WO2023140316A1

WO2023140316A1 - Adhesive composition and adhesive sheet

Info

Publication number: WO2023140316A1
Application number: PCT/JP2023/001479
Authority: WO
Inventors: 大介川西; 理仁丹羽; 翔希藤井
Original assignee: 日東電工株式会社
Priority date: 2022-01-21
Filing date: 2023-01-19
Publication date: 2023-07-27
Also published as: JP2023107051A

Abstract

The purpose of the present invention is to provide an adhesive composition that readily forms a thin, high-quality polyester adhesive in a composition that contains a polyester polymer and a crosslinking agent and additionally contains a prescribed amount or more of a tackifying resin. Provided is an adhesive composition containing a polyester polymer, a tackifying resin, and a crosslinking agent. The tackifying resin content is 20 parts by weight or greater per 100 parts by weight of the polyester polymer. The weight-average molecular weight of the polyester polymer is 110,000 or greater.

Description

Adhesive composition and adhesive sheet

The present invention relates to an adhesive composition and an adhesive sheet. This application claims priority based on Japanese Patent Application No. 2022-8141 filed on January 21, 2022, the entire contents of which are incorporated herein by reference.

In general, pressure-sensitive adhesives (also called pressure-sensitive adhesives; the same shall apply hereinafter) exhibit a soft solid (viscoelastic) state in a temperature range near room temperature, and have the property of easily adhering to adherends under pressure. Taking advantage of such properties, pressure-sensitive adhesives are typically in the form of pressure-sensitive adhesive sheets containing a layer of the pressure-sensitive adhesive in various industrial fields such as home appliances, automobiles, various machines, electrical equipment, and electronic devices. As the adhesive, various adhesives such as acrylic adhesives, rubber adhesives, polyester adhesives, etc. are used according to the purpose of use, the place of use, required properties, and the like. For example, Patent Documents 1 to 3 are cited as documents disclosing prior art regarding polyester pressure-sensitive adhesives.

Japanese Patent No. 4914132 Japanese Patent No. 6687997 Japanese Patent Application Publication No. 2020-79372

Adhesive sheets are preferably used, for example, for fixing members in mobile electronic devices such as mobile phones, smartphones, and tablet computers. As the pressure-sensitive adhesive for use in portable electronic devices, a thin-layer adhesive is preferably used in view of the demands for lighter weight, smaller size, thinner thickness, higher functionality, and the like of the above-mentioned portable electronic devices. As adhesive sheets for mobile electronic devices, those using an acrylic adhesive with an acrylic polymer as a base polymer are the mainstream, and in addition, for example, a synthetic rubber adhesive with a rubber block copolymer such as a styrene-butadiene block copolymer as a base polymer can be used. Polyester-based adhesives are excellent in various properties such as chemical resistance, water resistance, durability, and optical properties (transparency), and can exhibit adhesive properties equal to or higher than those of acrylic adhesives and synthetic rubber-based adhesives, so they are expected to be used as adhesives for mobile electronic devices. In addition, the polyester-based pressure-sensitive adhesive can be synthesized using biomass materials, so it has the advantage of being able to reduce dependence on fossil resource-based materials (for example, Patent Documents 1 and 2).

However, in general, polyester-based polymers used in polyester-based adhesives have a lower molecular weight than acrylic polymers and the like, so adhesive compositions containing polyester-based polymers tend to have low viscosities. Therefore, when forming a thin polyester-based pressure-sensitive adhesive, problems such as repelling tend to occur due to its low viscosity. Specifically, when a thin pressure-sensitive adhesive layer is applied, the pressure-sensitive adhesive composition is usually diluted with a solvent or the like. However, if a low-viscosity pressure-sensitive adhesive composition is diluted, the viscosity of the pressure-sensitive adhesive composition will further decrease, and problems such as repelling will easily occur after coating. For thin coating, the pressure-sensitive adhesive composition must have an appropriate viscosity even after dilution. Further, for example, if the solid content concentration is increased in order to increase the viscosity of the polyester-based pressure-sensitive adhesive composition, the crosslinking reaction may proceed before the pressure-sensitive adhesive layer is formed, and a sufficient pot life cannot be obtained. Therefore, in order to obtain a thin polyester-based pressure-sensitive adhesive with good quality, the actual situation is that there are restrictions on the selection of a pressure-sensitive adhesive sheet manufacturing machine, the adjustment of the viscosity of the pressure-sensitive adhesive composition, and the like.

In addition, it is considered essential to add a tackifying resin to the polyester-based adhesive in order to obtain sufficient adhesive properties for mobile electronic device applications, where the adhesive area tends to be limited. However, the addition of a tackifying resin further reduces the viscosity of the adhesive composition. Under these circumstances, it tends to be more difficult in terms of industrial production to achieve both adhesive properties required for use in portable electronic devices and the ability to form a thin adhesive layer. It would be useful from the viewpoint of industrial production if a thin polyester-based pressure-sensitive adhesive having good quality could be obtained by using a commonly used pressure-sensitive adhesive sheet manufacturing machine, reducing process restrictions and loads such as viscosity adjustment, and devising the components contained in the pressure-sensitive adhesive composition.

The present invention was created in view of the above circumstances, and aims to provide a pressure-sensitive adhesive composition containing a polyester-based polymer and a cross-linking agent, and containing a predetermined amount or more of a tackifying resin, based on the components contained in the pressure-sensitive adhesive composition, which facilitates the formation of a thin pressure-sensitive adhesive of good quality. Another related object is to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

According to this specification, a pressure-sensitive adhesive composition containing a polyester-based polymer, a tackifying resin and a cross-linking agent is provided. The content of the tackifying resin is 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer. Also, the weight average molecular weight (Mw) of the polyester polymer is 110,000 or more. According to the above composition, the adhesive composition contains a predetermined amount or more of a tackifying resin for adhesive properties and tends to have a low viscosity, but by using a polyester-based polymer having an Mw of 110,000 or more, the adhesive composition has an appropriate viscosity. That is, according to the above composition, it is possible to achieve both good adhesive properties based on the use of the tackifying resin and adhesive layer formability. In addition, since the pressure-sensitive adhesive composition contains a cross-linking agent, if the concentration is increased for viscosity adjustment or the like, the cross-linking reaction may proceed before the pressure-sensitive adhesive layer is formed. However, according to the above-described composition, the Mw of the polyester polymer makes it easy to obtain a good viscosity, so there is no need to increase the concentration of the pressure-sensitive adhesive composition excessively (meaning beyond the normal range). Such a pressure-sensitive adhesive composition is easy to handle and easy to form a thin pressure-sensitive adhesive.

In some preferred embodiments of the technology disclosed herein (including adhesive compositions and adhesive sheets; hereinafter the same), the content of the tackifying resin is 20 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the polyester polymer. By setting the amount of the tackifying resin within the above range, the effects of the technology disclosed herein are preferably exhibited.

Although not particularly limited, by using an adhesive composition having a solid content concentration of 10 to 70% by weight and a viscosity of 10 to 10000 mPa·s at 23°C, a thin adhesive can be formed with good productivity.

In some preferred embodiments, an isocyanate-based cross-linking agent is preferably used as the cross-linking agent. By using the isocyanate-based cross-linking agent, the degree of cross-linking of the polyester-based pressure-sensitive adhesive can be effectively increased.

In some embodiments, the adhesive composition (and thus the adhesive) contains a cross-linking catalyst. In a composition containing a cross-linking catalyst, if the concentration of the pressure-sensitive adhesive composition is increased for viscosity adjustment or the like, the cross-linking reaction tends to proceed before the formation of the pressure-sensitive adhesive layer. However, according to the technology disclosed herein, it is easy to obtain a good viscosity based on the Mw of the polyester polymer, so there is no need to increase the concentration of the pressure-sensitive adhesive composition excessively. The pressure-sensitive adhesive composition contains a cross-linking catalyst and can be suitable for forming a thin pressure-sensitive adhesive with good handleability.

In some preferred embodiments, a polyester polymer in which 50% or more of the constituent carbon is biomass-derived carbon is used as the polyester polymer. In recent years, environmental problems such as global warming have come to be emphasized, and it is desired to reduce the amount of fossil resource-based materials such as petroleum used. However, both the above acrylic adhesives and synthetic rubber adhesives are adhesives whose main raw materials are fossil resources such as petroleum, and in reality, it is difficult to reduce fossil resource-based materials, and there is a limit to switching to renewable organic resources. On the other hand, the polyester-based polymer used for the polyester-based pressure-sensitive adhesive can be synthesized using a biomass material. By using a polyester-based polymer having a bio rate of 50% or more, dependence on fossil resource-based materials can be reduced. Note that biomass materials typically refer to materials derived from biological resources (typically photosynthetic plants) that can be sustainably reproduced in the presence of sunlight, water, and carbon dioxide.

Also, according to the present specification, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer is provided. In this pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer contains a polyester polymer, a tackifying resin and a cross-linking agent. Moreover, the content of the tackifying resin in the adhesive layer is 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer. Also, the polyester-based polymer has a weight average molecular weight of 110,000 or more. According to the technology disclosed herein, the pressure-sensitive adhesive sheet having the above configuration can be produced with less restrictions and less load on the manufacturing process even if the pressure-sensitive adhesive layer is thin, and thus has excellent productivity and high industrial applicability. In addition, the pressure-sensitive adhesive sheet having the above-described structure can have excellent pressure-sensitive adhesive properties in which both adhesive strength and high-temperature holding power are achieved.

In some preferred embodiments, the pressure-sensitive adhesive layer has a thickness in the range of 5-50 μm. According to the technology disclosed herein, a pressure-sensitive adhesive sheet having a thin pressure-sensitive adhesive layer with a thickness of about 5 to 50 μm can be produced with good productivity with less restrictions and load on the manufacturing process.

The pressure-sensitive adhesive sheet disclosed herein has good adhesive properties obtained by using a tackifying resin, and the thin pressure-sensitive adhesive layer is formed with good quality and productivity. Therefore, it is suitable for use in mobile electronic devices, where a thin pressure-sensitive adhesive with high adhesive properties is required due to demands such as weight reduction, miniaturization, thin thickness, and high functionality. In addition, since the inside of a portable electronic device may include a heat-generating element such as a battery, it may be exposed to a temperature of 40° C. or higher, for example.

From the above, according to the present specification, a portable electronic device using any adhesive sheet disclosed herein, in other words, a portable electronic device including the adhesive sheet is provided.

1 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to one embodiment; FIG. FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment; FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment; 1 is a front view schematically showing an example of a mobile electronic device including an adhesive sheet; FIG.

Preferred embodiments of the present invention are described below. Matters other than the matters specifically referred to in the present specification and necessary for the practice of the present invention can be understood by those skilled in the art based on the teachings of the practice of the invention described herein and the common general knowledge at the time of filing. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.
In the drawings below, members and portions having the same function may be denoted by the same reference numerals, and redundant description may be omitted or simplified. In addition, the embodiments described in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product.

<Adhesive composition>
(polyester polymer)
The adhesive composition disclosed herein contains a polyester-based polymer (hereinafter, unless otherwise specified, the matters described for the adhesive composition can also be applied to the adhesive (layer) described later). Such a pressure-sensitive adhesive composition or pressure-sensitive adhesive containing a polyester-based polymer is also referred to as a polyester-based pressure-sensitive adhesive composition or a polyester-based pressure-sensitive adhesive. The above polyester-based polymer is typically contained in the pressure-sensitive adhesive layer as a base polymer. Here, the base polymer refers to a main component of a rubber-like polymer (a polymer exhibiting rubber elasticity in a temperature range around room temperature) contained in the pressure-sensitive adhesive composition or pressure-sensitive adhesive (layer). In this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified. Moreover, in this specification, the polyester-based polymer refers to a polymer obtained by polycondensation of a dicarboxylic acid and a diol.

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-based polymer having an Mw of 110,000 or more, even if the pressure-sensitive adhesive composition contains a predetermined amount or more of a tackifying resin for adhesive properties and tends to have a low viscosity, the pressure-sensitive adhesive composition can obtain an appropriate viscosity and easily form a thin pressure-sensitive adhesive having good quality. Such a pressure-sensitive adhesive composition does not need to be excessively concentrated, and even if it contains a cross-linking agent, it tends to have a sufficient pot life and is excellent in handleability. In some preferred embodiments, the Mw of the polyester-based polymer is 120,000 or greater, and may be 125,000 or greater. By using a polyester-based polymer having a Mw of a predetermined value or more, the cohesive force of the pressure-sensitive adhesive layer is increased, and the holding power and, in turn, the high-temperature holding power are improved. Also, by using a high-molecular-weight polyester-based polymer as described above, it is easy to obtain excellent repulsion resistance. The upper limit of the Mw of the polyester-based polymer is usually about 30×10 ⁴ or less, preferably about 20×10 ⁴ or less, more preferably about 15×10 ⁴ or less from the viewpoint of adhesive strength and the like.

