Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

Abstract

To provide an adhesive composition that readily forms a thin, good quality polyester adhesive in a composition that contains a polyester polymer and a crosslinking agent and also contains as least a prescribed amount of a tackifying resin.SOLUTION: Provided is an adhesive composition containing a polyester polymer, a tackifying resin, and a crosslinking agent. The tackifying resin content is 20 pts.wt. or greater per 100 pts.wt. of the polyester polymer. The weight-average molecular weight of the polyester polymer is 110,000 or greater.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet. [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] Patent No. 4914132 [Patent Document 2] Patent No. 6687997 [Patent Document 3] Japanese Patent Publication No. 2020-79372 Summary of the Invention [Problem to be solved by the invention]

[0004] Adhesive sheets are preferably used for fixing components in portable electronic devices such as mobile phones, smartphones, and tablet computers. Thin-layer adhesives are preferred for use in portable electronic devices due to demands for lightweight, compact, thin, and highly functional portable electronic devices. Most adhesive sheets for portable electronic devices use acrylic adhesives based on acrylic polymers. Alternatively, synthetic rubber adhesives based on rubber block copolymers such as styrene-butadiene block copolymers may also be used. Polyester adhesives offer excellent properties such as chemical resistance, water resistance, durability, and optical properties (transparency), and can exhibit adhesive properties equivalent to or superior to those of acrylic adhesives and synthetic rubber adhesives. Therefore, they are expected to be used as adhesives for portable electronic devices. Furthermore, polyester adhesives can be synthesized using biomass materials, which offers the advantage of reducing dependence on fossil-based materials (see, for example, Patent Documents 1 and 2).

[0005] However, polyester polymers used in polyester-based pressure-sensitive adhesives generally have lower molecular weights than acrylic polymers, etc., and therefore pressure-sensitive adhesive compositions containing polyester-based polymers tend to have lower viscosities. Therefore, when forming a thin polyester-based pressure-sensitive adhesive, problems such as repelling easily occur due to the low viscosity. Specifically, when coating a thin pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition is usually diluted with a solvent or the like. However, diluting a pressure-sensitive adhesive composition that already has a low viscosity further reduces the viscosity of the pressure-sensitive adhesive composition, making it more likely to experience problems such as repelling after coating. To achieve a thin coating, the pressure-sensitive adhesive composition must have an appropriate viscosity even after dilution. Furthermore, for example, if the solids concentration of a polyester-based pressure-sensitive adhesive composition is increased to increase its viscosity, a crosslinking reaction may occur before the pressure-sensitive adhesive layer is formed, resulting in insufficient pot life. Therefore, in order to obtain a thin polyester-based pressure-sensitive adhesive with good quality, there are limitations on the selection of a pressure-sensitive adhesive sheet manufacturing machine and the adjustment of the viscosity of the pressure-sensitive adhesive composition.

[0006] Furthermore, in applications for portable electronic devices where the adhesive area tends to be limited, the addition of a tackifier resin to a polyester-based pressure-sensitive adhesive is considered essential to obtain sufficient adhesive properties. However, the addition of a tackifier resin further reduces the viscosity of the pressure-sensitive adhesive composition. For these reasons, achieving both the adhesive properties required for applications such as portable electronic devices and the ability to form a thin pressure-sensitive adhesive layer tends to be more difficult in industrial production. If a thin polyester-based pressure-sensitive adhesive with good quality could be obtained by using a commonly used pressure-sensitive adhesive sheet manufacturing machine and by adjusting the components contained in the pressure-sensitive adhesive composition with minimal process limitations and burdens, such as viscosity adjustment, it would be useful from the perspective of industrial production.

[0007] The present invention has been created in view of the above circumstances, Po The present invention aims to provide a pressure-sensitive adhesive composition that contains a polyester polymer and a crosslinking agent, and a predetermined amount or more of a tackifier resin, and that can easily form a thin pressure-sensitive adhesive having good quality based on the components contained therein. Another related object is to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition. [Means for solving the problem]

[0008] According to the present specification, a PSA composition is provided that includes a polyester-based polymer, a tackifier resin, and a crosslinking agent. The content of the tackifier resin is 20 parts by weight or more per 100 parts by weight of the polyester-based polymer. The weight-average molecular weight (Mw) of the polyester-based polymer is 110,000 or more. While the PSA composition containing a predetermined amount of tackifier resin tends to result in low viscosity due to its adhesive properties, the use of a polyester-based polymer with an Mw of 110,000 or more allows the PSA composition to achieve a moderate viscosity, making it easy to form a thin PSA with good quality without restricting or burdening the manufacturing process. That is, the PSA composition can achieve both good adhesive properties based on the use of the tackifier resin and PSA layer formability. Furthermore, since the PSA composition contains a crosslinking agent, increasing the concentration to adjust viscosity or the like can lead to a risk of a crosslinking reaction proceeding before the PSA layer is formed. However, the PSA composition easily achieves good viscosity based on the Mw of the polyester-based polymer, eliminating the need to increase the concentration of the PSA composition excessively (meaning beyond the normal range). Such a pressure-sensitive adhesive composition is easy to handle and can easily form a thin pressure-sensitive adhesive.

[0009] In some preferred embodiments of the technology disclosed herein (including pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets; the same applies hereinafter), the content of the tackifier resin is 20 parts by weight or more and less than 100 parts by weight per 100 parts by weight of the polyester polymer. By setting the amount of tackifier resin within the above range, the effects of the technology disclosed herein are preferably exhibited.

