Pressure-sensitive adhesive sheet and portable electronic device

Abstract

To provide a pressure-sensitive adhesive sheet having an adhesive layer containing a polyester-based polymer, which is capable of suppressing deterioration in adhesive strength caused by handling conditions prior to bonding to an adherend.SOLUTION: A pressure-sensitive adhesive sheet having an adhesive layer is provided, wherein the adhesive layer contains a polyester-based polymer and has a storage modulus G' of 0.01 MPa or more and less than 0.40 MPa at 23°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive sheet and a portable electronic device.

Background Art

[0002] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter.) exhibits a state of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used as joining means with good workability and high adhesion reliability in various industrial fields such as home appliances, automobiles, various machines, electrical equipment, and electronic equipment, typically in the form of an adhesive sheet including a layer of the adhesive. As the adhesive, various adhesives such as acrylic adhesives, rubber adhesives, and polyester adhesives are used according to the purpose of use, the place of use, required characteristics, and the like. For example, Patent Document 1 can be cited as a document disclosing the prior art related to polyester adhesives.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The adhesive sheet is preferably used, for example, for fixing members in electronic devices such as mobile phones, smartphones, and tablet computers. As the adhesive for the above-mentioned electronic devices, acrylic adhesives based on acrylic polymers are the mainstream. In addition, for example, synthetic rubber adhesives based on rubber block copolymers such as styrene-butadiene block copolymers can be used. Polyester adhesives are excellent in properties such as chemical resistance, water resistance, durability, and optical properties (transparency), and are expected to be used as adhesives for electronic devices because they can exhibit adhesive properties equal to or better than those of acrylic adhesives and synthetic rubber adhesives. In addition, since polyester adhesives can be synthesized using biomass materials, they have the advantage of being able to reduce the dependence on fossil resource-based materials (for example, Patent Document 1).

[0005] By the way, usually, before use (that is, before being attached to the adherend), the adhesive sheet is circulated, stored, and processed in a form in which the adhesive surface is protected by a release liner from the viewpoint of handleability and the like. However, in the adhesive sheet having a release liner on the adhesive surface, the adhesive properties such as adhesive strength may deteriorate due to the transfer of a release treatment agent (for example, a silicone-based release treatment agent) from the release liner to the adhesive surface.

[0006] More specifically, for example, before the above-mentioned pressure-sensitive adhesive sheet for electronic devices is finally attached to the adherend, processing such as punching or cutting may be performed to adapt the outer shape of the pressure-sensitive adhesive sheet to the shape of the adherend. For such processing, the release liner that protects the adhesive surface of the pressure-sensitive adhesive sheet may be replaced with one having a thickness suitable for the processing. That is, the release liner used during the production of the pressure-sensitive adhesive sheet may be removed from the adhesive surface of the pressure-sensitive adhesive sheet, and the release surface of another release liner may be bonded to the exposed adhesive surface. Also, for example, for the purpose of improving the workability of attaching to the adherend, etc., before being attached to the adherend, it may be replaced from a release liner with low visibility to a release liner with high visibility. When the release liner is replaced as described above before being attached to the adherend, the release treatment agent may migrate from the release liners before and after replacement to the adhesive layer and accumulate on the adhesive surface, and therefore the adhesive strength may decrease. In particular, when stored for a long time after the replacement of the release liner, or when stored in an environment where temperature control is not performed, the decrease in adhesive strength tends to become significant due to the migration of the above-mentioned release treatment agent.

[0007] The present invention has been created in view of the above circumstances, and has a configuration having an adhesive layer containing a polyester-based polymer, and aims to provide a pressure-sensitive adhesive sheet capable of suppressing a decrease in adhesive strength caused by the handling before being attached to an adherend. Another related object is to provide a portable electronic device including the above pressure-sensitive adhesive sheet.

Means for Solving the Problems

[0008] According to this specification, a pressure-sensitive adhesive sheet having an adhesive layer is provided. The adhesive layer contains a polyester-based polymer and has a storage elastic modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa. According to the above configuration, even when handling such as replacing the release liner is performed before attaching to the adherend in a configuration having an adhesive layer containing a polyester-based polymer, a decrease in adhesive strength is suppressed, so that a decrease in adhesive strength can be suppressed regardless of the handling before attaching to the adherend.

[0009] In some preferred embodiments, the PSA layer contains 45 parts by weight or more of a tackifier resin relative to 100 parts by weight of the polyester-based polymer. By having a composition containing a polyester-based polymer and a predetermined amount or more of a tackifier resin relative to the polyester-based polymer in this manner, a PSA layer having a storage modulus at 23° C. within a predetermined range can be preferably formed.

[0010] In some embodiments, the softening point of the tackifier resin is 30° C. or higher and 200° C. or lower. By including a tackifier resin that contains a polyester-based polymer and has a softening point in the above range, a PSA layer having a storage modulus at 23° C. in a predetermined range can be preferably formed.

[0011] In some embodiments, the pressure-sensitive adhesive layer preferably contains, as the tackifier resin, either (1) 60 parts by weight or less of tackifier resin T1 having a softening point of 145° C. or more and 200° C. or less per 100 parts by weight of the polyester-based polymer, or (2) 60 parts by weight or less of tackifier resin T2 having a softening point of 30° C. or more and less than 145° C., or (3) 60 parts by weight or less of tackifier resin T1 per 100 parts by weight of the polyester-based polymer, and tackifier resin T2. ​​A pressure-sensitive adhesive layer that falls into any of the above (1) to (3) can preferably have a storage modulus at 23° C. in a predetermined range.

[0012] In some embodiments, the thickness of the adhesive layer is less than 80 μm. The effect of the technology disclosed herein (the effect of suppressing the decrease in adhesive strength) can be effectively achieved in a configuration having an adhesive layer with a thickness of less than 80 μm. In addition, the adhesive layer with a limited thickness as described above can be well suited to the thinning of products to which the adhesive sheet is applied.

[0013] In some preferred embodiments, the pressure-sensitive adhesive sheet has a 180-degree peel strength against a stainless steel plate (adhesive strength to SUS) of 5 N / 20 mm or more. A pressure-sensitive adhesive sheet having the above-mentioned adhesive strength to SUS can have good adhesion reliability.

[0014] The pressure-sensitive adhesive sheet disclosed herein can suppress a decrease in adhesive force even when it is handled such that the release liner is replaced before being attached to an adherend. Therefore, for example, it can be preferably used as a pressure-sensitive adhesive sheet for fixing members of a portable electronic device in which the release liner may be replaced before attachment to the adherend for the purpose of processing or the like. Accordingly, according to this specification, a portable electronic device using any of the pressure-sensitive adhesive sheets disclosed herein, in other words, a portable electronic device including the pressure-sensitive adhesive sheet is provided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be understood by those skilled in the art based on the teachings regarding the implementation of the invention described in this specification and the common general knowledge in the art at the time of filing. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the art. In the following drawings, members and parts having the same function may be denoted by the same reference numerals for description, and redundant descriptions may be omitted or simplified. Also, the embodiments shown in the drawings are schematized for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product.

[0017] In this specification, biomass-derived carbon means carbon (renewable carbon) derived from biomass materials, that is, materials derived from renewable organic resources. The above-mentioned biomass materials typically refer to materials derived from biological resources (typically plants that perform photosynthesis) that can be continuously reproduced if sunlight, water, and carbon dioxide are present. Therefore, materials derived from fossil resources (fossil resource-based materials) that are depleted by use after mining are excluded from the concept of biomass materials here. For example, the ratio of biomass-derived carbon in all carbon contained in a polyester-based polymer, that is, the biomass carbon ratio (also referred to as the bio rate), can be estimated from the carbon isotope content of mass number 14 measured in accordance with ASTM D6866-22 Method B. Also, the bio rate of the adhesive layer, the bio rate of the base material, and the bio rate of the adhesive sheet can be estimated by the same method. The same applies to the examples described later.

[0018] <Configuration example of the adhesive sheet> The adhesive sheet disclosed herein is configured to include an adhesive layer. The adhesive sheet can be in the form of a substrate-free double-sided adhesive sheet having, for example, a first adhesive surface formed by one surface of the adhesive layer and a second adhesive surface formed by the other surface of the adhesive layer. Alternatively, the adhesive sheet disclosed herein may be in the form of an adhesive sheet with a substrate in which the adhesive layer is laminated on one or both sides of a support substrate. Hereinafter, the support substrate may also be simply referred to as the "substrate".

[0019] The structure of the pressure-sensitive adhesive sheet according to one embodiment is schematically shown in FIG. 1. This pressure-sensitive adhesive sheet 1 is configured as a substrate-less double-sided pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer 21. The pressure-sensitive adhesive sheet 1 is used by attaching a first pressure-sensitive adhesive surface 21A formed by one surface (first surface) of the pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive surface 21B formed by the other surface (second surface) of the pressure-sensitive adhesive layer 21 to different locations on the adherend. The locations where the pressure-sensitive adhesive surfaces 21A and 21B are attached may be different locations on different members or different locations within a single member. Before use (i.e., before attaching to the adherend), as shown in FIG. 1, the pressure-sensitive adhesive sheet 1 can be a component of the pressure-sensitive adhesive sheet 100 with release liners in a form where the first pressure-sensitive adhesive surface 21A and the second pressure-sensitive adhesive surface 21B are each protected by release liners 31 and 32 whose at least the sides facing the pressure-sensitive adhesive layer 21 are release surfaces. As the release liners 31 and 32, for example, those configured such that one side of a sheet-like substrate (liner substrate) has a release layer formed by a release treatment agent and thus becomes a release surface can be preferably used. Alternatively, the release liner 32 can be omitted, and a release liner 31 with both sides being release surfaces can be used. By overlapping this with the pressure-sensitive adhesive sheet 1 and winding it in a spiral shape, a pressure-sensitive adhesive sheet with release liners in a form (roll form) where the second pressure-sensitive adhesive surface 21B abuts against the back surface of the release liner 31 and is protected may be configured.

[0020] The structure of the adhesive sheet according to another embodiment is schematically shown in FIG. 2. This adhesive sheet 2 is configured as a single-sided adhesive sheet with a substrate, which includes a sheet-like support substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side thereof. The adhesive layer 21 is fixedly provided on the first surface 10A side of the support substrate 10, that is, without the intention of separating the adhesive layer 21 from the support substrate 10. Before use, the adhesive sheet 2 can be a component of the adhesive sheet 200 with a release liner in a form where the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31 whose at least the side facing the adhesive layer 21 is a release surface, as shown in FIG. 2. Alternatively, the release liner 31 can be omitted, and the support substrate 10 with the second surface 10B being the release surface can be used, and the adhesive sheet 2 can be wound so that the adhesive surface 21A abuts against the second surface (back surface) 10B of the support substrate 10 and is protected (roll form).

[0021] The structure of the adhesive sheet according to still another embodiment is schematically shown in FIG. 3. This adhesive sheet 3 is configured as a double-sided adhesive sheet with a substrate, which includes a sheet-like support substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, a first adhesive layer 21 fixedly provided on the first surface 10A side thereof, and a second adhesive layer 22 fixedly provided on the second surface 10B side thereof. Before use, the adhesive sheet 3 can be a component of the adhesive sheet 300 with a release liner in a form where the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 are protected by release liners 31 and 32, as shown in FIG. 3. Alternatively, the release liner 32 can be omitted, and a release liner 31 with both sides being release surfaces can be used, and the adhesive sheet 3 and this release liner 31 can be overlapped and wound in a spiral shape so that the second adhesive surface 22A abuts against the back surface of the release liner 31 and is protected (roll form) to form an adhesive sheet with a release liner.

[0022] In the double-sided adhesive sheet with the above-mentioned substrate, at least one of the first adhesive layer and the second adhesive layer (for example, the first adhesive layer) may be an adhesive layer described below, and the other adhesive layer (for example, the second adhesive layer) may also be an adhesive layer described below, and may be an adhesive layer having a composition different from the adhesive layer disclosed herein (specifically, the above-mentioned one adhesive layer, for example, the first adhesive layer). Such another adhesive layer may be formed from, for example, a known or conventional adhesive.

[0023] Although not particularly limited, the technology disclosed herein can be preferably implemented in the form of a substrate-free double-sided adhesive sheet. Since the substrate-free double-sided adhesive sheet does not have a support substrate, it is easy to be thinned and is also advantageous in that it can maximize the adhesive characteristics such as adhesive strength. Further, in the substrate-free double-sided adhesive sheet, the thickness of the adhesive layer can be utilized to the maximum, and the effect based on the storage elastic modulus G' of the adhesive layer at 23°C described later can be effectively exerted.

[0024] Note that the concept of the adhesive sheet herein may include those referred to as adhesive tapes, adhesive films, adhesive labels, etc. The adhesive sheet may be in a roll form, may be in a sheet form, or may be cut or punched into an appropriate shape according to the application and usage mode.

[0025] <Adhesive layer> (Storage elastic modulus at 23°C) The pressure-sensitive adhesive layer disclosed herein is characterized in that the storage elastic modulus G' at 23°C is 0.01 MPa or more and less than 0.40 MPa. According to the pressure-sensitive adhesive sheet having a polyester-based polymer-containing pressure-sensitive adhesive layer with a storage elastic modulus at 23°C of less than 0.40 MPa, regardless of how it is handled before being attached to the adherend, for example, even if it has undergone a handling method in which the release liner is replaced before attachment to the adherend or it is stored in a harsh environment such as without temperature control, the decrease in adhesive strength can be suppressed. The reason is that in the pressure-sensitive adhesive layer with a storage elastic modulus at 23°C of less than 0.40 MPa, at the surface (adhesive surface) of the pressure-sensitive adhesive layer, the portion without the release treatment agent (e.g., silicone-based release treatment agent) transferred from the release liner to the adhesive surface follows the adherend well, so it is considered that the decrease in adhesive strength is suppressed. It should be noted that the technology disclosed herein is not limited to the above interpretation. Also, the pressure-sensitive adhesive layer with a storage elastic modulus at 23°C of 0.01 MPa or more has appropriate cohesive force, so it has good adhesive properties such as adhesive strength and holding power, processability, and handleability, and can be highly practical in various applications such as fixing members of electronic devices.

[0026] In some preferred embodiments, from the perspective of suppressing the decrease in the adhesive strength, the storage elastic modulus at 23°C is 0.30 MPa or less (e.g., less than 0.30 MPa), more preferably 0.25 MPa or less, even more preferably 0.20 MPa or less, still more preferably 0.15 MPa or less, particularly preferably 0.12 MPa or less, and may be 0.10 MPa or less (e.g., less than 0.10 MPa), 0.08 MPa or less, or 0.06 MPa or less. Also, from the perspectives of improving cohesive force, adhesive properties, processability, handleability, etc., in some embodiments, the storage elastic modulus at 23°C is preferably 0.03 MPa or more, more preferably 0.05 MPa or more, even more preferably 0.08 MPa or more, particularly preferably 0.10 MPa or more, and may be 0.14 MPa or more, 0.18 MPa or more, 0.20 MPa or more, or 0.22 MPa or more.

[0027] In the technology disclosed herein, the storage modulus of the pressure-sensitive adhesive layer at 23°C can be determined by dynamic viscoelasticity measurement. Specifically, a layered pressure-sensitive adhesive (in the case of a pressure-sensitive adhesive layer or a substrate-free pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet) is prepared, and a plurality of such pressure-sensitive adhesives are stacked to produce a pressure-sensitive adhesive layer with a thickness of approximately 1 mm. A sample punched out into a disk shape with a diameter of 7.9 mm from this pressure-sensitive adhesive layer is sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurement is performed under the following conditions using a viscoelasticity tester (for example, ARES or its equivalent manufactured by TA Instruments), and the storage modulus at 23°C is determined. · Measurement mode: Shear mode · Temperature range: -70°C to 150°C · Heating rate: 5°C / min · Measurement frequency: 1 Hz In the examples described below, the measurement is also performed by the above method. Note that, as the pressure-sensitive adhesive layer to be measured, a layer formed by applying the corresponding pressure-sensitive adhesive composition in a layer and drying or curing it may be used.

