Adhesive sheet

Abstract

To provide an adhesive sheet which can have the adhesive force, the inhibition of decrease in the adhesive force due to contact with oil, and the inhibition of decrease in the adhesive force due to contact with an aqueous solvent, all at high levels.SOLUTION: Provided is an adhesive sheet having an adhesive agent layer, the layer containing an acrylic polymer and a tackifier resin. The acrylic polymer is a polymer of a monomer component containing n-heptyl acrylate. The content of the tackifier resin is more than 10 pts.wt. based on 100 pts.wt. of the acrylic polymer. The degree of swelling of the adhesive agent layer with respect to ethyl acetate is 100 or less.SELECTED DRAWING: Figure 3

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 at temperatures around room temperature and have the property of adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used in various industrial fields, such as home appliances, automobiles, various machines, and electronic devices, typically in the form of adhesive sheets containing a layer of the adhesive, for purposes such as joining components and protecting surfaces.

[0003] Some adhesive sheets are used to fix components in portable devices such as mobile phones, smartphones, and tablet computers. Since such portable devices are used while being carried, they are prone to adhesion of secretions such as sebum and fingerprints, chemicals such as cosmetics, hair styling products, moisturizing creams, and sunscreens, or oils contained in foods. In particular, portable devices using touch panels, which have become increasingly popular in recent years, are equipped with a display unit / input unit in which the display unit also functions as an input unit, and the user operates the display unit / input unit by directly touching the surface of the display unit / input unit with the fingertips, so that there are many opportunities for oil to adhere to the device through the fingertips. In addition, some so-called wearable devices are used by being worn in contact with the skin, and in such a usage form, there are many opportunities for exposure to oils such as sebum and chemicals applied to the skin. Therefore, it is desirable that adhesive sheets used in portable devices have little decrease in adhesive strength due to contact with oil. Patent documents 1 and 2 are cited as technical documents related to the suppression of decrease in adhesive strength due to contact with oil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-132911 A [Patent Document 2] JP 2017-165977 A Summary of the Invention [Problem to be solved by the invention]

[0005] With the high performance and high functionality of portable devices, there is a demand for adhesive sheets used to fix components with higher adhesive strength. In addition, due to the recent increase in hygiene awareness, there is a tendency for aqueous solvents such as water and lower alcohols to be used more frequently to keep portable devices clean, and therefore it is desirable for adhesive sheets used in portable devices to have low adhesive strength loss even when contacted with aqueous solvents. However, in the field of adhesives, there is generally a trade-off between resistance to aqueous solvents and resistance to oil. Therefore, it is not easy to realize an adhesive sheet that has high adhesive strength and low adhesive strength loss even when contacted with both oil and aqueous solvents.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide an adhesive sheet that can achieve a high level of adhesive strength, inhibition of a decrease in adhesive strength due to contact with oil, and inhibition of a decrease in adhesive strength due to contact with an aqueous solvent. [Means for solving the problem]

[0007] According to this specification, a pressure-sensitive adhesive sheet is provided having a pressure-sensitive adhesive layer containing an acrylic polymer and a tackifier resin. The acrylic polymer is a polymer of a monomer component containing n-heptyl acrylate. The content of the tackifier resin in the pressure-sensitive adhesive layer is more than 10 parts by weight relative to 100 parts by weight of the acrylic polymer. The pressure-sensitive adhesive layer has a swelling degree of 100 or less with respect to ethyl acetate. By using an acrylic polymer containing n-heptyl acrylate as a monomer component and setting the content of the tackifier resin to more than 10 parts by weight relative to 100 parts by weight of the acrylic polymer under the condition that the swelling degree of the pressure-sensitive adhesive layer is 100 or less, it is possible to effectively increase the adhesive strength and suppress the decrease in adhesive strength due to contact with oil. In addition, by using n-heptyl acrylate as a monomer component of the acrylic polymer, it is possible to suitably suppress the decrease in adhesive strength due to contact with an aqueous solvent. In other words, with the above configuration, it is possible to achieve a high level of both adhesive strength, inhibition of a decrease in adhesive strength due to contact with oil (oil resistance), and inhibition of a decrease in adhesive strength due to contact with aqueous solvents (aqueous solvent resistance).

[0008] In some preferred embodiments, the monomer component contains 5.0% by weight or more of a carboxy group-containing monomer. A monomer component with such a composition tends to provide a pressure-sensitive adhesive sheet with higher adhesive strength.

[0009] In some preferred embodiments, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a combination of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. By using the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent in combination, the swelling degree of the pressure-sensitive adhesive layer can be appropriately adjusted, and a pressure-sensitive adhesive sheet that achieves high levels of adhesive strength, oil resistance, and aqueous solvent resistance can be suitably realized.

[0010] In some preferred embodiments, the pressure-sensitive adhesive layer contains a phenol-based tackifier resin as the tackifier resin. By using an acrylic polymer containing n-heptyl acrylate as a monomer component in combination with a phenol-based tackifier resin, the adhesive strength can be effectively increased.

[0011] In some preferred embodiments, the adhesive layer contains a terpene phenol resin as the phenol-based tackifier resin. By including the terpene phenol resin in the adhesive layer, the adhesive strength can be effectively increased. The content of the terpene phenol resin is preferably 20 parts by weight or more per 100 parts by weight of the acrylic polymer.

[0012] In some embodiments, the adhesive composition for forming the adhesive layer containing the phenol-based tackifier resin preferably contains a combination of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. By using a combination of an acrylic polymer containing n-heptyl acrylate as a monomer component, a phenol-based tackifier resin, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, it is possible to more suitably realize an adhesive sheet that has high levels of adhesion, oil resistance, and aqueous solvent resistance.

[0013] In some embodiments, the weight average molecular weight (Mw) of the acrylic polymer is preferably more than 500,000. According to such an embodiment, it is easy to obtain a PSA sheet that achieves high levels of adhesive strength, oil resistance, and aqueous solvent resistance.

[0014] Some preferred embodiments of the pressure-sensitive adhesive sheet have a 180 degree peel strength against a stainless steel plate (adhesive strength to SUS) of 8.0 N / 10 mm or more. Pressure-sensitive adhesive sheets having such adhesive strength to SUS can exhibit high member fixing performance.

[0015] Some preferred embodiments of the pressure-sensitive adhesive sheet are configured as a double-sided pressure-sensitive adhesive sheet. The double-sided pressure-sensitive adhesive sheet is used by attaching one surface and the other surface of the pressure-sensitive adhesive sheet to the adherend, so that oil and aqueous solvents are likely to penetrate into the adhesive interface with the adherend. Therefore, it is particularly meaningful to apply the technology disclosed herein to suppress the decrease in adhesive strength caused by the oil.

[0016] In some preferred embodiments, the pressure-sensitive adhesive sheet is configured as a double-sided pressure-sensitive adhesive sheet having a resin film as a supporting substrate and the pressure-sensitive adhesive layer provided on one surface and the other surface of the supporting substrate. A double-sided pressure-sensitive adhesive sheet having such a configuration is advantageous in terms of processability into a desired shape and shape retention (e.g., suppression of overflow).

[0017] The adhesive sheet disclosed herein is suitable for fixing members in, for example, a portable device (e.g., a portable electronic device such as a smartphone) because it can achieve high levels of adhesive strength, inhibition of a decrease in adhesive strength due to contact with oil, and inhibition of a decrease in adhesive strength due to contact with an aqueous solvent. Therefore, according to this specification, a portable device using any of the adhesive sheets disclosed herein, in other words, a portable device including the adhesive sheet, is provided. [Brief description of the drawings]

[0018] [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] FIG. 1 is a front view showing a schematic diagram of an example of a portable device (portable electronic device) configured to include an adhesive sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 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.

[0020] In this specification, the term "adhesive" refers to a material that exhibits a soft solid (viscoelastic) state in the temperature range around room temperature and has the property of easily adhering to an adherend by pressure, as described above. The adhesive referred to here is generally a material having a complex tensile modulus E * (1Hz)<10 7 dyne / cm 2 The material may be a material having the properties satisfying the above (typically, a material having the above properties at 25°C).

[0021] 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 through use after mining (fossil resource-based materials) are excluded from the concept of biomass materials here. The biomass carbon ratio of the pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet, i.e., the proportion of biomass-derived carbon in the total carbon contained in the pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet, can be estimated from the carbon isotope content with mass number 14 measured in accordance with ASTM D6866.

[0022] <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 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. The adhesive sheet disclosed herein may also 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.

[0023] 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).

[0024] 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.

[0025] 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.

[0026] In the 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.

[0027] <Adhesive layer> The adhesive layer constituting the adhesive sheet disclosed herein contains an acrylic polymer and a tackifier resin. The adhesive layer is typically an adhesive layer having the acrylic polymer as a base polymer. Such an adhesive layer is also called an acrylic adhesive layer. The base polymer of the adhesive layer refers to the main component of the rubber-like polymer (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 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.

[0028] 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.

