WO2024161911A1 - 粘着シート - Google Patents

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Publication number
WO2024161911A1
WO2024161911A1 PCT/JP2024/000153 JP2024000153W WO2024161911A1 WO 2024161911 A1 WO2024161911 A1 WO 2024161911A1 JP 2024000153 W JP2024000153 W JP 2024000153W WO 2024161911 A1 WO2024161911 A1 WO 2024161911A1
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acrylate
meth
adhesive
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PCT/JP2024/000153
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English (en)
French (fr)
Japanese (ja)
Inventor
徹 田上
栄一 井本
健一 山元
舜 名倉
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日東電工株式会社
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Priority to CN202480006490.8A priority Critical patent/CN120435529A/zh
Publication of WO2024161911A1 publication Critical patent/WO2024161911A1/ja

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/06—Non-macromolecular additives organic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/08—Macromolecular additives
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09J133/08—Homopolymers or copolymers of acrylic acid esters
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]

Definitions

  • the present invention relates to a pressure-sensitive adhesive sheet.
  • 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.
  • adhesives also called pressure-sensitive adhesives; the same applies below
  • adhesives are in a soft solid (viscoelastic) state at temperatures near room temperature, and have the property of adhering to an adherend when pressure is applied.
  • adhesives are widely used in various industrial fields, from portable electronic devices such as smartphones and home appliances to automobiles and office automation equipment, typically in the form of adhesive sheets containing an adhesive layer, for purposes such as joining parts and protecting surfaces.
  • Examples of technical documents related to adhesive sheets include Patent Documents 1 and 2.
  • Patent Documents 1 and 2 describe adhesives containing acrylic polymers polymerized using 2-octyl acrylate as a monomer component.
  • 2-octyl acrylate synthesized using 2-octanol can be obtained from biomass-derived materials, and therefore its use as an adhesive material that can reduce dependency on fossil resource-based materials is being considered.
  • the adhesive properties peel adhesion and shear strength
  • adhesives composed of polymers mainly composed of 2-octyl acrylate (2-octyl acrylate-based polymers) as proposed in Patent Document 1 tend to have a relatively high glass transition temperature and low flexibility. With such adhesives, it is difficult to obtain high adhesive strength due to their low flexibility, and the inventors' investigations have revealed that, for example, the adhesive strength on rough surfaces is insufficient.
  • Patent Document 2 tack, shear strength and adhesive strength were evaluated for an adhesive containing a copolymer of monomer components including 650 g of 2-octyl acrylate, 220 g of isobutyl acrylate and 100 g of methyl acrylate.
  • the properties based on 2-octyl acrylate tend to decrease.
  • high-temperature properties such as high-temperature adhesive strength
  • the present invention relates to improvements in adhesives that contain acrylic polymers synthesized using 2-octyl acrylate, and aims to provide an adhesive sheet that contains an acrylic polymer copolymerized with 2-octyl acrylate, has a flexible adhesive layer while retaining high-temperature properties, and can further improve adhesive strength.
  • an adhesive sheet having an adhesive layer includes an acrylic polymer containing 2-octyl acrylate as a monomer component.
  • the monomer component of the acrylic polymer includes more than 0% by weight and 20% by weight or less of another alkyl (meth)acrylate other than 2-octyl acrylate.
  • the adhesive layer further includes a tackifier. According to the above configuration, the flexibility of the adhesive containing the acrylic polymer synthesized using 2-octyl acrylate is improved.
  • the reasons for this which is not particularly limited, is that by copolymerizing the acrylic polymer with another alkyl (meth)acrylate other than 2-octyl acrylate, the side chain crystallinity of the acrylic polymer is reduced and the glass transition temperature of the adhesive is lowered.
  • the copolymerization ratio of the other alkyl (meth)acrylate is limited to 20% by weight or less, a sufficient amount of 2-octyl acrylate can be copolymerized, and the resulting adhesive can maintain high temperature properties.
  • the adhesive contains a tackifier, which can increase the adhesive strength.
  • the adhesive of the above configuration can have good flexibility while maintaining high-temperature properties, and can further improve the adhesive strength.
  • the other alkyl (meth)acrylate includes an alkyl (meth)acrylate having a linear alkyl group.
  • the tackifier preferably contains at least one selected from rosin-based tackifier resins, terpene-based tackifier resins, and acrylic oligomers.
  • the tackifier includes a tackifier resin having a softening point of 100°C or higher. By using a tackifier resin having the above softening point, it is easier to improve high-temperature adhesive strength.
  • the adhesive composition for forming the adhesive layer contains a crosslinking agent.
  • a crosslinking agent By using a crosslinking agent, the cohesive strength of the adhesive can be appropriately increased.
  • the weight average molecular weight (Mw) of the acrylic polymer is 400,000 or more.
  • Mw weight average molecular weight
  • the high-molecular-weight acrylic polymer in combination with a tackifier it is possible to preferably achieve both good high-temperature properties and rough-surface adhesion.
  • the adhesive sheet has a 180-degree peel strength against a stainless steel plate (adhesive strength against SUS) of 10 N/20 mm or more.
  • An adhesive sheet having the above-mentioned adhesive strength against SUS can exhibit excellent adhesive strength to the adherend.
  • the adhesive sheet disclosed herein has an adhesive that combines high-temperature properties with flexibility, and further has high adhesive strength, so it may be used in high-temperature environments and can be preferably used as an adhesive means with good adhesive reliability in various applications where flexibility is desirable. For example, it is suitable for fixing components in electronic devices including home appliances, office automation equipment, and mobile electronic devices such as smartphones. As described above, this specification provides an electronic device that uses any of the adhesive sheets disclosed herein, in other words, an electronic device that includes the adhesive sheet.
  • FIG. 1 is a cross-sectional view illustrating a schematic configuration of a pressure-sensitive adhesive sheet according to an embodiment.
  • FIG. 4 is a cross-sectional view illustrating a schematic configuration of a pressure-sensitive adhesive sheet according to another embodiment.
  • FIG. 4 is a cross-sectional view illustrating a schematic configuration of a pressure-sensitive adhesive sheet according to another embodiment.
  • 1 is a front view showing a schematic diagram of an example of a portable electronic device including an adhesive sheet.
  • the term "adhesive” refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range near room temperature and that has the property of easily adhering to an adherend by pressure, as described above.
  • the adhesive referred to here may generally be a material that has a complex tensile modulus E * (1Hz) ⁇ 107 dyne/ cm2 (typically, a material that has the above property at 25°C), as defined in "C. A. Dahlquist, "Adhesion: Fundamentals and Practice", McLaren & Sons, (1966) P. 143".
  • biomass-derived carbon means carbon (renewable carbon) derived from biomass materials, i.e., materials derived from renewable organic resources.
  • biomass materials typically refer to materials derived from biological resources (typically plants that perform photosynthesis) that can be reproduced sustainably in the presence of sunlight, water, and carbon dioxide. Therefore, materials derived from fossil resources that are depleted through use after mining (fossil resource-based materials) are excluded from the concept of biomass materials here.
  • the biomass carbon ratios of the acrylic polymer, adhesive layer, and adhesive sheet i.e., the proportion of biomass-derived carbon in the total carbon contained in the acrylic polymer, adhesive layer, and adhesive sheet, can be estimated from the carbon isotope content with mass number 14 measured in accordance with ASTM D6866.
  • the adhesive sheet disclosed herein is configured to include an adhesive layer.
  • the adhesive sheet may be in the form of a substrate-less double-sided adhesive sheet having, for example, a first adhesive surface constituted by one surface of the adhesive layer and a second adhesive surface constituted by the other surface of the adhesive layer.
  • the adhesive sheet disclosed herein may be in the form of a substrate-attached adhesive sheet in which the adhesive layer is laminated on one or both surfaces of a supporting substrate.
  • the supporting substrate may simply be referred to as a "substrate”.
  • the concept of the adhesive sheet here may include those referred to as adhesive tapes, adhesive labels, adhesive films, and the like.
  • the adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, it may be an adhesive sheet in the form of a processed form into various shapes.
  • the structure of an adhesive sheet according to one embodiment is shown in FIG. 1.
  • the adhesive sheet 1 is configured as a substrate-less double-sided adhesive sheet made of an adhesive layer 21.
  • the adhesive sheet 1 is used by attaching a first adhesive surface 21A, which is configured by one surface (first surface) of the adhesive layer 21, and a second adhesive surface 21B, which is configured by the other surface (second surface) of the adhesive layer 21, to different locations on an adherend.
  • the locations to which the adhesive surfaces 21A and 21B are attached may be locations on different members, or may be different locations within a single member.
  • the adhesive sheet 1 before use may be a component of an adhesive sheet with release liner 100 in a form in which the first adhesive surface 21A and the second adhesive surface 21B are protected by release liners 31 and 32, each of which has at least a release surface facing the adhesive layer 21, as shown in FIG. 1.
  • release liners 31 and 32 for example, a sheet-like substrate (liner substrate) may preferably be used in which a release layer made of a release treatment agent is provided on one side thereof, so that the one side is the release surface.
  • the release liner 32 may be omitted, and a release liner 31 may be used in which both sides are release surfaces, and the release liner 31 may be superimposed on the adhesive sheet 1 and rolled up in a spiral shape to form an adhesive sheet with a release liner in which the second adhesive surface 21B is protected by contacting the back surface of the release liner 31 (roll form).
  • the structure of an adhesive sheet according to another embodiment is shown in FIG. 2.
  • the adhesive sheet 2 is configured as a substrate-attached single-sided adhesive sheet including a sheet-like support 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 support substrate 10, that is, without the intention of separating the adhesive layer 21 from the support substrate 10.
  • 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 facing the adhesive layer 21 being the release surface.
  • the release liner 31 may be omitted, and a support substrate 10 with a second surface 10B being the release surface may be used, and the adhesive sheet 2 may be rolled up so that the adhesive surface 21A is protected by contacting the second surface (rear surface) 10B of the support substrate 10.
  • the structure of an adhesive sheet according to yet another embodiment is shown in FIG. 3.
  • the adhesive sheet 3 is configured as a substrate-attached double-sided adhesive sheet including a sheet-like support substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, a first 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.
  • the adhesive sheet 3 before use may be a component of an adhesive sheet 300 with a release liner in which the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 are protected by release liners 31, 32.
  • the release liner 32 may be omitted, and a release liner 31 with both sides being release surfaces may be used, which is superimposed on the adhesive sheet 3 and rolled up in a spiral shape to form an adhesive sheet with a release liner in which the second adhesive surface 22A is protected by contacting the back surface of the release liner 31 (roll form).
  • the first and second adhesive layers may be an adhesive layer described below, and the other adhesive layer (e.g., the second adhesive layer) may be an adhesive layer disclosed herein, or may be an adhesive layer having a different composition from the adhesive layer disclosed herein (specifically, the one adhesive layer, e.g., the first adhesive layer).
  • Such other adhesive layer may be formed, for example, from a known or conventional adhesive.
  • substrate-less double-sided adhesive sheets can be made thinner since they do not have a substrate, which can contribute to the miniaturization and space-saving of products to which the double-sided adhesive sheet is applied. Furthermore, substrate-less adhesive sheets can maximize the effect of the adhesive layer in improving adhesion to rough surfaces.
  • the adhesive layer constituting the adhesive sheet disclosed herein contains an acrylic polymer.
  • the above-mentioned adhesive layer is typically an adhesive layer having an acrylic polymer as a base polymer.
  • Such an adhesive layer is also called an acrylic adhesive layer.
  • the base polymer refers to the main component of the rubber-like polymer (polymer that exhibits rubber elasticity in a temperature range around room temperature) contained in the adhesive layer.
  • the "main component” refers to a component contained in an amount of more than 50% by weight, unless otherwise specified.
  • the following explanation of the adhesive and the components that may be contained in the adhesive layer are also applicable to the adhesive composition used to form the adhesive (layer) unless otherwise specified.
  • acrylic polymer refers to a polymer that contains, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule.