[0028] (Polyester-based polymer) The pressure-sensitive adhesive layer disclosed herein contains a polyester-based polymer. In this specification, a pressure-sensitive adhesive layer containing a polyester-based polymer is also referred to as a polyester-based pressure-sensitive adhesive layer. The above polyester-based polymer is typically included in the pressure-sensitive adhesive layer as a base polymer. Here, the base polymer refers to the main component of the rubber-like polymer (a polymer exhibiting rubber elasticity in a temperature range near room temperature) contained in the pressure-sensitive adhesive layer. Also, in this specification, "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified. Further, in this specification, the polyester-based polymer refers to a polymer obtained by polycondensing a dicarboxylic acid and a diol.

[0029] (Dicarboxylic acid) As the dicarboxylic acid used in the synthesis of the above polyester polymer, any of aliphatic dicarboxylic acids, dimer acids, alicyclic dicarboxylic acids, unsaturated dicarboxylic acids, and aromatic dicarboxylic acids can be used. Specific examples of the dicarboxylic acid include, for example, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, dodecanedioic acid, sebacic acid, thiodipropionic acid, and diglycolic acid; dimer acids obtained by dimerizing fatty acids such as oleic acid and erucic acid; alicyclic dicarboxylic acids such as 1,2-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, norbornanedicarboxylic acid, and adamantanedicarboxylic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, and dodecenyl succinic anhydride; aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; derivatives thereof; and the like. The derivatives of the above dicarboxylic acid include derivatives such as carboxylate salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters. By appropriately selecting one or more of these dicarboxylic acids and using them, a polyester polymer capable of forming an adhesive layer having desired properties (specifically, a desired storage elastic modulus at 23°C) can be obtained.

[0030] In some preferred embodiments, dimer acid is used as the dicarboxylic acid. According to a polyester-based polymer synthesized using dimer acid, that is, a polyester-based polymer containing a structure derived from dimer acid, it is easy to form an adhesive layer having a storage modulus at 23°C of 23°C or less. The reason is not particularly limited, but it is considered that the relatively long side chains introduced by copolymerization of dimer acid contribute to the improvement of the flexibility of the adhesive layer. Dimer acid can be used alone or in combination of two or more. In the embodiment where dimer acid is used as the dicarboxylic acid, the weight ratio of dimer acid in the total amount (total weight) of the dicarboxylic acid as a monomer component of the polyester-based polymer is preferably about 1% by weight or more, preferably about 10% by weight or more, more preferably about 30% by weight or more, still more preferably about 50% by weight or more (for example, more than 50% by weight), particularly preferably about 70% by weight or more, and may be about 75% by weight or more, about 80% by weight or more, about 85% by weight or more, about 90% by weight or more, or about 95 to 100% by weight. By setting the amount of dimer acid used to a predetermined amount or more, the polymer can be designed based on the properties of dimer acid. Also, the upper limit of the weight ratio of the dimer acid is 100% by weight, and from the viewpoint of cohesion and the like, in some embodiments, about 99% by weight or less is appropriate, preferably about 95% by weight or less, and may be about 90% by weight or less, or about 85% by weight or less.

[0031] In some embodiments, sebacic acid is used as the dicarboxylic acid. In the embodiment where sebacic acid is used as the dicarboxylic acid, the weight ratio of sebacic acid in the total amount (total weight) of the dicarboxylic acid as a monomer component of the polyester-based polymer may be approximately 1% by weight or more, for example, approximately 5% by weight or more, approximately 10% by weight or more, or approximately 15% by weight or more. Further, the upper limit of the weight ratio of the sebacic acid is 100% by weight. From the viewpoint of reducing the storage modulus at 23°C of the adhesive layer, in some embodiments, it may be approximately 50% by weight or less, or approximately 30% by weight or less. The technology disclosed herein can be implemented in any embodiment where the dicarboxylic acid as a monomer component used in the synthesis of the polyester-based polymer contains sebacic acid or does not contain sebacic acid. For example, the weight ratio of the sebacic acid may be approximately 10% by weight or less, approximately 3% by weight or less, less than 1% by weight, and the dicarboxylic acid used in the synthesis of the polyester-based polymer may not substantially contain sebacic acid.

[0032] Also, in some embodiments, an aromatic dicarboxylic acid may be used as the dicarboxylic acid used in the synthesis of the polyester-based polymer. By using a dicarboxylic acid containing an aromatic dicarboxylic acid, the cohesive force tends to increase and the storage modulus at 23°C tends to improve. Examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, and orthophthalic acid. The aromatic dicarboxylic acid can be used alone or in combination of two or more.

[0033] In an embodiment where an aromatic dicarboxylic acid is used as the dicarboxylic acid, the weight ratio of the aromatic dicarboxylic acid to the total amount (total weight) of the dicarboxylic acid in the monomer components of the polyester-based polymer may be approximately 1% by weight or more, and from the viewpoint of improving cohesive force and the like, it may be approximately 3% by weight or more, approximately 5% by weight or more, or approximately 7% by weight or more. Further, the upper limit of the weight ratio of the aromatic carboxylic acid is, in some embodiments, suitably approximately 50% by weight or less, and from the viewpoint of obtaining adhesive properties such as adhesive force with a storage elastic modulus within a predetermined range at 23°C, it is preferably approximately 30% by weight or less, more preferably approximately 20% by weight or less, still more preferably approximately 15% by weight or less, and particularly preferably approximately 10% by weight or less. The technology disclosed herein can be implemented in any of the embodiments where the dicarboxylic acid as a monomer component used in the synthesis of the polyester-based polymer contains an aromatic dicarboxylic acid or does not contain an aromatic dicarboxylic acid. In some preferred embodiments, the weight ratio of the aromatic dicarboxylic acid may be approximately 5% by weight or less, approximately 3% by weight or less, less than 1% by weight, and the dicarboxylic acid used in the synthesis of the polyester-based polymer may not substantially contain an aromatic dicarboxylic acid.

[0034] The molecular weight of the dicarboxylic acid as a monomer component used in the synthesis of the polyester-based polymer is not particularly limited, and it is suitable that it is 100 or more, and it may be 150 or more. In some embodiments, the molecular weight of the dicarboxylic acid used may be 200 or more, 250 or more, 350 or more, 450 or more, or 500 or more (for example, 530 or more). On the other hand, from the viewpoints of monomer availability, synthetic properties, and the like, in some embodiments, it is suitable that the molecular weight of the dicarboxylic acid is approximately 1000 or less, and it may be, for example, 800 or less, 700 or less, or 600 or less (for example, 550 or less).

[0035] In this specification, the molecular weight of the dicarboxylic acid is the molecular weight calculated from the chemical formula. In the case of using two or more kinds of dicarboxylic acids, the molecular weight of the dicarboxylic acid is the sum (total value) of the products of the molecular weights and weight fractions of the respective dicarboxylic acids.

[0036] Although not particularly limited, from the perspective of reducing the dependence on fossil resource-based materials, in some embodiments, it is preferable to use a plant-derived dicarboxylic acid as the dicarboxylic acid. Suitable examples of such dicarboxylic acids include sebacic acid derived from plants (e.g., castor oil), and dimer acids derived from fatty acids such as oleic acid and erucic acid. The plant-derived dicarboxylic acid can be used alone or in combination of two or more.

[0037] In some embodiments, the weight ratio of the plant-derived dicarboxylic acid in the total amount (total weight) of the dicarboxylic acid as a monomer component of the polyester-based polymer is suitably about 1% by weight or more, preferably about 10% by weight or more, more preferably about 50% by weight or more, still more preferably about 70% by weight or more, particularly preferably about 80% by weight or more, and may be about 90% by weight or more, or may be about 95% by weight or more (e.g., 95 to 100% by weight). The upper limit of the weight ratio of the above plant-derived dicarboxylic acid is 100% by weight, and from the perspective of adhesion characteristics and the like, in some other embodiments, it may be about 99% by weight or less, about 95% by weight or less, or about 90% by weight or less.

[0038] The technology disclosed herein includes embodiments of increasing the bio-based ratio of polyester-based polymers by using aromatic dicarboxylic acids derived from biomass. In some embodiments, terephthalic acid derived from biomass and its derivatives can be used as the dicarboxylic acid. The method for obtaining the dicarboxylic acid derived from biomass is not particularly limited. For example, for terephthalic acid derived from biomass, after obtaining isobutanol from corn, sugars, or wood, it is converted to isobutylene, which is dimerized to obtain isooctene, and then p-xylene is synthesized through radical cleavage, recombination, and cyclization as described in Chemische Technik, vol.38, No.3, p116-119; 1986, and this is oxidized to obtain terephthalic acid (International Publication No. WO 2009 / 079213).

[0039] (diol) As the diol used in the synthesis of the polyester polymer disclosed herein, any of (poly)alkylene glycols, aliphatic diols, dimer diols, alicyclic diols, aromatic diols, and unsaturated diols can be used. Specific examples of the above diols include, for example, (poly)alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol; aliphatic diols such as 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol; dimer diols (dimer diols derived from fatty acids such as oleic acid and erucic acid); alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; aromatic diols such as 4,4′-thiodiphenol, 4,4′-methylenediphenol, 4,4′-dihydroxybiphenyl, o-, m- and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol and their ethylene oxide, propylene oxide adducts; and the like. By appropriately selecting one or more of these diols and using them, a polyester polymer capable of forming an adhesive layer having desired properties (specifically, a desired storage elastic modulus at 23°C) can be obtained.

[0040] In some embodiments, as the diol, (poly)alkylene glycols, aliphatic diols, and alicyclic diols are preferred, and (poly)alkylene glycols and aliphatic diols are more preferred. By combining these diols (preferably ethylene glycol or aliphatic diols) with the above-mentioned dicarboxylic acids (preferably dimer acids), a polyester-based polymer with excellent adhesion properties can be preferably obtained. Preferred examples include (poly)ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. From the perspective of reactivity and the like, ethylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol are more preferred. These can be used alone or in combination of two or more. The above-mentioned (poly)alkylene glycols, aliphatic diols, and alicyclic diols may be of plant origin or of fossil resource origin. In this specification, the above-mentioned (poly)ethylene glycol is used in the sense of including ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

[0041] The weight ratio of (poly)alkylene glycols, aliphatic diols, and alicyclic diols (preferably the weight ratio of ethylene glycol and aliphatic diols) in the total amount (total weight) of diols in the monomer components of the polyester-based polymer is not particularly limited, and in some embodiments, it is suitably about 50% by weight or more. From the perspective of obtaining good adhesion properties, it is preferably about 70% by weight or more, more preferably about 80% by weight or more, still more preferably about 90% by weight or more, particularly preferably about 95% by weight or more (for example, 99 to 100% by weight). In some other embodiments, the weight ratio of the above-mentioned (poly)alkylene glycols, aliphatic diols, and alicyclic diols (preferably the weight ratio of ethylene glycol and aliphatic diols) may be, for example, about 95% by weight or less.

[0042] In some preferred embodiments, (poly)ethylene glycol is used as the diol. By using (poly)ethylene glycol in combination with a suitable dicarboxylic acid, a polyester-based polymer capable of forming an adhesive layer having a desired storage modulus at 23°C can be preferably obtained, and good adhesive properties (such as adhesive strength) can be preferably obtained. In the embodiment where the above (poly)ethylene glycol is used as the diol, the weight ratio of the above (poly)ethylene glycol in the total amount (total weight) of the diol as a monomer component of the polyester-based polymer is suitably about 1% by weight or more, preferably about 10% by weight or more, more preferably about 50% by weight or more, still more preferably about 80% by weight or more, and particularly preferably about 90% by weight or more (for example, 95 to 100% by weight). By setting the usage amount of (poly)ethylene glycol to a predetermined value or more, the polymer can be designed based on the properties of (poly)ethylene glycol. Also, for example, by using (poly)ethylene glycol, an adhesive layer with low haze is easily obtained. In some other embodiments, the weight ratio of the above (poly)ethylene glycol may be about 95% by weight or less, about 70% by weight or less, or about 50% by weight or less. The above-mentioned (poly)ethylene glycol may be derived from plants or from fossil resources. (Poly)ethylene glycol can be used alone or in combination of two or more.

[0043] In some other embodiments, a dimer diol is used as the diol. As the dimer diol, a plant-derived dimer diol is preferably used. By using the above dimer diol, the bio-based ratio of the polyester polymer can be increased. The dimer diol can be used alone or in combination of two or more. In the embodiment where the dimer diol is used as the diol, the weight ratio of the dimer diol in the total amount (total weight) of the diol as a monomer component of the polyester polymer may be approximately 1% by weight or more, for example, approximately 10% by weight or more, approximately 50% by weight or more, approximately 70% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more (for example, 95 to 100% by weight). Also, in some embodiments, the weight ratio of the above dimer diol may be approximately 95% by weight or less, approximately 85% by weight or less, or approximately 60% by weight or less. The technology disclosed herein can be implemented in any embodiment, either an embodiment in which the diol as a monomer component used in the synthesis of the polyester polymer contains a dimer diol or an embodiment in which it does not contain a dimer diol. In some embodiments, the weight ratio of the above dimer diol may be approximately 50% by weight or less (for example, less than 50% by weight), approximately 30% by weight or less, approximately 10% by weight or less, approximately 3% by weight or less, less than 1% by weight, and the diol used in the synthesis of the polyester polymer may not substantially contain a dimer diol.

[0044] Although not particularly limited, from the perspective of reducing the dependence on fossil resource-based materials, in some embodiments, it is preferable to use a plant-derived diol as the diol. Examples of such diols include biomass diols obtained from biomass ethanol as a raw material (for example, biomass (poly)ethylene glycol, etc.), fatty acid esters derived from plants (for example, castor oil), dimer diols derived from fatty acids such as oleic acid and erucic acid, and butanediol produced using glucose. The plant-derived diol can be used alone or in combination of two or more.

[0045] In some embodiments, the weight ratio of the plant-derived diol to the total amount (total weight) of the diol as a monomer component of the polyester polymer may be approximately 1% by weight or more, approximately 10% by weight or more, approximately 50% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more (for example, 95 to 100% by weight). Also, in some other embodiments, the weight ratio of the plant-derived diol may be approximately 95% by weight or less, approximately 70% by weight or less, or approximately 50% by weight or less. Thus, even in embodiments where the amount of the plant-derived diol used is relatively low and a diol derived from fossil resources is used, for example, by using a diol having a relatively low molecular weight as the diol derived from fossil resources, the polyester polymer can have a bio-based ratio of a predetermined value or more. From such a perspective, in some embodiments, the weight ratio of the plant-derived diol may be approximately 30% by weight or less, approximately 10% by weight or less, or approximately 3% by weight or less (for example, less than 1% by weight).

[0046] The molecular weight of the above diol is not particularly limited. In some embodiments, from the viewpoints of monomer availability, synthetic properties, etc., the molecular weight of the diol is suitably about 1000 or less, and may be, for example, 800 or less, 700 or less, or 600 or less. In some preferred embodiments, the molecular weight of the diol is suitably 500 or less, and may be 300 or less, 150 or less, 100 or less, or 80 or less. Also, the molecular weight of the diol is suitably about 50 or more, and may be, for example, more than 100. For example, in the embodiment where the above diol is derived from fossil resources, the molecular weight of the diol derived from fossil resources is suitably 500 or less, and may be 300 or less. The smaller the molecular weight of the diol derived from fossil resources, the more likely the polyester-based polymer is to have a high bio-based ratio. From such a viewpoint, the molecular weight of the diol derived from fossil resources may be 150 or less, 100 or less, or 80 or less. Also, the molecular weight of the diol derived from fossil resources is suitably about 50 or more, and may be, for example, more than 100. A preferred example of the diol having the above molecular weight is ethylene glycol. In some other embodiments, the molecular weight of the diol may be 150 or more, 200 or more, 250 or more, 350 or more, 450 or more, or 500 or more. As the diol having such a molecular weight of a predetermined value or more, a diol derived from plants is preferably used. A preferred example of the diol having such a molecular weight is dimer diol.

