Resin composition and adhesive tape

Abstract

To provide a resin composition and a pressure-sensitive adhesive tape, which exhibit high pressure-sensitive adhesive force at normal temperature, and in which the pressure-sensitive adhesive force is improved to be equal to or superior to the pressure-sensitive adhesive force at normal temperature when a product bonded at normal temperature is exposed to a high-temperature environment.SOLUTION: The (meth) acrylic copolymer (A) contains alkyl (meth) acrylate components (A1) as polymer chain components, and the (A1) contains at least two kinds of alkyl (meth) acrylate components. The content of (A1) is 60 to 94.99% by mass with respect to the total mass of (A), the content of the carboxyl group-containing monomer (A2) is 5 to 15% by mass with respect to the total mass of the (meth) acrylic copolymer (A) as a constituent of the polymer chain, the content of the hydroxyl group-containing monomer (A3) is 0.01 to 1.0% by mass with respect to the total mass of (A) as a constituent of the polymer chain, and the weight-average molecular weight of (A) is 200000 to 1,200,000.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition and an adhesive tape for use in electronic devices, for holding vehicle equipment, for buildings, etc. [Background technology]

[0002] In industries such as electrical and electronics, mobile, automotive, and construction, adhesive tapes are widely used in place of adhesives to secure parts, etc., from the perspective of workability and the working environment. Acrylic adhesives are particularly popular because they have superior heat resistance and weather resistance compared to rubber-based adhesives, and also offer a high degree of design freedom.

[0003] Adhesives are viscoelastic substances that are in a soft solid state near room temperature. Generally, adhesives soften and become more fluid at high temperatures, so their adhesive strength and bonding power tend to decrease in high temperature environments. However, in recent years, as products have become more sophisticated and functional, adhesive tapes used in the above-mentioned industrial applications are sometimes exposed to higher temperatures than before due to factors such as heat generation from electronic components. Furthermore, with the effects of global warming, adhesive tapes used outdoors, especially in the summer, are experiencing problems with their adhesive strength decreasing and peeling at high temperatures. For these reasons, there is a demand for adhesive tapes that can maintain high adhesiveness and adhesion even at high temperatures.

[0004] As a solution to these problems, for example, Patent Document 1 discloses an acrylic pressure-sensitive adhesive composition having an adhesive strength of 100 g / 25 mm or more at 80 to 120°C, which comprises: an acrylic polymer (A) obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester, a functional group-containing monomer, and optionally other radically polymerizable monomers, and having an adhesive strength of 200 g / 25 mm or more at 80 to 120°C; and an acrylic polymer (B) obtained by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester, a functional group-containing monomer, and optionally other radically polymerizable monomers, and having an adhesive strength of 500 g / 25 mm or more at room temperature (23°C), in a ratio of (A):(B) ranging from 10:90 to 90:10 (weight ratio). This technology aims to obtain an acrylic adhesive composition that has good adhesion at room temperature and maintains its adhesion even at high temperatures, and that can be used suitably for a variety of applications, such as paint masking tape and double-sided adhesive tape (including adhesive sheets), which undergo baking and high-temperature drying processes after painting.

[0005] Furthermore, for example, Patent Document 2 discloses a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has a breaking strength of 2 MPa or less in a tensile test carried out under the condition of a tensile speed of 10 mm / min, and the pressure-sensitive adhesive sheet has a 180-degree peel strength P RT and 180-degree peel strength P against stainless steel plate measured at 80°C 80℃ The 80℃ adhesive strength retention rate (P 80℃ / P RT × 100) is 50% or more. This technology aims to obtain an adhesive sheet that has good high-temperature shear retention properties and stress relaxation properties that make it difficult for the effects of protrusions or steps on one side of the adhesive sheet to appear on the other side, when used to fix components inside portable electronic devices. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 4-68074 [Patent Document 2] Japanese Patent Publication No. 2022-47704 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology of Patent Document 1 is aimed at obtaining adhesive strength sufficient to prevent peeling during the baking and high-temperature drying process in masking applications. Masking applications require removability after the process, which is different from the objective of maintaining adhesive strength for applications such as fixing and holding. The acrylic adhesive composition of this technology has relatively high adhesive strength at high temperatures, but is not suitable for strong adhesive applications, and its adhesive strength at room temperature is insufficient when used for various fixing applications.

[0008] The technology of Patent Document 2 has an adhesive strength retention rate at 80°C of 50% or more of the adhesive strength at room temperature, and although it can maintain adhesive strength at high temperatures to a certain extent, it cannot maintain adhesive strength at high temperatures to the same level as at room temperature. In other words, it does not increase adhesive strength significantly at high temperatures compared to room temperature.

[0009] To obtain excellent properties at high temperatures such as 80°C from resin compositions used in adhesives, one approach would be to increase the glass transition temperature (Tg) of the composition components and increase their molecular weight. However, increasing the polymer's glass transition temperature can lead to problems with poor adhesive properties at room temperature. Furthermore, increasing the crosslink density to prevent softening at high temperatures can lead to the adhesive becoming too hard and losing its adhesive properties. Due to these factors, it has not been possible to obtain a resin composition that can maintain its adhesive properties at both room and high temperatures.

[0010] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a resin composition and an adhesive tape which, while exhibiting high room temperature adhesive strength, when the room temperature bonded product is exposed to a high temperature environment, maintains at least 90% of the room temperature adhesive strength, and in particular maintains 96% or more, thereby significantly improving the adhesive strength. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention has the following aspects. [1] A resin composition containing a (meth)acrylic copolymer (A), the (meth)acrylic copolymer (A) contains, as polymer chain constituent components, a (meth)acrylic acid alkyl ester component (A1), a carboxyl group-containing monomer (A2), and a hydroxyl group-containing monomer (A3); the (meth)acrylic acid alkyl ester component (A1) contains (meth)acrylic acid alkyl ester monomer components (A1-1) and (A1-2) each having an alkyl group having 1 to 4 carbon atoms, the content of the (meth)acrylic acid alkyl ester component (A1) is 60% by mass or more and 94.99% by mass or less based on the total mass of the (meth)acrylic copolymer (A); the content of the carboxyl group-containing monomer (A2) is 5% by mass or more and 15% by mass or less relative to the total mass of the (meth)acrylic copolymer (A); the content of the hydroxyl group-containing monomer (A3) is 0.01% by mass or more and 1.0% by mass or less based on the total mass of the (meth)acrylic copolymer (A), A resin composition, wherein the (meth)acrylic copolymer (A) has a weight average molecular weight of 200,000 or more and 1,200,000 or less as measured by gel permeation chromatography (standard polystyrene equivalent). [2] The resin composition according to [1], wherein an adhesive tape having an adhesive layer formed from the resin composition has an adhesive strength retention rate (% when heated) of 90% or more ((adhesive strength measured in an 80°C atmosphere / adhesive strength measured in a 23°C atmosphere) x 100). [3] The resin composition according to [1] or [2], wherein the (meth)acrylic acid alkyl ester monomer component (A1-1) is a (meth)acrylic acid alkyl ester having an alkyl group having 4 carbon atoms. [4] The resin composition according to any one of [1] to [3], wherein the (meth)acrylic acid alkyl ester monomer component (A1-2) is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms. [5] The resin composition according to any one of [1] to [4], wherein the content of the (meth)acrylic acid alkyl ester monomer component (A1-1) is 55% by mass or more and 86% by mass or less, and the content of the (meth)acrylic acid alkyl ester monomer component (A1-2) is 3% by mass or more and 15% by mass or less, relative to the total mass of the (meth)acrylic copolymer (A). [6] The resin composition according to any one of [1] to [5], wherein the (meth)acrylic copolymer (A) further contains another monomer component (A4) as a polymer chain constituent, and the other monomer component (A4) is at least one selected from the group consisting of vinyl esters, alkoxyalkyl (meth)acrylates, and (meth)acrylic acid alkyl esters having an alkyl group having 8 or more carbon atoms. [7] The resin composition according to any one of [1] to [6], which has a theoretical glass transition temperature (theoretical Tg) of −50° C. (223 K) or higher and −25° C. (248 K) or lower. [8] A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer formed from the resin composition according to any one of [1] to [7]. [9] The storage modulus G' of the adhesive layer at 23°C and 80°C is 1.0 × 10 5 Over 3.0 x 10 6 (Pa) or less, and the complex viscosity measured under the following measurement conditions at 23°C and 80°C is 1.5 x 10 3 (Pa s) or more 6.0×10 4 (Pa·s) or less. (Measurement conditions) The measurement sample (adhesive layer thickness formed to 2.0 mm) is sandwiched between parallel disks (φ8 mm), and using a dynamic viscoelasticity measuring device, the storage modulus G´ (unit: Pa) and complex viscosity (unit: Pa·s) are measured at a temperature range of -60°C to 180°C and a heating rate of 10°C / min while applying a load of 10 g, a frequency of 10 Hz, and a shear strain of 0.1%. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a resin composition and an adhesive tape which exhibit high adhesive strength at room temperature, but which maintains at least 90% of the adhesive strength at room temperature, and in particular 96% or more, when exposed to a high-temperature environment after being bonded at room temperature, thereby achieving a significant improvement in adhesive strength. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic side cross-sectional view showing a pressure-sensitive adhesive tape according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The resin composition and pressure-sensitive adhesive tape according to the present invention will be described below with reference to embodiments, although the present invention is not limited to the following embodiments.

