Adhesive sheet

Abstract

To provide a pressure sensitive adhesive sheet having excellent high-temperature shear retention power and having stress relaxation properties of making it difficult for an effect of a protrusion or a step present on one side of the pressure sensitive adhesive sheet to appear on the other side.SOLUTION: A pressure sensitive adhesive sheet includes an adhesive layer. In the pressure sensitive adhesive sheet, the adhesive layer has a breaking strength of 2 MPa or less in a tensile test carried out in a condition at a tensile rate of 10 mm / min. Further, in the pressure sensitive adhesive sheet, 80°C adhesive force maintenance factor (P80°C / PRT×100) is 50% or more, obtained from a relation between 180 degree peeling strength PRT to a stainless steel plate measured at 23°C and 180 degree peeling strength P80°C to a stainless steel plate measured at 80°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an adhesive sheet. [Background technology]

[0002] Generally, adhesives (also called pressure-sensitive adhesives; the same applies hereinafter) exhibit a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to a substrate under pressure. Taking advantage of this property, adhesives are widely used for purposes such as joining, fixing, and protecting components in smartphones and other portable electronic devices, for example, in the form of adhesive sheets with an adhesive layer on a support substrate, or in the form of adhesive sheets without a support substrate. Patent documents 1 and 2 are examples of technical documents relating to adhesive tapes used for fixing components in portable electronic devices. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-70102 [Patent Document 2] Japanese Patent Publication No. 2018-28051 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Adhesive sheets used in environments exposed to high temperatures are required to have good adhesive properties even at high temperatures. For example, the aforementioned portable electronic devices may be used in high-temperature environments, and their internal spaces may become hot due to the heat generated by electronic components. Therefore, adhesive sheets used in such applications must have sufficient adhesive reliability even at high temperatures. Furthermore, because the adhesive area for fixing components within portable electronic devices is usually small due to size and weight constraints, adhesive sheets used in such applications must have adhesive reliability that can achieve good fixing even in small areas, and the required performance is becoming higher due to the demands for weight reduction and miniaturization. In particular, portable electronic devices equipped with touch panel displays, such as smartphones, are becoming smaller and thinner, while the screen size is increasing from the perspective of display visibility and operability. Therefore, the adhesives applied to them are required to have adhesive fixing performance under more severe conditions. For fixing components within portable electronic devices, it is desirable to use adhesive sheets that have excellent adhesive properties not only in the room temperature range but also in the high-temperature range (e.g., high-temperature shear holding performance).

[0005] Incidentally, some objects that are joined by adhesive sheets have steps or irregularities on the adhesive surface side or the back side (the side opposite to the surface that adheres to the adhesive sheet). Furthermore, even if the object to be attached to one adhesive surface of the adhesive sheet has a flat shape, if the component or article placed on the back side of that object has irregularities and is pressed against the adhesive sheet, the protrusions can be transmitted to the adhesive sheet through the object, causing deformation of the sheet surface. Then, deformation caused by these protrusions can be transmitted to other components (objects to be attached to the other adhesive surface of the adhesive sheet, or components placed on the back side of those objects, etc.) via the adhesive sheet.

[0006] In the fixing of components within the aforementioned portable electronic devices, components such as flexible printed circuit boards (FPCs) may be bent to accommodate the limited space within the device. Such components may form protrusions within a group of flat components. Furthermore, the combination and arrangement of multiple components may create steps between them. These protrusions and steps within the device deform the adhesive sheet via other components (adhered objects) when the group of components is pushed into the internal space or compressed. Such deformation of the sheet surface may appear as an indentation-like appearance on the opposite surface of the adhesive sheet (the side opposite to the side with the protrusions, etc.). Such deformation of the adhesive sheet surface caused by protrusions, etc., is undesirable because it can adversely affect the adhered components of the adhesive sheet, and furthermore, the group of components arranged on the back side of the adhered components, for example, by unevenly applying external forces such as impacts to the deformed portion, creating a point of damage.

[0007] The present invention was created in view of the above circumstances, and aims to provide an adhesive sheet that has good high-temperature shear holding properties and stress-relaxing properties that make it difficult for the effects of protrusions or steps present on one side of the adhesive sheet to appear on the other side. [Means for solving the problem]

[0008] This specification provides an adhesive sheet having an adhesive layer. In this adhesive sheet, the adhesive layer has a breaking strength of 2 MPa or less in a tensile test performed at a tensile speed of 10 mm / min. Furthermore, the adhesive sheet has a 180-degree peel strength P against a stainless steel plate measured at 23°C. RT And the 180-degree peel strength P for stainless steel plates measured at 80°C. 80℃ The 80°C adhesion retention rate (P) can be determined from the relationship. 80℃ / P RTThe ratio (×100) is 50% or more. The adhesive sheet with the above configuration maintains an adhesive strength at 80°C of 50% or more compared to the adhesive strength at 23°C (80°C adhesive strength maintenance rate of 50% or more), and maintains good high-temperature adhesive properties compared to room temperature. Such an adhesive suppresses the decrease in holding power that tends to deteriorate at high temperatures and has good high-temperature shear holding properties. Furthermore, since the breaking strength of the adhesive layer of the adhesive sheet is limited to 2 MPa or less, its stress relaxation properties prevent or reduce the effect of protrusions or steps on one side of the adhesive sheet from appearing on the other side. According to the technology disclosed herein, an adhesive sheet is provided in which high-temperature shear holding properties and stress relaxation properties, which are in a contradictory relationship, are well balanced.

[0009] In some embodiments, the adhesive sheet is a double-sided adhesive sheet with a substrate layer, where the total thickness of the adhesive layer accounts for more than 50% of the total thickness of the adhesive sheet. With such a double-sided adhesive sheet with a substrate, the advantages of processability and handling due to the presence of a substrate are enjoyed while the stress relaxation properties of the adhesive layer are better exhibited. In some other embodiments, the adhesive sheet is a substrate-less double-sided adhesive sheet consisting of the adhesive layer. With a substrate-less adhesive sheet, the adhesive properties and stress relaxation properties based on the adhesive layer can be maximized. Furthermore, because a substrate-less double-sided adhesive sheet does not have a substrate, it can be made thinner, which can contribute to the miniaturization and space saving of products to which the double-sided adhesive sheet is applied.

[0010] In some preferred embodiments, the adhesive layer includes a tackifying resin with a softening point of less than 145°C. By using a tackifying resin with a softening point of less than 145°C, it is possible to reduce the fracture strength while maintaining high-temperature shear resistance and exhibit superior stress relaxation properties.

[0011] The adhesive layer disclosed herein may be an acrylic adhesive layer comprising an acrylic polymer as a base polymer. The techniques disclosed herein are preferably implemented in configurations comprising an acrylic adhesive layer. In some preferred embodiments, the acrylic polymer is polymerized in a proportion of 50% by weight or more of alkyl (meth)acrylate having an alkyl group with 7 to 10 carbon atoms at its ester terminus. Acrylic polymers with the above monomer composition tend to have a low glass transition temperature (Tg), and can preferably achieve both excellent adhesive properties and stress relaxation properties.

[0012] In some embodiments, the adhesive layer contains an acrylic oligomer. By including an acrylic oligomer in the adhesive layer, the effects of the techniques disclosed herein are preferably achieved.

[0013] In some embodiments, the adhesive composition for forming the adhesive layer comprises an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. By using an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent in combination, it is possible to preferably achieve both high-temperature shear resistance and stress relaxation properties.

[0014] In some preferred embodiments, the total thickness of the adhesive layer is 30 μm or more. An adhesive layer having a thickness greater than a predetermined value is more likely to absorb the effects of protrusions and steps acting on the sheet surface of the adhesive sheet. Furthermore, an adhesive layer of sufficient thickness can exhibit superior adhesive properties.

[0015] The adhesive sheet disclosed herein has good high-temperature adhesive properties (particularly high-temperature shear holding properties), and is therefore suitable for use in portable electronic devices where it may be used in high-temperature environments and where the internal space may become hot due to heat generated by electronic components, for fixing components. Furthermore, multiple components are arranged inside portable electronic devices, some of which may have protrusions or steps. For example, components that may have steps, such as wiring boards and housings, may be arranged inside portable electronic devices. When these multiple components are pressed into the internal space or compressed, the aforementioned protrusions, etc., may directly or indirectly deform other components. In such portable electronic devices, by utilizing the stress-relaxing properties of the adhesive sheet disclosed herein, it is possible to prevent or reduce the influence of protrusions, etc., present on one side of the adhesive sheet from appearing on the other side. The adhesive sheet disclosed herein is particularly suitable for use in fixing components arranged inside portable electronic devices. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic cross-sectional view showing one example of the structure of an adhesive sheet. [Figure 2] This is a schematic cross-sectional view showing another example of the configuration of the adhesive sheet. [Figure 3] This is a schematic exploded perspective view showing an example of the configuration of a display device. [Modes for carrying out the invention]

[0017] Preferred embodiments of the present invention are described below. Matters other than those specifically mentioned herein but necessary for carrying out the present invention can be understood by those skilled in the art based on the teachings on carrying out the invention described herein and the common technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed herein and the common technical knowledge in the art. Furthermore, in the following drawings, members and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Also, the embodiments shown in the drawings are schematic for the purpose of clearly illustrating the present invention and do not necessarily accurately represent the size or scale of the adhesive sheets of the present invention that are actually provided as products.

[0018] In this specification, "adhesive" refers to a material that, as described above, exhibits a soft solid (viscoelastic) state at temperatures around room temperature and has the property of easily adhering to a substrate under pressure. The adhesive referred to here is generally defined as having a complex tensile modulus E, as defined in "CA Dahlquist, “Adhesion: Fundamental and Practice”, McLaren & Sons, (1966) p. 143". * (1Hz) < 10 7 dyne / cm 2 It may be a material having properties that satisfy the above conditions (typically, a material having the above properties at 25°C).

[0019] <Example of adhesive sheet configuration> The adhesive sheet disclosed herein may be an adhesive sheet with a substrate having the adhesive layer on one or both sides of a non-peelable substrate (support substrate), or it may be a substrate-less adhesive sheet (i.e., an adhesive sheet without a non-peelable substrate) in which the adhesive layer is held by a release liner. The concept of adhesive sheet as used herein may include adhesive tapes, adhesive labels, adhesive films, etc. The adhesive sheet disclosed herein may be in roll form or sheet form. Alternatively, it may be an adhesive sheet processed into various shapes.

[0020] Figure 1 shows an example of the configuration of a double-sided adhesive substrate-less adhesive sheet (substrate-less double-sided adhesive sheet). The adhesive sheet 1 shown in Figure 1 has a configuration in which both sides 21A and 21B of the substrate-less adhesive layer 21 are protected by release liners 31 and 32, each having a release surface on at least the side facing the adhesive layer. Alternatively, the adhesive sheet may have a configuration in which one surface (adhesive surface, first adhesive surface) of the substrate-less adhesive layer is protected by a release liner with release surfaces on both sides, and when wound, the other surface (adhesive surface, second adhesive surface) of the adhesive layer comes into contact with the back surface of the release liner, thereby enabling the second adhesive surface of the adhesive layer to also be protected by the release liner. The technology disclosed herein can preferably be implemented in such a substrate-less form from the viewpoint of reducing the thickness of the adhesive sheet. A substrate-less adhesive sheet is advantageous in that it is easy to make thin and can maximize the adhesive properties such as adhesive strength and impact resistance.

[0021] The adhesive sheet disclosed herein may, for example, have a cross-sectional structure schematically shown in Figure 2. The adhesive sheet 2 shown in Figure 2 has adhesive layers 21 and 22 (also referred to as the first adhesive layer 21 and the second adhesive layer 22, respectively) provided on each surface (both non-peelable) of the base material (base layer) 10, and these adhesive layers are protected by release liners 31 and 32, each having a release surface on at least the side with the adhesive layer. Alternatively, the adhesive sheet may have adhesive layers (first adhesive layer, second adhesive layer) provided on each surface (both non-peelable) of the base material, and one of these adhesive layers (first adhesive layer) may be protected by a release liner with release surfaces on both sides. This type of adhesive sheet can be configured such that the other adhesive layer (second adhesive layer) is also protected by the release liner by winding the adhesive sheet and bringing the other adhesive layer (second adhesive layer) into contact with the back surface of the release liner.

[0022] <80℃ adhesive force maintenance rate> The adhesive sheet disclosed herein has an adhesive strength P at 23°C. RT Adhesion P at 80℃80℃ The 80°C adhesion retention rate (P 80℃ / P RT ×100) obtained from the relationship with is 50% or more. The adhesive sheet satisfying the above characteristics has an adhesive force at 80°C maintained at 50% or more with respect to the adhesive force at 23°C (80°C adhesion retention rate of 50% or more), and has good high-temperature adhesion characteristics (especially high-temperature shear retention). From the viewpoint of maintaining high-temperature adhesion characteristics, the above 80°C adhesion retention rate is preferably 55% or more, more preferably 60% or more, still more preferably 65% or more, may be 70% or more, and may be 75% or more. The upper limit of the above 80°C adhesion retention rate is not particularly limited, but in some embodiments, it is usually 100% or less, may be 90% or less, and may be 80% or less. The adhesive having the above 80°C adhesion retention rate tends to be compatible with a breaking strength of a predetermined value or less described later. The adhesive force P RT at 23°C and the adhesive force P 80℃ at 80°C are the 180-degree peel strengths P RT against a stainless steel plate measured at 23°C and the 180-degree peel strength P 80℃ against a stainless steel plate measured at 80°C, respectively, and specifically, they are measured by the method described in the examples below.