[0047] In addition, in this specification, as the molecular weight of the diol, the molecular weight calculated from the chemical formula can be adopted. Also, in the embodiment where two or more kinds of diols are used, as the molecular weight of the diol, the sum (total value) of the product of the molecular weight and the weight fraction of each diol is adopted.

[0048] The polyester polymers disclosed herein can be substantially composed of the above-mentioned dicarboxylic acids and diols. However, for the purpose of introducing desired functional groups, adjusting the molecular weight, etc., other copolymerization components other than the dicarboxylic acids and diols may be copolymerized as long as the effects of the techniques disclosed herein are not impaired. Such other copolymerization components include polyvalent carboxylic acids containing three or more carboxy groups (trivalent or higher polyvalent carboxylic acids such as trimellitic acid, pyromellitic acid, adamantane tricarboxylic acid, trimesic acid, trimer acid, etc.), polyols containing three or more hydroxyl groups in one molecule (pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, adamantane triol, etc.), monocarboxylic acids, monoalcohols, hydroxycarboxylic acids, lactones, and the like. The above other copolymerization components can be used alone or in combination of two or more. These other copolymerization components may or may not be of plant origin. In some embodiments, the proportion of the above other copolymerization components is suitably less than, for example, 10% by weight, may be less than 3% by weight, may be less than 1% by weight, or may be less than 0.1% by weight in the monomer components of the polyester polymer. The techniques disclosed herein can be preferably implemented in an embodiment where the monomer components of the polyester polymer substantially do not contain the above other copolymerization components.

[0049] Among the monomer components used in the synthesis of the polyester polymers disclosed herein, although not particularly limited, the total proportion of the dicarboxylic acid and the diol is suitably approximately 90% by weight or more, preferably approximately 95% by weight or more, more preferably approximately 98% by weight or more, and still more preferably approximately 99% by weight or more (for example, 99 to 100% by weight). The techniques disclosed herein are preferably implemented in an embodiment using polyester polymers synthesized substantially from dicarboxylic acids and diols.

[0050] In some preferred embodiments, the monomer components of the polyester-based polymer are used in combination with dimer acid as the dicarboxylic acid and (poly)ethylene glycol as the diol. In the embodiment of using a polyester-based polymer synthesized by combining dimer acid and (poly)ethylene glycol, the technology disclosed herein is preferably implemented. The total proportion of dimer acid and (poly)ethylene glycol in the total amount of monomer components of the polyester-based polymer is suitably approximately 50% by weight or more, preferably approximately 60% by weight or more, more preferably approximately 70% by weight or more, still more preferably approximately 80% by weight or more, and may be approximately 90% by weight or more (for example, 99 to 100% by weight).

[0051] In some embodiments, it is preferable that the polyester-based polymer has a limited content of aromatic rings in its polymer molecules or substantially does not contain aromatic rings. Thereby, there is a tendency to easily obtain an adhesive layer having a storage modulus at 23°C of a predetermined value or less. Limiting the content of aromatic rings in the polyester-based polymer is also preferable from the viewpoint of improving adhesive strength and the like. In some preferred embodiments, the copolymerization ratio of aromatic ring-containing monomers (typically aromatic dicarboxylic acids and aromatic diols) in the polyester-based polymer is approximately 20% by weight or less, more preferably approximately 15% by weight or less, still more preferably approximately 10% by weight or less, may be approximately 5% by weight or less, may be approximately 3% by weight or less, and may be approximately 1% by weight or less (for example, less than 1% by weight) from the viewpoint of obtaining a storage modulus at 23°C of a predetermined value or less. The technology disclosed herein can be particularly preferably implemented in an embodiment using a polyester-based polymer that substantially does not contain aromatic rings in its molecules. Further, in the embodiment where the polyester-based polymer has aromatic rings, the copolymerization ratio of the aromatic ring-containing monomers may be, for example, approximately 1% by weight or more, may be approximately 5% by weight or more, and may be approximately 7% by weight or more from the viewpoints of enhancing cohesive force and obtaining good holding power.

[0052] The method for obtaining the polyester-based polymer disclosed herein is not particularly limited, and a polymerization method known as a synthesis method for polyester-based polymers can be appropriately employed. As the monomer raw materials used for the synthesis of the polyester-based polymer, for example, those in which monomers are blended so that the amount of dicarboxylic acid is 0.95 to 1.05 equivalents (preferably 0.98 to 1.02 equivalents) per 1 equivalent of diol can be used. By blending dicarboxylic acid and diol at the above ratio, a high molecular weight polyester-based polymer can be easily obtained. Further, by setting the molar ratio of dicarboxylic acid and diol within an appropriate range, an appropriate crosslinked structure (for example, crosslinking based on reaction with a crosslinking agent such as an isocyanate-based crosslinking agent) can be obtained to adjust the cohesive force.

[0053] In the technology disclosed herein, the weight ratio of the dicarboxylic acid and the diol as monomer components used in the synthesis of the polyester polymer is not particularly limited, and an appropriate weight ratio can be set in consideration of the intended polymer physical properties, synthetic properties, and the like. In some embodiments, the ratio of the weight A1 of the dicarboxylic acid to the weight A2 of the diol (weight ratio A1 / A2) used as the monomer component may be 10 / 90 or more, or may be 30 / 70 or more. In some preferred embodiments, the weight ratio (A1 / A2) is approximately 50 / 50 or more, more preferably 60 / 40 or more, still more preferably 70 / 30 or more, and may be 80 / 20 or more, or 90 / 10 or more. For example, by increasing the weight ratio of the dicarboxylic acid as described above, the characteristics based on the dicarboxylic acid (for example, dimer acid) can be preferably expressed. In the embodiment using a plant-derived dicarboxylic acid, the bio-based ratio of the obtained polyester polymer can be effectively increased. Further, the weight ratio (A1 / A2) may be, for example, 95 / 5 or less, or 85 / 15 or less. In some embodiments, from the viewpoint of preferably expressing the characteristics based on the diol, the weight ratio (A1 / A2) may be 75 / 25 or less, or 50 / 50 or less (for example, 30 / 70 or less). In the embodiment using a plant-derived diol, by setting the weight ratio as described above, the polyester polymer can increase the bio-based ratio based on the plant-derived diol. In addition, in the embodiment using plant-derived materials for both the dicarboxylic acid and the diol, a polyester polymer having a bio-based ratio of a predetermined value or more can be obtained regardless of the weight ratio of the dicarboxylic acid and the diol.

[0054] The polyester-based polymers in the technology disclosed herein can be obtained by polycondensation of dicarboxylic acids and diols, similar to general polyesters. More specifically, the polyester-based polymers can be synthesized by allowing the reaction between the carboxy groups of the dicarboxylic acids and the hydroxyl groups of the diols to proceed while typically removing water generated by the above reaction (water of formation) and the like outside the reaction system. As a method for removing the above water of formation outside the reaction system, a method of blowing an inert gas into the reaction system and taking out the water of formation together with the inert gas outside the reaction system, a method of azeotropic dehydration using a reaction water discharging solvent such as toluene or xylene, a method of distilling off the water of formation from the reaction system under reduced pressure (reduced pressure method), etc. can be used.

[0055] The reaction temperature, reaction time when performing the above reaction (including esterification and polycondensation), and the degree of reduced pressure (pressure inside the reaction system) when adopting the reduced pressure method can be appropriately set so that a polyester-based polymer with the desired properties (e.g., molecular weight) can be efficiently obtained. Although not particularly limited, usually, the above reaction temperature is preferably about 150 °C or higher (e.g., 180 °C to 260 °C). By setting the reaction temperature within the above range, a good reaction rate can be obtained, productivity is improved, and it is easy to prevent or suppress the deterioration of the produced polyester-based polymer. The reaction time is not particularly limited and can be about 3 to 48 hours (e.g., 10 to 30 hours). When adopting the reduced pressure method, although not particularly limited, usually, the above degree of reduced pressure is preferably 10 kPa or less (e.g., 10 kPa to 0.1 kPa), and can be, for example, 4 kPa to 0.1 kPa. By setting the pressure inside the reaction system within the above range, the water generated by the reaction can be efficiently distilled off outside the system, and it is easy to maintain a good reaction rate. Also, when the reaction temperature is relatively high, by setting the pressure inside the reaction system to be equal to or higher than the above lower limit value, it is easy to prevent the raw material dicarboxylic acids and diols from being distilled off outside the system. From the viewpoint of stably maintaining the pressure inside the reaction system, usually, it is appropriate to set the pressure inside the reaction system to be 0.1 kPa or higher.

[0056] For the above reaction, similar to the synthesis of general polyesters, known or commonly used catalysts can be used in appropriate amounts for esterification and condensation. Examples of such catalysts include various metal compounds such as titanium-based, germanium-based, antimony-based, tin-based, zinc-based, etc.; strong acids such as p-toluenesulfonic acid and sulfuric acid; and the like. Since the amount of catalyst used can be appropriately set according to the reaction rate and the like, detailed description is omitted here.

[0057] In the above process of synthesizing a polyester-based polymer by the reaction of a dicarboxylic acid and a diol, a solvent may or may not be used. The above synthesis can be carried out without substantially using an organic solvent (for example, in the sense of excluding the mode of intentionally using an organic solvent as the reaction solvent during the above reaction). Synthesizing a polyester-based polymer without substantially using an organic solvent in this way, and preparing a polyester-based adhesive layer using such a polyester-based polymer, meet the requirement of reducing the use of organic solvents in the manufacturing process and are preferable.

[0058] Note that during the above reaction, there is generally a correlation between the molecular weight of the synthesized polyester-based polymer and the viscosity of the reaction system, so the molecular weight of the polyester-based polymer can be controlled by utilizing this fact. For example, by continuously or intermittently measuring (monitoring) the torque of the stirrer or the viscosity of the reaction system during the reaction, it is possible to accurately synthesize a polyester-based polymer that meets the target molecular weight.

[0059] The weight average molecular weight (Mw) of the polyester-based polymer is not particularly limited and is usually approximately 10,000 or more, and for example, it is suitably approximately 20,000 or more. In some embodiments, the Mw of the polyester-based polymer is 30,000 or more, suitably more than 50,000, and from the viewpoint of obtaining more excellent properties, preferably more than 60,000, more preferably more than 70,000, still more preferably more than 80,000, particularly preferably more than 90,000, and may be 95,000 or more. By using a polyester-based polymer having an Mw of a predetermined value or more, an adhesive layer with high cohesive force can be easily obtained. In some preferred embodiments, the Mw of the polyester-based polymer is 100,000 or more (for example, more than 100,000), may be 110,000 or more, and may also be 115,000 or more. By using such a high molecular weight polyester-based polymer, for example, even in an adhesive composition that contains a predetermined amount or more of an adhesion-imparting resin and tends to have a low viscosity, an appropriate viscosity can be easily obtained, and a thin and thick adhesive layer having good quality can be easily formed. Such an adhesive composition does not need to be overly concentrated, and even in a composition containing a crosslinking agent, it tends to have a sufficient pot life and is excellent in handleability. The upper limit of the Mw of the polyester-based polymer is usually suitably approximately 30×10 4 or less, and from the viewpoint of adhesive strength and the like, in some embodiments, preferably approximately 20×10 4 or less, more preferably approximately 15×10 4 or less, and may be, for example, approximately 12×10 4 or less.

[0060] In the present specification, the Mw of the polyester-based polymer refers to a value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, the model name "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used. More specifically, the GPC measurement can be performed under the following conditions. The same method is also used for measurement in the examples described later. [GPC Measurement] Column: TSKgel GMH-H(S) Column temperature: 40 °C Eluent: THF (added with 0.1% by weight of amine component) Flow rate: 0.5 mL / min Injection volume: 100 μL Detector: Differential refractometer (RI) Standard sample: Polystyrene (PS)

[0061] Although not particularly limited, in some embodiments, the glass transition temperature (Tg) of the polyester-based polymer is advantageously approximately 15 °C or lower, preferably approximately 0 °C or lower, more preferably approximately -15 °C or lower, still more preferably approximately -25 °C or lower, and particularly preferably approximately -35 °C or lower (for example, approximately -45 °C or lower). By using a polyester-based polymer with a low Tg, the adhesive strength can be preferably improved. Also, from the perspective of the cohesive strength of the adhesive layer, in some embodiments, the Tg of the polyester-based polymer is usually approximately -80 °C or higher, preferably approximately -70 °C or higher, more preferably approximately -60 °C or higher, and may be approximately -50 °C or higher, or approximately -40 °C or higher. The Tg of the polyester-based polymer can be adjusted by appropriately changing the monomer composition (that is, the types and usage ratio of monomers used in the synthesis of the polymer).

[0062] The Tg of the polyester-based polymer is measured by the following method. That is, using the polyester-based polymer to be measured, a disk-shaped test piece with a thickness of 2 mm and a diameter of 8 mm is prepared. This test piece is sandwiched between parallel plates for shear testing, and using a measuring device (ARES, manufactured by Rheometric Scientific), the peak value of tanδ (loss modulus G'' / storage modulus G') is obtained at a frequency of 1 Hz, and the temperature of this peak value is taken as Tg (glass transition temperature) [°C]. The same method is also used in the examples described later.

[0063] Although not particularly limited, in some embodiments, 10% or more of the constituent carbon of the polyester-based polymer may be biomass-derived carbon, and 30% or more of the constituent carbon may also be biomass-derived carbon. In some preferred embodiments, 50% or more of the constituent carbon of the polyester-based polymer is biomass-derived carbon. In other words, the biomass carbon ratio (also referred to as the bio ratio) of the above polyester-based polymer is 50% or more. By using a polyester-based polymer having a bio ratio of a predetermined value or more in this way, the dependence on fossil resource-based materials in the adhesive layer can be reduced. The bio ratio of the polyester-based polymer may be 52% or more, 55% or more, or for example 60% or more. From the viewpoint of further reducing the dependence on fossil resource-based materials, the bio ratio of the polyester-based polymer is preferably 70% or more, more preferably 75% or more, still more preferably 80% or more, and may be 85% or more, 88% or more. Although the upper limit of the bio ratio is 100% by definition, in some embodiments, the bio ratio of the polyester-based polymer may be, for example, 95% or less, 92% or less, 90% or less, or 85% or less. By using a biomass-derived compound in at least one (for example, both) of the dicarboxylic acid and diol used in the synthesis of the polyester-based polymer, the bio ratio of the polyester-based polymer can be made 50% or more. In some other embodiments, the bio ratio of the polyester-based polymer may be less than 50%, less than 30%, less than 10%, or less than 1%. The bio ratio of the polyester-based polymer may be substantially 0%.

[0064] (Adhesion-imparting resin) In some embodiments, the adhesive layer contains an adhesion - imparting resin. According to the technology disclosed herein, in a composition containing an adhesion - imparting resin, the adhesive layer can have a predetermined storage modulus at 23°C. Also, by using an appropriate amount of the adhesion - imparting resin, the adhesion - improving effect based on the adhesion - imparting resin can be effectively exerted, and the adhesive properties such as adhesion can be preferably improved. As the above - mentioned adhesion - imparting resin, various adhesion - imparting resins such as rosin - based adhesion - imparting resins, terpene - based adhesion - imparting resins, hydrocarbon - based adhesion - imparting resins, epoxy - based adhesion - imparting resins, polyamide - based adhesion - imparting resins, elastomer - based adhesion - imparting resins, phenol - based adhesion - imparting resins, and ketone - based adhesion - imparting resins can be used. Such adhesion - imparting resins can be used alone or in combination of two or more. In the polyester - based adhesive layer, for example, rosin - based adhesion - imparting resins and terpene - based adhesion - imparting resins are preferably used.

