temperature of 50°C for 15 minutes. The sheet is then removed from the autoclave and left to stand in an environment of 23°C and 50% RH for 30 minutes. Then, under the same environment, the pressure-sensitive adhesive sheet is peeled from the stainless steel plate using a tensile tester at a peel angle of 180° and a pulling rate of 300 mm / min. During the peeling process, 20 μL of ethanol is dropped onto the point where the pressure-sensitive adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol drop is designated as the normal peel strength N0 [N / 20 mm], and the peel strength observed after the ethanol drop is designated as the ethanol peel strength N1 [N / 20 mm]. (Second Measurement) After drying the adhesive sheet used in the first measurement, the first adhesive surface of the adhesive sheet is attached to a new stainless steel plate, placed in an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50°C, removed from the autoclave and left to stand for 30 minutes in an environment of 23°C and 50% RH, and then peeled from the stainless steel plate using a tensile tester under the same conditions at a peel angle of 180° and a pulling speed of 300 mm / min. During the peeling process, 20 μL of ethanol is dropped at the point where the adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol drop is referred to as the normal peel strength NO. Ｓ[N / 20 mm], and the peel strength observed after dropping ethanol was the ethanol peel strength N1 Ｓ [N / 20 mm]. [2] The dismantling method according to [1] above, wherein the first member has a contact angle with distilled water of 50 degrees or more. [3] The dismantling method according to [1] or [2] above, wherein the first adhesive surface is the surface of an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. [4] The dismantling method according to [3] above, wherein the monomer component constituting the acrylic polymer includes an alkyl (meth)acrylate having an alkyl group having 10 to 14 carbon atoms. [5] The dismantling method according to [1] or [2] above, wherein the first adhesive surface is the surface of a polyester pressure-sensitive adhesive layer containing a polyester polymer as a base polymer. [6] The dismantling method according to any one of [1] to [5] above, wherein the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet having a second adhesive surface on the surface opposite to the first adhesive surface, and the joined body further includes a second member joined to the second adhesive surface. [7] A pressure-sensitive adhesive sheet having: a first pressure-sensitive adhesive layer constituting a first pressure-sensitive adhesive surface; a second pressure-sensitive adhesive layer constituting a second pressure-sensitive adhesive surface that is the surface opposite to the first pressure-sensitive adhesive surface; and a substrate disposed between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer, wherein the substrate has a weight loss rate of less than 1 wt % when immersed in ethanol for 10 minutes and then dried, and the pressure-sensitive adhesive sheet has a reduction rate R of ethanol peel force N1 [N / 20 mm] relative to normal peel force N0 [N / 20 mm] in the following peel test. ＡA pressure-sensitive adhesive sheet having a peel strength of 70% or more. [Peel Test] The first adhesive surface of the pressure-sensitive adhesive sheet is attached to a stainless steel plate, placed in an autoclave and treated at a pressure of 5 atm and a temperature of 50°C for 15 minutes. The sheet is then removed from the autoclave and allowed to stand for 30 minutes in an environment of 23°C and 50% RH. The sheet is then peeled from the stainless steel plate using a tensile tester under the same conditions at a peel angle of 180° and a pulling rate of 300 mm / min. During the peeling process, 20 μL of ethanol is dropped onto the point where the pressure-sensitive adhesive sheet begins to separate from the stainless steel plate. The peel strength measured before the ethanol drop is designated as normal peel strength N0 [N / 20 mm], and the peel strength measured after the ethanol drop is designated as ethanol peel strength N1 [N / 20 mm]. [8] The pressure-sensitive adhesive sheet according to [7] above, wherein the amount of ethanol absorbed when the substrate is immersed in ethanol for 10 minutes is 25 wt% or more of the weight of the substrate. [9] The pressure-sensitive adhesive sheet according to [7] or [8] above, wherein the first pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

[10] The pressure-sensitive adhesive sheet according to [9] above, wherein the monomer component constituting the acrylic polymer contains an alkyl(meth)acrylate having an alkyl group of 10 to 14 carbon atoms.