  • a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer”. Therefore, in this specification, an acrylic polymer is defined as a polymer that contains a monomer unit derived from an acrylic monomer.
  • (meth)acryloyl refers collectively to acryloyl and methacryloyl.
  • (meth)acrylate” refers collectively to acrylate and methacrylate
  • (meth)acrylic refers collectively to acrylic and methacrylic.
  • acrylic polymer a polymer of a monomer component containing 2-octyl acrylate is used.
  • Acrylic polymers polymerized using a monomer component containing 2-octyl acrylate tend to have excellent high-temperature properties (e.g. high-temperature adhesive strength) and are preferably used in applications where they may be exposed to high temperatures.
  • 2-octyl acrylate can be obtained from biomass-derived materials, so the use of 2-octyl acrylate can reduce dependency on fossil resource-based materials.
  • 2-octyl acrylate is preferably included as the main monomer of the acrylic polymer (the component that is most abundant among the monomer components), and the proportion of 2-octyl acrylate in the monomer components of the acrylic polymer may be, for example, approximately 34% by weight or more, and is appropriately 50% by weight or more (e.g., more than 50% by weight), and is preferably 60% by weight or more, more preferably 70% by weight or more, and even more preferably 75% by weight or more (e.g., more than 75% by weight), and may be 80% by weight or more, 82% by weight or more, 84% by weight or more, or 85% by weight or more.
  • the proportion of 2-octyl acrylate in the monomer components is appropriately 99% by weight or less, and may be 95% by weight or less, or may be 92% by weight or less.
  • the proportion of 2-octyl acrylate in the monomer component is 90% by weight or less, 87% by weight or less, 85% by weight or less, 80% by weight or less (e.g., less than 80% by weight), 75% by weight or less, 72% by weight or less, or 70% by weight or less.
  • the monomer component of the acrylic polymer contains more than 0% by weight and not more than 20% by weight of another alkyl (meth)acrylate different from 2-octyl acrylate. This makes it possible to improve the flexibility of the adhesive containing the acrylic polymer synthesized using 2-octyl acrylate while maintaining the high-temperature properties. It is believed that by copolymerizing the acrylic polymer with the other alkyl (meth)acrylate in the above range, the side chain crystallinity of the acrylic polymer decreases while maintaining the high-temperature properties based on the use of 2-octyl acrylate, and the glass transition temperature (Tg) of the adhesive decreases. Note that the technology disclosed herein is not limited to the above considerations. Also, by copolymerizing an appropriate amount of the other alkyl (meth)acrylate, it is easy to obtain good adhesive properties.
  • the ratio of other alkyl (meth)acrylates in the monomer components of the acrylic polymer may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), or 9% by weight or more.
  • the ratio of other alkyl (meth)acrylates 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.
  • the effect of lowering the Tg of the adhesive is more easily manifested, and the rough surface adhesion is effectively improved.
  • the effect of copolymerization of other alkyl (meth)acrylates is preferably obtained.
  • the upper limit of the ratio of other alkyl (meth)acrylates in the above-mentioned monomer components may be 15% by weight or less, or 12% by weight or less, in some preferred embodiments.
  • any alkyl (meth)acrylate other than 2-octyl acrylate can be used without any particular limitation.
  • a compound represented by the following formula (1) can be suitably used.
  • CH 2 C(R 1 )COOR 2 (1)
  • R 1 in the above formula (1) is a hydrogen atom or a methyl group.
  • R 2 is a chain alkyl group having 1 to 20 carbon atoms (excluding 2-octyl group when R 1 is a hydrogen atom).
  • alkyl (meth)acrylates mentioned above include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (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)acryl
  • alkyl (meth)acrylate either one in which the alkyl group is linear or branched can be used, but from the viewpoint of flexibility, an alkyl (meth)acrylate having a linear alkyl group is preferred. From the same viewpoint, alkyl acrylate is preferably used as the other alkyl (meth)acrylate.
  • the other alkyl (meth)acrylate is an alkyl (meth)acrylate in which R 2 in the above formula (1) is a chain alkyl group having 1 to 6 carbon atoms (hereinafter, such a range of carbon atoms may be expressed as "C 1-6 ", and an alkyl (meth)acrylate having an alkyl group in the above range of carbon atoms may be referred to as "C 1-6 alkyl (meth)acrylate” or the like).
  • C 1-6 alkyl (meth)acrylate By using a C 1-6 alkyl (meth)acrylate as the other alkyl (meth)acrylate, it is thought that the free volume between polymer molecules increases based on the difference in the side chain structure with 2-octyl acrylate, and flexibility is improved. As a result, good rough surface adhesion is easily obtained. Note that the technology disclosed herein is not limited to the above considerations.
  • a C 1-6 alkyl (meth)acrylate from the viewpoint of improving flexibility, a C 2-6 alkyl (meth)acrylate is preferable, a C 2-4 alkyl (meth)acrylate is more preferable, or a C 4-6 alkyl (meth)acrylate may also be preferably used.
  • the C 1-6 alkyl group may be either linear or branched, but from the viewpoint of flexibility, an alkyl (meth)acrylate having a C 1-6 linear alkyl group is preferred. From the same viewpoint, the use of a C 1-6 alkyl acrylate is preferred.
  • the C 1-6 alkyl (meth)acrylate may be used alone or in combination of two or more.
  • the proportion of the above C 1-6 alkyl (meth)acrylate preferably a C 2-6 alkyl (meth)acrylate, more preferably a C 2-4 alkyl (meth)acrylate or a C 4-6 alkyl (meth)acrylate, or for example a C 1-6 linear alkyl (meth)acrylate; the same applies hereinafter unless otherwise specified
  • the monomer components of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), 9% by weight or more, and in some preferred embodiments, 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, or 18% by weight or more.
  • the upper limit of the proportion of the C 1-6 alkyl (meth)acrylate in the monomer components is, in some preferred embodiments, 20% by weight or less, and may be 15% by weight or less, or may be 12% by weight or less.
  • the proportion of the C 1-6 alkyl (meth)acrylate in the other alkyl (meth)acrylates is not particularly limited, and in some embodiments is, for example, 10% by weight or more, and may be 30% by weight or more, preferably 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, and even more preferably 90% by weight or more (e.g., 95 to 100% by weight).
  • n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) are used as the other alkyl (meth)acrylate.
  • BA and 2EHA may be used alone or in combination.
  • BA or 2EHA as the other alkyl (meth)acrylate, the resulting adhesive has better flexibility and can better exhibit the effect of improving adhesion to rough surfaces.
  • the use of BA is particularly preferred.
  • the proportion of BA and/or 2EHA in the monomer components of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), 9% by weight or more, and in some preferred embodiments, 10% by weight or more, more preferably 12% by weight or more, 15% by weight or more, or 18% by weight or more.
  • 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.
  • the other alkyl (meth)acrylate may be an alkyl (meth)acrylate having a homopolymer glass transition temperature (Tg) of less than 0°C (low Tg alkyl (meth)acrylate).
  • Tg homopolymer glass transition temperature
  • the homopolymer Tg of the low Tg alkyl (meth)acrylate may be -10°C or less, or may be -20°C or less.
  • the homopolymer Tg of the low Tg alkyl (meth)acrylate is approximately -30°C or less, may be -35°C or less, may be -40°C or less, may be -45°C or less, may be -50°C or less, may be -55°C or less, may be -60°C or less, or may be -65°C or less.
  • an alkyl (meth)acrylate having a homopolymer Tg lower than the homopolymer Tg of 2-octyl acrylate may be preferably used as the low Tg alkyl (meth)acrylate.
  • the lower limit of the homopolymer Tg of the low Tg alkyl (meth)acrylate is, for example, ⁇ 80° C. or higher, suitably ⁇ 75° C. or higher, may be ⁇ 70° C. or higher, may be ⁇ 65° C. or higher, or may be ⁇ 60° C. or higher.
  • an alkyl acrylate is preferably used as the low Tg alkyl (meth)acrylate.
  • Suitable examples of the low Tg alkyl (meth)acrylate include, for example, BA and 2EHA.
  • low Tg alkyl (meth)acrylate examples include alkyl acrylates such as hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, and isononyl acrylate.
  • alkyl acrylates such as hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate, and isononyl acrylate.
  • the above low Tg alkyl (meth)acrylates can be used alone or in combination of two or more.
  • the value given in a publicly available source should be used.
  • the values given in "Polymer Handbook” (3rd ed., John Wiley & Sons, Inc., 1989) should be used. If multiple values are given in this document, the highest value should be used.
  • the mixture is then cooled to room temperature to obtain a homopolymer solution with a solids concentration of 33% by weight.
  • the homopolymer solution is then cast onto a release liner and dried to prepare a test sample (sheet-shaped homopolymer) with a thickness of approximately 2 mm.
  • the test sample was punched out into a disk with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity was measured in shear mode using a viscoelasticity tester (manufactured by TA Instruments Japan, model name "ARES") while applying a shear strain of 1 Hz frequency in the temperature range of -70°C to 150°C at a heating rate of 5°C/min.
  • the temperature corresponding to the peak temperature of tan ⁇ was taken as the Tg of the homopolymer.
  • the proportion of the low Tg alkyl (meth)acrylate in the monomer component of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 1% by weight or more, 5% by weight or more, 8% by weight or more (e.g., more than 8% by weight), or 9% by weight or more. In some preferred embodiments, the proportion of the low Tg alkyl (meth)acrylate in the 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.
  • the upper limit of the proportion of the low Tg alkyl (meth)acrylate in the monomer component may be 20% by weight or less, 15% by weight or less, or 12% by weight or less.
  • the monomer component may contain an alkyl (meth)acrylate having a biomass-derived alkyl group at the ester end (hereinafter also referred to as "biomass alkyl (meth)acrylate").
  • biomass alkyl (meth)acrylate having a biomass-derived alkyl group at the ester end
  • the biomass alkyl (meth)acrylate is not particularly limited, and may be, for example, an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived (meth)acrylic acid.
  • biomass-derived alkanols include biomass ethanol, alkanols derived from plant materials such as palm oil, palm kernel oil, coconut oil, and castor oil.
  • the biomass-derived alkanol may be linear or branched.
  • an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate used in the synthesis of an acrylic polymer.
  • the greater the number of carbon atoms in the alkanol the higher the ratio of the number of biomass-derived carbons to the total number of carbons contained in the biomass alkyl (meth)acrylate, i.e., the biomass carbon ratio of the alkyl (meth)acrylate. Therefore, in the above biomass alkyl (meth)acrylate, it is desirable that the alkyl group derived from biomass has a large number of carbon atoms in terms of reducing dependency on fossil resource-based materials.
  • the alkyl group constituting the alkyl (meth)acrylate has too many carbon atoms, it tends to be difficult to obtain adhesive properties such as adhesion, and it may also be disadvantageous in terms of productivity such as synthesis, handling, and cost.
  • an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate, it is desirable to use a material that has a good balance between adhesive properties and reduced dependency on fossil resource-based materials (more specifically, the biomass carbon ratio of the above alkyl (meth)acrylate).
  • biomass-derived 2-octyl acrylate biomass-derived 2-octyl acrylate
  • biomass 2-octyl acrylate is used as the 2-octyl acrylate.
  • biomass 2-octyl acrylate is an ester of a biomass-derived alkanol (specifically, 2-octanol) and a biomass-derived or non-biomass-derived acrylic acid, and for example, an ester of a biomass-derived alkanol and a non-biomass-derived acrylic acid can be used.
  • the 2-octyl group is biomass-derived.
  • the proportion of biomass alkyl (meth)acrylate (e.g., biomass 2-octyl acrylate) in the monomer components of the acrylic polymer is, for example, in some embodiments, 50% by weight or more (e.g., more than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 82% by weight or more, and may be 90% by weight or more.
  • the proportion of biomass alkyl (meth)acrylate in the monomer components may be 92% by weight or more, 94% by weight or more, or 96% by weight or more.
  • 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.
  • the monomer component of the acrylic polymer preferably contains a carboxyl group-containing monomer.
