Adhesive sheet

Abstract

To provide an adhesive sheet that exhibits both tack and holding power despite having a structure comprising a thin adhesive layer.SOLUTION: Provided is an adhesive sheet comprising an adhesive layer having a thickness of 10 μm or less. The adhesive layer is an acrylic adhesive layer containing an acrylic polymer. The adhesive layer has a storage elastic modulus of less than 0.1 MPa at a temperature of 25°C, and a storage elastic modulus of at least 0.025 MPa at a temperature of 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 a substrate having an adhesive layer on a support substrate, or in the form of adhesive sheets without a support substrate. Patent Document 1 is an example of prior art of this type. Patent Document 1 discloses an adhesive sheet used for fixing and covering ferrite sheets and graphite sheets, and it is stated that the thickness of the adhesive layer is 1 to 4 μm. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-224284 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Adhesive sheets may need to be thin depending on their application. For example, adhesive sheets used in portable electronic devices such as smartphones tend to be thinner in recent years due to the miniaturization and weight reduction of portable electronic devices. However, thinning the adhesive layer reduces the tack on the surface of the adhesive layer, which can lead to problems such as reduced alignment, longer curing and pressing times, and reduced adhesion to rough surfaces. One way to maintain and improve tack is to use a softer adhesive, but this leads to the problem of reduced holding power. In the design of thin-layer adhesives, there is a trade-off relationship between tack and holding power, and it would be practically beneficial if a thin-layer adhesive that balances both could be provided.

[0005] The present invention was created in view of the above circumstances, and aims to achieve both tack and holding power in a thin adhesive. Specifically, it aims to provide an adhesive sheet that can achieve both tack and holding power in a configuration having an adhesive layer with a thickness of 10 μm or less. [Means for solving the problem]

[0006] This specification provides an adhesive sheet having an adhesive layer with a thickness of 10 μm or less. The adhesive layer is an acrylic adhesive layer containing an acrylic polymer. The adhesive layer has a storage modulus of less than 0.1 MPa at 25°C and a storage modulus of 0.025 MPa or more at 80°C. By setting the storage modulus of the adhesive layer at 25°C to less than 0.1 MPa, good tack can be obtained in a thin adhesive layer. Furthermore, by setting the storage modulus of the adhesive layer at 80°C to 0.025 MPa or more, sufficient holding power can be obtained in a configuration with a thin adhesive layer. Such properties are preferably achieved using an acrylic adhesive. That is, in an acrylic adhesive layer with a thickness of 10 μm or less, both tack and holding power can be achieved by setting the storage modulus at 25°C to less than 0.1 MPa and the storage modulus at 80°C to 0.025 MPa or more.

[0007] In some preferred embodiments, the monomer component constituting the acrylic polymer contains 75% by weight or more of an alkyl (meth)acrylate having an alkyl group with 1 to 6 carbon atoms. By using an acrylic polymer having the above monomer composition, the effects of the techniques disclosed herein are preferably realized.

[0008] In some preferred embodiments, the adhesive layer is an adhesive resin T having a softening point of less than 145°C. L This includes using a tackifying resin with a softening point below a predetermined value, which effectively reduces the storage modulus at 25°C and makes it easier to achieve both the desired storage modulus at 25°C and 80°C.

[0009] In some preferred embodiments, the adhesive layer comprises a terpene phenol resin as the tackifying resin. By using a terpene phenol resin as the tackifying resin, the effects of the techniques disclosed herein are preferably realized.

[0010] In some preferred embodiments, the adhesive composition used to form the adhesive layer comprises an isocyanate-based crosslinking agent and a non-isocyanate-based crosslinking agent. By using an isocyanate-based crosslinking agent and a non-isocyanate-based crosslinking agent in combination, a balance between tack and holding power is preferably achieved. Furthermore, by using the two types of crosslinking agents in combination, it becomes easier to adjust the storage modulus of the formed adhesive layer to a desired range, making it easier to achieve both the target 25°C storage modulus and the 80°C storage modulus. An epoxy-based crosslinking agent is preferably used as the non-isocyanate-based crosslinking agent.

[0011] In some embodiments, the adhesive sheet further comprises a base layer that supports the adhesive layer. Adhesive sheets including a base layer tend to offer good processability and workability.

[0012] In some embodiments, the total thickness of the adhesive sheet is 20 μm or less. Adhesive sheets with such limited thickness can be advantageous in terms of thinning, miniaturization, weight reduction, and resource conservation of products to which the adhesive sheet is applied (e.g., portable electronic devices such as smartphones).

[0013] Adhesive sheets according to several embodiments are suitable as adhesive sheets to be attached to graphite sheets or ferrite sheets. For example, they are suitable as adhesive sheets to be used in graphite sheets placed in portable electronic devices such as mobile phones and smartphones. Graphite sheets can be placed in various electronic devices as heat dissipation sheets to release heat from heat-generating elements (batteries, IC chips, etc.). By applying an adhesive sheet having a thin adhesive layer to a graphite sheet, the heat dissipation effect of the graphite sheet can be fully realized. Therefore, the adhesive sheets provided in this specification may be laminated onto graphite sheets placed in portable electronic devices. Similar to applications for graphite sheets, thinning is required, so the adhesive sheets disclosed herein are also preferably used as adhesive sheets to be attached to ferrite sheets. For example, they are suitable as adhesive sheets to be used on ferrite sheets attached to portable electronic devices such as mobile phones and smartphones. Therefore, the adhesive sheets provided in this specification may be laminated onto ferrite sheets placed in portable electronic devices.

[0014] The adhesive sheet disclosed herein has a thin adhesive layer while achieving both tack and holding power, and therefore, taking advantage of this feature, it is preferably used in various applications where thinness is required. For example, it is preferably used in portable electronic devices where thinness is required. Specifically, it can be preferably used for fixing components of portable electronic devices. [Brief explanation of the drawing]

[0015] [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 cross-sectional view showing one example of the structure of a laminate. [Figure 4] This is a schematic exploded perspective view showing an example of the configuration of a display device. [Modes for carrying out the invention]

[0016] 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 actual adhesive sheets or other products provided.

[0017] 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: Fundamentals 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).

[0018] <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.

[0019] The adhesive sheet disclosed herein may, for example, have a cross-sectional structure schematically shown in Figure 1. The adhesive sheet 1 shown in Figure 1 comprises a sheet-like substrate (support) 10 and an adhesive layer 20 provided on one surface 10A of the substrate 10. In this adhesive sheet 1, the surface of the adhesive layer 20 is the adhesive surface 1A that constitutes one surface of the adhesive sheet 1. In this adhesive sheet 1, the other surface 10B of the substrate 10 is the other surface (back surface) 1B of the adhesive sheet 1. That is, the other surface 10B of the substrate 10 also serves as the back surface 1B of the adhesive sheet 1. The substrate 10 includes a substrate film 12 and a colored layer 14 disposed on the back side of the substrate film 12 (i.e., on the side of the back surface 1B of the adhesive sheet 1 that is closer to the substrate film 12; also called the second surface 12B), and further includes a matte layer 16 on the back side of the colored layer 14. The adhesive layer 20 is disposed on the other surface (first surface 12A) of the substrate film 12. In other words, an adhesive layer 20 is provided on the first surface 12A of the base film 12, and a colored layer 14 and a matte layer 16 are laminated in this order on the second surface 12B of the base film 12 (the side opposite the first surface 12A). Therefore, the base material 10 has a laminated structure in which the base film 12, the colored layer 14 and the matte layer 16 are laminated in this order. In this embodiment, the matte layer 16 is the outermost layer of the base material 10, and the outer surface 16A of the matte layer 16 is the back surface 1B of the adhesive sheet 1.

[0020] Before use, the adhesive sheet 1 has a structure in which the adhesive layer 20 is protected by a release liner 50, the side of which the adhesive layer 20 is the release surface 50B. When this adhesive sheet 1 with the release liner 50 is made into a roll (adhesive sheet roll) for purposes such as transport or storage, the outer surface 50A of the release liner 50 (the surface located on the opposite side from the release surface 50B) and the back surface 1B of the adhesive sheet (in this embodiment, the outer surface 16A of the mat layer 16) may come into contact.

[0021] Furthermore, the adhesive sheet disclosed herein may take the form of a double-sided adhesive type substrate-less adhesive sheet schematically shown in Figure 2. The adhesive sheet 2 shown in Figure 2 has a configuration in which both sides 21A and 21B of the substrate-less adhesive layer 21 are protected by release liners 51 and 52, 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.

[0022] <Storage modulus of the adhesive layer> In some preferred embodiments, the storage modulus of the adhesive layer at 25°C is less than 0.1 MPa (specifically less than 0.10 MPa), and the storage modulus at 80°C is 0.025 MPa or higher. By setting the 25°C storage modulus of the adhesive layer to less than 0.1 MPa, good tack can be obtained in a thin adhesive layer. Furthermore, by setting the 80°C storage modulus of the adhesive layer to 0.025 MPa or higher, sufficient holding power can be obtained in a configuration with a thin adhesive layer. In other words, both tack and holding power can be achieved in a thin adhesive layer. Such properties can be achieved by the monomer composition and molecular weight characteristics of the base polymer (typically an acrylic polymer) contained in the adhesive layer, the type, softening point, and amount of tackifying resin, the type and amount of crosslinking agent used, etc.

[0023] The storage modulus at 25°C of the adhesive layer is more preferably 0.09 MPa or less, and even more preferably 0.08 MPa or less. Furthermore, the lower limit of the above-mentioned storage modulus at 25°C is not particularly limited, but in some embodiments, the storage modulus at 25°C is, for example, 0.01 MPa or more, 0.02 MPa or more is appropriate, and from the viewpoint of compatibility with the 80°C storage modulus described later, it is preferably 0.03 MPa or more, it may also be 0.05 MPa or more, it may be 0.06 MPa or more, and it may also be 0.07 MPa or more. The higher the storage modulus at 25°C, the higher the cohesive force of the adhesive tends to be, and the better the holding power tends to be.

[0024] The storage elastic modulus of the adhesive layer at 80°C is more preferably 0.028 MPa or more, still more preferably 0.030 MPa or more, and may be 0.032 MPa or more. The higher the storage elastic modulus at 80°C, the easier it is to obtain good holding force (high-temperature holding force), for example, even when exposed to a high-temperature state of 80°C or higher. Also, the upper limit value of the storage elastic modulus at 80°C is not particularly limited, but in some embodiments, for example, it is 0.10 MPa or less, suitably 0.08 MPa or less, and from the perspective of compatibility with the storage elastic modulus at 25°C described above, it is preferably 0.06 MPa or less, may be 0.05 MPa or less, may be 0.04 MPa or less, and may be 0.035 MPa or less. The lower the storage elastic modulus at 80°C, the more likely the tack and adhesiveness are to improve.

