Protective adhesive tape

Abstract

To provide an adhesive tape for protection that shows proper ordinary adhesive strength to an adherend, has excellent heat-resistant re-peelability to the adherend, and excellent unwinding properties.SOLUTION: Provided is an adhesive tape for protection used in a dry thin film forming process, where the adhesive tape for protection has a substrate and an adhesive layer provided on one face of the substrate, and is a roll body in which a face on the opposite side of the substrate of the adhesive layer and the other face of the substrate are laminated in contact with each other. The adhesive layer includes (meth)acrylic copolymer containing a constitutional unit derived from a monomer having a carboxy group by 6 mass% to 14 mass% to the entire structural units, metal chelate-based crosslinking agent, and epoxy-based crosslinking agent, and is formed of an adhesive composition in which a ratio of the content mass of the epoxy-based crosslinking agent to the content of the metal chelate-based crosslinking agent is 0.25 to 2.0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an adhesive tape for protection.

Background Art

[0002] Conventionally, electronic components are provided with electromagnetic shielding to prevent malfunction of the electronic components due to external electromagnetic waves, leakage of electromagnetic waves generated from the electronic components, etc. In recent years, from the viewpoint of miniaturization of electronic components, electromagnetic shielding tends to be directly formed on the electronic components by methods such as sputtering and plating. On the other hand, it is difficult to say that it is preferable to perform shielding processing even on portions where formation of electromagnetic shielding is not substantially necessary, for example, because transparency is impaired. For this reason, in the process of forming electromagnetic shielding, an adhesive tape for protection for the purpose of partial protection of electronic components, protection of support members of electronic components, etc. is used. After attaching a protective tape to a portion where formation of electromagnetic shielding is not required and then performing shielding processing, it becomes possible to form electromagnetic shielding only on the portions that are originally necessary. For example, considering production efficiency, the shielding processing is preferably performed by a dry method such as sputtering or vapor deposition. In the process of forming a thin film by a dry method (so-called dry thin film forming process), the protective adhesive tape may be exposed to a high-temperature and reduced-pressure environment of 200°C or higher, and the protective adhesive tape exposed to the high-temperature and reduced-pressure environment is peeled off when protection is no longer required. For this reason, the adhesive tape for protection used in the dry thin film forming process is required to be easily peeled off from the adherend even when exposed to a high-temperature and reduced-pressure environment, and to have excellent properties (hereinafter also referred to as "heat-resistant re-peelability") in which residue hardly occurs. In addition, the adhesive tape for protection is required to have appropriate normal adhesion.

[0003] For example, Patent Document 1 discloses a masking adhesive tape used when forming a metal layer on a part of the surface of an electronic component by a vacuum film deposition method, comprising a base material and an adhesive layer disposed on one side of the base material, wherein the thickness of the adhesive layer is 5 μm or more, the 180-degree peel-off adhesive strength to a stainless steel plate at 23°C is 0.4 N / 20 mm or more, and after the masking adhesive tape is attached to a stainless steel plate and left at 200°C for 1 hour, the 180-degree peel-off adhesive strength to the stainless steel plate at 23°C becomes 10 N / 20 mm or less. Patent Document 2 discloses an adhesive tape that is excellent in heat resistance and re-peelability, characterized in that an adhesive layer is formed on at least one side of a substrate, comprising an acrylic copolymer mainly composed of an alkyl (meth)acrylate monomer having 4 to 12 C atoms in the alkyl group and containing a functional group in the molecule, an aluminum-based crosslinking agent, and an epoxy-based crosslinking agent. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-222863 [Patent Document 2] Japanese Patent Publication No. 2004-155853 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Generally, single-sided adhesive tapes are provided with a release film to protect the surface of the adhesive layer until they are put into practical use. In recent years, from the viewpoint of reducing the effort required to remove and dispose of the release film during the manufacturing process and improving production efficiency, there has been a demand for single-sided adhesive tapes that do not have a release film. For example, a form in which the exposed surface of the adhesive layer formed on one side of the substrate is brought into contact with the other side of the substrate and wound into a roll. However, because such adhesive tapes do not have a release film, they can be difficult to unwind during use in the manufacturing process, which can actually reduce production efficiency.

[0006] This disclosure is made in light of the circumstances described above. The problem that one embodiment of this disclosure aims to solve is to provide a protective adhesive tape that exhibits appropriate normal adhesive strength to the adherend, has excellent heat resistance and re-peelability to the adherend, and has good unwinding properties. [Means for solving the problem]

[0007] The following are examples of specific means for solving the problem: <1> A protective adhesive tape used in a dry thin film formation process, The above protective adhesive tape is a roll body comprising a base material and an adhesive layer provided on one surface of the base material, wherein the side of the adhesive layer opposite to the base material and the other surface of the base material are in contact and laminated together. A protective adhesive tape, wherein the adhesive layer is formed from an adhesive composition comprising a (meth)acrylic copolymer containing 6% to 14% by mass of constituent units derived from monomers having carboxyl groups relative to the total constituent units, a metal chelating crosslinking agent, and an epoxy crosslinking agent, and the ratio of the mass content of the epoxy crosslinking agent to the mass content of the metal chelating crosslinking agent is 0.25 to 2.0. <2> The total content of the metal chelating crosslinking agent and the epoxy crosslinking agent in the above adhesive composition is 1.0 to 3.3 parts by mass per 100 parts by mass of the (meth)acrylic copolymer. <1> The protective adhesive tape described. <3> The above (meth)acrylic copolymer contains constituent units derived from alkyl (meth)acrylate monomers having an alkyl group having 1 to 4 carbon atoms. <1> or <2> The protective adhesive tape described. <4> The above-mentioned base material is a polyetherimide base material, a polyethersulfone base material, or a polyphenylsulfone base material. <1> ~ <3> Protective adhesive tape as described in one of the following. <5> The wettability index of the side of the substrate on which the adhesive layer is provided is 50 mN / m or more. <1> ~ <4> Protective adhesive tape as described in one of the following. <6> The above substrate exhibits a weight loss rate of 1.0% or less when heated at 200°C for 2 hours under a nitrogen atmosphere. <1> ~ <5> Protective adhesive tape as described in one of the following. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, a protective adhesive tape is provided that exhibits appropriate normal adhesive strength to the adherend, has excellent heat resistance and re-peelability to the adherend, and has good unwinding properties. [Modes for carrying out the invention]

[0009] The protective adhesive tapes of this disclosure will be described in detail below. The requirements described below may be based on typical embodiments of this disclosure, but this disclosure is not limited to such embodiments and may be modified as appropriate within the scope of the purposes of this disclosure.

[0010] In this disclosure, a numerical range indicated using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0011] In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0012] In this disclosure, the amount of each component in the adhesive composition means the total amount of any multiple substances present in the adhesive composition, unless otherwise specified, if there are multiple substances corresponding to each component in the adhesive composition.

[0013] In this disclosure, "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. In this disclosure, "(meth)acrylic copolymer" means a copolymer that contains constituent units derived from (meth)acrylic monomers, and in which the proportion of constituent units derived from (meth)acrylic monomers is 50% by mass or more.

[0014] In this disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic," "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate," "(meth)acryloyl" is a term that encompasses both "acryloyl" and "methacryloyl," and "(meth)acrylamide" is a term that encompasses both "acrylamide" and "methacrylamide."

[0015] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0016] In the present disclosure, "appropriate normal adhesiveness" means adhesiveness such that, under normal temperature conditions, it does not easily peel off from an adherend or the like, and when it is necessary to peel it off from the adherend or the like, it can be easily peeled off without requiring excessive force. In the present disclosure, "normal temperature" means a temperature of 5°C to 35°C.

[0017] In the present disclosure, "under reduced pressure environment" means a pressure environment of 1 MPa or less. In the present disclosure, "high temperature" means a temperature of 200°C or higher.

[0018] In the present disclosure, the "back surface of the base material" refers to the surface on the side where the adhesive layer of the base material is not formed. In the present disclosure, the "back surface of the base material" is also the "self-back surface of the protective adhesive tape".