[0023] <Breaking strength of adhesive layer> The adhesive sheet disclosed herein has an adhesive layer having a breaking strength of 2 MPa or less. By limiting the breaking strength of the adhesive layer to 2 MPa or less, the adhesive layer tends to have excellent stress relaxation properties, which can prevent or reduce the influence of protrusions or steps present on one side of the adhesive sheet from appearing on the other side. The breaking strength is preferably 1.5 MPa or less, more preferably 1.2 MPa or less, even more preferably 1.0 MPa or less, and particularly preferably 0.8 MPa or less (e.g., 0.6 MPa or less). From the viewpoint of achieving compatibility with the above-mentioned 80°C adhesive strength retention rate of 50% or more, the breaking strength is appropriately 0.1 MPa or more, may be 0.3 MPa or more, may be 0.5 MPa or more, or may be 0.9 MPa or more (e.g., 1.4 MPa or more). The breaking strength of the adhesive layer is the breaking strength measured by a tensile test performed under the condition of a tensile speed of 10 mm / min, and is specifically measured by the method described in the examples below. In a double-sided adhesive sheet with a substrate having first and second adhesive layers on each surface of the substrate, at least one (preferably both) of the adhesive layers satisfies the above-mentioned breaking strength.

[0024] The configuration that achieves both the 80°C adhesion retention rate and the breaking strength can be adjusted according to the configuration of the adhesive sheet, based on the description in this specification, by selecting the type and amount of adhesive and adhesive-containing components (base polymer, tackifying resin, crosslinking agent, and other additives).

[0025] <Adhesive layer> (Base polymer) In the technology disclosed herein, the type of adhesive constituting the adhesive layer is not particularly limited. The adhesive may contain one or more types of rubber-like polymers that can be used in the field of adhesives, such as acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers, as the adhesive polymer (meaning the structural polymer that forms the adhesive, hereinafter also referred to as the "base polymer"). From the viewpoint of adhesive performance and cost, an adhesive containing an acrylic polymer or a rubber polymer as the base polymer is preferably used. Among these, an adhesive using an acrylic polymer as the base polymer (acrylic adhesive) is preferred. The technology disclosed herein is preferably implemented in a manner that uses an acrylic adhesive.

[0026] The following description will primarily focus on adhesive sheets having an acrylic adhesive layer, i.e., an adhesive sheet having an acrylic adhesive layer. However, the intention is not to limit the adhesive layer of the adhesive sheet disclosed herein to those composed of an acrylic adhesive.

[0027] Furthermore, the term "base polymer" in the context of an adhesive refers to the main component of the rubbery polymer contained in the adhesive, and is not intended to be interpreted in any other way. The rubbery polymer refers to a polymer that exhibits rubber elasticity in the temperature range around room temperature. In addition, in this specification, unless otherwise specified, "main component" refers to a component present in an amount exceeding 50% by weight. Furthermore, "acrylic polymer" refers to a polymer that contains monomer units derived from monomers having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, monomers having at least one (meth)acryloyl group in one molecule will also be referred to as "acrylic monomers." Therefore, in this specification, acrylic polymers are defined as polymers that contain monomer units derived from acrylic monomers. A typical example of an acrylic polymer is an acrylic polymer in which the proportion of acrylic monomers among all monomer components used in the synthesis of the acrylic polymer is greater than 50% by weight. Furthermore, "(meth)acryloyl" comprehensively refers to both acryloyl and methacryloyl. Similarly, "(meth)acrylate" comprehensively refers to both acrylate and methacrylate, and "(meth)acrylic" comprehensively refers to both acrylic and methacrylic.

[0028] (Acrylic polymer) The acrylic polymers in the technologies disclosed herein are preferably polymers of monomer raw materials that contain, for example, alkyl (meth)acrylate as a main monomer and may further contain sub-monomers copolymerizable with the main monomer. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the above monomer raw material.

[0029] As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used. CH2=C(R 1 )COOR 2 (1) Here, in equation (1) above, R 1 R is a hydrogen atom or a methyl group. 2 C is a chain-like alkyl group with 1 to 20 carbon atoms. Hereafter, this range of carbon atoms will be referred to as "C 1-20 It is sometimes expressed as ". From the viewpoint of the storage modulus of the adhesive, R 2 C 1-14 (For example C 1-10 Typically C 4-8It is appropriate to use alkyl(meth)acrylate, which is a chain-like alkyl group, as the main monomer. From the viewpoint of adhesive properties, 1 is a hydrogen atom and R 2 C 4-8 Alkyl acrylates (hereinafter simply referred to as C) are chain-like alkyl groups. 4-8 It is preferable to use alkyl acrylate (also known as alkyl acrylate) as the main monomer.

[0030] R 2 C 1-20 Specific examples of alkyl(meth)acrylates, which are chain-like alkyl groups, are not particularly limited, but include, for example, methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, t-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl( Examples include meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, isononyl(meth)acrylate, decyl(meth)acrylate, isodecyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, octadecyl(meth)acrylate, nonadecyl(meth)acrylate, eicosyl(meth)acrylate, etc. These alkyl(meth)acrylates can be used individually or in combination of two or more. Preferred examples of alkyl(meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

[0031] The proportion of alkyl (meth)acrylate in the monomer components constituting the acrylic polymer is typically more than 50% by weight, and can be, for example, 70% by weight or more, 85% by weight or more, or 90% by weight or more. There is no particular upper limit to the proportion of alkyl (meth)acrylate, but it is preferably 99.5% by weight or less (for example, 99% by weight or less), or from the viewpoint of favorably exhibiting properties (for example, cohesive force) based on sub-monomers such as carboxyl group-containing monomers, it may be 98% by weight or less (for example, less than 97% by weight). Alternatively, the acrylic polymer may be substantially polymerized from alkyl (meth)acrylate alone.

[0032] In addition, C is used as a monomer component. 4-8 When using alkyl acrylates, of the alkyl (meth)acrylates contained in the monomer component, C 4-8 The proportion of alkyl acrylate is preferably 70% by weight or more, and more preferably 90% by weight or more.

[0033] In some embodiments, the monomer component constituting the acrylic polymer is C 1-6 It contains 50% by weight or more of alkyl (meth)acrylate. In other words, the C in the above acrylic polymer. 1-6 The polymerization ratio of alkyl (meth)acrylate may be 50% by weight or more. 1-6 Using alkyl (meth)acrylate as the main monomer tends to easily yield high-temperature shear retention. In this embodiment, the amount of C in the monomer component 1-6 The proportion of alkyl (meth)acrylate (in other words, the polymerization ratio) is preferably 80% by weight or more, more preferably 90% by weight or more (for example, 92% by weight or more). 1-6 The upper limit of the alkyl (meth)acrylate percentage is not particularly limited, but is usually 99% by weight or less, and in relation to the percentage of other copolymerizable monomers used, it is appropriate to be 97% by weight or less, and preferably 95% by weight or less. 1-6Alkyl (meth)acrylates can be used individually or in combination of two or more types. 1-6 As for alkyl (meth)acrylates, C 1-6 Alkyl acrylates are preferred, C 2-6 Alkyl acrylates are more preferred, C 4-6 Alkyl acrylates are more preferred. In some other embodiments, C 1-6 The alkyl (meth)acrylate is preferably C 1-4 It is an alkyl acrylate, more preferably C 2-4 It is an alkyl acrylate. 1-6 A suitable example of an alkyl (meth)acrylate is BA.

[0034] In some preferred embodiments, the monomer component constituting the acrylic polymer is C 7-10 It contains 50% by weight or more of alkyl (meth)acrylate. In other words, the C in the above acrylic polymer. 7-10 The copolymerization ratio of alkyl (meth)acrylate is preferably 50% by weight or more. 7-10 By using alkyl (meth)acrylate as the main monomer, it is possible to design an acrylic polymer that better balances an 80°C adhesion retention rate above a predetermined value with a breaking strength below a predetermined value. 7-10 The proportion of alkyl (meth)acrylate (in other words, the copolymerization ratio) may be greater than 60% by weight, greater than 70% by weight, more preferably greater than 80% by weight, even more preferably 90% by weight or more, and particularly preferably 92% by weight or more (for example, 95% by weight or more). 7-10 The upper limit of the alkyl (meth)acrylate percentage is not particularly limited, but is usually 99% by weight or less, and in relation to the percentage of other copolymerizable monomers (e.g., acid group-containing monomers) used, it is appropriate to be 97% by weight or less, and preferably 96% by weight or less. 7-10 Alkyl (meth)acrylates can be used individually or in combination of two or more types. 7-10Preferred examples of alkyl (meth)acrylates include C2EHA, isooctyl acrylate, isononyl acrylate, etc. 7-10 Alkyl acrylates are examples, with 2EHA being particularly preferred.

[0035] The acrylic polymers in the technologies disclosed herein may be copolymerized with sub-monomers. Examples of sub-monomers that can introduce functional groups that can act as crosslinking sites into acrylic polymers or that can contribute to improved adhesion include carboxyl group-containing monomers, hydroxyl group (OH group)-containing monomers (2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.), acid anhydride group-containing monomers, amide group-containing monomers ((meth)acrylamide, N,N-dimethyl (meth)acrylamide, etc.), amino group-containing monomers (aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers having nitrogen atom-containing rings (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl group-containing monomers, imide group-containing monomers, and the like. The above sub-monomers can be used individually or in combination of two or more.

[0036] When the monomer component constituting the acrylic polymer contains the functional group-containing monomer described above, the content of the functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exhibiting the effects of using the functional group-containing monomer, the content of the functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, is appropriate to be 0.5% by weight or more, and may be 1% by weight or more. Furthermore, from the viewpoint of easily balancing the adhesive performance in relation to the main monomer, the content of the functional group-containing monomer in the monomer component is appropriate to be 40% by weight or less, is preferably 20% by weight or less, and may be 10% by weight or less (for example, 5% by weight or less).

[0037] In some preferred embodiments, an acidic group-containing monomer is used as a monomer copolymerizable with the alkyl (meth)acrylate, which is the main monomer. The acidic group-containing monomer can exhibit improved cohesiveness based on its polarity and good bonding strength to polar adherends. Furthermore, when a crosslinking agent such as an isocyanate-based or epoxy-based crosslinking agent is used, the acidic group (typically a carboxyl group) becomes the crosslinking point of the acrylic polymer. Through these actions, it is possible to suitably achieve high-temperature shear holding while possessing stress-relaxing properties.

[0038] As the acidic group-containing monomer, carboxyl group-containing monomers are preferably used. Examples of carboxyl group-containing monomers include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, crotonic acid, and isocrotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.). In addition, the acidic group-containing monomer may be a monomer having a metal salt (e.g., an alkali metal salt) of the carboxyl group. Among these, AA and MAA are preferred, and AA is particularly preferred. The acidic group-containing monomer can be used alone or in combination of two or more.

[0039] In the technologies disclosed herein, the content of acidic group-containing monomers (typically carboxyl group-containing monomers) in the monomer component (in other words, the copolymerization ratio of acidic group-containing monomers in acrylic polymers) is preferably 1.0% by weight or more. Using an amount of acidic group-containing monomers greater than a certain amount tends to improve the cohesiveness of the adhesive layer. The copolymerization ratio of acidic group-containing monomers in acrylic polymers is preferably more than 3.0% by weight, more preferably more than 3.5% by weight, even more preferably more than 4.0% by weight, and particularly preferably more than 4.5% by weight. The copolymerization ratio of acidic group-containing monomers in acrylic polymers is usually preferably 20% by weight or less, and from the viewpoint of improving stress relaxation, it is preferably less than 10% by weight, more preferably less than 8.0% by weight, even more preferably less than 7.0% by weight, and particularly preferably less than 6.0% by weight (for example, 5.5% by weight or less).

[0040] The acrylic polymers preferably used in the technologies disclosed herein may be copolymers obtained by copolymerizing an alkyl (meth)acrylate as a main monomer and an acidic group-containing monomer as a secondary monomer. In such acrylic polymers, the proportion of copolymer components other than the alkyl (meth)acrylate and the acidic group-containing monomer may be less than 10% by weight, less than 3% by weight, less than 1% by weight, less than 0.1% by weight, or less than 0.03% by weight (for example, less than 0.01% by weight). The monomer components constituting the acrylic polymer may substantially not contain functional group-containing monomers other than the acidic group-containing monomer. An acrylic polymer substantially composed of alkyl (meth)acrylate and an acidic group-containing monomer can maximize the effects of the alkyl (meth)acrylate and the acidic group-containing monomer. The alkyl (meth)acrylate is C 7-10 It is preferable that the monomer is an alkyl (meth)acrylate (more preferably 2EHA). The above acidic group-containing monomer is preferably a carboxyl group-containing monomer (more preferably AA).

[0041] The monomer components constituting the acrylic polymer may include other copolymer components other than the aforementioned sub-monomers for purposes such as improving cohesiveness. Examples of other copolymer components include vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as aryl (meth)acrylate (e.g., phenyl (meth)acrylate), aryloxyalkyl (meth)acrylate (e.g., phenoxyethyl (meth)acrylate), and arylalkyl (meth)acrylate (e.g., benzyl (meth)acrylate); olefin monomers; chlorine-containing monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; and the like. The other copolymerization components mentioned above can be used individually or in combination of two or more.