[0015] (1. Resin composition) (1-1. (Meth)acrylic copolymer (A)) The resin composition of the present embodiment comprises a (meth)acrylic copolymer (A), wherein the (meth)acrylic copolymer (A) comprises a (meth)acrylic acid alkyl ester component (A1) as a polymer chain constituent component, and the (meth)acrylic acid alkyl ester component (A1) comprises (A1-1) and (A1-2) (meth)acrylic acid alkyl ester monomers having an alkyl group having 1 to 4 carbon atoms, the (meth)acrylic acid alkyl ester component (A1) being 60% by mass or more and 94.99% by mass or less, based on the total mass of the (meth)acrylic copolymer (A), a carboxyl group-containing monomer (A2) as a polymer chain constituent component, and a hydroxyl group-containing monomer (A3) as a polymer chain constituent component, the hydroxyl group-containing monomer being 0.01% by mass or more and 1.0% by mass or less, based on the total mass of the (meth)acrylic copolymer (A). In the following description, "(meth)acrylic" is a general term for acrylic and methacrylic.

[0016] (1-1-1. (Meth)acrylic acid alkyl ester component (A1)) The (meth)acrylic acid alkyl ester component (A1) of this embodiment contains (meth)acrylic acid alkyl ester monomer components (A1-1) and (A1-2) as essential components, and it is preferred that the (meth)acrylic acid alkyl ester monomer component (A1-1) has an alkyl group with 4 carbon atoms, and the (meth)acrylic acid alkyl ester monomer component (A1-2) has an alkyl group with 1 to 3 carbon atoms.

[0017] The total amount of the (meth)acrylic acid alkyl ester components (A1) is 60% by mass or more and 94.99% by mass or less based on the total mass of the (meth)acrylic copolymer (A). A total of 60% by mass or more and 94.99% by mass or less contributes to improving the adhesive strength of a resin composition containing the (meth)acrylic copolymer (A) when heated. Furthermore, by setting the total amount to 60% by mass or more and 94.99% by mass or less, it becomes easy to adjust the theoretical glass transition temperature (Tg) of the (meth)acrylic copolymer (A). Furthermore, the total amount of the (A1) may be 94.95% by mass or less. The total amount of the (meth)acrylic acid alkyl ester component (A1) is preferably 70% by mass or more and 94% by mass or less, and more preferably 80% by mass or more and 92% by mass or less, based on the total mass of the (meth)acrylic copolymer (A).

[0018] Specific examples of the (meth)acrylic acid alkyl ester having an alkyl group having 4 carbon atoms include normal butyl (meth)acrylate, isobutyl (meth)acrylate, and tertiary butyl (meth)acrylate. Two or more of these may be used in combination. Among these, normal butyl (meth)acrylate is preferred.

[0019] Specific examples of the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, normal propyl (meth)acrylate, and isopropyl (meth)acrylate. Two or more of these may be used in combination. Among these, methyl (meth)acrylate and / or ethyl (meth)acrylate are preferred.

[0020] The content of the (meth)acrylic acid alkyl ester component (A1-1) is preferably 55% by mass or more and 86% by mass or less, more preferably 65% ​​by mass or more and 83% by mass or less, based on the total mass of the (meth)acrylic copolymer (A).

[0021] The content of the (meth)acrylic acid alkyl ester component (A1-2) is preferably 3% by mass or more and 15% by mass or less, more preferably 5% by mass or more and 13% by mass or less, based on the total mass of the (meth)acrylic copolymer (A).

[0022] (1-1-2. Carboxyl group-containing monomer (A2)) The (meth)acrylic copolymer (A) of this embodiment contains, as a polymer chain constituent, a carboxyl group-containing monomer (A2) in addition to the (meth)acrylic acid alkyl ester component (A1). Specific examples of the carboxyl group-containing monomer (A2) include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-carboxy-1-butene, 2-carboxy-1-pentene, 2-carboxy-1-hexene, 2-carboxy-1-heptene, 2-methacryloyloxyethyl succinic acid, and 2-acryloyloxyethyl succinic acid. Two or more of these may be used in combination. Among these, acrylic acid and / or methacrylic acid are preferred.

[0023] The content of the carboxyl group-containing monomer (A2) is 5% by mass or more and 15% by mass or less based on the total mass of the (meth)acrylic copolymer (A). The total content of 5% by mass or more and 15% by mass or less contributes to improving the adhesive strength of the resin composition containing the (meth)acrylic copolymer (A). The content of the carboxyl group-containing monomer (A2) is preferably 5% by mass or more and 13% by mass or less, and more preferably 6% by mass or more and 10% by mass or less, based on the total mass of the (meth)acrylic copolymer (A).

[0024] (1-1-3. Hydroxyl group-containing monomer (A3)) The (meth)acrylic copolymer (A) of this embodiment contains, as polymer chain constituents, a (meth)acrylic acid alkyl ester component (A1), a carboxyl group-containing monomer (A2), and a hydroxyl group-containing monomer (A3). Specific examples of the hydroxyl group-containing monomer (A3) include, but are not limited to, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-hydroxy-3-acryloyloxypropyl (meth)acrylate. Two or more of these may be used in combination. Among these, 2-hydroxyethyl (meth)acrylate and / or 4-hydroxybutyl (meth)acrylate are preferred.

[0025] The content of the hydroxyl group-containing monomer (A3) is 0.01% by mass or more and 1.0% by mass or less based on the total mass of the (meth)acrylic copolymer (A). By setting the total content to 0.01% by mass or more and 1.0% by mass or less, it becomes easy to adjust the degree of crosslinking of the resin composition containing the (meth)acrylic copolymer (A). The content of the hydroxyl group-containing monomer (A3) is preferably 0.05% by mass or more and 1.0% by mass or less, more preferably 0.05% by mass or more and 0.50% by mass or less, and even more preferably 0.05% by mass or more and 0.10% by mass or less, based on the total mass of the (meth)acrylic copolymer (A).