[0019] [Protective adhesive tape] The protective adhesive tape of the present disclosure is a protective adhesive tape used in a dry thin film forming process. The protective adhesive tape of the present disclosure has a base material and an adhesive layer provided on one surface of the base material, and is a roll body formed by laminating the surface of the adhesive layer opposite to the base material and the other surface of the base material in contact with each other. The adhesive layer contains a (meth)acrylic copolymer containing 6% to 14% by mass of a structural unit derived from a monomer having a carboxy group with respect to all structural units, a metal chelate crosslinking agent, and an epoxy crosslinking agent, and is formed of an adhesive composition in which the ratio of the content of the epoxy crosslinking agent to the content of the metal chelate crosslinking agent is 0.25 to 2.0. The protective adhesive tape of the present disclosure exhibits appropriate normal adhesiveness to an adherend, is excellent in heat-resistant re-peelability with respect to the adherend, and has good unwindability. The reason why the protective adhesive tape of the present disclosure can exhibit such effects is not clear, but the inventors presume as follows. However, the following presumption does not limit the protective adhesive tape of the present disclosure and is described as an example.

[0020] The adhesive layer of the protective adhesive tape of this disclosure is formed by an adhesive composition comprising a (meth)acrylic copolymer containing 6% to 14% by mass of constituent units derived from monomers having carboxyl groups relative to the total constituent units, a metal chelating crosslinking agent, and an epoxy crosslinking agent, wherein the ratio of the content of the epoxy crosslinking agent to the content of the metal chelating crosslinking agent is 0.25 to 2.0. The carboxyl groups of the (meth)acrylic copolymer contribute to the crosslinking reaction with the metal chelating crosslinking agent and the epoxy crosslinking agent. The adhesive composition of this disclosure hardens to a certain extent in a short time because the crosslinking reaction between the carboxyl groups of the (meth)acrylic copolymer and the metal chelating crosslinking agent precedes the crosslinking reaction between the carboxyl groups of the (meth)acrylic copolymer and the epoxy crosslinking agent. Therefore, even if the protective adhesive tape of this disclosure has a base material and an adhesive layer provided on one surface of the base material, and is configured as a roll body in which the surface of the adhesive layer opposite to the base material and the other surface of the base material (i.e., the back surface of the base material) are in contact and laminated, the adhesive force of the adhesive layer to the back surface of the base material is not excessively high, and it is considered to exhibit good unwinding properties. The adhesive composition, which has hardened to some extent by the crosslinking reaction between the carboxyl groups of the (meth)acrylic copolymer and the metal chelating crosslinking agent, becomes a firmly hardened adhesive layer after the curing period ends by the crosslinking reaction between the carboxyl groups of the (meth)acrylic copolymer and the epoxy crosslinking agent, so the protective adhesive tape of this disclosure is considered to have excellent heat resistance and re-peelability. Furthermore, because the ratio of the mass of the epoxy crosslinking agent to the mass of the metal chelating crosslinking agent is within a specific range, the protective adhesive tape of this disclosure is expected to exhibit an adhesive strength (i.e., moderate normal adhesive strength) that does not easily peel off the adherend at room temperature and, when it becomes necessary to peel it off the adherend, can be easily removed without requiring excessive force.

[0021] On the other hand, Patent Documents 1 and 2 (Japanese Patent Publication No. 2004-155853) do not focus on a configuration in which the exposed surface of the adhesive layer formed on one surface of the substrate is brought into contact with the other surface of the substrate and wound into a roll. In Patent Document 1, the adhesive layer is formed using an adhesive composition containing only an epoxy-based crosslinking agent as the crosslinking agent. Because the curing speed of the adhesive composition is slow, if the adhesive tape described in Patent Document 1 were made into a roll like the protective adhesive tape of this disclosure, the adhesive force of the adhesive layer to the back surface of the substrate would be excessively high, making it difficult to unwind properly. Furthermore, in Patent Document 2, aluminum-based crosslinking agents and epoxy-based crosslinking agents are used as crosslinking agents, but the content of constituent units derived from monomers having carboxyl groups, and the ratio of the content of epoxy-based crosslinking agents to the content of metal chelate-based crosslinking agents are not appropriate. Therefore, it is considered that an adhesive tape with appropriate normal adhesive strength, excellent heat resistance and re-peelability, and good unwinding properties cannot be obtained.

[0022] <<Application>> The protective adhesive tape of this disclosure is used in a dry thin film formation process. In this disclosure, "dry thin film formation process" means a process of forming a thin film by methods such as sputtering and vapor deposition (so-called dry method). The protective adhesive tape of this disclosure exhibits moderate normal adhesive strength, is difficult to peel off from the adherend, and is easy to reapply. Furthermore, the protective adhesive tape of this disclosure has excellent heat resistance and re-peelability, can be easily peeled off from the adherend even when exposed to a high-temperature, reduced-pressure environment, does not damage the substrate when peeled off from the adherend, and is less likely to leave adhesive residue. Incidentally, protective adhesive tapes are sometimes applied in layers to protect the adherend without any gaps. The protective adhesive tape of this disclosure has excellent heat resistance and re-peelability, and even when applied in layers and exposed to a high-temperature, reduced-pressure environment, can be easily peeled off from its own back side (i.e., the back side of the substrate), does not damage the substrate when peeled off from its own back side, and is less likely to leave adhesive residue. In addition, since the protective adhesive tape of this disclosure does not have a release film, the effort required to peel off and dispose of the release film when used in the process is reduced, and because it is easy to unwind, workability is improved and an improvement in production efficiency can be expected. Based on the above, the protective adhesive tape of this disclosure is suitable as a protective adhesive tape used in a dry thin film formation process.

[0023] <<Structure>> The protective adhesive tape of this disclosure is a roll body comprising a base material and an adhesive layer provided on one surface of the base material, wherein the surface of the adhesive layer opposite to the base material and the other surface of the base material (i.e., the back surface of the base material) are in contact and laminated together. In other words, the protective adhesive tape of this disclosure is an adhesive tape that does not have a release film (a so-called separator-less adhesive tape). In this disclosure, "release film" is synonymous with "release liner" as defined in JIS Z 0109:2015.

[0024] [Base material] The substrate of the protective adhesive tape of this disclosure is not particularly limited, as long as it can form an adhesive layer on one surface and can be wound up. The substrate is preferably in the form of a film, and more preferably a resin film. The base material is preferably, for example, a base material containing a thermoplastic resin and / or a thermoplastic elastomer, and more preferably a base material containing a thermoplastic resin.

[0025] Examples of thermoplastic resins include polyetherimide (PEI), polyethersulfone (PESU), polyphenylsulfone (PPSU), polysulfone (PSU), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyethylene (PE), polypropylene (PP), polycarbonate (PC), polystyrene (PS), acrylonitrile / styrene resin (AS), acrylonitrile / butadiene / styrene resin (ABS), polyvinyl chloride (PVC), polyamide (PA), polyimide (PI), polyamideimide (PAI), polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethylpentene (TPX), acrylic resin, and methacrylic resin. Examples of thermoplastic elastomers include styrene-based thermoplastic elastomers, polyester-based thermoplastic elastomers, urethane-based thermoplastic elastomers, and amide-based thermoplastic elastomers.

[0026] The substrate of the protective adhesive tape of this disclosure is preferably a polyetherimide substrate, a polyethersulfone substrate, a polyphenylsulfone substrate, a polysulfone substrate, or a polyimide substrate, and more preferably a polyetherimide substrate, a polyethersulfone substrate, or a polyphenylsulfone substrate.

[0027] The dry thin-film formation process is carried out under vacuum. If the substrate contains a high-boiling point solvent, the solvent may volatilize under vacuum, potentially leading to reduced production efficiency and contamination of the equipment. For example, if the substrate material is thermoplastic, it is difficult to preheat and dry it, making it impossible to remove the high-boiling point solvent from the substrate. In contrast, polyetherimide substrates, polyethersulfone substrates, polyphenylsulfone substrates, polysulfone substrates, and polyimide substrates are generally manufactured using methods that do not use high-boiling point solvents, or methods that reduce the amount of high-boiling point solvents. As a result, there is little or no residual high-boiling point solvent, and problems such as decreased production efficiency and contamination of equipment in the dry thin film formation process tend to occur less frequently.

