Pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and portable electronic device

Abstract

To provide a pressure-sensitive adhesive that contains a polyester-based polymer, is readily deformable when compressed, and exhibits superior holding force.SOLUTION: A pressure-sensitive adhesive is provided which contains a polyester-based polymer and has tanδ of 0.35 or more and 0.80 or less at 23°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive, 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 the property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used as a 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 adhesives, 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 regarding polyester adhesives.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The pressure-sensitive 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 reducing the dependence on fossil resource-based materials (for example, Patent Document 1).

[0005] The above-mentioned pressure-sensitive adhesive sheet for electronic devices is usually disposed on various members of the electronic device as the adherend, and is designed to exhibit the desired adhesive function, that is, the member fixing function, by an operation (pressure bonding) of applying a predetermined pressure from above and sticking. However, in recent years, various members of electronic devices to which pressure-sensitive adhesive sheets are applied have been becoming thinner due to demands for weight reduction, miniaturization, and high functionality, and members that are so thin as to be deformed by the load during pressure bonding of the pressure-sensitive adhesive sheet are being adopted. As a means of preventing deformation of such members, a method of reducing the load on the member as the adherend by deforming (shrinking) the adhesive during pressure bonding of the pressure-sensitive adhesive sheet can be considered. However, the compression deformability and the holding power of the adhesive are technically in a trade-off relationship, and when the deformability during compression of the adhesive is increased, the holding power tends to decrease. In particular, polyester polymers used in polyester adhesives usually have crosslinking points only at the ends of the polymer chains, and thus tend to be less likely to obtain a dense crosslinked structure that contributes to improving the holding power compared to other polymers such as acrylic polymers. It would be practically beneficial to provide a polyester adhesive that achieves both compression deformability and holding power.

[0006] The present invention has been created in view of the above circumstances, and aims to provide an adhesive having a configuration including a polyester-based polymer, which is easily deformed during compression and has good holding power. Another related object is to provide an adhesive sheet including the above adhesive and a portable electronic device including the adhesive sheet.

Means for Solving the Problems

[0007] According to the present specification, there is provided an adhesive including a polyester-based polymer and having a tanδ (tanδ at 23°C) of 0.35 or more and 0.80 or less at 23°C. The adhesive having the above configuration can be easily deformed during compression and can have good holding power. Note that the tanδ (loss tangent) of the adhesive refers to the ratio (G″ / G′) of the loss elastic modulus G″ to the storage elastic modulus G′ of the adhesive.

[0008] In some preferred embodiments, the polyester-based polymer includes a structure derived from dimer acid. According to the polyester-based polymer synthesized using dimer acid, an adhesive having a tanδ at 23°C of a predetermined value or more can be preferably formed.

[0009] In some preferred embodiments, the adhesive contains 45 parts by weight or more of an adhesion promoter resin with respect to 100 parts by weight of the above polyester-based polymer. By having a composition containing the adhesion promoter resin in a predetermined amount or more, an adhesive having a tanδ at 23°C of a predetermined value or more can be preferably formed.

[0010] In some embodiments, the adhesion promoter resin includes an adhesion promoter resin T1 having a softening point of 60°C or more and 150°C or less. By including the adhesion promoter resin T1 having a softening point within the above range, an adhesive having a tanδ at 23°C within a predetermined range can be preferably obtained.

[0011] In some embodiments, the adhesion promoter resin includes an adhesion promoter resin T including a structure derived from terpene. T including. The adhesion promoter resin T having the above structure Thas a tendency to have good compatibility with polyester-based polymers. The above-mentioned tackifier resin T T By using this, a polyester-based adhesive having good quality can be easily obtained.

[0012] Also, according to this specification, an adhesive sheet having an adhesive layer is provided. The above-mentioned adhesive layer contains a polyester-based polymer and has a tanδ at 23°C of 0.35 or more and 0.80 or less. According to the adhesive sheet having the adhesive layer of the above configuration, it is possible to achieve both compression deformability and holding power.

[0013] In some preferred embodiments, the adhesive sheet has a 180-degree peel strength (adhesion to SUS) of 10 N / 20 mm or more with respect to a stainless steel plate. The adhesive sheet having the above-mentioned adhesion to SUS can have high adhesion reliability.

[0014] The adhesive sheet disclosed herein can achieve both compression deformability and holding power, so it can be pressure-bonded to a member of a portable electronic device whose adherend tends to be thinned without deforming the member, and can be preferably used as a fixing means with good adhesion reliability. Therefore, according to this specification, a portable electronic device using any of the adhesive sheets disclosed herein, in other words, a portable electronic device including the adhesive sheet is provided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Modes 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 relevant field. In the following drawings, members and parts having the same function may be denoted by the same reference numerals for explanation, and duplicate explanations 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 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 proportion 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 in the same manner. The same applies to the examples described later.

[0018] <Adhesive> (23°C tanδ) The adhesive disclosed herein is characterized in that the tanδ at 23°C is 0.35 or more and 0.80 or less. The adhesive with a tanδ at 23°C of 0.35 or more is easily deformed during compression. For example, when pressure-bonding to a thin and low-rigidity adherend, the load due to the pressure-bonding to the adherend can be reduced, and deformation of the adherend can be prevented. Further, since the tanδ at 23°C is 0.80 or less, the adhesive can exhibit good holding power. From the viewpoint of pressure-bonding deformability, in some preferred embodiments, the 23°C tanδ is 0.40 or more, more preferably 0.45 or more, still more preferably 0.50 or more, may be 0.55 or more, may be 0.60 or more, may be 0.65 or more, may be 0.70 or more, may be 0.73 or more. Further, from the viewpoint of obtaining good holding power, in some embodiments, the 23°C tanδ may be 0.75 or less, may be 0.72 or less. In some other embodiments, the 23°C tanδ may be 0.70 or less, may be 0.66 or less, may be 0.62 or less, may be 0.58 or less, may be 0.54 or less, may be 0.50 or less, may be 0.46 or less.

[0019] In the technology disclosed herein, the 23°C tanδ of the adhesive can be determined by dynamic viscoelasticity measurement. Specifically, a layered adhesive (in the case of an adhesive layer or a pressure-sensitive adhesive sheet without a substrate, the pressure-sensitive adhesive sheet) is prepared, and a plurality of the adhesives are stacked to produce an adhesive layer with a thickness of about 1 mm. A sample obtained by punching out this adhesive layer into a disk shape with a diameter of 7.9 mm is sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurement is performed under the following conditions using a viscoelasticity tester (for example, manufactured by TA Instruments, ARES or its equivalent) to obtain the 23°C tanδ. · 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 adhesive to be measured, an adhesive formed by applying the corresponding adhesive composition in a layered manner and drying or curing it may be used.

[0020] (Polyester-based polymer) The pressure-sensitive adhesive disclosed herein contains a polyester-based polymer. In this specification, a pressure-sensitive adhesive containing a polyester-based polymer is also referred to as a polyester-based pressure-sensitive adhesive. The above-mentioned polyester-based polymer is typically included in the pressure-sensitive adhesive as a base polymer. Here, the base polymer refers to the main component of the rubber-like polymer (a polymer exhibiting rubber elasticity in the temperature range near room temperature) contained in the pressure-sensitive adhesive. Also, in this specification, the "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.

[0021] (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 having desired properties (specifically, a desired tanδ at 23°C) can be obtained.

