Adhesive sheets and portable electronic devices

Abstract

To provide an adhesive sheet that can achieve both suppression of elongation of the adhesive layer and good adhesive strength at room temperature and under heating, and to provide a portable electronic device including the above adhesive sheet. [Solution] An adhesive sheet having a base material and an adhesive layer, wherein the thickness of the base material is 10 to 70% of the thickness of the adhesive sheet, the adhesive layer contains a polyester polymer, and the storage modulus G' of the adhesive layer at 23°C is 0.4 to 1.5 MPa, and the storage modulus G' at 65°C is 0.3 to 1.0 MPa.

Description

Technical Field

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

Background Art

[0002] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter) exhibits a state of a soft solid (viscoelastic body) in a temperature range near room temperature and has the 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 equipment, typically in the form of an adhesive sheet including a layer of the adhesive. As adhesives, 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 are 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 larger, thinner, and have 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, especially those without a base material, there were concerns that using them in such narrow widths would reduce the durability of the adhesive sheet due to deformation accompanied by elongation of the adhesive layer, compounded by the heat emitted from the electronic device. Furthermore, while using a thicker base material to alleviate this concern suppresses the elongation of the adhesive layer, a new problem arises as a trade-off: the adhesive strength decreases.

[0006] The present invention has been completed in view of the above circumstances, and aims to provide an adhesive sheet that can achieve both suppression of elongation of the adhesive layer and good adhesive strength at room temperature and under heating. Another object of the present invention is to provide a portable electronic device including 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-mentioned problem can be solved by providing an adhesive sheet having a base material and an adhesive layer, wherein the thickness of the base material is 10 to 70% of the thickness of the adhesive sheet, the adhesive layer contains a polyester polymer, and the storage modulus G' of the adhesive layer at 23°C is 0.4 to 1.5 MPa and the storage modulus G' at 65°C is 0.3 to 1.0 MPa.

[0008] The means to solve the aforementioned problem are as follows: [1] An adhesive sheet having a base material and an adhesive layer, The thickness of the substrate is 10 to 70% of the thickness of the adhesive sheet. The adhesive layer contains a polyester polymer, An adhesive sheet having a storage modulus G' of 0.4 to 1.5 MPa at 23°C and a storage modulus G' of 0.3 to 1.0 MPa at 65°C. [2] An adhesive sheet as described in [1], having a thickness of 50 to 400 μm. [3] The adhesive sheet according to [1], wherein the thickness of the substrate is 5 to 280 μm. [4] The adhesive sheet described in [1] is a double-sided adhesive sheet. [5] The adhesive sheet according to [1], wherein the base material is polyethylene terephthalate (PET) film. [6] An adhesive sheet described in any one of [1] to [5] for use in fixing components of portable electronic devices. [7] A portable electronic device containing an adhesive sheet as described in any one of [1] to [5]. [Effects of the Invention]

[0009] The adhesive sheet of the present invention enables both suppression of elongation of the adhesive layer and good adhesive strength at room temperature and under heating conditions. [Brief explanation of the drawing]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically showing the configuration of a conventional adhesive sheet having no base material. [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.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

[0012] <Adhesive Sheet> The adhesive sheet according to an embodiment of the present invention is an adhesive sheet having a base material and an adhesive layer, wherein the thickness of the base material is 10 to 70% of the thickness of the adhesive sheet, the adhesive layer contains a polyester-based polymer, and the storage elastic modulus (sometimes referred to as the "23°C storage elastic modulus" in this specification) G' of the adhesive layer at 23°C is 0.4 to 1.5 MPa, and the storage elastic modulus (sometimes referred to as the "65°C storage elastic modulus" in this specification) G' at 65°C is 0.3 to 1.0 MPa. By using such an adhesive sheet, it is possible to achieve both suppression of elongation of the adhesive layer and good adhesive force at room temperature and under heating.