[0029] (Acrylic polymer) The acrylic polymer used in the technology disclosed herein is a polymer of a monomer component containing n-heptyl acrylate (n-HpA). The inventors have found that an acrylic polymer polymerized using a monomer component containing n-HpA (i.e., an alkyl acrylate having an n-heptyl group at the ester end) is more suitable for realizing a pressure-sensitive adhesive sheet that has high levels of adhesion, oil resistance, and aqueous solvent resistance than an acrylic polymer polymerized using a monomer component having a composition in which the n-HpA is replaced with other alkyl acrylates such as n-butyl acrylate (BA) or 2-ethylhexyl acrylate (2EHA). More specifically, it is easier to improve adhesion while suppressing swelling compared to a configuration in which n-HpA is replaced with 2EHA, and it has better resistance to aqueous solvents compared to a configuration in which n-HpA is replaced with BA. The reason for this is not particularly limited, but it is believed that the polymer containing n-HpA as a monomer unit has a low glass transition temperature, which allows the adhesive layer to adhere well to the adherend and prevents oil and aqueous solvents from penetrating into the interface between the two, and also has a relatively long linear side chain derived from n-HpA, which has good compatibility with the tackifier resin, making it easy to prevent the adhesive strength from decreasing due to contact with oil even if the content of the tackifier resin is increased, and the side chain derived from n-HpA is less lipophilic than the side chain derived from an alkyl acrylate with a larger number of carbon atoms, making it easy to suppress the degree of swelling. In addition, the side chain derived from n-HpA is less hydrophilic than the side chain derived from an alkyl acrylate with a smaller number of carbon atoms (e.g., BA), making it easy to prevent the adhesive strength from decreasing due to contact with an aqueous solvent (e.g., a mixed solvent of water and a lower alcohol).

[0030] In some embodiments, the proportion of n-HpA in the monomer components of the acrylic polymer is suitably 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 85% by weight or more, particularly preferably 90% by weight or more, may be 91% by weight or more, may be 92% by weight or more, may be 94% by weight or more, or may be 94.5% by weight or more. By increasing the amount of n-HpA used, the effect of its use tends to be more effectively manifested. In some embodiments, the proportion of n-HpA in the monomer components may be 98% by weight or more, 99% by weight or more, or may be 100% by weight. On the other hand, from the viewpoint of making it easier to suppress the swelling degree of the adhesive layer and to adjust the balance of properties, in some embodiments, the proportion of n-HpA in the monomer components is suitably 99.5% by weight or less, preferably 97% by weight or less (e.g., less than 97% by weight), more preferably 96% by weight or less, even more preferably 95% by weight or less, or may be 94% by weight or less, 93% by weight or less, or 91% by weight or less.

[0031] The acrylic polymer may be copolymerized with an alkyl (meth)acrylate other than n-HpA (hereinafter, also referred to as "any alkyl (meth)acrylate"). As the any alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used. CH 2 =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 (excluding an n-heptyl group).

[0032] Examples of the optional alkyl (meth)acrylate 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 methacrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, and isooctyl (meth)acrylate. Examples of the alkyl (meth)acrylate include 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, and eicosyl (meth)acrylate. These alkyl (meth)acrylates can be used alone or in combination of two or more. Examples of the alkyl (meth)acrylates that can be preferably used include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). These alkyl (meth)acrylates can be used alone or in combination of two or more.

[0033] In some embodiments, the proportion of any alkyl (meth)acrylate contained in the monomer component (the total proportion when two or more types are used) is preferably less than 50% by weight (e.g., 49.5% by weight or less) from the viewpoint of easily exerting the effect of using n-HpA, and is preferably less than 47% by weight, more preferably 45% by weight or less, and even more preferably 40% by weight or less, and may be 30% by weight or less, 10% by weight or less, 5% by weight or less, or 1% by weight or less. 2In the case of an optional alkyl (meth)acrylate in which R is an alkyl acrylate having 8 or more carbon atoms or an alkyl methacrylate having 7 or more carbon atoms, the proportion of the optional alkyl (meth)acrylate contained in the monomer component (the total proportion when two or more types are used) is suitably 30% by weight or less from the viewpoint of oil resistance, etc., preferably 20% by weight or less, more preferably 10% by weight or less, and may be 5% by weight or less, 1% by weight or less, or 0.5% by weight or less. 2 For any alkyl (meth)acrylate having 6 or less carbon atoms, the proportion of the above-mentioned optional alkyl (meth)acrylate contained in the monomer component (the total proportion when two or more types are used) is suitably 30% by weight or less of the monomer component from the viewpoint of resistance to aqueous solvents, preferably 20% by weight or less, more preferably 10% by weight or less, and may be 5% by weight or less, 1% by weight or less, or 0.5% by weight or less. In some embodiments, the technology disclosed herein may be preferably carried out in an embodiment in which the monomer component is substantially free of any alkyl (meth)acrylate.

[0034] In this specification, the monomer component being substantially free of monomer A (e.g., any alkyl (meth)acrylate) 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.

[0035] 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.

[0036] 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 swell excessively upon contact with oil, making the oil resistance more likely to decrease, 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).

[0037] In some preferred embodiments, biomass-derived n-heptyl acrylate (biomass n-HpA) is used as the n-heptyl acrylate. By using biomass n-HpA, the effect of the technology disclosed herein can be achieved while reducing the dependency on fossil resource-based materials. The biomass n-HpA is an ester of a biomass-derived alkanol 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 linear heptyl group is biomass-derived.

[0038] The proportion of biomass alkyl (meth)acrylate (preferably biomass n-HpA) in the monomer components of the acrylic polymer is, for example, 50% by weight or more (e.g., more than 50% by weight) in some embodiments, preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 85% by weight or more, particularly preferably 90% by weight or more, and may be 92% by weight or more, 94% by weight or more, or 96% by weight or more. The proportion of biomass alkyl (meth)acrylate (preferably biomass n-HpA) in the monomer components is less than 97% by weight, and in some embodiments, may be 95% by weight or less, 93% by weight or less, or 91% by weight or less. In some other embodiments, the proportion of biomass alkyl (meth)acrylate in the monomer components may be 90% by weight or less, 70% by weight or less, 50% by weight or less, 30% by weight or less, 10% by weight or less, or 1% by weight or less.

[0039] In some embodiments, the monomer component of the acrylic polymer preferably contains a carboxyl group-containing monomer. The carboxyl group-containing monomer can improve the adhesive strength by improving the cohesiveness based on its polarity, and can also suppress excessive swelling of the adhesive layer due to oil, thereby suppressing the decrease in adhesive strength due to contact with oil (for example, the adhesive strength maintenance rate R AIn addition, since the carboxy group can become a crosslinking point of the acrylic polymer, there is an advantage that the swelling degree of the pressure-sensitive adhesive layer can be easily adjusted.

[0040] Examples of the carboxyl group-containing monomer include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Of these, preferred carboxyl group-containing monomers include AA and MAA. AA is particularly preferred. The carboxyl group-containing monomer can be used alone or in combination of two or more.

[0041] The proportion of the carboxyl group-containing monomer in the monomer component of the acrylic polymer may be, for example, 0.5% by weight or more, 1.0% by weight or more, or 2.0% by weight or more. In some embodiments, the proportion of the carboxyl group-containing monomer in the monomer component of the acrylic polymer is suitably more than 3.0% by weight, advantageously 3.5% by weight or more, preferably 4.0% by weight or more, and more preferably 4.5% by weight or more or 5.0% by weight or more. By increasing the amount of the carboxyl group-containing monomer used, the decrease in adhesive strength due to contact with oil tends to be better suppressed, and the degree of swelling also tends to be suppressed. In some embodiments, the proportion of the carboxyl group-containing monomer in the monomer component may be more than 5.0% by weight, may be more than 5.5% by weight, may be more than 6.0% by weight, may be more than 7.0% by weight, may be more than 8.0% by weight (e.g., more than 8.0% by weight), or may be more than 9.0% by weight. In addition, the amount of the carboxyl group-containing monomer is, for example, appropriate to be 20% by weight or less of the total monomer components, and from the viewpoint of suppressing the decrease in adhesive strength due to contact with an aqueous solvent, is preferably 15% by weight or less, more preferably 12% by weight or less. In some embodiments, the amount of the carboxyl group-containing monomer may be less than 10% by weight, less than 9% by weight, less than 8% by weight, less than 6% by weight, or less than 5% by weight. By appropriately adjusting the amount of the carboxyl group-containing monomer used within the above range, adhesive strength, oil resistance, and aqueous solvent resistance can be well balanced.

[0042] The acrylic polymer may be copolymerized with a functional group-containing monomer other than the carboxy group-containing monomer. Hereinafter, the functional group-containing monomer other than the carboxy group-containing monomer is also referred to as "functional group-containing monomer B". Examples of the functional group-containing monomer B that can introduce a functional group that can be a crosslinking base point into the acrylic polymer or contribute to improving the 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 a nitrogen atom-containing ring (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl group-containing monomers, and imide group-containing monomers. The functional group-containing monomer B may be used alone or in combination of two or more. In an embodiment in which the monomer component constituting the acrylic polymer contains the functional group-containing monomer B, the monomer component may contain or may not substantially contain a carboxy group-containing monomer.

[0043] When the monomer component constituting the acrylic polymer contains the functional group-containing monomer B, the content of the functional group-containing monomer B in the monomer component is not particularly limited. From the viewpoint of appropriately exerting the effect of using the functional group-containing monomer B, the content of the functional group-containing monomer B 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 oil resistance and the aqueous solvent resistance in the monomer component containing n-HpA, the content of the functional group-containing monomer B 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 functional group-containing monomer B 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 functional group-containing monomer B.

[0044] In addition, when a hydroxyl group-containing monomer is used as the functional group-containing monomer B, the content thereof may be, for example, about 0.001% by weight or more, about 0.01% by weight or more, or about 0.02% by weight or more of the total monomer components. In addition, the content of the hydroxyl group-containing monomer is suitably about 10% by weight or less, preferably about 5% by weight or less, more preferably about 2% by weight or less, of the total monomer components. In some embodiments, the content of the hydroxyl group-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 group-containing monomer. According to the technology disclosed herein, the desired effect can be achieved without relying on a hydroxyl group-containing monomer.

