Adhesive sheet

Abstract

The invention provides an adhesive sheet having an adhesive layer. The pressure-sensitive adhesive layer contains an acrylic polymer that contains 2-octyl acrylate as a monomer component. In addition, the monomer component of the acrylic polymer contains more than 0 wt% and not more than 20 wt% of another alkyl (meth) acrylate different from 2-octyl acrylate. The adhesive layer further contains a tackifier.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet.

[0002] This application claims priority based on Japanese Patent Application No. 2023-014856 filed on February 2, 2023, the entire contents of which are incorporated herein by reference. Background Art

[0003] Generally, adhesives (also called pressure-sensitive adhesives, hereinafter the same) are in a soft solid (viscoelastic) state within a temperature range near room temperature, and have the property of adhering to adherends by pressure. Taking advantage of this property, adhesives are widely used in various industrial fields, from portable electronic devices such as smartphones, home appliances to automobiles, office automation (OA) equipment, and are typically in the form of adhesive sheets containing an adhesive layer for the purposes of joining components, surface protection, etc. As technical documents related to adhesive sheets, for example, Patent Documents 1 to 2 can be cited. Patent Documents 1 to 2 describe adhesives containing acrylic polymers obtained by polymerization using 2-octyl acrylate as a monomer component.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5457186

[0007] Patent Document 2: International Publication No. 2022 / 034247 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] 2-octyl acrylate synthesized using 2-octanol can be obtained from materials from biomass, and therefore is being studied as an adhesive material that can suppress dependence on fossil resource materials. For example, in Patent Document 1, an adhesive formed by an acrylic polymer synthesized from a monomer component of 95% by weight of 2-octyl acrylate and 5% by weight of acrylic acid was evaluated for adhesive properties (peel adhesive strength and shear strength) and thermal stability. However, the adhesive composed of a polymer (2-octyl acrylate-based polymer) based on 2-octyl acrylate as proposed in Patent Document 1 has a tendency that its glass transition temperature is higher and its flexibility is lower. The inventor's research results show that such an adhesive is difficult to obtain high adhesive strength due to its low flexibility, and for example, its adhesive strength to rough surfaces is insufficient.

[0010] In addition, Patent Document 2 evaluates the viscosity, shear strength, and adhesive strength of an adhesive comprising a copolymer containing 650 g of 2-octyl acrylate, 220 g of isobutyl acrylate, and 100 g of methyl acrylate. However, in the polymer proposed in Patent Document 2, in which the copolymerization of 2-octyl acrylate is restricted, the properties derived from 2-octyl acrylate are likely to be reduced. Specifically, the monomer composition described in Patent Document 2 reduces high-temperature properties (e.g., high-temperature adhesive strength).

[0011] The present inventors conducted intensive research to improve the flexibility of adhesives while enjoying the benefits of containing a polymer based on 2-octyl acrylate. As a result, they succeeded in producing an adhesive with excellent flexibility while maintaining the properties of 2-octyl acrylate, thus completing the present invention. Specifically, the present invention relates to improvements in adhesives containing acrylic polymers synthesized using 2-octyl acrylate. An object of the present invention is to provide an adhesive sheet having an adhesive layer containing an acrylic polymer copolymerized with 2-octyl acrylate, exhibiting excellent flexibility while maintaining high-temperature properties, and further improving adhesive strength.

[0012] Means used to solve problems

[0013] According to this specification, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer comprises an acrylic polymer comprising 2-octyl acrylate as a monomer component. In addition, the monomer component of the acrylic polymer comprises greater than 0 wt % and less than or equal to 20 wt % of other (meth) alkyl acrylates different from 2-octyl acrylate. The pressure-sensitive adhesive layer further comprises a tackifier. According to the above configuration, the flexibility of the pressure-sensitive adhesive comprising the acrylic polymer synthesized using 2-octyl acrylate is improved. As one of the reasons for this, it is believed that by copolymerizing other (meth) alkyl acrylates different from 2-octyl acrylate in the acrylic polymer, the side chain crystallinity of the acrylic polymer is reduced and the glass transition temperature of the pressure-sensitive adhesive is reduced, but this reason is not particularly restrictive. In addition, the copolymerization ratio of the other (meth) alkyl acrylates is limited to less than 20 wt %, so that a sufficient amount of 2-octyl acrylate can be copolymerized, and the pressure-sensitive adhesive obtained can maintain high-temperature properties. In addition, the pressure-sensitive adhesive comprises a tackifier, thereby improving the adhesive strength. In summary, the pressure-sensitive adhesive according to the above configuration can have good flexibility while maintaining high-temperature properties and can also improve the adhesive strength.

[0014] In some preferred embodiments, the above-mentioned other (meth) acrylates include those represented by the formula: CH2=C(R 1 )COOR 2 (Meth) acrylate represented by

[0015] (In the above formula, R 1 is a hydrogen atom or a methyl group, R 2 (a) is a chain alkyl group having 1 to 6 carbon atoms. By copolymerizing an alkyl (meth)acrylate having the above chemical structure, the flexibility of the adhesive can be further improved.

[0016] In some embodiments, the other alkyl (meth)acrylate includes an alkyl (meth)acrylate having a linear alkyl group. By using an alkyl (meth)acrylate having a linear alkyl group as the other alkyl (meth)acrylate, a pressure-sensitive adhesive having good flexibility can be easily obtained.

[0017] In some embodiments, the tackifier preferably comprises at least one selected from rosin-based tackifier resins, terpene-based tackifier resins, and acrylic oligomers. By using the above-mentioned tackifiers, the adhesive strength, high-temperature adhesive strength, and rough surface adhesion can be improved.

[0018] In some preferred embodiments, the tackifier includes a tackifier resin having a softening point of 100° C. or higher. By using a tackifier resin having such a softening point, it is easy to improve the high-temperature adhesive force.

[0019] In some embodiments, the adhesive composition used to form the adhesive layer includes a crosslinking agent. The use of a crosslinking agent can appropriately improve the cohesive force of the adhesive.

[0020] In some embodiments, the weight-average molecular weight (Mw) of the acrylic polymer is 400,000 or greater. Using an acrylic polymer with a high Mw makes it easier to produce an adhesive with excellent high-temperature properties. Furthermore, combining such a high-molecular-weight acrylic polymer with a tackifier achieves a satisfactory balance between excellent high-temperature properties and adhesion to rough surfaces.

[0021] In some preferred embodiments, the 180-degree peel strength of the PSA sheet to a stainless steel plate (adhesion to SUS) is 10 N / 20 mm or greater. PSA sheets having such adhesion to SUS can exhibit excellent adhesion to adherends.

[0022] The adhesive sheet disclosed herein has an adhesive that takes into account both high temperature properties and flexibility, and also has high adhesive strength. Therefore, it is sometimes used in high temperature environments. In various applications where flexibility is desired, it can be satisfactorily used as an adhesive means with good adhesive reliability. For example, it is suitable for fixing components in electronic devices including portable electronic devices such as home appliances, office automation equipment, and smartphones. Based on the above, according to this specification, an electronic device using any of the adhesive sheets disclosed herein, in other words, an electronic device containing the adhesive sheet is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a cross-sectional view schematically showing the structure of a pressure-sensitive adhesive sheet according to one embodiment.

[0024] Figure 2 This is a cross-sectional view schematically showing the structure of a pressure-sensitive adhesive sheet according to another embodiment.

[0025] Figure 3 This is a cross-sectional view schematically showing the structure of a pressure-sensitive adhesive sheet according to another embodiment.

[0026] Figure 4 This is a front view schematically showing an example of a portable electronic device including a pressure-sensitive adhesive sheet. DETAILED DESCRIPTION

[0027] Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than those specifically mentioned in this specification and required for the implementation of the present invention can be understood by those skilled in the art based on the teachings for the implementation of the invention recorded in this specification and the technical common sense at the time of application. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in this field. In addition, in the following drawings, components / parts that play the same role are sometimes marked with the same reference numerals for description, and repeated descriptions are sometimes omitted or simplified. In addition, in order to clearly illustrate the present invention, the embodiments described in the drawings are schematically illustrated and do not necessarily accurately represent the size and scale of the adhesive sheet of the present invention actually provided as a product.

[0028] In this specification, "adhesive" refers to a material that is in a soft solid (viscoelastic) state in the temperature range around room temperature as described above and has the property of being easily adhered to an adherend by pressure. The so-called adhesive herein is defined as "CADahlquist, "Adhesion: Fundamental and Practice", McLaren & Sons, (1966) p.143", which generally has a complex tensile modulus E * (1Hz)<10 7 dyne / cm 2 The material has the above properties at 25°C.

[0029] In this specification, carbon derived from biomass refers to carbon derived from biomass materials, i.e., materials derived from renewable organic resources (renewable carbon). The above-mentioned biomass materials typically refer to materials derived from biological resources (typically photosynthetic plants) that can be continuously reproduced as long as there is sunlight, water, and carbon dioxide. Therefore, materials derived from fossil resources that have been depleted due to use after mining (fossil resource materials) do not fall within the concept of biomass materials referred to herein. The biomass carbon ratio of the adhesive layer and the adhesive sheet, that is, the proportion of carbon derived from biomass in the total carbon contained in the adhesive layer and the adhesive sheet, can be estimated based on the carbon isotope content with mass number 14 measured in accordance with ASTM D6866.

[0030] <Composition of Adhesive Sheet>

[0031] The adhesive sheet disclosed herein is constituted by containing an adhesive layer. The above-mentioned adhesive sheet can be, for example, in the form of a double-sided adhesive sheet without a substrate having a first adhesive face constituted by one surface of an adhesive layer and a second adhesive face constituted by the other surface of the adhesive layer. Alternatively, the adhesive sheet disclosed herein can be in the form of an adhesive sheet with a substrate obtained by laminating the above-mentioned adhesive layer on one side or both sides of a supporting substrate. Hereinafter, the supporting substrate will sometimes be referred to as "substrate". It should be noted that the concept of the adhesive sheet mentioned herein can include articles referred to as adhesive tapes, adhesive labels, adhesive films, etc. It should be noted that the adhesive sheet disclosed herein can be in a roll shape or a sheet shape. Alternatively, it can be an adhesive sheet further processed into a form of various shapes.

[0032] The structure of a pressure-sensitive adhesive sheet according to one embodiment is schematically shown in FIG. Figure 1 The adhesive sheet 1 is formed in the form of a double-sided adhesive sheet without a substrate composed of an adhesive layer 21. The adhesive sheet 1 is used by sticking a first adhesive surface 21A composed of one surface (first surface) of the adhesive layer 21 and a second adhesive surface 21B composed of the other surface (second surface) of the adhesive layer 21 to different parts of the adherend. The parts where the adhesive surfaces 21A and 21B are stuck can be the respective parts of different components or different parts within a single component. Figure 1As shown, the adhesive sheet 1 before use (i.e., before being attached to an adherend) can 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 serves as a release surface on at least one side opposite to the adhesive layer 21. As the release liners 31 and 32, for example, a release liner formed by providing a release layer formed by a release treatment agent on one side of a sheet-like substrate (liner substrate) and forming the release surface on the single side can be preferably used. Alternatively, the release liner 32 can be omitted, and a release liner 31 having two release surfaces can be used, which is overlapped with the adhesive sheet 1 and wound into a spiral shape, thereby forming an adhesive sheet with a release liner in a form (roll form) in which the second adhesive surface 21B is in contact with the back surface of the release liner 31 and protected.

[0033] The structure of a pressure-sensitive adhesive sheet according to another embodiment is schematically shown in FIG. Figure 2 The adhesive sheet 2 is formed in the form of a single-sided adhesive sheet with a substrate, and the single-sided adhesive sheet with a substrate has: a sheet-shaped 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, it is not intended to be separated from the supporting substrate 10. Figure 2 As shown, the adhesive sheet 2 before use may be a component of an adhesive sheet 200 with a release liner, in which the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31, at least the side opposite to the adhesive layer 21 being the release surface. Alternatively, the release liner 31 may be omitted, and a support substrate 10 having a second surface 10B as the release surface may be used, and the adhesive sheet 2 may be wound so that the adhesive surface 21A contacts and is protected by the second surface (back surface) 10B of the support substrate 10 (roll form).

[0034] The structure of a pressure-sensitive adhesive sheet according to another embodiment is schematically shown in FIG. Figure 3 The adhesive sheet 3 is formed in the form of a double-sided adhesive sheet with a substrate, and the double-sided adhesive sheet with a substrate has: a sheet-shaped supporting substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, a first adhesive layer 21 fixedly provided on the first surface 10A side, and a second adhesive layer 22 fixedly provided on the second surface 10B side. Figure 3As shown, the PSA sheet 3 before use may be a component of a release-lined PSA sheet 300 in which the surface (first adhesive surface) 21A of the first PSA layer 21 and the surface (second adhesive surface) 22A of the second PSA layer 22 are protected by release liners 31 and 32. Alternatively, the release liner 32 may be omitted, and a release liner 31 having two release surfaces may be used. This may be overlapped with the PSA sheet 3 and wound into a spiral shape, thereby forming a release-lined PSA sheet in a form (roll form) in which the second adhesive surface 22A is in contact with and protected by the back surface of the release liner 31.

[0035] It should be noted that in the above-mentioned double-sided adhesive sheet with a substrate, at least one of the first adhesive layer and the second adhesive layer (e.g., the first adhesive layer) may be the adhesive layer described below, and the other adhesive layer (e.g., the second adhesive layer) may be the adhesive layer disclosed herein, or may be an adhesive layer having a different composition from the adhesive layer disclosed herein (specifically, the above-mentioned one adhesive layer, e.g., the first adhesive layer). Such another adhesive layer may be formed, for example, from a well-known or commonly used adhesive.

[0036] In addition, although not particularly limited, the technology disclosed herein can preferably be implemented in the form of a substrate-free double-sided adhesive sheet. A substrate-free double-sided adhesive sheet can be thinned to the extent that it does not have a substrate, which can contribute to the miniaturization and space-saving of products using the double-sided adhesive sheet. Furthermore, the substrate-free adhesive sheet can maximize the improvement in rough surface adhesion brought about by the adhesive layer.

[0037] <Adhesive Layer>

[0038] (Acrylic polymer)

[0039] The adhesive layer constituting the adhesive sheet disclosed herein comprises an acrylic polymer. The above-mentioned adhesive layer is typically an adhesive layer using an acrylic polymer as a base polymer. Such an adhesive layer is also referred to as an acrylic adhesive layer. It should be noted that the base polymer refers to the main component of the rubbery polymer (a polymer that demonstrates rubber elasticity in the temperature range near room temperature) contained in the adhesive layer. In addition, in this manual, in the absence of special descriptions, "main component" refers to a component having a content greater than 50% by weight. In addition, the following description of the components that may be included in the adhesive and the adhesive layer, as long as no special descriptions are given, can be applicable to the adhesive composition for forming an adhesive (layer).