[0042] The amount of such other copolymer components is not particularly limited and can be appropriately selected according to the purpose and application, but from the viewpoint of properly exhibiting the effects of use, it is appropriate to set it to 0.05% by weight or more, and may be set to 0.5% by weight or more. Furthermore, from the viewpoint of easily balancing the adhesive performance, it is appropriate to set the content of other copolymer components in the monomer component to 20% by weight or less, and may be set to 10% by weight or less (for example, 5% by weight or less). The technology disclosed herein can also be preferably implemented in a form in which the monomer component substantially does not contain other copolymer components. Here, "substantially free of other copolymer components" means that other copolymer components are not used at least intentionally, and it is permissible for other copolymer components to be unintentionally included in amounts of, for example, 0.01% by weight or less.

[0043] Acrylic polymers may also contain polyfunctional monomers as other monomer components, having at least two polymerizable functional groups (typically radical polymerizable functional groups) that have unsaturated double bonds, such as (meth)acryloyl groups or vinyl groups. By using polyfunctional monomers as monomer components, the cohesive force of the adhesive layer can be increased. Polyfunctional monomers can be used as crosslinking agents. Polyfunctional monomers are not particularly limited and include, for example, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, etc. Polyfunctional monomers can be used individually or in combination of two or more.

[0044] The amount of polyfunctional monomer used is not particularly limited and can be appropriately set so as to achieve the purpose of using the polyfunctional monomer. The amount of polyfunctional monomer used can be approximately 3% by weight or less of the monomer component, preferably approximately 2% by weight or less, and more preferably approximately 1% by weight or less (for example, approximately 0.5% by weight or less). The lower limit of the amount used when using polyfunctional monomer is not particularly limited as long as it is greater than 0% by weight. Usually, by using an amount of polyfunctional monomer of approximately 0.001% by weight or more of the monomer component (for example, approximately 0.01% by weight or more), the effect of using the polyfunctional monomer can be appropriately achieved.

[0045] The composition of the monomer components constituting the acrylic polymer is appropriately designed so that the glass transition temperature (Tg) of the acrylic polymer is approximately -15°C or lower (for example, approximately -70°C to -15°C). Here, the Tg of the acrylic polymer refers to the Tg determined by Fox's formula based on the above-mentioned monomer component composition. Fox's formula is a relationship 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 Fox's equation above, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the monomer i homopolymer (unit: K).

[0046] The glass transition temperature of the homopolymer used in calculating Tg shall be the value specified in publicly available documents. For example, for the monomers listed below, the following values ​​shall be used as the glass transition temperature of the homopolymer of the monomer. 2-Ethylhexyl acrylate -70℃ n-butyl acrylate -55℃ 2-Hydroxyethyl acrylate -15℃ 4-Hydroxybutyl acrylate -40℃ Vinyl acetate 32℃ Acrylic acid 106℃ Methacrylic acid 228℃

[0047] For the glass transition temperatures of monomer homopolymers other than those exemplified above, the values ​​listed in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. For monomers for which multiple values ​​are listed in this document, the highest value shall be adopted. If the value is not listed in the Polymer Handbook, the value obtained by the measurement method described in Japanese Patent Publication No. 2007-51271 shall be used.

[0048] While not particularly limited, from the viewpoint of stress relaxation, adhesion, and impact resistance, the Tg of the acrylic polymer is advantageous to be approximately -45°C or lower, preferably approximately -50°C or lower, more preferably approximately -55°C or lower, even more preferably -60°C or lower, and particularly preferably -62°C or lower (e.g., -64°C or lower). Furthermore, from the viewpoint of the cohesive force of the adhesive layer, the Tg of the acrylic polymer is usually approximately -70°C or higher, preferably approximately -68°C or higher, and may also be approximately -65°C or higher, or approximately -60°C or higher (e.g., approximately -55°C or higher). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the type and ratio of monomers used in the synthesis of the polymer).

[0049] The weight-average molecular weight (Mw) of the base polymer (preferably an acrylic polymer) in the technologies disclosed herein is not particularly limited, for example, approximately 10 × 10 4 ~500×10 4 It can be in the range of [this range]. From the standpoint of cohesiveness, the above Mw is usually about 30 × 10 4 That is all, approximately 45 × 10 4 (For example, approximately 65 x 10) 4 It is appropriate to set the above. In some preferred embodiments, from the viewpoint of improving high-temperature shear holding, the Mw of the acrylic polymer is 70 × 10 4 It is more than 90 × 10 4 More preferably, approximately 100 × 10 4 In particular, approximately 110 × 10 4 That's all. Also, the above Mw is usually 300 x 10 4 The following (more preferably approximately 200 x 10 4 For example, approximately 150 x 10 4 It is appropriate that the following apply.

[0050] The degree of dispersibility (Mw / Mn) of the base polymer (preferably an acrylic polymer) disclosed herein is not particularly limited. Here, degree of dispersibility (Mw / Mn) refers to the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn). In some preferred embodiments, the degree of dispersibility (Mw / Mn) of the base polymer is 40 or less, may be less than 20, less than 15 (e.g., 12 or less), less than 10, or less than 7.0. By limiting the molecular weight distribution to an appropriate range, stable properties are more likely to be obtained. The lower limit of Mw / Mn is not particularly limited and may be, for example, 3.0 or higher, 5.0 or higher, or 9.0 or higher. Having a certain degree of molecular weight distribution tends to allow for a balanced expression of the effects of low-molecular-weight and high-molecular-weight components. Such polymers also tend to have excellent productivity.

[0051] Mw, Mn, and Mw / Mn can be adjusted by polymerization conditions (time, temperature, etc.), the concentration of non-volatile components (monomer components) during polymerization, the amount of polymerization initiator used, the use of chain transfer agents, and the selection of polymerization solvents based on the chain transfer constant. Mw and Mn can be determined from values ​​obtained by GPC (gel permeation chromatography) on a standard polystyrene basis. For example, the "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used as a GPC instrument.

[0052] The method for obtaining the base polymer (e.g., acrylic polymer) is not particularly limited, and various polymerization methods known as polymer synthesis techniques, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, solution polymerization can be preferably employed. The polymerization temperature when performing solution polymerization can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and can be, for example, around 20°C to 170°C (typically around 40°C to 140°C).

[0053] The solvent used for solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents (toluene, ethyl acetate, etc.). The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators (e.g., azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN), peroxide-based initiators, etc.) depending on the type of polymerization method. The amount of polymerization initiator used can be the usual amount, for example, it can be selected from a range of approximately 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of monomer component.

[0054] (Adhesive-forming resin) The adhesive layer in the technology disclosed herein may contain a tackifying resin. This can increase the peel strength of the adhesive sheet. As the tackifying resin, one or more can be selected from phenolic tackifying resins, terpene tackifying resins, modified terpene tackifying resins, rosin tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomer tackifying resins, ketone tackifying resins, etc. Among these, phenolic tackifying resins, terpene tackifying resins, and modified terpene tackifying resins are preferred, and phenolic tackifying resins (preferably terpene phenolic resins) are more preferred.

[0055] Examples of phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkyl phenol resins, and rosin phenol resins. Terpene phenol resins refer to polymers containing terpene and phenol residues, and the concept encompasses both copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins) and homopolymers or copolymers of terpenes modified with phenol (phenol-modified terpene resins). Suitable examples of terpenes constituting such terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-isomers, l-isomers, and d / l-isomers (dipentene)). Hydrogenated terpene phenol resins refer to hydrogenated terpene phenol resins having a structure obtained by hydrogenating such terpene phenol resins. They are sometimes also called hydrogenated terpene phenol resins. Alkylphenol resins are resins (oil-based phenolic resins) obtained from alkylphenols and formaldehyde. Examples of alkylphenol resins include novolac and resol types. Rosinphenol resins are typically phenol-modified products of rosins or the various rosin derivatives mentioned above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosinphenol resins include those obtained by methods such as adding phenol to rosins or the various rosin derivatives mentioned above using an acid catalyst and then thermal polymerization.

[0056] Examples of terpene-based tackifying resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. These may be homopolymers of a single terpene or copolymers of two or more terpenes. Examples of homopolymers of a single terpene include α-pinene polymers, β-pinene polymers, and dipentene polymers. Examples of modified terpene resins include those obtained by modifying the above-mentioned terpene resins. Specifically, examples include styrene-modified terpene resins and hydrogenated terpene resins.

[0057] The concept of rosin-based tackifying resins as used here encompasses both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by hydrogenation, disproportionation, polymerization, etc.

[0058] Rosin derivative resins are typically derivatives of the rosins described above. The concept of rosin-based resins as used here includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). Examples include rosin esters such as unmodified rosin esters, which are esters of unmodified rosin with alcohols, and modified rosin esters, which are esters of modified rosin with alcohols; unsaturated fatty acid modified rosins, which are rosins modified with unsaturated fatty acids; unsaturated fatty acid modified rosin esters, which are rosin esters modified with unsaturated fatty acids; rosin alcohols, which are rosins or the above-mentioned rosin derivatives (including rosin esters, unsaturated fatty acid modified rosins, and unsaturated fatty acid modified rosin esters) obtained by reducing their carboxyl groups; and metal salts of rosins or the above-mentioned rosin derivatives. Specific examples of rosin esters include methyl esters, triethylene glycol esters, glycerol esters, and pentaerythritol esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

[0059] Examples of hydrocarbon-based tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins, among other hydrocarbon resins.

[0060] The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesive force, a tackifying resin with a softening point (softening temperature) of approximately 80°C or higher (preferably approximately 100°C or higher) can be preferably used. For example, a phenolic tackifying resin (such as a terpene phenol resin) having such a softening point can be preferably used. In some embodiments, a terpene phenol resin with a softening point of approximately 135°C or higher (more preferably approximately 140°C or higher) can be used. There is no particular upper limit to the softening point of the tackifying resin. From the viewpoint of adhesion to the adherend or substrate, a tackifying resin with a softening point of approximately 200°C or lower (more preferably approximately 180°C or lower) can be preferably used. The softening point of the tackifying resin can be measured based on the softening point test method (ring-ball method) specified in JIS K2207.

[0061] In some preferred embodiments, the tackifying resin is a tackifying resin T having a softening point of less than 145°C. L The following is used: Tackifying resin T with a softening point of less than 145℃ L By using this, an adhesive that better balances high-temperature shear resistance and stress relaxation properties can be preferably formed. Tackifying resin T L The softening point is preferably less than 135°C, more preferably less than 125°C, and may be 120°C or lower. Tackifying resin T L The lower limit of the softening point is not particularly limited, for example, 60°C or higher (and therefore solid at 30°C), 80°C or higher is suitable, and from the viewpoint of balancing stress relaxation and high-temperature adhesive properties (e.g., high-temperature shear holding properties), it is preferably 90°C or higher, more preferably 100°C or higher, and may also be 110°C or higher. Tackifying resin T L As such, an appropriate type can be selected from the above-mentioned types of tackifying resins, and among them, terpene phenol resin is preferably used. Tackifying resin T L These can be used individually or in combination of two or more types.

[0062] The adhesive layer is made of tackifying resin T L When including, tackifying resin T L The content of the tackifying resin TL From the viewpoint of suitably exhibiting the effects of using it, it is appropriate to use 1 part by weight or more of the tackifying resin T per 100 parts by weight of the base polymer (e.g., acrylic polymer) in the adhesive layer, preferably 5 parts by weight or more, more preferably 10 parts by weight or more, even more preferably 15 parts by weight or more (e.g., more than 15 parts by weight), and particularly preferably 18 parts by weight or more. Also, from the viewpoint of cohesive force, the tackifying resin T per 100 parts by weight of the base polymer L The amount is preferably less than 50 parts by weight, and from the viewpoint of high-temperature shear holding ability, it is preferably less than 40 parts by weight, more preferably less than 30 parts by weight, and may be less than 25 parts by weight.

[0063] Furthermore, a liquid tackifying resin that is liquid at 30°C can be used as the tackifying resin. By using a liquid tackifying resin, the tensile strength of the adhesive layer can be preferably reduced. The above liquid tackifying resin may be, for example, a tackifying resin with a softening point of approximately 50°C or less, more preferably approximately 40°C or less (typically rosin-based, terpene-based, hydrocarbon-based tackifying resins, such as hydrogenated rosin methyl ester). One type of liquid tackifying resin can be used alone or in combination of two or more types. The content of the liquid tackifying resin is not particularly limited, but from the viewpoint of suppressing the effect on adhesive properties (e.g., reduction in cohesiveness), it is preferably approximately 0.1 to 10% by weight of the total adhesive layer, and it is appropriate to have approximately 5% by weight or less (for example, 0.5 to 2% by weight).

[0064] Tackifying resin T with a softening point of less than 145°C L In embodiments in which this is used, the adhesive layer is made of a tackifying resin T having a softening point of less than 145°C. L High softening point tackifying resins that do not fall under the above category (typically, tackifying resins with a softening point of 145°C or higher) H It may or may not contain the adhesive layer, which is made of tackifying resin T. L In addition, adhesive resin T H If it contains tackifying resin T H The content of the tackifying resin T LIt is appropriate to use less than 100 parts by weight per 100 parts by weight, preferably less than 50 parts by weight, more preferably less than 30 parts by weight, and even more preferably less than 10 parts by weight, and it may be less than 1 part by weight or less than 0.1 parts by weight. Tackifying resin T L Adhesion resin T H Limiting the amount tends to improve the stress relaxation properties of the adhesive layer.