[0045] In an embodiment in which the monomer component constituting the acrylic polymer contains a carboxyl group-containing monomer, the proportion of the carboxyl group-containing monomer in the total functional group-containing monomers (total functional group-containing monomers including the carboxyl group-containing monomer) contained in the monomer component is 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) in terms of effectively exerting the effect of copolymerizing the carboxyl group-containing monomer. The upper limit of the proportion of the carboxyl group-containing monomer in the total functional group-containing monomers is 100% by weight, which corresponds to an embodiment in which the functional group-containing monomer B is not used. In some embodiments, the proportion of the carboxyl group-containing monomer in the total functional group-containing monomers may be, for example, 95% by weight or less.

[0046] The monomer components constituting the acrylic polymer may contain other copolymerization components other than the functional group-containing monomers described above 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)acrylates (e.g., phenyl (meth)acrylate), aryloxyalkyl (meth)acrylates (e.g., phenoxyethyl (meth)acrylate), and arylalkyl (meth)acrylates (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.

[0047] The amount of such other copolymerization components is not particularly limited and may be appropriately selected depending on the purpose and application, but from the viewpoint of appropriately exerting the effect of use, it is appropriate to set it to 0.05 wt% or more in the monomer component, and it may be 0.5 wt% or more. Furthermore, from the viewpoint of easily achieving a good balance between oil resistance and aqueous solvent resistance in a monomer component containing n-HpA, the content of other copolymerization components in the monomer component is appropriate to be 20 wt% or less, 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.

[0048] The monomer component constituting 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. By using a polyfunctional monomer as a monomer component, the cohesive force of the adhesive layer can be increased and the degree of swelling can be suppressed. 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, neopentyl glycol di(meth)acrylate, and the like. The polyfunctional monomer may be used alone or in combination of two or more.

[0049] The lower limit of the amount of polyfunctional monomer used is not particularly limited, as long as it is greater than 0% by weight. The amount of polyfunctional monomer used can be appropriately set so that the purpose of using the polyfunctional monomer is achieved. Usually, the effect of using the polyfunctional monomer can be appropriately exhibited by setting the amount of polyfunctional monomer used to about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component. In addition, in some embodiments, the amount of polyfunctional monomer used is appropriately about 3% by weight or less of the monomer component from the viewpoint of easily obtaining good adhesive strength, 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). The monomer component constituting the acrylic polymer may be substantially composed of a monofunctional monomer. That is, the monomer component may not contain a polyfunctional monomer.

[0050] 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.

[0051] 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).

[0052] 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.

[0053] 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.

[0054] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and may be, for example, approximately 300,000 or more and 5 million or less. The Mw of the acrylic polymer is usually preferably more than 500,000 (e.g., 550,000 or more), and more preferably more than 600,000 or more (e.g., 650,000 or more). With an acrylic polymer having such Mw, it is easy to obtain a PSA sheet that has high levels of adhesive strength, oil resistance, and aqueous solvent resistance. In some embodiments, the Mw of the acrylic polymer may be 700,000 or more, 800,000 or more, 900,000 or more or more, 950,000 or more, 1 million or more or more, 1.05 million or more or more, 1.15 million or more, 1.2 million or more, or more than 1.2 million. In addition, from the viewpoints of ease of synthesis of the acrylic polymer, ease of preparation of the pressure-sensitive adhesive composition, coatability, etc., it is appropriate that the Mw of the acrylic polymer is usually about 3 million or less (for example, 2.5 million or less). From the viewpoint of increasing the adhesion between the pressure-sensitive adhesive layer and the adherend and easily suppressing the penetration of oil or aqueous solvent into the interface between them, in some embodiments, the Mw of the acrylic polymer is preferably 2 million or less, more preferably 1.8 million or less, may be 1.6 million or less, may be 1.5 million or less, may be 1.4 million or less, may be 1.3 million or less, may be 1.2 million or less or less than 1.2 million, may be 1.1 million or less, may be 1 million or less, may be 900,000 or less or less than 900,000, may be 850,000 or less, or may be 750,000 or less.

[0055] The Mw of the acrylic polymer can be measured by gel permeation chromatography (GPC) and calculated as a standard polystyrene equivalent. Specifically, it can be measured under the following conditions using a GPC measuring device (trade name: "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

[0056] (tackifier resin) The adhesive layer disclosed herein contains more than 10 parts by weight of a tackifier resin relative to 100 parts by weight of the above-mentioned acrylic polymer, which is a polymer of a monomer component containing n-HpA. By containing such an amount of tackifier resin, the adhesive strength can be effectively improved. The content of the tackifier resin relative to 100 parts by weight of the acrylic polymer may be, for example, 12 parts by weight or more, 15 parts by weight or more, or 18 parts by weight or more. In some embodiments, from the viewpoint of obtaining a higher use effect, the content of the tackifier resin relative to 100 parts by weight of the acrylic polymer is suitably 18.5 parts by weight or more, preferably 20 parts by weight or more, may be 25 parts by weight or more, or may be 30 parts by weight or more. Since the acrylic polymer containing n-HpA as a monomer unit has good compatibility with the tackifier resin, the adhesive strength can be improved by containing more of the tackifier resin while maintaining a cohesive force suitable for suppressing the decrease in oil resistance and aqueous solvent resistance. The content of the tackifier resin relative to 100 parts by weight of the acrylic polymer may be, for example, 100 parts by weight or less or 90 parts by weight or less. From the viewpoint of better suppressing a decrease in adhesive strength due to contact with oil, it is appropriate to make it 80 parts by weight or less, preferably 60 parts by weight or less (for example, 55 parts by weight or less), more preferably 50 parts by weight or less, or it may be 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less.

[0057] The tackifier resin is not particularly limited, and for example, various tackifier resins such as phenol-based tackifier resins, rosin-based tackifier resins, terpene-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, ketone-based tackifier resins, etc. Such tackifier resins may be used alone or in combination of two or more.

[0058] Examples of phenol-based tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, and rosin phenol resins. 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. Alkylphenol resins are resins (oil-based phenolic resins) obtained from alkylphenols and formaldehyde. Examples of alkylphenol resins include novolac and resol types. Rosin phenolic resins are typically phenol-modified products of rosins or various rosin derivatives (including rosin esters, unsaturated fatty acid modified rosins, and unsaturated fatty acid modified rosin esters). Examples of rosin phenolic resins include rosin phenolic resins obtained by adding phenol to rosins or the various rosin derivatives described above using an acid catalyst and then thermally polymerizing the resulting mixture. Of these phenol-based tackifying resins, terpene phenol resins, hydrogenated terpene phenol resins and alkylphenol resins are preferred, terpene phenol resins and hydrogenated terpene phenol resins are more preferred, and terpene phenol resins are particularly preferred.

[0059] 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 derivatives 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; and the like. Among these, rosin esters are preferred. 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 ester, triethylene glycol ester, glycerin ester, pentaerythritol ester, etc.

[0060] Examples of terpene-based tackifier resins include polymers of terpenes (e.g., monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. The polymers may be homopolymers of one type of terpene, or copolymers of two or more types of terpenes. Examples of homopolymers of one type of terpene include α-pinene polymers, β-pinene polymers, and dipentene polymers.

[0061] 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.

[0062] In some embodiments, it is preferable to use a phenol-based tackifier resin as the tackifier resin. By using a phenol-based tackifier resin, the adhesive strength can be preferably improved while suppressing an increase in the degree of swelling. Among them, a terpene phenol resin is preferable. As the tackifier resin, only one or more phenol-based tackifier resins may be used, or a phenol-based tackifier resin may be used in combination with another tackifier resin (e.g., a rosin-based tackifier resin). The proportion of the phenol-based tackifier resin (e.g., a terpene phenol resin) in the total tackifier resin contained in the adhesive layer can be, for example, about 35% by weight or more, and from the viewpoint of preferably exerting the effect of using the phenol-based tackifier resin, it is preferable to make it more than about 50% by weight, may be about 70% by weight or more, or may be about 80% by weight or more. The technology disclosed herein can be preferably implemented in an embodiment in which substantially all of the tackifier resin (e.g., about 97% by weight or more, or 99% by weight or more, or may be 100% by weight) is a phenol-based tackifier resin.

[0063] In an embodiment using a terpene phenol resin as a tackifier resin, the content of the terpene phenol resin may be, for example, 1 part by weight or more, 3 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 9 parts by weight or more, 12 parts by weight or more, 15 parts by weight or more, or 18 parts by weight or more, relative to 100 parts by weight of an acrylic polymer. In some embodiments, from the viewpoint of obtaining a higher usage effect, the content of the terpene phenol resin relative to 100 parts by weight of an acrylic polymer is suitably 18.5 parts by weight or more, preferably 20 parts by weight or more, and may be 25 parts by weight or more. In some embodiments, the content of the terpene phenol resin relative to 100 parts by weight of an acrylic polymer is suitably 80 parts by weight or less, preferably 60 parts by weight or less (for example, 55 parts by weight or less), more preferably 50 parts by weight or less, may be 45 parts by weight or less, may be 40 parts by weight or less, may be 35 parts by weight or less, may be 30 parts by weight or less, or may be 25 parts by weight or less, from the viewpoint of oil resistance and the like. Here, the content of the terpene phenol resin being X parts by weight or less relative to 100 parts by weight of the acrylic polymer is used to mean both that the pressure-sensitive adhesive layer does not contain a terpene phenol resin and that the pressure-sensitive adhesive layer contains the terpene phenol resin in a proportion of X parts by weight or less relative to 100 parts by weight of the acrylic polymer. In some embodiments, the content of the terpene phenol resin in the pressure-sensitive adhesive layer may be 10 parts by weight or less, 5 parts by weight or less, 3 parts by weight or less, or 1 part by weight or less (e.g., 0 to 0.1 parts by weight) relative to 100 parts by weight of the acrylic polymer.