[0028] The substrate of the protective adhesive tape of this disclosure preferably has a weight loss rate of 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less when heated at 200°C for 2 hours in a nitrogen atmosphere. In the dry thin-film formation process, outgassing from the substrate can reduce production efficiency. A substrate with a weight loss rate of 1.0% or less when heated at 200°C for 2 hours under a nitrogen atmosphere will not cause, or will be less likely to cause, a reduction in production efficiency due to outgassing.

[0029] The substrate of the protective adhesive tape of this disclosure preferably has a wettability index of 50 mN / m or more on the side where the adhesive layer is provided, and more preferably 55 mN / m or more. When the wettability index of the side of the substrate on which the adhesive layer is provided is 50 mN / m or higher, the adhesion between the substrate and the adhesive layer is enhanced when forming the adhesive layer on the substrate surface, resulting in a stronger fixation of the adhesive layer on the substrate surface. This increases the difference between the adhesion between the substrate and the adhesive layer and the adhesion between the back surface of the substrate and the adhesive layer, allowing the protective adhesive tape to unwind more smoothly. In this disclosure, the "wetting index" is measured by placing a droplet of the wetting index reagent [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] on the side of the substrate where the adhesive layer is provided, under ambient temperature of 23°C and 50% RH.

[0030] The side of the substrate on which the adhesive layer is provided may be subjected to surface treatment such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatment) from the viewpoint of improving the adhesion between the substrate and the adhesive layer.

[0031] The substrate may have a functional layer on its back side, to the extent that it does not impair the effectiveness of the protective adhesive tape of this disclosure. The term "functional layer" means a layer that imparts a desired function to the substrate, and the functional layer forms a part of the substrate. Examples of functional layers include a hard coat layer, an easy-peel layer, and a low-friction layer.

[0032] In the dry thin film formation process, protective adhesive tape may be exposed to a high-temperature, low-pressure environment. If the back surface of the substrate is treated with a release agent (so-called easy-peel treatment), the release agent may volatilize when the protective adhesive tape is exposed to a high-temperature, low-pressure environment, potentially contaminating the inside of the equipment. From this perspective, it is preferable that the back surface of the substrate is not treated with a release agent. Examples of release agents include silicone-based release agents (e.g., silicone), wax-based release agents (e.g., paraffin wax), and fluorine-based release agents (e.g., fluorine-based resins).

[0033] The base material may contain various additives such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, and fillers. The base material may have a pattern applied to part or all of it.

[0034] The thickness of the substrate is not particularly limited, but is preferably 100 μm or less, more preferably 5 μm to 100 μm, and even more preferably 10 μm to 60 μm.

[0035] In this disclosure, "thickness of the substrate" refers to the average thickness of the substrate. The average thickness of the substrate is determined by the following method. The thickness of the substrate is measured at 10 randomly selected locations in the thickness direction using a film thickness gauge. The arithmetic mean of the measured values ​​is calculated, and this value is taken as the average thickness of the substrate.

[0036] [Adhesive layer] The adhesive layer of the protective adhesive tape of this disclosure is formed by an adhesive composition comprising a (meth)acrylic copolymer containing 6% to 14% by mass of constituent units derived from monomers having carboxyl groups relative to the total constituent units, a metal chelating crosslinking agent, and an epoxy crosslinking agent, wherein the ratio of the content mass of the epoxy crosslinking agent to the content mass of the metal chelating crosslinking agent is 0.25 to 2.0. In this disclosure, a (meth)acrylic copolymer containing 6% to 14% by mass of constituent units derived from monomers having carboxyl groups relative to the total constituent units is also referred to as a "specific (meth)acrylic copolymer." The adhesive layer of the protective adhesive tape of this disclosure includes a cured product of the adhesive composition of this disclosure. The cured product includes, for example, a crosslinked product of a specific (meth)acrylic copolymer that has been crosslinked and cured with a metal chelating crosslinking agent and an epoxy crosslinking agent.

[0037] The thickness of the adhesive layer of the protective adhesive tape of this disclosure is not particularly limited, but is preferably 1 μm to 100 μm, more preferably 5 μm to 75 μm, and even more preferably 10 μm to 50 μm.

[0038] In this disclosure, "thickness of the adhesive layer" refers to the average thickness of the adhesive layer. The average thickness of the adhesive layer is determined by the following method. The thickness of the adhesive layer is measured at 10 randomly selected locations in the thickness direction using a film thickness gauge. The arithmetic mean of the measured values ​​is calculated, and this value is taken as the average thickness of the adhesive layer.

[0039] (Adhesive composition) The adhesive composition in this disclosure comprises a specific (meth)acrylic copolymer, a metal chelating crosslinking agent, and an epoxy crosslinking agent, as described below.

[0040] <Specific (meth)acrylic copolymer> The adhesive composition in this disclosure includes a (meth)acrylic copolymer [i.e., a specific (meth)acrylic copolymer] that contains 6% to 14% by mass of constituent units derived from monomers having a carboxyl group, relative to the total constituent units. The adhesive composition in this disclosure may contain only one specific (meth)acrylic copolymer, or it may contain two or more specific (meth)acrylic copolymers.

[0041] -Constituent units derived from monomers containing a carboxyl group- The specific (meth)acrylic copolymer contains 6% to 14% by mass of constituent units derived from monomers having a carboxyl group, relative to the total number of constituent units. The carboxyl groups in the constituent units derived from monomers containing carboxyl groups in the specific (meth)acrylic copolymer contribute to the crosslinking reaction between the specific (meth)acrylic copolymer and the metal chelating crosslinking agent and epoxy crosslinking agent described later. In this disclosure, "constituent unit derived from a monomer having a carboxyl group" means a constituent unit formed by the addition polymerization of monomers having a carboxyl group.

[0042] The type of monomer having a carboxyl group is not particularly limited. Examples of monomers having a carboxyl group include monomers having at least one carboxyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited and includes, for example, a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. A (meth)acryloyl group is preferred as the ethylenically unsaturated group.

[0043] Specific examples of monomers having a carboxyl group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid derivatives (e.g., 2-acryloyloxyethyl succinic acid). As the monomer having a carboxyl group, a (meth)acrylic monomer having a carboxyl group is preferred, at least one selected from acrylic acid and methacrylic acid is more preferred, and acrylic acid is even more preferred.

[0044] The specific (meth)acrylic copolymer may contain only one or more constituent units derived from monomers having a carboxyl group.

[0045] The content of constituent units derived from monomers having carboxyl groups in the specific (meth)acrylic copolymer is 6% to 14% by mass, preferably 7% to 13% by mass, and more preferably 8% to 12% by mass, relative to the total constituent units of the specific (meth)acrylic copolymer. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic copolymer is 6% by mass or more relative to the total constituent units of the specific (meth)acrylic copolymer, the protective adhesive tape tends to exhibit good unwinding properties. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic copolymer is 14% by mass or less relative to the total constituent units of the specific (meth)acrylic copolymer, the protective adhesive tape tends to exhibit moderate normal adhesion to the adherend. Furthermore, the protective adhesive tape tends to exhibit moderate normal adhesion to its own back surface.

[0046] -Constituent units derived from alkyl (meth)acrylate monomers- The specific (meth)acrylic copolymer preferably contains constituent units derived from alkyl (meth)acrylate monomers. In this disclosure, "constituent units derived from (meth)acrylate alkyl ester monomers" means constituent units formed by the addition polymerization of (meth)acrylate alkyl ester monomers. In this disclosure, "(meth)acrylate alkyl ester monomers" do not include monomers having a carboxyl group or monomers having a hydroxyl group.

[0047] The type of alkyl (meth)acrylate monomer is not particularly limited. The alkyl (meth)acrylate monomer may be an alkyl acrylate monomer or an alkyl methacrylate monomer. The alkyl group in the alkyl (meth)acrylate monomer may be unsubstituted or may have substituents (excluding carboxyl and hydroxyl groups), but it is preferable that it be unsubstituted. The alkyl group in the alkyl (meth)acrylate monomer may be linear, branched, or cyclic.

[0048] The number of carbon atoms in the alkyl group of the (meth)acrylate monomer is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 8, and particularly preferably 1 to 4. When a specific (meth)acrylic copolymer contains structural units derived from alkyl (meth)acrylate monomers having an alkyl group with 1 to 4 carbon atoms, the unwinding properties of the protective adhesive tape tend to be improved.

