Adhesive sheet

Abstract

The present application provides an adhesive sheet that can balance the resilience resistance and the impact resistance at a high level. The adhesive sheet has an adhesive layer containing an acrylic polymer. The acrylic polymer is a polymer containing a monomer component of heptyl acrylate. In addition, the adhesive layer has a storage modulus G' of 20,000 Pa or more at 65°C, and a tan δ of 0.3 or more at -20°C.

Description

TECHNICAL FIELD

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

[0002] This application claims priority based on Japanese Patent Application No. 2022-108023, filed July 4, 2022, the entire contents of which are incorporated herein by reference. BACKGROUND

[0003] Generally, an adhesive (also referred to as a pressure-sensitive adhesive, hereinafter the same) exhibits a state of a soft solid (a viscoelastic body) in a temperature range around room temperature, and has a property of being adhered to an adherend by pressure. By utilizing this property, the adhesive is widely utilized in various industrial fields from portable electronic devices such as smartphones, home electric appliances, to automobiles, OA devices, and the like, typically in the form of an adhesive sheet containing an adhesive layer, for the purpose of joining of parts, surface protection, and the like. As technical documents related to the adhesive sheet, Patent Document 1, Patent Document 2 can be cited. In Patent Document 1, Patent Document 2, an adhesive containing an acrylic polymer polymerized using heptyl acrylate as a monomer component is described.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2021 / 125247

[0007] Patent Document 2: International Publication No. 2021 / 125278 SUMMARY

[0008] Problems to be Solved by the Invention

[0009] For an adhesive sheet, various properties are required depending on the application site, the use mode, and the like. For example, the fixing of members in portable electronic devices based on adhesive sheets is generally limited in size, weight, and the like. An adhesive sheet used in this use needs to have an adhesive force that enables good fixing even with a small area, and from the viewpoint of light weight and miniaturization, the required properties are at a higher level. In particular, portable electronic devices of the touch panel type display mounting type typified by smartphones are being made larger in screen size from the viewpoint of the miniaturization and thinness of the product itself, and from the viewpoint of the visual recognition and operability of the display, and due to the unique circumstances thereof, the adhesive used is required to have an adhesive fixing property under more severe conditions. Specifically, in this use, the adhesive area is of course limited, and for example, an elastic member such as a flexible printed wiring board (FPC) is bent and housed in the limited internal space in the portable electronic device, and such handling is performed as to position and stably fix the same with high precision with an adhesive sheet. In an adhesive sheet for such member fixing, since a continuous peeling load is applied in the thickness direction (also referred to as the Z-axis direction) of the adhesive sheet, it is required to have a resilience resistance (specifically, durability against a continuous peeling load in the thickness direction (Z-axis direction) of the adhesive sheet) that continuously resists the elastic repulsion of the member.

[0010] In addition, in recent years, in addition to the above-described light weight and miniaturization, the development of portable electronic device products having a curved surface shape such as a three-dimensional shape is progressing, and the surface shape thereof has a tendency to be more complex. For an adhesive sheet to be attached to a complex shape, properties that follow the shape and adhere well are required. For example, in the above-described portable electronic device, for an adhesive sheet that fixes a member such as a protective glass having a complex surface shape (may be a curved surface shape), there is a tendency to apply a larger continuous peeling load than in the past, and for an adhesive sheet for such use, a higher level of resilience resistance to a continuous peeling load is required.

[0011] Further, the temperature and humidity in the above-described portable electronic device are not only affected by the heat in the electronic device but also by the external environment, and sometimes become a high temperature state exceeding 50°C, and also can become high humidity. An adhesive for this use that exhibits stable Z-axis direction resilience resistance under such an environment is required.

[0012] In addition, portable electronic devices are subject to a risk of falling from the manner in which they are used, and thus there is a strong demand for improvement in impact resistance of adhesives used in portable electronic devices. Impact resistance can be improved by reducing the modulus of elasticity of an adhesive, for example, and when the modulus of elasticity of an adhesive is reduced by designing to reduce the degree of crosslinking or the like, the cohesive force required for resilience resistance also decreases, and it is difficult to obtain good resilience resistance. As can be seen, resilience resistance and impact resistance are mutually contradictory properties, and it is difficult to achieve both at the same time. It is meaningful to provide an adhesive sheet that exhibits good resilience resistance to a sustained load in the Z-axis direction (resilience resistance to a sustained load in the Z-axis direction) and excellent impact resistance even under harsh environments such as high temperature and high humidity.

[0013] The present inventors conducted intensive studies, and as a result, found that an adhesive that exhibits good resilience resistance to a sustained load in the Z-axis direction and excellent impact resistance even under harsh environments can be obtained by using an acrylic polymer containing heptyl acrylate as a monomer component, thereby completing the present application. That is, the object of the present application is to provide an adhesive sheet that can achieve both high levels of resilience resistance and impact resistance at the same time.

[0014] Means for solving the problem

[0015] According to the present specification, an adhesive sheet is provided. The adhesive sheet has an adhesive layer containing an acrylic polymer. The acrylic polymer is a polymer containing heptyl acrylate as a monomer component. In addition, the adhesive layer has a storage modulus G' of 20,000 Pa or more at 65°C, and a tan δ of 0.3 or more at -20°C. Here, tan δ refers to the ratio of the loss modulus G" to the storage modulus G' (G" / G') of the adhesive layer.

[0016] According to the above-described configuration, the adhesive layer has a storage modulus of 20,000 Pa or more at 65°C, and thus good resilience resistance can be exhibited. In addition, the adhesive layer has a tan δ of 0.3 or more at -20°C, and thus excellent impact resistance is easily obtained. The trade-off between the above-described storage modulus G' at 65°C and tan δ at -20°C can be appropriately achieved by using an acrylic polymer containing heptyl acrylate as a monomer component. According to the adhesive sheet configured as described above, high levels of resilience resistance and impact resistance can be achieved at the same time.

[0017] In some preferred modes, the acrylic polymer described above has a weight average molecular weight (Mw) of 700,000 or more. By using an acrylic polymer containing heptyl acrylate as a monomer unit and having a weight average molecular weight (Mw) of 700,000 or more, the viscoelastic properties described above (specifically, the storage modulus G' at 65°C and the tan δ at -20°C) can be preferably satisfied, and a trade-off between resilience resistance and impact resistance can be easily achieved at a high level.

[0018] In some preferred embodiments, the glass transition temperature (Tg) of the adhesive layer is in the range of -15°C to 15°C. Here, the glass transition temperature of the adhesive layer refers to the glass transition temperature determined from the peak temperature of tanδ in dynamic viscoelasticity measurements. Adhesive layers with a Tg range of -15°C to 15°C readily balance resilience and impact resistance.

[0019] In some preferred embodiments, the adhesive layer further comprises a tackifying resin. The technology disclosed herein is preferably implemented with an adhesive layer comprising a tackifying resin. As the tackifying resin, at least one selected from rosin-based and terpene-based tackifying resins is preferred. In some embodiments, the content of the tackifying resin in the adhesive layer is 70 parts by weight or less relative to 100 parts by weight of the acrylic polymer. The effect of the technology disclosed herein can preferably be achieved by appropriately adjusting the content of the tackifying resin in the adhesive layer within the aforementioned range.

[0020] In some preferred embodiments, the adhesive layer further comprises acrylic oligomers. The techniques disclosed herein preferably implement the method in which the adhesive layer comprises acrylic oligomers. More preferably, the tackifying resin and the acrylic oligomers are used in combination.

[0021] In some preferred embodiments, the adhesive composition used to form the adhesive layer comprises at least one selected from isocyanate crosslinking agents and epoxy crosslinking agents. By using a crosslinking agent selected from isocyanate crosslinking agents and epoxy crosslinking agents, the cohesive strength of the adhesive can be moderately improved, and the resilience can be satisfactorily improved while maintaining impact resistance.

[0022] Some preferred adhesive sheets exhibit a 180-degree peel strength (SUS adhesion) of 20 N / 25 mm or higher on stainless steel sheets. Adhesive sheets with the aforementioned SUS adhesion strength demonstrate excellent adhesive power.

[0023] The adhesive sheet disclosed herein offers a balance of resilience and impact resistance, making it ideally suited for joining components in portable electronic devices where high resilience and impact resistance are required. As described above, this specification provides a portable electronic device using any of the adhesive sheets disclosed herein; in other words, it provides a portable electronic device incorporating such an adhesive sheet. Attached Figure Description

[0024] Figure 1 A cross-sectional view illustrating the structure of an adhesive sheet according to one embodiment.

[0025] Figure 2 A cross-sectional view illustrating the structure of an adhesive sheet according to another embodiment.

[0026] Figure 3 A cross-sectional view for schematically showing the constitution of an adhesive sheet of another embodiment.

[0027] Figure 4 A front view for schematically showing an example of a portable electronic device constituted by including an adhesive sheet.

[0028] Figure 5 A schematic view for explaining a method of a Z-axis direction resilience resistance test. DETAILED DESCRIPTION

[0029] Hereinafter, preferred embodiments of the present application will be described. It should be noted that matters other than those specifically mentioned in the present specification, which are required for practicing the present application, can be understood by those skilled in the art from the teachings of the present specification with respect to the practice of the application and the technical knowledge at the time of filing. The present application can be practiced in accordance with the content disclosed in the present specification and the technical knowledge in the art. In addition, in the following drawings, sometimes the same reference numerals will be assigned to members / positions that play the same role, and repeated description will sometimes be omitted or simplified. In addition, in order to clearly describe the present application, the embodiments recited in the drawings are schematized, and do not necessarily accurately represent the size, scale of the adhesive sheet of the present application actually provided as a product.

[0030] In the present specification, an "adhesive" refers to a material that, as described above, is in a state of a soft solid (viscoelastic body) in a temperature range around room temperature, and has a property of easily adhering to an adherend by pressure. The so-called adhesive herein can be generally a material (typically, a material having the above property at 25°C) having a complex tensile elastic modulus E * (1 Hz) < 10 7 dyne / cm 2 .

[0031] In the present specification, carbon from biomass refers to carbon from a biomass material, i.e., a material of a renewable organic resource (renewable carbon). The above biomass material typically refers to a material from a biological resource (typically a plant that performs photosynthesis) that can be continuously reproduced as long as sunlight, water, and carbon dioxide are present. Therefore, a material from a fossil resource (fossil resource-based material) that is exhausted due to post-mining use does not fall within the concept of the biomass material herein. The biomass carbon ratio of the adhesive layer and the adhesive sheet, i.e., the proportion of carbon from biomass in the total carbon contained in the adhesive layer and the adhesive sheet, can be estimated from the carbon isotope content of mass number 14 determined in accordance with ASTM D6866.

[0032] <Configuration of Adhesive Sheet>

[0033] The adhesive sheet disclosed herein is configured by containing an adhesive layer. The above adhesive sheet can be, for example, in the form of a double-coated adhesive sheet without a support substrate having a first adhesive surface constituted by one surface of the adhesive layer and a second adhesive surface constituted by the other surface of the adhesive layer. Alternatively, the adhesive sheet disclosed herein can be in the form of a tape-adhesive sheet obtained by laminating the above adhesive layer on one or both surfaces of a support substrate. Hereinafter, the support substrate will be sometimes referred to simply as a "substrate". Note that the concept of the adhesive sheet herein can include articles referred to as adhesive tapes, adhesive labels, adhesive films, and the like. Note that the adhesive sheet disclosed herein can be in the form of a roll or in the form of a single sheet. Alternatively, it can be in the form of an adhesive sheet that has been further processed into various shapes.

[0034] The configuration of the adhesive sheet of one embodiment is schematically shown in Figure 1 The adhesive sheet 1 is configured in the form of a double-coated adhesive sheet without a support substrate constituted by an adhesive layer 21. The adhesive sheet 1 is used by adhering a first adhesive surface 21A constituted by one surface (first surface) of the adhesive layer 21 and a second adhesive surface 21B constituted by the other surface (second surface) of the adhesive layer 21 to different parts of an adherend. The parts to which the adhesive surfaces 21A and 21B are adhered can be respective parts of different members or different parts within a single member. As Figure 1As shown, the adhesive sheet 1 before use (i.e., before being pasted onto the object) can be an adhesive sheet 100 with release liner, in which the first adhesive surface 21A and the second adhesive surface 21B are protected by release liner 31, 32, respectively, on the side opposite to the adhesive layer 21, which respectively serve as the release surface. As the release liner 31, 32, for example, it is preferable to use a release liner formed by providing a release layer of release agent on one side of a sheet-like substrate (liner substrate), so that the single side serves as the release surface. Alternatively, the release liner 32 can be omitted, and the release liner 31 with two sides serving as release surfaces can be used, overlapped with the adhesive sheet 1 and wound into a spiral shape, thereby forming an adhesive sheet with release liner in which the second adhesive surface 21B is protected by contact with the back of the release liner 31 (roll shape).

[0035] The structure of the adhesive sheet according to another embodiment is schematically shown in Figure 2 The adhesive sheet 2 is configured as a single-sided adhesive sheet with a substrate, comprising: a sheet-like support substrate (e.g., a resin film) 10 having a first side 10A and a second side 10B, and an adhesive layer 21 disposed on the first side 10A. The adhesive layer 21 is fixedly disposed on the first side 10A of the support substrate 10, i.e., it is not intended to separate the adhesive layer 21 from the support substrate 10. Figure 2 As shown, the adhesive sheet 2 before use can 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 with at least one side opposite to the adhesive layer 21 as the release surface. Alternatively, it can be a roll form where the release liner 31 is omitted, and a support substrate 10 with a second surface 10B as the release surface is used, and the adhesive surface 21A is protected by contacting the second surface (back surface) 10B of the support substrate 10 when the adhesive sheet 2 is wound around it.

[0036] The structure of the adhesive sheet according to another embodiment is schematically shown in Figure 3 The adhesive sheet 3 is constructed as a double-sided adhesive sheet with a substrate, comprising: a sheet-like support substrate (e.g., a resin film) 10 having a first side 10A and a second side 10B; a first adhesive layer 21 fixedly disposed on the first side 10A; and a second adhesive layer 22 fixedly disposed on the second side 10B. Figure 3As shown, the adhesive sheet 3 before use can be a constituent element of a release liner-equipped adhesive sheet 300 in a form in which the surface (first adhesive face) 21A of the first adhesive layer 21 and the surface (second adhesive face) 22A of the second adhesive layer 22 are protected by the release liners 31, 32. Alternatively, the release liner 32 can be omitted, and the release liner 31 having both faces as release faces can be overlapped with the adhesive sheet 3 and wound in a spiral shape, thereby constituting a release liner-equipped adhesive sheet in a form in which the second adhesive face 22A is protected in contact with the back face of the release liner 31 (jelly-roll form).

[0037] Note that in the above-described double-faced adhesive sheet with a substrate, at least one of the first adhesive layer and the second adhesive layer (e.g., the first adhesive layer) can be the adhesive layer described below, and the other adhesive layer (e.g., the second adhesive layer) can be the adhesive layer disclosed herein, or an adhesive layer having a different composition from the adhesive layer disclosed herein (specifically, the above-described one adhesive layer, e.g., the first adhesive layer). Such other adhesive layer can be formed of a publicly known or conventional adhesive, for example.

[0038] In addition, although not particularly limited, according to the technology disclosed herein, in a configuration without a foamed substrate that is advantageous in improving impact resistance, both resilience resistance and impact resistance can be taken into account. Thus, the technology disclosed herein can be implemented in a form of a double-faced adhesive sheet without a substrate composed of an adhesive layer, or a double-faced adhesive sheet with a substrate other than a foamed substrate (non-foamed substrate). Of these, the form of the double-faced adhesive sheet without a substrate is preferred. The double-faced adhesive sheet without a substrate can be thinned to the extent that it does not have a substrate, and can contribute to the miniaturization and space saving of a product to which the double-faced adhesive sheet is applied. In addition, according to the double-faced adhesive sheet without a substrate, the effects of the adhesive layer, such as resilience resistance and impact resistance to a sustained load in the Z-axis direction, can be maximally exhibited.

[0039] <Adhesive Layer>

[0040] (Elastoviscous Properties)

[0041] The adhesive layer disclosed herein (in the case of the first adhesive layer and the second adhesive layer, at least one of the first adhesive layer and the second adhesive layer is the same unless otherwise specified) has a storage modulus G' of 20,000 Pa or more at 65°C. According to the adhesive having the above-mentioned storage modulus at 65°C, good resilience resistance (particularly, resilience resistance to a sustained load in the Z-axis direction under harsh environments such as high temperature conditions) is easily obtained. In some preferred embodiments, the above-mentioned storage modulus at 65°C is 21,000 Pa or more, can be 22,000 Pa or more, can be 23,000 Pa or more, is appropriately 24,000 Pa or more, more preferably 25,000 Pa or more, particularly preferably 26,000 Pa or more, can be 27,000 Pa or more, can be 28,000 Pa or more, can be 29,000 Pa or more, can be 30,000 Pa or more, can be 31,000 Pa or more, can be 32,000 Pa or more, and can be 33,000 Pa or more, from the viewpoint of improving resilience resistance. The upper limit of the above-mentioned storage modulus at 65°C can be set within an appropriate range that allows resilience resistance and impact resistance to be balanced. In some embodiments, the above-mentioned storage modulus at 65°C is appropriately about 60,000 Pa or less, preferably 50,000 Pa or less, more preferably 40,000 Pa or less, further preferably 35,000 Pa or less, can be 32,000 Pa or less, can be 30,000 Pa or less, can be 28,000 Pa or less, can be 26,000 Pa or less.

