Adhesive sheet and portable electronic device

Abstract

The invention relates to an adhesive sheet and a portable electronic device. The invention provides an adhesive sheet which has an adhesive layer containing a polyester-based polymer and can inhibit reduction of adhesive force caused by a processing mode before the adhesive sheet is adhered to an adherend. The invention provides an adhesive sheet having an adhesive layer. The pressure-sensitive adhesive layer contains a polyester-based polymer, and the storage modulus G'of the pressure-sensitive adhesive layer at 23 DEG C is 0.01 MPa or more and less than 0.40 MPa.

Description

Technical Field

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

[0002] Generally, an adhesive (also referred to as a pressure-sensitive adhesive, the same hereinafter) exhibits a state of a soft solid (viscoelastic body) within a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Utilizing such a property, the adhesive is typically used as a bonding means with good operability and high adhesion reliability in various industrial fields such as from household appliances to automobiles, various machines, electrical equipment, and electronic equipment, in the form of an adhesive sheet including a layer of the adhesive. As the adhesive, various adhesives such as acrylic adhesives, rubber adhesives, and polyester adhesives are used according to the purpose of use, the position of use, 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 are excellent in properties such as chemical resistance, water resistance, durability, and optical properties (transparency), and can exhibit adhesion characteristics equal to or better 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-based materials (for example, Patent Document 1).

[0008] However, before use (that is, before being pasted onto an adherend), the adhesive sheet is generally circulated, stored, and processed in a form in which the adhesive surface is protected by a release liner from the viewpoint of processability and the like. However, in the adhesive sheet having a form with a release liner on the adhesive surface, since a release treatment agent (for example, a polysiloxane-based release treatment agent) transfers from the release liner to the adhesive surface, the adhesive characteristics such as adhesive strength sometimes decrease.

[0009] More specifically, for example, with respect to the adhesive sheet for an electronic device described above, during the period before finally adhering to the adherend, processing such as punching or cutting can be performed so that the outer shape of the adhesive sheet conforms to the shape of the adherend. In order to perform such processing, the release liner that protects the adhesive surface of the adhesive sheet is sometimes replaced with a release liner having a thickness suitable for the processing. That is, sometimes the release liner used in manufacturing the adhesive sheet is removed from the adhesive surface of the adhesive sheet, and the release surface of another release liner is adhered to the exposed adhesive surface. Additionally, for example, in order to improve the adhesion operability to the adherend, etc., the release liner with low visual recognition is sometimes replaced with a release liner with high visual recognition before adhering to the adherend. When the replacement adhesion of the release liner is performed as described above before adhering to the adherend, the release treatment agent easily transfers from the release liner before and after the replacement adhesion to the adhesive layer and accumulates on the adhesive surface, thus sometimes resulting in a decrease in adhesive strength. Especially when stored for a long time after the replacement adhesion of the release liner, particularly when stored in an environment where temperature control is not performed, for example, due to the transfer of the above-mentioned release treatment agent, the decrease in adhesive strength is likely to become significant.

[0010] The present invention has been made in view of the above circumstances, and its object is to provide an adhesive sheet that can suppress a decrease in adhesive strength caused by the treatment method before adhering to the adherend by having a configuration including an adhesive layer containing a polyester-based polymer. Another related object is to provide a portable electronic device including the above adhesive sheet.

[0011] Means for Solving the Problem

[0012] According to the present specification, there is provided an adhesive sheet having an adhesive layer. The above adhesive layer contains a polyester-based polymer, and the storage modulus G' of the above adhesive layer at 23°C is greater than or equal to 0.01 MPa and less than 0.40 MPa. According to the above configuration, by having a configuration including an adhesive layer containing a polyester-based polymer, even when an operation such as replacing and adhering a release liner is performed before adhering to the adherend, a decrease in adhesive strength is suppressed. Therefore, regardless of the treatment method before adhering to the adherend, a decrease in adhesive strength can be suppressed.

[0013] In some preferred embodiments, the above adhesive layer contains 45 parts by weight or more of a tackifying resin with respect to 100 parts by weight of the above polyester-based polymer. By having a composition like this that contains a polyester-based polymer and contains a specified amount or more of a tackifying resin with respect to the polyester-based polymer, an adhesive layer having a storage modulus at 23°C within a specified range can be satisfactorily formed.

[0014] In some embodiments, the softening point of the tackifying resin described above is 30°C or higher and 200°C or lower. By including a polyester polymer and a tackifying resin having a softening point within the above range, an adhesive layer having a storage modulus at 23°C within a specified range can be satisfactorily formed.

[0015] In some embodiments, any one of the following (1) to (3) is preferred: (1) with respect to 100 parts by weight of the polyester polymer, the adhesive layer contains 60 parts by weight or less of a tackifying resin T1 having a softening point of 145°C or higher and 200°C or lower as the tackifying resin; or (2) the adhesive layer contains a tackifying resin T2 having a softening point of 30°C or higher and less than 145°C as the tackifying resin; or (3) the adhesive layer contains the tackifying resin T1 and the tackifying resin T2 as the tackifying resin, and with respect to 100 parts by weight of the polyester polymer, the content of the tackifying resin T1 is 60 parts by weight or less. According to the adhesive layer belonging to any one of the above (1) to (3), a storage modulus at 23°C within a specified range can be satisfactorily achieved.

[0016] In some embodiments, the thickness of the adhesive layer is less than 80 μm. The effect (effect of suppressing the decrease in adhesive force) produced by the technology disclosed herein can be effectively exerted in a configuration having an adhesive layer with a thickness less than 80 μm. In addition, the adhesive layer with the thickness limited as above can well cope with the thinning of the article to which the adhesive sheet is applied.

[0017] In some preferred embodiments, the 180-degree peel strength of the adhesive sheet on a stainless steel plate (adhesive force to SUS) is 5 N / 20 mm or more. The adhesive sheet having the above adhesive force to SUS can have good adhesion reliability.

[0018] The adhesive sheet disclosed herein can suppress the decrease in adhesive force even when an operation such as replacing the adhesive release liner before pasting onto the adherend is performed. Therefore, for example, it can preferably be used as an adhesive sheet for fixing components of a portable electronic device that is sometimes used for processing and the like and requires replacing the adhesive release liner before pasting onto the adherend. Accordingly, according to this specification, there is provided a portable electronic device using any one of the adhesive sheets disclosed herein, in other words, a portable electronic device including the adhesive sheet. 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 3A cross-sectional view schematically showing the structure of an adhesive sheet according to another embodiment.

[0022] Figure 4 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 sheets

[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 embodiments 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 described with the same reference numerals, and repeated descriptions may be omitted or simplified. In addition, for the sake of clearly explaining the present invention, the embodiments described 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 derived 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 extraction and use are excluded from the concept of biomass materials described herein. For example, the proportion of carbon derived from biomass in the total carbon contained in a polyester polymer, that is, the biomass carbon ratio (or also referred to as the biomass rate), can be estimated by the carbon isotope content of mass number 14 measured according to ASTM D6866-22 Method B. Additionally, 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 embodiments described below.

[0038] <Constitution Example of Adhesive Sheet>

[0039] The adhesive sheet disclosed herein is composed of an adhesive layer. For example, the adhesive sheet can be 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 can be in the form of a substrate-bearing adhesive sheet in which the above-mentioned 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".

[0040] The structure of an adhesive sheet according to one embodiment is schematically shown in Figure 1 . The adhesive sheet 1 is formed in the form of a substrate-free double-sided adhesive sheet composed of an adhesive layer 21. The adhesive sheet 1 is used by pasting the first adhesive surface 21A formed by one surface (the first surface) of the adhesive layer 21 and the second adhesive surface 21B formed by the other surface (the second surface) of the adhesive layer 21 to different parts of the adherend. The parts where the adhesive surfaces 21A and 21B are pasted can be parts of different members or different parts within a single member. The adhesive sheet 1 before use (that is, before being pasted onto the adherend) can 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 respectively protected by release liners 31 and 32 each 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 one surface of a sheet-like base material (liner base material) and having the one surface as a release surface can be preferably used. Alternatively, the release liner 32 can be omitted, and a release liner 31 having release surfaces on both sides can be used, and it can 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 (a roll form) to form an adhesive sheet with a release liner.

[0041] 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 Figure 2 shown as the constituent elements of the adhesive sheet 200 with a release liner in a form in which the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31 having a release surface on at least the side facing the adhesive layer 21. Alternatively, the release liner 31 can be omitted, and the support base material 10 having the second surface 10B as a release surface can 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 (a roll form).

[0042] 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 Figure 3The constituent elements of the adhesive sheet 300 with release liners 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 the release liners 31 and 32. Alternatively, the release liner 32 may be omitted, and a release liner 31 with release surfaces on both sides may be used, which is overlapped with the adhesive sheet 3 and wound in a spiral shape, thereby forming an adhesive sheet with release liners in a form in which the second adhesive surface 22A is in contact with the back surface of the release liner 31 and is protected (roll form).

[0043] It should be noted that in the above-mentioned 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 the adhesive layer described below, and the other adhesive layer (for example, the second adhesive layer) may be the adhesive layer described below or may be an adhesive layer having a composition different from that of the adhesive layer disclosed herein (specifically, the above-mentioned one adhesive layer. For example, the first adhesive layer). Such another adhesive layer may be formed of a known or conventional adhesive, for example.

[0044] Although there is no particular limitation, 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 supporting substrate, it is easy to be thinned, which is also advantageous in terms of being able to maximize adhesive properties such as adhesive strength. In addition, in the substrate-free double-sided adhesive sheet, the thickness of the adhesive layer can be maximally utilized to effectively exhibit the effect of the storage modulus G' at 23°C of the adhesive layer described below.

[0045] It should be noted that the concept of the adhesive sheet herein may include articles such as adhesive tapes, adhesive films, and adhesive labels. The adhesive sheet may be in a roll form, a single sheet form, or a form obtained by appropriately cutting, blanking, etc. according to the use and usage method.