  • the carboxyl group-containing monomer can improve the cohesive strength based on its polarity.
  • a crosslinking agent such as an isocyanate-based or epoxy-based crosslinking agent
  • the carboxyl group of the carboxyl group-containing monomer can become the crosslinking point of the acrylic polymer.
  • the use of the carboxyl group-containing monomer can also provide better adhesion to adherends such as highly polar materials.
  • Carboxy group-containing monomers include, for example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, crotonic acid, and isocrotonic acid; and ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid.
  • the carboxy group-containing monomer may also be a monomer having a metal salt of a carboxy group (e.g., an alkali metal salt).
  • the carboxy group-containing monomer may be used alone or in combination of two or more.
  • AA and MAA are preferred as carboxy group-containing monomers.
  • AA is particularly preferred.
  • the proportion of AA in the carboxy group-containing monomer is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more.
  • the carboxy group-containing monomer is substantially composed of AA alone.
  • the proportion of the carboxyl group-containing monomer in the monomer component of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 0.5% by weight or more, and in some preferred embodiments, 1.0% by weight or more, 2.0% by weight or more, 2.5% by weight or more, 3.0% by weight or more, 3.5% by weight or more, 4.0% by weight or more, 4.5% by weight or more, or 5.0% by weight or more.
  • the amount of the carboxyl group-containing monomer is, for example, appropriate to be 20% by weight or less of the total monomer component, preferably 15% by weight or less, and more preferably 12% by weight or less. In some preferred embodiments, the amount of the carboxyl group-containing monomer may be 10% by weight or less, 8.0% by weight or less, 6.0% by weight or less, or 5.0% by weight or less. By reducing the amount of carboxyl group-containing monomer used within a certain range, it tends to be easier to obtain good flexibility and good rough surface adhesion.
  • the monomer component of the acrylic polymer may contain a functional group-containing monomer (any functional group-containing monomer) other than the carboxy group-containing monomer.
  • a functional group-containing monomer any functional group-containing monomer
  • optional functional group-containing monomers that can introduce functional groups that can serve as crosslinking base points into acrylic polymers or contribute to improving adhesive strength include hydroxyl group (OH group)-containing monomers (hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate, etc.), acid anhydride group-containing monomers, amide group-containing monomers ((meth)acrylamide, N,N-dimethyl(meth)acrylamide, etc.), amino group-containing monomers (aminoethyl (meth)
  • the content of the optional functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exerting the effect of using the optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, and is suitably 0.5% by weight or more, and may be 1% by weight or more.
  • the content of the optional functional group-containing monomer in the monomer component is suitably 40% by weight or less, and is preferably 20% by weight or less, and may be 10% by weight or less (for example, 5% by weight or less).
  • the content of the optional functional group-containing monomer in the monomer component is, for example, less than 3% by weight, may be less than 1% by weight, may be less than 0.5% by weight, may be less than 0.3% by weight, or may be less than 0.1% by weight.
  • the technology disclosed herein can be preferably implemented in an embodiment in which the monomer components of the acrylic polymer are substantially free of any functional group-containing monomer.
  • the monomer components are substantially free of monomer A (e.g., the optional functional group-containing monomer described above), this means that the monomer A is not used at least intentionally, and it is acceptable for the monomer A to be unintentionally included in an amount of, for example, about 0.01% by weight or less.
  • a hydroxyl-containing monomer may be used as the optional functional group-containing monomer.
  • the content of the hydroxyl-containing monomer is suitably about 10% by weight or less (e.g., 0.001 to 10% by weight) of the total monomer components, preferably about 5% by weight or less, and more preferably about 2% by weight or less.
  • the content of the hydroxyl-containing monomer in the monomer components may be, for example, less than 1% by weight, less than 0.5% by weight, less than 0.3% by weight, less than 0.1% by weight, or less than 0.01% by weight.
  • the monomer components of the acrylic polymer may be substantially free of a hydroxyl-containing monomer. According to the technology disclosed herein, it is possible to achieve both high temperature properties and flexibility by limiting the amount of hydroxyl-containing monomer used or by eliminating it altogether.
  • the amount of such other copolymerization components is not particularly limited and may be appropriately selected depending on the purpose and application, but from the viewpoint of properly exerting the effect of use, it is appropriate to set it to 0.05% by weight or more, and it may be 0.5% by weight or more.
  • the content of other copolymerization components in the monomer component is appropriate to be 20% by weight or less, and from the viewpoint of properly exerting the adhesive properties based on the essential monomer components, it is preferably 10% by weight or less, more preferably 8% by weight or less, and even more preferably less than 5% by weight, for example, it may be less than 3% by weight, or it may be less than 1% by weight.
  • the technology disclosed herein may also be preferably implemented in an embodiment in which the monomer component does not substantially contain other copolymerization components.
  • the acrylic polymer may contain, as another monomer component, a polyfunctional monomer having at least two polymerizable functional groups (typically radically polymerizable functional groups) having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group.
  • a polyfunctional monomer typically radically polymerizable functional groups having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group.
  • the polyfunctional monomer can be used as a crosslinking agent.
  • the amount of polyfunctional monomer used is not particularly limited, and can be appropriately set so that the purpose of using the polyfunctional monomer is achieved.
  • the amount of polyfunctional monomer used can be about 3% by weight or less of the monomer component, preferably about 2% by weight or less, and more preferably about 1% by weight or less (e.g., about 0.5% by weight or less).
  • the lower limit of the amount used is not particularly limited as long as it is greater than 0% by weight.
  • the effect of using the polyfunctional monomer can be appropriately achieved by setting the amount of polyfunctional monomer used to about 0.001% by weight or more (e.g., about 0.01% by weight or more) of the monomer component.
  • the acrylic polymer is synthesized using monomer components consisting essentially of 2-octyl acrylate, other alkyl (meth)acrylates different from 2-octyl acrylate, and a carboxyl group-containing monomer.
  • monomer components consisting essentially of 2-octyl acrylate, other alkyl (meth)acrylates different from 2-octyl acrylate, and a carboxyl group-containing monomer.
  • the action of each of the monomers is effectively exerted, and the polymer has good adhesive properties (e.g., adhesive strength, cohesive strength, etc.), and high temperature properties and flexibility can be better combined.
  • the total proportion of 2-octyl acrylate, other alkyl (meth)acrylates, and carboxyl group-containing monomers in the above monomer components is appropriately 90% by weight or more (90 to 100% by weight), preferably 95% by weight or more, more preferably 99% by weight or more, even more preferably more than 99.5% by weight, particularly preferably more than 99.9% by weight (e.g. more than 99.99% by weight), and may be 100% by weight.
  • the biomass carbon ratio of the monomer components constituting the acrylic polymer may be, for example, 1% or more, with 10% or more being appropriate, preferably 30% or more, more preferably 50% or more (e.g., more than 50%), may be 70% or more, 80% or more, or may be 90% to 100%.
  • the solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents.
  • aromatic compounds such as toluene (typically aromatic hydrocarbons); acetate esters 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 (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc.
  • polymerization initiators can be used alone or in combination of two or more.
  • the amount of polymerization initiator used may be a normal amount, and can be selected, for example, from the range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of the total monomer components.
  • the weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and from the viewpoint of obtaining good adhesive properties, an acrylic polymer having a Mw of about 100,000 or more is usually used.
  • the Mw of the acrylic polymer is preferably 400,000 or more, more preferably 600,000 or more, even more preferably 700,000 or more, and may be 800,000 or more.
  • the higher the Mw of the acrylic polymer the easier it is to obtain an adhesive with good high-temperature properties, and by using such a high-molecular-weight acrylic polymer in combination with a tackifier, it is possible to preferably achieve both good high-temperature properties and rough surface adhesion.
  • the Mw of the acrylic polymer is usually about 3 million or less, preferably 2 million or less, more preferably 1.5 million or less, even more preferably 1.2 million or less, and may be 1 million or less (for example, less than 1 million).
  • the acrylic polymer is usually one 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).
  • the dispersity (Mw/Mn) may be approximately 40 or less, approximately 30 or less, or approximately 20 or less.
  • the dispersity (Mw/Mn) of the acrylic polymer is preferably 15 or less, and may be 12 or less, 10 or less, 8 or less, or 6 or less.
  • the dispersity (Mw/Mn) of the acrylic polymer is theoretically 1 or more, and from the viewpoint of ease of preparation, for example, may be 2 or more, 3 or more, or 4 or more (typically 5 or more).
  • An acrylic polymer having a dispersity (Mw/Mn) in the above range has a predetermined molecular weight distribution, and is likely to obtain adhesive strength and rough surface adhesion due to its wettability based on its low molecular weight, and is likely to obtain good adhesive properties due to its cohesive strength based on its high molecular weight.
  • any component that can improve adhesive strength by being added to the adhesive can be used without particular limitation, and typically, tackifier resins such as rosin-based tackifier resins and terpene-based tackifier resins described below, and acrylic oligomers can be used.
  • the tackifier can be used alone or in combination of two or more types. Although not particularly limited, in some embodiments, the effect of using a tackifier can be effectively exhibited in a composition containing an acrylic polymer with a high molecular weight (e.g., Mw 400,000 or more).
  • the content of the tackifier in the adhesive layer is usually about 1 part by weight or more per 100 parts by weight of the acrylic polymer, from the viewpoint of obtaining the effect of adding the tackifier, and is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (e.g., 15 parts by weight or more).
  • the content of the tackifier may be 20 parts by weight or more, or may be 25 parts by weight or more per 100 parts by weight of the acrylic polymer.
  • the upper limit of the content of the tackifier in the adhesive layer is not particularly limited, but from the viewpoint of compatibility with the acrylic polymer, it is appropriate to make it about 100 parts by weight or less (e.g., less than 100 parts by weight) per 100 parts by weight of the acrylic polymer, and may be about 80 parts by weight or less.
  • the content of the 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.
  • the content of the tackifier is 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.
  • the adhesive layer contains a tackifier resin.
  • a tackifier resin By using a tackifier resin, the adhesive strength and rough surface adhesion can be preferably improved.
  • the tackifier resin is not particularly limited, and various tackifier resins such as rosin-based tackifier resins, terpene-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, phenol-based tackifier resins, and ketone-based tackifier resins can be used. Such tackifier resins can be used alone or in combination of two or more.
  • rosin-based tackifying resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.; the same applies below); and various other rosin derivatives.
  • rosin derivatives examples include rosin esters such as unmodified rosin esterified with alcohols (i.e., esterified products of rosin) and modified rosin esterified with alcohols (i.e., esterified products of modified rosin); unsaturated fatty acid modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acid; unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acid; rosin alcohols obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid modified rosins, or unsaturated fatty acid modified rosin esters; metal salts of rosins (particularly rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, and
  • rosin esters include, but are not limited to, esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl esters, triethylene glycol esters, glycerin esters, pentaerythritol esters, etc.
  • terpene-based tackifying resins examples include terpene resins such as ⁇ -pinene polymers, ⁇ -pinene polymers, and dipentene polymers; modified terpene resins obtained by modifying these terpene resins (phenol-modified, aromatic-modified, hydrogen-modified, hydrocarbon-modified, etc.); and the like.
  • modified terpene resin is terpene phenol resin.
  • Terpene phenolic resin refers to a polymer containing terpene residues and phenol residues, and is a concept that includes both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and phenol-modified homopolymers or copolymers of terpenes (phenol-modified terpene resins).
  • terpenes that make up such terpene phenolic resins include monoterpenes such as ⁇ -pinene, ⁇ -pinene, and limonene (including d-, l-, and d/l-forms (dipentene)).
  • Hydrogenated terpene phenolic resins are those that have a structure in which such terpene phenolic resins have been hydrogenated. They are also sometimes called hydrogenated terpene phenolic resins.
  • hydrocarbon-based tackifying resins include various hydrocarbon resins such as aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic/aromatic copolymer (C5/C9) petroleum resins, hydrogenated versions of these (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), various modified versions of these (e.g., maleic anhydride modified versions), coumarone resins, and coumarone-indene resins.