[11] The pressure-sensitive adhesive sheet according to

[10] above, wherein the monomer component constituting the acrylic polymer further contains an alkyl(meth)acrylate having an alkyl group of 4 to 9 carbon atoms.

[12] The pressure-sensitive adhesive sheet according to any one of [9] to

[11] above, wherein the acrylic pressure-sensitive adhesive layer further contains an acrylic oligomer.

[13] The pressure-sensitive adhesive sheet according to [7] or [8] above, wherein the first pressure-sensitive adhesive layer is a polyester pressure-sensitive adhesive layer containing a polyester polymer as a base polymer.

[0183] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0184] <Preparation of Pressure-Sensitive Adhesive Composition> (Pressure-Sensitive Adhesive Composition A1) A monomer mixture containing 2-ethylhexyl acrylate (2EHA), lauryl acrylate (LA), and photopolymerization initiator A (trade name "Omnirad 184", manufactured by IGM Resins) in a weight ratio of 70 / 30 / 0.1 was charged into a four-neck flask and photopolymerized by irradiation with ultraviolet light under a nitrogen atmosphere until the viscosity (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature 30°C; the same applies hereinafter unless otherwise specified) reached approximately 15 Pa s, thereby preparing a monomer syrup S1 containing a partial polymer of the monomer mixture. To 100 parts of this monomer syrup S1, 0.1 parts of 1,6-hexanediol diacrylate (HDDA) as a crosslinking agent was added and mixed uniformly to prepare a pressure-sensitive adhesive composition A1.

[0185] (Pressure-sensitive adhesive composition A2) Monomer syrup S2 containing a partial polymer of the above-mentioned monomer mixture was prepared in the same manner as in the preparation of the above-mentioned monomer syrup S1, except that a monomer mixture containing 2EHA, LA, N-vinyl-2-pyrrolidone (NVP), and photopolymerization initiator A in a weight ratio of 70 / 30 / 10 / 0.1 was used. 0.1 parts of HDDA was added to 100 parts of this monomer syrup S2, and the mixture was mixed uniformly to prepare pressure-sensitive adhesive composition A2.

[0186] (Adhesive Composition A3) 0.1 parts of HDDA and 2 parts of acrylic oligomer A were added to 100 parts of the above-mentioned monomer syrup S2 and mixed uniformly to prepare Adhesive Composition A3. The acrylic oligomer A was synthesized by the following method. [Synthesis of Acrylic Oligomer A] 100 parts of toluene, 60 parts of dicyclopentanyl methacrylate (DCPMA) (trade name "FA-513M", manufactured by Hitachi Chemical Co., Ltd.), 40 parts of methyl methacrylate (MMA), and 3.5 parts of α-thioglycerol as a chain transfer agent were charged into a four-neck flask and stirred at 70°C under a nitrogen atmosphere for 1 hour. Then, 0.2 parts of 2,2'-azobisisobutyronitrile was charged as a thermal polymerization initiator, and the mixture was reacted at 70°C for 2 hours, followed by a reaction at 80°C for 2 hours. Thereafter, the reaction solution was placed in an atmosphere at a temperature of 130°C, and the toluene, chain transfer agent, and unreacted monomer were dried and removed to obtain a solid acrylic oligomer A. This acrylic oligomer A had a Tg of 144°C and a Mw of 4,300.

[0187] (Adhesive composition A4) Monomer syrup S4 containing a partial polymer of the above monomer mixture was prepared in the same manner as in the preparation of the above monomer syrup S1, except that a monomer mixture containing n-butyl acrylate (BA), LA, and photopolymerization initiator A in a weight ratio of 70 / 30 / 0.1 was used. 0.1 parts of HDDA and 2 parts of the above acrylic oligomer A were added to 100 parts of this monomer syrup S4, and the mixture was mixed uniformly to prepare adhesive composition A4.

