Adhesive sheets and portable electronic devices

Abstract

The objectives are to provide an adhesive sheet that is both chemically resistant and waterproof, and to provide a portable electronic device that includes the above-mentioned adhesive sheet. [Solution] An adhesive sheet having an adhesive layer, wherein the adhesive layer contains a polyester polymer, the swelling rate of the adhesive layer with respect to isopropyl alcohol is 2,000 wt% or less, the swelling rate with respect to oleic acid is 2,000 wt% or less, and the glass transition temperature (Tg) of the polyester polymer is -10 to 10°C.

Description

Technical Field

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

Background Art

[0002] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter.) exhibits a state of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used as joining means with good workability and high adhesion reliability in various industrial fields such as home appliances, automobiles, various machines, electrical equipment, and electronic devices, typically in the form of an adhesive sheet including a layer of the adhesive. As the adhesive, various adhesives such as acrylic adhesives, rubber adhesives, and polyester adhesives are used according to the purpose of use, the place of use, required characteristics, and the like. For example, Patent Documents 1 and 2 can be cited as documents disclosing the prior art regarding polyester adhesives.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Adhesive sheets are preferably used for fixing components in electronic devices such as mobile phones, smartphones, and tablet computers. As adhesives for the above-mentioned electronic devices, acrylic adhesives with acrylic polymers as the base polymer are the mainstream, but synthetic rubber adhesives with rubber block copolymers such as styrene-butadiene block copolymers as the base polymer can also be used. Polyester adhesives have excellent properties such as chemical resistance, water resistance, durability, and optical properties (transparency), and are expected to be used as adhesives for electronic devices as they can exhibit adhesive properties equal to or better than acrylic adhesives and synthetic rubber adhesives. Furthermore, Patent Documents 1 and 2 show that by specifying the polyester polymer and / or other additives contained in polyester adhesives, it is possible to achieve both durability (storage under heating and humidity) and adhesive properties of adhesive sheets.

[0005] Incidentally, recent electronic devices are increasingly becoming larger, thinner, and with narrower bezels. To address this trend, a new need is emerging for adhesive sheets that can be processed and cut to very narrow widths (for example, widths in millimeters). However, with conventional adhesive sheets, there have been concerns that using them in such narrow widths would reduce the chemical resistance and waterproofing (sealing) of the electronic device. In particular, for wearable electronic devices that are expected to be exposed to sebum or sebum decomposition products, disinfectants such as alcohol, and / or water, improving chemical resistance and waterproofing has become a particularly important issue.

[0006] This invention was completed in view of the above circumstances, and aims to provide an adhesive sheet that can achieve both chemical resistance and waterproofing. Another object of this invention is to provide a portable electronic device that includes the above adhesive sheet. [Means for solving the problem]

[0007] As a result of repeated studies by the present inventors, it has been found that the above problem can be solved by providing an adhesive sheet having an adhesive layer, wherein the adhesive layer contains a polyester polymer, the swelling rate of the adhesive layer with respect to isopropyl alcohol is 2,000 wt% or less, the swelling rate with respect to oleic acid is 2,000 wt% or less, and the glass transition temperature (Tg) of the polyester polymer is -10 to 10°C.

[0008] The means to solve the aforementioned problem are as follows: [1] An adhesive sheet having an adhesive layer, The adhesive layer contains a polyester polymer, The swelling rate of the adhesive layer with respect to isopropyl alcohol is 2,000 wt% or less, and the swelling rate with respect to oleic acid is 2,000 wt% or less. An adhesive sheet wherein the glass transition temperature (Tg) of the polyester polymer is -10 to 10°C. [2] The adhesive sheet described in [1], wherein the shear adhesive strength at 23°C is 0.8 MPa or more. [3] The adhesive sheet according to [1], wherein the adhesive layer comprises a tackifying resin. [4] The adhesive sheet according to [3], wherein the content of the tackifying resin is 4 parts or less when the total weight of the adhesive layer is 100 parts by weight.

[0009] [5] The adhesive sheet according to [1], wherein the gel fraction of the adhesive layer is 15 to 90%. [6] The adhesive sheet according to [1], wherein the weight-average molecular weight of the polyester polymer is 20,000 to 150,000. [7] The adhesive sheet according to [1], wherein the polyester polymer contains an aromatic dicarboxylic acid as a structural unit. [8] The adhesive sheet according to [1], wherein the total thickness of the adhesive layer is 50 to 400 μm. [9] The adhesive sheet according to [1], which is a double-sided adhesive sheet.

[0010]

[10] The adhesive sheet according to [1], which has a base material.

[11] The adhesive sheet according to

[10] , wherein the base material is a polyethylene terephthalate (PET) film, a polyolefin film, a polyurethane film or a polyimide film.

[12] The adhesive sheet according to

[10] , wherein the thickness of the base material is more than 0 μm and 150 μm or less.

[13] The adhesive sheet according to any one of [1] to

[12] , which is used for fixing a member of a portable electronic device.

[14] A portable electronic device including the adhesive sheet according to any one of [1] to

[12] .

Advantages of the Invention

[0011] The adhesive sheet of the present invention can achieve both chemical resistance and waterproofness.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a cross-sectional view schematically showing the configuration of an adhesive sheet according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the configuration of an adhesive sheet according to another embodiment. [Figure 3] FIG. 3 is a cross-sectional view schematically showing the configuration of an adhesive sheet according to another embodiment. [Figure 4] FIG. 4 is a front view schematically showing an example of a portable electronic device including an adhesive sheet.

Modes for Carrying Out the Invention

[0013] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below.

[0014] <Adhesive sheet> An adhesive sheet according to an embodiment of the present invention is an adhesive sheet having an adhesive layer, wherein the adhesive layer contains a polyester polymer, the swelling rate of the adhesive layer with respect to isopropyl alcohol is 2,000 wt% or less, the swelling rate with respect to oleic acid is 2,000 wt% or less, and the glass transition temperature (Tg) of the polyester polymer is -10 to 10°C. By using such adhesive sheets, it becomes possible to achieve both chemical resistance and waterproofing. To improve chemical resistance, it is necessary not only to prevent chemical penetration but also for the interface to adhere tightly to the substrate and for the bulk strength of the adhesive layer to be sufficient. On the other hand, for waterproofing, it is necessary for the interface to adhere tightly to the substrate and for the bulk strength to prevent displacement when external pressure is applied. In contrast, the adhesive sheet according to the embodiment of the present invention is thought to be able to achieve both chemical resistance and waterproofing by controlling the penetration of chemicals by the swelling rate, while controlling the adhesion of the interface and the strength of the bulk by Tg.

[0015] (Example of adhesive sheet configuration) An adhesive sheet according to an embodiment of the present invention is composed of an adhesive layer. The adhesive sheet may be in the form of a substrate-less double-sided adhesive sheet comprising, for example, a first adhesive surface formed by one surface of the adhesive layer and a second adhesive surface formed by the other surface of the adhesive layer. Alternatively, the adhesive sheet disclosed herein may be in the form of a substrate-attached adhesive sheet in which the adhesive layer is laminated on one or both sides of a support substrate. Hereinafter, the support substrate may simply be referred to as the "substrate".

[0016] Figure 1 schematically shows the structure of an adhesive sheet according to one embodiment. This adhesive sheet 1 is configured as a substrate-less double-sided adhesive sheet consisting of an adhesive layer 21. The adhesive sheet 1 is used by attaching a first adhesive surface 21A, which is formed by one surface (first surface) of the adhesive layer 21, and a second adhesive surface 21B, which is formed by the other surface (second surface) of the adhesive layer 21, to different locations on an object to be adhered to. The locations to which the adhesive surfaces 21A and 21B are attached may be different locations on different members, or they may be different locations within a single member. Before use (i.e., before being attached to an object to be adhered to), as shown in Figure 1, the adhesive sheet 1 may be a component of an adhesive sheet 100 with a release liner, in which the first adhesive surface 21A and the second adhesive surface 21B are protected by release liners 31 and 32, each having a release surface on at least the side facing the adhesive layer 21. As the release liners 31 and 32, for example, it is preferable to use a sheet-like base material (liner base material) on which a release layer is provided by a release agent on one side so that the one side becomes a release surface. Alternatively, the release liner 32 may be omitted, and a release liner 31 with release surfaces on both sides may be used, and the adhesive sheet 1 may be overlapped with this and wound in a spiral shape to form an adhesive sheet with a release liner in a form (roll form) where the second adhesive surface 21B abuts against the back surface of the release liner 31 and is protected.

[0017] Figure 2 schematically shows the structure of an adhesive sheet according to another embodiment. This adhesive sheet 2 is configured as a single-sided adhesive sheet with a substrate, comprising a sheet-like support substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side. The adhesive layer 21 is fixedly provided on the first surface 10A side of the support substrate 10, that is, without any intention to separate the adhesive layer 21 from the support substrate 10. Before use, the adhesive sheet 2 may be a component of an adhesive sheet 200 with a release liner, as shown in Figure 2, in which the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31, at least on the side facing the adhesive layer 21. Alternatively, the release liner 31 may be omitted, and a support substrate 10 with the second surface 10B as the release surface may be used, and the adhesive sheet 2 may be wound so that the adhesive surface 21A abuts against and is protected by the second surface (back surface) 10B of the support substrate 10 (roll form).

[0018] Furthermore, Figure 3 schematically shows the structure of an adhesive sheet according to another embodiment. This adhesive sheet 3 is configured as a double-sided adhesive sheet with a base material, comprising a sheet-like support base material (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, a first adhesive layer 21 fixedly provided on the first surface 10A side, and a second adhesive layer 22 fixedly provided on the second surface 10B side. Before use, the adhesive sheet 3 may be a component of an adhesive sheet with a release liner 300 in which the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 are protected by release liners 31 and 32, as shown in Figure 3. Alternatively, the release liner 32 may be omitted, and a release liner 31 with release surfaces on both sides may be used, and the adhesive sheet 3 may be overlapped and wound in a spiral shape to constitute an adhesive sheet with a release liner in which the second adhesive surface 22A abuts against and is protected by the back surface of the release liner 31 (roll form).

[0019] In the above-mentioned double-sided adhesive sheet with a substrate, at least one of the first adhesive layer and the second adhesive layer (for example, the first adhesive layer) may be an adhesive layer as described below, and the other adhesive layer (for example, the second adhesive layer) may be an adhesive layer as described below, or an adhesive layer having a different composition from the adhesive layer described below (specifically, the first adhesive layer mentioned above, for example, the first adhesive layer). Such the other adhesive layer may be formed from, for example, a known or conventional adhesive.

[0020] While not particularly limited, the adhesive sheet according to the embodiment of the present invention is preferably a double-sided adhesive sheet, and may also be in the form of a substrate-less double-sided adhesive sheet.

[0021] The concept of adhesive sheets used here may include items such as adhesive tapes, adhesive films, and adhesive labels. The adhesive sheet according to the embodiment of the present invention may be in roll form or sheet form, and may be cut, punched, or otherwise processed into an appropriate shape depending on the application and manner of use. In particular, the adhesive sheet can demonstrate its effects even more when processed and cut to a very narrow width (for example, a width in millimeters).

[0022] <Adhesive layer> The adhesive layer contained in the adhesive sheet according to the embodiment of the present invention contains a polyester polymer, has a swelling rate of 2,000 wt% or less with respect to isopropyl alcohol, a swelling rate of 2,000 wt% or less with respect to oleic acid, and a glass transition temperature (Tg) of the polyester polymer of -10 to 10°C.

[0023] (Polyester polymer) In embodiments of the present invention, the adhesive layer contains a polyester polymer. In this specification, an adhesive layer containing a polyester polymer is also referred to as a polyester adhesive layer. The polyester polymer is typically included in the adhesive layer as a base polymer. Here, the base polymer refers to the main component of the rubbery polymer (a polymer that exhibits rubber elasticity in the temperature range around room temperature) included in the adhesive layer. In this specification, unless otherwise specified, the "main component" refers to a component that is included in more than 50% by weight. In this specification, a polyester polymer refers to a polymer obtained by polycondensation of a dicarboxylic acid and a diol. If the adhesive layer does not contain polyester polymers, its affinity for oleic acid becomes particularly strong, which may cause the adhesive strength to be lost when exposed to sebum or sebum-degrading products.

