Resin for adhesive sheets and adhesive sheets

Abstract

Provided is a resin for an adhesive sheet that has reliability in joining so as not to peel away or shift, and that can be peeled away during removal without damaging an adherend, even when the resin for an adhesive sheet is affixed to a pliable adherend, an adherend having a brittle surface, or an adherend having low strength. In the provided resin for an adhesive sheet, the storage elastic modulus at 25°C is within the range of 10-500 MPa, the storage elastic modulus at 37°C is within the range of 0.5-20 MPa, and the surface hardness at 37°C is within the range of 0.1-2 MPa.

Description

[Technical Field]

[0001] The present invention relates to a resin for a pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet. This application claims priority based on Japanese Patent Application No. 2020-181692 filed on October 29, 2020, and Japanese Patent Application No. 2021-075785 filed on April 28, 2021, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Generally, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) are in a soft solid (viscoelastic) state in a temperature range around room temperature, and have the property of easily adhering to an adherend when pressure is applied. Utilizing these properties, pressure-sensitive adhesives are widely used in a variety of fields in the form of supported pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer on a support, or in the form of support-less pressure-sensitive adhesive sheets having no support. Patent documents 1 to 4 can be cited as technical documents related to pressure-sensitive adhesive sheets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent No. 6591841 [Patent Document 2] Japanese Patent Application Publication No. 2017-39856 [Patent Document 3] Japanese Patent Application Publication No. 2020-6166 [Patent Document 4] Japanese Patent Application Publication No. 2019-14852 Summary of the Invention [Problem to be solved by the invention]

[0004] Depending on the mode of use, adhesive sheets may be required to have properties such as not peeling or slipping after application, and not leaving any adhesive residue upon removal (clean peeling). For example, in the case of flexible substrates such as paper or human skin, peeling is likely to occur due to deformation of the adherend surface, and it is not easy to achieve such properties over a long period of time. Furthermore, if a strong adhesive is used to firmly adhere to the adherend and prevent peeling, problems may arise when peeling the adhesive sheet from the adherend, such as leaving adhesive residue due to the strong adhesion, or a portion of the adhesive sheet (e.g., a nonwoven fabric substrate) breaking, leaving part of the adhesive sheet remaining on the adherend. Such adhesive sheets require a great deal of effort to remove, which is undesirable. In the case of such flexible substrates, those with brittle surfaces, or those with low mechanical strength, peeling from the adherend tends to be even more difficult, and may even damage or destroy the adherend. In particular, adhesive sheets that are applied to human skin are required to not only not cause skin rashes during application but also to have peelability that causes minimal irritation or damage to the skin when removed. In such applications, it is important that the adhesive can be removed from the skin without or with minimal pain. However, if the adhesive is made harder in order to achieve such ease of removal, the adhesive strength will decrease, making it more likely to peel or slip during application and fixation, and thus not achieving reliable adhesion.

[0005] In relation to the above-mentioned issues, Patent Document 1 proposes a method for reducing adhesive residue by modifying a urethane-based adhesive with a silicone-based compound. However, the compatibility of non-peeling and non-slip properties has not been explored. Patent Document 2 proposes that a component having a UV-reactive functional group is introduced into the adhesive, and then irradiated with UV light after lamination to cause a reaction, thereby preventing adhesive residue and achieving releasability. However, this method is not easy to handle, as it requires UV irradiation after lamination. Furthermore, the adhesive disclosed in Patent Document 2 has low adhesive strength, making it unsuitable for applications requiring non-peeling and non-slip properties. Patent Document 3 proposes adding a specific fatty acid ester to the adhesive to reduce skin irritation, but the adhesive is weak and thus does not provide the expected non-peeling and non-slip properties. Meanwhile, Patent Document 4 discloses an adhesive with relatively high adhesive strength, and describes the method of cleaning and removing any adhesive residue with an organic solvent. However, wiping with an organic solvent is required to remove the adhesive sheet from the adherend, which limits its convenience and application.

[0006] The present invention was made in view of the above circumstances, and aims to provide a pressure-sensitive adhesive sheet that has adhesive reliability, such as not peeling off or slipping off, even when attached to a soft adherend, an adherend with a brittle surface, or an adherend with low strength, and that can be peeled off without damaging the adherend. Another related aim is to provide a resin for a pressure-sensitive adhesive sheet that can be used in such a pressure-sensitive adhesive sheet. [Means for solving the problem]

[0007] According to this specification, a resin for pressure-sensitive adhesive sheets is provided. This resin has a storage modulus at 25°C in the range of 10 MPa to 500 MPa, a storage modulus at 37°C in the range of 0.5 MPa to 20 MPa, and a surface hardness at 37°C in the range of 0.1 MPa to 2 MPa. By using a resin that satisfies the above properties, it is possible to produce a pressure-sensitive adhesive sheet that is resistant to peeling and slippage and can be peeled off without damaging the adherend. Specifically, by having the above properties, the resin disposed in the pressure-sensitive adhesive sheet, for example in a sheet form, gradually relaxes stress and deforms to conform to the adherend, thereby contributing to the realization of pressure-sensitive adhesive sheet performance that is resistant to peeling and slippage. On the other hand, the resin moderately resists deformation during peeling and reduces localized stress concentration on the adherend, so that when a pressure-sensitive adhesive sheet containing the resin is peeled off, the pressure-sensitive adhesive sheet can be peeled off while preventing damage to the adherend caused by the stress during peeling.

[0008] In some preferred embodiments, the resin exhibits an unloading curve displacement in the range of 400 nm to 1500 nm in nanoindenter measurement performed under conditions of a temperature of 37°C, an indentation depth of 1000 nm, and an indentation / withdrawal rate of 1000 nm / s. Pressure-sensitive adhesive sheets produced using resins satisfying the above characteristics preferably achieve the effects of the technology disclosed herein.

[0009] In some preferred embodiments, the resin has an internal area of ​​5 pJ or more under a load-displacement curve at or below 0 load in nanoindenter measurement performed under conditions of a temperature of 37°C, an indentation depth of 1000 nm, and an indentation / withdrawal rate of 1000 nm / s. The effects of the technology disclosed herein are preferably achieved by a pressure-sensitive adhesive sheet produced using a resin that satisfies the above characteristics.

[0010] In some embodiments, the glass transition temperature (Tg) of the resin is in the range of 5° C. to 40° C. By using a resin having a Tg in the above range, flexibility increases at temperatures near the Tg or above the Tg, and the resin tends to more easily conform to the adherend.

[0011] In some preferred embodiments, the resin is an acrylic resin. By using an acrylic resin as the resin, it is possible to preferably realize a configuration having a specific storage modulus and surface hardness.

[0012] The present specification also provides a pressure-sensitive adhesive sheet laminated with Layer A made of any of the resins disclosed herein. With a pressure-sensitive adhesive sheet having the above-described configuration, Layer A contained in the pressure-sensitive adhesive sheet gently conforms to the adherend, thereby achieving resistance to peeling and slippage. Furthermore, when peeling the pressure-sensitive adhesive sheet from the adherend, the pressure-sensitive adhesive sheet having Layer A adequately resists deformation during peeling, reducing localized stress concentration on the adherend, allowing peeling to be completed while preventing damage to the adherend caused by the stress.

[0013] Some preferred embodiments of the pressure-sensitive adhesive sheet have an adhesive surface with a 180-degree peel strength (adhesion strength to SUS) of 4 N / 10 mm or more against a stainless steel plate. Pressure-sensitive adhesive sheets with such an adhesive surface can exhibit good adhesive and fixing function to an adherend. Furthermore, with the pressure-sensitive adhesive sheet disclosed herein, even if the adhesive surface has an adhesive strength of a predetermined value or more as described above, the presence of Layer A makes it possible to peel the sheet from the adherend without leaving any adhesive residue.

[0014] Furthermore, the pressure-sensitive adhesive sheet provided herein may have Layer A, which has a storage modulus at 25°C in the range of 10 MPa to 500 MPa and a storage modulus at 37°C in the range of 0.5 MPa to 20 MPa. This pressure-sensitive adhesive sheet has an adhesive surface with a 180-degree peel strength from a stainless steel plate of 4 N / 10 mm or more. A pressure-sensitive adhesive sheet having the above configuration can exhibit excellent adhesive fixing function to an adherend, and Layer A contained in the pressure-sensitive adhesive sheet gently conforms to the adherend, thereby achieving resistance to peeling and slippage. Furthermore, when the pressure-sensitive adhesive sheet is peeled off from an adherend, the pressure-sensitive adhesive sheet having Layer A adequately resists deformation during peeling, reducing localized stress concentration on the adherend, making it possible to complete peeling without leaving any adhesive residue while preventing damage to the adherend caused by the stress.

[0015] In some preferred embodiments, the pressure-sensitive adhesive sheet has, in addition to the Layer A, a Layer B that constitutes the adhesive surface. By having the Layer B (typically a pressure-sensitive adhesive layer) that constitutes the adhesive surface, it is possible to control the adhesion to the adherend by designing the Layer B (interface control) while maintaining the function of the Layer A (bulk stress control function). Although not particularly limited, an acrylic pressure-sensitive adhesive layer is preferably used as the Layer B. By using an acrylic pressure-sensitive adhesive for the Layer B, it is possible to preferably obtain an adhesive strength (adhesion strength to SUS) of a predetermined value or more.

[0016] The thickness of the layer B may be 0.5 μm or more and 100 μm or less. In some embodiments, the thickness of the layer B may be 0.5 μm or more and less than 10 μm. In a configuration including such a thin layer B, the effects of the technology disclosed herein can be preferably realized.

[0017] In some embodiments, the pressure-sensitive adhesive sheet has a C layer in addition to the A layer. Here, the C layer is disposed on the side of the A layer opposite the adhesive surface. By arranging the adhesive surface, A layer, and C layer in this order, the function of A layer (bulk stress control function) can be effectively exerted on the adhesive surface while the function of C layer can be imparted to the pressure-sensitive adhesive sheet. For example, by using the C layer as a pressure-sensitive adhesive layer, not only the adhesive surface (also referred to as the first adhesive surface) but also the C layer side of the pressure-sensitive adhesive sheet becomes an adhesive surface (second adhesive surface), thereby providing a fixing function due to double-sided adhesiveness. Furthermore, for example, by providing cushioning properties to the C layer, the C layer can absorb the shape of the C layer side (e.g., the shape of the adherend) and external forces, preventing them from affecting the first adhesive surface side.

[0018] In some preferred embodiments, the C layer contains hollow particles, has air bubbles, or both. The use of a C layer containing hollow particles or air bubbles increases the amount of energy required to peel the PSA sheet from the adherend, which, in addition to the effects of the A layer, can make the sheet less susceptible to peeling and slippage. This effect of the C layer does not impair the releasability (prevention of damage to the adherend) provided by the A layer, but contributes to achieving a higher level of the effects of the technology disclosed herein (resistance to peeling from the adherend, resistance to slippage, and no damage to the adherend during peeling). The C layer has cushioning properties, so that, for example, when a hard member is placed on the C layer side, the C layer can absorb the influence of the shape of the member on the PSA sheet, preventing the influence on the adhesive surface located on the opposite side. In some embodiments, the C layer is an acrylic PSA layer. The technology disclosed herein is preferably implemented in a configuration including an acrylic PSA layer as the C layer (typically a double-sided PSA sheet configuration).

[0019] The adhesive sheet disclosed herein is preferably used in a mode in which the adhesive surface is attached to human skin. When attached to human skin, the adhesive sheet gently conforms to the attachment site due to body temperature, thereby achieving resistance to peeling and slippage. For example, the adhesive sheet can be resistant to peeling and slippage even when the person moves. Meanwhile, when peeling the adhesive sheet, the presence of Layer A allows the adhesive sheet to adequately resist deformation during peeling, reducing localized stress concentration on the adherend. Specifically, the adhesive sheet disclosed herein has a suppressed maximum stress value at the initial stage of peeling compared to its adhesive strength and peel resistance, so that peeling the adhesive from the skin involves little pulling (deformation), achieving a gentle peel that is painless or causes little pain.

[0020] The adhesive sheet disclosed herein is particularly suitable for applications in which a sensor is fixed to human skin. The adhesive sheet disclosed herein can be used for applications in which it is attached to human skin as described above. Furthermore, even when a sensor or the like is fixed to a specific part of a person via the adhesive sheet, it is difficult to peel off or shift, making it possible to achieve the sensing function associated with the sensor fixation part with high accuracy. Such an adhesive sheet capable of fixing a sensor to a part of the human body can be useful in fields such as medicine, healthcare, and sports science.

[0021] Furthermore, this specification can provide a pressure-sensitive adhesive sheet with a novel configuration suitable for achieving the effects of the technology disclosed herein. An example of such a pressure-sensitive adhesive sheet configuration is a pressure-sensitive adhesive sheet laminated with a layer B (adhesive layer) that forms the adhesive surface. This pressure-sensitive adhesive sheet has an adhesive surface with a 180-degree peel strength from a stainless steel plate of 4 N / 10 mm or more. An acrylic adhesive layer is preferably used as the layer B. Furthermore, although not particularly limited, the thickness of the layer B can be 0.5 μm or more and less than 10 μm. [Brief explanation of the drawings]

[0022] [Figure 1]1 is a cross-sectional view schematically illustrating the configuration of a resin for a pressure-sensitive adhesive sheet according to one embodiment. [Figure 2] 1 is a cross-sectional view schematically illustrating the configuration of a pressure-sensitive adhesive sheet according to one embodiment. [Figure 3] FIG. 10 is a cross-sectional view schematically illustrating the configuration of a pressure-sensitive adhesive sheet according to another embodiment. [Figure 4] FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of a sensor-equipped adhesive sheet. [Figure 5] 1 is a graph showing the results of measuring the peel stress distribution in Example 1. [Figure 6] 10 is a graph showing the results of measuring the peel stress distribution in Example 2. [Figure 7] 1 is a graph showing the results of measuring the peel stress distribution in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0023] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0024] As used herein, the term "adhesive" refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has the property of easily adhering to an adherend by pressure, as described above. The adhesive referred to here is generally a material having a complex tensile modulus E* (1Hz)<10 7 dyne / cm 2 The material may be a material having the properties satisfying the above (typically, a material having the above properties at 25°C).

[0025] <Resin for adhesive sheets> (Configuration example) The shape of the resin for PSA sheets disclosed herein is not particularly limited, and may be, for example, a resin sheet having a cross-sectional structure as schematically shown in Fig. 1. The resin sheet 10 shown in Fig. 1 is formed from a resin layer having a single-layer structure. Before use, this resin sheet 10 may be in the form of a resin sheet with a release liner, in which at least one surface is protected by a release liner.

[0026] (25℃ storage modulus) The resin for pressure-sensitive adhesive sheets disclosed herein has a storage modulus at 25°C in the range of 10 MPa to 500 MPa. Having the 25°C storage modulus within this range facilitates achieving appropriate shape retention and stress relaxation properties, and when used as a pressure-sensitive adhesive sheet material, it facilitates achieving both resistance to peeling and slippage from an adherend and prevention of damage to the adherend during peeling. The 25°C storage modulus may be, for example, approximately 30 MPa or more, approximately 60 MPa or more, or approximately 90 MPa or more. The 25°C storage modulus may be approximately 400 MPa or less, approximately 300 MPa or less, approximately 150 MPa or less, or approximately 100 MPa or less.

[0027] (37℃ storage modulus) The resin for pressure-sensitive adhesive sheets disclosed herein has a storage modulus at 37°C in the range of 0.5 MPa to 20 MPa. Having a storage modulus at 37°C within this range facilitates achieving appropriate shape retention and stress relaxation properties, and when used as a pressure-sensitive adhesive sheet material, it facilitates achieving both resistance to peeling and slippage from an adherend and prevention of damage to the adherend during peeling. For example, in an embodiment in which the pressure-sensitive adhesive sheet is applied to human skin, a pressure-sensitive adhesive sheet containing a resin satisfying the above properties gently conforms to the application site due to body temperature, thereby achieving resistance to peeling and slippage. Furthermore, the pressure-sensitive adhesive sheet can also maintain resistance to peeling and slippage even when the user moves. The 37°C storage modulus may be, for example, approximately 0.6 MPa or more, approximately 0.7 MPa or more, or approximately 0.8 MPa or more (e.g., 1.0 MPa or more). The 37°C storage modulus may be approximately 15 MPa or less, approximately 10 MPa or less, approximately 5 MPa or less, or approximately 3 MPa or less (for example, 1.5 MPa or less).

[0028] (glass transition temperature) Although not particularly limited, the glass transition temperature (Tg) of the resin is preferably in the range of 5°C to 40°C. By using a resin having a Tg in the above range, flexibility increases at temperatures near the Tg or above the Tg, and the resin tends to conform more easily to the adherend. The Tg is preferably 15°C or higher, more preferably 20°C or higher, and may be 25°C or higher or 30°C or higher. The Tg is preferably 35°C or lower, may be 30°C or lower, or may be 25°C or lower. Resins having the above Tg have increased flexibility and increased stress relaxation properties at temperatures near human body temperature, and therefore can conform well to the adherend when used in a pressure-sensitive adhesive sheet that is to be applied directly or indirectly to human skin.

[0029] The viscoelastic properties of the resin (25°C storage modulus, 37°C storage modulus, and Tg) can be determined by dynamic viscoelasticity measurement. Specifically, they are measured by the method described in the Examples below. The viscoelastic properties of the resin can be adjusted by selecting the resin constituents, composition, resin preparation conditions, etc. based on the description in this specification. In this specification, the Tg of the resin refers to the glass transition temperature determined from the peak temperature of tan δ in dynamic viscoelasticity measurement. The same applies to the Tg of the adhesive used as Layer B described below.

[0030] (37℃ surface hardness) The resin disclosed herein has a surface hardness at 37°C in the range of 0.1 MPa to 2 MPa. Having a surface hardness within this range allows the resin, when placed on a pressure-sensitive adhesive sheet, to deform through gentle stress relaxation and conform to the adherend, contributing to the realization of performance that is resistant to peeling and slippage. For example, when the resin is used as a material for a pressure-sensitive adhesive sheet that is applied directly or indirectly to human skin, the resin has the above surface hardness at temperatures near human body temperature, allowing it to conform well to the adherend and preferably exhibit excellent performance. Meanwhile, the resin adequately resists deformation when the pressure-sensitive adhesive sheet is peeled off and reduces localized stress concentration on the adherend, thereby contributing to the prevention of damage to the adherend caused by stress during peeling. The surface hardness is preferably 0.2 MPa or more, more preferably 0.3 MPa or more, and may be 0.4 MPa or more. The surface hardness is preferably 1.2 MPa or less, more preferably 1.0 MPa or less, and even more preferably 0.8 MPa or less, and may be 0.6 MPa or less (for example, 0.5 MPa or less).