[0049] Specific examples of alkyl (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. As the alkyl (meth)acrylate monomer, at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate is preferred, with n-butyl acrylate being more preferred.

[0050] When a specific (meth)acrylic copolymer contains constituent units derived from alkyl (meth)acrylate monomers, it may contain only one type of constituent unit derived from alkyl (meth)acrylate monomers, or it may contain two or more types.

[0051] When a specific (meth)acrylic copolymer contains structural units derived from alkyl (meth)acrylate monomers, the content of structural units derived from alkyl (meth)acrylate monomers in the specific (meth)acrylic copolymer is not particularly limited, but for example, it is preferably 50% to 94% by mass, more preferably 60% to 93% by mass, and even more preferably 70% to 92% by mass, relative to the total structural units of the specific (meth)acrylic copolymer. The content of constituent units derived from alkyl (meth)acrylate monomers in a specific (meth)acrylic copolymer being 50% by mass or more of the total constituent units of the specific (meth)acrylic copolymer means that constituent units derived from alkyl (meth)acrylate monomers are included as the main component of the constituent units of the specific (meth)acrylic copolymer.

[0052] -Other constituent units- Other constituent units that a specific (meth)acrylic copolymer may contain include: constituent units derived from (meth)acrylates having aromatic rings, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; constituent units derived from monomers having hydroxyl groups, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; constituent units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; constituent units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; constituent units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; and constituent units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate.

[0053] If the specific (meth)acrylic copolymer contains other constituent units, it may contain only one type of other constituent unit or two or more types.

[0054] If the specific (meth)acrylic copolymer contains other constituent units, the content of the other constituent units in the specific (meth)acrylic copolymer can be set appropriately within a range that does not impair the effectiveness of the protective adhesive tape of this disclosure.

[0055] <<Weight-average molecular weight of specific (meth)acrylic copolymers>> The weight-average molecular weight (hereinafter also referred to as "Mw") of the specific (meth)acrylic copolymer is not particularly limited, but is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,800,000, even more preferably 300,000 to 1,500,000, and particularly preferably 400,000 to 1,000,000.

[0056] The weight-average molecular weight of a specific (meth)acrylic copolymer is a value measured by the following method. Specifically, it is measured according to (1) to (3) below. (1) A solution of the specific (meth)acrylic copolymer is applied to release paper and dried at 100°C for 1 minute to obtain a film-like specific (meth)acrylic copolymer. (2) Using the film-like specific (meth)acrylic copolymer obtained in (1) above and tetrahydrofuran, a sample solution with a solid content concentration of 0.2% by mass is obtained. Here, "solid content concentration" refers to the mass ratio of the specific (meth)acrylic copolymer in the sample solution. (3) The weight-average molecular weight of the specific (meth)acrylic copolymer is determined as a standard polystyrene equivalent by gel permeation chromatography (GPC) under the following conditions.

[0057] ~Conditions~ Measurement device: High-speed GPC [Model number: HLC-8220 GPC, manufactured by Tosoh Corporation] Detector: Differential Refractometer (RI) [Integrated into HLC-8220, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Four units manufactured by Tosoh Corporation were used. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0058] The weight-average molecular weight of a specific (meth)acrylic copolymer can be adjusted to a desired value by controlling the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, and amount of polymerization initiator used during the polymerization of the monomers.

[0059] <<Content of specific (meth)acrylic copolymer>> The content of the specific (meth)acrylic copolymer in the adhesive composition is not particularly limited, but for example, it is preferably 70.0% to 99.0% by mass, more preferably 80.0% to 99.0% by mass, and even more preferably 90.0% to 98.9% by mass, based on the total solid content in the adhesive composition.

[0060] In this disclosure, "total solid content in the adhesive composition" means the total mass of the adhesive composition if the adhesive composition does not contain a solvent, and the mass of the residue remaining after removing the solvent from the adhesive composition if the adhesive composition contains a solvent. In this disclosure, "solvent" means water and organic solvents.

[0061] <<Meth)acrylic copolymer manufacturing method>> The method for producing the specific (meth)acrylic copolymer is not particularly limited. Specific (meth)acrylic copolymers can be produced by polymerizing the monomers described above using known polymerization methods, such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. As for the polymerization method, solution polymerization is preferred because the processing steps are relatively simple and can be carried out in a short time when preparing the adhesive composition after the production of the specific (meth)acrylic copolymer.

[0062] In solution polymerization, a predetermined organic solvent, monomer, polymerization initiator, and a chain transfer agent (if necessary) are generally placed in a polymerization tank, and the reaction is carried out by heating for several hours at, for example, the reflux temperature of the organic solvent while stirring. In this case, at least a portion of the organic solvent, monomer, polymerization initiator, and chain transfer agent (if necessary) may be added sequentially. Alternatively, the reaction may be carried out under a nitrogen atmosphere.

[0063] Examples of organic solvents used in polymerization reactions include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, organic solvents used in polymerization reactions include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirits, petroleum naphtha, and turpentine oil; ester compounds such as methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone; and methyl Examples include ketone compounds represented by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds represented by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds represented by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0064] In the production of specific (meth)acrylic copolymers, it is preferable to use organic solvents that do not easily cause chain transfer during polymerization reactions, such as aromatic hydrocarbon compounds, ester compounds, and ketone compounds. In particular, from the viewpoint of the solubility of the specific (meth)acrylic copolymer and the ease of polymerization, the use of ethyl acetate is preferred.

[0065] During the polymerization reaction, one organic solvent may be used, or two or more may be used.

[0066] Examples of polymerization initiators include organic peroxides and azo compounds commonly used in conventional solution polymerization methods. Specific examples of organic peroxides include t-butylperoxy-2-ethylhexanoate, t-butylhydroperoxide, cumenehydroperoxide, dicumylperoxide, benzoylperoxide, lauroylperoxide, caproylperoxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxypivalate, and 2,2-bis(4,4-di-t-butylperoxy). Examples include chlorohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitride), 2,2'-azobis(2-methylpropionic acid)dimethyl, and 2,2'-azobis(isobutyric acid)dimethyl.

[0067] During the polymerization reaction, one polymerization initiator may be used, or two or more may be used.

[0068] The amount of polymerization initiator used is not particularly limited and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0069] In the production of specific (meth)acrylic copolymers, chain transfer agents may be used as needed. Examples of chain transfer agents include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid with 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid with 1 to 8 carbon atoms, aromatic compounds represented by α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, and tetra- Examples include halogenated hydrocarbon compounds represented by carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene; aldehyde compounds represented by chloral and furaldihydes; alkyl mercaptan compounds having 1 to 18 carbon atoms; aromatic mercaptan compounds represented by thiophenol and toluene mercaptan; mercaptoacetic acid; alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms; hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms; and terpene compounds represented by pinene and terpinolene.

[0070] When using a chain transfer agent in the production of a specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0071] The polymerization temperature is not particularly limited and can be set appropriately depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0072] <Metal chelate crosslinking agents> The adhesive composition in this disclosure includes a metal chelating crosslinking agent. In this disclosure, "metal chelate crosslinking agent" refers to a metal chelate compound that functions as a crosslinking agent.

[0073] The type of metal chelating crosslinking agent is not particularly limited. Examples of metal chelating crosslinking agents include aluminum chelating compounds, titanium chelating compounds, zirconium chelating compounds, and cobalt chelating compounds. As a metal chelating crosslinking agent, aluminum chelating compounds are preferred. Examples of aluminum chelating compounds include aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum tris(ethylacetoacetate), and aluminum tris(acetylacetonate).

[0074] Commercially available metal chelating crosslinking agents can be used. Examples of commercially available metal chelating crosslinking agents include aluminum chelate A (trade name, aluminum tris(acetylacetonate), manufactured by Kawaken Fine Chemicals Co., Ltd.), aluminum chelate D (trade name, aluminum monoacetylacetonate bis(ethylacetoacetate), manufactured by Kawaken Fine Chemicals Co., Ltd.), and ALCH-TR (trade name, aluminum tris(ethylacetoacetate), manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0075] The adhesive composition in this disclosure may contain only one metal chelating crosslinking agent, or it may contain two or more.