[0064] When a phenolic tackifier resin is used as the tackifier resin, the content of a tackifier resin other than the phenolic tackifier resin (non-phenolic tackifier resin, for example, a rosin-based tackifier resin) in the adhesive layer is suitably, for example, 40 parts by weight or less relative to 100 parts by weight of the acrylic polymer. This makes it easier to favorably exhibit the effect of including the phenolic tackifier resin. In some embodiments, the amount of the non-phenolic tackifier resin used is preferably about 20 parts by weight or less (for example, less than 20 parts by weight), more preferably about 15 parts by weight or less, and may be about 10 parts by weight or less, or about 5 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.

[0065] In some embodiments, from the viewpoint of adhesion to an adherend, a tackifier resin having a softening point of less than 150° C. is used as the tackifier resin. L Tackifying resin T is used. L The lower limit of the softening point of the tackifier resin T is not particularly limited. L From the viewpoint of exerting an appropriate cohesive force, the softening point of the tackifier resin T is suitably about 60° C. or higher, and may be, for example, about 80° C. or higher, about 90° C. or higher, or about 100° C. or higher. L As the tackifier resin, one type appropriately selected from the above-exemplified tackifier resins having a softening point of less than 150° C. can be used alone or two or more types can be used in combination.

[0066] In some embodiments, tackifier resin T L Preferably, the tackifier resin T comprises a phenol-based tackifier resin. L may contain one type of phenol-based tackifying resin alone, or may contain two or more types of phenol-based tackifying resins. Lmay contain a combination of a phenolic tackifier resin and a non-phenolic tackifier resin. The non-phenolic tackifier resin may be one selected from the tackifier resins exemplified above that are other than the phenolic tackifier resins and have a softening point of less than 150° C., either singly or in combination of two or more. In some embodiments, the tackifier resin T L The proportion of the phenol-based tackifier resin in the total can be, for example, more than about 50% by weight, may be about 65% by weight or more, or may be about 75% 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 phenol-based tackifier resin.

[0067] Tackifying resin T L Content of tackifier resin T L The amount of the tackifier resin T (the total amount when it is included) is not particularly limited, but is suitably 80 parts by weight or less relative to 100 parts by weight of the acrylic polymer, and from the viewpoint of adhesion to the adherend, etc., is preferably 60 parts by weight or less (e.g., 55 parts by weight or less), more preferably 50 parts by weight or less, may be 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, or may be 25 parts by weight or less. In addition, the amount of the tackifier resin T relative to 100 parts by weight of the acrylic polymer is not particularly limited, but is suitably 80 parts by weight or less relative to 100 parts by weight of the acrylic polymer, and from the viewpoint of adhesion to the adherend, etc., is preferably 60 parts by weight or less (e.g., 55 parts by weight or less), more preferably 50 parts by weight or less, L The amount of the tackifier resin T used may be, for example, 5 parts by weight or more, 7 parts by weight or more, 9 parts by weight or more, 12 parts by weight or more, 15 parts by weight or more, or 18 parts by weight or more. In some embodiments, from the viewpoint of improving adhesive strength, the amount of the tackifier resin T used may be, for example, 5 parts by weight or more, 7 parts by weight or more, 9 parts by weight or more, 12 parts by weight or more, 15 parts by weight or more, or 18 parts by weight or more. L The amount of is suitably, for example, 18.5 parts by weight or more, preferably 20 parts by weight or more, and may be 25 parts by weight or more.

[0068] In some embodiments, the adhesive layer comprises a tackifier resin T L and tackifier resin T having a softening point of 150°C or higher (e.g., 150°C to 200°C). HThe 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.

[0069] 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.

[0070] 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 LFrom 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.

[0071] In some embodiments, the tackifier resin may include a tackifier resin having a hydroxyl value of 40 mgKOH / g or more (e.g., more than 40 mgKOH / g, preferably 45 mgKOH / g or more, more preferably 50 mgKOH / g or more). Hereinafter, a tackifier resin having such a hydroxyl value may be referred to as a "high hydroxyl value resin". Since an acrylic polymer containing n-HpA as a monomer unit has good compatibility with such a high hydroxyl value resin, such a high hydroxyl value resin can be used to increase adhesion while achieving a good balance between oil resistance and aqueous solvent resistance. In some embodiments, the hydroxyl value of the high hydroxyl value resin may be 60 mgKOH / g or more, 80 mgKOH / g or more, 90 mgKOH / g or more, or 100 mgKOH / g or more. The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited, and may be, for example, about 200 mgKOH / g or less, about 160 mgKOH / g or less, or about 140 mgKOH / g or less. In some embodiments, from the viewpoint of adhesion to the adherend, the hydroxyl value of the high hydroxyl value resin is preferably about 125 mgKOH / g or less, may be about 115 mgKOH / g or less, or may be about 90 mgKOH / g or less.

[0072] The high hydroxyl value resin may be one selected from the tackifier resins exemplified above that have a hydroxyl value corresponding to the high hydroxyl value resin, either alone or in combination of two or more. In some embodiments, the high hydroxyl value resin preferably comprises a phenolic tackifier resin (e.g., a terpene phenolic resin). The high hydroxyl value resin may comprise one phenolic tackifier resin alone, or may comprise two or more phenolic tackifier resins in combination. The high hydroxyl value resin may be the tackifier resin T described above. L The tackifier resin T H In some embodiments, the tackifier resin T L A high hydroxyl value resin having the following structure can be preferably used. L By using a high hydroxyl value resin, it is possible to suppress the deterioration of oil resistance and aqueous solvent resistance, while allowing a larger amount of tackifier resin to be contained, thereby improving adhesive strength.

[0073] Although not particularly limited, when a high hydroxyl value resin (e.g., a high hydroxyl value resin having a hydroxyl value of more than 40 mgKOH / g, preferably 45 mgKOH / g or more, more preferably 50 mgKOH / g or more) is used, the amount used (when two or more types of high hydroxyl value resins are included, the total amount thereof) can be, for example, 5 parts by weight or more relative to 100 parts by weight of the acrylic polymer, and from the viewpoint of obtaining a higher effect, it is preferably 10 parts by weight or more (e.g., more than 10 parts by weight), more preferably 12 parts by weight or more, may be 15 parts by weight or more, 18 parts by weight or more (e.g., 18.5 parts by weight or more), may be 20 parts by weight or more, or may be 25 parts by weight or more. In addition, from the viewpoint of suppressing the degree of swelling and oil resistance, in some embodiments, the amount of high hydroxyl value resin used per 100 parts by weight of the acrylic polymer is suitably 80 parts by weight or less, preferably 60 parts by weight or less (e.g., 55 parts by weight or less), more preferably 50 parts by weight or less, alternatively 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less.

[0074] In some embodiments, the high hydroxyl value resin (e.g., a high hydroxyl value resin having a hydroxyl value of more than 40 mgKOH / g, preferably 45 mgKOH / g or more, more preferably 50 mgKOH / g or more) preferably accounts for more than 30% by weight, more preferably more than 50% by weight, of the total amount of tackifier resin contained in the pressure-sensitive adhesive layer. This can preferably achieve the effect of enhancing adhesive strength while achieving a good balance between oil resistance and aqueous solvent resistance. In some embodiments, the proportion of the high hydroxyl value resin in the total amount of tackifier resin contained 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, particularly preferably 90% by weight or more, and may be 95% by weight or more, or may be 98% by weight or more, from the viewpoint of making it easier to exhibit the effect of using the high hydroxyl value resin. In some preferred embodiments, the tackifier resin contained in the pressure-sensitive adhesive layer is substantially composed of only the high hydroxyl value resin. In such an embodiment, the proportion of the high hydroxyl value resin in the total amount of tackifier resins contained in the pressure-sensitive adhesive layer is in the range of 99 to 100% by weight.

[0075] In some embodiments, the tackifier resin may include a tackifier resin having a hydroxyl value of less than 40 mgKOH / g (e.g., less than 30 mgKOH / g). Hereinafter, a tackifier resin having such a hydroxyl value may be referred to as a "low hydroxyl value resin". The hydroxyl value of the low hydroxyl value resin may be about 20 mgKOH / g or less, about 15 mgKOH / g or less, or about 10 mgKOH / g or less. The lower limit of the hydroxyl value of the low hydroxyl value resin is not particularly limited, and may be substantially 0 mgKOH / g. The low hydroxyl value resin is preferably used in combination with a high hydroxyl value resin, which may be useful for adjusting adhesive properties, etc. Alternatively, the technology disclosed herein may be implemented in an embodiment in which only a low hydroxyl value resin is used as a tackifier resin.

[0076] The low hydroxyl value resin may be one selected from the tackifier resins exemplified above that have a hydroxyl value corresponding to the low hydroxyl value resin, either alone or in combination of two or more. In some embodiments, the low hydroxyl value resin preferably includes a rosin-based tackifier resin. The example hydroxyl value resin may include one rosin-based tackifier resin alone, or may include two or more rosin-based tackifier resins in combination. The low hydroxyl value resin may also include the above-mentioned tackifier resin T. L The tackifier resin T H In some embodiments, the tackifier resin T L A low hydroxyl value resin having the above formula (I) can be preferably used.

[0077] Although not particularly limited, the amount of low hydroxyl value resin used (the total amount when two or more low hydroxyl value resins are included) may be, for example, 1 part by weight or more, 3 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, or 9 parts by weight or more relative to 100 parts by weight of acrylic polymer. In addition, the amount of low hydroxyl value resin used relative to 100 parts by weight of acrylic polymer is usually 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 4 parts by weight or less, or 2 parts by weight or less. It is not necessary to use a low hydroxyl value resin.