In addition, in this specification, Mw of a polyester-based polymer refers to a value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used. More specifically, GPC measurement can be performed under the following conditions. It is measured by the same method in the examples described later.
[GPC measurement]
Column: TSKgelGMH-H (S)
Column temperature: 40°C
Eluent: THF (0.1% by weight of amine component added)
Flow rate: 0.5mL/min
Injection volume: 100 μL
Detector: differential refractometer (RI)
Standard sample: polystyrene (PS)

The glass transition temperature (Tg) of the polyester-based polymer is advantageously about 15°C or less, preferably about 0°C or less, more preferably about -15°C or less, even more preferably about -20°C or less, particularly preferably about -25°C or less (for example, about -30°C or less). By using a polyester-based polymer with a low Tg, the adhesive strength can be preferably improved. Further, 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, still more preferably about -40°C or higher, and may be about -35°C or higher. The Tg of the polyester-based polymer can be adjusted by appropriately changing the monomer composition (that is, the types and usage ratio of the monomers used in synthesizing the polymer).

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

In some preferred embodiments, 50% or more of the constituent carbon of the polyester-based polymer is biomass-derived carbon. In other words, the biomass carbon ratio (also referred to as biorate) of the polyester-based polymer is preferably 50% or more. By using a polyester-based polymer having a bio rate of a predetermined value or more in this manner, the dependence of the adhesive on fossil resource-based materials can be reduced. By using a biomass-derived compound for at least one (for example, both) of the dicarboxylic acid and the diol used in the synthesis of the polyester polymer, the bio rate of the polyester polymer can be made 50% or more. In some embodiments using a biomass-derived polyester-based polymer, the bio-content of the polyester-based polymer is 52% or greater, suitably 55% or greater, and may be, for example, 60% or greater. The bio rate of the polyester-based polymer is preferably 70% or higher, more preferably 75% or higher, still more preferably 80% or higher, and may be 85% or higher, or 88% or higher. Although the upper limit of the bio rate is 100% by definition, in some embodiments, the bio rate of the polyester-based polymer may be, for example, 95% or less, and when more emphasis is placed on adhesive performance, it may be 92% or less, 90% or less, or 85% or less. In some other embodiments, the polyester-based polymer may have a bio-factor of less than 50%, less than 30%, less than 10%, or less than 1%. The bio-rate of the polyester-based polymer may be substantially 0%.

Here, biomass-derived carbon in this specification means carbon derived from biomass materials, that is, materials derived from renewable organic resources (renewable carbon). The biomass materials typically refer to materials derived from biological resources (typically photosynthetic plants) that can be sustainably reproduced in the presence of sunlight, water, and carbon dioxide. Therefore, materials derived from fossil resources that are depleted by use after mining (fossil resource-based materials) are excluded from the concept of biomass materials here. The bio-rate of a polyester-based polymer, that is, the ratio of biomass-derived carbon to the total carbon contained in the polyester-based polymer can be estimated from the carbon isotope content with a mass number of 14 measured according to ASTM D6866. The same applies to the examples described later.

(Dicarboxylic acid)
Any of aliphatic dicarboxylic acids, dimer acids, alicyclic dicarboxylic acids, unsaturated dicarboxylic acids, and aromatic dicarboxylic acids can be used as the dicarboxylic acid used for synthesizing the polyester-based polymer. Specific examples of dicarboxylic acids 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, Alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, norbornanedicarboxylic acid and adamantanedicarboxylic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid and dodecenylsuccinic anhydride; isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'- Aromatic dicarboxylic acids such as biphenyldicarboxylic acid, 4,4′-biphenyldicarboxylic acid, 4,4′-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; derivatives thereof; and the like. The dicarboxylic acid derivatives include derivatives such as carboxylates, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters. By appropriately selecting and using one or more of these dicarboxylic acids, it is possible to obtain a polyester polymer capable of exhibiting good adhesive properties such as being suitable for both adhesive strength and high temperature holding power.

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-based polymer with a high bio-ratio. Suitable examples of such dicarboxylic acids include sebacic acid derived from plants (eg, castor oil), and dimer acid derived from fatty acids such as oleic acid and erucic acid. Plant-derived dicarboxylic acids can be used singly or in combination of two or more.

In some preferred embodiments, from the viewpoint of reducing dependence on fossil resource-based materials, the weight ratio of the plant-derived dicarboxylic acid in the total amount (total weight) of the dicarboxylic acids as monomer components of the polyester polymer is appropriately set to about 1% by weight or more, preferably about 10% by weight or more, more preferably about 50% by weight or more, even more preferably about 70% by weight or more, particularly preferably about 80% by weight or more, and may be about 90% by weight or more, It may be approximately 95% by weight or more (eg, 95 to 100% by weight). In addition, the upper limit of the weight ratio of the plant-derived dicarboxylic acid is 100% by weight, and from the viewpoint of adhesive properties such as high-temperature holding power, it is suitably about 99% by weight or less, preferably about 95% by weight or less, and may be about 90% by weight or less.

In some preferred embodiments, a dimer acid is used as the plant-derived dicarboxylic acid. By using a dimer acid, the bio rate of the polyester-based polymer can be increased while obtaining good adhesive properties. A dimer acid can be used individually by 1 type or in combination of 2 or more types. In the embodiment using the dimer acid as the dicarboxylic acid, the weight ratio of the dimer acid to the total amount (total weight) of the dicarboxylic acid as the monomer component of the polyester polymer is suitably about 1% by weight or more, preferably about 10% by weight or more, more preferably about 50% by weight or more, even more preferably about 70% by weight or more, particularly preferably about 80% by weight or more, and may be about 90% by weight or more, or about 95% by weight or more (for example, 95 to 1%). 00% by weight). By setting the amount of the dimer acid to be used to a predetermined amount or more, the polymer can be designed based on the properties of the dimer acid. The upper limit of the weight ratio of the dimer acid is 100% by weight, and from the viewpoint of adhesive properties such as high-temperature holding power, it is suitably about 99% by weight or less, preferably about 95% by weight or less, and may be about 90% by weight or less.

In some embodiments, sebacic acid may be used as the plant-derived dicarboxylic acid. The use of sebacic acid can also increase the bio-rate of the polyester polymer. In the embodiment using sebacic acid as the dicarboxylic acid, the weight ratio of sebacic acid to the total amount (total weight) of the dicarboxylic acid as the monomer component of the polyester polymer may be about 1% by weight or more, for example about 10% by weight or more, about 50% by weight or more, about 70% by weight or more, or about 90% by weight or more (for example, 95 to 100% by weight). The weight ratio of the sebacic acid may be approximately 95% by weight or less, or may be approximately 75% by weight or less, or may be approximately 60% by weight or less from the viewpoint of adhesive properties such as high-temperature holding power. The technology disclosed herein can be practiced in either a mode in which the dicarboxylic acid used as a monomer component for synthesizing the polyester polymer contains sebacic acid or no sebacic acid. For example, the weight ratio of the sebacic acid may be about 50% by weight or less, about 30% by weight or less, about 10% by weight or less, about 3% by weight or less, or less than 1% by weight, and the dicarboxylic acid used for synthesizing the polyester polymer may be substantially free of sebacic acid.

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 greater the molecular weight of the plant-derived dicarboxylic acid, the easier it is to increase the bio-rate of the polyester-based polymer. From such a viewpoint, the molecular weight of the plant-derived dicarboxylic acid may be 250 or more, 350 or more, 450 or more, or 500 or more (for example, 550 or more). On the other hand, the molecular weight of the plant-derived dicarboxylic acid is suitably about 1,000 or less, for example, 800 or less, 700 or less, or 600 or less, from the standpoint of monomer availability and synthesizability. Preferred examples of dicarboxylic acids having the above molecular weights include dimer acids.

In addition, in this specification, the molecular weight calculated from the chemical formula is adopted as the molecular weight of the dicarboxylic acid. In an embodiment using two or more dicarboxylic acids (e.g., the plant-derived dicarboxylic acid), the molecular weight of the dicarboxylic acid (e.g., the plant-derived dicarboxylic acid) is the sum of the products of the molecular weight and weight fraction of each dicarboxylic acid (total value).

In addition, aromatic dicarboxylic acids are preferably used as the dicarboxylic acid used for synthesizing the polyester-based polymer disclosed herein. The use of a dicarboxylic acid containing an aromatic dicarboxylic acid tends to increase the cohesive force and improve the high-temperature holding power. By including an aromatic dicarboxylic acid as the dicarboxylic acid, the amount of the cross-linking agent used can be suppressed, so that it is easy to improve the high-temperature holding power while maintaining or improving the adhesive strength. Suitable examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid and orthophthalic acid, with terephthalic acid being more preferred. These can be used individually by 1 type or in combination of 2 or more types.

It should be noted that the technology disclosed herein includes an aspect of increasing the bio-rate of a polyester-based polymer 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 is converted to isobutylene after isobutanol is obtained from corn, sugars, and wood, which is then dimerized to obtain isooctene, and the method described in Chemische Technik, vol.38, No.3, p116-119; and oxidizing it to obtain terephthalic acid (International Publication No. 2009/079213).

In the embodiment in which an aromatic dicarboxylic acid is used as the dicarboxylic acid, the weight ratio of the aromatic dicarboxylic acid to the total amount (total weight) of the dicarboxylic acid in the monomer component of the polyester polymer is not particularly limited, and is suitably about 1% by weight or more, and from the viewpoint of improving high-temperature holding power, it is preferably about 3% by weight or more, more preferably about 5% by weight or more, and even more preferably about 7% by weight or more. In addition, the upper limit of the weight ratio of the aromatic carboxylic acid may vary depending on other dicarboxylic acid species, and is not limited to a specific range.

In addition, in some embodiments, dicarboxylic acids derived from fossil resources (for example, aliphatic dicarboxylic acids) are used from the viewpoint of obtaining desired adhesive properties in consideration of productivity, efficiency, and cost. Examples of such dicarboxylic acids (eg aliphatic dicarboxylic acids) include dimethylglutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid. Among them, adipic acid is preferably used as the aliphatic dicarboxylic acid. The dicarboxylic acids (eg, aliphatic dicarboxylic acids) derived from fossil resources may be used singly or in combination of two or more.

The molecular weight of the dicarboxylic acid used as a monomer component for synthesizing 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 greater, 250 or greater, 350 or greater, 450 or greater, or 500 or greater (eg, 530 or greater). On the other hand, the molecular weight of the dicarboxylic acid is suitably about 1000 or less from the viewpoint of monomer availability and synthesizability, 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 (having an Mw of a predetermined value or more, preferably having a Tg within a predetermined range) is preferably synthesized using a dicarboxylic acid having a molecular weight within the above range.

(diol)
Any of (poly)alkylene glycols, aliphatic diols, dimer diols, alicyclic diols, aromatic diols, and unsaturated diols can be used as diols used for synthesizing the polyester-based polymer disclosed herein. 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; Pandiol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and other aliphatic diols Ol; dimer diols (such as dimer diols derived from fatty acids such as oleic acid and erucic acid); alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxy aromatic diols such as biphenyl, o-, m- and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol and their ethylene oxide and propylene oxide adducts; By appropriately selecting and using one or more of these diols, it is possible to obtain a polyester polymer capable of exhibiting good adhesive properties such as being suitable for both adhesive strength and high-temperature holding power.

In some aspects, the diol is preferably (poly)alkylene glycols, aliphatic diols or alicyclic diols, more preferably (poly)alkylene glycols or aliphatic diols. By synthesizing these diols (preferably ethylene glycol and aliphatic diols) in combination with the above-described dicarboxylic acid (preferably dimer acid and aromatic dicarboxylic acid), a polyester polymer having excellent adhesive properties can be preferably obtained. Preferred examples include (poly)ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. More preferred are butanediol and 1,6-hexanediol. These can be used individually by 1 type or in combination of 2 or more types. The (poly)alkylene glycols, aliphatic diols, and alicyclic diols described above may be derived from plants or fossil resources. In this specification, the (poly)ethylene glycol is used in the sense of including ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

The weight ratio of (poly)alkylene glycols, aliphatic diols and alicyclic diols (preferably the weight ratio of ethylene glycol and aliphatic diols) to the total amount (total weight) of diols in the monomer component 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). Further, the weight ratio of the (poly)alkylene glycols, the aliphatic diol and the alicyclic diol (preferably the weight ratio of ethylene glycol and the aliphatic diol) may be, for example, approximately 95% by weight or less.

In some preferred embodiments, (poly)ethylene glycol is used as the diol. By using (poly)ethylene glycol in combination with a suitable dicarboxylic acid, good adhesive properties (adhesive strength and high temperature holding power) can preferably be obtained. In the embodiment using the (poly)ethylene glycol as the diol, the weight ratio of the (poly)ethylene glycol in the total amount (total weight) of the diol as the monomer component of the polyester polymer is suitably about 1% by weight or more, preferably about 10% by weight or more, more preferably about 50% by weight or more, still more preferably about 80% by weight or more, particularly preferably about 90% by weight or more (for example, 95 to 100% by weight). By setting the amount of (poly)ethylene glycol to a predetermined value or more, the polymer can be designed based on the properties of (poly)ethylene glycol. Further, for example, the use of (poly)ethylene glycol facilitates obtaining a pressure-sensitive adhesive layer with low haze. Further, the weight ratio of the (poly)ethylene glycol may be approximately 95% by weight or less, approximately 70% by weight or less, or approximately 50% by weight or less. The (poly)ethylene glycol mentioned above may be derived from plants or fossil resources. (Poly)ethylene glycol may be used alone or in combination of two or more.

In some embodiments, it is preferable to use a plant-derived diol as the diol from the viewpoint of obtaining a polyester-based polymer with a bio rate of 50% or more. Examples of such diols include biomass diols obtained from biomass ethanol (e.g., biomass (poly)ethylene glycol, etc.), 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. Plant-derived diols can be used singly or in combination of two or more.