[0024] (Dicarboxylic acid) Any of the following dicarboxylic acids can be used in the synthesis of the above-mentioned polyester polymers: aliphatic dicarboxylic acids, dimer acids, alicyclic dicarboxylic acids, unsaturated dicarboxylic acids, and aromatic dicarboxylic acids. Specific examples of dicarboxylic acids include, for example, 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; and 1,2-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 4-methyl-1,2-cyclohexanedicarboxylic acid. Examples include alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, norbornanedicarboxylic acid, and adamantanedicarboxylic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, and dodecenyl succinic anhydride; aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, and naphthalenedicarboxylic acid; and derivatives thereof. The derivatives of the above dicarboxylic acids 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, a polyester polymer capable of forming an adhesive layer with desired properties (specifically, a desired Tg) can be obtained.

[0025] In embodiments of the present invention, sebacic acid can be used as the dicarboxylic acid. In embodiments in which sebacic acid is used as the dicarboxylic acid, the proportion of sebacic acid in the total amount (total number of moles) of dicarboxylic acid as a monomer component of the polyester polymer may be 1 mol% or more, for example, 5 mol% or more, 10 mol% or more, or 15 mol% or more. Furthermore, the upper limit of the proportion of sebacic acid is 100 mol%, and from the viewpoint of lowering the Tg of the adhesive, in embodiments of the present invention, it may be 50 mol% or less, or 30 mol% or less. Embodiments of the present invention can be carried out in any form in which the dicarboxylic acid used as a monomer component in the synthesis of the polyester polymer contains sebacic acid, or in any form in which it does not contain sebacic acid. For example, the proportion of sebacic acid may be 10 mol% or less, 3 mol% or less, or less than 1 mol%, and the dicarboxylic acid used in the synthesis of the polyester polymer may substantially not contain sebacic acid.

[0026] In embodiments of the present invention, adipic acid can be used as the dicarboxylic acid. In embodiments in which adipic acid is used as the dicarboxylic acid, the proportion of adipic acid in the total amount (total number of moles) of dicarboxylic acid as a monomer component of the polyester polymer may be 1 mol% or more, for example, 5 mol% or more, 10 mol% or more, or 15 mol% or more. Furthermore, the upper limit of the proportion of adipic acid is 100 mol%, and from the viewpoint of lowering the Tg of the adhesive, in embodiments of the present invention, it may be 50 mol% or less, or 30 mol% or less. Embodiments of the present invention can be carried out in any form in which the dicarboxylic acid used as a monomer component in the synthesis of the polyester polymer contains adipic acid, or in any form in which it does not contain adipic acid. For example, the proportion of adipic acid may be 10 mol% or less, 3 mol% or less, or less than 1 mol%, and the dicarboxylic acid used in the synthesis of the polyester polymer may substantially not contain adipic acid.

[0027] In embodiments of the present invention, sebacic acid and adipic acid can be used in combination as dicarboxylic acids. When sebacic acid and adipic acid are used in combination, the combined ratio of sebacic acid and adipic acid to the total amount (total number of moles) of dicarboxylic acids as monomer components of the polyester polymer may be, for example, 10 mol% or less, 3 mol% or less, or less than 1 mol%.

[0028] Furthermore, in embodiments of the present invention, aromatic dicarboxylic acids may be used as the dicarboxylic acids used in the synthesis of polyester polymers. Using dicarboxylic acids containing aromatic dicarboxylic acids tends to increase cohesive strength and improve Tg. Examples of aromatic dicarboxylic acids include isophthalic acid, terephthalic acid, and orthophthalic acid, with isophthalic acid and terephthalic acid being preferred. Aromatic dicarboxylic acids can be used individually or in combination of two or more. From the viewpoint of improving cohesive force, the polyester polymer contained in the adhesive layer according to the embodiment of the present invention preferably contains aromatic dicarboxylic acid as a structural unit, more preferably contains at least one selected from the group consisting of isophthalic acid, terephthalic acid, and orthophthalic acid as a structural unit, and even more preferably contains at least one selected from the group consisting of isophthalic acid and terephthalic acid as a structural unit.

[0029] In embodiments where an aromatic dicarboxylic acid is used as the dicarboxylic acid, the proportion of aromatic dicarboxylic acid in the total amount (total number of moles) of dicarboxylic acid in the monomer component of the polyester polymer may be 1 mol% or more, and may be 3 mol% or more, 5 mol% or more, or 7 mol% or more from the viewpoint of improving cohesive strength, etc. Furthermore, the upper limit of the proportion of aromatic dicarboxylic acid is appropriately set to 90 mol% or less in embodiments of the present invention, for example, and from the viewpoint of obtaining adhesive properties such as adhesive strength with a predetermined Tg range, it is preferably 85 mol% or less, more preferably 80 mol% or less, even more preferably 75 mol% or less, and particularly preferably 70 mol% or less. In embodiments of the present invention, the dicarboxylic acid used as a monomer component in the synthesis of the polyester polymer can be carried out in a manner that includes an aromatic dicarboxylic acid.

[0030] The molecular weight of the dicarboxylic acid used as a monomer component in the synthesis of polyester polymers is not particularly limited, but is preferably 100 or more, and may be 150 or more. In embodiments of the present invention, the molecular weight of the dicarboxylic acid used may be 200 or more, 250 or more, 350 or more, 450 or more, or 500 or more (for example, 530 or more). On the other hand, from the viewpoint of monomer availability and synthesizability, in embodiments of the present invention, the molecular weight of the dicarboxylic acid is preferably 1000 or less, and may be, for example, 800 or less, 700 or less, or 600 or less (for example, 550 or less).

[0031] In this specification, the molecular weight of a dicarboxylic acid is the molecular weight calculated from its chemical formula. In embodiments using two or more dicarboxylic acids, the molecular weight of the dicarboxylic acid is the sum of the products of the molecular weight and weight fraction of each dicarboxylic acid.

[0032] (Diol) In embodiments of the present invention, any of the following can be used as the diol used in the synthesis of polyester polymers: (poly)alkylene glycols, aliphatic diols, dimer diols, alicyclic diols, aromatic diols, and unsaturated diols. Specific examples of the above diols include, for example, (poly)alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol, etc.; 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-hexanediol, 2,2,4-trimethyl-1, Examples include aliphatic diols such as 6-hexanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; dimergols (such as dimergols derived from fatty acids like oleic acid and erucic acid); alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; aromatic diols such as 4,4′-thiodiphenol, 4,4′-methylenediphenol, 4,4′-dihydroxybiphenyl, o-,m- and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and their ethylene oxide and propylene oxide adducts; and so on. By appropriately selecting and using one or more of these diols, a polyester polymer capable of forming an adhesive layer with desired properties (specifically, a desired Tg) can be obtained.

[0033] In embodiments of the present invention, the diol is preferably (poly)alkylene glycol, aliphatic diol, or alicyclic diol, and more preferably (poly)alkylene glycol or aliphatic diol. By synthesizing these diols (preferably ethylene glycol or aliphatic diol) in combination with the above-mentioned dicarboxylic acid (preferably dimer acid), a polyester polymer with excellent adhesive properties can be preferably obtained. Suitable examples include (poly)ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol (2,2-dimethyl-1,3-propanediol), 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol, and from the viewpoint of reactivity, ethylene glycol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol are more preferred. These can be used individually or in combination of two or more. In this specification, the term (poly)ethylene glycol is used to encompass ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol.

[0034] The proportion of (poly)alkylene glycols, aliphatic diols, and alicyclic diols (preferably the proportion of ethylene glycol and aliphatic diols) in the total amount (total number of moles) of diols in the monomer component of the polyester polymer is not particularly limited, but in embodiments of the present invention, it is appropriate to set it to 50 mol% or more, and from the viewpoint of obtaining good adhesive properties, it is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 95 mol% or more (for example, 99 to 100 mol%). In other embodiments of the present invention, the proportion of (poly)alkylene glycols, aliphatic diols, and alicyclic diols (preferably the proportion of ethylene glycol and aliphatic diols) may be, for example, 95 mol% or less.

[0035] In embodiments of the present invention, (poly)ethylene glycol can be used as the diol. By using (poly)ethylene glycol in combination with a suitable dicarboxylic acid, a polyester polymer capable of forming an adhesive layer having a desired 23°C storage modulus can be preferably obtained, and good adhesive properties (such as adhesive strength) can be preferably obtained. In embodiments in which (poly)ethylene glycol is used as the above-mentioned diol, the proportion of (poly)ethylene glycol to the total amount (total number of moles) of diols as monomer components of the polyester polymer is appropriately set to 1 mol% or more, preferably 10 mol% or more, more preferably 50 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more (for example, 95 to 100 mol%). By setting the amount of (poly)ethylene glycol used to a predetermined value or more, the polymer can be designed based on the properties of (poly)ethylene glycol. In other embodiments of the present invention, the proportion of (poly)ethylene glycol may be 95 mol% or less, 70 mol% or less, or 50 mol% or less. (Poly)ethylene glycol can be used alone or in combination of two or more types.

[0036] In embodiments of the present invention, dimer ol can be used as the diol. Dimer ol can be used alone or in combination of two or more types. In the embodiment in which dimerol is used as the diol described above, the proportion of dimerol to the total amount (total number of moles) of diol as a monomer component of the polyester polymer may be 1 mol% or more, for example, 10 mol% or more, 50 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more (for example, 95 to 100 mol%). Furthermore, in the embodiment of the present invention, the proportion of dimerol may be 95 mol% or less, 85 mol% or less, or 60 mol% or less. Furthermore, in the embodiment of the present invention, the diol used as a monomer component in the synthesis of the polyester polymer can be either a form containing dimerol or a form without dimerol. Furthermore, in embodiments of the present invention, the proportion of the dimerol may be 50 mol% or less (for example, less than 50 mol%), 30 mol% or less, 10 mol% or less, 3 mol% or less, or less than 1 mol%, and the diol used in the synthesis of the polyester polymer may substantially not contain dimerol.

[0037] The molecular weight of the diol described above is not particularly limited. In embodiments of the present invention, the molecular weight of the diol is suitable to be, for example, 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. In other embodiments of the present invention, the molecular weight of the diol is suitable to be 500 or less, and may be 300 or less, 150 or less, 100 or less, or 80 or less. In other embodiments of the present invention, the molecular weight of the diol is suitable to be 50 or more, and may be, for example, greater than 100. A suitable example of a diol having the above molecular weight is ethylene glycol. In other embodiments of the present invention, the molecular weight of the diol may be 150 or more, 200 or more, 250 or more, 350 or more, 450 or more, or 500 or more. A suitable example of a diol having such a molecular weight is dimer ol.

[0038] In this specification, the molecular weight of a diol may be the molecular weight calculated from its chemical formula. In embodiments using two or more diols, the molecular weight of the diol may be the sum of the products of the molecular weight and weight fraction of each diol.

[0039] The polyester polymers according to the embodiments of the present invention may be substantially composed of the dicarboxylic acid and diol described above, but other copolymer components other than dicarboxylic acid and diol may be copolymerized to the extent that the effects of the embodiments of the present invention are not impaired, for purposes such as introducing desired functional groups or adjusting molecular weight. Examples of such other copolymer components include polycarboxylic acids containing three or four or more carboxyl groups (trivalent or higher polycarboxylic acids such as trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, trimesic acid, trimeric acid, etc.), polyols containing three or four or more hydroxyl groups in one molecule (pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, adamantanetriol, etc.), monocarboxylic acids, monoalcohols, hydroxycarboxylic acids, lactones, etc. The above other copolymer components can be used individually or in combination of two or more. In embodiments of the present invention, the proportion of the above-mentioned other copolymer components is appropriately less than 10 mol%, for example, less than 3 mol%, less than 1 mol%, or less than 0.1 mol% of the monomer component of the polyester polymer. Embodiments of the present invention can preferably be carried out in a manner in which the monomer component of the polyester polymer substantially does not contain the above-mentioned other copolymer components.