[0046] <Adhesive layer>

[0047] (Storage modulus at 23°C)

[0048] The adhesive layer disclosed herein is characterized in that the storage modulus G' at 23°C of the adhesive layer is greater than or equal to 0.01 MPa and less than 0.40 MPa. For the adhesive sheet having an adhesive layer containing a polyester polymer with a storage modulus at 23°C of less than 0.40 MPa according to the above, regardless of the treatment method before being adhered to the adherend, for example, even in the case of undergoing treatment methods that are likely to reduce the adhesive force, such as replacing the adhesive release liner before being adhered to the adherend or further storing in a harsh environment without temperature management, etc., a decrease in the adhesive force can be suppressed. As the reason, it is considered that in the adhesive layer with a storage modulus at 23°C of less than 0.40 MPa, on the surface (adhesive surface) of the adhesive layer, the portion without the release treatment agent (such as a polysiloxane-based release treatment agent) transferred from the release liner follows the adherend well, thus suppressing the decrease in the adhesive force. It should be noted that the technology disclosed herein is not limited to the above explanation. In addition, the adhesive layer with a storage modulus at 23°C of 0.01 MPa or more has appropriate cohesion, so adhesive properties such as adhesive force and holding force, workability, and handleability are good. For example, it can be a highly practical adhesive layer in various applications such as fixing components of electronic devices.

[0049] In some preferred embodiments, from the perspective of suppressing the above-mentioned decrease in adhesive force, the storage modulus at 23°C is 0.30 MPa or less (e.g., less than 0.30 MPa), more preferably 0.25 MPa or less, further preferably 0.20 MPa or less, still further preferably 0.15 MPa or less, particularly preferably 0.12 MPa or less, can be 0.10 MPa or less (e.g., less than 0.10 MPa), can be 0.08 MPa or less, and can also be 0.06 MPa or less. In addition, from the perspectives of improving cohesion, adhesive properties, workability, handleability, etc., in some embodiments, the storage modulus at 23°C is preferably 0.03 MPa or more, more preferably 0.05 MPa or more, further preferably 0.08 MPa or more, particularly preferably 0.10 MPa or more, can be 0.14 MPa or more, can be 0.18 MPa or more, can be 0.20 MPa or more, and can also be 0.22 MPa or more.

[0050] In the technology disclosed herein, the storage modulus of the adhesive layer at 23°C 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 about 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 (for example, manufactured by TA Instruments, ARES or its equivalent) to determine the storage modulus at 23°C.

[0051] ･ Measurement mode: Shear mode

[0052] ･ Temperature range: -70°C to 150°C

[0053] ･ Heating rate: 5°C / minute

[0054] ･ Measurement frequency: 1 Hz

[0055] In the following examples, the measurement is also performed by the above method. It should be noted that for the adhesive layer to be measured, an adhesive formed by coating the corresponding adhesive composition in a layer and drying or curing it can be used.

[0056] (Polyester polymer)

[0057] The adhesive layer disclosed herein contains a polyester polymer. It should be noted that in this specification, the adhesive layer containing a polyester polymer is also referred to as a polyester adhesive layer. The above polyester polymer is typically included as a base polymer in the adhesive layer. 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 layer. 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.

[0058] (Dicarboxylic acid)

[0059] 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 acid esters. By appropriately selecting and using one or more of these dicarboxylic acids, a polyester polymer capable of forming an adhesive layer having desired properties (specifically, a desired storage modulus at 23°C) can be obtained.

[0060] 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 layer having a storage modulus at 23°C below 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 layer. 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, can be about 80% by weight or more, can be about 85% by weight or more, can be about 90% by weight or more, or can be about 95% to 100% by weight. By making the usage amount of the dimer acid be a specified amount or more, 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 viewpoints of cohesion and the like, in some embodiments, it is preferably about 99% by weight or less, more preferably about 95% by weight or less, can be about 90% by weight or less, or can be about 85% by weight or less.

[0061] In some embodiments, sebacic acid is used as the dicarboxylic acid. In the 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 the monomer component of the polyester polymer may be about 1% by weight or more, for example, it may be about 5% by weight or more, may be about 10% by weight or more, and may also be about 15% by weight or more. In addition, the upper limit of the weight ratio of the above-mentioned sebacic acid is 100% by weight. From the perspective of reducing the storage modulus at 23°C of the adhesive layer, in some embodiments, it may be about 50% by weight or less, or may be about 30% by weight or less. The technology disclosed herein can be implemented in either of the following two ways: one is that the dicarboxylic acid as the monomer component used in the synthesis of the polyester polymer contains sebacic acid, and the other is that the dicarboxylic acid as the monomer component used in the synthesis of the polyester polymer does not contain sebacic acid. For example, the weight ratio of the above-mentioned sebacic acid may be about 10% by weight or less, may be about 3% by weight or less, may be less than 1% by weight, and the dicarboxylic acid used in the synthesis of the polyester polymer may be substantially free of sebacic acid.

[0062] 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 and the storage modulus at 23°C 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.

[0063] 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 cohesion 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 above aromatic carboxylic acid is preferably about 50% by weight or less, for example. From the viewpoint of obtaining adhesion characteristics such as adhesiveness with a storage modulus at 23 °C within a specified range, the upper limit of the weight ratio of the above 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 any one of the methods in which the dicarboxylic acid as a monomer component used in the synthesis of the polyester polymer contains an aromatic dicarboxylic acid or the 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 above 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.

[0064] 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, synthesizability, etc., 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).

[0065] 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.

[0066] 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 dicarboxylic acids 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.

[0067] 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, and may be about 90% by weight or more, or may 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 properties 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 be about 90% by weight or less.

[0068] It should be noted that the technology disclosed herein includes a method of increasing the biomass ratio of the polyester polymer by using an aromatic dicarboxylic acid 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 and then 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).

[0069] (diol)

[0070] 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, 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 and other 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; 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 layer having desired properties (specifically, a desired storage modulus at 23°C) can be obtained.

[0071] 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 combining these diols (preferably ethylene glycol and aliphatic diols) with the above-mentioned dicarboxylic acids (preferably dimer acids) for synthesis, 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 perspective of reactivity and the like, ethylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol are more preferred. These can be used alone or in combination of two or more. The above-mentioned (poly)alkylene 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.

[0072] 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 perspective 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.

[0073] In some preferred embodiments, (poly)ethylene glycol is used as the diol. By combining (poly)ethylene glycol with a suitable dicarboxylic acid, a polyester polymer capable of forming an adhesive layer having a desired storage modulus at 23°C can be satisfactorily obtained, and good adhesion properties (such as adhesive strength) can be satisfactorily obtained. In the embodiment where the above-mentioned (poly)ethylene glycol is used as the above-mentioned diol, it is appropriate that the weight ratio of the (poly)ethylene glycol in the total amount (total weight) of the diol as the 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 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 properties of (poly)ethylene glycol. In addition, for example, by using (poly)ethylene glycol, an adhesive layer with low haze is easily obtained. In some other embodiments, the weight ratio of the above-mentioned (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-mentioned (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.

[0074] In some other embodiments, dimer diol is used as the diol. As the dimer diol, a dimer diol derived from plants can be preferably used. By using the dimer diol, the biomass ratio of the polyester polymer can be increased. The dimer diol can be used alone or in combination of two or more. In the embodiment where the dimer diol is used as the above-mentioned diol, the weight ratio of the dimer diol in the total amount (total weight) of the diol as the monomer component 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-mentioned 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-mentioned 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% by weight. The diol used in the synthesis of the polyester polymer can substantially not contain dimer diol.

[0075] 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 by using biomass ethanol as a raw material (such as biomass (poly)ethylene glycol, etc.), fatty acid esters derived from plants (such as castor oil), dimer 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.

[0076] In some embodiments, the weight ratio of the diols derived from plants in the total amount (total weight) of the diols as monomer components of the polyester polymer 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). Additionally, in some other embodiments, the weight ratio of the above-mentioned 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 equal to or higher than a specified value. From such a viewpoint, in some embodiments, the weight ratio of the above-mentioned 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).

[0077] The molecular weight of the above-mentioned diol is not particularly limited. In some embodiments, from the viewpoints of monomer availability, synthetic properties, etc., the molecular weight of the diol is preferably about 1000 or less, for example, it can be 800 or less, 700 or less, or 600 or less. In some preferred embodiments, the molecular weight of the diol is preferably 500 or less, it can be 300 or less, 150 or less, 100 or less, or 80 or less. Additionally, the molecular weight of the diol is preferably about 50 or more, for example, it can be greater than 100. For example, in the case where the above-mentioned diol is derived from fossil resources, the molecular weight of the diol derived from fossil resources is preferably 500 or less, and it 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, 100 or less, or 80 or less. Additionally, the molecular weight of the diol derived from fossil resources is preferably about 50 or more, for example, it can be greater than 100. Preferred examples of the diol having the above molecular weight include ethylene glycol. In some other embodiments, the molecular weight of the diol can be 150 or more, 200 or more, 250 or more, 350 or more, 450 or more, or 500 or more. As the diol having a molecular weight of more than the specified value, a diol derived from plants is preferably used. Preferred examples of the diol having this molecular weight include dimer diol.

[0078] 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 used.

[0079] 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., other copolymerization components in addition to the dicarboxylic acids and diols can also be copolymerized within the scope that does not impair the effects of the technology disclosed herein. Examples of such other copolymerization components include: polycarboxylic acids containing three or more carboxyl groups (trimellitic acid, pyromellitic acid, adamantane tricarboxylic acid, benzene-1,3,5-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 suitably less than 10% by weight, for example, less than 3% by weight, less than 1% by weight, or even less than 0.1% by weight. The technology disclosed herein can preferably be implemented in such a way that the monomer components of the polyester polymer substantially do not contain the above-mentioned other copolymerization components.

[0080] 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 suitably about 90% by weight or more, preferably about 95% by weight or more, more preferably about 98% by weight or more, and further preferably about 99% by weight or more (for example, about 99% by weight to about 100% by weight). The technology disclosed herein is preferably implemented in such a way that a polyester polymer synthesized from a dicarboxylic acid and a diol is substantially used.

[0081] 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. The technology disclosed herein can be satisfactorily implemented in the way of using a polyester polymer synthesized by combining dimer acid and (poly)ethylene glycol. The total proportion of dimer acid and (poly)ethylene glycol in the total amount of the monomer components of the polyester polymer is suitably about 50% by weight or more, preferably about 60% by weight or more, 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 (for example, about 99% by weight to about 100% by weight).