[0025] The ratio of the storage elastic modulus at 25°C to the storage elastic modulus at 80°C can be set within a range where each storage elastic modulus is within a desired range, and thus is not limited to a specific range. In some embodiments, the ratio (G' 80 ) of the storage elastic modulus at 25°C (G' 25 ) to the storage elastic modulus at 80°C (G' 25 ) (G' 80 ) is preferably 5 or less, more preferably 4 or less, and still more preferably 3 or less. The smaller the above ratio (G' 25 / G' 80 ), the relatively lower the storage elastic modulus at 25°C and the relatively higher the storage elastic modulus at 80°C, and it is easier to balance the tack and the holding force in the thin adhesive layer. The lower limit value of the above ratio (G' 25 / G' 80 ) may be 1.5 or more, may be 2 or more, and may be 2.2 or more from the perspective of ease of preparing the adhesive.

[0026] In this specification, the 25°C and 80°C storage moduli of the adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, an adhesive layer with a thickness of approximately 2 mm is prepared by stacking multiple adhesive layers (or adhesive sheets in the case of substrate-less adhesive sheets) to be measured. A sample of this adhesive layer, punched into a disc shape with a diameter of 7.9 mm, is sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurement is performed using a viscoelasticity tester (e.g., ARES or equivalent manufactured by T.A. Instruments Corporation) under the following conditions to determine the storage moduli [MPa] at 25°C and 80°C. • Measurement mode: Shear mode Temperature range: -70℃ to 150℃ • Heating rate: 5°C / min ·Measurement frequency: 1Hz The measurements in the examples described later will also be performed using the method described above. The adhesive layer to be measured can be formed by applying the corresponding adhesive composition in layers and then drying or curing it.

[0027] <Adhesive layer> In some preferred embodiments, the adhesive constituting the adhesive layer consists of an acrylic adhesive containing an acrylic polymer (preferably an acrylic adhesive containing the acrylic polymer as a base polymer). An adhesive that achieves both a storage modulus of less than 0.1 MPa at 25°C and a storage modulus of 0.025 MPa or more at 80°C can preferably be achieved by using an acrylic adhesive. According to the technology disclosed herein, a configuration using an acrylic adhesive can preferably achieve both tack and holding power in a thin adhesive layer. The use of acrylic polymers is also advantageous in terms of adhesive performance and cost.

[0028] 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.

[0029] (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.

[0030] As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably 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 having 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, R 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.

[0031] 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).

[0032] 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.

[0033] Also, C 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.

[0034] 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 yield better retention. In this embodiment, the C content of the monomer component 1-6 The proportion of alkyl (meth)acrylate (in other words, the polymerization ratio) is preferably 75% by weight or more, more preferably 80% by weight or more, and even 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.

[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 improving adhesion and cohesiveness, 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 due to 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) can serve as a crosslinking site for the acrylic polymer.

[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, may be 2.0% by weight or more, or 3.0% by weight or more. Using an amount or more of acidic group-containing monomers 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 adhesive strength, 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 1-6 It is preferable that the monomer is an alkyl (meth)acrylate (more preferably BA). 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, and even less than 1% by weight). The technology disclosed herein can also be preferably implemented in a manner in which the monomer component substantially does not contain other copolymer components. Here, substantially free from 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 impact resistance and adhesion to the adherend, the Tg of the acrylic polymer is advantageous to be approximately -25°C or lower, preferably approximately -35°C or lower, and more preferably approximately -40°C or lower. In some embodiments, from the viewpoint of cohesive force, the Tg of the acrylic polymer is, for example, approximately -70°C or higher, may also be approximately -65°C or higher, may be approximately -60°C or higher, or may be approximately -55°C or higher. The techniques disclosed herein can preferably be implemented in embodiments in which the Tg of the acrylic polymer is approximately -65°C or higher and -35°C or lower (for example, approximately -55°C or higher and -40°C or lower). 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 (typically 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 it as above. Also, the above Mw is usually 300 × 10 4 The following (more preferably approximately 200 x 10 4 For example, approximately 150 x 10 4 The following is appropriate: 120 × 10 4 The following are also acceptable: 100 x 10 4 It may be less than 100. Mw is determined from the value obtained by GPC (gel permeation chromatography) on a standard polystyrene basis. For GPC equipment, for example, the model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used.

[0050] The method for obtaining the base polymer (typically an 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).

[0051] 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.

[0052] (Adhesive-forming resin) The adhesive layer in the technology disclosed herein may contain a tackifying resin. This can increase the adhesive 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.).

[0057] 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.

[0058] 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 phenolic resin) having such a softening point can be preferably 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.

[0059] 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 method, it is possible to form an adhesive that has good tack and adheres well to the substrate, even when it is constructed in a thin layer. Furthermore, by using a tackifying resin with a softening point below a predetermined value, the storage modulus is reduced, making it easier to achieve the desired storage modulus characteristics. 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, 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.

[0060] The adhesive layer is made of tackifying resin T L When including, tackifying resin T L The content of the tackifying resin T LFrom 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 (typically an 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 holding power, it is preferably less than 40 parts by weight, more preferably less than 30 parts by weight, and may also be less than 25 parts by weight.

[0061] 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 L It 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. It may also be less than 1 part by weight, or even less than 0.1 parts by weight.

[0062] 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.

[0063] 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 This is possible. Furthermore, the hydroxyl value used above can be the value measured by potentiometric titration as specified in JIS K0070:1992.

[0064] 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 (typically an acrylic polymer). From the viewpoint of suitably exhibiting the effect of improving adhesive 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, 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, and it may also be 40 parts by weight or less, or 30 parts by weight or less.

[0065] (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 examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, hydrazine-based crosslinking agents, amine-based crosslinking agents, silane coupling agents, etc. Among these, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and melamine-based crosslinking agents are preferred, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are more preferred, and isocyanate-based crosslinking agents are particularly preferred. By appropriately selecting and using a crosslinking agent, the cohesive force of the adhesive layer can be obtained, and the adhesive force can be improved while having sufficient holding power (e.g., high-temperature holding power). The crosslinking agent can be used alone or in combination of two or more types. 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] The amount of isocyanate-based crosslinking agent used is not particularly limited. For example, it can be approximately 0.001 parts by weight or more per 100 parts by weight of the base polymer (typically an acrylic polymer). In some preferred embodiments, from the viewpoint of balancing cohesive force and adhesive force, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of the base polymer is, for example, 0.01 parts by weight or more, preferably 0.03 parts by weight or more, preferably 0.05 parts by weight or more, may also be 0.07 parts by weight or more, or 0.1 parts by weight or more. Also, from the viewpoint of improving adhesive force and tack, the amount of isocyanate-based crosslinking agent used is appropriate to be 10 parts by weight or less per 100 parts by weight of the base polymer, and in some embodiments, it may be less than 5 parts by weight, less than 3 parts by weight, or less than 2 parts by weight. In some preferred embodiments, the amount of isocyanate-based crosslinking agent used is less than 1.0 part by weight per 100 parts by weight of the base polymer, more preferably 0.5 parts by weight or less, even more preferably 0.3 parts by weight or less, or 0.2 parts by weight or less. By limiting the amount of isocyanate-based crosslinking agent used within the above range, it becomes easier to obtain good tack.

[0072] 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 tack and retention strength (e.g., high-temperature retention strength).

[0073] 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.

[0074] In some preferred embodiments, epoxy crosslinking agents can be used as non-isocyanate crosslinking agents. For example, by using an isocyanate crosslinking agent and an epoxy crosslinking agent in combination, it is easier to achieve both tack and retention strength. As the epoxy crosslinking agent, compounds 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.

[0075] 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.

[0076] 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 approximately 0.001 to 0.5 parts by weight) per 100 parts by weight of the base polymer (typically an acrylic polymer). From the viewpoint of suitably exhibiting the cohesive force improvement effect, it is appropriate to use approximately 0.003 parts by weight or more of epoxy crosslinking agent per 100 parts by weight of the base polymer, preferably approximately 0.005 parts by weight or more, and more preferably approximately 0.008 parts by weight or more. Furthermore, from the viewpoint of improving adhesion to the adherend, it is appropriate to use approximately 0.2 parts by weight or less of epoxy crosslinking agent per 100 parts by weight of the base polymer, preferably approximately 0.1 parts by weight or less, more preferably less than 0.05 parts by weight, and even more preferably less than 0.03 parts by weight (for example, 0.02 parts by weight or less). By limiting the amount of epoxy crosslinking agent used within the above range, it becomes easier to obtain good tack.

[0077] 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. In some embodiments, the content of non-isocyanate-based crosslinking agents is, for example, less than 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, preferably about 1 / 2 or less, more preferably about 1 / 3 or less, more preferably about 1 / 5 or less, even more preferably about 1 / 7 or less, and may be about 1 / 9 or less, on a weight basis, compared with the content of isocyanate-based crosslinking agents. 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 to be about 1 / 1000 or more, for example, about 1 / 500 or more, compared with the content of isocyanate-based crosslinking agents. In some preferred embodiments, the content of the non-isocyanate crosslinking agent is approximately 1 / 100 or more of the content of the isocyanate crosslinking agent, more preferably approximately 1 / 50 or more, even more preferably approximately 1 / 30 or more, and may also be approximately 1 / 20 or more, or 1 / 15 or more.

[0078] 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 (typically an acrylic polymer), and from the viewpoint of achieving a good balance between adhesiveness and cohesiveness, it is preferably selected from a range of approximately 0.005 to 10 parts by weight, and more preferably from approximately 0.01 to 5 parts by weight. In some preferred embodiments, the total amount of crosslinking agent used is approximately less than 3 parts by weight per 100 parts by weight of the base polymer (preferably an acrylic polymer), and may be less than 1 part by weight, 0.5 parts by weight or less, 0.3 parts by weight or less, or 0.2 parts by weight or less. Also, in some embodiments, the total amount of crosslinking agent used per 100 parts by weight of the base polymer is, for example, 0.03 parts by weight or more, preferably 0.05 parts by weight or more, and may be 0.07 parts by weight or more, or 0.1 parts by weight or more. By limiting the total amount of crosslinking agent used within the above range, it becomes easier to obtain good tack.

[0079] (Coloring agent) The adhesive layer disclosed herein may be colored to exhibit desired design properties or optical properties (e.g., light shielding). For coloring the adhesive layer, one or more known organic or inorganic colorants (pigments, dyes, etc.) can be used in appropriate combinations. For example, the adhesive layer can be colored black by including a black colorant such as carbon black in it. The content of the colorant is not particularly limited and can be less than 15 parts by weight per 100 parts by weight of the base polymer (typically an acrylic polymer). From the viewpoint of suppressing a decrease in adhesive properties, the content of the colorant is preferably less than 10 parts by weight (e.g., less than 5 parts by weight, typically less than 3 parts by weight) per 100 parts by weight of the base polymer. From the viewpoint of adhesive performance, the technology disclosed herein may preferably be implemented in a manner in which the adhesive layer substantially does not contain inorganic and organic colorants. For example, it may preferably be implemented in a manner in which the content of the colorant is 0 to 1 part by weight per 100 parts by weight of the base polymer.