[0078] 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.

[0079] As the tackifier resin contained in the adhesive layer disclosed herein, from the viewpoint of improving the biomass carbon ratio of the adhesive layer, a tackifier resin derived from a plant (vegetable tackifier resin) may preferably act. Examples of the vegetable tackifier resin 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. The proportion of the vegetable tackifier resin in the total amount of tackifier resin 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 resin 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 the vegetable tackifier resin.

[0080] In the technology disclosed herein, the total content of the acrylic polymer and the tackifier resin 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 order to achieve the effects of the technology disclosed herein, the total amount (total amount) of the acrylic polymer and the tackifier resin contained in the adhesive layer according to some preferred embodiments is more than 50% by weight, preferably about 70% by weight or more, more preferably about 90% by weight or more, and 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 97% by weight or more.

[0081] (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 epoxy-based crosslinking agents, isocyanate-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 agent may be used alone or in combination of two or more. Among these, epoxy-based crosslinking agents, isocyanate-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and melamine-based crosslinking agents are preferred, and epoxy-based crosslinking agents and isocyanate-based crosslinking agents are more preferred. By appropriately selecting and using a crosslinking agent, it is possible to preferably achieve a degree of aggregation of 100 or less. 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 partially crosslinked, 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.

[0082] 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.

[0083] Non-limiting 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, etc. Commercially available epoxy crosslinking agents include Mitsubishi Gas Chemical Company's product names "TETRAD-C" and "TETRAD-X," DIC Corporation's product name "Epicron CR-5L," Nagase ChemteX Corporation's product name "Denacol EX-512," Nissan Chemical Industries' product name "TEPIC-G," etc.

[0084] 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 suitably about 0.005 parts by weight or more relative to 100 parts by weight of the acrylic polymer, preferably about 0.01 parts by weight or more (for example, more than 0.01 parts by weight or 0.015 parts by weight or more), and more preferably about 0.02 parts by weight or more (for example, more than 0.02 parts by weight or 0.025 parts by weight or more). Furthermore, from the viewpoint of improving adhesion to the adherend, the amount of the epoxy-based crosslinking agent used is suitably about 0.5 parts by weight or less per 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 (e.g., less than 0.1 parts by weight), may be 0.07 parts by weight or less, may be 0.05 parts by weight or less, may be 0.04 parts by weight or less (e.g., less than 0.04 parts by weight), may be less than 0.035 parts by weight, or may be 0.03 parts by weight or less.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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. Commercially available examples of such polyfunctional isocyanates include those manufactured by Asahi Kasei Chemicals Corporation under the trade names "Duranate TPA-100," and those manufactured by Tosoh Corporation under the trade names "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096."

[0090] The amount of the isocyanate crosslinking agent used is not particularly limited, and 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 compatibility between adhesion, oil resistance, and aqueous solvent resistance, the amount of the isocyanate crosslinking agent used relative to 100 parts by weight of the acrylic polymer can be, for example, 0.5 parts by weight or more, and it is appropriate to make it 1.0 parts by weight or more, and it is advantageous to make it 1.5 parts by weight or more, and it is preferably 2.0 parts by weight or more, more preferably more than 2.5 parts by weight, and it may be 2.8 parts by weight or more, 3.0 parts by weight or more, or it may be 3.5 parts by weight or more. In addition, the amount of the isocyanate crosslinking agent used is appropriate to be 10 parts by weight or less relative to 100 parts by weight of the acrylic, and it is preferably less than 8.0 parts by weight, more preferably less than 7.0 parts by weight, and even more preferably less than 6.0 parts by weight, and it may be less than 5.0 parts by weight or less than 4.5 parts by weight.

[0091] In some preferred embodiments, the crosslinking agent is a combination of an epoxy-based crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from that of the epoxy-based crosslinking agent. According to the technology disclosed herein, by using a crosslinking agent other than an epoxy-based crosslinking agent (i.e., a crosslinking agent having a different type of crosslinkable reactive group from that of an epoxy-based crosslinking agent; hereinafter also referred to as a "non-epoxy-based crosslinking agent") in combination with an epoxy-based crosslinking agent, it is possible to suitably achieve both adhesive strength to different materials and high retention strength.

[0092] The type of non-epoxy crosslinking agent that can be used in combination with the epoxy crosslinking agent is not particularly limited, and can be appropriately selected from the above-mentioned crosslinking agents. The non-epoxy crosslinking agent can be used alone or in combination of two or more.

[0093] In some preferred embodiments, an isocyanate-based crosslinking agent can be used as the non-epoxy crosslinking agent. For example, by using an epoxy crosslinking agent and an isocyanate crosslinking agent in combination, better adhesive properties can be realized. The relationship between the content of the epoxy crosslinking agent and the content of the non-epoxy crosslinking agent (preferably an isocyanate crosslinking agent) is not particularly limited. The content of the epoxy crosslinking agent can be, for example, about 1 / 10 or less of the content of the non-epoxy crosslinking agent (preferably an isocyanate crosslinking agent). From the viewpoint of more suitably achieving both adhesion to the adherend and cohesive strength, the content of the epoxy crosslinking agent is suitably about 1 / 30 or less of the content of the non-epoxy crosslinking agent, preferably about 1 / 50 or less (for example, about 1 / 60 or less), more preferably about 1 / 75 or less, and may be about 1 / 90 or less. Furthermore, from the viewpoint of optimally exerting the effect of using an epoxy-based crosslinking agent in combination with a non-epoxy-based crosslinking agent (preferably an isocyanate-based crosslinking agent), the content of the epoxy-based crosslinking agent is usually about 1 / 1000 or more of the content of the non-epoxy-based crosslinking agent, for example, about 1 / 500 or more, preferably about 1 / 300 or more, more preferably 1 / 180 or more (for example, 1 / 150 or more), and even more preferably 1 / 120 or more.

[0094] The total amount of the crosslinking agent used is not particularly limited, and can be selected, for example, from a range of about 0.005 parts by weight or more (e.g., 0.01 parts by weight or more, typically 0.1 parts by weight or more) to about 10 parts by weight or less (e.g., about 8 parts by weight or less, preferably about 5 parts by weight or less) relative to 100 parts by weight of the acrylic polymer.

[0095] (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, 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.

[0096] (Swelling degree) The pressure-sensitive adhesive layer in the technology disclosed herein has a swelling degree with respect to ethyl acetate of 100 or less. By using an acrylic polymer containing n-HpA as a monomer component and setting the content of the tackifier resin to more than 10 parts by weight per 100 parts by weight of the acrylic polymer under the condition that the swelling degree is 100 or less, the adhesive strength can be effectively increased and the decrease in adhesive strength due to contact with oil or aqueous solvent can be suppressed. This makes it possible to realize a pressure-sensitive adhesive sheet that achieves high levels of adhesive strength, oil resistance, and aqueous solvent resistance. In some embodiments, the swelling degree of the pressure-sensitive adhesive layer is preferably 90 or less, more preferably 80 or less, from the viewpoint of improving oil resistance, and may be 75 or less, 70 or less, 65 or less, or 60 or less (for example, less than 60). The lower limit of the swelling degree is not particularly limited and may be, for example, 10 or more. From the viewpoint of adhesion to the adherend, in some embodiments, the swelling degree of the pressure-sensitive adhesive layer is suitably 30 or more, preferably 35 or more, more preferably 40 or more, may be 45 or more (e.g., more than 45), or may be 50 or more. By appropriately adjusting the swelling degree of the pressure-sensitive adhesive layer within the above range, the swelling degree of the pressure-sensitive adhesive layer is measured by the method described in the Examples below. The swelling degree can be adjusted by the pressure-sensitive adhesive composition such as the monomer composition and Mw of the acrylic polymer, the tackifier resin, and the crosslinking agent.

[0097] (Formation of adhesive layer) 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.

[0098] 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.

[0099] 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.

[0100] 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 μm to 500 μm, can be adopted depending on the application, purpose of use, etc. In some embodiments, from the viewpoint of avoiding an excessively thick adhesive sheet, the thickness of the adhesive layer is suitably about 100 μm or less, preferably about 70 μm or less, more preferably about 50 μm or less, and even more preferably about 35 μm or less. In the adhesive sheet according to some preferred embodiments, the thickness of the adhesive layer may be about 30 μm or less (e.g., less than 30 μm), about 25 μm or less (e.g., less than 25 μm), about 22 μm or less, or about 20 μm or less (e.g., less than 20 μm). An adhesive layer with a limited thickness can well meet the demand for a thinner and lighter adhesive. Generally, when the thickness of the adhesive layer is small, the adhesive strength tends to decrease, and the adhesion to the adherend tends to decrease, and the penetration of oil and aqueous solvents into the interface tends to progress. However, according to the technology disclosed herein, it is possible to realize an adhesive sheet that has a limited thickness of the adhesive layer and has high levels of adhesive strength, oil resistance, and aqueous solvent resistance. From the viewpoint of adhesion to the adherend, the lower limit of the thickness of the adhesive layer is, in some embodiments, about 0.5 μm or more, may be about 1 μm or more, and is advantageously about 3 μm or more, preferably about 7 μm or more, more preferably about 10 μm or more, and even more preferably about 12 μm or more (e.g., more than 12 μm), may be about 15 μm or more, or may be about 18 μm or more. The thicker the adhesive layer, the easier it is to achieve the target adhesive strength. In some embodiments, the thickness of the adhesive layer may be more than 20 μm, may be 24 μm or more, or may be 27 μm or more.