[0082] In some embodiments, the polyester polymer preferably limits the content rate of aromatic rings in its polymer molecules or substantially does not contain aromatic rings. Thus, there is a tendency to easily obtain an adhesive layer having a storage modulus at 23°C of a specified value or less. From the viewpoint of improving adhesion and the like, it is preferable to limit the content rate of aromatic rings in the polyester polymer. In some preferred embodiments, from the viewpoint of obtaining a storage modulus at 23°C of a specified value or less, 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, can be about 5% by weight or less, can be about 3% by weight or less, and can also 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 of using a polyester polymer that substantially does not contain aromatic rings in its molecules. Additionally, in the case where the polyester polymer has aromatic rings, from the viewpoints of improving cohesion and obtaining good holding power and the like, the copolymerization ratio of the 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.

[0083] The method for obtaining the polyester polymer disclosed herein is not particularly limited, and polymerization methods known as synthesis methods for polyester polymers can be appropriately employed. As the monomer raw materials for synthesizing the polyester polymer, for example, monomer raw materials obtained by mixing monomers in such a manner that the dicarboxylic acid is 0.95 to 1.05 equivalents (preferably 0.98 to 1.02 equivalents) relative to 1 equivalent of the diol can be used. By mixing the dicarboxylic acid and the diol in the above ratio, a high-molecular-weight polyester polymer can be easily obtained. 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.

[0084] In the technology disclosed herein, the weight ratio of the dicarboxylic acid to the diol as the 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 components 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 also 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 where the dicarboxylic acid derived from plants is used, 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 where the diol derived from plants is used, 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 where both the dicarboxylic acid and the diol use plant-derived materials, 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.

[0085] 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, etc. from the reaction system, whereby a polyester polymer can be synthesized. As a method for removing the above generated water from 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 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.

[0086] In order to effectively obtain a polyester polymer with target properties (such as molecular weight), the reaction temperature, reaction time, and degree of reduced pressure (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 keeping 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 resulting polyester polymer. 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 reduced pressure method, there is no particular limitation, but generally the above degree of reduced pressure 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 keeping 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 keeping the pressure within the reaction system 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.

[0087] 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 amount of the catalyst used can be appropriately set according to the reaction rate and the like, and thus detailed description is omitted herein.

[0088] In the above process of synthesizing a polyester polymer by the reaction of a dicarboxylic acid and a diol, a solvent can be used or not used. The above synthesis can be carried out in a manner that substantially does not use an organic solvent (which means, for example, excluding the intentional use of an organic solvent as the reaction solvent during the above reaction). Synthesizing a polyester polymer in such a manner that substantially does not use an organic solvent and using the polyester polymer to prepare a polyester adhesive layer are suitable for controlling the requirements for using organic solvents during its manufacturing process, and thus are preferred.

[0089] It should be noted that during the above reaction, there is usually a correlation between the molecular weight of the synthesized polyester polymer and the viscosity of the reaction system. Therefore, this point can be utilized to control the molecular weight of the polyester polymer. For example, by continuously or intermittently measuring (monitoring) the torque of the stirrer and the viscosity of the reaction system during the reaction, a polyester polymer that meets the target molecular weight can be synthesized with high precision.

[0090] The weight average molecular weight (Mw) of the polyester polymer is not particularly limited, and is generally about 10,000 or more, 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, preferably greater than 60,000, more preferably greater than 70,000, further 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 layer 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 likely to have a low viscosity can easily obtain 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 storage period and excellent processability. The upper limit of the Mw of the polyester polymer is generally 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, for example, may be about 12×10 4 The following.

[0091] 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.

[0092] [GPC Measurement]

[0093] Column: TSKgel GMH-H(S)

[0094] Column temperature: 40 °C

[0095] Eluent: THF (added with 0.1 wt% of amine component)

[0096] Flow rate: 0.5 mL / min

[0097] Injection volume: 100 μL

[0098] Detector: Differential refractometer (RI)

[0099] Standard specimen: Polystyrene (PS)

[0100] 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, still more 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. Additionally, from the perspective of the cohesion of the adhesive layer, 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 about -40°C or higher. The Tg of the polyester polymer can be adjusted by appropriately changing the monomer composition (i.e., the types and usage ratios of the monomers used in the synthesis of the polymer).

[0101] The Tg of the polyester polymer is measured by the following method. That is, using the polyester polymer to be measured, a disk-shaped test piece with a thickness of 2 mm and a diameter of 8 mm is fabricated. This test piece is clamped between parallel plates for a shear test, and using a measuring device (ARES, manufactured by Rheometric Scientific), the peak of tanδ (loss modulus G'' / storage modulus G') is obtained at a frequency of 1 Hz, and the temperature of this peak is set as the Tg (glass transition temperature) [°C]. The same method is also used for measurement in the examples described later.

[0102] 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 the polyester polymer 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 referred to as the biomass rate) of the above 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 layer 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 viewpoint 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 (for example, 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%.

[0103] (Tackifying resin)

[0104] In some embodiments, the adhesive layer contains a tackifying resin. According to the technology disclosed herein, by virtue of the composition containing a tackifying resin, the adhesive layer can become an adhesive layer having a specified storage modulus at 23°C. 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 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 layer, for example, rosin-based tackifying resins and terpene-based tackifying resins are preferably used.

[0105] 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 (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins; the same applies hereinafter) obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc.; various other rosin derivatives; and the like. 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), and other 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 (especially rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; 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; and the like.

[0106] Although not particularly limited, as specific examples of rosin esters, the following can be cited: esters of unmodified rosin or modified rosin (such as hydrogenated rosin, disproportionated rosin, and polymerized rosin), for example, methyl esters, triethylene glycol esters, glycerol esters, pentaerythritol esters, and the like.

[0107] 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.); and the like. 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.

[0108] Terpene phenol resin refers to a polymer containing terpene residues and phenol residues, and is a concept encompassing both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and resins obtained by phenol-modifying terpenes or their homopolymers or copolymers (phenol-modified terpene resins). As preferred examples of the terpenes constituting such terpene phenol resins, the following can be cited: monoterpenes such as α-pinene, β-pinene, and limonene (including the 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 terpene phenol resin. It is sometimes also referred to as hydrogenated terpene phenol resin.

[0109] 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, when the tackifying resin T T is used, the adhesive layer formed is likely 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.

[0110] 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 .

[0111] Although there is no particular limitation, in some other embodiments, a rosin-based tackifying resin is used as the tackifying resin. As the rosin-based tackifying resin, one or more suitable ones of the above-exemplified rosin-based tackifying resins can be used. For example, polymerized rosin ester and methyl hydrogenated rosin can be preferably used. In the embodiment where a rosin-based tackifying resin is used as the tackifying resin, the proportion of the rosin-based tackifying 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 50% by weight) of the total amount of the tackifying resin is the rosin-based tackifying resin, 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 rosin-based tackifying resin, 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 rosin-based tackifying resin.

[0112] 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 having a softening point below a specified value, it is easy to obtain a storage modulus at 23 °C below the specified value and there is a tendency to easily obtain adhesiveness. From this viewpoint, 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. As the tackifying resin, a liquid tackifying resin that is liquid at room temperature (25 °C) can also be used. In some preferred embodiments, the softening point of the tackifying resin is about 60 °C or higher, more preferably about 70 °C or higher, still more preferably about 75 °C or higher. In some other preferred embodiments, the softening point of the tackifying resin is about 85 °C or higher, more preferably about 95 °C or higher, still more preferably about 105 °C or higher. By using a tackifying resin having a softening point within the above range, the adhesiveness can be improved.

[0113] In some embodiments, a tackifying resin T1 having a softening point of 145 °C or higher and 200 °C or lower is used as the tackifying resin. For example, by using an appropriate amount of the tackifying resin T1 having the above softening point, an adhesive layer having a storage modulus at 23 °C within a specified range and having good adhesiveness can be satisfactorily obtained. From the viewpoint of reducing the storage modulus at 23 °C, in some preferred embodiments, the softening point of the tackifying resin T1 is about 180 °C or lower, more preferably about 160 °C or lower, still more preferably about 150 °C or lower (e.g., less than 150 °C). 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 145 °C or higher and 200 °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.

[0114] In the method of using tackifying resin T1 as the tackifying resin, the proportion of tackifying resin T1 in the total amount of the tackifying resin can be about 25% by weight or more, can be about 30% by weight or more, and can also be about 40% by weight or more. In some embodiments, about 50% by weight or more (such as greater than 50% by weight) of the total amount of the tackifying resin 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. Additionally, in some other embodiments, it is appropriate that the proportion of tackifying resin T1 in the total amount of the tackifying resin is about 50% by weight or less, preferably about 30% by weight or less, more preferably about 20% by weight or less, and further preferably about 10% by weight or less. By restricting the usage amount of tackifying resin T1 having a high softening point, there is a tendency to easily obtain a 23°C storage modulus within a specified range. From such a perspective, in some preferred embodiments, the proportion of tackifying resin T1 in the total amount of the tackifying resin 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 tackifying resin may also substantially not contain tackifying resin T1. The technology disclosed herein can preferably be implemented in a manner of not using tackifying resin T1 as the tackifying resin.

[0115] Although not particularly limited, in the method of using tackifying resin T1 as the tackifying resin, the usage amount of tackifying resin T1 is preferably restricted within a specified range. By restricting the usage amount of tackifying resin T1 within an appropriate range, an adhesive layer having a 23°C storage modulus within a specified range and having good adhesion can be satisfactorily formed. From such a perspective, in some embodiments, with respect to 100 parts by weight of the polyester polymer, the amount of tackifying resin T1 in the adhesive layer is, for example, appropriately about 70 parts by weight or less, preferably 60 parts by weight or less, more preferably about 50 parts by weight or less, further preferably about 40 parts by weight or less (such as less than 40 parts by weight), particularly preferably 35 parts by weight or less, can be about 30 parts by weight or less, and can also be about 20 parts by weight or less. Additionally, in some embodiments, with respect to 100 parts by weight of the polyester polymer, the amount of the above-mentioned tackifying resin T1 can be about 1 part by weight or more, preferably 5 parts by weight or more, more preferably about 15 parts by weight or more, further preferably about 25 parts by weight or more, can be about 35 parts by weight or more, and can also be about 45 parts by weight or more. In some other embodiments, with respect to 100 parts by weight of the polyester polymer, the amount of the above-mentioned tackifying resin T1 can be, for example, about 10 parts by weight or less, can be about 5 parts by weight or less, can be about 1 part by weight or less, and the adhesive layer may substantially not contain tackifying resin T1.