[0065] Some preferred embodiments include those in which the tackifying resin comprises one or more phenolic tackifying resins (typically terpene phenol resins). The techniques disclosed herein can preferably be implemented, for example, in which the total amount of the tackifying resin is 100% by weight, of which approximately 25% or more by weight (more preferably approximately 30% or more by weight) is terpene phenol resin. Approximately 50% or more by weight of the total amount of the tackifying resin may be terpene phenol resin, and approximately 80% or more by weight (for example, approximately 90% or more by weight) may be terpene phenol resin. Substantially all of the tackifying resin (for example, approximately 95-100% by weight, and even more precisely, approximately 99-100% by weight) may be terpene phenol resin.

[0066] While not particularly limited, in some embodiments, the tackifying resin may include a tackifying resin with a hydroxyl value higher than 20 mgKOH / g. Among these, a tackifying resin with a hydroxyl value of 30 mgKOH / g or higher is preferred. Hereinafter, a tackifying resin with a hydroxyl value of 30 mgKOH / g or higher may be referred to as a "high hydroxyl value resin." Using a tackifying resin containing such a high hydroxyl value resin, an adhesive layer with excellent adhesion to the adherend and high cohesive force can be realized. There is no particular upper limit to the hydroxyl value of the high hydroxyl value resin. From the viewpoint of compatibility with the base polymer, etc., the hydroxyl value of the high hydroxyl value resin is appropriate to be approximately 200 mgKOH / g or less, preferably approximately 100 mgKOH / g or less, and may also be approximately 70 mgKOH / g or less, or approximately 65 mgKOH / g or less. The high hydroxyl value resin can be used alone or in combination of two or more types. The technologies disclosed herein can preferably be implemented in which the tackifying resin comprises a high hydroxyl value resin (e.g., a phenolic tackifying resin, preferably a terpene phenolic resin) having a hydroxyl value of more than 20 mgKOH / g (e.g., 30 to 65 mgKOH / g). In some preferred embodiments, the high hydroxyl value resin is a tackifying resin T having a softening point of less than 145°C. L It is possible.

[0067] Here, the hydroxyl value can be the value measured by potentiometric titration as specified in JIS K0070:1992. The specific measurement method is as follows. [Method for measuring hydroxyl value] 1. Reagents (1) As the acetylation reagent, take approximately 12.5 g (approximately 11.8 mL) of acetic anhydride, add pyridine to make a total volume of 50 mL, and stir thoroughly before use. Alternatively, take approximately 25 g (approximately 23.5 mL) of acetic anhydride, add pyridine to make a total volume of 100 mL, and stir thoroughly before use. (2) A 0.5 mol / L potassium hydroxide ethanol solution is used as the measurement reagent. (3) Prepare toluene, pyridine, ethanol, and distilled water. 2.Operation (1) Accurately weigh out approximately 2 g of the sample into a flat-bottom flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and attach an air condenser. (2) After heating the flask in a 100°C bath for 70 minutes, allow it to cool, add 35 mL of toluene as a solvent from the top of the condenser and stir, then add 1 mL of distilled water and stir to decompose the acetic anhydride. To complete the decomposition, heat it again in the bath for 10 minutes and allow it to cool. (3) Wash the condenser with 5 mL of ethanol and remove it. Then add 50 mL of pyridine as a solvent and stir. (4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a volumetric pipette. (5) Perform potentiometric titration with a 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the resulting titration curve is taken as the endpoint. (6) For a blank test, perform steps (1) to (5) above without adding a sample. 3.Calculation The hydroxyl value is calculated using the following formula. Hydroxyl value (mgKOH / g) = [(BC) × f × 28.05] / S + D Here, B: Volume (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test. C: Volume (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the sample. f: Factor of 0.5 mol / L potassium hydroxide ethanol solution, S: Weight of the sample (g), D: Acid value, 28.05: Half the molecular weight of potassium hydroxide, 56.11. That is the case.

[0068] When the adhesive layer contains a tackifying resin, the amount (total amount) of the tackifying resin used is not particularly limited and can be appropriately set in the range of 1 to 100 parts by weight per 100 parts by weight of the base polymer. From the viewpoint of suitably exhibiting the effect of improving peel strength, it is appropriate to use 5 parts by weight or more of the tackifying resin per 100 parts by weight of the base polymer (e.g., an acrylic polymer), preferably 10 parts by weight or more, and it may also be 15 parts by weight or more. Furthermore, from the viewpoint of impact resistance and cohesive force, it is appropriate to use 50 parts by weight or less of the tackifying resin per 100 parts by weight of the base polymer (e.g., an acrylic polymer), may also be 40 parts by weight or less, or 30 parts by weight or less.

[0069] (Acrylic oligomers) In some preferred embodiments, the adhesive layer contains an acrylic oligomer. By including an acrylic oligomer in the adhesive layer, in addition to improving adhesive properties such as increased adhesion strength, it is possible to preferably achieve both high-temperature shear resistance and stress relaxation properties. As the acrylic oligomer, it is preferable to use a polymer with a Tg higher than the Tg of the copolymer corresponding to the composition of the above-mentioned monomer components (typically, this roughly corresponds to the Tg of the acrylic polymer contained in the adhesive formed from the adhesive composition). Including an acrylic oligomer can improve the adhesive strength of the adhesive. The acrylic oligomer can be used alone or in combination of two or more types.

[0070] The above acrylic oligomer preferably has a Tg of about 0°C to about 300°C, preferably about 20°C to about 300°C, and more preferably about 40°C to about 300°C. Having a Tg within this range allows for a favorable improvement in adhesive strength. In some preferred embodiments, from the viewpoint of adhesive cohesiveness, the Tg of the acrylic oligomer is about 30°C or higher, more preferably about 50°C or higher (e.g., about 60°C or higher), and from the viewpoint of adhesion, it is preferably about 200°C or lower, more preferably about 150°C or lower, and even more preferably about 100°C or lower (e.g., approximately 80°C or lower). The Tg of the acrylic oligomer is a value calculated based on Fox's formula, similar to the Tg of the copolymer corresponding to the monomer component composition.

[0071] The weight-average molecular weight (Mw) of the acrylic oligomer is typically between approximately 1,000 and less than approximately 30,000, preferably between approximately 1,500 and less than approximately 20,000, and more preferably between approximately 2,000 and less than approximately 10,000. Having Mw within this range is preferable because it allows for good adhesion and retention properties. In some preferred embodiments, from the viewpoint of high-temperature shear retention, the Mw of the acrylic oligomer is approximately 2,500 or more (e.g., approximately 3,000 or more), and from the viewpoint of adhesion, it is preferably approximately 7,000 or less, more preferably approximately 5,000 or less (e.g., approximately 4,500 or less, typically approximately 4,000 or less). The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and determined as a value equivalent to standard polystyrene. Specifically, the measurement is performed using a Tosoh HPLC-8020 with two TSKgelGMH-H(20) columns, in tetrahydrofuran solvent at a flow rate of approximately 0.5 mL / min.

[0072] Examples of monomers that make up acrylic oligomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and isononyl (meth)acrylate. Examples of (meth)acrylates include alkyl (meth)acrylates such as acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid with alicyclic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate (alicyclic hydrocarbon group-containing (meth)acrylate); aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols. Such (meth)acrylates can be used individually or in combination of two or more.

[0073] As acrylic oligomers, it is preferable from the viewpoint of further improving the adhesion of the adhesive layer if the monomer unit contains acrylic monomers with a relatively bulky structure, such as alkyl(meth)acrylates having a branched alkyl group structure, like isobutyl(meth)acrylate and t-butyl(meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates), like cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, and dicyclopentanyl(meth)acrylate; and aryl(meth)acrylates having a cyclic structure, such as phenyl(meth)acrylate and benzyl(meth)acrylate. Furthermore, when ultraviolet light is used during the synthesis of acrylic oligomers or the preparation of adhesive layers, saturated bonds are preferred because they are less likely to inhibit polymerization. Alkyl (meth)acrylates with branched alkyl groups, or esters with alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates), can be suitably used as monomers constituting acrylic oligomers. Note that the above-mentioned branched-chain alkyl (meth)acrylates, alicyclic hydrocarbon group (meth)acrylates, and aryl (meth)acrylates all correspond to (meth)acrylate monomers in the technology disclosed herein. The alicyclic hydrocarbon group may be saturated or unsaturated.

[0074] The proportion of (meth)acrylate monomers (e.g., alicyclic hydrocarbon group-containing (meth)acrylates) in the total monomer components constituting the acrylic oligomer is typically greater than 50% by weight, preferably 60% by weight or more, and more preferably 70% by weight or more (e.g., 80% by weight or more, and even more than 90% by weight or more). In some preferred embodiments, the acrylic oligomer has a monomer composition consisting substantially only of (meth)acrylate monomers.

[0075] In addition to the (meth)acrylate monomers mentioned above, functional group-containing monomers can be used as constituent monomer components of acrylic oligomers. Preferred examples of the functional group-containing monomers include monomers having nitrogen atom-containing rings (typically nitrogen atom-containing heterocycles) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxyl group-containing monomers such as AA and MAA; and hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers can be used individually or in combination of two or more. Among these, carboxyl group-containing monomers are preferred, and AA is particularly preferred.

[0076] When all monomer components constituting an acrylic oligomer include functional group-containing monomers, the proportion of functional group-containing monomers (for example, carboxyl group-containing monomers such as AA) in the total monomer components is appropriately set to approximately 1% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, and also appropriately set to approximately 15% by weight or less, preferably 10% by weight or less, and more preferably 7% by weight or less.

[0077] Acrylic oligomers can be formed by polymerizing their constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed in appropriate manner. The types of polymerization initiators that can be used as needed (e.g., azo polymerization initiators such as AIBN) are generally as exemplified in the synthesis of acrylic polymers, and the amount of polymerization initiator and the amount of chain transfer agent such as n-dodecyl mercaptan used optionally are appropriately set based on common technical knowledge to achieve the desired molecular weight, so a detailed explanation is omitted here.

[0078] From the above viewpoint, suitable acrylic oligomers include, for example, 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 CHMA and isobutyl methacrylate (IBMA), CHMA and IBXMA, CHMA and acryloylmorpholine (ACMO), CHMA and diethylacrylamide (DEAA), CHMA and AA, ADA and methyl methacrylate (MMA), DCPMA and IBXMA, DCPMA and MMA, and the like.

[0079] When an acrylic oligomer is included in the adhesive layer disclosed herein, its content is preferably 0.1 parts by weight or more (e.g., 1 part by weight or more) per 100 parts by weight of the base polymer (typically an acrylic polymer). From the viewpoint of better exhibiting the effects of the acrylic oligomer, the content of the acrylic oligomer is preferably approximately 5 parts by weight or more, more preferably approximately 8 parts by weight or more. Furthermore, from the viewpoint of compatibility with the base polymer (typically an acrylic polymer), the content of the acrylic oligomer is preferably less than 50 parts by weight, preferably less than 30 parts by weight, more preferably less than 20 parts by weight, and even more preferably less than 15 parts by weight (e.g., less than 12 parts by weight).

[0080] In some preferred embodiments, the adhesive layer is made of the tackifying resin described above (typically a tackifying resin T with a softening point of less than 145°C). L The tackifying resin (typically a tackifying resin with a softening point of less than 145°C) comprises one or more types of tackifying resins and one or more types of acrylic oligomers. By using the above tackifying resin and acrylic oligomer in combination, it is possible to preferably achieve both high-temperature shear holding and stress relaxation properties while exhibiting desired adhesive properties. LContent C of T and the content C of the acrylic oligomer O The ratio is not particularly limited. For example, C T / C O is preferably about 0.2 or more, preferably about 1 or more (e.g., more than 1), more preferably 1.5 or more, and may be 1.8 or more. Also, the above C T / C O is preferably about 20 or less, preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. Within the range of the above ratio, the combined effect of the tackifier resin and the acrylic oligomer can be preferably exhibited.

[0081] From the viewpoint of preferably exhibiting the effects of the technology disclosed herein, the total amount (total) of the tackifier resin and the acrylic oligomer contained in the adhesive layer according to some preferred embodiments is preferably about 1 part by weight or more, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, even more preferably 20 parts by weight or more, particularly preferably 25 parts by weight or more, per 100 parts by weight of the base polymer (preferably an acrylic polymer), and is preferably less than 120 parts by weight (e.g., about 80 parts by weight or less), preferably less than 60 parts by weight, more preferably about 50 parts by weight or less, and even more preferably about 40 parts by weight or less.

[0082] (Crosslinking agent) In the technology disclosed herein, the adhesive composition used to form the adhesive layer may optionally contain a crosslinking agent. 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 crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, hydrazine crosslinking agents, amine crosslinking agents, and silane coupling agents. Among these, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and melamine crosslinking agents are preferred, isocyanate crosslinking agents and epoxy crosslinking agents are more preferred, and isocyanate crosslinking agents are particularly preferred. By appropriately selecting and using a crosslinking agent, the cohesive force of the adhesive layer can be obtained, and stress relaxation properties and adhesive strength can be improved while maintaining high-temperature shear resistance. The adhesive layer in the technology disclosed herein may contain the crosslinking agent in the form after the crosslinking reaction, in the form before the crosslinking reaction, in a partially crosslinked form, or in intermediate or combined forms therein. Typically, the crosslinking agent is contained in the adhesive layer exclusively in the form after the crosslinking reaction.

[0083] As isocyanate-based crosslinking agents, polyfunctional isocyanates (compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. Isocyanate-based crosslinking agents can be used individually or in combination of two or more.

[0084] 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; and 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0085] 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.