[0022] 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 having a tanδ of 23°C or more. 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. Dimer acid can be used alone or in combination of two or more. In the embodiment where dimer acid is used as the above 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, or may be about 80% by weight or more. By setting the amount of dimer acid used to a predetermined amount or more, the polymer can be designed based on the characteristics of dimer acid. Further, the upper limit of the weight ratio of the above dimer acid is 100% by weight, and from the viewpoint of holding power 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 may be about 85% by weight or less.

[0023] 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. Also, the upper limit of the weight ratio of the sebacic acid is 100% by weight, and from the viewpoint of improving the tanδ at 23°C of the adhesive, 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.

[0024] 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, the tanδ at 23°C decreases, and the holding force 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.

[0025] In an embodiment where an aromatic dicarboxylic acid is used as the dicarboxylic acid, the weight ratio of the aromatic dicarboxylic acid in 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 the holding power 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, for example, approximately 50% by weight or less, 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, from the viewpoint of obtaining adhesion characteristics such as compression deformability and adhesive strength having a tanδ at 23°C within a predetermined range. 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 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, or 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.

[0026] 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 about 1000 or less, and it may be, for example, 800 or less, 700 or less, or 600 or less (for example, 550 or less).

[0027] In the present 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 weight and the weight fraction of each dicarboxylic acid.

[0028] Although not particularly limited, from the viewpoint 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. Preferable 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 acids can be used alone or in combination of two or more.

[0029] In some embodiments, the weight ratio of the plant-derived dicarboxylic acid to 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 viewpoint of adhesion properties 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.

[0030] Note that the technology disclosed herein includes aspects of increasing the bio-based ratio of polyester-based polymers by using aromatic dicarboxylic acids derived from biomass. In some aspects, terephthalic acid derived from biomass and its derivatives can be used as the above dicarboxylic acid. The method for obtaining the above biomass-derived dicarboxylic acid 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. WO2009 / 079213).

[0031] (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; etc. By appropriately selecting one or more of these diols and using them, a polyester polymer capable of forming an adhesive having desired properties (specifically, a desired tanδ at 23°C) can be obtained.

[0032] 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 synthesizing these diols (preferably ethylene glycol or aliphatic diol) in combination with the above-mentioned dicarboxylic acids (preferably dimer acid), a polyester-based polymer excellent in adhesive 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.

[0033] The weight ratio of (poly)alkylene glycols, aliphatic diols, and alicyclic diols (preferably the weight ratio of ethylene glycol and aliphatic diols) to 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 adhesive 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.

[0034] 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 having a desired tanδ at 23°C can be preferably obtained, and good adhesive properties (adhesive force, holding power, etc.) 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 amount of (poly)ethylene glycol used 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 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 (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.

[0035] In some 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-based 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-based 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 where the diol as a monomer component used in the synthesis of the polyester-based polymer contains a dimer diol or 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-based polymer may not substantially contain a dimer diol.

[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 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 diols can be used alone or in combination of two or more.

[0037] 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).

[0038] The molecular weight of the above diol is not particularly limited. In some embodiments, from the viewpoints of monomer availability and synthetic properties, etc., the molecular weight of the diol is suitably about 1000 or less, for example, it may be 800 or less, 700 or less, or 600 or less. In some preferred embodiments, the molecular weight of the diol is suitably, for example, 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 more than 100, for example. 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 more than 100, for example. A preferred example of the diol having the above molecular weight is ethylene glycol.

[0039] 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.

[0040] 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, monohydric alcohols, hydroxycarboxylic acids, lactones, etc. 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 derived from plants. 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.

[0041] In the monomer components used for synthesizing the polyester polymers disclosed herein, although not particularly limited, the total proportion of the dicarboxylic acids and diols 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.

[0042] 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 about 50% by weight or more, preferably about 60% by weight or more, more preferably about 70% by weight or more, still more preferably about 80% by weight or more, and may be about 90% by weight or more (for example, 99 to 100% by weight).

[0043] 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 that an adhesive having a tanδ of 23°C or higher is easily obtained. 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 about 20% by weight or less, more preferably about 15% by weight or less, still more preferably about 10% by weight or less, may be about 5% by weight or less, may be about 3% by weight or less, and may be about 1% by weight or less (for example, less than 1% by weight) from the viewpoint of increasing tanδ at 23°C. 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, about 1% by weight or more, may be about 5% by weight or more, and may be about 7% by weight or more from the viewpoint of increasing cohesive force and obtaining good holding power.

[0044] 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.

[0045] 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 above 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 also 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 (e.g., dimer acid) can be preferably expressed. Also, in the embodiment using a plant-derived dicarboxylic acid, the bio-based ratio of the resulting polyester polymer can be effectively increased. Further, the above 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 above weight ratio (A1 / A2) may be 75 / 25 or less, or may be 50 / 50 or less (e.g., 30 / 70 or less). In the embodiment using a plant-derived diol, by setting the above weight ratio, 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.

[0046] 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 hydroxy groups of the diols to proceed while typically removing water (generated water) generated by the above reaction, etc. outside the reaction system. As a method for removing the generated water outside the reaction system, a method of blowing an inert gas into the reaction system and taking out the generated water together with the inert gas outside the reaction system, a method of azeotropic dehydration using a reaction water discharge solvent such as toluene or xylene, a method of distilling off the generated water from the reaction system under reduced pressure (reduced pressure method), etc. can be used.

[0047] 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 can be 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 distillation of the raw material dicarboxylic acids and diols outside the system. From the viewpoint of maintaining the stability of the pressure inside the reaction system, usually, it is appropriate to set the pressure inside the reaction system to be 0.1 kPa or more.

[0048] 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. Such catalysts include, for example, 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.

[0049] 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 using such a polyester-based polymer, meet the requirement of reducing the use of organic solvents in the manufacturing process and are preferable.

[0050] In addition, during the above reaction, since there is generally a correlation between the molecular weight of the synthesized polyester-based polymer and the viscosity of the reaction system, 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.

[0051] 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 having 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 containing a predetermined amount or more of an adhesion-imparting resin and tending to have a low viscosity, an appropriate viscosity can be easily obtained, and a thin and thick adhesive 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 is likely 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.

[0052] In addition, in this 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. The GPC measurement can be more specifically 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 (0.1 wt% amine component added) Flow rate: 0.5 mL / min Injection volume: 100 μL Detector: Differential refractometer (RI) Standard sample: Polystyrene (PS)

[0053] 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 force of the adhesive, 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 (i.e., the types and usage ratio of the monomers used in the synthesis of the polymer).

[0054] 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 a shear test, and using a measuring device (ARES, manufactured by Rheometric Scientific), at a frequency of 1 Hz, the peak value of tanδ (loss elastic modulus G'' / storage elastic modulus G') is obtained, and the temperature of the peak value is taken as Tg (glass transition temperature) [°C]. The same method is used for measurement in the examples described later.

[0055] Although not particularly limited, in some embodiments, the polyester-based polymer may have 10% or more of its constituent carbon being biomass-derived carbon, or may have 30% or more of its constituent carbon being biomass-derived carbon. In some preferred embodiments, the polyester-based polymer has 50% or more of its constituent carbon being biomass-derived carbon. In other words, the biomass carbon ratio (also referred to as the bio rate) of the above polyester-based polymer is 50% or more. By using a polyester-based polymer with a bio rate of a predetermined value or more in this way, the dependence on fossil resource-based materials of the adhesive can be reduced. The bio rate of the polyester-based polymer may be 52% or more, 55% or more, for example 60% or more. From the perspective of further reducing the dependence on fossil resource-based materials, the bio rate 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 rate is 100% by definition, in some embodiments, the bio rate of the polyester-based polymer may be, for example, 95% or less, 92% or less, 90% or less, 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 rate of the polyester-based polymer can be made 50% or more. In some other embodiments, the bio rate of the polyester-based polymer may be less than 50%, less than 30%, less than 10%, less than 1%. The bio rate of the polyester-based polymer may be substantially 0%.

