Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

Abstract

Provided is an adhesive containing a polyester-based polymer synthesized using a biomass material, and more specifically, an adhesive composition combining an adhesive force and a high-temperature holding force, and containing a polyester-based polymer, wherein 50% or more of the constituent carbon is a biomass-derived carbon. The adhesive composition further contains a tackifier resin. The weight-average molecular weight of the polyester-based polymer is 30,000 or more.

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet. This application claims priority to Japanese Patent Application No. 2021-030200, filed on February 26, 2021, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Generally, adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) are in a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to an adherend when pressure is applied. Utilizing these properties, adhesives are widely used in a variety of industrial fields, from home appliances to automobiles, various machines, electrical appliances, and electronic appliances, as a joining means with good workability and high adhesive reliability, typically in the form of an adhesive sheet containing a layer of the adhesive. Various types of adhesives, such as acrylic adhesives, rubber adhesives, and polyester adhesives, are used depending on the purpose of use, the location of use, the required properties, etc. Patent Documents 1 to 3, for example, are cited as documents disclosing prior art related to polyester adhesives. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent No. 4914132 [Patent Document 2] Japanese Patent No. 6687997 [Patent Document 3] Japanese Patent Application Publication No. 2020-79372 Summary of the Invention [Problem to be solved by the invention]

[0004] Pressure-sensitive adhesive sheets are preferably used for fixing components in electronic devices such as mobile phones, smartphones, and tablet computers. Pressure-sensitive adhesive sheets for electronic devices mainly use acrylic pressure-sensitive adhesives with an acrylic polymer as the base polymer. Other examples of pressure-sensitive adhesives used in the above applications include synthetic rubber pressure-sensitive adhesives with a rubber block copolymer such as a styrene-butadiene block copolymer as the base polymer.

[0005] In recent years, environmental issues such as global warming have become increasingly important, creating a demand for reducing the use of fossil-based materials such as petroleum. It is also desirable to reduce the use of fossil-based materials in the above-mentioned pressure-sensitive adhesive sheets for electronic devices. However, both the above-mentioned acrylic and synthetic rubber pressure-sensitive adhesives are primarily made from fossil-based materials such as petroleum. In reality, reducing the use of fossil-based materials is difficult, and there are limits to switching to renewable organic resources. Polyester-based pressure-sensitive adhesives are an example of a pressure-sensitive adhesive that can reduce dependence on fossil-based materials and is expected to have adhesive properties equivalent to or better than those of acrylic and synthetic rubber pressure-sensitive adhesives. Polyester-based pressure-sensitive adhesives have excellent properties such as chemical resistance, water resistance, durability, and optical properties (transparency), making them suitable for a variety of applications, including portable electronic devices. Furthermore, because the polyester polymers used in polyester-based pressure-sensitive adhesives can be synthesized using biomass materials (e.g., Patent Documents 1 and 2), the use of such polyester polymers can reduce the use of petroleum-based materials. Biomass materials typically refer to materials derived from biological resources (typically plants that perform photosynthesis) that can be reproduced sustainably in the presence of sunlight, water, and carbon dioxide.

[0006] However, polyester polymers typically have crosslinking points only at the ends of the polymer chain, making it difficult to achieve an effective crosslinked structure compared to acrylic polymers. Such a polymer structure can hinder the realization of required performance, for example, in applications involving bonding and fixing portable electronic devices. Specifically, pressure-sensitive adhesives used in portable electronic devices are required to have sufficient adhesive strength for bonding and fixing, while also possessing a holding strength (high-temperature holding strength) that prevents slippage even at high temperatures. Portable electronic devices incorporate heat-generating elements such as batteries in a limited internal space. Prolonged use of portable electronic devices increases the internal temperature due to heat generated by the batteries, so pressure-sensitive adhesives used in portable electronic devices must also possess high-temperature holding strength. Furthermore, repeated exposure to high and room temperatures within portable electronic devices can cause internal shrinkage of the adherend material. Therefore, pressure-sensitive adhesives are required to have a holding strength that prevents slippage even in the face of such shrinkage of the adherend. As described above, polyester polymers often have a structure that makes it relatively difficult to increase the degree of crosslinking, making it difficult to improve high-temperature holding strength by utilizing the degree of crosslinking. For example, if an attempt is made to increase the degree of crosslinking by increasing the amount of crosslinking agent in order to improve holding power, there is a concern that the gel fraction will increase, resulting in a decrease in flexibility and adhesive strength, and a decrease in impact resistance. Compared to acrylic adhesives, polyester-based pressure-sensitive adhesives tend to find it more difficult to achieve both high-temperature holding power and other adhesive properties (typically adhesive strength).

[0007] The present invention was made in view of the above circumstances, and aims to provide a pressure-sensitive adhesive composition containing a polyester-based polymer synthesized using a biomass material, which is capable of achieving both adhesive strength and high-temperature retention. Another related aim is to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polyester-based polymer synthesized using a biomass material. [Means for solving the problem]

[0008] According to the present specification, there is provided a pressure-sensitive adhesive composition comprising a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived carbon. The pressure-sensitive adhesive composition further comprises a tackifying resin. The polyester-based polymer has a weight-average molecular weight of 30,000 or more.

[0009] The PSA composition is prepared using a polyester polymer in which 50% or more of the carbon in the composition is biomass-derived (bio content 50% or more), thereby reducing dependence on fossil resource-based materials. Furthermore, the PSA composition further contains a tackifier resin, and the weight-average molecular weight (Mw) of the polyester polymer is 30,000 or more. This allows for improved adhesive strength to be achieved through the actions of the polyester polymer and the tackifier resin. Furthermore, high-temperature cohesion can be achieved based on the Mw of the polyester polymer. A PSA composition with the above composition can achieve both adhesive strength and high-temperature cohesion.

[0010] Furthermore, a pressure-sensitive adhesive composition having the above-mentioned composition is likely to provide good repulsion resistance. For example, in recent years, displays having curved shapes such as three-dimensional shapes have been put to practical use as displays such as organic EL display devices used in electronic devices such as smartphones. It is desirable that the pressure-sensitive adhesive used for the above-mentioned applications has durability against bending, and has adhesive reliability that prevents lifting or peeling against the repulsive force that tries to return the member to its original shape, even if the member attached to the curved surface of the display is highly elastic. Pressure-sensitive adhesives that can exhibit the above-mentioned repulsion resistance tend to have excellent adhesive reliability against bending, and are therefore preferably used in embodiments in which the pressure-sensitive adhesive is attached to the surface of a curved shape such as a three-dimensional shape of a portable electronic device, for example.

[0011] In some preferred embodiments of the technology disclosed herein (including pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets; the same applies hereinafter), the weight-average molecular weight of the polyester polymer is greater than 60,000. By using a polyester polymer having the above Mw, better high-temperature retention strength is easily achieved.

[0012] In some embodiments, the glass transition temperature of the polyester polymer is equal to or lower than 0° C. By using a polyester polymer having a glass transition temperature (Tg) of 0° C. or lower, good adhesive properties (for example, adhesive strength) are likely to be obtained.

[0013] In some preferred embodiments, the polyester polymer contains an aromatic ring. By introducing an aromatic ring into the polyester polymer, excellent high-temperature retention is likely to be obtained.

[0014] In some preferred embodiments, the tackifier resin is selected from a terpene phenolic resin and a polymerized rosin ester. By using one or more selected from a terpene phenolic resin and a polymerized rosin ester as the tackifier resin, both adhesive strength and high-temperature retention can be achieved.

[0015] In some preferred embodiments, the polyester polymer contains an aromatic ring, and the tackifier resin also contains an aromatic ring. By making both the polyester polymer and the tackifier resin have a structure containing an aromatic ring, high-temperature holding power is easily obtained. Furthermore, the polyester polymer and the tackifier resin tend to have excellent compatibility.

[0016] Some preferred embodiments of the pressure-sensitive adhesive composition further include a crosslinking agent. The content of the crosslinking agent is 5 parts by weight or less per 100 parts by weight of the polyester polymer. According to the technology disclosed herein, a cohesive strength that realizes high-temperature holding power can be obtained with the limited amount of crosslinking agent used as described above. This can be an advantageous feature in achieving both high-temperature holding power and other adhesive properties such as adhesive strength. An isocyanate-based crosslinking agent is preferably used as the crosslinking agent. Among these, it is particularly preferable that the isocyanate-based crosslinking agent is an aliphatic isocyanate-based compound. By using an aliphatic isocyanate-based compound as the crosslinking agent, the degree of crosslinking can be effectively increased.

[0017] The pressure-sensitive adhesive composition according to some embodiments further comprises a crosslinking agent and a crosslinking catalyst. The crosslinking catalyst does not contain a tin-based compound. From the viewpoints of environmental impact and safety, it is preferable to reduce the amount of tin-containing compounds (typically organotin compounds) used. The pressure-sensitive adhesive composition disclosed herein can efficiently form a crosslinked structure that is suitable for achieving both adhesive strength and high-temperature holding power without using a tin-based crosslinking catalyst, which generally tends to have excellent reaction speed.

[0018] Furthermore, this specification provides a PSA sheet having a PSA layer containing a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived carbon. In this PSA sheet, the PSA layer further contains a tackifier resin. The polyester-based polymer has a weight-average molecular weight of 30,000 or more. Because the PSA sheet having the above configuration uses a polyester-based polymer with a bio-content of 50% or more as the PSA, it can reduce dependence on fossil resource-based materials. Furthermore, by using a polyester-based polymer having the above Mw in combination with a tackifier resin, it is possible to achieve both adhesive strength and high-temperature retention.

[0019] In some preferred embodiments, the PSA sheet has a 180-degree peel strength from a stainless steel plate of 10 N / 20 mm or more, and has a holding strength that prevents it from falling in a holding strength test conducted under conditions of 80°C, a load of 1 kg, and 1 hour. PSA sheets that satisfy the above two properties adhere well to the adherend, and are likely to exhibit high adhesive reliability without peeling or slippage, even when used in environments exposed to high temperatures, for example.

[0020] The PSA sheets disclosed herein have adhesive reliability that achieves both adhesive strength and high-temperature retention, and are therefore suitable for use in portable electronic devices that require high performance. The interiors of portable electronic devices may contain heat-generating elements such as batteries, and may be exposed to temperatures of, for example, 40°C or higher, making the use of PSA sheets with excellent high-temperature retention particularly useful. As described above, the present specification provides a portable electronic device that uses any of the PSA sheets disclosed herein, in other words, a portable electronic device that includes the PSA sheet. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view schematically illustrating the configuration of a pressure-sensitive adhesive sheet according to one embodiment. [Figure 2] FIG. 10 is a cross-sectional view schematically illustrating the configuration of a pressure-sensitive adhesive sheet according to another embodiment. [Figure 3] FIG. 10 is a cross-sectional view schematically illustrating the configuration of a pressure-sensitive adhesive sheet according to another embodiment. [Figure 4] 1 is a front view schematically illustrating an example of a portable electronic device configured to include an adhesive sheet. [Figure 5] FIG. 1 is a schematic diagram illustrating a method for testing repulsion resistance. DETAILED DESCRIPTION OF THE INVENTION

[0022] Preferred embodiments of the present invention will be described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings on carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and duplicate explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product.

[0023] The pressure-sensitive adhesive sheet disclosed herein is configured to include a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may be in the form of a substrate-less double-sided pressure-sensitive adhesive sheet having, for example, a first adhesive surface formed by one surface of the pressure-sensitive adhesive layer and a second adhesive surface formed by the other surface of the pressure-sensitive adhesive layer. Alternatively, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a substrate-attached pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is laminated on one or both surfaces of a supporting substrate. Hereinafter, the supporting substrate may also be simply referred to as the "substrate."

[0024] <Adhesive sheet configuration example> The structure of a pressure-sensitive adhesive sheet according to one embodiment is shown schematically in FIG. 1. This pressure-sensitive adhesive sheet 1 is configured as a substrate-less double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer 21. The pressure-sensitive adhesive sheet 1 is used by attaching a first adhesive surface 21A, which is configured as one surface (first surface) of the pressure-sensitive adhesive layer 21, and a second adhesive surface 21B, which is configured as the other surface (second surface) of the pressure-sensitive adhesive layer 21, to different locations on an adherend. The locations to which the adhesive surfaces 21A and 21B are attached may be different locations on different members, or may be different locations on a single member. Before use (i.e., before being attached to an adherend), the pressure-sensitive adhesive sheet 1 may be a component of a release-liner-attached pressure-sensitive adhesive sheet 100, as shown in FIG. 1, in which the first adhesive surface 21A and the second adhesive surface 21B are protected by release liners 31 and 32, each of which has a release surface at least on the side facing the pressure-sensitive adhesive layer 21. For example, a sheet-like substrate (liner substrate) configured such that one side serves as a release surface by providing a release layer made of a release treatment agent on that surface can be preferably used as release liners 31, 32. Alternatively, release liner 32 can be omitted, and release liner 31, which has release surfaces on both sides, can be used, and this can be superimposed on PSA sheet 1 and wound spirally to form a PSA sheet with release liner in a form (roll form) in which second PSA surface 21B is protected by being in contact with the back surface of release liner 31.

[0025] The structure of a PSA sheet according to another embodiment is shown schematically in FIG. 2. This PSA sheet 2 is configured as a substrate-attached single-sided PSA sheet comprising a sheet-like support substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, and a PSA layer 21 provided on the first surface 10A side of the support substrate 10. The PSA layer 21 is fixedly provided on the first surface 10A side of the support substrate 10, i.e., without any intention of separating the PSA layer 21 from the support substrate 10. As shown in FIG. 2, the PSA sheet 2 before use may be a component of a release-liner PSA sheet 200 in a form in which the surface (adhesive surface) 21A of the PSA layer 21 is protected by a release liner 31, at least the side facing the PSA layer 21 being a release surface. Alternatively, the release liner 31 may be omitted, and a support substrate 10 having a second surface 10B as a release surface may be used, and the PSA sheet 2 may be rolled up so that the adhesive surface 21A is in contact with and protected by the second surface (rear surface) 10B of the support substrate 10.

[0026] The structure of a PSA sheet according to yet another embodiment is shown schematically in Fig. 3. This PSA sheet 3 is configured as a substrate-attached double-sided PSA sheet comprising a sheet-like support substrate (e.g., a resin film) 10 having a first side 10A and a second side 10B, a first PSA layer 21 fixedly provided on the first side 10A, and a second PSA layer 22 fixedly provided on the second side 10B. As shown in Fig. 3, the PSA sheet 3 before use may be a component of a release-liner PSA sheet 300 in which the surface (first adhesive surface) 21A of the first PSA layer 21 and the surface (second adhesive surface) 22A of the second PSA layer 22 are protected by release liners 31, 32. Alternatively, the release liner 32 may be omitted, and a release liner 31 having release surfaces on both sides may be used, which may be superimposed on the PSA sheet 3 and wound into a spiral shape to form a release-liner PSA sheet in which the second adhesive surface 22A is protected by contacting the back surface of the release liner 31 (roll form).

[0027] The release liner may be a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or a release liner made of a low-adhesion material such as a polyolefin resin (e.g., polyethylene or polypropylene) or a fluorine-based resin. The release treatment layer may be formed by surface treating the liner substrate with a release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. In the field of electronic devices, a release liner having a release treatment layer on the surface of a resin film or a release liner made of a low-adhesion material is preferred from the viewpoint of avoiding the generation of paper dust.

[0028] The concept of adhesive sheet here may include those called adhesive tape, adhesive film, adhesive label, etc. The adhesive sheet may be in the form of a roll or a sheet, and may be cut, punched, or otherwise processed into an appropriate shape depending on the application or mode of use.

[0029] <Adhesive layer> (Polyester polymer) The pressure-sensitive adhesive sheet disclosed herein comprises a pressure-sensitive adhesive layer containing a polyester-based polymer. In other words, the pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contain a polyester-based polymer (hereinafter, unless otherwise specified, the matters described for the pressure-sensitive adhesive layer can also be applied to the pressure-sensitive adhesive composition). Such pressure-sensitive adhesives and pressure-sensitive adhesive compositions containing a polyester-based polymer are also referred to as polyester-based pressure-sensitive adhesives and polyester-based pressure-sensitive adhesive compositions. The polyester-based polymer is typically contained in the pressure-sensitive adhesive layer as a base polymer. Here, the base polymer refers to the main component of a rubbery polymer (a polymer that exhibits rubber elasticity in a temperature range around room temperature) contained in the pressure-sensitive adhesive layer. In this specification, unless otherwise specified, the term "main component" refers to a component contained in an amount of more than 50% by weight. In this specification, the term "polyester-based polymer" refers to a polymer obtained by polycondensation of a dicarboxylic acid and a diol.