  • hydrocarbon resins such as aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic/aromatic copolymer (C5/C9) petroleum resins, hydrogenated versions of these (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), various modified versions of these (e.g., maleic anhydride modified versions), coumarone resins, and coumarone-indene resins.
  • rosin-based tackifying resins it is preferable to use at least one selected from rosin-based tackifying resins and terpene-based tackifying resins as the tackifying resin.
  • a rosin-based tackifying resin and/or a terpene-based tackifying resin into an acrylic adhesive the adhesive strength, high-temperature adhesive strength, and rough surface adhesion can be favorably improved.
  • the total proportion of the rosin-based tackifying resin and the terpene-based tackifying resin in the entire tackifying resin contained in the adhesive layer can be, for example, more than approximately 50% by weight (more than 50% by weight and not more than 100% by weight), and may be approximately 70% by weight or more, approximately 80% by weight or more, approximately 90% by weight or more, 95% by weight or more, or 99% by weight or more.
  • Some preferred embodiments include those in which the tackifier resin contains one or more terpene phenol resins.
  • the technology disclosed herein may be preferably implemented, for example, in an embodiment in which the total amount of tackifier resin is about 25% by weight or more (more preferably about 30% by weight or more).
  • the proportion of terpene phenol resin in the total amount of tackifier resin may be about 50% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more.
  • Substantially all of the tackifier resin (for example, about 95% by weight or more and 100% by weight or less, or even about 99% by weight or more and 100% by weight or less) may be terpene phenol resin.
  • the content of the terpene phenol resin in the adhesive layer is not particularly limited as long as the desired properties are satisfied.
  • the content of the terpene phenol resin is usually about 1 part by weight or more, and is preferably about 5 parts by weight or more, and is preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (e.g., 15 parts by weight or more) per 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength, high-temperature adhesive strength, and rough surface adhesion.
  • the content of the terpene phenol resin may be 20 parts by weight or more, or may be 25 parts by weight or more, per 100 parts by weight of the acrylic polymer.
  • the content of the terpene phenol resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, or may be 50 parts by weight or less, per 100 parts by weight of the acrylic polymer.
  • the content of the terpene phenol resin is 40 parts by weight or less, may be 30 parts by weight or less, may be 25 parts by weight or less, may be 20 parts by weight or less, or may be 18 parts by weight or less.
  • the softening point of the tackifier resin is not particularly limited.
  • a tackifier resin having a softening point of approximately 50°C or higher can be used, and from the viewpoint of improving cohesive strength, a tackifier resin having a softening point (softening temperature) of approximately 80°C or higher can be preferably used.
  • a terpene-based tackifier resin such as a terpene phenol resin
  • the softening point of the tackifier resin may be approximately 100°C or higher, approximately 105°C or higher, or approximately 110°C or higher.
  • the upper limit of the softening point of the tackifier resin is not particularly limited. From the viewpoint of adhesion to the adherend, a tackifier resin having a softening point of approximately 200°C or lower (more preferably approximately 180°C or lower) can be preferably used. In some preferred embodiments, the softening point of the tackifier resin may be about 160°C or less (e.g., less than 160°C), about 150°C or less (e.g., less than 150°C), less than 145°C, less than 140°C, less than 130°C, or less than 120°C.
  • the softening point of the tackifier resin is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at a low temperature and filled into a ring placed on a flat metal plate, taking care not to create bubbles. After cooling, the part that protrudes from the flat surface including the top end of the ring is cut off with a slightly heated knife. Next, a 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 poured to a depth of 90 mm or more.
  • ring and ball method the softening point test method
  • a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in glycerin without touching each other, and the temperature of the glycerin is kept at 20°C ⁇ 5°C for 15 minutes.
  • a steel ball is placed in the center of the surface of the sample in the ring and placed in a fixed position on the support.
  • keeping the distance from the top of the ring to the glycerin surface at 50 mm place a thermometer, align the center of the thermometer's mercury bulb to the same height as the center of the ring, and heat the container.
  • the flame of the Bunsen burner used for heating should be midway between the center of the bottom of the container and its edge, and heat evenly.
  • the rate of increase in the bath temperature must be 5.0 ⁇ 0.5°C per minute.
  • the sample gradually softens and flows down the ring, and the temperature is read when it finally touches the bottom plate, and this is the softening point.
  • the softening point is measured for two or more samples at the same time, and the average value is used.
  • a tackifier resin T H having a softening point of 100° C. or more is used as the tackifier resin.
  • the softening point of the tackifier resin T H may be 105° C. or more, or 110° C. or more.
  • the upper limit of the softening point of the tackifier resin T H is not particularly limited, and is, for example, about 200° C. or less, and in some preferred embodiments, it may be less than 150° C., less than 140° C., less than 130° C., or less than 120° C.
  • a tackifier resin T H having a softening point in the above range it is easy to obtain high adhesion to various adherends, and it is easy to achieve both high-temperature adhesion and rough surface adhesion.
  • the tackifier resin T H one type appropriately selected from the tackifier resins exemplified above having a softening point of 100° C. or higher can be used alone or in combination of two or more types.
  • the tackifier resin T H preferably contains a terpene phenol resin.
  • the tackifier resin T H may contain one type of terpene phenol resin alone or may contain two or more types of terpene phenol resins in combination.
  • the proportion of the terpene phenol resin in the entire tackifier resin T H can be, for example, more than about 50% by weight, may be about 65% by weight or more, may be about 75% by weight or more, may be 85% by weight or more, or may be 95% by weight or more.
  • the technology disclosed herein can be preferably practiced in an embodiment in which substantially all of the tackifier resin T H (for example, about 97% by weight or more, or 99% by weight or more, or may be 100% by weight) is a terpene phenol resin.
  • the content of the tackifier resin T H is not particularly limited, but in some embodiments, it is, for example, 1 part by weight or more, 5 parts by weight or more, preferably 8 parts by weight or more, more preferably 10 parts by weight or more, even more preferably 12 parts by weight or more, and may be 15 parts by weight or more, relative to 100 parts by weight of the acrylic polymer.
  • the content of the tackifier resin T H is suitably about 100 parts by weight or less (for example, less than 100 parts by weight) relative to 100 parts by weight of the acrylic polymer, and may be about 80 parts by weight or less.
  • the content of the tackifier resin T H is appropriately about 70 parts by weight or less relative to 100 parts by weight of the acrylic polymer, and may be 60 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less.
  • the pressure-sensitive adhesive layer may contain a combination of a tackifier resin T H and a tackifier resin T L having a softening point of less than 100° C.
  • a tackifier resin T L one type selected from the tackifier resins exemplified above having a softening point of less than 100° C. may be used alone or two or more types may be used in combination.
  • the tackifier resin T L may or may not contain a tackifier resin having a softening point of less than 50° C., more preferably about 40° C. or less (typically a tackifier resin such as a rosin-based, terpene-based, or hydrocarbon-based resin, for example, hydrogenated rosin methyl ester).
  • a tackifier resin such as a rosin-based, terpene-based, or hydrocarbon-based resin, for example, hydrogenated rosin methyl ester.
  • Such a low-softening-point tackifier resin may be a liquid tackifier resin that is liquid at 30° C.
  • the liquid tackifier resin may be used alone or in combination of two or more.
  • the content of the liquid tackifier resin may be about 30% by weight or less of the entire tackifier resin T L , and is suitably about 10% by weight or less (for example, 0 to 10% by weight), and may be about 2% by weight or less (0.5 to 2% by weight), or may be less than 1% by weight.
  • the tackifier resin T H preferably accounts for more than 50% by weight of the total amount of tackifier resin contained in the pressure-sensitive adhesive layer. This makes it easier for the effect of containing the tackifier resin T H to be effectively expressed. From the viewpoint of more effectively exerting the effect of using the tackifier resin T H, the proportion of the tackifier resin T H in the total amount of tackifier resin contained in the pressure-sensitive adhesive layer is preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, particularly preferably 90% by weight or more, and may be 95% by weight or more, or may be 98% by weight or more.
  • the tackifier resin contained in the pressure-sensitive adhesive layer is substantially composed of only the tackifier resin T H.
  • the proportion of the tackifier resin T H in the total amount of tackifier resin contained in the pressure-sensitive adhesive layer is in the range of 99 to 100% by weight.
  • the hydroxyl value of the tackifier resin is not particularly limited.
  • the hydroxyl value of the tackifier resin is usually about 300 mgKOH/g or less, and about 200 mgKOH/g or less is appropriate, from the viewpoint of compatibility with the acrylic polymer, and in some preferred embodiments, it may be about 150 mgKOH/g or less, or may be 120 mgKOH/g or less.
  • the hydroxyl value of the tackifier resin is 0 mgKOH/g or more, may be about 10 mgKOH/g or more, or may be about 20 mgKOH/g or more.
  • the hydroxyl value can be a value measured by potentiometric titration as specified in JIS K0070: 1992.
  • a specific measurement method is as follows. [Method for measuring hydroxyl value] 1.
  • Reagent (1) As the acetylation reagent, take about 12.5 g (about 11.8 mL) of acetic anhydride, add pyridine to make the total volume 50 mL, and stir thoroughly. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to make the total volume 100 mL, and stir thoroughly.
  • a 0.5 mol/L ethanol solution of potassium hydroxide is used as the measurement reagent.
  • Hydroxyl value (mgKOH/g) [(B-C) x f x 28.05] / S + D
  • B Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used in the blank test
  • C Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used in the sample
  • f factor of 0.5 mol/L potassium hydroxide ethanol solution
  • S weight of sample (g)
  • D acid value
  • 28.05 1/2 of the molecular weight of potassium hydroxide, 56.11, It is.
  • the tackifier resin may include a tackifier resin having a hydroxyl value of less than 100 mgKOH/g.
  • a tackifier resin having a hydroxyl value of less than 100 mgKOH/g may be referred to as a "low hydroxyl value resin”.
  • the hydroxyl value of the low hydroxyl value resin may be less than 80 mgKOH/g, 70 mgKOH/g or less, or less than 65 mgKOH/g.
  • a tackifier resin containing such a low hydroxyl value resin is likely to provide good adhesive strength.
  • the lower limit of the hydroxyl value of the low hydroxyl value resin is 0 mgKOH/g or more, may be approximately 10 mgKOH/g or more, or may be approximately 15 mgKOH/g or more.
  • the higher the hydroxyl value the easier it is to provide good cohesive strength.
  • the low hydroxyl value resin one type selected from the tackifier resins exemplified above having a hydroxyl value of less than 100 mgKOH/g may be used alone or in combination of two or more types.
  • the low hydroxyl value resin preferably includes at least one selected from a rosin-based tackifier resin and a terpene-based tackifier resin.
  • a terpene phenol resin having a hydroxyl value of less than 100 mg KOH/g may be preferably used as the low hydroxyl value resin.
  • Terpene phenol resins are advantageous because the hydroxyl value can be controlled as desired by the copolymerization ratio of phenol.
  • the proportion of the low hydroxyl value resin (e.g., terpene phenol resin) in the total tackifier resin contained in the adhesive layer may be approximately 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 value resin in the total tackifier resin is preferably, for example, approximately 30% by weight or more. This allows the effect of using the low hydroxyl value resin to be preferably exerted.
  • the proportion of the low hydroxyl value resin in the total tackifier resin is approximately 40% by weight or more, approximately 50% by weight or more (e.g., more than 50% by weight), approximately 60% by weight or more, approximately 70% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more.
  • Substantially all of the tackifier resin may be a low hydroxyl value resin.
  • the softening point of the low hydroxyl value resin is not particularly limited.
  • the softening point of the low hydroxyl value resin may be, for example, approximately 50°C or higher, and from the viewpoint of improving cohesive strength, a low hydroxyl value resin having a softening point (softening temperature) of approximately 80°C or higher may be preferably used.
  • a rosin-based tackifier resin or a terpene phenol resin having such a softening point may be preferably used.
