Adhesive sheet

Abstract

To provide an adhesive sheet that allows for effective improvement of rough surface adhesion.SOLUTION: Provided is an adhesive sheet having an adhesive layer containing an acrylic polymer. The acrylic polymer includes 2-octyl acrylate (m1) as a monomer component and 10 wt.% or more of a copolymerizable monomer (m3) different from both the 2-octyl acrylate (m1) and a carboxy group-containing monomer (m2). The adhesive layer further includes a tackifier.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Generally, adhesives (also called pressure-sensitive adhesives; the same applies below) are in a soft solid (viscoelastic) state in a temperature range around room temperature, and have the property of adhering to an adherend when pressure is applied. Taking advantage of such properties, adhesives are widely used in various industrial fields, from portable electronic devices such as smartphones and home appliances to automobiles and office automation equipment, typically in the form of adhesive sheets containing an adhesive layer, for purposes such as joining parts and protecting surfaces. An example of a technical document related to adhesive sheets is Patent Document 1. Patent Document 1 describes an adhesive containing an acrylic polymer polymerized using 2-octyl acrylate as a monomer component. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5457186 Summary of the Invention [Problem to be solved by the invention]

[0004] 2-octyl acrylate synthesized using 2-octanol can be obtained from biomass-derived materials, and therefore its use as an adhesive material that can reduce dependency on fossil resource-based materials is being considered. For example, in Patent Document 1, the adhesive properties (peel adhesion and shear strength) and thermal stability of an adhesive formed from an acrylic polymer synthesized from monomer components of 95% by weight of 2-octyl acrylate and 5% by weight of acrylic acid are evaluated.

[0005] However, as proposed in Patent Document 1, adhesives composed of a polymer mainly composed of 2-octyl acrylate (2-octyl acrylate-based polymer) tend to have a relatively high glass transition temperature and low flexibility. The inventors of the present invention have found that such adhesives have difficulty in obtaining high adhesive strength due to their low flexibility, and that they have insufficient adhesive strength, particularly on rough surfaces. As a result of intensive research into improving rough surface adhesion while enjoying the effects of containing a 2-octyl acrylate-based polymer, the inventors have succeeded in creating an adhesive having good rough surface adhesion in a composition containing an acrylic polymer copolymerized with 2-octyl acrylate, and have completed the present invention. That is, the present invention relates to an improvement of an adhesive containing an acrylic polymer synthesized using 2-octyl acrylate, and aims to provide an adhesive sheet that can effectively improve rough surface adhesion in a composition containing an acrylic polymer copolymerized with 2-octyl acrylate. [Means for solving the problem]

[0006] According to this specification, a pressure-sensitive adhesive sheet is provided having a pressure-sensitive adhesive layer containing an acrylic polymer containing 2-octyl acrylate (m1) as a monomer component. The monomer component of the acrylic polymer contains 10% by weight or more of a copolymerizable monomer (m3) different from 2-octyl acrylate (m1) and a carboxyl group-containing monomer (m2). The pressure-sensitive adhesive layer further contains a tackifier. According to the above configuration, the rough surface adhesion of a pressure-sensitive adhesive containing an acrylic polymer synthesized using 2-octyl acrylate can be effectively improved. One of the reasons for this, which is not particularly limited, is that by copolymerizing a certain amount or more of the above-mentioned copolymerizable monomer (m3) with the acrylic polymer, the side chain crystallinity of the acrylic polymer is reduced, and as a result, the glass transition temperature of the pressure-sensitive adhesive is lowered, and the adhesive strength improving effect by adding a tackifier is well expressed, and it is considered that these actions effectively improve the rough surface adhesion. In short, according to the above configuration, a pressure-sensitive adhesive with good rough surface adhesion is realized while obtaining the effect of using 2-octyl acrylate.

[0007] In some embodiments, the copolymerizable monomer (m3) has the formula: CH2=C(R 1 )COOR 2 (In the above formula, R 1 is a hydrogen atom or a methyl group, and R 2 is a chain alkyl group having 1 to 20 carbon atoms (wherein R 1 When is a hydrogen atom, 2-octyl group is excluded. ) ). ); By selecting an appropriate type from among the alkyl (meth)acrylates having the above chemical structure as the copolymerizable monomer (m3), it is possible to obtain good adhesion properties while favorably improving rough surface adhesion.

[0008] In some preferred embodiments, the copolymerizable monomer (m3) comprises at least one selected from n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). By using at least one selected from BA and 2EHA as the copolymerizable monomer (m3), the effect of improving rough surface adhesion can be better exhibited.

[0009] In some embodiments, the tackifier preferably comprises at least one selected from a rosin-based tackifier resin, a terpene-based tackifier resin, and an acrylic oligomer. By using the above-mentioned types of tackifier, the effects of the technology disclosed herein can be preferably realized.

[0010] In some embodiments, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a crosslinking agent. By using the crosslinking agent, the cohesive strength of the pressure-sensitive adhesive can be appropriately increased.

[0011] In some embodiments, the weight average molecular weight (Mw) of the acrylic polymer is 400,000 or more. By using an acrylic polymer with a large Mw, a pressure-sensitive adhesive having good high-temperature properties is easily obtained. In addition, by using the high-molecular-weight acrylic polymer in combination with a tackifier, it is possible to preferably achieve both good high-temperature properties and rough surface adhesion.

[0012] In some embodiments, the dispersity (Mw / Mn) of the acrylic polymer is 2 or more and less than 50. The dispersity (Mw / Mn) is determined from the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic polymer. An acrylic polymer having a dispersity (Mw / Mn) in the above range has a predetermined molecular weight distribution, and is likely to provide rough surface adhesion due to the wettability based on its low molecular weight, and is likely to provide good adhesive properties due to the cohesive force based on its high molecular weight.

[0013] In some preferred embodiments, the pressure-sensitive adhesive sheet has a 180-degree peel strength against a stainless steel plate (adhesive strength to SUS) of 10 N / 20 mm or more. A pressure-sensitive adhesive sheet having the above-mentioned adhesive strength to SUS can exhibit excellent adhesive strength to an adherend.

[0014] The adhesive sheet disclosed herein has improved rough surface adhesion, and can be preferably used for fixing various members as an adhesive means with good adhesion reliability even when attached to a rough surface. For example, it is suitable for fixing members in electronic devices including home appliances, office automation equipment, and mobile electronic devices such as smartphones. As described above, this specification provides an electronic device using any of the adhesive sheets disclosed herein, in other words, an electronic device including the adhesive sheet. [Brief description of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of a pressure-sensitive adhesive sheet according to an embodiment. [Diagram 2] FIG. 4 is a cross-sectional view illustrating a schematic configuration of a pressure-sensitive adhesive sheet according to another embodiment. [Diagram 3]FIG. 4 is a cross-sectional view illustrating a schematic configuration of a pressure-sensitive adhesive sheet according to another embodiment. [Figure 4] 1 is a front view showing a schematic diagram of an example of a portable electronic device including an adhesive sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A preferred embodiment of the present invention will be described below. Matters other than those specifically mentioned in this specification that are necessary for carrying out the present invention can be understood by a person skilled in the art based on the teachings on carrying out the invention described in this specification and the common general 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 knowledge in the field. In addition, in the following drawings, members and parts that perform the same function may be described by using the same reference numerals, and duplicated descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product.

[0017] In this specification, the term "adhesive" refers to a material that exhibits a soft solid (viscoelastic) state at temperatures near room temperature and that 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).

[0018] In this specification, biomass-derived carbon means carbon (renewable carbon) derived from biomass materials, i.e., materials derived from renewable organic resources. The biomass materials typically refer to materials derived from biological resources (typically plants that perform photosynthesis) that can be reproduced sustainably in the presence of sunlight, water, and carbon dioxide. Therefore, materials derived from fossil resources that are depleted by use after mining (fossil resource-based materials) are excluded from the concept of biomass materials here. The biomass carbon ratios of the acrylic polymer, the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive sheet, i.e., the proportion of biomass-derived carbon in the total carbon contained in the acrylic polymer, the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive sheet, can be estimated from the carbon isotope content with mass number 14 measured in accordance with ASTM D6866.

[0019] <Composition of adhesive sheet> The adhesive sheet disclosed herein is configured to include an adhesive layer. The adhesive sheet may be in the form of a substrate-less double-sided adhesive sheet having, for example, a first adhesive surface constituted by one surface of the adhesive layer and a second adhesive surface constituted by the other surface of the adhesive layer. Alternatively, the adhesive sheet disclosed herein may be in the form of a substrate-attached adhesive sheet in which the adhesive layer is laminated on one or both surfaces of a supporting substrate. Hereinafter, the supporting substrate may simply be referred to as a "substrate". The concept of the adhesive sheet here may include those referred to as adhesive tapes, adhesive labels, adhesive films, and the like. The adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, it may be an adhesive sheet in the form of a processed form into various shapes.

[0020] The structure of an adhesive sheet according to an embodiment is shown in FIG. 1. The adhesive sheet 1 is configured as a substrate-less double-sided adhesive sheet made of an adhesive layer 21. The adhesive sheet 1 is used by attaching a first adhesive surface 21A, which is configured by one surface (first surface) of the adhesive layer 21, and a second adhesive surface 21B, which is configured by the other surface (second surface) of the adhesive layer 21, to different locations on an adherend. The locations to which the adhesive surfaces 21A and 21B are attached may be locations on different members, or may be different locations within a single member. The adhesive sheet 1 before use (i.e., before being attached to an adherend) may be a component of an adhesive sheet 100 with a release liner in which the first adhesive surface 21A and the second adhesive surface 21B are protected by release liners 31 and 32, each of which has a release surface at least on the side facing the adhesive layer 21, as shown in FIG. 1. As the release liners 31 and 32, for example, a sheet-like substrate (liner substrate) configured such that one side serves as a release surface by providing a release layer made of a release treatment agent on the one side can be preferably used. Alternatively, the release liner 32 can be omitted, and a release liner 31 having release surfaces on both sides can be used, which is then superimposed on the PSA sheet 1 and spirally rolled to form a PSA sheet with a release liner in a form in which the second adhesive surface 21B is protected by contacting the back surface of the release liner 31 (roll form).

[0021] The structure of an adhesive sheet according to another embodiment is shown in FIG. 2. The adhesive sheet 2 is configured as a substrate-attached single-sided adhesive sheet including a sheet-like supporting substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side. The adhesive layer 21 is fixedly provided on the first surface 10A side of the supporting substrate 10, that is, without the intention of separating the adhesive layer 21 from the supporting substrate 10. As shown in FIG. 2, the adhesive sheet 2 before use may be a component of an adhesive sheet 200 with a release liner in a form in which the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31, at least the side facing the adhesive layer 21 being a release surface. Alternatively, the release liner 31 may be omitted, and a supporting substrate 10 having a second surface 10B as a release surface may be used, and the adhesive sheet 2 may be rolled up so that the adhesive surface 21A is in contact with the second surface (rear surface) 10B of the supporting substrate 10 and protected.

[0022] The structure of a pressure-sensitive adhesive sheet according to yet another embodiment is shown in FIG. 3. The pressure-sensitive adhesive sheet 3 is configured as a substrate-attached double-sided pressure-sensitive adhesive sheet including a sheet-like support substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, a first pressure-sensitive adhesive layer 21 fixedly provided on the first surface 10A side, and a second pressure-sensitive adhesive layer 22 fixedly provided on the second surface 10B side. As shown in FIG. 3, the pressure-sensitive adhesive sheet 3 before use may be a component of a release-liner-attached pressure-sensitive adhesive sheet 300 in which the surface (first adhesive surface) 21A of the first pressure-sensitive adhesive layer 21 and the surface (second adhesive surface) 22A of the second pressure-sensitive adhesive layer 22 are protected by release liners 31, 32. Alternatively, the release liner 32 may be omitted, and a release liner 31 having both release surfaces may be used, which is then superimposed on the pressure-sensitive adhesive sheet 3 and wound in a spiral shape to form a release-liner-attached pressure-sensitive adhesive sheet in a form (roll form) in which the second adhesive surface 22A is protected by contacting the back surface of the release liner 31.

[0023] In the above-mentioned double-sided pressure-sensitive adhesive sheet with a substrate, at least one of the first and second pressure-sensitive adhesive layers (e.g., the first pressure-sensitive adhesive layer) may be a pressure-sensitive adhesive layer as described below, and the other pressure-sensitive adhesive layer (e.g., the second pressure-sensitive adhesive layer) may be a pressure-sensitive adhesive layer disclosed herein, or may be a pressure-sensitive adhesive layer having a composition different from that of the pressure-sensitive adhesive layer disclosed herein (specifically, the one pressure-sensitive adhesive layer, e.g., the first pressure-sensitive adhesive layer). Such other pressure-sensitive adhesive layer may be formed, for example, from a known or commonly used pressure-sensitive adhesive.

[0024] In addition, although not particularly limited, the technology disclosed herein can be preferably implemented in the form of a substrate-less double-sided pressure-sensitive adhesive sheet. Substrate-less double-sided pressure-sensitive adhesive sheet can be made thinner because it does not have a substrate, and can contribute to the miniaturization and space saving of the product to which the double-sided pressure-sensitive adhesive sheet is applied. In addition, substrate-less pressure-sensitive adhesive sheet can maximize the rough surface adhesion improvement effect of the pressure-sensitive adhesive layer.

[0025] <Adhesive layer> (Acrylic polymer) The adhesive layer constituting the adhesive sheet disclosed herein contains an acrylic polymer. The above-mentioned adhesive layer is typically an adhesive layer having an acrylic polymer as a base polymer. Such an adhesive layer is also called an acrylic adhesive layer. The base polymer refers to the main component of a rubber-like polymer (a polymer that exhibits rubber elasticity in a temperature range around room temperature) contained in the adhesive layer. In addition, in this specification, the "main component" refers to a component contained in an amount of more than 50% by weight, unless otherwise specified. In addition, the following explanation of the adhesive and the components that may be contained in the adhesive layer are also applicable to the adhesive composition used to form the adhesive (layer) unless otherwise specified.

[0026] In addition, in this specification, the term "acrylic polymer" refers to a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer". Therefore, in this specification, an acrylic polymer is defined as a polymer containing a monomer unit derived from an acrylic monomer. In this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, "(meth)acrylate" refers to acrylate and methacrylate, and "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.