[0026] The total content of the carboxyl group-containing monomer (A2) and the hydroxyl group-containing monomer (A3) is 5.01 mass% or more and 16.0 mass% or less, preferably 5.05 mass% or more and 13.5 mass% or less, and more preferably 6.05 mass% or more and 10.1 mass% or less, based on the total mass of the (meth)acrylic copolymer (A).

[0027] (1-1-4. Other Monomer Components (A4)) The (meth)acrylic copolymer (A) of this embodiment may contain, as polymer chain constituents, an additional monomer component (A4) in addition to the (meth)acrylic acid alkyl ester component (A1), the carboxyl group-containing monomer (A2), and the hydroxyl group-containing monomer (A3). The additional component (A4) is not particularly limited, but may be at least one selected from the group consisting of vinyl esters, alkoxyalkyl (meth)acrylates, and (meth)acrylic acid alkyl esters having an alkyl group having 8 or more carbon atoms. The additional component (A4) may be one or more components selected from the group consisting of components copolymerizable with the (meth)acrylic acid alkyl ester component (A1), the carboxyl group-containing monomer (A2), and the hydroxyl group-containing monomer (A3). Specific examples of the other component (A4) include aliphatic (meth)acrylates such as normal amyl (meth)acrylate, isoamyl (meth)acrylate, normal hexyl (meth)acrylate, normal heptyl (meth)acrylate, normal octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, normal decyl (meth)acrylate, isodecyl (meth)acrylate, normal lauryl (meth)acrylate, normal stearyl (meth)acrylate, and isostearyl (meth)acrylate. acrylates; alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; aromatic (meth)acrylates such as benzyl (meth)acrylate; nitrogen-containing vinyl monomers such as (meth)acrylonitrile, dimethylamino (meth)acrylate, (meth)acryloylmorpholine, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N-isopropyl (meth)acrylamide, and N-vinyl-2-pyrrolidone; phosphorus-containing vinyl monomers such as 2-methacryloyloxyethyl acid phosphate;Also, rosin-modified oligomer, 2-ethylhexyl-diglycol (meth)acrylate, tetrafurfuryl (meth)acrylate, methoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, vinyl acetate, butoxydiethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, glycidyl (meth)acrylate, 1,4-butanediol diglycidyl ether, diethylene glycol di(meth)acrylate, triethylene glycol Other monomers include cholesteryl di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trifluoroethyl (meth)acrylate, polyethylene glycol 200 dimethacrylate, polyethylene glycol 400 dimethacrylate, polyethylene glycol 600 dimethacrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5 pentanediol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0028] (1-1-5. Theoretical Glass Transition Temperature (Theoretical Tg)) The (meth)acrylic copolymer (A) of this embodiment has a theoretical glass transition temperature (theoretical Tg) of -50°C (223K) or higher and -25°C (248K) or lower. A theoretical glass transition temperature (Tg) of -50°C (223K) or higher contributes to improving the adhesive strength retention rate when heated, adhesive strength, and storage modulus and complex viscosity at high temperatures, while a Tg of -25°C (248K) or lower contributes to maintaining room temperature physical properties and strong adhesive strength. This leads to the effect of this embodiment that when a room temperature bonded product is exposed to a high temperature environment, the adhesive strength is maintained at least 90% or more of the room temperature adhesive strength, and in particular 96% or more, resulting in a significant improvement. The theoretical glass transition temperature (Tg) can be determined by a method using the FOX formula, as described in, for example, JP-A-2019-151837. The lower limit of the theoretical glass transition temperature (Tg) is −50° C. (223 K) or higher, preferably −45° C. (228 K) or higher, more preferably −43° C. (230 K) or higher, and the upper limit is −25° C. (248 K) or lower, preferably −30° C. (243 K) or lower, more preferably −35° C. (238 K) or lower.

[0029] (1-1-6.Weight average molecular weight (Mw)) The (meth)acrylic copolymer (A) of this embodiment has a weight average molecular weight (Mw) of 200,000 or more and 1,200,000 or less. The weight average molecular weight (Mw) is preferably 300,000 or more and 1,150,000 or less, and more preferably 400,000 or more and 1,100,000 or less. The weight average molecular weight (Mw) can be measured by a method using a GPC method, which will be described in detail later.

[0030] A weight average molecular weight (Mw) of 200,000 or more contributes to improving cohesive strength, and a weight average molecular weight of 1,200,000 or less contributes to maintaining physical properties such as adhesive strength at room temperature. Furthermore, a weight-average molecular weight (Mw) of 1,200,000 or less is preferable from the viewpoints of improving productivity, reducing material costs, and mitigating the burden on the environment and human body by reducing the amount of organic solvent used. Generally, in acrylic pressure-sensitive adhesives, as the theoretical glass transition temperature (Tg) of the acrylic copolymer contained in the resin composition increases, the viscosity of the resin composition tends to increase, and when obtaining a pressure-sensitive adhesive layer, it becomes necessary to dilute the resin composition with additional solvent from the viewpoint of workability. Since the (meth)acrylic copolymer (A) of this embodiment contains a (meth)acrylic acid alkyl ester component (A1) with a relatively high glass transition temperature (Tg), the theoretical glass transition temperature (Tg) also tends to be relatively high. Even in such cases, by setting the weight-average molecular weight (Mw) to 200,000 or more and 1,200,000 or less, the viscosity of the resin composition can be prevented from increasing, and the addition of a diluting solvent can be eliminated or reduced.

[0031] (1-1-7. Production method of (meth)acrylic copolymer (A) and other components) The (meth)acrylic copolymer (A) can be obtained by copolymerizing multiple monomers. The polymerization method is not particularly limited. For example, it can be produced by known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, or photopolymerization of these, using a thermal polymerization initiator such as benzoyl peroxide, azobisisobutyronitrile, or potassium persulfate, or a photopolymerization initiator such as an acetophenone compound, a triazine compound, an acylphosphine compound, a quinone compound, or a carbazole compound. During polymerization, components other than the components (A1) to (A4) can be used within the scope that does not impair the effects of this embodiment. The components other than the components (A1) to (A4) are not particularly limited, but include, for example, a chain transfer agent to facilitate molecular weight adjustment, a solvent to facilitate viscosity adjustment, an antioxidant to improve the stability of the polymer over time, and a tackifier or other additives to adjust adhesive properties.

[0032] (1-2. Crosslinking Agent) The resin composition of the present embodiment may contain a crosslinking agent to facilitate adjustment of the degree of crosslinking. The degree of crosslinking may be adjusted depending on the application of the resin composition of the present embodiment. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, as well as thermal crosslinking agents such as urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents; and photoreactive crosslinking agents such as acetophenone-based photocrosslinking agents, benzoin-based photocrosslinking agents, benzophenone-based photocrosslinking agents, thioxanthone-based photocrosslinking agents, and acylphosphine oxide-based photocrosslinking agents. Of these, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents are preferred. These crosslinking agents may be used alone or in combination. For example, an isocyanate crosslinking agent and an epoxy crosslinking agent may be used in combination.

[0033] Specific examples of isocyanate-based crosslinking agents include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and xylylene diisocyanate; and trimethylolpropane / tolylene diisocyanate ternary isocyanates. Examples of such polyisocyanates include isocyanate adducts such as a trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), a trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HL"), and an isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HX"), and HDI (hexamethylene diisocyanate)-based polyisocyanates (manufactured by Asahi Kasei Corporation, trade name "Duranate D101"); and commercially available products include, for example, Mitsui Chemicals' products under the trade names "Takenate D-101E" and "Takenate D-103."

[0034] The content of the isocyanate-based crosslinking agent, in terms of solid content, relative to 100 parts by mass of the (meth)acrylic copolymer (A), is typically 0.02 parts by mass or more and 20 parts by mass or less, more preferably 0.05 parts by mass or more and 15 parts by mass or less, particularly preferably 0.1 parts by mass or more and 10 parts by mass or less, and even more preferably 0.6 parts by mass or more and 8 parts by mass or less.