[0030] The polyester polymer contained in the PSA layer has a biomass-derived carbon content of 50% or more. In other words, the biomass carbon ratio (also referred to as the bio-fraction) of the polyester polymer is 50% or more. By using a polyester polymer having a bio-fraction of a predetermined value or more, the PSA's dependence on fossil resource-based materials can be reduced. In some embodiments, the bio-fraction of the polyester polymer is 52% or more, suitably 55% or more, and may be, for example, 60% or more. The bio-fraction of the polyester polymer is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more, and may be 85% or more, or even 88% or more. While the upper limit of the bio-fraction is 100% by definition, in some embodiments, the bio-fraction of the polyester polymer may be, for example, 95% or less. When adhesive performance is more important, it may be 92% or less, 90% or less, or 85% or less. By using a biomass-derived compound for at least one (for example, both) of the dicarboxylic acid and diol used in the synthesis of a polyester-based polymer, the bio content of the polyester-based polymer can be increased to 50% or more.

[0031] Here, in this specification, biomass-derived carbon refers to carbon (renewable carbon) derived from biomass materials, i.e., materials derived from renewable organic resources. The biomass materials typically refer to materials derived from biological resources (typically, plants that perform photosynthesis) that can be sustainably reproduced in the presence of sunlight, water, and carbon dioxide. Therefore, materials derived from fossil resources that are depleted through use after mining (fossil resource-based materials) are excluded from the concept of biomass materials. The biomass ratio of a polyester-based polymer, i.e., the proportion of biomass-derived carbon in the total carbon contained in the polyester-based polymer, can be estimated from the content of the carbon isotope with mass number 14 measured in accordance with ASTM D6866. The same applies to the examples described below.

[0032] The weight-average molecular weight (Mw) of the polyester polymer is 30,000 or more. By using a polyester polymer with a Mw of a predetermined value or more, the cohesive strength of the pressure-sensitive adhesive layer is increased, and the holding power, and therefore the high-temperature holding power, are improved. In some embodiments, the Mw of the polyester polymer is suitably more than 50,000, and from the viewpoint of obtaining better high-temperature holding power, it is preferably more than 60,000, more preferably more than 70,000, even more preferably more than 80,000, particularly preferably more than 90,000, and may even be 95,000 or more. In some preferred embodiments, the Mw of the polyester polymer is more than 100,000, more preferably more than 110,000 (e.g., more than 110,000), even more preferably more than 120,000, and may even be 125,000 or more. By using such a high-molecular-weight polyester polymer, excellent resilience is likely to be obtained. The upper limit of the Mw of the polyester polymer is usually about 30×10 4 From the viewpoint of adhesive strength, it is preferable that the thickness is about 20×10 4 or less, more preferably about 15×10 4 For example, approximately 12 × 10 4 It may be the following:

[0033] In this specification, the Mw of a polyester polymer refers to a value calculated in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As a GPC device, for example, a model "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used. More specifically, GPC measurement can be performed under the following conditions. Measurements are also performed in the examples described below using the same method. [GPC measurement] Column: TSKgel GMH-H(S) Column temperature: 40℃ Eluent: THF (0.1% by weight of amine components added) Flow rate: 0.5mL / min Injection volume: 100μL Detector: Differential refractometer (RI) Standard sample: Polystyrene (PS)

[0034] The glass transition temperature (Tg) of the polyester polymer is advantageously about 15°C or lower, preferably about 0°C or lower, more preferably about -15°C or lower, even more preferably about -20°C or lower, and particularly preferably about -25°C or lower (for example, about -30°C or lower). By using a polyester polymer with a low Tg, adhesive strength can be preferably improved. Furthermore, from the viewpoint of the cohesive strength of the pressure-sensitive adhesive layer, the Tg of the polyester polymer is usually about -80°C or higher, preferably about -60°C or higher, more preferably about -45°C or higher, even more preferably about -40°C or higher, and may be about -35°C or higher. The Tg of the polyester polymer can be adjusted by appropriately changing the monomer composition (i.e., the types and amount ratios of monomers used in the synthesis of the polymer).

[0035] The Tg of a polyester polymer is measured by the following method. Specifically, a disc-shaped test piece having a thickness of 2 mm and a diameter of 8 mm is prepared from the polyester polymer to be measured. This test piece is sandwiched between parallel plates for shear testing, and the peak value of tan δ (loss modulus G'' / storage modulus G') is determined at a frequency of 1 Hz using a measuring device (ARES, manufactured by Rheometric Scientific), and the temperature at which this peak value is obtained is defined as Tg (glass transition temperature) [°C]. Measurements are also made in the examples described below using a similar method.

[0036] (dicarboxylic acid) The dicarboxylic acid used in the synthesis of the polyester polymer may be any of aliphatic dicarboxylic acids, dimer acids, alicyclic dicarboxylic acids, unsaturated dicarboxylic acids, and aromatic dicarboxylic acids. Specific examples of the dicarboxylic acid include aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, dodecanedioic acid, sebacic acid, thiodipropionic acid, and diglycolic acid; dimer acids obtained by dimerizing fatty acids such as oleic acid and erucic acid; 1,2-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 4-methyl-1,2 Examples of suitable dicarboxylic acids include alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, norbornanedicarboxylic acid, and adamantanedicarboxylic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, and dodecenyl succinic anhydride; aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; and derivatives thereof. Derivatives of the above dicarboxylic acids include carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters. By appropriately selecting and using one or more of these dicarboxylic acids, polyester polymers suitable for achieving both adhesive strength and high-temperature holding power can be obtained.

[0037] As the dicarboxylic acid, it is preferable to use a plant-derived dicarboxylic acid from the viewpoint of obtaining a polyester polymer with a bio-content of 50% or more. Suitable examples of such dicarboxylic acids include sebacic acid derived from plants (e.g., castor oil) and dimer acids derived from fatty acids such as oleic acid and erucic acid. The plant-derived dicarboxylic acids can be used alone or in combination of two or more.

[0038] From the viewpoint of reducing dependence on petroleum-derived materials, the weight proportion of plant-derived dicarboxylic acids in the total amount (total weight) of dicarboxylic acids as monomer components of polyester-based polymers is suitably about 1 wt% or more, preferably about 10 wt% or more, more preferably about 50 wt% or more, even more preferably about 70 wt% or more, particularly preferably about 80 wt% or more, and may be about 90 wt% or more, or even about 95 wt% or more (e.g., 95 to 100 wt%). The upper limit of the weight proportion of the plant-derived dicarboxylic acids is 100 wt%, and from the viewpoint of adhesive properties such as high-temperature holding power, it is suitably about 99 wt% or less, preferably about 95 wt% or less, or may be about 90 wt% or less.

[0039] In some preferred embodiments, dimer acid is used as the plant-derived dicarboxylic acid. The use of dimer acid can increase the bio-content of the polyester polymer while achieving good adhesive properties. The dimer acid can be used alone or in combination of two or more. In embodiments where dimer acid is used as the dicarboxylic acid, the weight ratio of the dimer acid to the total amount (total weight) of dicarboxylic acids as monomer components of the polyester polymer is suitably approximately 1% by weight or more, preferably approximately 10% by weight or more, more preferably approximately 50% by weight or more, even more preferably approximately 70% by weight or more, particularly preferably approximately 80% by weight or more, and may even be approximately 90% by weight or more, or approximately 95% by weight or more (e.g., 95 to 100% by weight). By using a predetermined amount of dimer acid or more, the polymer can be designed based on the properties of the dimer acid. Furthermore, the upper limit of the weight proportion of the dimer acid is 100% by weight, and from the viewpoint of adhesive properties such as high-temperature retention, it is appropriate to have a weight proportion of approximately 99% by weight or less, preferably approximately 95% by weight or less, and may be approximately 90% by weight or less.

[0040] In some embodiments, sebacic acid may be used as the plant-derived dicarboxylic acid. The use of sebacic acid can also increase the biomass content of the polyester polymer. In embodiments using sebacic acid as the dicarboxylic acid, the weight percentage of sebacic acid relative to the total amount (total weight) of dicarboxylic acids as monomer components of the polyester polymer may be approximately 1% by weight or more, for example, approximately 10% by weight or more, approximately 50% by weight or more, approximately 70% by weight or more, or approximately 90% by weight or more (e.g., 95 to 100% by weight). The weight percentage of sebacic acid may be approximately 95% by weight or less, and from the viewpoint of adhesive properties such as high-temperature retention, may be approximately 75% by weight or less, or approximately 60% by weight or less. The technology disclosed herein can be implemented in either an embodiment in which the dicarboxylic acid as a monomer component used in the synthesis of the polyester polymer contains sebacic acid or an embodiment in which sebacic acid is not contained. For example, the weight proportion of the sebacic acid may be approximately 50% by weight or less, approximately 30% by weight or less, approximately 10% by weight or less, approximately 3% by weight or less, or less than 1% by weight, and the dicarboxylic acid used in the synthesis of the polyester-based polymer may be substantially free of sebacic acid.

[0041] The molecular weight of the plant-derived dicarboxylic acid is not particularly limited, and is suitably 100 or more, and may be 150 or more. The larger the molecular weight of the plant-derived dicarboxylic acid, the easier it is to increase the bio-content of the polyester polymer. From this perspective, the molecular weight of the plant-derived dicarboxylic acid may be 250 or more, 350 or more, 450 or more, or 500 or more (e.g., 550 or more). On the other hand, from the perspective of monomer availability and ease of synthesis, the molecular weight of the plant-derived dicarboxylic acid is suitably about 1000 or less, and may be, for example, 800 or less, 700 or less, or 600 or less. A suitable example of a dicarboxylic acid having the above molecular weight is dimer acid.

[0042] In this specification, the molecular weight of a dicarboxylic acid is the molecular weight calculated from the chemical formula. In addition, in an embodiment in which two or more dicarboxylic acids (e.g., the above-mentioned plant-derived dicarboxylic acids) are used, the molecular weight of the dicarboxylic acid (e.g., the above-mentioned plant-derived dicarboxylic acids) is the sum (total value) of the products of the molecular weights and weight fractions of the respective dicarboxylic acids.

[0043] Furthermore, aromatic dicarboxylic acids are preferably used as the dicarboxylic acid used in the synthesis of the polyester polymer disclosed herein. The use of a dicarboxylic acid containing an aromatic dicarboxylic acid tends to increase cohesive strength and improve high-temperature holding power. By including an aromatic dicarboxylic acid as the dicarboxylic acid, the amount of crosslinking agent used can be reduced, making it easier to improve high-temperature holding power while maintaining or improving adhesive strength. Suitable examples of aromatic dicarboxylic acids include isophthalic acid, terephthalic acid, and orthophthalic acid, with terephthalic acid being more preferred. These can be used alone or in combination of two or more.

[0044] The technology disclosed herein also encompasses embodiments in which the biomass content of a polyester polymer is increased by using a biomass-derived aromatic dicarboxylic acid. In some embodiments, biomass-derived terephthalic acid and its derivatives can be used as the dicarboxylic acid. The method for obtaining the biomass-derived dicarboxylic acid is not particularly limited. For example, biomass-derived terephthalic acid can be obtained by obtaining isobutanol from corn, sugars, or wood, converting it to isobutylene, dimerizing it to obtain isooctene, synthesizing p-xylene through radical cleavage, recombination, and cyclization, and then oxidizing it to obtain terephthalic acid (WO 2009 / 079213).

[0045] In the embodiment where aromatic dicarboxylic acid is used as dicarboxylic acid, the weight ratio of aromatic dicarboxylic acid to the total amount (total weight) of dicarboxylic acid in the monomer component of polyester polymer is not particularly limited, but is suitably about 1 wt% or more, and from the viewpoint of improving high-temperature holding power, it is preferably about 3 wt% or more, more preferably about 5 wt% or more, and even more preferably about 7 wt% or more. The upper limit of the weight ratio of the aromatic carboxylic acid is not limited to a specific range because it may vary depending on the type of other dicarboxylic acid, etc., and is suitably, for example, about 50 wt% or less, and from the viewpoint of adhesive properties such as adhesive strength, it is preferably about 30 wt% or less, more preferably about 20 wt% or less, even more preferably about 15 wt% or less, and particularly preferably about 10 wt% or less.

[0046] In some embodiments, dicarboxylic acids (e.g., aliphatic dicarboxylic acids) derived from fossil resources may be used in order to obtain desired adhesive properties, taking into consideration productivity, efficiency, and cost. Examples of such dicarboxylic acids (e.g., aliphatic dicarboxylic acids) include dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, and azelaic acid. Among these, adipic acid is preferably used as the aliphatic dicarboxylic acid. The above dicarboxylic acids (e.g., aliphatic dicarboxylic acids) derived from fossil resources may be used alone or in combination of two or more.

[0047] The molecular weight of the dicarboxylic acid as a monomer component used in the synthesis of the polyester-based polymer disclosed herein is not particularly limited, and is suitably 100 or more, and may be 150 or more. In some embodiments, the molecular weight of the dicarboxylic acid used may be 200 or more, 250 or more, 350 or more, 450 or more, or 500 or more (e.g., 530 or more). On the other hand, from the viewpoint of monomer availability, synthesis, etc., the molecular weight of the dicarboxylic acid is suitably about 1000 or less, and may be, for example, 800 or less, 700 or less, or 600 or less (e.g., 550 or less). The polyester-based polymer disclosed herein (a polyester-based polymer having an Mw of a predetermined value or more and preferably having a Tg within a predetermined range) is preferably synthesized using a dicarboxylic acid having a molecular weight within the above range.

[0048] (diol) As the diol used in the synthesis of the polyester polymer disclosed herein, any of (poly)alkylene glycols, aliphatic diols, dimer diols, alicyclic diols, aromatic diols, and unsaturated diols can be used. Specific examples of the diol include (poly)alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, and polytetramethylene glycol; 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-hexanediol, and 2,2,4-trimethyl-1,6 Aliphatic diols such as hexanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; dimer diols (e.g., dimer diols derived from fatty acids such as oleic acid and erucic acid); alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecane dimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; and aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and their ethylene oxide and propylene oxide adducts. By appropriately selecting and using one or more of these diols, polyester polymers suitable for achieving both adhesive strength and high-temperature holding power can be obtained.

[0049] In some embodiments, the diol is preferably a (poly)alkylene glycol, an aliphatic diol, or an alicyclic diol, with a (poly)alkylene glycol or an aliphatic diol being more preferred. By combining these diols (preferably ethylene glycol or an aliphatic diol) with the above-mentioned dicarboxylic acid (preferably a dimer acid or an aromatic dicarboxylic acid), a polyester-based polymer with excellent adhesive properties can be preferably obtained. Suitable examples include (poly)ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. From the viewpoint of reactivity, ethylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol are more preferred. These may be used alone or in combination of two or more. The above-mentioned (poly)alkylene glycols, aliphatic diols, and alicyclic diols may be derived from plants or fossil resources. In this specification, the term "(poly)ethylene glycol" is used to encompass ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

[0050] The weight proportion of (poly)alkylene glycols, aliphatic diols, and alicyclic diols (preferably the weight proportion of ethylene glycol and aliphatic diols) to the total amount (total weight) of diols in the monomer components of the polyester polymer is not particularly limited, and is suitably about 50% by weight or more. From the viewpoint of obtaining good adhesive properties, it is preferably about 70% by weight or more, more preferably about 80% by weight or more, even more preferably about 90% by weight or more, and particularly preferably about 95% by weight or more (for example, 99 to 100% by weight). Furthermore, the weight proportion of the (poly)alkylene glycols, aliphatic diols, and alicyclic diols (preferably the weight proportion of ethylene glycol and aliphatic diols) may be, for example, about 95% by weight or less.