[0065] Specific examples of rosin - based adhesion - imparting resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins. The same applies hereinafter) obtained by hydrogenating, disproportionating, polymerizing, etc. these unmodified rosins; various other rosin derivatives; etc. Examples of the above - mentioned rosin derivatives include rosin esters obtained by esterifying unmodified rosin with alcohols (i.e., esterified products of rosin), rosin esters obtained by esterifying modified rosin with alcohols (i.e., esterified products of modified rosin); unsaturated fatty acid - modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid - modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxy groups in unmodified rosin, modified rosin, unsaturated fatty acid - modified rosins, or unsaturated fatty acid - modified rosin esters; metal salts of rosins such as unmodified rosin, modified rosin, and various rosin derivatives (especially rosin esters); rosin - phenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and then subjecting them to thermal polymerization; etc.

[0066] Although not particularly limited, specific examples of rosin esters include esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl ester, triethylene glycol ester, glycerin ester, pentaerythritol ester, and the like.

[0067] Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymer, β-pinene polymer, dipentene polymer, etc.; modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.); and the like. The terpene-based tackifying resin may be a homopolymer of one type of terpene or a copolymer of two or more types of terpenes. As an example of the above-mentioned modified terpene resin, terpene phenol resin is mentioned.

[0068] Terpene phenol resin refers to a polymer containing terpene residues and phenol residues, and is a concept encompassing both a copolymer of terpenes and phenol compounds (terpene-phenol copolymer resin) and a product obtained by phenol-modifying terpenes or their homopolymers or copolymers (phenol-modified terpene resin). Preferred examples of the terpenes constituting such terpene phenol resin include monoterpenes such as α-pinene, β-pinene, limonene (including d-form, l-form, and d / l-form (dipentene)). Hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such terpene phenol resin. It is sometimes referred to as hydrogenated terpene phenol resin.

[0069] Although not particularly limited, in some embodiments, as the tackifying resin, a tackifying resin T containing a structure derived from terpene T is used. The tackifying resin T T has good compatibility with the polyester-based polymer, and the adhesive layer formed using the tackifying resin T T is likely to obtain good quality such as excellent stability during long-term storage. The tackifying resin T TAs the tackifier resin, one or more of the above-mentioned terpene-based tackifier resins can be used. Among them, terpene phenol resin is preferable.

[0070] In the mode of using tackifier resin T as the tackifier resin T in the total amount of the tackifier resin, the proportion of tackifier resin T T (preferably terpene phenol resin) is preferably about 25% by weight or more, and more preferably about 30% by weight or more. In some preferred embodiments, about 50% by weight or more (for example, more than 50% by weight) of the total amount of the tackifier resin is tackifier resin T T and more preferably about 75% by weight or more, still more preferably about 80% by weight or more, for example, about 90% by weight or more can be tackifier resin T T and it may even be that substantially all (for example, about 95% by weight or more to 100% by weight, and further about 99% by weight or more to 100% by weight) of the tackifier resin is tackifier resin T T and it may also be.

[0071] Although not particularly limited, in some other embodiments, rosin-based tackifier resins are used as the tackifier resin. As the rosin-based tackifier resin, one or more appropriate ones can be used from those exemplified above. For example, polymerized rosin ester and hydrogenated rosin methyl ester can be preferably used. In the mode of using rosin-based tackifier resin as the tackifier resin, the proportion of rosin-based tackifier resin in the total amount of the tackifier resin is preferably about 25% by weight or more, and more preferably about 30% by weight or more. In some preferred embodiments, about 50% by weight or more (for example, more than 50% by weight) of the total amount of the tackifier resin is rosin-based tackifier resin, and more preferably about 75% by weight or more, still more preferably about 80% by weight or more, for example, about 90% by weight or more can be rosin-based tackifier resin, and it may even be that substantially all (for example, about 95% by weight or more to 100% by weight, and further about 99% by weight or more to 100% by weight) of the tackifier resin is rosin-based tackifier resin.

[0072] The softening point of the tackifier resin is not particularly limited. In some embodiments, the softening point (softening temperature) of the tackifier resin may be, for example, approximately 200 °C or lower, approximately 180 °C or lower, approximately 160 °C or lower, or approximately 150 °C or lower (e.g., less than 150 °C). By using a tackifier resin having a softening point below a predetermined value, it is easy to obtain a storage modulus at 23 °C below the predetermined value and a tendency to obtain adhesiveness. From this perspective, in some preferred embodiments, the softening point of the tackifier resin may be less than 145 °C, more preferably approximately 135 °C or lower, even more preferably approximately 120 °C or lower, still more preferably approximately 110 °C or lower, particularly preferably approximately 100 °C or lower, and may also be approximately 90 °C or lower. In some embodiments, the softening point of the tackifier resin may be approximately 25 °C or higher, approximately 30 °C or higher, approximately 40 °C or higher, or approximately 50 °C or higher. As the tackifier resin, a liquid tackifier resin that is liquid at room temperature (25 °C) may be used. In some preferred embodiments, the softening point of the tackifier resin is approximately 60 °C or higher, more preferably approximately 70 °C or higher, and even more preferably approximately 75 °C or higher. In some other preferred embodiments, the softening point of the tackifier resin is approximately 85 °C or higher, more preferably approximately 95 °C or higher, and even more preferably approximately 105 °C or higher. By using a tackifier resin having a softening point within the above range, the adhesiveness can be improved.

[0073] In some embodiments, as the tackifier resin, a tackifier resin T1 having a softening point of 145 °C or higher and 200 °C or lower is used. For example, by using an appropriate amount of the tackifier resin T1 having the above softening point, an adhesive layer having a storage modulus at 23 °C within a predetermined range and good adhesiveness can be preferably obtained. From the perspective of reducing the storage modulus at 23 °C, in some preferred embodiments, the softening point of the tackifier resin T1 is approximately 180 °C or lower, more preferably approximately 160 °C or lower, and even more preferably approximately 150 °C or lower (e.g., less than 150 °C). As the tackifier resin T1, the above various tackifier resins can be used. For example, a tackifier resin T containing a terpene-derived structure having a softening point of 145 °C or higher and 200 °C or lowerT (For example, terpene phenol resin) is preferably used. The tackifying resin T1 can be used alone or in combination of two or more.

[0074] In the aspect of using the tackifying resin T1 as the tackifying resin, the proportion of the tackifying resin T1 in the total amount of the tackifying resin may be approximately 25% by weight or more, may be approximately 30% by weight or more, or may be approximately 40% by weight or more. In some aspects, approximately 50% by weight or more (for example, more than 50% by weight) of the total amount of the tackifying resin may be the tackifying resin T1, the proportion of the tackifying resin T1 in the total amount of the tackifying resin may be approximately 80% by weight or more, may be approximately 90% by weight or more, and substantially all (for example, approximately 95% by weight or more and 100% by weight or less, further approximately 99% by weight or more and 100% by weight or less) of the tackifying resin may be the tackifying resin T1. Also, in some other aspects, it is appropriate that the proportion of the tackifying resin T1 in the total amount of the tackifying resin is approximately 50% by weight or less, preferably approximately 30% by weight or less, more preferably approximately 20% by weight or less, and even more preferably approximately 10% by weight or less. By limiting the amount of the tackifying resin T1 having a high softening point, there is a tendency to easily obtain a storage modulus at 23°C within a predetermined range. From such a perspective, in some preferred aspects, the proportion of the tackifying resin T1 in the total amount of the tackifying resin may be approximately 5% by weight or less, may be approximately 3% by weight or less, or may be less than 1% by weight, and the tackifying resin may not substantially contain the tackifying resin T1. The technology disclosed herein can be preferably implemented in an aspect where the tackifying resin T1 is not used as the tackifying resin.

[0075] Although not particularly limited, in an embodiment where tackifier resin T1 is used as the tackifier resin, it is preferable that the amount of tackifier resin T1 used is restricted within a predetermined range. By restricting the amount of tackifier resin T1 used within an appropriate range, an adhesive layer having a storage elastic modulus at 23°C within a predetermined range and having good adhesive strength can be preferably formed. From such a perspective, in some embodiments, the amount of tackifier resin T1 in the adhesive layer is suitably, for example, approximately 70 parts by weight or less, preferably 60 parts by weight or less, more preferably approximately 50 parts by weight or less, still more preferably approximately 40 parts by weight or less (e.g., less than 40 parts by weight), particularly preferably 35 parts by weight or less, and may be approximately 30 parts by weight or less, or may be approximately 20 parts by weight or less, with respect to 100 parts by weight of the polyester-based polymer. Also, in some embodiments, the amount of the above-mentioned tackifier resin T1 may be approximately 1 part by weight or less with respect to 100 parts by weight of the polyester-based polymer, preferably 5 parts by weight or more, more preferably approximately 15 parts by weight or more, still more preferably approximately 25 parts by weight or more, and may be approximately 35 parts by weight or more, or may be approximately 45 parts by weight or more. In some other embodiments, the amount of the above-mentioned tackifier resin T1 may be, for example, approximately 10 parts by weight or less, or may be approximately 5 parts by weight or less, or may be approximately 1 part by weight or less with respect to 100 parts by weight of the polyester-based polymer, and the adhesive layer may not substantially contain tackifier resin T1.

[0076] In some preferred embodiments, as the tackifier resin, a tackifier resin T2 having a softening point of less than 145°C is used. By using the tackifier resin T2 having the above softening point, it is easy to obtain an adhesive layer having a desired storage modulus at 23°C, and it is also easy to obtain good adhesion properties. From such a viewpoint, the softening point of the tackifier resin T2 is preferably approximately 135°C or lower, more preferably approximately 120°C or lower, even more preferably approximately 110°C or lower, still more preferably approximately 100°C or lower (for example, less than 100°C), and particularly preferably approximately 90°C or lower. Also, in some embodiments, the softening point of the tackifier resin T2 may be approximately 25°C or higher, and preferably approximately 30°C or higher. As the tackifier resin T2, a liquid tackifier resin that is liquid at room temperature (25°C) may be used. By using a tackifier resin T2 having a softening point of a predetermined value or higher, the cohesive force of the adhesive layer is improved, and good adhesion properties such as improved adhesive strength are easily obtained. In some preferred embodiments, the softening point of the tackifier resin T2 is approximately 50°C or higher (for example, more than 50°C), more preferably approximately 60°C or higher, even more preferably approximately 70°C or higher, and particularly preferably approximately 75°C or higher. In some other preferred embodiments, the softening point of the tackifier resin T2 is approximately 85°C or higher, more preferably approximately 95°C or higher, and even more preferably approximately 105°C or higher. As the tackifier resin T2, the above various tackifier resins can be used. For example, a tackifier resin T having a softening point of less than 145°C and containing a terpene-derived structure T and a rosin-based tackifier resin are preferably used. Among them, the tackifier resin T T (for example, terpene phenol resin) is more preferred. The tackifier resin T2 can be used alone or in combination of two or more kinds.

[0077] In some preferred embodiments, as the tackifier resin T2, a tackifier resin T2a having a softening point in the range of 60°C or higher and less than 145°C is used. By using the tackifier resin T2a, an adhesive layer having better properties (storage modulus at 23°C and tack properties) can be easily obtained. The softening point of the tackifier resin T2a is preferably approximately 70°C or higher, more preferably approximately 75°C or higher, and may be approximately 85°C or higher, approximately 95°C or higher, or approximately 105°C or higher. Also, the softening point of the tackifier resin T2a is preferably approximately 135°C or lower, more preferably approximately 120°C or lower, even more preferably approximately 110°C or lower, still more preferably approximately 100°C or lower (for example, less than 100°C), and particularly preferably approximately 90°C or lower. As the tackifier resin T2a, the above-described various tackifier resins can be used. For example, a tackifier resin T T and a rosin-based tackifier resin are preferably used. Among them, the tackifier resin T T (for example, terpene phenol resin) is more preferred. The tackifier resin T2a can be used alone or in combination of two or more.

[0078] In the embodiment where the tackifier resin T2a is used as the tackifier resin, the proportion of the tackifier resin T2a in the tackifier resin T2 is preferably approximately 10% by weight or more, more preferably approximately 30% by weight or more, even more preferably approximately 50% by weight or more (for example, more than 50% by weight), still more preferably approximately 70% by weight or more, even more preferably approximately 90% by weight or more, and particularly preferably substantially all of the tackifier resin T2 (for example, approximately 95% by weight or more and 100% by weight or less, and further approximately 99% by weight or more and 100% by weight or less) is the tackifier resin T2a.

[0079] Also, in some embodiments, as the tackifier resin T2, a tackifier resin T2b having a softening point of less than 60°C is used. By using the tackifier resin T2b, a lower storage modulus at 23°C is likely to be obtained. The softening point of the tackifier resin T2b may be approximately 50°C or lower, or may be approximately 40°C or lower. The tackifier resin T2b may be a liquid tackifier resin that is liquid at room temperature (25°C). Also, the softening point of the tackifier resin T2b may be approximately 25°C or higher, and approximately 30°C or higher is preferred. As the tackifier resin T2b, the above-described various tackifier resins can be used. For example, a tackifier resin T T (e.g., terpene phenol resin) is preferably used. The tackifier resin T2b can be used alone or in combination of two or more.

[0080] In an embodiment where the tackifier resin T2b is used as the tackifier resin, the proportion of the tackifier resin T2b in the tackifier resin T2 may be approximately 10% by weight or more, or may be approximately 30% by weight or more, or may be approximately 50% by weight or more (e.g., more than 50% by weight), or may be approximately 70% by weight or more, or may be approximately 90% by weight or more. Substantially all of the tackifier resin T2 (e.g., approximately 95% by weight or more and 100% by weight or less, or further approximately 99% by weight or more and 100% by weight or less) may be the tackifier resin T2b.

[0081] In some embodiments, two or more tackifier resins T2 are used as the tackifier resin T2. For example, embodiments in which two or more tackifier resins T2 having different softening points are used can be mentioned. By blending and using two or more tackifier resins T2 having appropriate softening points, good tack characteristics such as tack strength can be obtained while adjusting the storage modulus at 23°C to a desired range. In an embodiment including two types of tackifier resins T2 having different softening points, the difference (T2H - T2L) in the softening points between the tackifier resin T2H having a relatively high softening point and the tackifier resin T2L having a relatively low softening point is not particularly limited. For example, approximately 5°C or more is appropriate, preferably approximately 10°C or more, more preferably approximately 20°C or more, further preferably approximately 30°C or more, and may be approximately 40°C or more, or may be approximately 50°C or more. Also, in some embodiments, the above difference (T2H - T2L) is, for example, less than 90°C, preferably approximately 70°C or less, more preferably approximately 60°C or less. Although not particularly limited, as the tackifier resin T2H and the tackifier resin T2L, the above-described tackifier resin T2a and tackifier resin T2b can be used respectively.

[0082] In an embodiment using the tackifier resins T2H and T2L, the weight-based ratio (T2H / T2L) of the amount of the tackifier resin T2H to the amount of the tackifier resin T2L is not particularly limited. In some embodiments, the above ratio (T2H / T2L) may be 1 / 9 or more, 2 / 8 or more, 3 / 7 or more, 4 / 6 or more, or 5 / 5 or more. By increasing the above ratio (T2H / T2L), the effect of containing the tackifier resin T2H is more likely to be effectively exerted. Also, in some embodiments, the above ratio (T2H / T2L) may be 9 / 1 or less, or 7 / 3 or less. By setting the range of the above ratio (T2H / T2L), the effect of containing the tackifier resin T2L is more likely to be effectively exerted.