[0035] Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "Tetrad C"), N,N,N',N'-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "Tetrad X"), 1,6-hexanediol diglycidyl ether (manufactured by Kyoeisha Chemical Company, Inc., trade name "Epolite 1600"), neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Company, Inc., trade name "Epolite 1600"). Co., Ltd., trade name "Epolite 1500NP"), ethylene glycol diglycidyl ether (Kyoeisha Chemical Co., Ltd., trade name "Epolite 40E"), propylene glycol diglycidyl ether (Kyoeisha Chemical Co., Ltd., trade name "Epolite 70P"), polyethylene glycol diglycidyl ether (NOF Corporation, trade name "Epiol E-400"), polypropylene glycol diglycidyl ether (NOF Corporation, trade name "Epiol P-200"), sorbitol polyglycidyl ether (Nagase ChemteX Corporation, trade name "Denacol") Examples of commercially available epoxy resins include those manufactured by Soken Chemical Co., Ltd. under the trade names "E-5CM" and "E-5XM."

[0036] The content of the epoxy-based crosslinking agent is from 0.001 to 5.0 parts by mass, preferably from 0.01 to 1.0 parts by mass, more preferably from 0.01 to 0.5 parts by mass, even more preferably from 0.02 to 0.1 parts by mass, and particularly preferably from 0.03 to 0.07 parts by mass, relative to 100 parts by mass of the (meth)acrylic copolymer (A).

[0037] As the metal chelate crosslinking agent, for example, a metal chelate compound whose metal atom is aluminum, zirconium, titanium, zinc, iron, tin, etc. Among them, an aluminum chelate compound or a titanium chelate compound is preferred. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethyl acetoacetate, diisopropoxyaluminum monolauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, diisopropoxyaluminum monoisostearyl acetoacetate, and monoisopropoxyaluminum mono-N-lauroyl-β-alanate monolauryl acetoacetate. acetylacetonate, aluminum tris(acetylacetonate) (manufactured by Kawaken Fine Chemicals Co., Ltd., trade name "Aluminum Chelate Aw"), acetylacetonate aluminum bis(ethyl acetoacetate), monoacetylacetonate aluminum bis(isobutyl acetoacetate) chelate, monoacetylacetonate aluminum bis(2-ethylhexyl acetoacetate) chelate, monoacetylacetonate aluminum bis(dodecyl acetoacetate) chelate, monoacetylacetonate aluminum bis(oleyl acetoacetate) chelate, and the like. Examples of titanium chelate compounds include titanium diisopropoxybis(acetylacetonate), titanium tetra-n-butylate, titanium tetra-2-ethylhexanoate, titanium tetraacetylacetonate, titanium diisopropoxybis(ethylacetoacetate), and titanium octylene glycolate. Other examples of the metal chelate compounds include zirconium tetraacetylacetonate and zirconium tributoxymonoacetylacetonate. The above metal chelate crosslinking agents may be used alone or in combination of two or more.

[0038] The content of the metal chelate crosslinking agent may be 0.01 parts by mass or more and 5.0 parts by mass or less, preferably 0.02 parts by mass or more and 1.0 parts by mass or less, more preferably 0.05 parts by mass or more and 0.2 parts by mass or less, and even more preferably 0.07 parts by mass or more and 0.14 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic copolymer (A).

[0039] The resin composition of this embodiment may not contain a crosslinking agent as long as the above-mentioned object can be achieved. When the total content of the carboxyl group-containing monomer (A2) and the hydroxyl group-containing monomer (A3) is relatively high, crosslinking points can be formed by self-crosslinking between the carboxyl group in the carboxyl group-containing monomer (A2) and the hydroxyl group in the hydroxyl group-containing monomer (A3) without the intervention of a crosslinking agent.

[0040] (1-3. Tackifier) A tackifier may be added to the resin composition of this embodiment as needed to improve adhesive strength. Specific examples of tackifiers include rosin-based resins, xylene-based resins, terpene-based resins, petroleum-based resins, alkylphenol-based resins, coumarone-indene-based resins, coumarone-based resins, indene-based resins, styrene-based resins, and other resins. These may be modified by hydrogenation or the like, or two or more types may be used in combination. Of these, rosin-based resins and / or xylene-based resins are particularly preferred.

[0041] The softening point of the tackifier is not particularly limited, but is preferably not less than 90° C., and more preferably not less than 95° C. This softening point is a value measured in accordance with JIS K 2531 (ring and ball method).

[0042] Examples of rosin resins used in the tackifier include hydrogenated resins, disproportionated resins, polymerized ester resins, other special rosin esters, etc. Commercially available products include Pencel D-125, Pencel D-135, Pencel D-160, Pine Crystal KE-100, Pine Crystal KE-359, Super Ester A-100, Super Ester A-115, and Super Ester A-125 manufactured by Arakawa Chemical Industries, Ltd., and Haritack PCJ, Haritack FK100, and Haritack FK125 manufactured by Harima Chemicals, Inc. Examples of xylene resins include alkylphenol-modified resins, etc. Commercially available products include Nikanol (Y-50, Y-100, Y-300, Y-1000, LLL, LL, L, H, G) manufactured by Fudow Corporation, alkylphenol-modified Nikanol (GHP-150, HP-120, H100, HP-210, HP-70), and novolac Nikanol (NP-100, GP-212, P-100, GP-200). Examples of the terpene resin include terpene phenol resin, α-pinene resin, and β-pinene resin. Examples of petroleum-based resins include aliphatic resins and aromatic resins.

[0043] When a tackifier is added, the proportion relative to 100 parts by mass of the (meth)acrylic copolymer (A) is not particularly limited, but can be selected from preferably more than 0 parts by mass to 20 parts by mass or less, and more preferably 1 part by mass to 15 parts by mass or less. If the amount of tackifier added is more than 20 parts by mass, the cohesive strength may decrease. When a tackifier is used, the lower limit of the content is not particularly limited and can be set appropriately, but can be set to 1 part by mass or more relative to 100 parts by mass of the (meth)acrylic copolymer (A).

[0044] (1-4. Other additives) The resin composition of the present embodiment may further contain various additives such as an antioxidant, an inorganic filler, a light-shielding filler, a pigment, a silane coupling agent, etc., within the range that does not impair the effects of the present embodiment. When an additive is used, the proportion thereof relative to 100 parts by mass of the (meth)acrylic copolymer (A) can be selected from the range of more than 0 parts by mass to 100 parts by mass or less. The lower limit is not particularly limited and can be set appropriately, but can be 0.1 parts by mass or more relative to 100 parts by mass of the (meth)acrylic copolymer (A).

[0045] Specific examples of antioxidants include hindered phenol-based antioxidants, etc. Commercially available products include, for example, "Irganox 1010" manufactured by BASF Japan Ltd. Specific examples of inorganic fillers include silica, calcium carbonate, and alumina. Specific examples of the light-shielding filler include carbon black, carbon nanotubes, and black inorganic fillers. Specific examples of pigments include carbon black, aniline black, acetylene black, and ketjen black. Specific examples of the silane coupling agent include epoxy group-containing silane coupling agents, amino group-containing silane coupling agents, mercapto group-containing silane coupling agents, vinyl group-containing silane coupling agents, etc. Representative examples are epoxy group-containing silane coupling agents, and examples of commercially available products thereof include KBM-303, KBM-402, KBM-403, KBE-402, and KBE-403 manufactured by Shin-Etsu Chemical Co., Ltd.