[0188] (Pressure-sensitive adhesive composition A5) Monomer syrup S5 containing a partial polymer of the above-mentioned monomer mixture was prepared in the same manner as in the preparation of the above-mentioned Monomer syrup S1, except that a monomer mixture containing 2EHA, LA, and photopolymerization initiator A in a weight ratio of 50 / 50 / 0.1 was used. 0.1 parts of HDDA was added to 100 parts of this Monomer syrup S5, and the mixture was mixed uniformly to prepare Pressure-sensitive adhesive composition A5.

[0189] (Adhesive composition A6) Monomer syrup S6 containing a partial polymer of the above monomer mixture was prepared in the same manner as in the preparation of monomer syrup S1, except that a monomer mixture containing 2EHA, LA, 4-hydroxybutyl acrylate (4HBA), and photopolymerization initiator A in a weight ratio of 70 / 30 / 10 / 0.1 was used. 0.1 parts of HDDA was added to 100 parts of this monomer syrup S6, and the mixture was mixed uniformly to prepare adhesive composition A6.

[0190] (Adhesive composition A7) Monomer syrup S7 containing a partial polymer of the above monomer mixture was prepared in the same manner as in the preparation of the above monomer syrup S1, except that a monomer mixture containing BA, 4HBA, cyclohexyl acrylate (CHA), and photopolymerization initiator A in a weight ratio of 80 / 20 / 20 / 0.1 was used. 0.1 parts of HDDA was added to 100 parts of this monomer syrup S7, and the mixture was mixed uniformly to prepare adhesive composition A7.

[0191] (Adhesive composition E1) A commercially available polyester polymer (grade name "SNT", manufactured by Mitsubishi Chemical Corporation, Tg: -15°C, hydroxyl value: 6 to 10 mgKOH / g, acid value: <1 mgKOH / g) was mixed uniformly with 3 parts of an isocyanate crosslinking agent (TDI polyisocyanate available from Mitsui Chemicals, Inc., shown as "Isocyanate A" in Table 2) per 100 parts of the polymer, on a solids basis, 0.01 parts of an organotin compound (trade name "dibutyltin(IV) dilaurate" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., hereinafter referred to as "DBTDL") as a crosslinking catalyst, and 1 part of a carbodiimide group-containing compound (trade name "Carbodilite V-07" manufactured by Nisshinbo Chemical Inc.) as a hydrolysis stabilizer, to prepare a pressure-sensitive adhesive composition E1.

[0192] (Adhesive composition E2) A commercially available polyester polymer (grade name "NP-111S50EO", manufactured by Mitsubishi Chemical Corporation, Tg: -48 ° C., hydroxyl value: 2 to 8 mg KOH / g, acid value: < 1 mg KOH / g) was added, on a solids basis, to 100 parts of the polymer, 1 part of an isocyanate crosslinking agent (trade name "Coronate HX", manufactured by Tosoh Corporation, HDI isocyanurate polyisocyanate. In Table 2, this is shown as "Isocyanate B"), 0.01 parts of DBTDL as a crosslinking catalyst, and 1 part of a carbodiimide group-containing compound (trade name "Carbodilite V-07", manufactured by Nisshinbo Chemical Inc.) as a hydrolysis stabilizer, and the mixture was uniformly mixed to prepare a pressure-sensitive adhesive composition E2.

[0193] (Adhesive composition E3) Adhesive composition E3 was prepared in the same manner as in the preparation of adhesive composition E2, except that no hydrolysis stabilizer or crosslinking catalyst was used and the crosslinking agent was changed from isocyanate-based B to isocyanate-based A.

[0194] <Preparation of Pressure-Sensitive Adhesive Sheet> (Example 1) Pressure-sensitive adhesive composition A1 was applied to a polyethylene terephthalate (PET) film R1 (thickness: 38 μm) having one side treated with silicone, and then covered with a PET film R2 (thickness: 38 μm) having one side treated with silicone to block air. The composition was then cured by irradiation with ultraviolet light, forming a pressure-sensitive adhesive layer having a thickness of 25 μm. The ultraviolet light was irradiated using a black light lamp at an illuminance of 2.5 mW / cm. ２ (Measured using an industrial UV checker (manufactured by Topcon Corporation, product name "UVR-T1") with a peak sensitivity wavelength of approximately 350 nm) for 960 seconds. In this way, a PSA sheet according to Example 1 (a substrate-less double-sided PSA sheet comprising a PSA layer) was obtained in which the first and second PSA surfaces were protected by the release films R1 and R2.