[0013] (Example of the Configuration of the Adhesive Sheet) The adhesive sheet according to an embodiment of the present invention includes a support base material and an adhesive layer. The adhesive sheet may be, for example, in the form of an adhesive sheet with a base material in which the adhesive layer is laminated on one or both sides of the support base material. Hereinafter, the support base material may also be simply referred to as the "base material".

[0014] Figure 1 schematically shows the structure of a conventional adhesive sheet without a base material. This adhesive sheet 1 is configured as a base material-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 components, or different locations within a single component. 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.

[0015] Figure 2 schematically shows the structure of an adhesive sheet according to one 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 up 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).

[0016] 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 configure 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).

[0017] 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.

[0018] While not particularly limited, the adhesive sheet according to the embodiment of the present invention is preferably a double-sided adhesive sheet.

[0019] 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).

[0020] <Adhesive layer> The adhesive layer contains a polyester polymer, and the storage modulus G' of the adhesive layer at 23°C is 0.4 to 1.5 MPa, and the storage modulus G' at 65°C is 0.3 to 1.0 MPa.

[0021] (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, "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.

[0022] (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 of 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 sheet with desired properties (specifically, a desired storage modulus at 23°C) can be obtained.

[0023] 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 reducing the 23°C storage modulus of the adhesive layer, 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.

[0024] 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.

[0025] 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%.

[0026] 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 the storage modulus at 23°C. 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.

[0027] 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 range of 23°C storage modulus, 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.

[0028] 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).

[0029] 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.

[0030] (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 storage modulus at 23°C) can be obtained.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In other embodiments of the present invention, dimer ols can be used as the diol. Dimer ols can be used individually 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.

[0035] 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.

[0036] 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.

[0037] 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 may 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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).

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The weight-average molecular weight (Mw) of the polyester polymer is not particularly limited, and is usually 10,000 or more, for example, 20,000 or more is appropriate. In embodiments of the present invention, the Mw of the polyester polymer can be 30,000 or more, and is preferably greater than 50,000. From the viewpoint of obtaining better properties, it is preferably greater than 60,000, more preferably greater than 70,000, even more preferably greater than 80,000, particularly preferably greater than 90,000, and may even 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, greater than 100,000), may be 110,000 or more, and may even be 115,000 or more. By using high molecular weight polyester polymers in this way, even adhesive compositions that tend to have low viscosity due to containing a certain 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 crosslinking agents tend to have a sufficient pot life and excellent handling properties. The upper limit of Mw for polyester polymers is usually 30 × 10 4 The following is appropriate, and from the viewpoint of adhesive strength, etc., in the embodiments of the present invention, preferably 20 × 10 4 The following is more preferable: 15×10 4 The following is an example: 12 × 10 4 The following is also acceptable.

[0047] 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)

[0048] In embodiments of the present invention, the glass transition temperature (Tg) of the polyester polymer is preferably -10°C or higher, more preferably -7°C or higher, even more preferably -3°C or higher, and particularly preferably 0°C or higher. Using a polyester polymer with a Tg of -10°C or higher is preferable because the intermolecular interactions are strong, the movement of the polymer chains is restricted, it is hard even at room temperature, and it is resistant to strain under deformation forces. Furthermore, there is no particular upper limit to the Tg, but for example, it can be 35°C or lower, 25°C or lower, 15°C or lower, or 5°C or lower. The Tg of a polyester polymer can be adjusted by appropriately changing the monomer composition (i.e., the type and ratio of monomers used in the synthesis of the polymer).

[0049] In this specification, the Tg of a polyester polymer is measured by the following method. Specifically, a disc-shaped test specimen with a thickness of 2 mm and a diameter of 8 mm is prepared using the polyester polymer to be measured. This test specimen is sandwiched between parallel plates for shear testing, and the peak value of tanδ (loss modulus G'' / storage modulus G') is determined at a frequency of 1 Hz using a measuring device (ARES, manufactured by Rheometric Scientific). The temperature of this peak value is defined as the Tg (glass transition temperature) [°C]. The same method is used in the examples described later.

[0050] (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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] (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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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).

[0065] 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 maintaining 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 moderately reducing the 23°C storage modulus within a predetermined range and moderately adjusting the 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.