[0080] (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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] In the technology disclosed herein, the adhesive layer is configured to be thin. Specifically, the thickness of the adhesive layer is 10 μm or less. According to the technology disclosed herein, both tack and holding power can be achieved with an adhesive layer of 10 μm or less in thickness. A thin adhesive layer is also advantageous in terms of thinning, miniaturizing, reducing weight, and conserving resources of the adhesive sheet. Furthermore, when the adhesive sheet is applied to a graphite sheet, a thin adhesive layer is preferable from the viewpoint of heat dissipation efficiency. From this viewpoint, the thickness of the adhesive layer is more preferably 8 μm or less, even more preferably 5 μm or less, and may be, for example, 3 μm or less. In some embodiments, the thickness of the adhesive layer is appropriate at about 0.5 μm or more from the viewpoint of adhesive performance and coating properties, preferably 1 μm or more, and may be 1.2 μm or more, or for example, 1.5 μm or more. The greater the thickness of the adhesive layer, the easier it is to obtain good tack and sufficient adhesive strength. In some other embodiments, the thickness of the adhesive layer is, for example, approximately 3 μm or more, may be approximately 5 μm or more, may be approximately 7 μm or more, or may be approximately 9 μm or more. By increasing the thickness of the adhesive layer, better adhesive properties are more likely to be obtained. In an adhesive sheet having an adhesive layer on each surface of the substrate, the thickness of each adhesive layer may be the same or different.

[0085] <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 (layer) that supports (backs) 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.

[0086] (Base film) In some preferred embodiments, the adhesive sheet has a base film as a substrate. The base film is not particularly limited, and for example, a resin film mainly composed of a resin material (for example, a component present in more than 50% by weight) may be preferably used. In this specification, "resin film" typically refers to a substantially non-foamed resin film. That is, the resin film in this specification may be one in which air bubbles are substantially absent (voidless). Therefore, the above resin film is a concept distinct from so-called foamed films. Furthermore, the above resin film is typically a substantially non-porous film and is a concept distinct from so-called nonwoven fabrics or woven fabrics. A base film that does not contain a porous layer such as foam, nonwoven fabric, or woven fabric, i.e., a base film consisting of a non-porous layer, may be preferably used. Resin films generally tend to have superior mechanical strength, such as tensile strength, compared to foam, nonwoven fabric, and woven fabric. They also have superior processability (e.g., die-cutting processability). Therefore, adhesive sheets using a base material containing a resin film are advantageous in terms of processability, dimensional accuracy, and handling. Substrates containing such resin films can also be preferred as substrates in the technologies disclosed herein from the viewpoint of dimensional stability, thickness accuracy, and economic efficiency (cost).

[0087] Preferred resin materials constituting the resin films disclosed herein include polyolefin resins and polyester resins. Here, a polyolefin resin refers to a resin containing polyolefin in a proportion of more than 50% by weight. Similarly, a polyester resin refers to a resin containing polyester in a proportion of more than 50% by weight. Examples of polyolefin resin films include polyethylene (PE) resins, polypropylene (PP) resins, ethylene-propylene copolymers, and ethylene-butene copolymers. Examples of polyester resins include polyethylene terephthalate (PET) resins, polybutylene terephthalate (PBT) resins, polyethylene naphthalate resins, and polybutylene naphthalate resins. Among these, polyester resins are preferred from the viewpoint of anchoring ability (especially the anchoring ability of the acrylic adhesive layer), and PET resins are particularly preferred from the viewpoint of strength and processability.

[0088] The above-mentioned base film (e.g., resin film) may contain various additives as needed, such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, and plasticizers. The proportion of each additive is usually less than 30% by weight (e.g., less than 20% by weight, typically less than 10% by weight).

[0089] A transparent film (e.g., a transparent resin film) can preferably be used as the base film (e.g., a resin film). Such a base film may be substantially free of colorants from the viewpoint of strength, etc. Here, "substantially free of colorants" means that the colorant content is less than 1% by weight, preferably less than 0.1% by weight. Alternatively, the base film in the technology disclosed herein may be colored black, white (e.g., milky white), or other colors in order to exhibit desired design and optical properties (e.g., light shielding) in the adhesive sheet. The above coloring can be carried out, for example, by blending a known organic or inorganic colorant (pigment, dye, etc.) into the material constituting the base film.

[0090] The base film disclosed herein 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, the base film is preferably a single-layer structure. The method for manufacturing the base film (typically a resin film) is not particularly limited and can 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 used as appropriate.

[0091] The surface of the above-mentioned base film (e.g., resin film) 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 (formation of a primer layer). Such surface treatments may be performed to improve the adhesion between the base film and the adhesive layer, or the adhesion between the base film and the colored layer laminated on its back surface. The technology disclosed herein can preferably be implemented in a manner in which no primer layer is formed between the base film and the adhesive layer and / or between the base film and the layer laminated on its back surface, and the base film and the adhesive layer, and / or the layer laminated on its back surface are in direct contact. An adhesive sheet with such a configuration can be thinner.

[0092] The thickness of the base film is not particularly limited. In some embodiments, the thickness of the base film may be, for example, approximately 200 μm or less, approximately 100 μm or less, 70 μm or less, or 50 μm or less. By making the base film thinner, the adhesive sheet can also be made thinner, which can be advantageous in terms of thinning, miniaturization, weight reduction, and resource conservation of the product to which the adhesive sheet is applied. In some preferred embodiments, the thickness of the base film may be, for example, 30 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, particularly preferably 5 μm or less, or for example, 3 μm or less. By limiting the thickness of the base film within the above range, for example, when the adhesive sheet disclosed herein is used as a heat dissipation sheet (typically a graphite sheet), the heat dissipation efficiency of the heat dissipation sheet can be improved. Note that in adhesive sheets with a thin base film, the rigidity of the adhesive sheet itself tends to be low, and workability and handling tend to decrease. Therefore, in embodiments where the adhesive sheet is handled together with a back support tape, there is a great advantage in using the back support tape to improve workability and other aspects. Furthermore, the lower limit of the thickness of the base film is preferably approximately 0.5 μm or more (for example, 1 μm or more) from the viewpoint of handling and processability. In some other embodiments, from the viewpoint of handling, the thickness of the base film may be 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more.

[0093] (colored layer) In some embodiments, the substrate may include a colored layer. In some preferred embodiments, the colored layer is laminated on the back side of the adhesive sheet of the substrate film and may be positioned between the matte layer (described later) and the substrate film. By positioning the colored layer on the back side of the adhesive sheet, the color and transparency of the adhesive sheet can be adjusted to obtain the desired design, light-shielding, and opacity. The color of the colored layer is not particularly limited, and various colors can be used depending on the purpose. In some preferred embodiments, the colored layer may be a black layer formed by, for example, black printing (e.g., a black printed layer). An adhesive sheet having a black layer as a colored layer can be preferably used, for example, for application to a graphite sheet.

[0094] The colored layer can be formed, for example, by applying a colored layer-forming composition containing a colorant and a binder to a substrate film. Any material known in the field of paints or printing can be used as the binder without particular limitations. Examples include polyurethane, phenolic resin, epoxy resin, urea-melamine resin, and polymethyl methacrylate. The colored layer-forming composition may be solvent-based, UV-curable, or thermosetting. The colored layer can be formed using any conventional method used for colored layer formation without particular limitations. For example, a method of forming the colored layer (printed layer) by printing, such as gravure printing, flexographic printing, or offset printing, can be preferred.

[0095] The colored layer may be a single-layer structure consisting of one layer, or it may be a multilayer structure including two, three or more sub-colored layers. A multilayer colored layer including two or more sub-colored layers can be formed, for example, by repeatedly applying (e.g., printing) a colored layer-forming composition. The color and amount of colorant contained in each sub-colored layer may be the same or different. For colored layers intended to provide light-shielding properties, a multilayer structure is particularly beneficial from the viewpoint of preventing the occurrence of pinholes and improving the reliability of light leakage prevention.

[0096] For coloring the colored layer, known pigments and dyes can be appropriately selected according to the desired color. While not particularly limited, examples of white pigments include titanium dioxide, zinc oxide, and lead white. Examples of black pigments include carbon black, acetylene black, pine soot, and graphite. These can be used individually or in combination of two or more.

[0097] The amount of coloring agent is set according to the required color and texture, and is not limited to a specific range, but it is appropriate to have approximately 1% by weight or more in the colored layer, preferably 2% by weight or more (for example, 5% by weight or more), and may be 15% by weight or more. Furthermore, it is appropriate to have approximately 65% ​​by weight or less of the above coloring agent, preferably 30% by weight or less (for example, 15% by weight or less), and may be 8% by weight or less.

[0098] The overall thickness of the colored layer is usually appropriate to be 0.1 μm or more, preferably 0.5 μm or more, and more preferably 0.7 μm or more. The overall thickness of the colored layer may also be approximately 0.8 μm or more, or approximately 1 μm or more. In some other embodiments, from the viewpoint of obtaining sufficient light shielding and opacity, the overall thickness of the colored layer may be 2 μm or more (e.g., 3 μm or more), or 4 μm or more. Furthermore, the overall thickness of the colored layer is usually appropriate to be 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. In some embodiments, the overall thickness of the colored layer can be approximately 3 μm or less, and even more preferably approximately 2 μm or less. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is usually preferably around 0.5 μm to 2 μm.

[0099] (Matte layer) In some embodiments, the substrate may include a matte layer. In some preferred embodiments, the matte layer may be laminated on the back side of the adhesive sheet of the substrate film and placed on the colored layer described above. Preferably, the matte layer is a layer (topcoat layer) that constitutes the back side of the substrate, and therefore the back side of the adhesive sheet. By placing the matte layer on the back side of the adhesive sheet, a desired appearance (specifically, a matte texture with suppressed gloss (reflected light)) can be obtained. In this specification, the term "matte layer" refers to a layer that reduces the gloss of the back side of the adhesive sheet when formed, and is also called a matte treatment layer or a matte layer. The presence or degree of gloss reduction can be determined by measuring the 60° gloss value described below. Since the surface of the matte layer may be the back side of the adhesive sheet, the 60° gloss value of the matte layer surface can take a value within the range shown above as the 60° gloss value of the back side of the adhesive sheet.

[0100] In some preferred embodiments, the matte layer may be positioned to cover the surface (outer surface) of the colored layer. This provides aesthetic appeal and texture through the lamination of the colored and matte layers, resulting in a desired appearance. The matte layer may also serve a protective function for the colored layer. From the viewpoint of efficiently adjusting the color of the adhesive sheet when viewed from the back using the colored layer, the matte layer is preferably transparent (including translucent). The matte layer may be a layer with a surface treatment such as embossing or sandblasting (a layer with a matte treated surface), or it may be a matte layer that has a matte finish when formed on the surface of the black layer by coating or the like. The matte layer typically has a single-layer structure, but it may also have a multi-layer structure.

[0101] The matte layer disclosed herein preferably has a matte finish due to its composition. For example, the matte layer may contain a matte material. This allows for the imparting of a matte finish without additional surface treatment. The matte material is typically granular and preferably transparent (typically colorless and transparent). The particle shape of the matte material is not particularly limited and may be spherical, etc.