[0195] (Examples 2 to 6, Comparative Example 1) Except for using adhesive compositions A2 to A7 instead of adhesive composition A1, the adhesive sheets (substrate-less double-sided adhesive sheets consisting of an adhesive layer) according to each example were obtained in a form in which the first and second adhesive surfaces were protected by the release films R1 and R2 in the same manner as in the production of the adhesive sheet according to Example 1.

[0196] Comparative Example 2 A mixture of 100 parts of polyamide (trade name "Platamid M1276", manufactured by Arkema, polyamide having a piperazine skeleton, weight-average molecular weight 21,000) and 0.5 parts of an epoxy-based crosslinking agent (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Co., Ltd.) was applied with an applicator to a resin sheet having a release-treated surface (release sheet: CA1 manufactured by Fujiko Co., Ltd.), and the sheet was placed in a constant temperature dryer and dried at 100°C for 5 minutes to produce a polyamide-based adhesive sheet (thickness 25 μm) according to Comparative Example 2.

[0197] Example 7 The pressure-sensitive adhesive composition E1 was applied to the release surface of a PET film R3 (75 μm thick) that had been silicone-treated on one side, and dried at 110°C for 2 minutes to form a pressure-sensitive adhesive layer with a thickness of 30 μm. The release surface of release film R2 was then bonded to the pressure-sensitive adhesive layer on release film R3. In this way, the pressure-sensitive adhesive sheet according to Example 7 (a substrate-less double-sided pressure-sensitive adhesive sheet consisting of a pressure-sensitive adhesive layer) was obtained in a form in which the first and second pressure-sensitive adhesive surfaces were protected by the release films R3 and R2.

[0198] (Examples 8 and 9) Except for using adhesive compositions E2 and E3 instead of adhesive composition E1, the adhesive sheets of each example (substrate-less double-sided adhesive sheets consisting of an adhesive layer) were obtained in a form in which the first and second adhesive surfaces were protected by the release films R3 and R2 described above in the same manner as in the preparation of the adhesive sheet of Example 7.

[0199] (Example 10) A pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet with substrate) having a structure of pressure-sensitive adhesive layer / polyurethane foam sheet A1 / pressure-sensitive adhesive layer was produced by bonding the pressure-sensitive adhesive layer of Example 2 to the first and second sides of a foamed polyurethane sheet A1 (thickness 1000 μm, product name "Rubylar L03", manufactured by Toyo Polymer Co., Ltd., abbreviated as "Urethane A1" in Table 3) used as a substrate.

[0200] (Example 11) A pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet with substrate) according to this example was produced in the same manner as the production of the pressure-sensitive adhesive sheet according to Example 10, except that a foamed polyurethane sheet A2 (thickness 400 μm, product name "Rubylar L03", manufactured by Toyo Polymer Co., Ltd., abbreviated as "Urethane A2" in Table 3) was used as the substrate.

[0201] (Example 12) A pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet with substrate) according to this example was produced in the same manner as the production of the pressure-sensitive adhesive sheet according to Example 10, except that a foamed polyurethane sheet B (thickness 1000 μm, product name "Rubylar L31", manufactured by Toyo Polymer Co., Ltd., abbreviated as "Urethane B" in Table 2) was used as the substrate.

[0202] (Example 13) A pressure-sensitive adhesive sheet according to this example (double-sided pressure-sensitive adhesive sheet with substrate) was produced in the same manner as the pressure-sensitive adhesive sheet according to Example 10, except that a nonwoven fabric (a polyester nonwoven fabric having a thickness of 1000 μm) was used as the substrate.

