Adhesive, adhesive sheet, and portable electronic device

Abstract

The invention relates to an adhesive, an adhesive sheet, and a portable electronic device. The present invention provides an adhesive agent which is easy to deform when compressed and has good holding power due to a composition comprising a polyester-based polymer. The present invention provides an adhesive containing a polyester-based polymer and having a tan [delta] at 23 DEG C of from 0.35 to 0.80 (inclusive).

Description

Technical Field

[0001] The present invention relates to adhesives, adhesive sheets, and portable electronic devices. Background Art

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

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-69282 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] The adhesive sheet is preferably used, for example, for fixing components in electronic devices such as mobile phones, smartphones, and tablet personal 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 expected to be used as adhesives for electronic devices because they have excellent properties such as chemical resistance, water resistance, durability, and optical properties (transparency), and can exhibit adhesion characteristics equal to or higher than those of acrylic adhesives and synthetic rubber adhesives. In addition, polyester adhesives can be synthesized using biomass materials, and thus have the advantage of being able to reduce the dependence on fossil resource materials (for example, Patent Document 1).

[0008] The above-mentioned adhesive sheet for electronic devices is usually disposed on various components of an electronic device as an adherend, and is designed to exhibit an expected adhesive function, i.e., a component fixing function, through an operation (crimping) of applying a predetermined pressure thereto for sticking. However, in recent years, various components of electronic devices to which the adhesive sheet is applied have been becoming thinner due to requirements such as weight reduction, miniaturization, and high functionality, and components that are so thin as to be deformed by the load during crimping of the adhesive sheet have started to be adopted. As one of the means for preventing deformation of such components, a method of reducing the load on the component as an adherend by deforming (shrinking) the adhesive during crimping of the adhesive sheet is considered. However, there is a trade-off relationship between the compression deformability and the holding force of the adhesive, and when the deformability during compression of the adhesive is increased, the holding force tends to decrease. In particular, polyester polymers used for polyester adhesives usually have crosslinking points only at the ends of the polymer chains, and thus, compared with other polymers such as acrylic polymers, there is a tendency that it is difficult to obtain a dense crosslinked structure that contributes to an increase in the holding force. If a polyester adhesive that balances compression deformability and holding force is provided, it is practically beneficial.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive that is easily deformed during compression and has good holding force by including a configuration of a polyester polymer. Related other objects are to provide an adhesive sheet including the above-mentioned adhesive and a portable electronic device including the adhesive sheet.

[0010] Means for Solving the Problem

[0011] According to the present specification, there is provided an adhesive including a polyester 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 is easily deformed during compression and can have good holding force. It should be noted that the tanδ (dielectric loss tangent) of the adhesive refers to the ratio (G″ / G′) of the loss modulus G″ of the adhesive to the storage modulus G′.

[0012] In some preferred embodiments, the above-mentioned polyester polymer includes a structure derived from a dimer acid. According to the polyester polymer synthesized using a dimer acid, an adhesive having a tanδ at 23°C of a predetermined value or more can be satisfactorily formed.

[0013] In some preferred embodiments, in the adhesive, 45 parts by weight or more of a tackifying resin is contained with respect to 100 parts by weight of the above-mentioned polyester polymer. By having a composition containing a tackifying resin in a predetermined amount or more in this way, an adhesive having a tanδ at 23°C of a predetermined value or more can be satisfactorily formed.

[0014] In some ways, the tackifying resin described above includes a tackifying resin T1 having a softening point of 60°C or higher and 150°C or lower. By including the tackifying resin T1 having a softening point within the above range, an adhesive having a 23°C tanδ within a specified range can be satisfactorily obtained.

[0015] In some ways, the tackifying resin described above includes a tackifying resin T T , and the tackifying resin T T includes a structure derived from terpenes. The tackifying resin T having the above structure T tends to have good compatibility with polyester polymers. By using the above tackifying resin T T , a polyester adhesive having good quality can be easily obtained.

[0016] In addition, according to this specification, an adhesive sheet having an adhesive layer is provided. The above adhesive layer includes a polyester polymer, and the tanδ at 23°C is 0.35 or higher and 0.80 or lower. The adhesive sheet having an adhesive layer with the above configuration can balance compression deformability and holding power.

[0017] In some preferred ways, the 180-degree peel strength of the adhesive sheet with respect to a stainless steel plate (adhesion to SUS) is 10 N / 20 mm or higher. The adhesive sheet having the above adhesion to SUS can have high adhesive reliability.

[0018] The adhesive sheet disclosed herein can balance compression deformability and holding power, and thus can be crimped onto a member of a portable electronic device having a tendency to be thinned without deformation of the member, and can preferably be used as a fixing means with good adhesive reliability. Therefore, according to this specification, a portable electronic device using any one of the adhesive sheets disclosed herein, in other words, a portable electronic device including the adhesive sheet, is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional view schematically showing the configuration of an adhesive sheet of one embodiment.

[0020] Figure 2 It is a cross-sectional view schematically showing the configuration of an adhesive sheet of another embodiment.

[0021] Figure 3 It is a cross-sectional view schematically showing the configuration of an adhesive sheet of another embodiment.

[0022] Figure 4 It is a front view schematically showing an example of a portable electronic device including an adhesive sheet.

[0023] REFERENCE NUMERAL DESCRIPTION

[0024] 1, 2, 3 Adhesive sheet

[0025] 10 Support substrate

[0026] 10A First side

[0027] 10B Second side (back side)

[0028] 21 Adhesive layer (first adhesive layer)

[0029] 21A Adhesive surface (first adhesive surface)

[0030] 21B Second adhesive surface

[0031] 22 Adhesive layer (second adhesive layer)

[0032] 22A Adhesive surface (second adhesive surface)

[0033] 31, 32 Release liners

[0034] 100, 200, 300 Adhesive sheets with release liners Detailed implementation manners

[0035] Hereinafter, preferred implementation manners of the present invention will be described. Matters required for implementing the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for implementing the invention described in this specification and the common general knowledge in the art at the time of application. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the art.

[0036] It should be noted that in the following drawings, sometimes components / parts that perform the same function are denoted by the same reference numerals for description, and repeated descriptions may be omitted or simplified. In addition, for the sake of clearly explaining the present invention, the implementation manners shown in the drawings are schematized, and do not necessarily accurately represent the dimensions and scales of the adhesive sheets of the present invention actually provided as products.

[0037] It should be noted that the carbon from biomass in this specification refers to the carbon from biomass materials, that is, materials from renewable organic resources (renewable carbon). The above-mentioned biomass materials typically refer to materials from biological resources (typically photosynthetic plants) that can be continuously reproduced if there is sunlight, water, and carbon dioxide. Therefore, materials from fossil resources (fossil resource-based materials) that are depleted after mining are excluded from the concept of biomass materials mentioned here. For example, the proportion of carbon from biomass in the total carbon contained in polyester polymers, that is, the biomass carbon ratio (or also called the biomass rate), can be estimated by the carbon isotope content of mass number 14 measured according to ASTM D6866-22 Method B. In addition, the biomass rate of the adhesive (layer), the biomass rate of the substrate, and the biomass rate of the adhesive sheet can also be estimated by the same method. The same applies to the examples described later.

[0038] <Adhesive>

[0039] (tanδ at 23°C)

[0040] The adhesive disclosed herein is characterized in that the tanδ of the adhesive at 23°C is 0.35 or more and 0.80 or less. The adhesive with a tanδ of 0.35 or more at 23°C is easily deformed during compression. For example, when pressed against a thin and low-rigidity adherend, it can reduce the load generated by the pressing against the adherend and prevent the deformation of the adherend. In addition, by the tanδ of the adhesive being 0.80 or less at 23°C, the adhesive can exhibit good holding power. From the perspective of press-bonding deformability, in some preferred embodiments, the above-mentioned 23°C tanδ is 0.40 or more, more preferably 0.45 or more, further preferably 0.50 or more, can be 0.55 or more, can be 0.60 or more, can be 0.65 or more, can also be 0.70 or more, and can further be 0.73 or more. In addition, from the perspective of obtaining good holding power, in some embodiments, the above-mentioned 23°C tanδ can be 0.75 or less, or can be 0.72 or less. In other embodiments, the above-mentioned 23°C tanδ can be 0.70 or less, can be 0.66 or less, can be 0.62 or less, can be 0.58 or less, can be 0.54 or less, can also be 0.50 or less, and can further be 0.46 or less.

[0041] In the technology disclosed herein, the tanδ at 23°C of the adhesive can be determined by dynamic viscoelasticity measurement. Specifically, a laminated adhesive (adhesive layer, or adhesive sheet in the case of a substrate-free adhesive sheet) is prepared, and an adhesive layer with a thickness of approximately 1 mm is produced by overlapping multiple sheets of this adhesive. The adhesive layer is punched into a disk shape with a diameter of 7.9 mm to obtain a specimen, which is clamped and fixed between parallel plates, and dynamic viscoelasticity measurement is performed under the following conditions using a viscoelasticity tester (e.g., manufactured by TA Instruments, ARES or its equivalent) to determine the tanδ at 23°C.

[0042] ･ Measurement mode: Shear mode

[0043] ･ Temperature range: -70°C to 150°C

[0044] ･ Heating rate: 5°C / minute

[0045] ･ Measurement frequency: 1 Hz

[0046] In the following examples, the measurement is also performed by the above method. It should be noted that for the adhesive to be measured, an adhesive formed by coating the corresponding adhesive composition in a layer and drying or curing it can be used.

[0047] (Polyester polymer)

[0048] The adhesive disclosed herein contains a polyester polymer. It should be noted that in this specification, an adhesive containing a polyester polymer is also referred to as a polyester adhesive. The above polyester polymer is typically included as a base polymer in the adhesive. Here, the base polymer refers to the main component of the rubber-like polymer (a polymer that exhibits rubber elasticity in the temperature range near room temperature) contained in the adhesive. In addition, in this specification, unless otherwise specified, "main component" refers to a component with a content greater than 50% by weight. In addition, in this specification, a polyester polymer refers to a polymer obtained by polycondensing a dicarboxylic acid and a diol.

[0049] (Dicarboxylic acid)

[0050] As the dicarboxylic acid used in the synthesis of the above polyester polymers, any one 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, dimethyl glutaric acid, adipic acid, trimethyl adipic 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, phthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; and their derivatives. It should be noted that the derivatives of the above dicarboxylic acids include derivatives such as carboxylates, carboxylic anhydrides, carboxylic acid halides, and carboxylic esters. By appropriately selecting and using one or more of these dicarboxylic acids, a polyester polymer capable of forming an adhesive having desired properties (specifically, a desired tanδ at 23°C) can be obtained.

[0051] In some preferred embodiments, a dimer acid is used as the dicarboxylic acid. A polyester polymer synthesized using a dimer acid, that is, a polyester polymer containing a structure derived from a dimer acid, easily forms an adhesive having a tanδ at 23°C above a specified value. Without being particularly limited, the reason is considered to be that the relatively long side chains introduced by the copolymerization of the dimer acid contribute to improving the flexibility of the adhesive. The dimer acid can be used alone or in combination of two or more. In the embodiment where a dimer acid is used as the above dicarboxylic acid, the weight ratio of the dimer acid in the total amount (total weight) of the dicarboxylic acid as a monomer component of the polyester polymer is preferably about 1% by weight or more, more preferably about 10% by weight or more, still more preferably about 30% by weight or more, further preferably about 50% by weight or more (for example, greater than 50% by weight), particularly preferably about 70% by weight or more, can be about 75% by weight or more, and can also be about 80% by weight or more. By making the usage amount of the dimer acid above a specified amount, the polymer can be designed based on the properties of the dimer acid. In addition, the upper limit of the weight ratio of the above dimer acid is 100% by weight. From the viewpoint of holding power and the like, in some embodiments, the upper limit of the weight ratio of the above dimer acid is preferably about 99% by weight or less, can be about 90% by weight or less, and can also be about 85% by weight or less.

[0052] In some embodiments, sebacic acid is used as the dicarboxylic acid. In embodiments where sebacic acid is used as the above-mentioned 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 polymer can be about 1 wt% or more, for example, it can be about 5 wt% or more, about 10 wt% or more, or about 15 wt% or more. In addition, the upper limit of the weight ratio of the above-mentioned sebacic acid is 100 wt%. From the perspective of improving the tanδ at 23°C of the adhesive, in some embodiments, it can be about 50 wt% or less, or about 30 wt% or less. The technology disclosed herein can be implemented in either an embodiment where the dicarboxylic acid used in the synthesis of the polyester polymer contains sebacic acid or an embodiment where the dicarboxylic acid used in the synthesis of the polyester polymer does not contain sebacic acid. For example, the weight ratio of the above-mentioned sebacic acid can be about 10 wt% or less, about 3 wt% or less, less than 1 wt%, and the dicarboxylic acid used in the synthesis of the polyester polymer can substantially not contain sebacic acid.

[0053] In addition, in some embodiments, an aromatic dicarboxylic acid can be used as the dicarboxylic acid used in the synthesis of the polyester polymer. By using a dicarboxylic acid containing an aromatic dicarboxylic acid, there is a tendency for the cohesion to increase, the tanδ at 23°C to decrease, and the holding power to increase. Examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, and phthalic acid. The aromatic dicarboxylic acid can be used alone or in combination of two or more.