[0116] In some preferred embodiments, a tackifying resin T2 with a softening point less than 145 °C can be used as the tackifying resin. By using the tackifying resin T2 with the above softening point, it is easy to obtain an adhesive layer with a desired storage modulus at 23 °C. Additionally, good adhesion characteristics can be easily obtained. From this perspective, the softening point of the tackifying resin T2 is preferably about 135 °C or lower, more preferably about 120 °C or lower, still more preferably about 110 °C or lower, further preferably about 100 °C or lower (e.g., less than 100 °C), and particularly preferably about 90 °C or lower. In addition, in some embodiments, the softening point of the tackifying resin T2 can be about 25 °C or higher, preferably about 30 °C or higher. As the tackifying resin T2, a liquid tackifying resin that is liquid at room temperature (25 °C) can be used. By using a tackifying resin T2 with a softening point above a specified value, the cohesion of the adhesive layer is improved, and good adhesion characteristics such as improved adhesive strength can be easily obtained. In some preferred embodiments, the softening point of the tackifying resin T2 is about 50 °C or higher (e.g., greater than 50 °C), more preferably about 60 °C or higher, still more preferably about 70 °C or higher, and particularly preferably about 75 °C or higher. In some other preferred embodiments, the softening point of the tackifying resin T2 is about 85 °C or higher, more preferably about 95 °C or higher, still more preferably about 105 °C or higher. As the tackifying resin T2, the above various tackifying resins can be used. For example, a tackifying resin T containing a structure derived from terpenes with a softening point less than 145 °C is preferably used. T and rosin-based tackifying resins. Among them, the tackifying resin T is more preferably T (e.g., terpene phenol resin). The tackifying resin T2 can be used alone or in combination of two or more.

[0117] In some preferred embodiments, a tackifying resin T2a with a softening point in the range of greater than or equal to 60 °C and less than 145 °C is used as the tackifying resin T2. By using the tackifying resin T2a, it is easy to obtain an adhesive layer with better characteristics (storage modulus at 23 °C and adhesion characteristics). The softening point of the tackifying resin T2a 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, the softening point of the tackifying resin T2a is preferably about 135 °C or lower, more preferably about 120 °C or lower, still more preferably about 110 °C or lower, further preferably about 100 °C or lower (e.g., less than 100 °C), and particularly preferably about 90 °C or lower. As the tackifying resin T2a, the above various tackifying resins can be used. For example, a tackifying resin T containing a structure derived from terpenes can be preferably used. T and rosin-based tackifying resins. Among them, the tackifying resin T is more preferably T (e.g., terpene phenol resin). The tackifying resin T2a can be used alone or in combination of two or more.

[0118] In the method of using tackifying resin T2a as the tackifying resin, the proportion of tackifying resin T2a in tackifying resin T2 is preferably about 10% by weight or more, more preferably about 30% by weight or more, still more preferably about 50% by weight or more (for example, greater than 50% by weight), further preferably about 70% by weight or more, still further preferably about 90% by weight or more, and particularly preferably substantially all of tackifying resin T2 (for example, 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) is tackifying resin T2a.

[0119] In addition, in some embodiments, a tackifying resin T2b having a softening point of less than 60 °C is used as the tackifying resin T2. By using the tackifying resin T2b, a lower storage modulus at 23 °C can be easily obtained. The softening point of the tackifying resin T2b can be about 50 °C or lower, or can be about 40 °C or lower. The tackifying resin T2b can also be a liquid tackifying resin that is liquid at room temperature (25 °C). In addition, the softening point of the tackifying resin T2b can be about 25 °C or higher, preferably about 30 °C or higher. As the tackifying resin T2b, various tackifying resins described above can be used. For example, a tackifying resin T T (such as terpene phenol resin) can be preferably used. The tackifying resin T2b can be used alone or in combination of two or more.

[0120] In the method of using the tackifying resin T2b as the tackifying resin, the proportion of the tackifying resin T2b in the tackifying resin T2 can be about 10% by weight or more, can be about 30% by weight or more, can be about 50% by weight or more (for example, 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 T2 (for example, 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) is the tackifying resin T2b.

[0121] In some embodiments, more than two tackifying resins T2 can be used as the tackifying resin T2. For example, embodiments can include using more than two tackifying resins T2 with different softening points. By blending and using more than two tackifying resins T2 having appropriate softening points, good adhesive properties such as adhesiveness can be obtained, and the storage modulus at 23°C can be adjusted to a desired range. In an embodiment including two tackifying resins T2 with different softening points, the difference in softening points (T2H - T2L) between the tackifying resin T2H having a relatively high softening point and the tackifying resin T2L having a relatively low softening point is not particularly limited. For example, it is preferably about 5°C or more, more preferably about 10°C or more, still more preferably about 20°C or more, further preferably about 30°C or more, can be about 40°C or more, and can also be about 50°C or more. In addition, in some embodiments, the above difference (T2H - T2L) is, for example, less than 90°C, preferably about 70°C or less, more preferably about 60°C or less. Although not particularly limited, as the tackifying resin T2H and the tackifying resin T2L, the above-mentioned tackifying resin T2a and tackifying resin T2b can be used respectively.

[0122] In an embodiment of using the tackifying resins T2H and T2L, the ratio (T2H / T2L) of the amount of the tackifying resin T2H to the amount of the tackifying resin T2L on a weight basis is not particularly limited. In some embodiments, the above ratio (T2H / T2L) can be 1 / 9 or more, can be 2 / 8 or more, can be 3 / 7 or more, can be 4 / 6 or more, and can also be 5 / 5 or more. By increasing the above ratio (T2H / T2L), the effect of containing the tackifying resin T2H can be easily and effectively exerted. In addition, in some embodiments, the above ratio (T2H / T2L) can be 9 / 1 or less, and can also be 7 / 3 or less. By setting the ratio (T2H / T2L) within the above range, the effect of containing the tackifying resin T2L can be easily and effectively exerted.

[0123] In an embodiment of using the tackifying resin T2 as the tackifying resin, the proportion of the tackifying resin T2 in the total amount of the tackifying resin is preferably about 25% by weight or more, more preferably about 30% by weight or more, and still more preferably about 40% by weight or more. In some embodiments, preferably, about 50% by weight or more (e.g., greater than 50% by weight) of the total amount of the tackifying resin is the tackifying resin T2, more preferably about 60% by weight or more, and still more preferably about 70% by weight or more can be the tackifying resin T2. In some preferred embodiments, the proportion of the tackifying resin T2 in the total amount of the tackifying resin is about 80% by weight or more, more preferably about 90% by weight or more, and still more preferably 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) is the tackifying resin T2.

[0124] In the method of using tackifying resin T2 as the tackifying resin, the amount of tackifying resin T2 used in the adhesive layer is appropriately set within the range having a target storage modulus at 23°C. In some embodiments, relative to 100 parts by weight of the polyester polymer, the amount of tackifying resin T2 in the adhesive layer may be about 1 part by weight or less, may be about 5 parts by weight or more, preferably 10 parts by weight or more, more preferably about 15 parts by weight or more, further preferably about 20 parts by weight or more, and particularly preferably about 25 parts by weight or more. Additionally, in some other embodiments, relative to 100 parts by weight of the polyester polymer, the amount of the above-mentioned tackifying resin T2 is preferably about 30 parts by weight or more, more preferably about 50 parts by weight or more (e.g., greater than 50 parts by weight), further preferably about 60 parts by weight or more, particularly preferably about 70 parts by weight or more, may be about 80 parts by weight or more, and may also be about 90 parts by weight or more. By the adhesive layer containing a specified amount or more of tackifying resin T2, the storage modulus at 23°C can be reduced, and moreover, good adhesion characteristics can be easily obtained. Additionally, in some embodiments, relative to 100 parts by weight of the polyester polymer, the amount of the above-mentioned tackifying resin T2 may be, for example, about 200 parts by weight or less, may be about 160 parts by weight or less, and may also be about 150 parts by weight or less (e.g., less than 150 parts by weight). From the viewpoint of having a storage modulus at 23°C below a specified value and obtaining better adhesion characteristics, in some preferred embodiments, relative to 100 parts by weight of the polyester polymer, the amount of the above-mentioned tackifying resin T2 is about 130 parts by weight or less, more preferably about 110 parts by weight or less, further preferably 100 parts by weight or less (e.g., less than 100 parts by weight), particularly preferably about 90 parts by weight or less, may be about 80 parts by weight or less, may be about 70 parts by weight or less, and may also be about 50 parts by weight or less. In some other embodiments, relative to 100 parts by weight of the polyester polymer, the amount of the above-mentioned tackifying resin T2 may be about 40 parts by weight or less, may be about 20 parts by weight or less, may be 10 parts by weight or less (e.g., less than 10 parts by weight), and may also be about 1 part by weight or less. The adhesive layer may substantially not contain tackifying resin T2.

[0125] In some embodiments, a tackifying resin T1 having a softening point of 145°C or higher and 200°C or lower and a tackifying resin T2 having a softening point less than 145°C may be used in combination as the tackifying resin. By using tackifying resins T1 and T2 in an appropriate ratio, the effects produced by the technology disclosed herein can be preferably exerted.

[0126] 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) is, for example, 1 / 99 or more, preferably 10 / 90 or more, more preferably 30 / 70 or more, still more preferably 40 / 60 or more, may be 50 / 50 or more, or may be 70 / 30 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) is, for example, 99 / 1 or less, preferably 90 / 10 or less, more preferably 80 / 20 or less, still more preferably 70 / 30 or less, particularly preferably 60 / 40 or less. By setting within the above range of the ratio (T2 / T1), it is easy to effectively exhibit the effects of the composition containing tackifying resin T1.