[0042] Further, the adhesive layer disclosed herein is characterized in that, in addition to the above-mentioned storage modulus of 20,000 Pa or more at 65°C, the tan δ at -20°C is 0.3 or more. The tan δ (loss tangent) is the ratio of the loss modulus G" of the adhesive layer to the storage modulus G' of the adhesive layer (G" / G'). -20°C corresponds to the impact velocity region at the time of falling according to the temperature-velocity conversion rule. According to the adhesive having the above-mentioned tan δ of 0.3 or more at -20°C, excellent impact resistance is easily obtained. In some embodiments, the above-mentioned tan δ at -20°C is 0.35 or more, can be 0.40 or more, or can be 0.45 or more. In some preferred embodiments, the above-mentioned tan δ at -20°C is 0.50 or more, more preferably 0.55 or more, and further preferably 0.60 or more, from the viewpoint of impact resistance. The upper limit of the above-mentioned tan δ at -20°C can be set within an appropriate range that can take into account both resilience resistance and impact resistance. The above-mentioned tan δ at -20°C can be, for example, about 2 or less, can be 1.8 or less, can be 1.6 or less, can be 1.4 or less. In some embodiments, the above-mentioned tan δ at -20°C is 1.2 or less, is preferably 1.0 or less, more preferably 0.80 or less, further preferably 0.70 or less, can be 0.60 or less, or can be 0.55 or less, from the viewpoint of resilience resistance.

[0043] Although not particularly limited, in some preferred embodiments, the glass transition temperature (Tg) of the adhesive layer is in the range of -15°C to 15°C. Here, the glass transition temperature of the adhesive layer refers to the glass transition temperature obtained from the peak temperature of tan δ in dynamic viscoelasticity measurement. By using an adhesive having a Tg in the range of -15°C to 15°C, resilience resistance and impact resistance can be satisfactorily taken into account. From the viewpoint of resilience resistance, the Tg of the adhesive layer is more preferably -12°C or more, further preferably -10°C or more, particularly preferably -7°C or more, can be -5°C or more, can be -3°C or more, can be -1°C or more, can be 0°C or more (e.g., greater than 0°C), or can be 1°C or more. Further, from the viewpoint of impact resistance, the Tg of the adhesive layer is preferably 12°C or less, more preferably 10°C or less, further preferably 7°C or less, particularly preferably 5°C or less, can be 3°C or less, can be 1°C or less, can be 0°C or less (e.g., less than 0°C), can be -1°C or less, or can be -3°C or less.

[0044] In the technology disclosed herein, the 65°C storage modulus, -20°C tan δ, and Tg of the adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, the adhesive layer having a thickness of about 2 mm is prepared by overlapping a plurality of adhesive layers (in the case of an adhesive sheet without a substrate, the adhesive sheet) as a measurement target. The adhesive layer is punched into a disc-shaped sample having a diameter of 7.9 mm and is fixed by being sandwiched between parallel plates, and dynamic viscoelasticity measurement is performed using a viscoelasticity tester (for example, ARES manufactured by TA Instruments, Inc., or an equivalent thereof) under the following conditions, whereby the 65°C storage modulus, -20°C tan δ, and Tg are determined.

[0045] • Measurement mode: shear mode

[0046] • Temperature range: -70°C to 150°C

[0047] • Temperature rate: 5°C / minute

[0048] • Measurement frequency: 1 Hz

[0049] In the examples described later, the measurement is also performed by the above method. Note that, as the measurement target, i.e., the adhesive layer, an adhesive layer formed by coating and drying or curing a corresponding adhesive composition in a layer shape can be used.

[0050] (Acrylic polymer)

[0051] The adhesive layer constituting the adhesive sheet disclosed herein contains an acrylic polymer. The above adhesive layer is typically an adhesive layer in which an acrylic polymer is used as a base polymer. Such an adhesive layer is also referred to as an acrylic adhesive layer. Note that the base polymer refers to a main component of a rubbery polymer (a polymer that exhibits rubber elasticity in a temperature range around room temperature) contained in the adhesive layer. In addition, in the present specification, “main component” refers to a component having a content of more than 50% by weight. In addition, the following description regarding components that can be contained in the adhesive and the adhesive layer applies to the adhesive composition used to form the adhesive (layer), unless otherwise specified.

[0052] In addition, in the present specification, "acrylic polymer" means a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule will also be referred to as "acrylic monomer". Thus, the acrylic polymer of the present specification is defined as a polymer containing monomer units derived from an acrylic monomer. Note that, in the present specification, "(meth)acryloyl group" collectively represents acryloyl group and methacryloyl group. Similarly, "(meth)acrylate" collectively represents acrylate and methacrylate, and "(meth)acrylic acid" collectively represents acrylic acid and methacrylic acid.

[0053] As the acrylic polymer used in the technology disclosed herein, a polymer containing a monomer component of heptyl acrylate is used. The acrylic polymer polymerized using a monomer component containing heptyl acrylate is more excellent in softness than a polymer of other alkyl acrylates such as n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and thus an adhesive containing the polymer easily becomes a value high in tan δ at -20°C, and excellent impact resistance is easily obtained. The reason for this is not particularly limited, but it is considered that a polymer containing heptyl acrylate as a monomer unit has relatively large space between main chains in an adhesive in addition to a low glass transition temperature. Among heptyl acrylates, n-heptyl acrylate is preferred from the viewpoint of softness. An acrylic polymer synthesized containing n-heptyl acrylate as a monomer component has a relatively long linear side chain, and thus it is considered that the space between main chains easily becomes larger.

[0054] In some embodiments, the proportion of heptyl acrylate in the monomer component of the acrylic polymer is, for example, 50% by weight or more (for example, greater than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, particularly preferably 90% by weight or more, can be 92% by weight or more, can be 94% by weight or more, can be 95% by weight or more, can be 96% by weight or more. By increasing the amount of heptyl acrylate used, the effects thereof (for example, improvement in tan δ at -20°C of the adhesive, and further improvement in impact resistance) can be effectively exhibited. On the other hand, the upper limit of the proportion of heptyl acrylate in the monomer component is 100% by weight, and can be 99% by weight or less, or 98% by weight or less. From the viewpoint of copolymerizing a carboxyl group-containing monomer and other monomers, in some embodiments, the proportion of heptyl acrylate in the monomer component is less than 97% by weight. In some preferred embodiments, the proportion of heptyl acrylate in the monomer component is 96% by weight or less, can be 95% by weight or less, or can be 94% by weight or less. Limiting the proportion of heptyl acrylate within the above range is preferable from the viewpoint of improving the storage modulus, and further advantageous from the viewpoint of improving the resilience resistance.

[0055] An alkyl (meth)acrylate other than heptyl acrylate (hereinafter also referred to as "optional alkyl (meth)acrylate") can be copolymerized in the acrylic polymer. As the optional alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.

[0056] CH2=C(R 1 )COOR 2 (1)

[0057] Herein, R 1 in the above formula (1) is a hydrogen atom or a methyl group. In addition, R 2 is a chain alkyl group having 1 to 20 carbon atoms (wherein, in the case where R 1 is a hydrogen atom, n-heptyl is excluded).

[0058] As the above-mentioned optional (meth) acrylic acid alkyl ester, for example, there can be mentioned methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, amyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl methacrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, myristyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and the like. These optional (meth) acrylic acid alkyl esters can be used singly or in combination of two or more.

[0059] In some modes, the proportion of heptyl acrylate in the total amount of the (meth) acrylic acid alkyl ester contained in the above-mentioned monomer component is, for example, 50% by weight or more (specifically, 50% by weight to 100% by weight, for example, more than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 90% by weight or more, particularly preferably 95% by weight or more, can be 99% by weight or more, or can be 100% by weight. By adopting such a monomer composition, the use effect of heptyl acrylate can be effectively exerted. According to the technology disclosed herein, based on the effect of heptyl acrylate, the resilience resistance and the impact resistance can be taken into account regardless of the optional (meth) acrylic acid alkyl ester such as 2EHA or BA. Therefore, the technology disclosed herein can be preferably implemented in a manner that the monomer component does not substantially contain the optional (meth) acrylic acid alkyl ester.

[0060] Note that, in the present specification, the monomer component substantially not containing the monomer A (for example, the above-mentioned optional (meth) acrylic acid alkyl ester) means that the monomer A is not intentionally used at least, and can allow the unintentional inclusion of, for example, about 0.01% by weight or less of the monomer A.

[0061] In some embodiments, the monomer component described above can include an alkyl (meth) acrylate having an alkyl group from biomass at the ester end (hereinafter, also referred to as "biomass alkyl (meth) acrylate"). In recent years, environmental problems such as global warming have been increasingly recognized, and it is desired to reduce the amount of use of fossil resource-based materials such as petroleum. In such a situation, it is also required to reduce the amount of use of fossil resource-based materials in the field of adhesives. By using a biomass alkyl (meth) acrylate, an acrylic adhesive that takes into account suppression of dependence on fossil resource-based materials can be appropriately achieved.

[0062] The biomass alkyl (meth) acrylate is not particularly limited, and is, for example, an ester of an alkyl alcohol from biomass and (meth) acrylic acid from biomass or not from biomass. Examples of the alkyl alcohol from biomass include biomass ethanol, an alkyl alcohol from palm oil or palm kernel oil, coconut oil, castor oil, and the like. In the case where the number of carbon atoms of the alkyl alcohol from biomass is 3 or more, the alkyl alcohol can be linear or can have a branched chain. In some embodiments, as the biomass alkyl (meth) acrylate used in the synthesis of an acrylic polymer, an ester of an alkyl alcohol from biomass and (meth) acrylic acid not from biomass can be used. In this biomass alkyl (meth) acrylate, the more the number of carbon atoms of the alkyl alcohol, the higher the proportion of the number of carbons from biomass in the total number of carbons contained in the biomass alkyl (meth) acrylate, that is, the biomass carbon ratio of the alkyl (meth) acrylate. Therefore, in the above biomass alkyl (meth) acrylate, it is desired that the number of carbons of the alkyl group from biomass be large from the viewpoint of reducing dependence on fossil resource-based materials. On the other hand, when the number of carbons of the alkyl group constituting the alkyl (meth) acrylate is too large, there is a tendency that it is difficult to obtain adhesive properties such as adhesive force, and in addition, it can become disadvantageous from the viewpoint of productivity such as synthesis or handleability, cost, and the like. In the embodiment in which an ester of an alkyl alcohol from biomass and (meth) acrylic acid not from biomass is used as the biomass alkyl (meth) acrylate, it is desired to use a material that balances adhesive properties and reduction of dependence on fossil resource-based materials (more specifically, the biomass carbon ratio of the above alkyl (meth) acrylate).

[0063] In some preferred embodiments, as the heptyl acrylate, a heptyl acrylate from biomass (biomass heptyl acrylate) is used. By using the biomass heptyl acrylate, it is possible to achieve the effects of the technology disclosed herein while reducing dependence on fossil resource-based materials. The above biomass heptyl acrylate is an ester of an alkyl alcohol from biomass and acrylic acid from biomass or not from biomass, and for example, an ester of an alkyl alcohol from biomass and acrylic acid not from biomass can be used. In this compound, only the heptyl group is from biomass. As the heptyl acrylate from biomass, it is preferable to use n-heptyl acrylate from biomass (biomass n-heptyl acrylate).

[0064] The proportion of the biomass (meth) alkyl acrylate (preferably biomass heptyl acrylate) in the monomer component of the acrylic polymer described above is, for example, 50% by weight or more (for example, greater than 50% by weight) in some modes, preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, particularly preferably 90% by weight or more, can be 92% by weight or more, can be 94% by weight or more, and can be 96% by weight or more. In addition, the proportion of the biomass (meth) alkyl acrylate (preferably biomass heptyl acrylate) in the monomer component is less than 97% by weight, and in some modes, can be 95% by weight or less, can be 93% by weight or less, and can be 91% by weight or less.

[0065] In addition, the monomer component of the acrylic polymer preferably contains a carboxyl group-containing monomer. The carboxyl group-containing monomer can increase cohesion based on its polarity. In addition, in the case of using an isocyanate-based, epoxy-based crosslinking agent, or the like, the carboxyl group can become a crosslinking point of the acrylic polymer. By using a carboxyl group-containing monomer, the 65°C storage modulus of the adhesive can be increased, and an adhesive excellent in resistance to resilience to a sustained load in the Z-axis direction can be easily obtained. In addition, by using a carboxyl group-containing monomer, for example, more excellent adhesiveness to a high-polar material or the like can be exerted.

[0066] As the carboxyl group-containing monomer, for example, the following can be listed: acrylic acid (AA), methacrylic acid (MAA), (meth) acrylate carboxyethyl ester, (meth) acrylate carboxypentyl ester, crotonic acid, isocrotonic acid, and the like, which are ethylenically unsaturated monobasic acids; maleic acid, itaconic acid, citraconic acid, and the like, which are ethylenically unsaturated dibasic acids. In addition, the carboxyl group-containing monomer can be a monomer of a metal salt (for example, an alkali metal salt) having a carboxyl group. The carboxyl group-containing monomer can be used alone or in combination with two or more kinds. Among them, as a preferred carboxyl group-containing monomer, AA and MAA can be listed. AA is particularly preferred. In the case of using one or two or more kinds of carboxyl group-containing monomers, the proportion of AA in the carboxyl group-containing monomers described above is preferably 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% by weight or more. In a particularly preferred mode, the carboxyl group-containing monomer contains substantially only AA. From the complex effects of the polarity based on the carboxyl group, the effect as a crosslinking point, Tg (106°C), and the like, AA is considered to be the most appropriate monomer material in terms of balancing the impact resistance and the resistance to resilience to a sustained load in the Z-axis direction among the carboxyl group-containing monomers disclosed herein.

[0067] The proportion of the carboxyl group-containing monomer in the monomer component of the acrylic polymer is not particularly limited and can be 0.1% by weight or more, can be 0.5% by weight or more, can be 1% by weight or more, or can be 2% by weight or more. In some preferred embodiments, the proportion of the carboxyl group-containing monomer in the above monomer component is greater than 3% by weight (more specifically, greater than 3.0% by weight), preferably 4.0% by weight or more, more preferably 4.5% by weight or more, further preferably 5.0% by weight or more (for example, greater than 5.0% by weight), and particularly preferably 5.5% by weight or more, or can be 6.0% by weight or more. By increasing the amount of the carboxyl group-containing monomer used, the cohesion of the adhesive layer is improved based on the effect of the carboxyl group-containing monomer, and thus the 65°C storage modulus of the adhesive can be increased, and an adhesive excellent in resilience resistance can be easily obtained. In addition, the amount of the carboxyl group-containing monomer is appropriately, for example, 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 above carboxyl group-containing monomer can be 10% by weight or less, can be 8% by weight or less, can be 6% by weight or less, or can be 5% by weight or less. By reducing the amount of the carboxyl group-containing monomer (for example, AA) used, there is a tendency that the -20°C tan δ becomes high. By appropriately adjusting the amount of the carboxyl group-containing monomer used within the above range, an adhesive that balances resilience resistance and impact resistance can be easily obtained.

[0068] A functional group-containing monomer (optional functional group-containing monomer) other than the carboxyl group-containing monomer can be copolymerized in the acrylic polymer. As the optional functional group-containing monomer that is introduced into the acrylic polymer to become a crosslinking group or to contribute to the improvement of adhesion, the following can be exemplified: a hydroxyl group-containing monomer ((meth)acrylic acid 2-hydroxyethyl ester, (meth)acrylic acid 2-hydroxypropyl ester, (meth)acrylic acid 3-hydroxypropyl ester, (meth)acrylic acid 2-hydroxybutyl ester, (meth)acrylic acid 4-hydroxybutyl ester, and the like (hydroxyalkyl (meth)acrylate); polypropylene glycol mono(meth)acrylate, and the like), an acid anhydride group-containing monomer, an amide group-containing monomer ((meth)acrylamide, N,N-dimethyl(meth)acrylamide, and the like), an amino group-containing monomer ((meth)acrylic acid aminoethyl ester, (meth)acrylic acid N,N-dimethylaminoethyl ester, and the like), an epoxy group-containing monomer, a cyano group-containing monomer, a ketone group-containing monomer, a monomer having a nitrogen atom-containing ring (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, and the like), an alkoxysilyl group-containing monomer, an imide group-containing monomer, and the like. The above optional functional group-containing monomer can be used alone or in combination with two or more.

[0069] In the case where the monomer component constituting the acrylic polymer contains the above-described optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exerting the effects brought about by the use of the optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component may be, for example, 0.1% by mass or more, and it is appropriate for the content to be 0.5% by mass or more, and it can be 1% by mass or more. In addition, for example, in a manner in which the monomer component of the acrylic polymer contains heptyl acrylate and a carboxyl group-containing monomer, from the viewpoint of easily achieving a balance in adhesion properties in relation to these monomer components, it is appropriate for the content of the optional functional group-containing monomer in the monomer component to be 40% by mass or less, and it is preferable for the content to be 20% by mass or less, and it can be 10% by mass or less (for example, 5% by mass or less). In some modes, the content of the optional functional group-containing monomer in the monomer component is, for example, less than 3% by mass, and it can be less than 1% by mass, and it can be less than 0.5% by mass, and it can be less than 0.3% by mass, and it can be less than 0.1% by mass. The technology disclosed herein can preferably be implemented in a manner in which the monomer component of the acrylic polymer does not substantially contain the optional functional group-containing monomer.

[0070] In addition, as the above-described optional functional group-containing monomer, a hydroxyl group-containing monomer can be used. In this case, the content of the hydroxyl group-containing monomer is appropriately 10% by mass or less (for example, 0.001% by mass to 10% by mass) in the entire monomer component, and it is preferably 5% by mass or less, and more preferably 2% by mass or less. In some modes, the content of the hydroxyl group-containing monomer in the monomer component may be, for example, less than 1% by mass, and it can be less than 0.5% by mass, and it can be less than 0.3% by mass, and it can be less than 0.1% by mass, and it can be less than 0.01% by mass. The monomer component of the acrylic polymer can not substantially contain the hydroxyl group-containing monomer. In the technology disclosed herein, by limiting the amount of use of the hydroxyl group-containing monomer or not using the hydroxyl group-containing monomer, it is possible to achieve a balance between the prescribed 65°C storage modulus G' and -20°C tan δ, and it is possible to satisfactorily achieve a balance between the resilience resistance and the impact resistance at a high level.