[0054] In the method of using an aromatic dicarboxylic acid 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 polymer can be about 1% by weight or more, and from the viewpoint of improving the holding power and the like, it can be about 3% by weight or more, it can be about 5% by weight or more, and it can also be about 7% by weight or more. In addition, in some embodiments, the upper limit of the weight ratio of the aromatic carboxylic acid is preferably about 50% by weight or less, for example. From the viewpoint of obtaining adhesive properties such as compression deformability and adhesiveness with a specified range of tan δ at 23°C, the upper limit of the weight ratio of the aromatic carboxylic acid is preferably about 30% by weight or less, more preferably about 20% by weight or less, still more preferably about 15% by weight or less, and particularly preferably about 10% by weight or less. The technology disclosed herein can be implemented by either a method in which the dicarboxylic acid as a monomer component used in the synthesis of the polyester polymer contains an aromatic dicarboxylic acid or a method in which the dicarboxylic acid as a monomer component used in the synthesis of the polyester polymer does not contain an aromatic dicarboxylic acid. In some preferred embodiments, the weight ratio of the aromatic dicarboxylic acid can be about 5% by weight or less, can be about 3% by weight or less, can be less than 1% by weight, and the dicarboxylic acid used in the synthesis of the polyester polymer can substantially not contain an aromatic dicarboxylic acid.

[0055] The molecular weight of the dicarboxylic acid as a monomer component used in the synthesis of the polyester polymer is not particularly limited, and it is appropriate that it is 100 or more, and it can also be 150 or more. In some embodiments, the molecular weight of the dicarboxylic acid used can be 200 or more, can be 250 or more, can be 350 or more, can be 450 or more, and can also be 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 appropriate that the molecular weight of the dicarboxylic acid is about 1000 or less, and for example, it can be 800 or less, can be 700 or less, and can also be 600 or less (for example, 550 or less).

[0056] It should be noted that in this specification, as the molecular weight of the dicarboxylic acid, the molecular weight calculated from the chemical formula is adopted. In addition, in the method of using two or more dicarboxylic acids, as the molecular weight of the dicarboxylic acid, the sum (total value) of the product of the molecular weight of each dicarboxylic acid and the weight fraction is adopted.

[0057] 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 dicarboxylic acid derived from plants as the dicarboxylic acid. Preferred examples of such a dicarboxylic acid include sebacic acid derived from plants (such as castor oil) and dimer acids derived from fatty acids such as oleic acid or erucic acid. The dicarboxylic acid derived from plants can be used alone or in combination of two or more.

[0058] In some embodiments, it is appropriate that the weight ratio of the dicarboxylic acid derived from plants in the total amount (total weight) of the dicarboxylic acid as a monomer component of the polyester polymer is about 1% by weight or more, preferably about 10% by weight or more, more preferably about 50% by weight or more, further preferably about 70% by weight or more, particularly preferably about 80% by weight or more, may be about 90% by weight or more, and may also be about 95% by weight or more (for example, about 95% by weight to about 100% by weight). In addition, the upper limit of the weight ratio of the above-mentioned dicarboxylic acid derived from plants is 100% by weight. From the viewpoint of adhesion characteristics and the like, in some other embodiments, it may be about 99% by weight or less, may be about 95% by weight or less, or may also be about 90% by weight or less.

[0059] It should be noted that the technology disclosed herein includes a method of increasing the biomass ratio of the polyester polymer by using aromatic dicarboxylic acids derived from biomass. In some embodiments, as the above-mentioned dicarboxylic acid, terephthalic acid derived from biomass and its derivatives can be used. The method for obtaining the above-mentioned dicarboxylic acid derived from biomass is not particularly limited. For example, the method for obtaining terephthalic acid derived from biomass may include the following method: obtaining isobutanol from corn, sugars, or wood, converting it into isobutene, dimerizing isobutene to obtain isooctene, synthesizing p-xylene through free radical cleavage, recombination, and cyclization by the method described in Chemische Technik, Vol. 38, No. 3, pp. 116-119, 1986, and then oxidizing p-xylene to obtain terephthalic acid (International Publication No. 2009 / 079213).

[0060] (Diol)

[0061] As the diol used in the synthesis of the polyester polymer disclosed herein, any one of (poly)alkylene diols, 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 diols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, and polytetramethylene glycol; 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, etc. aliphatic diols; dimer diols (dimer diols derived from fatty acids such as oleic acid and erucic acid, etc.); alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spirodiol, tricyclodecane dimethanol, adamantane diol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, etc.; aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, catechol, resorcinol, hydroquinone, 2,5-naphthalenediol, p-xylene glycol, and their ethylene oxide and propylene oxide adducts, etc. By appropriately selecting one or more of these diols, a polyester polymer capable of forming an adhesive having desired properties (specifically, a desired tanδ at 23°C) can be obtained.

[0062] In some embodiments, as the diol, (poly)alkylene diols, aliphatic diols, and alicyclic diols are preferred, and (poly)alkylene diols and aliphatic diols are more preferred. By synthesizing by combining these diols (preferably ethylene glycol and aliphatic diols) with the above-mentioned dicarboxylic acids (preferably dimer acids), a polyester polymer with excellent adhesion properties can be satisfactorily 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, 1,6-hexanediol. From the viewpoint 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 diols, aliphatic diols, and alicyclic diols can be derived from plants or fossil resources. It should be noted that 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.

[0063] The weight ratio of (poly)alkylene diols, aliphatic diols, and alicyclic diols (preferably the weight ratio of ethylene glycol and aliphatic diols) in the total amount (total weight) of diols in the monomer components of the polyester polymer is not particularly limited. In some embodiments, it is appropriate to be about 50% by weight or more. From the viewpoint of obtaining good adhesion properties, it is preferably about 70% by weight or more, more preferably about 80% by weight or more, further preferably about 90% by weight or more, and particularly preferably about 95% by weight or more (for example, about 99% by weight to about 100% by weight). In some other embodiments, the weight ratio of the above-mentioned (poly)alkylene diols, aliphatic diols, and alicyclic diols (preferably the weight ratio of ethylene glycol and aliphatic diols) can be, for example, about 95% by weight or less.

[0064] 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 polymer capable of forming an adhesive having a desired tanδ at 23 °C can be satisfactorily obtained, and good adhesive properties (adhesive strength, holding power, etc.) can be satisfactorily obtained. In the embodiment where the above (poly)ethylene glycol is used as the above diol, it is appropriate that the weight ratio of the (poly)ethylene glycol in the total amount (total weight) of the diols as the monomer components of the polyester polymer is about 1% by weight or more, preferably about 10% by weight or more, more preferably about 50% by weight or more, further preferably about 80% by weight or more, and particularly preferably about 90% by weight or more (for example, about 95% by weight to about 100%). By making the usage amount of (poly)ethylene glycol be above a specified value, the polymer can be designed based on the characteristics of (poly)ethylene glycol. In addition, 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 can be about 95% by weight or less, can be about 70% by weight or less, and can be about 50% by weight or less. The above (poly)ethylene glycol can be derived from plants or from fossil resources. (Poly)ethylene glycol can be used alone or in combination of two or more.

[0065] In some embodiments, dimer diol is used as the diol. As the dimer diol, dimer diol derived from plants can be preferably used. By using dimer diol, the biomass ratio of the polyester polymer can be increased. Dimer diol can be used alone or in combination of two or more. In the embodiment where dimer diol is used as the above diol, the weight ratio of dimer diol in the total amount (total weight) of the diols as the monomer components of the polyester polymer can be about 1% by weight or more, for example, can be about 10% by weight or more, can be about 50% by weight or more, can be about 70% by weight or more, can also be about 80% by weight or more, and can be about 90% by weight or more (for example, about 95% by weight to about 100%). In addition, in some embodiments, the weight ratio of the above dimer diol can be about 95% by weight or less, can also be about 85% by weight or less, and can further be about 60% by weight or less. The technology disclosed herein can be implemented in either an embodiment where the diol as the monomer component used in the synthesis of the polyester polymer contains dimer diol or an embodiment where the diol as the monomer component used in the synthesis of the polyester polymer does not contain dimer diol. In some embodiments, the weight ratio of the above dimer diol can be about 50% by weight or less (for example, less than 50%), can be about 30% by weight or less, can be about 10% by weight or less, can be about 3% by weight or less, and can be less than 1%, and the diol used in the synthesis of the polyester polymer can substantially not contain dimer diol.

[0066] Although there is no particular limitation, from the viewpoint of reducing the dependence on fossil resource-based materials, in some embodiments, it is preferable to use diols derived from plants as the diols. Examples of such diols include: biomass diols obtained using biomass ethanol as a raw material (such as biomass (poly)ethylene glycol, etc.), fatty acid esters derived from plants (such as castor oil), dimeric diols derived from fatty acids such as oleic acid and erucic acid, and butanediol produced using glucose. The diols derived from plants can be used alone or in combination of two or more.

[0067] In some embodiments, in the total amount (total weight) of the diols as monomer components of the polyester polymer, the weight ratio of the diols derived from plants can be about 1% by weight or more, can be about 10% by weight or more, can be about 50% by weight or more, can also be about 80% by weight or more, and can further be about 90% by weight or more (such as about 95% by weight to about 100% by weight). In addition, in some other embodiments, the weight ratio of the above diols derived from plants can be about 95% by weight or less, can be about 70% by weight or less, and can also be about 50% by weight or less. Even in embodiments where the amount of the diols derived from plants is used relatively low and the diols derived from fossil resources are used, for example, by using diols with a relatively low molecular weight as the diols derived from fossil resources, the polyester polymer can still have a biomass ratio of a specified value or more. From such a viewpoint, in some embodiments, the weight ratio of the above diols derived from plants can be about 30% by weight or less, can be about 10% by weight or less, and can also be about 3% by weight or less (such as less than 1% by weight).

[0068] The molecular weight of the above diols is not particularly limited. In some embodiments, from the viewpoints of monomer availability, synthetic properties, etc., it is appropriate for the molecular weight of the diol to be, for example, about 1000 or less, and can be, for example, 800 or less, 700 or less, or 600 or less. In some preferred embodiments, it is appropriate for the molecular weight of the diol to be, for example, 500 or less, can be 300 or less, can be 150 or less, can be 100 or less, or can also be 80 or less. In addition, it is appropriate for the molecular weight of the diol to be about 50 or more, and can be, for example, greater than 100. For example, in embodiments where the above diol is derived from fossil resources, it is appropriate for the molecular weight of the diol derived from fossil resources to be 500 or less, and can be 300 or less. The smaller the molecular weight of the diol derived from fossil resources, the easier it is for the polyester polymer to have a high biomass ratio. From this viewpoint, the molecular weight of the diol derived from fossil resources can be 150 or less, can be 100 or less, can be 80 or less. In addition, it is appropriate for the molecular weight of the diol derived from fossil resources to be about 50 or more, and can be, for example, greater than 100. Preferred examples of the diol having the above molecular weight include: ethylene glycol.

[0069] It should be noted that in this specification, as the molecular weight of the diol, the molecular weight calculated from the chemical formula can be used. Additionally, in the case of using two or more diols, as the molecular weight of the diol, the sum (total value) of the product of the molecular weight of each diol and its weight fraction is adopted.

[0070] The polyester polymers disclosed herein can substantially be composed of the above-mentioned dicarboxylic acids and diols. However, in order to introduce desired functional groups, adjust the molecular weight, etc., within the range that does not impair the effects of the technology disclosed herein, other copolymerization components in addition to dicarboxylic acids and diols can also be copolymerized. Examples of such other copolymerization components include: polycarboxylic acids containing three or more carboxyl groups (trimellitic acid, pyromellitic acid, adamantane tricarboxylic acid, benzene-1,2,4-tricarboxylic acid, trimeric acid, etc., polycarboxylic acids with three or more carboxyl groups), polyols containing three or more hydroxyl groups in one molecule (pentaerythritol, dipentaerythritol, tripentaerythritol, glycerol, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, adamantane triol, etc.), monocarboxylic acids, monohydric alcohols, hydroxycarboxylic acids, lactones, etc. The above-mentioned other copolymerization components can be used alone or in combination of two or more. These other copolymerization components can be derived from plants or not. In some embodiments, the proportion of the above-mentioned other copolymerization components in the monomer components of the polyester polymer is preferably less than 10% by weight, can be less than 3% by weight, can also be less than 1% by weight, and can further be less than 0.1% by weight. The technology disclosed herein can preferably be implemented in a manner where the monomer components of the polyester polymer substantially do not contain the above-mentioned other copolymerization components.

[0071] Among the monomer components used in the synthesis of the polyester polymers disclosed herein, there is no particular limitation. The total proportion of the dicarboxylic acid and the diol is preferably about 90% by weight or more, more preferably about 95% by weight or more, still more preferably about 98% by weight or more, and further preferably about 99% by weight or more (e.g., about 99% by weight to about 100% by weight). The technology disclosed herein is preferably implemented in a manner where a polyester polymer synthesized from a dicarboxylic acid and a diol is substantially used.