[0127] Although not particularly limited, the technology disclosed herein can be preferably implemented in any one of the following modes (1) to (3): (1) a mode in which the adhesive layer contains tackifying resin T1 as the tackifying resin; (2) a mode in which the adhesive layer contains tackifying resin T2 as the tackifying resin; or (3) a mode in which the adhesive layer contains both tackifying resin T1 and tackifying resin T2 as the tackifying resin.

[0128] 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 rapidly melted at as low a temperature as possible 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 at the center of the surface of the sample in the ring and placed 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, and the center of the mercury bulb of the thermometer is placed 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 uniformly heat. 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. Two or more softening point measurements are carried out simultaneously, and the average value thereof is used.

[0129] In the method where the tackifying resin is included in the adhesive layer, the total amount (total content) of the tackifying resin in the adhesive layer is appropriately set within the range having a target storage modulus 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, can be about 10 parts by weight or more, can be about 30 parts by weight or more, or can be about 40 parts by weight or more with respect to 100 parts by weight of the polyester-based polymer. In some methods, with respect to 100 parts by weight of the polyester-based polymer, the total amount of the above-mentioned tackifying resin is preferably 45 parts by weight or more. By having a composition containing a prescribed amount or more of the tackifying resin like this, an adhesive layer having a storage modulus at 23°C of a prescribed value or less 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 methods, with respect to 100 parts by weight of the polyester-based 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, still more preferably about 70 parts by weight or more, further preferably about 80 parts by weight or more, can be about 90 parts by weight or more, or can be about 100 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-based polymer and tackiness, in some methods, with respect to 100 parts by weight of the polyester-based polymer, it can be about 200 parts by weight or less, can be about 160 parts by weight or less, or can be about 150 parts by weight or less (for example, less than 150 parts by weight). From the viewpoint of making the storage modulus at 23°C a prescribed value or less to obtain good adhesion characteristics, in some preferred methods, with respect to 100 parts by weight of the polyester-based polymer, the total amount of the above-mentioned tackifying resin is about 130 parts by weight or less, more preferably about 110 parts by weight or less, still more preferably 100 parts by weight or less (for example, less than 100 parts by weight), particularly preferably about 90 parts by weight or less, can be about 80 parts by weight or less, can be about 70 parts by weight or less, or can be about 50 parts by weight or less.

[0130] In some embodiments, from the perspective of increasing the overall biomass ratio of the adhesive layer, it is preferable to use a tackifying resin derived from plants (plant-based tackifying resin) as the above-mentioned tackifying resin. A plant-based tackifying resin is a resin in which at least a part of the resin is composed of components derived from plants. It may also be that all of the resin is derived from plants, or a part of the resin is derived from plants and the other part is derived from fossil resources. Examples of plant-based tackifying resins 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 embodiments, the proportion of the plant-based tackifying resin in the total amount of the tackifying resin contained in the adhesive layer can be about 30% by weight or more, about 50% by weight or more, about 80% by weight or more, about 90% by weight or more, about 95% by weight or more, or even 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 plant-based tackifying resins.

[0131] (Crosslinking agent)

[0132] In some embodiments, the adhesive layer contains a crosslinking agent. According to the adhesive layer containing a crosslinking agent, based on the crosslinked structure obtained by using the crosslinking agent, the cohesive force can be improved. By using a crosslinking agent, good adhesion properties can be obtained, and the storage modulus at 23 °C can be adjusted. The crosslinking agent can be included in the adhesive layer in the form after the crosslinking reaction, the form before the crosslinking reaction, the form in which a part of the crosslinking reaction has occurred, their intermediate or composite forms, etc. The above-mentioned crosslinking agent is usually included in the adhesive layer 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.

[0133] The type of the crosslinking agent is not particularly limited, and it can be appropriately selected and used from the crosslinking agents known in the past. As such a crosslinking agent, for example, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, metal chelate-based crosslinking agents, etc. can be cited. The crosslinking agent can be used alone or in combination of two or more. Among them, isocyanate-based crosslinking agents are preferred.

[0134] As the isocyanate-based crosslinking agent, polyfunctional isocyanate-based compounds can preferably be used. Here, polyfunctional isocyanate-based compounds refer to compounds having an average of two or more isocyanate groups per molecule, and include polyfunctional isocyanate-based compounds having an isocyanurate structure. The isocyanate-based crosslinking agent can be used alone or in combination of two or more.

[0135] Examples of polyfunctional isocyanate compounds include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, aromatic polyisocyanate compounds, etc.

[0136] Specific examples of aliphatic polyisocyanate compounds include 1,2-ethylene diisocyanate; 1,2-butylene diisocyanate, 1,3-butylene diisocyanate, 1,4-butylene diisocyanate and other butylene diisocyanates; 1,2-hexylene diisocyanate, 1,3-hexylene diisocyanate, 1,4-hexylene diisocyanate, 1,5-hexylene diisocyanate, 1,6-hexylene diisocyanate, 2,5-hexylene diisocyanate and other hexylene diisocyanates; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, etc.

[0137] Specific examples of alicyclic polyisocyanate compounds include isophorone diisocyanate; 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate and other cyclohexyl diisocyanates; 1,2-cyclopentyl diisocyanate, 1,3-cyclopentyl diisocyanate and other cyclopentyl diisocyanates; hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc.

[0138] 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.

[0139] 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 (such as dimers or trimers), derivatives (such as the 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, dimers of diphenylmethane diisocyanate or trimers of diphenylmethane diisocyanate, isocyanurate forms of hexamethylene diisocyanate (trimer addition products having an isocyanurate structure), reaction products of trimethylolpropane and toluene diisocyanate, reaction products 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 such as the trade name "DURANATET TPA-100" manufactured by Asahi Kasei Chemicals Corporation, the trade name "DURANATET D101" manufactured by Asahi Kasei Chemicals Corporation, the trade name "Coronate HL" manufactured by Tosoh Corporation, the trade name "Coronate HK" manufactured by Tosoh Corporation, the trade name "Coronate HX" manufactured by Tosoh Corporation, the trade name "Coronate 2096" manufactured by Tosoh Corporation, etc. can be cited.

[0140] In some embodiments, as the crosslinking agent, a crosslinking agent without an aromatic ring (a crosslinking agent not containing 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 the adhesive layer 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 aromatic ring-free isocyanate, aliphatic isocyanate compounds can be cited.

[0141] 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 method of using one or two or more bifunctional crosslinking agents and one or two or more trifunctional or higher crosslinking agents (such as trifunctional crosslinking agents) in combination as the crosslinking agent can be cited.

[0142] The amount of the crosslinking agent used is not particularly limited. In some embodiments, the amount of the crosslinking agent (e.g., 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, may be about 0.01 parts by weight or more, and may also 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 viewpoints of having a moderate storage modulus at 23°C and improving cohesion, 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, and may be, for example, 2.5 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, may be about 7 parts by weight or less. From the viewpoint of moderately reducing the storage modulus at 23°C within a specified range, 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, may be about 2.0 parts by weight or less, and may also be about 1.6 parts by weight or less.

[0143] The amount of the crosslinking agent without an aromatic ring used is not particularly limited. In some embodiments, the amount of the crosslinking agent without an aromatic ring (e.g., 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, may be about 0.01 parts by weight or more, and 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 viewpoints of having a moderate storage modulus at 23°C and improving cohesion, 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, and may be, for example, 2.5 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, may be about 7 parts by weight or less. From the viewpoint of obtaining an adhesive layer having a storage modulus at 23°C below 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, may be about 2.0 parts by weight or less, and may also be about 1.6 parts by weight or less.

[0144] (Crosslinking catalyst)

[0145] 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. Examples of the crosslinking catalyst include: zirconium-containing compounds (zirconium-containing catalysts) such as zirconium acetylacetonate, monoacetylacetonate zirconium, zirconium ethylacetoacetate, and zirconium octoate compounds; 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 triacetylacetonate, 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.

[0146] 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 a usage mode where the adhesive layer is required to have transparency and optical properties, by avoiding the use of iron-containing compounds, coloring of the adhesive layer can be prevented or suppressed.

[0147] The amount of the crosslinking catalyst used is not particularly limited. For 100 parts by weight of the polyester polymer, the amount of the crosslinking catalyst used 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, for 100 parts by weight of the polyester polymer, the amount of the crosslinking catalyst used 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.

[0148] (Hydrolysis-resistant agent)

[0149] In addition, the adhesive layer disclosed herein can contain a hydrolysis-resistant agent (also referred to as a hydrolysis inhibitor). By adding the hydrolysis-resistant agent, the hydrolysis reaction in the adhesive layer 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 include oxazoline group-containing compounds, epoxy group-containing compounds, carbodiimide group-containing compounds, etc. Among them, carbodiimide group-containing compounds are preferred. The hydrolysis-resistant agent can be used alone or in combination of two or more.

[0150] 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. Herein, the monofunctional cyclic structure carbodiimide refers to a compound having one carbodiimide group in the molecular structure and binding the first nitrogen atom and the second nitrogen atom of the carbodiimide group through a binding group composed of an aliphatic group, an alicyclic group, an aromatic group or a combination thereof. It should be noted that the above binding group may contain heteroatoms and substituents. Preferred examples of the compound containing a carbodiimide group include dicyclohexylcarbodiimide, diisopropylcarbodiimide, and monofunctional cyclic structure carbodiimide.

[0151] 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, and 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 hydrolysis-resistant agent used is, for example, appropriately about 5 parts by weight or less, preferably about 3 parts by weight or less, and for example, it can be 1 part by weight or less, based on 100 parts by weight of the polyester polymer.

[0152] (Other additives)

[0153] In the adhesive layer, 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 colorant (pigment, dye, etc.), an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, a light stabilizer, etc., may be contained as needed. For the above various additives, substances known in the past can be used by conventional methods, which is not a feature of the present invention, and thus detailed description is omitted.

[0154] (Formation of the adhesive layer)

[0155] The adhesive layer disclosed herein can be formed, for example, from the above-described polyester polymers by a conventionally known method. For example, an adhesive composition can be applied onto a surface with releasability (release surface), and the adhesive layer can be formed on this surface by curing the adhesive composition. The adhesive layer 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 of directly applying (typically coating) the adhesive composition onto the substrate and curing it to form the adhesive layer (direct method) can be preferably employed. Alternatively, a method of applying the adhesive composition onto a surface with releasability (release surface), curing it to form the adhesive layer on this surface, and transferring the adhesive layer onto the substrate (transfer method) 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 preferred. 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 or stripes.