[0102] The mat material may consist of organic particles, inorganic particles, or a combination of both. Examples of organic particles include acrylic resin particles such as polymethyl methacrylate particles, polystyrene particles, styrene-acrylic resin particles, polycarbonate particles, urethane resin beads, epoxy resin beads, polyester resin beads, and polyester-urethane resin beads. Examples of inorganic particles include silicon dioxide (silica) particles, titanium dioxide particles, barium sulfate particles, calcium carbonate particles, mica, and talc. These may be used individually or in combination of two or more. Among these, acrylic resin particles, urethane resin beads, and silica particles are preferred.

[0103] The average particle diameter of the matting material is not particularly limited, and in some embodiments, it is appropriate to be approximately 0.1 μm or more, preferably 0.5 μm or more, and may be, for example, 1 μm or more, or even greater than 1 μm. Also, in some embodiments, the above average particle diameter is appropriate to be 20 μm or less, preferably 8 μm or less, and may be, for example, 3 μm or less, or even 2 μm or less. From the viewpoint of fully exhibiting mattiness, the average particle diameter of the matting material is preferably half or more of the thickness of the matting layer, and preferably equal to or greater than the thickness of the matting layer. From the viewpoint of appearance and coating properties, the average particle diameter of the matting material is preferably about 10 times or less (for example, 5 times or less, typically 3 times or less) the thickness of the matting layer. Note that the average particle diameter of the matting material refers to the particle size at which the cumulative particle size by volume in the particle size distribution obtained by measurement based on the laser diffraction-scattering method becomes 50%, i.e., the 50% volume average particle diameter (50% median diameter).

[0104] The content of the matting material is not particularly limited, and in some embodiments, the content of the matting material in the matting layer is suitable to be approximately 0.5% by weight or more, preferably 1% by weight or more, and may be, for example, 2% by weight or more, or 3% by weight or more. Also, in some embodiments, the content of the matting material in the matting layer is suitable to be approximately 40% by weight or less, preferably 20% by weight or less, and may be, for example, 10% by weight or less, or 8% by weight or less.

[0105] The matte layer may contain resin components and other additives such as dispersants. If the matte layer is transparent, it may have a composition that is substantially free of colorants. Here, "substantially free of colorants" means that the colorant content is less than 1% by weight, preferably less than 0.1% by weight.

[0106] Examples of resin components included in the mat layer include polyurethane resins, phenolic resins, epoxy resins, urea-melamine resins, silicone resins, phenoxy resins, methacrylic resins, acrylic resins, polyarylate resins, polyester resins, polyolefin resins, polystyrene resins, styrene-acrylic resins, styrene-maleic acid resins, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, polyvinyl acetate, polyvinylidene chloride, polycarbonate, celluloses, polyacetal, and alkyd resins. Polyurethane resins are preferably used. The resin components can be used individually or in combination of two or more. The resin composition for forming the above mat layer (resin composition for mat layer formation) may be a solvent-type composition, a thermosetting composition, or an ultraviolet-curing composition, but from the viewpoint of layer-forming properties and heat resistance, a thermosetting or ultraviolet-curing type is preferred. Examples of commercially available resin compositions for matte layer formation that can be used in the technology disclosed herein include products from Tokyo Ink Co., Ltd., such as "LG6620" and "LG6510".

[0107] The method for forming a matte layer using the above-mentioned matte layer-forming composition is not particularly limited, and various printing methods can be employed. The printing method is not particularly limited, and various known or conventional methods such as offset printing, screen printing, letterpress printing, flexographic printing, and gravure printing can be appropriately employed. Specifically, the matte layer can be formed by dissolving or dispersing the solid components constituting the above-mentioned composition (typically resin components and dispersants) in a suitable solvent, and then printing the resulting composition onto a black layer using an appropriate method from among the above-mentioned printing methods.

[0108] The thickness of the matte layer is appropriately set to approximately 0.1 μm or more, taking into consideration the imparting of a matte finish and the ease of coating. In some preferred embodiments, it is approximately 0.2 μm or more, for example, 0.3 μm or more, 0.5 μm or more, or 0.7 μm or more (for example, 0.9 μm or more). Furthermore, from the viewpoint of thinning, the above thickness is appropriately set to approximately 5 μm or less. In some preferred embodiments, it is approximately 3.0 μm or less, for example, 2 μm or less, 1.5 μm or less, or 1.2 μm or less.

[0109] (Other layers) The substrate may also have layers other than the substrate film, black layer, and matte layer described above. For example, an adhesive layer or an undercoat layer may be provided to obtain interlayer adhesion.

[0110] While not particularly limited, the total thickness of the substrate (layer) in the adhesive sheet disclosed herein is, for example, approximately 200 μm or less, but may also be approximately 100 μm or less, 70 μm or less, or 50 μm or less. By reducing the total thickness of the substrate, the adhesive sheet can also be made thinner, which can be advantageous in terms of thinning, miniaturization, weight reduction, and resource conservation of the product to which the adhesive sheet is applied. In some preferred embodiments, the total thickness of the substrate is, for example, 30 μm or less, more preferably 20 μm or less, even more preferably 12 μm or less, and particularly preferably 6 μm or less (for example, 5 μm or less). By limiting the total thickness of the substrate as described above, in a configuration in which the total thickness of the adhesive sheet is limited to below a predetermined level, the ratio of the thickness of the adhesive layer can be increased, and higher adhesive performance can be obtained. Also, for example, when the adhesive sheet disclosed herein is used as a heat dissipation sheet (typically a graphite sheet), the heat dissipation efficiency of the heat dissipation sheet can be improved. Furthermore, in adhesive sheets with a thin base material, the rigidity of the adhesive sheet itself tends to be low, resulting in reduced workability and handling. Therefore, in embodiments where the sheet is handled together with a back support tape, there is a significant advantage in improving workability and other aspects by using the back support tape. The lower limit of the total thickness of the base material is not particularly limited, but from the viewpoint of handling and processability, for example, it is 1 μm or more, usually 2 μm or more is appropriate, and 3 μm or more (for example, 3.5 μm or more) is preferred. The total thickness of the base material in some other embodiments may be 5 μm or more, 12 μm or more, 16 μm or more, 20 μm or more, or 25 μm or more, from the viewpoint of light shielding and handling.

[0111] <Characteristics of adhesive sheets, etc.> (holding force) In some embodiments, the adhesive sheet preferably exhibits a shear distance of 1.0 mm or less in a holding force test conducted under conditions of 80°C, 500 g load, and 60 minutes. Adhesive sheets satisfying this characteristic have excellent holding force (more specifically, high-temperature holding force), enabling reliable fixing and covering in various applications. Adhesive sheets having the above holding force characteristics are particularly suitable for portable electronic devices where the interior may be exposed to high temperatures. The shear distance in the above holding force test is preferably approximately 0.5 mm or less, more preferably approximately 0.3 mm or less, even more preferably approximately 0.2 mm or less, and particularly preferably approximately 0.1 mm or less. The above holding force test is specifically carried out by the method described in the examples below.

[0112] (Probe tack) In some embodiments, the adhesive sheet exhibits a probe tack of 100 kN / m² in a probe tack test conducted at a temperature of 23°C in accordance with ASTM D2979 (Test method for pressure-sensitive tackiness of adhesives using a fall test machine). 2 The above is preferable. An adhesive sheet satisfying these characteristics has good tack, making it easy to align, allowing the time required for pressing and curing to be within a predetermined range, and easily exhibiting good adhesion even to rough surfaces. According to the technology disclosed herein, the above tack characteristics are achieved in a thin adhesive layer. The above probe tack is 120 kN / m 2 It may be greater than or equal to 150 kN / m 2 The above is also acceptable, 180kN / m 2 The above is also acceptable. Furthermore, the upper limit of the probe tack is not particularly limited, but considering the balance with cohesive force and consequently holding force, 240 kN / m is appropriate. 2 The following is suitable, preferably 220 kN / m 2 The following applies, and the load is 200 kN / m 2 The following may also be true: 170 kN / m 2 The following is also acceptable: 140kN / m 2 The following is also acceptable: 130kN / m 2 The following is also acceptable: 120 kN / m 2 The following is also acceptable: 110kN / m 2The following is also acceptable. Specifically, the above probe tack test is carried out by the method described in the examples below.

[0113] In some preferred embodiments, the adhesive sheet has a shear distance of 1.0 mm or less in the holding force test and a probe tack value of 100 kN / m in the probe tack test. 2 The above is the conclusion. According to the adhesive sheet that satisfies the above holding force characteristics and tack characteristics, in the embodiment in which the adhesive layer is configured to be thin, it is possible to achieve reliable fixing and coating based on sufficient holding force (more specifically, high-temperature holding force), and the alignment, productivity and adhesion to rough surfaces are easily improved due to the good tack. Accordingly, according to this specification, an adhesive sheet having an acrylic adhesive layer with a thickness of 10 μm or less, wherein the shear distance in the above holding force test is 1.0 mm or less, and the probe tack value in the above probe tack test is 100 kN / m 2 The above adhesive sheet may be provided.

[0114] (Adhesion to SUS) While not particularly limited, in some embodiments, the adhesive sheet preferably has a 180-degree peel strength (adhesion to SUS) of 1.0 N / 25 mm or more against a stainless steel plate. An adhesive sheet exhibiting the above characteristics can adhere well to an adherend (e.g., a graphite sheet). It is also suitable for uses that include, for example, temporarily attaching a back support tape to the back for handling. The above adhesion to SUS is more preferably 1.5 N / 25 mm or more, even more preferably 2.0 N / 25 mm or more, and may be, for example, 2.5 N / 25 mm or more, or 3.0 N / 25 mm or more. In some other embodiments, with emphasis on adhesion to the adherend, the above adhesion to SUS is 5 N / 25 mm or more, and may be, for example, 8 N / 25 mm or more, or 12 N / 25 mm or more (e.g., 15 N / 25 mm or more). The upper limit of the adhesive strength to SUS mentioned above is not particularly limited; for example, it may be 30 N / 25 mm or less, 20 N / 25 mm or less, or 10 N / 25 mm or less (for example, 7 N / 25 mm or less).

[0115] The above adhesion strength to SUS is measured using a stainless steel plate as the adherend, under conditions of 23°C and 50% RH, in accordance with JIS Z 0237:2000, with a tensile speed of 300 mm / min and a peeling angle of 180 degrees. More specifically, it is measured using the following method: A measurement sample is prepared by cutting the adhesive sheet to a size of 25 mm in width and 100 mm in length. If the object to be measured is a single-sided adhesive sheet, a commercially available single-sided adhesive tape (for example, product name "No. 31B", acrylic single-sided adhesive tape with polyester film base manufactured by Nitto Denko Corporation; base thickness is approximately 25 μm, total thickness is approximately 53 μm) is attached to the back of the single-sided adhesive sheet to provide backing, and then the sample is cut to the specified size to prepare the measurement sample. If the object to be measured is a double-sided adhesive sheet, a 50 μm thick PET film is attached to one side (non-measurement surface) of the double-sided adhesive sheet to provide backing, and then the sample is cut to the specified size to prepare the measurement sample. For the prepared measurement sample, the adhesive surface of the measurement sample is pressed onto the surface of a stainless steel plate (SUS304BA plate) that has been cleaned with ethyl acetate by rolling a 2kg roller back and forth once, in an environment of 23°C and 50%RH. After leaving it in the same environment for 30 minutes, the peel strength (adhesion to SUS) [N / 25mm] to the stainless steel plate is measured using a tensile testing machine in accordance with JIS Z 0237:2000, under conditions of a tensile speed of 300mm / min and a peel angle of 180 degrees. The tensile testing machine is not particularly limited, and for example, Minebea's "Tensile and Compression Testing Machine, TG-1kN" or an equivalent product can be used.