[0051] In some preferred embodiments, (poly)ethylene glycol is used as the diol. By using (poly)ethylene glycol in combination with an appropriate dicarboxylic acid, favorable adhesive properties (adhesion strength and high-temperature retention) can be preferably obtained. In embodiments where (poly)ethylene glycol is used as the diol, the weight ratio of the (poly)ethylene glycol to the total amount (total weight) of diols as monomer components of the polyester-based polymer is suitably approximately 1 wt % or more, preferably approximately 10 wt % or more, more preferably approximately 50 wt % or more, even more preferably approximately 80 wt % or more, and particularly preferably approximately 90 wt % or more (e.g., 95 to 100 wt %). By using (poly)ethylene glycol in a predetermined amount or more, the polymer can be designed based on the properties of (poly)ethylene glycol. Furthermore, for example, the use of (poly)ethylene glycol makes it easier to obtain a pressure-sensitive adhesive layer with low haze. Furthermore, the weight ratio of the (poly)ethylene glycol may be approximately 95 wt % or less, approximately 70 wt % or less, or approximately 50 wt % or less. The (poly)ethylene glycols mentioned above may be derived from plants or fossil resources. The (poly)ethylene glycols may be used singly or in combination of two or more.

[0052] In some embodiments, it is preferable to use a plant-derived diol as the diol from the viewpoint of obtaining a polyester polymer with a bio content of 50% or more. Examples of such diols include biomass diols (e.g., biomass (poly)ethylene glycol) obtained from biomass ethanol, fatty acid esters derived from plants (e.g., castor oil), dimer diols derived from fatty acids such as oleic acid and erucic acid, and butanediol produced using glucose. The plant-derived diols can be used alone or in combination of two or more.

[0053] In some embodiments, from the viewpoint of reducing dependence on petroleum-derived materials, the weight percentage of the plant-derived diol relative to the total amount (total weight) of diols as monomer components of the polyester-based polymer may be approximately 1 wt% or more, approximately 10 wt% or more, approximately 50 wt% or more, approximately 80 wt% or more, or approximately 90 wt% or more (e.g., 95 to 100 wt%). Furthermore, the weight percentage of the plant-derived diol may be approximately 95 wt% or less, approximately 70 wt% or less, or approximately 50 wt% or less. Even in embodiments in which the amount of plant-derived diol used is relatively low and a petroleum-derived diol is used, for example, by using a petroleum-derived diol with a relatively low molecular weight, the polyester-based polymer can have a bio-content of a predetermined value or more. From this viewpoint, the weight percentage of the plant-derived diol may be approximately 30 wt% or less, approximately 10 wt% or less, or approximately 3 wt% or less (e.g., less than 1 wt%). The technology disclosed herein can also be preferably implemented in an embodiment in which the diol used as a monomer component in the synthesis of the polyester polymer does not substantially contain a plant-derived diol.

[0054] In some embodiments, dimer diol is used as the plant-derived diol. The use of dimer diol can also increase the biomass content of polyester polymers. Dimer diols can be used singly or in combination of two or more. In embodiments using dimer diol as the diol, the weight percentage of dimer diol relative to the total amount (total weight) of diols as monomer components of the polyester polymer may be approximately 1% by weight or more, for example, approximately 10% by weight or more, approximately 50% by weight or more, approximately 70% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more (e.g., 95 to 100% by weight). The weight percentage of dimer diol may be approximately 95% by weight or less, approximately 85% by weight or less, or approximately 60% by weight or less. The technology disclosed herein can be implemented in either an embodiment in which the diol as a monomer component used in the synthesis of a polyester polymer contains dimer diol or an embodiment in which dimer diol is not contained. For example, the weight proportion of the dimer diol may be approximately 50% by weight or less (e.g., less than 50% by weight), approximately 30% by weight or less, approximately 10% by weight or less, approximately 3% by weight or less, or less than 1% by weight, and the diol used in the synthesis of the polyester-based polymer may be substantially free of dimer diol.

[0055] The molecular weight of the diol is not particularly limited. From the viewpoints of monomer availability and ease of synthesis, the molecular weight of the diol is suitably, for example, 500 or less, and may be 300 or less, 150 or less, 100 or less, or 80 or less. The molecular weight of the diol is suitably about 50 or more, and may be, for example, more than 100. In an embodiment using a diol within the above molecular weight range, a polyester-based polymer that combines adhesive strength and high-temperature retention can be preferably synthesized. In an embodiment in which the diol is derived from a fossil resource, the molecular weight of the fossil resource-derived diol is suitably 500 or less, and may be 300 or less. The smaller the molecular weight of the fossil resource-derived diol, the higher the bio-content of the polyester-based polymer. From this viewpoint, the molecular weight of the fossil resource-derived diol may be 150 or less, 100 or less, or 80 or less. The molecular weight of the fossil resource-derived diol is suitably about 50 or more, and may be, for example, more than 100. A suitable example of a diol having the above molecular weight is ethylene glycol.

[0056] In this specification, the molecular weight of a diol can be calculated from a chemical formula. In addition, in an embodiment in which two or more diols (e.g., the diols derived from fossil resources) are used, the molecular weight of the diol (e.g., the diols derived from fossil resources) is the sum (total value) of the products of the molecular weights and weight fractions of the respective diols.

[0057] The polyester polymers disclosed herein may be substantially composed of the dicarboxylic acids and diols described above. However, other copolymerization components besides the dicarboxylic acids and diols may be copolymerized to the extent that the effects of the technology disclosed herein are not impaired, for purposes such as introducing desired functional groups or adjusting molecular weight. Examples of such other copolymerization components include polycarboxylic acids containing three or four or more carboxyl groups (trivalent or higher polycarboxylic acids such as trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, trimesic acid, and trimer acid), polyols containing three or four or more hydroxyl groups per molecule (pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, and adamantanetriol), monocarboxylic acids, monoalcohols, hydroxycarboxylic acids, and lactones. The above-mentioned other copolymerization components may be used alone or in combination of two or more. These other copolymerization components may be derived from plants or not. The proportion of the other copolymerization component in the monomer components of the polyester-based polymer is suitably, for example, less than 10% by weight, and may be less than 3% by weight, typically less than 1% by weight (or even less than 0.1% by weight). The technology disclosed herein can also be preferably implemented in an embodiment in which the monomer components of the polyester-based polymer are substantially free of the other copolymerization component.

[0058] The monomer components used in the synthesis of the polyester polymer disclosed herein are not particularly limited, but the total proportion of dicarboxylic acid and 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 even more preferably about 99% by weight or more (for example, 99 to 100% by weight). The technology disclosed herein is preferably implemented in an embodiment using a polyester polymer synthesized substantially from dicarboxylic acid and diol.

[0059] In some preferred embodiments, the monomer components of the polyester polymer use a combination of dimer acid as the dicarboxylic acid and (poly)ethylene glycol as the diol. By using a combination of dimer acid and (poly)ethylene glycol, a polyester polymer having a Mw of a predetermined value or more and suitable for achieving both adhesive strength and high-temperature holding power can be preferably synthesized. The total proportion of dimer acid and (poly)ethylene glycol in the total amount of monomer components of the polyester polymer is suitably approximately 50% by weight or more, preferably approximately 60% by weight or more, more preferably approximately 70% by weight or more, even more preferably approximately 80% by weight or more, and may be approximately 90% by weight or more (e.g., 99 to 100% by weight).

[0060] In some preferred embodiments, the polyester polymer has an aromatic ring in its polymer molecule. A polyester polymer containing an aromatic ring is likely to provide high-temperature holding power. The aromatic ring is introduced into the polymer by using a monomer (aromatic dicarboxylic acid or aromatic diol) having an aromatic ring. In embodiments in which the polyester polymer has an aromatic ring, the copolymerization ratio of the aromatic ring-containing monomer (typically, an aromatic dicarboxylic acid or aromatic diol) is not particularly limited, but is suitably about 1 wt% or more. From the viewpoint of improving high-temperature holding power, it is preferably about 3 wt% or more, more preferably about 5 wt% or more, and even more preferably about 7 wt% or more. The upper limit of the copolymerization ratio of the aromatic ring-containing monomer is suitably, for example, about 30 wt% or less. From the viewpoint of adhesive properties such as adhesive strength, it is preferably about 15 wt% or less, more preferably about 12 wt% or less, even more preferably about 10 wt% or less, and particularly preferably about 8 wt% or less.

[0061] The method for obtaining the polyester polymer disclosed herein is not particularly limited, and any polymerization method known as a synthetic method for polyester polymers can be appropriately employed. The monomer raw material used in the synthesis of the polyester polymer can be, for example, a mixture of monomers in such a manner that 0.95 to 1.05 equivalents (preferably 0.98 to 1.02 equivalents) of dicarboxylic acid per equivalent of diol. By combining dicarboxylic acid and diol in the above ratio, a high molecular weight polyester polymer can be easily obtained. Furthermore, the polymer can be appropriately crosslinked (for example, by reaction with a crosslinking agent such as an isocyanate-based crosslinking agent) to enhance cohesive strength.

[0062] In the technology disclosed herein, the weight ratio of dicarboxylic acid to diol as monomer components used in the synthesis of polyester-based polymers is not particularly limited, and an appropriate weight ratio can be set taking into consideration the desired polymer properties, synthesis, and the like. In some embodiments, the ratio of the weight A1 of dicarboxylic acid to the weight A2 of diol used as the monomer components (weight ratio A1 / A2) may be 10 / 90 or more, or may be 30 / 70 or more. In some preferred embodiments, the weight ratio (A1 / A2) is approximately 50 / 50 or more, more preferably 60 / 40 or more, even more preferably 70 / 30 or more, or may be 80 / 20 or more, or may be 90 / 10 or more. For example, by increasing the weight ratio of dicarboxylic acid as described above, the properties inherent in the dicarboxylic acid can be favorably expressed. Furthermore, in embodiments using plant-derived dicarboxylic acids, the bio-content of the resulting polyester-based polymer can be effectively increased. Furthermore, the weight ratio (A1 / A2) may be, for example, 95 / 5 or less, or 85 / 15 or less. In some embodiments, from the viewpoint of favorably expressing the properties based on the diol, the weight ratio (A1 / A2) may be 75 / 25 or less, or may be 50 / 50 or less (e.g., 30 / 70 or less). In embodiments using a plant-derived diol, the above weight ratio allows the polyester-based polymer to have a high bio-content. Note that in embodiments using plant-derived materials for both the dicarboxylic acid and the diol, a polyester-based polymer having a bio-content equal to or greater than a predetermined value can be obtained regardless of the weight ratio of the dicarboxylic acid to the diol.

[0063] The polyester polymers in the technology disclosed herein can be obtained by polycondensation of dicarboxylic acids and diols, as with general polyesters. More specifically, polyester polymers can be synthesized by proceeding with the reaction between carboxy groups of dicarboxylic acids and hydroxy groups of diols, typically while removing water (produced water) produced by the reaction from the reaction system. Methods for removing the produced water from the reaction system include a method of blowing an inert gas into the reaction system and removing the produced water together with the inert gas from the reaction system, a method of azeotropic dehydration using a reaction water discharge solvent such as toluene or xylene, and a method of distilling the produced water from the reaction system under reduced pressure (reduced pressure method).

[0064] The reaction temperature and reaction time during the above reaction (including esterification and polycondensation), and the degree of vacuum (pressure in the reaction system) when a reduced pressure method is used, can be appropriately set so as to efficiently obtain a polyester polymer with the desired properties (e.g., molecular weight). While not particularly limited, the reaction temperature is typically set to approximately 150°C or higher (e.g., 180°C to 260°C). Setting the reaction temperature within the above range ensures a good reaction rate, improves productivity, and facilitates the prevention or suppression of deterioration of the polyester polymer produced. The reaction time is also not particularly limited and can be approximately 3 to 48 hours (e.g., 10 to 30 hours). When a reduced pressure method is used, although not particularly limited, the degree of vacuum is typically set to 10 kPa or less (typically 10 kPa to 0.1 kPa), for example, 4 kPa to 0.1 kPa. By setting the pressure in the reaction system within the above range, water produced by the reaction can be efficiently distilled out of the system, making it easier to maintain a good reaction rate. Furthermore, when the reaction temperature is relatively high, by setting the pressure in the reaction system to the above-mentioned lower limit or higher, it is easy to prevent the distillation of the raw materials, dicarboxylic acid and diol, outside the system. From the viewpoint of maintaining a stable pressure in the reaction system, it is usually appropriate to set the pressure in the reaction system to 0.1 kPa or higher.

[0065] In the above reaction, a known or conventional catalyst can be used in an appropriate amount for esterification and condensation, as in the synthesis of general polyesters. Examples of such catalysts include various metal compounds such as titanium-based, germanium-based, antimony-based, tin-based, and zinc-based compounds; strong acids such as p-toluenesulfonic acid and sulfuric acid; and the like. The amount of catalyst used can be appropriately determined depending on the reaction rate, etc., so a detailed description thereof will be omitted here.

[0066] In the above process of synthesizing a polyester polymer by reacting a dicarboxylic acid with a diol, a solvent may or may not be used. The synthesis can be carried out substantially without using an organic solvent (meaning, for example, that an organic solvent is intentionally used as a reaction solvent during the reaction is excluded). Synthesizing a polyester polymer substantially without using an organic solvent and preparing a polyester pressure-sensitive adhesive using such a polyester polymer are preferable because they meet the demand for reducing the use of organic solvents in the production process.

[0067] In the above reaction, there is generally a correlation between the molecular weight of the polyester polymer synthesized and the viscosity of the reaction system, and this 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, it is possible to synthesize a polyester polymer having a target molecular weight with high accuracy.

[0068] (tackifying resin) The adhesive layer (and adhesive composition) disclosed herein contains a tackifier resin. By combining a polyester polymer having an Mw of a predetermined value or more with a tackifier resin, the adhesive strength-enhancing effect of the tackifier resin is effectively exhibited. The tackifier resin can be one or more selected from various known tackifier resins, such as phenolic tackifier resins, terpene tackifier resins, modified terpene tackifier resins, rosin tackifier resins, hydrocarbon tackifier resins, epoxy tackifier resins, polyamide tackifier resins, elastomer tackifier resins, and ketone tackifier resins.

[0069] Examples of phenolic tackifying resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkyl phenolic resins, and rosin phenolic resins. Terpene phenolic resin refers to a polymer containing terpene residues and phenol residues, and is a concept that encompasses both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and phenol-modified terpene resins (phenol-modified terpene resins) of terpenes or their homopolymers or copolymers. Suitable examples of terpenes that constitute such terpene phenolic resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l-, and d / l- (dipentene) forms). Hydrogenated terpene phenolic resins have a structure obtained by hydrogenating such terpene phenolic resins. They are also sometimes called hydrogenated terpene phenolic resins. Alkylphenol resins are resins (oil-based phenolic resins) obtained from alkylphenols and formaldehyde. Examples of alkylphenol resins include novolac and resol types. Rosin phenolic resins are typically phenol-modified products of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosin phenolic resins include those obtained by adding phenol to rosins or the various rosin derivatives described above using an acid catalyst and then thermally polymerizing the resulting mixture. Of these phenolic tackifying resins, terpene phenol resins, hydrogenated terpene phenol resins and alkylphenol resins are preferred, terpene phenol resins and hydrogenated terpene phenol resins are more preferred, and terpene phenol resins are particularly preferred.

[0070] Examples of terpene-based tackifying resins include polymers of terpenes (e.g., monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. They may be homopolymers of one type of terpene, or copolymers of two or more types of terpenes. Examples of homopolymers of one type of terpene include α-pinene polymers, β-pinene polymers, and dipentene polymers. Examples of modified terpene resins include those obtained by modifying the above-mentioned terpene resins, such as styrene-modified terpene resins and hydrogenated terpene resins.

[0071] The concept of rosin-based tackifying resins herein encompasses both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.).

[0072] Rosin derivative resins are typically derivatives of the rosins described above. The term "rosin-based resin" as used herein encompasses derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). Examples include rosin esters, such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; unsaturated fatty acid-modified rosins, which are rosin esters modified with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters, which are rosin esters modified with unsaturated fatty acids; rosin alcohols, which are obtained by reducing the carboxyl groups of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters); and metal salts of rosins or the various rosin derivatives described above. Specific examples of rosin esters include methyl esters, triethylene glycol esters, glycerin esters, pentaerythritol esters, and the like of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

[0073] Examples of hydrocarbon-based tackifying resins include various hydrocarbon-based resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0074] In some preferred embodiments, the tackifier resin comprises one or more phenolic tackifier resins (e.g., terpene phenolic resins) and rosin tackifier resins (polymerized rosin esters, etc.). More preferably, the tackifier resin is one or more selected from terpene phenolic resins and polymerized rosin esters. By selecting and using an appropriate tackifier resin from among terpene phenolic resins and polymerized rosin esters, both adhesive strength and high-temperature retention can be achieved.