[0031] (Unloading curve displacement) In some preferred embodiments, the resin exhibits an unloading curve displacement in the range of 400 nm to 1500 nm in nanoindenter measurements performed at 37°C. Resins with an unloading curve displacement of 400 nm or greater have appropriate viscosity and conform to the adherend when placed on a pressure-sensitive adhesive sheet, contributing to the realization of performance that is resistant to peeling and slippage. For example, when the resin is used as a pressure-sensitive adhesive sheet material to be applied directly or indirectly to human skin, the resin satisfies the unloading curve displacement at temperatures near human body temperature, thereby preferably exhibiting excellent performance. Furthermore, having the unloading curve displacement within the above range suppresses deformation in response to load when the pressure-sensitive adhesive sheet is peeled off, appropriately reducing stress on the adherend and contributing to preventing damage to the adherend caused by such stress during peeling. The unloading curve displacement may be 500 nm or greater, 700 nm or greater, 900 nm or greater, or 1100 nm or greater. Moreover, the unloading curve displacement may be 1300 nm or less, 1000 nm or less, 800 nm or less, or 600 nm or less.

[0032] (Internal area of ​​the load-displacement curve below load 0) In some preferred embodiments, the resin has an internal area under a load-displacement curve of 5 pJ or more at a load of 0 or less in nanoindenter measurement performed at 37°C. Resins satisfying this characteristic have appropriate viscosity and conform to the adherend when placed on a pressure-sensitive adhesive sheet, contributing to the realization of performance that is difficult to peel off and slip. For example, when the resin is used as a pressure-sensitive adhesive sheet material to be applied directly or indirectly to human skin, the resin satisfies the above characteristic at temperatures around human body temperature, thereby preferably exhibiting excellent performance. The internal area under a load-displacement curve of 0 or less [pJ] may be 8 or more, 10 or more, or 12 or more. Furthermore, the upper limit of the internal area under a load-displacement curve of 0 or less [pJ] is not particularly limited, and may be, for example, 50 or less, 30 or less, or 15 or less.

[0033] The 37°C surface hardness, unloading curve displacement, and load-displacement curve internal area at or below zero load can be determined by nanoindenter measurement performed under conditions of a temperature of 37°C, an indentation depth of 1000 nm, and an indentation / withdrawal rate (indentation rate and pull-out rate) of 1000 nm / s. Specifically, they are measured by the method described in the Examples below. Furthermore, the nanoindentation properties of the resin (the 37°C surface hardness, unloading curve displacement, and load-displacement curve internal area at or below zero load) can be adjusted by selecting the resin constituent components, composition, resin preparation conditions, etc., based on the description herein.

[0034] (resin material) The resin disclosed herein may be composed of one or more resins selected from various known resins, such as acrylic resins, rubber resins (natural rubber, synthetic rubber, mixtures thereof, etc.), silicone resins, polyester resins, urethane resins, polyether resins, polyamide resins, and fluorine resins. Here, acrylic resin refers to a resin whose main component (base polymer) is an acrylic polymer. The same applies to rubber resins and other resins.

[0035] The term "base polymer" of a resin refers to the main component of the polymer contained in the resin, and is not intended to be limiting in any other sense. In this specification, the term "main component" refers to the component that is contained in the largest proportion by weight among the components. Therefore, for example, if a resin is composed of three or more components, the content of the main component in the resin may be 34% by weight or more.

[0036] In this specification, the term "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight of an acrylic monomer, and is also referred to as an acrylic polymer. The acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule. In this specification, the term "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, the term "(meth)acrylate" refers to acrylate and methacrylate, and the term "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.

[0037] (acrylic resin) In some embodiments, an acrylic resin may be preferably used as a constituent material of the resin. Specifically, the resin disclosed herein may be an acrylic resin containing an acrylic polymer. Acrylic resins tend to have excellent flexibility in molecular design and are suitable for forming resins that satisfy the above-mentioned characteristics.

[0038] (acrylic polymer) The acrylic resin disclosed herein preferably contains, as a base polymer, an acrylic polymer constituted of a monomer component containing a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal. Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having X to Y carbon atoms at the ester terminal will be referred to as "(meth)acrylic acid C X-Y Among all the monomer components of the acrylic polymer according to some embodiments, (meth)acrylic acid C is sometimes referred to as "alkyl ester" because it is easy to balance the properties. 1-20 The proportion of alkyl ester is, for example, 25% by weight or more, suitably 30% by weight or more, and preferably 35% by weight or more. In some other embodiments, the proportion of (meth)acrylic acid C in the total monomer components of the acrylic polymer is 1-20The proportion of alkyl ester is suitably more than 50% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and may be, for example, 90% by weight or more. 1-20 The proportion of alkyl esters may be, for example, 99.9% by weight or less, 99% by weight or less, or 95% by weight or less. 1-20 The proportion of the (meth)acrylic acid alkyl ester may be, for example, 80% by weight or less, 60% by weight or less, 50% by weight or less (for example, less than 50% by weight), or 40% by weight or less, from the viewpoint of adjusting the surface hardness, storage modulus, Tg, etc. of the acrylic resin. 1-20 The alkyl esters can be used alone or in combination of two or more.

[0039] (Meth)acrylic acid C 1-20 Non-limiting examples of alkyl esters include 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, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isopropyl (meth)acrylate. Examples of the acrylate include 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, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0040] Among these, at least (meth)acrylic acid C4-20 It is preferable to use alkyl esters, and at least (meth)acrylic acid C 4-18 It is more preferable to use alkyl esters, and at least (meth)acrylic acid C 4-12 It is more preferable to use alkyl esters, and at least acrylic acid C 4-10 It is particularly preferred to use alkyl esters. For example, it is preferred to use one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) as the monomer component. (Meth)acrylic acid C that can be preferably used 4-20 Other examples of alkyl esters include isononyl acrylate, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA), etc. (Meth)acrylic acid C 4-18 The alkyl esters can be used alone or in combination of two or more.

[0041] In some embodiments, the monomer components constituting the acrylic polymer include (meth)acrylic acid C 1-20 (Meth)acrylic acid C in alkyl esters 4-18 Alkyl ester (preferably (meth)acrylic acid C 4-12 Alkyl esters, more preferably acrylic acid C 4-10 The proportion of the alkyl ester is preferably 30% by weight or more, more preferably 40% by weight or more, and may be 50% by weight or more, 70% by weight or more, for example, 80% by weight or more, 90% by weight or more, or may be 95 to 100% by weight.

[0042] In some other embodiments, the (meth)acrylic acid C having the linear or branched alkyl group is used for the purpose of increasing the Tg of the acrylic resin and adjusting the surface hardness, storage modulus, etc. 1-20Among alkyl esters, it is preferable to use (meth)acrylic acid alkyl esters (high Tg (meth)acrylic acid alkyl esters) whose homopolymer glass transition temperature (Tg) is 10°C or higher. Suitable examples of such (meth)acrylic acid alkyl esters include methyl methacrylate (MMA) (homopolymer Tg: 105°C) and BMA (homopolymer Tg: 20°C). The high Tg (meth)acrylic acid alkyl esters can be used alone or in combination of two or more.

[0043] Among the monomer components constituting the acrylic polymer, (meth)acrylic acid C 1-20 The proportion of the high Tg (meth)acrylic acid alkyl ester in the alkyl ester is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 30% by weight or more, and may be 35% by weight or more, for example, 40% by weight or more. 1-20 The proportion of the high Tg (meth)acrylic acid alkyl ester in the alkyl ester can be, for example, 70% by weight or less, preferably 60% by weight or less, and may be 50% by weight or less, 30% by weight or less, 10% by weight or less, or 3% by weight or less. 1-20 The alkyl ester may be substantially free of high Tg (meth)acrylic acid alkyl esters.

[0044] The monomer components constituting the acrylic polymer may contain, in addition to the (meth)acrylic acid alkyl ester, other monomers (copolymerizable monomers) copolymerizable with the (meth)acrylic acid alkyl ester, as necessary. Suitable copolymerizable monomers include monomers having polar groups (e.g., carboxyl groups, hydroxyl groups, nitrogen-containing rings, etc.) and monomers whose homopolymers have relatively high glass transition temperatures (e.g., 10°C or higher). Monomers having polar groups can be useful for introducing crosslinking points into the acrylic polymer or for increasing the cohesive strength of the acrylic resin. The copolymerizable monomers may be used alone or in combination of two or more.

[0045] Non-limiting examples of copolymerizable monomers include carboxyl group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, monomers containing sulfonic acid groups or phosphoric acid groups, epoxy group-containing monomers, cyano group-containing monomers, isocyanate group-containing monomers, amide group-containing monomers, amino group-containing monomers, monomers having a nitrogen atom-containing ring, monomers having a succinimide skeleton, maleimides, aminoalkyl (meth)acrylates, alkoxy group-containing monomers, alkoxysilyl group-containing monomers, vinyl esters, vinyl ethers, aromatic vinyl compounds, olefins, (meth)acrylic acid esters having an alicyclic hydrocarbon group, (meth)acrylic acid esters having an aromatic hydrocarbon group, as well as heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from terpene compound derivative alcohols. Among these, carboxy group-containing monomers, hydroxy group-containing monomers, monomers having a nitrogen atom-containing ring, and (meth)acrylic acid esters having an alicyclic hydrocarbon group are preferred.

[0046] Suitable examples of copolymerizable monomers, such as carboxyl group-containing monomers, include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Examples of monomers having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, and N-vinylpyridazine (e.g., lactams such as N-vinyl-2-caprolactam). Examples of the (meth)acrylic acid ester having an alicyclic hydrocarbon group include (meth)acrylates containing an alicyclic hydrocarbon group, such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.

[0047] When a polar group-containing monomer is used, its amount is not particularly limited, and is suitably, for example, 0.01% by weight or more of the total monomer components. From the viewpoint of better exerting the effect of using the polar group-containing monomer, the amount of polar group-containing monomer may be 0.1% by weight or more, or even 0.5% by weight or more of the total monomer components. Furthermore, from the viewpoint of easily balancing properties (surface hardness, storage modulus, Tg, etc.), the amount of polar group-containing monomer is suitably 60% by weight or less of the total monomer components, or may be 50% by weight or less, or may be 40% by weight or less.

[0048] When a high-Tg monomer having a homopolymer glass transition temperature of 10°C or higher is used, its amount is not particularly limited, and is suitably, for example, 1% by weight or more of the total monomer components. To maximize the effect of using the high-Tg monomer, the amount of the high-Tg monomer may be 10% by weight or more, 30% by weight or more, or 40% by weight or more (e.g., 50% by weight or more) of the total monomer components. To facilitate a balance of properties (surface hardness, storage modulus, Tg, etc.), the amount of the high-Tg monomer is suitably 80% by weight or less of the total monomer components, preferably 70% by weight or less, more preferably 60% by weight or less, and may be 50% by weight or less, 40% by weight or less, or 30% by weight or less (e.g., 10% by weight or less). It goes without saying that the high-Tg monomer may include a polar group-containing monomer, and vice versa.

[0049] In some embodiments, the monomer components constituting the acrylic polymer may include a hydroxyl group-containing monomer. The use of a hydroxyl group-containing monomer can suitably adjust the cohesive strength of the acrylic resin and the degree of crosslinking (e.g., crosslinking with an isocyanate crosslinking agent). Examples of the hydroxyl group-containing monomer that can be used include those exemplified above, and preferred examples include 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA). The hydroxyl group-containing monomer can be used alone or in combination of two or more.

[0050] When a hydroxyl group-containing monomer is used, the amount used is not particularly limited, and in some preferred embodiments, the amount used of the hydroxyl group-containing monomer is 0.01% by weight or more of the total monomer components, suitably 0.1% by weight or more, preferably 0.5% by weight or more, and more preferably 1% by weight or more. In some embodiments, the amount used of the hydroxyl group-containing monomer is suitably, for example, 10% by weight or less of the total monomer components, and may be 5% by weight or less, 3% by weight or less, or 1% by weight or less.

[0051] In some embodiments, the monomer components constituting the acrylic polymer may contain an alicyclic hydrocarbon group-containing (meth)acrylate. This can increase the cohesive strength and Tg of the acrylic resin. Examples of the alicyclic hydrocarbon group-containing (meth)acrylate include those exemplified above, and preferred examples include cyclohexyl acrylate (CHA) and isobornyl acrylate (IBXA). The alicyclic hydrocarbon group-containing (meth)acrylate may be used alone or in combination of two or more.

[0052] When an alicyclic hydrocarbon group-containing (meth)acrylate is used, the amount used is not particularly limited and can be, for example, 1% by weight or more, or even 10% by weight or more, of the total monomer components. In some preferred embodiments, the content of the alicyclic hydrocarbon group-containing (meth)acrylate is 30% by weight or more, more preferably 40% by weight or more, or even 50% by weight or more, of the total monomer components. Furthermore, from the viewpoint of easily balancing properties (surface hardness, storage modulus, Tg, etc.), the upper limit of the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used is suitably 80% by weight or less, preferably 70% by weight or less, more preferably 60% by weight or less, or may be 50% by weight or less, 40% by weight or less, or 30% by weight or less (e.g., 10% by weight or less). In some embodiments, the proportion of the alicyclic hydrocarbon group-containing (meth)acrylate in the monomer components constituting the acrylic polymer may be 3% by weight or less, or even 1% by weight or less. The above-mentioned monomer component may be substantially free of an alicyclic hydrocarbon group-containing (meth)acrylate.

[0053] In some preferred embodiments, the monomer components constituting the acrylic polymer may contain a nitrogen atom-containing monomer. This can increase the cohesive strength of the acrylic resin. The above-mentioned examples of the nitrogen atom-containing monomer can be used. Suitable examples of the nitrogen atom-containing monomer include monomers having a nitrogen atom-containing ring. For example, N-vinyl cyclic amides can be used, and among these, N-vinyl-2-pyrrolidone (NVP) can be preferably used. The nitrogen atom-containing monomer can be used alone or in combination of two or more.

[0054] The amount of the nitrogen atom-containing monomer (preferably the nitrogen atom-containing ring-containing monomer) used is not particularly limited, and may be, for example, 1% by weight or more, 3% by weight or more, or even 5% by weight or more of the total monomer components. The amount of the nitrogen atom-containing monomer used is suitably, for example, 30% by weight or less, or may be 15% by weight or less, or may be 10% by weight or less of the total monomer components. In some embodiments, the proportion of the nitrogen atom-containing monomer in the monomer components constituting the acrylic polymer may be 3% by weight or less, or may be 1% by weight or less. The above-mentioned monomer components may be substantially free of the nitrogen atom-containing monomer.

[0055] In some embodiments, the proportion of the carboxyl group-containing monomer in the monomer components of the acrylic polymer may be, for example, 0% by weight or more but less than 10% by weight, less than 3% by weight, or less than 1% by weight (e.g., less than 0.1% by weight). Substantially no carboxyl group-containing monomer may be used as a monomer component of the acrylic polymer. Here, "substantially no use" of a component means that the component is not used, at least intentionally.

[0056] In the polymerization, a known or commonly used thermal polymerization initiator or photopolymerization initiator can be used depending on the polymerization method, polymerization mode, etc. Such polymerization initiators can be used alone or in appropriate combination of two or more.

[0057] The thermal polymerization initiator is not particularly limited, and examples thereof include azo polymerization initiators, peroxide initiators, redox initiators formed by combining peroxides with reducing agents, and substituted ethane initiators. More specifically, examples thereof include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropane] dihydrochloride, and the like. Examples of initiators include, but are not limited to, azo initiators such as [pionamidine]tetrahydrate (VA-057); persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; and redox initiators such as a combination of a persulfate and sodium bisulfite, or a combination of a peroxide and sodium ascorbate. Thermal polymerization is preferably carried out at a temperature of, for example, about 20 to 100°C (typically 40 to 80°C).

[0058] The photopolymerization initiator is not particularly limited, but examples of usable photopolymerization initiators include ketal-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators.

[0059] The amount of such a thermal polymerization initiator or photopolymerization initiator used is not particularly limited and may be a normal amount depending on the polymerization method, polymerization mode, etc. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example, about 0.01 to 1 part by weight) of the polymerization initiator can be used per 100 parts by weight of the monomer to be polymerized.

[0060] In the polymerization, various conventionally known chain transfer agents (which may also be understood as molecular weight regulators or polymerization degree regulators) can be used as needed. Examples of the chain transfer agent include mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur chain transfer agent) may be used. The chain transfer agent may be used alone or in combination of two or more. When a chain transfer agent is used, the amount used may be, for example, about 0.01 to 1 part by weight per 100 parts by weight of the monomer components. The technology disclosed herein can also be preferably practiced in an embodiment in which a chain transfer agent is not used.

[0061] The resin disclosed herein can be formed using a resin composition containing the monomer components of the above-described composition in the form of a polymer, an unpolymer (i.e., a form in which the polymerizable functional group is unreacted), or a mixture thereof. The resin composition can be in various forms, such as a water-dispersed resin composition in which the resin (resin component) is dispersed in water, a solvent-based resin composition in which the resin is contained in an organic solvent, an active energy ray-curable resin composition prepared to form a resin upon curing with active energy rays such as ultraviolet light or radiation, or a hot-melt resin composition that is applied in a heated and molten state and forms a resin upon cooling to near room temperature. The resin composition according to some embodiments is a solvent-based resin composition or a solventless resin composition. Solventless resin compositions include active energy ray-curable resin compositions and hot-melt resin compositions.

[0062] The resin composition according to some embodiments may be an active energy ray-curable resin composition. As used herein, "active energy rays" refers to energy rays having energy capable of inducing chemical reactions such as polymerization reactions, crosslinking reactions, and decomposition of initiators. Examples of active energy rays include light such as ultraviolet rays, visible light, and infrared rays, and radioactive rays such as alpha rays, beta rays, gamma rays, electron beams, neutron beams, and X-rays. A suitable example of an active energy ray-curable resin composition is a photocurable resin composition. Photocurable resin compositions have the advantage that they can be easily formed into even thick resin sheets (resin layers). Among these, ultraviolet-curable resin compositions are preferred.