[0072] In some preferred embodiments, dimer acid as the dicarboxylic acid and (poly)ethylene glycol as the diol are used in the monomer components of the polyester polymer. In the case of using a polyester polymer synthesized by combining dimer acid and (poly)ethylene glycol, the technology disclosed herein can be satisfactorily implemented. The total proportion of dimer acid and (poly)ethylene glycol in the total amount of the monomer components of the polyester polymer is preferably about 50% by weight or more, more preferably about 60% by weight or more, still more preferably about 70% by weight or more, further preferably about 80% by weight or more, and can also be about 90% by weight or more (e.g., about 99% by weight to about 100% by weight).

[0073] In some embodiments, the polyester polymer preferably limits the content of aromatic rings in its polymer molecules or substantially does not contain aromatic rings. Thus, there is a tendency to easily obtain an adhesive having a tanδ at 23°C of more than a specified value. From the viewpoint of improving adhesiveness and the like, it is preferable to limit the content of aromatic rings in the polyester polymer. In some preferred embodiments, from the viewpoint of improving tanδ at 23°C, the copolymerization ratio of monomers containing aromatic rings (typically aromatic dicarboxylic acids and aromatic diols) in the polyester polymer is about 20% by weight or less, more preferably about 15% by weight or less, further preferably about 10% by weight or less, may be about 5% by weight or less, may also be about 3% by weight or less, and may further be about 1% by weight or less (for example, less than 1% by weight). The technology disclosed herein can be particularly preferably implemented in a manner using a polyester polymer that substantially does not contain aromatic rings in its molecules. Additionally, in embodiments where the polyester polymer has aromatic rings, from the viewpoint of improving cohesion to obtain good holding power and the like, the copolymerization ratio of monomers containing aromatic rings can be, for example, about 1% by weight or more, can be about 5% by weight or more, and can also be about 7% by weight or more.

[0074] The method for obtaining the polyester polymer disclosed herein is not particularly limited, and known polymerization methods that can be appropriately employed as the synthesis method of the polyester polymer can be used. As the monomer raw materials for synthesizing the polyester polymer, for example, monomer raw materials obtained by mixing monomers such that the amount of dicarboxylic acid is 0.95 to 1.05 equivalents (preferably 0.98 to 1.02 equivalents) relative to 1 equivalent of diol can be used. By mixing the dicarboxylic acid and diol in the above ratio, it is easy to obtain a high-molecular-weight polyester polymer. Additionally, by setting the molar ratio of the dicarboxylic acid to the diol within an appropriate range, a moderate crosslinked structure (for example, crosslinking based on reaction with a crosslinking agent such as an isocyanate crosslinking agent) can be obtained to adjust the cohesion.

[0075] In the technology disclosed herein, the weight ratio of the dicarboxylic acid to the diol, which are 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 physical properties, synthetic properties, etc. of the target polymer. 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 about 50 / 50 or more, more preferably 60 / 40 or more, further preferably 70 / 30 or more, may be 80 / 20 or more, and may also be 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 appropriately exhibited. In addition, in the embodiment of using a dicarboxylic acid derived from plants, the biomass ratio of the obtained polyester polymer can be effectively increased. In addition, the above weight ratio (A1 / A2) can be, for example, 95 / 5 or less, or can be 85 / 15 or less. In some embodiments, from the viewpoint of appropriately exhibiting the characteristics based on the diol, the above weight ratio (A1 / A2) can be 75 / 25 or less, and can also be 50 / 50 or less (e.g., 30 / 70 or less). In the embodiment of using a diol derived from plants, by setting the above weight ratio, the polyester polymer can increase the biomass ratio based on the diol derived from plants. It should be noted that in the embodiment of using materials derived from plants for both the dicarboxylic acid and the diol, a polyester polymer having a biomass ratio equal to or higher than a specified value can be obtained regardless of the weight ratio of the dicarboxylic acid to the diol.

[0076] Similar to ordinary polyesters, the polyester polymer in the technology disclosed herein can be obtained by polycondensation of a dicarboxylic acid and a diol. More specifically, the reaction of the carboxyl group of the dicarboxylic acid with the hydroxyl group of the diol typically proceeds while removing water (generated water) generated by the above reaction and the like out of the reaction system, whereby a polyester polymer can be synthesized. As a method for removing the above generated water out of the reaction system, the following methods can be used: a method of blowing an inert gas into the reaction system to discharge the generated water together with the inert gas out of the reaction system; a method of performing 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.

[0077] In order to effectively obtain polyester polymers with target properties (such as molecular weight), the reaction temperature, reaction time, and degree of vacuum (pressure within the reaction system) in the above reactions (including esterification and polycondensation) can be appropriately set. Although there is no particular limitation, generally, the above reaction temperature is preferably about 150 °C or higher (for example, 180 °C to 260 °C). By setting the reaction temperature within the above range, a good reaction rate can be obtained, the productivity can be improved, and it is easy to prevent or inhibit the degradation of the generated polyester polymers. As the reaction time, there is no particular limitation, and it can be about 3 hours to about 48 hours (for example, about 10 hours to about 30 hours). In the case of using the vacuum method, there is no particular limitation, but generally, the above degree of vacuum is preferably 10 kPa or lower (for example, 10 kPa to 0.1 kPa), and it can be, for example, 4 kPa to 0.1 kPa. By setting the pressure within the reaction system within the above range, the water generated by the reaction can be effectively distilled out of the system, and it is easy to maintain a good reaction rate. In addition, when the reaction temperature is relatively high, by setting the pressure within the reaction system to be above the above lower limit value, it is easy to prevent the dicarboxylic acid and diol as raw materials from being distilled out of the system. From the viewpoint of stably maintaining the pressure within the reaction system, generally, the pressure within the reaction system is preferably 0.1 kPa or higher.

[0078] Similar to the synthesis of ordinary polyesters, in order to carry out esterification and condensation, the above reactions can use an appropriate amount of known or conventional catalysts. As such catalysts, for example, various metal compounds such as titanium-containing type, germanium-containing type, antimony-containing type, tin-containing type, zinc-containing type, etc.; strong acids such as p-toluenesulfonic acid and sulfuric acid can be cited. The usage amount of the catalyst can be appropriately set according to the reaction rate, etc., and thus detailed description is omitted here.

[0079] In the above process of synthesizing polyester polymers by the reaction of dicarboxylic acids and diols, a solvent can be used or not used. The above synthesis can be carried out in a manner that substantially does not use organic solvents (which means, for example, excluding the intentional use of organic solvents as the reaction solvent during the above reactions). Synthesizing polyester polymers in such a manner that substantially does not use organic solvents and using such polyester polymers to prepare polyester adhesives are suitable for meeting the requirements of controlling the use of organic solvents during their manufacturing processes, and thus are preferred.

[0080] It should be noted that during the above reactions, there is usually a correlation between the molecular weight of the synthesized polyester polymers and the viscosity of the reaction system. Therefore, this point can be utilized to control the molecular weight of the polyester polymers. For example, by continuously or intermittently measuring (monitoring) the torque of the stirrer and the viscosity of the reaction system during the reaction, polyester polymers that meet the target molecular weight can be synthesized with high precision.

[0081] The weight-average molecular weight (Mw) of the polyester polymer is not particularly limited and is usually about 10,000 or more, and for example, about 20,000 or more is appropriate. In some embodiments, the Mw of the polyester polymer is 30,000 or more, preferably greater than 50,000, and from the viewpoint of obtaining more excellent properties, it is more preferably greater than 60,000, still more preferably greater than 70,000, further more preferably greater than 80,000, particularly preferably greater than 90,000, and may also be 95,000 or more. By using a polyester polymer having an Mw of a specified value or more, it is easy to obtain an adhesive having high cohesion. In some preferred embodiments, the Mw of the polyester polymer is 100,000 or more (for example, greater 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 polymer, for example, even an adhesive composition containing a specified amount or more of a tackifying resin and liable to have a low viscosity can easily have an appropriate viscosity and easily form a thin adhesive layer with good quality. The adhesive composition does not need to be overly concentrated, and even in a composition containing a crosslinking agent, it is easy to have a sufficient shelf life and excellent processability. The upper limit of the Mw of the polyester polymer is usually about 30×10 4 The following is appropriate, and from the viewpoint of adhesive strength and the like, in some embodiments, it is preferably about 20×10 4 The following, more preferably about 15×10 4 The following, and for example, may be about 12×10 4 The following.

[0082] It should be noted that in this specification, the Mw of the polyester polymer refers to the value converted to standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, a model name “HLC-8320GPC” (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used. More specifically, the GPC measurement can be carried out under the following conditions. The same method is also used for measurement in the examples described later.

[0083] [GPC Measurement]

[0084] Column: TSKgel GMH-H(S)

[0085] Column temperature: 40 °C

[0086] Eluent: THF (added with 0.1 wt% of an amine component)

[0087] Flow rate: 0.5 mL / min

[0088] Injection volume: 100 μL

[0089] Detector: Differential refractometer (RI)

[0090] Standard sample: Polystyrene (PS)

[0091] Although not particularly limited, in some embodiments, it is advantageous for the glass transition temperature (Tg) of the polyester polymer to be about 15°C or lower, preferably about 0°C or lower, more preferably about -15°C or lower, further preferably about -25°C or lower, and particularly preferably about -35°C or lower (for example, about -45°C or lower). By using a polyester polymer with a low Tg, the adhesion can be satisfactorily improved. In addition, from the viewpoint of the cohesion of the adhesive, in some embodiments, the Tg of the polyester polymer is generally about -80°C or higher, preferably about -70°C or higher, more preferably about -60°C or higher, and can be about -50°C or higher, or can be about -40°C or higher. The Tg of the polyester polymer can be adjusted by appropriately changing the monomer composition (that is, the types and usage ratios of the monomers used in the synthesis of the polymer).

[0092] The Tg of the polyester polymer is measured by the following method. That is, a disc-shaped test piece with a thickness of 2 mm and a diameter of 8 mm is made using the polyester polymer to be measured. This test piece is sandwiched between parallel plates for a shear test, and the peak of tanδ (loss modulus G'' / storage modulus G') is obtained at a frequency of 1 Hz using a measuring device (ARES, manufactured by Rheometric Scientific), and the temperature of this peak is set as Tg (glass transition temperature) [°C]. The same method is also used for measurement in the examples described later.

[0093] Although there is no particular limitation, in some embodiments, more than 10% of the carbon constituting the polyester polymer can be carbon derived from biomass, and more than 30% of the carbon constituting it can be carbon derived from biomass. In some preferred embodiments, more than 50% of the carbon constituting the polyester polymer can be carbon derived from biomass. In other words, the biomass carbon ratio (also known as the biomass rate) of the above-mentioned polyester polymer is 50% or more. By using a polyester polymer with a biomass rate of a specified value or more like this, the dependence of the adhesive on fossil resource materials can be reduced. The biomass rate of the polyester polymer can be 52% or more, can be 55% or more, for example, can be 60% or more. From the perspective of further reducing the dependence on fossil resource materials, the biomass rate of the polyester polymer is preferably 70% or more, more preferably 75% or more, further preferably 80% or more, can be 85% or more, and can also be 88% or more. The upper limit of the biomass rate is 100% by definition. In some embodiments, the biomass rate of the polyester polymer can be, for example, 95% or less, can be 92% or less, can be 90% or less, and can also be 85% or less. By using a compound derived from biomass in at least one (e.g., both) of the dicarboxylic acid and diol used in the synthesis of the polyester polymer, the biomass rate of the polyester polymer can be 50% or more. In some other embodiments, the biomass rate of the polyester polymer can be less than 50%, can be less than 30%, can be less than 10%, and can also be less than 1%. The biomass rate of the polyester polymer can substantially be 0%.

[0094] (Tackifying resin)

[0095] In some embodiments, the adhesive contains a tackifying resin. According to the technology disclosed herein, by virtue of the composition containing the tackifying resin, the adhesive becomes an adhesive having a specified tanδ at 23°C and can become an adhesive having sufficient compression deformability. In addition, by using an appropriate amount of the tackifying resin, the effect of improving the adhesive strength based on the tackifying resin can be effectively exerted, and the adhesive properties such as adhesive strength and holding power can be satisfactorily improved. As the above-mentioned tackifying resin, various tackifying resins such as rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins can be used. Such tackifying resins can be used alone or in combination of two or more. In the polyester adhesive, for example, rosin-based tackifying resins and terpene-based tackifying resins are preferably used.

[0096] As specific examples of rosin-based tackifying resins, the following can be cited: unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc. The same applies hereinafter); various other rosin derivatives; etc. As examples of the above-mentioned rosin derivatives, the following can be cited: substances obtained by esterifying unmodified rosin with alcohols (i.e., esters of rosin), substances obtained by esterifying modified rosin with alcohols (i.e., esters of modified rosin), etc., which are rosin esters; unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin and modified rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid-modified 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.) using an acid catalyst and performing thermal polymerization; etc.

[0097] Although not particularly limited, as specific examples of rosin esters, the following can be cited: esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl esters, triethylene glycol esters, glycerol esters, pentaerythritol esters, etc.