[0040] In addition, in this specification, "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule will also be referred to as an "acrylic monomer". Therefore, the acrylic polymer in this specification is defined as a polymer containing monomer units derived from an acrylic monomer. It should be noted that, in this specification, "(meth)acryloyl" collectively refers to acryloyl and methacryloyl. Similarly, "(meth)acrylate" collectively refers to acrylate and methacrylate, and "(meth)acrylic acid" collectively refers to acrylic acid and methacrylic acid.

[0041] As acrylic polymers, polymers containing 2-octyl acrylate as a monomer component can be used. Acrylic polymers polymerized using 2-octyl acrylate as a monomer component tend to exhibit excellent high-temperature properties (e.g., high-temperature adhesion) and are therefore preferably used in applications subject to high temperatures. Furthermore, although not particularly limited, 2-octyl acrylate can be obtained from biomass-derived materials. Therefore, using 2-octyl acrylate can reduce dependence on fossil resource materials.

[0042] In some embodiments, 2-octyl acrylate is preferably contained as the main monomer of acrylic polymer (the component most contained in the monomer component), and the proportion of 2-octyl acrylate in the monomer component of acrylic polymer can be, for example, about 34% by weight or more, 50% by weight or more (for example, greater than 50% by weight) is appropriate, preferably 60% by weight or more, more preferably 70% by weight or more, further preferably 75% by weight or more (for example, greater than 75% by weight), can be 80% by weight or more, can be 82% by weight or more, can be 84% by weight or more, can be 85% by weight or more. By increasing the usage amount of 2-octyl acrylate, its use effect (specifically, high temperature characteristics) can be effectively demonstrated. On the other hand, from the viewpoint of making other (meth) alkyl acrylates described later copolymerize and improve the flexibility of adhesive, the ratio of 2-octyl acrylate in the monomer component is appropriate to be less than 99% by weight, can be less than 95% by weight, can be less than 92% by weight. In some preferred embodiments, the proportion of 2-octyl acrylate in the monomer component is less than 90 weight %, less than 87 weight %, less than 85 weight %, less than 80 weight % (e.g., less than 80 weight %), less than 75 weight %, less than 72 weight %, or less than 70 weight %.

[0043] In addition, the monomer component of the acrylic polymer comprises other (methyl) alkyl acrylates different from 2-octyl acrylate that are greater than 0 wt % and are less than or equal to 20 wt %.Thus, flexibility can be improved while maintaining the high temperature characteristics of the adhesive of the acrylic polymer synthesized using 2-octyl acrylate.Think that this is because, by copolymerizing the above-mentioned other (methyl) alkyl acrylates in the acrylic polymer within the above-mentioned range, while maintaining the use of the high temperature characteristics based on 2-octyl acrylate, the side chain crystallinity of the acrylic polymer is reduced, and the glass transition temperature (Tg) of the adhesive is reduced.It should be noted that the technology disclosed herein is not limited to the above-mentioned investigation.In addition, by copolymerizing the above-mentioned other (methyl) alkyl acrylates with appropriate amount, good adhesive properties can be easily obtained.

[0044] In some embodiments, from the perspective of improving the flexibility of the adhesive, the proportion of other (meth) alkyl esters of acrylic acid in the monomer components of the acrylic polymer can be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., greater than 8% by weight), or 9% by weight or more. In some preferred embodiments, the proportion of other (meth) alkyl esters of acrylic acid in the monomer components of the acrylic polymer is 10% by weight or more, 12% by weight or more, 15% by weight or more, or 18% by weight or more. By increasing the copolymerization ratio of other (meth) alkyl esters of acrylic acid, the effect of lowering the Tg of the adhesive is easily achieved, effectively improving the adhesion of rough surfaces. In addition, the effect of copolymerization of other (meth) alkyl esters of acrylic acid can be satisfactorily obtained. In addition, the upper limit of the proportion of other (meth) alkyl esters of acrylic acid in the above-mentioned monomer components is 15% by weight or less in some preferred embodiments, or 12% by weight or less. By using other (meth) alkyl esters of acrylic acid in an appropriate amount within the above range, it is possible to satisfactorily balance high temperature properties and flexibility.

[0045] As the other alkyl (meth)acrylate, any alkyl (meth)acrylate other than 2-octyl acrylate can be used without particular limitation. As the other alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used.

[0046] CH2=C(R 1 )COOR 2 (1)

[0047] Here, R in the above formula (1) 1 is a hydrogen atom or a methyl group. 2 is a chain alkyl group with 1 to 20 carbon atoms (wherein R 1(When the alkyl group is a hydrogen atom, 2-octyl is excluded.) By selecting and using an appropriate type from the alkyl (meth)acrylates having the above-mentioned chemical structures, a pressure-sensitive adhesive having good adhesive properties and improved flexibility can be preferably obtained.

[0048] Examples of the other alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These other alkyl (meth)acrylates may be used alone or in combination of two or more.

[0049] As the other alkyl (meth)acrylate, any of those having a linear alkyl group and those having a branched alkyl group can be used. From the viewpoint of flexibility, those having a linear alkyl group are preferred. From the same viewpoint, as the other alkyl (meth)acrylate, alkyl acrylate is preferably used.

[0050] In some preferred embodiments, as other (meth)acrylic acid alkyl esters, R 2 (Meth)acrylic acid alkyl ester having a chain alkyl group with 1 to 6 carbon atoms (hereinafter, such a range of carbon atoms may be represented as "C 1-6 ", sometimes the (meth)acrylate alkyl ester having an alkyl group with the above-mentioned carbon number range is referred to as "(meth)acrylate C 1-6 Alkyl esters" etc. It is believed that by using (meth) acrylic acid C 1-6 Alkyl esters are other (meth)acrylic acid alkyl esters. Due to the difference in the side chain structure of 2-octyl acrylate, the free volume between polymer molecules is increased, and the flexibility is improved. As a result, good rough surface adhesion is easily obtained. It should be noted that the technology disclosed herein is not limited to the above-mentioned investigation. As (meth)acrylic acid C 1-6Alkyl esters are preferably (meth)acrylic acid C from the viewpoint of improving flexibility. 2-6 Alkyl esters, more preferably (meth) acrylic acid C 2-4 Alkyl esters, or (meth) acrylic acid C can also be preferably used 4-6 Alkyl ester. In addition, as C 1-6 Alkyl groups may be straight chain or branched chain. From the perspective of flexibility, C 1-6 From the same viewpoint, it is preferred to use acrylic acid C 1-6 Alkyl ester. (Meth) acrylic acid C 1-6 The alkyl esters may be used alone or in combination of two or more.

[0051] In the use of (meth) acrylic acid C 1-6 In the embodiment where the alkyl ester is another (meth)acrylic acid alkyl ester, the (meth)acrylic acid C 1-6 Alkyl ester (preferably (meth) acrylic acid C 2-6 Alkyl esters, more preferably (meth) acrylic acid C 2-4 Alkyl ester or (meth) acrylic acid C 4-6 Alkyl esters, or for example (meth) acrylic acid C 1-6 The proportion of the straight-chain alkyl ester (unless otherwise specified, the same applies hereinafter) in the monomer components of the acrylic polymer is not particularly limited and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., greater than 8% by weight), or 9% by weight or more. In some preferred embodiments, the proportion is 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, or 18% by weight or more. In addition, the (meth)acrylic acid C 1-6 The upper limit of the proportion of the alkyl ester in the above monomer components is 20% by weight or less in some preferred embodiments, can be 15% by weight or less, can be 12% by weight or less. 1-6 The proportion of the alkyl ester in the other alkyl (meth)acrylates is not particularly limited. In some embodiments, it is, for example, 10% by weight or more, 30% by weight or more, preferably 50% by weight or more (e.g., greater than 50% by weight), more preferably 70% by weight or more, and even more preferably 90% by weight or more (e.g., 95% to 100% by weight).

[0052] In some preferred embodiments, n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) are used as other alkyl (meth)acrylates. BA and 2EHA can be used alone or in combination. Using BA or 2EHA as other alkyl (meth)acrylates improves the flexibility of the resulting adhesive and enhances its adhesion to rough surfaces. BA is particularly preferred.

[0053] In embodiments using BA and / or 2EHA as the other alkyl (meth)acrylate, the proportion of BA and / or 2EHA in the monomer components of the acrylic polymer is not particularly limited and can be 0.1% by weight or greater, 1% by weight or greater, 5% by weight or greater, 8% by weight or greater (e.g., greater than 8% by weight), or 9% by weight or greater. In some preferred embodiments, it is 10% by weight or greater, more preferably 12% by weight or greater, 15% by weight or greater, or 18% by weight or greater. Furthermore, in some preferred embodiments, the upper limit of the proportion of BA and / or 2EHA in the monomer components is 20% by weight or less, 15% by weight or less, or 12% by weight or less.

[0054] In some embodiments, as other alkyl (meth)acrylates, alkyl (meth)acrylates whose homopolymers have a glass transition temperature (Tg) of less than 0°C (low-Tg alkyl (meth)acrylates) can be used. For example, by copolymerizing a predetermined amount or more of the low-Tg alkyl (meth)acrylate, the adhesive's Tg can be appropriately lowered. The homopolymer Tg of the low-Tg alkyl (meth)acrylate can be -10°C or lower, or -20°C or lower. In some preferred embodiments, the homopolymer Tg of the low-Tg alkyl (meth)acrylate is approximately -30°C or lower, -35°C or lower, -40°C or lower, -45°C or lower, -50°C or lower, -55°C or lower, -60°C or lower, or -65°C or lower. Although not particularly limited, in some embodiments, as the low-Tg alkyl (meth)acrylate, an alkyl (meth)acrylate having a homopolymer Tg lower than that of 2-octyl acrylate can be preferably used. The lower limit of the homopolymer Tg of the above-mentioned low Tg alkyl (meth)acrylate is, for example, above -80°C, and above -75°C is appropriate, and may be above -70°C, may be above -65°C, or may be above -60°C. There is no particular limitation on the above-mentioned low Tg alkyl (meth)acrylate, but alkyl acrylate is preferably used. Preferred examples of the above-mentioned low Tg alkyl (meth)acrylate include, for example, BA and 2EHA. Other examples of the above-mentioned low Tg alkyl (meth)acrylate include alkyl acrylates such as hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, and isononyl acrylate. The above-mentioned low Tg alkyl (meth)acrylate can be used alone or in combination of two or more.

[0055] As the homopolymer Tg of the monomer, the value described in the known literature is used. For example, the value described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) is used. When multiple values are described in this document, the highest value is adopted.

[0056] For monomers whose homopolymer Tg is not described in the above-mentioned "Polymer Handbook", the value obtained by the following measurement method is used (refer to Japanese Patent Application Publication No. 2007-51271). Specifically, 100 parts by weight of monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent are added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, and stirred for 1 hour while circulating nitrogen. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Then, the homopolymer solution is cast on a release liner and dried to produce a test sample (sheet-shaped homopolymer) with a thickness of about 2 mm. The test sample was punched into a disc shape with a diameter of 7.9 mm and sandwiched between parallel plates. The viscoelasticity was measured using a viscoelasticity tester (manufactured by TA Instruments Japan, model name "ARES") at a temperature of -70°C to 150°C and a heating rate of 5°C / min in a shear mode while applying a shear strain at a frequency of 1 Hz. The temperature corresponding to the peak temperature of tan δ was taken as the Tg of the homopolymer.

[0057] In the method of using the above-mentioned low Tg (meth) alkyl acrylate as other (meth) alkyl acrylate, the proportion of the low Tg (meth) alkyl acrylate in the monomer component of the acrylic polymer is not particularly limited, and can be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (for example, greater than 8% by weight), or 9% by weight or more. In some preferred embodiments, the proportion of the above-mentioned low Tg (meth) alkyl acrylate in the above-mentioned monomer component is 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, or 18% by weight or more. By copolymerizing the above-mentioned low Tg (meth) alkyl acrylate in a specified amount or more, it is easy to obtain the Tg effect based on the above-mentioned low Tg (meth) alkyl acrylate. In addition, the upper limit of the proportion of the above-mentioned low Tg (meth) alkyl acrylate in the above-mentioned monomer component can be 20% by weight or less, 15% by weight or less, or 12% by weight or less in some embodiments.

[0058] In some embodiments, the monomer component may include an alkyl (meth)acrylate having a biomass-derived alkyl group at the ester terminus (hereinafter also referred to as a "biomass (meth)acrylate alkyl ester"). In recent years, environmental issues such as global warming have gradually received attention, and there is a desire to reduce the use of fossil resource materials such as petroleum. In such circumstances, there is also a demand to reduce the use of fossil resource materials in the field of adhesives. By using a biomass alkyl (meth)acrylate, it is possible to appropriately implement an acrylic adhesive that takes into account the reduction of dependence on fossil resource materials.

[0059] Biomass (meth) acrylate alkyl esters are not particularly limited, and are, for example, esters of biomass-derived alkanols and (meth) acrylic acid derived from biomass or non-biomass-derived alkanols. Examples of biomass-derived alkanols include biomass ethanol, alkanols derived from plant materials such as palm oil or palm kernel oil, coconut oil, and castor oil. When the number of carbon atoms of the biomass-derived alkanol is 3 or more, the alkanol may be straight-chain or branched. In some embodiments, as the biomass (meth) acrylate alkyl esters used in the synthesis of acrylic polymers, esters of biomass-derived alkanols and (meth) acrylic acid derived from non-biomass-derived alkanols may be used. In the biomass (meth) acrylate alkyl esters, the more carbon atoms the alkanol has, the higher the proportion of the number of carbons derived from biomass to the total number of carbons contained in the biomass (meth) acrylate alkyl esters, i.e., the biomass carbon ratio of the (meth) acrylate alkyl esters. Therefore, in the above-mentioned biomass (meth) acrylate alkyl esters, it is desirable that the carbon number of the alkyl group derived from biomass is large in order to reduce the dependence on fossil resource-based materials. On the other hand, if the carbon number of the alkyl group constituting the alkyl (meth)acrylate is too large, it tends to be difficult to achieve adhesive properties such as adhesion, and this can also be disadvantageous in terms of productivity, such as synthesis, operability, and cost. In forms using esters of biomass-derived alkanols and non-biomass-derived (meth)acrylic acid as biomass alkyl (meth)acrylates, it is desirable to use a material that strikes a balance between adhesive properties and reduced dependence on fossil resource materials (more specifically, the biomass carbon ratio of the alkyl (meth)acrylate).

[0060] In some preferred embodiments, biomass-derived 2-octyl acrylate (biomass-derived 2-octyl acrylate) is used as 2-octyl acrylate. By using biomass-derived 2-octyl acrylate, the effects of the disclosed technology can be achieved while reducing dependence on fossil resource materials. The biomass-derived 2-octyl acrylate is an ester of a biomass-derived alkanol (specifically, 2-octanol) and a biomass-derived or non-biomass-derived acrylic acid. For example, an ester of a biomass-derived alkanol and a non-biomass-derived acrylic acid can be used. In this compound, only the 2-octyl group is derived from biomass.