[0086] 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'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0087] Examples of preferred polyfunctional isocyanates include those having an average of three or more isocyanate groups per molecule. Such trifunctional or trifunctional isocyanates may be macromers (typically dimers or trimers) of bifunctional or trifunctional or trifunctional isocyanates, derivatives (e.g., addition reaction products of a polyhydric alcohol and two or more polyfunctional isocyanates), polymers, etc. Examples include dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimeric adducts of isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and other polyfunctional isocyanates. Examples of commercially available polyfunctional isocyanates include "Duranate TPA-100" from Asahi Kasei Chemicals, and "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096" from Tosoh Corporation.

[0088] The amount of isocyanate-based crosslinking agent used is not particularly limited. For example, it can be approximately 0.5 parts by weight or more per 100 parts by weight of the base polymer. From the viewpoint of achieving both cohesive force and adhesion, and impact resistance, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of the base polymer can be, for example, more than 1.0 part by weight, more than 1.5 parts by weight is appropriate, preferably more than 2.0 parts by weight, more preferably more than 2.5 parts by weight (for example, 2.8 parts by weight or more). By adopting an amount of isocyanate-based crosslinking agent within the above range, it is possible to achieve a desirable balance between high-temperature shear resistance and stress relaxation. On the other hand, from the viewpoint of improving stress relaxation and adhesion to the adherend, it is appropriate to use 10 parts by weight or less per 100 parts by weight of the base polymer, preferably less than 5 parts by weight, more preferably less than 4.5 parts by weight, even more preferably less than 4.0 parts by weight, and particularly preferably less than 3.5 parts by weight (for example, 3.0 parts by weight or less).

[0089] In some preferred embodiments, an isocyanate-based crosslinking agent is used in combination with at least one crosslinking agent having a different type of crosslinkable functional group than the isocyanate-based crosslinking agent. According to the techniques disclosed herein, by using a crosslinking agent other than an isocyanate-based crosslinking agent (i.e., a crosslinking agent having a different type of crosslinkable reactive group than the isocyanate-based crosslinking agent; hereinafter also referred to as a "non-isocyanate-based crosslinking agent") in combination with an isocyanate-based crosslinking agent, it is possible to suitably achieve both high-temperature shear holding and stress relaxation properties.

[0090] The types of non-isocyanate crosslinking agents that can be used in combination with isocyanate crosslinking agents are not particularly limited, and can be appropriately selected from the crosslinking agents described above. Non-isocyanate crosslinking agents can be used individually or in combination of two or more.

[0091] In some preferred embodiments, epoxy crosslinking agents can be used as non-isocyanate crosslinking agents. For example, combining an isocyanate crosslinking agent with an epoxy crosslinking agent makes it easier to achieve both cohesiveness and impact resistance. As the epoxy crosslinking agent, any compound having two or more epoxy groups in one molecule can be used without particular limitation. Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. Epoxy crosslinking agents can be used individually or in combination of two or more.

[0092] While not particularly limited, specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. Commercially available epoxy crosslinking agents include "TETRAD-C" and "TETRAD-X" from Mitsubishi Gas Chemical Co., Ltd., "Epiclon CR-5L" from DIC Corporation, "Denacol EX-512" from Nagase ChemteX Corporation, and "TEPIC-G" from Nissan Chemical Industries, Ltd.

[0093] The amount of epoxy crosslinking agent used is not particularly limited. For example, the amount of epoxy crosslinking agent can be greater than 0 parts by weight and approximately 1 part by weight or less (typically about 0.001 to 0.5 parts by weight) per 100 parts by weight of the base polymer. From the viewpoint of suitably exhibiting the effect of improving cohesive force, it is appropriate to use about 0.005 parts by weight or more of epoxy crosslinking agent per 100 parts by weight of the base polymer, preferably about 0.01 parts by weight or more, and more preferably about 0.02 parts by weight or more. Furthermore, from the viewpoint of improving adhesion to the adherend, it is appropriate to use about 0.2 parts by weight or less of epoxy crosslinking agent per 100 parts by weight of the base polymer, preferably about 0.1 parts by weight or less, and more preferably less than about 0.05 parts by weight. Reducing the amount of epoxy crosslinking agent used tends to improve stress relaxation and impact resistance.

[0094] In the technologies disclosed herein, the relationship between the content of isocyanate-based crosslinking agents and the content of non-isocyanate-based crosslinking agents (e.g., epoxy-based crosslinking agents) is not particularly limited. The content of non-isocyanate-based crosslinking agents can be, for example, approximately 1 / 50 or less of the content of isocyanate-based crosslinking agents. From the viewpoint of more favorably achieving both adhesion to the adherend and cohesive force, the content of non-isocyanate-based crosslinking agents is appropriate, by weight, to be approximately 1 / 70 or less of the content of isocyanate-based crosslinking agents, and preferably approximately 1 / 90 or less. Furthermore, from the viewpoint of favorably exhibiting the effects of using isocyanate-based crosslinking agents and non-isocyanate-based crosslinking agents (e.g., epoxy-based crosslinking agents) in combination, the content of non-isocyanate-based crosslinking agents is appropriate, for example, approximately 1 / 500 or more of the content of isocyanate-based crosslinking agents, preferably 1 / 300 or more, and more preferably 1 / 150 or more.

[0095] The total amount of crosslinking agent used is not particularly limited. For example, it can be approximately 10 parts by weight or less per 100 parts by weight of the base polymer (preferably an acrylic polymer), preferably in the range of approximately 0.005 to 10 parts by weight, and more preferably in the range of approximately 0.01 to 5 parts by weight.

[0096] (Rust inhibitor) The adhesive layer according to some preferred embodiments may contain a rust inhibitor. Examples of rust inhibitors are not particularly limited and include azole rust inhibitors, amine compounds, nitrites, ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate, urea, urotropin, thiourea, phenyl carbamate, cyclohexylammonium-N-cyclohexylcarbamate (CHC), and the like. The rust inhibitors can be used individually or in combination of two or more.

[0097] As a rust inhibitor, azole-based rust inhibitors can be preferably used. Preferably, azole-based rust inhibitors contain a five-membered ring aromatic compound with two or more heteroatoms, where at least one of the heteroatoms is a nitrogen atom, as the active ingredient. A good example of a compound that can be used as an azole-based rust inhibitor is a benzotriazole-based rust inhibitor containing a benzotriazole compound as the active ingredient. Good examples of benzotriazole compounds include 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, and carboxybenzotriazole.

[0098] The amount of rust inhibitor is not particularly limited and can be, for example, 0.01 parts by weight or more (typically 0.05 parts by weight or more) per 100 parts by weight of the base polymer. From the viewpoint of obtaining a better metal corrosion prevention effect, the above amount may be 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. On the other hand, from the viewpoint of increasing the cohesive force of the adhesive, it is appropriate to have an amount of rust inhibitor less than 8 parts by weight per 100 parts by weight of the base polymer, and may be 5 parts by weight or less, or 2 parts by weight or less.

[0099] (Coloring agent) The adhesive layer may or may not contain a coloring agent. This allows for adjustment of the light transmittance (light shielding) of the adhesive layer. Adjusting the light transmittance of the adhesive layer may also be useful for adjusting the light transmittance of an adhesive sheet containing the adhesive layer. As the coloring agent, various materials can be used that can attenuate light by reflecting and / or absorbing light traveling through the adhesive layer. The color of the coloring agent is not particularly limited and may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl, etc. The coloring agent may typically be contained in the adhesive layer in a dispersed state (or dissolved state) within the constituent materials of the adhesive layer.

[0100] Various pigments and dyes can be used as colorants. Examples of pigments include inorganic pigments such as zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium dioxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide-based, iron hydroxide-based, chromium oxide-based, spinel-type calcined-based, chromic acid-based, chromium vermilion-based, Prussian blue-based, aluminum powder-based, bronze powder-based, silver powder-based, and calcium phosphate, as well as organic pigments such as phthalocyanine-based, azo-based, condensed azo-based, azo lake-based, anthraquinone-based, perylene / perinone-based, indigo-based, thioindigo-based, isoindolinone-based, azomethine-based, dioxazine-based, quinacridone-based, aniline black-based, triphenylmethane-based, and carbon black-based pigments. Examples of dyes include azo dyes, anthraquinone, quinophthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine. The colorants can be used individually or in appropriate combinations of two or more.

[0101] Since light-shielding properties can be efficiently adjusted with a small amount of colorant, black colorants are preferably used. Specific examples of black colorants include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine soot, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, hematite, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone-based colorants, etc. These can be used individually or in appropriate combinations of two or more. Carbon black is particularly preferred. It is also possible to use surface-modified carbon black particles having functional groups such as carboxyl groups, amino groups, sulfonic acid groups, and silicon-containing groups (e.g., alkoxysilyl groups, alkylsilyl groups) as carbon black particles. Such surface-modified carbon black particles are also called self-dispersing carbon black, and the addition of dispersants is unnecessary or can be reduced. The above carbon black particles can be used individually or in combination of two or more types.

[0102] Since the light-shielding properties of the adhesive layer can be efficiently adjusted with a small amount of colorant, particulate colorants (pigments) can be preferably used. In some preferred embodiments, a colorant with an average particle size of approximately 10 nm or more (for example, approximately 30 nm or more) (for example, a particulate black colorant such as carbon black) can be used. The above average particle size is, for example, approximately 50 nm or more, may be approximately 100 nm or more, or approximately 150 nm or more. The upper limit of the average particle size of the above colorant is not particularly limited, and may be, for example, approximately 3000 nm or less, or approximately 1000 nm or less. From the viewpoint of improving light-shielding properties, an average particle size of approximately 500 nm or less is appropriate for the above colorant.

[0103] In this specification, the average particle size of the colorant refers to the volume-average particle diameter, specifically the particle size at 50% of the cumulative value in the particle size distribution measured using a particle size distribution analyzer based on the laser scattering and diffraction method (50% volume-average particle diameter; hereafter, D50 It is sometimes abbreviated as ). This refers to ). As a measuring device, for example, the "Microtrac MT3000II" product manufactured by Microtrac-Bell or an equivalent product can be used.

[0104] The colorant content is not limited to a specific range. From the viewpoint of obtaining the effect of adding colorant, the colorant content in the adhesive layer can be approximately 0.1% by weight or more, and is suitable to be approximately 0.5% by weight or more. From the viewpoint of light shielding, it is preferably approximately 1% by weight or more, more preferably approximately 2% by weight or more, and even more preferably approximately 3% by weight or more (for example, approximately 5% by weight or more). Furthermore, the upper limit of the colorant content in the adhesive layer can be, for example, less than 15% by weight, is suitable to be less than 10% by weight, is preferably less than 8% by weight, and is more preferably less than 7% by weight. Limiting the amount of colorant used in the adhesive layer is also preferable from the viewpoint of suppressing a decrease in adhesive properties and maintaining the desired performance.

[0105] (Other additives) The adhesive composition may optionally contain various additives common in the field of adhesives, such as leveling agents, crosslinking aids, plasticizers, softeners, fillers, antistatic agents, anti-aging agents, UV absorbers, antioxidants, and light stabilizers. Such additives can be conventionally used by common methods and do not particularly characterize the present invention; therefore, a detailed explanation is omitted.

[0106] The adhesive layer (layer consisting of adhesive) disclosed herein may be formed from an aqueous adhesive composition, a solvent-type adhesive composition, a hot-melt adhesive composition, or an active energy ray-curable adhesive composition that hardens upon irradiation with active energy rays such as ultraviolet rays or electron beams. An aqueous adhesive composition refers to an adhesive composition in which an adhesive (adhesive layer-forming component) is contained in a solvent (aqueous solvent) mainly composed of water, and typically includes what is called a water-dispersible adhesive composition (a composition in which at least a part of the adhesive is dispersed in water). A solvent-type adhesive composition refers to an adhesive composition in which an adhesive is contained in an organic solvent. As the organic solvent contained in the solvent-type adhesive composition, one or more of the organic solvents exemplified above as organic solvents that can be used in solution polymerization (such as toluene and ethyl acetate) can be used without particular limitation. The technology disclosed herein can preferably be implemented in a form comprising an adhesive layer formed from a solvent-type adhesive composition, from the viewpoint of adhesive properties, etc. In embodiments comprising a solvent-type adhesive layer formed from a solvent-type adhesive composition, the effects of the techniques disclosed herein are preferably realized.

[0107] The adhesive layer disclosed herein can be formed by conventionally known methods. For example, a method can be employed in which an adhesive layer is formed by applying an adhesive composition to a release surface and drying it. In the case of an adhesive sheet having a substrate, for example, a method can be employed in which an adhesive layer is formed by directly applying (typically coating) the adhesive composition to the substrate and drying it (direct method). Alternatively, a method can be employed in which an adhesive layer is formed on a release surface by applying an adhesive composition to a release surface and drying it, and then the adhesive layer is transferred to the substrate (transfer method). As the release surface, for example, the surface of a release liner described later can be preferably used. Although the adhesive layer disclosed herein is typically formed continuously, it is not limited to this form, and may be formed in a regular or random pattern such as dots or stripes.

[0108] The adhesive composition can be applied using conventionally known coaters, such as gravure roll coaters, die coaters, or bar coaters. Alternatively, the adhesive composition may be applied by impregnation or curtain coating methods. From the viewpoint of promoting the crosslinking reaction and improving manufacturing efficiency, it is preferable to dry the adhesive composition under heating. The drying temperature can be, for example, around 40 to 150°C, and is preferably around 60 to 130°C. After drying the adhesive composition, aging may be performed for the purpose of adjusting the migration of components within the adhesive layer, promoting the crosslinking reaction, and alleviating any strain that may exist within the adhesive layer.

[0109] The adhesive layer disclosed herein may have a single-layer structure or a multilayer structure of two or more layers. From the viewpoint of productivity, etc., a single-layer structure of the adhesive layer is preferred.