[0098] As examples of terpene-based tackifying resins, the following can be cited: terpene resins such as α-pinene polymers, β-pinene polymers, and terpinene polymers; modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.); etc. The terpene-based tackifying resin can be a homopolymer of one type of terpene or a copolymer of two or more types of terpenes. As an example of the above-mentioned modified terpene resin, terpene phenol resin can be cited.

[0099] Terpene phenol resin refers to a polymer containing terpene residues and phenol residues, and is a concept that includes both copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins) and resins obtained by phenol-modifying terpenes or their homopolymers or their copolymers (phenol-modified terpene resins). As a preferred example of the terpene used to form such a terpene phenol resin, the following can be cited: monoterpenes such as α-pinene, β-pinene, and limonene (including d-form, l-form, and d / l-form (terpinene)). Hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is sometimes also referred to as hydrogenated terpene phenol resin.

[0100] Although there is no particular limitation, in some embodiments, as the tackifying resin, a tackifying resin T containing a structure derived from terpenes can be used T . The tackifying resin T T has good compatibility with polyester polymers. In addition, the adhesive formed by using the tackifying resin T T is liable to have good qualities such as excellent stability during long-term storage. As the tackifying resin T T , one or more of the above-mentioned terpene-based tackifying resins can be used. Among them, terpene phenol resin is preferred.

[0101] In the embodiment where the tackifying resin T T is used as the tackifying resin, the proportion of the tackifying resin T T (preferably terpene phenol resin) in the total amount of the tackifying resin is preferably about 25% by weight or more, more preferably about 30% by weight or more. In some preferred embodiments, about 50% by weight or more (e.g., greater than about 50% by weight) of the total amount of the tackifying resin is the tackifying resin T T , more preferably about 75% by weight or more, further preferably about 80% by weight or more. For example, about 90% by weight or more can be the tackifying resin T T , and it can be substantially all of the tackifying resin (e.g., about 95% by weight or more and about 100% by weight or less, further about 99% by weight or more and about 100% by weight or less) being the tackifying resin T T .

[0102] The softening point of the tackifying resin is not particularly limited. In some embodiments, the softening point (softening temperature) of the tackifying resin can be, for example, about 200 °C or lower, can be about 180 °C or lower, can be about 160 °C or lower, or can be about 150 °C or lower (e.g., less than 150 °C). By using a tackifying resin with a softening point below a specified value, there is a tendency to easily obtain a high tanδ at 23 °C and easily obtain sufficient compression deformability and adhesiveness. From this perspective, in some preferred embodiments, the softening point of the tackifying resin can be less than 145 °C, more preferably about 135 °C or lower, still more preferably about 120 °C or lower, further preferably about 110 °C or lower, particularly preferably about 100 °C or lower, and can be about 90 °C or lower. In addition, in some embodiments, the softening point of the tackifying resin can be about 25 °C or higher, can be about 30 °C or higher, can be about 40 °C or higher, or can be about 50 °C or higher. By using a tackifying resin with a softening point above a specified value, the adhesiveness can be improved. As the tackifying resin, a liquid tackifying resin that is liquid at room temperature (25 °C) can be used.

[0103] In some preferred embodiments, a tackifying resin T1 having a softening point of 60°C or higher and 150°C or lower is used as the tackifying resin. By using the tackifying 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 having good compression deformability. In addition, by using the tackifying resin T1 having a softening point above a specified value, the cohesion of the adhesive can be improved. The softening point of the tackifying resin T1 is preferably about 70°C or higher, more preferably about 75°C or higher, can be about 85°C or higher, can be about 95°C or higher, and can also be about 105°C or higher. In addition, from the viewpoint of improving tanδ at 23°C, in some preferred embodiments, the softening point of the tackifying resin T1 can be less than 145°C, more preferably about 135°C or lower, further preferably about 120°C or lower, further preferably about 110°C or lower, particularly preferably about 100°C or lower (e.g., less than 100°C), and can also be about 90°C or lower. As the tackifying resin T1, the above various tackifying resins can be used. For example, a tackifying resin T containing a structure derived from terpene and having a softening point of 60°C or higher and 150°C or lower can be preferably used. T (e.g., terpene phenol resin). The tackifying resin T1 can be used alone or in combination of two or more.

[0104] In some embodiments, a tackifying resin T1a having a softening point in the range of 100°C or higher and 150°C or lower is used as the tackifying resin T1. By using the tackifying resin T1a, it is possible to adjust tanδ at 23°C to a desired range while having high adhesive strength. The softening point of the tackifying resin T1a can be about 105°C or higher, and can also be about 110°C or higher. In addition, from the viewpoint of improving tanδ at 23°C, the softening point of the tackifying resin T1a can be less than 145°C, preferably about 140°C or lower, more preferably about 130°C or lower, and further preferably about 120°C or lower. As the tackifying resin T1a, the above various tackifying resins can be used. For example, a tackifying resin T containing a structure derived from terpene can be preferably used. T (e.g., terpene phenol resin). The tackifying resin T1a can be used alone or in combination of two or more.

[0105] In the embodiment where the tackifying resin T1a is used as the tackifying resin, the proportion of the tackifying resin T1a in the tackifying resin T1 can be about 10% by weight or higher, can be about 30% by weight or higher, can be about 50% by weight or higher (e.g., greater than 50% by weight), can be about 70% by weight or higher, can be about 90% by weight or higher, and can be substantially all of the tackifying resin T1 (e.g., about 95% by weight or higher and about 100% by weight or lower, further about 99% by weight or higher and about 100% by weight or lower) being the tackifying resin T1a.

[0106] In some preferred embodiments, a tackifying resin T1b having a softening point in the range of greater than or equal to 60 °C and less than 100 °C is used as the tackifying resin T1. By using the tackifying resin T1b, it is possible to satisfactorily design an adhesive having appropriate tan δ at 23 °C while having better adhesion properties (adhesive strength, holding power). The softening point of the tackifying resin T1b is preferably about 70 °C or higher, more preferably about 75 °C or higher. Additionally, from the perspective of increasing tan δ at 23 °C, the softening point of the tackifying resin T1b is preferably about 95 °C or lower, more preferably about 90 °C or lower, and can be about 85 °C or lower. As the tackifying resin T1b, various above-mentioned tackifying resins can be used. For example, a tackifying resin T T (such as terpene phenol resin) can be preferably used. The tackifying resin T1b can be used alone or in combination of two or more.

[0107] In the embodiment where the tackifying resin T1b is used as the tackifying resin, the proportion of the tackifying resin T1b in the tackifying resin T1 is preferably about 10% by weight or more, more preferably about 30% by weight or more, further preferably about 50% by weight or more (such as greater than 50% by weight), can be about 70% by weight or more, can be about 90% by weight or more, and can be substantially all of the tackifying resin T1 (such as about 95% by weight or more and about 100% by weight or less, further about 99% by weight or more and about 100% by weight or less) being the tackifying resin T1b.

[0108] In some embodiments, two or more tackifying resins T1 are used as the tackifying resin T1. For example, an embodiment of using two or more tackifying resins T1 having different softening points can be cited. By blending and using two or more tackifying resins T1 having appropriate softening points, while having good adhesion properties such as adhesive strength and holding power, the tan δ at 23 °C is adjusted to a desired range, thereby enabling excellent compression deformability to be satisfactorily achieved. In the embodiment including two tackifying resins T1 having different softening points, the difference in softening points (T1H - T1L) between the tackifying resin T1H having a relatively high softening point and the tackifying resin T1L having a relatively low softening point is not particularly limited. For example, it is appropriate to be about 5 °C or more, preferably about 10 °C or more, more preferably about 20 °C or more, further about 30 °C or more, can be about 40 °C or more, can be about 50 °C or more, and can also be about 60 °C or more. Additionally, in some embodiments, the above difference (T1H - T1L) is, for example, less than 90 °C, preferably about 70 °C or lower, more preferably about 50 °C or lower (such as less than 50 °C), and further preferably about 40 °C or lower. Although not particularly limited, as the tackifying resin T1H and the tackifying resin T1L, the above-mentioned tackifying resin T1a and the tackifying resin T1b can be used respectively.

[0109] In the manner of using tackifying resins T1H and T1L, the ratio (T1H / T1L) of the amount of tackifying resin T1H to the amount of tackifying resin T1L on a weight basis is not particularly limited. In some manners, the above ratio (T1H / T1L) can be 1 / 9 or more, can be 2 / 8 or more, can be 3 / 7 or more, can be 4 / 6 or more, or can be 5 / 5 or more. By increasing the above ratio (T1H / T1L), it is easy to effectively exhibit the effects of the tackifying resin T1H. Additionally, in some manners, the above ratio (T1H / T1L) can be 9 / 1 or less, can be 7 / 3 or less, can be 6 / 4 or less, can be 5 / 5 or less, can be 4 / 6 or less, or can be 3 / 7 or less. By setting within the range of the above ratio (T1H / T1L), it is easy to effectively exhibit the effects of the tackifying resin T1L.

[0110] In the manner of using tackifying resin T1 as the tackifying resin, the proportion of tackifying resin T1 in the total amount of the tackifying resin is preferably about 25% by weight or more, more preferably about 30% by weight or more. In some preferred manners, about 50% by weight or more (such as greater than 50% by weight) of the total amount of the tackifying resin is tackifying resin T1, more preferably about 60% by weight or more, and further preferably about 70% by weight or more can be tackifying resin T1. The proportion of tackifying resin T1 in the total amount of the tackifying resin can be about 80% by weight or more, can be about 90% by weight or more, and can be substantially all of the tackifying resin (such as about 95% by weight or more and about 100% by weight or less, further about 99% by weight or more and about 100% by weight or less) being tackifying resin T1.

[0111] In some manners, in addition to using tackifying resin T1 with a softening point of 60°C or more and 150°C or less as the tackifying resin, a tackifying resin T2 with a softening point less than 60°C is also used as the tackifying resin. By using tackifying resin T1 and an appropriate amount of tackifying resin T2, it is easy to obtain an adhesive having a desired tanδ at 23°C and easy to form an adhesive with good compression deformability. Additionally, according to the adhesive containing tackifying resin T2, high adhesive strength can be obtained. The softening point of tackifying resin T2 can be about 50°C or less, or can be about 40°C or less. Tackifying resin T2 can be a liquid tackifying resin that is liquid at room temperature (25°C). As tackifying resin T2, the above various tackifying resins can be used. For example, a tackifying resin T containing a structure derived from terpenes (such as terpene phenol resin) can be preferably used. T (For example, terpene phenol resin). Tackifying resin T2 can be used alone or in combination of two or more.

[0112] In the method of using tackifying resins T1 and T2, the ratio (T2 / T1) of the amount of tackifying resin T2 to the amount of tackifying resin T1 on a weight basis is not particularly limited. In some embodiments, the above ratio (T2 / T1) can be 1 / 99 or more, can be 5 / 95 or more, can be 10 / 90 or more, or can be 15 / 85 or more. By increasing the above ratio (T2 / T1), it is easy to effectively exhibit the effects of the composition containing tackifying resin T2. Further, in some embodiments, the above ratio (T2 / T1) can be 9 / 1 or less, can be 7 / 3 or less, can be 5 / 5 or less, or can be 3 / 7 or less. By setting within the range of the above ratio (T2 / T1), it is easy to effectively exhibit the effects of the composition containing tackifying resin T1.

[0113] It should be noted that 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 rapidly at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate without forming bubbles. After cooling, the raised portion is cut off from the plane including the upper end of the ring using a slightly heated knife. Next, a support (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured to a depth of 90 mm or more. Then, a steel ball (diameter: 9.5 mm, weight: 3.5 g) and the ring filled with the sample are immersed in the glycerin without contacting each other, and the temperature of the glycerin is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed on the center of the surface of the sample in the ring and positioned at a fixed position on the support. Then, the distance from the upper end of the ring to the glycerin surface is maintained at 50 mm, a thermometer is placed so that the center of the mercury bulb of the thermometer is at the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating is brought into contact with the middle between the center and the edge of the bottom of the container to heat it evenly. It should be noted that the rate of increase in the bath temperature after reaching 40°C from the start of heating must be 5.0°C ± 0.5°C per minute. The temperature at which the sample gradually softens and flows off the ring and finally contacts the bottom plate is read and taken as the softening point. The softening point is measured for two or more samples, and the average value is used.