[0040] In the monomer components used in the synthesis of the polyester polymer according to the embodiments of the present invention, the total proportion of dicarboxylic acid and diol is preferably 90 mol% or more, more preferably 95 mol% or more, more preferably 98 mol% or more, and even more preferably 99 mol% or more (for example, 99 to 100 mol%). Embodiments of the present invention are preferably carried out in a manner that uses a polyester polymer synthesized substantially from dicarboxylic acid and diol.

[0041] In a preferred embodiment of the present invention, the monomer component of the polyester polymer can be a combination of dimer acid as a dicarboxylic acid and (poly)ethylene glycol as a diol. The embodiments of the present invention are preferably carried out in an embodiment in which a polyester polymer synthesized using a combination of dimer acid and (poly)ethylene glycol is used. The total proportion of dimer acid and (poly)ethylene glycol in the total amount of monomer components of the polyester polymer is appropriately 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and may be 90 mol% or more (for example, 99 to 100 mol%).

[0042] The method for obtaining the polyester polymer according to the embodiment of the present invention is not particularly limited, and polymerization methods known as methods for synthesizing polyester polymers can be appropriately employed. For example, monomer raw materials used in the synthesis of the polyester polymer can be those formulated so that the amount of dicarboxylic acid is 0.95 to 1.05 equivalents (preferably 0.98 to 1.02 equivalents) per equivalent of diol. By formulating dicarboxylic acid and diol in the above proportions, high molecular weight polyester polymers can be easily obtained. Furthermore, by setting the molar ratio of dicarboxylic acid to diol within an appropriate range, a suitable crosslinked structure (for example, crosslinking based on reaction with a crosslinking agent such as an isocyanate-based crosslinking agent) can be obtained to adjust the cohesive force. When using a polycarboxylic acid containing three or four or more carboxyl groups and / or a polyol containing three or four or more hydroxyl groups, the above preferred equivalent can be appropriately adjusted depending on the valency of the polycarboxylic acid and / or polyol used.

[0043] In embodiments of the present invention, the molar ratio of dicarboxylic acid and diol used as monomer components in the synthesis of polyester polymers is not particularly limited, and an appropriate molar ratio can be set considering the desired polymer properties and synthesizability. In embodiments of the present invention, the ratio of the number of moles A1 of dicarboxylic acid and the number of moles A2 of diol used as monomer components (molar ratio A1 / A2) may be 10 / 90 or more, or 30 / 70 or more. In some preferred embodiments, the above molar ratio (A1 / A2) is 50 / 50 or more, more preferably 60 / 40 or more, even more preferably 70 / 30 or more, and may also be 80 / 20 or more, or 90 / 10 or more. For example, by increasing the molar ratio of dicarboxylic acid as described above, properties based on dicarboxylic acid (e.g., isophthalic acid, terephthalic acid, and orthophthalic acid) can be suitably expressed. Also, the above molar ratio (A1 / A2) may be, for example, 95 / 5 or less, or 85 / 15 or less. In embodiments of the present invention, from the viewpoint of suitably exhibiting properties based on diols, the above molar ratio (A1 / A2) may be 75 / 25 or less, or 50 / 50 or less (for example, 30 / 70 or less). When using polycarboxylic acids containing three or four or more carboxyl groups and / or polyols containing three or four or more hydroxyl groups, the above molar ratio can be appropriately adjusted depending on the valency of the polycarboxylic acid and / or polyol used.

[0044] In embodiments of the present invention, polyester polymers can be obtained by polycondensation of a dicarboxylic acid and a diol, similar to general polyesters. More specifically, polyester polymers can be synthesized by carrying out the reaction between the carboxyl group of the dicarboxylic acid and the hydroxyl group of the diol, while removing the water (product water) typically generated by the above reaction from the reaction system. Methods for removing the product water from the reaction system include blowing an inert gas into the reaction system and removing the product water along with the inert gas, azeotropic dehydration using a reaction water discharge solvent such as toluene or xylene, or distillation of the product water from the reaction system under reduced pressure (reduced pressure method).

[0045] The reaction temperature and reaction time when carrying out the above reactions (including esterification and polycondensation), and the degree of reduced pressure (pressure within the reaction system) when employing a reduced pressure method, can be appropriately set so that a polyester polymer with the desired properties (e.g., molecular weight) can be efficiently obtained. Although not particularly limited, it is generally appropriate to set the reaction temperature to 150°C or higher (e.g., 180°C to 260°C). By setting the reaction temperature within this range, a good reaction rate can be obtained, productivity can be improved, and degradation of the resulting polyester polymer can be easily prevented or suppressed. The reaction time is not particularly limited and may be 3 to 48 hours (e.g., 10 to 30 hours). When employing a reduced pressure method, although not particularly limited, it is generally appropriate to set the degree of reduced pressure to 10 kPa or less (e.g., 10 kPa to 0.1 kPa), for example, 4 kPa to 0.1 kPa. By setting the pressure within the reaction system within this range, the water produced by the reaction can be efficiently distilled out of the system, making it easier to maintain a good reaction rate. Furthermore, when the reaction temperature is relatively high, maintaining the pressure within the reaction system above the lower limit makes it easier to prevent the removal of the starting materials, such as dicarboxylic acids and diols, from the system. From the viewpoint of maintaining stable pressure within the reaction system, it is usually appropriate to set the pressure within the reaction system to 0.1 kPa or higher.

[0046] As with the synthesis of general polyesters, known or conventional catalysts can be used in appropriate amounts for esterification and condensation in the above reaction. Examples of such catalysts include various metal compounds such as titanium, germanium, antimony, tin, and zinc; and strong acids such as p-toluenesulfonic acid and sulfuric acid. The amount of catalyst used can be appropriately determined according to the reaction rate, etc., so a detailed explanation is omitted here.

[0047] In the above process of synthesizing a polyester polymer by reaction of a dicarboxylic acid and a diol, a solvent may or may not be used. The above synthesis can be carried out substantially without the use of organic solvents (for example, excluding the intentional use of organic solvents as reaction solvents in the above reaction). Synthesizing a polyester polymer substantially without the use of organic solvents in this way, and preparing a polyester adhesive layer using such a polyester polymer, is preferable as it meets the requirement to minimize the use of organic solvents in the manufacturing process.

[0048] Furthermore, since there is generally a correlation between the molecular weight of the synthesized polyester polymer and the viscosity of the reaction system during the above reaction, this 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 meets the target molecular weight.

[0049] The weight-average molecular weight (Mw) of the polyester polymer is preferably 20,000 to 150,000. In embodiments of the present invention, the Mw of the polyester polymer is more preferably 30,000 or more, even more preferably more than 50,000, and from the viewpoint of obtaining better properties, even more preferably more than 60,000, particularly preferably more than 70,000, even more preferably more than 80,000, most preferably more than 90,000, and may also be 95,000 or more. By using a polyester polymer with an Mw of a predetermined value or higher, it is easier to obtain an adhesive layer with high cohesive strength. In preferred embodiments of the present invention, the Mw of the polyester polymer can be 100,000 or more (for example, more than 100,000), may be 110,000 or more, and may also be 115,000 or more. By using a high molecular weight polyester polymer in this way, even adhesive compositions that tend to have low viscosity due to containing a predetermined amount or more of tackifying resin can easily obtain an appropriate viscosity and form a thin adhesive layer of good quality. Such adhesive compositions do not need to be excessively concentrated, and even compositions containing a crosslinking agent tend to have a sufficient pot life and are easy to handle. From the viewpoint of adhesive strength and other factors, the upper limit of Mw of the polyester polymer in the embodiments of the present invention is more preferably 130,000 or less, even more preferably 100,000 or less, and particularly preferably 50,000 or less.

[0050] In this specification, Mw of polyester polymers refers to the value obtained by GPC (gel permeation chromatography) on a standard polystyrene basis. As a GPC apparatus, for example, the model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used. More specifically, GPC measurements can be performed under the following conditions. The same method is used in the examples described later. [GPC measurement] Column: TSKgelGMH-H(S) Column temperature: 40℃ Eluent: THF (with 0.1% by weight of amine-based components added) Flow rate: 0.5mL / min Injection volume: 100μL Detector: Differential refractometer (RI) Standard sample: Polystyrene (PS)

[0051] In embodiments of the present invention, the glass transition temperature (Tg) of the polyester polymer is -10 to 10°C. If the Tg of the polyester polymer is below -10°C, the bulk strength of the adhesive may be weakened, and if it exceeds 10°C, the adhesion strength of the adhesive interface may be insufficient. The Tg of the polyester polymer is preferably -5°C or higher, more preferably 0°C or higher, and even more preferably 5°C or higher. Furthermore, it is preferably 8°C or lower, more preferably 5°C or lower, and even more preferably 0°C or lower.

[0052] In this specification, the Tg of polyester polymers is measured by the following method. Specifically, approximately 3 to 10 mg of the polymer is weighed into an aluminum open cell, and the reversing heat flow (specific heat component) behavior of the homopolymer is obtained using a temperature-modulated DSC (product name "Q-2000," manufactured by T.A. Instruments Corporation) at a heating rate of 10°C / min under a nitrogen atmosphere of 50 ml / min. Referring to JIS-K-7121, the temperature at which a line equidistant in the vertical direction from the line extending from the low-temperature baseline and high-temperature baseline of the obtained reversing heat flow intersects with the curve of the stepwise transition portion of the glass transition is defined as the Tg of the polymer.

[0053] The Tg of polyester polymers tends to increase with increasing the proportion of aromatic monomers, for example, and decrease with increasing the proportion of aliphatic monomers.

[0054] (Adhesive-granting resin) In embodiments of the present invention, the adhesive layer may include a tackifying resin. Even with a composition containing a tackifying resin, the adhesive layer according to the embodiments of the present invention can have a predetermined 23°C storage modulus. Furthermore, by using an appropriate amount of tackifying resin, the adhesive strength-improving effect based on the tackifying resin can be effectively exerted, and adhesive properties such as adhesive strength can be favorably improved. As the tackifying resin, various tackifying resins such as rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins can be used. Such tackifying resins can be used individually or in combination of two or more. In polyester-based adhesive layers, for example, rosin-based tackifying resins and terpene-based tackifying resins are preferably used.

[0055] Specific examples of rosin-based tackifying resins include unmodified rosins (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins; the same applies hereinafter); and various other rosin derivatives. Examples of the above rosin derivatives include rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., rosin esters) and modified rosin with alcohols (i.e., modified rosin esters); unsaturated fatty acid modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid modified rosins, or unsaturated fatty acid modified rosin esters; metal salts of rosins (especially rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; and rosinphenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and then thermal polymerization.

[0056] While not particularly limited, specific examples of rosin esters include esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl esters, triethylene glycol esters, glycerol esters, pentaerythritol esters, and the like.

[0057] Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; and modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.). A terpene-based tackifying resin may be a homopolymer of one type of terpene, or a copolymer of two or more types of terpenes. An example of the above-mentioned modified terpene resin is terpenephenol resin.

[0058] Terpene phenol resins refer to polymers containing terpene residues and phenol residues, and the concept encompasses both copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins) and phenol-modified terpenes or their homopolymers or copolymers (phenol-modified terpene resins). Suitable examples of terpenes constituting such terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-isomers, l-isomers, and d / l-isomers (dipentene)). Hydrogenated terpene phenol resins refer to hydrogenated terpene phenol resins having a structure obtained by hydrogenating such terpene phenol resins. They are sometimes also called hydrogenated terpene phenol resins.