[0063] Photocurable resin compositions typically contain at least a portion of the monomer components of the composition (which may be a portion of the types of monomers or a portion of the amounts) in the form of a polymer. The polymerization method used to form the polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately employed. For example, thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization (typically carried out in the presence of a thermal polymerization initiator); photopolymerization carried out by irradiation with light such as ultraviolet light (typically carried out in the presence of a photopolymerization initiator); and radiation polymerization carried out by irradiation with radiation such as beta rays and gamma rays can be appropriately employed. Among these, photopolymerization is preferred.

[0064] Photocurable resin compositions according to some preferred embodiments contain a partial polymer of a monomer component (e.g., an acrylic partial polymer). Such a partial polymer is typically a mixture of a polymer derived from the monomer component and an unreacted monomer, and preferably exhibits a syrup-like appearance (a viscous liquid). Hereinafter, a partial polymer of this nature may be referred to as a "monomer syrup" or simply as a "syrup." The polymerization method used to partially polymerize the monomer component is not particularly limited, and various polymerization methods such as those described above can be appropriately selected and used. From the viewpoints of efficiency and simplicity, a photopolymerization method can be preferably employed. Photopolymerization allows the polymerization conversion rate of the monomer component (monomer conversion) to be easily controlled by changing polymerization conditions such as the amount of light irradiation (light dose).

[0065] The polymerization conversion rate of the monomer mixture in the partially polymerized product is not particularly limited. The polymerization conversion rate can be, for example, about 70% by weight or less, and from the viewpoint of ease of preparation, coatability, moldability, etc. of a resin composition containing the partially polymerized product, it is suitably about 50% by weight or less, and preferably about 40% by weight or less. The lower limit of the polymerization conversion rate is not particularly limited, but is typically about 1% by weight or more, and suitably about 5% by weight or more.

[0066] The resin composition containing the partially polymerized product may contain other components (e.g., a photopolymerization initiator, a polyfunctional monomer as described below, a crosslinking agent, etc.) that are used as needed. The method for blending such other components is not particularly limited, and for example, the other components may be contained in the monomer mixture in advance, or may be added to the partially polymerized product.

[0067] The resin according to some embodiments is a resin formed from a water-dispersed resin composition. A typical example of a water-dispersed resin composition is an emulsion-type resin composition. An emulsion-type resin composition typically contains a polymer of a monomer component and additives used as needed. Emulsion polymerization of the monomer component is usually carried out in the presence of an emulsifier. Emulsion polymerization produces a polymerization reaction liquid in the form of an emulsion in which a polymer of the monomer component is dispersed in water. The water-dispersed resin composition used to form the resin can be preferably produced using the above-mentioned polymerization reaction liquid.

[0068] The emulsifier for emulsion polymerization is not particularly limited, and known anionic emulsifiers, nonionic emulsifiers, etc. can be used. The emulsifiers can be used alone or in combination of two or more. Non-limiting examples of anionic emulsifiers include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, and sodium polyoxyethylene alkyl sulfosuccinate. Non-limiting examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene polyoxypropylene block polymers. Emulsifiers having reactive functional groups (reactive emulsifiers) may also be used. Examples of reactive emulsifiers include radically polymerizable emulsifiers having a structure in which a radically polymerizable functional group such as a propenyl group or an allyl ether group is introduced into the above-mentioned anionic or nonionic emulsifiers.

[0069] The amount of emulsifier used in emulsion polymerization may be, for example, 0.2 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, or 1.5 parts by weight or more, relative to 100 parts by weight of the monomer components. Furthermore, from the viewpoint of improving water resistance or improving transparency of the resin, in some embodiments, the amount of emulsifier used is suitably 20 parts by weight or less, preferably 15 parts by weight or less, and may be 10 parts by weight or less, relative to 100 parts by weight of the monomer components.

[0070] The resin composition according to some embodiments may be a solvent-based resin composition. A solvent-based resin composition typically contains a solution polymer of a monomer component and an additive (e.g., a hydrophilic agent) that is used as needed. The solvent (polymerization solvent) used in the solution polymerization can be appropriately selected from conventionally known organic solvents (e.g., toluene, ethyl acetate, etc.). According to the solution polymerization, a polymerization reaction liquid is obtained in which a polymer of the monomer component is dissolved in the polymerization solvent. The solvent-based resin composition disclosed herein can be preferably produced using the above-mentioned polymerization reaction liquid.

[0071] (polyfunctional monomer) A polyfunctional monomer may be used in the resin composition (and thus the resin) as needed. The polyfunctional monomer may be useful for purposes such as adjusting cohesive strength. The polyfunctional monomer may form a crosslinked structure with appropriate flexibility by reacting the ethylenically unsaturated group with light (e.g., ultraviolet) irradiation during resin formation. Therefore, in this specification, the term "polyfunctional monomer" may be rephrased as a crosslinking agent. For example, a polyfunctional monomer may be preferably used in a resin formed from a photocurable resin composition. A compound having two or more ethylenically unsaturated groups may be used as the polyfunctional monomer. The polyfunctional monomer may be used alone or in combination of two or more.

[0072] Examples of the ethylenically unsaturated group contained in the polyfunctional monomer include, but are not limited to, an acryloyl group, a methacryloyl group, a vinyl group, and an allyl group. From the viewpoint of photoreactivity, preferred ethylenically unsaturated groups include an acryloyl group and a methacryloyl group. Among them, an acryloyl group is preferred.

[0073] Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl diol (meth)acrylate, and hexyl diol di(meth)acrylate. Of these, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are preferred.

[0074] The amount of polyfunctional monomer used varies depending on its molecular weight, number of functional groups, etc., but is suitably in the range of about 0.01 to 3.0 parts by weight per 100 parts by weight of the monomer components (typically, acrylic polymers or monomer components of the polymers) that form the polymer contained in the resin. In some embodiments, the amount of polyfunctional monomer used per 100 parts by weight of the monomer components may be, for example, 0.02 parts by weight or more, or even 0.1 parts by weight or more. In some embodiments, the amount of polyfunctional monomer used per 100 parts by weight of the monomer components is suitably, for example, 1.0 part by weight or less, preferably 0.5 parts by weight or less. By setting the amount of polyfunctional monomer used, the surface hardness and storage modulus of the resin can be adjusted.

[0075] (Crosslinking agent) The resin composition disclosed herein may optionally contain a crosslinking agent, primarily for the purpose of crosslinking within the resin (layer) or between the resin and its adjacent surface. The type of crosslinking agent is not particularly limited, and may be selected from conventionally known crosslinking agents, depending on the composition of the resin composition, for example, so that the crosslinking agent exerts an appropriate crosslinking function within the resin. Examples of crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These may be used alone or in combination of two or more.

[0076] The content of the crosslinking agent (the total amount when two or more crosslinking agents are included) is not particularly limited. From the viewpoint of achieving a resin with the desired surface hardness and viscoelastic properties, the content of the crosslinking agent is suitably approximately 5 parts by weight or less per 100 parts by weight of the monomer components forming the polymer contained in the resin (e.g., acrylic polymer or monomer components of the polymer), preferably approximately 0.001 to 5 parts by weight, more preferably approximately 0.001 to 4 parts by weight, and even more preferably approximately 0.001 to 3 parts by weight. Alternatively, the resin composition may be one that does not contain the above-mentioned crosslinking agent. When a photocurable resin composition is used as the resin composition disclosed herein, the resin composition may be substantially free of a crosslinking agent such as an isocyanate-based crosslinking agent. Here, "a resin composition that is substantially free of a crosslinking agent" means that the amount of crosslinking agent per 100 parts by weight of the monomer components is less than 0.05 parts by weight (e.g., less than 0.01 part by weight).

[0077] (surfactant) In some preferred embodiments, the resin composition may contain a surfactant. The resins (typically resin sheets) disclosed herein may be porous (preferably open-cell porous). Therefore, when forming a resin with such a porous structure (preferably an open-cell structure), a surfactant may be used to adjust the bubble size or stabilize the bubbles. Therefore, surfactants used for the above purposes are also referred to as bubble regulators or bubble stabilizers. Examples of surfactants that may be used include ionic surfactants (anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants), hydrocarbon surfactants, silicone surfactants, and fluorine-based surfactants. The surfactants may be used alone or in combination of two or more. For example, in a water-dispersible resin composition, in addition to the emulsifiers (anionic surfactants and nonionic surfactants) described above, amphoteric surfactants such as carboxybetaine surfactants may be preferably used.

[0078] When the resin composition contains a surfactant as a cell regulator, the amount of the surfactant used may be, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, or 1.0 parts by weight or more relative to 100 parts by weight of the monomer components forming the polymer contained in the resin (e.g., acrylic polymer or monomer components of the polymer). The amount of the surfactant used is suitably 10 parts by weight or less, preferably 8 parts by weight or less, and may be 5 parts by weight or less relative to 100 parts by weight of the monomer components.

[0079] (Other ingredients) The resins disclosed herein may contain, as necessary, various additives as other optional components, such as viscosity modifiers (e.g., thickeners), pH adjusters, leveling agents, foaming agents, tackifying resins, crosslinking aids, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antioxidants, etc. These various additives are conventionally known and can be used in the usual way, and are not particularly characteristic of the present invention, so detailed description thereof will be omitted.

[0080] In the technology disclosed herein, the amount of components other than the base polymer (preferably an acrylic polymer) in the resin may be limited. In the technology disclosed herein, the amount of components other than the base polymer in the resin is, for example, approximately 30% by weight or less, suitably approximately 10% by weight or less, preferably approximately 5% by weight or less, more preferably approximately 3% by weight or less, and may be approximately 1.5% by weight or less (e.g., less than 1% by weight). Compositions in which the amount of components other than the base polymer (e.g., an acrylic polymer) is limited in this way may be preferably employed for photocurable resin compositions.

[0081] (Resin formation) When the resin is in the form of a sheet (resin sheet), the resin sheet can be formed by applying (e.g., coating) the resin composition to a suitable surface and then appropriately performing a curing treatment. When two or more curing treatments (drying, crosslinking, polymerization, etc.) are performed, these can be performed simultaneously or in multiple stages. For a resin composition using a partially polymerized monomer component (acrylic monomer syrup), the curing treatment typically involves a final copolymerization reaction. That is, the partially polymerized component is subjected to a further copolymerization reaction to form a fully polymerized component. For example, in the case of a photocurable resin composition, light irradiation is performed. Curing treatments such as crosslinking and drying may be performed as needed. For example, when a photocurable resin composition requires drying (e.g., a photocurable resin composition in which a partially polymerized monomer component is dissolved in an organic solvent), the composition may be dried and then photocured. For a resin composition using a fully polymerized component, the curing treatment typically involves drying (heat drying), crosslinking, etc., as needed.

[0082] The resin composition can be applied using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater.

[0083] The resin sheet disclosed herein typically has a single-layer structure, but may have a multilayer structure containing one or more additional layers in addition to the resin (layer) as long as the effects of the PSA sheet resin disclosed herein are not impaired. Such additional layers may be, for example, a substrate layer supporting the resin layer. Examples of such additional layers include, but are not limited to, nonwoven fabrics, woven fabrics, and other porous films. When nonwoven fabrics or woven fabrics are used, the material is not particularly limited, and materials made from one or more of the following can be used: natural fibers such as cotton, linen, and wool; cellulosic fibers such as rayon and acetate; polyamide fibers such as vinylon and nylon; polyolefin fibers such as polyethylene and polypropylene; polyester fibers such as polyethylene terephthalate (PET); and synthetic fibers such as polyurethane fibers. Examples of porous films include resin porous films made from polypropylene, polyethylene, PET, polyurethane, and the like. Among these, nonwoven fabrics are preferred, and nonwoven fabrics made from synthetic fibers such as polyester fibers are more preferred. These substrate materials have suitable breathability and moisture permeability, and may also have suitable stretchability / non-stretchability, and therefore may be preferably used, for example, in applications where they are attached to human skin.

[0084] (Thickness of resin sheet (resin layer)) In embodiments in which the resin disclosed herein is in the form of a sheet, the thickness of the resin sheet is not particularly limited and may be, for example, approximately 3 μm to 2000 μm. From the viewpoints of handleability and processability, in some embodiments, the thickness of the resin sheet is, for example, appropriately 10 μm or more, preferably 50 μm or more, more preferably 70 μm or more, and even more preferably 90 μm or more. A resin sheet with a large thickness can effectively exhibit the properties of the resin sheet (hardness and viscoelastic properties). Furthermore, the thickness of the resin sheet may be, for example, 1000 μm or less, suitably 500 μm or less, preferably 300 μm or less, or may be 200 μm or less. A resin sheet with a limited thickness is suitable for applications in which lighter weight and thinner thickness are desired. In some preferred embodiments, the thickness of the resin sheet is, for example, 150 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, and may be 50 μm or less (e.g., 40 μm or less). Adhesive sheets using thin resin sheets have excellent conformability to the adherend and resistance to repulsion, and tend to be less likely to lift or peel off from the adherend (e.g., human skin) even when left attached for a long period of time.

[0085] (porous resin) In some preferred embodiments, the resin (typically a resin sheet) has porosity. Pressure-sensitive adhesive sheets comprising the resin disclosed herein are preferably used in a mode in which they are attached to human skin, and desirably have moisture permeability that allows moisture such as sweat to escape when attached to human skin. By using a resin with porosity, favorable moisture permeability can be achieved, making it less likely that stuffiness or itching caused by sweat or the like will occur. The porous resin preferably contains open cells. By using a resin with an open-cell structure, excellent moisture permeability is easily achieved.

[0086] The method for forming a porous structure (preferably an open-cell structure) in a resin is not particularly limited, and known foaming methods can be appropriately employed. For example, a method can be employed in which a resin composition is mechanically foamed and then cured by drying or other means to form a cell-containing resin. Specifically, for example, a bubble-mixing device is used to mix a bubble-forming gas, such as air, nitrogen, or carbon dioxide, into a resin composition under appropriate conditions (e.g., high-pressure conditions), and the resin composition containing the bubble-forming gas is cured to form a cell-containing resin. Alternatively, a porous resin containing open cells can be obtained by adding an appropriate amount of water to the resin composition, optionally adding a surfactant, and performing operations such as stirring, followed by heating to evaporate the water. The foaming device and bubble-mixing device are not particularly limited, and for example, a high-speed mixer (also known as an emulsifier or disperser) capable of high-speed shearing is preferably used. The conditions for bubble formation, heating, etc. can be determined depending on the desired bubble size and shape, the type of bubble-generating component, etc.

[0087] <Adhesive sheet> The pressure-sensitive adhesive sheet disclosed herein may be a single-sided pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) or a double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet). The pressure-sensitive adhesive sheet typically has a layer A made of the above-mentioned resin for pressure-sensitive adhesive sheets. The pressure-sensitive adhesive sheet may also have a layer B in addition to the layer A. In other words, it may be a pressure-sensitive adhesive sheet having a laminated structure of the layer A and the layer B. The pressure-sensitive adhesive sheet may also have a layer C in addition to the layer A. In other words, it may be a pressure-sensitive adhesive sheet having a laminated structure of the layer A and the layer C. Furthermore, the pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet comprising a layer B, a layer A, and a layer C in this order. In other embodiments, the pressure-sensitive adhesive sheet may have a layer B that forms the adhesive surface of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet may also have a layer A or layer B and a layer C. The concept of pressure-sensitive adhesive sheet as used herein may encompass what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films, etc. The pressure-sensitive adhesive sheets disclosed herein may be in the form of rolls or sheets. Alternatively, the pressure-sensitive adhesive sheet may be further processed into various shapes.

[0088] (Configuration example) The pressure-sensitive adhesive sheet disclosed herein may have, for example, the cross-sectional structure shown schematically in FIG. 2. This pressure-sensitive adhesive sheet 1 has a laminated structure of an A layer 10 and a B layer 20. One surface 1A of the pressure-sensitive adhesive sheet 1 is the surface to be attached to an adherend (adhesive surface) and is constituted by the B layer 20. The other surface 1B of the pressure-sensitive adhesive sheet 1 (the surface opposite to the one surface 1A) is the backside of the adhesive surface 1A and is constituted by the A layer 10. In this pressure-sensitive adhesive sheet 1, the B layer 20 is a pressure-sensitive adhesive layer, and its surface 20A is the surface to be attached to an adherend (adhesive surface). The A layer 10 is a support layer laminated on the other surface 20B of the B layer 20 and supports the B layer 20. The A layer 10 and the B layer 20 are fixedly bonded together. The PSA sheet 1 before use (before application to an adherend) may be in the form of a release-liner PSA sheet 100, in which the adhesive surface 1A is protected by a release liner 41, at least the adhesive surface side of which is a releasable surface (release surface), as shown in Figure 2. Although not particularly shown, the back surface 1B of the PSA sheet 1 may also be protected by a release liner. Note that, although not particularly limited, when Layer A has a substrate such as a nonwoven fabric, Layer B is preferably laminated to a resin layer (the surface of Layer A facing the resin layer) on which no substrate is disposed.

[0089] The adhesive sheet disclosed herein may be configured as, for example, the adhesive sheet 2 shown in FIG. 3. The adhesive sheet 2 shown in FIG. 3 has a C layer 30 in addition to an A layer 10 and a B layer 20, and has a structure in which the B layer 20, the A layer 10, and the C layer 30 are laminated in this order. The C layer 30 is a viscoelastic layer and is an adhesive layer in this embodiment. The adhesive sheet 2 includes the A layer 10 as an intermediate layer, and is configured as a double-sided adhesive sheet (double-sided adhesive sheet) in which the B layer 20 and the C layer 30 as adhesive layers are provided on each surface (both non-peeling surfaces) of the A layer 10 as the intermediate layer. The surface 20A of the B layer 20 and the surface 30A of the C layer 30 constitute the adhesive surfaces 2A and 2B of the adhesive sheet 2, respectively. The adhesive sheet 2 before use may be in the form of an adhesive sheet 200 with release liners, which is protected by two release liners 41 and 42, at least on the adhesive surface side, which are peeling surfaces. Alternatively, it may be in a form in which the back surface (the surface opposite to the adhesive surface 2A side) of the release liner 41 is the peeling surface, and the adhesive surfaces 2A and 2B are protected by winding or laminating so that the adhesive surface 2B abuts on the back surface of the release liner 41. Although not particularly limited, when the A layer has a base material such as a non-woven fabric, it is preferable that the B layer is laminated on the resin layer (the resin layer side surface of the A layer) where the base material is not disposed.