[0076] <Epoxy-based crosslinking agent> The adhesive composition in this disclosure includes an epoxy crosslinking agent. In this disclosure, "epoxy crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (a so-called bifunctional or multifunctional epoxy compound).

[0077] The type of epoxy crosslinking agent is not particularly limited. Examples of bifunctional or more epoxy compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, and Examples include ligcerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, diglycidyl adipate ester, diglycidyl phthalate ester, tris(glycidyl) isocyanurate, tris(glycidoxyethyl) isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-1,3-benzenedi(methaneamine).

[0078] Commercially available epoxy crosslinking agents can be used. Examples of commercially available epoxy crosslinking agents include "TETRAD(registered trademark)-X" and "TETRAD(registered trademark)-C" (both manufactured by Mitsubishi Gas Chemical Company, Inc.), and "Denacol(registered trademark) EX-201" and "Denacol(registered trademark) EX-931" (both manufactured by Nagase ChemteX Corporation).

[0079] The adhesive composition in this disclosure may contain only one epoxy crosslinking agent, or it may contain two or more epoxy crosslinking agents.

[0080] <<Contents of metal chelating crosslinking agents and epoxy crosslinking agents>> The adhesive composition in this disclosure has a ratio of the mass content of epoxy crosslinking agent to the mass content of metal chelating crosslinking agent (mass content of epoxy crosslinking agent / mass content of metal chelating crosslinking agent) of 0.25 to 2.0. In the adhesive composition described herein, if the ratio of the mass content of the epoxy crosslinking agent to the mass content of the metal chelating crosslinking agent is 0.25 or higher, the protective adhesive tape tends to have excellent heat resistance and re-peelability. In the adhesive composition described herein, if the ratio of the mass content of the epoxy crosslinking agent to the mass content of the metal chelating crosslinking agent is 2.0 or less, the protective adhesive tape tends to exhibit a moderate normal adhesion to the adherend. Furthermore, the protective adhesive tape tends to exhibit a moderate normal adhesion to its own back surface. In the adhesive composition of this disclosure, the ratio of the mass content of the epoxy crosslinking agent to the mass content of the metal chelating crosslinking agent is more preferably 0.3 to 1.6, and even more preferably 0.3 to 1.3.

[0081] The content of metal chelating crosslinking agents and epoxy crosslinking agents in the adhesive composition in this disclosure is not particularly limited. The total content of the metal chelating crosslinking agent and the epoxy crosslinking agent in the adhesive composition of this disclosure is preferably 0.5 to 5.0 parts by mass, more preferably 0.8 to 4.0 parts by mass, and even more preferably 1.0 to 3.3 parts by mass, per 100 parts by mass of the (meth)acrylic copolymer. The adhesive layer of the protective adhesive tape preferably exhibits moderate tack strength. When the total content of the metal chelating crosslinking agent and the epoxy crosslinking agent in the adhesive composition of this disclosure is within the above range relative to 100 parts by mass of (meth)acrylic copolymer, the formed adhesive layer tends to exhibit more moderate tack strength.

[0082] <Crosslinking retarder> The adhesive composition in this disclosure may contain a crosslinking retarder. The crosslinking retarder acts as a chelating agent for metal chelating crosslinking agents. When the adhesive composition in this disclosure contains a crosslinking retarder in addition to a metal chelating crosslinking agent, the crosslinking retarder blocks the metal chelating crosslinking agent, thereby suppressing excessive viscosity increase, gelation, etc., of the adhesive composition, and thus extending the pot life of the adhesive composition. The crosslinking retarder contained in the adhesive composition volatilizes when the coated film of the adhesive composition applied to a substrate or the like is dried. As the crosslinking retarder volatilizes, the metal chelating crosslinking agent that was blocked by the crosslinking retarder is activated, exhibiting a crosslinking promoting effect, and the crosslinking reaction in the adhesive composition proceeds. As described above, the crosslinking retarder makes it possible to extend the pot life of the adhesive composition without affecting the crosslinking formation in the adhesive composition.

[0083] Examples of crosslinking retarders include keto-enol tautomer compounds. Examples of keto-enol tautomer compounds include β-ketoester compounds such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, as well as β-diketone compounds such as acetylacetone, 2,4-hexanedione, and benzoylacetone. Among these, acetylacetone is preferred as a crosslinking retarder from the viewpoint of balancing pot life and curing speed.

[0084] If the adhesive composition in this disclosure contains a crosslinking retarder, it may contain only one crosslinking retarder or two or more.

[0085] When the adhesive composition in this disclosure contains a crosslinking retarder, the ratio of the crosslinking retarder content to the metal chelate crosslinking agent content (crosslinking retarder content / metal chelate crosslinking agent content) is preferably 1 / 10 to 1 / 0.01 by mass, more preferably 1 / 5 to 1 / 0.03, and even more preferably 1 / 2 to 1 / 0.05.

[0086] <Organic solvents> The adhesive composition in this disclosure may contain an organic solvent. The adhesive composition in this disclosure may have improved applicability and pot life when it contains an organic solvent. Examples of organic solvents include those similar to those used in the polymerization reaction of the specific (meth)acrylic copolymers described above.

[0087] If the adhesive composition in this disclosure contains an organic solvent, it may contain only one organic solvent or two or more organic solvents.

[0088] If the adhesive composition in this disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be set as appropriate depending on the purpose.

[0089] <Other ingredients> The adhesive composition in this disclosure may, if necessary, contain components other than those described herein (so-called other components), as long as they do not impair the effectiveness of the protective adhesive tape ultimately obtained in this disclosure. Other components include polymers other than specific (meth)acrylic copolymers, antioxidants, light stabilizers (e.g., UV absorbers), and various other additives.

[0090] If the adhesive composition in this disclosure contains other components, the content of these other components is not particularly limited and can be set as appropriate depending on the purpose.

[0091] [Method for manufacturing protective adhesive tape] The method for manufacturing the protective adhesive tape described herein is not particularly limited. The protective adhesive tapes of this disclosure can be manufactured by reference to known methods. Examples of methods for manufacturing the protective adhesive tapes of this disclosure include the following:

[0092] The adhesive composition of this disclosure is applied to one side of a substrate (preferably the easily bonded side) to form a coating film on one side of the substrate. Next, the formed coating film is dried to form an adhesive film on one side of the substrate. Then, the laminate having a substrate / adhesive film layer structure is wound into a roll shape with the substrate and adhesive film alternating, and after forming a roll body, it is left to stand to complete the crosslinking reaction. By doing so, a protective adhesive tape of this disclosure can be manufactured, which is a roll body having a substrate and an adhesive layer provided on one side of the substrate, and the side of the adhesive layer opposite to the substrate and the other side of the substrate are in contact and laminated together.

[0093] Furthermore, by applying the adhesive composition of this disclosure to one side of a substrate (preferably the easily adhesive treated side), a coating film is formed on one side of the substrate. Next, by drying the formed coating film, an adhesive film is formed on one side of the substrate. Then, the exposed side of the formed adhesive film is placed on top of the easily peeled side of a separately prepared release film and bonded together to form a laminate having a layer structure of substrate / adhesive film / release film, which is then wound into a roll. Next, the wound laminate is unwound, and while peeling off the release film, the laminate having a layer structure of substrate / adhesive film is rewound into a roll with the substrate and adhesive film alternating, and then left to stand to complete the crosslinking reaction. By doing so, a protective adhesive tape of this disclosure can be manufactured, which is a roll body having a substrate and an adhesive layer provided on one side of the substrate, and the side of the adhesive layer opposite to the substrate and the other side of the substrate are in contact and laminated together.

[0094] The method of applying the adhesive composition is not particularly limited. Examples of known methods for applying adhesive compositions include gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, knife coaters, spray coaters, bar coaters, applicators, and the like. The amount of adhesive composition applied is not particularly limited and can be appropriately set, for example, depending on the thickness of the adhesive layer to be formed.

[0095] The method for drying the coating film is not particularly limited. Methods for drying the coated film include, for example, natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited and are set appropriately according to the thickness of the coating film, the amount of organic solvent in the coating film, etc. One example of drying conditions is to use a hot air circulation dryer and dry at 60°C to 120°C for 30 to 180 seconds.