[0027] As the acrylic polymer, a polymer of a monomer component containing 2-octyl acrylate (m1) is used. The acrylic polymer polymerized using a monomer component containing 2-octyl acrylate (m1) tends to have excellent high-temperature properties (e.g., high-temperature adhesive strength), and is preferably used for applications that may be exposed to high temperatures. In addition, although not particularly limited, since 2-octyl acrylate (m1) can be obtained from a biomass-derived material, the use of 2-octyl acrylate (m1) can reduce the dependency on fossil resource-based materials.

[0028] In some embodiments, 2-octyl acrylate (m1) is preferably contained as the main monomer of the acrylic polymer (the component that is contained in the largest amount among the monomer components), and the ratio of 2-octyl acrylate (m1) in the monomer components of the acrylic polymer may be, for example, about 34% by weight or more, and is suitably 50% by weight or more (e.g., more than 50% by weight), preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 75% by weight or more (e.g., more than 75% by weight), particularly preferably 80% by weight or more, may be 82% by weight or more, may be 84% by weight or more, or may be 85% by weight or more. By increasing the amount of 2-octyl acrylate (m1) used, the effect of its use (e.g., high temperature properties) can be effectively expressed. On the other hand, from the viewpoint of improving rough surface adhesion by copolymerizing the copolymerizable monomer (m3) described later, the proportion of 2-octyl acrylate (m1) in the monomer components is 90% by weight or less, and in some preferred embodiments, it is 87% by weight or less, or may be 85% by weight or less, 80% by weight or less (e.g., less than 80% by weight), 75% by weight or less, 72% by weight or less, or 70% by weight or less.

[0029] The monomer component of the acrylic polymer preferably contains a carboxyl group-containing monomer (m2). The carboxyl group-containing monomer (m2) can improve the cohesive strength based on its polarity. When a crosslinking agent such as an isocyanate-based or epoxy-based crosslinking agent is used, the carboxyl group of the carboxyl group-containing monomer (m2) can become a crosslinking point of the acrylic polymer. The use of the carboxyl group-containing monomer (m2) can provide better adhesion to adherends such as highly polar materials.

[0030] Examples of the carboxyl group-containing monomer (m2) include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, crotonic acid, and isocrotonic acid; and ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid. The carboxyl group-containing monomer (m2) may be a monomer having a metal salt (e.g., an alkali metal salt) of a carboxyl group. The carboxyl group-containing monomer (m2) may be used alone or in combination of two or more. Among them, preferred carboxyl group-containing monomers (m2) include AA and MAA. AA is particularly preferred. When one or more carboxyl group-containing monomers (m2) are used, the proportion of AA in the carboxyl group-containing monomer (m2) is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. In a particularly preferred embodiment, the carboxyl group-containing monomer (m2) is substantially composed of AA alone.

[0031] The proportion of the carboxyl group-containing monomer (m2) in the monomer components of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 0.5% by weight or more, and in some preferred embodiments, 1.0% by weight or more, 2.0% by weight or more, 2.5% by weight or more, 3.0% by weight or more, 3.5% by weight or more, 4.0% by weight or more, 4.5% by weight or more, or 5.0% by weight or more. By increasing the amount of the carboxyl group-containing monomer (m2) used, the cohesive force of the adhesive layer is improved based on the action of the carboxyl group-containing monomer (m2), so that good adhesive properties are easily obtained. In addition, the amount of the carboxyl group-containing monomer (m2) is suitably, for example, 20% by weight or less of the total monomer components, preferably 15% by weight or less, more preferably 12% by weight or less. In some preferred embodiments, the amount of the carboxyl group-containing monomer (m2) may be 10% by weight or less, 8.0% by weight or less, 6.0% by weight or less, or 5.0% by weight or less. By reducing the amount of the carboxyl group-containing monomer (m2) used within a certain range, good rough surface adhesion tends to be obtained.

[0032] In an embodiment using an acrylic polymer copolymerized with a carboxyl group-containing monomer (m2), the proportion of the carboxyl group-containing monomer (m2) in the total functional group-containing monomers (total functional group-containing monomers including the carboxyl group-containing monomer (m2)) used as a copolymerization component of the acrylic polymer is, from the viewpoint of effectively exerting the effect of copolymerizing the carboxyl group-containing monomer (m2), suitably 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, particularly preferably 90% by weight or more, for example, 95% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more (for example, 99.9% by weight or more). The upper limit of the proportion of the carboxyl group-containing monomer (m2) in the total functional group-containing monomers is 100% by weight, and may be, for example, 95% by weight or less.

[0033] In addition, the monomer component of the acrylic polymer contains 10% by weight or more of a copolymerizable monomer (m3) different from 2-octyl acrylate (m1) and the carboxyl group-containing monomer (m2). This effectively improves the rough surface adhesion of the adhesive containing the acrylic polymer synthesized using 2-octyl acrylate (m1). It is believed that the side chain crystallinity of the acrylic polymer is reduced by copolymerizing a certain amount or more of the copolymerizable monomer (m3) with the acrylic polymer, and as a result, the glass transition temperature (Tg) of the adhesive is lowered. Note that the technology disclosed herein is not limited to the above considerations.

[0034] It is important that the ratio of the copolymerizable monomer (m3) in the monomer components of the acrylic polymer is 10% by weight or more. As confirmed by the results of the Examples described later, compared with the example in which the copolymerization ratio of the copolymerizable monomer (m3) is 8% by weight, it is considered that by increasing the copolymerization ratio of the copolymerizable monomer (m3) more than that, the effect of lowering the Tg of the adhesive is easily manifested, and the rough surface adhesion is effectively improved. From such a viewpoint, in some preferred embodiments, the ratio of the copolymerizable monomer (m3) in the above-mentioned monomer components may be 12% by weight or more, 15% by weight or more, 18% by weight or more, 20% by weight or more, 22% by weight or more, or 24% by weight or more. By increasing the copolymerization ratio of the copolymerizable monomer (m3), the effect of copolymerization of the copolymerizable monomer (m3) is preferably obtained. In addition, the upper limit of the proportion of the copolymerizable monomer (m3) in the monomer components is about 50% by weight or less (for example, less than 50% by weight), may be 40% by weight or less, 30% by weight or less, or 25% by weight or less in some embodiments. In some preferred embodiments, the proportion of the copolymerizable monomer (m3) in the monomer components is less than 25% by weight, may be 23% by weight or less, 20% by weight or less, 15% by weight or less, or 12% by weight or less. By using an appropriate amount of the copolymerizable monomer (m3) in the above range, it is possible to obtain the effect of using 2-octyl acrylate (m1) while preferably obtaining good rough surface adhesion.

[0035] As the copolymerizable monomer (m3), one or more monomers that are different from 2-octyl acrylate (m1) and the carboxyl group-containing monomer (m2) and are copolymerizable with 2-octyl acrylate (m1) can be used without any particular restrictions. A suitable example of the copolymerizable monomer (m3) is an alkyl (meth)acrylate other than 2-octyl acrylate (m1). As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used. CH2=C(R 1 )COOR 2 (1) Here, R in the above formula (1) 1 is a hydrogen atom or a methyl group. 2 is a chain alkyl group having 1 to 20 carbon atoms (wherein R 1 When is a hydrogen atom, 2-octyl group is excluded.) By selecting and using an appropriate type of alkyl (meth)acrylate having the above chemical structure, it is possible to preferably obtain an adhesive having good adhesive properties and good adhesion to rough surfaces.

[0036] Examples of alkyl (meth)acrylates that can be used as the copolymerizable monomer (m3) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl (meth)acrylate. , isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. These alkyl (meth)acrylates can be used alone or in combination of two or more.

[0037] As the alkyl (meth)acrylate, either one in which the alkyl group is linear or one in which the alkyl group is branched can be used, but from the viewpoint of flexibility, an alkyl (meth)acrylate having a linear alkyl group is preferred. From the same viewpoint, an alkyl acrylate is preferably used as the copolymerizable monomer (m3).

[0038] In an embodiment in which an alkyl (meth)acrylate is used as the copolymerizable monomer (m3), the proportion of the alkyl (meth)acrylate in the monomer components of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), or 9% by weight or more. In some preferred embodiments, the proportion of the alkyl (meth)acrylate in the monomer components is 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, 18% by weight or more, 20% by weight or more, 22% by weight or more, or 24% by weight or more. By copolymerizing the alkyl (meth)acrylate in a predetermined amount or more, the effect of the copolymerizable monomer (m3) is preferably obtained, and the effect of using the alkyl (meth)acrylate is preferably obtained. In addition, the upper limit of the proportion of the alkyl (meth)acrylate in the monomer component is about 50% by weight or less (for example, less than 50% by weight), may be 40% by weight or less, 30% by weight or less, or 25% by weight or less in some embodiments. In some preferred embodiments, the proportion of the alkyl (meth)acrylate in the monomer component is less than 25% by weight, may be 23% by weight or less, 20% by weight or less, 15% by weight or less, or 12% by weight or less. By using an appropriate amount of alkyl (meth)acrylate as the copolymerizable monomer (m3) within the above range, it is possible to obtain good rough surface adhesion while obtaining the effect of using 2-octyl acrylate (m1).

[0039] In an embodiment in which an alkyl (meth)acrylate is used as the copolymerizable monomer (m3), the proportion of the alkyl (meth)acrylate in the copolymerizable monomer (m3) is not particularly limited, and in some embodiments, for example, is 10% by weight or more, may be 30% by weight or more, preferably 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, and even more preferably 90% by weight or more (e.g., 95 to 100% by weight). In an embodiment in which an alkyl (meth)acrylate having a linear alkyl group is used as the copolymerizable monomer (m3), the proportion of the alkyl (meth)acrylate having a linear alkyl group in the copolymerizable monomer (m3) is not particularly limited, and in some embodiments, for example, is 10% by weight or more, may be 30% by weight or more, preferably 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, and even more preferably 90% by weight or more (e.g., 95 to 100% by weight). In addition, in an embodiment in which an alkyl acrylate is used as the copolymerizable monomer (m3), the proportion of the alkyl acrylate in the copolymerizable monomer (m3) is not particularly limited, and in some embodiments, is, for example, 10% by weight or more, may be 30% by weight or more, is preferably 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, and even more preferably 90% by weight or more (e.g., 95 to 100% by weight).

[0040] In some preferred embodiments, the copolymerizable monomer (m3) is R 2 is an alkyl (meth)acrylate having a chain alkyl group with 1 to 6 carbon atoms (hereinafter, such a range of carbon atoms is referred to as "C 1-6 " and alkyl (meth)acrylates having an alkyl group with the above carbon atom number range are sometimes represented as "C 1-6 As the copolymerizable monomer (m3), C 1-6By using alkyl (meth)acrylate, the free volume between polymer molecules increases due to the difference in side chain structure with 2-octyl acrylate, improving flexibility, which is believed to make it easier to obtain good rough surface adhesion. Note that the technology disclosed herein is not limited to the above considerations. 1-6 As for alkyl (meth)acrylate, from the viewpoint of improving flexibility, C 2-6 Alkyl (meth)acrylate is preferred, C 2-4 Alkyl (meth)acrylates are more preferred, or C 4-6 Alkyl (meth)acrylates can also be preferably used. 1-6 Either straight-chain or branched alkyl groups can be used. From the viewpoint of flexibility, however, 1-6 Alkyl (meth)acrylates having a linear alkyl group are preferred. 1-6 The use of alkyl acrylates is preferred. 1-6 The alkyl (meth)acrylates can be used alone or in combination of two or more.

[0041] Copolymerizable monomer (m3) C 1-6 In the embodiment in which alkyl (meth)acrylate is used, the above C accounts for a large proportion of the monomer components of the acrylic polymer. 1-6 Alkyl (meth)acrylate (preferably C 2-6 Alkyl (meth)acrylate, more preferably C 2-4 Alkyl (meth)acrylate or C 4-6 Alkyl (meth)acrylates, or e.g. C 1-6The proportion of the linear alkyl (meth)acrylate (hereinafter the same unless otherwise specified) is not particularly limited, and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), 9% by weight or more, and in some preferred embodiments, 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, 18% by weight or more, 20% by weight or more, 22% by weight or more, or 24% by weight or more. In addition, the proportion of the above C in the above monomer components is not particularly limited, and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), 9% by weight or more, and in some preferred embodiments, 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, 18% by weight or more, 20% by weight or more, 22% by weight or more, or 24% by weight or more. 1-6 The upper limit of the proportion of alkyl (meth)acrylate is about 50% by weight or less (for example, less than 50% by weight) in some embodiments, and may be 40% by weight or less, 30% by weight or less, or 25% by weight or less, and in some preferred embodiments, it is less than 25% by weight, may be 23% by weight or less, may be 20% by weight or less, may be 15% by weight or less, or may be 12% by weight or less. In addition, the proportion of C in the alkyl (meth)acrylate as the copolymerizable monomer (m3) is about 50% by weight or less (for example, less than 50% by weight), and may be 40% by weight or less, 30% by weight or less, or 25% by weight or less, and in some preferred embodiments, it is less than 25% by weight, may be 23% by weight or less, may be 20% by weight or less, may be 15% by weight or less, or may be 12% by weight or less. 1-6 The proportion of alkyl (meth)acrylate is not particularly limited, and in some embodiments, is, for example, 10% by weight or more, may be 30% by weight or more, is preferably 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, and even more preferably 90% by weight or more (e.g., 95 to 100% by weight).

[0042] In some preferred embodiments, n-butyl acrylate (BA) or 2-ethylhexyl acrylate (2EHA) is used as the copolymerizable monomer (m3). BA and 2EHA may be used alone or in combination. By using BA or 2EHA as the copolymerizable monomer (m3), the resulting adhesive has better flexibility and can better exhibit the effect of improving rough surface adhesion. Among them, the use of BA is particularly preferred.

[0043] In embodiments in which BA and / or 2EHA are used as the copolymerizable monomer (m3), the proportion of BA and / or 2EHA in the monomer components of the acrylic polymer is not particularly limited and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), 9% by weight or more, and in some preferred embodiments, 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, 18% by weight or more, 20% by weight or more, 22% by weight or more, or 24% by weight or more. In addition, the upper limit of the proportion of BA and / or 2EHA in the above monomer components is, in some embodiments, approximately 50% by weight or less (e.g., less than 50% by weight), and may be 40% by weight or less, 30% by weight or less, or 25% by weight or less, and in some preferred embodiments, it is less than 25% by weight, may be 23% by weight or less, 20% by weight or less, 15% by weight or less, or 12% by weight or less.