[0061] The proportion of biomass alkyl (meth)acrylate (e.g., biomass 2-octyl acrylate) in the monomer components of the acrylic polymer is, for example, in some embodiments, 50% by weight or more (e.g., greater than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 82% by weight or more, and can be 90% by weight or more. In some embodiments, the proportion of biomass alkyl (meth)acrylate in the monomer components can be 92% by weight or more, 94% by weight or more, or 96% by weight or more. In addition, in some embodiments, the proportion of biomass alkyl (meth)acrylate (e.g., biomass 2-octyl acrylate) in the monomer components is, for example, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less.

[0062] The acrylic polymer preferably comprises a carboxyl-containing monomer as its monomeric component. Carboxyl-containing monomers can enhance cohesive strength due to their polarity. Furthermore, when using a crosslinking agent such as an isocyanate or epoxy crosslinking agent, the carboxyl groups of the carboxyl-containing monomer can serve as crosslinking sites for the acrylic polymer. Furthermore, the use of a carboxyl-containing monomer can provide superior adhesion to adherends such as highly polar materials.

[0063] As carboxyl-containing monomers, for example, there can be listed: ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), (meth) carboxylethyl acrylate, (meth) carboxylpentyl acrylate, crotonic acid, isocrotonic acid, etc.; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid. In addition, the carboxyl-containing monomer can be a monomer of a metal salt (such as an alkali metal salt) having a carboxyl group. One or more carboxyl-containing monomers can be used alone or in combination. Among them, AA and MAA can be listed as preferred carboxyl-containing monomers. AA is particularly preferred. When using one or more carboxyl-containing monomers, the proportion of AA in the above-mentioned carboxyl-containing monomers is preferably 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% by weight or more. In a particularly preferred embodiment, the carboxyl-containing monomer substantially only contains AA.

[0064] The ratio of the carboxyl group-containing monomer in the monomer component of acrylic polymer is not particularly limited, can be more than 0.1 % by weight, can be more than 0.5 % by weight, in some preferred embodiments, the above ratio is more than 1.0 % by weight, can be more than 2.0 % by weight, can be more than 2.5 % by weight, can be more than 3.0 % by weight, can be more than 3.5 % by weight, can be more than 4.0 % by weight, can be more than 4.5 % by weight, can be more than 5.0 % by weight. By increasing the usage amount of carboxyl group-containing monomer, based on the effect of carboxyl group-containing monomer, the cohesive force of adhesive layer improves, therefore easily obtains good adhesive properties. In addition, the amount of carboxyl group-containing monomer is, for example, appropriate below 20 % by weight of total monomer components, is preferably below 15 % by weight, more preferably below 12 % by weight. In some preferred embodiments, the amount of above-mentioned carboxyl group-containing monomer can be below 10 % by weight, can be below 8.0 % by weight, can be below 6.0 % by weight, can be below 5.0 % by weight. By reducing the usage amount of carboxyl group-containing monomer within the prescribed range, there is good flexibility, easily obtains the tendency of good rough surface adhesion.

[0065] In addition, the monomer components of the acrylic polymer may contain a functional group-containing monomer (optional functional group-containing monomer) other than the carboxyl group-containing monomer. Optional functional group-containing monomers that can introduce functional groups that can serve as crosslinking points into acrylic polymers or contribute to improving adhesive strength include hydroxyl (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; and polypropylene glycol mono(meth)acrylate), 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, ketone 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 optional functional group-containing monomers may be used alone or in combination of two or more.

[0066] When the monomer composition constituting acrylic polymer comprises the above-mentioned optional monomer containing functional groups, the content of the optional monomer containing functional groups in this monomer composition is not particularly limited. From the viewpoint of suitably giving play to the effect brought by the use of optional monomer containing functional groups, the content of the optional monomer containing functional groups in the monomer composition can be, for example, more than 0.1 % by weight, more than 0.5 % by weight is appropriate, or more than 1 % by weight is also possible. In addition, for example, from the viewpoint of easily obtaining the balance of adhesive properties with the relationship of the monomer composition comprising 2-octyl acrylate, the content of the optional monomer containing functional groups in the monomer composition can be, for example, less than 40 % by weight, preferably less than 20 % by weight, or less than 10 % by weight (for example, less than 5 % by weight). In some ways, the content of the optional monomer containing functional groups in the monomer composition is, for example, less than 3 % by weight, can be less than 1 % by weight, can be less than 0.5 % by weight, can be less than 0.3 % by weight, or can be less than 0.1 % by weight. The technology disclosed herein can preferably be implemented in a manner that the monomer composition of acrylic polymer does not contain the optional monomer containing functional groups in fact.

[0067] It should be noted that, in this specification, "the monomer component is substantially free of monomer A (e.g., the optional functional group-containing monomer)" means that the monomer A is at least not intentionally used, and the unintentional inclusion of the monomer A may be allowed, for example, at a level of about 0.01% by weight or less.

[0068] In addition, as the above-mentioned optional functional group-containing monomer, a hydroxyl-containing monomer can be used. In this case, it is appropriate that the content of the hydroxyl-containing monomer is about 10% by weight or less (for example, 0.001% by weight to 10% by weight) in the total monomer components, preferably about 5% by weight or less, and more preferably about 2% by weight or less. In some embodiments, the content of the hydroxyl-containing monomer in the monomer component can 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 component of the acrylic polymer may be substantially free of hydroxyl-containing monomers. According to the technology disclosed herein, by limiting the amount of hydroxyl-containing monomers used or not using hydroxyl-containing monomers, it is possible to take into account both high temperature characteristics and flexibility.

[0069] In the mode of the acrylic polymer that uses copolymerization to have carboxyl-containing monomer, consider from the viewpoint of effectively bringing into play the effect that makes the copolymerization of carboxyl-containing monomer, carboxyl-containing monomer shared ratio in the functional group-containing monomer whole (comprising the functional group-containing monomer whole) that the copolymerization component of acrylic polymer uses is suitable for being more than 30 % by weight, be preferably more than 50 % by weight, more preferably more than 70 % by weight, further be preferably more than 80 % by weight, particularly preferably more than 90 % by weight, for example, can be more than 95 % by weight, can be more than 97 % by weight, can be more than 98 % by weight, can be more than 99 % by weight (for example, more than 99.9 % by weight).The upper limit of the shared ratio of carboxyl-containing monomer in the above-mentioned functional group-containing monomer whole is 100 % by weight, for example, can be below 95 % by weight.

[0070] For purposes such as improving cohesion, the monomer components constituting the acrylic polymer may contain other copolymer components in addition to the above-mentioned functional group-containing monomers. Examples of other copolymer components include: vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as aryl (meth)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-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether. These other copolymer components may be used alone or in combination of two or more.

[0071] The amount of the other copolymer components can be appropriately selected according to the purpose and use, and is not particularly limited. From the perspective of appropriately exerting the effect brought by its use, it is appropriate to be 0.05 weight % or more, and can be 0.5 weight % or more. In addition, from the perspective of easily obtaining a balance of adhesive properties, it is appropriate that the content of the other copolymer components in the monomer components is 20 weight % or less. From the perspective of appropriately exerting the adhesive properties based on the indispensable monomer components, it is preferably 10 weight % or less, more preferably 8 weight % or less, further preferably less than 5 weight %, for example, less than 3 weight %, or less than 1 weight %. The technology disclosed herein can preferably be implemented in a manner that the monomer components do not substantially contain the other copolymer components.

[0072] As other monomer components, the acrylic polymer may contain a polyfunctional monomer having at least two (meth)acryloyl groups, vinyl groups, and other polymerizable functional groups (typically free radical polymerizable functional groups) having unsaturated double bonds. By using a polyfunctional monomer as a monomer component, the cohesive force of the adhesive layer can be improved. The polyfunctional monomer can be used as a cross-linking agent. There are no particular restrictions on the polyfunctional monomer, 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 can be used alone or in combination of two or more.

[0073] The usage amount of multifunctional monomer is not particularly limited, and can be suitably set in the mode of realizing the purpose of use of this multifunctional monomer.The usage amount of multifunctional monomer can be below about 3 % by weight of above-mentioned monomer component, preferably below about 2 % by weight, more preferably below about 1 % by weight (for example below about 0.5 % by weight).As long as the lower limit of the usage amount in the case of using multifunctional monomer is greater than 0 % by weight, there is no particular restriction.Usually, by making the usage amount of multifunctional monomer be more than about 0.001 % by weight of monomer component (for example more than about 0.01 % by weight), the use effect of this multifunctional monomer can be suitably brought into play.

[0074] In a particularly preferred embodiment, the acrylic polymer used as the acrylic polymer is an acrylic polymer synthesized using a monomer component that substantially includes 2-octyl acrylate, other (meth) alkyl acrylates different from 2-octyl acrylate, and a carboxyl group-containing monomer. According to the above monomer composition, the role of each monomer is effectively exerted, good adhesive properties (such as adhesion, cohesion, etc.) are obtained, and high temperature properties and flexibility can be better balanced. From this point of view, it is appropriate that the total proportion of 2-octyl acrylate, other (meth) alkyl acrylates, and carboxyl group-containing monomers in the above monomer component is 90% by weight or more (90% to 100% by weight), preferably 95% by weight or more, more preferably 99% by weight or more, further preferably greater than 99.5% by weight, particularly preferably greater than 99.9% by weight (for example, greater than 99.99% by weight), and can be 100% by weight.

[0075] The biomass-to-carbon ratio of the monomer components constituting the acrylic polymer (the biomass-to-carbon ratio of the acrylic polymer) can be, for example, 1% or more, preferably 10% or more, preferably 30% or more, more preferably 50% or more (e.g., greater than 50%), 70% or more, 80% or more, or 90% to 100%. This design allows for the production of an acrylic adhesive that reduces reliance on fossil resource materials.

[0076] The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as methods for synthesizing acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately adopted. For example, solution polymerization can be preferably adopted. As the monomer supply method for solution polymerization, a one-time feeding method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a batch supply (dropping) method, etc. can be appropriately adopted. The polymerization temperature can be appropriately selected according to the types of monomers and solvents used, the type of polymerization initiator, etc., and can be, for example, about 20°C to about 170°C (typically about 40°C to about 140°C).

[0077] The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, any one solvent or a mixture of two or more selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (e.g., monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; and ketones such as methyl ethyl ketone can be used.

[0078] The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on 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; and aromatic carbonyl compounds. Other examples of polymerization initiators include redox-based initiators based on a combination of a peroxide and a reducing agent. Such polymerization initiators can be used alone or in combination of two or more. The amount of polymerization initiator used can be a typical amount, for example, from about 0.005 to about 1 part by weight (typically, from about 0.01 to about 1 part by weight) relative to 100 parts by weight of the total monomer components.

[0079] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited. From the perspective of obtaining good adhesive properties, acrylic polymers with a Mw of about 100,000 or more are generally used. In some embodiments, the Mw of the acrylic polymer is preferably 400,000 or more, more preferably 600,000 or more, further preferably 700,000 or more, and can be 800,000 or more. The larger the Mw of the acrylic polymer, the easier it is to obtain an adhesive with good high-temperature properties. By combining the high molecular weight acrylic polymer with a tackifier, it is possible to satisfactorily balance good high-temperature properties and rough surface adhesion. On the other hand, from the perspectives of adhesive force, rough surface adhesion, ease of synthesis, etc., it is appropriate that the Mw of the acrylic polymer is generally about 3 million or less, preferably 2 million or less, more preferably 1.5 million or less, further preferably 1.2 million or less, and can be 1 million or less (for example, less than 1 million).

[0080] Although there are no particular restrictions, as acrylic polymers, acrylic polymers having a dispersity (Mw / Mn) of less than 50, which is expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), are generally used. The above-mentioned dispersity (Mw / Mn) may be about 40 or less, about 30 or less, or about 20 or less. In some embodiments, the dispersity (Mw / Mn) of the acrylic polymer is preferably 15 or less, 12 or less, 10 or less, 8 or less, or 6 or less. In addition, the dispersity (Mw / Mn) of the acrylic polymer is theoretically 1 or more, and from the viewpoint of ease of preparation, for example, it may be 2 or more, 3 or more, or 4 or more (typically 5 or more). Acrylic polymers having a dispersity (Mw / Mn) within the above-mentioned range have a prescribed molecular weight distribution, and it is easy to obtain adhesive force and rough surface adhesion based on the wettability of their low molecular weight components. In addition, it is easy to obtain good adhesive properties based on the cohesive force of their high molecular weight components.

[0081] Mw, Mn, and Mw / Mn can be adjusted by polymerization conditions (time, temperature, etc.), the use of a chain transfer agent, and the like. The Mw and Mn of acrylic polymers can be determined by gel permeation chromatography (GPC) as values converted to standard polystyrene. Specifically, they can be determined using the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation) as a GPC measuring apparatus under the following conditions. This also applies to the examples described below.

[0082] [GPC measurement conditions]

[0083] Sample concentration: 0.2 wt% (tetrahydrofuran solution)

[0084] Sample injection volume: 10 μL

[0085] Eluent: tetrahydrofuran (THF)

[0086] Flow rate: 0.6 mL / min

[0087] Column temperature (measurement temperature): 40°C

[0088] column:

[0089] Sample column: 1 TSKguardcolumn SuperHZ-H + 2 TSKgel SuperHZM-H (manufactured by Tosoh Corporation)

[0090] Reference column: 1 TSKgel SuperH-RC (manufactured by Tosoh Corporation)

[0091] Detector: Differential Refractometer (RI)

[0092] Standard sample: polystyrene

[0093] (Thickener)

[0094] The adhesive layer disclosed herein comprises a tackifier. By using a tackifier, it is possible to improve bonding strength, for example, it is possible to improve the high temperature bonding strength and rough surface tackiness of the adhesive containing the acrylic polymer comprising 2-octyl acrylate as a monomer component. In addition, according to the technology disclosed herein, it is possible to effectively obtain the use effect of the tackifier while maintaining the high temperature characteristics and flexibility of the use based on the above-mentioned specific acrylic polymer. As a tackifier, it is possible to use, without particular limitation, a component that can improve bonding strength by being added to the adhesive, typically tackifier resins such as rosin-based tackifying resins, terpene-based tackifying resins, and acrylic oligomers described later. The tackifier can be used alone or in combination of two or more. Although not particularly limited, in some ways, it is possible to effectively play the effect of using a tackifier in the composition comprising an acrylic polymer of high molecular weight (for example, Mw 400,000 or more).