[0096] The conditions for standing are not particularly limited, but it is preferable to stand the mixture for 2 to 7 days in an environment with an ambient temperature of 20°C to 35°C and a relative humidity of 45% to 55% (i.e., 45%RH to 55%RH). The crosslinking reaction is completed by standing. [Examples]

[0097] The protective adhesive tapes of this disclosure will be described in more detail below with reference to examples. This disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0098] [Production of (meth)acrylic copolymers] [Manufacturing example A-1] 50.0 parts by mass of ethyl acetate [organic solvent] was placed in a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser. Next, 90.0 parts by mass of n-butyl acrylate [n-BA; alkyl acrylate monomer] and 10.0 parts by mass of acrylic acid [AA; monomer having a carboxyl group] were placed in a separate container and mixed to prepare a monomer mixture. 18.0% by mass of the prepared monomer mixture was placed in the reaction vessel. Next, while stirring the contents of the reaction vessel, the temperature of the contents was raised to 85°C, and then 0.01 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] was added and held for 0.2 hours. Then, the contents of the reaction vessel were reacted for 1.2 hours while simultaneously adding a mixture of the remaining monomer mixture, 43.0 parts by mass of ethyl acetate, and 0.04 parts by mass of AIBN to the reaction vessel over 2.0 hours to obtain reaction product (a1). Next, a mixture of 11.0 parts by mass of ethyl acetate and 0.17 parts by mass of AIBN was added dropwise over 1.0 hour. After the dropwise addition was complete, the reaction was allowed to continue for another 1.5 hours to obtain reaction product (a2). The obtained reaction product (a2) was diluted with toluene to a solid content concentration of 34% by mass to obtain a solution of (meth)acrylic copolymer A-1.

[0099] Here, "solid content concentration" refers to the mass ratio of (meth)acrylic copolymer A-1 to the solution of (meth)acrylic copolymer A-1. The same applies to each of the solutions of (meth)acrylic copolymers A-2 to A-10 prepared below.

[0100] [Manufacturing Examples A-2 and A-8] In production examples A-2 and A-8, the same procedure as in production example A-1 was followed, except that the weight-average molecular weight of the (meth)acrylic copolymer was adjusted to the weight-average molecular weight shown in Table 1 by adjusting at least one of the amounts of organic solvent and polymerization initiator used, to obtain solutions of (meth)acrylic copolymers A-2 and A-8, respectively, with a solid content concentration of 34% by mass.

[0101] [Manufacturing examples A-3 to A-7, A-9 and A-10] In production examples A-3 to A-7, A-9, and A-10, the monomer composition of the (meth)acrylic copolymer was changed to the monomer composition shown in Table 1, and the weight-average molecular weight of the (meth)acrylic copolymer was adjusted to the weight-average molecular weight shown in Table 1 by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used. The same procedure as in production example A-1 was followed to obtain solutions of (meth)acrylic copolymers A-3 to A-7, A-9, and A-10, each with a solid content concentration of 34% by mass.

[0102] Table 1 shows the monomer composition [unit: mass%] and weight-average molecular weight (denoted as "Mw") of (meth)acrylic copolymers A-1 to A-10.

[0103] The weight-average molecular weights of (meth)acrylic copolymers A-1 to A-10 were measured using the same method as described above for measuring the weight-average molecular weight of specific (meth)acrylic copolymers.

[0104] Of the (meth)acrylic copolymers A-1 to A-10, (meth)acrylic copolymers A-1 to A-8 correspond to the specified (meth)acrylic copolymers in this disclosure.

[0105] [Table 1]

[0106] Details of each monomer listed in Table 1 are as follows: <(meth)acrylate alkyl monomer> "n-BA": n-butyl acrylate "2EHA": 2-ethylhexyl acrylate "MMA": Methyl methacrylate <Monomers containing a carboxyl group> "AA": Acrylic acid "MAA": Methacrylic acid

[0107] [Example 1] 1. Preparation of adhesive composition A mixture was obtained by thoroughly mixing 294.1 parts by mass (100 parts by mass as solids) of a solution of (meth)acrylic copolymer A-1, 0.50 parts by mass (0.50 parts by mass as solids) of a metal chelating crosslinking agent [product name: Aluminum Chelate A, chemical name: aluminum tris(acetylacetonate), manufactured by Kawaken Fine Chemical Co., Ltd.], and 0.65 parts by mass (0.65 parts by mass as solids) of an epoxy crosslinking agent [product name: TETRAD®-X, manufactured by Mitsubishi Gas Chemical Co., Ltd.]. 5.0 parts by mass of acetylacetone was added to the obtained mixture as a crosslinking retarder. The mixture was then diluted with ethyl acetate (organic solvent) to a solids concentration of 26% by mass to obtain an adhesive composition.

[0108] 2. Manufacturing of evaluation sample X A polyetherimide (PEI) film (product name: Superior® UT, a film with one side treated for easy adhesion by corona treatment, thickness: 50 μm, manufactured by Mitsubishi Chemical Corporation) was used as a substrate. The easy-adhesion treated surface (wetting index: 60 mN / m) was coated with the adhesive composition prepared above to a thickness of 20 μm after drying, forming a coating film. Next, the formed coating film was dried by blowing 100°C air at a wind speed of 3 m / s for 1 minute using a hot air circulation dryer, forming an adhesive film on the PEI film. Then, the exposed side of the adhesive film was laminated onto the easy-release treated surface of a separately prepared release film. After that, the sample was left to stand for 7 days in an environment of 23°C and 50% RH to allow the crosslinking reaction to proceed, thereby obtaining an evaluation sample X having a layer structure of substrate (PEI film) / adhesive layer / release film.

[0109] 3. Manufacturing of evaluation sample Y A polyetherimide (PEI) film (product name: Superior® UT, a film with one side treated for easy adhesion by corona treatment, thickness: 50 μm, manufactured by Mitsubishi Chemical Corporation) was used as a base material. The adhesive composition prepared above was applied to the easily adhesive treated surface (wetting index: 60 mN / m) so that the thickness after drying would be 20 μm, forming a coating film. Next, the formed coating film was dried by blowing 100°C air at a wind speed of 3 m / s for 1 minute using a hot air circulation dryer, forming an adhesive film on the PEI film. Then, the exposed side of the adhesive film was laminated to the easily peeled surface of a separately prepared release film to form a laminate with a layer structure of base material (PEI film) / adhesive film / release film, and then wound into a roll. Next, the wound laminate was unwound, and while peeling off the release film, the laminate Y with a layer structure of base material (PEI film) / adhesive film was rewound so that the base material and adhesive film alternated. Subsequently, the sample was left to stand for 7 days in an environment with an ambient temperature of 23°C and 50% RH to allow the crosslinking reaction to proceed, thereby obtaining evaluation sample Y. Evaluation sample Y is a roll body having a substrate and an adhesive layer provided on one surface of the substrate, with the side of the adhesive layer opposite to the substrate in contact with the other surface of the substrate and laminated together.

[0110] [Examples 2-11, 14 and 15, and Comparative Examples 1-7] 1. Preparation of adhesive composition In Example 1, the same procedure as in Example 1 was followed, except that the composition of the adhesive composition was changed to the composition shown in Table 2, to obtain the adhesive composition.

[0111] 2. Manufacturing of evaluation sample X The same procedure as in "Production of evaluation sample X" in Example 1 was performed to obtain evaluation sample X.

[0112] 3. Manufacturing of evaluation sample Y The same procedure as in "Production of evaluation sample Y" in Example 1 was performed to obtain evaluation sample Y.

[0113] [Example 12] 1. Preparation of adhesive composition The same procedure as in "Preparation of Adhesive Composition" in Example 5 was performed to obtain the adhesive composition.

[0114] 2. Manufacturing of evaluation sample X In the "Preparation of Evaluation Sample X" in Example 1, instead of using a PEI film as the substrate, a polyethersulfone (PESU) film [product name: Veradel® PES 201 NT, thickness: 50 μm, manufactured by Solvay] was used, with one side treated with corona treatment to achieve a wettability index of 60 mN / m for easy adhesion. Otherwise, the same procedure as in Example 1 was followed to obtain Evaluation Sample X.