[0114] In the way that the adhesive contains a tackifying resin, the total amount (total content) of the tackifying resin in the adhesive is appropriately set within the range having a target tanδ at 23°C. The total amount (total content) of the above-mentioned tackifying resin can be, for example, about 1 part by weight or more, about 10 parts by weight or more, about 30 parts by weight or more, or about 40 parts by weight or more with respect to 100 parts by weight of the polyester polymer. In some ways, with respect to 100 parts by weight of the polyester polymer, the total amount of the above-mentioned tackifying resin is preferably 45 parts by weight or more. By having a composition containing a specified amount or more of the tackifying resin like this, an adhesive having a tanδ at 23°C of a specified value or more can be satisfactorily formed. In addition, the more the amount of the tackifying resin used, the more likely it is to obtain excellent adhesiveness. In some preferred ways, with respect to 100 parts by weight of the polyester polymer, the total amount of the tackifying resin is about 50 parts by weight or more, more preferably about 60 parts by weight or more, further preferably about 70 parts by weight or more, still further preferably about 80 parts by weight or more, particularly preferably about 90 parts by weight or more, can be about 100 parts by weight or more, or can be about 110 parts by weight or more. The upper limit of the total amount of the tackifying resin is not particularly limited. From the viewpoints of compatibility with the polyester polymer and tackiness, in some ways, with respect to 100 parts by weight of the polyester polymer, it can be about 200 parts by weight or less, about 160 parts by weight or less, or about 150 parts by weight or less (for example, less than 150 parts by weight). From the viewpoint of making the tanδ at 23°C a specified value or less to obtain good holding power, in some preferred ways, with respect to 100 parts by weight of the polyester polymer, the total amount of the above-mentioned tackifying resin is about 130 parts by weight or less, more preferably about 115 parts by weight or less, further preferably 110 parts by weight or less, particularly preferably about 105 parts by weight or less, can be about 100 parts by weight or less (for example, less than 100 parts by weight), can be about 90 parts by weight or less, or can be about 80 parts by weight or less.

[0115] In some ways, from the perspective of improving the overall biomass ratio of the adhesive, it is preferable to use a tackifying resin derived from plants (plant-based tackifying resin) as the above-mentioned tackifying resin. The plant-based tackifying resin is such that at least a part of the resin is composed of components derived from plants. It may also be the case that all of the resin is derived from plants, or that a part of the resin is derived from plants and another part is derived from fossil resources. Examples of the plant-based tackifying resin include the above-mentioned rosin-based tackifying resins and terpene-based tackifying resins. The plant-based tackifying resin can be used alone or in combination of two or more. In some preferred ways, the proportion of the plant-based tackifying resin in the total amount of the tackifying resin contained in the adhesive can be about 30% by weight or more, can be about 50% by weight or more, can be about 80% by weight or more, can be about 90% by weight or more, can also be about 95% by weight or more, and can further be 99% to 100% by weight. The technology disclosed herein can preferably be implemented in a manner that is substantially free of tackifying resins other than the plant-based tackifying resin.

[0116] (Crosslinking agent)

[0117] In some ways, the adhesive contains a crosslinking agent. For the adhesive containing a crosslinking agent, based on the crosslinked structure obtained by using the crosslinking agent, the cohesion can be improved. By using the crosslinking agent, the tanδ at 23°C can be adjusted and the holding power can be increased. The crosslinking agent can be included in the adhesive in the form after the crosslinking reaction, the form before the crosslinking reaction, the form in which part of the crosslinking reaction has occurred, their intermediate or composite forms, etc. The above-mentioned crosslinking agent is usually included in the adhesive only in the form after the crosslinking reaction. It should be noted that the crosslinking agent used in the crosslinking of polyester polymers can also function as a chain extender.

[0118] There is no particular limitation on the type of the crosslinking agent, and it can be appropriately selected and used from the crosslinking agents known in the past. As such a crosslinking agent, for example, the following can be cited: 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, etc. The crosslinking agent can be used alone or in combination of two or more. Among them, isocyanate-based crosslinking agents are preferred.

[0119] As the isocyanate-based crosslinking agent, a polyfunctional isocyanate compound can preferably be used. Here, the polyfunctional isocyanate compound refers to a compound having an average of two or more isocyanate groups per molecule, and includes polyfunctional isocyanate compounds having an isocyanurate structure. The isocyanate-based crosslinking agent can be used alone or in combination of two or more.

[0120] Examples of the polyfunctional isocyanate compound include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, aromatic polyisocyanate compounds, etc.

[0121] Specific examples of aliphatic polyisocyanate compounds include: 1,2-ethylene diisocyanate; butylene diisocyanates such as 1,2-butylene diisocyanate, 1,3-butylene diisocyanate, and 1,4-butylene diisocyanate; hexylene diisocyanates such as 1,2-hexylene diisocyanate, 1,3-hexylene diisocyanate, 1,4-hexylene diisocyanate, 1,5-hexylene diisocyanate, 1,6-hexylene diisocyanate, and 2,5-hexylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, etc.

[0122] Specific examples of alicyclic polyisocyanate compounds include: isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc.

[0123] Specific examples of aromatic polyisocyanate compounds include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrobiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyl diphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxy biphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, etc.

[0124] As the polyfunctional isocyanate, polyfunctional isocyanate compounds having on average 2 or more isocyanate groups per molecule can be exemplified. Such polyfunctional isocyanate compounds can be polymers (e.g., dimers or trimers), derivatives (e.g., addition reaction products of polyhydric alcohols and 2 or more molecules of polyfunctional isocyanates), polymers, etc. of bifunctional or trifunctional or higher isocyanates. For example, a dimer of diphenylmethane diisocyanate or a trimer of diphenylmethane diisocyanate, an isocyanurate form of hexamethylene diisocyanate (a trimer adduct having an isocyanurate structure), a reaction product of trimethylolpropane and toluene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, poly(methylene polyphenyl isocyanate), polyether polyisocyanate, polyester polyisocyanate and other polyfunctional isocyanate compounds can be cited. As commercially available products of such polyfunctional isocyanate compounds, products named "DURANATET TPA-100" manufactured by Asahi Kasei Chemicals Corporation, products named "DURANATET D101" manufactured by Asahi Kasei Chemicals Corporation, products named "Coronate HL" manufactured by Tosoh Corporation, products named "Coronate HK" manufactured by Tosoh Corporation, products named "Coronate HX" manufactured by Tosoh Corporation, products named "Coronate 2096" manufactured by Tosoh Corporation, etc. can be cited.

[0125] In some embodiments, as the crosslinking agent, a crosslinking agent without an aromatic ring (a crosslinking agent free of an aromatic ring) is preferably used. For example, among the above-mentioned isocyanate crosslinking agents, an isocyanate compound without an aromatic ring is preferably used. By using an isocyanate compound without an aromatic ring as the crosslinking agent, in an adhesive containing a polyester polymer, there is less crosslinking hindrance and the crosslinking degree can be effectively increased. As a preferred example of the above-mentioned isocyanate without an aromatic ring, aliphatic isocyanate compounds can be cited.

[0126] In some embodiments, from the viewpoint of balancing various adhesion characteristics, etc., two or more crosslinking agents having different numbers of functional groups (preferably isocyanate crosslinking agents) can be used. It should be noted that the above-mentioned functional group refers to a crosslinking reactive group, for example, in the above-mentioned polyfunctional isocyanate compounds, it refers to the isocyanate group. For example, a mode in which one or two or more bifunctional crosslinking agents and one or two or more trifunctional or higher crosslinking agents (e.g., trifunctional crosslinking agents) are used in combination as the crosslinking agent can be cited.

[0127] There is no particular limitation on the amount of the crosslinking agent used. In some embodiments, the amount of the crosslinking agent (such as an isocyanate crosslinking agent) used relative to 100 parts by weight of the polyester polymer may be about 0.005 parts by weight or more, for example, it may be about 0.01 parts by weight or more, it may be about 0.1 parts by weight or more. From the viewpoint of improving cohesion, it is appropriate to be about 0.5 parts by weight or more, and preferably about 1 part by weight or more. From the viewpoint of having a moderate tanδ at 23°C and improving the holding force, in some preferred embodiments, the amount of the crosslinking agent used relative to 100 parts by weight of the polyester polymer is about 1.2 parts by weight or more, more preferably about 1.5 parts by weight or more, further preferably about 1.8 parts by weight or more, for example, it may be 2.5 parts by weight or more, and it may also be 3.5 parts by weight or more. In addition, in some embodiments, the amount of the crosslinking agent used relative to 100 parts by weight of the polyester polymer may be about 10 parts by weight or less, for example, it may be about 7 parts by weight or less. From the viewpoint of having a sufficient compression deformability with a tanδ at 23°C above a specified value, in some preferred embodiments, the amount of the crosslinking agent used relative to 100 parts by weight of the polyester polymer is about 5 parts by weight or less, more preferably about 4 parts by weight or less, further preferably about 3 parts by weight or less, particularly preferably about 2.5 parts by weight or less, it may be about 2.0 parts by weight or less, and it may also be about 1.6 parts by weight or less.

[0128] There is no particular limitation on the amount of the crosslinking agent without an aromatic ring used. In some embodiments, the amount of the crosslinking agent without an aromatic ring (such as an aliphatic isocyanate compound) used relative to 100 parts by weight of the polyester polymer may be about 0.005 parts by weight or more, for example, it may be about 0.01 parts by weight or more, it may be about 0.1 parts by weight or more. From the viewpoint of improving cohesion, it is appropriate to be about 0.5 parts by weight or more, and preferably about 1 part by weight or more. From the viewpoint of having a moderate tanδ at 23°C and improving the holding force, in some preferred embodiments, the amount of the crosslinking agent without an aromatic ring used relative to 100 parts by weight of the polyester polymer is about 1.2 parts by weight or more, more preferably about 1.5 parts by weight or more, further preferably about 1.8 parts by weight or more, for example, it may be 2.5 parts by weight or more, and it may also be 3.5 parts by weight or more. In addition, in some embodiments, the amount of the crosslinking agent without an aromatic ring used relative to 100 parts by weight of the polyester polymer may be about 10 parts by weight or less, for example, it may be about 7 parts by weight or less. From the viewpoint of having a sufficient compression deformability with a tanδ at 23°C above a specified value, in some preferred embodiments, the amount of the crosslinking agent without an aromatic ring used relative to 100 parts by weight of the polyester polymer is about 5 parts by weight or less, more preferably about 4 parts by weight or less, further preferably about 3 parts by weight or less, particularly preferably about 2.5 parts by weight or less, it may be about 2.0 parts by weight or less, and it may also be about 1.6 parts by weight or less.

[0129] (Crosslinking catalyst)

[0130] In the technology disclosed herein, in order to carry out the crosslinking reaction more effectively, in addition to using the above crosslinking agent, it is preferable to use a crosslinking catalyst. As the crosslinking catalyst, zirconium-containing compounds (zirconium-containing catalysts) such as zirconium acetylacetonate, monoacetylacetonate zirconium, zirconium ethylacetoacetate, and zirconium octoate compounds can be cited; tin (Sn)-containing compounds (tin-containing catalysts) such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, trimethyltin hydroxide, and butyltin oxide; aluminum-containing compounds (aluminum-containing catalysts) such as sec-butoxyaluminum, aluminum acetylacetonate, aluminum diethylacetoacetate, and aluminum triethylacetoacetate; iron-containing compounds (iron-containing catalysts) such as NACEM iron(III) (iron(III) acetylacetonate); titanium-containing compounds (titanium-containing catalysts) such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, titanium acetylacetonate, tetraacetylacetonate titanium, and titanium ethylacetoacetate; and other organometallic catalysts. The crosslinking catalyst can be used alone or in combination of two or more.

[0131] Although there is no particular limitation, in some embodiments, it is preferable to use a tin-containing compound with high catalyst activity as the crosslinking catalyst. Alternatively, in some other embodiments, from the viewpoints of environmental impact and safety, a non-tin-containing compound can be used as the above crosslinking catalyst. In this embodiment, the crosslinking catalyst can substantially not contain a tin-containing compound. In addition, in some embodiments, the crosslinking catalyst does not contain an iron-containing catalyst. For example, in the usage mode where the adhesive is required to have transparency and optical properties, by avoiding the use of iron-containing compounds, coloring of the adhesive can be prevented or suppressed.

[0132] The usage amount of the crosslinking catalyst is not particularly limited. With respect to 100 parts by weight of the polyester polymer, the usage amount of the crosslinking catalyst can be, for example, about 0.001 part by weight or more, and it is appropriate to be about 0.01 part by weight or more. In addition, with respect to 100 parts by weight of the polyester polymer, the usage amount of the crosslinking catalyst can be, for example, about 3 parts by weight or less, and it is appropriate to be about 1 part by weight or less, can be about 0.3 part by weight or less, and can also be about 0.1 part by weight or less.

[0133] (Hydrolysis-resistant agent)

[0134] In addition, the adhesive disclosed herein can 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 inhibited, and good durability can be easily obtained. There is no particular limitation on the hydrolysis-resistant agent, and known or commonly used hydrolysis-resistant agents can be used. For example, it can be cited: containing Compounds containing oxazoline groups, compounds containing epoxy groups, compounds containing carbodiimide groups, etc. Among them, compounds containing carbodiimide groups are preferred. The hydrolysis-resistant agent can be used alone or in combination of two or more.

[0135] Examples of the compound containing a carbodiimide group include: dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, tert-butylisopropylcarbodiimide, diphenylcarbodiimide, di-tert-butylcarbodiimide, di-β-naphthylcarbodiimide, monofunctional cyclic structure carbodiimide, etc. Here, the monofunctional cyclic structure carbodiimide refers to a compound having one carbodiimide group in the molecular structure, and the first nitrogen atom and the second nitrogen atom of the carbodiimide group are bonded through a bonding group composed of an aliphatic group, an alicyclic group, an aromatic group or a combination thereof. It should be noted that the above bonding group may contain heteroatoms and substituents. Preferred examples of the compound containing a carbodiimide group include: dicyclohexylcarbodiimide, diisopropylcarbodiimide, monofunctional cyclic structure carbodiimide.