[0071] From the viewpoint of effectively exerting the effects of copolymerizing the carboxyl group-containing monomer, the proportion of the carboxyl group-containing monomer in the entire functional group-containing monomer used as the copolymerization component of the acrylic polymer (the entire functional group-containing monomer including the carboxyl group-containing monomer) is appropriately 30% by mass or more, and it is preferably 50% by mass or more, and more preferably 70% by mass or more, and further preferably 80% by mass or more, and particularly preferably 90% by mass or more, and it may be, for example, 95% by mass or more, and it can be 97% by mass or more, and it can be 98% by mass or more, and it can be 99% by mass or more (for example, 99.9% by mass or more). The upper limit of the proportion of the carboxyl group-containing monomer in the above-described entire functional group-containing monomer is 100% by mass, and it may be, for example, 95% by mass or less.

[0072] For the purpose of improving cohesiveness and the like, the monomer component constituting the acrylic polymer can also contain other copolymerization components other than the aforementioned functional group-containing monomers. As examples of the other copolymerization components, mention can be made of vinyl acetate and the like vinyl ester monomers; styrene and the like aromatic vinyl compounds; (meth)acrylic acid cyclohexyl ester, (meth)acrylic acid cyclopentyl ester, (meth)acrylic acid isobornyl ester and the like (meth)acrylic acid cycloalkyl esters; (meth)acrylic acid aryl esters (for example, (meth)acrylic acid phenyl ester), (meth)acrylic acid aryloxyalkyl esters (for example, (meth)acrylic acid phenoxyethyl ester), (meth)acrylic acid aralkyl esters (for example, (meth)acrylic acid benzyl ester) and the like (meth)acrylic acid esters containing an aromatic ring; olefin monomers; chlorine-containing monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxyl group-containing monomers such as (meth)acrylic acid methoxyethyl ester, (meth)acrylic acid ethoxyethyl ester; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether; and the like. The aforementioned other copolymerization components can be used singly or in combination of two or more.

[0073] The amount of the other copolymerization components can be appropriately selected depending on the purpose and use, and is not particularly limited, and from the viewpoint of appropriately exerting the effects brought about by the use thereof, it is appropriate that it be 0.05% by weight or more, and can be 0.5% by weight or more. In addition, from the viewpoint of easily achieving a balance of adhesive properties, it is appropriate that the content of the other copolymerization components in the monomer component be 20% by weight or less, and from the viewpoint of appropriately exerting the adhesive properties based on the essential monomer component, it is preferable that it be 10% by weight or less, more preferable that it be 8% by weight or less, further preferable that it be less than 5% by weight, and for example, it can be less than 3% by weight, or it can be less than 1% by weight. The technology disclosed herein can preferably be implemented in such a manner that the monomer component does not substantially contain the other copolymerization components.

[0074] As the other monomer component, the acrylic polymer can contain a multifunctional monomer having at least two (meth)acryloyl groups, vinyl groups and the like polymerizable functional groups (typically, free radical polymerizable functional groups) having unsaturated double bonds. By using a multifunctional monomer as the monomer component, it is possible to improve the cohesiveness of the adhesive layer. The multifunctional monomer can be used as a crosslinking agent. As the multifunctional monomer, there is no particular limitation, and for example, mention can be made of 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate and the like. The multifunctional monomer can be used singly or in combination of two or more.

[0075] The amount of the polyfunctional monomer used is not particularly limited and can be appropriately set in a manner that achieves the purpose of using the polyfunctional monomer. The amount of the polyfunctional monomer used can be about 3% by mass or less, preferably about 2% by mass or less, and more preferably about 1% by mass or less (for example, about 0.5% by mass or less) of the monomer component. The lower limit of the amount of the polyfunctional monomer used in the case of using the polyfunctional monomer is not particularly limited as long as it is more than 0% by mass. Generally, by setting the amount of the polyfunctional monomer used to be about 0.001% by mass or more (for example, about 0.01% by mass or more) of the monomer component, the effect of using the polyfunctional monomer can be appropriately exerted.

[0076] In a particularly preferable mode, as the acrylic polymer, an acrylic polymer synthesized using a monomer component consisting essentially of heptyl acrylate (preferably n-heptyl acrylate) and a carboxyl group-containing monomer (preferably acrylic acid) is used. According to the above-described monomer composition, the effects of heptyl acrylate and the carboxyl group-containing monomer can be effectively exerted, the prescribed 65°C storage modulus G' and -20°C tan δ can be taken into account, and the balance between the resilience resistance and the impact resistance at a high level can be satisfactorily achieved. From such a viewpoint, it is appropriate that the total proportion of heptyl acrylate and the carboxyl group-containing monomer in the above-described monomer component is 90% by mass or more (90% by mass to 100% by mass), is preferably 95% by mass or more, is more preferably 99% by mass or more, is further preferably more than 99.5% by mass, is particularly preferably more than 99.9% by mass (for example, more than 99.99% by mass), and the total proportion of heptyl acrylate and the carboxyl group-containing monomer in the above-described monomer component can be 100% by mass.

[0077] The biomass carbon ratio of the monomer component that constitutes the acrylic polymer (the biomass carbon ratio of the acrylic polymer) can be, for example, 1% or more, is appropriately 10% or more, is preferably 30% or more, and is more preferably 50% or more (for example, more than 50%). It can be 70% or more, 80% or more, or 90% to 100%. By so designing, an acrylic adhesive that takes into account the suppression of dependence on fossil resource-based materials can be obtained.

[0078] The method of obtaining the acrylic polymer is not particularly limited and various polymerization methods known as the synthesis method of the acrylic polymer, such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, and a photopolymerization method, can be appropriately used. For example, a solution polymerization method can be preferably used. As the monomer feeding method when solution polymerization is performed, a one-shot feeding method in which the total monomer raw material is fed at once, a continuous feeding (dropping) method, a batch feeding (dropping) method, and the like can be appropriately used. The polymerization temperature can be appropriately selected depending on the kind of the monomer and the solvent used, the kind of the polymerization initiator, and the like, and can be, for example, about 20°C to about 170°C (typically, about 40°C to about 140°C).

[0079] The solvent used for the solution polymerization (polymerization solvent) can be appropriately selected from the conventionally known organic solvents. For example, any one solvent selected from the group consisting of aromatic compounds (typically, aromatic hydrocarbons) such as toluene; acetate esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols (e.g., monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol; ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; or a mixed solvent of two or more of these solvents can be used.

[0080] The initiator used for the polymerization can be appropriately selected from the conventionally known polymerization initiators according to the kind of the polymerization method. For example, one or two or more of azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. As other examples of the polymerization initiator, there can be mentioned: persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide (BPO), hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; and the like. As further other examples of the polymerization initiator, there can be mentioned redox-based initiators based on the combination of a peroxide and a reducing agent. Such polymerization initiators can be used singly or in combination of two or more. The amount of the polymerization initiator used can be a usual amount, for example, can be selected from the range of about 0.005 parts by weight to about 1 part by weight (typically, about 0.01 part by weight to about 1 part by weight) with respect to 100 parts by weight of the total monomer components.

[0081] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and an acrylic polymer having an appropriate Mw that satisfies the above-mentioned 65°C storage modulus and -20°C tan δ can be used. In some embodiments, the Mw of the acrylic polymer can be greater than 600,000, can be greater than 650,000, 700,000 or more is appropriate, can be 750,000 or more. The greater the Mw of the acrylic polymer, the more likely it is to obtain an adhesive that exhibits good cohesiveness, with a tendency to improve resilience resistance. In some preferred embodiments, the Mw of the acrylic polymer is 800,000 or more, can be 850,000 or more, can be 900,000 or more, more preferably 1,000,000 or more (e.g., greater than 1,000,000), further preferably 1,200,000 or more, particularly preferably 1,400,000 or more, can be 1,500,000 or more, or can be 1,600,000 or more. Depending on the monomer composition including heptyl acrylate, it is easy to keep the viscosity low, and thus the synthesis of a high molecular weight polymer is good, and it is easy to obtain an acrylic polymer having the above-mentioned Mw. In addition, by using an acrylic polymer including heptyl acrylate as a monomer unit and having an Mw of a prescribed value or more, the above-mentioned viscoelastic properties (specifically, the 65°C storage modulus G' and the -20°C tan δ) are easily satisfied by the softness based on the chemical structure of the polymer and the cohesiveness based on the molecular weight, and it is possible to satisfactorily achieve a balance between resilience resistance and impact resistance at a high level. On the other hand, from the viewpoints of impact resistance, adhesive force, ease of synthesis, and the like, it is appropriate for the Mw of the acrylic polymer to be generally about 3,000,000 or less, preferably 2,500,000 or less, more preferably 2,000,000 or less, further preferably 1,800,000 or less, can be 1,500,000 or less, or can be 1,300,000 or less. In some preferred embodiments, the Mw of the acrylic polymer can be 1,100,000 or less, can be 1,000,000 or less, can be 950,000 or less, or can be 900,000 or less.

[0082] The Mw of the acrylic polymer can be measured by gel permeation chromatography (GPC) and is obtained as a standard polystyrene conversion value. Specifically, a commercially available product "HLC-8220 GPC" (manufactured by Tosoh Corporation) can be used as a GPC measuring device, and measurement under the following conditions can be used to obtain the value. The same applies in the examples described later.

[0083] [Measurement conditions for GPC]

[0084] Sample concentration: 0.2% by weight (tetrahydrofuran solution)

[0085] Sample injection amount: 10 μL

[0086] Eluent: tetrahydrofuran (THF)

[0087] Flow rate: 0.6 mL / min

[0088] Column temperature (measurement temperature) : 40°C

[0089] Column:

[0090] Sample column: Trade name "TSKguard column Super HZ-H" 1 piece + Trade name "TSKgel Super HZM-H" 2 pieces (manufactured by TOSOH CORPORATION)

[0091] Reference column: Trade name "TSKgel Super H-RC" 1 piece (manufactured by TOSOH CORPORATION)

[0092] Detector: Differential refractometer (RI)

[0093] Standard sample: Polystyrene

[0094] (tackifier resin)

[0095] In some preferred modes, the adhesive layer contains a tackifier resin. By using a tackifier resin, high adhesive force can be obtained. According to the technology disclosed herein, in a composition containing a tackifier resin, the adhesive layer has prescribed viscoelastic properties (specifically, 65°C storage modulus G' and -20°C tan δ), and excellent Z-axis direction resilience resistance can be exerted. In particular, the effect of using a tackifier resin can be effectively exerted in a composition containing a high-molecular-weight acrylic polymer. As the tackifier resin, there is no particular limitation, 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, ketone-based tackifier resins, and the like can be used, for example. Such a tackifier resin can be used alone or in combination with two or more.

[0096] As specific examples of the rosin-based tackifying resin, the following can be given: unmodified rosins (raw rosin) such as gum rosin, wood rosin, and floating oil rosin; modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins, etc.) obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, and the like; other various rosin derivatives; and the like. As examples of the above rosin derivatives, the following can be given: rosin esters such as substances obtained by esterifying unmodified rosin with an alcohol (i.e., esterification products of rosin), substances obtained by esterifying modified rosin with an alcohol (i.e., esterification products of modified rosin), and the like; unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin or modified rosin with an unsaturated fatty acid; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with an unsaturated fatty acid; rosin alcohols obtained by reducing the carboxyl group in unmodified rosin, modified rosin, unsaturated fatty acid-modified rosin, or unsaturated fatty acid-modified rosin esters; metal salts of rosin (particularly rosin esters) such as unmodified rosin, modified rosin, various rosin derivatives, and the like; rosin phenolic resins obtained by adding phenol to rosin (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and performing thermal polymerization; and the like. Among these, rosin esters are preferred.

[0097] As specific examples of the rosin esters, the following can be given: esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) such as methyl ester, triethylene glycol ester, glycerin ester, pentaerythritol ester, and the like, but there is no particular limitation.

[0098] As examples of the terpene-based tackifying resin, the following can be given: terpene resins such as α-pinene polymer, β-pinene polymer, and terpinolene polymer; modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.); and the like. As an example of the above modified terpene resin, a terpene phenolic resin can be given.

[0099] A terpene phenolic resin refers to a polymer containing a terpene residue and a phenol residue, and is a concept including both a copolymer of a terpene and a phenol compound (terpene-phenol copolymer resin) and a resin obtained by phenol-modifying a homopolymer or copolymer of a terpene (phenol-modified terpene resin). As specific examples of the terpene that constitutes such a terpene phenolic resin, the following can be given: monoterpene such as α-pinene, β-pinene, and limonene (including d form, l form, and d / l form (terpinolene)). A hydrogenated terpene phenolic resin refers to a hydrogenated terpene phenolic resin having a structure obtained by hydrogenating such a terpene phenolic resin. It is also sometimes referred to as a hydrogenated terpene phenolic resin.

[0100] As examples of the hydrocarbon-based tackifying resin, various hydrocarbon resins such as aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, hydrogenated products thereof (for example, an alicyclic petroleum resin obtained by hydrogenating an aromatic petroleum resin), various modified products thereof (for example, a maleic anhydride-modified product), coumarone resins, coumarone-indene resins, and the like can be listed.

[0101] In some embodiments, as the tackifying resin, at least one selected from the group consisting of a rosin-based tackifying resin and a terpene-based tackifying resin is preferably used. By containing a rosin-based tackifying resin and / or a terpene-based tackifying resin in the acrylic adhesive, excellent resistance to springback in the Z-axis direction is easily obtained, and in addition, the adhesive strength can be improved. In some preferred embodiments, the proportion of the total of the rosin-based tackifying resin and the terpene-based tackifying resin in the entire tackifying resin contained in the adhesive layer may, for example, be greater than about 50% by weight (greater than 50% by weight and less than or equal to 100% by weight), can be about 70% by weight or greater, can be about 80% by weight or greater, can be about 90% by weight or greater, can be 95% by weight or greater, or can be 99% by weight or greater.

[0102] As some preferred embodiments, a mode in which the above-described tackifying resin contains one or two or more terpene phenol resins can be listed. The technology disclosed herein can be preferably implemented, for example, in a mode in which about 25% by weight or greater (more preferably about 30% by weight or greater) of the total amount of the tackifying resin is a terpene phenol resin. The proportion of the terpene phenol resin in the total amount of the tackifying resin can be about 50% by weight or greater, can be about 70% by weight or greater, can be about 80% by weight or greater, or can be about 90% by weight or greater. It can be that substantially all (for example, about 95% by weight or greater and 100% by weight or less, further about 99% by weight or greater and 100% by weight or less) of the tackifying resin is a terpene phenol resin.

[0103] The content of the terpene phenol resin in the adhesive layer is not particularly limited as long as the target viscoelastic properties are satisfied. In some embodiments, from the viewpoint of improving adhesive strength, the content of the terpene phenol resin is usually about 1 part by weight or more, about 5 parts by weight or more, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and further preferably about 12 parts by weight or more (e.g., 15 parts by weight or more) relative to 100 parts by weight of the acrylic polymer. In addition, in some embodiments, the content of the terpene phenol resin in the adhesive layer is, for example, 70 parts by weight or less, can be 60 parts by weight or less, and can be 50 parts by weight or less relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the viewpoint of resistance to resilience, the content of the terpene phenol resin described above is 40 parts by weight or less, more preferably 30 parts by weight or less, further preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less, and can be 18 parts by weight or less.

[0104] Although not particularly limited, in some embodiments, the tackifying resin described above can include a tackifying resin (e.g., a terpene phenol resin) having a hydroxyl value of greater than 20 mgKOH / g. The tackifying resin can have a hydroxyl value of 30 mgKOH / g or more. Among these, a tackifying resin having a hydroxyl value of 50 mgKOH / g or more is preferred. Hereinafter, a tackifying resin having a hydroxyl value of 50 mgKOH / g or more is sometimes referred to as a “high hydroxyl value resin”. According to a tackifying resin including such a high hydroxyl value resin, in addition to adhesive strength, an adhesive layer having high cohesion can be achieved by interaction with a crosslinking agent such as an isocyanate-based crosslinking agent. In some embodiments, the tackifying resin described above can include a high hydroxyl value resin having a hydroxyl value of 60 mgKOH / g or more (more preferably 70 mgKOH / g or more). In addition, the high hydroxyl value resin (e.g., a terpene phenol resin) described above is preferably used in combination with an acrylic polymer containing heptyl acrylate as a monomer component, for example, and can exert good adhesive strength on the adherend and resistance to resilience to a sustained load in the Z-axis direction.

[0105] The upper limit of the hydroxyl value of the high-hydroxyl-value resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer and the like, the hydroxyl value of the high-hydroxyl-value resin is usually about 300 mgKOH / g or less, about 200 mgKOH / g or less is appropriate, preferably about 180 mgKOH / g or less, more preferably about 160 mgKOH / g or less, further preferably about 140 mgKOH / g or less, and can be less than 120 mgKOH / g (for example, 110 mgKOH / g or less). The technology disclosed herein can be preferably implemented in a manner that the tackifying resin contains a high-hydroxyl-value resin (for example, a terpene-based tackifying resin, preferably a terpene phenol resin) having a hydroxyl value of 50 mgKOH / g to 200 mgKOH / g. In some modes, it can be preferable to use a high-hydroxyl-value resin having a hydroxyl value of 60 mgKOH / g to 140 mgKOH / g (for example, 70 mgKOH / g to 110 mgKOH / g).

[0106] Here, as the value of the above hydroxyl value, a value measured by the potentiometric titration method prescribed in JIS K0070:1992 can be used. The specific measurement method is shown below.