[0044] The monomer component of the acrylic polymer may contain, as the copolymerizable monomer (m3), a functional group-containing monomer (any functional group-containing monomer) other than the carboxy group-containing monomer (m2). Examples of optional functional group-containing monomers that can introduce functional groups that can serve as crosslinking base points into acrylic polymers or contribute to improving adhesive strength include hydroxyl group (OH group)-containing monomers (hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate, etc.), acid anhydride group-containing monomers, amide group-containing monomers ((meth)acrylamide, N,N-dimethyl(meth)acrylamide, etc.), amino group-containing monomers (aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers having nitrogen atom-containing rings (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl group-containing monomers, and imide group-containing monomers. The above-mentioned optional functional group-containing monomers may be used alone or in combination of two or more.

[0045] When the monomer component constituting the acrylic polymer contains the above-mentioned optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exerting the effect of using the optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, suitably 0.5% by weight or more, and may be 1% by weight or more. In addition, from the viewpoint of easily balancing the adhesive performance in relation to the monomer component containing 2-octyl acrylate, the content of the optional functional group-containing monomer in the monomer component is suitably 40% by weight or less, preferably 20% by weight or less, and may be 10% by weight or less (for example, 5% by weight or less). In some embodiments, the content of the optional functional group-containing monomer in the monomer component is, for example, less than 3% by weight, may be less than 1% by weight, may be less than 0.5% by weight, may be less than 0.3% by weight, or may be less than 0.1% by weight. The technology disclosed herein can be preferably implemented in an embodiment in which the monomer component of the acrylic polymer does not substantially contain the optional functional group-containing monomer.

[0046] In this specification, the monomer component being substantially free of monomer A (e.g., the optional functional group-containing monomer) means that the monomer A is not used at least intentionally, and it is permissible for the monomer A to be unintentionally included in an amount of, for example, about 0.01% by weight or less.

[0047] In addition, a hydroxyl-containing monomer may be used as the optional functional group-containing monomer. In this case, the content of the hydroxyl-containing monomer is suitably about 10% by weight or less (for example, 0.001 to 10% by weight) in the total monomer components, preferably about 5% by weight or less, more preferably about 2% by weight or less. In some embodiments, the content of the hydroxyl-containing monomer in the monomer components may be, for example, less than 1% by weight, less than 0.5% by weight, less than 0.3% by weight, less than 0.1% by weight, or less than 0.01% by weight. The monomer components of the acrylic polymer may be substantially free of a hydroxyl-containing monomer. According to the technology disclosed herein, the rough surface adhesion can be improved by limiting the amount of the hydroxyl-containing monomer used or by not using it at all.

[0048] The monomer components constituting the acrylic polymer may contain other copolymerization components other than the functional group-containing monomers described above as the copolymerizable monomer (m3) for the purpose of improving cohesive strength, etc. Examples of other copolymerization components include vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as aryl (meth)acrylate (e.g., phenyl (meth)acrylate), aryloxyalkyl (meth)acrylate (e.g., phenoxyethyl (meth)acrylate), and arylalkyl (meth)acrylate (e.g., benzyl (meth)acrylate); olefin monomers; chlorine-containing monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; and the like. The other copolymerization components may be used alone or in combination of two or more.

[0049] The amount of such other copolymerization components is not particularly limited and may be appropriately selected according to the purpose and use, but from the viewpoint of appropriately exerting the effect of use, it is appropriate to set it to 0.05 wt% or more, and it may be 0.5 wt% or more. In addition, from the viewpoint of easily balancing the adhesive performance, the content of other copolymerization components in the monomer component is appropriate to be 20 wt% or less, and from the viewpoint of appropriately exerting the adhesive properties based on the essential monomer components, it is preferably 10 wt% or less, more preferably 8 wt% or less, and even more preferably less than 5 wt%, for example, it may be less than 3 wt%, or it may be less than 1 wt%. The technology disclosed herein can also be preferably implemented in an embodiment in which the monomer component does not substantially contain other copolymerization components.

[0050] The acrylic polymer may contain a polyfunctional monomer having at least two polymerizable functional groups (typically radically polymerizable functional groups) having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, as another monomer component included in the copolymerizable monomer (m3). By using a polyfunctional monomer as a monomer component, the cohesive force of the adhesive layer can be increased. The polyfunctional monomer can be used as a crosslinking agent. The polyfunctional monomer is not particularly limited, and examples thereof include 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and neopentyl glycol di(meth)acrylate. The polyfunctional monomer can be used alone or in combination of two or more.

[0051] The amount of the polyfunctional monomer used is not particularly limited, and can be appropriately set so that the purpose of using the polyfunctional monomer is achieved. The amount of the polyfunctional monomer used can be about 3% by weight or less of the monomer component, preferably about 2% by weight or less, and more preferably about 1% by weight or less (for example, about 0.5% by weight or less). When using a polyfunctional monomer, the lower limit of the amount used is not particularly limited as long as it is greater than 0% by weight. Usually, the effect of using the polyfunctional monomer can be appropriately exhibited by setting the amount of the polyfunctional monomer used to about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component.

[0052] In some preferred embodiments, a monomer (low Tg monomer) having a homopolymer glass transition temperature (Tg) of less than 0°C may be used as the copolymerizable monomer (m3). For example, by copolymerizing a predetermined amount or more of the low Tg monomer, the effect of lowering the Tg of the adhesive by copolymerization of the copolymerizable monomer (m3) can be suitably exhibited. The homopolymer Tg of the low Tg monomer may be -10°C or less, or -20°C or less. In some preferred embodiments, the homopolymer Tg of the low Tg monomer is approximately -30°C or less, -35°C or less, -40°C or less, -45°C or less, -50°C or less, -55°C or less, -60°C or less, or -65°C or less. Although not particularly limited, in some embodiments, a monomer having a homopolymer Tg lower than the homopolymer Tg of 2-octyl acrylate (m1) may be preferably used as the low Tg monomer. The lower limit of the homopolymer Tg of the low Tg monomer is, for example, -80°C or higher, suitably -75°C or higher, may be -70°C or higher, may be -65°C or higher, or may be -60°C or higher. The low Tg monomer is not particularly limited, but alkyl (meth)acrylate is preferably used. Suitable examples of the low Tg monomer include, for example, BA and 2EHA. Other examples of the low Tg monomer include alkyl acrylates such as hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, and isononyl acrylate. The low Tg monomer may be used alone or in combination of two or more.

[0053] As the homopolymer Tg of a monomer, a value described in a publicly known document is used. For example, the numerical value described in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) is used. When multiple values ​​are described in this document, the highest value is used.

[0054] For monomers for which the homopolymer Tg is not described in the Polymer Handbook, the value obtained by the following measurement method shall be used (see JP 2007-51271 A). Specifically, 100 parts by weight of monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent are charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and stirred for 1 hour while passing nitrogen gas through. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and reacted for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Then, the homopolymer solution is cast and applied onto a release liner, and dried to prepare a test sample (sheet-shaped homopolymer) with a thickness of about 2 mm. This test sample is punched out into a disk with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity is measured in shear mode using a viscoelasticity tester (TA Instruments Japan, model name "ARES") while applying a shear strain of 1 Hz at a temperature range of -70°C to 150°C and a heating rate of 5°C / min. The temperature corresponding to the peak temperature of tan δ is taken as the Tg of the homopolymer.

[0055] In an embodiment in which the low Tg monomer is used as the copolymerizable monomer (m3), the ratio of the low Tg monomer in the monomer components of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), or 9% by weight or more. In some preferred embodiments, the ratio of the low Tg monomer in the monomer components is 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, 18% by weight or more, 20% by weight or more, 22% by weight or more, or 24% by weight or more. By copolymerizing the low Tg monomer in a predetermined amount or more, in addition to the effect as the copolymerizable monomer (m3), the effect based on the Tg of the low Tg monomer is preferably obtained. In addition, the upper limit of the proportion of the low Tg monomer in the monomer components is, in some embodiments, about 50% by weight or less (e.g., less than 50% by weight), and may be 40% by weight or less, 30% by weight or less, or 25% by weight or less. In some embodiments, the proportion of the low Tg monomer in the monomer components may be less than 25% by weight, 23% by weight or less, 20% by weight or less, 15% by weight or less, or 12% by weight or less.

[0056] In some embodiments, the monomer component may contain an alkyl (meth)acrylate having an alkyl group derived from biomass at the ester end (hereinafter also referred to as "biomass alkyl (meth)acrylate"). In recent years, environmental issues such as global warming have become important, and it is desired to reduce the amount of fossil resource-based materials such as petroleum used. Under these circumstances, it is also desired to reduce the amount of fossil resource-based materials used in the field of adhesives. By using a biomass alkyl (meth)acrylate, it is possible to preferably realize an acrylic adhesive that takes into consideration the reduction of dependency on fossil resource-based materials.

[0057] The biomass alkyl (meth)acrylate is not particularly limited, and is, for example, an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived (meth)acrylic acid. Examples of biomass-derived alkanols include biomass ethanol, alkanols derived from plant materials such as palm oil, palm kernel oil, coconut oil, and castor oil. When the biomass-derived alkanol has 3 or more carbon atoms, the alkanol may be linear or branched. In some embodiments, an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate used in the synthesis of an acrylic polymer. In such a biomass alkyl (meth)acrylate, the higher the number of carbon atoms of the alkanol, the higher the ratio of the number of biomass-derived carbons to the total number of carbons contained in the biomass alkyl (meth)acrylate, that is, the biomass carbon ratio of the alkyl (meth)acrylate. Therefore, in the above biomass alkyl (meth)acrylate, it is desirable that the alkyl group derived from biomass has a large number of carbon atoms in terms of reducing the dependency on fossil resource-based materials. On the other hand, if the alkyl group constituting the alkyl (meth)acrylate has too many carbon atoms, it tends to be difficult to obtain adhesive properties such as adhesive strength, and it may also be disadvantageous in terms of productivity such as synthesis, handling, and cost. In an embodiment in which an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate, it is desirable to use a material that has a good balance between adhesive properties and reduced dependency on fossil resource-based materials (more specifically, the biomass carbon ratio of the above alkyl (meth)acrylate).

[0058] In some preferred embodiments, biomass-derived 2-octyl acrylate (biomass 2-octyl acrylate) is used as the 2-octyl acrylate. By using biomass 2-octyl acrylate, the effect of the technology disclosed herein can be realized while reducing the dependency on fossil resource-based materials. The biomass 2-octyl acrylate is an ester of a biomass-derived alkanol (specifically, 2-octanol) and a biomass-derived or non-biomass-derived acrylic acid, and for example, an ester of a biomass-derived alkanol and a non-biomass-derived acrylic acid can be used. In such a compound, only the 2-octyl group is biomass-derived.

[0059] The proportion of biomass alkyl (meth)acrylate (e.g., biomass 2-octyl acrylate) in the monomer components of the acrylic polymer is, for example, in some embodiments, 50% by weight or more (e.g., more than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 82% by weight or more, and may be 90% by weight or more. In some embodiments, the proportion of biomass alkyl (meth)acrylate in the monomer components may be 92% by weight or more, 94% by weight or more, or 96% by weight or more. In some embodiments, the proportion of biomass alkyl (meth)acrylate (e.g., biomass 2-octyl acrylate) in the monomer components is, for example, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less.

[0060] The biomass carbon ratio of the monomer components constituting the acrylic polymer (the biomass carbon ratio of the acrylic polymer) may be, for example, 1% or more, suitably 10% or more, preferably 30% or more, more preferably 50% or more (e.g., more than 50%), may be 70% or more, may be 80% or more, or may be 90% to 100%. By designing in this way, an acrylic pressure-sensitive adhesive that takes into consideration the reduction of dependency on fossil resource-based materials can be obtained.

[0061] The method for obtaining an acrylic polymer is not particularly limited, and various polymerization methods known as a synthesis method for an acrylic polymer, such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, and a photopolymerization method, can be appropriately adopted. For example, a solution polymerization method can be preferably adopted. As a monomer supply method when carrying out solution polymerization, a lump-sum charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and can be, for example, about 20°C to 170°C (typically about 40°C to 140°C).

[0062] The solvent (polymerization solvent) used in the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, any one of the following solvents or a mixture of two or more of them can be used: aromatic compounds (typically aromatic hydrocarbons) such as toluene; acetate esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols (e.g., monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol; ethers such as tert-butyl methyl ether; and ketones such as methyl ethyl ketone.

[0063] The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of polymerization method. For example, one or more azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide (BPO) and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; and the like. Still other examples of polymerization initiators include redox-based initiators obtained by combining peroxides with reducing agents. Such polymerization initiators can be used alone or in 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) relative to 100 parts by weight of the total monomer components.

[0064] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and from the viewpoint of obtaining good adhesive properties, an acrylic polymer having a Mw of about 100,000 or more is usually used. In some embodiments, the Mw of the acrylic polymer is preferably 400,000 or more, more preferably 600,000 or more, even more preferably 700,000 or more, and may be 800,000 or more. The larger the Mw of the acrylic polymer, the easier it is to obtain an adhesive having good high-temperature properties, and by using such a high-molecular-weight acrylic polymer in combination with a tackifier, it is possible to preferably achieve both good high-temperature properties and rough surface adhesion. On the other hand, from the viewpoint of adhesive strength, rough surface adhesion, ease of synthesis, etc., the Mw of the acrylic polymer is usually about 3 million or less, preferably 2 million or less, more preferably 1.5 million or less, even more preferably 1.2 million or less, and may be 1 million or less (for example, less than 1 million).

[0065] Although not particularly limited, the acrylic polymer is usually one having a dispersity (Mw / Mn) of less than 50, which is expressed as the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn). The dispersity (Mw / Mn) may be about 40 or less, about 30 or less, or about 20 or less. In some embodiments, the dispersity (Mw / Mn) of the acrylic polymer is preferably 15 or less, may be 12 or less, may be 10 or less, may be 8 or less, or may be 6 or less. The dispersity (Mw / Mn) of the acrylic polymer is theoretically 1 or more, and from the viewpoint of ease of preparation, etc., it may be, for example, 2 or more, 3 or more, or 4 or more (typically 5 or more). An acrylic polymer having a dispersity (Mw / Mn) in the above range has a predetermined molecular weight distribution, and is likely to have rough surface adhesion due to its wettability based on its low molecular weight, and is likely to have good adhesive properties due to its cohesive force based on its high molecular weight.