[0010] Although not particularly limited, by using a pressure-sensitive adhesive composition having a solid content concentration of 10 to 70 wt % and a viscosity at 23°C of 10 to 10,000 mPa·s, a thin pressure-sensitive adhesive can be formed with good productivity.

[0011] In some preferred embodiments, an isocyanate-based crosslinking agent is preferably used as the crosslinking agent, which can effectively increase the degree of crosslinking of the polyester-based pressure-sensitive adhesive.

[0012] In some embodiments, the PSA composition (and thus the PSA) contains a crosslinking catalyst. In a composition containing a crosslinking catalyst, increasing the concentration of the PSA composition for viscosity adjustment or the like tends to facilitate the crosslinking reaction before the PSA layer is formed. However, the technology disclosed herein makes it easy to obtain a good viscosity based on the Mw of the polyester polymer, eliminating the need to increase the PSA composition's concentration excessively. The PSA composition, which contains a crosslinking catalyst, can be easily handled and suitable for forming a thin PSA.

[0013] In some preferred embodiments, the polyester-based polymer used is a polyester-based polymer in which 50% or more of the constituent carbon is biomass-derived. In recent years, environmental issues such as global warming have become increasingly important, and it is desirable to reduce the amount of fossil resource-based materials used, such as petroleum. It is also desirable to reduce the amount of fossil resource-based materials used in adhesives. However, both the acrylic-based adhesives and synthetic rubber-based adhesives are adhesives whose main raw material is petroleum and other fossil resources. In reality, it is difficult to reduce the amount of fossil resource-based materials used, and there are limits to switching to renewable organic resources. On the other hand, the polyester-based polymer used in the polyester-based adhesive can be synthesized using biomass materials. By using a polyester-based polymer with a bio content of 50% or more, dependence on petroleum-based materials can be reduced. 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.

[0014] This specification also provides a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer. In this pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer contains a polyester-based polymer, a tackifier resin, and a crosslinking agent. The content of the tackifier resin in the pressure-sensitive adhesive layer is 20 parts by weight or more per 100 parts by weight of the polyester-based polymer. The weight-average molecular weight of the polyester-based polymer is 110,000 or more. According to the technology disclosed herein, a pressure-sensitive adhesive sheet having the above configuration can be produced with minimal limitations or burdens on the manufacturing process, even if the pressure-sensitive adhesive layer is thin, resulting in excellent productivity and high industrial applicability. Furthermore, a pressure-sensitive adhesive sheet having the above configuration can have excellent adhesive properties, achieving both adhesive strength and high-temperature retention.

[0015] In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is within the range of 5 to 50 μm. According to the technology disclosed herein, a pressure-sensitive adhesive sheet having a thin pressure-sensitive adhesive layer with a thickness of approximately 5 to 50 μm can be produced with good productivity and with fewer limitations and burdens on the manufacturing process.

[0016] The PSA sheet disclosed herein has good adhesive properties obtained by using a tackifier resin, and a thin PSA layer is formed with good quality and productivity, making it suitable for use in portable electronic devices, where thin PSA layers with high adhesive properties are required to meet demands for weight reduction, miniaturization, thinness, high functionality, etc. Furthermore, 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. The PSA sheet having the above configuration can have adhesive properties that combine adhesive strength and high-temperature retention, making it suitable for use in fixing components within a portable electronic device in this respect as well.

[0017] As described above, the present specification provides a portable electronic device using any of the pressure-sensitive adhesive sheets disclosed herein, in other words, a portable electronic device including the pressure-sensitive adhesive sheet. [Brief explanation of the drawings]

[0018] [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. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] <Adhesive composition> (Polyester polymer) The pressure-sensitive adhesive composition disclosed herein contains a polyester-based polymer (hereinafter, unless otherwise specified, matters relating to the pressure-sensitive adhesive composition can also be applied to the pressure-sensitive adhesive (layer) described below). Such pressure-sensitive adhesive compositions and pressure-sensitive adhesives containing a polyester-based polymer are also referred to as polyester-based pressure-sensitive adhesive compositions and polyester-based pressure-sensitive adhesives. 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 composition or 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.

[0021] The weight-average molecular weight (Mw) of the polyester polymer used in the technology disclosed herein is 110,000 or more. By using a polyester polymer with an Mw of 110,000 or more, even a PSA composition that contains a predetermined amount or more of a tackifier resin for adhesive properties and tends to have a low viscosity can obtain a moderate viscosity, making it easy to form a thin PSA with good quality. Such a PSA composition does not need to be excessively concentrated, and even a composition containing a crosslinker tends to have a sufficient pot life and excellent handleability. In some preferred embodiments, the Mw of the polyester polymer is 120,000 or more, or may be 125,000 or more. Using a polyester polymer with an Mw of a predetermined value or more increases the cohesive strength of the PSA layer, improving holding power and, ultimately, high-temperature holding power. Furthermore, by using a polyester polymer with a high molecular weight as described above, excellent resilience is easily 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 It may be the following:

[0022] 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)

[0023] 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).

[0024] 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.