[0090] The release liner is not particularly limited. For example, a release liner in which the surface of a liner base material such as a resin film or paper is subjected to a release treatment, or a release liner made of a low-adhesion material such as a fluorine-based polymer (such as polytetrafluoroethylene) or a polyolefin-based resin (such as polyethylene or polypropylene) can be used. For the above release treatment, for example, a release treatment agent such as a silicone-based or long-chain alkyl-based release treatment agent can be used. In some embodiments, a resin film subjected to a release treatment can be preferably adopted as the release liner.

[0091] The adhesive sheet disclosed herein may optionally have additional layers (such as a base material layer, a primer layer, an anchor layer, etc.) different from the A layer, the B layer, and the C layer, as long as the effects of the invention are not impaired.

[0092] The A layer constituting the adhesive sheet is made of the resin for adhesive sheet described above. Specifically, it is made of a sheet-shaped resin for adhesive sheet (resin sheet). The A layer is characterized in that the storage elastic modulus at 25°C is in the range of 10 MPa to 500 MPa, and the storage elastic modulus at 37°C is in the range of 0.5 MPa to 20 MPa. When the storage elastic modulus of the A layer at 25°C and 37°C is within the above numerical ranges respectively, the adhesive sheet can realize the performance of being difficult to peel off and shift by gently following the adherend. Also, when peeling the adhesive sheet from the adherend, the adhesive sheet moderately resists the deformation during peeling, and the local concentration of stress on the adherend is reduced. Thus, it is possible to complete the peeling while preventing the occurrence of damage to the adherend caused by the stress. The ranges of the storage elastic modulus at 25°C and 37°C that the A layer can take are the same as the ranges described as the storage elastic modulus at 25°C and 37°C of the resin for adhesive sheet, so the description will not be repeated. Also, the details (characteristics, structure, materials, composition, formation method, thickness, etc.) of the A layer disclosed here are the same as the description of the resin for adhesive sheet, so the description will not be repeated.

[0093] The B layer disclosed here is an adhesive layer. The type of the adhesive constituting the adhesive layer is not particularly limited. The above adhesive may contain one or more of various rubbery polymers such as acrylic polymers, rubbery polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluorine polymers, etc. as the adhesive polymer. From the viewpoints of adhesive performance and cost, etc., an adhesive containing an acrylic polymer or a rubbery polymer as the base polymer can be preferably adopted. Among them, an adhesive having an acrylic polymer as the base polymer (acrylic adhesive) is preferable. The technology disclosed here is preferably implemented in a mode using an acrylic adhesive. The "base polymer" of a pressure-sensitive adhesive refers to the main component (e.g., a component that accounts for more than 50% by weight of the polymer) of the polymer contained in the pressure-sensitive adhesive (typically, a polymer that exhibits rubber elasticity in a temperature range around room temperature).

[0094] Hereinafter, as a preferred example of Layer B, we will mainly explain a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive, i.e., a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer, but we do not intend to limit the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein to one made of an acrylic pressure-sensitive adhesive.

[0095] (acrylic polymer) The acrylic pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. Acrylic polymers have a high degree of freedom in molecular design and tend to easily achieve adhesive properties (typically adhesive strength) suitable for the technology disclosed herein. The acrylic polymer used in the acrylic pressure-sensitive adhesive is preferably, for example, a polymer of a monomer raw material that contains a (meth)acrylic acid alkyl ester as a main monomer and may further contain a secondary monomer 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 monomer raw material.

[0096] Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid C 1-20 Alkyl esters are preferably used. From the viewpoint of improving adhesive properties (adhesive strength, holding power, etc.), (meth)acrylic acid C 1-14 It is suitable to use alkyl ester as the main monomer, and (meth)acrylic acid C 1-10 It is preferable that alkyl ester is used as the main monomer, and (meth)acrylic acid C 4-8 It is more preferable that alkyl ester is used as the main monomer, and acrylic acid C 4-8 It is more preferable that the main monomer is an alkyl ester. 1-20 As the alkyl ester, (meth)acrylic acid C exemplified as a monomer component of the acrylic polymer that can be used for the resin for the pressure-sensitive adhesive sheet can be used. 1-20The same alkyl esters can be used. (Meth)acrylic acid C 1-20 The alkyl esters can be used alone or in combination of two or more. (Meth)acrylic acid C 1-20 As the alkyl ester, BA and 2EHA are preferred, and 2EHA is particularly preferred.

[0097] (Meth)acrylic acid C in the monomer components that make up acrylic polymers 1-20 The proportion of alkyl ester is suitably more than 50% by weight, preferably 60% by weight or more (for example, 65% by weight or more), and may be 70% by weight or more, 80% by weight or more, or 90% by weight or more. 1-20 The upper limit of the proportion of alkyl ester is not particularly limited, and is suitably 99% by weight or less. From the viewpoint of effectively exerting the properties (e.g., cohesive strength) based on the copolymerizable monomer such as the polar group-containing monomer, the upper limit is preferably 90% by weight or less, more preferably 80% by weight or less, and may be 75% by weight or less.

[0098] In some embodiments, the monomer components constituting the acrylic polymer include (meth)acrylic acid C 1-20 (Meth)acrylic acid C in alkyl esters 4-12 Alkyl ester (preferably (meth)acrylic acid C 4-10 Alkyl esters, more preferably acrylic acid C 4-8 The proportion of alkyl ester (particularly preferably 2EHA) is preferably 50% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, and may be 95 to 100% by weight. By using such a monomer composition, better adhesive properties are likely to be obtained.

[0099] The monomer components constituting the acrylic polymer preferably include, in addition to the (meth)acrylic acid alkyl ester, another monomer (copolymerizable monomer) copolymerizable with the (meth)acrylic acid alkyl ester. By using an appropriate copolymerizable monomer, excellent adhesive properties (adhesive strength and holding power) can be preferably achieved. As the copolymerizable monomer, a monomer having a functional group can be preferably used, and a monomer having a polar group (e.g., a carboxy group, a hydroxyl group, a nitrogen atom-containing ring, etc.) is more preferred. Monomers having a polar group can be useful for introducing crosslinking points into the acrylic polymer or for improving the cohesive strength and adhesive strength of the acrylic pressure-sensitive adhesive. As the copolymerizable monomer, the same copolymerizable monomers as those exemplified as the monomer components of the acrylic polymer that can be used in the resin for the pressure-sensitive adhesive sheet can be used. Among these, carboxy group-containing monomers, hydroxyl group-containing monomers, and monomers having a nitrogen atom-containing ring are preferred. The copolymerizable monomers can be used alone or in combination of two or more.

[0100] When the monomer component constituting the acrylic polymer contains a polar group-containing monomer as a copolymerizable monomer, the content of the polar group-containing monomer in the monomer component is not particularly limited. From the viewpoint of properly exerting the effects of using the polar group-containing monomer, the content of the polar group-containing monomer in the monomer component can be, for example, 0.1 wt% or more, suitably 1 wt% or more, or may be 3 wt% or more. Furthermore, from the viewpoint of easily balancing the adhesive performance in relation to the main monomer, the content of the polar group-containing monomer in the monomer component is suitably 50 wt% or less, preferably 40 wt% or less, or may be 30 wt% or less.

[0101] In some preferred embodiments, an acidic group-containing monomer is used as a monomer copolymerizable with the (meth)acrylic acid alkyl ester, which is the main monomer. The use of an acidic group-containing monomer can improve cohesion due to its polarity. Furthermore, when a crosslinking agent such as an isocyanate or epoxy crosslinking agent is used, the acidic group (typically a carboxy group) serves as a crosslinking point for the acrylic polymer. These actions allow for a favorable balance between adhesion to the adherend and holding power.

[0102] As the acidic group-containing monomer, a carboxyl group-containing monomer is preferably used. As the carboxyl group-containing monomer, those exemplified above can be used. Suitable examples of the carboxyl group-containing monomer include acrylic acid (AA) and methacrylic acid (MAA). Of these, AA is more preferred. As the acidic group-containing monomer, an ethylenically unsaturated dicarboxylic acid and its anhydride (maleic anhydride, itaconic anhydride, etc.) may also be used. The acidic group-containing monomer can be used alone or in combination of two or more.

[0103] The amount of acidic group-containing monomer (preferably carboxyl group-containing monomer) used (in other words, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer) is not particularly limited, and may be, for example, 0.1 wt% or more of the total monomer components, preferably 1.0 wt% or more, and more preferably 2.0 wt% or more (e.g., 2.5 wt% or more). By using a predetermined amount or more of the acidic group-containing monomer, the cohesive strength of the pressure-sensitive adhesive layer can be improved. Furthermore, the amount of acidic group-containing monomer used is suitably, for example, less than 10 wt% of the total monomer components, and from the viewpoint of achieving both adhesiveness and holding power, it is preferably less than 8.0 wt%, more preferably less than 5.0 wt%.

[0104] In some preferred embodiments, the monomer components constituting the acrylic polymer may contain a nitrogen atom-containing monomer. This can increase the cohesive strength of the adhesive. The above-mentioned examples of the nitrogen atom-containing monomer can be used. Suitable examples of the nitrogen atom-containing monomer include monomers having a nitrogen atom-containing ring. For example, N-vinyl cyclic amides can be mentioned, and among these, N-vinyl-2-pyrrolidone (NVP) can be preferably used. The nitrogen atom-containing monomer can be used alone or in combination of two or more.

[0105] The amount of the nitrogen atom-containing monomer (preferably the nitrogen atom-containing ring-containing monomer) used is not particularly limited, and may be, for example, 1% by weight or more of the total monomer components, suitably 10% by weight or more, preferably 15% by weight or more, and more preferably 20% by weight or more (e.g., 22% by weight or more). The amount of the nitrogen atom-containing monomer used is, for example, 50% by weight or less of the total monomer components, suitably 40% by weight or less, more preferably 35% by weight or less, and even more preferably 30% by weight or less, and may be 20% by weight or less, or may be 10% by weight or less.

[0106] In some preferred embodiments, an acidic group-containing monomer (preferably a carboxyl group-containing monomer) and a nitrogen atom-containing monomer (preferably a nitrogen atom-containing ring-containing monomer) are used in combination as monomer components of the acrylic polymer. This achieves better adhesive properties. For example, high adhesive strength can be achieved even in a thin adhesive layer. Although not intended to be particularly limiting, when an acidic group-containing monomer and a nitrogen atom-containing monomer coexist, high adhesive strength is achieved due to the acid-base interaction, and this effect is thought to be particularly effective in an adhesive layer with a limited thickness. Amount A of acidic group-containing monomer C Amount of monomer having nitrogen atom relative to A N The ratio (A N / A C) is not particularly limited, and may be, for example, 0.1 or more, suitably 1 or more, preferably 3 or more, more preferably 5 or more, and may be 7 or more. N / A C ) can be 20 or less, suitably 15 or less, preferably 12 or less, and may be 9 or less.

[0107] In some embodiments, the proportion of hydroxyl group-containing monomers in the monomer components of the acrylic polymer may be, for example, less than 10% by weight, less than 3% by weight, or less than 1% by weight (e.g., less than 0.1% by weight).Hydroxyl group-containing monomers may be substantially absent from the monomer components of the acrylic polymer.

[0108] In some other embodiments, the monomer components constituting the acrylic polymer may contain an alkoxy group-containing monomer. This facilitates the production of a flexible PSA and also provides excellent moisture permeability, allowing for easy permeation of water vapor and the release of moisture generated from the adherend (e.g., human skin) to the outside. Furthermore, it facilitates the production of a configuration that exhibits excellent conformability to the adherend (e.g., human skin) and excellent repulsion resistance. Suitable examples of the alkoxy group-containing monomer include alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylates) such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate. The alkoxy group-containing monomers may be used alone or in combination of two or more. The amount of the alkoxy group-containing monomer used is not particularly limited, and may be, for example, 1% by weight or more of the total monomer components, suitably 5% by weight or more, and preferably 10% by weight or more, and is, for example, 40% by weight or less of the total monomer components, suitably 30% by weight or less, and more preferably 20% by weight or less.

[0109] The acrylic polymer may contain, as another monomer component, a polyfunctional monomer having at least two polymerizable functional groups (typically radically polymerizable functional groups) with an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group. The use of a polyfunctional monomer as a monomer component can enhance the cohesive strength of the pressure-sensitive adhesive layer. The polyfunctional monomer can be used as a crosslinking agent. The same polyfunctional monomers as those used in the resin for the pressure-sensitive adhesive sheet can be used. The polyfunctional monomers can be used alone or in combination of two or more. The amount of the polyfunctional monomer used is not particularly limited and can be appropriately determined so as to achieve the intended purpose of the polyfunctional monomer. The amount of the polyfunctional monomer used can be in the range of approximately 0.001% by weight to 3% by weight of the monomer components.

[0110] The method for obtaining a polymer (e.g., 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 during solution polymerization can be appropriately selected depending on the types of monomers and solvents used, the type of polymerization initiator, and the like, and can be, for example, about 20°C to 170°C (typically about 40°C to 140°C).

[0111] The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents (toluene, ethyl acetate, etc.). The initiator used in polymerization can be the same as those exemplified as thermal polymerization initiators that can be used in the polymerization of the acrylic polymer in the resin for pressure-sensitive adhesive sheets. For example, azo-based polymerization initiators such as AIBN and peroxide-based initiators can be preferably used. The polymerization initiator can be used alone or in appropriate combination of two or more. The amount of polymerization initiator used may be a normal amount, and can be selected, for example, from the range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of the monomer component.

[0112] (Crosslinking agent) The pressure-sensitive adhesive composition used to form Layer B disclosed herein may contain a crosslinking agent as needed. The type of crosslinking agent is not particularly limited, and can be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agents can be used alone or in combination of two or more. Among these, from the viewpoint of improving cohesive strength, the use of isocyanate-based crosslinking agents and epoxy-based crosslinking agents is preferred, and isocyanate-based crosslinking agents are more preferred.

[0113] The amount of crosslinking agent used is not particularly limited and can be selected, for example, from a range of approximately 10 parts by weight or less (e.g., approximately 0.001 to 10 parts by weight, preferably approximately 0.01 to 5 parts by weight) per 100 parts by weight of base polymer (e.g., acrylic polymer). In some preferred embodiments, the amount of crosslinking agent used is less than 1 part by weight, or even less than 0.5 parts by weight, or even less than 0.1 part by weight (e.g., 0.05 parts by weight) per 100 parts by weight of base polymer (e.g., acrylic polymer). According to the technology disclosed herein, sufficient cohesive strength can be achieved by using a small amount of crosslinking agent by designing the monomer composition of the base polymer.

[0114] (Other optional ingredients) The layer B disclosed herein can optionally contain a tackifying resin for purposes such as improving adhesive strength. The tackifying resin can be one or more selected from tackifying resins such as 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, and ketone tackifying resins. When layer B contains a tackifying resin, the amount of the tackifying resin used is not particularly limited and can be appropriately set within the range of, for example, about 1 to 100 parts by weight per 100 parts by weight of the polymer.

[0115] The adhesive composition for forming Layer B may contain, as necessary, various additives commonly used in the field of adhesive compositions, such as leveling agents, crosslinking aids, plasticizers, softeners, fillers, colorants (dyes, pigments), antistatic agents, antioxidants, UV absorbers, antioxidants, light stabilizers, and dispersants. In an embodiment in which Layer B is attached to human skin, Layer B may contain a component for reducing skin irritation, such as a carboxylic acid ester or a fatty acid ester. The various additives described above can be conventionally known and can be used in the usual manner. Since they do not particularly characterize the present invention, detailed description thereof will be omitted.

[0116] In the technology disclosed herein, the amount of components other than the base polymer (preferably an acrylic polymer) in Layer B may be limited. In the technology disclosed herein, the amount of components other than the base polymer in Layer B is, for example, approximately 30% by weight or less, suitably approximately 10% by weight or less, preferably approximately 5% by weight or less, more preferably approximately 3% by weight or less, and may even be less than 1.0% by weight. In this manner, the effects of the technology disclosed herein are preferably achieved in a composition in which the amount of components other than the base polymer (e.g., an acrylic polymer) is limited.

[0117] (Adhesive composition) The layer B disclosed herein may be a pressure-sensitive adhesive layer formed from an aqueous pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. The aqueous pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive (a pressure-sensitive adhesive layer-forming component) in a solvent (aqueous solvent) whose main component is water, and typically includes what are called water-dispersed pressure-sensitive adhesive compositions (compositions in which at least a portion of the pressure-sensitive adhesive is dispersed in water). The solvent-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive in an organic solvent. The technology disclosed herein is preferably implemented in an embodiment having a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition, from the viewpoint of achieving desirable adhesive properties such as adhesive strength.

[0118] (Formation method) The layer B (pressure-sensitive adhesive layer) disclosed herein can be formed by a conventionally known method. For example, a method can be employed in which a pressure-sensitive adhesive composition is applied to a surface (release surface) having releasability and then dried to form a pressure-sensitive adhesive layer. In a pressure-sensitive adhesive sheet having an A layer, for example, a method (direct method) can be employed in which a pressure-sensitive adhesive composition is directly applied (typically coated) to the A layer and then dried to form a pressure-sensitive adhesive layer (transfer method). Alternatively, a pressure-sensitive adhesive composition can be applied to a surface (release surface) having releasability and then dried to form a pressure-sensitive adhesive layer on the surface, and then the pressure-sensitive adhesive layer can be transferred to the A layer (transfer method). For example, the surface of a release liner can be preferably used as the release surface. Note that the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form. For example, the pressure-sensitive adhesive layer may be formed in a regular or random pattern such as dots or stripes.

[0119] The pressure-sensitive adhesive composition can be applied using a conventional coater such as a gravure roll coater, die coater, or bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating. From the viewpoints of promoting the crosslinking reaction and improving production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. The drying temperature can be, for example, about 40 to 150°C, and preferably about 60 to 130°C. After drying the pressure-sensitive adhesive composition, aging may be performed for the purposes of adjusting component migration within the pressure-sensitive adhesive layer (layer B), promoting the crosslinking reaction, and alleviating distortion that may exist within the pressure-sensitive adhesive layer.