[0066] Mw, Mn and Mw / Mn can be adjusted by polymerization conditions (time, temperature, etc.), use of a chain transfer agent, etc. The Mw and Mn of the acrylic polymer can be measured by gel permeation chromatography (GPC) and calculated as standard polystyrene. Specifically, they can be measured under the following conditions using a GPC measuring device "HLC-8220GPC" (manufactured by Tosoh Corporation). The same applies to the examples described below. [GPC measurement conditions] Sample concentration: 0.2% by weight (tetrahydrofuran solution) Sample injection volume: 10 μL Eluent: tetrahydrofuran (THF) Flow rate (flow rate): 0.6mL / min Column temperature (measurement temperature): 40℃ column: Sample column: 1 "TSKguardcolumn SuperHZ-H" + 2 "TSKgel SuperHZM-H" (manufactured by Tosoh Corporation) Reference column: 1 "TSKgel SuperH-RC" (manufactured by Tosoh Corporation) Detector: Differential refractometer (RI) Standard sample: polystyrene

[0067] (tackifier) The adhesive layer disclosed herein includes a tackifier. The use of a tackifier can improve adhesive strength, and in particular, can improve the rough surface adhesion of an adhesive containing an acrylic polymer containing 2-octyl acrylate (m1) as a monomer component. As the tackifier, any component that can improve adhesive strength by being added to the adhesive can be used without particular limitation, and typically, tackifier resins such as rosin-based tackifier resins and terpene-based tackifier resins described below, and acrylic oligomers can be used. The tackifier can be used alone or in combination of two or more types. Although not particularly limited, in some embodiments, the effect of using a tackifier can be effectively exerted in a composition containing an acrylic polymer with a high molecular weight (e.g., Mw 400,000 or more).

[0068] The content of the tackifier in the adhesive layer is usually about 1 part by weight or more relative to 100 parts by weight of the acrylic polymer from the viewpoint of obtaining the effect of adding the tackifier, and is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). The more the amount of the tackifier used, the easier it is to obtain the effect of improving the rough surface adhesion. In some preferred embodiments, the content of the tackifier may be 20 parts by weight or more, or may be 25 parts by weight or more relative to 100 parts by weight of the acrylic polymer. The upper limit of the content of the tackifier in the adhesive layer is not particularly limited, but from the viewpoint of compatibility with the acrylic polymer, it is suitable to be about 100 parts by weight or less (for example, less than 100 parts by weight) relative to 100 parts by weight of the acrylic polymer, and may be about 80 parts by weight or less. In some embodiments, the content of the tackifier in the pressure-sensitive adhesive layer is, for example, 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the viewpoint of flexibility, adhesive properties (cohesive strength, etc.), etc., the content of the tackifier is 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.

[0069] (tackifier resin) In some preferred embodiments, the adhesive layer contains a tackifier resin. By using a tackifier resin, the rough surface adhesion can be preferably improved. The tackifier resin is not particularly limited, and various tackifier resins such as rosin-based tackifier resins, terpene-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, phenol-based tackifier resins, and ketone-based tackifier resins can be used. Such tackifier resins can be used alone or in combination of two or more.

[0070] Specific examples of rosin-based tackifying resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.; the same applies below); and various other rosin derivatives. Examples of the rosin derivative include rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., esterified products of rosin) and those obtained by esterifying modified rosin with alcohols (i.e., esterified products of modified rosin); unsaturated fatty acid modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acid; unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acid; rosin alcohols obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid modified rosins, or unsaturated fatty acid modified rosin esters; metal salts of rosins (particularly rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and thermally polymerizing the mixture; and the like. Among these, rosin esters are preferred.

[0071] Although not particularly limited, specific examples of rosin esters include esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl esters, triethylene glycol esters, glycerin esters, pentaerythritol esters, etc.

[0072] Examples of terpene-based tackifier resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; modified terpene resins obtained by modifying these terpene resins (phenol-modified, aromatic-modified, hydrogen-modified, hydrocarbon-modified, etc.); etc. An example of the modified terpene resin is a terpene phenol resin.

[0073] Terpene phenolic resin refers to a polymer containing a terpene residue and a phenol residue, and is a concept that includes both a copolymer of a terpene and a phenolic compound (terpene-phenol copolymer resin) and a homopolymer or copolymer of a terpene modified with phenol (phenol-modified terpene resin). Specific examples of terpenes that constitute such terpene phenolic resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l-, and d / l-forms (dipentene)). Hydrogenated terpene phenolic resin refers to a hydrogenated terpene phenolic resin having a structure obtained by hydrogenating such a terpene phenolic resin. It is also called hydrogenated terpene phenolic resin.

[0074] Examples of hydrocarbon-based tackifying resins include various hydrocarbon resins such as aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, hydrogenated products thereof (for example, alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), various modified products thereof (for example, maleic anhydride modified products), coumarone resins, and coumarone-indene resins.

[0075] In some embodiments, it is preferable to use at least one selected from rosin-based tackifier resins and terpene-based tackifier resins as the tackifier resin. By including rosin-based tackifier resins and / or terpene-based tackifier resins in the acrylic adhesive, the rough surface adhesion can be preferably improved. In some preferred embodiments, the total ratio of the rosin-based tackifier resin and the terpene-based tackifier resin to the total tackifier resin contained in the adhesive layer can be, for example, more than about 50% by weight (more than 50% by weight and 100% by weight or less), and may be more than about 70% by weight, more than about 80% by weight, more than about 90% by weight, more than 95% by weight, or more than 99% by weight.

[0076] Some preferred embodiments include an embodiment in which the tackifier resin contains one or more terpene phenol resins. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which the total amount of the tackifier resin is about 25% by weight or more (more preferably about 30% by weight or more). The proportion of the terpene phenol resin in the total amount of the tackifier resin may be about 50% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more. Substantially all of the tackifier resin (for example, about 95% by weight or more and 100% by weight or less, or even about 99% by weight or more and 100% by weight or less) may be a terpene phenol resin.

[0077] The content of the terpene phenol resin in the adhesive layer is not particularly limited as long as the desired properties are satisfied. In some embodiments, the content of the terpene phenol resin is usually about 1 part by weight or more, and is preferably about 5 parts by weight or more, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more) relative to 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength and rough surface adhesion. In some preferred embodiments, the content of the terpene phenol resin may be 20 parts by weight or more, or may be 25 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. In some embodiments, the content of the terpene phenol resin in the adhesive layer is, for example, 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the standpoint of cohesive strength, etc., the content of the terpene phenol resin is 40 parts by weight or less, optionally 30 parts by weight or less, optionally 25 parts by weight or less, optionally 20 parts by weight or less, or optionally 18 parts by weight or less.

[0078] The softening point of the tackifier resin is not particularly limited. For example, a tackifier resin having a softening point of about 50° C. or more can be used, and from the viewpoint of improving cohesive force, a tackifier resin having a softening point (softening temperature) of about 80° C. or more can be preferably used. For example, a terpene-based tackifier resin (such as a terpene phenol resin) having such a softening point can be preferably used. In some preferred embodiments, from the viewpoint of high-temperature adhesive strength, the softening point of the tackifier resin may be about 100° C. or more, about 105° C. or more, or about 110° C. or more. The upper limit of the softening point of the tackifier resin is not particularly limited. From the viewpoint of adhesion to an adherend, a tackifier resin having a softening point of about 200° C. or less (more preferably about 180° C. or less) can be preferably used. In some preferred embodiments, the softening point of the tackifier resin may be about 160°C or less (e.g., less than 160°C), about 150°C or less (e.g., less than 150°C), less than 145°C, less than 140°C, less than 130°C, or less than 120°C.

[0079] The softening point of the tackifier resin in this specification is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at a low temperature, and is carefully filled into a ring placed on a flat metal plate so as not to create bubbles. After cooling, the part that protrudes from the flat surface including the top end of the ring is cut off with a slightly heated knife. Next, a holder (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured to a depth of 90 mm or more. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in glycerin without touching each other, and the temperature of the glycerin is kept at 20°C ± 5°C for 15 minutes. Next, a steel ball is placed in the center of the surface of the sample in the ring, and this is placed in a fixed position on the holder. Next, keeping the distance from the top of the ring to the glycerin surface at 50 mm, place a thermometer and align the center of the thermometer's mercury bulb to the same height as the center of the ring, then heat the container. The flame of the Bunsen burner used for heating should be midway between the center of the bottom of the container and its edge, and heating should be uniform. After heating begins and the temperature of the bath reaches 40°C, the rate of increase must be 5.0 ± 0.5°C per minute. The sample gradually softens and flows down the ring, and the temperature is read when it finally touches the bottom plate, and this is the softening point. The softening point is measured for two or more samples at the same time, and the average value is used.

[0080] In some embodiments, the tackifier resin is a tackifier resin T having a softening point of less than 150° C. L Tackifying resin T is used. L By using the tackifier resin T, it is easy to obtain high adhesive strength to various adherends and to improve rough surface adhesion. L In some preferred embodiments, the softening point of the tackifier resin T may be 145° C. or less. L The softening point of the tackifier resin T is less than 140°C, and may be less than 130°C or may be less than 120°C. L The lower limit of the softening point of the tackifier resin T is not particularly limited. LFrom the viewpoint of exerting an appropriate cohesive strength, the softening point of the adhesive may be, for example, about 50° C. or higher, 60° C. or higher, 70° C. or higher, 80° C. or higher, or 90° C. or higher; and in some preferred embodiments, from the viewpoint of high-temperature adhesive strength and the like, the softening point is 100° C. or higher, 105° C. or higher, or 110° C. or higher.

[0081] Tackifying resin T L As the tackifier resin, one type selected from the tackifier resins exemplified above having a softening point of less than 150° C. can be used alone or in combination of two or more types. L Preferably, the tackifier resin T comprises a terpene phenol resin. L may contain one type of terpene phenol resin alone, or may contain two or more types of terpene phenol resins in combination.

[0082] In some embodiments, tackifier resin T L The proportion of the terpene phenol resin in the total can be, for example, more than about 50% by weight, may be about 65% by weight or more, may be about 75% by weight or more, may be 85% by weight or more, or may be 95% by weight or more. L The present invention can be preferably implemented in an embodiment in which substantially all of the above (for example, approximately 97% by weight or more, or 99% by weight or more, or may be 100% by weight) is a terpene phenol resin.

[0083] In addition, tackifier resin T L The tackifier resin may or may not contain a tackifier resin having a softening point of less than 50° C., more preferably about 40° C. or less (typically a rosin-based, terpene-based, or hydrocarbon-based tackifier resin, for example, hydrogenated rosin methyl ester). Such a low-softening-point tackifier resin may be a liquid tackifier resin that is liquid at 30° C. The liquid tackifier resin may be used alone or in combination of two or more. The content of the liquid tackifier resin is determined based on the tackifier resin T from the viewpoint of cohesive strength, etc. LIt can be about 30% by weight or less of the total, suitably about 10% by weight or less (for example, 0 to 10% by weight), may be about 2% by weight or less (0.5 to 2% by weight), or may be less than 1% by weight.

[0084] Tackifying resin T L The content of is not particularly limited, but in some embodiments, it is, for example, 1 part by weight or more, appropriately 5 parts by weight or more, preferably 8 parts by weight or more, more preferably 10 parts by weight or more, even more preferably 12 parts by weight or more, and may be 15 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. L The more the amount of tackifier resin T used, the more the adhesive strength, particularly the rough surface adhesion, tends to improve. From this viewpoint, in some preferred embodiments, L The content of the tackifier resin T may be 20 parts by weight or more, or 25 parts by weight or more, based on 100 parts by weight of the acrylic polymer. L The content of the tackifier resin T is suitably about 100 parts by weight or less (for example, less than 100 parts by weight) relative to 100 parts by weight of the acrylic polymer, and may be about 80 parts by weight or less. In some preferred embodiments, from the viewpoint of adhesive properties, etc., the content of the tackifier resin T L The content of is suitably about 70 parts by weight or less, alternatively 60 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.

[0085] In some embodiments, the adhesive layer comprises a tackifier resin T L and a tackifier resin T having a softening point of 150°C or higher (e.g., 150°C to 200°C). H The tackifier resin T may be used in combination with the above. H As the tackifier resin, one type may be used alone or two or more types may be used in combination from among the tackifier resins exemplified above that have a softening point of 150° C. or higher.

[0086] In some embodiments, tackifier resin T L It is preferable that the tackifier resin T accounts for more than 50% by weight of the total amount of the tackifier resin contained in the pressure-sensitive adhesive layer. L The effect of the inclusion of the tackifier resin T in the total amount of the tackifier resin contained in the adhesive layer is easily manifested. L The ratio of tackifier resin T L From the viewpoint of more effectively exerting the effect of use, the content of the tackifier resin in the pressure-sensitive adhesive layer is preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more, and may be 95% by weight or more, or may be 98% by weight or more. In some preferred embodiments, the tackifier resin contained in the pressure-sensitive adhesive layer is substantially tackifier resin T L In this embodiment, the tackifier resin T L The proportion is in the range of 99 to 100% by weight.

[0087] The hydroxyl value of the tackifier resin is not particularly limited. In some embodiments, the hydroxyl value of the tackifier resin is usually about 300 mgKOH / g or less, and about 200 mgKOH / g or less is appropriate from the viewpoint of compatibility with the acrylic polymer, and in some preferred embodiments, it may be about 150 mgKOH / g or less, or may be 120 mgKOH / g or less. In some embodiments, the hydroxyl value of the tackifier resin is 0 mgKOH / g or more, may be about 10 mgKOH / g or more, or may be about 20 mgKOH / g or more.