[0056] (Adhesive resin) In some embodiments, the adhesive includes a tackifier resin. According to the technology disclosed herein, in a composition containing a tackifier resin, the adhesive can have a predetermined tanδ at 23°C and can have sufficient compression deformability. Also, by using an appropriate amount of the tackifier resin, the effect of improving the adhesive force based on the tackifier resin can be effectively exerted, and the adhesive properties such as adhesive force and holding force can be preferably improved. As the above tackifier resin, various tackifier resins such as rosin-based tackifier resins, terpene-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, phenol-based tackifier resins, and ketone-based tackifier resins can be used. Such tackifier resins can be used alone or in combination of two or more. In polyester-based adhesives, for example, rosin-based tackifier resins and terpene-based tackifier resins are preferably used.

[0057] Specific examples of rosin-based tackifier 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; and the like. Examples of the above rosin derivatives include rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., esterified products of rosin), and those obtained by esterifying modified rosin with alcohols (i.e., esterified products of modified rosin); unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty 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 thermally polymerizing; and the like.

[0058] 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.

[0059] 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. An example of the above modified terpene resin is terpene phenol resin.

[0060] 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 homopolymer or copolymer (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.

[0061] 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 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 resin for imparting tack, one or more of the above-described terpene-based tackifying resins can be used. Among them, terpene phenol resin is preferable.

[0062] In the mode of using tackifying resin T as the tackifying resin T in the total amount of the tackifying resin, the proportion of tackifying resin T T (preferably terpene phenol resin) is preferably about 25% by weight or more, more preferably about 30% by weight or more. In some preferred modes, about 50% by weight or more (for example, more than 50% by weight) of the total amount of the tackifying resin is tackifying 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 is tackifying 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 tackifying resin is tackifying resin T T either.

[0063] The softening point of the tackifying resin is not particularly limited. In some modes, the softening point (softening temperature) of the tackifying resin may be, for example, about 200°C or lower, about 180°C or lower, about 160°C or lower, or about 150°C or lower (for example, less than 150°C). By using a tackifying resin with a softening point below a predetermined value, a high tanδ at 23°C is likely to be obtained, and sufficient compression deformability and adhesive force are likely to be obtained. From this perspective, in some preferred modes, the softening point of the tackifying resin may be less than 145°C, more preferably about 135°C or lower, even more preferably about 120°C or lower, still more preferably about 110°C or lower, particularly preferably about 100°C or lower, and may even be about 90°C or lower. Also, in some modes, the softening point of the tackifying resin may be about 25°C or higher, about 30°C or higher, about 40°C or higher, or about 50°C or higher. By using a tackifying resin with a softening point above a predetermined value, the adhesive force can be improved. As the tackifying resin, a liquid tackifying resin that is liquid at room temperature (25°C) may be used.

[0064] In some preferred embodiments, as the tackifier resin, a tackifier resin T1 having a softening point of 60°C or higher and 150°C or lower is used. By using the tackifier resin T1 having the above softening point, it is easy to obtain an adhesive having a desired tanδ at 23°C, and it is easy to form an adhesive with good compression deformability. Further, by using the tackifier resin T1 having a softening point of a predetermined value or higher, the cohesive force of the adhesive can be improved. The softening point of the tackifier resin T1 is preferably approximately 70°C or higher, more preferably approximately 75°C or higher, and may be approximately 85°C or higher, may be approximately 95°C or higher, or may be approximately 105°C or higher. Also, from the viewpoint of increasing the tanδ at 23°C, in some preferred embodiments, the softening point of the tackifier resin T1 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 (for example, less than 100°C), and may be approximately 90°C or lower. As the tackifier resin T1, the above various tackifier resins can be used. For example, a tackifier resin T having a terpene-derived structure and a softening point of 60°C or higher and 150°C or lower T (for example, terpene phenol resin) is preferably used. The tackifier resin T1 can be used alone or in combination of two or more kinds.

[0065] In some embodiments, as the tackifier resin T1, a tackifier resin T1a having a softening point in the range of 100°C or higher and 150°C or lower is used. By using the tackifier resin T1a, while having a high adhesive force, the tanδ at 23°C can be adjusted to a desired range. The softening point of the tackifier resin T1a may be approximately 105°C or higher, or may be approximately 110°C or higher. Also, from the viewpoint of increasing the tanδ at 23°C, the softening point of the tackifier resin T1a may be less than 145°C, preferably approximately 140°C or lower, more preferably approximately 130°C or lower, and even more preferably approximately 120°C or lower. As the tackifier resin T1a, the above various tackifier resins can be used. For example, a tackifier resin T having a terpene-derived structure T(For example, terpene phenol resin) is preferably used. The tackifier resin T1a can be used alone or in combination of two or more.

[0066] In the aspect of using the tackifier resin T1a as the tackifier resin, the proportion of the tackifier resin T1a in the tackifier resin T1 may be approximately 10% by weight or more, approximately 30% by weight or more, approximately 50% by weight or more (for example, more than 50% by weight), approximately 70% by weight or more, approximately 90% by weight or more, and substantially all of the tackifier resin T1 (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) may be the tackifier resin T1a.

[0067] In some preferred embodiments, as the tackifier resin T1, a tackifier resin T1b having a softening point in the range of 60°C or more and less than 100°C is used. By using the tackifier resin T1b, an adhesive having better tack characteristics (tack force, holding force) and a suitable 23°C tanδ can be preferably designed. The softening point of the tackifier resin T1b is preferably approximately 70°C or more, more preferably approximately 75°C or more. Also, from the viewpoint of increasing the 23°C tanδ, the softening point of the tackifier resin T1b is preferably approximately 95°C or less, more preferably approximately 90°C or less, and may be approximately 85°C or less. As the tackifier resin T1b, the above various tackifier resins can be used. For example, a tackifier resin T containing a terpene-derived structure T (For example, terpene phenol resin) is preferably used. The tackifier resin T1b can be used alone or in combination of two or more.

[0068] In an embodiment where tackifier resin T1b is used as the tackifier resin, the proportion of tackifier resin T1b in tackifier resin T1 is preferably approximately 10% by weight or more, more preferably approximately 30% by weight or more, still more preferably approximately 50% by weight or more (for example, more than 50% by weight), may be approximately 70% by weight or more, may be approximately 90% by weight or more, and substantially all of tackifier resin T1 (for example, approximately 95% by weight or more to 100% by weight, and further approximately 99% by weight or more to 100% by weight) may be tackifier resin T1b.

[0069] In some embodiments, two or more types of tackifier resins T1 are used as the tackifier resin T1. For example, an embodiment of using two or more types of tackifier resins T1 with different softening points can be mentioned. By blending and using two or more types of tackifier resins T1 having appropriate softening points, while having good adhesive properties such as adhesive force and holding force, the 23°C tanδ can be adjusted to a desired range to preferably achieve excellent compression deformability. In an embodiment including two types of tackifier resins T1 with different softening points, the difference in softening points (T1H - T1L) between the tackifier resin T1H having a relatively high softening point and the tackifier resin T1L 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, still more preferably approximately 30°C or more, may be approximately 40°C or more, may be approximately 50°C or more, and may be approximately 60°C or more. Also, in some embodiments, the above difference (T1H - T1L) is, for example, less than 90°C, preferably approximately 70°C or less, more preferably approximately 50°C or less (for example, less than 50°C), and still more preferably approximately 40°C or less. Although not particularly limited, as the tackifier resin T1H and the tackifier resin T1L, the above-mentioned tackifier resin T1a and tackifier resin T1b can be used respectively.

