Pressure-sensitive adhesive tape

Abstract

To provide a pressure-sensitive adhesive tape which is excellent in resistance against a strong alkaline solution and can be easily peeled from an adherend.SOLUTION: A pressure-sensitive adhesive tape is provided, having a base material, and a pressure-sensitive adhesive layer laminated on at least one surface of the base material. The pressure-sensitive adhesive layer contains a base polymer and a tackifier resin. The base polymer is a hydrogenated body of a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from a conjugated diene monomer, or a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from an olefin monomer. The tackifier resin contains a terpene phenol resin (T1) having a hydroxyl value of 50-140 mgKOH / g. In the adhesive layer, the total of contents of a terpene phenol resin (T2) having a hydroxyl value exceeding 140 mgKOH / g and a rosin ester resin (T3) is 5 pts.wt. or less based on 100 pts.wt. of the base polymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive tape that has excellent resistance to strong alkaline solutions and can be easily peeled from an adherend. [Background technology]

[0002] Conventionally, adhesives and adhesive tapes have been widely used to fix components in electronic devices. Adhesive tapes are also used as processing materials in the manufacturing process of electronic devices. For example, adhesive tapes are used to facilitate handling and prevent breakage when processing thin components in the manufacturing process of electronic devices. These adhesives and tapes are required to have not only high adhesiveness but also heat resistance, thermal conductivity, impact resistance, and other properties depending on the environment of the area where they are used (e.g., Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-052050 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-021067 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-120876 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, substrates such as printed wiring boards have become thinner, and in processes for manufacturing substrates from copper-clad laminates, problems have arisen in that the edges of the copper-clad laminates are damaged during the manufacturing process. To address this problem, adhesive tape has been applied to the edges of the copper-clad laminates to protect them before processing. Such adhesive tape is required to adequately protect the copper-clad laminate during processing, and to be easily peeled from the copper-clad laminate after processing without damaging the copper-clad laminate. However, in etching, desmearing, and other processes carried out in the manufacturing process of substrates, a strongly alkaline solution is used as a processing liquid. Conventional pressure-sensitive adhesive tapes are prone to peeling when exposed to such a strongly alkaline solution, resulting in problems such as insufficient protection of the edges of copper-clad laminates and corrosion of the copper on the surface of the copper-clad laminates.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive tape that has excellent resistance to strong alkaline solutions and can be easily peeled from an adherend. [Means for solving the problem]

[0006] The present invention provides a pressure-sensitive adhesive tape having a substrate and a pressure-sensitive adhesive layer laminated on at least one surface of the substrate, wherein the pressure-sensitive adhesive layer contains a base polymer and a tackifier resin, the base polymer being a hydrogenated product of a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from a conjugated diene monomer, or a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from an olefin monomer, the tackifier resin containing a terpene phenol resin (T1) having a hydroxyl value of 50 to 140 mgKOH / g, and the pressure-sensitive adhesive layer containing a terpene phenol resin (T2) having a hydroxyl value exceeding 140 mgKOH / g and a rosin ester resin (T3) in a total amount of 5 parts by weight or less per 100 parts by weight of the base polymer. The present invention will be described in detail below.

[0007] The present inventors have discovered that, in an adhesive tape having a substrate and an adhesive layer laminated on at least one surface of the substrate, the use of a specific block copolymer in the adhesive layer improves the removability of the adhesive tape, allowing the adhesive tape to adequately protect the adherend during processing, and allowing the adhesive tape to be easily removed without damaging the adherend after processing. Furthermore, the present inventors have investigated tackifier resins to be incorporated into the adhesive layer. The present inventors have found that by selecting and using a terpene phenolic resin (T1) having a hydroxyl value within a specific range among tackifier resins, and by controlling the total content of a terpene phenolic resin (T2) having a hydroxyl value higher than that of T1 and a rosin ester resin (T3) below a certain value, resistance to strong alkaline solutions can be significantly improved. This has led to the completion of the present invention.

[0008] The pressure-sensitive adhesive tape of the present invention has a substrate and a pressure-sensitive adhesive layer laminated on at least one surface of the substrate. The pressure-sensitive adhesive layer contains a base polymer and a tackifier resin. By containing the tackifier resin in addition to the base polymer, the pressure-sensitive adhesive layer improves the adhesive strength of the pressure-sensitive adhesive tape and can sufficiently protect the adherend.

[0009] The base polymer is a hydrogenated product of a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from a conjugated diene monomer, or a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from an olefin monomer (hereinafter, both of these may be collectively referred to as "block copolymer"). When the base polymer is the block copolymer, the adhesive strength of the pressure-sensitive adhesive layer is within an appropriate range, improving the removability of the pressure-sensitive adhesive tape. Furthermore, since the block copolymer has a relatively low polarity, when the base polymer is the block copolymer, strong alkaline solutions are less likely to penetrate into the pressure-sensitive adhesive layer than when the base polymer is an acrylic polymer, for example, and the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions is improved.