[0136] The amount of the hydrolysis-resistant agent (appropriately a compound containing a carbodiimide group) used is not particularly limited. In order to preferably exert the effect of the composition containing the hydrolysis-resistant agent, it is appropriate that the amount of the hydrolysis-resistant agent used is about 0.05 parts by weight or more, preferably about 0.1 parts by weight or more, for example, it can be about 0.3 parts by weight or more, based on 100 parts by weight of the polyester polymer. The upper limit of the amount of the above hydrolysis-resistant agent used is, for example, appropriately about 5 parts by weight or less, preferably about 3 parts by weight or less, and can be, for example, 1 part by weight or less, based on 100 parts by weight of the polyester polymer.

[0137] (Other additives)

[0138] In the adhesive, in addition to the above components, various additives commonly used in the field of adhesives such as a leveling agent, a filler, a plasticizer, a softening agent, a coloring agent (pigment, dye, etc.), an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, a light stabilizer, etc. may be included as needed. For the above various additives, conventionally known substances can be used by conventional methods, which is not the feature of the present invention, so the detailed description is omitted.

[0139] (Formation of the adhesive)

[0140] The adhesives disclosed herein can be formed, for example, from the above-described polyester polymers by conventionally known methods. For example, after applying an adhesive composition onto a releasable surface (release surface), a layer-like adhesive (adhesive layer) can be formed on the surface by curing the adhesive composition. The adhesive formed in this form can be used as a substrate-free double-sided adhesive sheet. In addition, in the case of an adhesive sheet with a substrate, a method (direct method) of directly applying (typically coating) the adhesive composition onto the substrate and curing it to form an adhesive (layer) can be preferably employed. Alternatively, a method (transfer method) of applying the adhesive composition onto a releasable surface (release surface), curing it to form an adhesive (layer) on the surface, and transferring the adhesive (layer) onto the substrate can also be used. As the above-described release surface, the surface of a release liner, the back surface of a substrate after release treatment, etc. can be utilized. In addition, the curing of the adhesive composition can be carried out by subjecting the adhesive composition to curing treatments such as drying, crosslinking, polymerization, cooling, etc. Two or more curing treatments can be carried out simultaneously or in stages. As the adhesive composition, there is no particular limitation, but from the viewpoints of adhesive properties, etc., a solvent-based adhesive composition in a form containing an adhesive in an organic solvent is preferably used. 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, ethyl acetate is preferably used. It should be noted that the adhesive (layer) disclosed herein is typically formed continuously, but is not limited to such a manner, and can be, for example, an adhesive layer formed in a regular or irregular pattern such as dots, stripes, etc.

[0141] Coating of the adhesive composition can be carried out, for example, using known or conventional coaters such as a gravure roll coater, a reverse roll coater, a roll kiss coater, an impregnating roll coater, a slot die coater, a bar coater, a knife coater, a spray coater, etc. Alternatively, the adhesive composition can also be coated by infiltration, curtain coating method, etc.

[0142] Drying of the adhesive composition can be carried out at normal temperature or under heating. From the viewpoints of promoting crosslinking reaction, improving manufacturing efficiency, etc., drying of the adhesive composition is preferably carried out under heating. The drying temperature can be, for example, about 40°C to about 150°C, and is usually preferably about 40°C to about 130°C. After drying the adhesive composition, it is preferably further aged for the purposes of adjusting the movement of components within the adhesive (layer), promoting the crosslinking reaction, relaxing the strain that may exist within the adhesive (layer), etc. The aging conditions are not particularly limited, and can generally be conditions of about 70°C or lower (for example, about 40°C to about 70°C) and one day or more (for example, three days or more).

[0143] (Biomass ratio of the adhesive)

[0144] Although not particularly limited, the adhesive preferably has a biomass ratio equal to or higher than a specified value. In some embodiments, the biomass ratio of the adhesive may be about 30% or higher, suitably about 40% or higher, and preferably 50% or higher. By designing in such a way that the biomass ratio of the adhesive becomes higher, the overall dependence of the adhesive on fossil resource-based materials can be reduced. From the viewpoint of further reducing the dependence on fossil resource-based materials, in some preferred embodiments, the biomass ratio of the adhesive may be 55% or higher, may be 60% or higher, may be 70% or higher, or may be 75% or higher. The upper limit of the biomass ratio is 100% by definition, but in the adhesives disclosed herein, since the components contained therein may include materials derived from fossil resources, the biomass ratio may be less than 100%. From the viewpoint of easily obtaining compression deformability and good adhesion characteristics (such as holding power), in some embodiments, the biomass ratio of the adhesive may be less than 90%, for example, and in cases where adhesion performance is more emphasized, the biomass ratio of the adhesive may be less than 80% or may be less than 70%.

[0145] <Adhesive sheet>

[0146] The adhesive sheet disclosed herein is constituted by including a layer containing the above-described adhesive, i.e., an adhesive layer. The adhesive sheet may be, for example, in the form of a substrate-free double-sided adhesive sheet having a first adhesive surface formed by one surface of the adhesive layer and a second adhesive surface formed by the other surface of the adhesive layer. Alternatively, the adhesive sheet disclosed herein may be in the form of a substrate-containing adhesive sheet in which the above-described adhesive layer is laminated on one or both sides of a support substrate. Hereinafter, the support substrate may sometimes be simply referred to as the "substrate".

[0147] (Constitution example)

[0148] The structure of an adhesive sheet of one embodiment is schematically shown in Figure 1 FIG. The adhesive sheet 1 is constituted in the form of a substrate-free double-sided adhesive sheet composed of an adhesive layer 21. The adhesive sheet 1 is used by attaching a first adhesive surface 21A formed by one surface (first surface) of the adhesive layer 21 and a second adhesive surface 21B formed by the other surface (second surface) of the adhesive layer 21 to different portions of an adherend. The portions to which the adhesive surfaces 21A and 21B are attached may be respective portions of different members or may be different portions within a single member. The adhesive sheet 1 before use (i.e., before being attached to the adherend) may be as shown in Figure 1The constituent elements of the adhesive sheet 100 with a release liner are shown in a form in which the first adhesive surface 21A and the second adhesive surface 21B are protected by release liners 31 and 32, respectively, having a release surface on at least the side facing the adhesive layer 21. As the release liners 31 and 32, for example, a release liner formed by providing a release layer formed of a release treatment agent on a single surface of a sheet-like base material (liner base material) and having the single surface as the release surface can be preferably used. Alternatively, the release liner 32 may be omitted, and a release liner 31 having release surfaces on both sides may be used, and it may be overlapped with the adhesive sheet 1 and wound in a spiral shape, whereby the second adhesive surface 21B is in contact with the back surface of the release liner 31 and is protected (roll form) in the form of an adhesive sheet with a release liner.

[0149] The structure of the adhesive sheet of another embodiment is schematically shown in Figure 2 FIG. The adhesive sheet 2 is formed in the form of a single-sided adhesive sheet with a base material, and the single-sided adhesive sheet with a base material has: a sheet-like support base material (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 base material 10, that is, it is provided on the first surface 10A side of the support base material 10 in a manner not intended to separate the adhesive layer 21 from the support base material 10. Before use, the adhesive sheet 2 can be as shown in Figure 2 FIG. The constituent elements of the adhesive sheet 200 with a release liner are shown in a form in which the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31 having a release surface on at least the side facing the adhesive layer 21. Alternatively, the release liner 31 may be omitted, and the support base material 10 having the second surface 10B as the release surface may be used to wind the adhesive sheet 2, whereby the adhesive surface 21A is in contact with the second surface (back surface) 10B of the support base material 10 and is protected (roll form).

[0150] The structure of the adhesive sheet of another embodiment is schematically shown in Figure 3 FIG. The adhesive sheet 3 is formed in the form of a double-sided adhesive sheet with a base material, and the double-sided adhesive sheet with a base material has: a sheet-like support base material (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 as shown in Figure 3The constituent elements of the adhesive sheet 300 with a release liner are shown 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. Alternatively, the release liner 32 may be omitted, and a release liner 31 having release surfaces on both sides may be used. The release liner 31 is overlapped with the adhesive sheet 3 and wound in a spiral shape, thereby forming a form (roll form) of the adhesive sheet with a release liner in which the second adhesive surface 22A is in contact with the back surface of the release liner 31 and is protected.

[0151] It should be noted that in the above-described double-sided adhesive sheet with a substrate, at least one of the first adhesive layer and the second adhesive layer (for example, the first adhesive layer) may be an adhesive layer containing the above-described adhesive, and the other adhesive layer (for example, the second adhesive layer) may be an adhesive layer containing the above-described adhesive or may be an adhesive layer having a composition different from that of the adhesive layer containing the adhesive disclosed herein (specifically, the above-described one adhesive layer. For example, the first adhesive layer). Such another adhesive layer may be formed of a known or conventional adhesive, for example.

[0152] Although not particularly limited, the technology disclosed herein can preferably be 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 easily thinned, and is also advantageous in terms of being able to maximize adhesive properties such as adhesive force and holding force. In addition, in the substrate-free double-sided adhesive sheet, the compressive deformability based on the 23°C tanδ of the adhesive layer can be maximally utilized by making the most of the thickness of the adhesive layer.

[0153] As the above-described 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 containing a low tack material such as a polyolefin resin (for example, polyethylene, polypropylene) or a fluororesin, etc. can be used. The above-described release treatment layer can be formed, for example, by subjecting the above-described liner substrate to a surface treatment with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide-based agent. 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 containing a low tack material is preferred.

[0154] It should be noted that the concept of the adhesive sheet herein may include articles referred to as adhesive tapes, adhesive films, adhesive labels, etc. The adhesive sheet may be in a roll form, a single sheet form, or a form obtained by appropriately cutting, die-cutting, etc. according to the use and usage method.

[0155] (Adhesive layer)

[0156] The adhesive layer is a layer containing the above-mentioned 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 about 500 μm. From the viewpoint of the adhesiveness to the adherend, in some embodiments, the thickness of the adhesive layer is usually preferably 3 μm or more, more preferably 5 μm or more. From the viewpoints of improving the adhesive strength and effectively obtaining the effect of the compressive 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, further preferably 15 μm or more, and particularly preferably 18 μm or more. In addition, from the viewpoints of weight reduction, miniaturization, thickness reduction, and high functionality of the articles (such as portable electronic devices) using the adhesive sheet, in some embodiments, the thickness of the adhesive layer can be 200 μm or less, can be 150 μm or less, and can also be 100 μm or less (for example, less than 100 μm). In some preferred embodiments, the thickness of the adhesive layer is preferably less than 80 μm, more preferably 50 μm or less, still more preferably 35 μm or less, further preferably 30 μm or less, and in embodiments where more emphasis is placed on thinness, the thickness of the adhesive layer is particularly preferably 25 μm or less, and can be, for example, 22 μm or less. In the case where the adhesive sheet disclosed herein is a double-sided adhesive sheet having adhesive layers on both sides of the substrate, the thicknesses of the respective adhesive layers can be the same or different. The thicknesses of the above-mentioned respective adhesive layers can be selected, for example, from the ranges exemplified as the thickness of the adhesive layer.

[0157] (Substrate)

[0158] The adhesive sheet disclosed herein can be in the form of a substrate-containing adhesive sheet having an adhesive layer on one or both sides of the substrate. As the substrate, various sheet-like substrates can be used, for example, resin films, papers, cloths, rubber sheets, foamed sheets, metal foils, composites thereof, etc. In the field of electronic devices, substrates that are not likely to be a source of dust (such as fine fibers or particles like paper powder) are preferably used. From this viewpoint, substrates that do not contain fibrous materials such as paper and cloth are preferred, and for example, resin films, rubber sheets, foamed sheets, metal foils, composites thereof, etc. can be preferably used.

[0159] 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 foamed sheet include: foamed polyurethane sheet, foamed polyolefin sheet, etc. Examples of the metal foil include: aluminum foil, copper foil, etc.

[0160] As the above-mentioned base material, it is appropriate to use a resin film. The resin film is preferably used as a material with excellent dimensional stability, thickness accuracy, economy (cost), processability, and tensile strength. In addition, since the resin film (such as a polyester film such as a PET film described later) can be recycled, regardless of whether materials derived from plants are used or not, by reusing the used resin film, continuous reproduction can be carried out, and the environmental load can be reduced. Such a recyclable resin film and a resin film that has been recycled are also called recycled films. The recyclability of such a resin film can also be applied to the resin film used for the above-mentioned release liner. It should be noted that in this specification, the "resin film" is typically a non-porous film, which is a concept different from so-called non-woven fabrics and woven fabrics.

[0161] In some embodiments, from the viewpoints of strength and processability, a polyester film can be preferably used 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.

[0162] In some embodiments, from the viewpoint of reducing the usage amount of fossil resource-based materials, the base material preferably contains a biomass material. The biomass material that can constitute the above-mentioned base material is not particularly limited. For example, it can include: biomass polyesters such as biomass PET and biomass poly(1,3-propanediol 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(polyphthalamide of sebacic acid and m-xylene diamine); biomass polyurethanes such as biomass polyester ether urethane and biomass polyether urethane; cellulose-based resins; etc. These substances can be used alone or in combination of two or more. Among them, biomass PET and biomass PTT are preferred, and biomass HDPE, biomass LDPE, biomass LLDPE, biomass PP, and biomass PET are particularly preferred. Since the above-mentioned biomass materials are resin materials, they can be preferably applied to the constitution where the base material is a resin film. By using the above-mentioned biomass materials, the usage amount of fossil resource-based materials can be reduced in the adhesive sheet with a resin film as the base material.