In some embodiments, from the viewpoint of reducing dependence on fossil resource-based materials, the weight ratio of the plant-derived diol in the total amount (total weight) of diols as monomer components of the polyester polymer may be about 1% by weight or more, may be about 10% by weight or more, may be about 50% by weight or more, may be about 80% by weight or more, or may be about 90% by weight or more (for example, 95 to 100% by weight). The weight ratio of the plant-derived diol may be approximately 95% by weight or less, approximately 70% by weight or less, or approximately 50% by weight or less. Thus, even in an embodiment in which the amount of the plant-derived diol used is relatively low and the fossil resource-derived diol is used, for example, by using a fossil resource-derived diol having a relatively low molecular weight, the polyester-based polymer can have a bio rate of a predetermined value or more. From such a point of view, the weight ratio of the plant-derived diol may be approximately 30% by weight or less, approximately 10% by weight or less, or approximately 3% by weight or less (for example, less than 1% by weight). The technology disclosed herein can also be preferably practiced in a mode in which the diol used as the monomer component for synthesizing the polyester-based polymer does not substantially contain a plant-derived diol.

In some embodiments, dimer diol is used as the plant-derived diol. The use of dimer diol can also increase the bio-rate of the polyester-based polymer. A dimer diol can be used individually by 1 type or in combination of 2 or more types. In the embodiment using the dimer diol as the diol, the weight ratio of the dimer diol to the total amount (total weight) of the diol as the monomer component of the polyester polymer may be about 1% by weight or more, for example about 10% by weight or more, about 50% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more (for example, 95 to 100% by weight). Further, the weight ratio of the 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 practiced in either a mode in which the diol used as a monomer component for synthesizing the polyester-based polymer contains dimer diol or a mode in which it does not contain dimer diol. For example, the weight percentage of the dimer diol may be approximately 50% by weight or less (for example, less than 50% by weight), approximately 30% by weight or less, approximately 10% by weight or less, approximately 3% by weight or less, or less than 1% by weight.

The molecular weight of the diol is not particularly limited. The molecular weight of the diol is suitably 500 or less, for example, from the viewpoint of monomer availability and synthesizing properties, and may be 300 or less, 150 or less, 100 or less, or 80 or less. Also, the molecular weight of the diol is suitably about 50 or more, and may be more than 100, for example. In an embodiment using a diol having a molecular weight within the above range, a polyester-based polymer capable of exhibiting good adhesive properties, such as achieving both adhesive strength and high-temperature holding power, can be preferably synthesized. Further, for example, in the embodiment in which the diol is derived from fossil resources, the molecular weight of the diol derived from fossil resources is suitably 500 or less, and may be 300 or less. The smaller the molecular weight of the diol derived from fossil resources, the more likely the polyester-based polymer will have a high bio-rate. From such a viewpoint, the molecular weight of the fossil resource-derived diol may be 150 or less, 100 or less, or 80 or less. In addition, the molecular weight of the fossil resource-derived diol is suitably about 50 or more, and may be more than 100, for example. Suitable examples of diols having the above molecular weights include ethylene glycol.

In addition, in this specification, the molecular weight calculated from the chemical formula can be adopted as the molecular weight of the diol. Further, in an embodiment using two or more kinds of diols (for example, the above-mentioned fossil resource-derived diols), the molecular weight of the diol (for example, the above-mentioned fossil resource-derived diol) is the sum of the products of the molecular weight and the weight fraction of each diol (total value).

The polyester-based polymer disclosed herein can be substantially composed of the dicarboxylic acid and the diol described above, but for the purpose of introducing desired functional groups, adjusting the molecular weight, etc., other copolymerization components other than the dicarboxylic acid and the diol may be copolymerized as long as the effects of the technology disclosed herein are not impaired. Such other copolymerization components include polyvalent carboxylic acids containing 3 or 4 or more carboxy groups (trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, trimesic acid, trivalent or higher polycarboxylic acids such as trimeric acid), polyols containing 3 or 4 or more hydroxyl groups per molecule (pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6- hexanetriol, adamantanetriol, etc.), monocarboxylic acids, monoalcohols, hydroxycarboxylic acids, lactones and the like. The above-mentioned other copolymerization components can be used singly or in combination of two or more. These other copolymer components may or may not be derived from plants. The ratio of the above-mentioned other copolymerization components in the monomer components of the polyester polymer is suitable, for example, less than 10% by weight, less than 3% by weight, typically less than 1% by weight (further less than 0.1% by weight). The technology disclosed herein can also be preferably carried out in a mode in which the monomer component of the polyester-based polymer does not substantially contain the other copolymer components.

In the monomer components used to synthesize the polyester-based polymer disclosed herein, although not particularly limited, the total ratio of the dicarboxylic acid and the diol is suitably about 90% by weight or more, preferably about 95% by weight or more, more preferably about 98% by weight or more, and even more preferably about 99% by weight or more (for example, 99 to 100% by weight). The technique disclosed herein is preferably practiced in a mode using a polyester-based polymer substantially synthesized from dicarboxylic acid and diol.

In some preferred embodiments, dimer acid as a dicarboxylic acid and (poly)ethylene glycol as a diol are used together as the monomer component of the polyester polymer. By using a combination of dimer acid and (poly)ethylene glycol, it is possible to preferably synthesize a polyester-based polymer that has Mw of a predetermined value or more and can exhibit good adhesive properties, such as being suitable for both adhesive strength and high-temperature holding power. The total proportion of dimer acid and (poly)ethylene glycol in the total amount of monomer components of the polyester polymer is suitably about 50% by weight or more, preferably about 60% by weight or more, more preferably about 70% by weight or more, more preferably about 80% by weight or more, and may be about 90% by weight or more (for example, 99 to 100% by weight).

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

The method for obtaining the polyester-based polymer disclosed herein is not particularly limited, and polymerization methods known as methods for synthesizing polyester-based polymers can be appropriately employed. As the monomer raw material used for the synthesis of the polyester-based polymer, for example, a monomer blended 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 can be used. By blending the dicarboxylic acid and the diol in the above ratio, a high-molecular-weight polyester-based polymer can be easily obtained. In addition, the polymer can be appropriately crosslinked (for example, crosslinked based on reaction with a crosslinking agent such as an isocyanate-based crosslinking agent) to increase cohesion.

In the technology disclosed herein, the weight ratio of the dicarboxylic acid and the diol as the monomer components used in the synthesis of the polyester-based polymer is not particularly limited, and an appropriate weight ratio can be set in consideration of the target polymer physical properties and synthetic properties. In some embodiments, the ratio (weight ratio A1/A2) between the weight A1 of the dicarboxylic acid and the weight A2 of the diol used as the monomer component may be 10/90 or more, or 30/70 or more. In some preferred embodiments, the weight ratio (A1/A2) is about 50/50 or higher, more preferably 60/40 or higher, even more preferably 70/30 or higher, 80/20 or higher, or 90/10 or higher. For example, by increasing the weight ratio of the dicarboxylic acid as described above, the properties based on the dicarboxylic acid can be favorably expressed. Moreover, in the embodiment using a plant-derived dicarboxylic acid, the bio rate of the obtained polyester-based polymer can be effectively increased. Further, the weight ratio (A1/A2) may be, for example, 95/5 or less, or 85/15 or less. In some embodiments, the weight ratio (A1/A2) may be 75/25 or less, or 50/50 or less (for example, 30/70 or less), from the viewpoint of favorably expressing diol-based properties. In an aspect using a plant-derived diol, the above weight ratio allows the polyester polymer to have a high bio-rate. In addition, in an embodiment in which plant-derived materials are used for both the dicarboxylic acid and the diol, a polyester-based polymer having a bio rate of a predetermined value or more can be obtained regardless of the weight ratio of the dicarboxylic acid and the diol.

The polyester-based polymer in the technology disclosed here can be obtained by polycondensation of a dicarboxylic acid and a diol, like general polyesters. More specifically, the reaction between the carboxyl group of the dicarboxylic acid and the hydroxyl group of the diol is allowed to proceed while removing water (generated water) and the like typically produced by the above reaction out of the reaction system, whereby a polyester polymer can be synthesized. As a method for removing the generated water out of the reaction system, a method of blowing an inert gas into the reaction system and removing the generated water out of the reaction system together with the inert gas, a method of azeotropic dehydration as a reaction water discharge solvent such as toluene or xylene, a method of distilling off the generated water from the reaction system under reduced pressure (a decompression method), and the like can be used.

The reaction temperature and reaction time when carrying out the above reactions (including esterification and polycondensation), and the degree of pressure reduction (pressure in the reaction system) when a pressure reduction method is employed can be appropriately set so that a polyester polymer having desired properties (e.g., molecular weight) can be efficiently obtained. Although it is not particularly limited, it is usually appropriate for the reaction temperature to be approximately 150° C. or higher (for example, 180° C. to 260° C.). By setting the reaction temperature within the above range, a favorable reaction rate is obtained, productivity is improved, and deterioration of the produced polyester polymer can be easily prevented or suppressed. The reaction time is not particularly limited and may be about 3 to 48 hours (eg 10 to 30 hours). When a decompression method is employed, it is not particularly limited, but it is usually appropriate to set the degree of decompression 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, the water produced by the reaction can be efficiently distilled out of the system, and a favorable reaction rate can be easily maintained. Further, when the reaction temperature is relatively high, the dicarboxylic acid and diol which are raw materials can be easily prevented from being distilled out of the system by setting the pressure in the reaction system to the above lower limit or higher. From the viewpoint of stably maintaining the pressure in the reaction system, it is usually appropriate to set the pressure in the reaction system to 0.1 kPa or more.

For the above reaction, a suitable amount of a known or commonly used catalyst can be used for esterification and condensation, as in general polyester synthesis. Examples of such catalysts include various metal compounds such as titanium, germanium, antimony, tin, and zinc; strong acids such as p-toluenesulfonic acid and sulfuric acid; and the like. Since the amount of the catalyst used can be appropriately set according to the reaction rate and the like, detailed description is omitted here.

A solvent may or may not be used in the process of synthesizing a polyester-based polymer by reacting a dicarboxylic acid and a diol. The above synthesis can be carried out substantially without using an organic solvent (for example, this means excluding an embodiment in which an organic solvent is intentionally used as a reaction solvent during the above reaction). Synthesizing a polyester polymer without substantially using an organic solvent in this way and preparing a polyester pressure-sensitive adhesive using such a polyester polymer meet the demand for avoiding the use of organic solvents in the production process and are preferable.

In the above reaction, there is generally a correlation between the molecular weight of the synthesized polyester polymer and the viscosity of the reaction system, and this fact can be used 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 accurately synthesize a polyester polymer that satisfies the target molecular weight.

(tackifying resin)
The adhesive composition (and thus the adhesive layer) disclosed herein includes a tackifying resin. By using an appropriate amount of the tackifying resin, the effect of improving the adhesive strength based on the tackifying resin is effectively exhibited, and adhesive properties such as adhesive strength and high-temperature holding power can be preferably improved. On the other hand, by containing a tackifying resin, the viscosity of the pressure-sensitive adhesive composition tends to decrease, but by using the polyester-based polymer having the above Mw and the tackifying resin in combination, the pressure-sensitive adhesive composition obtains an appropriate viscosity and easily forms a thin pressure-sensitive adhesive having good quality. As the tackifying resin, one or more selected from various known tackifying resins such as phenol-based tackifying resins, terpene-based tackifying resins, modified terpene-based tackifying resins, rosin-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, and ketone-based tackifying resins can be used.

Examples of phenolic tackifying resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkylphenolic resins and rosin phenolic resins.
Terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, and is a concept that includes both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and phenol-modified terpenes or homopolymers or copolymers thereof (phenol-modified terpene resins). Preferable examples of terpenes constituting such a terpene phenol resin include monoterpenes such as α-pinene, β-pinene and limonene (including d-, l- and d/l-forms (dipentene)). A hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is sometimes called a hydrogenated terpene phenolic resin.
Alkylphenol resins are resins obtained from alkylphenols and formaldehyde (oily phenolic resins). Examples of alkylphenol resins include novolac and resole types.
Rosin phenolic resins are typically rosins or phenol-modified products of the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosin phenol resins include rosin phenol resins obtained by a method of adding phenol to rosins or various rosin derivatives described above with an acid catalyst and thermally polymerizing the mixture.
Among 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.

Examples of terpene-based tackifying resins include polymers of terpenes (eg, monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one kind of terpenes, or a copolymer of two or more kinds of terpenes. One type of terpene homopolymer includes α-pinene polymer, β-pinene polymer, dipentene polymer and the like.
Examples of modified terpene resins include those obtained by modifying the above terpene resins. Specific examples include styrene-modified terpene resins and hydrogenated terpene resins.

The concept of rosin-based tackifying resins here includes both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (fresh rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosins, disproportionation rosins, polymerized rosins, other chemically modified rosins, etc.);

The rosin derivative resin is typically a derivative of the above rosins. The term "rosin-based resin" as used herein includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin and polymerized rosin). For example, rosin esters such as undenatured rosin esters, which are esters of undenatured rosin and alcohols, and denatured rosin esters, which are esters of denatured rosin and alcohols; for example, unsaturated fatty acid-modified rosins obtained by modifying rosins with unsaturated fatty acids; ), rosin alcohols obtained by reducing the carboxy group of .); Specific examples of rosin esters include methyl esters, triethylene glycol esters, glycerin esters and pentaerythritol esters of unmodified rosins or modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, etc.).