[0095] Consider from the viewpoint of the addition effect that obtains tackifier, relative to acrylic polymer 100 weight parts, the content of the tackifier in the adhesive layer is generally about 1 weight part or more is suitable, can be about 5 weight parts or more, be preferably about 8 weight parts or more, more preferably 10 weight parts or more, further preferably about 12 weight parts or more (for example more than 15 weight parts).The more the usage amount of tackifier is, the more there is the tendency that easily obtains adhesive force and improves effect, rough surface tackiness and improves effect.In addition, in some preferred embodiments, relative to acrylic polymer 100 weight parts, the content of above-mentioned tackifier can be more than 20 weight parts, also can be more than 25 weight parts.In addition, the upper limit of the content of the tackifier in the adhesive layer is not particularly limited, from the viewpoints such as the compatibility with acrylic polymer, relative to acrylic polymer 100 weight parts, be about below 100 weight parts (for example less than 100 weight parts) and be suitable, can be about below 80 weight parts. In some embodiments, the amount of tackifier in the adhesive layer is, for example, 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the perspectives of flexibility and adhesive properties (cohesion, etc.), the amount of tackifier is 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.

[0096] (Tackifying resin)

[0097] In some preferred embodiments, the adhesive layer includes a tackifying resin. By using a tackifying resin, adhesive strength and rough surface adhesion can be satisfactorily improved. As the tackifying resin, there are no particular restrictions, and various tackifying resins such as rosin tackifying resins, terpene tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomer tackifying resins, phenol tackifying resins, and ketone tackifying resins can be used. Such tackifying resins can be used alone or in combination of two or more.

[0098] Specific examples of rosin-based tackifying resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins, the same shall apply hereinafter); 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., rosin esters) and those obtained by esterifying modified rosin with alcohols (i.e., modified rosin esters); unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid-modified rosin, 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 rosin phenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and thermally polymerizing them. Among these, rosin esters are preferred.

[0099] 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, glycerol ester, pentaerythritol ester, etc., but are not particularly limited.

[0100] Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymers, β-pinene polymers, and pine oil polymers; and modified terpene resins obtained by modifying these terpene resins (e.g., by phenol modification, aromatic modification, hydrogenation modification, and hydrocarbon modification). An example of such a modified terpene resin is a terpene phenol resin.

[0101] Terpene-phenol resin refers to a polymer containing terpene residues and phenol residues. It is a concept that includes both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and resins obtained by phenol-modifying homopolymers or copolymers of terpenes (phenol-modified terpene resins). Specific examples of terpenes that constitute such terpene-phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-form, l-form, and d / l-form (pine oil). Hydrogenated terpene-phenol resin refers to a hydrogenated terpene-phenol resin having a structure obtained by hydrogenating such a terpene-phenol resin. It is sometimes also called a hydrogenated terpene-phenol resin.

[0102] Examples of hydrocarbon tackifying resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, their hydrogenated products (for example, alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), their various modified products (for example, maleic anhydride modified products), coumarone resins, coumarone indene resins and other various hydrocarbon resins.

[0103] In some embodiments, as the tackifying resin, at least one selected from rosin-based tackifying resins and terpene-based tackifying resins is preferably used. By making the acrylic adhesive contain rosin-based tackifying resins and / or terpene-based tackifying resins, it is possible to satisfactorily improve adhesion, high-temperature adhesion, and rough surface adhesion. In some preferred embodiments, the proportion of the total of rosin-based tackifying resins and terpene-based tackifying resins in the overall tackifying resin contained in the adhesive layer can be, for example, greater than about 50% by weight (greater than 50% by weight and less than or equal to 100% by weight), can be about 70% by weight or more, can be about 80% by weight or more, can be about 90% by weight or more, can be 95% by weight or more, and can be 99% by weight or more.

[0104] As some preferred modes, the mode in which the above-mentioned tackifying resin comprises one or more terpene-phenol resins can be enumerated. The technology disclosed herein can, for example, preferably be implemented in a mode in which more than about 25 wt % (more preferably more than about 30 wt %) of the total amount of tackifying resin is a terpene-phenol resin. The proportion shared by terpene-phenol resin in the total amount of tackifying resin can be more than about 50 wt %, can be more than about 70 wt %, can be more than about 80 wt %, can be more than about 90 wt %. It can be that substantially all (for example, more than about 95 wt % and less than 100 wt %, further more than about 99 wt % and less than 100 wt %) of tackifying resin is a terpene-phenol resin.

[0105] The content of the terpene-phenol resin in the adhesive layer is not particularly limited as long as it meets the target properties. In some embodiments, from the viewpoint of improving adhesion, high-temperature adhesion, and rough surface adhesion, the content of the terpene-phenol resin is generally about 1 part by weight or more relative to 100 parts by weight of acrylic polymer, and about 5 parts by weight or more is appropriate, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and further preferably about 12 parts by weight or more (for example, 15 parts by weight or more). In some preferred embodiments, the content of the terpene-phenol resin can be more than 20 parts by weight, or more than 25 parts by weight, relative to 100 parts by weight of acrylic polymer. In addition, in some embodiments, the content of the terpene-phenol resin in the adhesive layer is, for example, less than 70 parts by weight, less than 60 parts by weight, or less than 50 parts by weight, relative to 100 parts by weight of acrylic polymer. In some preferred embodiments, from the viewpoints of cohesion, the content of the above-mentioned terpene-phenol resin is less than 40 parts by weight, less than 30 parts by weight, less than 25 parts by weight, less than 20 parts by weight, or less than 18 parts by weight.

[0106] There is no particular restriction on the softening point of the tackifying resin. For example, a tackifying resin having a softening point of about 50°C or more can be used. From the perspective of improving cohesion, a tackifying resin having a softening point (softening temperature) of about 80°C or more can be preferably used. For example, a terpene tackifying resin (terpene phenol resin, etc.) having such a softening point can be preferably used. In some preferred embodiments, from the perspective of high-temperature adhesion, the softening point of the tackifying resin can be above about 100°C, above about 105°C, or above about 110°C. There is no particular restriction on the upper limit of the softening point of the tackifying resin. From the perspective of adhesion to the adherend, a tackifying resin having a softening point of about 200°C or less (more preferably below about 180°C) can be preferably used. In some preferred embodiments, the softening point of the tackifying resin may be below about 160°C (e.g., less than 160°C), below about 150°C (e.g., less than 150°C), less than 145°C, less than 140°C, less than 130°C, or less than 120°C.

[0107] It should be noted that the softening point of the tackifying resin in this specification is defined as the value measured according to the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is quickly melted at the lowest possible temperature and filled into a ring placed on a flat metal plate, taking care not to generate bubbles. After cooling, the raised portion is cut off from the plane containing the upper end of the ring with a slightly heated knife. Next, a support (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 injected until the depth reaches more than 90 mm. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in glycerin in a non-contact manner, and the temperature of the glycerin is maintained at 20°C ± 5°C for 15 minutes. Next, a steel ball is placed in the center of the sample surface in the ring and is placed in a fixed position on the support. Next, keep the distance from the upper end of the ring to the glycerin surface at 50 mm, place a thermometer so that the center of the mercury ball of the thermometer is at the same height as the center of the ring, and heat the container. Use the flame of the Bunsen burner used for heating to be located between the center and the edge of the bottom of the container to ensure uniform heating. It should be noted that the rate of increase in bath temperature after reaching 40°C after the start of heating must be 5.0°C ± 0.5°C per minute. The sample gradually softens and flows down from the ring. The temperature when it finally contacts the bottom plate is read and used as the softening point. The softening point is measured twice or more at the same time, and the average value is adopted.

[0108] In some preferred embodiments, as the tackifying resin, a tackifying resin T having a softening point of 100°C or higher is used. H By using tackifying resin T H , it is easy to improve the high temperature adhesiveness. H The softening point of the tackifying resin T may be above 105°C or above 110°C. H The upper limit of the softening point is not particularly limited, for example, it is about 200°C or less. In some preferred embodiments, it is less than 150°C, less than 140°C, less than 130°C, or less than 120°C. By using a tackifying resin T having a softening point within the above range, H It is easy to obtain high adhesion to various adherends, and it is easy to take into account both high temperature adhesion and rough surface adhesion.

[0109] As tackifying resin T H , one tackifying resin having a softening point of 100° C. or higher may be used alone or in combination of two or more tackifying resins. H Preferably, it contains terpene phenol resin. H The terpene-phenol resin may be contained alone or in combination of two or more terpene-phenol resins.

[0110] In some embodiments, the terpene phenolic resin is used in the tackifying resin T H The proportion of the total weight of the resin can be, for example, greater than about 50% by weight, about 65% by weight or more, about 75% by weight or more, about 85% by weight or more, or about 95% by weight or more. H The method is implemented so that substantially all (for example, about 97% by weight or more, or 99% by weight or more, or 100% by weight) of the terpene-phenol resin is terpene-phenol resin.

[0111] Tackifying resin T H The content of is not particularly limited. In some embodiments, it is, for example, 1 part by weight or more, 5 parts by weight or more is appropriate, preferably 8 parts by weight or more, more preferably 10 parts by weight or more, further preferably 12 parts by weight or more, and can be 15 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. H The more the amount of the acrylic acid polymer is used, the more the high temperature adhesive strength tends to be improved. H The content of the tackifying resin T can be 20 parts by weight or more, or 25 parts by weight or more. In addition, in some embodiments, relative to 100 parts by weight of the acrylic polymer, the tackifying resin T H The content of the tackifying resin T is preferably less than about 100 parts by weight (e.g., less than 100 parts by weight), and can be less than about 80 parts by weight. In some preferred embodiments, from the perspectives of flexibility, adhesive properties (cohesion, etc.), and rough surface adhesion, relative to 100 parts by weight of the acrylic polymer, the tackifying resin T is preferably less than about 100 parts by weight. H The content of is appropriately about 70 parts by weight or less, can be 60 parts by weight or less, can be 50 parts by weight or less, can be 40 parts by weight or less, can be 30 parts by weight or less, can be 25 parts by weight or less, can be 20 parts by weight or less, can be 18 parts by weight or less.

[0112] In some embodiments, the adhesive layer may include a tackifying resin T in combination. H and tackifying resin T with a softening point less than 100°C L As a tackifying resin T L Among the tackifying resins exemplified above and having a softening point of less than 100° C., one type thereof may be used alone or two or more types thereof may be used in combination.

[0113] In addition, as a tackifying resin T LFor example, it may or may not contain a tackifying resin having a softening point of less than 50°C, more preferably below about 40°C (typically a tackifying resin of rosin, terpenes, hydrocarbons, etc., such as hydrogenated rosin methyl ester). The tackifying resin showing such a low softening point may be a liquid tackifying resin that is liquid at 30°C. The liquid tackifying resin may be used alone or in combination of two or more. From the viewpoint of cohesion, etc., the content of the liquid tackifying resin may be tackifying resin T L The total weight is about 30% or less, and appropriately about 10% or less (eg, 0% to 10% by weight), and can be about 2% or less (0.5% to 2% by weight), or less than 1% by weight.

[0114] In some embodiments, the tackifying resin T H It is preferred that the tackifier resin accounts for more than 50% by weight of the total amount of the tackifier resin contained in the adhesive layer. This makes it easy to effectively express the tackifier resin T H By more effectively utilizing the tackifying resin T H Considering the effect of use, tackifying resin T H The proportion of the total amount of the tackifying resin contained in the adhesive layer is preferably 60% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more, 95% by weight or more, or 98% by weight or more. In some preferred embodiments, the tackifying resin contained in the adhesive layer substantially only comprises the tackifying resin T H In this method, the tackifying resin T H The ratio of the tackifier resin to the total amount contained in the adhesive layer is within a range of 99% by weight to 100% by weight.

[0115] The hydroxyl value of the tackifying resin is not particularly limited. In some embodiments, from the perspective of compatibility with acrylic polymers, the hydroxyl value of the tackifying resin is generally about 300 mgKOH / g or less, and about 200 mgKOH / g or less is appropriate. In some preferred embodiments, it can be about 150 mgKOH / g or less, or it can be about 120 mgKOH / g or less. In some embodiments, the hydroxyl value of the tackifying resin is 0 mgKOH / g or more, can be about 10 mgKOH / g or more, or can be about 20 mgKOH / g or more.

[0116] Here, as the value of the hydroxyl value, there can be adopted a value measured by the potentiometric titration method specified in JIS K0070: 1992. The specific measurement method is as follows.

[0117] [Method for measuring hydroxyl value]

[0118] 1. Reagents

[0119] (1) As the acetylating agent, an acetylating agent prepared by adding pyridine to approximately 12.5 g (approximately 11.8 mL) of acetic anhydride to a total volume of 50 mL was used, followed by thorough stirring. Alternatively, an acetylating agent prepared by adding pyridine to approximately 25 g (approximately 23.5 mL) of acetic anhydride to a total volume of 100 mL was used, followed by thorough stirring was used.

[0120] (2) As a measurement reagent, a 0.5 mol / L potassium hydroxide ethanol solution was used.

[0121] (3) Separately, prepare toluene, pyridine, ethanol, and distilled water.

[0122] 2. Operation

[0123] (1) Accurately weigh about 2 g of sample in a flat-bottom flask, add 5 mL of acetylating agent and 10 mL of pyridine, and install an air cooling tube.

[0124] (2) The flask was heated in a bath at 100°C for 70 minutes, then cooled naturally. 35 mL of toluene as a solvent was added from the top of the cooling tube and stirred. Then, 1 mL of distilled water was added and stirred to decompose the acetic anhydride. To complete the decomposition, the flask was heated in the bath again for 10 minutes and cooled naturally.

[0125] (3) The cooling tube was cleaned with 5 mL of ethanol and removed. Then, 50 mL of pyridine was added as a solvent and stirred.

[0126] (4) Use a full-volume pipette to add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution.

[0127] (5) Potentiometric titration was performed using a 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve was defined as the endpoint.

[0128] (6) In a blank test, the above (1) to (5) are carried out without adding a sample.

[0129] 3. Calculation

[0130] The hydroxyl value was calculated according to the following formula.

[0131] Hydroxyl value (mgKOH / g) = [(BC) × f × 28.05] / S + D

[0132] Here,

[0133] B: The amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (mL),

[0134] C: The amount of 0.5 mol / L potassium hydroxide ethanol solution used in the sample (mL),

[0135] f: Factor of 0.5 mol / L potassium hydroxide ethanol solution,

[0136] S: weight of the sample (g),

[0137] D: acid value,

[0138] 28.05: 1 / 2 of the molecular weight of potassium hydroxide, 56.11.