[0075] Furthermore, it is particularly preferable to use a tackifier resin containing one or more phenolic tackifier resins (e.g., terpene phenolic resins) as the tackifier resin. Phenolic tackifier resins tend to have better compatibility with polyester polymers than other tackifier resins (e.g., rosin-based tackifier resins). The technology disclosed herein can be preferably implemented, for example, in an embodiment in which approximately 25% by weight or more (more preferably approximately 30% by weight or more) of the total amount of tackifier resin is terpene phenolic resin. Approximately 50% by weight or more of the total amount of tackifier resin may be terpene phenolic resin, or approximately 80% by weight or more (e.g., approximately 90% by weight or more) may be terpene phenolic resin. Substantially all of the tackifier resin (e.g., approximately 95% by weight to 100% by weight, or even approximately 99% by weight to 100% by weight) may be terpene phenolic resin.

[0076] In some embodiments, a tackifier resin having an aromatic ring in the molecule is preferably used as the tackifier resin. A tackifier resin containing an aromatic ring is likely to provide high-temperature retention. A suitable example of a tackifier resin having an aromatic ring is a phenolic tackifier resin. Of these, terpene phenolic resins are more preferred. The technology disclosed herein is particularly preferably implemented in an embodiment in which the polyester polymer in the pressure-sensitive adhesive layer contains an aromatic ring and the tackifier resin also contains an aromatic ring. By making both the polyester polymer and the tackifier resin have a structure containing an aromatic ring, better high-temperature retention is likely to be obtained. Furthermore, by both the polyester polymer and the tackifier resin having an aromatic ring, they have excellent compatibility and can satisfactorily exhibit desired adhesive properties.

[0077] In embodiments using a tackifier resin having an aromatic ring in the molecule, it is preferable to use a tackifier resin with a high aromatic ring ratio. Among tackifier resins having a phenol structure as the aromatic ring, a tackifier resin with a high phenol ratio is preferably used. By using a tackifier resin with a high aromatic ring ratio (e.g., phenol ratio), excellent resilience is likely to be obtained. Furthermore, better high-temperature retention is likely to be obtained. The aromatic ring ratio (e.g., phenol ratio) of the tackifier resin is, for example, 10% by weight or more, and from the viewpoint of resilience, it is preferably 15% by weight or more, more preferably 20% by weight or more, even more preferably 25% by weight or more, and particularly preferably 30% by weight or more. The upper limit of the aromatic ring ratio (e.g., phenol ratio) of the tackifier resin is, for example, 65% by weight or less, and from the viewpoint of adhesive strength, etc., it may be 50% by weight or less, 40% by weight or less, or 35% by weight or less.

[0078] In this specification, the aromatic ring ratio (e.g., phenol ratio) of the tackifier resin is measured by a nuclear magnetic resonance (NMR) device. 1 The aromatic ring ratio (e.g., phenol ratio) calculated by H-NMR spectroscopy. For example, if the tackifier resin has the following chemical structure: 1 In the H-NMR spectrum, the peaks with chemical shifts between 7.5 and 6.3 ppm are thought to be derived from the phenol skeleton, and the peaks with chemical shifts between 5.6 and 0.1 ppm are thought to be derived from the pinene skeleton. [ka] If the total integral value of the former peak is A and the total integral value of the latter peak is B, the molar ratio of the phenol skeleton to the pinene skeleton in the tackifier resin can be calculated by dividing them by the number of H atoms contained in the repeating unit of each skeleton. Molar ratio [phenol skeleton:pinene skeleton] = [A / 3:B / 16] Next, the weight ratio of the phenol skeleton to the pinene skeleton in the tackifier resin can be calculated by multiplying the calculated molar ratio by the molecular weight of phenol (molecular weight 94.1) and pinene (molecular weight 136.2), respectively. Weight ratio [phenolic skeleton:pinene skeleton] = [(A / 3) x 94.1:(B / 16) x 136.2] Then, when the weight ratio of the phenol skeleton thus determined is a and the weight ratio of the pinene skeleton is b, the aromatic ring ratio (phenol ratio) of the tackifier resin can be calculated by the following formula. Aromatic ring ratio (%)=100×(a / (a+b)) As the NMR device, for example, the model "AVANCE III-400" (manufactured by Bruker Biospin) can be used. 1 More specifically, H-NMR spectrum measurement can be performed under the following conditions. Measurements are also performed in the examples described below using the same method. [ 1 H-NMR measurement] Observation frequency: 400MHz Measurement temperature: 23℃ Measurement solvent: 1,1,2,2-tetrachloroethane-d2 (TCE-d2) Measured concentration: 33mg / mL

[0079] In some embodiments, the tackifier resin is preferably a plant-derived tackifier resin (plant-based tackifier resin) from the viewpoint of increasing the bio content of the entire PSA layer. The plant-based tackifier resin is composed of components at least partially derived from plants. The resin may be entirely plant-derived, or a portion of the resin may be plant-derived with the remaining portion derived from fossil resources. Examples of plant-based tackifier resins include the above-mentioned rosin-based tackifier resins, terpene-based tackifier resins, terpene phenolic resins, hydrogenated terpene phenolic resins, and rosin phenolic resins. One plant-based tackifier resin may be used alone, or two or more plant-based tackifier resins may be used in combination. In some embodiments, the proportion of the plant-based tackifier resin in the total amount of tackifier resins contained in the PSA layer may be 30% by weight or more (e.g., 50% by weight or more, typically 80% by weight or more), and the proportion of the plant-based tackifier resin in the total amount of tackifier resins may be 90% by weight or more (e.g., 95% by weight or more, typically 99 to 100% by weight). The technology disclosed herein can be practiced in an embodiment that is substantially free of tackifying resins other than vegetable tackifying resins.

[0080] The softening point of the tackifier resin is not particularly limited. From the viewpoint of improving cohesive strength, in some embodiments, the softening point (softening temperature) of the tackifier resin is suitably approximately 50°C or higher, and a tackifier resin having a softening point (softening temperature) of approximately 80°C or higher (preferably approximately 100°C or higher, for example, approximately 115°C or higher) can be preferably used. In other embodiments, the softening point of the tackifier resin used may be approximately 120°C or higher (for example, 135°C or higher or 145°C or higher). The technology disclosed herein can be preferably implemented in an embodiment in which the tackifier resin having the above softening point accounts for more than 50% by weight (more preferably more than 70% by weight, for example, more than 90% by weight) of the total tackifier resin contained in the PSA layer. For example, a phenolic tackifier resin (such as a terpene phenolic resin) or a rosin tackifier resin (such as a polymerized rosin ester) having such a softening point can be preferably used. In some preferred embodiments, a terpene phenol resin having a softening point of approximately 120°C or higher (more preferably 135°C or higher, for example 145°C or higher) can be used. There is no particular upper limit to the softening point of the tackifier resin. In terms of adhesive strength, etc., in some embodiments, a tackifier resin having a softening point of approximately 200°C or lower (more preferably approximately 180°C or lower, even more preferably less than 160°C, for example 155°C or lower or 150°C or lower) can be preferably used. The softening point of the tackifier resin can be measured based on the softening point test method (ring and ball method) specified in JIS K2207.

[0081] Although not particularly limited, tackifier resins with an acid value limited to a predetermined value or less are preferably used. Tackifier resins with a low acid value are preferred because they do not inhibit the crosslinking reaction during the formation of the adhesive. Furthermore, adhesives containing tackifier resins with an acid value limited to a predetermined value or less tend to have excellent durability. From this perspective, the acid value of the tackifier resin is suitably approximately 20 mgKOH / g or less, preferably less than 10 mgKOH / g, more preferably less than 7 mgKOH / g, and even more preferably less than 4 mgKOH / g (e.g., 0 to 4 mgKOH / g), and may even be less than 3 mgKOH / g (e.g., less than 1 mgKOH / g). The acid value of the tackifier resin can be measured by potentiometric titration according to JIS K 0070:1992.

[0082] The content of the tackifier resin can be, for example, more than 0 parts by weight per 100 parts by weight of the polyester-based polymer, and may be approximately 3 parts by weight or more (e.g., approximately 5 parts by weight or more). In some preferred embodiments, the content of the tackifier resin per 100 parts by weight of the polyester-based polymer is approximately 10 parts by weight or more, more preferably approximately 20 parts by weight or more, even more preferably approximately 30 parts by weight or more, and particularly preferably approximately 35 parts by weight or more. The greater the amount of tackifier resin used, the more likely it is that excellent adhesive strength will be obtained. There is no particular upper limit to the content of the tackifier resin. From the viewpoint of compatibility with the polyester-based polymer and adhesiveness, in some embodiments, the content of the tackifier resin per 100 parts by weight of the polyester-based polymer is typically approximately 120 parts by weight or less, preferably less than 80 parts by weight, and more preferably approximately 70 parts by weight or less (e.g., approximately 50 parts by weight or less). For example, it is effective to use a tackifier resin in the amount within the above range for a polyester-based polymer having a Tg of 0°C or less.

[0083] (Crosslinking agent) The pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer preferably contains a crosslinking agent as an optional component. The pressure-sensitive adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after crosslinking reaction, a form before crosslinking reaction, a partially crosslinked form, or an intermediate or composite form thereof. The crosslinking agent is usually contained in the pressure-sensitive adhesive layer exclusively in a form after crosslinking reaction. Note that the crosslinking agent used to crosslink the polyester polymer may also function as a chain extender.

[0084] The type of crosslinking agent is not particularly limited, and can be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agents can be used alone or in combination of two or more. Among these, isocyanate-based crosslinking agents are preferred.

[0085] As the isocyanate-based crosslinking agent, a polyfunctional isocyanate-based compound (which refers to a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent can be used alone or in combination of two or more.

[0086] Examples of polyfunctional isocyanate compounds include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds. Specific examples of the aliphatic polyisocyanate compound include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0087] Specific examples of the alicyclic polyisocyanate compound include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0088] Specific examples of aromatic polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. , 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, and the like.

[0089] Examples of polyfunctional isocyanates include polyfunctional isocyanate compounds having an average of two or more isocyanate groups per molecule. Such polyfunctional isocyanate compounds may be multimers (e.g., dimers or trimers) of bifunctional or trifunctional or higher isocyanates, derivatives (e.g., addition reaction products of polyhydric alcohols with two or more molecules of polyfunctional isocyanates), polymers, etc. Examples of polyfunctional isocyanate compounds include dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimer adducts with isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, etc. Commercially available products of such polyfunctional isocyanate compounds include those manufactured by Asahi Kasei Chemicals Corporation under the trade names "Duranate TPA-100" and "Duranate D101," and those manufactured by Tosoh Corporation under the trade names "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096."

[0090] As the crosslinking agent, a crosslinking agent without an aromatic ring is preferably used. For example, among the above-mentioned isocyanate-based crosslinking agents, it is preferable to use an isocyanate-based compound without an aromatic ring. By using an isocyanate-based compound without an aromatic ring as the crosslinking agent, the degree of crosslinking can be effectively increased with less crosslinking inhibition in a pressure-sensitive adhesive composition containing a polyester-based polymer and a tackifying resin. Typical examples of the above-mentioned isocyanate without an aromatic ring include aliphatic isocyanate compounds. A particularly preferred embodiment is one in which a polyester-based polymer and a tackifying resin both have aromatic rings and an isocyanate-based compound without an aromatic ring (typically an aliphatic isocyanate compound) is used as the crosslinking agent.

[0091] In some embodiments, it is preferable to use two or more crosslinking agents (preferably isocyanate-based crosslinking agents) with different numbers of functional groups. Using two or more crosslinking agents with different numbers of functional groups makes it easier to achieve a good balance of multiple properties (e.g., high-temperature holding power, repulsion resistance, etc.). The functional group refers to a crosslinking reactive group, such as an isocyanate group in the polyfunctional isocyanate compound described above. In some preferred embodiments, one or more bifunctional crosslinking agents are used in combination with one or more trifunctional or higher crosslinking agents (e.g., trifunctional crosslinking agents) as the crosslinking agents. The combined use of a bifunctional crosslinking agent and a trifunctional or higher crosslinking agent makes it easier to obtain a pressure-sensitive adhesive with excellent repulsion resistance, and to achieve both high-temperature holding power and repulsion resistance. The bifunctional crosslinking agent primarily functions as a chain extender, extending the chain length of the polyester polymer during curing of the pressure-sensitive adhesive composition, thereby contributing to improved repulsion resistance. Meanwhile, the use of a trifunctional or higher crosslinking agent is thought to enhance the cohesive strength of the pressure-sensitive adhesive and thereby achieve high-temperature holding power. The technology disclosed herein is not limited to the above interpretation. As the bifunctional crosslinking agent and trifunctional or higher functional crosslinking agent, any bifunctional or trifunctional or higher functional crosslinking agent can be used from the above-mentioned various crosslinking agents without any particular limitation. In some preferred embodiments, an isocyanate-based compound is preferably used as the bifunctional or trifunctional or higher functional crosslinking agent.

[0092] In an embodiment in which a bifunctional crosslinking agent is used as the crosslinking agent, the amount of the bifunctional crosslinking agent used is not particularly limited, and for example, from the viewpoint of obtaining the effect of using the bifunctional crosslinking agent, the amount of the bifunctional crosslinking agent used relative to 100 parts by weight of the polyester-based polymer is suitably about 0.01 parts by weight or more, preferably about 0.1 parts by weight or more, more preferably about 0.5 parts by weight or more, even more preferably about 0.8 parts by weight or more, and may be about 1.5 parts by weight or more, or may be about 3 parts by weight or more. Furthermore, the amount of the bifunctional crosslinking agent used relative to 100 parts by weight of the polyester-based polymer is usually suitably about 10 parts by weight or less, preferably about 7 parts by weight or less, and may be 4 parts by weight or less.

[0093] In embodiments using a trifunctional or higher crosslinking agent as a crosslinking agent, the amount of trifunctional or higher crosslinking agent used is not particularly limited. For example, the amount of trifunctional or higher crosslinking agent used per 100 parts by weight of polyester polymer is approximately 0.01 parts by weight or more, preferably approximately 0.1 parts by weight or more, more preferably approximately 0.5 parts by weight or more, even more preferably approximately 1 part by weight or more, and particularly preferably approximately 2 parts by weight or more (e.g., approximately 2.5 parts by weight or more). By using an appropriate amount of trifunctional or higher crosslinking agent, cohesive strength is increased and excellent properties (adhesion strength, high-temperature retention, etc.) are easily obtained. Furthermore, the amount of trifunctional or higher crosslinking agent used per 100 parts by weight of polyester polymer is usually approximately 8 parts by weight or less, preferably approximately 5 parts by weight or less, and may be 4 parts by weight or less.

[0094] In the embodiment where a bifunctional crosslinking agent and a trifunctional or higher functional crosslinking agent are used in combination, the ratio of the bifunctional crosslinking agent to the trifunctional or higher functional crosslinking agent is appropriately set so as to achieve a good balance of the desired adhesive properties (adhesive strength, high temperature holding power, repulsion resistance, etc.), and is not limited to a specific range. A Amount of trifunctional or higher crosslinking agent C B The ratio (C B / C A) is, for example, 0.1 or more, and from the viewpoint of improving the cohesive force, it is appropriate that it is 0.3 or more, preferably 0.5 or more, more preferably 0.8 or more, and may be 1.5 or more, or may be 2 or more. B / C A ) is, for example, 10 or less, and from the viewpoint of improving repulsion resistance, is preferably 7 or less, more preferably 5 or less, may be 4 or less, may be 2.5 or less, or may be 1.5 or less.