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-based resins, and coumarone-indene-based resins.

Some preferred embodiments include embodiments in which the tackifier resin contains one or more phenol-based tackifier resins (eg, terpene phenol resins) and rosin-based tackifier resins (polymerized rosin esters, etc.). More preferably, one or more selected from terpene phenol resins and polymerized rosin esters are used as the tackifying resin. By selecting and using an appropriate tackifying resin from terpene phenol resins and polymerized rosin esters, excellent adhesive properties such as better adhesion and high-temperature holding power can be achieved.

In addition, it is particularly preferable to use a tackifying resin containing one or more phenolic tackifying resins (eg, terpene phenolic resin) as the tackifying resin. Phenolic tackifying resins tend to be more compatible with polyester-based polymers than other tackifying resins (for example, rosin-based tackifying resins). The technology disclosed herein can be preferably practiced, for example, in an aspect in which approximately 25% by weight or more (more preferably approximately 30% by weight or more) of the total amount of tackifying resin is a terpene phenolic resin. Approximately 50% by weight or more of the total amount of tackifying resin may be the terpene phenolic resin, and approximately 80% by weight or more (eg, approximately 90% by weight or more) may be the terpene phenolic resin. Substantially all of the tackifying resin (eg, approximately 95% to 100% by weight, or even approximately 99% to 100% by weight) may be a terpene phenolic resin.

In some embodiments, a tackifying resin having an aromatic ring in the molecule is preferably used as the tackifying resin. A tackifying resin containing an aromatic ring tends to provide high-temperature holding power. Preferable examples of tackifying resins having aromatic rings include phenol-based tackifying resins. Among them, terpene phenol resin is more preferable. The technology disclosed herein is particularly preferably carried out in a mode in which the polyester-based polymer in the pressure-sensitive adhesive layer contains an aromatic ring, and the tackifier resin also contains an aromatic ring. Both the polyester-based polymer and the tackifier resin have a structure containing an aromatic ring, so that more excellent high-temperature holding power can be easily obtained. In addition, since both the polyester-based polymer and the tackifying resin have an aromatic ring, they have excellent compatibility and can satisfactorily exhibit desired adhesive properties.

In the embodiment using a tackifying resin having an aromatic ring in the molecule, it is preferable to use a tackifying resin with a high aromatic ring ratio. In the tackifying resin having a phenol structure as an aromatic ring, a tackifying resin having a high phenol ratio is preferably used. By using a tackifying resin with a high aromatic ring ratio (for example, phenol ratio), more excellent high-temperature holding power is likely to be obtained. The aromatic ring ratio (e.g., phenol ratio) of the tackifying resin is, for example, 10% by weight or more, and from the viewpoint of high temperature holding power, is preferably 15% by weight or more, more preferably 20% by weight or more, still 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 tackifying 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.

As used herein, the aromatic ring ratio (eg, phenol ratio) of the tackifier resin refers to the aromatic ring ratio (eg, phenol ratio) calculated from ¹ H-NMR spectrum measured by a nuclear magnetic resonance (NMR) apparatus. For example, when the tackifying resin has the chemical structure shown below, in the ¹ H-NMR spectrum, the peaks with chemical shifts between 7.5 and 6.3 ppm are derived from the phenol skeleton, and the peaks between 5.6 and 0.1 ppm are considered to be derived from the pinene skeleton.

When the total integral value of the former peak is A and the total integral value of the latter peak is B, by dividing them by the number of H contained in the repeating unit of each skeleton, the molar ratio of the phenol skeleton and the pinene skeleton in the tackifying resin can be calculated.
Molar ratio [phenol skeleton: pinene skeleton] = [A/3:B/16]
Next, by multiplying the calculated molar ratio by the respective molecular weights of phenol (molecular weight 94.1) and pinene (molecular weight 136.2), the weight ratio of the phenol skeleton and the pinene skeleton in the tackifying resin can be calculated.
Weight ratio [phenol skeleton: pinene skeleton] = [(A/3) × 94.1: (B/16) × 136.2]
Then, when the obtained weight ratio of the phenol skeleton 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 x (a/(a+b))
As the NMR apparatus, for example, model name "AVANCE III-400" (manufactured by Bruker Biospin) can be used. More specifically, ¹ H-NMR spectrum measurement can be performed under the following conditions. It is measured by the same method in the examples described later.
[ ¹ H-NMR measurement]
Observation frequency: 400MHz
Measurement temperature: 23°C
Measurement solvent: 1,1,2,2-tetrachloroethane-d ₂ (TCE-d ₂ )
Measured concentration: 33 mg/mL

In some embodiments, a plant-derived tackifying resin (vegetable tackifying resin) is preferably used as the tackifying resin from the viewpoint of improving the bio rate of the entire pressure-sensitive adhesive layer. The vegetable tackifying resin is composed of at least a part of the resin derived from a plant, and the entire resin may be derived from a plant, a part of the resin may be derived from a plant, and the other part may be derived from fossil resources. Examples of vegetable tackifying resins include the above-described rosin-based tackifying resins, terpene-based tackifying resins, terpene phenolic resins, hydrogenated terpene phenolic resins, rosin phenolic resins, and the like. Vegetable tackifying resins can be used singly or in combination of two or more. In some embodiments, the proportion of the vegetable tackifying resin in the total amount of the tackifying resin contained in the pressure-sensitive adhesive 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 vegetable tackifying resin in the total amount of the tackifying resin 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 a manner substantially free of tackifying resins other than vegetable tackifying resins.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving the cohesive strength, in some aspects, the softening point (softening temperature) of the tackifying resin is suitably about 50° C. or higher, and a tackifying resin having a softening point (softening temperature) of about 80° C. or higher (preferably about 100° C. or higher, for example about 115° C. or higher) can be preferably used. In some other embodiments, the softening point of the tackifying resin used may be on the order of 120° C. or higher (eg, 135° C. or higher or 145° C. or higher). The technology disclosed herein can be preferably carried out in a mode in which the tackifying resin having the 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 tackifying resin contained in the pressure-sensitive adhesive layer. For example, a phenol-based tackifier resin (terpene phenol resin, etc.) or a rosin-based tackifier resin (polymerized rosin ester, etc.) 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, such as 145° C. or higher) can be used. There is no particular upper limit for the softening point of the tackifying resin. From the viewpoint of adhesion and the like, in some embodiments, a tackifying resin having a softening point of approximately 200° C. or less (more preferably approximately 180° C. or less, still more preferably less than 160° C., for example, 155° C. or less or 150° C. or less) can be preferably used. The softening point of the tackifying resin can be measured based on the softening point test method (ring and ball method) specified in JIS K2207.

Although not particularly limited, as the tackifying resin, one having an acid value limited to a predetermined value or less is preferably used. A tackifier resin having a low acid value is preferred because it does not inhibit the cross-linking reaction during the formation of the pressure-sensitive adhesive. Moreover, a pressure-sensitive adhesive containing a tackifying resin whose acid value is limited to a predetermined value or less tends to be excellent in durability. From such a viewpoint, the acid value of the tackifying resin is suitably about 20 mgKOH/g or less, preferably less than 10 mgKOH/g, more preferably 7 mgKOH/g or less, still more preferably 4 mgKOH/g or less (eg 0 to 4 mgKOH/g), and may be less than 3 mgKOH/g (eg less than 1 mgKOH/g). The acid value of the tackifying resin can be measured by the potentiometric titration method specified in JIS K 0070:1992.

In the technology disclosed here, the tackifying resin is used at a ratio of 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer. By using the tackifying resin in the above amounts, the desired tack properties can preferably be achieved. In some preferred embodiments, the content of the tackifying resin relative to 100 parts by weight of the polyester polymer is about 25 parts by weight or more, more preferably about 30 parts by weight or more, even more preferably about 35 parts by weight or more, and may be about 40 parts by weight or more. There is a tendency that the greater the amount of tackifying resin used, the easier it is to obtain excellent adhesive strength. The upper limit of the content of the tackifying resin is not particularly limited, and in some embodiments, the content of the tackifying resin with respect to 100 parts by weight of the polyester polymer is usually about 120 parts by weight or less, preferably less than 100 parts by weight, more preferably about 80 parts by weight or less, and even more preferably about 60 parts by weight or less (e.g., about 50 parts by weight or less). By limiting the content of the tackifying resin within a predetermined range, it is possible to effectively obtain the effect of adding the tackifying resin and easily maintain the pressure-sensitive adhesive composition within an appropriate viscosity range.

(crosslinking agent)
The adhesive composition disclosed herein contains a cross-linking agent. The pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition may contain the cross-linking agent in the form after the cross-linking reaction, the form before the cross-linking reaction, the form in which the cross-linking reaction is partially performed, the intermediate or composite form thereof, or the like. The above-mentioned cross-linking agent is usually contained in the pressure-sensitive adhesive layer exclusively in the form after the cross-linking reaction. The cross-linking agent used for cross-linking the polyester polymer may also function as a chain extender.

The type of cross-linking agent is not particularly limited, and can be appropriately selected and used from conventionally known cross-linking agents. Examples of such cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, and metal chelate-based cross-linking agents. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Among them, an isocyanate-based cross-linking agent is preferable.

As the isocyanate-based cross-linking agent, polyfunctional isocyanate-based compounds (compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based cross-linking agents may be used singly or in combination of two or more.

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

Specific examples of alicyclic polyisocyanate compounds include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like.

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'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyl diisocyanate, Phenylmethane-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.

Examples of polyfunctional isocyanates include polyfunctional isocyanate compounds having an average of 2 or 3 or more isocyanate groups per molecule. Such polyfunctional isocyanate compounds may be difunctional or trifunctional or higher functional isocyanate polymers (e.g., dimers or trimers), derivatives (e.g., addition reaction products of polyhydric alcohols and polyfunctional isocyanates having two or more molecules), polymers, and the like. Examples thereof include dimers and trimers of diphenylmethane diisocyanate, isocyanurate of hexamethylene diisocyanate (trimer adduct of isocyanurate structure), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, and polyfunctional isocyanate compounds such as polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercially available products of such polyfunctional isocyanate compounds include trade names "Duranate TPA-100" and "Duranate D101" manufactured by Asahi Kasei Chemicals, trade names "Coronate L", "Coronate HL", "Coronate HK", "Coronate HX", and "Coronate 2096" manufactured by Tosoh Corporation.

A cross-linking agent having no aromatic ring is preferably used as the cross-linking agent. For example, among the isocyanate-based cross-linking agents described above, it is preferable to use an isocyanate-based compound having no aromatic ring. By using an aromatic ring-free isocyanate compound as a cross-linking agent, it is possible to effectively increase the degree of cross-linking with less hindrance to cross-linking in the pressure-sensitive adhesive composition containing the polyester-based polymer and the tackifying resin. Typical examples of the aromatic ring-free isocyanates include aliphatic isocyanate compounds. A particularly preferred embodiment includes an embodiment in which an aromatic ring-free isocyanate compound (typically an aliphatic isocyanate compound) is used as a cross-linking agent in a configuration in which both the polyester polymer and the tackifying resin have aromatic rings.

In some embodiments, two or more cross-linking agents having different numbers of functional groups (preferably isocyanate-based cross-linking agents) may be used. By using two or more types of cross-linking agents having different numbers of functional groups, it is easy to achieve both a plurality of properties (for example, adhesive strength, high-temperature holding power, etc.) in a well-balanced manner. In addition, the functional group refers to a cross-linking reactive group, and for example, refers to an isocyanate group in the polyfunctional isocyanate compound described above. In some embodiments, one or more bifunctional cross-linking agents and one or more tri- or more tri-functional cross-linking agents (eg, tri-functional cross-linking agents) are used in combination as cross-linking agents. By using a bifunctional type and a trifunctional or more functional type together, it is easy to achieve both adhesive strength and high-temperature holding power. As the bifunctional cross-linking agent and tri- or higher functional cross-linking agent, bi-functional cross-linking agents and tri- or higher functional cross-linking agents can be used without particular limitation. In some preferred embodiments, isocyanate compounds are preferably used as the bifunctional cross-linking agent and the tri- or higher functional cross-linking agent.

In embodiments where a bifunctional cross-linking agent is used as the cross-linking agent, the amount of the bi-functional cross-linking agent used is not particularly limited. For example, the amount of the bi-functional cross-linking agent used relative to 100 parts by weight of the polyester 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. , about 3 parts by weight or more. Also, the amount of the bifunctional cross-linking agent to be used relative to 100 parts by weight of the polyester polymer is usually about 10 parts by weight or less, preferably about 7 parts by weight or less, and may be 4 parts by weight or less.

In embodiments in which a tri- or higher-functional cross-linking agent is used as the cross-linking agent, the amount of the tri- or higher-functional cross-linking agent used is not particularly limited. For example, the amount of the tri- or higher-functional cross-linking agent used relative to 100 parts by weight of the polyester polymer is appropriately about 0.01 part by weight or more, preferably about 0.1 part by weight or more, more preferably about 0.5 part by weight or more, and may be about 1 part by weight or more, from the viewpoint of obtaining the effect of using the tri- or more functional cross-linking agent. By using an appropriate amount of a tri- or higher functional cross-linking agent, the cohesive force is increased, and excellent properties (adhesive force, high-temperature holding power, etc.) can be easily obtained. In addition, the amount of the trifunctional or higher cross-linking agent used relative to 100 parts by weight of the polyester polymer is usually appropriately about 8 parts by weight or less, preferably about 5 parts by weight or less, about 4 parts by weight or less, may be about 3 parts by weight or less, or may be 2 parts by weight or less.