[0101] The pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers of the above thickness on both sides of a substrate. In a substrate-attached double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on each side of the substrate, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may have the same thickness or may have different thicknesses.

[0102] (surface free energy γ) In some embodiments, the surface free energy γ of the pressure-sensitive adhesive layer is 40 mJ / m 2 The surface free energy γ of the pressure-sensitive adhesive layer is preferably less than γ d +γ p +γ h ; where γ in the above formula is d , γ p and γ h represent the dispersion component, polar component, and hydrogen bond component of the surface free energy, respectively. The surface free energy γ of the adhesive layer can be determined from the contact angle of each probe liquid using water, diiodomethane, and 1-bromonaphthalene as the probe liquid according to the Kitazaki-Hata method (Japan Adhesion Association Journal, Vol. 8, No. 3, 1972, pp. 131-141). The contact angle can be measured using a commercially available contact angle meter. As the contact angle meter, a product name "CA-X" manufactured by Kyowa Interface Science Co., Ltd. can be used. The measurement is performed using a droplet method, and the contact angle is measured from the shape of the droplet 1500 ms after the droplet is attached. The same method is also used in the examples described below.

[0103] When the surface free energy γ of the pressure-sensitive adhesive layer is low, the wettability of the pressure-sensitive adhesive layer to the adherend is improved, and the adhesion of the interface (adhesive interface) between the pressure-sensitive adhesive layer and the adherend tends to be high. By increasing the adhesion of the adhesive interface in this way, it is possible to suppress the infiltration of oil or aqueous solvent from the outer edge of the pressure-sensitive adhesive sheet into the adhesive interface. Therefore, increasing the adhesion of the interface between the pressure-sensitive adhesive layer and the adherend is preferable from the viewpoint of suppressing the decrease in adhesive strength due to contact with oil or aqueous solvent. Increasing the adhesion of the interface between the pressure-sensitive adhesive layer and the adherend is preferable from the viewpoint of suppressing the decrease in adhesive strength due to contact with oil or aqueous solvent.

[0104] From the viewpoint of facilitating obtaining higher adhesion, in some embodiments, the surface free energy γ of the pressure-sensitive adhesive layer is preferably about 35 mJ / m 2 Less than or equal to 30 mJ / m 2 Less than 27 mJ / m 2 may be less than 25 mJ / m2 may be less than 20 mJ / m 2 The lower limit of the surface free energy γ of the pressure-sensitive adhesive layer is not particularly limited, but is usually about 7 mJ / m 2 More than 10 mJ / m 2 In some embodiments, the surface free energy γ of the pressure-sensitive adhesive layer is 15 mJ / m 2 or more, 20 mJ / m 2 The surface free energy γ of the pressure-sensitive adhesive layer can be adjusted, for example, by the composition of the monomer components constituting the acrylic polymer, the type and amount of the tackifier resin used, and the like.

[0105] (Gel fraction) The gel fraction of the pressure-sensitive adhesive layer disclosed herein is not particularly limited, and may be, for example, within the range of 20% to 80% (by weight). By increasing the gel fraction of the pressure-sensitive adhesive layer within an appropriate range, the pressure-sensitive adhesive layer is given cohesiveness, and a decrease in adhesive strength due to contact with oil or an aqueous solvent can be suppressed. In some embodiments, the gel fraction of the pressure-sensitive adhesive layer is suitably more than 30%, advantageously more than 40%, may be more than 45%, may be more than 50%, may be 55% or more, may be 60% or more, and may be, for example, more than 63%. In addition, from the viewpoint of adhesion to an adherend, in some embodiments, the gel fraction of the pressure-sensitive adhesive layer is preferably 75% or less, more preferably 70% or less (for example, less than 70%), may be 68% or less, and may be 66% by weight or less.

[0106] The gel fraction is measured by the following method. 1 ) was applied to a porous polytetrafluoroethylene membrane (weight Wg 2 ) into a pouch shape, and the opening is closed with a string (weight Wg 3The porous polytetrafluoroethylene (PTFE) membrane is available from Nitto Denko Corporation under the trade name "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or an equivalent product. The package is immersed in 50 mL of ethyl acetate and kept at room temperature (about 23° C.) for 7 days, after which the package is taken out and the ethyl acetate adhering to the outer surface is wiped off. The package is then dried at 130° C. for 2 hours, and the weight (Wg 4 The gel fraction of the pressure-sensitive adhesive layer is determined by substituting each value into the following formula. Gel fraction (%) = [(Wg 4 -Wg 2 -Wg 3 ) / Wg 1 ] x 100

[0107] (Biomass carbon ratio) In some embodiments, the pressure-sensitive adhesive layer contains a biomass-derived material, and the biomass carbon ratio thereof 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 from the viewpoint of material availability, it may be 95% or less, or 90% or less. From the viewpoint of easily exerting good adhesive performance, in some embodiments, the biomass carbon ratio of the pressure-sensitive adhesive layer may be, for example, 90% or less, 85% or less, or 80% or less.

[0108] <Base material> In an embodiment in which the pressure-sensitive adhesive sheet disclosed herein is in the form of a single-sided or double-sided pressure-sensitive adhesive sheet with a substrate, the substrate supporting (backing) the pressure-sensitive adhesive layer may be a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or a composite of these. Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane, and the like. Examples of paper include Japanese paper, craft paper, glassine paper, wood-free paper, synthetic paper, and top-coated paper. Examples of cloth include woven fabrics and nonwoven fabrics made by spinning various fibrous materials alone or in combination. Examples of the fibrous materials include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of the foam sheet include a foamed polyolefin sheet, a foamed polyurethane sheet, a foamed polychloroprene rubber sheet, etc. Examples of the metal foil include an aluminum foil, a copper foil, etc. The substrate supporting the pressure-sensitive adhesive layer is also called the substrate layer in the pressure-sensitive adhesive sheet.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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).

[0114] 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).

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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 film layer 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. Increasing the thickness of the pressure-sensitive adhesive layer 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 suitably 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, may be about 8 μm or more, or may be about 10 μm or more. In some embodiments, the thickness of the substrate may be about 15 μm or more, or may be about 25 μm or more.

[0119] <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.

[0120] <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 preferred embodiments, the thickness of the adhesive sheet can be about 70 μm or less, and may be, for example, about 55 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, preferably about 10 μm or more, more preferably about 15 μm or more, may be about 20 μm or more, or may be about 40 μm or more. An adhesive sheet having a thickness of a predetermined value or more tends to easily obtain adhesion to an adherend and also tends to be excellent in handleability. In addition, in the case of 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.

[0121] <Characteristics of adhesive sheet> (Adhesive strength to SUS (Initial adhesive strength F 0 )) In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet preferably has a 180-degree peel strength against a stainless steel plate (adhesive strength against SUS) of 8.0 N / 10 mm or more. A pressure-sensitive adhesive sheet exhibiting such adhesive strength against SUS can exhibit good fixing performance, for example, in applications for fixing members. The adhesive strength against SUS is more preferably about 8.2 N / 10 mm or more, even more preferably 8.5 N / 10 mm or more, and may be 8.8 N / 10 mm or more, 9.0 N / 10 mm or more, 9.2 N / 10 mm or more, 9.5 N / 10 mm or more, or 9.7 N / 10 mm or more. A higher adhesive strength against SUS can be advantageous in fixing small or narrow members or fixing members in which a relatively large load may be applied to the joint due to their own weight or external force. The upper limit of the adhesive strength to SUS is not particularly limited, but may be, for example, 20N / 10mm or less, 18N / 10mm or less, or 16N / 10mm or less, taking into account other requirements (e.g., thinning of the adhesive layer, etc.). The adhesive strength to SUS is measured using a SUS plate as the adherend under conditions of 23°C, 50% RH, a pulling speed of 300mm / min, and a peel angle of 180°. The adhesive strength to SUS is a characteristic that is measured after application to the adherend without supplying oil or aqueous solvent. The post-immersion adhesive strength F described later is A ,F B In order to show the relationship between the above adhesive strength and SUS, the above adhesive strength is referred to as "initial adhesive strength F 0 " Initial adhesive strength F 0 More specifically, it is measured by the method described in the Examples below.

[0122] (Adhesive force maintenance rate R A ) In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet comprises a compound represented by the following formula: Adhesion retention rate R A [%]=(Adhesion strength F after immersion A / Initial adhesion F 0 )×100; The adhesive strength retention rate R is expressed by A It is preferable that the adhesive strength after immersion F in the above formula is 60% or more. Ais the 180-degree peel strength measured after attaching the pressure-sensitive adhesive sheet to be evaluated to a stainless steel plate and immersing it in oleic acid for two weeks under an environment of 40°C and 90% RH, and the initial adhesive strength F in the above formula is 0 is the adhesive strength to SUS mentioned above. Adhesive strength after immersion F A More specifically, the adhesive strength retention rate R is measured by the method described in the Examples section below. A is the adhesive strength after immersion F A and the initial adhesive strength F 0 It is calculated by the above formula.