[0107] [Measurement method of hydroxyl value]

[0108] 1. Reagents

[0109] (1) As an acetylating agent, an acetylating agent obtained by taking about 12.5 g (about 11.8 mL) of acetic anhydride, adding pyridine thereto so that the total amount is 50 mL, and stirring well was used. Alternatively, an acetylating agent obtained by taking about 25 g (about 23.5 mL) of acetic anhydride, adding pyridine thereto so that the total amount is 100 mL, and stirring well was used.

[0110] (2) As a measurement reagent, a 0.5 mol / L potassium hydroxide ethanol solution was used.

[0111] (3) In addition, toluene, pyridine, ethanol, and distilled water were prepared.

[0112] 2. Operation

[0113] (1) About 2 g of a sample was accurately weighed in a flat-bottomed flask, 5 mL of an acetylating agent and 10 mL of pyridine were added, and an air cooling tube was installed.

[0114] (2) The above flask was heated in a bath at 100°C for 70 minutes, then naturally cooled, 35 mL of toluene as a solvent was added from the upper part of the cooling tube and stirred, then 1 mL of distilled water was added and stirred, thereby decomposing the acetic anhydride. In order to complete the decomposition, it was heated again in the bath for 10 minutes and naturally cooled.

[0115] (3) The cooling tube was washed with 5 mL of ethanol and removed. Next, 50 mL of pyridine was added as a solvent and stirred.

[0116] (4) 25 mL of 0.5 mole / L potassium hydroxide ethanol solution was added using a vollpipette.

[0117] (5) Potentiometric titration was performed using the 0.5 mole / L potassium hydroxide ethanol solution. The inflection point of the resulting titration curve was used as the end point.

[0118] (6) In the blank test, (1) to (5) above were performed without adding the sample.

[0119] 3. Calculation

[0120] The hydroxyl value was calculated according to the following formula.

[0121] Hydroxyl value (mgKOH / g) = [(B - C) x f x 28.05] / S + D

[0122] Here,

[0123] B: The amount (mL) of 0.5 mole / L potassium hydroxide ethanol solution used in the blank test,

[0124] C: The amount (mL) of 0.5 mole / L potassium hydroxide ethanol solution used in the sample,

[0125] f: The factor of 0.5 mole / L potassium hydroxide ethanol solution,

[0126] S: The weight (g) of the sample,

[0127] D: The acid value,

[0128] 28.05: 1 / 2 of the molecular weight 56.11 of potassium hydroxide.

[0129] As the high hydroxyl value resin, a tackifying resin having a hydroxyl value of a prescribed value or more among the various tackifying resins described above can be used. The high hydroxyl value resin can be used singly or in combination of two or more. For example, as the high hydroxyl value resin, a terpene phenol resin having a hydroxyl value of 50 mgKOH / g or more can be preferably used. The terpene phenol resin can arbitrarily control the hydroxyl value according to the copolymerization ratio of phenol, and is therefore suitable.

[0130] While not particularly limited, in the case of using a high-hydroxyl value resin, the proportion of the high-hydroxyl value resin (e.g., terpene phenol resin) in the tackifying resin as a whole contained in the adhesive layer can be about 5% by weight or more, can be 10% by weight or more, can be 15% by weight or more, can be 20% by weight or more. In some modes, the proportion of the high-hydroxyl value resin in the tackifying resin as a whole is preferably about 30% by weight or more, for example. Thereby, the effects of using a high-hydroxyl value resin can be satisfactorily exerted, and it is possible to improve the adhesive force and the resilience to the sustained load in the Z-axis direction while having impact resistance. In some preferred modes, the proportion of the high-hydroxyl value resin in the tackifying resin as a whole is about 40% by weight or more, can be about 50% by weight or more (e.g., more than 50% by weight), can be about 60% by weight or more, can be about 70% by weight or more, can be about 80% by weight or more, or can be about 90% by weight or more. It can be that substantially all (e.g., about 95% by weight to about 100% by weight, further about 99% by weight to about 100% by weight) of the tackifying resin is the high-hydroxyl value resin.

[0131] The softening point of the high-hydroxyl value resin described above is not particularly limited. The softening point of the high-hydroxyl value resin can be about 50°C or more, and from the viewpoint of improving the coagulating force, it can be preferable to use a high-hydroxyl value resin having a softening point (softening temperature) of about 80°C or more. For example, it can be preferable to use a terpene phenol resin having such a softening point. The softening point of the high-hydroxyl value resin can be about 100°C or more, or can be about 110°C or more. In some preferred modes, the softening point of the high-hydroxyl value resin is about 120°C or more, can be about 130°C or more, or can be about 135°C or more (further about 140°C or more). The upper limit of the softening point of the high-hydroxyl value resin is not particularly limited. From the viewpoint of the adhesiveness to the adherend, it can be preferable to use a high-hydroxyl value resin having a softening point of about 200°C or less (more preferably about 180°C or less). In some modes, the softening point of the high-hydroxyl value resin can be less than 160°C. In some preferred modes, as the high-hydroxyl value resin, a high-hydroxyl value resin having a softening point of less than 150°C is used. By using a high-hydroxyl value resin having a softening point of less than 150°C, it is possible to obtain an adhesive that has both resilience and impact resistance, and also has excellent adhesive force. The softening point of the high-hydroxyl value resin can be 145°C or less.

[0132] Note that the softening point of the tackifying resin in the present specification is defined as a value measured according to the softening point test method (ring and ball method) prescribed in JIS K5902 and JIS K2207. Specifically, a test sample is rapidly melted at as low a temperature as possible, and is filled in a ring placed on a flat metal plate, taking care not to generate air bubbles. After cooling, the raised portion is cut off from the plane including the upper end of the ring with a slightly heated knife. Next, a support (ring stand) is placed in a glass container (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured until the depth reaches 90 mm or more. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the test sample are immersed in the glycerin so as not to contact each other, and the temperature of the glycerin is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed at the center of the surface of the test sample in the ring, and is placed at a fixed position on the support. Next, the distance from the upper end of the ring to the surface of the glycerin is maintained at 50 mm, a thermometer is placed so that the center of the mercury ball of the thermometer is at the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating is placed at the center of the bottom of the container and the middle of the edge so as to heat uniformly. Note that the rate of increase in the bath temperature after reaching 40°C from the start of heating must be 5.0°C ± 0.5°C per minute. The test sample gradually softens and flows down from the ring, and the temperature at which the final contact with the bottom plate is made is read as the softening point. The determination of the softening point is performed two or more times simultaneously, and the average value thereof is adopted.

[0133] The content of the high-hydroxyl-value resin in the adhesive layer is not particularly limited as long as the viscoelastic properties targeted are satisfied. In some embodiments, the content of the high-hydroxyl-value resin is usually about 1 part by weight or more, and it is appropriate to be about 5 parts by weight or more, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and further preferably about 12 parts by weight or more (for example, 15 parts by weight or more), with respect to 100 parts by weight of the acrylic polymer, from the viewpoint of improving the adhesive strength. In addition, in some embodiments, the content of the high-hydroxyl-value resin in the adhesive layer is, for example, 70 parts by weight or less, and can be 60 parts by weight or less, or 50 parts by weight or less, with respect to 100 parts by weight of the acrylic polymer. In some preferred embodiments, the content of the above high-hydroxyl-value resin is 40 parts by weight or less, more preferably 30 parts by weight or less, further preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less, and can be 18 parts by weight or less, from the viewpoint of the resilience resistance.

[0134] Although not particularly limited, in some embodiments, the tackifying resin can include a tackifying resin having a hydroxyl value of less than 50 mgKOH / g. Hereinafter, the tackifying resin having a hydroxyl value of less than 50 mgKOH / g is sometimes referred to as a "low hydroxyl value resin". Although not particularly limited, the low hydroxyl value resin is preferably used in combination with a high hydroxyl value resin. The low hydroxyl value resin can have a hydroxyl value of less than 40 mgKOH / g. The lower limit of the hydroxyl value of the low hydroxyl value resin is more than 0 mgKOH / g, can be more than about 10 mgKOH / g, and can be more than about 15 mgKOH / g. As the low hydroxyl value resin, one or more than two kinds of tackifying resins having a hydroxyl value of less than 50 mgKOH / g selected from the above-mentioned exemplified tackifying resins can be used alone or in combination. In some embodiments, the low hydroxyl value resin preferably includes a rosin-based tackifying resin. The low hydroxyl value resin can include one kind of rosin-based tackifying resin alone or two or more kinds of rosin-based tackifying resins in combination.

[0135] In some embodiments, the proportion of the rosin-based tackifying resin in the entire low hydroxyl value resin can be, for example, more than about 50% by weight, can be more than about 65% by weight, can be more than about 75% by weight, can be more than 85% by weight, or can be more than 95% by weight. The technology disclosed herein can be preferably implemented in such a manner that substantially all (for example, more than about 97% by weight or more than about 99% by weight, or can be 100% by weight) of the low hydroxyl value resin is a rosin-based tackifying resin.

[0136] The softening point of the above-mentioned low hydroxyl value resin is not particularly limited. From the viewpoint of improving cohesiveness, it can be preferable to use a low hydroxyl value resin having a softening point (softening temperature) of more than about 80°C. For example, it can be preferable to use a rosin-based tackifying resin having such a softening point. The softening point of the low hydroxyl value resin can be more than about 100°C, can be more than about 110°C, or can be more than about 120°C. The upper limit of the softening point of the low hydroxyl value resin is not particularly limited. From the viewpoint of adhesiveness to an adherend, it can be preferable to use a low hydroxyl value resin having a softening point of less than about 200°C (more preferably less than about 180°C). In some embodiments, the softening point of the low hydroxyl value resin can be less than about 160°C, can be less than about 150°C (for example, less than 150°C), can be less than about 140°C, or can be less than 130°C.

[0137] In some embodiments, as the tackifying resin, a tackifying resin T L having a softening point of less than 150°C is used. By using the tackifying resin T L , it is possible to obtain higher adhesive force to various adherends. The softening point of the above-mentioned tackifying resin T L may be less than 145°C. The lower limit of the softening point of the tackifying resin T L is not particularly limited. In some embodiments, from the viewpoint of exerting moderate cohesiveness, the tackifying resin TL The softening point can be, for example, about 50°C or higher, preferably about 80°C or higher, more preferably about 100°C or higher, and even more preferably about 110°C or higher. In some preferred embodiments, the softening point of the tackifying resin is about 120°C or higher, can be 130°C or higher, or can be 135°C or higher (even more about 140°C or higher).

[0138] As a tackifying resin T L One or more tackifying resins selected from those exemplified above, with a softening point less than 150°C, can be used alone. In some embodiments, tackifying resin T... L Preferably, it contains terpene phenol resin. Tackifying resin T L It may contain only one type of terpene phenol resin, or it may contain a combination of two or more terpene phenol resins.

[0139] In some methods, terpene phenol resins are used in tackifying resins T L The proportion of the total component can be, for example, greater than about 50% by weight, more than about 65% by weight, more than about 75% by weight, more than 85% by weight, or more than 95% by weight. The technique disclosed herein preferably uses tackifying resin T. L It is implemented in a manner in which substantially all (e.g., more than 97% by weight, or more than 99% by weight, or even 100% by weight) is a terpene phenol resin.

[0140] In addition, as a tackifying resin T L For example, it may or may not contain a tackifying resin with a softening point of less than 50°C, more preferably about 40°C or less (typically tackifying resins such as rosin, terpenes, hydrocarbons, etc., such as hydrogenated rosin methyl ester). The tackifying resin exhibiting such a low softening point can be a liquid tackifying resin that is liquid at 30°C. The liquid tackifying resin can be used alone or in combination of two or more. From the viewpoint of cohesion, the content of the liquid tackifying resin can be [T]. L It is appropriate for the total amount to be less than about 30% by weight, less than about 10% by weight (e.g., 0% to 10% by weight), less than about 2% by weight (0.5% to 2% by weight), or even less than 1% by weight.

[0141] Tackifying resin T L There is no particular limitation on the content of [the substance], but in some methods, about 70 parts by weight or less relative to 100 parts by weight of acrylic polymer is appropriate. This is achieved by using tackifying resin T... L By limiting the amount used to below a specified level, it is possible to improve impact resistance while maintaining good resilience and adhesive strength. In some preferred embodiments, from the viewpoint of impact resistance, the tackifying resin T is used in proportion to 100 parts by weight of acrylic polymer.L The amount of use of the tackifier resin T L The amount of use of the tackifier resin T

[0142] In some embodiments, the above-mentioned adhesive layer can contain the tackifier resin T L and a tackifier resin T H The tackifier resin T H One or more of the tackifier resins T

[0143] In some embodiments, the tackifier resin T L The total amount of the tackifier resin T L The total amount of the tackifier resin T L The total amount of the tackifier resin T L The total amount of the tackifier resin T L In some preferred embodiments, the tackifier resin T L The total amount of the tackifier resin T

[0144] The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving the cohesiveness, it is preferable to use a tackifying resin having a softening point (softening temperature) of about 80°C or higher. For example, it is preferable to use a terpene-based tackifying resin (terpene phenol resin, etc.) having such a softening point. The softening point of the tackifying resin can be about 100°C or higher, or about 110°C or higher. In some preferable modes, the softening point of the tackifying resin is about 120°C or higher, can be about 130°C or higher, or can be about 135°C or higher (further, about 140°C or higher). Among them, it is preferable to use a terpene phenol resin having the above-mentioned softening point. The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoint of the adhesiveness to the adherend, it is preferable to use a tackifying resin having a softening point of about 200°C or lower (more preferably, about 180°C or lower). In some modes, the softening point of the tackifying resin can be less than 160°C, or can be less than 150°C.

[0145] In the case where the adhesive layer disclosed herein contains a tackifying resin, as the tackifying resin, from the viewpoint of improving the biomass carbon ratio of the adhesive layer, it is preferable to use a tackifying resin derived from a plant (plant-derived tackifying resin). As examples of the plant-derived tackifying resin, for example, the above-mentioned rosin-based tackifying resin, terpene-based tackifying resin can be listed. The plant-derived tackifying resin can be used alone or in combination with two or more kinds. In the case where the adhesive layer disclosed herein contains a tackifying resin, the proportion of the plant-derived tackifying resin in the total amount of the tackifying resin is preferably 30% by mass or more (for example, 50% by mass or more, typically, 80% by mass or more). In some modes, the proportion of the plant-derived tackifying resin in the total amount of the tackifying resin is 90% by mass or more (for example, 95% by mass or more, typically, 99% by mass to 100% by mass). The technology disclosed herein can be preferably implemented in a manner that substantially does not contain a tackifying resin other than the plant-derived tackifying resin.

[0146] The content of the tackifying resin in the adhesive layer is not particularly limited as long as the target viscoelastic properties are satisfied. In some embodiments, from the viewpoint of improving the adhesive strength, the content of the tackifying resin is usually about 1 part by weight or more, and it is appropriate for it to be about 5 parts by weight or more, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and further preferably about 12 parts by weight or more (for example, 15 parts by weight or more), with respect to 100 parts by weight of the acrylic polymer. In addition, in some embodiments, the content of the tackifying resin in the adhesive layer is, for example, 70 parts by weight or less, and it can be 60 parts by weight or less, or 50 parts by weight or less, with respect to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the viewpoint of the resilience resistance, the content of the tackifying resin described above is 40 parts by weight or less, more preferably 30 parts by weight or less, further preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less, and it can be 18 parts by weight or less. The acrylic polymer containing heptyl acrylate as a monomer unit used in the technology disclosed herein has good compatibility with the tackifying resin, and thus the desired properties can be achieved by including an appropriate amount of the tackifying resin.

[0147] (acrylic oligomer)

[0148] In some preferred embodiments, the adhesive layer contains an acrylic oligomer. By containing the acrylic oligomer, the adhesive strength of the adhesive can be improved. According to the technology disclosed herein, in the composition containing the acrylic oligomer, the adhesive layer has prescribed viscoelastic properties (specifically, the storage modulus G' at 65°C and the tan δ at -20°C), and excellent resilience resistance in the Z-axis direction can be exerted. In particular, in the composition containing the acrylic polymer of high molecular weight, the effect of using the acrylic oligomer can be effectively exerted.

[0149] The Tg of the acrylic oligomer described above is preferably about 0°C or more and about 300°C or less, preferably about 20°C or more and about 300°C or less, and further preferably about 40°C or more and about 300°C or less. By having the Tg in the above range, the adhesive strength can be appropriately improved. In some preferred embodiments, from the viewpoint of the cohesiveness of the adhesive, the Tg of the acrylic oligomer is about 30°C or more, and more preferably about 50°C or more (for example, about 60°C or more), and in addition, from the viewpoint of the adhesive strength, it is preferably about 200°C or less, more preferably about 150°C or less, and further preferably about 100°C or less (for example, about 80°C or less).

[0150] In the present specification, the Tg of the acrylic oligomer refers to the Tg calculated based on the composition of the monomer components by the Fox formula. The Fox formula is a formula for the relationship between the Tg of a copolymer and the glass transition temperatures Tgi of the homopolymers obtained by homopolymerizing the respective monomers constituting the copolymer.

[0151] 1 / Tg=Σ(Wi / Tgi)

[0152] It should be noted that in the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0153] The glass transition temperature of the homopolymer used in the calculation of Tg can be the value recorded in known sources. For example, the value recorded in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. For monomers for which multiple values ​​are recorded in this document, the highest value is adopted.

[0154] For monomers for which the glass transition temperature of homopolymers is not recorded in the aforementioned literature, the values ​​obtained by the following determination method shall be used.