[0139] In some embodiments, the tackifying resin may include a tackifying resin having a hydroxyl value of less than 100 mgKOH / g. Hereinafter, a tackifying resin having a hydroxyl value of less than 100 mgKOH / g will sometimes be referred to as a "low hydroxyl value resin". The hydroxyl value of the low hydroxyl value resin may be less than 80 mgKOH / g, may be less than 70 mgKOH / g, or may be less than 65 mgKOH / g. By including such a tackifying resin with a low hydroxyl value resin, good adhesion is easily obtained. The lower limit of the hydroxyl value of the low hydroxyl value resin is 0 mgKOH / g or more, may be about 10 mgKOH / g or more, or may be about 15 mgKOH / g or more. The higher the hydroxyl value, the easier it is to obtain good cohesion. As the low hydroxyl value resin, one of the tackifying resins having a hydroxyl value of less than 100 mgKOH / g selected from the tackifying resins exemplified above may be used alone or in combination of two or more. In some embodiments, the low hydroxyl value resin preferably includes at least one selected from a rosin-based tackifying resin and a terpene-based tackifying resin. For example, a terpene-phenol resin having a hydroxyl value of less than 100 mgKOH / g can be preferably used as a low-hydroxyl-value resin. Terpene-phenol resins are suitable because their hydroxyl value can be arbitrarily controlled by adjusting the copolymerization ratio of phenol.

[0140] Although not particularly limited, when a low-hydroxyl resin is used, the proportion of the low-hydroxyl resin (e.g., terpene-phenol resin) in the total tackifying resin contained in the adhesive layer can be about 5% by weight or more, 10% by weight or more, 15% by weight or more, or 20% by weight or more. In some embodiments, the proportion of the low-hydroxyl resin in the total tackifying resin is, for example, preferably about 30% by weight or more. This satisfactorily achieves the effect of the low-hydroxyl resin. In some preferred embodiments, the proportion of the low-hydroxyl resin in the total tackifying resin is about 40% by weight or more, about 50% by weight or more (e.g., greater than 50% by weight), about 60% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more. It is also possible that substantially all of the tackifying resin (e.g., about 95% to about 100% by weight, and further about 99% to about 100% by weight) is a low-hydroxyl resin.

[0141] The softening point of the low hydroxyl value resin is not particularly limited. The softening point of the low hydroxyl value resin can be, for example, above about 50°C. From the perspective of improving cohesion, a low hydroxyl value resin with a softening point (softening temperature) of about 80°C or above can be preferably used. For example, rosin-based tackifying resins and terpene phenol resins with such a softening point can be preferably used. In some preferred embodiments, from the perspective of high-temperature adhesion, the softening point of the low hydroxyl value resin can be above about 100°C, above 105°C, or above about 110°C. In addition, in some embodiments, from the perspective of adhesion and rough surface adhesion, a low hydroxyl value resin with a softening point of about 200°C or less (more preferably about 180°C or less) can be preferably used. In some preferred embodiments, the softening point of the low hydroxyl value resin can be below about 160°C, below about 150°C (for example, less than 150°C), less than 145°C, less than 140°C, less than 130°C, or less than 120°C.

[0142] The content of the low hydroxyl value resin in the adhesive layer is not particularly limited. In some embodiments, relative to 100 weight parts of acrylic polymers, it is usually about 1 weight part or more, and it is appropriate to be about 5 weight parts or more, preferably about 8 weight parts or more, more preferably about 10 weight parts or more, and further preferably about 12 weight parts or more (for example, more than 15 weight parts). The more the usage amount of low hydroxyl value resin is, the more there is the tendency that bonding force, rough surface adhesion improve. From this viewpoint, in some preferred embodiments, relative to 100 weight parts of acrylic polymers, the content of low hydroxyl value resin can be more than 20 weight parts, or more than 25 weight parts. In addition, in some embodiments, relative to 100 weight parts of acrylic polymers, the content of the low hydroxyl value resin in the adhesive layer is, for example, below 70 weight parts, can be below 60 weight parts, or below 50 weight parts. In some preferred embodiments, from viewpoints such as cohesive force, the content of above-mentioned low hydroxyl value resin is below 40 weight parts, can be below 30 weight parts, can be below 25 weight parts, can be below 20 weight parts, or can be below 18 weight parts.

[0143] In the case where the adhesive layer disclosed herein includes a tackifying resin, as the tackifying resin, from the viewpoint of increasing the biomass carbon ratio of the adhesive layer, a tackifying resin from a plant (plant-based tackifying resin) can be preferably used. Examples of plant-based tackifying resins include the above-mentioned rosin-based tackifying resins and terpene-based tackifying resins. Plant-based tackifying resins can be used alone or in combination of two or more. In the case where the adhesive layer disclosed herein includes a tackifying resin, the proportion of the plant-based tackifying resin in the total amount of the tackifying 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 plant-based tackifying resin in the total amount of the tackifying resin is 90% by weight or more (e.g., 95% by weight or more, typically 99% to 100% by weight). The technology disclosed herein can preferably be implemented in a manner that does not substantially contain a tackifying resin other than the plant-based tackifying resin.

[0144] The content of the tackifying resin in the adhesive layer is not particularly limited. In the mode of using tackifying resin as tackifier, relative to acrylic polymer 100 weight parts, the content of tackifying resin is generally about more than 1 weight part, for about more than 5 weight parts is appropriate, preferably about more than 8 weight parts, more preferably more than 10 weight parts, further preferably about more than 12 weight parts (for example more than 15 weight parts). The usage amount of tackifying resin is more, the easier it is to improve bonding force, high temperature bonding force, rough surface tackiness. Consider from this viewpoint, in some preferred embodiments, relative to acrylic polymer 100 weight parts, the content of above-mentioned tackifying resin can be more than 20 weight parts, also can be more than 25 weight parts. In addition, relative to acrylic polymer 100 weight parts, the content of the tackifying resin in the adhesive layer is, for example, about below 100 weight parts (for example less than 100 weight parts) is appropriate, can be about below 80 weight parts. In some embodiments, the content of the tackifying resin in the adhesive layer is, for example, 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the perspectives of flexibility and cohesive strength, the content of the tackifying resin is 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.

[0145] (Acrylic oligomer)

[0146] In some embodiments, the adhesive layer contains an acrylic oligomer. By containing an acrylic oligomer, the adhesive strength of the adhesive can be improved. According to the technology disclosed herein, by including a composition containing an acrylic oligomer, the adhesive layer can have both high-temperature adhesion and flexibility. Although not particularly limited, in some embodiments, the effect of using an acrylic oligomer can be effectively exerted in a composition containing a high molecular weight (e.g., Mw 400,000 or more) acrylic polymer.

[0147] The Tg of the acrylic oligomer is preferably from about 0°C to about 300°C, preferably from about 20°C to about 300°C, and more preferably from about 40°C to about 300°C. By setting the Tg within the above range, the adhesive force can be appropriately improved. In some preferred embodiments, from the perspective of the cohesiveness of the adhesive, the Tg of the acrylic oligomer is from about 30°C to about 30°C, more preferably from about 50°C to about 60°C (for example, from about 60°C). From the perspective of adhesiveness, it is preferably from about 200°C to about 200°C, more preferably from about 150°C to about 100°C, and more preferably from about 80°C to about 100°C (for example, from about 80°C).

[0148] In this specification, the Tg of an acrylic oligomer refers to the Tg calculated using the Fox equation based on the composition of the above-mentioned monomer components. The Fox equation is shown below and represents the relationship between the Tg of a copolymer and the glass transition temperature (Tgi) of a homopolymer obtained by homopolymerizing the monomers constituting the copolymer.

[0149] 1 / Tg=Σ(Wi / Tgi)

[0150] In the above Fox equation, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). The Tg of the homopolymer used in the calculation of Tg is as described in the description of the homopolymer Tg of the monomer of the acrylic polymer.

[0151] The weight average molecular weight (Mw) of the acrylic oligomer can typically be greater than or equal to about 1000 and less than about 30000, preferably greater than or equal to about 1500 and less than about 20000, and more preferably greater than or equal to about 2000 and less than about 10000. By having Mw within the above range, good adhesiveness can be obtained, so it is preferred. In some preferred embodiments, the Mw of the acrylic oligomer is about 2500 or more (for example, about 3000 or more), and in addition, from the viewpoint of adhesiveness, it is preferably about 7000 or less, more preferably about 5000 or less (for example, about 4500 or less, typically about 4000 or less). The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and obtained as a value converted to standard polystyrene. Specifically, TSKgelGMH-H (20) × 2 roots are used as columns in HPLC8020 manufactured by Tosoh Corporation and measured in tetrahydrofuran solvent at a flow rate of about 0.5 mL / min.

[0152] Examples of monomers constituting acrylic oligomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and (meth)acrylate. Alkyl (meth)acrylates such as isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and tetrahydrodicyclopentadienyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates derived from terpene compound derivative alcohols. These (meth)acrylates can be used alone or in combination of two or more.

[0153] From the perspective of further improving the adhesiveness of the adhesive layer, acrylic oligomers preferably contain, as monomer units, alkyl (meth)acrylates with branched alkyl groups, such as isobutyl (meth)acrylate and tert-butyl (meth)acrylate; esters of (meth)acrylic acid with alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates), such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and tetrahydrodicyclopentadienyl (meth)acrylate; and relatively bulky acrylic monomers, such as (meth)acrylates with cyclic structures, such as aryl (meth)acrylates, such as phenyl (meth)acrylate and benzyl (meth)acrylate. Furthermore, when ultraviolet light is used during the synthesis of the acrylic oligomer or during the formation of the adhesive layer, saturated bonds are preferred to minimize polymerization inhibition. Alkyl (meth)acrylates with branched alkyl groups or esters with alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) are preferably used as monomers constituting the acrylic oligomer. It should be noted that the aforementioned branched alkyl (meth)acrylates, alicyclic (meth)acrylates, and aryl (meth)acrylates are equivalent to the (meth)acrylate monomers in the technology disclosed herein. The alicyclic hydrocarbon group may be saturated or unsaturated.

[0154] The proportion of (meth)acrylate monomers (e.g., alicyclic hydrocarbon group-containing (meth)acrylates) in the total monomer components constituting the acrylic oligomer is typically greater than 50% by weight, preferably 60% by weight or greater, and more preferably 70% by weight or greater (e.g., 80% by weight or greater, further 90% by weight or greater). In some preferred embodiments, the acrylic oligomer has a monomer composition consisting essentially solely of (meth)acrylate monomers.

[0155] As the constituent monomer components of acrylic oligomers, in addition to the above-mentioned (meth)acrylate monomers, functional group-containing monomers can also be used. Preferred examples of the above-mentioned functional group-containing monomers include: monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxyl group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers can be used alone or in combination of two or more. Among them, carboxyl group-containing monomers are preferred, and AA is particularly preferred.

[0156] When all monomer components constituting the acrylic oligomer include a functional group-containing monomer, the proportion of the functional group-containing monomer (e.g., a carboxyl group-containing monomer such as AA) in the above-mentioned total monomer components is suitably about 1% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, and suitably about 15% by weight or less, preferably 10% by weight or less, more preferably 7% by weight or less.

[0157] Acrylic oligomers can be formed by polymerizing their constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be appropriately adopted. The types of polymerization initiators (e.g., azo-based polymerization initiators such as AIBN) that can be used as needed are generally the same as those exemplified in the synthesis of acrylic polymers. The amount of the polymerization initiator and the amount of any chain transfer agent, such as n-dodecyl mercaptan, can be appropriately adjusted based on common technical knowledge to achieve the desired molecular weight, and therefore a detailed description thereof is omitted herein.

[0158] From the above viewpoints, preferred acrylic oligomers include, for example, homopolymers of tetrahydrodicyclopentadienyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), tetrahydrodicyclopentadienyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA). In addition, copolymers of CHMA and isobutyl methacrylate (IBMA), copolymers of CHMA and IBXMA, copolymers of CHMA and acryloylmorpholine (ACMO), copolymers of CHMA and diethylacrylamide (DEAA), copolymers of CHMA and AA, copolymers of ADA and methyl methacrylate (MMA), copolymers of DCPMA and IBXMA, and copolymers of DCPMA and MMA can be mentioned.

[0159] In the case of containing acrylic oligomer in the adhesive layer disclosed herein, its content is not particularly limited, and it is suitable for example to be more than 0.1 weight part (for example, more than 1 weight part) relative to 100 weight parts of acrylic polymers. Consider from the viewpoint of giving full play to the effect of acrylic oligomers, in some ways, the content of above-mentioned acrylic oligomers is more than about 3 weight parts, can be more than about 5 weight parts, can be more than about 10 weight parts, and can also be more than about 12 weight parts. In addition, from the viewpoints such as compatibility with acrylic polymers, it is suitable for the content of above-mentioned acrylic oligomers to be less than 50 weight parts (for example, less than 40 weight parts) relative to 100 weight parts of acrylic polymers, preferably less than 30 weight parts, more preferably about 25 weight parts or less, further preferably about 20 weight parts or less. In some ways, the content of above-mentioned acrylic oligomers can be less than 10 weight parts, can be less than 5 weight parts, and can also be less than 1 weight part (for example, less than 1 weight part) relative to 100 weight parts of acrylic polymers. The adhesive layer can be substantially free of acrylic oligomers.

[0160] In some embodiments, the adhesive layer may contain one or more of the above-mentioned tackifying resins and one or more of the acrylic oligomers. The content of the tackifying resin in the adhesive layer is C T [Weight %] relative to the content of acrylic oligomer C O [wt%] ratio (C T / C O ) is not particularly limited. In some embodiments, the above (C T / C O ) is suitably 0.1 or more, preferably 0.5 or more, and may be 1 or more (e.g., greater than 1), 2 or more, 3 or more, or 4 or more. T / C O ) is larger, the easier it is to obtain the effect of using the tackifying resin. In addition, in some embodiments, the above (C T / C O ) is suitably 10 or less, preferably 8 or less, and may be 6 or less, or may be 5 or less. This allows the effect of using the acrylic oligomer to be preferably exhibited.

[0161] In the disclosed technology, the combined amount (total amount) of the acrylic polymer and tackifier in the adhesive layer is appropriately set to maximize the effects of the disclosed technology, and is not limited to a specific range. In some preferred embodiments, to maximize the effects of the disclosed technology, the combined amount (total amount) of the acrylic polymer and tackifier in the adhesive layer is suitably greater than 50% by weight of the adhesive layer, preferably at least about 70% by weight, more preferably at least about 90% by weight, and even more preferably at least 95% by weight (e.g., from 95% to 100% by weight, or from 95% to less than 100% by weight), and may be at least 98% by weight.

[0162] (cross-linking agent)

[0163] In the technology disclosed herein, the adhesive composition used in forming the adhesive layer may contain a crosslinking agent as needed. The type of crosslinking agent is not particularly limited, and examples thereof include isocyanate crosslinking agents, epoxy crosslinking agents, Azoline crosslinking agent, aziridine crosslinking agent, melamine crosslinking agent, peroxide crosslinking agent, urea crosslinking agent, metal alkoxide crosslinking agent, metal chelate crosslinking agent, metal salt crosslinking agent, carbodiimide crosslinking agent, hydrazine crosslinking agent, amine crosslinking agent, silane coupling agent, etc. The crosslinking agent can be used alone or in combination of two or more. Among them, isocyanate crosslinking agent, epoxy crosslinking agent, The cross-linking agent can be oxazoline cross-linking agent, aziridine cross-linking agent, melamine cross-linking agent, more preferably isocyanate cross-linking agent, epoxy cross-linking agent. By appropriately selecting and using a cross-linking agent, the adhesive layer can obtain appropriate cohesive force. It should be noted that the adhesive layer in the technology disclosed herein can contain the above-mentioned cross-linking agent in the form after the cross-linking reaction, the form before the cross-linking reaction, the form partially carried out the cross-linking reaction, the intermediate or composite form thereof, etc. The above-mentioned cross-linking agent is typically mainly included in the adhesive layer in the form after the cross-linking reaction.