[0059] In embodiments of the present invention, it is preferable that the content of the tackifying resin is 4 parts or less when the total weight of the adhesive layer is 100 parts by weight.

[0060] (Crosslinking agent) In embodiments of the present invention, the adhesive layer may contain a crosslinking agent. An adhesive layer containing a crosslinking agent can enhance cohesive force based on the crosslinked structure obtained by using the crosslinking agent. By using a crosslinking agent, the storage modulus at 23°C can be adjusted while maintaining good adhesive properties. The crosslinking agent may be included in the adhesive layer in the form after the crosslinking reaction, the form before the crosslinking reaction, a partially crosslinked form, or intermediate or complex forms therebetween. The above-mentioned crosslinking agent is usually included in the adhesive layer exclusively in the form after the crosslinking reaction. Furthermore, the crosslinking agent used for crosslinking polyester polymers may also function as a chain extender. Moreover, the polycarboxylic acids containing three or four or more carboxyl groups, and the polyols containing three or four or more hydroxyl groups mentioned above are not included in the crosslinking agents as defined herein.

[0061] The type of crosslinking agent is not particularly limited and can be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agent can be used alone or in combination of two or more types. Among these, isocyanate-based crosslinking agents and epoxy-based crosslinking agents, as well as combinations thereof, are preferred.

[0062] As isocyanate crosslinking agents, polyfunctional isocyanate compounds can be preferably used. Here, a polyfunctional isocyanate compound refers to a compound having an average of two or more isocyanate groups per molecule, and includes those having an isocyanurate structure. Isocyanate crosslinking agents can be used individually or in combination of two or more.

[0063] 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; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; and 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, and the like.

[0064] Specific examples of alicyclic polyisocyanate compounds include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0065] 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, and 2,2'-diphenylpropane-4,4'-diisocyanate. Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0066] Examples of polyfunctional isocyanates include polyfunctional isocyanate compounds having an average of two or three or more isocyanate groups per molecule. Such polyfunctional isocyanate compounds may be macromers of bifunctional or trifunctional or more isocyanates (e.g., dimers or trimers), derivatives (e.g., addition reaction products of polyhydric alcohols and two or more polyfunctional isocyanates), polymers, etc. Examples of polyfunctional isocyanate compounds include dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimeric adducts of isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and other polyfunctional isocyanate compounds. Examples of commercially available polyfunctional isocyanate compounds include "Duranate TPA-100," "Duranate D101," and "Duranate D201" from Asahi Kasei Chemicals Corporation, "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096" from Tosoh Corporation, and "Takenate D-101E," "Takenate D-127N," and "Takenate D-131N" from Mitsui Chemicals, Inc.

[0067] Furthermore, polyfunctional epoxy compounds can preferably be used as epoxy crosslinking agents. Here, a polyfunctional epoxy compound refers to a compound having an average of two or more epoxy groups per molecule. Epoxy crosslinking agents can be used individually or in combination of two or more. Examples of commercially available polyfunctional epoxy compounds include "TETRAD-C," manufactured by Mitsubishi Gas Chemical Company, Inc.

[0068] In embodiments of the present invention, a crosslinking agent without an aromatic ring (aromatic ring-free crosslinking agent) is preferably used as the crosslinking agent. For example, among the isocyanate-based crosslinking agents described above, the use of an isocyanate compound without an aromatic ring is preferred. By using an aromatic ring-free isocyanate compound as the crosslinking agent, the degree of crosslinking can be effectively increased with less crosslinking inhibition in an adhesive layer containing a polyester polymer. A suitable example of the above aromatic ring-free isocyanate is an aliphatic isocyanate compound.

[0069] In embodiments of the present invention, two or more crosslinking agents with different numbers of functional groups (preferably isocyanate-based crosslinking agents) may be used, from the viewpoint of achieving a good balance of multiple adhesive properties. The above-mentioned functional group refers to a crosslinking reactive group, and for example, in the polyfunctional isocyanate-based compound described above, it refers to an isocyanate group. For example, one embodiment may be used in combination with one or more difunctional crosslinking agents and one or more trifunctional or higher crosslinking agents (for example, trifunctional crosslinking agents).

[0070] The amount of crosslinking agent used is not particularly limited. In embodiments of the present invention, the amount of crosslinking agent (e.g., isocyanate-based crosslinking agent) used per 100 parts by weight of polyester polymer can be 0.005 parts by weight or more from the viewpoint of improving cohesive strength while having a 23°C storage modulus, for example, it may be 0.01 parts by weight or more, or 0.1 parts by weight or more, and from the viewpoint of improving cohesive strength, it is appropriate to use 0.5 parts by weight or more, preferably 1 part by weight or more. From the viewpoint of appropriately adjusting cohesive strength, and from the viewpoint of appropriately adjusting crosslink density and cohesive strength, in embodiments of the present invention, the amount of crosslinking agent used per 100 parts by weight of polyester polymer can be 5 parts by weight or less, more preferably 4 parts by weight or less, even more preferably 3 parts by weight or less, particularly preferably 2.5 parts by weight or less, and may be 2.0 parts by weight or less, or 1.6 parts by weight or less.

[0071] The amount of aromatic ring-free crosslinking agent used is not particularly limited. In embodiments of the present invention, the amount of aromatic ring-free crosslinking agent (e.g., aliphatic isocyanate compound) used per 100 parts by weight of polyester polymer can be 0.005 parts by weight or more, for example, 0.01 parts by weight or more, or 0.1 parts by weight or more. From the viewpoint of improving cohesiveness, it is appropriate to use 0.5 parts by weight or more, preferably 1 part by weight or more. From the viewpoint of improving cohesiveness while having an appropriate 23°C storage modulus, in embodiments of the present invention, the amount of aromatic ring-free crosslinking agent used per 100 parts by weight of polyester polymer can be 1.2 parts by weight or more, more preferably 1.5 parts by weight or more, even more preferably 1.8 parts by weight or more, for example, 2.5 parts by weight or more. Also, in embodiments of the present invention, the amount of aromatic ring-free crosslinking agent used per 100 parts by weight of polyester polymer may be 10 parts by weight or less, for example, 7 parts by weight or less. From the viewpoint of obtaining an adhesive layer having a storage modulus at 23°C of less than or equal to a predetermined value, and from the viewpoint of appropriately adjusting the cohesive force, in embodiments of the present invention, the amount of aromatic ring-free crosslinking agent used per 100 parts by weight of polyester polymer can be 5 parts by weight or less, more preferably 4 parts by weight or less, even more preferably 3 parts by weight or less, and particularly preferably 2.5 parts by weight or less, and may also be 2.0 parts by weight or less, or 1.6 parts by weight or less.

[0072] (Crosslinking catalyst) In embodiments of the present invention, it is preferable to use a crosslinking catalyst in addition to the above crosslinking agent to more effectively advance the crosslinking reaction. Examples of crosslinking catalysts include zirconium-containing compounds such as zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethylacetoacetate, and zirconium octoate compounds (zirconium-based catalysts); tin (Sn)-containing compounds such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, trimethyltin hydroxide, and butyltin oxide (tin-based catalysts); and aluminum secondary butoxides. Examples of organometallic catalysts include aluminum-containing compounds such as aluminum trisacetylacetonate, aluminum bisethylacetoacetate, and aluminum trisethylacetoacetate (aluminum-based catalysts); iron-containing compounds such as ferric narsem (iron-based catalysts); and titanium-containing compounds such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetraoctyl titanate, titanium acetylacetonate, titanium tetraacetylacetonate, and titanium ethylacetoacetate (titanium-based catalysts). Crosslinking catalysts can be used individually or in combination of two or more.

[0073] While not particularly limited, in embodiments of the present invention, it is preferable to use a tin-containing compound with high catalytic activity as the crosslinking catalyst. Alternatively, in other embodiments of the present invention, a non-tin compound may be used as the crosslinking catalyst from the viewpoint of environmental impact and safety. In such embodiments, the crosslinking catalyst does not need to substantially contain a tin-containing compound. Furthermore, in embodiments of the present invention, the crosslinking catalyst may not contain an iron-based catalyst. For example, in usage embodiments where transparency and optical properties are required for the adhesive layer, discoloration of the adhesive layer can be prevented or suppressed by avoiding the use of iron-based compounds.

[0074] The amount of crosslinking catalyst used is not particularly limited. The amount of crosslinking catalyst used can be, for example, 0.001 parts by weight or more per 100 parts by weight of polyester polymer, with 0.01 parts by weight or more being appropriate. Alternatively, the amount of crosslinking catalyst used can be, for example, 3 parts by weight or less per 100 parts by weight of polyester polymer, with 1 part by weight or less being appropriate, and it may also be 0.3 parts by weight or less, or even 0.1 parts by weight or less.

[0075] (Hydrolysis-resistant agent) Furthermore, the adhesive layer according to the embodiment of the present invention may contain a hydrolysis-resistant agent (also called a hydrolysis inhibitor). By adding a hydrolysis-resistant agent, hydrolysis reactions in the adhesive layer are suppressed, and good durability is easily obtained. The hydrolysis-resistant agent is not particularly limited, and known or conventional hydrolysis-resistant agents can be used. Examples include oxazoline group-containing compounds, epoxy group-containing compounds, and carbodiimide group-containing compounds. Among these, carbodiimide group-containing compounds are preferred. The hydrolysis-resistant agent can be used alone or in combination of two or more types.

[0076] Examples of carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and monofunctional cyclic carbodiimides. Here, a monofunctional cyclic carbodiimide is a compound having one carbodiimide group in its molecular structure, in which the first and second nitrogen atoms of the carbodiimide group are bonded by a bonding group composed of an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. The above bonding group may also include heteroatoms and substituents. Preferred examples of carbodiimide group-containing compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, and monofunctional cyclic carbodiimides.

[0077] The amount of hydrolysis-resistant agent (preferably a carbodiimide group-containing compound) used is not particularly limited, but it is appropriate to use 0.05 parts by weight or more per 100 parts by weight of polyester polymer, preferably 0.1 parts by weight or more, and for example, 0.3 parts by weight or more, so that the effect of containing the hydrolysis-resistant agent is preferably expressed. The upper limit of the amount of hydrolysis-resistant agent used is appropriately 5 parts by weight or less per 100 parts by weight of polyester polymer, preferably 3 parts by weight or less, and for example, 1 part by weight or less.

[0078] (Other additives) In addition to the components described above, the adhesive layer may contain, as needed, various additives common in the field of adhesives, such as leveling agents, fillers, plasticizers, softeners, colorants (pigments, dyes, etc.), antistatic agents, anti-aging agents, UV absorbers, antioxidants, and light stabilizers. These additives can be conventionally used by established methods and do not particularly characterize the present invention; therefore, a detailed explanation is omitted.

[0079] (Formation of the adhesive layer) The adhesive layer according to the embodiment of the present invention can be formed by conventionally known methods, for example, using the polyester polymer described above. For example, an adhesive layer can be formed on a surface by applying an adhesive composition to a release surface and then curing the adhesive composition. An adhesive layer formed in this manner can be used as a substrate-less double-sided adhesive sheet. In the case of an adhesive sheet with a substrate, a method of forming the adhesive layer by directly applying (typically coating) the adhesive composition to the substrate and curing it (direct method) can be preferably employed. Alternatively, a method of forming an adhesive layer on a release surface by applying an adhesive composition to a release surface and curing it, and then transferring the adhesive layer to the substrate (transfer method), may be employed. As the release surface, the surface of a release liner or the back surface of a substrate that has undergone a release treatment can be used. Furthermore, the curing of the adhesive composition can be performed by subjecting the adhesive composition to a curing treatment such as drying, crosslinking, polymerization, or cooling. Two or more curing treatments may be performed simultaneously or in stages. The adhesive composition is not particularly limited, but from the viewpoint of adhesive properties, a solvent-type adhesive composition containing the adhesive in an organic solvent is preferred. As the organic solvent, organic solvents such as toluene, ethyl acetate, methyl ethyl ketone, methylcyclohexane, cyclohexane, xylene, and butyl acetate can be used. Among these, the use of ethyl acetate is preferred. The adhesive layer according to the embodiment of the present invention is typically formed continuously, but is not limited to this form, and may be formed in regular or random patterns such as dots or stripes, for example.