[0120] (25℃ storage modulus) The storage modulus at 25°C of the B layer disclosed herein is not particularly limited. The 25°C storage modulus of the B layer is, for example, 0.03 MPa or more, and may be 0.1 MPa or more, or even 0.3 MPa or more. From the viewpoint of improving adhesive properties (adhesive strength and holding power), the 25°C storage modulus is preferably 1 MPa or more, more preferably 1.5 MPa or more, and even more preferably 2.0 MPa or more. The 25°C storage modulus may be, for example, less than 10 MPa or less than 5 MPa. A B layer having the above 25°C storage modulus can exhibit high adhesive strength while maintaining good holding power. In some preferred embodiments, the 25°C storage modulus of the B layer is 3 MPa or less.

[0121] In an embodiment in which the PSA sheet disclosed herein comprises Layer A and Layer B, the 25°C storage modulus G' of Layer B B is the storage modulus G' of layer A at 25°C A This allows the adhesive strength of Layer B to be exerted while the effects of Layer A (such as resistance to peeling and slippage during adhesion and prevention of damage to the adherend during peeling) can be effectively realized. The storage modulus G' at 25°C of Layer B can be set to be smaller than 25°C. B Storage modulus G' of layer A at 25°C A The ratio of (G′ A / G′ B) is preferably greater than 1, more preferably 10 or more, and even more preferably 20 or more, and may be 30 or more, or may be 40 or more. A / G′ B ) is suitably 200 or less, preferably 100 or less, more preferably 80 or less, and even more preferably 60 or less, and may be 45 or less, or may be 30 or less.

[0122] (glass transition temperature) The glass transition temperature (Tg) of Layer B is set so as to exhibit the desired adhesive properties and is not limited to a specific range. From the viewpoint of adhesive strength, the Tg of Layer B is suitably, for example, about 30°C or less, preferably 20°C or less, more preferably 15°C or less, and may be 0°C or less or -20°C or less. From the viewpoint of cohesive strength, etc., the Tg is suitably -50°C or more, preferably -30°C or more, more preferably -20°C or more, even more preferably -10°C or more, and may be 5°C or more (for example, 10°C or more).

[0123] In an embodiment in which the PSA sheet disclosed herein comprises Layer A and Layer B, the Tg B is the Tg of layer A A This allows the adhesive strength of Layer B to be exerted while the effects of Layer A (such as resistance to peeling and slippage during adhesion and prevention of damage to the adherend during peeling) can be effectively realized. A and Tg of layer B B Difference from (Tg A -Tg B ) is preferably 5°C or higher, more preferably 10°C or higher, and may be 15°C or higher. A -Tg B The temperature is suitably 80°C or lower, preferably 60°C or lower, more preferably 40°C or lower, and even more preferably 25°C or lower.

[0124] The viscoelastic properties of Layer B (storage modulus at 25°C and Tg) can be determined by dynamic viscoelasticity measurement. Specifically, they are measured by the method described in the Examples below. The viscoelastic properties of Layer B can be adjusted by selecting the adhesive constituents and composition, adhesive preparation conditions, etc., based on the description in this specification.

[0125] (Thickness of layer B) The thickness of Layer B is not particularly limited. The thickness of Layer B is usually approximately 300 μm or less, suitably approximately 100 μm or less, preferably approximately 30 μm or less, more preferably less than 10 μm, and may be 5 μm or less (e.g., 3 μm or less). The Layer B disclosed herein can exhibit the desired adhesive strength with the thickness limited as described above. Furthermore, a pressure-sensitive adhesive layer with a limited thickness can effectively meet the demands for thinner and lighter weight. The lower limit of the thickness of Layer B is not particularly limited, and from the viewpoints of adhesiveness and conformability to the adherend, it is, for example, approximately 0.5 μm or more, suitably approximately 1.0 μm or more. In some preferred embodiments, the thickness of Layer B is more than 1.0 μm, more preferably 1.5 μm or more, and may be approximately 3 μm or more. Increasing the thickness of the pressure-sensitive adhesive layer tends to make it easier to obtain better adhesive properties. In some other embodiments, the thickness of Layer B is approximately 5 μm or more, preferably approximately 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more, and may be, for example, 30 μm or more. In embodiments employing a highly flexible Layer B (adhesive), setting the thickness of Layer B to a predetermined value or more makes it easier to obtain a configuration that is excellent in conformability to the adherend (e.g., human skin) and repulsion resistance. In such embodiments, the thickness of Layer B may be, for example, approximately 80 μm or less, 60 μm or less, or 45 μm or less.

[0126] In an embodiment in which the PSA sheet disclosed herein comprises Layer A and Layer B, the thicknesses of Layer A and Layer B are appropriately set so that the effects of each layer are exerted, and are not limited to a specific range. B Thickness of layer A relative to T A The ratio (T A / T B) is preferably about 1 or more. From the viewpoint of effectively exhibiting the effects of providing the A layer (such as difficulty in peeling and displacement during adhesion and fixing, and prevention of damage to the adherend during peeling), the above ratio (T A / T B ) is preferably 5 or more, more preferably 10 or more, still more preferably 30 or more, and may be 40 or more (for example, 45 or more). Also, from the viewpoint of expressing the adhesive force by the B layer, etc., the above ratio (T A / T B ) is suitably 200 or less, preferably 100 or less, more preferably 80 or less, and may be, for example, 60 or less. In some other embodiments, the above ratio (T A / T B ) may be 0.1 or more, may be 0.3 or more, may be 0.5 or more, or may be 0.7 or more (for example, 0.8 or more). The technology disclosed herein can also be preferably implemented in a configuration where the thickness of the B layer is relatively large with respect to the A layer, or a configuration where the thickness of the B layer is equal to the thickness of the A layer. For example, in an embodiment using a highly flexible B layer (adhesive layer), by providing the A layer in a configuration that satisfies the above range of the ratio (T A / T B ), the effects such as difficulty in peeling and displacement during adhesion and fixing, and prevention of damage to the adherend during peeling can be realized. In such an embodiment, the above ratio (T A / T B ) may be, for example, 50 or less, may be 10 or less, or may be 3 or less (for example, 1.5 or less).

[0127] <C layer> The C layer disclosed herein is a layer having viscoelasticity, that is, a viscoelastic body layer. The viscoelastic body here is a material having both viscous and elastic properties, that is, a material that satisfies the property that the phase of the complex elastic modulus exceeds 0 and is less than π / 2 (typically a material having the above properties at 25°C). From the viewpoint of flexibility, etc., the complex tensile elastic modulus E * (1 Hz) < 10 7 dyne / cm 2A material having the properties that satisfy the above (typically, a material having the above properties at 25°C) is preferred. A pressure-sensitive adhesive sheet having a C layer made of a viscoelastic body increases the amount of energy required to peel it off from an adherend, and can be flexible and therefore less likely to peel off even from a moving adherend such as human skin.

[0128] The composition of Layer C is not particularly limited as long as it exhibits the properties of a viscoelastic material in a temperature range near room temperature. Layer C can be a layer composed of one or more viscoelastic materials selected from various viscoelastic materials, such as acrylic viscoelastic materials, rubber viscoelastic materials, silicone viscoelastic materials, polyester viscoelastic materials, urethane viscoelastic materials, polyether viscoelastic materials, polyamide viscoelastic materials, and fluorine viscoelastic materials. Here, the term "acrylic viscoelastic material" refers to a viscoelastic material having an acrylic polymer as the base polymer (the main component of the polymer components, i.e., a component contained in an amount exceeding 50% by weight). The same applies to rubber-based and other viscoelastic materials.

[0129] Layer C may be either an adhesive layer or a non-adhesive layer. Here, the term "adhesive layer" refers to a layer that, in accordance with JIS Z0237 (2004), uses a SUS304 stainless steel plate as an adherend, is pressed against the adherend by rolling a 2 kg roller back and forth once at 23°C, and then 30 minutes later is peeled off in a 180° direction at a tensile speed of 300 mm / min. It is also referred to as a pressure-sensitive adhesive layer. Furthermore, the term "non-adhesive layer" refers to a layer that does not fall under the category of adhesive layer, and typically has a peel strength of less than 0.1 N / 20 mm. A layer that does not adhere to a SUS304 stainless steel plate when pressed against the stainless steel plate by rolling a 2 kg roller back and forth once at 23°C (a layer that does not substantially exhibit adhesiveness) is a typical example of a non-adhesive layer. Although not particularly limited, the technology disclosed herein can be preferably implemented in a form including Layer C corresponding to the adhesive layer, i.e., in the form of a pressure-sensitive adhesive sheet including Layer C as a pressure-sensitive adhesive layer. For example, in a configuration in which a pressure-sensitive adhesive sheet has Layer A on one side of Layer A and Layer C on the other side, if Layer C is a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet will have double-sided adhesiveness.

[0130] In some preferred embodiments, the C layer may be a layer containing an acrylic polymer as a base polymer, i.e., an acrylic viscoelastic layer. A C layer having such a composition is preferred because it is easy to adjust the balance between flexibility and cohesion. The proportion of the acrylic polymer in the C layer is not particularly limited, but is typically 50% by weight or more, preferably 70% by weight or more, and more preferably 80% by weight or more.

[0131] The acrylic polymer is preferably a polymer of a monomer raw material that contains, for example, a (meth)acrylic acid alkyl ester as a main monomer and may further contain a secondary monomer copolymerizable with the main monomer. Here, the main monomer refers to a component that accounts for more than 50% by weight of all the monomer components contained in the monomer raw material. The composition of the monomer components contained in the monomer raw material typically roughly corresponds to the composition of the monomer units contained in the acrylic polymer.

[0132] Examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid C 1-20 From the viewpoint of the viscoelastic properties (which may be adhesive properties) of the C layer, (meth)acrylic acid C is preferably used. 1-14 It is suitable to use alkyl ester as the main monomer, and (meth)acrylic acid C 1-10 It is preferable that alkyl ester is used as the main monomer, and (meth)acrylic acid C 4-8 It is more preferable that alkyl ester is used as the main monomer, and acrylic acid C 4-8 It is more preferable that the main monomer is an alkyl ester. 1-20 As the alkyl ester, (meth)acrylic acid C exemplified as a monomer component of the acrylic polymer that can be used for the resin for the pressure-sensitive adhesive sheet can be used. 1-20 The same alkyl esters can be used. (Meth)acrylic acid C 1-20 The alkyl esters can be used alone or in combination of two or more. (Meth)acrylic acid C 1-20As the alkyl ester, BA and 2EHA are preferred, and 2EHA is particularly preferred.

[0133] Although not particularly limited, (meth)acrylic acid C 1-20 The amount of alkyl ester can be, for example, 60% by weight or more of the total monomer components constituting the acrylic polymer, and is usually preferably 70% by weight or more, and more preferably 80% by weight or more (for example, 90% by weight or more). From the viewpoint of the cohesion of the C layer, etc., the amount of (meth)acrylic acid C 1-20 The amount of alkyl ester is suitably 99.5% by weight or less, preferably 99% by weight or less, and more preferably 95% by weight or less.

[0134] Examples of secondary monomers include monomers having a functional group (hereinafter also referred to as "functional group-containing monomers"). Such functional group-containing monomers can be used for the purpose of introducing crosslinking points into the acrylic polymer and increasing the cohesive strength of Layer C. As such functional group-containing monomers, the same monomers having a functional group as those copolymerizable monomers exemplified as monomer components of the acrylic polymer that can be used in the resin for the pressure-sensitive adhesive sheet can be used. The functional group-containing monomers can be used alone or in combination of two or more.

[0135] When the functional group-containing monomer described above is used as a secondary monomer, its amount is not particularly limited and may be appropriately selected so as to achieve the desired cohesive strength. The amount of functional group-containing monomer used may be, for example, 0.5% by weight or more of the total monomer components constituting the acrylic polymer, and is usually suitably 1% by weight or more, preferably 3% by weight or more, and more preferably 5% by weight or more. Furthermore, from the viewpoint of achieving a good balance between flexibility and cohesive strength, the amount of functional group-containing monomer is suitably 30% by weight or less of the total monomer components, preferably 25% by weight or less, and more preferably 20% by weight or less.

[0136] The monomer raw material may contain a secondary monomer other than the functional group-containing monomer described above for the purpose of adjusting the glass transition temperature (Tg) or improving the cohesive strength. Such secondary monomers include: For example, vinyl carboxylic acid vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl cyclohexanecarboxylate, and vinyl benzoate; For example, aromatic vinyl compounds such as styrene, substituted styrenes (such as α-methylstyrene), and vinyltoluene; For example, 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); olefinic monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers, such as vinyl chloride and vinylidene chloride; For example, vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; These can be used alone or in combination of two or more. The amount of such secondary monomers used is not particularly limited and may be appropriately selected depending on the purpose and application, but is preferably, for example, 10% by weight or less of the total monomer components.

[0137] The monomer raw material may contain a polyfunctional monomer as needed for purposes such as crosslinking. The polyfunctional monomer may be the same as the polyfunctional monomer that can be used in the resin for the pressure-sensitive adhesive sheet. The polyfunctional monomer may be used alone or in combination of two or more. From the viewpoint of reactivity, a polyfunctional monomer having two or more (typically three or more) acryloyl groups in one molecule is generally preferred. When using such a polyfunctional monomer, its amount is not particularly limited, but from the viewpoint of the flexibility of the C layer, it is generally appropriate to use more than 0% by weight and not more than 2% by weight (more preferably not more than 1% by weight) of the total monomer components.

[0138] The monomer composition of the acrylic polymer can be set so that the Tg of the acrylic polymer is, for example, −70° C. or higher and −10° C. or lower. From the viewpoint of flexibility, the Tg of the acrylic polymer is suitably −20° C. or lower, preferably −30° C. or lower, more preferably −40° C. or lower, and even more preferably −50° C. or lower. Furthermore, from the viewpoint of the cohesiveness of the C layer, the Tg may be −65° C. or higher.

[0139] Here, the Tg of the acrylic polymer refers to the value calculated from the Fox equation based on the Tg of the homopolymer of each monomer constituting the acrylic polymer and the weight fraction (copolymerization ratio by weight) of the monomer. Therefore, the Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the type and amount ratio of the monomers used in the synthesis of the acrylic polymer). The Tg of the homopolymer is determined from known sources (e.g., "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989)).

[0140] The acrylic polymer can be prepared by a known or conventional polymerization method. Examples of polymerization methods that can be used include thermal polymerization (typically carried out in the presence of a thermal polymerization initiator), such as solution polymerization, emulsion polymerization, and bulk polymerization; and active energy ray polymerization, which involves irradiating with active energy rays, such as ultraviolet light or other light, or radiation, such as beta rays or gamma rays. Examples of active energy ray polymerization include photopolymerization (typically carried out in the presence of a photopolymerization initiator), which involves irradiating with ultraviolet light or other light, and radiation polymerization, which involves irradiating with ionizing radiation, such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams. These polymerization methods can be used alone or in combination of two or more.

[0141] For polymerization, a known or conventional polymerization initiator can be used depending on the polymerization method, polymerization mode, etc. As the polymerization initiator, the same initiators as those exemplified as those usable in the polymerization of the acrylic polymer in the resin for pressure-sensitive adhesive sheets can be used. The polymerization initiators can be used alone or in appropriate combinations of two or more. Photopolymerization initiators are preferably used because of their advantage of being able to shorten the polymerization time. The amount of such thermal polymerization initiator or photopolymerization initiator used can be a normal amount depending on the polymerization method, polymerization mode, etc., and is not particularly limited. For example, 0.001 to 5 parts by weight (typically 0.01 to 2 parts by weight, for example 0.01 to 1 part by weight) of initiator can be used per 100 parts by weight of the monomer raw material.

[0142] The composition for forming the C layer preferably contains a partially polymerized product of a portion of the monomer components. Alternatively, the composition for forming the C layer (the composition for forming the viscoelastic layer) may contain an acrylic polymer as a complete polymer of the monomer components (e.g., an acrylic polymer having a polymerization conversion rate of 95% by weight or more of the monomer components). For example, the composition may be a solvent-based composition containing such an acrylic polymer in an organic solvent, or an aqueous dispersion-based composition in which the acrylic polymer is dispersed in an aqueous solvent.

[0143] The composition for forming Layer C may contain a crosslinking agent. Examples of crosslinking agents that can be used include those known or commonly used in the field of pressure-sensitive adhesives (e.g., acrylic pressure-sensitive adhesives). Examples of crosslinking agents include epoxy-based crosslinking agents, isocyanate-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl-etherified melamine-based crosslinking agents, and metal chelate-based crosslinking agents. Alternatively, the composition may be substantially free of such crosslinking agents.

[0144] The C layer may contain a filler. By including a filler in the C layer, the shear strength of the C layer can be increased. This can improve the resistance (peel strength) to peeling the PSA sheet from the adherend. Furthermore, the use of a filler can suppress excessive deformation of the C layer and suitably adjust the balance between flexibility and cohesion of the entire PSA sheet.

[0145] Various particulate materials can be used as fillers. Examples of materials constituting such particulate materials include metals such as copper, nickel, aluminum, chromium, iron, and stainless steel; metal oxides such as alumina and zirconia; carbides such as silicon carbide, boron carbide, and nitrogen carbide; nitrides such as aluminum nitride, silicon nitride, and boron nitride; inorganic materials such as calcium carbide, calcium carbonate, aluminum hydroxide, glass, and silica; and polymers such as polystyrene, acrylic resins (e.g., polymethyl methacrylate), phenolic resins, benzoguanamine resins, urea resins, silicone resins, nylon, polyester, polyurethane, polyethylene, polypropylene, polyamides, polyimides, silicones, and vinylidene chloride. Alternatively, particles of natural materials such as volcanic ash and sand may be used. These materials can be used alone or in combination of two or more. The outer shape or particle form of the particulate substance is not particularly limited. The outer shape of the particulate substance may be, for example, spherical, flaky, irregular, etc. The particle structure of the particulate substance may be, for example, a dense structure, a porous structure, a hollow structure, etc.