[0095] The amount of crosslinking agent used is not particularly limited. For example, the amount of crosslinking agent used per 100 parts by weight of polyester-based polymer can be approximately 0.005 parts by weight or more (e.g., 0.01 parts by weight or more, typically 0.1 parts by weight or more). From the viewpoint of improving cohesive strength, the amount of crosslinking agent used per 100 parts by weight of polyester-based polymer is usually approximately 0.5 parts by weight or more, preferably approximately 1 part by weight or more, more preferably approximately 2 parts by weight or more (e.g., more than 2 parts by weight), and even more preferably 2.5 parts by weight or more. Furthermore, the amount of crosslinking agent used per 100 parts by weight of polyester-based polymer is usually approximately 12 parts by weight or less, for example, approximately 10 parts by weight or less, preferably approximately 8 parts by weight or less, and preferably approximately 5 parts by weight or less. According to the technology disclosed herein, cohesive strength that favorably exhibits high-temperature holding power can be obtained with the amount of crosslinking agent used limited as described above. The amount of crosslinking agent used per 100 parts by weight of polyester-based polymer is more preferably 4 parts by weight or less, and even more preferably approximately 3.5 parts by weight or less.

[0096] In embodiments using an isocyanate-based crosslinking agent, the amount used is not particularly limited. The amount of isocyanate-based crosslinking agent used can be, for example, approximately 0.5 parts by weight or more and approximately 10 parts by weight or less per 100 parts by weight of polyester-based polymer. From the perspective of improving cohesive strength, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of polyester-based polymer is typically approximately 1 part by weight or more, preferably approximately 2 parts by weight or more (e.g., more than 2 parts by weight), more preferably approximately 2.5 parts by weight or more, even more preferably 2.8 parts by weight or more, and may be approximately 3.5 parts by weight or more, approximately 4.0 parts by weight or more, or even 4.5 parts by weight or more. Furthermore, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of polyester-based polymer is typically approximately 8 parts by weight or less, preferably approximately 5 parts by weight or less. According to the technology disclosed herein, a cohesive strength that exhibits favorable high-temperature holding power can be obtained with the amount of isocyanate-based crosslinking agent limited as described above. The amount of isocyanate-based crosslinking agent used per 100 parts by weight of polyester-based polymer is more preferably 4.5 parts by weight or less, even more preferably approximately 4.2 parts by weight or less, and particularly preferably 3.8 parts by weight or less (for example, 3.5 parts by weight or less), and may be approximately 3.2 parts by weight or less.

[0097] (Crosslinking catalyst) In the technology disclosed herein, in order to more effectively promote the crosslinking reaction, it is preferable to use a crosslinking catalyst in addition to the crosslinking agent. Examples of the crosslinking catalyst include zirconium-containing compounds (zirconium-based catalysts) such as zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethylacetoacetate, and zirconium octylate compounds; tin (Sn)-containing compounds (tin-based catalysts) such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, trimethyltin hydroxide, and butyltin oxide; aluminum sec-butoxide, aluminum sec-butoxide, and aluminum octylate. Examples of the crosslinking catalyst include aluminum-containing compounds (aluminum-based catalysts) such as aluminum tris acetylacetonate, aluminum bis ethylacetoacetate, and aluminum tris ethylacetoacetate; iron-containing compounds (iron-based catalysts) such as ferric naphthem; and titanium-containing compounds (titanium-based catalysts) such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, titanium acetylacetonate, titanium tetraacetylacetonate, and titanium ethylacetoacetate. The crosslinking catalyst can be used alone or in combination of two or more.

[0098] In some preferred embodiments, the crosslinking catalyst does not contain a tin-containing compound, from the viewpoints of environmental impact and safety. By using a non-tin-based compound as the crosslinking catalyst, the amount of tin-based compounds (typically organotin compounds) used in the PSA can be reduced. The PSA composition disclosed herein can efficiently form a good crosslinked structure that can achieve both adhesive strength and high-temperature retention without using a tin-based crosslinking catalyst, which generally tends to have excellent reaction speed. Furthermore, in some embodiments, the crosslinking catalyst does not contain an iron-based catalyst. For example, in applications where the PSA requires transparency and optical properties, it is desirable to avoid the use of iron-based compounds, which may discolor the PSA.

[0099] The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used can be, for example, about 0.001 parts by weight or more, suitably about 0.01 parts by weight or more, and may be about 0.05 parts by weight or more (for example, 0.10 parts by weight or more) relative to 100 parts by weight of the polyester polymer. Furthermore, the amount of the crosslinking catalyst used can be, for example, about 3 parts by weight or less, suitably about 1 part by weight or less, and may be about 0.3 parts by weight or less, relative to 100 parts by weight of the polyester polymer.

[0100] (hydrolysis stabilizer) The adhesive composition disclosed herein may also contain a hydrolysis stabilizer (also referred to as a hydrolysis inhibitor). The addition of a hydrolysis stabilizer inhibits hydrolysis reactions in the adhesive, making it easier to achieve good durability. The hydrolysis stabilizer is not particularly limited, and known or commonly used hydrolysis stabilizers can be used. Examples include oxazoline group-containing compounds, epoxy group-containing compounds, and carbodiimide group-containing compounds. Of these, carbodiimide group-containing compounds are preferred. One hydrolysis stabilizer can be used alone, or two or more can be used in combination.

[0101] Examples of carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and monofunctional cyclic carbodiimides. Here, a monofunctional cyclic carbodiimide refers to a compound having one carbodiimide group in its molecular structure, in which the first and second nitrogen atoms of the carbodiimide group are bonded by a linking group composed of an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. The linking group may contain a heteroatom or a substituent. Suitable examples of carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, and monofunctional cyclic carbodiimides.

[0102] The amount of hydrolysis stabilizer (preferably a carbodiimide group-containing compound) used is not particularly limited, and is suitably about 0.05 parts by weight or more, preferably about 0.1 parts by weight or more, for example, about 0.3 parts by weight or more, per 100 parts by weight of polyester polymer so that the effect of the hydrolysis stabilizer is preferably exhibited. The upper limit of the amount of the hydrolysis stabilizer used is suitably about 5 parts by weight or less, preferably about 3 parts by weight or less, for example, 1 part by weight or less, per 100 parts by weight of polyester polymer.

[0103] (Other additives) In addition to the above-mentioned components, the pressure-sensitive adhesive composition may contain, as necessary, various additives commonly used in the field of pressure-sensitive adhesives, such as leveling agents, fillers, plasticizers, softeners, colorants (pigments, dyes, etc.), antistatic agents, antioxidants, UV absorbers, antioxidants, light stabilizers, etc. As for the above-mentioned various additives, conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed description thereof will be omitted.

[0104] (Adhesive composition) The adhesive layer (layer made of adhesive) disclosed herein is formed from an adhesive composition containing the above-mentioned polyester polymer and tackifier resin. From the viewpoint of adhesive properties, etc., a solvent-based adhesive composition containing an adhesive in an organic solvent is preferred. As the organic solvent, organic solvents such as toluene and ethyl acetate can be used.

[0105] As described above, the present specification provides a PSA composition containing one or more of the components that can be contained in the PSA layer disclosed herein. Specifically, the PSA composition may contain a polyester polymer in which 50% or more of the carbon components is biomass-derived carbon and has an Mw of 30,000 or more, and may further contain a tackifier resin. This PSA composition can reduce dependence on fossil resource-derived materials and form a PSA that combines adhesive strength and high-temperature retention. The PSA composition may further contain components such as a crosslinking agent, a crosslinking catalyst, and a hydrolysis stabilizer. Details of the components that can be contained in the PSA composition are as described for the PSA layer, so a repeated description will be omitted.

[0106] (Formation of adhesive layer) A pressure-sensitive adhesive layer can be formed from a pressure-sensitive adhesive composition by a conventionally known method. For example, in the case of a substrate-less double-sided pressure-sensitive adhesive sheet, a pressure-sensitive adhesive composition can be applied to a surface (release surface) having releasability, and then the pressure-sensitive adhesive composition is cured to form a pressure-sensitive adhesive layer on the surface, thereby forming a pressure-sensitive adhesive sheet. In the case of a pressure-sensitive adhesive sheet with a substrate, a method (direct method) in which a pressure-sensitive adhesive composition is directly applied (typically coated) to the substrate and cured to form a pressure-sensitive adhesive layer can be preferably employed. Alternatively, a method (transfer method) in which a pressure-sensitive adhesive composition is applied to a surface (release surface) having releasability and cured to form a pressure-sensitive adhesive layer on the surface, and then the pressure-sensitive adhesive layer is transferred to the substrate may also be employed. The release surface may be the surface of a release liner, the back surface of a release-treated substrate, or the like. The pressure-sensitive adhesive composition can be cured by subjecting the pressure-sensitive adhesive composition to a curing treatment such as drying, crosslinking, polymerization, or cooling. Two or more curing treatments may be performed simultaneously or stepwise. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may be a pressure-sensitive adhesive layer formed in a regular or random pattern such as a dotted or striped pattern.

[0107] The pressure-sensitive adhesive composition can be applied using a known or commonly used coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a die coater, a bar coater, a knife coater, a spray coater, etc. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, curtain coating, or the like. The pressure-sensitive adhesive composition can be dried at room temperature or under heating. From the viewpoints of promoting the crosslinking reaction and improving production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. The drying temperature can be, for example, about 40 to 150°C, and is usually preferably about 40 to 130°C. After drying the pressure-sensitive adhesive composition, it is preferable to perform aging for the purposes of adjusting component migration within the pressure-sensitive adhesive layer, promoting the crosslinking reaction, and alleviating distortion that may exist in the substrate or pressure-sensitive adhesive layer. The aging conditions are not particularly limited, and can be, for example, about 70°C or less (typically about 40 to 70°C) for one day or more (e.g., three days or more).

[0108] (Adhesive layer thickness) In the pressure-sensitive adhesive sheet disclosed herein, the thickness of the pressure-sensitive adhesive layer is not particularly limited and can be appropriately selected depending on the purpose. Considering the balance between adhesion to the adherend and high-temperature retention, the thickness of the pressure-sensitive adhesive layer can be, for example, approximately 2 μm to 500 μm. From the viewpoint of adhesion to the adherend, the thickness of the pressure-sensitive adhesive layer is typically 3 μm or more, preferably 5 μm or more. To facilitate the realization of a pressure-sensitive adhesive sheet that exhibits higher high-temperature retention, in some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 8 μm or more, preferably 12 μm or more, or even 15 μm or more, or even 18 μm or more. Furthermore, from the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive layer may be, for example, 200 μm or less, 150 μm or less, 100 μm or less, 70 μm or less, 50 μm or less, or 30 μm or less. In embodiments where greater emphasis is placed on reducing the thickness, the thickness of the pressure-sensitive adhesive layer may be, for example, 25 μm or less, or even 22 μm or less. When the PSA sheet disclosed herein is a double-sided PSA sheet having PSA layers on both sides of a substrate, the thicknesses of the PSA layers may be the same or different.

[0109] (Bio content of adhesive layer) The technology disclosed herein is implemented using a PSA containing a polyester polymer with a bio-content of 50% or more, and therefore the PSA layer (and PSA composition; the same applies hereinafter unless otherwise specified) has a bio-content of a predetermined value or more. While not particularly limited, the bio-content of the PSA layer may be approximately 30% or more (e.g., more than 30%), suitably approximately 40% or more, and preferably 50% or more. A high bio-content of the PSA layer means that the amount of fossil resource-based materials, such as petroleum, used is reduced. By designing the PSA layer to have a high bio-content, the PSA layer's overall dependency on fossil resource-based materials can be reduced. For example, the bio-content of the PSA layer may be 55% or more, 60% or more, 70% or more, or 75% or more. While the upper limit of the bio-content is 100% by definition, the PSA layer disclosed herein may typically have a bio-content of less than 100% because its components may contain materials derived from fossil resources. In order to facilitate obtaining performance (e.g., high-temperature retention) suitable for use in portable electronic devices, in some embodiments, the bio-content of the adhesive layer may be, for example, less than 90%, or, when adhesive performance is more important, less than 80% or less than 70%.

[0110] The bio content of the PSA layer, i.e., the proportion of biomass-derived carbon in the total carbon contained in the PSA layer, can be estimated from the content of the carbon isotope with mass number 14 measured in accordance with ASTM D6866. The bio content of the substrate and the PSA sheet, which will be described later, can also be estimated in a similar manner.

[0111] <Base material> The pressure-sensitive adhesive sheet disclosed herein may be in the form of a substrate-attached pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of the substrate. Various sheet-like substrates can be used as the substrate, such as resin films, paper, cloth, rubber sheets, foam sheets, metal foils, and composites thereof. In the field of electronic devices, substrates that are less likely to be a source of dust (e.g., minute fibers or particles such as paper dust) are preferably used. From this perspective, substrates that do not contain fibrous materials such as paper or cloth are preferred, and for example, resin films, rubber sheets, foam sheets, metal foils, and composites thereof can be preferably used.

[0112] Examples of resin films include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate; 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; and the like. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of foam sheets include foamed polyurethane sheets and foamed polyolefin sheets. Examples of metal foils include aluminum foil and copper foil.

[0113] Resin films are preferably used as the substrate. Resin films are preferably used as materials that are excellent in dimensional stability, thickness accuracy, economy (cost), processability, and tensile strength. Furthermore, resin films (for example, polyester films such as PET films, which will be described later) are recyclable, so that, regardless of whether plant-derived materials are used, by reusing used resin films, sustainable reproduction is possible and the environmental burden can be reduced. Such recyclable resin films and recycled resin films are also called recycled films. The recyclability of such resin films can also be applied to resin films used in the release liners described above. In this specification, the term "resin film" refers to a typically non-porous film, a concept that is distinguished from so-called nonwoven fabrics and woven fabrics.

[0114] In some embodiments, a polyester film may be preferably used as the substrate from the viewpoints of strength and processability. The polyester resin constituting the polyester film is typically a polyester resin containing, as a main component, a polyester obtained by polycondensation of a dicarboxylic acid and a diol.

[0115] Examples of dicarboxylic acids constituting the polyester include phthalic acid, isophthalic acid, terephthalic acid, 2-methylterephthalic acid, 5-sulfoisophthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid. aromatic dicarboxylic acids such as cyclohexanedicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanoic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, and fumaric acid; and derivatives thereof (for example, lower alkyl esters of the above dicarboxylic acids such as terephthalic acid). These can be used alone or in combination of two or more.

[0116] Examples of diols constituting the polyester include aliphatic diols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and polyoxytetramethylene glycol; alicyclic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, and 1,4-cyclohexanedimethylol; and aromatic diols such as xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone. These may be used alone or in combination of two or more. From the viewpoint of transparency, etc., aliphatic diols are preferred, and ethylene glycol is particularly preferred. The proportion of the aliphatic diol (preferably ethylene glycol) in the diol constituting the polyester is preferably 50% by weight or more (e.g., 80% by weight or more, typically 95% by weight or more). The diol may be composed essentially of ethylene glycol alone. As the ethylene glycol, biomass-derived ethylene glycol (typically, biomass ethylene glycol obtained using biomass ethanol as a raw material) can be preferably used. For example, the proportion of biomass-derived ethylene glycol in the ethylene glycol constituting the polyester may be, for example, 50% by weight or more, preferably 75% by weight or more, or may be 90% by weight or more, or may be 95% by weight or more. Substantially all of the ethylene glycol may be biomass-derived ethylene glycol.

[0117] Examples of polyester resin films include polyethylene terephthalate (PET) films, polybutylene terephthalate (PBT) films, polyethylene naphthalate (PEN) films, and polybutylene naphthalate films.

[0118] When the substrate disclosed herein is a polyester film substrate, the polyester film substrate may contain, in addition to polyester, a polymer other than the polyester. Suitable examples of the polymer other than polyester include those polymer materials other than polyester among the various polymer materials exemplified as resin films that can constitute the substrate. When the polyester film substrate disclosed herein contains, in addition to polyester, a polymer other than polyester, the content of the polymer other than polyester is suitably less than 100 parts by weight per 100 parts by weight of polyester, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less. The content of the polymer other than polyester may be 5 parts by weight or less, or even 1 part by weight or less, per 100 parts by weight of polyester. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which 99.5 to 100% by weight of the polyester film substrate is polyester.