[0066] 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.

[0067] (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.

[0068] 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.

[0069] 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.

[0070] (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.

[0071] 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.

[0072] 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.

[0073] (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.

[0074] (Formation of the adhesive layer) The adhesive layer according to the embodiment of the present invention can be formed, for example, by conventionally known methods using the polyester polymer described above. 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 surface with release properties (release surface) by applying the adhesive composition and curing it, and then transferring the adhesive layer to the substrate (transfer method), may be employed. The release surface can be the surface of a release liner or the back surface of a substrate that has undergone a release treatment. 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 in which the adhesive is contained 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. In the embodiment of the present invention, the adhesive layer is typically formed continuously, but is not limited to this form. For example, it may be formed in a regular or random pattern such as dots or stripes.

[0075] 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).

[0076] (Thickness of the adhesive layer) The thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness of the adhesive layer can be 2 μm to 500 μm. From the viewpoint of adhesion to the adherend, in embodiments of the present invention, the thickness of the adhesive layer is usually appropriate to be 3 μm or more, and preferably 5 μm or more. From the viewpoint of effectively obtaining the effects of improving adhesive strength and suppressing the decrease in adhesive strength, in embodiments of the present invention, the thickness of the adhesive layer can be, for example, 8 μm or more, more preferably 12 μm or more, even more preferably 15 μm or more, and particularly preferably 18 μm or more. Furthermore, 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 layer may be, for example, 200 μm or less, 150 μm or less, or 100 μm or less (e.g., less than 100 μm). In embodiments of the present invention, the thickness of the adhesive layer is preferably less than 80 μm, more preferably 50 μm or less, even more preferably 40 μm or less, even more preferably 35 μm or less, and even more preferably 30 μm or less. In embodiments where thinning is a priority, it is particularly preferably 25 μm or less, for example, 22 μm or less. In other embodiments of the present invention, the thickness of the adhesive layer may be less than 20 μm, less than 15 μm, less than 10 μm, or 5 μm or less. According to embodiments of the present invention, a decrease in adhesive strength can be effectively suppressed even with a configuration having such a thin adhesive layer. In the case of a double-sided adhesive sheet having adhesive layers on both sides of a substrate according to an embodiment of the present invention, the thickness of each adhesive layer may be the same or different. The thickness of each adhesive layer can be selected, for example, from the range exemplified above.

[0077] <Base material> An adhesive sheet according to an embodiment of the present invention includes a substrate. The adhesive sheet according to an embodiment of the present invention may be in the form of an adhesive sheet with a substrate having an adhesive layer on one or both sides of the substrate. Various sheet-like substrates can be used as the substrate, for example, resin films, paper, cloth, rubber sheets, foam sheets, metal foils, composites thereof, etc. In the field of electronic equipment, a substrate that is less likely to be a source of dust (for example, fine fibers or particles such as paper dust) may be preferably used. From this viewpoint, a substrate that does not contain fibrous materials such as paper or cloth is preferred, and for example, resin films, rubber sheets, foam sheets, metal foils, composites thereof, etc., can be preferably used.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] Alternatively, in embodiments of the present invention, among the above-mentioned substrates, PET film, polyolefin film, polyurethane film, and polyimide film are preferred, and PET film is more preferred.

[0082] 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.

[0083] 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.

[0084] 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).

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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 is preferable because it stabilizes the undercoat layer and also stabilizes the adhesive properties of the adhesive sheet.

[0091] 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.

[0092] 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).

[0093] The thickness of the substrate is not particularly limited, but it is preferably 5 to 280 μm, as this makes it easier for the thickness of the substrate to fall within 10 to 70% of the thickness of the adhesive sheet. The thickness of the substrate is not limited to the above range, and from the viewpoint of handling the substrate, it 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, 150 μm or less, 100 μm or less, 50 μm or less, 25 μm or less, 20 μm or less, 10 μm or less, 7 μm or less, less than 5 μm, or less than 4 μm.