[0070] In the embodiment of using the tackifier resins T1H and T1L, the weight ratio (T1H / T1L) of the amount of the tackifier resin T1H to the amount of the tackifier resin T1L is not particularly limited. In some embodiments, the above ratio (T1H / T1L) 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 (T1H / T1L), the effects of containing the tackifier resin T1H are more likely to be effectively exerted. Also, in some embodiments, the above ratio (T1H / T1L) may be 9 / 1 or less, 7 / 3 or less, 6 / 4 or less, 5 / 5 or less, 4 / 6 or less, or 3 / 7 or less. By setting the range of the above ratio (T1H / T1L), the effects of containing the tackifier resin T1L are more likely to be effectively exerted.

[0071] In the embodiment of using the tackifier resin T1 as the tackifier resin, the proportion of the tackifier resin T1 in the total amount of the tackifier resin is preferably approximately 25% by weight or more, and more preferably approximately 30% by weight or more. In some preferred embodiments, approximately 50% by weight or more (for example, more than 50% by weight) of the total amount of the tackifier resin is the tackifier resin T1, more preferably approximately 60% by weight or more, and even more preferably approximately 70% by weight or more may be the tackifier resin T1. The proportion of the tackifier resin T1 in the total amount of the tackifier 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 to 100% by weight, and further approximately 99% by weight or more to 100% by weight) of the tackifier resin may be the tackifier resin T1.

[0072] In some embodiments, as the tackifier resin, in addition to the tackifier resin T1 having a softening point of 60°C or higher and 150°C or lower, a tackifier resin T2 having a softening point of less than 60°C is used. By using the tackifier resin T1 and an appropriate amount of the tackifier resin T2, it is easy to obtain an adhesive having a desired tanδ at 23°C and to form an adhesive with good compression deformability. Further, according to the adhesive containing the tackifier resin T2, a high adhesive force can be obtained. The softening point of the tackifier resin T2 may be approximately 50°C or lower, or may be approximately 40°C or lower. The tackifier resin T2 may be a liquid tackifier resin that is liquid at room temperature (25°C). As the tackifier resin T2, the above-described various tackifier resins can be used. For example, a tackifier resin T T (for example, terpene phenol resin) is preferably used. The tackifier resin T2 can be used alone or in combination of two or more.

[0073] In the embodiment of 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) may be 1 / 99 or higher, 5 / 95 or higher, 10 / 90 or higher, or 15 / 85 or higher. By increasing the above ratio (T2 / T1), the effect of containing the tackifier resin T2 is likely to be effectively exerted. Further, in some embodiments, the above ratio (T2 / T1) may be 9 / 1 or lower, 7 / 3 or lower, 5 / 5 or lower, or 3 / 7 or lower. By setting the range of the above ratio (T2 / T1), the effect of containing the tackifier resin T1 is likely to be effectively exerted.

[0074] 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 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 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 heating starts must 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.

[0075] In an embodiment where the pressure-sensitive adhesive contains a tackifier resin, the total amount (total content) of the tackifier resin in the pressure-sensitive adhesive is appropriately set within a range having a target tanδ at 23°C. The total amount (total content) of the above-mentioned tackifier resin can be, for example, approximately 1 part by weight or more, preferably approximately 10 part by weight or more, more preferably approximately 30 part by weight or more, and even more preferably approximately 40 part by weight or more, based on 100 parts by weight of the polyester-based polymer. In some embodiments, the total amount of the above-mentioned tackifier resin is preferably 45 parts by weight or more based on 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 having a tanδ at 23°C of a predetermined value or more can be preferably formed. Also, the greater 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 based on 100 parts by weight of the polyester-based polymer is approximately 50 parts by weight or more, more preferably approximately 60 parts by weight or more, even more preferably approximately 70 parts by weight or more, still more preferably approximately 80 parts by weight or more, particularly preferably approximately 90 parts by weight or more, and may be approximately 100 parts by weight or more, or approximately 110 parts by weight or more. The upper limit of the total amount of the tackifier resin is not particularly limited, and in some embodiments, based on the viewpoints of compatibility and adhesiveness with the polyester-based polymer, it may be approximately 200 parts by weight or less, preferably approximately 160 parts by weight or less, and more preferably 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 obtaining good holding power with a tanδ at 23°C of a predetermined value or less, in some preferred embodiments, the total amount of the above-mentioned tackifier resin is approximately 130 parts by weight or less, more preferably approximately 115 parts by weight or less, even more preferably 110 parts by weight or less, particularly preferably approximately 105 parts by weight or less, and may be approximately 100 parts by weight or less (for example, less than 100 parts by weight), preferably approximately 90 parts by weight or less, and more preferably approximately 80 parts by weight or less, based on 100 parts by weight of the polyester-based polymer.

[0076] In some embodiments, as the tackifier resin, from the viewpoint of improving the bio-based ratio of the entire adhesive, a tackifier resin derived from plants (plant-derived tackifier resin) is preferably used. The plant-derived tackifier resin is composed of components in which at least a part of the resin is derived from plants. All of the resin may be derived from plants, or a part of the resin may be derived from plants and the other part may be derived from fossil resources. Examples of the plant-derived tackifier resin include the above-mentioned rosin-based tackifier resin and terpene-based tackifier resin. The plant-derived tackifier resin can be used alone or in combination of two or more. In some preferred embodiments, the proportion of the plant-derived tackifier resin in the total amount of the tackifier resin contained in the adhesive 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 to 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-derived tackifier resin.

[0077] (Crosslinking agent) In some embodiments, the adhesive contains a crosslinking agent. According to the adhesive containing a crosslinking agent, the cohesive force can be increased based on the crosslinked structure obtained by using the crosslinking agent. By using the crosslinking agent, the tanδ at 23°C can be adjusted and the holding power can be improved. The crosslinking agent can be contained in the adhesive 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 exclusively in the form after the crosslinking reaction. It should be noted that the crosslinking agent used for crosslinking the polyester-based polymer can also function as a chain extender.

[0078] 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 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.

[0079] As the isocyanate-based crosslinking agent, a polyfunctional isocyanate-based compound 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.

[0080] Examples of the polyfunctional isocyanate-based compound include aliphatic polyisocyanate-based compounds, alicyclic polyisocyanate-based compounds, aromatic polyisocyanate-based compounds, and the like. Specific examples of the aliphatic polyisocyanate-based compound 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.

[0081] Specific examples of the alicyclic polyisocyanate-based compound include isophorone diisocyanate; cyclohexyl diisocyanate such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanate 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.

[0082] Specific examples of the 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.

[0083] Examples of the polyfunctional isocyanate include polyfunctional isocyanate compounds having an average of two or more isocyanate groups per molecule. Such polyfunctional isocyanate compounds can be dimers or trimers (for example, dimers or trimers) of bifunctional or trifunctional or higher-functional isocyanates, derivatives (for example, addition reaction products of polyhydric alcohols and two or more molecules of polyfunctional isocyanates), polymers, and the like. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurate forms of hexamethylene diisocyanate (trimer addition products 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 the product names "Durate TPA-100" and "Durate D101" manufactured by Asahi Kasei Chemicals Corporation, and the product names "Coronate HL", "Coronate HK", "Coronate HX", "Coronate 2096", etc. manufactured by Tosoh Corporation.