  • the softening point of the low hydroxyl value resin may be approximately 100°C or higher, 105°C or higher, or approximately 110°C or higher.
  • a low hydroxyl value resin having a softening point of approximately 200°C or lower may be preferably used.
  • the softening point of the low hydroxyl value resin may be about 160°C or less, about 150°C or less (e.g., less than 150°C), less than 145°C, less than 140°C, less than 130°C, or less than 120°C.
  • the content of the low hydroxyl value resin in the adhesive layer is not particularly limited, and in some embodiments, it is usually about 1 part by weight or more, and it is appropriate to make it about 5 parts by weight or more, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (e.g., 15 parts by weight or more) per 100 parts by weight of the acrylic polymer.
  • the content of the low hydroxyl value resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, or may be 50 parts by weight or less, per 100 parts by weight of the acrylic polymer.
  • the content of the low hydroxyl value resin is 40 parts by weight or less, may be 30 parts by weight or less, may be 25 parts by weight or less, may be 20 parts by weight or less, or may be 18 parts by weight or less.
  • a tackifier resin derived from a plant may preferably act as the tackifier resin from the viewpoint of improving the biomass carbon ratio of the adhesive layer.
  • vegetable tackifier resins include the above-mentioned rosin-based tackifier resin and terpene-based tackifier resin.
  • the vegetable tackifier resin may be used alone or in combination of two or more.
  • the proportion of the vegetable tackifier resin in the total amount of tackifier resin is preferably 30% by weight or more (e.g., 50% by weight or more, typically 80% by weight or more).
  • the proportion of the vegetable tackifier resin in the total amount of tackifier resin is 90% by weight or more (e.g., 95% by weight or more, typically 99 to 100% by weight).
  • the technology disclosed herein may be preferably implemented in an embodiment that does not substantially contain tackifier resins other than vegetable tackifier resins.
  • the content of the tackifier resin in the adhesive layer is not particularly limited.
  • the content of the tackifier resin is usually about 1 part by weight or more, and it is appropriate to set it to about 5 parts by weight or more, and preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably about 12 parts by weight or more (e.g., 15 parts by weight or more) per 100 parts by weight of the acrylic polymer.
  • the more the amount of the tackifier resin used the easier it is to improve the adhesive strength, high-temperature adhesive strength, and rough surface adhesion.
  • the content of the tackifier resin may be 20 parts by weight or more, or may be 25 parts by weight or more, per 100 parts by weight of the acrylic polymer.
  • the content of the tackifier resin in the adhesive layer is, for example, appropriate to set it to about 100 parts by weight or less (e.g., less than 100 parts by weight) per 100 parts by weight of the acrylic polymer, and it may be about 80 parts by weight or less.
  • the content of the tackifier 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.
  • the content of the tackifier resin is 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, or 18 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.
  • the adhesive layer contains an acrylic oligomer.
  • the adhesive strength of the adhesive can be improved.
  • the adhesive layer can achieve both high-temperature adhesive strength and flexibility in a composition including the acrylic oligomer.
  • the effect of using the acrylic oligomer can be effectively exhibited in a composition including an acrylic polymer with a high molecular weight (e.g., Mw 400,000 or more).
  • the acrylic oligomer has a Tg of about 0°C or more and about 300°C or less, preferably about 20°C or more and about 300°C or less, and more preferably about 40°C or more and about 300°C or less.
  • Tg the adhesive strength
  • the Tg of the acrylic oligomer is about 30°C or more, more preferably about 50°C or more (e.g. about 60°C or more), and from the viewpoint of adhesiveness, it is preferably about 200°C or less, more preferably about 150°C or less, and even more preferably about 100°C or less (e.g. about 80°C or less).
  • the Tg of the acrylic oligomer refers to the Tg calculated by the Fox formula based on the composition of the above monomer components.
  • Tg represents the glass transition temperature (unit: K) of the copolymer
  • Wi represents the weight fraction (copolymerization ratio on a weight basis) of monomer i in the copolymer
  • Tgi represents the glass transition temperature (unit: K) of a homopolymer of monomer i.
  • the Tg of the homopolymer used in the calculation of Tg is as described for the homopolymer Tg of the acrylic polymer monomer.
  • the weight average molecular weight (Mw) of the acrylic oligomer can typically be about 1000 or more and less than about 30000, preferably about 1500 or more and less than about 20000, and more preferably about 2000 or more and less than about 10000. Having Mw within the above range is preferable because good adhesion can be obtained.
  • the Mw of the acrylic oligomer is about 2500 or more (e.g., about 3000 or more), and from the viewpoint of adhesion, it is preferably about 7000 or less, more preferably about 5000 or less (e.g., about 4500 or less, typically about 4000 or less).
  • the Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and calculated as a value in terms of standard polystyrene. Specifically, measurements were performed using a Tosoh HPLC 8020 with two TSKgel GMH-H (20) columns at a flow rate of approximately 0.5 mL/min with tetrahydrofuran as the solvent.
  • GPC gel permeation chromatography
  • Examples of monomers constituting acrylic oligomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl ( Examples of such (meth)acrylates include alkyl (meth)acrylates such as decyl (meth)acrylate, isodecyl (meth)acrylate,
  • an acrylic monomer having a relatively bulky structure such as alkyl (meth)acrylates in which the alkyl group has a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates), such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; and (meth)acrylates having a cyclic structure, such as aryl (meth)acrylates, such as phenyl (meth)acrylate and benzyl (meth)acrylate, from the viewpoint of further improving the adhesiveness of the adhesive layer.
  • alkyl (meth)acrylates in which the alkyl group has a branched structure such as isobutyl (meth)acrylate and t-butyl (meth)acryl
  • alkyl (meth)acrylates in which the alkyl group has a branched structure, or esters with alicyclic alcohols can be suitably used as monomers constituting the acrylic oligomer.
  • the above-mentioned branched alkyl (meth)acrylates, alicyclic hydrocarbon group (meth)acrylates, and aryl (meth)acrylates all fall under the category of (meth)acrylate monomers in the technology disclosed herein.
  • the alicyclic hydrocarbon group may be a saturated or unsaturated alicyclic hydrocarbon group.
  • 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 more, and more preferably 70% by weight or more (e.g., 80% by weight or more, or even 90% by weight or more).
  • the acrylic oligomer has a monomer composition consisting essentially of (meth)acrylate monomers.
  • functional group-containing monomers can be used as constituent monomer components of the acrylic oligomer.
  • suitable examples of the 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; carboxy group-containing monomers such as AA and MAA; and hydroxy group-containing monomers such as 2-hydroxyethyl (meth)acrylate.
  • These functional group-containing monomers can be used alone or in combination of two or more. Among them, carboxy group-containing monomers are preferred, with AA being particularly preferred.
  • the proportion of functional group-containing monomers (e.g., carboxyl group-containing monomers such as AA) in the 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.
  • Acrylic oligomers can be formed by polymerizing their constituent monomer components.
  • polymerization method or polymerization mode There are no particular limitations on the polymerization method or polymerization mode, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be used in an appropriate mode.
  • polymerization initiators e.g., azo-based polymerization initiators such as AIBN
  • azo-based polymerization initiators such as AIBN
  • chain transfer agent such as n-dodecyl mercaptan
  • suitable acrylic oligomers include, for example, homopolymers of dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), as well as copolymers of CHMA and isobutyl methacrylate (IBMA), copolymers of CHMA and IBXMA, copolymers of CHMA and acryloylmorpholine (ACMO), copolymers of CHMA and diethylacrylamide (DEAA), copolymers of CHMA and AA, copolymers of ADA and methyl methacrylate (MMA), copolymers of DCPMA and IBXMA, and copolymers of DCPMA and MMA.
  • DCPMA dicyclopen
  • the adhesive layer disclosed herein contains an acrylic oligomer
  • its content is not particularly limited, and is suitably, for example, 0.1 parts by weight or more (e.g., 1 part by weight or more) per 100 parts by weight of the acrylic polymer.
  • the content of the acrylic oligomer is approximately 3 parts by weight or more, may be approximately 5 parts by weight or more, may be approximately 10 parts by weight or more, or may be approximately 12 parts by weight or more.
  • the content of the acrylic oligomer is suitably less than 50 parts by weight (e.g., less than 40 parts by weight) per 100 parts by weight of the acrylic polymer, preferably less than 30 parts by weight, more preferably approximately 25 parts by weight or less, and even more preferably approximately 20 parts by weight or less.
  • the content of the acrylic oligomer may be 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less (e.g., less than 1 part by weight) relative to 100 parts by weight of the acrylic polymer.
  • the pressure-sensitive adhesive layer may be substantially free of acrylic oligomer.
  • the pressure-sensitive adhesive layer may contain one or more of the above-mentioned tackifier resins and one or more of the acrylic oligomers.
  • the ratio ( CT /CO) of the content CT [ wt %] of the tackifier resin to the content CO [wt%] of the acrylic oligomer in the pressure-sensitive adhesive layer is not particularly limited.
  • the above ( CT / CO ) is suitably set to, for example, 0.1 or more on a weight basis, preferably 0.5 or more, and may be 1 or more (e.g., more than 1), 2 or more, 3 or more, or 4 or more.
  • the above ( CT / CO ) is suitably set to, for example, 10 or less on a weight basis, preferably 8 or less, 6 or less, or 5 or less. This allows the effect of using the acrylic oligomer to be preferably exhibited.
  • the combined amount (total amount) of the acrylic polymer and tackifier in the adhesive layer is appropriately set so as to achieve the effects of the technology disclosed herein, and is not limited to a specific range.
  • the combined amount (total amount) of the acrylic polymer and tackifier contained in the adhesive layer is appropriate for more than 50% by weight of the adhesive layer, from the viewpoint of preferably achieving the effects of the technology disclosed herein, and is preferably approximately 70% by weight or more, more preferably approximately 90% by weight or more, and even more preferably 95% by weight or more (for example, 95% by weight or more and 100% by weight or less, or less than 100% by weight), and may be 98% by weight or more.
  • the adhesive composition used to form the adhesive layer may contain a crosslinking agent as necessary.
  • the type of crosslinking agent is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, hydrazine-based crosslinking agents, amine-based crosslinking agents, and silane coupling agents.
  • the crosslinking agents may be used alone or in combination of two or more. Among them, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and melamine-based crosslinking agents are preferred, and isocyanate-based crosslinking agents and epoxy-based crosslinking agents are more preferred.
  • the adhesive layer may have an appropriate cohesive force.
  • the pressure-sensitive adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after crosslinking reaction, a form before crosslinking reaction, a form after partial crosslinking reaction, an intermediate or composite form thereof, etc.
  • the crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in a form after crosslinking reaction.
  • an isocyanate-based crosslinking agent a polyfunctional isocyanate (a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used.
  • the isocyanate-based crosslinking agents can be used alone or in combination of two or more types.
  • polyfunctional isocyanate examples include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.
  • aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.
  • alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.
  • aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4
  • Preferred polyfunctional isocyanates include polyfunctional isocyanates having an average of three or more isocyanate groups per molecule.
  • Such trifunctional or higher isocyanates may be multimers (typically dimers or trimers) of bifunctional or trifunctional or higher isocyanates, derivatives (e.g., addition reaction products of polyhydric alcohols and two or more molecules of polyfunctional isocyanates), polymers, etc.
  • polyfunctional isocyanates include dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimer adducts of isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and other polyfunctional isocyanates.
  • the technology disclosed herein can be preferably implemented in an embodiment using at least an isocyanate-based crosslinking agent as a crosslinking agent.
  • the amount of the isocyanate-based crosslinking agent used is not particularly limited.
  • the amount of the isocyanate-based crosslinking agent used can be, for example, approximately 0.1 parts by weight or more per 100 parts by weight of the acrylic polymer. From the viewpoint of achieving both cohesive strength and adhesion, it is usually preferable that the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the acrylic polymer is approximately 0.3 parts by weight or more (for example, 0.5 parts by weight or more).