[0094] The substrate may be included in only one layer in the adhesive sheet, or in two or more layers. From the viewpoint of maintaining adhesion between the adhesive layer and the substrate layer, it is preferable that the substrate be included in only one layer in the adhesive sheet. In this specification, the "thickness" of a substrate refers to the thickness of an individual substrate, and the "total thickness" of a substrate refers to the sum of the thicknesses of the substrates included in the adhesive sheet. If the adhesive sheet contains only one layer of substrate, the thickness of the substrate is equal to the total thickness of the substrates. If the adhesive sheet contains two or more layers of substrate, the thickness of each of the two or more substrates exists, and the total thickness of the substrate is the sum of the thicknesses of each of the two or more substrates. If the adhesive sheet contains two or more layers of substrate, it is preferable that at least one layer of substrate satisfies the above preferred embodiment, and it is more preferable that all of the substrates satisfy the above preferred embodiment.

[0095] In the adhesive sheet of this embodiment, the total thickness of the base material is 10 to 70% of the thickness of the adhesive sheet. If the total thickness of the base material is less than 10% of the thickness of the adhesive sheet, the durability of the adhesive sheet may be significantly reduced, and if it exceeds 70%, the adhesive strength of the adhesive sheet may be significantly reduced.

[0096] In adhesive sheets, the total thickness of the base material is preferably 20% or more of the thickness of the adhesive sheet, more preferably 30% or more, and even more preferably 40% or more. Furthermore, it is preferably 65% ​​or less, more preferably 60% or less, and even more preferably 55% or less.

[0097] <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 release liner) disposed on the surface (adhesive surface; e.g., first adhesive surface) of the adhesive layer. The 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 is preferably used. The 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 is preferably used. The effect of suppressing the reduction of adhesive strength according to embodiments of the present invention can be effectively exhibited when 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.

[0098] 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).

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] <Total thickness of adhesive sheet> The thickness (total thickness) of the adhesive sheet (including a substrate and an adhesive layer, but not a release liner) according to an embodiment of the present invention is not particularly limited and can be in the range of 2 to 1000 μm, for example. In embodiments of the present invention, the thickness of the adhesive sheet is preferably 50 to 400 μm, taking into consideration adhesive properties, etc. 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 350 μm or less, more preferably 300 μm or less, even more preferably 280 μm or less, still more preferably 260 μm or less, and particularly preferably 250 μm or less, for example it may be 240 μm or less or 230 μm or less. In other embodiments of the present invention, the thickness of the adhesive sheet may be 220 μm or less, 215 μm or less, 210 μm or less, or 205 μm or less. The lower limit of the thickness of the adhesive sheet is not particularly limited, and may be 80 μm or more, preferably 100 μm or more, more preferably 120 μm or more, even more preferably 140 μm or more, particularly preferably 160 μm or more, and most preferably 180 μm or more.

[0104] <Characteristics of the adhesive layer> (Storage modulus G' at 23°C and 65°C for the adhesive layer) In embodiments of the present invention, the adhesive layer has a storage modulus G' at 23°C of 0.4 to 1.5 MPa. If the storage modulus G' of the adhesive layer at 23°C is less than 0.4 MPa, the cohesive force of the adhesive sheet will be insufficient, and shear adhesion may not be achieved. If it exceeds 1.5 MPa, adhesion may not be achieved. The storage modulus G' of the adhesive layer at 23°C is preferably 0.5 MPa or higher, more preferably 0.6 MPa or higher, even more preferably 0.7 MPa or higher, even more preferably 0.8 MPa or higher, particularly preferably 0.9 MPa or higher, and most particularly preferably 1.0 MPa or higher. It is also preferably 1.4 MPa or lower, more preferably 1.3 MPa or lower, and even more preferably 1.2 MPa or lower.