[0119] In some other embodiments, a polyolefin film may be preferably used as the substrate from the viewpoint of strength and flexibility. A polyolefin film is a film whose main component is a polymer in which an α-olefin is the main monomer (the main component among the monomer components). The proportion of the polymer is usually 50% by weight or more (e.g., 80% by weight or more, typically 90 to 100% by weight). Specific examples of polyolefins include those in which ethylene is the main monomer (polyethylene) and those in which propylene is the main monomer (polypropylene). The polyethylene may be a homopolymer of ethylene, a copolymer of ethylene and another olefin (e.g., one or more α-olefins having 3 to 10 carbon atoms), or a copolymer of ethylene and a monomer other than an olefin (e.g., one or more ethylenically unsaturated monomers selected from vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, etc.). The polypropylene may be a homopolymer of propylene, a copolymer of propylene and another olefin (for example, one or more α-olefins having 2, 4 to 10 carbon atoms), or a copolymer of propylene and a monomer other than an olefin. The substrate disclosed herein may contain only one of the above polyolefins, or may contain two or more polyolefins.

[0120] When the substrate disclosed herein is a polyolefin film substrate, the polyolefin film substrate may contain, in addition to a polyolefin, a polymer other than the polyolefin. Suitable examples of the polymer other than the polyolefin include those polymer materials other than polyolefins among the various polymer materials exemplified as the resin films that can constitute the substrate. When the polyolefin film substrate disclosed herein contains, in addition to a polyolefin, a polymer other than the polyolefin, the content of the polymer other than the polyolefin is suitably less than 100 parts by weight per 100 parts by weight of the polyolefin, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less. The content of the polymer other than the polyolefin may be 5 parts by weight or less, or even 1 part by weight or less, per 100 parts by weight of the polyolefin. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which 99.5 to 100% by weight of the polyolefin film substrate is polyolefin.

[0121] The substrate disclosed herein preferably contains a biomass material from the viewpoint of reducing the amount of fossil resource-based materials used. Biomass materials that can constitute the substrate are not particularly limited, but examples include biomass polyesters such as biomass PET and biomass polytrimethylene terephthalate (biomass PTT); polylactic acid; biomass polyethylenes such as biomass high-density polyethylene (biomass HDPE), biomass low-density polyethylene (biomass LDPE), and biomass linear low-density polyethylene (biomass LLDPE), and biomass polyolefins such as biomass poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); biomass polyamides such as polyhexamethylene sebacamide and poly(xylylene sebacamide); biomass polyurethanes such as biomass polyester ether urethane and biomass polyether urethane; and cellulose-based resins. These materials can be used alone or in combination of two or more. Among these, biomass PET and biomass PTT are preferred, with biomass HDPE, biomass LDPE, biomass LLDPE, biomass PP, and biomass PET being particularly preferred. Because the above biomass materials are resin materials, they can be preferably applied to configurations in which the substrate is a resin film. By using the above biomass materials, the amount of fossil resource-based materials used can be reduced in PSA sheets with a resin film (preferably a polyolefin film) as the substrate.

[0122] In PSA sheets having a substrate, the bio content of the substrate is preferably 20% or more, and more preferably 35% or more. When greater emphasis is placed on reducing the amount of fossil resource-based materials used, the bio content of the substrate may be, for example, 50% or more, 70% or more, 85% or more, or 90% or more. The upper limit of the bio content is 100%, but in some embodiments, taking into account processability, strength, and the like, the bio content of the substrate may be, for example, 80% or less, 60% or less, 40% or less, or less than 20%.

[0123] The substrate may be transparent, or may have light-shielding or light-reducing properties. In some embodiments, a colorant may be contained in the substrate (e.g., a resin film). This allows the light transmittance (light-shielding properties) of the substrate to be adjusted. Adjusting the light transmittance (e.g., perpendicular light transmittance) of the substrate can also be useful for adjusting the light transmittance of the substrate and, further, the light transmittance of a pressure-sensitive adhesive sheet including the substrate.

[0124] As with the colorants that can be contained in the pressure-sensitive adhesive layer, conventionally known pigments and dyes can be used as the colorant. The colorant is not particularly limited and may be, for example, a colorant of black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl color, or the like.

[0125] The substrate may be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In a substrate having such a configuration including a base film and a colored layer, the base film may or may not contain a colorant. The colored layer may be disposed on either one surface of the base film, or on both surfaces. In a configuration in which colored layers are disposed on both surfaces of the base film, the configurations of the colored layers may be the same or different. By disposing a colored layer, the color and transparency of the PSA sheet can be adjusted, and desired design, light-blocking properties, and concealing properties can be obtained. The color of the colored layer is not particularly limited, and various colors can be adopted depending on the purpose. In some embodiments, the colored layer may be a black layer (e.g., a black printed layer) formed, for example, by black printing.

[0126] The colored layer can be formed, for example, by applying a colored layer-forming composition containing a colorant and a binder to a base film. Materials known in the fields of paint or printing can be used as the binder without particular limitation. Examples include polyurethane, phenolic resin, epoxy resin, urea melamine resin, and polymethyl methacrylate. The colored layer-forming composition can be, for example, solvent-based, UV-curable, or heat-curable. The colored layer can be formed using any method conventionally used for forming colored layers without particular limitation. For example, methods of forming a colored layer (printed layer) by printing such as gravure printing, flexographic printing, and offset printing can be preferably used.

[0127] The colored layer may have a single layer structure consisting of a single layer, or a multilayer structure including two, three, or more sub-colored layers. A colored layer having a multilayer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (e.g., printing) a colored layer-forming composition. The color and amount of colorant contained in each sub-colored layer may be the same or different. For a colored layer intended to impart light-blocking properties, a multilayer structure is particularly useful from the viewpoint of preventing pinholes from occurring and increasing the reliability of preventing light leakage.

[0128] As the colorant used to color the colored layer, known pigments or dyes can be appropriately selected according to the desired color. Examples of white pigments include, but are not limited to, titanium dioxide, zinc white, and white lead. Examples of black pigments include carbon black, acetylene black, pine soot, and graphite. These can be used alone or in combination of two or more.

[0129] The content of the colorant is not limited to a specific range, as it is set depending on the required color tone, light transmittance, etc., but is suitably about 1% by weight or more in the colored layer, preferably 2% by weight or more (e.g., 5% by weight or more), and may be 15% by weight or more. The content of the colorant is suitably about 65% by weight or less, preferably 30% by weight or less (e.g., 15% by weight or less), and may be 8% by weight or less.

[0130] The thickness of the entire colored layer is typically 0.1 μm or more, preferably 0.5 μm or more, and more preferably 0.7 μm or more. The thickness of the entire colored layer may be approximately 0.8 μm or more, or may be approximately 1 μm or more. In some other embodiments, from the viewpoint of obtaining sufficient light-blocking properties, the thickness of the entire colored layer may be 2 μm or more (e.g., 3 μm or more), or may be 4 μm or more. Furthermore, the thickness of the entire colored layer is typically 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. In some embodiments, the thickness of the entire colored layer can be approximately 3 μm or less, or even approximately 2 μm or less. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is typically preferably about 0.5 μm to 2 μm.

[0131] The surface of the substrate (e.g., a resin film, rubber sheet, foam sheet, etc.) on which the PSA layer is to be disposed (the surface on the PSA layer side) may be subjected to a known or conventional surface treatment, such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or formation of an undercoat layer. Such a surface treatment may be a treatment for improving the adhesion between the substrate and the PSA layer, in other words, the anchoring ability of the PSA layer to the substrate. Alternatively, the substrate may not be subjected to a surface treatment for improving the anchoring ability of the PSA layer side. When an undercoat layer is formed, the undercoat agent (primer) used for the formation is not particularly limited and can be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited and can be, for example, more than 0.01 μm, and is usually suitably 0.1 μm or more. From the viewpoint of enhancing the effect, it may be 0.2 μm or more. The thickness of the undercoat layer is preferably less than 1.0 μm, and may be 0.7 μm or less, or 0.5 μm or less. Generally, primers are highly dependent on fossil resource-derived materials, so not having an undercoat layer that is too thick can be advantageous from the perspective of reducing the bio-ratio of the PSA sheet, as described below.

[0132] In the case of a single-sided PSA sheet in which a PSA layer is provided on one side of a substrate, the side of the substrate on which the PSA layer is not formed (the back side) may be subjected to a release treatment using a release treatment agent (backside treatment agent). The backside treatment agent that can be used to form the backside treatment layer is not particularly limited, and silicone-based backside treatment agents, fluorine-based backside treatment agents, long-chain alkyl-based backside treatment agents, and other known or commonly used treatment agents can be used depending on the purpose and application. Backside treatment agents can be used alone or in combination of two or more.

[0133] The substrate (e.g., a resin film substrate) may contain various additives, such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.), as needed. The blending ratio of the various additives is usually about 30% by weight or less (e.g., 20% by weight or less, typically 10% by weight or less). For example, when a pigment (e.g., a white pigment) is incorporated into the substrate, the blending ratio is suitably about 0.1 to 10% by weight (e.g., 1 to 8% by weight, typically 1 to 5% by weight).

[0134] The thickness of the substrate is not particularly limited and can be selected appropriately depending on the purpose, but is generally about 1 μm to 500 μm. From the viewpoint of handleability of the substrate, the thickness of the substrate may be, for example, 1.5 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 4.5 μm or more. Furthermore, from the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet, in some embodiments, the thickness of the substrate may be, for example, 150 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, 20 μm or less, 10 μm or less, 7 μm or less, less than 5 μm, or less than 4 μm.

[0135] <Adhesive sheet> The thickness (total thickness) of the pressure-sensitive adhesive sheet disclosed herein (which includes a pressure-sensitive adhesive layer, and in the case of a pressure-sensitive adhesive sheet with a substrate, which further includes a substrate but does not include a release liner) is not particularly limited and can be, for example, in the range of approximately 2 μm to 1000 μm. In some embodiments, the thickness of the pressure-sensitive adhesive sheet is preferably about 5 μm to 500 μm (e.g., 10 μm to 300 μm, typically 15 μm to 200 μm), taking into consideration adhesive properties and the like. Alternatively, in some embodiments where thinning is important, the thickness of the pressure-sensitive adhesive sheet may be 100 μm or less (e.g., 5 μm to 100 μm), 70 μm or less (e.g., 5 μm to 70 μm), 45 μm or less (e.g., 5 μm to 45 μm), or 30 μm or less (e.g., 5 μm to 30 μm).

[0136] In the PSA sheet disclosed herein, it is preferable that approximately 30% or more (e.g., more than 30%) of the total carbon contained in the PSA sheet is biomass-derived carbon. That is, it is preferable that the PSA sheet has a biomass-derived content of 30% or more. By using a PSA sheet with such a high biomass-derived content, the amount of fossil resource-derived materials used can be reduced. From this perspective, the higher the biomass-derived content of the PSA sheet, the more preferable it is. The biomass-derived content of the PSA sheet is preferably 40% or more, and may be 50% or more, 60% or more, 70% or more, or even 75% or more. Although the upper limit of the biomass-derived content is 100% by definition, using all of the materials constituting the PSA sheet from plants may not be efficient in terms of productivity, performance, etc., so the biomass-derived content of the PSA sheet may be less than 100%. From the viewpoint of easily achieving performance suitable for use in portable electronic devices (e.g., high-temperature retention), in some embodiments, the biomass-derived content of the PSA sheet may be, for example, 90% or less. When adhesive performance is more important, the biomass-derived content may be 80% or less, or even 70% or less. In a substrate-less pressure-sensitive adhesive sheet consisting of a pressure-sensitive adhesive layer, the bio content of the pressure-sensitive adhesive layer and the bio content of the entire pressure-sensitive adhesive sheet are the same.

[0137] In some embodiments, the PSA sheet preferably has a 180-degree peel strength (adhesion strength to SUS) from a stainless steel plate of 10 N / 20 mm or more. PSA sheets exhibiting the above characteristics are firmly bonded to the adherend, and are therefore typically preferably used in embodiments where re-peeling is not intended. From the viewpoint of achieving a more reliable bond, the adhesive strength may be, for example, 11 N / 20 mm or more, preferably 12 N / 20 mm or more, or 13 N / 20 mm or more, or 14 N / 20 mm or more, or even 15 N / 20 mm or more. The upper limit of the adhesive strength is not particularly limited, and in some embodiments, the adhesive strength may be, for example, 50 N / 20 mm or less, or 30 N / 20 mm or less, or 25 N / 20 mm or less. The adhesive strength to SUS is specifically measured by the method described in the Examples below.

[0138] The PSA sheet disclosed herein preferably has a holding power such that it does not fall within one hour of a holding power test conducted under conditions of 80°C, a load of 1 kg, and one hour. PSA sheets exhibiting such high-temperature holding power can also exhibit good holding performance at temperatures higher than room temperature (e.g., temperatures of 40°C or higher). It is appropriate for the PSA sheet to have a slippage distance of 5.0 mm or less (e.g., 3.0 mm or less) after the holding power test. From the viewpoint of exhibiting higher holding performance, the slippage distance is preferably less than 2.0 mm, more preferably less than 1.0 mm, even more preferably less than 0.5 mm, and particularly preferably less than 0.3 mm (e.g., 0.1 mm or less). The lower limit of the slippage distance is 0.0 mm, which means that no slippage is observed in the holding power test. The holding power test is specifically conducted by the method described in the Examples below.

[0139] Furthermore, the pressure-sensitive adhesive sheet disclosed herein may have a pass level of repulsion resistance (i.e., no peeling) in a repulsion resistance test measured using a 125 μm thick PET film in the Examples described below. The pressure-sensitive adhesive sheet having the above repulsion resistance is durable against bending, and can exhibit adhesive reliability without lifting or peeling even when attached to the surface of a curved shape such as a three-dimensional shape.

[0140] <Application> The applications of the PSA sheets disclosed herein are not particularly limited, and they can be used for a variety of applications without limitation. For example, the PSA sheets can be attached to components constituting electronic devices, for example, for purposes such as fixing, joining, and reinforcing the components. The PSA sheets disclosed herein, for example, in the form of double-sided PSA sheets, can be preferably used for applications in which components are fixed or joined. In such applications, it is particularly useful for the PSA sheets to exhibit good adhesive strength and holding power. The double-sided PSA sheets may be substrate-less or may have a substrate. From the perspective of thinning, in some embodiments, substrate-less double-sided PSA sheets or substrate-attached double-sided PSA sheets using a thin substrate can be preferably employed. As the thin substrate, a substrate having a thickness of 10 μm or less (e.g., less than 5 μm) can be preferably used.

[0141] The pressure-sensitive adhesive sheet disclosed herein is suitable for use in, for example, fixing components in portable electronic devices. The pressure-sensitive adhesive sheet disclosed herein has adhesive reliability that achieves both adhesive strength and high-temperature retention, and is therefore suitable for use in portable electronic devices that require high performance. The interior of a portable electronic device may contain heat-generating elements such as a battery, and may be exposed to temperatures of, for example, 40°C or higher, making the use of a pressure-sensitive adhesive sheet with excellent high-temperature retention particularly useful. Non-limiting examples of the portable electronic device include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including eyeglasses (monocular and binocular devices, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. as an accessory, earwear devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, e-books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. The adhesive sheet disclosed herein can be preferably used, for example, for the purpose of fixing a pressure-sensitive sensor to other components within a portable electronic device equipped with a pressure-sensitive sensor among such portable electronic devices. In some preferred embodiments, the adhesive sheet can be used to fix a pressure-sensitive sensor and other members in an electronic device (typically a portable electronic device) that has a function that enables an absolute position to be specified on a plate (typically a touch panel) corresponding to the screen using a device for indicating a position on the screen (typically a pen-type or mouse-type device) and a device for detecting the position. In this specification, "portable" does not simply mean being portable, but rather means having a level of portability that allows an individual (average adult) to carry it relatively easily.

[0142] Furthermore, because the PSA sheets according to some preferred embodiments have good repulsion resistance, they exhibit excellent adhesive reliability even when bent based on this repulsion resistance, and are preferably used in embodiments in which they are attached to the curved surfaces of portable electronic devices having curved shapes such as three-dimensional shapes (for example, portable electronic devices equipped with curved displays). As mentioned above, the inside of portable electronic devices can become hot, so it is particularly significant that the PSA sheets can exhibit adhesive reliability without lifting or peeling even in such high-temperature conditions.