[0203] (Example 14) The adhesive layer of Example 7 was bonded to the first and second surfaces of polyurethane sheet C (thickness 30 μm, manufactured by Sheedom Co., Ltd., abbreviated as "urethane C" in Table 3) used as a substrate, to produce an adhesive sheet (double-sided adhesive sheet with substrate) having a structure of adhesive layer / polyurethane sheet C / adhesive layer.

[0204] The ethanol absorption amount [%] and the weight loss rate [%] due to ethanol immersion were measured for each of the substrates used in Examples 10 to 14 using the above-mentioned method, and the results are shown in Table 3.

[0205] <Measurement and Evaluation> (1) Peel Test (Normal Peel Force N0) A 50 μm thick PET film was attached to the second adhesive surface of the pressure-sensitive adhesive sheet to be measured, and then cut into a rectangular shape with a width of 20 mm and a length of 120 mm to prepare a test piece. The first adhesive surface of the test piece was attached to a stainless steel plate (SUS430BA plate) as an adherend using a hand roller to form an evaluation sample, which was then placed in an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50 ° C. The evaluation sample removed from the autoclave was then left to stand in an environment of 23 ° C. and 50% RH for 30 minutes, and then, under the same environment, the test piece was peeled from the stainless steel plate using a tensile tester (Minebea Co., Ltd., universal tension and compression tester, device name "Tension and Compression Tester, TCM-1kNB") at a tensile speed of 300 mm / min and a peel angle of 180 degrees, and the peel strength at this time was measured. The measurement was carried out three times, and the average value thereof is shown in Tables 1 to 3 as the normal peel force N0 in the first measurement.

[0206] (Ethanol peeling force N1) In the measurement of the normal peeling force N0, 20 μL of ethanol was supplied to the location (peel interface) where the test piece began to separate from the stainless steel plate during the process of peeling the pressure-sensitive adhesive sheet from the stainless steel plate, and the peel strength after the ethanol supply was measured. The measurement was performed for each measurement of peel strength N0 (i.e., three times), and the average value thereof is shown in Tables 1 to 3 as the ethanol peeling force N1 in the first measurement.

[0207] (Normal peeling force N0 Ｓ The test pieces used to measure the normal peel strength N0 and the ethanol peel strength N1 were dried at 23°C for 60 minutes to volatilize the ethanol that had adhered during the measurement of the ethanol peel strength N1. The first adhesive surface of the test piece was then attached to a new stainless steel plate (SUS430BA plate) as an adherend using a hand roller. The resulting evaluation sample was placed in an autoclave and treated for 15 minutes at a pressure of 5 atm and a temperature of 50°C. The evaluation sample removed from the autoclave was then left to stand in an environment of 23°C and 50% RH for 30 minutes. Then, under the same environment, the test piece was peeled from the stainless steel plate using a tensile tester (Minebea Co., Ltd., universal tension and compression tester, device name "Tension and Compression Tester, TCM-1kNB") at a tensile speed of 300 mm / min and a peel angle of 180°, and the peel strength at this time was measured. The measurement was performed three times, and the average value was used to determine the normal peel strength N0 in the second measurement. Ｓ The results are shown in Tables 1 to 3.

[0208] (Ethanol peeling force N1 Ｓ ) The above normal peeling force N0 Ｓ In the measurement of peel strength, 20 μL of ethanol was supplied to the location where the test piece began to separate from the stainless steel plate (peel interface) while the pressure-sensitive adhesive sheet was being peeled off from the stainless steel plate, and the peel strength after the supply of ethanol was measured. The measurement was carried out for each measurement of peel strength N0 (i.e., three times), and the average value thereof was taken as the ethanol peel strength N1 in the second measurement. Ｓ The results are shown in Tables 1 to 3.

[0209] From the obtained measured values, the peel force reduction rate RＡ , peel force reduction rate R ＡＳ and the normal peel force reduction rate R Ｂ was calculated.