[0080] The adhesive composition can be applied using known or conventional coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, die coaters, bar coaters, knife coaters, and spray coaters. Alternatively, the adhesive composition may be applied by impregnation or curtain coating methods. The adhesive composition can be dried at room temperature or under heating. From the viewpoint of promoting the crosslinking reaction and improving manufacturing efficiency, it is preferable to dry the adhesive composition under heating. The drying temperature can be, for example, 40 to 150°C, and is usually preferably 40 to 130°C. After drying the adhesive composition, it is preferable to perform aging for the purpose of adjusting the migration of components within the adhesive layer, promoting the crosslinking reaction, and alleviating any strain that may exist within the adhesive layer. The aging conditions are not particularly limited, and can usually be 70°C or lower (for example, 40 to 70°C) and for one day or more (for example, three days or more).

[0081] (Total thickness of the adhesive layer) The total thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose. A total thickness of 50 to 400 μm is preferred. A total thickness of 30 μm or more is more preferred, 50 μm or more is even more preferred, and 80 μm or more is particularly preferred. Furthermore, 250 μm or less is more preferred, 150 μm or less is even more preferred, and 100 μm or less is particularly preferred.

[0082] In this specification, the total thickness of the adhesive layer refers to the sum of the thicknesses of the adhesive layers contained in the adhesive sheet. That is, if the adhesive sheet has only one adhesive layer, the thickness of that adhesive layer is considered the total thickness of the adhesive layer. On the other hand, if the adhesive sheet has two or more adhesive layers, the sum of the thicknesses of each adhesive layer is considered the total thickness of the adhesive layer.

[0083] <Base material> An adhesive sheet according to an embodiment of the present invention may have a base material. An adhesive sheet according to an embodiment of the present invention may be in the form of an adhesive sheet with a base material having an adhesive layer on one or both sides of the base material. Various sheet-like base materials can be used as the base material, for example, resin films, paper, cloth, rubber sheets, foam sheets, metal foils, composites thereof, etc. In the field of electronic equipment, base materials that are less likely to become a source of dust (for example, fine fibers or particles such as paper dust) may be preferably used. From this viewpoint, base materials that do not contain fibrous materials such as paper or cloth are preferred, and for example, resin films, rubber sheets, foam sheets, metal foils, composites thereof, etc., can be preferably used.

[0084] Examples of resin films include polyester film; polyvinyl chloride resin film; polyolefin films such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer; vinylidene chloride resin film; vinyl acetate resin film; polystyrene film; polyacetal film; polyurethane film; polyimide film; polyamide film; fluororesin film; cellophane; and others. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of foamed sheets include foamed polyurethane sheets and foamed polyolefin sheets. Examples of metal foils include aluminum foil and copper foil.

[0085] As the above-mentioned substrate, resin film is preferred. Resin film is preferably used as a material that is excellent in dimensional stability, thickness accuracy, economy (cost), processability, and tensile strength. In this specification, "resin film" is typically a non-porous film and is a concept distinct from so-called nonwoven fabrics or woven fabrics.

[0086] In embodiments of the present invention, a polyester film may be preferably used as the base material from the viewpoint of strength and processability. Examples of polyester films include polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, polyethylene naphthalate (PEN) film, and polybutylene naphthalate film.

[0087] Alternatively, in embodiments of the present invention, among the above-mentioned substrates, PET film, polyolefin film, polyurethane film, or polyimide film is preferred, and PET film is more preferred.

[0088] The substrate may be transparent, or it may have light-shielding or light-reducing properties. In embodiments of the present invention, the substrate (e.g., a resin film) may contain a coloring agent. This allows for adjustment of the light transmittance (light-shielding properties) of the substrate. Adjusting the light transmittance (e.g., vertical light transmittance) of the substrate can also be useful in adjusting the light transmittance of the substrate, and further, the light transmittance of the adhesive sheet containing the substrate.

[0089] As a coloring agent, conventionally known pigments and dyes can be used, similar to the coloring agents 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, etc.

[0090] The substrate may be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In a substrate having a base film and a colored layer, the base film may or may not contain a coloring agent. The colored layer may be disposed on either one surface of the base film, or on both surfaces. In a configuration where colored layers are disposed on both surfaces of the base film, the composition of these colored layers may be the same or different. By arranging the colored layer, the color and transparency of the adhesive sheet can be adjusted to obtain the desired design, light-shielding properties, and opacity. The color of the colored layer is not particularly limited, and various colors can be used depending on the purpose. In embodiments of the present invention, the colored layer may be, for example, a black layer formed by black printing (e.g., a black printed layer).

[0091] The colored layer can be formed, for example, by applying a colored layer-forming composition containing a colorant and a binder to a base film. Any material known in the field of paints or printing can be used as the binder without particular limitations. Examples include polyurethane, phenolic resin, epoxy resin, urea-melamine resin, and polymethyl methacrylate. The colored layer-forming composition may be solvent-based, UV-curable, or thermosetting. The colored layer can be formed using any conventional method used for colored layer formation without particular limitations. For example, a method of forming the colored layer (printed layer) by printing, such as gravure printing, flexographic printing, or offset printing, can be preferred.

[0092] The colored layer may be a single-layer structure consisting of one layer, or it may be a multilayer structure including two, three or more sub-colored layers. A multilayer colored layer including two or more sub-colored layers can be formed, for example, by repeatedly applying (e.g., printing) a colored layer-forming composition. The color and amount of colorant contained in each sub-colored layer may be the same or different. For colored layers intended to provide light-shielding properties, a multilayer structure is particularly beneficial from the viewpoint of preventing the occurrence of pinholes and improving the reliability of light leakage prevention.

[0093] For coloring the colored layer, known pigments and dyes can be appropriately selected according to the desired color. While not particularly limited, examples of white pigments include titanium dioxide, zinc oxide, and lead white. Examples of black pigments include carbon black, acetylene black, pine soot, and graphite. These can be used individually or in combination of two or more.

[0094] The amount of coloring agent is set according to the required color and light transmittance, and is not limited to a specific range, but it is appropriate to have 1% by weight or more in the colored layer, preferably 2% by weight or more (for example, 5% by weight or more), and may be 15% by weight or more. Furthermore, it is appropriate to have 65% by weight or less of the above coloring agent, preferably 30% by weight or less (for example, 15% by weight or less), and may be 8% by weight or less.

[0095] The overall thickness of the colored layer is usually appropriate to be 0.1 μm or more, preferably 0.5 μm or more, and more preferably 0.7 μm or more. The overall thickness of the colored layer may also be 0.8 μm or more, or 1 μm or more. In embodiments of the present invention, from the viewpoint of obtaining sufficient light shielding, the overall thickness of the colored layer may be 2 μm or more (for example, 3 μm or more), or 4 μm or more. Furthermore, the overall thickness of the colored layer is usually appropriate to be 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. In embodiments of the present invention, the overall thickness of the colored layer can be 3 μm or less, and even more preferably 2 μm or less. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is usually preferably 0.5 μm to 2 μm.

[0096] The surface of the substrate (e.g., resin film, rubber sheet, foam sheet, etc.) on which the adhesive layer is placed (adhesive layer side surface) may be subjected to known or conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or formation of an undercoat layer. Such surface treatments may be treatments to improve the adhesion between the substrate and the adhesive layer, in other words, the anchoring ability of the adhesive layer to the substrate. Alternatively, the substrate may not have any surface treatment applied to the adhesive layer side surface to improve anchoring ability. When forming an undercoat layer, the undercoat agent (primer) used for 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, greater than 0.01 μm, usually 0.1 μm or more is appropriate, and may be 0.2 μm or more from the viewpoint of enhancing the effect. Furthermore, the thickness of the undercoat layer is preferably less than 1.0 μm, may be 0.7 μm or less, or 0.5 μm or less. A thickness of less than 1.0 μm for the undercoat layer is preferable because it stabilizes the undercoat layer, which in turn stabilizes the adhesive properties of the adhesive sheet.

[0097] In the case of a single-sided adhesive sheet in which an adhesive layer is provided on one side of the substrate, the non-adhesive side (back side) of the substrate may be treated with a release agent (backside treatment agent). The backside treatment agent that can be used to form the backside treatment layer is not particularly limited, and silicone-based backside treatment agents, fluorine-based backside treatment agents, long-chain alkyl-based backside treatment agents, and other known or conventional treatment agents can be used depending on the purpose and application. The backside treatment agent can be used alone or in combination of two or more types.

[0098] The substrate (e.g., resin film substrate) may contain various additives as needed, such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.). The proportion of each additive is usually 30% by weight or less, but may also be 20% by weight or less, or 10% by weight or less. For example, when the substrate contains a pigment (e.g., white pigment), its content is appropriately 0.1 to 10% by weight (e.g., 1 to 8% by weight or 1 to 5% by weight).

[0099] The thickness of the substrate is not particularly limited and can be appropriately selected depending on the purpose, but for example it can be greater than 0 μm and less than or equal to 150 μm. From the viewpoint of handling the substrate, the thickness of the substrate may be, for example, 1.5 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 4.5 μm or more. Furthermore, from the viewpoint of thinning the adhesive sheet, in the embodiments of the present invention, the thickness of the substrate may be, for example, 100 μm or less, 50 μm or less, 25 μm or less, 20 μm or less, 10 μm or less, 7 μm or less, less than 5 μm, or less than 4 μm.

[0100] <Removable Liner> An adhesive sheet according to an embodiment of the present invention may have the form of an adhesive sheet with a release liner, having a release liner (e.g., a first release liner) disposed on the surface (adhesive surface, e.g., first adhesive surface) of the adhesive layer. The above-mentioned release liner (including the first release liner and the second release liner; the same applies hereinafter unless otherwise specified) is not particularly limited, and for example, one having a release treatment layer on a release liner substrate may be preferably used. The above-mentioned release treatment layer may be formed by surface treating the release liner substrate with a release treatment agent. The release treatment agent may be a known release treatment agent such as a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, a fluorine-based release treatment agent, or molybdenum(IV) sulfide. In embodiments of the present invention, a release liner having a release treatment layer made of a silicone-based release treatment agent may be preferably used. The effect of suppressing the reduction of adhesive strength according to embodiments of the present invention can be effectively exhibited in a manner in which a release liner having a release treatment layer formed of a silicone-based release treatment agent is used. The thickness and formation method of the release layer are not particularly limited and can be set so that appropriate release properties are exhibited on the adhesive side surface of the release liner.

[0101] Various plastic films can be used as the release liner substrate. In this specification, a plastic film is typically a non-porous sheet and is distinct from, for example, nonwoven fabrics (i.e., does not include nonwoven fabrics). Preferably, a resin film having a non-porous structure and typically being substantially void-free can be used as the release liner substrate. The resin film may have a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure).

[0102] Examples of materials for the above-mentioned plastic film include polyester resins such as PET, PBT, and PEN; polyolefin resins such as PE, PP, ethylene-propylene copolymer, and ethylene-butene copolymer; cellulose resins such as triacetylcellulose; acetate resins; polysulfone resins; polyethersulfone resins; polycarbonate resins; polyamide resins; polyimide resins; norbornene resins; cyclic polyolefin resins; (meth)acrylic resins; polyvinyl chloride resins; polyvinylidene chloride resins; polystyrene resins; polyvinyl alcohol resins; ethylene-vinyl acetate copolymer resins; ethylene-vinyl alcohol copolymer resins; polyarylate resins; and polyphenylene sulfide resins. A peel liner substrate formed from any one or a mixture of two or more of these resins can be used. Among these, a polyester resin film (e.g., PET film) formed from a polyester resin is a preferred peel liner substrate.