[0084] In some embodiments, a crosslinking agent having no aromatic ring (aromatic ring-free crosslinking agent) is preferably used as the crosslinking agent. For example, among the isocyanate-based crosslinking agents described above, it is preferable to use an isocyanate-based compound having no aromatic ring. By using an aromatic ring-free isocyanate-based compound as the crosslinking agent, in an adhesive containing a polyester-based polymer, the degree of crosslinking can be effectively increased with less crosslinking inhibition. Preferable examples of the aromatic ring-free isocyanate include aliphatic isocyanate-based compounds.

[0085] In some embodiments, from the viewpoint of achieving a good balance of multiple adhesive properties, two or more crosslinking agents having different numbers of functional groups (preferably isocyanate-based crosslinking agents) may be used. The above-mentioned functional group refers to a crosslinking-reactive group. For example, in the above-mentioned polyfunctional isocyanate-based compound, it refers to an isocyanate group. For example, as the crosslinking agent, an embodiment in which one or more difunctional crosslinking agents and one or more trifunctional or higher-functional crosslinking agents (for example, trifunctional crosslinking agents) are used in combination can be mentioned.

[0086] The usage amount of the crosslinking agent is not particularly limited. In some embodiments, the usage amount of the crosslinking agent (for example, an isocyanate-based crosslinking agent) with respect 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 may be approximately 0.1 parts by weight or more. From the viewpoint of improving the cohesive force, it is appropriate to be approximately 0.5 parts by weight or more, preferably approximately 1 part by weight or more. From the viewpoint of having an appropriate tanδ at 23°C and improving the holding force, in some preferred embodiments, the usage amount of the crosslinking agent with respect 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, still more preferably approximately 1.8 parts by weight or more, and for example, it may be 2.5 parts by weight or more, or 3.5 parts by weight or more. Also, in some embodiments, the usage amount of the crosslinking agent with respect to 100 parts by weight of the polyester-based polymer may be approximately 10 parts by weight or less, for example, it may be approximately 7 parts by weight or less. From the viewpoint of having a tanδ at 23°C above a predetermined value and obtaining sufficient compression deformability, in some preferred embodiments, the usage amount of the crosslinking agent with respect 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, still 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 may be approximately 1.6 parts by weight or less.

[0087] 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 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 may be approximately 0.1 parts by weight or more. From the viewpoint of improving the cohesive force, it is appropriate to be approximately 0.5 parts by weight or more, preferably approximately 1 part by weight or more. From the viewpoint of having a suitable tanδ at 23°C and improving the holding power, in some preferred embodiments, the amount of the aromatic ring-free crosslinking agent used per 100 parts by weight of the polyester polymer is approximately 1.2 parts by weight or more, more preferably approximately 1.5 parts by weight or more, still more preferably approximately 1.8 parts by weight or more, and may be, for example, 2.5 parts by weight or more, or 3.5 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 polymer may be approximately 10 parts by weight or less, for example, may be approximately 7 parts by weight or less. From the viewpoint of having a tanδ at 23°C above a predetermined value and obtaining sufficient compression deformability, in some preferred embodiments, the amount of the aromatic ring-free crosslinking agent used per 100 parts by weight of the polyester polymer is approximately 5 parts by weight or less, more preferably approximately 4 parts by weight or less, still 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 may be approximately 1.6 parts by weight or less.

[0088] (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.

[0089] Although not particularly limited, in some embodiments, it is preferable to use a tin-containing compound with 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, by avoiding the use of an iron-based compound, coloring of the adhesive can be prevented or suppressed.

[0090] 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, 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, 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.

[0091] (Hydrolysis-resistant agent) In addition, the adhesive 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 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.

[0092] Examples of carbodiimide group-containing compounds 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 carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, and monofunctional cyclic structure carbodiimide.

[0093] 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 may be, for example, 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 appropriately approximately 5 parts by weight or less, preferably approximately 3 parts by weight or less, and may be, for example, 1 part by weight or less, based on 100 parts by weight of the polyester-based polymer.

[0094] (Other additives) In addition to the above-described components, the pressure-sensitive adhesive 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-described 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.

[0095] (Formation of pressure-sensitive adhesive) The adhesive disclosed herein can be formed by a conventionally known method using, for example, the polyester-based polymer described above. For example, after applying an adhesive composition to a surface having releasability (release surface), a layer-like adhesive (adhesive layer) can be formed on the surface by curing the adhesive composition. The adhesive formed in such a form can be used as a substrate-free double-sided adhesive sheet. In the case of an adhesive sheet with a substrate, a method (direct method) of directly applying (typically coating) the adhesive composition to the substrate and curing it to form an adhesive (layer) can be preferably employed. Alternatively, a method (transfer method) of forming an adhesive (layer) on the surface by applying and curing the adhesive composition to a surface having releasability (release surface) and then transferring the 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, etc. can be used. Further, the curing of the adhesive composition can be carried out by subjecting the adhesive composition to a curing treatment such as drying, crosslinking, polymerization, cooling, etc. Two or more kinds of curing treatments may be carried out simultaneously or stepwise. The adhesive composition is not particularly limited, but from the viewpoint of adhesive properties, etc., a solvent-type adhesive composition in which an adhesive is contained in an organic solvent is suitable. 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 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.

[0096] The application of the 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 adhesive composition may be applied by impregnation, the curtain coating method, etc. The drying of the adhesive composition can be carried out at room temperature or under heating. From the viewpoints of promoting the crosslinking reaction and improving the production efficiency, etc., it is preferable to carry out the drying of the adhesive composition under heating. The drying temperature can be, for example, approximately 40 to 150 °C, and usually it is preferably approximately 40 to 130 °C. After drying the adhesive composition, it is preferable to carry out aging for the purpose of adjusting the component migration in the adhesive (layer), promoting the crosslinking reaction, relaxing the strain that may exist in the adhesive (layer), etc. The conditions of aging are not particularly limited, and usually, the conditions can be, for example, 70 °C or lower (for example, approximately 40 to 70 °C) and 1 day or more (for example, 3 days or more).

[0097] (Bio - rate of the adhesive) Although not particularly limited, the adhesive preferably has a bio - rate of a predetermined value or more. In some embodiments, the bio - rate of the adhesive may be approximately 30% or more, suitably approximately 40% or more, and preferably 50% or more. By designing to increase the bio - rate of the adhesive, the dependence on fossil - resource - based materials of the whole adhesive can be reduced. From the viewpoint of further reducing the dependence on fossil - resource - based materials, in some preferred embodiments, the bio - rate of the adhesive may be 55% or more, 60% or more, 70% or more, or 75% or more. Although the upper limit of the bio - rate is 100% by definition, in the adhesives disclosed herein, since the components may include materials derived from fossil resources, the bio - rate may be less than 100%. From the viewpoints of easily obtaining compression deformability and good adhesive properties (such as holding power), in some embodiments, the bio - rate of the adhesive may be, for example, less than 90%, and when more importance is attached to the adhesive performance, it may be less than 80% or less than 70%.

[0098] <Adhesive sheet> The pressure-sensitive adhesive sheet disclosed herein is configured to include a layer made of the pressure-sensitive adhesive described above, that is, a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may be in the form of a substrate-free double-sided pressure-sensitive adhesive sheet including, for example, a first pressure-sensitive adhesive surface formed by one surface of the pressure-sensitive adhesive layer and a second pressure-sensitive adhesive surface formed by the other surface of the pressure-sensitive adhesive layer. Alternatively, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a pressure-sensitive adhesive sheet with a substrate, in which the pressure-sensitive adhesive layer is laminated on one or both sides of a support substrate. Hereinafter, the support substrate may be simply referred to as the "substrate".