[0088] Here, the hydroxyl value may be a value measured by potentiometric titration as specified in JIS K0070: 1992. The specific measurement method is as follows. [Method for measuring hydroxyl value] 1. Reagents (1) As the acetylation reagent, take about 12.5 g (about 11.8 mL) of acetic anhydride, add pyridine to make the total volume 50 mL, and stir thoroughly before use. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to make the total volume 100 mL, and stir thoroughly before use. (2) Use a 0.5 mol / L potassium hydroxide ethanol solution as the measurement reagent. (3) In addition, prepare toluene, pyridine, ethanol and distilled water. 2.Operation (1) Accurately weigh out approximately 2 g of sample into a flat-bottom flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and attach an air condenser. (2) Heat the flask in a 100°C bath for 70 minutes, then allow it to cool, add 35 mL of toluene as a solvent from the top of the cooling tube and stir, then add 1 mL of distilled water and stir to decompose the acetic anhydride. Heat again in the bath for 10 minutes to complete the decomposition, then allow it to cool. (3) Wash the cooling tube with 5 mL of ethanol and remove it. Then, add 50 mL of pyridine as a solvent and stir. (4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a volumetric pipette. (5) Perform potentiometric titration with 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is the endpoint. (6) A blank test is carried out by carrying out steps (1) to (5) above without adding any sample. 3.Calculation The hydroxyl value is calculated according to the following formula. Hydroxyl value (mgKOH / g) = [(BC) x f x 28.05] / S + D Where: B: Amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test. C: Amount of 0.5 mol / L potassium hydroxide ethanol solution used for the sample (mL), f: Factor of 0.5 mol / L potassium hydroxide ethanol solution, S: weight of sample (g), D: acid number, 28.05: 1 / 2 the molecular weight of potassium hydroxide, 56.11. It is.

[0089] In some embodiments, the tackifier resin may include a tackifier resin having a hydroxyl value of less than 100 mgKOH / g. Hereinafter, a tackifier resin having a hydroxyl value of less than 100 mgKOH / g may be referred to as a "low hydroxyl value resin". The hydroxyl value of the low hydroxyl value resin may be less than 80 mgKOH / g, 70 mgKOH / g or less, or less than 65 mgKOH / g. A tackifier resin containing such a low hydroxyl value resin is likely to provide good rough surface adhesion. The lower limit of the hydroxyl value of the low hydroxyl value resin is 0 mgKOH / g or more, may be approximately 10 mgKOH / g or more, or may be approximately 15 mgKOH / g or more. The higher the hydroxyl value, the more likely it is that good cohesive strength is obtained. As the low hydroxyl value resin, one type selected from the tackifier resins exemplified above having a hydroxyl value of less than 100 mgKOH / g may be used alone or in combination of two or more types. In some embodiments, the low hydroxyl value resin preferably comprises at least one selected from rosin-based tackifier resin and terpene-based tackifier resin.For example, as the low hydroxyl value resin, a terpene phenol resin having a hydroxyl value of less than 100mgKOH / g can be preferably adopted.Terpene phenol resin is advantageous because its hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol.

[0090] Although not particularly limited, when a low hydroxyl value resin is used, the ratio of the low hydroxyl value resin (e.g., terpene phenol resin) to the entire tackifier resin contained in the adhesive layer may be about 5% by weight or more, 10% by weight or more, 15% by weight or more, or 20% by weight or more. In some embodiments, the ratio of the low hydroxyl value resin to the entire tackifier resin is preferably, for example, about 30% by weight or more. This allows the effect of using the low hydroxyl value resin to be preferably exhibited. In some preferred embodiments, the ratio of the low hydroxyl value resin to the entire tackifier resin is about 40% by weight or more, about 50% by weight or more (e.g., more than 50% by weight), about 60% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more. Substantially all of the tackifier resin (e.g., about 95 to 100% by weight, or even about 99 to 100% by weight) may be a low hydroxyl value resin.

[0091] The softening point of the low hydroxyl value resin is not particularly limited. The softening point of the low hydroxyl value resin may be, for example, about 50° C. or higher, and from the viewpoint of improving cohesive strength, a low hydroxyl value resin having a softening point (softening temperature) of about 80° C. or higher may be preferably used. For example, a rosin-based tackifier resin or a terpene phenol resin having such a softening point may be preferably used. In some preferred embodiments, from the viewpoint of high-temperature adhesive strength, the softening point of the low hydroxyl value resin may be about 100° C. or higher, 105° C. or higher, or about 110° C. or higher. In some embodiments, from the viewpoint of adhesive strength and rough surface adhesion, a low hydroxyl value resin having a softening point of about 200° C. or lower (more preferably about 180° C. or lower) may be preferably used. In some preferred embodiments, the softening point of the low hydroxyl value resin may be about 160°C or less, about 150°C or less (e.g., less than 150°C), less than 145°C, less than 140°C, less than 130°C, or less than 120°C.

[0092] The content of the low hydroxyl value resin in the adhesive layer is not particularly limited, and in some embodiments, it is usually about 1 part by weight or more, and it is appropriate to make it about 5 parts by weight or more, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more) relative to 100 parts by weight of the acrylic polymer. The more the amount of the low hydroxyl value resin used, the more the adhesive strength and rough surface adhesion tend to improve. From this viewpoint, in some preferred embodiments, the content of the low hydroxyl value resin may be 20 parts by weight or more, or may be 25 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. In addition, in some embodiments, the content of the low hydroxyl value resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, or may be 50 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the viewpoint of cohesive strength and the like, the content of the low hydroxyl value resin is 40 parts by weight or less, optionally 30 parts by weight or less, optionally 25 parts by weight or less, optionally 20 parts by weight or less, or optionally 18 parts by weight or less.

[0093] When the adhesive layer disclosed herein contains a tackifier resin, a tackifier resin derived from a plant (vegetable tackifier resin) may preferably act as the tackifier resin from the viewpoint of improving the biomass carbon ratio of the adhesive layer. Examples of vegetable tackifier resins include the above-mentioned rosin-based tackifier resin and terpene-based tackifier resin. The vegetable tackifier resin may be used alone or in combination of two or more. When the adhesive layer disclosed herein contains a tackifier resin, the proportion of the vegetable tackifier resin in the total amount of tackifier resins is preferably 30% by weight or more (e.g., 50% by weight or more, typically 80% by weight or more). In some embodiments, the proportion of the vegetable tackifier resin in the total amount of tackifier resins is 90% by weight or more (e.g., 95% by weight or more, typically 99 to 100% by weight). The technology disclosed herein may be preferably implemented in an embodiment that does not substantially contain tackifier resins other than vegetable tackifier resins.

[0094] The content of the tackifier resin in the adhesive layer is not particularly limited. In an embodiment in which a tackifier resin is used as a tackifier, the content of the tackifier resin is usually about 1 part by weight or more, and is preferably about 5 parts by weight or more, and is preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more) relative to 100 parts by weight of the acrylic polymer. The more the amount of the tackifier resin used, the more the adhesive strength and rough surface adhesion tend to improve. From this viewpoint, in some preferred embodiments, the content of the tackifier resin may be 20 parts by weight or more, or may be 25 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. In addition, the content of the tackifier resin in the adhesive layer is, for example, about 100 parts by weight or less (for example, less than 100 parts by weight) relative to 100 parts by weight of the acrylic polymer, and may be about 80 parts by weight or less. In some embodiments, the content of the tackifier resin in the pressure-sensitive adhesive layer is, for example, 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the viewpoint of flexibility, cohesive strength, etc., the content of the tackifier resin is 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.

[0095] (Acrylic Oligomer) In some embodiments, the pressure-sensitive adhesive layer contains an acrylic oligomer. By including an acrylic oligomer, the adhesive strength of the pressure-sensitive adhesive can be improved. According to the technology disclosed herein, the pressure-sensitive adhesive layer can exhibit excellent rough surface adhesion in a composition containing an acrylic oligomer. Although not particularly limited, in some embodiments, the effect of using an acrylic oligomer can be effectively exhibited in a composition containing an acrylic polymer with a high molecular weight (e.g., Mw 400,000 or more).

[0096] The acrylic oligomer has a Tg of about 0° C. or more and about 300° C. or less, preferably about 20° C. or more and about 300° C. or less, and more preferably about 40° C. or more and about 300° C. or less. By having the Tg within the above range, the adhesive strength can be suitably improved. In some preferred embodiments, from the viewpoint of the cohesiveness of the adhesive, the Tg of the acrylic oligomer is about 30° C. or more, more preferably about 50° C. or more (e.g. about 60° C. or more), and from the viewpoint of adhesiveness, it is preferably about 200° C. or less, more preferably about 150° C. or less, and even more preferably about 100° C. or less (e.g. about 80° C. or less).

[0097] In this specification, the Tg of an acrylic oligomer refers to the Tg calculated by the Fox formula based on the composition of the above-mentioned monomer components. The Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. 1 / Tg=Σ(Wi / Tgi) In the above Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction (copolymerization ratio by weight) of monomer i in the copolymer, and Tgi is the glass transition temperature (unit: K) of the homopolymer of monomer i. The Tg of the homopolymer used to calculate Tg is as explained for the homopolymer Tg of the acrylic polymer monomer.

[0098] The weight average molecular weight (Mw) of the acrylic oligomer can typically be about 1000 or more and less than about 30000, preferably about 1500 or more and less than about 20000, and more preferably about 2000 or more and less than about 10000. It is preferable that Mw is within the above range because good adhesiveness can be obtained. In some preferred embodiments, the Mw of the acrylic oligomer is about 2500 or more (e.g., about 3000 or more), and from the viewpoint of adhesiveness, it is preferably about 7000 or less, more preferably about 5000 or less (e.g., about 4500 or less, typically about 4000 or less). The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and calculated as a value in terms of standard polystyrene. Specifically, it is measured using 2 columns of TSKgel GMH-H (20) on a Tosoh HPLC 8020 at a flow rate of about 0.5 mL / min with tetrahydrofuran solvent.

[0099] Examples of monomers constituting acrylic oligomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, Examples of the (meth)acrylate include alkyl (meth)acrylates such as butyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from alcohols derived from terpene compounds. These (meth)acrylates may be used alone or in combination of two or more.

[0100] The acrylic oligomer preferably contains, as a monomer unit, an acrylic monomer having a relatively bulky structure, typified by alkyl (meth)acrylates in which the alkyl group has a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates), such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate; and (meth)acrylates having a cyclic structure, such as aryl (meth)acrylates, such as phenyl (meth)acrylate and benzyl (meth)acrylate, from the viewpoint of further improving the adhesiveness of the pressure-sensitive adhesive layer. In addition, when ultraviolet light is used in synthesizing an acrylic oligomer or preparing an adhesive layer, those having saturated bonds are preferred in that they are less likely to cause polymerization inhibition, and alkyl (meth)acrylates in which the alkyl group has a branched structure, or esters with alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) can be suitably used as monomers constituting the acrylic oligomer. The above-mentioned branched alkyl (meth)acrylates, alicyclic hydrocarbon group (meth)acrylates, and aryl (meth)acrylates all fall under the category of (meth)acrylate monomers in the technology disclosed herein. The alicyclic hydrocarbon group may be a saturated or unsaturated alicyclic hydrocarbon group.

[0101] The proportion of (meth)acrylate monomers (e.g., alicyclic hydrocarbon group-containing (meth)acrylates) in all monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight or more, and more preferably 70% by weight or more (e.g., 80% by weight or more, or even 90% by weight or more). In some preferred embodiments, the acrylic oligomer has a monomer composition consisting essentially of (meth)acrylate monomers.

[0102] As the constituent monomer component of the acrylic oligomer, in addition to the above (meth)acrylate monomer, a functional group-containing monomer can be used. Suitable examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers such as AA and MAA; and hydroxy group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers can be used alone or in combination of two or more. Among them, carboxy group-containing monomers are preferred, and AA is particularly preferred.

[0103] When all monomer components constituting the acrylic oligomer contain a functional group-containing monomer, the proportion of the functional group-containing monomer (e.g., a carboxy group-containing monomer such as AA) in the above all monomer components is suitably about 1 wt % or more, preferably 2 wt % or more, more preferably 3 wt % or more, and is suitably about 15 wt % or less, preferably 10 wt % or less, more preferably 7 wt % or less.

[0104] The acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be used in an appropriate mode. The type of polymerization initiator (e.g., azo-based polymerization initiator such as AIBN) that can be used as necessary is generally as exemplified in the synthesis of the acrylic polymer, and the amount of the polymerization initiator and the amount of the chain transfer agent, such as n-dodecyl mercaptan, that is optionally used, are appropriately set based on technical common sense so as to obtain a desired molecular weight, so detailed explanations are omitted here.

[0105] From the above viewpoint, suitable acrylic oligomers include, for example, homopolymers of dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), as well as copolymers of CHMA and isobutyl methacrylate (IBMA), copolymers of CHMA and IBXMA, copolymers of CHMA and acryloylmorpholine (ACMO), copolymers of CHMA and diethylacrylamide (DEAA), copolymers of CHMA and AA, copolymers of ADA and methyl methacrylate (MMA), copolymers of DCPMA and IBXMA, and copolymers of DCPMA and MMA.

[0106] When the adhesive layer disclosed herein contains an acrylic oligomer, the content is not particularly limited, and is suitably, for example, 0.1 parts by weight or more (e.g., 1 part by weight or more) relative to 100 parts by weight of the acrylic polymer. From the viewpoint of better exerting the effect of the acrylic oligomer, in some embodiments, the content of the acrylic oligomer is about 3 parts by weight or more, may be about 5 parts by weight or more, may be about 10 parts by weight or more, or may be about 12 parts by weight or more. In addition, from the viewpoint of compatibility with the acrylic polymer, the content of the acrylic oligomer is suitably less than 50 parts by weight (e.g., less than 40 parts by weight) relative to 100 parts by weight of the acrylic polymer, preferably less than 30 parts by weight, more preferably less than about 25 parts by weight, and even more preferably less than about 20 parts by weight. In some embodiments, the content of the acrylic oligomer may be 10 parts by weight or less, may be 5 parts by weight or less, or may be 1 part by weight or less (e.g., less than 1 part by weight) relative to 100 parts by weight of the acrylic polymer. The pressure-sensitive adhesive layer may be substantially free of acrylic oligomer.

[0107] In some embodiments, the pressure-sensitive adhesive layer may contain one or more of the above-mentioned tackifier resins and one or more of the acrylic oligomers. O [wt%] Tackifier resin content C T [weight%] ratio (C T / C O ) is not particularly limited. In some embodiments, the above (C T / C O ) is suitably, for example, 0.1 or more, preferably 0.5 or more, and may be 1 or more (e.g., more than 1), 2 or more, 3 or more, or 4 or more, on a weight basis. T / C O The larger the (C) is, the easier it is to obtain the effect of using the tackifier resin. T / C O ) is suitably, for example, 10 or less, preferably 8 or less, may be 6 or less, or may be 5 or less, on a weight basis. This allows the effect of using the acrylic oligomer to be preferably exhibited.