[0010] The aromatic vinyl monomer is not particularly limited, and examples thereof include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, t-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, vinylnaphthalene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene. The tertiary amino group-containing diphenylethylene is not particularly limited, and examples thereof include 1-(4-N,N-dimethylaminophenyl)-1-phenylethylene. These aromatic vinyl monomers may be used alone or in combination of two or more.

[0011] The conjugated diene monomer is not particularly limited, and examples thereof include isoprene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2-phenyl-1,3-butadiene, 3-methyl-1,3-pentadiene, 2-chloro-1,3-butadiene, etc. These conjugated diene monomers may be used alone or in combination of two or more. The olefin monomer is not particularly limited, and examples thereof include ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, isobutene, 1-pentene, cis-2-pentene, trans-2-pentene, 1-hexene, cis-2-hexene, trans-2-hexene, cis-3-hexene, trans-3-hexene, cyclohexene, etc. These olefin monomers may be used alone or in combination of two or more.

[0012] The block copolymer is not particularly limited, and may be a block copolymer or a hydrogenated product thereof that has rubber elasticity at room temperature and has a hard segment portion and a soft segment portion. The block derived from the aromatic vinyl monomer is the hard segment portion, and the block derived from the conjugated diene monomer or the block derived from the olefin monomer is the soft segment portion. More specifically, hydrogenated styrene-based block copolymers are preferred as the block copolymers. Examples of the hydrogenated styrene-based block copolymers include styrene-ethylene-butylene-styrene (SEBS) block copolymers, styrene-ethylene-propylene-styrene (SEPS) block copolymers, and styrene-ethylene-ethylene-propylene-styrene (SEEPS). Other examples of the block copolymers include styrene-isobutylene-styrene (SIBS) block copolymers. Among these, SEBS block copolymers, SEPS copolymers, and SIBS block copolymers are preferred, and SEBS block copolymers are more preferred, because their adhesive strength can be adjusted to a low level. These block copolymers may be used alone or in combination of two or more.

[0013] The styrene content of the styrene-ethylene-butylene-styrene (SEBS) block copolymer is not particularly limited, but a preferred upper limit is 30 wt %, more preferably 25 wt %, and even more preferably 20 wt %. If the styrene content is within the above range, the pressure-sensitive adhesive layer does not become too hard and exhibits high adhesion to the adherend, thereby further improving the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions. Therefore, even when the pressure-sensitive adhesive tape is attached to an adherend with greater surface roughness and exposed to a strong alkaline solution, peeling is less likely to occur. The lower limit of the styrene content is not particularly limited, but from the viewpoint of maintaining the cohesive strength of the pressure-sensitive adhesive layer, a preferred lower limit is 8 wt %. The styrene content is 1 It can be calculated from the peak area ratio of each block measured by H-NMR.

[0014] The molar ratio of ethylene to butylene in the styrene-ethylene-butylene-styrene (SEBS) block copolymer (mol % of ethylene / mol % of butylene) (hereinafter also referred to as the "ethylene-butylene ratio") is not particularly limited, but a preferred lower limit is 1.0, and a more preferred lower limit is 1.2. When the ethylene-butylene ratio is within the above range, the pressure-sensitive adhesive tape's resistance to strong alkaline solutions is further improved. Therefore, even when the pressure-sensitive adhesive tape is attached to an adherend with greater surface roughness and exposed to a strong alkaline solution, peeling is less likely to occur. While not bound by this theory, the reason for the improved resistance of the pressure-sensitive adhesive tape to strong alkaline solutions is thought to be that, due to the higher ratio of ethylene compared to butylene, partial packing of ethylene moieties occurs within the molecule, making it difficult for the strong alkaline solution to penetrate. The upper limit of the ethylene-butylene ratio is not particularly limited, but a preferred upper limit is 2, from the viewpoint of preventing the pressure-sensitive adhesive layer from becoming too hard and achieving excellent adhesion to the adherend. The ethylene butylene ratio is 1 It can be calculated from the peak area ratio of each component measured by H-NMR.

[0015] The styrene content of the styrene-ethylene-propylene-styrene (SEPS) block copolymer is not particularly limited, but from the same viewpoint as in the case of the styrene-ethylene-butylene-styrene (SEBS) block copolymer, the lower limit is preferably 8% by weight, the upper limit is preferably 30% by weight, the upper limit of the styrene content is more preferably 15% by weight, and the upper limit is still more preferably 13% by weight. The styrene content of the styrene-isobutylene-styrene (SIBS) block copolymer is not particularly limited, but from the same viewpoint as in the case of the styrene-ethylene-butylene-styrene (SEBS) block copolymer, the lower limit is preferably 8% by weight, the upper limit is preferably 30% by weight, the upper limit is more preferably 25% by weight, and the upper limit is even more preferably 20% by weight.