[0025] In some preferred embodiments, the polyester polymer contains 50% or more of its constituent carbon as biomass-derived carbon. In other words, the biomass carbon ratio (also referred to as biofraction) of the polyester polymer is preferably 50% or more. By using a polyester polymer having a biofraction of a predetermined value or more, the PSA's dependence on fossil resource-based materials can be reduced. By using a biomass-derived compound for at least one (e.g., both) of the dicarboxylic acid and diol used in the synthesis of the polyester polymer, the biofraction of the polyester polymer can be increased to 50% or more. In some embodiments using a biomass-derived polyester polymer, the biofraction of the polyester polymer is 52% or more, suitably 55% or more, and may be, for example, 60% or more. The biofraction of the polyester polymer is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and may be 85% or more, or even 88% or more. Although the upper limit of the biocontent is 100% by definition, in some embodiments, the biocontent of the polyester-based polymer may be, for example, 95% or less, and when adhesive performance is more important, it may be 92% or less, 90% or less, or 85% or less. In other embodiments, the biocontent of the polyester-based polymer may be less than 50%, less than 30%, less than 10%, or less than 1%. The biocontent of the polyester-based polymer may even be substantially 0%.

[0026] 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.

[0027] (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 can be obtained that exhibit excellent adhesive properties, such as excellent adhesive strength and high-temperature retention.

[0028] In some preferred embodiments, it is preferable to use a plant-derived dicarboxylic acid as the dicarboxylic acid from the viewpoint of obtaining a polyester polymer with a high bio-content. 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.

[0029] In some preferred embodiments, from the viewpoint of reducing dependence on petroleum-derived materials, the weight ratio of plant-derived dicarboxylic acids to 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 ratio 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.

[0030] 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.

[0031] 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). Furthermore, 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 the method described in Chemische Technik, Vol. 38, No. 3, pp. 116-119; 1986, in which isobutanol is obtained from corn, sugars, or wood, converted to isobutylene, and then dimerized to obtain isooctene. This is followed by synthesizing p-xylene through radical cleavage, recombination, and cyclization, and then oxidizing this to obtain terephthalic acid (WO 2009 / 079213).

[0036] 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.

[0037] In some embodiments, dicarboxylic acids (e.g., aliphatic dicarboxylic acids) derived from fossil resources are used in order to obtain desired adhesive properties while 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 can be used alone or in combination of two or more.

[0038] 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.

[0039] (diol) As the diol used in the synthesis of the polyester polymer disclosed herein, any of (poly)alkylene glycols, aliphatic diols, dimer diols, alicyclic diols, aromatic diols, and unsaturated diols can be used. Specific examples of the 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 1,2-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; 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; and the like. By appropriately selecting and using one or more of these diols, it is possible to obtain a polyester polymer that can exhibit good adhesive properties, such as being suitable for achieving both adhesive strength and high-temperature retention.

[0040] 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.

[0041] 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.

[0042] 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 in which (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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 can exhibit good adhesive properties, such as both adhesive strength and high-temperature retention, can be preferably synthesized. Furthermore, 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 can be preferably synthesized that has a Mw of a predetermined value or more and exhibits good adhesive properties, such as being suitable for achieving both adhesive strength and high-temperature retention. 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, and 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).

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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).

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] (tackifying resin) The PSA composition (and thus the PSA layer) disclosed herein contains a tackifier resin. By using an appropriate amount of tackifier resin, the adhesive strength-enhancing effect of the tackifier resin is effectively exerted, resulting in favorable improvements in adhesive properties such as adhesive strength and high-temperature retention. While the inclusion of a tackifier resin tends to decrease the viscosity of the PSA composition, the combined use of a polyester polymer having the above-mentioned Mw with a tackifier resin allows the PSA composition to achieve an appropriate viscosity, making it easier to form a thin PSA with good quality. 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.

[0060] 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.

[0061] 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.

[0062] 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.).

[0063] 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.).

[0064] 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.

[0065] 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, excellent adhesive properties can be obtained, such as a better balance between adhesive strength and high-temperature retention.

[0066] 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.

[0067] 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.

[0068] In an embodiment 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), better high-temperature holding power 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 high-temperature holding power, 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.

[0069] 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

[0070] 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.

[0071] 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.

[0072] 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.

[0073] In the technology disclosed herein, the tackifier resin is used in a proportion of 20 parts by weight or more per 100 parts by weight of the polyester-based polymer. By using the tackifier resin in the above amount, the desired adhesive properties can be preferably achieved. In some preferred embodiments, the content of the tackifier resin per 100 parts by weight of the polyester-based polymer is approximately 25 parts by weight or more, more preferably approximately 30 parts by weight or more, even more preferably approximately 35 parts by weight or more, and may even be approximately 40 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 100 parts by weight, more preferably approximately 80 parts by weight or less, and even more preferably approximately 60 parts by weight or less (e.g., approximately 50 parts by weight or less). By limiting the content of the tackifier resin within a predetermined range, it is possible to effectively obtain the effect of adding the tackifier resin while easily maintaining the viscosity of the PSA composition within an appropriate range.

[0074] (Crosslinking agent) The pressure-sensitive adhesive composition disclosed herein contains a crosslinking agent. The pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition 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. The crosslinking agent used for crosslinking the polyester polymer may also function as a chain extender.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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."

[0081] 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.