[0103] The plastic film used as the peel-off liner substrate described above may be an unoriented film, a uniaxially oriented film, or a biaxially oriented film. Furthermore, the plastic film may have a single-layer structure or a multilayer structure including two or more sublayers. The plastic film may contain known additives that can be used in peel-off liner substrates, such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, UV absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, slip agents, antiblocking agents, and nucleating agents. In a multilayer plastic film, each additive may be incorporated into all sublayers or into only some of the sublayers.

[0104] The release liner as a component of the adhesive sheet with a release liner may be the release liner used during the manufacture of the adhesive sheet, that is, the release liner as a component of the adhesive sheet with a release liner immediately after manufacture, or it may be a release liner (replacement liner) that has been replaced from the original release liner (the release liner at the time of manufacture) before the adhesive sheet is attached to the substrate, or another replacement liner that has been replaced from one replacement liner to another. Therefore, the adhesive sheet according to the embodiment of the present invention may be used in a manner in which the release liner is replaced (re-attached) to another release liner (replacement liner) as desired before being attached to the substrate. According to the embodiment of the present invention, even if the release liner is replaced before attachment to the substrate, and the release agent is handled in a way that makes it easy for the release agent to migrate from the release liner before and after replacement to the adhesive layer and accumulate on the adhesive surface, it is possible to suppress the decrease in adhesive strength caused by the migration of the release agent. Therefore, whether the release liner protecting the adhesive surface of the adhesive sheet is the original release liner from the time of manufacture or a replaced release liner, it is possible to suppress the decrease in adhesive strength and maintain the desired adhesive strength. As a replacement liner, one with the same configuration (material, thickness, etc.) as the release liner before replacement may be used, or one with a different configuration may be used.

[0105] The thickness of the release liner is not particularly limited and may be, for example, 10 μm to 500 μm. From the viewpoint of the strength and dimensional stability of the release liner, it is appropriate for the thickness of the release liner to be 20 μm or more, preferably 30 μm or more, and it may also be 40 μm or more, 50 μm or more, 60 μm or more, or 70 μm or more. By protecting the adhesive surface with a release liner of sufficient thickness, the smoothness of the adhesive surface is easily maintained. Also, from the viewpoint of the handling of the release liner (e.g., ease of winding), it is appropriate for the thickness of the release liner to be 300 μm or less, preferably 200 μm or less, and it may also be 150 μm or less, or 100 μm or less. By setting the thickness of the release liner to a predetermined value or less, removal from the double-sided adhesive sheet is made smoother. The thicknesses of the first release liner and the second release liner may be the same or different.

[0106] <Total thickness of adhesive sheet> The thickness (total thickness) of the adhesive sheet (including an adhesive layer, and in the case of an adhesive sheet with a substrate, further including a substrate, but not including a release liner) according to the embodiments of the present invention is not particularly limited and can be in the range of 2 μm to 1000 μm, for example. In embodiments of the present invention, the thickness of the adhesive sheet is preferably 5 μm to 500 μm, taking into consideration adhesive properties, etc., and may be, for example, 300 μm or less, or 200 μm or less. From the viewpoint of making products to which the adhesive sheet is applied (e.g., portable electronic devices) lighter, smaller, thinner, and more functional, in embodiments of the present invention the thickness of the adhesive sheet can be 300 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and still more preferably 100 μm or less, for example, 30 μm or less, or 25 μm or less. In other embodiments of the present invention, the thickness of the adhesive sheet may be less than 20 μm, less than 15 μm, less than 10 μm, or 5 μm or less. The minimum thickness of the adhesive sheet is not particularly limited, but is usually appropriate to be 3 μm or more. For example, it may be 5 μm or more, and from the viewpoint of productivity, it may be 10 μm or more, or 15 μm or more (for example, 18 μm or more).

[0107] <Characteristics of the adhesive layer and adhesive sheet> (Swelling rate of the adhesive layer relative to isopropyl alcohol) In embodiments of the present invention, the swelling rate of the adhesive layer with respect to isopropyl alcohol is 2,000 wt% or less. If the swelling rate of the adhesive layer with respect to isopropyl alcohol exceeds 2,000 wt%, it may cause a decrease in bulk strength due to volume swelling and a decrease in adhesion due to seepage to the interface.

[0108] The swelling rate of the adhesive layer with respect to isopropyl alcohol is preferably 2000 wt% or less, more preferably 1800 wt% or less, and even more preferably 1500 wt% or less. On the other hand, a lower swelling rate of the adhesive layer with respect to isopropyl alcohol is preferable, and there is no particular lower limit, but for example, it can be 100 wt% or more, 200 wt% or more, or 300 wt% or more.

[0109] In this specification, the swelling rate of the adhesive layer with respect to isopropyl alcohol can be measured by the following method. Specifically, 0.1 g of the adhesive layer is weighed out, and only the adhesive layer is removed. The weight of the removed adhesive layer is denoted as WS1. This adhesive layer is wrapped in a drawstring shape with a porous polytetrafluoroethylene membrane having an average pore size of 0.2 μm, a porosity of 75%, and a thickness of 85 μm, and the opening is tied with string. The weight of the porous polytetrafluoroethylene membrane used is denoted as WS2, and the weight of the string as WS3. The adhesive layer wrapped in the porous polytetrafluoroethylene membrane and tied with string is immersed in 50 mL of a water / isopropanol = 35 / 65 (weight ratio) solution and kept at 23°C for 3 days to swell the adhesive layer. After that, the adhesive layer wrapped in the porous polytetrafluoroethylene membrane is removed while the opening is still tied with string, the water / isopropanol solution adhering to the outer surface is wiped off with a cloth, and the weight is measured. Let WS4 be the weight of the adhesive layer, which is tied at the opening with string and encased in a porous polytetrafluoroethylene film. Using the obtained weights WS1 to WS4, the swelling rate Fs (unit: wt%) is calculated using the following formula. Swelling rate Fs(wt%) = [(WS4-WS2-WS3) / WS1] × 100

[0110] The swelling rate of the adhesive layer with respect to isopropyl alcohol tends to increase when the crosslinking density and polymer Tg are low, for example, and tends to decrease when the crosslinking density and polymer Tg are high.

[0111] (Swelling rate of the adhesive layer relative to oleic acid) In embodiments of the present invention, the swelling rate of the adhesive layer with respect to oleic acid is 2,000 wt% or less. If the swelling rate of the adhesive layer with respect to oleic acid exceeds 2,000 wt%, it may cause a decrease in bulk strength due to volume swelling and a decrease in adhesion due to seepage to the interface.

[0112] The swelling rate of the adhesive layer with respect to oleic acid is preferably 2000 wt% or less, more preferably 1800 wt% or less, and even more preferably 1000 wt% or less. On the other hand, a lower swelling rate of the adhesive layer with respect to oleic acid is preferable, and there is no particular lower limit, but for example, it can be 100 wt% or more, 200 wt% or more, or 300 wt% or more.

[0113] In this specification, the swelling rate of the adhesive layer with respect to oleic acid can be determined by the same method as described above for determining the swelling rate of the adhesive layer with respect to isopropyl alcohol, except that 50 mL of oleic acid is used instead of 50 mL of a water / isopropanol = 35 / 65 (weight ratio) solution.

[0114] The swelling rate of the adhesive layer with respect to oleic acid tends to increase when the crosslinking density and polymer Tg are low, for example, and tends to decrease when the crosslinking density and polymer Tg are high.

[0115] (Shear adhesion strength of adhesive sheet at 23°C) The shear adhesive strength of the adhesive sheet according to the embodiment of the present invention at 23°C is preferably 0.8 MPa or higher, preferably 1.0 MPa or higher, more preferably 1.2 MPa or higher, and particularly preferably 1.5 MPa or higher. There is no particular upper limit, but for example, it can be 6.0 MPa or lower, or 5.0 MPa or lower.

[0116] In this specification, the shear adhesive strength of an adhesive sheet at 23°C can be measured by the following method. Specifically, the adhesive sheet is cut to a length of 20 mm and a width of 20 mm. Two pieces of 50 μm thick stainless steel foil are prepared, and the cut adhesive sheet is used to attach the stainless steel foils so that they overlap by 20 mm in the longitudinal direction. A 2 kg roller is passed back and forth once over the stainless steel foils attached by the adhesive sheet to press them together, and then cured at room temperature for 30 minutes to obtain a test specimen. The longitudinal ends of the test specimen are set in the fixtures of a tensile testing machine, and the shear adhesive strength at 23°C can be measured as the load (maximum load) when pulled under the conditions of 23°C and a tensile speed of 50 mm / min. Note: N / 400 mm 2 The measured values ​​obtained in units of MPa should be converted to MPa and used as the shear adhesion strength at 23°C.

[0117] The shear adhesive strength of an adhesive sheet tends to increase when the crosslinking density is increased to improve bulk strength, and tends to decrease when the crosslinking density is decreased to reduce bulk strength.

[0118] (Gel fraction of the adhesive layer) In embodiments of the present invention, the gel fraction of the adhesive layer is preferably 15 to 90%. More preferably 15% or more, even more preferably 20% or more, and particularly preferably 30% or more. Furthermore, 90% or less is more preferably, 80% or less is even more preferably, and 70% or less is particularly preferably.

[0119] In this specification, the gel fraction of the adhesive layer can be measured by the following method. Specifically, 0.1 g of the adhesive layer is weighed out. Let the weight of the removed adhesive layer be Wg1. This adhesive layer is wrapped in a drawstring shape with a porous polytetrafluoroethylene membrane having an average pore size of 0.2 μm, a porosity of 75%, and a thickness of 85 μm, and the opening is tied with string. Let the weight of the porous polytetrafluoroethylene membrane used be Wg2, and the weight of the string be Wg3. The adhesive layer wrapped in the porous polytetrafluoroethylene membrane and tied with string is immersed in 50 mL of ethyl acetate and kept at 23°C for 7 days to allow only the sol component of the adhesive layer to leach out of the porous polytetrafluoroethylene membrane. After that, the adhesive layer wrapped in the porous polytetrafluoroethylene membrane, with the opening still tied with string, is removed, the ethyl acetate adhering to the outer surface is wiped off, and it is dried at 130°C for 2 hours, and its weight is measured. Let Wg5 be the weight of the adhesive layer, which is tied at the opening with string and encased in a porous polytetrafluoroethylene film. Using the obtained Wg1, Wg2, Wg3, and Wg4, the gel fraction Fg (unit: %) of the adhesive layer is determined using the following formula. Gel fraction of the adhesive layer Fg(%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0120] The gel fraction of the adhesive layer tends to increase with increasing the amount of crosslinking agent, for example, and tends to decrease with decreasing the amount of crosslinking agent.

[0121] (Storage modulus G' of adhesive sheet at 25°C) The storage modulus G' at 25°C (hereinafter sometimes referred to as "25°C storage modulus") of the adhesive sheet according to the embodiment of the present invention is preferably 10.0 MPa or higher.

[0122] In this specification, the 25°C storage modulus G' of an adhesive sheet can be measured by the following dynamic viscoelastic measurement. Specifically, an adhesive sheet is prepared, and multiple sheets are stacked to create an adhesive layer with a thickness of approximately 1 mm. A sample of this adhesive layer, punched out into a disc shape with a diameter of 7.9 mm, is sandwiched and fixed between parallel plates, and a dynamic viscoelastic measurement is performed using a viscoelasticity tester (e.g., ARES or equivalent manufactured by T.A. Instruments) under the following conditions to determine the 23°C storage modulus. • Measurement mode: Shear mode Temperature range: -70℃ to 150℃ • Heating rate: 5°C / min ·Measurement frequency: 1Hz The measurements in the examples described later will also be performed using the method described above. The adhesive layer to be measured may be one formed by applying the corresponding adhesive composition in layers and then drying or curing it.