[0163] In the adhesive sheet having a substrate, the biomass ratio of the substrate is preferably 20% or more, more preferably 35% or more. In cases where more importance is attached to reducing the usage amount of fossil resource-based materials, the biomass ratio of the substrate can be, for example, 50% or more, can be 70% or more, can be 85% or more, can be 90% or more. The upper limit of the above-mentioned biomass ratio is 100% or less, but in some embodiments, considering processability, strength, etc., the biomass ratio of the substrate can be, for example, 80% or less, can be 60% or less, can be 40% or less, can be less than 20%.

[0164] The substrate can have transparency, or can have light barrier properties and light reduction properties. In some embodiments, a colorant can be included in the substrate (e.g., a resin film). Thereby, the light transmittance (light barrier property) of the substrate can be adjusted. Adjusting the light transmittance of the substrate (e.g., the perpendicular light transmittance) can also contribute to the adjustment of the light transmittance of the substrate and the adhesive sheet including the substrate.

[0165] As the colorant, similar to the colorant that can be included in the adhesive layer, conventionally known pigments and dyes can be used. The colorant is not particularly limited, and can be, for example, a colorant such as black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent color, etc.

[0166] The substrate can be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In a substrate having a structure including a base film and a colored layer like this, the above-mentioned base film can include a colorant or can not include a colorant. The above-mentioned colored layer can be disposed on any one surface of the base film, or can be respectively disposed on two surfaces. In a structure where colored layers are respectively disposed on two surfaces of the base film, the structures of these colored layers can be the same or different. By disposing the colored layer, the hue and transmittance of the adhesive sheet can be adjusted, and desired designability, light barrier property, and masking property can be obtained. The color of the colored layer is not particularly limited, and various colors can be adopted according to the purpose. In some embodiments, the colored layer can be, for example, a black layer (e.g., a black printing layer) formed by black printing.

[0167] The colored layer can be formed, for example, by coating a colored layer-forming composition containing a colorant and a binder on the base film. As the binder, materials known in the coating or printing field can be used without particular limitation. For example, polyurethane, phenolic resin, epoxy resin, urea melamine resin, polymethyl methacrylate, etc. can be exemplified. The colored layer-forming composition can be, for example, solvent-based, ultraviolet curable, heat curable, etc. The formation of the colored layer can be carried out by means conventionally used in the formation of colored layers without particular limitation. For example, a method of forming a colored layer (printing layer) by printing such as gravure printing, flexographic printing, offset printing, etc. can be preferably adopted.

[0168] The coloring layer may be a single-layer structure composed entirely of one layer, or a multi-layer structure including two, three or more sub-coloring layers. The coloring layer of the multi-layer structure including two or more sub-coloring layers can be formed, for example, by repeatedly coating (e.g., printing) the composition for forming the coloring layer. The colors and compounding amounts of the colorants contained in each sub-coloring layer may be the same or different. In the coloring layer for imparting light-blocking properties, it is particularly meaningful to form a multi-layer structure from the viewpoint of preventing the generation of pinholes and improving the reliability of light leakage prevention.

[0169] As the colorant for coloring the coloring layer, known pigments and dyes corresponding to the target color can be appropriately selected. Although there is no particular limitation, examples of white pigments include titanium dioxide, zinc oxide, lead white, etc. Examples of black pigments include carbon black, acetylene black, pine soot, graphite, etc. These can be used alone or in combination of two or more.

[0170] The content of the colorant is set according to the required hue (color tone), light transmittance, etc., and thus is not limited to a specific range. In the coloring layer, the content of the colorant is preferably about 1% by weight or more, more preferably 2% by weight or more (e.g., 5% by weight or more), and can be 15% by weight or more. In addition, the content of the above-mentioned colorant is preferably about 65% by weight or less, more preferably 30% by weight or less (e.g., 15% by weight or less), and can be 8% by weight or less.

[0171] The overall thickness of the coloring layer is usually preferably 0.1 μm or more, more preferably 0.5 μm or more, and still more preferably 0.7 μm or more. The overall thickness of the coloring layer can be about 0.8 μm or more, and can be about 1 μm or more. In other embodiments, from the viewpoint of obtaining sufficient light-blocking properties, the overall thickness of the coloring layer can be 2 μm or more (e.g., 3 μm or more), and can also be 4 μm or more. In addition, the above-mentioned overall thickness of the coloring layer is usually preferably 10 μm or less, more preferably 7 μm or less, and still more preferably 5 μm or less. In some embodiments, the overall thickness of the coloring layer can be about 3 μm or less, and further can be about 2 μm or less. In the coloring layer including two or more sub-coloring layers, the thickness of each sub-coloring layer is usually preferably about 0.5 μm to about 2 μm.

[0172] Known or conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and formation of a primer coat can be applied to the surface (the side surface on the adhesive layer side) of a base material (such as a resin film, a rubber sheet, a foam sheet, etc.) where the adhesive layer is to be disposed. Such surface treatment can be a treatment for improving the adhesion between the base material and the adhesive layer, in other words, the anchoring property of the adhesive layer to the base material. Alternatively, the above base material can be a base material that has not been subjected to surface treatment such as improving the anchoring property on the side surface on the adhesive layer side. In the case of forming a primer coat, the primer (primer coat agent) used in the formation is not particularly limited and can be appropriately selected from known primer coat agents. The thickness of the primer coat is not particularly limited. For example, it can be greater than 0.01 μm, and usually 0.1 μm or more is appropriate. From the viewpoint of improving the effect, it can be 0.2 μm or more. In addition, the thickness of the primer coat is preferably less than 1.0 μm, and can be 0.7 μm or less, and can be 0.5 μm or less. Generally, primer coat agents have a high dependence on fossil resource-based materials. Therefore, from the viewpoint of increasing the biomass ratio of the adhesive sheet described later, it is advantageous that the thickness of the primer coat is not too large.

[0173] In the case of a single-sided adhesive sheet having an adhesive layer provided on one side of a base material, a release treatment can be performed on the surface (the back surface) of the base material where the adhesive layer is not formed using a release treatment agent (back surface treatment agent). As the back surface treatment agent that can be used in the formation of the back surface treatment layer, there is no particular limitation, and a silicone-based back surface treatment agent, a fluorine-containing back surface treatment agent, a long-chain alkyl-based back surface treatment agent, or other known or conventional treatment agents can be used according to the purpose and application. The back surface treatment agent can be used alone or in combination of two or more.

[0174] Various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.) can be incorporated into the base material (such as a resin film base material) as needed. The blending ratio of various additives is usually about 30% by weight or less. For example, it can be about 20% by weight or less, or can be about 10% by weight or less. For example, when the base material contains a pigment (such as a white pigment), its content ratio is appropriately about 0.1% by weight to about 10% by weight (such as about 1% by weight to about 8% by weight or about 1% by weight to about 5% by weight).

[0175] The thickness of the base material is not particularly limited and can be appropriately selected according to the purpose. Generally, it is about 1 μm to about 500 μm. From the perspective of the processability of the base material, the thickness of the above-mentioned base material can 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. In addition, from the perspective of thinning the adhesive sheet, in some embodiments, the thickness of the base material can 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, less than 4 μm.

[0176] (Total thickness)

[0177] The thickness (total thickness) of the adhesive sheet (including the adhesive layer, and the base material in the adhesive sheet with a base material but not including the release liner) disclosed herein is not particularly limited. For example, it can be in the range of about 2 μm to about 1000 μm. In some embodiments, considering the adhesion characteristics and the like, the thickness of the adhesive sheet is preferably about 5 μm to about 500 μm. For example, it can be 300 μm or less, or 200 μm or less. From the perspectives of lightening the weight, miniaturizing, thinning the thickness, and enhancing the functionality of the article (such as a portable electronic device) to which the adhesive sheet is applied, in some preferred embodiments, the thickness of the adhesive sheet is 100 μm or less, more preferably 70 μm or less, further preferably 50 μm or less, and particularly preferably 35 μm or less. For example, it can be 30 μm or less, or 25 μm or less. The lower limit value of the thickness of the adhesive sheet is not particularly limited. For example, it can be about 5 μm or more, and from the perspective of productivity, it can be about 10 μm or more, or about 15 μm or more (such as about 18 μm or more).

[0178] (Properties of the adhesive sheet)

[0179] In some embodiments, the 180-degree peel strength of the adhesive sheet on a stainless steel plate (adhesion to SUS) is preferably 10 N / 20 mm or more. The adhesive sheet showing the above characteristics firmly adheres to the adherend, so typically it can be preferably used in a manner that it is not intended to be peeled off again. From the perspective of achieving a more reliable bond, in some preferred embodiments, the above adhesion to SUS is 12 N / 20 mm or more, more preferably 14 N / 20 mm or more, further preferably 16 N / 20 mm or more, can 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. In some embodiments, the above adhesion can 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 following examples.

[0180] In some embodiments, in the holding force test of the adhesive sheet conducted under the conditions of 40 °C, a load of 500 g, and 1 hour, the offset distance after the holding force test is preferably less than 0.6 mm. The adhesive sheet having the above characteristics can exhibit good holding performance. From the perspective of achieving higher holding performance, the above offset distance is more preferably less than 0.5 mm, further preferably 0.3 mm or less, and particularly preferably 0.1 mm or less. The lower limit of the above offset distance is 0.0 mm, which means that no offset is observed in the above holding force test. The above holding force test is specifically conducted by the method described in the following examples.

[0181] In some embodiments, in the compression test of the adhesive sheet (typically a substrate-free adhesive sheet) or the adhesive conducted at a compression speed of 1 mm / minute, the deformation rate when the compressive stress is 0.35 MPa is preferably 20% or more. The adhesive sheet and the adhesive having the above compression deformation rate are easily deformed during compression. For example, when pressed against a thin and low-rigidity adherend, the load generated by pressing against the adherend can be reduced, and deformation of the adherend can be prevented. From this perspective, in some preferred embodiments, the above deformation rate is 22% or more, further preferably 25% or more, particularly preferably 27% or more, can be 30% or more, or can be 33% or more. In addition, from the perspectives of balancing with the holding force, adhesive properties, etc., the upper limit of the above compression deformation rate can be, for example, 50% or less, or 40% or less. The above compression test is specifically conducted by the method described in the following examples.

[0182] Although not particularly limited, in some embodiments, it is preferred that about 30% or more of the total carbon contained in the adhesive sheet is carbon derived from biomass. That is, the biomass ratio of the adhesive sheet is preferably 30% or more. By using an adhesive sheet with such a high biomass ratio, the usage amount of fossil resource-based materials can be reduced. From this perspective, in some preferred embodiments, the biomass ratio of the adhesive sheet is 40% or more, can be 50% or more, can be 60% or more, can be 70% or more, or can be 75% or more. The upper limit of the above biomass ratio is 100% by definition, but it is sometimes not effective in terms of productivity, performance, etc. to make all the materials constituting the adhesive sheet come from plants. Therefore, the above biomass ratio can be less than 100%. From the perspective of easily obtaining compression deformability and good adhesive properties (such as holding force), in some embodiments, the biomass ratio of the adhesive sheet can be, for example, 90% or less. In cases where adhesive performance is more emphasized, it can be 80% or less, or 70% or less. It should be noted that in a substrate-free adhesive sheet composed of an adhesive layer, the biomass ratio of the adhesive layer is the same as that of the entire adhesive sheet.

[0183] <Usage>

[0184] The uses of the adhesive sheet disclosed herein are not particularly limited and can be used for various purposes without limitation. For example, the adhesive sheet can be used in a manner of being pasted on the components constituting an electronic device, for purposes such as fixing, joining, and strengthening of the components. For example, in the use mode of being pasted on a thin component constituting an electronic device, by utilizing the compressive deformability of the adhesive, the load on the component as the adherend during the crimping of the adhesive sheet can be reduced, and deformation of the component can be prevented. The adhesive sheet disclosed herein can be preferably used, for example, in the form of a double-sided adhesive sheet for the purpose of fixing or joining components. The above double-sided adhesive sheet may or may not have a substrate.

[0185] The adhesive sheet disclosed herein is suitable, for example, for the use of fixing components in portable electronic devices. Various components constituting portable electronic devices have strong requirements for thinning due to the requirements of light weight, miniaturization, high functionality, etc. As described above, the adhesive sheet disclosed herein can utilize the compressive deformability of the adhesive to prevent deformation of the component as the adherend, and has good holding force. Therefore, it is particularly suitable as a highly reliable adhesive means for thin components constituting portable electronic devices. Non-limiting examples of the above portable electronic devices include: mobile phones, smart phones, tablet personal computers, notebook personal computers, various wearable devices (such as wrist-worn types like watches, module types worn on a part of the body with clips or straps, eye-worn types including glasses types (monocular, binocular. Also includes helmet types), clothing types worn on shirts, socks, hats, etc. in the form of ornaments, ear-worn types worn on ears like earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, voice recorders, etc.), calculators (desktop calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, e-books, in-vehicle information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. It should be noted that in this specification, "portable" is not merely interpreted as being able to be carried, but means having a level of portability that can be relatively easily carried by an individual (standard adult).