[0082] In some embodiments, two or more crosslinking agents (preferably isocyanate-based crosslinking agents) with different numbers of functional groups may be used. Using two or more crosslinking agents with different numbers of functional groups makes it easier to achieve a good balance between multiple properties (e.g., adhesive strength, high-temperature retention, etc.). The functional group refers to a crosslinking reactive group, such as an isocyanate group in the case of the polyfunctional isocyanate-based compound described above. In some embodiments, one or more bifunctional crosslinking agents and one or more trifunctional or higher crosslinking agents (e.g., trifunctional crosslinking agents) are used in combination as the crosslinking agent. Using a bifunctional type and a trifunctional or higher functional type in combination makes it easier to achieve both adhesive strength and high-temperature retention. As the bifunctional crosslinking agent or trifunctional or higher crosslinking agent, any bifunctional or trifunctional or higher crosslinking agent can be used without particular limitation from among the various crosslinking agents described above. In some preferred embodiments, an isocyanate-based compound is preferably used as the bifunctional crosslinking agent or trifunctional or higher crosslinking agent.

[0083] 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.

[0084] In embodiments where a trifunctional or higher crosslinking agent is used as the crosslinking agent, the amount of the trifunctional or higher crosslinking agent used is not particularly limited. For example, the amount of the 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, and may be approximately 1 part by weight or more, from the viewpoint of obtaining the effect of using the trifunctional or higher crosslinking agent. By using an appropriate amount of the trifunctional or higher crosslinking agent, cohesive strength is increased and excellent properties (adhesion strength, high-temperature retention, etc.) are likely to be obtained. Furthermore, the amount of the 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 approximately 4 parts by weight or less, approximately 3 parts by weight or less, or approximately 2 parts by weight or less.

[0085] 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, 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, 0.2 or more is appropriate. B / C A) is, for example, 10 or less, preferably 7 or less, more preferably 5 or less, may be 2 or less, may be 1 or less, or may be 0.5 or less.

[0086] 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. According to the technology disclosed herein, there is no need to excessively increase the concentration of the pressure-sensitive adhesive composition for coatability, so even if the amount of crosslinking agent is increased, the pressure-sensitive adhesive composition can have good storage stability before the formation of the pressure-sensitive adhesive layer. 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, suitably approximately 8 parts by weight or less, and preferably approximately 5 parts by weight or less. According to the technology disclosed herein, it is possible to obtain a cohesive force that satisfies the high-temperature holding power with the amount of crosslinking agent used limited as described above. The amount of crosslinking agent used per 100 parts by weight of polyester polymer is preferably 4 parts by weight or less, and even more preferably approximately 3.5 parts by weight or less.

[0087] 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, from about 0.5 parts by weight to about 10 parts by weight per 100 parts by weight of the polyester-based polymer. From the viewpoint of improving cohesive strength, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of the polyester-based polymer is usually about 1 part by weight or more, preferably about 2 parts by weight or more (e.g., more than 2 parts by weight), more preferably about 2.5 parts by weight or more, even more preferably 2.8 parts by weight or more, and may be about 3.5 parts by weight or more, about 4.0 parts by weight or more, or even 4.5 parts by weight or more. According to the technology disclosed herein, there is no need to excessively increase the concentration of the pressure-sensitive adhesive composition for coatability, so even if the amount of isocyanate-based crosslinking agent is increased, the pressure-sensitive adhesive composition can have good storage stability before the formation of the pressure-sensitive adhesive layer. Furthermore, the amount of isocyanate crosslinking agent used per 100 parts by weight of polyester polymer is typically approximately 8 parts by weight or less, and preferably approximately 5 parts by weight or less. According to the technology disclosed herein, a cohesive force that satisfies the high-temperature holding power can be obtained with the amount of isocyanate crosslinking agent limited as described above. The amount of isocyanate crosslinking agent used per 100 parts by weight of polyester 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 (e.g., 3.5 parts by weight or less), and may be approximately 3.2 parts by weight or less.

[0088] (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.

[0089] 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.

[0090] 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.

[0091] (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.

[0092] 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.

[0093] 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.

[0094] (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.

[0095] (solvent or dispersion medium) The PSA composition disclosed herein may further contain a known or conventional solvent or dispersion medium for the purpose of adjusting the solid content concentration, viscosity, etc. For example, from the viewpoint of adhesive properties, a solvent-based PSA composition containing a PSA in an organic solvent is preferred. The organic solvent is not particularly limited, and one or more known or conventional organic solvents that can be used for polyester PSAs can be used. For example, organic solvents such as toluene, ethyl acetate, methyl ethyl ketone, methylcyclohexane, cyclohexane, xylene, and butyl acetate can be used. Among these, the use of ethyl acetate is preferred.

[0096] (viscosity) Although not particularly limited, the viscosity of the PSA composition disclosed herein at 23°C is, for example, approximately 10 mPa·s or more, optionally approximately 20 mPa·s or more, or approximately 30 mPa·s or more, or, for example, approximately 10,000 mPa·s or less, optionally approximately 8,000 mPa·s or less, or optionally approximately 6,000 mPa·s or less. In some embodiments, the viscosity may be greater than 100 mPa·s, optionally greater than 300 mPa·s, optionally greater than 500 mPa·s, or optionally greater than 700 mPa·s. By using a PSA composition having a viscosity within the above range, a thin PSA can be formed with good productivity.

[0097] (solid content concentration) Furthermore, although not particularly limited, the solid content concentration of the adhesive composition disclosed herein is, for example, about 10 wt % or more, or may be about 20 wt % or more, or may be about 30 wt % or more, or may be, for example, about 70 wt % or less, or may be about 60 wt % or less, or may be about 55 wt % or less. Adhesive compositions with the above solid content concentrations are easy to handle and can easily be formed into thin adhesives with good productivity.