[0146] The technology disclosed herein can be preferably implemented in an embodiment in which Layer C contains a particulate material with a hollow structure (hereinafter also referred to as "hollow particles") as the filler. From the viewpoint of photocurability (polymerization reactivity), hollow particles made of inorganic materials can be preferably used. Examples of such hollow particles include glass balloons such as hollow glass balloons; hollow balloons made of metal compounds such as hollow alumina balloons; and hollow balloons made of porcelain such as hollow ceramic balloons.

[0147] Examples of hollow glass balloons that can be used include commercially available products such as "Glass Microballoons," "Fuji Balloon H-40," and "Fuji Balloon H-35" manufactured by Fuji Silysia Chemical Ltd.; "Cellstar Z-20," "Cellstar Z-27," "Cellstar CZ-31T," "Cellstar Z-36," "Cellstar Z-39," "Cellstar T-36," and "Cellstar PZ-6000" manufactured by Tokai Kogyo Co., Ltd.; "Cyrax Fine Balloon" manufactured by Fine Balloon Co., Ltd.; "Q-CEL™ 5020," "Q-CEL™ 7014," "Sphericel™ 110P8," "Sphericel™ 25P45," "Sphericel™ 34P30," and "Sphericel™ 60P18" manufactured by Potters Ballottini; and "Super Balloon BA-15" and "Super Balloon 732C" manufactured by Showa Chemical Industry Co., Ltd.

[0148] The average particle size of the hollow particles used is not particularly limited. For example, it can be selected within the range of 1 μm to 500 μm, preferably 5 μm to 400 μm, more preferably 10 μm to 300 μm, and even more preferably 10 μm to 200 μm (e.g., 10 to 150 μm). The average particle size of the hollow particles is usually suitably 50% or less of the thickness of layer C, and preferably 30% or less (e.g., 10% or less). The specific gravity of the hollow particles is not particularly limited, but is set to, for example, 0.1 to 1.8 g / cm3 in consideration of uniform dispersion and mechanical strength. 3 , preferably 0.1 to 1.5 g / cm 3 , and more preferably 0.1 to 0.5 g / cm 3 (e.g. 0.2-0.5g / cm 3 ) can be selected from the range. The amount of hollow particles used is not particularly limited, and can be, for example, about 1 to 70 volume % of the total volume of Layer C, usually about 5 to 50 volume % is appropriate, and about 10 to 40 volume % is preferable.

[0149] The C layer may contain air bubbles. By incorporating air bubbles into the C layer, the cushioning properties of the pressure-sensitive adhesive sheet can be improved, thereby increasing its flexibility. When the flexibility of the pressure-sensitive adhesive sheet is increased, the pressure-sensitive adhesive sheet can more easily absorb unevenness or steps on the surface of the adherend due to deformation, thereby allowing the adhesive surface to better adhere to the surface of the adherend. With a cushioning C layer, when the adhesive surface on the C layer side is attached to, for example, a hard adherend, the presence of the C layer can absorb the shape of the hard adherend, preventing or reducing the influence on the opposite side of the pressure-sensitive adhesive sheet. Furthermore, improved flexibility of the pressure-sensitive adhesive sheet can also contribute to the pressure-sensitive adhesive sheet's resistance to slippage. When a pressure-sensitive adhesive sheet is attached along the surface of an adherend having a curved or uneven surface, or when the adherend to which the pressure-sensitive adhesive sheet is attached is deformed, the pressure-sensitive adhesive sheet can effectively be prevented from peeling (lifting) from the surface of the adherend due to its own repulsive force. Layer C may contain both the above-mentioned filler (for example, hollow particles) and air bubbles. A pressure-sensitive adhesive sheet containing such a layer C is preferred because it tends to have an excellent balance between flexibility and cohesive strength.

[0150] The bubbles contained in Layer C may be closed bubbles, open bubbles, or a mixture of these. From the viewpoint of cushioning properties, a Layer C having a configuration containing many closed bubbles is more preferable. In the case of closed bubbles, the gas components contained in the bubbles (gas components that form bubbles, hereinafter sometimes referred to as "bubble-forming gas") are not particularly limited and may be various gas components such as air, as well as inert gases such as nitrogen, carbon dioxide, and argon. When a polymerization reaction or the like is carried out in a state in which the bubble-forming gas is contained, it is preferable to use a bubble-forming gas that does not inhibit the reaction. From this viewpoint as well as from the viewpoint of cost, nitrogen can be preferably used as the bubble-forming gas.

[0151] The shape of the bubbles is typically roughly spherical, but is not limited thereto. The average diameter of the bubbles (average bubble diameter) is not particularly limited and can be selected, for example, within the range of 1 μm to 1000 μm, preferably 10 μm to 500 μm, and more preferably 30 μm to 300 μm. The average bubble diameter is usually suitably 50% or less of the thickness of layer C, and preferably 30% or less (e.g., 10% or less). The average cell diameter can be determined by arithmetically averaging the diameters of preferably 10 or more cells measured using a scanning electron microscope (SEM). In this case, for non-spherical cells, the average cell diameter is calculated by converting the diameter into that of spherical cells having the same volume.

[0152] When the C layer has bubbles, the volume ratio of the bubbles in the C layer (bubble content) is not particularly limited and can be appropriately set so as to achieve the desired cushioning and flexibility. For example, the volume ratio of the bubbles in the C layer (referring to the apparent volume, which can be calculated from the thickness and area of ​​the C layer) can be about 3 to 70 volume %, usually about 5 to 50 volume %, and preferably about 8 to 40 volume %.

[0153] In the technology disclosed herein, the method for forming the bubble-containing layer C (bubble-containing viscoelastic layer) is not particularly limited, and any known method can be appropriately employed. For example, (1) a method of curing a viscoelastic layer-forming composition (preferably a composition that cures with active energy rays such as ultraviolet light to form a viscoelastic body) containing a bubble-forming gas to form a bubble-containing viscoelastic layer, or (2) a method of forming a bubble-containing viscoelastic layer by using a viscoelastic layer-forming composition containing a foaming agent and forming bubbles from the foaming agent, etc., can be appropriately employed. The foaming agent used is not particularly limited, and can be appropriately selected from known foaming agents. For example, a foaming agent such as heat-expandable microspheres can be preferably used. In forming a bubble-containing viscoelastic layer by the method (1) above, the method for preparing the viscoelastic layer-forming composition containing the bubble-forming gas is not particularly limited, and known bubble mixing methods can be used. For example, an example of a bubble mixing device includes a device equipped with a stator having a central through-hole, a disk with many fine teeth, and a rotor facing the stator, the disk having fine teeth similar to those on the stator. In such a bubble mixing device, the viscoelastic layer-forming composition (viscoelastic layer-forming composition precursor) is introduced between the teeth on the stator and the teeth on the rotor. While the rotor is rotating at high speed, a gas component for forming bubbles (bubble-forming gas) is introduced into the viscoelastic layer-forming composition precursor through the through-holes. This results in a viscoelastic layer-forming composition containing finely dispersed and mixed bubbles. A bubble-containing viscoelastic layer can be formed by applying the bubble-forming gas-mixed composition to a predetermined surface and curing it. A preferred curing method is heating or irradiating with active energy rays (e.g., ultraviolet rays). The bubble-forming gas-mixed viscoelastic layer-forming composition can be cured by heating or irradiating with active energy rays while stably maintaining the bubbles, thereby suitably forming a bubble-containing viscoelastic layer.

[0154] From the viewpoint of the incorporation of bubble-forming gas and bubble stability, a surfactant may be added to the composition for forming the viscoelastic layer. Examples of such surfactants include ionic surfactants, hydrocarbon surfactants, silicone surfactants, and fluorine-based surfactants. Among these, fluorine-based surfactants are preferred, and fluorine-based surfactants having an oxyalkylene group (typically an oxyalkylene group having 2 to 3 carbon atoms) and a fluorinated hydrocarbon group in the molecule are particularly preferred. One type of fluorine-based surfactant can be used alone, or two or more types can be used in combination. An example of a commercially available fluorine-based surfactant that can be preferably used is "Surflon S-393" manufactured by AGC Seimi Chemical Co., Ltd. The amount of surfactant used is not particularly limited, and can be, for example, about 0.01 to 3 parts by weight on a solids basis relative to 100 parts by weight of the base polymer (for example, an acrylic polymer) contained in the C layer.

[0155] Layer C may contain known additives such as plasticizers, softeners, colorants (pigments, dyes, etc.), antioxidants, leveling agents, stabilizers, and preservatives as needed, provided that the effects of the present invention are not significantly impaired.

[0156] The method for forming a pressure-sensitive adhesive sheet including a C layer is not particularly limited. For example, a method can be preferably employed in which a composition for forming a C layer is applied to a surface with good releasability (a release surface, for example, the surface of a release liner) and cured (for example, by ultraviolet curing) to form a C layer, and the resulting C layer is then laminated (transferred) to the surface of an A layer. Alternatively, a pressure-sensitive adhesive sheet including a C layer may be formed by applying a C layer-forming composition to the surface of, for example, an A layer and curing (for example, by ultraviolet curing).

[0157] In some embodiments, a substrate-less or substrate-attached double-sided PSA sheet containing a PSA layer may be used as Layer C. The PSA used in the PSA layer is a layer composed of one or more PSA layers selected from various PSA layers, such as acrylic PSAs, rubber PSAs, silicone PSAs, polyester PSAs, urethane PSAs, polyether PSAs, polyamide PSAs, and fluorine PSAs. Of these, Layer C containing an acrylic PSA layer is preferred. For details of such PSA, see the description of the viscoelastic body of Layer C, and redundant description will not be repeated here. The substrate of the substrate-attached double-sided PSA sheet is not particularly limited, and resin films, paper, cloth, woven fabrics, nonwoven fabrics, foam sheets, composites thereof, and the like can be used. Among these, nonwoven fabrics are preferred. One preferred example is a substrate-attached double-sided PSA sheet in which acrylic PSA layers are provided on both sides of a nonwoven fabric substrate.

[0158] The thickness of the C layer is not particularly limited and is, for example, 200 μm or more. The C layer is a viscoelastic body and therefore has excellent flexibility. By disposing the C layer, the surface (adhesive surface) of the pressure-sensitive adhesive sheet can be suitably adhered to the adherend. From the viewpoint of this flexibility, the thickness of the C layer is preferably 250 μm or more, and more preferably 300 μm or more (e.g., 350 μm or more). From the viewpoint of obtaining even greater flexibility, the thickness of the C layer can be set to 500 μm or more, and may be set to 700 μm or more. The technology disclosed herein can also be preferably implemented in an embodiment in which the C layer is 1 mm or more thick. By increasing the thickness of the C layer, the effects of the C layer (e.g., resistance to peeling from an adherend such as flexible and mobile human skin, ability to absorb the uneven shape of the adherend, cushioning, etc.) tend to be favorably exhibited. The upper limit of the thickness of the C layer is not particularly limited and can be, for example, approximately 10 mm or less. From the viewpoint of ease of formation and cohesion of the C layer, the thickness of the C layer is usually appropriate to be 5 mm or less, and preferably 3 mm or less (e.g., 2 mm or less). In some other embodiments, the thickness of Layer C (which may be in the form of, for example, a substrate-less double-sided PSA sheet or a substrate-attached double-sided PSA sheet) may be approximately 30 μm or more, approximately 50 μm or more, approximately 80 μm or more, or 120 μm or more. In such embodiments, the thickness of Layer C may be, for example, approximately 1 mm or less, approximately 500 μm or less, or less than 300 μm (e.g., less than 200 μm). According to the technology disclosed herein, by providing a PSA sheet with Layer A and Layer C of the above thickness, stable adhesion and fixation can be achieved for adherends attached to both sides of the PSA sheet.

[0159] <Other layers> The pressure-sensitive adhesive sheet disclosed herein may optionally have, in addition to the above-mentioned layer A, other layers different from the above-mentioned layers A, B, and C. Examples of such other layers include a layer disposed between layers A and B, a layer disposed between layers A and C, and a layer disposed on the back surface of layer A (the surface opposite the adhesive surface side; for example, in a configuration having a laminated structure of layers A and B (pressure-sensitive adhesive layers), the surface of layer A opposite the layer B side). Such other layers may be, for example, layers supporting layer A, layer B, or layer C. Examples of such other layers include, but are not limited to, nonwoven fabrics, woven fabrics, and other porous films. Examples of nonwoven fabrics, woven fabrics, and other porous films include the materials described as the base layer of layer A. Repetitive explanations will be omitted here.

[0160] <Characteristics of adhesive sheets> (180 degree peel strength) The adhesive strength (180-degree peel strength against a stainless steel plate) of the adhesive surface of the adhesive sheet disclosed herein (in a configuration including Layer B, the adhesive surface on the Layer B side) is not limited to a specific range, as it may vary depending on the intended use and the application site. The adhesive strength of the adhesive sheet can be, for example, approximately 1 N / 10 mm or more, and is suitably approximately 2 N / 10 mm or more. From the viewpoint of adhesion reliability, the adhesive strength is preferably 4 N / 10 mm or more, more preferably 4.5 N / 10 mm or more, and even more preferably 5.0 N / 10 mm or more, and may be 5.5 N / 10 mm or more (e.g., 6.0 N / 10 mm or more). An adhesive sheet having the above adhesive strength can exhibit good adhesive and fixing function, and can exhibit adhesiveness that is difficult to peel, even against flexible and mobile human skin, for example. The upper limit of the adhesive strength is not particularly limited, and may be approximately 12 N / 10 mm or less (e.g., 8 N / 10 mm or less). The adhesive strength can be measured by the method described in the Examples below. In the case of a double-sided pressure-sensitive adhesive sheet having adhesive surfaces on both sides, the adhesive strength on each side may be the same or different.

[0161] (holding force) In a holding power evaluation test carried out by the method described in the Examples below, the PSA sheet disclosed herein preferably exhibits a displacement of less than 0.1 mm from the initial application position one hour after the start of the test. Such a PSA sheet is unlikely to slip from its state when applied to an adherend, and can exhibit excellent adhesive reliability in applications where it is applied for a long period of time.

[0162] (double-sided adhesive sheet) Some preferred embodiments of the PSA sheet are double-sided PSA sheets having a B layer, an A layer, and a C layer in this order. This configuration allows the B layer adhesive surface and the C layer adhesive surface to be attached to different adherends, respectively, to exhibit adhesive and fixing functions. While not particularly limited, by attaching the B layer adhesive surface to a flexible and mobile adherend (typically human skin), the sheet is less likely to peel or slip off the adherend, while achieving peeling without damaging the adherend. Furthermore, when the C layer adhesive surface is attached to, for example, a hard adherend (e.g., a sensor containing resin or metal), the presence of the C layer can prevent or reduce the influence of the shape of the hard adherend on the B layer adherend. For example, in an embodiment in which the B layer side is attached to human skin, discomfort caused by the presence of an adherend attached to the C layer side can be eliminated or reduced.

[0163] (Total thickness of adhesive sheet) The total thickness of the PSA sheet disclosed herein (including Layers A to C, but excluding the release liner) is not particularly limited. In some preferred embodiments, the total thickness of the PSA sheet can be, for example, approximately 12 mm or less. From the viewpoints of handleability and formability, it is suitably approximately 5 mm or less, preferably approximately 2 mm or less, more preferably approximately 1.5 mm or less, and may be approximately 1 mm or less. The lower limit of the thickness of the PSA sheet according to such embodiments is not particularly limited, but is suitably, for example, approximately 200 μm or more, preferably approximately 400 μm or more, more preferably approximately 600 μm or more, and may be approximately 800 μm or more. Although not particularly limited, the above total thickness can be preferably adopted as the total thickness of a PSA sheet having Layers A, B, and C. In some other embodiments, the thickness of the PSA sheet is suitably, for example, approximately 10 μm or more, preferably approximately 50 μm or more, more preferably approximately 80 μm or more, and may be approximately 100 μm or more. In this embodiment, the upper limit of the thickness of the pressure-sensitive adhesive sheet is not particularly limited, but can be approximately 2500 μm or less, and may be, for example, approximately 1000 μm or less, 500 μm or less, 300 μm or less, or even 200 μm or less. Pressure-sensitive adhesive sheets with limited thickness are suitable for applications where lighter weight and thinner thickness are desired.

[0164] <Application> The uses of the pressure-sensitive adhesive sheet disclosed herein are not particularly limited, and it can be used in a variety of applications. The pressure-sensitive adhesive sheet disclosed herein has adhesive reliability that makes it difficult to peel and slip, and the ability to not damage the adherend when peeled, so it can be preferably used in applications where the above-mentioned adhesive reliability is required and damage to the adherend is undesirable. For example, it can be used in applications where it is attached to adherends with brittle surfaces or adherends with low mechanical strength. Furthermore, because it has adhesive reliability that can withstand long-term attachment, it can be used in applications where attachment and fixation for several days or weeks or more are required. In particular, the pressure-sensitive adhesive sheet disclosed herein can be preferably used in an embodiment where its adhesive surface (specifically, the adhesive surface on the layer B side) is directly or indirectly attached to the skin of a living body (typically a human). Once attached to the skin, the pressure-sensitive adhesive sheet gently conforms to the attachment site due to body temperature, thereby achieving resistance to peeling and slippage. For example, it can have resistance to peeling and slippage even when the person moves. On the other hand, when peeling off the adhesive sheet, the adhesive sheet moderately resists deformation during peeling, reducing the local concentration of stress on the adherend, so there is less pulling (deformation) on the skin when peeling the adhesive off the skin, resulting in a peeling that is gentle on the skin and causes no or little pain.

[0165] Furthermore, the PSA sheets (typically double-sided PSA sheets) disclosed herein are suitable for applications in which a hard adherend is attached to the skin. The type of hard adherend is not particularly limited, and various metal or resin products and components having a predetermined shape can be attached to human skin. When the above-mentioned products are attached to the skin, their shape and hardness are transmitted to the skin, which can cause discomfort. However, the PSA sheets disclosed herein can preferably have cushioning properties that absorb the shape of the adherend, and by adopting such a configuration, it is possible to fix various products to the skin without any discomfort.