[0164] As the isocyanate crosslinking agent, polyfunctional isocyanates (compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate crosslinking agents can be used alone or in combination of two or more.

[0165] Examples of the polyfunctional isocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

[0166] Specific examples of aliphatic polyisocyanates include: 1,2-ethylene diisocyanate; butylene diisocyanates such as 1,2-butylene diisocyanate, 1,3-butylene diisocyanate, and 1,4-butylene 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.

[0167] 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 toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0168] Specific examples of aromatic polyisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrobiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Isocyanate, 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'-dimethoxybiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, etc.

[0169] Preferred polyfunctional isocyanates include those having an average of three or more isocyanate groups per molecule. The trifunctional or higher-functional isocyanates may be polymers (typically dimers or trimers) of difunctional or higher-functional isocyanates, derivatives (e.g., addition reaction products of a polyol and two or more molecules of a polyfunctional isocyanate), polymers, and the like. Examples include dimers or trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimeric adducts of an isocyanurate structure), reaction products of trimethylolpropane and toluene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanates, polyether polyisocyanates, polyester polyisocyanates, and the like.

[0170] The technology disclosed herein can preferably be implemented in a manner that at least an isocyanate cross-linking agent is used as a cross-linking agent. The amount of the isocyanate cross-linking agent used is not particularly limited. Relative to 100 parts by weight of the acrylic polymer, the amount of the isocyanate cross-linking agent used can, for example, be about 0.1 parts by weight or more. From the viewpoints of taking into account cohesion and adhesion, the amount of the isocyanate cross-linking agent used is generally preferably about 0.3 parts by weight or more (for example, 0.5 parts by weight or more) relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, the amount of the isocyanate cross-linking agent used is about 0.8 parts by weight or more, more preferably about 1.0 parts by weight or more, further preferably about 1.2 parts by weight or more, and can be about 1.5 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. Furthermore, the amount of the isocyanate crosslinking agent used is suitably 10 parts by weight or less, preferably less than 5 parts by weight, more preferably less than 4.0 parts by weight, further preferably less than 3.0 parts by weight, and particularly preferably 2.5 parts by weight or less, and can be 2.0 parts by weight or less (e.g., 1.7 parts by weight or less) relative to 100 parts by weight of the acrylic polymer. By limiting the amount of the isocyanate crosslinking agent used to a specified range, it is possible to achieve good rough surface adhesion while maintaining cohesive strength due to the use of the isocyanate crosslinking agent.

[0171] As the epoxy crosslinking agent, any compound having two or more epoxy groups in one molecule can be used without particular limitation. Preferably, the epoxy crosslinking agent has three to five epoxy groups in one molecule. One epoxy crosslinking agent can be used alone or in combination of two or more.

[0172] Specific examples of epoxy crosslinking agents are not particularly limited, and examples thereof include N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether.

[0173] The usage amount of the epoxy cross-linking agent is not particularly limited. Relative to 100 parts by weight of the acrylic polymer, the usage amount of the epoxy cross-linking agent can be, for example, greater than 0 parts by weight and less than or equal to about 1 part by weight (typically about 0.001 parts by weight to about 1 part by weight). From the viewpoint of properly exerting the effect of improving cohesion, it is usually appropriate to use an amount of the epoxy cross-linking agent of about 0.002 parts by weight or more relative to 100 parts by weight of the acrylic polymer, preferably about 0.005 parts by weight or more, for example, it can be about 0.01 parts by weight or more. In addition, from the viewpoint of improving the adhesion to the adherend, it is appropriate to use an amount of the epoxy cross-linking agent of about 0.5 parts by weight or less relative to 100 parts by weight of the acrylic polymer, preferably about 0.2 parts by weight or less, more preferably about 0.1 parts by weight or less (for example, less than 0.1 parts by weight), or it can be about 0.07 parts by weight or less, or it can be about 0.04 parts by weight or less. Furthermore, to avoid a decrease in adhesive strength and flexibility due to excessive cross-linking, in some embodiments, the amount of epoxy cross-linking agent used is appropriately about 0.03 parts by weight or less, preferably about 0.02 parts by weight or less, per 100 parts by weight of the acrylic polymer. By limiting the amount of epoxy cross-linking agent used to a specified range, it is easier to maintain sufficient adhesive strength while maintaining good cohesive strength.

[0174] In some preferred embodiments, an isocyanate crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group than the isocyanate crosslinking agent are used in combination as the crosslinking agent. The type of non-isocyanate crosslinking agent that can be used in combination with the isocyanate crosslinking agent is not particularly limited, and can be appropriately selected from the above-mentioned crosslinking agents. A single non-isocyanate crosslinking agent can be used alone or in combination of two or more. In some preferred embodiments, an epoxy crosslinking agent can be used as the non-isocyanate crosslinking agent. For example, by using an isocyanate crosslinking agent and an epoxy crosslinking agent in combination, even better adhesion properties can be achieved.

[0175] The relationship between the content of the isocyanate crosslinking agent and the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) is not particularly limited. In some embodiments, the content of the isocyanate crosslinking agent is, for example, greater than 1 times the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent), and is appropriately about 10 times or more, preferably about 50 times or more, more preferably about 80 times or more, further preferably about 100 times or more (for example, greater than 100 times), and particularly preferably about 120 times or more (for example, about 150 times or more). In addition, from the perspective of appropriately exerting the effect obtained by using the isocyanate crosslinking agent and the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) in combination, generally, the content of the isocyanate crosslinking agent is, for example, less than about 1000 times, more preferably less than about 500 times, preferably less than about 300 times, or less than about 200 times relative to the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent).

[0176] The content of the cross-linking agent in the adhesive composition disclosed herein (the total amount of cross-linking agent) is not particularly limited. From the viewpoint of cohesion, usually relative to 100 parts by weight of acrylic polymer, the content of the above-mentioned cross-linking agent is about 0.001 parts by weight or more, about 0.002 parts by weight or more is appropriate, preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, further preferably about 0.02 parts by weight or more, particularly preferably about 0.03 parts by weight or more. In some ways, relative to 100 parts by weight of acrylic polymer, the content of the cross-linking agent is about 0.1 parts by weight or more, more preferably about 0.5 parts by weight or more, further preferably about 1.0 parts by weight or more, can be about 1.2 parts by weight or more, also can be about 1.5 parts by weight or more. In addition, usually relative to 100 parts by weight of acrylic polymer, the content of the cross-linking agent in the adhesive composition is about 20 parts by weight or less, about 15 parts by weight or less is appropriate, preferably about 10 parts by weight or less (for example, about 5 parts by weight or less). In some embodiments, the crosslinking agent content is 4.0 parts by weight or less, more preferably 3.0 parts by weight or less, and even more preferably 2.5 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. It can be 2.0 parts by weight or less (e.g., less than 2.0 parts by weight), or even 1.8 parts by weight or less. In configurations where the amount of crosslinking agent used is limited to the above range, good adhesive strength and flexibility tend to be readily achieved.

[0177] (Other additives)

[0178] In addition to the above-mentioned components, the adhesive composition may contain various additives commonly used in the adhesive field, such as a leveling agent, a crosslinking aid, a plasticizer, a softener, a filler, a colorant (pigment, dye, etc.), an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, a rust inhibitor, and a light stabilizer, as needed. Conventionally known additives can be used, but they are not a feature of the present invention, and therefore detailed description thereof is omitted.

[0179] The adhesive layer disclosed herein (a layer containing an adhesive) can be an adhesive layer formed by an aqueous adhesive composition, a solvent-based adhesive composition, a hot melt adhesive composition, or an active energy ray-curable adhesive composition. An aqueous adhesive composition refers to an adhesive composition in the form of an adhesive (adhesive layer forming component) contained in a solvent (aqueous solvent) having water as its main component, typically an aqueous adhesive composition containing what is called a water-dispersible adhesive composition (a composition in the form of at least a portion of the adhesive dispersed in water). In addition, a solvent-based adhesive composition refers to an adhesive composition in the form of an adhesive contained in an organic solvent. As the organic solvent contained in the solvent-based adhesive composition, one or more of the organic solvents (toluene, ethyl acetate, etc.) that can be used in the above-mentioned solution polymerization can be used without particular limitation. From the viewpoint of adhesive properties, the technology disclosed herein can be preferably implemented in a manner having an adhesive layer formed by a solvent-based adhesive composition.

[0180] Adhesive layer disclosed herein can be formed by known methods in the past. For example, it is possible to adopt a method for forming an adhesive layer by applying an adhesive composition on a surface with peelability (peel-off surface) or a non-peel-off surface and making it dry. For the adhesive sheet with the formation of a base material, for example, it is possible to adopt a method (direct method) by directly applying (typically coating) an adhesive composition on this base material and making it dry to form an adhesive layer. In addition, it is also possible to adopt a method (transfer method) by applying an adhesive composition on a surface with peelability (peel-off surface) and making it dry to form an adhesive layer on this surface, and transferring this adhesive layer to the base material. From the viewpoint of productivity, it is preferred to use a transfer method. As the above-mentioned peel-off surface, the surface of a release liner, the back side of the base material that has been peeled off, etc. It should be noted that the adhesive layer disclosed herein is typically formed continuously, but is not limited to such a mode, for example, it is also possible to be an adhesive layer formed into regular or irregular patterns such as dot-shaped and strip-shaped.

[0181] The adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the adhesive composition can be applied by dipping, curtain coating, or the like.

[0182] To promote the crosslinking reaction and improve manufacturing efficiency, the adhesive composition is preferably dried under heating. The drying temperature can be, for example, about 40°C to about 150°C, and is generally preferably about 60°C to about 130°C. After drying, the adhesive composition may be further aged for purposes such as regulating component migration within the adhesive layer, promoting the crosslinking reaction, and relaxing any strain that may exist within the adhesive layer.

[0183] (thickness)

[0184] There is no particular limitation on the thickness of the adhesive layer, and the adhesive layer may be constructed with an appropriate thickness, for example, in the range of 0.1 μm to 500 μm, depending on the application and purpose of use. In some embodiments, from the perspective of avoiding the adhesive sheet from becoming too thick, it is appropriate that the thickness of the adhesive layer is generally about 100 μm or less, preferably about 70 μm or less, more preferably about 60 μm or less, and further preferably about 50 μm or less. In some preferred embodiments, the thickness of the adhesive layer may be about 35 μm or less, for example, about 30 μm or less, about 25 μm or less, or about 22 μm or less. An adhesive layer with a limited thickness can well meet the requirements of thickness reduction and lightweighting. In addition, from the viewpoint of adhesion to the adherend, in some ways, it is appropriate that the lower limit of the thickness of the adhesive layer is about 0.5 μm or more, can be about 1 μm or more, preferably about 3 μm or more, preferably about 10 μm or more, more preferably about 12 μm or more (for example, greater than 12 μm), further preferably about 15 μm or more, for example, can be about 18 μm or more. The greater the thickness of the adhesive layer, the more it tends to improve the adhesive force. The adhesive sheet disclosed herein can be an adhesive sheet having an adhesive layer of the above-mentioned thickness on both sides of the substrate. In addition, in a double-sided adhesive sheet with a substrate having a first adhesive layer and a second adhesive layer on each side of the substrate, the first adhesive layer and the second adhesive layer can be the same thickness or different thicknesses from each other.

[0185] (Glass transition temperature of adhesive)

[0186] Although there are no particular restrictions, in some embodiments, the glass transition temperature (Tg) of the adhesive (layer) is 10°C or less (for example, less than 10°C), may be 8.0°C or less, or may be 6.0°C or less. Here, the glass transition temperature of the adhesive (layer) refers to the glass transition temperature obtained from the peak temperature of tanδ in the dynamic viscoelasticity measurement. Adhesives containing a tackifier and having a low Tg have high flexibility and are prone to exhibiting excellent rough surface adhesion. In some preferred embodiments, the Tg of the adhesive (layer) is less than 5.0°C, may be less than 4.0°C, may be less than 3.0°C, may be less than 2.0°C, may be less than 1.0°C, may be less than 0°C (for example, less than 0.0°C), may be less than -1.0°C, may be less than -3.0°C, or may be less than -5.0°C. In addition, in some embodiments, from the perspective of cohesion, etc., the Tg of the adhesive (layer) is, for example, appropriate to be above -30°C, preferably above -15°C, can be above -12°C, can be above -10°C, can be above -7.0°C (for example, greater than -7.0°C), can be above -5.0°C, can be above -3.0°C, can be above -1.0°C, can be above 0°C (for example, greater than 0.0°C), can be above 1.0°C, and can be above 3.0°C (for example, greater than 4.0°C).

[0187] In the technology disclosed herein, the Tg of the adhesive (layer) can be obtained by dynamic viscoelasticity measurement. Specifically, by overlapping a plurality of adhesive layers (adhesive sheets in the case of no substrate adhesive sheet) as the object of measurement, an adhesive layer with a thickness of about 2 mm is made. The adhesive layer is punched into a disc-shaped sample with a diameter of 7.9 mm and clamped between parallel plates and fixed, and dynamic viscoelasticity is measured under the following conditions using a viscoelasticity testing machine (such as TA Instruments, ARES or its equivalent), and Tg is obtained by the peak temperature of the loss tangent tanδ (G'' / G'), which is the ratio of the loss modulus G' to the storage elastic modulus G'.

[0188] Measurement mode: Shear mode

[0189] Temperature range: -70℃~150℃

[0190] Heating rate: 5℃ / min

[0191] Measuring frequency: 1Hz

[0192] The measurement is also performed by the above method in the Examples described below. It should be noted that the PSA layer to be measured can be formed by applying the corresponding PSA composition in a layer and then drying or curing it.

[0193] (Biomass carbon ratio)

[0194] In some embodiments, the adhesive layer contains a biomass-derived material, and its biomass-to-carbon ratio (also known as bio-based ratio) can be above a specified value. The biomass-to-carbon ratio of the adhesive layer is, for example, above 1%, above 10%, preferably above 30%, and more preferably above 50%. A high biomass-to-carbon ratio of the adhesive indicates that less fossil resource materials, such as petroleum, are used. In this viewpoint, the higher the biomass-to-carbon ratio of the adhesive, the more preferred. For example, the biomass-to-carbon ratio of the adhesive layer can be above 55%, above 60%, above 70%, above 75%, above 80%, or above 80%. The upper limit of the biomass-to-carbon ratio is defined as 100%, but can be below 99%. From the perspective of material availability, it can be below 95%, or below 90%. From the perspective of easily achieving good adhesive properties, in some embodiments, the biomass-to-carbon ratio of the adhesive layer can be, for example, below 90%, below 85%, below 80%, below 75%, below 70%, or below 65%.