[0108] In the technology disclosed herein, the total amount (total amount) of the acrylic polymer and tackifier in the adhesive layer is appropriately set so as to achieve the effects of the technology disclosed herein, and is not limited to a specific range. In some preferred embodiments, the total amount (total amount) of the acrylic polymer and tackifier contained in the adhesive layer is appropriate to account for more than 50% by weight of the adhesive layer, preferably about 70% by weight or more, more preferably about 90% by weight or more, even more preferably 95% by weight or more (for example, 95% by weight or more and 100% by weight or less, or less than 100% by weight), and may be 98% by weight or more, from the viewpoint of preferably achieving the effects of the technology disclosed herein.

[0109] (Crosslinking agent) In the technology disclosed herein, the adhesive composition used to form the adhesive layer may contain a crosslinking agent as necessary. The type of crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, hydrazine-based crosslinking agents, amine-based crosslinking agents, and silane coupling agents. The crosslinking agents may be used alone or in combination of two or more. Among them, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and melamine-based crosslinking agents are preferred, and isocyanate-based crosslinking agents and epoxy-based crosslinking agents are more preferred. By appropriately selecting and using a crosslinking agent, the adhesive layer may have an appropriate cohesive force. The pressure-sensitive adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after crosslinking reaction, a form before crosslinking reaction, a form after partial crosslinking reaction, an intermediate or composite form thereof, etc. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in a form after crosslinking reaction.

[0110] As the isocyanate-based crosslinking agent, a polyfunctional isocyanate (which refers to a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent can be used alone or in combination of two or more kinds.

[0111] Examples of the polyfunctional isocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0112] Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0113] Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Examples of the diisocyanate include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0114] A preferred polyfunctional isocyanate is one having an average of three or more isocyanate groups per molecule. Such a trifunctional or higher isocyanate may be a multimer (typically a dimer or trimer) of a bifunctional or trifunctional or higher isocyanate, a derivative (for example, an addition reaction product of a polyhydric alcohol and two or more molecules of a polyfunctional isocyanate), a polymer, etc. For example, a dimer or trimer of diphenylmethane diisocyanate, an isocyanurate of hexamethylene diisocyanate (a trimer adduct of an isocyanurate structure), a reaction product of trimethylolpropane and tolylene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and other polyfunctional isocyanates may be mentioned.

[0115] The technology disclosed herein can be preferably implemented in an embodiment using at least an isocyanate-based crosslinking agent as a crosslinking agent. The amount of the isocyanate-based crosslinking agent used is not particularly limited. The amount of the isocyanate-based crosslinking agent used can be, for example, about 0.1 parts by weight or more relative to 100 parts by weight of the acrylic polymer. From the viewpoint of achieving both cohesive strength and adhesion, the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of the acrylic polymer is usually preferably about 0.3 parts by weight or more (for example, 0.5 parts by weight or more). In some preferred embodiments, the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of the acrylic polymer is about 0.8 parts by weight or more, more preferably about 1.0 parts by weight or more, even more preferably about 1.2 parts by weight or more, and may be about 1.5 parts by weight or more. The amount of the isocyanate crosslinking agent used is suitably 10 parts by weight or less relative to 100 parts by weight of the acrylic polymer, preferably less than 5 parts by weight, more preferably less than 4.0 parts by weight, even more preferably less than 3.0 parts by weight, particularly preferably 2.5 parts by weight or less, and may be 2.0 parts by weight or less (for example, 1.7 parts by weight or less). By limiting the amount of the isocyanate crosslinking agent used within a predetermined range, it is possible to obtain good rough surface adhesion while maintaining cohesive force based on the use of the isocyanate crosslinking agent.

[0116] As the epoxy crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without any particular limitation. An epoxy crosslinking agent having 3 to 5 epoxy groups in one molecule is preferred. The epoxy crosslinking agent can be used alone or in combination of two or more kinds.

[0117] Although not particularly limited, specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like.

[0118] The amount of the epoxy crosslinking agent used is not particularly limited. The amount of the epoxy crosslinking agent used can be, for example, more than 0 parts by weight and about 1 part by weight or less (typically about 0.001 to 1 part by weight) relative to 100 parts by weight of the acrylic polymer. From the viewpoint of favorably exerting the effect of improving the cohesive force, the amount of the epoxy crosslinking agent used is usually about 0.002 parts by weight or more relative to 100 parts by weight of the acrylic polymer, preferably about 0.005 parts by weight or more, and may be, for example, about 0.01 parts by weight or more. In addition, from the viewpoint of improving the adhesion to the adherend, the amount of the epoxy crosslinking agent used is suitable to be about 0.5 parts by weight or less relative to 100 parts by weight of the acrylic polymer, preferably about 0.2 parts by weight or less, more preferably about 0.1 parts by weight or less (for example, less than 0.1 parts by weight), and may be 0.07 parts by weight or less, or may be 0.04 parts by weight or less. In order to avoid a decrease in rough surface adhesion caused by excessive crosslinking, in some embodiments, the amount of epoxy crosslinking agent used is suitably about 0.03 parts by weight or less, and preferably about 0.02 parts by weight or less, per 100 parts by weight of the acrylic polymer. By limiting the amount of epoxy crosslinking agent used within a predetermined range, it is easy to maintain sufficient adhesive strength and rough surface adhesion while having good cohesive strength.

[0119] In some preferred embodiments, the crosslinking agent is a combination of an isocyanate crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from the isocyanate crosslinking agent. The type of non-isocyanate crosslinking agent that can be used in combination with the isocyanate crosslinking agent is not particularly limited, and can be appropriately selected from the above-mentioned crosslinking agents. The non-isocyanate crosslinking agent can be used alone or in combination of two or more. In some preferred embodiments, an epoxy crosslinking agent can be used as the non-isocyanate crosslinking agent. For example, by using an isocyanate crosslinking agent and an epoxy crosslinking agent in combination, better adhesion properties can be achieved.

[0120] The relationship between the content of the isocyanate crosslinking agent and the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) is not particularly limited. In some embodiments, the content of the isocyanate crosslinking agent is, for example, more than 1 time the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent), and is suitably about 10 times or more, preferably about 50 times or more, more preferably about 80 times or more, even more preferably about 100 times or more (for example, more than 100 times), and particularly preferably about 120 times or more (for example, about 150 times or more). Furthermore, from the viewpoint of optimally exerting the effect of using an isocyanate-based crosslinking agent in combination with a non-isocyanate-based crosslinking agent (preferably an epoxy-based crosslinking agent), the content of the isocyanate-based crosslinking agent relative to the content of the non-isocyanate-based crosslinking agent (preferably an epoxy-based crosslinking agent) is usually, for example, approximately 1000 times or less, and it is appropriate to set it to approximately 500 times or less, and it is preferably approximately 300 times or less, and it may be approximately 200 times or less.

[0121] The content of the crosslinking agent in the adhesive composition disclosed herein (total amount of crosslinking agent) is not particularly limited. From the viewpoint of cohesion, the content of the crosslinking agent is usually about 0.001 parts by weight or more, and it is appropriate to set it to about 0.002 parts by weight or more relative to 100 parts by weight of acrylic polymer, and it is preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, even more preferably about 0.02 parts by weight or more, and particularly preferably about 0.03 parts by weight or more. In some embodiments, the content of the crosslinking agent relative to 100 parts by weight of acrylic polymer is about 0.1 parts by weight or more, more preferably about 0.5 parts by weight or more, even more preferably about 1.0 parts by weight or more, and it may be about 1.2 parts by weight or more, or it may be about 1.5 parts by weight or more. The content of the crosslinking agent in the pressure-sensitive adhesive composition is usually about 20 parts by weight or less, preferably about 15 parts by weight or less, and preferably about 10 parts by weight or less (for example, about 5 parts by weight or less) relative to 100 parts by weight of the acrylic polymer. In some embodiments, the content of the crosslinking agent relative to 100 parts by weight of the acrylic polymer is 4.0 parts by weight or less, more preferably 3.0 parts by weight or less, even more preferably 2.5 parts by weight or less, and may be 2.0 parts by weight or less (for example, less than 2.0 parts by weight), or may be 1.8 parts by weight or less. In a configuration in which the amount of the crosslinking agent used is limited within the above range, good adhesion and rough surface adhesion tend to be easily obtained.

[0122] (Other additives) In addition to the above-mentioned components, the adhesive composition may contain various additives, as necessary, that are common in the field of adhesives, such as leveling agents, crosslinking assistants, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, antiaging agents, UV absorbers, antioxidants, rust inhibitors, light stabilizers, etc. As for such various additives, conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed explanations will be omitted.

[0123] The adhesive layer (layer made of adhesive) disclosed herein may be an adhesive layer formed from an aqueous adhesive composition, a solvent-based adhesive composition, a hot melt-type adhesive composition, or an active energy ray curable adhesive composition. The aqueous adhesive composition refers to an adhesive composition in a form containing an adhesive (adhesive layer forming component) in a solvent (aqueous solvent) mainly composed of water, and typically includes those called water-dispersed adhesive compositions (compositions in a form in which at least a part of the adhesive is dispersed in water). The solvent-based adhesive composition refers to an adhesive composition in a form containing an adhesive in an organic solvent. As the organic solvent contained in the solvent-based adhesive composition, one or more of the organic solvents exemplified as those usable in the above-mentioned solution polymerization (toluene, ethyl acetate, etc.) can be used without particular limitation. The technology disclosed herein can be preferably implemented in an embodiment having an adhesive layer formed from a solvent-based adhesive composition from the viewpoint of adhesion properties, etc.

[0124] The adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method can be adopted in which an adhesive composition is applied to a surface having releasability (release surface) or a non-release surface and dried to form an adhesive layer. In the case of an adhesive sheet having a substrate, for example, a method (direct method) can be adopted in which an adhesive composition is directly applied (typically coated) to the substrate and dried to form an adhesive layer. In addition, a method (transfer method) can be adopted in which an adhesive composition is applied to a surface having releasability (release surface) and dried to form an adhesive layer on the surface, and the adhesive layer is transferred to a substrate. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of a release liner, the back surface of a substrate treated for release, etc. can be used. The adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may be an adhesive layer formed in a regular or random pattern such as a dotted or striped pattern.

[0125] The pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, a bar coater, etc. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating. From the viewpoints of promoting the crosslinking reaction, improving production efficiency, etc., the pressure-sensitive adhesive composition is preferably dried under heating. The drying temperature can be, for example, about 40 to 150° C., and is usually preferably about 60 to 130° C. After drying the pressure-sensitive adhesive composition, aging may be further performed for the purpose of adjusting the component migration in the pressure-sensitive adhesive layer, advancing the crosslinking reaction, relaxing distortion that may exist in the pressure-sensitive adhesive layer, etc.

[0126] (Thickness) The thickness of the adhesive layer is not particularly limited, and a configuration having an adhesive layer having an appropriate thickness, for example, in the range of 0.1 to 500 μm, can be adopted depending on the application and purpose of use. In some embodiments, from the viewpoint of avoiding an excessively thick adhesive sheet, the thickness of the adhesive layer is usually about 100 μm or less, preferably about 70 μm or less, more preferably about 60 μm or less, and even more preferably about 50 μm or less. In some preferred embodiments, the thickness of the adhesive layer can be about 35 μm or less, for example, about 30 μm or less, about 25 μm or less, or about 22 μm or less. An adhesive layer with a limited thickness can well meet the demand for a thinner and lighter product. In addition, in terms of adhesion to the adherend, the lower limit of the thickness of the adhesive layer is, in some embodiments, appropriately about 0.5 μm or more, may be about 1 μm or more, and is advantageously about 3 μm or more, preferably about 10 μm or more, more preferably about 12 μm or more (e.g., more than 12 μm), even more preferably about 15 μm or more, and may be, for example, about 18 μm or more. The greater the thickness of the adhesive layer, the greater the tendency for the adhesive strength and rough surface adhesion to be improved. The adhesive sheet disclosed herein may be an adhesive sheet having an adhesive layer of the above thickness on both sides of the substrate. In addition, in a substrate-attached double-sided adhesive sheet having a first adhesive layer and a second adhesive layer on each side of the substrate, the first adhesive layer and the second adhesive layer may be the same thickness or may be different thicknesses.

[0127] (glass transition temperature of adhesive) Although not particularly limited, in some embodiments, the glass transition temperature (Tg) of the adhesive (layer) is 10°C or less (for example, less than 10°C), may be 8.0°C or less, or may be 6.0°C or less. Here, the glass transition temperature of the adhesive (layer) refers to the glass transition temperature determined from the peak temperature of tan δ in dynamic viscoelasticity measurement. An adhesive containing a tackifier and having a low Tg is highly flexible and tends to exhibit excellent rough surface adhesion. In some preferred embodiments, the Tg of the adhesive (layer) is lower than 5.0°C, may be 4.0°C or less, 3.0°C or less, 2.0°C or less, 1.0°C or less, 0°C or less (for example, less than 0.0°C), -1.0°C or less, -3.0°C or less, or -5.0°C or less. In addition, in some embodiments, the Tg of the adhesive (layer) is, for example, suitably -30°C or higher from the standpoint of cohesive strength, etc., and is preferably -15°C or higher, and may be -12°C or higher, -10°C or higher, -7.0°C or higher (e.g., greater than -7.0°C), -5.0°C or higher, -3.0°C or higher, -1.0°C or higher, 0°C or higher (e.g., greater than 0.0°C), 1.0°C or higher, or 3.0°C or higher (e.g., 4.0°C or higher).

[0128] In the technology disclosed herein, the Tg of the adhesive (layer) can be determined by dynamic viscoelasticity measurement. Specifically, a plurality of adhesive layers (adhesive sheets in the case of substrate-less adhesive sheets) to be measured are stacked to prepare an adhesive layer having a thickness of about 2 mm. A sample obtained by punching out the adhesive layer into a disk shape having a diameter of 7.9 mm is sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurement is performed under the following conditions using a viscoelasticity tester (e.g., ARES or its equivalent, manufactured by TA Instruments), and Tg is determined from the peak temperature of the loss tangent tanδ (G″ / G′), which is the ratio of the loss modulus G″ to the storage modulus G′. Measurement mode: Shear mode Temperature range: -70℃~150℃ Heating rate: 5℃ / min ·Measurement frequency: 1Hz The above method is also used in the Examples described later. The pressure-sensitive adhesive layer to be measured may be one formed by applying the corresponding pressure-sensitive adhesive composition in a layer form and drying or curing it.