[0110] The thickness of the adhesive layer is not particularly limited. The thickness of the adhesive layer is usually approximately 300 μm or less, preferably approximately 100 μm or less, more preferably approximately 70 μm or less, and more preferably approximately 50 μm or less. The thickness of the adhesive layer can be approximately 35 μm or less, and may be, for example, approximately 25 μm or less. An adhesive layer with limited thickness can effectively meet the demands for thinning and weight reduction. The lower limit of the adhesive layer thickness is, for example, approximately 3 μm or more, and preferably approximately 10 μm or more. In some preferred embodiments, the thickness of the adhesive layer may be approximately 20 μm or more, more preferably approximately 30 μm or more, and may be approximately 40 μm or more. Increasing the thickness of the adhesive layer tends to yield better adhesive properties. Furthermore, an adhesive layer of sufficient thickness easily absorbs the effects of protrusions and steps acting on the sheet surface of the adhesive sheet. In an adhesive sheet having adhesive layers (a first adhesive layer and a second adhesive layer) on each surface of a substrate, the thickness of each adhesive layer may be the same or different.

[0111] In some preferred embodiments, the total thickness of the adhesive layers constituting the adhesive sheet is 20 μm or more. Adhesive layers having the above thickness are more likely to absorb the effects of protrusions and steps acting on the sheet surface of the adhesive sheet. Furthermore, having a thickness above a predetermined value tends to allow the adhesive layer to exhibit superior adhesive properties (e.g., adhesive strength and impact resistance). In the case of a substrate-less adhesive sheet consisting only of adhesive layers, the total thickness of the adhesive layers is the same as the thickness of the adhesive sheet, and in the case of a double-sided adhesive sheet with a substrate, it is the total thickness of the adhesive layers (first adhesive layer and second adhesive layer) arranged on each side of the substrate. The total thickness of the adhesive layers is more preferably 30 μm or more, but may also be 35 μm or more, 45 μm or more, or 55 μm or more. The upper limit of the total thickness of the adhesive layers is, for example, approximately 200 μm or less, and from the viewpoint of thinning and weight reduction, it is preferably approximately 100 μm or less, but may also be approximately 75 μm or less, or approximately 60 μm or less. The above total thickness range is preferably applied to adhesive sheets with a substrate.

[0112] In some embodiments, the adhesive layer constituting the adhesive sheet may have limited light transmittance. In some embodiments, the light transmittance of the adhesive layer is 30% or less. An adhesive sheet having such an adhesive layer may have light-shielding properties. The light transmittance of the adhesive layer may be 20% or less, or less than 10%. The lower limit of the above light transmittance is not particularly limited and may be substantially 0%, i.e., below the detection limit, or 1% or more, 5% or more, or 15% or more. In some other embodiments, the light transmittance of the adhesive layer is greater than 30%. The light transmittance of the adhesive layer may be, for example, greater than 50%, or 70% or more (e.g., 85% or more). An adhesive layer having light transmittance (and therefore transparency) is preferably used in optical applications and various other applications where light transmittance is appropriate.

[0113] The light transmittance [%] of the adhesive layer is the light transmittance in the thickness direction of the adhesive layer (light transmittance at a wavelength of 550 nm), and is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. A spectrophotometer manufactured by Hitachi, Ltd. (device name "U4150 type spectrophotometer") or an equivalent is used as the transmittance meter. The light transmittance of the adhesive sheet is measured using the same method.

[0114] <Base material (base material layer)> In embodiments where the adhesive sheet disclosed herein is in the form of a single-sided adhesive type or a double-sided adhesive type adhesive sheet with a substrate, the substrate supporting (backing) the adhesive layer can be a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, composites thereof, etc. Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; cellophane, etc. Examples of paper include Japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, topcoat paper, etc. Examples of cloth include woven fabrics and nonwoven fabrics made by combining or blending various fibrous materials. Examples of the above fibrous materials include cotton, rayon, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of foamed sheets include foamed polyurethane sheets and foamed polychloroprene rubber sheets. Examples of metal foils include aluminum foil and copper foil.

[0115] The term "nonwoven fabric" as used herein primarily refers to nonwoven fabrics used for adhesive sheets, particularly in the field of adhesive tapes and other adhesive sheets. Typically, this refers to nonwoven fabrics produced using general-purpose paper machines (sometimes referred to simply as "paper"). Furthermore, the term "resin film" as used herein typically refers to a non-porous resin sheet and is distinct from, for example, nonwoven fabric (i.e., it does not include nonwoven fabric). The resin film may be an unoriented film, a uniaxially oriented film, or a biaxially oriented film.

[0116] As the substrate constituting the adhesive sheet with a substrate, a resin film is preferably used as the base film. The base film is typically an independently shape-retaining (independent) component. The substrate in the art disclosed herein may be substantially composed of such a base film. Alternatively, the substrate may include auxiliary layers in addition to the base film. Examples of such auxiliary layers include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc., provided on the surface of the base film.

[0117] The above-mentioned resin film is a film whose main component is a resin material (for example, a component that is present in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; and the like. The resin film may also be a rubber film such as natural rubber film or butyl rubber film. Among these, polyester films are preferred from the viewpoint of handling and processability, and PET films are particularly preferred among them.

[0118] The substrate may be transparent or light-shielding. In some embodiments, the substrate (e.g., a resin film) may contain a colorant. This allows for adjustment of the light transmittance (light-shielding properties) of the substrate. Adjusting the light transmittance (e.g., vertical light transmittance) of the substrate may also help in adjusting the light transmittance of the substrate, and further, the light transmittance of the adhesive sheet containing the substrate.

[0119] As a coloring agent, conventionally known pigments and dyes can be used, similar to the coloring agents that can be contained in the adhesive layer. The coloring agent is not particularly limited and may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl, etc.

[0120] The above-mentioned substrate (e.g., resin film) may contain various additives as needed, such as fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, and plasticizers. The proportion of each additive is less than 30% by weight (e.g., less than 20% by weight, typically less than 10% by weight).

[0121] The above-mentioned substrate (e.g., resin film) may have a single-layer structure, or it may have a multilayer structure of two, three, or more layers. From the viewpoint of shape stability, a single-layer structure is preferred for the substrate. In the case of a multilayer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the above-mentioned resin (e.g., polyester resin). The method for manufacturing the substrate (typically resin film) is not particularly limited and may be any conventionally known method as appropriate. For example, conventionally known general film molding methods such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be appropriately employed.

[0122] The substrate may be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In a substrate having a base film and a colored layer, the base film may or may not contain a coloring agent. The colored layer may be disposed on either one surface of the base film, or on both surfaces. In a configuration where colored layers are disposed on both surfaces of the base film, the composition of these colored layers may be the same or different.

[0123] The surface of the substrate may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer. Such surface treatments may be intended to improve the adhesion between the substrate and the adhesive layer, in other words, the anchoring ability of the adhesive layer to the substrate.

[0124] Furthermore, when the technology disclosed herein is implemented in the form of a single-sided adhesive sheet with a substrate, the back surface of the substrate may be subjected to a release treatment as needed. The release treatment may involve applying a release agent such as a general silicone-based, long-chain alkyl-based, or fluorine-based release agent in a thin film typically of about 0.01 μm to 1 μm (e.g., 0.01 μm to 0.1 μm). By performing such a release treatment, effects such as facilitating the unwinding of a roll of adhesive sheets can be obtained.

[0125] The thickness of the substrate is not particularly limited. The thickness of the substrate can be, for example, approximately 200 μm or less (for example, approximately 100 μm or less). Depending on the purpose and manner of use of the adhesive sheet, the thickness of the substrate may be approximately 70 μm or less, approximately 30 μm or less, approximately 15 μm or less, approximately 8 μm or less, or approximately 5 μm or less (for example, 3 μm or less). A substrate with a limited thickness can better meet the demands for thinning and weight reduction. Furthermore, an adhesive sheet with a substrate with a limited thickness tends to exhibit better stress relaxation properties due to the adhesive layer. The lower limit of the substrate thickness is not particularly limited, for example, 0.5 μm or more. From the viewpoint of handling and processability of the adhesive sheet, a substrate thickness of approximately 1 μm or more is appropriate, but it may also be approximately 2 μm or more, approximately 5 μm or more, or for example, approximately 10 μm or more.

[0126] In adhesive sheets with a base layer that are single-sided or double-sided adhesive, it is appropriate that the ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet be greater than 50%. With such an adhesive sheet with a base layer, the advantages of processability and handling due to the base layer are enjoyed while the stress relaxation properties of the adhesive layer are better exhibited. The ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more. From the viewpoint of obtaining the effects of having a base layer, it is appropriate that the ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet be 99% or less, and it may be less than 95% or less than 90%.

[0127] <Removable Liner> In the technologies disclosed herein, release liners can be used in the formation of adhesive layers, the manufacture of adhesive sheets, storage of adhesive sheets before use, distribution, and shaping. The release liners are not particularly limited, and for example, release liners having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or release liners made of low-adhesion materials such as fluoropolymers (polytetrafluoroethylene, etc.) or polyolefin resins (polyethylene, polypropylene, etc.) can be used. The release treatment layer may be formed by surface treating the liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide agent.

[0128] <Characteristics of adhesive sheets, etc.> (23℃ adhesive strength) The 23°C adhesive strength (180°C peel strength against a stainless steel plate measured at 23°C) of the adhesive sheet disclosed herein may vary depending on the intended use and application location, and is not limited to a specific range. The 23°C adhesive strength of the adhesive sheet can be, for example, approximately 1 N / 25 mm or more, and approximately 5 N / 25 mm or more is appropriate. From the viewpoint of adhesive reliability, the above 23°C adhesive strength is preferably 10 N / 25 mm or more, more preferably 15 N / 25 mm or more, even more preferably 18 N / 25 mm or more, and particularly preferably 20 N / 25 mm or more. The adhesive sheet having the above 23°C adhesive strength has adhesive strength suitable for bonding and fixing, and is suitable for bonding and fixing in portable electronic devices where high adhesive reliability is required in a limited bonding area, for example. The upper limit of the above 23°C adhesive strength is not particularly limited and may be approximately 30 N / 25 mm or less (for example, 25 N / 25 mm or less). The above 23°C adhesive strength can be measured by the method described in the examples below. In the case of a double-sided adhesive sheet having adhesive surfaces on both sides, the 23°C adhesive strength on each side may be the same or different.

[0129] (80℃ adhesive strength) The 80°C adhesive strength (180°C peel strength against a stainless steel plate measured at 80°C) of the adhesive sheet disclosed herein may vary depending on the intended use and application location, and is not limited to a specific range. The 80°C adhesive strength of the adhesive sheet can be, for example, approximately 1 N / 25 mm or more, and approximately 5 N / 25 mm or more is suitable. From the viewpoint of adhesive reliability at high temperatures, the above 80°C adhesive strength is preferably 8 N / 25 mm or more, more preferably 10 N / 25 mm or more, even more preferably 12 N / 25 mm or more, and may also be 15 N / 25 mm or more. The adhesive sheet having the above 80°C adhesive strength has adhesive strength suitable for bonding and fixing in applications that may be exposed to high temperatures, and is suitable, for example, for bonding and fixing in portable electronic devices where high adhesive reliability is required in a limited bonding area and where heat may be generated. The upper limit of the above 80°C adhesive strength is not particularly limited and may be approximately 30 N / 25 mm or less (for example, 20 N / 25 mm or less). The 80°C adhesive strength described above can be measured by the method described in the examples below. In the case of a double-sided adhesive sheet having adhesive surfaces on both sides, the 80°C adhesive strength on each side may be the same or different.

[0130] (Stress relaxation time) The adhesive sheets disclosed herein may exhibit a stress half-life (stress relaxation time) of 40 seconds or less in a stress relaxation test performed by the method described in the embodiments below. Adhesive sheets satisfying this characteristic tend to have excellent stress relaxation properties and may have stress relaxation properties that make the influence of protrusions or steps on one side of the adhesive sheet less likely to appear on the other side. The above stress relaxation time is preferably 30 seconds or less, more preferably 20 seconds or less, even more preferably 15 seconds or less, and particularly preferably 10 seconds or less (for example, 7 seconds or less). From the viewpoint of compatibility with high-temperature shear holding properties, the above stress relaxation time may be 1 second or more, 3 seconds or more, or 8 seconds or more.

[0131] (High-temperature shear holding strength) The adhesive sheet disclosed herein may not fall off the adherend for one hour from the start of the high-temperature shear holding test, as performed by the method described in the examples below. Such an adhesive sheet has excellent high-temperature shear holding properties.

[0132] (light transmittance) In some embodiments, the adhesive sheet is preferably 30% or less in light transmittance, although this is not particularly limited. Such an adhesive sheet may have light-shielding properties. The light transmittance of the adhesive sheet may be 20% or less, or less than 10%. The lower limit of the above light transmittance is not particularly limited and may be substantially 0%, i.e., below the detection limit, or 1% or more, 5% or more, or 15% or more. In some other embodiments, the light transmittance of the adhesive sheet is greater than 30%. The light transmittance of the adhesive sheet may be, for example, more than 50%, or 70% or more (e.g., 85% or more). Adhesive sheets with light transmittance (and therefore transparency) are preferably used in optical applications and various other applications where light transmittance is appropriate.