[0116] (60° gross value) While not particularly limited, in some embodiments, the 60° gloss value of the back surface of the adhesive sheet (typically a single-sided adhesive sheet) may be 15 or less. Such low gloss can give the back surface of the adhesive sheet a high-quality appearance with suppressed gloss. The 60° gloss value of the back surface of the adhesive sheet is preferably 10 or less (e.g., less than 9), more preferably 8 or less, and may also be 6 or less, or 5 or less. The lower limit of the 60° gloss value of the back surface of the adhesive sheet is not particularly limited, and in some embodiments, it may practically be 0.5 or more, 1.0 or more, 2.0 or more, 3.0 or more, or 4.0 or more. The gloss value can be adjusted by the composition of the matte layer formed on the back side of the adhesive sheet, or by matte treatment (surface treatment) methods such as embossing or sandblasting.

[0117] The 60° gloss value on the back of the adhesive sheet is measured using a commercially available gloss meter (for example, the "High Gloss Checker IG-410" manufactured by Horiba, Ltd.) under conditions of a 60° measurement angle. The same applies to the examples described later.

[0118] (light transmittance) The light transmittance of the adhesive sheet disclosed herein is not particularly limited and may be, for example, 50% or less, or 30% or less. In some embodiments, the light transmittance of the adhesive sheet is preferably 20% or less. This allows the adhesive sheet to exhibit good light shielding properties. In some other embodiments, the light transmittance may be 15% or less, 10% or less, 5% or less, or 3% or less, 2.5% or less, or less than 1%, from the viewpoint of obtaining sufficient light shielding and masking (concealing) properties of the adherend. Also, in some embodiments, the light transmittance may be 0.5% or more, 1% or more, or 5% or more. Such an adhesive sheet can appropriately reflect the color of the adherend (e.g., a graphite sheet) to impart the desired color, texture, and design. From this viewpoint, the light transmittance may be 10% or more, 12% or more, 14% or more, or 15% or more.

[0119] The light transmittance of the adhesive sheet is determined by irradiating light with wavelengths of 380 to 780 nm perpendicularly to one surface of the adhesive sheet using a commercially available spectrophotometer and measuring the intensity of the light transmitted through the other surface. As the spectrophotometer, for example, a spectrophotometer manufactured by Hitachi, Ltd. (device name "U4100 type spectrophotometer") can be used. The same applies to the examples described later.

[0120] (L * a * b * (Colorimetric characteristics) Although not particularly limited, in some embodiments, the back surface of the adhesive sheet (typically a single-sided adhesive sheet) has a lightness L * a * b * specified in the L * a * b color system of 50 or less, and may be, for example, 40 or less, or 35 or less. The above lightness L * is preferably 30 or less, and may be less than 25. The adhesive sheet having such a lightness can have a color tone suitable for various applications where black is desired. The adhesive sheet having the above lightness is preferably used for applications where it is pasted on a graphite sheet. There is no particular limitation on the lower limit value of the above lightness L * and it can be set to approximately 15 or more (for example, 20 or more) from the viewpoint of appearance and the like. The adhesive sheet having a back surface with the 60° gloss value and lightness L

[0121] appropriately adjusted can exhibit a thick and heavy black color with suppressed gloss, and thus can be particularly preferably applied to applications where that kind of design property is required. The adhesive sheet having the above back surface can have a color tone that is well coordinated with its peripheral members (for example, a battery) by being laminated on a graphite sheet, for example. * a * b * The chromaticity a specified in the L * a b color system is not particularly limited, and it is preferably in the range of ±15 (for example, ±5, typically ±2) in consideration of the color tone harmony with the periphery of the part (which can be a member) to which the adhesive sheet is applied. The chromaticity b<C *This range is not particularly limited, but is preferably within ±15 (for example, ±10, typically ±5). In this specification, "range of ±X" means the range from -X to +X.

[0122] Note that L in this specification * a * b * The color system shall conform to the regulations recommended by the International Commission on Illumination in 1976 or the regulations of JIS Z 8729. Specifically, L * a * b * To do this, use a colorimeter (product name "CR-400" manufactured by Minolta Corporation; colorimeter) to take measurements at multiple locations (for example, 5 or more points) on the back of the adhesive sheet and use the average value.

[0123] (Surface properties of the back of the adhesive sheet) While not particularly limited, in some embodiments, it is appropriate that the surface roughness (Sa) of the back surface of the adhesive sheet (typically a single-sided adhesive sheet) be in the range of 0.15 μm to 0.70 μm. Here, surface roughness (Sa) is the surface roughness (Sa) as defined in ISO 25178, and is the average value of the height from the average surface obtained by three-dimensional surface texture measurement. By setting the surface roughness (Sa) of the back surface of the adhesive sheet to the range of 0.15 to 0.70 μm, good workability can be easily obtained when handling it together with back support tape. For example, even when using different back support tapes, it is possible to maintain the peelability of the release liner and the removeability of the back support tape, thereby obtaining good workability. In maintaining or improving good workability, the degree of dependence on the back support tape and release liner can be reduced. Also, for example, by improving the removeability of the back removal tape, it is easier to prevent the occurrence of problems such as damage to the adherend when removing the back support tape from the back surface of the adhesive sheet after application to the adherend. According to some aspects of the technology disclosed herein, for example, when handled together with a back support tape, good workability can be easily obtained in a series of processes, such as from removing the release liner to attaching to the substrate and then removing the back support tape.

[0124] In some preferred embodiments, the surface roughness (Sa) of the back surface of the adhesive sheet may be 0.20 μm or more, 0.25 μm or more, 0.30 μm or more, 0.35 μm or more, 0.40 μm or more, or 0.45 μm or more (for example, 0.60 μm or more). The greater the surface roughness (Sa) of the back surface of the adhesive sheet, the easier it tends to peel the back support tape from the back surface. In particular, the effect of improving the peelability of back support tapes with relatively high adhesive strength tends to be greater. In some preferred embodiments, the surface roughness (Sa) of the back surface of the adhesive sheet may be 0.65 μm or less, 0.60 μm or less, 0.55 μm or less, 0.50 μm or less, 0.45 μm or less, 0.40 μm or less, 0.35 μm or less, or 0.30 μm or less. The lower the surface roughness (Sa) of the back of the adhesive sheet, the easier it tends to be to peel off the release liner. For example, even when a back support tape is attached to the back of the adhesive sheet, it tends to be easier to peel off the release liner.

[0125] In some embodiments, the back surface of the adhesive sheet (typically a single-sided adhesive sheet) has a core void volume (Vvc) of 0.10 to 1.20 μm in the load curve obtained by three-dimensional surface property measurement. 3 / μm 2 It is preferable that this is the case. Here, the void volume (Vvc) of the core portion on the back of the adhesive sheet is a type of functional (volume) parameter defined in ISO 25178, and refers to the volume of voids (space; space other than the back protrusions) in the region (core portion) corresponding to the load area ratio of 10% to 80% in the load curve (cumulative histogram) of the total height data obtained by three-dimensional surface property measurement. The void volume (Vvc) of the core portion is 0.10 to 1.20 μm 3 / μm 2By being within this range, the back support tape adheres to the back of the adhesive sheet with appropriate adhesion, making it easier to achieve both the peelability of the release liner and the removeability of the back support tape. More specifically, this is based on the following findings. That is, the adhesive surface of the back support tape adheres to fill the irregularities on the back of the adhesive sheet, and it is thought that the spatial volume of the core (Vvc) among the functional (volume) parameters defined in ISO 25178 is particularly related to the portion to which the adhesive surface of the back support tape adheres. Therefore, as a result of verifying the relationship between the spatial volume of the core (Vvc) and the adhesion of the back support tape, it was found that when the spatial volume of the core (Vvc) is within a predetermined range, the adhesion of the back support tape can be controlled and adjusted to a range that makes it easy to achieve both the peelability of the release liner and the removeability of the back support tape. It should be noted that the above explanation is based on one of the inventors' findings and considerations, and the technology disclosed herein is not limited to the above interpretation.

[0126] In some preferred embodiments, the void volume (Vvc) of the core is 0.20 μm 3 / μm 2 It may be greater than or equal to 0.30 μm 3 / μm 2 The above is also acceptable, 0.50 μm 3 / μm 2 The above is also acceptable, 0.70 μm 3 / μm 2 The above is also acceptable, 0.90 μm 3 / μm 2 The above is also acceptable. In some preferred embodiments, the void volume (Vvc) of the core portion is 1.10 μm 3 / μm 2 The following is also acceptable: 1.00 μm 3 / μm 2 The following is also acceptable: 0.80 μm 3 / μm 2 The following is also acceptable: 0.60 μm 3 / μm 2 The following is also acceptable: 0.45 μm 3 / μm 2 The following is also acceptable.

[0127] The surface roughness (Sa) and core void volume (Vvc) of the back surface of the adhesive sheet described above are the three-dimensional surface roughness (Sa) and core void volume (Vvc) as defined in ISO 25178, respectively, and are determined by three-dimensional surface property measurement. Specifically, the surface roughness (Sa) and core void volume (Vvc) can be measured using a 3D measuring laser microscope (for example, the "LEXT OLS4000" product name from Olympus Corporation). The specific measurement operation and measurement conditions are appropriately set according to the object to be measured and the measuring device. The surface roughness (Sa) and core void volume (Vvc) described in the examples below were measured using the "LEXT OLS4000" product name from Olympus Corporation under the conditions of objective lens: 50x and measurement area: 1024 μm × 1024 μm.

[0128] The surface roughness (Sa) of the back surface of the adhesive sheet and the void volume (Vvc) of the core can be adjusted by, for example, the composition of the mat layer (e.g., the inclusion of organic or inorganic particles, the type and size of the particles, the amount, etc.) or the method of forming the mat layer (e.g., the selection of a printing method such as gravure printing, the setting of the gravure printing plate size, the surface treatment of the mat layer surface such as embossing or sandblasting, etc.).