[0098] The viscosity of the pressure-sensitive adhesive composition at 23°C refers to the viscosity measured using a BH-type viscometer at a rotation speed of 20 rpm at a sample (pressure-sensitive adhesive composition to be measured) temperature of 23°C ± 5°C. The rotor used in the measurement is selected from the appropriate type (number) depending on the viscosity of the sample. The solid content (non-volatile content) of the pressure-sensitive adhesive composition refers to the weight ratio of the residue after heating the pressure-sensitive adhesive composition at 130° C. for 120 minutes to the entire pressure-sensitive adhesive composition.

[0099] (bio rate) A PSA composition according to some embodiments can be prepared containing a polyester polymer having a biomass content of 50% or more. In such embodiments, the PSA composition has a biomass content of a predetermined value or more. While not particularly limited, the biomass content of the non-volatile (solid) content of the PSA composition may be approximately 30% or more (e.g., more than 30%), suitably approximately 40% or more, and preferably 50% or more. A high biomass content of the non-volatile content of the PSA composition means that the amount of fossil resource-derived materials, such as petroleum, used is reduced. By designing the PSA composition to have a high biomass content of the non-volatile content, the PSA's overall dependence on fossil resource-derived materials can be reduced. For example, the biomass content of the non-volatile content of the PSA composition may be 55% or more, 60% or more, 70% or more, or even 75% or more. While the upper limit of the biomass content is 100% by definition, the PSA composition disclosed herein typically has a biomass content of less than 100% because its components may contain materials derived from fossil resources. From the viewpoint of easily obtaining performance (e.g., high-temperature retention) suitable for portable electronic device applications, in some embodiments, the bio-ratio of the non-volatile content of the PSA composition may be, for example, less than 90%, and when adhesive performance is more important, may be less than 80% or even less than 70%. In other embodiments, the bio-ratio of the non-volatile content of the PSA composition may be less than 30%, less than 10%, or even less than 1%. The bio-ratio of the non-volatile content of the PSA composition may be substantially 0%. Note that the bio-ratio of the non-volatile content of the PSA composition is basically the same as the bio-ratio of the PSA layer formed using the PSA composition, and therefore the above-mentioned numerical range for the bio-ratio of the non-volatile content of the PSA composition may also be applied to the bio-ratio of the PSA layer.

[0100] The bio content of the PSA composition and the PSA layer, i.e., the proportion of biomass-derived carbon in the total carbon contained in the PSA composition and 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.

[0101] (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.

[0102] 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 comma 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 coating speed of the pressure-sensitive adhesive composition is not particularly limited. For example, a substrate or a release liner having a surface to be coated is fed at a speed (coating speed) of approximately 3 to 100 m / min (e.g., 5 to 50 m / min) while the pressure-sensitive adhesive composition is supplied from a coater to the surface to be coated, thereby coating the pressure-sensitive adhesive composition to a predetermined thickness. 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).

[0103] According to the technology disclosed herein, a thin adhesive layer of good quality can be formed based on the components contained in the adhesive composition, so there are fewer restrictions on the type of coater that the adhesive sheet manufacturing machine is equipped with, and there are also fewer restrictions on the coating speed and drying temperature, making it possible to form a thin adhesive layer of good quality.

[0104] <Adhesive sheet> The pressure-sensitive adhesive sheet disclosed herein is configured to include a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition. The pressure-sensitive adhesive sheet may be in the form of a substrate-less double-sided pressure-sensitive adhesive sheet having 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."

[0105] (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.

[0106] 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.

[0107] 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).

[0108] 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.

[0109] 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.

[0110] (Total thickness) 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, 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. From the viewpoint of achieving lighter weight, smaller size, thinner thickness, and higher functionality in products to which the pressure-sensitive adhesive sheet is applied (e.g., portable electronic devices), in some preferred embodiments, the thickness of the pressure-sensitive adhesive sheet is 100 μm or less, more preferably 70 μm or less, even more preferably 50 μm or less, and particularly preferably 35 μm or less, and may be, for example, 30 μm or less, or may be 25 μm or less. According to the technology disclosed herein, a thin pressure-sensitive adhesive layer can be formed with good quality and high productivity, and therefore the total thickness of the pressure-sensitive adhesive sheet can also be set within the above-mentioned range or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet is not particularly limited, and may be, for example, about 5 μm or more, or from the viewpoint of productivity, about 10 μm or more, or about 15 μm or more (for example, about 20 μm or more).

[0111] (bio rate) In some embodiments, 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, it can be said that 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 obtaining 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, or, when adhesive performance is more important, 80% or less, or 70% or less. In some other embodiments, the bio content of the PSA sheet may be less than 30%, less than 10%, or less than 1%. The bio content of the PSA sheet may be substantially 0%. 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.

[0112] (adhesive properties) 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.

[0113] 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.

[0114] <Adhesive layer> 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. In some embodiments, from the viewpoint of achieving lighter weight, smaller size, thinner thickness, and higher functionality of products (e.g., portable electronic devices) to which the pressure-sensitive adhesive sheet is applied, the thickness of the pressure-sensitive adhesive layer is, for example, suitably 100 μm or less, preferably 50 μm or less, more preferably 35 μm or less, even more preferably 30 μm or less, and particularly preferably 25 μm or less, and may be, for example, 22 μm or less. According to the technology disclosed herein, such thin pressure-sensitive adhesive layers can be formed with good quality and high productivity. The thickness of the pressure-sensitive adhesive layer is usually suitably 3 μm or more, and preferably 5 μm or more. From the viewpoint of easily realizing a pressure-sensitive adhesive sheet exhibiting higher high-temperature holding power, 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 may be 15 μm or more, or may be 18 μm or more. 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.