[0099] (Configuration example) 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-free double-sided pressure-sensitive adhesive sheet made 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 of an adherend. The locations where the pressure-sensitive adhesive surfaces 21A and 21B are attached may be respective locations of different members or different locations within a single member. Before use (i.e., before attachment to the adherend), the pressure-sensitive adhesive sheet 1 may be a component of the pressure-sensitive adhesive sheet 100 with a release liner, in which the first pressure-sensitive adhesive surface 21A and the second pressure-sensitive adhesive surface 21B are protected by release liners 31 and 32, respectively, whose at least the sides facing the pressure-sensitive adhesive layer 21 are release surfaces, as shown in FIG. 1. As the release liners 31 and 32, for example, those configured such that a release layer by a release treatment agent is provided on one side of a sheet-like substrate (liner substrate) and the one side becomes a release surface can be preferably used. Alternatively, the release liner 32 may be omitted, and a release liner 31 with both sides being release surfaces may be used, and the second pressure-sensitive adhesive surface 21B may be brought into contact with and protected by the back surface of the release liner 31 by overlapping this with the pressure-sensitive adhesive sheet 1 and winding it in a spiral shape to form a pressure-sensitive adhesive sheet with a release liner in a roll form.

[0100] 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 in which 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 a release surface can be used, and the adhesive sheet 2 can be wound so that the adhesive surface 21A abuts against and is protected by the second surface (back surface) 10B of the support substrate 10 (roll form).

[0101] 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 in which the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 are protected by release liners 31 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 and is protected by the back surface of the release liner 31 (roll form) to form an adhesive sheet with a release liner.

[0102] In the double-sided adhesive sheet with the above-mentioned base material, at least one of the adhesive layers (for example, the first adhesive layer) of the first adhesive layer and the second adhesive layer may be an adhesive layer made of the above-mentioned adhesive, and the other adhesive layer (for example, the second adhesive layer) may also be an adhesive layer made of the above-mentioned adhesive, or may be an adhesive layer having a composition different from that of the adhesive layer made of the adhesive disclosed herein (specifically, the above-mentioned one adhesive layer. For example, the first adhesive layer). Such another adhesive layer may be formed of, for example, a known or conventional adhesive.

[0103] 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 adhesive characteristics such as adhesive force and holding power. Further, in the substrate-free double-sided adhesive sheet, the thickness of the adhesive layer can be maximally utilized to exhibit the compression deformability based on the tan δ at 23°C of the adhesive layer.

[0104] As the above-mentioned release liner, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a release liner made of a low-adhesion material such as a polyolefin-based resin (for example, polyethylene, polypropylene), a fluorine-based resin, etc. can be used. The above-mentioned release treatment layer can be formed, for example, by surface-treating the above-mentioned liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide, etc. In the field of electronic devices, from the viewpoint of avoiding the generation of paper dust, a release liner having a release treatment layer on the surface of a resin film or a release liner made of a low-adhesion material is preferable.

[0105] Note that the concept of the adhesive sheet referred to 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, punched, etc. into an appropriate shape according to the application and usage mode.

[0106] (Adhesive layer) The adhesive layer is a layer made of the above-described adhesive. 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 adhesion 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 improved adhesive strength and the effect of compression deformation of the adhesive, 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 products (such as portable electronic devices) 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 (for example, 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 35 μm or less, still more preferably 30 μm or less, and 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 the case of a double-sided adhesive sheet in which the adhesive sheet disclosed herein has adhesive layers on both sides of the substrate, the thicknesses of the respective adhesive layers may be the same or different. The thickness of each of the above adhesive layers can be selected, for example, from within the range exemplified as the thickness of the adhesive layer above.

[0107] (Substrate) The adhesive sheet disclosed herein can be in the form of an adhesive sheet with a substrate having an adhesive layer on one side or both sides of the substrate. As the substrate, various sheet-like substrates can be used, for example, resin films, paper, cloth, rubber sheets, foam sheets, metal foils, composites thereof, and the like. In the field of electronic devices, a substrate that is less likely to be a source of dust (such as minute fibers or particles such as paper dust) is preferably used. From such a viewpoint, a substrate that does not contain fibrous substances such as paper and cloth is preferred, and for example, resin films, rubber sheets, foam sheets, metal foils, composites thereof, and the like can be preferably used.

[0108] 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; etc. Examples of the rubber sheet include natural rubber sheet, butyl rubber sheet, etc. Examples of the foam sheet include foamed polyurethane sheet, foamed polyolefin sheet, etc. Examples of the metal foil include aluminum foil, copper foil, etc.

[0109] 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), workability, 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 a plant-derived material is used or not, by reusing the used resin film, sustainable reproduction is possible and the environmental load can be reduced. Such a recyclable resin film and a recycled resin film are also referred to as a recycled film. Such recyclability of the resin film can also be applied to the resin film used for the above-mentioned release liner. 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.

[0110] In some aspects, from the viewpoints of strength and workability, 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, etc.

[0111] In some aspects, from the perspective of reducing the usage amount of fossil resource-based materials, it is preferable that the base material 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 preferable, and biomass HDPE, biomass LDPE, biomass LLDPE, biomass PP, and biomass PET are particularly preferable. 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.

[0112] 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 paying more attention to 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%.

[0113] 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 (for example, 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 (for example, the perpendicular light transmittance) can also help adjust the light transmittance of the base material and further the light transmittance of the adhesive sheet containing the base material.

[0114] 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, pearl color, etc.

[0115] The base material may be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In such a base material configured to include a base film and a colored layer, 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 a 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 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 (for example, a black printing layer) formed by black printing.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] The content of the colorant is not limited to a specific range because it is set according to the required color tone, light transmittance, etc. However, in the colored layer, it is preferably about 1% by weight or 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, preferably 30% by weight or less (for example, 15% by weight or less), and may be 8% by weight or less.

[0120] The thickness of the entire colored layer is usually preferably 0.1 μm or more, preferably 0.5 μm or more, 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, preferably 7 μm or less, 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.

[0121] 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 a 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, and usually it is appropriate to be 0.1 μm or more, and it 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, and may be 0.7 μm or less, or 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-based ratio of the adhesive sheet described later.

[0122] 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 release treatment with a release treatment agent (back surface treatment agent). The release 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 release treatment agent can be used alone or in combination of two or more.

[0123] The base material (e.g., a 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., a white pigment), the content ratio is suitably about 0.1 to 10% by weight (e.g., 1 to 8% by weight or 1 to 5% by weight).

[0124] 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.

[0125] (Total thickness) The thickness (total thickness) of the pressure-sensitive adhesive sheet disclosed herein (including a pressure-sensitive adhesive layer, and further including a base material in the case of a pressure-sensitive adhesive sheet with a base material, but not including a release liner) 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 pressure-sensitive adhesive sheet is preferably about 5 μm to 500 μm in consideration of pressure-sensitive adhesive properties and the like, 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 products (such as portable electronic devices) to which the pressure-sensitive adhesive sheet is applied, in some preferred embodiments, the thickness of the pressure-sensitive adhesive sheet is 100 μm or less, more preferably 70 μm or less, still more preferably 50 μm or less, particularly preferably 35 μm or less, and may be, for example, 30 μm or less, or 25 μm or less. The lower limit value of the thickness of the pressure-sensitive adhesive sheet is not particularly limited, and may be, for example, approximately 5 μm or more, or from the viewpoint of productivity, approximately 10 μm or more, or approximately 15 μm or more (such as approximately 18 μm or more).