[0123] In order to better suppress the decrease in adhesive strength due to contact with oil, in some embodiments, the adhesive strength retention rate R A is more preferably 63% or more (e.g., 65% or more), further preferably 67% or more (e.g., 70% or more), may be 73% or more, may be 75% or more, may be 80% or more, or may be 85% or more. A There is no particular upper limit for the adhesive strength retention rate R A is typically less than 100%, and other properties (e.g., initial adhesion F 0 From the viewpoint of compatibility with the above-mentioned adhesion strength after immersion F, in some embodiments, the adhesion strength may be, for example, 98% or less, 95% or less, 90% or less, 85% or less, or 80% or less, from the viewpoint of bonding reliability against contact with oil. A is preferably 4.8 N / 10 mm or more (e.g., 5.0 N / 10 mm or more), more preferably 5.3 N / 10 mm or more (e.g., 5.5 N / 10 mm or more), even more preferably 6.0 N / 10 mm or more, may be 6.5 N / 10 mm or more, may be 7.0 N / 10 mm or more, or may be 7.5 N / 10 mm or more. A The upper limit of is not particularly limited. In some embodiments, other properties (e.g., initial adhesion F 0 From the viewpoint of compatibility with water-based solvent resistance, the adhesive strength after immersion F Amay be, for example, 19 N / 10 mm or less, 17 N / 10 mm or less, or 15 N / 10 mm or less.

[0124] (Adhesive force maintenance rate R B ) In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet comprises a compound represented by the following formula: Adhesion retention rate R B [%]=(Adhesion strength F after immersion B / Initial adhesion F 0 )×100; The adhesive strength retention rate R is expressed by B It is preferable that the adhesive strength after immersion F in the above formula is 70% or more. B is the 180-degree peel strength measured after attaching the pressure-sensitive adhesive sheet to be evaluated to a stainless steel plate and immersing it in a 50% aqueous isopropyl alcohol solution (a mixed solvent with a volume ratio of 1:1) for two weeks in an environment of 40°C and 90% RH. The initial adhesive strength F in the above formula is 0 is the adhesive strength to SUS mentioned above. Adhesive strength after immersion F B More specifically, the adhesive strength retention rate R is measured by the method described in the Examples section below. B is the adhesive strength after immersion F B and the initial adhesive strength F 0 It is calculated by the above formula.

[0125] In order to better suppress the decrease in adhesive strength due to contact with an aqueous solvent (e.g., an aqueous solvent such as water, a lower alcohol, or a mixed solvent of water and a lower alcohol), in some embodiments, the adhesive strength retention rate R B is preferably 75% or more, more preferably 80% or more, and even more preferably 84% or more (e.g., 85% or more), and may be 87% or more, or may be 90% or more. B There is no particular upper limit for the adhesive strength retention rate R B is typically less than 100%, and other properties (e.g., initial adhesion F 0From the viewpoint of compatibility with the above properties (resistance to water and oil), in some embodiments, the adhesive strength after immersion F may be, for example, 99% or less, 98% or less, 96% or less, 95% or less, or 94% or less. B is preferably 6.0 N / 10 mm or more (e.g., 6.5 N / 10 mm or more), more preferably 7.0 N / 10 mm or more (e.g., 7.5 N / 10 mm or more), even more preferably 8.0 N / 10 mm or more, may be 8.2 N / 10 mm or more, may be 8.5 N / 10 mm or more, or may be 8.7 N / 10 mm or more. B The upper limit of is not particularly limited. In some embodiments, other properties (e.g., initial adhesion F 0 From the viewpoint of compatibility with water-based solvent resistance, the adhesive strength after immersion F B may be, for example, 19 N / 10 mm or less, 18 N / 10 mm or less, 17 N / 10 mm or less, or 15 N / 10 mm or less.

[0126] In some embodiments, the pressure-sensitive adhesive sheet contains a biomass-derived material, and the biomass carbon ratio thereof 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. In this respect, 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 material availability, it may be 95% or less, or 90% or less. From the viewpoint of easily exerting good adhesive performance, in some embodiments, the biomass carbon ratio of the pressure-sensitive adhesive sheet may be, for example, 90% or less, 85% or less, or 80% or less.

[0127] <Application> The use of the adhesive sheet disclosed herein is not particularly limited, and it can be used for various applications. The adhesive sheet disclosed herein can be preferably used for fixing various members that may come into contact with one or both of oil and aqueous solvent, taking advantage of its characteristics of being able to achieve high levels of adhesive strength, oil resistance, and aqueous solvent resistance. A representative example of such an application is the application of fixing members in various mobile devices (portable devices). For example, it is suitable for fixing members in portable electronic devices. 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-type devices (monocular and binocular types, including head-mounted types), 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. Non-limiting examples of portable devices other than portable electronic devices include mechanical wristwatches, pocket watches, flashlights, hand mirrors, commuter pass holders, etc. In this specification, "portable" does not mean that it is sufficient to simply be able to be carried around, but rather that it has a level of portability that allows an individual (average adult) to carry it relatively easily.

[0128] 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.

[0129] 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.

[0130] The matters disclosed by this specification include the following: [1] A pressure-sensitive adhesive layer including an acrylic polymer and a tackifier resin, The acrylic polymer is a polymer of a monomer component including n-heptyl acrylate, The content of the tackifier resin is more than 10 parts by weight based on 100 parts by weight of the acrylic polymer, The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a swelling degree of 100 or less in ethyl acetate. [2] The pressure-sensitive adhesive sheet according to the above-mentioned [1], wherein the monomer component contains 5.0% by weight or more of a carboxy group-containing monomer. [3] The pressure-sensitive adhesive sheet according to the above-mentioned [1] or [2], wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a combination of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. [4] The pressure-sensitive adhesive sheet according to any one of the above [1] to [3], wherein the pressure-sensitive adhesive layer contains a phenol-based tackifier resin as the tackifier resin. [5] The phenolic tackifier resin contains a terpene phenolic resin, The pressure-sensitive adhesive sheet according to [4] above, wherein the content of the terpene phenol resin is 20 parts by weight or more per 100 parts by weight of the acrylic polymer. [6] The pressure-sensitive adhesive sheet according to any one of the above [1] to [5], wherein the acrylic polymer has a weight average molecular weight of more than 500,000. [7] The pressure-sensitive adhesive sheet according to any one of the above [1] to [6], which has a 180 degree peel strength against a stainless steel plate of 8.0 N / 10 mm or more. [8] The pressure-sensitive adhesive sheet according to any one of the above [1] to [7], which is configured as a double-sided pressure-sensitive adhesive sheet. [9] The pressure-sensitive adhesive sheet according to any one of the above [1] to [8], which is configured as a double-sided pressure-sensitive adhesive sheet having a resin film as a supporting substrate, and the pressure-sensitive adhesive layer provided on one surface and the other surface of the supporting substrate.

[10] The pressure-sensitive adhesive sheet according to any one of the above [1] to [9], which is used for fixing members in a portable device.

[0131]

[11] A portable device, an adhesive sheet is bonded to a member constituting the electronic device, the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer containing an acrylic polymer and a tackifier resin, The acrylic polymer is a polymer of a monomer component including n-heptyl acrylate, The content of the tackifier resin is more than 10 parts by weight based on 100 parts by weight of the acrylic polymer, A portable device, wherein the pressure-sensitive adhesive layer has a swelling degree with respect to ethyl acetate of 100 or less.

[12] The portable device according to

[11] above, wherein the portable device is a portable electronic device.

[13] The mobile device according to the above

[11] or

[12] , wherein the monomer component of the acrylic polymer contains 5.0% by weight or more of a carboxyl group-containing monomer.

[14] The mobile device according to any one of the above

[11] to

[13] , wherein the adhesive composition for forming the adhesive layer contains a combination of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

[15] The mobile device according to any one of the above

[11] to

[14] , wherein the pressure-sensitive adhesive layer contains a phenol-based tackifier resin as the tackifier resin.

[16] The phenolic tackifier resin comprises a terpene phenolic resin, The mobile device according to

[15] above, wherein the content of the terpene phenol resin is 20 parts by weight or more per 100 parts by weight of the acrylic polymer.

[17] The mobile device according to any one of the above

[11] to

[16] , wherein the acrylic polymer has a weight average molecular weight of more than 500,000.

[18] The mobile device according to any one of the above

[11] to

[17] , wherein the pressure-sensitive adhesive sheet has a 180 degree peel strength against a stainless steel plate of 8.0 N / 10 mm or more.

[19] The mobile device according to any one of the above

[11] to

[18] , which is configured as a double-sided adhesive sheet.

[20] The mobile device according to any one of the above

[11] to

[19] , wherein the adhesive sheet is configured as a double-sided adhesive sheet having a resin film as a supporting substrate, and the adhesive layer provided on one surface and the other surface of the supporting substrate. EXAMPLES

[0132] 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.

[0133] <Evaluation method> (Initial adhesion F 0 ) In a measurement environment of 23°C and 50% RH, a 50 μm thick PET film is attached to one adhesive side of a pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) to provide a backing, and the sheet is cut to a size of 10 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 is pressed against the surface of a stainless steel plate (SUS304BA plate) that has been washed with ethyl acetate by rolling a 2 kg roller back and forth once. After leaving it in the same environment for 30 minutes, the peel strength (initial adhesive strength F) is measured using a tensile tester at a pulling speed of 150 mm / min and a peel angle of 180 degrees in accordance with JIS Z 0237:2000. 0 ) [N / 10mm].

[0134] (Oil resistance) In a measurement environment of 23°C and 50% RH, a 50 μm thick PET film is attached to one adhesive side of a pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) to provide a backing, and the sheet is cut to a size of 10 mm wide and 100 mm long to prepare a measurement sample. In an environment of 23°C and 50% RH, a 2 kg roller is rolled back and forth once to press the other adhesive surface of the measurement sample against the surface of a stainless steel plate (SUS304BA plate) that has been washed with ethyl acetate. After leaving it in the same environment for 30 minutes, it is immersed in an oleic acid bath and kept in an environment of 40°C and 90% RH for 2 weeks. Thereafter, the measurement sample is removed from the oleic acid bath, the oleic acid adhering to the periphery is lightly wiped off, and it is left in an environment of 23°C and 50% RH for 30 minutes. After that, the peel strength after immersion in oleic acid (adhesive strength after immersion F) is measured using a tensile tester in accordance with JIS Z 0237:2000 at a pulling speed of 150 mm / min and a peel angle of 180 degrees. A ) [N / 10mm]. From the measured values ​​obtained, the following formula: Adhesion retention rate R A [%]=(Adhesion strength F after immersion A / Initial adhesion F 0 )×100; This results in a high adhesive strength R A Calculate.