[0166] Suitable examples of hard adherends that can be attached to the skin include various sensors. The technology disclosed herein is particularly suitable for applications involving attaching sensors that can be attached to a living body, such as a human, to acquire information about the body's internal and movement information. The adhesive sheet disclosed herein is resistant to peeling and shifting, even when a sensor or the like is fixed to a specific part of a human body via the adhesive sheet, allowing the sensing function associated with the sensor fixation part to be exhibited with high accuracy. By using such an adhesive sheet capable of fixing a sensor to a part of the human body, medical professionals can obtain information such as a patient's health condition without directly contacting the patient, which can be useful, for example, for home medical care and remote medical examinations and treatments. The adhesive sheet can also be used in the fields of healthcare and preventive medicine. Furthermore, if the adhesive sheet disclosed herein can be used to accurately grasp, for example, the movements of each part of a human body, it can be expected to be used in the sports field. The adhesive sheet disclosed herein can be useful in fields such as medicine, healthcare, and sports science.

[0167] As described above, this specification provides an adhesive sheet to which a sensor is attached, i.e., an adhesive sheet with a sensor. The adhesive sheet with a sensor may have, for example, a cross-sectional structure as shown schematically in FIG. 4. In the adhesive sheet with a sensor 300 shown in FIG. 4, the adhesive sheet 2 is a double-sided adhesive sheet, and a sensor 50 is fixed to one adhesive surface 2B thereof. In this embodiment, the other adhesive surface 2A of the adhesive sheet 2 is attached to human skin. The other configuration of the adhesive sheet 2 is basically the same as the configuration shown in FIG. 3, so description will not be repeated.

[0168] In an embodiment in which the technology disclosed herein is implemented in the form of a single-sided adhesive sheet (single-sided adhesive sheet), when the single-sided adhesive sheet is used to fix an adherend, one adherend can be fixed to the back surface (non-adhesive surface) of the single-sided adhesive sheet using a known or conventional adhesive or pressure-sensitive adhesive (which may be in the form of double-sided adhesive tape), and the adhesive surface of the single-sided adhesive sheet can be attached to the other adherend. For example, the adhesive sheet disclosed herein can be preferably used in an embodiment in which a sensor is fixed to the back surface of the single-sided adhesive sheet using double-sided adhesive tape, and the adhesive surface of the single-sided adhesive sheet is attached to human skin. [Example]

[0169] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0170] <Experiment 1> [Preparation of Resin Sheet A] (Preparation example A1) A flask equipped with a reflux condenser, thermometer, and dropping funnel was charged with 156 g of 2-ethylhexyl acrylate (2EHA), 36 g of N-vinylpyrrolidone (NVP), 8 g of 4-hydroxybutyl acrylate (4HBA), and 0.2 g each of 2,2-dimethoxy-1,2-diphenylethan-1-one (IGM Resins, product name "Omnirad 651") and 1-hydroxycyclohexyl phenyl ketone (IGM Resins, product name "Omnirad 184") as photopolymerization initiators. The atmosphere was then purged with nitrogen. The mixture was then irradiated with ultraviolet light from a high-pressure mercury lamp (EXECURE 4000, HOYA CANDEO OPTRONICS CORPORATION) to obtain a viscous liquid (UV syrup) containing a partial polymerization product of the monomer mixture. 50 g of this UV syrup was mixed with 50 g of isobornyl acrylate (IBXA) and 0.1 g of 1,6-hexanediol diacrylate (HDDA) as a crosslinking agent to obtain an ultraviolet-curable resin composition according to this example.

[0171] The resin composition obtained above was applied to the release-treated surface of a 38 μm-thick release film R1 (manufactured by Mitsubishi Plastics, product name "MRF#38"), a polyethylene terephthalate (PET) film with one side treated with a silicone release agent. The resin composition was then covered with a 38 μm-thick release film R2 (manufactured by Mitsubishi Plastics, product name "MRE#38"), a PET film with one side treated with a silicone release agent (light release agent), to block air. The resin sheet A1 was then cured (polymerized) by irradiation with ultraviolet light (black light), forming a 100 μm-thick resin sheet A1. The ultraviolet light was irradiated using a black light lamp at an illuminance of 5 mW / cm. 2 (Measured using an industrial UV checker (manufactured by Topcon Corporation, product name "UVR-T1") with a peak sensitivity wavelength of approximately 350 nm.) The obtained resin sheet A1 was protected on each side by release films (release liners) R1 and R2.

[0172] (Preparation example A2) A UV-curable resin composition was prepared in the same manner as in Preparation Example A1. 50 g of the resulting resin composition was added to 50 g of water and stirred at 5,000 rpm for 2 minutes using a TK Robomix (manufactured by PRIMIX). The resulting resin composition emulsion was applied to a release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF #38") in the same manner as in Preparation Example A1. Next, a release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE #38") was placed over the composition to block air. The composition was then irradiated with UV light (black light) to cure the composition (to complete the polymerization). This resin sheet A2 was then dried in a dryer at 120 °C for 2 minutes to form a 100 μm-thick resin sheet A2. This resin sheet A2 is a porous resin sheet with an open-cell structure.

[0173] (Preparation example A3) 75 g of IBXA and 0.1 g of HDDA were added to 50 g of the UV syrup prepared in Preparation Example A1 to obtain an ultraviolet-curable resin composition according to this example. A resin sheet A3 having a thickness of 100 μm was formed in the same manner as in Preparation Example A1, except that the obtained resin composition was used.

[0174] (Preparation example A4) A UV-curable resin composition was prepared in the same manner as in Preparation Example A3. 50 g of the resulting resin composition was mixed with 50 g of water and stirred at 5,000 rpm for 2 minutes using a TK Robomix (PRIMIX Corporation). A 100 μm-thick resin sheet A4 was formed in the same manner as in Preparation Example A2, except that the resulting resin composition emulsion was used. This resin sheet A4 is a porous resin sheet with an open-cell structure.

[0175] (Preparation example A5) A UV-curable resin composition was prepared in the same manner as in Preparation Example A1. 50 g of the resulting resin composition was mixed with 80 g of water and stirred at 5,000 rpm for 2 minutes using a TK Robomix (manufactured by PRIMIX Corporation). A 100 μm-thick resin sheet A5 was formed in the same manner as in Preparation Example A2, except that the resulting resin composition emulsion was used. This resin sheet A5 is a porous resin sheet with an open-cell structure.

[0176] (Preparation example A6) A flask equipped with a reflux condenser, thermometer, and dropping funnel was charged with 72 g of 2EHA, 15 g of NVP, 3 g of AA, and 100 g of IBXA as monomer components. 1 g of the silane coupling agent "KBM-503" (Shin-Etsu Chemical Co., Ltd., γ-methacryloxypropyltrimethoxysilane), 10 g of an emulsifier ("Latemul E-118B" Kao Corporation), and 200 g of water were added, and the mixture was emulsified for 5 minutes using a homomixer. The resulting emulsion was then purged with nitrogen (deoxygenated) for 1 hour, then heated to 60°C, and 0.2 g of a polymerization initiator (VA-057, Wako Pure Chemical Industries, Ltd.) was added. Polymerization was then carried out for 3 hours. The system was then heated to 70°C, and polymerization was continued for another 3 hours, after which it was cooled to room temperature. To obtain the resin composition of this example, 1 g of a thickener (product name "A-30H" manufactured by Toagosei Co., Ltd.) was added per 100 g of the obtained polymer emulsion (aqueous dispersion of the polymer). The resin composition thus obtained was applied to a 38 μm-thick release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38"), which had been treated with a silicone release agent on one side of a PET film, and dried at 120°C for 2 minutes to form a 100 μm-thick resin sheet A6. The exposed surface of the obtained resin sheet A6 was covered with a 38 μm-thick release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38"), which had been treated with a silicone release agent (light release agent) on one side of a PET film, to protect both sides of the resin sheet A6 with release films (release liners) R1 and R2.

[0177] (Preparation example A7) A polymer emulsion (aqueous polymer dispersion) was prepared in the same manner as in Preparation Example A6. Per 100 g of polymer emulsion, 1 g of thickener (product name "A-30H" manufactured by Toagosei Co., Ltd.), 2 g of surfactant (product name "Amogen CB-H" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., a carboxybetaine-type amphoteric surfactant), and 0.5 g of foam stabilizer (product name "Nopco DC-100-A" manufactured by San Nopco Co., Ltd.) were added. The mixture was stirred at 5000 rpm for 5 minutes using a TK Robomix (manufactured by PRIMIX Co., Ltd.). The resulting resin composition was applied to a release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF #38") in the same manner as in Preparation Example A6. A 100 μm-thick resin sheet A7 was formed by drying. The exposed surface of the resulting resin sheet A7 was protected by covering it with a release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE #38"). This resin sheet A7 is a porous resin sheet having an open-cell structure.

[0178] (Preparation example A8) A resin composition was obtained by polymerization in the same manner and under the same conditions as in Preparation Example A6, except that the monomer components were changed to 42 g of n-butyl acrylate (BA), 50 g of methyl methacrylate (MMA), 1 g of hydroxyethyl acrylate (HEA), and 7 g of polyethylene glycol monoacrylate (trade name "Blemmer AE200" manufactured by NOF Corporation). Using the obtained resin composition, a 100 μm-thick resin sheet A8 was obtained, protected on each side with release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38") and release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38"), respectively, in the same manner as in Preparation Example A6.

[0179] (Preparation example A9) To 100 g of commercially available acrylic latex (product name "AE986B", manufactured by E-Tech Co., Ltd.), 1 g of thickener (product name "A-30H", manufactured by Toagosei Co., Ltd.) was added, stirred and mixed, and then degassed to obtain a resin composition according to this example. Using the obtained resin composition, a 100 μm-thick resin sheet A9 was obtained in the same manner as in Preparation Example A6, with each surface protected by release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38") and release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38") respectively.

[0180] (Preparation example A10) A commercially available acrylic latex and thickener were mixed in the same manner as in Preparation Example A9. To 50 g of this mixture, 1 g of a surfactant (trade name "Amogen CB-H," manufactured by Daiichi Kogyo Seiyaku Co., Ltd., a carboxybetaine-type amphoteric surfactant) and 0.25 g of a foam stabilizer (trade name "Nopco DC-100-A," manufactured by San Nopco) were added, and the mixture was stirred at 5,000 rpm for 5 minutes using a TK Robomix (manufactured by PRIMIX). The resulting resin composition was used in the same manner as in Preparation Example A6 to obtain a 100 μm-thick resin sheet A10, protected on each side by release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38") and release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38"), respectively. This resin sheet A10 is a porous resin sheet with an open-cell structure.

[0181] (Preparation Example A11) A resin composition according to this example was obtained by adding 1 g of a thickener (product name "A-30H" manufactured by Toagosei Co., Ltd.) to 100 g of a commercially available acrylic latex (product name "Nipol LX855EX1" manufactured by Zeon Corporation), stirring and mixing, and then degassing. Using the resulting resin composition, a 100 μm-thick resin sheet A11 was obtained in the same manner as in Preparation Example A6, with each surface protected by a release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38") and a release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38") respectively.

[0182] (Preparation example A12) To 100 g of commercially available urethane latex (product name "Superflex 150HS" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 0.8 g of thickener (product name "A-30H" manufactured by Toagosei Co., Ltd.) was added, and the mixture was stirred and mixed, followed by degassing to obtain a resin composition according to this example. Using the resulting resin composition, a 100 μm-thick resin sheet A12 was obtained in the same manner as in Preparation Example A6, with each surface protected by a release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38") and a release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38") respectively.

[0183] (Preparation example A13) A commercially available urethane latex and thickener were mixed in the same manner as in Preparation Example A12. To 50 g of this mixture, 1 g of a surfactant (trade name "Amogen CB-H," manufactured by Daiichi Kogyo Seiyaku Co., Ltd., a carboxybetaine-type amphoteric surfactant) and 0.25 g of a foam stabilizer (trade name "Nopco DC-100-A," manufactured by San Nopco) were added, and the mixture was stirred at 5,000 rpm for 5 minutes using a TK Robomix (manufactured by PRIMIX). The resulting resin composition was used in the same manner as in Preparation Example A6 to obtain a 100 μm-thick resin sheet A13, protected on each side by release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38") and release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38"), respectively. This resin sheet A13 is a porous resin sheet with an open-cell structure.

[0184] (Preparation example A14) To 100 g of commercially available acrylic latex (product name "N975(A)1", manufactured by E-Tech Co., Ltd.), 1 g of thickener (product name "A-30H", manufactured by Toagosei Co., Ltd.) was added, stirred and mixed, and then degassed to obtain a resin composition according to this example. Using the obtained resin composition, a 100 μm-thick resin sheet A14 was obtained in the same manner as in Preparation Example A6, with each surface protected by release film R1 (manufactured by Mitsubishi Plastics, Inc., product name "MRF#38") and release film R2 (manufactured by Mitsubishi Plastics, Inc., product name "MRE#38") respectively.

[0185] [Preparation of Adhesive Layer B] (Preparation example B1) A flask equipped with a reflux condenser, thermometer, and dropping funnel was charged with 190 g of 2EHA and 10 g of AA as monomer components, and 300 g of ethyl acetate as a solvent. After nitrogen substitution, the mixture was heated to 60°C, and 0.2 g of 2,2'-azobisisobutyronitrile (AIBN) was added to initiate polymerization. After 3 hours of polymerization, the temperature was raised to 70°C, and the polymerization reaction was continued for another 3 hours to obtain a polymer solution. 50 g of this polymer solution was added with 0.05 g of an isocyanate-based crosslinker (product name "Coronate HL" manufactured by Tosoh Corporation) and 50 g of ethyl acetate to prepare a pressure-sensitive adhesive composition B1 according to this example. The pressure-sensitive adhesive composition B1 obtained above was applied to the release-treated surface of a 38 μm-thick release film (manufactured by Mitsubishi Plastics, product name "MRF#38"), one side of which had been treated with a silicone release agent. The pressure-sensitive adhesive composition B1 was then applied and dried at 120°C for 2 minutes to obtain a 2 μm-thick pressure-sensitive adhesive layer B1.

[0186] (Preparation example B2) A polymer solution was prepared in the same manner as in Preparation Example B1, except that the monomer components were changed to 144 g of 2EHA, 50 g of NVP, and 6 g of AA, and the amount of AIBN used was changed to 0.4 g. 0.05 g of an isocyanate-based crosslinking agent (product name "Coronate HL", manufactured by Tosoh Corporation) and 50 g of ethyl acetate were added to 50 g of this polymer solution to prepare a pressure-sensitive adhesive composition B2 according to this example. Using the obtained pressure-sensitive adhesive composition B2, a pressure-sensitive adhesive layer B2 having a thickness of 2 μm was prepared in the same manner as in Preparation Example B1.

[0187] [Preparation of Adhesive Layer C] (Preparation example C1) A monomer mixture consisting of 90 parts 2EHA and 10 parts AA was blended with 0.05 parts of Omnirad 651 (IGM Resins) and 0.05 parts of Omnirad 184 (IGM Resins) photopolymerization initiators, and then irradiated with UV light until the viscosity reached approximately 15 Pa·s, producing a partially polymerized monomer syrup. Viscosity was measured using a BH viscometer with a No. 5 rotor at 10 rpm and a temperature of 30°C. To 100 parts of this monomer syrup, 0.10 parts of dipentaerythritol hexaacrylate as a crosslinker and 12.5 parts of hollow glass balloons (average particle size 40 μm, Fuji Balloon H-40, Fuji Silysia Chemical Ltd.) were added, followed by a degassing treatment. After degassing, 0.7 parts of a fluorochemical surfactant (manufactured by AGC Seimi Chemical Co., Ltd., trade name "Surflon S-393") was added to obtain a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was stirred with nitrogen gas introduced through the through-holes of an air bubble mixing device to obtain a pressure-sensitive adhesive composition C1 in which air bubbles were dispersed and mixed.

[0188] Two 38 μm thick PET films, one of whose release surfaces had been treated with a silicone release agent, were prepared. 0.04 parts of "Omnirad 651" (manufactured by IGM Resins) was added to 100 parts of the pressure-sensitive adhesive composition, and this was applied to the release surface of the first PET film. The release surface of the second PET film was then placed on top of this, and the illuminance was 5 mW / cm. 2 The adhesive was cured by irradiating both sides with UV light for 3 minutes. A Toshiba product called "Black Light" was used for UV irradiation. UV measurements were performed using an industrial UV checker (Topcon product called "UVR-T1" with a photoreceptor model number UD-T36) with a peak sensitivity wavelength of approximately 350 nm. In this way, an 800 μm thick adhesive layer C1 was formed. Each side of this adhesive layer C1 was covered with a release liner (PET film). The proportion of air bubbles in the adhesive layer C1 was approximately 20% by volume.

[0189] [Adhesive sheet production] Example 1 The release liner covering one side of resin sheet (resin layer) A1 was peeled off, and pressure-sensitive adhesive layer B1 was attached to the exposed side of resin sheet A1, followed by autoclaving (50°C, 5 atmospheres, 15 minutes) to obtain a laminate of resin layer A1 as layer A and pressure-sensitive adhesive layer B1 as layer B. Next, the release liner covering the other side of resin layer A1 was peeled off, and the release liner covering one side of pressure-sensitive adhesive layer C1 was peeled off, and the exposed side of pressure-sensitive adhesive layer C1 was attached to the exposed side of resin layer A1 of the laminate to obtain a double-sided pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layer B1 as layer B, resin layer A1 as layer A, and pressure-sensitive adhesive layer C1 as layer C were laminated in this order.

[0190] (Examples 2 to 14 and Comparative Examples 1 to 4) The double-sided pressure-sensitive adhesive sheets for each example were obtained in the same manner as in Example 1, except that the resin layers A1 to A14 as layer A, the pressure-sensitive adhesive layers B1 to B2 as layer B, and the pressure-sensitive adhesive layer C1 as layer C were changed to the combinations shown in Table 1.