[0210] (2) Disassembly of the Assembled Assembly The double-sided PSA sheet according to each example was cut to a size of 100 mm x 50 mm, and the release liner was peeled off to expose the first adhesive surface, which was then bonded to a stainless steel plate (SUS430BA plate, size 100 mm x 50 mm, thickness 0.5 mm) as a first member. The release liner was peeled off to expose the second adhesive surface, which was then bonded to an alkali glass plate (manufactured by Matsunami Glass Industry Co., Ltd., size 165 mm x 65 mm, thickness 1.35 mm, blue plate edge polished) as a second member. This assembly was then placed in an autoclave and treated at 50°C and 5 atmospheres for 15 minutes (autoclave treatment). After removal from the autoclave, it was left to stand at room temperature and normal pressure (23°C, 1 atmosphere) for 30 minutes. In this way, an assembly having a laminate structure consisting of stainless steel plate / adhesive layer / alkali glass plate was obtained as an evaluation sample. In this evaluation sample, the stainless steel plate and the alkali glass plate were bonded together with an adhesive layer over an adhesive area of ​​100 mm x 50 mm. The alkali glass plate had a tensile modulus of elasticity of 7 x 10 １０ Pa and bending rigidity is about 14 Pa m ３ The Poisson's ratio was 0.23. At room temperature (approximately 25°C), ethanol (stripping solution) was poured into a container to a depth of approximately 2 cm, and the above-mentioned bonded body was immersed in the ethanol. After 10 minutes, the bonded body was removed from the ethanol, and an attempt was made to manually disassemble the bonded body (an adult female; all evaluations were performed by the same person). Specifically, a ruler (or a metal plate) was inserted between the layers at the end of the evaluation sample, and after inserting it approximately 10 mm, a force was applied in the vertical direction (thickness direction of the evaluation sample) to attempt disassembly. If the bonded body could be disassembled, it was evaluated as "pass," and if the bonded body could not be disassembled, it was evaluated as "fail."

[0211]

[0212]

[0213]

[0214] As shown in Tables 1 to 3, the peel force reduction rate R Ａ All of the joined bodies constructed using the pressure-sensitive adhesive sheets of Examples 1 to 14, in which the peel force reduction rate R was 70% or more, could be efficiently disassembled by immersion in ethanol (stripping solution) for a short period of 10 minutes. Ａ The bonded structure constructed using the PSA sheet of Comparative Example 1, which had low adhesive strength, could not be disassembled under the above immersion conditions. Furthermore, in Comparative Example 2, the dissolution of the polyamide-based adhesive in the stripping solution allowed the bonded structure to be disassembled under the above immersion conditions. However, in the first measurement of the peel test, the peel force measured after the ethanol was dropped became significantly unstable, and no meaningful measurement results could be obtained. Furthermore, the test piece peeled in the first measurement had almost completely lost its adhesiveness, making it impossible to carry out a second measurement.

[0215] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0216] REFERENCE SIGNS LIST 1, 2 Pressure-sensitive adhesive sheet 11 First pressure-sensitive adhesive layer 11a First pressure-sensitive adhesive surface 12 Second pressure-sensitive adhesive layer 12a Second pressure-sensitive adhesive surface 20 Substrate 20a First surface 20b Second surface 31, 32 Release liner 50 Pressure-sensitive adhesive sheet with release liner 61 First member 62 Second member 100, 200 Joint