[0083] In an embodiment where tackifier resin T2 is used as the tackifier resin, the proportion of tackifier resin T2 in the total amount of the tackifier resin is preferably about 25% by weight or more, more preferably about 30% by weight or more, and even more preferably about 40% by weight or more. In some embodiments, it is preferable that about 50% by weight or more (for example, more than 50% by weight) of the total amount of the tackifier resin is tackifier resin T2, more preferably about 60% by weight or more, and even more preferably about 70% by weight or more may be tackifier resin T2. In some preferred embodiments, the proportion of tackifier resin T2 in the total amount of the tackifier resin is about 80% by weight or more, more preferably about 90% by weight or more, and even more preferably, substantially all (for example, about 95% by weight or more to 100% by weight, and further about 99% by weight or more to 100% by weight) of the tackifier resin is tackifier resin T2.

[0084] In the embodiment of using tackifier resin T2 as the tackifier resin, the amount of tackifier resin T2 used in the adhesive layer is appropriately set within the range having the target storage modulus at 23°C. In some embodiments, the amount of tackifier resin T2 in the adhesive layer may be approximately 1 part by weight or less, may be approximately 5 parts by weight or more, preferably 10 parts by weight or more, more preferably approximately 15 parts by weight or more, still more preferably approximately 20 parts by weight or more, and particularly preferably approximately 25 parts by weight or more, based on 100 parts by weight of the polyester-based polymer. Also, in some other embodiments, the amount of the above-mentioned tackifier resin T2 is preferably approximately 30 parts by weight or more, more preferably approximately 50 parts by weight or more (for example, more than 50 parts by weight), still more preferably approximately 60 parts by weight or more, particularly preferably approximately 70 parts by weight or more, and may be approximately 80 parts by weight or more, or may be approximately 90 parts by weight or more, based on 100 parts by weight of the polyester-based polymer. By the adhesive layer containing the tackifier resin T2 in a predetermined amount or more, the storage modulus at 23°C can be decreased, and good adhesive properties are easily obtained. Also, in some embodiments, the amount of the above-mentioned tackifier resin T2 may be, for example, approximately 200 parts by weight or less, may be approximately 160 parts by weight or less, or may be approximately 150 parts by weight or less (for example, less than 150 parts by weight), based on 100 parts by weight of the polyester-based polymer. From the viewpoint of having a storage modulus at 23°C below a predetermined value and obtaining better adhesive properties, in some preferred embodiments, the amount of the above-mentioned tackifier resin T2 is approximately 130 parts by weight or less, more preferably approximately 110 parts by weight or less, still more preferably 100 parts by weight or less (for example, less than 100 parts by weight), particularly preferably approximately 90 parts by weight or less, and may be approximately 80 parts by weight or less, may be approximately 70 parts by weight or less, or may be approximately 50 parts by weight or less, based on 100 parts by weight of the polyester-based polymer. In some other embodiments, the amount of the above-mentioned tackifier resin T2 may be approximately 40 parts by weight or less, may be approximately 20 parts by weight or less, may be 10 parts by weight or less (for example, less than 10 parts by weight), or may be approximately 1 part by weight or less, based on 100 parts by weight of the polyester-based polymer. The adhesive layer may not substantially contain the tackifier resin T2.

[0085] In some embodiments, as the tackifier resin, a tackifier resin T1 having a softening point of 145°C or higher and 200°C or lower and a tackifier resin T2 having a softening point of less than 145°C may be used in combination. By using the tackifier resins T1 and T2 in an appropriate ratio, the effects of the technology disclosed herein can be preferably exerted.

[0086] In the embodiments using the tackifier resins T1 and T2, the weight-based ratio (T2 / T1) of the amount of the tackifier resin T2 to the amount of the tackifier resin T1 is not particularly limited. In some embodiments, the above ratio (T2 / T1) is, for example, 1 / 99 or more, preferably 10 / 90 or more, more preferably 30 / 70 or more, still more preferably 40 / 60 or more, and may be 50 / 50 or more, or 70 / 30 or more. By increasing the above ratio (T2 / T1), the effects of containing the tackifier resin T2 are likely to be effectively exerted. Also, in some embodiments, the above ratio (T2 / T1) is, for example, 99 / 1 or less, preferably 90 / 10 or less, more preferably 80 / 20 or less, still more preferably 70 / 30 or less, and particularly preferably 60 / 40 or less. By setting the range of the above ratio (T2 / T1), the effects of containing the tackifier resin T1 are likely to be effectively exerted.

[0087] Although not particularly limited, the technology disclosed herein can be preferably implemented in any of the following embodiments for the adhesive layer: (1) an embodiment containing the tackifier resin T1 as the tackifier resin, (2) an embodiment containing the tackifier resin T2, or (3) an embodiment containing both the tackifier resin T1 and the tackifier resin T2.

[0088] In addition, the softening point of the tackifying resin in this specification is defined as the value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at a low temperature, and this is carefully filled into a ring placed on a flat metal plate without forming bubbles. After it has cooled, the raised part including the upper end of the ring is cut off with a slightly heated small knife. Next, a support (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured 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 sample are immersed in glycerin so as not to contact each other, and the temperature of the glycerin is maintained at 20 °C plus or minus 5 °C for 15 minutes. Next, the steel ball is placed on the center of the surface of the sample in the ring, and this is placed at a fixed position on the support. Next, the distance from the upper end of the ring to the glycerin surface is maintained at 50 mm, a thermometer is placed, the center position of the mercury bulb of the thermometer is set at the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating should be at the middle between the center and the edge of the bottom of the container to make the heating uniform. In addition, the rate of increase in the bath temperature after reaching 40 °C after the start of heating should be 5.0 plus or minus 0.5 °C per minute. The temperature when the sample gradually softens and flows out of the ring and finally contacts the bottom plate is read, and this is taken as the softening point. The softening point is measured simultaneously for two or more samples, and the average value is adopted.

[0089] In an embodiment where the pressure-sensitive adhesive layer contains a tackifier resin, the total amount (total content) of the tackifier resin in the pressure-sensitive adhesive layer is appropriately set within a range having a target storage modulus at 23°C. The total amount (total content) of the tackifier resin can be, for example, about 1 part by weight or more, about 10 parts by weight or more, about 30 parts by weight or more, or about 40 parts by weight or more with respect to 100 parts by weight of the polyester-based polymer. In some embodiments, it is preferable that the total amount of the tackifier resin is 45 parts by weight or more with respect to 100 parts by weight of the polyester-based polymer. By having a composition containing a predetermined amount or more of the tackifier resin in this way, a pressure-sensitive adhesive layer having a storage modulus at 23°C of a predetermined value or less can be preferably formed. Also, the more the amount of the tackifier resin used, the more likely it is to obtain excellent adhesive strength. In some preferred embodiments, the total amount of the tackifier resin with respect to 100 parts by weight of the polyester-based polymer is about 50 parts by weight or more, more preferably about 60 parts by weight or more, even more preferably about 70 parts by weight or more, still more preferably about 80 parts by weight or more, and it may be about 90 parts by weight or more or about 100 parts by weight or more. The upper limit of the total amount of the tackifier resin is not particularly limited, and in some embodiments, it may be about 200 parts by weight or less, about 160 parts by weight or less, or about 150 parts by weight or less (for example, less than 150 parts by weight) with respect to 100 parts by weight of the polyester-based polymer from the viewpoints of compatibility and adhesiveness with the polyester-based polymer. From the viewpoint of obtaining good adhesive properties with the storage modulus at 23°C being a predetermined value or less, in some preferred embodiments, the total amount of the tackifier resin is about 130 parts by weight or less with respect to 100 parts by weight of the polyester-based polymer, more preferably about 110 parts by weight or less, even more preferably 100 parts by weight or less (for example, less than 100 parts by weight), particularly preferably about 90 parts by weight or less, and it may be about 80 parts by weight or less, about 70 parts by weight or less, or about 50 parts by weight or less.

[0090] In some embodiments, as the tackifier resin, from the perspective of improving the bio-based ratio of the entire adhesive layer, a tackifier resin derived from plants (plant-based tackifier resin) is preferably used. The plant-based tackifier resin is composed of components at least partially derived from plants, and all of the resin may be derived from plants, or a part of the resin may be derived from plants and another part may be derived from fossil resources. Examples of the plant-based tackifier resin include the above-mentioned rosin-based tackifier resin and terpene-based tackifier resin. The plant-based tackifier resin can be used alone or in combination of two or more. In some preferred embodiments, the proportion of the plant-based tackifier resin in the total amount of the tackifier resin contained in the adhesive layer may be approximately 30% by weight or more, approximately 50% by weight or more, approximately 80% by weight or more, approximately 90% by weight or more, approximately 95% by weight or more, or 99 - 100% by weight. The technology disclosed herein can be preferably implemented in an embodiment that substantially does not contain a tackifier resin other than the plant-based tackifier resin.

[0091] (Crosslinking agent) In some embodiments, the adhesive layer contains a crosslinking agent. According to the adhesive layer containing a crosslinking agent, based on the crosslinked structure obtained by using the crosslinking agent, the cohesive force can be enhanced. By using a crosslinking agent, while having good adhesive properties, the storage modulus at 23°C can be adjusted. The crosslinking agent can be contained in the adhesive layer in the form after the crosslinking reaction, the form before the crosslinking reaction, a partially crosslinked form, or an intermediate or composite form thereof. The above crosslinking agent is usually contained in the adhesive layer exclusively in the form after the crosslinking reaction. It should be noted that the crosslinking agent used for crosslinking the polyester-based polymer may also function as a chain extender.

[0092] The type of the crosslinking agent is not particularly limited, and it can be appropriately selected and used from conventionally known crosslinking agents. Examples of such crosslinking agents include, for example, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, metal chelate-based crosslinking agents, and the like. The crosslinking agent can be used alone or in combination of two or more. Among them, isocyanate-based crosslinking agents are preferred.

[0093] As the isocyanate-based crosslinking agent, polyfunctional isocyanate-based compounds can be preferably used. Here, the polyfunctional isocyanate-based compound refers to a compound having an average of two or more isocyanate groups per molecule, and includes those having an isocyanurate structure. The isocyanate-based crosslinking agent can be used alone or in combination of two or more.

[0094] Examples of polyfunctional isocyanate-based compounds include aliphatic polyisocyanate-based compounds, alicyclic polyisocyanate-based compounds, aromatic polyisocyanate-based compounds, and the like. Specific examples of aliphatic polyisocyanate-based compounds include 1,2-ethylene diisocyanate; tetramethylene diisocyanate such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, 1,4-tetramethylene diisocyanate; hexamethylene diisocyanate such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, and the like.

[0095] Specific examples of alicyclic polyisocyanate compounds include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate, 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like.

[0096] Specific examples of aromatic polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-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, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, and the like.

[0097] Examples of the polyfunctional isocyanate include polyfunctional isocyanate compounds having on average two or more isocyanate groups per molecule. Such polyfunctional isocyanate compounds can be dimers or trimers or higher multimers of bifunctional or trifunctional or higher functional isocyanates (e.g., dimers or trimers), derivatives (e.g., addition reaction products of polyhydric alcohols and two or more molecules of polyfunctional isocyanates), polymers, etc. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurate forms of hexamethylene diisocyanate (trimers adducts having an isocyanurate structure), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, poly(methylene polyphenyl isocyanate), polyether polyisocyanate, polyester polyisocyanate, and other polyfunctional isocyanate compounds can be mentioned. Examples of commercially available products of such polyfunctional isocyanate compounds include "Durate TPA-100" and "Durate D101" manufactured by Asahi Kasei Chemicals Corporation, and "Coronate HL", "Coronate HK", "Coronate HX", "Coronate 2096" and others manufactured by Tosoh Corporation.

[0098] In some embodiments, as the crosslinking agent, a crosslinking agent having no aromatic ring (aromatic ring-free crosslinking agent) is preferably used. For example, among the above-described isocyanate-based crosslinking agents, the use of an isocyanate-based compound having no aromatic ring is preferred. By using an aromatic ring-free isocyanate-based compound as the crosslinking agent, in the pressure-sensitive adhesive layer containing a polyester-based polymer, the degree of crosslinking can be effectively increased with less crosslinking inhibition. Preferable examples of the above aromatic ring-free isocyanate include aliphatic isocyanate-based compounds.

[0099] In some embodiments, from the perspective of achieving a well-balanced combination of multiple adhesive properties, two or more crosslinking agents with different functional group numbers (preferably isocyanate-based crosslinking agents) may be used. Here, the functional group refers to a crosslinking reactive group. For example, in the above-mentioned polyfunctional isocyanate-based compounds, it refers to the isocyanate group. For example, as crosslinking agents, there are embodiments where one or more difunctional crosslinking agents are used in combination with one or more trifunctional or higher-functional crosslinking agents (such as trifunctional crosslinking agents).

[0100] The usage amount of the crosslinking agent is not particularly limited. In some embodiments, the usage amount of the crosslinking agent (such as an isocyanate-based crosslinking agent) relative to 100 parts by weight of the polyester-based polymer can be approximately 0.005 parts by weight or more, for example, it may be approximately 0.01 parts by weight or more, or approximately 0.1 parts by weight or more. From the perspective of improving cohesion, it is appropriate to be approximately 0.5 parts by weight or more, preferably approximately 1 part by weight or more. From the perspective of improving cohesion while having an appropriate storage modulus at 23°C, in some preferred embodiments, the usage amount of the crosslinking agent relative to 100 parts by weight of the polyester-based polymer is approximately 1.2 parts by weight or more, more preferably approximately 1.5 parts by weight or more, even more preferably approximately 1.8 parts by weight or more, and for example, it may be 2.5 parts by weight or more. Also, in some embodiments, the usage amount of the crosslinking agent relative to 100 parts by weight of the polyester-based polymer may be approximately 10 parts by weight or less, for example, approximately 7 parts by weight or less. From the perspective of moderately reducing the storage modulus at 23°C within a predetermined range, in some preferred embodiments, the usage amount of the crosslinking agent relative to 100 parts by weight of the polyester-based polymer is approximately 5 parts by weight or less, more preferably approximately 4 parts by weight or less, even more preferably approximately 3 parts by weight or less, particularly preferably approximately 2.5 parts by weight or less, and may be approximately 2.0 parts by weight or less, or approximately 1.6 parts by weight or less.

[0101] The amount of the aromatic ring-free crosslinking agent used is not particularly limited. In some embodiments, the amount of the aromatic ring-free crosslinking agent (for example, an aliphatic isocyanate compound) used per 100 parts by weight of the polyester-based polymer can be about 0.005 parts by weight or more, for example, it may be about 0.01 parts by weight or more, or may be about 0.1 parts by weight or more. From the viewpoint of improving the cohesive force, it is appropriate to be about 0.5 parts by weight or more, preferably about 1 part by weight or more. From the viewpoint of improving the cohesive force while having an appropriate storage elastic modulus at 23°C, in some preferred embodiments, the amount of the aromatic ring-free crosslinking agent used per 100 parts by weight of the polyester-based polymer is about 1.2 parts by weight or more, more preferably about 1.5 parts by weight or more, still more preferably about 1.8 parts by weight or more, and may be, for example, 2.5 parts by weight or more. Also, in some embodiments, the amount of the aromatic ring-free crosslinking agent used per 100 parts by weight of the polyester-based polymer may be about 10 parts by weight or less, for example, may be about 7 parts by weight or less. From the viewpoint of obtaining an adhesive layer having a storage elastic modulus at 23°C below a predetermined value, in some preferred embodiments, the amount of the aromatic ring-free crosslinking agent used per 100 parts by weight of the polyester-based polymer is about 5 parts by weight or less, more preferably about 4 parts by weight or less, still more preferably about 3 parts by weight or less, particularly preferably about 2.5 parts by weight or less, and may be about 2.0 parts by weight or less, or may be about 1.6 parts by weight or less.