[0191] <Evaluation> [Nanoindenter measurement] Nanoindenter measurement was performed on resin sheet A (also resin layer A, A layer) according to each example to measure the surface hardness [MPa], unloading curve displacement [nm], and internal area [pJ] of the load-displacement curve below a load of 0 at 37°C. Specifically, the release liner protecting the surface of resin sheet A was peeled off, and the sheet was cut into a 1 cm x 1 cm size and set on a measurement table. Measurement was performed under the following conditions using a nanoindenter device (Triboindentar, manufactured by Hysitron), and the surface hardness [MPa], unloading curve displacement [nm], and internal area [pJ] of the load-displacement curve below a load of 0 were determined. (Measurement conditions) Indenter used: Berkovich (triangular pyramidal) diamond indenter Measurement method: Single indentation measurement Measurement temperature: 37℃ ambient temperature Indentation depth: 1 μm (1000 nm) Push-in speed: 1000nm / s Pulling speed: 1000nm / s

[0192] [Storage modulus and Tg] Resin sheet A alone was laminated to a thickness of approximately 1 mm, which was then punched out to a diameter of 8 mm to create a cylindrical pellet for use as the measurement sample. The measurement sample was fixed to a diameter of 8 mm parallel plate fixture and measured under the following conditions using a dynamic viscoelasticity measuring device (TA Instruments, "ARES-G2"), and the storage modulus G' [MPa] at 25°C and 37°C and the peak top temperature of the loss tangent tanδ (G" / G') were calculated as the glass transition temperature (Tg) [°C]. (conditions) Measurement mode: Shear mode Temperature range: -50℃~150℃ Heating rate: 5℃ / min Frequency: 1Hz The 25°C storage modulus G' and Tg of adhesive layer B were also measured using the same method as above. The 25°C storage modulus G' and Tg of adhesive layer B1 were 0.6 MPa and -25°C, respectively, and the 25°C storage modulus of adhesive layer B2 was 2.2 MPa and 11°C, respectively.

[0193] [180 degree peel strength (adhesive strength)] For each pressure-sensitive adhesive sheet according to the present invention, the release liner covering the adhesive surface of the C layer (adhesive layer C) was removed, and a 25 μm-thick PET film (product name "Lumirror S10" manufactured by Toray Industries, Inc.) was attached as a backing to obtain a measurement sample. The measurement sample was cut to a size of 5 cm × 1 cm, and the adhesive surface of the B layer (adhesive layer B) was exposed. The sample was then attached to a stainless steel plate (SUS304BA plate) as an adherend, and autoclaved. After that, the pressure-sensitive adhesive sheet was peeled from the adherend using a tensile tester (Shimadzu Corporation, product name "Autograph AG-Xplus HS 6000 mm / min High-Speed ​​Model (AG-50NX plus)") at a peel angle of 180° and a peel speed (tensile speed) of 300 mm / min, and the load was measured to determine the peel strength [N / 10 mm].

[0194] [Holding force] A holding power test was conducted in accordance with JIS Z0237:2009. Specifically, a 50 μm thick PET film was attached to the adhesive surface of the C layer (adhesive layer C) of a double-sided pressure-sensitive adhesive sheet under an environment of 23°C and 50% RH, and the sheet was then cut into a 20 mm wide strip to prepare a measurement sample. Next, the adhesive surface of the B layer (adhesive layer B) of the measurement sample was attached to a Bakelite plate (adherend) using a 2 kg roller. The adhesive area between the measurement sample and the adherend was 20 mm wide and 20 mm long. The measurement sample thus attached to the adherend was then draped in a 40°C environment and left for 30 minutes. A 500 g load was then applied to the free end of the measurement sample, and the sample was left in a 40°C environment with the load applied for 1 hour. After the sample had been left for 1 hour, the displacement distance [mm] from the initial attachment position was measured. If the sample peeled off from the substrate and fell off within one hour, it was recorded as "fell off."

[0195] [Peel stress distribution measurement] The stress distribution during peeling was measured, and the peel resistance was evaluated from the stress integral value. The pressure-sensitive adhesive sheet (three-layer structure) of each example was punched out to a diameter of 5 mm to prepare a measurement sample. The measurement sample was fixed to a glass plate for evaluation, and a stainless steel probe (5 mm diameter) was pressed against it until a force of 100 N was detected. After holding the sample for 30 seconds, the sample was peeled off at a pulling rate (probe rising speed) of 10 mm / min. The behavior was observed with a video camera, and the strain-stress distribution was measured. The peel stress integral value and the maximum peel stress value at the start of peeling were calculated from the obtained values. The larger the peel stress integral value, the greater the amount of energy required for peeling, making peeling more difficult. Furthermore, the greater the maximum peel stress, the greater the damage to the adherend due to localized stress concentration.

[0196] The surface hardness [MPa], 25°C storage modulus [MPa], 37°C storage modulus [MPa], Tg [°C], unloading curve displacement [nm], load-displacement curve internal area [pJ] at or below a load of 0, layer structure of the pressure-sensitive adhesive sheet, adhesive strength [N / 10 mm], holding strength [mm], peel stress integrated value, and maximum peel stress measurement results for the resin sheet A (layer A) of each example are shown in Table 1. The results of measuring the peel stress distribution (strain-stress curves) for the pressure-sensitive adhesive sheets of Examples 1 and 2 and Comparative Example 1 are shown in Figures 5 to 7, respectively.

[0197] [Table 1]

[0198] As shown in Table 1, the pressure-sensitive adhesive sheets according to Examples 1 to 14, which were laminated with resins (A1 to A10) having a 25°C storage modulus in the range of 10 MPa to 500 MPa, a 37°C storage modulus in the range of 0.5 MPa to 20 MPa, and a 37°C surface hardness in the range of 0.1 MPa to 2 MPa, exhibited relatively high adhesive strength and coercive force, and a large integrated peel stress, while the maximum peel stress was suppressed to less than 0.4 MPa. In contrast, the pressure-sensitive adhesive sheets according to Comparative Examples 1 to 4, which did not satisfy at least one of the following conditions: a 25°C storage modulus of 10 MPa to 500 MPa, a 37°C storage modulus of 0.5 MPa to 20 MPa, and a 37°C surface hardness of 0.1 MPa to 2 MPa, tended to exhibit lower adhesive strength and poorer coercive force, a low integrated peel stress, and a maximum peel stress of 0.4 MPa or greater, compared to Examples 1 to 14. None of Comparative Examples 1 to 4 satisfied an adhesive strength of 4 N / 10 mm or greater. The above results show that by using a resin whose storage modulus at 25°C is in the range of 10 MPa to 500 MPa, whose storage modulus at 37°C is in the range of 0.5 MPa to 20 MPa, and whose surface hardness at 37°C is in the range of 0.1 MPa to 2 MPa, it is possible to obtain an adhesive sheet that is resistant to peeling and slippage and that can be removed without damaging the adherend.

[0199] <Experiment 2> [Preparation of Resin Sheet A] (Preparation example A2-1) An ultraviolet-curable resin composition obtained by the same method as in Preparation Example A1 of Experiment 1 was applied to the release-treated surface of Release Film R1 (Mitsubishi Plastics, product name "MRF#38") so that the thickness after curing would be 30 μm. Next, a polyester nonwoven fabric substrate (product name "Sontara#8010", Jacob-Holm) was laminated in a wet state, and then Release Film R2 (Mitsubishi Plastics, product name "MRE#38") was placed on top to block out air. Resin sheet A2-1 was formed by curing (completion of polymerization) by irradiating with ultraviolet light (black light) using a black light lamp at an illuminance of 5 mW / cm. 2 The measurement was performed under the condition of 300 seconds of irradiation with an industrial UV checker (manufactured by Topcon Corporation, product name "UVR-T1") with a peak sensitivity wavelength of approximately 350 nm. The obtained resin sheet A2-1 with a nonwoven fabric substrate was protected on each side by release films (release liners) R1 and R2.

[0200] (Preparation example A2-2) A resin composition obtained by the same method as in Preparation Example A9 of Experiment 1 was applied to the release-treated surface of Release Film R1 (Mitsubishi Plastics, Inc., product name "MRF#38") so that the thickness after curing would be 30 μm. Next, a polyester nonwoven fabric substrate (product name "Sontara#8010", Jacob-Holm) was attached in a wet state, and then dried at 110°C for 3 minutes to obtain a resin sheet A2-2 with a nonwoven fabric substrate.

[0201] [Preparation of Adhesive Layer B] (Preparation example B2-1) The adhesive composition B1 obtained by the same method as in Preparation Example B1 of Experiment 1 was applied to the release-treated surface of a release film (manufactured by Mitsubishi Chemical Corporation, product name "MRF#38") and dried at 120°C for 2 minutes to obtain an adhesive layer B2-1 having a thickness of 30 μm.

[0202] (Preparation example B2-2) A pressure-sensitive adhesive layer B2-2 having a thickness of 60 μm was obtained in the same manner as in Preparation Example B2-1, except that the thickness was changed.

[0203] (Adjustment example B2-3) 130 g of isononyl acrylate, 60 g of 2-methoxyethyl acrylate, and 10 g of AA were added as monomer components, and 75 g of toluene was added as a solvent, followed by nitrogen substitution. The mixture was then heated to 60°C, 0.4 g of AIBN was added, and the reaction was allowed to proceed for 3 hours while maintaining the temperature at 60°C. During this reaction, 140 g of toluene was added dropwise as needed while monitoring the viscosity. The mixture was then heated to 70°C, and the polymerization reaction was allowed to proceed for another 3 hours, yielding a polymer solution. 0.05 g of an isocyanate-based crosslinker (product name "Coronate HL" manufactured by Tosoh Corporation) and 50 g of toluene were added to 50 g of this polymer solution to prepare a pressure-sensitive adhesive composition B2-3 according to this example. Using the resulting pressure-sensitive adhesive composition B2-3, a 30 μm-thick pressure-sensitive adhesive layer B2-3 was obtained in the same manner as in Preparation Example B2-1.

[0204] (Preparation example B2-4) A pressure-sensitive adhesive layer B2-4 having a thickness of 60 μm was obtained in the same manner as in Preparation Example B2-3, except that the thickness was changed.

[0205] [Adhesive sheet production] Example 15 The release liner R1 was peeled off from the resin sheet (resin layer) A2-1, and the adhesive layer B2-1 was attached to the exposed surface of the resin sheet A2-1, to obtain a single-sided adhesive sheet laminated with the resin layer A2-1 with a nonwoven fabric substrate as layer A and the adhesive layer B2-1 as layer B.

[0206] Example 16 The release liner R1 was peeled off from the resin sheet (resin layer) A2-1, and the adhesive layer B2-3 was attached to the exposed surface of the resin sheet A2-1, to obtain a single-sided adhesive sheet laminated with the resin layer A2-1 with a nonwoven fabric substrate as layer A and the adhesive layer B2-3 as layer B.

[0207] Example 17 The release liner R1 was peeled off from the resin sheet (resin layer) A2-2, and an adhesive layer B2-1 was bonded to the exposed surface of the resin layer, to obtain a single-sided adhesive sheet laminated with the resin layer A2-2 with a nonwoven fabric substrate as layer A and the adhesive layer B2-1 as layer B.

[0208] Example 18 The release liner R1 was peeled off from the resin sheet (resin layer) A2-2, and an adhesive layer B2-3 was bonded to the exposed surface of the resin layer, to obtain a single-sided adhesive sheet laminated with the resin layer A2-2 with a nonwoven fabric substrate as layer A and the adhesive layer B2-3 as layer B.

[0209] (Comparative Example 5) The pressure-sensitive adhesive layer B2-2 was attached to a polyester nonwoven fabric substrate (product name "Sontara #8010", manufactured by Jacob-Holm) to obtain a single-sided pressure-sensitive adhesive sheet with a nonwoven fabric substrate according to this example.

[0210] (Comparative Example 6) The pressure-sensitive adhesive layer B2-4 was attached to a polyester nonwoven fabric substrate (product name "Sontara #8010", manufactured by Jacob-Holm) to obtain a single-sided pressure-sensitive adhesive sheet with a nonwoven fabric substrate according to this example.

[0211] <Evaluation> [Wrist rebound resistance test] One adhesive surface of a commercially available double-sided tape ("No. 5000NS" manufactured by Nitto Denko Corporation) was attached to a 1 mm thick polyolefin film cut to a length of 10 cm and a width of 1 cm. The nonwoven fabric side of a single-sided PSA sheet according to each example (Examples 15-18 and Comparative Examples 5-6) was attached to the other adhesive surface of this double-sided tape. Next, the release liner covering the adhesive surface of the single-sided PSA sheet was peeled off, and the exposed adhesive surface was attached to a person's wrist. After leaving it for 5 minutes, the height [cm] of the edge lift from the wrist was measured to evaluate repulsion resistance.

[0212] [120g holding force measurement using human skin gel] One adhesive side of a commercially available double-sided tape ("No. 5000NS" manufactured by Nitto Denko Corporation) was attached to the back surface (nonwoven fabric substrate side) of the single-sided PSA sheet of each example (Examples 15-18 and Comparative Examples 5-6), and then cut into a 1 cm square to obtain a measurement sample. The other adhesive side of the double-sided tape of the measurement sample was attached to a metal plate (total weight 120 g) to which a weight was fixed, and the opposite adhesive side of the single-sided PSA sheet was attached to the surface of a 1 mm thick skin gel (product name "H0-1K" manufactured by Exseal Co., Ltd.) fixed to a SUS plate. The time (minutes) from attachment to the skin gel until the weight fell was measured.

[0213] [Long-term measurement of skin application] One adhesive surface of a commercially available double-sided tape ("No. 5000NS" manufactured by Nitto Denko Corporation) was attached to a 250 μm-thick polyimide film cut to a length of 10 cm and a width of 1 cm. The nonwoven fabric side of the single-sided PSA sheet according to each example (Examples 15-18 and Comparative Examples 5-6) was attached to the other adhesive surface of this double-sided tape. Next, the release liner covering the adhesive surface of the single-sided PSA sheet was peeled off, and the sheet was attached to a human's outer arm. The number of days or time until the edge of the single-sided PSA sheet lifted from the outer arm (application period) and the sensation during application (wearability) were evaluated. If no lifting was observed, the sheet was left in application for up to two weeks. Regarding the sensation during application, the sheet was classified as either uncomfortable or not, and if any discomfort was felt, the symptom was recorded.

[0214] The evaluation results for Examples 15 to 18 and Comparative Examples 5 to 6 are shown in Table 2. The resin sheets and pressure-sensitive adhesive sheets of each example were evaluated in the same manner as in Experiment 1. For Examples 15 to 18, the adhesive strength [N / 10 mm] and holding power [mm] were measured in the same manner as in Experiment 1, except that no PET film backing was used. In Experiment 2, the integrated peel stress and maximum peel stress were measured in the same manner as in Experiment 1, except that a measurement sample was used in which a commercially available double-sided tape ("No. 5000NS" manufactured by Nitto Denko Corporation) was attached to the back of the single-sided pressure-sensitive adhesive sheet of each example. Table 2 also shows an overview of each example.

[0215] [Table 2]

[0216] As shown in Table 2, in the repulsion resistance evaluation using a wrist, the pressure-sensitive adhesive sheets of Examples 15 to 18, each containing Layer A, showed less than 1 cm of edge lift, whereas Comparative Examples 5 to 6, each lacking Layer A, all showed significant lift, with heights of 2 cm or more. Furthermore, in a holding power evaluation using a 120 g weight with human skin gel, Examples 15 to 18, each containing Layer A, showed a shortest time to fall of 60 minutes and a maximum of 300 minutes of fixation without falling, whereas Comparative Examples 5 to 6, each lacking Layer A, all fell within a short period of time. Furthermore, in a long-term adhesiveness evaluation using a 250 μm-thick polyimide film, Comparative Examples 5 to 6, each lacking Layer A, showed a tight, taut feeling (uncomfortable sensation) from the beginning, and within a few hours, edge lift was observed, leading to peeling from this point. On the other hand, in Examples 15 to 18, each containing Layer A, no taut, taut feeling was observed throughout the application period. Furthermore, the sheets could be applied for 10 days or more, demonstrating excellent long-term adhesiveness.

[0217] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0218] 1,2 Adhesive sheet 10 Resin sheet, layer A 20 B layer 30 C layer 41,42 Release liner 50 sensors

Claims

1. An acrylic resin used in layer A of an adhesive sheet having layer A and layer B constituting an adhesive surface, The storage modulus at 25°C is in the range of 10 MPa to 500 MPa, The storage modulus at 37°C is in the range of 0.5 MPa to 20 MPa, and An acrylic resin for adhesive sheets, having a surface hardness at 37°C in the range of 0.1 MPa to 2 MPa.

2. 2. The acrylic resin according to claim 1, wherein the unloading curve displacement in nanoindenter measurement performed under conditions of a temperature of 37°C, an indentation depth of 1000 nm, and an indentation / withdrawal rate of 1000 nm / s is in the range of 400 nm to 1500 nm.

3. 3. The acrylic resin according to claim 1, wherein the internal area of ​​a load-displacement curve at a load of 0 or less in a nanoindenter measurement performed under conditions of a temperature of 37°C, an indentation depth of 1000 nm, and an indentation / withdrawal rate of 1000 nm / s is 5 pJ or more.

4. The acrylic resin according to any one of claims 1 to 3, having a glass transition temperature in the range of 5°C to 40°C.

5. A pressure-sensitive adhesive sheet having a layer A made of the acrylic resin according to any one of claims 1 to 4 and a layer B constituting an adhesive surface.

6. An adhesive sheet as described in claim 5, wherein the adhesive surface has a 180-degree peel strength against a stainless steel plate of 4 N / 10 mm or more.

7. The storage elastic modulus at 25°C is in the range of 10 MPa to 500 MPa, and the storage elastic modulus at 37°C is in the range of 0.5 MPa to 20 MPa. The adhesive surface has a 180-degree peel strength of 4 N / 10 mm or more against a stainless steel plate, A pressure-sensitive adhesive sheet having, in addition to the layer A, a layer B that constitutes the adhesive surface.

8. The pressure-sensitive adhesive sheet according to claim 7 , wherein the layer B is an acrylic pressure-sensitive adhesive layer.

9. The pressure-sensitive adhesive sheet according to claim 7 or 8, wherein the thickness of the layer B is 0.5 μm or more and 100 μm or less.

10. In addition to the layer A, a layer C is provided, The pressure-sensitive adhesive sheet according to any one of claims 5 to 9, wherein the C layer is disposed on the side opposite to the adhesive surface of the A layer.

11. The pressure-sensitive adhesive sheet according to claim 10 , wherein the layer C contains hollow particles, has bubbles, or both.

12. The pressure-sensitive adhesive sheet according to claim 10 or 11, wherein the layer C is an acrylic pressure-sensitive adhesive layer.

13. An adhesive sheet described in any one of claims 5 to 12, which is used by being attached to human skin.

14. The adhesive sheet according to any one of claims 5 to 13, which is used to fix a sensor to human skin.

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