[0156] Coating of the adhesive composition can be carried out, for example, using a known or conventional coater such as a gravure roll coater, reverse roll coater, roll kiss coater, dip roll coater, slot die coater, bar coater, knife coater, spray coater, etc. Alternatively, the adhesive composition can also be coated by impregnation, curtain coating method, etc.

[0157] Drying of the adhesive composition can be carried out at normal temperature or under heating. From the viewpoints of promoting the crosslinking reaction, improving the 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 strains that may exist within the adhesive layer, etc. The aging conditions are not particularly limited, and can generally be conditions of 70°C or lower (for example, about 40°C to 70°C) and one day or more (for example, three days or more).

[0158] (Thickness of the adhesive layer)

[0159] 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, from 2 μm to 500 μm. From the viewpoint of the adhesiveness to the adherend, in some embodiments, it is usually appropriate that the thickness of the adhesive layer is 3 μm or more, and preferably 5 μm or more. From the viewpoints of improving the adhesive strength and effectively obtaining the effect of suppressing the decrease in adhesive strength, in some preferred embodiments, the thickness of the adhesive layer is, for example, 8 μm or more, more preferably 12 μm or more, further preferably 15 μm or more, and particularly preferably 18 μm or more. In addition, from the viewpoints of lightening the weight, miniaturizing, thinning the thickness, and high-functionalizing the product (such as a portable electronic device) to which the adhesive sheet is applied, 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, it is appropriate that the thickness of the adhesive layer is less than 80 μm, more preferably 50 μm or less, still more preferably 40 μm or less, further preferably 35 μm or less, further more preferably 30 μm or less, and in embodiments where thinner thickness is more emphasized, it is particularly preferably 25 μm or less, and can be, for example, 22 μm or less. In some other embodiments, the thickness of the adhesive layer can be less than 20 μm, can be less than 15 μm, can be less than 10 μm, and can also be 5 μm or less. According to the technology disclosed herein, in a configuration having an adhesive layer with a thin thickness as described above, the adhesive strength can also be effectively reduced. It should be noted that 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 above.

[0160] (Biomass ratio of the adhesive layer)

[0161] Although there is no particular limitation, the adhesive layer preferably has a biomass ratio equal to or higher than a specified value. In some embodiments, the biomass ratio of the adhesive layer may be about 30% or higher, suitably about 40% or higher, and preferably 50% or higher. By designing the adhesive layer in such a way that the biomass ratio is increased, the overall dependence of the adhesive layer on fossil resource-based materials can be reduced. From the perspective of further reducing the dependence on fossil resource-based materials, in some preferred embodiments, the biomass ratio of the adhesive layer may be 55% or higher, 60% or higher, 70% or higher, or 75% or higher. The upper limit of the biomass ratio is defined as 100%, but in the adhesive layer disclosed herein, since the components contained may include materials derived from fossil resources, the biomass ratio may be less than 100%. From the perspective of easily obtaining the effect of suppressing the decrease in adhesive force and having good adhesive properties (such as holding power), in some embodiments, the biomass ratio of the adhesive layer may be less than 90%, for example. In cases where adhesive performance is more emphasized, the biomass ratio of the adhesive layer may be less than 80% or less than 70%.

[0162] <Substrate>

[0163] The adhesive sheet disclosed herein may be in the form of a substrate-bearing adhesive sheet having an adhesive layer on one or both sides of the substrate. As the substrate, various sheet-like substrates can be used, such as resin films, papers, cloths, rubber sheets, foamed sheets, metal foils, and composites thereof. In the field of electronic devices, substrates that are not likely to be sources of dust (such as fine fibers or particles like paper dust) are preferably used. From this perspective, 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, and composites thereof can be preferably used.

[0164] Examples of resin films include: polyester films; vinyl chloride resin films; polyolefin films such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymers, and ethylene-butene copolymers; vinylidene chloride resin films; vinyl acetate resin films; polystyrene films; polyacetal films; polyimide films; polyamide films; fluororesin films; cellophane, etc. Examples of rubber sheets include: natural rubber sheets, butyl rubber sheets, etc. Examples of foamed sheets include: foamed polyurethane sheets, foamed polyolefin sheets, etc. Examples of metal foils include: aluminum foils, copper foils, etc.

[0165] 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, 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 release liner described later. 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.

[0166] In some embodiments, from the viewpoints of strength and processability, as the above-mentioned base material, a polyester film can be preferably adopted. Examples of the polyester film include: polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, polyethylene naphthalate (PEN) film, polybutylene naphthalate film, etc.

[0167] 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(trimethylene 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(polyhexamethylene terephthalamide); 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, in the adhesive sheet with a resin film as the base material, the usage amount of fossil resource-based materials can be reduced.

[0168] In the adhesive sheet having a substrate, the biomass ratio of the substrate is preferably 20% or more, more preferably 35% or more. In the case of paying more attention to reducing the use amount of fossil resource-based materials, the biomass ratio of the substrate can be, for example, 50% or more, 70% or more, 85% or more, 90% or more. The upper limit of the above biomass ratio is 100% or less. However, in some embodiments, considering processability, strength, etc., the biomass ratio of the substrate can be, for example, 80% or less, 60% or less, 40% or less, less than 20%.

[0169] 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 (such as a resin film). Thereby, the light transmittance (light barrier property) of the substrate can be adjusted. Adjusting the light transmittance of the substrate (such as the perpendicular light transmittance) can also contribute to the adjustment of the light transmittance of the substrate and the adhesive sheet including the substrate.

[0170] 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. For example, it can be a colorant such as black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent color, etc.

[0171] The substrate can be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In the substrate having a structure including a base film and a colored layer like this, the above base film can include a colorant or can not include a colorant. The above colored layer can be disposed on either surface of the base film, or can be disposed on both surfaces respectively. In the structure where colored layers are respectively disposed on both 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 the desired designability, light barrier property, and masking property can be obtained. The color of the colored layer is not particularly limited and can be various colors according to the purpose. In some embodiments, the colored layer can be, for example, a black layer (such as a black printing layer) formed by black printing.

[0172] 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, thermosetting, 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, or offset printing is preferably adopted.

[0173] 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 blending 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.

[0174] 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.

[0175] 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 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.

[0176] 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 some 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 overall thickness of the above 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.

[0177] 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 performed on the surface (adhesive layer side surface) of a base material (such as a resin film, rubber sheet, 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 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 anchoring on the adhesive layer side surface. 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.

[0178] 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 (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.

[0179] 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).

[0180] The thickness of the base material is not particularly limited and can be appropriately selected according to the purpose, and is usually about 1 μm to about 500 μm. From the viewpoint 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 viewpoint 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.

[0181] <Release liner>

[0182] The adhesive sheet disclosed herein can be an adhesive sheet in the form of an adhesive sheet with a release liner, and the adhesive sheet with a release liner has a release liner (for example, a first release liner) disposed on the surface (adhesive surface, for example, the first adhesive surface) of the adhesive layer. The above-mentioned release liner (including the first release liner and the second release liner. The same shall apply hereinafter unless otherwise specified) is not particularly limited, and for example, a release liner having a release treatment layer on a release liner substrate can be preferably used. The above-mentioned release treatment layer can be formed by surface-treating the release liner substrate with a release treatment agent. The release treatment agent can be a known release treatment agent such as a polysiloxane-based release treatment agent, a long-chain alkyl-based release treatment agent, a fluorine-containing release treatment agent, molybdenum(IV) sulfide, etc. In some embodiments, a release liner having a release treatment layer formed by a polysiloxane-based release treatment agent can be preferably used. The effect of suppressing the decrease in adhesive force produced by the technology disclosed herein can be effectively exerted by using a release liner having a release treatment layer formed by a polysiloxane-based release treatment agent. The thickness and formation method of the release treatment layer are not particularly limited and can be set in such a way as to exhibit appropriate releasability on the surface on the adhesive side of the release liner.

[0183] As the release liner substrate, various plastic films can be used. In this specification, a plastic film is typically a non-porous sheet, which is a concept different from, for example, a non-woven fabric (i.e., does not include non-woven fabrics). As the above-mentioned release liner substrate, a resin film having a non-porous structure and typically substantially free of air bubbles (void-free) can be preferably used. The resin film can be a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

[0184] Examples of the material for the above-mentioned plastic film include: polyester resins such as PET (polyethylene terephthalate), PBT (polybutylene terephthalate), and PEN (polyethylene naphthalate); polyolefin resins such as PE (polyethylene), PP (polypropylene), ethylene-propylene copolymer, and ethylene-butene copolymer; cellulose resins such as triacetyl cellulose; cyclic polyolefin resins such as acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, and norbornene resins; (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymer resins, polyarylate resins, polyphenylene sulfide resins, etc. A release liner substrate formed of any one or a mixture of two or more of these resins can be used. Among them, as a preferred release liner substrate, a polyester resin film (such as a PET film) formed of a polyester resin can be cited.

[0185] The plastic film used as the above-mentioned release liner substrate can be any one of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, the above-mentioned plastic film can have a single-layer structure or a multi-layer structure including two or more sub-layers. Known additives that can be used for the release liner substrate, such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, slip agents, anti-blocking agents, and nucleating agents, can be incorporated into the above-mentioned plastic film. In the multi-layer plastic film, each additive can be incorporated into all sub-layers or only into a part of the sub-layers.

[0186] The release liner, which is a component of the adhesive sheet with a release liner, can be the release liner used in the production of the adhesive sheet, that is, the release liner as a component of the adhesive sheet with a release liner immediately after production, or can be a release liner (replacement liner) that is replaced and pasted during the period before the adhesive sheet is adhered to the adherend by the original release liner (the release liner at the time of initial production), or another replacement liner that is further replaced and pasted from one replacement liner. Therefore, the adhesive sheet disclosed herein can be used in such a manner that it is adhered to the adherend through a process (replacement pasting) of replacing the release liner with another release liner (replacement liner) as needed. According to the technology disclosed herein, even in the case where the release liner is replaced and pasted before being adhered to the adherend, and the release treatment agent transfers from the release liner before and after replacement pasting to the adhesive layer and easily accumulates on the adhesive surface, it is possible to suppress a decrease in adhesive strength caused by the transfer of the release treatment agent. Therefore, the release liner that protects the adhesive surface of the adhesive sheet can suppress a decrease in adhesive strength and maintain the desired adhesive strength in either case of the release liner at the time of initial production or the release liner that is replaced and pasted. As the replacement liner, a liner having the same constitution (material, thickness, etc.) as the release liner before replacement can be used, or a liner having a different constitution can be used.