In the embodiment in which a bifunctional cross-linking agent and a tri- or more functional cross-linking agent are used in combination, the ratio of the bi-functional cross-linking agent and the tri- or more functional cross-linking agent is appropriately set so that the desired multiple adhesive properties (adhesive strength, high temperature holding power, etc.) are achieved in a well-balanced manner, and is not limited to a specific range. The weight ratio (C _B /C _A ₎ of the amount C _B of the tri- or higher-functional cross-linking agent to the amount C _A of the bi-functional cross-linking agent _is , for example, 0.1 or more, and from the viewpoint of improving the cohesive strength, it is suitably 0.2 or more.

The amount of the cross-linking agent used is not particularly limited. For example, the amount of the cross-linking agent used relative to 100 parts by weight of the polyester polymer can be about 0.005 parts by weight or more (for example, 0.01 parts by weight or more, typically 0.1 parts by weight or more). From the viewpoint of improving the cohesive strength, the amount of the cross-linking agent to be used relative to 100 parts by weight of the polyester polymer is usually appropriately about 0.5 parts by weight or more, preferably about 1 part by weight or more, more preferably about 2 parts by weight or more (for example, more than 2 parts by weight), and still more preferably 2.5 parts by weight or more. According to the technique disclosed herein, the pressure-sensitive adhesive composition does not need to be excessively concentrated for coatability, so even if the amount of the cross-linking agent is increased, the pressure-sensitive adhesive composition can have good storage stability before forming the pressure-sensitive adhesive layer. In addition, the amount of the cross-linking agent used relative to 100 parts by weight of the polyester polymer is usually about 12 parts by weight or less, for example about 10 parts by weight or less, suitably about 8 parts by weight or less, and about 5 parts by weight or less. According to the technology disclosed herein, it is possible to obtain a cohesive force that preferably exhibits high-temperature holding power with the use amount of the cross-linking agent being limited as described above. The amount of the cross-linking agent to be used is more preferably 4 parts by weight or less, more preferably about 3.5 parts by weight or less based on 100 parts by weight of the polyester polymer.

In embodiments using an isocyanate-based cross-linking agent, the amount used is not particularly limited. The amount of the isocyanate-based cross-linking agent used can be, for example, about 0.5 parts by weight or more and about 10 parts by weight or less with respect to 100 parts by weight of the polyester polymer. From the viewpoint of improving the cohesive force, the amount of the isocyanate-based cross-linking agent used relative to 100 parts by weight of the polyester polymer is usually appropriately 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, still more preferably 2.8 parts by weight or more, may be about 3.5 parts by weight or more, may be about 4.0 parts by weight or more, or may be 4.5 parts by weight or more. According to the technique disclosed herein, it is not necessary to increase the concentration of the PSA composition excessively for coatability. Therefore, even if the amount of the isocyanate-based cross-linking agent is increased, the PSA composition can have good storage stability before the formation of the PSA layer. The amount of the isocyanate cross-linking agent to be used for 100 parts by weight of the polyester polymer is usually about 8 parts by weight or less, preferably about 5 parts by weight or less. According to the technique disclosed herein, it is possible to obtain a cohesive force that preferably exhibits high-temperature holding power with the use amount of the isocyanate-based cross-linking agent limited as described above. The amount of the isocyanate cross-linking agent used relative to 100 parts by weight of the polyester polymer is more preferably 4.5 parts by weight or less, more preferably about 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 about 3.2 parts by weight or less.

(crosslinking catalyst)
In the technology disclosed herein, it is preferable to use a cross-linking catalyst in addition to the above-described cross-linking agent in order to promote the cross-linking reaction more effectively. Examples of crosslinking catalysts include zirconium-containing compounds (zirconium-based catalysts) such as zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethylacetoacetate, and zirconium octylate compounds; Aluminum-containing compounds (aluminum-based catalysts) such as aluminum secondary butoxide, aluminum trisacetylacetonate, aluminum bisethylacetoacetate, and aluminum trisethylacetoacetate (aluminum-based catalysts); Iron-containing compounds (iron-based catalysts) such as Nasem ferric iron (iron-based catalysts); ); and other organometallic catalysts. A crosslinking catalyst can be used individually by 1 type or in combination of 2 or more types.

In some preferred embodiments, the cross-linking catalyst does not contain a tin-containing compound from the viewpoint of environmental impact and safety. By using a non-tin-based compound as a cross-linking catalyst, the amount of tin-based compound (typically organic tin) used in the pressure-sensitive adhesive can be reduced. According to the pressure-sensitive adhesive composition disclosed herein, a good crosslinked structure capable of achieving both adhesive strength and high-temperature holding power can be formed with good productivity without using a tin-based crosslinking catalyst, which generally tends to have an excellent reaction rate. Also, in some embodiments, the cross-linking catalyst does not include an iron-based catalyst. For example, in a mode of use in which the adhesive is required to have transparency and optical properties, it is desirable to avoid using an iron-based compound that may color the adhesive.

The amount of cross-linking 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, preferably about 0.01 parts by weight or more, and about 0.05 parts by weight or more (for example, 0.10 parts by weight or more) per 100 parts by weight of the polyester polymer. The amount of the cross-linking catalyst used can be, for example, about 3 parts by weight or less, preferably about 1 part by weight or less, and may be about 0.3 parts by weight or less with respect to 100 parts by weight of the polyester polymer.

(Hydrolysis resistant agent)
In addition, the pressure-sensitive adhesive composition disclosed herein may contain a hydrolysis-resistant agent (also referred to as an anti-hydrolysis agent). By adding a hydrolysis-resistant agent, the hydrolysis reaction in the pressure-sensitive adhesive is suppressed, making it easier to obtain good durability. The hydrolysis-resistant agent is not particularly limited, and known or commonly used hydrolysis-resistant agents can be used. Examples thereof include oxazoline group-containing compounds, epoxy group-containing compounds, carbodiimide group-containing compounds, and the like. Among them, carbodiimide group-containing compounds are preferred. The hydrolysis resistant agents can be used singly or in combination of two or more.

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

The amount of the hydrolysis-resistant agent (preferably, a carbodiimide group-containing compound) used is not particularly limited, and is preferably 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, relative to 100 parts by weight of the polyester polymer so that the effect of containing the hydrolysis-resistant agent is preferably expressed. The upper limit of the amount of the anti-hydrolysis agent to be used is, for example, about 5 parts by weight or less, preferably about 3 parts by weight or less, and may be, for example, 1 part by weight or less per 100 parts by weight of the polyester polymer.

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

(solvent or dispersion medium)
The pressure-sensitive adhesive composition disclosed herein may further contain a known or commonly used solvent or dispersion medium for the purpose of adjusting the solid content concentration or viscosity. For example, from the viewpoint of adhesive properties, etc., a solvent-type adhesive composition containing an adhesive in an organic solvent is suitable. The organic solvent is not particularly limited, and one or more of known or commonly used organic solvents that can be used for polyester pressure-sensitive adhesives 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 them, it is preferable to use ethyl acetate.

(viscosity)
Although not particularly limited, the viscosity of the adhesive composition disclosed herein at 23° C. is, for example, about 10 mPa s or more, may be about 20 mPa s or more, may be about 30 mPa s or more, may be about 10000 mPa s or less, may be about 8000 mPa s or less, or may be about 6000 mPa s or less. In some embodiments, the viscosity may be greater than 100 mPa·s, greater than 300 mPa·s, greater than 500 mPa·s, or greater than 700 mPa·s. By using the pressure-sensitive adhesive composition having the above viscosity range, a thin pressure-sensitive adhesive can be formed with good productivity.

(Solid content concentration)
In addition, although not particularly limited, the solid content concentration of the pressure-sensitive adhesive composition disclosed herein is, for example, approximately 10% by weight or more, may be approximately 20% by weight or more, may be approximately 30% by weight or more, may be approximately 70% by weight or less, may be approximately 60% by weight or less, or may be approximately 55% by weight or less. The pressure-sensitive adhesive composition having the above-described solid content concentration is easy to handle and easily forms a thin pressure-sensitive adhesive with high productivity.

The viscosity of the pressure-sensitive adhesive composition at 23° C. refers to the viscosity measured at a sample (pressure-sensitive adhesive composition to be measured) temperature of 23° C.±5° C. using a BH viscometer at a rotation speed of 20 rpm. The appropriate type (number) of rotors to be used for the measurement is selected according to the viscosity of the sample.
Moreover, 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 with respect to the entire pressure-sensitive adhesive composition.

(bio rate)
Since the adhesive composition according to some aspects can be prepared containing a polyester-based polymer having a bio rate of 50% or more, in such aspects the adhesive composition has a bio rate of a predetermined value or more. Although not particularly limited, the non-volatile content (solid content) of the pressure-sensitive adhesive composition may have a bio rate of approximately 30% or more (for example, more than 30%), suitably approximately 40% or more, and preferably 50% or more. A high non-volatile bio rate of the pressure-sensitive adhesive composition means that the amount of fossil resource-based materials such as petroleum used is small. By designing the pressure-sensitive adhesive composition so as to increase the bio-ratio of the non-volatile matter, it is possible to reduce the dependence of the pressure-sensitive adhesive as a whole on fossil resource-based materials. For example, the non-volatile content of the pressure-sensitive adhesive composition may have a bio rate of 55% or more, 60% or more, 70% or more, or 75% or more. Although the upper limit of bio-percentage is by definition 100%, in the pressure-sensitive adhesive compositions disclosed herein, the bio-percentage can typically be less than 100% because the ingredients may include materials derived from fossil resources. From the viewpoint of making it easier to obtain performance (e.g., high-temperature holding power) suitable for use in portable electronic devices, in some embodiments, the non-volatile content of the adhesive composition may be, for example, less than 90%. In some other embodiments, the adhesive composition may have a non-volatile bio-fraction of less than 30%, less than 10%, or less than 1%. The non-volatile bio-rate of the pressure-sensitive adhesive composition may be substantially 0%. Note that the bio rate of the non-volatile content of the adhesive composition is basically the same as the bio rate of the adhesive layer formed using the pressure-sensitive adhesive composition, so the above numerical range as the bio rate of the non-volatile content of the pressure-sensitive adhesive composition can also be applied to the bio rate of the pressure-sensitive adhesive layer.

The biorate of the adhesive composition and adhesive layer, that is, the ratio of biomass-derived carbon to the total carbon contained in the adhesive composition and adhesive layer can be estimated from the carbon isotope content with a mass number of 14 measured according to ASTM D6866. The biorate of the base material and the biorate of the pressure-sensitive adhesive sheet, which will be described later, can also be estimated by the same method.

(Formation of adhesive layer)
A pressure-sensitive adhesive layer can be formed from the pressure-sensitive adhesive composition by a conventionally known method. For example, in the case of a substrate-less double-sided PSA sheet, a PSA sheet can be formed by applying a PSA composition to a surface having releasability (release surface) and then curing the PSA composition to form a PSA layer on the surface. In the case of a pressure-sensitive adhesive sheet with a substrate, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) a pressure-sensitive adhesive composition to the substrate and curing it can be preferably employed. In addition, a method (transfer method) of forming a pressure-sensitive adhesive layer on the surface by applying a pressure-sensitive adhesive composition to a surface having releasability (release surface) and curing the composition, and transferring the pressure-sensitive adhesive layer to a substrate may be employed. As the release surface, the surface of a release liner, the back surface of a base material subjected to a release treatment, or the like can be used. Moreover, curing of the pressure-sensitive adhesive composition can be performed 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 dots or stripes.

Application of the pressure-sensitive adhesive composition can be performed using known or conventional coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, die coaters, comma coaters, bar coaters, knife coaters, and spray coaters. Alternatively, the 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, the pressure-sensitive adhesive composition is applied to a predetermined thickness by supplying the pressure-sensitive adhesive composition from a coater to the surface to be coated while feeding a substrate or release liner having a surface to be coated at a speed (coating speed) of about 3 to 100 m / min (for example, 5 to 50 m / min).
The pressure-sensitive adhesive composition can be dried at room temperature or under heating. From the viewpoint of promoting the cross-linking reaction, improving production efficiency, etc., it is preferable to dry the pressure-sensitive adhesive composition under heating. The drying temperature can be, for example, about 40 to 150°C, and usually about 40 to 130°C is preferable. After drying the pressure-sensitive adhesive composition, aging is preferably performed for the purpose of adjusting component migration in the pressure-sensitive adhesive layer, progressing the cross-linking reaction, alleviating distortion that may exist in the substrate and the pressure-sensitive adhesive layer, and the like. The aging conditions are not particularly limited, and can be, for example, about 70° C. or lower (typically about 40 to 70° C.) for 1 day or longer (eg, 3 days or longer).

According to the technology disclosed herein, a thin adhesive layer having good quality can be formed based on the components contained in the adhesive composition, so there are few restrictions on the types of coaters provided in the adhesive sheet manufacturing machine, and there are also few restrictions on the coating speed and drying temperature, and a thin adhesive layer with good quality can be formed.

<Adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein includes a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition described above. The pressure-sensitive adhesive sheet may be, for example, in the form of a substrate-less double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive surface formed by one surface of the pressure-sensitive adhesive layer and a second pressure-sensitive adhesive surface formed by the other surface of the pressure-sensitive adhesive layer. Alternatively, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a substrate-attached pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is laminated on one or both sides of a supporting substrate. Hereinafter, the supporting substrate may be simply referred to as "substrate".

(Example of composition of adhesive sheet)
FIG. 1 schematically shows the structure of a pressure-sensitive adhesive sheet according to one embodiment. 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 adhesive sheet 1 is used by attaching a first adhesive surface 21A constituted by one surface (first surface) of the adhesive layer 21 and a second adhesive surface 21B constituted by the other surface (second surface) of the adhesive layer 21 to different parts of the adherend. The locations where the

adhesive surfaces

21A and 21B are attached may be locations on different members or different locations within a single member. The pressure-sensitive adhesive sheet 1 before use (that is, before being attached to an adherend) can be a constituent element of a pressure-sensitive adhesive sheet 100 with a release liner in which the first pressure-sensitive adhesive surface 21A and the second pressure-sensitive adhesive surface 21B are protected by

release liners

31 and 32, respectively, at least on the side facing the pressure-sensitive adhesive layer 21, respectively, as shown in FIG. As the

release liners

31 and 32, for example, a sheet-like base material (liner base material) having a release layer provided on one side thereof with a release treatment agent so that the one side becomes a release surface can be preferably used. Alternatively, a release liner 31 having release surfaces on both sides may be used without the release liner 32, and the release liner 31 may be superimposed on the pressure-sensitive adhesive sheet 1 and spirally wound to form a release liner-attached pressure-sensitive adhesive sheet in a form (roll form) in which the second pressure-sensitive adhesive surface 21B is in contact with the back surface of the release liner 31 and protected.

FIG. 2 schematically shows the structure of a pressure-sensitive adhesive sheet according to another embodiment. This pressure-sensitive adhesive sheet 2 is configured as a single-sided pressure-sensitive adhesive sheet with a substrate, which includes a sheet-like supporting substrate (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side. The pressure-sensitive adhesive layer 21 is fixedly provided on the first surface 10A side of the support substrate 10 , that is, without the intention of separating the pressure-sensitive adhesive layer 21 from the support substrate 10 . As shown in FIG. 2, the pressure-sensitive adhesive sheet 2 before use can be a component of a pressure-sensitive adhesive sheet 200 with a release liner, in which the surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is protected by a release liner 31 having a release surface on at least the side facing the pressure-sensitive adhesive layer 21. Alternatively, the release liner 31 may be omitted, the support substrate 10 having the second surface 10B serving as a release surface may be used, and the adhesive surface 21A may be protected by contacting the second surface (back surface) 10B of the support substrate 10 by rolling the adhesive sheet 2 (roll configuration).

FIG. 3 schematically shows the structure of a pressure-sensitive adhesive sheet according to yet another embodiment. This pressure-sensitive adhesive sheet 3 is configured as a double-sided pressure-sensitive adhesive sheet with a substrate, which includes a sheet-like supporting substrate (for example, a resin film) 10 having a first surface 10A and a second surface 10B, a first pressure-sensitive adhesive layer 21 fixedly provided on the first surface 10A side, and a second pressure-sensitive adhesive layer 22 fixedly provided on the second surface 10B side. The pressure-sensitive adhesive sheet 3 before use can be a component of a release liner-equipped pressure-sensitive adhesive sheet 300 in which the surface (first pressure-sensitive adhesive surface) 21A of the first pressure-sensitive adhesive layer 21 and the surface (second pressure-sensitive adhesive surface) 22A of the second pressure-sensitive adhesive layer 22 are protected by

release liners

31 and 32, as shown in FIG. Alternatively, the release liner 32 may be omitted, and a release liner 31 having release surfaces on both sides may be used, and the release liner 31 may be superimposed on the pressure-sensitive adhesive sheet 3 and spirally wound to form a release liner-attached pressure-sensitive adhesive sheet in a form (roll form) in which the second pressure-sensitive adhesive surface 22A is protected by coming into contact with the back surface of the release liner 31.

As the above-mentioned release liner, a release liner having a release treatment layer on the surface of a liner base material such as resin film or paper, or a release liner made of a low-adhesive material such as polyolefin resin (e.g. polyethylene, polypropylene) or fluorine resin can be used. The release treatment layer may be formed by surface-treating the liner base material with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based release agent. 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-adhesive material is preferable from the viewpoint of avoiding the generation of paper dust.

It should be noted that the concept of the adhesive sheet here can include what is called adhesive tape, adhesive film, adhesive label, and the like. The pressure-sensitive adhesive sheet may be in the form of a roll or sheet, or may be cut or punched into an appropriate shape according to the purpose and mode of use.

(total thickness)
The thickness (total thickness) of the pressure-sensitive adhesive sheet disclosed herein (including a pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet with a substrate, which further includes a substrate, but does not include a release liner) is not particularly limited, and can be in the range of, for example, approximately 2 μm to 1000 μm. In some aspects, the thickness of the pressure-sensitive adhesive sheet is preferably about 5 μm to 500 μm (eg, 10 μm to 300 μm, typically 15 μm to 200 μm) in consideration of adhesive properties. In some preferred embodiments, the thickness of the adhesive sheet is 100 μm or less, more preferably 70 μm or less, still more preferably 50 μm or less, particularly preferably 35 μm or less, for example, 30 μm or less, or 25 μm or less, from the viewpoint of reducing the weight, size, thickness, and functionality of products to which the adhesive sheet is applied (for example, portable electronic devices). According to the technology disclosed herein, a thin pressure-sensitive adhesive layer can be formed with good quality and high productivity, so that the total thickness of the pressure-sensitive adhesive sheet can also be within the range of the predetermined value or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet is not particularly limited.

(bio rate)
In some aspects, it is preferred that approximately 30% or more (eg, more than 30%) of the total carbon contained in the adhesive sheet is biomass-derived carbon. That is, it is preferable that the adhesive sheet has a bio rate of 30% or more. By using a pressure-sensitive adhesive sheet with such a high bio-ratio, it is possible to reduce the amount of fossil resource-based materials used. From this point of view, it can be said that the higher the bio rate of the pressure-sensitive adhesive sheet, the better. The bio rate of the adhesive sheet is preferably 40% or more, may be 50% or more, may be 60% or more, may be 70% or more, or may be 75% or more. Although the upper limit of the bio rate is 100% by definition, the bio rate of the adhesive sheet may be less than 100% because it may not be efficient in terms of productivity, performance, etc. to make all the materials that make up the adhesive sheet derived from plants. From the viewpoint of making it easier to obtain performance (e.g., high temperature holding power) suitable for use in portable electronic devices, in some embodiments, the bio rate of the adhesive sheet may be, for example, 90% or less, and when more emphasis is placed on adhesive performance, it may be 80% or less, or 70% or less. In some other embodiments, the adhesive sheet bio-factor may be less than 30%, may be less than 10%, or may be less than 1%. The bio rate of the adhesive sheet may be substantially 0%.
In addition, in a substrate-less pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer, the bio rate of the pressure-sensitive adhesive layer matches the bio rate of the entire pressure-sensitive adhesive sheet.

(Adhesive properties)
The pressure-sensitive adhesive sheet according to some aspects preferably has a 180-degree peel strength (adhesive strength to SUS) of 10 N/20 mm or more to a stainless steel plate. A pressure-sensitive adhesive sheet exhibiting the above properties can be preferably used in a manner in which re-peeling is not intended, typically, because it is strongly bonded to an adherend. From the viewpoint of achieving more reliable bonding, the adhesive strength may be, for example, 11 N/20 mm or more, preferably 12 N/20 mm or more, 13 N/20 mm or more, 14 N/20 mm or more, or 15 N/20 mm or more. The upper limit of the adhesive strength is not particularly limited, and in some aspects, the adhesive strength may be, for example, 50 N/20 mm or less, 30 N/20 mm or less, or 25 N/20 mm or less. Specifically, the adhesion to SUS is measured by the method described in Examples below.

The pressure-sensitive adhesive sheet disclosed herein preferably has a holding power that does not fall off within 1 hour of the holding power test conducted under the conditions of 80°C, 1 kg load, and 1 hour. A pressure-sensitive adhesive sheet exhibiting such high-temperature holding power can exhibit good holding performance even in a temperature range higher than room temperature (for example, a temperature of 40° C. or higher). It is suitable that the pressure-sensitive adhesive sheet has a displacement distance of 5.0 mm or less (for example, 3.0 mm or less) after the holding force test. From the viewpoint of exhibiting higher retention performance, the displacement 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 displacement distance is 0.0 mm, which means that no displacement is observed in the holding force test. Specifically, the holding force test is carried out by the method described in Examples below.

<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, the thickness of the adhesive layer is, for example, 100 μm or less, preferably 50 μm or less, more preferably 35 μm or less, even more preferably 30 μm or less, particularly preferably 25 μm or less, and may be, for example, 22 μm or less, from the viewpoint of weight reduction, miniaturization, thin thickness, high functionality, etc. of products to which the adhesive sheet is applied (e.g., portable electronic devices). According to the technology disclosed herein, it is possible to form such a thin pressure-sensitive adhesive layer with good quality and high productivity. The thickness of the pressure-sensitive adhesive layer is usually suitably 3 μm or more, preferably 5 μm or more. From the viewpoint of facilitating the realization of 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, 15 μm or more, or 18 μm or more. When the pressure-sensitive adhesive sheet disclosed herein is a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a substrate, the thickness of each pressure-sensitive adhesive layer may be the same or different.

<Base material>
The pressure-sensitive adhesive sheet disclosed herein can be in the form of a pressure-sensitive adhesive sheet with a substrate having a pressure-sensitive adhesive layer on one or both sides of the substrate. Various sheet-like substrates can be used as the substrate, and for example, resin films, papers, cloths, rubber sheets, foam sheets, metal foils, composites thereof, and the like can be used. In the field of electronic devices, substrates that are less likely to generate dust (for example, fine fibers or particles such as paper dust) can be preferably used. From this point of view, substrates that do not contain fibrous materials such as paper and cloth are preferable, and for example, resin films, rubber sheets, foam sheets, metal foils, composites thereof, and the like can be preferably used.

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; 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 foil include aluminum foil and copper foil.

A resin film is preferably used as the base material. A resin film is preferably used as a material excellent in dimensional stability, thickness accuracy, economy (cost), workability and tensile strength. In addition, since the resin film (for example, a polyester film such as a PET film described later) can be recycled, by reusing the resin film after use, regardless of whether or not a plant-derived material is used, sustainable reproduction is possible and the environmental load can be reduced. Such recyclable resin films and recycled resin films are also referred to as recycled films. Such recyclability of the resin film can also be applied to the resin film used for the release liner described above. In this specification, the term "resin film" is typically a non-porous film, and is a concept distinguished from so-called nonwoven fabrics and woven fabrics.

In some embodiments, a polyester film can be preferably used as the substrate from the viewpoint of strength and workability. As the polyester resin constituting the polyester film, a polyester resin containing polyester obtained by polycondensation of a dicarboxylic acid and a diol as a main component is typically used.

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- aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic 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 leic acid and fumaric acid; derivatives thereof (for example, lower alkyl esters of the above dicarboxylic acids such as terephthalic acid); These can be used individually by 1 type or in combination of 2 or more types.

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; 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, , 4-cyclohexanedimethylol, xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and other aromatic diols. These can be used individually by 1 type or in combination of 2 or more types. Aliphatic diols are preferred from the viewpoint of transparency and the like, and ethylene glycol is particularly preferred. The ratio of the aliphatic diol (preferably ethylene glycol) to the diols constituting the polyester is preferably 50% by weight or more (for example, 80% by weight or more, typically 95% by weight or more). The diol may consist essentially of ethylene glycol. 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, 90% by weight or more, or 95% by weight or more. Substantially all of the ethylene glycol may be biomass-derived ethylene glycol.

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

When the substrate disclosed herein is a polyester film substrate, the polyester film substrate may contain a polymer other than the above polyester in addition to polyester. Preferred examples of the polymer other than polyester include, among the various polymer materials exemplified as the resin film that can constitute the base material, those other than polyester. When the polyester film substrate disclosed herein contains a polymer other than the polyester in addition to the polyester, the content of the polymer other than the polyester is suitably less than 100 parts by weight, 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, relative to 100 parts by weight of the polyester. The content of the polymer other than polyester may be 5 parts by weight or less, or may be 1 part by weight or less with respect to 100 parts by weight of polyester. The technology disclosed herein can be preferably practiced, for example, in a mode in which 99.5 to 100% by weight of the polyester film substrate is polyester.

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

When the substrate disclosed herein is a polyolefin film substrate, the polyolefin film substrate may contain a polymer other than the above polyolefin in addition to polyolefin. Preferred examples of the polymer other than polyolefin include those other than polyolefin among the various polymer materials exemplified as the resin film that can constitute the base material. When the polyolefin film substrate disclosed herein contains a polymer other than the polyolefin in addition to the polyolefin, the content of the polymer other than the polyolefin is suitably less than 100 parts by weight, 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, relative to 100 parts by weight of the polyolefin. The content of the polymer other than polyolefin may be 5 parts by weight or less, or may be 1 part by weight or less with respect to 100 parts by weight of polyolefin. The technology disclosed herein can be preferably practiced, for example, in a mode in which 99.5 to 100% by weight of the polyolefin film substrate is polyolefin.