  • the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the acrylic polymer is approximately 0.8 parts by weight or more, more preferably approximately 1.0 parts by weight or more, even more preferably approximately 1.2 parts by weight or more, and may be approximately 1.5 parts by weight or more.
  • the amount of the isocyanate-based crosslinking agent used is suitably 10 parts by weight or less per 100 parts by weight of the acrylic polymer, preferably less than 5 parts by weight, more preferably less than 4.0 parts by weight, even more preferably less than 3.0 parts by weight, and particularly preferably 2.5 parts by weight or less, and may be 2.0 parts by weight or less (for example, 1.7 parts by weight or less).
  • epoxy-based crosslinking agent any compound having two or more epoxy groups in one molecule can be used without any particular restrictions. Epoxy-based crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. Epoxy-based crosslinking agents can be used alone or in combination of two or more types.
  • epoxy crosslinking agents include, but are not limited to, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc.
  • the amount of epoxy crosslinking agent used is not particularly limited.
  • the amount of epoxy crosslinking agent used can be, for example, more than 0 parts by weight and about 1 part by weight or less (typically about 0.001 to 1 part by weight) per 100 parts by weight of acrylic polymer. From the viewpoint of favorably exerting the effect of improving the cohesive force, it is usually appropriate that the amount of epoxy crosslinking agent used is about 0.002 parts by weight or more per 100 parts by weight of acrylic polymer, preferably about 0.005 parts by weight or more, and may be, for example, about 0.01 parts by weight or more.
  • the amount of epoxy crosslinking agent used is about 0.5 parts by weight or less per 100 parts by weight of acrylic polymer, preferably about 0.2 parts by weight or less, more preferably about 0.1 parts by weight or less (for example, less than 0.1 parts by weight), and may be 0.07 parts by weight or less, or may be 0.04 parts by weight or less.
  • the amount of epoxy-based crosslinking agent used is appropriately about 0.03 parts by weight or less per 100 parts by weight of the acrylic polymer, and preferably about 0.02 parts by weight or less.
  • an isocyanate-based crosslinking agent is used in combination with at least one crosslinking agent having a different type of crosslinkable functional group from that of the isocyanate-based crosslinking agent.
  • the type of non-isocyanate-based crosslinking agent that can be used in combination with the isocyanate-based crosslinking agent is not particularly limited, and can be appropriately selected from the crosslinking agents described above.
  • the non-isocyanate-based crosslinking agent can be used alone or in combination with two or more types.
  • an epoxy-based crosslinking agent can be used as the non-isocyanate-based crosslinking agent. For example, by using an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent in combination, better adhesive properties can be achieved.
  • the relationship between the content of the isocyanate-based crosslinking agent and the content of the non-isocyanate-based crosslinking agent (preferably an epoxy-based crosslinking agent) is not particularly limited.
  • the content of the isocyanate-based crosslinking agent is, for example, more than 1 time the content of the non-isocyanate-based crosslinking agent (preferably an epoxy-based crosslinking agent), and is suitably approximately 10 times or more, preferably approximately 50 times or more, more preferably approximately 80 times or more, even more preferably approximately 100 times or more (e.g., more than 100 times), and particularly preferably approximately 120 times or more (e.g., approximately 150 times or more).
  • the content of the isocyanate-based crosslinking agent relative to the content of the non-isocyanate-based crosslinking agent is usually, for example, approximately 1000 times or less, and it is appropriate to set it to approximately 500 times or less, and preferably approximately 300 times or less, and it may be approximately 200 times or less.
  • the content of the crosslinking agent (total amount of crosslinking agent) in the adhesive composition disclosed herein is not particularly limited. From the viewpoint of cohesion, the content of the crosslinking agent is usually about 0.001 parts by weight or more, and it is appropriate to set it to about 0.002 parts by weight or more relative to 100 parts by weight of the acrylic polymer, and it is preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, even more preferably about 0.02 parts by weight or more, and particularly preferably about 0.03 parts by weight or more.
  • the content of the crosslinking agent relative to 100 parts by weight of the acrylic polymer is about 0.1 parts by weight or more, more preferably about 0.5 parts by weight or more, even more preferably about 1.0 parts by weight or more, and it may be about 1.2 parts by weight or more, or it may be about 1.5 parts by weight or more.
  • the content of the crosslinking agent in the adhesive composition is usually about 20 parts by weight or less, preferably about 15 parts by weight or less, and preferably about 10 parts by weight or less (e.g., about 5 parts by weight or less) relative to 100 parts by weight of the acrylic polymer.
  • the content of the crosslinking agent relative to 100 parts by weight of the acrylic polymer is 4.0 parts by weight or less, more preferably 3.0 parts by weight or less, and even more preferably 2.5 parts by weight or less, and may be 2.0 parts by weight or less (e.g., less than 2.0 parts by weight), or may be 1.8 parts by weight or less.
  • the amount of the crosslinking agent used is limited within the above range, good adhesive strength and flexibility tend to be obtained.
  • the adhesive composition may contain, as necessary, various additives that are common in the field of adhesives, such as leveling agents, crosslinking assistants, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, antiaging agents, UV absorbers, antioxidants, rust inhibitors, light stabilizers, etc.
  • various additives such as leveling agents, crosslinking assistants, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, antiaging agents, UV absorbers, antioxidants, rust inhibitors, light stabilizers, etc.
  • additives conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed explanations will be omitted.
  • the adhesive layer (layer made of adhesive) disclosed herein may be an adhesive layer formed from an aqueous adhesive composition, a solvent-based adhesive composition, a hot melt-type adhesive composition, or an active energy ray curable adhesive composition.
  • the aqueous adhesive composition refers to an adhesive composition in a form containing an adhesive (adhesive layer forming component) in a solvent (aqueous solvent) mainly composed of water, and typically includes those called aqueous dispersion-type adhesive compositions (compositions in which at least a part of the adhesive is dispersed in water).
  • the solvent-type adhesive composition refers to an adhesive composition in a form containing an adhesive in an organic solvent.
  • organic solvent contained in the solvent-type adhesive composition one or more of the organic solvents (toluene, ethyl acetate, etc.) exemplified as those that can be used in the above-mentioned solution polymerization can be used without any particular restrictions.
  • the technology disclosed herein can be preferably implemented in an embodiment having an adhesive layer formed from a solvent-type adhesive composition from the viewpoint of adhesive properties, etc.
  • the adhesive layer disclosed herein can be formed by a conventional method.
  • a method can be adopted in which an adhesive composition is applied to a surface having releasability (release surface) or a non-release surface and then dried to form an adhesive layer.
  • a method direct method
  • an adhesive composition is directly applied (typically coated) to the substrate and then dried to form an adhesive layer.
  • a method transfer method
  • an adhesive composition is applied to a surface having releasability (release surface) and then dried to form an adhesive layer on the surface, and the adhesive layer is then transferred to a substrate. From the viewpoint of productivity, the transfer method is preferred.
  • the adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may be an adhesive layer formed in a regular or random pattern such as dots or stripes.
  • the pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, a bar coater, etc. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating. From the viewpoints of promoting the crosslinking reaction, improving production efficiency, etc., the pressure-sensitive adhesive composition is preferably dried under heating. The drying temperature can be, for example, about 40 to 150° C., and is usually preferably about 60 to 130° C. After drying the pressure-sensitive adhesive composition, aging may be further performed for the purpose of adjusting component migration in the pressure-sensitive adhesive layer, advancing the crosslinking reaction, relaxing distortion that may exist in the pressure-sensitive adhesive layer, etc.
  • the thickness of the adhesive layer is not particularly limited, and a configuration having an adhesive layer having an appropriate thickness, for example, in the range of 0.1 to 500 ⁇ m, can be adopted depending on the application and purpose of use.
  • the thickness of the adhesive layer is usually about 100 ⁇ m or less, preferably about 70 ⁇ m or less, more preferably about 60 ⁇ m or less, and even more preferably about 50 ⁇ m or less.
  • the thickness of the adhesive layer can be about 35 ⁇ m or less, for example, about 30 ⁇ m or less, about 25 ⁇ m or less, or about 22 ⁇ m or less.
  • the lower limit of the thickness of the adhesive layer is, in some embodiments, appropriate to be about 0.5 ⁇ m or more, may be about 1 ⁇ m or more, and is advantageously about 3 ⁇ m or more, preferably about 10 ⁇ m or more, more preferably about 12 ⁇ m or more (e.g., more than 12 ⁇ m), even more preferably about 15 ⁇ m or more, and may be, for example, about 18 ⁇ m or more.
  • the greater the adhesive layer thickness the greater the tendency for adhesive strength to improve.
  • the adhesive sheet disclosed herein may be an adhesive sheet having an adhesive layer of the above thickness on both sides of the substrate.
  • the first adhesive layer and the second adhesive layer may be the same thickness or may be different thicknesses.
  • the glass transition temperature (Tg) of the adhesive (layer) is 10°C or less (e.g., less than 10°C), may be 8.0°C or less, or may be 6.0°C or less.
  • the glass transition temperature of the adhesive (layer) refers to the glass transition temperature determined from the peak temperature of tan ⁇ in dynamic viscoelasticity measurement.
  • An adhesive containing a tackifier and having a low Tg is highly flexible and tends to exhibit excellent rough surface adhesion.
  • the Tg of the adhesive (layer) is lower than 5.0°C, may be 4.0°C or less, 3.0°C or less, 2.0°C or less, 1.0°C or less, 0°C or less (e.g., less than 0.0°C), -1.0°C or less, -3.0°C or less, or -5.0°C or less.
  • the Tg of the pressure-sensitive adhesive (layer) is, from the viewpoint of cohesive strength and the like, suitably, for example, -30°C or higher, and preferably -15°C or higher, and may be -12°C or higher, -10°C or higher, -7.0°C or higher (e.g., greater than -7.0°C), -5.0°C or higher, -3.0°C or higher, -1.0°C or higher, 0°C or higher (e.g., greater than 0.0°C), 1.0°C or higher, or 3.0°C or higher (e.g., 4.0°C or higher).
  • the Tg of the adhesive can be determined by dynamic viscoelasticity measurement. Specifically, a plurality of adhesive layers (adhesive sheets in the case of substrate-less adhesive sheets) to be measured are stacked to prepare an adhesive layer having a thickness of about 2 mm. The adhesive layer is punched into a disk shape having a diameter of 7.9 mm, and a sample is sandwiched and fixed between parallel plates.
  • Dynamic viscoelasticity measurement is performed under the following conditions using a viscoelasticity tester (e.g., ARES or its equivalent, manufactured by TA Instruments), and Tg is determined from the peak temperature of the loss tangent tan ⁇ (G′′/G′), which is the ratio of the loss modulus G′′ to the storage modulus G′.
  • a viscoelasticity tester e.g., ARES or its equivalent, manufactured by TA Instruments
  • Tg is determined from the peak temperature of the loss tangent tan ⁇ (G′′/G′), which is the ratio of the loss modulus G′′ to the storage modulus G′.
  • ⁇ Measurement mode Shear mode
  • ⁇ Temperature range -70°C to 150°C Heating rate: 5°C/min
  • ⁇ Measurement frequency 1Hz
  • the above method is also used in the Examples described later.
  • the pressure-sensitive adhesive layer to be measured may be one formed by applying a corresponding pressure-sensitive adhesive composition in a layer form and drying
  • the pressure-sensitive adhesive layer contains a biomass-derived material, and the biomass carbon ratio (also referred to as bio-based ratio) may be a predetermined value or more.
  • the biomass carbon ratio of the pressure-sensitive adhesive layer is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more.
  • a high biomass carbon ratio of the pressure-sensitive adhesive means that the amount of fossil resource-based materials, such as petroleum, used is small. In this respect, the higher the biomass carbon ratio of the pressure-sensitive adhesive, the more preferable it is.
  • the biomass carbon ratio of the pressure-sensitive adhesive layer may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%.
  • the upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and may be 95% or less or 90% or less from the viewpoint of material availability.
  • the biomass carbon ratio of the adhesive layer may be, for example, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less.