[0195] <Base Material>

[0196] In the form of a single-sided adhesive or double-sided adhesive sheet with a substrate, the adhesive sheet disclosed herein can be a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or a composite thereof as a substrate supporting (lining) the adhesive layer. Examples of paper include Japanese paper, kraft paper, glassine paper, high-quality paper, synthetic paper, and surface-coated paper. Examples of cloth include woven fabrics and non-woven fabrics obtained by spinning various fibrous materials alone or in blends. Examples of the above-mentioned 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 foam sheets include foamed polyolefin sheets, foamed polyurethane sheets, and foamed chloroprene rubber sheets. Examples of metal foil include aluminum foil and copper foil. It should be noted that the substrate supporting the adhesive layer is also referred to as a substrate layer in the adhesive sheet.

[0197] The substrate may be formed of a biomass-derived material or a non-biomass-derived material. From the perspective of producing a PSA sheet that reduces dependence on fossil resource materials, a biomass-derived substrate material (typically a resin film) is preferably used.

[0198] In addition, the base material can also be formed using recyclable materials, recycled materials (also referred to as regenerated materials). As the regenerated material, a resin film is preferably used. Since the resin film (for example, a polyester film such as a PET film) can be reused, regardless of whether or not plant-derived materials are used, continuous reproduction can be carried out by reusing the used resin film, and the environmental load can be reduced. Such reusable resin films and recycled resin films are also referred to as regenerated films. The above-mentioned regenerated materials (for example, regenerated films) can be formed from materials derived from biomass, or they can be formed from materials not derived from biomass.

[0199] As the base material constituting the adhesive sheet with a base material, a base material containing a resin film as a base film can be preferably used. The above-mentioned base film is typically a (non-dependent) member that can independently maintain a shape. The base material in the technology disclosed herein can be substantially composed of such a base film. Alternatively, the above-mentioned base material can also include an auxiliary layer in addition to the above-mentioned base film. As examples of the above-mentioned auxiliary layer, a colored layer, a reflective layer, a primer layer, an antistatic layer, etc. arranged on the surface of the above-mentioned base film can be listed.

[0200] The resin film is a film containing a resin material as its main component (e.g., a component comprising greater than 50% by weight of the resin film). Examples of resin films include: polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; 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; fluorine-containing resin 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 these, polyester films are preferred from the perspective of operability and processability, with PET films being particularly preferred.

[0201] It should be noted that, in this specification, "resin film" is typically a non-porous sheet, which is a concept different from so-called non-woven fabrics and woven fabrics (in other words, a concept other than non-woven fabrics and woven fabrics). The above-mentioned resin film can be any one of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, such a resin film can be non-foamed. Here, a non-foamed resin film refers to a resin film that has not been intentionally treated to form a foam body. Specifically, the non-foamed resin film can be a resin film having a foaming ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).

[0202] The above-mentioned base material (e.g., resin film) may be mixed with various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, etc., as needed. The mixing ratio of each additive may be less than about 30% by weight (e.g., less than about 20% by weight, typically less than about 10% by weight).

[0203] The above-mentioned substrate (e.g., resin film) can be a single-layer structure, or can have a multilayer structure of two, three, or more layers. From the viewpoint of shape stability, the substrate is preferably a single-layer structure. In the case of a multilayer structure, it is preferred that at least one layer (preferably all layers) is a layer having a continuous structure of the above-mentioned resin (e.g., polyester resin). The manufacturing method of the substrate (typically a resin film) can appropriately adopt a conventionally known method without particular limitation. For example, conventionally known film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calendering roll molding can be appropriately adopted.

[0204] The surface of the substrate may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and primer application. Such surface treatments may be used to improve the adhesion between the substrate and the adhesive layer, in other words, to enhance the anchoring properties of the adhesive layer to the substrate.

[0205] In addition, when the technology disclosed herein is implemented in the form of a single-sided adhesive sheet with a substrate, a release treatment can be applied to the back of the substrate as needed. The release treatment can be, for example, a process in which a conventional silicone, long-chain alkyl, or fluorine-containing release agent is applied in the form of a film typically having a thickness of about 0.01 μm to about 1 μm (for example, 0.01 μm to 0.1 μm). By implementing this release treatment, it is possible to achieve an effect such as facilitating the unwinding of a roll of the adhesive sheet.

[0206] In the adhesive sheet of the mode comprising substrate, the thickness of the substrate is not particularly limited. From the viewpoint of avoiding the adhesive sheet from becoming too thick, the thickness of the substrate can be, for example, less than about 200 μm, preferably less than about 150 μm, more preferably less than about 100 μm. According to the purpose of use and the mode of use of the adhesive sheet, the thickness of the substrate can be less than about 70 μm, or less than about 50 μm, or less than about 30 μm (for example, less than about 25 μm). In some ways, the thickness of the substrate can be less than about 20 μm, or less than about 15 μm, or less than about 10 μm (for example, less than about 5 μm). By reducing the thickness of the substrate, even if the total thickness of the adhesive sheet is the same, the thickness of the adhesive layer can be further increased. It is advantageous to consider it from the viewpoint of improving the adhesion to the adherend and the substrate. The lower limit of the substrate is not particularly limited. From the perspective of the handleability (processability) and processability of the adhesive sheet, the thickness of the substrate is generally about 0.5 μm or greater (e.g., 1 μm or greater), preferably about 2 μm or greater, for example, about 6 μm or greater. In some embodiments, the thickness of the substrate can be about 15 μm or greater, or about 25 μm or greater.

[0207] <Release liner>

[0208] In the technology disclosed herein, a release liner can be used when forming an adhesive layer, making an adhesive sheet, storing, circulating, or shaping the adhesive sheet before use. There are no particular restrictions on the release liner, 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 can be used; a release liner comprising a fluoropolymer (polytetrafluoroethylene, etc.); etc. The above-mentioned release treatment layer can be formed by surface-treating the above-mentioned liner substrate with a release treatment agent such as an organosilicon, a long-chain alkyl, a fluorine-containing type, or molybdenum sulfide. As the liner substrate, as with the substrate of the aforementioned adhesive sheet, a substrate formed from a biomass material or a recycled material (recycled film, etc.) can be preferably used.

[0209] <Total Thickness of PSA Sheet>

[0210] The total thickness of the adhesive sheet disclosed herein (comprising an adhesive layer, and may further comprise a substrate layer, but excluding 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, may be about 300 μm or less, and from the viewpoint of thinning, about 200 μm or less is appropriate, and may be about 150 μm or less (for example, about 100 μm or less). In some embodiments, the thickness of the adhesive sheet may be about 50 μm or less, for example, about 35 μm or less, about 30 μm or less, about 25 μm or less, or about 22 μm or less. The lower limit of the thickness of the adhesive sheet is, for example, 0.1 μm or more (for example, 0.5 μm or more), and about 3 μm or more is appropriate, preferably about 10 μm or more, more preferably about 15 μm or more, or about 18 μm or more. An adhesive sheet having a thickness above a specified value is easy to obtain adhesion to an adherend, and further, has a tendency to be excellent in operability. In addition, in a PSA sheet without a substrate, the thickness of the PSA layer is the total thickness of the PSA sheet.

[0211] <Properties of the Adhesive Sheet>

[0212] Although there is no particular restriction, in some embodiments, the 180-degree peel strength of the adhesive sheet to the stainless steel plate (adhesion to SUS) is preferably about 10N / 20mm or more. An adhesive sheet that exhibits such adhesion to SUS can exhibit excellent adhesiveness. In some preferred embodiments, the above-mentioned adhesion to SUS can be about 12N / 20mm or more, about 14N / 20mm or more, or 16N / 20mm or more (for example, 17N / 20mm or more). There is no particular restriction on the upper limit of the above-mentioned adhesion to SUS. From the perspective of taking into account other adhesive properties such as cohesion, it can generally be, for example, about 50N / 20mm or less. The above-mentioned adhesion to SUS is measured as follows: using a SUS plate as the adherend, the measurement is carried out under the conditions of a pulling speed of 300mm / min and a peeling angle of 180 degrees under a measurement environment of 23°C and 50%RH. More specifically, the measurement is carried out using the method described in the examples described later.

[0213] In addition, in some embodiments, the 180-degree peel strength (high-temperature adhesion) of the adhesive sheet to the stainless steel plate at 65°C is preferably greater than about 4.5N / 20mm. Adhesive sheets that exhibit such high-temperature adhesion tend to have excellent high-temperature properties and can exhibit high adhesive reliability even when used in a high-temperature environment. In some preferred embodiments, the above-mentioned high-temperature adhesion can be greater than about 5.0N / 20mm, greater than about 5.5N / 20mm, or greater than 6.0N / 20mm. There is no particular limit to the upper limit of the above-mentioned high-temperature adhesion. From the perspective of taking into account other adhesive properties such as cohesion, it can generally be, for example, less than about 15N / 20mm, or less than about 10N / 20mm. The above-mentioned high-temperature adhesion is measured as follows: using a SUS plate as the adherend, the measurement is carried out under the conditions of a pulling speed of 300 mm / min and a peeling angle of 180 degrees under a measurement environment of 65°C. More specifically, the measurement is carried out using the method described in the examples described below.

[0214] In addition, although not particularly limited, in some ways, the rough surface adhesive force measured by the method described in the embodiment described later of the adhesive sheet is preferably about 1.0N / 20mm or more. The adhesive sheet showing such rough surface adhesive force can play good adhesiveness to the rough surface of various adherends, so it can be used as an adhesive means with good adhesive reliability. In some preferred embodiments, the above-mentioned rough surface adhesive force is about 2.0N / 20mm or more, more preferably about 2.5N / 20mm or more, further preferably about 3.0N / 20mm or more, particularly preferably about 3.5N / 20mm or more (for example, 4.0N / 20mm or more). The upper limit of the above-mentioned rough surface adhesive force is not particularly limited, and from the viewpoint of taking into account other adhesive properties such as cohesion, it can be usually for example about 10N / 20mm or less.

[0215] In some embodiments, the adhesive sheet includes a material from biomass, and its biomass carbon ratio (also referred to as bio-based degree) can be above a specified value. The biomass carbon ratio of the adhesive sheet is, for example, above 1%, can be above 10%, preferably above 30%, and more preferably above 50%. A high biomass carbon ratio of the adhesive sheet indicates that the amount of fossil resource materials represented by petroleum is small. In this viewpoint, the higher the biomass carbon ratio of the adhesive sheet, the more preferred. For example, the biomass carbon ratio of the adhesive sheet can be above 55%, can be above 60%, can be above 70%, can be above 75%, can be above 80%, and can be greater than 80%. The upper limit of the biomass carbon ratio is defined as 100%, can be below 99%, and from the perspective of the availability of the material, can be below 95%, or can be below 90%. From the perspective of easily exerting good adhesive properties, in some embodiments, the biomass carbon ratio of the adhesive sheet can be, for example, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less.

[0216] <Purpose>

[0217] The use of the adhesive sheet disclosed herein is not particularly limited and can be used for various purposes. The adhesive sheet disclosed herein has an adhesive that takes into account both high temperature properties and flexibility, and also has high adhesive strength. Therefore, it is sometimes used in high temperature environments. In various uses where flexibility is desired, it can be satisfactorily used as an adhesive means with good adhesive reliability for fixing various components. For example, it can be preferably used for fixing components in electronic devices such as various portable electronic devices. For example, the component fixation in portable electronic devices performed using an adhesive sheet is usually small due to limitations such as size and weight. The adhesive sheet used for this purpose needs to have an adhesive strength that can achieve good fixation even in a small area. From the requirements of high functionality, lightweight and miniaturization, its required performance is a higher level. In particular, portable electronic devices with touch panel displays, represented by smart phones, are being developed from the perspective of miniaturization and thinning of the product itself, and from the perspective of visual recognition and operability of the display. Large screens are being developed. Due to its unique situation, the adhesive used requires adhesive fixing performance under more stringent conditions. According to the adhesive sheet disclosed herein, when used for the portable electronic device as described above, excellent adhesive reliability can be achieved. In addition, electronic devices such as portable electronic devices are sometimes used under high temperature environment, and in addition, their inner space sometimes has heat because of the heating of electronic components. The adhesive disclosed here has good high temperature characteristics by containing the acrylic polymer copolymerized with 2-octyl acrylate, so from this point of view, it is also preferably applied to electronic devices such as portable electronic devices. In addition, the adhesive sheets of some preferred modes have good rough surface adhesion, so in various applications, the mode on the adherend with rough surface such as being pasted on foam material, mesh material, graphite, metal or resin having implemented roughening treatment is satisfactorily used. For example, owing to constituting the member of electronic devices such as portable electronic devices comprising the material with rough surface (for example, foam material, mesh material, graphite, metal and resin having implemented roughening treatment), the adhesive sheet with good rough surface adhesion in such applications is suitable.

[0218] Non-limiting examples of the portable electronic devices include: mobile phones, smartphones, tablet personal computers, notebook personal computers, various wearable devices (e.g., wrist-worn devices such as watches, modular devices worn on a part of the body with a clip, a strap, etc., eyewear devices including glasses (monocular, binocular, and also helmet-type), clothing devices such as accessories worn on shirts, socks, hats, etc., and ear-worn devices such as headphones), digital cameras, digital video cameras, audio equipment (portable music players, voice recorders, etc.), calculators (desktop calculators, etc.), portable gaming devices, electronic dictionaries, electronic organizers, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. It should be noted that in this specification, "portable" is not sufficiently interpreted as simply being portable; it essentially means having a level of portability that can be carried relatively easily by an individual (a standard adult). Examples of the electronic devices include personal computers (desktop, notebook, tablet, etc.), televisions, etc. These may include built-in display devices (display elements) such as liquid crystal and organic EL.

[0219] Although not particularly limited, in some embodiments, the PSA sheet is preferably used in electronic devices that include various light sources such as LEDs (light-emitting diodes) or light-emitting elements such as self-luminous organic ELs. For example, it can be preferably used in electronic devices (typically portable electronic devices) that include organic EL displays or liquid crystal displays.

[0220] Figure 4 Schematically illustrates an example of a portable electronic device (smartphone) using the adhesive sheet disclosed herein. Figure 4 As shown, a battery (heating element) 540 is built into the interior of the housing 520 of the portable electronic device 500. In addition, the portable electronic device 500 is 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) for fixing the components constituting the portable electronic device 500. It should be noted that the portable electronic device 500 has a touch panel 570 that also functions as an input unit and a display unit. The adhesive sheet disclosed herein is preferably used as a constituent element (component bonding means) of the portable electronic device as described above.