From the viewpoint of reducing the amount of fossil resource-based materials used, the base material disclosed here preferably contains a biomass material. The biomass material that can constitute the base material is not particularly limited, but for example, biomass polyester such as biomass PET and biomass polytrimethylene terephthalate (biomass PTT); polylactic acid; hexanoate); biomass polyamides such as polyhexamethylene sebacamide and poly(xylylene sebacamide); biomass polyurethanes such as biomass polyester ether urethane and biomass polyether urethane; cellulosic resin; These can be used individually by 1 type or in combination of 2 or more types. Among them, biomass PET and biomass PTT are preferred, and biomass HDPE, biomass LDPE, biomass LLDPE, biomass PP and biomass PET are particularly preferred. Since the biomass material described above is a resin material, it can be preferably applied to a configuration in which the substrate is a resin film. By using the above biomass material, the amount of fossil resource-based material used can be reduced in the pressure-sensitive adhesive sheet having a resin film (preferably polyolefin film) as a base material.

In the pressure-sensitive adhesive sheet having a base material, the bio rate of the base material is preferably 20% or more, more preferably 35% or more. When more emphasis is placed on reducing the amount of fossil resource-based materials used, the bio rate of the substrate may be, for example, 50% or higher, 70% or higher, 85% or higher, or 90% or higher. Although the upper limit of the bio rate is 100% or less, in some embodiments, the bio rate of the base material may be, for example, 80% or less, 60% or less, 40% or less, or less than 20% in consideration of workability, strength, and the like.

The base material may have transparency, or may have light shielding or dimming properties. In some embodiments, the substrate (eg, resin film) can contain a colorant. Thereby, the light transmittance (light shielding property) of the substrate can be adjusted. Adjusting the light transmittance (for example, normal light transmittance) of the substrate can also help adjust the light transmittance of the substrate and further the light transmittance of the pressure-sensitive adhesive sheet including the substrate.

As the coloring agent, conventionally known pigments and dyes can be used in the same manner as the coloring agent that can be contained in the adhesive layer. The coloring agent is not particularly limited, and may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl color, and the like.

The substrate may be colored with a colored layer arranged on the surface of the base film (preferably resin film). In such a substrate having a structure including a base film and a colored layer, the base film may or may not contain a coloring agent. The colored layer may be arranged on either one surface of the base film, or may be arranged on both surfaces. In the configuration in which the colored layers are arranged on both surfaces of the base film, the configurations of the colored layers may be the same or different. By arranging the colored layer, the color and transparency of the pressure-sensitive adhesive sheet can be adjusted, and desired design properties, light-shielding properties, and hiding 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 (eg, black printed layer) formed by, for example, black printing.

The colored layer can be formed, for example, by applying a colored layer-forming composition containing a coloring agent and a binder to the base film. Materials known in the field of coatings or printing can be used as binders without particular limitations. Examples include polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate, and the like. The colored layer-forming composition may be, for example, a solvent type, an ultraviolet curable type, a heat curable type, or the like. The formation of the colored layer can be carried out by adopting means conventionally used for forming the colored layer without particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexographic printing, and offset printing can be preferably employed.

The colored layer may have a single layer structure consisting entirely of one layer, or may have a multilayer structure including two, three or more sub-colored layers. A colored layer having a multi-layer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (for example, printing) a composition for forming a colored layer. The colors and blending amounts of the colorants contained in each sub-colored layer may be the same or different. From the viewpoint of preventing the formation of pinholes and increasing the reliability of preventing light leakage, it is particularly significant to have a multi-layer structure in the colored layer for imparting light-shielding properties.

As the coloring agent used for coloring the colored layer, a known pigment or dye can be appropriately selected according to the desired color. Examples of white pigments include, but are not limited to, titanium dioxide, zinc white, white lead, and the like. Examples of black pigments include carbon black, acetylene black, pine smoke, graphite and the like. These can be used individually by 1 type or in combination of 2 or more types.

The content of the coloring agent is set according to the required color tone, light transmittance, etc., and is not limited to a specific range. The content of the coloring agent is suitably about 65% by weight or less, preferably 30% by weight or less (for example, 15% by weight or less), and may be 8% by weight or less.

The thickness of the entire colored layer is usually appropriately 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 about 0.8 μm or more, or about 1 μm or more. In some other embodiments, the thickness of the entire colored layer may be 2 μm or more (eg, 3 μm or more) or 4 μm or more from the viewpoint of obtaining sufficient light shielding properties. The thickness of the entire colored layer is usually 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. In some embodiments, the total color layer thickness can be about 3 μm or less, or even about 2 μm or less. In the colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably about 0.5 μm to 2 μm.

The surface (adhesive layer side surface) of the base material (for example, resin film, rubber sheet, foam sheet, etc.) on which the adhesive layer is arranged may be subjected to known or commonly used surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and formation of an undercoat layer. Such a surface treatment can be a treatment for improving the adhesion between the substrate and the adhesive layer, in other words, the anchoring property of the adhesive layer to the substrate. Alternatively, the base material may not be subjected to a surface treatment for improving the anchoring property on the pressure-sensitive adhesive layer side surface. When forming the undercoat layer, the undercoat agent (primer) used for the formation is not particularly limited, and can be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, and can be, for example, more than 0.01 μm. 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. Since primers are generally highly dependent on fossil resource-based materials, not having an excessively large thickness of the undercoat layer can be advantageous from the viewpoint of reducing the bio-rate of the pressure-sensitive adhesive sheet, which will be described later.

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

Various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, colorants (pigments, dyes, etc.) may be added to the base material (for example, resin film base material) as necessary. The blending ratio of various additives is usually about 30% by weight or less (for example, 20% by weight or less, typically 10% by weight or less). For example, when a pigment (for example, a white pigment) is included in the base material, the content is appropriately about 0.1 to 10% by weight (for example, 1 to 8% by weight, typically 1 to 5% by weight).

The thickness of the base material is not particularly limited and can be appropriately selected according to the purpose, but is generally about 1 μm to 500 μm. From the standpoint 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. Further, from the viewpoint of thinning the pressure-sensitive adhesive sheet, in some aspects, 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, 5 μm or less, or 4 μm or less.

As described above, according to the technology disclosed herein, a method for manufacturing an adhesive sheet having an adhesive layer is provided. Details thereof are as described in the above-mentioned adhesive composition and adhesive sheet, and redundant description is omitted.

<Application>
The use of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and it can be used for various purposes without limitation. For example, the pressure-sensitive adhesive sheet can be used for the purpose of fixing, bonding, reinforcing, etc. of the members in a mode of being attached to the members constituting the electronic device. The PSA sheet disclosed herein can be preferably used for fixing or joining members, for example, in the form of a double-sided PSA sheet. In such applications it is particularly significant that the adhesive sheet exhibits good adhesion and holding power. The double-sided pressure-sensitive adhesive sheet may be substrateless or may have a substrate. From the viewpoint of thinning, in some embodiments, a substrate-less double-sided PSA sheet or a substrate-attached double-sided PSA sheet using a thin substrate can be preferably employed. As the thin base material, a base material having a thickness of 10 μm or less (for example, less than 5 μm) can be preferably used.

The adhesive sheet disclosed here is suitable for use in fixing members in mobile electronic devices, for example. The pressure-sensitive adhesive sheet disclosed herein has good adhesive properties, and a thin pressure-sensitive adhesive layer is formed with good quality and high productivity. Therefore, the pressure-sensitive adhesive sheet disclosed herein is suitable for use in mobile electronic devices in which a thin layer pressure-sensitive adhesive is required due to demands such as weight reduction, miniaturization, thinness, and high functionality. In addition, the pressure-sensitive adhesive sheet disclosed herein can have adhesion reliability that achieves both adhesive strength and high-temperature holding power, and is therefore suitable for use in portable electronic devices that require high performance. Since the inside of a portable electronic device may contain a heat-generating element such as a battery, it may be exposed to temperatures of, for example, 40° C. or higher. Non-limiting examples of the above portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist wear type worn on the wrist like a wristwatch, modular type worn on a part of the body with a clip or strap, eyewear type including glasses type (monocular type or binocular type, including head-mounted type), clothing type attached to shirts, socks, hats, etc. in the form of accessories, earwear type attached to 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 notebooks, electronic books, in-vehicle information equipment, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. The pressure-sensitive adhesive sheet disclosed herein can be preferably used, for example, for the purpose of fixing a pressure-sensitive sensor and other members in a portable electronic device having a pressure-sensitive sensor among such portable electronic devices. In some preferred embodiments, the pressure-sensitive adhesive sheet is a device for indicating a position on the screen (typically a pen-type or mouse-type device) and a device for detecting the position, and can be used to fix pressure sensors and other members in an electronic device (typically a portable electronic device) having a function of specifying an absolute position on a board (typically a touch panel) corresponding to the screen. In this specification, the term “portable” means not only being able to be simply carried, but also having a level of portability that allows an individual (a typical adult) to carry it relatively easily.

The material (adherend material) to which the adhesive sheet disclosed herein is attached is not particularly limited, but examples include metal materials such as copper, iron, aluminum, and stainless steel; various resin materials (typically plastic materials); inorganic materials such as glass; Examples of the resin material include polyimide-based resins, acrylic-based resins, polyethernitrile-based resins, polyethersulfone-based resins, polyester-based resins (PET-based resins, polyethylene naphthalate-based resins, etc.), polyvinyl chloride-based resins, polyphenylene sulfide-based resins, polyetheretherketone-based resins, polyamide-based resins (such as so-called aramid resins), polyarylate-based resins, polycarbonate-based resins, and liquid crystal polymers. Among others, the adhesive sheet disclosed herein is preferably used for bonding the metal materials, polyester resins such as PET, polyimide resins, aramid resins, polyphenylene sulfide resins, polycarbonate resins, and the like. The above materials may be member materials that constitute products such as portable electronic devices. The adhesive sheet disclosed herein can be used by being attached to a member made of the above materials.

FIG. 4 is an example schematically showing a portable electronic device (smartphone) using the adhesive sheet disclosed herein. As shown in FIG. 4 , a battery (heat generating element) 540 is built inside a housing 520 of the portable electronic device 500 . Moreover, the portable electronic device 500 is configured including an adhesive sheet 550 . In this configuration example, the adhesive sheet 550 has the form of a double-sided adhesive sheet (double-sided adhesive sheet) for fixing members constituting the portable electronic device 500 . The portable electronic device 500 includes a touch panel 570 whose display unit also functions as an input unit. The pressure-sensitive adhesive sheet disclosed herein is preferably used as a constituent element (member joining means) of the portable electronic device as described above.

Matters disclosed by this specification include the following.
[1] A portable electronic device,
A housing and a touch panel whose display unit also functions as an input unit,
A heating element (e.g., battery) is built in the housing,
At least a first member and a second member among a large number of members constituting the portable electronic device are joined by an adhesive sheet,
The adhesive sheet has an adhesive layer,
The pressure-sensitive adhesive layer contains a polyester polymer, a tackifying resin and a cross-linking agent,
The content of the tackifying resin in the adhesive layer is 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer,
The portable electronic device, wherein the polyester polymer has a weight average molecular weight of 110,000 or more.
[2] The mobile electronic device according to [1] above, wherein the content of the tackifying resin in the pressure-sensitive adhesive layer is 20 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the polyester polymer.
[3] The portable electronic device according to [1] or [2] above, wherein the cross-linking agent includes an isocyanate-based cross-linking agent.
[4] The portable electronic device according to any one of [1] to [3] above, wherein 50% or more of the constituent carbon of the polyester-based polymer is biomass-derived carbon.
[5] The portable electronic device according to any one of [1] to [4] above, wherein the pressure-sensitive adhesive layer has a thickness of 5 to 50 μm.
[6] The portable electronic device according to any one of [1] to [5] above, wherein the polyester polymer has a glass transition temperature of 0° C. or lower.
[7] The portable electronic device according to any one of [1] to [6] above, wherein the polyester polymer contains an aromatic ring.
[8] The portable electronic device according to any one of [1] to [7] above, wherein the tackifying resin is selected from terpene phenol resins and polymerized rosin esters.
[9] The portable electronic device according to any one of [1] to [8] above, wherein the polyester polymer contains an aromatic ring, and the tackifying resin also contains an aromatic ring.
[10] The portable electronic device according to any one of [1] to [9] above, wherein the pressure-sensitive adhesive layer further contains a cross-linking catalyst, and the cross-linking catalyst does not contain a tin-based compound.

[11] containing a polyester polymer, a tackifying resin and a cross-linking agent,
The content of the tackifying resin is 20 parts by weight or more with respect to 100 parts by weight of the polyester 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 [11] above, wherein the content of the tackifying resin is 20 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the polyester polymer.
[13] The pressure-sensitive adhesive composition of [11] or [12] above, which has a solid content concentration of 10 to 70% by weight and a viscosity of 10 to 10,000 mPa·s at 23°C.
[14] The pressure-sensitive adhesive composition according to any one of [11] to [13] above, wherein the cross-linking agent includes an isocyanate-based cross-linking agent.
[15] The pressure-sensitive adhesive composition according to any one of [11] to [14] above, further comprising a crosslinking catalyst.
[16] The pressure-sensitive adhesive composition according to any one of [11] to [15] above, wherein 50% or more of the constituent carbon of the polyester-based polymer is biomass-derived carbon.
[17] The pressure-sensitive adhesive composition as described in any one of [11] to [16] above, wherein the polyester polymer has a glass transition temperature of 0° C. or lower.
[18] The pressure-sensitive adhesive composition according to any one of [11] to [17] above, wherein the polyester polymer contains an aromatic ring.
[19] The adhesive composition according to any one of [11] to [18] above, wherein the tackifying resin is selected from terpene phenol resins and polymerized rosin esters.
[20] The pressure-sensitive adhesive composition according to any one of [11] to [19] above, wherein the polyester polymer contains an aromatic ring, and the tackifying resin also contains an aromatic ring.