[0143] Materials (adherend materials) to which the pressure-sensitive adhesive sheet disclosed herein can be attached include, but are not limited to, metal materials such as copper, iron, aluminum, and stainless steel; various resin materials (typically plastic materials); and inorganic materials such as glass. Examples of the resin materials include polyimide resins, acrylic resins, polyethernitrile resins, polyethersulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyetheretherketone resins, polyamide resins (so-called aramid resins, etc.), polyarylate resins, polycarbonate resins, and liquid crystal polymers. The pressure-sensitive adhesive sheets disclosed herein are particularly suitable for bonding the above-mentioned metal materials, polyester resins such as PET, polyimide resins, aramid resins, polyphenylene sulfide resins, and polycarbonate resins. The above-mentioned materials can be used as component materials for products such as portable electronic devices. The pressure-sensitive adhesive sheets disclosed herein can be attached to components made of the above-mentioned materials.

[0144] FIG. 4 is a schematic diagram of an example of a portable electronic device (smartphone) using the adhesive sheet disclosed herein. As shown in FIG. 4, a battery (heat-generating element) 540 is built into a housing 520 of the portable electronic device 500. The portable electronic device 500 is also configured to include an adhesive sheet 550. In this configuration example, the adhesive sheet 550 is in the form of a double-sided adhesive sheet (double-sided adhesive sheet) that fixes the components that make up the portable electronic device 500. The portable electronic device 500 is also equipped with a touch panel 570 whose display unit also functions as an input unit. The adhesive sheet disclosed herein is preferably used as a component (member joining means) of the portable electronic device described above.

[0145] The matters disclosed by this specification include the following: [1] A portable electronic device, The device comprises a housing and a touch panel whose display unit also functions as an input unit, A heat generating element (e.g., a battery) is built into the housing, Among the many members constituting the portable electronic device, at least the first member and the second member are joined by an adhesive sheet, The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer containing a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived carbon, The pressure-sensitive adhesive layer further contains a tackifying resin, The weight-average molecular weight of the polyester-based polymer is 30,000 or more. [2] The portable electronic device according to [1] above, wherein the weight average molecular weight of the polyester polymer is greater than 60,000. [3] The portable electronic device according to [1] or [2] above, wherein the glass transition temperature of the polyester polymer is 0°C or lower. [4] The portable electronic device according to any one of the above [1] to [3], wherein the polyester polymer contains an aromatic ring. [5] The portable electronic device according to any one of the above [1] to [4], wherein the tackifier resin is selected from a terpene phenol resin and a polymerized rosin ester. [6] The portable electronic device according to any one of the above [1] to [5], wherein the polyester polymer contains an aromatic ring, and the tackifier resin also contains an aromatic ring. [7] The portable electronic device according to any one of [1] to [6] above, wherein the pressure-sensitive adhesive layer further contains a crosslinking agent, and the content of the crosslinking agent is 5 parts by weight or less relative to 100 parts by weight of the polyester-based polymer. [8] The portable electronic device according to [7], wherein the pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent as the crosslinking agent. [9] The portable electronic device according to [8], wherein the isocyanate-based crosslinking agent is an aliphatic isocyanate-based compound.

[10] The portable electronic device according to any one of the above [1] to [9], wherein the pressure-sensitive adhesive layer further contains a crosslinking agent and a crosslinking catalyst, and the crosslinking catalyst does not contain a tin-based compound.

[0146]

[11] A pressure-sensitive adhesive composition comprising a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived carbon, further comprising a tackifying resin; The pressure-sensitive adhesive composition, wherein the polyester polymer has a weight average molecular weight of 30,000 or more.

[12] The pressure-sensitive adhesive composition according to the above

[11] , wherein the weight-average molecular weight of the polyester polymer is greater than 60,000.

[13] The pressure-sensitive adhesive composition according to the above

[11] or

[12] , wherein the glass transition temperature of the polyester polymer is 0°C or lower.

[14] The pressure-sensitive adhesive composition according to any one of the above

[11] to

[13] , wherein the polyester polymer contains an aromatic ring.

[15] The pressure-sensitive adhesive composition according to any one of the above

[11] to

[14] , wherein the tackifier resin is selected from a terpene phenol resin and a polymerized rosin ester.

[16] The pressure-sensitive adhesive composition according to any one of the above

[11] to

[15] , wherein the polyester polymer contains an aromatic ring, and the tackifier resin also contains an aromatic ring.

[17] The pressure-sensitive adhesive composition according to any one of the above

[11] to

[16] , further comprising a crosslinking agent, the content of the crosslinking agent being 5 parts by weight or less per 100 parts by weight of the polyester polymer.

[18] The pressure-sensitive adhesive composition according to the above

[17] , wherein the crosslinking agent is an isocyanate-based crosslinking agent.

[19] The pressure-sensitive adhesive composition according to the above

[18] , wherein the isocyanate-based crosslinking agent is an aliphatic isocyanate-based compound.

[20] The pressure-sensitive adhesive composition according to any one of the above

[11] to

[19] , further comprising a crosslinking agent and a crosslinking catalyst, wherein the crosslinking catalyst does not contain a tin-based compound.

[21] The pressure-sensitive adhesive composition according to any one of the above

[11] to

[20] , wherein the weight-average molecular weight of the polyester polymer is greater than 100,000.

[22] The pressure-sensitive adhesive composition according to any one of the above

[11] to

[20] , which contains a bifunctional crosslinking agent and a trifunctional or higher crosslinking agent as the crosslinking agent.

[0147]

[31] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polyester polymer in which 50% or more of the constituent carbon is biomass-derived carbon, The pressure-sensitive adhesive layer further contains a tackifying resin, The pressure-sensitive adhesive sheet, wherein the polyester polymer has a weight average molecular weight of 30,000 or more.

[32] The pressure-sensitive adhesive sheet according to

[31] above, wherein the weight-average molecular weight of the polyester polymer is greater than 60,000.

[33] The pressure-sensitive adhesive sheet according to the above

[31] or

[32] , wherein the glass transition temperature of the polyester polymer is 0°C or lower.

[34] The pressure-sensitive adhesive sheet according to any one of the above

[31] to

[33] , wherein the polyester polymer contains an aromatic ring.

[35] The pressure-sensitive adhesive sheet according to any one of the above

[31] to

[34] , wherein the tackifier resin is selected from a terpene phenol resin and a polymerized rosin ester.

[36] The pressure-sensitive adhesive sheet according to any one of the above

[31] to

[35] , wherein the polyester polymer contains an aromatic ring, and the tackifier resin also contains an aromatic ring.

[37] The pressure-sensitive adhesive sheet according to any one of

[31] to

[36] above, wherein the pressure-sensitive adhesive layer further contains a crosslinking agent, and the content of the crosslinking agent is 5 parts by weight or less per 100 parts by weight of the polyester-based polymer.

[38] The pressure-sensitive adhesive sheet according to

[37] above, wherein the pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent as the crosslinking agent.

[39] The pressure-sensitive adhesive sheet according to

[38] above, wherein the isocyanate-based crosslinking agent is an aliphatic isocyanate-based compound.

[40] The pressure-sensitive adhesive sheet according to any one of the above

[31] to

[39] , wherein the pressure-sensitive adhesive layer further comprises a crosslinking agent and a crosslinking catalyst, and the crosslinking catalyst does not contain a tin-based compound.

[41] The pressure-sensitive adhesive sheet according to any one of

[31] to

[40] above, which has a 180-degree peel strength against a stainless steel plate of 10 N / 20 mm or more and does not fall in a holding strength test carried out under conditions of 80°C, a load of 1 kg, and 1 hour.

[42] The pressure-sensitive adhesive sheet according to any one of the above

[31] to

[41] , wherein the weight-average molecular weight of the polyester polymer is greater than 100,000.

[43] The pressure-sensitive adhesive sheet according to any one of the above

[31] to

[42] , wherein the pressure-sensitive adhesive layer contains, as crosslinking agents, a bifunctional crosslinking agent and a trifunctional or higher crosslinking agent.

[0148]

[51] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polyester polymer in which 50% or more of the constituent carbon is biomass-derived carbon, An adhesive sheet that has a 180-degree peel strength of 10N / 20mm or more against a stainless steel plate and does not fall off in a holding strength test conducted at 80°C, with a load of 1kg, for 1 hour.

[52] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polyester polymer in which 50% or more of the constituent carbon is biomass-derived carbon, The pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer further comprises a crosslinking agent and a crosslinking catalyst, and the crosslinking catalyst does not contain a tin-based compound.

[53] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived carbon, the pressure-sensitive adhesive layer further comprises a tackifying resin and a crosslinking agent, A pressure-sensitive adhesive sheet, wherein the polyester polymer contains an aromatic ring, the tackifier resin also contains an aromatic ring, and the crosslinking agent does not contain an aromatic ring.

[54] The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[53] , wherein the weight-average molecular weight of the polyester polymer is 30,000 or more.

[55] The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[54] , wherein the weight-average molecular weight of the polyester polymer is greater than 60,000.

[56] The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[55] , wherein the glass transition temperature of the polyester polymer is 0°C or lower.

[57] The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[56] , wherein the polyester polymer contains an aromatic ring.

[58] The pressure-sensitive adhesive layer further contains a tackifying resin, The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[57] , wherein the tackifier resin is selected from a terpene phenol resin and a polymerized rosin ester.

[59] The pressure-sensitive adhesive layer further contains a tackifying resin, The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[58] , wherein the polyester polymer contains an aromatic ring, and the tackifier resin also contains an aromatic ring.

[60] The pressure-sensitive adhesive sheet according to any one of

[51] to

[59] above, wherein the pressure-sensitive adhesive layer further contains a crosslinking agent, and the content of the crosslinking agent is 5 parts by weight or less per 100 parts by weight of the polyester-based polymer.

[61] The pressure-sensitive adhesive sheet according to

[60] above, wherein the pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent as the crosslinking agent.

[62] The pressure-sensitive adhesive sheet according to

[61] above, wherein the isocyanate-based crosslinking agent is an aliphatic isocyanate-based compound.

[63] The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[62] , wherein the pressure-sensitive adhesive layer further comprises a crosslinking agent and a crosslinking catalyst, and the crosslinking catalyst does not contain a tin-based compound.

[64] The pressure-sensitive adhesive sheet according to any one of

[51] to

[63] above, which has a 180-degree peel strength against a stainless steel plate of 10 N / 20 mm or more and does not fall in a holding strength test carried out under conditions of 80°C, a load of 1 kg, and 1 hour.

[65] The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[64] , wherein the weight-average molecular weight of the polyester polymer is greater than 100,000.

[66] The pressure-sensitive adhesive sheet according to any one of the above

[51] to

[65] , wherein the pressure-sensitive adhesive layer contains, as crosslinking agents, a bifunctional crosslinking agent and a trifunctional or higher crosslinking agent.

[0149]

[71] The pressure-sensitive adhesive sheet according to any one of

[31] to

[65] above, which is used in a portable electronic device.

[72] A portable electronic device comprising the adhesive sheet according to any one of

[31] to

[65] above.

[0150]

[81] A pressure-sensitive adhesive composition comprising a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived carbon, A pressure-sensitive adhesive composition further comprising a crosslinking agent and a crosslinking catalyst, wherein the crosslinking catalyst does not contain a tin-based compound.

[82] A pressure-sensitive adhesive composition comprising a polyester polymer in which 50% or more of the constituent carbon is biomass-derived carbon, further comprising a tackifying resin and a crosslinker; A pressure-sensitive adhesive composition, wherein the polyester polymer contains an aromatic ring, the tackifying resin also contains an aromatic ring, and the crosslinking agent does not contain an aromatic ring.

[83] The pressure-sensitive adhesive composition according to the above

[81] or

[82] , wherein the weight-average molecular weight of the polyester polymer is 30,000 or more.

[84] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[83] , wherein the weight-average molecular weight of the polyester polymer is greater than 60,000.

[85] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[84] , wherein the glass transition temperature of the polyester polymer is 0°C or lower.

[86] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[85] , wherein the polyester polymer contains an aromatic ring.

[87] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[86] , further comprising a tackifier resin, the tackifier resin being selected from a terpene phenol resin and a polymerized rosin ester.

[88] Further comprising a tackifying resin; The pressure-sensitive adhesive composition according to any one of the above

[81] to

[87] , wherein the polyester polymer contains an aromatic ring, and the tackifier resin also contains an aromatic ring.

[89] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[88] , further comprising a crosslinking agent, the content of the crosslinking agent being 5 parts by weight or less per 100 parts by weight of the polyester polymer.

[90] The pressure-sensitive adhesive composition according to the above

[89] , wherein the crosslinking agent is an isocyanate-based crosslinking agent.

[91] The pressure-sensitive adhesive composition according to the above

[90] , wherein the isocyanate-based crosslinking agent is an aliphatic isocyanate-based compound.

[91] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[90] , further comprising a crosslinking agent and a crosslinking catalyst, wherein the crosslinking catalyst does not contain a tin-based compound.

[92] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[91] , wherein the weight-average molecular weight of the polyester polymer is greater than 100,000.

[93] The pressure-sensitive adhesive composition according to any one of the above

[81] to

[92] , which contains a bifunctional crosslinking agent and a trifunctional or higher crosslinking agent as the crosslinking agent. [Example]

[0151] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0152] <Evaluation method> [Adhesion to SUS] The adhesive sheet was cut to a size of 20 mm wide and 150 mm long to prepare a measurement sample. The adhesive surface of the measurement sample was exposed at 23°C and 50% RH, and the adhesive surface was pressed against a stainless steel plate (SUS304BA plate) using a 2 kg rubber roller, moving back and forth once. The sample was left at 23°C and 50% RH for 30 minutes, and then the peel strength (adhesion to SUS) [N / 20 mm] was measured in the same environment using a tensile tester at a peel angle of 180° and a tensile speed of 300 mm / min, in accordance with JIS Z0237:2000. A universal tension-compression tester (TCM-1kNB, manufactured by Minebea Co., Ltd.) can be used as the tensile tester.

[0153] [High temperature holding power] A measurement sample (test piece) was prepared by cutting the adhesive sheet to a size of 10 mm wide and 100 mm long. The adhesive surface of the measurement sample was then pressed against a Bakelite plate (phenolic resin plate) as an adherend, with a 2 kg roller moving back and forth once, over an area of 10 mm wide and 20 mm long, in an environment of 23°C and 50% RH. The adherend with the test piece attached in this manner was then suspended in an environment at 80°C with the length of the test piece aligned vertically and left for 30 minutes. Next, a 1 kg load was applied to the free end of the test piece, and the test piece was left in an environment at 80°C with the load applied for 1 hour in accordance with JIS Z0237. After this time, the distance (mm) of displacement of the test piece from the initial attachment position (displacement length, hereinafter also referred to as displacement distance) was measured. If the test piece fell from the Bakelite plate within 1 hour, it was evaluated as "dropped" (failed).

[0154] When measuring the adhesive strength to SUS and the high-temperature holding power, if necessary (for example, in the case of a substrate-less double-sided PSA sheet, or in the case of a PSA sheet with a substrate that is prone to deformation), the PSA sheet to be measured can be reinforced by attaching an appropriate backing material. For example, a PET film with a thickness of about 50 μm can be used as the backing material, and this backing material was used in the examples.