[0123] <Application> The uses of the adhesive sheet according to the embodiment of the present invention are not particularly limited and can be used without restriction for various purposes. For example, the adhesive sheet can be used in a manner in which it is attached to a component of an electronic device, for example, for purposes such as fixing, joining, and reinforcing the component. The adhesive sheet according to the embodiment of the present invention can suppress a decrease in adhesive strength even when the release liner is replaced before being attached to the substrate. Therefore, it can be preferably used as a reliable fixing means for electronic device components where the release liner may be replaced before being attached to the substrate for processing such as punching or cutting, or for visibility purposes. The adhesive sheet according to the embodiment of the present invention is particularly suitable for fixing components of portable electronic devices. For example, a portable electronic device can include the adhesive sheet according to the embodiment of the present invention. The adhesive sheet according to the embodiment of the present invention can be preferably used, for example, in the form of a double-sided adhesive sheet for applications such as fixing or joining members. The double-sided adhesive sheet may be substrate-less or may have a substrate attached.

[0124] Non-exclusive examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (e.g., wristwear-type devices worn on the wrist like watches, modular devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information systems, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, "portable" means not merely being able to carry something, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily.

[0125] Figure 4 is a schematic example of a portable electronic device (smartphone) using an adhesive sheet according to an embodiment of the present invention. As shown in Figure 4, a battery (heat-generating element) 540 is built into the housing 520 of the portable electronic device 500. The portable electronic device 500 is also configured to include an adhesive sheet 550. In this configuration example, the adhesive sheet 550 is a double-sided adhesive sheet (double-sided adhesive sheet) that fixes the components constituting the portable electronic device 500. The portable electronic device 500 is equipped with a touch panel 570 whose display unit also functions as an input unit. The adhesive sheet according to an embodiment of the present invention is preferably used as a component (component joining means) of the portable electronic device described above.

[0126] The matters disclosed herein include the following: <1> An adhesive sheet having an adhesive layer, The adhesive layer contains a polyester polymer, The swelling rate of the adhesive layer with respect to isopropyl alcohol is 2,000 wt% or less, and the swelling rate with respect to oleic acid is 2,000 wt% or less. An adhesive sheet wherein the glass transition temperature (Tg) of the polyester polymer is -10 to 10°C. <2> The shear adhesion strength at 23°C is 0.8 MPa or higher. <1> The adhesive sheet described above. <3> The adhesive layer includes a tackifying resin. <1> or <2> The adhesive sheet described above. <4> The content of the tackifying resin is 4 parts or less when the total weight of the adhesive layer is 100 parts by weight. <3> The adhesive sheet described above.

[0127] <5> The gel fraction of the adhesive layer is 15-90%. <1> ~ <5> An adhesive sheet described in one of the following terms. <6> The weight-average molecular weight of the aforementioned polyester polymer is 20,000 to 150,000. <1> ~ <5> An adhesive sheet described in one of the following terms. <7> The aforementioned polyester polymer contains an aromatic dicarboxylic acid as a structural unit. <1> ~ <6> An adhesive sheet described in one of the following terms. <8> The total thickness of the adhesive layer is 50 to 400 μm. <1> ~ <7> An adhesive sheet described in one of the following terms. <9> It is a double-sided adhesive sheet. <1> ~ <8> An adhesive sheet described in one of the following terms.

[0128] <10> Having a base material, <1> ~ <9> An adhesive sheet described in one of the following terms. <11> The substrate is a polyethylene terephthalate (PET) film, a polyolefin film, a polyurethane film, or a polyimide film. <10> The adhesive sheet described above. <12> The thickness of the substrate is greater than 0 μm and less than or equal to 150 μm. <10> or <11> The adhesive sheet described above. <13> For use in fixing components of portable electronic devices, <1> ~ <12> An adhesive sheet described in one of the following terms. <14> <1> ~ <13> A portable electronic device containing an adhesive sheet as described in any one of the following. [Examples]

[0129] The following describes several embodiments of the present invention, but the present invention is not intended to be limited to those shown in these embodiments. In the following description, "parts" and "%" refer to weight unless otherwise specified.

[0130] (Synthesis Example 1) A four-necked separable flask was equipped with a stirrer, thermometer, nitrogen tube, and water separator, and polycarboxylic acid and polyol were charged in amounts of 1 equivalent each. Di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) was added as a polymerization catalyst at a rate of 0.05 parts per 100 parts of the total amount of polycarboxylic acid and polyol. Xylene was added as a solvent for evaporating reaction water, and the mixture was heated to 180°C while stirring under a nitrogen atmosphere, and this temperature was maintained. After a while, the efflux and separation of reaction water was observed, and the reaction began to proceed. The reaction was continued for approximately 24 hours to obtain the polyester polymer (polymer A-1) of Synthesis Example 1. In Synthesis Example 1, adipic acid (AD), sebacic acid (SB), isophthalic acid (IP), and terephthalic acid (TP) were used as polycarboxylic acids in a molar ratio of AD:SB:IP:TP = 3:12:35:0.1. Additionally, neopentyl glycol (NPG) and a mixture of 1,4-butanediol (BD) and 1,6-hexanediol (HD) were used as polyols in a molar ratio of 32:18. The weight-average molecular weight (Mw) of the polyester polymer (polymer A-1) obtained in Synthesis Example 1 was 130,000, and its glass transition temperature (Tg) was -2°C.

[0131] (Synthesis Example 2) A polyester polymer (polymer A-2) was obtained in the same manner as in Synthesis Example 1, except that the reaction, which involved raising the temperature to 180°C and continuing for approximately 24 hours, was changed to a reaction involving raising the temperature to 180°C and continuing for approximately 12 hours. The weight-average molecular weight (Mw) of this polyester polymer (polymer A-2) was 90,000, and the glass transition temperature (Tg) was -2°C.

[0132] (Synthesis Example 3) A polyester polymer (polymer A-3) was obtained in the same manner as in Synthesis Example 1, except that the reaction, which involved raising the temperature to 180°C and continuing for approximately 24 hours, was changed to a reaction involving raising the temperature to 200°C and continuing for approximately 14 hours. The weight-average molecular weight (Mw) of this polyester polymer (polymer A-3) was 60,000, and the glass transition temperature (Tg) was -2°C.

[0133] (Synthesis Example 4) A polyester polymer (polymer A-4) was obtained in the same manner as in Synthesis Example 1, except that the reaction, which involved raising the temperature to 180°C and continuing for approximately 24 hours, was changed to a reaction involving raising the temperature to 200°C and continuing for approximately 7 hours. The weight-average molecular weight (Mw) of this polyester polymer (polymer A-4) was 40,000, and the glass transition temperature (Tg) was -2°C.

[0134] (Synthesis Example 5) A polyester polymer (polymer B) was synthesized in the same manner as in Synthesis Example 1, except that adipic acid (AD), isophthalic acid (IP), and terephthalic acid (TP) were used as polycarboxylic acids in a molar ratio of AD:IP:TP = 14:35:1, and a mixture of ethylene glycol (EG), neopentyl glycol (NPG), 1,4-butanediol (BD), and 1,6-hexanediol (HD) was used as a polyol in a molar ratio of 19:17:14. The weight-average molecular weight (Mw) of the polyester polymer (polymer B) obtained in Synthesis Example 5 was 30,000, and its glass transition temperature (Tg) was -8°C.

[0135] (Synthesis Example 6) A four-necked separable flask was equipped with a stirrer, thermometer, nitrogen tube, and water separator, and polycarboxylic acid and polyol were charged in amounts of 1 equivalent each. Di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) was added as a polymerization catalyst at a rate of 0.05 parts per 100 parts of the total amount of polycarboxylic acid and polyol. Xylene was added as a solvent for evaporating reaction water, and the mixture was heated to 180°C while stirring under a nitrogen atmosphere, and this temperature was maintained. After a while, the efflux and separation of reaction water was observed, and the reaction began to proceed. The reaction was continued for approximately 24 hours to obtain the polyester polymer (polymer C) of Synthesis Example 6. In Synthesis Example 6, sebacic acid (SB) and isophthalic acid (IP) were used as polycarboxylic acids in a molar ratio of SB:IP = 5:45. Furthermore, neopentyl glycol (NPG) and a mixture of 1,4-butanediol (BD) and 1,6-hexanediol (HD) were used as polyols in a molar ratio of 25:25. The weight-average molecular weight (Mw) of the polyester polymer (polymer C) obtained in Synthesis Example 6 was 130,000, and its glass transition temperature (Tg) was 15°C.

[0136] (Synthesis Example 7) A four-necked separable flask was equipped with a stirrer, thermometer, nitrogen tube, and water separator, and polycarboxylic acid and polyol were charged in amounts of 1 equivalent each. Di-n-butyltin oxide (manufactured by Kishida Chemical Co., Ltd., molecular weight 249) was added as a polymerization catalyst at a rate of 0.05 parts per 100 parts of the total amount of polycarboxylic acid and polyol. Xylene was added as a solvent for evaporating reaction water, and the mixture was heated to 180°C while stirring under a nitrogen atmosphere, and this temperature was maintained. After a while, the efflux and separation of reaction water was observed, and the reaction began to proceed. The reaction was continued for approximately 24 hours to obtain the polyester polymer (polymer D) of Synthesis Example 7. In Synthesis Example 7, sebacic acid (SB), isophthalic acid (IP), and terephthalic acid (TP) were used as polycarboxylic acids in a molar ratio of SB:IP:TP = 37:13:0.1. As polyols, neopentyl glycol (NPG) and a mixture of 1,4-butanediol (BD) and 1,6-hexanediol (HD) were used in a molar ratio of 23:27. The weight-average molecular weight (Mw) of the polyester polymer (polymer D) obtained in Synthesis Example 7 was 25,000, and its glass transition temperature (Tg) was -50°C.

[0137] <Example 1> A polyester polymer A obtained in Synthesis Example 1 was mixed with an isocyanate crosslinking agent (product name "Takenate D-101E", a 75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Mitsui Chemicals, Inc.), an epoxy crosslinking agent (product name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Company, Inc.), a crosslinking catalyst (DBTDL (dibutyltin dilaurate), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and a pigment (product name "MHI-PD837M", a pigment dispersion, manufactured by Mikuni Pigment Co., Ltd.) in the composition shown in Table 1 to prepare an adhesive composition. This adhesive composition was coated onto a peeled PET film (product name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) and dried at 110°C for 2 minutes to form an adhesive layer. Similarly, it was coated onto another peeled PET film (product name "Diafoil MRV", manufactured by Mitsubishi Chemical Corporation) to obtain two adhesive layers. A PET substrate (product name "Lumirror S10," manufactured by Toray Industries, Inc.) was sandwiched between these two adhesive layers. Then, it was aged at 50°C for 96 hours. In this way, a double-sided adhesive sheet with a substrate, protected on both sides by the two release films mentioned above, was obtained.

[0138] <Examples 2-11, Comparative Examples 1-4> The types and / or amounts of the constituent ingredients were changed as shown in Tables 1 to 4. The adhesive compositions for each example were prepared in the same manner as in Example 1, and for each example, double-sided adhesive sheets having adhesive layers and substrates of the thicknesses shown in Tables 1 to 4 were prepared.

[0139] The functional group ratio in Tables 1-4 refers to the ratio (molar ratio) of isocyanate groups (NCO) contained in the isocyanate crosslinking agent to the number of hydroxyl groups (OH) contained in the polyester polymer. Furthermore, the base materials used in each example are indicated by the "● (black circle)" in Tables 1-4.

[0140] The components and base materials used in the above examples and comparative examples are as follows. (SIS-based polymer) Quintac 3520: Styrene-isoprene-styrene block copolymer (product name "Quintac 3520", manufactured by Nippon Zeon Co., Ltd.)

[0141] (Adhesive-granting resin) YS Polystar S145: Terpene phenol resin (product name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd.) YS Resin PX1150N: Terpene-based resin (product name "YS Resin PX1150N", manufactured by Yasuhara Chemical Co., Ltd.) (Hydrolysis inhibitor) V-05: Solvent-soluble polycarbodiimide resin (product name "V-05", manufactured by Nisshinbo Chemical Co., Ltd.)