[0115] <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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] Examples of polyester resin films include polyethylene terephthalate (PET) films, polybutylene terephthalate (PBT) films, polyethylene naphthalate (PEN) films, and polybutylene naphthalate films.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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%.

[0127] 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.

[0128] 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, etc.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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).

[0138] 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.

[0139] As described above, the technology disclosed herein provides a method for producing a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer. The details are as explained above in connection with the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet, and therefore a duplicated explanation will be omitted.

[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 good adhesive properties and a thin pressure-sensitive adhesive layer formed with good quality and productivity, making it suitable for use in portable electronic devices where thin layers of pressure-sensitive adhesive are required due to demands for weight reduction, miniaturization, thinning, high functionality, etc. Furthermore, the pressure-sensitive adhesive sheet disclosed herein can have adhesive reliability that achieves both adhesive strength and high-temperature retention, making it suitable for use in portable electronic devices where high performance is required. 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 meaningful. 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] 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.

[0143] 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.

[0144] 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, the pressure-sensitive adhesive layer contains a polyester-based polymer, a tackifying resin, and a crosslinking agent, the content of the tackifier resin in the pressure-sensitive adhesive layer is 20 parts by weight or more relative to 100 parts by weight of the polyester-based polymer; The weight-average molecular weight of the polyester-based polymer is 110,000 or more. [2] The portable electronic device according to [1] above, wherein the content of the tackifier resin in the adhesive layer is 20 parts by weight or more and less than 100 parts by weight per 100 parts by weight of the polyester-based polymer. [3] The portable electronic device according to [1] or [2] above, wherein the crosslinking agent includes an isocyanate-based crosslinking agent. [4] The portable electronic device according to any one of the above [1] to [3], wherein 50% or more of the carbon constituting the polyester polymer is biomass-derived carbon. [5] The portable electronic device according to any one of the above [1] to [4], wherein the thickness of the pressure-sensitive adhesive layer is in the range of 5 to 50 μm. [6] The portable electronic device according to any one of the above [1] to [5], wherein the glass transition temperature of the polyester polymer is 0°C or lower. [7] The portable electronic device according to any one of the above [1] to [6], wherein the polyester polymer contains an aromatic ring. [8] The portable electronic device according to any one of the above [1] to [7], wherein the tackifier resin is selected from a terpene phenol resin and a polymerized rosin ester. [9] The portable electronic device according to any one of the above [1] to [8], wherein the polyester polymer contains an aromatic ring, and the tackifier resin also contains an aromatic ring.

[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 catalyst, and the crosslinking catalyst does not contain a tin-based compound.

[0145]

[11] A composition comprising a polyester polymer, a tackifying resin, and a crosslinking agent, the content of the tackifier resin is 20 parts by weight or more relative to 100 parts by weight of the polyester-based polymer, The pressure-sensitive adhesive composition, wherein the polyester polymer has a weight-average molecular weight of 110,000 or more.

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

[11] , wherein the content of the tackifier resin is 20 parts by weight or more and less than 100 parts by weight per 100 parts by weight of the polyester-based polymer.

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

[11] or

[12] , which has a solid content of 10 to 70% by weight and a viscosity at 23°C of 10 to 10,000 mPa·s.

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

[11] to

[13] , wherein the crosslinking agent includes an isocyanate-based crosslinking agent.

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

[11] to

[14] , further comprising a crosslinking catalyst.

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

[11] to

[15] , wherein 50% or more of the carbon constituting the polyester polymer is biomass-derived carbon.

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

[11] to

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

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

[11] to

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

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

[11] to

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

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

[11] to

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

[0146]

[21] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer contains a polyester-based polymer, a tackifying resin, and a crosslinking agent, the content of the tackifier resin in the pressure-sensitive adhesive layer is 20 parts by weight or more relative to 100 parts by weight of the polyester-based polymer; The pressure-sensitive adhesive sheet, wherein the polyester polymer has a weight average molecular weight of 110,000 or more.

[22] The pressure-sensitive adhesive sheet according to

[21] above, wherein the content of the tackifier resin in the pressure-sensitive adhesive layer is 20 parts by weight or more and less than 100 parts by weight per 100 parts by weight of the polyester-based polymer.

[23] The pressure-sensitive adhesive sheet according to

[21] or

[22] above, wherein the crosslinking agent includes an isocyanate-based crosslinking agent.

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

[21] to

[23] , wherein 50% or more of the carbon constituting the polyester polymer is biomass-derived carbon.

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

[21] to

[24] , wherein the pressure-sensitive adhesive layer has a thickness in the range of 5 to 50 μm.

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

[21] to

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

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

[21] to

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

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

[21] to

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

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

[21] to

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

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

[21] to

[29] 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 power test carried out under the conditions of 80°C, a load of 1 kg, and 1 hour.

[0147]

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

[21] to

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

[32] A portable electronic device comprising the pressure-sensitive adhesive sheet according to any one of

[21] to

[30] above.