[0133] (Total thickness) The total thickness of the adhesive sheet disclosed herein (including the adhesive layer and substrate, but not the release liner) is not particularly limited. The total thickness of the adhesive sheet can be, for example, approximately 300 μm or less, and from the viewpoint of thinning, approximately 200 μm or less is appropriate, and it may also be approximately 150 μm or less (for example, approximately 100 μm or less). In some preferred embodiments, the thickness of the adhesive sheet can be approximately 50 μm or less, and for example, it may be approximately 35 μm or less. The lower limit of the thickness of the adhesive sheet is not particularly limited, but for example, approximately 10 μm or more is appropriate, preferably approximately 20 μm or more, more preferably approximately 30 μm or more, and it may also be approximately 40 μm or more, and it may also be approximately 80 μm or more. Adhesive sheets having a thickness of a predetermined value or more tend to absorb the effects of protrusions and steps acting on the sheet surface of the adhesive sheet. They also tend to have good handling properties and excellent adhesion and impact resistance. In the case of a substrate-less adhesive sheet, the thickness of the adhesive layer becomes the total thickness of the adhesive sheet.

[0134] <Application> The adhesive sheet disclosed herein has good high-temperature shear holding properties and stress-relaxing properties that reduce the influence of protrusions or steps on one side of the adhesive sheet on the other side. Taking advantage of these characteristics, the adhesive sheet can be used for various applications. For example, it can be preferably used for fixing various components in environments exposed to high temperatures. For example, the adhesive sheet disclosed herein is suitable for fixing components in various portable electronic devices. Portable electronic devices can have internal spaces that become hot, so it is desirable to use an adhesive sheet with excellent high-temperature adhesive properties. Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (e.g., wristwear-type devices worn on the wrist like watches, modular devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information systems, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, "portable" means not merely being able to carry, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily.

[0135] Furthermore, the adhesive sheet has stress-relieving properties that make it difficult for the effects of protrusions or steps on one side to appear on the other side, making it suitable for fixing various components such as the adherend or components and articles placed on the back side of the adherend that have irregularities or steps. Even if such irregularities are pressed against the adhesive sheet, the adhesive sheet disclosed herein can prevent or reduce the effects of those protrusions. For example, in fixing components in the aforementioned portable electronic device, components such as FPCs may be bent to accommodate the limited space within the device, and such components may form protrusions within a group of flat components. Also, steps may occur between multiple components due to the combination and arrangement of multiple components. By using the adhesive sheet disclosed herein, the effects of the above-mentioned protrusions within the device can be prevented or reduced.

[0136] The adhesive sheet disclosed herein can be used in various applications where light shielding is required. For example, some electronic devices, such as portable electronic devices, include light-emitting elements for purposes such as image display, and therefore the adhesive sheet may require limited light transmittance (e.g., light shielding) to prevent light leakage. For such electronic devices, an adhesive sheet with a predetermined light-shielding configuration can be used. For example, the adhesive sheet can be used in electronic devices that include various light sources such as LEDs (light-emitting diodes) or light-emitting elements such as self-emitting organic EL displays. The electronic device may be an electronic device equipped with an organic EL display device or a liquid crystal display device (typically a portable electronic device). For example, the adhesive sheet disclosed herein is suitable for use on the back surface of a display screen (display unit) such as a touch panel display in a portable electronic device.

[0137] The materials to which the adhesive sheets disclosed herein are attached (adhered materials) are not particularly limited, but include, for example, metallic materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc., or alloys containing two or more of these; various resin materials such as polyimide resins, acrylic resins, polyethernitrile resins, polyethersulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyetheretherketone resins, polyamide resins (so-called aramid resins, etc.), polyarylate resins, polycarbonate resins, liquid crystal polymers, etc. (typically plastic materials); and inorganic materials such as alumina, zirconia, soda glass, quartz glass, and carbon. Among these, metallic materials such as copper, aluminum, and stainless steel, and resin materials such as polyester resins such as PET, polyimide resins, aramid resins, and polyphenylene sulfide resins (typically plastic materials) are widely used. The above materials may be materials for components that make up products such as electronic devices. The adhesive sheet disclosed herein may be used by being attached to a component made of the above materials. The above materials may also be materials that make up the object to which the pressure sensor or display unit is fixed (for example, a back surface component such as an electromagnetic wave shield or a reinforcing plate). The object to which the adhesive sheet is fixed refers to the object to which the adhesive sheet is attached, i.e., the adherend. The back surface component refers to a component that is located on the opposite side of the front surface (viewing side) of the pressure sensor or display unit in, for example, in a portable electronic device, and may be a component that makes up the support part 240 located on the back surface of the display device 200 shown in Figure 3 below. The object to which the adhesive sheet is fixed may be in the form of a single-layer structure or a multi-layer structure, and the surface to which the adhesive sheet is attached (the adhesive surface) may be subjected to various surface treatments. While not particularly limited, an example of an object to be fixed is a back surface member with a thickness of 1 μm or more (typically 5 μm or more, e.g., 60 μm or more, and even 120 μm or more) and 1500 μm or less (e.g., 800 μm or less).

[0138] FIG. 3 is an exploded perspective view schematically showing a configuration example of a display device to which the adhesive sheet disclosed herein can be applied. As shown in FIG. 3, a display device 200 included in a portable electronic device 100 includes a display unit 220 composed of a cover member, an organic EL unit, etc., and a support unit 240. The display device 200 is further configured to include an adhesive sheet 230. In this configuration example, the adhesive sheet 230 is in the form of a double-sided adhesive sheet (double-sided adhesive tape) that fixes the members constituting the display unit 220 and the support unit 240. Note that the support unit 240 is configured to include a substrate (a metal plate such as a stainless steel plate or an aluminum plate). The adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

[0139] The matters disclosed by this specification include the following. [1] A portable electronic device including a display device including a display unit including a cover member and an organic EL unit, and a support unit, where an adhesive sheet is joined to the support unit, the adhesive sheet has an adhesive layer, the adhesive layer has a breaking strength of 2 MPa or less in a tensile test performed under the condition of a tensile speed of 10 mm / min, the adhesive sheet has a 180-degree peel strength P with respect to a stainless steel plate measured at 23°C RT and a 180-degree peel strength P with respect to a stainless steel plate measured at 80°C 80℃ and an 80°C adhesive force retention rate (P 80℃ / P RT × 100) of 50% or more, the portable electronic device. [2] The portable electronic device according to [1] above, further including a touch panel in which the display unit also functions as an input unit. [3] The portable electronic device according to [1] or [2] above, wherein the adhesive sheet is a double-sided adhesive sheet with a base material layer, and the ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet is greater than 50%. [4] The portable electronic device according to [1] or [2] above, wherein the adhesive sheet is a substrate-less double-sided adhesive sheet consisting of the adhesive layer. [5] The portable electronic device according to any one of [1] to [4] above, wherein the adhesive layer contains a tackifying resin with a softening point of less than 145°C. [6] The portable electronic device according to any one of [1] to [5] above, wherein the adhesive layer is an acrylic adhesive layer containing an acrylic polymer as a base polymer. [7] The portable electronic device according to [6] above, wherein the acrylic polymer is polymerized in a proportion of 50% by weight or more of alkyl (meth)acrylate having an alkyl group with 7 to 10 carbon atoms at its ester terminus. [8] The portable electronic device according to [6] or [7] above, wherein the adhesive layer comprises an acrylic oligomer. [9] The portable electronic device according to any one of [1] to [8] above, wherein the adhesive composition for forming the adhesive layer comprises an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

[10] The portable electronic device according to any one of [1] to [9] above, wherein the total thickness of the adhesive layer is 30 μm or more.

[0140]

[11] An adhesive sheet having an adhesive layer, The adhesive layer has a breaking strength of 2 MPa or less in a tensile test conducted at a tensile speed of 10 mm / min. The adhesive sheet has a 180-degree peel strength P measured at 23°C against a stainless steel plate. RT And the 180-degree peel strength P for stainless steel plates measured at 80°C. 80℃ The 80°C adhesion retention rate (P) can be determined from the relationship. 80℃ / P RT An adhesive sheet with a multiplier of 50% or more (x100).

[12] The adhesive sheet according to

[11] , which is a double-sided adhesive sheet with a base material having a base material layer, wherein the ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet is greater than 50%.

[13] The adhesive sheet according to

[11] above, which is a substrate-less double-sided adhesive sheet comprising the adhesive layer.

[14] The adhesive sheet according to any one of

[11] to

[13] above, wherein the adhesive layer contains a tackifying resin with a softening point of less than 145°C.

[15] The adhesive sheet according to any one of

[11] to

[14] above, wherein the adhesive layer is an acrylic adhesive layer containing an acrylic polymer as a base polymer.

[16] The adhesive sheet according to

[15] above, wherein the acrylic polymer is polymerized in a proportion of 50% by weight or more of alkyl (meth)acrylate having an alkyl group with 7 to 10 carbon atoms at its ester terminus.

[17] The adhesive sheet according to

[15] or

[16] above, wherein the adhesive layer comprises an acrylic oligomer.

[18] The adhesive sheet according to any one of

[11] to

[17] above, wherein the adhesive composition for forming the adhesive layer comprises an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

[19] The adhesive sheet according to any of

[11] to

[18] above, wherein the total thickness of the adhesive layer is 30 μm or more.

[20] An adhesive sheet as described in any of

[11] to

[19] above, used for fixing components in portable electronic devices. [Examples]

[0141] The following describes several embodiments of the present invention, but the present invention is not intended to be limited to those shown in these embodiments. In the following description, "parts" and "%" refer to weight unless otherwise specified.

[0142] <Example 1> (Preparation of acrylic polymers) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 95 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components, along with 233 parts of ethyl acetate as the polymerization solvent, were charged and stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this manner, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 8 hours to obtain a solution of acrylic polymer (A1). The Mw of this acrylic polymer (A1) was approximately 70 × 10⁻⁶ 4 That was the case.

[0143] (Preparation of adhesive composition) To the above acrylic polymer solution, 20 parts of tackifying resin (B1), 3 parts of an isocyanate crosslinking agent, and 0.01 parts of an epoxy crosslinking agent were added to 100 parts of the acrylic polymer (A1) contained in the solution, and the mixture was stirred to prepare an adhesive composition. As the tackifying resin (B1), a terpene phenol resin (trade name "YS Polystar T-115", manufactured by Yasuhara Chemical Co., Ltd., softening point approximately 115°C, hydroxyl value 30-60 mg KOH / g) was used. As the isocyanate crosslinking agent, "Coronate L" (trade name "Coronate L" manufactured by Tosoh Corporation, 75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct) was used. As the epoxy crosslinking agent, "TETRAD-C" (trade name "TETRAD-C" manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) was used.

[0144] (Making adhesive sheets) The obtained adhesive composition was applied to one surface (first surface) of a 2 μm thick polyethylene terephthalate (PET) film (product name "Lumirror", manufactured by Toray Industries, Inc.) as a base layer, and dried at 100°C for 2 minutes to form a 24 μm thick first adhesive layer. A polyester release film (product name "Diafoil MRF", 38 μm thick, manufactured by Mitsubishi Polyester Corporation) with both sides treated for release was prepared as a release liner, and the prepared adhesive composition was applied to one of the release surfaces of the release liner, and dried at 100°C for 2 minutes to form a 24 μm thick second adhesive layer. This second adhesive layer was transferred to the non-adhesive surface of the base layer on which the first adhesive layer was formed, and a double-sided adhesive sheet with a base material according to this example was produced.

[0145] <Example 2> A PET film with a thickness of 12 μm (product name "Lumirror", manufactured by Toray Industries, Inc.) was used as the base layer, and a double-sided adhesive sheet with a base material according to this example was prepared in the same manner as in Example 1, except that the thickness of each adhesive layer (first adhesive layer and second adhesive layer) was changed to 44 μm.

[0146] <Example 3> (Preparation of adhesive composition) Acrylic polymer (A2) was synthesized using essentially the same method as the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 95 parts of 2-ethylhexyl acrylate (2EHA) and 5 parts of AA, and the concentration of non-volatile components (monomer components) was adjusted by increasing the amount of polymerization solvent. A solution of acrylic polymer (A2) was obtained. The Mw of this acrylic polymer (A2) is approximately 120 × 10⁻¹⁴ 4The acrylic polymer solution was prepared by adding 20 parts of tackifying resin (B1), 10 parts of acrylic oligomer, 6.58 parts of black coloring agent, 3 parts of isocyanate crosslinking agent and 0.03 parts of epoxy crosslinking agent to 100 parts of the acrylic polymer (A2) contained in the solution, stirring and mixing. The tackifying resin, isocyanate crosslinking agent and epoxy crosslinking agent were the same as those used in Example 1. As the black coloring agent, the product name "ATDN101 Black" (containing carbon black particles with an average particle size of 350 nm) manufactured by Dainichi Seika Kogyo Co., Ltd. was used. Note that the adhesive composition in this example contains a small amount of liquid tackifying resin (approximately 1 to 1.5% by weight based on solid content). The acrylic oligomer used was prepared by the following method. Specifically, 95 parts of cyclohexyl methacrylate (CHMA), 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel. The mixture was stirred under a nitrogen stream for 1 hour to remove oxygen from the polymerization system, and then the temperature was raised to 85°C and the reaction was carried out for 5 hours to obtain an acrylic oligomer with a solid content of 50%. The Mw of the obtained acrylic oligomer was 3600.

[0147] (Making adhesive sheets) The above adhesive composition was applied to the release surface of a 38 μm thick polyester release liner (product name "Diafoil MRF", manufactured by Mitsubishi Polyester Co., Ltd.) and dried at 100°C for 2 minutes to form a 35 μm thick adhesive layer. The release surface of a 25 μm thick polyester release liner (product name "Diafoil MRF", manufactured by Mitsubishi Polyester Co., Ltd.) was then bonded to this adhesive layer. In this way, a 35 μm thick substrate-less double-sided adhesive sheet was obtained, with both sides protected by the two polyester release liners described above.