[0129] (Total thickness of adhesive sheet) The total thickness of the adhesive sheet disclosed herein (including the adhesive layer and substrate, but not the release liner) is not particularly limited, but is preferably about 250 μm or less, and may be 150 μm or less. In some embodiments, the total thickness of the adhesive sheet is preferably, for example, 100 μm or less, may be 50 μm or less, or 30 μm or less. An adhesive sheet configured to be so thin can be advantageous in terms of thinning, miniaturization, weight reduction, and resource conservation of the product to which the adhesive sheet is applied (e.g., portable electronic devices such as smartphones). Also, for example, an adhesive sheet with a limited thickness as described above is advantageous when handled with a back support tape attached. In some preferred embodiments, the total thickness of the adhesive sheet is 20 μm or less, more preferably 15 μm or less, even more preferably 12 μm or less, particularly preferably 10 μm or less, may be 8 μm or less, or 5 μm or less. When the adhesive sheet disclosed herein is used for attaching to a graphite sheet, the heat dissipation effect of the graphite sheet is fully realized by making the adhesive sheet thin. Furthermore, with thin adhesive sheets, the rigidity of the adhesive sheet itself tends to decrease, reducing workability and handling. Therefore, there is a significant advantage in improving workability and other aspects by using a back support tape. In addition, the lower limit of the total thickness of the adhesive sheet is appropriately set to approximately 2 μm or more, for example, it may be 3 μm or more, 5 μm or more, 7 μm or more, or 9 μm or more. This allows the components of the adhesive sheet to have sufficient thickness, making it easier to exhibit desired properties (adhesion strength, handling, processability, etc.). In some other embodiments, from the viewpoint of handling and obtaining sufficient adhesive properties (e.g., adhesion strength) by increasing the thickness of the adhesive layer, the total thickness of the adhesive sheet is 10 μm or more, for example, it may be 20 μm or more, 30 μm or more, or 40 μm or more.

[0130] <Removable Liner> In the technologies disclosed herein, release liners can be used during the formation of the adhesive layer, the manufacture of adhesive sheets, storage of adhesive sheets before use, distribution, and shaping. The release liner is not particularly limited, and for example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or a release liner made of a low-adhesion material such as a fluoropolymer (polytetrafluoroethylene, etc.) or a polyolefin resin (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. In a release liner used for a single-sided adhesive sheet, the surface that contacts the adhesive surface of the adhesive sheet is usually configured as a release surface (release treatment surface), and the other surface may be a non-release treatment surface.

[0131] The thickness of the release liner (total thickness of the release liner) is not particularly limited, but from the viewpoint of peelability, handling, strength, etc., it is preferably about 10 μm or more (more preferably 15 μm or more, for example 25 μm or more), and preferably about 500 μm or less (typically 200 μm or less, preferably 100 μm or less, for example 75 μm or less).

[0132] <Back support tape> In some embodiments, an adhesive sheet (typically a single-sided adhesive sheet) may be used in a manner in which a back support tape is attached to its back surface (typically temporarily attached). This protects the back surface of the adhesive sheet while improving workability and handling during application to the substrate, regardless of the thickness, strength, rigidity, etc., of the adhesive sheet.

[0133] The back support tape is not particularly limited and can be appropriately selected from known adhesive sheets. Typically, a back support tape having an adhesive layer on one or both sides of the substrate can be used. A preferred example of a back support tape is a single-sided adhesive tape with an adhesive layer on one side of the substrate. Various types of surface protection films and surface protection sheets are preferably used as back support tapes with such a configuration.

[0134] The base material constituting the back support tape can be a resin film, paper, cloth, rubber film, foam film, metal foil, composites or laminates thereof, etc. For example, a base material containing a resin film is preferably used. Suitable examples of resin materials constituting the resin film include polyolefin resins (e.g., PE resins) and polyester resins (e.g., PET), which were exemplified as base films for adhesive sheets. The thickness of the base material is not particularly limited, but from the viewpoint of achieving a good balance between the purpose of back support and flexibility, it is usually appropriate to use a back support tape with a base material having a thickness of about 10 μm to 200 μm. The thickness of the base material of the above back support tape may be 20 μm or more, or 30 μm or more. Also, the thickness may be 100 μm or less, or 80 μm or less.

[0135] The type of adhesive constituting the adhesive layer of the back support tape is not particularly limited and may be, for example, rubber-based (natural rubber, synthetic rubber, mixtures thereof, etc.), acrylic-based, polyester-based, urethane-based, polyether-based, silicone-based, or polyamide-based adhesives. In some embodiments, rubber-based adhesives such as natural rubber-based adhesives and acrylic-based adhesives are preferably used due to their versatility and cost-effectiveness. In some other embodiments, silicone-based adhesives may be preferably used from the viewpoint of low contamination and re-peelability. The thickness of the adhesive layer is not particularly limited, and considering the balance between adhesion to the back of the adhesive sheet that is adhered to and re-peelability, it is usually appropriate to use a back support tape having an adhesive layer with a thickness of about 2 μm to 50 μm. The thickness of the adhesive layer of the above back support tape is preferably 5 μm or more, and may be, for example, 7 μm or more. Also, the above thickness is preferably 30 μm or less, and may be, for example, 20 μm or less.

[0136] (Peel strength of the back support tape) While not particularly limited, in some embodiments, the peel force of the back support tape on the back of the adhesive sheet disclosed herein is preferably less than 1.4 N / 50 mm. A peel force less than a predetermined value makes it easier to peel the back support tape from the back of the adhesive sheet, thus preventing damage to the adherend when removing the back support tape from the back of the adhesive sheet after application. From this viewpoint, the peel force of the back support tape is more preferably less than 1.0 N / 50 mm, even more preferably less than 0.8 N / 50 mm, and particularly preferably less than 0.6 N / 50 mm. Furthermore, in some embodiments, a peel force greater than 0.05 N / 50 mm is appropriate. A peel force of the back support tape above a predetermined value ensures that the back support tape adheres closely to the back of the adhesive sheet, and the back of the adhesive sheet is adequately protected by the back support tape. Additionally, handling the back support tape while it is in close contact with the back of the adhesive sheet allows for good workability. Furthermore, when the back support tape is attached to the back of the adhesive sheet, the peeling liner tends to be easier to remove. From this viewpoint, the peeling force of the back support tape is preferably greater than 0.07 N / 50 mm, more preferably greater than 0.09 N / 50 mm, and even more preferably greater than 0.10 N / 50 mm (for example, 0.12 N / 50 mm or more).

[0137] In embodiments using various types of back support tapes, such as acrylic and natural rubber, the peeling force of the various back support tapes (e.g., acrylic back support tape and natural rubber back support tape) can fall within the above range, based on the surface roughness (Sa) of the back surface of the adhesive sheet. This makes it easier to obtain good workability when peeling the release liner or removing the back support tape. In some preferred embodiments, it is preferable that the peeling force of the back support tapes measured using two or more types of back support tapes (acrylic back support tape and natural rubber back support tape) all fall within the above range. By satisfying these characteristics, it is possible to maintain the peelability of the release liner and the removeability of the back support tape even in embodiments where two or more types of back support tapes are used, thereby obtaining good workability.

[0138] The peel force of the back support tape described above is measured by peeling off the back support tape attached to the back of the adhesive sheet disclosed herein in a 180-degree direction at a tensile speed of 300 mm / min in accordance with JIS Z 0237, under conditions of 23°C and 50% humidity. More specifically, it is measured by the following method: Under conditions of 23°C and 50% humidity, a 50 μm thick transparent PET film (product name "Lumirror", manufactured by Toray Industries, Inc.) for reinforcement is attached to the adhesive surface of a single-sided adhesive sheet. Next, a back support tape cut to a width of 50 mm is pressed onto the back of the adhesive sheet by pressing a 5 kg roller back and forth once. After leaving this in a 23°C and 50% humidity environment for 30 minutes, the peel force [N / 50 mm] of the back support tape is measured by peeling off the back support tape in a 180-degree direction at a tensile speed of 300 mm / min in accordance with JIS Z 0237, under the same conditions.

[0139] While not particularly limited, the back support tape preferably uses an adhesive tape (e.g., a surface protective film) with a 180-degree peel strength (adhesion to SUS) of approximately 0.1 N / 20 mm to 5.0 N / 20 mm on a stainless steel plate. From the viewpoint of adhesion to the back of the adhesive sheet, the above adhesion to SUS may be, for example, 0.5 N / 20 mm or more, 0.8 N / 20 mm or more, or 1.0 N / 20 mm or more. Furthermore, the adhesion to SUS of the back support tape may be 4.0 N / 20 mm or less, 3.0 N / 20 mm or less, or 2.0 N / 20 mm or less (e.g., 1.5 N / 20 mm or less). The above adhesion to SUS is measured using a stainless steel plate (SUS430BA plate) as the adherend, in an environment of 23°C and 50% RH, in accordance with JIS Z 0237:2000, under conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees. The appropriate conditions for pressing the stainless steel plate are 23°C, 50% RH, and one pass-through pressing with a 2kg roller. After pressing, the plate should be left in the same environment for 30 minutes before taking measurements.

[0140] The thickness of the back support tape is not particularly limited, but from the viewpoint of achieving a good balance between the purpose of back support and flexibility, it is usually appropriate to use a back support tape with a thickness of 15 μm to 250 μm. The thickness of the above back support tape may be 25 μm or more, for example, 35 μm or more. Alternatively, the thickness of the above back support tape may be 150 μm or less, for example, 85 μm or less.

[0141] <How to use> While not particularly limited, in embodiments where the adhesive sheet disclosed herein is a single-sided adhesive sheet, the single-sided adhesive sheet can be used in the following manner, for example. That is, the adhesive sheet (single-sided adhesive sheet) has a back support tape attached to its back surface, with the adhesive surface of the adhesive layer covered by a release liner. This protects the back surface of the adhesive sheet and makes it easier to maintain the appearance of the back surface. Furthermore, by attaching the back support tape, the workability and handling until application to the substrate can be improved, regardless of the thickness, strength, rigidity, etc., of the single-sided adhesive sheet. Next, the release liner covering the adhesive surface of the adhesive sheet is peeled off. By using an adhesive sheet according to some embodiments disclosed herein, the release liner can be peeled off smoothly without any separation between the back support tape and the back surface of the adhesive sheet. Then, the adhesive surface exposed after the release liner is peeled off is attached to the substrate. In this way, the adhesive sheet is attached to the substrate. After the adhesive sheet is attached to the substrate, the back support tape attached to the back surface of the adhesive sheet is peeled off and removed from the adhesive sheet. In this case, the adhesive sheet described above makes it easier to prevent problems such as damage to the adherend when removing the back support tape from the back of the adhesive sheet. According to some aspects of the technology disclosed herein, the peelability of the release liner and the removeability of the back support tape can be maintained or improved, so good workability can be easily obtained in the series of processes from the removal of the release liner to application to the adherend and further removal of the back support tape. Details of the release liner and back support tape are as described above, so redundant explanations will be omitted.

[0142] As described above, the technology disclosed herein includes a method comprising the steps of: preparing an adhesive sheet with a release liner; attaching a back support tape to the back of the adhesive sheet; peeling off the release liner covering the adhesive surface of the adhesive sheet; attaching the adhesive surface of the adhesive sheet exposed by the peeling off of the release liner to a substrate; and removing the back support tape from the back of the adhesive sheet. Details of such a method are as described above, so redundant explanations will be omitted.