[0148]

[41] A method for producing a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, comprising: preparing a pressure-sensitive adhesive composition comprising a polyester-based polymer, a tackifying resin, and a crosslinking agent; applying the pressure-sensitive adhesive composition to a substrate surface or a release surface to form a pressure-sensitive adhesive layer; Including, where: the content of the tackifier resin is 20 parts by weight or more relative to 100 parts by weight of the polyester-based polymer, The method for producing a pressure-sensitive adhesive sheet, wherein the polyester polymer has a weight average molecular weight of 110,000 or more.

[42] The method for producing a pressure-sensitive adhesive sheet according to

[41] above, wherein the content of the tackifier resin in the pressure-sensitive adhesive composition is 20 parts by weight or more but less than 100 parts by weight per 100 parts by weight of the polyester-based polymer.

[43] The method for producing a pressure-sensitive adhesive sheet according to the above

[41] or

[42] , wherein the pressure-sensitive adhesive composition has a solids concentration of 10 to 70 wt % and a viscosity at 23°C of 10 to 10,000 mPa·s.

[44] The method for producing a pressure-sensitive adhesive sheet according to any one of

[41] to

[43] above, wherein the crosslinking agent includes an isocyanate-based crosslinking agent.

[45] The method for producing a pressure-sensitive adhesive sheet according to any one of

[41] to

[44] above, further comprising a crosslinking catalyst.

[46] The method for producing a pressure-sensitive adhesive sheet according to any one of

[41] to

[45] above, wherein 50% or more of the carbon constituting the polyester polymer is biomass-derived carbon.

[47] The method for producing a pressure-sensitive adhesive sheet according to any one of the above

[41] to

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

[48] The method for producing a pressure-sensitive adhesive sheet according to any one of the above

[41] to

[47] , wherein the thickness of the pressure-sensitive adhesive layer is within the range of 5 to 50 μm.

[49] The method for producing a pressure-sensitive adhesive sheet according to any one of

[41] to

[48] above, wherein the pressure-sensitive adhesive sheet 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 strength test carried out under conditions of 80°C, a load of 1 kg, and 1 hour.

[50] The method for producing a pressure-sensitive adhesive sheet according to any one of

[41] to

[47] above, wherein the pressure-sensitive adhesive sheet is used in a portable electronic device. [Example]

[0149] 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.

[0150] <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-based polymer (A1) with a biocontent of 81%. The weight-average molecular weight (Mw) of this polyester-based polymer (A1) was 100,000 and the glass transition temperature (Tg) was -33°C.

[0151] (Synthesis Example 2) A polyester polymer (A2) 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 (A2) was the same as that of the polyester polymer (A1), and its Mw was 130,000.

[0152] <Example 1> A pressure-sensitive adhesive composition (adhesive solution) according to this example was prepared by blending 100 parts of polyester polymer (A1) with 40 parts of a tackifying resin (trade name "YS Polystar S145," manufactured by Yasuhara Chemical Co., Ltd., phenol content 22%, hereinafter referred to as "S145"), 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. Ethyl acetate was then added to the resulting mixture. The solids concentration of this pressure-sensitive adhesive composition was 40%, and the viscosity at 23°C was approximately 300 mPa·s.

[0153] <Example 2> An adhesive composition according to this example was prepared in the same manner as in Example 1, except that 0.01 parts of an organotin compound (trade name "dibutyltin(IV) dilaurate", manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the crosslinking catalyst instead of the organozirconium compound. The solids concentration of this adhesive composition was 40%, and the viscosity at 23°C was approximately 300 mPa s.

[0154] <Example 3> A pressure-sensitive adhesive composition (adhesive solution) according to this example was prepared by blending 100 parts of polyester polymer (A2) with 40 parts of a tackifying resin (trade name "YS Polystar G150," manufactured by Yasuhara Chemical Co., Ltd., phenol content 32%, hereafter referred to as "G150"), 2 parts of an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX," manufactured by Tosoh 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 Inc.) as a hydrolysis stabilizer. Ethyl acetate was then added to the resulting mixture. The solids concentration of this pressure-sensitive adhesive composition was 40%, and the viscosity at 23°C was approximately 800 mPa·s.

[0155] <Example 4> A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 3, except that 100 parts of polyester polymer (A2) were used, 40 parts of a terpene phenol resin (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd., phenol content 22%) as a tackifier 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. The solids concentration of this pressure-sensitive adhesive composition was 40%, and the viscosity at 23°C was approximately 800 mPa s.

[0156] <Example 5 to Example 8> The adhesive compositions of each example were prepared in the same manner as in Example 4, except that the amounts of tackifier resin and crosslinking agent used were changed as shown in Table 1.

[0157] <Evaluation> [Adhesive coating properties] Using a comma coater or die coater type pressure-sensitive adhesive sheet manufacturing machine (both line machines, also referred to as actual machines), the pressure-sensitive adhesive composition according to each example was coated onto the release-treated surface of a release-treated polyethylene terephthalate (PET) film (trade name "Diafoil MRF#38", manufactured by Mitsubishi Chemical Corporation) at a coating speed of 20 m / min so that the thickness after drying would be 20 μm, and the film was dried for 3 minutes at 120° C. In both the comma coater and die coater coating methods, if the pressure-sensitive adhesive layer after drying was visually observed to have no cissing or other defects and had good quality, it was judged as "good" (passed). If either the comma coater or die coater coating method caused visual defects such as cissing or the pressure-sensitive adhesive could not be applied, it was judged as "bad" (failed).