[0115] 3. Manufacturing of evaluation sample Y In the "Preparation of Evaluation Sample Y" in Example 1, instead of using a PEI film as the substrate, a polyethersulfone (PESU) film [product name: Veradel® PES 201 NT, thickness: 50 μm, manufactured by Solvay] was used, with one side treated with corona treatment to achieve a wettability index of 60 mN / m for easy adhesion. Otherwise, the same procedure as in Example 1 was followed to obtain Evaluation Sample Y.

[0116] [Example 13] 1. Preparation of adhesive composition The same procedure as in "Preparation of Adhesive Composition" in Example 5 was performed to obtain the adhesive composition.

[0117] 2. Manufacturing of evaluation sample X In the "Preparation of Evaluation Sample X" in Example 1, instead of using a PEI film as the substrate, a polyphenylsulfone (PPSU) film [product name: Radel® R-5100 NT-15, thickness: 50 μm, manufactured by Solvay] was used, with one side treated with corona treatment to achieve a wettability index of 60 mN / m. The same procedure as in Example 1 was followed to obtain Evaluation Sample X.

[0118] 3. Manufacturing of evaluation sample Y In the "Preparation of Evaluation Sample Y" in Example 1, instead of using a PEI film as the base material, a polyphenylsulfone (PPSU) film [product name: Radel® R-5100 NT-15, thickness: 50 μm, manufactured by Solvay] was used, with one side treated with corona treatment to achieve a wettability index of 60 mN / m. The same procedure as in Example 1 was followed to obtain Evaluation Sample Y.

[0119] [Measurement and Evaluation] 1.Normal adhesive strength (1) Normal adhesive strength to the adherend The evaluation sample X prepared as described above was cut to a size of 25 mm × 150 mm (long side) to obtain an evaluation sample piece X. Next, the release film was peeled off the evaluation sample piece X. Hereafter, the evaluation sample piece X from which the release film was peeled off will be referred to as "evaluation sample piece X'". Next, the side of the exposed adhesive layer of evaluation sample piece X' was placed on one side of an aluminum plate (thickness: 1 mm) to be adhered. Then, a 2 kg load was applied to adhere them together, and a laminate with a layer structure of aluminum plate (adherent) / adhesive layer / substrate was obtained. The obtained laminate was left to stand for 24 hours in an environment with an ambient temperature of 23°C and 50% RH. For the laminated material after standing, the adhesive strength (unit: N / 25mm) was measured when an evaluation sample piece X' (layer structure: adhesive layer / substrate) was peeled 180° along the long side (100mm) from the aluminum plate. This was measured using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under ambient temperature of 23°C and 50% RH, and peeling speed of 300mm / min. The evaluation was then performed according to the evaluation criteria described below. The evaluation results and measured adhesive strength are shown in Table 2. In the evaluation criteria below, "2" is a level that is acceptable for practical use. On the other hand, both "1" and "3" are levels that pose practical problems. Specifically, "1" is a level where the adhesive strength is too low, causing it to easily peel off the object being protected and rendering it ineffective as a protective adhesive film. "3" is a level where the adhesive strength is too high, making it difficult to remove if the need arises to peel it off, such as for repositioning.

[0120] -Evaluation Criteria- 3. The adhesive strength is 9.0 N / 25 mm or higher. 2: The adhesive strength is in the range of 1.0 N / 25 mm or more and less than 9.0 N / 25 mm. 1: The adhesive strength is less than 1.0 N / 25 mm.

[0121] (2) Adhesion to the back surface of the substrate under normal conditions The evaluation sample X prepared as described above was cut to a size of 25 mm × 150 mm (long side) to obtain evaluation sample piece X. Next, the same substrate used to prepare evaluation sample X was prepared. This prepared substrate will be called "substrate Z". Next, the release film was peeled off evaluation sample piece X' to obtain evaluation sample piece X'. Then, the side of the exposed adhesive layer of evaluation sample piece X' was placed on the side of substrate Z that was not treated for easy adhesion. After that, a 2 kg load was applied to bond them together, and a laminate with a layer structure of substrate Z / adhesive layer / substrate was obtained. The obtained laminate was left to stand for 24 hours in an environment with an ambient temperature of 23°C and 50% RH. For the laminated material after standing, the adhesive strength (unit: N / 25mm) was measured when an evaluation sample piece X' (layer structure: adhesive layer / substrate) was peeled 180° along the long side (100mm) from the substrate Z using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under ambient temperature of 23°C and 50% RH conditions, and peeling speed of 300mm / min. The evaluation was then performed according to the evaluation criteria below. The evaluation results and measured adhesive strength are shown in Table 2. In the evaluation criteria below, "2" is a level that is acceptable for practical use. On the other hand, both "1" and "3" are levels that pose practical problems. Specifically, "1" is a level where the adhesive strength is too low, and when protective adhesive films are layered to completely protect the object to be protected, the protective adhesive film easily peels off from its own back and cannot function as a protective adhesive film. "3" is a level where the adhesive strength is too high, and when it becomes necessary to peel it off, such as for repositioning, it cannot be easily removed.

[0122] -Evaluation Criteria- 3. The adhesive strength is 9.0 N / 25 mm or higher. 2: The adhesive strength is in the range of 1.0 N / 25 mm or more and less than 9.0 N / 25 mm. 1: The adhesive strength is less than 1.0 N / 25 mm.

[0123] 2. Heat-resistant and re-peelable (1) Heat resistance and re-peelability to the adherend The evaluation sample X prepared as described above was cut to a size of 25 mm × 150 mm (long side) to obtain evaluation sample piece X. Next, the release film was peeled off evaluation sample piece X' to obtain evaluation sample piece X'. Then, the side with the exposed adhesive layer of evaluation sample piece X' was placed on one side of an aluminum plate (thickness: 1 mm) to be used as the adherend. Subsequently, a 2 kg load was applied to adhere them together, obtaining a laminate having a layer structure of aluminum plate (adherend) / adhesive layer / substrate. The obtained laminate was placed in a vacuum constant temperature drying oven [model number: DRV420DA, manufactured by Advantec Toyo Co., Ltd.] set to a heating temperature of 250°C. After placement, the pressure inside the vacuum constant temperature drying oven was reduced (gauge pressure: -0.1 MPa or less), and it was left to stand for 1 hour. Next, the laminate was removed from the vacuum constant temperature drying oven and left to stand for 24 hours in an environment with an ambient temperature of 23°C and 50% RH. For this laminated structure after standing, the adhesive strength (unit: N / 25mm) was measured when an evaluation sample piece X' (layer structure: adhesive layer / substrate) was peeled off from the aluminum plate at a 180° angle along its long side (100mm) using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under ambient temperature of 23°C and 50% RH, and peeling speed of 300mm / min. In addition, the peeled surface of the aluminum plate after peeling off the evaluation sample piece X' was visually observed to confirm the presence and degree of adhesive residue (so-called glue residue) on the aluminum plate, as well as the presence or absence of substrate damage. The evaluation was then performed according to the evaluation criteria described below. The evaluation results and measured adhesive strength are shown in Table 2. In the evaluation criteria below, "3" and "2" are at a level that is acceptable in practical use, and "3" is the most preferable.

[0124] -Evaluation Criteria- 3. No adhesive residue is observed, and the adhesive strength is 15.0 N / 25 mm or less. 2: A small amount of adhesive residue was observed at the edges of the peeled surface, but the adhesive strength was 15.0 N / 25 mm or less. 1: At least one of the following (a) to (c) applies. (a) Clear adhesive residue is observed on the peeled surface. (b) The adhesive strength exceeds 15.0 N / 25 mm. (c) Substrate damage occurs.