[0155] Specifically, 100 parts by weight of monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as the polymerization solvent were added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet pipe, and a reflux condenser. The mixture was stirred for 1 hour while nitrogen was being circulated. After removing oxygen from the polymerization system, the temperature was raised to 63°C and the reaction was carried out for 10 hours. Then, the mixture was cooled to room temperature to obtain a homopolymer solution with a solids concentration of 33% by weight. This homopolymer solution was then cast onto a release liner and dried to produce a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. The test sample was punched into a disc shape with a diameter of 7.9 mm and sandwiched between parallel plates. The viscoelasticity was measured in shear mode using a viscoelasticity testing machine (manufactured by TA Instruments Japan, model name "ARES") while applying a shear strain at a frequency of 1 Hz in a temperature range of -70℃ to 150℃ at a heating rate of 5℃ / min. The temperature corresponding to the peak temperature of tanδ was taken as the Tg of the homopolymer.

[0156] The weight average molecular weight (Mw) of the acrylic oligomer can typically be greater than or equal to about 1000 and less than about 30000, preferably greater than or equal to about 1500 and less than about 20000, further preferably greater than or equal to about 2000 and less than about 10000. By having the Mw within the above range, good adhesive force and resistance to resilience can be obtained, and thus is preferred. In some preferred embodiments, the Mw of the acrylic oligomer is about 2500 or more (e.g., about 3000 or more) from the viewpoint of resistance to resilience under a constant load in the Z-axis direction, and is preferably about 7000 or less, more preferably about 5000 or less (e.g., about 4500 or less, typically about 4000 or less) from the viewpoint of adhesive force. The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) as a value converted to standard polystyrene. Specifically, measurement is performed in an HPLC 8020 manufactured by Tosoh Corporation using TSK gel GMH-H (20) x 2 as columns, in a tetrahydrofuran solvent at a flow rate of about 0.5 mL / min.

[0157] As the monomer constituting the acrylic oligomer, for example, the following can be listed: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, and the like (alkyl (meth)acrylates); cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrodicyclopentadienyl (meth)acrylate, and the like (esters of (meth)acrylic acid with alicyclic alcohols ( (meth)acrylates containing alicyclic hydrocarbon groups)); phenyl (meth)acrylate, benzyl (meth)acrylate, and the like (aryl (meth)acrylates); (meth)acrylates obtained from terpene compound derivative alcohols, and the like. Such (meth)acrylates can be used alone or in combination with two or more kinds.

[0158] As the acrylic oligomer, from the viewpoint of further improving the adhesiveness of the adhesive layer, it is preferable to contain, as the monomer unit, an alkyl (meth)acrylate having a branched structure in the alkyl group such as isobutyl (meth)acrylate, t-butyl (meth)acrylate, an ester of a (meth)acrylic acid with an alicyclic alcohol (an alicyclic hydrocarbon group-containing (meth)acrylate) such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrodicyclopentadienyl (meth)acrylate, and a (meth)acrylate having a cyclic structure such as phenyl (meth)acrylate, benzyl (meth)acrylate, and the like having a relatively large volume. In addition, in the case where ultraviolet rays are used in the synthesis of the acrylic oligomer and the production of the adhesive layer, from the viewpoint of not easily causing polymerization inhibition, it is preferable to use a substance having a saturated bond, and it is preferable to use an alkyl (meth)acrylate having a branched structure in the alkyl group, or an ester of a (meth)acrylate with an alicyclic alcohol (an alicyclic hydrocarbon group-containing (meth)acrylate) as the monomer constituting the acrylic oligomer. Note that the above-mentioned branched alkyl (meth)acrylate, alicyclic hydrocarbon group-containing (meth)acrylate, and aryl (meth)acrylate correspond to the (meth)acrylate monomer in the technology disclosed herein. The alicyclic hydrocarbon group can be a saturated or unsaturated alicyclic hydrocarbon group.

[0159] The proportion of the (meth)acrylate monomer (e.g., alicyclic hydrocarbon group-containing (meth)acrylate) in the total monomer component constituting the acrylic oligomer is typically greater than 50% by weight, preferably 60% by weight or greater, more preferably 70% by weight or greater (e.g., 80% by weight or greater, further 90% by weight or greater). In some preferred modes, the acrylic oligomer has a monomer composition that contains substantially only the (meth)acrylate monomer.

[0160] As the monomer component constituting the acrylic oligomer, in addition to the above-mentioned (meth)acrylate monomer, a functional group-containing monomer can also be used. As the above-mentioned functional group-containing monomer, examples of the preferable ones include a monomer having a ring containing a nitrogen atom (typically, a heterocycle containing a nitrogen atom) such as N-vinyl-2-pyrrolidone, N-acryloyl morpholine, an amino group-containing monomer such as N,N-dimethylaminoethyl (meth)acrylate, an amide group-containing monomer such as N,N-diethyl (meth)acrylamide, a carboxyl group-containing monomer such as AA, MAA, and a hydroxyl group-containing monomer such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers can be used alone or in combination with two or more. Among them, the carboxyl group-containing monomer is preferable, and AA is particularly preferable.

[0161] In the case where the entire monomer component constituting the acrylic oligomer contains a functional group-containing monomer, it is appropriate that the proportion of the functional group-containing monomer (for example, a carboxyl group-containing monomer such as AA) in the entire monomer component is about 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and in addition, is about 15% by mass or less, preferably 10% by mass or less, more preferably 7% by mass or less.

[0162] The acrylic oligomer can be formed by polymerizing the monomer component constituting it. The polymerization method and the polymerization mode are not particularly limited, and various polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, and the like) known in the past can be employed in an appropriate manner. The kind of polymerization initiator (for example, an azo-based polymerization initiator such as AIBN) that can be used as needed is basically as exemplified in the synthesis of the acrylic polymer, and the amount of the polymerization initiator and the amount of the chain transfer agent such as n-dodecyl mercaptan that is optionally used are appropriately set based on technical common sense so as to achieve the desired molecular weight, and thus a detailed description is omitted here.

[0163] From the above viewpoint, as the preferred acrylic oligomer, for example, the following can be listed: respective homopolymers of methyltetrahydrodicyclopentadienyl acrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), tetrahydrodicyclopentadienyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), 1-adamantyl acrylate (ADA), and in addition to these, a copolymer of CHMA and isobutyl methacrylate (IBMA), a copolymer of CHMA and IBXMA, a copolymer of CHMA and acryloylmorpholine (ACMO), a copolymer of CHMA and diethyl acrylamide (DEAA), a copolymer of CHMA and AA, a copolymer of ADA and methyl methacrylate (MMA), a copolymer of DCPMA and IBXMA, a copolymer of DCPMA and MMA, and the like.

[0164] In the case where the adhesive layer disclosed herein contains the acrylic oligomer, the content thereof is, for example, 0.1 parts by weight or more (e.g., 1 part by weight or more) relative to 100 parts by weight of the acrylic polymer. From the viewpoint of better exerting the effect of the acrylic oligomer, the content of the above-described acrylic oligomer is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, further preferably about 10 parts by weight or more, and particularly preferably about 12 parts by weight or more. In addition, from the viewpoint of compatibility with the acrylic polymer and the like, the content of the above-described acrylic oligomer is appropriately less than 50 parts by weight (e.g., less than 40 parts by weight) relative to 100 parts by weight of the acrylic polymer, preferably less than 30 parts by weight, more preferably about 25 parts by weight or less, and further preferably about 20 parts by weight or less.

[0165] In some preferred modes, the adhesive layer contains one or two or more of the above-described tackifying resins and one or two or more of the acrylic oligomers. In a composition containing an acrylic polymer containing heptyl acrylate as a monomer component, by using the tackifying resin and the acrylic oligomer in combination, it is possible to exert highly excellent resilience resistance to the sustained load in the Z-axis direction while obtaining excellent adhesiveness, even in use modes under severe conditions such as strong resilience. In particular, in a composition containing an acrylic polymer of high molecular weight, it is possible to effectively exert the effect of using the tackifying resin and the acrylic oligomer in combination. The content C T [wt%] of the tackifying resin in the adhesive layer O [wt%] relative to the content C T of the acrylic oligomer O is not particularly limited. The above-described (C T / C O ) is, for example, appropriately 0.1 or more and 9 or less, preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2 or less, and further preferably 0.7 or more and 1.5 or less, and can be 0.8 or more and 1.2 or less.

[0166] In some preferred modes, from the viewpoint of satisfactorily exerting the effect of the technology disclosed herein, the total amount (total quantity) of the tackifying resin and the acrylic oligomer contained in the adhesive layer is about 1 part by weight or more relative to 100 parts by weight of the acrylic polymer, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, further preferably 20 parts by weight or more, particularly preferably 25 parts by weight or more, and in addition, less than 120 parts by weight (e.g., about 80 parts by weight or less) is appropriate, preferably less than 60 parts by weight, more preferably about 50 parts by weight or less, and further preferably about 40 parts by weight or less.

[0167] In the technology disclosed herein, the total amount of the acrylic polymer, tackifying resin, and acrylic oligomer in the adhesive layer is appropriately set in a manner to exert the effects of the technology disclosed herein, and is not limited to a particular range. In some preferred modes, from the viewpoint of satisfactorily exerting the effects of the technology disclosed herein, it is appropriate for the total amount of the acrylic polymer, tackifying resin, and acrylic oligomer contained in the adhesive layer to be greater than 50% by weight, preferably about 70% by weight or more, more preferably about 90% by weight or more, further preferably 95% by weight or more (for example, 95% by weight or more and 100% by weight or less, or 95% by weight or more and less than 100% by weight), and can be 98% by weight or more.

[0168] (Cross-linking agent)

[0169] In the technology disclosed herein, the adhesive composition used in the formation of the adhesive layer can include a cross-linking agent as needed. The type of cross-linking agent is not particularly limited, and examples that can be cited include: isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, peroxide-based cross-linking agents, urea-based cross-linking agents, metal alkoxide-based cross-linking agents, metal chelate-based cross-linking agents, metal salt-based cross-linking agents, carbodiimide-based cross-linking agents, hydrazine-based cross-linking agents, amine-based cross-linking agents, silane coupling agents, and the like. The cross-linking agent can be used alone or in combination with two or more. Among these, isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, and more preferably isocyanate-based cross-linking agents, epoxy-based cross-linking agents. By appropriately selecting the cross-linking agent to be used, the adhesive layer can be given cohesion, and thus it is possible to satisfactorily achieve a balance between the resilience resistance and the impact resistance while improving the resilience resistance. Note that the adhesive layer in the technology disclosed herein can contain the above cross-linking agent in the form after the cross-linking reaction, the form before the cross-linking reaction, the form in which the cross-linking reaction has been partially performed, an intermediate or a composite of these, and the like. The above cross-linking agent is typically contained in the adhesive layer mainly in the form after the cross-linking reaction.

[0170] As the isocyanate-based cross-linking agent, a polyfunctional isocyanate (refers to a compound having two or more isocyanate groups per molecule, including a substance having an isocyanurate structure.) can be preferably used. The isocyanate-based cross-linking agent can be used alone or in combination with two or more.

[0171] As examples of the polyfunctional isocyanate, aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and the like can be cited.

[0172] As specific examples of the aliphatic polyisocyanates, 1,2-ethylenediisocyanate; 1,2-butylene diisocyanate, 1,3-butylene diisocyanate, 1,4-butylene diisocyanate, and the like butylene diisocyanates; 1,2-hexylene diisocyanate, 1,3-hexylene diisocyanate, 1,4-hexylene diisocyanate, 1,5-hexylene diisocyanate, 1,6-hexylene diisocyanate, 2,5-hexylene diisocyanate, and the like hexylene diisocyanates; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, and the like can be mentioned.

[0173] As specific examples of the alicyclic polyisocyanates, isophorone diisocyanate; 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate, and the like cyclohexyl diisocyanates; 1,2-cyclopentyl diisocyanate, 1,3-cyclopentyl diisocyanate, and the like cyclopentyl diisocyanates; hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethyl xylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like can be mentioned.

[0174] As specific examples of the aromatic polyisocyanates, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrophenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthalene 1,4-diisocyanate, naphthalene 1,5-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, xylene 1,4-diisocyanate, xylene 1,3-diisocyanate, and the like can be mentioned.

[0175] As the preferred polyfunctional isocyanate, a polyfunctional isocyanate having three or more isocyanate groups per molecule can be exemplified. The tri- or higher functional isocyanate can be a polymer (typically a dimer or a trimer) of di- or tri- or higher functional isocyanate, a derivative (e.g., a product of addition reaction of a polyol with two or more molecules of a polyfunctional isocyanate), a polymer, or the like. For example, a dimer of diphenylmethane diisocyanate or a trimer of diphenylmethane diisocyanate, an isocyanurate of hexamethylene diisocyanate (a trimer adduct of isocyanurate structure), a reaction product of trimethylolpropane with toluene diisocyanate, a reaction product of trimethylolpropane with hexamethylene diisocyanate, a poly methylene polyphenyl isocyanate, a polyether polyisocyanate, a polyester polyisocyanate, and the like polyfunctional isocyanate can be exemplified. As the commercially available product of the polyfunctional isocyanate, "DURANATE TPA-100" manufactured by Asahi Kasei Chemicals Corporation, "Coronate L" manufactured by Nippon Shokubai Co., Ltd., "Coronate HL" by Nippon Shokubai Co., Ltd., "Coronate HK" by Nippon Shokubai Co., Ltd., "Coronate HX" by Nippon Shokubai Co., Ltd., "Coronate 2096" by Nippon Shokubai Co., Ltd., and the like can be exemplified.

[0176] The technology disclosed herein can be preferably implemented in a manner of using at least an isocyanate-based crosslinking agent as a crosslinking agent. By using the isocyanate-based crosslinking agent, satisfactory resilience against a sustained load in the Z-axis direction can be obtained.

[0177] The use amount of the isocyanate-based crosslinking agent is not particularly limited. For example, it can be about 0.1 parts by weight or more per 100 parts by weight of the acrylic polymer. From the viewpoint of giving consideration to cohesiveness and adhesiveness, and the like, the use amount of the isocyanate-based crosslinking agent is generally preferably about 0.3 parts by weight or more (e.g., 0.5 parts by weight or more) per 100 parts by weight of the acrylic polymer. In some preferred modes, the use amount of the isocyanate-based crosslinking agent is about 0.8 parts by weight or more, more preferably about 1.0 parts by weight or more, and further preferably about 1.2 parts by weight or more, and can be about 1.5 parts by weight or more per 100 parts by weight of the acrylic polymer. In addition, the use amount of the above-described isocyanate-based crosslinking agent is appropriately 10 parts by weight or less, preferably less than 5 parts by weight, more preferably less than 4.0 parts by weight, further preferably less than 3.0 parts by weight, and particularly preferably 2.5 parts by weight or less, and can be 2.0 parts by weight or less (e.g., 1.7 parts by weight or less) per 100 parts by weight of the acrylic polymer. By limiting the use amount of the isocyanate-based crosslinking agent within the prescribed range, it is possible to give consideration to resilience and impact resistance while obtaining resilience against a sustained load in the Z-axis direction based on the use of the isocyanate-based crosslinking agent.

[0178] As the epoxy crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy crosslinking agent having three to five epoxy groups in one molecule is preferred. The epoxy crosslinking agent can be used alone or in combination with two or more kinds.

[0179] Specific examples of the epoxy crosslinking agent include, without particular limitation, N,N,N',N'-tetraglycidyl-m-phenylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Commercially available products of the epoxy crosslinking agent include "TETRAD-C" and "TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc., "EPICRON CR-5L" manufactured by DIC Corporation, "DENACOL EX-512" manufactured by Nagase Chemtex Corporation, "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., and the like.

[0180] The amount of the epoxy crosslinking agent used is not particularly limited. For example, the amount of the epoxy crosslinking agent used can be greater than 0 parts by weight and less than or equal to about 1 part by weight (typically, about 0.001 parts by weight to about 1 part by weight) relative to 100 parts by weight of the acrylic polymer. From the viewpoint of appropriately exerting the effect of improving cohesiveness, generally, it is appropriate that the amount of the epoxy crosslinking agent used be about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, and for example, can be about 0.01 parts by weight or more relative to 100 parts by weight of the acrylic polymer. From the viewpoint of improving adhesion to an adherend, it is appropriate that the amount of the epoxy crosslinking agent used be about 0.5 parts by weight or less, 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 can be 0.07 parts by weight or less, or 0.04 parts by weight or less relative to 100 parts by weight of the acrylic polymer. From the viewpoint of avoiding a decrease in impact resistance caused by excessive crosslinking, generally, it is appropriate that the amount of the epoxy crosslinking agent used be about 0.03 parts by weight or less, preferably about 0.02 parts by weight or less relative to 100 parts by weight of the acrylic polymer. By limiting the amount of the epoxy crosslinking agent used within the prescribed range, it is easy to maintain sufficient adhesive strength, and in addition, it is also easy to obtain resilience to a sustained load in the Z-axis direction.

[0181] In some preferred embodiments, as the crosslinking agent, an isocyanate-based crosslinking agent and at least one crosslinking agent different in kind from the crosslinking functional group of the isocyanate-based crosslinking agent are used in combination. According to the technology disclosed herein, by using a crosslinking agent other than the isocyanate-based crosslinking agent (i.e., a crosslinking agent different in kind from the isocyanate-based crosslinking agent crosslinking reactive group, hereinafter also referred to as "non-isocyanate-based crosslinking agent") in combination with the isocyanate-based crosslinking agent, it is possible to appropriately balance the resilience resistance and impact resistance.

[0182] The kind 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. In some preferred embodiments, as the non-isocyanate-based crosslinking agent, an epoxy-based crosslinking agent can be used. For example, by using an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent in combination, it is possible to more favorably balance the resilience resistance and impact resistance to the sustained load in the Z-axis direction.