[0221] Furthermore, in some embodiments, the PSA sheet disclosed herein may include an PSA layer comprising an acrylic polymer having a high biomass carbon ratio. Therefore, by being used as a substitute for conventional acrylic adhesives (i.e., acrylic adhesives having a low biomass carbon ratio) in various applications where such adhesives are used, it can help reduce dependence on fossil resource materials. The PSA sheet disclosed herein can be preferably used as a PSA sheet that reduces dependence on fossil resource materials.

[0222] The matters disclosed in this specification include the following.

[0223] [1] A portable electronic device, wherein a pressure-sensitive adhesive sheet is bonded to a member constituting the portable electronic device, the pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer comprising an acrylic polymer, the acrylic polymer comprising 2-octyl acrylate as a monomer component, the monomer component of the acrylic polymer comprising greater than 0% by weight and less than or equal to 20% by weight of an alkyl (meth)acrylate other than 2-octyl acrylate, and the pressure-sensitive adhesive layer further comprising a tackifier.

[0224] [2] The portable electronic device according to [1], wherein the other (meth)acrylate alkyl ester comprises a alkyl ester having the formula: CH2=C(R 1 )COOR 2 (Meth) acrylate represented by

[0225] (In the above formula, R 1 is a hydrogen atom or a methyl group, R 2 is a chain alkyl group having 1 to 6 carbon atoms).

[0226] [3] The portable electronic device according to [1] or [2] above, wherein the other alkyl (meth)acrylate comprises an alkyl (meth)acrylate having a linear alkyl group.

[0227] [4] The portable electronic device according to any one of [1] to [3] above, wherein the tackifier comprises at least one selected from the group consisting of a rosin-based tackifying resin, a terpene-based tackifying resin, and an acrylic oligomer.

[0228] [5] The portable electronic device according to any one of [1] to [4] above, wherein the tackifier contains a tackifier resin having a softening point of 100° C. or higher.

[0229] [6] The portable electronic device according to any one of [1] to [5] above, wherein the adhesive composition for forming the adhesive layer contains a crosslinking agent.

[0230] [7] The portable electronic device according to any one of [1] to [6] above, wherein the acrylic polymer has a weight average molecular weight of 400,000 or more.

[0231] [8] A portable electronic device according to any one of [1] to [7] above, wherein the glass transition temperature of the adhesive layer is 10°C or less, wherein the glass transition temperature of the adhesive layer refers to the glass transition temperature obtained from the peak temperature of tan δ in dynamic viscoelasticity measurement.

[0232] [9] The portable electronic device according to any one of [1] to [8] above, wherein the adhesive sheet has a 180-degree peel strength to a stainless steel plate of 10 N / 20 mm or more.

[0233]

[11] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising an acrylic polymer, the acrylic polymer comprising 2-octyl acrylate as a monomer component, the monomer component of the acrylic polymer comprising greater than 0 wt % and less than 20 wt % of an alkyl (meth)acrylate other than 2-octyl acrylate, and the pressure-sensitive adhesive layer further comprising a tackifier.

[0234]

[12] The adhesive sheet according to

[11] above, wherein the other (meth)acrylate alkyl ester comprises a alkyl ester represented by the formula: CH2=C(R 1 )COOR 2 (Meth) alkyl acrylate represented by (in the above formula, R 1 is a hydrogen atom or a methyl group, R 2 is a chain alkyl group having 1 to 6 carbon atoms).

[0235]

[13] The pressure-sensitive adhesive sheet according to

[11] or

[12] above, wherein the other alkyl (meth)acrylate comprises an alkyl (meth)acrylate having a linear alkyl group.

[0236]

[14] The adhesive sheet according to any one of

[11] to

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

[0237]

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

[11] to

[14] above, wherein the tackifier comprises a tackifying resin having a softening point of 100° C. or higher.

[0238]

[16] The adhesive sheet according to any one of

[11] to

[15] above, wherein the adhesive composition for forming the adhesive layer contains a crosslinking agent.

[0239]

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

[11] to

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

[0240]

[18] The adhesive sheet according to any one of

[11] to

[17] above, wherein the glass transition temperature of the adhesive layer is 10°C or lower, wherein the glass transition temperature of the adhesive layer refers to the glass transition temperature obtained from the peak temperature of tan δ in dynamic viscoelasticity measurement.

[0241]

[19] The adhesive sheet according to any one of

[11] to

[18] above, wherein the adhesive sheet has a 180-degree peel strength against a stainless steel plate of 10 N / 20 mm or more.

[0242]

[20] The adhesive sheet according to any one of

[11] to

[19] above, wherein the adhesive sheet is used for fixing components in electronic devices.

[0243]

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

[11] to

[20] above.

[0244] Example

[0245] Hereinafter, some embodiments of the present invention will be described, but it is not intended to limit the present invention to the contents shown in these embodiments. It should be noted that, unless otherwise specified, in the following description, "parts" and "%" are by weight.

[0246] <Example 1>

[0247] (Synthesis of Acrylic Polymer)

[0248] In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser, and a dropping funnel, 85 parts of 2-octyl acrylate (2OcA) as monomer components, 10 parts of n-butyl acrylate (BA), and 5 parts of acrylic acid (AA) and ethyl acetate as a polymerization solvent were added, and stirred for 2 hours while introducing nitrogen. By this operation, oxygen in the polymerization system was removed, and then 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator. Solution polymerization was carried out at 60°C to 70°C for 8 hours to obtain a solution of an acrylic polymer. The weight average molecular weight (Mw) of the acrylic polymer was 880,000, and the dispersity (Mw / Mn) was 5.5. It should be noted that the above-mentioned 2OcA is a compound synthesized using 2-octanol from biomass and has an alkyl group from biomass at the ester end.

[0249] (Preparation of Adhesive Composition)

[0250] To the acrylic polymer solution obtained above, 15 parts of a terpene-phenol resin (trade name "YS Polystar T-115", manufactured by Yasuhara Chemical Co., Ltd., softening point of approximately 115°C, hydroxyl value of 30 mgKOH / g to 60 mgKOH / g) as a tackifying resin, 2 parts (based on solid content) of an isocyanate crosslinking agent (trade name "Takenate D-101E", manufactured by Mitsui Chemicals, Inc.), and 0.01 part of an epoxy crosslinking agent (trade name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Co., Ltd.) were added, with respect to 100 parts of the acrylic polymer contained in the solution, and the mixture was stirred and mixed to prepare the adhesive composition of this example.

[0251] (Production of Adhesive Sheet)

[0252] The obtained adhesive composition was applied to the release surface of a polyester release film (trade name "DIAFOIL MRF", manufactured by Mitsubishi Chemical Corporation) with a thickness of 38 μm and dried at 100°C for 2 minutes to form an adhesive layer with a thickness of 20 μm. The release surface of a polyester release film (trade name "DIAFOIL MRF", thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) with a thickness of 25 μm was attached to the adhesive layer. By doing so, a substrate-free double-sided adhesive sheet with a thickness of 20 μm, the two sides of which were protected by the above-mentioned two polyester release films, was obtained. The glass transition temperature (Tg) of the above-mentioned adhesive layer is -5.9°C, and the biobase (determined based on ASTM D6866) is 60%.

[0253] <Examples 2 to 7 and Comparative Examples 1 to 5>

[0254] Each PSA composition was prepared in the same manner as in Example 1, except that the monomer composition of the acrylic polymer, the type and amount of the tackifier, and the type and amount of the crosslinking agent were changed as shown in Table 1. Using the resulting PSA compositions, each substrate-free double-sided PSA sheet (20 μm thick) was produced in the same manner as in Example 1. In Table 1, 2EHA stands for 2-ethylhexyl acrylate.

[0255] An acrylic oligomer prepared by the following method was used. Specifically, 95 parts of cyclohexyl methacrylate (CHMA), 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent were added to a reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser, and a dropping funnel. The mixture was stirred for 1 hour in a nitrogen stream to remove oxygen from the polymerization system. The temperature was then raised to 85°C and the reaction was allowed to proceed for 5 hours to obtain an acrylic oligomer with a solids concentration of 50%. The resulting acrylic oligomer had an Mw of 3600.

[0256] <Evaluation Method>

[0257] [Adhesion to SUS]

[0258] A 50μm-thick PET film was attached to one adhesive surface of a double-sided adhesive sheet for backing, and then cut into 20mm-wide and 100mm-long dimensions to prepare a test sample. Under a 23°C, 50% RH environment, the other adhesive surface of the test sample was pressed against the surface of a stainless steel plate (SUS304BA plate) cleaned with ethyl acetate using a 2kg roller, which was moved back and forth once. This was left in the same environment for 30 minutes, and then the peel strength (adhesion to SUS) [N / 20mm] was measured using a universal tensile-compression tester according to JIS Z0237:2000 at a pulling speed of 300mm / min and a peel angle of 180 degrees.

[0259] [High temperature adhesion]

[0260] A 50μm-thick PET film was attached to one adhesive surface of a double-sided adhesive sheet for backing, and the sample was cut into a 20mm wide x 100mm long size. Under a 23°C, 50% RH environment, the other adhesive surface of the sample was press-bonded to the surface of a stainless steel plate (SUS304BA plate) cleaned with ethyl acetate using a 2kg roller moving back and forth once. The sample was then left at 65°C for 30 minutes. The peel strength (high-temperature adhesion) [N / 20mm] was then measured using a universal tensile-compression tester in accordance with JIS Z0237:2000 at a pulling speed of 300mm / min and a peel angle of 180 degrees.

[0261] [Adhesion to rough surface]

[0262] A PET film with a thickness of 50 μm was pasted on one adhesive surface of the adhesive sheet (double-sided adhesive sheet) for lining, and the film was cut into a size of 20 mm in width and 100 mm in length to prepare a measurement sample. In addition, as an adherend, an adherend obtained by fixing sandpaper (manufactured by Riken Corundum Co., Ltd., with a particle size of 320) on a stainless steel plate (SUS304BA plate) was prepared. Under an environment of 23°C and 50% RH, a 2 kg roller was moved back and forth once to press the other adhesive surface of the measurement sample onto the sandpaper surface (rough surface) of the adherend. It was placed under the same environment for 72 hours, and then a universal tensile compression testing machine was used to measure the peel strength (rough surface adhesion) [N / 20mm] under the conditions of a pulling speed of 300 mm / min and a peeling angle of 180 degrees according to JIS Z 0237: 2000.

[0263] It should be noted that in the above-mentioned adhesive strength measurements, a universal tensile-compression tester, "Tension-Compression Tester, TG-1 kN" manufactured by Minebea, or its equivalent, was used. When measuring single-sided PSA sheets, a PET film backing is not required. However, a PET film backing may be used when the substrate thickness is thin (e.g., 25 μm or less).

[0264] Table 1 shows the summary and evaluation results of the PSA sheet of each example.

[0265]

[0266] As shown in Table 1, the adhesives of Examples 1 to 7 contain an acrylic polymer and a tackifier, wherein the acrylic polymer contains 2OcA as a monomer component and contains other (meth) alkyl acrylates different from 2OcA at a ratio of 20% or less. The adhesives of Examples 1 to 7 have good high-temperature adhesion and flexibility (adhesive Tg). In contrast, in Comparative Examples 1 and 2, in which the copolymerization ratio of other (meth) alkyl acrylates is greater than 20%, the high-temperature adhesion is lower than that of the above-mentioned examples. In addition, in Comparative Example 3, in which no other (meth) alkyl acrylate is used, the adhesive Tg is higher than that of the above-mentioned examples, and good flexibility is not obtained (especially refer to the comparison results with Examples 4 and 7). In addition, in Comparative Examples 4 to 5, in which no tackifier is used, the crosslinking degree is reduced to make the adhesive soft, but the adhesion is reduced and rough surface adhesion is not obtained. It should be noted that, as can be seen from the comparison of Examples 1 and 3, Examples 4 and 7, Comparative Examples 1 and 2, and Comparative Examples 4 and 5, when copolymerizing BA having a higher homopolymer Tg than 2EHA, the Tg of the adhesive tends to decrease. This is presumably because copolymerization with BA having a side chain structure more different from that of 2OcA further reduces the crystallinity of the side chains derived from 2OcA, thereby increasing the free volume between polymer molecules.

[0267] The above results indicate that a PSA sheet having a PSA layer comprising an acrylic polymer and a tackifier, wherein the acrylic polymer comprises 2OcA as a monomer component and contains 20% or less of an alkyl (meth)acrylate different from 2OcA, can provide a PSA layer having excellent flexibility while maintaining high-temperature properties, thereby further improving adhesive strength.

[0268] While specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples described above.

[0269] Label Description

[0270] 1, 2, 3 adhesive sheets

[0271] 10 Support substrate

[0272] 10A first page

[0273] 10B Second side (back)

[0274] 21 Adhesive layer (first adhesive layer)

[0275] 21A adhesive surface (first adhesive surface)

[0276] 21B Second adhesive surface

[0277] 22 Adhesive layer (second adhesive layer)

[0278] 22A adhesive surface (second adhesive surface)

[0279] 31, 32 release liner

[0280] 100, 200, 300 adhesive sheets with release liner

Claims

1. An adhesive sheet, wherein: The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer containing an acrylic polymer containing 2-octyl acrylate as a monomer component. The monomer component of the acrylic polymer contains more than 0 wt % and less than or equal to 20 wt % of other alkyl (meth)acrylates other than 2-octyl acrylate, The adhesive layer further comprises a tackifier.

2. The adhesive sheet according to claim 1, wherein The other (meth)acrylic acid alkyl esters include those represented by the formula: CH2=C(R 1 )COOR 2 (Meth) acrylate represented by (In the above formula, R 1 is a hydrogen atom or a methyl group, R 2 is a chain alkyl group having 1 to 6 carbon atoms).

3. The adhesive sheet according to claim 1 or 2, wherein The other alkyl (meth)acrylates include alkyl (meth)acrylates having a linear alkyl group.

4. The adhesive sheet according to claim 1 or 2, wherein The tackifier comprises at least one selected from the group consisting of rosin-based tackifying resins, terpene-based tackifying resins, and acrylic oligomers.

5. The adhesive sheet according to claim 1 or 2, wherein The tackifier includes a tackifying resin having a softening point of 100° C. or higher.

6. The adhesive sheet according to claim 1 or 2, wherein The adhesive composition for forming the adhesive layer includes a cross-linking agent.

7. The adhesive sheet according to claim 1 or 2, wherein The acrylic polymer has a weight average molecular weight of 400,000 or more.

8. The adhesive sheet according to claim 1 or 2, wherein The adhesive sheet has a 180-degree peel strength against a stainless steel plate of 10 N / 20 mm or greater.

9. The adhesive sheet according to claim 1 or 2, wherein The adhesive sheet is used for fixing components in electronic devices.

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