[0102] (Crosslinking catalyst) In the technology disclosed herein, in order to make the crosslinking reaction proceed more effectively, in addition to the above crosslinking agent, it is preferable to use a crosslinking catalyst. Examples of the crosslinking catalyst include zirconium-containing compounds (zirconium-based catalysts) such as zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethyl acetoacetate, and zirconium octylate compounds; tin (Sn)-containing compounds (tin-based catalysts) such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, trimethyltin hydroxide, and butyltin oxide; aluminum-containing compounds (aluminum-based catalysts) such as aluminum secondary butoxide, aluminum trisacetylacetonate, aluminum bisethylacetoacetate, and aluminum trisethylacetoacetate; iron-containing compounds (iron-based catalysts) such as ferric naphthenate; titanium-containing compounds (titanium-based catalysts) such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, titanium acetylacetonate, titanium tetraacetylacetonate, and titanium ethyl acetoacetate; and other organometallic catalysts. The crosslinking catalyst can be used alone or in combination of two or more kinds.

[0103] Although not particularly limited, in some embodiments, it is preferable to use a tin-containing compound having high catalytic activity as the crosslinking catalyst. Alternatively, in some other embodiments, from the viewpoints of environmental impact and safety, a non-tin-based compound may be used as the above crosslinking catalyst. In such embodiments, the crosslinking catalyst may not substantially contain a tin-containing compound. Also, in some embodiments, the crosslinking catalyst does not contain an iron-based catalyst. For example, in a usage mode where transparency and optical properties are required for the adhesive layer, by avoiding the use of an iron-based compound, coloring of the adhesive layer can be prevented or suppressed.

[0104] The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used can be, for example, approximately 0.001 parts by weight or more, and preferably approximately 0.01 parts by weight or more, based on 100 parts by weight of the polyester-based polymer. Also, the amount of the crosslinking catalyst used can be, for example, approximately 3 parts by weight or less, and preferably approximately 1 part by weight or less, based on 100 parts by weight of the polyester-based polymer, and may be approximately 0.3 parts by weight or less, or may be approximately 0.1 parts by weight or less.

[0105] (Hydrolysis-resistant agent) In addition, the adhesive layer disclosed herein may contain a hydrolysis-resistant agent (also referred to as a hydrolysis inhibitor). By adding a hydrolysis-resistant agent, the hydrolysis reaction in the adhesive layer is suppressed, and good durability is easily obtained. The hydrolysis-resistant agent is not particularly limited, and known or commonly used hydrolysis-resistant agents can be used. For example, oxazoline group-containing compounds, epoxy group-containing compounds, carbodiimide group-containing compounds, etc. can be mentioned. Among them, carbodiimide group-containing compounds are preferred. The hydrolysis-resistant agent can be used alone or in combination of two or more.

[0106] Examples of the carbodiimide group-containing compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, monofunctional cyclic structure carbodiimide, etc. Here, the monofunctional cyclic structure carbodiimide refers to a compound in which one carbodiimide group is present in the molecular structure, and the first nitrogen atom and the second nitrogen atom of the carbodiimide group are bonded by a bonding group composed of an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. The above bonding group may contain a hetero atom or a substituent. Preferable examples of the carbodiimide group-containing compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, and monofunctional cyclic structure carbodiimide.

[0107] The amount of the hydrolysis-resistant agent (preferably a carbodiimide group-containing compound) used is not particularly limited, and it is appropriate to be approximately 0.05 parts by weight or more, preferably approximately 0.1 parts by weight or more, and for example, it may be approximately 0.3 parts by weight or more, based on 100 parts by weight of the polyester-based polymer so that the effect of containing the hydrolysis-resistant agent is preferably exhibited. The upper limit of the amount of the hydrolysis-resistant agent used is, for example, appropriately approximately 5 parts by weight or less, preferably approximately 3 parts by weight or less, and for example, it may be 1 part by weight or less, based on 100 parts by weight of the polyester-based polymer.

[0108] (Other additives) In addition to the above-described components, the pressure-sensitive adhesive layer may contain various general additives in the field of pressure-sensitive adhesives, such as a leveling agent, a filler, a plasticizer, a softening agent, a colorant (pigment, dye, etc.), an antistatic agent, an antioxidant, an ultraviolet absorber, an antioxidant, a light stabilizer, etc., as necessary. Since the above various additives can be used by conventional methods using those conventionally known and are not particularly characteristic of the present invention, detailed description thereof is omitted.

[0109] (Formation of the pressure-sensitive adhesive layer) The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method using, for example, the polyester-based polymer described above. For example, after applying a pressure-sensitive adhesive composition to a surface having peelability (release surface), the pressure-sensitive adhesive layer can be formed on the surface by curing the pressure-sensitive adhesive composition. The pressure-sensitive adhesive layer formed in such a form can be used as a substrate-free double-sided pressure-sensitive adhesive sheet. In the case of a pressure-sensitive adhesive sheet with a substrate, a method (direct method) of directly applying (typically coating) the pressure-sensitive adhesive composition to the substrate and curing it to form the pressure-sensitive adhesive layer can be preferably employed. Alternatively, a method (transfer method) of forming a pressure-sensitive adhesive layer on a surface having peelability (release surface) by applying and curing a pressure-sensitive adhesive composition and transferring the pressure-sensitive adhesive layer to a substrate may be adopted. As the release surface, the surface of a release liner, the back surface of a substrate subjected to a release treatment, or the like can be used. Further, the curing of the pressure-sensitive adhesive composition can be carried out by subjecting the pressure-sensitive adhesive composition to a curing treatment such as drying, crosslinking, polymerization, cooling, etc. Two or more curing treatments may be carried out simultaneously or stepwise. The pressure-sensitive adhesive composition is not particularly limited, but from the viewpoint of adhesive properties and the like, a solvent-type pressure-sensitive adhesive composition in which a pressure-sensitive adhesive is contained in an organic solvent is preferable. As the organic solvent, organic solvents such as toluene, ethyl acetate, methyl ethyl ketone, methyl cyclohexane, cyclohexane, xylene, butyl acetate, etc. can be used. Among them, the use of ethyl acetate is preferable. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may be formed in a regular or random pattern such as a dot pattern or a stripe pattern, for example.

[0110] The application of the pressure-sensitive adhesive composition can be carried out using a known or conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a die coater, a bar coater, a knife coater, a spray coater, etc. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, the curtain coating method, or the like. Drying of the pressure-sensitive adhesive composition can be carried out at normal temperature or under heating. From the viewpoints of promoting the crosslinking reaction and improving the production efficiency, etc., drying of the pressure-sensitive adhesive composition is preferably carried out under heating. The drying temperature can be, for example, about 40 to 150 °C, and usually it is preferably about 40 to 130 °C. After drying the pressure-sensitive adhesive composition, it is preferable to carry out aging for the purpose of adjusting the component migration in the pressure-sensitive adhesive layer, promoting the crosslinking reaction, relaxing the strain that may exist in the pressure-sensitive adhesive layer, etc. The conditions for aging are not particularly limited, and usually they can be conditions of about 70 °C or lower (for example, about 40 to 70 °C) and 1 day or longer (for example, 3 days or longer).

[0111] (Thickness of the pressure-sensitive adhesive layer) The thickness of the adhesive layer is not particularly limited and can be appropriately selected according to the purpose. The thickness of the adhesive layer can be, for example, about 2 μm to 500 μm. From the viewpoint of adhesiveness to the adherend, in some embodiments, the thickness of the adhesive layer is usually suitably 3 μm or more, preferably 5 μm or more. From the viewpoint of effectively obtaining the effects of improving the adhesive strength and suppressing the decrease in the adhesive strength, in some preferred embodiments, the thickness of the adhesive layer is, for example, 8 μm or more, more preferably 12 μm or more, still more preferably 15 μm or more, and particularly preferably 18 μm or more. Also, from the viewpoints of weight reduction, miniaturization, thinning, and high functionality of the product (e.g., portable electronic device) to which the adhesive sheet is applied, in some embodiments, the thickness of the adhesive layer can be, for example, 200 μm or less, may be 150 μm or less, or may be 100 μm or less (e.g., less than 100 μm). In some preferred embodiments, the thickness of the adhesive layer is suitably less than 80 μm, more preferably 50 μm or less, even more preferably 40 μm or less, still more preferably 35 μm or less, and even more preferably 30 μm or less. In embodiments that particularly emphasize further thinning, it is particularly preferably 25 μm or less, and may be, for example, 22 μm or less. In some other embodiments, the thickness of the adhesive layer may be less than 20 μm, may be less than 15 μm, may be less than 10 μm, or may be less than 5 μm. According to the technology disclosed herein, it is possible to effectively suppress a decrease in the adhesive strength even for a configuration having an adhesive layer with the above-described thickness. In the case of the double-sided adhesive sheet in which the adhesive sheet disclosed herein has adhesive layers on both sides of the base material, the thicknesses of the respective adhesive layers may be the same or different. The thickness of each of the above-described adhesive layers can be selected, for example, from within the range exemplified as the thickness of the adhesive layer above.

[0112] (Bio-rate of the adhesive layer) Although not particularly limited, the adhesive layer preferably has a bio-based ratio of a predetermined value or more. In some embodiments, the bio-based ratio of the adhesive layer may be approximately 30% or more, suitably approximately 40% or more, and preferably 50% or more. By designing the adhesive layer to have a higher bio-based ratio, the dependence on fossil resource-based materials as a whole for the adhesive layer can be reduced. From the perspective of further reducing the dependence on fossil resource-based materials, in some preferred embodiments, the bio-based ratio of the adhesive layer may be 55% or more, 60% or more, 70% or more, or 75% or more. Although the upper limit of the bio-based ratio is 100% by definition, in the adhesive layer disclosed herein, since the components may include materials derived from fossil resources, the bio-based ratio may be less than 100%. From the perspective of easily obtaining the effect of suppressing the decrease in adhesive force and good adhesive properties (for example, holding power), in some embodiments, the bio-based ratio of the adhesive layer may be, for example, less than 90%, and may be less than 80% or less than 70% when more emphasis is placed on adhesive performance.

[0113] <Base material> The pressure-sensitive adhesive sheet disclosed herein can be in the form of a pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on one or both sides of the base material. As the base material, various sheet-like base materials can be used, for example, resin films, papers, cloths, rubber sheets, foam sheets, metal foils, composites thereof, and the like. In the field of electronic devices, a base material that is less likely to be a source of dust (for example, minute fibers or particles such as paper powder) is preferably used. From such a perspective, a base material that does not contain fibrous substances such as paper or cloth is preferred, and for example, resin films, rubber sheets, foam sheets, metal foils, composites thereof, and the like can be preferably used.

[0114] Examples of the resin film include polyester film; vinyl chloride resin film; polyolefin films such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer; vinylidene chloride resin film; vinyl acetate resin film; polystyrene film; polyacetal film; polyimide film; polyamide film; fluororesin film; cellophane; and the like. Examples of the rubber sheet include natural rubber sheet and butyl rubber sheet. Examples of the foam sheet include foamed polyurethane sheet and foamed polyolefin sheet. Examples of the metal foil include aluminum foil and copper foil.

[0115] As the above-mentioned base material, it is preferable to use a resin film. The resin film is preferably used as a material excellent in dimensional stability, thickness accuracy, economy (cost), processability, and tensile strength. In addition, since the resin film (for example, a polyester film such as a PET film described later) can be recycled, regardless of whether it uses plant-derived materials or not, by recycling the used resin film, sustainable reproduction is possible and the environmental load can be reduced. Such recyclable resin films and recycled resin films are also referred to as recycled films. Such recyclability of the resin film can also be applied to the resin film used for the release liner described later. In this specification, the "resin film" is typically a non-porous film, which is a concept distinct from so-called non-woven fabrics and woven fabrics.

[0116] In some aspects, from the viewpoints of strength and processability, a polyester film can be preferably adopted as the above-mentioned base material. Examples of the polyester film include polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, polyethylene naphthalate (PEN) film, polybutylene naphthalate film, and the like.

[0117] In some aspects, from the perspective of reducing the usage amount of fossil resource-based materials, the base material preferably contains biomass materials. The biomass materials that can constitute the above base material are not particularly limited. For example, biomass polyesters such as biomass PET and biomass polytrimethylene terephthalate (biomass PTT); polylactic acid; biomass polyethylenes such as biomass high-density polyethylene (biomass HDPE), biomass low-density polyethylene (biomass LDPE), and biomass linear low-density polyethylene (biomass LLDPE), and biomass polyolefins such as biomass polypropylene (biomass PP); biomass poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); biomass polyamides such as polyhexamethylene sebacamide and poly(xylene sebacamide); biomass polyurethanes such as biomass polyester ether urethane and biomass polyether urethane; cellulose-based resins; and the like. These can be used alone or in combination of two or more. Among them, biomass PET and biomass PTT are preferred, and biomass HDPE, biomass LDPE, biomass LLDPE, biomass PP, and biomass PET are particularly preferred. Since the above biomass materials are resin materials, they can be preferably applied to a configuration in which the base material is a resin film. By using the above biomass materials, the usage amount of fossil resource-based materials can be reduced in an adhesive sheet having a resin film as the base material.

[0118] In the adhesive sheet of the aspect including the base material, the bio ratio of the base material is preferably 20% or more, and more preferably 35% or more. When more emphasis is placed on reducing the usage amount of fossil resource-based materials, the bio ratio of the base material may be, for example, 50% or more, 70% or more, 85% or more, or 90% or more. The upper limit of the above bio ratio is 100% or less. However, in some aspects, considering processability, strength, etc., the bio ratio of the base material may be, for example, 80% or less, 60% or less, 40% or less, or less than 20%.

[0119] The base material may have transparency, or may have light-shielding properties or light-reducing properties. In some embodiments, a colorant can be contained in the base material (e.g., a resin film). Thereby, the light transmittance (light-shielding property) of the base material can be adjusted. Adjusting the light transmittance of the base material (e.g., the perpendicular light transmittance) can also be useful for adjusting the light transmittance of the base material and further the light transmittance of the adhesive sheet including the base material.

[0120] As the colorant, conventionally known pigments and dyes can be used, similar to the colorants that can be contained in the adhesive layer. The colorant is not particularly limited, and can be, for example, colorants such as black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, and pearl color.

[0121] The base material may be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In the base material configured to include the base film and the colored layer in this way, the base film may or may not contain a colorant. The colored layer may be disposed on either one surface or both surfaces of the base film. In the configuration where colored layers are disposed on both surfaces of the base film, the configurations of these colored layers may be the same or different. By disposing the colored layer, the color tone and transmittance of the adhesive sheet can be adjusted, and desired design properties, light-shielding properties, and concealment properties can be obtained. The color of the colored layer is not particularly limited, and various colors can be adopted according to the purpose. In some embodiments, the colored layer can be, for example, a black layer (e.g., a black printed layer) formed by black printing.

[0122] The coloring layer can be formed, for example, by applying a composition for forming a coloring layer containing a colorant and a binder to a base film. As the binder, materials known in the fields of paints or printing can be used without particular limitation. For example, polyurethane, phenolic resin, epoxy resin, urea melamine resin, polymethyl methacrylate, etc. are exemplified. The composition for forming a coloring layer can be, for example, solvent-based, ultraviolet curable, thermosetting, etc. The formation of the coloring layer can be carried out by adopting, without particular limitation, the means conventionally employed for forming a coloring layer. For example, a method of forming a coloring layer (printing layer) by printing such as gravure printing, flexographic printing, offset printing, etc. can be preferably adopted.

[0123] The coloring layer may have a single-layer structure consisting of one layer in total, or may have a multilayer structure including two, three or more sub-coloring layers. The coloring layer having a multilayer structure including two or more sub-coloring layers can be formed, for example, by repeating the application (for example, printing) of the composition for forming a coloring layer. The color and blending amount of the colorant contained in each sub-coloring layer may be the same or different. In the coloring layer for imparting light-shielding properties, from the viewpoint of preventing the generation of pinholes and enhancing the reliability of preventing light leakage, it is particularly meaningful to adopt a multilayer structure.