[0183] The relationship between the content of the isocyanate-based crosslinking agent and the content of the non-isocyanate-based crosslinking agent (preferably, the epoxy-based crosslinking agent) is not particularly limited, and is appropriately set in a manner that satisfies the 65°C storage modulus and -20°C tan δ described above. For example, it is appropriate for the content of the isocyanate-based crosslinking agent to be greater than 1 times, about 10 times or more, preferably about 50 times or more, more preferably about 80 times or more, further preferably about 100 times or more (e.g., greater than 100 times), particularly preferably about 120 times or more (e.g., about 140 times or more), relative to the content of the non-isocyanate-based crosslinking agent (preferably, the epoxy-based crosslinking agent). In addition, from the viewpoint of appropriately exerting the effects obtained by using the isocyanate-based crosslinking agent in combination with the non-isocyanate-based crosslinking agent (preferably, the epoxy-based crosslinking agent), generally, it is appropriate for the content of the isocyanate-based crosslinking agent to be about 1000 times or less, about 500 times or less, preferably about 300 times or less, more preferably about 200 times or less, further preferably about 180 times or less (e.g., about 160 times or less), relative to the content of the non-isocyanate-based crosslinking agent (preferably, the epoxy-based crosslinking agent).

[0184] The content of the crosslinking agent (total amount of the crosslinking agent) in the adhesive composition disclosed herein is not particularly limited. From the viewpoint of cohesiveness, it is appropriate that the content of the above crosslinking agent is about 0.001 parts by weight or more, about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, further preferably about 0.02 parts by weight or more, particularly preferably about 0.03 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. In some modes, the content of the crosslinking agent is about 0.1 parts by weight or more, more preferably about 0.5 parts by weight or more, further preferably about 1.0 parts by weight or more, can be about 1.2 parts by weight or more, or can be about 1.5 parts by weight or more, relative to 100 parts by weight of the acrylic polymer. In addition, it is appropriate that the content of the crosslinking agent in the adhesive composition is about 20 parts by weight or less, about 15 parts by weight or less, preferably about 10 parts by weight or less (for example, about 5 parts by weight or less), relative to 100 parts by weight of the acrylic polymer. In some modes, the content of the crosslinking agent is 4.0 parts by weight or less, more preferably 3.0 parts by weight or less, further preferably 2.5 parts by weight or less, can be 2.0 parts by weight or less (for example, less than 2.0 parts by weight), or can be 1.8 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. By appropriately setting the total amount of use of the crosslinking agent within the above range, both the resilience resistance and the impact resistance can be satisfied.

[0185] (Other additives)

[0186] In addition to the above components, various additives commonly used in the field of adhesives, such as leveling agents, crosslinking aids, plasticizers, softening agents, fillers, coloring agents (pigments, dyes, etc.), antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, rust inhibitors, light stabilizers, etc., can be contained in the adhesive composition as needed. As for such various additives, conventionally known substances can be used by using conventional methods, and are not the features of the present application, so detailed description is omitted.

[0187] The adhesive layer (layer containing the adhesive) disclosed herein can be an adhesive layer formed from an aqueous adhesive composition, a solvent-based adhesive composition, a hot-melt adhesive composition, or an active energy radiation-curable adhesive composition. An aqueous adhesive composition refers to an adhesive composition in which the adhesive (adhesive layer forming component) is contained in a solvent (aqueous solvent) with water as the main component, typically including an aqueous adhesive composition such as a water-dispersible adhesive composition (a composition in which at least a portion of the adhesive is dispersed in water). A solvent-based adhesive composition refers to an adhesive composition in which the adhesive is contained in an organic solvent. As the organic solvent contained in the solvent-based adhesive composition, one or more examples of organic solvents (toluene, ethyl acetate, etc.) that can be used in the above-described solution polymerization can be used without particular limitation. From the viewpoint of adhesive properties, the technology disclosed herein is preferably implemented in a manner having an adhesive layer formed from a solvent-based adhesive composition.

[0188] The adhesive layer disclosed herein can be formed using methods known in the art. For example, it can be formed by applying an adhesive composition to a peelable surface (peel surface) or a non-peelable surface and allowing it to dry. For adhesive sheets having a substrate, for example, it can be formed by directly applying (typically coating) an adhesive composition to the substrate and allowing it to dry (direct method). Alternatively, it can be formed by applying an adhesive composition to a peelable surface (peel surface) and allowing it to dry, and then transferring the adhesive layer to the substrate (transfer method). From a productivity point of view, the transfer method is preferred. The peel surface can be the surface of a release liner, the back of a substrate that has undergone a peeling treatment, etc. It should be noted that the adhesive layer disclosed herein is typically formed continuously, but is not limited to this manner; for example, it can also be formed as a regular or irregular pattern such as dots or stripes.

[0189] The adhesive composition can be coated using conventionally known coating machines such as gravure roller coaters, die coaters, and bar coaters. Alternatively, the adhesive composition can be coated using methods such as dip coating or curtain coating.

[0190] From the viewpoint of promoting cross-linking reactions and improving manufacturing efficiency, the drying of the adhesive composition is preferably carried out under heating. The drying temperature can be, for example, about 40°C to about 150°C, and is generally preferred to be about 60°C to about 130°C. After the adhesive composition is dried, it can be further cured for purposes such as adjusting the transfer of components within the adhesive layer, proceeding with the cross-linking reaction, and relaxing any strain that may exist within the adhesive layer.

[0191] (thickness)

[0192] The thickness of the adhesive layer is not particularly limited, and a configuration having an adhesive layer with an appropriate thickness in the range of, for example, 0.1 μm to 500 μm can be employed according to the use, purpose of use, and the like. In some aspects, from the viewpoint of avoiding an excessively thick adhesive sheet, it is generally appropriate for the thickness of the adhesive layer to be about 100 μm or less, preferably about 70 μm or less, more preferably about 60 μm or less, and further preferably about 50 μm or less. The thickness of the adhesive layer can be about 35 μm or less, for example, about 30 μm or less. An adhesive layer having a limited thickness can well satisfy the requirements for thickness reduction and light weight. In addition, generally, when the thickness of the adhesive layer is reduced, there is a tendency for the impact resistance and adhesion to the adherend to be easily reduced, but according to the technology disclosed herein, by the configuration of the adhesive layer having a limited thickness, sufficient impact resistance and adhesive force can be achieved. From the viewpoint of adhesion to the adherend, in some aspects, it is generally appropriate for the lower limit of the thickness of the adhesive layer to be about 0.5 μm or more, can be about 1 μm or more, is advantageous to be about 3 μm or more, is preferably about 10 μm or more, more preferably about 12 μm or more (for example, greater than 12 μm), and further preferably about 15 μm or more, for example, can be about 18 μm or more. In some preferred aspects, the thickness of the adhesive layer is greater than 20 μm, can be 24 μm or more, and can be 27 μm or more. The adhesive sheet disclosed herein can be an adhesive sheet having an adhesive layer having the above-described thickness on both faces of the substrate. In addition, in a double-sided adhesive sheet with a substrate having a first adhesive layer and a second adhesive layer on each face of the substrate, the first adhesive layer and the second adhesive layer can have the same thickness, or can have different thicknesses from each other.

[0193] (biomass carbon ratio)

[0194] In some aspects, the adhesive layer contains a material from biomass, and the biomass carbon ratio thereof can be a prescribed value or more. The biomass carbon ratio of the adhesive layer is, for example, 1% or more, can be 10% or more, and is preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the adhesive indicates a small amount of use of fossil resource-based materials represented by petroleum and the like. In this regard, the higher the biomass carbon ratio of the adhesive is, the more preferable it is. For example, the biomass carbon ratio of the adhesive layer can be 55% or more, can be 60% or more, can be 70% or more, can be 75% or more, can be 80% or more, and can be greater than 80%. The upper limit of the biomass carbon ratio is 100% by definition, and can be 99% or less, can be 95% or less, and can be 90% or less from the viewpoint of the ease of availability of the material. From the viewpoint of easily exhibiting good adhesive properties, in some aspects, the biomass carbon ratio of the adhesive layer can be, for example, 90% or less, can be 85% or less, and can be 80% or less.

[0195] <Substrate>

[0196] The adhesive sheet disclosed herein is in the form of a single- or double-sided adhesive sheet with a substrate, and as a substrate to support (backing) the adhesive layer, a resin film, paper, cloth, a rubber sheet, a foamed sheet, a metal foil, a composite thereof, or the like can be used. As examples of paper, Japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, surface-coated paper, and the like can be listed. As examples of cloth, woven cloth, nonwoven cloth, and the like obtained by various fiber-like substances alone or blended, or the like can be listed. As the fiber-like substances, cotton, spun rayon, abaca, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, and the like can be exemplified. As examples of rubber sheets, natural rubber sheets, butyl rubber sheets, and the like can be listed. As examples of foamed sheets, foamed polyolefin sheets, foamed polyurethane sheets, foamed chloroprene rubber sheets, and the like can be listed. As examples of metal foils, aluminum foils, copper foils, and the like can be listed. Note that the substrate to support the adhesive layer is also referred to as a substrate layer in the adhesive sheet.

[0197] The substrate can be formed of a material from biomass or a material not from biomass. From the viewpoint of producing an adhesive sheet that takes into account the suppression of dependence on fossil resource-based materials, it is preferable to use a substrate material (typically, a resin film) from biomass.

[0198] In addition, the substrate can also be formed of a material that can be recycled, a recycled material (also referred to as a regenerated material). As the regenerated material, it is preferable to use a resin film. Since a resin film (e.g., a polyester film such as a PET film) can be reused, regardless of whether a material from plants is used, by reusing a resin film after use, sustainable reproduction can be performed, and environmental load can be reduced. Such a reusable resin film, a recycled resin film is also referred to as a regenerated film. The above-mentioned regenerated material (e.g., a regenerated film) can be formed of a material from biomass or a material not from biomass.

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

[0200] The resin film is a film in which a resin material is used as a main component (e.g., a component included in the resin film at a content of more than 50% by weight). As examples of the resin film, polyethylene (PE), polypropylene (PP), an ethylene-propylene copolymer, and the like polyolefin-based resin films; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and the like polyester-based resin films; a vinyl chloride-based resin film; a vinyl acetate-based resin film; a polyimide-based resin film; a polyamide-based resin film; a fluorine-containing resin film; glass paper; and the like can be listed. The resin film can be a rubber-based film such as a natural rubber film or a butyl rubber film. Among them, from the viewpoint of workability and processability, a polyester film is preferred, and a PET film is particularly preferred.

[0201] Note that, in the present specification, the "resin film" is typically a non-porous sheet, and is a concept that is distinguished from (in other words, is a concept other than) so-called nonwoven fabric and woven fabric. The resin film can be any one of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, such a resin film can be non-foamed. Here, the non-foamed resin film refers to a resin film that has not been subjected to an intentional process for forming a foam. Specifically, the non-foamed resin film can be a resin film having a foaming ratio of less than 1.1 times (e.g., less than 1.05 times, typically less than 1.01 times).

[0202] Various additives such as a filler (an inorganic filler, an organic filler, and the like), a coloring agent, a dispersing agent (a surfactant and the like), an anti-aging agent, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a plasticizer, and the like can be incorporated in the above-described substrate (e.g., resin film) as needed. The incorporation ratio of the various additives can be about less than 30% by weight (e.g., about less than 20% by weight, typically about less than 10% by weight).

[0203] The above-described substrate (e.g., resin film) can be a single-layer structure, or can have a multi-layer structure of two layers, three layers, or more than three layers. From the viewpoint of shape stability, the substrate is preferably 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 above-described resin (e.g., a polyester-based resin). The method for producing the substrate (typically, the resin film) can be appropriately adopted from the conventionally known methods, and is not particularly limited. For example, a conventionally known general film molding method such as extrusion molding, inflation molding, T-die casting molding, calender roll molding, and the like can be appropriately adopted.

[0204] As for the surface of the substrate, a conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, and the like can be performed. Such a surface treatment can be a treatment for improving the adhesion of the substrate to the adhesive layer, in other words, the anchoring of the adhesive layer to the substrate.

[0205] In addition, in the case where the technology disclosed herein is implemented in the form of a single-faced adhesive sheet with a substrate, a release treatment can be performed on the back surface of the substrate as needed. The release treatment can be, for example, a treatment in which a typical release treatment agent such as a general silicone-based, long-chain alkyl-based, fluorine-containing type, or the like is applied in a thin film shape of typically about 0.01 μm to about 1 μm (for example, 0.01 μm to 0.1 μm). By performing this release treatment, effects such as easy unwinding of an adhesive sheet wound in a roll shape into a roll body can be obtained.

[0206] In the adhesive sheet including a substrate, the thickness of the substrate is not particularly limited. From the viewpoint of avoiding the adhesive sheet from becoming too thick, the thickness of the substrate can be, for example, about 200 μm or less, preferably about 150 μm or less, and more preferably about 100 μm or less. Depending on the purpose of use and the use mode of the adhesive sheet, the thickness of the substrate can be about 70 μm or less, about 50 μm or less, or about 30 μm or less (for example, about 25 μm or less). In some modes, the thickness of the substrate can be about 20 μm or less, about 15 μm or less, or about 10 μm or less (for example, about 5 μm or less). By reducing the thickness of the substrate, even if the total thickness of the adhesive sheet is the same, the thickness of the adhesive layer can be further increased. This is advantageous from the viewpoint of improving the adhesion to the adherend and the substrate. The lower limit of the thickness of the substrate is not particularly limited. From the viewpoint of the handleability (workability), processability, and the like of the adhesive sheet, the thickness of the substrate is usually about 0.5 μm or more (for example, 1 μm or more), and preferably about 2 μm or more, for example, about 6 μm or more. In some modes, the thickness of the substrate can be about 15 μm or more, or about 25 μm or more.

[0207] <foamed substrate>

[0208] In other modes, a foamed substrate is used as the substrate. The foamed substrate disclosed herein is a substrate having a portion having a bubble (bubble structure), and is typically a substrate including at least one layer of a foamed body (foamed body layer). The foamed substrate described above can be a substrate composed of one or two or more foamed body layers. The foamed substrate described above can be, for example, a substrate composed substantially of one or two or more foamed body layers. Without particular limitation, as one preferred example of the foamed substrate in the technology disclosed herein, a foamed substrate including a single layer (one layer) of a foamed body layer can be cited.

[0209] The thickness of the foamed substrate is not particularly limited and can be appropriately set in accordance with the strength, softness, purpose of use, or the like of the adhesive sheet. From the viewpoint of thinness, the thickness of the foamed substrate is usually 1 mm or less, 0.70 mm or less is appropriate, 0.40 mm or less is preferred, and 0.30 mm or less is more preferred. The technology disclosed herein can be preferably implemented in a manner that the thickness of the foamed substrate is 0.25 mm or less (typically 0.18 mm or less, for example, 0.16 mm or less) from the viewpoint of processability or the like. In addition, from the viewpoint of impact resistance or the like of the adhesive sheet, the thickness of the foamed substrate is usually 0.04 mm or more, 0.05 mm or more is appropriate, 0.06 mm or more is preferred, and 0.07 mm or more (for example, 0.08 mm or more) is more preferred. The technology disclosed herein can be preferably implemented in a manner that the thickness of the foamed substrate is 0.10 mm or more (typically more than 0.10 mm, preferably 0.12 mm or more, for example, 0.13 mm or more). When the thickness of the foamed substrate is larger, there is a tendency to improve the impact resistance.

[0210] The density of the foamed substrate (referred to as apparent density, which is the same in the case where it is not particularly described) is not particularly limited and can be, for example, 0.1 g / cm 3 or more, 0.2 g / cm 3 or more is appropriate, 0.3 g / cm 3 or more is preferred, and 0.4 g / cm 3 or more (for example, 0.5 g / cm 3 or more) is more preferred. In one embodiment, the density of the foamed substrate can be 0.5 g / cm 3 or less (for example, less than 0.5 g / cm 3 ), and can be less than 0.4 g / cm 3 . In addition, from the viewpoint of impact resistance, the density of the foamed substrate is preferably 0.12 g / cm 3 or more, more preferably 0.15 g / cm 3 or more, further preferably 0.2 g / cm 3 or more (for example, 0.3 g / cm 3 or more). In one embodiment, the density of the foamed substrate can be 0.4 g / cm 3 or more, and can be 0.5 g / cm 3 or more (for example, more than 0.5 g / cm 3 ), and further can be 0.55 g / cm 3 or more. Note that the density (apparent density) of the foamed substrate can be measured in accordance with JIS K6767.

[0211] The average cell diameter of the foamed substrate is not particularly limited, and from the viewpoint of stress dispersion, it is preferably 300 μm or less, more preferably 200 μm or less, and further preferably 150 μm or less. The lower limit of the average cell diameter is not particularly limited, and from the viewpoint of high differential followability, it is generally appropriate that it is 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and further preferably 40 μm or more (for example, 50 μm or more). In one embodiment, the average cell diameter can be 55 μm or more, or 60 μm or more. Note that the average cell diameter referred to herein is the average cell diameter in terms of a sphere, as observed by electron microscopy of a cross section of the foamed substrate.

[0212] The cell structure of the foamed body constituting the foamed substrate disclosed herein is not particularly limited. As the cell structure, it can be any one of a continuous cell structure, an independent cell structure, and a semi-continuous semi-independent cell structure. From the viewpoint of impact absorbability, an independent cell structure or a semi-continuous semi-independent cell structure is preferred.

[0213] The 25% compression strength C of the foamed substrate 25 There is no particular limitation, and it can be, for example, 20 kPa or more (typically 30 kPa or more, and further 40 kPa or more). C 25 It is generally appropriate that it is 250 kPa or more, and preferably 300 kPa or more (for example, 400 kPa or more). An adhesive sheet having such a foamed substrate can exhibit good durability against impact caused by dropping or the like. For example, it can better prevent breakage of the adhesive sheet caused by impact. 25 The upper limit of C is not particularly limited, and it is generally appropriate that it is 1300 kPa or less (for example, 1200 kPa or less). In one embodiment, C 25 It can be 1000 kPa or less, 800 kPa or less, further 600 kPa or less (for example, 500 kPa or less), or 360 kPa or less. In another preferred embodiment, the foamed substrate has a C 25 It can be 20 kPa to 200 kPa (typically 30 kPa to 150 kPa, for example, 40 kPa to 120 kPa). An adhesive sheet having such a foamed substrate can be an adhesive sheet excellent in cushioning property. For example, by absorbing dropping impact with the foamed substrate, it can better prevent peeling of the adhesive sheet.