[0016] The block copolymer may contain a triblock copolymer of a block derived from the aromatic vinyl monomer and a block derived from the conjugated diene monomer or a block derived from the olefin monomer, as well as a diblock copolymer of a block derived from the aromatic vinyl monomer and a block derived from the conjugated diene monomer or a block derived from the olefin monomer. The content of the diblock copolymer in the block copolymer (hereinafter also referred to as the "diblock ratio") is not particularly limited, but a preferred lower limit is 10% by weight, and a more preferred lower limit is 30% by weight. If the diblock ratio is within the above range, the adhesiveness of the pressure-sensitive adhesive layer to the adherend is increased, thereby further improving the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions. Therefore, even when the pressure-sensitive adhesive tape is attached to an adherend with greater surface roughness and exposed to a strong alkaline solution, peeling is less likely to occur. The upper limit of the diblock ratio is not particularly limited, but from the viewpoint of maintaining the cohesive strength of the pressure-sensitive adhesive layer, a preferred upper limit is 90% by weight. The diblock ratio can be calculated from the peak area ratio of each copolymer measured by gel permeation chromatography (GPC).

[0017] The weight-average molecular weight of the block copolymer is not particularly limited, but a preferred lower limit is 50,000 and a preferred upper limit is 600,000. If the weight-average molecular weight is 50,000 or more, the heat resistance of the pressure-sensitive adhesive tape will be higher. If the weight-average molecular weight is 600,000 or less, excessive deterioration in compatibility between the block copolymer and other components can be prevented. A more preferred lower limit of the weight-average molecular weight is 100,000 and a more preferred upper limit is 500,000. The weight-average molecular weight of the block copolymer refers to the weight-average molecular weight measured as a polystyrene-equivalent molecular weight by gel permeation chromatography (GPC). The weight-average molecular weight can be measured by GPC using, for example, Column LF-804 (manufactured by Showa Denko K.K.).

[0018] The tackifier resin contains a terpene phenol resin (T1) having a hydroxyl value of 50 to 140 mgKOH / g. When the tackifier resin contains, among various tackifier resins, a terpene phenol resin (T1) having a hydroxyl value within the above range, the adhesive tape has improved resistance to strong alkaline solutions. The term "terpene phenolic resin" refers to a polymer containing a terpene residue and a phenol residue. The term "terpene phenolic resin" encompasses a copolymer of a terpene and a phenolic compound (terpene-phenol copolymer resin), a phenol-modified terpene resin obtained by phenol-modifying a terpene homopolymer or copolymer (terpene resin, typically an unmodified terpene resin), and a resin obtained by hydrogenating the terpene moiety in these resins.

[0019] The terpene constituting the terpene phenol resin (T1) is not particularly limited, but is preferably a monoterpene such as α-pinene, β-pinene, limonene, camphene, etc. Limonene includes d-, l- and d / l-isomers (dipentene).

[0020] The hydroxyl value of the terpene phenol resin (T1) has a lower limit of 50 mgKOH / g and an upper limit of 140 mgKOH / g. When the hydroxyl value of the terpene phenol resin (T1) is within the above range, the polarity of the terpene phenol resin (T1) is within an appropriate range, which makes it difficult for a strong alkaline solution to penetrate into the pressure-sensitive adhesive layer, thereby improving the resistance of the pressure-sensitive adhesive tape to a strong alkaline solution. The hydroxyl value of the terpene phenol resin (T1) preferably has a lower limit of 55 mgKOH / g and an upper limit of 100 mgKOH / g, a more preferred lower limit of 60 mgKOH / g, and an even more preferred upper limit of 80 mgKOH / g. That is, the terpene phenol resin (T1) more preferably contains a terpene phenol resin having a hydroxyl value of 60 to 80 mgKOH / g. The hydroxyl value of a tackifier resin is the number of milligrams of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when 1 g of the tackifier resin is acetylated, and is defined as a value measured based on the potentiometric titration method specified in JIS K 0070:1992.

[0021] The softening point of the terpene phenol resin (T1) is not particularly limited, but a preferred lower limit is 145°C. When the softening point of the terpene phenol resin (T1) is 145°C or higher, the molecular weight of the terpene phenol resin increases and its solubility in strong alkaline solutions decreases, making it difficult for strong alkaline solutions to penetrate into the pressure-sensitive adhesive layer, thereby further improving the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions. Therefore, even when the pressure-sensitive adhesive tape is attached to an adherend with greater surface roughness and exposed to a strong alkaline solution, peeling is unlikely to occur. Furthermore, when the softening point of the terpene phenol resin (T1) is 145°C or higher, the heat resistance of the pressure-sensitive adhesive tape is further improved. A more preferred lower limit of the softening point of the terpene phenol resin (T1) is 150°C. The upper limit of the softening point of the terpene phenol resin (T1) is not particularly limited, but a practical upper limit is about 180°C. The softening point of a tackifier resin is the temperature at which a solid resin softens and begins to deform, and is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K 5902 and JIS K 2207.