[21] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer contains a polyester polymer, a tackifying resin and a cross-linking agent,
The content of the tackifying resin in the adhesive layer is 20 parts by weight or more with respect to 100 parts by weight of the polyester 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 tackifying resin in the pressure-sensitive adhesive layer is 20 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the polyester polymer.
[23] The pressure-sensitive adhesive sheet of [21] or [22] above, wherein the cross-linking agent includes an isocyanate-based cross-linking agent.
[24] The adhesive sheet according to any one of [21] to [23] above, wherein 50% or more of the constituent carbon of the polyester polymer is biomass-derived carbon.
[25] The pressure-sensitive adhesive sheet according to any one of [21] to [24] above, wherein the thickness of the pressure-sensitive adhesive layer is in the range of 5 to 50 µm.
[26] The pressure-sensitive adhesive sheet according to any one of [21] to [25] above, 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 [21] to [26] above, wherein the polyester polymer contains an aromatic ring.
[28] The pressure-sensitive adhesive sheet according to any one of [21] to [27] above, wherein the tackifying resin is selected from terpene phenol resins and polymerized rosin esters.
[29] The pressure-sensitive adhesive sheet according to any one of [21] to [28] above, wherein the polyester-based polymer contains an aromatic ring, and the tackifying 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 drop in a holding force test conducted under the conditions of 80° C., a load of 1 kg, and 1 hour.

[31] The pressure-sensitive adhesive sheet according to any one of [21] to [30] above, which is used in portable electronic devices.
[32] A portable electronic device comprising the adhesive sheet according to any one of [21] to [30] above.

[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 cross-linking agent;
applying the pressure-sensitive adhesive composition to a substrate surface or a releasable surface to form a pressure-sensitive adhesive layer;
including
here,
The content of the tackifying resin is 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer,
A 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 tackifying resin in the pressure-sensitive adhesive composition is 20 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the polyester polymer.
[43] The method for producing a pressure-sensitive adhesive sheet according to [41] or [42] above, wherein the pressure-sensitive adhesive composition has a solid content concentration of 10 to 70% by weight 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 cross-linking agent includes an isocyanate-based cross-linking agent.
[45] The method for producing a pressure-sensitive adhesive sheet as described in any one of [41] to [44] above, further comprising a cross-linking 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 constituent carbon of the polyester polymer is biomass-derived carbon.
[47] The method for producing a pressure-sensitive adhesive sheet according to any one of [41] to [46] above, wherein the tackifying resin is selected from terpene phenol resins and polymerized rosin esters.
[48] The method for producing a pressure-sensitive adhesive sheet as described in any one of [41] to [47] above, wherein the thickness of the pressure-sensitive adhesive layer is in 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 against a stainless steel plate of 10 N/20 mm or more, and does not drop in a holding force test conducted 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 portable electronic devices.

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

<Synthesis example>
(Synthesis example 1)
A four-necked separable flask was equipped with a stirrer, a thermometer, a nitrogen tube and a water separation tube, and 100 g of ethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 62), 700 g of dimer acid (product name "PRIPOL 1009", manufactured by Croda, molecular weight 567), 63 g of terephthalic acid (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 166), and di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) as a polymerization catalyst. ) and 40 g of xylene as a solvent for discharging the reaction water were charged, heated to 180° C. while stirring in a nitrogen atmosphere, and maintained at this temperature. After a while, outflow and separation of the reaction water was observed, and the reaction started to progress. The reaction was continued for about 24 hours to obtain a polyester polymer (A1) with a bio rate of 81%. This polyester polymer (A1) had a weight average molecular weight (Mw) of 100,000 and a glass transition temperature (Tg) of -33°C.

(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 Mw was 130,000.

<Example 1>
To 100 parts of the polyester polymer (A1), 40 parts of a terpene phenol resin (trade name "YS Polyster S145", manufactured by Yasuhara Chemical Co., Ltd., phenol ratio 22%, hereinafter sometimes referred to as "S145") as a tackifying resin, 3 parts of an isocyanurate body of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) as a cross-linking agent, an organic zirconium compound (trade name "Orgatics ZC-162") as a cross-linking catalyst. , Matsumoto Fine Chemical Co., Ltd.) 0.13 parts, 0.5 parts of a carbodiimide group-containing compound (trade name "Carbodilite V-03", Nisshinbo Chemical Co., Ltd.) as a hydrolysis resistant agent are blended, and ethyl acetate is added to prepare an adhesive composition (adhesive solution) according to this example. The solid content concentration of this adhesive composition was 40%, and the viscosity at 23° C. was about 300 mPa·s.

<Example 2>
A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1, except that 0.01 part of an organic tin compound (trade name “dibutyltin (IV) dilaurate”, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as a cross-linking catalyst instead of the organic zirconium compound. The solid content concentration of this adhesive composition was 40%, and the viscosity at 23° C. was about 300 mPa·s.

<Example 3>
To 100 parts of the polyester polymer (A2), 40 parts of a terpene phenol resin (trade name "YS Polystar G150", manufactured by Yasuhara Chemical Co., Ltd., phenol ratio 32%, hereinafter sometimes referred to as "G150") as a tackifying resin, 2 parts of an isocyanurate body of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) as a cross-linking agent, an organic zirconium compound (trade name "Orgatics ZC-162") as a cross-linking catalyst. , Matsumoto Fine Chemical Co., Ltd.) 0.03 part, 0.5 part of a carbodiimide group-containing compound (trade name "Carbodilite V-03", manufactured by Nisshinbo Chemical Co., Ltd.) as a hydrolysis resistant agent was blended, ethyl acetate was added, and an adhesive composition (adhesive solution) according to this example was prepared. The solid content concentration of this adhesive composition was 40%, and the viscosity at 23° C. was about 800 mPa·s.

<Example 4>
To 100 parts of the polyester polymer (A2), 40 parts of a terpene phenol resin (trade name “YS Polystar S145”, manufactured by Yasuhara Chemical Co., Ltd., phenol ratio 22%) as a tackifying resin, isocyanurate of hexamethylene diisocyanate (trade name “Coronate HX”, manufactured by Tosoh Corporation) as a cross-linking agent 3 parts, an organic tin compound (trade name “dibutyltin dilaurate (IV)”, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 0.01 as a cross-linking catalyst. A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 3, except that 1 part was used. The solid content concentration of this adhesive composition was 40%, and the viscosity at 23° C. was about 800 mPa·s.

<Examples 5 to 8>
A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 4, except that the amounts of the tackifier resin and cross-linking agent used were changed as shown in Table 1.

<Evaluation>
[Adhesive Coatability]
Using a comma coater type and 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 applied at a coating speed of 20 m/min to the release-treated surface of a polyethylene terephthalate (PET) film (trade name “Diafoil MRF #38”, manufactured by Mitsubishi Chemical Corporation) so that the thickness after drying was 20 μm, and dried at 120 ° C. for 3 minutes. In both cases of comma coater type and die coater type coating, if the adhesive layer after drying had good quality without repelling etc. by visual observation, it was judged as "G" (pass), and if defects such as repelling visually occurred in either comma coater type or die coater type coating, or if the adhesive could not be applied, it was judged as "P" (fail).

[Adhesive strength against SUS]
A pressure-sensitive adhesive layer was formed by the method described in the evaluation of the pressure-sensitive adhesive coatability, and the pressure-sensitive adhesive layer was attached to the release-treated surface of a release-treated PET film (trade name “Diafoil MRE #38” manufactured by Mitsubishi Chemical Corporation).
The obtained adhesive sheet was cut into a size of 20 mm in width and 150 mm in length to prepare a measurement sample. The adhesive surface of the measurement sample was exposed in an environment of 23° C. and 50% RH, and the adhesive surface was press-bonded to a stainless steel plate (SUS304BA plate) as an adherend by reciprocating a 2-kg rubber roller once. This was left in an environment of 23 ° C. and 50% RH for 30 minutes, and then using a tensile tester in the same environment according to JIS Z0237: 2000, the peel strength (adhesive strength to SUS) [N / 20 mm] was measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. As the tensile tester, a universal tensile and compression tester (equipment name “Tensile and Compression Tester, TCM-1kNB”, manufactured by Minebea Co., Ltd.) was used.

[High temperature holding power]
A pressure-sensitive adhesive layer was formed by the method described in the evaluation of the pressure-sensitive adhesive coatability, and the pressure-sensitive adhesive layer was attached to the release-treated surface of a release-treated PET film (trade name “Diafoil MRE #38” manufactured by Mitsubishi Chemical Corporation).
A measurement sample (test piece) was prepared by cutting the adhesive sheet into a size of 10 mm in width and 100 mm in length. Under 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 10 mm wide and 20 mm long pasting area with a 2 kg roller. The adherend to which the test piece was adhered in this manner was allowed to stand in an environment of 80° C. for 30 minutes with the length direction of the test piece oriented vertically. Next, a load of 1 kg was applied to the free end of the test piece, and the test piece was left under the load at 80° C. for 1 hour according to JIS Z0237. For the test piece after the standing, the distance (length of displacement; hereinafter also referred to as displacement distance) [mm] deviated from the initial sticking position was measured. If the specimen fell from the bakelite plate within 1 hour, it was rated as "dropped" (failed).

In addition, when measuring the adhesive strength to SUS and the high temperature holding power, if necessary (for example, in the case of a double-sided adhesive sheet without a substrate, or in the case of an adhesive sheet with a substrate and the substrate is easily deformed, etc.), the adhesive sheet to be measured can be reinforced by attaching an appropriate backing material. As the backing material, for example, a PET film having a thickness of about 50 μm can be used, and this backing material was used in the examples.

Table 1 shows the evaluation results of the adhesive composition and adhesive sheet according to each example.

As shown in Table 1, in the adhesive compositions according to Examples 1 to 4 and Examples 6 to 8, which contain a polyester polymer, a tackifying resin, and a cross-linking agent, and the content of the tackifying resin is 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer, in Examples 3 to 4 and Examples 6 to 8, in which a polyester polymer having an Mw of 110,000 or more was used, the evaluation of the adhesive coating property by an actual machine was passed, and the obtained adhesive sheets had excellent adhesion to SUS and high-temperature holding power. and had excellent adhesive properties. On the other hand, in Examples 1 and 2 in which Mw used a polyester-based polymer of less than 110,000, the evaluation of the adhesive coating property was unsatisfactory, and an evaluable adhesive sheet could not be produced due to poor coating, and the adhesive sheet was not evaluated. In Example 5, in which the amount of the tackifying resin used was less than 20 parts by weight with respect to 100 parts by weight of the polyester polymer, the adhesion to SUS was low.
From the above results, it can be seen that a PSA composition containing a polyester polymer, a tackifier resin and a cross-linking agent, wherein the content of the tackifier resin is 20 parts by weight or more relative to 100 parts by weight of the polyester polymer, and the Mw of the polyester polymer is 110,000 or more, can form a thin PSA with good quality. Also, it can be seen that such adhesives can exhibit good adhesive properties based on the use of tackifying resins.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Reference Signs List

1, 2, 3 Adhesive sheet 10 Supporting substrate 10A First surface 10B Second surface (back surface)
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 PSA sheet with release liner

Claims

including a polyester-based polymer, a tackifying resin and a cross-linking agent,
The content of the tackifying resin is 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer,
The pressure-sensitive adhesive composition, wherein the polyester polymer has a weight average molecular weight of 110,000 or more.
The pressure-sensitive adhesive composition according to claim 1, wherein the content of the tackifying resin is 20 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the polyester polymer.
The adhesive composition according to claim 1 or 2, which has a solid content concentration of 10 to 70% by weight and a viscosity of 10 to 10,000 mPa·s at 23°C.
The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the cross-linking agent includes an isocyanate-based cross-linking agent.
The pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising a cross-linking catalyst.
The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein 50% or more of the constituent carbon of the polyester-based polymer is biomass-derived carbon.
A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer contains a polyester polymer, a tackifying resin and a cross-linking agent,
The content of the tackifying resin in the adhesive layer is 20 parts by weight or more with respect to 100 parts by weight of the polyester polymer,
The pressure-sensitive adhesive sheet, wherein the polyester polymer has a weight average molecular weight of 110,000 or more.
The pressure-sensitive adhesive sheet according to claim 7, wherein the content of the tackifying resin in the pressure-sensitive adhesive layer is 20 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the polyester polymer.
The pressure-sensitive adhesive sheet according to claim 7 or 8, wherein the cross-linking agent contains an isocyanate-based cross-linking agent.
The pressure-sensitive adhesive sheet according to any one of claims 7 to 9, wherein 50% or more of the constituent carbon of the polyester-based polymer is biomass-derived carbon.
The pressure-sensitive adhesive sheet according to any one of claims 7 to 10, wherein the pressure-sensitive adhesive layer has a thickness in the range of 5 to 50 µm.
The pressure-sensitive adhesive sheet according to any one of claims 7 to 11, which is used for portable electronic devices.