[0126] (Properties of the pressure-sensitive adhesive sheet) In some embodiments, the pressure-sensitive adhesive sheet preferably has a 180-degree peel strength (adhesion to SUS) of 10 N / 20 mm or more with respect to a stainless steel plate. The pressure-sensitive adhesive sheet having the above properties can be preferably used typically in a mode where re-peeling is not intended because it firmly adheres to the adherend. From the viewpoint of achieving a more reliable bonding, in some preferred embodiments, the above adhesion to SUS is 12 N / 20 mm or more, more preferably 14 N / 20 mm or more, still more preferably 16 N / 20 mm or more, and may be 18 N / 20 mm or more, or 20 N / 20 mm or more. The upper limit of the above adhesion to SUS is not particularly limited, and in some embodiments, the above adhesion may be, for example, 50 N / 20 mm or less, or 30 N / 20 mm or less. The above adhesion to SUS is specifically measured by the method described in the examples below.

[0127] In some embodiments, it is preferable that in the holding force test conducted under the conditions of 40°C, a load of 500 g, and 1 hour, the deviation distance after the holding force test is less than 0.6 mm. The adhesive sheet having the above characteristics can exhibit good holding performance. From the viewpoint of exhibiting higher holding performance, the above deviation distance is more preferably less than 0.5 mm, even more preferably 0.3 mm or less, and particularly preferably 0.1 mm or less. The lower limit of the above deviation distance is 0.0 mm, which means that no deviation is observed in the above holding force test. The above holding force test is specifically carried out by the method described in the examples below.

[0128] In some embodiments, an adhesive sheet (typically a substrate-free adhesive sheet) or an adhesive preferably has a deformation rate of 20% or more at the time when the compression stress is 0.35 MPa in the compression test conducted at a compression speed of 1 mm / min. The adhesive sheet and the adhesive having the above compression deformation rate are easily deformed during compression. For example, when pressure-bonding to an adherend with a small thickness and low rigidity, the load due to the pressure-bonding to the adherend can be reduced, and the deformation of the adherend can be prevented. From such a viewpoint, in some preferred embodiments, the above deformation rate is 22% or more, more preferably 25% or more, particularly preferably 27% or more, and may be 30% or more, or 33% or more. Also, from the viewpoints of compatibility with the holding force, adhesive characteristics, etc., the upper limit of the above compression deformation rate may be, for example, 50% or less, or 40% or less. The above compression test is specifically carried out by the method described in the examples below.

[0129] 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-based ratio of the pressure-sensitive adhesive sheet is 30% or more. By using a pressure-sensitive adhesive sheet with such a high bio-based ratio, the amount of fossil resource-based materials used can be reduced. From this perspective, in some preferred embodiments, the bio-based 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-based ratio is 100% by definition, since it may not be efficient in terms of productivity and performance to make all the materials constituting the pressure-sensitive adhesive sheet derived from plants, the above bio-based ratio may be less than 100%. From the perspective of easily obtaining compression deformability and good adhesive properties (e.g., holding power), in some embodiments, the bio-based 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-based ratio of the adhesive layer coincides with the bio-based ratio of the entire pressure-sensitive adhesive sheet.

[0130] <Use> The use of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited and can be used without limitation for various applications. For example, the pressure-sensitive adhesive sheet can be used for purposes such as fixing, joining, and reinforcing members in a mode of being attached to the members constituting an electronic device. For example, in a use mode of attaching to a thin member constituting an electronic device, by utilizing the compression deformability of the adhesive, the load on the member as the adherend during crimping of the pressure-sensitive adhesive sheet can be reduced, and deformation of the member can be prevented. The pressure-sensitive adhesive sheet disclosed herein can be preferably used for applications such as 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.

[0131] The adhesive sheet disclosed herein is suitable, for example, for use in fixing members in portable electronic devices. Various members constituting a portable electronic device are particularly strongly required to be thinned due to requirements such as weight reduction, size reduction, and high functionality. As described above, the adhesive sheet disclosed herein can utilize the compression deformability of the adhesive to prevent deformation of a member that is an adherend, and has good holding power. Therefore, it is particularly suitable as a highly reliable adhesion means for thin members constituting a portable electronic device. Non-limiting examples of the above portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, a wristwear type worn on the wrist like a wristwatch, a modular type worn on a part of the body with a clip or a strap, etc., an eyewear type including a glasses type (monocular type or binocular type. Also including a head-mounted type.), a clothing type attached to a shirt, socks, a hat, etc. in the form of an accessory, an earwear type attached to the ear like an earphone, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (electronic calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In addition, 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.

[0132] FIG. 4 is an example schematically showing a portable electronic device (smartphone) in which the adhesive sheet disclosed herein is used. As shown in FIG. 4, a battery (heating element) 540 is built inside a housing 520 of a portable electronic device 500. Further, the portable electronic device 500 includes an adhesive sheet 550. In this configuration example, the adhesive sheet 550 has a form of a double-sided adhesive sheet (double-sided adhesive tape) that fixes members constituting the portable electronic device 500. 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 a portable electronic device as described above.

[0133] The matters disclosed by this specification include the following. 〔1〕 A portable electronic device, comprising a housing and a touch panel in which a display unit also functions as an input unit, wherein a heat generating element (e.g., a battery) is built into the housing, and at least a first member and a second member among a number of members constituting the portable electronic device are joined by an adhesive sheet, the adhesive sheet having an adhesive layer, the adhesive layer containing a polyester-based polymer and having a tanδ at 23°C of 0.35 or more and 0.80 or less, a portable electronic device. 〔2〕 The portable electronic device according to the above 〔1〕, wherein the polyester-based polymer contains a structure derived from dimer acid. 〔3〕 The portable electronic device according to the above 〔1〕 or 〔2〕, wherein a tackifier resin is contained in an amount of 45 parts by weight or more with respect to 100 parts by weight of the polyester-based polymer. 〔4〕 The portable electronic device according to the above 〔3〕, wherein the tackifier resin contains a tackifier resin T1 having a softening point of 60°C or more and 150°C or less. 〔5〕 The portable electronic device according to the above 〔3〕 or 〔4〕, wherein the tackifier resin contains a tackifier resin T T containing a structure derived from terpene. 〔6〕 An adhesive containing a polyester-based polymer, having a tanδ at 23°C of 0.35 or more and 0.80 or less. 〔7〕 The adhesive according to the above 〔6〕, wherein the polyester-based polymer contains a structure derived from dimer acid. 〔8〕 The adhesive according to the above 〔6〕 or 〔7〕, wherein a tackifier resin is contained in an amount of 45 parts by weight or more with respect to 100 parts by weight of the polyester-based polymer. 〔9〕 The adhesive according to the above 〔8〕, wherein the tackifier resin contains a tackifier resin T1 having a softening point of 60°C or more and 150°C or less. 〔10〕 The adhesive according to the above 〔8〕, wherein the tackifier resin contains a tackifier resin T TThe pressure-sensitive adhesive according to the above [8] or [9], which contains

[0134] 〔11〕 A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a polyester-based polymer and has a tanδ of 0.35 or more and 0.80 or less at 23°C. 〔12〕 The pressure-sensitive adhesive sheet according to the above

[11] , wherein the 180° peel strength from a stainless steel plate is 10 N / 20 mm or more. 〔13〕 The pressure-sensitive adhesive sheet according to the above

[11] or

[12] , wherein the polyester-based polymer contains a structure derived from dimer acid. 〔14〕 The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[13] , wherein the pressure-sensitive adhesive layer contains 45 parts by weight or more of an adhesion promoter resin with respect to 100 parts by weight of the polyester-based polymer. 〔15〕 The pressure-sensitive adhesive sheet according to the above

[14] , wherein the adhesion promoter resin contains an adhesion promoter resin T1 having a softening point of 60°C or more and 150°C or less. 〔16〕 The adhesion promoter resin contains an adhesion promoter resin T containing a structure derived from terpene T The pressure-sensitive adhesive sheet according to the above

[14] or

[15] , which contains 〔17〕 The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[16] , which is used for a portable electronic device. 〔18〕 A portable electronic device including the pressure-sensitive adhesive sheet according to any one of the above

[11] to

[16] .