[0046] (Storage modulus G' and complex viscosity at 1-5.23°C) The pressure-sensitive adhesive layer formed from the resin composition of this embodiment has a specific storage modulus G' and complex viscosity. Here, the "storage modulus G'" and "complex viscosity" in this embodiment are values ​​measured under the following measurement conditions. The measurement sample (adhesive layer thickness formed to 2.0 mm) is sandwiched between parallel disks (φ8 mm), and using a dynamic viscoelasticity measuring device, the storage modulus G´ (unit: Pa) and complex viscosity (unit: Pa·s) are measured at a heating rate of 10°C / min in the range of -60°C to 180°C while applying a load of 10 g, a frequency of 10 Hz, and a shear strain of 0.1%.

[0047] When the resin composition of this embodiment is used as a pressure-sensitive adhesive layer, the storage modulus G' at 23°C is 1.0 × 10 5 (Pa) or more 3.0×10 6 (Pa) or less, and the complex viscosity is 1.5 × 10 3 (Pa s) or more 6.0×10 4 (Pa·s) or less. The storage modulus G' is preferably 2.0 x 10 5 (Pa) or more 2.5×10 6 (Pa) or less, more preferably 2.5 × 10 5 (Pa) or more 2.2×10 6 (Pa) or less, and the complex viscosity is preferably 4.0 × 10 3 (Pa s) or more 5.0×10 4 (Pa·s) or less, preferably 4.5×10 3 (Pa s) or more 4.6×10 4 (Pa·s) or less.

[0048] (Storage modulus G' and complex viscosity at 1-6.80℃) When the resin composition of this embodiment is used as a pressure-sensitive adhesive layer, the storage modulus G' at 80°C is 1.0 × 10 5 (Pa) or more 3.0×10 6 (Pa) or less, and the complex viscosity is 1.5 × 10 3 (Pa s) or more 6.0×10 4 (Pa·s) or less. The storage modulus G' is preferably 1.0 x 10 5 (Pa) or more 1.0×10 6 (Pa) or less, more preferably 1.0 × 10 5 (Pa) or more 5.0×10 5(Pa) or less, and the complex viscosity is preferably 1.6×10 3 (Pa s) or more 6.0×10 3 (Pa·s) or less, preferably 1.7×10 3 (Pa s) or more 5.5×10 3 (Pa·s) or less. The storage modulus is measured by sandwiching the sample (adhesive layer thickness 2.0 mm) between parallel disks (φ8 mm) and measuring the storage modulus G´ (unit: Pa) and complex viscosity (unit: Pa·s) at a temperature range of -60°C to 180°C at a heating rate of 10°C / min using a dynamic viscoelasticity measuring device while applying a load of 10 g, a frequency of 10 Hz, and a shear strain of 0.1%.

[0049] (1-7. Adhesive strength retention rate when heated %) An adhesive tape having an adhesive layer formed from the resin composition of this embodiment has an adhesive strength retention rate upon heating ((adhesive strength measured in an 80°C atmosphere / adhesive strength measured in a 23°C atmosphere) × 100) of 90% or more, preferably 96% or more, and more preferably 100% or more.

[0050] Here, the "adhesive strength" in the present embodiment refers to the adhesive strength measured using a stainless steel plate (SUS304BA plate) as the adherend using a test method in accordance with JIS Z 0237:2000. The adhesive strength in an atmosphere of 23°C is measured after a 20 mm wide adhesive tape is pressure-bonded to an adherend in an environment of 23°C and 50% RH, and then left to stand for 30 minutes. The adhesive strength in an atmosphere of 80°C is measured after a 20 mm wide adhesive tape is pressure-bonded to an adherend in an environment of 23°C and 50% RH, and then left to stand for 30 minutes in a thermostatic chamber set to 80°C, and then measured in an atmosphere of 80°C.

[0051] The adhesive strength is a value measured using an adhesive tape sample in which a 50 μm thick adhesive layer is provided on a 50 μm thick aluminum foil. The adhesive strength retention rate under heating can be calculated using the following formula (1). Adhesive strength retention rate when heated (%) = (AF 80℃ / AF 23℃)×100···(1) Here, AF 80℃ indicates adhesive strength measured in an 80°C atmosphere, and AF 23℃ indicates adhesive strength measured in an atmosphere of 23°C.

[0052] By making the adhesive strength retention rate when heated 90% or more, it is possible to adhere the tape to an adherend at room temperature, while suppressing problems such as peeling, shifting, and curling in a high-temperature atmosphere (e.g., 80°C).

[0053] In this embodiment, the adhesive strength (AF) measured in an atmosphere of 23°C 23℃ The adhesive strength (AF) measured in an atmosphere of 80°C is preferably 2.5 N / 20 mm or more, more preferably 6.0 N / 20 mm or more, even more preferably 8.0 N / 20 mm or more, and particularly preferably 10.0 N / 20 mm or more. 80℃ ) is preferably 2.5 N / 20 mm or more, more preferably 6.0 N / 20 mm or more, even more preferably 8.0 N / 20 mm or more, and particularly preferably 10.0 N / 20 mm or more. The resin composition of the present embodiment has the above-described adhesive strength and can therefore be suitably used mainly as an adhesive, a component of an adhesive composition, a component of an adhesive layer, etc. The resin composition of the present embodiment can also be suitably used for other applications in which high adhesive strength is primarily preferred.

[0054] (2. Pressure-sensitive adhesive tape using the resin composition of the present embodiment) The adhesive tape of this embodiment uses the resin composition described above. FIG. 1 is a diagram showing an embodiment of the pressure-sensitive adhesive tape according to the present invention. The pressure-sensitive adhesive tape shown in (a) is a single-sided pressure-sensitive adhesive tape, and has a pressure-sensitive adhesive layer 2 formed from the resin composition on the upper surface (side A) of a tape-shaped substrate 1.

[0055] 1(b) is a diagram showing a pressure-sensitive adhesive tape according to another embodiment. This pressure-sensitive adhesive tape is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers 2-1 and 2-2 on both sides (upper surface: side A and lower surface: side B) of a tape-like substrate 1, at least one of the two pressure-sensitive adhesive layers being a pressure-sensitive adhesive layer formed from the resin composition according to this embodiment.

[0056] 1(c) is a view showing a pressure-sensitive adhesive tape according to another embodiment, which is a substrate-less type pressure-sensitive adhesive tape that does not use a substrate and is composed of only a pressure-sensitive adhesive layer 2.

[0057] (2-1. Adhesive tape form) The pressure-sensitive adhesive tape of this embodiment has multiple layers, at least one of which is a pressure-sensitive adhesive layer formed from the resin composition of this embodiment. For example, it may be a single-sided pressure-sensitive adhesive tape ((a) in the figure) having a pressure-sensitive adhesive layer on one side of a substrate, or a double-sided pressure-sensitive adhesive tape ((b) in the figure) having pressure-sensitive adhesive layers on both sides of a substrate. In the case of a double-sided pressure-sensitive adhesive tape, the pressure-sensitive adhesive layers on both sides may be pressure-sensitive adhesive layers formed from the resin composition of this embodiment, or only one side may be a pressure-sensitive adhesive layer formed from the resin composition of this embodiment. Similarly, when the tape includes three or more pressure-sensitive adhesive layers, at least one of the pressure-sensitive adhesive layers may be a pressure-sensitive adhesive layer formed from the resin composition of this embodiment.

[0058] The pressure-sensitive adhesive tape of the present embodiment may also be a substrate-less pressure-sensitive adhesive tape ((c) in the figure). In this case, during the production of the substrate-less pressure-sensitive adhesive tape, both sides of the pressure-sensitive adhesive layer are covered with release layers before use, and the release layers are peeled off when the tape is used.