[0187] The thickness of the release liner is not particularly limited and can be, for example, about 10 μm to about 500 μm. From the viewpoints of the strength and dimensional stability of the release liner, a thickness of 20 μm or more for the release liner is appropriate, preferably 30 μm or more, can be 40 μm or more, can be 50 μm or more, can be 60 μm or more, and can also be 70 μm or more. By protecting the adhesive surface with a release liner having a sufficient thickness, it is easy to maintain the smoothness of the adhesive surface. In addition, from the viewpoints of the processability of the release liner (such as ease of winding), etc., a thickness of 300 μm or less for the release liner is appropriate, preferably 200 μm or less, can be 150 μm or less, and can also be 100 μm or less. By making the thickness of the release liner below a specified value, it is easy to smoothly remove it from the double-sided adhesive sheet. The thicknesses of the first release liner and the second release liner can be the same or different.

[0188] <Total Thickness of the Adhesive Sheet>

[0189] The thickness (total thickness) of the adhesive sheet disclosed herein (including the adhesive layer, and including the substrate in the adhesive sheet with a substrate, but not including the release liner) is not particularly limited, and can be, for example, in the range of about 2 μm to about 1000 μm. In some embodiments, considering the adhesive properties 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 can be 200 μm or less. From the viewpoints of weight reduction, miniaturization, thickness reduction, and high 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, still more preferably 50 μm or less, further preferably 40 μm or less, particularly preferably 35 μm or less. For example, it can be 30 μm or less, or can be 25 μm or less. In some other embodiments, the thickness of the adhesive sheet can be less than 20 μm, can be less than 15 μm, can be less than 10 μm, or can be 5 μm or less. The lower limit value of the thickness of the adhesive sheet is not particularly limited, and it is generally appropriate to be 3 μm or more. For example, it can be about 5 μm or more. From the viewpoint of productivity, it can be about 10 μm or more, or can be about 15 μm or more (such as about 18 μm or more).

[0190] <Properties of the Adhesive Sheet>

[0191] In some embodiments, the 180-degree peel strength of the adhesive sheet on a stainless steel plate (adhesion to SUS) is preferably 5 N / 20 mm or more. The adhesive sheet showing the above properties can be well adhered to the adherend, and thus can typically be preferably used in a manner that is not intended to be peeled off again. The above adhesion to SUS can be 7 N / 20 mm or more, or can be 9 N / 20 mm or more. From the viewpoint of achieving highly reliable bonding, in some preferred embodiments, the above adhesion to SUS is 10 N / 20 mm or more, more preferably 12 N / 20 mm or more, still more preferably 14 N / 20 mm or more, further preferably 16 N / 20 mm or more, particularly preferably 18 N / 20 mm or more, or can be 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, for example, can be 50 N / 20 mm or less, or can be 30 N / 20 mm or less. The above adhesion to SUS is specifically measured by the method described in the examples below.

[0192] In some embodiments, the adhesion retention rate after replacement and pasting of the release liner is preferably 70% or more, more preferably 75% or more, and still more preferably 80% or more. For the adhesive sheet having the above characteristics, even when an operation such as replacing the release liner before pasting onto the adherend is performed, it can be an adhesive sheet in which the decrease in adhesion is sufficiently suppressed. In some preferred embodiments, the adhesion retention rate after replacement and pasting of the release liner is 85% or more, more preferably 90% or more, and still more preferably 95% or more. The adhesion retention rate after replacement and pasting of the release liner is measured and calculated by the method described in the examples below. As the adhesion retention rate after replacement and pasting of the release liner, it may be the adhesion retention rate after replacement and pasting of the release liner measured and calculated when using one of the two release liners for replacement and pasting used in the measurement method described in the examples below. The adhesive sheet disclosed herein preferably has the above adhesion retention rate after replacement and pasting of the release liner when using any one of the two release liners for replacement and pasting.

[0193] Although not particularly limited, in some embodiments, it is preferable 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 having such a high biomass ratio, the amount of use of fossil resource-based materials can be reduced. From this viewpoint, in some preferred embodiments, the biomass ratio of the adhesive sheet is 40% or more, may be 50% or more, may be 60% or more, may be 70% or more, or may be 75% or more. 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 from plants, so the above biomass ratio may be less than 100%. From the viewpoint of easily obtaining the effect of suppressing the decrease in adhesion and good adhesive properties (such as adhesion), in some embodiments, the biomass ratio of the adhesive sheet can be, for example, 90% or less, and in the case of paying more attention to adhesive performance, it can be 80% or less, or can be 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 the biomass ratio of the entire adhesive sheet.

[0194] <Usage>

[0195] 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 for purposes such as fixing, joining, and strengthening components that make up an electronic device by being pasted onto the components. Even when an operation such as replacing the paste release liner before pasting onto the adherend is performed on the adhesive sheet disclosed herein, a decrease in adhesive strength can be suppressed. Therefore, it can preferably be used as a fixing means with good adhesive reliability for components of an electronic device that can replace the paste release liner before pasting onto the adherend for processing such as blanking and cutting, visual recognition, etc. In particular, it is suitable for fixing components of portable electronic devices. The adhesive sheet disclosed herein can preferably be used for purposes of fixing or joining components, for example, in the form of a double-sided adhesive sheet. The above double-sided adhesive sheet can be without a substrate or can have a substrate.

[0196] Non-limiting examples of the above portable electronic devices include: mobile phones, smartphones, tablet personal computers, notebook personal computers, various wearable devices (such as wrist-worn types like watches, modular types worn on a part of the body with clips or bands, eye-worn types including glasses types (monocular, binocular. Also includes helmet types), clothing types worn on shirts, socks, hats, etc. in the form of accessories, ear-worn types like earphones worn on the ears, etc.), digital cameras, digital video cameras, audio equipment (portable music players, recording pens, 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" being merely carryable is not sufficient. It means having a level of portability that an individual (standard adult) can relatively easily move.

[0197] Figure 4 To schematically show an example of a portable electronic device (smartphone) using the adhesive sheet disclosed herein. As Figure 4 shown, a battery (heating element) 540 is built into the interior of the housing 520 of the 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 double-sided adhesive sheet having double-sided adhesiveness for fixing components that make up the portable electronic device 500. It should be noted that the portable electronic device 500 has a touch panel 570 whose display portion also functions as an input portion. The adhesive sheet disclosed herein is preferably used as a component (component joining means) of the above portable electronic device.

[0198] The matters disclosed by this specification include the following.

[0199] [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. Inside the housing, a heating element (such as a battery) is built in. Among the multiple 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 polymer, and the storage modulus G' of the adhesive layer at 23°C is greater than or equal to 0.01 MPa and less than 0.40 MPa.

[0200] [2]The portable electronic device according to [1] above, wherein, relative to 100 parts by weight of the polyester polymer, the adhesive layer contains 45 parts by weight or more of a tackifying resin.

[0201] [3]The portable electronic device according to [2] above, wherein the softening point of the tackifying resin is 30°C or higher and 200°C or lower.

[0202] [4]The portable electronic device according to [2] or [3] above, wherein, relative to 100 parts by weight of the polyester polymer, the adhesive layer contains 60 parts by weight or less of a tackifying resin T1 having a softening point of 145°C or higher and 200°C or lower as the tackifying resin, or the adhesive layer contains a tackifying resin T2 having a softening point of 30°C or higher and lower than 145°C as the tackifying resin, or the adhesive layer contains the tackifying resin T1 and the tackifying resin T2 as the tackifying resin, and relative to 100 parts by weight of the polyester polymer, the content of the tackifying resin T1 is 60 parts by weight or less.

[0203] [5]The portable electronic device according to any one of [1] to [4] above, wherein the thickness of the adhesive layer is less than 80 μm.

[0204] [6]The portable electronic device according to any one of [1] to [5] above, wherein the 180-degree peel strength of the adhesive sheet from a stainless steel plate is 5 N / 20 mm or more.

[0205] [7]An adhesive sheet having an adhesive layer, wherein,

[0206] The adhesive layer contains a polyester polymer, and the storage modulus G' of the adhesive layer at 23°C is greater than or equal to 0.01 MPa and less than 0.40 MPa.

[0207] [8]The adhesive sheet according to [7] above, wherein, relative to 100 parts by weight of the polyester polymer, the adhesive layer contains 45 parts by weight or more of a tackifying resin.

[0208] [9] The adhesive sheet as described in [8] above, wherein the softening point of the tackifying resin is 30°C or higher and 200°C or lower.

[0209]

[10] The adhesive sheet as described in [8] or [9] above, wherein, based on 100 parts by weight of the polyester polymer, the adhesive layer contains 60 parts by weight or less of a tackifying resin T1 having a softening point of 145°C or higher and 200°C or lower as the tackifying resin; or the adhesive layer contains a tackifying resin T2 having a softening point of 30°C or higher and less than 145°C as the tackifying resin; or the adhesive layer contains the tackifying resin T1 and the tackifying resin T2 as the tackifying resin, and based on 100 parts by weight of the polyester polymer, the content of the tackifying resin T1 is 60 parts by weight or less.

[0210]

[11] The adhesive sheet as described in any one of [7] to

[10] above, wherein the thickness of the adhesive layer is less than 80 μm.

[0211]

[12] The adhesive sheet as described in any one of [7] to

[11] above, wherein the 180-degree peel strength of the adhesive sheet from a stainless steel plate is 5 N / 20 mm or higher.

[0212]

[13] The adhesive sheet as described in any one of [7] to

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

[0213]

[14] A portable electronic device, wherein the portable electronic device includes the adhesive sheet as described in any one of [7] to

[12] above.

[0214] Examples

[0215] Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to the contents shown in these examples. It should be noted that, unless otherwise specified, "parts" and "%" in the following description are based on weight.