  • the substrate supporting (backing) the pressure-sensitive adhesive layer may be a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or a composite of these.
  • paper include Japanese paper, craft paper, glassine paper, wood-free paper, synthetic paper, and top-coated paper.
  • cloth include woven fabrics and nonwoven fabrics made by spinning various fibrous materials alone or in combination. Examples of the fibrous material include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, 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 polychloroprene rubber sheets.
  • Examples of metal foils include aluminum foil and copper foil.
  • the substrate supporting the pressure-sensitive adhesive layer is also called the substrate layer in the pressure-sensitive adhesive sheet.
  • the substrate may be formed from a biomass-derived material or a non-biomass-derived material.
  • a biomass-derived substrate material typically a resin film is preferably used.
  • the substrate may also be formed using a recyclable material or a recycled material (also called a recycled material).
  • a resin film is preferably used as such a recycled material. Since a resin film (e.g., a polyester film such as a PET film) is recyclable, it is possible to continuously reproduce the resin film after use, regardless of whether or not it uses a plant-derived material, and the environmental burden can be reduced. Such a recyclable resin film or recycled resin film is also called a recycled film.
  • the recycled material e.g., a recycled film
  • a substrate containing a resin film as the base film can be preferably used as the substrate constituting the substrate-attached adhesive sheet.
  • the base film is typically a member that can independently maintain its shape (independent).
  • the substrate in the technology disclosed herein may be substantially composed of such a base film.
  • the substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc., provided on the surface of the base film.
  • the resin film is a film whose main component is a resin material (for example, a component contained in the resin film at more than 50% by weight).
  • resin films include polyolefin-based resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyester-based resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride-based resin films; vinyl acetate-based resin films; polyimide-based resin films; polyamide-based resin films; fluororesin films; cellophane; and the like.
  • the resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Among these, polyester films are preferred from the viewpoint of handling and processability, and PET films are particularly preferred.
  • the term "resin film” refers to a typically non-porous sheet, and is a concept that is distinct from so-called nonwoven fabric or woven fabric (in other words, a concept that excludes nonwoven fabric or woven fabric).
  • the resin film may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film.
  • a resin film may be non-foamed.
  • a non-foamed resin film refers to a resin film that has not been intentionally treated to become a foam.
  • a non-foamed resin film may be a resin film with an expansion ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).
  • the above-mentioned substrate may contain various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, etc., as necessary.
  • the blending ratio of the various additives is about less than 30% by weight (e.g., less than 20% by weight, typically less than 10% by weight).
  • the substrate e.g., a resin film
  • the substrate may have a single-layer structure, or a multi-layer structure of two, three or more layers. From the viewpoint of shape stability, the substrate preferably has a single-layer structure. In the case of a multi-layer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (e.g., a polyester-based resin).
  • the method for producing the substrate is not particularly limited and may be any conventionally known method. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calendar roll molding may be appropriately used.
  • the surface of the substrate may be subjected to a conventional surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, etc.
  • a surface treatment may be a treatment for improving the adhesion between the substrate and the adhesive layer, in other words, the anchoring ability of the adhesive layer to the substrate.
  • a release treatment may be applied to the back surface of the substrate as necessary.
  • the release treatment may be, for example, a treatment in which a general silicone-based, long-chain alkyl-based, fluorine-based or other release agent is applied in the form of a thin film, typically of about 0.01 ⁇ m to 1 ⁇ m (e.g., 0.01 ⁇ m to 0.1 ⁇ m).
  • the thickness of the substrate is not particularly limited.
  • the thickness of the substrate can be, for example, approximately 200 ⁇ m or less, preferably approximately 150 ⁇ m or less, and more preferably approximately 100 ⁇ m or less.
  • the thickness of the substrate may be approximately 70 ⁇ m or less, approximately 50 ⁇ m or less, or approximately 30 ⁇ m or less (e.g., approximately 25 ⁇ m or less).
  • the thickness of the substrate may be approximately 20 ⁇ m or less, approximately 15 ⁇ m or less, or approximately 10 ⁇ m or less (e.g., approximately 5 ⁇ m or less).
  • the thickness of the adhesive layer can be made larger even if the total thickness of the adhesive sheet is the same. This can be advantageous in terms of improving adhesion to the adherend and the substrate.
  • the lower limit of the substrate is not particularly limited. From the viewpoint of the handleability and processability of the adhesive sheet, the thickness of the substrate is usually about 0.5 ⁇ m or more (e.g., 1 ⁇ m or more), preferably about 2 ⁇ m or more, for example, about 6 ⁇ m or more. In some embodiments, the thickness of the substrate can be about 15 ⁇ m or more, and may be about 25 ⁇ m or more.
  • a release liner can be used during the formation of the adhesive layer, the preparation of the adhesive sheet, the storage, distribution, and shaping of the adhesive sheet before use.
  • the release liner is not particularly limited, and for example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or a release liner made of a fluorine-based polymer (polytetrafluoroethylene, etc.) can be used.
  • the release treatment layer can be formed by surface treating the liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.
  • a substrate formed using a material derived from biomass or a recycled material (recycled film, etc.) can be preferably used, similar to the substrate of the above-mentioned adhesive sheet.
  • the total thickness of the adhesive sheet disclosed herein (including the adhesive layer and may further include a base layer, but not including a release liner) is not particularly limited.
  • the total thickness of the adhesive sheet is, for example, about 1 mm or less, may be about 500 ⁇ m or less, or may be about 300 ⁇ m or less, and from the viewpoint of thinning, it is appropriate to be about 200 ⁇ m or less, and may be about 150 ⁇ m or less (for example, about 100 ⁇ m or less).
  • the thickness of the adhesive sheet can be about 50 ⁇ m or less, for example, it may be about 35 ⁇ m or less, may be about 30 ⁇ m or less, may be about 25 ⁇ m or less, or may be about 22 ⁇ m or less.
  • the lower limit of the thickness of the adhesive sheet is, for example, 0.1 ⁇ m or more (for example, 0.5 ⁇ m or more), and it is appropriate to be about 3 ⁇ m or more, preferably about 10 ⁇ m or more, more preferably about 15 ⁇ m or more, and may be about 18 ⁇ m or more.
  • a pressure-sensitive adhesive sheet having a thickness equal to or greater than a certain value is likely to be able to adhere to an adherend and also tends to be easy to handle.
  • the thickness of the pressure-sensitive adhesive layer is the total thickness of the pressure-sensitive adhesive sheet.
  • the pressure-sensitive adhesive sheet preferably has a 180-degree peel strength (adhesive strength against SUS) against a stainless steel plate of about 10 N/20 mm or more.
  • a pressure-sensitive adhesive sheet exhibiting such adhesive strength against SUS can exhibit excellent adhesion.
  • the adhesive strength against SUS may be about 12 N/20 mm or more, about 14 N/20 mm or more, or about 16 N/20 mm or more (e.g., 17 N/20 mm or more).
  • the upper limit of the adhesive strength against SUS is not particularly limited, but from the viewpoint of compatibility with other adhesive properties such as cohesive strength, it may usually be, for example, about 50 N/20 mm or less.
  • the adhesive strength against SUS is measured using a SUS plate as an adherend under the conditions of a measurement environment of 23° C. and 50% RH, a pulling speed of 300 mm/min, and a peel angle of 180 degrees. More specifically, it is measured by the method described in the Examples below.
  • the adhesive sheet preferably has a 180-degree peel strength (high-temperature adhesive strength) at 65°C against a stainless steel plate of greater than about 4.5 N/20 mm.
  • Adhesive sheets exhibiting such high-temperature adhesive strength tend to have excellent high-temperature characteristics, and can exhibit high adhesion reliability even when used in a high-temperature environment.
  • the high-temperature adhesive strength may be about 5.0 N/20 mm or more, about 5.5 N/20 mm or more, or about 6.0 N/20 mm or more.
  • the high-temperature adhesive strength is measured using a SUS plate as the adherend, in a measurement environment of 65°C, at a tensile speed of 300 mm/min and a peel angle of 180 degrees. More specifically, it is measured by the method described in the Examples below.
  • the adhesive sheet preferably has a rough surface adhesion of about 1.0 N/20 mm or more as measured by the method described in the Examples below.
  • An adhesive sheet exhibiting such a rough surface adhesion can exhibit good adhesion to the rough surfaces of various adherends, and can be used as an adhesive means with good adhesion reliability.
  • the rough surface adhesion is about 2.0 N/20 mm or more, more preferably about 2.5 N/20 mm or more, even more preferably about 3.0 N/20 mm or more, and particularly preferably about 3.5 N/20 mm or more (e.g., 4.0 N/20 mm or more).
  • the rough surface adhesion there is no particular upper limit to the rough surface adhesion, and from the viewpoint of compatibility with other adhesive properties such as cohesive strength, it may usually be, for example, about 10 N/20 mm or less.
  • the adhesive sheet contains a biomass-derived material, and the biomass carbon ratio (also referred to as biobased ratio) may be a predetermined value or more.
  • the biomass carbon ratio of the adhesive sheet is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more.
  • a high biomass carbon ratio of the adhesive sheet means that the amount of fossil resource-based materials, such as petroleum, used is small. From this perspective, the higher the biomass carbon ratio of the adhesive sheet, the more preferable it is.
  • the biomass carbon ratio of the adhesive sheet may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%.
  • the upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and from the viewpoint of ease of material availability, it may be 95% or less, or 90% or less. From the viewpoint of making it easier to exhibit good adhesive performance, in some embodiments, the biomass carbon ratio of the adhesive sheet may be, for example, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, or 65% or less.
  • the use of the adhesive sheet disclosed herein is not particularly limited, and it can be used for various applications.
  • the adhesive sheet disclosed herein has an adhesive that combines high-temperature properties and flexibility, and further has high adhesive strength, so that it may be used in high-temperature environments and can be preferably used for fixing various members as an adhesive means with good adhesion reliability in various applications where flexibility is desirable.
  • it can be preferably used for applications in which members are fixed in electronic devices such as various portable electronic devices.
  • the adhesive sheet is usually small in adhesion area due to size, weight, and other restrictions when fixing members in a portable electronic device.
  • the adhesive sheet used for this application needs to have an adhesive strength that can achieve good fixation even in a small area, and the required performance is becoming higher due to the demand for high functionality, weight reduction, and miniaturization.
  • portable electronic devices equipped with touch panel displays, such as smartphones are becoming smaller and thinner in the product itself, while the screen size is becoming larger from the viewpoint of visibility and operability of the display, and due to this unique situation, the adhesive used is required to have adhesion and fixing performance under harsher conditions.
  • the adhesive sheet disclosed herein can be used in the above-mentioned portable electronic device applications to achieve excellent adhesion reliability.
  • electronic devices such as portable electronic devices may be used in high-temperature environments, and the internal space may become heated due to heat generation from electronic components.
  • the adhesive disclosed herein has good high-temperature properties due to the inclusion of an acrylic polymer in which 2-octyl acrylate is copolymerized, and in this respect, is also preferably applied to electronic devices such as portable electronic devices.
  • the adhesive sheets according to some preferred embodiments have good rough surface adhesion, they are preferably used in various applications in an embodiment in which they are attached to adherends having rough surfaces, such as foam materials, mesh materials, graphite, metals and resins that have been roughened.
  • adherends having rough surfaces such as foam materials, mesh materials, graphite, metals and resins that have been roughened.
  • the members constituting electronic devices such as portable electronic devices include materials having rough surfaces (e.g., foam materials, mesh materials, graphite, metals and resins that have been roughened), adhesive sheets having good rough surface adhesion are suitable for such applications.
  • Non-limiting examples of the portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including glasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc.
  • various wearable devices for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including glasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc.
  • earwear devices attached to the ears like earphones, etc.
  • digital cameras digital video cameras
  • audio devices portable music players, IC recorders, etc.
  • calculators calculators (calculators, etc.)
  • portable game devices electronic dictionaries, electronic organizers, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc.