[0059] (2-2. Thickness of adhesive tape) The thickness (thickness) of the pressure-sensitive adhesive tape of the present embodiment is not particularly limited. For example, when a plastic film is used as the substrate, it is preferably 2 μm or more and 550 μm or less, more preferably 5 μm or more and 300 μm or less, and even more preferably 10 μm or more and 250 μm or less. Furthermore, when a substrate-less tape is used, it is preferably 1 μm or more and 250 μm or less, more preferably 2 μm or more and 150 μm or less, and even more preferably 10 μm or more and 125 μm or less. If the pressure-sensitive adhesive tape is appropriately thin, it can be suitably used in applications requiring thinness (for example, applications in PCs and portable devices such as displays). When a foam is used as the substrate, the thickness is, for example, 60 μm or more and 5.5 mm or less; when a metal foil is used as the substrate, the thickness is, for example, 6 μm or more and 400 μm or less; when a woven fabric, nonwoven fabric, or paper is used as the substrate, the thickness is, for example, 30 μm or more and 5.5 mm or less.

[0060] (2-3. Adhesive layer) (2-3-1. Thickness of adhesive layer) The thickness of the adhesive layer is preferably 1 μm or more and 250 μm or less, more preferably 2 μm or more and 200 μm or less, even more preferably 5 μm or more and 125 μm or less, and particularly preferably 10 μm or more and 125 μm or less. If the adhesive layer is moderately thick, the degree of deformability of the adhesive layer increases, allowing it to adequately follow dimensional changes in the member and suppress the occurrence of wrinkles in the member. On the other hand, if the adhesive layer is moderately thin, it can be suitably used in applications requiring thinness (for example, applications in liquid crystal displays).

[0061] (2-4. Base material) (2-4-1. Types of substrate) The type of substrate is not particularly limited, and any known substrate may be used. Specific examples include plastic films, foams, metal foils, woven fabrics, nonwoven fabrics, and paper. Two or more of these may be used in combination. When a plastic film is used as the substrate, examples of the constituent material of the plastic film include polyether ether ketone (PEEK), polyimide (PI), polyamide (PA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polyethylene (PE), and polyphenylene sulfide (PPS). When a foam is used as the substrate, examples of the foam's constituent materials include polyurethane (PU), polyethylene (PE), polyethylene vinyl acetate copolymer (EVA), polypropylene (PP), poly(meth)acrylic (co)polymer, and polyethylene-propylene copolymer. These may be used alone or in combination of two or more. A composite foam may be used in which a foam is laminated with the same or a different foam, or a foam or composite foam may be laminated with a substrate such as a film. When a metal foil is used as the substrate, examples of the material of the metal foil include copper and aluminum. When a woven fabric, mesh fabric, nonwoven fabric or paper is used as the substrate, the constituent materials of the woven fabric, mesh fabric, nonwoven fabric or paper include natural materials, synthetic fibers, semi-synthetic fibers and recycled fibers.

[0062] When the substrate is required to have functions such as easy adhesion, antistatic properties, color discrimination properties, light-shielding properties, flame retardancy, sealability, hand tearability, antibacterial properties, etc., it is sufficient to use a substrate whose surface has been subjected to printing, coating, painting, lamination, plating, vapor deposition, sputtering, antibacterial treatment, etc., or a substrate whose surface has been subjected to corona discharge treatment, plasma discharge treatment, etc. Alternatively, it is sufficient to use a substrate whose material itself contains functional components such as pigments, antibacterial agents, flame retardants, dyes, etc., by mixing, immersion, etc.

[0063] (2-4-2. Thickness of the base material) The thickness of the substrate is not particularly limited. For example, in the case of a plastic film, it is preferably 1 μm or more and 300 μm or less, more preferably 2 μm or more and 250 μm or less, and even more preferably 2 μm or more and 150 μm or less. If the substrate is appropriately thin, it can be suitably used in applications requiring thinness (for example, applications in PCs and mobile devices such as displays). When the substrate is a foam, it is, for example, 50 μm to 5 mm; when it is a metal foil, it is, for example, 5 μm to 150 μm; and when it is a woven fabric, nonwoven fabric, or paper, it is, for example, 20 μm to 5 mm.

[0064] (2-5. Manufacturing method of adhesive tape) The method for producing the pressure-sensitive adhesive tape of the present embodiment is not particularly limited, and the tape can be produced by a conventionally known production method. For example, a solution obtained by diluting the resin composition of the present embodiment with an organic solvent or the like as necessary, or an acrylic syrup prepared by adding an acrylic monomer, a multifunctional crosslinking agent, and a photopolymerization initiator to the resin composition of the present embodiment, is prepared, and the resultant solution is applied to a support such as a release sheet, film, paper, or cloth, and is then heated and dried or irradiated with light as necessary to form a pressure-sensitive adhesive layer. When the pressure-sensitive adhesive layer is formed on the release surface of the release sheet, it can be further laminated to a support such as film, paper, cloth, etc. to obtain a pressure-sensitive adhesive tape having a substrate. Alternatively, the resin composition can be directly applied to the non-release surface of film, paper, cloth, or a release sheet to obtain a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer provided on a substrate. When a double-sided pressure-sensitive adhesive tape is produced, a pressure-sensitive adhesive layer may be formed on each of the two surfaces of the substrate by any of the methods described above. A substrate-less pressure-sensitive adhesive tape can be obtained by laminating an adhesive layer formed on the release surface of a release sheet to another release sheet, or by winding up an adhesive layer formed on one surface of a release sheet having release surfaces on both sides. The release sheet can be release paper, a plastic film having a releasable surface, or the like.

[0065] (2-6. Uses of adhesive tape) The adhesive tape of this embodiment has sufficient adhesive strength even at room temperature, and is not particularly limited thereto, but is useful in applications where adhesive strength must be maintained even under temperature changes, particularly at high temperatures. The pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed from the resin composition of the present embodiment can be suitably used in various applications such as vehicles, electronic devices, and buildings. Applications of the pressure-sensitive adhesive tape of the present embodiment for use in vehicles include decorative sheets and marking films used on vehicle exteriors, paint masking tapes used when painting vehicles, fixing vehicle interior components, components for in-vehicle displays (so-called car navigation systems), fixing components in engine compartments, fixing airbags, and bundling harnesses. The pressure-sensitive adhesive tape of the present embodiment is particularly effective as a masking tape when painting curved surfaces such as vehicle bumpers and motorcycle tanks, and can suppress lifting and peeling during high-temperature baking processes. Furthermore, when used to seal and fix airbags (inflators), it can suppress malfunctions caused by peeling of the pressure-sensitive adhesive tape at high temperatures. Furthermore, when used to fasten automobile interior components such as ceiling materials, seat covering materials, car mats, and floor carpets, problems such as peeling at high temperatures can be prevented. Applications in electronic devices include fixing components of portable electronic devices, large displays, and personal computers (PCs). Fixing components of portable electronic devices includes fixing anti-reflection films, alignment films, retardation films, brightness enhancement films, etc. that make up liquid crystal displays (LCDs), organic EL films and electrodes that make up organic light-emitting diode displays (OLEDs), and fixing surface cover glass to a housing. Fixing components in PCs includes fixing central processing units (CPUs), which tend to generate high heat, to heat dissipation components such as heat sinks.

[0066] A more specific application of the pressure-sensitive adhesive tape of this embodiment is in the manufacturing process of the entire electronic component, in which lifting and peeling can be suppressed, particularly during the heating step. In addition, solder masking, especially in the manufacturing process, can prevent lifting and peeling during the reflow process. Another example is the fixing of display members, which can be used to adhere the tape to curved or deformable display members, such as flexible displays, by allowing the tape to conform to them. Another example is the fixing of components that are prone to high temperatures, such as heat sinks and fans that are heat dissipation components. Even when these components become very hot, peeling can be prevented. It is also used for electrical insulation, particularly for F and H type insulation, and can prevent peeling at terminals at high temperatures. Further, the film can be used for batteries. In batteries, the film can be used for core fasteners, insulation of electrode outlets, terminal fasteners, insulating spacers, etc. Peeling can be suppressed in these components and applications. In buildings, the film can be used for outdoor curing, for example, to prevent peeling from rough surfaces such as concrete when temperatures rise in the summer.