[0125] (2) Heat-resistant and re-peelable properties on the back surface of the substrate The evaluation sample X prepared as described above was cut to a size of 25 mm x 150 mm (long side) to obtain evaluation sample piece X. Next, the same substrate used to prepare evaluation sample X was prepared. This prepared substrate is referred to as "substrate Z". Next, the release film was peeled off evaluation sample piece X' to obtain evaluation sample piece X'. Next, the side of evaluation sample piece X' with the exposed adhesive layer was placed on the side of substrate Z that had not been treated for easy adhesion. Then, a 2 kg load was applied to bond them together, obtaining a laminate with a layer structure of substrate Z / adhesive layer / substrate. The obtained laminate was placed in a vacuum constant temperature drying oven [model number: DRV420DA, manufactured by Advantec Toyo Co., Ltd.] set to a heating temperature of 250°C. After placement, the pressure inside the vacuum constant temperature drying oven was reduced (gauge pressure: -0.1 MPa or less), and it was left to stand for 1 hour. Next, the laminate was removed from the vacuum constant temperature drying oven and left to stand for 24 hours in an environment with an ambient temperature of 23°C and 50% RH. For this laminate after standing, the adhesive strength (unit: N / 25mm) was measured when an evaluation sample piece X' (layer structure: adhesive layer / substrate) was peeled 180° along the long side (100mm) from the substrate Z using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under ambient temperature of 23°C and 50% RH conditions, and peeling speed of 300mm / min. In addition, the peeled surface of the substrate Z after peeling off the evaluation sample piece X' was visually observed to confirm the presence and degree of adhesive residue (so-called adhesive residue) on the substrate Z, as well as whether or not the substrate was damaged. The evaluation was then performed according to the evaluation criteria below. The results of the evaluation, including measured adhesive strength, are shown in Table 2. In the evaluation criteria below, "3" and "2" are at a level that is acceptable in practical use, and "3" is the most preferable.

[0126] -Evaluation Criteria- 3. No adhesive residue is observed, and the adhesive strength is 15.0 N / 25 mm or less. 2: A small amount of adhesive residue was observed at the edges of the peeled surface, but the adhesive strength was 15.0 N / 25 mm or less. 1: At least one of the following (a) to (c) applies. (a) Clear adhesive residue is observed on the peeled surface. (b) The adhesive strength exceeds 15.0 N / 25 mm. (c) Substrate damage occurs.

[0127] 3. Adhesion to the back surface For the evaluation sample Y prepared as described above, the adhesive strength (unit: N / 25mm) was measured when the laminate Y (layer structure: adhesive layer / substrate) was peeled 180° in the unwinding direction from the back side of the substrate (the side not treated for easy adhesion) using a single-column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd., under conditions of an ambient temperature of 23°C and 50% RH, and a peeling speed of 300 mm / min. In addition, the peeled surface of the substrate after peeling off the laminate Y was visually observed to check for the presence and degree of adhesive residue (so-called glue residue) on the back side of the substrate, as well as whether or not the substrate was damaged. The evaluation was then performed according to the evaluation criteria below. The results of the evaluation, including measured adhesive strength, are shown in Table 2. In the evaluation criteria below, "3" and "2" are at a level that is acceptable for practical use, and "3" is the most preferable. If the evaluation result is "3" or "2", it is judged that the unwinding performance is good.

[0128] -Evaluation Criteria- 3. No adhesive residue is observed, and the adhesive strength is 5.0 N / 25 mm or less. 2: No adhesive residue is observed, and the adhesive strength is in the range of over 5.0 N / 25 mm and 10.0 N / 25 mm or less. 1: At least one of the following (a) to (c) applies. (a) Adhesive residue is observed. (b) The adhesive strength exceeds 10.0 N / 25 mm. (c) Substrate damage occurs.

[0129] [Table 2]

[0130] Details of the crosslinking agents listed in Table 2 are as follows. -Metal chelate crosslinking agents- "Aluminum Chelate A" [Product name, manufactured by Kawaken Fine Chemical Co., Ltd.] -Epoxy-based crosslinking agent- "TETRAD-X" [Product name, manufactured by Mitsubishi Gas Chemical Company, Inc.] "TETRAD-C" [Product name, manufactured by Mitsubishi Gas Chemical Company, Inc.] -Isocyanate-based crosslinking agents- "Coronate L-45E" [Product name, manufactured by Tosoh Corporation] The terms "TETRAD" and "Coronate" mentioned above are both registered trademarks.

[0131] In Table 2, all values ​​listed in the "Amount" column are based on solid content. In Table 2, "-" indicates that the ingredient corresponding to that column is not included.

[0132] As shown in Table 2, the adhesive tapes of Examples 1 to 15 all exhibited moderate normal adhesive strength, excellent heat resistance and re-peelability, and good unwinding properties, confirming their suitability as protective adhesive tapes used in dry thin film formation processes.

[0133] [Weight loss rate of resin film due to heating] The weight loss rate of the resin film used as a base material due to heating was measured. A resin film was placed in an aluminum cell (a so-called sample container for thermal analysis measurement), and the sample was prepared for measurement by heating it at 105°C for 15 minutes under a nitrogen atmosphere using a differential thermogravimetric analyzer (model number: STA7200RV) manufactured by Hitachi High-Tech Science Co., Ltd., and then allowing it to cool to 50°C to remove moisture absorbed into the resin film. Next, approximately 10 mg of the prepared sample was placed in an aluminum cell (a so-called sample container for thermal analysis), and differential thermal-thermogravimetric analysis (TG-DTA) was performed using a differential thermal-thermogravimetric analyzer (model: STA7200RV) manufactured by Hitachi High-Tech Science Corporation. The sample was heated from 50°C to 250°C under a nitrogen atmosphere at a heating rate of 10°C / min, and then held at 250°C for 2 hours. The weight loss rate of the resin film due to heating was then calculated based on the following formula. The results are shown in Table 3. Weight loss rate of resin film due to heating (%) =[Weight of resin film before TG-DTA (mg)] - [Weight of resin film after TG-DTA (mg)] / [Weight of resin film before TG-DTA (mg)]

[0134] [Table 3]

[0135] Details of the resin films listed in Table 3 are as follows. "PEI": Polyetherimide film [Product name: Superior® UT, manufactured by Mitsubishi Chemical Corporation] "PESU": Polyethersulfone film [Product name: Veradel (registered trademark) PES 201 NT, manufactured by Solvay] "PSU": Polysulfone film [Product name: Udel(registered trademark) PSU, manufactured by Solvay] "PPSU": Polyphenylene sulfone film [Product name: Radel® R-5100 NT-15, manufactured by Solvay] "PI": Polyimide film [Product name: Kapton® 200H, manufactured by Toray DuPont Co., Ltd.]

[0136] As shown in Table 3, the weight loss rate upon heating under the above conditions for PEI film, PESU film, PSU film, PPSU film, and PI film was 1.0% or less. These results indicate that PEI film, PESU film, PSU film, PPSU film, and PI film are resin films that generate little outgassing, suggesting that they are suitable as substrates for protective adhesive tapes used in dry thin film formation processes.

Claims

1. A protective adhesive tape used in a dry thin film formation process, The protective adhesive tape is a roll body comprising a base material and an adhesive layer provided on one surface of the base material, wherein the side of the adhesive layer opposite to the base material and the other surface of the base material are in contact and laminated together. A protective adhesive tape, wherein the adhesive layer is formed from an adhesive composition comprising: a (meth)acrylic copolymer containing 6% to 14% by mass of constituent units derived from monomers having carboxyl groups relative to the total constituent units; a metal chelating crosslinking agent; and an epoxy crosslinking agent, wherein the ratio of the mass content of the epoxy crosslinking agent to the mass content of the metal chelating crosslinking agent is 0.3 to 1.6; and the total content of the metal chelating crosslinking agent and the epoxy crosslinking agent is 1.0 to 3.3 parts by mass per 100 parts by mass of the (meth)acrylic copolymer.

2. The protective adhesive tape according to claim 1, wherein the (meth)acrylic copolymer comprises structural units derived from alkyl (meth)acrylate monomers having an alkyl group having 1 to 4 carbon atoms.

3. The protective adhesive tape according to claim 1 or claim 2, wherein the base material is a polyetherimide base material, a polyethersulfone base material, or a polyphenylsulfone base material.

4. The protective adhesive tape according to claim 1 or claim 2, wherein the wettability index of the side of the substrate on which the adhesive layer is provided is 50 mN / m or more.

5. The protective adhesive tape according to claim 1 or 2, wherein the substrate has a weight loss rate of 1.0% or less when heated at 200°C for 2 hours in a nitrogen atmosphere.

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