Examples

[0135] 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.

[0136] <Evaluation method> [Adhesion to SUS] Cut the adhesive sheet 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, expose the adhesive surface of the above measurement sample, and press it against a stainless steel plate (SUS304BA plate) as an adherend with a 2 kg rubber roller for one round trip. Leave this in an environment of 23°C and 50% RH for 30 minutes, and then, in the same environment, use a tensile testing machine to measure the peel strength (adhesion to SUS) [N / 20 mm] under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min in accordance with JIS Z0237:2000. As the tensile testing machine, a universal tensile compression testing machine (device name: "Tensile Compression Testing Machine, TCM-1kNB", manufactured by Minebea Co., Ltd.) can be used. In measuring the adhesion to SUS, if necessary (for example, in the case of a double-sided adhesive sheet without a substrate or in the case of an adhesive sheet with a substrate where the substrate is easily deformed), an appropriate backing material can be attached to the 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 the examples.

[0137] [Retention force] Cut the adhesive sheet into a size of 10 mm in width and 100 mm in length to prepare a measurement sample (test piece). In an environment of 23°C and 50% RH, press the adhesive surface of the above measurement sample against a bakelite plate (phenolic resin plate) as an adherend with a sticking area of 10 mm in width and 20 mm in length with a 2 kg roller for one round trip. Hang the adherend with the test piece attached in this way in an environment of 40°C with the length direction of the above test piece being vertical and leave it for 30 minutes. Then, apply a load of 500 g to the free end of the above test piece and leave it in an environment of 40°C for 1 hour with the load applied in accordance with JIS Z0237. Measure the distance (displacement length. Hereinafter, also referred to as displacement distance) [mm] displaced from the initial sticking position for the test piece after the above leaving. If the displacement distance after 1 hour is less than 0.6 mm, it is evaluated as qualified. If the displacement distance is 0.6 mm or more, or if the test piece falls off the bakelite plate within 1 hour, it is evaluated as unqualified.

[0138] [Compression test] The adhesive layer (substrate-free adhesive sheet) is laminated to a thickness of 1 mm using a hand roller, and a measurement sample is prepared by punching with an 8 mmφ metal punch. In an environment of 23°C and 50% RH, the adhesive surface of the above measurement sample is crimped to a jig (8 mmφ) of a compression test apparatus, and a compression test is carried out at a compression speed of 1 mm / min. The deformation rate at the time when the compression stress is 0.35 MPa is read. If the deformation rate is 20% or more, it is evaluated as qualified, and if the deformation rate is less than 20%, it is evaluated as unqualified. As the compression test apparatus, a dynamic viscoelasticity measuring apparatus (product name "RSA-G2", manufactured by TA Instruments) can be used.

[0139] <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, and 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 (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.

[0140] (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, and 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 (A2) with a bio-based ratio of 81%. The Mw of this polyester-based polymer (A2) was 100,000, and the Tg was -33 °C.

[0141] <Example 1> To 100 parts of a polyester-based polymer (A1), 60 parts of a terpene phenol resin (trade name "YS Polyster T115", softening point 115 °C, manufactured by Yasuhara Chemical Co., Ltd., hereinafter sometimes referred to as "T115") as a tackifier resin, 2 parts of an isocyanurate form of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation, non-aromatic ring-containing, trifunctional) as a crosslinking agent, 0.02 part of an organotin compound (trade name "Dibutyltin(IV) dilaurate", manufactured by Fujifilm Wako Pure Chemical Corporation) as a crosslinking catalyst, and 0.5 part 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) 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), and further left at 50 °C for 3 days to obtain a base material-free pressure-sensitive adhesive sheet according to this example. The tanδ of the above adhesive layer at 23 °C was 0.42.

[0142] <Examples 2 to 14, Comparative Examples 1 to 5> The types of polyester polymers, the types and amounts of tackifier resins, and the amounts of crosslinking agents were changed as shown in Table 1. Other than that, the pressure-sensitive adhesive compositions according to each example were prepared in the same manner as in Example 1, and the base material-free pressure-sensitive adhesive sheets according to each example were obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive compositions were used. The tackifier resins used in the above Examples and Comparative Examples are as follows. T80: terpene phenol resin (trade name "YS Polyster T80", softening point 80 °C, manufactured by Yasuhara Chemical Co., Ltd.) S145: terpene phenol resin (trade name "YS Polyster S145", softening point 145 °C, manufactured by Yasuhara Chemical Co., Ltd.) T30: terpene phenol resin (trade name "YS Polyster T30", softening point 30 °C, manufactured by Yasuhara Chemical Co., Ltd.)

[0143] The outlines and evaluation results of each example are shown in Table 1.

[0144]

Table 1

[0145] As shown in Table 1, in Examples 1 to 14 using a pressure-sensitive adhesive containing a polyester polymer and having a tanδ at 23 °C of 0.35 or more and 0.80 or less, good holding power was exhibited, the deformation rate in the compression test was 20% or more, and the compression deformability was also good. On the other hand, in Comparative Examples 1, 3 to 5 using a pressure-sensitive adhesive having a tanδ at 23 °C of less than 0.35, the deformation rate in the compression test was small, and a tendency to be inferior in compression deformability compared to the Examples was confirmed. Further, in Comparative Example 2 using a pressure-sensitive adhesive having a tanδ at 23 °C of greater than 0.80, the deviation distance in the holding power test was as large as 0.8 mm, and the holding power was inferior to that of the Examples.

[0146] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

Explanation of Signs

[0147] 1,2,3 Adhesive Sheet 10 Support Substrate 10A First Side 10B Second Side (Back Side) 21 Adhesive Layer (First Adhesive Layer) 21A Adhesive Surface (First Adhesive Surface) 21B Second Adhesive Surface 22 Adhesive Layer (Second Adhesive Layer) 22A Adhesive Surface (Second Adhesive Surface) 31, 32 Release Liner 100, 200, 300 Adhesive Sheet with Release Liner

Claims

1. An adhesive comprising a polyester-based polymer, having a tanδ at 23°C of 0.35 or more and 0.80 or less.

2. The adhesive according to Claim 1, wherein the polyester-based polymer contains a structure derived from dimer acid.

3. The adhesive according to Claim 1 or 2, wherein the tackifier resin is contained in an amount of 45 parts by weight or more per 100 parts by weight of the polyester-based polymer.

4. The adhesive according to Claim 3, wherein the tackifier resin contains a tackifier resin T1 having a softening point of 60°C or more and 150°C or less.

5. The tackifier resin contains a tackifier resin T having a structure derived from terpene. Ｔ The pressure-sensitive adhesive according to claim 3 or 4, comprising the same.

6. An adhesive sheet having an adhesive layer, wherein the adhesive layer comprises a polyester-based polymer and has a tanδ at 23°C of 0.35 or more and 0.80 or less.

7. The adhesive sheet according to Claim 6, having a 180-degree peel strength of 10 N / 20 mm or more with respect to a stainless steel plate.

8. A portable electronic device including the adhesive sheet according to Claim 6 or 7.

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