[0105] Furthermore, in the embodiments of the present invention, the adhesive layer has a storage modulus G' at 65°C of 0.3 to 1.0 MPa. If the storage modulus G' of the adhesive layer at 65°C is less than 0.3 MPa, the cohesive force of the adhesive sheet will be insufficient, and shear adhesion may not be achieved. If it exceeds 1.0 MPa, adhesion may not be achieved. The storage modulus G' of the adhesive layer at 65°C is preferably 0.4 MPa or higher, more preferably 0.5 MPa or higher. It is also preferably 0.9 MPa or lower, more preferably 0.8 MPa or lower, even more preferably 0.7 MPa or lower, and particularly preferably 0.6 MPa or lower.

[0106] In this specification, the 23°C and 65°C storage moduli G' of the adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, a layered adhesive (adhesive layer, or adhesive sheet in the case of a substrate-less adhesive sheet) is prepared, and multiple layers of the adhesive 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 dynamic viscoelasticity 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 and 65°C storage moduli G'. • 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.

[0107] The 23°C and 65°C storage moduli G' of the adhesive layer tend to increase, for example, by increasing the amount of crosslinking agent added or by increasing the amount of aromatic compounds contained in the polyester adhesive.

[0108] <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.

[0109] 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.

[0110] 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.

[0111] The matters disclosed herein include the following: <1> An adhesive sheet having a base material and an adhesive layer, The thickness of the substrate is 10 to 70% of the thickness of the adhesive sheet. The adhesive layer contains a polyester polymer, An adhesive sheet having a storage modulus G' of 0.4 to 1.5 MPa at 23°C and a storage modulus G' of 0.3 to 1.0 MPa at 65°C. <2> The thickness is 50-400 μm. <1> The adhesive sheet described above. <3> The thickness of the substrate is 5 to 280 μm. <1> or <2> The adhesive sheet described above. <4> It is a double-sided adhesive sheet. <1> ~ <3> An adhesive sheet described in one of the following terms. <5> The substrate is polyethylene terephthalate (PET) film. <1> ~ <4> An adhesive sheet described in one of the following terms. <6> For use in fixing components of portable electronic devices, <1> ~ <5> An adhesive sheet described in one of the following terms. <7> <1> ~ <6> A portable electronic device containing an adhesive sheet as described in any one of the following. [Examples]

[0112] 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.

[0113] <Example of synthesis> (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) 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. In addition, 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) obtained in Synthesis Example 1 was 130,000, and its glass transition temperature (Tg) was -2°C.

[0114] (Synthesis Example 2) 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 19:14:17. The weight-average molecular weight (Mw) of the polyester polymer (polymer B) obtained in synthesis example 2 was 30,000, and its glass transition temperature (Tg) was -8°C.

[0115] (Synthesis Example 3) A polyester polymer (polymer C) was synthesized in the same manner as in Synthesis Example 1, except that 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 = 3:21:26:0.1, and a mixture of neopentyl glycol (NPG), 1,4-butanediol (BD), and 1,6-hexanediol (HD) was used as a polyol in a molar ratio of 32:18. The weight-average molecular weight (Mw) of the polyester polymer (polymer C) obtained in Synthesis Example 3 was 130,000, and its glass transition temperature (Tg) was -12°C.

[0116] (Synthesis Example 4) A polyester polymer (polymer D) was synthesized in the same manner as in Synthesis Example 1, except that 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 = 3:37:10:0.1, and a mixture of neopentyl glycol (NPG), 1,4-butanediol (BD), and 1,6-hexanediol (HD) was used as a polyol in a molar ratio of 32:18. The weight-average molecular weight (Mw) of the polyester polymer (polymer D) obtained in Synthesis Example 4 was 80,000, and its glass transition temperature (Tg) was -53°C.

[0117] (Synthesis Example 5) A polyester polymer (polymer E) was synthesized in the same manner as in Synthesis Example 1, except that adipic acid (AD), sebacic acid (SB), dimer acid (DA), and terephthalic acid (TP) were used as polycarboxylic acids in a molar ratio of AD:SB:DA:TP = 3:17:30:0.1, and ethylene glycol (EG) was used as a polyol in equivalent amounts to the polycarboxylic acids. The weight-average molecular weight (Mw) of the polyester polymer (polymer E) obtained in Synthesis Example 5 was 130,000, and its glass transition temperature (Tg) was -47°C.