[0129] (Biomass carbon ratio) In some embodiments, the pressure-sensitive adhesive layer contains a biomass-derived material, and the biomass carbon ratio (also referred to as bio-based ratio) may be a predetermined value or more. The biomass carbon ratio of the pressure-sensitive adhesive layer is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the pressure-sensitive adhesive means that the amount of fossil resource-based materials, such as petroleum, used is small. In this respect, the higher the biomass carbon ratio of the pressure-sensitive adhesive, the more preferable it is. For example, the biomass carbon ratio of the pressure-sensitive adhesive layer may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and may be 95% or less, or 90% or less, from the viewpoint of ease of material availability. From the viewpoint of making it easier to exhibit good adhesive performance, in some embodiments, the biomass carbon ratio of the adhesive layer may be, for example, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less.

[0130] <Base material> In an embodiment in which the adhesive sheet disclosed herein is in the form of a single-sided or double-sided adhesive type adhesive sheet with a substrate, the substrate supporting (backing) the adhesive layer may be a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, a composite of these, or the like. Examples of paper include Japanese paper, craft paper, glassine paper, wood-free paper, synthetic paper, topcoat paper, and the like. Examples of cloth include woven fabrics and nonwoven fabrics made by spinning various fibrous materials alone or in combination. Examples of the fibrous material include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, and the like. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets, and the like. Examples of foam sheets include foamed polyolefin sheets, foamed polyurethane sheets, and foamed polychloroprene rubber sheets, and the like. Examples of metal foils include aluminum foil and copper foil, and the like. The substrate supporting the adhesive layer is also called the substrate layer in the adhesive sheet.

[0131] The substrate may be formed from a material derived from biomass or a material derived from non-biomass. From the viewpoint of producing a PSA sheet that takes into consideration the reduction of dependency on fossil resource-based materials, a substrate material derived from biomass (typically a resin film) is preferably used.

[0132] The substrate may be formed using a recyclable material or a recycled material (also called a recycled material). A resin film is preferably used as such a recycled material. Since a resin film (for example, a polyester film such as a PET film) is recyclable, it is possible to continuously reproduce the resin film after use, regardless of whether or not a plant-derived material is used, and the environmental load can be reduced by reusing the resin film after use. Such a recyclable resin film or recycled resin film is also called a recycled film. The recycled material (for example, a recycled film) may be formed from a biomass-derived material or a non-biomass-derived material.

[0133] As the substrate constituting the substrate-attached pressure-sensitive adhesive sheet, a substrate containing a resin film as the base film can be preferably used. The above-mentioned base film is typically a member capable of independently maintaining its shape (independent). The substrate in the technology disclosed herein may be substantially composed of such a base film. Alternatively, the substrate may include an auxiliary layer in addition to the above-mentioned base film. Examples of the above-mentioned auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc., provided on the surface of the above-mentioned base film.

[0134] The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount of more than 50% by weight). Examples of the resin film include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; and the like. The resin film may be a rubber film such as a natural rubber film or a butyl rubber film. Among them, from the viewpoint of handling and processability, polyester films are preferred, and PET films are particularly preferred.

[0135] In this specification, the term "resin film" refers to a typically non-porous sheet, and is a concept that is distinguished from so-called nonwoven fabric or woven fabric (in other words, a concept that excludes nonwoven fabric or woven fabric). The resin film may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, such a resin film may be non-foamed. Here, a non-foamed resin film refers to a resin film that has not been intentionally treated to form a foam. Specifically, a non-foamed resin film may be a resin film with an expansion ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).

[0136] The above-mentioned substrate (e.g., resin film) may contain various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, etc. The blending ratio of various additives is about less than 30% by weight (e.g., less than 20% by weight, typically less than 10% by weight).

[0137] The substrate (e.g., resin film) may have a single-layer structure, or may have a multi-layer structure of two, three or more layers. From the viewpoint of shape stability, the substrate preferably has a single-layer structure. In the case of a multi-layer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (e.g., polyester resin). The method for producing the substrate (typically a resin film) is not particularly limited and may be any conventionally known method. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calendar roll molding may be appropriately used.

[0138] The surface of the substrate may be subjected to a conventionally known surface treatment such as a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment, an acid treatment, an alkali treatment, application of a primer, etc. Such a surface treatment may be a treatment for improving the adhesion between the substrate and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the substrate.

[0139] In addition, when the technology disclosed herein is implemented in the form of a single-sided pressure-sensitive adhesive sheet with a substrate, the back surface of the substrate may be subjected to a release treatment as necessary. The release treatment may be, for example, a treatment in which a general silicone-based, long-chain alkyl-based, fluorine-based or other release treating agent is applied in the form of a thin film typically of about 0.01 μm to 1 μm (for example, 0.01 μm to 0.1 μm). By carrying out such a release treatment, it is possible to obtain an effect such as facilitating unwinding of a roll of the pressure-sensitive adhesive sheet.

[0140] In the pressure-sensitive adhesive sheet of an embodiment including a substrate, the thickness of the substrate is not particularly limited. In order to prevent the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the substrate can be, for example, about 200 μm or less, preferably about 150 μm or less, more preferably about 100 μm or less. Depending on the purpose and mode of use of the pressure-sensitive adhesive sheet, the thickness of the substrate may be about 70 μm or less, about 50 μm or less, or about 30 μm or less (for example, about 25 μm or less). In some embodiments, the thickness of the substrate may be about 20 μm or less, about 15 μm or less, or about 10 μm or less (for example, about 5 μm or less). By reducing the thickness of the substrate, the thickness of the pressure-sensitive adhesive layer can be made larger even if the total thickness of the pressure-sensitive adhesive sheet is the same. This can be advantageous in terms of improving adhesion to the adherend or substrate. The lower limit of the substrate is not particularly limited. From the viewpoint of the handling property and processability of the pressure-sensitive adhesive sheet, the thickness of the substrate is usually about 0.5 μm or more (e.g., 1 μm or more), preferably about 2 μm or more, for example, about 6 μm or more. In some embodiments, the thickness of the substrate can be about 15 μm or more, and may be about 25 μm or more.

[0141] <Release liner> In the technology disclosed herein, a release liner can be used during the formation of the adhesive layer, the preparation of the adhesive sheet, the storage, distribution, and shaping of the adhesive sheet before use. The release liner is not particularly limited, and for example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or a release liner made of a fluorine-based polymer (polytetrafluoroethylene, etc.) can be used. The release treatment layer can be formed by surface treating the liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. As the liner substrate, a substrate formed using a biomass-derived material or a recycled material (recycled film, etc.) can be preferably used, similar to the substrate of the above-mentioned adhesive sheet.

[0142] <Total thickness of adhesive sheet> The total thickness of the adhesive sheet disclosed herein (including the adhesive layer and may further include a base layer, but not including a release liner) is not particularly limited. The total thickness of the adhesive sheet is, for example, about 1 mm or less, may be about 500 μm or less, or may be about 300 μm or less, and from the viewpoint of thinning, is appropriately about 200 μm or less, and may be about 150 μm or less (for example, about 100 μm or less). In some embodiments, the thickness of the adhesive sheet can be about 50 μm or less, for example, may be about 35 μm or less, may be about 30 μm or less, may be about 25 μm or less, or may be about 22 μm or less. The lower limit of the thickness of the adhesive sheet is, for example, 0.1 μm or more (for example, 0.5 μm or more), is appropriately about 3 μm or more, is preferably about 10 μm or more, more preferably about 15 μm or more, and may be about 18 μm or more. A pressure-sensitive adhesive sheet having a thickness equal to or greater than a certain value is likely to be able to adhere to an adherend and also tends to be easy to handle. In a substrate-less pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive layer is the total thickness of the pressure-sensitive adhesive sheet.

[0143] <Characteristics of adhesive sheet> Although not particularly limited, in some embodiments, the pressure-sensitive adhesive sheet preferably has a 180-degree peel strength (adhesive strength to SUS) against a stainless steel plate of about 10 N / 20 mm or more. A pressure-sensitive adhesive sheet exhibiting such adhesive strength to SUS can exhibit excellent adhesion. In some preferred embodiments, the adhesive strength to SUS may be about 12 N / 20 mm or more, about 14 N / 20 mm or more, or about 16 N / 20 mm or more (e.g., 18 N / 20 mm or more). The upper limit of the adhesive strength to SUS is not particularly limited, but from the viewpoint of compatibility with other adhesive properties such as cohesive strength, it may usually be, for example, about 50 N / 20 mm or less. The adhesive strength to SUS is measured using a SUS plate as an adherend under conditions of 23°C, 50% RH, a pulling speed of 300 mm / min, and a peel angle of 180°. More specifically, it is measured by the method described in the Examples below.

[0144] In addition, the adhesive sheet disclosed herein preferably has a rough surface adhesive strength of about 1.0 N / 20 mm or more, as measured by the method described in the Examples below. An adhesive sheet exhibiting such a rough surface adhesive strength can exhibit good adhesion to the rough surfaces of various adherends, and can be used as an adhesive means with good adhesion reliability. In some embodiments, the rough surface adhesive strength is more preferably about 2.0 N / 20 mm or more, even more preferably about 3.0 N / 20 mm or more, and particularly preferably about 4.0 N / 20 mm or more or about 5.0 N / 20 mm or more (for example, 5.5 N / 20 mm or more). The upper limit of the rough surface adhesive strength is not particularly limited, and from the viewpoint of compatibility with other adhesive properties such as cohesive strength, it may usually be, for example, about 10 N / 20 mm or less.

[0145] In addition, although not particularly limited, in some embodiments, the adhesive sheet preferably has a 180° peel strength (high-temperature adhesive strength) at 65°C against a stainless steel plate of more than about 4.5N / 20mm. An adhesive sheet exhibiting such high-temperature adhesive strength tends to have excellent high-temperature characteristics, and can exhibit high adhesion reliability even when used in a high-temperature environment. In some preferred embodiments, the high-temperature adhesive strength may be about 5.0N / 20mm or more, about 5.5N / 20mm or more, or about 6.0N / 20mm or more. The upper limit of the high-temperature adhesive strength is not particularly limited, but from the viewpoint of compatibility with other adhesive properties such as cohesive strength, it may usually be, for example, about 15N / 20mm or less, or about 10N / 20mm or less. The high-temperature adhesive strength is measured using a SUS plate as an adherend, in a measurement environment of 65°C, at a tensile speed of 300mm / min and a peel angle of 180°. Specific measurement conditions are the same as those for the above-mentioned adhesive strength against SUS, except that the temperature of the measurement environment is 65°C.

[0146] In some embodiments, the pressure-sensitive adhesive sheet contains a biomass-derived material, and the biomass carbon ratio (also referred to as biobased ratio) may be a predetermined value or more. The biomass carbon ratio of the pressure-sensitive adhesive sheet is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the pressure-sensitive adhesive sheet means that the amount of fossil resource-based materials, such as petroleum, used is small. From this perspective, the higher the biomass carbon ratio of the pressure-sensitive adhesive sheet, the more preferable it is. For example, the biomass carbon ratio of the pressure-sensitive adhesive sheet may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and from the viewpoint of ease of material availability, may be 95% or less, or 90% or less. In order to facilitate the exertion of good adhesive performance, in some embodiments, the biomass carbon ratio of the adhesive sheet may be, for example, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less.

[0147] <Application> The use of the adhesive sheet disclosed herein is not particularly limited. Since the adhesive sheet disclosed herein has improved rough surface adhesion, it is preferably used in various applications in the form of being attached to an adherend having a rough surface, such as a foam material, a mesh material, graphite, or a metal or resin that has been roughened. The adhesive sheet disclosed herein can be preferably used for fixing various members as an adhesive means with good adhesion reliability even when used by attaching it to a rough surface. For example, it can be preferably used for fixing members in electronic devices such as various portable electronic devices. For example, the adhesive sheet is usually used for fixing members in a portable electronic device due to size, weight, and other restrictions, and therefore the adhesive area is small. The adhesive sheet used for this application needs to have an adhesive force that can achieve good fixation even in a small area, and the required performance is at a higher level due to the demands for high functionality, weight reduction, and miniaturization. In particular, in the case of mobile electronic devices equipped with touch panel displays, such as smartphones, the products themselves are becoming smaller and thinner, while the screens are becoming larger from the viewpoint of visibility and operability of the displays. Due to this unique situation, the adhesives used are required to have adhesion and fixing performance under more severe conditions. The adhesive sheet disclosed herein can be used for the above-mentioned mobile electronic device applications to achieve excellent adhesion reliability. In addition, since the members constituting electronic devices such as mobile electronic devices include materials having rough surfaces (e.g., foam materials, mesh materials, graphite, metals and resins subjected to roughening treatment, etc.), adhesive sheets having good rough surface adhesion are suitable for such applications. Furthermore, electronic devices such as mobile electronic devices may be used in high-temperature environments, and the internal space may become heated due to heat generation by electronic components. The adhesive disclosed herein also has excellent high-temperature properties due to the inclusion of an acrylic polymer in which 2-octyl acrylate is copolymerized, and in this respect, it is also preferably applied to electronic devices such as mobile electronic devices.

[0148] Non-limiting examples of the portable electronic device include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear type devices worn on the wrist like a wristwatch, modular type devices worn on a part of the body with a clip or strap, eyewear type devices including glasses (monocular type and binocular type devices, including head-mounted type devices), clothing type devices attached to shirts, socks, hats, etc. in the form of accessories, earwear type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, "portable" does not mean that it is sufficient to simply be portable, but rather that it has a level of portability that allows an individual (average adult) to carry it relatively easily. Examples of the electronic device include personal computers (desktop type, notebook type, tablet type, etc.), televisions, etc. These may include a built-in display device such as a liquid crystal or organic electroluminescence display device.

[0149] Although not particularly limited, in some embodiments, the pressure-sensitive adhesive sheet is preferably used in electronic devices that include various light sources such as LEDs (light emitting diodes) and light-emitting elements such as self-emitting organic ELs. For example, it is preferably used in electronic devices (typically mobile electronic devices) equipped with organic EL displays or liquid crystal displays.