[0022] The content of the terpene phenol resin (T1) is not particularly limited, but a preferred lower limit is 3 parts by weight and a preferred upper limit is 80 parts by weight per 100 parts by weight of the base polymer. If the content of the terpene phenol resin (T1) is 3 parts by weight or more, the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions is further improved. If the content of the terpene phenol resin (T1) is 80 parts by weight or less, increased adhesion of the pressure-sensitive adhesive layer is suppressed, adhesive residue is suppressed, and the removability of the pressure-sensitive adhesive tape is further improved. A more preferred lower limit of the content of the terpene phenol resin (T1) is 10 parts by weight and a more preferred upper limit is 60 parts by weight. Furthermore, the content of the terpene phenol resin having a hydroxyl value of 50 to 80 mgKOH / g in the viscous terpene phenol resin (T1) is not particularly limited, and the preferred lower limit is 3 parts by weight, the preferred upper limit is 80 parts by weight, the more preferred lower limit is 10 parts by weight, and the more preferred upper limit is 60 parts by weight, relative to 100 parts by weight of the base polymer.

[0023] The tackifier resin may contain a tackifier resin other than the terpene phenol resin (T1). The tackifier resin other than the terpene phenol resin (T1) is not particularly limited, and examples thereof include coumarone resins, terpene resins, terpene phenol resins, rosin resins, rosin derivative resins, petroleum resins, alkylphenol resins, and hydrogenated versions thereof. These tackifier resins may be used alone or in combination of two or more.

[0024] More specific examples of the rosin resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, as well as modified rosins obtained by modifying these unmodified rosins. Modifications of the modified rosins include, for example, hydrogenation, disproportionation, and polymerization. More specific examples of the modified rosins include hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins.

[0025] More specific examples of the rosin derivative resin include a rosin ester resin obtained by esterifying the rosin resin with an alcohol, an unsaturated fatty acid-modified rosin resin obtained by modifying the rosin resin with an unsaturated fatty acid, and an unsaturated fatty acid-modified rosin ester resin obtained by modifying the rosin ester resin with an unsaturated fatty acid. Examples of the rosin derivative resin include rosin alcohol resins obtained by reducing the carboxyl groups in the unsaturated fatty acid modified rosin resins or unsaturated fatty acid modified rosin ester resins. Further examples of the rosin derivative resin include metal salts of the rosin resin or rosin derivative resin (particularly, rosin ester resin), and rosin phenol resin. The rosin phenol resin can be obtained by adding phenol to the rosin resin or rosin derivative resin in the presence of an acid catalyst and then thermally polymerizing the resultant.

[0026] More specific examples of the petroleum resin include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, C5 / C9 copolymer petroleum resins, and alicyclic petroleum resins.

[0027] However, in the pressure-sensitive adhesive layer, the total content of the terpene phenol resin (T2) having a hydroxyl value exceeding 140 mgKOH / g and the rosin ester resin (T3) is 5 parts by weight or less per 100 parts by weight of the base polymer. When the total content of the terpene phenol resin (T2) and the rosin ester resin (T3) is 5 parts by weight or less, the pressure-sensitive adhesive tape has improved resistance to strong alkaline solutions. The terpene phenol resin (T2) has a higher hydroxyl value and higher polarity than the terpene phenol resin (T1). Therefore, if the content of the terpene phenol resin (T2) is too high, a strong alkaline solution will easily penetrate into the pressure-sensitive adhesive layer, thereby reducing the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions. Furthermore, since the rosin ester resin (T3) has functional groups such as ester groups, hydroxyl groups, and carboxyl groups, if the content of the rosin ester resin (T3) is too high, a strong alkaline solution will easily penetrate into the pressure-sensitive adhesive layer, thereby reducing the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions. The total content of the terpene phenol resin (T2) and the rosin ester resin (T3) is preferably 2 parts by weight or less, and more preferably 0 part by weight. Furthermore, from the viewpoint of further improving the resistance of the pressure-sensitive adhesive tape to strong alkaline solutions, it is preferable that the total content of the terpene phenol resin (T2) and the rosin ester resin (T3) is equal to or less than the content of the terpene phenol resin (T1).

[0028] The pressure-sensitive adhesive layer may contain additives such as plasticizers, emulsifiers, softeners, fillers, pigments, and dyes, other resins, and the like, as needed.

[0029] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but the preferred lower limit is 5 μm and the preferred upper limit is 100 μm. If the thickness of the pressure-sensitive adhesive layer is 5 μm or more, the adhesive strength of the pressure-sensitive adhesive tape will be higher. If the thickness of the pressure-sensitive adhesive layer is 100 μm or less, the processability of the pressure-sensitive adhesive tape will be improved.