[0148] <Example 4> A double-sided adhesive sheet with a substrate was prepared in the same manner as in Example 1, except that the adhesive composition according to Example 3 was used, and each surface of a 2 μm thick PET film substrate had an adhesive layer (first adhesive layer and second adhesive layer) with a thickness of 24 μm.

[0149] <Example 5> Acrylic polymer (A3) was synthesized in essentially the same manner as the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 70 parts BA, 30 parts 2EHA, 3 parts AA, and 0.05 parts 4-hydroxybutyl acrylate (4HBA), and a solution of acrylic polymer (A3) was obtained. To this acrylic polymer solution, 30 parts of tackifying resin (B2) and 2 parts of isocyanate-based crosslinking agent were added to 100 parts of the acrylic polymer (A3) contained in the solution, and the mixture was stirred to prepare an adhesive composition. As the tackifying resin (B2), a polymerized rosin ester with a softening point of 125°C (manufactured by Arakawa Chemical Industries, Ltd., trade name "Pencel D125") was used. As the isocyanate-based crosslinking agent, the same type as that used in Example 1 was used. The obtained adhesive composition was applied to one surface (first surface) of a 12 μm thick PET film substrate (product name "Lumirror", manufactured by Toray Industries, Inc.) and dried at 100°C for 2 minutes to form a 19 μm thick first adhesive layer. A polyester release film (product name "Diafoil MRF", 38 μm thick, manufactured by Mitsubishi Polyester Corporation) with both sides treated for release was prepared as a release liner. The prepared adhesive composition was applied to one of the release surfaces of the release liner and dried at 100°C for 2 minutes to form a 19 μm thick second adhesive layer. This second adhesive layer was transferred to the non-adhesive surface of the substrate on which the first adhesive layer was formed to produce a double-sided adhesive sheet with a substrate according to this example.

[0150] <Example 6> A solution of acrylic polymer (A1) was prepared in the same manner as in Example 1. To this acrylic polymer solution, 25 parts of acrylic oligomer, 1 part of isocyanate-based crosslinking agent, and 0.075 parts of epoxy-based crosslinking agent were added per 100 parts of acrylic polymer (A1) contained in the solution, and the mixture was stirred to prepare an adhesive composition. The acrylic oligomer, isocyanate-based crosslinking agent, and epoxy-based crosslinking agent were the same types used as in Example 3. A double-sided adhesive sheet with a substrate was prepared in the same manner as in Example 5, except that the obtained adhesive composition was used, and each surface of the 12 μm thick PET film substrate had an adhesive layer (first adhesive layer and second adhesive layer) with a thickness of 19 μm.

[0151] <Example 7> (Preparation of adhesive composition) Acrylic polymer (A4) was synthesized in essentially the same manner as the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 93 parts BA, 7 parts AA, and 0.04 parts 4HBA, and a solution of acrylic polymer (A4) was obtained. To this acrylic polymer solution, 15 parts of tackifying resin (B3), 15 parts of acrylic oligomer, and 1.2 parts of isocyanate crosslinking agent and 0.01 parts of epoxy crosslinking agent were added per 100 parts of acrylic polymer (A4) contained in the solution, and the mixture was stirred to prepare an adhesive composition. The acrylic oligomer, isocyanate crosslinking agent, and epoxy crosslinking agent were the same as those used in Example 3. As the tackifying resin (B3), a terpene phenol resin (trade name "Tamanol 803L", manufactured by Arakawa Chemical Industries, Ltd., softening point approximately 145-160°C, hydroxyl value 1-20 mgKOH / g) was used. Using the obtained adhesive composition, a 50 μm thick adhesive layer was formed, and otherwise, in the same manner as in Example 3, a 50 μm thick substrate-less double-sided adhesive sheet was obtained, with both sides protected by the two polyester release liners described above.

[0152] <Rating> [Breaking strength in tensile tests] An adhesive layer laminate with a thickness of approximately 0.4 mm was obtained by laminating adhesive layers. This laminate was covered only on the top and bottom surfaces with release liners. The laminate was autoclaved for 20 minutes (50°C, 0.5 MPa) to ensure that no air bubbles remained between the layers, and then cut to a size of 10 mm in width and 100 mm in length to obtain test specimens. Under conditions of 23°C and 50% RH, the two release films covering the top and bottom surfaces were peeled off to expose the adhesive layer laminate, and a tensile test was performed on the test specimen using a tensile testing machine (Minebea Co., Ltd., universal tensile and compression testing machine, machine name "Tensile and Compression Testing Machine, TCM-1kNB") with a chuck distance of 10 mm and a tensile speed of 10 mm / min to obtain the SS curve, and the strength at which the test specimen broke (breaking strength) [MPa] was measured. Note that an adhesive layer laminate with a thickness of approximately 0.4 mm can be obtained for a substrate-less adhesive sheet by peeling off the release liner and laminating it. For adhesive sheets with a substrate, an adhesive layer can be formed on a release support under the same conditions as when forming the adhesive sheet, using an adhesive composition for forming the adhesive to be measured. By laminating these layers, an adhesive layer laminate with a thickness of approximately 0.4 mm can be obtained. Furthermore, during testing, it is preferable to apply powder to the adhesive surface of the area to be chucked to eliminate the effect of stickiness from the adhesive.

[0153] [Adhesive strength at 23℃] Under a measurement environment of 23°C and 50%RH, a 50μm thick PET film was attached to one adhesive side of a double-sided adhesive sheet as a backing, and the sheet was cut to a size of 25mm wide and 100mm long to prepare a measurement sample. The prepared measurement sample was then pressed against the surface of a stainless steel plate (SUS304BA plate) by applying pressure with a 2kg roller for one back-and-forth motion under the same environment of 23°C and 50%RH. After leaving it in the same environment for 30 minutes, the 180-degree peel strength (23°C adhesive strength) [N / 25mm] was measured using a universal tensile and compression tester in accordance with JIS Z 0237:2000, under conditions of a tensile speed of 300mm / min and a peel angle of 180 degrees. The universal tensile and compression tester used was the "Tensile and Compression Tester, TG-1kN" manufactured by Minebea Co., Ltd. or an equivalent product. Note that the PET film backing is not necessary for single-sided adhesive sheets.

[0154] [80℃ adhesive strength] A measurement sample was prepared in the same manner as for measuring the adhesive strength at 23°C. The adhesive surface of the measurement sample was pressed onto the surface of a stainless steel plate (SUS304BA plate) by rolling a 2kg roller back and forth once. This was left in the same environment for 30 minutes, and then left in an 80°C environment for another 30 minutes. Then, using a universal tensile and compression tester, the 180-degree peel strength (80°C adhesive strength) [N / 25mm] was measured in accordance with JIS Z 0237:2000, under conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees. As the universal tensile and compression tester, Minebea's "Tensile and Compression Tester, TG-1kN" or an equivalent product was used. Note that for single-sided adhesive sheets, the PET film backing mentioned above is not necessary.

[0155] [Stress relaxation test] A laminate of adhesive sheets with a thickness of 1 mm was obtained by laminating adhesive sheets. This laminate was protected only on the top and bottom surfaces by release liners. The laminate was cured at 50°C for one day to ensure no air bubbles remained between the layers, and then cut into 10 mm x 10 mm pieces to obtain test specimens. The two release films covering the top and bottom surfaces were peeled off to expose the adhesive sheets, and the laminate obtained above was compressed vertically (in the thickness direction) at a speed of 50 mm / min using a commercially available microautograph under a measurement environment of 23°C and 50% RH, and the compression was stopped when the stress reached 50 N. This state was maintained, and the stress that decreased over time was measured, and the time when the stress reached 25 N was recorded as the stress relaxation time (stress half-life). The shorter the stress relaxation time, the more the adhesive sheet tends to have superior stress relaxation properties, and if the stress relaxation time is within 40 seconds, it is judged that the adhesive sheet has stress relaxation properties that make the effects of protrusions or steps on one side less likely to appear on the other side. For the micro-autograph, the Shimadzu Corporation product "MST-200NX" or an equivalent model is used.

[0156] [High-temperature shear holding test] High-temperature shear strength was evaluated by conducting a high-temperature holding strength test at a temperature of 80°C in accordance with JIS Z0237:2009. Specifically, a 50 μm thick PET film was attached to one adhesive side of a double-sided adhesive sheet as a backing in an environment of 23°C and 50% RH, and the sheet was cut to a width of 10 mm to prepare a measurement sample. The other adhesive side of the measurement sample was attached to a bakelite plate, which served as the substrate, by rolling a 2 kg roller back and forth once. The adhesive area between the measurement sample and the substrate was 10 mm wide and 20 mm long. The measurement sample attached to the substrate in this manner was suspended in an 80°C environment and left for 30 minutes. Then, a load of 500 g was applied to the free end of the measurement sample, and it was left in an 80°C environment for 1 hour with the load applied. If the measurement sample remained attached to the substrate after 1 hour, it was judged as "pass," and if the measurement sample peeled off from the substrate and fell within 1 hour, it was judged as "fail." Note that in the case of single-sided adhesive sheets, the PET film backing mentioned above is not necessary.

[0157] For each example, an overview of the adhesive sheet structure and adhesive, the breaking strength [MPa] obtained by tensile testing, and the adhesive strength P at 23°C are provided. RT [N / 25mm], 80℃ adhesive strength P 80℃ [N / 25mm], 80℃ adhesive strength maintenance rate (P 80℃ / P RT Table 1 shows the evaluation results for stress relaxation time (in seconds) and high-temperature shear resistance (×100) [%].

[0158] [Table 1]

[0159] As shown in Table 1, the adhesive sheets for Examples 1-4 have a tensile strength of 2 MPa or less in the adhesive layer, and an 80°C adhesion retention rate (P 80℃ / P RTThe 80°C adhesion retention rate (P) was 50% or higher. These adhesive sheets had a stress relaxation time of 40 seconds or less, and passed the high-temperature shear holding test. In particular, the adhesive sheets related to Examples 3-4 had a short stress relaxation time and excellent stress relaxation properties while maintaining high-temperature shear holding properties. On the other hand, the 80°C adhesion retention rate (P) was 50% or higher. 80℃ / P RT In Example 5, the adhesive sheet with a ×100 ratio of less than 50% failed the high-temperature shear holding test. Furthermore, in Examples 6-7, the adhesive sheets with a rupture strength exceeding 2 MPa either required a stress relaxation time of more than 40 seconds or the stress did not halve even after observation over time. From the above results, the rupture strength of the adhesive layer is 2 MPa or less, and the adhesion retention rate at 80°C (P 80℃ / P RT Adhesive sheets with a ×100 ratio of 50% or more tend to have good high-temperature shear resistance and excellent stress relaxation properties, and it can be seen that the effects of protrusions or steps present on one side of the adhesive sheet can be prevented or mitigated from appearing on the other side.

[0160] Although specific examples of the present invention have been described in detail above, these are merely illustrative examples, and the scope of the claims is as follows: This is not an exhaustive list. The technologies described in the claims include a variety of specific examples as illustrated above. This includes modified and altered versions. [Explanation of Symbols]

[0161] 1,2 Adhesive sheets 10 Base material (base material layer) 21 Adhesive layer (first adhesive layer) 22 Adhesive layer (second adhesive layer) 31,32 Release Liner

Claims

1. An adhesive sheet having an adhesive layer, The adhesive layer contains an acrylic polymer as the base polymer. The aforementioned acrylic polymer is polymerized in a proportion of 50% by weight or more of alkyl acrylate having an alkyl group with 7 to 10 carbon atoms at its ester terminus. The aforementioned acrylic polymer is copolymerized with an acidic group-containing monomer. The monomer component constituting the acrylic polymer contains 1.0% to 20% by weight of the acidic group-containing monomer. The adhesive layer is made of tackifying resin T with a softening point of less than 145°C. Ｌ and further containing acrylic oligomers, The tackifying resin T Ｌ It contains a terpene phenol resin with a softening point of less than 135°C. The tackifying resin T Ｌ The content is 5 parts by weight or more and less than 40 parts by weight per 100 parts by weight of the acrylic polymer. The adhesive composition used to form the adhesive layer contains a crosslinking agent, The amount of the crosslinking agent is 0.005 to 10 parts by weight per 100 parts by weight of the acrylic polymer. The adhesive layer has a breaking strength of 2 MPa or less in a tensile test conducted under the conditions of 23°C, a chuck distance of 10 mm, and a tensile speed of 10 mm / min. The adhesive sheet has a 180° peel strength P measured at 23°C against a stainless steel plate. ＲＴ And the 180° peel strength P for stainless steel plate measured at 80°C. ８０℃ The 80°C adhesion retention rate (P) can be determined from the relationship. ８０℃ / P ＲＴ An adhesive sheet with a multiplier of 50% or more (x100).

2. The adhesive sheet according to claim 1, which is a double-sided adhesive sheet with a base material having a base material layer, wherein the ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet is greater than 50%.

3. The adhesive sheet according to claim 1, which is a substrate-less double-sided adhesive sheet comprising the adhesive layer.

4. The adhesive sheet according to any one of claims 1 to 3, wherein the crosslinking agent comprises an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

5. The adhesive sheet according to any one of claims 1 to 4, wherein the total thickness of the adhesive layer is 30 μm or more.

6. An adhesive sheet according to any one of claims 1 to 5, used for fixing components inside a portable electronic device.

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