[0124] As the colorant used for coloring the coloring layer, known pigments and dyes corresponding to the target color can be appropriately selected. Although not particularly limited, examples of white pigments include titanium dioxide, zinc white, lead white, etc. Examples of black pigments include carbon black, acetylene black, lampblack, graphite, etc. These can be used alone or in combination of two or more.

[0125] The content of the colorant is not limited to a specific range as it is set according to the required flavor, light transmittance, etc. However, in the colored layer, it is preferably about 1% by weight or more, more preferably 2% by weight or more (for example, 5% by weight or more), and may be 15% by weight or more. Also, the content of the above colorant is preferably about 65% by weight or less, more preferably 30% by weight or less (for example, 15% by weight or less), and may be 8% by weight or less.

[0126] The thickness of the entire colored layer is usually preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more. The thickness of the entire colored layer may be about 0.8 μm or more, or may be about 1 μm or more. In some other embodiments, from the viewpoint of obtaining sufficient light shielding properties, the thickness of the entire colored layer may be 2 μm or more (for example, 3 μm or more), or may be 4 μm or more. Also, the thickness of the above entire colored layer is usually preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less. In some embodiments, the thickness of the entire colored layer can be about 3 μm or less, and further can be about 2 μm or less. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is usually preferably about 0.5 μm to 2 μm.

[0127] On the surface (the surface on the adhesive layer side) where the adhesive layer of the base material (such as a resin film, a rubber sheet, a foam sheet, etc.) is disposed, known or conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, formation of an undercoat layer, etc. may be performed. Such surface treatment can be a treatment for improving the adhesion between the base material and the adhesive layer, in other words, the anchoring property of the adhesive layer to the base material. Alternatively, the above base material may not be subjected to a surface treatment for improving the anchoring property on the surface on the adhesive layer side. When forming an undercoat layer, the undercoat agent (primer) used for the formation is not particularly limited and can be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, and for example, it can be more than 0.01 μm, usually appropriately 0.1 μm or more, and may be 0.2 μm or more from the viewpoint of enhancing the effect. Also, the thickness of the undercoat layer is preferably less than 1.0 μm, may be 0.7 μm or less, and may be 0.5 μm or less. Generally, since primers have a high dependence on fossil resource-based materials, the fact that the thickness of the undercoat layer is not too large can be advantageous from the viewpoint of improving the bio-rate of the adhesive sheet described later.

[0128] In the case of a single-sided adhesive sheet having an adhesive layer provided on one side of the base material, the non-adhesive layer forming surface (back surface) of the base material may be subjected to a peeling treatment with a peeling treatment agent (back surface treatment agent). The back surface treatment agent that can be used for forming the back surface treatment layer is not particularly limited, and silicone-based back surface treatment agents, fluorine-based back surface treatment agents, long-chain alkyl-based back surface treatment agents, and other known or conventional treatment agents can be used according to the purpose and application. The back surface treatment agent can be used alone or in combination of two or more kinds.

[0129] The base material (e.g., resin film base material) may be blended with various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, colorants (pigments, dyes, etc.) as required. The blending ratio of various additives is usually about 30% by weight or less, and may be, for example, about 20% by weight or less, or about 10% by weight or less. For example, when the base material contains a pigment (e.g., white pigment), its content ratio is appropriately about 0.1 to 10% by weight (e.g., 1 to 8% by weight or 1 to 5% by weight).

[0130] The thickness of the base material is not particularly limited and can be appropriately selected according to the purpose, but generally it is about 1 μm to 500 μm. From the viewpoint of the handleability of the base material, the thickness of the base material may be, for example, 1.5 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 4.5 μm or more. Also, from the viewpoint of thinning the adhesive sheet, in some embodiments, the thickness of the base material may be, for example, 150 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, 20 μm or less, 10 μm or less, 7 μm or less, less than 5 μm, or less than 4 μm.

[0131] <Release liner> The pressure-sensitive adhesive sheet disclosed herein may be in the form of a pressure-sensitive adhesive sheet with a release liner having a release liner (e.g., a first release liner) disposed on the surface of the pressure-sensitive adhesive layer (adhesive surface; e.g., a first adhesive surface). The above release liner (including the first release liner and the second release liner; the same shall apply hereinafter unless otherwise specified) is not particularly limited, and for example, those having a release treatment layer on a release liner substrate may be preferably employed. The above release treatment layer may be formed by surface-treating the release liner substrate with a release treatment agent. The release treatment agent may be a known release treatment agent such as a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, a fluorine-based release treatment agent, molybdenum(IV) sulfide, etc. In some embodiments, a release liner having a release treatment layer formed by a silicone-based release treatment agent may be preferably employed. The effect of suppressing the decrease in adhesive strength by the technology disclosed herein can be effectively exerted in an embodiment using a release liner having a release treatment layer formed by a silicone-based release treatment agent. The thickness and formation method of the release treatment layer are not particularly limited and can be set so that appropriate releasability is exhibited on the surface on the adhesive surface side of the release liner.

[0132] As the release liner substrate, various plastic films can be used. In this specification, a plastic film is typically a non-porous sheet and is a concept that is distinguished from, for example, a non-woven fabric (i.e., does not include a non-woven fabric). As the above release liner substrate, a resin film having a non-porous structure and typically substantially free of air bubbles (voidless) may be preferably used. The above resin film may have a single-layer structure or a multi-layer structure of two or more layers (e.g., a three-layer structure).

[0133] Examples of the material of the plastic film include polyester resins such as PET, PBT, and PEN; polyolefin resins such as PE, PP, ethylene-propylene copolymer, and ethylene-butene copolymer; cellulose resins such as triacetyl cellulose; acetate resins; polysulfone resins; polyethersulfone resins; polycarbonate resins; polyamide resins; polyimide resins; cyclic polyolefin resins such as norbornene resins; (meth)acrylic resins; polyvinyl chloride resins; polyvinylidene chloride resins; polystyrene resins; polyvinyl alcohol resins; ethylene-vinyl acetate copolymer resins; ethylene-vinyl alcohol copolymer resins; polyarylate resins; polyphenylene sulfide resins, etc. A release liner substrate formed from any one or a mixture of two or more of these resins can be used. Among them, a polyester resin film (e.g., PET film) formed from a polyester resin is preferably used as the release liner substrate.

[0134] The plastic film used as the above-described release liner substrate may be any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. Also, the plastic film may have a single-layer structure or a multilayer structure including two or more sub-layers. The plastic film may be blended with known additives that can be used for a release liner substrate, such as an antioxidant, an anti-aging agent, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a colorant such as a pigment or a dye, a lubricant, a filler, an antistatic agent, a slip agent, an antiblocking agent, a nucleating agent, etc. In a multilayer-structured plastic film, each additive may be blended in all sub-layers or only in some sub-layers.

[0135] The release liner as a component of the pressure-sensitive adhesive sheet with a release liner may be the release liner used during the production of the pressure-sensitive adhesive sheet, that is, the release liner as a component of the pressure-sensitive adhesive sheet with a release liner immediately after production. It may also be a release liner (replacement liner) replaced from the original release liner (the release liner at the beginning of production) until the pressure-sensitive adhesive sheet is attached to the adherend, or another replacement liner further replaced from one replacement liner. Therefore, the pressure-sensitive adhesive sheet disclosed herein can be used in a manner that it is attached to the adherend through a process of replacing (switching) the release liner with another release liner (replacement liner) if desired. According to the technology disclosed herein, even when the release liner is replaced before attachment to the adherend and the release treatment agent migrates from the release liners before and after replacement to the adhesive layer and is likely to accumulate on the adhesive surface, the decrease in adhesive strength caused by the migration of the release treatment agent can be suppressed. Therefore, regardless of whether the release liner protecting the adhesive surface of the pressure-sensitive adhesive sheet is the release liner at the beginning of production or the replaced release liner, the decrease in adhesive strength can be suppressed and the intended adhesive strength can be maintained. As the replacement liner, one having the same configuration (material, thickness, etc.) as the release liner before replacement may be used, or one having a different configuration may be used.

[0136] The thickness of the release liner is not particularly limited and can be, for example, about 10 μm to 500 μm. From the viewpoints of the strength and dimensional stability of the release liner, the thickness of the release liner is suitably 20 μm or more, preferably 30 μm or more, and may be 40 μm or more, 50 μm or more, 60 μm or more, or 70 μm or more. By protecting the adhesive surface with a release liner having a sufficient thickness, the smoothness of the adhesive surface is easily maintained. Also, from the viewpoints of the handleability of the release liner (for example, ease of winding), etc., the thickness of the release liner is suitably 300 μm or less, preferably 200 μm or less, and may be 150 μm or less or 100 μm or less. By setting the thickness of the release liner to a predetermined value or less, removal from the double-sided adhesive sheet is likely to be smooth. The thicknesses of the first release liner and the second release liner may be the same or different.

[0137] <Total thickness of the adhesive sheet> The thickness (total thickness) of the adhesive sheet (including the adhesive layer, and including the base material in the case of an adhesive sheet with a base material, but not including the release liner) disclosed herein is not particularly limited and can be, for example, in the range of approximately 2 μm to 1000 μm. In some embodiments, the thickness of the adhesive sheet is preferably about 5 μm to 500 μm in consideration of adhesive properties, etc., and may be, for example, about 300 μm or less or about 200 μm or less. From the viewpoints of weight reduction, miniaturization, thinning, and high functionality of the product (for example, a portable electronic device) to which the adhesive sheet is applied, in some preferred embodiments, the thickness of the adhesive sheet is 100 μm or less, more preferably 70 μm or less, even more preferably 50 μm or less, still more preferably 40 μm or less, particularly preferably 35 μm or less, and may be, for example, 30 μm or less or 25 μm or less. In some other embodiments, the thickness of the adhesive sheet may be less than 20 μm, less than 15 μm, less than 10 μm, or less than 5 μm. The lower limit value of the thickness of the adhesive sheet is not particularly limited and is usually suitably 3 μm or more, and may be, for example, about 5 μm or more, and from the viewpoint of productivity, may be about 10 μm or more or about 15 μm or more (for example, about 18 μm or more).

[0138] <Properties of the Adhesive Sheet> In some embodiments, the adhesive sheet preferably has a 180-degree peel strength (adhesion to SUS) of 5 N / 20 mm or more with respect to a stainless steel plate. Since the adhesive sheet having the above characteristics can adhere well to the adherend, it can typically be preferably used in embodiments where re-peeling is not intended. The adhesion to SUS may be 7 N / 20 mm or more, or may be 9 N / 20 mm or more. From the viewpoint of realizing highly reliable bonding, in some preferred embodiments, the adhesion to SUS is 10 N / 20 mm or more, more preferably 12 N / 20 mm or more, even more preferably 14 N / 20 mm or more, still more preferably 16 N / 20 mm or more, particularly preferably 18 N / 20 mm or more, and may be 20 N / 20 mm or more. The upper limit of the adhesion to SUS is not particularly limited, and in some embodiments, the adhesion may be, for example, 50 N / 20 mm or less, or may be 30 N / 20 mm or less. The adhesion to SUS is specifically measured by the method described in the examples below.

[0139] In some embodiments, the adhesion retention rate after replacement of the release liner is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more. The adhesive sheet having the above characteristics can have a sufficiently suppressed decrease in adhesion even when handled such that the release liner is replaced before attachment to the adherend. In some preferred embodiments, the adhesion retention rate after replacement of the release liner is 85% or more, more preferably 90% or more, and even more preferably 95% or more. The adhesion retention rate after replacement of the release liner is measured and calculated by the method described in the examples below. The adhesion retention rate after replacement of the release liner may be the adhesion retention rate after replacement of the release liner measured and calculated when using one of the two types of release liners for replacement used in the measurement method described in the examples below. The adhesive sheet disclosed herein preferably has the adhesion retention rate after replacement of the release liner when using any of the two types of release liners for replacement.

[0140] Although not particularly limited, in some embodiments, it is preferable that approximately 30% or more of all the carbon contained in the pressure-sensitive adhesive sheet is carbon derived from biomass. That is, it is preferable that the bio ratio of the pressure-sensitive adhesive sheet is 30% or more. By using a pressure-sensitive adhesive sheet with such a high bio ratio, the amount of fossil resource-based materials used can be reduced. From such a perspective, in some preferred embodiments, the bio ratio of the pressure-sensitive adhesive sheet is 40% or more, may be 50% or more, may be 60% or more, may be 70% or more, or may be 75% or more. Although the upper limit of the above bio ratio is 100% by definition, making all the materials constituting the pressure-sensitive adhesive sheet derived from plants may not be efficient in terms of productivity, performance, etc., so the above bio ratio may be less than 100%. From the perspective of easily obtaining an effect of suppressing a decrease in adhesive force and good adhesive properties (e.g., adhesive force), in some embodiments, the bio ratio of the pressure-sensitive adhesive sheet may be, for example, 90% or less, may be 80% or less when more emphasis is placed on adhesive performance, or may be 70% or less. In the case of a substrate-free pressure-sensitive adhesive sheet composed of an adhesive layer, the bio ratio of the adhesive layer coincides with the bio ratio of the entire pressure-sensitive adhesive sheet.

[0141] <Use> The use of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and it can be used without limitation for various uses. For example, the pressure-sensitive adhesive sheet can be used for purposes such as fixing, joining, and reinforcing members in a manner of being attached to the members constituting an electronic device. The pressure-sensitive adhesive sheet disclosed herein can suppress a decrease in adhesive force even when handled such that the release liner is replaced before being attached to the adherend. Therefore, for example, it can be preferably used as a fixing means with good adhesive reliability for members of an electronic device where the release liner can be replaced before being attached to the adherend for processing such as punching and cutting, or for visibility. In particular, it is suitable for fixing members of portable electronic devices. The pressure-sensitive adhesive sheet disclosed herein can be preferably used for purposes of fixing or joining members, for example, in the form of a double-sided pressure-sensitive adhesive sheet. The above double-sided pressure-sensitive adhesive sheet may be substrate-free or may have a substrate.

[0142] Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist-wearable listware like a wristwatch, modular type wearable on a part of the body with a clip or a strap, etc., eyewear type including glasses type (monocular or binocular, including head-mounted type), clothing type attached to a shirt, socks, hat, etc. in the form of an accessory, earwear type attached to the ear like earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), computers (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, e-books, in-vehicle information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. In this specification, "portable" does not simply mean that it can be carried, but means having a level of portability that an individual (standard adult) can relatively easily carry around.

[0143] FIG. 4 is an example schematically showing a portable electronic device (smartphone) using the adhesive sheet disclosed herein. As shown in FIG. 4, inside the housing 520 of the portable electronic device 500, a battery (heating element) 540 is built in. Further, the portable electronic device 500 includes an adhesive sheet 550. In this configuration example, the adhesive sheet 550 has the form of a double-sided adhesive sheet (double-sided sticky sheet) that fixes the members constituting the portable electronic device 500. Note that the portable electronic device 500 includes a touch panel 570 whose display portion also functions as an input portion. The adhesive sheet disclosed herein is preferably used as a component (member joining means) of the portable electronic device as described above.