Claims

1. A method for dismantling an assembly including an adhesive sheet having a first adhesive surface and a first member bonded to the first adhesive surface, the method comprising: immersing the assembly in a stripping solution containing a lower alcohol having 1 to 5 carbon atoms as a main component; and dismantling the assembly after the immersion, wherein the adhesive sheet has a reduction rate R of ethanol peeling force N1 [N / 20 mm] relative to normal peeling force N0 [N / 20 mm] in a first measurement in the following peeling test. Ａ is 70% or more, and the normal peel force N0 [N / 20 mm] at the time of the first measurement is the normal peel force N0 at the time of the second measurement. Ｓ Reduction rate R of [N / 20mm] Ｂ Disassembly method in which the peel strength is 30% or less. [Peel test] (First measurement) The first adhesive surface of the adhesive sheet is attached to a stainless steel plate, put into an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50° C., removed from the autoclave and left to stand for 30 minutes under an environment of 23° C. and 50% RH, and then peeled off the adhesive sheet from the stainless steel plate using a tensile tester under the same environment at a peel angle of 180 degrees and a tensile speed of 300 mm / min. During the peeling, 20 μL of ethanol is dropped onto the location where the adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol is dropped is the normal peel strength N0 [N / 20 mm], and the peel strength observed after the ethanol is dropped is the ethanol peel strength N1 [N / 20 mm]. (Second measurement) After drying the adhesive sheet used in the first measurement, the first adhesive surface of the adhesive sheet is attached to a new stainless steel plate, placed in an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50° C., removed from the autoclave and left to stand for 30 minutes in an environment of 23° C. and 50% RH, and then peeled off the adhesive sheet from the stainless steel plate using a tensile tester under the same conditions at a peel angle of 180 degrees and a tensile speed of 300 mm / min. During the peeling, 20 μL of ethanol is dropped onto the location where the adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol is dropped is defined as the normal peel strength N0. Ｓ [N / 20 mm], and the peel strength observed after dropping ethanol was defined as the ethanol peel strength N1 Ｓ [N / 20mm].

2. The disassembly method according to claim 1, wherein the first member has a contact angle with distilled water of 50 degrees or more.

3. The disassembly method according to claim 1 or 2, wherein the first adhesive surface is a surface of an acrylic adhesive layer containing an acrylic polymer as a base polymer.

4. The dismantling method according to claim 3, wherein the monomer component constituting the acrylic polymer includes an alkyl (meth)acrylate having an alkyl group having 10 to 14 carbon atoms.

5. The disassembly method according to claim 1 or 2, wherein the first adhesive surface is a surface of a polyester-based adhesive layer containing a polyester-based polymer as a base polymer.

6. The dismantling method according to claim 1 or 2, wherein the adhesive sheet is a double-sided adhesive sheet having a second adhesive surface on the surface opposite to the first adhesive surface, and the joined body further includes a second member joined to the second adhesive surface.

7. An adhesive sheet having a first adhesive layer constituting a first adhesive surface, a second adhesive layer constituting a second adhesive surface which is a surface opposite to the first adhesive surface, and a substrate disposed between the first adhesive layer and the second adhesive layer, wherein the substrate has a weight loss rate of less than 1% by weight when immersed in ethanol for 10 minutes and then dried, and the adhesive sheet has a reduction rate R of ethanol peel force N1 [N / 20 mm] relative to normal peel force N0 [N / 20 mm] in the following peel test. Ａ An adhesive sheet having a peel strength of 70% or more. [Peel test] The first adhesive surface of the adhesive sheet is attached to a stainless steel plate, put into an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50° C., removed from the autoclave and left to stand for 30 minutes under an environment of 23° C. and 50% RH, and then peeled off the adhesive sheet from the stainless steel plate using a tensile tester under the same environment at a peel angle of 180 degrees and a tensile speed of 300 mm / min. During the peeling, 20 μL of ethanol is dropped onto the location where the adhesive sheet begins to separate from the stainless steel plate. The peel strength observed before the ethanol is dropped is defined as normal peel strength N0 [N / 20 mm], and the peel strength observed after the ethanol is dropped is defined as ethanol peel strength N1 [N / 20 mm].

8. The pressure-sensitive adhesive sheet according to claim 7, wherein the amount of ethanol absorbed when the substrate is immersed in ethanol for 10 minutes is 25% by weight or more of the substrate.

9. The adhesive sheet according to claim 7 or 8, wherein the first adhesive layer is an acrylic adhesive layer containing an acrylic polymer as a base polymer.

10. The pressure-sensitive adhesive sheet according to claim 9, wherein the monomer component constituting the acrylic polymer includes an alkyl (meth)acrylate having an alkyl group having 10 to 14 carbon atoms.

11. The adhesive sheet according to claim 7 or 8, wherein the first adhesive layer is a polyester-based adhesive layer containing a polyester-based polymer as a base polymer.

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