[0150] FIG. 4 is a schematic example of a portable electronic device (smartphone) using the adhesive sheet disclosed herein. As shown in FIG. 4, a battery (heat generating element) 540 is built into a housing 520 of the portable electronic device 500. The portable electronic device 500 is also configured to include an adhesive sheet 550. In this configuration example, the adhesive sheet 550 has the form of a double-sided adhesive sheet (double-sided adhesive sheet) that fixes the members that constitute the portable electronic device 500. The portable electronic device 500 is provided with a touch panel 570 whose display unit also functions as an input unit. The adhesive sheet disclosed herein is preferably used as a component (member joining means) of the portable electronic device described above.

[0151] In addition, in some embodiments, the PSA sheet disclosed herein may have a PSA layer containing an acrylic polymer with a high biomass carbon ratio, and therefore may be used as a substitute for a conventional acrylic PSA in various applications in which the acrylic PSA (i.e., an acrylic PSA with a low biomass carbon ratio) is used, thereby contributing to reducing dependency on fossil resource-based materials. The PSA sheet disclosed herein may be preferably used as a PSA sheet with reduced dependency on fossil resource-based materials.

[0152] The matters disclosed by this specification include the following: [1] A portable electronic device, an adhesive sheet is bonded to a member constituting the portable electronic device, The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer contains an acrylic polymer containing 2-octyl acrylate (m1) as a monomer component, the monomer component of the acrylic polymer contains 10% by weight or more of a copolymerizable monomer (m3) different from 2-octyl acrylate (m1) and the carboxyl group-containing monomer (m2); The portable electronic device, wherein the adhesive layer further comprises a tackifier. [2] The copolymerizable monomer (m3) is represented by the formula: CH2=C(R1 )COOR 2 (In the above formula, R 1 is a hydrogen atom or a methyl group, and R 2 is a chain alkyl group having 1 to 20 carbon atoms (wherein R 1 When is a hydrogen atom, the 2-octyl group is excluded. The portable electronic device according to the above item [1], which contains an alkyl (meth)acrylate represented by the following formula: [3] The portable electronic device according to the above [1] or [2], wherein the copolymerizable monomer (m3) includes at least one selected from n-butyl acrylate and 2-ethylhexyl acrylate. [4] The mobile electronic device according to any one of the above [1] to [3], wherein the tackifier includes at least one selected from a rosin-based tackifier resin, a terpene-based tackifier resin, and an acrylic oligomer. [5] The mobile electronic device according to any one of the above [1] to [4], wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a crosslinking agent. [6] The portable electronic device according to any one of the above [1] to [5], wherein the acrylic polymer has a weight average molecular weight of 400,000 or more. [7] The mobile electronic device according to any one of the above [1] to [6], wherein the polydispersity (Mw / Mn) of the acrylic polymer is 2 or more and less than 50, the polydispersity being determined from the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic polymer. [8] The mobile electronic device according to any one of the above [1] to [7], wherein the pressure-sensitive adhesive layer has a glass transition temperature of 10° C. or lower, and the glass transition temperature of the pressure-sensitive adhesive layer refers to a glass transition temperature determined from a peak temperature of tan δ in dynamic viscoelasticity measurement. [9] The portable electronic device according to any one of the above [1] to [8], wherein the pressure-sensitive adhesive sheet has a 180 degree peel strength against a stainless steel plate of 10 N / 20 mm or more.

[0153]

[11] A pressure-sensitive adhesive layer including an acrylic polymer including 2-octyl acrylate (m1) as a monomer component, the monomer component of the acrylic polymer contains 10% by weight or more of a copolymerizable monomer (m3) different from 2-octyl acrylate (m1) and the carboxyl group-containing monomer (m2); The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer further comprises a tackifier.

[12] The copolymerizable monomer (m3) is represented by the formula: CH2=C(R 1 )COOR 2 (In the above formula, R 1 is a hydrogen atom or a methyl group, and R 2 is a chain alkyl group having 1 to 20 carbon atoms (wherein R 1 When is a hydrogen atom, the 2-octyl group is excluded. The pressure-sensitive adhesive sheet according to the above item

[11] , which contains an alkyl (meth)acrylate represented by the following formula:

[13] The pressure-sensitive adhesive sheet according to the above

[11] or

[12] , wherein the copolymerizable monomer (m3) includes at least one selected from n-butyl acrylate and 2-ethylhexyl acrylate.

[14] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[13] , wherein the tackifier comprises at least one selected from a rosin-based tackifier resin, a terpene-based tackifier resin, and an acrylic oligomer.

[15] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[14] , wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a crosslinking agent.

[16] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[15] , wherein the acrylic polymer has a weight average molecular weight of 400,000 or more.

[17] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[16] , wherein the polydispersity (Mw / Mn) of the acrylic polymer is 2 or more and less than 50, the polydispersity being determined from the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic polymer.

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

[11] to

[17] above, wherein the pressure-sensitive adhesive layer has a glass transition temperature of 10° C. or lower, the glass transition temperature of the pressure-sensitive adhesive layer being determined from the peak temperature of tan δ in dynamic viscoelasticity measurement.

[19] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[18] , which has a 180 degree peel strength against a stainless steel plate of 10 N / 20 mm or more.

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

[11] to

[19] above, which is used for fixing components in an electronic device.

[21] An electronic device comprising the pressure-sensitive adhesive sheet according to any one of

[11] to

[20] above. EXAMPLES

[0154] Some 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.

[0155] <Example 1> (Synthesis of acrylic polymers) In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel, 85 parts of 2-octyl acrylate (2OcA), 10 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components, and ethyl acetate as a polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60°C to 70°C for 8 hours to obtain a solution of an acrylic polymer. The weight average molecular weight (Mw) of this acrylic polymer was 880,000, and the dispersity (Mw / Mn) was 5.5. The above 2OcA is a compound synthesized using 2-octanol derived from biomass and having an alkyl group derived from biomass at the ester end.

[0156] (Preparation of Pressure-Sensitive Adhesive Composition) To the acrylic polymer solution obtained above, 15 parts of a terpene phenol resin (product name "YS Polystar T-115", manufactured by Yasuhara Chemical Co., Ltd., softening point approximately 115°C, hydroxyl value 30-60 mgKOH / g) as a tackifier resin, 2 parts (solid content basis) of an isocyanate crosslinking agent (product name "Takenate D-101E", manufactured by Mitsui Chemicals, Inc.), and 0.01 part of an epoxy crosslinking agent (product name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Co., Ltd.) were added per 100 parts of the acrylic polymer contained in the solution, and the mixture was stirred to prepare a pressure-sensitive adhesive composition according to this example.

[0157] (Preparation of adhesive sheet) The obtained adhesive composition was applied to the release surface of a 38 μm thick polyester release film (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) and dried at 100° C. for 2 minutes to form an adhesive layer having a thickness of 20 μm. The release surface of a 25 μm thick polyester release film (trade name "Diafoil MRF", thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) was attached to this adhesive layer. In this way, a substrateless double-sided adhesive sheet having a thickness of 20 μm, both sides of which were protected by the two polyester release films, was obtained. The glass transition temperature (Tg) of the adhesive layer was −5.9° C., and the biobased content (measured according to ASTM D6866) was 60%.

[0158] <Examples 2 to 9 and Comparative Examples 1 to 4> The pressure-sensitive adhesive compositions of each example were prepared in the same manner as in Example 1, except that the monomer composition of the acrylic polymer, the type and amount of the tackifier, and the type and amount of the crosslinking agent were changed as shown in Table 1, and the resulting pressure-sensitive adhesive compositions were used to produce substrate-less double-sided pressure-sensitive adhesive sheets (thickness 20 μm) of each example in the same manner as in Example 1. In Table 1, 2EHA stands for 2-ethylhexyl acrylate.

[0159] The acrylic oligomer used was prepared by the following method. Specifically, 95 parts of cyclohexyl methacrylate (CHMA), 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel, and the mixture was stirred in a nitrogen stream for 1 hour to remove oxygen from the polymerization system, and then heated to 85°C and reacted for 5 hours to obtain an acrylic oligomer with a solid content concentration of 50%. The Mw of the obtained acrylic oligomer was 3600.

[0160] <Evaluation method> [Adhesion to SUS] A 50 μm thick PET film was attached to one adhesive surface of the adhesive sheet (double-sided adhesive sheet) to form a backing, and the sheet was cut to a size of 20 mm wide and 100 mm long to prepare a measurement sample. In an environment of 23°C and 50% RH, the other adhesive surface of the measurement sample was pressed against the surface of a stainless steel plate (SUS304BA plate) washed with ethyl acetate by rolling a 2 kg roller back and forth once. After leaving the sample in the same environment for 30 minutes, a universal tensile compression tester was used to measure the peel strength (adhesive strength to SUS) [N / 20 mm] in accordance with JIS Z 0237:2000 at a tensile speed of 300 mm / min and a peel angle of 180 degrees.

[0161] [Adhesion to rough surfaces] A 50 μm thick PET film was attached to one of the adhesive surfaces of the adhesive sheet (double-sided adhesive sheet) to provide a backing, and the sheet was cut to a size of 20 mm wide and 100 mm long to prepare a measurement sample. In addition, sandpaper (Riken Corundum Co., Ltd., grain size 320) was fixed to a stainless steel plate (SUS304BA plate) as an adherend. In an environment of 23°C and 50% RH, the other adhesive surface of the measurement sample was pressed against the sandpaper surface (rough surface) of the adherend by rolling a 2 kg roller back and forth once. After leaving the sample in the same environment for 72 hours, a universal tensile compression tester was used to measure the peel strength (rough surface adhesion) [N / 20 mm] in accordance with JIS Z 0237:2000 at a tensile speed of 300 mm / min and a peel angle of 180 degrees.

[0162] In addition, in the measurement of each of the above adhesive strengths, the universal tensile and compression tester is a Minebea "tensile and compression tester, TG-1kN" or an equivalent product. When performing measurements on a single-sided adhesive sheet, PET film backing is not required. When the substrate thickness is thin (for example, when the substrate thickness is 25 μm or less), PET film backing may be used.

[0163] Table 1 shows the outline of the pressure-sensitive adhesive sheet and the evaluation results of each example.

[0164] [Table 1]

[0165] As shown in Table 1, the adhesives according to Examples 1 to 9 contain an acrylic polymer containing 2OcA as a monomer component and 10% or more of BA or 2EHA as a copolymerizable monomer, and a tackifier, and the adhesive sheets using the adhesives had good rough surface adhesion. On the other hand, in Comparative Examples 1 and 2, in which the amount of the copolymerizable monomer used was less than 10%, high adhesion to SUS was obtained, but good rough surface adhesion was not obtained. In particular, a comparison between Example 4 and Comparative Example 2 confirmed that the rough surface adhesion changed significantly between the amount of copolymerizable monomer of 10% (Example 4) and the amount of copolymerizable monomer of 8% (Comparative Example 2). This change is considered to be largely due to the change in the side chain crystallinity of the acrylic polymer based on the difference in the amount of copolymerization of the copolymerizable monomer, rather than the influence of the homopolymer Tg of the copolymerizable monomer. In Comparative Examples 3 and 4, in which a tackifier was not used, the degree of crosslinking was reduced to design the adhesive to be flexible, but rough surface adhesion was not obtained. From these results, it is found that the use of a tackifier is necessary to obtain good rough surface adhesion. In addition, from comparisons between Examples 1 and 3, Examples 4 and 7, and Comparative Examples 3 and 4, it was found that the adhesive Tg was lower and the rough surface adhesion tended to improve when BA with a higher homopolymer Tg than 2EHA was copolymerized. The reason for this is thought to be that the copolymerization of BA with a side chain structure that is more different from 2OcA than 2EHA caused a greater decrease in the side chain crystallinity derived from 2OcA and an increase in the free volume between polymer molecules. The above results show that an adhesive sheet containing 2OcA as a monomer component, and further containing 10% or more of a copolymerizable monomer different from 2OcA and a carboxy group-containing monomer, and in which the adhesive layer further contains a tackifier, can effectively improve the rough surface adhesion of an adhesive containing an acrylic polymer copolymerized with 2OcA.

[0166] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above. [Explanation of symbols]

[0167] 1,2,3 Adhesive sheet 10 Supporting base material 10A front page 10B Second side (back) 21 Adhesive layer (first adhesive layer) 21A Adhesive surface (first adhesive surface) 21B Second adhesive surface 22 Adhesive layer (second adhesive layer) 22A Adhesive surface (second adhesive surface) 31,32 Release liner 100,200,300 Adhesive sheet with release liner

Claims

1. A pressure-sensitive adhesive layer containing an acrylic polymer, The monomer component of the acrylic polymer is Contains more than 75% by weight of 2-octyl acrylate (m1), Contains a carboxy group-containing monomer (m2), containing 10% by weight or more of a copolymerizable monomer (m3) different from the carboxy group-containing monomer (m2), the copolymerizable monomer (m3) includes an alkyl (meth)acrylate, The alkyl(meth)acrylate as the copolymerizable monomer (m3) has the formula: CH2=C(R1)COOR2 (wherein R 1 is a hydrogen atom or a methyl group, and R 2 is a chain alkyl group having 1 to 20 carbon atoms (provided that when R 1 is a hydrogen atom, a 2-octyl group is excluded)); and the glass transition temperature of the homopolymer is less than 0°C; The pressure-sensitive adhesive layer further comprises a tackifier, a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition comprising 0.5 parts by weight or more and less than 5 parts by weight of an isocyanate-based crosslinking agent relative to 100 parts by weight of the acrylic polymer;

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the copolymerizable monomer (m3) includes at least one selected from n-butyl acrylate and 2-ethylhexyl acrylate.

3. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the tackifier comprises at least one selected from the group consisting of a rosin-based tackifier resin, a terpene-based tackifier resin, and an acrylic oligomer.

4. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the acrylic polymer has a weight average molecular weight of 400,000 or more.

5. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the polydispersity (Mw / Mn) of the acrylic polymer is 2 or more and less than 50, and the polydispersity is determined from the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic polymer.

6. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the 180-degree peel strength from a stainless steel plate is 10 N / 20 mm or more.

7. The pressure-sensitive adhesive sheet according to claim 1 or 2, which is used to fix components in an electronic device.

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