[0143] Furthermore, according to this specification, a laminate is provided comprising an adhesive sheet and a back support tape attached to the back surface of the adhesive sheet. In some embodiments, the adhesive sheet may be used in the form of a laminate in which the back support tape is laminated to the back surface of the adhesive sheet. Such a laminate may be in the form of a laminate with a release liner, which covers the adhesive surface of the adhesive sheet before being attached to an adherend. Such a laminate has a laminated structure in which the release liner, adhesive sheet and back support tape are arranged in this order. An example of the configuration of the above laminate is shown in Figure 3. The laminate 100 shown in Figure 3 comprises an adhesive sheet 1 and a back support tape 70 attached to the back surface 1B of the adhesive sheet 1. The adhesive sheet 1 comprises an adhesive layer 20 provided on one surface 10A of a base material 10. In addition, the laminate 100 before use has a configuration in which the adhesive layer 20 of the adhesive sheet 1 is protected by a release liner 50, the side of the adhesive layer 20 of the adhesive sheet 1 that has a release surface 50B. The specific configurations of the adhesive sheet 1 and the release liner 50 are as described in Figure 1 and will be omitted here. Although not shown in the figure, the back support tape 70 specifically comprises a base material and an adhesive layer provided on one side of the base material, with the adhesive layer side surface (adhesive surface) attached to the back surface 1B of the adhesive sheet 1.

[0144] <Application> The adhesive sheet disclosed herein has a thin adhesive layer while achieving both tack and holding power, and can therefore be used without particular limitations in various applications where a thin adhesive layer is required. For example, the adhesive sheet disclosed herein can be preferably applied to portable electronic devices where there is a strong need for thinness. For example, it is suitable for fixing components of portable electronic devices. Portable electronic devices can become hot inside, and it is desirable to use an adhesive sheet with sufficient high-temperature holding power. Specifically, it can be preferably used in portable electronic devices such as mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear-type devices worn on the wrist like watches, modular-type devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular types, 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 devices, electronic dictionaries, electronic organizers, e-books, in-car information equipment, portable radios, portable televisions, portable printers, portable scanners, and portable modems for purposes such as protecting various components, adding design elements, fixing various components, and fixing logos (design characters) and various designs (including various marks). In this specification, "portable" means not merely being able to carry something, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily.

[0145] In some preferred embodiments, the adhesive sheet disclosed herein is used by being attached to a graphite sheet. Graphite sheets are preferably used in various small electronic devices as heat dissipation sheets to release heat from heat-generating elements (batteries, IC chips, etc.). For example, the graphite sheet is placed adjacent to or around power-generating elements such as batteries and IC chips within the electronic device. By applying an adhesive sheet having a thin adhesive layer to a graphite sheet, the heat dissipation effect of the graphite sheet is easily fully realized. Furthermore, since graphite sheets can have uneven appearances, and thin ones are easily damaged, an adhesive sheet is preferably attached to their surface for purposes such as improving appearance and protection. The adhesive sheet disclosed herein, despite having a thin adhesive layer, has good tack and sufficient holding power, so it can be reliably adhered to the graphite sheet without impairing the heat dissipation performance of the graphite sheet. Furthermore, since some embodiments of the adhesive sheet have a colored layer and a matte layer on the back, applying such an adhesive sheet to a graphite sheet can provide a high-quality appearance with suppressed gloss due to the presence of the colored and matte layers on the back of the adhesive sheet. In particular, if the adhesive sheet has a black layer as the colored layer and a low light transmittance configuration, the back of the adhesive sheet can exhibit a rich black color, which can harmonize well with the color of the graphite sheet and its surrounding components. In addition, with some embodiments of the adhesive sheet, even when the adherend is a brittle material such as a graphite sheet, damage to the graphite sheet is less likely to occur, and good workability can be easily obtained. The thickness of the graphite sheet is approximately 4 to 100 μm, although this is not particularly limited.

[0146] In several other embodiments, the adhesive sheet disclosed herein is used by being attached to a ferrite sheet. Ferrite sheets are preferably used in various electronic devices as magnetic sheets that absorb electromagnetic waves emitted from, for example, electronic devices, or electromagnetic waves that penetrate electronic devices. For example, the ferrite sheet is placed in a position close to the antenna coil in an RFID (Radio Frequency Identification) tag in the above-mentioned electronic device, specifically between the antenna coil and a conductive member. Since thin ferrite sheets are brittle and easily damaged, an adhesive sheet is preferably attached to their surface for protection. By applying the adhesive sheet disclosed herein to a ferrite sheet, the ferrite sheet can be well protected. Furthermore, since the adhesive sheet according to some embodiments has a colored layer and a matte layer on the back surface, an improvement in appearance quality can be preferably achieved.

[0147] Figure 4 is a schematic exploded perspective view showing an example of the configuration of a display device in a portable electronic device to which the adhesive sheet disclosed herein may be applied. As shown in Figure 4, the display device 200 of the portable electronic device 300 comprises a display unit 220 composed of a cover member, an organic EL unit, etc., and a support unit 240. The display device 200 further includes 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 sheet) that fixes the members constituting the display unit 220 and the support unit 240. The support unit 240 is composed of a substrate (a metal plate such as a stainless steel plate or an aluminum plate), etc. The adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

[0148] The matters disclosed in this specification include the following: [1] A portable electronic device comprising a display unit including a cover member and an organic EL unit, and a support unit, An adhesive sheet is attached to the support portion. The aforementioned adhesive sheet has an adhesive layer with a thickness of 10 μm or less. The adhesive layer is an acrylic adhesive layer containing an acrylic polymer. The adhesive layer has a storage modulus of less than 0.1 MPa at 25°C and a storage modulus of 0.025 MPa or more at 80°C, in a portable electronic device. [2] The portable electronic device according to [1] above, wherein the monomer component constituting the acrylic polymer contains 75% by weight or more of alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms. [3] The adhesive layer is made of an adhesive resin T having a softening point of less than 145°C. L A portable electronic device as described in [1] or [2] above, including the above. [4] The portable electronic device according to any one of [1] to [3] above, wherein the adhesive layer contains a terpene phenol resin as a tackifying resin. [5] The portable electronic device according to any one of [1] to [4] above, wherein the adhesive composition used to form the adhesive layer comprises an isocyanate crosslinking agent and a non-isocyanate crosslinking agent. [6] The portable electronic device according to [5] above, wherein the adhesive composition comprises an epoxy crosslinking agent as the non-isocyanate crosslinking agent. [7] The portable electronic device according to any one of [1] to [6] above, further comprising a substrate layer supporting the adhesive layer. [8] The portable electronic device according to any one of [1] to [7] above, wherein the total thickness of the adhesive sheet is 20 μm or less. [9] The adhesive sheet is a portable electronic device according to any of [1] to [8] above, wherein the shear distance in a holding force test performed at a temperature of 80°C, a load of 500g, and for 60 minutes is 1.0 mm or less.

[10] The adhesive sheet has a probe tack value of 100 kN / m² in a probe tack test conducted at a temperature of 23°C in accordance with ASTM D2979 (Test method for pressure-sensitive tackiness of adhesives using a fall test machine). 2 The above-mentioned portable electronic device is one of the items described in [1] to [9] above.

[0149]

[11] An adhesive sheet having an adhesive layer with a thickness of 10 μm or less, The adhesive layer is an acrylic adhesive layer containing an acrylic polymer. The adhesive layer is an adhesive sheet having a storage modulus of less than 0.1 MPa at 25°C and a storage modulus of 0.025 MPa or more at 80°C.

[12] An adhesive sheet having an adhesive layer with a thickness of 10 μm or less, The adhesive layer is an acrylic adhesive layer containing an acrylic polymer. In a holding strength test conducted at a temperature of 80°C, a load of 500g, and for 60 minutes, the shear distance is 1.0 mm or less, and in a probe tack test conducted at a temperature of 23°C in accordance with ASTM D2979 (Test method for pressure-sensitive adhesion of adhesives using a fall test machine), the probe tack value is 100 kN / m 2 That's all for the adhesive sheet.

[13] The adhesive sheet according to

[11] or

[12] above, wherein the monomer component constituting the acrylic polymer contains 75% by weight or more of alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms.

[14] The adhesive layer is made of an adhesive resin T having a softening point of less than 145°C. L An adhesive sheet as described in any of the above

[11] to

[13] , including the above.

[15] The adhesive sheet according to any one of

[11] to

[14] above, wherein the adhesive layer contains a terpene phenol resin as a tackifying resin.

[16] The adhesive sheet according to any one of

[11] to

[15] above, wherein the adhesive composition used to form the adhesive layer comprises an isocyanate crosslinking agent and a non-isocyanate crosslinking agent.

[17] The adhesive sheet according to

[16] , wherein the adhesive composition comprises an epoxy crosslinking agent as the non-isocyanate crosslinking agent.

[18] The adhesive sheet according to any one of

[11] to

[17] , further comprising a substrate layer supporting the adhesive layer.

[19] The adhesive sheet according to any one of

[11] to

[18] above, wherein the total thickness of the adhesive sheet is 20 μm or less.

[0150]

[21] An adhesive sheet according to any one of

[11] to

[19] above, comprising a base film and the adhesive layer provided on one side of the base film, wherein the adhesive sheet is adhesive on one side.

[22] The adhesive sheet according to

[21] , wherein a colored layer and a matte layer are laminated in this order on the other side of the base film.

[23] The adhesive sheet according to

[21] or

[22] above, wherein the surface roughness (Sa) of the back surface of the adhesive sheet is in the range of 0.15 μm or more and 0.70 μm or less.

[24] The back surface of the adhesive sheet has a core void volume (Vvc) of 0.10 to 1.20 μm in the load curve obtained by three-dimensional surface property measurement. 3 / μm 2 The adhesive sheet described in any of the above

[21] to

[23] .

[25] The adhesive sheet according to any one of

[21] to

[24] above, wherein the thickness of the mat layer is 0.2 μm or more and 3.0 μm or less.

[26] The adhesive sheet according to any one of

[21] to

[25] above, wherein the total thickness of the adhesive sheet is 100 μm or less.

[27] An adhesive sheet according to any of

[21] to

[26] above, wherein the 180-degree peel strength to stainless steel plate is 1.0 N / 25 mm or more.

[0151]

[28] An adhesive sheet as described in any of

[11] to

[27] above, which is used by attaching it to a graphite sheet or a ferrite sheet.

[29] An adhesive sheet used in portable electronic devices, as described in any of

[11] to

[28] above.

[30] An adhesive sheet with a release liner, comprising an adhesive sheet as described in any of

[11] to

[29] above, and a release liner that covers the adhesive surface of the adhesive sheet.

[31] A laminate comprising an adhesive sheet as described in any of

[11] to

[29] above, and a back support tape attached to the back of the adhesive sheet. [Examples]

[0152] 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.

[0153] <Example 1> 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 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 way, 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. The Mw of this acrylic polymer was approximately 70 × 10⁻⁶ 4 That was the case. To 100 parts of the acrylic polymer contained in the above acrylic polymer solution, 20 parts of terpene phenol resin (product name "YS Polystar T-115", manufactured by Yasuhara Chemical Co., Ltd., softening point approximately 115°C, hydroxyl value 30-60 mg KOH / g) as a tackifying resin, 0.1 parts on a solids basis of isocyanate crosslinking agent (product name "Coronate L", manufactured by Tosoh Corporation, solids content 75%), and 0.01 parts of epoxy crosslinking agent (product name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) were added and stirred to prepare an adhesive composition.