[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 reaction water discharging solvent 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 reaction water discharging solvent 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] (Synthesis Example 3)

[0222] A separable four-necked flask was equipped with a stirrer, a thermometer, a nitrogen tube, and a water separation tube. 100 g of dimer acid (product name "Pripol 1009", manufactured by Croda Co., Ltd., molecular weight 567), 95 g of dimer diol (product name "Pripol2033", manufactured by Croda Co., Ltd., molecular weight 537), 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 reaction water discharging solvent 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 (A3) with a biomass ratio of 100% was obtained. The Mw of this polyester polymer (A3) was 30,000, and the Tg was -50 °C.

[0223] <Example 1>

[0224] To 100 parts of a polyester polymer (A1), 30 parts of a terpene phenol resin (trade name “YSPolyster S115”, softening point 115°C, manufactured by Yasuhara Chemical Co., hereinafter sometimes referred to as “T115”), 30 parts of a terpene phenol resin (trade name “YS Polyster S145”, softening point 145°C, manufactured by Yasuhara Chemical Co., hereinafter sometimes referred to as “S145”), 3 parts of an isocyanurate form of hexamethylene diisocyanate as a crosslinking agent (trade name “Coronate HX”, manufactured by Tosoh Corporation, free of aromatic rings, 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 added, 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, thickness 38 μm, hereinafter sometimes referred to as “the first release liner”) so that the dried thickness became 20 μm, and dried at 120°C for 3 minutes, whereby an adhesive layer was obtained. Then, the adhesive layer was laminated on the release-treated surface of a PET film (trade name “Diafoil MRF♯25”, manufactured by Mitsubishi Chemical Corporation, thickness 25 μm, hereinafter sometimes referred to as “the second release liner”), and further allowed to stand at 50°C for 3 days, whereby a substrate-free double-sided adhesive sheet (thickness 20 μm) with release liners of this example was obtained. The storage modulus G’ of the above adhesive layer at 23°C was 0.22 MPa. It should be noted that the substrate-free double-sided adhesive sheet with release liners has a form in which the first adhesive surface and the second adhesive surface of the double-sided adhesive sheet are protected by the first release liner and the second release liner, respectively.

[0225] In addition, except that the thickness of the dried adhesive layer was changed to 4 μm, the same operation as above was carried out, whereby a substrate-free double-sided adhesive sheet (thickness 4 μm) of this example was obtained.

[0226] <Examples 2 to 11 Comparative Examples 1 to 4>

[0227] As shown in Table 1, the types of polyester polymers, the types and amounts of tackifying resins, the amounts of crosslinking agents, and the amounts of crosslinking catalysts were changed. The adhesive compositions of each example were prepared by operating in the same manner as in Example 1. Using this adhesive composition, except for this, operating in the same manner as in Example 1, non-substrate double-sided adhesive sheets with a thickness of 4 μm and non-substrate double-sided adhesive sheets with a thickness of 20 μm were produced for each example.

[0228] The tackifying resins used in the above Examples and Comparative Examples are as described below.

[0229] T30: Terpene phenol resin (trade name “YS Polyster T30”, softening point 30 °C, manufactured by Yasuhara Chemical Co., Ltd.)

[0230] T80: Terpene phenol resin (trade name “YS Polyster T80”, softening point 80 °C, manufactured by Yasuhara Chemical Co., Ltd.)

[0231] D125: Rosin ester (trade name “Pensel D125”, softening point 125 °C, pentaerythritol ester of polymerized rosin, manufactured by Arakawa Chemical Industries, Ltd.)

[0232] SE10: Rosin ester (trade name “Haritac SE10”, softening point 75 °C to 85 °C, hydrogenated rosin glyceride, manufactured by Harima Chemicals, Inc.)

[0233] <Evaluation>

[0234] [Adhesion to SUS]

[0235] The adhesive sheet was cut into a size of 20 mm in width and 150 mm in length to prepare a measurement sample. In an environment of 23 °C and 50% RH, the adhesive surface of the above measurement sample was exposed, and a 2 kg rubber roller was reciprocated once to press the adhesive surface of the above measurement sample against a stainless steel plate (SUS304BA plate) as the adherend. It was left in an environment of 23 °C and 50% RH for 30 minutes, and then in the same environment, using a tensile testing machine, according to JIS Z0237:2000, the peel strength (adhesion to SUS) [N / 20 mm] was measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / minute. As the tensile testing machine, a universal tensile and compression testing machine (device name “Tensile and Compression Testing Machine, TCM-1kNB”, manufactured by Minebea Co., Ltd.) can be used.

[0236] It should be noted that when measuring the adhesion to SUS, according to needs (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 was used in the examples.

[0237] [Adhesion and adhesion retention rate after replacement and pasting of the release liner]

[0238] The second release liner (Diafoil MRF♯25) was peeled off from a double-sided adhesive sheet with release liners protected by the first release liner (Diafoil MRV♯38) and the second release liner (Diafoil MRF♯25) from the first adhesive surface and the second adhesive surface respectively. A PET film with a thickness of 50 μm was pasted (lined) on the exposed second adhesive surface. The above double-sided adhesive sheet was cut into a size of 30 mm wide and 160 mm long to produce a measurement sample. In an environment of 23°C and 50% RH, the first release liner was peeled from the first adhesive surface of the above adhesive sheet with release liners by hand in the 180-degree direction, and an adhesive sheet for replacement and pasting (more specifically, the release treatment surface of this release liner) was immediately overlapped and pasted on the exposed first adhesive surface, and a 2-kg manual roller was reciprocated 2 times for crimping. It was placed in an environment of 70°C for 24 hours while maintaining a state of applying a pressure of 5 kg to the first adhesive surface from the replacement and pasting release liner. Then, the above 5-kg load was removed, and it was placed in an environment of 23°C and 50% RH for about 3 to 5 hours. Then, by the same method as the above measurement of the adhesion to SUS, using a measurement sample cut into a size of 20 mm wide and 150 mm long, in accordance with JIS Z0237:2000, the peel strength (adhesion after replacement and pasting of the liner) [N / 20 mm] to the SUS plate was measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min.

[0239] As the release liner for replacement and pasting, a release liner manufactured by Fujico Co., Ltd. (product name "SCA1", a PET release liner with a polysiloxane-based release treatment agent layer, thickness 75 μm) and a PET release liner manufactured by Toray Industries, Inc. (product name "Cerapeel BX8A", a PET release liner with a polysiloxane-based release treatment agent layer, thickness 75 μm) were used to measure the adhesion after replacement and pasting of the liner.

[0240] Regarding the adhesion retention rate [%] after replacement and pasting of the release liner, the ratio of the adhesion [N / 20 mm] after replacement and pasting of the liner to the adhesion before replacement and pasting of the liner (the above adhesion to SUS) [N / 20 mm] was calculated in percentage form.

[0241] The outlines and evaluation results of each example are shown in Table 1. It should be noted that in Table 1, the adhesive force and adhesive force retention rate after replacing and pasting the liner with a 4-μm or 20-μm adhesive layer using SCA1 are recorded in the columns of SCA1_4μm and SCA1_20μm respectively, and the adhesive force and adhesive force retention rate after replacing and pasting the liner with a 4-μm or 20-μm adhesive layer using BX8A are recorded in the columns of BX8A_4μm and BX8A_20μm respectively.

[0242]

[0243] As shown in Table 1, for the adhesive sheets of Examples 1 to 11 having an adhesive layer containing a polyester polymer and having a storage modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa, the adhesive force retention rate after replacing and pasting the liner evaluated by two types of replacement and pasting liners is 70% or more when the adhesive layer thickness is 4 μm, and 80% or more when the adhesive layer thickness is 20 μm. After replacing and pasting the liner, a decrease in the adhesive force after storage under specified conditions (70°C, 5 kg, 24 hours) is suppressed. In addition, the adhesive force of the adhesive sheets of Examples 1 to 11 to SUS is 5 N / 20 mm or more, showing good adhesive force. On the other hand, in Comparative Examples 1 to 4 where the storage modulus G' of the adhesive layer at 23°C is 0.40 MPa or more, the above-mentioned adhesive force retention rate after replacing and pasting the liner is less than 70% when the adhesive layer thickness is 4 μm, and less than 80% when the adhesive layer thickness is 20 μm, which is a result worse than that of the above examples.

[0244] From the above results, it can be seen that for an adhesive sheet having an adhesive layer containing a polyester polymer and having a storage modulus G' at 23°C of 0.01 MPa or more and less than 0.40 MPa, regardless of the treatment method before pasting to the adherend, even in the case of undergoing treatment methods that are likely to reduce the adhesive force, such as replacing and pasting the release liner before pasting to the adherend or further storing in a harsh environment without temperature control, etc., a decrease in the adhesive force can be suppressed.

[0245] The specific examples of the present invention have been described in detail above, but they are merely illustrative and do not limit the claims. The technology described in the claims includes technical solutions obtained by various deformations and changes of the above-mentioned specific examples.

Claims

1. An adhesive sheet comprising an adhesive layer, wherein: The adhesive layer includes a polyester polymer, and a storage modulus G′ of the adhesive layer at 23° C. is greater than or equal to 0.01 MPa and less than 0.40 MPa.

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

3. The adhesive sheet according to claim 2, wherein The tackifier resin has a softening point of 30° C. or higher and 200° C. or lower.

4. The adhesive sheet according to claim 2 or 3, wherein The adhesive layer contains 60 parts by weight or less of a tackifier resin T1 having a softening point of 145° C. or more and 200° C. or less, relative to 100 parts by weight of the polyester polymer, as the tackifier resin; or The adhesive layer contains a tackifying resin T2 having a softening point of 30° C. or more and less than 145° C. as the tackifying resin, or The adhesive layer includes the tackifier resin T1 and the tackifier resin T2 as the tackifier resins, and the content of the tackifier resin T1 is 60 parts by weight or less relative to 100 parts by weight of the polyester-based polymer.

5. The adhesive sheet according to any one of claims 1 to 3, wherein The adhesive layer has a thickness of less than 80 μm.

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

7. A portable electronic device, wherein: The portable electronic device comprises the pressure-sensitive adhesive sheet according to claim 1 or 2.

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