[0214] The 25% compression strength C of the foamed substrate 25is a load at the time when the measurement sample is compressed to a thickness of 75% of the initial thickness. The compression strength is measured according to JIS K6767. As a specific measurement procedure, the measurement sample is disposed in the center of the pair of plates, and the plates are continuously compressed to a prescribed compression ratio by reducing the interval of the plates, and the plates are stopped at this point, and the load after 10 seconds is measured. The compression strength of the foam substrate can be controlled, for example, by the crosslinking degree, density, size, shape, and the like of the material constituting the foam substrate.

[0215] The tensile elongation of the foam substrate is not particularly limited. For example, a foam substrate having a tensile elongation in the length direction (MD) of 200% to 800% (more preferably 400% to 600%) can be preferably used. In addition, a foam substrate having a tensile elongation in the width direction (TD) of 50% to 800% (more preferably 200% to 500%) can be preferably used. The elongation of the foam substrate is measured according to JIS K6767. The elongation of the foam substrate can be controlled, for example, by the crosslinking degree, apparent density (foaming ratio), and the like.

[0216] The tensile strength (tensile resistance) of the foam substrate is not particularly limited. For example, a foam substrate having a tensile strength in the length direction (MD) of 5 MPa to 35 MPa (preferably 10 MPa to 30 MPa) can be preferably used. In addition, a foam substrate having a tensile strength in the width direction (TD) of 1 MPa to 25 MPa (more preferably 5 MPa to 20 MPa) can be preferably used. The tensile strength of the foam substrate is measured according to JIS K6767. The tensile strength of the foam substrate can be controlled, for example, by the crosslinking degree, apparent density (foaming ratio), and the like.

[0217] The material of the foam substrate is not particularly limited. In general, a foam substrate including a foam layer formed of a plastic material (plastic foam) is preferable. The plastic material (which includes a rubber material) used to form the plastic foam is not particularly limited, and can be appropriately selected from publicly known plastic materials. The plastic material can be used alone or two or more kinds can be appropriately combined.

[0218] As specific examples of the plastic foam, there can be mentioned: polyolefin-based resin foams such as PE-based foams, PP-based foams, and the like; polyester-based resin foams such as PET-based foams, PEN-based foams, PBT-based foams, and the like; polyvinyl chloride-based resin foams such as polyvinyl chloride foams; vinyl acetate-based resin foams; polyphenylene sulfide resin foams; amide-based resin foams such as aliphatic polyamide (nylon) resin foams, wholly aromatic polyamide (aromatic polyamide) resin foams, and the like; polyimide-based resin foams; polyether ether ketone (PEEK) foams; styrene-based resin foams such as polystyrene foams; urethane-based resin foams such as polyurethane resin foams; and the like. In addition, as the plastic foam, rubber-based resin foams such as polychloroprene rubber foams can also be used.

[0219] As the preferred foam, there can be exemplified polyolefin-based resin foams (hereinafter also referred to as "polyolefin-based foams"). As the plastic material (i.e., polyolefin-based resin) constituting the polyolefin-based foams, there can be used various polyolefin-based resins known or conventionally used without particular limitation. For example, there can be mentioned PE such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), PP, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and the like. As examples of the LLDPE, there can be mentioned Ziegler-Natta catalyst-based linear low-density polyethylene, metallocene catalyst-based linear low-density polyethylene, and the like. Such polyolefin-based resins can be used singly or two or more kinds thereof can be used in appropriate combination.

[0220] As the preferred example of the foam substrate in the technology disclosed herein, there can be exemplified polyolefin-based foam substrates such as PE-based foam substrates substantially composed of foams of PE-based resins, PP-based foam substrates substantially composed of foams of PP-based resins, and the like, from the viewpoints of impact resistance, water resistance, dust resistance, and the like. Herein, the PE-based resin refers to a resin in which ethylene is the main monomer (i.e., the main component among monomers), and in addition to HDPE, LDPE, LLDPE, and the like, can include ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, and the like, in which the copolymerization ratio of ethylene is greater than 50% by weight. Likewise, the PP-based resin refers to a resin in which propylene is the main monomer. As the foam substrate in the technology disclosed herein, the PE-based foam substrate can be preferably employed.

[0221] The method for producing the above-described plastic foam (typically, polyolefin-based foam) is not particularly limited, and various methods known or conventionally used can be appropriately employed. For example, it can be produced by a method including a molding step, a crosslinking step, and a foaming step of the above-described plastic material or the above-described plastic foam. In addition, a stretching step can be included as necessary.

[0222] As the method of crosslinking the above-mentioned plastic foam, for example, a chemical crosslinking method using an organic peroxide or the like, or an ionizing radiation crosslinking method of irradiating ionizing radiation, or the like can be exemplified, and these methods can be used in combination. As the above-mentioned ionizing radiation, electron rays, α rays, β rays, γ rays, or the like can be exemplified. The dose of the ionizing radiation is not particularly limited, and can be set to an appropriate irradiation dose in consideration of the target properties (for example, the degree of crosslinking) of the foam substrate or the like.

[0223] In the above-mentioned foam substrate, various additives such as a filler (an inorganic filler, an organic filler, or the like), an anti-aging agent, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a plasticizer, a flame retardant, a surfactant, or the like can be incorporated as needed.

[0224] The foam substrate in the technology disclosed herein can also be colored black, white, or the like in order to exhibit desired design properties, optical properties (for example, light shielding properties, light reflecting properties, or the like), or the like in an adhesive sheet having the foam substrate. The coloring can be performed using one or two or more kinds of known coloring agents of organic or inorganic types alone or in appropriate combination.

[0225] The surface of the foam substrate can be subjected to an appropriate surface treatment as needed. The surface treatment can be, for example, a chemical or physical treatment for improving the adhesion to an adjacent material (for example, an adhesive layer). As examples of the surface treatment, a corona discharge treatment, a chromic acid treatment, ozone exposure, flame exposure, ultraviolet irradiation treatment, plasma treatment, application of a primer (a primer paint), or the like can be exemplified.

[0226] <Release Liner>

[0227] In the technology disclosed herein, a release liner can be used at the time of formation of an adhesive layer, production of an adhesive sheet, storage of an adhesive sheet before use, circulation, shape processing, or the like. As the release liner, there is no particular limitation, and for example, a release liner having a release-treated layer on the surface of a liner substrate of a resin film, paper, or the like; a release liner containing a fluorine-containing polymer (polytetrafluoroethylene or the like); or the like can be used. The above-mentioned release-treated layer can be formed, for example, by surface treatment of the above-mentioned liner substrate with a silicone-based, long-chain alkyl-based, fluorine-containing, molybdenum sulfide, or the like release treatment agent. As the liner substrate, as with the above-mentioned substrate of an adhesive sheet, a substrate formed using a material derived from biomass, a recycled material (a recycled film or the like) can be preferably used.

[0228] <Total Thickness of Adhesive Sheet>

[0229] The total thickness of the adhesive sheet (comprising an adhesive layer, and can comprise a substrate layer, but does not comprise a release liner) disclosed herein is not particularly limited. The total thickness of the adhesive sheet can be, for example, about 1 mm or less, can be about 500 μm or less, can be about 300 μm or less, from the viewpoint of thinness, about 200 μm or less is appropriate, can be about 150 μm or less (for example, about 100 μm or less). In some preferred modes, the thickness of the adhesive sheet can be about 50 μm or less, for example, can be about 35 μm or less. The lower limit of the thickness of the adhesive sheet is, for example, 0.1 μm or more (for example, 0.5 μm or more), about 3 μm or more is appropriate, preferably about 10 μm or more, more preferably about 15 μm or more, can be about 50 μm or more, can be about 100 μm or more. The adhesive sheet having a thickness of the prescribed value or more tends to have adhesion to an adherend, in addition, has a tendency to have excellent workability. Note that, in the adhesive sheet without a substrate, the thickness of the adhesive layer is the total thickness of the adhesive sheet.

[0230] <Properties of the adhesive sheet>

[0231] In some modes, the 180-degree peeling strength of the adhesive sheet to a stainless steel plate (adhesion to SUS) is preferably about 15 N / 25 mm or more (for example, 17 N / 25 mm or more). The adhesive sheet showing such adhesion to SUS can exert excellent adhesive force. The adhesion to SUS described above is more preferably about 20 N / 25 mm or more, further preferably about 23 N / 25 mm or more, particularly preferably 25 N / 25 mm or more (for example, 26 N / 25 mm or more). The upper limit of the adhesion to SUS described above is not particularly limited, and, in general, for example, can be about 50 N / 25 mm or less from the viewpoint of taking into account other adhesive properties such as resilience resistance. The adhesion to SUS described above is measured by using a SUS plate as an adherend in a measurement environment of 23°C, 50% RH, under conditions of a tensile speed of 300 mm / minute, and a peeling angle of 180 degrees. More specifically, the measurement is performed by the method described in the Examples described later.

[0232] In addition, the adhesive sheet disclosed herein preferably has a bulging height of 2.0 mm or less at the end of the resilience resistance evaluation test performed using the following method. An adhesive sheet satisfying the above-described characteristics has particularly excellent resilience resistance to a peeling load in the thickness direction (Z-axis direction) of the adhesive sheet alone, and is particularly difficult to peel against a continuous peeling load in this direction. In addition, in the case where the adhesive sheet attached to an adherend (for example, a portable electronic device, a module as a constituent member thereof) is in a high-temperature and high-humidity condition during storage or the like, stable resilience resistance can also be exerted. The above-described bulging height is preferably 1.5 mm or less, more preferably 1.0 mm or less, even more preferably 0.7 mm or less, further preferably 0.5 mm or less, and particularly preferably 0.4 mm or less. Note that the above-described bulging height is the height including the thickness of the adhesive sheet (30 μm in the examples described later).

[0233] [Resilience Resistance Evaluation Test]

[0234] A polyethylene terephthalate (PET) film having a length of 70 mm, a width of 10 mm, and a thickness of 75 μm was fixed to the lower surface of a polycarbonate plate having a length of 30 mm, a width of 10 mm, and a thickness of 2 mm at one end in the length direction of the PET film. Next, the PET film was bent along the length direction, and the other end in the length direction of the bent PET film was fixed to the upper surface of the polycarbonate plate with an adhesive area of 3 mm x 10 mm using an adhesive sheet. This state was maintained (resilience resistance evaluation test) under conditions of 65°C, 90% RH, and 72 hours. Then, the bulging height [mm] of the adhesive sheet from the polycarbonate plate after 72 hours (at the end of the test) was measured.

[0235] More specifically, the above-described resilience resistance evaluation test was performed by the method described in the Z-axis direction resilience resistance test of the examples described later.

[0236] The adhesive sheet disclosed herein preferably has an impact adhesion strength of 0.3 J / cm 2 The adhesive sheet satisfying this characteristic can be an excellent joining means in terms of durability against impact in the shearing direction. Therefore, for example, it can be preferably used as a member fixing unit in a portable electronic device that is expected to be exposed to impact caused by dropping or collision. According to the technology disclosed herein, an adhesive sheet exhibiting an impact adhesion strength of 0.35 J / cm 2 or more, more preferably 0.40 J / cm 2 or more, even more preferably 0.45 J / cm 2 or more, and particularly preferably 0.50 J / cm 2 or more) can be provided. The upper limit of the impact adhesion strength is not particularly limited, and can be, for example, 3.00 J / cm2 The impact adhesive strength can be, for example, 1.00 J / cm 2 The impact adhesive strength can be, for example, 0.80 J / cm 2 The impact adhesive strength can be, for example, 0.60 J / cm 2 More specifically, the above-described impact resistance test is performed by the method described in the impact resistance test of the Examples described below.

[0237] In some embodiments, the adhesive sheet contains a material from biomass, and the biomass carbon ratio of the adhesive sheet can be 1% or more. The biomass carbon ratio of the adhesive sheet is, for example, 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the adhesive sheet indicates that the amount of use of fossil resource-based materials represented by petroleum and the like is small. In this regard, the higher the biomass carbon ratio of the adhesive sheet, the more preferable it is. For example, the biomass carbon ratio of the adhesive sheet can be 55% or more, can be 60% or more, can be 70% or more, can be 75% or more, can be 80% or more, or can be more than 80%. The upper limit of the biomass carbon ratio is 100% by definition, and can be 99% or less, can be 95% or less, or can be 90% or less from the viewpoint of the availability of the material. From the viewpoint of easily exhibiting good adhesive properties, in some embodiments, the biomass carbon ratio of the adhesive sheet can be, for example, 90% or less, can be 85% or less, or can be 80% or less.

[0238] <Uses>

[0239] The use of the adhesive sheet disclosed herein is not particularly limited, and can be used for various uses. The adhesive sheet disclosed herein can achieve both the resilience resistance and the impact resistance, and thus can be suitable for the adhesive fixing of members in uses requiring high resilience resistance and impact resistance. For example, it can be satisfactorily used for the fixing of components in various portable devices (portable devices). Non-limiting examples of the above portable electronic devices include: a mobile phone, a smartphone, a tablet personal computer, a notebook personal computer, various wearable devices (for example, a wrist-wearing type worn on a wrist like a watch, a modular type worn on a part of a body with a clip, a band, or the like, an eyewear type including a glasses type (a monocular type, a binocular type. Also included is a helmet type.), a clothing type worn on a shirt, a sock, a hat, or the like in the form of, for example, a piece of jewelry, an ear-wearing type worn on an ear like an earphone, and the like), a digital camera, a digital video camera, a sound equipment (a portable music player, a voice recorder, and the like), a calculator (a desk calculator, and the like), a portable game device, an electronic dictionary, an electronic notebook, an electronic book, an in-vehicle information device, a portable radio, a portable television, a portable printer, a portable scanner, a portable modem, and the like. Note that, in the present specification, "portable" is not sufficient to mean only that it can be carried, but actually has portability at a level that a person (a standard adult) can move relatively easily.

[0240] The adhesive sheet (typically, double-sided adhesive sheet) disclosed herein can be used for fixing members constituting portable electronic devices as described above in the form of a joining material processed into various shapes. Among them, it can be satisfactorily used for portable electronic devices having liquid crystal display devices. For example, in electronic devices (typically, portable electronic devices such as smartphones) having a display portion (may be a display portion of a liquid crystal display device) such as a touch panel type display, in devices in which an elastic member such as an FPC is bent and housed in an internal space for large-screening and the like, it is preferable to use the adhesive sheet disclosed herein in the use for fixing the elastic adherend. By using the adhesive sheet disclosed herein, the elastic adherend can be stably fixed in a bent state, and the fixed state can be continuously maintained. Thus, the above-mentioned elastic member housed in a limited internal space of a portable electronic device in a bent state is highly precisely positioned by the adhesive sheet disclosed herein, and can be maintained in a stable fixed state. In addition, as a material disposed inside the above-mentioned portable electronic device, a polar and rigid material such as polycarbonate, polyimide, and the like can be exemplified. For such a material (polar and rigid resin material), the adhesive sheet disclosed herein can satisfactorily exert the resilience resistance to the continuous load in the Z-axis direction. Alternatively, the adhesive sheet disclosed herein is satisfactorily used in the use for fixing a member having a protective glass or the like constituting a three-dimensional shape (typically, a curved surface shape) of the portable electronic device in the portable electronic device. In the adhesive sheet used for the fixing use of a member having such a three-dimensional surface shape, there is a tendency to apply a relatively large continuous load in the Z-axis direction. By using the adhesive sheet disclosed herein, even a member having a three-dimensional shape as described above can be stably fixed.

[0241] In recent years, in particular, the development of electronic devices (typically smartphones, tablets, and other portable electronic devices) with display units such as touch panel displays (which may be the display units of liquid crystal display devices) has focused on balancing larger screens and higher functionality. Regarding larger screens, measures have been taken to bend and house flexible components such as FPCs (Flexible Printed Circuits) within the internal space. On the other hand, regarding higher functionality, new features such as pressure-sensitive sensors with higher accuracy and facial recognition unlocking have been implemented. To achieve higher performance and higher quality products, high integration of the circuitry, including the FPC, is indispensable. Examples of highly integrated circuitry units include two-sided or multi-layer FPCs, but all represent a direction of increased FPC rigidity. It is anticipated that improved resilience under sustained loads in the Z-axis direction, as evaluated through a resilience test in the Z-axis direction (described later), will become a required characteristic. The adhesive sheet of the preferred embodiment of the technology disclosed herein can exhibit excellent resilience under harsh high temperature and high humidity conditions (strong resilience conditions), as described later in the Z-axis resilience test, and is therefore better suited for use in the aforementioned next-generation touch panel display-equipped electronic devices (typically smartphones and other touch panel display-equipped portable electronic devices).

[0242] While there are no particular limitations, in some applications, adhesive sheets are preferred for electronic devices that incorporate various light sources, such as LEDs (light-emitting diodes), and self-emissive organic EL (organic EL) light-emitting elements. For example, they are preferred for electronic devices with organic EL display devices or liquid crystal display devices (typically portable electronic devices).

[0243] Figure 4 An example of a portable electronic device (smartphone) using the adhesive sheet disclosed herein is shown for illustrative purposes. Figure 4 As shown, a battery (heating element) 540 is built into the housing 520 of the portable electronic device 500. Furthermore, the portable electronic device 500 is configured to include an adhesive sheet 550. In this configuration, the adhesive sheet 550 has the form of a double-sided adhesive sheet (double-sided adhesive sheet) that secures the components constituting the portable electronic device 500. It should be noted that the portable electronic device 500 has a touch panel 570 that also functions as an input unit, in addition to a display unit. The adhesive sheet disclosed herein is preferably used as a component (component joining means) of the portable electronic device as described above.