[0135] (Aqueous solvent resistance) Instead of immersing in an oleic acid bath, the adhesive strength F was immersed in a 50% (volume ratio) aqueous isopropyl alcohol bath. A The peel strength after immersion in an aqueous solvent (adhesive strength after immersion F B ) [N / 10mm]. From the measured values ​​obtained, the following formula: Adhesion retention rate R B [%]=(Adhesion strength F after immersion B / Initial adhesion F 0 )×100; This results in a high adhesive strength R B Calculate.

[0136] (Swelling degree) Approximately 0.1 g of adhesive sample (weight W S1 ) was applied to a porous polytetrafluoroethylene membrane (weight W S2 ) into a pouch shape, and the opening is closed with a string (weight Ws 3 ) and tie it up. As the porous polytetrafluoroethylene (PTFE) membrane, "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) available from Nitto Denko Corporation or an equivalent product is used. The package is immersed in 50 mL of ethyl acetate and kept at room temperature (about 23° C.) for 7 days. Thereafter, the package is taken out and the ethyl acetate adhering to the outer surface is wiped off, and the weight (W S4 The package is then dried at 130° C. for 2 hours, and the weight (Wg 5 The swelling degree of the pressure-sensitive adhesive layer is calculated by substituting each value into the following formula. Swelling degree = (W S4 -W S2 -W S3 ) / (W S5 -W S2 -W S3 )

[0137] <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, 96 parts of n-heptyl acrylate (n-HpA) and 4 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 (A1). The weight average molecular weight (Mw) of the acrylic polymer (A1) was 900,000. The above n-HpA is a compound synthesized using heptyl alcohol derived from biomass and having a heptyl group derived from biomass at the ester end.

[0138] (Preparation of Pressure-Sensitive Adhesive Composition) The adhesive composition according to this example was prepared by mixing and stirring 100 parts of the acrylic polymer (A1), 30 parts of tackifier resin B (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 145°C, hydroxyl value 70 to 110 mgKOH / g), 3 parts of isocyanate crosslinking agent (based on solid content; the same applies below), and 0.03 parts of epoxy crosslinking agent. As the isocyanate crosslinking agent, Tosoh Corporation's trade name "Coronate L" (75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct) was used, and Mitsubishi Gas Chemical Co., Ltd.'s trade name "TETRAD-C" (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) was used as the epoxy crosslinking agent.

[0139] (Preparation of adhesive sheet) Two 38 μm thick polyester release films (trade name "Diafoil MRF", thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) were prepared. The above-mentioned adhesive composition was applied to the release surfaces of these release films and dried at 100° C. for 2 minutes to form an adhesive layer having a thickness of 19 μm. The adhesive layers formed on the above-mentioned two release films were attached to the first and second surfaces of a 12 μm thick PET film (trade name "Lumirror", manufactured by Toray Industries, Inc.) as a substrate, respectively. The above-mentioned release film was left on the adhesive layer as it was and used to protect the surface (adhesive surface) of the adhesive layer. In this way, a 50 μm thick double-sided adhesive sheet with a substrate, both adhesive surfaces of which were protected by the above-mentioned two polyester release films, was obtained.

[0140] <Example 2> In preparing the adhesive composition of Example 1, tackifier resin A (product name "YS Polystar T115", manufactured by Yasuhara Chemical Co., Ltd., terpene phenol resin, softening point 115°C, hydroxyl value 60 mgKOH / g) was used in place of tackifier resin B. A substrate-attached double-sided adhesive sheet according to this example was produced in the same manner as in Example 1, except that the obtained adhesive composition was used.

[0141] <Examples 3 to 9> A solution of acrylic polymer (A2) was obtained in the same manner as in the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 94 parts of n-HpA and 6 parts of AA, and the concentration of the monomer components during polymerization was adjusted. The above acrylic polymer (A2) was used, and the pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1, except that the composition was changed to that shown in Table 1, and the substrate-attached double-sided pressure-sensitive adhesive sheet according to each example was produced using the pressure-sensitive adhesive composition. As the tackifier resin C shown in Table 1, Arakawa Chemical Industries Co., Ltd.'s product name "Pensel D125" (pentaerythritol ester of polymerized rosin, softening point 125°C, hydroxyl value 34 mgKOH / g) was used.

[0142] <Examples 10 to 12> A solution of acrylic polymer (A3) was obtained in the same manner as in the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 90 parts of n-HpA and 10 parts of AA, and the concentration of the monomer components during polymerization was adjusted. A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1, except that the composition was changed to that shown in Table 1, using the above acrylic polymer (A3), and a substrate-attached double-sided pressure-sensitive adhesive sheet according to each example was produced using the pressure-sensitive adhesive composition.

[0143] <Comparative Examples 1 to 2> An adhesive composition according to this example was prepared in the same manner as in Example 5, except that the amount of tackifier resin A used was 0 parts (Comparative Example 1) or 5 parts (Comparative Example 2), and a substrate-attached double-sided adhesive sheet according to this example was produced using the adhesive composition.

[0144] <Comparative Examples 3 to 4> A solution of acrylic polymer (A4) was obtained in the same manner as in the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 90 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of AA. The adhesive compositions according to each example were prepared in the same manner as in Example 1, except that the composition was changed to that shown in Table 2, using the above acrylic polymer (A4), and the substrate-attached double-sided adhesive sheets according to each example were produced using the adhesive compositions.

[0145] <Comparative Example 5> A solution of acrylic polymer (A5) was obtained in the same manner as in the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 95 parts of n-butyl acrylate (BA) and 5 parts of AA. A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1, except that the composition was changed to that shown in Table 2, using the acrylic polymer (A5). A double-sided pressure-sensitive adhesive sheet with a substrate according to this example was produced using the pressure-sensitive adhesive composition.

[0146] Tables 1 and 2 show the outline of the pressure-sensitive adhesive sheet according to each example and the evaluation results.

[0147] [Table 1]

[0148] [Table 2]

[0149] As shown in Table 1, the pressure-sensitive adhesive layers according to Examples 1 to 12 contained an acrylic polymer containing n-heptyl acrylate as a monomer component and a tackifier resin in an amount of more than 10 parts per 100 parts of the acrylic polymer, and had a degree of swelling with ethyl acetate of 100 or less. 0 , Adhesion retention rate against oil R A and the adhesive strength retention rate R B In other words, the adhesive strength, oil resistance, and aqueous solvent resistance were all at high levels. The surface free energy γ of the adhesive layer according to Examples 1 to 12 was 10 to 35 mJ / m 2 was within the range.

[0150] On the other hand, the PSA sheets of Comparative Example 1, which did not contain a tackifier resin, and Comparative Example 2, which contained a small amount of tackifier resin, had an initial adhesive strength F 0 Comparative Examples 3 and 4 are examples in which an acrylic polymer that does not contain n-heptyl acrylate and is a polymer of a monomer component mainly composed of 2EHA is used. Comparative Example 3 had a low initial adhesive strength F 0 In Comparative Example 4, in which the content of the tackifier resin was increased, the initial adhesive strength F 0 Although the degree of swelling increased, it was still well over 100, and the adhesive strength retention rate R A Comparative Example 5 is an example in which an acrylic polymer that does not contain n-heptyl acrylate and is a polymer of a monomer component mainly composed of BA is used, and the resistance to aqueous solvents was insufficient.

[0151] 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]

[0152] 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. It has an adhesive layer containing an acrylic polymer and a tackifier resin, wherein the acrylic polymer is a polymer of a monomer component containing 80% by weight or more of n-heptyl acrylate, the monomer component contains more than 3.0% by weight of a carboxy group-containing monomer, the content of the tackifier resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer, the adhesive layer contains a phenolic tackifier resin as the tackifier resin, and the content of the rosin-based tackifier resin with respect to 100 parts by weight of the acrylic polymer is 20 parts by weight or less, the adhesive composition for forming the adhesive layer contains an isocyanate-based crosslinking agent, the adhesive layer has a swelling degree with respect to ethyl acetate of 100 or less, the thickness of the adhesive layer is 35 μm or less, an adhesive sheet having a 180-degree peel strength with respect to a stainless steel plate of 8.0 N / 10 mm or more.

2. The adhesive sheet according to claim 1, wherein the monomer component contains 5.0% by weight or more of a carboxy group-containing monomer.

3. The adhesive sheet according to claim 1 or 2, wherein the adhesive composition for forming the adhesive layer contains a combination of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

4. The adhesive sheet according to claim 1 or 2, wherein the content of the non-phenolic tackifier resin with respect to 100 parts by weight of the acrylic polymer in the adhesive layer is 20 parts by weight or less.

5. contains a terpene phenol resin as the phenolic tackifier resin, The adhesive sheet according to claim 1 or 2, wherein the content of the terpene phenol resin is 20 parts by weight or more with respect to 100 parts by weight of the acrylic polymer.

6. The adhesive sheet according to claim 1 or 2, wherein the weight average molecular weight of the acrylic polymer exceeds 500,000.

7. It is configured as a double-sided adhesive sheet having a resin film as a support substrate and the adhesive layer provided on one surface and the other surface of the support substrate.

8. The adhesive sheet according to claim 1 or 2, which is used for fixing members in portable devices.

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