[0142] (base material) Polyurethane film: Product name "DUS203", manufactured by Seedam Co., Ltd.

[0143] <Rating> The adhesive sheets obtained in each example and comparative example were evaluated as follows. The results are shown in Tables 1 to 4.

[0144] [Swelling rate of the adhesive layer relative to isopropyl alcohol (swelling rate of the adhesive layer relative to IPA)] The swelling rate of the adhesive layer relative to IPA was measured by the following method. 0.1 g of adhesive sheet was weighed out, and only the adhesive layer was extracted. The weight of the extracted adhesive layer was designated WS1. This adhesive layer was wrapped in a drawstring-like shape with a porous polytetrafluoroethylene membrane (product name "Nitoflon (registered trademark) NTF1122," manufactured by Nitto Denko Corporation) with an average pore size of 0.2 μm, a porosity of 75%, and a thickness of 85 μm, and the opening was tied with string. The weight of the porous polytetrafluoroethylene membrane used was designated WS2, and the weight of the string was designated WS3. The adhesive layer, wrapped in the porous polytetrafluoroethylene membrane and tied with string, was immersed in a water / isopropanol = 35 / 65 (weight ratio) solution and kept at 23°C for 3 days to swell the adhesive sheet. After that, the adhesive layer wrapped in the porous polytetrafluoroethylene membrane, with the opening still tied with string, was removed, the liquid adhering to the outer surface was wiped off with a cloth, and its weight was measured. The weight of the adhesive layer, which was tied with string and encased in a porous polytetrafluoroethylene film, was defined as WS4. Using the obtained weights WS1 to WS4, the swelling rate Fs (unit: wt%) of the adhesive layer relative to IPA was determined using the following formula. Swelling rate Fs(wt%) = [(WS4-WS2-WS3) / WS1] × 100

[0145] [Swelling rate of the adhesive layer relative to oleic acid (Swelling rate of the adhesive layer relative to oleic acid)] The oleic acid swelling rate of the adhesive layer was determined using the same method as described above for determining the IPA swelling rate, except that oleic acid was used instead of the water / isopropanol = 35 / 65 (weight ratio) solution.

[0146] [Shear adhesive strength of adhesive sheets at 23°C] The shear adhesive strength of the adhesive sheet at 23°C was measured using the following method. Adhesive sheets were cut to a length of 20 mm and a width of 20 mm. Two 50 μm thick stainless steel foils (manufactured by Nippon Test Panel Co., Ltd.) were prepared, and the stainless steel foils were attached to the adhesive sheets so that they overlapped by 20 mm in the longitudinal direction. A 2 kg roller was passed back and forth once over the stainless steel foils attached with the adhesive sheets to press them together, and then cured at room temperature for 30 minutes to obtain a test specimen. Both ends of the test specimen in the longitudinal direction were set in the fixtures of a tensile testing machine (product name "TG-1kN", manufactured by Minebea Co., Ltd.), and the shear adhesive strength at 23°C was measured as the load (maximum load) when pulled under conditions of 23°C and a tensile speed of 50 mm / min. Note: N / 400 mm 2 The measured values ​​obtained in units were converted to MPa and used as the shear adhesion strength at 23°C.

[0147] [Gel fraction of the adhesive layer] The gel fraction of the adhesive layer was measured by the following method. A 0.1g adhesive sheet was weighed out, and only the adhesive layer was extracted. The weight of the extracted adhesive layer was designated as Wg1. This adhesive layer was wrapped in a drawstring-like structure using a porous polytetrafluoroethylene membrane (product name "Nitoflon (registered trademark) NTF1122," manufactured by Nitto Denko Corporation) with an average pore size of 0.2μm, a porosity of 75%, and a thickness of 85μm, and the opening was tied with string. The weight of the porous polytetrafluoroethylene membrane used was designated as Wg2, and the weight of the string as Wg3. The adhesive layer, wrapped in the porous polytetrafluoroethylene membrane and tied with string, was immersed in 50mL of ethyl acetate and kept at 23°C for 7 days to allow only the sol component of the adhesive layer to leach out of the porous polytetrafluoroethylene membrane. After that, the adhesive layer wrapped in the porous polytetrafluoroethylene membrane, with the opening still tied with string, was removed, the ethyl acetate adhering to the outer surface was wiped off, and it was further dried at 130°C for 2 hours before its weight was measured. The opening was tied with string, and the weight of the adhesive layer, which was wrapped in a porous polytetrafluoroethylene film, was defined as Wg5. Using the obtained Wg1, Wg2, Wg3, and Wg4, the gel fraction Fg (unit: %) of the adhesive layer was determined using the following formula. Gel fraction of the adhesive layer Fg(%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0148] [Adhesion retention rate of adhesive sheets against isopropyl alcohol (Adhesion retention rate of adhesive sheets against IPA)] The IPA adhesion retention rate of the adhesive sheet was measured using the following method. (Initial 180-degree peel strength) Under a measurement environment of 23°C and 50% RH, a 50 μm thick PET film was attached to one adhesive surface of a double-sided adhesive sheet as a backing, and the sheet was cut to a size of 5 mm wide and 100 mm long to obtain an adhesive sheet test specimen. For single-sided adhesive sheets, the same method was used as for double-sided adhesive sheets, except that the PET film backing was omitted. Under the same conditions as for preparing the adhesive sheet test specimen, the other adhesive surface of the adhesive sheet test specimen was pressed against the surface of a stainless steel plate (SUS304BA plate) by applying pressure with a 2kg roller for one back-and-forth motion, and then cured for 30 minutes to obtain a measurement sample. Under the same conditions as for preparing the adhesive sheet test specimen, the obtained measurement sample was left for another 24 hours, and then mounted on a universal tensile and compression testing machine (product name "TG-1kN", manufactured by Minebea Co., Ltd.). The initial peel strength [N / 5mm] was measured in accordance with JIS Z 0237:2000, under conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees.

[0149] (180° peel strength after immersion in isopropyl alcohol) The measurement samples were prepared using the same method as for measuring the initial 180° peel strength. The measurement samples were immersed in a water / isopropanol = 30 / 70 (weight ratio) solution at 50°C for 4 days. After that, the measurement samples were removed, the water / isopropanol solution adhering to the surrounding area was lightly wiped off with a dry cloth, and the 180° peel strength [N / 5mm] after isopropyl alcohol immersion was measured using the same method as for measuring the initial 180° peel strength.

[0150] (IPA adhesion retention rate of adhesive sheets) The IPA adhesion retention rate of the adhesive sheet was determined using the following formula. Adhesive strength maintenance rate (%) = Peel strength at 180°C after chemical immersion [N / 5mm] / Initial peel strength at 180°C [N / 5mm] × 100

[0151] [Adhesion retention rate of adhesive sheets against oleic acid (Adhesion retention rate of adhesive sheets against oleic acid)] The oleic acid adhesion retention rate of the adhesive sheet was determined using the same method as described above for determining the IPA adhesion retention rate of the adhesive sheet, except that oleic acid was used instead of the water / isopropanol = 30 / 70 (weight ratio) solution.

[0152] [Waterproof] A polycarbonate sheet (product name "PC-1600," manufactured by Takiron CI Co., Ltd.) was cut to 40mm x 40mm to create a base. Similarly, a polycarbonate sheet was cut to 25mm x 25mm to create a chip. A double-sided adhesive sheet was cut to 25mm x 25mm, and the center portion was further punched out to 23mm x 23mm to create a 1mm wide frame-shaped double-sided adhesive sheet. The base and chip were attached using the punched-out double-sided adhesive sheet, ensuring that the sheet did not protrude from the chip and that the chip was centered on the base. A pressure of 0.5 MPa was applied from above the chip for 60 seconds to press the base and chip together, and a measurement sample was obtained. The sample was submerged in a water-filled tray, and the pressure was gradually increased using an autoclave. The presence or absence of water ingress between the tip and the base was checked before pressurization, and after applying pressures of 10kPa, 50kPa, 500kPa, and 700kPa for 30 minutes, and then returning to atmospheric pressure. The pressure at which water ingress was observed was evaluated as follows. 0 (Very Poor): The chip and base could not be secured with the adhesive sheet. 1 (Very Poor): Water entered between the tip and the base before being placed in the autoclave or due to an applied pressure of less than 10 kPa. 2 (Bad): Water seeped between the chip and the base when 10kPa was applied. 3 (Good): No water entered between the chip and the base when 50kPa was applied. 4 (Excellent): No water entered between the chip and the base when 500kPa pressure was applied. 5 (Excellent): No water entered between the tip and the base even when the pressure was higher than 700kPa.

[0153] [Table 1]

[0154] [Table 2]

[0155] [Table 3]

[0156] [Table 4]

[0157] As shown in Tables 1 to 3, the adhesive sheets of Examples 1 to 11, which have an adhesive layer, the adhesive layer containing a polyester polymer, the swelling rate of the adhesive layer with respect to isopropyl alcohol of 2,000 wt% or less, the swelling rate with respect to oleic acid of 2,000 wt% or less, and the glass transition temperature (Tg) of the polyester polymer of -10 to 10°C, showed good IPA adhesion retention rate, oleic acid adhesion retention rate, and waterproofing. This indicates that the adhesive sheets according to the embodiments of the present invention can achieve both chemical resistance and waterproofing. In contrast, as shown in Table 4, the adhesive sheets of Comparative Examples 1 to 4 showed inferior results compared to the above examples, with insufficient IPA adhesion retention rate, oleic acid adhesion retention rate, and waterproofing.

[0158] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Industrial applicability]

[0159] The adhesive sheet of the present invention can be particularly suitable for fixing components of portable electronic devices. [Explanation of Symbols]

[0160] 1, 2, 3 Adhesive sheets 10 Supporting base material 10A front page 10B Second side (back) 21 Adhesive layer (first adhesive layer) 21A Adhesive surface (first adhesive surface) 21B Adhesive surface (second adhesive surface) 22 Adhesive layer (second adhesive layer) 22A Adhesive surface (second adhesive surface) 31,32 Peel-off liner 100, 200, 300 Adhesive sheets with release liner

Claims

1. An adhesive sheet having an adhesive layer, The adhesive layer contains a polyester polymer, The swelling rate of the adhesive layer with respect to isopropyl alcohol is 2,000 wt% or less, and the swelling rate with respect to oleic acid is 2,000 wt% or less. An adhesive sheet wherein the glass transition temperature (Tg) of the polyester polymer is -10 to 10°C.

2. The adhesive sheet according to claim 1, wherein the shear adhesive strength at 23°C is 0.8 MPa or more.

3. The adhesive sheet according to claim 1, wherein the adhesive layer includes a tackifying resin.

4. The adhesive sheet according to claim 3, wherein the content of the tackifying resin is 4 parts or less when the total weight of the adhesive layer is 100 parts by weight.

5. The adhesive sheet according to claim 1, wherein the gel fraction of the adhesive layer is 15 to 90%.

6. The adhesive sheet according to claim 1, wherein the weight-average molecular weight of the polyester polymer is 20,000 to 150,000.

7. The adhesive sheet according to claim 1, wherein the polyester polymer contains an aromatic dicarboxylic acid as a structural unit.

8. The adhesive sheet according to claim 1, wherein the total thickness of the adhesive layer is 50 to 400 μm.

9. The adhesive sheet according to claim 1, which is a double-sided adhesive sheet.

10. The adhesive sheet according to claim 1, having a base material.

11. The adhesive sheet according to claim 10, wherein the substrate is a polyethylene terephthalate (PET) film, a polyolefin film, a polyurethane film, or a polyimide film.

12. The adhesive sheet according to claim 10, wherein the thickness of the substrate is greater than 0 μm and less than or equal to 150 μm.

13. An adhesive sheet according to any one of claims 1 to 12, for use in fixing components of portable electronic devices.

14. A portable electronic device comprising an adhesive sheet according to any one of claims 1 to 12.

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