[0244] In addition, the adhesive sheet disclosed herein can have, in some aspects, an adhesive layer containing an acrylic polymer having a high biomass carbon ratio, and thus can contribute to reducing dependence on fossil resource-based materials by being used as a substitute for a conventional acrylic adhesive (i.e., an acrylic adhesive having a low biomass carbon ratio) in various uses in which the acrylic adhesive is used. The adhesive sheet disclosed herein can preferably be used as an adhesive sheet that reduces the degree of dependence on fossil resource-based materials.

[0245] The following is included in the matters disclosed by the specification.

[0246] [1] A portable electronic device in which an adhesive sheet is joined to a member constituting the electronic device, the adhesive sheet having an adhesive layer containing an acrylic polymer that is a polymer containing a monomer component of heptyl acrylate, the adhesive layer having a storage modulus G' of 20,000 Pa or more at 65°C and a tan δ of 0.3 or more at -20°C, where the tan δ is the ratio of the loss modulus G" to the storage modulus G' (G" / G') of the adhesive layer.

[0247] [2] The portable electronic device according to the above [1], wherein the acrylic polymer has a weight average molecular weight of 700,000 or more.

[0248] [3] The portable electronic device according to the above [1] or [2], wherein the adhesive layer has a glass transition temperature in the range of -15°C to 15°C, where the glass transition temperature of the adhesive layer is the glass transition temperature found from the peak temperature of tan δ in dynamic viscoelasticity measurement.

[0249] [4] The portable electronic device according to any one of the above [1] to [3], wherein the adhesive layer further contains a tackifying resin.

[0250] [5] The portable electronic device according to any one of the above [1] to [4], wherein the adhesive layer contains at least one selected from the group consisting of a rosin-based tackifying resin and a terpene-based tackifying resin.

[0251] [6] The portable electronic device according to any one of the above [1] to [5], wherein the content of the tackifying resin in the adhesive layer is 70 parts by weight or less relative to 100 parts by weight of the acrylic polymer.

[0252] [7] The portable electronic device according to any one of the above [1] to [6], wherein the adhesive layer further contains an acrylic oligomer.

[0253] [8] The portable electronic device according to any one of [1] to [7] above, wherein the adhesive composition for forming the adhesive layer contains at least one selected from the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents.

[0254] [9] The portable electronic device according to any one of [1] to [8] above, wherein the adhesive sheet has a 180-degree peeling strength to a stainless steel plate of 20 N / 25 mm or more.

[0255]

[11] An adhesive sheet, wherein the adhesive sheet has an adhesive layer containing an acrylic polymer which is a polymer containing a monomer component of heptyl acrylate, the adhesive layer has a storage modulus G' of 20,000 Pa or more at 65°C and a tan δ of 0.3 or more at -20°C, where the tan δ is a ratio (G" / G') of a loss modulus G" to a storage modulus G' of the adhesive layer.

[0256]

[12] The adhesive sheet according to

[11] above, wherein the acrylic polymer has a weight average molecular weight of 700,000 or more.

[0257]

[13] The adhesive sheet according to

[11] or

[12] above, wherein the adhesive layer has a glass transition temperature in the range of -15°C to 15°C, where the glass transition temperature of the adhesive layer is a glass transition temperature found from a peak temperature of tan δ in dynamic viscoelasticity measurement.

[0258]

[14] The adhesive sheet according to any one of

[11] to

[13] above, wherein the adhesive layer further contains a tackifying resin.

[0259]

[15] The adhesive sheet according to any one of

[11] to

[14] above, wherein the adhesive layer contains at least one selected from the group consisting of rosin-based tackifying resins and terpene-based tackifying resins.

[0260]

[16] The adhesive sheet according to any one of

[11] to

[15] above, wherein the content of the tackifying resin in the adhesive layer is 70 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.

[0261]

[17] The adhesive sheet according to any one of

[11] to

[16] above, wherein the adhesive layer further contains an acrylic oligomer.

[0262]

[18] The adhesive sheet according to any one of

[11] to

[17] above, wherein the adhesive composition for forming the adhesive layer contains at least one selected from the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents.

[0263]

[19] The adhesive sheet according to any one of

[11] to

[18] above, wherein the 180-degree peeling strength of the adhesive sheet to a stainless steel plate is 20 N / 25 mm or greater.

[0264]

[20] The adhesive sheet according to any one of

[11] to

[19] above, wherein the adhesive sheet is used for fixing a member in a portable electronic device.

[0265]

[21] A portable electronic device, wherein the portable electronic device contains the adhesive sheet according to any one of

[11] to

[20] above.

[0266] Embodiments

[0267] Hereinafter, some embodiments of the present application will be described, but the present application is not intended to be limited to what is shown in these embodiments. Note that, unless otherwise specified, "parts" and "%" in the following description are on a weight basis.

[0268] <Example 1>

[0269] (Synthesis of acrylic polymer)

[0270] In a reaction vessel having a stirrer, a thermometer, a nitrogen introduction tube, a reflux condenser, and a dropping funnel, n-heptyl acrylate (n-HpA) 94 parts and acrylic acid (AA) 6 parts as monomer components, and ethyl acetate as a polymerization solvent were added, and stirred for 2 hours while introducing nitrogen. Oxygen in the polymerization system was removed by this operation, and then 2,2'-azobisisobutyronitrile (AIBN) 0.2 parts as a polymerization initiator was added, and solution polymerization was performed at 60°C to 70°C for 8 hours, thereby obtaining an acrylic polymer solution. The weight average molecular weight (Mw) of the acrylic polymer was 1.2 million. Adjustment of Mw was performed by adjusting the concentration of the monomer components at the time of polymerization. Note that the above n-HpA is a compound synthesized using heptanol from biomass, having a heptyl group from biomass at the ester terminal.

[0271] (Preparation of adhesive composition)

[0272] To the above-obtained solution of the acrylic polymer, 30 parts of terpene phenol A (trade name "YS POLYSTER T-115", terpene phenol resin manufactured by AnGore Chemical Co., Ltd., softening point about 115°C, hydroxyl value 30 mgKOH / g to 60 mgKOH / g) as a tackifying resin, 3 parts (solid content basis) of isocyanate crosslinking agent (trade name "CORONATE L", 75% ethyl acetate solution of trimethylolpropane / toluene diisocyanate trimer adduct, manufactured by Nippon Polyurethane Industry Co., Ltd.), and 0.03 parts of epoxy crosslinking agent (trade name "TETRAD-C", 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, manufactured by Mitsubishi Gas Chemical Co., Inc.) were added with respect to 100 parts of the acrylic polymer contained in the solution, and the mixture was stirred to prepare the adhesive composition of the present example.

[0273] (Production of Adhesive Sheet)

[0274] The obtained adhesive composition was applied to the release surface of a polyester release film (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) having a thickness of 38 μm, and dried at 100°C for 2 minutes to form an adhesive layer having a thickness of 30 μm. A release surface of a polyester release film (trade name "Diafoil MRF", thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) having a thickness of 25 μm was attached to the adhesive layer. In this way, a double-coated adhesive sheet having a thickness of 30 μm without a substrate and protected by the above two polyester release films was obtained.

[0275] (Examples 2 to 6 and Comparative Examples 1 to 4)

[0276] The adhesive compositions of the respective examples were prepared by substantially the same method as in Example 1, except that the monomer composition, Mw of the acrylic polymer, the type and amount of tackifying resin, the amount of acrylic oligomer, and the type and amount of crosslinking agent were changed as shown in Table 1. Using the obtained adhesive compositions, the double-coated adhesive sheets (thickness 30 μm) of the respective examples were produced in the same manner as in Example 1. The adjustment of the Mw of the acrylic polymer was performed by adjusting the concentration of the monomer components during polymerization.

[0277] Note that in Table 1, 2EHA denotes 2-ethylhexyl acrylate, BA denotes n-butyl acrylate, 4HBA denotes 4-hydroxybutyl acrylate, and HEA denotes hydroxyethyl acrylate. In addition, terpene phenol B is a terpene phenol resin manufactured by YASUHARA CHEMICAL CO., LTD. under the trade name "YS Polystar S-145" (softening point: about 145°C, hydroxyl value: 70 mgKOH / g to 110 mgKOH / g), and rosin ester is a polymeric rosin ester manufactured by ARAKAWA CHEMICAL INDUSTRIES, LTD. under the trade name "PENSEL D125" (softening point: 125°C, hydroxyl value: 32 mgKOH / g).

[0278] In addition, as the acrylic oligomer, an acrylic oligomer prepared by the following method was used. Specifically, in a reaction vessel having a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser, and a dropping funnel, cyclohexyl methacrylate (CHMA) 95 parts and AA 5 parts, AIBN 10 parts as a polymerization initiator, and ethyl acetate as a polymerization solvent were added, the system was stirred for 1 hour under a nitrogen stream to remove oxygen in the polymerization system, and then the temperature was raised to 85°C, and the reaction was performed for 5 hours, thereby obtaining an acrylic oligomer having a solid content concentration of 50%. The Mw of the obtained acrylic oligomer was 3600.

[0279] [Method of Evaluation]

[0280] [Adhesion to SUS]

[0281] An evaluation sample was produced by pasting a PET film having a thickness of 50 μm on one adhesive surface of an adhesive sheet (double-sided adhesive sheet) to perform lining, and cutting to a size of 25 mm in width and 100 mm in length, under an evaluation environment of 23°C and 50% RH. The other adhesive surface of the evaluation sample was pressure-bonded to the surface of a stainless steel plate (SUS304BA plate) obtained by cleaning with ethyl acetate, by reciprocating a 2 kg roller once, under an environment of 23°C and 50% RH. This was left to stand for 72 hours under the same environment, and then the peeling strength (adhesion to SUS) [N / 25 mm] was measured using a universal tensile compression tester, according to JIS Z 0237:2000, under conditions of a tensile speed of 300 mm / minute and a peeling angle of 180 degrees. In the measurement of the peeling strength, as the universal tensile compression tester, "Tensile Compression Tester, TG-1 kN" manufactured by Minebea Co., Ltd. or an equivalent thereof can be used. Note that in the case where the peeling strength measurement is performed on a single-sided adhesive sheet, lining with a PET film is not necessary. In the case where the substrate is thin (for example, in the case where the substrate has a thickness of 25 μm or less), lining with a PET film can be performed.

[0282] [Impact Resistance Test (Charpy)]

[0283] The impact resistance (impact adhesive strength) [J / cm] was determined using a pendulum-type adhesive shear impact tester according to JIS K6855 (corresponding to international standard ISO9653). 2 As test pieces, each example of substrate-free double-sided adhesive sheet was cut into 10mm square adhesive sheets. A 10mm square, 5mm thick stainless steel (SUS304) plate was glued onto another stainless steel plate (SUS304) with a load of 35N for 10 seconds, and then cured at room temperature for 48 hours. The measurements were conducted under the conditions of hammer energy of 2.75J and hammer velocity (impact velocity) of 3.5m / s.

[0284] [Z-axis resilience test (high temperature and high humidity conditions)]

[0285] like Figure 5 As shown in (a), a polycarbonate (PC) sheet 50 with a length of 30 mm, a width of 10 mm, and a thickness of 2 mm and a PET film 60 with a length of 70 mm, a width of 10 mm, and a thickness of 75 μm are prepared. The PC sheet 50 and the PET film 60 are overlapped such that one end of their length is aligned, and the PC sheet 50 and the PET film 60 are fixed with the remaining portion of the PET film 60 protruding from the other end of the PC sheet 50. The above fixing is performed using commercially available double-sided adhesive tape (manufactured by Nitto Denko Co., Ltd., "No. 5000NS").

[0286] Each adhesive sheet, protected by two release liner pads on both adhesive surfaces, is cut to a size of 3 mm wide and 10 mm long, thus preparing an adhesive sheet sample 70. With the surface of the PC board 50 opposite to the fixing surface of the PET film set as the upper side, a release liner is peeled off from the adhesive sheet sample 70, aligning the width direction of the PC board 50 with the length direction of the adhesive sheet sample 70. The adhesive sheet sample 70 is then glued and fixed to the upper surface of the PC board 50 such that its two ends in the width direction are located on lines 7 mm and 10 mm from the other end of the upper surface of the PC board 50. This fixing is performed by reciprocating once with a 2 kg roller on the upper surface of the adhesive sheet sample 70 protected by the other release liner.

[0287] Next, at 23°C and 50% RH, the other release liner of the adhesive sheet sample 70, which is bonded to the PC board 50, is peeled off, as shown below. Figure 5As shown in (b), the protruding portion (40 mm in length) of the PET film 60 fixed to the PC board 50 is folded back towards the PC board 50, aligning the adhesive sheet sample 70 with the other end (free end) of the PET film 60. A 0.1 kg roller is then rolled back and forth once on the PET film 60, thereby fixing the other end of the folded PET film 60 to the upper surface of the PC board 50 via the adhesive sheet sample 70, and exposing it to an environment of 65°C and 90% RH. After 72 hours of exposure in this environment, it is confirmed whether the adhesive bond between the adhesive sheet sample 70 and the PET film 60 is maintained. Figure 5 As shown in (c), the peeling of the PET film 60 is defined as "peeling". With the PET film 60 in place, the height of the PET film 60 protruding from the adhesive sheet sample 70 [mm] was measured using a microscope. The measurement was performed three times, and the lowest value was recorded. It should be noted that the above-mentioned height includes the thickness of the adhesive sheet sample 70.

[0288] According to this evaluation method, unlike previous resilience evaluations, it is possible to evaluate the resilience of peel loads that essentially only include the thickness direction (Z-axis direction) of the adhesive sheet under harsh conditions such as high temperature and high humidity (65°C, 90% RH). Furthermore, by observing over time, the sustained resilience can be evaluated.

[0289] The summary and evaluation results of each example adhesive sheet are shown in Table 1.

[0290]

[0291] As shown in Table 1, the adhesives of Examples 1 to 6 contain acrylic polymers as monomer components, have a storage modulus G' of 20000 Pa or more at 65°C, and a tanδ of 0.3 or more at -20°C. The impact resistance test results of the adhesive sheets of Examples 1 to 6 are 0.3 J / cm. 2 The above results show that the bulge height in the Z-axis resilience test is less than 2.0 mm. In contrast, the adhesive of Comparative Example 1 does not contain heptyl acrylate, but contains an acrylic polymer with 2EHA as the main monomer. Its storage modulus G' at 65°C is less than 20000 Pa, and it failed to withstand the Z-axis resilience test. The adhesives of Comparative Examples 3 to 4 also have a storage modulus G' of less than 20000 Pa at 65°C, and they peel off in the Z-axis resilience test (Comparative Example 3), or the bulge height in the Z-axis resilience test is greater than that of Examples 1 to 6. In addition, the adhesive of Comparative Example 2 does not contain heptyl acrylate, but contains an acrylic polymer with BA as the main monomer. Its tanδ at -20°C is less than 0.3, and the impact resistance test result is lower than that of Examples 1 to 6.

[0292] The above detailed specific examples of the present application are merely illustrative and do not limit the claims. The technology recited in the claims includes various modifications, alterations, and variations of the above-illustrated specific examples.

[0293] Label Explanation

[0294] 1, 2, 3 Adhesive sheet

[0295] 10 Support base material

[0296] 10A First surface

[0297] 10B Second surface (back surface)

[0298] 21 Adhesive layer (first adhesive layer)

[0299] 21A Adhesive surface (first adhesive surface)

[0300] 21B Second adhesive surface

[0301] 22 Adhesive layer (second adhesive layer)

[0302] 22A Adhesive surface (second adhesive surface)

[0303] 31, 32 Release liner

[0304] 100, 200, 300 Adhesive sheet with release liner

Claims

1. An adhesive sheet, wherein the adhesive sheet has an adhesive layer containing an acrylic polymer, the adhesive sheet is a double-coated adhesive sheet without a substrate composed of the adhesive layer, or an adhesive sheet with a substrate other than a foamed body substrate, the acrylic polymer is a polymer containing a monomer component of heptyl acrylate, the monomer component contains a carboxyl group-containing monomer in a proportion of 2% by weight or more and 15% by weight or less, the acrylic polymer has a weight average molecular weight of 700,000 or more, the adhesive layer further contains a tackifying resin, the tackifying resin contains a tackifying resin other than a tackifier having a softening point of 120°C or more, or the tackifying resin contains a tackifying resin having a hydroxyl value of 50 mgKOH / g or more, the tackifying resin contains a terpene phenol-based tackifying resin, and the content of the terpene phenol-based tackifying resin is 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, an adhesive composition for forming the adhesive layer contains a crosslinking agent, the adhesive layer has a storage modulus G' of 20,000 Pa or more at 65°C and a tan δ of 0.3 or more at -20°C, here, the tan δ refers to a ratio of a loss modulus G" to a storage modulus G' (G" / G') of the adhesive layer.

2. The adhesive sheet according to claim 1, wherein the adhesive layer has a glass transition temperature in the range of -15°C to 15°C, here, the glass transition temperature of the adhesive layer refers to a glass transition temperature obtained from a peak temperature of tan δ in dynamic viscoelasticity measurement.

3. The adhesive sheet according to claim 1 or 2, wherein the tackifying resin contains at least one selected from the group consisting of a rosin-based tackifying resin and a terpene-based tackifying resin.

4. The adhesive sheet according to claim 1 or 2, wherein the content of the tackifying resin in the adhesive layer is 70 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.

5. The adhesive sheet according to claim 1 or 2, wherein the adhesive layer further contains an acrylic oligomer, and the acrylic oligomer has a glass transition temperature of 0°C or more and 300°C or less.

6. The adhesive sheet according to claim 1 or 2, wherein the crosslinking agent contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

7. The adhesive sheet according to claim 1 or 2, wherein the adhesive sheet has a 180-degree peeling strength to a stainless steel plate of 20 N / 25 mm or more.

8. The adhesive sheet according to claim 1 or 2, wherein the adhesive sheet is used for fixing a member in a portable electronic device.

Images