[0154] As a release liner, a polyester release film (product name "Diafoil MRF", thickness 38 μm, manufactured by Mitsubishi Polyester Co., Ltd.) with one side treated for release was prepared. The above adhesive composition was applied to the release surface of the release liner to a thickness of 2 μm after drying, and dried at 100°C for 2 minutes. In this way, an adhesive layer was formed on the release surface of the release liner. The storage modulus of the obtained adhesive layer at 25°C was 0.080 MPa, and the storage modulus at 80°C was 0.032 MPa. A back layer forming substrate film (substrate) was prepared, in which a black printed layer of approximately 1 μm thickness was formed on one side (second surface) of a transparent PET film (product name "Mylar," manufactured by Teijin DuPont Films) with a thickness of 2 μm by gravure printing, and a matte layer of approximately 1 μm thickness was further formed on the black printed layer by gravure printing. The black printed layer was formed from materials available from Dainichi Seika Kogyo Co., Ltd. The matte layer was formed by applying a matte layer forming composition, which is made by adding and mixing a matting material to a resin material, to the surface of the black printed layer, and was formed from materials available from Tokyo Ink Co., Ltd. In the formation of the matte layer, the surface properties of the back of the substrate (back of the adhesive sheet) were adjusted by controlling the size of the gravure printing plate. A single-sided adhesive sheet according to this example was prepared by laminating the adhesive layer formed on the release liner onto the PET film side surface (first surface of the PET film layer) of the above-mentioned substrate (transfer method). This single-sided adhesive sheet comprises a base film and an adhesive layer provided on one side of the base film, with a colored layer and a matte layer laminated in that order on the other side of the base film. The release liner was left on the adhesive layer and used to protect the surface (adhesive surface) of the adhesive layer. The surface roughness (Sa) of the back of the adhesive sheet is 0.66 μm, and the void volume (Vvc) of the core is 1.08 μm. 3 / μm 2 Furthermore, the 60° gloss value on the back of the single-sided adhesive sheet in this example was 4.2, and the brightness L on the back was 4.2. * is 24.6, chromaticity a * is -0.4, chromaticity b * The value was -0.2, and the light transmittance was 2.4%.

[0155] <Examples 2-4 and Comparative Example 1> Using the adhesive composition used in Example 1, substrate-less double-sided adhesive sheets with adhesive layer thicknesses of 3 μm (Example 2), 5 μm (Example 3), 10 μm (Example), and 15 μm (Comparative Example 1) were obtained. Specifically, the 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 adhesive layers of the thicknesses shown in Table 1. The release surface of a 25 μm thick polyester release liner (product name "Diafoil MRF", manufactured by Mitsubishi Polyester Co., Ltd.) was bonded to each of the obtained adhesive layers. In this way, substrate-less double-sided adhesive sheets according to each example, in which both sides were protected by the two polyester release liners described above, were obtained.

[0156] <Comparative Example 2> In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 70 parts BA, 30 parts 2-ethylhexyl acrylate (2EHA), 3 parts AA, and 0.05 parts 4-hydroxybutyl acrylate as monomer components, along with toluene as the polymerization solvent, were charged and stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.1 parts AIBN as a polymerization initiator was added, and solution polymerization was carried out at 60°C for 6 hours, followed by aging at 80°C for 3 hours to obtain a toluene solution of acrylic polymer. The Mw of this acrylic polymer was approximately 40 × 10⁻⁶. 4 That was the case. To 100 parts of the acrylic polymer contained in the above toluene solution, 30 parts of polymerized rosin ester (trade name "Pencel D-125", softening point 120-130°C, manufactured by Arakawa Chemical Industries, Ltd.) and 2 parts of isocyanate crosslinking agent (trade name "Coronate L", manufactured by Tosoh Corporation, solids content 75%) (based on solids content) were added as tackifying resin to prepare the adhesive composition according to this example. A substrate-less double-sided adhesive sheet according to this example was prepared in the same manner as in Example 3, except that the obtained adhesive composition was used. The storage modulus of the adhesive layer according to this example was 0.122 MPa at 25°C and 0.023 MPa at 80°C.

[0157] <Comparative Example 3> 100 parts of the acrylic polymer obtained in Example 1, 30 parts of terpene phenol resin as a tackifying resin (product name "YS Polystar S-145", softening point approximately 145°C, manufactured by Yasuhara Chemical Co., Ltd.), 2 parts of the above isocyanate crosslinking agent (based on solid content), and 0.01 parts of the above epoxy crosslinking agent were added and stirred to prepare the adhesive composition according to this example. A substrate-less double-sided adhesive sheet according to this example was prepared in the same manner as in Example 3, except that the obtained adhesive composition was used. The storage modulus of the adhesive layer according to this example was 0.242 MPa at 25°C and 0.049 MPa at 80°C.

[0158] <Rating> [Retention strength test] Measurement samples were prepared by cutting adhesive sheets to a size of 10 mm in width and 100 mm in length. If the object to be measured was a single-sided adhesive sheet, a commercially available single-sided adhesive tape (product name "No. 31B", acrylic single-sided adhesive tape with polyester film base manufactured by Nitto Denko Corporation; base thickness approximately 25 μm, total thickness approximately 53 μm) was attached to the back of the single-sided adhesive sheet to provide backing, and then the sample was prepared by cutting it to the specified size. If the object to be measured was a double-sided adhesive sheet, a 50 μm thick PET film was attached to one side (non-measurement side) of the double-sided adhesive sheet to provide backing, and then the sample was prepared by cutting it to the specified size. Under conditions of 23°C and 50% RH, the adhesive surface of the measurement sample was pressed onto a bakelite plate (phenol resin plate) serving as the substrate, covering an area of ​​10 mm in width and 20 mm in length, by applying pressure with a 2 kg roller over one pass. The substrate to which the measurement sample was attached was then suspended in an 80°C environment with the length of the measurement sample oriented vertically, and left undisturbed for 30 minutes. Next, a load of 500 g was applied to the free end of the test piece, and it was left in an 80°C environment for 60 minutes under this load, in accordance with JIS Z0237. After 60 minutes, the displacement distance [mm] from the initial attachment position of the measurement sample was measured, and if the measurement sample peeled off and fell within 60 minutes, it was recorded as "fallen". In the holding power test, if the displacement distance after 60 minutes is 1.0 mm or less, it is judged to have sufficient holding power.

[0159] [Probe Tack Test] On the surface of the adhesive layer of the adhesive sheet, the probe tack [kN / m] was tested in accordance with ASTM D2979 (Test method for pressure-sensitive adhesion of adhesives using a fall test machine). 2 The probe tack value of the adhesive layer [kN / m] was measured. Specifically, a circular stainless steel probe (5 mm in diameter) in a tipping test machine was brought into contact with the surface of the adhesive layer (adhesive surface) exposed by peeling off the release liner, under a constant load (20 gf / 5 mmφ) for 1 second in an environment of 23°C. The force required to pull the probe perpendicularly away from the adhesive surface was then determined, and this was used as the probe tack value of the adhesive layer [kN / m 2 The probe contact and withdrawal speeds were set to 30 mm / min. The probe tack value was 100 kN / m 2 If the above conditions are met, the adhesive layer is determined to have sufficient tack.

[0160] The evaluation results, along with a summary of each case, are shown in Table 1.

[0161] [Table 1]

[0162] As shown in Table 1, the adhesive sheets according to Examples 1 to 4, which had an acrylic adhesive layer with a thickness of 10 μm or less, a storage modulus of elasticity at 25°C of less than 0.1 MPa, and a storage modulus of elasticity at 80°C of 0.025 MPa or more, showed a shear distance of 1.0 mm or less in the holding force test and a measured probe tack of 100 kN / m 2 The above results demonstrate a balance between tack and holding power. On the other hand, Comparative Example 1, in which the thickness of the adhesive layer was greater than 10 μm, had a storage modulus of less than 0.1 MPa at 25°C and a storage modulus of 0.025 MPa or higher at 80°C, but the shear distance in the holding power test was large. Furthermore, in Comparative Example 2, in which the storage modulus of the adhesive layer with a thickness of 10 μm or less was 0.1 MPa or higher at 25°C and less than 0.025 MPa at 80°C, both tack and holding power were insufficient. In Comparative Example 3, in which the storage modulus of the adhesive layer with a thickness of 10 μm or less was 0.025 MPa or higher at 80°C and 0.1 MPa or higher at 25°C, the results of the holding power test were at an acceptable level, but the tack was low. From the above results, it can be seen that in an acrylic adhesive layer with a thickness of 10 μm or less, both tack and holding power can be achieved by setting the storage modulus at 25°C to less than 0.1 MPa and the storage modulus at 80°C to 0.025 MPa or more.

[0163] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. [Explanation of symbols]

[0164] 1, 2 Adhesive sheets 1A Adhesive surface 1B Back 10 Base material (support) 10A One surface of the substrate (the surface with the adhesive layer) 10B The other surface of the substrate (back surface) 12. Base film 12A First surface of the substrate film 12B Second surface of the substrate film 14 Colored layer 16 matte layers 20, 21 Adhesive layer 50, 51, 52 Release Liner 70 Rear support tape 100-layer structure

Claims

1. An adhesive sheet having an adhesive layer with a thickness of 10 μm or less, The adhesive layer is an acrylic adhesive layer comprising an acrylic polymer and a tackifying resin. The acrylic polymer is of formula (1): CH 2 =C(R 1 )COOR 2 (1) A polymer of a monomer component containing more than 50% by weight of an alkyl (meth)acrylate represented by the above formula (1): (In the above formula (1), R1 is a hydrogen atom or a methyl group, and R2 is a chain alkyl group having 1 to 14 carbon atoms.) The adhesive composition used to form the adhesive layer comprises at least one crosslinking agent selected from 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. The adhesive layer has a storage modulus of 0.08 MPa or less at 25°C and a storage modulus of 0.030 MPa or more at 80°C. The adhesive sheet is an adhesive sheet in which the probe tack in a probe tack test conducted at a temperature of 23°C in accordance with ASTM D2979 (Test method for pressure-sensitive tackiness of adhesives using a fall test machine) is 100 kN / m² or more.

2. The adhesive sheet according to claim 1, wherein the monomer component constituting the acrylic polymer contains 75% by weight or more of an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms.

3. The adhesive layer comprises a tackifying resin T having a softening point of less than 145°C. Ｌ The adhesive sheet according to claim 1 or 2, comprising:

4. The adhesive sheet according to any one of claims 1 to 3, wherein the adhesive layer comprises a terpene phenol resin as the tackifying resin.

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

6. The adhesive sheet according to claim 5, wherein the adhesive composition comprises an epoxy crosslinking agent as the non-isocyanate crosslinking agent.

7. The adhesive sheet according to any one of claims 1 to 6, further comprising a base layer supporting the adhesive layer.

8. The adhesive sheet according to any one of claims 1 to 7, wherein the total thickness of the adhesive sheet is 20 μm or less.

9. An adhesive sheet according to any one of claims 1 to 8, which is used by attaching it to a graphite sheet or a ferrite sheet.

10. An adhesive sheet according to any one of claims 1 to 9, for use in portable electronic devices.

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