[0030] In the pressure-sensitive adhesive tape of the present invention, the pressure-sensitive adhesive layer is laminated on at least one surface of the substrate, and may be laminated on one surface of the substrate or on both surfaces of the substrate. The substrate is not particularly limited, and examples thereof include resin films, metal foils, etc. The resin film is not particularly limited, and examples thereof include polyolefin resin films such as polyethylene films and polypropylene films, polyester resin films such as polyethylene terephthalate (PET) films, ethylene-vinyl acetate copolymer films, polyvinyl chloride resin films, and polyurethane resin films. Other examples of the substrate include polyolefin foam sheets such as polyethylene foam sheets and polypropylene foam sheets, and polyurethane foam sheets. PET films are particularly preferred.

[0031] The substrate preferably has a metal layer on the outermost surface opposite to the surface on which the pressure-sensitive adhesive layer is laminated. By having the metal layer on the substrate, even when the pressure-sensitive adhesive tape is folded (bent) and attached to an adherend, the metal layer maintains its shape, suppressing the restoring force caused by folding the substrate, making it less likely for a gap to form between the adherend and the pressure-sensitive adhesive layer, and making peeling less likely to occur (hereinafter, such performance is also referred to as "fold-back attachment ability"). If the substrate does not have the metal layer and is made of, for example, only the resin film, a gap is likely to form between the adherend and the pressure-sensitive adhesive layer due to the restoring force of the resin film, making peeling more likely to occur. An example of an application in which an adhesive tape is folded back and attached to an adherend is when, in a substrate manufacturing process, the edge of a copper-clad laminate is protected by adhesive tape attached to prevent damage to the copper-clad laminate while processing is performed. In such cases, the adhesive tape is folded back and attached along the edge of the copper-clad laminate in a U-shape, >-shape,}-shape, or the like.

[0032] The metal constituting the metal layer is not particularly limited, and examples thereof include copper, aluminum, nickel, titanium, etc. Further examples of the metal constituting the metal layer include alloys such as stainless steel and Monel. Among these, copper is preferred because it has a small restoring force after folding, thereby improving the fold-back adhesion of the pressure-sensitive adhesive tape, and is tear-resistant, thereby improving the handleability of the pressure-sensitive adhesive tape.

[0033] The thickness of the metal layer is not particularly limited, but a preferred lower limit for the ratio of the thickness of the metal layer to the total thickness of the substrate (thickness of the metal layer / total thickness of the substrate) is 15%. If the thickness ratio of the metal layer is 15% or more, the foldback adhesion of the adhesive tape is further improved. A more preferred lower limit for the thickness ratio of the metal layer is 25%. The upper limit of the thickness ratio of the metal layer is not particularly limited and may be 100%. That is, the substrate may be a metal substrate. When the substrate is a metal substrate, the fold-back adhesion of the adhesive tape is further improved, and the anchoring property between the substrate and the adhesive layer is increased without the need for a resin layer as described below, thereby reducing adhesive residue of the adhesive layer and further improving the removability of the adhesive tape. The metal constituting the metal substrate is not particularly limited and may be the same metal as the metal constituting the metal layer. Among these, it is preferable that the substrate be copper foil, since copper foil has a small restoring force after folding, thereby further improving the fold-back adhesion of the adhesive tape, and is less likely to tear, thereby improving the handleability of the adhesive tape.

[0034] The thickness of the substrate is not particularly limited, but a preferred lower limit is 5 μm and a preferred upper limit is 30 μm. If the thickness of the substrate is within the above range, the fold-back adhesion of the adhesive tape is further improved. A more preferred lower limit of the thickness of the substrate is 8 μm and a more preferred upper limit is 20 μm.

[0035] The pressure-sensitive adhesive tape of the present invention preferably further comprises a resin layer between the substrate and the pressure-sensitive adhesive layer, and the resin layer preferably contains a resin having a polar functional group. The adhesive tape of the present invention has the resin layer, which enhances the anchoring property between the substrate and the adhesive layer, making it more difficult for a strong alkaline solution to penetrate into the adhesive layer, and further improving the resistance of the adhesive tape to a strong alkaline solution. Furthermore, the enhanced anchoring property between the substrate and the adhesive layer reduces adhesive residue of the adhesive layer, further improving the removability of the adhesive tape.

[0036] The polar functional group is not particularly limited, but is preferably at least one selected from the group consisting of a nitrile group, a carbonyl group, a carboxyl group, and an amino group, because they have excellent adhesion to resin substrates such as PET films and the metal substrates. Of these, a nitrile group and a carbonyl group are more preferred.

[0037] Specific examples of the resin having the polar functional group include acrylonitrile butadiene rubber (NBR), maleic anhydride-modified styrene-ethylene-butylene-styrene (maleic anhydride-modified SEBS), amine-modified styrene-ethylene-butylene-styrene (amine-modified SEBS), etc. Among these, NBR and maleic anhydride-modified SEBS are preferred because of their excellent adhesion to resin substrates such as PET films and also to the pressure-sensitive adhesive layer.