[0118] (Synthesis Example 6) A polyester polymer (polymer F) was synthesized in the same manner as in Synthesis Example 1, except that 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 = 3:27:20:0.1, and a mixture of neopentyl glycol (NPG), 1,4-butanediol (BD), and 1,6-hexanediol (HD) was used as a polyol in a molar ratio of 32:18. The weight-average molecular weight (Mw) of the polyester polymer (polymer F) obtained in Synthesis Example 6 was 130,000, and its glass transition temperature (Tg) was -34°C.

[0119] (Synthesis Example 7) A polyester polymer (polymer G) was synthesized using the same method as in Synthesis Example 1, except that dimer acid (DA), isophthalic acid (IP), and terephthalic acid (TP) were used as polycarboxylic acids in a molar ratio of DA:IP:TP = 37:0.1:13, and ethylene glycol (EG) was used as a polyol in equivalent amounts to the polycarboxylic acids. The weight-average molecular weight (Mw) of the polyester polymer (polymer G) obtained in Synthesis Example 7 was 130,000, and its glass transition temperature (Tg) was -36°C.

[0120] <Example 1> Synthesis Example 1: To 100 parts of polymer A obtained, 1.1 parts of an isocyanate-based crosslinking agent (trade name "Takenate D-101E", a 75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Mitsui Chemicals, Inc.), 0.01 parts of an epoxy-based crosslinking agent (trade name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Company, Inc.), 0.02 parts of a crosslinking catalyst (DBTDL (dibutyltin dilaurate), manufactured by Tokyo Chemical Industry Co., Ltd.), and 0.5 parts of a carbodiimide group-containing compound (trade name "Carbodilite V-03", manufactured by Nisshinbo Chemical Co., Ltd.) as a hydrolysis resistance agent were added, and ethyl acetate was added to prepare an adhesive composition (adhesive solution). Two layers of this adhesive solution were applied to the release-treated surface of a release-treated PET film (product name "Diafoil MRV #38," manufactured by Mitsubishi Chemical Corporation) so that the thickness after drying was 50 μm. The film was dried at 120°C for 3 minutes to obtain two adhesive layers. Subsequently, the adhesive layers were bonded to both sides of a 100 μm PET film and left at 50°C for 3 days to obtain the adhesive sheet according to this example.

[0121] <Examples 2-17, Comparative Examples 1-7> The types and / or amounts of ingredients used 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 were prepared having adhesive layers and substrates of the thicknesses shown in Tables 1 to 4. Here, the base material used in each example is indicated by the "● (black circle)" in Tables 1-4.

[0122] The crosslinking agent, crosslinking catalyst, pigment, and substrate used in the above examples and comparative examples are as follows. (Crosslinking agent) Duranate D101: A polyfunctional isocyanate compound (trade name "Duranate D101", manufactured by Asahi Kasei Chemicals Corporation) Duranate D201: A polyfunctional isocyanate compound (trade name "Duranate D201", manufactured by Asahi Kasei Chemicals Corporation) Takenate D-127N: Polyfunctional isocyanate compound (product name "Takenate D-127N", manufactured by Mitsui Chemicals, Inc.) Takenate D-131N: Polyfunctional isocyanate compound (product name "Takenate D-131N", manufactured by Mitsui Chemicals, Inc.) (Crosslinking catalyst) ZC-162: Organozirconium compound (product name "Orgatics ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) (Pigment) MHI-PD837M: Pigment (Product name "MHI-PD837M", pigment dispersion, manufactured by Mikuni Shikkei Co., Ltd.)

[0123] (base material) Polyurethane film: Product name "DUS203", manufactured by Seedam Co., Ltd. Polyimide film: Product name "Kapton", manufactured by Toray Industries, Inc. Polyolefin film: Product name "Toraypef", manufactured by Toray Industries, Inc.

[0124] <Rating> The adhesive sheets obtained in each example and comparative example were evaluated as follows. The results are shown in Tables 1 to 4.