[0144] The matters disclosed by this specification include the following. [1] A portable electronic device, comprising a housing and a touch panel whose display portion also functions as an input portion, wherein a heating element (for example, a battery) is built inside the housing, Among a number of members constituting the portable electronic device, at least a first member and a second member are joined by an adhesive sheet. The adhesive sheet has an adhesive layer. The adhesive layer contains a polyester-based polymer and has a storage elastic modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa, the portable electronic device. 〔2〕 The adhesive layer contains 45 parts by weight or more of an adhesion-imparting resin with respect to 100 parts by weight of the polyester-based polymer, the portable electronic device according to 〔1〕 above. 〔3〕 The softening point of the adhesion-imparting resin is 30°C or more and 200°C or less, the portable electronic device according to 〔2〕 above. 〔4〕 The adhesive layer, as the adhesion-imparting resin, contains 60 parts by weight or less of an adhesion-imparting resin T1 having a softening point of 145°C or more and 200°C or less with respect to 100 parts by weight of the polyester-based polymer, or contains an adhesion-imparting resin T2 having a softening point of 30°C or more and less than 145°C, or contains 60 parts by weight or less of the adhesion-imparting resin T1 with respect to 100 parts by weight of the polyester-based polymer and contains the adhesion-imparting resin T2, the portable electronic device according to 〔2〕 or 〔3〕 above. 〔5〕 The thickness of the adhesive layer is less than 80 μm, the portable electronic device according to any one of 〔1〕 to 〔4〕 above. 〔6〕 The adhesive sheet has a 180-degree peel strength with respect to a stainless steel plate of 5 N / 20 mm or more, the portable electronic device according to any one of 〔1〕 to 〔5〕 above.

[0145] 〔7〕 An adhesive sheet having an adhesive layer, wherein the adhesive layer contains a polyester-based polymer and has a storage elastic modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa, the adhesive sheet. 〔8〕 The adhesive layer contains 45 parts by weight or more of an adhesion-imparting resin with respect to 100 parts by weight of the polyester-based polymer, the adhesive sheet according to 〔7〕 above. 〔9〕 The pressure-sensitive adhesive sheet according to the above 〔8〕, wherein the softening point of the tackifier resin is 30°C or higher and 200°C or lower. 〔10〕 The pressure-sensitive adhesive layer contains, as the tackifier resin, either 60 parts by weight or less of a tackifier resin T1 having a softening point of 145°C or higher and 200°C or lower with respect to 100 parts by weight of the polyester-based polymer, or contains a tackifier resin T2 having a softening point of 30°C or higher and less than 145°C, or The pressure-sensitive adhesive sheet according to the above 〔8〕 or 〔9〕, which contains 60 parts by weight or less of the tackifier resin T1 with respect to 100 parts by weight of the polyester-based polymer and contains the tackifier resin T2. 〔11〕 The pressure-sensitive adhesive sheet according to any one of the above 〔7〕 to 〔10〕, wherein the thickness of the pressure-sensitive adhesive layer is less than 80 μm. 〔12〕 The pressure-sensitive adhesive sheet according to any one of the above 〔7〕 to 〔11〕, wherein the 180-degree peel strength with respect to a stainless steel plate is 5 N / 20 mm or higher. 〔13〕 The pressure-sensitive adhesive sheet according to any one of the above 〔7〕 to 〔12〕, which is used for a portable electronic device. 〔14〕 A portable electronic device including the pressure-sensitive adhesive sheet according to any one of the above 〔7〕 to 〔12〕.

Examples

[0146] Hereinafter, several examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the examples. In the following description, "parts" and "%" are based on weight unless otherwise specified.

[0147] <Synthesis Example> (Synthesis Example 1) A four-neck separable flask was equipped with a stirrer, a thermometer, a nitrogen tube, and a water separation tube. 100 g of ethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 62), 549 g of dimer acid (product name "Pripol 1009", manufactured by Croda Co., Ltd., molecular weight 567), 130 g of sebacic acid (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 202), 0.46 g of di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a reaction water discharge solvent were charged therein. While stirring in a nitrogen atmosphere, the temperature was raised to 180 °C and this temperature was maintained. After a while, the outflow and separation of the reaction water were observed and the reaction began to proceed. The reaction was continued for about 24 hours to obtain a polyester-based polymer (A1) with a bio ratio of 92%. The weight average molecular weight (Mw) of this polyester-based polymer (A1) was 120,000 and the glass transition temperature (Tg) was -50 °C.

[0148] (Synthesis Example 2) A four-neck separable flask was equipped with a stirrer, a thermometer, a nitrogen tube, and a water separation tube. 100 g of ethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 62), 700 g of dimer acid (product name "Pripol 1009", manufactured by Croda Co., Ltd., molecular weight 567), 63 g of terephthalic acid (manufactured by Tokyo Chemical Co., Ltd., molecular weight 166), 0.46 g of di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a reaction water discharge solvent were charged therein. While stirring in a nitrogen atmosphere, the temperature was raised to 180 °C and this temperature was maintained. After a while, the outflow and separation of the reaction water were observed and the reaction began to proceed. The reaction was continued for about 24 hours to obtain a polyester-based polymer (A2) with a bio ratio of 81%. The Mw of this polyester-based polymer (A2) was 100,000 and the Tg was -33 °C.

[0149] (Synthesis Example 3) A four-neck separable flask was equipped with a stirrer, a thermometer, a nitrogen tube, and a water separation tube. 100 g of dimer acid (product name "Pripol 1009", manufactured by Croda, molecular weight 567), 95 g of dimer diol (product name "Pripol 2033", manufactured by Croda, molecular weight 537), 0.46 g of di-n-butyltin oxide (manufactured by Kishida Chemical Co., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a reaction water discharge solvent were charged therein. The temperature was raised to 180°C while stirring in a nitrogen atmosphere, and this temperature was maintained. After a while, the outflow and separation of the reaction water were observed, and the reaction began to proceed. The reaction was continued for about 24 hours to obtain a polyester-based polymer (A3) with a bio-based ratio of 100%. The Mw of this polyester-based polymer (A3) was 30,000, and the Tg was -50°C.

[0150] <Example 1> To 100 parts of a polyester-based polymer (A1), 30 parts of a terpene phenol resin (trade name "YS Polyster T115", softening point 115°C, manufactured by Yasuhara Chemical Co., Ltd., hereinafter may be referred to as "T115"), 30 parts of a terpene phenol resin (trade name "YS Polyster S145", softening point 145°C, manufactured by Yasuhara Chemical Co., Ltd., hereinafter may be referred to as "S145") as tackifying resins, 3 parts of an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation, aromatic ring-free, trifunctional) as a crosslinking agent, 0.02 parts of an organic tin compound (trade name "dibutyltin(IV) dilaurate", manufactured by Fujifilm Wako Pure Chemical Corporation) as a crosslinking catalyst, and 0.5 parts of a carbodiimide group-containing compound (trade name "Carbodilite V-03", manufactured by Nisshinbo Chemical Inc.) as a hydrolysis-resistant agent were blended, and ethyl acetate was added to prepare an adhesive composition (adhesive solution). This adhesive solution was applied to the release-treated surface of a release-treated PET film (trade name "Diafoil MRV#38", manufactured by Mitsubishi Chemical Corporation, thickness 38 μm, hereinafter may be referred to as "the first release liner") so that the thickness after drying would be 20 μm, and dried at 120°C for 3 minutes to obtain an adhesive layer. Then, the above adhesive layer was laminated on the release-treated surface of a release-treated PET film (trade name "Diafoil MRF#25", manufactured by Mitsubishi Chemical Corporation, thickness 25 μm, hereinafter may be referred to as "the second release liner"), and further left at 50°C for 3 days to obtain a substrate-free double-sided adhesive sheet with a release liner (thickness 20 μm) according to this example. The storage elastic modulus G' of the above adhesive layer at 23°C was 0.22 MPa. Note that the substrate-free double-sided adhesive sheet with a release liner has a form in which the first adhesive surface and the second adhesive surface of the double-sided adhesive sheet are protected by the first release liner and the second release liner, respectively. Also, a substrate-free double-sided adhesive sheet (thickness 4 μm) according to this example was obtained in the same manner as above, except that the thickness of the adhesive layer after drying was changed to 4 μm.

[0151] <Examples 2 to 11, Comparative Examples 1 to 4> The types of polyester polymers, the types and amounts of tackifier resins, the amounts of crosslinking agents, and the amounts of crosslinking catalysts were changed as shown in Table 1. Other than that, the adhesive compositions according to each example were prepared in the same manner as in Example 1. Except for using the adhesive composition, in the same manner as in Example 1, for each example, a substrate-free double-sided adhesive sheet with a thickness of 4 μm and a substrate-free double-sided adhesive sheet with a thickness of 20 μm were produced. The tackifier resins used in the above Examples and Comparative Examples are as follows. T30: Terpene phenol resin (trade name "YS Polyster T30", softening point 30 °C, manufactured by Yasuhara Chemical Co., Ltd.) T80: Terpene phenol resin (trade name "YS Polyster T80", softening point 80 °C, manufactured by Yasuhara Chemical Co., Ltd.) D125: Rosin ester (trade name "Pensel D125", softening point 125 °C, pentaerythritol ester of polymerized rosin, manufactured by Arakawa Chemical Industries, Ltd.) SE10: Rosin ester (trade name "Haritack SE10", softening point 75 - 85 °C, hydrogenated rosin glycerin ester, manufactured by Harima Chemicals, Inc.)

[0152] <Evaluation> [Adhesion to SUS] The adhesive sheet was cut into a size of 20 mm in width and 150 mm in length to prepare a measurement sample. In an environment of 23 °C and 50% RH, the adhesive surface of the above measurement sample was exposed, and the adhesive surface was pressure-bonded to a stainless steel plate (SUS304BA plate) as an adherend with a 2 kg rubber roller for one round trip. This was left in an environment of 23 °C and 50% RH for 30 minutes, and then in the same environment, using a tensile testing machine, in accordance with JIS Z0237:2000, the peel strength (adhesion to SUS) [N / 20 mm] was measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. As the tensile testing machine, a universal tensile compression testing machine (device name "Tensile Compression Testing Machine, TCM-1kNB", manufactured by Minebea Co., Ltd.) was used. In the measurement of the adhesion to SUS, if necessary (for example, in the case of a double-sided adhesive sheet without a substrate or a pressure-sensitive adhesive sheet with a substrate that is easily deformed), an appropriate backing material can be attached to the pressure-sensitive adhesive sheet to be measured for reinforcement. As the backing material, for example, a PET film with a thickness of about 50 μm can be used, and this backing material was used in this example.

[0153] [Adhesion and adhesion retention rate after replacement of the release liner] The second release liner (diafoil MRF#25) was peeled off from a double-sided pressure-sensitive adhesive sheet with release liners, where the first and second adhesive surfaces were protected by the first release liner (diafoil MRV#38) and the second release liner (diafoil MRF#25), respectively. A PET film with a thickness of 50 μm was attached (backed) to the exposed second adhesive surface, and the above double-sided pressure-sensitive adhesive sheet was cut into a size of 30 mm in width and 160 mm in length to prepare a measurement sample. In an environment of 23°C and 50% RH, the first release liner was manually peeled from the first adhesive surface of the pressure-sensitive adhesive sheet with release liners in a 180-degree direction, and an alternative release liner (more specifically, the release-treated surface of the release liner) was immediately overlaid on the exposed first adhesive surface, and a 2-kg hand roller was reciprocated twice for crimping. This was left for 24 hours in an environment of 70°C while maintaining a state where a pressure of 5 kg was applied to the first adhesive surface from above the alternative release liner. Then, the above 5-kg load was removed, and it was left for about 3 to 5 hours in an environment of 23°C and 50% RH. Thereafter, in the same manner as the measurement of the adhesion to SUS, using a measurement sample cut into a size of 20 mm in width and 150 mm in length, in accordance with JIS Z0237:2000, the peel strength (adhesion after liner replacement) [N / 20 mm] to the SUS plate was measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. As the replacement release liner, a release liner manufactured by Fujiko Co., Ltd. (product name: "SCA1", a PET release liner having a silicone-based release treatment layer, thickness 75 μm) and a PET release liner manufactured by Toray Industries, Inc. (product name: "Celapeel BX8A", a PET release liner having a silicone-based release treatment layer, thickness 75 μm) were each used to measure the adhesive strength after liner replacement. The adhesion retention rate [%] after release liner replacement was calculated as a percentage of the ratio of the adhesive strength [N / 20 mm] after liner replacement to the adhesive strength (the above-mentioned adhesion to SUS) [N / 20 mm] before liner replacement.

[0154] The outlines and evaluation results of each example are shown in Table 1. In Table 1, the adhesive strength and adhesion retention rate after liner replacement with a 4-μm and 20-μm adhesive layer thickness using SCA1 as the replacement release liner are respectively shown in the columns of SCA1_4μm and SCA1_20μm, and the adhesive strength and adhesion retention rate after liner replacement with a 4-μm and 20-μm adhesive layer thickness using BX8A as the replacement release liner are respectively shown in the columns of BX8A_4μm and BX8A_20μm.

[0155]

Table 1

[0156] As shown in Table 1, the pressure-sensitive adhesive sheets according to Examples 1 to 11, which contain a polyester-based polymer and have a pressure-sensitive adhesive layer with a storage elastic modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa, had a liner replacement adhesion retention rate evaluated by two types of replacement release liners of 70% or more in all cases when the pressure-sensitive adhesive layer thickness was 4 μm, and 80% or more in all cases when the pressure-sensitive adhesive layer thickness was 20 μm. After liner replacement, the decrease in adhesive strength after storage under predetermined conditions (70°C, 5 kg, 24 hours) was suppressed. Further, the pressure-sensitive adhesive sheets of Examples 1 to 11 all had an adhesive strength to SUS of 5 N / 20 mm or more and had good adhesive strength. On the other hand, in Comparative Examples 1 to 4 where the storage elastic modulus G' of the pressure-sensitive adhesive layer at 23°C was 0.40 MPa or more, the liner replacement adhesion retention rate was less than 70% when the pressure-sensitive adhesive layer thickness was 4 μm, and less than 80% when the pressure-sensitive adhesive layer thickness was 20 μm, resulting in inferior results compared to the above examples. From the above results, according to the pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polyester-based polymer and having a storage elastic modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa, regardless of the handling before attachment to the adherend, for example, even when it has undergone handling methods in which the adhesive strength is likely to decrease, such as replacing the release liner before attachment to the adherend or being stored in a harsh environment where temperature control is not performed, the decrease in adhesive strength can be suppressed.

[0157] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Explanation of Reference Numerals

[0158] 1, 2, 3 Pressure-sensitive adhesive sheet 10 Support substrate 10A First surface 10B Second surface (back surface) 21 Pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) 21A Adhesive surface (first adhesive surface) 21B Second adhesive surface 22 Adhesive layer (second adhesive layer) 22A Adhesive surface (second adhesive surface) 31, 32 Release liner 100, 200, 300 Adhesive sheet with release liner

Claims

1. An adhesive sheet having an adhesive layer, wherein the adhesive layer contains a polyester-based polymer and has a storage elastic modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa.

2. The adhesive sheet according to Claim 1, wherein the adhesive layer contains 45 parts by weight or more of an adhesion-imparting resin with respect to 100 parts by weight of the polyester-based polymer.

3. The adhesive sheet according to Claim 2, wherein the softening point of the adhesion-imparting resin is 30°C or more and 200°C or less.

4. The adhesive layer contains, as the adhesion-imparting resin, 60 parts by weight or less of an adhesion-imparting resin T1 having a softening point of 145°C or more and 200°C or less with respect to 100 parts by weight of the polyester-based polymer, or contains an adhesion-imparting resin T2 having a softening point of 30°C or more and less than 145°C, or The adhesive sheet according to Claim 2 or 3, wherein the adhesive layer contains 60 parts by weight or less of the adhesion-imparting resin T1 with respect to 100 parts by weight of the polyester-based polymer and contains the adhesion-imparting resin T2.

5. The adhesive sheet according to any one of Claims 1 to 3, wherein the thickness of the adhesive layer is less than 80 μm.

6. The adhesive sheet according to any one of Claims 1 to 3, wherein the 180-degree peel strength with respect to a stainless steel plate is 5 N / 20 mm or more.

7. A portable electronic device including the adhesive sheet according to Claim 1 or 2.

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