[0038] The thickness of the resin layer is not particularly limited, but a preferred lower limit is 0.1 μm and a preferred upper limit is 3 μm. If the thickness of the resin layer is within the above range, the adhesive tape will have improved resistance to strong alkaline solutions and improved removability. A more preferred lower limit of the thickness of the resin layer is 0.5 μm and a more preferred upper limit is 2 μm.

[0039] The resin layer may contain additives such as plasticizers, emulsifiers, softeners, fillers, pigments, and dyes, as well as other resins, if necessary.

[0040] The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited, and examples thereof include the following method. First, a pressure-sensitive adhesive solution containing the base polymer and the tackifier resin is prepared. Next, the pressure-sensitive adhesive solution obtained above is applied to the release-treated surface of a release film, one side of which has been release-treated, and dried to produce a laminate sheet having a pressure-sensitive adhesive layer on the release-treated surface of the release film. Next, the pressure-sensitive adhesive layer of the laminate sheet is transferred to the substrate, if necessary via the resin layer, and laminated together to obtain a pressure-sensitive adhesive tape.

[0041] The use of the pressure-sensitive adhesive tape of the present invention is not particularly limited, but it can be suitably used in applications where it is exposed to a strong alkaline solution. Examples of applications involving exposure to the strong alkaline solution include applications in the manufacturing process of a substrate in which a treatment is performed while protecting the edges of a copper-clad laminate by attaching an adhesive tape to the edges to prevent damage to the copper-clad laminate. In such cases, for example, etching treatment, desmear treatment, etc. are performed, and a strong alkaline solution is used as the treatment liquid. That is, the adhesive tape of the present invention is preferably used to protect a substrate having a metal layer, such as a copper-clad laminate, in the etching treatment or desmear treatment in the manufacturing process of the substrate.

[0042] Furthermore, the pressure-sensitive adhesive tape of the present invention has excellent fold-back application properties, and can therefore be suitably used in applications where the pressure-sensitive adhesive tape is folded back (bent) and applied to an adherend. One application in which the above-mentioned adhesive tape is folded back and attached to an adherend is, for example, in the manufacturing process of a substrate, where the adhesive tape is attached to the edge of a copper-clad laminate to protect the copper-clad laminate from damage and processing is performed in that state. In such cases, the adhesive tape is folded back and attached along the edge of the copper-clad laminate in a U-shape, >-shape,}-shape, or the like. [Effects of the Invention]

[0043] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that has excellent resistance to strong alkaline solutions and can be easily peeled from an adherend. DETAILED DESCRIPTION OF THE INVENTION

[0044] The following examples will further illustrate the present invention, but the present invention is not limited to these examples.

[0045] The polymers shown in Tables 1 to 4 were used as base polymers. DYNARON 8300P and DYNARON 8600P were manufactured by JSR Corporation, Kraton G1643 and Kraton G1657 were manufactured by Kraton Polymers, Tuftec H1052, Tuftec H1053, and Tuftec H1041 were styrene-ethylene-butylene-styrene (SEBS) block copolymers manufactured by Asahi Kasei Corporation, Septon 2063, Septon 2004F, and Septon 2002 were styrene-ethylene-propylene-styrene (SEPS) block copolymers manufactured by Kuraray Co., Ltd., SIBSTAR 102T and SIBSTAR 103T were styrene-isobutylene-styrene (SIBS) block copolymers manufactured by Kaneka Corporation, and Quintac 3520 was a styrene-isoprene-styrene block copolymer manufactured by Zeon Corporation.

[0046] As the tackifying resin, the tackifying resins shown in Tables 1 to 4 were used. U-115, T-80, T-130, T-145, T-160, S-145, G-125, G-150, and K-125 were terpene phenol resins (YS Polyster) manufactured by Yasuhara Chemical Co., Ltd. P-125 was a hydrogenated petroleum resin (Arcon) manufactured by Arakawa Chemical Industries, Ltd. PX-1250 was a polyterpene resin (YS Resin) manufactured by Yasuhara Chemical Co., Ltd. A-125 was a rosin ester resin (disproportionated rosin ester) (Super Ester) manufactured by Arakawa Chemical Industries, Ltd.

[0047] (Examples 1 to 32, Comparative Examples 1 to 9) The types and amounts of base polymer and tackifier resin shown in Tables 1 to 4 were added to a solvent (toluene) and stirred to a solution concentration of 30% by weight to prepare a pressure-sensitive adhesive solution. A polyethylene terephthalate film with one surface treated for release was prepared. The pressure-sensitive adhesive solution obtained above was applied to the release-treated surface of this polyethylene terephthalate film to a dry thickness of 30 μm, and then dried at 110°C for 5 minutes to produce a laminate sheet having a pressure-sensitive adhesive layer on the release-treated surface of the polyethylene terephthalate film.