[0158] [Adhesion to SUS] An adhesive layer was formed using the method described above for evaluating adhesive coating properties, and the adhesive layer was attached to the release-treated surface of a release-treated PET film (product name "Diafoil MRE#38", manufactured by Mitsubishi Chemical Corporation), and then left at 50°C for 3 days to obtain a substrateless adhesive sheet protected on both sides by release liners. The resulting 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 then 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 accordance with JIS Z0237:2000 at a peel angle of 180° and a tensile speed of 300 mm / min. A universal tension-compression tester (TCM-1kNB, manufactured by Minebea Co., Ltd.) was used as the tensile tester.

[0159] [High temperature holding power] An adhesive layer was formed using the method described above for evaluating adhesive coating properties, and the adhesive layer was attached to the release-treated surface of a release-treated PET film (product name "Diafoil MRE#38", manufactured by Mitsubishi Chemical Corporation), and then left at 50°C for 3 days to obtain a substrateless adhesive sheet protected on both sides by release liners. A measurement sample (test piece) was prepared by cutting the pressure-sensitive adhesive sheet to a size of 10 mm wide and 100 mm long. In an environment of 23°C and 50% RH, the adhesive surface of the measurement sample was pressed against a Bakelite plate (phenolic resin plate) as an adherend, with a 2 kg roller moving back and forth once over an adhesion area of 10 mm wide and 20 mm long. The adherend to which the test piece was attached 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 in accordance with JIS Z0237, the test piece was left in an environment at 80°C with the load applied for 1 hour. 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).

[0160] 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.

[0161] Table 1 shows the evaluation results of the pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet according to each example.

[0162] [Table 1]

[0163] As shown in Table 1, among the PSA compositions according to Examples 1 to 4 and 6 to 8, which comprise a polyester polymer, a tackifier resin, and a crosslinker, and in which the tackifier resin content is 20 parts by weight or more per 100 parts by weight of the polyester polymer, Examples 3 to 4 and 6 to 8, in which a polyester polymer with an Mw of 110,000 or more was used, passed the PSA coatability evaluation using an actual machine, and the resulting PSA sheets exhibited excellent adhesive properties, achieving both adhesive strength to SUS and high-temperature holding power. On the other hand, Examples 1 and 2, in which a polyester polymer with an Mw of less than 110,000 was used, failed the PSA coatability evaluation, and due to poor coating, an evaluable PSA sheet could not be produced, and the PSA sheet was not evaluated. Note that Example 5, in which the amount of tackifier resin used was less than 20 parts by weight per 100 parts by weight of the polyester polymer, resulted in low adhesive strength to SUS. The above results demonstrate that a PSA composition comprising a polyester polymer, a tackifying resin, and a crosslinking agent, in which the tackifying resin content is 20 parts by weight or more per 100 parts by weight of the polyester polymer, and the polyester polymer has an Mw of 110,000 or more, can form a thin PSA of good quality. It also demonstrates that such PSA exhibits good adhesive properties due to the use of the tackifying resin.

[0164] 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]

[0165] 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. An adhesive composition for use in a portable electronic device, comprising: comprising a polyester-based polymer, a tackifying resin, and a crosslinking agent; the content of the tackifier resin is 20 parts by weight or more relative to 100 parts by weight of the polyester-based polymer, the total proportion of dicarboxylic acid and diol in the monomer components used in the synthesis of the polyester-based polymer is 90% by weight or more; The weight average molecular weight of the polyester polymer is 110,000 or more, A pressure-sensitive adhesive composition having a solids concentration of 10 to 70% by weight and a viscosity at 23°C of more than 500 mPa·s and not more than 10,000 mPa·s.

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the content of the tackifier resin is 20 parts by weight or more and less than 100 parts by weight based on 100 parts by weight of the polyester-based polymer.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the crosslinking agent comprises an isocyanate-based crosslinking agent.

4. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, further comprising a crosslinking catalyst.

5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein 50% or more of the carbon constituting the polyester-based polymer is biomass-derived carbon.

6. An adhesive sheet for use in a portable electronic device, It has a pressure-sensitive adhesive layer, The thickness of the pressure-sensitive adhesive layer is 3 μm or more and 22 μm or less, the pressure-sensitive adhesive layer contains a polyester-based polymer, a tackifying resin, and a crosslinking agent, the content of the tackifier resin in the pressure-sensitive adhesive layer is 20 parts by weight or more relative to 100 parts by weight of the polyester-based polymer; the total proportion of dicarboxylic acid and diol in the monomer components used in the synthesis of the polyester-based polymer is 90% by weight or more; The pressure-sensitive adhesive sheet, wherein the weight average molecular weight of the polyester polymer is 110,000 or more.

7. The pressure-sensitive adhesive sheet according to claim 6 , wherein the content of the tackifier resin in the pressure-sensitive adhesive layer is 20 parts by weight or more and less than 100 parts by weight relative to 100 parts by weight of the polyester-based polymer.

8. The pressure-sensitive adhesive sheet according to claim 6 or 7, wherein the crosslinking agent includes an isocyanate-based crosslinking agent.

9. The pressure-sensitive adhesive sheet according to any one of claims 6 to 8, wherein 50% or more of the carbon constituting the polyester polymer is biomass-derived carbon.

10. The pressure-sensitive adhesive sheet according to any one of claims 6 to 9, wherein the thickness of the pressure-sensitive adhesive layer is in the range of 5 µm or more and 22 µm or less.

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