[0125] [Storage modulus G' at 23°C and 65°C for the adhesive layer] The storage modulus G' at 23°C and 65°C of the adhesive layer was measured using a viscoelasticity measuring device (device name "ARES", manufactured by Rheometrics) with a film jig, under the conditions of a heating rate of 5°C / min, a frequency of 1 Hz, and a strain of 0.1%.

[0126] [Adhesive sheet's pressure-sensitive adhesive strength] The adhesive sheet, sandwiched between release liners, was punched out into a frame shape with an outer diameter of 24.5 mm and a width of 2 mm. The release liners on both sides were peeled off the adhesive sheet, and it was sandwiched between a square stainless steel plate with a square hole in the center (dimensions of stainless steel plate: 50 mm x 50 mm, thickness 2 mm; hole dimensions: 20 mm x 20 mm) and a square stainless steel plate (25 mm x 25 mm, thickness 3 mm), pressed together, left to stand in an environment of 50°C for 2 hours, and then returned to room temperature to be used as an evaluation sample. A 10mm diameter cylinder was attached to the upper fixture of a tensile testing machine (product name "Precision Universal Testing Machine Autograph AG-IS," manufactured by Shimadzu Corporation), and a base was placed on the lower fixture. The evaluation sample was placed on the base with a square stainless steel plate without holes facing downwards (towards the base). The cylinder was used to press the lower stainless steel plate through the holes in the upper stainless steel plate of the evaluation sample at a speed of 50mm / min. The stress was measured when the strain in the thickness direction of the adhesive sheet reached 200%, and this was defined as the compressive adhesive force. The pressure adhesion strength at 23°C or 65°C was measured after placing the evaluation sample on a tensile testing machine and leaving it in an environment of 23°C or 65°C, respectively, for 30 minutes.

[0127] The evaluation of the pressure adhesion strength at 23°C or 65°C was as follows: A (good): over 250N B (acceptable): 150N or more, 250N or less C (Defective): Less than 150N

[0128] [Table 1]

[0129] [Table 2]

[0130] [Table 3]

[0131] [Table 4]

[0132] As shown in Tables 1-3, the adhesive sheets of Examples 1-17, in which the total thickness of the substrate was 10-70% of the thickness of the adhesive sheet, the adhesive layer contained a polyester polymer, the storage modulus G' of the adhesive layer at 23°C was 0.4-1.5 MPa, and the storage modulus G' at 65°C was 0.3-1.0 MPa, received an A (good) or B (acceptable) rating in the evaluation of the pressed adhesive strength at 23°C or 65°C. This indicates that the adhesive sheets according to the embodiment of the present invention can achieve both suppression of elongation of the adhesive layer and good adhesive strength at room temperature and under heating. In contrast, as shown in Table 4, the adhesive sheets of Comparative Examples 1-7 all received a C (poor) rating in at least one of the evaluations of the pressed adhesive strength at 23°C or 65°C, showing inferior results compared to the above examples.

[0133] 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]

[0134] The adhesive sheet of the present invention can be particularly suitable for fixing components of portable electronic devices. [Explanation of Symbols]

[0135] 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 a base material and an adhesive layer, The thickness of the substrate is 10 to 70% of the thickness of the adhesive sheet. The adhesive layer contains a polyester polymer, An adhesive sheet wherein the storage modulus G' of the adhesive layer at 23°C is 0.4 to 1.5 MPa, and the storage modulus G' at 65°C is 0.3 to 1.0 MPa.

2. The adhesive sheet according to claim 1, having a thickness of 50 to 400 μm.

3. The adhesive sheet according to claim 1, wherein the thickness of the substrate is 5 to 280 μm.

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

5. The adhesive sheet according to claim 1, wherein the substrate is polyethylene terephthalate (PET) film.

6. An adhesive sheet according to any one of claims 1 to 5, for use in fixing components of portable electronic devices.

7. A portable electronic device comprising an adhesive sheet according to any one of claims 1 to 5.

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