[0048] A 12 μm thick (t=12 μm) polyethylene terephthalate film was prepared as the substrate. Nipol 1042 (acrylonitrile butadiene rubber, manufactured by Nippon Zeon Co., Ltd.) was added to a solvent (methyl ethyl ketone) to a solution concentration of 5 wt % and stirred to prepare a resin solution. The resulting resin solution was applied to one side of the substrate to a thickness of 1 μm after drying and dried at 110°C for 5 minutes to form a resin layer. A laminated sheet was laminated on the obtained resin layer with its adhesive layer facing the resin layer, and the adhesive layer was transferred to the substrate via the resin layer and laminated together, thereby obtaining an adhesive tape having an adhesive layer with a thickness of 30 μm on one side of the substrate via the resin layer.

[0049] <Rating 1> The pressure-sensitive adhesive tapes obtained in Examples 1 to 32 and Comparative Examples 1 to 9 were evaluated as follows. The results are shown in Tables 1 to 4.

[0050] (1) Evaluation of resistance to strong alkaline solutions Copper plates with a surface roughness Ra of 0.06 μm and 0.26 μm were used as the low-surface-roughness copper plate and the high-surface-roughness copper plate, respectively. An adhesive tape was attached to the surface of the copper plate with a surface roughness Ra of 0.06 μm or 0.26 μm to produce a laminate. This laminate was immersed in a 5 wt% aqueous sodium hydroxide solution at 50°C for 30 minutes, then removed, the sodium hydroxide solution was removed, and the laminate was left at room temperature for 30 minutes. After leaving it at room temperature for 30 minutes, the adhesive tape was peeled off from the copper plate. The protection rate was calculated as the area ratio of the non-corroded area of the copper plate where the adhesive tape had been applied to the entire area of the copper plate where the adhesive tape had been applied (area of the non-corroded area / area of the entire area where the adhesive tape had been applied × 100 (%)). A protection rate (area of the non-corroded part / total area of the part where the adhesive tape was attached x 100 (%)) of 80% or more was indicated by ◎, a rate of 50% or more but less than 80% was indicated by ○, and a rate of less than 50% was indicated by ×.

[0051] (2) Evaluation of adhesive strength (180° peel adhesive strength to copper) The adhesive tape was cut into 25 mm wide pieces to serve as test pieces, and a copper plate with a surface roughness Ra of 0.06 μm was used as the adherend. Under a standard environment of 23°C and 50% RH, the adhesive side of the test piece was pressed against the adherend by rolling a 2 kg roller back and forth once. The test piece thus pressed against the adherend was then left under the standard environment for 20 minutes, after which the 180° peel adhesive strength was measured in accordance with JIS-Z0237 at a peel angle of 180° and a tensile speed of 300 mm / min. The measurement was performed three times, and the average value was used as the adhesive strength. When the adhesive strength was 2N / 25mm or less, it was indicated as ◎, when it was more than 2N / 25mm but less than 15N / 25mm, it was indicated as ◯, and when it was 15N / 25mm or more, it was indicated as ×.

[0052] Example 33 An adhesive tape was obtained in the same manner as in Example 4, except that no resin layer was provided between the substrate and the adhesive layer.

[0053] Examples 34 to 36 Pressure-sensitive adhesive tapes were obtained in the same manner as in Example 4, except that resins having polar functional groups of the types shown in Table 5 were used when forming the resin layer. Nipol 1042 was acrylonitrile butadiene rubber manufactured by Zeon Corporation, Tuftec M1943 was maleic anhydride-modified styrene-ethylene-butylene-styrene manufactured by Asahi Kasei Corporation, and Tuftec MP10 was amine-modified styrene-ethylene-butylene-styrene manufactured by Asahi Kasei Corporation.

[0054] Example 37 An adhesive tape was obtained in the same manner as in Example 4, except that a copper foil having a thickness of 18 μm (t=18 μm) was used as the substrate instead of a polyethylene terephthalate film having a thickness of 12 μm (t=12 μm), and no resin layer was provided between the substrate and the adhesive layer.

[0055] <Rating 2> The following evaluations were carried out on the pressure-sensitive adhesive tapes obtained in Examples 33 to 37. The results are shown in Table 5.

[0056] (1) Evaluation of adhesive residue after high-temperature treatment The adhesive tape was cut into 25 mm wide pieces to be used as test pieces, and a copper plate was used as the adherend. Under a standard environment of 23°C and 50% RH, the adhesive side of the test piece was pressed against the adherend by rolling a 2 kg roller back and forth once. The test piece thus pressed against the adherend was left in the standard environment for 20 minutes, and then left to stand in an 80°C atmosphere for 24 hours. The test piece pressed against the adherend was then returned to 23°C and peeled off at a peel angle of 180° and a tensile speed of 300 mm / min in accordance with JIS-Z0237. The presence or absence of adhesive residue on the copper plate was confirmed.