[0155] [Rebound resistance test] 5(a), a polycarbonate (PC) plate 50 measuring 30 mm in length, 10 mm in width, and 2 mm in thickness and a PET film 60 measuring 100 mm in length, 10 mm in width, and 125 μm in thickness are prepared, and the PC plate 50 and the PET film 60 are overlapped so that one end of each is aligned in the longitudinal direction, and the remaining portion of the PET film 60 protrudes from the other end of the PC plate 50. Commercially available double-sided adhesive tape (manufactured by Nitto Denko Corporation, "No. 5000NS") is used for the above-mentioned fixation. The PSA sheet according to each example, both adhesive surfaces of which are protected by two release liners, is cut to a size of 10 mm x 10 mm to prepare PSA sheet sample piece 70. The surface of PC board 50 opposite the fixing surface of the PET film is placed upward, one release liner is peeled off from PSA sheet sample piece 70, and PSA sheet sample piece 70 is attached and fixed to the top surface of PC board 50 so that the other longitudinal end of PC board 50 coincides with one side of PSA sheet sample piece 70. The fixing is performed by rolling a 2 kg roller back and forth once over the top surface of PSA sheet sample piece 70 protected by the other release liner. Next, in an environment of 23°C and 50% RH, the other release liner of the adhesive sheet sample piece 70 attached to the PC plate 50 is peeled off, and as shown in Figure 5(b), the protruding portion (70 mm long) of the PET film 60 fixed to the PC plate 50 is folded back toward the PC plate 50, so that the adhesive sheet sample piece 70 and the other end (free end) of the PET film 60 are aligned, and a 0.1 kg roller is moved back and forth from above the PET film 60, thereby fixing the other end of the folded PET film 60 to the upper surface of the PC plate 50 via the adhesive sheet sample piece 70. Whether the PET film 60 peels from the adhesive sheet sample piece 70 is observed for 24 hours under an environment of 60°C and 95% RH and under an environment of room temperature (23°C), and the adhesive holding strength of the adhesive sheet sample piece 70 in the thickness direction of the adhesive sheet based on the elastic repulsion of the folded PET film 60 is evaluated as repulsion resistance. The adhesive sheet sample piece 70 and the PET film 60 were evaluated as having an excellent repulsion resistance (i.e., passed) when the adhesive state between the sample piece 70 and the PET film 60 was maintained for 24 hours in a 60°C, 95% RH environment and a room temperature environment, as shown in Fig. 5(c) when the PET film 60 peeled off within 24 hours in a 60°C, 95% RH environment and a room temperature environment, as shown in Fig. 5(c). If the result of the repulsion resistance test is excellent or excellent, the repulsion resistance is evaluated as good (i.e., passed), and if the result is poor, the repulsion resistance is evaluated as insufficient (i.e., failed).

[0156] <Synthesis example> (Synthesis Example 1) A four-neck separable flask equipped with a stirrer, thermometer, nitrogen tube, and water separation tube was charged with 100 g of ethylene glycol (Tokyo Chemical Industry Co., Ltd., molecular weight 62), 700 g of dimer acid (product name "Pripol 1009" Croda, molecular weight 567), 63 g of terephthalic acid (Tokyo Chemical Industry Co., Ltd., molecular weight 166), 0.46 g of di-n-butyltin oxide (Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a solvent for discharging reaction water. The mixture was heated to 180°C with stirring under a nitrogen atmosphere and maintained at this temperature. After a while, reaction water was observed to separate and the reaction began to progress. The reaction was continued for approximately 24 hours, yielding a polyester polymer (A1) with a biocontent of 81%. The weight-average molecular weight (Mw) of this polyester polymer (A1) was 100,000 and the glass transition temperature (Tg) was -33°C.

[0157] (Synthesis Example 2) A four-neck separable flask equipped with a stirrer, thermometer, nitrogen tube, and water separation tube was charged with 100 g of ethylene glycol (Tokyo Chemical Industry Co., Ltd., molecular weight 62), 915 g of dimer acid (product name "Pripol 1009" Croda, molecular weight 567), 0.46 g of di-n-butyltin oxide (Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst, and 40 g of xylene as a solvent for discharging reaction water. The mixture was heated to 180°C with stirring under a nitrogen atmosphere and maintained at this temperature. After a while, reaction water was observed to separate and the reaction began to progress. The reaction was continued for approximately 24 hours, yielding a polyester-based polymer (A2) with a biocontent of 89%. The Mw of this polyester-based polymer (A2) was 100,000 and the glass transition temperature (Tg) was -36°C.

[0158] (Synthesis Example 3) A three-neck separable flask was equipped with a stirrer, thermometer, and vacuum pump. 97.8 g of dimer acid (product name "Pripol 1009", Croda, molecular weight 567), 102.2 g of dimer diol (product name "Pripol 2033", Croda, molecular weight 537), and 0.2 g of dibutyltin oxide (Kanto Chemical) as a catalyst were charged. The mixture was heated to 200°C under reduced pressure (2.0 kPa or less) with stirring and maintained at this temperature. The reaction was continued for approximately 5 hours, yielding a polyester-based polymer (A3) with a biocontent of over 99%. The Mw of this polyester-based polymer (A3) was 28,000.

[0159] (Synthesis Example 4) A polyester polymer (A4) having a higher molecular weight than the polyester polymer (A1) was obtained in the same manner as in Synthesis Example 1, except that the reaction time in Synthesis Example 1 was changed to about 36 hours. The monomer composition of this polyester polymer (A4) was the same as that of the polyester polymer (A1), and its Mw was 130,000.

[0160] <Example 1> A pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) was prepared by blending 100 parts of the polyester polymer (A1) with 40 parts of a terpene phenol resin (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., phenol ratio 22%, hereinafter referred to as "S145") as a tackifier resin, 3 parts of an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, 0.13 parts of an organic zirconium compound (trade name "Orgatix ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) as a crosslinking catalyst, and 0.5 parts of a carbodiimide group-containing compound (trade name "Carbodilite V-03", manufactured by Nisshinbo Chemical Inc.) as a hydrolysis stabilizer, and adding ethyl acetate. This adhesive solution was applied to the release-treated surface of a release-treated polyethylene terephthalate (PET) film (trade name "Diafoil MRF#38", manufactured by Mitsubishi Chemical Corporation) so that the thickness after drying would be 20 μm, and the coating was dried for 3 minutes at 120° C. to obtain an adhesive layer. The adhesive layer was then attached to the release-treated surface of a release-treated PET film (trade name "Diafoil MRE#38", manufactured by Mitsubishi Chemical Corporation) and left at 50° C. for a further 3 days to obtain a substrateless adhesive sheet according to this example.

[0161] <Example 2> The adhesive composition of this example was prepared in the same manner as in Example 1, except that 0.01 parts of an organic tin compound (trade name "dibutyltin(IV) dilaurate", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of the organic zirconium compound as the crosslinking catalyst, and the substrateless adhesive sheet of this example was obtained in the same manner as in Example 1, except that this adhesive composition was used.

[0162] <Example 3> The adhesive composition of this example was prepared in the same manner as in Example 1, except that the amount of crosslinking agent used was changed to 2 parts per 100 parts of polyester-based polymer (A1). A substrateless adhesive sheet of this example was obtained in the same manner as in Example 1, except that this adhesive composition was used.

[0163] <Example 4> The amount of crosslinking agent used was changed to 4 parts per 100 parts of polyester polymer (A1), and 0.13 parts of an organoaluminum compound (trade name "Nasem Aluminum", manufactured by Nippon Chemical Industry Co., Ltd.) was used as the crosslinking catalyst instead of the organozirconium compound. A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1, and a substrate-less pressure-sensitive adhesive sheet according to this example was obtained in the same manner as in Example 1, except for using this pressure-sensitive adhesive composition.

[0164] <Examples 5-7> A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 4, except that the type and amount of crosslinking catalyst used was changed as shown in Table 1, and a substrate-less pressure-sensitive adhesive sheet according to each example was obtained in the same manner as in Example 4, except that the pressure-sensitive adhesive composition obtained was used. In Table 1, the iron-based catalyst is an organic iron compound (trade name "Nasem Ferric Iron", manufactured by Nippon Chemical Industry Co., Ltd.), and the titanium-based catalyst is an organic titanium compound (trade name "Orgatix TA-30", manufactured by Matsumoto Fine Chemical Co., Ltd.).

[0165] <Example 8> The polyester polymer (A1) was replaced with polyester polymer (A2), and the amount of crosslinking agent used was changed to 5 parts (5.3 parts) per 100 parts of polyester polymer (A2). A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 2, and a substrateless pressure-sensitive adhesive sheet according to this example was obtained in the same manner as in Example 2, except for using this pressure-sensitive adhesive composition.

[0166] <Example 9> As the tackifier resin, 40 parts of polymerized rosin ester (trade name "Pensel D-125", manufactured by Arakawa Chemical Industries, Ltd., phenol ratio 0%, hereinafter sometimes referred to as "D125") was used instead of the terpene phenol resin, and the amount of crosslinker used was changed to 5 parts (5.3 parts) per 100 parts of polyester polymer (A1). A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 2, and a substrateless pressure-sensitive adhesive sheet according to this example was obtained in the same manner as in Example 2, except for using this pressure-sensitive adhesive composition.

[0167] <Examples 10 and 11> Except for using polyester polymer (A3) instead of polyester polymer (A1), a pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1 or Example 2. Except for using the pressure-sensitive adhesive composition obtained, a substrate-less pressure-sensitive adhesive sheet according to each example was obtained in the same manner as in Example 1 or Example 2.

[0168] <Example 12> The adhesive composition of this example was prepared in the same manner as in Example 1, except that no tackifying resin was used, and the substrateless adhesive sheet of this example was obtained in the same manner as in Example 1, except that this adhesive composition was used.

[0169] <Example 13> 100 parts of polyester polymer (A4) was blended with 40 parts of a tackifying resin (trade name "YS Polystar G150", manufactured by Yasuhara Chemical Co., Ltd., phenol ratio 32%, hereinafter sometimes referred to as "G150"), 2 parts of an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation, hereinafter sometimes referred to as "trifunctional crosslinker") as a crosslinking agent, 0.03 parts of an organic zirconium compound (trade name "Orgatix ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) as a crosslinking catalyst, and 0.5 parts of a carbodiimide group-containing compound (trade name "Carbodilite V-03", manufactured by Nisshinbo Chemical Inc.) as a hydrolysis stabilizer, and ethyl acetate was added to prepare a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution). A substrateless pressure-sensitive adhesive sheet (thickness 20 μm) according to this example was obtained in the same manner as in Example 1, except that the resulting pressure-sensitive adhesive composition was used.

[0170] <Example 14> The adhesive composition of this example was prepared in the same manner as in Example 13, except that 100 parts of polyester polymer (A4) were used, 40 parts of terpene phenol resin (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., phenol ratio 22%) as a tackifying resin, 3 parts of an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, and 0.01 parts of an organotin compound (trade name "dibutyltin(IV) dilaurate", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a crosslinking catalyst. A substrateless adhesive sheet of this example was obtained in the same manner as in Example 13, except that this adhesive composition was used.

[0171] <Example 15> 100 parts of polyester polymer (A1) was mixed with 40 parts of terpene phenol resin (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., phenol ratio 22%) as a tackifier, 1 part of an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) and 5 parts of a bifunctional crosslinker (trade name "Duranate D101", manufactured by Asahi Kasei Corporation) as a crosslinking agent, 0.03 parts of an organic zirconium compound (trade name "Orgatix ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) as a crosslinking catalyst, and 0.5 parts of a carbodiimide group-containing compound (trade name "Carbodilite V-03", manufactured by Nisshinbo Chemical Co., Ltd.) as a hydrolysis stabilizer, and ethyl acetate was added to prepare a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution). A substrateless pressure-sensitive adhesive sheet (thickness 20 μm) according to this example was obtained in the same manner as in Example 1, except that the resulting pressure-sensitive adhesive composition was used.

[0172] <Examples 16-17> The adhesive compositions of each example were prepared in the same manner as in Example 15, except that the type of tackifier resin and the proportion of crosslinker used were changed as shown in Table 3, and the substrateless adhesive sheets of each example were obtained in the same manner as in Example 15, except that the obtained adhesive compositions were used.

[0173] The adhesive strength to SUS and high-temperature holding power of the pressure-sensitive adhesive sheets obtained in each example were measured using the methods described above. The results are shown in Tables 1 and 3. A repulsion resistance test was also conducted for Examples 2, 9', and 13 to 17. The results are shown in Tables 2 and 3. Example 9' is a modification of Example 9 in which the amount of crosslinking agent (product name "Coronate HX") used in the pressure-sensitive adhesive composition of Example 9 was changed from 5.3 parts to 4.4 parts.

[0174] [Table 1]

[0175] [Table 2]

[0176] [Table 3]

[0177] As shown in Tables 1 to 3, in PSA compositions containing a polyester-based polymer with a biocontent of 50% or more, Examples 1 to 9 and 13 to 17, which used PSA compositions containing a polyester-based polymer with an Mw of 30,000 or more and a tackifier resin, had adhesive strengths to SUS of 10 N / 20 mm or more and passed the high-temperature holding power test. In particular, as can be seen from a comparison between Examples 5 and 8, compositions using a polyester-based polymer containing an aromatic ring in the molecule achieved a better balance between adhesive strength and high-temperature holding power. On the other hand, Examples 10 and 11, which used a polyester-based polymer with an Mw of less than 30,000, failed the high-temperature holding power test. Furthermore, Example 12, which did not use a tackifier resin, had inferior adhesive strength to SUS compared to Examples 1 to 9. Furthermore, in the measurement of adhesive strength to SUS in Example 10, cohesive failure occurred in the PSA layer. The above results show that a pressure-sensitive adhesive containing a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived carbon and a tackifying resin, wherein the polyester-based polymer has an Mw of 30,000 or more, can achieve both adhesive strength and high-temperature retention.

[0178] Furthermore, as shown in Tables 2 and 3, the PSA sheets according to Examples 9' and 13 to 17, which are modifications of Example 2 and Example 9, passed the repulsion resistance test. In Examples 2, 9', and 13 to 14, the use of a high-molecular-weight polyester polymer is thought to have contributed to the improvement in repulsion resistance. In particular, Examples 13 and 14, which used a polyester polymer with an Mw of 130,000, showed particularly excellent results in the repulsion resistance test. In Examples 15 to 17, compared with Example 2, the use of a bifunctional and trifunctional crosslinking agent in combination is thought to have improved repulsion resistance. More specifically, the use of a bifunctional crosslinking agent elongated the polyester polymer chain during the crosslinking reaction, resulting in improved repulsion resistance. Although not specifically shown in the tables, Examples 13 and 16 to 17, which used a tackifier resin with a high phenol ratio, tended to exhibit better repulsion resistance compared to Examples 14 and 15. This is consistent with the fact that the rebound resistance test results of Examples 13 and 14 were better than those of Example 9', which used a tackifier resin with a phenol ratio of 0%.

[0179] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0180] 1,2,3 Adhesive sheet 10 Supporting base material 10A front page 10B Second side (back) 21 Adhesive layer (first adhesive layer) 21A Adhesive surface (first adhesive surface) 21B Second adhesive surface 22 Adhesive layer (second adhesive layer) 22A Adhesive surface (second adhesive surface) 31,32 Release liner 100, 200, 300 Adhesive sheet with release liner

Claims

1. A pressure-sensitive adhesive composition comprising a polyester polymer in which 50% or more of the constituent carbon is biomass-derived carbon, further comprising a tackifying resin; The polyester polymer is copolymerized with an aromatic dicarboxylic acid in a ratio of 1% by weight or more and 30% by weight or less, The pressure-sensitive adhesive composition, wherein the weight average molecular weight of the polyester polymer exceeds 100,000.

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the polyester polymer has a glass transition temperature of 0° C. or lower.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the tackifier resin is selected from a terpene phenolic resin and a polymerized rosin ester.

4. An adhesive composition described in any one of claims 1 to 3, wherein the tackifying resin contains an aromatic ring.

5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising a crosslinking agent, the content of which is 5 parts by weight or less relative to 100 parts by weight of the polyester polymer.

6. The pressure-sensitive adhesive composition according to claim 5 , wherein the crosslinking agent comprises an isocyanate-based crosslinking agent.

7. The pressure-sensitive adhesive composition according to claim 6 , wherein the isocyanate-based crosslinking agent is an aliphatic isocyanate-based compound.

8. The pressure-sensitive adhesive composition according to any one of claims 1 to 7, further comprising a crosslinking agent and a crosslinking catalyst, wherein the crosslinking catalyst does not contain a tin-based compound.

9. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polyester polymer in which 50% or more of the constituent carbon is biomass-derived carbon, The pressure-sensitive adhesive layer further comprises a tackifying resin, The polyester polymer is copolymerized with an aromatic dicarboxylic acid in a ratio of 1% by weight or more and 30% by weight or less, The weight average molecular weight of the polyester polymer is more than 100,000.

10. 10. The pressure-sensitive adhesive sheet according to claim 9, which has a 180-degree peel strength from a stainless steel plate of 10 N / 20 mm or more and does not fall in a holding power test carried out under conditions of 80°C, a load of 1 kg, and 1 hour.

11. The pressure-sensitive adhesive sheet according to claim 9 or 10, which is used in a portable electronic device.

12. A portable electronic device comprising the pressure-sensitive adhesive sheet according to claim 9 or 10.

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