[0067] (3. Effects of this embodiment) According to this embodiment, it is possible to provide a resin composition and an adhesive tape that exhibit high adhesive strength at room temperature, but when the adhesive strength is exposed to a high-temperature environment after being bonded at room temperature, the adhesive strength is maintained at least 90% or more of the adhesive strength at room temperature, and in particular, 96% or more, and is thus significantly improved.

[0068] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. [Example]

[0069] The effects of the present invention will be made clearer by the following examples and comparative examples. Note that the present invention is not limited to the following examples, and can be practiced by making appropriate changes within the scope of the present invention.

[0070] (4-1. Preparation of (meth)acrylic copolymer (A)) A reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with the monomer components shown in the table, ethyl acetate as a solvent, n-dodecanethiol as a chain transfer agent, and Perloyl L as a radical polymerization initiator. Nitrogen gas was sealed into the reactor, and the polymerization reaction was carried out under a nitrogen gas stream with stirring at 68°C for 3 hours, then at 78°C for 3 hours, at a polymerization concentration of 50%. The mixture was then diluted with ethyl acetate as a solvent to a concentration that made it easy to remove, and cooled to room temperature to obtain (meth)acrylic copolymer (A). The abbreviations for the monomer components listed in the table are as follows (in no particular order): "MA": methyl acrylate "MMA": Methyl methacrylate "EA": Ethyl acrylate "BA": normal butyl acrylate "tBA": tertiary butyl acrylate "AA": acrylic acid "MAA": methacrylic acid "2-HEA": 2-hydroxyethyl acrylate "4-HBA": 4-hydroxybutyl acrylate "2-EHA": 2-ethylhexyl acrylate "Vac": Vinyl acetate "AME": methoxyethyl acrylate "nDSH": 1-dodecanethiol (n-dodecanethiol, chain transfer agent), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. "Perloyl L": NOF Corporation, trade name "Perloyl (registered trademark) L" (radical polymerization initiator)

[0071] (4-2. Preparation of adhesive tape samples and samples for dynamic viscoelasticity measurement) Resin compositions of Examples 1 to 16 and Comparative Examples 1 to 6 were prepared by adding and mixing the crosslinking agent, tackifier, and other additives in the amounts shown in the table to 100 parts by mass of the solid content of the (meth)acrylic copolymer (A). The amounts shown in the table are all amounts excluding the solvent. If necessary, the components were diluted with an organic solvent such as ethyl acetate or toluene before mixing. This resin composition was applied to the release-treated surface of a 75-μm-thick silicone-treated release film so that the thickness of the adhesive layer after drying would be 50 μm. The film was then heated at 110°C for 2 minutes to remove the solvent and induce a crosslinking reaction, yielding an adhesive layer with a thickness of 50 μm. The adhesive layer was attached to one side of a 50-μm-thick aluminum foil and allowed to stand at 40°C for 3 days to prepare a single-sided adhesive tape for adhesive strength measurement. The pressure-sensitive adhesive layer was attached to the release surface of a 50 μm-thick silicone-treated release film and cured at 40° C. for 3 days to produce a substrate-less double-sided pressure-sensitive adhesive tape with a thickness of 50 μm. The substrate-less double-sided pressure-sensitive adhesive tapes were laminated to a thickness of 2 mm to produce a sample for measuring dynamic viscoelasticity.

[0072] The symbols for the crosslinking agents, tackifiers, and other additives listed in the table correspond to the following (in no particular order):

[0073] In the table, for crosslinking agents (i) to (v), (i) Mitsui Chemicals, Inc., product name "Takenate D-101E" (isocyanate-based crosslinking agent, solids concentration approximately 75%) (ii) Soken Chemical Co., Ltd., product name "E-5CM" (epoxy crosslinking agent, solid content concentration approximately 5%) (iii) Kawaken Fine Chemicals Co., Ltd., trade name "Aluminum Chelate Aw" (metal chelate crosslinking agent) (iv) Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L" (isocyanate-based crosslinking agent, solid content concentration approximately 75%) (v) Soken Chemical Co., Ltd., product name "E-5C" (epoxy crosslinking agent, solid content approximately 5%)

[0074] In the table, the tackifiers (i) to (iii) are as follows: (i) Nikanol GHP-150 (xylene-based resin), manufactured by Fudow Co., Ltd. (ii) Arakawa Chemical Industries, Ltd., product name "Super Ester A-100" (rosin-based resin) (iii) Arakawa Chemical Industries, Ltd., trade name "Pensel D-135" (rosin-based resin)

[0075] In the table, for other additives (i) and (ii), (i) BASF Japan, product name "Irganox 1010" (antioxidant) (ii) Shin-Etsu Silicones Co., Ltd., product name "KBM-403" (silane coupling agent)

[0076] (5.Measurement method) The evaluation items in the examples and comparative examples were measured by the following methods.

[0077] (5-1. Weight average molecular weight (Mw)) The weight average molecular weight of the (meth)acrylic copolymer (A) was measured as a molecular weight converted into standard polystyrene by GPC (gel permeation chromatography) using the following measuring device and conditions: Equipment: LC-2000 series (JASCO Corporation) Columns: Shodex KF-806M x 2, Shodex KF-802 x 1 Eluent: THF (tetrahydrofuran) Flow rate: 1.0mL / min Column temperature: 40℃ Injection volume: 100μL Detector: Refractometer (RI) Measurement sample: (Meth)acrylic copolymer (A) was dissolved in THF, and then filtered to remove any impurities.

[0078] (5-2. Theoretical Glass Transition Temperature (Tg)) The theoretical glass transition temperature (Tg) of the (meth)acrylic copolymer (A) was calculated using the FOX equation. The Tg values ​​of the homopolymers of each monomer component were calculated based on literature values: MA: 8°C, MMA: 105°C, EA: -22°C, BA: -55°C, tBA: 41°C, AA: 106°C, MAA: 144°C, 2-HEA: -15°C, 4-HBA: -32°C, 2-EHA: -85°C, Vac: 28°C, and AME: -50°C.

[0079] (5-3. Adhesive strength) The adhesive strength was measured using the aluminum foil-based single-sided adhesive tape as a sample and a stainless steel plate (SUS304BA plate) as an adherend, using a test method in accordance with JIS Z 0237:2000. Measurements were made in an atmosphere of 23°C using a Strograph (Strograph EL, manufactured by Toyo Seiki Co., Ltd.) in an environment of 23°C and 50% RH. A 20 mm wide, 125 mm long adhesive tape was attached to the adherend and pressed back and forth once with a 2 kg rubber roller. After leaving the tape to stand for 30 minutes in an environment of 23°C and 50% RH, measurements were made at a peel angle of 180° and a peel speed of 300 mm / min. For measurements in an 80°C atmosphere, a Strograph with a thermostatic chamber (manufactured by Toyo Seiki, device name: Strograph T) was used. In an environment of 23°C and 50% RH, a 20 mm wide, 125 mm long adhesive tape was attached to the adherend, pressed back and forth once with a 2 kg rubber roller, and then left to stand for 30 minutes in the thermostatic chamber attached to the Strograph, which was set to 80°C, before measurements were made at a peel angle of 180° and a peel speed of 300 mm / min.