[0057] (2) Evaluation of fold-over adhesiveness A laminate was fabricated by folding adhesive tape back (bending) along the edge of a 50 μm-thick copper foil, applying pressure at 0.5 MPa, and leaving it to stand for 24 hours. The adhesive tape was folded back so that it overlapped the folded portion by 5 mm. This laminate was then immersed in water at 50°C for 30 minutes, and the base of the folded adhesive tape was checked for water penetration. The case where water did not penetrate into the base of the folded adhesive tape was marked with an ◯, and the case where water did penetrate into the base of the folded adhesive tape was marked with an X.

[0058] [Table 1]

[0059] [Table 2]

[0060] [Table 3]

[0061] [Table 4]

[0062] [Table 5] [Industrial Applicability]

[0063] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that has excellent resistance to strong alkaline solutions and can be easily peeled from an adherend.

Claims

1. An adhesive tape having a substrate and an adhesive layer laminated on at least one surface of the substrate, the pressure-sensitive adhesive layer contains a base polymer and a tackifying resin, the base polymer is a hydrogenated product of a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from a conjugated diene monomer, or a block copolymer having at least a block derived from an aromatic vinyl monomer and a block derived from an olefin monomer, The tackifier resin contains a terpene phenol resin (T1) having a hydroxyl value of 50 to 140 mgKOH / g, In the pressure-sensitive adhesive layer, the total content of the terpene phenol resin (T2) having a hydroxyl value exceeding 140 mgKOH / g and the rosin ester resin (T3) is 5 parts by weight or less per 100 parts by weight of the base polymer. An adhesive tape characterized by:

2. 2. The pressure-sensitive adhesive tape according to claim 1, wherein the content of the terpene phenol resin (T1) having a hydroxyl value of 50 to 140 mgKOH / g is 3 to 80 parts by weight per 100 parts by weight of the base polymer.

3. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the terpene phenol resin (T1) having a hydroxyl value of 50 to 140 mgKOH / g contains a terpene phenol resin having a hydroxyl value of 50 to 80 mgKOH / g.

4. 4. The adhesive tape according to claim 3, wherein the content of the terpene phenol resin having a hydroxyl value of 50 to 80 mgKOH / g is 3 to 80 parts by weight per 100 parts by weight of the base polymer.

5. 5. The pressure-sensitive adhesive tape according to claim 1, wherein the terpene phenol resin (T1) having a hydroxyl value of 50 to 140 mgKOH / g has a softening point of 145° C. or higher.

6. 6. The adhesive tape according to claim 1, wherein the base polymer is a hydrogenated styrene-based block copolymer.

7. 7. The pressure-sensitive adhesive tape according to claim 6, wherein the hydrogenated styrene-based block copolymer is a styrene-ethylene-butylene-styrene (SEBS) block copolymer.

8. 8. The pressure-sensitive adhesive tape according to claim 7, wherein the styrene-ethylene-butylene-styrene (SEBS) block copolymer has a styrene content of 25% by weight or less.

9. 9. The pressure-sensitive adhesive tape according to claim 7, wherein the styrene-ethylene-butylene-styrene (SEBS) block copolymer has an ethylene-butylene ratio of 1.0 or more.

10. 7. The pressure-sensitive adhesive tape according to claim 6, wherein the hydrogenated styrene-based block copolymer is a styrene-ethylene-propylene-styrene (SEPS) block copolymer.

11. 11. The pressure-sensitive adhesive tape according to claim 10, wherein the styrene-ethylene-propylene-styrene (SEPS) block copolymer has a styrene content of 15% by weight or less.

12. 6. The adhesive tape according to claim 1, wherein the base polymer is a styrene-isobutylene-styrene (SIBS) block copolymer.

13. 13. The pressure-sensitive adhesive tape according to claim 12, wherein the styrene-isobutylene-styrene (SIBS) block copolymer has a styrene content of 25% by weight or less.

14. 14. The adhesive tape according to claim 1, further comprising a resin layer between the substrate and the adhesive layer, the resin layer containing a resin having a polar functional group.

15. 15. The pressure-sensitive adhesive tape according to claim 14, wherein the polar functional group of the resin having a polar functional group is at least one selected from the group consisting of a nitrile group, a carbonyl group, a carboxyl group, and an amino group.

16. 16. The adhesive tape according to claim 1, wherein the substrate has a metal layer on the outermost surface opposite to the surface on which the adhesive layer is laminated.

17. 17. The adhesive tape according to claim 16, wherein the metal layer is made of copper.

18. 18. The adhesive tape according to claim 16, wherein the substrate is a copper foil.

19. 19. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18, which is used to protect a substrate having a metal layer during etching or desmearing in the manufacturing process of the substrate.

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