  • portable does not mean that it is merely possible to carry it around, but rather that it has a level of portability that allows an individual (average adult) to carry it around relatively easily.
  • the electronic devices include personal computers (desktop, notebook, tablet, etc.), televisions, etc. These may include built-in display devices such as liquid crystal or organic electroluminescence.
  • the adhesive sheet is preferably used in electronic devices that include various light sources such as LEDs (light emitting diodes) and light emitting elements such as self-emitting organic electroluminescence (EL).
  • the adhesive sheet can be preferably used in electronic devices (typically portable electronic devices) that include an organic electroluminescence display device or a liquid crystal display device.
  • FIG. 4 is a schematic example of a portable electronic device (smartphone) using the adhesive sheet disclosed herein.
  • a battery (heat generating element) 540 is built into the housing 520 of the portable electronic device 500.
  • the portable electronic device 500 is also configured to include an adhesive sheet 550.
  • the adhesive sheet 550 has the form of a double-sided adhesive sheet (double-sided adhesive sheet) that fixes the members that make up the portable electronic device 500.
  • the portable electronic device 500 is equipped with a touch panel 570 whose display unit also functions as an input unit.
  • the adhesive sheet disclosed herein is preferably used as a component (member joining means) of the portable electronic device described above.
  • the adhesive sheet disclosed herein may have an adhesive layer containing an acrylic polymer with a high biomass carbon ratio, and therefore may be used as a substitute for conventional acrylic adhesives (i.e., acrylic adhesives with a low biomass carbon ratio) in various applications where such acrylic adhesives are used, thereby contributing to reducing dependency on fossil resource-based materials.
  • the adhesive sheet disclosed herein may be preferably used as an adhesive sheet with reduced dependency on fossil resource-based materials.
  • a portable electronic device an adhesive sheet is bonded to a member constituting the portable electronic device,
  • the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer contains an acrylic polymer containing 2-octyl acrylate as a monomer component,
  • the monomer component of the acrylic polymer contains more than 0% by weight and not more than 20% by weight of an alkyl (meth)acrylate other than 2-octyl acrylate,
  • the portable electronic device wherein the adhesive layer further comprises a tackifier.
  • the portable electronic device according to the above item [1] comprising an alkyl (meth)acrylate represented by the following formula: [3]
  • the tackifier includes at least one selected from a rosin-based tackifier resin, a terpene-based tackifier resin, and an acrylic oligomer.
  • the tackifier includes a tackifier resin having a softening point of 100° C. or higher.
  • the adhesive composition for forming the adhesive layer contains a crosslinking agent.
  • a pressure-sensitive adhesive layer including an acrylic polymer including 2-octyl acrylate as a monomer component,
  • the monomer component of the acrylic polymer contains more than 0% by weight and not more than 20% by weight of an alkyl (meth)acrylate other than 2-octyl acrylate,
  • the pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer further comprises a tackifier.
  • the pressure-sensitive adhesive sheet according to the above [11] or [12], wherein the other alkyl (meth)acrylate includes an alkyl (meth)acrylate having a linear alkyl group.
  • the tackifier comprises a tackifier resin having a softening point of 100° C. or higher.
  • the pressure-sensitive adhesive layer has a glass transition temperature of 10° C. or lower, wherein the glass transition temperature of the pressure-sensitive adhesive layer refers to a glass transition temperature determined from a peak temperature of tan ⁇ in dynamic viscoelasticity measurement.
  • An electronic device comprising the pressure-sensitive adhesive sheet according to any one of [11] to [20] above.
  • Example 1 Synthesis of Acrylic Polymer
  • a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel 85 parts of 2-octyl acrylate (2OcA), 10 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components, and ethyl acetate as a polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas.
  • 2OcA 2-octyl acrylate
  • BA n-butyl acrylate
  • acrylic acid AA
  • the above 2OcA is a compound having an alkyl group derived from biomass at the ester end, synthesized using 2-octanol derived from biomass.
  • the obtained adhesive composition was applied to the release surface of a 38 ⁇ m thick polyester release film (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) and dried at 100° C. for 2 minutes to form an adhesive layer having a thickness of 20 ⁇ m.
  • the release surface of a 25 ⁇ m thick polyester release film (trade name "Diafoil MRF", thickness 25 ⁇ m, manufactured by Mitsubishi Chemical Corporation) was bonded to this adhesive layer.
  • Tg glass transition temperature
  • the biobased content measured according to ASTM D6866
  • Examples 2 to 7 and Comparative Examples 1 to 5> A pressure-sensitive adhesive composition according to each example 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, and the resulting pressure-sensitive adhesive composition was used to produce a substrate-less double-sided adhesive sheet (thickness 20 ⁇ m) according to each example in the same manner as in Example 1.
  • 2EHA stands for 2-ethylhexyl acrylate.
  • the acrylic oligomer used was prepared by the following method. Specifically, 95 parts of cyclohexyl methacrylate (CHMA), 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, and the mixture was stirred in a nitrogen stream for 1 hour to remove oxygen from the polymerization system, after which the temperature was raised to 85°C and reacted for 5 hours to obtain an acrylic oligomer with a solids concentration of 50%.
  • the Mw of the obtained acrylic oligomer was 3600.
  • peel strength adheresive strength against SUS [N/20 mm] in accordance with JIS Z 0237:2000 at a tensile speed of 300 mm/min and a peel angle of 180 degrees.
  • a 50 ⁇ m thick PET film was attached to one adhesive surface of the adhesive sheet (double-sided adhesive sheet) to back it, and the sample was cut to a size of 20 mm wide and 100 mm long to prepare a measurement sample.
  • the other adhesive surface of the measurement sample was pressed against the surface of a stainless steel plate (SUS304BA plate) washed with ethyl acetate by rolling a 2 kg roller back and forth once. After leaving this in an environment of 65° C.
  • a 50 ⁇ m thick PET film was attached to one of the adhesive surfaces of the adhesive sheet (double-sided adhesive sheet) to back it, and the sheet was cut to a size of 20 mm wide and 100 mm long to prepare a measurement sample.
  • sandpaper (Riken Corundum Co., Ltd., grain size 320) was fixed to a stainless steel plate (SUS304BA plate) as an adherend.
  • SUS304BA plate stainless steel plate
  • a universal tensile compression tester was used to measure the peel strength (rough surface adhesive strength) [N / 20 mm] in accordance with JIS Z 0237: 2000 under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees.
  • a universal tensile/compression tester such as Minebea's "Tension/Compression Tester, TG-1kN" or an equivalent product is used.
  • a PET film backing is not required.
  • the substrate thickness is thin (for example, when the substrate thickness is 25 ⁇ m or less), a PET film backing may be used.
  • Table 1 shows an overview of the adhesive sheets for each example and the evaluation results.
  • the adhesives according to Examples 1 to 7 contain 2OcA as a monomer component, an acrylic polymer containing 20% or less of another alkyl (meth)acrylate different from 2OcA, and a tackifier, and have good high-temperature adhesive strength and flexibility (adhesive Tg).
  • Adhesive Tg high-temperature adhesive strength and flexibility
  • Comparative Examples 1 and 2 in which the copolymerization ratio of the other alkyl (meth)acrylate exceeded 20%, the high-temperature adhesive strength was lower than that of the above Examples.
  • Comparative Example 3 in which no other alkyl (meth)acrylate was used, the adhesive Tg was higher than that of the above Examples, and good flexibility was not obtained (see, in particular, the results of the comparison with Examples 4 and 7).
  • an adhesive sheet having an adhesive layer containing an acrylic polymer that contains 2OcA as a monomer component and further contains an alkyl (meth)acrylate other than 2OcA in a proportion of 20% or less, and a tackifier has an adhesive layer that is flexible while retaining high temperature properties, and can further improve adhesive strength.
  • Adhesive sheet 10 Support base material 10A First side 10B Second side (back side) 21 Adhesive layer (first adhesive layer) 21A Adhesive surface (first adhesive surface) 21B Second adhesive surface 22 Adhesive layer (second adhesive layer) 22A Adhesive surface (second adhesive surface) 31, 32 Release liner 100, 200, 300 Adhesive sheet with release liner

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7708474B1 (ja) * 2024-12-19 2025-07-15 サイデン化学株式会社 再剥離用粘着剤組成物及び粘着シート

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7586265B1 (ja) * 2023-09-06 2024-11-19 ａｒｔｉｅｎｃｅ株式会社 粘着剤および粘着剤組成物、粘着シート、積層体および該積層体を備えるディスプレイ
KR102769725B1 (ko) * 2023-11-24 2025-02-20 주식회사 에이지엠지 저온 접착이 가능한 서브가스켓 접착필름용 접착제 조성물
JP7697567B1 (ja) * 2024-06-20 2025-06-24 ａｒｔｉｅｎｃｅ株式会社 粘着剤および粘着剤組成物、それを用いた粘着剤層、粘着シート、積層体並びに粘着剤層付きデバイス
JP7691791B1 (ja) * 2024-11-06 2025-06-12 サイデン化学株式会社 再剥離用粘着剤組成物、表面保護フィルム、及び粘着剤層付き光学部材

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011516690A (ja) * 2008-04-14 2011-05-26 スリーエム イノベイティブ プロパティズ カンパニー ２−オクチル（メタ）アクリレート接着剤組成物
WO2014093141A1 (en) * 2012-12-14 2014-06-19 3M Innovative Properties Company Method of making packaged viscoelastic compositions by polymerizing ethylenically-unsaturated materials using ionizing radiation
JP2018501378A (ja) * 2014-12-30 2018-01-18 スリーエム イノベイティブ プロパティズ カンパニー ハロゲンフリー難燃性感圧性接着剤及びテープ
JP2018506612A (ja) * 2014-12-30 2018-03-08 スリーエム イノベイティブ プロパティズ カンパニー 水性感圧接着剤組成物
JP2020100826A (ja) * 2013-04-15 2020-07-02 スリーエム イノベイティブ プロパティズ カンパニー （メタ）アクリレート基及びオレフィン基を有する架橋剤を含む接着剤並びに方法
WO2022034247A1 (de) * 2020-08-14 2022-02-17 Tesa Se Haftklebmasse

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016102195A (ja) * 2014-11-18 2016-06-02 日東電工株式会社 粘着シート
WO2017098870A1 (ja) * 2015-12-10 2017-06-15 綜研化学株式会社 粘着剤組成物およびその製造方法、粘着シート、粘着剤層付き偏光板ならびに積層体
JP2018002999A (ja) * 2016-06-23 2018-01-11 積水化学工業株式会社 粘着テープ及び研磨材固定用両面粘着テープ
JP7087162B2 (ja) * 2020-08-31 2022-06-20 日東電工株式会社 粘着シート
JP2022047704A (ja) * 2020-09-14 2022-03-25 日東電工株式会社 粘着シート

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011516690A (ja) * 2008-04-14 2011-05-26 スリーエム イノベイティブ プロパティズ カンパニー ２−オクチル（メタ）アクリレート接着剤組成物
WO2014093141A1 (en) * 2012-12-14 2014-06-19 3M Innovative Properties Company Method of making packaged viscoelastic compositions by polymerizing ethylenically-unsaturated materials using ionizing radiation
JP2020100826A (ja) * 2013-04-15 2020-07-02 スリーエム イノベイティブ プロパティズ カンパニー （メタ）アクリレート基及びオレフィン基を有する架橋剤を含む接着剤並びに方法
JP2018501378A (ja) * 2014-12-30 2018-01-18 スリーエム イノベイティブ プロパティズ カンパニー ハロゲンフリー難燃性感圧性接着剤及びテープ
JP2018506612A (ja) * 2014-12-30 2018-03-08 スリーエム イノベイティブ プロパティズ カンパニー 水性感圧接着剤組成物
WO2022034247A1 (de) * 2020-08-14 2022-02-17 Tesa Se Haftklebmasse

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7708474B1 (ja) * 2024-12-19 2025-07-15 サイデン化学株式会社 再剥離用粘着剤組成物及び粘着シート

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