[0080] (5-4. Storage modulus G´ and complex viscosity) The dynamic viscoelasticity was measured using the above-mentioned sample for measuring dynamic viscoelasticity. The sample was sandwiched between parallel disks (φ8 mm) and measured for storage modulus G´ (unit: Pa) and complex viscosity (unit: Pa·s) using a dynamic viscoelasticity measuring device (TA Instruments Japan, device name: ARES-G2) at a temperature range of -60°C to 180°C at a heating rate of 10°C / min while applying a load of 10 g, a frequency of 10 Hz, and a shear strain of 0.1%.

[0081] (6-1. Evaluation Results) The measurement results of each of the Examples and Comparative Examples are shown in Tables 1 to 3, and the obtained measurement results were evaluated as follows. ·Adhesion retention rate when heated 110% or more: ◎+ 100% or more but less than 110%: ◎ 96% or more but less than 100%: Yes 90% or more but less than 96%: △ Less than 90%: ×

[0082] ·Adhesive strength (23℃) 20Nmm / 20mm or more: ◎+ 10N / 20mm or more and less than 20N / 20mm: ◎ 8N / 20mm or more and less than 10N / 20mm: Yes 6N / 20mm or more and less than 8N / 20mm: △ Less than 6N / 20mm: ×

[0083] ·Adhesive strength (80℃) 20Nmm / 20mm or more: ◎+ 10N / 20mm or more and less than 20N / 20mm: ◎ 8N / 20mm or more and less than 10N / 20mm: Yes 6N / 20mm or more and less than 8N / 20mm: △ Less than 6N / 20mm: ×

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3]

[0087] As shown in the table, the adhesive strength retention rate when heated and the adhesive strength at 23 ° C. and 80 ° C. were both evaluated as ○ to ◎+ when the content of the (meth)acrylic acid alkyl ester component (A1) was 60 mass% or more (Example 14) or 94.99 mass% or less (Example 6), the content of the carboxyl group-containing monomer (A2) was 5 mass% or more (Example 6) or 15 mass% or less (Examples 14 to 16), the content of the hydroxyl group-containing monomer (A3) was 0.01 mass% or more (Example 4) or 1.0 mass% or less (Example 15), the content of the (meth)acrylic acid alkyl ester (A1-1) was 55 mass% or more (Example 14) or 86 mass% or less (Example 6), and the content of the (meth)acrylic acid alkyl ester (A1-2) was 5 mass% or more (Examples 14 and 15) or 15 mass% or less (Example 16), relative to the total mass of the (meth)acrylic copolymer (A). This shows that the adhesive tapes of the examples have sufficient adhesive strength to be used at room temperature, and that the adhesive strength does not decrease or increases significantly even at high temperatures, making them suitable for use as adhesive tapes at high temperatures for a variety of applications.

[0088] On the other hand, when the content of the (meth)acrylic acid alkyl ester component (A1) was less than 60% by mass (Comparative Examples 1 to 5) or more than 94.99% by mass (Comparative Example 6), the content of the carboxyl group-containing monomer (A2) was less than 5% by mass (Comparative Example 6), the content of the hydroxyl group-containing monomer (A3) was more than 1.0% by mass (Comparative Example 2), and the content of the (meth)acrylic acid alkyl ester (A1-1) was less than 55% by mass (Comparative Examples 1 to 5) or more than 86% by mass (Comparative Example 6), the adhesive strength at 23°C and 80°C was relatively good, but the adhesive strength retention rate when heated was always poor.

[0089] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Industrial Applicability]

[0090] According to this embodiment, it is possible to provide a resin composition and adhesive tape that exhibit high room temperature adhesive strength, but when the room temperature bonded product is exposed to a high temperature environment, the adhesive strength is maintained at at least 90% or more of the room temperature adhesive strength, particularly at least 96%, thereby significantly improving. Because the present invention is capable of room temperature bonding, it is useful for room temperature applications, but is particularly useful for high temperature adhesive applications. The high temperature adhesive applications are primarily applications suitable for bonding components at high temperatures. For example, the resin composition and adhesive tape can be used for structural bonding, sealing, and other fixing applications for heat-generating electronic devices and automotive parts exposed to high temperature environments, as well as for construction applications.

Claims

1. A resin composition containing a (meth)acrylic copolymer (A), the (meth)acrylic copolymer (A) contains, as polymer chain constituent components, a (meth)acrylic acid alkyl ester component (A1), a carboxyl group-containing monomer (A2), and a hydroxyl group-containing monomer (A3); the (meth)acrylic acid alkyl ester component (A1) contains (meth)acrylic acid alkyl ester monomer components (A1-1) and (A1-2) each having an alkyl group having 1 to 4 carbon atoms, the content of the (meth)acrylic acid alkyl ester component (A1) is 60% by mass or more and 94.99% by mass or less based on the total mass of the (meth)acrylic copolymer (A); the content of the carboxyl group-containing monomer (A2) is 5% by mass or more and 15% by mass or less based on the total mass of the (meth)acrylic copolymer (A), the content of the hydroxyl group-containing monomer (A3) is 0.01% by mass or more and 1.0% by mass or less based on the total mass of the (meth)acrylic copolymer (A), The resin composition, wherein the (meth)acrylic copolymer (A) has a weight average molecular weight of 200,000 or more and 1,200,000 or less as measured by gel permeation chromatography (standard polystyrene equivalent).

2. 2. The resin composition according to claim 1, wherein an adhesive tape having an adhesive layer formed from the resin composition has an adhesive strength retention rate upon heating of 90% or more ((adhesive strength measured in an 80°C atmosphere / adhesive strength measured in a 23°C atmosphere) x 100).

3. 3. The resin composition according to claim 1, wherein the (meth)acrylic acid alkyl ester monomer component (A1-1) is a (meth)acrylic acid alkyl ester having an alkyl group having 4 carbon atoms.

4. 3. The resin composition according to claim 1, wherein the (meth)acrylic acid alkyl ester monomer component (A1-2) is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms.

5. 2. The resin composition according to claim 1, wherein the content of the (meth)acrylic acid alkyl ester monomer component (A1-1) is 55% by mass or more and 86% by mass or less, and the content of the (meth)acrylic acid alkyl ester monomer component (A1-2) is 3% by mass or more and 15% by mass or less, relative to the total mass of the (meth)acrylic copolymer (A).

6. 2. The resin composition according to claim 1, wherein the (meth)acrylic copolymer (A) further contains another monomer component (A4) as a polymer chain constituent, and the other monomer component (A4) is at least one selected from the group consisting of vinyl esters, alkoxyalkyl (meth)acrylates, and (meth)acrylic acid alkyl esters having an alkyl group having 8 or more carbon atoms.

7. The resin composition according to claim 1, wherein the theoretical glass transition temperature (theoretical Tg) is −50° C. (223 K) or higher and −25° C. (248 K) or lower.

8. A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer formed from the resin composition according to claim 1 or 2.

9. The pressure-sensitive adhesive layer has a storage modulus G' of 1.0 x 10 measured under the following conditions at 23°C and 80°C. ５ Above 3.0 x 10 ６ (Pa) or less, and the complex viscosity measured under the following measurement conditions at 23°C and 80°C is 1.5 × 10 ３ (Pa・s) or more 6.0×10 ４ The pressure-sensitive adhesive tape according to claim 8, having a viscosity of (Pa·s) or less. (Measurement conditions) A measurement sample (adhesive layer thickness formed to 2.0 mm) is sandwiched between parallel disks (φ8 mm), and using a dynamic viscoelasticity measuring device, the storage modulus G' (unit: Pa) and complex viscosity (unit: Pa s) are measured at a temperature rise rate of 10°C / min in the temperature range of -60°C to 180°C while applying a shear strain of 0.1% at a load of 10 g and a frequency of 10 Hz.

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