[0186] Figure 4 To schematically show an example of a portable electronic device (smart phone) using the adhesive sheet disclosed herein. As Figure 4As shown, a battery (heating element) 540 is built inside a housing 520 of a portable electronic device 500. In addition, the portable electronic device 500 is configured to include an adhesive sheet 550. In this configuration example, the adhesive sheet 550 has the form of a sheet (double-sided adhesive sheet) with double-sided adhesive properties for fixing components constituting the portable electronic device 500. It should be noted that the portable electronic device 500 has a touch panel 570 in which a display unit also functions as an input unit. The adhesive sheet disclosed herein is preferably used as a component (component joining means) of the above-described portable electronic device.

[0187] The matters disclosed in this specification include the following.

[0188] [1] A portable electronic device, wherein the portable electronic device has: a housing, and a touch panel in which a display unit also functions as an input unit, a heating element (such as a battery) is built inside the housing, and among the plurality of components constituting the portable electronic device, at least a first component and a second component are joined by an adhesive sheet, the adhesive sheet has an adhesive layer, the adhesive layer contains a polyester-based polymer, and the tanδ of the adhesive layer at 23 °C is 0.35 or more and 0.80 or less.

[0189] [2] The portable electronic device according to [1] above, wherein the polyester-based polymer contains a structure derived from dimer acid.

[0190] [3] The portable electronic device according to [1] or [2] above, wherein, relative to 100 parts by weight of the polyester-based polymer, the adhesive layer contains 45 parts by weight or more of a tackifying resin.

[0191] [4] The portable electronic device according to [3] above, wherein the tackifying resin contains a tackifying resin T1 having a softening point of 60 °C or more and 150 °C or less.

[0192] [5] The portable electronic device according to [3] or [4] above, wherein the tackifying resin contains a tackifying resin T T , the tackifying resin T T contains a structure derived from terpene.

[0193] [6] An adhesive, wherein the adhesive contains a polyester-based polymer, and the tanδ of the adhesive at 23 °C is 0.35 or more and 0.80 or less.

[0194] [7] The adhesive according to [6] above, wherein the polyester-based polymer contains a structure derived from dimer acid.

[0195] [8] The adhesive as described in [6] or [7] above, wherein, based on 100 parts by weight of the polyester polymer, the adhesive contains 45 parts by weight or more of a tackifying resin.

[0196] [9] The adhesive as described in [8] above, wherein the tackifying resin contains a tackifying resin T1 having a softening point of 60 °C or higher and 150 °C or lower.

[0197]

[10] The adhesive as described in [8] or [9] above, wherein the tackifying resin contains a tackifying resin T T , and the tackifying resin T T contains a structure derived from terpene.

[0198]

[11] An adhesive sheet having an adhesive layer, wherein the adhesive layer contains a polyester polymer, and the tanδ of the adhesive layer at 23 °C is 0.35 or higher and 0.80 or lower.

[0199]

[12] The adhesive sheet as described in

[11] above, wherein the 180-degree peel strength of the adhesive sheet from a stainless steel plate is 10 N / 20 mm or higher.

[0200]

[13] The adhesive sheet as described in

[11] or

[12] above, wherein the polyester polymer contains a structure derived from dimer acid.

[0201]

[14] The adhesive sheet as described in any one of

[11] to

[13] above, wherein, based on 100 parts by weight of the polyester polymer, the adhesive layer contains 45 parts by weight or more of a tackifying resin.

[0202]

[15] The adhesive sheet as described in

[14] above, wherein the tackifying resin contains a tackifying resin T1 having a softening point of 60 °C or higher and 150 °C or lower.

[0203]

[16] The adhesive sheet as described in

[14] or

[15] above, wherein the tackifying resin contains a tackifying resin T T , and the tackifying resin T T contains a structure derived from terpene.

[0204]

[17] The adhesive sheet as described in any one of

[11] to

[16] above, wherein the adhesive sheet is used for a portable electronic device.

[0205]

[18] A portable electronic device, wherein the portable electronic device contains the adhesive sheet as described in any one of

[11] to

[16] above.

[0206] Examples

[0207] Hereinafter, some embodiments of the present invention will be described, but the present invention is not intended to be limited to the content shown in these embodiments. It should be noted that, unless otherwise specified, "parts" and "%" in the following description are based on weight.

[0208] <Evaluation method>

[0209] [Adhesion to SUS]

[0210] The adhesive sheet is cut into a size of 20 mm in width and 150 mm in length to prepare a measurement sample. In an environment of 23°C and 50% RH, the adhesive surface of the above measurement sample is exposed, and a 2-kg rubber roller is reciprocated once to press the adhesive surface of the above measurement sample against a stainless steel plate (SUS304BA plate) as the adherend. It is left in an environment of 23°C and 50% RH for 30 minutes, and then, in the same environment, using a tensile testing machine, according to JIS Z0237:2000, the peel strength (adhesion to SUS) [N / 20 mm] is measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. As the tensile testing machine, a universal tensile-compression testing machine (device name "Tensile-Compression Testing Machine, TCM-1kNB", manufactured by Minebea Co., Ltd.) can be used.

[0211] It should be noted that when measuring the adhesion to SUS, if necessary (for example, in the case of a double-sided adhesive sheet without a substrate, in the case of an adhesive sheet with a substrate and the substrate is easily deformed, etc.), an appropriate backing material can be pasted on 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 is used in the examples.

[0212] [Retention force]

[0213] The adhesive sheet was cut into pieces with a width of 10 mm and a length of 100 mm to produce measurement samples (test pieces). In an environment of 23°C and 50% RH, with a pasting area of 10 mm in width and 20 mm in length, a 2-kg roller was reciprocated once to press the adhesive surface of the above measurement sample onto a bakelite board (phenolic resin board) as the adherend. The adherend with the test piece pasted thereon by such an operation was suspended in an environment of 40°C with the length direction of the above test piece being the vertical direction and allowed to stand for 30 minutes. Then, a load of 500 g was applied to the free end of the above test piece, and in accordance with JIS Z0237, in the state where this load was applied, it was placed in an environment of 40°C for 1 hour. Regarding the test piece after this placement, the distance of deviation (deviation length. Hereinafter, also referred to as deviation distance) [mm] from the initial pasting position was measured. When the deviation distance after 1 hour of placement was less than 0.6 mm, it was evaluated as qualified, and when the deviation distance was 0.6 mm or more or when the test piece fell off the bakelite board within 1 hour, it was evaluated as unqualified.

[0214] [Compression Test]

[0215] The adhesive layer (adhesive sheet without substrate) was laminated to a thickness of 1 mm using a manual roller, and a punching measurement sample was produced using an 8-mmφ metal punch. In an environment of 23°C and 50% RH, the adhesive surface of the above measurement sample was pressed onto the fixture (8 mmφ) of a compression test device, and a compression test was carried out at a compression speed of 1 mm / minute. The deformation rate when the compressive stress was 0.35 MPa was read. When the deformation rate was 20% or more, it was evaluated as qualified, and when the deformation rate was less than 20%, it was evaluated as unqualified. As the compression test device, a dynamic viscoelasticity measurement device (product name “RSA-G2”, manufactured by TA Instruments) can be used.

[0216] <Synthesis Example>

[0217] (Synthesis Example 1)

[0218] A separable four-necked 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 dibutyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a solvent for discharging the reaction water were added thereto. While stirring in a nitrogen atmosphere, the temperature was raised to 180 °C and this temperature was maintained. Soon, it was found that the reaction water flowed out and separated, and the reaction started. The reaction was continued for about 24 hours, whereby a polyester polymer (A1) with a biomass ratio of 92% was obtained. The weight-average molecular weight (Mw) of this polyester polymer (A1) was 120,000, and the glass transition temperature (Tg) was -50 °C.

[0219] (Synthesis Example 2)

[0220] A separable four-necked 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 dibutyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a solvent for discharging the reaction water were added thereto. While stirring in a nitrogen atmosphere, the temperature was raised to 180 °C and this temperature was maintained. Soon, it was found that the reaction water flowed out and separated, and the reaction started. The reaction was continued for about 24 hours, whereby a polyester polymer (A2) with a biomass ratio of 81% was obtained. The Mw of this polyester polymer (A2) was 100,000, and the Tg was -33 °C.

[0221] <Example 1>

[0222] In 100 parts of a polyester polymer (A1), 60 parts of a terpene phenol resin as a tackifying resin (trade name “YSPolyster T115”, softening point 115 °C, manufactured by Yasuhara Chemical Co., hereinafter sometimes referred to as “T115”), 2 parts of an isocyanurate form of hexamethylene diisocyanate as a crosslinking agent (trade name “Coronate HX”, manufactured by Tosoh Corporation, aromatic ring-free, trifunctional), 0.02 parts of an organotin compound as a crosslinking catalyst (trade name “dibutyltin(IV) dilaurate”, manufactured by Fujifilm Wako Pure Chemical Corporation), and 0.5 parts of a carbodiimide group-containing compound as a hydrolysis-resistant agent (trade name “CARBODILITE V-03”, manufactured by Nisshinbo Chemical Inc.) were blended, and ethyl acetate was added thereto, whereby an adhesive composition (adhesive solution) was prepared. The adhesive solution was applied to the release-treated surface of a PET film (trade name “Diafoil MRF#38”, manufactured by Mitsubishi Chemical Corporation) so that the thickness after drying became 20 μm, and dried at 120 °C for 3 minutes, whereby an adhesive layer was obtained. Then, the above adhesive layer was laminated on the release-treated surface of a PET film (trade name “Diafoil MRE#38”, manufactured by Mitsubishi Chemical Corporation) subjected to release treatment, and further allowed to stand at 50 °C for 3 days, whereby a substrate-free adhesive sheet of this example was obtained. The tanδ of the above adhesive layer at 23 °C was 0.42.

[0223] <Examples 2 to 14, Comparative Examples 1 to 5>

[0224] As shown in Table 1, the type of the polyester polymer, the type and amount of the tackifying resin, and the amount of the crosslinking agent were changed. An adhesive composition of each example was prepared by operating in the same manner as in Example 1, and using this adhesive composition, a substrate-free adhesive sheet of each example was obtained by operating in the same manner as in Example 1 except for this.

[0225] The tackifying resins used in the above examples and comparative examples are as follows.

[0226] T80: terpene phenol resin (trade name “YS Polyster T80”, softening point 80 °C, manufactured by Yasuhara Chemical Co

[0227] S145: terpene phenol resin (trade name “YS Polyster S145”, softening point 145 °C, manufactured by Yasuhara Chemical Co

[0228] T30: terpene phenol resin (trade name “YS Polyster T30”, softening point 30 °C, manufactured by Yasuhara Chemical Co

[0229] The outlines and evaluation results of each example are shown in Table 1.

[0230]

[0231] As shown in Table 1, in Examples 1 to 14 using an adhesive containing a polyester polymer and having a tanδ of 0.35 or more and 0.80 or less at 23°C, good holding power was exhibited, and the deformation rate in the compression test was 20% or more, indicating good compression deformability. On the other hand, in Comparative Examples 1, 3 to 5 using an adhesive having a tanδ less than 0.35 at 23°C, a tendency of a small deformation rate in the compression test and poor compression deformability compared to the examples was confirmed. In addition, in Comparative Example 2 using an adhesive having a tanδ greater than 0.80 at 23°C, the offset distance in the holding power test was as high as 0.8 mm, indicating poor holding power compared to the examples.

[0232] As described above, specific examples of the present invention have been described in detail, but they are merely illustrative and do not limit the claims. The technology described in the claims includes technical solutions obtained by various modifications and changes to the above-described specific examples.

Claims

1. An adhesive, wherein: The adhesive includes a polyester polymer, and tan δ of the adhesive at 23° C. is greater than or equal to 0.35 and less than or equal to 0.

80.

2. The adhesive according to claim 1, wherein The polyester-based polymer includes a structure derived from a dimer acid.

3. The adhesive according to claim 1 or 2, wherein The adhesive includes 45 parts by weight or more of a tackifying resin relative to 100 parts by weight of the polyester polymer.

4. The adhesive according to claim 3, wherein The tackifier resin includes a tackifier resin T1 having a softening point of 60° C. or higher and 150° C. or lower.

5. The adhesive according to claim 3 or 4, wherein The tackifying resin comprises tackifying resin T T , the tackifying resin T T Contains structures derived from terpenes.

6. An adhesive sheet comprising an adhesive layer, wherein: The adhesive layer includes a polyester-based polymer, and tan δ of the adhesive layer at 23° C. is greater than or equal to 0.35 and less than or equal to 0.

80.

7. The adhesive sheet according to claim 6, wherein The adhesive sheet has a 180-degree peel strength to a stainless steel plate of 10 N / 20 mm or more.

8. A portable electronic device, wherein: The portable electronic device comprises the pressure-sensitive adhesive sheet according to claim 6 or 7.

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